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1.
The electrochemical oxidation of dissolved hydrogen gas has been studied in a range of room-temperature ionic liquids (RTILs), namely [C(2)mim][NTf(2)], [C(4)mim][NTf(2)], [N(6,2,2,2)][NTf(2)], [P(14,6,6,6)][NTf(2)], [C(4)mpyrr][NTf(2)], [C(4)mim][BF(4)], [C(4)mim][PF(6)], [C(4)mim][OTf], and [C(6)mim]Cl on a platinum microdisk electrode of diameter 10 microm. In all cases, except [C(6)mim]Cl, a broad quasi-electrochemically reversible oxidation peak between 0.3 to 1.3 V vs Ag was seen prior to electrode activation ([C(6)mim]Cl showed an almost irreversible wave). When the electrode was pre-anodized ("activated") at 2.0 V vs Ag for 1 min, the peak separations became smaller, and the peak shape became more electrochemically reversible. It is thought that the electrogenerated protons chemically combine with the anions (A-) of the RTIL. The appearance and position of the reverse (reduction) peak on the voltammograms is thought to depend on three factors: (1) the stability of the protonated anion, HA, (2) the position of equilibrium of the protonation reaction HA<==> H+ + A- , and (3) any follow-up chemistry, e.g., dissociation or reaction of the protonated anion, HA. This is discussed for the five different anions studied. The reduction of HNTf(2) was also studied in two [NTf(2)]- -based RTILs and was compared to the oxidation waves from hydrogen. The results have implications for the defining of pKa in RTIL media, for the development of suitable reference electrodes for use in RTILs, and in the possible amperometric sensing of H2 gas.  相似文献   

2.
This study focuses on the solubility behaviors of CO2, CH4, and N2 gases in binary mixtures of imidazolium-based room-temperature ionic liquids (RTILs) using 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][Tf2N]) and 1-ethyl-3-methylimidazolium tetrafluoroborate ([C2mim][BF4]) at 40 degrees C and low pressures (approximately 1 atm). The mixtures tested were 0, 25, 50, 75, 90, 95, and 100 mol % [C2mim][BF4] in [C2mim][Tf2N]. Results show that regular solution theory (RST) can be used to describe the gas solubility and selectivity behaviors in RTIL mixtures using an average mixture solubility parameter or an average measured mixture molar volume. Interestingly, the solubility selectivity, defined as the ratio of gas mole fractions in the RTIL mixture, of CO2 with N2 or CH4 in pure [C2mim][BF4] can be enhanced by adding 5 mol % [C2mim][Tf2N].  相似文献   

3.
The direct electrochemistry of a HRP-chi-[C(4)mim][BF(4)] film (where HRP = horseradish peroxidase, chi = chitosan, and [C(4)mim][BF(4)] = the room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium tetrafluoroborate) has been studied by cyclic voltammetry on a glassy carbon electrode. The mechanism for the electrochemical reaction of HRP is suggested to be EC for the reduction, and CE for the following re-oxidation, as the oxidative peak potential remained approximately unchanged across the scan rate range. The half wave potential of HRP reduction was found to be pH dependent, suggesting that a concomitant proton and electron transfer is occurring. Using theoretical simulations of the experimentally obtained peak positions, the standard electron transfer rate constant, k(0), was found to be 98 (+/-16) s(-1) at 295 K in pH 7 phosphate buffer solution, which is very close to the value reported in the absence of ionic liquid. This suggests that the ionic liquid used here in the HRP-chi-[C(4)mim][BF(4)]/GC electrode does not enhance the rate of electron transfer. k(0) was found to increase systematically with increasing temperature and followed a linear Arrhenius relation, giving an activation energy of 14.20 kJ mol(-1). The electrode kinetics and activation energies obtained are identical to those reported for HRP films in aqueous media. This leads us to question if the use of RTIL films provide any unique benefits for enzyme/protein voltammetry. Rather the films may likely contain aqueous zones in which the enzymes are located and undergo electron transfer.  相似文献   

4.
Light scattering and dielectric spectroscopy measurements were performed on the room temperature ionic liquid (RTIL) [C4mim][NTf2] in a broad temperature and frequency range. Ionic conductivity was used to estimate self-diffusion of ions, while light scattering was used to study structural relaxation. We demonstrate that the ionic diffusion decouples from the structural relaxation process as the temperature of the sample decreases toward T(g). The strength of the decoupling appears to be significantly lower than that expected for a supercooled liquid of similar fragility. The structural relaxation process in the RTIL follows well the high-temperature mode coupling theory (MCT) scenario. Using the MCT analysis we estimated the dynamic crossover temperature in [C4mim][NTf2] to be T(c) ~ 225 ± 5 K. However, our analysis reveals no sign of the dynamic crossover in the ionic diffusion process.  相似文献   

5.
Proven electrochemical approaches were applied to study heterogeneous electron transfer (ET) between selected redox couples and gold electrodes modified with alkanethiol self-assembled monolayers (SAMs), using the room-temperature ionic liquid (RTIL) [bmim][NTf2] as reaction medium; ferrocene as freely diffusing redox probe in the RTIL was tested for ET through both thin (butanethiol) and thick (dodecanethiol) assemblages at pressures up to 150 MPa; well behaved kinetic patterns and reproducibility of data were demonstrated for ET within the unique Au/SAM/RTIL arrays.  相似文献   

6.
Marked solubility differences of nicotine in the ionic liquids [C(2)mim][NTf(2)], [C(2)mim][EtOSO(3)], and [C(n)mim]Cl, 6 相似文献   

7.
This article reports a study of the effect of anions on the optical Kerr effect (OKE) spectra of binary ionic liquid mixtures with one mixture comprising the 3-methyl-1-pentylimidazolium ([C 5mim] (+)) cation and the anions PF 6 (-) and CF 3CO 2 (-) (TFA (-)), and another mixture comprising the [C 5mim] (+) cation and the anions Br (-) and bis(trifluomethanesulfonyl)imide (NTf 2 (-)). The spectra were obtained by the use of optical heterodyne-detected Raman-induced Kerr Effect Spectroscopy at 295 K. The OKE spectra of the mixtures are compared with the calculated mole-fraction weighted sum of the normalized OKE spectra of the neat liquids. The OKE spectra are nearly additive for [C 5mim]Br/[C 5mim][NTf 2] mixtures, but nonadditive for [C 5mim][PF 6]/[C 5mim][TFA] mixtures. In the case of the equimolar [C 5mim][PF 6]/[C 5mim][TFA] mixture, the nonadditivity is such that the experimental OKE spectrum is narrower than the calculated OKE spectrum. The additivity or nonadditivity of OKE spectra for IL mixtures can be explained by assuming ionic liquids are nanostructurally organized into nonpolar regions and ionic networks. The ionic networks in mixtures will be characterized by "random co-networks" for anions that are nearly the same in size (PF 6 (-) and TFA (-)) and by "block co-networks" for anions that differ greatly in size (Br (-) and NTf 2 (-)).  相似文献   

8.
咪唑基离子液体的物理化学性质估算及预测(英文)   总被引:1,自引:0,他引:1  
根据经验和半经验方程及空隙模型理论,可以估算及预测离子液体在298.15K的物理化学性质.本文讨论了离子液体的分子体积,密度,标准熵,晶格能,表面张力,等张比容,摩尔蒸发焓,空隙体积,空隙率和热膨胀系数.通过实验测得的三种离子液体1-乙基-3-甲基咪唑硫酸乙酯([C2mim][EtSO4)]),1-丁基-3-甲基咪唑硫酸辛酯([C4mim][OcSO4])和1-乙基-3-甲基咪唑双三氟甲磺酰亚胺盐([C2mim][NTf2])的密度和表面张力估算了它们的其它物理化学性质.由这三种离子液体的分子体积及等张比容预测了同系列中其它离子液体[Cnmim][EtSO4],[Cnmim][OcSO4]和[Cnmim][NTf2](n=1-6)的分子体积及等张比容,由此计算出它们的密度及表面张力.进而预测了它们的物理化学性质.将预测的离子液体[C4mim][NTf2]和[C2mim][OcSO4]的密度值与文献报导的实验值进行比较,其偏差在实验误差范围内.最后,将由Kabo经验方程计算的七个离子液体[C2mim][EtSO4]、[C4mim][OcSO4]、[C2mim][NTf2]、[C4mim][NTf2]、丁基三甲基铵双三氟甲磺酰亚胺盐([N4111][NTf2])、甲基三辛基铵双三氟甲磺酰亚胺盐([N8881][NTf2])和1-辛基-3-甲基吡啶四氟硼酸盐([m3opy][BF4])的摩尔蒸发焓与由Verevkin简单规则预测的摩尔蒸发焓进行比较,发现两者符合很好.因此,在缺乏密度和表面张力实验数据的情况下,可以用Verevkin简单规则来预测离子液体的摩尔蒸发焓.  相似文献   

9.
The dispersion of silica nanoparticles made an ionic liquid, 1-ethyl-3-methyl imidazolium bis(trifluoromethanesulfonyl)amide ([C(2)mim][NTf(2)]), gelled even by the addition of 2-3 wt %, due to the formation of interconnected particulate silica networks in [C(2)mim][NTf(2)]. The ionic transport and viscoelastic properties of these nanocomposite ion gels were investigated in relation to the microstructure. Despite their solid-like behavior, the nanocomposite ion gels exhibited a high ionic conductivity of approximately 10(-2) S cm(-1) at 30 degrees C, which is comparable to that of neat [C(2)mim][NTf(2)]. Intriguing viscoelastic responses, such as shear-thinning and shear-induced sol-gel transitions, were found in all of the nanocomposite ion gels. By adjusting the silica concentration, the elastic modulus ( G') could be precisely controlled in a range of more than 3 orders of magnitude and reached approximately 10(6) Pa without a considerable decrease in the ionic conductivity; the characteristic viscoelastic response was also maintained. For the aggregation mechanism in [C 2 mim][NTf(2)], the reaction-limited cluster aggregation (RLCA) model was proposed by rheology and light scattering measurements.  相似文献   

10.
The solvent and rotational relaxation of Coumarin 153 (C-153) was investigated by picosecond time-resolved fluorescence spectroscopy in a room temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium octyl sulfate ([C4mim][C8SO4]). This is a typical RTIL, which form micellar structure above certain concentration of the RTIL (0.031 M). Dynamic light scattering (DLS) measurements show that the average hydrodynamic diameter ( Dh) of a [C4mim][C8SO4]-water micelle is 2.8 (+/-0.2) nm. Both the solvent and rotational relaxation of C-153 are retarded in this micelle compared to the solvation time of a similar type of dye in neat water. However, the solvent relaxation in this ionic liquid surfactant is different from that of a conventional ionic surfactant. The slow component of the solvation dynamics in C8H17SO4Na or TX-100 micelle is on the nanoseconds time scale, whereas in [C4mim][C8SO4] micelle the same component is on the subnanoseconds time scale. The different molecular motions with different time scale is the main reason behind this difference in the solvation time in micelles composed of RTIL with other conventional micelles.  相似文献   

11.
The kinetics and mechanism of the proton reduction reaction in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(2)mim][NTf(2)]) was studied at gold, molybdenum, nickel, titanium and platinum electrodes. Significant differences in electrochemical rate constants were observed between the different metals and with the corresponding processes in aqueous solution. The hydrogen evolution mechanism was consistent at all five metals in the ionic liquid, in stark contrast to the known behaviour in aqueous systems.  相似文献   

12.
The influence of the alkyl-substituent chain in 1-alkyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide ionic liquids ([C(n)mim][NTf(2)], where n is the length of a linear alkyl chain) as solvents for the separation of benzene and hexane by liquid extraction was investigated. The liquid-liquid equilibrium (LLE) at 25 degrees C for the ternary systems ([C(n)mim][NTf(2)] + hexane + benzene), with n taking the values 4, 8, 10, and 12, were determined. These data were analyzed and compared to those previously reported for the system ([C(2)mim][NTf(2)] + hexane + benzene). The results show that short alkyl chains on the imidazolium cation of the ionic liquid lead to a better extractive separation of benzene and hexane, and reveal the influence of the relative degree of ordering in the ionic liquids on the extraction parameters.  相似文献   

13.
Poly(benzyl methacrylate) (PBzMA) and its copolymers exhibit lower critical solution temperature (LCST)-type phase separation in common hydrophobic ionic liquids (ILs) such as 1-ethyl-3-methylimidazolium bis(trifluoromethane sulfone)imide ([C(2)mim][NTf2]). The turbidity measurements for PBzMA/IL mixed systems reveal that the LCST-type phase separation temperatures change significantly with the changes in the chemical structures of polymers and ILs. Moreover, cross-linked PBzMA gels show reversible and discontinuous volume phase transition in [C(2)mim][NTf2] with the changes in temperature.  相似文献   

14.
The unique physical and chemical properties of room-temperature ionic liquids(RTILs) have recently received increasing attention as solvent alternatives for possible application in the field of nuclear industry, particularly in liquid-liquid separations of radioactive nuclides. We investigated solvent extraction of U(VI) from aqueous solutions into a commonly used ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([C4mim][NTf2]) using trioctylphosphine oxide(TOPO) as an extractant. The effects of contact time, TOPO concentration, acidity, and nitrate ions on the U(VI) extraction are discussed in detail. The extraction mechanism was proposed based on slope analysis and UV-Vis measurement. The results clearly show that TOPO/[C4mim][NTf2] provides a highly efficient extraction of U(VI) from aqueous solution under near-neutral conditions. When the TOPO concentration was 10 mmol/L, the extraction of 1 mmol/L U(VI) was almost complete( 97%). Both the extraction efficiency and distribution coefficient were much larger than in conventional organic solvents such as dichloromethane. Slope analysis confirmed that three TOPO molecules in [C4mim][NTf2] bound with one U(VI) ion and one nitrate ion was also involved in the complexation and formed the final extracted species of [UO2(NO3)(TOPO)3]+. Such a complex suggests that extraction occurs by a cation-exchange mode, which was subsequently evidenced by the fact that the concentration of C4mim+ in the aqueous phase increased linearly with the extraction percent of U(VI) recorded by UV-Vis measurement.  相似文献   

15.
The intermolecular spectra of three imidazolium ionic liquids were studied as a function of temperature by the use of optical heterodyne-detected Raman-induced Kerr effect spectroscopy. The ionic liquids comprise the 1,3-pentylmethylimidazolium cation ([C(5)mim]+), and the anions, bromide (Br-), hexafluorophosphate (PF(6)-), and bis(trifluoromethanesulfonyl)imide (NTf(2)-). Whereas the optical Kerr effect (OKE) spectrum of [C(5)mim][NTf(2)] is temperature-dependent, the OKE spectra of [C(5)mim]Br and [C(5)mim][PF6] are temperature-independent. These results are surprising in light of the fact that the bulk densities of these room temperature ionic liquids (RTILs) are temperature-dependent. The temperature independence of the OKE spectra and the temperature dependence of the bulk density in [C(5)mim]Br and [C(5)mim][PF(6)] suggest that there are inhomogeneities in the densities of these liquids. The existence of density inhomogeneities is consistent with recent molecular dynamics simulations that show RTILs to be nanostructurally organized with nonpolar regions arising from clustering of the alkyl chains and ionic networks arising from charge ordering of the anions and imidazolium rings of the cations. Differences in the temperature dependences of the OKE spectra are rationalized on the basis of the degree of charge ordering in the polar regions of the RTILs.  相似文献   

16.
The radiation effect on a hydrophobic room-temperature ionic liquid (RTIL), 1-butyl-3-methyl-imidazolium bis[(trifluoromethyl)sulfonyl]imide ([C4mim][NTf2]), was studied by γ-irradiation under nitrogen atmosphere. Accompanied by color darkening and increase of light absorbance in a wide wavelength range, a distinct absorption peak at around 290 nm for irradiated [C4mim][NTf2] appeared when acetonitrile was used as solvent, and the intensity of the peak enhanced with increasing dose. The spectrophotometric study on the irradiated RTILs containing 1,3-dialkylimidazolium cations associated with different inorganic anions revealed that the peak is ascribed to the radiolysis products of the [C4mim]+. And the wavelength of the peak was affected by alkyl chain length on imidazolium cation, while the intensity of the peak was influenced by anions. With incorporating a little amounts of oxidants, such as KMnO4 and HNO3 into irradiated [C4mim][NTf2], the intensity of the peak at 290 nm decreased obviously and the decoloration of [C4mim][NTf2] occurred, suggesting that the peak at 290 nm is assigned to the colored species and the species can be oxidized.  相似文献   

17.
New experimental results are presented for the solubility of carbon dioxide, hydrogen sulfide in the ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate ([C8mim][PF6]) at temperatures range from (303.15 to 353.15) K and pressures up to about 2 MPa. The solubility of the mixture of CO2/H2S in [C8mim][PF6] under various feed compositions were also measured at temperatures of (303.15, 323.15 and 343.15) K and the pressure up to 1 MPa. The solubility of carbon dioxide and hydrogen sulfide increased with increasing pressure and decreased with increasing temperature and the solubility of H2S is about three times that of CO2 in the particular ionic liquid studied. The measured data were correlated using extended Henry’s law included Pitzer’s virial expansion for the excess Gibbs energy, and the generic Redlich–Kwong cubic equation of state proposed for gas/ionic liquid systems. The correlations from the two models show quite good consistency with the experimental data for CO2/IL and H2S/IL binary mixtures within experimental uncertainties. For CO2/H2S/IL ternary mixtures, the RK model shows better correlation with the experimental values. We also studied the effect of cation alkyl chain length on the CO2 and H2S solubility by comparison of the experimental data of this study with those of previous reports. As the cation alkyl chain length became longer, the solubility of CO2 and H2S increased in the ionic liquid. Additionally, the influence of the anion on the solubility is studied by comparing the solubility of CO2 and H2S in [C8mim][PF6] with those in [C8mim][Tf2N]. As a result, CO2 and H2S have higher solubility in the IL with [Tf2N] as the anion.  相似文献   

18.
Lignin is potentially a major renewable, nonfossil source of aromatic and cyclohexyl compounds. In this study, we have investigated the abrasive stripping voltammetry of lignin and four lignin model compounds in the room temperature ionic liquids (RTILs) [C4mim][NTf2], [N6,2,2,2][NTf2] and [C4mim][OTf] (where [C4mim]+=1‐butyl‐3‐methylimidazolium, [N6,2,2,2]+=n‐hexyltriethylammonium, [NTf2]?=bis(trifluoromethanesulfonyl)imide and [OTf]? =trifluoromethanesulfonate) on a gold macrodisk and in 0.1 M H2SO4 and 0.1 M NaOH on a boron‐doped diamond (BDD) macroelectrode, with the hope of using the voltammetry to fingerprint the functional groups within the lignin molecule. The use of RTILs on metal electrodes, or either acidic or basic media in combination with BDD electrodes allows solvent systems with wide electrochemical potential windows, useful for studying voltammetry which may be difficult to observe in systems where early breakdown of the solvent occurs.  相似文献   

19.
The electrochemistry of water dissolved in 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]) was studied by cyclic voltammetry and electrochemical impedance spectroscopy using a nickel electrode. Hydrogen peroxide is being produced by direct electrolysis of water in a cooperative process between the nickel electrode and [C4mim][BF4]. There is linear response between the concentration of water and the oxidation peak current at 1.60 V. Impedance decreases significantly with increasing concentration of water. The findings resulted in two promising applications: The first is the production of hydrogen peroxide, and the second is in water sensing. Both methods are environmentally friendly and convenient.  相似文献   

20.
The colloidal stability of bare and poly(methyl methacrylate) (PMMA)-grafted silica nanoparticles was studied in 1-alkyl-3-methylimidazolium ([C(n)mim])-based ionic liquids (ILs) with different anionic structures. The theoretical estimation of the colloidal interaction between monodispersed bare silica particles by using the Derjaguin-Landau-Verwey-Overbeek theory indicates that bare silica particles cannot be stabilized and they rapidly form aggregates in all the ILs used in this study. The instability of bare silica particles was experimentally confirmed by dynamic light scattering measurement and in situ transmission electron microscopy observations by utilizing the negligible vapor pressure of ILs. This evidence suggests that electrostatic stabilization is inefficient in ILs because of the high ionic atmosphere and the resulting surface-charge screening. The PMMA-grafted silica particles exhibited long-term colloidal stability in [C(4)mim][PF(6)] and [C(n)mim][NTf(2)], which are compatible with the grafted PMMA. On the other hand, the PMMA-grafted particles could not be stabilized in [C 4mim][BF 4] due to the poor solubility of the grafted PMMA in the IL. Effective steric stabilization is important for obtaining stable colloidal particles in ILs.  相似文献   

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