Photophysical Studies of Luminescent Metal-Organic Frameworks and Bacterial Interaction with Cationic Conjugated Polymers

This thesis investigates the photophysical characteristics of two types of luminescent materials: luminescent metal-organic frameworks (LMOFs) and cationic conjugated polymers. LMOFs combine organic and inorganic components, resulting in materials with adjustable luminescence and high porosity, rendering them promising for sensing, light-emitting devices, and biomedicine applications. In the first part of this work, we modulated the fluorescence of LMOFs by altering the structure of their donor-acceptor-donor type organic components. Through steady-state and time-resolved photoluminescence experiments, as well as time-resolved confocal fluorescence microscopy, we demonstrated the efficacy of linker engineering in adjusting the emission properties of LMOFs. In the second part, we generated anion radicals within LMOFs and achieved promising yields in debromination reactions employing such species. Ultrafast transient absorption spectroscopy was utilized to probe the absorption and lifetimes of radical anion-excited states, revealing the strong photocatalytic capabilities of anion radicals within LMOFs. Fluorescent cationic conjugated polymers were studied in the last part. Cationic conjugated polymers have extensive applications in bacterial killing and detection, primarily through their ability to interact with bacterial cell membranes via electrostatic and hydrophobic interactions. Employing time-resolved confocal fluorescence microscopy with point emission and lifetime measurements, we evaluated the fluorescence intensity and lifetime distributions of various concentrations of cationic conjugated polymers upon interaction with bacterial cell surfaces over different durations under varying light conditions. Our observations indicated a pronounced affinity and bactericidal effect of these polymers against Gram-positive bacteria compared to Gram-negative bacteria.