Anodic Electrochemiluminescence of CdTe Quantum Dots Using Tripropylamine as Coreactant: Size-dependent Effect

Abstract

Quantum size effect of CdTe quantum dots (QDs) has been one of the targets of extensive research of the optical spectroscopy of semiconductors, but little is known about their effects on electrochemiluminescence (ECL) behavior, especially in the anodic potential range. In this present study, water-soluble CdTe QDs with different sizes are synthesized with a microwave assisted hydrothermal method. Upon electrochemical oxidation of the CdTe QD in the presence of tri-n-propylamine (TPrA) as coreactant, two ECL signals called ECL1 and ECL2 are observed at the potentials corresponding to the oxidation of TPrA (at +0.8 V) and CdTe QDs (at +1.2 V), respectively. The relative intensity of ECL1 has significantly increased with increasing the particle size of CdTe QDs, and disappeared when particle size is less than 2.4 nm. Upon an anodic potential of +0.8 V, TPrA is oxidized at the electrode surface, where the intermediate radical species like TPrA • + radical cation and CdTe QDs • − radical anion are supposed to be formed to give the excited chemical species of CdTe QDs*. The possible ECL mechanisms are proposed from a view point of thermodynamics.