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improved detection sensitivity. Last but not least, light-harvesting systems
were fabricated making use of fluorophore-labeled coat proteins and self-
assembly methods. Some examples are discussed below (see also Table 4.1).
4.4.1 Electro-Acive CPMV Complexes
To test the potential of VNPs to serve as a platform for the development of
redox-active materials, CPMV particles were covalently modified with redox-
active species. Decoration of CPMV with approximately 240 ferrocenes
and 180 viologen moieties has been achieved (Steinmetz
, 2006b,c).
In both cases, electrochemical studies confirmed the presence of redox-
active nanoparticles; the redox couple was electrochemically reversible.
Simultaneous multielectron transfer was observed, indicating that the
multiple redox centers are independent and behave as essentially non-
interacting redox units. The resulting robust and monodisperse particles
could serve as multielectron reservoirs and nanoscale electron transfer
mediators in redox catalysis or amperometric biosensors.
et al.
4.4.1.1 Self-assembly of conducing networks on the surface of CPMV
CPMV particles have been used as a scaffold for a bottom-up self-assembly
approach to generate conductive networks at the nanoscale (Blum
,
2005b). This study highlights how the use of VNPs facilitates high-precision
control over the attachment sites. In brief, two different CPMV Cys-added
mutants were designed that displayed the Cys-reactive residues in different
surface loops on the capsid surface. One mutant displayed 60 Cys residues,
whereas a double mutant offered 120 Cys-derived attachment sites. Gold
nanoparticles were bound to the genetically engineered sites based on
gold-sulfur interaction (Fig. 4.19) (Blum
et al.
, 2005b). The attached gold
nanoparticles were subsequently interconnected by molecular wires, thus
creating a 3D conducting molecular network. To achieve this, the following
molecules were used: 1,4-C
et al.
and
oligophenylenevinylene. Molecular attachment of the linkers was confirmed
by fluorescence spectroscopy. Physical measurements confirmed the
conductance of the self-assembled molecular network (Blum
H
[
trans
-(
-AcSC
6
H
4
C
≡
CPt-(PBu
)
C
≡
C]
2
6
4
4
3
2
, 2005b).
Not only can materials be attached with high precision to the VNP
surface, but also materials can be interlinked on the particle surface. This
holds great promise in assembling and interconnecting conducting materials
on the nanometer scale and may lead to the development of nanoelectronic
systems, such as nanocircuits and data storage devices.
et al.
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