Generalized Ratiometric Indicator Based Surface-Enhanced Raman Spectroscopy for the Detection of Cd2+ in Environmental Water Samples

The concept of generalized ratiometric indicator based surface-enhanced Raman spectroscopy was first introduced and successfully implemented in the detection of Cd2+ in environmental water samples using Au nanoparticles (AuNPs) modified by trithiocyanuric acid (TMT). Without the use of any internal standard, the proposed method achieved accurate concentration predictions for Cd2+ in environmental water samples with recoveries in the ranges of 91.8-108.1%, comparable to the corresponding values obtained by atomic absorption spectroscopy. The limit of detection and limit of quantification were estimated to be 2.9 and 8.7 nM, respectively. More importantly, other species present in water samples which cannot react with TMT and have weaker binding ability to AuNPs than TMT do not interfere with the quantification of Cd2+. Therefore, it is expected that the combination of the generalized ratiometric indicator based surface-enhanced Raman spectroscopy with the proposed AuNP-TMT probing system can be a competitive alternative for the primary screening of Cd2+ pollution.