The Effect of SiO₂ shell on the suppression of photocatalytic activity of TiO₂ and zno nanoparticles

In this study, we investigate the potential use of TiO₂@SiO ₂ 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.