Nanothermometers, while not a brand new idea, are still at the cutting edge of science. We've seen impressive results to date, but accuracy and resolution can always improve, and this is what researchers from the University of Technology Sydney (UTS) in Australia believe they've achieved.

The potential applications for nanothermometry are incredibly broad. From diseased cells to micro/nano components in computer and communications technology; being able to accurately measure temperature (and monitor fluctuations) at the nano scale is a game changer. The team, led by Senior Investigator Dr. Carlo Bradac at the UTS School of Mathematical and Physical Sciences, has taken a novel approach to nanothermometry, using flaws in diamond nanoparticles as thermal sensors on the quantum level.

While pure diamond is regarded as transparent, imperfections at the atomic level are often present, and it's these foreign atoms, with their respective color impurities, that the technique is built around. These diamond nanoparticles are extremely small – up to 10,000 times smaller than the width of a human hair – and when the imperfections in them are illuminated with a laser, they fluoresce. It's this very fluorescence which the system employs to measure temperature.

The researchers used a regime known as Anti-Stokes, in which the intensity of the light emitted by the impurities in the diamond nanoparticles depends strongly upon temperature of their surroundings. The colored impurities within the diamonds are illuminated by a low energy light source, and as temperature increases, the particles' color centers become excited, thereby increasing the luminosity exponentially. This provides an incredibly accurate method for sensing the temperature. All that's required is that diamond nanoparticles in a water solution are placed in contact with the sample, and their optical fluorescence is then measured.

While similar optical nanothermometer systems have been proposed in the past, the sensitivity and spatial resolution of this new method is reported to be what sets it apart. And according to the team, this is no proof-of-concept, it's ready to roll right now.

"The method is immediately deployable," says Dr. Bradac. "We are currently using it for measuring temperature variations both in biological samples and in high-power electronic circuits whose performance strongly rely on monitoring and controlling their temperature with sensitivities and at a scale hard to achieve with other methods."

The study, published in Science Advances, is a collaboration between UTS, the Russian Academy of Science, Nanyang Technological University and Harvard University.

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