Aizat Turdalieva

Title: Synthesis and Optical Properties of ZnO and CdSe Nanoparticle Based Biomarkers

Abstract:

The first part of this Licentiate work is about the fabrication and characterization of ZnO nanoparticles because these nanoparticles are chemically and optically stable and have been reported to have a low toxicity. Many methods of fabricating ZnO nanoparticles have been reported in literature. We adopted one of the well-established methods then modified the method so that our ZnO nanoparticles were all synthesized at room temperature (thus Green Growth). We then characterized these ZnO nanoparticles by transmission electron microscopy and optical spectroscopies (fluorescence, Rayleigh scattering, absorption, and fluorescence lifetime spectra). It was found that the mechanisms of fluorescence of ZnO nanoparticles were very different from CdSe-based quantum dots (QDs). They were closely related to deep energy levels in the energy bandgap of ZnO material and the fluorescence lifetime was in the microsecond range, much longer than the fluorescence lifetime of CdSe-based QDs (in nanoseconds).

Colloidal CdSe-based quantum dots (QDs) have unique electrical and optical properties due to its exciton confined in three spatial dimensions. They have been widely researched and developed for many applications. For biomedical applications, cell toxicity of nanoparticles is of vital importance and their underlying mechanisms have been studied extensively. Nanoparticles may enter the human body via skin, gastrointestinal tract, and respiratory system, while the respiratory system, i.e., the lung, has been considered to be the major gateway. The study of the effects of colloidal CdSe-based QDs on human airway epithelial cells is the second topic of this Licentiate work where water-dispersible 3-mercaptopropionic acid (3-MPA) coated CdSe-CdS/ZnS core-multishell QDs were used to study the effects of CdSe-based QDs on the monolayer of cultured human airway epithelial (Calu-3) cells. Trans-epithelial electrical resistance (TEER) of a Calu-3 monolayer was shown to drop almost instantaneously to the CdSe-QD exposure, but it recovered in a few hours.