Oriented Mesoporous Silica Films Obtained by Electro-Assisted Self-Assembly (EASA)
Oriented Mesoporous Silica Films Obtained by Electro-Assisted Self-Assembly (EASA)
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DOI：
10.1021/cm8029664
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发表时间：
2009-02-24
影响因子：
8.6
通讯作者：
Walcarius, Alain
中科院分区：
文献类型：
--
作者：
Goux, Aurelie;Etienne, Mathieu;Walcarius, Alain
高度有序和垂直取向的介孔二氧化硅薄膜可以通过电辅助自组装（EASA）产生。该方法涉及在浸入水解溶胶溶液（通常含有四乙氧基硅烷、TEOS 和十六烷基三甲基溴化铵，CTAB）的电极表面电生成氢氧根离子，以催化前体的缩聚和垂直于支撑物生长的六边形堆积的一维通道的自组装。 TEM 成像和掠入射 X 射线衍射 (GIXD) 已经证明了垂直排列的介观结构，后一种技术能够直接在其下面的电极表面上表征薄膜。电合成介质成分（前体和表面活性剂浓度、表面活性剂链长）对介观结构顺序和膜厚度的影响已得到彻底研究。结果表明，可以在多种起始溶胶组成（即 10-200 mM CTAB 和 50-350 mM TEOS）上获得高度有序和定向的介孔二氧化硅薄膜，并且可以通过改变表面活性剂模板的链长来适度调整晶格参数。这些薄膜的厚度可以通过施加恒电流条件和改变沉积时间来精确控制，这提供了以相同方式应用于不同性质的电极的多功能性，而不会在恒电位模式中遇到过电位问题。介孔薄膜通常覆盖有额外的副产品，该副产品由电极/溶液界面处的整体凝胶化产生的颗粒聚集体制成。通过在稀释溶液中工作（即 [TEOS] < 125 mM 且 CTAB/TEOS 比率
Highly ordered and vertically oriented mesoporous silica films can be generated by electro-assisted self-assembly (EASA). The method involves the electrogeneration of hydroxide ions at an electrode surface immersed in an hydrolyzed sol solution (containing typically tetraethoxysilane, TEOS, and cetyltrimethylammonium bromide, CTAB) in order to catalyze polycondensation of the precursors and self-assembly of hexagonally packed one-dimensional channels that grow perpendicularly to the support. Vertically aligned mesostructures have been demonstrated by TEM imaging and by grazing incidence X-ray diffraction (GIXD), this latter technique enabling characterization of thin films directly on their underlying electrode surface. The influence of the electrosynthesis medium composition (precursor and surfactant concentrations, surfactant chain length) on the mesostructural order and film thickness has been thoroughly examined. It was shown that the highly ordered and oriented mesoporous silica films can be obtained over a wide composition of the starting sol (i.e., 10-200 mM CTAB and 50-350 mM TEOS) and that the lattice parameter can be moderately tuned by changing the chain length of the surfactant template. Thickness of these films can be accurately controlled by applying galvanostatic conditions and by varying the deposition time, which offer the versatility to be applied in the same way to electrodes of different nature without overpotential problems encountered in the potentiostatic mode. Thin mesoporous films are often covered with an additional byproduct made of particulate aggregates arising from bulk gelification at the electrode/solution interface. Getting aggregate-free thin films is possible by working in diluted solutions (i.e., [TEOS] < 125 mM and CTAB/TEOS ratio