Single Molecules Observed by Near-Field Scanning Optical Microscopy

Individual carbocyanine dye molecules in a sub-monolayer spread have been imaged with near-field scanning optical microscopy. Molecules can be repeatedly detected and spatially localized (to approximately lambda/50 where lambda is the wavelength of light) with a sensitivity of at least 0.005 molecules/(Hz)(1/2) and the orientation of each molecular dipole can be determined. This information is exploited to map the electric field distribution in the near-field aperture with molecular spatial resolution.