Chemists have found a way to make metal nitride nanocrystals via solution-based colloidal synthesis (Nature 2026, DOI: 10.1038/s41586-026-10801-3). Having the materials as colloidal nanocrystals would allow manufacturers to concoct inks with them, then spray or print those inks to coat medical implants and produce flexible electronics and vibrant displays.
This is “the first colloidal synthesis and to date the most uniform nanocrystals of these technologically important metal nitrides,” says Ruiming Lin, a PhD student in chemist Dmitri V. Talapin’s lab at the University of Chicago. “Also, our method is scalable and relatively cheap.”
A colloidal solution comprises tiny particles of a material dispersed in a solvent. Colloidal synthesis can produce suspensions of inorganic nanocrystals, but the method doesn’t work for all materials.
In the case of metal nitrides, their strong chemical bonds, which give the materials strength and stability, are a detriment when it comes to colloidal synthesis. Making materials with such strong bonds usually requires vapor deposition at temperatures above 700 °C, and the organic compounds commonly used in colloidal synthesis start falling apart at about 400 °C.
This is why colloidal metal nitride nanocrystals have evaded researchers for years, Talapin says. “Many people, many, many graduate students, tried for 30 years, approaching from every possible direction . . . with no success.” But in 2017, researchers in Talapin’s group found that it is possible to make stable colloidal particles in molten inorganic salts, which can handle higher temperatures than organic solvents.
This transmission electron micrograph shows discrete nanocrystals of gallium nitride, the semiconductor used in electronics and light-emitting diodes. After decades of effort, researchers have found a way to synthesize GaN nanocrystals in solution, paving the way for easier manufacturing. Credit:
Nature
Now the researchers have found a way to create tiny metal nitride crystals by adding ammonia to the reaction mixture. They first dissolve a metal halide in the molten salt and then inject ammonia gas, which dissolves into the molten salt and reacts with the halides to form metal nitrides.
The researchers get the best results when the mixture’s temperature is 500–550 °C and the pressure of the ammonia gas is 20–50 bars. That “was a sweet spot where many different nitrides nucleated and grew in the form of discrete colloidal nanocrystals,” Talapin says. But the exact sweet spot for producing colloidal nanocrystals differs for different metal nitrides.
Of the many metal nitride nanocrystals the researchers made, two of note are gallium nitride (GaN) and titanium nitride (TiN) nanocrystals. TiN is used to coat tools and medical implants, which currently requires high-temperature vapor deposition, and GaN is the semiconductor used in high-power electronics and Nobel Prize–winning blue light-emitting diodes. Talapin says the inability to make colloidal nanocrystals, or quantum dots, from GaN has limited the progress of quantum dot TVs.
People have previously attempted to make metal nitride nanocrystals, including GaN and TiN, says Brandi M. Cossairt, a professor of chemistry at the University of Washington who was not involved in the new work. But the materials created by past methods “have had limited tunability and generally poor properties resulting from poor crystalline quality,” she adds. This new method is “a truly innovative approach to colloidal metal nitride nanocrystal synthesis and potentially opens these materials as solution-processable materials for the first time,” she says.
Prachi Patel is a senior editor and physical sciences reporter at C&EN based in Pittsburgh.
