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Monitoring Nanocrystal Self‐Assembly in Real Time Using In Situ Small‐Angle X‐Ray Scattering
Author(s) -
Lokteva Irina,
Koof Michael,
Walther Michael,
Grübel Gerhard,
Lehmkühler Felix
Publication year - 2019
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201900438
Subject(s) - small angle x ray scattering , superlattice , nanocrystal , materials science , nucleation , self assembly , scattering , chemical physics , evaporation , nanotechnology , bragg's law , crystallography , optics , chemistry , optoelectronics , organic chemistry , physics , thermodynamics , diffraction
Self‐assembled nanocrystal superlattices have attracted large scientific attention due to their potential technological applications. However, the nucleation and growth mechanisms of superlattice assemblies remain largely unresolved due to experimental difficulties to monitor intermediate states. Here, the self‐assembly of colloidal PbS nanocrystals is studied in real time by a combination of controlled solvent evaporation from the bulk solution and in situ small‐angle X‐ray scattering (SAXS) in transmission geometry. For the first time for the investigated system a hexagonal closed‐packed (hcp) superlattice formed in a solvent vapor saturated atmosphere is observed during slow solvent evaporation from a colloidal suspension. The highly ordered hcp superlattice is followed by a transition into the final body‐centered cubic superlattice upon complete drying. Additionally, X‐ray cross‐correlation analysis of Bragg reflections is applied to access information on precursor structures in the assembly process, which is not evident from conventional SAXS analysis. The detailed evolution of the crystal structure with time provides key results for understanding the assembly mechanism and the role of ligand–solvent interactions, which is important both for fundamental research and for fabrication of superlattices with desired properties.