Ratiometric and sensitive cyanide sensing using dual-emissive gold nanoclusters.

The detection of cyanide anion (CN-), a highly toxic pollutant, has attracted growing attention in the past years. In this work, a nanosensor composed of hyperbranched polyethyleneimine (hPEI)-assisted dual-emissive gold nanoclusters (DE-Au NCs) is proposed for ratiometric detection of CN- based on surface valence state-driving etch. The ratiometric color change of fluorescence is based on a fact that the red-emissive Au NCs with a high content of surface Au(I) can be easily etched by CN-, while the blue-emissive Au NCs with nearly neutral character can resist CN-. Because of the specific gold-CN- chemistry and electrostatic attraction between the positively charged hPEI protecting layer and the negatively charged CN-, the DE-Au NC-based nanosensor provides high selectivity toward CN- over other anions with a limit of detection of 10 nM. Practical application of the proposed DE-Au NC nanosensor is verified by satisfying recoveries of CN- determination in river water and urine samples. Graphical abstract.