Silver nanoflower SERS substrate incorporating polyoxometalate as an internal standard for selective quantification...

Silver nanoparticles (AgNPs) serve as traditional surface-enhanced Raman scattering (SERS) substrates, exhibiting advantages such as low cost, facile synthesis, and high sensitivity. However, conventional AgNPs-based SERS substrates encounter significant limitations regarding quantitative analysis and attaining adequate selectivity in practical applications. In this work, a novel silver nanoflower SERS substrate (W₁₂@AgNFs) with high stability and uniform morphology was fabricated by the chemical reduction of a structure-defined silver clusters precursor. The Raman signals originating from polyoxometalates (POMs) within the W₁₂@AgNFs substrate serve as a reliable internal standard for quantitative detection. Furthermore, due to the substantial negative charge of POMs, the SERS substrate exhibits selective adsorption towards cationic dyes. The ratiometric SERS signal intensities are proportional to the logarithm of the cationic dye concentrations, facilitating analyte-specific quantitative SERS analysis. Under optimized conditions, this substrate allows for the selective and quantitative detection of crystal violet dye at a concentration as low as 10^-11 M, with its detection performance notably outperforming most existing testing methods. This study proposes an innovative approach for designing POM-Ag nanocomposites as highly efficient SERS substrates with integrated internal standards, enabling the progression of SERS spectroscopy toward the challenging quantitative and selective analyses of cationic hazards.