Boosted antioxidant, anticancer and photocatalytic power: Non-metal doped TiO ₂ nanoparticles for effective wastewater treatment

The sol-gel method was employed to prepare the pure TiO 2 (T), Nitrogen-doped TiO 2 (NT), and carbon-nitrogen co-doped TiO 2 (CNT) nanoparticles (NPs). The T, NT and CNT NPs are fully characterized. With average particle sizes of 36, 38, and 40 nm for T, NT, and CNT , respectively, all samples crystallized in the anatase phase. The measured band gaps (Eg) were 3.16, 2.90, and 2.80 eV for T, NT and CNT NPs respectively, suggesting dopant-dependent morphological and surface functional alterations as well as a red shift of optical absorption into the visible region. In 2 h visible-light tests at pH 1, CNT completely (100%) degraded both Reactive Red 195 (RR195) and Reactive Blue 4 (RB4) dyes, whereas NT degradation activity reached 27.7% and 21% of RR195 and RB4 respectively, while T reached 18.7% and 16.6% of RR195 and RB4 respectively. With CNT NPs , dye elimination increased with contact time, reaching 96.07% of RB4 and 100% of RR195 after 45 min and total degradation after 1 h CNT NPs eliminated 92% of RR195 and 88.6% of RB4 in 15 min when raw wastewater was diluted. For at least five reuse cycles, CNT’s better activity which is ascribed to increased charge separation and transfer, enhanced visible light absorption, and the action of electrons and hydroxyl radicals remained stable. CNT showed intracellular ROS and showed considerable cytotoxicity against HepG-2 and HCT-116 cell lines (IC 50 = 18.05 μM and 28.23 μM, respectively), indicating potential for anticancer uses and further investigation as therapeutic or antioxidant possibilities.