Fabrication of UL-AuAgMSs@β-CD Composite Substrate for Synergistically Enhanced SERS Trace Detection of Organophosphorus Pesticide Residues

Organophosphorus pesticides (OPPs) seriously threaten human health and ecosystems due to their environmental persistence, creating an urgent demand for highly efficient and sensitive detection technologies in environmental monitoring. UL-AuAgMSs@β-CD composite substrate was fabricated through the integration of urchin-like Au-Ag microspheres (UL-AuAgMSs) with β-cyclodextrin (β-CD) to overcome three persistent challenges in surface-enhanced Raman scattering (SERS) detection, i.e., low molecular selectivity, substrate instability, and complex matrix interference. Optimizing the three-dimensional branched structure of UL-AuAgMSs through controlled silver nitrate (AgNO 3 ) addition, a dual enhancement becomes available from both electromagnetic effects (nanotip-localized hotspots) and chemical effects (β-CD's molecular recognition capabilities). The composite substrate presented superior performances, a detection limit of 10⁻ 13 M for crystal violet (CV), excellent reproducibility (RSD = 9.10%, n = 13), and long-term stability (73.35% signal retention after 21 days), surpassing conventional single-metal substrates. Its versatility is further demonstrated in detecting methylene blue (MB), methyl orange (MO), the OPP chlorpyrifos (CPF), and the pesticide intermediate 4-aminothiophenol (4-ATP). This study proposes a synergistic strategy combining morphological engineering and molecular recognition. It offers a stable and adaptable SERS platform for rapid trace pollutant monitoring in food safety and complex environments.