Valiullin Rustem, Kortunov Pavel, Kärger Jörg, Timoshenko Viktor
Department of Molecular Physics, Kazan State University, Kazan 420008, Russia.
J Phys Chem B. 2005 Mar 31;109(12):5746-52. doi: 10.1021/jp045721p.
The pulsed field gradient nuclear magnetic resonance method has been employed to probe self-diffusion of organic guest molecules adsorbed in porous silicon with a 3.6 nm pore size. The molecular self-diffusion coefficient and intrapore adsorption were simultaneously measured as a function of the external vapor pressure. The latter was varied in a broad range to provide pore loading from less than monolayer surface coverage to full pore saturation. The measured diffusivities are found to be well-correlated with the adsorption isotherms. At low molecular concentrations in the pores, corresponding to surface coverages of less than one monolayer, the self-diffusion coefficient strongly increases with increasing concentration. This observation is attributed to the occurrence of activated diffusion on a heterogeneous surface. Additional experiments in a broad temperature range and using binary mixtures confirm this hypothesis.
脉冲场梯度核磁共振方法已被用于探测吸附在孔径为3.6纳米的多孔硅中的有机客体分子的自扩散。分子自扩散系数和孔内吸附量作为外部蒸气压的函数被同时测量。后者在很宽的范围内变化，以提供从小于单层表面覆盖到完全孔饱和的孔负载。发现测得的扩散率与吸附等温线有很好的相关性。在孔内低分子浓度下，对应于小于一个单层的表面覆盖，自扩散系数随着浓度的增加而强烈增加。这一观察结果归因于在异质表面上发生的活化扩散。在很宽的温度范围内以及使用二元混合物进行的额外实验证实了这一假设。
