The present invention relates generally to compositions and methods of killing biofilm using a surface plasmon coupled to a photosensitizer. A nanostructure (10) may include a silver nanoparticle core (12), a mesoporous silica shell (14), and a photosensitizer (16). A method of killing biofilm may include contacting biofilm with a nanostructure (10) including a silver nanoparticle core (12), a mesoporous silica shell (14), and a photosensitizer (16) to form a blend and exposing the blend to light.