Luminescence properties of aligned-electrospun fibers of poly(9-vinylcarbazole) doped with a europium (III) complex

Unaligned and aligned poly(9-vinylcarbazole) (PVK)/NaEu(TTA)₄ (TTA=2-thenoyltrifluoracetone) composite fibers were prepared by electrospinning, using tetrahydrofuran (THF) and 1,2-dichoroethane (DCE) as solvents. Scanning electron microscopy (SEM) measurements showed that aligned fibers were wider and thicker than unaligned fibers. Characterization by Fourier transform-infrared (FTIR) spectroscopy indicated that there were weak interactions between PVK and NaEu(TTA)₄. Alignment of composite fibers promoted packing of the molecules of the Eu(III)-complex, increased the population of fully overlapping carbazoles (f-PVK) and decreased the asymmetric ratio (R) of the NaEu(TTA)₄, leading to less efficient energy transfer and lower lifetimes, as determined using steady-state and dynamic fluorescence spectroscopy. Yet, shorter lifetimes as compared to NaEu(TTA)₄ in powder form were found in unaligned and aligned electrospun fibers, ascribed mainly to introduction of defect states during electrospinning. Unaligned electrospun PVK fibers doped with loosen packed europium complexes preferably could be used as promising luminescence materials.