![]() The shaded portion of the nanotube in Figure 1(b) represents one unit cell of the resulting armchair nanotube in this case, and it results from rolling the initial planar sheet in Figure 1(a), so that points A and C coincide with points B and D, respectively. Figure 1 illustrates the hexagonal lattice of a perfectly flat graphene sheet and the resulting nanotube after it is rolled along the vector labeled C h. Graphene is a two-dimensional carbon nanomaterial with a single layer of sp 2-hybridized carbon atoms arranged in a crystalline structure of six-membered rings. Since graphene can be considered as the conceptual parent material for all other sp 2 nanocarbons, it is the first in our discussion of the two-dimensional characteristics obtainable via Raman spectroscopy. The elucidation of novel physics related to 2D electronic systems (2DES) has received wide recognition in the form of three Nobel Prizes in Physics in 1985 (Klaus von Klitzing, Max Planck Institute, for the discovery of the integer Quantum Hall Effect), in 1998 (Robert Laughlin, Stanford University, Horst Stormer, Columbia University, and Daniel Tsui, Princeton University, for the discovery of the fractional Quantum Hall Effect), and in 2010 (Andre Geim and Konstantin Novoselov, University of Manchester, for ground-breaking experiments relating to the 2D material graphene). Scanning electron microscope (SEM) images of functionalized graphene nanoplatelet aggregates doped with argon (A), carboxyl (B), oxygen (C), ammonia (D), fluorocarbon (E), and nitrogen (F), have also been recorded and analyzed using the Gwyddion software. The G-band peak located at ~1586 cm−1, common to all sp2 carbons, has been used extensively by us in the estimation of thermal conductivity and thermal expansion characteristics of the sp2 nanocarbon associated with single walled carbon nanotubes (SWCNT). The following chapter describes our studies of the G, D, and G′ bands of graphene and graphite, and the characteristic information provided by each material. The information derived from the unique Raman bands from a single layer of carbon atoms also helps in understanding the new physics associated with this material, as well as other two-dimensional materials. ![]() Theoretical discoveries, associated with sp2 carbons, such as the Kohn anomaly, electron-phonon interactions, and other exciton-related effects, may be transferred to other potential 2D materials. ![]() The theoretical simplicity of sp2 carbons, owing to their having a single atomic type per unit cell, makes these materials excellent candidates in quantum chemical descriptions of vibrational and electronic energy levels.
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