Fabrication and characterization of chitosan-based bionanocomposite coating reinforced with TiO nanoparticles and carbon quantum dots for enhanced antimicrobial efficacy.

Polymer-based nanocomposite coatings that are enhanced with nanoparticles have gained recognition as effective materials for antibacterial purposes, providing improved durability and biocidal effectiveness. This research introduces an innovative chitosan-based polymer nanocomposite, enhanced with titanium oxide nanopowders and carbon quantum dots. The material was synthesized via the sol-gel process and applied to 316L stainless steel through dip-coating. Structural and morphological properties, including crystal structure, microstructure, elemental dispersion, particle size distribution, chemical composition, and surface morphology, were thoroughly characterized. The results demonstrated that carbon quantum dots and titanium oxide nanopowders were uniformly dispersed within the chitosan matrix, forming a homogeneous, non-agglomerated coating. The antibacterial efficacy of the synthesized samples against 7 different Gram-positive and Gram-negative bacteria was assessed through disk diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) tests. The results confirmed the antibacterial activity of synthesized samples against most of the bacterial pathogens tested but exhibited stronger antibacterial effects on Gram-negative bacteria compared to Gram-positive bacteria. The largest inhibition zones, measuring 21 mm and 16 mm, were observed for Pseudomonas and E. coli for titanium dioxide nanoparticles and the final nanocomposite, respectively. Additionally, the MIC and MBC values for all 7 bacteria were determined.