Low-potential electrochemiluminescent sensing based on surface unpassivation of CdTe quantum dots and competition of analyte cation to stabilizer

A novel electrocbemiluminescent (ECL) sensing system was constructed for low-potential detection of metal ion by immobilizing surface-unpassivated CdTe quantum dots (QDs) on a glassy carbon electrode. The surface-unpassivated CdTe QDs were prepared using meso-2,3-dimercaptosuccinic acid (DMSA) as a stabilizer to cap CdTe QDs and characterized with scanning electron micrograph and X-ray photoelectron spectroscopy. The immobilized QDs showed a strong cathodic ECL emission peak at -0.87 V with an onset potential at -0.64 V (vs Ag/AgCl/ saturated KCl) in air-saturated, pH 9.0 HC1--Tris buffer. On the basis of the competition of metal ion to the stabilizer, the quenching effect of metal ion on ECL emission was observed, which led to a sensitive chemical sensing application. Using cupric cation as a model analyte, the sensor showed a linear range from 5.0 nM to 7.0 [micro]M with a detection limit of 3.0 nM and had been successfully applied in the detection of copper in human hair. It could be extended to detect other metal ions with stronger metal--S interaction than with the Cd--S bond. As an example, the sensor could be used to detect [Hg.sup.2+] down to 1.4 nM. The bidentate chelate QD-basod sensor exhibited a promising platform for rapid detection of cations with strong metal--S interaction and could be further applied for development of other low-potential electrochemical sensing systems. 10.1021/ac100315a