Electrospinning Preparation Of Fluorescent Tare-Earth/Polymer Composite Nanofibers And Studies On Its Structure And Properties

Nanofibers prepared by electrospinning technique are characterized with large specific surface area, small aperture size, easy to be surface functionalized and excellent mechanical properties, and thus can be widely applied as optical and chemical sensors, high efficient filtering materials, biomaterials, and nano-composite materials, etc. However, the current research focuses of electrospinning are limited to plastic materials and the nano-fibrosis of rubber materials has been rarely reported. As the glass transition temperature (Tg) of rubber-like material is low, the prepared fibers are easy to rebound after electrospinning and thus difficult to obtain nano-fibrous structure. In view of these problems, the coaxial electrospinning technique was adopted in the present work to realize the nano-fibrosis of rubber-like materials by means of the protective effect of outer rigid plastic materials. Finally, the room temperature vulcanized silicone rubber (RTV) nanofiber with the diameter in the range of 400～600 nm had been successfully prepared by coaxial electrospinning. Besides, in combination of the excellent fluorescent properties of rare-earthβ-diketone complexes such as extremely sharp emission bands, long lifetime, and potential high internal quantum efficiency, rare-earth complex/composite nanofibers with good dispersion state and outstanding optical properties were successfully prepared by electrospinning. The main works of the present thesis are listed as follows:(1) Eu(TTA)3phen/PVP (TTA=2-thenoyltrifluoroacetone, phen= 1,10-phenanthroline, PVP=polyvinylpyrrolidone) composite nanofibers (120～170nm) with high fluorescent intensity and quantum efficicency were successfully prepared by electrospinning. High resolution TEM, EDS, and XRD measurements revealed that the Eu(TTA)3phen complex predominantly dispersed as molecular clusters and/or nanoparticles with sizes smaller than 10nm in the PVP fiber matrix. This kind of distribution state of Eu(TTA)3phen was similar as the unimolecular distribution of the complex units along macromolecular chains fabricated by copolymerization. Fluorescence investigation and Judd-Ofelt analysis revealed that the fine dispersion of Eu(TTA)3phen decreased the nonradiative transition rate and further resulting in the significant enhancement of the fluorescent intensity and quantum efficiency of the composite nanofiber.(2) The RTV/PVP nanofibers with core-sheath structure were successfully prepared by coaxial electrospinning. SEM and TEM measurements were applied to investigate the effects of polymer chain structure, solution concentration and viscosity, solvent miscibility, electrospinning rate, and driving voltage on the co-axial electrospinning process and morphology of electrospun fibers; and thus to provide some references for the elucidation of co-axial electrospinning mechanism and fiber morphology control methods. Moreover, combined with the excellent low temperature performance of RTV and outstanding fluorescent properties of Eu(TTA)3phen, the Eu(TTA)3phen/RTV/PVP core-sheath nanofibers were fabricated by coaxial electrospinning. By investigating the fluorescent spectral characteristics, fluorescence lifetime and Judd-Ofelt parameters of the composite, the contribution of RTV matrix to the low temperature fluorescence properties of Eu(TTA)3phen and the relationship between the dispersion of Eu(TTA)3phen and the fluorescent properties of the composite were deeply discussed.