Session: Advances in Spectroscopy:

Surface plasmon resonance (SPR) is a surface-related optical phenomenon generated by the resonant excitation of surface plasmons (SPs)-coupled oscillations of the electromagnetic field and the electron density at an interface between a dielectric and a metal. While, the resonance always reach their maxima at the interface and decay exponentially into both metallic film and dielectric medium. When an ultrathin metallic film (i.e., ∼ 20 nm) imbedded in a symmetrical dielectrics which the refractive indices on either side of the film are equal, SPR on the two opposite surfaces can couple through the thin film giving rise to a new type of SPR mode referred to as long-range surface plasmons resonance (LR-SPR). Here, we described a simple approach to fabricate LR-SERS substrate by easily transferring a large-area ordered Au hexagonal nanoplates array between water/hexane interface to a refractive index matched Cytop-coated silicon substrate with a 100 nm Au film inserted between the Cytop layer (n=1.33) and the bottom silicon substrate. We then added different molecular weights (2, 5, and 10 kDa) of thiol-terminated polystyrene ligands (PS-SH) or thiol-terminated poly(ethylene glycol) (PEG-SH) to the organic phase to adjust the neighbouring distance of hexagonal nanoplate to form different arrangements of LR-SERS substrates. Our designed LR-SERS multilayered nanostructures perform highly sensitive, reproducible and long-range SERS signals. Then, the LR-SERS effect was further verified by experiment through two approaches: one is detecting methylene bule (MB) solution on the Au HNAs surface to compare their SERS enhancement ability and reproducibility. The other is by designing different lengths of methylene blue (MB) modified straight double-strand DNA (dsDNA) sequences to monitor the SERS intensity change at different distances away from the substrate. Therefore, our designed LR-SERS substrate exhibits higher electric field extension ability than conventional SERS substrates, which have promising potential for the SERS detection of many biomacromolecules and acquiring more biochemical characteristics.

Dr Xiaojun Luo

Nanjing Normal University

Appearances