Three-dimensional SERS sensor based on the sandwiched G@AgNPs@G/PDMS film

Three-dimensional (3D) SERS substrate with the denser “hotspots” is synthesized by the constriction of PDMS film decorated with sandwiched graphene@AgNPs@graphene (G@AgNPs@G) nanostructure. Graphene layers above and below the AgNPs are used to absorb molecules onto the “hotspots”, and prevent the oxidation of AgNPs in our design. PDMS films can be easily shrunk for 3D structures, causing advantages in enhancement ability and light-matter interaction. Benefiting from the above advantages, a detection limit of 10−14 M (CV) and enhancement factor (EF) of 3.9 × 109 were obtained in our experiment. Theoretical analyses (FDTD) were also used to study the enhancement mechanism. For practical purposes, in-situ detection of MG molecules on the fish surface and the label-free detection of DNA base of adenine (A) and cytosine (C) were also studied. The high enhancement factor, great sensitivity, reliability, and stability of substrate reasonably proved that it can be used as an excellent SERS substrate for biomolecular detection. Fig. 1. (a) Schematic diagram of the fabrication process of corrugated G@AgNPs@G/PDMS film. (b) The SEM image of AgNPs@G/PDMS film generated by spin-coating AgNPs on PDMS film. (c) The SEM image of the corrugated G@AgNPs@G/PDMS film. (d) The close-up views of the corrugated G@AgNPs@G/PDMS film. [Display omitted] •The formation of 3D structure with high density of hot spots as shrinkage of PDMS film decorated with AgNPs.•The higher SERS enhancement effect obtained by controlling shrinkage of substrate to obtain enrichment of molecules.•Such a substrate has a high enhancement factor (EF = 3.9*109), great sensitivity, reliability, and stability.•The single-molecule SERS detection of DNA base of A and C.•The method has simple steps and can achieve reproducible large-scale fabrication.