Biology Reference
In-Depth Information
shows a significant number of Lys and Arg side chains; at around pH 7, the
exterior surface exhibits positive charge (Namba & Stubbs, 1986). Thus,
the different surface properties of the exterior and interior surface may be
exploited to allow spatial and controlled deposition of metals.
In 1999, the first article describing the use of TMV as a biotemplate for
mineralization was published (Shenton
., 1999). The utility of TMV as
a template for co-crystallization with PbS and CdS, oxidative hydrolysis of
iron oxides, and sol-gel condensation of SiO
et al
was demonstrated (Fig. 6.5).
The nucleation of PbS and CdS was achieved by incubating TMV with the
precursor salts Pb(NO
3
2
S gas. TMV particles were
coated with a dense layer of PbS crystallites up to 30 nm in size and about
5 nm-sized CdS nanocrystals, respectively (Fig. 6.5a,b). Exposure of TMV to
NaOH and a Fe(II)/Fe(III) solution yielded rods coated with an amorphous
iron oxide mineral (Fig. 6.5c). Sol-gel condensation using tetraethoxysilane
(TEOS) under acidic conditions resulted in coating TMV with a uniform 3 nm
amorphous silica shell. End-to-end alignment of the VNPs was observed, a
typical phenomenon of TMV under acidic conditions (Fig. 6.5d) (Shenton
)
or CdCl
2
, and exposure to H
2
2
et
al
., 1999).
Noble metals such as platinum, gold, and silver can also be deposited on
TMV to form metallic TMV nanotubular composites (Bromley
et al
., 2008;
Dujardin
., 2003). This is achieved by exposure of TMV to platinum, gold,
and silver precursors followed by chemical or photochemical reduction.
Platinum and gold coatings were found on the exterior surface whereas silver
nanoparticles were incorporated inside the central channel (Fig. 6.6) (Dujardin
et al
et al
., 2003). The differential nucleation is electrostatically driven and can be
explained by the distinct exterior and interior surface charge (positive versus
negative). To test this, a TMV mutant with reduced interior anionic charge
Figure 6.6
Transmission electron micrographs of (a) gold nanoparticles produced
on the TMV biotemplate (scale bar is 100 nm) and (b) silver nanoparticles grown
inside the hollow channel of TMV. Arrows indicate nanoparticles that prevented the
stain (uranyl acetate) from penetrating further in the cavity. One of these is magnified
in the inset. Scale bar for the main image is 50 nm. Reproduced with permission
from Dujardin, E., Peet, C., Stubbs, G., Culver, J. N., and Mann, S. (2003) Organisation
of metallic nanoparticles using
Tobacco mosaic virus
,
Nano Lett.
,
3
, 413-417.
Search WWH ::
Custom Search