Optimization of Ruthenium Dioxide Solid Contact in Ion-Selective Electrodes

Abstract

Ruthenium dioxide occurs in two morphologically varied structures: anhydrous and hydrous form; both of them were studied in the scope of this work and applied as mediation layers in ion-selective electrodes. The differences between the electrochemical properties of those two materials underlie their diverse structure and hydration properties, which was demonstrated in the paper. One of the main differences is the occurrence of structural water in RuO2•xH2O, which creates a large inner surface available for ion transport and was shown to be a favorable feature in the context of designing potentiometric sensors. Both materials were examined with SEM microscope, X-ray diffractometer, and contact angle microscope, and the results revealed that the hydrous form can be characterized as a porous structure with a smaller crystallite size and more hydrophobic properties contrary to the anhydrous form. Potentiometric and electrochemical tests carried out on designed GCD/RuO2/K+-ISM and GCD/RuO2•xH2O/K+-ISM electrodes proved that the loose porous microstructure with chemically bounded water, which is characteristic for the hydrous form, ensures the high electrical capacitance of electrodes (up to 1.2 mF) with consequently more stable potential (with the potential drift of 0.0015 mV/h) and a faster response (of a few seconds).

Electrosynthesis of Electrochromic Polymer Membranes Based on 3,6-Di(2-thienyl)carbazole and Thiophene Derivatives

“…Electrochromism refers to when electroactive species undergo a reversible change in optical absorption properties during the electrochemical oxidation/reduction process, and the species are electrochromic materials [1][2][3]. In the past 20 years, electrochromic materials and electrochemical membrane materials have been utilized in several fields such as for architectural windows, helmet visors, rearview mirrors, optical displays [4], fuel cells [5][6][7], and supercapacitors [8,9]. Electrochromic materials are generally classified into two categories: (a) inorganic complexes and transition metal oxides and (b) organic polymers and viologen derivatives [10].…”

Potassium-Selective Solid-Contact Electrode with High-Capacitance Hydrous Iridium Dioxide in the Transduction Layer

“…In the previous works published by our group [ 8 , 9 , 14 ], the other transition metal oxide, ruthenium dioxide, was discussed. Similarly to RuO 2 , IrO 2 crystallizes in the rutile structure [ 12 ] and exists in two forms—hydrous and anhydrous.…”

“…Taking into consideration the mentioned features and differences between both types of oxides, it can be concluded that hydrous oxide exhibits more favorable characteristics in the context of designing potentiometric sensors. In the case of ruthenium, the hydrous form turned out to be more favorable for ion-selective electrodes than anhydrous, as presented in [ 14 ]; therefore, when applying iridium oxide as a mediation layer, its hydrous form was chosen.…”

Special Issue “Advances in Artificial and Biological Membranes: Mechanisms of Ionic Sensitivity, Ion-Sensor Designs, and Applications for Ion Measurement”

“…In a convincing way, the authors underline a possible mutual influence of CPs on the properties of plastic ISE membrane and vice-versa. Lenar et al [ 14 ] describe an application of ruthenium oxide as the mediating material in a solid-contact potassium-sensitive ISE. The authors point out the increase of redox capacity and response reproducibility when the hydrated ruthenium oxide is used.…”

“…Maksymiuk et al [ 13 ] correctly argue though that the conventional electrodes with internal solution are by far more stable: “a classic ISM-containing arrangement offers high stability of potential readings in time due to well-defined, reversible ion-electron transfer through all sensor interfaces”. On the other hand, in the paper of Lenar et al [ 14 ], we can read that “the occurrence of structural water in RuO 2 •xH 2 O, which creates a large inner surface available for ion transport and was shown to be a favourable feature in the context of designing potentiometric sensors”. Accordingly, the authors provide evidence that the solid contact with chemically bounded hydration water in it can be as good as highly hydrophobic.…”