Deactivation of photocatalytically active ZnO nanoparticle by surface capping with poly vinyl pyrrolidone

Nanoparticles of zinc oxide (ZnO) were prepared by the precipitation method from zinc sulphate (ZnSO4.7H2O) and sodium bicarbonate (NaHCO3). Organization, stabilization of the ZnO nanoparticles from further growth and partially inhibiting the photodegradation was achieved by capping with poly vinyl pyrrolidone (PVP). Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate the structure, morphology and particle size. Thermogravimetric-differential thermal analysis (TG-DTA) was used to study the thermal behavior. In addition, photocatalytic degradation of Rhodamine B (RhB) in aqueous solution was performed using bare and modified ZnO nanoparticles under the illumination of UV light. Various parameters affecting the degradation performance such as catalyst loading, initial dye concentrations, pH and concentration of capping agent were examined. The results showed that PVP capped ZnO nanoparticles have reduced photocatalytic activity than that of bare ZnO nanoparticles. The reduction in the chemical oxygen demand (COD) and total organic carbon (TOC) results revealed the reduced photocatalytic activity of PVP capped ZnO. The UV-shielding property was evaluated by measuring the transmittance. The reduced photocatalytic activity of PVP capped ZnO nanoparticles will enhance their performance as durable, safe and non reactive UV blockers in cosmetics.