Quantum Sensing with Nanodiamond Droplets: A New Frontier in Chemical Detection

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What do you get when you combine a green laser, microwaves with the energy of Wi-Fi, and diamond dust suspended in tiny water droplets? A highly precise chemical detection tool.

For the first time, researchers have successfully integrated nanodiamonds within microdroplets of liquid for quantum sensing. This breakthrough technique is fast, sensitive, and requires only minute amounts of material—making it especially useful for detecting trace chemicals or studying individual cells. The findings were published in Science Advances in December.

"We weren’t sure whether our technique would work, but it turned out to be surprisingly easy and effective," said Ashok Ajoy, a faculty scientist in the Chemical Sciences Division at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and an assistant professor at UC Berkeley, who led the research. "These sensors could be deployed in a wide range of environments to detect substances that are typically hard to find."
Harnessing Quantum Properties for Precision Detection

Quantum sensing takes advantage of unique behaviors that emerge at the atomic and subatomic levels. In this new approach, researchers created microscopic droplets—millions of times smaller than a raindrop—containing specially engineered diamonds. Some carbon atoms in these diamonds were replaced with nitrogen, forming "nitrogen vacancies" that act as quantum sensors.

As the droplets flow past a laser and are exposed to microwaves, the nanodiamonds emit light. The intensity of this light changes in response to nearby chemical environments, allowing researchers to detect the presence of specific molecules with high precision.

By combining flowing droplets with precisely modulated microwaves, the technique filters out background noise, making it one of the most sensitive methods available for detecting trace amounts of paramagnetic chemicals—substances that interact weakly with magnetic fields. Remarkably, this advanced sensing capability is cost-effective: hundreds of thousands of droplets can be analyzed for just 63 cents worth of diamond dust.
Expanding Applications: From Medicine to Environmental Monitoring

With further refinement, this technique could revolutionize multiple fields.

In the study, a team led by UC Berkeley graduate student Adrisha Sarkar and Berkeley Lab postdoc Zack Jones demonstrated the detection of trace amounts of two paramagnetic substances: gadolinium ions and TEMPOL, a stable radical molecule that reacts to oxygen.

This method could be especially useful for studying reactive oxygen species (ROS)—highly reactive molecules linked to metabolism, aging, and cellular stress. Because ROS play a role in conditions like cancer, the ability to detect them within single cells could significantly advance disease research. The team is already preparing experiments to explore this application.

Researchers are also working on functionalizing nanodiamonds with additional markers, such as antibodies, to make them even more powerful tools for biological research. This could pave the way for advanced diagnostic tests capable of detecting viruses when only trace amounts are present.

Beyond healthcare, this method could be used for environmental monitoring, allowing portable systems to detect harmful trace contaminants in air or water, whether in industrial settings or remote locations. Because the nanodiamond droplets are inexpensive and scalable, they could process hundreds of different samples efficiently, providing real-time insights into chemical compositions.
Toward Self-Driving Bioreactors

The technique could also help build the self-regulating bioreactors of the future. Bioreactors create controlled environments for microorganisms that produce medicines, biofuels, or food ingredients. Since each nanodiamond droplet can act as a tiny reaction vessel containing a single cell, researchers envision using this approach to fine-tune bioreactors.

"You can imagine setting up bioreactors in remote locations—or even in space—to produce food or other essential compounds that can't be delivered daily," said Deepti Tanjore, director of the Advanced Biofuels and Bioproducts Process Development Unit at Berkeley Lab. "To build a self-regulating bioreactor, we need real-time intracellular data, and precise quantum sensors like these bring us closer to that goal."

With its ability to provide highly sensitive, low-cost, and scalable chemical detection, this quantum sensing technique has the potential to transform medicine, environmental science, and biotechnology, bringing us closer to a future of smarter diagnostics and self-sustaining systems.