Optics and Spectroscopy for Fluid Characterization

Kiefer, Johannes

doi:10.3390/app8050828

Cited by 2 publications

(3 citation statements)

References 19 publications

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“…The differences in the spectral absorptions of Figure 2c (0.7 GPa) and d (1.1 GPa) can be related to the generation of an anisotropic environment in Figure 2d, owing to the local alkyl C–H structure changes. It is known that hydrogen bonding leads to ring stacking of ILs and vibrational frequency shifts of imidazolium cations [7,8,9]. Our results in Figure 2 indicate the important roles played by micro-heterogeneity and hydrogen bonding in [C 2 C 1 Im][BF 4 ].…”

Section: Resultsmentioning

confidence: 61%

“…Ionic liquids (ILs) are salts whose melt temperature is less than 100 ºC because of the difficulty of stacking asymmetric and bulky cations and anions [7,8,9,10,11,12,13,14,15,16,17]. Due to the non-volatility and liquid state at room temperature, ILs have been used in energy storage devices, carbon dioxide absorptions, and dye-sensitized solar cells [7,8,9,10,12]. Typically, imidazolium-based ionic liquids are most extensively studied, and the cations are characterized by an imidazolium polar head and alkyl tail [7,8,9,10].…”

Section: Introductionmentioning

confidence: 99%

“…Due to the non-volatility and liquid state at room temperature, ILs have been used in energy storage devices, carbon dioxide absorptions, and dye-sensitized solar cells [7,8,9,10,12]. Typically, imidazolium-based ionic liquids are most extensively studied, and the cations are characterized by an imidazolium polar head and alkyl tail [7,8,9,10]. Aggregation of cations and anions in bulk ILs via Coulombic forces and hydrogen bonding has been proposed, where the cation-anion interactions lead to heterogeneous or organized cluster structures in the IL [7,8,9,10].…”

Section: Introductionmentioning

confidence: 99%

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Pressure-Dependent Confinement Effect of Ionic Liquids in Porous Silica

2019

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The effect of confining ionic liquids (ILs) such as 1-ethyl-3-methylimidazolium tetrafluoroborate [C2C1Im][BF4] or 1-butyl-3-methylimidazolium tetrafluoroborate [C4C1Im][BF4] in silica matrices was investigated by high-pressure IR spectroscopy. The samples were prepared via the sol-gel method, and the pressure-dependent changes in the C–H absorption bands were investigated. No appreciable changes were observed in the spectral features when the ILs were confined in silica matrices under ambient pressure. That is, the infrared measurements obtained under ambient pressure were not sufficient to detect the interfacial interactions between the ILs and the porous silica. However, dramatic differences were observed in the spectral features of [C2C1Im][BF4] and [C4C1Im][BF4] in silica matrices under the conditions of high pressures. The surfaces of porous silica appeared to weaken the cation-anion interactions caused by pressure-enhanced interfacial IL-silica interactions. This confinement effect under high pressures was less obvious for [C4C1Im][BF4]. The size of the cations appeared to play a prominent role in the IL-silica systems.

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Section: Resultsmentioning

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Pressure-Dependent Confinement Effect of Ionic Liquids in Porous Silica

2019

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The validity of high pressure IR for detecting the interactions between β-cyclodextrin and imidazolium based ionic liquids

2019

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The effects of alkyl side-chain length on the interactions between imidazolium ionic liquids (ILs) and β-cyclodextrin (β-CD) were studied at ambient pressure and up to 2.5GPa. No noticeable changes in the C-H band frequencies of 1-methyl-3-propylimidazolium hexafluorophosphate ([MPIM][PF6]) were observed upon β-CD addition under ambient pressure. Nevertheless, β-CD addition inhibited the formation of the [MPIM][PF6] aggregated structure under pressures of ≤0.7 GPa. As the pressure was raised to 1.1–2.5 GPa, [MPIM][PF6] aggregated and formed self-associated configurations. This pressure-induced dissociation was not detected in the 1-butyl-3-methylimidazolium hexafluorophosphate and β-CD mixture ([BMIM][PF6]-β-CD) due to the long side chain in the [BMIM] cation. This indicates that the alkyl side-chain length of the imidazolium ILs plays a non-negligible role in controlling the order and strength of IL-β-CD interactions. It is well known that the validity of infrared spectroscopy for detecting the inclusion complexation is questionable in the literature. However, this study demonstrates that the combination of high pressure and IR spectroscopy may provide a suitable way to monitor the IL-β-CD interactions.

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Optics and Spectroscopy for Fluid Characterization

Abstract: Abstract:This Editorial provides an introduction to and an overview of the special issue "Optics and Spectroscopy for Fluid Characterization".

Cited by 2 publications

References 19 publications

Pressure-Dependent Confinement Effect of Ionic Liquids in Porous Silica

Pressure-Dependent Confinement Effect of Ionic Liquids in Porous Silica

The validity of high pressure IR for detecting the interactions between β-cyclodextrin and imidazolium based ionic liquids

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