研究者詳細 - 長田　実

Free-Standing Molecularly Thin Amorphous Silica Nanosheets 査読有り

Yamamoto, E; Fujihara, K; Takezaki, Y; Ito, K; Shi, Y; Kobayashi, M; Osada, M

SMALL 19 巻 ( 22 ) 頁： e2300022 - 2300022 2023年6月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Small

Recent progress in 2D materials has initiated new fields of molecularly thin amorphous materials with mysterious properties and structures. However, designed synthesis of molecularly thin amorphous silica still remains a challenge; whether free-standing molecularly thin amorphous silica nanosheets can exist is unclear. Here, this issue is addressed by using a new chemical protocol; solid-state surfactant lamellae with ordered alkyl-chain arrangements can serve as superior templates guiding free-standing amorphous silica nanosheets. Simple sonication of the lamellar hybrids allows exfoliation into monolayer amorphous silica nanosheets with 0.9 nm thickness. In addition, the nanosheets show the distinctive feature of high colloidal stability that enables atomic layer engineering of silica nanocoatings and dielectric nanofilms. The approach may shed new light on the properties and applications of old silica.

DOI： 10.1002/smll.202300022

その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/smll.202300022

Gigantic Thermal Shielding in 2D Oxide Nanosheets 査読有り

Hirofumi Tsunematsu, Yue Shi, Eisuke Yamamoto, Makoto Kobayashi, Tomohiro Yoshida, Minoru Osada

ACS Nano 17 巻 ( 12 ) 頁： 11396 - 11405 2023年5月

Ultrahigh Energy Storage in 2D High-κ Perovskites 国際誌

Kim, HJ; Morita, S; Byun, KN; Shi, Y; Taniguchi, T; Yamamoto, E; Kobayashi, M; Ebina, Y; Sasaki, T; Osada, M

NANO LETTERS 23 巻 ( 9 ) 頁： 3788 - 3795 2023年5月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Nano Letters

Dielectric capacitors have greater power densities than batteries, and, unlike batteries, they do not utilize chemical reactions during cycling. Thus, they can become ideal, safe energy storage devices. However, dielectric capacitors yield rather low energy densities compared with other energy storage devices such as batteries and supercapacitors. Here, we present a rational approach for designing ultrahigh energy storage capacitors using two-dimensional (2D) high-κ dielectric perovskites (Ca2Nam-3NbmO3m+1; m = 3-6). Individual Ca2Nam-3NbmO3m+1 nanosheets exhibit an ultrahigh dielectric strength (638-1195 MV m-1) even in the monolayer form, which exceeds those of conventional dielectric materials. Multilayer stacked nanosheet capacitors exhibit ultrahigh energy densities (174-272 J cm-3), high efficiencies (>90%), excellent reliability (>107 cycles), and temperature stability (−50-300 °C); the maximum energy density is much higher than those of conventional dielectric materials and even comparable to those of lithium-ion batteries. Enhancing the energy density may make dielectric capacitors more competitive with batteries.

DOI： 10.1021/acs.nanolett.3c00079

Autonomous Light Intensity Adaptation in an Energy-Efficient Retinomorphic Organic Ferroelectric Neuristor

Li, LF; Dai, QY; Li, YT; Pei, MJ; Osada, M; Li, Y

ADVANCED OPTICAL MATERIALS 2024年3月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Advanced Optical Materials

In biological visual systems, retina with bidirectional photoresponse can adapt to variable environments and modulate their photosensitivity dependent on illumination conditions in an energy-efficient way. However, to emulate the visual functionality, current systems still require a sustained power supply and manipulate the electrical stimulation manually according to light intensity, thus incurring high energy consumption and the lack of autonomous adaptive function. Herein, an organic ferroelectric neuristor emulating the visual self-adaptation function of retina is introduced. Such autonomous adaptive behavior of device originates from the trap-assisted ferroelectric polarization reversal under light illumination. It allows to realize bidirectional photoresponse in a single device according to light intensity, thus breaking through the limitation of commonly adaptive devices with single photoresponse mechanisms. In particular, only a single gate voltage pulse with an ultralow energy consumption of ≈34 pJ is required to accomplish the adaptation behavior, endowing the visual perception with high autonomy and power efficiency. Finally, the application potential of the neuristor in image pre-processing and recognition under bright and dim light conditions is demonstrated. Therefore, this work opens up a path for the development of retina-like visual systems with highly energy efficient.

DOI： 10.1002/adom.202303172

Multiemission of Ce3+ from a Single Crystallographic Site Induced by Disordering of Ions

Yasunaga, T; Kobayashi, M; Oqmhula, K; Qi, H; Ichibha, T; Hongo, K; Yamamoto, S; Maezono, R; Mitsuishi, M; Osada, M; Kato, H; Kakihana, M

INORGANIC CHEMISTRY 63 巻 ( 2 ) 頁： 1288 - 1295 2024年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Inorganic Chemistry

White-light emission with a single activator is an attractive function of phosphors. In this work, we investigated the photoluminescence properties of Ca5.7Y1.3Si7O16.7N3.3, which is a compound denoted as Ca4+xY3-xSi7O15+xN5-x discovered by our group, with Ce-activation using optical measurements and density functional theory (DFT) calculation. Samples showed a tunable emission from purple to white under ultraviolet (UV) light. In this compound, Ca and Y as well as anions are distributed disorderly, and Ca/Y ions occupy two crystallographically distinct sites; those sites are possible sites for Ce substitution. DFT calculation and structural refinement revealed that the tunable emission was generated by Ce at the crystallographically equivalent site but with distinct local structures caused by the disordering of cations and anions. As far as we know, this is the first report about a white-light-emitting phosphor with only Ce activation.

DOI： 10.1021/acs.inorgchem.3c03789

Understanding the role of solvents in bottom-up synthesis of multi-element hydroxides

Li, F; Yoshida, K; Chuc, NV; Osada, M; Abe, H

RSC ADVANCES 14 巻 ( 1 ) 頁： 75 - 82 2024年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：RSC Advances

Here we report a comparative study on the bottom-up synthesis of multi-element hydroxides composed of Mg, Al, Fe and Zn cations to understand the role of solvents. Two common solvents, water and ethylene glycol, a typical polyol, are used. The polyol-derived MgAlFeZn-OH are nanosheets with homogeneous elemental distribution, while the hydrothermal-derived MgAlFeZn-OH are mixtures of plate-like hydroxide layers and rod-like spinel oxides. The coordinating properties and the high viscosity of the ethylene glycol provide the possibility to mediate the hydrolysis rates and to control the particle growth. The high specific surface area of the polyol-derived multi-element hydroxide nanosheets (352.4 m2 g−1) guarantees them as excellent adsorbents for adsorbing anionic dyes in aqueous solution.

DOI： 10.1039/d3ra07344k

Hetero-assembly design of 2D oxide nanosheets for tailored thermal shielding materials

Tsunematsu, H; Nishibashi, K; Yamamoto, E; Kobayashi, M; Yoshida, T; Osada, M

APPLIED PHYSICS EXPRESS 17 巻 ( 1 ) 頁： 015002-1 - 015002-5 2024年1月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Express

We present a new approach for designing thermal shielding materials using two-dimensional oxide nanosheets. Our approach uses hetero-assembly design [(Ti0.87O2)m (Cs2.7W11O35−d )20 (m = 0, 5, 10)] by overlaying high refractive index (n) Ti0.87O2 nanosheets with transparent conducting Cs2.7W11O35−d nanosheets. Through proper design of the thickness of high-n Ti0.87O2 layers, we achieved the optimum thermal shielding properties with a high NIR reflectance (>46%), a high visible transparency (>76%) and a neutral color in an ultrathin form (<60 nm). Our nanosheet approach is of technological importance for exploring new thermal shielding materials.

DOI： 10.35848/1882-0786/ad13ce

Tuning the structures and conductivity of nanoporous TiO2-TiO films through anodizing electrolytes as LIB anodes with ultra-high capacity and excellent cycling performance 査読有り

Chen, XW; Kure-Chu, SZ; Liu, JC; Matsubara, T; Sakurai, Y; Hihara, T; Lee, SH; Osada, M; Okido, M

JOURNAL OF ENERGY STORAGE 73 巻頁： 109231 2023年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Energy Storage

Titanium dioxide (TiO2) is a typical lithium-ion storage material with various advantages including a stable structure, an abundant source, and facile preparation. To further improve the lithium-ion diffusion, we employed a smart anodization method to prepare nanoporous TiO2–TiO (TT) films with a fast growth rate and excellent charge/discharge performance. The key feature is the use of nitric-based electrolytes with the addition of glycine and ethanol, which rapidly form approximately five times thicker TiO2 nanoporous films compared to previous studies. The addition of glycine and ethanol to nitric-based electrolytes improve both the nanoporous structures and conductivity of titania films, thereby forming highly active TiO and a large surface area, which further accelerates the diffusion of lithium ions. As a lithium-ion battery (LIB) anode, the E-G-TT specimen offers the highest initial discharge capacity (3418 μA h−1 cm−2, 30 μA cm−2), which is approximately eight times higher than that of the titania film obtained without additives (TT). Furthermore, a high discharge capacity of >1100 μA h−1 cm−2 can be maintained after 100 cycles, which can be mainly attributed to the enhancement of conductivity and charge transition of the composite films due to the synergistic effect of ethanol and glycine addition.

DOI： 10.1016/j.est.2023.109231

Understanding the fast formation mechanism of hard nanoporous alumina films on aluminum in acidic solutions containing nitric acid 査読有り

Liu, JC; Kure-Chu, SZ; Sakurai, Y; Chen, XW; Osada, M

MATERIALS CHEMISTRY AND PHYSICS 309 巻頁： 128271 2023年11月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Chemistry and Physics

Nanoporous alumina films formed on aluminum via anodization are widely used for scientific and technical purposes owing to their various advantageous properties, including excellent corrosion and wear resistance, good thermal and electrical insulation, and facile producibility at low cost. Herein, we report a novel approach to fabricate hard porous anodic alumina (PAA) films by adding an appropriate amount of nitric acid to sulfuric-, oxalic-, and phosphoric-acid solutions at critical high current densities. The effects of the nitric additives on the anodizing behavior, film growth mechanism, microstructure, chemical composition, film thickness, microhardness, and appearance of the PAA films formed from various solutions were systematically investigated. The addition of nitric acid enhanced the formation of alumina and resulted in fast growth rates of 196 μm/h and 166 μm/h for sulfuric- and oxalic-based solutions, respectively, while maintaining high hardness of approximately 380 and 430 HV0.1, respectively. The surface hardness of the films decreased to some extent with the increase in nitric acid concentration and/or film thickness owing to the strong corrosive nature of nitric acid during prolonged anodization, although nitrogen inclusion in anodic alumina films was not detected through X-ray photo-electron spectroscopy, which differs from the other acidic anions. In particular, the barrier layer thickness and pore intervals of PAA films increased with the nitric concentration in the aforementioned solutions, leading to a fast growth rate and high hardness inside the films.

DOI： 10.1016/j.matchemphys.2023.128271

Emerging ceramic nanosheets: From tailored synthesis to electronic applications 査読有り

Osada, M

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 131 巻 ( 11 ) 頁： 851 - 862 2023年11月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Ceramic Society of Japan

Two-dimensional (2D) nanosheets, which possess atomic or molecular thicknesses and infinite lateral lengths, have received increasing attention due to their intriguing physicochemical properties distinct from those of their bulk counterparts. In particular, the discovery of graphene has opened new possibilities for exploring the fascinating properties of 2D nanosheets of other layered and non-layered compounds. 2D inorganic nanosheets (ceramic nanosheets) are important targets in this regard due to their diversity in chemical composition, structure and functionality beyond graphene. Here, we review recent advances in the synthesis, assembly and properties of 2D oxide nanosheets, highlighting emerging functionalities in electronic applications.

DOI： 10.2109/jcersj2.23126

CiNii Research

Engineering Interface Defects and Interdiffusion at the Degenerate Conductive In2O3/Al2O3 Interface for Stable Electrodes in a Saline Solution 査読有り

Z. Zhu, T. Yasui, X. Zhao, Q. Liu, S. Morita, Y. Li, A. Yonezu, K. Nagashima, T. Takahashi, M. Osada, R. Matsuda, T. Yanagida, Y. Baba

ACS Applied Materials & Interfaces 15 巻 ( 30 ) 頁： 36866 - 36876 2023年7月

Thermal and Chemical Phase Engineering of Two-Dimensional Ruthenate 査読有り

Leanddas Nurdiwijayanto, Kensuke Hayashi, Nobuyuki Sakai, Yasuo Ebina, Dai-Ming Tang, Shigenori Ueda, Minoru Osada, Kazuhito Tsukagoshi, Takayoshi Sasaki, Takaaki Taniguchi

ACS Nano 17 巻 ( 13 ) 頁： 12305 - 12315 2023年6月

Layer-dependent stability of 2D mica nanosheets 査読有り国際共著

Jae-Hun Kim, Vadym V Kulish, Shunnian Wu, Ping Wu, Yue Shi, Minoru Osada, Hyoun Woo Kim, Sang Sub Kim

Scientific Reports 13 巻頁： 7880 2023年5月

2D bismuth oxyfluorides: a new member of cationic nanosheets 査読有り

M. Kobayashi, T. Tasaka, E. Yamamoto, M. Osada

Chem. Lett. 52 巻 ( 6 ) 頁： 449 - 451 2023年4月

Pseudo-topotactic Transformation from Oxide Nanosheets to Amorphous Nanosheets 査読有り

Sugimoto, H; Kobayashi, M; Yamamoto, E; Osada, M

CHEMISTRY LETTERS 52 巻 ( 5 ) 頁： 322 - 324 2023年4月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Chemistry Letters

We demonstrated the synthesis of amorphous oxide nanosheets from crystalline nanosheets prepared by the exfoliation of layered compounds. Single-crystalline oxide nanosheets were calcined with C3N4 powder in flowing nitrogen and annealed in air to produce amorphous oxide nanosheets. The cation composition and valence, shape, lateral size, surface roughness, and thickness were not changed by treatment. This approach enables the production of amorphous oxide nanosheets with distinct morphologies and compositions and large lateral sizes.

DOI： 10.1246/cl.230073