Highly sensitive SERS detection of Pb2+ ions in aqueous media using citrate functionalised gold nanoparticles

Citrate functionalised gold nanoparticles (AuNPs) display strong surface enhanced Raman scattering, which can be used for surface enhanced Raman spectroscopy (SERS). The specific and strong interaction between the heavy metal ions and surface-bound citrate molecules lead to a sensing application for the detection of Pb2+ ions. Herein we report a citrate functionalised gold nanoparticle (AuNP) surface enhanced Raman spectroscopy (SERS) based sensor, employing the metal-affinity properties of the citrate molecule to detect Pb2+ ions. The Pb2+ ions interact with the citrate molecules via their carboxylate and hydroxyl groups altering the molecular spectra pertaining to the νas(COO−), νs(COO−) and ν(COH) bands. The ν(COH) band was used for the determination of the Pb2+ ion concentration. It decreased upon reducing the ion concentration and was found to be linear between 50 ng/L and 1000 ng/L with a 0.9982 correlation coefficient (R2) value. This method also showed good recovery and relative standard deviation (RSD) values.