Surface-enhanced Raman spectroscopy method for active capture of targets by interlayer small-gap hot spot structures.

Surface-enhanced Raman scattering (SERS) technology has been widely used in the field of analytical detection owing to its high sensitivity and fingerprint-recognition ability. However, SERS faces challenges in practical applications related to the precise control of the location of hot spots and molecules entering the hot spot regions. In this study, silver nanoparticles (AgNPs) were used to construct a novel AgNP/AgNP structure by assembling two layers of AgNP thin films using a liquid-liquid interface self-assembly method to obtain a large number of interlayer nanogap structures. A single layer of tungsten disulfide (WS) was inserted between the two layers of the AgNP thin films, and the electromagnetic field enhancement effect of the interlayer ultrasmall gaps was studied using the Raman signal of WS. The results showed that the strong near-field enhancement, generated by WS as a sub-nanometer spacer layer, mainly originated from the plasmon coupling effect between the AgNP layers; the corresponding SERS enhancement factor reached 9.72 × 10, which was much greater than the enhancement effect when WS was on a single layer of AgNPs. Finite element theoretical simulations confirmed this result. In addition, using the AgNP/AgNP interlayer small-gap structure, highly sensitive SERS detection of various target molecules was achieved. This method was also successfully applied for the detection of antibiotic residues in poultry feathers, providing a new approach for food safety monitoring. The interlayer small-gap structure proposed in this study provides a new strategy for constructing high-performance SERS substrates and is expected to promote the practical application of SERS technology in fields such as environmental monitoring and food safety.