Nanoparticles help microscopes go extreme-ultraviolet

Physicists at The Australian National University (ANU) and the University of Adelaide are using nanoparticles to develop new sources of light that will allow us to peel back the curtain into the world of extremely small objects — thousands of times smaller than a human hair — with major gains for medical and other technologies. Their research has been published in the journal Science Advances.

Beams of light that we perceive as different colours of the rainbow are electromagnetic waves that oscillate with different frequencies. What we see as red is the lowest frequency that our eyes can detect, while lower frequencies not visible to the human eye are called infrared. Violet has the highest light frequency that we can see; ultraviolet, which has an even higher frequency, is invisible to the human eye.

Although our eyes cannot detect infrared and ultraviolet light, it is possible for us to ‘see’ it using cameras and other technologies. Study co-author Dr Sergey Kruk, from ANU, said researchers are interested in achieving very high frequencies of light, also known as ‘extreme-ultraviolet’.

“With violet light we can see much smaller things compared to using red light,” Kruk said. “And with extreme-ultraviolet light sources we can see things beyond what’s possible using conventional microscopes of today.”

The ANU technology uses carefully engineered nanoparticles to increase the frequency of light that cameras and other technologies see by up to seven times. The researchers say there is no limit to how high the frequency of light can be increased — and the higher the frequency, the smaller the object we are able to see using that light source.

The technology, which requires only a single nanoparticle to work, could be implemented into microscopes to help scientists zoom into the world of super-small things at 10 times the resolution of conventional microscopes, which are only able to study objects bigger than about ten-millionth of a metre.

“There is growing demand across a range of sectors, including the medical field, to be able to analyse much smaller objects down to one-billionth of a metre,” said lead author Anastasiia Zalogina, from the ANU Research School of Physics and the University of Adelaide.

“Scientists who want to generate a highly magnified image of an extremely small, nanoscale object can’t use a conventional optical microscope. Instead, they must rely on either super-resolution microscopy techniques or use an electron microscope to study these tiny objects.

“But such techniques are slow and the technology is very expensive, often costing more than $1 million.

“Another disadvantage of electron microscopy is that it may damage delicate samples being analysed, whereas light-based microscopes mitigate this issue.”

The ANU technology would thus enable researchers to study objects that would otherwise be too small to see, such as the inner structures of cells and individual viruses. Being able to analyse such small objects could help scientists better understand and fight certain diseases and health conditions. It could also be used in the semiconductor industry as a quality control measure to ensure a streamlined manufacturing process.

“Computer chips consist of very tiny components with feature sizes almost as small as one-billionth of a metre,” Kruk said. “During the chip production process, it would be beneficial for manufacturers to use tiny sources of extreme-ultraviolet light to monitor this process in real time to diagnose any problems early on.

“That way, manufacturers could save resources and time on bad batches of chips, thereby increasing yields of chip manufacturing. It’s estimated that a 1% increase in yields of computer chip manufacturing translates into $2 billion in savings.”

Image caption: An illustration showing a single nanoparticle converting low-frequency red light into extreme-ultraviolet light, which has a very high frequency. Image credit: Dr Anastasiia Zalogina/ANU.