Commissioning of a versatile grazing-incidence platform at a very small angle neutron scattering instrument for investigating nano-to-microscopic colloidal assembly

Abstract

Grazing-incidence small-angle neutron scattering (GISANS) is a powerful technique for probing buried interfacial structures, yet its in-plane length-scale sensitivity is typically limited to a few hundred nanometres. Here, we report the successful commissioning of a standard GISANS and a novel grazing-incidence very small angle neutron scattering (GI-VSANS) setup at the China Spallation Neutron Source (CSNS), which extends the accessible in-plane length scale of conventional GISANS to several micrometres. This breakthrough establishes GI-VSANS as an essential complementary tool to standard GISANS for investigating hierarchical and microscopic structures at thin film interfaces. To overcome the challenges of low neutron flux and high sensitivity to the alignment of sample planes, which are inherent to VSANS instruments, we developed and implemented an apparatus that integrates a four-blade slit system and a multi-slit collimation array for precise beam focusing over the sample plane. We demonstrate the capability of this platform by resolving the in-plane size, distribution and hierarchical assembly patterns of colloids with diameters ranging from the nano- to submicrometre scale, and prepared from different coating methods. Based on this platform, colloidal assembly patterns are resolved at the nanoscale (by the GISANS configuration) and the microscale (by the GI-VSANS configuration) through quantitative analysis. The successful commissioning and validation of this user-friendly, modular GI-VSANS setup not only overcome significant instrumental challenges but also provide users at spallation neutron sources with a unique tool for probing previously inaccessible microscale in-plane interfacial structure.