Multiscale Reciprocal Space Mapping of Magnetite Mesocrystals

Abstract

orientation-exhibit a multiple-lengthscale structure. Mesocrystals can occur naturally in abiotic and biogenic minerals or can be synthesized artificially. [1] Due to the crystallographic alignment of nanoparticles, mesocrystals exhibit a sharp wide-angle diffraction pattern. In addition, special types of mesocrystals (Type 1), which are characterized by a long-range packing order of (monodisperse) nanoparticles, additionally show single-crystallike diffraction patterns in the small-angle scattering region. [2] Resolving the mesocrystal structure is quite challenging, due to their structuration on different length scales. Whereas the external morphology and structural features of mesocrystals are relatively simple to analyze by scanning electron microscopy (SEM) techniques, the analysis of the internal structure of 3D mesocrystals via the combination of scanning and transmission electron microscopy (TEM) requires time-consuming and difficult sample preparation (for example by focused ion beam milling). The combination of small-and wide-angle X-ray scattering (SAXS and WAXS) techniques offers the possibility to non-destructively probe mesocrystalline structures Mesocrystals are a class of nanostructured material, where a multiple-lengthscale structure is a prerequisite of many interesting phenomena. Resolving the mesocrystal structure is quite challenging due to their structuration on different length scales. The combination of small-and wide-angle X-ray scattering (SAXS and WAXS) techniques offers the possibility of non-destructively probing mesocrystalline structures simultaneously, over multiple length scales to reveal their microscopic structure. This work describes how high dynamical range of modern detectors sheds light on the weak features of scattering, significantly increasing the information content. The detailed analysis of X-ray diffraction (XRD) from the magnetite mesocrystals with different particle sizes and shapes is described, in tandem with electron microscopy. The revealed features provide valuable input to the models of mesocrystal growth and the choice of structural motif; the impact on magnetic properties is discussed.

Exploring the Crystalline Structure of Gold Mesocrystals Using X-ray Diffraction

“…No resolved ripples were observed along the 110 or 111 directions, indicating either a large facet-to-facet distance spread along those directions or their small surface. Some insights could be obtained from the considerations of a packing mode with a fixed surface shell thickness [26]. Comparing the packing periodicity with D(100), we calculate the shell thickness as ~5 nm and D(110) as ~62 nm.…”