Fabrication of BSA-protected AgNPs modified MIL-53(Al) as SERS substrate for trace determination of diquat and dipterex

Ultrasensitive Surface-enhanced Raman spectroscopy (SERS) method for the detection of diquat/dipterex was established using bovine serum albumin (BSA)-protected silver nanoparticles (AgNPs) modified MIL-53(Al) (named as BSA/MIL-53(Al)/AgNPs). Compared with unmodified AgNPs, BSA/MIL-53(Al)/AgNPs significantly enhanced the Raman signals of diquat and dipterex and the enhancement factors (EFs) were 1.58 × 10⁷ and 2.34 × 10⁷, respectively. The TEM, XRD, TGA, XPS, UV-vis and FT-IR were utilized to characterize BSA/MIL-53(Al)/AgNPs and the binding of the substrate with diquat/dipterex. The optimal measurement conditions were investigated in detail by single factor experiment and response surface model. The impacts of common pesticides and coexisting substances on the determination of diquat/dipterex were studied. Under optimum conditions, linear calibration curves for detecting diquat/dipterex were established with a limit of detection (LOD) of 0.17/0.89 pmol L^-1 (3S₀/S). The SERS approaches were used to detect diquat and dipterex in several fruits and vegetables. The recovery was 97.10 %-104.82 % with the relative standard deviation (RSD) of 1.04 %-4.15 % (n = 5).