Tongming Sun

Yolk–shell ZnWO4 microspheres: one-pot synthesis, characterization and photocatalytic properties

Novel yolk–shell ZnWO4 microspheres have been fabricated via a one-pot hydrothermal process in the presence of L-aspartic acid (L-Asp). The as-obtained products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption–desorption experimentation and UV-vis absorption spectroscopy. The effects of the reaction conditions on the morphology and crystallinity of the products were studied, as well as the amount of L-Asp, reaction time and reaction temperature. As the chelating agent and shape modifier, L-Asp plays a key role in the crystal growth of the yolk–shell ZnWO4 microspheres. A possible formation mechanism for the yolk–shell microspheres is proposed. The photocatalytic properties of the yolk–shell ZnWO4 microspheres were investigated by the decomposition of Rhodamine B (RhB) and methylene blue (MB) under UV light irradiation and the results show that they have excellent photocatalytic activities. Furthermore, the obtained yolk–shell ZnWO4 microspheres are chemically stable and the efficiency remained almost the same after being recycled five times, suggesting that the yolk–shell ZnWO4 microspheres are promising photocatalysts for practical applications.

3D hierarchical ZnOHF nanostructures: synthesis, characterization and photocatalytic properties

3D hierarchical ZnOHF nanoflowers with mean diameter of 200 nm have been synthesized via a simple template-free hydrothermal route by using (NH4)2SiF6 as the fluoride source. The crystalline phase and morphologies of the as-prepared products have been characterized by XRD, SEM and TEM. The XRD results show that the products are well-crystallized orthorhombic phase of ZnOHF. The SEM and TEM results indicate that the ZnOHF nanoflowers are assembled by numerous nanoflakes with mean thickness of 20 nm. Some factors influencing the morphologies of the ZnOHF nanostructures have been systematically investigated, such as the reaction time, temperature and fluoride source. A growth mechanism is proposed on the basis of a series of time-dependent morphological evolution results. The hierarchical ZnOHF nanoflowers exhibit a high specific surface area up to 97.1919 m2 g−1 with a pore size of 50.098 nm. The as-obtained ZnOHF can be transformed into ZnO nanoflowers by calcination in air at 600 °C. The photocatalytic properties of ZnOHF have been studied by the decomposition of methyl orange (MO) under UV light irradiation. The results indicate that the flower-like ZnO nanostructures are chemically stable, and the efficiency remained almost the same after five times recycling.

Controlled synthesis of CeVO4 hierarchical hollow microspheres with tunable hollowness and their efficient photocatalytic activity

Well-dispersed hollow CeVO4 microspheres with tunable hollowness and porosity have been synthesized via a simple hydrothermal method using L-aspartic acid (L-Asp) as the capping agent. The products were characterized by XRD, SEM, TEM and DRS. The XRD results showed that the as-prepared samples were tetragonal phase CeVO4 with high crystallinity. SEM and TEM observations indicated that the hierarchical hollow microspheres with different hollowness were constructed from nanoparticles, cubes or nanoflakes. N2 adsorption–desorption measurements revealed that the BET specific surface area of the typical CeVO4 hollow microspheres was up to 106.54 m2 g−1. During the synthesis, the amount of L-Asp and the reaction time were found to play important roles in determining the growth process and final morphologies of the CeVO4 products. Time-dependent experiments clearly revealed that the CeVO4 hierarchical hollow microspheres were governed by the self-assembly and Ostwald ripening process. Rhodamine B (RhB) was used as the dye pollutant for evaluating the photocatalytic properties of the products under UV radiation. The CeVO4 hierarchical hollow microspheres exhibited excellent photocatalytic activity and good stability even after five repeated cycles of use, indicating that the CeVO4 hierarchical hollow microspheres can be good candidates for photocatalytic degradation of organic pollutants.

Synthesis and characterization of a novel polymeric ultraviolet absorber and its properties

A novel polymeric ultraviolet absorber (UVA) poly (HAB-co-AMC-co-AA) (PHHA) has been prepared by solution copolymerization from 2-hydroxy-4-acryloy benzophenone (HAB), p-acryloy-methyl cinnamate (AMC) and acrylic acid and analyzed using FT-IR, UV–Vis, 1H NMR and GPC. The results revealed two PHHA absorption peaks in UV-A and UV-B. Polymerizable monomer HAB was synthesized by the reaction of 2,4-dihydroxybenzophenone (UV-0) and acryloyl chloride (AC). Another monomer, AMC, was prepared from p-hydroxy-methyl cinnamate and AC. The results showed that HAB and AMC have high UV-absorbing performance in UV-A and UV-B, respectively. The photoantioxidant ability tests indicated that PHHA is an effective polymeric UVA that covers UV-A and UV-B ranges, and a synergism between the two monomers was observed.