Comparative study on sensing abilities of polyaniline and graphene polyaniline composite sensors toward methylamine and ammonia

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.