ABSTRACT
Graphene is a single-atom-thick sheet containing sp2-bonded carbon atoms in a hexagonal lattice. Although graphene is the origin of 0D fullerene, 1D carbon nanotubes (CNTs), and 3D graphite that have been widely studied for decades, not too much attention was given to graphene previously (Geim and Novoselov 2007). Graphene is an exclusive material that has the bene t of being both conducting and transparent. It is gaining more attention for their applications in condensed-matter physics, chemical, electronics, and materials science (Geim and Novoselov 2007) and due to its remarkable electrical, thermal, optical, and mechanical properties (Peigney et al. 2001; Zhang et al. 2005; Ghosh et al. 2008; Lee et al. 2008; Lu et al. 2009). Graphene-based materials have been used in various elds such as nanoelectronic devices, biomaterials, intercalation materials, drug delivery, and catalysis (Stankovich et al. 2006; Gilje et al. 2007; Robinson et al. 2008; Arsat et al. 2009; Pasricha et al. 2009; Seger and Kamat 2009; Liang et al. 2010; Akhavan et al. 2011). Currently, several methods have been presented in the literature for the preparation of graphene nanosheets that includes micromechanical exfoliation (Novoselov et al. 2004), chemical vapor deposition (Reina et al. 2009), epitaxial growth (Sutter et al. 2008), scotch tape method (Novoselov et al. 2004), electrostatic deposition of graphene (Sidorov et al. 2007), thermal or chemical decomposition of graphitic materials (Dujardin et al. 1998), and thermal (Hannes et al. 2006) and substrate-free gasphase synthesis (Dato et al. 2008). Further, for bulk synthesis of graphene, the common process is the chemical exfoliation of graphite (Dresselhaus and Dresselhaus 2002), in which graphite at rst has been oxidized to graphite oxide by oxidation with oxidizing agents such as KMnO4 (Hummers and Offeman 1958), K2Cr2O7 (Chandra et al. 2010), and KClO3 (McAllister et al. 2007). These methods have been used for the preparation of a graphene dispersion; however, its critical disadvantages are low yield (1%–10%), a signi cant amount of solvent requirements, and poor stability of the graphene dispersion making many applications unworkable (Hamilton et al. 2009; Wang et al. 2009).
