Design of a TiO2/Poly(Ani-co-Cz) Macromolecular Nanocomposite With Enhanced Solar Photocatalytic and Antibacterial Performance

Abstract

A titanium dioxide (TiO₂)-based polymeric nanocomposite incorporating a carbazole-aniline copolymer (poly(Ani-co-Cz)) was synthesized for sunlight-driven photocatalytic water remediation using methylene blue (MB) as a model organic pollutant, and its antibacterial activity was also evaluated. The TiO₂/Poly(Ani-co-Cz) nanocomposite was characterized, revealing a band gap energy (Eg) of 3.06 eV, calculated using Tauc's equation. Under natural solar irradiation, the nanocomposite with an optimal TiO₂/Poly(Ani-co-Cz) ratio of 5 achieves up to 99% MB degradation, exceeding pristine TiO₂ by over 33%. This improvement is attributed to enhanced charge separation and light absorption induced by the conductive copolymer. Photocatalysis kinetics were evaluated using the Langmuir–Hinshelwood model, and potential mechanisms were examined through hydroxyl radical trapping experiments. The pseudo-first-order rate constant (k_app) for MB photodegradation was found to be 0.0301 min⁻¹, indicating strong compatibility with pseudo-first-order kinetics. The study confirms the generation of hydroxyl (OH^•) and superoxide (O₂^•−) radicals during dye degradation by the nanocomposite. Antibacterial testing revealed strong inhibition against Bacillus subtilis, a moderate effect against Staphylococcus aureus, minimal impact against Escherichia coli, and a negligible effect against Pseudomonas aeruginosa. These findings indicate that the TiO₂/poly(Ani-co-Cz) nanocomposite is a promising dual-function material for solar-driven, sustainable water treatment, enabling simultaneous photocatalytic pollutant removal and antibacterial action.