Mingwen Zhang

Efficient photocatalytic reduction of aqueous Cr(VI) over porous BNNSs/TiO2 nanocomposites under visible light irradiation

Photocatalytic reduction of aqueous Cr(VI) was successfully achieved on porous boron nitride nanosheets/TiO2 (P-BNNSs/TiO2) composites. Porous boron nitride (BN) nanosheets as a catalyst support material play an important role in extending the optical absorption spectrum of TiO2 into the visible light region. The photocatalytic reduction of aqueous Cr(VI) by P-BNNSs/TiO2 composites was evaluated under simulated solar light (λ > 300 nm) and visible light (λ > 420 nm) irradiation. The P-BNNSs/TiO2 composites exhibit excellent removal efficiency of Cr(VI) (∼99%). The excellent photocatalytic activity of P-BNNSs/TiO2 composites in the visible-light region is derived from their large surface area, which induces a strong absorption of pollutants and a lower recombination rate of electron–hole pairs.

Protection of silica-coated ZnO nanoparticles on pre-dyed polyester fabrics against photofading

This work was designed to investigate the ability of silica-coated ZnO (ZnO&SiO2) nanoparticles (NPs) as ultraviolet (UV) absorbers for protecting pre-dyed polyester fabrics against photofading. Despite that ZnO NPs are excellent UV absorbers, their strong photocatalytic activity limits the application in UV protection. In this study, a silica layer was coated onto ZnO NPs to form a physical barrier between the ZnO and a polyester substrate, which allowed effective UV shielding while minimising the harmful effects of photocatalytic activity on the substrate. The structure and optical proprieties of ZnO&SiO2 NPs were observed. The bare ZnO and ZnO&SiO2 NPs were, respectively, applied to polyester fabrics coloured with three kinds of dyes by a dip coating method. The photofading level of treated fabrics after exposure under simulated sunlight was evaluated. The ZnO&SiO2 NPs exhibited excellent protection on pre-dyed polyester fabrics against photofading.

Reducing photoyellowing of wool fabrics with silica coated ZnO nanoparticles

Though ZnO nanoparticles (NPs) are an excellent UV absorber, their photocatalytic activity greatly limits the application areas of these particles. Under sunlight exposure, ZnO NPs used as a UV absorber can accelerate the wool yellowing process by generating free radicals. To reduce this photocatalysis effect, a physical barrier has been fabricated by coating the ZnO NPs with a silica layer (ZnO@SiO2), hence providing good UV-shielding with low photocatalytic activity. The structure and optical properties of ZnO and ZnO@SiO2 NPs were characterized by transmission electron microscope (TEM) and UV–Vis spectrum. The photocatalytic activity of ZnO and ZnO@SiO2 NPs was evaluated by photo-degradation of Rhodamine B. The ZnO and ZnO@SiO2 NPs were applied to knitted wool fabrics using the dip coating method. The treated wool fabrics were characterized by a scanning electron microscope (SEM) and the photoyellowing level of treated fabrics after exposure under simulated sunlight was evaluated by a Datacolor Spectraflash spectrophotometer. The ZnO@SiO2 NPs demonstrated excellent protection of wool against photoyellowing.

Synthesis of TiO2&SiO2 nanoparticles as efficient UV absorbers and their application on wool

Uniform core-shell structured TiO2&SiO2 nanoparticles (NPs) were fabricated by synthesizing TiO2 NPs, which were then coated with shells of SiO2. The structure and optical properties of TiO2&SiO2 NPs were characterized with a transmission electron microscope and a UV/Vis spectrophotometer. The photocatalysis was evaluated by photodegradation of rhodamine B. TiO2&SiO2 NPs were coated onto wool fabrics to improve their photostability. The treated wool fabrics were characterized using scanning electron microscopy. Photoyellowing of treated wool fabrics after exposure to simulated sunlight was evaluated using a Datacolor Spectraflash spectrophotometer. At an application level of 5% o.w.f. of the composite nanoparticles, the treated wool fabrics exhibited considerable photostability. Polydimethylsiloxane was applied as an after-treatment, which provides good fastness to washing. This simple but effective coating could be useful for the development of UV protection methods for various substrates.