Figure 5
(a) Sensing response towards hydrogen sulfide for different temperatures and concentrations. At 450 °C the sensors show a chemisorption induced increase in electrical resistance as a function of the H2S concentration. At 350 °C the behavior differs for spherical and octahedral particles at 1 ppm. For higher concentrations the formation of CuS structures becomes dominant, yet unstable, as the sensing resistance recovers after exposure. At 250 °C the CuS structures are stable on the surface and no recovery of the sensing signal is observed. (b) However, applying a heating protocol the sensor characteristics can be reproducibly recovered. The temperature is indicated in the middle panel by depicting the corresponding heater resistivity RH. (c) Measuring tPercol enables selectively determining the H2S concentration using the trace gas induced phase transition from semiconducting to conducting overall behavior.
