Carbon quantum dots (CQDs) modified ZnO/CdS nanoparticles based fluorescence sensor for highly selective and...

A simple and fast spectrofluorimetric method coupled with carbon quantum dots (CQDs) modified ZnO/CdS nanoparticles was developed for the detection of Ferric iron (Fe(III)). The fluorescence of CQDs/ZnO/CdS NPs was effectively quenched by Fe(III) due to the strong interaction between the CQDs/ZnO/CdS NPs and Fe(III). In addition, the detection limit of Fe(III) was about 1.72×10^-7M. The effect of foreign ions on the fluorescence intensity of CQDs/ZnO/CdS NPs showed that the interference response in detecting of Fe(III) ions was low. Moreover, the quenching of Fe(III) and CQDs/ZnO/CdS NPs was discussed to be a static quenching procedure, which was proved by quenching constant K_SV and fluorescence lifetime τ. The study of thermodynamics showed that the values of entropy change (ΔS) and enthalpy change (ΔH) were both positive, and the value of free energy (ΔG) was negative, which implied that the weak interaction of the molecular between CQDs/ZnO/CdS NPs and Fe(III) was hydrophobic force, and the quenching process was endothermic and spontaneous.