Abstract
Colloidal crystals have applications in water treatments, including water purification and desalination technologies. It is, therefore, important to understand the interactions between colloids as a function of electrolyte concentration. We study the assembly of DNA-grafted gold nanoparticles immersed in concentrated electrolyte solutions. Increasing the concentration of divalent Ca2+ ions leads to the condensation of nanoparticles into face-centered-cubic (FCC) crystals at low electrolyte concentrations. As the electrolyte concentration increases, the system undergoes a phase change to body-centered-cubic (BCC) crystals. This phase change occurs as the interparticle distance decreases. Molecular dynamics analysis suggests that the interparticle interactions change from strongly repulsive to short-range attractive as the divalent-electrolyte concentration increases. A thermodynamic analysis suggests that increasing the salt concentration leads to significant dehydration of the nanoparticle environment. We conjecture that the intercolloid attractive interactions and dehydrated states favour the BCC structure. Our results gain insight into salting out of colloids such as proteins as the concentration of salt increases in the solution.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 408-423 |
| Number of pages | 16 |
| Journal | Faraday Discussions |
| Volume | 249 |
| DOIs | |
| State | Published - Jun 16 2023 |
Funding
This work was funded by the Department of Energy (DOE), Office of Basic Energy Sciences under Contract No. DE-FG02-08ER46539. This work made use of the IMSERC MS facility at Northwestern University, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-2025633), the State of Illinois, and the International Institute for Nanotechnology (IIN). Portions of this work were performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by Northwestern University, The Dow Chemical Company, and DuPont de Nemours, Inc. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE), Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. We thank Steven Weigand of DND-CAT for assistance with the SAXS setup and data reduction, as well as the Mirkin Lab of Northwestern University for allowing our use of their facilities, in particular Jennifer Delgado, Kaitlin Landy, and Vinzenz Mayer for assistance with oligonucleotide synthesis and purification.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry