Glutathione and l-cysteine modified silver nanoplates-based colorimetric assay for a simple, fast, sensitive and selective determination of nickel

A novel colorimetric assay based on silver nanoplates (AgNPls) for detecting nickel ions (Ni2+) has been developed. Glutathione (GSH) and l-cysteine (Cys) were used to modify the AgNPls surface, exhibiting extremely high selectivity towards Ni2+ over other metal ions under specific conditions. Upon addition of Ni2+ to the modified AgNPls solution, a distinctive color change can be clearly observed by naked eyes as a result of the aggregation of AgNPls induced by the binding between Ni2+ and the modified ligands. To verify a complete self-assembly of the GSH and Cys onto AgNPls surface, the modified AgNPls were characterized using Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–vis) and transmission electron microscopy (TEM), respectively. Moreover, various parameters affecting the Ni2+ quantification including the modifier ratio, pH, reaction time, and interferences were investigated. With UV–vis spectrophotometric measurement under optimal conditions, a quantitative linearity was established in the range of 10–150 ppb (R2=0.9971) with the detection limit of 7.02 ppb or 120 nM (S/N=3). In addition, the developed sensor was applied to the determination of Ni2+ in waste samples from a jewelry factory and a car manufacturer with satisfactory results. Overall, this alternative approach presents a simple, rapid, sensitive and selective detection of Ni2+.