Graphene Via Self-Assembly

Adapted with permission, © 2009 Wiley-VCH
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A pyrrole compound (red and blue) self-assembles with tetraethoxysilane to form a layered structure (silica sheets are gray). Polymerizing and heating converts the ordered material to a single layer of carbon sandwiched between sheets of silica, which can be removed with dilute acid to yield single-layer graphene.

By using a surfactant that serves as a structure-directing agent and a source of carbon, researchers in China have developed a synthesis method for producing graphene—a single layer of carbon atoms. The method yields purer products, is more reproducible, and offers additional advantages relative to other ways of making this ultrathin form of carbon (Angew. Chem. Int. Ed., DOI: 10.1002/anie.200902365).

Owing to its outstanding electronic, mechanical, and structural properties, graphene holds promise as a key component in various applications, including nanoelectronic devices and supercapacitors. As a result, researchers have developed a number of "top down" preparation methods based on peeling apart sheets of graphene from bulk graphite and high-temperature treatment of silicon carbide.

Weixia Zhang and Guangtao Li of Tsinghua University, in Beijing, and coworkers now demonstrate a "bottom up" synthesis that proceeds under mild conditions and yields gram-scale quantities of pure single-layer graphene.

By reacting a lysine-based surfactant bearing a terminal pyrrole moiety with tetraethoxysilane, the team exploits a self-assembly process that packs the pyrrole units into a confined layer between sheets of silica. They then polymerize the pyrrole and heat the intermediate product to convert the organic component to a single layer of carbon. Finally, they remove the silica sheets with dilute acid to yield single-layer graphene.

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