Synthesis and Application of Graphene/Silver Nanowires/Gold Nanoparticles Hybrid for Ammonia Gas Sensing

Abstract

Graphene material synthesized from chemical method (reduced Graphene Oxide -rGO) is a promising candidate for gas sensors due to their unique properties. With structure of single layer of bonded sp 2 carbons in a two-dimensional (2D) lattice, rGO have large surface to volume ratio, high conductivity and electron mobility at room temperature. Meanwhile, the different oxygencontaining functional groups (contain dangling bonds) decorated on carbon networks make rGO easily respond with compatible gas molecules. However, the investigating of structure of rGO in micrometer scale shows that the chemical method often results in non-uniform film thickness on substrate due to overlap of rGO sheets. These may disrupt the conductive paths in rGO films and decrease their conductivity. Therefore, gas sensing signal of pristine rGO based sensors is tarnished and the sensors do not recover to their baseline at room temperature. In this study, silver nanowires (AgNWs) and gold nanoparticles (AuNPs) are combined with rGO material to form rGO/AgNWs/AuNPs hybrid. With one-dimensional nanostructure, the AgNWs connects effectively together many rGO islands and reduce significantly their contact resistance so that NH 3 sensing signal is improved and complete recovery of the sensor is nearly achieved at room temperature. Especially, all these signals are further enhanced when the AuNPs (diameter ~ 30 nm) are added into the hybrid.