Citrate-capped gold nanoparticle SERS platforms for ultrasensitive detection of cypermethrin

Cypermethrin (CYP), a pyrethroid pesticide, is of paramount importance in detection owing to its broad-spectrum toxicity, which poses risks to both brain tumors in infants and the stability of aquatic ecosystems. Herein, we report rapid, cost-effective, and ultrasensitive detection of CYP using surface-enhanced Raman spectroscopy by citrate-capped gold nanoparticles. Our characterization experiments and density functional theory calculation research revealed that CYP exhibits strong binding affinity to citrate-capped gold nanoparticles, particularly when citrate is in monocarboxylate binding mode. Combined with a pressurized filter substrate and the surface plasmonic effect of gold nanoparticles, the detection limit of CYP can reach 1 × 10^-7 M (∼0.04 ppm), which is below the maximum residual limit of CYP in the environment (∼0.5 ppm). This method paves the way for a new paradigm in the detection of CYP residues in environmental and agricultural monitoring.