Production of size-controlled nanoscopic cap-shaped metal shells

A method of producing precisely size-controlled metal nanoparticles is described. Polystyrene (PS) spheres placed on a substrate were used as a cast for the metal nanoparticles. The diameters of the PS spheres were processed into the desired sizes by oxygen plasma etching, and metal was deposited on the PS to the desired thickness by thermal evaporation. The PS casts were then removed by the UV-excited ozone oxidization reaction. The diameters of the obtained cap-shaped metal shells had a distribution within 5% of the coefficient of variation. These particles can be used as simultaneously applicable biological labels along with different-sized nanoparticles in immuno-electron microscopy.