Abstract

The detection of single fluorescent molecules in liquid phase has proven challenging because of the limited available luminescence and high background levels. The number of fluorescent photons emitted by a single molecule is limited by photolysis (≈10⁶ for the best fluorophores) while the background signal in condensed phase is fundamentally bound by inelastic scattering from the solvent. These two constraints require the experiments to be performed in small probe volumes (≈1 pL). In our experiments the probe volume is conveniently defined by the spatial extent of a microdroplet (≈10-μm diameter). Microdroplets provide a number of advantages as a medium for single molecule detection, including their optical properties. Experimental evidence of single molecule detection and quantum electrodynamic effects in microdroplets will be presented.

© 1992 Optical Society of America