Probing Memory Effects in Confined Fluids via Diffusion Measurements

• Published in: Langmuir Vol. 24; no. 13; pp. 6429 - 6432
• Main Authors: Naumov, Sergei, Valiullin, Rustem, Monson, Peter A, Kärger, Jörg
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.07.2008
• Subjects: Catalysis; Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Porous materials; Surface physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Confinement; Separation; Fluid; NMR spectrometry; Density; Porous material; Diffusivity; Heterogeneous catalysis; Chemical conversion; Hysteresis loop; Equilibrium state; Spatial distribution; Adsorption; Pore; Technology; Diffusion; Memory effect
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la801349y

Confinement of fluids in porous materials is widely exploited in a variety of technologies, including chemical conversion by heterogeneous catalysis and adsorption separations. Important fundamental phenomena associated with many-molecule interactions occur in such systems, including a remarkably long “memory” of the past when the actual amount of molecules in the pores dramatically depends on the history of how the external conditions have been changed. We demonstrate that the intrinsic diffusivity as measured by NMR serves as an excellent probe of the history-dependent states of the confined fluid. A remarkable feature of our results are differences in diffusivity between out-of-equilibrium states with the same density within the hysteresis loop. This reflects different spatial distributions of the confined fluid that accompany the arrested equilibration of the system in this region.