Kalytchuk S. Optical and luminescent properties of CdTe nanocrystals in colloidal solutions and polymer matrices.

This dissertation is aiming at investigating optical and luminescent properties of CdTe nanocrystals (NCs) having been synthesized by means of colloid chemistry methods in aqueous colloidal solution and transferred to polymer matrix, as well as the influence of technologic synthesis modes and post-synthetic processing on the properties of such structures. The research has revealed low-energy shift of photoluminescence (PL) peak in the freezing process of the water solution containing CdTe NCs having been capped with thioglycolic acid. The model to describe probable surface charge neutralization processes and to qualitatively explain this effect has been introduced. It has been experimentally determined that the defect degree of CdTe NCs increases with their size decreasing. It has been shown that heat treatment of CdTe NCs, capped with thioglycolic acid results in a bimodal distribution of NCs sizes. A bimodal sizes distribution of CdTe NCs, having been incorporated into polymer matrix of poly(dimethyldiallylammonium chloride) (PDDA) as a result of their prolonged exposure to room temperature, has been defined. The experiment has shown the excitonic mechanism of luminescence of CdTe NCs, incorporated in the PDDA. The Stokes shift in CdTe quantum dots has been investigated by means of experimental and theoretical methods.