We describe here a one-step method for the synthesis of Au/TiO2 nanosphere materials, which were formed by layered deposition of multiple anatase TiO2 nanosheets. The Au nanoparticles were stabilized by structural defects in each TiO2 nanosheet, including crystal steps and edges, thereby fixing the Au–TiO2 perimeter interface. Reactant transfer occurred along the gaps between these TiO2 nanosheet layers and in contact with catalytically active sites at the Au–TiO2 interface. The doped Au induced the formation of oxygen vacancies in the Au–TiO2 interface. Such vacancies are essential for generating active oxygen species (*O−) on the TiO2 surface and Ti3 + ions in bulk TiO2. These ions can then form Ti3 +–O−–Ti4 + species, which are known to enhance the catalytic activity of formaldehyde (HCHO) oxidation. These studies on structural and oxygen vacancy defects in Au/TiO2 samples provide a theoretical foundation for the catalytic mechanism of HCHO oxidation on oxide-supported Au materials. 相似文献
Surface sediments of rivers can exhibit spatial and temporal variations in contaminant concentrations that may significantly affect risk evaluations. As to pollution control and remediation of watershed, large-scale and further background data on PAHs in China were required urgently. Spatial distribution and compositional characteristics of 16 polycyclic aromatic hydrocarbons (PAHs) in surface sediments from Haihe River Basin were investigated. A method based on effects range (ER) was used to assess ecosystem risk of ∑PAHs (the total of 16 PAH) sensitively and accurately. The results indicated that ∑PAHs content levels ranged from 257 to 16901 μg·kg−1 dry weight. The lower rings predominated in the samples, and 2-, 3-, 4-, 5- and 6-ring PAHs accounted for 12%, 21%, 30%, 30%, and 7% respectively in total PAHs. The ratio of Fl / (Fl+ Py) uniformly distributed in the interval 0.20–0.80, indicating that it may be affected by petroleum origin, oil combustion, biomass and coal combustion jointly. ∑PAHs in Cetian (S6), Dongwushi (S19), Handan (S20), Aixinzhuang (S21) and Tianjin (S37) exceeded effects range low (ERL), in which biologic effects were in a medium level with an adverse effect on biologic organisms. Thus, it is necessary to strengthen the PAHs monitoring and research of the Haihe River Basin. 相似文献
To improve nitrogen removal performance of wastewater treatment plants (WWTPs), it is essential to understand the behavior of nitrogen cycling communities, which comprise various microorganisms. This study characterized the quantity and diversity of nitrogen cycling genes in various processes of municipal WWTPs by employing two molecular-based methods:most probable number-polymerase chain reaction (MPN-PCR) and DNA microarray. MPN-PCR analysis revealed that gene quantities were not statistically different among processes, suggesting that conventional activated sludge processes (CAS) are similar to nitrogen removal processes in their ability to retain an adequate population of nitrogen cycling microorganisms. Furthermore, most processes in the WWTPs that were researched shared a pattern:the nirS and the bacterial amoA genes were more abundant than the nirK and archaeal amoA genes, respectively. DNA microarray analysis revealed that several kinds of nitrification and denitrification genes were detected in both CAS and anaerobic-oxic processes (AO), whereas limited genes were detected in nitrogen removal processes. Results of this study suggest that CAS maintains a diverse community of nitrogen cycling microorganisms; moreover, the microbial communities in nitrogen removal processes may be specific.
