Ionic Liquid Particles Research Articles

Direct synthesis of fluoropolymer particles in ionic liquids via the photopolymerization of solid lubricants

A method for synthesizing fluorine-based polymer particles as additive agents in ionic liquid (ILs)-based lubricants for vacuum is proposed. This method can directly generate fluoropolymer nanoparticles inside an IL, while protecting the IL from light damage during polymerization. In this study, photocurable materials that are expected to be used as solid lubricants were selected, and the synthesis method, details of the polymer particles, and their effect on lubrication performance are described. This method reduced the friction coefficient, and traces of the polymer were observed on the surface of the test piece. The outgassed product from the lubricant did not differ from that from the pure IL under high vacuum.

Solvation Environments in Porous Ionic Liquids Determine Selectivity in CO2 Conversion to Cyclic Carbonates.

Porous ionic liquids, which are suspensions of nanoporous particles in ionic liquids that maintain permanent porosity, are effective and selective media for the conversion of styrene oxide into styrene carbonate, absorbing CO2 [Zhou et al. Chem. Commun. 2021, 57, 7922-7925]. Here we elucidate the mechanism of selectivity using polarizable molecular dynamics simulations, which provide a detailed view on the structure of the porous ionic liquid and on the local solvation environments of the reacting species. The porous ionic liquids studied are composed of tetradecyltrihexylphosphonium chloride, or [P66614]Cl, and the ZIF-8 zinc-methylimidazolate metal-organic framework (MOF). The CL&Pol polarizable force field was extended to represent epoxide and cyclic carbonate functional groups, allowing the ionic liquid, the reactants, and the MOF to be all represented by fully flexible, polarizable force fields, providing a detailed description of interactions. The presence of reactant and product molecules leads to changes in the structure of the ionic liquid, revealed by domain analysis. The structure of local solvation environments, namely, the arrangement of charged moieties and CO2 around the epoxide ring of the reactant molecules, clearly indicate ring-opening the reaction mechanism. The MOF acts as a reservoir of CO2 through its free volume. The solute molecules are found in the accessible outer cavities of the MOF, which promotes reaction of the epoxide with CO2 excluding other epoxide molecules, thereby preventing the formation of oligomers, which explains the selectivity toward conversion to cyclic carbonates.

Experimental investigation on thermophysical properties of iobiofluids

The aim of this research was to investigate the density, thermal conductivity, and viscosity of dispersions of agricultural biomass particles in ionic liquid [HMIM][NTf2] used as a base fluid. This research is a continuation of the development of IoBioFluids, a new class of dispersions obtained by suspending particles produced from agricultural biomass, as a sustainable alternative to IoNanoFluids. Dispersions with different mass concentration of particles (0, 0.5, 1, 2.5, and 5 wt%) were studied at different temperatures (20°C, 30°C, 40°C, and 50°C). Agricultural biomass, namely sunflower stalks, was used for particle production. The dispersion was prepared by applying the commonly used two-step method. In the first step, particles were produced as dry powder from hydrothermal carbonization and heat treatment in the inert atmosphere oven. In the second step, the particles were dispersed into ionic liquid. A rheological investigation showed that dispersions exhibited Newtonian behavior for shear rates over 10 s−1. Density, thermal conductivity, and dynamic viscosity of dispersions increased with greater mass concentration of particles. Two applied merit criteria suggested a lack of any currently benefit of using the dispersions for heat transfer in the laminar flow regime due to high viscosity of dispersion. The results of criterial analysis showed that experimental data are relatively close to the limit values. Indications are suggesting the possibility of further improvement of IoBioFluid properties as a new heat transfer fluid.

Experimental studies of electrorheological properties of lubricating oils containing ionic liquid. Part 3. Microscopic examination of the ER effect mechanism

The article presents the results of in situ microscopic observations of quasihomogenic mixtures of hydrocarbon oils containing ionic liquids. Observations were made using NIKON ECLIPSE LV 100 D optical microscope. The mechanism of generating the ER effect in two mixtures was observed, i.e., in silicone damping liquid GP-1, which is polimethylsiloksane mixture containing 2% (v/v) of ionic liquid CJ 001, i.e., tetrafluoroboran 1-methyl-3-octyloxymethylimidazolium and base polialfaolefine oil PAO-6 which containing 2% (v/v) of ionic liquid CJ 008, i.e., trihexyltertradecylfosfonium bis(trifluoromethylsulfonyl) imide as well as in the two-component standard liquid LID3354s. The ob-servations carried out showed that the prepared mixtures had generated the ER effect. At the threshold value E = 0.3 kV·mm–1, the ER effect disappeared. Photographs, presented in the paper, show changes in the structure of mixtures containing ionic liquids that occur under the influence of an external elec-tric field, consisting in the formation of „fibril chains and/or fibril streams” and then, their destruction and accumulation of ionic liquid particles at the electrodes. Keywords: electrorheological effect (ER), lubricating oils, ionic liquids, microscopy.

Electrodeposition of metals and electrochemical preparation of metal nano particles in ionic liquids

Electrodeposition of metals and electrochemical preparation of metal nano particles in ionic liquids

Effects of carbon chain length of imidazolium-based ionic liquid in the interactions between heavy crude oil and sand particles for enhanced oil recovery

Increasing demand and dwindling supply of crude oil have spurred efforts towards enhancing heavy oil recovery. Recently, applications of ionic liquids (ILs) for heavy oil recovery and catalytic upgrading have been intensively studied due to their novelty as green surfactants. This paper presents the effects of different carbon chain lengths (n = 0, 2, 4, 6, 8, 10, 12) and concentrations from 1000 to 8000 ppm of imidazolium-based ILs on the oil-sand detachment efficiency at room temperature. Overall, the longest carbon chain length (n = 12), 1-dodecyl-3-methylimidazolium chloride ([DODmim][Cl]), showed highest oil-sand detachment efficiency of approximately 80% at 4000 ppm and beyond, indicating that a CMC point has been achieved. In contrary, the IL without carbon chain length (n = 0), 1-methylimidazolium chloride ([Mmim][Cl]), showed lowest oil-sand separation of a mere 5.7% at all concentrations. Interfacial tension (IFT) and zeta potential measurements further verified the above oil-sand detachment efficiencies, whereby the high oil-sand detachment efficiencies correlated to low IFT of approximately 9.78 mN/m for [DODmim][Cl] at 8000 ppm and high net zeta potential measurements of positively charged oil and sand particles. It is interesting to note that while the zeta potential measurements were all positive for oil particles in IL, the zeta potential measurements of sand particles in IL turned to negative for low concentrations of [Omim][Cl] and shorter carbon chain lengths (n ≤ 6), thus resulting in a mild attraction between the oil and sand particles. Further analysis using the Derjaguin-Landau, Verwey Overbeek (DLVO) theory which showed the inter-particle forces further validated the former oil-sand detachment efficiencies whereby repulsive forces between oil and sand particles occurred only for longer carbon chain lengths of [DODmim][Cl] and [Dmim][Cl].

An experimental evaluation on thermophysical properties of functionalized graphene nanoplatelets ionanofluids

Ionanofluids (ionic liquid-based nanofluids) as newly introduced types of nanofluids with promising potential for heat transfer and thermal storage applications are created through complex dispersion of ultrafine nanometer-sized particles in ionic liquids. As innovative agents for development of energy sustainability, ionanofluids are widely employed in some applications, i.e., solar panels, catalysts, heat insulators and so forth. Non-flammability and non-volatility features of ionic liquids, make them applicable as green working fluids for any chemical processes. In the present paper, an experimental investigation was conducted on some thermophysical properties (viscosity, electrical conductivity and surface tension) of graphene based ionanofluid as main effective parameters in performance analysis. For this purpose, ionanofluid was prepared at three levels of weight fractions (1%, 2% and 3%) by adding and dispersing polycarboxylate functionalized graphene nanoplatelets (GNPs) in BMIM-PF6 (1-Butyl-3-methylimidazolium hexafluorophosphate) with 98 + % purity as the base fluid. The experimental data was acquired within the temperature range of 293.15 to 333.15 K and at atmospheric pressure (~101 kPa). The results show that the viscosity of ionanofluid decreases with enhancement of temperature and nanoparticle concentration. On the other hand, electrical conductivity of ionanofluid augments as temperature and particle loading increase. For instance, EC at 1% wt. nanoparticles and 303.15 K enhances around 64% compared to the pure IL. Surface tension of the ionanofluids was also determined experimentally as a function of temperature for different mass loadings of nanoparticles. The results reveal that surface tension of ionanofluids decreases slightly as temperature enhances and it reduces with enhancement of nanoparticle fraction as well.

Soft materials based on colloidal self-assembly in ionic liquids

Ionic liquids (ILs) have attracted much attention as dispersion media for colloidal systems as alternatives to organic solvents and electrolyte solutions. Although colloidal stability is an essential factor for determining the properties and performance of colloidal systems containing ILs, detailed mechanisms for colloidal stabilization have not yet been studied. In the first part of this paper, we highlight our fundamental studies on colloidal stability. Three different repulsive forces, electrostatic, solvation, and steric interactions, are examined for their effectiveness in stabilizing colloidal particles in ILs. In the second part of this report, we provide an overview of our recent studies on colloidal soft materials in the presence of ILs. On the basis of the suspended state of the silica colloid particles, two different soft materials, a colloidal gel and a colloidal glass, were prepared in ILs. Their functional properties, including ionic transport, rheological, and optical properties, are discussed in relation to the microstructures of the colloidal materials. Soft materials based on colloidal self-assembly in ionic liquids: fundamental studies on the colloidal stability in ionic liquids (ILs) are highlighted. Three different repulsive forces—electrostatic, solvation, and steric—are examined for their effectiveness to stabilize colloidal particles in ILs. An overview of recent studies on colloidal soft materials in the presence of ILs is also provided. Based on suspended states of colloid particles, two different soft materials—colloidal gel and colloidal glass—were prepared in ILs. Their functional properties, including ionic transport, rheological and optical properties, are discussed in relation to the microstructures of the colloidal materials.

Semisoft Colloidal Crystals in Ionic Liquids.

Here, we introduce a technique for the direct formation of semisoft colloidal crystals of hybrid particles in nonvolatile ionic liquid (IL) solvents. The hybrid particles are comprised of a silica core and a densely grafted polymer brush shell, which were synthesized by surface-initiated living radical polymerization. A phase transition of the suspensions from a disordered fluid to a crystallized system was observed within a narrow concentration range. Confocal laser scanning microscopy observation and ultraviolet-visible light (UV-vis) spectrometry confirmed the highly ordered structure of the hybrid particles in ionic liquids. The effect of the hybrid particle structure on the photonic band gap of the colloidal crystals was investigated, and the band gaps varied by changing graft chain lengths. In addition, the colloidal crystal suspensions were successfully immobilized in ILs.

Creating nanoparticle stability in ionic liquid [C4mim][BF4] by inducing solvation layering.

The critical role of solvation forces in dispersing and stabilizing nanoparticles and colloids in 1-butyl-3-methylimidazolium tetrafluoroborate [C4mim][BF4] is demonstrated. Stable silica nanoparticle suspensions over 60 wt % solids are achieved by particle surface chemical functionalization with a fluorinated alcohol. A combination of techniques including rheology, dynamic light scattering (DLS), transmission electron microscopy (TEM), and small angle neutron scattering (SANS) are employed to determine the mechanism of colloidal stability. Solvation layers of ∼5 nm at room temperature are measured by multiple techniques and are thought to be initiated by hydrogen bonds between the anion [BF4](-) and the fluorinated group on the surface coating. Inducing structured solvation layering at particle surfaces through hydrogen bonding is demonstrated as a method to stabilize particles in ionic liquids.

Formation of Metal Nanoparticles in Ionic Liquids By Low-Energy Quantum Beam Irradiation Technique

In our previous study, we reported a novel method on synthesizing Au nanoparticles via a reductive reaction in an ionic liquid droplet containing Au3+ ions using a low-energy electron beam irradiation technique1,2). The formed Au nanoparticles are dispersed well and crystallized. This new technique can be applied to many industrial fields. For example, this could be applicable to electron-beam lithography if we could firmly anchor the formed particles to the substrate surface. Besides, we can easily prepare the metal alloy particles (which is very important in the field of catalysis) without considering the redox potential of metal ions. Of course, this technique is attractive from the point of view of pure chemistry, because there is a possibility that we will find novel types of reductive reaction in the ionic liquids.Development of techniques for controlling the size and morphology of the metal particles is very important for adapting those particles to the actual devices or the catalyst. To achieve this aim, control of the formation manner of metal particles in ionic liquids is needed. Thus, we investigated how electron beam conditions (acceleration energy, beam current and irradiation time) and the combination of cations and anions of ionic liquids affect the size and shape of Au particles. Fig. 1 shows the averaged sizes of the particles plotted against the viscosity of ionic liquids. We can see that the anion of the ionic liquid strongly affected the size and shape of the primary particles, which was due to the different local structure of the ionic liquid around the Au particles. Besides, it was found that the sizes of the primary particles increased with higher acceleration energy of the electron beam, whereas they did not depend so much on the beam current and irradiation time.On the other hand, it is known that ILs confined in small spaces exhibit characteristic properties which are different from those of bulk ILs. Therefore, it is an interesting subject to study how Au particles are formed in ILs confined in the nano-micro sized space. We should also note that such confined space can be used as structural template with which the size and shape of metal particles can be controlled. Nanopore is good template for controlling the formation process of Au particle. Fig. 2 shows a TEM image of Au nanoparticles formed in nanopores of mesoporous silica by X-ray irradiation. Highly dispersed Au particles whose size was limited by the pore diameter were observed. The particles were stable even after annealing at 373K, indicating that the IL molecules surrounding the Au nanoparticles prevented the aggregation. The chemical states of IL and Au particles confined in nanopores were characterized by XPS measurements. Au 4f spectra revealed that the Au particles formed in nanopore was positively charged. Interestingly, the result of N 1s spectra revealed that cation and anion of IL were organized in the nanopores. Such characteristic local structure in nanospace may affect not only the formation process of Au particles but also the catalytic reaction in the pore.

Study on the properties and stability of ionic liquid-based ferrofluids

Ionic liquid (IL)-based ferrofluids have been prepared dispersing both bare and sterically stabilized CoFe2O4 nanoparticles. The precipitated particles were characterized by X-ray diffraction, scanning electronic microscopy, transmission electron microscopy, Fourier transform infrared, and vibrating sample magnetometry studies. The water-absorbing property of ferrofluids at ambient temperature was estimated by weight and viscosity measurements. Colloidal dispersion stability of the ferrofluids was evaluated by particle suspension percentage. Experimental results indicate that interparticle electrostatic repulsion is not effective in stabilizing bare magnetic particles in IL. There is no significant increase on the dispersion stability when the particles were coated with a monolayer of oleic acid. The reason could be caused by the incompatibility between the nonpolar tail of surfactant and carrier liquid. When excess oleic acid was added into IL, stable magnetic colloid was achieved by a steric stabilization layer coated to be compatible with the IL.

Green Preparation of Ultra-Fine Silver Particles in Ionic Liquid

A room-temperature ionic liquid, 1-n-butyl-3-methylimidazolium tetrafluoroborate([bmim]BF4), was synthesized with two-step method and its structure was characterized by IR, H-NMR. Putting p-benzenediol and AgNO3 ethanol solution into [bmim] BF4, ultra-fine silver powder were prepared successfully in this paper. The effects of the temperature and material mol ratio of AgNO3 and p-benzenediol on the shape of products were studied. The products were characterized by XRD, SEM, IR and TEM. The results showed that the particle size of silver was much smaller and in the range of nanometers, and had narrowly, uniform distribution, which indicates that the synthesis method using ionic liquid, is the better “green” and “environment friendly” method to prepare ultra-fine silver powder.

Preparation of Nylon‐6 Particles in Ionic Liquids

AbstractSummary: Utilizing the thermal stability of ionic liquid, micrometer‐sized Nylon‐6 particles were successfully prepared by hydrolytic polymerization of ε‐caprolactam at high temperature with polyvinyl pyrrolidone as stabilizer in ionic liquids, 1‐butyl‐3‐methyl imidazolium tetrafluoroborate, [Bmim][BF4] and N,N‐diethyl‐N‐methyl‐N‐(2‐methoxyethyl)ammonium bis(trifluoro‐methanesulfonyl)amide, [DEME][TFSA]. The obtained particles had a unique shape because Nylon‐6 is a crystalline polymer. Viscosity‐average molecular weights of Nylon‐6 prepared in [Bmim][BF4] and [DEME][TFSA] at 180 °C for 48 h were 4200 and 2200, respectively.

Plasma electrochemistry in ionic liquids: deposition of coppernanoparticles

We report on the synthesis of copper nanoparticles in two different water- and air-stable ionic liquids using plasma electrochemical deposition. The copper nanoparticles were deposited in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py(1,4)]Tf(2)N) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([EMIm]Tf(2)N). To get information on the dimensions of the particles made, we have applied in situ transmission electron microscopy (TEM) (particles in ionic liquid). The chemical composition was investigated by ex situ X-ray photoelectron spectroscopy (XPS). We found that the copper particles produced in [Py(1,4)]Tf(2)N were larger in size compared to the particles obtained in [EMIm] Tf(2)N (roughly 20 vs. 10 nm). The chemical composition of the particle surface differs too. In both cases the particles are partly oxidised leading to a CuO shell, but the particles obtained in [Py(1,4)]Tf(2)N carry a lot of residues from the ionic liquid.

Colloidal Stability of Bare and Polymer-Grafted Silica Nanoparticles in Ionic Liquids

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.