NiFe ₂ O ₄ /Carbon Black Nanocomposite-Based Strip Sensor for the Selective Electrochemical Recognition of Bisphenol A and 2-Nitrophenol

Bisphenol-A (BPA) and ortho -nitrophenol ( o -NP) are widely used in dye, rubber, plastic, and resin industries and recognized as emerging contaminants responsible for the degradation of water and soil quality. Although onsite detection of these phenolic pollutants is highly important, such techniques remain scarce; consequently, samples are predominantly analyzed using laboratory-intensive methodologies. In the present work, we report the development of a simple, low-cost, and highly sensitive carbon black–NiFe 2 O 4 (CB–NF) nanocomposite-based working electrode for a conventional three-electrode system and a portable strip sensor capable of detecting both BPA and o -NP at different applied threshold voltages, with detection limits of 0.02 μM for BPA and 0.1 μM for o -NP for a conventional three-electrode and 0.53 μM for BPA and 2.16 μM for o -NP for the portable strip electrode, respectively. The prepared CB–NF composite has been characterized in terms of their phase formation behavior and structural features to understand the sensing behavior. The enhanced sensing performance of CB–NF is attributed to the interaction between redox-active NFO and conductive CB, which facilitates efficient analyte reception and signal transduction. The concentration-dependent sensing response obtained at the respective threshold voltages demonstrates linear variation enabling the sensor to predict unknown concentrations of o -NP and BPA. The obtained repeatability, long-term stability, and selectivity of the developed electrode are appropriate for commercial viability. The sensing responses obtained by the strip sensor for detecting BPA and o -NP are further classified using machine learning algorithms for making it suitable for hand-held applications. This approach offers valuable insights toward the development of a sensitive, low-cost dual electrochemical sensing platform for the simultaneous detection of multiple analytes.