Ag@ZIF-8 core-shell nanocomposites as sensitive and stable SERS substrates: Synthesis, optimization, and application in pollutant detection

Although surface-enhanced Raman scattering (SERS) is a powerful spectral analysis technique, its practical application is restricted due to the poor chemical stability of some noble metal nanoparticles. In this work, Ag@ZIF-8 nanocomposites with different ZIF-8 core-shell thicknesses were prepared by coating AgNP surfaces with polyvinylpyrrolidone and adjusting the dosage of zinc nitrate and 2-methylimidazole. Several characterizations have confirmed that the Ag@ZIF-8 nanocomposites was successfully prepared. Based on transmission electron microscopy images and SERS spectral intensity, it was determined that Ag@ZIF-8 nanocomposites with a ZIF-8 shell thickness of 30 nm exhibited optimal SERS performance. As a result of evaluating the uniformity and stability of the composite with 4-ATP as the probe molecule, it showed a relative standard deviation of 6.91 % and a decrease in SERS intensity of 4.5 % after 28 days. Based on the results obtained with Ag@ZIF-8 nanocomposites as the SERS substrate, the detection limits of 4-mercaptopyridine and thiram were as low as 5.87×10 −9 M and 6.61×10 −8 M, respectively. Furthermore, the finite-difference time-domain simulation reveals an enhancement factor of 2.6×10 6 , which is in good agreement with the experimental value of 1.8×10 6 , confirming its effectiveness as a SERS substrate.