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Low-potential electrochemiluminescent sensing based on surface unpassivation of CdTe quantum dots and competition of
Lingxiao Cheng1, Xuan Liu, Jianping Lei
1Key Laboratory of Analytical Chemistry for Life Science (Ministry of Education of China), Department of Chemistry, Nanjing University, Nanjing 210093, PR China.
Abstract:
A novel electrochemiluminescent (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 HCl-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 muM 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(2+) down to 1.4 nM. The bidentate chelate QD-based 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.
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