Synthesis, Modification, And Application Of CdTe Quantum Dots

The size of Quantum dots （QDs） which are composed of groups II-VI or III-V elements is less than or close to the exciton Bohr radius. Fluorescent CdTe quantum dots have caused wide interests in their preparation, properties, and applications. At present, synthesis of high quality CdTe quantum dots are often carried out with high temperature such as 200℃and the stabilizing agent of high toxicity such as TOP. A liquid-liquid interphase method was adopted in this paper to synthesize CdTe QDs which was a very mild one with many advantages, including being of room temperature and the stabilizing agent of low toxicity. Effects of reactant’s concentration, additive and temperature etc. on the properties of CdTe QDs were discussed. At the same time, the CdTe quantum dots were deposited with PAA to change the surface from hydrophobic to hydrophilic. Additively, CdTe quantum dots were initially attempted to be a probe for detecting the drug content. The main results we obtained are outlines as follows:（1） CdTe QDs were successfully synthesized using liquid-liquid interphase method. The size of CdTe QDs is 2.1 nm and the fluorescence quantum efficiency is up to 70.2% （Rdm560 is the benchmark level in aqueous solution）. Effects of reactant’s concentration, additive and organic reagents etc. on the CdTe QDs were discussed. When the ratio of [Cd²⁺]/[Te^2-] is 1:2, we obtain the highest quantum efficiency.（2） The CdTe QDs were modified hydrophilically by ligand exchange and cyclodextrin inclusion. The CdTe quantum dots were deposited with PAA, and then effect of the ratio of PAA on the intensity of CdTe fluorescence was investigated, average diameter of CdTe/PAA QDs is 5 nm. Meanwhile, CdTe QDs were also modified by using theβ-cyclodextrin, the size of CdTe QDs is about 100 nm with a decrease in their intensity.（3） The principle of fluorescence quenching for quantification of captopril by CdTe QDs as luminescent probes is described. The standard curve was drawn by the drug content and intensity of fluorescence. The linear relationship is good between 0.19 and 3.2 mg.mL^-1, the correlation coefficient （r） is 0.9989. The unknown captopril can be detected by this method. However, the results had a certain deviation in comparison with the iodometric assay, possibly caused by other ions in aqueous solution or the environment factors. To some extent, this method needs to be further optimized to improve its accuracy.