Syntheses And Antibacterial Abilities Of TiO₂ And Ag/ZnO

The inorganic antibacterial materials are becoming a hot topic these years because of their advantages in a broad spectrum, safety and permanence. They are composed of metallic oxides and noble metals, the former focused on titanium dioxide and zinc oxide, the latter focused on silver. In this paper, exhaustive research was conducted on preparation and performances of titanium dioxide and Ag/ZnO composites. The main results were summarized as follows:The rutile TiO2 microspheres were prepared through a hydrothermal method. The SEM and TEM observations showed that TiO2 microspheres exposed 100% reactive{111} facets on the extrasurface. According to the calculated results, the summed areas of the exposed{111} facets of the microsphere were larger than the spherical area of the microsphere (about 113% as the spherical surface area of the whole microsphere). The photocatalytic antibacterial tests suggested that the microsphere could still achieve excellent photocatalytic antibacterial activity higher than P25 under the same conditions. It was demonstrated by fluorescence spectrophotometry that the TiO2 microspheres could decrease the electron-hole recombination rate effectively compared with P25. The results from confocal laser scanning microscope (CLSM) suggested that under the UV irradiation, the microspheres can make the photoinduced holes highly disperse on the whole spherical extrasurfaces to possibly form a like·OH@TiO2 core-shell spheres. In summary, the rutile TiO2 microspheres with 100% exposed{111} facets could decrease the electron-hole recombination rate by dispersing the holes and the electrons on different crystal facets, and allow the photoinduced holes to highly disperse on the extrasurface to generate the reactive·OH species, which were responsible for its high photocatalytic antibacterial performance.The Ag/ZnO composites prepared by photo-reduction showed excellent antibacterial performance. The MIC value of Ag in Ag/ZnO composites was 7.1μg/ml, better than Ag/ZnO composites prepared by traditional H2-reduction and some other inorganic antibacterial materials reported by papers. According to the outcome of XRD and TEM, the as-synthesized small size metallic Ag on the surface of ZnO was highly dispersed. The XPS results showed that there was a strong relationship between Ag and ZnO. In summary, the main reason for excellent antibacterial activity was the strong interaction between Ag/ZnO metal-support composites as silver was highly dispersed on the surface of ZnO.