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

DOI： 10.1016/j.jphotochemrev.2022.100569

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

DOI： 10.1063/5.0144271

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

DOI： 10.1021/acsami.2c21232

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

DOI： 10.1021/acs.jpclett.2c01077

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

DOI： 10.1039/d2cp01461k

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

DOI： 10.1021/acsami.2c06503

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

DOI： 10.1038/s41427-022-00414-3

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

DOI： 10.1364/OPTICA.447557

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

Phthalocyanine ruthenium complexes were identified as red-light activatable catalysts for trifluoromethylation reactions.

DOI： 10.1039/d1cc06307c

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsanm.1c02335

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

Multinary semiconductor quantum dots (QDs) composed of group I-III-VI elements have received much attention for wide-ranging applications due to their low level of toxicity and tunable optical properties. The chemical composition and particle size are important parameters for controlling the physicochemical properties of these QDs. In this study, we prepared quinary QDs of an Ag-(In,Ga)-(S,Se) semiconductor (AIGSSe) by thermolysis of precursors in an organic solution with two-step heat treatment and evaluated their physicochemical properties as a function of Se fraction. The energy gap (Eg) of QDs decreased from 1.9 to 1.5 eV with an increase in the Se/(S + Se) ratio from 0 to 1, accompanied by a shift of the valence band maximum to a higher energy level. The obtained AIGSSe QDs exhibited a sharp band-edge PL peak, the wavelength of which was red-shifted from 580 to 790 nm with a decrease in theirEg. The PL intensity was remarkably enlarged by the surface coating with a GaSxshell, the highest PL quantum yield being 50% for the PL peak at 580 nm. AIGSSe QDs with an Se/(S + Se) ratio of 0.50 exhibited a near-IR PL peak at 790 nm, which is suitable forin vivobioimaging in the wavelength range of the first biological window. By incorporating GaSx-coated AIGSSe QDs (Se/(S + Se) = 0.50) into liposomes, the QDs were transferred into aqueous solutions without significant deterioration of both the PL peak outline and quantum yield, though a broad PL peak originating from defect sites appeared with a relatively large PL intensity when GaSx-coated Ag-(In,Ga)-S QDs that did not contain Se were used.In vivoimaging of a mouse was successfully performed by detecting the band-edge emission at 790 nm of AIGSSe QDs injected subcutaneously in the back of the mouse.

DOI： 10.1039/d1tc02746h

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Scopus

Language：English  

DOI： 10.1002/chem.202101738

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

<title>Abstract</title>Three-dimensional (3D) information of the optical response in the nanometre scale is important in the field of nanophotonics science. Using photoinduced force microscopy (PiFM), we can visualize the nano-scale optical field using the optical gradient force between the tip and sample. Here, we demonstrate 3D photoinduced force field visualization around a quantum dot in the single-nanometre spatial resolution with heterodyne frequency modulation technique, using which, the effect of the photothermal expansion of the tip and sample in the ultra-high vacuum condition can be avoided. The obtained 3D mapping shows the spatially localized photoinduced interaction potential and force field vectors in the single nano-scale for composite quantum dots with photocatalytic activity. Furthermore, the spatial resolution of PiFM imaging achieved is ~0.7 nm. The single-nanometer scale photoinduced field visualization is crucial for applications such as photo catalysts, optical functional devices, and optical manipulation.

DOI： 10.1038/s41467-021-24136-2

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Other Link： http://www.nature.com/articles/s41467-021-24136-2

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsami.1c04929

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Language：English  

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Publishing type：Research paper (scientific journal)   Publisher：Institute of Image Information and Television Engineers  

DOI： 10.3169/mta.9.222

DOI： 10.1117/12.2616174

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

DOI： 10.1063/5.0018132

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

Nanoparticles composed of molybdenum oxide, MoOx, were successfully prepared by room-temperature ionic liquid (RTIL)/metal sputtering followed by heat treatment. Hydroxyl groups in RTIL molecules retarded the coalescence between MoOx NPs during heat treatment at 473 K in air, while the oxidation state of Mo species in MoOx nanoparticles (NPs) could be modified by changing the heat treatment time. An LSPR peak was observed at 840 nm in the near-IR region for MoOx NPs of 55 nm or larger in size that were annealed in a hydroxyl-functionalized RTIL. Photoexcitation of the LSPR peak of MoOx NPs induced electron transfer from NPs to ITO electrodes.

DOI： 10.1039/d0ra05165a

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Scopus

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

DOI： 10.1039/d0ta04127k

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

DOI： 10.1039/d0ra02842h

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

© 2020 American Chemical Society. Multinary semiconductor quantum dots (QDs) that have less toxicity and show near-infrared light responsivity have attracted much attention for in vivo bioimaging. In this study, we controlled the optical properties of Ag-In-Se QDs by modulating the nonstoichiometry and the degree of Ga3+ doping. Precise tuning of the Ag/In ratio of Ag-In-Se QDs enabled a sharp band-edge emission to emerge without broad defect-site emission. Ga3+ doping into Ag-In-Se (AIGSe) QDs enlarged their energy gap, resulting in a blue shift of the band-edge PL peak from from 890 to 630 nm. The band-edge PL intensity was remarkably enlarged by surface coating with a thin GaSx shell followed by treatment with trioctylphosphine, the highest PL yield being 38% for the PL peak at 800 nm. Thus-obtained QDs were successfully used as near-IR PL probes for three-dimensional in vivo bioimaging in which the wavelengths of excitation and detection lights could be selected in the first biological window, and then the signals were clearly detected from AIGSe@GaSx core-shell QDs injected into biological tissues by ca. 5 mm in depth.

DOI： 10.1021/acsanm.9b02608

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Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：SPIE-Intl Soc Optical Eng  

DOI： 10.1117/1.JNP.14.026013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Colloidal quantum dots (QDs), which exhibit highly saturated color emission, are expected to be used as emitting materials in wide-color-gamut displays. However, the development of low-toxicity alternatives is necessary because QDs with high color purity and highly efficient emission contain toxic materials such as Cd and Pb. In this study, QD light-emitting diodes (QD-LEDs) with ZnS-AgInS2 solid-solution nanoparticles [(AgIn)(x)Zn2(1-x)S2, ZAIS] as low-toxicity QDs were fabricated and their electroluminescence properties were investigated. The ZAIS QDs exhibited red photoluminescence, with a peak wavelength of ca. 700nm. Because the charge-injection barrier of ZAIS QDs without a wide-bandgap shell is relatively low, the QD-LEDs with red ZAIS QDs in combination with organic charge-transport materials induce electron injection from an organic electron-transport layer. These QD-LEDs exhibit an external quantum efficiency of 2.2%, a turn-on voltage of 2.4V, and red emission with chromaticity coordinates (0.66, 0.33).

DOI： 10.1063/1.5143618

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：SPIE-Intl Soc Optical Eng  

DOI： 10.1117/1.JNP.14.016010

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Authorship：Lead author   Language：English  

DOI： 10.1117/12.2573520

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

DOI： 10.1021/acs.jpcc.9b05077

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Language：English  

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

© 2019 Wiley-VCH Verlag GmbH &amp; Co. KGaA, Weinheim Multinary nanocrystals (NCs) of I-III-VI-based semiconductors with less toxicity have attracted much attention for the fabrication of efficient light-energy conversion systems. Here we report unique photoelectrochemical properties of ZnTe−AgInTe2 solid solution (ZAITe) NCs with a controllable energy gap in near-IR region. The photoelectrochemical behavior of ZAITe NCs immobilized on an ITO electrode with a thickness of less than one monoparticle layer, resembling a p-type semiconductor photoresponse, was remarkably different from that of ZAITe NC multilayer films: The onset of a cathodic photocurrent was shifted more positively than that of the valence band maximum of ZAITe NCs and the photocurrent generation efficiency was significantly increased, when photons with energy higher than ca. 2.5 eV were irradiated. These phenomena can be explained well by the direct hot hole transfer from ZAITe NCs to the ITO electrode.

DOI： 10.1002/cnma.201900241

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Scopus

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

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

DOI： 10.1088/1742-6596/1220/1/012039

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

The nonstoichiometry of semiconductor I-III-VI semiconductor nanoparticles, especially the ratio of group Ito group III elements, has been utilized to control their physicochemical properties. We report the solution-phase synthesis of non-stoichiometric Ag-In-S and Ag-In-Ga-S nanoparticles and results of the investigation of their photoluminescence (PL) properties in relation to their chemical compositions. While stoichiometric AgInS2 nanoparticles simply exhibited only a broad PL band originating from defect sites in the particles, a narrow band edge PL peak newly appeared with a decrease in the Ag fraction in the nonstoichiometric Ag-In-S nano-particles. The relative PL intensity of this band edge emission with respect to the defect-site emission was optimal at a Ag/(Ag + In) value of ca. 0.4. The peak wavelength of the band edge emission was tunable from 610 to 500 nm by increased doping with Ga3+ into Ag-In-S nanoparticles due to an increase of the energy gap. Furthermore, surface coating of Ga3+-doped Ag-In-S nanoparticles, that is, Ag-In-Ga-S nanoparticles, with a GaSx shell drastically and selectively suppressed the broad defect-site PL peak and, at the same time, led to an increase in the PL quantum yield (QY) of the band edge emission peak. The optimal PL QY was 28% for Ag-In-Ga-S@GaSx core-shell particles, with green band-edge emission at 530 nm and a full width at half-maximum of 181 meV (41 nm). The observed wavelength tunability of the band-edge PL peak will facilitate possible use of these toxic-element-free I-III-VI-based nanoparticles in a wide area of applications.

DOI： 10.1021/acsami.8b15222

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Quantum dots (QDs) are semiconductor nanoparticles showing many advantages for photoluminescence (PL) applications. Since common QDs contain toxic elements such as Cd, Pb, Se, and Te, ZnS-AgInS2 (ZAIS) has been developed a a quantum nanomaterial with low cytotoxicity. In this study, ZAIS@ZnS core-shell QDs coated with carboxyl groups (ZAIS@ZnS-MPA) were prepared as water-soluble nanoparticles. The PL characteristics of ZAIS@ZnS-MPA were studied on a plasmonic chip, which is a substrate with wavelength-scale periodic structures coated with thin metal films, and the PL enhancement of ZAIS by an electromagnetic field derived from grating-coupled surface plasmon resonance (GC-SPR) was also evaluated. The PL spectroscopic characteristics obtained on the grating patterns with a 480 nm-pitch were enhanced in a wider wavelength range. Furthermore, photobleaching, which occurs in conventional fluorescence molecules, was not observed under halogen lamp illumination. The PL and spectroscopic imaging under a microscope indicated the PL characteristics of the ZAIS@ZnS-MPA nanoparticles on the plasmonic chip under appropriate conditions.

DOI： 10.1016/j.jphotochem.2018.08.032

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

© 2018 The Chemical Society of Japan Two-photon absorption behavior of dispersion of solid solution nanocrystals of ZnS-AgInS2 was investigated, the measured maximum two-photon absorption cross-section of this nanoparticle being 3900 GM (1 GM = 10150 cm4 s photon11 mol(particle)11) at 850 nm. The two-photon excited red photoluminescence was observed even by using a femtosecond fiber laser oscillating at 1030 nm.

DOI： 10.1246/cl.180718

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Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

© 2018, The Author(s). Nanoparticles of I–III–VI semiconductors are promising candidates for novel non-toxic fluorescent materials. However, removal of defect levels responsible for their broad-band emission has not been successful to date. The present study demonstrates, for the first time, the coating of core AgInS2 nanoparticles—one of the I–III–VI group semiconductors with a bandgap in the visible region—with III–VI group semiconductors. The AgInS2/InSx and AgInS2/GaSx (x = 0.8–1.5) core/shell structures generate intense narrow-band photoluminescence originating from a band-edge transition at a wavelength shorter than that of the original defect emission. Microscopic analyses reveal that the GaSx shell has an amorphous nature, which is unexpected for typical shell materials such as crystalline lattice-matching ZnS. Single-particle spectroscopy shows that the average linewidth of the band-edge photoluminescence is as small as 80.0 meV (or 24 nm), which is comparable with that of industry-standard II–VI semiconductor quantum dots. In terms of photoluminescence quantum yield, a value of 56% with nearly single-band emission has been achieved as a result of several modifications to the reaction conditions and post-treatment to the core/shell nanoparticles. This work indicates the increasing potential of AgInS2 nanoparticles for use as practical cadmium-free quantum dots.

DOI： 10.1038/s41427-018-0067-9

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Scopus

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

Nanocrystals with a heterojunction of type-II band alignment have attracted much interest for the construction of solar energy conversion systems because photogenerated electrons and holes can be effectively separated at the heterojunction. Here, we report the preparation of heterostructured multinary nanocrystals composed of ZnS-AgInS2 solid solution (ZAIS), which have tunability of the electronic energy structure depending on their chemical composition. Ellipsoidal ZAIS nanocrystal domains with various compositions were epitaxially grown on both termini of preformed ZAIS nanorods as seeds. The resulting nanocrystals had a dumbbell shape composed of two ellipsoidal nanocrystals (ca. 4-6 nm in width x 7-11 nm in length) connected by a nanorod (ca. 4 nm in width x 16-23 nm in length). Because the Zn fraction in the chemical composition was larger in the rod part than in the two tip parts in the nanodumbbell, heterojunctions of type-II or quasi-type-II were formed at the interface between the rod and tip parts, as confirmed by photoluminescence lifetime measurements. Analysis of the energy structure of ZAIS nanodumbbells indicated that photogenerated electrons and holes were effectively and spatially separated at the heterojunction, resulting in localization of the photogenerated electrons in ellipsoidal ZAIS tips in the nanodumbbell but delocalization of holes over the whole nanocrystal. The photocatalytic H-2 evolution rate of ZAIS nanodumbbells was remarkably improved in comparison to those of single-component counterparts, ZAIS nanorods or free ellipsoidal ZAIS nanocrystals with similar sizes, by tuning the chemical composition of the tip parts to optimize the energy structure of thetype-II heterojunction for H-2 evolution.

DOI： 10.1021/acs.jpcc.8b00255

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

Rod-shaped nanocrystals (NCs) composed of ZnTe-AgInTe2 solid solution ((AgIn)xZn2(1-x)Te2, ZAITe) were synthesized in a 1-dodecanethiol solution. The resulting ZAITe NCs of 4-5 nm in width and 16-18 nm in length showed exciton peaks in the absorption spectra, regardless of their composition. The energy gap was enlarged from 1.2 to 1.6 eV by decreasing the x value of the NCs from 1.0 to 0.25. A sharp photoluminescence (PL) peak was observed in each PL spectrum of the NCs with x values of 1.0-0.5, assignable to band-edge emission, while NCs with x = 0.25 showed an additional broad PL peak originating from the defect sites due to the increased non-stoichiometry of NCs. With a decrease in x from 1.0 to 0.25, the band-edge PL peak was blue-shifted from 1010 to 809 nm in the near-IR region, accompanied by a decrease in the corresponding PL quantum yield from 47% to 0.07% due to the diminution of radiative recombination rate.

DOI： 10.1039/c7tc05624a

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Scopus

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

Group I-III-VI2 semiconductor-based quantum dots, such as AgInS2, CuInS2 and their solid solution with ZnS, have recently been reported to show intense photoluminescence, the wavelength of which is tunable in a wide range from visible to near-infrared (NIR) light regions by controlling their chemical composition and/or size. Due to their low toxicity and tunable optical properties, these multinary semiconductor quantum dots (QDs) have been intensively developed as alternative materials to conventional Cd-and Pb-based QDs for applications to photoluminescent devices, photocatalysts, quantum dot solar cells, and biological imaging materials. In this review, the recent progress in the photofunctionality of I-III-VI2-based semiconductor QDs prepared by the colloidal method is outlined with foucus on two advances: (1) extension of the photoluminescence wavelength to NIR light for in vivo biological imaging and (2) improvement of photoenergy conversion properties by nanostructure control of QDs. (c) The Electrochemical Society of Japan, All rights reserved.

DOI： 10.5796/electrochemistry.18-6-E2670

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Language：Japanese   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

A tightly focused laser beam exerts optical force on nanoparticles dispersed in an aqueous solution, leading to an optical trapping of them at the focal point. Recently, we have developed plasmonic optical tweezers for soft nano-matters such as DNA, thermoresponsive polymer chains, and dye aggregates. We observed the interested trapping behaviors of the soft nanomaterials on such liquid-solid interfaces. Our attention is paid to such optical trapping of them on interfaces because optical force strongly depends on the dielectric constant of the surrounding medium. In the present study, we demonstrated that optical trapping of quantum dots and octahedral gold nanocrystals at water-oil interface. Dark-field microscopy was a powerful tool to observe the trapping behaviors of the gold nanoparticles, while fluorescence microscopy was used for the observations of the quantum dots.

DOI： 10.1117/12.2319571

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Language：Japanese   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

Semiconductor quantum dots (QDs) composed of ZnTe-AgInTe2 solid solution ((AgIn)(x)Zn2(1-x)Te2, ZAITe) were synthesized by a thermal reaction of corresponding metal acetates and a Te precursor in 1-dodecanethiol. TEM observations revealed that rod-shaped QDs with width of ca. 4 nm and length of ca. 16 nm were formed regardless of chemical composition of particles, x value. The absorption onset and the band-edge PL peak energy were enlarged from 1.13 to 1.53 eV and from 1.23 eV to 1.53 eV, respectively, with a decrease in x from 1.0 to 0.25. The observed optical properties of ZAITe QDs were largely tunable in the near-IR region, being suitable for optical applications.

DOI： 10.1117/12.2317057

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

Bimetallic Pd-Au nanoparticle films were sputter-deposited on the surface of hydroxyl-functionalized ionic liquid by sequential metal sputtering of Pd and Au. The resulting films having a partially alloyed surface exhibited high electrocatalytic activity for ethanol oxidation, the degree being dependent on both the order of metal sputtering and the chemical composition of resulting bimetallic particles. The optimum catalytic activity was obtained for the bimetallic film with a Au fraction of 41% prepared by sequential sputtering of Pd followed by Au.

DOI： 10.1246/cl.170242

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

DOI： 10.1039/c6cp07550a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

The facile synthesis of ZnS-AgInS2 (ZAIS) as cadmium-free QDs and their application, mainly in solar cells, has been reported by our groups. In the present study, we investigated the safety and the usefulness for labeling and in vivo imaging of a newly synthesized aqueous ZnS-coated ZAIS (ZnS-ZAIS) carboxylated nanoparticles (ZZC) to stem cells. ZZC shows the strong fluorescence in aqueous solutions such as PBS and cell culture medium, and a complex of ZZC and octa-arginine (R8) peptides (R8-ZZC) can achieve the highly efficient labeling of adipose tissue-derived stem cells (ASCs). The cytotoxicity of R8-ZZC to ASCs was found to be extremely low in comparison to that of CdSe-based QDs, and R8-ZZC was confirmed to have no influence on the proliferation rate or the differentiation ability of ASCs. Moreover, R8-ZZC was not found to induce the production of major inflammatory cytokines(TNF-alpha, IFN-gamma, IL-12p70, IL-6 and MCP-1) in ASCs. Transplanted R8-ZZC-labeled ASCs could be quantitatively detected in the lungs and liver mainly using an in vivo imaging system. In addition, high-speed multiphoton confocal laser microscopy revealed the presence of aggregates of transplanted ASCs at many sites in the lungs, whereas individual ASCs were found to have accumulated in the liver.

DOI： 10.1038/srep40047

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Language：Japanese   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

DOI： 10.1117/12.2274899

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Language：Japanese   Publisher：The Surface Science Society of Japan  

<p>Multinary I-III-VI₂ group semiconductor nanocrystals, such as CuInS₂, Cu(InGa)Se₂, AgInS₂ and their solid solutions with ZnS, have been attracting increasing attention due to their low toxicity, wide range of absorption from UV to visible or near-infrared regions, and tunable energy gap. In this review, we introduce recent progress of solution-phase syntheses of high-quality multinary nanocrystals, which are candidates for alternative materials of Cd- and Pb-based binary nanocrystals showing high toxicity. Physicochemical properties of multinary nanocrystals are tunable depending on their crystal size and chemical composition. For example, nanocrystals of solid solution between AgInS₂ and ZnS exhibited strong photoluminescence, the color of which was controlled from red to green with an increase in the ZnS fraction. The controllability of their photochemical properties is useful to develop novel photofunctional materials for the applications, such as photocatalyst and biomolecule marker.</p>

DOI： 10.1380/jsssj.38.18

CiNii Books

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

Independently controlling the shape anisotropy and chemical composition of multinary semiconductor particles is important for preparing highly efficient photo catalysts. In this study, we prepared ZnS-AgInS2 solid solution ((AgIn)(x)Zn2(i1-)S2, ZAIS) nanoparticles with well-controlled anisotropic shapes, rod, and rice shapes, by reacting corresponding metal acetates with a mixture of sulfur compounds with different reactivities, elemental sulfur, and 1,3-dibutylthiourea, via a two-step heating-up process. The chemical composition predominantly determined the energy gap of ZAIS particles: the fraction of Zn2+ in rod-shaped particles was tuned by the ratio of metal precursors used in the nanocrystal formation, while postpreparative Zn2+ doping was necessary to increase the Zn2+ fraction in the rice-shaped particles. The photocatalytic H-2 evolution rate with irradiation to ZAIS particles dispersed in an aqueous solution was significantly dependent on the chemical composition in the case of using photocatalyst particles with a constant morphology. In contrast, photocatalytic activity at the optimum ZAIS composition, x of 0.35-0.45, increased with particle morphology in the order of rice (size: ca. 9 X ca. 16 nm) < sphere (diameter: ca. 5.5 run) < rod (size: 4.6 X 27 nm). The highest apparent quantum yield for photocatalytic H-2 evolution was 5.9% for rod-shaped ZAIS particles, being about two times larger than that obtained with spherical particles.

DOI： 10.1021/acsami.6b10408

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Language：English   Publishing type：Part of collection (book)   Publisher：wiley  

DOI： 10.1002/9783527693283.ch9

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

An effective preparation method of Au nanoparticles (NPs) is presented, wherein an arc plasma deposition technique is combined with ionic liquids (ILs) used as capture media. This method requires no chemical reaction. By selecting ILs, size-controlled Au NPs are produced easily and on a massive scale. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2016.06.044

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

We have investigated the electronic structures and optical properties of Fe, Co, and Ni ferrocyanide nanoparticles using first-principles relativistic many-electron calculations. The overall features of the theoretical absorption spectra for Fe, Ni, and Co ferrocyanides calculated using a first-principles many-electron method well reproduced the experimental one. The origins of the experimental absorption spectra were clarified by performing a configuration analysis based on the many-electron wave functions. For Fe ferrocyanide, the experimental absorption peaks originated from not only the charge-transfer transitions from Fe2+ to Fe3+ but also the 3d-3d intra-transitions of Fe3+ ions. In addition, the spin crossover transition of Fe3+ predicted by the many-electron calculations was about 0.24 eV. For Co ferrocyanide, the experimental absorption peaks were mainly attributed to the 3d-3d intra-transitions of Fe2+ ions. In contrast to the Fe and Co ferrocyanides, Ni ferrocyanide showed that the absorption peaks originated from the 3d-3d intra-transitions of Ni3+ ions in a low-energy region, while from both the 3d-3d intra-transitions of Fe2+ ions and the charge-transfer transitions from Fe2+ to Ni3+ in a high-energy region. These results were quite different from those of density-functional theory (DFT) calculations. The discrepancy between the results of DFT calculations and those of many-electron calculations suggested that the intra-and inter-atomic transitions of transition metal ions are significantly affected by the many-body effects of strongly correlated 3d electrons. Published by AIP Publishing.

DOI： 10.1063/1.4954070

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

A novel strategy to prepare a bimetallic Au-Pt particle film was developed through sequential sputter deposition of Au and Pt on a room temperature ionic liquid (RTIL). Au sputter deposition onto an RTIL containing hydroxyl-functionalized cations produced a monolayer of Au particles 4.2 nm in size on the liquid surface. Subsequent Pt sputtering onto the original Au particle monolayer floating on the RTIL enabled decoration of individual Au particles with Pt metals, resulting in the formation of a bimetallic Au-Pt particle monolayer with a Pt-enriched particle surface. The particle size slightly increased to 4.8 nm with Pt deposition for 120 min. The shell layer of a bimetallic particle was composed of Au-Pt alloy, the composition of which was tunable by controlling the Pt sputter deposition time. The electrochemical surface area (ECSA) was determined by cyclic voltammetry of bimetallic Au-Pt particle monolayers transferred onto HOPG electrodes by a horizontal liftoff method. The Pt surface coverage, determined by ECSAs of Au and Pt, increased from 0 to 56 mol % with elapse of the Pt sputter deposition time up to 120 min. Thus-obtained Au-Pt particle films exhibited electrocatalytic activity for methanol oxidation reaction (MOR) superior to the activities of pure Au or Pt particles. Volcano-type dependence was observed between the MOR activity and Pt surface coverage on the particles. Maximum activity was obtained for Au-Pt particles with a Pt coverage of 49 mol %, being ca. 120 times higher than that of pure Pt particles. This method enables direct decoration of metal particles with different noble metal atoms, providing a novel strategy to develop highly efficient multinary particle catalysts.

DOI： 10.1021/acsami.6b01978

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

Language：Japanese  

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

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

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

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

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

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

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

Rod-shaped AgInTe2 nanocrystals (NCs) exhibiting intense nearband edge photoluminescence in the near-infrared (NIR) wavelength region, were successfully prepared by the thermal reaction of metal acetates and Te precursors in 1-dodecanethiol. Increasing the reaction temperature resulted in the formation of larger AgInTe2 NCs with crystal structures varying from hexagonal to tetragonal at reaction temperatures of 280 degrees C or higher. The energy gap was increased from 1.13 to 1.20 eV with a decrease in rod width from 8.3 to 5.6 nm, accompanied by a blue shift in the photoluminescence (PL) peak wavelength from 1097 to 1033 nm. The optimal PL quantum yield was approximately 18% for AgInTe2 NCs with rod widths of 5.6 nm. The applicability of AgInTe2 NCs as a NIR-emitting material for in vivo biological imaging was examined by injecting AgInTe2 NC-incorporated liposomes into the back of a C57BL/6 mouse, followed by in vivo photoluminescence imaging in the NIR region.

DOI： 10.1039/c5nr07532g

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Scopus

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

CiNii Books

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

Oxidation of molten In-Sn alloys was carried out in ionic liquids by heat treatment with vigorous stirring, resulting in the formation of indium tin oxide (ITO) nanocrystals. The ITO nanocrystals exhibited a plasmon peak, the peak wavelength of which was blue-shifted with an increase in the Sn fraction in ITO.

DOI： 10.1039/c6cc06517a

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Scopus

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

Ternary I-III-VI semiconductor nanocrystals have been explored as non-toxic alternatives to II-VI semiconductors for optoelectronic and sensing applications, but large photoluminescence spectral width and moderate brightness restrict their practical use. Here, using single-particle photoluminescence spectroscopy on nanocrystals of (AgIn)(x)Zn2(1-x)S2 we show that the photoluminescence band is inhomogeneously broadened and that size distribution is the dominant factor in the broadening. The residual homogeneous linewidth of individual nanocrystals reaches up to 75% of the ensemble spectral width. Single nanocrystals undergo spectral diffusion which also contributes to the inhomogeneous band. Excitation with two lasers with energies above and below the bandgap reveals coexistence of two emitting donor states within one particle. Spectral diffusion in such particles is due to temporal activation and deactivation of one such state. Filling of a trap state with a lower-energy laser enables optical modulation of photoluminescence intermittency (blinking) and leads to an almost two-fold increase in brightness.

DOI： 10.1039/c6nr03950b

Web of Science

Language：Japanese   Publisher：The Surface Science Society of Japan  

DOI： 10.14886/sssj2008.36.0_105

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

Simultaneous control of the size and chemical composition is an advantageous strategy to obtain the desired photochemical properties of multinary semiconductor nanocrystals, ZnS-AgInS2 solid solution ((AgIn)(x)Zn2(1-x)S2, ZAIS) nanocrystals (NCs), being different from conventional binary nano crystals. The energy gap (E-g of ZAIS NCs was enlarged with a decrease in particle size due to the quantum size effect or with an increase in ZnS content in the ZAIS solid solution. The levels of the conduction band edge and valence band edge, determined by photoelectron spectroscopy in air, were shifted more negatively and more positively, respectively, with an increase in Eg. A volcano-type dependence was observed between the PL quantum yield (QY) and the size of ZAIS NCs, in which the optimal PL QY for each x value was obtained at a similar particle size around 5-6 nm, except for x = 1.0, and maximum QY was recorded to be 79% for ZAIS NCs prepared with x = 0.5. The photocatalytic activity for H-2 evolution was also greatly dependent on both the size and the chemical composition of ZAIS NCs, and then the highest activity was observed for ZAIS NCs having an average diameter of about 4.2-5.5 nm and E-g of 2.3-2.4 eV. This can be reasonably explained by the enlargement of the driving force to reduce protons in the solution with a negative shift of the conduction band edge of ZAIS NCs and by the quenching of photoexcited ZAIS NCs with an increase in the amount of surface defect sites and/or with the formation of deeper trap sites along with a decrease in the particle size.

DOI： 10.1021/acs.jpcc.5b07994

Web of Science

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

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

Language：Japanese  

DOI： 10.4011/shikizai.87.430

Language：Japanese  

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

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

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

Sputtering of noble metals, such as Au, Ag, Pd, and Pt, onto room-temperature ionic liquids (RTILs) enabled the formation of monoparticle films composed of spherical noble metal nanoparticles on the liquid surface only when the RTILs used contained hydroxyl-functionalized cations as a component. Sputter deposition of these metals under the same conditions simply produced well-dispersed metal particles without the formation of any films on the solution surface when pure RTILs with non-functionalized cations were employed. Anionic species, even those containing a hydroxyl group, did not significantly affect the formation of the particle film on the RTIL surface or dispersion of particles in the solution. The size of Au particles could be controlled by varying the sputtering condition regardless of the two-dimensional particle density, which was determined by the composition of RTILs used. An Au monoparticle film on the RTIL surface was easily transferred onto various solid substrates via the horizontal liftoff method without large aggregation even when the substrate surface was highly curved.

DOI： 10.1039/c5cp01602a

Web of Science

Scopus

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

Wurtzite-type copper zinc tin sulfide (Cu2ZnSnS4) nanoparticles were prepared in dodecanethiol (DDT) solutions by reacting corresponding metal acetates with a mixture of sulfur compounds with different reactivities, elemental sulfur (S) and dibutylthiourea (DBTU), via a two-step heat treatment. Initial heating at 200 degrees C enabled the nucleation of metal sulfide nanoparticles composed of two crystal phases, and subsequent heat treatment at 240 degrees C resulted in the formation of Cu2ZnSnS4 nanoparticles with a wurtzite-type crystal structure. The resulting particles had rod shapes with a stoichiometric composition, the size and shape of which could be controlled by changing both the reaction time and the molar ratio of S and DBTU used in a sulfur precursor. In contrast, spherical Cu2ZnSnS4 nanoparticles with a kesterite-type crystal structure were produced by reaction with pure S as a precursor. The electronic energy levels of the conduction band and valence band edges were determined for wurtzite-type Cu2ZnSnS4 nanoparticles by photoelectrochemical measurement, the individual levels being comparable to those of kesterite-type ones. The light-electricity conversion efficiency varied remarkably depending on the kind of crystal structure: wurtzite-type Cu2ZnSnS4 particles exhibited an efficiency superior to that of the particles with a kesterite-type crystal structure.

DOI： 10.1039/c4ce01852d

Web of Science

Scopus

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

The surface coating of metal nanoparticles resulting into core-shell structures is expected to improve the physicochemical properties of the nanoparticle cores without changing their size and shape. Here, we developed a novel strategy to coat Au, AuPd or Pt catalyst cores having average sizes smaller than 2.5 nm, which were pre-synthesized in ionic liquids by corresponding metal sputtering, with an extremely thin In2O3 layer (ca. &lt;1.5 nm) by sputter deposition of indium in a room-temperature ionic liquid. The metal cores of Au or AuPd in core-shell particles exhibited superior stability against heat treatments or during electrocatalytic reactions compared to the corresponding bare metal particles. The In2O3 shell coating considerably enhanced the durability of electrocatalytically active Pt particles (1.2 nm). This sequential metal sputter deposition of different metals in ionic liquids will considerably contribute to the exploitation of key nanostructured components for next-generation energy-conversion systems.

DOI： 10.1039/c4ta06643j

Web of Science

Scopus

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

IIIIVI2-semiconductor-based nanocrystals of ZnSeAgInSe2 solid solution ((AgIn)(x)Zn2(1-x)Se2, ZAISe) with average sizes of 3.5-6.2 nm were successfully synthesized through thermal reaction of corresponding metal acetates and selenourea in a hot oleylamine solution. The optical property of ZAISe solid solution nanocrystals was tunable in a broad wavelength region from visible to near-infrared light by changing the composition of solid solution, where the energy gap of ZAISe nanocrystals was enlarged from 1.44 to 3.00 eV with an increase in the fraction of ZnSe in ZAISe, that is, with a decrease in x from 1.0 to 0. Both levels of conduction band and valence band edges, determined by photoelectron spectroscopy in air, were monotonously shifted to higher levels with an increase in the fraction of ZnSe. Quantum-dot-sensitized solar cells were fabricated with porous TiO2 film electrodes immobilized with ZAISe nanocrystals using 3-mercaptopropionic acid as a cross-linking agent. The light conversion efficiency of the thus-obtained cells was enhanced by covering ZAISe nanocrystals with a CdS thin layer by the SILAR method. The photocurrent action spectra agreed well with absorption spectra of ZAISe nanocrystals immobilized on TiO2 electrodes. Maximum energy conversion efficiency of 1.9% was obtained for the cell fabricated with ZAISe nanocrystals with x = 0.5 as a sensitizer under irradiation with simulated solar light of AM 1.5G.

DOI： 10.1021/jp508769f

Web of Science

Scopus

Language：Japanese  

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

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/ppsc.201400054

Web of Science

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

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

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

Over the past decade, many researchers have made efforts to develop high-quality I-III-VI2 group chalcopyrite-type semiconductor nanoparticles of Cu-based or Ag-based materials, such as CuInS2 Cu(InGa)Se-2, and AgInS2, due to their low toxicity, wide range of absorption from UV to visible or near-infrared regions, and tunable energy gap depending on the chemical composition. Ag-based chalcopyrite-type nanoparticles have attracted much attention because they have physicochemical properties that can be controlled in a manner similar to that for Cu-based nanoparticles but can be synthesized easily under milder reaction conditions than those of Cu-based ones. In this Perspective, we review recent works relating to the preparation of low-toxic nanoparticles of Ag-based chalcopyrite-type semiconductors and their solid solutions, and then we introduce their application as photofunctional materials. Tunability of optical properties has considerably contributed to recent advances in photofunctional applications of chalcopyrite-type semiconductor nanoparticles to sensors, photocatalysts, and solar cells.

DOI： 10.1021/jz402378x

Web of Science

Scopus

Language：Japanese  

Language：Japanese  

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

CiNii Books

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

CiNii Books

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Luminescent semiconductor nanoparticles have been applied to temperature measurements, because their emission is intense and the emission wavelength can be adjusted by particle size. However, most of luminescent nanoparticles contain highly toxic elements such as Cd, Se, and Te. In this study, the temperature characteristics of a new low-toxic luminescent nanoparticles, ZnS-AgInS2 (ZAIS), have been investigated. The temperature sensitivity of luminescent intensity of ca. -1 %/K was comparable to other luminescent nanoparticles. The thermally induced red shift of ca. 0.1 nm/K was observed, which is similar to other nanoparticles. The measurement revealed that the oxygen sensitivity of ZAIS is negligibly small. It is also shown that ZAIS nanoparticles are photostable compared with CdSe/ZnS. As a result, ZAIS is one of the most preferable candidates to take the place of other toxic nanoparticles especially for bio-related experiments. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2012.09.005

Web of Science

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

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

Size-selective photoetching enabled precise size control of chalcopyrite AgInS2 nanoparticles in a basic aqueous solution containing ammonia by selecting the wavelength of monochromatic irradiation light in the range between 650 and 520 nm. The energy gap of the photoetched particles was enlarged from 1.8 to 2.4 eV with a decrease in particle size from 5.1 to 2.7 nm due to the quantum size effect, while the crystal structure and chemical composition of the particles were unchanged after the photoetching processes. AgInS2 nanoparticle-immobilized electrodes exhibited an anodic photocurrent similar to that of n-type semiconductors, the onset potential of which was negatively shifted with a decrease in particle size. Potentials of the conduction band edge (E-CB) and the valence band edge (E-VB) of AgInS2 nanoparticles were estimated from their photoelectrochemical measurements, and they exhibited remarkable size dependence: with a decrease in particle size from 5.1 to 2.7 nm, E-CB was shifted negatively from -0.6 to -1.0 V vs Ag/AgCl, accompanied by a positive shift of E-VB from 1.3 to 1.7 V vs Ag/AgCl.

DOI： 10.1021/jp307305q

Web of Science

Scopus

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

Ag2ZnSnS4 (AZTS) nanoparticles were successfully synthesized at relatively low temperature via thermal reaction of corresponding metal acetates and a sulfur source in a hot oleylamine solution, the purity of the particles being dependent on the amount of metal acetates and the reaction temperature. The obtained pure AZTS particles with size of ca. 15 nm exhibited photoresponse with visible light irradiation similar to that of n-type semiconductors.

DOI： 10.1246/cl.2012.1009

Web of Science

Scopus

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

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

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

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

Non-stoichiometric AgInS2 (AIS) semiconductor particles were synthesized by the thermal decomposition of single-source precursors in solutions of two kinds of primary amines (oleylamine and octylamine). The Ag content in the resulting nanoparticles was controlled by adjusting the chemical composition of the precursor used, in which the mole ratio of Ag+ to total metal ions was varied from 0.1 to 0.7, resulting in the production of non-stoichiometric AIS particles with varying amounts of Ag vacancies. The average size of AIS particles was slightly decreased from 4.3 to 3.8 nm on changing the solvent from oleylamine to octylamine in the preparation, while the particle size seemed to be constant regardless of the content of Ag. On the other hand, the optical properties of AIS particles were considerably modified depending on the Ag content in the particles. The absorption onset was blue-shifted from 750 to 580 nm with a decrease in the Ag content, due to the enlargement of the energy gap of particles. Intense photoluminescence originating from the donor-acceptor pair recombination was observed for each kind of AIS particle and then the photoluminescence peak wavelength was also blue-shifted from 830 to 650 nm, being similar to the behavior of the absorption onset. The maximum photoluminescence quantum yield was ca. 70% for octylamine-modified AIS nanoparticles having a ratio of Ag+ to total metal ions of 0.37, which probably contained the optimum amount of Ag vacancies acting as the sites of donor-acceptor pair recombination with few surface defect sites for non-radiative recombination.

DOI： 10.1039/c2jm31463k

Web of Science

Scopus

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

Irradiation with a nanosecond pulse laser (lambda = 532 nm) was performed on spherical hollow silica particles modified with gold nanoparticles to photoexcite the localized surface plasmon resonance, resulting in the formation of pores on the shell wall accompanied with the fragmentation of the original Au particles to much smaller ones. The size of pores was tunable from 17 to 56 nm by varying the size of original Au particles on SiO2 shell from 6 to 39 nm.

DOI： 10.1246/cl.2011.1411

Web of Science

Language：English  

Web of Science

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

Inorganic semiconductor multilayer thin films of CdS nanoparticles and titania nanosheet (TNS) were prepared by an electrostatic layer-by-layer accumulation technique. The absorbance of immobilized CdS and TNS linearly increased in proportion to the number of accumulated films, but the photoluminescence of CdS nanoparticles was dramatically quenched by being tucked into the TNS layer. Accumulation of the TNS/CdS layer remarkably enhanced the photocurrent generation compared to the case of films layer-by-layer-deposited with CdS nanoparticles and polystyrene sulfonate of an inert polymer. These observations can be explained by the efficient photoinduced electron transfer from photoexcited CdS nanoparticles to adjacent TNS layers.

Web of Science

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

Nanocomposite photocatalysts of CdS nanoparticles immobilized on Au core-SiO2 shell particles, in which the SiO2 layer acts as an insulator layer to prevent direct electron transfer from photoexcited CdS to Au particles, were prepared. The photocatalytic activity of CdS particles for H-2 evolution was greatly dependent on the distance between CdS and Au particles, due to the locally enhanced electric field produced by photoexcitation of the localized surface plasmon resonance (LSPR) peak of Au particles. Increase in Au core size enlarged the optimal distance between Au and CdS for the enhancement of photocatalysis. This behavior was theoretically reproduced by solving a self-consistent equation system, in which the range of energy dissipation became wider for larger diameter of the Au sphere, and then the balance with the enhancement of photoexcitation of CdS particles by the LSPR-induced electric field was changed.

DOI： 10.1021/jz2009049

Web of Science

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Multilayer films composed of Au particle/titania nanosheet (TNS)/CdTe nanoparticle were successfully prepared using a layer-by-layer-deposition technique. CdTe nanoparticles were accumulated as the topmost layer on TNS/poly(diallyldimethylammonium) (PDDA) bilayers deposited on the substrates of an Au particle film or an F-doped SnO2 (Fro) electrode. CdTe nanoparticles were acted as a photosensitizer. The photogenerated electrons in CdTe nanoparticles were injected into the conduction band of titania nanosheets to produce anodic photocurrent at a more positive potential than 0.4 V vs. Ag/AgCl. The magnitude of photocurrent was much larger for the films prepared on the Au particle film rather than that on the FTO electrode. Furthermore, with an increase in the thickness of (TNS/PDDA) bilayers, that is, the distance between Au and CdTe nanoparticles, the photocurrent was drastically decreased. The enhancement factor of photocurrent, defined as the ratio of the magnitude of photocurrent obtained with CdTe particle layer immobilized on Au layer to that on FTO, was varied from 2 to 10 by changing the wavelength of irradiation light. The broad peak at 520 nm appeared in the action spectrum of the enhancement factor and its profile roughly corresponded to the localized surface plasmon resonance peak of Au particle layer whose peak wavelength was ca. 540 nm. These facts indicated that the photoexcitation of the surface plasmon of Au particles, which produced a locally enhanced electric field near Au particle layer, played an important role in the increase in the photoexcitation probability of CdTe nanoparticles deposited as the topmost layer. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jphotochem.2011.02.029

Web of Science

Scopus

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

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

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

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

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

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

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

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

Colloidal Cu2ZnSnS4 (CZTS) nanoparticles with sizes of 5-6 nm that contain no highly toxic elements were successfully synthesized through thermal reactions of metal acetate and sulfur in high-temperature oleylamine solution. The reaction temperature was a key factor for the synthesis of CZTS nanoparticles: synthesis at temperatures higher than 240 degrees C gave a pure CZTS crystal phase, whereas a secondary phase of CuS was formed at reaction temperatures lower than 180 degrees C. Nanoparticles were successfully accumulated on ITO-coated or quartz glass substrates via layer-bylayer deposition using 1,2-ethanedithiol as a cross-linking agent. The resulting CZTS particle films exhibited a photoresponse similar to that of p-type semiconductor photoelectrodes in an aqueous solution containing Eu(NO3)(3) as an electron scavenger. Potentials of the valence band edge and conduction band edge were determined from the onset potential of the cathodic photocurrent to be +0.3 and -1.2 V vs. Ag/AgCl, respectively.

DOI： 10.1039/c0jm00454e

Web of Science

Scopus

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

Gold (Au) nanoparticles were prepared by sputter deposition of Au metal in an ionic liquid (IL) of 1-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF6). The size of Au nanoparticles was increased from 2.6 to 4.8 nm by heat treatment at 373 K. The nanoparticles uniformly dispersed in the IL were densely immobilized on a glass substrate surface modified with a silane coupling agent having an imidazole functional group by spreading the Au particle IL solution on the substrates, followed by heat treatment at 373 K. The optical property of the thus-obtained films was tunable by controlling the size of Au nanoparticles in the IL and the degree of immobilization. An intense localized surface plasmon resonance (LSPR) peak was observed in each Au particle film, and the wavelength of the LSPR peak could be controlled by changing the size of nanoparticles in the IL solution before immobilization. Photoexcitation of the LSPR peak caused enhancement of the photoluminescence of CdTe nanoparticles immobilized on Au nanoparticle films, probably due to the locally enhanced electric field formed around Au nanoparticles.

DOI： 10.1039/b914230d

Web of Science

Scopus

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

The photoluminescence intensity of ZnS-AgInS2 solid solution nanoparticles was remarkably enhanced by increasing the heating temperature to 180 degrees C, above which the emission was simply diminished, while ZnS coating of the particles resulted in further enhancement of PL intensity, giving the highest quantum yield of ca. 80%.

DOI： 10.1039/b924186h

Web of Science

Scopus

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

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

Inorganic multilayer films were prepared by layer-by-layer accumulation of positively charged layered double hydroxide (LDH) nanosheets and negatively charged CdS nanoparticles of different sizes. Nanoparticles were densely immobilized on LDH sheets to form a monolayer without coalescence into larger particles. The absorbance and photoluminescence intensity of immobilized CdS particles were enlarged with an increase in the accumulation number of the film. Hybrid films produced by accumulation of both monolayers of CdS particles (diameter: 5 nm) and those of smaller CdS particles (2.1 nm) exhibited characteristic photoluminescence spectra indicating the efficient energy transfer of photogenerated excitons from nanoparticle layers of smaller CdS particles to those of larger ones. LDH/CdS multilayers deposited on an F-doped SnO2 (FTO) electrode behaved as an n-type semiconductor photoelectrode in an acetonitrile solution regardless of the size of the CdS particles immobilized, but their efficiency for photocurrent generation was greatly dependent on the stacked structure of the films. Accumulation of CdS particles of 2.1 nm in diameter on pre-coated LDH/CdS layers of 5 nm-sized CdS particles on FTO remarkably enhanced the photocurrent intensity in comparison to that in the case of accumulation of these two kinds of CdS particles in the opposite sequence. These observations can be explained by photoinduced electron transfer and energy transfer along with the band gap gradient in the films.

DOI： 10.1039/b902023c

Web of Science

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

Multilayer films of layered double hydroxide (LDH) nano-sheets and semiconductor nanoparticles of ZnS-AgInS2 solid solution (ZAIS) or US were prepared by a layer-by-layer deposition technique. The photoluminescence properties were remarkably dependent on the stacked structure of the films owing to the energy transfer from US to ZAIS nanoparticles.

DOI： 10.1246/cl.2008.700

Web of Science

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

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

Language：English  

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WORLD SCI PUBL CO INC  

Nano-ordered hybrid films of layered double hydroxide (LDH) nanosheets and two types of anionic dye molecules, i.e. tetrakis(4-carboxyphenyl)porphyrin (TCPP) and 1,3,6,8-pyre-netetrasulfonic acid (PTSA), were prepared by a layer by-layer deposition (LBL) method. Photo-induced energy transfers (PET) between the PTSA and TCPP layers were investigated for two differently stacked structures of the TCPP/LDH/PTSA hybrid films, Le; (a) PTSA/LDH multilayers independently stacked on the TCPP/LDH multilayers to form (TCPP/LDH)(n)/(PTSA/LDH)(n) and (b) TCPP/ LDH and PTSA/LDH monolayers deposited alternately to form [(TCPP/LDH)/(PTSA/LDH)](n) hybrid films, which were both prepared by varying the successivie-and alternate stacking of-the (TCPP/LDH) and (PTSA/LDH) unit layers. A Foerster type resonance energy transfer is observed in the present hybrid films, where the efficiency of PET was strongly affected by changing the distance between the TCPP and PTSA molecules in the (TCPP/LDH)(3)/(PSS/LDH)(m)/(PTSA/LDH)(3) hybrid films (m = 1-10) obtained by the insertion of the photochemically inert poly (styrenesulfonic acid) (PSS) and LDH hybrid layers, i.e. the insertion of (PSS/LDH). between the (TCPP/LDH), and (PTSA/LDH), layers. Copyright (C) 2007 Society of Porphyrins & Phthalocyanines.

DOI： 10.1142/S1088424607000485

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Responsible for pages：223-237   Language：English

DOI： 10.1007/978-981-15-5451-3_13

Language：English Book type：Scholarly book

J-GLOBAL

J-GLOBAL

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：Royal Society of Chemistry  

Rod-shaped nanocrystals (NCs) composed of ZnTe-AgInTe2 solid solution ((AgIn)xZn2(1-x)Te2, ZAITe) were synthesized in a 1-dodecanethiol solution. The resulting ZAITe NCs of 4-5 nm in width and 16-18 nm in length showed exciton peaks in the absorption spectra, regardless of their composition. The energy gap was enlarged from 1.2 to 1.6 eV by decreasing the x value of the NCs from 1.0 to 0.25. A sharp photoluminescence (PL) peak was observed in each PL spectrum of the NCs with x values of 1.0-0.5, assignable to band-edge emission, while NCs with x = 0.25 showed an additional broad PL peak originating from the defect sites due to the increased non-stoichiometry of NCs. With a decrease in x from 1.0 to 0.25, the band-edge PL peak was blue-shifted from 1010 to 809 nm in the near-IR region, accompanied by a decrease in the corresponding PL quantum yield from 47% to 0.07% due to the diminution of radiative recombination rate.

DOI： 10.1039/c7tc05624a

Scopus

Language：Japanese  

J-GLOBAL

J-GLOBAL

J-GLOBAL

J-GLOBAL

J-GLOBAL

J-GLOBAL

J-GLOBAL

J-GLOBAL

J-GLOBAL

Language：Japanese  

CiNii Books

Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)   Publisher：日本化学会  

CiNii Books

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