Among these metal oxides, titanium dioxide (TiO 2) has attracted much attention due to its wide range of applications such as paint industry, biomedicine, electronics, and environmental engineering. Various types of photocatalysts such as TiO 2, ZnO, Al 2O 3, WO 3, Fe 3O 4, CeO 2, and their composites have been used for the degradation of organic pollutants. In addition, as per literature reports, enough research work has also been carried out related to the purification of water by photocatalysis. It has been found that photocatalysis is a promising technique for the destruction of dyes using semiconductor catalysts under light irradiation. Physical methods also have the disadvantages such as the pollutants simply transfer from one phase to another rather than their destruction. Although the biological method is cost-effective, the dyes are only adsorbed on the sludge and are not degraded in this method. A number of technologies have been developed to remove the organic pollutants including chemical treatment such as chlorination and ozonation, electrochemical treatment, physical treatment such as adsorption by activated carbon and membranes, biological treatment, and a combined chemical-biological method. Among the pollutants, synthetic organic dyes used as coloring agents are considered as one of the potential sources of nonaesthetic pollutants which contaminate surface and ground water and can harm ecological resources including water quality, soils, plants, and animals and also human health. However, different industries such as textile, paper, leather, ceramic, cosmetics, and ink and food processing release various organic and inorganic pollutants, which cause a great health hazard to humans and the aquatic environment when discharged to the environment without further treatment. The boom in industrialization and mass production undoubtedly benefit humans with numerous latest products and services. This study may provide some inspiration for the synthesis of other metal oxide-metal oxide core-shell nanocomposite materials through ultrasound irradiation. After treatment, the catalysts were separated with low-speed centrifugation and successfully reused four times without loss of activity. SiO 2 core-shell particles demonstrated better decolorization of methylene blue dye compared to commercial TiO 2 in aqueous solution under UV light. Zeta potential measurements confirmed that the surface property of the SiO 2 changed after TiO 2 coating. Results showed that TiO 2 nanoparticles coated on the surface of SiO 2 were 6–10 nm in size and retained an anatase crystalline phase. The resulting core-shell nanocomposite particles were characterized by SEM, TEM, FT-IR, XPS, XRF, zeta potential measurements, XRD, and UV-visible spectroscopy. In this study, we report the synthesis of SiO 2 core-shell nanocomposite particles by ultrasound irradiation of a mixture of dispersed SiO 2 nanoparticles, titanium-tetra-n-butoxide (TBOT), and ammonia in an ethanol-water solution medium.

Sio2 tio2 core shell