Reaction-Derived Pickering Emulsion SERS Arrays for Discriminative Quantitation of Analogous Furfuran in Honey

Conventional chromatographic and SERS methods can quantify furfural and 5-hydroxymethylfurfural individually, yet they suffer from inherent limitations: chromatographic systems are cumbersome for field deployment, while routine SERS cannot resolve these structurally homologous furan analogs. Herein, we develop an exogenous modifier-free plasmonic Pickering emulsion SERS platform constructed via in-situ Schiff base reaction self-assembly, which fundamentally resolves the long-standing tradeoff between substrate stability and hotspot accessibility. Using 4-aminothiophenol (4-ATP) as a bifunctional probe, Schiff base derivatization introduces rigid benzene-imine skeletons to amplify subtle structural disparities between the two analogous furan toxins into distinguishable spectral fingerprints, yielding a furfural-exclusive peak at 1661 cm-1 for unambiguous differentiation. The thiol-containing Schiff base products and residual 4-ATP simultaneously act as surface modifiers to tailor silver nanoparticles (Ag NPs) wettability, driving spontaneous three-dimensional interfacial array formation at the water/cyclohexane interface without exogenous stabilizers. The as-fabricated substrate delivers outstanding signal uniformity (RSD = 4.7%), completes full detection within 60 min, and achieves reliable quantification over the range of 10-5-10-3 M (R2 > 0.95). Satisfactory spike recoveries of 91.2-109.6% are obtained in complex honey matrices, and the results show good agreement with HPLC in actual sample testing. This work establishes an in-situ self-stabilized Pickering emulsion SERS paradigm for filed-deployable discriminative quantitation of structurally similar food furan contaminants and provides a universal design strategy for high-hotspot-accessibility plasmonic sensing platforms for rapid on-site food safety analysis.