Fluorescence “turn-ON” nanosensor for cyanide ion using supramolecular hybrid of graphene quantum dots and cobalt pyrene-derivatized phthalocyanine

A functional hybrid of graphene quantum dots (GQDs) and cobalt pyrene-derivatized phthalocyanine (CoPc) used as a sensitive nanoprobe for the recognition of cyanide ion (CN⁻) is described in this work. The fluorescence of GQDs was quenched upon non-covalent (π-π stacking) hybrid formation with CoPc via a possible energy transfer pathway. However, in the presence of CN⁻, the interaction between GQDs and CoPc was perturbed, such that the fluorescence of GQDs initially quenched by CoPc was found to be efficiently recovered in the presence of CN⁻. Amongst the molecules and anions tested to ascertain their effects on the fluorescence behaviour of the hybrid, only CN⁻ ion induced the tunable “off-on” restoration of the fluorescence of GQDs, which demonstrates the selectivity of the hybrid towards CN⁻. The restored fluorescence signals of the GQDs were linearly modulated by different concentrations of CN⁻ and were used for the quantitative assay of CN⁻ with high sensitivity coupled with rapid detection time. The detection was in the linear range of 1.0–50.0 nM with limits of detection (LOD) of 0.5 nM. The analysis of spiked samples for the recovery of CN⁻ further demonstrated the applicability of the hybrid for the satisfactory detection of the target analyte.