Researchers at the University of Iowa and the University of Chicago have developed a framework that could yield more accurate readings of the inner workings of cells via quantum sensors. 

Denis Candido, assistant professor in the Department of Physics and Astronomy, developed the theoretical model that led to understanding how a coating will improve the sensitivity of ultra-tiny diamonds — known as nanodiamonds — while also minimizing their disturbance in live cells. University of Chicago scientists had observed that silica coating produced nanodiamonds that were more stable and accurate at picking up signals. Candido’s theoretical modeling explained why. 

The research is important because it could help monitor signals, such as temperature within an individual cell, and lead to earlier detection of cellular-driven illnesses, such as cancer.

Diamonds contain defects known as nitrogen-vacancy centers. The energy levels of these centers respond to slight changes in magnetic fields, temperature, and electric signals, highlighting their value and versatility as sensors. However, within nano-scale diamonds, the nitrogen-vacancy centers lose their effectiveness in reading these signals, hampering their sensing capabilities within small settings, such as cells.

Candido’s theoretical modeling revealed that the silica coating depletes surface charges that create noise and can interfere with the nanodiamonds’ sensing capabilities. He also found that the coating stabilizes the movement of charges between the nanodiamond and its surroundings. The net effect is that the sensors’ signals become clearer and more reliable over longer periods of time. 

In experiments testing Candido’s modeling, the Chicago team found that these coatings improved signal strength and outperformed nanodiamonds without the coating, supporting Candido’s theory.

“The final theory is not merely a pathway towards superior nanodiamond sensors but a comprehensive framework for designing coherence and charge stability in diamonds,” Candido says.

“It is remarkable that the coated nanodiamonds of the same size as uncoated ones produce better results, even though the amount of diamond is much less,” adds Michael Flatté, professor in the Department of Physics and Astronomy at Iowa and a co-author on the study. 

The study, “Engineering Spin Coherence in Core-Shell Diamond Nanocrystals,” was published in the journal Proceedings of the National Academy of Sciences. 

Researchers at the University of Chicago were Uri Zvi, Adam Weiss, Aidan Jones, Lingjie Chen, Iryna Golovina, Xiaofei Yu, Stella Wang, Dmitri Talapin, Aaron Esser-Kahn, and Peter Maurer.

Candido and Flatté’s work was funded by the U.S. Department of Energy’s Office of Science, Basic Energy Sciences.