Water-soluble, thiol protected cadmium telluride CdTe quantum dots (QDs) exhibit size dependent excitation/emission wavelength tunability. The heating period ensuring the growth of CdTe nanocrystals capped with thioglycolic acid (CdTe@TGA) in aqueous solution is critical to reach a required/desirable diameter. Thus, reaction medium was monitored using a capillary zone electrophoresis (CZE) technique in order to select an appropriate heating time. QDs migrate as anionic species in a borate buffer pH 8.5 used as background electrolyte and they were separated according to their size (larger ones have shorter migration times), as confirmed by measuring their maximum wavelength of absorption, with on-line diode array detection. A relationship between electrophoretic mobilities and λmax was tentatively proposed. Efficiency of the purification process of crude QDs using multiple step alcohol precipitation was also confirmed with the developed CZE technique.
Keywords: Quantum dots, synthesis, size-selective precipitation, capillary zone electrophoresis, diode array detection, size-dependent migration