Weiyan He

Enhancing visible light photocatalytic activity of BiOBr/rod-like BiPO4 through a heterojunction by a two-step method

Visible light driven BiOBr/rod-like BiPO4 composites with different BiOBr to BiPO4 molar ratios were fabricated via a facile deposition-precipitation method. X-ray powder diffraction, field emission scanning electron microscopy, transmission electron microscopy, UV-Vis diffuse reflectance spectroscopy and Brunauer–Emmett–Teller surface area were used to characterize the as-synthesized samples. Results showed that the BiOBr/rod-like BiPO4 composite with equal mole ratio exhibited the best photocatalytic performance for rhodamine B (RhB) degradation under visible light irradiation. The enhanced photocatalytic performance could be mainly attributed to the effective separation of the photogenerated electrons and holes at the heterojunction interface of p-BiOBr and n-BiPO4.

Enhancing photocatalytic activity by tuning the ratio of hexagonal and orthorhombic phase Nb2O5 hollow fibers

Cotton was used as template for the fabrication of a biomorphic Nb2O5 photocatalyst with hexagonal and orthorhombic structures. The as-prepared Nb2O5 was characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area and UV-Vis diffused reflectance spectra measurements. The photocatalytic activity of the Nb2O5 fibers was evaluated through degradation of methylene blue (MB) in aqueous solution exposed to UV light. SEM results show that biomorphic Nb2O5 fibers are both hollow and have porous walls. The architectures allow a more accessible surface for the photocatalytic decomposition of dyes molecules. The photocatalytic activity of physically mixed fibers with 75% H-Nb2O5 and 25% O-Nb2O5 phases is superior to those of pure H- and O-Nb2O5 phases, and other samples with different H- and O-Nb2O5 ratios. Such superior photocatalytic activity is mainly due to an optimal balance between the adsorption of MB and the absorption of UV light. Moreover, the large size of the Nb2O5 hollow fibers allows them to be easily separated from the solution.

Biogenic synthesis of photocatalytically active ZnS/ESM composites

The ZnS/ESM composites have been successfully fabricated using ESM (eggshell membrane), sodium sulfide and zinc sulfate as the main raw materials through an environmental and economical liquid impregnation method. The obtained samples were characterized via X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, UV-vis diffuse reflectance spectra and Fourier-transform infrared spectra. The results demonstrated that the formed ZnS nanoparticles uniformly distributed on the surface of the egg membrane fibers, and the crystallinity and the amount of the ZnS loaded on the ESM fibers could be adjusted by changing the cycle indices of the impregnation. Furthermore, we tested the photocatalytic effects and analyzed the mechanism of the resulting ZnS/ESM composites as photocatalysts to degrade the harmful organic pollutant methyl orange under UV light irradiation. The results showed that the ESM support made it easy to recover the photocatalysts and enhanced the intensity of light absorption and the stability of the ZnS/ESM composites as photocatalysts. Based on the high photocatalytic activity and good stability, the ZnS/ESM composites with 4 cycle indices of the impregnation can be expected to be a practical photocatalyst.

Effect of temperature on the phase behavior and microstructure of aggregates in SDS/Triton X-100/aH2O systems

ABSTRACT The phase behavior and microstructure of a system containing polyoxyethylene tert-octylphenyl (Triton X-100), sodium dodecyl sulfate (SDS) and water were investigated using polarized optical microscopy (POM), differential scanning calorimetry (DSC) and small-angle X-ray diffraction (XRD). Phase-behavior study revealed that lamellar and hexagonal phases occurred in different compositions, and that lyotropic liquid crystal phases tended to form an H phase with increased Triton X-100 content. The effects of temperature on the phase behavior and microstructure of lyotropic liquid crystals were also studied. Heating induced a change from hexagonal to lamellar phase and from gel to hexagonal phase. POM and small-angle X-ray diffraction (SXRD) revealed that the phase-transition temperature of LLCs increased with increased Triton X-100 content, as further supported by DSC data.

Effect of TritonX-100 on the aggregation behavior of SDS in water

ABSTRACT The phase behavior patterns and microstructures of surfactant systems containing sodium dodecyl sulfate (SDS)/TritonX-100/H2O were investigated under a polarizing microscope. Ternary mixtures of SDS/TritonX-100/H2O form two types of well-ordered lyotropic liquid crystals: a hexagonal phase linked to the SDS/water axis and a lamellar phase located at the corner of their phase diagram. Surface tension measurements were conducted for TritonX-100 in the SDS solutions. In the SDS/TritonX-100/H2O system, transition points were found in the surface tension concentration curves at different quality ratios. On the basis of the critical micelle concentration values, the thermodynamic parameters of the aggregate formation, namely, , , and , were estimated. Results show that the addition of TritonX-100 is beneficial to the formation of surfactant aggregates, and thermodynamic data indicate that the micellization of binary mixture of SDS/TritonX-100 in aqueous solution is an entropy-driven spontaneous process. Therefore, the addition of TritonX-100 in SDS aqueous solutions may have potential applications in nanomaterial preparation.