Sol-gel Combined Electrospinning Preparation And Characteration Of Semiconductor Oxide Nanostructured Fibers

This paper is focused on fabrication and property investigation of functional metal oxide nanostructured-fibers via a sol-gel combined electrospinning techinique. The preparation and structure control of the fibers, the photocatalytic property and sensing property of the as-prepares fibers were studied thoroughly. The aim is to investigate the controlled synthesis of metal oxide nanostructured-fibers via electrospinning techinique further, find simpler synthetic system suitable for electrospinning, set forth the relationship between the morphology, structure and property of the nanostructures to improve the properties of the nanofibers.1. Fabrication and photo-catalytic property of Fe³⁺ doped TiO₂ mesoporous fibersFe³⁺ doped TiO₂ mesoporous nanostructured-fibers were fabricated through electrospinning techinique using titanium(â…£) isopropoxide (Ti(OC₃H₇)₄) and Fe(NO₃)₃·9H₂O as reagent and doping reagent, P123 as pore-directing agent and PVP as spinnable aids. The products were characterized by XRD, SEM, FT-IR, TG, and low temperature nitrogen adsorption-desorption technique. The as-prepared gel fibers were longer than several micrometers with uniform diameter of 600-800 nm. The diameter of Fe³⁺ doped TiO₂ mesoporous fibers obtained after calcination decreased to 200-300 nm, which were composed of nanoparticle of 20-30 nm. The fiber walls were composed of mesopores with an average pore size of 3.6 nm calculated from N₂ adsorption-desorption isotherms. The BET surface area of the fibers calcined at 600℃was 76.7 m²/g. It was found that the amounts of Fe³⁺ dopant have little effects on the morphology and structure of the gel fibers and the TiO₂ fibers. However, the doping amount has significant effect on the photo-catalytic property of the TiO₂ fibers. With Congo Red solution as investigation target, it was found that when the doping amount was less than 1%, the photo-catalytic activity increased obviously with the doping amount. But when the doping amount was 2%, the photo-catalytic activity decreased significantly. Further experiments found that the 1% Fe³⁺ doped TiO₂ fibers have no catalytic activity toward methylene blue, indicating that the as-prepared products exhibit photo-catalytic selectivity for different dyes, which may find potential application in selective degradation of waste water.2. Preparation and ethanol-sensing properties investigation of ultra-fine SnO₂ nanofibersAs a wide band gap n-type semiconductor, tin oxide is widely used for gas sensing, and it is well known that the morphologies and microstructures of the sensing materials such as particle size, shape, surface/volume ratio, and porosity have significant effects on their gas-sensing characteristics. SnO₂ nanofibers were prepared by electrospinning method with SnCl₄·5H₂O as raw material and PVA as spinnable reagent. The process including the preparation of spinnable sol and electrospinning is both simple and low-cost, which is suitable for large-scale preparation. The rutile SnO₂ nanofibers calcined at 500℃were composed of nanoparticles of ca. 10 nm and many wormlike nanopores and gaps appeared on the nanofibers, which may benefit the improvement of the sensing property. The as-prepared SnO₂ gas sensors have been tested for ethanol vapor sensing behavior and the sensor show response signal in the temperature range of 200-350℃. The response reaches a maximum at 260℃, which is relative low in the reported data, benefit for the stability of the sensors and the practical application. Furthermore, the corresponding recovery time was less than 10 s, indicating the high sensitive and fast-responding character of the sensors.