Biomolecular Architecture for Nanotechnology - Bionanoelectronics: Bioinquiring and Bioinspired Devices - page 159

a b c

linker

silver

d e

Au layer

Au

Fig. 5.6 Fabrication of a trilayered nanocable: ( a ) hollow peptide nanotubes, ( b ) silver reduction
on the inner surface of the nanotube, ( c ) addition of linker peptides, ( d ) binding of Au nanoparti-
cles, and ( e ) the final nanocable

photogenerated charge carriers in comparison to TiO 2 nanoparticles, used in
common dye-sensitized solar cells. Thus, the 10-nm-thick hollow TiO 2 nanoribbons
fabricated by uniformly coating the diphenylalanine aromatic peptide template
allowed an increase of the power conversion efficiency to 3.8%, compared to the
3.5% value of conventional dye-sensitized solar cells that use TiO 2 nanoparticles.
This peptide has a high thermal stability and supports atomic layer deposition
processes. The peptide is then removed by calcination at temperatures as high as
500 ı C. The thickness of the polycrystalline nanoribbon can be controlled by the
calcinating temperature.

5.3 Two- and Three-Dimensional Bioarchitectures

as Scaffolds

More complex patterns of nanoparticles than lines are required for writing DNA-
assisted electronic circuits. Functionalized inorganic nanoparticles can link to DNA
strands, which can be either painstakingly assembled one by one on a surface with
the help of an AFM tip ( Puchner et al. 2008 ) or can self-assemble in sophisticated
architectures. For nanotechnological applications, the latter situation is desirable,
although in the first case, a larger freedom of pattern shapes and sizes and available
locations can be achieved.
An example of a two-dimensional array, consisting of alternating rows of
nanocomponents with different size, self-assembled on a DNA scaffold is presented
in Pinto et al ( 2005 ). In this case, Au particles with diameters of 5-10 nm were
coated with 3 0 -thiol-modified ssDNA strands complementary to the strands on
specific sites on different rows, the interrow spacing being of 32 nm. The self-
assembly of Au nanoparticles was caused by DNA hybridization. The pattern of
the DNA scaffold consists of rows of different tiles, denoted by A, B, C, and D