研究者詳細 - 長田　実

酸化物ナノシートのヘテロ構造集積と電子材料応用

長田実

応用物理 93 巻 ( 12 ) 頁： 690 - 695 2024年12月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：公益社団法人応用物理学会

<p>酸化物ナノシートは究極の2次元性とともに，グラフェンにはない組成，構造，機能の多様性を具備しており，グラフェンで実現できない機能発現を目指す「ポストグラフェン材料」の新しい舞台として注目されている．特に，超伝導性，強誘電性，強磁性など，酸化物の示す多彩な物性は，新しい電子材料，環境・エネルギー材料として興味深いものであり，ナノシート単体，複合体として多岐にわたる応用が検討されている．本稿では，筆者らのグループの研究を中心に，酸化物ナノシートの合成・集積技術とともに，電子材料応用について紹介したい．</p>

DOI： 10.11470/oubutsu.93.12_690

CiNii Research

Atomic Layer Engineering of Ferroelectricity in Dion-Jacobson Perovskites 査読有り

Morita, S; Urushihara, D; Nishibashi, K; Kobayashi, M; Yamamoto, E; Asaka, T; Nakajima, H; Mori, S; Osada, M

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 146 巻 ( 36 ) 頁： 25221 - 25231 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：Journal of the American Chemical Society

Recent advances in “hybrid-improper” ferroelectricity in Dion-Jacobson (DJ)-type layered perovskites have caused renewed interest in the search for new ferroelectrics. Here, we present an approach for the tailored synthesis of a new homologous series of DJ-type layered perovskites Cs(Bi2Srn-3)(Tin-1Nb)O3n+1. Starting from CsBi2Ti2NbO10 (n = 3), higher-order homologous phases with n = 4 and 5 were successfully synthesized by repeated solid-state calcination with SrTiO3. Characterizations by X-ray diffraction, electron diffraction, transmission electron microscopy, Raman scattering, and second harmonic generation showed the detailed structural features in Cs(Bi2Srn-3)(Tin-1Nb)O3n+1, and the polar structures could be stabilized by proper or hybrid-improper ferroelectricity, depending on the odd or even number of the perovskite layers. Our results provide important insights into the competition between the different mechanisms and the consequences of the ferroelectric properties in homologous layered perovskites.

DOI： 10.1021/jacs.4c09214

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

ナノ材料でつくる高性能誘電体キャパシタ

長田実

自動車技術 78 巻頁： 114 - 115 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