Revealing complex formation in acetone-n-alkane mixtures by MAS PFG NMR diffusion measurement in nanoporous hosts.
Magic-angle spinning pulsed field gradient nuclear magnetic resonance (MAS PFG NMR) was applied for selective self-diffusion measurements of acetone-n-alkane (C(6) up to C(9)) mixtures in nanoporous silica gel. Two specimens of silica gel with mean pore sizes of about 4 and 10 nm are considered. In the smaller pores, the n-alkane diffusivities are by about one and the acetone diffusivities by about two orders of magnitude smaller than in the larger pores. In addition, the acetone diffusivities in the narrow-pore specimen exhibit a pronounced oscillation with increasing chain length of the solvent n-alkanes: the diffusivities of acetone dissolved in odd-carbon number n-alkanes exceed those of acetone dissolved in even-carbon number n-alkanes by about 50%! These findings reproduce the tendencies observed in previous macroscopic release studies (Phys. Chem. Chem. Phys. 2003, 5, 2476) and suggest the formation of acetone-n-alkane complex-like assemblages in the narrow-pore silica gel.
Fernandez
Moises
M
Abteilung Grenzflächenphysik, Universität Leipzig, Linnéstrasse 5, 04103, Leipzig, Germany.
Pampel
André
A
Takahashi
Ryoji
R
Sato
Satoshi
S
Freude
Dieter
D
Kärger
Jörg
J
D000096:Acetone / Q000737:chemistry*; D000473:Alkanes / Q000737:chemistry*; D004058:Diffusion; D009682:Magnetic Resonance Spectroscopy; D049329:Nanostructures / Q000737:chemistry*; D016062:Porosity; D058428:Silica Gel; D012822:Silicon Dioxide / Q000737:chemistry
D000473:Alkanes; D000096:Acetone; D058428:Silica Gel; D012822:Silicon Dioxide