Scattering methods particle information

Standard static and dynamic light scattering methods assume that there is very little multiple scattering by the particles, that is, the dispersion has to be sufficiently dilute so that the photons are scattered only once as they pass through the sample. Is there a way to look inside a dispersion that is cloudy or milky, such as a foam, and to extract information on the local structure and its kinetics and relaxation Or, is it possible to tailor a dispersion so that... 

Compared to the colligative methods light scattering can yield information on a possible dissymmetry of the aggregates. For anisotropic particles the direction of the electric field associated with the incident light may not coincide with the shift of the electron cloud. The intensity of light scattered at (usually) 90° from anisotropic aggregates is increased over the value predicted on the basis of isotropy by the Cabannes factor. 

Scattering methods provide detailed information about the structural parameters of colloidal particles. In the field of polyelectrolyte complexes, mainly light scattering techniques such as static, dynamic, and electrophoretic light scattering were employed. 

An introduction to practical scattering methods applied to particles is given by NIST [5]. For more information, see [6, 32, 50, 51]. 

For very small particles, there is no angular dependence of the scattering intensity, and not even an gyration radius can be extracted. However, the absolute scattering intensity contains information about the particle size, but in most cases only an average particle size can be extracted. However, if the system investigated allows a systematic variation of the optical contrast, one has a powerful method at hand, from which even small polydispersities can be obtained reliably. Such situations are not that uncommon - they readily occur for water-in-oil microemulsions, but are also conceivable for other types of layered nanoparticles. 

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