Purpose The purpose of this study is use to density functional theory (DFT) to investigate the molecular adsorption by PEDOT:PSS for different doping levels. DFT calculations are performed using the SIESTA code. In addition, the non-equilibrium Green’s function method is used within the TranSIESTA code to determine the quantum transport properties of molecular nanodevices. Design/methodology/approach Density functional theory (DFT) is used to investigate the molecular adsorption by PEDOT:PSS for different doping levels. DFT calculations are performed using the SIESTA code. In addition, the non-equilibrium Green’s function method is used within the TranSIESTA code to determine the quantum transport properties of molecular nanodevices. Findings Simulation results show very good sensitivity of Pd-doped PEDOT:PSS to ammonia, carbon dioxide and methane, so this structure cannot be used for simultaneous exposure to these gases. Silver-doped PEDOT:PSS structure provides a favorable sensitivity to ammonia in addition to exhibiting a better selectivity. If the experiment is repeated, the sensitivity is increased for a larger concentration of the applied gas. However, the sensitivity will decrease at a higher ratio than smaller concentrations of gas. Originality/value The advantages of the proposed sensor are its low-cost implementation and simple fabrication process compared to other sensors. Moreover, the proposed sensor exhibits appropriate sensitivity and repeatability at room temperature.

The interactions between poly (3,4‐ethylene dioxythiophene) poly (styrenesulfonate) (PEDOT:PSS) and small gas molecules are studied using non‐equilibrium Green's function formalism based on the density functional theory. The proposed method is implemented in the Tran SIESTA code to benefit from the potential application of PEDOT:PSS as a gas sensor. The results show that doping with nanoparticles can drastically improve the sensitivity of polymer‐based chemical gas sensors. Moreover, among various PEDOT:PSS doping materials, silver nanoparticles have an appropriate response to ammonia, while platinum shows the best response to carbon dioxide. The numerical results can be useful to design PEDOT:PSS‐based gas sensors.