Electrochemical hole injection into the valence band of thiol stabilised CdTe quantum dots

The electrochemical injection of holes into the valence band of mercaptopropionic acid stabilised CdTe quantum dots in aqueous solution was investigated employing a glassy carbon rotating disc electrode. Analysis of the first exciton peak and the electrochemical responses as a function of the particle size was performed within the framework of the effective mass approximation and tight-binding models. It is demonstrated that the energy of the quantum dot band edges can be predicted from capacitance data of bulk semiconductor electrodes modified by the same stabilising groups as on the dots. In this paper we show that the thiol binding shifts the band edges of the CdTe particles by approximately 0.7 eV with respect to the theoretical value in the absence of stabilising groups. The results also revealed a significant dependence of the hole-injection rate on the electrochemical potential.