Preparation of PVP-coated copper oxide nanosheets as antibacterial and antifungal agents

Copper oxide (CuO) nanosheets synthesized in polyvinylpyrrolidone (PVP) were characterized with respect to antimicrobial activity by quick precipitation method. Different sizes and shapes of CuO nanosheets were obtained by simple variations of PVP concentrations. The x-ray diffraction results revealed the formation of pure-phase CuO with monoclinic structure. Transmission electron microscopy analysis showed that the average ratio of length to width of these nanosheets increased with increasing PVP concentrations. Due to the quantum size effect, CuO nanosheets exhibit a blue shift in the ultraviolet-visible spectra. Field emission scanning electron microscopy results showed that as the concentration of PVP increased, well-defined morphologies were formed on the surface of the products. Energy dispersive analysis of x-ray clearly confirmed the presence of Cu and O with an atomic ratio of 1:1. Fourier transform infrared spectroscopy results showed that C=O in PVP coordinated with CuO and formed a protective layer. The mechanism of the reaction was also discussed. CuO nanosheets in suspension showed activity against a range of bacterial pathogens and fungi with minimum bactericidal concentrations (MBCs) ranging from 100 to 5000 µg/mL. The extent of the inhibition zones and the MBCs was found to be size-dependent.