Functionalization of gold nanoparticles using guanidine thiocyanate for sensitive and selective visual detection of Cd2+

Abstract

Various methods have been developed for metal ion detection, and most of them suffer from limitations including requirement of multiple-step analysis, low sensitivity, and serious interference from organic and inorganic molecules. Herein, a facile, selective, and sensitive optical method is presented for the quantification of Cd2+ in environmental water samples using guanidine thiocyanate (GT)-functionalized gold nanoparticles (AuNPs) based on the surface plasmon resonance properties of AuNPs. The proposed method uses GT to control the size of the bare AuNPs and selectively detects Cd2+ by forming a stable complex. The formation of GT-AuNPs was characterized by spectroscopic and microscopic techniques. The interaction between Cd2+ and GT-AuNPs results in the aggregation of functionalized GT-AuNPs, resulting in a color change detectable by the naked eye, which can also be observed by UV–vis spectroscopy. Under the optimum conditions, the visual signal is linear in the range between 0.025–50 μM, and the limit of detection is 10 nM. The interference study demonstrated good selectivity, and the suggested approach was effectively applied to an environmental water sample. © 2021 Elsevier B.V.