Raman scattering images of carbon nanotubes using standard diffraction limited microscopy, and the near-field Raman microscopy technique developed by Lukas Novotny of the University of Rochester and colleagues. The new technique can resolve features as small as 20 nanometers across.
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Researchers have created the highest-resolution optical image ever, revealing structures as small as carbon nanotubes just a few billionths of an inch across. The new method, developed by scientists at the University of Rochester with colleagues at Portland State and Harvard Universities, should literally shed light on previously inaccessible chemical and structural information in samples as small as the proteins in a cell's membrane. This is the highest-resolution, optical spectroscopic measurement ever made. Although there are other methods that can see smaller structures, they do not use light, which is rich in information.
The Rochester team's light-based technique--called near-field Raman microscopy--allows researchers to glean a great deal of visual information. Other ultra-high-resolution imaging techniques, such as atomic force microscopes, detect the presence of objects and image them, but do not have the ability to directly view light bouncing off an object.
To light up the nanoscale, researchers sharpen a gold wire to a point just a few billionths of an inch across. A laser then shines against the side of the gold tip, creating a tiny bubble of electromagnetic energy that interacts with the vibrations of the atoms in the sample. This interaction, called Raman scattering, releases packets of light from the sample that can be used to identify the chemical composition of the material.
This research appeared in the March 7, 2003, issue of Physical Review Letters, and was supported by the National Science Foundation (NSF). This excerpt was taken from the story Shining Light on the Nanoscale, which appeared in the April 16, 2003, NSF News Tip. (Year of image: 2003)