Synthesis and Characterization of CdSe Quantum Dots by UV-Vis Spectroscopy

Abstract

The results of the experimental investigations of the synthesis and characterization of Cds and CdSe quantum dots is presented. In this work cadmium sulphide (CdS) and cadmium selenide(CdSe) quantum dots are synthesized successfully by adopting the hot injection /solvo thermal chemical synthesis method using oct-decane as a non-coordinating high boiling point organic solvent in place of trioctyphosphine (Top) which posed environmental hazard. A sudden injection of room temperature sulphur and selenium solution into the hot cadmium solution produce seed crystals which grow quickly and they are monodispersed. Samples are withdrawn from the hot solution and quench at room temperature to produce a series of increasing quantum dots size. Subsequent characterization studies were carried out on the synthesized Cds and CdSe QDs using Uv-vis spectroscopy machine and irradiation with uv-Light. The absorption spectra exhibit a strong blue-shift with decreasing size of QDs size, which is attributed to the quantum size effect (QSE). The sizes and band gaps of the Cds and CdSe were calculated, from the outcome of the calculation, it was deduced that the band gap energies varies from larger value to smaller values due to depletion of the band gap as a result of increased temperature. The results of this research are likely to be useful toward the understanding formation mechanism of CdS and CdSe .