Practical applications of small-angle neutron scattering

Abstract

Recent improvements in beam-line accessibility and technology have led to small-angle neutron scattering (SANS) becoming more frequently applied to materials problems. SANS has been used to study the assembly, dispersion, alignment and mixing of nanoscale condensed matter, as well as to characterise the internal structure of organic thin films, porous structures and inclusions within steel.Using time-resolved SANS, growth mechanisms in materials systems and soft matter phase transitions can also be explored. This review is intended for newcomers to SANS as well as experts. Therefore, the basic knowledge required for its use is first summarised. After this introduction, various examples are given of the types of soft and hard matter that have been studied by SANS. The information that can be extracted from the data is highlighted, alongside the methods used to obtain it. In addition to presenting the findings, explanations are provided on how the SANS measurements were optimised, such as the use of contrast variation to highlight specific parts of a structure. Emphasis is placed on the use of complementary techniques to improve data quality (e.g. using other scattering methods) and the accuracy of data analysis (e.g. using microscopy to separately determine shape and size). This is done with a view to providing guidance on how best to design and analyse future SANS measurements on materials not listed below.

Everything SAXS: small-angle scattering pattern collection and correction

“…Such small-angle scattering (SAS) occurs in all kinds of materials, be they (partially) crystalline or amorphous solids, liquids or even gases, and can take place for a wide variety of radiation, such as electrons (SAES) [159,21], gamma rays (SAGS) [91,90], light (LS) [73,27], x-rays (SAXS) [102,63,2] and even neutrons (SANS) [2,10,75]. For the purpose of this review, we shall limit ourselves to x-ray scattering.…”

Simultaneous SAXS and SANS Analysis for the Detection of Toroidal Supramolecular Polymers Composed of Noncovalent Supermacrocycles in Solution

“…The SAXS signal arises from regions contrasting in electron density, while SANS (in this case) highlights 1 H-rich regions of an assembly dispersed in a 2 D-rich solvent. [9] Therefore, for molecules comprising both π-conjugated (e − -rich, 1 H-poor) and aliphatic ( 1 H-rich, e − -poor) parts such as asphaltenes [18] or alkyl-fullerene derivatives, [2] the SAXS and SANS signals will derive from the π-conjugated-rich and aliphatic-rich parts of an assembly, respectively. In these cases, combined SAXS and SANS allows the detection not only of a particular assembly morphology in solution but also of the internal structure.…”

“…Conversely, small-angle scattering (SAS) techniques using Xrays (SAXS) [8] or neutrons (SANS) [9] can detect molecular assemblies with dimensions typically between 1-100 nm in solution. SAS results offer a bulk average over an appreciable volume, are dominated by the most commonly existing assembly structure, and therefore have a high statistical relevancy.…”

“…Unfortunately, this is often difficult to do, and, while cryo-electron microscopy can reveal high-resolution structures in (frozen) solution, [1,7] there are only a few reports of its use in non-aqueous solutions. [2] Conversely, small-angle scattering (SAS) techniques using Xrays (SAXS) [8] or neutrons (SANS) [9] can detect molecular assemblies with dimensions typically between 1-100 nm in solution. SAS results offer a bulk average over an appreciable volume, are dominated by the most commonly existing assembly structure, and therefore have a high statistical relevancy.…”

“…This relative difference is indicative of a core-shell structure. [9] To obtain more detailed information, the data has been modeled using a form factor for a monodisperse toroid with an ellipsoidal core-shell cross-section, [22] with an attractive Ornstein-Zernike structure factor, S(Q) accounting for the increased scattering at low Q (see SI for details). [3] A similar model without shell, has previously been used to model SANS data from toroidal charged block copolymer micelles, [23] with others using hollow cylinders to approximate the toroidal structure.…”