Chiral spiny L-au@ag@ZIF-8 three-layer core-shell SERS substrate for sensitive detection of quinalphos in tangerines

The sensitive detection of quinalphos in food is crucial due to its improper use and the potential for serious harm. Surface-enhanced Raman spectroscopy (SERS) technology, provides a new way for rapid and ultra-sensitive detection. To exploit the molecular sieving effect of metal-organic frameworks (MOFs) in mitigating interference from food matrix components during pesticide residue detection, a novel chiral spiny L-Au@Ag@ZIF-8 (L-AAZ) three-layer core-shell composite was developed as an effective SERS substrate, with chiral L-AABPs providing abundant "hot spots" and spiny ZIF-8 shell provides excellent absorption properties, causing a five-fold increase in SERS intensity compared to traditional Au@Ag NPs. The experimental results revealed that L-AAZ achieved a high enhancement factor (EF) of 3.15 × 10⁵, a low limit of detection (LOD) of 6.56 × 10^-10 M, and a relative standard deviation (RSD) of 14.6 % for malachite green (MG), indicating its superior SERS sensitivity and consistency. Moreover, it demonstrated stable performance, maintaining good storage stability for up to 55 days. The substrate's suitability for the actual fruit sample (tangerine) was confirmed, showing an LOD of 10 ng/mL, demonstrating its capability for rapid and sensitive detection of trace amounts of pesticide residues in food.