Enhanced antibacterial performance of hybrid semiconductor nanomaterials: ZnO/SnO2nanocomposite thin films

Highlights
Preparation of ZnO/SnO2 hybrid nanostructure films with a sustainable photocatalytic antibacterial activity compared with single component semiconductors.
Chemical composition critically influences the improved antibacterial performance of hybrids.
Bacterial growth inhibition observed under dark conditions, indicating undetermined mechanisms additional to photocatalytic ROS production for toxicity.
Abstract
The nano-sized coupled oxides ZnO/SnO2 thin films in a molar ratio of 2:1 (Z2S), 1:1 (ZS) and 1:2 (ZS2) were prepared using sol–gel dip coating method and characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–vis spectroscopy. Escherichia coli (E. coli, ATCC 25922) was selected as a model for the Gram-negative bacteria to evaluate antibacterial property of composite samples compared with single ZnO (Z) and single SnO2 (S) films. The antibacterial activity has been studied applying the so-called antibacterial drop test under UV illumination. The bactericidal activity was estimated by relative number of bacteria survived calculated from the number of viable cells which form colonies on the nutrient agar plates. The influence of the SnO2–ZnO nanocomposite composition on the structural features and on the antibacterial properties of the thin films are reported and discussed. It is found that all coatings exhibited a high antibacterial activity. The coupled oxide photocatalyst Z2S has better photocatalytic activity to bacteria inactivation than ZS, ZS2, Z and S films. Furthermore, nanostructured films were active even in the absence of irradiation.