Influencing Factor Investigation on Dynamic Hydrothermal Growth of Gapped Hollow BaTiO3 Nanospheres.

Gapped hollow BaTiO3 nanospheres with an apparent diameter of 93 ± 19 nm (shell thickness of 10-20 nm) were synthesized via a dynamic hydrothermal process using TiO2 sols and Ba(2+) ions as the Ti and Ba sources in alkaline aqueous solutions. The phases and morphologies of the BaTiO3 samples were characterized by X-ray diffraction (XRD), SEM, TEM, and Raman spectra. The effects of the hydrothermal temperatures and durations, NaOH concentrations, and Ba/Ti ratios on the formation of gapped hollow BaTiO3 nanospheres were systematically investigated. The optimum conditions for forming gapped hollow BaTiO3 nanospheres are hydrothermal treatment at 180 °C for 10-20 h under a continuous magnetic stirring with NaOH concentrations of about 1 mol/L and molar Ba/Ti ratios of 1.2-1.5. The formation mechanism of the gapped hollow BaTiO3 nanospheres is understood as the combination of the orientated attachment and reversed crystal growth.

Hierarchically plasmonic photocatalysts of Ag/AgCl nanocrystals coupled with single-crystalline WO3 nanoplates.

The hierarchical photocatalysts of Ag/AgCl@plate-WO3 have been synthesized by anchoring Ag/AgCl nanocrystals on the surfaces of single-crystalline WO3 nanoplates that were obtained via an intercalation and topochemical approach. The heterogeneous precipitation process of the PVP-Ag⁺-WO3 suspensions with a Cl⁻ solution added drop-wise was developed to synthesize AgCl@WO3 composites, which were then photoreduced to form Ag/AgCl@WO3 nanostructures in situ. WO3 nanocrystals with various shapes (i.e., nanoplates, nanorods, and nanoparticles) were used as the substrates to synthesize Ag/AgCl@WO3 photocatalysts, and the effects of the WO3 contents and photoreduction times on their visible-light-driven photocatalytic performance were investigated. The techniques of TEM, SEM, XPS, EDS, XRD, N2 adsorption-desorption and UV-vis DR spectra were used to characterize the compositions, phases and microstructures of the samples. The RhB aqueous solutions were used as the model system to estimate the photocatalytic performance of the as-obtained Ag/AgCl@WO3 nanostructures under visible light (λ ≥ 420 nm) and sunlight. The results indicated that the hierarchical Ag/AgCl@plate-WO3 photocatalyst has a higher photodegradation rate than Ag/AgCl, AgCl, AgCl@WO3 and TiO2 (P25). The contents and morphologies of the WO3 substrates in the Ag/AgCl@plate-WO3 photocatalysts have important effects on their photocatalytic performance. The related mechanisms for the enhancement in visible-light-driven photodegradation of RhB molecules were analyzed.