Quantum microscope sheds new light on an old problem

Our understanding of the function transition metals play in biology is changing. The emergence of transition metal signalling roles suggests a broader contribution beyond traditional metabolic cofactors. A group of interdisciplinary researchers within the Sensors and Imaging theme at the Centre for Neural Engineering (CFNE) is working on a new technology to change the way we image these important components of life, and may ultimately shed new light on their function and role in neurodegenerative diseases.

To date, the majority of techniques looking to image transition metals have focused on the development of specific target molecules to bind metal complexes; a process that results in a change of the molecule’s florescence properties. However, new research at the University of Melbourne suggests that tiny atomic sensors in diamond may be the key to visualising paramagnetic transition ions in their natural environment.

Researchers in the School of Physics have been investigating the properties of atomic defects in diamonds over the past decade. These tiny room temperature quantum based systems offer a playground for nanoscale sensing of magnetic, electric and thermal fields. Prof Lloyd Hollenberg and his team are looking at new ways to probe electronic and nuclear spins at the nanoscale with such systems. 

In collaboration with Prof Dmitry Budker’s group at the University of California Berkeley, Prof Hollenberg’s team recently demonstrated a non-invasive, all optical approach to magnetic sensing and spectroscopy. The team was able to show, through the application of a well-controlled magnetic field, that the NV sensors and target electronic spin species within the diamond can be brought into resonance. At this resonance point, the target spins and NV sensors can exchange energy efficiently which results in a significant decrease in the spin lifetime of the NV quantum sensors. Dr Liam Hall, the lead author of the study published earlier this year in Nature Communications 1, describes the technique as “a significant breakthrough in electronic and nuclear spin detection. The quantum resonance detection scheme is non-invasive, microwave free and can be applied to a variety of unpaired electronic spin targets”.

The next step in the research is to apply this sensing scheme to detect spins targets external to the diamond and imaging these spins species.  Dr David Simpson, lead researcher working at the School of Physics and CFNE, has been developing the technology to image the weak magnetic fields 2 and paramagnetic molecules, and in a world first, has demonstrated external spin detection, imaging and spectroscopy using a quantum resonance microscope. 

Together with Mr Robert Ryan, the pair successfully performed the first external detection of Cu2+ metal ions in ambient aqueous environments. The quantum resonance microscope is able to spatially resolve transition metal ions with diffraction limited resolution (~300 nm) and with sensitivity 104 times greater than the current state-of-the-art electron paramagnetic resonance techniques.  Dr Simpson says “Quantum resonance microscopy will open up new possibilities for the study and characterisation of transition metals at the nanoscale in functioning biological systems.

This could provide biologists and neuroscientists with new information regarding the presence and oxidation state of transition metals in the complex environment of a living cell”.

Further information

Sensors and Imaging Research Team

Quantum Science and Technology

References

1.  Hall, L. T., Kehayias, P., Simpson, D. A., Jarmola, A., Stacey, A., Budker, D., Hollenberg, L. C. L., Detection of nanoscale electron spin resonance spectra demonstrated using nitrogen-vacancy centre probes in diamond. Nature Communications 2016, 7, 10211.

2. Simpson, D. A., Tetienne, J.-P., McCoey, J. M., Ganesan, K., Hall, L. T., Petrou, S., Scholten, R. E., Hollenberg, L. C. L., Magneto-optical imaging of thin magnetic films using spins in diamond. Sci Rep 2016, 6, 22797.