Rational Design of PANI Sensors for Detection of Ammonia and Ethyl-Substituted Aliphatic Amines: A Dual Experimental-Theoretical Strategy.

Accurate prediction and validation of interactions between target gases and sensors through combined theoretical and experimental studies remain important for the rational design of next-generation sensors. In this work, we present a comprehensive dual approach, i.e., first-principles density functional theory (DFT) analysis coupled with precise experimental validation, to demonstrate polyaniline (PANI) as a sensing material for the detection of ammonia and a homologous series of ethyl-substituted aliphatic amines (ethylamine, diethylamine, and triethylamine). These vapors are not only essential indicators of food spoilage but also serve as noninvasive breath biomarkers for kidney-related disorders in humans. DFT calculations reveal distinct interaction trends governed by molecular basicity and steric hindrance, with the strongest affinity observed for ethylamine, followed by ammonia, diethylamine, and triethylamine. The theoretical predictions are validated using chemiresistive PANI-based sensors, demonstrating an excellent correlation between interaction strength and sensor response. Moreover, the kinetics of interactions between the studied vapors and PANI were studied by using the Langmuir adsorption mechanism to estimate reaction rate constants. The strong agreement between computational and experimental results demonstrates the reliability of this integrated approach in accurately correlating molecular interactions of PANI for the sensing of ammonia and amine vapors.