Detection of organic vapors by graphene films functionalized with metallic nanoparticles

Abstract

Graphene synthesized by chemical vapor deposition has been used to study the sensing behavior of graphene for different organic vapors in ppm level. All the measurements were carried out at a room temperature with dry air as the background gas. Synthesis of graphene was carried out on a copper foil using methane gas as a precursor. The Raman spectroscopy was used to monitor the quality of graphene films transferred to SiO2/Si substrates, revealing the sensing channel to be mostly monolayer, bilayer, or tri-layer graphene. Graphene surface was functionalized with gold and platinum nanoparticles to enhance the gas sensing behavior. The adsorption/desorption behavior of organic vapors in dry air was analyzed based on the change in the conductivity with the different exposure times in different concentrations. Among the vapors tested, the sensitivity was in the order: acetic acid > ethanol > acetone from all surfaces (bare graphene, graphene decorated with gold and platinum nanoparticles). The devices were successfully tested for four key characteristics (response, recovery, repeatability, and reliability) of any practical gas sensors. The dynamic response behavior of the devices was also analyzed and fitted with the first order exponential function relating to the Langmuir approach. Based on the fit, the average response rate was obtained between 0.22% and 1.04% per ppm for different organic vapors with different surfaces. Average response rate of around 0.5% per ppm for organic vapors demonstrates a high sensitivity of the device at the room temperature under the ambient conditions.