3D Image of Nanocrystal Created Using X-Rays

A critical development towards the ultimate goal of being able to capture images of individual molecules in action has been recently achieved by scientists.

An international team of investigators from University College London (UCL) researchers at the London Center for Nanotechnology (UK) reported in the July 6, 2006, issue of the journal Nature on an innovative technique whereby they obtained a complete three-dimensional (3D) image of the interior of nanocrystals and constructed an image of the inside of nanocrystals by measuring and inverting diffraction patterns.

Eventually, the technique will help in the development of x-ray free-electron lasers, which will allow single-molecule imaging. It will also allow researchers to more accurately assess the defects in any given material that gives them specific properties.

Prof. Ian Robinson, of the UCL department of physics and astronomy and the London Center for Nanotechnology, who led the study, remarked, "This new imaging method shows that the interior structure of atomic displacements within single nanocrystals can be obtained by direct inversion of the diffraction pattern. We hope one day this will be applied to determine the structure of single protein molecules placed in the femtosecond beam of a free-electron laser. Coherent x-ray diffraction imaging emerged from the realization that over-sampled diffraction patterns can be inverted to obtain real space images. It is an attractive alternative to electron microscopy because of the better penetration of the electromagnetic waves in materials of interest, which are often less damaging to the sample than electrons.”

The inversion of a diffraction pattern returned to an image has already been shown to provide a unique image in two or higher dimensions. However, researchers earlier have had problems with 3D structures with deformations as these interfere with the symmetry of the pattern. To overcome this obstacle, the UCL team utilized a lead nanocrystal that was crystallized in an ultrahigh vacuum. It showed that asymmetries in the diffraction pattern can be mapped to deformities, providing a detailed 3D map of the location of them in the crystal.



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