Quick assessment of a Small Scattering data using Guinier-Porod model: Introducing the correlative size

Abstract

A straightforward method is proposed to process the non-linear parameters obtained from Guinier-Porod (GP) functions, commonly used for a fast evaluation of Small Angle Scattering (SAS) data. The GP function could be used for a first structural assessment before selecting a specific model or to use as it is depending on the complexity of the system. However, functions are highly-non-linear, so parameters from the model are strongly correlated, hence, releasing all parameters free for fitting may lead to data interpretation pitfalls. In this work, a correlative size is introduced in order to avoid numerical artifacts and simplify the comparison between samples. This correlative size is calculated from the intersection point between the Guinier and the Porod region, which estimates the radius of a given geometry placed at the same intersection point in the scattering momentum transfer q-axis. The correlative size can be considered a radius for spheroidal or cylindrical objects while a thickness for 2D materials. This methodology could be applied to follow in situ processes like precipitation or polymerization reactions which are usually affected by aggregation, and for the fast analysis of hierarchical structures, where the procedure was also tested for fractal-like structures

In Situ SAXS Study of the Formation of Aluminum Hydroxide-Based Hydrogels with Excellent Optical Properties

“…However, this value is largely affected by the s parameter. Therefore, in order to compare the size of particles among different samples regardless of the correlation among nonlinear parameters from the model, the radius of gyration R g of the particles was expressed in terms of the size of a correlative spherical radius ( R eq ) . The increase of R eq shifts the SAXS curve toward smaller scattering vector ( q ) values (i.e., the larger the particle size, the smaller the q ).…”