▎ 摘　　要

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. (C) 2016 Elsevier B.V. All rights reserved.