Palombo M, Gabrielli A, Servedio V D P, Ruocco G, Capuani S
1] Physics Department, Sapienza University of Rome, P. le A. Moro, 5 00185 Rome, Italy [2] CNR IPCF UOS Roma, Physics Department, Sapienza University of Rome, P. le A. Moro, 5 00185 Rome, Italy.
Sci Rep. 2013;3:2631. doi: 10.1038/srep02631.
Nowadays Nuclear Magnetic Resonance diffusion (dNMR) measurements of water molecules in heterogeneous systems have broad applications in material science, biophysics and medicine. Up to now, microstructural rearrangement in media has been experimentally investigated by studying the diffusion coefficient (D(t)) behavior in the tortuosity limit. However, this method is not able to describe structural disorder and transitions in complex systems. Here we show that, according to the continuous time random walk framework, the dNMR measurable parameter α, quantifying the anomalous regime of D(t), provides a quantitative characterization of structural disorder and structural transition in heterogeneous systems. To demonstrate this, we compare α measurements obtained in random packed monodisperse micro-spheres with Molecular Dynamics simulations of disordered porous media and 3D Monte Carlo simulation of particles diffusion in these kind of systems. Experimental results agree well with simulations that correlate the most used parameters and functions characterizing the disorder in porous media.
如今，在非均匀体系中对水分子进行核磁共振扩散（dNMR）测量在材料科学、生物物理学和医学领域有着广泛应用。到目前为止，通过研究曲折度极限下的扩散系数D(t)行为，对介质中的微观结构重排进行了实验研究。然而，这种方法无法描述复杂体系中的结构无序和转变。在此我们表明，根据连续时间随机游走框架，dNMR可测量参数α（量化D(t)的反常区域）为非均匀体系中的结构无序和结构转变提供了定量表征。为了证明这一点，我们将在随机堆积的单分散微球中获得的α测量值与无序多孔介质的分子动力学模拟以及这类体系中粒子扩散的三维蒙特卡罗模拟进行了比较。实验结果与模拟结果吻合良好，模拟结果关联了表征多孔介质无序的最常用参数和函数。
