Highly Sensitive Potentiometric pH Sensor Based on\nPolyaniline Modified Carbon Fiber Cloth for Food and Pharmaceutical\nApplications

This study introduces\na potentiometric pH sensor that is extremely\nsensitive and specifically designed for food and pharmaceutical applications.\nThe sensor utilizes a pH-sensitive interface fabricated by electropolymerizing\npolyaniline (PANI) on carbon fiber cloth (CFC). Structural and morphological\nanalyses of PANI-CFC and CFC have been conducted by using X-ray diffraction\n(XRD), field emission scanning electron microscopy (FESEM), and X-ray\nphotoelectron spectroscopy (XPS). The investigation of the functional\ngroups was conducted by using Fourier transform infrared spectroscopy\n(FTIR) and Raman spectroscopy. The electrochemical characteristics\nwere assessed by utilization of cyclic voltammetry (CV) and open-circuit\npotential (OCP) measurements in a three-electrode configuration. The\nsensor exhibited a sensitivity of 60.9 mV/pH, while retaining consistent\nperformance within the pH range of 4 to 12. The repeatability and\nrobustness of the sensors were verified. The accuracy of the PANI-CFC\nsensor was confirmed by validation using real samples, demonstrating\nits compatibility with commercially available pH sensors. The application\nof density functional theory (DFT) calculations revealed an interaction\nenergy of −173.2886 kcal/mol, indicating a strong affinity\nof H<sup>+</sup> ions towards PANI-CFC electrode. Further investigation\nwas conducted to examine the chemical reactivity of PANI, revealing\na HOMO–LUMO energy gap of −0.98 eV. This study highlights\nthe PANI-CFC sensor as a reliable and efficient pH-sensing platform\nfor food and pharmaceuticals applications, performing robustly in\nboth laboratory and real-world settings.