3 nm-Wide WO_3-x Nanorods with Abundant Oxygen Vacancies as Substrates for High-Sensitivity SERS Detection

Oxygen vacancy (V-o) engineering is a powerful tool to improve semiconductor metal oxide-based surface-enhanced Raman scattering (SERS) activity due to the enriched surface states of substrates. However, the current energy-consuming high temperature hydrogen reduction methods of introducing V-o and the poor sensitivity impede practical applications of semiconductor SERS. In this work, a facile solvothermal method was developed to prepare ultrafine WO3-x nanorods (similar to 3 nm width) for highperformance SERS substrates. The lowest detection limit of the rhodamine 6G (R6G) molecule on the Vo substrate can be as low as 10(-10) mol/L and exceeds that of unmodified WO3 by more than two orders of magnitude. Experimental and calculated results suggest that the V-o-induced localized surface plasmon resonance (LSPR), diverse vibronic coupling, and enhanced charge transfer synergistically account for this outstanding activity. These findings can provide insights into the rational design of oxygen vacancy tailored semiconductor SERS substrates.