Direct evidence for fixed ionic groups in the hydrogel of an electrolyte diode

Iván, Kristóf; Kirschner, Norbert; Wittmann, Mária; Šimon, Peter; Jakab, Viktor; Noszticzius, Zoltán; Merkin, J. H.; Scott, Stephen K.

doi:10.1039/b109016j

Cited by 23 publications

(24 citation statements)

References 14 publications

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“…Moreover this way we can check whether electroconvection really occurs in the anodic boundary layer of the gel. This hypothesis was introduced in our previous paper [8] (based on analogous phenomena in ion exchange membrane studies [16]) to explain the lower than expected concentration polarization in the anodic boundary layer.…”

Section: B Aims Of the Present Papermentioning

confidence: 94%

“…Nonlinear chemistry [1][2][3][4], engineered complexity [5], biological analogies, and possible analytical applications [6] motivated the research initiated in the past few years in the field of the electrolyte diodes and transistors [3,4,[6][7][8][9][10]. The "building block" of these devices is a hydrogel cylinder connecting reservoirs of two different electrolytes.…”

Section: A Background Of the Researchmentioning

confidence: 99%

“…In a recent paper [8] we made an attempt to determine the concentration and the chemical nature of the ionizable groups of the PVA gels. To eliminate any reactions of the acidic or alkaline solutions with the gel matrix we studied the CV characteristics of PVA based gel cylinders in various KCl solutions.…”

Section: A Background Of the Researchmentioning

confidence: 99%

“…To sustain constant KCl concentrations at both ends of the cylinder steady flows of KCl solutions were maintained during the experiment by a peristaltic pump. In our previous work [8] we recorded CV characteristics, which were strongly non-linear due to concentration polarization in the boundary layers of the gel. While this proved the presence of fixed negative charges in the gel qualitatively, at the same time it prevented quantitative measurements, as the exact thickness of the boundary layers was unknown.…”

Section: A Background Of the Researchmentioning

confidence: 99%

“…After this procedure the PVC disks with the gel samples were stored under distilled water at laboratory temperature in the dark at least for 10 days before measurements, because the swelling in the narrow bore is a slow process. Using wider bores could shorten this time, but in that case the gel cylinder creeps out of the hole at high voltages [8].…”

Section: A the Gelmentioning

confidence: 99%

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Electrolyte diodes and hydrogels: Determination of concentration andpKvalue of fixed acidic groups in a weakly charged hydrogel

et al. 2004

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Current-voltage (CV) characteristics of polyvinyl alcohol (PVA)-glutardialdehyde hydrogel cylinders were measured in aqueous KCl solutions. To this end a new special apparatus was constructed where the gel cylinder connects two electrolyte reservoirs. The measured quantities are the electric current flowing through the gel and the potential difference between the two reservoirs. Concentration polarization near the gel-liquid interfaces is decreased considerably by applying an intense mechanical stirring in both reservoirs. Under these conditions below 1 V concentration polarization is negligible, and the CV curves are nearly straight lines. It was found that the gel applied here is a weakly charged anionic hydrogel. Concentration of fixed anions was determined from the slope of these lines measured in 0.001 and 0.01 molar KCl solutions. Fixed anion concentration of the same piece of gel was measured also with a different method, when the gel was used in an acid-base diode. In this case one reservoir contained 0.1 molar HCl, and the other 0.1 molar KOH. From the results of the two measurements, the concentration (4.45 x 10(-3) M) and the pK value (4.03) of the fixed acid groups responsible for the anionic character of the gel was calculated. The pK value is compatible with fixed carboxylic acid groups contaminating the PVA gel. Furthermore, concentration polarization phenomena in the boundary layers nearby the gel were studied in 0.001 M KCl solutions, measuring the diodelike CV characteristic of a gel cylinder, when stirring was applied only at one side of the gel. Boundary layers facing the cathode or the anode responded in a different way to stirring. The difference cannot be explained completely with the hypothesis of electroconvection suggested previously.

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Section: B Aims Of the Present Papermentioning

confidence: 94%