Preparation of chitosan coated zinc oxide nanocomposite for enhanced antibacterial and photocatalytic activity: As a bionanocomposite.

The surface coating of metal oxide nanoparticles using biopolymer chitosan has evolved to become an important area of polymer nanotechnology. Herein, we report the preparation of chitosan coated zinc oxide (CS-ZnO) nanocomposite for the first time by a green chemistry approach using bioflavonoid rutin. The formation of CS-ZnO nanocomposite was preliminarily confirmed by color change and UV-Visible spectroscopy. FE-SEM images revealed agglomeration of CS-ZnO nanocomposite having predominant rod shaped structure. The surface coating of chitosan polymer on ZnO was confirmed by XRD, EDS, FTIR, DLS and zeta potential analysis. The prepared CS-ZnO nanocomposite showed significant antibacterial activity against both Gram-positive and Gram-negative bacterial pathogens. However, the prepared nanocomposite was more effective against Gram-negative bacteria compared to Gram-positive bacteria. The highest zone of inhibition by CS-ZnO nanocomposite was reported against E. coli (25.5 mm) followed by K. pneumoniae (24.5 mm), S. aureus (22.5 mm) and least against B. subtilis (21 mm). Furthermore, the prepared nanocomposite acted as photocatalyst for the degradation of Methylene blue and Congo red under sunlight irradiation.