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Imagine combining a standard green laser, microwaves similar to those used in Wi-Fi, and tiny particles of diamond suspended in droplets of water. The result? An advanced tool for chemical detection.
Recently, researchers have pioneered a method that merges nanodiamonds within microdroplets of liquid for the purpose of quantum sensing. This innovative technique is characterized by its speed, sensitivity, and precision, requiring only minute quantities of the targeted material. Such capabilities are crucial for analyzing trace chemicals or single cells. These findings were detailed in the journal Science Advances in December.
“Initially, we were uncertain if our approach would be viable, but we found it surprisingly simple and effective,” stated Ashok Ajoy, a faculty scientist at the Chemical Sciences Division of the Department of Energy’s Lawrence Berkeley National Laboratory and an assistant professor at UC Berkeley who oversaw the research. “There are extensive possibilities for deploying these sensors in diverse environments where detecting specific substances is particularly challenging.”
Quantum sensing leverages unique phenomena that arise at the nanoscale. In the new approach developed by the researchers, they create microdroplets that are millions of times smaller than a typical raindrop, each containing specialized diamonds that have nitrogen atoms replacing some carbon atoms. These “nitrogen vacancies” serve as quantum sensors, imparting unique properties to the nanodiamonds. When these droplets flow past a laser and are subjected to microwaves, the nanodiamonds emit light. The intensity of this light, influenced by surrounding materials, enables researchers to identify the presence of specific chemicals.
The interplay of flowing droplets and finely tuned microwaves allows scientists to filter out irrelevant background noise, enhancing the precision of their measurements. This technique has demonstrated superior performance compared to existing methods for detecting trace amounts of slightly magnetic (or “paramagnetic”) chemicals in small sample volumes.
(Concerns about high research costs can be alleviated; analyzing hundreds of thousands of droplets costs approximately 63 cents’ worth of diamond dust, making it an economically viable method.)
Compact sensors with vast potential
With continued refinement, the applications for nanodiamonds in droplets are promising.
In the recent study, a research team led by graduate student Adrisha Sarkar and postdoctoral researcher Zack Jones at Berkeley successfully detected trace amounts of two paramagnetic substances: gadolinium ions and TEMPOL, a stable radical that reacts with oxygen.
Numerous other paramagnetic ions, which are currently challenging to analyze through traditional methods, hold significant interest. One example is reactive oxygen species (ROS), fleeting molecules linked to various biological processes such as metabolism, aging, and stress. The newly developed technique offers a potential advancement in identifying reactive oxygen within single cells, which could aid in monitoring cellular health and broaden insights into diseases like cancer. The research team is proactively preparing for such investigations.
Moreover, they are exploring methods to attach additional identifying elements, such as antibodies, to the nanodiamonds, thus enhancing their applicability for biological research. This could lead to the development of improved diagnostic tests capable of identifying viruses even in trace amounts. Furthermore, due to the simplicity of this method, Ajoy envisions creating portable systems to monitor air or water for harmful contaminants, both in field environments and industrial applications. As these nanodiamond microdroplets are inexpensive and abundant, the technique can be scaled up to analyze numerous samples with high sensitivity, potentially addressing intricate real-world challenges.
Additionally, this novel approach could significantly contribute to the evolution of self-regulating bioreactors. These systems create controlled environments for the cultivation of microorganisms that produce medicines, biofuels, or food ingredients. Each nanodiamond droplet functioning as a microscopic “beaker” could enable researchers to finely tune bioreactor conditions.
“Envision setting up bioreactors in remote locations worldwide or even in outer space to yield food not feasible for daily delivery,” remarked Deepti Tanjore, director of the Advanced Biofuels and Bioproducts Process Development Unit at Berkeley Lab. “Employing precise quantum sensors to monitor the behavior of microorganism cultures is a pivotal move towards realizing that vision. To construct a self-regulating bioreactor, we require real-time intracellular data.”
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