Graphene is an atom-thick layer of carbon that was the first two-dimensional material ever discovered. Under an atomic microscope graphene is a flat lattice of hexagons linked in a honeycomb pattern. Graphene’s structure allows electrons to move across the lattice unimpeded by other layers at high speed. Graphene can carry a thousand times more electricity than copper. Andre Geim and Kostya Novoselov are authors of a 2004 Science paper that first describes graphene based on research conducted in Russia and the UK. Geim and Novoselov, who are both at University of Manchester were awarded the 2010 Nobel Prize in Physics “for groundbreaking experiments regarding the two-dimensional material graphene”.
Graphene was discovered by Andre Geim, a physics professor at the University of Manchester. Geim specializes in microscopically thin materials and wondered how very thin layers of carbon might behave under certain conditions. Geim’s research group discovered that graphite, which consists of stacks of atom-thick carbon layers, comes off onto Scotch tape in thin flakes. By folding the tape and then pressing and pulling apart, the flakes were further peeled down to thinner layers until it reached the thinness of an atom-thick layer of carbon.
Geim’s group discovered that graphene, like silicon, has a pronounced field effect, suggesting it could replace silicon in some applications. The field effect shown by graphene when placed near an electric field indicated that conductivity could be controlled. Semiconductors like silicon can turn on and off in the presence of an electric field and that switching generates the ones and zeros in computer chips. Graphene is a semi-metal that cannot be off without modifying the material in a process called doping. However doping graphene has been found to reduce electron mobility. Doping graphene can be achieved by the deposition of different adsorbates, either atoms or molecules, on the graphene surface.
Graphene is a material that is thin and strong with high thermal and electrical conductivity. These characteristics along with its high permeability and high electron mobility make graphene potentially useful for applications in electronics such as semiconductors, energy storage and generation devices and sensors. Graphene films can be used in protective coatings on smartphones and flexible electronic devices. In various applications graphene replaces silicon.
Graphene quantum dots (GQDs) are nanometer-sized material derived form one or a few layers of graphene. GQDs have a large surface to mass ratio and are fluorescent. GQDs have applications in organic photovoltaic devices, catalysis, sensors and biomedicine. GQDs have been shown to enter the cytoplasm of human cells without significantly affecting cell viability. GQDs have been used in research related to tissue imaging, cancer diagnostics, intracellular sensing and drug delivery.
