Nanoparticles of superconducting γ-Mo2N and δ-MoN

We have been able to prepare nanoparticles (∼4 nm diameter) of cubic γ-Mo2N by a simple procedure involving the reaction of MoCl5 with urea at 873 K. The nanoparticles show a superconducting transition around 6.5 K. The γ-Mo2N nanoparticles are readily transformed to nanoparticles of δ-MoN with a slightly larger diameter on heating in a NH3 atmosphere at 573 K. Phase-pure δ-MoN obtained by this means shows a superconducting transition around 5 K.