Fluorescence enhancement and lifetime modification of single nanodiamonds near a nanocrystalline silver surface

Fluorescent nanodiamond (FND) contains nitrogen-vacancy defect centers as fluorophores. The intensity of its fluorescence can be significantly enhanced after deposition of the particle (35 or 140 nm in size) on a nanocrystalline Ag film without a buffer layer. The excellent photostability (i.e. neither photobleaching nor photoblinking) of the material is preserved even on the Ag film. Concurrent decrease of excited state lifetimes and increase of fluorescence intensities indicate that the enhancement results from surface plasmon resonance. Such a fluorescence enhancement effect is diminished when the individual FND particle is wrapped around by DNA molecules, as a result of an increase in the distance between the color-center emitters inside the FND and the nearby Ag nanoparticles. A fluorescence intensity enhancement up to 10-fold is observed for 35 nm FNDs, confirmed by fluorescence lifetime imaging microscopy.