In this work, we investigated the effect of thermal treatments on the transduction of HCl-doped polyaniline (PANI) nanofibers integrated in conductometric devices upon exposure to 1% H-2 (carried by N-2). After drying in N-2 at similar to 25 degrees C for 12 h, our devices showed a similar to 10% decrease in electrical resistance upon exposure to 1% H-2. However, devices subject to 12-h drying in N-2 at similar to 25 degrees C followed by further thermal treatments in N-2 at 100 degrees C, 164 degrees C or 200 degrees C for 30 min showed different transduction behaviors. The devices subject to thermal treatments at 100 degrees C and 164 degrees C showed a similar to 7% decrease and <0.5% variation in electrical resistance, respectively. More interestingly, the device subject to the thermal treatment at 200 degrees C showed a transduction behavior with obvious opposite polarity, i.e. a similar to 5% increase in electrical resistance upon exposure to 1% H-2. Further analysis indicated that the observed results were related to the thermal treatments which caused HCl-doped PANI nanofibers to undergo (i) water desorption, (ii) crosslinking and/or (iii) partial carbonization. (C) 2014 Elsevier B.V. All rights reserved.