Preparation of nickel, nickel-iron, and silver-copper nanoparticles in ionic liquids

Room-temperature ionic liquids (RTILs), i.e. organic molten salts with melting points below 100 ◦C, have been intensively developed for electrolytic media in various electrochemical systems due to the fact that RTILs have unique physicochemical properties such as favorable solubility of organic and inorganic compounds, relatively high ionic conductivity, no measurable vapor pressure, high thermal stability, low flammability, etc. Particularly, RTILs have been regarded as potential electrolytic media for electropolymerization processes.1 Many kinds of RTILs have been investigated for the electropolymerizations; however, highly conductive and stable RTILs based on quaternary phosphonium cations2 have been rarely employed for this application. In this work, we report the electrooxidative polymerization of aniline in triethylpentylphosphonium bis(trifluoromethylsulfonly)amide (P2225-TFSA) and tributylmethylphosphonium bis(trifluoromethylsulfonly)amide (P4441-TFSA) in comparison with the other type of RTILs, characterizing the obtained polyaniline films. The preparation of the phosphonium RTILs was performed by aqueous ion exchange reaction of the precursor quaternary phosphonium halides with lithium TFSA. The electrooxidative polymerization of aniline in phosphonium RTILs containing 0.1 M H-TFSA was carried out by cyclic voltammetry (CV) method using a three-electrode cell equipped with a Pt disk working electrode. The electrochemical activity of the polyaniline films were evaluated by extended CV scanning technique.Figure 1 shows typical cyclic voltammograms for the electrooxidative pocesses of aniline. As shown in Fig. 1, it was found that relatively large voltammetric response was observed in P2225-TFSA when compared to that in P4441-TFSA. This seems to be attributed to the relatively low viscosity and high conductivity of P2225-TFSA. In addition, the voltammetric responses were enhanced by cycling, which indicates that ionic species could be efficiently doped into the polyaniline film. The surface morphology based on SEM images of the polyaniline films will be also discussed.References 1 K. Sekiguchi, et al, J. Electroanal. Chem. , 557, 1 (2003).2 K. Tsunashima, et al, Electrochem. Commun., 9, 2353 (2007). Figure 1

Efficient removal of phenolic compounds from model oil using benzyl Imidazolium-based ionic liquids

Tribological characteristics of two imidazolium-based room temperature ionic liquids (RTILs), 1-hexyl-3-methylimidazolium tetrafluoroborate, and 1-hexyl-3-methylimidazolium hexafluorophosphate were investigated under high vacuum conditions. Viscosity–temperature characteristics and thermogravimetric characteristics of these compounds were also investigated. Imidazolium-based RTILs have relatively good viscosity–temperature characteristics that are comparable to those of multiply-alkylated cyclopentane (MAC). Thermogravimetric results showed that ionic liquids have high thermal stability and low vapor pressure. Ionic liquids showed low friction and low wear rate under high vacuum conditions, and high load-carrying capacity was observed.

The nanoscale interactions of room temperature ionic liquids (RTILs) at uncharged (graphene) and charged (muscovite mica) solid surfaces were evaluated with high resolution X-ray interface scattering and fully atomistic molecular dynamics simulations. At uncharged graphene surfaces, the imidazolium-based RTIL ([bmim(+)][Tf(2)N(-)]) exhibits a mixed cation/anion layering with a strong interfacial densification of the first RTIL layer. The first layer density observed via experiment is larger than that predicted by simulation and the apparent discrepancy can be understood with the inclusion of, dominantly, image charge and π-stacking interactions between the RTIL and the graphene sheet. In contrast, the RTIL structure adjacent to the charged mica surface exhibits an alternating cation-anion layering extending 3.5 nm into the bulk fluid. The associated charge density profile demonstrates a pronounced charge overscreening (i.e., excess first-layer counterions with respect to the adjacent surface charge), highlighting the critical role of charge-induced nanoscale correlations of the RTIL. These observations confirm key aspects of a predicted electric double layer structure from an analytical Landau-Ginzburg-type continuum theory incorporating ion correlation effects, and provide a new baseline for understanding the fundamental nanoscale response of RTILs at charged interfaces.

Introduction Transparent and electrically conductive metal oxide nanoparticles (NPs) prepared by solution phase synthetic methods have attracted much attention due to their applicability to wet processing, such as ink-jet printing or spin coating, for fabrication of densely packed particulate films, which can be used to improve the performance of solar cells, transparent electrode, and sensors. Among various kinds of metal oxide particles, indium tin oxide (ITO) NPs are useful nanomaterials because of their high electronic conductivity, chemical stability, or unique optical properties induced by their surface plasmon resonance (LSPR) in the near-infrared region. So far, well-dispersed ITO NPs have been prepared by sol-gel technique or solvothermal method, though these conventional techniques required well-trained skills for obtaining particles with well-controlled size and shape. Recently a facile preparation method of colloidal metal particles in organic solvent has been reported with use of low-melting-point metals such as gallium, indium, and tin,[1] in which molten metals were mechanically dispersed in organic solvent containing surfactant molecules by ultrasonication and/or magnetic stirring, resulting in the formation of metal nanoparticles. On the other hand, room temperature ionic liquids (RTILs) with extremely low vapor pressure and thermal stability have been reported to be a useful medium for the preparation and stabilization of noble metal NPs. For example we have reported that the sputter deposition of noble metals such as Au, Ag, or Pt into RTILs produced corresponding ultrafine metal nanoparticles uniformly dispersed in the solution.[2]RTILs are also expected to act as a good medium not only for the preparation of low-melting-point metal NPs by mechanically dispersing but also for the oxidation of resulting metal particles with heat treatment due to high thermal stability of RTILs. However such attempt has not been carried out. In this study, we report a facile preparation of uniformly dispersed ITO NPs via direct oxidation of In-Sn alloy as a precursor in RTILs. Experimental Indium (0.5 g) was added in RTILs (2.0 cm3) of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF4), 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate (HyEMI-BF4), 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)amide (HyEMI-TFSA), N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)amide (TMPA-TFSA), or 2-hydroxyethyl-N,N,N-trimethylammonium bis(trifluoromethanesulfonyl)amide (Ch-TFSA). The mixture was heated at 523 K for 10 h in air with vigorous stirring. Thus-obtained NPs dispersed in the solution were collected by a centrifugation and re-dispersed in acetonitrile for characterization. ITO NPs with different Sn content were prepared in the same method except for the use of an In-Sn alloy (Sn content; 3, 5, 10, 20, 30 wt%) as a precursor in the Ch-TFSA. Results and discussions The particles prepared by the oxidation of pure In metal as a precursor in RTILs of EMI-BF4, HyEMI-TFSA, TMPA-TFSA and Ch-TFSA, exhibited broad diffraction peaks in XRD pattern assignable to cubic In2O3. In contrast, the XRD pattern of particles prepared in HyEMI-BF4 was assignable to orthorhombic InOF. These results indicated that In metal was oxidized with oxygen molecule dissolved in TFSA-based RTILs to produce In2O3 or reacted with fluoride ion produced by the decomposition of BF4 - anion in HyEMI-BF during heat treatment, resulting in the formation of InOF. TEM observation revealed that uniformly dispersed spherical particles with average diameter of 27 and 39 nm were observed in hydroxyl-functionalized RTILs of HyEMI-TFSA and Ch-TFSA, respectively, while largely aggregated In2O3 particles appeared in EMI-BF4 and TMPA-TFSA. These indicated that hydroxyl group in cationic species of RTILs played an important role in the prevention of In2O3NPs in RTILs. To prepare ITO NPs, we carried out the similar preparation protocol, in which In-Sn alloy containing different Sn content (3-30 wt%) were oxidized in Ch-TFSA with vigorous stirring. Thus-obtained particles exhibited the XRD pattern assignable to ITO crystal structure. Figure 1 shows a TEM image of ITO NPs prepared with alloy containing 30 wt% Sn. Polygonal particles with average diameter ca. 40 nm were observed. With an increase in the Sn content from 3 to 30 wt% in alloy as a precursor, the amount of Sn doping in ITO NPs was enlarged from 0.67 to 10 wt%. ITO NPs exhibited a LSPR peak in the near-IR wavelength region in the extinction spectra, the peak wavelength being blue-shifted from 2860 to 2400 nm with an increase in the amount of Sn doping in NPs from 0.67 to 10 wt%.

Transport properties of imidazolium-based room temperature ionic liquids in confinement of slit charged carbon nanopores: New insights from molecular simulations

Recent studies show that Ionic Liquids (ILs) have the ability to improve oil recovery. In this experimental study, an imidazolium-based Room-Temperature Ionic Liquid (RTIL), 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]), was used to extract heavy oil (14 °API) from unconsolidated packed sand samples. The RTIL was injected as slug, with different concentrations and sizes. The [EMIM][OAc] results were compared with the efficiency of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Tf2N]) and 1-dodecyl-3-methylimidazolium chloride ([DMIM][Cl]) ILs. The results indicate that the efficiency of IL depends mainly on the type of IL. A comparison with a well-known commercial surfactant (Sodium Dodecyl Sulfate, SDS) was performed, and the results confirmed the higher efficiency of the ionic liquids. Changes in Interfacial Tension (IFT), Surface Tension (SFT), and Zeta Potential (ZP) in the solution supported the recovery factor results. Finding the optimum concentration and slug size are significant factors in making the oil extraction process more economical.

We extend our previous molecular dynamics analysis of confined aqueous electrolytes within cylindrical hydrophobic pores of nanometric dimensions [Videla et al. J. Chem. Phys.2011, 135, 104503] to the case of room temperature ionic liquid (RTIL) solutions, with concentrations close to c ∼ 1 M. Equilibrium and dynamical characteristics of two imidazolium-based RTILs, differing in the hydrophobicity of the corresponding anionic species, were considered. The solutions within the pore were modeled in contact with “bulk-like” reservoirs, which served as reference systems to gauge the magnitude of the modifications observed in the global densities and in the transport coefficients. The density fields associated to the ionic species present a marked enhancement near the pore walls; this leads to increments of the global RTIL concentration within the pores, which are intermediate between 2 and 3 times the ones observed in the bulk reservoirs. These modifications are more marked in solutions containing more hydrophobic anionic species. In both cases, selective adsorption of imidazolium groups at the pore walls prevails; these wall-solvation states are characterized by a parallel orientation of the imidazolium ring, with respect to the pore surface. Mass and charge transport were also investigated. The segregation of the ionic species towards the pore wall promotes a sharp drop in the individual ionic diffusion coefficients. Nonuniform trends in the modifications of the ionic conductivity were found. Our results show that charge transport is the result of a complex interplay between competing effects involving modifications in the local concentrations, retardations in the ionic mobility, and dynamical cross-correlations, as well. A physical interpretation of the latter effects is provided in terms of the differences in the spatial correlations of the ionic species within the interior of the pore.

Metal organic framework-ionic liquid hybrid catalysts for the selective electrochemical reduction of CO2 to CH4

Raman spectroscopy study of water confinement in ionic liquid 1-butyl-3-methylimidzolium nitrate

The scientific interest in room-temperature ionic liquids (RTILs) became extraordinarily high over the last two decades. While in the earlier days most of the studies focused on the synthesis and chemical properties, recently the interest in there physical, dynamical and structural properties is increasing. This thesis is aiming at the dynamical properties using dielectric relaxation spectroscopy. The first part of the thesis presents the development of new experimental routes and mathematical routines to record the dielectric spectra of liquids at microwave to far-infrared frequencies. It is followed by the discussion of the dielectric spectra of the neat, mainly imidazolium-based RTILs. Beside the extraction of the static dielectric constants, detailed information on the dynamics is obtained, including activation parameters. At room-temperature, the spectra are extended to terahertz and far-infrared frequencies, to cover the whole frequencies range relevant for intermolecular dynamics. Additional insight is gained by comparing these broadband spectra to molecular-dynamics simulations as well as to optical Kerr effect spectra. Finally, binary mixtures of RTILs with polar solvents are investigated. The studies on mixtures with dichloromethane are indicating an expanded RTIL-like range, where the dielectric characteristics remain similar to the neat RTIL. Only at high dilutions, the mixtures behave rather like a conventional electrolyte solution with pronounced formation of contact ion-pairs. On the other hand the mixtures with water indicate a more complex, heterogeneous structure.

We use Monte Carlo simulations of a coarse-grained model to investigate structure and electrochemical behaviours at an electrode immersed in room temperature ionic liquids (RTILs). The simple RTIL model, which we denote the asymmetric restricted primitive model (ARPM), is composed of monovalent hard-sphere ions, all of the same size, in which the charge is asymmetrically placed. Not only the hard-sphere size (d), but also the charge displacement (b), is identical for all species, i.e. the monovalent RTIL ions are fully described by only two parameters (d, b). In earlier work, it was demonstrated that the ARPM can capture typical static RTIL properties in bulk solutions with remarkable accuracy. Here, we investigate its behaviour at an electrode surface. The electrode is assumed to be a perfect conductor and image charge methods are utilized to handle polarization effects. We find that the ARPM of the ionic liquid reproduces typical (static) electrochemical properties of RTILs. Our model predicts a declining differential capacitance with increasing temperature, which is expected from simple physical arguments. We also compare our ARPM, with the corresponding RPM description, at an elevated temperature (1000 K). We conclude that, even though ion pairing occurs in the ARPM system, reducing the concentration of ‘free’ ions, it is still better able to screen charge than a corresponding RPM melt. Finally, we evaluate the option to coarse-grain the model even further, by treating the fraction of the ions that form ion pairs implicitly, only through the contribution to the dielectric constant of the corresponding dipolar (ion pair) fluid. We conclude that this primitive representation of ion pairing is not able to reproduce the structures and differential capacitances of the system with explicit ion pairs. The main problem seems to be due to a limited dielectric screening in a layer near the electrode surface, resulting from a combination of orientational restrictions and a depleted dipole density.

The aqueous solution of a kind of room-temperature ionic liquids (RTILs), 1-ethyl-3-methylimidazolium-tetrafluoroborate (1E-3MI-TFB), demonstrated its exclusive electroosmotic property in microchip electrophoresis. It was applied as the working electrolyte for chiral separation in glass microchip electrophoresis. Compared with boric acid buffer, 1E-3MI-TFB aqueous solution exhibited a broader separation window for enantiomers of dipeptides. Then the influences of chiral selector, pH and concentration on efficiency of chiral separation were discussed in detail. The unique mechanism of the generation of EOF was explored in a glass microchannel using 1E-3MI-TFB aqueous solution as working electrolyte. A possible status of 1E-3MI cation in water was suggested at the first time, which facilitated the explanation of EOF and its characteristics in glass microchannel. Additionally, microchip electrophoresis using 1E-3MI-TFB aqueous solution was successfully applied to the chiral separation of complex enantiomers of dipeptides. RTILs aqueous solution, as the electrolyte for the separation of complicated optical isomers, could lead to a revolution in the analytical methods of chiral or conformational analysis for biomolecules.

The efficiency of charge transfer in electrochemical devices is largely determined by the ion concentration profile near the electrode surface, i.e., the electrical double layer (EDL). Room temperature ionic liquids (RTILs) are attractive for electrochemical applications due to their high charge density as well as for their tunable anion/cation design, low vapor pressure, and wide electrochemical window. The EDL structure in RTILs is profoundly different from that in traditional (dilute) electrolytes in that opposite charges tend to layer in a spatially alternating, segregated structure that decays toward the bulk region. Such charge layering becomes crucial for applications that require confinement of RTILs into narrow spaces, where RTILs are interfaced with nanostructured electrodes. Layering in the EDL is frequently explained by electrostatic interactions of the ions with the electrode, assuming that RTILs are homogeneous liquids made of ions only. However, a growing evidence points to the presence of ...

Magnesium anode batteries: Batteries with pure Mg metal anodes have been noted as being potential post Li-ion technologies for the following reasons: -Mg holds almost 6 times the specific energy of LiC6 -Mg is cheaper than Li -Mg is a safer material than Li Despite the clear motivation for assembling Mg batteries, their shortfall to date has been in large part due to the fact that conventional Mg electrolytes are simply not compatible with reversible Mg electrodeposition and dissolution. Electrolytes providing a reversible Mg2+/Mg0 couple: Families of Mg electrolytes known to give reversible deposition and dissolution of Mg include RMgX, Mg(BR4)2, Rm,,(RO)mMgX2-m + AX3-nR’n (A=Al,B; X=F,Cl,Br; R=alkyl or aryl group). Unfortunately, these materials have not found commercial success primarily due to issues with one or more of the following: low anodic stability, low conductivity, low cycling efficiency, corrosiveness, difficulty with production on a large scale, high nucleophilicity, and or lack of compatible cathode materials. The reader is referred to the literature to understand specific drawbacks for each species.1,2 The Case for Room Temperature Ionic Liquids (RTILs): In recent years, ionic liquids have generated a lot of excitement in several branches of science, one of them being energy storage. To date, use of ionic liquid media for Mg electrochemistry has been met with very limited success. There have been claims of reversible Mg deposition and dissolution using conventional Mg salts in RTILs but not without considerable subsequent criticism.3,4It may be that RTILs simply cannot provide an appropriate environment, however, we feel as though they may be overlooked and are more compatible than previously suggested. The obvious benefits from using RTILs in batteries are the following general physical properties: Non-volatileHigh Thermal stability and liquid rangeIntrinsically conductiveWide electrochemical windows The first two characteristics allow us to create extremely dry and inert environments by performing electrochemistry under vacuum as well as high temperatures. In such conditions (0.4mTorr, 100°C) we show moderate stripping behavior, not observed under normal inert gas atmospheres (fig 1 black curve). Furthermore, we believe there are interesting lessons to be learned from work being done with Li and Zn batteries using RTIL solvents. Specifically, double layer structures and solvation environments behave much differently in RTILs than in conventional solvents and have been shown to drastically alter the electrochemical response. For instance, the voltammograms in figure 1 with Zn and Mg salts show unusual cathodic current dips possibly due to a compact ion double layer changing as the potential is swept. See Figure 1:Comparison of Mg, Zn, & Li-TFSI electrolyte solutions in BMPTFSI (~0.1M). We will here present the challenges faced with using Mg electrolytes in RTILs and the possible strategies for using them to create an environment capable of providing facile, reversible Mg/Mg2+electrochemistry. Acknowledgment We acknowledge support from the Army Research Office grant number W911NF-11-1-0432.