Preparation, characterization and the antimicrobial properties of metal ion-doped TiO2 nano-powders

TiO2 samples doped with lithium, sodium, magnesium, iron or cobalt were prepared by high-energy ball milling for different periods of time. The crystalline phase, chemical composition, crystalline size and photo-absorption were characterized by X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS) and Ultraviolet visible diffuse reflectance spectroscopy (UV - Vis - DRS), Fourier transform infrared spectroscopy (FT - IR) and scanning electron microscopy (SEM). The antimicrobial properties of the modified TiO2 samples were evaluated with E. colt and S.aureus assays. The results of the XRD show that the TiOSO4, Ti3O5, Li2TiO3 and NaTi2O4 phases appear along with Li, Na and Mg doped TiO2. However, XPS spectra indicated that Ti exists as both Ti3+ and Ti4+ in Na-doped TiO2 samples. Ti3+, due to its narrow band gap, is highly active in promoting visible light-induced photocatalytic activity. SEM images showed that the crystalline size of TiO2 is reduced and has a common-round and hexagonal plate morphology after milling. The modified TiO2 samples had the best antimicrobial activities after 3 h of milling. In particular, the antimicrobial rate of TiO2 5% doped with transition metals (Co, Fe) reached 100% against E. coli, but the antibacterial rate against S. aureus for Co and Fe dopants was 98.4% and 98.2%, respectively.