Search

ZnO/Ag composites were synthesized by photochemical deposition of Ag nanoparticles onto pre-synthesized three dimensional hierarchical cake-like ZnO microstructures, which were fabricated by DMF (N,N-dimethylformamide)-mediated solvothermal method. The crystal phase and microstructures of the as-obtained ZnO and ZnO/Ag were characterized by XRD, DRS, SEM, EDS, TEM and PL. The SEM and TEM results indicated that Ag nanodisks with diameters of 120 nm are uniformly deposited on the surface of hierarchical cake-like ZnO. Furthermore, the visible-light photocatalytic activity of the ZnO/Ag composites was evaluated by the degradation of Rhodamine B (RhB) under Xe lamp irradiation. Such ZnO/Ag composites showed an enhanced visible-light photocatalytic activity, the rate of degradation was nearly five times faster than that of bare hierarchical cake-like ZnO under visible-light irradiation due to the increase of electron-transfer rate of ZnO after hybridized with Ag nanoparticles.

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.

Employing NH4BF4 as a fluoride source, novel hierarchical cake-like ZnO microstructures have been fabricated by a simple, template-free, environmentally-friendly DMF (N,N-dimethylformamide)-mediated solvothermal route. The products were characterized by XRD, SEM, TEM and nitrogen adsorption–desorption and PL. The SEM and TEM results indicated that the hierarchical cake-like ZnO were assembled from numerous tiny nanoplates. DMF acted as solvent and structure-directing agent to guide the formation of ZnO nuclei and the self-assembled preferential growth from smaller building units (nanoplates) to larger cake-like ZnO microstructures. The as-prepared samples, ZnO or ZnOHF could be regulated by altering the two major reaction parameters (the amount of DMF and fluoride source). Time-dependent morphological evolution results revealed that self-assembly and Ostwald ripening were the main formation mechanism for the hierarchical ZnO microstructure. Furthermore, the photocatalytic activity of the as-prepared ZnO samples was evaluated by the degradation of Rhodamine B (RhB) under UV light irradiation. Such hierarchical cake-like ZnO microstructures showed an excellent photocatalytic activity. Additionally, the cake-like ZnO microstructures were chemically stable, and the efficiency remained almost the same after being recycled five times.

A facile one-step solution-based method with the assistance of N,N-dimethylformamide (DMF) has been developed to prepare well-dispersed hierarchical flower-like ZnOHF nanostructures, in which DMF acts not only as solvent but also as surface-functionalizing agent. The prepared ZnOHF are characterized for the structural and morphological properties by XRD, SEM and TEM. The SEM and TEM results indicate that the hierarchical ZnOHF nanoflowers are assembled by numerous nanowires. The amount of DMF and reaction time play crucial roles in the formation of hierarchical nanowires-assembled ZnOHF nanoflowers. After calcination, the ZnOHF is completely transformed into ZnO while the flower structures are perfectly retained. The hierarchical ZnOHF and ZnO nanoflowers exhibit specific surface areas up to 48.8 m2/g and 71.2 m2/g, respectively. The as-obtained ZnOHF and ZnO nanoflowers exhibit excellent UV light photocatalytic activity for photodegradation of Rhodamine B.

Hierarchical YVO 4 microspheres have been prepared via L-aspartic acid (L-Asp) assisted hydrothermal route. X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to characterize the crystalline phase and morphologies of the products. The SEM results from different reaction stages indicate that YVO 4 microspheres are self-assembled by numerous nanowires with diameter of 30–50 nm. It is found that the amount of L-Asp and reaction time play crucial roles in the formation of hierarchical nanowires-assembled YVO 4 microspheres. The photocatalytic properties of YVO 4 were investigated by the decomposition of Rhodamine B (RhB) under UV light irradiation and exhibit good photocatalytic activities.

3D hierarchical flower-like Zn3(OH)2V2O7·2H2O microcrystals have been fabricated in a high yield via a simple hydrothermal process in the presence of l-aspartic acid (l-Asp). The purity, crystalline phase and morphologies of the products were characterized by XRD, TEM and SEM. The SEM results indicate that the microflowers are self-assembled by numerous nanobelts with mean diameter of 100 nm. During the process, l-Asp is chosen as the complexing and surface-functionalizing agent. It is found that the amount of l-Asp and reaction time have significant effects on the morphology of the Zn3(OH)2V2O7·2H2O micro/nanostructures. The photocatalytic properties of Zn3(OH)2V2O7·2H2O were investigated by the decomposition of RhB under UV light irradiation and exhibit good photocatalytic activities.

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 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.

Employing NH4BF4 as the fluoride source, large scale fan-shaped ZnOHF hierarchical structures have been synthesized successfully with a template-free hydrothermal approach. The purity, crystalline phase, thermal stability and morphologies of the as-prepared ZnOHF were characterized by XRD, TG-DSC and SEM. Time-dependent experiments indicate that the hierarchical ZnOHF microfans are self-assembled by numerous nanotubes with diameter of 100 nm. A possible chemical mechanism is proposed. The as-prepared ZnOHF can be transformed into hexagonal phased netlike ZnO by calcination in air at 600 °C. Furthermore, the as-prepared ZnOHF and ZnO were investigated by the decomposition of methylene orange under UV light irradiation and the results show that they have good photocatalytic activities.