The present invention relates to nanoparticles comprising a metallic core with a surface coating, wherein the coating comprises at least an excitable radiative molecule attached thereto or impregnated therein, and wherein the excitable molecule is positioned at a sufficient distance from metallic core to enhance emissions when excited. The nanoparticles are included in compositions that may be used for surface coatings, cosmetics, assays, flow velocity measurements and targeting of tissue.