No abstract

The orientation of cations at the interface between water and a room-temperature ionic liquid (RTIL) has been analyzed using optical second harmonic generation. To detect second harmonic light from the RTIL|water interface with high sensitivity, a RTIL, N-dodecylisoquinolinium bis(pentafluoroethylsulfonyl)imide, which is based on N-dodecylisoquinolinium (C12Iq) having strong hydrophobicity and high hyperpolarizability, has been used. A polarizationdependence measurement of the light intensity of the second harmonic light has suggested that C12Iq is orientated at the RTIL|water interface with the isoquinolinium moiety tilting at 50°with respect to the surface normal, and with the dodecyl moiety protruding to the RTIL phase.