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.