Fabrication of Graphene-Based TiO2@CeO2 and CeO2@TiO2 Core–Shell Heterostructures for Enhanced Photocatalytic Activity and Cytotoxicity

Development of light-harvesting properties and inhibition of photogenerated charge carrier recombination are of paramount significance in the photocatalytic process. In the present work, we described the synthesis of core–shell heterostructures, which are composed of titanium oxide (TiO2) and cerium oxide (CeO2) deposited on a reduced graphene oxide (rGO) surface as a conductive substrate. Following the synthesis of ternary rGO-CeO2@TiO2 and rGO-TiO2@CeO2 nanostructures, their photocatalytic activity was investigated toward the degradation of rhodamine B dye as an organic pollutant under UV light irradiation. The obtained structures were characterized with high-resolution transmission electron microscopy, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller, X-ray photoelectron spectroscopy surface analysis, and UV–Vis spectroscopy. Various parameters including pH, catalyst dosage, temperature, and contact time were studied for photocatalysis optimization. Heterostructures showed considerable advantages because of their high surface area and superior photocatalytic performance. In contrast, rGO-CeO2@TiO2 showed the highest photocatalytic activity, which is attributed to the more effective electron–hole separation and quick suppression of charge recombination at core–shell phases. A biological assay of the prepared heterostructure was performed to determine the cytotoxicity against breast cancer cells (MCF-7) and demonstrated a very low survival rate at 7.65% of cells at the 17.5 mg mL–1 concentration of applied photocatalyst.