Self-Assembly Kinetics of Two-Dimensional Nanocrystal Superlattices

Two-dimensional assembly of gold nanocrystals at a toluene-air interface during colloidal droplet evaporation process: in situ optical microscopy (top panel, inset is a TEM image of the array after drying) and time-resolved GISAXS (bottom panel a-b).

Self-assembly of a crystalline phase with quasi-long-range positional order for two-dimensional nanocrystal superlattice (NSC) domains at the liquid-air interface during droplet evaporation has been observed. The NSCs were formed by depositing a colloidal suspension of highly monodisperse dodecanethiol-ligated gold nanocrystals. The kinetics of the self-assembly were immediately captured by in situ time-resolved grazing-incidence small-angle X-ray scattering (GISAXS) at the Advanced Photon Source (APS). NSCs self-assembled from weakly interacting nanocrystals have potential applications in photonic, electronic, and magnetic devices. Such critical applications usually require perfect single-crystal nanostructural phases with long-range order and limited defects. For two-dimensional NCSs composed of colloidal nanocrystals, quantitative characterization of the phase behavior has been lacking. The CNM users from the APS, working collaboratively with researchers in the Electronic & Magnetic Materials & Devices Group, have contributed to comprehensive and quantitative understanding of the structural evolution in NCSs during their formation with these studies.

Z. Jiang, X.-M. Lin, M. Sprung, S. Narayanan, and J. Wang, Nano. Lett. 10, 799 (2010).

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April 2010