vital step towards the ultimate goal of being able
to take ‘photographs' of
individual molecules in action has been achieved by an international team led
by UCL (University College London) researchers at the London Centre for Nanotechnology.
They report in the journal Nature on a novel method of obtaining a full 3-D image
of the interior of nanocrystals. Using a process known as coherent X-ray diffraction
imaging, they were able to build a picture of the inside of nanocrystals by measuring
and inverting diffraction patterns.
Ultimately, 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 which gives them
Professor Ian Robinson, of the UCL Department of Physics & Astronomy and
the London Centre for Nanotechnology, who led the study, says: “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 realisation 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
The inversion of a diffraction pattern back to an image has already been proven
to yield a unique ‘photograph' in two or higher dimensions. However, previously
researchers have encountered difficulties with 3-D structures with deformations
as these interfere with the symmetry of the pattern. To overcome this problem,
the UCL team used a lead nanocrystal that was crystallised in an ultrahigh vacuum.
It showed that asymmetries in the diffraction pattern can be mapped to deformities,
providing a detailed 3-D map of the location of them in the crystal.
Founded in 1826, UCL was the first English university established after Oxford
and Cambridge, the first to admit students regardless of race, class, religion
or gender, and the first to provide systematic teaching of law, architecture
and medicine. In the government's most recent Research Assessment Exercise, 59
UCL departments achieved top ratings of 5* and 5, indicating research quality
of international excellence.
UCL is the fourth-ranked UK university in the 2005 league table of the top 500
world universities produced by the Shanghai Jiao Tong University. UCL alumni
include Mahatma Gandhi (Laws 1889, Indian political and spiritual leader); Jonathan
Dimbleby (Philosophy 1969, writer and television presenter); Junichiro Koizumi
(Economics 1969, Prime Minister of Japan); Lord Woolf (Laws 1954, former Lord
Chief Justice of England & Wales); Alexander Graham Bell (Phonetics 1860s,
inventor of the telephone); and members of the band Coldplay.
paper ‘Three-dimensional mapping of a deformation
field inside a nanocrystal' will be published in
the July 6 edition of the journal Nature. The authors
are: Mark A. Pfeifer1†, Garth J. Williams1†, Ivan
A. Vartanyants1†, Ross Harder1 & Ian K. Robinson1
1 Physics Department, University of Illinois, Urbana,
Illinois 61801, USA. †Present
addresses: Department of Physics, University of Oregon, Eugene, Oregon 97403,
USA (M.A.P.), School of Physics, University of Melbourne, Australia (G.J.W.),
HASYLAB, DESY, Hamburg, Germany (I.A.V.), Department of Physics & Astronomy,
University College London, UK.