Highly sensitive chemiresistive H2S gas sensor based on graphene decorated with Ag nanoparticles and charged impurities

Abstract

Herein, we report a highly sensitive and selective H2S gas sensor based on graphene decorated with Ag nanoparticles (AgNPs) and charged impurities fabricated using a simple wet chemical method. Doping on as-grown chemical vapor deposited graphene was achieved by immersion in an aqueous solution of AgNO3/Fe(NO3)3 for 4 min followed by the decoration with adsorbed AgNPs and charged impurities. The AgNPs utilized in this process were formed by the reduction of Ag+ ions, since the Ag+/Ag0 reduction potential is higher than that of Fe3+/Fe0. The above treatment changed the electronic properties of graphene, achieving a dramatic resistivity change in the presence of H2S gas by generating surface sites for its adsorption and dissociation and thus allowing real time H2S level monitoring at ambient temperature with an immediate response. Doped graphene was demonstrated to selectively and repeatedly sense H2S gas within six minutes, with the limit of detection being below 100 ppb. The corresponding mechanism is believed to feature a charge carrier density change of graphene to adsorbate charge transfer, with the sensor surface trapping or releasing electrons upon exposure to H2S gas.