In a composition including a plurality of coated diamond nanoparticles, each diamond nanoparticle may have at least one silane functional group covalently bonded to a surface thereof. A method of forming coated diamond nanoparticles may include functionalizing surfaces of diamond nanoparticles with at least one of a fluorine-containing compound and an oxidant; dispersing the functionalized diamond nanoparticles in a solvent comprising a silane functional group; and forming covalent bonds between the silane functional group and the diamond nanoparticles. A method of forming a diamond coating may include depositing the diamond nanoparticles over a substrate.