Anomalous surface diffusion of water compared to aprotic liquids in nanopores.
Anomalous surface diffusion of water compared to aprotic liquids in nanopores.
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DOI：
10.1103/physreve.60.3097
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发表时间：
1999-09
期刊：
影响因子：
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通讯作者：
J. Korb;M. W. Hodges;T. Gobron;R. Bryant
中科院分区：
文献类型：
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作者：
J. Korb;M. W. Hodges;T. Gobron;R. Bryant
1H核磁弛豫色散实验表明，水和丙酮与含有微量顺磁性杂质的微孔玻璃表面接触时存在显着差异。通过对模型多孔系统的表面弛豫理论进行分析，获得的水数据表明，受与本体相化学交换限制的质子表面扩散允许沿孔隙进行长距离有效的一维探索。这种磁场依赖性与弛豫率的异常温度依赖性相结合，允许根据孔表面的质子平移扩散系数进行直接解释。对针对不同孔径、各种频率和温度收集的这些数据进行通用重新调整，支持了这种解释。分析表明，丙酮扩散速度更慢，这增加了表观限制，并产生了接近表面弛豫汇的分子动力学二维模型。然而，表面增强的水质子扩散允许质子探索更大的孔隙空间范围，这导致了主导核自旋弛豫的水扩散运动的明显一维模型。
1H nuclear magnetic relaxation dispersion experiments show remarkable differences between water and acetone in contact with microporous glass surfaces containing trace paramagnetic impurities. Analyzed with surface relaxation theory on a model porous system, the data obtained for water show that proton surface diffusion limited by chemical exchange with the bulk phase permits long-range effectively one-dimensional exploration along the pores. This magnetic-field dependence coupled with the anomalous temperature dependence of the relaxation rates permits a direct interpretation in terms of the proton translational diffusion coefficient at the surface of the pores. A universal rescaling applied to these data collected for different pore sizes and on a large variety of frequencies and temperatures, supports this interpretation. The analysis demonstrates that acetone diffuses more slowly, which increases the apparent confinement and results in a two-dimensional model for the molecular dynamics close to surface relaxation sinks. Surface-enhanced water proton diffusion, however, permits the proton to explore a greater spatial extent of the pore, which results in an apparent one-dimensional model for the diffusive motions of the water that dominate nuclear spin relaxation.