Selective Metallization of DNA Origami Towards Self-Assembled Nanoelectronic Systems
The fabrication of inorganic nanostructures with controlled morphology, composition and size is essential
for making nanodevices. Although existing top-down methods for nanofabrication offer some of these
capabilities, issues such as cost, complexity and reliability become major considerations as overall feature
dimensions approach 100 nm and linewidths decrease to ~10 nm. Thus, alternative strategies for the
tailored construction of nanosystems become attractive. One very exciting possibility is to use molecular
interactions to form nanometer-scale features from the bottom up through self-assembly processes. We
are studying the formation of designed nanostructures with narrow (~10 nm) linewidths and overall
footprints of a few hundreds of nanometers. We use the method of scaffolded DNA origami [1] to form
branching templates having a diversity of architectures, consisting largely of open space and having
asymmetric junctions [2]. We have explored a number of distinct ways to allow DNA templates to be
coated selectively with inorganic materials. We have developed methods for silver and palladium seeding
on DNA origami. These seeds then allow electroless plating of metals such as gold, palladium and copper
to yield designed nanostructures with linewidths as small as 30 nm [3, 4]. Importantly, the metal
nanostructures formed have the same morphology as the initial DNA template. Moreover, we are
evaluating site-specific placement of gold nanoparticles within DNA origami. We have demonstrated that
these nanoparticles can serve as seeds for the selective plating of metal onto targeted regions within
designed DNA nanostructures, while also allowing for the formation of controlled gaps in desired
locations. For example, using this seeding process we have shown that a three-branched DNA origami
can have gold selectively plated onto one or two arms of the structure. Furthermore, we have formed gold
nanowires of ~200 nm lengths with controlled, insulating gaps in the middle. We have used atomic force
microscopy and electron microscopy to evaluate the formation of DNA templates, the extent of seeding,
the amount of plating and the size of gaps. We have also nanofabricated lithographically patterned
electrodes on top of these nanostructures to enable resistance measurements to be made on individual
metal-coated DNA origami constructs. Importantly, we have determined for the first time the electrical
resistance of copper nanowires formed on these DNA nanostructures [5]. Our experiments confirm that
metal-coated DNA nanostructures have desirable properties for nanoelectronics. We expect our hybrid
DNA-inorganic systems to find application in fields such as nanofabrication, photonics, sensing and
electronics.
Acknowledgment
This work was funded by the National Science Foundation (CBET 0708347).
References
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