Antitags are reported. These materials bring together two or more metallic nanoparticles by using a dithiolated organic molecule and contain antibodies on the surface to function as antigen-specific recognition elements. The linker position leads to a behavior characteristic of surface enhanced Raman spectroscopy (SERS). In conjunction with a surface containing capture antibodies, antitags can be used to detect antigens with sensitivities approaching those of the widely used enzyme linked immunosorbent assay (ELISA).