Tracking 2D-to-3D crystal growth of a layered material <i>in situ</i> with X-ray scattering

The dimensionality of a layered material, <i>i.e.</i> the number of 2D layers bound together, is a structural property underpinning the functional properties of the material. Uncovering synthetic methodologies for controlling dimensionality is therefore crucial for enabling the targeted design of high-functioning materials. This <i>in situ</i> X-ray total scattering study demonstrates the crystal growth of anisotropic Bi₂₄O₃₁Br₁₀, a layered material increasingly utilised for its promising photocatalytic properties. Interlayer and intralayer crystal growth were facilitated by calcining Bi₂₄O₃₁Br₁₀ over the temperature range of 30-600 °C. Analyses of the scattering data were conducted in reciprocal space and real space, combining model-free, model-based, and simulation-based analyses, with all conferring that the Bi₂₄O₃₁Br₁₀ sample exhibits low dimensionality at lower temperatures, which gradually transitions to higher dimensionality as the calcination temperature increases. The inevitable thermal effects brought on by conducting measurements at elevated temperatures were analysed using the Python package, diffpy.morph, facilitating insight into the extent of thermal expansion and vibration throughout the data series, which in turn facilitated a focused analysis of crystal growth in an anisotropic nanomaterial. This study provides novel insight into structural analyses of 2D-to-3D transitions in anisotropic nanomaterials <i>via</i> X-ray scattering, and contributes significantly to the structural understanding of an emerging functional layered material.