Abstract:

CdTe quantum dots (QDs) with fantastic optical properties were synthesized in an aqueous solution by thiol ligands. Reaction conditions, such as Cd-to-ligand molar ratio and precursor concentrations, were optimized to well control the QD size and to achieve high quantum yield (QY). High quality water-dispersed CdTe QDs (QY 45%) were obtained in a hydrothermal systemand the QD emission wavelength ranged from 485 to 660 nm detected at room temperature. The full width at half maximum (FWHM) of the emission peaks broadened from 40 to 75 nm. Thiourea was innovatively utilized to chemically modify the surface of CdTe by the hydrolysis and photolysis of thiourea which can release free sulfide ions. The changes in optical properties of these treated QDs were monitored within 12 days. When n(CdTe)/n(thiourea)=1:4 (concentration of QDs according to the cadmium ion concentration), the fluorescence intensity of the CdTe QDs (λex= 505 nm) increased 5 times. The QY increased to 68.3%.

Key words: Quantum dot, CdTe, Nanoparticle, 3-Mercaptopropionic acid, Thiourea