We have studied the ultrafast dynamics of forty aprotic molecular liquids by femtosecond optical heterodyne-detected Raman-induced Kerr effect spectroscopy. Some physical properties such as shear viscosity, density, and surface tension of the molecular liquids have also been measured. From the Fourier transform Kerr spectra in the frequency range of about 0–200 cm−1, we have found that the first moment of the low-frequency intermolecular vibrational spectrum is moderately correlated with the root of the value of surface tension divided by density. This fact indicates that the microscopic intermolecular interaction is related to the macroscopic physical property of intermolecular force in molecular liquids. On the other hand, a correlation between the first moment of the intermolecular vibrational spectrum and the interaction energy of two identical molecules is almost nonexistent. The difference between the two relations suggests that the many-body interaction effect takes a hand in the intermolecular vibrational dynamics in molecular liquids. We have also found that the shapes of the broad low-frequency vibrational spectra for aromatic molecular liquids show a clearer bimodal feature than those for non-aromatic molecular liquids. Picosecond Kerr transients for most of the molecular liquids are non-exponential. The slowest relaxation time is qualitatively explained by the Stokes–Einstein–Debye model.

We studied the hydration characteristics of room-temperature ionic liquids (IL). We experimentally determined the excess chemical potentials, , the excess partial molar enthalpies, , and the excess partial molar entropies in IL−H2O systems at 25 °C. The ionic liquids studied were 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) and the iodide ([bmim]I). From these data, the excess (integral) molar enthalpy and entropy, and , and the IL−IL enthalpic interaction, , were calculated. Using these thermodynamic data, we deduced the mixing schemes, or the “solution structures”, of IL−H2O systems. At infinite dilution IL dissociates in H2O, but the subsequent hydration is much weaker than for NaCl. As the concentration of IL increases, [bmim]+ ions and the counteranions begin to attract each other up to a threshold mole fraction, x IL = 0.015 for [bmim]BF4 and 0.013 for [bmim]I. At still higher mole fractions, IL ions start to organize themselves, directly or in an H2O-mediated manner. Eventually for x IL > 0.5−0.6, IL molecules form clusters of their own kind, as in their pure states. We show that , a third derivative of G, provided finer details than and , second derivatives, which in turn gave more detailed information than and , first derivative quantities.

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It was recently discovered that the sputter deposition of metal onto the surface of an ionic liquid generates nanoparticles in the liquid with no additional stabilizing agents. We performed small-angle X-ray scattering (SAXS) experiments to investigate the structure of Au nanoparticles synthesized by this method and to reveal the properties of the ionic liquid that affect the formation process. For a systematic study of these properties, we selected imidazolium-based ionic liquids with different alkyl chain lengths fixing the anion BF 4-. The Au concentration dependence for the formation of the nanoparticles was also studied. The SAXS results revealed that Au nanoparticles with 0.75-3.5 nm diameter were generated under the experimental conditions and that the particle size was relatively uniform for a fixed condition. The results demonstrated that the particle size depends on the type of ionic liquid and on the concentration if the ionic liquid is fixed. Integrating the experimental results, it was concluded that the surface tension and viscosity of the ionic liquid played important roles in conjunction with the Au concentration. It was interpreted that the surface tension influences the initial formation process of nanoparticles on the surface of an ionic liquid, and the viscosity affects the aggregation process during the dispersion of the Au particles from the surface into the liquid.