Effect of metal ion doping on the optical properties and the deactivation of photocatalytic activity of ZnO nanopowder for application in sunscreens

The synthesis and characterization of ZnO nanoparticles doped with different metals (Al, Fe, Cu) were studied in order to reduce the photocatalytic activity of ZnO without modifying its optical properties for application in sunscreen. The metal doped ZnO materials were prepared by a simple co-precipitation method from corresponding metal precursors. The effect of metal ion doping on the crystal structure, morphology and optical properties of ZnO was respectively characterized by XRD, SEM and UV-visible diffuse reflectance. The photocatalytic activity was evaluated via the bleaching of methylene blue under UV irradiation. According to the results, the metal ion doping modified the cell volume, reduced the crystallinity and decreased the particle size of ZnO, which induces the increase of structural defects and then the suppression of its photocatalytic activity. The metal doped ZnO materials exhibited the UV absorption capacity comparable to the undoped ZnO. However, the optical properties in the visible region of ZnO were influenced by the nature of metal dopant The Fe and Cu doping strongly enhanced the visible light absorption whereas the Al doped ZnO sample showed the visible light transparency, which make this material a promising constituent of sunscreen. (C) 2015 Elsevier B.V. All rights reserved.