Researchers are attaching chains of carbon atoms to C₆₀ ‘buckyball’ molecules causing them to controllably self-assemble into spheres, wires and sheets. The strings are semiconductive and photoconductive, and the structures could improve doping in organic solar cells.

Once the chains are attached, the resulting molecule is an ‘amphiphile’ (see box below) – its ends have a different affinity to certain solvents, much like washing-up detergent in water.

Detergents are well understood, and are increasingly being exploited to create order in liquid, forming ‘soft’ structures, some of which can used as the basis for solid structures.

“We have applied science that is normally applied to detergent, and applied it to molecules you wouldn’t normally expect it to apply to,” Dr Martin Hollamby of Keele University told Electronics Weekly.

This means that self-assembly techniques developed using detergents can be adapted for C₆₀.

Hollamby is working with Dr Takashi Nakanishi of the Japanese National Institute for Materials Science.

In their experiments, the chains attached to C₆₀ are branched alkanes (a form of hydrocarbon).

When dissolved in a liquid n-alkane (octane is an alkane eight carbon atoms long, so n=8), the new molecules assemble to form a spherical core of C₆₀ molecules within a shell of carbon chain tails (see box below).

“Changing the chemistry of the chains can lead to gels made of bundled C60 wires that have a measureable photoconductivity,” said Hollamby. “By adding pristine C₆₀ in place of the solvent, we instead prepare a sheet-like material now with totally different properties.”

The wires are hexagonally-packed gel-fibres containing insulated C60 nanowires, according to a Nature Chemistry paper on the work (‘Directed assembly of optoelectronically active alkyl–π-conjugated molecules by adding n-alkanes or π-conjugated species‘).

“The assembled structures contain a large fraction of opto-electronically active material and exhibit comparably high photo-conductivities. This method is shown to be applicable to several molecules, and can be used to construct organised functional materials,” said the paper.

Neutron beamline D11 at the Institut Laue-Langevin (ILL) allows scientists to watch molecular self-assembly

Many different structures can be produced by making small changes to the chemical structure and the additives (solvent or C₆₀) used, according to the team, and this level of control over self-assembly in complex molecules such as C60 is not accessible by any other method reported to date.

So what has all this got to do with electronics?

Importantly for electronics, C₆₀ is a strong electron acceptor, and is already used to dope organic solar cells.

However, according to Hollamby, unstructured C₆₀ is an insulator and only becomes a semiconductor if C₆₀s are bought in close proximity, as they are in the amphiphilic wires, for example. And the wires come ready-insulated by being surrounded by the alkane tails.

What Keele and the National Institute for Materials Science have done is put another tool in the toolbox of organic electronics research. Dots, wires and sheets of C₆₀ are now available for experimentation – although currently only in solution.

Already Hollamby is trying to make solar cells and capacitors using the structures.

The neutron scattering facility (Beamline D11, see photo) at the Institut Laue-Langevin (ILL) was used to investigate assembly and resulting structures.

“The light elements that makes up these molecules are easily located by neutrons” said Dr Isabelle Grillo at ILL.”Small-angle neutron scattering which we use at the ILL allows us to characterise the self-assembled systems from the nanometre scale to tenth of micrometres and observes the coming together of C₆₀s into beautiful core structures.”

Professor Chris Toumazou, Regius Professor of Engineering at Imperial College and founder of chip firms, has won Inventor of the Year (Research category) in the European Inventor Awards – the only UK inventor to receive an award this year.

Run by the European Patent Office (EPO), the awards recognised Toumazou for developing a device called the SNP Doctor, which uses silicon chips to identify genetic mutations that determine a person’s predisposition to certain hereditary diseases.

The portable, low-power device can analyse data on the spot, within minutes, without recourse to a lab, and could shift emphasis from treating some illnesses to preventing them.

“The technologies that Chris has developed over the years not only have the ability to improve patient care, they are also important for the UK economy. His work is a perfect example of translating research into viable businesses that are helping to make the UK a leader in personalised healthcare,” said Imperial dean of engineering professor Jeff Magee.

Toumazou has established the DNA Electronics company through Imperial Innovations to market SNP Dr. Already the company has entered into collaborations with companies including Roche and Pfizer, and it has licenced patents to licensees including Life Technologies and the National Institute for Health Research.

Previously, he founded what is now Toumaz Group, which owns DAB chip firm Frontier Silicon.

His decision to delve into the world of genetic disorders came about after his son Marcus was diagnosed with a rare hereditary form of kidney disease.

These achievement all the more remarkable for someone who left school at 16 with no qualifications. He went on to receive a degree in electrical engineering at Imperial, developed energy-efficient chips for mobile phones and, at 33, became the youngest professor to teach at the College.

“This award really underlines what Imperial researchers do best – taking world leading research and applying it to help solve global challenges,” said Imperial college provost Professor James Stirling.