A reagent and its method of production are provided. The reagent includes at least one zero-valent atom, whether metal, metalloid, or non-metal, in complex with at least one hydride molecule. The method of production includes ball-milling a mixture which includes an elemental (i.e. zero-valent) material and a hydride. In some cases, the elemental material is a non-metal such as carbon. The reagent can be useful as a reagent for the synthesis of elemental nanoparticles composed of zero-valent metal, metalloid, or non-metal.