Papers - Imai, Hiroaki

Enhanced and stabilized photoluminescence of perovskite cesium lead bromide nanocubes through ordered assemblies

Sasaki M., Hashimoto S., Iso Y., Oaki Y., Isobe T., Imai H.

Nanoscale Advances (Nanoscale Advances)  5 ( 9 ) 2553 - 2557 2023.04

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This work clarified the effects of self-assembly of perovskite cesium lead bromide (CsPbBr3) nanocubes (NCs) covered with didodecyldimethyl ammonium bromide (DDAB) on photoluminescence (PL) properties. Although the PL intensity of isolated NCs was weakened in the solid state even under inert conditions, the quantum yield of PL (PLQY) and the photostability of DDAB-covered NCs were drastically improved by the formation of two-dimensional (2D) ordered arrays on a substrate. The PLQY of the 2D arrays increased to ca. 60% by initial excitation illumination at 468 nm and was maintained for over 4000 h. The improved PL properties are attributable to the fixation of the surface ligand around the NCs in the specific ordered arrays.

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Construction of Millimeter-Wide Monolayers of Ordered Nanocubes as a Stain of “Wineglass Tears” Driven by the Marangoni Flow

Takatsuji Y., Matsumoto R., Sazaki G., Oaki Y., Imai H.

Langmuir (Langmuir)  39 ( 11 ) 4091 - 4099 2023.03

ISSN  07437463

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We constructed millimeter-wide monolayers consisting of tetragonally ordered BaTiO3 (BT) nanocubes through the liquid film formation caused by the Marangoni flow in a toluene-hexane binary liquid containing oleic acid. A thin liquid film containing BT nanocubes was overspread on a standing silicon substrate through the condensation of toluene at the advancing front after the preferential evaporation of hexane. Then, the oscillatory droplet formation like “wineglass tears” occurred on the substrate. Finally, two-dimensionally ordered BT nanocubes were observed as a stain of “wineglass tears” on the substrate after the liquid film receded through evaporation. The presence of a thin liquid film in the binary system is essential for the production of millimeter-wide monolayers on the substrate because multilayer deposition occurs without the formation of a thin liquid film in monocomponent systems. We improved the regularity of the ordered arrays of nanocubes by adjusting the liquid component and evaporation conditions.

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Stimuli-Responsive Sponge for Imaging and Measuring Weak Compression Stresses

Ono N., Seishima R., Okabayashi K., Imai H., Fujii S., Oaki Y.

Advanced Science (Advanced Science)  10 ( 3 )  2023.01

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Imaging and measuring compression stresses secure a safe and healthy life. Compression stresses in kPa range are not easily detected by conventional mechanoresponsive materials because microscopic molecular motion of the chromophores is not induced by such weak stresses. Moreover, imaging of the stress distribution is not achieved so far. The present study shows a sponge device combining two stimuli-responsive materials, a capsule releasing interior liquid and color-changing polymer in responses to compression stress and chemical stimulus, respectively. The stimuli-responsive capsule is dispersed on a melamine sponge comprised of the fibers with coating the layered polydiacetylene (PDA). The application of weak compression stresses induces collapse of the capsules, outflow of the interior liquid, and subsequent irreversible color change of PDA. The cascading response in the sponge device colorimetrically enables imaging of the distribution and measuring the strength of the compression stresses in kPa range. Furthermore, the device demonstrates imaging and measuring unknown weak compression stresses applied by the irregular-shaped objects. A couple of clinical issues in surgical operation of intestine are studied using the stress-imaging sponge device. The device and its design strategy can be applied to stress imaging in a variety of fields.

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Fabrication process development and basic evaluation of eggshell-based column packing material for reversed-phase preparative separation

Yoshii T., Sakama A., Kanamori K., Nakanishi K., Imai H., Citterio D., Hiruta Y.

Journal of Chromatography A (Journal of Chromatography A)  1688 2023.01

ISSN  00219673

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Purification of basic drugs in reversed-phase mode is often difficult, mainly due to adsorption of positively charged compounds to the silica gel-based stationary phase. Since this adsorption can be suppressed under alkaline condition, columns with alkali-resistance are required. In addition, compounds with acid-sensitive structures are sometimes degraded during separation on silica gel-based columns which exhibit acidity due to their surface structure. We prepared an alkali-resistant reversed-phase packing material, Eggshell-PMAcO based on eggshells modified with an amphiphilic copolymer, poly(maleic acid-alt-1-octadecene) (PMAcO). The height equivalent to a theoretical plate (HETP) of the Eggshell-PMAcO column was improved by surface treatment with ammonium acetate buffer (900 mM, pH = 3.7), which is an inexpensive reagent, and the retention behavior for hydrophobic compounds was compared to a typical ODS column based on silica gel, resulting in sufficient selectivity of the eggshell-based column for hydrophobic compounds, as indicated by the ratio of retention factors of pentylbenzene and butylbenzene (Eggshell-PMAcO column: 1.55, ODS column: 1.65). Column temperature-dependent retention behavior of naphthalene was investigated in the temperature range from 25 °C to 45 °C, followed by the calculation of thermodynamic parameters. There was little difference in the standard molar enthalpy (Eggshell-PMAcO: −19.6 kJ/mol, ODS: −21.7 kJ/mol). The absolute value of the standard free Gibbs energy for the Eggshell-PMAcO column was much smaller than that of the ODS column (Eggshell-PMAcO: −0.284 kJ/mol, ODS: −13.0 kJ/mol), indicating that the Eggshell-PMAcO column had a weaker retention strength for naphthalene than the ODS column mainly due to the large difference in the standard molar entropy (Eggshell-PMAcO: −64.9 J/mol K, ODS column: −29.2 J/mol K). The retention capacities for imipramine under neutral (water/methanol) and alkaline (0.1% triethylamine water/methanol) conditions were 0.2 mg and 5 mg, respectively, based on injection mass-dependent HETP, retention factor and symmetry factor. Finally, the prepared column was applied to the purification of a building block for nucleic acid drugs. This study demonstrated that reversed-phase columns, which can be fabricated from eggshells and an amphiphilic copolymer in an inexpensive and eco-friendly way, have the ability to purify basic compounds and acid-sensitive compounds.

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A highly sensitive friction-imaging device based on cascading stimuli responsiveness

Shioda N., Kobayashi R., Katsura S., Imai H., Fujii S., Oaki Y.

Materials Horizons (Materials Horizons)   2023

ISSN  20516347

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Imaging and measurement of friction forces are required in a variety of fields. If the friction forces originating from the motions of professionals are quantitatively analyzed, the data can be applied to a motion-copying system by a robot. However, weak friction forces have not been visualized and quantified using conventional sensing materials and devices because of their low sensitivity. Here we present a highly sensitive friction-imaging device based on the cascading responses of stimuli-responsive materials, namely polydiacetylene (PDA) and dry liquid (DL). Weak friction forces disrupt the DL, which is composed of liquid droplets surrounded by solid particles. The outflowing liquid under chemical stress changes the color of PDA. The cascading responses enable colorimetric imaging and measurement of weak friction forces in the range of 0.006-0.080 N. Furthermore, the device visualizes the force distribution of handwriting in calligraphy depending on the individual characteristics of an expert, a practician, and a beginner. A high-sensitivity friction-imaging device can be used to understand various motions.

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Micro- and nanometric characterization of the celestite skeleton of acantharian species (Radiolaria, Rhizaria)

Fujimaki R., Suzuki N., Kimoto K., Nagai Y., Oaki Y., Shimode S., Toyofuku T., Imai H.

Scientific Reports (Scientific Reports)  12 ( 1 )  2022.12

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We clarified the specific micrometric arrangement and nanometric structure of the radiolarian crystalline spines that are not a simple single crystal. A body of the celestite (SrSO4) skeleton of acantharian Acanthometra cf. multispina (Acanthometridae) composed of 20 radial spines having four blades was characterized using microfocus X-ray computed tomography. The regular arrangement of three types of spines was clarified with the connection of the blades around the root of each spine. The surface of the spines was covered with a chitin-based organic membrane to prevent from dissolution in seawater. In the nanometric scale, the mesocrystalline structure that consists of nanoscale grains having distorted single-crystal nature was revealed using scanning- and transmission electron microscopies, electron diffraction, and Raman spectroscopy. The acantharian skeletons have a crystallographically controlled architecture that is covered with a protective organic membrane. These facts are important for penetrating the nature of biogenic minerals.

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Ultrastructure of setae of a planktonic diatom, Chaetoceros coarctatus

Owari Y., Nakamura F., Oaki Y., Tsuda H., Shimode S., Imai H.

Scientific Reports (Scientific Reports)  12 ( 1 )  2022.12

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Silica frustules of most planktonic diatoms have many shallow holes in which the length (L) is smaller than the width (W). The present study focuses on a silica ultrastructure of setae of a planktonic diatom having deep (L/W > 1) holes. Here, we characterized microscopically patterned nanoholes on the silica walls of thick, robust, and hollow setae of a colony of Chaetoceros coarctatus. Basically, tetragonal poroid arrangements with and without a costa pattern are observed on the inner and outer surfaces, respectively, for three kinds of curving hollow setae attached to the anterior, intercalary, and posterior parts of the colony. The seta structures including specific poroid arrangements and continuity of deep nanoholes depend on the location. The deep nanoholes ∼90 nm wide are elongated from 150 to 1500 nm (L/W ∼17) with an increase in the wall thickness of the polygonal tubes of the setae. The inside poroid array, with a period of 190 nm in the extension direction of setae, is lined by parallel plates of the costae. However, the poroid arrangement on the outer surface is disordered, with several holes obstructed with increasing wall thickness of the posterior terminal setae. According to the movement of a colony in a fluid microchannel, the thick curving terminal setae is suggested to involve attitude control and mechanical protection. Using an optical simulation, the patterned deep through-holes on the intercalary setae were suggested to contribute anti-reflection of blue light in the wavelength range of 400 to 500 nm for the promotion of photosynthesis in seawater.

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Preparation of conductive Cu<inf>1.5</inf>Mn<inf>1.5</inf>O<inf>4</inf> and Mn<inf>3</inf>O<inf>4</inf> spinel mixture powders as positive active materials in rechargeable Mg batteries operative at room temperature

Takemitsu H., Hayashi Y., Watanabe H., Mandai T., Yagi S., Oaki Y., Imai H.

Journal of Sol-Gel Science and Technology (Journal of Sol-Gel Science and Technology)  104 ( 3 ) 635 - 646 2022.12

ISSN  09280707

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We prepared conductive mixtures of Cu1.5Mn1.5O4 and Mn3O4 spinels (CMO–MOs) as positive electrode active materials in rechargeable Mg batteries (RMBs) using a sol–gel complex polymerization method. The CMO–MO spinel mixtures with high specific surface areas above 100 m2 g−1 were obtained with mild calcination in Ar at 300 °C. The conductivity of CMO–MOs was estimated to be approximately 1000 times higher than that of a conventional MgMn2O4 (MMO) spinel powder. The discharge capacities evaluated using 2032-type coin-cell battery with a Mg-alloy negative electrode at room temperature increase with an increase in the specific surface area of the spinel powders. The specific surface area for providing the theoretical capacity of the conductive CMO–MOs was about one-third that of the insulative MMO. High specific surface area and high conductivity are key parameters for the positive active material to realize practical room-temperature operation of RMBs.

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Amphiphilic Copolymer-Modified Eggshell-Based Column Packing Materials for the Preparative Separation of Basic Drugs

Yoshii T., Mochida M., Kaizu K., Soda Y., Kanamori K., Nakanishi K., Sato T., Imai H., Citterio D., Hiruta Y.

ACS Applied Polymer Materials (ACS Applied Polymer Materials)  4 ( 10 ) 6949 - 6957 2022.10

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A way to utilize eggshells is desired because most of the eggshell waste is disposed of in landfills. Despite eggshells having attractive features such as a thermodynamically stable porous crystalline structure, their effective utilization as a functional material has yet to be demonstrated. Herein, we developed an alkali-stable column packing material for reversed-phase preparative high-performance liquid chromatography (HPLC) based on eggshells. Nanocrystals and biopolymers present on eggshell powder were removed by surface treatment with buffered ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite solutions, resulting in bare calcium carbonate with a uniform porous surface. The obtained particles were modified with poly(maleic acid-alt-1-octadecene) (PMAcO) having hydrophobic alkyl chains and anionic carboxylate groups. The prepared PMAcO-modified eggshell-based material was applied to an HPLC column, and its performance is evaluated. The column succeeded in the separation of alkylbenzenes, steroids, and diastereomers. It was also used for the separation of basic tricyclic antidepressants in an alkaline mobile phase, showing excellent retention capacity and alkali stability. This study demonstrates the potential of eggshell utilization, providing not only a practical stationary phase for HPLC but also a solution for recycling calcium carbonate-based biomineral waste.

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Coatable 2D Conjugated Polymers Containing Bulky Macromolecular Guests for Thermal Imaging

Edagawa A., Matsuda S., Kawakubo H., Imai H., Oaki Y.

ACS Applied Materials and Interfaces (ACS Applied Materials and Interfaces)  14 ( 38 ) 43792 - 43801 2022.09

ISSN  19448244

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Dynamic properties are derived from the structural flexibility of 2D polymers. Softening layered structures has the potential for tuning and enhancing the dynamic properties. In the present work, the flexibility of layered polydiacetylene (PDA) is tuned by the interlayer polymeric guests with different branching structures. PDA shows thermoresponsive color-change properties through shortening the effective conjugation length with molecular motion. Whereas the blue-to-red color transition is observed at certain threshold temperatures for the layered PDA without the interlayer guest, the intercalation of the bulky polymer guests lowers the starting temperature and widens the temperature range for the thermoresponsive color changes. The resultant layered composite of PDA and bulky polymer affords the homogeneous coating on substrates on the centimeter scale. The thermoresponsive color-change coating is applied to temperature-distribution imaging. The specific heat of liquids is colorimetrically estimated using the coating on the bottle. The coating on a silk cloth visualizes the temperature distribution on a simulated tissue during surgical operation using an ultrasonic coagulation cutting device. The coating can be applied to thermal imaging in a variety of fields. Moreover, the softening strategy contributes to explore dynamic properties of soft 2D materials.

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Selective syntheses of thick and thin nanosheets based on correlation between thickness and lateral-size distribution

Haraguchi Y., Imai H., Oaki Y.

iScience (iScience)  25 ( 9 )  2022.09

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Exfoliation of layered materials, a typical route to obtain 2D materials, is not easily controlled because of the unpredictable downsizing processes. In particular, the thickness control remains as a complex challenge. Here, we found a correlation between the thickness and lateral size distribution of the exfoliated nanosheets, such as transition metal oxides and graphene oxide. The layered composites of the host metal oxides and interlayer organic guests are delaminated into the surface-modified nanosheets in organic dispersion media. The exfoliation behavior varies by combination of the hosts, guests, and dispersion media. Here, we found that the thick and thin nanosheets were obtained on the monodispersed and polydispersed conditions, respectively. The selective syntheses of the thick and thin nanosheets were achieved using a prediction model of the lateral size distribution. The correlation between the thickness and lateral size distribution can be applied to thickness-selective syntheses of 2D materials.

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Nanosheet-Based Uneven Thin Film Exhibiting Angle-Independent Structural Color and Its Application to Detection of Biogenic Amines

Haraguchi Y., Imai H., Oaki Y.

Advanced Materials Interfaces (Advanced Materials Interfaces)  9 ( 25 )  2022.09

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Anisotropic ultrathin 2D materials are used as building blocks to obtain higher-order structures. Tailoring the size, surface chemistry, and assembly state of exfoliated nanosheets is required for the design of functional materials. However, these factors are not easily controlled during the down-sizing exfoliation process, which is a general route for obtaining 2D materials. In the present work, polydispersed nanosheets of a transition metal oxide are prepared based on prediction model for the size distribution constructed by a combination of machine learning and chemical perspective on small data. Self-assembly of the exfoliated nanosheets results in the uneven thin films exhibiting an angle-independent structural color. As the nanosheets vary in thickness and lateral size, their assembled thin films exhibit structural color independent of the incident angle. The structural color is changed by casting only 20 µL of an aqueous solution containing biogenic amines such as histamine within a sensing time of 5 min. The biogenic amines are intercalated into the interlayer space of the stacked nanosheets and the resulting increase in the thickness changes the color of the thin-film device. The new design strategies can be applied to constructing other thin-film sensing devices based on nanosheets.

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Quantitative evaluation of reversed-phase packing material based on calcium carbonate microspheres modified with an alternating copolymer

Kaizu K., Mochida M., Imai H., Citterio D., Hiruta Y.

Journal of Chromatography A (Journal of Chromatography A)  1677 2022.08

ISSN  00219673

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Considering the vulnerability of silica gel to alkaline mobile phases, a highly alkaline stable stationary phase for HPLC is required to separate basic compounds with high separation efficiency. To address this issue, we have developed a high alkaline stable packing material (CaCO3-PMAcO) based on mesoporous calcium carbonate microspheres modified with poly(maleic acid-alt-1-octadecene). In this study, we report further investigation of the separation performance of CaCO3-PMAcO column by systematically evaluating the effects of particle size and chromatographic conditions. Based on the theory of the van Deemter equation, the separation efficiency was related to the size of CaCO3-PMAcO particles (2.9 – 5.7 µm). The evaluation of thermodynamics of retention by changing the column temperature from 20 °C to 45 °C implied that the retention mode was dominated by hydrophobic interaction associated with the exothermic enthalpy changes (-11.1 to -12.5 kJ/mol). The results of column selectivity tests revealed that the CaCO3-PMAcO column had hydrophobic selectivity comparable to C18 silica gel columns (αP/B; CaCO3-PMAcO column: 1.53, C18 column: 1.69), and higher shape/steric selectivity (αTri/Ter; CaCO3-PMAcO column: 1.56, C18 column: 0.955). In practice, the CaCO3-PMAcO column could be applied to the separation of not only alkylbenzenes and polycyclic aromatic hydrocarbons, but also to basic tricyclic antidepressants by using an alkaline mobile phase (pH 12).

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A Capacity-Prediction Model for Exploration of Organic Anodes: Discovery of 5-Formylsalicylic Acid as a High-Performance Anode Active Material

Komura T., Sakano K., Igarashi Y., Numazawa H., Imai H., Oaki Y.

ACS Applied Energy Materials (ACS Applied Energy Materials)  5 ( 7 ) 8990 - 8998 2022.07

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Development of high-performance organic energy storage is one of the important challenges in recent materials science. Molecular design and synthesis have potential for enhancement of the performances. Efficient exploration and design of the molecules are required in a wide search space. In the present work, a capacity prediction model for organic anodes was constructed on small experimental data by sparse modeling, a method of machine learning, combined with our chemical insights. The straightforward linear regression model facilitated discovery of a high-performance active material for organic anodes in a limited number of experiments. A recommended compound, 5-formylsalicylic acid (SA-CHO), showed one of the highest performances in recent works, i.e., a specific capacity of 873 mA h g-1at 100 mA g-1(sample number: n = 3) with rate performance and cycle stability. The model can be applied to explore organic anode active materials with higher specific capacity.

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Demonstrated gradual evolution of disorder in crystalline structures between single crystal and polycrystal via chemical and physicochemical approaches

Kanazawa S., Oaki Y., Imai H.

CrystEngComm (CrystEngComm)  24 ( 25 ) 4546 - 4550 2022.06

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Various biological and biomimetic minerals are composed of mesocrystals, in which nanoscale crystalline units are ordered in approximately the same crystallographic direction. However, the variation of the crystallographic regularity of mesocrystals has not been clarified using experimental evidence. This work demonstrated the gradual evolution of disorder in crystalline structures between single crystal and polycrystal by monitoring the crystallographic regularity using electron diffraction patterns. Single-crystal rods of fluorapatite elongated in the c direction are switched to mesocrystals consisting of iso-oriented nanorods by adding a specific molecule having a carboxy group (chemical approach) and to roughly arranged nanograins by increasing the degree of supersaturation at the growth front (physicochemical approach). Lateral and vertical miniaturization of the growth units is achieved through stepwise nucleation and near-epitaxial growth. The crystallographic regularity gradually decreases with deviation of the c axis and rotation of the a axes through reduction of the growth unit size. Here we can tune the disorder in crystalline structures via the chemical and physicochemical approaches.

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A nonclassical pathway to biomimetic strained SrSO<inf>4</inf> crystals

Fujimaki R., Oaki Y., Imai H.

CrystEngComm (CrystEngComm)  24 ( 24 ) 4356 - 4360 2022.05

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Biomimetic strained SrSO4 crystals were produced through a nonclassical pathway involving fiber-by-fiber accumulation with poly(acrylic acid) in an aqueous solution system. Polymer-stabilized fibrous hydrate crystals 20-40 nm wide and several micrometers long were formed in the initial stage. Spindle-shaped microrods of SrSO4 were then constructed by oriented attachment of the hydrous fibrils and subsequent dehydration. The strained structure of the anhydrous SrSO4 crystals is similar to biogenic SrSO4 spines of acantharian species, a marine unicellular holoplanktonic protist.

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Performance Predictors for Organic Cathodes of Lithium-Ion Battery

Sakano K., Igarashi Y., Imai H., Miyakawa S., Saito T., Takayanagi Y., Nishiyama K., Oaki Y.

ACS Applied Energy Materials (ACS Applied Energy Materials)  5 ( 2 ) 2074 - 2082 2022.02

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Organic cathodes for lithium-ion batteries are one of the most promising and significant materials toward a sustainable society. The molecular design is a key to achieve superior performances beyond inorganic cathodes. The present work shows predictors of the reaction potential, specific capacity, and ideal energy density for organic cathodes. Straightforward prediction models of the performance were constructed by a combination of machine learning and chemical insight, namely, sparse modeling for small data (SpM-S), on a small data set as training data found in the literature. The prediction accuracy was validated using different literature data. The predictors can be applied to explore high-performance organic cathodes in a wide search space efficiently. Moreover, SpM-S afforded straightforward, interpretable, and generalizable prediction models compared to other machine-learning algorithms. The small-data-driven methodology can be applied for further exploration of materials, enhancement of performances, and optimization of processes.

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Designed nanostructures created via physicochemical switching of the growth mode between single crystals and mesocrystals†

Kanazawa S., Oaki Y., Imai H.

Nanoscale Advances (Nanoscale Advances)  4 ( 6 ) 1538 - 1544 2022.02

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Most biominerals are composed of mesocrystals, in which individual nanoparticle building units have a defined long-range order on the atomic scale in at least one direction. Although the crystal size and orientation of the mesostructures are spatially designed in biological architectures, it has been difficult to achieve adequate control of the crystal growth to produce modulated mesostructures in artificial aqueous systems. Here, we propose a simple physicochemical approach for the spatial design of nanostructures using an aqueous solution system. The ordered arrays of oriented fluorapatite (FA) rods similar to tooth enamel are produced on a polymer substrate in a supersaturated solution. We succeeded in reversible switching of the growth mode of FA between single-crystalline rods and mesocrystalline grains through the disturbance of the solution. The primary crystal size was tuned between micrometric rods ∼0.5 μm wide and >5 μm long and nanoscale grains ∼10 nm wide and 50 nm long without a drastic change in the c direction. Hierarchical architectures consisting of iso-oriented FA microrods and nanograins were constructed via temporal control of the crystal growth mode by switching a physicochemical parameter, such as the degree of supersaturation at the growth front.

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Electroless nickel plating on a biomineral-based sponge structure

Takeoka H., Seike M., Nakamura Y., Imai H., Oaki Y., Fujii S.

Materials Advances (Materials Advances)  3 ( 2 ) 931 - 936 2022.01

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A 3-dimensional polypyrrole-palladium nanocomposite material was prepared by transferring a sponge structure of a sea urchin spine via chemical oxidative polymerization. The nanocomposite material was successfully coated with nickel, maintaining the 3-dimensional sponge structure by electroless plating in an aqueous medium.

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Characterization of calcite spines of planktonic foraminifers (Globigerinidae)

Izumida K., Takasaki M., Fujimaki R., Nagai Y., Oaki Y., Naito K., Tanaka Y., Shimode S., Toyofuku T., Imai H.

CrystEngComm (CrystEngComm)  24 ( 13 ) 2446 - 2450 2022

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Calcitic spines ∼1 μm in diameter are projecting from a trochospiral test of a spinose planktonic foraminifer. According to electron diffraction, Raman spectra, and detailed electron microscope observation, the spines were found to be a single-crystal-like calcite that has a nanogranular texture containing microstrain. An organic envelope protects the biogenic calcite against dissolution in water. Their unique mechanical and chemical properties are ascribed to the specific micro- and nanoscopic structures. This journal is

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Ultraporous, Ultrasmall MgMn<inf>2</inf>O<inf>4</inf> Spinel Cathode for a Room-Temperature Magnesium Rechargeable Battery

Kobayashi H., Fukumi Y., Watanabe H., Iimura R., Nishimura N., Mandai T., Tominaga Y., Nakayama M., Ichitsubo T., Honma I., Imai H.

ACS Nano (ACS Nano)   2022

ISSN  19360851

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Magnesium rechargeable batteries (MRBs) promise to be the next post lithium-ion batteries that can help meet the increasing demand for high-energy, cost-effective, high-safety energy storage devices. Early prototype MRBs that use molybdenum-sulfide cathodes have low terminal voltages, requiring the development of oxide-based cathodes capable of overcoming the sulfide’s low Mg2+ conductivity. Here, we fabricate an ultraporous (>500 m2 g-1) and ultrasmall (<2.5 nm) cubic spinel MgMn2O4 (MMO) by a freeze-dry assisted room-temperature alcohol reduction process. While the as-fabricated MMO exhibits a discharge capacity of 160 mAh g-1, the removal of its surface hydroxy groups by heat-treatment activates it without structural change, improving its discharge capacity to 270 mAh g-1─the theoretical capacity at room temperature. These results are made possible by the ultraporous, ultrasmall particles that stabilize the metastable cubic spinel phase, promoting both the Mg2+ insertion/deintercalation in the MMO and the reversible transformation between the cubic spinel and cubic rock-salt phases.

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Emergence of practical fluorescence in a confined space of nanoporous silica: Significantly enhanced quantum yields of a conjugated molecule

Hayashi K., Fujimaki Y., Mishiba K., Watanabe H., Imai H.

Chemical Communications (Chemical Communications)  57 ( 97 ) 13150 - 13153 2021.12

ISSN  13597345

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The fluorescence of benzanthrone, which is a conjugated molecule bearing a carbonyl group, is activated by confinement in a pore with a diameter close to the molecular size. An intense emission originating from the aromatic character π-π∗ transition is achieved through suppression of the nonradiative n-π∗ transition by strong hydrogen bonding between carbonyl groups and silanol groups with a micropore-filling effect in the nanospace.

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Preparation of titania with double band structure derived from a quantum size effect: Drastic increase in the photocatalytic activity

Somekawa S., Watanabe H., Ono Y., Oaki Y., Imai H.

Materials Letters (Materials Letters)  304 2021.12

ISSN  0167577X

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Titania is a competent photocatalyst widely used in environmental purification. Unfortunately, its photocatalytic ability to generate hydrogen by water decomposition without a co-catalyst is poor. Here, an efficient enhancement of noble-metal-free photocatalytic activity was studied on the basis of titania prepared in a supermicroporous silica template using TiCl3 aqueous solution as a precursor. The amount of evolved hydrogen increased sharply by 37 times as the concentration of TiCl3 was increased from 5 to 10 wt%. The existence of two species of titania was determined by XAFS analysis at concentrations of 10 wt% or greater. It is suggested that titania quantum dots inside the supermicropores and titania particles outside the supermicropores were prepared at the optimum precursor concentration and the resultant composite band structures suppressed electron–hole recombination.

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Cellulose intrafibrillar mineralization of biological silica in a rice plant

Nakamura E., Ozaki N., Oaki Y., Imai H.

Scientific Reports (Scientific Reports)  11 ( 1 )  2021.12

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The essence of morphological design has been a fascinating scientific problem with regard to understanding biological mineralization. Particularly shaped amorphous silicas (plant opals) play an important role in the vital activity in rice plants. Although various organic matters are associated with silica accumulation, their detailed functions in the shape-controlled mineralization process have not been sufficiently clarified. In the present study, cellulose nanofibers (CNFs) were found to be essential as a scaffold for silica accumulation in rice husks and leaf blades. Prior to silicification, CNFs ~ 10 nm wide are sparsely stacked in a space between the epidermal cell wall and the cuticle layer. Silica nanoparticles 20–50 nm in diameter are then deposited in the framework of the CNFs. The shape-controlled plant opals are formed through the intrafibrillar mineralization of silica nanoparticles on the CNF scaffold.

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A Layered Polydiacetylene Containing Hydrogen-Bonding 4,4′-Bipyridyl Guests: Reversible Color Changes with a Wide-Range Temperature Response

Mochizuki Y., Imai H., Oaki Y.

ChemPlusChem (ChemPlusChem)  86 ( 12 ) 1563 - 1568 2021.12

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Layered organic polymers have intercalation capabilities and dynamic properties. In classical intercalation chemistry, the interlayer guests are intercalated in the host layers via electrostatic interaction. The present work shows the organic layered materials with the host-guest interlayer interaction via hydrogen bond. Polydiacetylene (PDA) exhibits color changes from blue to red with the application of external stimuli, such as thermal and mechanical stresses. Here we report on a layered PDA containing 4,4′-bipyridyl in the interlayer space as a hydrogen-bonding guest. Whereas the layered PDA without interlayer guest shows the color transition at 65 °C, gradual color changes with two-stage reversibility are observed in the temperature range of −20–240 °C by the introduction of the hydrogen-bonding guest. The weaker interlayer interaction via the hydrogen bond promotes the dynamic motion directing the thermoresponsive color changes in a wide temperature range.

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Efficient photocatalytic conversion of benzene to phenol on stabilized subnanometer WO<inf>3</inf>quantum dots

Ohno A., Watanabe H., Matsui T., Somekawa S., Tomisaki M., Einaga Y., Oaki Y., Imai H.

Catalysis Science and Technology (Catalysis Science and Technology)  11 ( 19 ) 6537 - 6542 2021.10

ISSN  20444753

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Band engineering with a quantum size effect is proposed to be utilized to design photocatalytic activity for the conversion of organic compounds. Subnanometer WO3 quantum dots (QDs) are spontaneously produced with the enhancement of the photocatalytic activity in a mesoporous silica matrix by preliminary photochemical dissolution. An appropriate upshift of the conduction band of subnanometer WO3 QDs stabilized by the coverage with the surface WO bonds promotes the efficient conversion of benzene to phenol without decomposition of the product into CO2 under ultraviolet illumination.

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Size-Distribution Control of Exfoliated Nanosheets Assisted by Machine Learning: Small-Data-Driven Materials Science Using Sparse Modeling

Haraguchi Y., Igarashi Y., Imai H., Oaki Y.

Advanced Theory and Simulations (Advanced Theory and Simulations)  4 ( 10 )  2021.10

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2D materials exhibit emergent properties originating from their characteristic nanostructures. In general, monolayered and few-layered nanosheets are obtained by exfoliation of the precursor layered materials. However, lateral-size distribution of the nanosheets is not easily controlled through the exfoliation because of the unpredictable down-sizing processes. The present work shows selective syntheses of transition-metal-oxide nanosheets with the monodisperse and polydisperse lateral sizes by the assistance of machine learning on small experimental data. The precursor layered composites of host transition-metal oxides and interlayer organic guests are exfoliated into the surface-modified nanosheets in organic dispersion media. A prediction model of the size distribution is constructed by sparse modeling, a method of machine learning, on the experimental data. The host-guest-medium combinations achieving the monodisperse and polydisperse lateral sizes are recommended by the prediction model. Therefore, the nanosheets with the controlled lateral-size distribution are selectively obtained in a limited number of the experiments. Moreover, self-assembly of the polydispersed nanosheets forms the homogeneous thin film exhibiting interference color. The prediction model and its construction method can be applied to the other 2D materials. Moreover, the present work implies that sparse modeling is an effective approach for small-data-driven materials science.

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Yield-prediction models for efficient exfoliation of soft layered materials into nanosheets

Noda K., Igarashi Y., Imai H., Oaki Y.

Chemical Communications (Chemical Communications)  57 ( 48 ) 5921 - 5924 2021.06

ISSN  13597345

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Yield-prediction models were studied for efficient exfoliation of soft layered materials stackedviavan der Waals interactions with the assistance of machine learning on small experimental data. High-yield exfoliation of graphite and layered organic polymer was achieved under the conditions guided by the models in a limited number of experiments.

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Wide-area multilayered self-assembly of fluorapatite nanorods vertically oriented on a substrate as a non-classical crystal growth

Hagiwara Y., Oaki Y., Imai H.

Nanoscale (Nanoscale)  13 ( 21 ) 9698 - 9705 2021.06

ISSN  20403364

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Oriented attachment of homogeneously shaped nanoblocks, such as nanocubes and nanorods, is attracting attention as a fundamental process of non-classical crystal growth to produce specific ordered architectures of functional materials. Although lateral alignments of horizontally oriented nanorod are commonly observed at the air-liquid and liquid-solid interfaces in dispersion systems, the accumulation of vertically oriented nanorods on a substrate has rarely been produced in a wide area over a millimeter-sized flat surface. Here, we achieved homogeneous stacking of vertical fluorapatite nanorods with a large aspect ratio (~6) in a toluene-hexane mixture system through a gradual decrease in the dispersibility. Micrometer-thick flat films in which the c direction of fluorapatite nanorods was arranged perpendicularly to the surface were deposited on a substrate with a diameter of over 20 mm. The wide-area accumulation of vertical nanorods occurs through the self-assembly of laterally arranged clusters of nanorods covered with a stabilizing agent and subsequent gentle sedimentation on the substrate surface. This journal is

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Self-Assembly of 2D Nematic and Random Arrays of Sterically Stabilized Nanoscale Rods with and without Evaporation

Tago M., Takasaki M., Tokura Y., Oaki Y., Imai H.

Langmuir (Langmuir)  37 ( 21 ) 6533 - 6539 2021.06

ISSN  07437463

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The adequate manipulation of nanometer-scale building blocks using dispersion systems is regarded as a fundamental technique to fabricate elaborate microstructures. Although a liquid flow with evaporation is generally regarded as an essential factor for the self-assembly of floating blocks, experimental evidence has not been sufficient to clarify the importance of the flow in the dispersion systems. In the present study, 2D nematic layers of sterically stabilized nanoscale calcite rods were achieved in a millimeter-scale region on a solid substrate via the very slow recession of an organic dispersion with evaporation. 2D random arrays of the nanorods were obtained via recession of the liquid in the same system without evaporation. When the nanorods were not sterically stabilized, 3D random arrays were formed even with evaporation. We demonstrated that the evaporation-driven flow of sterically stabilized nanorods to a confined space at the air-liquid-solid interface is essential for the formation of 2D nematic structures on a substrate.

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Morphological study of fibrous aragonite in the skeletal framework of a stony coral

Sugiura M., Yasumoto K., Iijima M., Oaki Y., Imai H.

CrystEngComm (CrystEngComm)  23 ( 20 ) 3693 - 3700 2021.05

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Calcareous skeletons of stony corals are composed of a low-crystalline core (center of calcification: COC) and surrounding fibrous crystals. We characterized the overall framework of juvenile Acropora digitifera corals to clarify the entire calcic architecture and the contribution of abiotic processes. Skeletal and tubular frameworks contain string and sheet COCs, respectively, consisting of strained aragonite nanograins. Parallel and curved structures of fibrous aragonite develop around the COC cores through geometric selection and a gradual change in the growth direction of the c-direction-elongated nanorods. Based on a study of the nanoscale morphology of the coral frameworks by comparing them to fibrous crystals grown in artificial systems, it appears that subsequent precipitation of the fibrous aragonite on the COC is primarily regulated by environmental abiotic parameters. The architecture of the COC network is deduced to be designed biologically and then thickened by the fibrous crystals that are produced with morphology formation through physicochemical processes although the vital activity controls the total mineralization.

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Phenylphosphonate surface functionalisation of MgMn<inf>2</inf>O<inf>4</inf>with 3D open-channel nanostructures for composite slurry-coated cathodes of rechargeable magnesium batteries operated at room temperature

Kajihara K., Takahashi D., Kobayashi H., Mandai T., Imai H., Kanamura K.

RSC Advances (RSC Advances)  11 ( 31 ) 19076 - 19082 2021.05

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Spinel-type MgMn2O4, prepared by a propylene-oxide-driven sol-gel method, has a high surface area and structured bimodal macro- and mesopores, and exhibits good electrochemical properties as a cathode active material for rechargeable magnesium batteries. However, because of its hydrophilicity and significant water adsorption properties, macroscopic aggregates are formed in composite slurry-coated cathodes when 1-methyl-2-pyrrolidone (NMP) is used as a non-aqueous solvent. Functionalising the surface with phenylphosphonate groups was found to be an easy and effective technique to render the structured MgMn2O4hydrophobic and suppress aggregate formation in NMP-based slurries. This surface functionalisation also reduced side reactions during charging, while maintaining the discharge capacity, and significantly improved the coulombic efficiency. Uniform slurry-coated cathodes with active material fractions as high as 93 wt% can be produced on Al foils by this technique employing carbon nanotubes as an electrically conductive support. A coin-type full cell consisting of this slurry-coated cathode and a magnesium alloy anode delivered an initial discharge capacity of ∼100 mA h g−1at 25 °C.

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Morphological evolution of carbonated hydroxyapatite to faceted nanorods through intermediate states

Hagiwara Y., Takasaki M., Oaki Y., Imai H.

CrystEngComm (CrystEngComm)  23 ( 16 ) 2968 - 2972 2021.04

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Pure and carbonated hydroxyapatite (HA) nanocrystals are regarded as capital biocompatible materials. However, the formation process for faceted nanorods of HA has not been sufficiently clarified in supersaturated aqueous solution systems. Here, we monitored morphological evolution of carbonated HA to faceted crystals on the conversion of a parent calcite nanocrystal under hydrothermal conditions. In the initial stage, low-crystalline carbonated HA nanosheets ∼5 nm thick are formed as metastable intermediates. In the progressive stage, faceted nanorods ∼50 nm wide and ∼200 nm long grow as a relatively stable form of HA through the intermediates. The morphological evolution is ascribed to a stabilizing process of HA for improvement of the crystallinity and a decrease in the specific surface area and carbonate content.

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Ultrahigh-Sensitive Compression-Stress Sensor Using Integrated Stimuli-Responsive Materials

Nakamitsu M., Oyama K., Imai H., Fujii S., Oaki Y.

Advanced Materials (Advanced Materials)  33 ( 14 )  2021.04

ISSN  09359648

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Measurement of mechanical stresses, such as compression, shear, and tensile stresses, contributes toward achieving a safer and healthier life. In particular, the detection of weak compression stresses is required for healthcare monitoring and biomedical applications. Compression stresses in the order of 106–1010 Pa have been visualized and/or quantified using mechano-responsive materials in previous works. However, in general, it is not easy to detect compression stresses weaker than 103 Pa using conventional mechano-responsive materials because the dynamic motion of the rigid mechano-responsive molecules is not induced by such a weak stress. In the present work, weak compression stresses in the order of 100–103 Pa are visualized and measured via the integration of stimuli-responsive materials, such as layered polydiacetylene (PDA) and dry liquid (DL), through response cascades. DLs consisting of liquid droplets covered by solid particles release the interior liquid and collapse with application of a weak compression stress. The color of the layered PDA is changed by the spilled liquid as a chemical stress. A variety of weak compression stresses, such as expiratory pressure, are visualized and colorimetrically measured using the paper-based device of the integrated stimuli-responsive materials. Diverse mechano-sensing devices can be designed via the integration of stimuli-responsive materials.

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Effective 3D open-channel nanostructures of a MgMn<inf>2</inf>O<inf>4</inf>positive electrode for rechargeable Mg batteries operated at room temperature

Sone K., Hayashi Y., Mandai T., Yagi S., Oaki Y., Imai H.

Journal of Materials Chemistry A (Journal of Materials Chemistry A)  9 ( 11 ) 6851 - 6860 2021.03

ISSN  20507488

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Room-temperature operations of rechargeable Mg coin-cell batteries have been achieved using a Mg alloy negative electrode and a spinel MgMn2O4(MMO)-positive electrode. The present work focuses on clarifying the effects of the physiochemical properties of the MMO powder including the specific surface area (SBET) and porosity of the positive electrode on Mg battery performances in practical applications. Finally, optimal specific surface area and porosity parameters were obtained that ensured excellent battery performances as a standard coin-cell at room temperature. A typical MMO powder synthesized using a modified sol-gel method with propylene oxide-driven complex polymerization had a largeSBET> 200 m2g−1, and more than 90% porosity with a triple-tiered 3D open-channel network. Here we evaluated the discharge capacity and the cyclability for room-temperature operation as a function ofSBETin a full cell with a Mg negative electrode as well as half cells with a carbon graphite electrode. Irrespective of whether half cells or a full cell was used, the initial discharge capacity was found to depend linearly on theSBETof the porous MMO powder in a Mg tetrakis(hexafluoroisopropyl)borate/triglyme electrolyte with a wide potential window, ΔE> 3.6 V. Eventually, the maximum discharge capacity of 220 mA h g−1was realized at 25 °C in the full cell using the 3D open-channel nanostructure withSBET= 236 m2g−1. The cyclability in the full cell with the Mg alloy negative electrode, however, degraded with the increasingSBET, while no cyclability degradation was observed in the half cell with the carbon electrode. A possible mechanism is discussed regarding passivation of the Mg alloy electrode in discharge/charge cycles.

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Lateral-size control of exfoliated transition-metal-oxide 2D materials by machine learning on small data

Mizuguchi R., Igarashi Y., Imai H., Oaki Y.

Nanoscale (Nanoscale)  13 ( 6 ) 3853 - 3859 2021.02

ISSN  20403364

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A wide variety of nanosheets including monolayers and few-layers have attracted much interest as two-dimensional (2D) materials for the unique anisotropic structures and properties. On the other hand, one of the significant remaining and challenging issues is the lateral-size control. Since 2D materials are generally synthesized by the exfoliation of layered materials, the lateral size is not easily controlled in the breaking-down processes. The experimental factors have not been found for the control and prediction. In the present work, lateral sizes of the exfoliated transition-metal-oxide nanosheets were predicted and controlled by the assistance of machine learning. Layered composites of host inorganic layers and guest organic molecules were exfoliated into nanosheets in organic dispersion media. The lateral size of the nanosheets was estimated by dynamic light scattering (DLS), instead of microscopy methods, to achieve high-throughput analyses. Factors governing the lateral size are explored on the small experimental data by the assistance of sparse modeling, a method of machine learning. The eight physicochemical parameters of the organic guests and dispersion media were extracted by sparse modeling for the construction of the size-prediction model. The size-prediction model accelerated the selective syntheses of the nanosheets with large and small lateral sizes in a limited number of experiments. The results indicate that the prediction model is a guideline to find suitable exfoliation conditions for size control. Size-selective syntheses of a variety of 2D materials can be achieved by similar methods using sparse modeling on small experimental data. Moreover, sparse modeling is applicable to control the design and exploration of other materials and their processing based on small data. This journal is

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Phase Transition Behavior of MgMn<inf>2</inf>O<inf>4</inf> Spinel Oxide Cathode during Magnesium Ion Insertion

Tuerxun F., Otani S., Yamamoto K., Matsunaga T., Imai H., Mandai T., Watanabe T., Uchiyama T., Kanamura K., Uchimoto Y.

Chemistry of Materials (Chemistry of Materials)  33 ( 3 ) 1006 - 1012 2021.02

ISSN  08974756

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The 3d transition metal oxides with a spinel structure are among the most promising cathode materials for magnesium batteries. In this study, we investigated the reaction mechanism of magnesium ion insertion for magnesium spinel oxides, MgMn2O4, by electrochemical measurements, X-ray absorption spectroscopy (XAS), and synchrotron X-ray diffraction (XRD) with Rietveld analysis. Open-circuit-potential and XAS measurements showed that Mg2+ insertion into MgMn2O4 does not proceed via a simple two-phase coexistence reaction between the spinel and rock-salt phases. Synchrotron XRD measurements showed that Mg2+ insertion into MgMn2O4 involves crystal structural changes in three stages. In the early stage of the Mg2+ insertion process (0 < x < 0.2), Mg2+ is inserted into the spinel (MgMn2O4) phase and rock-salt (Mg1.2Mn2O4) phases, which are included in the pristine samples, without significant volume changes. In the middle stage of the Mg2+ insertion process (0.2 < x < 0.4), Mg2+ is inserted into the Mg1+αMn2O4 spinel phase and the Mg2-βMn2O4 rock-salt phases with a large volume change. In the last stage of Mg2+ insertion process (0.4 < x < 0.56), Mg2+ insertion proceeds via a two-phase coexistence reaction between Mg1.4Mn2O4 spinel and Mg1.6Mn2O4 rock-salt phases without Mg content changes in either phase. The phase transition from the Mg1+αMn2O4 spinel phase to the Mg2-βMn2O4 rock-salt phase with a large volume change resulted in significant polarization during the Mg2+ insertion process. Suppressing the phase transition, accompanied by a large volume change, is important in designing a spinel oxide cathode with a high rate performance.

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Diatom-mimetic channeled mesoporous silica membranes: Self-organized formation of a hierarchical porous framework

Kitamura R., Watanabe H., Somekawa S., Ono Y., Owari Y., Oaki Y., Imai H.

Materials Chemistry Frontiers (Materials Chemistry Frontiers)  5 ( 2 ) 862 - 868 2021.01

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Silica membranes having macrochannels with mesoporous walls were spontaneously fabricated using a self-organized process with rapid gelation of concentrated silicate and surfactant precursor solutions. The specific hierarchical porous framework consisting of straight macrochannels ca. 1 μm in diameter is similar to that of a biological silica frustule of diatoms. We applied the diatom-mimetic channeled mesoporous silica membranes to high-permeability-rate filtration and enhanced photocatalytic systems. The presence of macrochannels was found to improve the performance of the mesoporous silica membranes in filtration and as a photocatalyst carrier.

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Guanine crystals regulated by chitin-based honeycomb frameworks for tunable structural colors of sapphirinid copepod, Sapphirina nigromaculata

Kimura T., Takasaki M., Hatai R., Nagai Y., Uematsu K., Oaki Y., Osada M., Tsuda H., Ishigure T., Toyofuku T., Shimode S., Imai H.

Scientific Reports (Scientific Reports)  10 ( 1 )  2020.12

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Sapphirinid copepods, which are marine zooplankton, exhibit tunable structural colors originating from a layered structure of guanine crystal plates. In the present study, the coloring portion of adult male of a sapphirinid copepod, Sapphirina nigromaculata, under the dorsal body surface was characterized to clarify the regulation and actuation mechanism of the layered guanine crystals for spectral control. The coloring portions are separated into small domains 70–100 µm wide consisting of an ordered array of stacked hexagonal plates ~1.5 µm wide and ~80 nm thick. We found the presence of chitin-based honeycomb frameworks that are composed of flat compartments regulating the guanine crystal plates. The structural color is deduced to be tuned from blue to achromatic via yellow and purple by changing the interplate distance according to vital observation and optical simulation using a photonic array model. The framework structures are essential for the organization and actuation of the particular photonic arrays for the exhibition of the tunable structural color.

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Strained calcite crystals from amorphous calcium carbonate containing an organic molecule

Sugiyama S., Takasaki M., Oaki Y., Imai H.

CrystEngComm (CrystEngComm)  22 ( 42 ) 7054 - 7058 2020.11

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Amorphous calcium carbonate (ACC) is regarded as an important precursor of biogenic crystal phases having specific shapes and mechanical properties. In the present work, calcite that was produced from ACC nanoparticles containing aspartic acid was characterized by Raman scattering spectroscopy and nanoindentation techniques. The tensile strain of the calcite lattice that was estimated from the vibrational spectroscopy varied with the organic content and the mild calcination condition of ACC nanoparticles. Calcite was found to be hardened by the presence of residual organic components inside the crystal lattice. On the other hand, the modulus of calcite decreased as the content of external organic components increased. Here, the mechanical properties of the calcite framework are successfully tuned by the crystallization of the specific amorphous phases containing organic molecules. The mechanical modulation of calcite can be associated with lattice expansion by using vibrational spectroscopy. This journal is

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Solid-State Low-Temperature Thermoresponsive and Reversible Color Changes of Conjugated Polymer in Layered Structure: Beyond Infrared Thermography

Watanabe K., Imai H., Oaki Y.

Small (Small)  16 ( 41 )  2020.10

ISSN  16136810

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Emergence of thermoresponsive and reversible color changes at low temperature is a challenging target. In general, it is not easy to induce sufficient dynamic motion of rigid molecules including chromophore at a lower temperature. The present work shows unusually low-temperature color-change properties originating from the dynamic motion of rigid conjugated polymer in solid state. The layered composites of polydiacetylene (PDA) and guest l-arginine (L-Arg) (PDA-(L-Arg)) exhibit temperature-responsive gradual color changes with reversibility in the range of 123–333 K in solid crystalline state. The dynamic properties are induced by gradual and reversible distortion of the π-conjugated main chain in response to temperature. The tuned flexibility of the layered structure facilitates motion of the rigid π-conjugated molecule at low temperature. The PDA-(L-Arg)-coated substrates are applied to visualization and quantification of 2D and 3D temperature distributions generated by cooling with liquid nitrogen. These thermographic devices afford to image lower temperature range than typical infrared thermography. The present work indicates potentials of layered architectures with tunable flexibility for emergence of dynamic properties.

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Spinel-Type MgMn<inf>2</inf>O<inf>4</inf>Nanoplates with Vanadate Coating for a Positive Electrode of Magnesium Rechargeable Batteries

Doi S., Ise R., Mandai T., Oaki Y., Yagi S., Imai H.

Langmuir (Langmuir)  36 ( 29 ) 8537 - 8542 2020.07

ISSN  07437463

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Spinel-type MgMn2O4 nanoplates ∼10 nm thick were prepared as a positive electrode for magnesium rechargeable batteries by the transformation of metal hydroxide nanoplates. Homogeneous coating with a vanadate layer thinner than 3 nm was achieved on the spinel oxide nanoplates via coverage of the precursor and subsequent mild calcination. We found that the spinel oxide nanoplates with the homogeneous coating exhibit improved electrochemical properties, such as discharge potential, capacity, and cyclability, due to the enhanced insertion and extraction of magnesium ions and suppressed decomposition of electrolytes. The nanometric platy morphology of the spinel oxide and the vanadate coating act synergistically for the improvement of the electrochemical performance.

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Amorphous flexible covalent organic networks containing redox-active moieties: A noncrystalline approach to the assembly of functional molecules

Suzuki J., Ishizone A., Sato K., Imai H., Tseng Y.J., Peng C.H., Oaki Y.

Chemical Science (Chemical Science)  11 ( 27 ) 7003 - 7008 2020.07

ISSN  20416520

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The organization states of functional molecules have a significant impact on the properties of materials. A variety of approaches have been studied to obtain well-organized molecular assemblies. The present work shows a new non-organized state of isolated and dispersed functional molecules in amorphous flexible covalent organic networks. Redox-active quinone molecules are embedded in the amorphous network polymers. Consecutive reactions between benzoquinone (BQ) and linker molecules generate random network structures through polymerization at different rates and in multiple directions. The low-crystalline stackings of the amorphous network polymers facilitate the formation of nanoflakes through exfoliation in dispersion media. Enhanced electrochemical performances, one of the highest specific capacities in recent studies, were achieved by efficient redox reactions of the quinone moiety. The present noncrystalline approach, low-crystalline stacking of designer amorphous covalent organic networks, can be applied to construct similar nanostructured polymer materials containing functional units. This journal is

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Efficient Syntheses of 2D Materials from Soft Layered Composites Guided by Yield Prediction Model: Potential of Experiment-Oriented Materials Informatics

Noda K., Igarashi Y., Imai H., Oaki Y.

Advanced Theory and Simulations (Advanced Theory and Simulations)  3 ( 7 )  2020.07

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Exfoliation is a common route to synthesize 2D materials such as monolayered and few-layered nanosheets. However, it is not easy to control the breaking-down process. This work shows a new exfoliation strategy for generation of nanosheets from soft layered composites in high yield. Soft layered composites of inorganic hosts and organic guests are exfoliated into nanosheets in organic dispersion media. A simple yield prediction model is constructed on small-scale experimental data by sparse modeling, a data-scientific approach, combined with chemical perspective. The prediction model indicates the guest–medium combinations enabling high- and low-yield syntheses of the nanosheets. The high- and low-yield syntheses are actually achieved on different types of layered transition metal oxides in a minimum number of experiments. The number of experiments is reduced by 94%. The experimental optimization realizes further improvement of the yield, namely, shortening the exfoliation time. The present strategies can be applied to obtain a variety of 2D materials through exfoliation. Moreover, the present work suggests that combination of small experimental data, data-scientific approach, and chemical perspective, i.e., experiment-oriented materials informatics, has potentials for acceleration of materials design.

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Biomimetic Morphology-Controlled Anhydrous Guanine via an Amorphous Intermediate

Kimura T., Takasaki M., Oaki Y., Imai H.

Crystal Growth and Design (Crystal Growth and Design)  20 ( 5 ) 3341 - 3346 2020.05

ISSN  15287483

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The micrometric morphology of anhydrous β-guanine crystals is adequately designed by various organisms for their specific optical properties. We successfully controlled the morphology of an anhydrous β-guanine crystal through the transformation of an amorphous intermediate consisting of guanine sodium salt under aqueous conditions. Biomimetic platy and columnar guanine crystals were selectively produced from the amorphous intermediate by changing the crystallization conditions.

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Enhancement of coercivity of self-assembled stacking of ferrimagnetic and antiferromagnetic nanocubes

Sawano K., Tsukiyama K., Shimizu M., Takasaki M., Oaki Y., Yamamoto T., Einaga Y., Jenewein C., Cölfen H., Kaiju H., Sato T., Imai H.

Nanoscale (Nanoscale)  12 ( 14 ) 7792 - 7796 2020.04

ISSN  20403364

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The coercivity of magnetic nanoparticles is enhanced by the exchange coupling effect at the interface of ferrimagnetic and antiferromagnetic self-assembled monolayers. Antiferromagnetic Co3O4 nanocubes were regularly stacked on an ordered monolayer of ferrimagnetic Fe3O4 nanocubes by layer-by-layer manipulation using evaporation-driven self-assembly. The ordered arrangements of the ferrimagnetic and antiferromagnetic nanocubes are effective for the enhancement of the ferromagnetic character.

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Structured spinel oxide positive electrodes of magnesium rechargeable batteries: High rate performance and high cyclability by interconnected bimodal pores and vanadium oxide coating

Ishii K., Doi S., Ise R., Mandai T., Oaki Y., Yagi S., Imai H.

Journal of Alloys and Compounds (Journal of Alloys and Compounds)  816 2020.03

ISSN  09258388

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A structured spinel oxide as a positive-electrode active material for magnesium rechargeable batteries was produced using a propylene-oxide-driven sol–gel method and subsequent vanadium oxide coating. Porous frameworks consisting of MgMn2O4 nanoparticles having diameters of ∼10 nm exhibited a large specific surface area of ∼150 m2 g−1 and interconnected bimodal pores distributed in the micrometer (1–10 μm) and nanometer (10–100 nm) regions. Hierarchical conduction paths constructed by mixing the porous frameworks with carbon nanoparticles reduced the overpotential for the insertion and extraction of magnesium ions and increased the redox capacity in an ionic-liquid electrolyte system. Moreover, the surface coating of vanadium oxide on the spinel oxide nanoparticles enhanced the extraction of magnesium ions and suppressed the decomposition of the electrolyte. The electrochemical properties, such as the capacities, rate capabilities, and cyclabilities, of the positive electrodes were largely improved by the structured spinel oxide frameworks.

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Formation processes, size changes, and properties of nanosheets derived from exfoliation of soft layered inorganic-organic composites

Mizuguchi R., Imai H., Oaki Y.

Nanoscale Advances (Nanoscale Advances)  2 ( 3 ) 1168 - 1176 2020.03

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Exfoliation is a general route to obtain two-dimensional (2D) nanomaterials. A variety of methods have been developed for controlled exfoliation of layered materials based on stacking via van der Waals interaction, such as graphite and transition-metal dichalcogenides. On the other hand, rigid layered materials consisting of inorganic layers and interlayer metal ions stacked via electrostatic interaction, such as transition-metal oxides and clays, have a limited number of exfoliation methods. Here we studied a new exfoliation route through formation of soft layered composites. Intercalation of guest organic molecules changed rigid inorganic layered compounds into soft layered composites with stacking via van der Waals interaction. The soft layered inorganic-organic composites were exfoliated into surface-modified nanosheets in organic media. The layered composites showed swelling with dispersion in organic media. The time-course analyses suggest that the layered composites were simultaneously exfoliated in the vertical direction and fractured in the lateral direction. Thinner and smaller nanosheets were obtained with an increase in the exfoliation time. Although the resultant nanosheets gradually aggregated in the colloidal liquid, the original dispersion state was recovered with sonication for 5 min at room temperature. This exfoliation route using soft layered composites can be used in the synthesis and application of a variety of 2D nanomaterials.

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Visualization and Quantification of Microwaves Using Thermoresponsive Color-Change Hydrogel

Nakamitsu M., Imai H., Oaki Y.

ACS Sensors (ACS Sensors)  5 ( 1 ) 133 - 139 2020.01

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Visualization and quantification of invisible lights, such as microwaves, are significant for their safe use. In general, a sensitizer material combined with a transistor is used as electronic devices for the measurement. Here, we developed a thermoresponsive color-change hydrogel of poly(N-isopropylacrylamide) (PNIPAAm) cross-linked by a layered organic composite based on polydiacetylene (PDA) for visualization and colorimetric quantification of microwaves. The layered PDA in the PNIPAAm hydrogel showed the temperature-dependent gradual color change with heating. Irradiation of microwaves induced the color change of PDA through heating of water in the hydrogel and subsequent volume shrinkage. The color of the gel was applied to visualize the temperature distribution with increasing irradiation time of microwaves. Moreover, the power of the irradiated microwave was quantified by time to the complete color change of the gel. The results indicate that the stimulus conversion process has potentials for development of a variety of imaging and quantification devices based on the layered PDA.

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A paper-based device of a specially designed soft layered polymer composite for measurement of weak friction force

Watanabe K., Imai H., Oaki Y.

Journal of Materials Chemistry C (Journal of Materials Chemistry C)  8 ( 4 ) 1265 - 1272 2020

ISSN  20507534

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Measurement of friction force is important for safety, security, and health. Excessive friction force causes degradation of materials and biological bodies. For example, tooth enamel and gums are damaged by strong toothbrushing force. However, friction force is not easily measured by conventional materials and devices. Here, we proposed design strategies of a paper-based device for measurement of friction force. Toothbrushing force, a model of weak friction force, is the measurement target in the present work. Soft layered composites of polydiacetylene (PDA) and interlayer guest macromolecules were designed and synthesized to achieve a visible color change in response to weak friction force. A data-scientific approach assisted in the selection of the interlayer guest molecule to control the stimuli responsivity of the layered PDA. The guest polyethyleneimine (PEI) formed soft layered composites exhibiting a color change in response to weak friction force. The paper-based device of the layered PDA/PEI composite showed a gradual color change from blue to red in response to the strength and number of the applied friction force. As a model case, toothbrushing force was measured using the paper-based device. The present work shows new design strategies of molecules and materials toward measurement of a wide variety of friction forces.

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Thermally induced fragmentation of nanoscale calcite

Takasaki M., Tago M., Oaki Y., Imai H.

RSC Advances (RSC Advances)  10 ( 10 ) 6088 - 6091 2020

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Calcite nanorods ∼50 nm wide are thermally separated into nanoblocks. The fragmentation is ascribed to the ion diffusion on metastable crystal surfaces at temperatures (∼400 °C) much lower than the melting point. The presence of water molecules enhances the surface diffusion and induces deformation of the nanorods even at ∼60 °C.

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Amorphous 2D materials containing a conjugated-polymer network

Yano S., Sato K., Suzuki J., Imai H., Oaki Y.

Communications Chemistry (Communications Chemistry)  2 ( 1 )  2019.12

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Two-dimensional materials, such as layered compounds and nanosheets, have attracted interest for their characteristic structures and properties. If layered materials containing functional organic molecules are synthesized, designed nanosheets can be obtained by exfoliation. Here we show the design and synthesis of an amorphous organic layered material containing a conjugated-polymer network, its exfoliation into nanosheets, and their applications. Copolymerization of benzoquinone and pyrrole generates random stacks of the conjugated polymer layers through successive C-C bond formation and pericyclic reaction under mild conditions at 60 °C. The amorphous organic layered materials are efficiently exfoliated into nanosheets in 44.6% after 1 h. The nanosheets are used as a metal-free electrocatalyst for hydrogen evolution reaction with the overpotential 0.28 V (vs. RHE). The present approach may be applied to the design of functional nanosheets with graphene-like structures under mild conditions.

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Carbon nitride and titania nanoparticles prepared using porous silica templates and photocatalytic activity

Somekawa S., Watanabe H., Ono Y., Tachibana N., Imai H.

Materials Letters (Materials Letters)  256 2019.12

ISSN  0167577X

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This work examined the band structure and photocatalytic activity of carbon nitride and titania nanoparticles prepared using porous silica templates with pore sizes of approximately 1 and 3 nm. The carbon nitride and titania specimens prepared in this manner exhibited absorption edge blue shifts compared to bulk samples, due to expansion of their band gap resulting from quantum size effects. The photocatalytic activity of these materials during hydrogen production from water was assessed, and the activity of carbon nitride prepared in the 1 nm pores was higher than that of the material made using 3 nm pores as well as that of the bulk carbon nitride. These results suggest that the expansion of the HOMO-LUMO energy gap contributed to increasing the catalytic performance. In contrast, the titania materials did not generate hydrogen. X-ray absorption fine structure analyses demonstrated that the titania in the silica templates had a distorted structure, which may have decreased its photocatalytic activity.

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Experiment-Oriented Materials Informatics for Efficient Exploration of Design Strategy and New Compounds for High-Performance Organic Anode

Numazawa H., Igarashi Y., Sato K., Imai H., Oaki Y.

Advanced Theory and Simulations (Advanced Theory and Simulations)  2 ( 10 )  2019.10

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High-performance organic energy storage has attracted much interest as a future battery. Organic anode has been developed as an alternate of graphite in the past decade. However, the design strategies are not fully studied for further development. The present work shows experiment-oriented materials informatics (MI) for efficient exploration of design strategy and new compounds for an active material of high-performance organic anode. A few important factors to achieve high specific capacity are extracted from training dataset containing experimentally measured specific capacity, calculation results, and literature data of the model compounds using sparse modeling, an informatics approach. Although the prediction model is not sufficiently accurate, the model assists in exploration of new compounds in combination with experience and intuition of experimental scientists. New compounds with high specific capacity, such as 227 mA h g–1 at 100 mA g–1 for benzo[1,2-b:4,5-b′]dithiophene (BdiTp), are efficiently discovered in a minimum number of experiments. Furthermore, polymerization of BdiTp exhibits the enhanced performances, such as 933 mA h g–1 at 20 mA g–1 and cycle stability, and rate performance. MI combined with experiment, calculation, and data accelerates design new materials and functions by experimental scientists having their small data, experience, and intuition.

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Evolution of Co<inf>3</inf>O<inf>4</inf> Nanocubes through Stepwise Oriented Attachment

Tsukiyama K., Takasaki M., Oaki Y., Imai H.

Langmuir (Langmuir)  35 ( 24 ) 8025 - 8030 2019.06

ISSN  07437463

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Uniformly sized building units are generally required to construct highly elaborate architectures over a wide range. Defined nanocubes of Co3O4 evolved from deformed precursor nanograins 2-5 nm in diameter through direct oriented attachment in a nonpolar medium. Uniformly sized primary nanocubes -8 nm on a side with {100} faces were formed by adjusting the coverage of the oxide nanograins with oleic acid. Larger nanocubes 20-40 nm on a side were produced with further direct oriented attachment of the primary nanocubes. Ordered arrays, such as superlattices, were found to be constructed by the indirect oriented attachment of the primary and larger nanocubes covered with organic molecules.

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Quantitative detection of near-infrared (NIR) light using organic layered composites

Takeuchi M., Kawashima H., Imai H., Fujii S., Oaki Y.

Journal of Materials Chemistry C (Journal of Materials Chemistry C)  7 ( 14 ) 4089 - 4095 2019.04

ISSN  20507534

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Quantitative detection of external stimuli, such as light, heat, and force, is an important challenge for sensing materials. Near-infrared (NIR) light is used in a variety of fields, such as biological, physical, medical, and engineering applications. Visualization and quantitative detection of invisible NIR are significant for its safe use. Here we fabricate a paper-based device coated with polypyrrole (PPy) and layered polydiacetylene (PDA). As PPy induces evolution of heat with irradiation of NIR, the effective conjugation length of the layered PDA is changed by the dynamic structure changed through the heat conduction. The visible color change from blue to red proceeds on the paper device. The red-color intensity has a relationship with the irradiation power of NIR. These facts suggest that the irradiation time and power of NIR are quantified by the color. Moreover, the results indicate that layered PDA can be applied to the quantification of external stimuli through conversion from the desired stimulus to the detectable one.

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Materials-Informatics-Assisted High-Yield Synthesis of 2D Nanomaterials through Exfoliation

Nakada G., Igarashi Y., Imai H., Oaki Y.

Advanced Theory and Simulations (Advanced Theory and Simulations)  2 ( 4 )  2019.04

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A variety of inorganic and organic nanosheets with characteristic structures and properties can be synthesized through exfoliation of layered materials. However, in general, immense time and efforts are required for exploration of exfoliation conditions and characterization of nanosheets. In addition, it is challenging to improve the yield of nanosheets obtained through exfoliation. Here a materials-informatics-assisted high-yield synthesis of nanosheets is proposed, which does not require experience and intuition. Layered composites containing inorganic layers and interlayer organic guests are delaminated into nanosheets in a variety of dispersion media. First, an experimental screening is performed to find efficient exfoliation conditions and obtain a training dataset for the informatics approach. Sparse modeling is then used facilitating the extraction of important factors predicting the yield of nanosheets. High-yield (up to ≈50%) synthesis of nanosheets is demonstrated in unknown systems in a minimum number of experiments. The yield is higher than those typically reported for layered materials. It is expected that the effective combination has potentials for not only discovery of compounds but also structure control of materials.

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Enhanced oxide-ion conductivity of solid-state electrolyte mesocrystals

Tsukiyama K., Takasaki M., Kitamura N., Idemoto Y., Oaki Y., Osada M., Imai H.

Nanoscale (Nanoscale)  11 ( 10 ) 4523 - 4530 2019.03

ISSN  20403364

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Oxide ion-conducting porous films were produced on a substrate by evaporation-induced self-assembly of rare earth-doped CeO 2 (REDC) nanocubes 4-5 nm in size and subsequent mild calcination at 400 °C. Mesocrystalline structures comprising iso-oriented REDC nanocubes were formed by ordered assembly based on strict attachment of their {100} faces. Enhanced oxide-ion conductivities in a temperature range of 250-350 °C were observed on the mesocrystalline films consisting of Sm-doped CeO 2 (SDC) nanocubes. The specific electrical properties of the mesocrystalline films are ascribed to improved surface-ion conduction due to a large specific surface area and a high crystallographic connectivity of SDC nanocubes.

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Bending Fibers of Hydroxyapatite for Ordered Parallel Architecture in Bovine Tooth Enamel

Yukimasa Y., Takasaki M., Oaki Y., Imai H.

ACS Omega (ACS Omega)  4 ( 2 ) 3739 - 3744 2019.02

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Copyright © 2019 American Chemical Society. The nanometer-scale bending structure in the enamel-dentin interfacial region of bovine teeth was clarified using detailed electron micrographs. We found that enamel prisms of width 5-10 μm in the enamel are regarded as a bundle of nanometer-scale hydroxyapatite (HA) fibers of width 20-30 nm that are connected to the enamel-dentin interface. The radial arrangements of HA fibers elongated in the c-axis were formed on the dentin surface at the boundary. The orientation adjustment of the HA fibers was observed through stepwise bending with a gradual change of the c direction in the ordered parallel array of the enamel prisms. Our observation suggests that the crystallographic ordering in the enamel layer originates from the growth-induced orientation of HA crystals in the interfacial region.

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Highly porous polymer dendrites of pyrrole derivatives synthesized through rapid oxidative polymerization

Ishii K., Sato K., Oaki Y., Imai H.

Polymer Journal (Polymer Journal)  51 ( 1 ) 11 - 18 2019.01

ISSN  00323896

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© 2018, The Society of Polymer Science, Japan. Highly porous organic structures are synthesized by the oxidative polymerization of pyrrole derivatives in a concentrated monomer and oxidant solution. The rapid polymerization of pyrrole by oxidation with FeCl 3 in CHCl 3 as a cosolvent for the monomer and the oxidant leads to nanometer-scale branching morphologies that have a specific surface area of ~200 m 2 g −1 . The polymerization of pyrrole derivatives, such as 1-methylpyrrole and 1-ethylpyrrole, produced intragranular micropores of ~1 nm in diameter in the polymer grains of nanoscale dendrites. We obtained highly porous polymers of polypyrrole derivatives that have high specific surface areas (~900 m 2 g −1 ) with bimodal pore-size distribution. The enhanced adsorbability of porous polymer dendrites for aromatic molecules was confirmed, in comparison with that of conventional polystyrene adsorbents.

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A biomimetic hybrid material consisting of CaCO<inf>3</inf> mesoporous microspheres and an alternating copolymer for reversed-phase HPLC

Mochida M., Nagai Y., Kumagai H., Imai H., Citterio D., Hiruta Y.

Journal of Materials Chemistry B (Journal of Materials Chemistry B)  7 ( 31 ) 4771 - 4777 2019

ISSN  2050750X

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We developed a biomineral-inspired hybrid material composed of CaCO3 and an organic polymer as a column packing material for HPLC. This material combines a hierarchical mesoporous structure and the functionality of the polymer. The surface of monodispersed mesoporous CaCO3 microspheres was modified with poly(maleic acid-alt-1-octadecene) (PMAcO) comprising hydrophobic alkyl chains and anionic carboxylate groups. PMAcO adsorbed onto the surface of CaCO3 through electrostatic interaction between Ca2+ sites and carboxylate groups, resulting in an octadecene coated microsphere interface. These microspheres were applied as a HPLC column and exhibited reversed-phase retention behavior in the separation of alkylbenzenes. This column showed high alkaline mobile phase resistance compared with the conventionally applied ODS column packing material. Quantitative analysis of the basic antidepressants clomipramine and imipramine spiked into whole blood was achieved with an alkaline mobile phase, demonstrating the potential of the biomineral-inspired material as a HPLC stationary phase for practical applications in routine analyses of basic drugs requiring alkaline mobile phases.

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Supermicroporous Silica Nanograins: Synthesis and Application

Kitamura R., Watanabe H., Oaki Y., Imai H.

Langmuir (Langmuir)   2019

ISSN  07437463

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Supermicroporous silicas having micropores 1-2 nm in diameter were miniaturized to 30-40 nm in diameter using a combination of binary organic agents: cationic surfactant as a porogen and polyethylene glycol as a growth suppressor in a concentrated system. The miniaturized nanograins of the porous silica were effective as a porous and transparent matrix for WO 3 quantum dots that exhibit enhanced photocatalytic activity.

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Redox-mediated high-yield exfoliation of layered composites into nanosheets

Yamamoto Y., Imai H., Oaki Y.

Bulletin of the Chemical Society of Japan (Bulletin of the Chemical Society of Japan)  92 ( 4 ) 779 - 784 2019

ISSN  00092673

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A variety of organic and inorganic layered compounds are exfoliated into 2D nanomaterials in liquid phase. Improvement of exfoliation yield is a significant challenge for further applications of 2D nanomaterials. However, yield of transition-metal-oxide nanosheets is not so high, such as around 5% for 240 h and 15% for 120 h, in previous exfoliation methods. Here we show a new exfoliation approach to high-yield synthesis of nanosheets. A layered composite of cobalt hydroxide and guest quinone derivative was exfoliated into nanosheets through redox reactions of the interlayer guests in the yield 1657% for 1 h under mild conditions. The redox reactions of the guest molecules on the layer facilitate efficient exfoliation through improvement of the affinity between the guest and dispersion medium. The present redox-mediated exfoliation approach can be applied to efficient synthesis of a variety of 2D nanomaterials from layered composites.

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Pyrolytic production of fluorescent pyrone derivatives produced in the confined space of super-microporous silicas

Hayashi K., Ogawa S., Watanabe H., Fujimaki Y., Oaki Y., Imai H.

Bulletin of the Chemical Society of Japan (Bulletin of the Chemical Society of Japan)  92 ( 7 ) 1170 - 1174 2019

ISSN  00092673

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Fluorescent pyrone derivatives were extracted from the pyrolitic product of citric acid confined in supermicroporous silicas (SMPSs). We utilized the tiny spaces of SMPSs to produce fluorescent molecules as small fragments of carbogenic dots. We characterized their optical properties and investigated their structual information. The obtained molecule was determined as a pyrone derivative. The isolated product showed similar optical properties to those of reported carbogenic dots. Therefore, we suggest that the pyrone structure is the key fragment structure of carbogenic dots.

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Modifications in coordination structure of Mg[TFSA]<inf>2</inf>-based supporting salts for high-voltage magnesium rechargeable batteries

Mandai T., Tatesaka K., Soh K., Masu H., Choudhary A., Tateyama Y., Ise R., Imai H., Takeguchi T., Kanamura K.

Physical Chemistry Chemical Physics (Physical Chemistry Chemical Physics)  21 ( 23 ) 12100 - 12111 2019

ISSN  14639076

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To achieve a sustainable-energy society in the future, next-generation highly efficient energy storage technologies, particularly those based on multivalent metal negative electrodes, are urgently required to be developed. Magnesium rechargeable batteries (MRBs) are promising options owing to the many advantageous chemical and electrochemical properties of magnesium. However, the substantially low working voltage of sulfur-based positive electrodes may hinder MRBs in becoming alternatives to current Li-ion batteries. We proposed halide-free noncorrosive ionic liquid-based electrolytes incorporating Mg[TFSA]2 for high-voltage MRB applications. Upon the complexation of Mg[TFSA]2 with tetraglyme (G4) and strict control of the liquid states, the electrolytes achieved excellent anodic stability up to 4.1 V vs. Mg2+/Mg even at 100 °C. The modest electrochemical activities for magnesium deposition/dissolution in the [Mg(G4)][TFSA]2/ionic liquid electrolyte can be improved by certain modifications to the coordination state of [TFSA]-. Dialkyl sulfone was found to be effective in changing the coordination state of [TFSA]- from associated to isolated (free). This coordination change successfully promoted magnesium deposition/dissolution reactions, particularly in the coexistence of ether ligand. By contrast, the coordination of Mg2+ by strongly donating agents such as dimethyl sulfoxide and alkylimidazole led to the complexes inactive electrochemically, suggesting that interaction between Mg2+ and coordination agents predominates the fundamental electrochemical activity. We also demonstrated that an enhancement in the electrochemical activity of electrolytes contributed to improvements in the cycling ability of magnesium batteries with 2.5 V-class MgMn2O4 positive electrodes.

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Highly dispersive mono-sized nanoparticles of Y <inf>2</inf> O <inf>3</inf> -stabilized ZrO <inf>2</inf>

Tsukiyama K., Takasaki M., Oaki Y., Imai H.

Chemistry Letters (Chemistry Letters)  48 ( 4 ) 390 - 393 2019

ISSN  03667022

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Uniformly sized nanoparticles 35nm in diameter of Y 2 O 3 - stabilized ZrO 2 (YSZ) were fabricated by a water-toluene twophase solvothermal method. The nanoparticles that were covered with oleic acid were highly dispersed in organic media. The size and doping concentration were tuned by adjusting the preparation conditions. The fabrication of YSZ thin films was achieved through hexagonal arrangement by evaporation-induced selfassembly of highly dispersive mono-sized nanoparticles.

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Glass-transition-induced color-changing resins containing layered polydiacetylene

Ishioka S., Watanabe K., Imai H., Tseng Y.J., Peng C.H., Oaki Y.

Chemical Communications (Chemical Communications)  55 ( 78 ) 11723 - 11726 2019

ISSN  13597345

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A phase-segregated composite of polystyrene (PSt) and layered polydiacetylene (PDA) was formed through simultaneous polymerization and crystallization. As the motion of PSt chains with glass transition is transferred to that of PDA, the color change was achieved by the shortening of the conjugation length with deformation of the layered structure.

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Evaporation-driven manipulation of nanoscale brickwork structures for the design of 1D, 2D, and 3D microarrays of rectangular building blocks

Imai H., Matsumoto R., Takasaki M., Tsukiyama K., Sawano K., Nakagawa Y.

CrystEngComm (CrystEngComm)  21 ( 45 ) 6905 - 6914 2019

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As children play with wooden building blocks, we would like to construct elaborate architectures through the one-by-one accumulation of nanocrystals. Recently, ordered microarrays of nanosized building blocks have attracted attention as a sophisticated bottom-up approach to fabricate adequate nanomaterials. However, their dimensions, scale, and orientations have not been strictly controlled. The present highlight article reports the potential of brickwork structures using evaporation-driven manipulation as a nanoscale architectural method. Here, the essence of controlled assembly is shown with a demonstration of 1D, 2D, and 3D brickwork structures designed with various inorganic rectangular building nanoblocks covered by stabilizing organic agents. The structures of the ordered assemblies are found to be controlled by changing several parameters, such as particle concentration and the properties of dispersion media and stabilizing agents. This brickwork technique is applicable to multicomponent systems using a library of rectangular nanoblocks. Homogeneous and heterogeneous ordered architectures with spatial and sequential control are selectively produced through the self-assembly of nanocubes and nanocuboids. These elaborate nanoscale brickwork structures are now being developed for the production of designed microstructures with novel functions.

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Enhanced quantum yield of nanographenes incorporated in supermicroporous silicas and the co-adsorption effect of water molecules

Watanabe H., Fujimaki Y., Hayashi K., Imai H.

Bulletin of the Chemical Society of Japan (Bulletin of the Chemical Society of Japan)  92 ( 5 ) 923 - 926 2019

ISSN  00092673

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Nanographene with various molecular sizes was synthesized and incorporated into the size-controlled pores of super-microporous silica (SMPS). It was found that when the pore diameter of the SMPS matched the molecular size of the nanographene, the fluorescence quantum yield was greatly enhanced. Furthermore, co-adsorption of water molecules improved the quantum yield. This improvement is attributed to a suppression of the interaction between the nanographene and silica walls, which lowers the quantum yield. Since nanographene is insoluble in water, it becomes surrounded by water molecules, almost like in aqueous solution. Finally, highly fluorescent solid materials were obtained by incorporating nanographene into SMPS.

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Biomimetic macroscopic mesocrystalline films produced by oriented assembly of nanorods under magnetic field

Takasaki M., Suzuki T., Oaki Y., Imai H.

Nanoscale (Nanoscale)  10 ( 47 ) 22161 - 22165 2018.12

ISSN  20403364

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Millimeter-scale mesocrystals and cross-lamellae mimicking the nanostructure of seashells were produced on a substrate through the three-dimensionally oriented assembly of c-axis-elongated calcite nanorods ∼50 nm wide and ∼500-1000 nm long by combining arrangement with evaporation-driven capillary force and alignment under an intense magnetic field.

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Tunable Stimuli-Responsive Color-Change Properties of Layered Organic Composites

Takeuchi M., Gnanasekaran K., Friedrich H., Imai H., Sommerdijk N., Oaki Y.

Advanced Functional Materials (Advanced Functional Materials)  28 ( 45 )  2018.11

ISSN  1616301X

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© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Stimuli-responsive properties of soft materials originate from dynamic structure changes. Layered polydiacetylene (PDA) shows color-change properties with the application of external stimuli, such as thermal and mechanical stresses. Layered organic materials possessing intercalation capabilities and dynamic properties have potentials for tuning their structures and properties by the intercalated guests. A variety of sensing and imaging devices can be developed by control of the stimuli responsivity. Here, the key structures, processes, and mechanisms for tuning the stimuli-responsive color-change properties of layered PDA are studied by in situ analyses with heating and cooling. The in situ analyses indicate that heating initiates thermal motion of the alkyl side chains of the PDA main chain in the host layers around 60 °C, regardless of the type of intercalated guests. Further heating induces torsion of the PDA main chain leading to color changes at different temperatures, depending on the types of the intercalated guest. Then, the layered structure is irreversibly deformed with lowering the crystallinity. The results indicate that the stimuli-responsive color-change properties are controlled by the rigidity of the layered structures consisting of the host layers and guests. The control strategy based on rigidity tuning can be applied to a variety of soft materials with stimuli responsivity.

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Layer-by-Layer Manipulation of Heterogeneous Rectangular Nanoblocks: Brick Work for Multilayered Structures with Specific Heterojunction

Matsumoto R., Takasaki M., Tsukiyama K., Oaki Y., Imai H.

Inorganic Chemistry (Inorganic Chemistry)  57 ( 18 ) 11655 - 11661 2018.09

ISSN  00201669

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© 2018 American Chemical Society. The combination of heterogeneous inorganic nanocrystals provides novel nanometer-scale architectures for exploration of novel functions. In the present study, heterogeneous bilayers, such as BaTiO3-Fe3O4 and Mn3O4-CeO2, are fabricated via layer-by-layer stacking of several rectangular nanoblocks 5-23 nm in size by evaporation-driven self-assembly. Specific heterojunctions between inorganic crystals are constructed by nanoscale simple brick work through spontaneous adjustment of the crystallographic orientations of the nanoblocks in the lower and upper layers.

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Two-Dimensional Conductive and Redox-Active Nanostructures Synthesized by Crystal-Controlled Polymerization for Electrochemical Applications

Sato K., Imai H., Oaki Y.

ACS Applied Nano Materials (ACS Applied Nano Materials)  1 ( 8 ) 4218 - 4226 2018.08

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Two-dimensional nanomaterials have attracted much interest for their anisotropic structures and emergent properties. Whereas a variety of inorganic nanosheets are prepared by exfoliation, design and synthetic strategies of organic nanosheets are still developing. Here we report on crystal-controlled synthesis of conductive and redox-active organic polymer nanosheets with tunable thickness and lateral size. Although the nanosheets consist of classical conductive polymers, such as polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT), a new crystal-controlled polymerization approach provides 2D nanomaterials with enhanced and characteristic properties. Oxidative polymerization proceeds on the crystal surface of organic oxidants, such as quinone derivatives, with diffusion of the monomer vapor at low temperature under ambient pressure. The present method affords the control of lateral size and thickness of the nanosheets. The resultant nanosheets show the characteristic and enhanced properties originating from a 2D nature, such as the high structure anisotropy with aspect ratio around 104, enhanced conductivity 287 S cm-1, and specific charge-discharge capacitance 523 F g-1 at the current density of 18 A g-1. The organic nanosheets with conductivity and redox activity can be used as a building block for development of functional materials and devices. ©

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Layer-by-layer manipulation of anisotropic nanoblocks: Orientation-switched superlattices through orthogonal stacking of: A and c directions

Nakagawa Y., Matsumoto R., Kageyama H., Oaki Y., Imai H.

Nanoscale (Nanoscale)  10 ( 27 ) 12957 - 12962 2018.07

ISSN  20403364

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© 2018 The Royal Society of Chemistry. Nanometer-scale switching of the crystallographic orientation enables production of novel superlattices for exploration of new functions. Elaborate multilayered architectures of Mn3O4 nanocuboids were constructed by a convective self-assembly process. The nanometric cuboids were accumulated into orientation-switched superlattices on micrometric scales by controlling the a and c directions of the tetragonal crystal periodically. The orthogonal stacking of the tetragonal nanoblocks was achieved through the layer-by-layer manipulation process of two types of 2D arrays with different orientations.

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Visualization and Quantitative Detection of Friction Force by Self-Organized Organic Layered Composites

Terada H., Imai H., Oaki Y.

Advanced Materials (Advanced Materials)  30 ( 27 )  2018.07

ISSN  09359648

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© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Visualization and quantitative detection of external stimuli are significant challenges in materials science. Quantitative detection of friction force, a mechanical stress, is not easily achieved using conventional stimuli-responsive materials. Here, the quantitative detection of friction force is reported, such as the strength and accumulated ammount, from the visible color of organic layered composites consisting of polydiacetylene (PDA) and organic amines without an excitation light source. The composites of the layered diacetylene monomer crystal and interlayer organic amine are synthesized through self-organization from the precursor solution. After topochemical polymerization, the layered composites based on PDA show tunable temperature-responsive and mechanoresponsive color-change properties depending on the types of interlayer amines. The layered composites are homogeneously coated on a filter paper. The change in color of the paper is quantitatively used to visualize the strength and accumulated amount of the applied friction force. Furthermore, writing pressure is measured by friction force using the paper device.

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Multistage redox reactions of conductive-polymer nanostructures with lithium ions: potential for high-performance organic anodes

Numazawa H., Sato K., Imai H., Oaki Y.

NPG Asia Materials (NPG Asia Materials)  10 ( 5 ) 397 - 405 2018.05

ISSN  18844049

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© 2018, The Author(s). Conducive polymers have a wide range of applications originating from their π-conjugated systems. The redox reactions of conductive polymers with doping and dedoping of anions have been applied to cathodes for charge storage. In contrast, the redox reactions with cations have not been fully studied in anodes for charge storage. Here, we found that the nanostructures of conductive polymers, such as polypyrrole (PPy) and polythiophene (PTp) derivatives, have reversible redox reactions with cations. The PPy and PTp nanostructures acted as anodes with specific capacities of 157 and 44.4 mA h g–1, respectively, at a current density of 20 mA g–1. The introduction of a carboxy group to the pyrrole and thiophene rings enhanced the specific capacities up to 730 and 963 mAh g–1, respectively. The enhanced electrochemical properties were not observed in the bulk-size conductive polymers. The results suggest that conductive-polymer nanostructures have potential for developing metal-free, high-performance charge storage devices.

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Nanoscale Mosaic Works: Tetragonal Lattices of Iso-Oriented Heterogeneous Nanocubes

Matsumoto R., Yamazaki H., Takasaki M., Oaki Y., Sato T., Imai H.

Langmuir (Langmuir)  34 ( 13 ) 4031 - 4035 2018.04

ISSN  07437463

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© 2018 American Chemical Society. Tetragonal 2D lattices are spontaneously formed by the self-assembly of homogeneous nanocubes. However, ordered arrays consisting of differently sized rectangular nanoblocks have not been achieved because the regulation of the assembly is weakened by the combination of binary units. In the present work, ordered arrays comprising binary nanocubes were investigated using the combination of 10 nm Pt nanocubes and 20 nm BaTiO3 nanocubes. Heterogeneous but ordered 2D tetragonal lattices were successfully produced using differently sized rectangular nanoblocks. The highly ordered self-assembly in the heterogeneous system requires the matching of the size ratio of binary nanocubes with the buffer effect of oleic acid covering the building units.

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Enhanced electrochemical properties of MgCo <inf>2</inf> O <inf>4</inf> mesocrystals as a positive electrode active material for Mg batteries

Kotani Y., Ise R., Ishii K., Mandai T., Oaki Y., Yagi S., Imai H.

Journal of Alloys and Compounds (Journal of Alloys and Compounds)  739   793 - 798 2018.03

ISSN  09258388

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© 2017 Elsevier B.V. Mesocrystals of MgCo 2 O 4 spinel oxide exhibiting porous and single-crystalline structures were synthesized by the reaction of magnesium ions with calcite-type CoCO 3 mesocrystal precursors grown in micrometer-sized agar gels. The mesocrystals consisted of single-crystalline porous grains measuring 200–300 nm in diameter with iso-oriented subunits of approximately 10 nm. The single-crystalline porous framework structure of the MgCo 2 O 4 mesocrystals enhanced the discharge capacity and positively shifted the discharge potential compared with MgCo 2 O 4 nanoparticles prepared by the inverse co-precipitation method. These enhancements were attributed to a combination of the high specific surface areas of the mesocrystals and the high connectivity of the magnesium ion diffusion paths in the solid-phase.

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Enhanced Electrochemical Properties of MgCo2O4 Mesocrystals as a Positive Electrode Active Material for Mg Batteries

Y. Kotani, R. Ise, K. Ishii, T. Mandai, Y. Oaki, S. Yagi, H. Imai

Journal of Alloys and Compounds 739   793 - 798 2018.03

Research paper (scientific journal), Joint Work, Accepted

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Few-layered titanate nanosheets with large lateral size and surface functionalization: Potentials for controlled exfoliation of inorganic-organic layered composite

G. Nakada、H. Imai, Y. Oaki

Chemical Communications (Chemical Communications)  54 ( 3 ) 244 - 247 2018.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  13597345

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Herein, few-layered titanate nanosheets with a large lateral size and surface functionalization were synthesized via the exfoliation of precursor layered composites in an organic medium. The combination of layered compounds, intercalated guests, and dispersion media has the potential for the synthesis of nanosheets with controlled lateral sizes, thicknesses, and surface chemistry through exfoliation.

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Emergence of temperature-dependent and reversible color-change properties by stabilization of layeredpolydiacetylene through intercalation

Y. Oaki, Y. Ishijima, H. Imai

Polymer Journal (Polymer Journal)  50 ( 4 ) 319 - 326 2018.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  00323896

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The stimuli-responsive color-changing properties of functional polymers are applied to the development of sensing and imaging devices. Tuning the stimuli responsivity is required for a wide range of applications. Polydiacetylene (PDA) derivatives show color changes with the application of external stimuli, such as heat and mechanical stress. Our group has focused on the layered crystal structure of PDA and its intercalation chemistry. The original layered PDA shows an irreversible color transition from blue to red upon heating to the threshold temperature. Here, we found that alkyldiamine-intercalated PDA possessed different color-changing properties, such as a higher color transition temperature and a temperature-dependent and reversible color change, than the original PDA. As the alkyl-chain length increased, the color-changing behavior gradually converted from the irreversible color transition type to the reversible temperature-dependent one. Since the intercalated diamine had a stabilizing effect on the layered structure, the stimuli responsivity varied according to the type of diamine. The results suggest that the stimuli-responsive color-changing properties of layered PDA can be finely and systematically tuned by the intercalation of organic guests.

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Artificial Mineral Films Similar to Biogenic Calcareous Shells: Oriented Calcite Nanorods on a Self-Standing Polymer Sheet

Y. Nagai, Y. Oaki, H. Imai

CrystEngComm (CrystEngComm)  20 ( 12 ) 1656 - 1661 2018.01

Research paper (scientific journal), Joint Work, Accepted

　View Summary

Micrometre-thick calcareous shells consisting of c-axis-oriented calcite nanorods are produced on an organic sheet as foraminiferal tests and isopod cornea cuticles. Here, we produced mineral films similar to biogenic calcareous shells on a self-standing polymer sheet in a supersaturated solution system by multistep crystal growth with the adjustment of the concentration ratio of poly(acrylic acid) (PAA) as a soluble controlling agent. In the initial stage, selective high-density nucleation was achieved at a relatively low PAA to calcium ion ratio (R = 1.0-1.2) to form of a calcite seed layer on the surface of conventional polyvinyl alcohol. Calcite nanorods elongated in the c direction were then grown perpendicularly to the seed layer in the progressive stages at a relatively high PAA ratio (R = 1.5-2.0). The artificial mineral films consisting of c-axis-oriented nanorods are suggested to exhibit mechanical properties similar to those of biogenic calcareous shells.

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Evolution of Calcite Nanocrystals through Oriented Attachment and Fragmentation: Multi-Step Pathway Involving Bottom-Up and Break-Down Stages

M. Takasaki, Y. Kezuka, M. Tajika, Y. Oaki, H. Imai

ACS Omega 2   8997 - 9001 2017.12

Research paper (scientific journal), Joint Work, Accepted

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Spatial Control of Crystallographic Direction in 2D Microarrays of Anisotropic Nanoblocks on Trenched Substrates

今井 宏明

R. Matsumoto, Y. Nakagawa, K. Kato, Y. Oaki, H. Imai (Langmuir)  33   13805 - 13810 2017.12

Research paper (scientific journal), Joint Work, Accepted

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Hierarchical Textures on Aragonitic Shells of a Hyaline Radial Foraminifer Hoeglundina elegans

K. Nakajima, M. Suzuki, Y. Nagai, K. Izumida, Y. Oaki, T. Toyofuku, J. Bijma, G. Nehrke, M. Raitzsch, K. Tani, H. Imai

CrystEngComm 19   7191 - 7196 2017.11

Research paper (scientific journal), Joint Work, Accepted

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Polymer-Assisted Shapeable Synthesis of Porous Frameworks Consisting of Silica Nanoparticles with Mechanical Property Tuning

K. Sato, K. Ishii, Y. Oaki, K. Nakanishi, H. Imai

Polymer Journal 49   825 - 830 2017.10

Research paper (scientific journal), Joint Work, Accepted

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Ultrasensitive Detection of Methylmercaptan Gas Using Layered Manganese Oxide Nanosheets with a Quartz Crystal Microbalance Sensor

Y. Tokura, G. Nakada, Y. Moriyama, Y. Oaki, H. Imai, S. Shiratori

Analytical Chemistry 89   12123 - 12130 2017.10

Research paper (scientific journal), Joint Work, Accepted

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Enhanced quantum yield of fluorophores in confined spaces of supermicroporous silicas

S. Ogawa, T. Wakayama, H. Watanabe, K. Hayashi, S. Ogata, Y. Oaki, M. Hasegawa, H. Imai

The Bulletin of the Chemical Society of Japan (Bulletin of the Chemical Society of Japan)  91 ( 1 ) 87 - 91 2017.10

Research paper (scientific journal), Joint Work, Accepted,  ISSN  00092673

　View Summary

The optical properties of polycyclic aromatic hydrocarbon fluorophores, such as pyrene and perylene, are controlled by confined spaces of meso- and supermicropores in a silica matrix. The quantum yield of fluorescence from monodispersed pyrene and perylene increases with limitation of the excimer formation in 1 nm supermicropores. When the pore diameter is close to the molecular size, solid-state fluorescence having a high quantum yield is achieved via the fluorophores in the confined spaces by suppressing the aggregation, the interaction with charge-transfer sites and the stabilization of the excited state.

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Two exfoliation approaches for organic layered compounds: hydrophilic and hydrophobic polydiacetylene nanosheets

Y. Ishijima, M. Okaniwa, Y. Oaki, Hiroaki Imai

Chemical Science 8   647 - 653 2017.08

Research paper (scientific journal), Joint Work, Accepted

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Effects of intercalation rate on layered crystal structures and stimuli-responsive color-change properties of polydiacetylene

M. Takeuchi, H. Imai, Y. Oaki

Journal of Materials Chemistry C 5   8250 - 8255 2017.07

Research paper (scientific journal), Joint Work, Accepted

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Evolution analysis of V2O5·nH2O gels for preparation of xerogels having a high specific surface area and their replicas

K. Ishii, Y. Kimura, T. Yamazaki, Y. Oaki, H. Imai

RSC Advances 7   35711 - 35716 2017.07

Research paper (scientific journal), Joint Work, Accepted

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Dispersion of Hydroxyapatite Nanocrystals Stabilized by Polymeric Molecules Bearing Carboxy and SulfoGroups

K. Watanabe, I. Nishida, H. Imai

Colloid and Polymer Science 295   1491 - 1498 2017.06

Research paper (scientific journal), Joint Work, Accepted

Tunable Mechano-responsive Color-Change Properties of Organic Layered Material by Intercalation

Y. Ishijima, H. Imai, Y. Oaki

Chem 3   509 - 521 2017.05

Research paper (scientific journal), Joint Work, Accepted

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Hierarchical bicontinuous structure of redox-active organic composites and their enhanced electrochemical properties

K. Sato, M. Arayasu, H. Masaki, H. Imai, Y. Oaki

Chemical Communications 53   7329 - 7332 2017.05

Research paper (scientific journal), Joint Work, Accepted

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Self-organized Formation of Parallel-banded Structures through Synchronization of Twisted Growth

S. Mizue, S. Ibaraki, R. Ise, G. Sazaki, Y. Oaki, H. Imai

Crystal Growth and Design 17   3694 - 3699 2017.05

Research paper (scientific journal), Joint Work, Accepted

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Coupled Exfoliation and Surface Functionalization of Titanate Monolayer for Bandgap Engineering

Y. Yamamoto, Y. Oaki, H. Imai

Advanced Materials Interface 4 ( 7 ) 1601014 2017.04

Research paper (scientific journal), Joint Work, Accepted

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Real-Time Imaging of 2D and 3D Temperature Distribution: Coating of Metal-Ion-Intercalated Organic Layered Composites with Tunable Stimuli-Responsive Properties

M. Takeuchi, H. Imai, Y. Oaki

ACS Applied Materials and Interfaces 9   16546 - 16552 2017.04

Research paper (scientific journal), Joint Work, Accepted

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Synthesis of dispersible nanosheets based on monolayer clays with imidazolium and ammonium ations aving long-chain alkyl groups

A. Suzuki, Y. Oaki, H. Ima

Journal of the Ceramics Society of Japan 125 ( 4 ) 353 - 356 2017.04

Research paper (scientific journal), Joint Work, Accepted

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Phase separation through simultaneous polymerization and crystallization for composite materials, Asian Materials

K. Sato, Y. Oaki, H. Imai

MPG Asia Materials 9   e377 2017.04

Research paper (scientific journal), Joint Work, Accepted

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Synthesis of poly(amidoamine) dendrimer having a 1,10-bis(decyloxy)decane core and its use in fabrication of carbon nanotubes/calcium carbonate hybrids through biomimetic mineralization

S. Nishimura, T. Tajima, T. Hasegawa, T. Tanaka, Y. Takaguchi, Y. Oaki, H. Imai

Canadian Journal of Chemistry    935 - 941 2017.04

Joint Work, Accepted

• Access to Document (DOI)

Significant increase in bandgap and emission efficiency of In2O3 quantum dots by size-tuning around 1 nm in supermicroporous silicas

T. Suzuki, H. Watanabe, T. Ueno, Y. Oaki, H. Imai

Langmuir 33   3014 - 3017 2017.03

Research paper (scientific journal), Joint Work, Accepted

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Conductive Polymer Nanosheets Generated from the Crystal Surface of Organic Oxidant

K. Sato, H. Masaki, M. Arayasu, Y. Oaki, H. Imai

ChemPlusChem 82   177 - 180 2017.02

Research paper (scientific journal), Joint Work, Accepted

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Effects of Nanostructured Biosilica in Rice Plant Mechanics

K. Sato, N. Ozaki, K. Nakanishi, Y. Sugahara, Y. Oaki, C. Salinas, S. Herrera, D. Kisailus, H. Imai

RSC Advances 7   13065 - 13071 2017.02

Research paper (scientific journal), Joint Work, Accepted

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Oriented Attachment of Calcite Nanocrystals: Formation of Single-Crystalline Configurations as 3D Bundles via Lateral Stacking of 1D Chains

M. Takasaki, Y. Oaki, H. Imai

Langmuir 33   1516 - 1520 2017.02

Research paper (scientific journal), Joint Work, Accepted

• Access to Document (DOI)

Stepwise Rotation of Nanometric Building Blocks in Aragonite Helix of a Pteropod Shell

M. Suzuki, T. Sasaki, Y. Oaki, H. Imai

Crystal Growth and Design 17   191 - 196 2017.01

Research paper (scientific journal), Joint Work, Accepted

• Access to Document (DOI)

Multistep Crystal Growth of Oriented Fluorapatite Nanorod Arrays for Fabrication of Enamel-Like Architectures on a Polymer Sheet

K. Nakamura, Y. Oaki, H. Imai

CrystEngComm 19   669 - 674 2017.01

Research paper (scientific journal), Joint Work, Accepted

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Stepwise Rotation of Nanometric Building Blocks in Aragonite Helix of a Pteropod Shell

IMAI HIROAKI

Crystal Growth and Design 17   191 - 196 2016.12

Optical Properties of Biosilicas in Rice Plants

K. Sato, A. Yamauchi, N. Ozaki, T. Ishigure, Y. Oaki, H. Imai

RSC Advances 6   109168 - 109173 2016

Research paper (scientific journal), Joint Work, Accepted

Plant Opal-Mimetic Bunching Silica Nanoparticles Mediated by Long-Chain Polyethyleneimine

T. Hoshino, K. Sato, Y. Oaki, A. Sugawara-Narutaki, K. Shimizu, N. Ozaki, H. Imai

RSC Advances 6   1301 - 1306 2016

Research paper (scientific journal), Joint Work, Accepted

Incorporation of Redox-Active Guest in Conductive and Redox-Active Host: Hierarchically Structured Composite of a Conductive Polymer and Quinone Derivative

K. Sato, Y. Oaki, H. Imai

Chemistry Letters 45   324 - 326 2016

Research paper (scientific journal), Joint Work

Selectively Assembled 2D Microarrays from Binary Nanocrystals

C. Hou, T. Liua, Y. Fan, H. Imai, R. Fan, H. Lin, Q. He, N. Wang, F. Dang, Z. Guo,

CrystEngComm 18   3008 - 3014 2016

Research paper (scientific journal), Joint Work, Accepted

Intercalation-Induced Tunable Stimuli-Responsive Color-Change Properties of Crystalline Organic Layered Compound

M. Okaniwa, Y. Oaki, H. Imai

Advanced Functional Materials 26   3463 - 3471 2016

Research paper (scientific journal), Joint Work, Accepted

Orientation-Selective Alignments of Nanoblocks in a and c Directions of Tetragonal System through Molecularly Mediated Manipulation

Y. Nakagawa, H. Kageyama, Y. Oaki, H. Imai

Chemical Communications 52   5597 - 5600 2016

Research paper (scientific journal), Joint Work, Accepted

Orientation-Selective Alignments of Hydroxyapatite Nanoblocks through Epitaxial Attachment in a and c Directions

K. Nakamura, Y. Nakagawa, H. Kageyama, Y. Oaki, H. Imai

Langmuir 32   4066 - 4070 2016

Research paper (scientific journal), Joint Work, Accepted

Tuning of photocatalytic reduction by conduction band engineering of semiconductor quantum dots with experimental evaluation of band edge potential

T. Suzuki, H. Watanabe, Y. Oaki, H. Imai

Chemical Communications 52   6185 - 6188 2016

Research paper (scientific journal), Joint Work, Accepted

UV-induced Epitaxial Attachment of TiO2 Nanocrystals in Molecularly Mediated 1D and 2D Alignments

T. Hiraide, H. Kageyama, Y. Nakagawa, Y. Oaki, H. Imai

Chemical Communications 52   7545 - 7548 2016

Research paper (scientific journal), Joint Work, Accepted

Aragonite Nanorod Arrays through Molecular Controlled Growth on Single-Crystalline Substrate and Polysaccharide Surface

M. Suzuki, Y. Oaki, H. Imai,

Crystal Growth and Design 16   3741 - 3747 2016

Research paper (scientific journal), Joint Work, Accepted

Tunable photochemical properties of a covalently anchored and spatially confined organic polymer in a layered compound

H. Matsui, Y. Oaki, H. Imai

Nanoscale 8   11076 - 11083 2016

Research paper (scientific journal), Joint Work, Accepted

1D Oriented Attachment of Calcite Nanocrystals: Formation of Single-Crystalline Rods through Collision

M. Takasaki, Y. Kimura, Y. Yamazaki, Y. Oaki, H. Imai

RSC Advances 6   61346 - 61350 2016

Research paper (scientific journal), Joint Work

Surface-functionalized hydrophilic monolayer of titanate and its application to dopamine detection, Chemical Communications

H. Matsui, Y. Oaki, H. Imai

Chemical Communications 52   9466 - 9469 2016

Research paper (scientific journal), Joint Work, Accepted

Dendritic Growth of NaCl Crystals in a Gel Matrix: Variation of Branching and Control of Bending

M. Goto, Y. Oaki, H. Imai

Crystal Growth and Design 16   4278 - 4284 2016

Research paper (scientific journal), Joint Work, Accepted

Mesostructured crystals: Growth processes and features

H. Imai

Progress in Crystal Growth and Characterization of Materials 62   212 - 226 2016

Research paper (scientific journal), Joint Work, Accepted

Evaporation-Driven Regularization of Crystallographically Ordered Arrangements of Truncated Nanoblocks: From 1D Chains to 2D Rhombic Superlattices

R. Matsumoto, Y. Nakagawa, H. Kageyama, Y. Oaki, H. Imai

CrystEngComm 18   6138 - 6142 2016

Research paper (scientific journal), Joint Work, Accepted

Mesoscopic Crystallographic Textures on Shells of a Hyaline Radial Foraminifer Ammonia beccarii

K. Nakajima, Y. Nagai, M. Suzuki, Y. Oaki, K. Naito, Y. Tanaka, T. Toyofuku, H. Imai

CrystEngComm 18   7135 - 7139 2016

Research paper (scientific journal), Joint Work, Accepted

Bio-inspired synthesis of xLi2MnO3-(1−x) LiNi0.33Co0.33Mn0.33O2 lithium-rich layered cathode materials

C. Hou, Y. Oaki, E. Hosono, H. Lin, H. Imai

Materials and Design 109   718 - 725 2016

Research paper (scientific journal), Joint Work, Accepted

Switchable Oriented Attachment and Detachment of Calcite Nanocrystal

M. Takasaki, Y. Oaki, H. Imai

CrystEngComm 18   8999 - 9002 2016

Research paper (scientific journal), Joint Work, Accepted

Surface-functionalized monolayered nanodots of a transition metal oxide and their properties

M. Honda, Y. Oaki, H. Imai

Physical Chemistry Chemical Physics 17   32498 - 32504 2015

Research paper (scientific journal), Joint Work, Accepted

Incorporation of Organic Crystals in the Interspace of Oriented Nanocrystals: Morphologies and Properties

Yurika Munekawa, *Yuya Oaki, Kosuke Sato and *Hiroaki Imai

Nanoscale 7   3466 - 3473 2015

Research paper (scientific journal), Joint Work, Accepted

Hierarchical CaCO3 Chromatography: A Stationary Phase Based on Biominerals

Kosuke Sato, *Yuya Oaki, Daisuke Takahashi, Kazunobu Toshima, *Hiroaki Imai

Chem. Eur. J. 21   5034 - 5040 2015

Research paper (scientific journal), Joint Work, Accepted

An Advanced Biomimetic Approach for Crystal Growth in Nonaqueous Media: Morphology and Orientation Control of Pentacosadiynoic Acid and the Applications

Mamoru Okaniwa, *Yuya Oaki, Soichiro Kaneko, Kazuki Ishida, Hideyuki Maki and *Hiroaki Imai

Chem. Mater. 27   2627 - 2632 2015

Research paper (scientific journal), Joint Work, Accepted

Microwave-assisted rapid synthesis of anatase TiO2 nanosized particles in an ionic liquid-water system

A. Suzuki, H. Yamaguchi, H. Kageyama, Y. Oaki, H. Imai

Journal of the Ceramic Society of Japan 123   79 - 82 2015

Research paper (scientific journal), Joint Work, Accepted

Switchable Dispersivity and Molecular-Trapping Performance of Mesostructured CaCO3/Thermosensitive Polymer Composite Microspheres

A. Inoue, H. Tamagawa, S.Aoshima, Y. Oaki, H. Imai

Journal of Materials Chemistry B 3   3604 - 3608 2015

Research paper (scientific journal), Joint Work, Accepted

A hydrophobic adsorbent based on hierarchical porous polymers derived from morphologies of a biomineral

K. Sato, Y. Oaki, H. Imai

Chemical Communications 51   7919 - 7922 2015

Research paper (scientific journal), Joint Work, Accepted

Oscillatory Growth for Twisting Crystal

S. Ibaraki, R. Ise, K. Ishimori, Y. Oaki, G. Sazaki, E. Yokoyama, K. Tsukamoto, H. Imai

Chemical Communications 51   8516 - 8519 2015

Research paper (scientific journal), Joint Work, Accepted

Dynamic Adsorption of Toluene on Pore-Size Tuned Supermicroporous Silicas

H. Watanabe, K. Fujikata, Y. Oaki, H. Imai

Microporous & Mesoporous Materials 214   41 - 44 2015

Research paper (scientific journal), Joint Work, Accepted

Hydrophobic monolayered nanoflakes of tungsten oxide: Coupled exfoliation and fracture in a nonpolar organic medium

M. Honda, Y. Oaki, H. Imai

Chemical Communications 51   10046 - 10049 2015

Research paper (scientific journal), Joint Work, Accepted

Crystal-surface-induced simultaneous synthesis and hierarchical morphogenesis of conductive polymers

K. Kuwabara, Y. Oaki, H. Imai

Chemical Communications 51   9698 - 9701 2015

Research paper (scientific journal), Joint Work, Accepted

Formation of Monocrystalline 1D and 2D Architectures via Epitaxial Attachment: Bottom-Up Routes through Surfactant-Mediated Arrays of Oriented Nanocrystal

Y. Nakagawa, H. Kageyama, Y. Oaki, H. Imai

Langmuir 31   6197 - 6201 2015

Research paper (scientific journal), Joint Work, Accepted

Controlled Radical Polymerization of Styrene with Magnetic Iron Oxides Prepared through Hydrothermal, Bioinspired, and Bacterial Processes

A. Kanazawa, K. Satoh, S. Kanaoka, M. Kakihana, M. Kobayashi, J. Sato, H. Imai, Y. Oaki, A. Arakaki, K. Katagiri, M. Kamigaito, S. Aoshima

RSC Advances 5   51122 - 51129 2015

Research paper (scientific journal), Joint Work, Accepted

Fabrication of nanocellulose/hydroxyapatite composites and their application as water-resistant transparent coatings

IMAI HIROAKI

Journal of Materials Chemistry B 3   5858 - 5863 2015

Research paper (scientific journal), Joint Work, Accepted

Fabrication of Self-Standing Films Consisting of Enamel-Like Oriented Nanorods Using Artificial Peptide

K. Aita, Y. Oaki, C. Ohtsuki, H. Imai

CrystEngComm 17   5551 - 5555 2015

Research paper (scientific journal), Joint Work, Accepted

Fabrication of Transparent ZnO Thick Film with Unusual Orientation by the Chemical Bath Deposition

T. Morita, S. Ueno, T. Tokunaga, E. Hosono, Y. Oaki, H. Imai, H. Matsuda, H. Zhou, M. Hagiwara, S. Fujihara

Crystal Growth and Design 15   3150 - 3156 2015

Research paper (scientific journal), Joint Work, Accepted

Morphology and Orientation Control of Organic Crystals in Organic Media through Advanced Biomimetic Approach

M. Okaniwa, H. Kageyama, Y. Oaki, H. Imai

Bulletin of the Chemical Society of Japan 88   1459 - 1465 2015

Research paper (scientific journal), Joint Work, Accepted

Variation in Mesoscopic Textures of Biogenic and Biomimetic Calcite Crystals

R. Miyajima, Y. Oaki, T. Kogure, H. Imai

Crystal Growth and Design 15   3755 - 3761 2015

Research paper (scientific journal), Joint Work, Accepted

Application of Biogenic Iron Phosphate for Lithium-Ion Battery

H. Kageyama, Y. Hashimoto, S. Saito, Y. Konishi, Y. Oaki, H. Imai

RSC Advances 5   68751 - 68757 2015

Research paper (scientific journal), Joint Work, Accepted

Inverse pH-Response of Temperature-Sensitive Copolymers by Combination with Porous CaCO3 Framework

H. Tamagawa, H. Kageyama, Y. Oaki, Y. Hoshino, Y. Miura, H. Imai

Chemistry Letters 44   1425 - 1427 2015

Research paper (scientific journal), Joint Work, Accepted

Formation of Uniformly Sized Metal Oxide Nanocuboids in the Presence of Precursor Grains in an Apolar Medium

Y. Nakagawa, H. Kageyama, Y. Oaki, H. Imai

CrystEngComm 17   7477 - 7481 2015

Research paper (scientific journal), Joint Work, Accepted

VOC decomposition over a wide range of temperatures using thermally stable Cr6+ sites in a porous silica matrix

S. Somekawa, H. Watanabe, Y. Oaki, H. Imai

Catalysis Communications 72   161 - 164 2015

Research paper (scientific journal), Joint Work, Accepted

Six-Armed Twin Crystals Composed of Lithium Iron Silicate Nanoplates and Their Electrochemical Properties

H. Kageyama, Y. Hashimoto, Y. Oaki, H. Imai

CrystEngComm 17   8486 - 8491 2015

Research paper (scientific journal), Joint Work, Accepted

Conductive polymer-mediated 2D and 3D arrays of Mn3O4 nanoblocks and mesoporous conductive polymers as their replicas

Y. Nakagawa, H. Kageyama, R. Matsumoto, Y. Oaki, H. Imai

Nanoscale 7   18471 - 18476 2015

Research paper (scientific journal), Joint Work, Accepted

Nano-sized cube-shaped single crystalline oxides and their potentials; composition, assembly and functions

K. Kato, F. Dang, K. Mimura, Y. Kinemuchi, H. Imai, S. Wada, M. Osada, H. Haneda, M. Kuwabara

Advanced Powder Technology 25   1401 - 1414 2014

Research paper (scientific journal), Joint Work, Accepted

An Experimental Study on the Processes of Hierarchical Morphology Replication by Means of a Mesocrystal: A Case Study of poly(3,4-ethylenedioxythiophene)

Yurika Munekawa, Yuya Oaki and Hiroaki Imai

Langmuir 30   3236 - 3242 2014

Research paper (scientific journal), Joint Work, Accepted

Hydrophobic Inorganic-Organic Composite Nanosheets Based on Monolayers of Transition Metal Oxides

Masashi Honda, *Yuya Oaki, *Hiroaki Imai

Chem. Mater. 26   3579 - 3585 2014

Research paper (scientific journal), Joint Work, Accepted

Solvent-free Synthesis, Coating and Morphogenesis of Conductive Polymer Materials through Spontaneous Generation of Activated Monomers

Ryo Muramatsu, *Yuya Oaki, Kento Kuwabara, Kosei Hayashi, *Hiroaki Imai

Chem. Commun. 50   11840 - 11843 2014

Research paper (scientific journal), Joint Work, Accepted

Size-Dependent Thermochromism through Enhanced Electron-Phonon Coupling in 1 nm Quantum Dots

Haruna Tamaki, Hiroto Watanabe, Sachiko Kamiyama, Yuya Oaki and *Hiroaki Imai

Angew. Chem. Int. Ed. 53   10706 - 10709 2014

Research paper (scientific journal), Joint Work, Accepted

Basicity-controlled Synthesis of Li4Ti5O12 Nanocrystals by a Solvothermal Method

Hiroyuki Kageyama, Yuya Oaki, *Hiroaki Imai

RSC Adv. 4   44124 - 44129 2014

Research paper (scientific journal), Joint Work, Accepted

Polymer-mediated Dendritic Growth of a Transition Metal Salt Crystal as a Template for Morphogenesis

*Yuya Oaki, Ryo Muramatsu, and *Hiroaki Imai

Polym. J. 47   183 - 189 2014

Research paper (scientific journal), Joint Work, Accepted

Mesocrystals and Their Related Structures as Intermediates between Single Crystals and Polycrystals

IMAI HIROAKI

J. Ceram. Soc. Japan 122   737 - 747 2014

Accepted

鉄酸化細菌を模倣したプロセスによる多様な酸化鉄の合成と応用

IMAI HIROAKI

セラミックス 49   446 - 449 2014

Research paper (scientific journal), Joint Work, Accepted

Direction control of oriented self-assembly for 1D, 2D, and 3D microarrays of anisotropic rectangular nanoblocks

Y. Nakagawa, H. Kageyama, Y. Oaki, H. Imai

Journal of the American Chemical Society 136   3716 - 3719 2014

Research paper (scientific journal), Joint Work, Accepted

Synthesis and Morphogenesis of Organic and Inorganic Polymers by Means of Biominerals and Biomimetic Materials

M. Kijima, Y. Oaki, Y. Munekawa, H. Imai

Chemistry- A European Journal 19   2284 - 2283 2013

Research paper (scientific journal), Joint Work, Accepted

Artificial peptides binding to the c face of hydroxyapatite obtained by molecular display

Shohei Ono, Toru Tsuji, Yuya Oaki, and Hiroaki Imai

RSC Advances 3   1885-1889 2013

Research paper (scientific journal), Joint Work, Accepted

Monolayered Nanodots of Transition Metal Oxides

Keisuke Nakamura, Yuya Oaki, and Hiroaki Imai

Journal of the American Chemical Society 135   4501-4508 2013

Research paper (scientific journal), Joint Work, Accepted

Formation of Nanostructured MnO/Co/Solid–Electrolyte Interphase Ternary Composites as a Durable Anode Material for Lithium-Ion Batteries

Feng Dang, Yuya Oaki, Takao Kokubu, Eiji Hosono, Haoshen Zhou, and Hiroaki Imai

Chemistry–An Asian Journal 8   760 - 764 2013

Research paper (scientific journal), Joint Work, Accepted

A Microbial-Mineralization Approach for Syntheses of Iron Oxides with a High Specific Surface Area

Naoki Yagita, Yuya Oaki, and Hiroaki Imai

Chemistry–A European Journal 19   4419-4422 2013

Research paper (scientific journal), Joint Work, Accepted

バイオミネラルにまなぶ材料化学

IMAI HIROAKI

農業機械学会誌 75 ( 1 ) 4-10 2013

Research paper (scientific journal), Joint Work, Accepted

Synthesis of Li–Mn–O Mesocrystals with Controlled Crystal Phases through Topotactic Transformation of MnCO3

Feng Dang, Tatsuhiko Hoshino, Yuya Oaki, Eiji Hosono, Haoshen Zhou, and Hiroaki Imai

Nanoscale 5   2352 - 2357 2013

Research paper (scientific journal), Joint Work, Accepted

Formation of Nanostructured MnO/Co/Solid–Electrolyte Interphase Ternary Composites as a Durable Anode Material for Lithium-Ion Batteries

Feng Dang, Yuya Oaki, Takao Kokubu, Eiji Hosono, Haoshen Zhou, and Hiroaki Imai

Chemistry–An Asian Journal 8   760 - 764 2013

Research paper (scientific journal), Joint Work, Accepted

A Microbial-Mineralization Approach for Syntheses of Iron Oxides with a High Specific Surface Area

Naoki Yagita, Yuya Oaki, and Hiroaki Imai

Chemistry–A European Journal 19   4419 - 4422 2013

Research paper (scientific journal), Joint Work, Accepted

Low-temperature syntheses of cubic BaTiO3 nanoparticles in highly basic aqueous solution

Hiroyuki Kageyama, Yuya Oaki, Yoko Takezawa, Toshimasa Suzuki and Hiroaki Imai

Journal of the Ceramic Society of Japan 121   388 - 392 2013

Research paper (scientific journal), Joint Work, Accepted

Formation of Trigonal Microarrays with Cubic Ba(NO3)2 in a Polymer Matrix

Ryuta Ise, Yuya Oaki, Hiroaki Imai

Journal of Ceramics Society of Japan 121   555 - 558 2013

Research paper (scientific journal), Joint Work, Accepted

Syntheses of LiCoO2 Mesocrystals via Topotactic Transformation and Their Improved Electrochemical Properties

Keisuke Nakajima, Yuya Oaki and Hiroaki Imai

ChemPlusChem 78   1379 - 1383 2013

Research paper (scientific journal), Joint Work, Accepted

Thin Film of CuO Mesocrystal Nanosheets: Microbial-Mineralization-Inspired Approaches Applied to Formation of Thin Films

Tatsuya Ikeda, Yuya Oaki and Hiroaki Imai

Chem. Asian J. 8   2064 - 2069 2013

Research paper (scientific journal), Joint Work, Accepted

Microscale Pin Holders of β-Co(OH)2 and LiCoO2 Having a Single-crystalline Feature

Keisuke Nakajima, Yuya Oaki and Hiroaki Imai

CrystEngComm 15   6465 - 6468 2013

Research paper (scientific journal), Joint Work, Accepted

Spontaneous Formation of 2D Micropatterns with Straight and/or Curving Dendrites through Crystal Growth of Ba(NO3)2 in Polymer Matrix

Daijiro Tokutomi, Ryuta Ise, Yuya Oaki, Hiroaki Imai

Crystal Growth and Design 13   3011 - 3017 2013

Research paper (scientific journal), Joint Work, Accepted

A Microbial-Mineralization-Inspired Approach for Systematic Syntheses of Copper Oxides with Controlled Morphologies in an Aqueous Solution at Room Temperature

Yuya Oaki, Tatsuya Ikeda and Hiroaki Imai

Bull. Chem. Soc. Jpn. 86   821 - 828 2013

Research paper (scientific journal), Joint Work, Accepted

Monolayered Nanodots of Transition Metal Oxides

Keisuke Nakamura, Yuya Oaki and Hiroaki Imai

J. Am. Chem. Soc. 135   4501 - 4508 2013

Research paper (scientific journal), Joint Work, Accepted

BaTiO3 nanocube and assembly to ferroelectric supracrystals

K. Kato, K. Mimura, F. Dang, H. Imai, S. Wada, M. Osada, H. Haneda, M. Kuwabara

Journal of Materials Research 28   2932 - 2945 2013

Research paper (scientific journal), Joint Work, Accepted

Band-Gap Expansion of Tungsten Oxide Quantum Dots Synthesized in Sub-nano Porous Silica

H. Watanabe, K. Fujikata, Y. Oaki, H. Imai

Chemical Communications 49   8477 - 8479 2013

Research paper (scientific journal), Joint Work, Accepted

Formation of c-axis-oriented columnar structures through controlled epitaxial growth of hydroxyapatite

W. Wang, Y. Oaki, C. Ohtsuki, T. Nakano, H. Imai

Journal of Asian Ceramic Societies 1   143 - 148 2013

Research paper (scientific journal), Joint Work, Accepted

バイオミネラリゼーションにならう無機結晶の合成―分子制御による構造構築―

IMAI HIROAKI

高分子 62 ( 2月 ) 79-81 2012

Research paper (scientific journal), Joint Work, Accepted

Oriented Nanocrystal Mosaic in Monodispersed CaCO3 Microspheres with Functional Organic Molecules

Hiroaki Imai, Natsuki Tochimoto, Yuichi Nishino, Yoko Takezawa, and Yuya Oaki

Crystal Growth & Design 12   876-882 2012

Research paper (scientific journal), Joint Work, Accepted

Electrically Guided Microweb Formation with Ag Nanofibers under UV Irradiation and Its Application to Electrochemical and Plasmonic Devices

Masahiro Takeji, Yuya Oaki, and *Hiroaki Imai

Journal of Physical Chemistry C 116   6103-6107 2012

Research paper (scientific journal), Joint Work, Accepted

One-Pot Aqueous Solution Syntheses of Iron Oxide Nanostructures with Controlled Crystal Phases through a Microbial-Mineralization-Inspired Approach

Yuya Oaki, Naoki Yagita, and Hiroaki Imai

Chemistry–A European Journal 18   110-116 2012

Research paper (scientific journal), Joint Work, Accepted

Mesocrystal Nanosheet of Rutile TiO2 and Its Reaction Selectivity as a Photocatalyst

Yuka Aoyama, Yuya Oaki, Ryuta Ise, and Hiroaki Imai

CrystEngComm 14   1405-1411 2012

Research paper (scientific journal), Joint Work, Accepted

Homogeneous and Disordered Assembly of Densely Packed Titanium Oxide Nanocrystals: An Approach to Coupled Synthesis and Assembly in Aqueous Solution

Yuya Oaki, Keisuke Nakamura, and Hiroaki Imai

Chemistry–A European Journal 18   2825-2831 2012

Research paper (scientific journal), Joint Work, Accepted

Morphological Variation of Hydroxyapatite Grown in Aqueous Solution Based on Simulated Body Fluid

Toru Kobayashi, Shohei Ono, Shou Hirakura, Yuya Oaki, and Hiroaki Imai

CrystEngComm 14   1143-1149 2012

Research paper (scientific journal), Joint Work, Accepted

バイオミネラリゼーションにならう酸化物合成プロセス

IMAI HIROAKI

機能材料 32   48-55 2012

Research paper (scientific journal), Joint Work, Accepted

Self-Organization of Hollow-Coned Carbonate Crystals through Molecular Control by Using an Acid Organic Polymer

Yuya Oaki, Ryota Adachi, and *Hiroaki Imai

Polymer Journal 44   612-619 2012

Research paper (scientific journal), Joint Work, Accepted

Synthesis and Morphogenesis of Organic and Inorganic Polymers by Means of Biominerals and Biomimetic Materials

Misako Kijima, *Yuya Oaki, Yurika Munekawa, and *Hiroaki Imai

Chemistry–A European Journal 19   2284-2293 2012

Research paper (scientific journal), Joint Work, Accepted

Biologically Synthesized or Bioinspired Process-Derived Iron Oxides as Catalysts for Living Cationic Polymerization of Vinyl Ether

Arihiro Kanazawa, Shokyoku Kanaoka, Naoki Yagita, Yuya Oaki, Hiroaki Imai, Mayumi Oda, Atsushi Arakaki, Tadashi Matsunaga, and Sadahito Aoshima

Chemical Communications 48   10904-10906 2012

Research paper (scientific journal), Joint Work, Accepted

Enhanced Photoconductive Properties on a Simple Composite Coaxial Nanostructure of Zinc Oxide and Polypyrrole

Yuya Oaki, Takahiro Oki, and Hiroaki Imai

Journal of Materials Chemistry 22   21195-21200 2012

Research paper (scientific journal), Joint Work, Accepted

Morphology and Orientation Control of Guanine Crystals: A Biogenic Architecture and Its Structure Mimetics

Yuya Oaki, Soichiro Kaneko, and Hiroaki Imai

Journal of Materials Chemistry 22   22686–22691 2012

Research paper (scientific journal), Joint Work, Accepted

ZnO nano-rectangular framework-like structure from zinc hydroxide acetate plates

Eiji Hosono, Takashi Tokunaga, Shintaro Ueno, Yuya Oaki, Hiroaki Imai, *Haoshen Zhou, and *Sinobu Fujihara

Journal of the Ceramics Society of Japan 120   171-174 2012

Research paper (scientific journal), Joint Work, Accepted

Crystal-Growth Process of Single-Crystal-like Mesoporous ZnO through a Competitive Reaction in Solution

Eiji Hosono, Takashi Tokunaga, Shintaro Ueno, Yuya Oaki, Hiroaki Imai, Haoshen Zhou, and Sinobu Fujihara

Crystal Growth & Design 12   2923-2931 2012

Research paper (scientific journal), Joint Work, Accepted

Spontaneous Formation of Sinuous and Wavy Micropatterns with Helical Growth of CuSO4•5H2O in Polymer Matrix

Ryuta Ise, Yuya Oaki, and Hiroaki Imai

Crystal Growth & Design 12   4397-4402 2012

Research paper (scientific journal), Joint Work, Accepted

Twisted growth of organic crystal in a polymer matrix: sigmoidal and helical morphologies of pyrene

Soichiro Ibe, Ryuta Ise, Yuya Oaki, and Hiroaki Imai

CrystEngComm 14   7444-7449 2012

Research paper (scientific journal), Joint Work, Accepted

バイオミネラリゼーションにならう酸化物合成プロセス

IMAI HIROAKI

機能材料 32   48-55 2012

Research paper (scientific journal), Joint Work, Accepted

Preparation of Thin-film Hydroxyapatite/Polymer Hybrids

Tatsuya Nishimura, Hirotaka Imai, Yuya Oaki, Takeshi Sakamoto, and Takashi Kato

Chemistry Letters 40   458–460 2011

Research paper (scientific journal), Joint Work, Accepted

Control of Cellular Activity of Fibroblasts on Size-Tuned Fibrous Hydroxyapatite Nanocrystals

Shinnoske Okada, Atsushi Nagai, Yuya Oaki, Jun Komotori, and Hiroaki Imai

Acta Biomaterialia 7   1290-1297 2011

Research paper (scientific journal), Joint Work

In vitro Repairing of a Biomineral with Mesocrystal Structure

Misako Kijima, Yuya Oaki, and Hiroaki Imai

Chemistry–A European Journal 17   2828-2832 2011

Research paper (scientific journal), Joint Work, Accepted

充放電を繰り返しても劣化の少ない電極材料

IMAI HIROAKI

化学 66   74 2011

Research paper (scientific journal), Single Work

Synthesis and Morphogenesis of Organic Polymer Materials with Hierarchical Structures in Biominerals

Yuya Oaki, Misako Kijima, and *Hiroaki Imai

Journal of the American Chemical Society 133   8594-8599 2011

Research paper (scientific journal), Joint Work, Accepted

Biomimetic Solid-Solution Precursors of Metal Carbonate for Nanostructured Metal Oxides: MnO/Co and MnO-CoO Nanostructures and Their Electrochemical Properties

Takao Kokubu, Yuya Oaki, Eiji Hosono, *Haoshen Zhou, and *Hiroaki Imai

Advanced Functional Materials 21   3673-3680 2011

Research paper (scientific journal), Joint Work, Accepted

Aqueous solution synthesis of SnO nanosheets and their photoelectrochemical and electrochemical properties

K. Sakaushi, Y. Oaki, H. Uchiyama, E. Hosono, H. Zhou, H. Imai

Small 6   776-781 2010

Research paper (scientific journal), Joint Work, Accepted

Adhesion of osteoblast-like cells on nanostructured hydroxyapatite

S. Okada, H. Ito, A. Nagai, J. Komotori, H. Imai

Acta Biomaterialia 6   591-597 2010

Research paper (scientific journal), Joint Work, Accepted

Biomimetic synthesis of metal ion-doped hierarchical crystals using a gel matrix: formation of cobalt-doped LiMn₂O₄ via cobalt-doped MnCO₃ precursor and the improved electrochemical properties

T. Kokubu, H. Uchiyama, Y. Oaki, E. Hosono, H. Zhou, H. Imai

Chemistry - An Asian Journal 5 2010

Research paper (scientific journal), Joint Work, Accepted

Optically transparent superhydrophobic TEOS-derived silica films by surface silylation method

S. S. Latthe, H. Imai, V. Ganesan, C. Kappenstein, A. V. Rao

Journal of Sol-Gel Science and Technology 53   208-215 2010

Research paper (scientific journal), Joint Work, Accepted

Control on wetting properties of spin-deposited silica films by surface silylation method

A. V. Rao, S. S. Latthe, S. L. Dhere, S. S. Pawar, H. Imai, V. Ganesan, S. C. Gupta, P. B. Wagh

Applied Surface Science 256   2115-2121 2010

Research paper (scientific journal), Joint Work, Accepted

A new effect of ultrasonication on the formation of BaTiO₃ nanoparticles

Dang, K. Kato, H. Imai, S. Wada, H. Haneda, M. Kuwabara

Ultrasonics Sonochemistry 17   310-314 2010

Research paper (scientific journal), Joint Work, Accepted

Bioinspired Hierarchical Crystals

Hiroaki Imai, Yuya Oaki

MRS Bulletin 35   138-144 2010

Research paper (scientific journal), Joint Work, Accepted

Characteristics of CeO2 Nanocubes and Related Polyhedra Prepared by Using a Liquid-Liquid Interface

Feng Dang, Kazumi Kato, Hiroaki Imai, Satoshi Wada, Hajime Haneda, and Makoto Kuwabara

Crystal Growth and Design 10   4537-4541 2010

Research paper (scientific journal), Joint Work, Accepted

Aqueous Solution Synthesis of SnO Nanostructures with Tuned Optical Absorption Behavior and Photoelectrochemical Properties through Morphological Evolution

Ken Sakaushi, Yuya Oaki, Hiroaki Uchiyama, Eiji Hosono, Haoshen Zhou, and Hiroaki Imai

Nanoscale 2   2424-2430 2010

Research paper (scientific journal), Joint Work, Accepted

Homogeneous and Disordered Assembly of Densely-Packed Nanocrystals

Yuya Oaki, Takeo Anzai, and Hiroaki Imai

Advanced Functional Materials 20   4127-4132 2010

Research paper (scientific journal), Joint Work, Accepted

A Microbial-Mineralization-Inspired Approach for Synthesis of Manganese Oxide Nanostructures with Controlled Oxidation States and Morphologies

Manabu Oba, Yuya Oaki, and *Hiroaki Imai

Advanced Functional Materials 20   4279-4286 2010

Research paper (scientific journal), Joint Work, Accepted

バイオミネラルに学ぶメソクリスタルの合成と応用

IMAI HIROAKI

触媒 53   44-48 2010

Research paper (scientific journal), Joint Work, Accepted

Nanoscale Morphological Design of ZnO Crystals Grown in Aqueous Solutions

Tetsuo Kawano and Hiroaki Imai

Journal of the Ceramic Society of Japan 118   969-976 2010

Research paper (scientific journal), Joint Work, Accepted

Enhanced photocatalytic activity of quantum-confined tungsten trioxide nanoparticles in mesoporous silica

D. Tanaka, Y. Oaki, H. Imai

Chemical Communications 46   5286-5288 2010

Research paper (scientific journal), Joint Work, Accepted

Specific Photocatalytic Performance of Nanostructured Rutile-Type TiO2: Selective Oxidation of Thiazin Dye with a Bundled Architecture onsisting of Oriented Nanoneedles

Y. Tokunaga, H. Uchiyama, Y. Oaki, H. Imai

Science of Advanced Materials 2   69-73 2010

Research paper (scientific journal), Joint Work, Accepted

Fibrous nanocrystals of hydroxyapatite loaded with TiO2 nanoparticles for the capture and photocatalytic decomposition of specific proteins

S. Hirakura, T. Kobayashi, S. Ono, Y. Oaki, H. Imai

Colloids and Surfaces B: Biointerfaces 79   131-135 2010

Research paper (scientific journal), Joint Work, Accepted

Preparation of LiFePO4 Mesocrystals Consisting of Nanorods through Organic-Mediated Parallel Growth from a Precursor Phase

H. Uchiyama, H. Imai

Crystal Growth and Design 10   1777-1781 2010

Research paper (scientific journal), Joint Work, Accepted

Emergence of helical morphologies with crystals: twisted growth under diffusion-limited conditions and chirality control with molecular recognition

H. Imai, Y. Oaki

Crystal Engineering Communications 12   1679-1687 2010

Research paper (scientific journal), Joint Work, Accepted

メソクリスタル

IMAI HIROAKI

化学 64   68-69 2009

Research paper (scientific journal), Single Work

Lithium insertion into nanometer-sized rutile-type Ti_xSn_1−xO₂ solid solutions

H. Uchiyama, E. Hosono, H. Zhou, H. Imai

Solid State Ionics 180   956-960 2009

Research paper (scientific journal), Joint Work, Accepted

Photochemical reactions in nanoscopic organic domains generated from oriented crystals with polymers: nanocrystalline mosaics as a new family of host materials

Y. Oaki, H. Imai

The Bulletin of the Chemical Society of Japan 82   613–617 2009

Research paper (scientific journal), Joint Work, Accepted

Epitaxial growth of winding ZnO nanowires on a single-crystalline substrate

T. Kawano, H. Uchiyama, T. Kiguchi, S. Wada, H. Imai

Journal of the Ceramic Society of Japan 117   255-257 2009

Research paper (scientific journal), Joint Work, Accepted

Magnesium-mediated nanocrystalline mosaics of calcite

Y. Nishino, Y. Oaki, H. Imai

Crystal Growth and Design 9   223-226 2009

Research paper (scientific journal), Joint Work, Accepted

バイオミネラル類似ナノ結晶集積体の合成

IMAI HIROAKI

セラミックス 44   626-629 2009

Research paper (scientific journal), Single Work, Accepted

Three-dimensional architectures of spinel-type LiMn₂O₄ prepared from biomimetic porous carbonates and their application to a cathode for lithium-ion batteries

H. Uchiyama, E. Hosono, H. Zhou, H. Imai

Journal of Materials Chemistry 19   4012-4016 2009

Research paper (scientific journal), Joint Work, Accepted

Mn-doped BaTiO₃ thin films sintered using nanocrystals and its dielectric properties

Y. Takewzawa, K. Kobayashi, F. Nakasone, T. Suzuki, Y. Mizuno, H. Imai

Japanese Journal of Applied Physics 48   111408 2009

Research paper (scientific journal), Joint Work, Accepted

Characteristics of BaTiO₃ particles sonochemically-synthesized in aqueous solution

F. Dang, K. Kato, H. Imai, S. Wada, H. Haneda, M. Kuwabara

Japanese Journal of Applied Physics 48   09KC02 2009

Research paper (scientific journal), Joint Work, Accepted

Superhydrophobic silica films by sol-gel co-precursor method

S. S. Latthe, H. Imai, V. Ganesan, A. V. Rao

Applied Surface Science 256   217-222 2009

Research paper (scientific journal), Joint Work, Accepted

Ultralow refractive index coatings consisting of mesoporous silica nanoparticles

M. Yamaguchi, H. Nakayama, K. Yamada, H. Imai

Optics Letters 34   2060-2062 2009

Research paper (scientific journal), Joint Work, Accepted

A nanoscale meshed electrode of single-crystalline SnO for lithium-ion rechargeable batteries

H. Uchiyama, E. Hosono, I. Honma, H. Zhou, H. Imai

Electrochemistry Communications 10   52-55 2008

Research paper (scientific journal), Joint Work, Accepted

Nanoparticle-sintered BaTiO₃ thin films and its orientation control by solid phase epitaxy

F. Nakasone, K. Kobayashi, T. Suzuki, Y. Mizuno, H. Chazono, H. Imai

Japanese Journal of Applied Physics 47   8518-8524 2008

Research paper (scientific journal), Joint Work, Accepted

Nanosegregated amorphous composites of calcium carbonate and an organic polymer

Y. Oaki, S. Kajiyama, T. Nishimura, H. Imai, T. Kato

Advanced Materials 20   3633-3637 2008

Research paper (scientific journal), Joint Work, Accepted

Matrix-mediated formation of hierarchically structured SnO crystals as intermediates between single crystals and polycrystalline aggregates

H. Uchiyama, H. Imai

Langmuir 24   9038-9042 2008

Research paper (scientific journal), Joint Work, Accepted

Formation of e-Fe₂O₃ nanocrystals through segregation in mesoporous silica particles

K. Mori, Y. Oaki, M. Suda, Y. Einaga, H. Imai

Chemistry Letters 37   814-815 2008

Research paper (scientific journal), Joint Work, Accepted

Photoluminescence of nitrogen-doped anatase

T. Okumura, H. Uchiyama, H. Imai

Materials Chemistry and Physics 111   486-490 2008

Research paper (scientific journal), Joint Work, Accepted

A simple preparation technique for shape-controlled zinc oxide nanoparticles: Formation of narrow size-distributed nanorods using seeds in aqueous solutions

T. Kawano, H. Imai

Colloids and Surfaces A: Physicochemical and Engineering Aspects 319   130-135 2008

Research paper (scientific journal), Joint Work, Accepted

ペルヒドロポリシラザンから作製したSiO₂膜の構造分析と生体活性能の評価

土師正聖、上出篤、小茂鳥潤、仙名保、今井宏明、進藤豊彦

材料 57   174-180 2008

Research paper (scientific journal), Joint Work, Accepted

Selective production of various morphologies of hydroxyapatite via an intermediate phase

H. Ito, Y. Oaki, H. Imai

Crystal Growth and Design 8   1055-1059 2008

Research paper (scientific journal), Joint Work, Accepted

バイオミネラルとナノ結晶集積体

IMAI HIROAKI

日本接着学会誌 43   405-411 2007

Research paper (scientific journal), Single Work, Accepted

Biomimetic morphological design for manganese oxide and cobalt hydroxide nanoflakes having a mosaic interior

IMAI HIROAKI, YUYA OAKI

Journal of Materials Chemistry 17   316-321 2007

Research paper (scientific journal), Joint Work, Accepted

Nanometric morphological variation of zinc oxide crystals using organic molecules with carboxy and sulfonic groups

IMAI HIROAKI, JUNKO YAHIRO, TETSUO KAWANO

Journal of Colloid and Interface Science 310   302-311 2007

Research paper (scientific journal), Joint Work, Accepted

Stereospecific morphogenesis of aspartic acid helical crystals through molecular recognition

IMAI HIROAKI, YUYA OAKI

Langmuir 23   5466-5470 2007

Research paper (scientific journal), Joint Work, Accepted

One-pot synthesis of manganese oxide nanosheets in an aqueous solution: chelation-mediated parallel control of reaction and morphology toward a novel green route

IMAI HIROAKI, YUYA OAKI

Angewandte Chemie-International Edition 46   4951-4955 2007

Research paper (scientific journal), Joint Work, Accepted

Tin oxide meshes consisting of nanoribbons prepared through an intermediate phase in an aqueous solution

IMAI HIROAKI, HIROAKI UCHIYAMA

Crystal Growth and Design 7   841-843 2007

Research paper (scientific journal), Joint Work, Accepted

A herarchical self-similar structure of oriented calcite with association of an agar gel matrix: Inheritance of crystal habit from nanoscale

IMAI HIROAKI, SHINICHIRO HAYASHI, YUYA OAKI

Chemical Communications    2841-2843 2007

Research paper (scientific journal), Joint Work, Accepted

Chelation-mediated aqueous synthesis of metal oxyhydroxide and oxide nanostructures: combination of ligand-controlled oxidation and -cooperative morphogenesis

IMAI HIROAKI, YUYA OAKI

Chemistry - A European Journal 13   8564-8571 2007

Research paper (scientific journal), Joint Work, Accepted

Structural control on crystal growth of titanate in aqueous system: selective production of nanostructures of layered titanate and anatase-type titania

IMAI HIROAKI, YOKO TAKEZAWA

Journal of Crystal Growth 308   117–121 2007

Research paper (scientific journal), Joint Work, Accepted

Photocatalytic activities of rutile and anatase nanoparticles selectively prepared from an aqueous solution

IMAI HIROAKI, MUNEHIRO SAKANOUE, YOSUHIRO KINOSHITA, YUICHI OSTUKA

Journal of the Ceramic Society of Japan 115   ,821-825 2007

Research paper (scientific journal), Joint Work, Accepted

One-step synthesis of nano-micro chestnut TiO₂ with rutile nano-pin on the micro-anatase octahedron

E. Hosono, S. Fujihara, I. Honma, I. Masaki, H. Imai, H. Zhou

ACS Nano 1   273–278 2007

Research paper (scientific journal), Joint Work, Accepted

Self-organized formation of hierarchical structures

Hiroaki Imai

Topics in Current Chemistry 270   43-72 2007

Research paper (scientific journal), Single Work, Accepted

Selective preparation of SnO₂ and SnO crystals with controlled morphologies in an aqueous solution system

IMAI HIROAKI, HIROAKI UCHIYAMA

Crystal Growth and Design 6   2186-2190 2006

Research paper (scientific journal), Joint Work, Accepted

Control of nanoscale morphology of oxide crystals using aqueous solution systems

H. Imai, H Ohgi, Y. Takezawa, J. Yahiro

Key Engineering Materials 301   211-214 2006

Research paper (scientific journal), Joint Work, Accepted

Nanoengineering in echinoderms: Emergence of morphology from nanobricks

Y. Oaki, H. Imai

Small 2   66-70 2006

Research paper (scientific journal), Joint Work, Accepted

Low-temperature preparation of dye-sensitized solar cells through crystal growth of anatase titania in aqueous solutions

T. Watanabe, H. Hayashi, H. Imai

Solar Energy Materials and Solar Cells 90   640-648 2006

Research paper (scientific journal), Joint Work, Accepted

Bottom-up synthesis of titanate nanosheets having hierarchical structures with a high specific surface area

Y. Takezawa, H. Imai

Small 2   390-393 2006

Research paper (scientific journal), Joint Work, Accepted

Preparation of nanotextured and nanofibrous hydroxyapatite through dicalcium phosphate with gelatin

K. Furuichi, Y. Oaki, H. Imai

Chemistry of Materials 18   229-234 2006

Research paper (scientific journal), Joint Work, Accepted

Structural control of mesoporous silica nanoparticles in a binary surfactant system

K. Ikari, K. Suzuki, H. Imai

Langmuir 22   802-806 2006

Research paper (scientific journal), Joint Work, Accepted

Development of ordered calcium carbonate microarrays from polymorph specific planar films

A. Kotachi, H. Imai

Chemistry Letters 35   204-205 2006

Research paper (scientific journal), Joint Work, Accepted

Preparation of hierarchically organized calcium phosphate-organic polymer composites by calcification of hydrogel

K. Furuichi, Y. Oaki, H. Ichimiya, J. Komotori, H. Imai

Science and Technology of Advanced Materials 7   219-225 2006

Research paper (scientific journal), Joint Work, Accepted

Epitaxial growth of wurtzite ZnO crystals in an aqueous solution system

T. Kawano, J. Yahiro, H. Maki, H. Imai

Chemistry Letters 35   442-443 2006

Research paper (scientific journal), Joint Work, Accepted

Emergence of acute morphologies consisting of iso-oriented calcite nanobricks in a binary poly(acrylic acid) system

T. Miura, A. Kotachi, Y. Oaki, H. Imai

Crystal Growth and Design 6   612-615 2006

Research paper (scientific journal), Joint Work, Accepted

Fabrication of ZnO nanoparticles with various aspect ratios through acidic and basic routes

T. Kawano, H. Imai

Crystal Growth and Design 6   1054-1056 2006

Research paper (scientific journal), Joint Work, Accepted

Morphological design of zinc oxide films grown in aqueous solutions

J. Yahiro, H. Imai

Key Engineering Materials  2006

Research paper (scientific journal), Joint Work, Accepted

Polymorph control of calcium carbonate films in a poly(acrylic acid) - chitosan system

A. Kotachi, H. Imai

Crystal Growth and Design  2006

Research paper (scientific journal), Joint Work, Accepted

Room-temperature aqueous synthesis of highly luminescent BaWO₄/polymer nanohybrid and its spontaneous conversion to hexagonal WO₃ nanosheets

Y. Oaki, H. Imai

Advanced Materials  2006

Research paper (scientific journal), Joint Work, Accepted

Bridged-nanocrystals in biominerals and its mimetics: classical yet modern crystal growth in nanoscale

Y. Oaki, H. Imai

Advanced Functional Materials  2006

Research paper (scientific journal), Joint Work, Accepted

A biomimetic approach for hierarchically structured inorganic crystals through self-organization

H. Imai, Y. Oaki, A. Kotachi

Bulletin of the Chemical Society of Japan  2006

Research paper (scientific journal), Joint Work, Accepted

Relationship between mesostructures and pH conditions for the formation of silica-cationic surfactant complexes

S. Muto, H. Imai

Microporous & Mesoporous Materials  2006

Research paper (scientific journal), Joint Work, Accepted

無機結晶のらせん状成長とキラルな有機分子によるキラリティ制御

IMAI HIROAKI、Oaki Yuya

結晶成長学会誌 33   32-38 2006

Research paper (scientific journal), Joint Work, Accepted

Incorporation of dyes into silica-surfactant mesostructured nanoparticles as a nanoscale host material for organic molecules

IMAI HIROAKI,SIGEYUKI MUTO, YUYA OAKI

Chemistry Letters 35   880-881 2006

Research paper (scientific journal), Joint Work, Accepted

Biomimetic synthesis of wurtzite ZnO nanowires having a mosaic structure

IMAI HIROAKI, JUNKO YAHIRO, YUYA OAKI

Small 2   1183-1187 2006

Research paper (scientific journal), Joint Work, Accepted

Morphological evolution of inorganic crystal into zigzag and helical architectures with exquisite association of polymer: a novel approach for morphological complexity

Y. Oaki, H. Imai

Langmuir (The American Chemical Society)  21   863-869 2005

Research paper (scientific journal), Joint Work, Accepted

Anisotropic growth of silver crystals with ethylenediamine tetraacetate and formation of planar and stacked wires

H. Imai, H. Nakamura, T. Fukuyo

Crystal Growth and Design (The American Chemical Society)  5   1073-1077 2005

Research paper (scientific journal), Joint Work, Accepted

Fabrication of high porous and micropatterned SnO₂ films by oxygen bubbles generated on the anode electrode

E. Hosono, S. Fujihara, H. Imai, I. Honma, H. Zhou

Chemical Communications (Royal Society of Chemistry)     2609&#8211;2611 2005

Research paper (scientific journal), Joint Work, Accepted

Evolution of nanoscale SnO₂ grains, flakes and plates into versatile particles and films through crystal growth in aqueous solutions

H. Ohgi, T. Maeda, E. Hosono, S. Fujihara, H. Imai

Crystal Growth and Design 5   1079-1083 2005

Research paper (scientific journal), Joint Work, Accepted

Fabrication of two-and three-dimensional photonic crystals of titania with sub-micrometer resolution by deep X-ray lithography

K. Awazu, X. Wang, M. Fujimaki, T. Kuriyama, A. Sai, Y. Ohki, H. Imai

Journal of Vacuum Science and Technology B 23   934-939 2005

Research paper (scientific journal), Joint Work, Accepted

Self-organization of inorganic helical crystals: design of structure, chirality, and function with an exquisite association of molecular recognition

Y. Oaki, T. Miura, H. Imai

Transaction of the Materials Research Society of Japan 30   353-356 2005

Research paper (scientific journal), Joint Work, Accepted

Synthesis and structural characterization of thermally stable Pt/SnO₂ nanocomposite particles

S. Fujihara, Y. Ogino, H. Imai, S. H. Kim

Nanotechnology 16   1396-1399 2005

Research paper (scientific journal), Joint Work, Accepted

Formation of cellular films consisting of wurtzite-type zinc oxide nanosheets by mediation of phosphate anions

S. Yamabi, J. Yahiro, S. Iwai, H. Imai

Thin Solid Films 489   23&#8211;30 2005

Research paper (scientific journal), Joint Work, Accepted

Hierarchicaly organized superstructure emerging from exquisite association of inorganic crystals, organic polymers, and dyes: a model approach toward suprabiomineral material

Y. Oaki, H. Imai

Advanced Functional Materials 15   1407-1414 2005

Research paper (scientific journal), Joint Work, Accepted

Characteristically shaped ZnO particles produced by periodic precipitation in organic gel media

T. Kawano, H. Imai

Journal of Crystal Growth 283   490&#8211;499 2005

Research paper (scientific journal), Joint Work, Accepted

The hierarchical architecture of nacre and its mimetic material

Y. Oaki, H. Imai

Angewandte Chemie-International Edition 44   6571-6575 2005

Research paper (scientific journal), Joint Work, Accepted

A novel adsorbent photocatalysts consising of titania and mesoporous silica nanoparticles

H. Uchiyama, K. Suzuki, Y. Oaki, H. Imai

Materials Science and Engineering B: Solid State Materials for Advanced Technology 123   248&#8211;251 2005

Research paper (scientific journal), Joint Work, Accepted

Hierarchically organized architecture of potassium hydrogen phthalate and poly(acrylic acid): toward a general strategy for biomimetic crystal design

Y. Oaki, H. Imai

Chemical Communications    6011-6013 2005

Research paper (scientific journal), Joint Work, Accepted

Crystal growth of metastable rutile-type Ti_XSn_1-XO₂ solid solutions in an aqueous system

H. Uchiyama, H. Imai

Chemical Communications    6014-6016 2005

Research paper (scientific journal), Joint Work, Accepted

生物のように複雑で美しい結晶をデザインする－自己組織化と結晶成長－

IMAI HIROAKI

現代化学 410   32-38 2005

Research paper (scientific journal), Single Work

メソポーラスシリカナノ粒子の作製と透明薄膜への応用

IMAI HIROAKI

化学工業 56   688-693 2005

Research paper (scientific journal), Single Work

Synthesis of silica nanoparticles having a well-ordered mesostructure using a double surfactant system

IMAI HIROAKI

Journal of the American Chemical Society 126 ( 2 ) 462-463 2004

Research paper (scientific journal), Joint Work, Accepted

Growth of layered basic zinc acetate in methanolic solutions and its pyrolytic transformation into porous zinc oxide films

IMAI HIROAKI

Journal of Colloid and Interface Science 272 ( - ) 391-398 2004

Research paper (scientific journal), Joint Work, Accepted

Emergence of morphological chirality with twinned crystals

IMAI HIROAKI

Angewandte Chemie-International Edition 43 ( 11 ) 1363-1368 2004

Research paper (scientific journal), Joint Work, Accepted

Non-basic solution routes to prepare ZnO nanoparticles

IMAI HIROAKI

Journal of Sol-Gel Science and Technology 29 ( - ) 71-79 2004

Research paper (scientific journal), Joint Work, Accepted

Preparation of mesoporous titania with polymer templating

IMAI HIROAKI

Journal of the Ceramic Society of Japan 112 ( - ) S112-S113 2004

Research paper (scientific journal), Joint Work, Accepted

Emanation thermal analysis (ETA) of sol-gel derived mesoporous titania

IMAI HIROAKI

Journal of the Ceramic Society of Japan 112 ( - ) S252-S255. 2004

Research paper (scientific journal), Joint Work, Accepted

Preparation of titania visible-light active photocatalysts from titanyl sulfate and urea

IMAI HIROAKI

Journal of the Ceramic Society of Japan 112 ( - ) S1419-S1421. 2004

Research paper (scientific journal), Joint Work, Accepted

Phosphate-mediated ZnO nanosheets with a mosaic structure

IMAI HIROAKI

Chemistry Letters 33 ( - ) 768-769 2004

Research paper (scientific journal), Joint Work, Accepted

Preparation of porous SnO₂ particles having a high specific surface area through an aqueous solution route and subsequent hydrothermal treatment

IMAI HIROAKI

Chemistry Letters 33 ( - ) 738-739 2004

Research paper (scientific journal), Joint Work, Accepted

Formation of planer aragonite-type carbonate crystals consisting of iso-oriented subunits

IMAI HIROAKI

Crystal Growth and Design 4 ( 4 ) 725-729 2004

Research paper (scientific journal), Joint Work, Accepted

Hydrothermal routes to prepare nanocrystalline mesoporous SnO₂ having high thermal stability

IMAI HIROAKI

Langmuir 20 ( 15 ) 6476-6481 2004

Research paper (scientific journal), Joint Work, Accepted

Growth of sub-micron scale rectangular parallelepiped rutile TiO₂ films in aqueous TiCl₃ solutions under hydrothermal conditions

IMAI HIROAKI

Journal of the American Chemical Society 126 ( 25 ) 7790-7791 2004

Research paper (scientific journal), Joint Work, Accepted

Amplification of chirality from molecules into morphology of crystals through molecular recognition

IMAI HIROAKI

Journal of the American Chemical Society 126 ( 30 ) 9271-9275 2004

Research paper (scientific journal), Joint Work, Accepted

Preparation of titania foams having an open cellular structure and their application to photocatalysis

IMAI HIROAKI

Journal of Catalysis 226 ( - ) 462-465 2004

Research paper (scientific journal), Joint Work, Accepted

Morphological evaluation and film formation with iso-oriented calcite crystals using binary poly (acrylic acid)

IMAI HIROAKI

Chemistry of Materials 16 ( 16 ) 3191-3196 2004

Research paper (scientific journal), Joint Work, Accepted

Silicate-mediated film formation of alkaline-earth metal carbonates

IMAI HIROAKI

Transaction of the Materials Research Society of Japan 29 ( - ) 2257-2259 2004

Research paper (scientific journal), Joint Work, Accepted

Preparation of mesoporous titania gel films and their characterization

IMAI HIROAKI, H. Hirashima, M. Y. Miah, I. M. Bountseva, I. N. Beckman, V. Balek

Journal of Non-Crystalline Solids 350   266-270 2004

Research paper (scientific journal), Joint Work, Accepted

Layer-by-layer self-assembly replication technique: application to photoelectrode of dye-sensitized solar cell

IMAI HIROAKI

Thin Solid Films 438 ( - ) 346-351 2003

Research paper (scientific journal), Joint Work, Accepted

Preparation of mesoporous titania by templating with polymer and surfactant and its characterization

IMAI HIROAKI

Journal of Sol-Gel Science and Technology 28 ( - ) 97-104 2003

Research paper (scientific journal), Joint Work, Accepted

Photoinduced hydroxylation at ZnO surface

IMAI HIROAKI

Thin Solid Films 445 ( - ) 284-287 2003

Research paper (scientific journal), Joint Work, Accepted

Experimental demonstration for the morphological evolution of crystals grown in gel media

IMAI HIROAKI

Crystal Growth & Design 3 ( 5 ) 711-716 2003

Research paper (scientific journal), Joint Work, Accepted

Crystallization and reduction of sol-gel-derived zinc oxide films by irradiation with ultraviolet lamp

今井 宏明

Journal of Sol-Gel Science and Technology 26   181-184 2003

Research paper (scientific journal), Joint Work, Accepted

Structure of hybrid silica gels incorporated with hydrophobic dye molecules

今井 宏明

Journal of Sol-Gel Science and Technology 26   383-388 2003

Research paper (scientific journal), Joint Work, Accepted

Preparation and characterization of porous titania by modified sol-gel method

今井 宏明

Journal of Sol-Gel Science and Technology 26   635-640 2003

Research paper (scientific journal), Joint Work, Accepted

Self-organized formation of a hierarchcal self-similar structure with calcium carbonate

今井 宏明

Chemical Communications    484-485 2003

Research paper (scientific journal), Joint Work, Accepted

Low-temperature synthesis of ITO thin films using an ultraviolet laser for conductive coatings on organic polymer substrates

今井 宏明

Journal of Sol-Gel Science and Technology 27   91-95 2003

Research paper (scientific journal), Joint Work, Accepted

Formation process of sheets and helical forms consisting of strontium carbonate fibrous crystals with silicate

今井 宏明

Journal of Crystal Growth 253   435-444 2003

Research paper (scientific journal), Joint Work, Accepted

Synthesis of ｒutile and anatase films with high surface areas in aqueous solutions containing urea

今井 宏明

Thin Solid Films 434   86-93 2003

Research paper (scientific journal), Joint Work, Accepted

Synthesis of mesoporous silica foams with hierarchical trimodal pore structures

今井 宏明

Journal of Materials Chemistry 13   1812-1816 2003

Research paper (scientific journal), Joint Work, Accepted

Crystal Phase Control for Metal Oxide Films Grown in Aqueous Solution

今井 宏明

Transaction of the Materials Research Society of Japan 28   329-332 2003

Research paper (conference, symposium, etc.), Joint Work, Accepted

Formation of calcium phosphate having a hierarchically laminated architecture through periodic precipitation in organic gel

今井 宏明

Chemical Communications    1952-1953 2003

Research paper (scientific journal), Joint Work, Accepted

Formation of Silicate-Mediated CaCO₃ Films

今井 宏明

Chemistry Letters 32   820-821 2003

Research paper (scientific journal), Joint Work, Accepted

Growth condition for wurtzite zinc oxide films in aqueous solutions

今井 宏明

Journal of Materials Chemistry 12   3773-3778 2002

Research paper (scientific journal), Joint Work, Accepted

Crystal phase control for titanium dioxide films by direct deposition in aqueous solutions

S.Yamabi, H. Imai

Chemistry of Materials 14   609-614 2002

Research paper (scientific journal), Single Work, Accepted

Morphological evolution of silver crystals produced by reduction with ascorbic acid

今井 宏明

Journal of Crystal Growth 241   193-199 2002

Research paper (scientific journal), Joint Work, Accepted

Preparation of porous titania film by modified sol-gel method and its application to photocatalyst

今井 宏明

Journal of Sol-Gel Science and Technology 25   65-74 2002

Research paper (scientific journal), Joint Work, Accepted

Biomimetic approach for exact control of TiO2 periodic microstructures

今井 宏明

Chemistry Letters    714-715 2002

Research paper (scientific journal), Joint Work, Accepted

Photoreduction of amorphous and crystalline ZnO films

今井 宏明

Japanese Journal of Applied Physics 41   3909-3915 2002

Research paper (scientific journal), Joint Work, Accepted

Self-organized formation of porous aragonite with silicate

今井 宏明

Journal of Crystal Growth 244   200-205 2002

Research paper (scientific journal), Joint Work, Accepted

Control of porous structure in TiO2 thin films using nano replica prepared by layer-by-layer self-assembly process

今井 宏明

Transaction of the Materials Research Society of Japan 27   525-528 2002

Research paper (conference, symposium, etc.), Joint Work, Accepted

Morphology transcription with TiO2 using chemical solution growth and its application for photocatalysts

今井 宏明

Solid State Ionics 151   183-187 2002

Research paper (scientific journal), Joint Work, Accepted

Photocrystallization of amorphous ZnO

今井 宏明

Journal of Applied Physics 92   5707-5710 2002

Research paper (scientific journal), Joint Work, Accepted

自己組織化する結晶

IMAI HIROAKI

無機マテリアル 8 ( - ) 234-240 2001

Research paper (scientific journal), Single Work

Hydrolysis deposition of thin films of antimony-doped tin oxide

K. Tsukuma, T. Akiyama, H. Imai

Journal of American Ceramic Society 84   869-871 2001

Research paper (scientific journal), Joint Work, Accepted

Preparation of mesoporous TiO2 thin films by surfactant templating

M. M. Yusuf, H. Imai, H. Hirashima

Journal of Non-Crystalline Solids 285   90-95 2001

Joint Work, Accepted

Preparation of meso-porous TiO2 gels and their characterization

H. Hirashima, H. Imai, V. H. Balek

Journal of Non-Crystalline Solids 285   96-100 2001

Research paper (scientific journal), Joint Work, Accepted

Catalyst activity of alumina-galia aerogels for selective reduction of NOx

T. Chono, H. Hamada, M. Haneda, H. Imai, H. Hirashima

Journal of Non-Crystalline Solids 285   333-337 2001

Joint Work, Accepted

Formation of whiskers of silicate mesostructures

N. Takahashi, R. Tamura, H. Hirashima

Langmuir 17   17-20 2001

Joint Work, Accepted

Fabrication of rutile TiO2 foils with high specific surface area via Heterogeneous nucleation in aqueous solutions

S. Yamabi

Chemistry Letters  2001

Joint Work, Accepted

Hydrolysis deposition of thin films of antimony-doped tin oxide

　　K. Tsukuma, T. Akiyama, H. Imai

Journal of American Ceramic Society 84   869-871 2001

Joint Work

Preparation of mesoporous TiO2 thin films by surfactant templating

　　M. M. Yusuf, H. Imai, H. Hirashima

Journal of Non-Crystalline Solids 285   90-95 2001

Research paper (scientific journal), Joint Work, Accepted

Preparation of meso-porous TiO2 gels and their characterization

H. Hirashima, H. Imai, V. H. Balek

Journal of Non-Crystalline Solids 285   96-100 2001

Research paper (scientific journal), Joint Work, Accepted

Catalyst activity of alumina-galia aerogels for selective reduction of NOx

T. Chono, H. Hamada, M. Haneda, H. Imai, H. Hirashima

Journal of Non-Crystalline Solids 285   333-337 2001

Research paper (scientific journal), Joint Work, Accepted

Barium titanate nanoparticles in block copolymer

今井 宏明

Langmuir 17   7656-7663 2001

Research paper (scientific journal), Joint Work, Accepted

バイオミメティクプロセッシングにおける自己組織化

IMAI HIROAKI

化学工業 52 ( - ) 354-359 2001

Research paper (scientific journal), Single Work

Evolution of cristobalite clusters on silica glass in molten silicon

H. Imai, H. Hirashima

Journal of Electrochemical Society 147 ( - ) 1182-1185 2000.03

Research paper (scientific journal), Joint Work, Accepted

Fibrillation and morphological evolution of alkaline-earth carbonates with silicate

S. Yamabi, T. Terada, N. Shikazono, H. Hirashima

Transaction of the Materials Research Society of Japan 25 25 ( - )  2000

Research paper (scientific journal), Joint Work, Accepted

Preparation of hollow fibers of tin oxide with and without antimony doping

Y. Iwaya, K. Shimizu, H. Hirashima

Chemistry Letters 2000  2000

Joint Work

Preparation of TiO2 fibers with well-organized structures

M. Matsuta, K. Shimizu,H. Hirashima, N. Negishi

Journal of Materials Chemistry 10 ( - )  2000

Research paper (scientific journal), Joint Work, Accepted

Ultraviolet-laser-crystallization of sol-gel derived inorganic oxide films

N. Asakuma, T. Fukui, M. Aizawa, M. Toki, H. Hirashima

Journal of Sol-Gel Science and Technology 19 ( - )  2000

Research paper (scientific journal), Joint Work, Accepted

Characterization of alumina gel catalysts by emanation thermal analysis (ETA)

H. Hirashima, V. Balek

Journal of Sol-Gel Science and Technology 19 ( - )  2000

Research paper (scientific journal), Joint Work, Accepted

Preparation of SrBi2Ta2O9 from metal alkoxides

Y. M. Miah, H. Hirashima

Journal of Sol-Gel Science and Technology 19 ( - )  2000

Research paper (scientific journal), Joint Work, Accepted

Morphological control of silicate mesostructures using flat and grooved substrates

H. Imai, H. Hirashima,

Transaction of Materials Research Society of Japan Vol. 24   493-495 1999.12

Joint Work, Accepted

Direct preparation of anatase-type TiO₂ nanotubes in porous alumina membranes

H. Imai, Y. Takei, K. Shimizu, M. Matsuda, H. Hirashima

Journal of Materials Chemistry 9   2971-2973 1999.11

Research paper (scientific journal), Joint Work

Direct deposition methods of silica and silica/organic composite coatings in alkoxide solutions

H. Imai, J. Oh, H. Hirashima,

Proceeding of 2nd International Conference on Coatings on Glass    126-131 1999.10

Research paper (conference, symposium, etc.), Joint Work, Accepted

Doping of sodium ions for second-order nonlinearity of silica glass

H. Imai, D. Matsuki, H. Hirashima, S. Horinouchi, K. Sasaki,

Nonlinear Optics 22    111-114 1999.10

Joint Work

Preparation of porous anatase coating from sol-gel-derived titanium dioxide and titanium dioxide-silica by water vapor exposure　

H. Imai, H. Hirashima,

Journal of American Ceramics Society 82    2301-2304 1999.09

Research paper (scientific journal), Joint Work

Alternative modification methods for sol-gel　coatings of silica, titania and silica-titania using ultraviolet irradiation and water vapor

H. Imai, H. Hirashima,

Thin Solid Films 351    91-94 1999.09

Joint Work

Low-temperature synthesis of anatase coatings on glass and organic substrates

K. Shimizu, H. Imai, H. Hirashima, K. Tsukuma,

Thin Solid Films 351    220- 224 1999.09

Joint Work

Optical quadratic nonlinearity in corona-poled glass film waveguides　

S.Horinouchi, H.Imai, H. Yamasaki, G.J.Zhang, K. Mito, H.Hirashima, K.Sasaki,

Electronics and Communications in Japan part II-Electronics 82,    53-61 1999.08

Joint Work

自己組織化する無機材料

IMAI HIROAKI

色材 72 ( - ) 698-703 1999

Research paper (scientific journal), Single Work

Ultraviolet-induced reduction and crystallization in indium oxide films

H. Imai, A. Timinaga, H. Hirashima, M. Toki, N. Asakuma

Journal of Applied Physics 85 1999

Research paper (scientific journal), Joint Work, Accepted

　View Summary

紫外光照射によるITOゲル薄膜の還元と結晶化を報告した。(５頁）

自己組織化による無機・界面活性剤複合メソ構造体のマクロな形態形成と制御

IMAI HIROAKI

化学工業 50 ( - ) 424-430 1999

Research paper (scientific journal), Single Work

Application of ZrO2-Al2O3 aerogels to catalysts

K. Kohama, H. Imai, H. Hirashima, H. Hamada, M. Inaba,

Journal of Sol-Gel Science and Technology13 (1998) 1033(1036.  1998.12

Research paper (scientific journal), Joint Work

　View Summary

ZrO2-Al2O3系アエロゲルのNOx還元触媒としての評価をおこない、そのメカニズムを検討した。

Ultraviolet-laser-induced crystallization of sol-gel derived indium oxide films

H. Imai, A. Tomonaga, H. Hirashima, M. Toki, M. Aizawa

Journal of Sol-Gel Science and Technology 13 ( - ) 991-994 1998.12

Research paper (scientific journal), Joint Work

　View Summary

ゾルゲル法によって得られた酸化インジウム薄膜の紫外光照射による結晶化を見出した。

Direct deposition of silica films using silicon alkoxide solution

J. Oh, H. Imai, H. Hirashima

J.Non-Cryst.Solids 241  1998

Joint Work

　View Summary

アルコキシド溶液からのシリカ薄膜の作製法を見出した。(７頁）

Direct deposition of mesoscopically assembled dye-doped silica films from aqueous solutions of silicon alkoxides

J. Oh, H. Imai, H. Hirashima

Chem. Mater. 10  1998

Joint Work

　View Summary

色素含有シリカ膜の溶液からの新奇な合成法を報告した。（7頁）

Defects in amorphous silica induced with monochromatic VUV rays

K. Awazu, K. Kanehira, H. Imai, H. Hirashima

Nuclear Instruments and Methods in Physics Research B 141  1998

Joint Work

　View Summary

紫外光によるシリカガラス中の欠陥生成について検討した。（5頁）

Oxide aerogel catalysts

H. Hirashima, C. Kojima, K. Kohama, H. Imai, V. Balek, H. Hamada, M. Inaba

J. Non-Cryst. Solids 225  1998

Joint Work

　View Summary

酸化物のエアロゲルの触媒応用について報告した。（4頁）

Liquid phase deposition of a film of silica with an organic functional group

K. Tsukuma, T. Akiyama, N. Yamada, H. Imai

J. Non-Cryst. Solids 231  1998

Joint Work

　View Summary

有機官能基を有するアルコキシド溶液からのシリカ薄膜の合成について報告した。（8頁）

Effects of introduction of sodium and water on second-order nonlinearity in poled synthetic silica glass

H. Imai, S. Horinouchi, N. Asakuma,　K. Fukao, D. Matsuki, H. Hirashima, 　K. Sasaki

J. Appl.Phys. 84  1998

Joint Work

　View Summary

シリカガラスの２次の非線形性とナトリウムおよび水との相関を明らかにした。（4頁）

Structural changes in Sol-Gel derived SiO2 and TiO2 films by exposure to water vapor

H. Imai, H. Morimoto, A. Tominaga,　H. Hirashima

J. Sol-Gel Science and Technology 10  1997

Joint Work

　View Summary

水蒸気によるゾルゲルシリカおよびチタニア膜の構造変化を報告した。（10頁）

Liquid phase deposition film of tin oxide

K. Tukuma, T. Akiyama, H. Imai

J. Non-Cryst. Solids 210 1997

Joint Work

　View Summary

溶液からの酸化スズ薄膜の合成を報告した。（7頁）

ゾルゲル法によるコーディエライトセラミックスの結晶化過程に及ぼすAl/Si比率の影響

呉濬禄、今井宏明、平島碩

日本セラミックス協会学術論文誌  1997

Research paper (conference, symposium, etc.), Joint Work

　View Summary

ゾルゲル法によるコーディエライトの合成について検討した。（5頁）

Densification of sol-gel thin films by ultraviolet and vacuum ultraviolet irradiation

H. Imai, K. Awazu, M. Yasumori, H. Onuki, H. Hirashima

J. Sol-Gel Science and Technology 8 1997

Joint Work

　View Summary

紫外光照射によるシリカとチタニア膜の緻密化を報告した。（5頁）

Application of alumina aerogels as catalysts

H. Hirashima, C. Kojima, H. Imai

J. Sol-Gel Science and Technology 8 1997

Joint Work

　View Summary

アルミナエアロゲルの触媒応用ついて検討した。（4頁）

Deposition process and property of silica films containing organic groups from aqueous solution of alkoxides

J. Oh, H. Imai, H. Hirashima, K. Tsukuma

J. Mater. Res. 12 1997

Joint Work

　View Summary

アルコキシド溶液からのシリカ膜の析出過程を検討した。（9頁）

シリカガラスの基礎と新展開

今井宏明

分光研究 45   157-167 1996

Research paper (scientific journal), Single Work

　View Summary

シリカガラスの基礎知識とこれからの展開について概説した。 （11頁）

非線形ガラス薄膜光導波路による第二高調波発生

堀之内英, 山崎英亮, 今井宏明, 深尾和弘,張公倹, 木下岳司, 三戸慶一, 平島碩,佐々木敬介

回路実装学会誌11  1996

Research paper (scientific journal), Joint Work

　View Summary

非線形ガラス薄膜光導波路による第二高調波発生を検討した。（7頁）

Time dependence decay of quadratic non-linearity in corona-poled silicate glass films

H. Imai, S. Horinouchi, Y. Uchida,H. Yamasaki, K. Fukao, G. Zhang,T. Kinoshita, K. Mito, H. Hirashima,　K. Sasaki

J.Non-Cryst.Solids 196 1996

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薄膜光導波路による第二高調波の減衰を検討した。（4頁）

Second order nonlinear optical properties in silica-based glass film waveguides

S. Horinouchi, H. Imai, H. Yamasaki,　K. Fukao, G. Zhang, T. Kinoshita, K. Mito,　H. Hirashima, K. Sasaki

J. Nonlinear Optical Physics and Materials 5  1996

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シリカベースガラス薄膜光導波路による２次の非線形性を明らかにした。（6頁）

Photo-induced structural change in a-SiO2 with undulator radiation

K. Awazu, H. Onuki, H. Imai, H. Hirashima

J. Electron Spectroscopy and Related Phenomena 80  1996

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光によるシリカ薄膜の構造変化を検討した。（4頁）

Optical quadratic nonlinearity in multilayer corona-poled glass films

S. Horinouchi, H. Imai, G. J. Zhang,　K. Mito, K. Sasaki

Appl. Phys. Lett. 68 1996

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多層ガラス薄膜における２次の非線形性を検討した。（3頁）

Significant densification of sol-gel derived amorphous silica films by vacuum ultraviolet irradiation

H. Imai, M. Yasumori, H. Hirashima,　K. Awazu, H. Onuki

J. Appl. Phys. 79  1996

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紫外光の照射によるゾルゲルシリカ膜の緻密化を検討した。（7頁）

Chemical modification of alkoxide precursors for lead zirconate titanate formation

S. Trasiroadi, H. Imai, H. Hirashima

Australian Journal of Chemistry 49  1996

Research paper (scientific journal), Joint Work

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PZTを合成するためのアルコキシドの修飾を検討した。（4頁）

Dissociative mechanisms of monosilane and arsine on copper(II) oxide

T. Watanabe, H. Imai, T. Suzuki

J. Electrochem. Soc. 143 1996

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酸化銅におけるシランの分解を見出した。

ガラス薄膜光導波路における２次の非線形光学効果

堀之内英, 今井宏明, 山崎英亮, 張公倹,三戸慶一, 平島碩,　佐々木敬介

電子情報通信学会論文誌　 Vol. J79-C-I 1996

Research paper (conference, symposium, etc.), Joint Work

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ガラス薄膜光導波路における２次の非線形光学効果を検討した （8頁）

Crystalization and sintering behavior of PZT prepared from metal alkoxides

S. Trasiroadi, H. Imai, H. Hirashima

J. Ceram. Soc. Jpn 103 1995

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ゾルゲルPZTの結晶化と焼結について検討した。（4頁）

Effects of aging and drying structure of V2O5 gels

H. Hirashima, M. Gengyo, C. Kojima, H. Imai

J. Non-Cryst. Solids 186 1995

Joint Work

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5酸化バナジウムゲルの構造変化を検討した。（5頁）

Monosilane adsorption on porous alumina

H. Imai, T. Watanabe, T. Suzuki

J. Electrochem. Soc. 142  1995

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アルミナ表面におけるシランの吸着を報告した。（3頁）

Novel modification method of sol-gel thin films: densification of silica gel films with electronic excitation

H. Imai, H. Hirashima

J. Ceram. Soc. Jpn 102  1994

Joint Work

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ゾルゲルシリカ膜の電子励起による緻密を見出した。（3頁）

Similarity of defect generation in silica glasses irradiated with gamma-rays and 5.0- and 6.4-eV excimer lasers

H. Imai, H. Hirashima

Nuclear Instruments and Methods in Physics Research B91 1994

Research paper (scientific journal), Joint Work

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ガンマ線とエキシマレーザの照射によるシリカガラス中の欠陥生成の類似性について検討した。（5頁）

Intrinsic- and extrinsic-defect formation in silica glasses by radiation

H. Imai, H.Hirashima

J. Non-Cryst. Solids 179  1994

Joint Work

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シリカガラスにおける外因性および内因性の欠陥生成について検討した。（12頁）

Reduction kinetics oxygen-deficient centers with diffusing oxygen molecules in silica glass

H. Imagawa, T. Arai, H. Hosono, H. Imai,K. Arai

J. Non-Cryst. Solids 179 1994

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シリカガラスにおける酸素欠乏欠陥の減少について検討した。（5頁）

Generation of E' centers and oxygen hole centers in synthetic silica glasses by gamma irradiation

H. Imai, K. Arai, J. Isoya, H. Hosono,Y. Abe, H. Imagawa

Physical Review B 48  1993

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ガンマ線によるシリカガラス中の欠陥生成について検討した。（8頁）

Evidence for pair generation of an E' center and a nonbridging oxygen-hole center in gamma-ray-irradiated fluorine-doped low-OH synthetic silica glasses

K. Arai, H. Imai, J. Isoya,H. Hosono,Y. Abe, H. Imagawa

Physical Review B 45  1991

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Ｅ’中心と酸素正孔中心が対生成することを見出した。（4頁）

Experimental evidence for the Si-Si bond model of the 7.6-eV band in SiO2 glass

H. Hosono, Y. Abe, H. Imagawa, H. Imai,K. Arai

Physical Review B 44  1991

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7.6eV吸収帯の起源がSi-Si結合であることを明らかにした。（3頁）

Dependence of defects induced by excimer laser on intrinsic defects in synthetic silica glasses

H. Imai, K. Arai, H. Hosono, Y. Abe, T. Arai, H. Imagawa

Physical Review B 44  1991

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エキシマレーザの照射によるシリカガラスにおける欠陥生成について報告した。（7頁）

Two types of oxygen-deficient centers in synthetic silica glass

H. Imai, K. Arai, H. Imagawa, H. Hosono,Y. Abe, T. Arai

Physical Review B 38  1988

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シリカガラスにおいて２種類の酸素欠乏欠陥を見出した。（4頁）

The role of fluorine as a codopant in cerium activated silica glass

H. Imai, K. Arai, Y. Fujino, Y. Ishii,H. Namikawa

Physics and Chemistry of Glasses 29 1988

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シリカガラスにおけるフッ素の役割を検討した。（5頁）

Two-photon processes in defect formation by excimer lasers in synthetic silica glass

K. Arai, H. Imai, H. Hosono, Y. Abe,H. Imagawa

Appl. Phys. Lett. 53 1988

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２光子吸収によるシリカガラス中の欠陥生成を見出した。（3頁）

ガラスの微視的不均質と性質-高純度シリカガラスの点欠陥と真空紫外吸収を例として-

細野秀雄、阿部良弘、荒井和雄、今井宏明、今川宏

セラミックス 22   1047-1051 1987

Research paper (scientific journal), Joint Work

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シリカガラスにおける微視的不均質と性質との関係を解説した。（5頁）

Nature of doping into pure silica glass by plasma torch CVD

K. Arai, H. Namikawa, Y. Ishii, H. Imai,H. Hosono, Y. Abe

J. Non-Cryst. Solids 95&96  1987

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シリカガラス内における希土類イオンの挙動を検討した。（8頁）

加圧圧縮過程の初期段階におけるヘマタイト顆粒強度の影響

久野洋, 今井宏明

粉体および粉末冶金 33 1986

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加圧圧縮過程の初期段階におけるヘマタイト顆粒強度の影響を検討した。（5頁）

顆粒の圧縮成形過程における顆粒間および顆粒内空隙の変化

今井宏明, 久野洋

粉体および粉末冶金 33 1986

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顆粒の圧縮成形過程における顆粒間および顆粒内空隙の変化を検討した。（4頁）