Preparation, characterisation and antibacterial properties of thermoplastic chitosan/nano ZnO composites

This study prepares thermoplastic chitosan/nano ZnO (CZ) composites by thermomechanical treatment in an internal mixer. Dilute hydrochloric acid aqueous solution is used as the destructuring agent of chitosan and solvent of nano ZnO. Fourier transform infrared spectroscopy and scanning electron microscopy confirm the chitosan–ZnO interaction. The crystallinity and UV transmittance of the composites decreases, while their thermal stability increases due to the addition of nano ZnO. The antibacterial activity of the CZ composites is examined in terms of their inhibitory and bactericidal effects against Escherichia coli, Staphylococcus aureus, and Bacillus subtilis. Improved antibacterial properties are obtained for the CZ composites, compared to pure chitosan sheet. Gram-positive bacteria (S. aureus and B. subtilis) are more sensitive to the antibacterial activity of the CZ composites than Gram-negative bacteria (E. coli). This work provides a simple method to prepare chitosan-based materials and obtains CZ composites with improved antibacterial activities, which can be applied in agriculture and food safety.