Biocidal properties of sputtered CdO:ZnO multi-component thin films for potential use in pathogenic bacteria control

Abstract

We report the reduced toxicity level of the CdO thin films by the addition of ZnO in various ratios (10%, 20%, 30% and 40%) and its anti-microbial activities. This investigation also aimed to explore the biocidal properties of the multi-component thin films showing antimicrobial activity against human pathogenic bacteria (HPB). CdO:ZnO mixed oxide thin films are extensively studied due to the importance acquired by the Transparent Conducting Oxide (TCO) in optoelectronic device applications. Radio frequency (RF) magnetron sputtering with a constant power of 40 W at a substrate temperature of 200 °C has been used to deposit thin films. The antibacterial properties of CdO:ZnO multi-component thin films were also compared with that of pure CdO thin films. The biocidal investigation proves CdO:ZnO multi-component thin films as an alternative, eco-friendly, cost-effective biocidal agent. Among the pure CdO and multi-component films, the CdO:ZnO (90:10) films has a maximum inhibition zone (18 mm) observed in Escherichia coli while minimum inhibition zone (10 mm) was shown in B. subtilis at 80 μg ml−1. Toxicity studies revealed 43.30 ± 0.57% (LC50) mortality for Artemia salina larvae at 100 μg ml−1 concentrations within 48 hrs, indicating less toxicity to non-target species. The results showed that CdO:ZnO (90:10) has higher bactericidal effect against Escherichia coli in comparison with pure CdO. As for the high toxicity of cadmium oxide nanoparticles, CdO:ZnO (90:10) can be used to eliminate Escherichia coli like pathogens. From this investigation, it is also revealed that CdO:ZnO (60:40) multi-component thin films possess less toxicity to non-target species and can be considered as a potential TCO with effective bactericidal properties.