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

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] = 3.121 h−1) was found to be 28 times higher than that of undoped nanoporous TiO2 ([k] = 0.112 h−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 ∼ 5.5 nm) showed very strong antimicrobial properties against both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) compared to 5 nm anatase TiO2 and undoped TiO2 photocatalysts after visible-light exposure for 3 h. 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.

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► The nanoporous C- and S-TiO2 photocatalysts were successfully synthesized at room-temperature.
► The photocatalytic activity of C- and S-TiO2 was found to be higher than that of other TiO2 photocatalysts.
► Moreover, C- and S-TiO2 exhibited excellent antibacterial activity.