Abstract Nanocrystalline titanium oxynitride has been synthesized by a thermal liquid–solid metathesis reaction between TiCl 4 and NaN 3 at 350 °C. XRD shows the product is TiN 0.91O 0.09 with a NaCl-type structure ( a=4.236 Å). TEM reveals the product is granular nanocrystals with size of 15–35 nm. XPS measurements indicate that the product is titanium oxynitride rather than titanium nitride. The photoluminescence spectra of the as-prepared nanocrystallites show the ultraviolet light emission at about 330–350 nm, which is reported for the first time.