Used to measure magnetic fields, charge, and temperature, nanodiamonds with luminescent nitrogen-vacancy (NV) centers function as highly sensitive, nanosized probes for various applications. The NV center, embedded in the diamond lattice, is fluorescent and emits light when it is illuminated. The intensity and timing of this light depend on changes in the surrounding environment, and allow the nanodiamond to detect individual molecules or temperature changes inside cells with sub-micron resolution. The conventional method for creating high-quality NV centers in nanodiamonds requires irradiation in particle accelerators and annealing. It is costly, labor-intensive, and extremely time-consuming, limiting the use of nanodiamonds in technology and research. Quantum-grade nanodiamonds can now be produced in a matter of minutes by placing diamond powder in a modified commercial sintering press apparatus. Courtesy of the Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences. A new, streamlined method for producing quantum-grade nanodiamonds, developed at the Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences (IOCB Prague), in collaboration with international institutions, could help drive the commercial adoption of nanodiamonds, broadening their use across industries. This single-step method, based on high-temperature plastic deformation, yields high-quality, affordable, luminescent nanodiamonds at industrial scale. To produce quantum-grade nanodiamonds in just 4 min., the researchers place diamond powder in a commercial sintering press apparatus modified for nanodiamond processing. The press generates extremely high pressures and temperatures, reproducing the immense pressures found deep within the Earth’s mantle. Under these conditions, quantum centers are formed inside the nanodiamonds. To prevent the particles from fusing together, the researchers add ordinary table salt, which melts during heating, creating a protective environment. When the process is complete, the researchers remove the salt with water, which leaves a pure, luminescent material. The technique, called Pressure and Temperature Qubits (PTQ), produces 50-nm, luminescent nanodiamonds, with outstanding optical and spin properties, from non-luminescent material. Compared to electron-irradiated nanodiamonds, PTQ produces NV centers with better charge stability, spin-lattice relaxation (T1) times approaching 1 ms, and an approximately 5-fold enhancement in optical Rabi contrast. The high-temperature plastic deformation preserves the diamond crystallinity and prevents graphitization. It also induces lattice healing, which shows up in the reduced lattice strain and prolonged NV and spin relaxation, compared to standard methods of NV production. The single-step PTQ method produces about 250 g of luminescent NDs per day. Using just one press, it produces >1 kg of high-quality fluorescent NDs per week, in contrast to current approaches that produce gram levels per week at best, and other emerging methods with yields that are insufficient for practical applications. In just one week, the PTQ process can yield as much material as conventional irradiation and annealing methods can produce in more than 40 years. The research team is working with MegaDiamond, a U.S. company that plans to launch industrial production of the nanosensors. The commercialization of the PTQ process for creating quantum-grade nanodiamonds could open new opportunities for the application of diamonds in a range of areas. Overall, this high-yield production method enables abundant use of fluorescent nanodiamonds without over-consumption of resources. “Thanks to the new method, laboratories and companies around the world can obtain large quantities of high-quality nanodiamonds with NV centers, which opens the door to new technologies, from precision sensors for medical diagnostics to local molecular detectors based on principles such as magnetic resonance,” research team leader Petr Cígler said. The research was published in Advanced Functional Materials (www.doi.org/10.1002/adfm.202520907).
