Percolation effect of reduced graphene oxide (rGO) on ammonia sensing of rGO-SnO2 composite based sensor

Abstract Reduced graphene oxide (rGO) was added to SnO2 to implement a room temperature chemoresistive ammonia sensor. The percolation effect of rGO on the ammonia sensing properties of SnO2 based sensor was observed. rGO was added physically to SnO2 followed with a magnetic stirring. The sensor using rGO-SnO2 composites exhibited a switch from an n-type semiconductor response behavior to a p-type semiconductor behavior as the rGO content increased from 0.1 wt% to 1 wt%. The p-type response to ammonia indicated an enhanced sensitivity, better signal stability and faster response/recovery speeds compared to the n-type response. The p-type response can be due to the p-type rGO in the composite and the enhanced room temperature n-type response of SnO2 could be assisted by the added rGO which facilitated the redox reactions of ammonia with oxygen in air. A physical model for prediction of the critical weight ratio of rGO in the composite was developed. The calculated results were reasonably consistent with the experimental ones.