Highly sensitive Cu-ethylenediamine/PANI composite sensor for NH₃ detection at room temperature

Ammonia detection is needed in several sectors including environmental monitoring, automobile industry, and in medical diagnosis. Conducting polymers, such as polyaniline (PANI), have been utilized to develop NH₃ sensors operating at room temperature. However, the performance of these sensors in terms of sensitivity and selectivity need improvement. Functionalization of conducting PANI with metal nanocomposites have shown improved sensor performance. In this work, we report a highly sensitive copper-based nanocomposite for NH₃ detection. The novelty lies in utilization of copper-ethylenediamine (Cu-en) nanocomposite functionalized over PANI for gas sensing. Resistance of the 20 wt% Cu-en with PANI increased 3.8 times upon exposure to 100 ppm of NH₃. The nanocomposite sensor detected NH₃ concentrations as low as 2 ppm. Further, the sensing mechanism was studied by in-situ IV characteristics and impedance spectroscopy during NH₃ exposure. NH₃ showed ionic interaction with PANI, and Cu²⁺. The strong affinity of Cu²⁺ for the lone pair of NH₃ enhanced the sensor response from 0.78 to 3.8 for 100 ppm of NH₃ at 20 °C. The sensor response was completely recovered after heating at 75 °C, which indicates reusability of the sensor. The sensor showed selectivity for NH₃ over ethanol and H₂S. The response was reasonably stable after bending the flexible sensor for 1000 times at a radius of 5 mm.