研究者詳細 - 小林　亮

論文 - 小林　亮

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Development of Z-Scheme Photocatalyst Systems Combining Nonmetal Oxide Materials for Water Splitting under Visible Light Irradiation: (CuGa)0.5ZnS2 as a H2-Evolving Photocatalyst and TaON as an O2-Evolving Photocatalyst 査読有り国際共著 Open Access

Moriya M., Yoshino S., Kobayashi M., Kato H., Ng Y.H., Iwase A.

Advanced Energy and Sustainability Research 6 巻 ( 7 ) 頁： 2400371 2025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：Advanced Energy and Sustainability Research

Water splitting under visible light irradiation using a Z-scheme system combining nonmetal oxides of TaON and (CuGa)<inf>0.5</inf>ZnS<inf>2</inf> is demonstrated. The key factors lie in coloading with Ir and CoO<inf>x</inf> cocatalysts on TaON and using reduced graphene oxide (RGO) as a solid-state electron mediator. Ir is loaded by an impregnation method, while CoO<inf>x</inf> is loaded by either impregnation or photodeposition methods. Loaded Ir boosts the electron migration from TaON to RGO, and loaded CoO<inf>x</inf> works as an active site for O<inf>2</inf> evolution. Photocatalytic reduction of graphene oxide to RGO accompanied by simultaneous oxidation of Co<sup>2+</sup> ions to CoO<inf>x</inf> over Ir-loaded TaON is the optimum process for the formation of an RGO-(CoO<inf>x</inf>/Ir/TaON) composite.

DOI： 10.1002/aesr.202400371

Mechanical exfoliation of non-var der Waals solids: A study of layered perovskite ferroelectric CsPb₂Nb₃O₁₀ 査読有り

Masanari Shimada, Yan Li, Makoto Kobayashi, Eisuke Yamamoto, Rubén Cantón Vitoria, Minoru Osada

Chemistry Letters 64 巻 ( 2 ) 頁： upaf006 2025年1月

Covalent Functionalization of MXenes with Porphyrin for Visible-Light Activation in Energy Conversion Nanodevices 査読有り Open Access

Li H., Canton-Vitoria R., Urano Y., Nayak S.K., Yamamoto E., Kobayashi M., Kitaura R., Osada M.

Small 頁： e03895 2025年

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

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12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：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

Ferroelectricity in CsPb2Nb3O10 and exfoliated 2D nanosheets 査読有り国際共著

Li Y., Shimada M., Kobayashi M., Yamamoto E., Canton-Vitoria R., Liu X., Osada M.

Dalton Transactions 53 巻 ( 45 ) 頁： 18122 - 18127 2024年9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：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 CsPb<inf>2</inf>Nb<inf>3</inf>O<inf>10</inf> and exfoliated 2D nanosheets. Ferroelectricity in CsPb<inf>2</inf>Nb<inf>3</inf>O<inf>10</inf> was demonstrated for the first time. CsPb<inf>2</inf>Nb<inf>3</inf>O<inf>10</inf> adopted a polar tetragonal structure with a modest T<inf>C</inf> = 260 °C and polarization P<inf>S</inf> = 7.93 μC cm<sup>−2</sup>; the polarization mainly arose from the out-of-plane displacements of Nb<sup>5+</sup> ions and nearby oxygens. CsPb<inf>2</inf>Nb<inf>3</inf>O<inf>10</inf> 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 Pb<inf>2</inf>Nb<inf>3</inf>O<inf>10</inf> nanosheets.

DOI： 10.1039/d4dt02343a

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

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(Bi<inf>2</inf>Sr<inf>n</inf><inf>-3</inf>)(Ti<inf>n</inf><inf>-1</inf>Nb)O<inf>3n+1</inf>. Starting from CsBi<inf>2</inf>Ti<inf>2</inf>NbO<inf>10</inf> (n = 3), higher-order homologous phases with n = 4 and 5 were successfully synthesized by repeated solid-state calcination with SrTiO<inf>3</inf>. Characterizations by X-ray diffraction, electron diffraction, transmission electron microscopy, Raman scattering, and second harmonic generation showed the detailed structural features in Cs(Bi<inf>2</inf>Sr<inf>n</inf><inf>-3</inf>)(Ti<inf>n</inf><inf>-1</inf>Nb)O<inf>3n+1</inf>, 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 査読有り

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

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 C.W., Osada M.

Small 20 巻 ( 36 ) 頁： e2403915 2024年7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：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, MoS<inf>2</inf>, 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

Multiemission of Ce³⁺ from Single Crystallographic Site Induced by Disordering of Ions 査読有り

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 63 巻 ( 2 ) 頁： 1288 - 1295 2024年1月

Hetero-assembly design of 2D oxide nanosheets for tailored thermal shielding materials 査読有り Open Access

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

Applied Physics Express 17 巻 ( 1 ) 頁： 015002 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：Applied Physics Express

We present a new approach for designing thermal shielding materials using two-dimensional oxide nanosheets. Our approach uses hetero-assembly design [(Ti<inf>0.87</inf>O<inf>2</inf>)<inf>m </inf>(Cs<inf>2.7</inf>W<inf>11</inf>O<inf>35−d </inf>)<inf>20</inf> (m = 0, 5, 10)] by overlaying high refractive index (n) Ti<inf>0.87</inf>O<inf>2</inf> nanosheets with transparent conducting Cs<inf>2.7</inf>W<inf>11</inf>O<inf>35−d </inf> nanosheets. Through proper design of the thickness of high-n Ti<inf>0.87</inf>O<inf>2</inf> 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

Z-scheme water splitting utilizing CuLi1/3Ti2/3O2 as a hydrogen-evolving photocatalyst with photo-response up to 600 nm 査読有り Open Access

Yoshino S., Kurutach T., Liu Q., Yamanaka T., Nozawa S., Kobayashi M., Kumagai H., Kato H.

Sustainable Energy and Fuels 8 巻 ( 6 ) 頁： 1260 - 1268 2024年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Sustainable Energy and Fuels

CuLi<inf>1/3</inf>Ti<inf>2/3</inf>O<inf>2</inf> (CLTO) is a visible-responsive photocatalyst, whose photo-response reaches up to 600 nm, for H<inf>2</inf> evolution using sacrificial electron donors such as methanol and S<sup>2−</sup>. In this study, utilization of CLTO in Z-scheme water splitting (Z-WS) was investigated. The photocatalytic performance of Cr<inf>2</inf>O<inf>3</inf>/M/CLTO as a H<inf>2</inf>-evolving photocatalyst, which was prepared by sequential photodeposition of cocatalysts (M: Ru, Rh, Pd and Pt) and Cr<inf>2</inf>O<inf>3</inf>, was evaluated for Z-WS using BiVO<inf>4</inf>, an O<inf>2</inf>-evolving photocatalyst, and a Co(bpy)<inf>3</inf><sup>3+/2+</sup> redox shuttle under visible light. Among the examined samples, Cr<inf>2</inf>O<inf>3</inf>/Ru/CLTO produced both H<inf>2</inf> and O<inf>2</inf> with meaningful rates. Thus, CLTO was first utilized in a visible responsive Z-scheme system for water splitting. The Cr<inf>2</inf>O<inf>3</inf> layer played a significant role in the suppression of backward reactions, such as reduction of Co(bpy)<inf>3</inf><sup>3+</sup>. The activity of Cr<inf>2</inf>O<inf>3</inf>/Ru/CLTO for Z-WS was remarkably affected by the deposition conditions of the Ru cocatalyst. The activity for Z-WS was remarkably improved when the photodeposition of the Ru cocatalyst was conducted in a methanol solution of RuCl<inf>3</inf>. Unusually large plate Ru species with 100-200 nm sizes and about 30 nm thickness were present in the highly active sample. Characterization using X-ray photoelectron spectroscopy and X-ray absorption spectroscopy indicated that the Ru cocatalyst was deposited as mainly the oxyhydroxide of Ru. Z-WS also proceeded in the absence of Co(bpy)<inf>3</inf><sup>3+/2+</sup> (the system based on interparticle electron transfer), however, the Z-scheme system using the Co(bpy)<inf>3</inf><sup>3+/2+</sup> electron shuttle showed 10 times higher activity than the interparticle electron transfer system. The external quantum yield and efficiency of solar energy conversion to hydrogen were determined to be 0.5% at 430 nm and 0.029%, respectively.

DOI： 10.1039/d3se01622f

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

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 査読有り国際誌

Tsunematsu H., Shi Y., Yamamoto E., Kobayashi M., Yoshida T., Osada M.

ACS Nano 17 巻 ( 12 ) 頁： 11396 - 11405 2023年6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：ACS Nano

Thermal shielding materials that can block near-infrared (NIR) light from the sunlight while maintaining visible transparency have become increasingly important from an energy-saving perspective. Here, we demonstrate a gigantic NIR shielding by an engineered plasmonic material based on a two-dimensional (2D) polytungstate (Cs<inf>4-x</inf>W<inf>11</inf>O<inf>35-d</inf>). Starting from a charge-neutral polytungstate (Cs<inf>4</inf>W<inf>11</inf>O<inf>35</inf>), we synthesize charge-imbalanced 2D nanosheets (Cs<inf>4-x</inf>W<inf>11</inf>O<inf>35-d</inf>) that undergo an unusual structural change with the semiconductor-to-metal transition in a reduced atmosphere. Layer-by-layer engineering of the 2D nanosheets enables a plasmon-induced enhancement of the NIR reflectance (>53%) with a high visible transparency (>71%), realizing high-performance thermal shielding. Our approach offers a solution for future thermal management technology.

DOI： 10.1021/acsnano.3c00815

Ultrahigh Energy Storage in 2D High-κ Perovskites 査読有り国際誌

Kim H.J., Morita S., Byun K.N., 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

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 (Ca<inf>2</inf>Na<inf>m-3</inf>Nb<inf>m</inf>O<inf>3m+1</inf>; m = 3-6). Individual Ca<inf>2</inf>Na<inf>m-3</inf>Nb<inf>m</inf>O<inf>3m+1</inf> nanosheets exhibit an ultrahigh dielectric strength (638-1195 MV m<sup>-1</sup>) even in the monolayer form, which exceeds those of conventional dielectric materials. Multilayer stacked nanosheet capacitors exhibit ultrahigh energy densities (174-272 J cm<sup>-3</sup>), high efficiencies (>90%), excellent reliability (>10<sup>7</sup> 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

2D Bismuth Oxyfluorides: A New Member of Cationic Nanosheets 査読有り Open Access

Kobayashi M., Tasaka T., Yamamoto E., Osada M.

Chemistry Letters 52 巻 ( 6 ) 頁： 449 - 451 2023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：Chemistry Letters

Two kinds of single-crystalline oxyfluoride nanosheets were synthesized by exfoliation of layered bismuth oxyfluorides intercalated with nitrates. The solution-based exfoliation process produced multilayered cationic oxyfluoride nanosheets with thicknesses of several nanometers. A second harmonic generation measurement clarified that one of the nanosheets had a noncentrosymmetric structure. This is the first example of a cationic nanosheet with nonlinear optical properties.

DOI： 10.1246/cl.230136

Pseudo-topotactic Transformation from Oxide Nanosheets to Amorphous Nanosheets 査読有り Open Access

Sugimoto H., Kobayashi M., Yamamoto E., Osada M.

Chemistry Letters 52 巻 ( 5 ) 頁： 322 - 324 2023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：Chemistry Letters

We demonstrated the synthesis of amorphous oxide nanosheets from crystalline nanosheets prepared by the exfoliation of layered compounds. Single-crystalline oxide nanosheets were calcined with C<inf>3</inf>N<inf>4</inf> powder in flowing nitrogen and annealed in air to produce amorphous oxide nanosheets. The cation composition and valence, shape, lateral size, surface roughness, and thickness were not changed by treatment. This approach enables the production of amorphous oxide nanosheets with distinct morphologies and compositions and large lateral sizes.

DOI： 10.1246/cl.230073

Composite design of two-dimensional inorganic nanosheets for flexible energy storage capacitors Open Access

Byun K.N., Shi Y., Yamamoto E., Kobayashi M., Osada M.

Journal of the Ceramic Society of Japan 131 巻 ( 4 ) 頁： 77 - 82 2023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 Ceramic Society of Japan

We present a new approach for designing flexible energy storage capacitors using two-dimensional (2D) inorganic nanosheets. 2D dielectric Ca<inf>2</inf>Nb<inf>3</inf>O<inf>10</inf> nanosheet and ferroelectric poly(vinylidene fluoride) (PVDF) were selected as model material systems. LangmuirBlodgett deposition was utilized for layer-by-layer engineering of (Ca<inf>2</inf>Nb<inf>3</inf>O<inf>10</inf>/PVDF) nanocomposite films on an indium tin oxide (ITO)-coated polyethylene terephthalate (PET) substrate. Such a new composite design realized the simultaneous improvement of energy density (<sup>3</sup>7 J cm<sup>13</sup>) and efficiency (<sup>3</sup>78 %) even in the ultrathin form (<sup>3</sup>20 nm) on the ITO-coated PET substrate. Nanosheet-based flexible capacitors also maintained a stable performance even after 10<sup>4</sup> times bending cycles. These results indicate that our nanosheet approach is of technological importance for exploring new flexible dielectric capacitors.

DOI： 10.2109/jcersj2.22150

Automated One-Drop Assembly for Facile 2D Film Deposition 査読有り

Shi Y., Yamamoto E., Kobayashi M., Osada M.

ACS Applied Materials and Interfaces 15 巻 ( 18 ) 頁： 22737 - 22743 2023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：ACS Applied Materials and Interfaces

The effective application of 2D materials is strongly dependent on the mass production of high-quality large-area 2D thin films. Here, we demonstrate a strategy for the automated manufacturing of high-quality 2D thin films using a modified drop-casting approach. Our approach is simple; by using an automated pipette, a dilute aqueous suspension is dropped onto a substrate heated on a hotplate, and controlled convection by Marangoni flow and liquid removal causes the nanosheets to come together to form a tile-like monolayer film in 1-2 min. Ti<inf>0.87</inf>O<inf>2</inf> nanosheets are utilized as a model system for investigating the control parameters such as concentrations, suction speeds, and substrate temperatures. We perform the automated one-drop assembly of a range of 2D nanosheets (metal oxides, graphene oxide, and hexagonal boron nitride) and successfully fabricate various functional thin films in multilayered, heterostructured, and sub-micrometer-thick forms. Our deposition method enables on-demand large-size (>2 inchϕ) manufacturing of high-quality 2D thin films while reducing the time and sample consumption.

DOI： 10.1021/acsami.3c02250

Free-Standing Molecularly Thin Amorphous Silica Nanosheets 査読有り Open Access

Yamamoto E., Fujihara K., Takezaki Y., Ito K., Shi Y., Kobayashi M., Osada M.

Small 19 巻 ( 22 ) 頁： 2300022 - 2300022 2023年2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：Small

Recent progress in 2D materials has initiated new fields of molecularly thin amorphous materials with mysterious properties and structures. However, designed synthesis of molecularly thin amorphous silica still remains a challenge; whether free-standing molecularly thin amorphous silica nanosheets can exist is unclear. Here, this issue is addressed by using a new chemical protocol; solid-state surfactant lamellae with ordered alkyl-chain arrangements can serve as superior templates guiding free-standing amorphous silica nanosheets. Simple sonication of the lamellar hybrids allows exfoliation into monolayer amorphous silica nanosheets with 0.9 nm thickness. In addition, the nanosheets show the distinctive feature of high colloidal stability that enables atomic layer engineering of silica nanocoatings and dielectric nanofilms. The approach may shed new light on the properties and applications of old silica.

DOI： 10.1002/smll.202300022

その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/smll.202300022

Molecularly Thin BaTiO₃ Nanosheets with Stable Ferroelectric Response 査読有り国際共著 Open Access

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

Advanced Electronic Materials 9 巻 ( 3 ) 頁： 2291239 2023年2月

Damage-free LED lithography for atomically thin 2D material devices 査読有り Open Access

Shi Y., Taniguchi T., Byun K.N., Kurimoto D., Yamamoto E., Kobayashi M., Tsukagoshi K., Osada M.

Scientific Reports 13 巻 ( 1 ) 頁： 2583 2023年2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：Scientific Reports

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<inf>2</inf>, graphene oxides and RuO<inf>2</inf>), 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.

DOI： 10.1038/s41598-023-29281-w

その他リンク： https://www.nature.com/articles/s41598-023-29281-w

Improved Energy Storage Performance of PVDF Nanocapacitors by Utilizing 2D Inorganic Barrier Layers 査読有り国際共著

Byun K.N., Yamamoto E., Kobayashi M., Osada M.

Chemistry Letters 52 巻 ( 1 ) 頁： 51 - 54 2023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：Chemistry Letters

We demonstrated a rational approach for designing highperformance polymer-based energy storage capacitors. Twodimensional paraelectric Ca2Nb3O10 nanosheets were deposited on a ferroelectric poly(vinylidene fluoride) (PVDF) film to form paraelectric/ferroelectric hetero-assemblies. Such an artificial structuring enabled tailoring of the breakdown strength and dielectric response, realizing an enhanced energy density (∼10 J cm-3) compared to pristine PVDF film (∼1 J cm-3).

DOI： 10.1246/cl.220466

Tailored synthesis of molecularly thin platinum nanosheets using designed 2D surfactant solids 査読有り

Yamamoto E., Suzuki A., Kobayashi M., Osada M.

Nanoscale 14 巻 ( 32 ) 頁： 11561 - 11567 2022年

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

The assembly of the surfactants has been utilized as unique templates for the controlled synthesis of metal nanosheets. However, current strategies for metal nanosheets have mainly focused on the liquid-phase surfactant assembly. Herein, we found the 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. The 2D surfactant crystals containing planarly arranged Pt complexes were prepared, and the subsequent UV-ozone treatment and reduction process allowed us to obtain Pt metal nanosheets. Pt metal nanosheets had a distinct morphology with various thicknesses (from 1.5 nm to 3.0 nm), characteristic of 2D surfactant crystals.

DOI： 10.1039/d2nr01807a

Influences of pulverization and annealing treatment on the photocatalytic activity of BiVO4 for oxygen evolution 査読有り

Okuno K., Kumagai H., Vequizo J.J.M., Kato K., Kobayashi M., Yamakata A., Kakihana M., Kato H.

Sustainable Energy and Fuels 6 巻 ( 7 ) 頁： 1698 - 1707 2022年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Sustainable Energy and Fuels

In this study, the photocatalytic activity of small particles of BiVO<inf>4</inf> for O<inf>2</inf> evolution using Fe<sup>3+</sup> as an electron acceptor was investigated. Characterization by X-ray diffraction and electron microscopy revealed that small particles of BiVO<inf>4</inf> with 20-50 nm of sizes were obtained from micron-sized monoclinic scheelite-type BiVO<inf>4</inf> without changes in the crystal structure by ball milling treatment. The specific surface area increased from 0.7 to 22.6 m<sup>2</sup> g<sup>−1</sup> by the milling treatment. Although the milling treatment decreased the photocatalytic activity, the successive annealing treatment at 400 °C remarkably improved the activity of milled BiVO<inf>4</inf>. As a result, the annealed small particles of BiVO<inf>4</inf> achieved a slightly higher external quantum yield than the pristine one, 22.6% versus 20.8%. In contrast, the activity of non-milled BiVO<inf>4</inf> decreased due to the annealing treatment. Transient absorption spectroscopy using femtosecond and nanosecond pump lasers clarified the influences of the ball milling and annealing treatment on the carrier dynamics of BiVO<inf>4</inf>. The ball milling treatment accelerated recombination in picosecond and microsecond regions. For example, only 40% of photogenerated holes survived in milled BiVO<inf>4</inf> at 10 ps whereas 60% of holes remained in the non-milled sample. Annealing treatment at 400 °C suppressed the recombination in milled BiVO<inf>4</inf> but facilitated the recombination in the non-milled sample. The small BiVO<inf>4</inf> particles annealed at 400 °C, which exhibited high activity in sacrificial O<inf>2</inf> evolution, also showed high performance in overall water splitting by Z-scheme systems combined with Ru/SrTiO<inf>3</inf>:Rh of a H<inf>2</inf>-evolving photocatalyst. A small amount of annealed small BiVO<inf>4</inf> particles (5 mg) showed comparable activity in Z-scheme water splitting to the reaction with 30 mg of non-milled sample. In addition, in the Z-scheme water splitting based on interparticle electron transfer, the annealed small BiVO<inf>4</inf> allowed 17% higher activity than the non-milled sample.

DOI： 10.1039/d2se00065b

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

Kasuya K., Shahiduzzaman M., Kobayashi M., Yin S., Kakihana M., Tomita K.

Journal of the Ceramic Society of Japan 129 巻 ( 12 ) 頁： 720 - 724 2021年12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 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 30nm 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 査読有り国際誌 Open Access

Yue Shi, Eisuke Yamamoto, Makoto Kobayashi, Minoru Osada

Journal of the Ceramic Society of Japan 2021年4月

Synthesis of NaMoO3F and Na5W3O9F5with Morphological Controllability in Non-Aqueous Solvents 査読有り国際誌

Asakura Y., Akahira T., Kobayashi M., Osada M., Yin S.

Inorganic Chemistry 59 巻 ( 15 ) 頁： 10707 - 10716 2020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：Inorganic Chemistry

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 査読有り国際誌

Duong H.P., Mashiyama T., Kobayashi M., Iwase A., Kudo A., Asakura Y., Yin S., Kakihana M., Kato H.

Applied Catalysis B Environmental 252 巻頁： 222 - 229 2019年9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：Applied Catalysis B Environmental

Microspherical particles of Rh-doped SrTiO<inf>3</inf> (SrTiO<inf>3</inf>:Rh) having size of 1–2 μm were synthesized by a spray drying (SD) method employing a water-soluble ammonium trilactatotitanate. When the calcination temperature increased up to 1200 °C, primary particles grew significantly while the microspherical morphology of the secondary particles was kept. Dynamic light scattering analysis proved well-dispersive nature of the SD sample. Photocatalytic activities of SrTiO<inf>3</inf>:Rh synthesized by the SD method, solid state reaction (SSR), and a polymerizable complex (PC) method were evaluated for H<inf>2</inf> evolution using an electron donor such as methanol, Fe<sup>2+</sup>, or [Co(bpy)<inf>3</inf>]<sup>2+</sup> and Z-scheme water splitting combined with BiVO<inf>4</inf> of an O<inf>2</inf>-evolving photocatalyst and either Fe<sup>3+/2+</sup>, [Co(bpy)<inf>3</inf>]<sup>3+/2+</sup>, or reduced graphene oxide as an electron mediator. SrTiO<inf>3</inf>:Rh prepared by the SD method showed much higher activities for all Z-scheme water splitting than the samples synthesized by the SSR method. Activities of the SD sample for Z-scheme water splitting using electron shuttles, Fe<sup>3+/2+</sup> and [Co(bpy)<inf>3</inf>]<sup>3+/2+</sup>, were slightly higher or comparable to those of the PC sample whereas the SD sample achieved higher activity in Z-scheme water splitting based on interparticle electron transfer. In addition, even when the mass of SrTiO<inf>3</inf>:Rh used for the Z-scheme system with Fe<sup>3+/2+</sup> was decreased from 50 mg to 30 mg, the SD sample still showed high activity while the activity decreased for the SSR and PC samples. Thus, usefulness of the SD method to obtain highly active SrTiO<inf>3</inf>:Rh with well-dispersive nature has been demonstrated.

DOI： 10.1016/j.apcatb.2019.04.009

Anisotropy in Stable Conformations of Hydroxylate Ions between the {001} and {110} Planes of TiO<sub>2</sub> Rutile Crystals for Glycolate, Lactate, and 2-Hydroxybutyrate Ions Studied by Metadynamics Method. 査読有り国際誌 Open Access

Nada H, Kobayashi M, Kakihana M

ACS omega 4 巻 ( 6 ) 頁： 11014 - 11024 2019年6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：ACS Omega

Control over TiO<inf>2</inf> 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<sup>-</sup> 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<sup>-</sup> group was oriented toward water was the most stable for the glycolate ion. At the {110} plane, a conformation in which the COO<sup>-</sup> 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 査読有り国際誌

Nishioka S., Kobayashi M., Lu D., Kakihana M., Maeda K.

Bulletin of the Chemical Society of Japan 92 巻 ( 6 ) 頁： 1032 - 1038 2019年6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：Bulletin of the Chemical Society of Japan

Tantalum/nitrogen codoped titanium dioxide (TiO<inf>2</inf>: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 TiO<inf>2</inf>: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<inf>2</inf> evolution from an aqueous silver nitrate solution under visible light ( > 400 nm) were investigated. Experimental results indicated that defect formation during the nitridation procedure was the dominant factor for photocatalytic activity. Anatase TiO<inf>2</inf>:Ta,N was the most active for O<inf>2</inf> evolution among the three polymorphs, and also served as an O<inf>2</inf> evolution photocatalyst in Z-scheme overall water splitting in combination with Rh-doped strontium titanate (SrTiO<inf>3</inf>:Rh) and an Fe<sup>3+</sup>/ Fe<sup>2+</sup> redox-shuttle mediator.

DOI： 10.1246/bcsj.20190037

Synthesis of Ba<sub>1-<i>x</i></sub>Sr<sub><i>x</i></sub>YSi<sub>2</sub>O<sub>5</sub>N and Discussion Based on Structure Analysis and DFT Calculation 査読有り国際誌 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 276 巻頁： 266-271 - 271 2019年5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 Solid State Chemistry

Cation substitution for inorganic solid materials is a practical approach to control their functions. Here, synthesis, structure analysis, density functional theory (DFT) calculation of novel oxynitrides Ba<inf>1−x</inf>Sr<inf>x</inf>YSi<inf>2</inf>O<inf>5</inf>N, and investigation of their photoluminescence properties with Eu<sup>2+</sup>- or Ce<sup>3+</sup>-activator were conducted. Single crystal and powder X-ray analyses revealed that Ba<inf>1−x</inf>Sr<inf>x</inf>YSi<inf>2</inf>O<inf>5</inf>N were formed at x ≤ 0.75 and they were isotypic while the synthesis of SrYSi<inf>2</inf>O<inf>5</inf>N (x = 1) was not achieved by any synthesis conditions examined. Based on phonon calculation, it was concluded that the synthesis of SrYSi<inf>2</inf>O<inf>5</inf>N with the isostructure to BaYSi<inf>2</inf>O<inf>5</inf>N was impossible due to the thermodynamical unstability. Substitution of Ba with Sr decreased the average bond length of AE-(O,N) (AE = Ba and Sr) and increased distortion of AE sites. On the other hand, coordination environments of Y sites were rarely affected by the substitution. As a result, redshift and broadening of emission spectra for Eu-doped samples were observed, whereas there was almost no spectral change in Ce-doped samples.

DOI： 10.1016/j.jssc.2019.05.012

Crystal structures of Ca4+x Y3-x Si7O15+x N5-x (0≤ x ≤ 1) comprising of an isolated [Si7 (O,N) 19] unit 査読有り国際誌 Open Access

Kobayashi M., Yasunaga T., Kato H., Fujii K., Yashima M., Kakihana M.

Acta Crystallographica Section E Crystallographic Communications 75 巻 ( Pt 2 ) 頁： 260 - + 2019年2月

担当区分：筆頭著者,　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：Acta Crystallographica Section E Crystallographic Communications

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 Ca 4 Y 3 Si 7 O 15 N 5 (tetracalcium triyttrium heptasilicon oxynitride), Ca 4.5 Y 2.5 Si 7 O 15.5 N 4.5 and Ca 5 Y 2 Si 7 O 16 N 4 (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. Ca 2+ and Y 3+ cations are distributed over two crystallographic sites (site symmetry.. 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 [Si 6 O 15 N 3 ]. The present compounds are the first to have such an [Si 7 (O,N) 19 ] unit in their structures.

DOI： 10.1107/S2056989019001257

Hydrothermal Synthesis of Pseudocubic Rutile-Type Titania Particles 国際誌 Open Access

Makoto Kobayashi, Hideki Kato, Takamichi Miyazaki, Masato Kakihana

Ceramics 2 巻 ( 1 ) 頁： 56-63 - 63 2019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：Ceramics

The functional properties of materials depend strongly on their morphologies. Here, the hydrothermal synthesis of rutile-type titania crystals with pseudocubic shapes using a water-soluble titanium complex is reported. This approach does not require extra additives or doping. Transmission electron microscopy and selected-area electron diffraction analysis revealed that they exposed high-index facets, such as {121}, and high-energy facets, such as {001}, which do not usually appear in rutile crystal. In terms of the formation of steps and kinks on pseudocubic rutile and coexisting anatase and brookite nanoparticles, the adsorption of nanoparticles might inhibit crystal growth, resulting in the formation of crystals with uncommon shapes exposing high-index and high-energy facets.

DOI： 10.3390/ceramics2010005

Sodium titanium oxide bronze nanoparticles synthesized: Via concurrent reduction and Na + -doping into TiO 2 (B) 査読有り国際誌

Hasegawa G., Tanaka M., Vequizo J.J.M., Yamakata A., Hojo H., Kobayashi M., Kakihana M., Inada M., Akamatsu H., Hayashi K.

Nanoscale 11 巻 ( 3 ) 頁： 1442 - 1450 2019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：Nanoscale

A mixed valence compound, sodium titanium oxide bronze (Na <inf>x</inf> TiO <inf>2</inf> -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 Na <inf>x</inf> TiO <inf>2</inf> -B with high specific surface area (>130 m <sup>2</sup> g <sup>-1</sup> ) from TiO <inf>2</inf> (B) nanoparticles has been demonstrated. The reaction of metastable TiO <inf>2</inf> (B) with NaBH <inf>4</inf> allows carrier electrons to be doped simultaneously with incorporation of Na <sup>+</sup> ions into the interstitial sites of the host Ti-O lattice at relatively low temperature. An electrochemical investigation of Li <sup>+</sup> - and Na <sup>+</sup> -ion storage behaviors suggests that the incorporated Na <sup>+</sup> 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 Na <inf>x</inf> TiO <inf>2</inf> -B nanoparticles are predominantly in the Ti <sup>3+</sup> state and behave as a small polaron. The pelletized Na <inf>x</inf> TiO <inf>2</inf> -B nanoparticles shows a good electronic conductivity of 1.4 × 10 <sup>-2</sup> S cm <sup>-1</sup> at 30 °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 査読有り国際誌 Open Access

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

JOURNAL OF PHOTOPOLYMER SCIENCE AND TECHNOLOGY 32 巻 ( 4 ) 頁： 593 - 596 2019年

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 Photopolymer Science and Technology

B-site-ordered double-perovskite oxide up-conversion phosphors La<inf>2</inf>ZnTiO<inf>6</inf>, La<inf>2</inf>MgTiO<inf>6</inf>, and Ba<inf>2</inf>LaTaO<inf>6</inf> 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 (La<inf>2</inf>ZnTiO<inf>6</inf> and La<inf>2</inf>MgTiO<inf>6</inf>) showed stronger up-conversion emission than the phosphor doped with luminescent ions at the B-site (Ba<inf>2</inf>LaTaO<inf>6</inf>). La<inf>2</inf>ZnTiO<inf>6</inf> and La<inf>2</inf>MgTiO<inf>6</inf>, 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

Ce 4+ -Based Compounds Capable of Photoluminescence by Charge Transfer Excitation under Near-Ultraviolet-Visible Light 査読有り国際誌

Wen D., Kato H., Kobayashi M., Yamamoto S., Mitsuishi M., Fujii K., Yashima M., Kakihana M.

Inorganic Chemistry 57 巻 ( 23 ) 頁： 14524 - 14531 2018年12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

Ce <sup>4+</sup> -based charge transfer phosphor is not common and has been reported mainly in Sr <inf>2</inf> CeO <inf>4</inf> with an excitation band peaking at ∼290 nm, mismatching with the near-ultraviolet light emitting diodes. Herein, we report a new series of Ce <sup>4+</sup> -based compounds Sr <inf>4.4</inf> Ce <inf>2.6</inf> REZnO <inf>12</inf> (RE = Y, La, and Eu) capable of photoluminescence induced by O <sup>2-</sup> -Ce <sup>4+</sup> charge transfer excitation under near-ultraviolet-visible light. The crystal structure of Sr <inf>4.4</inf> Ce <inf>2.6</inf> EuZnO <inf>12</inf> 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 Zn <sup>2+</sup> -O <sup>2-</sup> bonds into the framework, the Ce <sup>4+</sup> -O <sup>2-</sup> bonds are lengthened due to the effect of the Ce <sup>4+</sup> -O <sup>2-</sup> -Zn <sup>2+</sup> stretch. The lengthened Ce <sup>4+</sup> -O <sup>2-</sup> bond weakens the repulsion of the electrons between Ce <sup>4+</sup> and O <sup>2-</sup> , thereby lowering the charge transfer energy to the visible light region. Incorporation of Eu <sup>3+</sup> into the present compounds realized red emission under near-ultraviolet-visible excitation by the O <sup>2-</sup> -Ce <sup>4+</sup> charge transfer followed by energy transfer to Eu <sup>3+</sup> .

DOI： 10.1021/acs.inorgchem.8b01900

Expansion of Photoresponse Window of BiVO<sub>4</sub> Photocatalyst by Doping of Chromium(VI) 査読有り国際誌 Open Access

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

RSC Advances 8 巻 ( 67 ) 頁： 38140-38145 - 38145 2018年11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：Rsc Advances

Doping of Cr<sup>6+</sup> into BiVO<inf>4</inf> was examined in this study. A new absorption band with a 1.84 eV energy threshold appeared with Cr-doping. The theoretical band calculation has revealed that the new absorption is ascribed to the electron transition from the valence band to acceptor levels formed by empty Cr 3d orbitals. It was confirmed that photocatalytic water oxidation in the presence of Ag<sup>+</sup> or Fe<sup>3+</sup> of an oxidizing reagent was induced by excitation of the new absorption although activity under band gap excitation decreased with Cr-doping. Characteristics of carrier dynamics were also investigated by transient absorption spectroscopy.

DOI： 10.1039/C8RA07830K

Photoluminescence Properties of Layered Perovskite-type Strontium Scandium Oxyfluoride Activated with Mn⁴⁺ 査読有り Open Access

Hideki Kato*, Yohei Takeda, Makoto Kobayashi, Hisayoshi Kobayashi, Masato Kakihana

Frontiers in Chemistry 6 巻頁： 467 2018年10月

Structural Change in SrSiO₃ Induced by Introduction of Nitrogen 査読有り

Makoto Kobayashi, Jihae Kim, Hironori Sato, Takuya Yasunaga, Hideki Kato*, Kotaro Fujii, Masahiro Shiraiwa, Masatomo Yashima, Masato Kakihana

Chemistry Letters 47 巻 ( 10 ) 頁： 1327-1329 2018年10月

Effects of Crystal Structure on Up-Conversion Luminescence in Er<sup>3+</sup>/Yb<sup>3+</sup> Co-Doped SrTa<sub>4</sub>O<sub>11</sub> 査読有り国際誌 Open Access

Sayaka Tamura, Michio Iwaoka, Yasushi Sato, Makoto Kobayasi, Masato Kakihana, Koji Tomita

Chemistry Letters 47 巻 ( 10 ) 頁： 1282-1284 - 1284 2018年10月

High Temperature Hydrogen Gas Sensing Property of GaN Prepared from α-GaOOH 査読有り

Angga Hermawan, Yusuke Asakura, Makoto Kobayashi, Masato Kakihana, and Shu Yin*

Sensors and Actuators B: Chemical 276 巻頁： 388-396 2018年8月

Water-dispersed silicates and water-soluble phosphates, and their use in sol-gel synthesis of silicate- and phosphate-based materials 査読有り

Kobayashi M., Kato H., Kakihana M.

Handbook of Sol Gel Science and Technology Processing Characterization and Applications 頁： 205 - 231 2018年7月

記述言語：英語掲載種別：論文集(書籍)内論文出版者・発行元：Handbook of Sol Gel Science and Technology Processing Characterization and Applications

Silicon and phosphorous are important elements in materials science. There are less proper raw materials for synthesis of their compounds by aqueous solution- based sol-gel methods, because the conventional raw materials have low stability in aqueous conditions and/or high reactivity with other elements such as metal ions. In this chapter, preparation, chemistry, property, and stability of glycol-modified silanes (GMSs) and glycol-conjugated phosphate esters are summarized. The former is dispersed in an aqueous solution as silicon clusters, and the latter is dissolved in water. In addition, their applications for synthesis of silicates and phosphates by aqueous solution-based sol-gel methods are also documented using examples. The materials obtained showed high performance and phase purity caused by homogeneity of constituents at the atomic level. It is also clearly showed that introduction of such unconventional raw materials enables us to develop new compounds and new synthetic routes for synthesizing high-performance materials.

DOI： 10.1007/978-3-319-32101-1_135

複合アニオン化合物を母体とする新規蛍光体の探索招待有り査読有り

小林亮, 加藤英樹, 垣花眞人

セラミックス 52 巻 ( 12 ) 頁： 816-819 2017年12月

Synthesis of rare earth niobate and tantalate powders via a peroxo complex route 査読有り国際誌 Open Access

Kato H., Shimizu K., Nakajima K., Kobayashi M., Kakihana M.

Chemistry Letters 46 巻 ( 10 ) 頁： 1515 - 1517 2017年10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：Chemistry Letters

Powders of REMO<inf>4</inf> (RE: rare earth, M: Nb and Ta) were synthesized by a coprecipitation method employing watersoluble peroxo Nb/Ta complexes. This peroxo-based method is an aqueous solution route free from organics and halides. REMO<inf>4</inf> was directly crystallized by annealing the precursor under moderate conditions. It has been revealed that the precursors are also useful for synthesis of oxynitrides under mild nitriding conditions.

DOI： 10.1246/cl.170652

Effect of hydroxy and carboxy groups on anisotropic growth of rutile-type titania under hydrothermal conditions 査読有り国際誌 Open Access

Kobayashi M., Lee S., Kato H., Kakihana M.

Journal of Asian Ceramic Societies 5 巻 ( 3 ) 頁： 320 - 325 2017年9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 Asian Ceramic Societies

Control of crystal growth leads to highly functional materials with desired morphologies. In this study, the relationship between select additives and the crystal growth of rutile-type titania under hydrothermal conditions using α-hydroxy acids, carboxylic acids, or alcohols as additives was systematically investigated. Without additives, rod-like rutile crystals with average dimensions of 295 nm × 67 nm were formed. Acceleration of the crystal growth was observed and the aspect ratios of the resulting rod-like crystals were found to increase in the presence of the additives. Alcohols promoted crystal growth along the c-axis, but not in the direction to perpendicular to [001]. Carboxylic acids accelerated the overall crystal growth and this increase was more enhanced along the c-axis than that along others. Both effects were observed using α-hydroxy acids. In addition, the present results implied that the size of the hydrocarbon groups in alcohols and α-hydroxy acids appeared to be related to the acceleration of crystal growth along the c-axis. Hydroxy groups may reduce the surface energy of the crystal facets perpendicular to the c-axis by their adsorption on those facets, resulting in the formation of rod-like crystals with high aspect ratio.

DOI： 10.1016/j.jascer.2017.06.006

Growth of TiO2 microspheres with a radially oriented configuration 査読有り国際誌

Truong Q., Kato H., Kobayashi M., Kakihana M.

Crystengcomm 19 巻 ( 32 ) 頁： 4832 - 4837 2017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：Crystengcomm

Crystalline mesoporous materials with oriented configurations are promising for high-performance energy storage and conversion devices. In this work, hierarchical microspheres constructed from radially oriented single-crystalline TiO<inf>2</inf> nanorods have been fabricated by a facile hydrothermal approach using oxalic acid as a chelating and structure-directing agent. The obtained mesoporous TiO<inf>2</inf> microspheres have been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller specific surface area measurement to reveal their unique properties. The growth and assembly process of the nanorod-based microspheres were elucidated in view of chelation-assisted assembly. It was found that oxalic acid played a crucial role in the oriented assembly of nanorods into well-defined microspheres.

DOI： 10.1039/c7ce01158j

Photoluminescence Properties of Double Perovskite Tantalates Activated with Mn4+, AE2LaTaO6:Mn4+ (AE = Ca, Sr, and Ba) 査読有り国際誌

Takeda Y., Kato H., Kobayashi M., Nozawa S., Kobayashi H., Kakihana M.

Journal of Physical Chemistry C 121 巻 ( 34 ) 頁： 18837 - 18844 2017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：Journal of Physical Chemistry C

Tetravalent manganese is known as one of the candidate luminous centers to obtain red emission. There are still unclear factors in Mn<sup>4+</sup>-activated oxide phosphors to achieve intense emission. In this paper, we studied the photoluminescence properties of double perovskite-type tantalates AE<inf>2</inf>LaTaO<inf>6</inf> (AE = Ca, Sr, and Ba) activated with Mn<sup>4+</sup>. All AE<inf>2</inf>LaTaO<inf>6</inf>:Mn exhibited Mn<sup>4+</sup>-emission in the deep red region under excitation by near-ultraviolet-green light (300-570 nm) at room temperature. Co-substitution of Mg<sup>2+</sup>, Al<sup>3+</sup>, and Ti<sup>4+</sup> compensates unbalanced charge caused by oxygen defects, resulting in the enhancement of Mn<sup>4+</sup>-emission. The present cosubstitution effect is different from the usual cosubstitution, such as the replacement of two Al<sup>3+</sup> by Mn<sup>4+</sup> and Mg<sup>2+</sup>, taking into consideration the charge balance between cations. Theoretical calculation of band structures based on density functional theory suggests the presence of two kinds of quenching schemes in AE<inf>2</inf>LaTaO<inf>6</inf>:Mn, photoionization and electron transfer from valence band to t<inf>2g</inf> orbitals of Mn.

DOI： 10.1021/acs.jpcc.7b06280

水溶媒を用いた結晶成長の展開招待有り査読有り

小林亮

セラミックス 52 巻 ( 7 ) 頁： 502-503 2017年7月

Synthesis and photocatalytic properties of tetragonal tungsten bronze type oxynitrides 査読有り国際誌

Shimizu K., Kato H., Kobayashi M., Kakihana M.

Applied Catalysis B Environmental 206 巻頁： 444 - 448 2017年6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：Applied Catalysis B Environmental

Synthesis of a series of oxynitride Ba<inf>3-x</inf>La<inf>x</inf>Ta<inf>5</inf>O<inf>14−x</inf>N<inf>1+x</inf>(x = 0–1.5) with a tetragonal tungsten bronze (TTB) structure was examined using moist-NH<inf>3</inf>and 5% NH<inf>3</inf>-N<inf>2</inf>as nitriding atmosphere. The samples with x = 0–1 were successfully obtained as phase pure TTB oxynitride whereas the x = 1.5 samples gave a mixture of TTB oxynitride, Ta<inf>3</inf>N<inf>5</inf>, and LaTaO<inf>4</inf>. Absorption of TTB oxynitrides in visible region was enhanced as increasing the content of nitrogen. TTB oxynitrides exhibited both of H<inf>2</inf>and O<inf>2</inf>evolution under visible light in the presence of methanol and silver ions, respectively, as sacrificial reagents. Nitrogen poor surface in the samples synthesized under moist-NH<inf>3</inf>atmosphere was modified by annealing treatment using 5% NH<inf>3</inf>, resulting in improvement of photocatalytic activity for H<inf>2</inf>evolution. Evaluation using monochromatic light revealed that the apparent quantum efficiency of Ba<inf>2</inf>LaTa<inf>5</inf>O<inf>13</inf>N<inf>2</inf>was higher than that of Ba<inf>3</inf>Ta<inf>5</inf>O<inf>14</inf>N.

DOI： 10.1016/j.apcatb.2017.01.057

Synthesis, structure, and photoluminescence of a novel oxynitride baysi2o5n activated by Eu2+ and Ce3+ 査読有り国際誌 Open Access

Kobayashi M., Yasunaga T., Sato H., Kato H., Fujii K., Yashima M., Kakihana M.

Chemistry Letters 46 巻 ( 6 ) 頁： 795 - 797 2017年6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：Chemistry Letters

A novel oxynitride, BaYSi<inf>2</inf>O<inf>5</inf>N, has been synthesized by a solid-state reaction method. Its crystal structure was determined by single-crystal X-ray analysis. Eu<sup>2+</sup>- and Ce<sup>3+</sup>-doped BaYSi<inf>2</inf>O<inf>5</inf>N exhibit broad blue emission with peaks around 459 and 412 nm under excitation at 250-450 and 250-370 nm, respectively. This is the first report on the synthesis of oxynitrides in the BaO-Y<inf>2</inf>O<inf>3</inf>-SiO<inf>2</inf>-Si<inf>3</inf>N<inf>4</inf> system.

DOI： 10.1246/cl.170144

Site occupancy and luminescence properties of Ca3Ln(AlO)3(BO3)4:Ce3+,Tb3+,Mn2+ (Ln = Y, Gd) 査読有り国際誌

Wen D., Kato H., Kobayashi M., Yamamoto S., Mitsuishi M., Kakihana M.

Journal of Materials Chemistry C 5 巻 ( 18 ) 頁： 4578 - 4583 2017年5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 Materials Chemistry C

In this work, novel single-phase white emitting Ca<inf>3</inf>Ln(AlO)<inf>3</inf>(BO<inf>3</inf>)<inf>4</inf>:Ce<sup>3+</sup>,Tb<sup>3+</sup>,Mn<sup>2+</sup> (Ln = Y and Gd) phosphors were synthesized by a conventional solid-state reaction method. The crystal structure and photoluminescence properties were investigated for the first time. The structure of Ca<inf>3</inf>Ln(AlO)<inf>3</inf>(BO<inf>3</inf>)<inf>4</inf> was formed by AlO<inf>6</inf> octahedral chains interconnected by BO<inf>3</inf> triangles. Along the [001] direction, the Ca/Ln cations fill in the trigonal and hexagonal tunnels. For Ca<inf>3</inf>Ln(AlO)<inf>3</inf>(BO<inf>3</inf>)<inf>4</inf>:Ce<sup>3+</sup> and Ca<inf>3</inf>Ln(AlO)<inf>3</inf>(BO<inf>3</inf>)<inf>4</inf>:Mn<sup>2+</sup>, large Ce<sup>3+</sup> preferred to occupy the smaller coordination site, while small Mn<sup>2+</sup> occupied the larger coordination site, which was explained by the space hindrance. Due to the cation disorder, the local environment of Ce<sup>3+</sup> was complicated and the emission band was extremely broad. In Ca<inf>3</inf>Ln(AlO)<inf>3</inf>(BO<inf>3</inf>)<inf>4</inf>, the emission color can be tuned from blue to green or red by tuning the Ce<sup>3+</sup>-Tb<sup>3+</sup> or Ce<sup>3+</sup>-Mn<sup>2+</sup> concentration based on energy transfer. Thus, the combination of blue, green and red emitting Ce<sup>3+</sup>, Tb<sup>3+</sup> and Mn<sup>2+</sup> generated white emission.

DOI： 10.1039/c7tc00941k

Hydrothermal synthesis of brookite-type titania crystals using water-soluble titanium complexes 査読有り

Kobayashi M., Kato H., Kakihana M.

Titanium Dioxide Nanoparticles Characterizations Properties and Syntheses 頁： 71 - 92 2017年1月

記述言語：英語掲載種別：論文集(書籍)内論文出版者・発行元：Titanium Dioxide Nanoparticles Characterizations Properties and Syntheses

Brookite is a polymorph of titania found in nature. Synthesis of single-phase brookite is difficult in comparison to anatase and rutile. It is well known that brookite has various potential applications. Therefore, methods for the synthesis of brookite with high purity are highly desirable. This chapter summarizes simple hydrothermal methods for the synthesis of brookite crystals with various morphologies using water-soluble titaniumcomplexes. Physical properties of the brookite powders obtained are also described. In addition, the formation mechanisms are discussed. A series of studies have indicated that the structures and nature of the complexes have a strong influence on the formation of brookite nuclei. Therefore, the titanium source is quite important for the selective synthesis of titania polymorphs. Application of the present approach allows the synthesis of rod-like brookite crystals with aspect ratios of 1 - 10, as well as snowflake-like crystal agglomerations. The mechanism of morphological control is also discussed.

Investigation of the up-conversion properties of Er–Yb-doped calcium tantalates with various Ca/Ta ratios 査読有り国際誌 Open Access

Tamura S., Iwaoka M., Sato Y., Kobayashi M., Kakihana M., Tomita K.

Journal of Photopolymer Science and Technology 30 巻 ( 4 ) 頁： 507 - 512 2017年

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 Photopolymer Science and Technology

Er<sup>3+</sup>/Yb<sup>3+</sup> co-doped calcium tantalate up-conversion (UC) phosphors were synthesized via a parallel synthesis scheme using the gelable citrate complex method. Samples with various Ca/Ta atomic ratios were prepared, and their UC emission properties were compared. Under 980-nm near-infrared laser excitation, α-Ca<inf>2</inf>Ta<inf>2</inf>O<inf>7</inf>: Er<sup>3+</sup>, Yb<sup>3+</sup> showed an extremely weak UC emission intensity and CaTa<inf>4</inf>O<inf>11</inf>: Er<sup>3+</sup>, Yb<sup>3+</sup> demonstrated an excellent UC emission intensity. In addition, the local symmetry around the rare-earth dopant ions affected the UC luminescence properties.

DOI： 10.2494/photopolymer.30.507

真空加圧焼成炉を利用した新規酸窒化物蛍光体の探索招待有り

加藤英樹, 佐藤大典, 安永拓矢, 小林亮, 垣花眞人, 磯部史佳

島津評論 73 巻 ( 3・4 ) 頁： 129-135 2016年12月

Synthesis and Development of Titania with Controlled Structures 招待有り査読有り Open Access

Makoto Kobayashi

Journal of the Ceramic Society of Japan 124 巻 ( 9 ) 頁： 863-869 2016年9月

Screening of Er3+/Yb3+ codoped RE-Ta-O and RE-Nb-O (RE = Y, La, or Gd) upconversion phosphors 査読有り国際誌 Open Access

Tamura S., Iwaoka M., Sato Y., Kobayashi M., Kakihana M., Tomita K.

Chemistry Letters 45 巻 ( 8 ) 頁： 890 - 891 2016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：Chemistry Letters

Upconversion (UC) phosphors comprising Er<sup>3+</sup>/Yb<sup>3+</sup> codoped rare-earth complex oxides, RE<inf>x</inf>Ta<inf>y</inf>O<inf>z</inf> and RE<inf>x</inf>Nb<inf>y</inf>O<inf>z</inf> (RE = Y, La, or Gd), were synthesized via the gelable citrate complex method, and their UC emission properties were compared. This led to the discovery of an intense green-emitting UC phosphor, YTa<inf>7</inf>O<inf>19</inf>:Er<sup>3+</sup>/Yb<sup>3+</sup>, which is the first example of a YTa<inf>7</inf>O<inf>19</inf> UC phosphor host material. Green UC emission obtained using optimum Er<sup>3+</sup> and Yb<sup>3+</sup> content was 20 times stronger than that obtained using a Y<inf>2</inf>O<inf>3</inf> host.

DOI： 10.1246/cl.160413

Anomalous Orange Light-Emitting (Sr,Ba)2SiO4:Eu2+ Phosphors for Warm White LEDs 査読有り国際誌

Wen D., Kuwahara H., Kato H., Kobayashi M., Sato Y., Masaki T., Kakihana M.

ACS Applied Materials and Interfaces 8 巻 ( 18 ) 頁： 11615 - 20 2016年5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：ACS Applied Materials and Interfaces

Phosphors with sufficient red emission component are necessary for warm white light-emitting diodes. In this work on (Sr,Ba)<inf>2(1-x)</inf>Eu<inf>2x</inf>SiO<inf>4</inf> phosphors, (Sr,Ba)<inf>1.5</inf>Eu<inf>0.5</inf>SiO<inf>4</inf> achieved 75% of an internal quantum efficiency under excitation by blue light. Surprisingly, the (Sr,Ba)<inf>1.5</inf>Eu<inf>0.5</inf>SiO<inf>4</inf> exhibited orange emission, against the well-known traditional green-yellow emission of (Sr,Ba)<inf>2</inf>SiO<inf>4</inf>:Eu<sup>2+</sup>. Moreover, the concentration quenching of Eu<sup>2+</sup> in (Sr,Ba)<inf>2</inf>SiO<inf>4</inf> was abnormally unobvious. With the help of calculations based on the density functional theory, it was discovered that the distinct local environment of luminescence centers rather than usual explanation such as self-absorption or intensified crystal field splitting, is responsible to the interesting red shifts in excitation and emission spectra. The refinement analysis based on X-ray diffraction revealed that the unequal distribution of Eu<sup>2+</sup> to two crystallographic sites caused low concentration of Eu<sup>2+</sup> at the 9-coordination site, inhibiting the concentration quenching. The (Sr,Ba)<inf>1.5</inf>Eu<inf>0.5</inf>SiO<inf>4</inf> phosphor has warmer emission than the commercial Y<inf>3</inf>Al<inf>5</inf>O<inf>12</inf>:Ce<sup>3+</sup>. This study also promotes research on the effect of site occupancy and the local environment of luminescence centers.

DOI： 10.1021/acsami.6b02237

Anisotropy in Conformation and Dynamics of a Glycolate Ion Near the Surface of a TiO2 Rutile Crystal between Its {001} and {110} Planes: A Molecular Dynamics Study 査読有り国際誌

Nada H., Kobayashi M., Kakihana M.

Journal of Physical Chemistry C 120 巻 ( 12 ) 頁： 6502 - 6514 2016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：Journal of Physical Chemistry C

A molecular dynamics simulation was conducted to elucidate the conformation and dynamics of a glycolate ion (CH<inf>2</inf>(OH)COO<sup>-</sup>) at the surface of a TiO<inf>2</inf> rutile crystal. The simulation was performed for the {001} and {110} planes of the crystal. The results indicate that, for both planes, the conformation and dynamics of the ion are strongly dominated by a layered structure of water on the surface. The simulation suggests that the ion binds to the surface more stably on the {110} plane than on the {001} plane, and that the stable conformation of the ion at the surface differs between the planes: on the {110} plane the carboxyl group of the ion is preferentially oriented toward the surface, whereas on the {001} plane it is oriented toward liquid water. These simulation results are compared with the growth shapes of rutile crystals synthesized in the presence of glycolic acid, and the role of glycolate ions in controlling the morphology of rutile crystals is discussed. (Figure Presented).

DOI： 10.1021/acs.jpcc.5b11087

Effect of site occupancies on deep-red emission from Eu2+-activated Ca22-SiO4 phosphor 査読有り国際誌

Kuwahara H., Sato Y., Kato H., Kobayashi M., Masaki T., Kakihana M.

Chemistry Letters 45 巻 ( 3 ) 頁： 321 - 323 2016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：Chemistry Letters

Calcium silicate cosubstituted with Sr<sup>2+</sup> and Eu<sup>2+</sup> was studied in order to examine the relationship between emission characteristics and Eu<sup>2+</sup> occupancy at two types of Ca sites (Ca(1n) and Ca(2n)). The results clearly indicate that red emission of the Ca2<inf>2</inf>-SiO<inf>4</inf>:Eu<sup>2+</sup> phosphor is caused by Eu<sup>2+</sup> substitution at the Ca(2n) site. In addition, red shift in emission of Eu(2n) occurs when large amounts of Eu were substituted.

DOI： 10.1246/cl.151145

Self-assembly of polyethyleneamine-intercalated H2Ti2O5 nanoparticles into spherical agglomerates 査読有り国際誌

Kobayashi M., Kato H., Kakihana M.

Journal of Materials Research 31 巻 ( 5 ) 頁： 564 - 572 2016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：Journal of Materials Research

Although there are numerous reports on the synthesis of spherical materials, the development of new approaches remains important for theory construction to realize tailor-made synthesis of spherical materials. Herein, we report the synthesis of polydispersed spherical particles of H2Ti2O5 intercalated with a polyethyleneamine, such as an ethylenediamine, on the basis of a solvothermal treatment using concentrated polyethyleneamine aqueous solutions. The diameter of the micrometer-sized spheres enlarged with increasing amine concentration in the reaction solution. It was speculated that high ionic strength caused the self-assembly of polyethyleneamine-intercalated H2Ti2O5, resulting in the formation of spherical agglomerates. The spheres had a specific a surface area of 200 m<sup>2</sup> g<sup>-1</sup> and approximately 5 nm pores, and these values were controlled by amine concentration and treatment time. Conversion to single phase anatase and rutile without changes in spherical morphology was achieved by heat treatment. The present approach may assist with the design morphology of agglomerates.

DOI： 10.1557/jmr.2016.67

水熱法によるバリウムタンタレートナノシート光触媒の合成とその水分解活性査読有り

高杉壮一, 冨田恒之, 岩岡道夫, 小林亮, 加藤英樹, 垣花眞人

Journal of the Society of Inorganic Materials, Japan 23 巻 ( 380 ) 頁： 25-29 2016年

酸化チタン多形の水熱結晶成長(<特集>水が関係する結晶成長のトピックス) 査読有り国際誌 Open Access

小林亮, 加藤英樹, 垣花眞人

日本結晶成長学会誌 42 巻 ( 4 ) 頁： 283 - 289 2016年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：日本結晶成長学会

Control of crystal growth is rather important in the field of materials, because the shape directly affects their functional abilities. Our research group engages in hydrothermal synthesis of titanium dioxide, which is regarded as one of the representative ceramics, using water-soluble titanium complexes. The high chemical stability and peculiar molecule structures of these titanium complexes allowed us to use various compounds which play a role in control of crystal growth, resulting in the selective synthesis of four titanium dioxide polymorphs, that is, rutile, anatase, brookite and TiO_2(B), with a controlled shape. This paper summarizes our past study and reported researches on synthesis of titania polymorph crystals by classification of zero-, one-, two-, and three-dimensional structures.

DOI： 10.19009/jjacg.42.4_283

水熱法によるバリウムタンタレートナノシート光触媒の合成とその水分解活性査読有り国際誌

高杉壮一, 冨田恒之, 岩岡道夫, 小林亮, 加藤英樹, 垣花眞人

Journal of the Society of Inorganic Materials, Japan 23 巻 ( 380 ) 頁： 25-29 2016年

Synthesis of titania with controlled structures and its development 査読有り Open Access

小林亮

Journal of the Ceramic Society of Japan 掲載確定巻 2016年

Graphene/MxWO3 (M = Na, K) nanohybrids with excellent electrical properties 査読有り国際誌

Liu B., Yin S., Wu X., Wang Y., Huang Y., Wu J., Sekino T., Matsushita J., Lee S.W., Kobayashi M., Kakihana M., Sato T.

Carbon 94 巻頁： 309 - 316 2015年11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：Carbon

Graphene/M<inf>x</inf>WO<inf>3</inf> (M = Na, K) nanocomposites with different weight ratios were successfully synthesized using MBH<inf>4</inf> as a reducing agent in aqueous solution, followed by crystallization of amorphous precursors under calcination in H<inf>2</inf> (5 vol.%)/N<inf>2</inf> atmosphere at 600 °C. The coupled samples showed good shielding properties in NIR wavelength range together with certain visible lights transparency. The as-prepared tungsten bronze nanoparticles are homogeneously anchored on graphene sheets, and the graphene/tungsten bronze nanocomposite showed an enhanced electrical conductivity with good shielding properties in the NIR range together with certain visible lights transparency. With the increment of graphene amount in the composites, the contact between the graphene sheets was enhanced, and the M<inf>x</inf>WO<inf>3</inf> might enhance the charge transport properties of graphene by generating the short conductive path for electrons over the remained oxygenated functional groups. The synergistic effects could be observed in the composites. When 5 wt.% or more graphene were composed into M<inf>x</inf>WO<inf>3</inf>, the hybrid composite showed the higher electrical conductivity than those of uncoupled graphene and tungsten bronze alone.

DOI： 10.1016/j.carbon.2015.06.072

Large Redshifts in Emission and Excitation from Eu<sup>2+</sup>-Activated Sr<sub>2</sub>SiO<sub>4</sub> and Ba<sub>2</sub>SiO<sub>4</sub> Phosphors Induced by Controlling Eu<sup>2+</sup> Occupancy on the Basis on Crystal-Site-Engineering 査読有り国際誌 Open Access

Yasushi Sato, Hiroki Kuwahara, Hideki Kato, Makoto Kobayashi, Takaki Masaki, Masato Kakihana

Optics and Photonics Journal 5 巻 ( 11 ) 頁： 326-333 - 333 2015年11月

Photoluminescence properties of Mn4+-activated perovskite-type titanates, La2MTiO6:Mn4+ (M = Mg and Zn) 査読有り国際誌 Open Access

Takeda Y., Kato H., Kobayashi M., Kobayashi H., Kakihana M.

Chemistry Letters 44 巻 ( 11 ) 頁： 1541 - 1543 2015年11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：Chemistry Letters

It has been found that Mn<sup>4+</sup>-activated La<inf>2</inf>MTiO<inf>6</inf> (M = Mg and Zn) functions as novel Eu-free phosphors for red emission in this work. La<inf>2</inf>MTiO<inf>6</inf>:Mn<sup>4+</sup> exhibited emission with a peak at 710 nm under excitation by ultraviolet to blue light (300-550 nm). La<inf>2</inf>MgTiO<inf>6</inf>:Mn<sup>4+</sup> exhibited stronger emission than La<inf>2</inf>ZnTiO<inf>6</inf>:Mn<sup>4+</sup>. The internal quantum yield of La<inf>2</inf>MgTiO<inf>6</inf>:Mn<sup>4+</sup> was 58.7% under the excitation at 330 nm.

DOI： 10.1246/cl.150748

A facile one-step solvothermal synthesis and electrical properties of reduced graphene oxide/rod-shaped Potassium Tungsten Bronze Nanocomposite 査読有り国際誌

Liu B., Yin S., Wang Y., Guo C., Wu X., Dong Q., Kobayashi M., Kakihana M., Sato T.

Journal of Nanoscience and Nanotechnology 15 巻 ( 9 ) 頁： 7305 - 10 2015年9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 Nanoscience and Nanotechnology

Reduced graphene oxide (rGO)/rod-shaped potassium tungsten bronze nanocomposites with the different ratio were successfully synthesized by solvothermal reaction and followed by the reduction in H<inf>2</inf>(5 vol.%)/N<inf>2</inf> atmosphere at 550 °C. The coupled samples showed excellent shielding ability of NIR light as well as certain visible lights transparency. The synergistic effects could be observed in the composites, i.e., when 15 wt% and 20 wt% of rGO which was fabricated by chemical reduction of graphene oxide, were composed into K<inf>x</inf>WO<inf>3</inf>, the composite showed the higher electrical conductivity than those of rGO and potassium tungsten bronze.

DOI： 10.1166/jnn.2015.10579

Synthesis of picolinate-iron(III) compounds through an aqueous solution process 査読有り国際誌 Open Access

Sato J., Kobayashi M., Kato H., Kwon E., Kakihana M.

Journal of the Ceramic Society of Japan 123 巻 ( 1441 ) 頁： 751 - 755 2015年9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 Ceramic Society of Japan

A novel picolinate-iron(III) compound, Fe(C<inf>6</inf>H<inf>4</inf>NO<inf>2</inf>)<inf>2</inf>(OH) (1), was synthesized from an aqueous solution of a picolinate-iron(II) complex. Compound 1 was obtained by a thermal treatment of the picolinate-iron complex aqueous solution, whose pH was adjusted to 37, containing more than twice molar picolinic acid (Hpa) to Fe at 353K for 72 h. When the iron aqueous solution in the presence of more than six times molar Hpa to Fe at pH 25 was heated, Fe(C<inf>6</inf>H<inf>4</inf>NO<inf>2</inf>)<inf>3</inf>-H<inf>2</inf>O (2) appeared. Millimeter-sized yellow-green single crystals of 2 could be obtained by the heat treatment of the picolinate-iron aqueous solution, whose pH was adjusted to 3, with Fe<sup>2+</sup>:Hpa = 1:10 at 373K for 72 h. Formation mechanism of 1 and 2 was also discussed through investigations of relationship between synthesis conditions and products. Our approach opens a promising new route for preparation of precursors for synthesis of high functional ceramics and development of new organicinorganic hybrids.

DOI： 10.2109/jcersj2.123.751

Novel titanium complexes with a reversible structural change on solvent adsorption and desorption 査読有り国際誌

Kobayashi M., Okuhara T., Kato H., Sato S., Kakihana M.

Chemistry Letters 44 巻 ( 8 ) 頁： 1050 - 1052 2015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：Chemistry Letters

Two novel pyrazine-2-carboxylate titanium complexes were synthesized from an aqueous solution (1) and 1 in N,Ndimethylformamide (DMF) (2). The structure of 2 was determined to be [Ti<inf>6</inf>O<inf>8</inf>(C<inf>4</inf>H<inf>3</inf>N<inf>2</inf> COO)<inf>8</inf>(C<inf>3</inf>H<inf>7</inf>NO)<inf>4</inf>]• 4C<inf>3</inf>H<inf>7</inf>NO• H<inf>2</inf>O by single-crystal X-ray analysis. Both complexes exhibited solvent adsorptiondesorption accompanying reversible structural change. 1 and 2 were compatible, and 1 was vital for the synthesis of 2. The degassed 1 showed gate adsorption property for water vapor.

DOI： 10.1246/cl.150393

Discovery of Novel Delafossite-type Compounds Composed of Copper(I) Lithium Titanium with Photocatalytic Activity for H<sub>2</sub> Evolution under Visible Light 査読有り国際誌

Kato, H; Fujisawa, T; Kobayashi, M; Kakihana, M

CHEMISTRY LETTERS 44 巻 ( 7 ) 頁： 973 - 975 2015年7月

Hierarchical structures of rutile exposing high-index facets 査読有り国際誌

Truong Q., Kato H., Kobayashi M., Kakihana M.

Journal of Crystal Growth 418 巻頁： 86 - 91 2015年5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 Crystal Growth

Recently, shape-controlled synthesis of crystals exposing high-index facets has attracted much research interest due to their importance for both fundamental studies and technological applications. Herein, crystals of rutile-type TiO<inf>2</inf> with hierarchical structures exposing high-index facets have been synthesized by a facile hydrothermal method using water-soluble titanium complex as a precursor and picolinic acid as structure-directing and shape-controlling agents. The synthesized particles were composed of several branches of pyramidal crystals with relatively smooth surface. On the basis of investigation results, it was speculated that the mutual π-stacking and selective adsorption of picolinic acid on specific {111} facets resulted in the formation of rutile crystals bound by high-index surfaces such as {331}.

DOI： 10.1016/j.jcrysgro.2015.02.056

水に分散可能な無機Siクラスターを活用した水溶液プロセスによるケイ酸塩蛍光体の合成査読有り国際誌 Open Access

佐藤泰史, 加藤英樹, 小林亮, 金知慧, 垣花眞人

粉体および粉末冶金 62 巻 ( 4 ) 頁： 127 - 133 2015年4月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Funtai Oyobi Fummatsu Yakin Journal of the Japan Society of Powder and Powder Metallurgy

In this paper, we demonstrated the synthesis of silicate-based phosphors by solution techniques using glycolmodified silane (GMS) as a Si source. GMS is a water-dispersible inorganic Si cluster, which is vitally involatile and nonflammable compounds, compared to volatile and flammable Si-alkoxides such as tetraethoxysilane (TEOS). Therefore, GMS has allowed the silicon containing compounds to be synthesized through various solution processes for ceramic compounds such as polymerizable complex (PC) and amorphous metal complex (AMC) methods. This paper provides examples of synthesis of new silicate-based phosphors such as NaAlSiO<inf>4</inf>:Eu<sup>2+</sup>, BaZrSi<inf>3</inf>O<inf>9</inf>:Eu<sup>2+</sup>, and CaSrSiO<inf>4</inf>:Eu<sup>2+</sup>. In addition, other examples of improvement of emission for conventional silicate-based phosphors, Y<inf>2</inf>SiO<inf>5</inf>:Ce<sup>3+</sup>-Tb<sup>3+</sup> and Zn2SiO<inf>4</inf>:Mn<sup>2+</sup>, prepared by the above solution techniques including homogeneous precipitation using GMS are also given in this paper.

DOI： 10.2497/jjspm.62.127

Design of crystal structures, morphologies and functionalities of titanium oxide using water-soluble complexes and molecular control agents 招待有り査読有り国際誌 Open Access

Kobayashi M., Osada M., Kato H., Kakihana M.

Polymer Journal 47 巻 ( 2 ) 頁： 78 - 83 2015年2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：Polymer Journal

Nature produces materials with excellent physical and chemical properties using water as a medium under ambient temperature and pressure. The current need for more highly functional and compact materials makes the mimicking of natural processes to produce these materials a very interesting approach, not only to obtain highly functionalized materials but also to reduce the environmental impact. Our research group is engaged in the development of new stable water-soluble compounds that follow natural processes for the synthesis of materials using water as a medium. This paper summarizes a hydrothermal synthesis of rutile-type titanium oxide using water-soluble titanium complexes, controlling the crystal morphology by utilizing organic molecules as shape-control agents as well as their speculative formation mechanism and superior dielectric properties of unusually shaped titanium oxide crystals. By recapitulating our results, we indicate that control of the nano- and macro-structures and functional improvement are accomplished through the development of new precursor compounds.

DOI： 10.1038/pj.2014.89

Crystal structures and luminescence properties of Eu2+-activated new NaBa0.5Ca0.5PO4 and Na3Ba2Ca(PO4)3 査読有り国際誌

Kim M., Kobayashi M., Kato H., Yamane H., Sato Y., Kakihana M.

Dalton Transactions 44 巻 ( 4 ) 頁： 1900 - 4 2015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：Dalton Transactions

NaBa<inf>1-x</inf>Ca<inf>x</inf>PO<inf>4</inf>:Eu<sup>2+</sup> were synthesized using polymerizable complex method. New phases were observed at x = 1/3 and 0.5, which were identified by single-crystal XRD analysis as Na<inf>3</inf>Ba<inf>2</inf>Ca(PO<inf>4</inf>)<inf>3</inf> and NaBa<inf>0.5</inf>Ca<inf>0.5</inf>PO<inf>4</inf> with a trigonal system. Though both phases pretend to be solid solutions between NaBaPO<inf>4</inf> and NaCaPO<inf>4</inf>, they have different coordination environments and PO<inf>4</inf> orderings. 1 mol% Eu<sup>2+</sup>-activated NaBaPO<inf>4</inf>, Na<inf>3</inf>Ba<inf>2</inf>Ca(PO<inf>4</inf>)<inf>3</inf>, and NaBa<inf>0.5</inf>Ca<inf>0.5</inf>PO<inf>4</inf> exhibited an emission maximum at 435 nm, 458 nm, and 460 nm, respectively. The shift of the emission maximum might be due to a change in the Eu-O bond length. This journal is

DOI： 10.1039/c4dt03024a

Controlled radical polymerization of styrene with magnetic iron oxides prepared through hydrothermal, bioinspired, and bacterial processes 査読有り国際誌

Kanazawa A., Satoh K., Kanaoka S., Kakihana M., Kobayashi M., Sato J., Imai H., Oaki Y., Arakaki A., Katagiri K., Kamigaito M., Aoshima S.

Rsc Advances 5 巻 ( 63 ) 頁： 51122 - 51129 2015年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Rsc Advances

Controlled/living radical polymerization was examined with the use of magnetic iron oxide (Fe<inf>3</inf>O<inf>4</inf>) prepared through various processes, including hydrothermal synthesis, a bioinspired process, and magnetotactic bacteria. Prior to the use of various types of Fe<inf>3</inf>O<inf>4</inf>, commercially available Fe<inf>3</inf>O<inf>4</inf> was employed as a heterogeneous catalyst for styrene polymerization in conjunction with an alkyl halide as an initiator. Under appropriately optimized conditions, with the addition of Ph<inf>3</inf>P in a solvent mixture of toluene and DMF, the polymerization proceeded in a well-controlled manner. In addition, solid Fe<inf>3</inf>O<inf>4</inf> was recovered using a magnetic approach and was reused for a polymerization reaction. The effects of stirring on the polymerization rate suggest that the surface of Fe<inf>3</inf>O<inf>4</inf> is responsible for the catalysis in polymerization. Fe<inf>3</inf>O<inf>4</inf> samples prepared through various processes were then used for styrene polymerization and showed different activities depending on the preparation process. In particular, Fe<inf>3</inf>O<inf>4</inf> prepared through hydrothermal synthesis exhibited a much higher activity compared with commercial Fe<inf>3</inf>O<inf>4</inf>.

DOI： 10.1039/c5ra09149g

Improvement of hydrogen evolution under visible light over Zn1-2x(CuGa)xGa2S4 photocatalysts by synthesis utilizing a polymerizable complex method 査読有り国際誌

Quintans C.S., Kato H., Kobayashi M., Kaga H., Iwase A., Kudo A., Kakihana M.

Journal of Materials Chemistry A 3 巻 ( 27 ) 頁： 14239 - 14244 2015年

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 Materials Chemistry A

Single phase Zn<inf>1-2x</inf>(CuGa)<inf>x</inf>Ga<inf>2</inf>S<inf>4</inf> was successfully synthesized by a two-step route: synthesis of an oxide precursor by a polymerizable complex (PC) method followed by sulfurization under a H<inf>2</inf>S-Ar flow. The samples thus obtained were porous aggregates consisting of fine crystals with 50 nm size. Among the examined compositions, Zn<inf>0.4</inf>(CuGa)<inf>0.3</inf>Ga<inf>2</inf>S<inf>4</inf> (x = 0.3) showed the highest activity for H<inf>2</inf> evolution from an aqueous solution containing S<sup>2-</sup> and SO<inf>3</inf><sup>2-</sup> as electron donors under visible light irradiation. The apparent quantum yield of the optimized sample with deposition of 2 wt% of Rh was 19% at 420 nm. This value is higher than that of the sample synthesized by a solid state reaction (15%). Therefore, improvement of the photocatalytic performance of Zn<inf>0.4</inf>(CuGa)<inf>0.3</inf>Ga<inf>2</inf>S<inf>4</inf> for H<inf>2</inf> evolution has been achieved by using the two-step synthesis method including the preparation of an oxide precursor by the PC method.

DOI： 10.1039/c5ta02114f

Photocatalytic water oxidation under visible light by valence band controlled oxynitride solid solutions LaTaON2-SrTiO3 査読有り国際誌

Hideki Kato, Koichiro Ueda, Makoto Kobayashi, Masato Kakihana Masato

Journal of Materials Chemistry A 3 巻 ( 22 ) 頁： 11824-11829 - 11829 2015年

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 Materials Chemistry A

Solid solutions between LaTaON<inf>2</inf> and SrTiO<inf>3</inf> were successfully synthesized. In this solid solution, the valence band maxima (VBM) shifted to positive sides as the fraction of SrTiO<inf>3</inf> increased, resulting in the appearance of activity for O<inf>2</inf> evolution even without any cocatalysts. Despite widening of the band gap (E<inf>g</inf>) by only 0.15 eV, La<inf>0.5</inf>Sr<inf>0.5</inf>Ta<inf>0.5</inf>Ti<inf>0.5</inf>O<inf>2</inf>N gained 0.5 V larger driving force for water oxidation, which corresponds to the potential difference between VBM and potential for water oxidation, than LaTaON<inf>2</inf>. It suggested that the contribution of Ti 3d to the conduction band suppressed the widening of E<inf>g</inf>. This is an interesting feature in the present LaTaON<inf>2</inf>-SrTiO<inf>3</inf> solid solution. The bare La<inf>0.5</inf>Sr<inf>0.5</inf>Ta<inf>0.5</inf>Ti<inf>0.5</inf>O<inf>2</inf>N exhibited the activity for O<inf>2</inf> evolution 9 times higher than LaTaON<inf>2</inf> modified with a CoO<inf>x</inf> cocatalyst. It has been found that the driving force for water oxidation of La<inf>0.5</inf>Sr<inf>0.5</inf>Ta<inf>0.5</inf>Ti<inf>0.5</inf>O<inf>2</inf>N was 0.8 V, and was larger than those in other perovskite-type oxynitrides.

DOI： 10.1039/c5ta02482j

酸化チタン多形の水熱結晶成長（Crystal Growth of Titania Polymorphs by Hydrothermal Method）査読有り Open Access

小林亮

結晶成長学会誌 42 巻頁： 283 - 289 2015年

水に分散可能な無機Siクラスター活用した水溶液プロセスによるケイ酸塩蛍光体の合成査読有り Open Access

小林亮, 垣花眞人

粉体および粉末冶金 62 巻頁： 127 - 133 2015年

A carbon modified NaTaO3 mesocrystal nanoparticle with excellent efficiency of visible light induced photocatalysis 査読有り国際誌

Wu X., Yin S., Liu B., Kobayashi M., Kakihana M., Sato T.

Journal of Materials Chemistry A 2 巻 ( 48 ) 頁： 20832 - 20840 2014年12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 Materials Chemistry A

A carbon modified NaTaO<inf>3</inf> mesocrystal nanoparticle (ca. 20 nm) was successfully synthesized by a one-pot solvothermal method, employing TaCl<inf>5</inf> and NaOH as the starting materials and distilled water/EG mixed solution as a reaction solvent in the presence of appropriate amounts of glucose. The mesocrystal sample presented a high specific surface area 90.8 m<sup>2</sup> g<sup>-1</sup> with large amounts of well-dispersed mesopores in the particle, owing to the co-effect of EG and glucose during the reaction process. A non-classic mechanism of formation was proposed for the growth of the NaTaO<inf>3</inf> mesocrystal. Furthermore, the NaTaO<inf>3</inf> mesocrystal exhibited considerably improved visible light absorption in addition to the intrinsic UV light absorption as a result of carbon modification originated from glucose. On the basis of the large specific surface area, high crystallinity and optical property, the carbon modified NaTaO<inf>3</inf> mesocrystal demonstrated excellent efficiency for continuous NO gas destruction under irradiation of UV, short wavelength visible lights (>400 m) and even long wavelength visible light (>510 nm), considerably superior to those of the unmodified NaTaO<inf>3</inf> specimen and commercial titania, P25. The carbon modified NaTaO<inf>3</inf> mesocrystal nanoparticles prepared in this work would probably have potential utilization in environmental purification and energy conversion.

DOI： 10.1039/c4ta04132a

Development of two novel Eu2+-activated phosphors in the Na-Sc-Si-O system and their photoluminescence properties 査読有り国際誌

Min J., Yamaguchi T., Kato H., Kobayashi M., Yamane H., Kakihana M.

Journal of Luminescence 154 巻頁： 285 - 289 2014年10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 Luminescence

Two novel Eu<sup>2+</sup>-activated phosphors in the Na-Sc-Si-O system were developed in this study, NaScSi<inf>2</inf>O<inf>6</inf>:Eu and Na <inf>3</inf>ScSi<inf>3</inf>O<inf>9</inf>:Eu. NaScSi<inf>2</inf>O <inf>6</inf>:Eu<sup>2+</sup> showed yellow emission with a peak at 555 nm under excitation at 220-430 nm. When flux-treatment was performed for NaScSi <inf>2</inf>O<inf>6</inf>:Eu<sup>2+</sup>, we found the existence of a new phase. We then succeeded in synthesis of a high-purity sample of this new compound by a parallel solution synthesis method. It was revealed that the new phase was Na<inf>3</inf>ScSi<inf>3</inf>O<inf>9</inf> with isostructure to Na<inf>3</inf>YSi<inf>3</inf>O<inf>9</inf>, and Eu<sup>2+</sup>-activated Na<inf>3</inf>ScSi<inf>3</inf>O<inf>9</inf> exhibited photoluminescence. Na <inf>3</inf>ScSi<inf>3</inf>O<inf>9</inf>:Eu showed green emission with a peak at 530 nm and a corresponding broad excitation band up to 500 nm. However, photoluminescence of Eu<sup>2+</sup> was negligible for Na<inf>3</inf>YSi <inf>3</inf>O<inf>9</inf>:Eu because of the stabilization of Eu<sup>3+</sup> at the Y<sup>3+</sup> site. © 2014 Elsevier B.V.

DOI： 10.1016/j.jlumin.2014.05.006

Synthesis of (Ca1-xSrx)4Si2O7F2oxyfluoride solid solutions and their photoluminescence properties activated by Eu2+ions 査読有り国際誌 Open Access

Min J., Kato H., Kobayashi M., Sato Y., Kakihana M.

Journal of the Ceramic Society of Japan 122 巻 ( 1428 ) 頁： 630 - 633 2014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：Journal of the Ceramic Society of Japan

The synthesis of oxyfluoride solid solutions with the composition (Ca<inf>1-x</inf>Sr<inf>x</inf>)<inf>4</inf>Si<inf>2</inf>O<inf>7</inf>F<inf>2</inf>is reported in this study. (Ca<inf>1-x</inf>Sr<inf>x</inf>)<inf>4</inf>Si<inf>2</inf>O<inf>7</inf>F<inf>2</inf>is found to form a solid solution within the entire composition range. Synthesis of Sr<inf>4</inf>Si<inf>2</inf>O<inf>7</inf>F<inf>2</inf>, which is the first compound in the SrSiOF system, can be regarded as one of the interesting results of this study. The Eu<sup>2+</sup>-activated (Ca<inf>1-x</inf>Sr<inf>x</inf>)<inf>4</inf>Si<inf>2</inf>O<inf>7</inf>F<inf>2</inf>solid solutions, except for Sr<inf>4</inf>Si<inf>2</inf>O<inf>7</inf>F<inf>2</inf>exhibited photoluminescence under excitation at 300450nm at room temperature. The samples with x = 0.250.75 showed a broad red emission band with a peak around 630 nm, whereas the Ca<inf>4</inf>Si<inf>2</inf>O<inf>7</inf>F<inf>2</inf>:Eu<sup>2+</sup>(x = 0) showed blue emission with a peak at 470 nm. Thus, the substitution of Sr for Ca in Ca<inf>4</inf>SiO<inf>7</inf>F<inf>2</inf>:Eu<sup>2+</sup>changed the photoluminescence properties remarkably.

DOI： 10.2109/jcersj2.122.630

The significance of phosphate source in the preparation of functional luminescent phosphate materials 査読有り国際誌 Open Access

Kim M., Kobayashi M., Kato H., Kakihana M.

Journal of the Ceramic Society of Japan 122 巻 ( 1428 ) 頁： 626 - 629 2014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：Journal of the Ceramic Society of Japan

The stability and reactivity of phosphate raw materials, including two water-soluble phosphates, ethylene glycol-conjugated phosphate (EG-P), and polyethylene glycol-conjugated phosphate (PEG-P) developed by our group, were examined with the aim of synthesizing phosphates with high functionalities. EG-P was found to gradually hydrolyze in an aqueous solution, resulting in the formation of H<inf>3</inf>PO<inf>4</inf>, while PEG-P was stable for more than two months. EG-P and PEG-P did not form insoluble materials in aqueous solution in the presence of many other cations, while precipitates were often observed using conventional phosphate raw materials. In particular, there were no precipitates in an aqueous solution of PEG-P in the presence of Ca2<sup>+</sup>and Li<sup>+</sup>ions, which easily formed insoluble phosphates in a given aqueous condition. Consequently, single-phase LiCaPO<inf>4</inf>with high luminescence properties could be obtained by a polymerizable complex method employing PEG-P, while impurity phases were formed using other P sources, and KSrPO<inf>4</inf>was formed as a single phase using EG-P and PEG-P.

DOI： 10.2109/jcersj2.122.626

Tailoring of deep-red luminescence in Ca2SiO4:Eu 2+ 査読有り国際誌

Sato Y., Kato H., Kobayashi M., Masaki T., Yoon D., Kakihana M.

Angewandte Chemie International Edition 53 巻 ( 30 ) 頁： 7756 - 9 2014年7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：Angewandte Chemie International Edition

We report a new dicalcium silicate phosphor, Ca<inf>2-x</inf>Eu <inf>x</inf>SiO<inf>4</inf>, which emits red light in response to blue-light excitation. When excited at 450 nm, deep-red emission at 650 nm was clearly observed in Ca<inf>1.2</inf>Eu<inf>0.8</inf>SiO<inf>4</inf>, the external and internal quantum efficiencies of which were 44 % and 50 %, respectively. The red emission from Ca<inf>2-x</inf>Eu<inf>x</inf>SiO<inf>4</inf> was strongly related to the peculiar coordination environments of Eu<sup>2+</sup> in two types of Ca sites. The red-emitting Ca<inf>2</inf>SiO<inf>4</inf>:Eu <sup>2+</sup> phosphors are promising materials for next-generation, white-light-emitting diode applications. A dicalcium silicate phosphor, Ca <inf>2-x</inf>Eu<inf>x</inf>SiO<inf>4</inf>, emits red light in response to blue-light excitation. When excited at 450 nm, deep-red emission at 650 nm was clearly observed in Ca<inf>1.2</inf>Eu<inf>0.8</inf>SiO<inf>4</inf>. The picture shows a photograph of the corresponding Ca<inf>1.20</inf>Eu <inf>0.80</inf>SiO<inf>4</inf> phosphor upon excitation with blue LEDs. The external and internal quantum efficiencies were 44 % and 50 %, respectively. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI： 10.1002/anie.201402520

Ca2SiO4:Eu2+赤色蛍光体の発光特性国際誌

佐藤泰史, 加藤英樹, 小林亮, 垣花眞人

希土類 64 巻頁： 122 - 123 2014年5月

Insights into a selective synthesis of anatase, rutile, and brookite-type titanium dioxides by a hydrothermal treatment of titanium complexes 査読有り国際誌

Yoshizawa M., Kobayashi M., Petrykin V., Kato H., Kakihana M.

Journal of Materials Research 29 巻 ( 1 ) 頁： 90 - 97 2014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：Journal of Materials Research

Novel water-soluble titanium complexes coordinated by hydroxycarboxylic acids or amines were developed, and the hydrothermal treatment of the new complexes was carried out to elucidate the formation mechanism of the titania polymorphs including rutile, anatase, and brookite. An empirical relationship among the crystal structure of TiO2, the ligand, and the complex structure was found. Anatase, rutile, or a mixture of both was obtained by the hydrothermal treatment of the complexes coordinated by hydroxycarboxylic acids. The structure of complexes prepared using hydroxycarboxylic acids, which have one hydroxyl and one carboxylic groups, seems to be preferable for the formation of rutile. It was also found that the hydrothermal treatment of titanium complexes coordinated by amine with NAc2 structure resulted in the formation of brookite. Thus, the effect of ligand and complex structure on the crystal structure of TiO2 synthesized by the hydrothermal treatment of the complexes was proposed. © Materials Research Society 2013.

DOI： 10.1557/jmr.2013.229

Hydrothermal synthesis of magnetite particles with uncommon crystal facets 査読有り国際誌 Open Access

Sato J., Kobayashi M., Kato H., Miyazaki T., Kakihana M.

Journal of Asian Ceramic Societies 2 巻 ( 3 ) 頁： 258 - 262 2014年

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 Asian Ceramic Societies

Hydrothermal synthesis of Fe <inf>3</inf> O <inf>4</inf> (magnetite) particles was carried out using organic compounds as morphology control agents to obtain magnetite crystals with uncommon facets. It was established that the morphology of Fe <inf>3</inf> O <inf>4</inf> crystals obtained by hydrothermal treatment of an aqueous solution containing Fe <sup>2+</sup> and organic compounds depended on the organic compound used. The shape of the Fe <inf>3</inf> O <inf>4</inf> particles obtained when no additives were used was quasi-octahedral. In contrast, the addition of picolinic acid, citric acid or pyridine resulted in the formation of polyhedral crystals, indicating the presence of not only {111}, {100} and {110} facets but also high-index facets including at least {311} and {331}. When citric acid was used as an additive, octahedral crystals with {111} facets also appeared, and their size decreased as the amount of citric acid was increased. Thus, control of Fe <inf>3</inf> O <inf>4</inf> particle morphology was achieved by a simple hydrothermal treatment using additives. © 2014 The Ceramic Society of Japan and the Korean Ceramic Society.

DOI： 10.1016/j.jascer.2014.05.008

水溶性チタン錯体を用いたbrookite型酸化チタン粒子の調製招待有り査読有り

小林亮

Colloid and Interface Communication 38 巻 ( 4 ) 頁： 7-8 2013年12月

水を反応場として用いた機能性無機材料の合成～環境調和型プロセスの設計と新規水溶性金属錯体の開発～招待有り査読有り

小林亮, 垣花眞人

分離技術 41 巻 ( 6 ) 頁： 32(368)-36(372) 2013年12月

Synthesis of Titanium Dioxide Nanocrystals with Controlled Crystal- and Micro-structures from Titanium Complexes 招待有り査読有り Open Access

Kobayashi, M; Kato, H; Kakihana, M

NANOMATERIALS AND NANOTECHNOLOGY 3 巻 ( 23 ) 頁： 1-10 2013年12月

A Highly Luminous LiCaPO<sub>4</sub>:Eu<sup>+2</sup> Phosphor Synthesized by a Solution Method Employing a Water-Soluble Phosphate Ester 査読有り国際誌 Open Access

Minsung Kim, Makoto Kobayashi, Hideki Kato, Masato Kakihana

Optics and Photonics Journal 3 巻 ( 6A ) 頁： 13-18 2013年10月

Exploration of New Phosphors Using a Mineral-Inspired Approach in Combination with Solution Parallel Synthesis 招待有り査読有り国際誌 Open Access

Masato Kakihana, Jihae Kim, Tetsufumi Komukai, Hideki Kato, Yasushi Sato, Makoto Kobayashi, Yuji Takatsuka

Optics and Photonics Journal 3 巻 ( 6A ) 頁： 5-12 - 12 2013年10月

Development of a Novel Green Emitting Phosphate Phosphor KSrY(PO<sub>4</sub>)<sub>2</sub>:Eu<sup>+2</sup> 査読有り国際誌 Open Access

Akiko Saito, Hideki Kato, Makoto Kobayashi, Yasushi Sato, Masato Kakihana

Optics and Photonics Journal 3 巻 ( 6A ) 頁： 19-24 - 24 2013年10月

Synthesis of a Novel Bluish-Green Emitting Oxynitride Ca<sub>3</sub>Al<sub>8</sub>Si<sub>4</sub>O<sub>17</sub>N<sub>4</sub>:Eu<sup>+2</sup> Phosphor in a CaAl<sub>4-<i>x</i></sub>Si<sub><i>x</i></sub>O<sub>7-<i>x</i></sub>N<sub><i>x</i></sub> Solid Soluti 査読有り国際誌 Open Access

Jihae Kim, Hideki Kato, Makoto Kobayashi, Yasushi Sato, Masato Kakihana

Optics and Photonics Journal 3 巻 ( 6A ) 頁： 29-33 - 33 2013年10月

Enhanced Dielectric Response Induced by Controlled Morphology in Rutile TiO₂ Nanocrystals 査読有り Open Access

Minoru Osada, Makoto Kobayashi, Masato Kakihana

Journal of the Ceramic Society of Japan 121 巻 ( 8 ) 頁： 593-597 2013年8月

Luminescence properties of a novel green-emitting phosphate phosphor KSrY(PO₄)₂:Eu²⁺ 査読有り

Akiko Saito, Hideki Kato, Makoto Kobayashi, Masato Kakihana

IMID 2013 Digest 頁： 261-261 2013年8月

Synthesis of new thiogallate phosphors (Ba_1-xSr_x)₄Ga₂S₇:Eu and their luminescence properties 査読有り

Kohei Takeuchi, Takahiko Hasegawa, Hideki Kato, Makoto Kobayashi, Masato Kakihana

IMID 2013 Digest 頁： 260-260 2013年8月

Luminescence properties of a novel green-emitting phosphate phosphor KSrY(PO₄)₂:Eu²⁺ 査読有り国際誌

Akiko Saito, Hideki Kato, Makoto Kobayashi, Masato Kakihana

IMID 2013 Digest 頁： 261-261 2013年8月

Synthesis of new thiogallate phosphors (Ba<sub>1-<i>x</i></sub>Sr<sub><i>x</i></sub>)<sub>4</sub>Ga<sub>2</sub>S<sub>7</sub>:Eu and their luminescence properties 査読有り国際誌

Kohei Takeuchi, Takahiko Hasegawa, Hideki Kato, Makoto Kobayashi, Masato Kakihana

IMID 2013 Digest 頁： 260-260 2013年8月

Synthesis of a LiCaPO<SUB>4</SUB>:Eu<SUP>2+</SUP> phosphor by a polymerizable complex method using a novel water-soluble phosphate precursor 国際誌

Minsung Kim, Makoto Kobayashi, Hideki Kato, Masato Kakihana

IMID 2013 Digest 頁： 264 - 264 2013年8月

Photocatalytic Water Splitting over LaTa<sub>7</sub>O<sub>19</sub> Composed of TaO<sub>7</sub> Pentagonal Bipyramids and TaO<sub>6</sub> Octahedra 査読有り国際誌

Kato, H; Takeda, A; Kobayashi, M; Kakihana, M

CHEMISTRY LETTERS 42 巻 ( 7 ) 頁： 744 - 746 2013年7月

Effect of carboxyl group on the visible-light photocatalytic activity of SrTiO<sub>3</sub> nanoparticles 査読有り国際誌

Li, HH; Yin, S; Wang, YH; Kobayashi, M; Tezuka, S; Kakihana, M; Sato, T

RESEARCH ON CHEMICAL INTERMEDIATES 39 巻 ( 4 ) 頁： 1615 - 1621 2013年4月

水を溶媒に用いた機能性酸化物の低温合成のためのグリーンプレカーサーの開発招待有り査読有り

小林亮, 垣花眞人

機能材料 33 巻 ( 1 ) 頁： 4-10 2013年1月

Control of valence band potential and photocatalytic properties of Na<i><sub>x</sub></i>La<sub>1-<i>x</i></sub>TaO<sub>1+2<i>x</i></sub>N<sub>2-2<i>x</i></sub> oxynitride solid solutions 査読有り国際誌

Ueda, K; Kato, H; Kobayashi, M; Hara, M; Kakihana, M

JOURNAL OF MATERIALS CHEMISTRY A 1 巻 ( 11 ) 頁： 3667 - 3674 2013年

Fabrication of SrTiO<sub>3</sub> exposing characteristic facets using molten salt flux and improvement of photocatalytic activity for water splitting 査読有り国際誌

Kato, H; Kobayashi, M; Hara, M; Kakihana, M

CATALYSIS SCIENCE & TECHNOLOGY 3 巻 ( 7 ) 頁： 1733 - 1738 2013年

Enhancement of luminescence properties of a KSrPO<sub>4</sub>:Eu<SUP>2+</SUP> phosphor prepared using a solution method with a water-soluble phosphate oligomer 査読有り国際誌

Kim, M; Kobayashi, M; Kato, H; Kakihana, M

JOURNAL OF MATERIALS CHEMISTRY C 1 巻 ( 36 ) 頁： 5741 - 5746 2013年

Orange Emission from (Ba<sub>1-<i>X</i></sub>Sr<i><sub>X</sub></i>)<sub>4</sub>Al<sub>2</sub>S<sub>7</sub>:Eu<SUP>2+</SUP> Thioaluminate Phosphors with Visible Light Excitation 査読有り国際誌

Hasegawa, T; Kato, H; Takatsuka, Y; Kobayashi, M; Yamane, H; Kakihana, M

ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY 2 巻 ( 2 ) 頁： R3107 - R3111 2013年

Photocatalytic activities of Cu<sub>3x</sub>La<sub>1-</sub> xTa<sub>7</sub>O<sub>19</sub> solid solutions for H<sub>2</sub> evolution under visible light irradiation 査読有り国際誌

Kato, H; Takeda, A; Kobayashi, M; Hara, M; Kakihana, M

CATALYSIS SCIENCE & TECHNOLOGY 3 巻 ( 12 ) 頁： 3147 - 3154 2013年

Synthesis of spindle and square bipyramid-shaped anatase-type titanium dioxide crystals by a solvothermal method using ethylenediamine 査読有り国際誌 Open Access

Kobayashi, M; Kato, H; Kakihana, M

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 120 巻 ( 1407 ) 頁： 494 - 499 2012年11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：公益社団法人日本セラミックス協会

Morphological control as well as formation of nanoparticles of anatase-type titanium dioxide has been achieved by a solvothermal treatment of a water-soluble citratoperoxotitanium (CPT) complex using ethylenediamine (EDA) as a key solvent in the presence of a given amount of water. When the EDA concentration in the whole solvent (EDA + H<sub>2</sub>O) remained low less than 12 M, the powder obtained after the solvothermal treatment consisted of spindle-like anatase particles. With an increase of the EDA concentration in the solvent, the shape of the obtained particles changed from spindle to square bipyramid. When another water-soluble oxoglycolatoperoxotitanate complex or TiCl<sub>4</sub> was used as a starting source of Ti, similar shaped anatase particles could be obtained by a careful choice of synthetic conditions. Using a mixed solvent of EDA and water, sheet-like titanic acid was produced as an intermediate phase, regardless of the EDA concentration. Therefore, the formation of anatase in the current system may take place through dissolution-recrystallization of titanic acid. The formation of square bipyramidal anatase particle achieved in the present study is not agreement with a reported theoretical calculation of equilibrium phase, because the calculation reveals that truncated square bipyramid-like anatase is obtained under an acidic condition and spindle-like anatase was formed under a basic condition. An adsorption of EDA on particle surface and the pH of the solvent may contribute to the achievement of morphological control.

DOI： 10.2109/jcersj2.120.494

Synthesis of new thioaluminate phosphors (Ba_1-XSr_X)₄Al₂S₇:Eu and their luminescence properties 査読有り

Takahiko Hasegawa, Makoto Kobayashi, Hideki Kato, Hisanori Yamane, Masato Kakihana

Technical digest of the 12th International Meeting on Information Display 頁： 640-641 2012年8月

Impact of synthesis methodology on the optimization of photoluminescence emission intensity of NaBaScSi<SUB>2</SUB>O<SUB>7</SUB>:Eu<SUP>2+</SUP> phosphor 査読有り国際誌

Sudeshna Ray, Kenji Toda, Shinnosuke Kamei, Tadashi Ishigaki, Kazuyoshi Uematsu, Mineo Sato, Hideki Kato, Makoto Kobayashi, Masato Kakihana

Technical digest of the 12th International Meeting on Information Display 頁： 128 - 129 2012年8月

Synthesis of the new compound in a Na-Sc-Si-O system and Luminescence properties activated by Eu<sup>2+</sup> 査読有り国際誌

Jihong Min, Hideki Kato, Makoto Kobayashi, Hisanori Yamane, Masato Kakihana

Technical digest of the 12th International Meeting on Information Display 頁： 638-639 2012年8月

Synthesis of new thioaluminate phosphors (Ba<sub>1-X</sub>Sr<sub>X</sub>)<sub>4</sub>Al<sub>2</sub>S<sub>7</sub>:Eu and their luminescence properties 査読有り国際誌

Takahiko Hasegawa, Makoto Kobayashi, Hideki Kato, Hisanori Yamane, Masato Kakihana

Technical digest of the 12th International Meeting on Information Display 頁： 640-641 2012年8月

Synthesis of KSrPO<sub>4</sub>:Eu<sup>2+</sup> Phosphor with High Luminescence Property Using a Water-Soluble Phosphorus Precursor 査読有り国際誌

Minsung Kim, Makoto Kobayashi, Hideki Kato, Masato Kakihana

Technical digest of the 12th International Meeting on Information Display 頁： 130-131 2012年8月

Preparation of Hollow TiO2 Spheres of the Desired Polymorphs by Layer-by-Layer Assembly of a Water-Soluble Titanium Complex and Hydrothermal Treatment 査読有り国際誌

Katagiri, K; Inami, H; Koumoto, K; Inumaru, K; Tomita, K; Kobayashi, M; Kakihana, M

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY ( 20 ) 頁： 3267 - 3272 2012年7月

Morphology-Controlled Synthesis of W₁₈O₄₉ Nanostructures and Their Near-Infrared Absorption Properties 査読有り国際誌

Guo Chongshen, Yin Shu, Yan Mei, Kobayashi Makoto, Kakihana Masato, Sato Tsugio

INORGANIC CHEMISTRY 51 巻 ( 8 ) 頁： 4763 - 71 2012年4月

Hydrothermal synthesis of brookite-type titanium dioxide with snowflake-like nanostructures using a water-soluble citratoperoxotitanate complex 査読有り国際誌

Kobayashi, M; Petrykin, V; Tomita, K; Kakihana, M

JOURNAL OF CRYSTAL GROWTH 337 巻 ( 1 ) 頁： 30 - 37 2011年12月

Hydrothermal synthesis of hierarchical TiO<sub>2</sub> microspheres using a novel titanium complex coordinated by picolinic acid 査読有り国際誌 Open Access

Truong, D; Kobayashi, M; Kato, H; Kakihana, M

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 119 巻 ( 1390 ) 頁： 513 - 516 2011年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：公益社団法人日本セラミックス協会

Phase- and morphology-control of TiO<sub>2</sub> was performed by a facile hydrothermal method using a novel water-soluble titanium–picolinato complex as a precursor. Single-phase rutile or brookite type titania can be obtained by tailoring the pH of the complex solution. Rutile with a hierarchical microstructure was synthesized using an excess amount of ligand as an additive and the final product consisted of microspheres with mesopores formed by a self-assembly of nanorods. The anisotropic growth of nanorods with a high aspect ratio was explained by a capping mechanism.

DOI： 10.2109/jcersj2.119.513

Application of Water-Soluble Titanium Complexes as Precursors for Synthesis of Titanium-Containing Oxides via Aqueous Solution Processes 招待有り査読有り国際誌

Kakihana, M; Kobayashi, M; Tomita, K; Petrykin, V

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 83 巻 ( 11 ) 頁： 1285 - 1308 2010年11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：公益社団法人日本化学会

The growing significance of nanocrystalline inorganic functional materials in the fields of catalysis, electronics, and energy conversion together with the increasing demand of the society for safer, softer, and “greener” technologies has drawn considerable attention of the researchers toward water-based solution processes for synthesis of such materials. In this respect complex oxides, containing d<sup>0</sup>-transition metals, such as Ti, Nb, Ta, or Si represent an outstanding challenge for materials chemists due to the extremely narrow range or almost complete absence of suitable precursor compounds compatible with aqueous systems. In the recent 10 years, a remarkable progress has been achieved in the development of new water-soluble complexes of titanium and considerable experience was accumulated in the application of these compounds for synthesis of nanocrystalline titanium-containing materials. The essential knowledge of coordination chemistry of such water-soluble titanium complexes is reviewed in this work, which succeeded to identify the key structural features responsible for stability of the compounds against hydrolysis and to provide guidelines for synthesis of these complexes. Finally, an extensive overview of highly selective aqueous solution based synthesis of TiO<sub>2</sub> polymorphs as well as complex oxide materials with the help of the novel water-soluble titanium complexes is provided.

DOI： 10.1246/bcsj.20100103

酸化チタンのテーラメイド合成招待有り査読有り

小林亮, 垣花眞人

現代化学 465 巻 ( 12 ) 頁： 57-62 2009年11月

新規水溶性チタン錯体を用いた水熱法による酸化チタン多形の選択的合成招待有り査読有り国際誌 Open Access

垣花眞人, 小林亮, Petrykin Valery, 冨田恒之

粉体および粉末冶金 56 巻 ( 4 ) 頁： 188-193 - 193 2009年4月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人粉体粉末冶金協会

A panel of new stable and water soluble complexes of titanium (IV) with natural hydroxy-carboxylic acids such as citric, tartaric, lactic or glycolic acid as ligands was developed. A typical structure of these complex ions includes a peroxo-group, and a hydroxy-carboxylic acid molecule attached to the metal ion by carboxylic and hydroxylic groups to form stable species. The tight coordination and negative charge of complex ions are responsible for stability of these new compounds in water solutions in a wide range of temperatures and pH. Use of natural non-toxic ligands and ammonium as counterions make such titanium compounds convenient reagents for "green" synthesis of titanium containing materials by aqueous solution methods.<BR>The architecture of titanium complexes includes structural motifs of different polymorphic forms of TiO<SUB>2</SUB>, which allows for application of these compounds as building blocks (tecton) for synthesis of titania with different crystal structures by a simple hydrothermal processes. In this way anatase, rutile, TiO<SUB>2</SUB>(B) and brookite were prepared in a reproducible and highly selective way. For the first time TiO<SUB>2</SUB>(B) and brookite were synthesized as single phase nano-crystals by a "one-pot" hydrothermal process, and their outstanding photo-catalytic activities were revealed.

DOI： 10.2497/jjspm.56.188

Hydrothermal synthesis of brookite type TiO<sub>2</sub> photocatalysts using a water-soluble Ti-complex coordinated by ethylenediaminetetraacetic acid 査読有り国際誌 Open Access

Morishima, Y; Kobayashi, M; Petrykin, V; Yin, S; Sato, T; Kakihana, M; Tomita, K

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 117 巻 ( 1363 ) 頁： 320 - 325 2009年3月

Photocatalytic activity of nanocrystalline TiO<sub>2</sub>(B) synthesized from titanium glycolate complex by hydrothermal method 査読有り国際誌 Open Access

Yamamoto, K; Shimoita, H; Tomita, K; Fujita, K; Kobayashi, M; Petrykin, V; Kakihana, M

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 117 巻 ( 1363 ) 頁： 347 - 350 2009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：公益社団法人日本セラミックス協会

The metastable phase of TiO_2(B), one of the polymorphs of titanium dioxide (TiO_2), was prepared by a hydrothermal treatment of a titanium glycolate complex ([Ti_4(C_2H_2O_3)_4(C_2H_3O_3)_2(O_2)_4O_2]^<6->) at 473K for 1-72h in the presence of H_2SO_4. Characterization by X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that the obtained samples were composed of single phase TiO_2(B) and the particles had plate-like morphology. After post-synthetic hydrothermal crystal growth (PHCG) applied to the as-prepared sample, thicker plate-like shaped particles were obtained. The photocatalytic activities of the samples obtained by the hydrothermal treatment and after the subsequent PHCG were evaluated in terms of methanol decomposition.

DOI： 10.2109/jcersj2.117.347

チタン錯体水溶液からの酸化チタン光触媒の合成招待有り査読有り

小林亮, Petykin Valery, 垣花眞人, 冨田恒之

化学工業 60 巻 ( 1 ) 頁： 71-77 2009年1月

Hydrothermal Synthesis and Photocatalytic Activity of Whisker-Like Rutile-Type Titanium Dioxide 査読有り国際誌 Open Access

Kobayashi, M; Petrykin, V; Kakihana, M; Tomita, K

JOURNAL OF THE AMERICAN CERAMIC SOCIETY 92 巻 ( 1 ) 頁： S21 - S26 2009年1月

Synthesis of TiO<sub>2</sub>(B) using glycolato titanium complex and post-synthetic hydrothermal crystal growth of TiO<sub>2</sub>(B) 査読有り国際誌

Yamamoto, K; Tomita, K; Fujita, K; Kobayashi, M; Petrykin, V; Kakihana, M

JOURNAL OF CRYSTAL GROWTH 311 巻 ( 3 ) 頁： 619 - 622 2009年1月

Synthesis of TiO_2 (B) using glycolato titanium complex and post-synthetic hydrothermal crystal growth of TiO_2 (B) 査読有り

冨田恒之, 小林亮, 垣花眞人

Journal of Crystal Growth 311 頁： 619 - 622 2009年

Hydrothermal Synthesis and Photocatalytic Activity of Whisker-like Rutile-type Titanium Dioxide 査読有り Open Access

小林亮

Journal of the American Ceramic Society 92 2009年

チタン錯体水溶液からの酸化チタン光触媒の合成査読有り

小林亮, 冨田恒之

化学工業 60 頁： 71 - 77 2009年

Selective synthesis of nano-crystalline TiO₂ polymorphs from new water-soluble titanium complexes 査読有り

Masato Kakihana, Makoto Kobayashi, Valery Petrykin, Koji Tomita

Acta Crystallographica Section A ( 64 ) 頁： C20 2008年8月

Selective synthesis of nano-crystalline TiO<sub>2</sub> polymorphs from new water-soluble titanium complexes 査読有り Open Access

Masato Kakihana, Makoto Kobayashi, Valery Petrykin, Koji Tomita

Acta Crystallographica Section A ( 64 ) 頁： C20 2008年8月

Direct synthesis of brookite-type titanium oxide by hydrothermal method using water-soluble titanium complexes 査読有り国際誌

Kobayashi, M; Tomita, K; Petrykin, V; Yoshimura, M; Kakihana, M

JOURNAL OF MATERIALS SCIENCE 43 巻 ( 7 ) 頁： 2158 - 2162 2008年4月

Hydrothermal synthesis of TiO<sub>2</sub> nano-particles using novel water-soluble titanium complexes 査読有り国際誌

Tomita, K; Kobayashi, M; Petrykin, V; Yin, S; Sato, T; Yoshimura, M; Kakihana, M

JOURNAL OF MATERIALS SCIENCE 43 巻 ( 7 ) 頁： 2217 - 2221 2008年4月

New water-soluble complexes of titanium with amino acids and their application for synthesis of TiO<sub>2</sub> nanoparticles 査読有り国際誌 Open Access

Kobayashi, M; Petrykin, V; Tomita, K; Kakihana, M

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 116 巻 ( 1352 ) 頁： 578 - 583 2008年4月

INOR 1052-Synthesis of oxide materials using new water soluble titanium and tantalum complexes 査読有り国際誌

Petrykin, V; Kobayashi, M; Tomita, K; Kakihana, M

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 235 巻 2008年4月

Selective synthesis of nano-crystalline TiO_2 polymorphs from new water-soluble titanium complexes 査読有り Open Access

小林亮

Acta Crystallographica Section A 64 2008年

Microwave-assisted hydrothermal synthesis of brookite nanoparticles from a water-soluble titanium complex and their photocatalytic activity 査読有り国際誌 Open Access

Yusuke Morishima, Makoto Kobayashi, Valery Petrykin, Masato Kakihana, Koji Tomita

Journal of the Ceramic Society of Japan 115 巻 ( 1348 ) 頁： 826 - 830 2007年12月

Morphology control of rutile nanoparticles in a hydrothermal synthesis from water-soluble titanium complex aqueous solution 査読有り国際誌 Open Access

Makoto Kobayashi, Valery Petrykin, Masato Kakihana, Koji Tomita

Journal of the Ceramic Society of Japan 115 巻 ( 1348 ) 頁： 835 - 839 2007年12月

One-step synthesis of TiO<sub>2</sub>(B) nanoparticles from a Water-Soluble titanium complex 査読有り国際誌

Makoto Kobayashi, Valery V. Petrykin, Masato Kakihana, Koji Tomita, Masahiro Yoshimura

Chemistry of Materials 19 巻 ( 22 ) 頁： 5373-5376 - 5376 2007年10月

ゾル－ゲルコーティング材料としての新規水溶性チタン錯体招待有り査読有り

垣花眞人, 冨田恒之, 小林亮

化学工業 57 巻 ( 12 ) 頁： 13-19 2006年12月

Hydrothermal synthesis of nanosized titania photocatalysts using novel water-soluble titanium complexes 査読有り国際誌

Makoto Kobayashi, Koji Tomita, Valery Petrykin, Syu Yin, Tsugio Sato, Masahiro Yoshimura, Masato Kakihana

Solid State Phenomena 124-126 巻頁： 723-726 2006年9月

A water-soluble titanium complex for the selective synthesis of nanocrystalline brookite, rutile, and anatase by a hydrothermal method 査読有り国際誌

Tomita, K; Petrykin, V; Kobayashi, M; Shiro, M; Yoshimura, M; Kakihana, M

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 45 巻 ( 15 ) 頁： 2378 - 81 2006年4月

水溶液から酸化チタンを作る招待有り査読有り

小林亮, 冨田恒之, 垣花眞人

色材協会コラム ( 20 ) 頁： 1 2006年

箱根火山大涌谷テフラ群 : 最新マグマ噴火後の水蒸気爆発堆積物査読有り Open Access

小林淳, 萬年一剛, 奥野充, 中村俊夫, 袴田和夫

火山 51 巻 ( 4 ) 頁： 245 - 256 2006年

水溶性プロセスを利用したセラミックスの合成招待有り査読有り

冨田恒之, 小林亮, 垣花眞人

未来材料 5 巻 ( 10 ) 頁： 37 - 43 2005年10月

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