الفهرس 
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Abstract
Great scientific and technological interests have been devoted to semiconductor nanocrystals quantum dots because of their promising applications such as display devices, biological tagging materials, photovoltaic and lasers. The colloidal synthesis of semiconductor nanomaterials allows for engineering their optical properties and electronic structure. Tuning the size of type II-VI semiconductor such as CdS, CdSe and CdTe allows for controlling their band gap all over the UV, visible and near IR regions. We prepare different types of II-VI semiconductor such as CdSe and CdTe nanoparticles and studied how their absorption spectra and emission properties depend on the size and the surface of these properties nanomaterials. In addition, hetero-structure of CdTe/CdSe core shell nano-system has been prepared and their optical properties have been examined. These nanostructure materials are very promising to be used as lasing materials, because of the large stock shift and the long lifetime of these. Especially, the CdTe/CdSe core shell hetero-structure has a tunable band gap near the IR region depending on the ratio of the core to the shell size. The optical properties of CdSe, CdTe, CdTe/CdSe core shell quantum dots have been investigated under different lasing excitation intensity and at different temperatures. The optical gain and its dependence on the excitation power were examined and the lifetime of the emitting stat was determined.