The use of dynamically bonding molecules designed to reversibly link solvent-dispersed nanocrystals (NCs) is a promising strategy to form colloidal assemblies with controlled structure and macroscopic properties. In this work, tin-doped indium oxide NCs are functionalized with ligands that form reversible covalent bonds with linking molecules to drive assembly of NC gels. We monitor gelation using small angle X-ray scattering and characterize how changes in the gel structure affect infrared optical properties arising from the localized surface plasmon resonance of the NCs. The assembly is reversible because of the designed linking chemistry, and we disassemble the gels using two strategies: addition of excess NCs to change the ratio of linking molecules to NCs and addition of a capping molecule that displaces
the linking molecules. The assembly behavior is rationalized using a thermodynamic perturbation theory to compute the phase diagram of the NC–linking molecule mixture. Coarse-grained molecular dynamics simulations reveal the competition between loop and bridge linking motifs essential for understanding NC gelation. This combined experimental, computational, and theoretical work provides a platform for controlling and designing the properties of reversible colloidal assemblies that incorporate NC and solvent compositions beyond those compatible with other contemporary (e.g, DNA-based) linking strategies.We would like to acknowledge the UT Mass Spectrometry Facility for their
instrumental help and the UT NMR facilities for equipment use and assistance: NIH
Grant Number 1 S10 OD021508-01. This work was primarily supported by the
National Science Foundation through the Center for Dynamics and Control of
Materials: an NSF Materials Research Science and Engineering Center (NSF
MRSEC) under Cooperative Agreement DMR-1720595. This work was also
supported by NSF Graduate Research Fellowships DGE-1610403 (M.N.D. and
S.V.), an Arnold O. Beckman Postdoctoral Fellowship (Z.M.S.), NSF (CHE-
1905263), and the Welch Foundation (F-1848 and F-1696). E.V.A. acknowledges
support from the Welch Regents Chair (F-0046). We acknowledge the Texas
Advanced Computing Center (TACC) at The University of Texas at Austin for
providing HPC resources.Center for Dynamics and Control of Material
