Solar-active biogenic CQD-TiO2 nanorods: toward safe and efficient water treatment systems

Biomass-derived carbon quantum dots (CQDs) were integrated with TiO₂ nanorods to enhance visible-light photocatalytic performance. Photocatalytic performance was evaluated for the degradation of an organic dye and removal of a heavy metal under visible-light irradiation; the incorporation of C-CQDs reduced the band gap of TiO₂ nanorods from 3.11 eV to 2.84 eV, resulting in enhanced photocatalytic performance with 88.04% dye degradation and 88.39% Cr(VI) reduction. In addition, the hybrid photocatalyst showed enhanced antimicrobial activity against Escherichia coli compared with pristine TiO₂, while cytotoxicity assays confirmed acceptable biocompatibility. The C-CQDs/TNRs photocatalyst retained more than 95% of its initial activity after three consecutive reuse cycles, demonstrating excellent stability and reusability. This work demonstrates a promising biomass-to-functional-nanomaterial pathway for multifunctional photocatalytic systems, offering potential for wastewater treatment and microbial disinfection applications.