Liu Yi-Hsin, Lin Hong-Ping, Mou Chung-Yuan
Department of Chemistry and Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan 106.
Langmuir. 2004 Apr 13;20(8):3231-9. doi: 10.1021/la0358421.
A direct method of surface silyl modification and simultaneous surfactant removal of mesoporous silica is investigated in its physicochemical details. Twelve different silanes of various functionalities are studied. The method employs an alcohol solution of silanes to allow the simultaneous surfactant/silyl exchange process, which results in a more uniform monolayer coverage of the surface and a higher amount of surface attachments of silane. We vary the solution concentration of silanes to study the effect on loadings. It is found that the variation of the surface loading of the silyl group follows a Langmuir adsorption model closely. The method gives one a well-controlled monolayer coverage of the surface. The loadings are determined by the exchange equilibrium. Fittings of the loading data to Langmuir adsorption isotherms give one the adsorption equilibrium constants and maximum surface loadings. We categorize the silanes into three different groups according to the values of the equilibrium constants and discuss them with respect to molecular structures. We also report on the extensive characterizations of the surface-functionalized mesoporous materials, such as nitrogen adsorptions, X-ray diffraction, 29Si magic-angle spinning NMR, 13C magic-angle spinning NMR, and IR spectroscopy. The method provides one with a convenient and highly controllable approach to the surface functionalization of mesoporous silica.
本文详细研究了一种直接对介孔二氧化硅进行表面硅烷基修饰并同时去除表面活性剂的方法。研究了十二种具有不同官能团的硅烷。该方法采用硅烷的醇溶液，以实现表面活性剂/硅烷基的同时交换过程，从而使表面形成更均匀的单层覆盖，并增加硅烷在表面的附着量。我们改变硅烷溶液的浓度，以研究其对负载量的影响。结果发现，硅烷基表面负载量的变化紧密遵循朗缪尔吸附模型。该方法能够很好地控制表面的单层覆盖。负载量由交换平衡决定。将负载数据拟合到朗缪尔吸附等温线，可以得到吸附平衡常数和最大表面负载量。根据平衡常数的值，我们将硅烷分为三类，并结合分子结构进行讨论。我们还报道了对表面功能化介孔材料的广泛表征，如氮气吸附、X射线衍射、29Si魔角旋转核磁共振、13C魔角旋转核磁共振和红外光谱。该方法为介孔二氧化硅的表面功能化提供了一种方便且高度可控的途径。
