Carbon-based nanoelectronic materials have attracted significant attention due to their potential to enable and/or improve applications such as transistors, transparent conductors, solar cells, and biosensors. This paper delineates chemical strategies for enhancing the electronic and optical properties of these promising nanomaterials. For example, we have recently developed a scalable technique for sorting single-walled carbon nanotubes (SWNTs) by their physical and electronic structure using density gradient ultracentrifugation (DGU). The resulting monodisperse SWNTs possess unprecedented uniformity in their electronic and optical properties, thus enabling the fabrication of high performance thin film field-effect transistors and transparent conductors. The DGU technique also enables multi-walled carbon nanotubes to be sorted by the number of walls, which facilitates the preparation of high purity solutions of double-walled carbon nanotubes (DWNTs). Monodisperse DWNT samples yield enhanced performance in transparent conductors and help elucidate the fundamental photophysics of DWNTs. As a final example, this paper will discuss the preparation and characterization of highly ordered self-assembled monolayers on graphene. In this case, organic functionalization allows the chemical properties of graphene to be tailored for subsequent materials deposition in addition to presenting opportunities for graphene-based molecular electronic and sensing devices.