Abstract：When we use nano-structured materials for surface-enhanced Raman scattering (SERS), we will first test the absorption spectrum because original researchers believe that the reason why nano-structured materials generate SERS is that the absorption of incident light by nano-structured materials causes the localized surface plasmon resonance (LSPR), so we equate the curve of SERS enhancement factor with wavelength to the absorption spectrum curve. In recent years, some scholars believe that the connection between them can be very indirect and can be misleading in many cases. AgNPs are famous for their ability to significantly improve Raman scattering due to their local surface plasmon resonance, so AgNPs are the ideal nanomaterial for the substrate. In order to clarify the specific relationship, we studied the enhancement factor (EF) of surface-enhanced Raman scattering, absorption spectra and spatial electric field distribution of silver nanoparticles (AgNPs) in three different states, experimentally and theoretically. Experimentally, we prepared Ag-sol by chemical reduction method. They were characterized by a transmission electron microscope (TEM), ultraviolet-visible spectrophotometer (UV-Vis) and Raman’s measurements and statistics and calculations of the EF and absorption spectra of silver sols were carried on. Theoretically, we used the simulation software COMSOL Multiphysics to establish different aggregation types of AgNPs models, and simulated the EF curve with wavelength and absorption spectra corresponding to the experiments. The results show that the spatial distribution of surface plasmon resonance plays an important role in absorption and maximum EF value. The resonance absorption peak with a fixed position(first peak position) is mainly affected by the “single particle type” effect, and the absorption peak at the maximum EF (the second peak position) is dominated by the blue-shifted resonance peak caused by the “coupling gap type” effect, the maximum EF value and the position of the second absorption peak will be influenced by the particle gap, polarization angle and other factors. Studies have shown that the absorption spectrum of the AgNps sample is partially related to the maximum EF curve.
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