Diamond Dust Tracks Chemistry in Real Time express
A pinch of diamond dust dropped into a glass of liquid acts like hundreds of tiny magnetic compasses. When molecules with unpaired electrons, known as paramagnetic, appear nearby, the needles of these compasses start to quiver. From that quiver, you can tell what the molecule is and how much of it is there.
Previously, such measurements were slow: diamond particles were interrogated one by one with laser pulses, and each answer took minutes. In the new work, the team built a setup where thousands of diamond grains are probed simultaneously, and the signal is read by a fast detector — an avalanche photodiode that works like a highly sensitive eye. Electronics on a programmable chip (FPGA) instantly sum up the responses from all particles.
Now chemists can watch reactions involving paramagnetic particles almost live. If the technique is improved, processes shorter than a second, such as how proteins in a cell exchange electrons, will become visible.
Original abstract
as written by the authors arXiv:2602.17965
Spin relaxometry using fluorescent nanodiamonds (FNDs) has been applied successfully to sense numerous paramagnetic target molecules such as free radicals and metalloproteins. However, despite their high sensitivity, T1 spin relaxation measurements are often hampered by their slow acquisition speed. Here, we demonstrate a method that allows for real-time monitoring of paramagnetic chemical reactions. We demonstrate T1 spin relaxometry from thousands of FNDs using an optimised cuvette-based system integrating an avalanche photodiode operated in linear mode, and a fast, fieldprogrammable gate array (FPGA) for data collation. We demonstrate chemical monitoring of the reduction of Cu(II) to Cu(I) ions in-solution with a 15 second integration using an optimised T1 sensing protocol. Our method achieves more than two orders of magnitude speed up with an order of magnitude reduction in cost when compared with traditional techniques. With further technical improvements, we believe this in-solution method could be extended to sense the sub-second chemical kinetics of paramagnetic molecules in solution.
Diamond dust for such experiments doesn't sparkle like jewelry: the particles are smaller than a hundredth of a hair's thickness, and they contain a deliberately created defect — a spot where a carbon atom is missing, with a nitrogen atom sitting nearby. This defect is what captures magnetic signals.
In Neal Stephenson's novel The Diamond Age, nanoparticles become building blocks of the future; here, diamond dust is not a construction material but a scout in the world of molecules.