Interactions of molecular species with graphene and graphene sensing

Since its first isolation in 2004, graphene has been the subject of intensive research for its remarkable properties. Graphene is a two-dimensional (2D) net of sp2 hybridized carbon atoms. This particular 2D system possesses fascinating physical and chemical properties that have been explored in several fronts. In addition to the isolation of graphene via Scotch tape exfoliation of mineral graphite reported in 2004, other approaches to synthesize large-area graphene samples were developed including the epitaxial growth through silicon carbide annealing and the chemical vapor deposition (CVD) method. The CVD technique has the advantage of allowing the inclusion of heteroatoms during the growth, so as to produce doped graphene. The nature of the dopant atoms, the way they bind to the honeycomb lattice of carbon atoms, and their concentration have important effects on the graphene properties. For example, the charge carrier concentration, the mechanical properties, and the lattice vibrations vary significantly after doping. Graphene and doped graphene are very sensitive to the environment due to their large surface-to-volume ratio, thus making them well suited for sensor devices. It has been demonstrated that trace amounts of specific molecules adsorbed on graphene can be detected by Raman scattering. In this chapter, we review the recent research on the electronic structure of graphene and doped graphene interacting with adsorbed molecules, the ways these interactions affect the substrate properties, and some methods to detect the presence of adsorbates. We will focus on the graphene-enhanced Raman scattering detection method and discuss the possible mechanisms that originate the effect.