Surface enhanced fluorescence
A certain fraction of the visits paid to my blog every month come here through searching for surface-enhanced fluorescence. So I guess writing up a few words about this effect isn't totally useless...
Surface-enhanced fluorescence deals with the improvement (enhancement) of the detection sensitivity for fluorescent molecules. Increasing the emission rate of fluorescent molecules and/or shaping their emission properties (lifetime, spectrum, polarization,...) is generally performed close to metal surfaces that are textured on the nanometer scale. The idea behind the use of metals is to take advantage of surface plasmon resonances, that couple light to collective oscillations of electrons in the metal, and give rise to huge electromagnetic intensity enhancements close to metal surfaces.
Up to a certain extend, it is the equivalent for fluorescence that surface-enhanced Raman spectroscopy (SERS) is for Raman scattering. The main difference is that Raman scattering is insensitive to quenching losses to the metal, whereas fluorescence in the very close vicinity to metal surfaces (< 5nm) is dominated by non-radiative energy transfer to the metal, which imposes a trade-off between gain and losses.
I highly recommend reading the following references (I don't get any money for advertising):
- Principles of Nano-Optics, by L. Novotny and B. Hecht
- Principles of Fluorescence Spectroscopy, by J. R. Lakowicz
- Radiative decay engineering 5: metal-enhanced fluorescence and plasmon emission, J. R. Lakowicz, Analytical Biochemistry 337 (2005) 171–194
- Surface enhanced fluorescence, E. Fort and S. Gresillon, J. Phys. D: Appl. Phys. 41 (2008) 013001.
- You may also have a look at my own work, mostly on nanoaperture-enhanced detection of fluorescent molecules in solution (see the selected papers, a citation is always appreciated )