Occurrence and suppression of transition behavior of reduced graphene oxide thin film for gas sensing

Abstract

In this paper, we prepared reduced graphene oxide (RGO) thin film by simple airbrush technology and then studied its gas-sensing behaviors at room temperature. On exposure to dynamic NO2 gas, RGO thin film showed a time-resolved n–p transition process (n-type switched to p-type), due to its weak n-type properties arising from hydrazine-reduction method and strong electron-accepting NO2 molecules. As RGO amount was added, the time taken to run through this transition became longer. On consecutive exposures to NO2 and NH3 gases, p–n transition (p-type switched to n-type) emerged as well. To suppress these transition behaviors, CuCl was incorporated into RGO material, resulting in opposite p-type characteristics for the composite film as well as no occurrence of p–n transition during the sensing tests. Compared to pure RGO counterpart, RGO/CuCl film had a six-fold response enhancement and a likewise good repeatability toward 10 ppm NH3 within four cyclic periods. We expect that the proposed research on transition behaviors and relevant suppression methods will shed new light on gas-sensing mechanisms and improve operation stability of RGO based sensors.