Effect of Thermal Treatments on the Transduction Behaviors of Conductometric Hydrogen Gas Sensors Integrated with HCl-Doped Polyaniline Nanofibers

We present the effect of thermal treatments on the transduction behaviors of HCl-doped polyaniline (PANI) nanofibers integrated in conductometric devices upon exposure to 1% H2 (carried by N2). After drying in N2 at 25oC for 12 hours, devices showed a ~10% decrease in electrical resistance upon exposure to 1% H2. However, devices subject to 12-hour drying in N2 at 25oC followed by further thermal treatments in N2 at 100oC, 164oC or 200oC for 30 minutes showed different transduction behaviors. Specifically, devices subject to thermal treatments at 100oC and 164oC showed a decrease in electrical resistance by ~7% and <0.5%, respectively. More interestingly, the device subject to thermal treatment at 200oC showed a transduction behavior with opposite polarity, i.e. a ~5% increase in electrical resistance upon exposure to 1% H2. SEM, FTIR and TGA were employed to investigate the effect of thermal treatments on the morphology and chemical characteristics of HCl-doped polyaniline nanofibers. The results indicated that the change in the devices? interesting transduction behaviors might be related to the thermal treatment effects on the HCldoped PANI nanofibers in (i) removal of adsorbed water, and (ii) crosslinking and/or degradation of polymer backbones.