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Colloidal nanocrystal gels from thermodynamic principles

By: Thomas Truskett
From: The University of Texas at Austin, USA
At: Online - Zoom ( https://videoconf-colibri.zoom.us/j/82719493129?
[2021-02-02] 16:00

Gels assembled from solvent-dispersed nanocrystals are of interest for functional materials because they promise the opportunity to retain distinctive properties of individual nanocrystals combined with tunable, structure-dependent collective behavior. However, nanocrystal gels have so far been formed mostly through irreversible aggregation, which has limited realization of these possibilities. Meanwhile, gelation strategies for larger colloidal microparticles have been developed using reversible physical or chemical interactions. These approaches have enabled experimental navigation of theoretically predicted phase diagrams, helping to establish an understanding of how thermodynamic behavior can guide gel formation in these materials. The translation of these principles to the nanoscale poses both practical and fundamental challenges. In this talk, I present recent progress toward assembly of tunable nanocrystal gels using two strategies guided by equilibrium considerations: (1) reversible chemical bonding between functionalized nanocrystals and difunctional linker molecules and (2) nonspecific, polymer-induced depletion attractions. The effective nanocrystal attractions, mediated in both approaches by a secondary molecule, compete against stabilizing repulsions to promote reversible assembly. The structure and properties of the nanocrystal gels can be controlled microscopically by design of the secondary molecule and macroscopically by its concentration. This mode of control is compelling because it largely decouples nanocrystal synthesis and functionalization from the design of interactions that drive assembly.