Silver nanocubes-enhanced tapered fiber SERS probe for highly sensitive detection of levofloxacin residues

Surface-Enhanced Raman Scattering (SERS) has emerged as a powerful analytical technique due to its exceptional molecular specificity and ultra-high sensitivity. However, conventional SERS substrates are challenged by spatial inhomogeneity of hotspots and low light-collection efficiency. A highly sensitive tapered Fiber SERS probe is thus developed, which can enable remote and in-situ detection with an improved reproducibility. Tapered fibers with precisely controllable cone angles were fabricated by chemical etching. Monodisperse silver nanocubes (Ag NCs) were then decorated onto their silanized surfaces through electrostatic assembly. Ag NC generates approximately threefold stronger local electric fields compared to conventional nanospheres under 532-nm laser excitation as revealed by finite-difference time-domain simulations, and there are more obvious electromagnetic hotspots at the particle gaps of the Ag NCs (112 V/m). Experimentally, the probe can achieve a limit of detection of 10^-9 M for crystal violet with an enhancement factor of 3.91 × 10⁶, and exhibits excellent spectral reproducibility and temporal stability. Ultrasensitive detection of levofloxacin residues in milk can be further realized with the presented silver nanocubes-enhanced tapered fiber SERS probe, which can provide a highly sensitive in-situ SERS platform for environmental monitoring, biomedical diagnostics, food-safety, and so on.