Terahertz dynamics of ionic liquids from a combined dielectric relaxation, terahertz, and optical Kerr effect study: evidence for mesoscopic aggregation

David A. Turton, Johannes Hunger, Alexander Stoppa, Glenn Hefter, Andreas Thoman, Markus Walther, Richard Buchner, Klaas Wynne, LP Sadwick (Editor), CMM OSullivan (Editor)

Research output: Contribution to conferencePaper

2 Citations (Scopus)

Abstract

To exploit the great potential of room-temperature ionic liquids (RTILs) as solvents that offer both low environmental impact and product selectivity, an understanding of the liquid structure, the microscopic dynamics, and the way in which the pertinent macroscopic properties, such as viscosity, thermal conductivity, ionic diffusion, and solvation dynamics depend on these properties, is essential. We have measured the intermolecular dynamics of the 1,3-dialkylimidazolium-based RTILs [emim][BF4], [emim][DCA], and [bmim][DCA], at 25 degrees C from below 1 GHz to 10 THz by ultrafast optical Kerr effect (OKE) spectroscopy and dielectric relaxation spectroscopy (DRS) augmented by time-domain terahertz and far-infrared FTIR spectroscopy. This concerted approach allows a more detailed analysis to be made of the relatively featureless terahertz region, where the higher frequency diffusional modes are strongly overlapped with librations and intermolecular vibrations. In the terahertz region, the signal-to-noise ratio of the OKE spectra is particularly high and the data show that there is a greater number of librational and intermolecular vibrational modes than previously detected. Of greatest interest though, is an intense low frequency (sub-alpha) relaxation that we show is in strong accordance with recent simulations that observe mesoscopic structure arising from aggregates or clusters; structure that explains the anomalous and inconveniently-high viscosities of these liquids.

Conference

ConferenceConference on Terahertz Technology and Applications III
CountryUnited States
CitySan Francisco
Period27/01/1028/01/10

Fingerprint

Kerr effects
liquids
viscosity
ionic diffusion
libration
room temperature
spectroscopy
solvation
vibration mode
signal to noise ratios
thermal conductivity
selectivity
infrared spectroscopy
low frequencies
vibration
products
simulation

Keywords

  • Terahertz spectroscopy
  • room-temperature ionic liquids
  • Kerr spectroscopy
  • dielectric relaxation spectroscopy

Cite this

Turton, D. A., Hunger, J., Stoppa, A., Hefter, G., Thoman, A., Walther, M., ... OSullivan, CMM. (Ed.) (2010). Terahertz dynamics of ionic liquids from a combined dielectric relaxation, terahertz, and optical Kerr effect study: evidence for mesoscopic aggregation. Paper presented at Conference on Terahertz Technology and Applications III, San Francisco, United States. https://doi.org/10.1117/12.840185
Turton, David A. ; Hunger, Johannes ; Stoppa, Alexander ; Hefter, Glenn ; Thoman, Andreas ; Walther, Markus ; Buchner, Richard ; Wynne, Klaas ; Sadwick, LP (Editor) ; OSullivan, CMM (Editor). / Terahertz dynamics of ionic liquids from a combined dielectric relaxation, terahertz, and optical Kerr effect study: evidence for mesoscopic aggregation. Paper presented at Conference on Terahertz Technology and Applications III, San Francisco, United States.
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abstract = "To exploit the great potential of room-temperature ionic liquids (RTILs) as solvents that offer both low environmental impact and product selectivity, an understanding of the liquid structure, the microscopic dynamics, and the way in which the pertinent macroscopic properties, such as viscosity, thermal conductivity, ionic diffusion, and solvation dynamics depend on these properties, is essential. We have measured the intermolecular dynamics of the 1,3-dialkylimidazolium-based RTILs [emim][BF4], [emim][DCA], and [bmim][DCA], at 25 degrees C from below 1 GHz to 10 THz by ultrafast optical Kerr effect (OKE) spectroscopy and dielectric relaxation spectroscopy (DRS) augmented by time-domain terahertz and far-infrared FTIR spectroscopy. This concerted approach allows a more detailed analysis to be made of the relatively featureless terahertz region, where the higher frequency diffusional modes are strongly overlapped with librations and intermolecular vibrations. In the terahertz region, the signal-to-noise ratio of the OKE spectra is particularly high and the data show that there is a greater number of librational and intermolecular vibrational modes than previously detected. Of greatest interest though, is an intense low frequency (sub-alpha) relaxation that we show is in strong accordance with recent simulations that observe mesoscopic structure arising from aggregates or clusters; structure that explains the anomalous and inconveniently-high viscosities of these liquids.",
keywords = "Terahertz spectroscopy, room-temperature ionic liquids , Kerr spectroscopy, dielectric relaxation spectroscopy",
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Turton, DA, Hunger, J, Stoppa, A, Hefter, G, Thoman, A, Walther, M, Buchner, R, Wynne, K, Sadwick, LP (ed.) & OSullivan, CMM (ed.) 2010, 'Terahertz dynamics of ionic liquids from a combined dielectric relaxation, terahertz, and optical Kerr effect study: evidence for mesoscopic aggregation' Paper presented at Conference on Terahertz Technology and Applications III, San Francisco, United States, 27/01/10 - 28/01/10, . https://doi.org/10.1117/12.840185

Terahertz dynamics of ionic liquids from a combined dielectric relaxation, terahertz, and optical Kerr effect study: evidence for mesoscopic aggregation. / Turton, David A.; Hunger, Johannes; Stoppa, Alexander; Hefter, Glenn; Thoman, Andreas; Walther, Markus; Buchner, Richard; Wynne, Klaas; Sadwick, LP (Editor); OSullivan, CMM (Editor).

2010. Paper presented at Conference on Terahertz Technology and Applications III, San Francisco, United States.

Research output: Contribution to conferencePaper

TY - CONF

T1 - Terahertz dynamics of ionic liquids from a combined dielectric relaxation, terahertz, and optical Kerr effect study: evidence for mesoscopic aggregation

AU - Turton, David A.

AU - Hunger, Johannes

AU - Stoppa, Alexander

AU - Hefter, Glenn

AU - Thoman, Andreas

AU - Walther, Markus

AU - Buchner, Richard

AU - Wynne, Klaas

A2 - Sadwick, LP

A2 - OSullivan, CMM

PY - 2010

Y1 - 2010

N2 - To exploit the great potential of room-temperature ionic liquids (RTILs) as solvents that offer both low environmental impact and product selectivity, an understanding of the liquid structure, the microscopic dynamics, and the way in which the pertinent macroscopic properties, such as viscosity, thermal conductivity, ionic diffusion, and solvation dynamics depend on these properties, is essential. We have measured the intermolecular dynamics of the 1,3-dialkylimidazolium-based RTILs [emim][BF4], [emim][DCA], and [bmim][DCA], at 25 degrees C from below 1 GHz to 10 THz by ultrafast optical Kerr effect (OKE) spectroscopy and dielectric relaxation spectroscopy (DRS) augmented by time-domain terahertz and far-infrared FTIR spectroscopy. This concerted approach allows a more detailed analysis to be made of the relatively featureless terahertz region, where the higher frequency diffusional modes are strongly overlapped with librations and intermolecular vibrations. In the terahertz region, the signal-to-noise ratio of the OKE spectra is particularly high and the data show that there is a greater number of librational and intermolecular vibrational modes than previously detected. Of greatest interest though, is an intense low frequency (sub-alpha) relaxation that we show is in strong accordance with recent simulations that observe mesoscopic structure arising from aggregates or clusters; structure that explains the anomalous and inconveniently-high viscosities of these liquids.

AB - To exploit the great potential of room-temperature ionic liquids (RTILs) as solvents that offer both low environmental impact and product selectivity, an understanding of the liquid structure, the microscopic dynamics, and the way in which the pertinent macroscopic properties, such as viscosity, thermal conductivity, ionic diffusion, and solvation dynamics depend on these properties, is essential. We have measured the intermolecular dynamics of the 1,3-dialkylimidazolium-based RTILs [emim][BF4], [emim][DCA], and [bmim][DCA], at 25 degrees C from below 1 GHz to 10 THz by ultrafast optical Kerr effect (OKE) spectroscopy and dielectric relaxation spectroscopy (DRS) augmented by time-domain terahertz and far-infrared FTIR spectroscopy. This concerted approach allows a more detailed analysis to be made of the relatively featureless terahertz region, where the higher frequency diffusional modes are strongly overlapped with librations and intermolecular vibrations. In the terahertz region, the signal-to-noise ratio of the OKE spectra is particularly high and the data show that there is a greater number of librational and intermolecular vibrational modes than previously detected. Of greatest interest though, is an intense low frequency (sub-alpha) relaxation that we show is in strong accordance with recent simulations that observe mesoscopic structure arising from aggregates or clusters; structure that explains the anomalous and inconveniently-high viscosities of these liquids.

KW - Terahertz spectroscopy

KW - room-temperature ionic liquids

KW - Kerr spectroscopy

KW - dielectric relaxation spectroscopy

UR - http://www.scopus.com/inward/record.url?scp=77951576499&partnerID=8YFLogxK

U2 - 10.1117/12.840185

DO - 10.1117/12.840185

M3 - Paper

ER -

Turton DA, Hunger J, Stoppa A, Hefter G, Thoman A, Walther M et al. Terahertz dynamics of ionic liquids from a combined dielectric relaxation, terahertz, and optical Kerr effect study: evidence for mesoscopic aggregation. 2010. Paper presented at Conference on Terahertz Technology and Applications III, San Francisco, United States. https://doi.org/10.1117/12.840185