The Characteristics And Properties Of The Gold Films Deposited On The Electrospun Fibers

Information technology, biotechnology and nano-technology have been proved to be three major technologies which will bring a great impact on the future of mankind. Nano-technology will become the basal technology for information technology and biotechnology research in the future development. Electrospinning technique is a novel method to prepare nanaofibers. It is a process that polymer fibers (with diameter lower than 1000 nm and lengths up to kilometers) can be produced using static electricity of high-voltage to compel polymer solution (or polymer melt) to jet. The diameter of fibers produced by conventional spinning technology (wet spinning, dry spinning, melt spinning, gel spinning etc.) is from several to several hundred microns. However, the diameter of electrospinning fibers can be less than 100 nm. Because of its small size, the fiber has large specific surface area. In this paper, we fabricated the composite nanofibers by electrospinning technology. Then the gold is plated on the surface of these nanofibers by electroless plating. The metallized fibers have been characterized and the properties of these metallized fibers have also been investigated.(1) Polyacrylonitrile (PAN) nanofibers containing different amounts of gold salt have been prepared by electrospinning technique. After the gold salt was reduced by NaBH₄, the gold nanoparticles are formed. By using the gold nanoparticles as seeds, thin continuous gold films have been depositeded on the surface of PAN fibers through self-catalyzed reduction of chloroauric acid in solution. The gold-coated fibrous mats were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffractometer (XRD). The conductivities of the fibrous mats increase with the amount of gold deposited on the fibers increase. The smooth continuous thin gold films tend to form on the fibers surface when the organic fibers contain more gold seeds, while coarse films tended to form on the fibers containing less gold seeds. The electrocatalytic activity of the fibrous mats electrodes towards the methanol oxidation in alkaline medium has been investigated, indicating that these electrodes exhibit higher electrocatalytic activity than pure gold electrode because of their three-dimensional structures. The results also indicate that the mats with smooth gold coating exhibit higher electrocatalytic activity than that with coarse gold coating.(2) Polyacrylonitrile fibers containing different amounts of gold nanoparticles (GNPs) have been prepared by electrospinning technique. Using the GNPs as seeds, thin continuous gold films have been deposited on the PAN nanofibers surface through self-catalyzed reduction of gold salt in solution. When these fibrous mats were thermally treated, the morphology of the fibers changed. The conductivities of the fibrous mats increase with the amount of gold deposited on the fibers increase, and they increased after the metallized mats treated at 280℃and 600℃, but decreased dramatically after treated at 900℃. The changes of the morphology were not only related to the temperature, but also to the amount of the gold seeds dispersed in the fibers and gold deposited on the fibers surface.(3) The polymethylmethacrylate/gold salt nanofibers were prepared by using electrospinning technique, and conductive continuous gold films have been successfully assembled on flexible electrospun PMMA ultrafine fibrous mat substrates containing gold nanoparticles reduced from a gold salt by filtering a HAuCl₄·2H₂O and NH₂OH·HCl solution through the mats. In this procedure, the gold particles already attached to the fiber surface grow through the surface-catalyzed reduction of Au³⁺ by hydroxylamine, and the enlarged gold particles increase the fraction of the surface covered with gold until a shiny continuous gold layer is formed on the fibrous mat. The conductivities of the fibrous mats increase with the amount of gold deposited on the fibers increase. The gold particles coalesce and form ultrafine gold fibers with a smooth surface after thermal treatment.(4) The polymethylmethacrylate/gold salt nanofibers were prepared by using electrospinning technique. Using the gold nanoparticles as seeds, the continuous gold films were deposited on the fibers surface by using self-catalysis solution method. The morphology of gold particles deposited on the organic fibers was adjusted by adding certain concentration of AgNO₃ into the plating solution. The optimum thorny gold films exhibit more surface-enhanced Raman scattering activity than the sphere gold particles deposited on the organic fibers.