Impedance Sensor for Real-Time Ammonium Detection Based on MWCNT/ZnO Nanocomposites

This work reports on the development of an impedance sensor-based real-time-field specific system to monitor aqueous Ammonium (NH4+). The sensing element was fabricated by modifying screen-printed interdigitated electrodes (IDEs) with a hybrid nanocomposite of Multi-Wall Carbon Nanotube (MWCNT) with Zinc Oxide (ZnO) nanocrystals. The NH4+ of the water was monitored, and it exhibited a sensitivity of <inline-formula> <tex-math notation="LaTeX">$67.13 \,\,\Omega $ </tex-math></inline-formula>/mM with average correlation coefficients of 0.80. The impedance magnitude (<inline-formula> <tex-math notation="LaTeX">$\Omega$ </tex-math></inline-formula>) of the NH4+ sensor was unaffected by the presence of Fe2+, Ni2+, K+ and P+ interfering cations. The developed sensor was interfaced with an IoT-enabled NodeMCU microcontroller, enabling a direct method for continuous monitoring of NH4+ concentrations. This integrated system is interconnected to the field-deployed sensor nodes, which provide real-time NH4+ levels to the remote user through web applications.