A comparison of antibacterial activity in dark-UV light in perspective of surface and structural properties of spray pyrolysis grown Cu doped Cr2O3 thin films

Thin films of Cr2O3 and Cu doped Cr2O3 thin films were prepared using the spray pyrolysis technique with different Cu/Cr ratios. Precursor solution of 0.2 M was sprayed on a pre-heated (≈ 400 °C) soda lime glass substrate using air as the carrier gas. XRD analysis confirmed polycrystalline nature of the films with rhombohedral structure. Crystallite size and lattice strain have been estimated using Williamson-Hall method. These films were porous and presented a rough morphology and showed a strong signature on the presence of vibrational Cr-O bonding. The solid-liquid surface contact angle measurements revealed a large contact angle which is indicative of reduced surface energy. Vickers hardness measurement reveals that Cr2O3 thin film with 2% Cu/Cr ratio have high hardness value of 903 HV (0.2 kgf). The antibacterial activity of the films was investigated against two gram-positive (Bacillus Subtilus and Bacillus Meurellus) and two gram-negative bacteria (Escherichia Coli and Acetobacter Rhizopherensis). A comparison was established both under dark and UVA light in terms of structural properties of the films. Antibacterial activity was significantly enhanced with the increase in Cu/Cr ratio. Interestingly, the UVA light further facilitated to boost the antibacterial effect against both types of bacteria. A good correlation was found between the structural parameters and the zone of inhibition.