DNA
is more than a carrier of genetic information; it is also an
interesting building material for nanotechnology. This is because of its
extraordinary self-organizational properties. DNA is thus often used as
a “mold” for the production of nanoscale structures. Its use in the
assembly of electronic circuits is hampered by the fact that DNA is a
very poor conductor of electricity. One way to get around this is by
depositing metal onto the DNA strands.
Scientists
at the RWTH Aachen and the University of Munich have now developed a
new strategy for the controlled production and metallization of DNA
nanostructures. Led by Ulrich Simon, the team used a DNA strand
consisting of an immobilization sequence and a metallization sequence.
Several such strands are strung together so that the resulting DNA is
made of alternating sequences.
The
immobilization sequence contains alkyne groups. These allow the DNA to
be snapped into place on a silicon wafer coated with azide groups in
what is known as a “click” reaction. The other DNA segment has two
tasks: it is equipped with functional groups that cause the aggregation
of silver particles and can also attach DNA strands to each other.
The
DNA strands are stretched, deposited onto the wafers, and attached by
the “click” reaction. During the subsequent metallization with silver
particles, neighboring strands are simultaneously cross-linked to form
multistrands. These have significantly higher structural stability than
single strands. In the future, this method could also be used to
integrate the DNA strands into programmable DNA architectures to allow
for the positioning and binding of complex structures on prestructured
substrates.
Deposition
of the silver particles does not complete the metallization process. In
a second step, which resembles the development of photographs, gold
from a solution can be deposited onto the silver particles. Changing the
duration of the gold deposition process allows for variation of the
diameter of the resulting nanowires.
This
new method allowed the scientists to obtain micrometer-long,
electrically contactable nanowires that have potential for development
into further miniaturized circuits.
Source: Wiley
