Design of SAW hydrogen detector based on graphene-palladium nanoparticles

This article proposes a surface acoustic wave sensing system to detect the presence of hydrogen gas. In this regard, the graphene layer decorated with palladium nanoparticles is considered as a sensing layer between the input and output interdigitated electrodes of the SAW detector. It is demonstrated that the graphene layer, which is an inherently atomic-scale thin layer with free dangling bonds, can enhance the adsorption of gases and sensitivity of the sensing platform. To further increase both sensitivity and selectivity of the sensing layer to hydrogen molecules, palladium nanoparticles are deposited on the graphene layer. A 3D numerical model of hydrogen detector, whose operational frequency is 110 MHz, presented. We investigate the impacts of the number of graphene layers, palladium nanoparticle size as well as their spacing on the time response of the SAW detector. We numerically show that palladium nanoparticles with a smaller diameter, i.e., 100 nm, can result in about 1.6 ns time shift in the response of the proposed SAW detector. Eventually, by using the optimum sizes of the graphene layers and palladium nanoparticles, hydrogen gas with a 3% concentration can be accurately detected by our proposed SAW sensing system.