Five acetate-based ionic liquids (AcAILs) [C n mim][OAc](n = 2, 3, 4, 5, 6) (1-alkyl-3-methylimidazolium acetate) were prepared by the neutralization method and characterized by 1H NMR spectroscopy and differential scanning calorimetry (DSC). Their density, surface tension, and refractive index were measured at 298.15 to 338.15 K. Since the AcAILs can form strong hydrogen bonds with water, small amounts of water are difficult to remove by common methods. In order to eliminate the effect of the impurity water, the standard addition method (SAM) was applied to these measurements. On the basis of the experimental data, the molecular volume (sum of positive and negative ion volumes), V m, of [C n mim][OAc](n = 2, 3, 4, 5, 6), the entropy of surface formation, S a, the Gibbs energy of surface formation E a, the parachor, P, and the molar refraction, R m, the polarization coefficient, αp, were calculated. The results show that E a, P, and R m are approximately temperature-independent and the contribution to these properties per methylene (−CH2−) on alkyl chain of [C n mim][OAc](n = 2, 3, 4, 5, 6) was discussed. According to both Kabo’s and Rebelo’s methods, the molar enthalpy of evaporation of the [C n mim][OAc](n = 2, 3, 4, 5, 6) was estimated using surface tension and molar volume. In the same time, the surface tension of the AcAILs may be estimated using the parachor and the refractive index. The estimated values of the surface tension and the corresponding experimental one are extremely similar.

The values of density, surface tension, and refractive index were measured for a classic series of air and water stable ionic liquids (ILs) based on tetrafluoroborate, [C n mim][BF 4 ](n = 2,3,4,5,6)(1-alkyl-3-methylimidazolium tetrafluoroborate) in the temperature range of (298.15 to 338.15 ± 0.02) K. In terms of Glasser's theory, the standard molar entropy and lattice energy of the ILs were calculated. Using Kabo's method, the molar enthalpy of vaporization of the IL, Δ l g H m 0 (298 K), was estimated. According to the interstice model, the thermal expansion coefficient of ILs [C n mim][BF 4 ] (n = 2,3,4,5,6), α, were calculated, and in comparison with experimental value, their magnitude order is in good agreement. To test this new concept of ionic parachor, [BF 4 ] − was chosen as a reference ion and its individual value of ionic parachor was determined in terms of extrathermodynamic assumption. Then, using ionic parachor of [BF 4 ] − , the ionic parachors for all corresponding imidazolium cations, [C n mim] + , were calculated and in good agreement with those obtained by Guan's estimation, and the 17 anion ionic parachors were also obtained. In terms of ionic parachor, the surface tension and refractive index of the investigated ionic liquids were estimated, and the estimated values correlate quite well with their matching experimental values.

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Two new lanthanide-based room temperature ionic liquids [Bmim]­[Ln­(NO3)4] (Bmim = 1-butyl-3-methylimidazolium; Ln = Dy, Sm) were synthesized and characterized. They show good luminescent properties and could be used as good soft luminescent materials. These kinds of hydrostable and eco-friendly ionic liquids were first used to explore the sensing behavior for Fe­(III) ions, exhibit a highly specific recognition, and are not interfered by the following common mental ions: Ca­(II), Al­(III), Zn­(II), Cu­(II), Pb­(II), Hg­(II), Cd­(II), Co­(II), Fe­(II), Ni­(II), and Cr­(III). These lanthanide-based ionic liquids with strong luminescence have an outstanding application prospect in “green” fluorescent sensor and can be widely used in actual detection of Fe­(III) in aqueous solutions.