Fluorescence correlation spectroscopy evidence for structural heterogeneity in ionic liquids

Jianchang Guo; Gary A. Baker; Patrick C. Hillesheim; Sheng Dai; Robert W. Shaw; Shannon M. Mahurin

doi:10.1039/c1cp20929a

Fluorescence correlation spectroscopy evidence for structural heterogeneity in ionic liquids

Jianchang Guo, Gary A. Baker, Patrick C. Hillesheim, Sheng Dai, Robert W. Shaw, Shannon M. Mahurin

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Abstract

In this work, we provide new experimental evidence for chain length-dependent self-aggregation in room temperature ionic liquids (RTILs) using fluorescence correlation spectroscopy (FCS). In studying a homologous series of N-alkyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide, [C_nMPy][Tf₂N] RTILs of varying alkyl chain length (n = 3, 4, 6, 8, and 10), biphasic rhodamine 6G solute diffusion dynamics were observed; both the fast and slow diffusion coefficients decreased with increasing alkyl chain length, with the relative contribution from slower diffusion increasing for longer-chain [C_nMPy][Tf₂N]. We propose that the biphasic diffusion dynamics originate from self-aggregation of the nonpolar alkyl chains in the cationic [C_nMPy]⁺.

Original language	English
Pages (from-to)	12395-12398
Number of pages	4
Journal	Physical Chemistry Chemical Physics
Volume	13
Issue number	27
DOIs	https://doi.org/10.1039/c1cp20929a
State	Published - Jul 21 2011

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abstract = "In this work, we provide new experimental evidence for chain length-dependent self-aggregation in room temperature ionic liquids (RTILs) using fluorescence correlation spectroscopy (FCS). In studying a homologous series of N-alkyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide, [CnMPy][Tf2N] RTILs of varying alkyl chain length (n = 3, 4, 6, 8, and 10), biphasic rhodamine 6G solute diffusion dynamics were observed; both the fast and slow diffusion coefficients decreased with increasing alkyl chain length, with the relative contribution from slower diffusion increasing for longer-chain [CnMPy][Tf2N]. We propose that the biphasic diffusion dynamics originate from self-aggregation of the nonpolar alkyl chains in the cationic [CnMPy]+.",

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T1 - Fluorescence correlation spectroscopy evidence for structural heterogeneity in ionic liquids

AU - Guo, Jianchang

AU - Baker, Gary A.

AU - Hillesheim, Patrick C.

AU - Dai, Sheng

AU - Shaw, Robert W.

AU - Mahurin, Shannon M.

PY - 2011/7/21

Y1 - 2011/7/21

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AB - In this work, we provide new experimental evidence for chain length-dependent self-aggregation in room temperature ionic liquids (RTILs) using fluorescence correlation spectroscopy (FCS). In studying a homologous series of N-alkyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide, [CnMPy][Tf2N] RTILs of varying alkyl chain length (n = 3, 4, 6, 8, and 10), biphasic rhodamine 6G solute diffusion dynamics were observed; both the fast and slow diffusion coefficients decreased with increasing alkyl chain length, with the relative contribution from slower diffusion increasing for longer-chain [CnMPy][Tf2N]. We propose that the biphasic diffusion dynamics originate from self-aggregation of the nonpolar alkyl chains in the cationic [CnMPy]+.

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Fluorescence correlation spectroscopy evidence for structural heterogeneity in ionic liquids

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