Naoya Nishi

The structure of the self-assembled monolayers (SAMs) of n-alkanethiols [CH3(CH2)nSH, n=3–11, 13–15, 17] on Au(111) has been studied using broad-bandwidth sum frequency generation spectroscopy. Sum-frequency vibrational spectra show three pronounced CH3 vibrational modes for all alkanethiol investigated, indicating that the commonly accepted picture that the alkyl chain for the long-chain alkanethiol SAMs has the all-trans conformation applies even to the short chain SAMs. The chain-length depen

Ionic liquids composed of a hydrophobic anion, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (TFPB-), and various aromatic and aliphatic ammonium have been prepared. TFPB salts of N-octadecylisoquinolinium (C18Iq+) and trioctylmethylammonium (TOMA+) show low melting points of 31 and 36 degrees C, respectively, whereas TFPB-based ionic liquids of 1-alkyl-3-methylimidazolium with the alkyl chain length of 5-12 show melting points lower than 90 degrees C. The [C(18)Iq][TFPB]|water (W) and [TOMA][T

The relaxation of the structure in the electrical double layer at the ionic liquid|gold interface to the steps of the electrode potential has been studied using surface plasmon resonance (SPR) measurements. The relaxation of the SPR resonance angle occurs on the order of 100 s, which is distinctively slower than the RC time constant of the cell, about 0.1 s. A relaxation model considering the distribution of the time constants well reproduces the SPR curves. The potential steps to the positive d

The presence of ionic multilayers at the free surface of an ionic liquid, trioctylmethylammonium bis(nonafluorobutanesulfonyl)amide ([TOMA(+)][C(4)C(4)N(-)]), extending into the bulk from the surface to the depth of approximately 60 A has been probed by x-ray reflectivity measurements. The reflectivity versus momentum transfer (Q) plot shows a broad peak at Q approximately 0.4 A(-1), implying the presence of ionic layers at the [TOMA(+)][C(4)C(4)N(-)] surface. The analysis using model fittings r

The facilitated transfer of alkali metal cations (Li+, Na+, K+, Rb+, Cs+) by dibenzo-18-crown-6 (DB18C6) across the electrochemically polarizable interface between an aqueous solution (W) and a hydrophobic ionic liquid, N-octadecylisoquinolinium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate ([C18Iq][TFPB]), has been studied using cyclic voltammetry at the interface formed at the tip of a micropipet. In cyclic voltammograms (CVs), the current due to the facilitated transfer of the cations by DB1

Fluorine-free and hydrophobic room-temperature ionic liquids (RTILs) composed of the bis(2-ethylhexyl)sulfosuccinate (BEHSS) ion, which is known as the surface-active anion constituting Aerosol OT®, and symmetric tetraalkylammonium ions ((CnH2n+1)4N+; n = 4–8), have been prepared. Physicochemical properties of the water-saturated RTILs such as density, conductivity, viscosity and mutual solubility with water (W) have been measured. The RTIL|W interface is polarizable for the RTILs with n = 5–8 i

The effect of the temperature on the surface layering of ionic liquids has been studied for two ionic liquids, trioctylmethylammonium bis(nonafluorobutanesulfonyl)amide([TOMA(+)][C(4)C(4)N(-)]) and trihexyltetradecylphosphonium bis(nonafluorobutanesulfonyl)amide ([THTDP(+)][C(4)C(4)N(-)]), using X-ray reflectivity measurements at 285, 300, and 315 K. Both [TOMA(+)][C(4)C(4)N(-)] and [THTDP(+)][C(4)C(4)N(-)] develop multilayers at the surface. The structure of the multilayers at the [TOMA(+)][C(4

The interfacial structure at the quaternary ammonium-based ionic liquids(ILs)|gold(Au) electrode interface has been studied using surface-enhanced infrared absorption spectroscopy (SEIRAS). Four anions, bis(perfluoroalkanesulfonyl)amide (CₙCₙN⁻; n = 0, 1, 2, 4), have been combined with a quaternary ammonium cation, trioctylmethylammonium (N₈₈₈₁⁺), to investigate the influence of the perfluoroalkyl chain length of the anion on the behavior of the quaternary ammonium cation at the interface. In ad

The transfer of Rose Bengal dianion (RB2-), a fluorescent ion with asymmetric charge distribution, across the 1,2-dichloroethane (DCE)|water (W) interface, has been studied using ac-modulated voltfluorometry, a method that combines ac voltammetry with fluorometry. The phase angle of the ac component of the fluorescence shifts to a value that cannot be explained by the theory based on the simple combination of the heterogeneous ion transfer and mass transfer. This anomaly strongly suggests that R

Neutron reflectometry (NR) has been performed at the electrochemical interface between a Nb film and an ionic liquid, trihexyltetradecylphosphonium tetrakis(pentafluorophenyl)borate ([THTDP+][PFPB–]). THTDP+ and PFPB– have large sizes and a large difference in the scattering length density, both of which are suitable to sensitively probe the potential-dependent structure of the electric double layer (EDL) at the electrode interface of ionic liquids using NR. The neutron reflectivity profiles as

Gold nanofibers have been found to be formed via a heterogeneous electron-transfer reaction at the ionic liquid|water interface. The tips of the nanofibers show a dendritic structure and the dendrites are bundled to nanofibers except around the tips. The roles of the ionic liquid for the dendritic nanofiber formation have been discussed.