| The one-dimensional nanostructured silica-based materials not only possess the natural biocompatibility, hydrophility, photoluminescence and stable chemical properties of amorphous silica material, but also have significant potential to modulate the microstructure to adapt different applications. Therefore, by tailoring the component and microstructure of nanofibers, the performance of nanofibers can be controlled in a large scale to adopt different application purposes. Until now, the preparation and study of silica-based nanostructured materials have been focus on the zero-dimentional nanostructure due to the limitation of1-D nanostructures’ produce method. But comparing to0-D nanostructures, the1-D nanostructures have better tunability and ability to construct the2-D and3-D structure, thus the study on preparation and application of1-D silica-based nanostructures has theoretical and practical significance.We adopted the sol-gel combined single-nozzle electrospinning to systematically prepare1-D silica-based nanofibers, and the corresponding morphology, microstructure and component of these nanofibers were intensively studied by a variety of characterization methods, such as SEM, HRTEM, XRD, XPS and FTIR. The effects of doping and microstructure on1-D silica-based nanofibers were discussed by antibacterial, bioactive and optical property tests. The main contents are listed as follows:(1) Spinnable precursor solutions were prepared by sol-gel for electrospinning, and the viscosity and Si-O-Si ratio of sols were controlled by the condensation time of TEOS and the concentration of nonionic surfactant Pluronic F127(EO106PO70EO106), which was used as template to form mesopores. The effects of parameters of sols preparation and electrospinning on silica nanofibers’ morphology, diameter and mesoporous structure were studied systematically. It was found that, with the increase of condensation time of TEOS, the sol viscosity, linear Si-O-Si content of sol and the fiber diameter were all increased, and the uniformity of fiber was first improved and then decreased due to the excessive viscosity. The variation of F127content would not only change the size and morphology of silica fibers, but also change the mesopores’ size and order. When the condensation time of TEOS was13hours, and the mass ratio of F127/TEOS was0.26and0.28, the formed mesopores were disordered with diameter of～4nm. When the mass ratio of F127/TEOS was in the range of0.14-0.18, a line of ordered mesopores parallel to the axis of fibers were formed.(2) Silica nanotubes can be successfully fabricated via single-nozzle electrospinning based on phase separation effect. The effects of molar ratio of TEOS/PVP, concentration of PVP and H2O on the morphology, diameter and wall thickness of tubes were discussed. It was found that the addition of PVP could ajust the sol viscosity and induct the phase-separation during the electrospinning, forming the hollow structure of fibers. With the concentration of PVP increased, sol viscosity was increased, and the uniformity of fibers was also improved. Uniform fiber morphology was observed when PVP concentration was0.08mM/L. The diameter of silica tubes was increased from0.6±0.1μm to0.94±0.09μm, and the wall thickness was increased from107±6.9nm to199±21.3nm, with the molar ratio of H2O/TEOS increase from1.1to1.8..(3) For the first time, We found that, instead of H2O, AgNO3could decompose TEOS and assist the polycondensation of TEOS to Si-O-Si. By increasing AgNO3concentration, not only the higher Ag-loading amout was achieved, but also the wall structure of Ag-silica tubes could be controlled. With the AgNO3concentration increased from0.04M/L to0.09M/L, the wall structure varied from dense to porous, and eventually turned into a’lace-like’structure, and the specific surface area was increased accordingly.(4) Antibacterial properties of Ag-silica composite nanotubes with different Ag content and wall structure were studied. The’lace-like’nanotubes showed robust antibacterial activity against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli microorganisms. These nanotubes could kill E. coli in7hours and S. aureus in48hours, due to their higher specific surface area and more contact area with bacterial, comparing with nanotubes of dense wall structure.(5) Photoluminescence and surface-enhanced Raman scatting properties of Ag-silica composite nanotubes with different Ag content and wall structure were studied. The doping of Ag could effect the-OH defect property dramaticlly, which further controlled the position and intensity of luminescence peak. The size and density of Ag nanoparticles in silica tubes have a great effect on the surface enhanced Raman spectroscopy results.(6) For the first time, hollow silica-based nanofibers with tunable bioactivity were prepared by single-nozzle electrospinning. The effects of calcium salt, PVP concentration and silica content on the morphology, phase component and crystallinity of hollow fibers were studied. Comparing to Ca(NO3)2·4H2O, addition of CaCl2·6H2O increased the crystallinity of hollow fibers, and the increasing of PVP concentration improved the fiber uniformity, but decreased the fiber crystallinity. The increase of silica content could decrese the crystallinity remarkably. The bioactive Ca, P doped silica hollow fibers were successfully prepared, with diameter in range of200～300nm, wall thickness in range of10～50nm, and tunable crystallinity in range of0～81.2%. Besides, by doping of AgNO3, silica-based bioactive hollow fibers with good antibacterial property were achieved.(7) The bioactivity and degradation of Ca, P doped silica-based hollow fibers were studied systematically. After immersing in the simulated body fluid for a few hours, mixture of HA and a-TCP nanocrystals could grow from inside and outside surface of fibers. The size of HA and a-TCP nanoparticles increased from several nanometers to more than a dozen nanometers, with the immersing time increasing from6hours to12hours. What’s more, the growth rate of HA and a-TCP nanocrystals could accelerate with the increase of silica content in fibers. Due to the special hollow structures, the silica-based fibers pocessed faster growth rate of HA and better degradability, comparing with bulk material. |
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