Au-Ag bimetallic nanostructures for enhanced SERS detection of pyridine and TNT

Surface-enhanced Raman scattering (SERS) has become an amazing technique for the detection of organic pollutants at a trace level. Study on utilizing Au - Ag bimetallic nanomaterials for application as SERS substrates for analysis of pyridine and 2,4,6-trinitrotoluene (TNT): We systematically investigated the effects of bimetallic composition on pyridine SERS spectra, and we developed a novel cysteine-mediated strategy for selective TNT enrichment and detection. Au@Ag core-shell NP Au@Ag core-shell NPs with different Ag shell thicknesses were prepared to search for the optimal SERS performance. The results show that the molecular adsorption orientation of the pyridine turns from vertical to tilted/parallel with increasing Ag content, which is indicated by the changes in the relative intensity ratios of the characteristic Raman peaks at 1005 cm −1 and 1032 cm −1 . For detecting TNT, cysteine modifications can make Meisenheimer complexes, greatly improving molecular capture on metals. Au@Ag core-shell with appropriately tuned Ag shell thickness can reach a detection limit as low as 10 −10 M (ppt level) for TNT, which is much lower than that of traditional methods. A quantitative relationship is established between Ag contents, hotspot density, and detection limit, providing some theoretical guidance for SERS substrates. This work puts forward some new ideas about high-sensible, on-location detection of explosive materials in environmental-related applications.