Shown on the left is the three dimensional image of a gold nanocrystal obtained previously while on the right is the image using the newly developed method. The features of the nanocrystal are vastly improved in the image on the left. The black scale bar is 100 nm. |
A
new advance in X-ray imaging has revealed the dramatic 3D shape of gold
nanocrystals, and is likely to shine a light on the structure of other
nanoscale materials.
Described today in Nature Communications,
the new technique improves the quality of nanomaterial images, made
using X-ray diffraction, by accurately correcting distortions in the
X-ray light.
Dr
Jesse Clark, lead author of the study from the London Centre for
Nanotechnology said: “With nanomaterials playing an increasingly
important role in many applications, there is a real need to be able to
obtain very high quality three dimensional images of these samples.
“Up
until now we have been limited by the quality of our X-rays. Here we
have demonstrated that with imperfect X-ray sources we can still obtain
very high quality images of nanomaterials.”
Up
until now, most nanomaterial imaging has been done using electron
microscopy. X-ray imaging is an attractive alternative as X-rays
penetrate further into the material than electrons and can be used in
ambient or controlled environments.
However,
making lenses that focus X-rays is very difficult. As an alternative,
scientists use the indirect method of coherent diffraction imaging
(CDI), where the diffraction pattern of the sample is measured (without
lenses) and inverted to an image by computer.
Nobel
Prize winner Lawrence Bragg suggested this method in 1939 but had no
way to determine the missing phases of the diffraction, which are today
provided by computer algorithms.
CDI
can be performed very well at the latest synchrotron X-ray sources such
as the UK’s Diamond Light Source which have much higher coherent flux
than earlier machines. CDI is gaining momentum in the study of
nanomaterials, but, until now, has suffered from poor image quality,
with broken or non-uniform density. This had been attributed to
imperfect coherence of the X-ray light used.
The
dramatic 3D images of gold nanocrystals presented in this study
demonstrate that this distortion can be corrected by appropriate
modelling of the coherence function.
Professor
Ian Robinson, London Centre for Nanotechnology and author of the paper
said: “The corrected images are far more interpretable that ever
obtained previously and will likely lead to new understanding of
structure of nanoscale materials.”
The method should also work for free-electron-laser, electron- and atom-based diffractive imaging.
High-resolution three-dimensional partially coherent diffraction imaging
Source: London Centre for Nanotechnology
