Triple-role β-cyclodextrin functionalized silver nanoparticles for selective SERS detection of diazinon residue

A multifunctional β-cyclodextrin-functionalized silver nanoparticle (β-CD-AgNP) substrate was developed for selective surface-enhanced Raman scattering (SERS) detection of the organophosphorus pesticide diazinon (DZN). Diazinon is widely used in agriculture to control insect pests on fruits and vegetables, and its residues in food and water are linked to acetylcholinesterase inhibition, neurotoxicity, and aquatic ecotoxicity, prompting strict regulatory residue limits and a pressing need for rapid, sensitive, field-deployable detection methods. In this system, β-CD simultaneously acts as a reducing agent, stabilizer, and host–guest recognition molecule, promoting nanoparticle formation while selectively enriching diazinon near SERS-active sites. UV–Vis spectroscopy, TEM, zeta potential, and SERS analyses confirmed successful nanoparticle formation, effective β-CD functionalization, improved colloidal stability, and enhanced Raman signal amplification relative to bare AgNPs. The platform showed a linear response from 0.01 to 2 ppm ( R 2 > 0.94), a detection limit of 3.15×10⁻ 3  ppm, and good reproducibility (RSD < 6%) in aqueous solution. The application of the method to spiked cucumber samples resulted in recoveries ranging from 101.81% to 119.93%, with a relative standard deviation (RSD) of less than 7% at both 0.5 and 1.0 ppm. A matrix-matched calibration built directly in cucumber extract confirmed near-quantitative recovery (98–100%) at these levels, indicating that the higher aqueous-calibration recoveries reflect matrix-related bias rather than a limitation of the SERS substrate; quantification at 0.01 ppm remained unreliable under both approaches. The β-CD-functionalized substrate also showed improved selectivity toward diazinon over structurally related pesticides, reflecting host–guest molecular recognition. Given its low cost, minimal sample preparation, and portability relative to chromatographic methods, this platform is well suited to on-site regulatory screening and could help close the gap between routine laboratory testing and the growing demand for real-time food safety surveillance. These findings demonstrate a simple strategy for integrating green nanoparticle synthesis with molecular recognition to achieve selective SERS detection of pesticide residues, offering a promising platform for rapid food safety monitoring.