Basics
The term X-ray scattering refers to a group of techniques, including small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), and X-ray reflectivity. X-ray diffraction is also a form X-ray scattering but is specifically applied to ordered, crystalline materials. X-ray scattering techniques rely on the interaction of X-rays with electrons of atoms. Unlike diffraction, however, the X-rays are not scattered in patterns based on the crystallinity of the sample. Therefore, crystalline samples are not required for measurement, and the technique is suitable for analysing of disordered materials. While X-ray scattering lacks the detailed information obtained from diffraction, it compensates with a broader applicability across various samples.
Benefits
X-ray scattering techniques give information on the shapes, sizes, and orientations of large molecules (e.g., proteins, enzymes, polymers) or particles of similar dimensions (e.g., nanoparticles, nanotubes, etc.), up to structures on the micrometre scale. For instance, the X-ray scattering technique will produce distinct and diagnostic curves from folded, partially unfolded, or completely unfolded proteins. The grazing-incidence small-angle X-ray scattering technique (GISAXS) is particularly useful for gaining information on interface and surface structures of thin films. The high-intensity X-ray radiation available at DESY allows real-time measurements of dynamic processes, such as monitoring of structural changes of materials during stretching (devices for stretching samples under investigation are available at the HASYLAB SAXS facility).
Types of samples
Crystalline samples are not necessary for X-ray scattering techniques; the samples can be liquids, solids, or combinations thereof. The technique is also non-destructive, making it suitable for sensitive samples and those with limited material..
Applications of X-ray scattering at DESY
The technique is primarily used to measure materials ranging from large molecules to nanomaterials with micrometre superstructures. Applications are most prevalent in the fields of soft-condensed matter (e.g., polymers, foams, gels), nanoscience, and structural biology.
Examples of specific applications:
- Determining the extent of folding in large protein molecules.
- Assessing the thickness and density of thin films.
- Measuring the crystallinity of polymer samples.
- Monitoring of structural changes of materials under stress in situ.
- Real-time observation of industrial deposition processes such as ink-jet printing and the microscale deposition of materials for data storage devices.
