Leading nanoscale imaging centre opens in UK

THE new electron Physical Sciences Imaging Centre (ePSIC), including two state-of-the-art electron microscopes, has opened in Oxfordshire, UK.

The centre is a collaboration between the University of Oxford, speciality chemical company Johnson Matthey, and Diamond Light Source, home to the UK’s synchrotron. Angus Kirkland, a professor of materials science at Oxford, is the science director of ePSIC. The centre will enable researchers to determine the atomic structure and characteristics of materials for wearable and flexible technologies and batteries, catalysts and nuclear materials, amongst other things, leading to improvements and new developments. The electron microscopes can image static materials, or observe reactions as they happen. The resolution of the images produced by the electron microscopes goes down to an astonishing 48 pm (48 x 10^-12 m). There are only four such facilities in the world.

The two electron microscopes, provided by Oxford and Johnson Matthey, have slightly different functions. Oxford’s JEOL 300 kV electron microscope for transmission electron microscopy, is optimised for imaging materials, so researchers can see the detailed structure of a material such as a catalyst.

Johnson Matthey’s electron microscope has more detectors and is more suitable for detailed chemical analysis of a substance. It can work in two modes. The first is transmission electron microscopy (TEM), in which the sample, which must be just tens of nanometres thick, is illuminated with a broad beam of electrons, giving one image. It is extremely fast, capable of taking 200 images per second. This allows for slow-motion imaging of reactions at an atomic scale. In the second mode, scanning transmission electron microscopy (STEM), the electron beam is focussed, and as the name suggests, scans over the surface of the sample. This is slower, but provides much more information in a single image. The individual motors moving the scanning probe are accurate to 1 nm. In addition, the power of the microscope can be varied, from 30 kEV (kilo electron volts) to 300 kEV. The lower power images are less detailed but cause less damage to sensitive samples.

For such high resolution images, the electron microscopes need to be extremely stable. For that reason, the building which houses them is built on top of 15 m deep piles and 1 m thick concrete. Each of the microscopes is situated on top of its own concrete slab, isolated from the rest of the building and anchored into bedrock. The walls are soundproofed and are fitted with cooling panels, as the circulated air from air conditioning is undesirable, to keep temperature fluctuations below 0.2?C. The walls are also fitted with electromagnetic coils, to minimise outside electromagnetic disturbance. Overall, each electron microscope is stable to vibrations within 6 nm.

The potential uses for the ePSIC are vast. As well as looking at battery components, including lithium ion batteries and renewable energy storage batteries, Johnson Matthey research fellow Paul Collier tells The Chemical Engineer that one of the main areas of research at ePSIC will be in looking at the zeolite catalysts used to eliminate NOx emissions from vehicle exhausts. This will help researchers to understand the structure, and exactly where precious metal atoms sit and how they interact with oxygen in real time reactions. Synchrotron beamlines destroy the zeolite structure. They will also look at zeolite catalysts used in fluidised catalytic cracking of crude oil, in real-time reactions.

'What we’re really trying to do is get away from an age where people would just try things without being sure whether or not it will work. If it does work, then you do a bit more, add a bit of this and a bit of that. It’s trial and error and that’s an awful way to do science. It should be about design and understanding. You can use computational modelling as well, and shine a light on the direction you want to go to. This is about getting towards that point where we can use that understanding to design better materials, atom by atom,' said Collier.

ePSIC has been sited next to Diamond for a number of reasons. Andy Dent, physical science co-ordinator for Diamond, says that one of the main reasons is cost. Electron microscopes are expensive to run and to leave idle; Diamond, on the 200 days a year it is operational, runs around the clock. This means that there are staff available to run the electron microscopes 24 hours a day as well, maximising the use and the efficiency of running the microscopes. In a university, it would be much more difficult to staff the microscopes at weekends, holidays and during the night. In addition, the technology necessary for handling samples and data for both synchrotron and electron microscopes is very similar.

The new building housing ePSIC will also include the electron Bio Imaging Centre (eBIC) and the I14 hard x-ray nanoprobe, linked to the Diamond Light synchrotron. The I14 hard x-ray nanoprobe will use one of Diamond’s synchrotron light beamlines, and will allow imaging down to the nanoscale to allow 2D and 3D structural analysis of components. Collier explains that while a material, such as a catalyst, is in use, it often undergoes changes on the tens of nanometre scale, as well as on the atomic scale. In addition, the x-ray beamline can penetrate further into a material. I14 will therefore complement the work of ePSIC in understanding the changes in a material.

'Diamond is a world-leading centre for visualising physical and biological materials at the atomic and molecular level and it makes sense to complement our capabilities with electron microscopy. Information gained will give us microscopic properties and valuable insight into the electronic structure of materials, strength and much more. The centre will be opened to all and will operate like our beamlines, through both academic peer review and proprietary access. As a result, the Diamond synchrotron will become the first in the world to house such a complementary set of techniques,' said Diamond CEO Andrew Harrison.