【作者】 贺海晏；

【导师】 韩高荣； 李翔；

【作者基本信息】 浙江大学 ， 材料科学与工程， 2013， 博士

【摘要】 一维氧化硅基的纳米结构材料不仅具有非晶态氧化硅材料天然的生物相容性、亲水性、光致发光特性以及稳定的化学性质等突出优势,还可以通过微结构的调控,实现对多种性能的优化和拓展。一直以来,由于制备方法的局限,氧化硅基的纳米材料的制备、性能和应用研究都主要集中在零维结构,对于一维的氧化硅复合材料以及微结构可控的氧化硅基纤维的研究还相对较少,而一维纳米结构相对零维纳米结构而言往往具有更广的结构可调控性以及更有效的构建二维和三维的能力。因此,解决一维氧化硅基纳米结构的可控制备问题以及研究其性能与微结构的关系,具有重要的理论意义和实际应用价值。本文采用溶胶凝胶结合单针头静电纺丝法成功地制备了一维氧化硅基纳米材料,通过SEM、HRTEM、XRD、XPS、FTIR等多种分析测试方法深入系统地研究了氧化硅基纳米纤维的形貌、微结构以及组成,通过抗菌性、生物活性以及光学性能测试系统研究了一维氧化硅基纳米材料的掺杂以及微结构对性能的影响规律,主要结果如下：(1)采用溶胶凝胶法制备了具有可纺性的静电纺丝前驱体溶液,通过控制溶胶中TEOS的水解缩聚时间以及作为介孔模板物的三嵌段聚合物F127(EO106PO70EO106)的浓度,能够调节溶胶的粘度和Si-O-Si网络的比例。系统研究了溶胶制备参数和电纺参数对氧化硅纳米纤维的形貌、尺寸以及介孔结构的影响,发现随着TEOS水解缩聚时间的增加,溶胶的粘度增大,Si-O-Si网络中线性氧化硅键的比例显著增加,得到的纺丝直径增加,纺丝形貌均匀性先增加后降低,这是由于溶液粘度过高时反而会降低可纺性。而改变F127的含量,则不仅能显著改变氧化硅纤维的尺寸和形态,也会同时改变纤维中介孔的尺寸和有序性。当水解缩聚时间为13小时,F127/TEOS质量比为0.26和0.28时,纺丝中形成的是尺寸分布均匀(直径约为4nm)的无序介孔,当F127/TEOS质量比为0.14～0.18区间时,圆柱形纺丝内部会形成一列与轴向平行的高度有序介孔结构。(2)利用电纺过程中高分子溶液的溶剂快速挥发导致的相分离现象,使用传统单针头电纺法制备出了中空结构的氧化硅纳米纤维,研究了TEOS/PVP的摩尔比例、PVP的摩尔浓度以及H2O含量对电纺纤维形貌、尺寸和管壁厚度的影响。发现高分子PVP载体的加入,不仅能够调节溶胶粘度,还可促进在电纺过程中的相分离,形成中空管状纤维结构。随着PVP浓度的增加,溶液的粘度值增加,纺丝的尺寸均匀性提高,当PVP=0.08mM/L时,能得到最均匀的纤维形貌,随着H2O/TEOS的摩尔比例从1.1增加到1.8,溶液中Si-O-Si网络的含量增加,纳米管的纤维直径从0.6士0.1μm增加到0.94+0.09μm,管壁厚度从107+6.9nm增加到199+21.3nm。(3)首次发现AgNO3(?)够替代H20来进行TEOS的分解和缩聚反应,AgN03含量的增加一方面能调控纳米氧化硅管中Ag的加载量,同时也能对Si-O-Si网络的形成与完整性起到调控作用。随着AgNO3摩尔含量从0.04M/L增加到0.09M/L,氧化硅管的管壁会逐渐从致密结构变成多孔、甚至是镂空的结构,其相应的比表面积也得到了增加。(4)研究了不同Ag含量和氧化硅管壁结构的纳米管的生物抗菌性能,发现镂空状的掺银氧化硅纳米管在7小时内就能完全杀灭大肠杆菌,48小时内完全杀灭金色葡萄球菌,这是由于镂空状的掺银氧化硅纳米管比表面积大、具有与细菌更多的接触面积而具有最强的抗菌性能。(5)研究了不同Ag含量和管壁结构的氧化硅纳米管的发光性质与拉曼增强性质,发现致密管壁的氧化硅管中由于Ag的掺入,导致氧化硅网络中的-OH缺陷状态发生变化,从而能对缺陷发光的峰位和强度具有明显的调控作用,而具有镂空结构的掺银氧化硅纳米管则由于Ag纳米颗粒的尺寸和密度增加,能起到最佳的拉曼增强效果。(6)首次利用单针头电纺法直接制备成型了中空结构、生物活性可调节的氧化硅基生物活性纤维。研究了前驱体种类、高分子PVP载体浓度和氧化硅含量对纤维形貌、相组分和结晶性的影响。发现了作为Ca源,CaCl2-6H20比Ca(NO3)2·4H2O能得到更高的纤维结晶率,PVP高分子摩尔浓度的提高会改善纤维形貌的均匀性,但会降低纤维的结晶率,而氧化硅含量的增加会显著降低纤维的结晶率,成功获得了直径在200-300nm范围内、管壁厚度在10-50nm,结晶率在0-81.2%可调的Ca、P共掺中空氧化硅基生物活性纤维。此外,通过引入AgNO3,成功制备了Ca、P、Ag三元共掺的同时具有生物活性和抗菌性能的中空氧化硅基纳米材料(7)系统研究了Ca、P共掺的中空氧化硅基纤维的生物活性及降解率,发现经过SBF模拟体液浸泡后,纤维内部及表面都生长出结晶性良好的HA和α-TCP混合组织,随着浸泡时间从6小时增加到12小时,HA的纳米晶粒尺寸从几纳米增加到十几纳米,随着Si02含量的增加会提高骨组织结构在纤维表面生长的速率,且得益于特殊的中空微结构,当浸泡时间超过72小时后,纤维的绝大部分氧化硅组分得到了降解,获得具有比块体和普通纤维结构更好的降解性。更多还原

【Abstract】 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.更多还原