The last two decades have witnessed a tremendous growth in the development and understanding of ${sp}^2$ carbon-based nanostructures. The impact of this research has led to a number of fundamental discoveries that have played a central role in the understanding of many aspects of materials physics and their applications. Much of this progress has been enabled by the development of new techniques to prepare, modify, and assemble low-dimensional materials into devices. The field has also benefited greatly from much progress in theoretical and computational modeling, as well as from advances in characterization techniques developed to probe and manipulate single atomic layers, nanoribbons, and nanotubes. Some of the most fundamental physical properties of ${sp}^2$ carbon-based nanostructures are reviewed and their role as model systems for solid-state physics in one and two dimensions is highlighted. The objective of this review is to provide a thorough account on current understanding of how the details of the atomic structure affect phonons, electrons, and transport in these nanomaterials. The review starts with a description of the behavior of single-layer and few-layer graphene and then expands into the analysis of nanoribbons and nanotubes in terms of their reduced dimensionality and curvature. How the properties can be modified and tailored for specific applications is then discussed. The review concludes with a historical perspective and considers some open questions concerning future directions in the physics of low-dimensional systems and their impact on continued advances in solid-state physics, and also looks beyond carbon nanosystems.

The recently developed pitch-based graphitic foams have a very high thermal conductivity to weight ratio. This property allows graphitic foams to be used in several thermal management applications, especially in the aeronautics and aerospace industries. Raman spectroscopy studies were performed on the different structural regions of the foam, yelding important information on the structural properties of the graphitic foams, as well as on the physical properties of graphite. The graphitic foam was found to be composed of two intermixed graphitic structures, one with stacked planes and one with a turbostratic structure. This special structure allowed for a simultaneous study of the properties of two-dimensional (2D) and three-dimensional (3D) graphitic structures. The dispersion of the $G^{\prime }$ band was found to be different for 2D and 3D graphite. The intensity of the $D$-band Raman feature was used to probe the density of defects in the structure, leading to the conclusion that the defects are mainly localized in the 2D structures. A simple model is proposed to explain the origin of the two different structures within the graphitic foam. Also, the dependence of the $G^{\prime }$ band on polarization is addressed.