The formation of the mesoporous material MCM-41 as studied by EPR line shape analysis of spin probes.
The formation of the mesoporous material MCM-41 as studied by EPR line shape analysis of spin probes.
复制标题
通过自旋探针的 EPR 线形分析研究介孔材料 MCM-41 的形成。
DOI：
--
复制
发表时间：
2000
期刊：
影响因子：
--
通讯作者：
D. Goldfarb
中科院分区：
文献类型：
--
作者：
Jingyan Zhang;Z. Luz;H. Zimmermann;D. Goldfarb
通过自旋探针 5-doxyl 硬脂酸 (5DSA) 的运动特性研究了由四乙基原硅 (TEOS) 和十六烷基三甲基氯化铵 (溴化物) (CTAC/B) 制备的六方介孔材料 MCM-41 的形成机制。对最终产品进行的电子自旋回波包络调制（ESEEM）实验表明，自旋探针被纳入有机部分，并且硝基氧自由基位于有机-无机界面附近。 5DSA 的 EPR 光谱是在 298 K 下 MCM-41 形成过程中原位测量的。通过计算机模拟对光谱进行了分析，提供了旋转扩散速率、R⊥ 和 R∥ 以及有序势随时间的演变。随着反应的进行，反映表面活性剂分子行为的自旋探针的有序参数 S 增加，而其旋转扩散速率降低。从这些参数的时间演变来看，可以分为两个阶段......
The formation mechanism of the hexagonal mesoporous material MCM-41, prepared with tetraethyl-orthosilicon (TEOS) and cetyl-trimethylammonium chloride (bromide) (CTAC/B), was investigated through the motional characteristics of the spin probe 5-doxyl stearic acid (5DSA). Electron spin echo envelope modulation (ESEEM) experiments, carried out on the final product, showed that the spin probe is incorporated into the organic part and the nitroxide radical is located near the organic-inorganic interface. The EPR spectra of 5DSA were measured in situ during the formation of MCM-41 at 298 K. The spectra were analyzed by computer simulations that provide the time evolution of the rotational diffusion rates, R⊥ and R∥, and of the ordering potential. As the reaction progresses, the spin probe, which reflects the behavior of the surfactant molecules, experiences an increasing order parameter, S, while its rotational diffusion rates decrease. From the time evolution of these parameters two stages were distinguished....