Fumiyuki Shiba

Size control of monodisperse Au nanoparticles synthesized via a citrate reduction process associated with a pH-shifting procedure

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.

Effect of the filtration of PbI2 solution for zinc oxide nanowire based perovskite solar cells

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 0.79 V and fill factor of 0.63.

Hydrothermal synthesis of one-dimensional yttrium hydroxide particles by a two-step alkali-addition method

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 ∼ 6.8 for a few minutes before raising the pH to the sufficient level (pH ∼ 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.

Size Control of Monodisperse Prussian Blue Nanoparticles by Enforced-Nucleation and Additional-Growth Procedures in a Citrate Reduction System

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 20−100 nm in the mean size with narrow size distribution.

Controlling the shape of wedge-like α-GaOOH particles formed by a hydrolysis process using sodium acetate as a growth modifier

Nearly monodisperse, single-crystalline gallium oxide hydroxide particles have been synthesized via a hydrolysis process in the presence of sodium acetate, under acidic conditions, at 70 °C. The presence of sodium acetate resulted in the formation of α-GaOOH particles shaped in the form of wedges, bound by four {110} and eight {212} faces (orthorhombic, Pbnm space group). Varying the sodium acetate concentration enabled us to control the shape of the wedge-like particles, by suppressing growth along the c-axis.