SERS methods for detecting acetamiprid and pymetrozine in fruits using the substrate of CuO-protected silver nanoparticles modified with β-cyclodextrin

Acetamiprid and pymetrozine are effective pyridine insecticides used to kill aphids and whiteflies in agricultural products such as fruits, vegetables and rice, whose residues pose a serious threat to human health. Herein, the silver nanoparticles (AgNPs) modified by β -cyclodextrin ( β -CD) and nano-CuO (named as β -CD/CuO@AgNPs) were synthesized and it was used as surface-enhanced Raman spectroscopy (SERS) substrate to determine acetamiprid and pymetrozine. Among four SERS substrates such as AgNPs, β -CD/AgNPs, CuO@AgNPs and β -CD/CuO@AgNPs, β -CD/CuO@AgNPs exhibited the most substantial enhancement of the Raman signals for acetamiprid and pymetrozine, with the enhancement factors (EFs) of 2.16 × 10 6 and 3.86 × 10 6 , respectively. The XRD, TGA, TEM, HAADF-STEM, UV–vis and FT-IR were used to characterize β -CD/CuO@AgNPs and the combination of the substrate with acetamiprid/pymetrozine. Single factor experiment and response surface method were used to optimize pH, dosage of coagulant and nanosubstrate and mixing time. The influences of various interfering substances on the detection system were studied. The excellent linear relationships were respectively established for acetamiprid and pymetrozine in the range of 6.67 × 10 −9 –6.67 × 10 −7 and 1.00 × 10 −8 –1.00 × 10 −6 mol L −1 , with the limits of detection (LODs) were 0.36 and 0.94 nmol L −1 (S/N = 3). This project was successfully used for the detection of acetamiprid and pymetrozine in apple, pear and peach samples. The recoveries in the fruit samples were in the range of 95.5 %–105.0 %.