Visible-Light-Responsive Photocatalytic Activity Significantly Enhanced by Active [VZn+VO+] Defects in Self-Assembled ZnO Nanoparticles.

Defect influences on the photoactivity of ZnO nanoparticles prepared by a powdered coconut water (ACP) assisted synthesis have been studied. The crystalline phase and morphology of ZnO nanoparticles were effectively controlled by adjusting the calcination temperature (400-700 °C). An induced transition of hybrid Zn5(CO3)2(OH)6/ZnO nanoparticles to single-phase ZnO nanoparticles was obtained at 480 °C. The morphological analysis revealed a formation of ZnO nanoparticles with semispherical (∼6.5 nm)- and rod-like (∼96 nm) shapes when the calcination temperatures were 400 and 700 °C, respectively. Photoluminescence characterizations revealed several defects types in the samples with VZn and VO+ being in the self-assembly of semispherical- and rod-like ZnO nanoparticles. The photocatalytic activity of the ZnO nanoparticles was examined by assessing the degradation of methylene blue in an aqueous solution under low-intensity visible-light irradiation (∼3 W m-2). The results point toward the self-assembly of semispherical- and rod-like ZnO nanoparticles that had significantly better photocatalytic activity (∼31%) in comparison to that of spherical-agglomerated- or near-spherical-like species within 120 min of irradiation. The possible photocatalytic mechanism is discussed in detail, and the morphology-driven intrinsic [VZn+VO+] defects are proposed to be among the active sites of the ZnO nanoparticles enhancing the photocatalytic activity.

Piezoelectric coefficients d14, d16, d34 and d36 of an L-arginine hydrochloride monohydrate crystal by X-ray three-beam diffraction.

Previous work employed X-ray three-beam diffraction techniques to obtain part of the L-arginine hydrochloride monohydrate (L-AHCL.H(2)O) piezoelectric coefficients, namely d(21), d(22), d(23) and d(25). Those coefficients were obtained by measuring the shift in the angular position of a number of secondary reflections as a function of the electric field applied in the [010] piezoelectric direction. In this paper a similar procedure has been used to measure the remaining four piezoelectric coefficients in L-AHCL.H(2)O: with the electric field applied in the [100] direction, d(14) and d(16) were measured; with the electric field applied in the [001] direction, d(34) and d(36) were obtained. Therefore the entire piezoelectric matrix of the L-AHCL.H(2)O crystal has been successfully measured.

New crystals in the lithium sulfate family.

The preparation and structures of caesium lithium sulfate, Cs(1.15)Li(2.85)(SO(4))(2), and caesium lithium rubidium sulfate, Cs(0.90)Li(2.88)Rb(0.22)(SO(4))(2), are described and discussed in the context of simple and double sulfate polymorphism. The latter structure is related to the former through the substitution of Rb for Cs. In both crystals, the sulfate ions occupy two non-equivalent sites, but the ions are disordered in Cs(1.15)Li(2.85)(SO(4))(2).