Application of a novel ionic-liquid-based membrane reference electrode with inorganic insertion material paste to a calibration-free all-solid-state ion sensor chip

• Published in: Sensors and actuators. B, Chemical Chemical, 2021-11, Vol.347, p.130625, Article 130625
• Main Authors: Kojima, Junko, Uchiyama, Kenichi, Yoshida, Yumi
• Format: Article
• Language: English
• Subjects: All-solid reference electrode; Aluminum oxide; Calibration; Calibration-free ion sensor; Chip formation; Coated electrodes; Electrodes; Inorganic insertion materials; Insertion; Ionic liquids; Ionic-liquid; Mass production; Membranes; Na0.33MnO2; Redox reactions; Reproducibility; Sensors; Sodium; Solid electrolytes; β”-alumina
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2021.130625

We propose an all-solid ionic-liquid-based membrane reference electrode (IL-RE) with the inner solid electrode coated with insertion material paste. This material paste contains an inorganic insertion material (Na0.33MnO2) and a solid electrolyte (β’’-alumina). The inorganic insertion material, Na0.33MnO2, in the paste exhibits a redox reaction accompanied by the disinsertion/insertion of Na+ and acts as an ion-to-electron transducer. Furthermore, β’’-alumina in the paste acts as a supply source of Na+ for Na0.33MnO2. The insertion material paste stabilizes the phase boundary potential of the inner solid electrode in the IL-RE, even if the IL membrane contains no inserted ions (Na+). The fabricated IL-RE exhibited high device-to-device reproducibility (the standard deviation of the IL-RE potential: ± 0.6 mV, 8 sensors). The IL-RE was integrated into a K+ sensor chip with the all-solid K+-ion selective electrode (K+-ISE) for calibration-free measurements. The K+ sensor chip was designed to prevent the effect of the IL eluted from the IL-RE on K+-ISE potential by optimizing IL concentration in the IL membrane and distance between IL-RE and K+-ISE. The fabricated K+ sensor chips exhibited a very high device-to-device potential reproducibility of ± 1.3 mV in KCl solutions and ± 2.2 mV even in blood serum samples. This ion sensor chip realized calibration-free measurement as disposable sensors and showed the possibility of facilitating mass production. [Display omitted] •Novel all-solid ionic-liquid-based membrane reference electrode (IL-RE) is proposed.•IL-RE contains an inner solid electrode coated with insertion material paste (IMP).•IMP contains Na0.33MnO2 and a solid electrolyte (β’’-alumina).•IL-RE was applied to a K+ sensor chip with K+-ISE for calibration-free measurements.