Proceedings of Online nanoGe Fall Meeting 20 (OnlineNFM20)
Publication date: 4th October 2020
Directing the self-assembly of colloidal nanocrystals into ordered superstructures is of fundamental and technological interest for creating designer materials that bridge multiple length scales. The assembly of polyhedral nanocrystals at the interface of two immiscible fluids presents a promising approach to create high-fidelity superlattices with exceptional translational order and enables control over the orientational order of constituent building blocks. However, the full potential of this assembly approach remains elusive since despite the ostensible simplicity of the interfacial assembly, many knowledge gaps persist concerning the nuanced physicochemical phenomena that occur during assembly.
Using synchrotron-source grazing incidence small angle X-ray scattering (GISAXS), the fluid and particle dynamics which lead to the final highly ordered superlattices can be elucidated. In this work, we used high time resolution GISAXS to characterize the spreading and drying dynamics of PbSe nanocrystals assembling from droplet contact with the liquid substrate to the final superlattice structure. Additionally, we explain how tuning the solvent parameters, such as volatility, surface tension and polarity, determines the mesoscale morphology of 2D superlattices on ethylene glycol. Specifically, the solvent interaction with the liquid substrate and ligand shell dynamics during evaporation have significant effects on the final superlattice morphology. Improved understanding of the kinetic phenomena giving rise to superlattice topology will enable growth of high-quality superlattices with long-range order at both nano- and micro- scales.
This work was supported by the US Department of Energy, Office of Basic Energy Sciences program on synthesis and processing methods (DE-SC0018026). TEM characterization was performed at the Cornell Center for Materials Research Shared Facilities which are supported through the NSF MRSEC program (DMR-1719875). This work is based upon research conducted at the Cornell High Energy Synchrotron Source (CHESS) which is supported by the National Science Foundation under award DMR-1332208. The authors thank Deniz Erkan for help with data collection.
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