Campus Units

Chemistry, Ames Laboratory

Document Type

Article

Publication Version

Accepted Manuscript

Publication Date

5-16-2019

Journal or Book Title

Journal of Physical Chemistry B

Volume

123

Issue

23

First Page

4943

Last Page

4949

DOI

10.1021/acs.jpcb.9b01476

Abstract

Fluorescence correlation spectroscopy (FCS) is applied to investigate the diffusional dynamics of hydrophilic (Atto 590) and amphiphilic (DiD) fluorophores in a series of alkylphosphonium ionic liquid (IL) films ([P4448][Cl], [P6668][Cl], [P66614][Cl], and [P66614][NTf2]) in order to determine diffusional parameters and to elucidate nanoscale structural heterogeneities within the IL. From the measured correlation functions, the diffusion coefficients of the fluorescent molecules are estimated, rendering values that span from 0.39-1.2 and 0.146-5.2 µm2/s, for Atto 590 and DiD, respectively. A decrease in the diffusion coefficients is measured as the alkyl chain increases, coincident with a decrease in their viscosity. Interestingly, deviations from the Brownian diffusion behavior of the fluorescent probes in the ILs are observed, showing a time-dependent diffusion coefficient in most of the cases. These deviations can be attributed to the presence of nanoscale structural heterogeneities in the tetraalkylphosphonium ILs. These results confirm experimentally the presence of nanosegregation in tetraalkylphosphonium ILs, which has previously been observed in molecular dynamics (MD) studies.

Comments

This document is the Accepted Manuscript version of a Published Work that appeared in final form in the Journal of Physical Chemistry B, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see 10.1021/acs.jpcb.9b01476. Posted with permission.

Copyright Owner

American Chemical Society

Language

en

File Format

application/pdf

Available for download on Saturday, May 16, 2020

Published Version

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