Nanoparticle size and size distribution play an important role in nanotechnology, because the intended effects depend on the size of the particles in the nanomaterial. In the regulatory context, the definition of a nanomaterial is based on the number size distribution of the particles. The EC recommendation for the definition of a nanomaterial gives “50 % or more of the particles in the number size distribution, one or more external dimensions is in the size range 1 nm – 100 nm”.
SAXS (“Small Angle X-Rays Scattering”) allowed a precise structural characterization of nanoparticles on a large number of objects by performing in-situ and non-destructive measurements (shape, size, size distribution, specific surface). Recent publications, Europeans projects (EMPIR Innanopart) and works on intercomparison measurements showed that SAXS and microscopy techniques gives very comparable results.