Plasma-Engineered\nMonolayer MoS<sub>2</sub> Films\nfor Ultra-Sensitive Molecular Detection

Recent surface-enhanced Raman spectroscopy\n(SERS) developments\ninvolve using nonmetallic materials as substrates. Molybdenum disulfide\n(MoS<sub>2</sub>) is a notable nonmetal semiconductor surface-enhanced\nRaman scattering (SERS) substrate because of its low cost, abundance,\nremarkable stability, and considerable chemical activity. However,\nits limited SERS activity has significantly impeded its advancement\nin SERS research. Herein, we report a facile and efficient approach\nfor rapidly producing monolayer MoS<sub>2</sub> films with adjustable\nsulfur vacancies via nitrogen plasma treatment. Monolayer MoS<sub>2</sub> films exhibit exceptional sensitivity for SERS detection\nby manipulating the vacancy density. The optimized MoS<sub>2</sub> substrate achieved a detection limit of roughly 10<sup>–10</sup> M and an enhancement factor of 2.29 × 10<sup>5</sup> for rhodamine\n6G (R6G) probe molecules. We further illustrated that introducing\nsulfur vacancies can alter the bandgap structure of MoS<sub>2</sub>, thereby facilitating the separation of internal charge carriers\nand intensifying interactions with the target components. The vacancy-assisted\ntechnique paves the path for the widespread use of semiconductor-based\nultrasensitive molecular detection.