Photocatalytic degradation and photo-generated hydrophilicity of Methylene Blue over ZnO/ZnCr2O4 nanocomposite under stimulated UV light irradiation

This paper deals with the relationship between photocatalysis and photo-generated hydrophilicity under UV
light irradiation of ZnO/ZnCr2O4 nanocomposite film prepared via spray pyrolysis method. XRD investigations
indicate that the nanocomposite sample show the presence of würtzite ZnO phase having crystallites oriented
preferentially along c-axis with the presence of a secondary phase spinel of ZnCr2O4. Indeed, a special emphasis
has been focused on the photoluminescence study of such nanocomposite film which point out the considerable
role of the surface and bulk defects in this nanocomposite. Consequently, the synergistic effect between ZnO and
ZnCr2O4 has a notable beneficial effect on photocatalytic activity improving as well as hydrophobic to hydrophilic transition under UV light irradiation which may be attributed to the active surface area, the adsorption of
the dye as well as efficient electron-hole charge separation and transfer at the interfaces of ZnO/ZnCr2O4 nanocomposite allowing the enhanced hydroxyl and superoxide radicals production. Such important contribution
of radicals was confirmed experimentally when using scavengers in the photocatalytic reaction.