Sb2S3 micro-ring SERS substrates fabricated via femtosecond laser direct writing

Noble-metal-free surface-enhanced Raman spectroscopy (SERS) substrates have the advantages, such as abundant resources, uniformity, good biocompatibility, and chemical stability, and they have sparked widespread attention in food safety assessment. However, the lack of controllable synthesis and fabrication method limits their performance in practical applications, especially in the production of high SERS activity substrates. In this study, we introduce a femtosecond laser direct writing technique to precisely manipulate and modify microstructures, successfully fabricating micro-rings of different sizes. Benefiting from the localized field enhancement effect of the optical microcavity, the Sb 2 S 3 micro ring exhibits significantly enhanced Raman signals compared to the unmodified Sb 2 S 3 thin film and the degree of signal enhancement is closely related to the size of the micro rings. Notably, the in-situ formed Sb nanoparticles during the micro ring fabrication process generate pronounced plasmonic effects. These plasmonic hot spots synergistically couple with the localized field enhancement of the optical microcavity, enabling secondary amplification of Raman signals. Furthermore, we used rhodamine 6G (R6G) and basic orange II as probe molecules, and the results indicate that the proposed Sb 2 S 3 micro-ring substrate exhibits excellent SERS performance. This study demonstrates the potential of using advanced laser technology to manufacture highly active noble-metal-free SERS substrates and highlights the importance of microstructure design in enhancing Raman signals, providing new insights for future applications in food safety detection and other fields. • Innovative Fabrication : Femtosecond laser writing yields reproducible and controllable micro-rings on noble-metal-free SERS substrates. • Signal Enhancement : Sb₂S₃ micro-rings greatly enhance Raman signals, with performance tied to ring width and structure design. • Wide Applications : The substrates show strong SERS response for Rhodamine 6G and Orange II in food safety applications.