PNNL

Abstract

Nanoparticle assembly and attachment are common pathways of crystal growth by which particles organize into larger scale materials with hierarchical structure and long-range order. In particular, oriented attachment (OA), which is a special type of particle assembly, has attracted great attention in recent years because of the wide range of single crystal material structures that result from this process, such as 1-dimensional (1D) nanowires, 2D sheets, 3D branched structures, twinned crystals, defects, etc. With the advancements of in situ transmission electron microscopy techniques, researchers directly observed detailed particle motions in liquids and discovered that orientation-specific forces acting over short distances (~1 nm) from the particle surfaces drive the OA process. Integrating recently developed 3D fast force mapping via atomic force microscopy with theories and simulations, researchers have revealed the near-surface solution structure, the molecular details of charge states at particle/fluid interfaces, inhomogeneity of surface charges, and dielectric/magnetic properties of particles that influence short- and long-rang forces, such as electrostatic, van der Waals, hydration, and dipole-dipole. However, the molecular details of structure, interparticle forces, local/ensemble responses, and resulting microstructure over various spatial and temporal scales are intertwined via a “structure-property-force” relationship, which is not fully understood. A multidisciplinary approach, including in situ measurements, machine-learning-assisted simulations, and multiscale theories, is needed to decipher the molecular scale complexity and heterogeneity of structure and the resulting interparticle forces and particle motions. The knowledge will guide rigorous coupling between phenomena over different scales for better understanding of the emergent properties. In this review, we discuss the fundamental principles for understanding particle assembly and attachment processes, and the controlling factors and resulting structures. We review recent progress in the field via examples of both experiments and modeling, and discuss current developments and the future outlook.