Effects of Solubilized Water on the Relaxation Dynamics Surrounding 6-Propionyl-2-(N,N-dimethylamino)naphthalene Dissolved in 1-Butyl-3-methylimidazolium Hexafluorophosphate at 298 K

Abstract

We report on the picosecond time-resolved fluorescence of 6-propionyl-2-(N,N-dimethylamino)naphthalene (PRODAN) dissolved in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]-[PF 6 ]) at 298 K as a function of solubilized water in the [bmim][PF 6 ] phase. The observed solvent relaxation dynamics can be described by three components with apparent relaxation times that occur over a large time regime (<15 ps to >10 ns). The average relaxation dynamics become faster as the water concentration in the [bmim][PF 6 ] phase increases. Libration and vibration, ion ballistic motion, ion local basin exploration, and ion basin hopping, ion diffusion, and/or the ultrafast relaxation from water (or other small molecules/impurities) are suggested as possible reasons for the yet unquantified sub-15-ps dynamics. The sub-nanosecond dynamics are consistent with [PF 6 ] anion relaxation. This process was found to be water-dependent, slowing as the amount of solubilized water in the [bmim][PF 6 ] phase increased. We speculate that this slowing arises from the formation of 1:2 H-bonded [PF 6 ]‚‚‚HOH‚‚‚[PF 6 ] complexes. The nanosecond dynamics are consistent with the cation, decreasing slightly with an increase in the amount of solubilized water. We suggest that the decrease in this relaxation time arises from a decrease in the bulk viscosity on adding water.

Effect of added ionic liquid on aqueous Triton X-100 micelles

“…Apart from the fact that ILs are constituted of cations/anions and are still in the liquid state at the ambient, most of the recent investigations with ILs are driven by the possibility of their potential environmentally-benign nature; they possess almost negligible vapor pressure and can be recycled easily. As a consequence, it is logical to employ these ILs in concert with other environmentally-friendly systems such as, supercritical fluids [20][21][22][23][24][25][26], aqueous [27][28][29][30][31][32][33][34] and polymer [35][36][37][38][39] solutions, surfactant-based systems [40][41][42][43][44][45][46][47][48][49][50][51], etc.…”

Modulating properties of aqueous sodium dodecyl sulfate by adding hydrophobic ionic liquid

“…Most of the ILs have almost negligible vapor pressure and can be recycled easily. As a consequence, it is logical to employ these ILs in concert with other environmentallyfriendly systems such as supercritical fluids [52][53][54][55][56][57][58], aqueous [59][60][61][62][63][64][65][66], and polymer [67][68][69][70][71] solutions, surfactant-based systems [72][73][74][75][76][77][78][79][80][81][82], etc. Although efforts have been invested by many research groups including our own to study surfactant behavior and possibility of surfactant self-assembly within ILs [72][73][74][75][76][77][78][79][80][81][82], utilization of ILs to effectively and favorably alter/modify properties of dilute aqueous surfactant solutions is an appealing concept from both environmental and application points-of-view.…”

TGA decomposition kinetics of 1-butyl-2,3-dimethylimidazolium tetrafluoroborate and the thermal effects of contaminants

“…More importantly, these impurities have been shown to significantly affect numerous chemical and physical properties of the RTILs [10,12,14,15]. The impact of impurities on the thermal stabilities of RTILs is not well understood, but it is clear that this impact can potentially be significant.…”