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510 results on '"Yoshimura, Masamichi"'

4. Direct growth of germanene at interfaces between van der Waals materials and Ag(111)

Author

Suzuki, Seiya, Iwasaki, Takuya, De Silva, K. Kanishka H., Suehara, Shigeru, Watanabe, Kenji, Taniguchi, Takashi, Moriyama, Satoshi, Yoshimura, Masamichi, Aizawa, Takashi, and Nakayama, Tomonobu

Subjects
Condensed Matter - Materials Science
Abstract

Germanene, a two-dimensional honeycomb germanium crystal, is grown at graphene/Ag(111) and hexagonal boron nitride (h-BN)/Ag(111) interfaces by segregating germanium atoms. A simple annealing process in N2 or H2/Ar at ambient pressure leads to the formation of germanene, indicating that an ultrahigh-vacuum condition is not necessary. The grown germanene is stable in air and uniform over the entire area covered with a van der Waals (vdW) material. As an important finding, it is necessary to use a vdW material as a cap layer for the present germanene growth method since the use of an Al2O3 cap layer resulted in no germanene formation. The present study also proved that Raman spectroscopy in air is a powerful tool for characterizing germanene at the interfaces, which is concluded by multiple analyses including first-principles density functional theory calculations. The direct growth of h-BN-capped germanene on Ag(111), which is demonstrated in the present study, is considered to be a promising technique for the fabrication of future germanene-based electronic devices., Comment: 34 Pages, 11 Figures

Published
2020
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5. Enhanced graphitic domains of unreduced graphene oxide and the interplay of hydration behaviour and catalytic activity

Author

Foller, Tobias, Daiyan, Rahman, Jin, Xiaoheng, Leverett, Joshua, Kim, Hangyel, Webster, Richard, Yap, Jeaniffer E., Wen, Xinyue, Rawal, Aditya, DeSilva, K. Kanishka H., Yoshimura, Masamichi, Bustamante, Heriberto, Chang, Shery L. Y., Kumar, Priyank, You, Yi, Lee, Gwan Hyoung, Amal, Rose, and Joshi, Rakesh

Subjects
Physics - Applied Physics, Condensed Matter - Materials Science
Abstract

Previous studies indicate that the properties of graphene oxide (GO) can be significantly improved by enhancing its graphitic domain size through thermal diffusion and clustering of functional groups. Remarkably, this transition takes place below the decomposition temperature of the functional groups and thus allows fine-tuning of graphitic domains without compromising with the functionality of GO. By studying the transformation of GO under mild thermal treatment, we directly observe this size enhancement of graphitic domains from originally 40 nm2 to 200 nm2 through an extensive transmission electron microscopy (TEM) study. Additionally, we confirm the integrity of the functional groups during this process by comprehensive chemical analysis. A closer look into the process confirms the theoretically predicted relevance for the room temperature stability of GO. We further investigate the influence of enlarged graphitic domains on the hydration behaviour of GO and catalytic performance of single-atom catalysts supported by GO.

Published
2020

26. Hydrogen-Substituted Graphdiyne Encapsulated Cu2O Nanowires as Binder-Free Electrodes for Non-Enzymatic Glucose Sensing.

Author

Jeganathan, Chellamuthu, Mitsuboshi, Hibiki, Yamamoto, Hikaru, Motoyama, Yukihiro, Kokado, Kenta, Hara, Masanori, and Yoshimura, Masamichi

Abstract

The fabrication of electrochemical biosensors without any binder or enzymes is in high demand in the clinical diagnostic and industrial sectors. This work presents the development of hydrogen-substituted graphdiyne encapsulated Cu2O nanowires (Cu2O NWs@ HsGDY) hybrid electrode, directly grown on Cu foils. The sp and sp2 hybridization of HsGDY is confirmed by Raman and X-ray photoelectron spectroscopy, and the HsGDY encapsulation over Cu2O NWs is observed in transmission electron microscope images. The fabricated binder-free, nonenzymatic electrode exhibits the highest sensitivity of 584.2 μA·cm2·μM–1 (Cu2O NWs@HsGDY-1 h), the lowest detection limits of 0.035 μM (Cu2O NWs@HsGDY-6 h) and a linear detection range of 0.5–2500 μM. The Cu2O NWs@HsGDY-6 h electrode demonstrates 70 days of stability (82%) and excellent reproducibility (RSD = 1.97%) compared to other hybrid electrodes. The improved glucose sensing performance and stability is a combined effect of semiconducting nature and catalytic ability are attributed to Cu2O NWs@HsGDY hybrid electrodes. The successful glucose detection in actual food samples indicates the practical applicability of the Cu2O NWs@HsGDY sensor. [ABSTRACT FROM AUTHOR]

Published
2024
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37. Angstrom‐confined Electrochemical Synthesis of Sub‐unit Cell non van der Waals 2D Metal Oxides

Author

Ji, Dali, Lee, Yunah, Nishina, Yuta, Kamiya, Kazuhide, Daiyan, Rahman ; https://orcid.org/0000-0002-3543-3944, Chu, Dewei ; https://orcid.org/0000-0003-4581-0560, Wen, Xinyue ; https://orcid.org/0000-0003-3785-2218, Yoshimura, Masamichi, Kumar, Priyank ; https://orcid.org/0000-0002-8203-7223, Andreeva, Daria V, Novoselov, Kostya S, Lee, Gwan‐Hyoung, Joshi, Rakesh ; https://orcid.org/0000-0002-7497-9499, Foller, Tobias ; https://orcid.org/0000-0003-2636-4542, Ji, Dali, Lee, Yunah, Nishina, Yuta, Kamiya, Kazuhide, Daiyan, Rahman ; https://orcid.org/0000-0002-3543-3944, Chu, Dewei ; https://orcid.org/0000-0003-4581-0560, Wen, Xinyue ; https://orcid.org/0000-0003-3785-2218, Yoshimura, Masamichi, Kumar, Priyank ; https://orcid.org/0000-0002-8203-7223, Andreeva, Daria V, Novoselov, Kostya S, Lee, Gwan‐Hyoung, Joshi, Rakesh ; https://orcid.org/0000-0002-7497-9499, and Foller, Tobias ; https://orcid.org/0000-0003-2636-4542

Abstract

Bottom-up electrochemical synthesis of atomically thin materials is desirable yet challenging, especially for non-van der Waals (vdW) materials. Thicknesses below few nm have not been reported yet, posing the question how thin can non-vdW materials be electrochemically synthesized? This is important as materials with (sub-) unit cell thickness often show remarkably different properties compared to their bulk form or thin films of several nm thickness. Here, we introduce a straightforward electrochemical method utilizing the angstrom-confinement of laminar reduced graphene oxide (rGO) nanochannels to obtain a centimeter-scale network of atomically thin (< 4.3 Å) 2D-transition metal oxides (2D-TMO). The angstrom-confinement provides a thickness limitation, forcing sub-unit cell growth of 2D-TMO with oxygen and metal vacancies. We showcase that Cr2O3, a material without significant catalytic activity for OER in bulk form, can be activated as a high-performing catalyst if synthesized in the 2D sub-unit cell form. Our method displays the high activity of sub-unit cell form while retaining the stability of bulk form, promising to yield unexplored fundamental science and applications. We show that while retaining the advantages of bottom-up electrochemical synthesis like simplicity, high yield, and mild conditions, the thickness of TMO can be limited to sub-unit cell dimensions.

Published
2023

38. Angstrom-confined electrochemical synthesis of sub-unit cell non van der Waals 2D metal oxides

Author

Ji, Dali, primary, Lee, Yunah, additional, Nishina, Yuta, additional, Kamiya, Kazuhide, additional, Daiyan, Rahman, additional, Wen, Xinyue, additional, Chu, Dewei, additional, Yoshimura, Masamichi, additional, Kumar, Priyank, additional, Andreeva, Daria, additional, Novoselov, Kostya, additional, Lee, Gwan-Hyoung, additional, Joshi, Rakesh, additional, and Foller, Tobias, additional

Published
2023
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40. Crystallization of charged gold particles mediated by nonadsorbing like-charged polyelectrolyte.

Author

Ioka, Miyu, Toyotama, Akiko, Yamaguchi, Megumi, Nozawa, Jun, Uda, Satoshi, Okuzono, Tohru, Yoshimura, Masamichi, and Yamanaka, Junpei

Subjects
COLLOIDAL crystals, VAN der Waals forces, ELECTRIC charge, RAMAN scattering, CRYSTALLIZATION
Abstract

We report that the aqueous dispersions of negatively charged submicron-sized colloidal Au particles formed non-close-packed colloidal crystals by the addition of a like-charged linear polyelectrolyte, sodium polyacrylate (NaPAA). Au particles often form irregular aggregates in dispersions because of a strong van der Waals force acting between them. To prevent aggregation, we introduced negative electric charges on particle surfaces. By the addition of NaPAA, colloidal crystals were formed on the bottom of a sample cell because of the supply of Au particles by sedimentation and 2D diffusion even under very dilute conditions. Interparticle potential calculations demonstrated that the addition of NaPAA caused depletion attraction between the particles as well as a significant reduction in the interparticle repulsion because of the electrostatic screening effect. However, the electrostatic repulsion was strong enough to prevent the direct contact of particles in the excluded region between Au particles. Large-area crystals could be obtained by tilting the sample cell. By drying the sample, the Au particles came into contact and the non-space-filling crystals changed into closest packed crystals. These closest packed crystals exhibited a significant enhancement of Raman scattering intensity because of high hot-spot density. [ABSTRACT FROM AUTHOR]

Published
2021
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41. Angstrom-confined electrochemical synthesis of non van der Waals 2D metal oxides

Author

Ji, Dali, primary, Lee, Yunah, additional, Nishina, Yuta, additional, Kamiya, Kazuhide, additional, Daiyan, Rahman, additional, Wen, Xinyue, additional, Chu, Dewei, additional, Yoshimura, Masamichi, additional, Kumar, Priyank, additional, Andreeva, Daria, additional, Novoselov, Kostya, additional, Lee, Gwan-Hyoung, additional, Joshi, Rakesh, additional, and Foller, Tobias, additional

Published
2023
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45. Probe Technology

Author

Yoshimura, Masamichi, Avouris, Phaedon, editor, Bhushan, Bharat, editor, Bimberg, Dieter, editor, von Klitzing, Dres. h.c. Klaus, editor, Sakaki, Hiroyuki, editor, Wiesendanger, Roland, editor, and Morita, Seizo, editor

Published
2007
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