Submicron Size C@TiO₂ with Multiple Resonance Effects for Surface-Enhanced Raman Spectroscopy and Photocatalysis

Semiconductor materials are biocompatible and stable and have excellent controllable properties; nevertheless, their low sensitivity and enhancement factor limit their application and development in the field of surface-enhanced Raman scattering (SERS). Herein and for the first time, noble-metal-free submicrometer C@TiO₂ was developed as a bifunctional photocatalyst and SERS-enhanced material. Equally, by optimizing the thickness of the C@TiO₂ shell to regulate the electric field strength, the degradation rates of R6G and antibiotic CIP under simulated sunlight irradiation reached 97% and 93% within 14 and 40 min, respectively, which were much higher than those previously reported. Additionally, the C@TiO₂ demonstrated outstanding SERS sensitivity with an EF of 1.13 × 10⁵. Both experiments and theoretical simulations show that the submicrometer hollow-shell C@TiO₂ has multiple resonance effects, i.e., Mie resonance and CT resonance. The efficient SERS and photocatalytic activity of C@TiO₂ are mainly attributed to the strong light trapping ability of the hollow shells as well as the Mie-resonance-induced electric field, providing an additional driving force that reduces the recombination of photogenerated carriers. The electric field strength around C@TiO₂ is directly proportional to its photocatalytic activity, making it feasible to predict catalytic performance by analyzing the spectral information on molecules. As a bifunctional material, the hollow-shell C@TiO₂ not only provides favorable evidence for the study of the SERS synergistic enhancement mechanism but also brings new ideas for the development of photocatalysts.