Electro-Plasmonic Gas Sensing Based on Reduced Graphene Oxide/Ag Nanoparticle Heterostructure

Graphene has been entitled as a promising candidate for gas sensing applications, however suffers from low selectivity, as a limit for commercialization. We propose a gas sensor based on reduced graphene oxide (rGO)/Ag nanoparticles (Ag NPs), which can overcome this limitation by benefiting from both localized surface plasmon resonance of Ag NPs, and chemisorption capability of gas molecules on rGO sheets. These simultaneous gas detection mechanisms help to reveal both physical and chemical aspects of gas molecules. We show that gas-induced plasmonic shift is enhanced in rGO/Ag NPs (Delta lambda(LSPR) approximate to 5 nm), comparing with Ag NPs (Delta lambda(LSPR) approximate to 1.4 nm) versus 250 ppm of nitrogen concentration. Furthermore, electrical measurements prove that gas-induced variation in the conductivity- response is higher in rGO/Ag NPs (Delta G/G(0) approximate to 3.6%), in comparison with Ag NPs (Delta G/G(0) approximate to 1.5%). Finally, we have utilized electro-plasmonic measurement in the proposed structure, leading to about 47% enhancement in the measured sensitivity, when lambda(incident) = 440 nm is illuminated during nitrogen exposure. The proposed structure allows both electrical sensing and electro-plasmonic sensing by means of a simple measurement configuration, revealing both chemisorption and physisorption finger prints of the test gas.