Enhancement of NO₂ Gas Sensing Properties of Polypyrrole by Polarization Doping with DBS: Experimental and DFT Studies

A new technique of polarization doping was adopted to improve NO₂ gas sensing properties of the polypyrrole (PPy) sensor. PPy nanosheets polarization doped with sodium dodecyl benzenesulfonate (SDBS) were synthesized by low-temperature polymerization. The semiagglomerated PPy nanosheets were well-dispersed and a large specific surface areas due to the introduction of dodecyl benzenesulfonate (DBS). The DBS doped PPy sensor shows excellent NO₂ sensing performance. Polarization of sulfonate ions to PPy enhanced the adsorption ability of NO₂ with the synergistic effect of NO₂. The adsorption energy (-0.676 eV) and electron transfer (0.521 |e|) of PPy to NO₂ increased greatly after doping. An unoccupied electron state is observed in the valence band electron structure of PPy/DBS after the adsorption of NO₂ by calculations of Density Functional Theory (DFT). The intermolecular synergy between NO₂ and PPy/DBS causes a strong polarization, resulting in a high polarization potential, which enhances the NO₂ sensing performance of PPy sensor. It is of great significance to develop NO₂ detection device based on PPy that works at room temperature.