Sensor Application of Co-Polymer of Pyrrole and Aniline for Volatile Organic Compounds: A DFT Study

Abstract

Density functional theory calculations are performed to evaluate the sensing ability of co-polymer of pyrrole aniline for volatile organic compounds (VOCs). Interaction energies of PPA-X (X = Cl2, NH3, SO3, CH2O and HF) are calculated at B3LYP/6-31G (d) levels of theory and compared with the high level calibrated method (M05-2X/aug-cc-pVDZ). B3LYP/6-31G (d) gives the best correlation with the high level calibrated method. Interaction of oligopyrroleaniline with analytes shows a significant effect on the geometric and electronic properties; the conjugation is increased in the pyrroleanilineoligomers and movement of charge is increased over the polymeric backbone. The charge is transferred from analytes to pyrroleaniline oligomers and a more pronounced effect of charge transfer is observed in the case of sulphur trioxide (SO3) compared to Cl2, NH3, CH2O and HF. In nPA@SO3, the charge is transferred from polymer to analyte. This transfer of charge indicates the n-type doping effect of analytes. The HOMO- LUMO gap decreases after interaction with analytes, which results in a drop of resistance (conductivity increases). These theoretical outcomes are consistent with the experimental results; co-polymer of pyrroleaniline has more sensing ability toward the sulphure trioxide (SO3).