Chemistry

Forcing Patterns onto Graphene

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Science  26 Jul 2013:
Vol. 341, Issue 6144, pp. 321
DOI: 10.1126/science.341.6144.321-a
CREDIT: S. BIAN ET AL., JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 135, 25 (11 JUNE 2013) © 2013 AMERICAN CHEMICAL SOCIETY

The Diels-Alder reaction is used to create ring compounds between dienes and dienophile, which include a variety of substituted alkenes. A recent study showed that double bonds in the graphene surface can also act as dienophiles at elevated temperatures (50°C). Bian et al. harnessed this reactivity for patterning single-layer graphene supported on silica surfaces. They synthesized diene-bearing molecules—cyclopentadiene molecules functionalized either with a Raman-active dye or with electrochemically active ferrocene—and created an ink of these molecules with polyethylene glycol (PEG). They then loaded this ink onto an elastomeric tip array that was mounted on an atomic-force microscope tip and used it to write patterns. The Diels-Alder reaction has a negative activation volume and speeds up at elevated pressure. When sufficient force was applied with the elastomeric tips, the graphene reaction proceeded at room temperature. After washing off the PEG and unreacted molecules, they imaged the patterns with Raman microscopy and observed changes in characteristic graphene bands indicative of covalent bonding at the surface. Cyclic voltammetry studies revealed a much higher coverage than would be expected from the density of reactive double bonds on graphene. The authors suggest that cyclopentadiene is undergoing further oligomerization reactions under these conditions.

J. Am. Chem. Soc. 135, 9240 (2013).

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