Fabrication of bifunctional gold nanoparticles for self-calibration UV–Vis/surface-enhanced Raman spectroscopy dual-mode analysis of Hg2+ in milk

Multimodal optical detection are good candidates in accuracy improvement in complex food detection, without sacrificing rapidity and sensitivity. Herein, bifunctional gold nanoparticles (AuNPs/4-MBA/Cy/T) based on step-by-step modification of 4-mercaptobenzoic acid, cysteamine, and thymine-1-acetic acid were fabricated for self-calibration ultraviolet-visible spectroscopy (UV–Vis)/surface-enhanced Raman spectroscopy (SERS) dual-mode detection of mercury ions (Hg 2+ ) in milks. The bifunctional UV–Vis and SERS analysis can be attributed to the localized surface plasmon resonance (LSPR) properties of AuNPs. The stable aggregation structure of AuNPs/4-MBA/Cy/T-Hg 2+ can be formed in the presence of Hg 2+ based on specific recognition of thymine, simultaneously decreasing UV–Vis signals and increasing SERS signals, also verified by theoretical simulations. Under the optimum conditions, the AuNPs/4-MBA/Cy/T was applied to establish UV–Vis/SERS dual-mode method for Hg 2+ detection in various milk samples with satisfied analytical performance including rapidity, sensitivity, specificity, accuracy, and repeatability. It offers a novel strategy in developing of self-calibration dual-mode detection for food contaminants analysis.