A solution-based SERS sensing protocol via the ultra-rapid and highly efficient molecule enrichment strategy

The solution-based SERS detection has been considered as one of the most mature commercial SERS detection protocols owing to its features of high sensitivity and timeliness. However, poor molecular generality is a challenge for weakly-adsorbed species, such as anionic molecules and complicated organic compositions, on the surfaces of the plasmonic nanostructures. Many molecules in solution especially the weakly-adsorbed organic pollutants cannot be effectively adsorbed onto the surface of metal nanoparticles quickly due to the low affinities towards the metal, hence showing the weak Raman activity. Herein, we report a solution-based SERS sensing protocol via the highly efficient molecule enrichment strategy to achieve highly sensitive detection in solution. With the help of pH adjustment in solution, the porous β-cyclodextrin polymer/magnetic nanoparticles (PCDP-MNs) can availably capture various types of molecules, including cationic dyes (e.g., methylene blue and crystal violet), anionic pigment (e.g., sunset yellow), and neutral organic pollutants (e.g., carbendazim and bisphenol A). Based on the molecule enrichment strategy, the enrichment factors of various molecules are up to 10²–10³, thus their Raman signals are enhanced by 2–3 orders of magnitude. The molecule enrichment strategy provides a new way for the practical SERS detection to improve the ultra-trace detection in solution.