For some years now the unique electronic properties of graphene have attracted interest in this material. There are many research areas that involve it, from high-speed electronics to sensors. The latter together with molecular electronics promise the creation of graphene sensors capable of identifying individual molecules. This is the sector in which this thesis work belongs, in which graphene is analyzed as a possible sensor for the aflatoxin molecule. In the first part the main characteristics of graphene are reviewed, with its physical structure, the particular electronic band structure, the transport behavior, the density of the states, its finite-dimensional structures, the presence of defects and the doping.