Highly sensitive evanescent wave SERS probe based on exposed-core optical fibers and its application

In this study, we developed a convenient and effective method for the fabrication of evanescent wave fiber surface-enhanced Raman scattering (SERS) probes constructed with ordered silver nanocolumn arrays on the curved surface of an exposed core. An exposed core optical fiber (ECF) is a type of fiber in which the cladding is intentionally removed, providing direct access to the evanescent field of the core. Such fibers enable obtaining high evanescent field power on the core side and rapid liquid infiltration and offer a strong interaction of the evanescent wave with analytes and a long effective interaction path. Besides, the silver nanocolumn array structure coated on the curved surface of the exposed core has a larger specific surface area. Furthermore, the silver nanocolumn array structures enhance the local evanescent field surrounding the ECF to excite the target molecules and have strong light capture for the incident light, providing light-matter overlap and enhanced interaction to improve sensitivity. Such ECF SERS probes can efficiently detect 4-aminothiophenol (4-ATP) and thiram in situ, and a low detection limit of 10^-10 M for 4-ATP is achieved. This paper presents an easy and cost-effective technique for fabricating a highly effective and good reproducible evanescent wave fiber SERS probe, taking advantage of the synergy between manipulated ECF properties and silver nanocolumn array structures, and the probe exhibits great potential for label-free sensing and detection of biomolecules.