ABSTRACT
The photophysical properties of a π-conjugated polymer containing 2,2'-bipyridyl alternated with 2,5-dihexyloxyphenylene units (PBPyDHP) are investigated experimentally in terms of the conditions used (solvent, concentration, presence or absence of molecular oxygen, and optical excitation power). The experimental results have suggested that the fluorescence from PBPyDHP can be tuned by proper selection of the experimental conditions showing only one or two emission peaks: 445 nm (blue) and 555 nm (green). The observed effects were interpreted in terms of the twisted intramolecular charge transfer (TICT) theory. This is the first experimental report showing the interconversion of an usual fluorescence, called locally emission state (LE), to a TICT state in second scale time by varying the excitation power; that is, even though the torsion of only one fluorophore occurs in a nano or picosecond scale, the global change (the interconversion for all fluorophores) has occurred in the second time scale.
ABSTRACT
Oxygen permeabilities of nanocomposite films consisting of poly(methyl methacrylate) (PMMA) and different amounts of spherical zinc oxide (ZnO) nanoparticles were determined to investigate the barrier effect of this material with respect to particle content. A method was applied which is based on quenching of an excited phosphorescent dye by oxygen. Possible effects of the nanoparticles on the response of the dye molecules were investigated and were ruled out.
