Liu Ming-Chang, Sheu Hwo-Shuenn, Cheng Soofin
Department of Chemistry, National Taiwan University, Taipei 106, Taiwan.
J Am Chem Soc. 2009 Mar 25;131(11):3998-4005. doi: 10.1021/ja808025m.
Mesostructured silica synthesized using cetyltriethylammonium (CTEA) ion as the pore-directing agent in acidic environments was ready to have interfacial anions exchanged at ambient temperature. In situ techniques including small-angle X-ray scattering (SAXS) and optical microscopy were used to examine the structural and morphological changes of the as-made mesostructured materials, and pyrene fluorescence quenching experiment was used to probe the variation in interfacial environment during the anion-exchange processes. About one-half of the interfacial anions between the silica framework and micelle were exchanged based on the fluorescence quenching experiments of pyrene, which was dissolved in the hydrophobic core of the micelle. Altering in the pore structure and the architecture of the silica framework was observed when the interfacial anions were exchanged by anions of higher salting-in power. The resultant phase transformation and morphological change were always toward pore structures of lower curvature. The influence of anion follows the Hofmeister series commonly encountered in macromolecular and biological systems. The mesophase transformation induced by the interfacial anion exchange provides a unique technique to study anions which are not yet included in the Hofmeister series.
在酸性环境中使用十六烷基三乙铵（CTEA）离子作为孔导向剂合成的介孔二氧化硅，在室温下易于进行界面阴离子交换。采用小角X射线散射（SAXS）和光学显微镜等原位技术来研究所制备的介孔材料的结构和形态变化，并利用芘荧光猝灭实验来探测阴离子交换过程中界面环境的变化。基于溶解在胶束疏水核中的芘的荧光猝灭实验，二氧化硅骨架与胶束之间约一半的界面阴离子发生了交换。当界面阴离子被盐析能力更强的阴离子交换时，观察到了二氧化硅骨架的孔结构和结构的改变。由此产生的相变和形态变化总是朝着曲率较低的孔结构发展。阴离子的影响遵循大分子和生物系统中常见的霍夫迈斯特序列。界面阴离子交换引起的中间相转变提供了一种独特的技术来研究尚未包含在霍夫迈斯特序列中的阴离子。
