Inkjet-printed Nafion films on Ag/AgCl reference electrodes for enhanced stability in potentiometric sensing of nitrates

Abstract Nitrates play a significant role in plant growth and agriculture, but excessive fertilizer application can lead to leaching into groundwater, causing significant damage to ecosystems. Accurate and timely nitrate detection is needed to minimize environmental impacts and support sustainable agricultural practices. Electrochemical sensing methods, particularly potentiometry, are valued for their high sensitivity, rapid response, and miniaturization potential. Despite aforementioned advantages, the instability of reference electrodes in potentiometric sensors limits their reliability. In this study, we report the development and optimization of an inkjet-printable Nafion ink for use as a proton exchange layer to enhance the stability of Ag/AgCl reference electrodes in potentiometric nitrate sensors. The rheological and printing parameters of an inkjet-printable Nafion ink are investigated. The inkjet-printed Nafion reference electrodes show greater stability in different pH conditions and good sensitivity (-58.31 mV/dec) in aqueous nitrate solutions compared to drop-cast Nafion or bare Ag/AgCl electrode counterparts. Additionally, the use of inkjet-printed Nafion reduces material consumption while enabling automation and scalability, marking a significant advancement toward reliable, cost-effective nitrate sensors. The findings can be extended to other electrochemical techniques for detecting a wide range of analytes.