Synthesis Of Cdte Quantum Dots And Its Analytical Application

In this thesis, we investigated the effect side of the surface transformation of CdTe QDs on their fluorescence.In order to achieve this aim a serial of experiments have been implemented to have a further clear vision about the advantage that OVA and glutathione molecules when they are used on the process of the surface transformation of CdTe QDs.In the first part of this research, the interaction between OVA and CdTe QDs was studied in details. The best parameters of the reaction between CdTe QDs and OVA were set. Herein, the result showed that the best reaction time was about 30 minutes.For a fixed concentration of OVA equal to 1.0x10-4 mol L"1, the dilution factor of CdTe QDs corresponds to 5, wich corresponds to a concentration value equal to 1.46×10-6mol L-and the best pH value was set at about 7.4. All of these parameters were implemented to investigate the effect of temperature on the fluorescence intensity of OVA.After the addition of different concentration of CdTe QDs, the fluorescence intensity of OVA decreased. The interaction between protein and the QDs was following Stern-Volmer equation where Ksv was 4.67×106 L mol-1, moreover, the results showed that the quenching process was mostly static. The value of Ksv was increased with temperature. Thermodynamic parameters such asΔGθ,ΔSθandΔHθwere also studied, and there values were,-37.88 KJ.mol-1,23.08 J.mol-1·K-1 and-30.66 kJ.mol-1, respectively. These results showed that the electrostatic force plays key role on the interaction betweenof CdTe QDs and OVA.The interaction mechanism was studied based on spectrometry techniques. The best capping material was chosen and used to give best fluorescence intensity of the nanoparticules.The results obtained from these studies were functionalized for the settlement of an original method proposed to detect Hg2+ions by using water soluble CdTe QDs. The results showed that the developed method is reliable when the concentration of Hg2+ is between 2.75x10-5and 2.5 x 10-6 mol L-1.The RSD was equal to 8.98% and the value of the detection limit of the method was 3.8 x10-5Mol L-1.The mechanism of interaction between the QDs and the Hg2+ ions as well as the interaction between OVA and CdTe QDs were studied in details with UV-Vis, RLS and FT-IR spectra which showed that the fluorescence of CdTe QDs became vulnerable after an addition of small concentrations of Hg2+ ions,and vise versa.According to us, this result is mainly due to the formation of HgS precipitate on the surface of the quantum dots,preventing their fluorescence emission.