Abstract
A pH-sensitive RuO2 electrode coated in a commercial cyanoacrylate adhesive typically exhibits very low pH sensitivity, and could be paired with a RuO2 working electrode as a differential type pH sensor. However, such sensors display poor performance in real sample matrices. A pH sensor employing a RuO2 pH-sensitive working electrode and a SiO2-PVB junction-modified RuO2 reference electrode is developed as an alternative high-performance solution. This sensor exhibits a performance similar to that of a commercial glass pH sensor in some common sample matrices, particularly, an excellent pH sensitivity of 55.7 mV/pH, a hysteresis as low as 2.7 mV, and a drift below 2.2 mV/h. The developed sensor structure opens the way towards the development of a simple, cost effective, and robust pH sensor for pH analysis in various sample matrices.
Highlights
The use of RuO2 films for the manufacture of solid state potentiometric pH sensors has several advantages, namely Nernstian pH sensitivity, insolubility over a wide pH range, good reproducibility, low hysteresis, and reduced cost [1,2,3,4].The pH sensing properties of RuO2 films have been reported by numerous groups [5,6,7]
Radio frequency magnetron sputtering (RFMS) is a convenient technique for the deposition of thin films with well-controlled thickness and stoichiometry [8]. This technique is attractive for the development of RuO2 pH sensors featuring high purity and reproducible performance
Metal oxide pH sensors are commonly paired with quasi Ag|AgCl reference electrodes for potentiometry, since they are simple to construct [9,10,11]
Summary
The use of RuO2 films for the manufacture of solid state potentiometric pH sensors has several advantages, namely Nernstian pH sensitivity, insolubility over a wide pH range, good reproducibility, low hysteresis, and reduced cost (in comparison to the more commonly studied IrO2 films) [1,2,3,4].The pH sensing properties of RuO2 films have been reported by numerous groups [5,6,7]. Radio frequency magnetron sputtering (RFMS) is a convenient technique for the deposition of thin films with well-controlled thickness and stoichiometry [8]. This technique is attractive for the development of RuO2 pH sensors featuring high purity and reproducible performance. Metal oxide pH sensors are commonly paired with quasi Ag|AgCl reference electrodes for potentiometry, since they are simple to construct [9,10,11]. Quasi reference electrodes are not always suitable for application in samples due to their cross sensitivities. An Ag|AgCl electrode is sensitive to the concentration of Cl− ions in solution, according to the following equations: AgCl(s) + e− ↔ Ag(s) + Cl−
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