The present invention relates in part to a method of fabricating multimetallic nanoparticles, the method comprising the steps of providing a substrate; activating the substrate surface; adsorbing a cationic transition metal complex onto the substrate surface to form a substrate-supported cationic transition metal complex; adsorbing an anionic transition metal complex onto the substrate-supported cationic transition metal complex to form a substrate-supported multimetallic complex salt; and reducing the substrate-supported multimetallic complex salt to provide a plurality of multimetallic nanoparticles. The invention also relates in part to a composition of multimetallic nanoparticles comprising at least two metals Ma and Mb; wherein the ratio of Ma to Mb is between about 2:1 and about 1:2.