研究者詳細 - 長田　実

Atomic Layer Engineering of Pd Nanosheets for an Enhanced Hydrogen Evolution Reaction

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

NANO LETTERS 24 巻 ( 36 ) 頁： 11239 - 11245 2024年8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

Thickness control of two-dimensional (2D) metal nanosheets (metallenes) has scientific significance for energy and catalyst applications, yet is unexplored owing to the lack of an efficient approach for the tailored synthesis of metallenes with controlled atomic layers. Here we report a 2D template-directed synthesis of ultrathin Pd nanosheets with well-controlled thicknesses. Molecularly thin single-crystalline Pd nanosheets with well-defined hexagonal morphologies were synthesized via a one-pot method with 2,4,6-trichlorophenyl formate. Such Pd nanosheets were used as hard templates for the tailored synthesis of the Pd nanosheets with controlled thicknesses (9, 11, 13, and 15 atomic layers). Hard X-ray photoelectron spectroscopy and density functional theory calculations revealed unique electronic states in thickness-controlled Pd nanosheets; these states included reduced surface charges to bulk, increased work functions, and decreased d-band centers. Thus, atomic layer engineering of Pd nanosheets enabled the fine-tuning of the surface electronic states to improve the hydrogen evolution reaction.

DOI： 10.1021/acs.nanolett.4c02741

Solid-state surfactant templating for controlled synthesis of amorphous 2D oxide/oxyhydroxide nanosheets 査読有り

Yamamoto, E; Kurimoto, D; Ito, K; Hayashi, K; Kobayashi, M; Osada, M

NATURE COMMUNICATIONS 15 巻 ( 1 ) 頁： 6612 2024年8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：Nature Communications

As a member of 2D family, amorphous 2D nanosheets have received increasing attention due to their unique properties that are distinct from crystalline 2D nanosheets. However, compared with the vast library of crystalline 2D nanosheets, amorphous 2D nanosheets are still infancy due to the lack of an efficient synthetic approach. Here, we present a strategy that yields a library of 10 distinct amorphous 2D metal oxides/oxyhydroxides using solid-state surfactant crystals. A key feature of this process is a stepwise reaction using solid surfactant; the solid-state surfactant crystals have metal ions arranged in the interlayer space, and hydrolysis of the metal ions leads to the formation of isolated clusters in the surfactant crystals via limited condensation reactions. Immersing the surfactant crystals in formamide promotes nanosheet formation through the self-assembly of clusters by templating the morphologies of the crystals generated from surfactants crystals. Our approach opens a flatland in amorphous 2D world.

DOI： 10.1038/s41467-024-51040-2

Ultrafast 2D Nanosheet Assembly via Spontaneous Spreading Phenomenon 査読有り国際共著

Shi, Y; Li, H; Tsunematsu, H; Ozeki, H; Kano, K; Yamamoto, E; Kobayashi, M; Abe, H; Chen, CW; Osada, M

SMALL 20 巻 ( 36 ) 頁： e2403915 2024年7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

In 2D materials, a key engineering challenge is the mass production of large-area thin films without sacrificing their uniform 2D nature and unique properties. Here, it is demonstrated that a simple fluid phenomenon of water/alcohol solvents can become a sophisticated tool for self-assembly and designing organized structures of 2D nanosheets on a water surface. In situ, surface characterizations show that water/alcohol droplets of 2D nanosheets with cationic surfactants exhibit spontaneous spreading of large uniform monolayers within 10 s. Facile transfer of the monolayers onto solid or flexible substrates results in high-quality mono- and multilayer films with high coverages (>95%) and homogeneous electronic/optical properties. This spontaneous spreading is quite general and can be applied to various 2D nanosheets, including metal oxides, graphene oxide, h-BN, MoS2, and transition metal carbides, enabling on-demand smart manufacture of large-size (>4 inchϕ) 2D nanofilms and free-standing membranes.

DOI： 10.1002/smll.202403915

その他リンク： https://onlinelibrary.wiley.com/doi/pdf/10.1002/smll.202403915

ナノシートでつくる高性能日射遮蔽膜

長田実

クリーンエネルギー 33 巻頁： 47 - 50 2024年

無機ナノシートの精密合成と機能材料への応用

長田実

科学と工業 98 巻頁： 35 - 41 2024年

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

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：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

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

Single droplet assembly for two-dimensional nanosheet tiling 査読有り国際誌

Shi Yue, Osada Minoru, Ebina Yasuo, Sasaki Takayoshi

ACS Nano 14 巻 ( 11 ) 頁： 15216 - 15226 2020年11月

Ferroelectricity in CsPb2Nb3O10 and exfoliated 2D nanosheets 査読有り

Li, Y; Shimada, M; Kobayashi, M; Yamamoto, E; Canton-Vitoria, R; Liu, XY; Osada, M

DALTON TRANSACTIONS 2024年9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：Dalton Transactions

Pb-based perovskites play pivotal roles in ferroelectric research. In the search for new Pb-based ferroelectrics, we investigated the ferroelectric properties of Dion-Jacobson type CsPb2Nb3O10 and exfoliated 2D nanosheets. Ferroelectricity in CsPb2Nb3O10 was demonstrated for the first time. CsPb2Nb3O10 adopted a polar tetragonal structure with a modest TC = 260 °C and polarization PS = 7.93 μC cm−2; the polarization mainly arose from the out-of-plane displacements of Nb5+ ions and nearby oxygens. CsPb2Nb3O10 layered perovskite offers additional advantages for tailoring ferroelectric nanomaterials, as exfoliated 2D nanosheets provide novel platforms for investigating ferroelectric properties down to the 2D limit. Piezoresponse force microscopy confirmed stable ferroelectricity even in exfoliated 2D Pb2Nb3O10 nanosheets.

DOI： 10.1039/d4dt02343a

Synthesis of Gold Nanoparticles Using Au(OH)₃ as a Precursor in Aqueous Media 査読有り

スマートプロセス学会誌 13 巻 ( 4 ) 頁： 200 - 204 2024年7月

Autonomous Light Intensity Adaptation in an Energy-Efficient Retinomorphic Organic Ferroelectric Neuristor 査読有り国際共著

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 査読有り

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 査読有り

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 査読有り

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