Quasi-two-dimensional, collective electron oscillations known as localized surface plasmons (LSP) can be excited in metal nanoparticles (typically gold or silver) along a dielectric surface resulting in strong amplification of the local electromagnetic field and appearance of surface plasmon absorption bands. These enhanced fields are evanescent i.e. they are confined to a distance of within 300 nm from the particles and decay significantly beyond it. State-of-the-art lithographic techniques provide tools for tailoring the interaction of nanosize structures with light; they provide precise control of size and spacing for the fabrication of a wide variety of complex shapes. These nanoparticles can be used to control, transmit, scatter, amplify, radiate and modify electromagnetic field of the incident light for applications in subwavelength optics, data storage, biophotonics, detection and sensing.
 

The use of fluorophore-metal interactions has the potential to dramatically increase the detectability ofsingle fluorophores for both SMD and FCS experiments. Our ensemble measurements have shown increased quantum yields, decreased lifetimes and increased photostabilities. Decreased lifetimes will result in higher emission rates prior to saturation. This is possible because the fluorophores can cycle faster between the ground and excited states. Decreased lifetimes should result in higher photostability because there is less time for chemical reactions to occur in the excited state. Decreased lifetimes should also result in decrease blinking because there will be less time for the fluorophores to go to the triplet state. These effects will provide longer observation times prior to photobleaching. We will use these effects to create the next generation of probes, which could be fluorophores in nanoshells, fluorophores bound to colloids, or fluorophores trapped in small volumes. These effects may also be used for increased detectability of single molecules bound to surfaces which contain metallic structures, for either biophysical studies or high sensitivity assays.
 

An understanding of MEF, SPCE and PCF will ultimately be based on an understanding of the interactions of incident light with plasmonic structures and the interactions of excited state fluorophores with electron oscillations in these structures. A complete emphasis on such calculations would be diversion from our efforts on nanofabrication and experimentation. Most of these experiments measured light extinction or transmission, not fluorescence. Many of the recently discovered properties of plasmonic structures are based on experimentation rather than theory. Our goal is to use commercially available software and selective calculations to allow comparison of our experimental results with electrodynamics theory for a more complete understanding of the underlying phenomena.