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

► New cysteamine capped CdS quantum dots were synthesized. ► Fluorescence intensity can be quenched by Cu2+ and reversibly recovered by CN−. ► Use as sensitive and selective CN− sensor. ► Very low limit of detection (1.13 μM) for CN−.