Localized Surface Plasmon Resonance of Reduced Graphene Oxide/Ag Hybrid for Gas Sensing Application

Abstract

Localized surface plasmon resonance of metallic nanoparticles has been widely employed for gas sensing applications. Since the response of bare nanoparticles is usually weak, it is possible to improve their responses by utilizing the high gas adsorption capability of 2-D materials. In this paper, we developed an optical gas sensor by decorating reduced graphene oxide (rGO) sheets with Ag nanoparticles for the detection of ethanol vapor at the room temperature. We showed that the gas sensitivity of bare Ag nanoparticles can be enhanced by utilizing rGO sheets. We observed improved responses for structures in which rGO was fabricated above the nanoparticles (rGO _up /Ag) compared with the structures with rGO below the nanoparticles (Ag/rGO _down ). Gas sensitivity was improved 1.47 and 2.75 times, respectively, in the Ag/rGO _down and rGO _up /Ag structures compared with the bare Ag nanoparticles. Our results demonstrate that the adsorption of ethanol molecules on the Ag nanoparticles/rGO hybrids leads to not only a plasmonic shift occurring in bare Ag nanoparticles but also an intensity change in the extinction spectrum. In other words, alteration of rGO conductivity due to the gas adsorption leads to an intensity variation in optical spectrum, which can be utilized for improving gas sensing. Finally, we performed a finite-element analysis by assuming the electron exchange between Ag nanoparticles/rGO hybrids and target gas through redox reactions to assess the validity of observed experimental results. Our numerical results confirmed the observed experimental results.