Oxygen-Tailored MoS₂ as a High-Performance Substrate for Pressure-Induced Surface-Enhanced Raman Spectroscopy

Pressure-induced SERS (PI-SERS) has garnered increasing attention due to its applications in enhancing Raman signals under extreme conditions. However, the effective implementation of PI-SERS enhancement and the elucidation of its underlying mechanisms remain open questions. In this study, we introduce an innovative approach utilizing oxygen-tailored MoS₂ as SERS substrates, significantly improving PI-SERS performance. This method enables the detection of trace dye molecules at ambient conditions and enhances SERS performance under high-pressure environments. Compared to MoS₂, the oxygen-incorporated MoS₂ (MoS_1.4O_1.6) substrate lowers the detection limit to 10^-7 M of Rhodamine 6G (R6G) molecules and achieves a maximum enhancement factor (EF) of 1.53 × 10⁶. Density functional theory (DFT) calculations reveal the significant intermolecular charge transfer (CT), which consequently results in pronounced Raman enhancement. The SERS performance of MoO₃ substrates exhibits a gradual decrease with increasing pressure, with an abrupt increase observed at 8.49 GPa. This increase can be attributed to the resonant coupling between pressure-induced bandgap narrowing of MoO₃ and the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of R6G molecules. This study provides new insights into the PI-SERS enhancement mechanism, offering promising perspectives for advancing SERS applications in high-pressure scenarios.