Abstract

Fluorescence spectroscopy and microscopy have emerged in the last few decades as robust methods to unravel the secrets of materials, their interactions and photophysical properties, on the nanoscale level. Confocal laser scanning microscopy (CLSM) is an important technique that utilizes the versatility of fluorescence as a tool to explore phenomena in the life- and material- sciences. In the scope of this thesis, a home built CLSM was upgraded and its advanced fluorescence method capabilities were used to investigate metal-organic frameworks (MOFs) and organic light emitting diodes (OLEDs). The interaction of differently functionalized MOF nanoparticles and serum proteins was studied by monitoring the fluorescence intensity fluctuations arising from the diffusion of fluorescently labeled nanoparticles through the small (~fL) confocal volume. This approach, known as the fluorescence correlation spectroscopy (FCS) analyzes the fluctuations of the recorded signal and extracts information regarding the rate of diffusion and the interaction between the MOFs and the proteins. In a second study, contrary to what was anticipated, rigid MOFs showed that a bulky linker was able to post-synthetically replace the organic likers of the original framework. Investigating the linker exchange via fluorescence imaging, combining the intensity and lifetime information, a new post synthetic linker exchange (PSE) mechanism in rigid MOFs was established. These studies show the versatility of utilizing CLSM measurements for FCS and fluorescence lifetime imaging microscopy (FLIM). The FLIM approach is a useful technique that relates the spatial variations in lifetime with the morphology of the examined structures. Investigating crystals and crystal-like luminescent structures via FLIM combined with the Hirshfeld surface (HS) analysis, provides information regarding the intermolecular interactions, structural-photophysical relationships could be established. Employing this tool on luminescent materials such as potential OLEDs structures provided new insights regarding their emissive properties, which is important for display and lighting technologies. Another application of fluorescence lifetime, via fluorescence spectroscopy, was employed to investigate the active center of a europium-dependent methanol dehydrogenase enzyme (Eu-MDH). Simultaneous measurements of the fluorescent cofactor and Eu metal ion, present in the MDH active center, showed their proximity to one another and provided a tool to characterize their photophysical behavior. Overall, utilizing the strengths of the upgraded CLSM, capable of the fluorescence methods presented within the scope of this thesis, elucidates a vast of relevant nanostructure properties especially in the field of material science.