How Viscous Is the Solidlike Structure at the Interface of Ionic Liquids? A Study Using Total Internal Reflection Fluorescence Spectroscopy with a Fluorescent Molecular Probe Sensitive to High Viscosity
| Autor: | Naoya Nishi, Kenjiro Hanaoka, Hiromi Takahashi, Takashi Yamazawa, Takayuki Ikeno, Tetsuo Sakka, Hiroki Hotta |
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| Rok vydání: | 2020 |
| Předmět: |
Materials science
Interfaces 02 engineering and technology 010402 general chemistry 01 natural sciences Fluorescence Viscosity chemistry.chemical_compound Amorphous materials Electrochemistry General Materials Science Spectroscopy Total internal reflection fluorescence microscope Liquids Surfaces and Interfaces 021001 nanoscience & nanotechnology Condensed Matter Physics 0104 chemical sciences Amorphous solid chemistry Chemical physics Ionic liquid 0210 nano-technology Molecular probe |
| Zdroj: | Langmuir : the ACS journal of surfaces and colloids. 36(35) |
| ISSN: | 1520-5827 |
| Popis: | Aiming at the evaluation of the viscosity of the interfacial solidlike structure of ionic liquids (ILs), we performed total internal reflection fluorescence (TIRF) spectroscopy for N, N-diethyl-N′-phenyl-rhodamine (Ph-DER), a fluorescent probe that is sensitive to viscosity in a high-viscosity range. TIRF spectra at the glass interface of trioctylmethylammonium bis(nonafluorobutanesulfonyl)amide (TOMAC4C4N), a hydrophobic IL, showed that the fluorescence intensity of Ph-DER increases with the decrease of the evanescence penetration depth, suggesting that there exists a high-viscosity region at the interface. In contrast, glycerol, which is a molecular liquid with a bulk viscosity similar to that of TOMAC4C4N, did not show such a fluorescence increase, supporting that the formation of a highly viscous solidlike structure at the interface is intrinsic to ILs. A model analysis suggested that the high viscous region at the glass interface of TOMAC4C4N is at least twice thicker than the ionic multilayers at the air interface, implying that the solid substrate enhances the ordering of the interfacial structure of ILs. The viscosity at the glass interface of TOMAC4C4N was found to be at least 40 times higher than that of the liquid bulk. |
| Databáze: | OpenAIRE |
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