研究者詳細 - 長田　実

論文 - 長田　実

分割表示 213 件中 1 - 20 件目／全件表示 >>

Molecularly Thin Nanosheet Films as Water Dissociation Reaction Catalysts Enhanced by Strong Electric Fields in Bipolar Membranes 査読有り国際共著

Yamamoto, E; Gao, TY; Xiao, LQ; Kopera, K; Marth, S; Park, H; Bae, C; Osada, M; Mallouk, TE

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 147 巻 ( 17 ) 頁： 14270 - 14279 2025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 American Chemical Society

Bipolar membranes (BPMs) are interesting materials for the development of next-generation electrochemical energy conversion and separations processes. One of the key challenges in optimizing BPM performance is enhancing the rate of the water dissociation (WD) reaction. While electric field effects, specifically the second Wien effect, have been demonstrated to enhance the rate of WD reaction, making BPMs with low overpotentials for WD using primary electric field effects has been difficult to achieve. In this study, we constructed an abrupt interfacial structure between the anion exchange membrane (AEM) and cation exchange membrane (CEM) of BPMs to maximize the intensity of local electric field. A film of densely tiled, molecularly thin titanium oxide nanosheets was deposited as the interfacial layer to create an abrupt interface for studying extreme electric field effects. Although BPMs with titanium oxide nanosheet films exhibited higher WD reaction resistance compared to thicker catalyst layers composed of nanoparticles at low current density, they showed superior performance at higher current densities, where strong electric fields were present, and an apparent WD overpotential of 0.25 V at 300 mA cm<sup>-2</sup> was extracted from electrochemical impedance measurements. These results highlight the potential of optimizing BPM performance by maximizing the second Wien effect through the utilization of two-dimensionally assembled nanosheet films.

DOI： 10.1021/jacs.4c17830

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 Open Access

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

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

Tunable plasticity and multilevel photo-memory enabled by type-II heterojunctions in 2D nanosheet-based organic optical synapses 査読有り国際共著国際誌

Li, LF; Huang, QM; Osada, M; Zhao, JC; Li, Y

JOURNAL OF PHYSICS D-APPLIED PHYSICS 58 巻 ( 35 ) 2025年9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：Journal of Physics D Applied Physics

The rapid development of the Internet of Things is driving advances in neuromorphic photonic computing systems that leverage light for highly efficient and parallel information processing. Note that to achieve neuromorphic computing with artificial optical synapses, tunable synaptic plasticity and photo-memory functions enabled by direct optical modulation are essential. In this study, we design an organic optical synaptic device with a two-dimensional (2D) metal oxide nanosheet as the charge storage layer, demonstrating bimodal synaptic plasticity and multilevel photo-memory. The precise layer-by-layer liquid deposition technology enables direct integration of 2D Cs<inf>2.7</inf>W<inf>11</inf>O<inf>35</inf><sup>1.3−</sup> nanosheet films with controllable thickness into the device for charge storage. Through interfacial band engineering, a type-II heterojunction is established between the organic semiconductor channel and the inorganic nanosheet, enabling gate-voltage-free photogenerated charge transfer and storage. Under optical modulation, the device exhibits tunable synaptic behaviors ranging from short- to long-term plasticity and a multilevel photo-memory capability with a retention time of 10<sup>3</sup> s. Then, we confirm the potential of the synaptic device for highly efficient neuromorphic computing, demonstrating a recognition capability with a high accuracy of 97.8%. Therefore, our device sheds new light on the development of optical computing systems.

DOI： 10.1088/1361-6463/adfbfa

Covalent Functionalization of MXenes with Porphyrin for Visible-Light Activation in Energy Conversion Nanodevices 査読有り国際共著国際誌 Open Access

Li, H; Canton-Vitoria, R; Urano, Y; Nayak, SK; Yamamoto, E; Kobayashi, M; Kitaura, R; Osada, M

SMALL 21 巻 ( 38 ) 頁： e03895 2025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：Small

MXenes such as Ti<inf>3</inf>C<inf>2</inf> and Ti<inf>3</inf>CN are 2D materials characterized by the presence of a T<inf>x</inf> phase that passivates the reactive titanium surface. Modifying their chemical composition to anchor target molecules is of great interest for addressing key challenges, such as enhancing the conversion of visible light into electricity. In this study, a covalent functionalization strategy is developed to modify the T<inf>x</inf> phase of Ti<inf>3</inf>C<inf>2</inf> or Ti<inf>3</inf>CN with alkyl amines, followed by coupling with Zn-porphyrin. This process activates the optical properties of MXenes without causing any damage. X-ray photoelectron spectroscopy and infrared spectroscopy are pivotal in confirming the covalent functionalization, while thermogravimetric analysis, transmission electron microscopy, and additional techniques provided further insights into structural and chemical features. Spectroelectrochemical investigations reveal carrier injection into MXenes under light illumination, potentially enhancing conductivity. Photodetectors fabricated from these films demonstrate responsivities of 1.4–15.0 A W<sup>−1</sup> and external quantum efficiencies ranging from 1300 to 2830% in the visible range, making them comparable to well-established hybrid 2D nanomaterials like MoS<inf>2</inf> and WS<inf>2</inf>.

DOI： 10.1002/smll.202503895

Beyond Fertilizers: NH<sub>4</sub>ZnPO<sub>4</sub> for the Reversible Chemical Storage of Ammonia 査読有り国際誌 Open Access

Kozawa, T; Hashiba, T; Fukuyama, K; Abe, H; Morita, S; Osada, M; Naito, M

ADVANCED MATERIALS INTERFACES 12 巻 ( 8 ) 2025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 Materials Interfaces

Enhancing NH<inf>3</inf> as a carbon-free energy carrier of H<inf>2</inf> and next-generation fuel is a promising approach for a sustainable society. Chemically storing NH<inf>3</inf> molecules in crystal structures offers better selectivity and reusability than storage in traditional porous materials based on physicochemical adsorption; however, designing materials that can be reversibly stored in structural gaps is still a significant challenge. Herein, the use of NH<inf>4</inf>ZnPO<inf>4</inf>, which is previously used as a fertilizer, is proposed as an NH<inf>3</inf> uptake material through a chemical storage mechanism. The NH<inf>4</inf>ZnPO<inf>4</inf> particles synthesized by a wet mechanochemical method with monoclinic and hexagonal crystal structures can incorporate NH<inf>3</inf> molecules and directly transform them into NH<inf>4</inf>Zn(NH<inf>3</inf>)PO<inf>4</inf> without producing byproducts. The chemical storage mechanism depends on the particle morphology; therefore, the uptake amount per surface area surpasses that of porous materials. NH<inf>4</inf>ZnPO<inf>4</inf> exhibited excellent cycling performance due to its reusability, which is regenerated by releasing NH<inf>3</inf> from NH<inf>4</inf>Zn(NH<inf>3</inf>)PO<inf>4</inf> when heated in air at ≈100 °C. Taking inspiration from previously used and familiar fertilizers further extends this new area of innovative materials that can be used for the reversible storage of low-molecular-weight gases.

DOI： 10.1002/admi.202400729

Covalent functionalization of transition metal dichalcogenides with perylene for light harvesting devices 査読有り国際共著国際誌 Open Access

Canton-Vitoria, R; Matsunaga, Y; Zhang, SC; Xue, MS; Osada, M; Kitaura, R

NANOSCALE 17 巻 ( 13 ) 頁： 8084 - 8100 2025年3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：Nanoscale

This study investigates the optical and electronic properties of eight two-dimensional transition metal chalcogenides (TMDs)—MoS<inf>2</inf>, WS<inf>2</inf>, MoSe<inf>2</inf>, WSe<inf>2</inf>, MoTe<inf>2</inf>, WTe<inf>2</inf>, MoO<inf>2</inf>, and WO<inf>2</inf>—covalently functionalized with perylene, forming zero-dimensional/two-dimensional hybrid materials. Comprehensive characterization was conducted using techniques including XPS, Raman, EDX, TEM, and AFM. Optical properties were assessed using UV-Vis-NIR absorption and photoluminescence spectroscopy, while electronic properties were examined through cyclic voltammetry and field-effect transistor devices. Notably, the spectroscopic signatures of isolated perylene predominate in the hybrid materials, while WSe<inf>2</inf> and MoSe<inf>2</inf> displayed a novel band in the near-IR region, and MoTe<inf>2</inf> exhibited enhanced conductivity. Perylene significantly boosted absorption between 400-600 nm, leading to remarkable improvements in the photo-response and responsivities showing values exceeding 2 × 10<sup>5</sup>% and 2 × 10<sup>4</sup> mA W<sup>−1</sup>, respectively. The presented hybrid materials rival the best examples of non-covalent functionalization, underscoring the potential of covalent functionalization as a powerful technique for further tailoring the optical and electronic properties of 2D materials.

DOI： 10.1039/d4nr05364h

Mechanical exfoliation of non-van der Waals solids: a study of layered perovskite ferroelectric CsPb<sub>2</sub>Nb<sub>3</sub>O<sub>10</sub> 査読有り国際誌 Open Access

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

CHEMISTRY LETTERS 54 巻 ( 2 ) 頁： upaf006 2025年2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

Mechanical exfoliation of layered materials is one of the most effective methods for obtaining 2D nanosheets. However, this approach is still limited to van der Waals (vdW) layered materials, where interlayer interactions are governed by weak vdW forces. In this study, we used a layered perovskite ferroelectric (CsPb<inf>2</inf>Nb<inf>3</inf>O<inf>10</inf>) as a model system to explore the mechanical exfoliation behavior of ionically bonded non-vdW layered materials. Due to the relatively weak out-of-plane bonds involving the interlayer Cs<sup>+</sup> ions, CsPb<inf>2</inf>Nb<inf>3</inf>O<inf>10</inf> could be cleaved into ultrathin sheets with thicknesses ranging from 7.5 to 50 nm. Using piezoresponse force microscopy, we investigated the thickness-dependent ferroelectric properties of CsPb<inf>2</inf>Nb<inf>3</inf>O<inf>10</inf> nanosheets.

DOI： 10.1093/chemle/upaf006

その他リンク： https://academic.oup.com/chemlett/article-pdf/54/2/upaf006/61648459/upaf006.pdf

Ferroelectricity in CsPb<sub>2</sub>Nb<sub>3</sub>O<sub>10</sub> 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

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