Antagonistic Salts Research Articles

Single gold nanowires with ultrahigh (>104) aspect ratios by triphasic electrodeposition.

Due to their superior optical and electrical properties, gold nanowires are used ubiquitously across industries. Current techniques for fabricating such structures are often expensive, involving multiple steps, cleanroom operation, and limited ability for a user to controllably place a nanowire at a desired location. Here, we introduce the concept of triphasic electrodeposition, where metal salts act as antagonistic salts at the liquid|liquid interface, leading to their increased concentration at this phase boundary. We show that the electrodeposition of ultra-high aspect ratio gold nanowires may be achieved in a one-step, one-pot method by submerging a conductor in contact with two phases: an organic phase containing HAuCl4 and a quaternary ammonium salt, and an aqueous phase containing potassium chloride. Changing electrodeposition parameters in the triphasic system allows tunability of important features of the nanowire, such as size and thickness. Furthermore, this new method provides an impressive ability to choose the geometry and precise positioning of deposited nanowires simply by changing where a liquid|liquid interface contacts the electrode surface.

Surface tension between liquids containing antagonistic and regular salts.

We investigate theoretically the surface tension between two immiscible liquids containing antagonistic and regular salts. The mean-field model includes the electrostatic energy and the Gibbs transfer energy of the ions. We find the Donnan potential difference between the liquids and solve the Poisson-Boltzmann equation to calculate the potential and ion density profiles. When the liquids contain only a regular salt, the surface tension increases when compared to the no-salt case; in contrast, the surface tension is reduced when they contain only an antagonistic salt. When both salts are present, the surface tension can either further decrease or increase depending on the preferential solvation of the ions, in agreement with published experimental observations.

Using Microemulsions: Formulation Based on Knowledge of Their Mesostructure.

Microemulsions, as thermodynamically stable mixtures of oil, water, and surfactant, are known and have been studied for more than 70 years. However, even today there are still quite a number of unclear aspects, and more recent research work has modified and extended our picture. This review gives a short overview of how the understanding of microemulsions has developed, the current view on their properties and structural features, and in particular, how they are related to applications. We also discuss more recent developments regarding nonclassical microemulsions such as surfactant-free (ultraflexible) microemulsions or ones containing uncommon solvents or amphiphiles (like antagonistic salts). These new findings challenge to some extent our previous understanding of microemulsions, which therefore has to be extended to look at the different types of microemulsions in a unified way. In particular, the flexibility of the amphiphilic film is the key property to classify different microemulsion types and their properties in this review. Such a classification of microemulsions requires a thorough determination of their structural properties, and therefore, the experimental methods to determine microemulsion structure and dynamics are reviewed briefly, with a particular emphasis on recent developments in the field of direct imaging by means of electron microscopy. Based on this classification of microemulsions, we then discuss their applications, where the application demands have to be met by the properties of the microemulsion, which in turn are controlled by the flexibility of their amphiphilic interface. Another frequently important aspect for applications is the control of the rheological properties. Normally, microemulsions are low viscous and therefore enhancing viscosity has to be achieved by either having high concentrations (often not wished for) or additives, which do not significantly interfere with the microemulsion. Accordingly, this review gives a comprehensive account of the properties of microemulsions, including most recent developments and bringing them together from a united viewpoint, with an emphasis on how this affects the way of formulating microemulsions for a given application with desired properties.

Monolayer Structures of Supramolecular Antagonistic Salt Aggregates.

The speculated presence of monomolecular lamellae of antagonistic salts in oil-water mixtures has left several open questions besides their hypothetical existence, including their microscopic structure and stabilization mechanism. Here, we simulate the spontaneous formation of supramolecular aggregates of the antagonistic salt sodium tetraphenylborate (NaBPh4) in water and 3-methylpyridine (3-MP) at the atomistic level. We show that, indeed, the lamellae are formed by a monomolecular layer of the anion, enveloped by 3-MP and hydrated sodium counterions. To understand which thermodynamic forces drive the aggregation, we compare the full-atomistic model with a simplified one for the salt and show that the strong hydrophobic effect granted by the large excluded volume of the anion, together with electrostatic repulsion, suffice to explain the stability of the monomolecular lamellae.

The Vanishing water/oil interface in the presence of antagonistic salt.

Antagonistic salts are salts that consist of hydrophilic and hydrophobic ions. In a binary mixture of water and an organic solvent, these ions preferentially dissolve into different phases. We investigate the effect of an antagonistic salt, tetraphenylphosphonium chloride PPh4 +Cl-, in a mixture of water and 2,6-lutidine by means of Molecular Dynamics (MD) simulations. For increasing concentrations of the salt, the two-phase region is shrunk and the interfacial tension in reduced, in contrast to what happens when a normal salt is added to such a mixture. The MD simulations allow us to investigate in detail the mechanism behind the reduction of the surface tension. We obtain the ion and composition distributions around the interface and determine the hydrogen bonds in the system and conclude that the addition of salt alters the hydrogen bonding.

Detection of Water-in-Oil Droplet Formation within an Interfacial Region Formed by an Aqueous/1, 2-Dichloroethane Interface Using Transient Cell Impedance Measurements at a Single High Frequency

The detection of water-in-oil (w/o) droplet formation within an interfacial region formed by an interface between an aqueous phase and 1,2-DCE using transient impedance measurements in an unconventional electrochemical cell is herein reported. Droplet formation causes a large peak-like increase in transient real cell impedance. Peaks are likely caused by significant decrease in ion concentration within the interfacial region by formation of w/o droplets containing electrolyte. Droplet formation and an accompanying interfacial stability was observed when antagonistic salts (consisting of a hydrophobic ion of $${\rm{\Delta }}G_{{\rm{tr}}}^{^ \circ ,{\rm{water}} \to 1,2 - {\rm{DCE}}} \le $$ TBA+) were mixed with conventional aqueous electrolytes in the aqueous phase. The instability manifests as Marangoni convection, causing rapid mass transport in the adjacent fluid on both sides of the liquid/liquid interface.

How antagonistic salts cause nematic ordering and behave like diblock copolymers.

We present simulation results and an explanatory theory on how antagonistic salts affect the spinodal decomposition of binary fluid mixtures. We find that spinodal decomposition is arrested and complex structures form only when electrostatic ion-ion interactions are small. In this case, the fluid and ion concentrations couple and the charge field can be approximated as a polynomial function of the relative fluid concentrations alone. When the solvation energy associated with transferring an ion from one fluid phase to the other is of the order of a few kBT, the coupled fluid and charge fields evolve according to the Ohta-Kawasaki free energy functional. This allows us to accurately predict structure sizes and reduce the parameter space to two dimensionless numbers. The lamellar structures induced by the presence of the antagonistic salt in our simulations exhibit a high degree of nematic ordering and the growth of ordered domains over time follows a power law. This power law carries a time exponent proportional to the salt concentration. We qualitatively reproduce and interpret neutron scattering data from previous experiments of similar systems. The dissolution of structures at high salt concentrations observed in these experiments agrees with our simulations, and we explain it as the result of a vanishing surface tension due to electrostatic contributions. We conclude by presenting 3D results showing the same morphologies as predicted by the Ohta-Kawasaki model as a function of volume fraction and suggesting that our findings from 2D systems remain valid in 3D.

Membrane Formation in Liquids by Adding an Antagonistic Salt

Antagonistic salts are composed of hydrophilic and hydrophobic ions. In a binary mixture, such as water and organic solvent, these ion pairs preferentially dissolve to those phases, respectively, and there is a coupling between the charge density and the composition. The heterogeneous distribution of ions forms a large electric double layer at the interface between these solvents. This reduces the interfacial tension between water and organic solvent, and stabilizes an ordered structure, such as a membrane. These phenomena have been extensively studied from both theoretical and experimental point of view. In addition, the numerical simulations can reproduce such ordered structures.

Salt-induced microheterogeneities in binary liquid mixtures.

The salt-induced microheterogeneity (MH) formation in binary liquid mixtures is studied by small-angle x-ray scattering (SAXS) and liquid state theory. Previous experiments have shown that this phenomenon occurs for antagonistic salts, whose cations and anions prefer different components of the solvent mixture. However, so far the precise mechanism leading to the characteristic length scale of MHs has remained unclear. Here, it is shown that MHs can be generated by the competition of short-ranged interactions and long-ranged monopole-dipole interactions. The experimental SAXS patterns can be reproduced quantitatively by fitting to the derived correlation functions without assuming any specific model. The dependency of the MH structure with respect to ionic strength and temperature is analyzed. Close to the demixing phase transition, critical-like behavior occurs with respect to the spinodal line in the phase diagram.

Are antagonistic salts surfactants?

It is well known that surfactants decrease both water/air and water/oil interfacial tensions whereas in contrast inorganic salts increase both. We study a new, third class of surface-active ionic solutes, which have been called antagonistic salts, consisting of an organic group with a small inorganic counterion. These show decreased interfacial tension at the oil/water interface due to a redistribution of the organic group in the oil but do not show any surface activity at the air/water interface and are consequently different from surfactants that lower both tensions. We use a simple modeling using Poisson-Boltzmann theory that accounts for the surface activity of the antagonistic salt at the water/oil interface.

A Test Method for Evaluating Water Conditioning Adjuvants

Abstract Glyphosate is a weak acid herbicide and can bind with antagonistic salts in the spray carrier. Diammonium sulfate (AMS) is commonly used as an adjuvant with glyphosate to enhance activity and overcome antagonistic salts. Water conditioning (WC) adjuvants are used at low rates and are used as AMS replacement adjuvants. However, an ASTM approved method for testing WC adjuvants has not been established. Appropriate research parameters were used to test the water conditioner definition. Glyphosate plus NIS and glyphosate plus AMS and nonionic surfactant (NIS) were used as standards from comparing WC adjuvants. WC were compared to NIS and AMS plus NIS to determine the potential to reduce or eliminate antagonism between glyphosate and antagonistic cations. Velvetleaf was a good indicator to show antagonism, the ability for AMS and WC adjuvants to overcome antagonism, and also show greater bioefficacy. Velvetleaf, a mixture of broadleaf species, and a mixture of grass species all showed similar response to WC adjuvants. Studies to test water conditioning adjuvants were conducted at multiple locations provided a high degree of precision.

Optimizing MCPA (K-salt) activity with adjuvants

MCPA [2-methyl-4-chloro phenoxy acetic acid] is applied with various water sources containing antagonistic salts. It is applied without an adjuvant but is often mixed with bromoxynil for a broader spectrum of weeds. MCPA (K-salt) was applied in carriers containing calcium chloride and sodium bicarbonate. Ammonium salts and other adjuvants were tested to overcome possible antagonism. Control of Fallopia convolvulus with MCPA was decreased with the calcium chloride as carrier but not when sodium bicarbonate was the carrier. Ammonium sulphate and ammonium nitrate overcame the calcium chloride antagonism and ammonium bicarbonate partially overcame the antagonism. Ammonium hydroxide and potassium chloride could not overcome calcium chloride antagonism, even in the presence of other adjuvants. An alkylated phenol-ethylene oxide surfactant could not overcome antagonism when applied in the absence of ammonium nitrate. Calcium chloride antagonism of MCPA in a mixture with a bromoxynil formulation blank was similar to the antagonism of MCPA applied alone. Both a petroleum oil/nonionic surfactant blend and the alkylated phenol-ethylene oxide surfactant reduced the ability of ammonium bicarbonate to overcome calcium chloride antagonism. MCPA (K-salt) should be registered with ammonium sulphate or ammonium nitrate in areas with hard water.

Optimizing Adjuvants to Overcome Glyphosate Antagonistic Salts

Glyphosate toxicity to wheat was antagonized more by calcium chloride than sodium bicarbonate. Mixtures of the salts at greater than 100 mg L−1sodium bicarbonate and 200 mg L−1calcium chloride were additive in antagonism of glyphosate in the greenhouse experiments. Surfactant and oil adjuvants did not overcome sodium bicarbonate or calcium chloride antagonism of glyphosate. Oil adjuvants were generally antagonistic to glyphosate. An equation is presented that determines the amount of diammonium sulfate required to overcome glyphosate antagonism based upon the sodium, potassium, calcium, and magnesium cations in the spray carrier.

Influence of diammonium sulfate and other salts on glyphosate phytotoxicity

AbstractDiammonium sulfate is commonly used as an adjuvant with glyphosate, but reports vary regarding its effect on weed control, and its possible function in enhancing glyphosate phytotoxicity is not fully understood. Several experiments were conducted in the glasshouse to determine glyphosate phytotoxicity to various species as influenced by diammonium sulfate in distilled water and in the presence of antagonistic salts. Diammonium sulfate overcame sodium hydrogen carbonate, calcium chloride, and 2,4‐D antagonism of glyphosate phytotoxicity to wheat (Triticum aestivum L.). Sulfate anions were important for overcoming calcium antagonism, possibly by forming calcium sulfate. Scanning electron micrographs of spray droplets of glyphosate with calcium chloride and diammonium sulfate indicated the presence of crystals, presumed to be calcium sulfate, that were independent of the glyphosate deposit. Diammonium sulfate may also provide ammonium ions to form effective glyphosate‐ammonia complexes rather than less effective calcium, sodium, diethylamine, or other cation complexes. Diammonium sulfate also may influence susceptibility to glyphosate by affecting herbicide absorption into foliage of certain species. Glyphosate phytotoxicity to sunflower (Helianthus annuus L.) was increased whereas phytotoxicity to kochia [Kochia scoparia (L.) Schrad.] and soybean [Glycine max (L.) Merr.] was reduced by diammonium sulfate applied in the absence of antagonistic salts; diammonium sulfate apparently has several functions as an adjuvant with glyphosate.

Salt Antagonism of Glyphosate

Glyphosate is often applied with diammonium sulfate to increase weed control. However, many other salts in the spray carrier have antagonized glyphosate phytotoxicity. Research was conducted with wheat as a bioassay species to further determine the influence of various salts on glyphosate phytotoxicity. Cation antagonism of glyphosate occurred with iron > zinc > calcium ≥ magnesium > sodium > potassium. Ammonium cation with hydroxide or most other anions was not antagonistic. Anions of ammonium compounds were of primary importance in overcoming glyphosate antagonistic salts, while the ammonium cation was neutral or slightly stimulatory with certain anions. Sulfate, phosphate, citrate, and acetate anions were not antagonistic, but nitrate and chloride anions were slightly antagonistic when applied as ammonium salts or acids. Antagonism of glyphosate action by sodium bicarbonate and calcium chloride was overcome by phosphoric, sulfuric, and citric acid and phosphate, sulfate, and citrate ammonium salts. Acid and ammonium salts of nitrate and chloride were more effective in overcoming sodium bicarbonate than calcium chloride antagonists of glyphosate. Ferric sulfate antagonism was overcome only by citric, partly by phosphoric and sulfuric but not by nitric and hydrochloric acids or their ammonium salts. Acetic acid, ammonium acetate, and ammonium hydroxide did not overcome any salt antagonism of glyphosate. Glyphosate response to salts was independent of spray carrier pH.

THE ANTAGONISTIC ACTION BETWEEN SALTS ON THE SURFACE TENSION OF ORGANIC COLLOIDAL SOLUTION

Journal Article THE ANTAGONISTIC ACTION BETWEEN SALTS ON THE SURFACE TENSION OF ORGANIC COLLOIDAL SOLUTION Get access TETSUTARO TADOKORO TETSUTARO TADOKORO Institute of Agrcultural Chemistry of Hokkaido Imperial UniversitySapporo Search for other works by this author on: Oxford Academic PubMed Google Scholar The Journal of Biochemistry, Volume 2, Issue 2, January 1923, Pages 361–365, https://doi.org/10.1093/oxfordjournals.jbchem.a125855 Published: 01 January 1923 Article history Received: 07 December 1922 Published: 01 January 1923