ABSTRACT
Several methods have been developed over the years for the synthesis of graphene [1,4,18-22]. These include mechanical exfoliation [1], chemical exfoliation [20], chemical vapor deposition (CVD) [21], and thermal decomposition of silicon carbide [22]. One of the economical yet effective routes to produce bulk quantities of graphene is chemical reduction of exfoliated graphite oxide [23-27]. Using inexpensive graphite as the starting material, graphite is first oxidized to graphite oxide by insertion of strong acids and oxidizing agents within the interlayer spacing of graphite [26]. Graphite oxide is then chemically exfoliated into individual layers called graphene oxide [23,26,27]. Just as each layer of graphite is graphene, each layer of graphite oxide is graphene oxide [4], but graphene oxide is nonconducting or has very low electrical conductivity due to disruption of the sp2 bonding system [19,25]. These graphene oxide layers are precursors for the production of graphene by the removal of oxygen groups, that is, by reduction of graphene oxide [23]. Graphene oxide is easier to process since presence of oxygen-containing groups in the layered material makes it easier to disperse in water and other solvents [19,23,28-31]. Reduction of graphene oxide to reduced graphene oxide restores the structure and properties, particularly electrical conductivity of graphene, though complete removal of oxygen is not achieved [23,26,28]. Graphene oxide and reduced graphene oxide can be chemically modified due to the existence of oxygen-containing functional groups on their surface to obtain chemically modified graphene-based materials [25,26,32,33].
