Faculty Profiles - OSADA Minoru

Ultrafast 2D Nanosheet Assembly via Spontaneous Spreading Phenomenon Reviewed International coauthorship

Yue Shi, Hong Li, Hirofumi Tsunematsu, Harumi Ozeki, Kimiko Kano, Eisuke Yamamoto, Makoto Kobayashi, Hiroya Abe, Chun‐Wei Chen, Minoru Osada

Small Vol. 20 ( 36 ) page： e2403915 2024.7

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Wiley

Abstract

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

Facile Synthesis of Pd Nanosheets and Implications for Superior Catalytic Activity Reviewed

Other Link： 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 Vol. 33 page： 47 - 50 2024

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 Vol. 98 page： 35 - 41 2024

Sumiya Ando, Eisuke Yamamoto, Makoto Kobayashi, Akichika Kumatani, Minoru Osada

ACS Nano Vol. 18 ( 1 ) page： 461 - 469 2023.11

Gigantic Thermal Shielding in 2D Oxide Nanosheets Reviewed

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

ACS Nano Vol. 17 ( 12 ) page： 11396 - 11405 2023.5

Ultrahigh Energy Storage in 2D High-κ Perovskites. International journal

Hyung-Jun Kim, Shu Morita, Ki-Nam Byun, Yue Shi, Takaaki Taniguchi, Eisuke Yamamoto, Makoto Kobayashi, Yasuo Ebina, Takayoshi Sasaki, Minoru Osada

Nano letters Vol. 23 ( 9 ) page： 3788 - 3795 2023.5

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal)

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

Ferroelectricity in CsPb2Nb3O10 and exfoliated 2D nanosheets Reviewed

Single droplet assembly for two-dimensional nanosheet tiling Reviewed International journal

Shi Yue, Osada Minoru, Ebina Yasuo, Sasaki Takayoshi

ACS Nano Vol. 14 ( 11 ) page： 15216 - 15226 2020.11

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

DALTON TRANSACTIONS 2024.9

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

YAGI Yuina, YOSHIDA Kanako, KOZAWA Takahiro, OSADA Minoru, ABE Hiroya

Journal of Smart Processing Vol. 13 ( 4 ) page： 200 - 204 2024.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Smart Processing Society for Materials, Environment & Energy (High Temperature Society of Japan)

With the advance of nanotechnology, gold nanoparticles (AuNPs) with interesting optical and chemical properties are attracting
attention. The reduction reaction of soluble Au precursors such as chloroauric acid (HAuCl4
) in an aqueous solution is widely used
as the synthetic route of AuNPs. However, coexisting ionic species, especially Cl−, can negatively affect the application of AuNPs,
so an additional removal process is necessary. Herein, we report the synthesis of AuNPs using almost insoluble gold hydroxide
(Au(OH)3
) as the Au precursor in aqueous media. AuNPs were successfully synthesized under mild conditions (pH ～7, 60℃
and 80℃) in the presence of a non-toxic triblock copolymer acting as a reducing and stabilizing agent. The sizes of the AuNPs
were 39.3±11.7 nm and 51.0±12.9 nm at 60℃ and 80℃, respectively. The resulting colloidal dispersions of the AuNPs obtained
under neutral conditions and without the influence of coexisting the ionic species are expected to apply to catalytic and biological
applications where surface activity plays an important role.

DOI： 10.7791/jspmee.13.200

CiNii Research

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

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

ADVANCED OPTICAL MATERIALS 2024.3

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

Takuya Yasunaga, Makoto Kobayashi, Kenji Oqmhula, Huan Qi, Tom Ichibha, Kenta Hongo, Shunsuke Yamamoto, Ryo Maezono, Masaya Mitsuishi, Minoru Osada, Hideki Kato, Masato Kakihana

Inorganic Chemistry Vol. 63 ( 2 ) page： 1288 - 1295 2024.1

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

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

RSC ADVANCES Vol. 14 ( 1 ) page： 75 - 82 2024.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

APPLIED PHYSICS EXPRESS Vol. 17 ( 1 ) page： 015002-1 - 015002-5 2024.1

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

JOURNAL OF ENERGY STORAGE Vol. 73 page： 109231 2023.12

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

MATERIALS CHEMISTRY AND PHYSICS Vol. 309 page： 128271 2023.11

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

Osada Minoru

Journal of the Ceramic Society of Japan Vol. 131 ( 11 ) page： 851 - 862 2023.11

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：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