Fabrication of bio-based cellulose-stabilized TiO2/ZnO nanocomposite coatings for multifunctional cotton fabrics with synergistic flame retardancy, photocatalytic self-cleaning, and antibacterial activity.

Cotton fabrics are widely used in apparel and technical textiles, yet their intrinsic flammability and susceptibility to microbial contamination limit their use in safety-critical applications. In this study, bio-based cellulose-stabilized TiO2/ZnO nanocomposite coatings were developed and applied to cotton substrates using an industrially scalable knife-over-roll process followed by ethanol coagulation. Seven formulations with systematically varied TiO2/ZnO ratios were prepared to optimize multifunctional performance. The optimized [CTC,10Ti,3Zn] formulation exhibited self-extinguishing behavior (after-flame time = 0 s), high residual mass (96.9%), and a significant reduction in total heat release (THR) from 14.61 to 3.97 kJ/g. In addition, near-complete surface discoloration of methylene blue and rhodamine B was observed within 2 h under simulated solar irradiation, indicating effective photocatalytic self-cleaning activity. The coating also exhibited measurable antibacterial activity, with inhibition zones of 10 mm against Staphylococcus aureus and 9 mm against Escherichia coli, tentatively attributed to a combination of reactive oxygen species (ROS) generation and Zn2+ ion release. Mechanical reinforcement was observed, with tensile strength increasing from 6.2 ± 0.4 MPa for untreated cotton to 12.8 ± 0.6 MPa for the [CTC,3Ti] formulation. Additionally, compost burial resulted in a 48% mass loss after 30 days, indicating partial biodegradability of the cellulose-based matrix. Overall, these results suggest that cellulose-assisted TiO2/ZnO coatings provide a promising scalable strategy for multifunctional textile applications, combining flame retardancy, self-cleaning, antibacterial activity, and environmental compatibility.