Ag@Au@4-NPH@ZIF-8 based nucleophilic addition strategy for SERS detection of gaseous acetone

Surface-enhanced Raman scattering (SERS) technique has significant advantages in the detection of gaseous small molecules, but it still faces challenges such as low adsorption capacity of gaseous small molecules on the surface of the SERS substrate, and low detection sensitivity due to the small Raman scattering cross section. In this paper, a nucleophilic addition strategy based on Ag@Au@4-nitrophenylhydrazine (4-NPH) @zeolite imidazolium ester backbone material-8 (ZIF-8) is proposed for achieving highly sensitive SERS detection of gaseous acetone. The SERS sensing platform was constructed by synthesizing Ag@Au nanoparticles with a core-shell structure modified with 4-NPH as a Raman reporter molecule, which was then encapsulated in a ZIF-8 porous framework. The nucleophilic addition reaction mechanism between acetone and 4-NPH was systematically investigated using density-functional theory (DFT), which revealed the changes in Raman spectra of 4-NPH due to the reaction and provided a theoretical basis for the specific detection of acetone. In addition, the charge transfer effect of more adsorption sites between the reaction product and the nanogold surface further enhanced the SERS signal. The constructed SERS substrate was demonstrated to have a low relative standard deviation (RSD) as low as 4.8 % for the detection of gaseous acetone, which ensured high sensitivity and reliability, and could detect at a concentration of 100 ppb. The method's excellent immunity to interference in complex exhaled gases gives it the potential to be applied to the non-invasive diagnosis of diabetes, demonstrating significant clinical applications.