Poly(O-mercaptoaniline)-iodide nanofiber composite as a promising potentiometric sensor for the detection of Hg²⁺ ions in water

A promising cost-effective, easily fabricated, and mass-produced sensor for Hg²⁺ detection, based on poly(o-mercaptoaniline)-iodide (I⁻-POMA), has been developed. The fabrication of I⁻-POMA nanofibers is accomplished through a one-step process involving the oxidation of o-amino-benzenethiol monomers with iodine (I₂). The I⁻-POMA nanofibers exhibit a remarkable elongated structure, and their actual length is measured to be approximately 77 nm. The effectiveness of the I⁻-POMA electrode sensor in detecting Hg²⁺ ions is tested using two different methods: a simple potentiometric two-electrode system and a cyclic voltammetry three-electrode system. In the simple potentiometric system, the calculated slope is found to be 25.2 mV per decade, indicating the high sensitivity and effectiveness of the I⁻-POMA electrode sensor, especially at a pH of 5.5, for Hg²⁺ ion detection. In the cyclic voltammetry method, both the cyclic curve area and the generated current density (I) values increase proportionally with varying concentrations of Hg²⁺ ions. The sensitivity calculated from this method is 2.2 µA per micromolar (µA/M), confirming the sensor's precision in detecting Hg²⁺ ions over a wide range of concentrations. Importantly, the I⁻-POMA electrode sensor demonstrates exceptional potential for detecting Hg²⁺ ions even in the presence of other interfering ions like Ni²⁺, Zn²⁺, Ca²⁺, Mg²⁺, K⁺, and Al³⁺, showcasing its outstanding selectivity. Furthermore, the I⁻-POMA electrode sensor is tested in various natural samples and consistently shows exceptional sensitivity to Hg²⁺ ions, highlighting its suitability for practical applications in environmental monitoring and water quality assessment. In summary, the I⁻-POMA electrode sensor displays remarkable responsiveness, sensitivity, and selectivity in detecting Hg²⁺ ions, making it a promising candidate for a wide range of Hg²⁺ sensing applications in real-world life.