Advances in Fiber Optic Surface-Enhanced Raman Spectroscopy Sensors

Surface-enhanced Raman spectroscopy (SERS) is a highly specific and sensitive analytical technique that identifies molecules by amplifying Raman fingerprints through electromagnetic (EM) and chemical (CM) enhancement mechanisms. When SERS is integrated with microstructured optical fibers, the resulting fiber optic SERS sensors extend the applications for in vivo and in situ analysis. This Review discusses recent advancements in fiber optic SERS sensors. It focuses on the additional Raman signal enhancement achieved through specialty optical fibers, their interaction with SERS active materials, and the corresponding sensing systems. We also highlight the unique advantages, such as enhanced sensitivity, remote sensing capability, and challenges including stability, reproducibility, and background noise. Finally, we discuss the technical development trends, provide an overview of fiber optic SERS sensor applications in liquid-, gas-, and solid-phase analytes, and propose future research directions to overcome current limitations.