A Molecular Detection Strategy via Confined-Enhanced Raman Spectroscopy on a Self-Assembled Au Nanoparticle Film

Promoting the efficiency of placing target molecules into hot spots and anchoring analytes onto the surface of plasmonic nanoparticles to maximize the enhancement effect and further improve the sensitivity of the surface-enhanced Raman spectroscopy (SERS) signal is an important challenge. Here, we report a molecular detection strategy via confined-enhanced Raman spectroscopy on a self-assembled Au nanoparticle (NP) film called solid substrate based confined-enhanced Raman spectroscopy (SS-CERS) to achieve highly sensitive and uniform molecular detection. The SS-CERS substrate was obtained by the interfacial self-assembly process of Au NPs, and then NaCl and AgNO₃ were introduced to form a AgCl encapsulation shell on the Au NPs. The in situ packaged active shells formed on the surface of gold nanoparticles can significantly improve overall SERS properties. Importantly, compared with the traditional SERS substrate strategy, in which the limit of detection of crystal violet (CV) molecules is only 10^–9 M, SS-CERS has an enhanced sensitivity of 10^–12 M for CV molecules and excellent homogeneity with a RSD of about 5.63%. In addition, we applied the nanodetection strategy to the detection of Rhodamine 6G (R6G), Malachite green (MG) in fish, and carbendazim (CBZ) and other molecules in aquatic products, which showed excellent performance with clear Raman peaks obtained at 10^–8 M or even lower concentrations. Therefore, this indicates its enormous potential for molecular detection in practical applications.