Supercrystalline nanocomposite materials with micromechanical properties approaching those of nacre or similar structural biomaterials can be produced by self-assembly of organically modified nanoparticles and further strengthened by cross-linking. The strengthening of these nanocomposites is controlled via thermal treatment, which promotes the formation of covalent bonds between interdigitated ligands on the nanoparticle surface. In this work, it is shown how the extent of the mechanical properties enhancement can be controlled by the solvent used during the self-assembly step. We find that the resulting mechanical properties correlate with the Hansen solubility parameters of the solvents and ligands used for the supercrystal assembly: the hardness and elastic modulus decrease as the Hansen solubility parameter of the solvent approaches the Hansen solubility parameter of the ligands that stabilize the nanoparticles. Moreover, it is shown that self-assembled supercrystals that are subsequently uniaxially pressed can deform up to 6 %. The extent of this deformation is also closely related to the solvent used during the self-assembly step. These results indicate that the conformation and arrangement of the organic ligands on the nanoparticle surface not only control the self-assembly itself but also influence the mechanical properties of the resulting supercrystalline material. The Hansen solubility parameters may therefore serve as a tool to predict what solvents and ligands should be used to obtain supercrystalline materials with good mechanical properties.

No abstract

published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User

Controlling the nanoscale interactions of colloidal building blocks is a key step for the transition from single nanoparticles to tailor-made, architected morphologies and their further integration into functional materials. Solvent evaporationinduced self-assembly within emulsion droplets emerges as a fast, versatile, and low-cost approach to obtain spherical, complex structures, such as supraparticles. Nevertheless, some process− structure relationships able to describe the effects of emulsion conditions on the synthesis outcomes still remain to be understood. Here, we explore the effect of different physicochemical parameters of emulsion-templated self-assembly (ETSA) on supraparticles' formation. Supraparticle size, size dispersity, microporosity, and sample homogeneity are rationalized based on the used surfactant formulation, stabilization mechanism, and viscosity of the emulsion. We further demonstrate the significance of the parameters found by optimizing a transferable, large-scale (gram-size) ETSA setup for the controlled synthesis of spherical supraparticles in a range of defined sizes (from 0.1−10 μm). Ultimately, our results provide new key synthetic parameters able to control the process, promoting the development of supraparticle-based, functional nanomaterials for a wide range of applications.

Supercrystalline nanocomposites (SCNCs) are a new category of nanostructured materials, with organically functionalized nanoparticles assembled into periodic structures, reminiscent of atomic crystals. Thanks to this nanoarchitecture, SCNCs show great promise for functional applications, and understanding and controlling their mechanical properties becomes key. Nanoindentation is a powerful tool to assess the mechanical behavior of virtually any material, and it is particularly suitable for studies on nanostructured materials. While investigating SCNCs in nanoindentation, a linear proportionality has emerged between elastic modulus and hardness. This is not uncommon in nanoindentation studies, and here we compare and contrast the behavior of SCNCs with that of other material categories that share some of the key features of SCNCs: mineral-rich biocomposites (where mineral building blocks are packed into a protein-interfaced network), ultrafine grained materials (where the characteristic nano-grain sizes are analogous to those of the SCNC building blocks), and face-centered cubic atomic crystals (which share the typical SCNC periodic structure). A strong analogy emerges with biomaterials, both in terms of the hardness/elastic modulus relationship, and of the correlation between this ratio and the dissipative mechanisms occurring upon material deformation. Insights into the suitability of SCNCs as building blocks of the next-generation hierarchical materials are drawn.