Investigation of the Contribution of Allotropic Modifications of Carbon to the Morphology and the Optical and Photocatalytic Properties of Nanostructured Zinc Oxide Films

Zinc oxide films doped with different allotropic modifications of carbon, such as carbon nanospheres, graphite, graphene oxide, and multilayer carbon nanotubes, were synthesized using the sol-gel technology. The scanning electron microscopy analysis of the surface morphology of the samples showed that in one of the allotropic modifications, carbon particles act as growth sites for zinc oxide branches, resulting in the hierarchically organized surface of the samples. Optical spectrophotometric measurements showed that in all cases there was a decrease in the band gap of the samples compared to undoped zinc oxide, as well as an increase in the energy of the Urbach tail, indicating an increase in the degree of energy disorder at the band edges. The observed complex non-monotonic dependence of the changes in the optical absorption of aqueous Nile blue A solutions during photocatalytic degradation may indicate the formation of stable intermediates, as confirmed by IR spectroscopy.