EPR Spectroscopy in the Study of 2D Graphene-based Nanomaterials and Nanographites

Graphene-based nanomaterials and nanographites represent 2D and 3D materials, where the transition from one type of materials to the other is without clear boundaryies. In this type of materials, where the leitmotiv is represented by the presence of single or multi-stacked graphene layers, EPR has been fruitfully employed as spectroscopy for structural characterization, as well as for the quantification of paramagnetic defects and for the study of magnetic properties. In this type of carbon-based materials, a fundamental role is played by two main actors a) conduction electrons, belonging to the extended π-system, and b) edge states: electrons described by wavefunctions of limited extension associated to zigzag termination of the graphenic layers. A strong interaction between conduction and localized electrons, and in the presence of other minor paramagnetic contributions like other types of defects (crystal vacancies), or so-called molecular states (very small graphenic fragments), a vast spectrum of magnetic responses is obtained from the materials, from a ferromagnetic to an antiferromagnetic behavior. In this Chapter, methodological and introductory Sections are followed by a list of examples which highlight the use of EPR in this field.