Known techniques for forming nanoparticles require a multiple-step process to coat a surface with nanoparticles. The present invention provides a single-step process that requires the deposition of a substrate in a mixture of a solvent, ligands and organometallic precursors. The mixture containing the substrate is heated under pressure in a dihydrogen environment for a predetermined period of time, during which supercrystals of nanoparticles form on the substrate.