The densities and viscosities for mixtures of 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid with acetonitrile, dichloromethane, 2-butanone and N,N-dimethylformamide have been determined at 298.15 K. From these measurements, it was found that viscosities of the mixtures can generally be described by an exponential equation. Their densities are linear functions of the mass fraction of the ionic liquid in the mixtures. These physical properties can be predicted as a function of the concentration of ionic liquid provided that the properties for pure components are known. The excess molar volume V E m and the excess logarithm viscosities (ln h) E were calculated and fitted to the Redlich-Kister polynomials. It is shown that the values of V E m are negative but those of (ln h) E are positive. Surprisingly, the minimum in V E m and the maximum in (ln h) E are observed at about the same mole fraction of the ionic liquid, x ≈ 0.3. The results are discussed in terms of the ion-dipole interactions between the cations of the ionic liquid and the organic solutes.

N/S/P-co-doped carbon dots with tunable luminescence properties were synthesized from cucumber juice, and used as fluorescent probes for Hg2+ detection.

No abstract

Considering the ionic nature of ionic liquids (ILs), ionic association is expected to be essential in solutions of ILs and to have an important influence on their applications. Although numerous studies have been reported for the ionic association behavior of ILs in solution, quantitative results are quite scarce. Herein, the conductivities of the ILs [Cnmim]Br (n=4, 6, 8, 10, 12), [C4mim][BF4], and [C4mim][PF6] in various molecular solvents (water, methanol, 1-propanol, 1-pentanol, acetonitrile, and acetone) are determined at 298.15 K as a function of IL concentration. The conductance data are analyzed by the Lee-Wheaton conductivity equation in terms of the ionic association constant (KA) and the limiting molar conductance (Lambda(m)(0)). Combined with the values for the Br- anion reported in the literature, the limiting molar conductivities and the transference numbers of the cations and [BF4]- and [PF6]- anions are calculated in the molecular solvents. It is shown that the alkyl chain length of the cations and type of anion affect the ionic association constants and limiting molar conductivities of the ILs. For a given anion (Br-), the Lambda(m)(0) values decrease with increasing alkyl chain length of the cations in all the molecular solvents, whereas the KA values of the ILs decrease in organic solvents but increase in water as the alkyl chain length of the cations increases. For the [C4mim]+ cation, the limiting molar conductivities of the ILs decrease in the order Br- > [BF4]- > [PF6]-, and their ionic association constants follow the order [BF4]- > [PF6]- > Br- in water, acetone, and acetonitrile. Furthermore, and similar to the classical electrolytes, a linear relationship is observed between ln KA of the ILs and the reciprocal of the dielectric constants of the molecular solvents. The ILs are solvated to a different extent by the molecular solvents, and ionic association is affected significantly by ionic solvation. This information is expected to be useful for the modulation of the IL conductance by the alkyl chain length of the cations, type of anion, and physical properties of the molecular solvents.