Prepration And Antibacterial Property Of AG/T-Zno And Its Composite

The antibacterial activity of nano-silver (n-Ag) has been restrained for its agglomeration behavior, bad distribution and stability. In this thesis, we hope to obtain a new kind of antibacterial material with multi-scaled hybrid of nanostructures by loading nano-silver (n-Ag) on the tetrapod ZnO (T-ZnO) whisker that also displays good effect of antibacterial.The n-Ag was in situ synthesized on the surface of the T-ZnO by decomposing silver-containing precursor. The results of characterization of structure and morphology indicated that a hybrid structure had been formed, and the silver mostly existed as single substance. The antibacterial activities were evaluated, and the results showed that n-Ag/T-ZnO displayed better activity than that of T-ZnO, and the higher the silver loading, the better the effect of antibacterial, whether under simulated sunlight or in dark. Comparative experiments revealed that both n-Ag/T-ZnO and T-ZnO exerted higher activity against E. coli than that against S. aureus under same light condition, which was ascribed to the structural difference of the cell walls.In order to explore the antibacterial mechanism, we detected the active species in the aqueous suspensions of n-Ag/T-ZnO and T-ZnO respectively. Although H2O2,·OH and·O2-were detected in n-Ag/T-ZnO or T-ZnO systems, the amounts of H2O2and·O2decreased while·OH increased after n-Ag loading. What is more, only H2O2could be detected in dark, and the mounts in n-Ag/T-ZnO suspensions were much lower than in T-ZnO. The affect mechanism was suggested that T-ZnO exerted its activity by releasing H2O2, and n-Ag/T-ZnO by ionizing Ag+.The as-prepared n-Ag/T-ZnO hybrid nanostructured antibacterial agent with1.5%n-Ag loading was applied to polymer composites such as PP (polypropylene), LDPE (low density polyethylene) and EPDM (ethylene propylene diene monomer). Antibacterial property tests indicated that the antibacterial efficiency increased with increasing of the content of the n-Ag/T-ZnO in the composites. The antibacterial ratios against E. coli for PP (4wt%n-Ag/T-ZnO), LDPE (6wt%of n-Ag/T-ZnO) and EPDM (6wt%of n-Ag/T-ZnO) were100%,98.6%and97.8%, respectively.The lasting effect of the composites containing n-Ag/T-ZnO was evaluated by wanning scouring and natural aging experiments respectively. The results showed that the antibacterial ratio of PP composite (4%n-Ag/T-ZnO) reduced by1%after scouring in55℃water for15days, and the ratio of LDPE composite (6%n-Ag/T-ZnO) reduced by about5% after natural aging for6months. The amounts of Ag+during scouring were measured and reckoned according to its release rate, which demonstrated that the total amount of Ag+could last much longer than20years.