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

The quantum size effect of CdTe quantum dots (QDs) has been one of the targets of extensive research concerning 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 were synthesized with a microwave-assisted hydrothermal method. Upon electrochemical oxidation of the CdTe QD in the presence of tri-n-propylamine (TPrA) as a coreactant, two ECL signals, called ECL and ECL, were observed at potentials corresponding to the oxidation of TPrA (at +0.8 V) and CdTe QDs (at +1.2 V), respectively. The relative intensity of ECL significantly increased with increasing the particle size of CdTe QDs, and disappeared when the particle size was 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*. Possible ECL mechanisms are proposed from a view point of thermodynamics.