Cysteamine modified core-shell nanoparticles for rapid assessment of oxamyl and thiacloprid pesticides in milk using SERS

Surface-enhanced Raman spectroscopy (SERS) with cysteamine modified silver-coated gold nanoparticles (Au@Ag-CysNPs) was presented for fast screening of oxamyl and thiacloprid in liquid samples of milk. Concentrations at different levels were detected ranging from 0.5 to 10 ppm by choosing 500-1600 cm(-1)spectral range. A strongest Raman peak at 679 cm(-1)was ascribed to oxamyl, whereas a band at 1095 cm(-1)was associated with thiacloprid in milk samples. The morphology and average size of core-shell nanoparticles (Au@AgNPs) and Au@Ag-CysNPs were acquired by High-resolution transition electron microscopy images and dynamic light scattering. Images showed that Au@AgNPs which had a core size of 28 nm and a shell of 6 nm thickness was modified with 6 nm cysteamine hydrochloride successfully. High coefficient of determination (R-2) values of 0.9968 and 0.9875 was calculated for oxamyl and thiacloprid with the limits of detection of 0.031 ppm and 0.023 ppm, respectively. The current novel nanoparticle was easy to prepare and was suitable to serve as a sensitive substrate for SERS detection applications, which could be employed for assessing other accidental contaminants in other food matrices in future studies.