Preparation Of One-dimensional Composite Nanofibers Via Electrospinning

One-dimensional （1D） composite nano-materials have attracted plenty of attention due to itsspecial properties, such as photoelectricity, physical and chemical performances, and potentialapplications in sensor, biological scaffold materials, photocatalyst and carrier materials, andhydrogen storage material. Compared with the traditional techniques, electrospinning seems tobe the simplest and most effective technique capable of generating1D nanostructures （nanfibers,nanorods, nanotubes, nanobelts, and so on）. In this paper, we mainly discussed three kinds ofcomposite nanomaterials via sol-gel and electrospinning methods. The main results achieved inthis paper were listed as below:1. Several important electrospinning parameters to the morphology and diameterdistribution of the precursor nanofibers were investigated, including PVP concentration, viscosity,voltage, the distance between the syringe needle and collector, and the rate of extrusion. Theexperimental results indicated that the continuous nanofibers with smooth morphology could beobtained when the PVP concentration is12-14wt%, and the corresponding viscosity is600-1100cp. The electrospinning process could be continuously at the voltage of16-18kV, distance of10cm, and rate of0.6mL/h.2. Synthesis of1D Ce_xZr_1-xO₂solid solution nanofibers by electrospinning. Firstly, weprepared the precursor solution by keeping the PVP concentration12wt%and different molarratio of Ce（NO₃）₃to Zr（NO₃）₄. The results revealed that the continuous precursor nanofibers withaverage diameter about130nm could be obtained. After annealed at800℃for2h, thecontinuous, rough and polycrystalline structure Ce_xZr_1-xO₂solid solution nanofibers were formed.When the temperature rising to900℃, the morphology of the nanofibers was destroyed, butwhen there is a quartz substrate, the morphology of the nanofibers could remain well.3. Synthesis of ZnO/CeO₂nanotubes by coaxial electrospinning. Firstly,polyvinylpyrrolidone and acetic acid were added into N, N-dimethylformamide （DMF） undermagnetic stirring to form a homogeneous precursor solution （inner solution） at room temperature. Secondly, Ce（NO₃）₃·6H₂O and Zn（Ac）₂·2H2O were added into the inner solution （outer solution）.Thirdly, the inner and outer solutions were transferred into two springs for electrospinning,respectively. Fourthly, the as-spun core-shell nanofibers were placed in the drying oven for8h at60℃to remove the surplus solvent. Finally, the products were calcined at500℃for2h toobtain the ZnO/CeO₂nanotubes. The experimental results indicated that the morphology of theas-spun nanofibers is smooth and continuously. After being anneal at500℃for2h, themorphology of the nanotubes is rough with the average diameter reduced by about50%. Thephase structures of ZnO/CeO₂nanotubes were composited by hexagonal wurtzite ZnO and cubicfluorite CeO₂with the particle size of about10to15nm. The photocatalytic activity experimentsindicated that the ZnO/CeO₂nanotubes exhibit excellent photocatalytic performance in thedegradation of Rhodamine B.90percent of Rhodamine B molecules was decomposed byZnO/CeO₂nanotubes in90minutes, which is much faster than by ZnO/CeO₂nanofibers or ZnOand CeO₂single component nanofibers.4. Synthesis of TiO₂/ZnTiO₃and TiO₂/ZnTiO₃@Ag nanofibers by electrospinning.PVP/Ti（OC₄H₉）₄/Zn（Ac）₂as-spun nanofibers were prepared via the electrospinning techniqueusing zinc acetate and tetrabutyl titanate as the precursors, poly（vinylpyrrolidone） as the fibertemplate, and2:1（v/v） ethanol/water mixtures as the co-solvent. Then, TiO₂/ZnTiO₃compositenanofibers were obtained by high temperature calcinations of above composite nanofibers.TiO₂/ZnTiO₃@Ag nanofibers were fabricated by ethanol reduction method. The results indicatedthat the morphology of nanofibers change from the smooth to the rough, the diameter changefrom237nm to121nm after annealed at700℃for2h. Moreover, these fibers were consistedof two kinds of nanoparticles, one was rutile type TiO₂, and the other was ilmenite type ZnTiO₃.The photoluminescent properties of TiO₂/ZnTiO₃nanofibers at different annealed temperaturewere investigated, and the enhancement of luminescence could be observed because of theimprovement of the crystalline at higher temperature. The morphology and crystal structures ofthe TiO₂/ZnTiO₃@Ag nanofibers were investigated.