Joined: 16 Mar 2004
|Posted: Wed Sep 20, 2006 10:50 am Post subject: Researchers Use DNA to Direct Nanowire Assembly & Growth
|Brown University Researchers Use DNA to Direct Nanowire Assembly and Growth
The coding qualities of DNA have been harnessed by a research team from Brown University to create zinc oxide nanowires on top of carbon nanotube tips. The journal ‘Nanotechnology’ explains that DNA has never before been used to direct the assembly and growth of complex nanowires.
The tiny new structures can create and detect light and also generate electricity, when mechanical pressure is applied. The optical and electrical properties of the wires allows for many applications, from fibre optical networks and computer circuits to medical diagnostics and security sensors.
Adam Lazareck, a graduate student in Brown’s Division of Engineering stated that “the use of DNA to assemble nano-materials is one of the first steps toward using biological molecules as a manufacturing tool. If you want to make something, turn to Mother Nature. From skin to sea shells, remarkable structures are engineered using DNA.”
The work is an example of “bottom up” nano-engineering. This is where engineers experiment with ways to get biological molecules to do their own assembly work rather than moulding or etching materials into smaller components. Molecular design and machinery can be used to create miniscule devices and materials, under the right chemical conditions
The team of engineers and scientists successfully harnessed DNA to provide instructions for this self-assembly. The new structures, created in the Xu laboratory, are the first example of DNA-directed self-assembly and synthesis in nano-materials.
The Xu laboratory is the first in the world to make uniform arrays of carbon nanotubes. Lazareck, with collaborators at Brown and Boston College, built on this platform to make their structures. They started with arrays of billions of carbon nanotubes of the same height and diameter, which were evenly spaced on a base of aluminium oxide film. On the tips of the tubes, they introduced a tiny synthetic snippet of DNA.
This DNA carries a sequence of 15 “letters” of genetic code. It was chosen because it attracts only one complement – another sequence made up of a different string of 15 “letters” of genetic code. This second sequence was coupled with a gold nanoparticle, which acted as a chemical delivery system, bringing the complementary sequences of DNA together. To make the wires, the team put the arrays in a furnace set at 600° C and added zinc arsenide. What grew: Zinc oxide wires measuring about 100-200 nanometers in length.
The team conducted control experiments – introducing gold nanoparticles into the array with no DNA attached or using nanotubes with no DNA at the tips in the nanotube array – and found that very few DNA sequences stuck and no wires could be made. According to Lazareck the key is DNA hybridization - the process of bringing single, complimentary strands of DNA together to reform the double helixes for which DNA is famous.
“DNA provides an unparalleled instruction manual because it is so specific. Strands of DNA only join together with their complements. So with this biological specificity, you get manufacturing precision. The functional materials that result have attractive properties that can be applied in many ways,” said Lazareck.
“We’re seeing the beginning of the next generation of nanomaterials,” said Xu, senior author of the article. “Many labs are experimenting with self-assembly. And they are making beautiful, but simple, structures. What’s been missing is a way to convey information – the instruction code – to make complex materials.”
Source and more information:
Brown University News Bureau
This story was first posted on 13th July 2006.