In situ thermally induced reduction of silver nitrate by polyvinyl alcohol to prepare a three-dimensional porous Ag substrate with excellent adsorption and surface-enhanced Raman scattering properties

Abstract

With the development of surface enhanced Raman spectroscopy (SERS) technology, an efficient and low-cost SERS substrate is urgently needed. In this study, we used polyvinyl alcohol (PVA) as a template and reductant to in situ reduce silver ions through thermal induction, and degraded PVA to obtain a pure Ag substrate. The unique three-dimensional (3D) porous Ag substrate has a multilayered skeleton structure with an average skeleton size of 0.71 μm and an average pore diameter of 0.86 μm. According to the Raman mapping and finite-difference time-domain (FDTD) simulation results, the multilayered Ag skeleton has strong electromagnetic enhancement performance, and can generate more SERS “hot spots” and effectively amplify Raman signals. In the actual application process, using pyridine, Rhodamine 6G (R6G) and crystal violet (CV) as probe molecules, the porous Ag substrates show high SERS reproducibility and sensitivity. The enhancement factor (EF) could reach 10⁷, and the limit of detection (LOD) could reach a concentration of 6.8 × 10⁻¹¹ M. Meanwhile, the complex porous structure provides a high adsorption ability toward dye molecules. After 8 hours of immersion, the UV-vis absorption peaks of R6G and CV solutions decreased by 77.0% and 72.4%, respectively, and the detection concentration could reach 10⁻¹⁴ M, meeting the single molecule detection standard. This substrate provides a new idea for the development of portable Raman equipment that can be used for accurate detection of trace environmental pollutants.