ABSTRACT

Graphene can be regarded as a ¦at monolayer of carbon atoms tightly packed into a two-dimensional honeycomb lattice, and a basic building block for graphitic materials of all other dimensionalities. Despite its short history, graphene has attracted considerable attention and signi•cant progress has been made in both academic research and application studies, because of its exceptional electronic and mechanical properties. Among numerous widely investigated graphene-based materials, nanosized graphenes represent an intriguing class of compounds that are somewhat different from the in•nite graphene sheet. Generally speaking, nanosized graphene is the name given to a family of polycyclic aromatic hydrocarbons (PAHs) with average diameters between 1 and 10 nm, which can be regarded as two-dimensional graphene segments consisting of all-sp2 carbons. Although certain types of nanosized graphenes can be found in the residue of domestic and natural combustion of coal, wood, and other organic materials, development of new methods toward functionalized nanosized graphenes, especially for aromatics with high molecular weights, is crucial. The history of synthesis and characterization of nanosized graphenes can be dated back to the •rst half of the twentieth century, when Scholl et al. (1910) and Clar (1964) made pioneering contributions to this area. Harsh conditions (such as high temperature and strong oxidants and bases) were inevitably used at that time, and some earlier conclusions have gradually proven to be incorrect, which is a result of the limited characterization method and technique.