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@SiO2 and ZnO@SiO2 core/shell nanoparticles (NPs) as effective UV shielding agent. En 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 similar to 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.