High-Performance pH Sensing for Water Quality Assessment Using RuO ₂ Nanorods on FTO Substrates

This study introduces a high-performance pH sensor designed for water quality assessment, leveraging ruthenium dioxide (RuO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>) nanorods grown on fluorine-doped tin oxide (FTO) substrates. The sensor, fabricated through chemical vapor deposition (CVD), achieves a super-Nernstian pH sensitivity of 67.52 mV/pH, surpassing the theoretical Nernstian limit due to the nanorods’ high surface-to-volume ratio, which enhances proton adsorption and charge transfer at the electrode-electrolyte interface. The sensor exhibits linearity with a correlation coefficient of 0.995 across a pH range of 5 to 10, ensuring accurate measurements. Hysteresis is minimized to 3.92 ± 0.26 mV, reflecting robust reversibility during pH cycling. A low average drift rate of 0.23 mV/hour indicates excellent temporal stability, critical for continuous monitoring. Long-term stability tests over 30 days confirm consistent performance, with negligible degradation in sensitivity or linearity. The CVD process ensures uniform nanorod morphology, contributing to reproducibility and scalability. This RuO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nanorod-based pH sensor offers a reliable, durable, and highly sensitive solution for real-time water quality monitoring in environmental and industrial applications.