PREPARATION OF HIGHLY LUMINESCENT CDTE QUANTUM DOTS AND ITS PROBES

We have prepared CdTe QDs in the size range from 2.8 to 4.4 nm with different organic ligands bonded on the QD surface. The organic ligands usually contain thiol, carboxyl or amino groups. These ionic groups provide QDs water solubility and should serve as linkers for conjugation of QD with important molecules to create selective luminescent probes. We have prepared QDs with mercaptopropionic acid, thioglycolic acid, cystein, mercaptoundecanoic acid, mercaptoethanol and cysteamine on the surface. Various synthesis procedures were also tested. The luminescence quantum yields of prepared QDs were compared. The secondary method was used for the determination of quantum yield with fluorescein as a standard. The determined quantum yields vary from 0.02 to 12% depending on synthesis conditions and organic ligand used. The highest quantum yield have been obtained for QD with cysteamine on the surface prepared at pH = 3. Preparation conditions of luminescent probes via conjugation of QDs with macrocyclic ligand using zero-length cross-linkers such as 1-ethyl-3-(3-dimethyl-3-aminopropyl) carbodiimide hydrochloride and N-hydroxysulfosuccinimide were optimized. Metal ion complexation ability of the conjugate and possibility of metal ion complex conjugation were also tested. Complexes of conjugates of macrocyclic ligands with Zn(II) and Eu(III) ions were prepared and analyzed by capillary zone electrophoresis with laser-induced fluorescence detection. These types of luminescent probes are intended to be used as Forster resonance energy transfers and for a DNA labeling.