The Chemical Analysis Facility (CAF) has state-of-the-art facilities for single-crystal, powder and small-angle scattering X-ray diffraction. Members of staff have considerable expertise in these analytical techniques and are happy to discuss potential projects on a sample-by-sample basis, as part of a formal contract or, for longer-term studies, in collaboration.
Single-crystal X-ray diffraction
The EPSRC funded Oxford Diffraction Gemini Ultra diffractometer operates using either CuKα or MoKα radiation allowing crystal structures to be determined for a range of materials including pharmaceutical and small biological molecules, as well as molecular and extended organic and inorganic compounds. Data can be collected under an inert nitrogen atmosphere between 90 and 500 K (-183 and 227 °C), useful for studying phase transitions, changes in molecular geometry and intermolecular interactions as a function of temperature. We can offer data collection solely or data collection with full structure determination. Full structural reports are available in a choice of standard formats.
Powder X-ray diffraction
The two Bruker D8 powder diffractometers (primary monochromatic CuKα radiation) operate in both reflection (flat plate) and transmission (flat plate or capillary) geometries. Both instruments are equipped with a position-sensitive detector allowing rapid data collection for qualitative and quantitative identification of crystalline phases, such as polymorphs. Powder patterns can often be obtained from only a few mg of sample, although bulk sample holders are also available. More advanced applications, such as structure solution of inorganic, organic and pharmaceutical materials, Rietveld refinement, and particle size/ strain analysis are also possible. One of the diffractometers is equipped with a sample-changing robot, allowing the collection of data from up to 90 samples, which provides a useful facility for users requiring high throughput. Variable temperature stages on the second instrument allow data to be recorded under vacuum at temperatures between 90 and 1473 K (-183 and 1200 °C) or under humidity controlled conditions at temperatures up to 473 K (200 °C). Such data are suitable for phase-transition and hydration/dehydrations studies. We can offer data collection only, routine characterisation and 'advanced applications' as above. Again full structural reports are available in standard formats.
NanoStar Small-Angle X-ray Scattering
The small-angle X-ray scattering instrument is designed to investigate the structure of materials with nanoscale structure, such as polymers, proteins, colloids and ceramics. The state-of-the-art instrument features an Incoatec microfocus X-ray source, Montel optics, three pinhole collimation, a large sample chamber for different environments and a Vantec area detector (2048 x 2048 pixels, 100 µm resolution). The available range of 'd-spacings' is from approximately 2 nm to 125 nm, i.e. : qmin = 0.05 nm-1, qmax = 3.1 nm-1, the lowest accessible q value depending on whether the instrument is set up in high resolution or high-flux mode. A simultaneous wide-angle X-ray scattering (WAXS) capability is also available, using an image plate system, covering d spacings in the 0.1-1 nm range. The system can handle liquids mounted in custom made capillaries and also powders, sandwiched between X-ray windows (mica or kapton). Temperature control using an MRI electrical heating unit, with water cooling, is available from room temperature to 300 °C. It is also possible to use Couette and capillary flow cells for shearing samples to investigate flow orientation.