A Practical Guide to Acquisition, Treatment and Model Free Analysis of SAXS/SANS Data: Methodologies and Pitfalls

Abstract

Small angle X-ray and neutron scattering (SAXS and SANS) are widely used tools for probing the nanoscale structures in soft materials like polymers, colloids, proteins etc. Often data interpretation is based on the fitting of a physical model to the scattering data. However, there are methods for model free data analysis that offer valuable understanding in form of the physcial parameters, while avoiding the potential artifacts induced due to the assumption of incorrect models. This tutorial systematically discusses these analysis methods in detail, starting with the key considerations for scattering experimentation and data treatment. The tutorial provides a stepwise description of the Invariant calculation for quantifying volume fraction, Guinier analysis for estimating radius of gyration and Porod analysis for determining specific surface area of scatterer. Appropriate examples from diverse systems in literature such as polymers, fibers, microemulsions, nanoparticles etc are discussed for illustration. A special emphasis has been given to the common pitfalls encountered during data analysis including the effect of polydispersity, background scattering and deviations from the ideal Porod’s behaviour. Explaining the useful protocols of data acquisition, treatment, analysis and corrections for deviations, this tutorial aims at supporting new as well as the experienced users in obtaining reliable structural insights of materials from SAXS and SANS.