Desenvolvimento de um sensor de pH com base em grafeno

Abstract

Since its discovery in 2004 graphene is seen as a great material, to be used in new electronic devices, because of its special properties such as high electron mobility, excellent flexibility and mechanical resistance, biocompatibility and large surface area to volume ratio. In particular, these last two properties have motivated the use of graphene as the basis for chemical and biological sensors [1]. In this dissertation, we present a study of a device based on graphene that acts as a chemical sensors, more specifically as a pH sensor. The fabrication of this sensor and the electrical measurements will constitute a preliminary study of the use of graphene as a basis for a biosensor. We have measured the changes in the resistance of a graphene device with the pH of a solution in contact with it. We have also studied how this resistance changes when a voltage is applied between the graphene and an electrode placed in the solution. We also present a theoretical analysis of the measurements of conductance as a function of the top gate voltage. With this analysis, we have been able to infer the carrier density and mobility of graphene as a function of pH solution. Changes in the mobility and carrier density of graphene can be explained by the adsorption of ions on the surface of graphene and by an electrical double layer which is formed in the surface-electrolyte interface.