Biomedical Engineering Reference
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Fig. 8.11
Assembly of gold nanoparticles on SWNTs via DNA hybridization (Copyright (2007)
Wiley. Used with permission from Ref. [
57
])
the two components were combined in a buffer solution with the AuNPs in large
excess to allow for an efficient hybridization and to minimize the formation of
cross-linked structures. The assembled products were separated from free AuNPs
by agarose gel electrophoresis. AFM imaging clearly revealed the high specificity
of the assembly process, with the gold nanoparticles randomly decorated along
the SWNTs. The realization of DNA-guided hetero-nanomaterials provides rich
opportunities for the building of SWNT-based electronic and sensing devices as
well as catalytically active nano-composites.
Graphene, a rising star among the carbon allotropes, represents the world's
thinnest free-standing material that can be mechanically exfoliated from graphite
or directly grown from molecular carbon precursors by chemical vapor deposition
(CVD) on a suitable substrate such as copper [
60
,
61
]. Alternatively, strong chemical
oxidation results in an oxide form of graphite that can be easily exfoliated into
single-layer graphene oxide (GO) nanosheets [
62
]. Further reduction of graphene
oxide by hydrazine or other chemical reductants generates a reduced form of GO
(namely reduced graphene oxdie, RGO). These graphene-based materials have been
attracting tremendous research efforts in various fundamental and technological
aspects. The ultimately large surface area, superior fracture strength, high ther-
mal conductivity, and optical and electronic transport properties render graphene
suitable for a wide range of applications. The resemblance between graphene and
carbon nanotube in their
-conjugated electrons suggested to us that a noncovalent
DNA decoration may be realizable for graphene following our success with carbon
nanotubes (Fig.
8.12
)[
63
]. This possibility would be especially worthy of being
investigated because graphene represents a unique form of two-dimensional carbon
material (carbon nanotubes are 1D) that may result in novel assembly controls.
Different from SWNTs, the oxide form of graphene can easily dissolve in
water in the absence of any dispersing agents. Our experiments confirmed that
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