日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

The COVID-19 pandemic has significantly increased interest in affordable point-of-care testing (POCT) technologies. As demand grows for medical devices that can be used at home, there is a particular need for compact and easy-to-use systems. Blood gas analyzers, which are used to assess a patient’s respiratory and metabolic status using arterial blood, are an important example of such diagnostic tools. Conventional oxygen sensors typically use Ag/AgCl as the reference electrode. However, this type of electrode is not suitable for miniaturized devices because it can release small amounts of silver ions. These ions may contaminate the working electrode and degrade the performance of the sensor. To overcome this limitation, we developed a new reference electrode using Prussian Blue (PB) dispersed in graphene-coated porous silica spheres (G/PSS). Prussian Blue has extremely low solubility in water, with a solubility product approximately one part in 10³¹ compared to AgCl. This makes it highly resistant to metal ion leaching, which is ideal for use in small devices. The G/PSS material provides conductive mesopores that physically support the PB clusters and ensure stable contact with the electrolyte, resulting in a consistent and reliable electrode potential. Additionally, the uniform spherical shape of the PB/G/PSS particles makes them suitable for screen printing. This allows for low-cost and reproducible manufacturing of the reference electrodes, supporting their use in next-generation POCT devices.