Strengthening engineered nanocrystalt three-dimensional superlattices via ligand conformation and reactivity

Nanocrystal assembly into ordered structures provides mesostructural functional materials with a precise control that starts at the atomic scale. However, the lack of understanding on the self-assembly itself plus the poor structural integrity of the resulting supercrystalline materials still limits their application into engineered materials and devices. Surface functionalization of the nanobuilding blocks with organic ligands can be used not only as a means to control the interparticle interactions during self-assembly but also as a reactive platform to further strengthen the final material via ligand cross-linking. Here, we explore the influence of the ligands on superlattice formation and during cross-linking via thermal annealing. We elucidate the effect of the surface functionalization on the nanostructure during self-assembly and show how the ligand-promoted superlattice changes subsequently alter the cross-linking behavior. By gaining further insights on the chemical species derived from the thermally activated cross-linking and its effect in the overall mechanical response, we identify an oxidative radical polymerization as the main mechanism responsible for the ligand cross-linking. In the cascade of reactions occurring during the surface-ligands polymerization, the nanocrystal core material plays a catalytic role, being strongly affected by the anchoring group of the surface ligands. Ultimately, we demonstrate how the found mechanistic insights can be used to adjust the mechanical and nanostructural properties of the obtained nanocomposites. These results enable engineering supercrystalline nanocomposites with improved cohesion while preserving their characteristic nanostructure, which is required to achieve the collective properties for broad functional applications.

Subjects

Cross-linking

nanocrystals

nanoindentation

organic ligands

robustness

self-assembly

supercrystals

DDC Class

620: Ingenieurwissenschaften

Funding(s)

SFB 986: Teilprojekt B06 - Modellierung und Simulation der Interphaseneigenschaften von Kompositwerkstoffen aus Metall und Polymer auf der Nanoskala

More Funding Information

B.B. gratefully acknowledges the support from the Ministry of National Education of the Republic of Turkey. The authors are very
thankful to Emad Maawad (Deutsches Elektronen-Synchrotron, DESY) for his assistance in the SAXS acquisition, to Lea Klauke (Universität Hamburg) for her assistance in EA data acquisition, and to Vedran Vonk (DESY) for fruitful discussions about X-ray analyses.

Publication version

publishedVersion

Lizenz

https://creativecommons.org/licenses/by-nc-nd/4.0/

Name

acsnano.2c01332.pdf

Size

5.35 MB

Format

Adobe PDF

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Strengthening engineered nanocrystalt three-dimensional superlattices via ligand conformation and reactivity