Design of a MoS2@Au SERS substrate with synergistic electromagnetic and chemical enhancement for ultra-sensitive detection of tramadol hydrochloride

The integration of noble metals onto semiconductor surfaces has become a key focus in advancing surface-enhanced Raman spectroscopy (SERS) research. Two-dimensional materials such as MoS 2 are valued for their exceptional thermal and chemical stability, making them promising candidates for advanced SERS sensor development. In this study, we synthesized flower-like MoS 2 microspheres (~380 nm in diameter) through a facile hydrothermal method and functionalized their surfaces with gold nanoparticles (AuNPs) to produce MoS 2 @Au composites. Rhodamine 6G, used as a Raman probe, revealed that the enhancement factor of the MoS 2 @Au system increased substantially from 2.78 × 10 5 to 3.79 × 10 7 , and the detection limit improved to an impressive 3.13 × 10 −10  mol/L—exhibiting a two-order-of-magnitude improvement in sensitivity compared with pristine MoS 2 . Detecting trace tramadol hydrochloride holds immense significance. It enables the precise identification of minuscule drug quantities, facilitating early detection of abuse. This provides crucial support for clinical treatment, rehabilitation interventions, and holds vital importance in judicial appraisal and related fields. The composite demonstrated exceptional proficiency in detecting tramadol hydrochloride, achieving an unprecedented detection limit of 10 −10  mol/L, well below clinically relevant thresholds. Finite-difference time-domain simulations revealed the spatial distribution of the electromagnetic field, while density functional theory calculations elucidated the intricacies of charge transfer and bandgap modulation upon tramadol adsorption. These theoretical insights uncovered the fundamental mechanisms driving the observed SERS enhancement. Experimental validation confirmed that AuNP modification substantially enhanced charge transfer efficiency, highlighting the synergistic contributions of electromagnetic and chemical enhancement effects in improving SERS sensitivity. This work not only deepens our understanding of SERS phenomena but also broadens its potential applications in biomedical sensing.