Graphene edge

C. Casiraghi, A. Hartschuh, H. Qian, S. Piscanec, C. Georgi, A. Fasoli, et al., Raman spectroscopy of graphene edges, Nano Letters, 9 (2008) 1433-1441. 

So, the true relevance of the phenalenyl radical to graphene edge chemistry and physics resides in the fact that, as graphene layers grow by condensation/dehydro-genation processes, and rather than trapping n radicals as a consequence of edge sat-... 

The issue of the chemical nature of graphene edges, and thus of (re)active sites, was addressed head-on by Radovic and Bockrath [29]. Density functional theory was used to minimize problems that truly ab initio approaches such as Hartree-Fock are known to have, but careful comparison with experimental results in several seemingly unrelated fields was also performed. The key argument of relevance here is that, rather than being H-terminated, the sites that are most relevant for the chemical (re)activity of sp2 hybridized carbon materials are of carbene- and carbyne-type, as illustrated below for the zigzag (a) and armchair edges (b). 

Fig. 19.3 Schematic representation of the role of carbene-type graphene edge sites in the photoluminescence effect of graphene quantum dots. (Adapted from [44].)...

The issue of zigzag graphene edge saturation was explicitly addressed by Kudin [67], albeit by considering not the more reasonable aromatic H saturation but the con-... 

In a follow-up study, Malola et al. [126] used density-functional tight-binding theory to explore the structural, chemical and dynamical trends in a graphene sample formed by merging two graphene edges with the same chirality but different ori-... 

Enoki T, Kobayashi Y, Eukui K (2007) Electronic structures of graphene edges and nanographene. Int Rev Phys Chem 26 609-645... 

FIGURE 5.3 Examples of nitrogen-containing surface functional groups in carbons (1) pyridine-type N, (2) pyrrole-type N, (3) basal-plane N (edge), (4) amine-type N, (5) substitutional N, and (6) quaternary N. (The top layer shown represents the graphene edge.)... 

Figure 5.4 summarizes in a schematic way the current state of knowledge of carbon surface chemistry, with an emphasis on the details of graphene edges. As discussed in Section 5.2.1, it shows the dominant surface functionalities, all containing oxygen because of the often inevitable contact of realistic carbon materials with 02 from air. The main features of interest here are (i) the existence of free edge sites and (ii) the notion that the basal plane is not as chemically inert as is often... 

Casiraghi C, Hartschuh A, Qian H, Piscanec S, Georgi C, Fasoli A, Novoselov KS, Basko DM, Ferrari AC (2009) Raman spectroscopy of graphene edge. Nano Lett 9 1433-1441... 

So the key fundamental question here is the following Which precursor-and/or process-driven factors are responsible for this detour from fiat to curved sp structures In competition with the well-documented tendency of (fused) benzene rings to stack parallel to each other and thus retain planarity and resist curvature, there is an apparently effective mechanism for the elimination of pentagons at graphene edges. It is summarized in Table 1.2 and Figure 1.7 and is discussed in some detail below. 

Figure 1.7 One possible mechanism of elimination of pentagons at graphene edges. (From ref. 61.)...

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