Ratiometric fluorometric and visual determination of cyanide based on the use of carbon dots and gold nanoclusters.

An optical method is described for the ratiometric fluorometric determination of cyanide ions. It is based on the use of a mixture of aqueous solutions of blue-emitting carbon dots (CDs) and red-emitting gold nanoclusters (AuNCs). The presence of cyanide reduces the red fluorescence of the AuNCs through the formation of a stable complex [Au(CN)2−]. The blue emission of the CDs, in contrast, stays constant. Hence, the color of fluorescence changes from red to purple to blue. The ratio of the fluorescence intensities located at 612 and 438 nm varies over a wide range, with 2 linear responses ranges (from 8 nM to 12.5 μM, and from 12.5 to 75 μM). The method was applied to the determination and visual discrimination of cyanide in food and drink samples.