A straightforward method for visualization and quantification of surfactant effectiveness within different electrolyte environments based on using reconfigurable Janus emulsions as novel optical ...probes is reported. More specifically, we investigated the effect of different types and concentrations of salt counter-ions on the surfactant surface excess of commercial ionic and non-ionic surfactants, namely sodium dodecyl sulfate (SDS) and Tween 80 via in situ monitoring the morphological reconfigurations of biphasic Janus emulsions comprising hydrocarbon and fluorocarbon oils. We find that significant variations in interfacial tensions of SDS-stabilized interfaces (up to 15 mN·m–1) can be evoked by titrating mono-, di-, and trivalent cationic counter-ions, which is coherent with the lyotropic (Hofmeister) series. In contrast, the salt counter-ion effect on the surfactant effectiveness was less pronounced for the non-ionic surfactant Tween 80 (∼3 mN·m–1). Our results reveal a facile in situ method for monitoring the central role of electrolyte type and concentration on surfactant effectiveness and, more broadly, illustrate that Janus emulsions serve as powerful optical probes to dynamically study the properties of surfactants at liquid interfaces. We demonstrate the utility of our findings for an electro-induced morphological reconfiguration of Janus droplet morphologies by dynamically tuning Cu2+ concentration in solution using an electrode setup. The latter provides a unique platform for liquid-phase, real-time, and continuous tuning of Janus droplet morphologies, e.g., for their application in sensing and dynamic optical device platforms.
The cationic content of water represents a major quality control parameter that needs to be followed by a rapid, on-site, and low-cost method. Herein, we report a novel method for a facile monitoring ...of the mineral content of drinking water by making use of responsive complex emulsions. The morphology of biphasic oil-in-water droplets solely depends on the balance of interfacial tensions, and we demonstrate that changes in the surfactant effectiveness, caused by variations in the mineral content inside the continuous phase, can be visualized by monitoring internal droplet shapes. An addition of metal cations can significantly influence the surfactant critical micelle concentrations and the surface excess values and therefore induce changes in the effectiveness of ionic surfactants, such as sodium dodecyl sulfate. The morphological response of Janus emulsions droplets was tracked via a simple microscopic setup. We observed that the extent of the droplet response was dependent on the salt concentration and valency, with divalent cations (responsive for water hardness), resulting in a more pronounced response. In this way, Ca2+ and Mg2+ levels could be quantitatively measured, which we showcased by determination of the mineral content of commercial water samples. The herein demonstrated device concept may provide a new alternative rapid monitoring of water hardness levels in a simple and cost-effective setup.
Due to their appealing physiochemical properties, particularly in the pharmaceutical industry, deep eutectic solvents (DESs) and ionic liquids (ILs) are utilized in various research fields and ...industries. The presented research analyzes the thermodynamic properties of a deep eutectic solvent created from natural molecules, menthol and lauric acid in a 2:1 molar ratio, and an ionic liquid based on two active pharmaceutical ingredients, benzocainium ibuprofenate. Initially, the low solubility of benzocainium ibuprofenate in water was observed, and a hydrophobic natural deep eutectic mixture of menthol:lauric acid in a 2:1 ratio was prepared to improve benzocainium ibuprofenate solubility. In order to determine the solvent properties of DESs and ILs mixtures at different temperatures and their molecular interactions to enhance the solvent performance, the apparent molar volume, limiting apparent molar expansibility, and viscosity B coefficient were estimated in temperature range from 293.15 K to 313.15 K and varying concentration of benzocainium ibuprofenate.
A series of 1-alkyl-3-vinylimidazolium-based ionic liquids (ILs) and salts that carry unsaturation in the head group on cation, (C n CCimBr, n = 2, 4, 6, 8, 10, and 12), were synthesized and ...characterized in the current study. Differential scanning calorimetry and thermogravimetric analysis were used to determine the thermal behavior and evaluate the phase changes of all the obtained ionic compounds. Further investigation was focused on ILs (C n CCimBr, n = 4, 6, and 8) and their dependence of temperature for density, electrical conductivity, and viscosity. The data were collected within the temperature range T = 293.15–343.15 K and at atmospheric pressure (p = 0.1 MPa). The transport properties for three ILs were analyzed using the Vogel–Fulcher–Tammann equation. The correlation between viscosity and molar conductivity has been examined using the Walden rule and ionicity, which indicates that the investigated ILs are found in the largest percentage in the form of ion pairs. The obtained experimental data were compared with the available values from the literature for their corresponding saturated counterparts elucidating the impact of the double bond.
The present work focuses on modifying a local anaesthetic drug procaine into an ionic liquid and evaluating the resulting thermal behaviour and structural changes. Counter ions, salicylate, ...ibuprofenate, and docusate, were chosen due to different hydrogen-bonding abilities, molecular size, charge distribution, and functional groups. After synthesis of procaine salicylate, procaine ibuprofenate, and procaine docusate, spectroscopic investigations were performed using infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy to confirm proton transfer. Differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis were used to determine the obtained ionic liquids' thermal behaviour. Experimental measurements of density, viscosity, and electrical conductivity were performed to get insight into the interactions occurring in the obtained ionic liquids. The viscosity and electrical conductivity data were analysed using the Vogel-Fulcher-Tammann (VFT) equation, while thermal expansion coefficients were calculated from measured density data. The obtained results found that the synthesised procaine salicylate and procaine docusate an ionic liquid's behaviours, including weak intermolecular forces, while procaine ibuprofenate showed more liquid co-crystal behaviour due to the absence of proton transfer for ibuprofen. In a theoretical phase of the investigation, the density functional theory (DFT) and molecular dynamics (MD) calculations were conducted. The obtained descriptors and radial distribution functions were used to analyse the interactions between ions of synthesised ionic liquids. In addition, solubility determination results proved that procaine transformation into procaine salicylate and procaine ibuprofenate ionic liquids enhanced its solubility in water, while procaine docusate reduces procaine solubility.
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The influence of gemini surfactants (GSs) on the charging and aggregation features of anionic sulfate modified latex (SL) particles was investigated by light scattering techniques in aqueous ...dispersions. The GSs of short alkyl chains (2-4-2 and 4-4-4) resembled simple inert salts and aggregated the particles by charge screening. The adsorption of GSs of longer alkyl chains (8-4-8, 12-4-12, and 12-6-12) on SL led to charge neutralization and overcharging of the particles, giving rise to destabilization and restabilization of the dispersions, respectively. The comparison of the interfacial behavior of dimeric and the corresponding monomeric surfactants revealed that the former shows a more profound influence on the colloidal stability due to the presence of double positively charged head groups and hydrophobic tails, which is favorable to enhancing both electrostatic and hydrophobic particle–GS and GS–GS interactions at the interface. The different extent of the particle–GS interactions was responsible for the variation of the GS destabilization power, following the 2-4-2 < 4-4-4 < 8-4-8 < 12-4-12 order, while the length of the GS spacer did not affect the adsorption and aggregation processes. The valence of the background salts strongly influenced the stability of the SL-GS dispersions through altering the electrostatic interactions, which was more pronounced for multivalent counterions. These findings indicate that both electrostatic and hydrophobic effects play crucial roles in the adsorption of GSs on oppositely charged particles and in the corresponding aggregation mechanism. The major interparticle forces can be adjusted by changing the structure and concentration of the GSs and inorganic electrolytes present in the systems.
The rapid and sensitive voltammetric determination of organic UV filters benzophenone-3 (BP-3) and avobenzone (AVO) was performed by an ionic liquid carbon paste electrode (IL-CPE). Namely, the ...synthesized pyridinium-based ILs, 1-butyl-3-methylpyridinium chloride (N–C4–3C1PyCl) and 1-ethoxyethyl-3-methylpyridinium chloride (N–C2OC2–3C1PyCl) were compared as bulk CPE modifiers for BP-3 determination. N–C4–3C1PyCl-CPE showed more favorable interactions with the target analyte, and it was tested for AVO determination, too. Cyclic voltammetric (CV) studies suggested that the irreversible electrode reaction is adsorption controlled in the case of both UV filters. Also, the square-wave adsorptive stripping voltammetric (SW-AdSV) method was optimized for quantifying selected UV filters. In the model solutions, the linear calibration curve was obtained by the SW-AdSV method in the concentration range from 0.05 to 0.89 μg mL−1 at pH 3.0 for BP-3 (Eacc = −0.7 V, tacc = 100 s), and from 0.05 to 1.77 μg mL−1 at pH 11.98 for AVO (Eacc = 0.2 V, tacc = 100 s). The evaluated limit of detection (LOD) was 0.015 μg mL−1 in both cases, while the relative standard deviation (RSD) was lower than 1.5%. The affordable IL-based voltammetric sensor fulfills the main requirements for application in real samples due to an adequate selectivity towards selected analytes in the presence of interferents usually found in swimming pool water. Therefore, the BP-3 and AVO were quantified in a swimming pool water matrix with good repeatability and recovery. The obtained results demonstrate an excellent potential of the IL-CPEs, especially of the N–C4–3C1PyCl-CPE, for determining selected UV filters in various real samples.
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•Pyridinium-based ionic liquids were used for carbon paste electrode modification.•Simple and reliable SW-AdSV method for selected UV filters sensing was developed.•Achieved LOD for benzophenone-3 (BP-3) and avobenzone (AVO) was 0.015 μg mL−1.•N–C4–3C1PyCl-CPE enables determination of BP-3 and AVO in swimming pool water sample.•Good repeatability and high selectivity towards UV filters sensing were obtained.
•Aqueous solutions of metformin and artificial sweeteners of varying molalities were created.•Density, sound velocity and viscosity measurements of the solutions were performed from 278.15 to ...318.15 K.•Metformin solutions with Na-saccharin and acesulfame-K behave differently.•Metformin has strong interactions with water, acts as a structure maker in all three systems.•The addition of artificial sweeteners did not significantly improve taste.
Measurements of the density, sound velocity, and viscosity of metformin hydrochloride (MetHCl) solutions in water and 0.1 mol∙kg−1 aqueous solution of sodium saccharin (Na-Sah) and acesulfame potassium (Ace-K) were carried out over the concentration range up ∼ 0.16 mol∙kg−1 to MetHCl at nine temperatures T = (278.15, 283.15, 288.15, 293.15, 298.15, 303.15, 308.15, 313.15, 318.15) K. Several physicochemical properties of these systems were determined from the experimental data, including apparent molar volumes, apparent molar volumes at infinite dilution, finite apparent molar volumes of transfer, apparent specific volumes at infinite dilution, apparent molar isentropic compressibility at infinite dilution, hydration numbers, viscosity B coefficients, and thermodynamic parameters of viscous flow. The results were further discussed in terms of solute–solvent and solute–solute interactions to enlighten the interactions of metformin with artificial sweeteners in water and the possibility that artificial sweeteners mask the bitter taste of metformin.
1-butyl-3-ethylimidazolium bromide ionic liquid, beimBr, was studied experimentally and theoretically as a potential inhibitor of copper corrosion in acidic media (pH = 3) by dc polarization, quartz ...crystal microbalance (QCM), scanning electron microscopy (SEM) and density functional theory (DFT). This ionic liquid is selected to study an effect of the alkyl chain length at the position N-3, since so far only ionic liquids with different alkyl substituents at the position N-1 are investigated. Improved inhibitory properties of the investigated ionic liquid against corrosion of copper in acidic solution at the given conditions are confirmed comparing to corresponding 1-butyl-3-methylimidazolium bromide ionic liquid. It is found that beimBr acts as a cathodic corrosion inhibitor, whereby its effectiveness depends on the applied concentration. The inhibitory effect of the studied ionic liquid (IL) was achieved through quick and spontaneous adsorption on the copper surface following the Langmuir's adsorption isotherm. Results obtained by SEM showed that copper protection is achieved through the less damaged copper surface in the presence of inhibitor. Applying DFT calculations, it is found that interactions with the metal surface occur by donating electron from the Br− anion to the copper. Based on the obtained Fukui functions influence of the inductive effect of ethyl/methyl group on the inhibitory activity is also discussed.
•Effect of the alkyl chain length at the position N-3 of the imidazolium ion on the Cu corrosion is studied.•Good inhibitory properties of beimBr against copper corrosion confirmed.•Inhibitor protects the copper surface during physisorption process.•Langmuir's adsorption isotherm is followed.•Influence of inductive effect of ethyl group at position N-3 is discussed.
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Ion specific effects on the charging and aggregation features of zein nanoparticles (ZNP) were studied in aqueous suspensions by electrophoretic and time-resolved dynamic light ...scattering techniques. The influence of mono- and multivalent counterions on the colloidal stability was investigated for positively and negatively charged particles at pH values below and above the isoelectric point, respectively. The sequence of the destabilization power of monovalent salts followed the prediction of the indirect Hofmeister series for positively charged particles, while the direct Hofmeister series for negatively charged ones assumed a hydrophobic character for their surface. The multivalent ions destabilized the oppositely charged ZNPs more effectively and the aggregation process followed the Schulze-Hardy rule. For some multivalent ions, strong adsorption led to charge reversal resulting in restabilization of the suspensions. The experimental critical coagulation concentrations (CCCs) could be well-predicted with the theory developed by Derjaguin, Landau, Verwey and Overbeek indicating that the aggregation processes were mainly driven by electrical double layer repulsion and van der Waals attraction. The ion specific dependence of the CCCs is owing to the modification of the surface charge through ion adsorption at different extents. These results are crucial for drug delivery applications, where inorganic electrolytes are present in ZNP samples.
