Fabrication of Helical Mesoporous Silica Nanostructures Using Gelators and the Mixtures with CTAC
Fabrication of Helical Mesoporous Silica Nanostructures Using Gelators and the Mixtures with CTAC
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DOI：
10.2115/fiber.65.80
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发表时间：
2009-02
期刊：
影响因子：
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通讯作者：
Hiroko Hoshizawa;Masahiro Suzuki;H. Shirai;K. Hanabusa;Yonggang Yang
中科院分区：
文献类型：
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作者：
Hiroko Hoshizawa;Masahiro Suzuki;H. Shirai;K. Hanabusa;Yonggang Yang
合成了两种手性水凝胶剂L-18 ValPyBr和D-18 ValPyBr。它们在纯水中高浓度下自组装成薄膜，低浓度下自组装成螺旋状纳米纤维。溶胶-凝胶转录反应在酸性和碱性条件下进行使用这两个胶凝因子的自组装和混合物与CTAC为模板和TEOS为前体。在酸性条件下，L-18 ValPyBr和D-18 ValPyBr的最小凝胶浓度非常低。通过溶胶-凝胶聚合，得到了由扭曲的介孔硅带构成的棉状二氧化硅。这些带的宽度为60 nm，厚度为10 nm。在碱性条件下，得到了扭曲的中孔带和由紧密卷曲的中孔带构成的纳米管。通常，通过使用L-18 ValPyBr获得左手螺旋结构，而通过使用D-18 ValPyBr获得右手螺旋结构。形貌对NH3浓度敏感。当NH_3浓度为2.5wt%时，得到扭曲的条带。当NH_3浓度大于5.0wt%时，得到了由紧密卷曲的带状结构构成的纳米管。以L-18 ValPyBr和CTAC为原料，在酸性和碱性条件下制备了纳米级和微米级的介孔氧化硅。在酸性条件下，得到了螺旋状的介孔纤维，其直径随CTAC与凝胶剂比例的增加而增大。在碱性条件下获得的纳米纤维比在酸性条件下获得的纳米纤维短。介孔孔道相互平行，沿着纳米纤维的轴向延伸。
Two chiral hydrogelators, L-18ValPyBr and D-18ValPyBr, composed of L- or D-valine, were synthesized. They self-assembled into thin membranes under high concentration and helical nanofibers under low concentration in pure water. Sol-gel transcription reactions were carried out under both acidic and basic conditions using the selfassemblies of these two gelators and the mixtures with CTAC as templates and TEOS as precursor. Under acidic conditions, minimum gel concentrations of L-18ValPyBr and D-18ValPyBr are very low. After sol-gel polymerization, a kind of cotton-like silica constructed by twisted mesoporous silica ribbons was obtained. These ribbons were 60 nm in width and 10 nm in thickness. Under basic conditions, both mesoporous twisted ribbons and nanotubes constructed by tightly coiled ribbons were obtained. Generally, left-handed helical structures were obtained by using L-18ValPyBr, while right-handed helical structures were obtained by using D-18ValPyBr. The morphologies were sensitive to the concentration of NH3. When the concentration of NH3 was 2.5 wt%, twisted ribbons were obtained. When the concentration of NH3 was higher than 5.0 wt%, nanotubes constructed by tightly coiled ribbons were obtained. Mesoporous silica structures in nano- and micro-size were prepared by using the mixtures of L-18ValPyBr and CTAC under both acidic and basic conditions. Under acidic conditions, helical mesoporous fibers were obtained, and their diameter was increased with increasing the ratio of CTAC to gelator. The nanofibers obtained under basic conditions were shorter than those obtained under acidic conditions. The mesoporous channels were parallel each other and running along the axis of nanofibers.