Effects Of Multivalent Cations Research Articles

Exploring multivalent cations-based electrolytes for CO2 electroreduction

Electrochemical reduction of CO2 (CO2RR) to value-added chemicals is a promising, potentially carbon-neutral alternative to the existing thermochemical fossil fuels-based, carbon-positive chemical manufacturing processes. The CO2 electrolysis field has devoted significant attention to the effects of electrolyte composition and concentration on the rates and selectivities of the desired products; however, the effects of multivalent cations have not been widely studied. Here, we explore the feasibility of using multivalent cations-based electrolytes to intensify CO2RR electrochemical performance. We provide experimental evidence that electrolytes containing multivalent cations, in contrast to those containing monovalent alkali metal cations, hinder the rates and selectivities for CO production on Ag nanoparticles. To explain these trends, we explore the possible origin of the reduced CO2RR performance in the presence of multivalent cations-based electrolytes. Using a combination of electrochemical (electrochemical impedance spectroscopy) and physicochemical (grazing incidence X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy) characterization methods, we provide evidence that in the presence of multivalent cations metal oxides and/or metal hydrides deposit on the electrode surface, possibly blocking the catalytically active sites, and thus impairing the adsorption of CO2 on the catalyst surface.

Charge reversal of sulfate latex particles in the presence of lanthanum ion

Effects of multivalent cations and its hydrolyzed forms on the charge reversal are investigated by measuring electrophoretic mobilities of three different sulfate latex particles bearing pH-independent surface charge densities as a function of LaCl3 concentration and pH. The obtained experimental results are analyzed by using a simple adsorption model including an ion-ion correlation model, intrinsic energy of adsorption for hydrolyzed La ions, and the speciation calculation of La. From the experimental electrophoretic mobilities at pH = 4 without hydrolyzed La ions, we observed that the LaCl3 concentrations at charge reversal increased with decreasing the magnitude of the latex charge density. This experimental trend can be qualitatively captured by the ionic correlation model used here. While the sulfate latex particles bear pH-independent surface charge and the LaCl3 concentration was lower than the concentration where the charge reversal took place at pH 4, the increase in pH significantly gave rise to the charge reversal at pH above 7.8 where the hydrolyzed La ions begin to form. Therefore, this charge reversal at higher pH can be assigned to the stronger adsorption of hydrolyzed La ions. In addition, we demonstrate that the simple model can capture such experimental trends of charge reversal by introducing surmised values of its intrinsic energy of adsorption. Therefore, our results confirm that the ion correlation can be a prevailing mechanism on the charge reversal at low pH, while the stronger adsorption of hydrolyzed La ions predominates to induce the reversal with increasing pH.

Role of metallic core for the stability of virus-like particles in strongly coupled electrostatics

Electrostatic interactions play important roles in the formation and stability of viruses and virus-like particles (VLPs) through processes that often involve added, or naturally occurring, multivalent ions. Here, we investigate the electrostatic or osmotic pressure acting on the proteinaceous shell of a generic model of VLPs, comprising a charged outer shell and a metallic nanoparticle core, coated by a charged layer and bathed in an aqueous electrolyte solution. Motivated by the recent studies accentuating the role of multivalent ions for the stability of VLPs, we focus on the effects of multivalent cations and anions in an otherwise monovalent ionic solution. We perform extensive Monte-Carlo simulations based on appropriate Coulombic interactions that consistently take into account the effects of salt screening, the dielectric polarization of the metallic core, and the strong-coupling electrostatics due to multivalent ions. We specifically study the intricate roles these factors play in the electrostatic stability of the model VLPs. It is shown that while the insertion of a metallic nanoparticle by itself can produce negative, inward-directed, pressure on the outer shell, addition of only a small amount of multivalent counterions can robustly engender negative pressures, enhancing the VLP stability across a wide range of values for the system parameters.

Effects of multivalent cations on aggregation behavior of poly(methacrylic acid)-grafting nylon microcapsules

A poly(1,4-piperazine- alt-terephthalic acid) (polyPT) microcapsule surface was modified by grafting poly(methacrylic acid) (polyMA). Three kinds of polymer-grafting microcapsules were prepared. These microcapsule surfaces were all negatively charged, but different in the amount of MA grafting on the polyPT microcapsules. The effects of multivalent cations (Mg 2+, Ca 2+ and La 3+) on the aggregation behavior of these polymer-grafting microcapsules were studied by using a spectrophotometer. The critical cation concentration at which aggregation of the polymer-grafting microcapsules occurs was found to depend strongly on the amount of polyMA grafted on the microcapsules as well as on the types of cations and the ionic strength and pH of the suspending media.

Effects of barium, lanthanum and gadolinium on endogenous chloride and potassium currents in Xenopus oocytes.

1. The effects of multivalent cations on membrane currents recorded from Xenopus oocytes were studied. 2. The hyperpolarization-activated chloride current was reversibly blocked by lanthanum; half-maximal block occurred at a concentration of 8 microM. Zinc, cadmium, cobalt and nickel were less potent than lanthanum, and gadolinium, manganese, barium and strontium had no effect at a concentration of 100 microM. 3. The calcium-activated chloride current was blocked by gadolinium (50 microM), and lanthanum, cadmium, cobalt, nickel and manganese were equally effective. The actions of gadolinium and lanthanum were almost irreversible, while partial (30-80%) recovery was observed with the other cations. Zinc (100 microM) had no effect. 4. In lanthanum (100 microM), membrane depolarizations from -70 mV activated an outward potassium current that was partially blocked by barium (0.1-2 mM). The barium-sensitive current was confined to potentials less negative than -70 mV. The current consisted of a time-independent as well as a time-dependent component, the latter of which had voltage dependence similar to the M-current. 5. It is proposed that lanthanum, gadolinium and barium can usefully separate these endogenous membrane currents in Xenopus oocytes.

Effects of multivalent cations on low-rank coal solubilities in alkaline solutions and microbial cultures

Microorganisms are able to solubilize low-rank coals using the mechanism of base solubilization, but a pH values of ≤8. Pretreatment of coals with HCl under nonoxidizing conditions removes organically bound multivalent cations and results in an increase in the amounts of coal solubilized either by microorganisms or in alkaline buffers. These results indicate the importance of cations in the organic structure of coal and suggest that metal complexation and removal is another mechanism used by microorganisms to solubilize low-rank coals

The effects of external potassium, multivalent cations and temperature on caffeine contractures in rat skeletal muscle.

The effects of multivalent cations, membrane potential and temperature on caffeine contractures of rat soleus and extensor digitorus longus (e.d.l.) muscles were investigated. The amplitude of the caffeine contracture was depressed by the removal of calcium and by the addition of a high concentration (1 mM) of lanthanum. Low concentrations of lanthanum (0.1-0.5 mM) augmented the caffeine contracture. Low levels of depolarization by potassium (10-40 mM) augmented the amplitude of the caffeine contracture, while higher concentrations of potassium depressed the contracture. Maximum augmentation of the caffeine contracture occurred with a higher concentration of potassium (20 mM vs 10 mM) in the e.d.l. than in the soleus muscle. The amplitude of contractures was directly related to temperature between 22 and 37 degrees C and inversely related to temperature below 22 degrees C. The effects of caffeine in rat skeletal muscle are suggested to be exerted on the sarcolemma and the mechanisms of action are by modification of the processes of activation and inactivation.

Potassium contractures and mechanical activation in rat skeletal muscle: effects of multivalent cations, temperature and tetracaine.

The effects of cations, temperature and tetracaine on potassium-induced contractures of rat soleus and extensor digitorus longus (e.d.l.) muscles were investigated. In the soleus, the threshold for the potassium contracture was lower (10-20 vs 20-40 mM), the peak amplitude was up to fourteen times larger, and the time course was about one half that in the e.d.l. muscle. The extent of inactivation of a test potassium contracture was directly related to the concentration of potassium in the conditioning solution and the period of exposure. Removal of calcium reduced the amplitude and time course of potassium contractures in both preparations. Addition of cobalt (10 mM) reduced the amplitude but prolonged the time course of contractures. Exposure of muscles to tetracaine (10(-5)-10(-6) M for 30 min) increased, but higher concentrations reduced, the amplitude of potassium contractures. When present for one minute, tetracaine (1 mM) moved the potassium activation curve to higher, and the potassium inactivation curve to lower, potassium concentrations.