Decay rate, metal-enhanced fluorescence, spectral

To understand the importance of spectral overlap to metal-enhanced fluorescence, it is useful to review the basics of metal-enhanced fluorescence. Metal nanostructures can alter the apparent fluorescence from nearby fluorophores in two ways. First, metal nanoparticles can enhance the excitation rate of the nearby fluorophore, as the excitation rate is proportional to the electric field intensity that is increased by the local-field enhancement. Fluorophores in such "hot spots" absorb more light than in the absence of the metal nanoparticle. Second, metal nanoparticles can alter the radiative decay rate and nonradiative decay rate of the nearby fluorophore, thus changing both quantum yield and the lifetime of the emitting species. We can summarize the various effects of a nanoparticle on the apparent fluorescence intensity, Y p, of a nearby fluorophore as ... 

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