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A. Adetayo, D. Runsewe 1900s as the pencil industry was developed [3]. Other carbon allotropes, such as zero-dimensional (0D) fullerene [1] and one-dimensional (1D) carbon nano- tubes [2] were discovered in the 1980s and 1990s (Figure 1). However, there remained an argument on the existence of two-dimensional (2D) allotrope of carbon until 2004, when a publication by Andre Geim and Konstantin Novose- lov documented a successful isolation of a single layer of graphite (graphene) on a sticky tape by micromechanical cleavage (scotch tape method) of highly or- dered pyrolytic graphite (HOPG) [4]. Graphene is a two dimensional (2D) single layer structure of covalently bonded sp2-hybridized carbon atoms arranged in a hexagonal honeycomb net- work. It is a single-atom thick allotrope of carbon which serves as the basic structural unit for other carbon allotropic forms: 1) 0D fullerenes formed by wrapping up graphene sheet to form a sphere (Bucky ball), 2) 1D carbon nano- tube (CNT) formed by rolling of a graphene sheet to form a cylindrical struc- ture, and 3) 3D graphite formed by stacking several layers of individual gra- phene sheet held together by van der Waals bonds as shown in Figure 1 [5]. Single, double, and triple graphitic layers are commonly known as monolayer, bilayer, and trilayer graphene’s respectively. Graphene layers exceeding 5 and up to 30 aregenerally called multilayer graphene/thick graphene [6]. In graphene, the carbon-carbon bond distance is about 0.142 nm (1.42 Å) with the layer height (thickness) of about 0.33 nm (3.3 Å) (Figure 2) [3]. Graphene shows exceptional properties including a large theoretical specific surface area (2630 m2g−1) [7], high intrinsic mobility (200,000 cm2V−1s−1) [8] [9], high Young’s modulus (~1.0 TPa) [10], and thermal conductivity (~5000 Wm−1K−1) [11]. It also has good optical transmittance (~97.7%), good electrical conductiv- ity, and ability to withstand current density of 108 A/cm2 [12]. Graphene is also known to be a zero-bandgap semiconductor; therefore, the band gap can be tuned through simple physicochemical processes [13]. Owing to its exciting properties, study on graphene and its derivatives in the field of materials science and condensed-matter physics has generated immense attention over the past few years with various applications including membranes [14] [15], nanoelectronics [16] [17] [18], Li-ion batteries [19], electrodes [20] [21] [22], supercapacitors [23], sensors [24], drug delivery [25], etc. Graphene produced through micromechanical cleavage of graphite was pure with high quality, although it was time consuming and incapable of mass scale production. Recently, several other techniques have been reported for the fabri- cation and synthesis of graphene, such as epitaxial growth by chemical vapor deposition on copper (Cu) substrate [26] [27], epitaxial growth by thermal de- position of Si atom from SiC surface [28], colloidal suspension from graphite oxide [29], and many others. 2. Synthesis of Graphene The process of fabricating or extracting graphene based on desired size and quality is regarded as synthesis of graphene. So far, numerous approaches to DOI: 10.4236/ojcm.2019.92012 208 Open Journal of Composite MaterialsPDF Image | Synthesis and Fabrication of Graphene and Graphene Oxide
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