Ultrafast FRET to study spontaneous micelle-to-vesicle transitions in an aqueous mixed surface-active ionic-liquid system
| Autor: | Debasis Banik, Chiranjib Banerjee, Vijaykant Khorwal, Jagannath Kuchlyan, Sarthak Mandal, Surajit Ghosh, Nilmoni Sarkar |
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| Rok vydání: | 2014 |
| Předmět: |
Rotational-Relaxation
Ionic Liquids Mole fraction Micelle Resonance Energy-Transfer Rhodamine 6G chemistry.chemical_compound Dynamic light scattering Fret Vesicles Molten-Salts Physical and Theoretical Chemistry Micelles Fluorescent Dyes 1-Butyl-3-Methylimidazolium Octyl Sulfate Forster Theory Chemistry Vesicle Bilayer Photoinduced Electron-Transfer C4mim Atomic and Molecular Physics and Optics Dynamics Self-Assembly Crystallography Ionic liquid Aggregation Behavior Mechanism |
| Zdroj: | Chemphyschem : a European journal of chemical physics and physical chemistry. 15(16) |
| ISSN: | 1439-7641 |
| Popis: | The spontaneous micelle-to-vesicle transition in an aqueous mixture of two surface-active ionic liquids (SAILs), namely, 1-butyl-3-methylimidazolium n-octylsulfate ([C(4)mim][C8SO4]) and 1-dodecyl-3-methylimidazoium chloride ([C(12)mim]Cl) is described. In addition to detailed structural characterization obtained by using dynamic light scattering, transmission electron microscopy (TEM), and cryogenic TEM techniques, ultrafast fluorescence resonance energy transfer (FRET) from coumarin 153 (C153) as a donor (D) to rhodamine 6G (R6G) as an acceptor (A) is also used to study micelle-vesicle transitions in the present system. Structural transitions of SAIL micelles ([C(4)mim][C8SO4] or [C(12)mim] Cl micelles) to mixed SAIL vesicles resulted in significantly increased D-A distances, and therefore, increased timescale of FRET. In [C(4)mim][C8SO4] micelles, FRET between C153 and R6G occurs on an ultrafast timescale of 3.3 ps, which corresponds to a D-A distance of about 15 angstrom. As [C(4)mim][C8SO4] micelles are transformed into mixed micelles upon the addition of a 0.25 molar fraction of [C(12)mim] Cl, the timescale of FRET increases to 300 ps, which suggests an increase in the D-A distance to 31 angstrom. At a 0.5 molar fraction of [C(12)mim] Cl, unilamellar vesicles are formed in which FRET occurs on multiple timescales of about 250 and 2100 ps, which correspond to D-A distances of 33 and 47 angstrom. Although in micelles and mixed micelles the obtained D-A distances are well correlated with their radius, in vesicles the obtained D-A distance is within the range of the bilayer thickness. |
| Databáze: | OpenAIRE |
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