Preparation Of Nano-Scale Fiber-Based Carrier Materials Via Electrospinning Technology And Study On Their Functionalization

Nano-scale polymer fibers have high surface volume ration and excellent mechanical property, so they can be exploited for the applications of drug delivery or target release, tissue engineering, surface modification of insert and so on. Electrospinning is currently the only versatile method of fabricating continuous fibers with diameters down to a few nanometers. The method can be applied to synthetic and natural polymers, polymer alloys, and polymers loaded with chromophores, nanoparticles, or active agents, as well as to metals and ceramics. If the electrospun fibers were used as carrier matrix and chemically modified, they can be endowed with different functions, various nano-structures, tailorable morphology and excellent property, which can be applied to the fields as diverse as optoelectronics, sensor technology, catalysis, filtration, and medicine or medical care. This dissertation paid attention to the advantages of high aspect ratio, high surface volume ration, talorable morphology and easy functionalization ascribed to electrospun fibers, and synthesized mesoporous silica nanofibers via electrospinning. These fibers were then used as template and followed by chemical modification so as to combine with nano particles or biomolecules, which showed excellent electrochemical activity and biocompatibility. Main completed researches are shown as follows:(1) Mesoporous silica nanofibers were synthesized by a facile combination of electrospinning technique and sol-gel method. Tetraethyl orthosilicate, polyvinylpyrrolidone (PVP), triblock poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) copolymer Pluronic P123 were the components of sol for the production of silica fibers. Heat removal of structure-directing agent P123 and excipient PVP in the hybrid fibers at high temperatures resulted in mesoporous morphology. The effect of pH value, silica water ratio, PVP molecular weight, aging temperature and time, stirring and time point of PVP addition on electrospining precess were investigated. Simultaneously, the effect of evaporation induced self-assembly (EISA) on the ordered assemble of P123 template was also investigated, and the influencing parameters on electrospinning were optimized. Experiments showed that silica fibers with uniform size and integrated morphology were prepared on the optimal electrospun conditions of 10 kV driving voltage and 20 cm receiving distance. The silical fibers have bimodal size distribution, and the average pore diameter, surface area and pore volume are 3.70 nm,2988.70 m2/g and 4.40 cm3/g respectively. Changing post treatment process, after the as-electrospun fibers were aged in hot vapor and extracted in H2O2 the silica-sustained PVP hybrid fibers were successfully synthesized. These fibers have narrow pore size distribution, and the average pore diameter, surface area and pore volume are 14.98 nm,32.07 m2/g and 0.12 cm3/g respectively.(2) Novel silver nanoparticles doped silica fibers with ribbon morphology were synthesized by in situ adding silver nitrate to electrospun sol followed by thermal decomposition of siver and protective reducing mechanism of PVP. The composite nanoribbons present the width of approximately 10μm The content and size of silver nanoparticles encapsulated in ribbons can be readily controlled by varying the concentration of silver nitrate and thermal treatment conditions. Average size of silver particles is 31.50 nm. The silver nanoparticles in the ribbons exhibit good catalytic activity on the reduction of methylene blue dye with NaBH4 as a reducing agent, which is given by the ultra-high surface of the ribbons and their very small thickness. After loading glucose oxidase (GOx) and cytochrome C (Cyt C), the Ag-doped silica ribbons were used to fabricate GOx and Cyt C amperometric biosensors. Electrochemical results show that the hybrid ribbons facilitate electron transfer from active center of enzyme to electrode surface.(3) Mesoporous silica fibers were used as templates for the modification of gold nanoparticles via layer by layer self-assemble method (LbL), and then the gold-seeded silica fibers were further coated by continuous and uniform gold shells via solution-phase reduction of an appropriate metal ion in PVP or K2CO3 solution. The thickness and morphology of gold shell could be tailored by the molar ration of repeating units of PVP to gold ions (R), operation process and growth time. Experimental results show that the low R tend to form the thick gold layer with sharp tips, whereas high R favor obtaining the thin and uniform Au shell. The SiO2@Au fiber hybrid nanostructures are further used as substrates for fabrication of GOx biosensor, which exhibites excellent bio-electrochemical activity with high sensitivity and rapid response. These hybrid nanostructures are, therefore, regarded as molecule wires for potential application in highly sensitive chemical or biological sensors.