Strengthening Engineered Nanocrystal Three-Dimensional Superlattices via Ligand Conformation and Reactivity

Abstract

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Bridging Nanocrystals to Robust, Multifunctional, Bulk Materials through Nature-Inspired, Hierarchical Design

“…Our group has recently demonstrated that the micro-mechanical properties of periodically arranged NCs can be significantly boosted by creating a sub-nm thin, crosslinked, organic network in-between them, using small C-18 fatty acids or phospholipids as surface functionality. [26][27][28][29] The crosslinking of self-assembled organo-functionalized NCs can be achieved by thermal annealing at moderate temperatures (150 -350 °C) and allows reaching record-high values of strength, hardness, and stiffness, while still maintaining the nano-characteristic functionalities and a moderate degree of fracture toughness. 5,[25][26][27][28][29][30][31][32][33] However, the interactions that dictate the nanobuilding blocks' ordering during the first step of the nanocomposite's development (i.e.…”

“…[26][27][28][29] The crosslinking of self-assembled organo-functionalized NCs can be achieved by thermal annealing at moderate temperatures (150 -350 °C) and allows reaching record-high values of strength, hardness, and stiffness, while still maintaining the nano-characteristic functionalities and a moderate degree of fracture toughness. 5,[25][26][27][28][29][30][31][32][33] However, the interactions that dictate the nanobuilding blocks' ordering during the first step of the nanocomposite's development (i.e. self-assembly) do not provide structural control at larger length scales.…”

“…These interfaces offer a great opportunity to improve the material's robustness, by promoting an optimal bonding among the single constituents. At the atomic level, the NC surface ligands are selected so as to obtain a strong bond between the organic ligands and the NC surfaces (via-carboxylate binding to the magnetite surface 26,28 ).…”

“…At the nanoscale, weak van der Waals, magnetic, or capillary forces between adjacent ligands and NCs define the cohesion within the SPs. 26,38,39 Following our previous studies, [26][27][28][29][30] we apply a thermally activated crosslinking approach to enhance the NC-NC cohesion within the SPs. [26][27][28]30 When the NPs' surface ligands are crosslinked, these interfaces are dominated by covalent bonds between neighbouring ligands, increasing the overall strength and stiffness of the supraparticles.…”

“…26,38,39 Following our previous studies, [26][27][28][29][30] we apply a thermally activated crosslinking approach to enhance the NC-NC cohesion within the SPs. [26][27][28]30 When the NPs' surface ligands are crosslinked, these interfaces are dominated by covalent bonds between neighbouring ligands, increasing the overall strength and stiffness of the supraparticles. At the 2nd hierarchical level, the interface between the secondary building blocks (i.e.…”