Single nanoparticle images for (a) silica spheres with 20 nm diameter, (b) monometallic silver shells on the silica spheres, (c) monometallic gold shells on the silica spheres, (d) heterogeneous bimetallic shells of silica/Ag/Au on the silica spheres, (e) heterogeneous bimetallic shells of silica/Au/Ag on the silica spheres, and (f) homogeneous bimetallic Ag-Au alloy shells on the silica spheres. The images were collected upon excitation with a laser of 470 nm. The scales of the diagrams were 5 × 5 μm and the resolutions of diagrams were 100 × 100 pixel with an integration of 0.6 ms/pixel.