Electronic structure of polythiophene gas sensors for chlorinated analytes.

Density functional theory studies are performed to investigate the response of polythiophene as a sensor for chlorinated gaseous analytes. Interaction of polythiophene with these analytes is studied from both H-side (dipole-dipole) and Cl-side (halogen bonding) of analyte to get the most stable interaction site. Inferences from interaction energy, natural bond orbital, and Mulliken charge analyses are in line with those from geometric analysis. Interaction energies reveal that polythiophene has specificity and selectivity towards chlorine. Interestingly, the halogen bond in PT-Cl2 complexes is stronger than ion-dipole bond in the complexes of polythiophene with other analytes. The sensing of polythiophene towards these analytes is also measured by perturbing the electronic properties including ionization potential, electron affinity, λmax, and H→L gap. The spectroscopic properties (UV absorption spectra) reveal the interaction behavior of polythiophene with these chlorinated analytes. All these parameters including orbital analysis and H→L energies indicate high sensitivity of polythiophene for chlorine. Graphical abstractInteraction of chlorinated gaseous analytes with polythiophene surface.