Promoting the Molecular Enrichment Effects in Surface-Enhanced Raman Scattering Detection via Cross-Linked β-Cyclodextrin Adsorption Layer Integrated Plasmonic Nanostructures

Owing to the heterogeneous electromagnetic fields in hot spots, free movement of analytes near hot spots, weak adsorption or nonadsorption of molecules, among other factors, the enhancement of surface-enhanced Raman scattering (SERS) signals cannot be well manipulated; thus, highly sensitive detection of many molecules with weak Raman scatter peculiarity cannot be accomplished. A simple and reliable method is described to prepare the β-cyclodextrin (β-CD) adsorption layers, coated on the surface of β-CD-capped Au nanoparticles (NPs) so that various analytes can be driven and attached to the Au NPs, thus positioning the analytes at specific hot spots to enhance the electromagnetic field. Based on the β-CD adsorption layers, SERS enrichment measures are not only improved on the solid substrate by combining the functions of molecule adsorption and molecule interception but also increased in solution via integrating the effects of molecule adsorption and molecule anchoring. Various types of molecular enrichment effects are effectively incorporated, thereby significantly enhancing the SERS intensity by 2-3 orders of magnitude both on the substrate and in the solution. Therefore, the proposed method contributes to stimulating the active transport of target molecules to optimal hot spots to achieve ultrasensitive detection, expanding the practical applications for both substrate-based and solution-based SERS protocols.