The Effect of SiO2Shell on the Suppression of Photocatalytic Activity of TiO2and ZnO Nanoparticles

In this study, we investigate the potential use of TiO₂@SiO₂ and ZnO@SiO₂ core/shell nanoparticles (NPs) as effective UV shielding agent. In the typical synthesis, SiO₂ was coated over different types of TiO₂ (anatase and rutile) and ZnO by sol-gel method. The synthesized TiO₂@SiO₂ and ZnO@SiO₂ NPs were characterized by UV-Vis, XRD, SEM and TEM. The UV-vis absorbance and transmittance spectra of core@shell NPs showed an efficient blocking effect in the UV region and more than 90% transmittance in the visible region. XRD and SAED studies confirmed the formation of amorphous SiO₂ coated over the TiO₂ and ZnO NPs. The FESEM and TEM images shows that coating of SiO₂ over the surface of anatase, rutile TiO₂ and ZnO NPs resulted in the increase in particle size by ~30 nm. In order to study the UV light shielding capability of the samples, photocatalytic degradation of methylene blue dye on TiO₂@SiO₂ and ZnO@SiO₂ NPs was performed. Photocatalytic activity for both types of TiO₂ NPs was partially suppressed. In comparison, the photocatalytic activity of ZnO almost vanished after the SiO₂ coating.