Electrochemically Synthesized Polyaniline Nanofibers on Flexible Electrode for pH Sensing

pH monitoring is essential in diverse fields such as clinical diagnostics, environmental surveillance, food quality control, and industrial process management. Wound exudate pH serves as a noninvasive biomarker of wound status. Here, we report a flexible electrochemical pH sensor based on polyaniline nanofiber (PANI NF) modified polyimide electrodes prepared by electrochemical deposition. The nanofibrous PANI layer exhibits a porous interconnected architecture, as confirmed by scanning electron microscope (SEM), Fourier transform infrared (FTIR), Raman, and X-ray photoelectron spectroscopy (XPS) analyses. The PANI NF electrode displayed a near-Nernstian sensitivity of 57 mV pH⁻¹ over the pH 5–9 range with excellent linearity (R² > 0.99), low hysteresis (<4 mV), and high reproducibility (RSD 0.54%). Long-term drift studies revealed minimal potential drift (<1 mV h⁻¹), and the calibration slope remained unchanged after 5 days of floating. The sensor accurately measured the pH of serum-containing simulated wound fluid (SWF), with deviations ≤ 0.06 from a commercial glass-electrode pH meter. After 90 days of storage at 4°C in the dark, the sensor retained its sensitivity with only minor variability (RSD 2.77%). These results demonstrate that the flexible PANI based sensor offers fast response, high sensitivity, and excellent stability, making it a promising platform for real-time, continuous monitoring of wound exudate pH and other biomedical or environmental applications.