Kinetics of the self-assembly of nanocrystal superlattices measured by real-time in situ X-ray scattering

• Published in: Nature materials Vol. 15; no. 7; pp. 775 - 781
• Main Authors: Weidman, Mark C., Smilgies, Detlef-M., Tisdale, William A.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.07.2016; Nature Publishing Group
• Subjects: 639/301/357/1017; 639/301/357/341; 639/925/357/1017; 639/925/357/341; Biomaterials; Colloids; Condensed Matter Physics; Evaporation; Kinetics; Materials Science; Nanocrystals; Nanotechnology; Optical and Electronic Materials; Order disorder; Real time; Scattering; Self assembly; solar (photovoltaic), solid state lighting, photosynthesis (natural and artificial), charge transport, optics, synthesis (novel materials), synthesis (self-assembly), synthesis (scalable processing); Solvents; Superlattices; X-rays
• ISSN: 1476-1122; 1476-4660; 1476-4660
• DOI: 10.1038/nmat4600

On solvent evaporation, non-interacting monodisperse colloidal particles self-assemble into a close-packed superlattice. Although the initial and final states can be readily characterized, little is known about the dynamic transformation from colloid to superlattice. Here, by using in situ grazing-incidence X-ray scattering, we tracked the self-assembly of lead sulfide nanocrystals in real time. Following the first appearance of an ordered arrangement, the superlattice underwent uniaxial contraction and collective rotation as it approached its final body-centred cubic structure. The nanocrystals became crystallographically aligned early in the overall self-assembly process, showing that nanocrystal ordering occurs on a faster timescale than superlattice densification. Our findings demonstrate that synchrotron X-ray scattering is a viable method for studying self-assembly in its native environment, with ample time resolution to extract kinetic rates and observe intermediate configurations. The method could be used for real-time direction of self-assembly processes and to better understand the forces governing self-organization of soft materials. The self-assembly of lead sulfide nanocrystals into a body-centred cubic lattice can be tracked in real time by using in situ grazing-incidence X-ray scattering.