Scientists have developed a new chemical method for producing nanocrystals from metal nitrides, overcoming a long-standing materials science challenge and opening new possibilities for flexible electronics, printable devices, medical technologies and superconducting applications.
The breakthrough was achieved by researchers at the University of Chicago and Argonne National Laboratory, who successfully produced nanocrystals from a class of technologically important materials that had previously been extremely difficult to synthesize at the nanoscale.
The study, published in Nature, demonstrates a new approach for creating nearly a dozen metal nitride nanomaterials, including compounds already widely used in lighting, medical implants, catalysis and superconducting technologies.
Why Metal Nitride Nanocrystals Matter
Nanocrystals are extremely small crystals whose properties can differ significantly from those of the same materials in bulk form.
At the nanoscale, materials can display unusual optical, electronic and chemical behaviour. Quantum dots, for example, have become important components in modern displays and were central to the scientific work recognised by the 2023 Nobel Prize in Chemistry.
However, despite the growing importance of nanocrystals, scientists have historically been able to make them from only a limited selection of materials.
Metal nitrides presented a particularly difficult challenge.
These compounds are formed from metals bonded with nitrogen and are valued for their strength, heat resistance, corrosion resistance and, in some cases, biocompatibility.
The same stability that makes them technologically useful also makes them difficult to convert into nanocrystals.
From LEDs to Flexible Electronics
One of the most important metal nitrides is gallium nitride, a semiconductor widely used in modern lighting and electronic displays.
Gallium nitride is found in technologies ranging from LED bulbs to laptop screens.
At present, such materials are commonly manufactured as rigid films. Turning them into nanocrystals could enable entirely different manufacturing approaches.
Researchers envision metal nitride nanocrystals being mixed into polymers, deposited through inkjet-style printing processes or incorporated into fabrics and other flexible materials.
This could eventually support new generations of flexible lighting, printable electronics and wearable technologies.
Why These Nanocrystals Were So Difficult to Make
Crystal formation requires atoms and ions to rearrange themselves into an ordered structure.
For this to happen efficiently, chemical bonds must be capable of breaking and reforming while the crystal grows.
Metal-nitrogen bonds, however, are particularly strong.
According to the researchers, this meant that once atoms formed an incorrect bond during conventional synthesis, they could become trapped in the wrong configuration and prevent the nanocrystal from developing correctly.
The team therefore needed to find conditions that would allow the strong metal-nitrogen bonds to rearrange while still maintaining the stability necessary for nanocrystal formation.
Molten Salts Provide Part of the Solution
The first key element of the method came from previous work by the research group involving molten salts.
Instead of relying on conventional liquid solvents, the scientists used molten salts as the medium in which the nanocrystals could form.
These salts helped stabilize the developing crystals under the unusual conditions required for metal nitride synthesis.
But molten salts alone were not enough.
The researchers continued experimenting with different combinations of temperature, pressure and chemical conditions to identify an environment where crystal formation could proceed successfully.
Finding the Temperature and Ammonia โSweet Spotโ
The decisive breakthrough came when the researchers identified a suitable combination of temperature and ammonia pressure.
Under these conditions, bonds between metal and nitrogen atoms were able to break and reform more readily.
This gave the atoms enough freedom to reorganize themselves into the correct crystalline structures.
Senior author Dmitri Talapin, the Ernest DeWitt Burton Distinguished Service Professor of Chemistry and Molecular Engineering at the University of Chicago and a scientist at Argonne National Laboratory, described the process as highly unconventional.
The approach required the researchers to rethink some of the standard assumptions governing nanocrystal synthesis.
Nearly a Dozen Previously Difficult Nanomaterials
The method proved useful for far more than gallium nitride.
First author Ruiming Lin, a graduate student at the University of Chicago, and colleagues demonstrated that the technique could produce nearly a dozen metal nitride materials that conventional nanocrystal synthesis methods had struggled to create.
Among them was titanium nitride, a material already used in medical implants because of its durability and biocompatibility.
The researchers also produced niobium nitride, which has important superconducting properties, and molybdenum nitride, a material commonly used in catalytic applications.
The ability to manufacture these materials as nanocrystals could create entirely new ways of incorporating their properties into devices.
Potential for Medical and Superconducting Technologies
The possible applications extend well beyond lighting.
Titanium nitride nanocrystals could provide new opportunities in biomedical materials and implant technologies.
Niobium nitride, meanwhile, is an important superconducting material. Producing it as nanocrystals could potentially enable researchers to investigate new architectures for superconducting devices and nanoscale electronic systems.
Molybdenum nitride nanocrystals may also offer advantages in catalysis because nanoscale materials provide large surface areas where chemical reactions can occur.
However, the study establishes a new synthesis method rather than demonstrating commercial products based on these applications.
Further research will be needed to determine how effectively the nanocrystals can be incorporated into practical devices.
Expanding the Boundaries of Nanomaterials
One of the broader implications of the research is that materials previously regarded as unsuitable for conventional nanocrystal synthesis may no longer be out of reach.
By combining molten salts with carefully controlled ammonia pressure and temperature, researchers now have a strategy for overcoming some of the chemical constraints imposed by extremely strong bonds.
Talapin said the work expands the boundaries of nanocrystal chemistry and provides a foundation for treating nitrides as a broader family of functional nanomaterials.
The researchers hope the technique will encourage scientists to explore additional metal nitrides and related compounds.
A Platform for Future Technologies
Metal nitrides are already common in modern industry because many are durable, relatively inexpensive and resistant to harsh environments.
Giving these materials the versatility of nanocrystals could substantially increase the ways in which they can be processed and incorporated into technology.
Instead of relying solely on rigid crystalline films, future devices could potentially use nitride nanocrystals in printable inks, polymers, flexible surfaces and other unconventional formats.
For materials science, the advance is significant not simply because it produces new nanocrystals, but because it demonstrates that a fundamental synthesis barrier can be overcome by changing the chemical environment in which crystals form.
The researchers now expect the method to provide a starting point for exploring applications across electronics, lighting, medicine, catalysis and superconducting technologies.
Journal reference
Ruiming Lin, Vikash Khokhar, Ningxin Jiang, Wooje Cho, Zirui Zhou, Di Wang, Justin C. Ondry, Zehan Mi, James Cassidy, Alex M. Hinkle, Alexander S. Filatov, John S. Anderson, Richard D. Schaller, De-en Jiang and Dmitri V. Talapin. โAmmonia pressure controls colloidal metal nitride synthesis in molten salts.โ Nature, 2026, 655(8125), 1174.