Polyoxyethylene Lauryl Ether Research Articles

The kinetics of cellulase in reverse micelles using an isothermal titration microcalorimetry technique

We report the activities of cellulase in reverse micelles was investigated via microcrystalline cellulose as substrates using isothermal titration microcalorimetry (ITC). The ITC can record the heat evolved in enzyme catalysis reactions, and the resulting thermal power can be further used to calculate the apparent Michaelis constant (KM) and the maximum rate of the reaction (Vm) of enzymes. Importantly, ITC in enzyme kinetics is not limited to soluble systems—it is equally effective in monitoring reaction heats in suspensions. The reverse micelles studied here were formed by polyoxyethylene lauryl ether (Brij35), n-hexanol, and cyclohexane. The effects of ωo, the molar ratio of water to surfactant, pH, temperature, and ionic effects on the kinetics of cellulase in Brij-35/n-hexanol/cyclohexane reverse micelles were investigated, and the optimal conditions of ωo (the molar ratio of water to surfactant), pH, and temperature were obtained. Furthermore, K+, Na+, Cl−, and NO3− enhanced the cellulase activity in Brij-35/n-hexanol/cyclohexane reverse micelles; Mg2+, Ba2+, SO42-, and SO32- inhibited entrapped cellulase. These results are of interest in understanding the kinetics of cellulase in reverse micelles. The findings might have industrial applications for reverse micelles system that degrades cellulose into sugar.

AuCu/CeO2 bimetallic catalysts for the selective oxidation of fatty alcohol ethoxylates to alkyl ether carboxylic acids

We describe in this work the preparation of a series of bimetallic Au-Cu catalysts supported over nanoceria for the direct oxidation of C12-C14-alcohol polyethyleneglycol ether with on average 7 ethyl oxide units (AEO7) to polyoxyethylene lauryl ether carboxylic acid (AECA6), using H2O2 as an oxidant, under basic conditions. Different preparation methods have been used, including deposition-precipitation, incipient wetness impregnation and wet impregnation for engineering the interaction between Au, Cu and nanoceria. The structure of the bimetallic catalysts is discussed in detail on the basis of refined characterization by XRD, HR-TEM, STEM-EDX-SDD, XPS and ICP-AES. The formation of a AuCu alloy over nanoceria at a Cu/Au molar ratio of 0.11 on Au allows a significant enhancement of the catalytic activity, resulting in an AECA6 yield up to 80% with a selectivity of 90%. The catalyst can be recycled and reused for at least 10 consecutive runs without apparent loss of activity. Detailed DFT calculations on Au, Cu and Au-Cu model alloys reveal a positive role of Cu on Au by favoring the adsorption of AEO7, H2O2 and OH− on the catalyst surface compared to pure Au, as well as by reducing the energy barrier for H2O2 cleavage. Isolated Cu sites on the Au-Cu alloy appear as crucial for enhancing the catalytic properties for AEO7 oxidation.

Development of eco-friendly cleaning solution for industrial silicon wafer solar cell

In the cleaning process to fabricate silicon solar cell wafers, removal of stains and metal impurities on the wafer surface is important since they can affect the surface texturing of silicon solar cells. The surfactants included in a cleaning solution used for the cleaning process have a significant effect on the detergency by slightly altering the temperature, concentration, or molecular structure of the adsorbent. In this study, the eco-friendly and reusable cleaning solution have been developed to remove the generation of stains and increase the recyclability of the cleaning solution by adjusting the ratio of polyoxyethylene lauryl ether, which is a nonionic surfactant with several advantages such as, no ion pollution and strong osmosis. The stain inspection revealed that the generation rate of stains reduced from 0.35% to 0.01% when the ratio of the polyoxyethylene lauryl ether included in the cleaning solution was the highest. It was confirmed that the cleaning solution with the highest ratio of polyoxyethylene lauryl ether can be reused over 60 times by the investigation of the concentration of metal impurities, the texturing result and the reflectance values. The cleaning solution with the highest ratio of the polyoxyethylene lauryl ether is the most suitable for the mass-production process, owing to the low generation rate of stains and re-useable solution.

Interaction between ethoxylated emulsifiers and propylene glycol based solvents: Gelation and rheology study

Gelation behavior of two ethoxylated emulsifiers, polyoxyethylene(25) cetosteryl ether (PCSE) and polyoxyethylene(23) lauryl ether (PLE), was studied in the glycol ether solvent mixtures. Solvents used for this work were tripropylene glycol (TPG) and tripropylene glycol n-butyl ether (TPnB), where gelation behavior was studied in various ratios of these two solvents. Stability of gel structure was monitored using shear ramp rheology study. Results showed that presence of hydroxyl groups at both ends in TPG molecule is helping to form a more ordered gel structure, while uneven entanglement of the free ‘butyl ether end’ is making the gel structure weak in TPnB. Scanning electron microscopy images confirmed the predictions where entangled ribbon structure and flower like morphology was observed in TPG and TPnB respectively. Thixotropy loop test was used to study the structural breakdown of the gel under applied shear stress and its recovery when allowed to rest. Increase in thixoptropic loop area of PCSE-TPG gels from 6470 Pa/s to 9460 Pa/s with increase of gelator content from 25% to 30% suggests higher thixotropic nature of gel with higher gelator content. Viscoelastic nature of the gels was investigated using amplitude sweep measurements. Gels were characterized by linear viscoelastic region (LVR), storage and loss modulus in the rheology profile. Higher storage modulus (G’) for 25% PCSE-TPG gel (46,700 Pa) than PLE-TPG (21,890 Pa) suggested better mechanical strength for PCSE gel. This paper presents complex aggregation behavior of ethoxylated emulsifiers in low molecular weight glycol based solvents and also discusses the viscoelastic characterization of gels.

Mixed micellar liquid chromatographic method for simultaneous determination of norfloxacin and tinidazole in pharmaceutical tablets

A new green mixed micellar liquid chromatographic method was developed, validated, and successfully applied for the determination of norfloxacin and tinidazole in bulk and in pharmaceutical dosage form. The developed method used the anionic surfactant; sodium dodecyl sulphate and the neutral surfactant polyoxyethylene (23) lauryl ether without need of organic solvent in the mobile phase. Optimization of the chromatographic condition was performed by 23 full factorial design. Chromatographic separation and quantitation was performed on ODS Hypersil® column (250 × 4.6 mm, 5 μm). Mixed-micellar mobile phase consisted of 0.14 M SDS, 0.03 M Brij-35 and 0.3% triethylamine. pH of the mobile phase was adjusted to 2.9 by orthophosphoric acid. The flow rate was 1 mL/min. The injection volume was 20 μL. UV detection was performed at 313 nm. Linearity ranges were found to be 2–10 μg/mL and 2–12 μg/mL for norfloxacin and tinidazole, respectively. The developed method was validated and successfully applied to the simultaneous determination of both drugs in their tablet. The mean percentage recovery ± S.D. values were found to be 97.745 ± 0.664 and 100.441 ± 1.379 for norfloxacin and tinidazole, respectively. The assay results obtained were statistically compared to those obtained by a reported method and good agreement was observed. The present method offers significant advantages compared to previously reported chromatographic methods concerning column efficiency, selectivity and resolution. The green property of the method was evaluated. The method is verified to obtain excellent greenness. The calculated analytical Eco-Scale of the method was also compared to those of other reported liquid chromatographic methods.

Microbial community assembly in detergent wastewater treatment bioreactors: Influent rather than inoculum source plays a more important role

In this study, three sequencing batch reactors Ra, Rb, Rc with different inoculum sources (activated sludge; activated sludge plus detergent degrading consortium; detergent degrading consortium) were used to treat detergent wastewater [consisting of sodium dodecyl sulfate, polyoxyethylene lauryl ether and tetrasodium ethylenediamine tetraacetate (Na4EDTA)]. Fast start-up and highest performance in phase I and II (organic loading rate were 0.28, 0.39 kgCOD/kgMLSS/d, respectively) were observed in Rc. In contrast, Rb showed highest impact resistance to the increase of EDTA concentration in phase III. High-throughput sequencing analysis showed that inoculum sources led to significant differences on microbial community in phase I. However, regardless of the influent variation in phases II and III, the differences on microbial community among three SBRs were diminished along long-term operation. Pseudomonas, Sphingopyxis, Luteimonas, Pseudoxanthomonas and SM1A02 were found to be the core taxa, they might contribute to the excellent performance of detergent wastewater treatment.

Isocratic micellar liquid chromatography using mixed anionic and non-ionic surfactants as mobile phase additives for separation of 17 free amino acids

In this work, an isocratic micellar chromatographic method for separation of 17 free amino acids was first established. Mixed anionic and non-ionic surfactants were used as mobile phase additives. Besides, a chromatographic environment was simulated and the possible mechanism was discussed. Pre-column derivatization with 9-fluorenylmethyl chloroformate was used before chromatographic analysis. The optimized chromatographic conditions were the mobile phase A (0.075 M sodium dodecyl sulfate solutions and 0.010 M polyoxyethylene lauryl ether containing 20 mM ammonium acetate at pH 3.5) and B (100% acetonitrile) (85:15, v/v) running at 1.2 mL/min by a Venusil XBP C18 column (5 µm, 250 × 4.6 mm) at 35.0 °C. Compared with the conventional reversed phase liquid chromatography, the consumption of organic solvent in the method is lower which reduces the analysis cost and being environment-friendly. In addition, complex gradient elution is not required. This provides an alternative way for the separation of amino acids.

Development of an Eco-friendly HPLC method for the simultaneous determination of three benzodiazepines using green mobile phase

The analysis of the class of benzodiazepines (BDZs) is of a great importance on the levels of forensic, clinical and pharmaceutical uses. The study is focusing on the separation of three BDZs which are diazepam, clonazepam, and bromazepam using a green micellar mobile phase. It was found that the non-ionic surfactant Brij-35 can replace the organic solvent, as it decreases the retention time significantly and contributes to environmentally friendly or Eco-friendly separation procedures. The study was achieved on monolithic C18 column. Combination of sodium dodecyl sulphate (SDS): polyoxyethylene(23)lauryl ether (Brij-35) in a ratio of 50:50% v/v, was used as a mobile phase. The UV detection was set at 240 nm at a flow rate of 1.0 mL/min. The separation of diazepam, clonazepam and bromazepam was achieved in less than ten minutes even though there is no organic modifier in the mobile phase. A detailed study for the chromatographic parameters in this micellar system is carried out, in addition to a comparison with that achieved with other systems containing a single surfactant with low percent of organic modifier or other traditional mobile phase systems. Additionally, assessment of the greenness of the method is carried out using analytical eco-scale and the developed micellar HPLC method was proved to be an excellent green method for the analysis of the three drugs.

Preparing stable pigment dispersion utilizing polyoxyethylene lauryl ether as dispersant

PurposeThis study aims to evaluate the use of polyoxyethylene lauryl ether (PLE) as a dispersant in the preparation of novel pigment dispersion with enhanced dispersion ability, which can find application in the printing industry.Design/methodology/approachTo obtain a good dispersion, PLE was used as a dispersant in pigments dispersion. The colloidal and rheological properties of the PLE-based dispersion, such as particle distribution, zeta potentials and apparent viscosity were evaluated.FindingsThe particle sizes of the pigment dispersions were within the range of 150 to 200 nm. The measurement of zeta potentials varied between −24 to −32 mV, revealing a strong surface charge interaction between pigments and PLE. Subsequently, its stability to high-speed centrifuge and freeze-thaw treatment was carefully investigated. To demonstrate the coverage of pigment particles by PLE, thermogravimetric analysis was carried out. Moreover, X-ray diffraction was used to disclose the combined impacts of PLE and ultrasonic power on the crystal structures of the pigments. Finally, the coloring performance and leveling properties of pigment dispersions on cotton substrates were evaluated by measuring their K/S values (color strength), rub and color fastness properties, which possessed good results.Research limitations/implicationsThe dispersant used is incompatible with strong oxidizing agents and strong bases. More so, modification to improve its dispersion properties can be studied.Practical implicationsThe use of PLE as a dispersant could be readily used in pigment dispersion processes and other suitable applications. PLE could also be used as a co-surfactant in synergy with other surfactants or dispersants in the dispersion process.Originality/valueThe use of PLE in pigment dispersion as well as investigating its coloring properties on cotton fabric is novel and can find various applications in the dying, printing and coating industry.

Solvothermal synthesis of hydrophobic carbon dots in reversed micelles

Synthesis of hydrophobic luminescent carbon nanostructures in non-aqueous solution has been performed. The system consisted of hexane as nonpolar “oil” phase, nonionic polyoxyethylene (4) lauryl ether (Brij L4) as a surfactant, and either water or dextran sulfate aqueous solution as a polar phase. Carbon nanodots (CND) with a particle size of 5.0 ± 0.7 nm were formed by solvothermal treatment at 180 °C of two- (hexane–Brij L4) and three-component (hexane–Brij L4–aqua solutions) systems. It was found that CND with blue-green-yellow photoluminescence (PL) with linear dependence of emission peak position on excitation wavelength and stability of PL over at least 3 weeks were formed from Brij L4. We found that using small volume of water as the third component helps to reorganize Brij L4 molecules which results in CND PL intensity increase by a factor of 1.5 and quantum yield increase from 2.0 to 2.6% compared to CND from the two-component micellar system. Replacing water with dextran sulfate solution resulted in a lower quantum yield to 2.2%. Thus, addition of small amount of water clearly shows an effect of molecular level organization on properties of CND and results in enhanced quantum yield.

Facile synthesis of IrO 2 nanoclusters and their application as catalysts in the degradation of azo dyes

A robust synthesis of iridium oxide (IrO 2 ) role=presentation> 2 ) 2 ) _{2}) nanoclusters using methanol as a reducing agent via the chemical reduction method is reported in this article. Polyvinylpyrrolidone (PVP) and polyoxyethylene(23) lauryl ether (POLE) were used as stabilizers. The formation of IrO 2 role=presentation> 2 2 _{2} nanoclusters was confirmed by the appearance of new absorption peak at 230 nm in UV-vis spectra. XRD and TEM were used to determine the degree of crystallinity and size of nanoclusters, respectively. Further characterization studies were carried out by FT-IR spectroscopy to investigate the coordination between IrO 2 role=presentation> 2 2 _{2} nanoclusters and stabilizers. The size of the nanoclusters was found to be a factor of the ratio of solvent to reductant and precursor to stabilizer. It was found that PVP-stabilized IrO 2 role=presentation> 2 2 _{2} nanoclusters are smaller in size with narrow distribution in contrast to POLE-stabilized IrO 2 role=presentation> 2 2 _{2} nanoclusters. The catalytic activity of these nanoclusters was examined in the degradation of some azo dyes, acid orange 10 (AO 10), acid red 14 (AR 14), and acid red 26 (AR 26), in aqueous medium. PVP-stabilized IrO 2 role=presentation> 2 2 _{2} nanoclusters are catalytically more efficient than POLE-stabilized IrO 2 role=presentation> 2 2 _{2} nanoclusters, which was supported by the calculation of turnover frequencies. Thus, IrO 2 role=presentation> 2 2 _{2} nanoclusters are expected to play an imperative role in the field of catalysis and environmental remediation.

Advantage of Sodium Polyoxyethylene Lauryl Ether Carboxylate as a Mild Cleansing Agent. Part 2: Effects on Skin Functions and Conditions

Advantage of Sodium Polyoxyethylene Lauryl Ether Carboxylate as a Mild Cleansing Agent. Part 2: Effects on Skin Functions and Conditions

Search of non-ionic surfactants suitable for micellar liquid chromatography.

Most reports in reversed-phase liquid chromatography (RPLC) with micellar mobile phases make use of the anionic sodium dodecyl sulfate. This surfactant masks efficiently the silanol groups that are the origin of the poor efficiencies and tailing peaks observed for basic compounds in conventional RPLC. However, it has the handicap of yielding excessive retention, which forces the addition of an organic solvent to reduce the retention times to practical values. Other surfactants, such as the non-ionic polyoxyethylene(23)lauryl ether (Brij-35), are rarely used. Brij-35 allows the separation of a large range of analytes in adequate retention times, without the need of adding an organic solvent to the mobile phase. However, this non-ionic surfactant shows irreversible adsorption on chromatographic columns and peak shape is poorer. Therefore, the search of non-ionic surfactants with similar properties to Brij-35, but showing reversible adsorption and better peak shape, can be of great interest. In this work, the adequacy of several non-ionic surfactants as modifiers in RPLC has been explored, being polyoxyethylene(10)tridecyl ether particularly attractive. The separation of different types of compounds was checked: sulfonamides (acidic), β-adrenoceptor antagonists and tricyclic antidepressants (basic with diverse polarity), and flavonoids (with and without hydroxyl groups on the aromatic rings). The chromatographic behaviors were examined in terms of retention and peak shape. The results were compared with those obtained with Brij-35.

Cleaning protocols using surfactants and electrocleaning to remove food deposits on stainless steel surfaces

Electrocleaning was used in the cleaning of food soils (starch and heat-denatured whey protein) adhered to stainless steel. The influence of anionic (linear alkylbenzene sulfonate, two polyoxyethylene lauryl ether carboxylic acids) and nonionic (fatty ethoxylated alcohol, alkylpolyglucoside, two polyoxyethylene glycerin esters) surfactants on detersive efficacy has been assessed. High levels of detergency (88.9%) were obtained when starchy dirt was used, doubling in some cases the washing efficiency achieved by cleaning-in-place methods. All the surfactants studied improved the detergency results with respect to that obtained with pH 13 solutions. However, when a denatured and dried whey protein was used, the electrocleaning method did not substantially improve detergency results, obtaining the highest detergency with 1 g/L alkylpolyglucoside at 60 °C (19.3%).

Effect of salinity on the IFT between aqueous surfactant solution and crude oil

ABSTRACTThe effect of salts and different surfactants on the equilibrium as well as dynamic interfacial tension (DIFT) between crude oil and water was investigated. Three different types of surfactants with identical hydrophobic chain length C12: Sodium Lauryl Ether Sulphate (SLES), Dodecyl Trimethyl Ammonium Bromide (DTAB), Polyoxyethylene (23) lauryl ether (C12E23) were used in this study. SLES shows better synergism of salt and surfactant mixture amongst the surfactants studied. The order of synergism of salts with the surfactant observed was MgCl2>CaCl2> NaCl. The results obtained from partition coefficient study show that the addition of salts favours the partition of surfactants into the oil phase hence reduce IFT more effectively. DIFT results reveal that, salt accelerates the surfactant migration towards the interface, hence, reducing the t* value.

Synthesis of fluorapatite nanopowders by a surfactant-assisted microwave method under isothermal conditions

Fluorapatite nanopowders with different amounts of fluoride ions were prepared using the surfactant-assisted microwave method under isothermal conditions. Microwave irradiation was applied for the rapid formation of crystals. A micellar solution of polyoxyethylene (23) lauryl ether was used as a regulator of nucleation and crystal growth. Characterization studies from X-ray diffraction, field-emission scaning electron microscopy and Fourier-transform infrared spectra showed that crystals have an apatite structure and particles of all samples are nano size, with an average length of 50 nm and about 15-25 nm in diameter. Antimicrobial studies have demonstrated that synthesized fluorapatite nanopowders exhibit activity against tested pathogens: Escherichia coli, Staphylococcus aureus and Candida albicans. Activity increased with the amount of fluoride ions. The synthesized fluorapatite nanomaterials are promising as materials in environmental protection and medicine for orthopedics and dental restorations.

Synergism of thiocyanate ions and microinterfacial surface as driving forces for heavy multi-metals extraction

A comprehensive study has been carried out to evaluate the extraction of heavy metals mixture (Co2+, Cr3+, Cu2+, Ni2+) from aqueous media by Winsor II non-ionic microemulsion, containing polyoxyethylene (4) lauryl ether as non-ionic surfactant and butyl acetate as organic phase. The extraction mechanism is based on the formation of thiocyanate complexes of metals and their transfer from aqueous to microemulsion phase, either towards the interfacial film of surfactant (Co2+) or into the core of micelles (Cr3+, Cu2+, Ni2+). The value of the distribution coefficient for Co2+ was higher than for the other studied metals and its extraction efficiency was not dependent on the working conditions, showing a maximum value (99.99%) in all cases. By using successive extractions, chromium, nickel and copper ions that remained in the aqueous phase after first extraction were transported into the microemulsion phase, leading to an increase in the extraction efficiency up to 99.99% for chromium and copper, and 85% for nickel. Based on pH influence, a selective extraction of Co2+ and Cr3+ can be achieved, since the cobalt ions were completely extracted into the microemulsion phase at pH = 1, and the chromium ions still remained in the aqueous phase.

Effect of Surfactants on Mechanical, Thermal, and Photostability of a Monoclonal Antibody.

The purpose of this work was to evaluate the effect of commonly used surfactants (at 0.01% w/v concentration) on mechanical, thermal, and photostability of a monoclonal antibody (MAb1) of IgG1 sub-class and to evaluate the minimum concentration of surfactant (Polysorbate 80) required in protecting MAb1 from mechanical stress. Surfactants evaluated were non-ionic surfactants, Polysorbate 80, Polysorbate 20, Pluronic F-68 (polyoxyethylene-polyoxypropylene block polymer), Brij 35 (polyoxyethylene lauryl ether), Triton X-100, and an anionic surfactant, Caprylic acid (1-Heptanecarboxylic acid). After evaluating effect of surfactants and determining stabilizing effect of Polysorbate 80 against mechanical stress without compromising thermal and photostability of MAb1, the minimum concentration of Polysorbate 80 required for mechanical stability was further examined. Polysorbate 80 concentration was varied from 0 to 0.02%. Mechanical stability was evaluated by agitation of MAb1 at 300 rotations per minute at room temperature for 72h. Samples were analyzed for purity by SEC-HPLC, turbidity by absorbance at 350nm, visible particles by visual inspection, and sub-visible particles by light obscuration technique on a particle analyzer. All non-ionic surfactants tested showed a similar effect in protecting against mechanical stress and did not exhibit any significant negative effect on thermal and photostability. However, Caprylic acid had a slightly negative effect on mechanical and photostability when compared to the non-ionic surfactants or sample without surfactant. This work demonstrated that polysorbate 80 is better than other surfactants tested and that a concentration of at least 0.005% (w/v) Polysorbate 80 is needed to protect MAb1 against mechanical stress.

Insight into Water Structure at the Surfactant Surfaces and in Microemulsion Confinement.

Interactions with surfactant molecules can significantly alter the structure of interfacial water. We present a comparative study of water-surfactant interactions using two different spectroscopic approaches: water at planar surfactant monolayers by sum frequency generation (SFG) spectroscopy and interfacial water confined in reverse micelles formed by the same surfactants using IR absorption spectroscopy. We report spectral features in the OH-stretching region (3200-3700 cm-1) that are observed in both IR and SFG spectra, albeit with different relative amplitudes, for ionic surfactant sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT) and nonionic surfactant polyoxyethylene(4)lauryl ether (Brij L-4) reverse micelles in hexane and the corresponding monolayers at the air/water interface. A prominent feature in the SFG spectra of the OH stretch at 3560 cm-1 is attributed to water molecules that have a weak donor hydrogen bond to the surfactant headgroup. The same feature is observed in the IR spectra of reverse micelles after deconvoluting the interfacial versus bulk spectral contributions. We performed an orientational analysis of these water molecules utilizing the polarization-dependent SFG spectra, which shows an average tilt angle of the OH stretch of surfactant-bound water molecules of ∼155° with respect to the surface normal.

A comparative study on the effect of imidazolium-based ionic liquid on self-aggregation of cationic, anionic and nonionic surfactants studied by surface tension, conductivity, fluorescence and FTIR spectroscopy

The surfactants aggregation morphology may be modified by varying the choice of suitable ionic liquids. The aggregation behavior of cetyltrimethylammonium bromide (CTAB), sodium dodecylsulphate (SDS) and polyoxyethylene lauryl ether (Brij-35) have been investigated in the presence of 1-ethyl-3-methylimidazolium bromide[Emim][Br]. The effect of [Emim][Br] was also studied on the micellization of 1-butyl-3-methylimidazolium octylsulphate [Bmim][OS] in comparison to other surfactants. Various interfacial properties and thermodynamic parameters were determined by the surface tension and conductivity method. The local microenvironment (I1/I3), the aggregation number (Nagg) and Stern Volmer constant (Ksv) were also obtained from steady-state fluorescence quenching method. Analysis of tensiometry and conductivity data were suggested and confirmed by fluorescence results. The micellization behavior of surfactants sytems were studied from the stretching vibrational bands between 400 and 2800cm−1 by FTIR spectroscopy. It has been observed that the CMC values of all surfactants systems decrease with [Emim][Br]. Among all the surfactants, micellization of SDS was significantly influenced by [Emim][Br] due to the reason that the sulphate ion of SDS shows stronger electrostatic interaction with imidazolium cation of [Emim][Br].