Study about Electrostatic Deposition of CdTe Quantum Dots on Glassy Carbon Electrodes

Abstract

Quantum Dots (QDs) are semiconductor nanocrystals. These materials are characterized for its continuous absorption spectra at wavelengths ranging from ultraviolet to visible. This feature is directly related to the size of the nanoparticle. Considering their applications, these materials can be employed in solar cells, lasers, light emitting diodes, electronic devices, among others. However, one of the most attractive applications for QDs has been as sensors or biosensor. In this work, the synthesis of CdTe Quantum Dots was carried out in aqueous media using Na2TeO3 and CdCl2 as precursors of Te2- and Cd2+ ions, respectively, mercaptosuccinic acid (MSA) as capping agent and NaBH4 as reducing agent. The QDs obtained as colloids were purified and characterized by transmission electron microscopy (TEM), while their optical properties were characterized by UV-visible spectroscopy. After, an electrostatic deposition of the QDs on a Glassy Carbon (GC) electrode was done. This last was carried out applying a positive potential value regarding to the zero charge potential of the electrode in an aqueous media, and the influence of the potential value, deposition time was determined by means cyclic voltammetry. A study of surface conductivity changes of the glassy carbon electrodes after QDs deposition was performed by means Scanning Electrochemical Microscopy (SECM). With this was possible to observe aggregates of CdTe QDs deposited on GC electrodes indicating a possible irreversible electrostatic deposition