論文 - 中嶋　敦

Designable formation of metal nanoparticle array with the deposition of negatively charged nanoparticles

S. Kawabata, Y. Naono, Y. Taguchi, S. H. Huh, A, Nakajima

Applied Surface Science （Elsevier Science BV）  253 （ 16 ） 6690 - 6696 2007年06月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  0169-4332

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Ultrafine gold and platinum nanoparticles (NPs) were fabricated by pulsed laser ablation in helium gas and the NPs 2-15 nm in diameter were selectively classified by an electrostatic size-selection technique employing a low-pressure differential mobility analyzer (LP-DMA). The spherical NPs obtained showed a narrower distribution of diameters of anionic NPs over cationic NPs. With this knowledge, the anionic NPs were deposited onto silicon substrates designed by electron beam lithography processing, and designable patterns of arrayed NPs were produced by removing the photoresist layer. © 2007 Elsevier B.V. All rights reserved.

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Formation of Large molecular cluster anions and elucidation of their electronic structures

M. Mitsui, A. Nakajima

Bulletin of the Chemical Society of Japan （Chemical Society of Japan）  80 （ 6 ） 1058 - 1074 2007年06月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  0009-2673

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The present account describes our efforts to understand the microscopic aspects of condense phase phenomena, such as ion solvation in molecular liquids and charge carrier localization in molecular solids, by viewing finite-size molecular clusters as their embryonic forms. In this effort, we efficiently prepared supersonically cooled, isolated molecular cluster anions with up to more than 100 constituent molecules and size-selectively investigated their electronic structures using anion photoelectron spectroscopy. Large anionic clusters of two different types of organic molecule; acetonitrile and naphthalene reported as examples of the noteworthy results obtained in our studies. In these two systems, we found that energetically close anionic isomers coexist over a broad range in size, and their contribution in the photoelectron spectra could be separated using anion beam hole-burning technique. A detailed inspection into the electronic states and size-dependent energetics of each isomer has enabled us to establish a link from the large finite cluster to the infinite bulk system. © 2007 The Chemical Society of Japan.

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Fabrication and characterization of a granular film consisting of size-selected silver nanoparticles: Application to a SERS substrate

S. Kawabata, N. Ishikawa, M. Mitsui, A. Nakajima

European Physical Journal D （Springer Nature）  43 （ 1-3 ） 155 - 158 2007年05月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  14346060

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Uniform-sized silver nanoparticles with average diameter of 13.7 nm have been prepared in the gas-phase by combining a pulsed laser ablation method with a low pressure-differential mobility analyzer (LP-DMA). By depositing the silver nanoparticles onto a silicon substrate, a granular film consisting of size-selected silver nanoparticles has been fabricated and its morphology and electronic properties have been examined using transmission electron microscopy (TEM) and UV-visible absorption spectroscopy. This granular silver film serves as a highly active substrate for surface-enhanced Raman scattering (SERS). © EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2007.

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Magnetic trapping of nanometer- and micrometer-sized particles

S. H. Huh, C. Y. Kim, H. S. Jeong, A. Nakajima

Journal of Applied Physics （American Institute of Physics）  101 （ 10 ） 104317 2007年05月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  0021-8979

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Nanometer- and micrometer-sized particles (NPs and MPs) of gas-phase Co, Fe, and Fe-Nd-Dy-B were magnetically trapped on a substrate. For the magnetic trapping of NPs, two stepwise evolutions were investigated: (1) the formation of NP aggregates above a critical diameter of 8 nm and (2) increase in the length to a few micrometers, which is the result of the equilibrium between the magnetostatic and thermal energies of NPs and the granular linear chains such as granular nanorods and nanofibers. The magnetic trapping of MPs or MPsNPs is particularly interesting because of the sequential pearl-necklace-like growth and magnetic separation in the linear chains. © 2007 American Institute of Physics.

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Soft-landing isolation of multidecker V₂(benzene)₃ complexes in an organic monolayer matrix: An infrared spectroscopy and thermal desorption study

S. Nagaoka, T. Matsumoto, K. Ikemoto, M. Mitsui, A. Nakajima

Journal of the American Chemical Society （American Chemical Society）  129 （ 6 ） 1528 - 1529 2007年01月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  00027863

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Gas-phase synthesized multidecker V2(benzene)3 sandwich complexes were soft-landed onto a self-assembled monolayer of an n-octadecanethiol (C18-SAM). The infrared absorption spectrum of this complex supported on the C18-SAM was obtained by infrared reflection absorption spectroscopy (IRAS). The vibrational assignment of the IRAS spectrum for the V2(benzene)3 sandwich was based on a harmonic frequency analysis that employed density functional theory. The close similarity between the experimental and calculated results for the IR absorption frequencies demonstrates that the V2(benzene)3 complexes have a multidecker sandwich structure on the SAM substrate. Moreover, our thermal desorption study established that the sandwich complexes can be isolated on the SAM substrate up to a high temperature of ∼350 K. Copyright © 2007 American Chemical Society.

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Electronic properties of Si and Ge atoms doped In clusters: In_nSi_m and In_nGe_m

M. Akutsu, K. Koyasu, J. Atobe, K. Miyajima, M. Mitsui, A. Nakajima

Journal of Physical Chemistry A （American Chemical Society）  111 （ 4 ） 573 - 577 2007年01月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  10895639

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Electronic properties of silicon and germanium atom doped indium clusters, InnSim and InnGem, were investigated by photoionization spectroscopy of the neutrals and photoelectron spectroscopy of the anions. Size dependence of ionization energy and electron affinity for InnSi1 and InnGe1 exhibit pronounced even-odd alternation at cluster sizes of n = 10-16, as compared to those for pure Inn clusters. This result shows that symmetry lowering with the doped atom of Si or Ge results in undegeneration of electronic states in the Id shell formed by monovalent In atoms. © 2007 American Chemical Society.

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Electronic and geometric stabilities of clusters with transition metal encapsulated by silicon

K. Koyasu, J. Atobe, M. Akutsu, M. Mitsui, A. Nakajima

Journal of Physical Chemistry A （American Chemical Society）  111 （ 1 ） 42 - 49 2006年12月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  1089-5639

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Silicon clusters mixed with a transition metal atom, MSia, were generated by a double-laser vaporization method, and the electronic and geometric stabilities for the resulting clusters with transition metal encapsulated by silicon were examined experimentally. By means of a systematic doping with transition metal atoms of groups 3, 4, and 5 (M = Sc, Y, Lu, Ti, Zr, Hf, V, Nb, and Ta), followed by changes of charge states, we explored the use of an electronic closing of a silicon caged cluster and variations in its cavity size to facilitate metal-atom encapsulation. Results obtained by mass spectrometry, anion photoelectron spectroscopy, and adsorption reactivity toward H2O show that the neutral cluster doped with a group 4 atom features an electronic and a geometric closing at n = 16. The MSi16 cluster with a group 4 atom undergoes an electronic change in (i) the number of valence electrons when the metal atom is substituted by the neighboring metals with a group 3 or 5 atom and in (ii) atomic radii with the substitution of the same group elements of Zr and Hf. The reactivity of a halogen atom with the MSi 16 clusters reveals that VSi16F forms a superatom complex with ionic bonding. © 2007 American Chemical Society.

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Experimental and theoretical characterization of aluminum-based binary superatoms of Al₁₂X and their cluster salts

M. Akutsu, K. Koyasu, J. Atobe, N. Hosoya, K. Miyajima, M. Mitsui, A. Nakajima

Journal of Physical Chemistry A （American Chemical Society）  110 （ 44 ） 12073 - 12076 2006年10月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  10895639

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The geometric and electronic structures of aluminum binary clusters, AlnX (X = Si and P), have been investigated, using mass spectrometry, anion photoelectron spectroscopy, photoionization spectroscopy, and theoretical calculations. Both experimental and theoretical results show that Al 12Si has a high ionization energy and low electron affinity and Al12P has a low ionization energy, both with the icosahedral structure having a central Si or P atom, revealing that Al12Si and Al12P exhibit rare-gas-like and alkali superatoms, respectively. Experiments confirmed the possibility that the change in the total number of valence electrons on substitution could produce ionically bound binary superatom complexes, the binary cluster salts Al12P+F- and Al12B-Cs+. © 2006 American Chemical Society.

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Adiabatic electron affinities of oligophenyls: Anion photoelectron spectroscopy and density functional theory study

Nakamura T., Ando N., Matsumoto Y., Furuse S., Mitsui M., Nakajima A.

Chemistry Letters （CHEMICAL SOC JAPAN）  35 （ 8 ） 888 - 889 2006年08月

研究論文（学術雑誌）, 最終著者, 責任著者, 査読有り,  ISSN  03667022

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Adiabatic electron affinities (EA a's) of seven oligophenyls: biphenyl (BP), 4-cyanobiphenyl (CNBP), o-terphenyl (o-TP), m-terphenyl (m-TP), p-terphenyl (p-TP), p-quaterphenyl (p-QP), and 1,3,5-triphenylbenzene (TPB), have been evaluated by anion photoelectron spectroscopy and density functional theory calculations. The result provides the direct determination of the EA a values of the isolated CNBP, p-TP, p-QP, and TPB molecules, while EA a of BP, o-TP, and m-TP were estimated from the extrapolation of EA a vs cluster size. The excellent agreement between the experimental and calculated EA a were obtained. Copyright © 2006 The Chemical Society of Japan.

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Room-temperature isolation of V(benzene)₂ sandwich clusters via soft-landing into n-alkanethiol self-assembled monolayers

S. Nagaoka, T. Matsumoto, E. Okada, M. Mitsui, A. Nakajima

Journal of Physical Chemistry B （American Chemical Society）  110 （ 32 ） 16008 - 16017 2006年07月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  15206106

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The adsorption state and thermal stability of V(benzene)2 sandwich clusters soft-landed onto a self-assembled monolayer of different chain-length n-alkanethiols (Cn-SAM, n -8, 12, 16, 18, and 22) were studied by means of infrared reflection absorption spectroscopy (IRAS) and temperature-programmed desorption (TPD). The IRAS measurement confirmed that V(benzene)2 clusters are molecularly adsorbed and maintain a sandwich structure on all of the SAM substrates. In addition, the clusters supported on the SAM substrates are oriented with their molecular axes tilted 70-80° off the surface normal. An Arrhenius analysis of the TPD spectra reveals that the activation energy for the desorption of the supported clusters increases linearly with the chain length of the SAMs. For the longest chain C22-SAM, the activation energy reaches ∼150 kJ/mol, and the thermal desorption of the supported clusters can be considerably suppressed near room temperature. The clear chain-length-dependent thermal stability of the supported clusters observed here can be explained well in terms of the cluster penetration into the SAM matrixes. © 2006 American Chemical Society.

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Photoelectron spectroscopy of binary Au cluster anions with a doped metal atom: Au_nM^- (n = 2-7), M = Pd, Ni, Zn, Cu, and Mg

K. Koyasu, Y. Naono, M. Akutsu, M. Mitsui, A. Nakajima

Chemical Physics Letters （Elsevier Science BV）  422 （ 1-3 ） 62 - 66 2006年04月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  00092614

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The electronic structures of binary gold cluster anions: AunM- (M = Pd, Ni, Zn, Cu, Mg) were investigated by anion photoelectron spectroscopy at the photon energy of 4.66 eV. The spectra exhibit even-odd alternation of electron affinities and characteristic spectral changes with n, which are accountable in terms of the interactions between the Au clusters and doped metal atoms. For the binary clusters containing Pd, Ni, and Cu, their valence electrons are shared with those of the Au clusters, whereas for Mg the doped atom is weakly bound to Au clusters. A size-dependent spectral change is clearly observed for AunPd- at n ≈ 5. © 2006 Elsevier B.V. All rights reserved.

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Electronic properties of Cs-atom doped aluminum and silicon clusters: Al_nCs_m and Si_nCs_m

K. Koyasu, M. Akutsu, J. Atobe, M. Mitsui, A. Nakajima

Chemical Physics Letters （Elsevier Science BV）  421 （ 4-6 ） 534 - 539 2006年04月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  00092614

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The effect of Cs atom doping on metallic aluminum clusters and covalent silicon clusters, AlnCsm (n = 5-14, m = 0-3) and SinCsm (n = 5-16, m = 0-3), was examined by mass spectrometry and anion photoelectron spectroscopy. For clusters containing Cs atom(s), the electron affinities of both clusters are generally decreased and the following characteristic features are observed: for AlnCsm, Cs-atom doping causes (1) electron filling into the electronic shell structure of the Aln clusters and (2) geometrical packing of icosahedral 13-atoms, while for SinCsm Cs-atom doping enhances electronic stability to be ascribed to pure Sin clusters, particularly at (n, m) = (10, 3) and (13, 1). © 2006 Elsevier B.V. All rights reserved.

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Laser synthesis and magnetism of amorphous iron and cobalt carbide nanoparticles with carbon onion

S. H. Huh, A. Nakajima

Journal of Applied Physics （American Institute of Physics）  99 （ 6 ） 064302 - (5 pages) 2006年03月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  0021-8979

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Amorphous iron or cobalt carbide nanoparticles with a carbon onion structure were produced using a pulsed laser ablation of metallocene powders at room temperature. While they are ferromagnetic at room temperature, they exhibit a drastic change in magnetic spin moments at 20-30 K. These magnetic properties are ascribed to a considerable magnetic contribution of superparamagnetism for the amorphous iron or cobalt carbide nanoparticles with a carbon onion and the origin of the magnetic properties is discussed. © 2006 American Institute of Physics.

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Classification and characterization of gold and nickel nanoparticles with a differential mobility analyzer

Y. Naono, S. Kawabata, S. H. Huh, A. Nakajima

Science and Technology of Advanced Materials （National Institute for Material Science）  7 （ 2 ） 209 - 215 2006年03月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  1468-6996

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Ultrafine gold and nickel nanoparticles (NPs) were fabricated by pulsed laser ablation in helium gas, and the NPs 2-15 nm in diameter were selectively classified by an electrostatic size-selection technique employing a low-pressure differential mobility analyzer (LP-DMA). In the classification of the NPs, a chain of several gold NPs or doubly charged NPs were produced as well as singly charged spherical NPs. The morphological selection was performed with the LP-DMA, using a relationship in which the cross section of the spherical NP chains was governed by the product of the diameter and the length, instead of by the square of the diameter. Below a blocking temperature of about 100 K, the Ni NPs that were 3.1 nm in diameter exhibited ferromagnetism. © 2006 Elsevier Ltd. All rights reserved.

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Soft-landing isolation of vanadium-benzene sandwich clusters on a room-temperature substrate using n-alkanethiolate self-assembled monolayer matrixes

M. Mitsui, S. Nagaoka, T. Matsumoto, A. Nakajima

Journal of Physical Chemistry B （American Chemical Society）  110 （ 7 ） 2968 - 2971 2006年02月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  1520-6106

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Gas-phase synthesized vanadium-benzene 1:2 (VBz2) sandwich clusters were size-selectively deposited onto bare gold and long-chain n-alkanethiolate [-S-(CH2)n-1-CH3; n = 16, 18, and 22] self-assembled monolayer (SAM)-coated gold substrates under ultrahigh vacuum (UHV) conditions. Investigation of the resulting deposited clusters was performed by infrared reflection absorption spectroscopy (IRAS) and thermal desorption spectroscopy (TDS). The IR frequencies of the soft-landed VBz 2 clusters show excellent agreement with the fundamentals reported in IR data of VBz2 in an argon matrix. The analysis of IRAS spectra reveals that while there was no orientational preference of the VBz2 clusters on a bare gold substrate, the VBz2 clusters deposited onto the SAM substrates were highly oriented with the molecular axis 70-80° tilted off the surface normal. In addition, analysis of TDS spectra revealed unusually large adsorption heats of the physisorbed VBz2 clusters. The present results are explained by cluster penetration into the long-chain alkanethiolate SAM and for the first time demonstrate the matrix isolation of gas-phase organometallic clusters around room temperature. © 2006 American Chemical Society.

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From Si₁₆ to Ge₁₆: Geometric Origins of Robustness in Binary Cage Superatoms on Organic Substrates

Yugo Osada, Ryoichi Sato, Takashi Nishikawa, Miwa Tokita, Toshiaki Kamoshida, Masahiro Shibuta, Tsugunosuke Masubuchi, Miho Hatanaka, Atsushi Nakajima*

Journal of Physical Chemistry C （American Chemical Society）  in press 2006年02月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り

Determination of the excited-state structure of 7-azaindole-water cluster using a Franck-Condon analysis

R. Brause, D. Krügler, M. Schmitt, K. Kleinermanns, A. Nakajima, T. A. Miller

Journal of Chemical Physics （American Institute of Physics）  123 （ 22 ） 224311 2005年12月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  0021-9606

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The change of the 7-azaindole-water cluster structure upon electronic excitation was determined by a Franck-Condon analysis of the intensities in the fluorescence emission spectra obtained via excitation of five different vibronic bands. A total of 105 emission band intensities were fitted, together with the changes of rotational constants of one isotopomer. These rotational constants have been obtained from a fit to the rovibronic contour of the cluster. The geometry change upon electronic excitation to the π π* state can be described by a strong and asymmetric shortening of the hydrogen bonds and a deformation of both the pyridine and the pyrrole rings of 7-azaindole. The resulting geometry changes are interpreted on the basis of ab initio calculations. © 2005 American Institute of Physics.

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New world in soft-nano-materials

K. Kaya, A. Nakajima, M. Mitsui

Proceedings - 2005 International Conference on MEMS, NANO and Smart Systems, ICMENS 2005 （IEEE COMPUTER SOC）     231 - 232 2005年11月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

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Magnetic properties of lanthanide organometallic sandwich complexes produced in a molecular beam

K. Miyajima, M. B. Knickelbein, A. Nakajima

Polyhedron （Pergamon-Elsevier Science Ltd.）  24 （ 16-17 ） 2341 - 2345 2005年11月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  0277-5387

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The magnetic properties of gas-phase terbium-cyclooctatetraene multi-decker sandwich complexes, Tbn(C8H8)n+1 were measured using a Stern-Gerlach type magnetic deflection approach. Beams of Tbn(C8H8)n+1 complexes displayed one-sided deflection toward high field - indicating that fast spin relaxation occurs within the complexes as they pass through the magnetic field. The magnetic moment for Tbn(C8H8)n+1 (n = 1-5) was evaluated using the Langevin model. Evolution of magnetic moment with the complex size is discussed with electronic structures for oxidation states of Tb3+/2+ ions, implying the possibility of antiferromagnetic interaction of two adjacent Tb2+ ions. © 2005 Elsevier Ltd. All rights reserved.

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Preparation of a SERS substrate using vacuum-synthesized silver nanoparticles

N. Horimoto, N. Ishikawa, A. Nakajima

Chemical Physics Letters （Elsevier Science BV）  413 （ 1-3 ） 78 - 83 2005年09月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  0009-2614

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Vacuum-synthesized Ag nanoparticles were dispersed and immobilized on an organosilane-functionalized glass surface in water. Nearly spherical particles with diameters of ≈ 200 nm were used for a substrate for surface enhanced Raman scattering (SERS). Molecules deposited on this substrate in both gas and liquid phases were detected by SERS. The SERS efficiency of this substrate was compared with that of Ag colloidal substrate and the morphological difference of these SERS substrates was studied by scanning electron microscopy. The aggregates of 5-10 Ag nanoparticles formed at the spread area exhibited prominent SERS activity. © 2005 Elsevier B.V. All rights reserved.

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