Highly visible-light active nanoporous TiO2 photocatalysts for efficient solar photocatalytic applications

Abstract

We report highly visible-light active nanoporous carbon-doped TiO2 (C-TiO2) and sulfur-doped TiO2 (S-TiO2) for environmental and biomedical applications. C-TiO2 and S-TiO2 were synthesized at room temperature without thermal treatment using modified sol–gel processing and ultrasound irradiation. Under visible-light irradiation, the highest photocatalytic activity for S-TiO2 ([k]=3.121h−1) was found to be 28 times higher than that of undoped nanoporous TiO2 ([k]=0.112h−1). The recyclability of the S-TiO2 photocatalyst was found to be high with the decolorization rate at ∼92% of the initial value after fifteen cycles. Very interestingly, the C-TiO2 and S-TiO2 photocatalysts (crystallite size∼5.5nm) showed very strong antimicrobial properties against both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) compared to 5nm anatase TiO2 and undoped TiO2 photocatalysts after visible-light exposure for 3h. More than ∼95% of E. coli was killed, even after ten cycles of use for the S-TiO2 photocatalyst. Thus, we have demonstrated that C-TiO2 and S-TiO2 can serve as multifunctional generic bactericides, as well as highly visible-light active photocatalysts.