Ceramic ZnO-SnO2-Fe2O3 Powders and Coatings -Effective Photogenerators of Reactive Oxygen Species

Abstract

Ceramic ZnO-SnO2-Fe2O3 powders and transparent coatings on glasses prepared using the non-isothermal polymer-salt method demonstrate a strong ability to generate chemically active oxygen species under UV and visible irradiation. Crystal structures and morphologies of these materials were studied using the XRD and the SEM analysis. It was found that there are significant differences in the crystal structure of ceramic powders and thin coatings. The powders consist of randomly oriented oxide nanocrystals of size ~47 nm. The strong orientation of the ZnO nanocrystals due to their interaction with the glass substrate is observed in the coating structure. Experimental data show that thin ceramic coatings are transparent (~90%) in the visible spectral range and the band gap of the ceramic material is 3.44 eV. The band gap value of this multi-component ceramic material is described sufficiently using Verlag’s law. Ceramic powders and coatings demonstrate the intensive photogeneration of reactive oxygen species, both in liquid and air. High photocatalytic activity of ZnO-SnO2-Fe2O3 ceramic coatings and powders was observed upon the oxidation of the diazo dye, Chicago Sky Blue. In the presence of transparent photocatalytic coating, the value of the constant rate of the dye photodecomposition was high (k = 0.056 min−1). It was found that, in spite of their short life time, photogenerated reactive oxygen species demonstrate the ability to decompose dye molecules located up to a distance of 0.5 mm from the surface of ceramic coating. Obtained experimental results suggest that the prepared ceramic materials are promising for different practical applications of the photocatalytic materials.

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

“…This phenomenon was explained by the significant increase in the process of photogenerated electron-hole pairs recombination at the growth of exciting light intensity. Non-linear dependence I SO = f(I ex ) observed in [34] was similar to the dependencies of the photocatalytic activities of different semiconductors from the intensities of exciting light irradiation reported in [51][52][53]. Observed linear dependence I SO = f(I ex ) for powder 2 indicates the high effectiveness of enhancing singlet oxygen photogeneration by increasing the exciting light intensity.…”

“…The deviation from the linearity of the dependence ISO = f(Iex) was observed in [34] at the relatively high intensity of exciting light (Iex > 1200 mW/cm 2 ). This phenomenon was explained by the significant increase in the process of photogenerated electron-hole pairs recombination at the growth of exciting light intensity.…”

“…The polymer-salt method is simple, cheap and is applied for the synthesis of different oxides nanoparticles (NPs) [11,15,[31][32][33][34]. Solutions containing soluble polymer and thermally decomposable metal salts are used as oxide NPs precursors in this method.…”