An investigation on the structural and optical properties of MSA capped CdTe quantum dots

Abstract

In this work, a modified sonication induced wet chemical approach is adopted to synthesize highly luminescent and water soluble Cadmium Telluride (CdTe) quantum dots (QDs). Cadmium Chloride and Sodium Tellurite are used as the source of Cadmium and Tellurium. To limit the size of the QDs, Mercaptosuccinic acid is used as a capping agent. The refluxing time dependence on morphology, size, crystal structural, and optical properties of CdTe QDs are investigated. The refluxing time-dependent optical constants viz. band gap energy and Urbach energy of the QDs are estimated from UV-Vis absorption spectra. The fluorescence spectra of the QDs are also investigated by recording the spectra under the excitation wavelength at 320 nm. CdTe QDs are found to uniform in size. The average size of the QDs estimated from the HRTEM image analysis is about 5.8 nm and 8.2 nm for refluxing times 1 and 4 hours, respectively. The growth mechanism of the QDs as a function of refluxing time has also been discussed. Two phases of the CdTe QDs, namely hexagonal and cubic are confirmed from the HRTEM images and SAED patterns analysis. The phase transformation from hexagonal to cubic is successfully achieved by tuning the refluxing time from 1 to 4 hours.