Preparation,Structures And Properties Of Functional Nanofiber Composites By Electrospinning

Electrospinning has the advantage of high efficiency, low cost and universality for a variety of materials, and provides a simple method for the convenient fabrication of continuous fibers with diameters ranging from tens to hundreds of nanometers. The polymer nanofiber membranes obtained by electrospinning are flexible with high porosity and surface-area-to-volume ratio, which have potential for use in many fields, such as catalysis, biology, sensing and filters.Electrospun nanofibers were applied as the matrix to load different functional nano-sized particles to fabricate the functional fiber materials. In this thesis, the sol-gel method, calcination and in situ growth method were used. The relationship between structure and properties of the materials was studied. The performance of the materials in the fields of noble metal catalysis, semiconductor photocatalysis and antibacterial agents was investigated, respectively. Materials with various morphologies and structures were prepared via different approaches, opening up opportunities for designing and constructing hierarchical structure of electrospun nanofibers. The thesis consists of the following two parts.In the first part, an efficient and green method was developed to synthesize Ag nanoparticles-coated tea polyphenols/polystyrene (Ag-TP/PS) nanofibers via electrospinning and in situ reduction using TP as the reductant and stabilizer. While TP was being released from TP/PS nanofibers, nanofibers could function as reactive sites for reduction of [Ag(NH3)2]+. Therefore, Ag nanoparticles could be uniformly coated on the surface of TP/PS nanofibers. The effect of [Ag(NH3)2]+ concentration on the morphology and catalytic activity of the membranes was also investigated. The functional nanofiber membranes with excellent properties could be obtained by altering [Ag(NH3)2]+ concentration. Ag-TP/PS nanofiber membranes exhibited good catalytic stability for the degradation of dye pollutant. Furthermore, Ag-TP/PS membranes possessed good antibacterial abilities against Staphylococcus aureus and Escherichia coli microorganisms.In the second part, we presented a simple and practical strategy for preparing polyaniline (PANi) coated TiO2/SiO2 (P/TS) nanofiber membranes by a combination of electrospinning, calcination and in situ polymerization. PANi nanoparticles could be densely and uniformly coated on the surface of TS nanofibers. The nanofiber membranes thus obtained were flexible and exhibited enhanced photocatalytic activity for degradation of methyl orange under visible light, which could be due to the synergistic effect of PANi and TiO2. The influence of polymerization time on the morphology and photocatalytic activity of the membranes was investigated. The recycling tests revealed that the P/TS nanofiber membrane was stable and effective for the degradation of dye pollutant.