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Graphene composite of polyaniline (PANI) emeraldine salt is systematically studied to explain its experimentally observed enhanced sensitivity for methylamine and ammonia as compared with simple PANI emeraldine salt conducting polymer sensor. The interaction behavior is studied with M062X method of density functional theory. Optimization of geometries, calculation of interaction energies, and natural bond orbital charge analyses are performed to study and explain the sensing behavior. Charge analysis is performed to know the magnitude and direction of electronic charge flow during sensing phenomenon. Frontier orbitals interaction theory is used to compare the strength of interaction of analytes with simple and composite sensors. The selectivity of both sensors toward analytes is also verified using the same theory. Absorption behavior of simple and composite sensors against incident electromagnetic radiations is also studied before and after sensing. Non‐covalent interaction analysis is performed to identify and distinguish different types of attractive and repulsive forces present within addition products. It is concluded that graphene composited PANI sensor shows greater sensitivity toward considered analytes as compared with PANI emeraldine salt sensor and this outcome is in agreement with reported results based on experimental observations. The better efficiency of composite sensor is due to direct interaction of analytes with graphene in addition to their interaction with PANI conducting polymer. [ABSTRACT FROM AUTHOR]

Polyaniline emeraldine salt and Polyaniline Zinc Oxide composite are comprehensively studied to compare their sensing ability towards ammonia, acetone, methanol and ethanol. Sensing ability is evaluated through thermodynamic, geometric and electronic parameters. A number of orientations are evaluated in search for the lowest energy structure. The comparison of thermodynamic, geometric and electronic parameters of simple and composite sensors confirmed that composite sensor shows better sensing ability than simple PANI. Composite formation between polyaniline and zinc oxide is a thermodynamically feasible process with interaction energy of −42.8 kcal/mol. Both sensor shows highest interaction energy for ethanol among four analytes. Composite sensor shows almost twice the interaction with ethanol, methanol and acetone while 1.5 times the interaction energy for ammonia. The results of run simulations and subsequent calculations showed that in composite sensors, zinc oxide not only enhances the binding power of conducting polymer with analytes but also interacts directly with analytes. Strong hydrogen bonding as well as weak dispersion forces of attraction are responsible for the stability of composite and all complexes, as revealed by non-covalent interaction (NCI) studies. Acetone shows a different behaviour in composite sensor complex than other analytes. Image 1 • Polyaniline-Zinc Oxide composite sensor for industrial effluents is studied. • The composite sensor has superior performance as electrochemical sensor than its constituents. • Excellent thermodynamic and electronic properties of the composite are due to synergic effect of PANI and graphene. • The composite is fairly stable thermodynamically to survive adsorption-desorption cycle. • PANI and PANI-ZnO sensors are selective towards the detection of ethanol. [ABSTRACT FROM AUTHOR]