Total X-ray Scattering and Small-Angle X-ray Scattering for Determining the Structures, Sizes, Shapes, and Aggregation Extents of Iron (Hydr)Oxide Nanoparticles

Obtaining in situ and time-resolved information about atomic structure, crystallinity, size, shape, and aggregation extent of nanoparticulates during their nucleation, growth, their phase transformation is challenging. Because newly formed iron (hydr)oxides are small and poorly crystalline, the real-time identification of their structural information is even more difficult. However, this information is crucial to advance our understanding of iron (hydr)oxide thermodynamics and kinetics, as well as mechanisms of precipitation, surface sorption, incorporation, and redox reactions involving iron (hydr)oxides in the environment. In this book chapter, we first present total X-ray scattering with pair distribution function (PDF) for atomic structure analysis of ferrihydrite-the most poorly crystalline iron (hydr)oxide. Then, we discuss transmission and grazing incidence small angle X-ray scattering (SAXS/GISAXS) techniques for determining the particle size, shape, and aggregation extent of newly formed iron (hydr)oxide particles during their nucleation and growth process. New capability and application case studies are provided along with specific examples.