Polyaniline-based gas sensors: DFT study on the effect of side groups

Polyaniline (PANI) derivatives are promising compounds for chemical sensor applications due to their low relative cost and high versatility of synthesis. However, at the same time that the great chemical versatility of these compounds allows the design of a number of derivatives, it is difficult to identify optimized materials only via trial and error. Here we present a theoretical study on the opto-electronic responses of PANI derivatives in relation to a series of gaseous compounds. Distinct branched PANI-based compounds were designed considering specific side groups, rationalized by Hammett indexes, and investigated via density functional theory (DFT). The results indicate that the presence of side groups can modulate the local reactivity and electronic properties of the compounds, tuning their capability to detect chemical species. In particular, higher reactivity on accessible side groups are obtained for the derivatives PANI-CCH, PANI-CN and PANI-NO2, facilitating their interaction with analytes.