二元阴、 阳离子表面活性剂调控合成不同形貌的介孔二氧化硅

经过简单的水热处理, 以二元阴、 阳离子表面活性剂[十六烷基三甲基溴化铵(CTAB)和十二烷基磺酸钠(SDS)分别作为阳离子表面活性剂和阴离子表面活性剂]为模板剂合成了不同形貌的介孔二氧化硅. 通过调控2种表面活性剂摩尔分数R(R=n(SDS)/[n(SDS)+n(CTAB)]), 合成了多种形貌的介孔二氧化硅. 对合成的不同形貌样品通过扫描电子显微镜(SEM)、 透射电子显微镜(TEM)、 X射线粉末衍射仪(XRD) 及比表面和孔隙分析仪进行了表征. 结果表明, 随着R值从0.01变化到0.50, 介孔二氧化硅的形貌经历了一系列规律性的变化, 出现了二维六方、 层状相和反相堆积的形貌: 在R=0.01~0.18之间, 主要产物为六方相棒状结构, 且长径比随着R值增大而增大; 在R=0.20~0.28之间主要得到空心泡状结构且具有明显的演变过程; 在R=0.32~0.40之间发生了多层囊泡到单层囊泡的结构转变; 当R值超过一定范围时会产生反相堆积的形貌. 分析认为, SDS在加入过程中通过影响堆积参数g影响胶束的形貌变化, 调控了不同形貌介孔二氧化硅的合成. 各阶段产物形貌和R值的变化有直接关系, 可通过改变R值来合成特定形貌的产物.

Morphological Transformation of Mesoporous Silica Using Binary Cationic-anionic Surfactant as Template†

Mesoporous silica with various morphologies were obtained using binary cationic-anionic surfactant as template after a facile hydrothermal treatment. Cetyltrimethyl ammonium bromide(CTAB) and sodium dodecyl sulfonate(SDS) were selected as cationic and anionic structure direct agent respectively. Mechanism of morphological control during this process was investigated by regulating the molar ratio of SDS/CTAB. The as-synthesized samples were characterized by scanning electron microscopy(SEM), small angle X-ray diffraction(SXRD), transmission electron microscopy(TEM) and nitrogen adsorption-desorption isotherms measurements. Formation of the different stable morphologies were attributed to the structural transition of SDS/CTAB assembly from micelle to bilayer commitment with the ascending ratio of SDS.