Abstract: A process for preparing superparamagnetic transition metal nanoparticles by introducing into a gas stream a hydrocarbon and a transition metal carboxyl wherein the transition metal carbonyl is introduced downstream from the hydrocarbon; wherein at the point of introduction of the hydrocarbon the gas stream is in the form of a plasma, and wherein at the point of introduction of the transition metal carbonyl the gas stream is at a temperature of at least 1000° C.; followed by quenching to form carbon-coated transition metal nanoparticles; and wherein the gas stream consists essentially of at least one inert gas and hydrogen.

Abstract: The present invention is a dispersion composition comprising (1) a curable mixture of monomers, oligomers, or a combination thereof; and (2) superparamagnetic particles dispersed in the mixture of part (1) and a method for preparing such superparamagnetic particles. The composition of the present invention can be useful as a tool for detecting and/or deterring theft, counterfeiting, or the like in commercial transactions.