Dynamic molecular ordering in multiphasic nanoconfined ionic liquids detected with time-resolved diffusion NMR

Marina Karagianni, Lydia Gkoura, Amit Srivastava, Aris Chatzichristos, Nikolaos Tsolakis, George Romanos, Savvas Orfanidis, Nikolaos Panopoulos, Saeed Alhassan, Dirar Homouz, Jamal Hassan, Michael Fardis, Georgios Papavassiliou

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Molecular motion in nanosized channels can be highly complicated. For example, water molecules in ultranarrow hydrophobic nanopores move rapidly and coherently in a single file, whereas by increasing the pore size they organize into coaxial tubes, displaying stratified diffusion. Interestingly, an analogous complex motion is predicted in viscous charged fluids, such as room temperature ionic liquids (RTILs) confined in nanoporous carbon or silica; however, experimental evidence is still pending. Here, by combining 1H NMR diffusion experiments in different relaxation windows with molecular dynamics simulations, we show that the imidazolium-based RTIL [BMIM]+[TCM], entrapped in the MCM-41 silica nanopores, exhibits an intricate dynamic molecular ordering; adsorbed RTIL molecules form a fluctuating charged layer near the pore walls, while in the bulk pore space they diffuse discretely in coaxial tubular shells, with molecular mean square displacement following a nearly ∼τ0.5 time dependence, characteristic of single file diffusion.

Original languageBritish English
Article number9
JournalCommunications Materials
Volume4
Issue number1
DOIs
StatePublished - Dec 2023

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