Tunable assembly of truncated nanocubes by evaporation-driven poor-solvent enrichment

Abstract

Self-assembly of nanocrystals is extensively used to generate superlattices with long-range translational order and atomic crystallographic orientation, i.e. mesocrystals, with emergent mesoscale properties, but the predictability and tunability of the assembly methods are poorly understood. Here, we report how mesocrystals produced by poor-solvent enrichment can be tuned by solvent composition, initial nanocrystal concentration, poor-solvent enrichment rate, and excess surfactant. The crystallographic coherence and mesoscopic order within the mesocrystal were characterized using techniques in real and reciprocal spaces, and superlattice growth was followed in real time by small-angle X-ray scattering. We show that formation of highly ordered superlattices is dominated by the evaporation-driven increase of the solvent polarity and particle concentration, and facilitated by excess surfactant. Poor-solvent enrichment is a versatile nanoparticle assembly method that offers a promising production route with high predictability to modulate and maximize the size and morphology of nanocrystal metamaterials.

Radiation Chemistry Provides Nanoscopic Insights into the Role of Intermediate Phases in CeO2 Mesocrystal Formation

“…It is important to mention that these supracrystals fall apart into separate units (mesocrystals) when immersed in water and ultrasonicated for a few minutes. This indicates that while drying, adsorbed water molecules leave the surface of the particles, leading to the changes of the surface properties [52, 53] . Capillary forces guide the formation of the supracrystals but no strong bonding is formed between individual mesocrystals.…”

“…This indicates that while drying, adsorbed water molecules leave the surface of the particles,leading to the changes of the surface properties. [52,53] Capillary forces guide the formation of the supracrystals but no strong bonding is formed between individual mesocrystals.…”

Time‐Resolved SAXS Study of Polarity‐ and Surfactant‐Controlled Superlattice Transformations of Oleate‐Capped Nanocubes During Solvent Removal

“…This suggests that free OA in the dispersions with added OA (GP48) increased the inter-particle spacing and promoted the growth of large superlattices, which corresponds well to previous studies that concluded that the addition of free OA is required to form large and well-ordered Small 2022, 18, 2106768 superlattices from oleate-capped nanoparticles by evaporationdriven self-assembly. [29,37] No structural transformation could be deduced from the SAXS data during t = 245 to 600 s of the second stage of solvent removal when the medium is dominated by 1-pentanol (Figure 4c) and the polarity remained unchanged at ε = 13.7 (Figure 4d). Although no lattice transformation occurred during the lattice expansion, the displacement increased dramatically from 2.65 nm to 3.33 nm and the characteristic length slightly decreased from 113 nm to 91 nm (Figure S2d, Supporting Information).…”

Recent Notable Approaches to Study Self‐Assembly of Nanoparticles with X‐Ray Scattering and Electron Microscopy

“…Lv et al used a multi-method approach to investigate the superlattice formation by poor-solvent enrichment, modifying solvent composition, initial nanocrystal concentration, poor-solvent enrichment rate, and excess surfactants. [275] In situ SAXS experiments were performed using different solvent modification on evaporating droplets, as introduced in the previous subsection. It was found that a higher crystalline quality of superlattices is achieved with a sufficient addition of excess oleic acid as surfactant which resulted in large and well-ordered supercrystals.…”