Effects Of Imidazolium-based Ionic Liquids Research Articles

Inhibition effect of imidazolium-based ionic liquids on pyrophorisity of FeS

To explore the inhibition of imidazolium-based ionic liquids on the pyrophorisity of sulfur corrosion products in oil tanks, FeS, the main component of sulfur corrosion products, was used as experimental samples in this paper. Four ionic liquids, [BMIM][I], [BMIM][BF4], [EMIM][BF4] and [BMIM][NO3], were selected to process the samples. The microstructure of the samples was characterized by a scanning electron microscope. The processes of spontaneous combustion and the changes of specific heat capacity of the sample were analyzed by TG-DSC. On this basis, the apparent activation energy, pre-exponential factor, and reaction mechanism function of the samples in the process of spontaneous combustion were obtained by the Kissinger method and the Malek method. The results show that the reaction process of the samples can be divided into four stages, and the third stage is the spontaneous combustion stage, in which the samples have a violent oxidation reaction and release a lot of heat. The ionic liquids have different degrees of inhibition effect on the pyrophorisity of FeS, among which [BMIM][I] have the most obvious inhibition effect, and the exothermic peak of the treated samples 25.7% lower than that of the untreated samples. The average activation energy of the samples treated with the four ionic liquids respectively increased by 65.28, 25.62, 35.27, and 33.88 kJ/mol, and the activation energy of the samples treated with ionic liquid [BMIM][I] showed the greatest overall improvement and the best inhibition effect.

To probe the binding of TMPyP4 to c-MYC G-quadruplex with in water and in imidazolium-based ionic liquids using spectroscopy coupled with molecular dynamics simulations

TMPyP4 is known to stabilize c-MYC Pu22 G-quadruplexes and decrease c-MYC oncogene expression. Ionic liquids (ILs) were demonstrated to modulate G-quadruplex stability, serving as attractive alternatives in nucleic acid storage for biomedical applications. However, no high-resolution structure of TMPyP4 complexed with Pu22 has been solved. Additionally, the effect of imidazolium-based ILs on G-quadruplex structure is unknown. Finally, the effect of ILs on ligand binding to G-quadruplexes has not been investigated. Using spectroscopy coupled with molecular dynamics (MD) simulations in this study, we elucidate the detailed binding interactions and effects of ligand TMPyP4 and four imidazolium-based ILs with increasing hydrophobic chains on the structure of a 22mer c-MYC parallel-stranded DNA G-quadruplex (Pu22) and the effect of these ILs on TMPyP4 binding to Pu22. UV–Vis and CD spectroscopy revealed 1) OMIM-Cl increases the melting temperature of the G-quadruplex from ∼ 80 °C to ∼ 90 °C. 2) TMPyP4 binds G-quadruplex in 2:1 ratio, 3) the four IL decreases TMPyP4 binding to Pu22 in a cation-dependent manner. MD simulations suggest that 1) TMPyP4 primarily binds to the top G-quadruplex layer, 2) the four ILs prevent TMPyP4 ligand binding via hydrophobic and electrostatic interactions. This study supports ILs could increase the thermal stability of G-quadruplex structure.

Effect of imidazolium-based ionic liquids on the pore wetting characteristics and mechanical properties of coal

Exploring the pore wetting pattern of the imidazolium-based ionic liquids-water system is necessary to understand the dust reduction effect from the source of the coal seam and its influence on the mechanical properties. Low-field nuclear magnetic resonance (LF-NMR) is used to analyze the wetting effect of different concentrations and types of ionic liquids-water systems on different pore sizes from the pore size distribution. Uniaxial compression mechanics experiments are used to investigate the changes in mechanical properties of the coal after wetting, and a scanning electron microscope is used to observe the differences in surface morphology of the coal after treatment with aqueous solutions of ionic liquids. The results show that the wetting effect of aqueous solutions of different concentrations of imidazolium-based ionic liquids is different for micropores, mesopores and macropores compared to pure aqueous solutions. At the same time, the pore wetting of the coal samples by the aqueous solution of the imidazolium-based ionic liquids altered their mechanical properties, with a minimum strength of 8.57 MPa for the 2 wt% [Bmim][BF4] treated coal samples. Analysis of microscopic morphology shows that the surface minerals of coal samples treated with imidazolium-based ionic liquids are dissolved, forming linked fissures or pores between minerals, which positively affect pore wetting. The revelation of the pore wetting properties of ionic liquids systems on coal is conducive to enriching the theory of coal seam dust control and is of practical significance for efficient dust reduction in mines.

The critical evaluation of the effects of imidazolium-based ionic liquids on the separation efficiency of selected biogenic amines and their metabolites during MEKC analysis

Ionic liquids (ILs) such as imidazole can be used to prevent the sorption of analytes onto the quartz walls of the capillary. Coating the capillary wall with a cation layer increases its surface stability, consequently improving the repeatability of separation process. Currently, examining the effects of dynamic coatings on the capillary wall is an emerging trend in capillary electrophoresis (CE) research. This study uses micellar electrokinetic chromatography (MEKC) to evaluate how ILs in the background electrolyte (BGE) affect the separation efficiency of biogenic amines (BAs). Specifically, this research focuses on 12 ILs built from cations containing an imidazole ring with different alkyl substituents and anions, as well as one IL containing a pyridinium cation with tetrafluoroborate anion. All analyzed ILs, which were added to the BGE in concentrations ranging from 1 to 20 mM, were tested for their ability to improve the electrophoretic separation of selected BAs, namely: homovanillic acid (HVA), vanililmandelic acid (VMA), dihydroxyphenylglicol (DHPG), 3-metoxy-4-hydroxyphenyl glicol (MHPG), normetanephrine (NM), metanephrine (M), and dihydroxyphenylacetic acid (DOPAC). The results showed that the most effective ILs added to the BGE were those with a chloride anion (1-hexyl-3-methylimidazolium chloride [HMIM+Cl−] and 1-ethyl-3-methylimidazolium chloride [EMIM+Cl−]) and those with a tetrafluoroborate anion (1-hexyl-3-methylimidazolium tetrafluoroborate [HMIM + BF4−]). Improved separation efficiency was also obtained for the BGE containing 1-hexyl-3-methylimidazolium hexafluorophosphate [HMIM + PF6−]. On the other hand, ILs with trifluoromethanesulfonate [OTf−] or bis(trifluoromethylsulfonyl)imide [NTf2-] anions, even at low concentrations in the BGE, disturbed the flow of current through the capillary and worsened the separation process. Overall, this study provides a critical evaluation of the impact of different types and concentrations of ILs on the performance of the MEKC method during the analysis of selected BAs.

Processes and Properties of Ionic Liquid-Modified Nanofiller/Polymer Nanocomposites—A Succinct Review

Ionic liquids can typically be synthesized via protonation, alkylation, metathesis, or neutralization reactions. The many types of ionic liquids have increased their attractiveness to researchers for employment in various areas, including in polymer composites. Recently, ionic liquids have been employed to modify nanofillers for the fabrication of polymer nanocomposites with improved physicochemical properties. In this succinct review, four types of imidazolium-based ionic liquids that are employed as modifiers—specifically alkylimidazolium halide, alkylimidazolium hexafluorophosphate, alkylimidazolium tetrafluoroborate, and alkylimidazolium bistriflimide—are reviewed. Additionally, three types of ionic liquid-modified nanofiller/polymer nanocomposites—namely ionic liquid-nanofiller/thermoplastic nanocomposites, ionic liquid-nanofiller/elastomer nanocomposites, and ionic liquid-nanofiller/thermoset nanocomposites—are described as well. The effect of imidazolium-based ionic liquids on the thermo-mechanico-chemical properties of the polymer nanocomposites is also succinctly reviewed. This review can serve as an initial guide for polymer composite researchers in modifying nanofillers by means of ionic liquids for improving the performance of polymer nanocomposites.

Ionic liquid synergistic effect between preparation of hybrid supports and immobilization of lipase applied to esters production

The present work aims to evaluate the synergistic effect of imidazolium-based ionic liquids (IL) in the preparation and immobilization of Burkholderia cepacia lipase in a new hybrid support of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) and silica. In addition, these biocatalysts were applied in transesterification reactions of crude coconut oil for the production of ethyl esters. Lipase immobilized on hybrid support with [C4min][NTf2] or [C6min][NTf2] ionic liquid exhibited nearly ≈ 1.6-fold immobilization yield greater than IB-Control. The use of IL during the preparation of the hybrid support promoted changes in its morphological structure as presented by B.E.T. and FTIR. Thermogravimetric analyzes were used to characterize the prepared derivatives and support the results of immobilization yields and the synergic effect of IL used. Transesterification reactions applying biocatalysts showed that the conversion maximum in esters (59%) was found under conditions of molar ratio 1:7 (oil:ethanol) in 72 h of reaction. These results were obtained using [C4min][NTf2] during the preparation of the hybrid support for the immobilization of Burkholderia cepacia lipase, thus showing the potential of these new biocatalysts.

Synergistic interactions of ionic liquids and antimicrobials improve drug efficacy.

SummaryCombinations of ionic liquids (ILs) with antimicrobial compounds have been shown to produce synergistic activities in model liposomes. In this study, imidazolium chloride-based ILs with alkyl tail length variations are combined with commercially available, small-molecule antimicrobials to examine the potential for combinatorial and synergistic antimicrobial effects on P. aeruginosa, E. coli, S. aureus, and S. cerevisiae. The effects of these treatments in a human cell culture model indicate the cytotoxic limits of ILs paired with antimicrobials. The analysis of these ILs demonstrates that the length of the alkyl chain on the IL molecule is proportional to both antimicrobial activity and cytotoxicity. Moreover, the ILs which exhibit synergy with small-molecule antibiotics appear to be acting in a membrane permeabilizing manner. Collectively, results from these experiments demonstrate an increase in antimicrobial efficacy with specific IL + antimicrobial combinations on microbial cultures while maintaining low cytotoxicity in a mammalian cell culture model.

Effects of imidazolium-based ionic liquids on the isobaric vapor–liquid equilibria of methanol + dimethyl carbonate azeotropic systems

Abstract The separation of methanol (MeOH) and dimethyl carbonate (DMC) is important but difficult due to the formation of an azeotropic mixture. In this work, isobaric vapor–liquid equilibrium (VLE) data for the ternary systems containing different imidazolium–based ionic liquids (ILs), i.e. MeOH + DMC + 1-butyl-3-methy-limidazolium bis[(trifluoromethyl)sulfonyl]imide ([Bmim][Tf2N]), MeOH + DMC + 1-ethyl-3-methyl-imidazolium bis[(trifluoromethyl)sulfonyl]imide ([Emim][Tf2N]), and MeOH + DMC + 1-ethyl-3-methylimidazolium hexafluorophosphate ([Emim][PF6])) were measured at 101.3 kPa. The mole fraction of IL was varied from 0.05 to 0.20. The experimental data were correlated with the NRTL and Wilson equations, respectively. The results show that imidazolium-based ILs were beneficial to improve the relative volatility of MeOH to DMC, and [Bmim][Tf2N] showed a much more excellent performance on the activity coefficient of MeOH. The interaction energies of system components were calculated using Gaussian program, and the effects of cation and anion on the separation coefficient of the azeotropic system were discussed.

Effect of Imidazolium-Based Ionic Liquids on the Structure and Phase Behavior of Palmitoyl-oleoyl-phosphatidylethanolamine.

Among various applications, ionic liquids (ILs) have been used as antimicrobial agents in laboratories, possibly through induction of the leakage of bacteria. A molecular-level understanding of the mechanism that describes how ILs enhance the permeation of membranes is still lacking. In this study, the effects of imidazolium-based ILs with different alky chain lengths on the structure and phase behavior of 1-palmitoyl-2-oleoyl-phosphatidylethanolamine (POPE), which is a representative bacteria-membrane-rich lipid, have been investigated. By employing differential scanning calorimetry and synchrotron small- and wide-angle X-ray scattering techniques, we found that ILs with longer alkyl chains influenced the phase behavior more effectively, and lower IL concentrations are needed to induce phase separation for both lamellar liquid crystalline phase and nonlamellar inverted hexagonal phase of POPE. Interestingly, the IL with an alkyl chain of 12 carbon atoms ([C12mim]Cl) shows a difference. It exhibits a stronger disturbing effect on the POPE bilayer structure than [C16mim]Cl, indicating that the ability of ILs to influence the membrane structures is dependent not only on the alkyl chain length of ILs, but also on the degree of matching of the alkyl chain lengths of ILs and lipids. The new lamellar and nonlamellar structures induced by ILs both have smaller repeat distances than that of pure POPE, implying thinner membrane structures. Data of the fluorescence-based vesicle dye leakage assay are consistent with these results, particularly the defects caused by IL-induced phase separation can enhance the membrane permeability markedly. The present work may shed light on our understanding of the antimicrobial mechanism of ILs.

Insights into the effect of imidazolium-based ionic liquids on chemical structure and hydrolytic activity of microbial lipase.

This work studied the effect of the cation alkyl chain length of 1-alkyl-n-methylimidazolium chloride ([Cnmim]Cl)-based ILs on the activity of Aspergillus niger lipase. First, the lipase activity in the presence of different ILs concentration over time was determined. ILs with shorter cation alkyl side chain length, namely [C4mim]Cl and [C6mim]Cl, promoted an increase of lipase activity; while, [C8mim]Cl, depending on its concentration, maintained or decreased the enzyme activity. In the presence of ILs with longer cation alkyl chain length, i.e., [C10mim]Cl and [C12mim]Cl, the lipase relative activity was reduced with 0.1 (%v/v) and until suppressed ([C12mim]Cl at 0.3 (%v/v)) as a result of irreversible changes in its secondary structure. Fluorescence and circular dichroism spectroscopy analysis confirmed the results achieved. These findings show that [Cnmim]Cl-based ILs can exert different behavior on the lipase' activity (enhance, maintain or even inhibit) and structural conformation, depending on the cation alkyl chain length and their relative concentration.

Effect of Imidazolium-Based Ionic Liquids on the Structure and Stability of Stem Bromelain: Concentration and Alkyl Chain Length Effect.

In the present work, changes in the structure and stability of stem bromelain (BM) are observed in the presence of a set of four imidazolium-based ionic liquids (ILs) such as 1-ethyl-3-methylimidazolium chloride ([Emim][Cl]), 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]), 1-hexyl-3-methylimidazolium chloride ([Hmim][Cl]), and 1-decyl-3-methylimidazolium chloride ([Dmim][Cl]), using various biophysical techniques. Fluorescence spectroscopy is used to observe the changes taking place in the microenvironment around the tryptophan (Trp) residues of BM and its thermal stability because of its interactions with the ILs at different concentrations. Near-UV circular dichroism results showed that the native structure of BM remained preserved only at lower concentrations of ILs. In agreement with these results, dynamic light scattering revealed the formation of large aggregates of BM at higher concentrations of ILs, indicating the unfolding of BM. In addition to this, the results also show that higher alkyl chain length imidazolium-based ILs have a more denaturing effect on the BM structure as compared to the lower alkyl chain length ILs because of the increased hydrophobic interaction between the ILs and the BM structure. Interestingly, it is noted that low concentrations (0.01-0.10 M) of short alkyl chain ILs only alter the structural arrangement of the protein without any significant effect on its stability. However, high concentrations of all five ILs are found to disrupt the structural stability of BM.

Effect of imidazolium-based ionic liquids with varying carbon chain lengths on Arabidopsis thaliana: Response of growth and photosynthetic fluorescence parameters

As green and novel solvents, ionic liquids (ILs) are popular in many industries, which may threaten ecosystems. The effects of three imidazolium-based ILs with different alkyl chain lengths, including 1-octyl-3-methylimidazolium chloride ([C8mim]Cl), 1-decyl-3-methylimidazolium chloride ([C10mim]Cl), and 1-dodecyl-3-methylimidazolium chloride ([C12mim]Cl) on growth and photosystem of Arabidopsis thaliana were investigated. Root length, fresh weight, cell membrane permeability, and chlorophyll content of whole plant were significantly affected by ILs. Vein clearing, leaf chlorosis, and browning on the A. thaliana leaf abaxial surface occurred, with a dose-response relationship. The effect of ILs on whole plant increased with alkyl chain lengths. Chlorophyll fluorescence parameters of photosynthetic system II (PSII) were all affected in [C8mim]Cl and [C10mim]Cl treatments, electron-transfer was blocked, and photochemical energy conversion was damaged. There were no significant changes in chlorophyll fluorescence of newly-growing leaves in [C12mim]Cl treatment, but has severe effect on aged leaves. The number and size of starch granules and osmiophilic globules increased, plasmolysis and the chloroplast swelling occurred in [C8mim]Cl, [C10mim]Cl treatments and on aged leaves in [C12mim]Cl treatment, but no significant damages occurred on newly-growing leaves of [C12mim]Cl treatment, perhaps due to plant self-protection of plant. The results indicating the appropriate use of ILs is needed.

Inhibiting effect of imidazolium-based ionic liquids on the spontaneous combustion characteristics of lignite

In this study, three imidazolium-based ionic liquids (ILs) and distilled water flushing were used to treat lignite subsamples to ascertain the inhibiting effect of ILs on the spontaneous combustion characteristics of lignite. The combustion characteristics, gas generation results during decomposition, and changes in the functional groups in these IL- and water-treated coal subsamples were compared with those of untreated coal through thermogravimetry and Fourier transform infrared spectroscopy analysis. The results showed that 1,3-dimethylimidazolium iodide ([Mmim][I]) was the most capable of reducing the −OH groups in lignite and inhibiting the spontaneous combustion of lignite. Furthermore, 1-ethyl-3-methylimidazolium iodide ([Emim][I]) was the most capable of increasing the −COOH groups in lignite and reducing the maximum mass loss rate of lignite. Analysis of the recovered ILs revealed that the ILs did not substantially change after the treatment, and recovery rates higher than 92% were achieved.

Effects of imidazolium-based ionic liquids with different anions on wheat seedlings

The effects of five imidazolium ionic liquids with different anions were studied in hydroponically grown wheat seedlings at concentrations of 50, 100, 150, 200, 250, and 300 mg L−1. The results showed that shoots and roots grew shorter and dry weight decreased with increasing concentrations of ionic liquids. Moreover, the antioxidant enzyme activities decreased and malondialdehyde (MDA) content was greater in the leaves of wheat seedlings subjected to ionic liquid (IL) treatments. The order of influence of ionic liquids on these indexes was [C4mim][TfO]> [C4mim][Cl]> [C4mim][BF4]> [C4mim][Lact]> [C4mim][Ala]. A transmission electron microscope (TEM) was used to observe leaf and root cellular structures, such as chloroplast, nucleus, mitochondria, and rough endoplasmic reticulum, in wheat exposed to ionic liquids at a concentration of 150 mg L−1. The results showed that the cellular structures of wheat were affected, and the degree of the effect of five ILs was consistent with the general trend of the measured indexes in this study. Ionic liquids influence the growth of plants by impeding growth, disrupting metabolic physiology and changing cellular structures. The degree of toxicity of imidazolium-based ionic liquids with different anions varies.

Effect of Imidazolium-Based Ionic Liquids on the Interfacial Tension of the Alkane–Water System and Its Influence on the Wettability Alteration of Quartz under Saline Conditions through Contact Angle Measurements

Depleted matured reservoirs contain almost two-thirds trapped oil, which remains unrecovered even after primary and secondary oil recovery methods. Chemical enhanced oil recovery (EOR) methods involve the usage of chemical agents that improve the mobility of the residual oil by mechanisms involving alteration of wettability, viscous fingering reduction within the pay zone, and interfacial tension (IFT) between interfaces of fluids (oil/water) and rock, followed by reduced capillary forces during flooding. Chemical EOR methods need more research for high saline reservoir conditions. In this work, the effect of six imidazolium ionic liquids (ILs) on the IFT of alkane–water systems and alteration of wettability of quartz surface was investigated as a function of IL concentration (0–10000 ppm) and temperature (288.15, 298.15, 308.15, and 318.15 K). Initially, the effect of the various ILs on the IFT of the alkane–aqueous IL system was studied and compared with the neat alkane–water system. Subsequently, syner...

Effects of Imidazolium-Based Ionic Liquids on the Rheological Behavior of Heavy Crude Oil under High-Pressure and High-Temperature Conditions

The production, processing, and transportation of heavy crude oil (HCO) is difficult because of its high viscosity. For practical applications, information on the rheological behavior of HCO plays an important role, especially in flow assurance investigations. In this work, six different imidazolium ionic liquids (ILs) were tested for their effects on the rheological behavior of HCO under high-pressure and high-temperature conditions. The rheological studies were carried out at three different pressures (0.1, 5, and 10 MPa) and four experimental temperatures (298.15, 323.15, 348.15, and 373.15 K). The HCO + IL systems showed favorable viscosity reductions of 26.5% and 31.5% for the systems of HCO + 1-butyl-3-methylimidazolium chloride ([BMIM]+[Cl]−) and HCO + 1-octyl-3-methylimidazolium chloride ([OMIM]+[Cl]−), respectively, at 298.15 K and 0.1 MPa as compared to the pure HCO system. At 298.15 K and 0.1 MPa, the yield stress of the HCO + IL systems was reduced by about 15–20%, whereas when the temperature...

The acute toxic effects of imidazolium-based ionic liquids with different alkyl-chain lengths and anions on zebrafish (Danio rerio)

With the increasing applications of ionic liquids (ILs), the toxicity of ILs has drawn increasing attention in recent years, especially the influences of different anions and alkyl-chain lengths on the acute toxicity to aquatic organisms. We performed a study on the acute toxicity of 1-alkyl-3-methylimidazolium nitrate ([Cnmim]NO3 (n=2, 4, 6, 8, 10, 12)), 1-hexyl-3-methylimidazolium ILs ([C6mim]R (R=Cl–, Br–, BF4–, PF6–)) to zebrafish (Danio rerio). We also evaluated the sensibility of the investigated animals and the stability of ILs in water via high performance liquid chromatography (HPLC, Agilent 1260, Agilent Technologies Inc., USA) to prove the reliability of the present study. The results illustrated that the test zebrafish (Danio rerio) were sensitive to the reference toxicant and that the investigated ILs in water were stable. The 50% lethal concentration (LC50) was used to represent the acute toxicity to zebrafish (Danio rerio). The present study showed that the highest toxic IL is [C12mim]NO3 and the lowest toxic IL is [C2mim]NO3 on Danio rerio. The LC50s for ILs with different anions had similar values. Accordingly, we believe that ILs with different alkyl-chain lengths cause greater effects than other anions on acute toxicity to aquatic organisms. Furthermore, the present study can also provide scientific methods for future studies to select and assess ILs.

Thermo-responsive triblock copolymer phase transition behaviour in imidazolium-based ionic liquids: Role of the effect of alkyl chain length of cations

Different biophysical techniques such as fluorescence spectroscopy, dynamic light scattering (DLS), viscosity (η) and Fourier transform infrared (FTIR) spectroscopy have been carried out to characterize the effect of imidazolium-based ionic liquids (ILs) on the thermo-responsive triblock copolymer, poly(ethylene glycol)-block-poly(propylene glycol)-block-poly-(ethylene glycol) (PEG-PPG-PEG). In addition, to demonstrate the distinct morphological changes of various self-assembled morphologies, we further employed field emission scanning electron microscope (FESEM). To investigate the effect of alkyl chain length of the cation, concentration of the ILs and the related Hofmeister series on the phase behaviour of PEG-PPG-PEG, we used a series of ILs possessing same Cl− anion and a set of cation [Cnmim]+ with increasing alkyl chain length of cation such as 1-ethyl-3-methylimidazolium chloride ([Emim][Cl]), 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]), 1-hexyl-3-methylimidazolium chloride ([Hmim][Cl]) and 1-decyl-3-methylimidazolium chloride ([Dmim][Cl]). The critical micellization temperature (CMT) of the copolymer in the presence of well hydrated cations is directly correlated to their hydration. The overall specific ranking of ILs in decreasing the CMT of PEG-PPG-PEG in aqueous solution was [Emim][Cl]>[Bmim][Cl]>[Hmim][Cl]>[Dmim][Cl]. The trend of these ILs followed the well-known Hofmeister series of cations of ILs. The present study provides important information about the solution properties that can be helpful to tune the IL or temperature-sensitive copolymer CMT and micelle shapes which are crucial for understanding the drug delivery mechanisms.

Effect of imidazolium-based ionic liquids on the aggregation behavior of twin-tailed cationic gemini surfactant in aqueous solution

ABSTRACTMicellization behavior of the twin-tailed surfactants can be modulated by the addition of various modifiers. Ionic liquids (ILs) are one of them and are documented here. The beauty of these environmentally benign neoteric molecules lies in their structural versatility. Here, we have investigated the effect of three ILs: 1-butyl-3-methylimidazolium bromide ([C4mim][Br]), 1-hexyl-3-methylimidazolium bromide ([C6mim][Br]), and 1-octyl-3-methylimidazolium bromide ([C8mim][Br]) on the aggregation and surface adsorption behavior of cationic gemini surfactant, bis(hexadecyldimethyl ammonium)propane dibromide (16-3-16) through experimentally measured electrical conductivities, surface tensions, and by spectral methods (UV-vis absorbance and fluorescence measurements). The main focus of the study is to observe the effect of added ILs on the critical micelle concentration (cmc), various surface parameters, aggregation number, and size of the aggregates of gemini surfactant. The results show that the more hydrophobic ILs, that is, [C6mim][Br] and [C8mim][Br] behave as electrolyte at lower concentration and cosurfactant at higher concentration, whereas moderately hydrophobic IL [C4mim][Br] acts as an electrolyte at all concentration ranges studied. The modulating effects of ILs were also compared with conventional electrolyte (NaBr) at similar conditions.

Time-dependent effects of [apyr]BF4 and key contributors to their mixture stimulation on Vibrio qinghaiensis sp.-Q67 at apical and biochemical levels

Earlier reports studied the time-dependent effects of imidazolium-based ionic liquids ([amim]X) in the aspect of biochemical explanation and that of key contributor in mixture effects. Presently, the effects of N-alkylpyridinium-based ILs ([apyr]BF4) were studied combining the above two aspects, i.e., the time-dependent effects of [bpyr]BF4, [hpyr]BF4 and [opyr]BF4 on luminescence and biochemical indicators in Vibrio qinghaiensis sp.-Q67, and those of the mixtures. In individual results, the inhibition on luminescence increased over concentrations and the side chain length, showing concentration- and side chain-dependence. Moreover, the inhibition of [apyr]BF4 decreased from 0.25 to 24h, showing a time-dependence. Notably, [hpyr]BF4 stimulated the luminescence at 24h. The biochemical effects, including inhibition and stimulation, were well correlated to those on luminescence. In mixture results, the inhibition on luminescence was lower than the predicted effects by concentration addition model which was based on individual results. Moreover, the mixture stimulation on luminescence was significantly higher than individual ones, and the mixture stimulation on biochemical indicators was even greater than that on luminescence. In mixture effects, [bpyr]BF4 was the positive contributor, and [hpyr]BF4 was the negative contributor. Similarities and differences between [amim]X and [apyr]BF4 indicated underlying mechanisms of the commonly observed hormetic effects of ionic liquids.