研究者詳細 - 山本　瑛祐

Facile Synthesis of Pd Nanosheets and Implications for Superior Catalytic Activity 査読有り

Ando, S; Yamamoto, E; Kobayashi, M; Kumatani, A; Osada, M

ACS NANO 18 巻 ( 1 ) 頁： 461 - 469 2023年11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：ACS Nano

As a member of the 2D materials family, 2D metal nanosheets (metallenes) have received increasing attention due to their intriguing properties distinct from those of graphene and other inorganic 2D nanosheets. However, the synthesis of metallenes is still challenging, owing to the lack of an efficient synthetic approach. Here we present a facile one-pot approach to the controlled synthesis of Pd nanosheets. A key feature of this process is a stepwise reaction using 2,4,6-trichlorophenyl formate (TCPF); TCPF emits carbon monoxide gas, which acts as both a reductant and a surface capping agent, promoting the anisotropic 2D growth of the Pd nanosheets. Photoemission spectroscopy revealed some peculiar features of the surface charge and valence band states due to suppressed electron transfer at the 2D surface. This surface state caused improved catalytic activity for the hydrogen evolution reaction compared to that of bulk Pd.

DOI： 10.1021/acsnano.3c07861

2D Bismuth Oxyfluorides: A New Member of Cationic Nanosheets 査読有り

Kobayash, M; Tasaka, T; Yamamoto, E; Osada, M

CHEMISTRY LETTERS 52 巻 ( 6 ) 頁： 449 - 451 2023年6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：Chemistry Letters

Two kinds of single-crystalline oxyfluoride nanosheets were synthesized by exfoliation of layered bismuth oxyfluorides intercalated with nitrates. The solution-based exfoliation process produced multilayered cationic oxyfluoride nanosheets with thicknesses of several nanometers. A second harmonic generation measurement clarified that one of the nanosheets had a noncentrosymmetric structure. This is the first example of a cationic nanosheet with nonlinear optical properties.

DOI： 10.1246/cl.230136

CiNii Research

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：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：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 査読有り国際誌

Tsunematsu, H; Shi, Y; Yamamoto, E; Kobayashi, M; Yoshida, T; Osada, M

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

Thermal shielding materials that can block near-infrared (NIR) light from the sunlight while maintaining visible transparency have become increasingly important from an energy-saving perspective. Here, we demonstrate a gigantic NIR shielding by an engineered plasmonic material based on a two-dimensional (2D) polytungstate (Cs4-xW11O35-d). Starting from a charge-neutral polytungstate (Cs4W11O35), we synthesize charge-imbalanced 2D nanosheets (Cs4-xW11O35-d) that undergo an unusual structural change with the semiconductor-to-metal transition in a reduced atmosphere. Layer-by-layer engineering of the 2D nanosheets enables a plasmon-induced enhancement of the NIR reflectance (>53%) with a high visible transparency (>71%), realizing high-performance thermal shielding. Our approach offers a solution for future thermal management technology.

DOI： 10.1021/acsnano.3c00815

Automated One-Drop Assembly for Facile 2D Film Deposition 査読有り

Shi, Y; Yamamoto, E; Kobayashi, M; Osada, M

ACS APPLIED MATERIALS & INTERFACES 15 巻 ( 18 ) 頁： 22737 - 22743 2023年5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：ACS Applied Materials and Interfaces

The effective application of 2D materials is strongly dependent on the mass production of high-quality large-area 2D thin films. Here, we demonstrate a strategy for the automated manufacturing of high-quality 2D thin films using a modified drop-casting approach. Our approach is simple; by using an automated pipette, a dilute aqueous suspension is dropped onto a substrate heated on a hotplate, and controlled convection by Marangoni flow and liquid removal causes the nanosheets to come together to form a tile-like monolayer film in 1-2 min. Ti0.87O2 nanosheets are utilized as a model system for investigating the control parameters such as concentrations, suction speeds, and substrate temperatures. We perform the automated one-drop assembly of a range of 2D nanosheets (metal oxides, graphene oxide, and hexagonal boron nitride) and successfully fabricate various functional thin films in multilayered, heterostructured, and sub-micrometer-thick forms. Our deposition method enables on-demand large-size (>2 inchϕ) manufacturing of high-quality 2D thin films while reducing the time and sample consumption.

DOI： 10.1021/acsami.3c02250

Ultrahigh Energy Storage in 2D High-κ Perovskites 査読有り

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

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

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5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：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

CiNii Research

Composite design of two-dimensional inorganic nanosheets for flexible energy storage capacitors 査読有り

Byun, KN; Shi, Y; Yamamoto, E; Kobayashi, M; Osada, M

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 131 巻 ( 4 ) 頁： 77 - 82 2023年4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 the Ceramic Society of Japan

We present a new approach for designing flexible energy storage capacitors using two-dimensional (2D) inorganic nanosheets. 2D dielectric Ca2Nb3O10 nanosheet and ferroelectric poly(vinylidene fluoride) (PVDF) were selected as model material systems. LangmuirBlodgett deposition was utilized for layer-by-layer engineering of (Ca2Nb3O10/PVDF) nanocomposite films on an indium tin oxide (ITO)-coated polyethylene terephthalate (PET) substrate. Such a new composite design realized the simultaneous improvement of energy density (37 J cm13) and efficiency (378 %) even in the ultrathin form (320 nm) on the ITO-coated PET substrate. Nanosheet-based flexible capacitors also maintained a stable performance even after 104 times bending cycles. These results indicate that our nanosheet approach is of technological importance for exploring new flexible dielectric capacitors.

DOI： 10.2109/jcersj2.22150

CiNii Research

Molecularly Thin BaTiO<sub>3</sub> Nanosheets with Stable Ferroelectric Response 査読有り

Hagiwara, K; Byun, KN; Morita, S; Yamamoto, E; Kobayashi, M; Liu, XY; Osada, M

ADVANCED ELECTRONIC MATERIALS 9 巻 ( 4 ) 頁： 2201239 - 2201239 2023年4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：Advanced Electronic Materials

2D ferroelectrics provide great promise for future electronics owing to their unique properties at 2D limit. Although simple perovskite oxides (such as BaTiO3 and PbTiO3) are an important target for 2D ferroelectrics, controlled synthesis of 2D nanosheets still remains a challenge. Here, this issue is addressed by using a new chemical protocol; unilamellar Ti0.87O2 nanosheets can serve as templates, guiding the solvothermal synthesis of 2D BaTiO3 nanosheets with a molecularly thin thickness (< 3 nm). Raman spectroscopy, second-harmonic generation, and transmission electron microscopy characterizations suggest the formation of tetragonal ferroelectric BaTiO3 nanosheets. Based on piezoresponse force microscopy, BaTiO3 nanosheets exhibit a clear ferroelectric response with a high Curie temperature (≈100 °C) even down to 1.8 nm thickness. This study provides new opportunities to investigate perovskite ferroelectrics with the critical thickness.

DOI： 10.1002/aelm.202201239