Fabrication of\nGraphene-Based TiO₂@CeO₂ and CeO₂@TiO₂ Core–Shell Heterostructures\nfor Enhanced Photocatalytic Activity and Cytotoxicity

Abstract

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