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Honolulu, HI, United States, 2006/08/28 - Researchers in Germany found a way to make objects smaller than the wavelength of light detectable by standard far-field optical infrared microscopy..
Objects a thousand times smaller than the wavelength of infrared light (10 micrometers) are undetectable by standard far-field optical infrared microscopy since the weak nanoparticle signals would be buried far below the background level. To overcome this drawback and to achieve nanoscale spatial resolution researchers in Germany illuminate the nanoparticles by a highly intensive nanoscale infrared light spot. It is generated in the nano-gap between a laser-illuminated scanning metal tip and the substrate supporting the particles. The simple but very efficient trick finally allowing detection of sub-10 nm particles is the use of highly reflecting substrates instead of glass slides typically used as a sample carrier in optical microscopy.
There is still a strong need in material-specific methods for chemical identification of nanocomposite materials. While the classical optical and infrared microscopies are highly sensitive to the chemical composition of materials, the diffraction limit prevents imaging of nanoscopic details, like the electron microscope does. In addition to the high chemical sensitivity, light microscopy offers several further advantages which are essential for applications in biology and biochemistry: it is nondestructive, radiation damage is negligible and objects can be imaged in liquids.
Researchers at the Max Planck Institute (MPI) of Biochemistry near Munich, Germany, are developing a new optical microscopy that allows a significantly better resolution than conventional optical microscopy. The microscope is based on an atomic force microscope (AFM) where the scanning tip is used for both mechanical and near-field optical probing. They call this scattering-type scanning near-field optical microscopy, s-SNOM. The laser-illuminated tip concentrates the light at the very tip apex thereby generating an optical nanofocus scanning the sample. It was already shown that a resolution at the nanometer-scale can be achieved, up to 1000 times better than in conventional infrared microscopy.
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By Michael Berger, Copyright 2006 Nanowerk LLC