| Abstract [eng] |
With advances in semiconductor technology in recent years, quantum dots are playing an increasingly important role in various applications. However, the growing demand for quantum dots poses risks as they often contain heavy metals. The question is what happens to quantum dots once they are in their natural environment. The aim of this MSc thesis is to evaluate the photostability of the spectral properties of hydrophilic CdSe/ZnS-COOH (Cd-QDs) and CuInZnS/ZnS-COOH (Cu-QDs) quantum dots in different biological aqueous media. Objectives: To compare the photostability of the spectral properties of CdSe/ZnS-COOH and CuInZnS/ZnS-COOH quantum dots in different biological aqueous media; to determine the influence of bovine serum albumin (BSA) and the green unicellular alga Scenedesmus quadricauda on the photostability of the CdSe/ZnS-COOH and CuInZnS/ZnS-COOH quantum dots; to assess the dose-dependent photostability of the CdSe/ZnS-COOH and CuInZnS/ZnS-COOH quantum dot spectral properties. The studies were carried out using optical spectroscopy techniques. Quantum dot solutions were prepared in deionised water, deep well water, and mwc algae culture medium. In addition, BSA and the green unicellular algae Scenedesmus quadricauda were added to the samples. Microscopy images were obtained using fluorescence and confocal microscopes. Using spectroscopic techniques, it was observed that the ionic composition of the medium has a greater effect on the stability of the spectral properties of Cd-QDs than Cu-QDs, which remains stable in the dark, regardless of the composition of the medium. When exposed to light, Cd-QDs is more photostable than Cu-QDs in terms of spectral properties, depending on the medium. Depending on the dose of light and the type of ligands, the radiation affects the integrity of the stabilising layer of the quantum dots, but its effect is independent of the chemical composition of the quantum dot core and shell. When the effect of BSA on Cd-QDs and Cu-QDs is included, it is observed that BSA forms a protective coating on the surface of the Cd-QDs independent of the ionic composition of the medium, thus improving the initial optical properties of the Cd-KT compared to the sample without BSA. The presence of the Cu-QDs protein in the solution does not improve the initial optical properties, but at higher irradiation doses, BSA protects the optical properties of both quantum dots from light-induced depletion of the surface ligand layer. Green unicellular algae do not improve the initial optical properties of Cd-QDs and Cu-QDs, but reduce the negative effect of light on the Cd-QDs quantum dots due to their localisation on the surface of the algal cells. |
