Structural and optical characterization and efficacy of hydrothermal synthesized Cu and Ag doped zinc oxide nanoplate bactericides

This study reports on a novel synthesis of pure zinc oxide and both Cu and Ag doped ZnO nanoplates using a simple and low­cost hydrothermal method. The structural and optical properties of the nanoplates were quantified and the materials were tested for antibacterial activity. X­ray diffraction revealed the formation of the wurtzite phase of ZnO and scanning and transmission electron microscopy showed the formation of randomly oriented ZnO nanoplates, having thickness less than 80 nm and diameter less than 350 nm. The elemental analyses of both the pure and doped samples were evaluated by energy dispersive X­ray spectrometry. The FTIR spectra of ZnO nanomaterials showed the predictable bands at 3385 cm ­1 (O–H stretching), 1637 cm ­1 (stretching vibration of H 2 O), 400 cm ­1 to 570 cm ­1 (M­O stretching). The as synthesized samples showed a strong absorption peak in the UV region (~376 nm) and a near band edge emission at 392 nm with some defect peaks in the visible region. Escherichia coli, Staphylococcus aureus and Salmonella typhi bacteria were used to evaluate the antibacterial activity of undoped and doped ZnO. Although all the materials showed some antibacterial characteristics, the Ag doped ZnO exhibited remarkable destruction of bacteria with low minimum inhibitory concentration (MIC) values of 40 µg/ml for E.coli and S.aureus and only 20 µg/ml (S.typhi), which are comparable to commercial antibiotics without optimization. Further, these chemically modified nanoparticles will be applicable for various industrial or medicinal applications such as the deposition of antimicrobial coatings and food packaging applications.