Defect-Engineered Monolayer MoS2 via Chemical Etching: A Facile Route to Study SERS Sensitivity

Abstract

Controlled sulfur vacancies (Sv) engineering in monolayer molybdenum disulfide (ML-MoS2) has emerged as a powerful strategy to enhance its surface-enhanced Raman scattering (SERS) performance. In this study, we investigate the effect of chemical (H2O2) etching time on Sv formation in ML-MoS2 and its subsequent impact on SERS activity. An optimal etching time (similar to 3 min for 20% H2O2) yields a high density of Sv sites that act as active adsorption centers and localized donor states, resulting in an similar to 80-fold increase in enhancement factor (EF) and a similar to 100-fold improvement in the detection limit (2.35 x 10-10 m) compared to pristine MoS2 (1 x 10-8 m), while performing SERS measurements. In addition, donor-like behavior of the Sv sites is confirmed by computational simulations. However, prolonged etching beyond the optimal Sv concentration results in oxygen substitution at Sv sites, significantly reducing the adsorption capacity and surface chemical activity of ML-MoS2, ultimately impairing its SERS performance. This study highlights the critical role of the etching duration in modulating Sv-defects to tune the opto-chemical properties of ML-MoS2, offering a promising strategy for the development of chemical mechanism-based SERS sensing platforms.