Interaction of Several Toxic Heterocarbonyl Gases with Polypyrrole as a Potential Gas Sensor

Abstract

The interactions of the toxic heterocarbonyl gases phosgene, carbonyl fluoride, formaldehyde, carbonyl sulfide, and acetone with polypyrrole as a toxic heterocarbonyl gas sensor, were extensively studied by density functional theory (DFT). The Becke 3-parameter, Lee-Yang-Parr (B3LYP) exchange-correlation functional methods were first tested against several high-level DFT methods employing the Dunning’s double-ζ and triple-ζ basis sets and were found to be sufficient in describing the non-covalent interactions involved in this study. The interaction of pyrrole with the heterocarbonyl gases resulted in changes in the structure and optoelectronic properties of the polymer and it was observed that acetone and formaldehyde had the strongest H-bonding interaction with polypyrrole, while the interaction of phosgene and formaldehyde resulted in the lowest energy gap and may result in its high sensitivity towards these gases. The UV-Vis absorption revealed significant red-shifted first singlet excited states (Eexcited, 1st) of the complexes and follows the same trend as the EGap values. It is shown that the Eexcited, 1st was due to the π(HOMOPy) ⟶ π*(LUMOHC) transitions and the excited state at maximum absorption (Eexcited, max) was due to the π(HOMOPy) ⟶ π*(LUMOPy) transitions. This study demonstrates the potential sensitivity and selectivity of polypyrrole as a toxic heterocarbonyl sensor.