Papers - Isobe, Tetsuhiko

Review-synthesis, luminescent properties, and stabilities of cesium lead halide perovskite nanocrystals

Iso Y., Isobe T.

ECS Journal of Solid State Science and Technology (ECS Journal of Solid State Science and Technology)  7 ( 1 ) R3040 - R3045 2018

Research paper (scientific journal), Joint Work, Accepted,  ISSN  21628769

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© The Author(s) 2017. Published by ECS. All-inorganic cesium lead halide perovskite CsPbX3(X = Cl, Br, I) nanocrystals have emerged as promising luminescent quantum dots. In this review, we summarize recent work on their synthesis, luminescent properties, and stabilities. Through controlling the composition of the alloyed halides and quantum size effects, the band gaps and emission wavelengths of CsPbX3nanocrystals are readily tunable over the entire visible range. Their sharp emission line-widths extend the color gamut of liquid crystal displays. They also exhibit high photoluminescence (PL) quantum yields and fast PL lifetimes. CsPbX3nanocrystals with both cubic and plate shapes have been successfully synthesized through several liquid-phase methods, such as hot-injection, room-temperature, and amine-free methods. The sizes and shapes of CsPbX3nanocrystals can be controlled via the reaction temperature and the length of the n-alkyl carboxylic acids and n-alkylamines used in their synthesis. Several attempts have been made to improve their stabilities during storage, at high temperature, and under light irradiation, for example by incorporation of CsPbX3nanocrystals into silica or polymer matrixes.

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Photoluminescence color stability of green-emitting InP/ZnS core/shell quantum dots embedded in silica prepared via hydrophobic routes

Watanabe T., Iso Y., Isobe T., Sasaki H.

RSC Advances (RSC Advances)  8 ( 45 ) 25526 - 25533 2018

Research paper (scientific journal), Joint Work, Accepted

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© The Royal Society of Chemistry 2018. In this work, green-emitting InP/ZnS quantum dots (QDs) modified with 1-dodecanethiol were embedded into silica by two methods to improve their photostability while maintaining a high photoluminescence quantum yield (PLQY) and a color coordinate. A monolithic QD-silica composite prepared by a non-aqueous route with tetraethyl orthosilicate and lactic acid featured low transparency, a loss of the color purity of green, and a PLQY of 1.6%, which was considerably lower than that of the original QDs (67%). The decrease of the PLQY was attributed to QD aggregation in the sol-gel process and degradation of the QDs by the acid. The alternative method involved stirring a toluene dispersion of the QDs with tetramethyl orthosilicate (TMOS) for 20 h or 7 days. The PLQY of the TMOS-modified InP/ZnS QDs (20 h) was 62%, which was only slightly lower than that of the original QDs. The PLQY decreased to 52% when the duration of aging was prolonged to 7 days. This decrease was attributed to desorption of surface modifiers from the QD surface and oxidative degradation by oxygen dissolved in toluene. Herein, the color coordinate was maintained stably. Photostability was evaluated by continuous irradiation of the samples by a blue light emitting diode. The decrease of photoluminescence (PL) intensity was suppressed by the silica encapsulation. In particular, the PL intensity of the TMOS-modified InP/ZnS QD sample (7 d) maintained 99% of its initial intensity. Silica encapsulation of InP/ZnS QDs prevented contact of the QDs with oxygen in the air, resulting in improved photostability.

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Improved Photostability of Tetramethyl Orthosilicate-Modified InP/ZnS Quantum Dots

Taichi Watanabe, Yoshiki Iso, Tetsuhiko Isobe, Hirokazu Sasaki

Proceedings of the 24th International Display Workshops    671 - 672 2017.12

Research paper (international conference proceedings), Joint Work

Preparation of Photostable Fluorescent InP/ZnS Quantum Dots Embedded in TMAS-Derived Silica

Taichi Watanabe, Chikako Wada, Yoshiki Iso, Tetsuhiko Isobe, Hirokazu Sasaki

ECS J. Solid State Sci. Technol. 6 ( 7 ) R75 - R80 2017.05

Research paper (scientific journal), Joint Work, Accepted

Combinatorial optimization of the atomic compositions for green-emitting YBO3:Ce3+,Tb3+ and red-emitting YBO3:Ce3+,Tb3+,Eu3+ phosphors using a microplate reader

Kohei Yano, Satoru Takeshita, Yoshiki Iso, Tetsuhiko Isobe

RSC Adv. 7   17586 - 17592 2017.03

Research paper (scientific journal), Joint Work, Accepted

Synthesis of Y2O3:Bi3+,Eu3+ nanosheets from layered yttrium hydroxide precursor and their photoluminescence properties

Tomotaka Watanabe, Yoshiki Iso, Tetsuhiko Isobe

RSC Adv. 7   14107 - 14113 2017.03

Research paper (scientific journal), Joint Work, Accepted

Preparation and photoluminescence properties of yellow-emitting CuInS2/ZnS quantum dots embedded in TMAS-derived silica

Chikako Wada, Yoshiki Iso, Tetsuhiko Isobe, Hirokazu Sasaki

RSC Adv. 7   7936 - 7943 2017.01

Research paper (scientific journal), Joint Work, Accepted

Synthesis of Y2O3:Bi3+,Yb3+ nanosheets from layered yttrium hydroxide precursor and their photoluminescence properties

Keita Higashi, Yutaka Watanabe, Yoshiki Iso, Tetsuhiko Isobe

RSC Adv. 7   6671 - 6678 2017.01

Research paper (scientific journal), Joint Work, Accepted

Influence of chemical states of doped nitrogen on photoluminescence intensity of hydrothermally synthesized carbon dots

Shinichiro Niino, Satoru Takeshita, Yoshiki Iso, Tetsuhiko Isobe

J. Lumin. 180   123 - 131 2016.12

Research paper (scientific journal), Joint Work, Accepted

Low-temperature synthesis of YVO4:Bi3+,Eu3+ nanoparticle phosphors using a methanol solution of trivalent cations

Takayuki Ohno, Yoshiki Iso, Tetsuhiko Isobe

ECS J. Solid State Sci. Technol. 5 ( 9 ) R142 - R145 2016.09

Research paper (scientific journal), Joint Work, Accepted

Photoluminescence and photostability of YVO4:Eu3+ nanoparticle/layered double hydroxide multilayer films prepared via layer-by-layer assembly

Wataru Onishi, Satoru Takeshita, Yoshiki Iso, Tetsuhiko Isobe

J. Lumin. 175   71 - 77 2016.07

Research paper (scientific journal), Joint Work, Accepted

Solvothermal synthesis of YBO3:Ce3+,Tb3+ nanophosphor: influence of B/(Y + Ce + Tb) ratio on particle size and photoluminescence intensity

Akihiro Nohara, Satoru Takeshita, Yoshiki Iso, Tetsuhiko Isobe

J. Mater. Sci. 51 ( 7 ) 3311 - 3317 2016.04

Research paper (scientific journal), Joint Work, Accepted

Preparation, Photoluminescence, and Photostability of Transparent Composite Films of Glycothermally Synthesized YAG:Ce3+ Nanoparticles for White LED

Yuta Sasaki, Satoru Takeshita, Tetsuhiko Isobe

ECS J. Solid State Sci. Technol. 5 ( 1 ) R3049 - R3054 2016.01

Research paper (scientific journal), Joint Work, Accepted

Synthesis, photoluminescence, and photostability of Y2O3:Bi3+,Eu3+ nanosheets

Takuya Matsunaga, Satoru Takeshita, Tetsuhiko Isobe

J. Lumin. 165   62 - 67 2015.09

Research paper (scientific journal), Joint Work, Accepted

Two Photoenergy Conversion Modes of YVO4:Eu3+ Nanoparticles: Photoluminescence and Photocatalytic Activity

Yusuke Shiraishi, Satoru Takeshita, Tetsuhiko Isobe

J. Phys. Chem. C 119   13502 - 13508 2015.06

Research paper (scientific journal), Joint Work, Accepted

太陽電池応用に向けた波長変換材料の研究動向

磯部 徹彦

セラミックス 50 ( 3 ) 197-200 2015.03

Research paper (scientific journal), Single Work

Composites of Eu3+-doped calcium apatite nanoparticles and silica particles: comparative study of two preparation methods

Ayumu Isobe, Satoru Takeshita, Tetsuhiko Isobe

Langmuir 31   1811 - 1819 2015.01

Research paper (scientific journal), Joint Work, Accepted

Formation of Cu2SnS3 nanoparticles by sequential injection of tin and sulfur oleylamine solutions into Cu1.8S nanoparticle dispersion

Shin Okano, Satoru Takeshita, Tetsuhiko Isobe

Mater. Lett. 145   79 - 82 2015.01

Research paper (scientific journal), Joint Work, Accepted

ナノ蛍光材料の特性・作製方法と波長変換機能を用いた応用

磯部 徹彦

光アライアンス 25 ( 10 ) 9-12 2014.10

Research paper (scientific journal), Single Work

Effects of Annealing on the Photoluminescence Properties of Citrate-Capped YVO4:Bi3+,Eu3+ Nanophosphor

Yoshiki Iso, Satoru Takeshita, Tetsuhiko Isobe

J. Phys. Chem. C 118   11006 - 11013 2014.05

Research paper (scientific journal), Joint Work, Accepted