Silver nanoparticles were used to develop a simple turn-on fluorescent assay based on glutathione-capped
CdTe quantum dot for the determination of trace amounts of the lethal poison, cyanide. It was found that
the fluorescence intensity of glutathione-capped CdTe quantum dots increased with increasing cyanide
concentration. Several experimental variables, such as pH and amounts of quantum dots and silver
nanoparticles and their effect on the analytical signals, were optimized. Using this optical sensor under
optimum conditions, cyanide was measured in the range of 0.01–2.5 micro-g mL
1 with a detection limit as
low as 0.004 micro-g mL
1. Relative standard deviations of 2.0% (for 0.5 micro-g mL
1, n ¼ 10) and 1.8% (for 2.0 mg
mL
1, n ¼ 10) were obtained. Investigation of the effects of potential interfering anions on the response
of the sensor revealed its high selectivity for the detection of cyanide in real samples. High sensitivity,
superior selectivity, low detection limit (0.004 micro-g mL
1) and ease of production are the most important
advantages of the present sensor. Finally, the sensor was applied for the determination of cyanide in real
samples.