Preparation of water-soluble CdSe quantum dots and its application for nitrite detection in the anodic electrochemiluminescence.

Water-soluble CdSe quantum dots (QDs) have been prepared by using L-cysteine as the stabilizer in an aqueous phase under the optimized conditions. The characteristics and shapes of CdSe QDs have been proposed on the basis of UV-Vis and fluorescence spectra. A rapid analytical method for electrochemiluminescence (ECL) determination of nitrite has been developed on the basis of the quenching effect on anodic ECL emission of CdSe QDs under the optimum experimental conditions. In a neutral system and at a relatively low potential (+0.960 V), the ECL emission of CdSe QDs could be greatly enhanced by sulfite and could be gradually quenched by nitrite at an indium tin oxide (ITO) electrode. The proposed method may allow the measurement of nitrite ranging from 1 μM to 0.5 mM with a correlation coefficient of 0.9956 (n = 10) and a detection limit of 0.2 μM (3σ), and the relative standard deviation for 10 μM nitrite (n = 9) is 1.72 %. The proposed method could be adopted for the sensitive detection of ECL quenchers by using nitrite as a model molecule.