SERS Detection of Hg²⁺ using Rhenium Carbonyl Labelled Nanoparticle Films

Abstract Modified silver nanoparticles with a self‐assembled disulfide functionalized 2,2'‐bipyridine (L1 and L2) monolayer, and the corresponding rhenium complex [Re(L2)(CO) 3 Br] are shown to provide a method to position the nanoparticles at a water/dichloromethane interface forming a lustrous metal‐like‐liquid film (MeLLF) with a unique SERS response. The film formed using L2 showed divergent behaviour in the presence of a range of metal ions whilst bound to the surface. [Re(L)(CO) 3 Br] (where L=2,2'‐bipyridine, L1 and L2) in solution demonstrates a selective interaction with Hg 2+ , observed by UV‐vis, emission and 1 H NMR spectroscopy, attributed to abstraction of the bromide. This interaction was demonstrated by subtle changes in the characteristic Raman Re‐CO stretch at 510 cm −1 both with the MeLLF, and when the film is immobilized in a PVA surface‐exposed‐nano‐sheet (SENS). The work provides proof of concept that the organometallic complexes can be employed as “labels” to generate SERS‐active nanoparticle films that possess detection capabilities.