DNA used as template for graphene electronic components

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ENGINEERS at MIT and Harvard University are using DNA templates to allow precision cutting of graphene patterns, which can then be used in electronic circuits.

DNA has a unique structure which allows it to carry genetic information. However, scientists have found that by controlling DNA sequences, they can manipulate the molecule to form many different nanoscale shapes.

Now, the researchers have expanded the approach, by using folded DNA to inorganic materials, such as graphene.

The chemical engineers first built DNA nanostructures of various shapes, before using the molecules as templates to create nanoscale patterns on sheets of graphene. According to the scientists, this is a step toward large-scale production of graphene-based electronic chips.

The scientists used single-stranded tiles (short synthetic DNA strands) to bind to each other, and thus construct complex DNA nanostructures.

The researchers experimented by using the single-strand tiles to create more than 100 distinct nanoscale shapes, including the full alphabet of capital English letters and emoticons. Computer software is used to design the structures, and they are then assembled in a simple reaction.

Since DNA degrades when exposed to sunlight or oxygen, and is not very chemically stable, it is not the perfect molecule for manufacturing purposes.

The scientists instead chemically transferred the precise structural information encoded in DNA to graphene. This is done by anchoring the DNA onto a graphene surface using aminopyrine. The DNA is then coated with silver, then gold, as a way to stabilise it with metallisation.

The metallised DNA is then used as a mask in plasma lithography, with oxygen plasma used to wear away the graphene not covered by the DNA, leaving behind a graphene structure identical to the original DNA shape. The DNA is then washed away with sodium cyanide.

The metallisation process causes the loss of some information, so the process is as yet imperfect. More precision can be achieved through the use of e-beam lithography. However, the latter technique is expensive and slow, and could pose problems for scaling up to mass-production.

Other applications for DNA on graphene is for the creation of graphene ribbons and graphene rings.

A graphene ribbon is a very narrow strip of graphene that confines the material’s electrons, giving it new properties. Unlike normal graphene, graphene ribbons have a bandgap, so they could be used as components of electronic circuits.

Graphene rings can be used as quantum interference transistors, a novel type of transistor created when electrons flow around a circle.