Faculty Profiles - KOBAYASHI Makoto

Papers - KOBAYASHI Makoto

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Automated One-Drop Assembly for Facile 2D Film Deposition Reviewed

Yue Shi, Eisuke Yamamoto, Makoto Kobayashi, Minoru Osada

ACS Applied Materials & Interfaces Vol. 15 ( 18 ) page： 22737 - 22743 2023.3

Free-Standing Molecularly Thin Amorphous Silica Nanosheets Reviewed Open Access

Eisuke Yamamoto, Kosuke Fujihara, Yuma Takezaki, Kentaro Ito, Yue Shi, Makoto Kobayashi, Minoru Osada

Small Vol. 19 ( 22 ) page： 2300022 - 2300022 2023.2

Molecularly Thin BaTiO₃ Nanosheets with Stable Ferroelectric Response Reviewed International coauthorship Open Access

Kazuki Hagiwara, Ki Nam Byun, Shu Morita, Eisuke Yamamoto, Makoto Kobayashi, Xioyang Liu, Minoru Osada

Advanced Electronic Materials Vol. 9 ( 3 ) page： 2291239 2023.2

Damage-free LED lithography for atomically thin 2D material devices Reviewed Open Access

Yue Shi, Takaaki Taniguchi, Ki-Nam Byun, Daiki Kurimoto, Eisuke Yamamoto, Makoto Kobayashi, Kazuhito Tsukagoshi, Minoru Osada

Scientific Reports Vol. 13 ( 1 ) page： 2583 2023.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

<jats:title>Abstract</jats:title><jats:p>Desired electrode patterning on two-dimensional (2D) materials is a foremost step for realizing the full potentials of 2D materials in electronic devices. Here, we introduce an approach for damage-free, on-demand manufacturing of 2D material devices using light-emitting diode (LED) lithography. The advantage of this method lies in mild photolithography by simply combining an ordinary optical microscope with a commercially available LED projector; the low-energy red component is utilized for optical characterization and alignment of devices, whereas the high-energy blue component is utilized for photoresist exposure and development of personal computer designed electrode patterns. This method offers maskless, damage-free photolithography, which is particularly suitable for 2D materials that are sensitive to conventional lithography. We applied this LED lithography to device fabrication of selected nanosheets (MoS<jats:sub>2</jats:sub>, graphene oxides and RuO<jats:sub>2</jats:sub>), and achieved damage-free lithography of various patterned electrodes with feature sizes as small as 1–2 μm. The LED lithography offers a useful approach for cost-effective mild lithography without any costly instruments, high vacuum, or complex operation.</jats:p>

DOI： 10.1038/s41598-023-29281-w

Other Link： https://www.nature.com/articles/s41598-023-29281-w

Improved Energy Storage Performance of PVDF Nanocapacitors by Utilizing 2D Inorganic Barrier Layers Reviewed International coauthorship

Ki-Nam Byun, Eisuke Yamamoto, Makoto Kobayashi, Minoru Osada

Chemistry Letters Vol. 52 ( 1 ) page： 51 - 54 2023.1

Tailored synthesis of molecularly thin platinum nanosheets using designed 2D surfactant solids Reviewed

Eisuke Yamamoto, Akiko Suzuki, Makoto Kobayashi, Minoru Osada

Nanoscale Vol. 14 ( 32 ) page： 11561 - 11567 2022

Language：English Publishing type：Research paper (scientific journal) Publisher：Royal Society of Chemistry (RSC)

We found solid-state surfactants as designable crystals suitable for nanostructural control and proposed a novel synthetic route for molecularly-thin Pt metal nanosheets using solid surfactant crystals as a precursor.

DOI： 10.1039/d2nr01807a

Influences of pulverization and annealing treatment on the photocatalytic activity of BiVO4 for oxygen evolution Reviewed

Kazuya Okuno, Hiromu Kumagai, Junie Jhon M. Vequizo, Kosaku Kato, Makoto Kobayashi, Akira Yamakata, Masato Kakihana, Hideki Kato

Sustainable Energy & Fuels Vol. 6 ( 7 ) page： 1698 - 1707 2022

Language：English Publishing type：Research paper (scientific journal) Publisher：Royal Society of Chemistry (RSC)

Pulverization followed by annealing treatment improved the activity of BiVO4 although the annealing treatment had a negative impact on the non-milled sample.

DOI： 10.1039/d2se00065b

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Synthesis of brookite-type TiO2 nanoparticles by emulsion-assisted hydrothermal method using titanium glycolate complex Open Access

Kohei KASUYA, Md. SHAHIDUZZAMAN, Makoto KOBAYASHI, Shu YIN, Masato KAKIHANA, Koji TOMITA

Journal of the Ceramic Society of Japan Vol. 129 ( 12 ) page： 720 - 724 2021.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Ceramic Society of Japan

We present a method for synthesizing brookite-type titanium dioxide (TiO2) using an emulsion-assisted hydrothermal approach and a water-soluble titanium complex with glycolic acid as a complexing agent. In this study, stirred hydrothermal synthesis was used to synthesize water-in-oil emulsions with titanium glycolate complex in the aqueous phase. The resulting brookite-type TiO2 was investigated using Raman spectroscopy for crystal polymorph identification, X-ray Diffraction to identify crystal polymorphs and crystallite size, Transmission Electron Microscope for primary particle size, and crystal shape, and Dynamic Light Scattering for TiO2 secondary particle size in aqueous dispersion. The synthesized brookite-type TiO2 was a needle-like crystal with a width between 20 and 30 nm and a length of more than 70 nm, growing in the b-axis direction at an angle of about 70° from the (120) plane. Furthermore, compared to the conventional synthesis method, the secondary particle size was smaller, and the dispersibility in water was improved. The results show that the brookite-type TiO2 dispersion obtained using the emulsion-assisted hydrothermal method can facilitate the formation of uniform films and can be applied to the electron transport layer of organic perovskite solar cells.

DOI： 10.2109/jcersj2.21127

Facile titania nanocoating using single droplet assembly of 2D nanosheets Reviewed International journal Open Access

Yue Shi, Eisuke Yamamoto, Makoto Kobayashi, Minoru Osada

Journal of the Ceramic Society of Japan 2021.4

Synthesis of NaMoO3F and Na5W3O9F5 with Morphological Controllability in Non-Aqueous Solvents. Reviewed International journal

Yusuke Asakura, Tomoyo Akahira, Makoto Kobayashi, Minoru Osada, Shu Yin

Inorganic chemistry Vol. 59 ( 15 ) page： 10707 - 10716 2020.8

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

NaMoO3F and Na5W3O9F5 were synthesized by solvothermal reaction of MoO3 and WO3, respectively, with NaF in nonaqueous solvents. These reactions were realized at low temperatures (150-200 °C) without the use of HF. This synthesis method is much more facile and safe procedure compared with general synthesis methods for oxyfluorides which includes hydrothermal reaction under a presence of HF or solid-state reaction at high temperatures in vacuum sealed tube or under high pressure. In the case of the reaction of MoO3 with NaF, the kind of solvent largely affected the obtained morphologies of NaMoO3F. The morphology in the case of acetonitrile as a solvent was rodlike with a micrometer-scale size, while that in the case of ethanol was polyhedral with a size of several hundred nanometers. In addition, the solvothermal reaction of WO3 with NaF led to the formation of Na5W3O9F5. Also, the difference of solvents for the solvothermal reaction affected the obtained particle sizes. The effect of the solvents on the morphologies of the obtained oxyfluorides probably resulted from the difference of the solubility of NaF and the subsequent dissolution ratio of MoO3 or WO3 in the used solvents. Our synthesis method can expand the applicability of oxyfluorides by providing a new phase and/or unique morphology.

DOI： 10.1021/acs.inorgchem.0c01175

Z-scheme water splitting by microspherical Rh-doped SrTiO3 photocatalysts prepared by a spray drying method Reviewed International journal

Hong Phong Duong, Takahiro Mashiyama, Makoto Kobayashi, Akihide Iwase, Akihiko Kudo, Yusuke Asakura, Shu Yin, Masato Kakihana, Hideki Kato

Applied Catalysis B: Environmental Vol. 252 page： 222 - 229 2019.9

Anisotropy in Stable Conformations of Hydroxylate Ions between the {001} and {110} Planes of TiO2 Rutile Crystals for Glycolate, Lactate, and 2-Hydroxybutyrate Ions Studied by Metadynamics Method. Reviewed International journal Open Access

Hiroki Nada, Makoto Kobayashi, Masato Kakihana

ACS omega Vol. 4 ( 6 ) page： 11014 - 11024 2019.6

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Control over TiO2 rutile crystal growth and morphology using additives is essential for the development of functional materials. Computer simulation studies on the thermodynamically stable conformations of additives at the surfaces of rutile crystals contribute to understanding the mechanisms underlying this control. In this study, a metadynamics method was combined with molecular dynamics simulations to investigate the thermodynamically stable conformations of glycolate, lactate, and 2-hydroxybutyrate ions at the {001} and {110} planes of rutile crystals. Two simple atom-atom distances were selected as collective variables for the metadynamics method. At the {001} plane, a conformation in which the COO- group was oriented toward the surface was found to be the most stable for the lactate and 2-hydroxybutyrate ions, whereas a conformation in which the COO- group was oriented toward water was the most stable for the glycolate ion. At the {110} plane, a conformation in which the COO- group was oriented toward the surface was the most stable for all three hydroxylate ions, and a second most stable conformation was also observed for the lactate ion at positions close to the {110} plane. For all three hydroxylate ions (α-hydroxycarboxylate ions), the stability of the most stable conformation was higher for the {110} plane than for the {001} plane. At both planes, the stability of the most stable conformation was highest for the 2-hydroxybutyrate ion and lowest for the glycolate ion. Supposing that all three hydroxylate ions serve to decrease the surface free energy at the rutile surface and that a more stable conformation at the rutile surface leads to a greater decrease in the surface free energy, the present results partially explain experimentally observed differences in the changes in growth rate and morphology of rutile crystals in the presence of glycolic, lactic, and 2-hydroxybutyric acids.

DOI： 10.1021/acsomega.9b01100

Selective Synthesis and Photocatalytic Oxygen Evolution Activities of Tantalum/Nitrogen-Codoped Anatase, Brookite and Rutile Titanium Dioxide Reviewed International journal

Nishioka, Shunta, Kobayashi, Makoto, Lu, Daling, Kakihana, Masato, Maeda, Kazuhiko

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN Vol. 92 ( 6 ) page： 1032 - 1038 2019.6

Language：English Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

Tantalum/nitrogen codoped titanium dioxide (TiO2:Ta,N) having a rutile structure has recently been reported to be a good photocatalyst for visible-light water oxidation. In this work, three different polymorphs of TiO2:Ta,N (anatase, brookite and rutile) were synthesized by a hydrothermal method using water-soluble titanium/tantalum complexes as precursors, followed by thermal nitridation with dry ammonia gas. Effects of the physicochemical properties on photocatalytic activity for O-2 evolution from an aqueous silver nitrate solution under visible light (lambda > 400 nm) were investigated. Experimental results indicated that defect formation during the nitridation procedure was the dominant factor for photocatalytic activity. Anatase TiO2:Ta,N was the most active for O-2 evolution among the three polymorphs, and also served as an O-2 evolution photocatalyst in Z-scheme overall water splitting in combination with Rh-doped strontium titanate (SrTiO3:Rh) and an Fe3+/Fe2+ redox-shuttle mediator.

DOI： 10.1246/bcsj.20190037

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Synthesis of Ba1-xSrxYSi2O5N and Discussion Based on Structure Analysis and DFT Calculation Reviewed International journal Open Access

Takuya Yasunaga, Makoto Kobayashi, Kenta Hongo, Kotaro Fujii, Shunsuke Yamamoto, Ryo Maezono, Masatomo Yashima, Masaya Mitsuishi, Hideki Kato, Masato Kakihana

Journal of Solid State Chemistry Vol. 276 page： 266-271 - 271 2019.5

Crystal structures of Ca4+xY3-xSi7O15+xN5-x (0 <= x <= 1) comprising of an isolated [Si7(O,N)19] unit Reviewed International journal Open Access

Kobayashi, Makoto, Yasunaga, Takuya, Kato, Hideki, Fujii, Kotaro, Yashima, Masatomo, Kakihana, Masato

ACTA CRYSTALLOGRAPHICA SECTION E-CRYSTALLOGRAPHIC COMMUNICATIONS Vol. 75 ( Pt 2 ) page： 260 - + 2019.2

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

Single crystals of the solid solution series Ca(4+x)Y(3-x)Si(7)O(15+x)N(5-x )were obtained by a solid-state reaction method using a flux for x = 0, 0.5 and 1, resulting in Ca4Y3Si7O15N5 (tetracalcium triyttrium heptasilicon oxynitride), Ca-4.5 Y-2.5 Si7O15.5N4.5 and Ca5Y2Si7O16N4 (pentacalcium diyttrium heptasilicon oxynitride). Single-crystal X-ray analysis revealed that the three compounds are isotypic and belong to space-group type P6(3)/m. Ca2+ and Y3+ cations are distributed over two crystallographic sites (site symmetry (3) over bar.. and 1) in a disordered manner. The corresponding (Ca,Y)-centred polyhedra are connected by edge-sharing, resulting in the formation of a layer structure extending parallel to (001). Three [Si(O,N)](4) tetrahedra (two with point group symmetry m one with 3.. and half-occupancy) are condensed into an isolated [Si-7(O,N)(19)] unit, in which an [Si(O,N)](4) tetrahedron is located at the center of a 12-membered oxynitride ring with composition [Si6O15N3]. The present compounds are the first to have such an [Si-7(O,N)(1)(9)] unit in their structures.

DOI： 10.1107/S2056989019001257

Hydrothermal Synthesis of Pseudocubic Rutile-Type Titania Particles International journal Open Access

Makoto Kobayashi, Hideki Kato, Takamichi Miyazaki, Masato Kakihana

Ceramics Vol. 2 ( 1 ) page： 56-63 - 63 2019.1

Sodium titanium oxide bronze nanoparticles synthesized via concurrent reduction and Na+-doping into TiO2(B) Reviewed International journal

Hasegawa, George, Tanaka, Moeko, Vequizo, Junie Jhon M., Yamakata, Akira, Hojo, Hajime, Kobayashi, Makoto, Kakihana, Masato, Inada, Miki, Akamatsu, Hirofumi, Hayashi, Katsuro

NANOSCALE Vol. 11 ( 3 ) page： 1442 - 1450 2019.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

A mixed valence compound, sodium titanium oxide bronze (NaxTiO2-B), combines intriguing properties of high electric conductivity and good chemical stability together with a unique one-dimensional tunnel crystal structure available for cation storage. However, this compound has not been studied for a long period because of the strongly reductive condition at high temperature required for its preparation, which limits the morphological control such as the preparation of nanocrystals. For the first time in this paper, the topotactic synthesis of nano-sized NaxTiO2-B with high specific surface area (>130 m(2) g(-1)) from TiO2(B) nanoparticles has been demonstrated. The reaction of metastable TiO2(B) with NaBH4 allows carrier electrons to be doped simultaneously with incorporation of Na+ ions into the interstitial sites of the host Ti-O lattice at relatively low temperature. An electrochemical investigation of Li+- and Na+-ion storage behaviors suggests that the incorporated Na+ ions are mainly placed in the 6-fold coordination sites of bronze. In addition, optical measurements including time-resolved transient spectroscopy revealed that the doped electrons in the NaxTiO2-B nanoparticles are predominantly in the Ti3+ state and behave as a small polaron. The pelletized NaxTiO2-B nanoparticles shows a good electronic conductivity of 1.4 x 10(-2) S cm(-1) at 30 degrees C with an activation energy of 0.17 eV, which is attributable to the thermal barrier for the polaron hopping.

DOI： 10.1039/c8nr08372j

B-site-ordered Double-perovskite Oxide Up-conversion Phosphors Doped with Yb and Ho, Er, or Tm Reviewed International journal Open Access

Kasuya, Kohei, Sato, Yasushi, Kobayashi, Makoto, Kato, Hideki, Kakihana, Masato, Tomita, Koji

JOURNAL OF PHOTOPOLYMER SCIENCE AND TECHNOLOGY Vol. 32 ( 4 ) page： 593 - 596 2019

Language：English Publishing type：Research paper (scientific journal) Publisher：The Society of Photopolymer Science and Technology(SPST)

B-site-ordered double-perovskite oxide up-conversion phosphors La2ZnTiO6, La2MgTiO6, and Ba2LaTaO6 doped with Yb and Ho, Er, or Tm were synthesized by a citric acid complex gelation method and a polymerizable complex method. Under 980-nm excitation, the double-perovskite oxide phosphors doped with luminescent ions at the A-site (La2ZnTiO6 and La2MgTiO6) showed stronger up-conversion emission than the phosphor doped with luminescent ions at the B-site (Ba2LaTaO6). La2ZnTiO6 and La2MgTiO6, in which dopants occupied the A-site, showed different up-conversion emission behaviors because of structural distortion resulting from the substitution of B-site cations.

DOI： 10.2494/photopolymer.32.593

Ce4+-Based Compounds Capable of Photoluminescence by Charge Transfer Excitation under Near-Ultraviolet-Visible Light. Reviewed International journal

Dawei Wen, Hideki Kato, Makoto Kobayashi, Shunsuke Yamamoto, Masaya Mitsuishi, Kotaro Fujii, Masatomo Yashima, Masato Kakihana

Inorganic chemistry Vol. 57 ( 23 ) page： 14524 - 14531 2018.12

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

Ce4+-based charge transfer phosphor is not common and has been reported mainly in Sr2CeO4 with an excitation band peaking at ∼290 nm, mismatching with the near-ultraviolet light emitting diodes. Herein, we report a new series of Ce4+-based compounds Sr4.4Ce2.6REZnO12 (RE = Y, La, and Eu) capable of photoluminescence induced by O2--Ce4+ charge transfer excitation under near-ultraviolet-visible light. The crystal structure of Sr4.4Ce2.6EuZnO12 was determined by single crystal X-ray diffraction. The RE = La and Y samples were confirmed to be iso-structure compounds of the RE = Eu sample by powder X-ray diffraction. By introducing highly covalent Zn2+-O2- bonds into the framework, the Ce4+-O2- bonds are lengthened due to the effect of the Ce4+-O2--Zn2+ stretch. The lengthened Ce4+-O2- bond weakens the repulsion of the electrons between Ce4+ and O2-, thereby lowering the charge transfer energy to the visible light region. Incorporation of Eu3+ into the present compounds realized red emission under near-ultraviolet-visible excitation by the O2--Ce4+ charge transfer followed by energy transfer to Eu3+.

DOI： 10.1021/acs.inorgchem.8b01900

Expansion of Photoresponse Window of BiVO4 Photocatalyst by Doping of Chromium(VI) Reviewed International journal Open Access

Kazuya Okuno, Hideki Kato, Junie Jhon, M. Vequizo, Yamakata Akira, Hisayoshi Kobayashi, Makoto Kobayashi, Masato Kakihana

RSC Advances Vol. 8 ( 67 ) page： 38140-38145 - 38145 2018.11

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Papers - KOBAYASHI Makoto