Functionalized Graphene Nanocomposites

Abstract

Graphene is one of the most exciting materials being investigated today, not only out of academic curiosity but also its potential applications. Graphene, a single layer of carbon packed in a hexagonal lattice, with a carbon-carbon distance of 0.142 nm is the first truly two-dimensional crystalline material, which is stable at room conditions. Graphene has displayed a variety of intriguing properties including high electron mobility at room temperature (250,000 cm2/Vs) exceptional thermal conductivity (5000 W m-1 K-1) and superior mechanical properties with Young’s modulus of 1TPa (Singh, Joung et al. 2011). Thus, graphene sheets offer extraordinary electronic, thermal and mechanical properties and are expected to find a variety of applications, such as sensors, batteries, supercapacitors, hydrogen storage systems and as reinforcement fillers of nanocomposites (Soldano C., Mahmood et al. 2010). The joint award of the 2010 Physics Nobel Prize to Andre Geim and Konstantin Novoselov, as stated by the Royal Swedish Academy (2010), for groundbreaking experiments regarding the two-dimensional material highlights the importance of this single atomic layer of carbon. This discovery is considered a breakthrough in the nanotechnology era, bringing the concept of single atomic component closer to reality. Even before the studies of Novoselov and Geim, efforts had been carried out to prepare very thin graphite or graphene layers, since interesting properties were expected (Boehm 2010), but there were experimental difficulties in isolating single layers in such a way that electrical measurements could be performed on them, and there were doubts that this was practically possible. Graphene discovery marked the onset of experimental physics on graphene, which then made it relevant to revisit successfully all other methods to produce graphene which had reputedly failed in the past four decades. So far, the original top-down approach of mechanical exfoliation using the Scotch-tape method has produced the highest quality samples, but the method is neither high throughput nor high-yield, the probability of finding individual graphene sheets of good quality is often low. In order to exfoliate a single sheet, van der Waals attraction between exactly the first and second layers must be overcome without disturbing any subsequent sheets (Allen, Tung et al. 2010). Many studies emerged over the last years with alternatives to mechanical exfoliation including chemical vapour deposition (Zhao, Rim et al. 2011), epitaxial growth (Ushio S, Arata Yoshii et al. 2011), carbon nanotube cutting (Janowska,