For this, spherical silica nanoparticles (~ 300 nm) were developed by a biomimetic approach and their coating with ceria was performed through a precipitation method. Τhe present work investigates the parameters for the successful coating of silicon oxide nanoparticles surface with a homogeneous cerium oxide shell in an effort to develop core–shell nanostructures. What is more, the experimental results also showed the CSTNs with Ti/Si molar ratio of 5 : 1 had the highest photocatalytic activity and showed higher photocatalytic efficiency compared with other TiO2-SiO2 composites reported for photodegradation of phenol and MB. Since the molar ratio of Ti/Si increased from 1 : 1 to 8 : 1 by degradating both colorless organic pollutant of phenol and colored substances of methylene blue (MB) under UV irradiation, the photocatalytic activity of CSTNs exhibited higher photodegradation efficiency compared with TiO2. Surface charges showed the isoelectric point (IEP) of the CSTNs ranged between silica (IEP at pH 3.10) and titania (IEP at pH 5.29). In addition, the CSTNs with the Ti/Si molar ratio of 5 : 1 had the highest surface area of 176.79 m2/g. The N2 adsorption-desorption isotherms demonstrated the CSTNs with the molar ratio of Ti/Si increased from 1 : 1 to 8 : 1 can be categorized as type IV with hysteresis loop of type H2 and showed to be mesoporous materials. Besides, the TiO2 and the CSTN had the anatase phase after hydrothermal process and calcination at 450☌ for 2 h. It was found that the CSTNs showed different size and surface morphology as the Ti/Si molar ratio changed. Both materials exhibited excellent catalytic activity (100%), making the core-shell material a promising alternative catalyst to pure titania for various applications.Īfter the core-shell nanoparticles (CSTNs) were synthesized by hydrothermal method, we investigated the influence of different molar ratios of Ti/Si on morphology, structure, and photocatalytic activity of the CSTNs. In addition, catalytic activities of the CSNp and pure titania were investigated by monitoring the reduction of 4-nitrophenol to 4-aminophenol by an excess of NaBH4. The results revealed a very potent photocatalyst as the degradation percentage reached 84.27% for the core-shell material compared to the 82% of pure titania with the photodecomposition rates measured at 0.62 and 0.55 μg The photocatalytic activity for NO was examined in a continuous flux photocatalytic reactor under real environmental conditions. The optimization of processing parameters led to well-developed core-shell structures bearing a homogeneous nanocrystalline anatase coating over each silica core. Washing with ethanol and heat treatment followed. To create the core-shell structure, various amounts of titanium isopropoxide were added to the cores and after that a HBPEI-water solution was added to hydrolyze the titanium precursor. First, silica cores were prepared through the hydrolysis-condensation reaction of silicic acid in the presence of hyperbranched poly(ethylene)imine (HBPEI) followed by repeating washing, centrifugation and, finally, calcination steps. Silica-titania core-shell nanospheres, CSNp, were prepared via a simple and environmentally friendly two step route.
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