Surface Modified Core-Double Shell CdSe/CdS/ZnS Quantum Dots as a Fluorescent Nanosensor for Determination of Copper in Environmental and Biological Samples
A simple and efficient method was used for surface modification of core-double shell CdSe/CdS/ZnS quantum dots (QDs) by mercaptoacetic acid (MAA) and imidazole (IM) as capping ligands. The resultant QDs were water dispersible and possesed advantages of low toxicity, high photostability and excellent fluorescence in comparison with CdSe QDs. The studies showed that the fluorescence intensity of the modified QDs was selectively quenched in presence of copper ions respect to other common metal cations. Thus, it was used as a nanosensor for detection of copper ions in aqueous solutions. In the optimal conditions, Cu2+ ion could be detected in the concentration range of 2.0 × 10–9–1.38 × 10–6 mol L–1 with a limit of detection 1.0 × 10–9 mol L–1 (1 nM). The new designed nanosensor based QDs was then successfully applied for the determination of Cu2+ ions in real samples including tap water, ground water, human urine and human blood serum with satisfactory recovery of 97.8–102.6%.