Blocking antibiotic pollution and bacteria contamination via efficient photocatalysis using N-carbon dots doped Ni@TiO2

Wastewater contamination from pharmaceuticals and pathogens poses an urgent global challenge that conventional water treatment processes struggle to address effectively. This research reports the multifunctionality of Ni-doped titania (Ni@TiO2) decorated with green nitrogen-doped carbon quantum dots (NCD), as a visible-light photocatalyst for drug degradation and as an antibacterial agent. To overcome the limitations of titania-based catalysts, a dual-modification strategy is proposed. The dual presence of NCD and Ni introduces localized energy levels that successfully narrow the TiO2 bandgap, promoting charge carrier separation and photo-electron transfer and optimizing photocatalytic behavior. Besides, the NCDs act as electron sinks and photo-induced electron transfer mediators, promoting charge separation and transfer at the heterojunction interface and extending charge-carrier lifetime. The presence of NCD and the Ni addition into Ni@TiO₂/NCD (NCD = 4% wt) composite achieved high paracetamol degradation (≈99%, TOC removal of 98%), ceftriaxone (70%), and vancomycin (75%) after 180 min of irradiation. Antibacterial activity of Ni@TiO₂/NCD (NCD = 4% wt) was proved, reducing the viability of S. aureus by 96.71% and 68.37%, and E. coli by 95.41% and 68.23%, at 1000 and 500 μg/mL, respectively. Finally, MIC values and residual antibacterial activity of water containing photocatalytically treated antibiotics prove the great performance of the developed composite system in achieving multiple functions, emphasizing its potential in wastewater treatment and infection control.