ABSTRACT
There has been realized several strategies to incorporate and to functionalize carbon nanomaterials for NLO applications. The graphenes and CNTs achieve the open-shell character due to the localization of α and β spins on zigzag edges (Yoneda et al., 2011), while in fullerenes, the spin density are usually localized on terminal edges with highly constrain bonding parameters (Muhammad et al., 2013a). These magnetizations in carbon nanomaterials have been reported even in the absence of transition metal complexes. The proposal about the origin of open-shell character from the zigzag edges of graphenes and CNTs is very important especially for their functionalization. The zigzag edges can have two types of CNTs and graphenes, that is, nonpassivated or hydrogen-passivated (Son et al., 2006). A ‰at band at the Fermi level is present in both cases of edges, which cause an open-shell ground state with nonzero magnetic moments at the edges. An antiferromagnetic (AFM) coupling can be observed in mutually opposite edges of nanographenes and CNTs. Furthermore, under the strong electric eld, the spin-polarized edges of nanographenes and CNTs result in half-metallicity, which is a useful property for the practical application of graphenes and CNTs in spintronic devices (Son et al., 2006). Although the openshell character for graphenes, CNTs, and fullerenes have extensively studied (Cervantes-Sodi et al., 2008), the research in their open-shell character with reference to their diradical character is still rare and is limited to few nanomaterial systems. In the present chapter, we will spotlight not only the origin of open-shell diradical character in carbon nanomaterials but also check the in‰uence on the third-order NLO properties. An overview of different design strategies for functionalization of nanomaterials will be presented based on several previous reports of magnetic properties of carbon nanomaterials.
