Electrogenerated chemiluminescence of quantum dots with lucigenin as coreactant for sensitive detection of catechol

Electrogenerated chemiluminescence (ECL) of quantum dots (QDs), including CdS, CdSe, CdTe, and CdSe@ZnS QDs, was comparatively studied in neutral lucigenin solution without coreactants. Cathodic ECL signals were obtained at -1.2 V at different QDs modified gold electrodes (QDs/GEs) and the strongest ECL emission was obtained at the CdSe@ZnS QDs modified GE, which is nearly 7-times larger than other QDs modified GEs. The electrochemical results and the ECL spectrum revealed that the luminophor of the cathodic ECL is the excited state of QDs but not lucigenin, revealing that lucigenin can act as coreactant to generate cathodic ECL with QDs. Several impact factors, such as the amount of QDs, the supporting electrolytes, and the pH were investigated. Under the optimal condition, catechol exhibited apparent inhibiting effect on the cathodic ECL signal, based on which a new ECL sensor was developed and applied in the sensitive detection of catechol. The inhibited ECL intensity varied linearly with catechol concentration in the range of 5-1000 nM with a detection limit of 2 nM (S/N=3). The ECL sensor exhibited satisfied stability, repeatability, and selectivity. The mechanism of cathodic ECL was also proposed.