Electrogenerated chemiluminescence from a Cdse nanocrystal film and its sensing application in aqueous solution

Electrogenerated chemiluminescence (ECL) of semiconductor quantum dots in aqueous solutions and its first sensing application were studied by depositing CdSe nanocrystals (NCs) on a paraffin-impregnated graphite electrode (PIGE). The CdSe nanocrystal thin film exhibited two ECL peaks at -1.20 (ECL-1) and -1.50 V (ECL-2) in pH 9.3, 0.1 M PBS during the cyclic sweep between 0 and -1.8 V at 20 mV s(-1). The electron-transfer reaction between individual electrochemically reduced nanocrystal species and oxidant coreactants such as H2O2 and reduced dissolved oxygen led to ECL-1. When mass NCs packed densely in the film were reduced electrochemically, assembly of reduced nanocrystal species could react with coreactants to produce another ECL signal, ECL-2. ECL-1 showed higher sensitivity to the concentration of oxidant coreactants than ECL-2 and thus was used for ECL detection of coreactant, H2O2. A linear response of ECL-1 to H2O2 was observed in the concentration range of 2.5 x 10(-7)-6 x 10(-5) M with a detection limit of 1.0 x 10(-7) M. The fabrication of 10 CdSe nanocrystal thin-film modified PIGEs displayed an acceptable reproducibility with a RSD of 1.18% obtained at H2O2 level of 10 muM.