Core-shell Ag/MOFs SERS platform for trace detection of organic dye contaminants

The exploration of robust, sensitive, and reliable surface-enhanced Raman scattering (SERS) substrates is depend on the fabrication of high-density "hot spots". An innovative SERS substrate was fabricated by integrating spherical Ag with multi-cavity metal-organic frameworks (MOFs). The immobilization of MOFs on the Ag surface significantly enhanced the enrichment efficiency of target molecules. Scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and Brunauer-Emmett-Teller measurements were utilized to characterize the morphology, elemental composition, and crystal phase structure of the Ag/MOFs substrate. As anticipated, the adsorption behaviors of crystal violet (CV) and Congo red (CR) on the Ag/MOFs substrate were well fitted by the Freundlich adsorption isotherm, with a correlation coefficient (R²) exceeding 0.98, indicative of a heterogeneous adsorption process on the substrate surface. The Ag/MOFs substrate achieved a minimum detection as low as 1.0 × 10^-10 mol L^-1 for both CV and CR. Furthermore, a favorable linear relationship was observed between the SERS intensity and the negative logarithm of analyte concentration over the range of 1.0 × 10^-9 mol L^-1 to 1.0 × 10^-4 mol L^-1. The enhancement factor of the Ag/MOFs substrate toward CV was determined to be 3.4 × 10⁶. Additionally, the Ag/MOFs substrate shows excellent uniformity and reliable signal reproducibility. Collectively, this work provides a promising strategy for the sensitive detection of organic pollutants in aqueous environment.