A novel method for aqueous synthesis of CdTe duantum dots.

We have developed a simple and an economical one-pot method to synthesize water-soluble CdTe quantum dots (QDs) using hydroxylamine hydrochloride (HAH) as reduction and l-cysteine (CYS) as the ligand. The size of the CdTe QDs could easily be controlled by the duration of reflux and monitored by absorption and photoluminescence spectra. The factors influencing the photoluminescence quantum yields (PL QYs) on the QYs of CdTe NCs were investigated and the optimum conditions were determined. Under the optimum conditions (pH=11.0, the concentration of Cd(2+) was 1.0mmolL(-1) and the molar ratio of Cd(2+):Te(2)(-):CYS:HAH was 1:0.05:2.4:5), photoluminescence quantum yields of the CdTe QDs have been improved significantly and the maximum QYs of the QDs can achieve to 47%. The QDs were characterized by Fourier transform infrared spectrometry (FTIR), transmission-electron microscopy (TEM) and X-ray powder diffraction (XRD). The XRD patterns indicated that CdS was formed in the preparation process of CdTe QDs. This CdS shell could effectively passivate the surface trap states, and enhance the PL QY and stability of the CdTe QDs.