VNPs as Templates for Materials Synthesis - Viral Nanoparticles: Tools for Materials Science and Biomedicine - page 153

., 2006). TMV disk
structures (recall Chapter 3 — Section 3.5) were also obtained. The disk
structures contained hollow metal oxide tubes with an exterior diameter of
4 nm and an interior diameter of around 1.0-1.5 nm; these are one of the
smallest metal oxide structures generated to date by this method (Knez

TMV rods with metalized interior only (Knez et al

et

al ., 2006).

In a different approach, TMV particles coated with a thick silica mineral
layer (>20 nm) were used as templates for the metallization reaction.
Deposition of metals, such as silver, gold, palladium, and platinum, was
accomplished through conventional silica mineralization strategies. Here,
mercaptopropyl trimethylsilane (MPS) is used as heterobivalent linker
molecule to bridge the silica (silane group of MPS) and the metal (sulfur
group of MPS) (Fig. 6.8) (Royston

., 2009).
The metal nanotubes and nanowires described here are expected to find
applications in the field of nanoelectronics; the feasibility of TMV-templated
metallic nanomaterials for potential data storage devices has already
been reported (Tseng

et al

., 2006) (see below). For potential industrial
applications, it will be of interest to remove the infectious biotemplate
prior to embedding into devices. The removal of the TMV template from
mineralized structures can be achieved using either a plasma treatment
or calcination (thermal degradation). For example, hollow titanium tubes
were generated by coating TMV with an ultrathin film of titanium followed
by removal of the organic template by oxygen plasma treatment (Fujikawa
& Kunitake, 2003). Also, mesoporous inverse silica replicas have been
prepared by sol-gel condensation of SiO
2

et al

on TMV followed by calcination

(Fowler ., 2001).

So far, the techniques described in this section have been mostly applied
to TMV. In principle, these techniques could be applied to any other VNP.
The possibility has been demonstrated; for example, ELD has been applied
to CIV-yielding gold-coated icosahedral VNPs (see Section 6.2; Radloff

et al

et al .,

2005).

..1 tMV data Storage device

Platinum-metalized TMV particles served as a building block to fabricate a bio-
memory device (Tseng

., 2006). In brief, TMV particles were coated with
Pt nanoparticles via ELD. The Pt nanoparticles were evenly distributed over
the surface area of TMV and had an average size of approximately 10 nm (Fig.
6.9a). A functional device was fabricated by embedding the TMV-Pt hybrids
in a polyvinyl alcohol (PVA) matrix, which was sandwiched between two
aluminum electrodes (Fig. 6.9b). Current-voltage characteristics indicated
that the TMV-based device exhibited unique conductance switching behavior.

et al