Preparation And Photoluminescence Properties Of Nanofibers Of PVK/C₆₀

The nanofibers have been attracted by many researchers and have become the hot study of nano-technology due to their superior optical, acoustic, electrical, magnetic, thermal and mechanical properties. The photoluminescence materials have been widely used in high-tech fields. The technologies for the preparation of Polymer nanofibers include electrospinning, sea-island model spinning, molecular spinneret spinning, biologic synthesis, chemical synthesis etc. Electrospinng is an effective method of high efficiency and small waste of preparing polymer nanofibers. Electrospinning is the focus way recently and has demonstrated a large potential. Nanofibers with photoluminescence properties can provide us a wide range of applications in nanophotovoltaic devices, photodiodes, sensors,wave-guiding and all-optical switching.PVK nanofibers and PVK/C60 composite fibers were successfully prepared by electrospining of PVK blend solutions in solvent mixtures of N, N-dimethylformamide (DMF) / Toluene. The morphology the eletrospun fibers were characterized by scanning electron microscopy, while the effects of concentration,applied voltage,electrospun distance on morphology of PVK electrospun fibers were investigated. The luminescence property of the fibers was observed by fluorescence microscopy. The ultraviolet (UV) spectrophotometer and fluorescence spectrophotometer were used to character the UV spectrum and fluorescence spectrum of composite nanofibers. The results show that the fiber diameter is increased with its spinning solution wt ratio, and first decreased and then increased with its voltage, and decreased with its electrospinning distance. The absorption spectra of both the blends thin films and the electrospun fibers of PVK/C60 can be understood as a simple superposition of the absorption spectra of PVK and C60, without indication of additional absorption in the investigated spectral range (190-900nm). It is interesting to observe that the PVK nanofibers have a very strong blue-violet luminescence, while'bright spots'due to C60 can be observed on the PVK / C60 fibers under UV irradiation in a fluorescence optical microscope. Compared to the emission spectra of PVK thin films, the photoluminescence of the PVK nanofibers shows a new emission peak at 437 nm. As the C60 concentration in the blends is increased, the intensity of PL emission peak from PVK (thin film and nanofibers) decreased, it is even completely quenched at 1.75 wt% doping concentration. The observed decrease in the intensity of the PVK emission peak in the blend thin films and nanofibers suggests that the excitation energies in PVK (donor) can effectively transfer to C60 (acceptor).