Electrostatic self-assembly of ZIF-8/Ag nanocomposites as versatile SERS substrates for sensitive detection of environmental pollutants

This study reports the development of an electrostatic self-assembly surface-enhanced Raman scattering (SERS) substrate based on zeolitic imidazolate framework-8 (ZIF-8) decorated with silver nanoparticles (AgNPs). A seed-mediated growth method was employed to synthesize AgNPs with an average diameter of 30 nm, and a mild synthesis process was used to prepare ZIF-8 nanoparticles with an average diameter of 350 nm. The ZIF-8/Ag nanocomposites have been optimized and characterized using a variety of techniques. As a probe molecule, 4-aminothiophenol was used to evaluate the SERS performance of the ZIF-8/Ag nanocomposites, demonstrating low limit of detection to 8.32 × 10 −8  M, respectively. ZIF-8/Ag nanocomposites also demonstrated good signal reproducibility with a relative standard deviation of 12.5 % for 10 −6  M 4-aminothiophenol. Furthermore, the ZIF-8/Ag nanocomposites have successfully been used to detect 4-mercaptopyridine and the pesticide thiram in laboratory tap water with recoveries ranging from 87 % to 113 %. The ZIF-8/Ag nanocomposites were further investigated for their potential use as SERS substrates for the detection of thiram residues on the surface of apples. A finite difference time-domain simulation was also conducted to investigate the SERS enhancement mechanism of the ZIF-8/Ag nanocomposites.