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Takayoshi Sasaki - One of the best experts on this subject based on the ideXlab platform.
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Titanoniobate and niobate Nanosheet photocatalysts: superior photoinduced hydrophilicity and enhanced thermal stability of unilamellar Nb3O8 Nanosheet
Energy and Environmental Science, 2020Co-Authors: Tatsuo Shibata, Yasuo Ebina, Katsutoshi Fukuda, Genki Takanashi, Takashi Nakamura, Takayoshi SasakiAbstract:Unique photocatalysts based on novel two-dimensional (2D) oxide Nanosheets have been synthesized and their photochemical activity has been examined. Monolayer films of titanoniobate and niobate (TiNbO5, Ti2NbO7, Ti5NbO14, and Nb3O8) Nanosheets, synthesized by exfoliating layered oxide precursors through a soft-chemical procedure, were fabricated on quartz glass substrate via a sequential adsorption method. All the Nanosheet films exhibited good photoinduced hydrophilicity, while their oxidation activity was very low. This behavior can be regarded as inherent features of Nanosheet-type photocatalysts having molecularly thin 2D anisotropy. Such ultrathin flexible structures are advantageous for facilitating photo-driven surface wettability change. Especially, the hydrophilic conversion property of Nb3O8 Nanosheet was highly efficient, showing activity that was at least one order of magnitude superior to that of the widely used photocatalyst film of polycrystalline anatase TiO2. Moreover, the monolayer film of Nb3O8 Nanosheet was found to have enhanced thermal stability and chemical resistance, particularly against diffusion of sodium ions at elevated temperature: Nb3O8 Nanosheet film heated on sodium-rich glass (soda-lime glass) substrate maintained excellent hydrophilic conversion activity, whereas Ti0.87O2 Nanosheet as well as anatase (TiO2) based photocatalysts was virtually deactivated. These features are a great advantage of Nb3O8 Nanosheet photocatalysts for developing the practical super-hydrophilic applications where post-annealing is indispensable.
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Structure Analysis of Conducting Nanosheet Crystallites
2020Co-Authors: Jun Sato, Yasuo Ebina, Katsutoshi Fukuda, Wataru Sugimoto, Tatsuo Shibata, Hisato Kato, Takayoshi SasakiAbstract:stimulated huge quantities of researches as to applications associated with energy harvesting and storage technology because their unique dimension and structure often trigger unexpectable physicochemical properties. Understanding of their crystal structure, therefore, is of significantly importance in order to utilize and control their properties. In this study, we investigated two-dimensional periodic structure of several conducting Nanosheets by means of grazing-incidence X-ray diffraction analysis. Experimental Layered ruthenates, KRuO2.1 and NaRuO2, were delaminated into elemental host layer, i.e. ruthenium oxide Nanosheet called K-type 1 and Na-type 2 , respectively, in this study. Graphite oxide was obtained via chemical reaction of graphite with conc. H2SO4 solution including KMnO4 and NaNO3 and then dispersed into TBAOH aqueous solution, yielding a suspension of graphite oxide Nanosheets. Sub-monolayer films in which these anionic Nanosheets lay flat to Si substrate were fabricated through electrostatic adsorption with cationic polymer used as a binder. Graphene-restacked film on SiO2 substrate was obtained by simple dry-cast method of the suspension of the graphite oxide Nanosheets and subsequent reduction process induced by heating at 900oC for 1h under 10% hydrogen gas flow. In-plane diffraction pattern of these Nanosheet films was measured by a four-axis diffractometer equipped with NaI scintillation counter at the BL-6C in Photon Factory.
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All-Nanosheet ultrathin capacitors assembled layer-by-layer via solution-based processes
ACS Nano, 2014Co-Authors: Chengxiang Wang, Kosho Akatsuka, Yasuo Ebina, Bao Wen Li, Katsutoshi Fukuda, Renzhi Ma, Minoru Osada, Wataru Sugimoto, Takayoshi SasakiAbstract:All-Nanosheet ultrathin capacitors of Ru0.95O20.2-/Ca2Nb3O10-/Ru0.95O20.2- were successfully assembled through facile room-temperature solution-based processes. As a bottom electrode, conductive Ru0.95O20.2- Nanosheets were first assembled on a quartz glass substrate through a sequential adsorption process with polycations. On top of the Ru0.95O20.2- Nanosheet film, Ca2Nb3O10- Nanosheets were deposited by the Langmuir-Blodgett technique to serve as a dielectric layer. Deposition parameters were optimized for each process to construct a densely packed multilayer structure. The multilayer buildup process was monitored by various characterizations such as atomic force microscopy (AFM), ultraviolet-visible absorption spectra, and X-ray diffraction data, which provided compelling evidence for regular growth of Ru0.95O20.2- and Ca2Nb3O10- Nanosheet films with the designed multilayer structures. Finally, an array of circular films (50 μm ϕ) of Ru0.95O20.2- Nanosheets was fabricated as top electrodes on the as-deposited Nanosheet films by combining the standard photolithography and sequential adsorption processes. Microscopic observations by AFM and cross-sectional transmission electron microscopy, as well as nanoscopic elemental analysis, visualized the sandwich metal-insulator-metal structure of Ru0.95O20.2-/Ca2Nb3O10-/Ru0.95O20.2- with a total thickness less than 30 nm. Electrical measurements indicate that the system really works as an ultrathin capacitor, achieving a capacitance density of ∼27.5 μF cm(-2), which is far superior to currently available commercial capacitor devices. This work demonstrates the great potential of functional oxide Nanosheets as components for nanoelectronics, thus contributing to the development of next-generation high-performance electronic devices.
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electronic band structure of exfoliated titanium and or niobium based oxide Nanosheets probed by electrochemical and photoelectrochemical measurements
Journal of Physical Chemistry C, 2012Co-Authors: Kosho Akatsuka, Yasuo Ebina, Genki Takanashi, Masaaki Haga, Takayoshi SasakiAbstract:Exfoliated two-dimensional (2D) unilamellar Nanosheets of Ca2Nb3O10–, TiNbO5–, Ti2NbO7–, and Ti5NbO143– were deposited layer-by-layer to produce multilayer films on indium–tin–oxide (ITO)-coated glass electrodes, and their electrochemical and photoelectrochemical properties were explored. The layer-by-layer assembly process via sequential adsorption with counter polycations was monitored by UV–visible absorption spectra and X-ray diffraction measurements, which confirmed the successful growth of films, where Nanosheets and polycations are alternately stacked at a separation of 1.6–2.4 nm. Exposure to UV light totally removed polycations, producing inorganic films. Cyclic voltammetry on Ti and/or Nb oxide Nanosheet electrodes thus fabricated showed reduction/oxidation (Ti3+/Ti4+ and Nb4+/Nb5+) peaks associated with insertion/extraction of Li+ ions into/from intersheet galleries of the films. The extent of the redox reaction is found to be governed by the cation density in the Nanosheet gallery. Anodic phot...
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Two-dimensional dielectric Nanosheets: Novel nanoelectronics from nanocrystal building blocks
Advanced Materials, 2012Co-Authors: Minoru Osada, Takayoshi SasakiAbstract:Two-dimensional (2D) Nanosheets, which possess atomic or molecular thickness and infinite planar lengths, are regarded as the thinnest functional nanomaterials. The recent development of methods for manipulating graphene (carbon Nanosheet) has provided new possibilities and applications for 2D systems; many amazing functionalities such as high electron mobility and quantum Hall effects have been discovered. However, graphene is a conductor, and electronic technology also requires insulators, which are essential for many devices such as memories, capacitors, and gate dielectrics. Along with graphene, inorganic Nanosheets have thus increasingly attracted fundamental research interest because they have the potential to be used as dielectric alternatives in next-generation nanoelectronics. Here, we review the progress made in the properties of dielectric Nanosheets, highlighting emerging functionalities in electronic applications. We also present a perspective on the advantages offered by this class of materials for future nanoelectronics.
Chandra Sekhar Rout - One of the best experts on this subject based on the ideXlab platform.
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electrochemical synthesis of a ternary transition metal sulfide Nanosheets on nickel foam and energy storage application
Journal of Alloys and Compounds, 2017Co-Authors: Surjit Sahoo, Kusha Kumar Naik, Dattatray J. Late, Chandra Sekhar RoutAbstract:Abstract We report growth of nickel cobalt sulfide (NCS) ultrathin Nanosheets directly on Ni foam substrate by a facile and novel electrodeposition method. The as-prepared NCS sample is used as an electrode material for supercapacitor application due to their large electrochemically active surface area and interconnected Nanosheet channels for the facilitation of ion transportation. The NCS Nanosheets possess enhanced electrochemical performance in terms of fast and high reversible faradaic reactions characterized by prominent oxidation and reduction peaks. NCS Nanosheets showed an ultrahigh specific capacitance of 1712 Fg−1 at a current density of 1 Ag−1 with excellent cyclic stability. The excellent supercapacitor performance of NCS Nanosheets can be attributed to its rich redox reactions as well as high transport rate for both electrolyte ions and electrons.
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Field emission properties of ZnO Nanosheet arrays
Applied Physics Letters, 2014Co-Authors: Kusha Kumar Naik, Disha Chakravarty, Ruchita Khare, Resham Thapa, Dattatray J. Late, Mahendra A. More, Chandra Sekhar RoutAbstract:Electron emission properties of electrodeposited ZnO Nanosheet arrays grown on Indium tin oxide coated glass substrates have been studied. Influence of oxygen vacancies on electronic structures and field emission properties of ZnO Nanosheets are investigated using density functional theory. The oxygen vacancies produce unshared d electrons which form an impurity energy state; this causes shifting of Fermi level towards the vacuum, and so the barrier energy for electron extraction reduces. The ZnO Nanosheet arrays exhibit a low turn-on field of 2.4V/μm at 0.1 μA/cm2 and current density of 50.1 μA/cm2 at an applied field of 6.4 V/lm with field enhancement factor, β = 5812 and good field emission current stability. The Nanosheet arrays grown by a facile electrodeposition process have great potential as robust high performance vertical structure electron emitters for future flat panel displays and vacuum electronic device applications.
Yongfang Wang - One of the best experts on this subject based on the ideXlab platform.
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preparation of graphene Nanosheet alumina composites by spark plasma sintering
Materials Research Bulletin, 2011Co-Authors: Kai Wang, Yongfang WangAbstract:Abstract Graphene Nanosheet/alumina composite has been prepared by spark plasma sintering. A homogeneous distribution of Nanosheets in an alumina matrix could be obtained by the electrostatic attraction between graphite oxide and alumina particles and their subsequent reduction. The introduction of graphene Nanosheet leads to refinement of grain size of alumina after hot pressing. The experimental results have shown that the fracture toughness and conductivity of the graphene Nanosheet/alumina composite are about 53% and 13 orders of magnitude higher than those of unreinforced alumina material, respectively.
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Preparation of graphene Nanosheet/alumina composites by spark plasma sintering
Materials Research Bulletin, 2011Co-Authors: Kai Wang, Zhuangjun Fan, Yongfang Wang, Jun Yan, Tong WeiAbstract:Graphene Nanosheet/alumina composite has been prepared by spark plasma sintering. A homogeneous distribution of Nanosheets in an alumina matrix could be obtained by the electrostatic attraction between graphite oxide and alumina particles and their subsequent reduction. The introduction of graphene Nanosheet leads to refinement of grain size of alumina after hot pressing. The experimental results have shown that the fracture toughness and conductivity of the graphene Nanosheet/alumina composite are about 53% and 13 orders of magnitude higher than those of unreinforced alumina material, respectively. © 2010 Elsevier Ltd. All rights reserved.
Yasuo Ebina - One of the best experts on this subject based on the ideXlab platform.
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Titanoniobate and niobate Nanosheet photocatalysts: superior photoinduced hydrophilicity and enhanced thermal stability of unilamellar Nb3O8 Nanosheet
Energy and Environmental Science, 2020Co-Authors: Tatsuo Shibata, Yasuo Ebina, Katsutoshi Fukuda, Genki Takanashi, Takashi Nakamura, Takayoshi SasakiAbstract:Unique photocatalysts based on novel two-dimensional (2D) oxide Nanosheets have been synthesized and their photochemical activity has been examined. Monolayer films of titanoniobate and niobate (TiNbO5, Ti2NbO7, Ti5NbO14, and Nb3O8) Nanosheets, synthesized by exfoliating layered oxide precursors through a soft-chemical procedure, were fabricated on quartz glass substrate via a sequential adsorption method. All the Nanosheet films exhibited good photoinduced hydrophilicity, while their oxidation activity was very low. This behavior can be regarded as inherent features of Nanosheet-type photocatalysts having molecularly thin 2D anisotropy. Such ultrathin flexible structures are advantageous for facilitating photo-driven surface wettability change. Especially, the hydrophilic conversion property of Nb3O8 Nanosheet was highly efficient, showing activity that was at least one order of magnitude superior to that of the widely used photocatalyst film of polycrystalline anatase TiO2. Moreover, the monolayer film of Nb3O8 Nanosheet was found to have enhanced thermal stability and chemical resistance, particularly against diffusion of sodium ions at elevated temperature: Nb3O8 Nanosheet film heated on sodium-rich glass (soda-lime glass) substrate maintained excellent hydrophilic conversion activity, whereas Ti0.87O2 Nanosheet as well as anatase (TiO2) based photocatalysts was virtually deactivated. These features are a great advantage of Nb3O8 Nanosheet photocatalysts for developing the practical super-hydrophilic applications where post-annealing is indispensable.
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Structure Analysis of Conducting Nanosheet Crystallites
2020Co-Authors: Jun Sato, Yasuo Ebina, Katsutoshi Fukuda, Wataru Sugimoto, Tatsuo Shibata, Hisato Kato, Takayoshi SasakiAbstract:stimulated huge quantities of researches as to applications associated with energy harvesting and storage technology because their unique dimension and structure often trigger unexpectable physicochemical properties. Understanding of their crystal structure, therefore, is of significantly importance in order to utilize and control their properties. In this study, we investigated two-dimensional periodic structure of several conducting Nanosheets by means of grazing-incidence X-ray diffraction analysis. Experimental Layered ruthenates, KRuO2.1 and NaRuO2, were delaminated into elemental host layer, i.e. ruthenium oxide Nanosheet called K-type 1 and Na-type 2 , respectively, in this study. Graphite oxide was obtained via chemical reaction of graphite with conc. H2SO4 solution including KMnO4 and NaNO3 and then dispersed into TBAOH aqueous solution, yielding a suspension of graphite oxide Nanosheets. Sub-monolayer films in which these anionic Nanosheets lay flat to Si substrate were fabricated through electrostatic adsorption with cationic polymer used as a binder. Graphene-restacked film on SiO2 substrate was obtained by simple dry-cast method of the suspension of the graphite oxide Nanosheets and subsequent reduction process induced by heating at 900oC for 1h under 10% hydrogen gas flow. In-plane diffraction pattern of these Nanosheet films was measured by a four-axis diffractometer equipped with NaI scintillation counter at the BL-6C in Photon Factory.
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All-Nanosheet ultrathin capacitors assembled layer-by-layer via solution-based processes
ACS Nano, 2014Co-Authors: Chengxiang Wang, Kosho Akatsuka, Yasuo Ebina, Bao Wen Li, Katsutoshi Fukuda, Renzhi Ma, Minoru Osada, Wataru Sugimoto, Takayoshi SasakiAbstract:All-Nanosheet ultrathin capacitors of Ru0.95O20.2-/Ca2Nb3O10-/Ru0.95O20.2- were successfully assembled through facile room-temperature solution-based processes. As a bottom electrode, conductive Ru0.95O20.2- Nanosheets were first assembled on a quartz glass substrate through a sequential adsorption process with polycations. On top of the Ru0.95O20.2- Nanosheet film, Ca2Nb3O10- Nanosheets were deposited by the Langmuir-Blodgett technique to serve as a dielectric layer. Deposition parameters were optimized for each process to construct a densely packed multilayer structure. The multilayer buildup process was monitored by various characterizations such as atomic force microscopy (AFM), ultraviolet-visible absorption spectra, and X-ray diffraction data, which provided compelling evidence for regular growth of Ru0.95O20.2- and Ca2Nb3O10- Nanosheet films with the designed multilayer structures. Finally, an array of circular films (50 μm ϕ) of Ru0.95O20.2- Nanosheets was fabricated as top electrodes on the as-deposited Nanosheet films by combining the standard photolithography and sequential adsorption processes. Microscopic observations by AFM and cross-sectional transmission electron microscopy, as well as nanoscopic elemental analysis, visualized the sandwich metal-insulator-metal structure of Ru0.95O20.2-/Ca2Nb3O10-/Ru0.95O20.2- with a total thickness less than 30 nm. Electrical measurements indicate that the system really works as an ultrathin capacitor, achieving a capacitance density of ∼27.5 μF cm(-2), which is far superior to currently available commercial capacitor devices. This work demonstrates the great potential of functional oxide Nanosheets as components for nanoelectronics, thus contributing to the development of next-generation high-performance electronic devices.
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electronic band structure of exfoliated titanium and or niobium based oxide Nanosheets probed by electrochemical and photoelectrochemical measurements
Journal of Physical Chemistry C, 2012Co-Authors: Kosho Akatsuka, Yasuo Ebina, Genki Takanashi, Masaaki Haga, Takayoshi SasakiAbstract:Exfoliated two-dimensional (2D) unilamellar Nanosheets of Ca2Nb3O10–, TiNbO5–, Ti2NbO7–, and Ti5NbO143– were deposited layer-by-layer to produce multilayer films on indium–tin–oxide (ITO)-coated glass electrodes, and their electrochemical and photoelectrochemical properties were explored. The layer-by-layer assembly process via sequential adsorption with counter polycations was monitored by UV–visible absorption spectra and X-ray diffraction measurements, which confirmed the successful growth of films, where Nanosheets and polycations are alternately stacked at a separation of 1.6–2.4 nm. Exposure to UV light totally removed polycations, producing inorganic films. Cyclic voltammetry on Ti and/or Nb oxide Nanosheet electrodes thus fabricated showed reduction/oxidation (Ti3+/Ti4+ and Nb4+/Nb5+) peaks associated with insertion/extraction of Li+ ions into/from intersheet galleries of the films. The extent of the redox reaction is found to be governed by the cation density in the Nanosheet gallery. Anodic phot...
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Synthesis and Atomic Characterization of a Ti2O3 Nanosheet
Journal of Physical Chemistry Letters, 2011Co-Authors: Megumi Ohwada, Yasuo Ebina, Koji Kimoto, Kazutomo Suenaga, Yuta Sato, Takayoshi SasakiAbstract:Titanium oxide Nanosheets have been attracting much attention owing to their photocatalytic property. Here, we synthesized a Ti2O3 Nanosheet by the reduction of a titania Nanosheet (Ti0.87O2) that was one or two atoms in thickness. The atomic structure of the Ti2O3 Nanosheet was quantitatively revealed by electron diffraction analysis, electron energy-loss spectroscopy, and high-resolution transmission electron microscopy (TEM). A titania Nanosheet (Ti0.87O2) consisting of edge-shared TiO6 octahedra was transformed to a Ti2O3 Nanosheet consisting of face-shared octahedra by electron beam irradiation. This represents a stable crystal phase of titania Nanosheets like the Magneli phase in oxygen-deficient environments. The atomic arrangement of the Ti2O3 Nanosheet was directly observed by newly developed aberration-corrected TEM.
Kai Wang - One of the best experts on this subject based on the ideXlab platform.
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preparation of graphene Nanosheet alumina composites by spark plasma sintering
Materials Research Bulletin, 2011Co-Authors: Kai Wang, Yongfang WangAbstract:Abstract Graphene Nanosheet/alumina composite has been prepared by spark plasma sintering. A homogeneous distribution of Nanosheets in an alumina matrix could be obtained by the electrostatic attraction between graphite oxide and alumina particles and their subsequent reduction. The introduction of graphene Nanosheet leads to refinement of grain size of alumina after hot pressing. The experimental results have shown that the fracture toughness and conductivity of the graphene Nanosheet/alumina composite are about 53% and 13 orders of magnitude higher than those of unreinforced alumina material, respectively.
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Preparation of graphene Nanosheet/alumina composites by spark plasma sintering
Materials Research Bulletin, 2011Co-Authors: Kai Wang, Zhuangjun Fan, Yongfang Wang, Jun Yan, Tong WeiAbstract:Graphene Nanosheet/alumina composite has been prepared by spark plasma sintering. A homogeneous distribution of Nanosheets in an alumina matrix could be obtained by the electrostatic attraction between graphite oxide and alumina particles and their subsequent reduction. The introduction of graphene Nanosheet leads to refinement of grain size of alumina after hot pressing. The experimental results have shown that the fracture toughness and conductivity of the graphene Nanosheet/alumina composite are about 53% and 13 orders of magnitude higher than those of unreinforced alumina material, respectively. © 2010 Elsevier Ltd. All rights reserved.
