Cu2+-modulated cysteamine-capped CdS quantum dots as a turn-on fluorescence sensor for cyanide recognition

A new fluorescence sensor for detection of cyanide ions (CN-) in aqueous media based on the recovered fluorescence of cysteamine capped CdS quantum dots [Cys-CdS QDs]-Cu2+ system was proposed. The fluorescence intensity of Cys-CdS QDs was quenched by Cu2+ due to the binding of Cu2+ to cysteamine on the surface of the QDs. The degree of fluorescence quenching was proportional to the concentration of Cu2+. However, in the presence of CN-, the fluorescence intensity of Cys-CdS QDs was found to be efficiently recovered. Experimental results showed that the pH of the buffer solution and the concentration of Cu2+ affected the fluorescence intensity upon adding CN-. Under the optimal condition, the recovered fluorescence intensity was linearly proportional to the increasing CN- concentration in the range 2.5-20 mu M. The limit of detection and the limit of quantification were found to be 1.13 mu M and 3.23 mu M, respectively. In addition, among the tested ions, only CN- could turn on the fluorescence intensity suggesting that the [Cys-CdS QDs]-Cu2+ system was a highly selective sensor for CN-. Moreover, this proposed sensor was demonstrated to detect CN- in drinking water with satisfactory results. (C) 2012 Elsevier B.V. All rights reserved.