Ammonia gas sensing behavior of graphene synthesized by CVD on copper substrate using a methane and hydrogen gas mixture was investigated. The Raman spectroscopy was used to monitor the quality of graphene films transferred onto SiO2/Si substrates. The sensitivity and the recovery time of the device were enhanced by the deposition of gold nanoparticles on the surface of graphene films. The dependence of the sensing response with the operating temperature was studied. The adsorption and desorption curves were analyzed using Langmuir kinetic theory and Freundlich isotherm for the adsorption of ammonia gas. The activation energy and the heat of adsorption were estimated to be around 38 and 41 meV, respectively for NH3 gas concentration of 58 ppm at room temperature. (C) 2012 Elsevier Ltd. All rights reserved.