Rock Stars

We publish courtesy of Sydney Morning Herald

Author: Deborah Smith

 

It was the highest price ever paid for a jewel. When a rare pink diamond fetched $46.8 million last month, the sale almost doubled the previous record price, eclipsing a blue diamond sold in 2008 for $24.3 million.

Since antiquity, the brilliance of the sparkling gems has made them the most coveted of stones and these recent purchases attest to their enduring allure.

The hardness of diamonds has also made them sought-after for more mundane applications, such as polishing, cutting and drilling. When those hoping to rescue trapped miners in the Pike River coalmine in New Zealand struck hard rock while drilling a shaft last month, they switched to a diamond

But diamonds have a very different, high-tech future in store, which goes far beyond their historical role as beautiful adornments or handy tools.

A physicist at the University of Melbourne, Dr Andy Greentree, says we are rapidly moving into the ”fourth age of diamonds”, where some of the other unusual properties of this special form of carbon will be exploited by scientists in a wide range of areas, from medicine to computing.

Diamond is being used to develop bionic eyes for the blind, the next generation of extremely fast quantum computers and unhackable communication systems.

Diamond lasers are also being developed that have the potential to treat skin diseases or detect dangerous substances such as explosives at airports. ”Diamond is a wonderful material,” Greentree says.

While diamonds are treasured here on Earth, on some other planets there could be oceans of liquified diamond, with solid diamonds floating in them like icebergs, recent research suggests. Neptune and Uranus have up to 10 per cent carbon and these giant gas planets have the ultra-high temperatures and pressures necessary for diamonds to exist.

Here, the temperatures and pressures that turn carbon into diamond naturally, with its unique crystal structure, are found deep underground. The glittering gems were forged millions of years ago at depths of up to 200 kilometres, before being brought near the surface in volcanic pipes. The first age of diamonds, when their usefulness and beauty were discovered, could have begun as far back as 6000 years ago. A study of four ceremonial stone burial axes found in the tombs of wealthy individuals in China suggests ancient artisans used diamonds to grind and polish them.

It was thought quartz had been used to smooth the axes, which are between 4500 and 6000 years old. But American researchers, led by Dr Peter Lu of Harvard University, used microscopic studies and other tests to show that only diamond could have achieved the mirror-like lustre of the very hard stones.

While this evidence for diamond use is circumstantial, it is clear that people in India had discovered diamonds in river gravel by 2500 years ago, pioneering a still-flourishing worldwide market for the hard and glamorous stones.

The second age of diamonds began after World War II with the manufacture of synthetic diamonds, Greentree says. One technique is to emulate nature using high pressures and temperatures in an energy-intensive laboratory process. ”It is quite expensive, although it is still cheaper than the market price of natural diamonds,” Greentree says.

A less costly alternative is to cook up methane in a fancy microwave oven in a process called chemical vapour deposition, in which released carbon builds up as diamond on a surface. And nanodiamonds can be made by detonating explosives under the right conditions.

While the word ”synthetic” makes them sound fake, synthetic diamonds are identical to natural diamonds, just man-made. And synthetic diamonds have many uses, including to drill into rocks and teeth.

We are now in the third age of diamonds, Greentree says. Access to high-quality synthetic diamonds has expanded their use into electronics, optics and as refined cutting materials, such as scalpel blades.

But the fourth age, where scientists can not only exploit but also manipulate the properties of diamonds, is about to begin.

”The recent breakthrough is the availability of batches of synthetic diamonds [that] are more or less identical,” Greentree says. ”When you dig diamonds out of the ground, every diamond is different.”

Associate professor Richard Mildren of Macquarie University and his colleagues used some of these new, very pure, reproducible, man-made diamonds about eight millimetres long to develop the world’s first diamond laser in 2008. Diamond conducts heat faster than any other material, which means they make small lasers of unprecedented power possible by drawing away waste heat.

”If you want a really small, compact laser, you have got to get the heat out quickly and diamond is by far the best material,” Mildren says.

Diamonds are not only the most transparent material in the visible light range – which is why their clarity is renowned – they are also transparent at other wavelengths, such as in the ultraviolet and infrared regions.

”So we can make lasers at almost any wavelength we like,” Mildren says. One exciting possibility is to make a laser at a wavelength that would be absorbed by proteins specifically. It could then be used in neurosurgery, for example, to precisely carve away a tumour without affecting surrounding brain tissue.

Diamond lasers at different wavelengths could also be developed to detect vapour emitted by explosives at airports. ”Similar detection methods are needed in the military for roadside bombs,” Mildren says.

The US recently began to invest heavily in developing very-high-powered diamond lasers that could be used as weapons, he says.

New techniques to carve diamond into the desired configurations have been developed. One is to bombard it with a beam of ions, or charged particles, to break the diamond away at the atomic level. Another is to convert some of the diamond into graphite – the form of carbon in a pencil – and then remove it, leaving the shaped diamond. ”We can then sculpt any shape we want,” Greentree says.

In 2008 he was part of a University of Melbourne team led by Professor Steven Prawer that made the world’s smallest diamond ring – a tiny loop only 300 nanometres thick and five microns wide (20 would fit across a human hair). Making these tiny diamond structures allows researchers to manipulate light in new ways.

Another important advance has been to create ”colour centres”. One example is where a carbon atom in diamond is replaced with a nitrogen atom and the neighbouring carbon atom is also removed to leave a gap.

By shining light on these colour centres, single photons – the smallest packets of light – are emitted one by one. This could lead to a range of new quantum mechanical technology, including ways to overcome eavesdropping when information is sent down optical fibres. The laws of quantum physics prevent a robber stealing a single photon and resending it without anyone knowing, a concept called quantum cryptography.

Prawer’s team at Quantum Communications Victoria has developed single-photon devices from diamond that are being commercialised for incorporation into ultra-secure communication systems.

The tiny diamonds doped with nitrogen look a very promising way to build computers of the future, which will be able to carry out enormous numbers of processes simultaneously. These diamond-based quantum computers would use the spin of an electron to store information.

Researchers led by associate professor James Rabeau at Macquarie University are also working on light emitting nanodiamonds about five nanometres wide (1000 could fit across a human hair). An important application could be to attach these tiny beacons to proteins for medical imaging, so the movement of the proteins could be tracked in cells and tissues, Rabeau says.

As if all these unusual properties of diamonds weren’t enough, the material is also biocompatible, which means it is not rejected by the body. ”As far as we understand, it does less to the body than medical-grade silicon,” Greentree says.

Diamonds will have an important role in the bionic eye being developed by Bionic Vision Australia with a $42 million federal government grant. Images captured by glasses worn by the blind person will be sent wirelessly to an implant in the retina at the back of the eye.

The signals will then be sent by a diamond electrode array to the optic nerve to create an image that the person can see, Prawer says; his team is designing the electrode array.

To prevent corrosion of the implanted chip by body fluids, it will also be encased in a biocompatible diamond block.

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