Porous Ceramic ZnO Nanopowders: Features of Photoluminescence, Adsorption and Photocatalytic Properties

The grainy and porous ZnO powders were synthesized by thermal decomposition of zinc nitrate and polymer-salt method. The comparative study of the crystal structure, morphology, luminescence, adsorptive and photocatalytic properties of ZnO powders was carried out. The addition of PVP in initial aqueous solutions of zinc nitrate determines the remarkable change of powder morphology and decreases the average size of ZnO nanocrystals. Luminescence spectra in the visible spectral range indicate the significant difference of structural defects types in grainy and porous powders. Porous powders demonstrate high ability for singlet oxygen photogeneration and photocatalytic properties. The kinetics of diazo dye adsorption on both powders is described successfully by the kinetic equation of pseudo-second order. Kinetic dependencies of photocatalytic oxidation of Chicago Sky Blue diazo dye using as grain ZnO powder so as porous ZnO powders are described by the Langmuir–Hinshelwood model but process rates are different. Porous ZnO powder demonstrates strong ability for photogeneration of singlet oxygen under visible irradiation and high photocatalytic properties (rate constant 0.042 min−1).