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was produced and exposed to silver precursors and reductants. Nucleation of
silver occurred preferably on the exterior versus the interior, thus indicating
that indeed surface charge and electrostatic interactions are the key players
in the mineral deposition mechanism (Dujardin
., 2003).
A range of methods have been developed that allow coating of TMV with
a broad range of inorganic materials (see Table 6.1). These methods include
electroless deposition (ELD) and atomic layer deposition (ALD, see below).
In ELD, which is also known as autocatalytic or chemical plating, nano-
objects are metalized with a metallization bath containing metal ions and
a reductant. The redox-reaction leading to the metallization event can only
occur on a surface that catalyzes the oxidation of the reductant (the surface
can be a noble metal). ELD is an alternative to electroplating where an ionic
metal is supplied with electrons to give the desired metal coating.
ELD has been successfully applied to TMV nanostructures, and metals
have been plated on the exterior and interior surface. First, TMV is coated
and activated with a noble metal, such as Pd, Pt, or Au. The activated TMV
particles are then subjected to the metallization bath. The ionic strength and
et al
Figure 6.7
Transmission electron micrographs of metalized TMV particles produced
by electroless deposition. (a) TMV after Pd(II) activation, followed by electroless
deposition of Ni. TMV is filled with a nickel wire with a diameter of approximately
3 nm. Reproduced from Knez M, Bittner AM, Boes F, Wege C, Jeske H, Maiß E, Kern
K (2003) Biotemplate synthesis of 3-nm nickel and cobalt nanowires.
Nano Lett.
,
3
(8), 1079-1082. (b) TMV metalized with nickel on the exterior surface. Reproduced
with permission from Knez, M., Bittner, A. M., Boes, F., Wege, C., Jeske, H., Maiß, E.,
and Kern, K. (2004) Spatially selective nucleation of metal clusters on the tobacco
mosaic virus,
Adv. Funct. Mater.
,
14
(2), 116-124.
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