Quantum dots (QDS), which belong to the group of nanostructures, have great potential for use in many applications, technical, biological and medical. Despite of their great potential, there is an enormous disadvantage for quantum dots containing some metalloid elements and heavy metals especially. This disadvantage is caused by the gradual release of metal ions and instability of QDs under various conditionin. Covering QDs by various modifiers is usually used for QDs stabilization and decrease of heavy metals ions release. The accomplishment of desired effect and efficiency of QDs modifications is questionable [cit?]. In the present study, ODs stability via their fluorescent properties, size and release of cadmium ions were studied. To measure the release of Cd2+ from the core of QDs an electrochemical method, differential pulse voltammetry (DPV), was used. Study conducted in mildly alkaline pH, which was close to the actual pH of QDs was performed. Four types of CdTe based QDs were used: MPA – CdTe (mercaptopropionic acid), MSA – CdTe (mercaptosuccinic acid), GSH – CdTe (glutathione), CdTe / ZnSe (core/shell). During 14 days period measurement of fluorescence, zeta potential and release of Cd2+ ions from QDs in two alkaline buffers were performed. Fist was phosphate buffer pH 7.6 and and further used a special neutral buffer pH 7.6, which simulated the cellular environment. From these data the stability of given modified and core shell QDs were assessed. At the end of the study it was found that CdTe / ZnSe core shell QDs maintain high fluorescence values together with the lowest released cadmium ions concentration.Keywords: Quantum dots, stability, fluorescence, zeta potential, electrochemistry
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