Description:

Rapid progress in science on nanoscopic scales has promoted increasing interest in techniques of ultrahigh-resolution optical microscopy. The diffraction limit can be surpassed by illuminating an object in the near field through a sub-wavelength aperture at the end of a sharp metallic probe.  One method to improve this resolution limit is to replace the physical aperture by a nanoscopic active light source. Advances in the spatial and spectral detection of individual fluorescent molecules, using near-field and far-field methods, suggest the possibility of using a single molecule as the illumination source. Above are optical images taken with a single molecule as a point-like source of illumination, by combining fluorescence excitation spectroscopy with shear-force microscopy.  The successive images are taken with the molecule at different distances from the surface.  This single-molecule probe has potential for achieving molecular resolution in optical microscopy; it should also facilitate controlled studies of nanometer-scale phenomena (such as resonant energy transfer) with improved lateral and axial spatial resolution.

 

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