Nanomineral aggregation leading to hierarchical assemblies and even mineral growth is now recognized as a broadly important geochemical processes. However, a major knowledge gap exists in fundamentally understanding the interactions between particles in situ during growth and the resulting response dynamics. Focusing on hematite as the model system, herein we describe additive-free synthesis protocols that yield diverse uniform hematite nanoparticles, such as bipyramids with twelve {111} facets and rhomboids with six {104} facets. Their growth, investigated in detail using scanning electron microscopy (SEM) and scanning/transmission electron microscopy (S/TEM), suggests a combination of particle mediated assembly and ion-by-ion coarsening leading to euhedral nanoparticles. We then report measurement of the anisotropic particle-particle forces between these hematite nanocrystals, as a function of their azimuthal orientation about the [001] axis via using atomic force microscopy (AFM)-based dynamic force spectroscopy (DFS). The collective findings help shed new light on hematite particle-based growth and the formation mechanism of hierarchical assemblies that define the physical characteristics of these nanomaterials. In addition to improving understanding of the occurrence, transformation, and fate of minerals in environmental and industrial settings, the results may help enable the development of novel materials for various catalytic applications.

Facet-dependent aggregation of hematite nanoparticles

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.