Biosensing of malachite green in fish using a high-stability fiber-optic SERS probe biosensor fabricated via...

Surface-enhanced Raman scattering (SERS) fiber-optic probes have attracted significant interest in environmental monitoring and food safety due to their high sensitivity and remote detection capabilities. However, conventional fiber-optic SERS probes face limitations in practical applications, including susceptibility to oxidation of nanostructures and insufficient long-term stability. This study developed a hybrid fabrication strategy integrating laser-induced self-assembly and the Stöber method to controllably assemble silver nanocubes (Ag NCs) arrays on the end faces of optical fibers, followed by silica (SiO₂) thin-film encapsulation, thereby producing a high-stability SERS probe. Experimental results demonstrate that the SiO₂ coating effectively inhibits Ag NCs oxidation, with the probe retaining 83 % of its initial SERS intensity after 30 days, compared to 57 % for uncoated counterparts. When using crystal violet (CV) as the probe molecule, the enhancement factor (EF) is 1.59 × 10⁵. Practical validation demonstrates a linear detection range of 10^-7-10^-3 M (R² = 0.95173) for malachite green (MG) in aquaculture samples, with a limit of detection (LOD) of 1.27 × 10^-7 M. To further verify its matrix effect, MG residues were detected in lake water, fish blood, and fish meat, respectively. The probe was ultimately integrated into a standardized FC-compatible device, which succeeded in detecting MG residues in fish that had been cultured in MG-contaminated water for 24 h. This work not only provides a novel anti-oxidation design strategy for SERS probes but also advances a highly sensitive, low-toxicity, and portable sensing solution for aquatic product safety monitoring.