An reduced graphene oxide (RGO) resistive gas sensor was prepared to detect ammonia at room temperature, the result indicated that the desorption of gas (NH ${}_3$ ) molecules from a graphene-based sensor was difficult, which lead to a baseline drift. The responses of different concentrations were compared and studied. It was found that both the response rate and its acceleration were affected by the gas concentration. An Intermolecular Forces Based Model was established to explain the adsorption and desorption dynamic response curves. A new method was proposed based on this model. The first and second derivative extrema (FSDE) of the response curve can be attained quickly to calibrate the gas concentrations. The experiment results demonstrated that this new method could eliminate the baseline drift and was capable of increasing the efficiency of gas calibration significantly.

RGO/SnO ${}_2$ nanocomposites were prepared by a simple blending method and then airbrushed on interdigitated electrodes to obtain the corresponding gas sensors. The characterizations of SEM, TEM, Raman, XRD and FTIR were used to characterize the microstructures, morphologies and surface chemical compositions of the nanocomposites, indicating that the two materials coexist in the composite films and the concentration of surface defects is affected by the amount of SnO ${}_2$ nanoparticles. It is also found that the room temperature sensing performance of RGO to NO ${}_2$ can be improved by introducing appropriate amount of SnO ${}_2$ nanoparticles. The enhanced NO ${}_2$ sensing properties are attributed to the rough surface structure and increased surface area and surface defects of the nanocomposite films. Since further reduction of RGO, heat treating the sensing films resulted in a decrease in the response and recovery times of the sensors. Furthermore, the sensor annealed at 200 ${}^{\circ }$ C exhibited a small baseline drift, wide detection range, good linearity, high stability and better selectivity.

A new approach was proposed to evaluate the performance of organic thin film transistors (OTFTs) gas sensors. Back-gated OTFTs gas sensors with poly (3-hexylthiophene) (P3HT)/Zinc oxide (ZnO) nanorods composite film as the active layers and gas sensing layers were prepared for nitrogen dioxide (NO2) detection. Electrical parameters of OTFTs based on pure P3HT film and P3HT/ZnO-nanorods composite film were calculated and analyzed. Response characteristics of gas sensors to NO2 were studied. It can be found that responses of OTFTs gas sensors were inaccurate according to conventional definition. The slope of fitting line (ΔI versus log t) was proposed as a new method to evaluation gas properties of OTFTs sensors. The calculate results illustrated that the sensitivity can be increased 40.2% due to appropriate amount of ZnO-nanorods doping.