Single Molecule Detection in Levitated Microdroplets
W.B. Whitten, J.M. Ramsey, S. Arnold, and B.V. Bronk
Anal. Chem. 63, 1027-1031(1991)

Laser-excited fluorescence from electrodynamically levitated microdroplets is used to detect small nmbers of rhodamine-6G molecules. The small sample volume, typically a few picoleters reduces the background due to solvent and impurity Raman and fluorescence emission. With 514.5nm excitation from an argon ion laser, as few as 12 molecules have been detected in glycerol-water droplets. Our present detection limit, due to vibration in the impurity concentration in the blanks, corresponds to a signal-to-noise ratio of 3 for a single molecule of rhodamine-6G contained in a 1-pL volume (droplet diameter of apprx. 12um).