Developing a new and improved way to measure quantities at the nanoscale, where everything is billionths of meters small, is the focus of a new international study involving Trent researchers.

Dr. Carlo Bradac, an assistant professor in the Department of Physics at Trent, co-authored the study. He explains that the research focuses on hexagonal boron-nitride (hBN)—a two-dimensional material made of one-atom-thin layers that has everyday uses in cosmetics, dentistry and laser printing, and is also quickly becoming an exceptional candidate material for advanced applications, including nano-electronics, nano-photonics and nano-sensing.

The recent study, which also involved the University of Würzburg in Germany, the University of Technology Sydney in Australia and the Ioffe Institute in Russia, developed a new type of hBN quantum sensors for measuring extremely small quantities. Researchers were able to measure magnetic fields, temperature and pressure with exceptional sensitivity, nanoscale spatial resolution and down to just a few degrees Kelvin (roughly -440 F, or -270 C).

“These results are really exciting,” Professor Bradac says. “We have just gotten a new set of powerful goggles to explore the nanoworld and investigate objects and processes at a very, very small scale.”

Study published in leading journal
The study, published in Nature Communications, shows that light-emitting impurities in hBN make ideal nanoscale measuring devices. These impurities act as ‘spin-defects,’ whose spin state (‘up,’ ‘down,’ or ‘anything in between’) is extremely sensitive to the surrounding environment. For instance, magnetic and electric fields, as well as pressure and temperature, alter their spin and optical properties, which allows them to be used as small probes to map changes in their surroundings with nanoscale spatial resolution.

“This is because when you are single-atom small, even the tiniest change in your surrounding environment becomes easy to detect,” says Prof. Bradac.

Quantum sensors working on a similar principle already exist and are used in areas such as global GPS-free navigation, nano-thermometry in cells and detection of single electrons on the surface of solids.

What makes these newly demonstrated hBN quantum sensors different is that they offer improved features, including exceptional sensitivity, large temperature range of operation and nanometer spatial resolution. These stem from the fact that the sensing elements — these atom-like emitters — can exist in ultrasmall hBN nanoparticles made of as few as three atomic layers (i.e., less than one nanometer-thick). They are therefore excellent probes that can be placed in contact with an object of interest or dispersed in a target environment, such as in a plant or animal cell to measure their behavior at the nanoscale.

Future research
Prof. Bradac says the study sets the foundation for developing advanced, practical quantum-based sensing technologies based on 2D materials.

“These promise to improve our measurement capabilities beyond those of our best classical approaches—from detecting individual spins in spintronic devices to sensing and imaging biological processes with single-protein and single-molecule resolution within cells,” he says.

He adds that the research has exciting potential for humankind, although much research needs to be done in the long-term.

“Imagine you could measure—or even better, control—the temperature in a cell and discover that a certain immune response is triggered at a certain temperature. You could now use this knowledge to devise strategies to trigger that response at will such as for cancer therapies.”

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