A method and apparatus for interrogating a target having a plurality of plasmon resonant particles (PREs) distributed in the target are disclosed. In the method, a field containing the target is illuminated, and one or more spectral emission characteristics of the light-scattering particles in the field are detected. From this data, an image of positions and spectral characteristic values in the field is constructed, allowing PREs with a selected spectral signature to be discriminated from other light-scattering entities, to provide information about the field. Also disclosed are a novel PRE composition for use in practicing the method, and a variety of diagnostic applications of the method.
This application is a division of application Ser. No. 09/027,048, filed Feb. 20, 1998, now U.S. Pat. No. 6,180,415 which claims priority to U.S. Provisional Application Ser. No. 60/038,677, filed Feb. 20, 1997, now abandoned, both of which are hereby incorporated by reference in their entirety.
