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 mu M, and the limit of detection is 10 mu M. The interference study demonstrated good selectivity, and the suggested approach was effectively applied to an environmental water sample.