Nitrogen Vacancy (NV) defect in diamonds boosts non-gem applications

Diamond-based Maser
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Various companies including De Beers Group-led Element Six are involved in making Lab-grown diamonds for technological implications. They make special diamonds catering to scientific and hi-tech requirements of physicists. These diamonds have nitrogen impurities which help in creating nitrogen vacancy (NV) centres for their applications in various industrial uses. They are currently being used in developing new and enhancing existing technologies.

Nitrogen Vacancy (NV) centres in diamonds used to develop first continuous room-temperature maser

Masers (microwave amplification by simulated emission of radiation) are the older siblings of lasers. While lasers are optical in nature, masers operate at microwave frequencies. Lasers became widespread because of their easy application in telescopes, medicines etc., but masers require temperature close to absolute zero (-273 degree C) to function.

In 2012, a group of researchers from Imperial College London (ICL) led by Dr Jonathan Breeze built a maser out of organic molecule pentacene in place of hard, inorganic maser crystal. But, it was unable to work continuously as the radiation would have melted the crystal molecule.

However, recently the same group of researchers were able to built a maser that can work continuously and on room-temperature. It was achieved using Lab-grown diamonds grown in nitrogen-rich environment. The diamond was then subjected to high-energy electron beam to knock down carbon atoms, thus creating vacancies in the atomic structure. On heating the diamond, nitrogen atoms and carbon vacancies paired off, forming NV centres.

The diamond was then placed in a sapphire ring and beamed with a green laser light and a continuous stream of laser light was produced, giving birth to maser.

Dr Jonathan Breeze said “This breakthrough paves the way for the widespread adoption of masers and opens the door for a wide array of applications that we are keen to explore. We hope the maser will now enjoy as much success as the laser.”

Apart from its application in radio astronomy and deep space communication, with the latest development, masers can now be used in varied fields from medical imaging to quantum computing.

Enhancing medical imaging using diamond-based quantum technology

By increasing the strength of the magnetic field produced by the molecules, resulting in increased signal when measured by MRI, researchers at the University of Melbourne have developed a technique that increases the sensitivity of MRI for patient diagnoses.

They shone a light through a diamond layer 100 micron thick, which changed the magnetic spin of nuclei in the molecules on the diamond surface, hyperpolarising (lining them up) them in the same way. This helped the nuclei to produce a stronger magnetic field among themselves.

The hyperpolarisation happens due to the quantum properties of the nitrogen defects occurring naturally in the lattice of diamond crystals. These defects are called NV centres and they can be lined up or polarised by subjecting it to a green laser.

Dr Liam Hall, post-doctoral research physicist at the University of Melbourne says, “One of the applications is that it could allow us to improve the production of molecular contrast agents that target certain parts of the body and “light” up magnetically, significantly increasing the amount of detail that can be picked up by an MRI scan.”

A group of Japanese researchers have also worked on optimising the design of Lab-grown diamonds to enhance biosensing applications. They have created a sandwich-like structure with a 10 mm thick NV centre filling between, phosphorus doped (altered chemical composition) diamond. These structures can detect changes in the magnetic field and are a powerful tool for detection and diagnoses of disease.

Norikazu Mizuochi from the research group said, “At the moment, we have just demonstrated stabilization, but we expect it to also improve sensitivity.”

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