Immobilization of ZnO nanoparticles onto glass spheres: effects of annealing temperature, zinc oxide concentration, and number of coating rounds on the photocatalytic activity under visible light

Abstract

Zinc oxide is a versatile semiconductor material, widely used for its electronic and photocatalytic properties. In this work, we report a response-surface investigation of a simple technique for the immobilization of nanosized ZnO powder onto 5.0-mm glass beads. The nanoparticles are suspended in ultrapure water, and the glass beads are immersed in this suspension under vigorous stirring. The beads are removed from the suspension and calcined, after which a ZnO layer is formed on their surface. Using a modified response-surface methodology (modified Doehlert design), we investigated the effect of the nominal ZnO suspension concentration, the annealing temperature and the number of coating rounds on the amount of ZnO fixed onto the substrates and on the photocatalytic performance of the resulting films under visible light. Our results show that the coated beads have good photocatalytic activity, being able to remove up to 50% of a load of acetaminophen (used as a model contaminant) from a 5.0 ppm solution under simulated solar irradiation. We present and discuss the effects of temperature and precursor concentration, shown to be statistically significant only to a certain extent; limited to the number of coating rounds.