Type Of Electrolyte Solution Research Articles

Electrochromic characteristics of poly(o-toluidine) coated onto flexible indium tin oxide: Effect of H2SO4 and 1-butyl-3-methylimidazolium chloride electrolytes

Poly(o-toluidine) (POT) was synthesized via electrochemical polymerization on a flexible indium tin oxide sheet using two supporting electrolytes: sulfuric acid (H2SO4) and 1-butyl-3-methylimidazolium chloride (BmimCl). The coloring response time and efficiency were investigated with respect to polymerization time, electric field strength, H2SO4 concentration, and types of electrolyte solution. In addition, the cyclic voltammetric study of POT was studied in the potential range between −1.0V and +1.5V vs. Ag/AgCl. The synthesized POT displayed many distinct colors: colorless in the fully reduced form; yellow in the reduced form; green in the intermediated form; and blue in the oxidized form. With increasing applied electrical potential and acid concentration, the response time for the color change of the POT films became increasingly shorter. Perchloric acid provided the shortest response time due to its high dissociation constant value. The optimum response time was within 6s for the coloring change from blue (oxidized form) to colorless (reduced form), under the testing conditions of 1.0M H2SO4, 3.0V. The response time for POT synthesized in BmimCl was longer than that of POT synthesized in H2SO4. However, the additional advantage of using BmimCl as the supporting electrolyte was to provide a smooth POT film surface.

Density functional theory study on ion adsorption and electroosmotic flow in a membrane with charged cylindrical pores

ABSTRACTIon adsorption and electroosmotic flow induced by an external electric field have a variety of practical applications, especially for membrane technology. In this work, a partially perturbative density functional theory (DFT) based on the modified fundamental measure theory was applied to investigate the ion density distributions and partitions in a charged cylindrical pore. Different types of electrolyte solutions, including both charge symmetric and asymmetric, were examined using the proposed theory with various pore diameters, bulk densities, ion valencies and surface charge densities. The ion concentration profiles calculated with the theory exhibit good agreements with the results of the Monte Carlo simulations, while the results of the Poisson–Boltzmann equation deviate greatly especially for the high valence electrolytes in narrow cylindrical pores. Some interesting phenomena discovered in both experiments and simulations, such as the reverse distribution of the ions and charge inversion, can be well reproduced with the DFT. Based on the ion concentration distributions obtained from the DFT, the transient velocity profiles of the electroosmotic flow in the charged cylindrical nanopores were calculated with the Navier–Stokes (NS) equation. The characteristics of the electroosmotic flow were discussed under the different bulk electrolyte concentrations and thickness of the electric double layer inside the nanopore. The enhancement of the velocity near the pore wall, which cannot be described by the traditional theory, was well characterised by the DFT combined with the NS equation.

Influences of Electric Potential and Electrolyte on Electrochemical Chloride Removal in Reinforced Concrete

The first purpose of this paper was to find appropriate parameters for the electrochemical chloride removal method; that is, type of electrolyte solution, electric potential and charging duration. The second was to determine the efficiency of the chloride removal at remote areas from the position of installation. The 30×30×10 cm3 and 70×70×7.5 cm3 concrete specimens were prepared for the first and second purposes respectively. The chloride removal process was performed by applying electric potential between the reinforcement bars embedded in concrete and an external electrode installed on the concrete surface submersed in external electrolyte. With 28 days charging, this method could remove up to 76% of chloride by using the Ca(OH)2 solution as electrolyte with 15 V DC electric potential. The efficiency of chloride removal decreased as the distance from the position of installation increased. This was consistent with the equation of Nernst Planck which described the movement of chloride ions mobility through the concrete by electric current. As a result, there was a good tendency for using electrochemical chloride removal method to remove chloride ions from reinforced concrete.

Analytical expressions for pH-regulated electroosmotic flow in microchannels

We derived analytical expressions for the pH-regulated electroosmotic flow in a microchannel for arbitrary level of surface potential and type of electrolyte solution; previous results are almost always based on the conditions of low, constant surface potential, which are inaccurate and unrealistic. In addition, an analytical expression for the dependence of the surface potential on the electrolyte concentration and solution pH is obtained, which is capable of explaining the behavior of the empirical relation used in the literature. The analytical results derived are readily applicable to further electrokinetic analyses, and to interpret experimental observations and/or design devices involving electroosmosis such as biosensors and lab-on-a-chip.

Dielectric analysis of nanofiltration membrane in electrolyte solutions: Influences of permittivity of wet membrane and volume charge density on ion permeability

Dielectric measurements were carried out for the systems composed of nanofiltration membranes and electrolyte solutions over a frequency range of 40Hz to 10MHz, and double dielectric relaxations were observed at about 102–106Hz. Based on the interfacial polarization theory, the dielectric relaxation at high frequency was analyzed theoretically, and the permittivity and conductivity of the membrane and electrolyte solutions, were obtained. By using the permittivity of wet membrane, the ion solvation energy barrier in eight electrolyte solutions was calculated. The results showed that the ion solvation energy barrier of 2-2 type of electrolyte solution was the biggest among all types of electrolyte. The influence of solvation energy barrier on separation performance was also evaluated. Because the permittivity of wet membrane takes the place of that of dry membrane, the calculations can ensure more accurate results close to practical separation process. Furthermore, the variation of the ratio of membrane/solution conductivity, κm/κw, with the electrolyte concentration was explained by Donnan equilibrium theory, and the ratio together with the TMS model was used to calculate the volume charge density of membrane. On the basis of this, by using the volume charge density of membrane and the existing transport models, such as TMS, TMS-DE, DSPM model, four transport parameters were calculated. It was concluded that in the process of ion permeation through the membrane, Donnan exclusion is the most important influencing factor and steric effect is secondary in low electrolyte concentration, whereas dielectric exclusion plays a dominant role in high electrolyte concentration.

Anionic and Cationic Effects on the Crevice Corrosion Susceptibility of Alloy 22

AbstractAlloy 22 is highly resistant to all forms of corrosion; however, it may suffer crevice corrosion in presence of chloride ions especially at temperatures higher than ambient and at anodic potentials. The susceptibility of Alloy 22 to suffer crevice corrosion is highly dependent on the type of electrolyte solution that is in contact with the alloy including variety of species in solution and their relative concentration. Laboratory research has shown that at a constant chloride concentration, the susceptibility of Alloy 22 to crevice corrosion is not influenced by the nature of the cations present in solution. On the other hand, that nature of the anions is highly influential. Of the anions present in ground water, only chloride is detrimental and the others are inhibitors or innocuous for crevice corrosion susceptibility. That is, the presence of the other anions counter balances the negative effect of chloride. The inhibition effect is explained and the likelihood that Alloy 22 would suffer crevice corrosion in contact with ground water is discussed.

Nanocrystalline TiO<SUB align=right>2 based natural dye sensitized solar cells

Dye sensitised solar cells using natural organic dyes were prepared. Sensitisation of wide gap oxides semiconductor materials was accomplished using nanocrystalline TiO2 with henna (Lawsonia inermis L.) and raspberries (Rubus spp.) photosensitisers as a local natural organic dyes. It was shown that the nanocrystalline material based solar cell system exhibits an excellent optical absorption parameters for visible and near infrared portion of the EM spectrum. Henna and raspberries natural dyes were extracted from the corresponding dried plant using Soxhlet extractor. The open-circuit voltage and short-circuit current were measured for both of the nanocrystalline solar cell samples. Typical open circuit voltage of 400 mV and short-circuit current density of 0.47 mA/cm² were measured for raspberries cell samples for an active area of ∼3 cm² at 1.5 AM solar illumination. Henna cells samples prepared by the same technique produced an open-circuit voltage and short-circuit current density of much lesser values (200 mV, 0.04 mA/cm²). The performance of both nanocrystalline solar cell samples can be appreciably enhanced by optimising the preparation technique and using different types of electrolyte solutions.

Preparation and characteristic of electric stimuli responsive hydrogel composed of polyvinyl alcohol/poly (sodium maleate‐co‐sodium acrylate)

AbstractMaleic anhydride was used to preparare polyvinyl alcohol/poly (sodium maleate‐co‐sodium acrylate) hydrogels (PVA/poly(SMA‐SAA)) by a repeated frost‐defrost process because of its higher charge density and potential electric stimuli sensitivity. The bending angle was measured in a noncontact electric field using carbon as plate electrodes. It was found that the bending angle was dependent on various factors, including composition of hydrogel, concentration of NaCl solution, types of electrolyte solution, and electric voltage. It exhibited that the bending angle increased when the concentration of NaCl solutions and the electric voltages increased. An abnormal bending direction was observed, and it was affected not only by the kinds of hydrogels, but also by the exterior variations. The hydrogel showed good reversibility in on‐off electric field and could be a candidate for practical application. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Getting a Charge Out of Microporous Oxides: Building a Better Ultracapacitor

AbstractMicroporous nickel oxides consisting of nano-sized particles have been utilized as active electrode materials for ultracapacitors. Both the physical adsorption of ions near the charged surface of these particles and surface oxidation/reduction reactions play a role in the capacitative charge storing mechanism. These are therefore appropriately referred to as pseudo-capacitors since they rely on mechanisms in addition to double layer charging in order to store energy. In this study, it has been shown that surface hydration contributes to the formation of an initial compound which participates in the electrochemical reactions of ultracapacitors. The specific capacitance of this material is ranging from 60 to 120 F/g depending upon the types of electrolyte solution used in the ultracapacitor.

Polypyrrole nanoplating on HOPG utilizing an STM tip (biosensor fabrication)

The authors describe the plating of polypyrrole utilizing STM tips as the plating probe. Pyrrole is oxidized in electrolyte solution to form a polymer that can switch between conducting and insulating states. The combination of small effective tip surface area, small tunneling gap and a short applied-pulse duration results in nanoscale size features of polypyrrole plated on highly oriented pyrolytic graphite. It is shown that tip-induced deposition can proceed only above a certain threshold pulse potential value. Polypyrrole was deposited from two types of electrolyte solution: one containing supporting electrolyte and the monomer and the other containing, in addition, 1000 units ml-1 of the enzyme glucose oxidase. The reason for studying the deposition in the solution containing the enzyme is to simulate the conditions of fabricating an enzyme-immobilized biosensor. The results presented for pyrrole/glucose oxidase deposit agree with earlier macroscale data for this biosensor.

SERS effect of isonicotinic acid adsorbed on a copper electrode

The surface enhanced Raman spectra (SERS) of isonicotinic acid adsorbed on a copper electrode were obtained in order to verify their dependence on the type of electrolyte solution, pH and applied potential. The results are discussed considering the most characteristic bands of the species (protonated or nonprotonated) in the ring nitrogen and in the carboxylic group. In specifically adsorbed electrolytes (Cl − and mainly I −) the completely protonated species is more stabilized on the electrode surface than it is in non-specifically adsorbed anions (ClO − 4), because of the formation of ion pairs with the coadsorbed halide ions. For more negative potentials, even at low pH values, the spectra are characteristic of the nonprotonated species.

Differential pulse anodic stripping voltammetry as a rapid screening technique for heavy metal intoxications.

This paper describes a relatively simple and rapid analytical procedure capable to carry out systematic screening for 10 heavy metals, namely mercury, bismuth, antimony, copper, lead, tin, thallium, indium, cadmium and zinc. Differential pulse anodic stripping voltammetry was chosen because of its simplicity, speed, low cost, low detection limits, screening potential for a wide selection of metals and the combined qualitative and quantitative output. The method of identification is based on measuring peak potentials in 2 different types of electrolyte solution, using 2 different electrodes. Complexing agents are used to mask certain elements.

ATP in the cortex of canine kidneys undergoing hypothermic storage

Adenosine-triphosphate (ATP) was determined in the cortex of canine kidneys undergoing hypothermic storage in vitro for 24–72 hours. After a rapid initial decrease during normathermia, continuous hypothermic perfusion resulted in partial restoration of the ATP level. Hypothermic storage with only initial perfusion resulted in a much slower decrease in ATP than did normothermia. The rate of disappearance was slower for an intracellular than an extracellular type of electrolyte solution. The efficacy of the various preservation methods as reflected in the results of functional studies, seems to be correlated with the ATP level in the renal cortex.

Liver function after cooling with two types of electrolyte solution.

Pig livers were cooled in situ by portal vein infusion with cold electrolyte solutions, and then excised and perfused in an isolated circuit with diluted autologous blood. Bile flow and bromsulphthalein excretion in bile were then measured over a 90‐minute period. In one group of experiments the livers were coaled with Hartmann's/dextrose solution, and in the second group the solution was “Tis‐u‐sol” buffered with tromethamine (“Tham”). The livers cooled with “Tis‐u‐sol” had significantly greater bile flows, and excreted significantly more bromsulphthalein, than those cooled with Hartmann's/dextrose.