柴 史之

The unique morphology was spontaneously constructed during precipitation under acidic conditions without specific growth modifiers.

One-dimensional hydroxyapatite (1D-HAP) particles were synthesized via a hydrothermal process using calcium sodium nitrilotriacetate (CaNa-NTA) as a Ca2+ reservoir. CaNa-NTA dissolved slowly at 150°C to enable Ca2+ to be supplied to the aqueous phase to react with phosphate and hydroxide ions. The average length and width of the 1D-HAP particles were 6.0μm and 60 nm, respectively the former depended on the amount of CaNa-NTA loaded but the latter did not. We investigated the formation of 1D-HAP particles by powder X-ray diffraction measurement and electron microscopy observation.

Zinc oxide (ZnO) nanowires (NWs) are grown on fluorine-doped tin oxide (FTO) glass substrates via a simple reactive evaporation method without the presence of any catalysts or additives. The ZnO NWs show high crystallinity and preferential elongation along the c-axis of the hexagonal wurtzite crystal structure. The highly crystalline NWs as electron transporting layer have been used to fabricate the CH3NH3PbI3 perovskite solar cells and their photovoltaic performance were investigated. In this report, we studied the effect of filtration of PbI2-solution on surface morphology of CH3NH3PbI3 layer. Spin-coating of the filtered PbI2-solution leads to a better crystallization and relatively homogenous coverage of the CH3NH3PbI3 film, resulting in an enhancement of the solar cell efficiency compared to the cell fabricated using non-filtrated PbI2-solution. By synthesizing the CH3NH3PbI3 film using filtrated PbI2-solution, we achieved the best power conversion efficiency of 4.8% with a current density of 7.6 mA cm(-2), the open circuit voltage of 0.79V and fill factor of 0.63. (C) 2016 The Japan Society of Applied Physics

Synthesis procedures of monodisperse Prussian blue nanoparticles have been investigated to control their size in a citric acid reduction system. Two different procedures, enforced-nucleation and additional-growth ones, are applied to decrease and to increase the particle size, respectively. In the former, small amount of ascorbic acid is added in the citric acid solution as the enforced-nucleation agent, which varies the number of nuclei and thus the particle size depending on its amount. In the latter, a part of Prussian blue dispersion preliminarily prepared is introduced into the reactant solution that provides additional reaction resources for the further growth. As a result, Prussian blue nanoparticles are prepared in the range of 20-100nm in the mean size with narrow size distribution.

A reagentless electrochemical biosensor for hydrogen peroxide was fabricated. The sensor carries a monolayer of nanocomplex composed of horseradish peroxidase and Au-nanoparticle, and responds to hydrogen peroxide through the highly efficient direct electron transfer at a mild electrode potential without any soluble mediator. Formation of the nanocomplex was studied with visible spectroscopy and size exclusion chromatography. The sensor performance was analyzed based on a hydrodynamic electrochemical technique and enzyme kinetics. The sensor was applied to fabrication of sensors for glucose and uric acid through further modification of the nanocomplex-carrying electrode with the corresponding hydrogen peroxide-generating oxidases, glucose oxidase and urate oxidase, respectively.

One-dimensional yttrium hydroxide particles of hexagonal crystal structure were selectively synthesized through a hydrothermal reaction of yttrium chloride solution that was alkalized by two-step addition of sodium hydroxide solution. Keeping the YCl3 solution at pH similar to 6.8 for a few minutes before raising the pH to the sufficient level (pH similar to 13) was concluded to be the practical requirement for the one-dimensional Y(OH)(3) particle formation. This requirement was successfully achieved by the two-step addition procedure that was applicable to adjust the pH values independently. The size distribution of one-dimensional particles was changed depending on the interval time between alkali-additions and on the pH of the hydrothermal reaction. The formation mechanism of the one-dimensional particles was also discussed.

This report proposes a procedure to synthesize monodisperse Au nanoparticles of different mean sizes (6-15 nm) under a constitute reaction condition only by altering the interval time between additions of citric acid and NaOH solutions into boiling HAuCl4 solution without any growth modifiers.

A procedure to obtain monodisperse nanoparticles of cobalt(1) hexacyanoferrate(III) was investigated. To prevent a reaction with [Fe(CN)(6)](3-), Co2+ was stored in the form of a citrate complex at pH 7.8. By lowering the pH to 3.4 by the addition of acid, part of the Co2+ was released and reacted with [Fe(CN)(6)](3-) to form nuclei, followed by their growth via mass-transfer of Co2+ from the citrate complex to the solid. Here, gelatin was employed as a protective colloid. The particles obtained were cubic and fairly monodisperse. The mean particle size was typically 160 nm and varied from 30 to 450 nm, depending on the reactant contents. The formation mechanism associated with equilibrium shifts was supported by a calculated estimation of free Co2+ on the basis of the equilibrium relationships involved in the preparation system.

A new procedure to prepare monodisperse Prussian blue nanoparticles was investigated. Using gelatin as a protective colloid, citric acid solution was added to the starting solution containing Fe(NO(3))(3), K(3)Fe(CN)(6), and HNO(3). where the acid was added to avoid cross-linking among gelatin molecules to coagulate by Fe(CN)(6)(3-) ions. Monodisperse Prussian blue nanoparticles having 70 nm of mean size were obtained via reduction reaction of Fe(3+) by citric acid at 35 degrees C. The XRD pattern was in good agreement with the face-centered cubic structure with 10.15 angstrom of lattice parameter. The crystallite size estimated from the XRD peak with Scherrer equation was 32 nm, suggesting polycrystalline structure of the particles. Effect of citric acid concentration was also evaluated. The linear time increase of particle size and 94 kJ mol(-1) of the activation energy for the growth process suggest that the growth of Prussian blue nanoparticles was controlled by surface reaction process in the present system. (C) 2010 Elsevier B.V. All rights reserved.

Heating the mixture of ZnS precipitate and ethylene glycol at 328K for 24h formed a stable sol with homogeneous dispersion of ZnS nanoparticles. According to TEM image of the ZnS particles in the obtained sol, the average particle size was 3.8 nm. The formation process was examined by measuring the change in the UV-vis absorption spectra of the mixed solution with increases in the heating time. When the heating temperature was 408K. the shift in the absorption edge due to the band gap transition of ZnS to a longer wavelength was observed with increases in the heating time. This shift of absorption edge indicated that the growth process occurred in the sol during the heating process. On the other hand, the qualitative analysis of the concentration of Zn(2+) ions in the sol showed the presence of the dissolving process of the ZnS nanoparticles. Therefore, the dissolution precipitation process in the mixed solution of the ZnS precipitate and ethylene glycol played an important role in the formation of the homogeneous sol. (C) 2010 Elsevier B.V. All rights reserved.

A novel electrochemical biosensor for hydrogen peroxide with high electron transfer efficiency was developed using a nanocomplex composed of horseradish peroxidase and Au-nanoparticle. The nanocomplex was prepared through adsorption of horseradish peroxidase on an Au-nanoparticle. The nanocomplexes were easily coagulated and immobilized on an ITO electrode as a monolayer film by simply casting the nanocomplex dispersion and drying below 10 degrees C. The electrode worked as a hydrogen peroxide biosensor featuring high electron transfer efficiency without any soluble mediator at a mild electrode potential of +0.15V vs. Ag/AgCl.

Supersaturation ratio, S, has been theoretically related to the supply rate of solute, Q, from growth rate and mass-balance equations in the quasi-steady state in the growth process of isotropic monodisperse particles. The derived equation, (S - 1) = (1/D + 1/kr)(Q/beta C(0)nr) + 2V(m)gamma/rRT, suggests a linear dependence of S on Q under constant n and r, where D is the diffusion coefficient, k is the rate constant for surface-reaction, C-0 is the solubility, n and r are the number and radius of growing particles, respectively, V-m is the molar volume of particles, R is the gas constant, T is the absolute temperature, and beta is the shape factor defined by beta equivalent to (1/r(2)) dv/dr, where v is the volume of an individual particle. The equation was applied to the analysis of growth kinetics and determinations of critical supersaturation ratio in monodisperse AgBr particles in the controlled double-jet system with the assistance of a potentiometric supersaturation measurement. In both cubic and octahedral particles, growth rates were completely limited by diffusion and surface-reaction at pBr (equivalent to -log[Br-]) 3.0 and 1.0, respectively, while the growths were intermediate of them at pBr 2.0 and 4.0. The growth parameters, DC0 and kC(0), were experimentally determined. Also, critical supersaturation ratio was estimated as 1.28 as an average in the present study.

The spontaneous nucleation process of monodispersed AgBr particles by gradual release of silver ions from a Ag+-gelatin complex was studied on the basis of the fundamental theory and analytical procedures for a AgCl system in the preceding report in this volume. The nucleation mechanism is basically the same as the AgCl system, in which the nucleation of the stable nuclei is governed by the growth of the generated stable nuclei and the final particle number n(infinity) is determined by the equation, n(infinity) = Q(o)V(M)/(upsilon)over dot, where Q(o) is the rate of increasing concentration of solute, V-m is the molar volume of the solid, and (upsilon)over dot is the volumic growth rate of a stable nucleus during the nucleation period. However, the final particle size in diameter was much smaller by a factor of 1/6 and the nucleation time was about 30 times longer than those in the AgCl system. This is mainly due to the much smaller (upsilon)over dot in the AgBr system as a result of the lower solubility of AgBr. (C) 2000 Elsevier Science B.V. All rights reserved.

Theoretical formulae for the final number density of the generated stable nuclei per unit volume, n(infinity), and duration of nucleation period, t(N), in the homogeneous system for the formation of monodispersed particles have been derived based on a nucleation model, in which a concept of growth-limited nucleation in the mass balance for consumption of furnished solute is introduced: n(infinity) = Q(0)V(m)/(upsilon)over dot and t(N) = upsilon(0)/upsilon, where Q(0) is the supply rate of the solute, V-m is the molar volume of the solid, and upsilon(0) and upsilon are the initial particle volume and mean volumic growth rate of the stable nuclei during the nucleation period, respectively. This theory has been developed to offer a theoretical background for the size control of monodispersed particles in closed systems. The equations were experimentally examined in the spontaneous nucleation of a monodisperse AgCl system containing silver ions as a gelatin complex, chloride ions, and diethyl sulfate, in which silver ions were gradually released from the gelatin by reduction of pH with hydrolysis of diethyl sulfate and the change of silver ion concentration was automatically monitored with a Ag2S-coated Ag electrode to follow the change of supersaturation for nucleation and growth of AgCl particles. In this experiment, the LaMer diagram has actually been visualized. Typical results are (upsilon)over dot = 2.62 x 10(3) nm(3) s(-1), upsilon(0) = 6.18 x 10(2) nm(3), and t(N) = 0.236 s under the standard conditions at 25 degrees C. The maximum supersaturation ratio, S-m, was found to be 3.56 under the standard conditions at 25 degrees C, leading to the radius and free energy of formation of a stable nucleus at the maximum supersaturation as r(m)* = 1.66 nm and Delta G(m)* = 1.16 x 10(-18) J, respectively. Effects of the content of diethyl sulfate, initial concentration of KCl, and reaction temperature on S-m, r(m)*, Delta G(m)*, (upsilon)over dot, upsilon(0), n(infinity), and t(N) were also examined. (C) 2000 Elsevier Science B.V. All rights reserved.

The characteristics of sol-gel transition of a mixture made by mixing two kinds of gelling agents of different nature, i.e. gelatin and carrageenan were examined. The sample solutions consisted of 3.00 wt % gelatin solution, 1.00 Wt % K-carrageenan solution and 4.00 wt % mixed solution which was prepared by mixing the said gelatin and carrageenan solutions in the ratio 3: 1. In the experiment, the optical rotation and the dynamic viscoelasticity were measured under the same temperature change program. As the sample solutions were cooled, the carrageenan solution started to show a change in the specific rotation in the first place, followed by the mixed solution and finally the gelatin solution. The gelatin and the mixed solutions had the same increasing tendency in the specific rotation, whereas the carrageenan solution changed a little. When the mixed solution was chilled to set, it turned into a highly elastic gel. In the mixed solution, the gelation of carrageenan was found to precede that of gelatin.

Based on the fundamental theory of interfacial energy in parts 1 (J. Colloid Interface Sci. 1996, 181, 259; 1996, 183, 299), 2, and 3, theoretical formulas have been derived for the specific interfacial energy gamma of solid-liquid interface changing with adsorption of the constituent anions or cations of the solid and foreign adsorbates to different crystal faces. Adsorption isotherms of silver and halide ions and experimental results for gamma obtained from potentiometry of silver ions on the basis of the Gibbs-Thomson effect in AgCl, AgBr, and AgI sol systems under the influence of the adsorption of the constituent halide ions and gelatin were analyzed in light of the theoretical formulas. Finally, the characteristics of the adsorption behavior of these species including the slight deviations from the theory have been discussed.

A new theoretical formula for the absolute value of the interfacial energy of the solid-liquid interface has been derived on the basis of the fundamental theory of interfacial energy described in J. Colloid Interface Sci. 1996, 181, 259; 1996, 183, 299. Namely, the intrinsic specific interfacial energy of a solid-liquid interface without adsorption is given by gamma = -N(sigma)lambda kT In x((infinity)), where N-sigma is the surface density of the surface monomers of the solid, ii is the ratio of the number of open bonding sites of a surface monomer to that of a free monomer, k is the Boltzmann constant, T is the absolute temperature, and x((infinity)) is the solubility of the bulk solid in terms of mole fraction of the monomers in the liquid phase against the total mole numbers of the solution components including the solvent molecules. Here, "monomer" refers to the minimum subunit of the solid such as AgCl, AgBr, etc. The formula has been collated to the experimental results of gamma for AgCl, AgBr, and AgI, determined by potentiometric measurement of the size-dependent solubilities of these silver halide particles with the Gibbs-Thomson equation. The experimental results were in excellent agreement with the theoretical values for the silver halides. Also, some fundamental problems were found to be involved in Tolman's theory for size dependence of gamma, and it has been deduced that gamma must be independent of particle size, as has been confirmed by experiment.