Rotational fluctuations of water inside the nanopores of SBA-type molecular sieves.
Rotational fluctuations of water inside the nanopores of SBA-type molecular sieves.
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DOI：
10.1021/jp044503t
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发表时间：
2005-04
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影响因子：
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通讯作者：
L. Frunza;H. Kosslick;I. Pitsch;Ş. Frunzǎ;A. Schönhals
中科院分区：
文献类型：
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作者：
L. Frunza;H. Kosslick;I. Pitsch;Ş. Frunzǎ;A. Schönhals
本文用介电谱法研究了水在六方纳米孔分子筛（SBA-15）和泡沫状纳米孔分子筛（SBA-15）中的旋转分子动力学。两个弛豫过程进行了观察：在较低的频率的过程是有关的水分子形成一个层，这是强烈吸附在孔隙表面，而在较高的频率的弛豫过程被分配到位于靠近中心的孔的水分子的波动。这两种材料的低频过程和SBA-15材料的高频过程的弛豫时间具有不寻常的鞍形温度依赖性，这里首次报道。为了描述这种温度依赖性，应用了Ryabov等人[J. Phys. Chem. B 2001，105，1845]针对限制在纳米多孔玻璃中的水开发的模型，该模型考虑了两种竞争效应。这两个竞争过程的特征进行了比较与其他多孔系统的报告。
The rotational molecular dynamics of water confined to nanoporous molecular sieves of a regular hexagonal (SBA-15) and of a foamlike pore structure was studied by dielectric spectroscopy in the frequency range from 10(-2) to 10(9) Hz and in a broad temperature interval. Two relaxation processes were observed: the process at lower frequencies is related to water molecules forming a layer, which is strongly adsorbed at the pore surface, whereas the relaxation process at higher frequencies is assigned to fluctuations of water molecules situated close to the center of the pore. The relaxation times of the low-frequency process for both materials and of the high-frequency process for the SBA-15 material have an unusual saddlelike temperature dependence, reported here for the first time. To describe this temperature dependence, a model developed for water confined to nanoporous glasses by Ryabov et al. [J. Phys. Chem. B 2001, 105, 1845] was applied, which considers two competing effects. The characteristic features of these two competing processes were compared with those reported for other porous systems.