Predicting Outcomes of Nanoparticle Attachment by Connecting Atomistic, Interfacial, Particle, and Aggregate Scales

Abstract

Predicting nanoparticle aggregation and attachment phenomena requires a rigorous understanding of the interplay among crystal structure, particle morphology, surface chemistry, solution conditions, and interparticle forces, yet no comprehensive picture exists. We used an integrated suite of experimental, theoretical, and simulation methods to resolve the effect of solution pH on the aggregation of boehmite nanoplatelets, a case study with important implications for the environmental management of legacy nuclear waste. Real-time observations showed that the particles attach preferentially along the (010) planes at pH 8.5 and the (101) planes at pH 11. To rationalize these results, we established the connection between key physicochemical phenomena across the relevant length scales. Starting from molecular-scale simulations of surface hydroxyl reactivity, we developed an interfacial-scale model of the corresponding electrostatic potentials, with subsequent particle-scale calculations of the resulting driving forces allowing successful prediction of the attachment modes. Finally, we scaled these phenomena to understand the collective structure at the aggregate-scale. Our results indicate that facet-specific differences in surface chemistry produce heterogeneous surface charge distributions that are coupled to particle anisotropy and shapedependent hydrodynamic forces, to play a key role in controlling aggregation behavior.

Molecular Mechanisms of Sorbed Ion Effects during Boehmite Particle Aggregation

“…for boehmite platelets, 8.5–9.5. , This corresponds to the p.z.c. of the basal (010) surface . When surface charge is present, boehmite still has been observed to aggregate, e.g., at pH 11 (no added electrolyte, liquid-cell TEM) and 12 (with added electrolyte, particle size by dynamic light scattering) .…”

“…(8.5–9.5) favor aggregation by basal (010) surfaces sites because the edge sites have significant positive surface charge and basal surfaces have zero charge. Higher pHs favor aggregation by edge sites (e.g., (101), (100), (001)) because these are uncharged under alkaline conditions, whereas the basal surfaces develop a negative charge. , Despite this ongoing research, the energetics and detailed interfacial structure for particle aggregation in the absence/presence of electrolytes are still a principle knowledge gap from this system.…”

Kinetics of Oriented Attachment of Mica Crystals

“…This study focuses on OA between mica basal surfaces, whose atomic structure does not vary with pH . However, as for oxide or oxyhydroxide crystals, the atomic facet structure is sensitive to pH, so that OA between specific surfaces is pH dependent. , In addition, the salt type and concentration might affect the OA process. The simulation and sampling technique here can hopefully be utilized to reveal OA in a variety of environments and guide the design of nanostructured materials facilitated by OA.…”

“…The electrostatic and van der Waals forces in the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory are applicable for the long-ranged interactions between dispersed particles, but they cannot explain the short-ranged (nanometer scale) interactions. − In the nanometer scale, the correlation between approaching atomic lattices becomes important, as well as forces arising due to specific arrangement of water molecules intervening particles. ,, From a kinetic point of view, it remains to be demonstrated why the OA pathway is preferred over the non-OA one. It was suggested that OA is a two-stage phenomenon. , In the first stage, two crystals approach, and coalignment is achieved through crystal rotation; but they are separated by a nanometer scale liquid layer .…”

Bridging Smart Nanosystems with Clinically Relevant Models and Advanced Imaging for Precision Drug Delivery

“…have demonstrated that the heterogeneous surface charge distributions due to different surface chemistry may contribute to the aggregation behavior of the particles. [ 103 ] Kenzaoui et al. have observed caveolae‐mediated endocytosis in well‐dispersed silica NPs but discovered a predominant micropinocytosis for aggregated NPs.…”