Graphene/boron nitride

Hitherto known 2-D polymers include graphene [1], boron nitride [51] as well as metal oxides, hydroxides, and chalcogenides [2,23c]. These inorganic 2-D polymers are usually obtained by exfoliation from their parent laminar crystals this can be achieved using physical methods such as the scotch tape approach [1] or intercalation [52]. Many reports have been made on the preparation of laminar crystals which can, in principle, be regarded as the parent materials for 2-D polymers. For example, Antonietti and coworkers reported the details of graphitic carbon nitrides based on heptazine motifs, prepared by the thermal condensation ofcyanamide (>560 °C) [53] however, individual layers have not yet been separated from the bulk products. 

Two-dimensional (2D) nanocrystals are now recognised as a new form of matter with unusual physical properties and a number of potential exciting applications. Recent developments in the field of two-dimensional nanocrystals such as the chemical modification of graphene and the isolation of monolayers of molybdenum disulfide and boron nitride are reviewed. The different techniques that have been employed to prepare the materials such as mechanical and solution exfoliation, and chemical vapour deposition are discussed briefly. The techniques employed to characterise these 2D materials are described and their properties discussed. Potential engineering applications of 2D materials in fields such as nanocomposites and catalysis are then described. 

The future applications of 2D nanocrystals will be many and varied. It is possible to speculate over potential uses such as in electronic components and high performance nanocomposites. It is not, of course, necessary to use different individual types of 2D nanocrystals and hybrid systems have already been investigated. It is possible to create multilayer heterostructures and devices with designed electronic properties by stacking various 2D atomic nanocrystals crystals, such as graphene and boron nitride, on top of each other. These are essentially new forms of matter and the scope for developing hybrid systems is clearly vast and a whole host of unexpected applications of these novel materials will no doubt be forthcoming. 

Turbostratic A type of crystalline structure where the basal planes, such as graphene layers, have slipped sideways relative to each other, causing the spacing between planes to be greater than ideal. This structure is found in incompletely heat-treated carbon and boron nitride. 

Recent studies have started to broaden the choice of substrates to include surfaces that possess intriguing properties that could be used to interface with the adsorbed supramolecular structure or to influence the self-assembly process via substrate-adsorbate interactions. Examples of such surfaces include two surfaces that exhibit a moire superstructure, graphene, and boron-nitride monolayers. ... 

Boron nitride, for instance, having electronic properties that resemble carbon can exist in a hexagonal structure h-BN similar to the graphite layered geometry. Much like graphene sheets, BN sheets can be grown on more or less lattice-matched transition metal surfaces (Corso et al. 2004 Huda and Kleinman 2006). A model BN sheet is shown in O Fig. 27-14. 

Dean CR, Young AF et al (2010) Boron nitride substrates for high-quality graphene electronics. Nat Nanotechnol 5(10) 722-726... 

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