Confinement, Detection, and Manipulation of Individual Molecules in Attoliter Volumes

Abstract

We report observation of fluorescence from individual rhodamine 6G molecules in streams of charged 1-μm diameter water droplets. With this approach, probe volumes comparable to diffraction-limited fluorescence microscopy1 techniques (≤ 500 attoliters) are achieved, resulting in similarly high contrast between single molecule fluorescence signals and nonfluorescent background. However, since the fluorescent molecules are confined to electrically charged droplets, in situ electrodynamic manipulation can be accomplished in a straightforward manner, allowing experimental control over both the delivery of molecules of interest to the observation region and the laser-molecule interaction time.