Electrolyte-Mediated Assembly of Charged Nanoparticles

Journal Article · Mon Apr 04 00:00:00 EDT 2016 · ACS Central Science

DOI:https://doi.org/10.1021/acscentsci.6b00023· OSTI ID:1245329

Kewalramani, Sumit ^[1]; Guerrero-García, Guillermo I. ^[2]; Moreau, Liane M. ^[1]; Zwanikken, Jos W. ^[1]; Mirkin, Chad A. ^[3]; Olvera de la Cruz, Monica ^[4]; Bedzyk, Michael J. ^[5]

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1. Materials Science and Engineering Department, Northwestern University, Evanston, Illinois 60208, United States
2. Materials Science and Engineering Department, Northwestern University, Evanston, Illinois 60208, United States, Instituto de Física, Universidad Autónoma de San Luis Potosí, Àlvaro Obregón 64, 78000 San Luis Potosí, San Luis Potosí, Mexico
3. Materials Science and Engineering Department, Northwestern University, Evanston, Illinois 60208, United States, Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
4. Materials Science and Engineering Department, Northwestern University, Evanston, Illinois 60208, United States, Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States, Physics and Astronomy Department, Northwestern University, Evanston, Illinois 60208, United States
5. Materials Science and Engineering Department, Northwestern University, Evanston, Illinois 60208, United States, Physics and Astronomy Department, Northwestern University, Evanston, Illinois 60208, United States

Solutions at high salt concentrations are used to crystallize or segregate charged colloids, including proteins and polyelectrolytes via a complex mechanism referred to as “salting-out”. Here, we combine small-angle X-ray scattering (SAXS), molecular dynamics (MD) simulations, and liquid-state theory to show that salting-out is a long-range interaction, which is controlled by electrolyte concentration and colloid charge density. As a model system, we analyze Au nanoparticles coated with noncomplementary DNA designed to prevent interparticle assembly via Watson–Crick hybridization. SAXS shows that these highly charged nanoparticles undergo “gas” to face-centered cubic (FCC) to “glass-like” transitions with increasing NaCl or CaCl₂ concentration. MD simulations reveal that the crystallization is concomitant with interparticle interactions changing from purely repulsive to a “long-range potential well” condition. Liquid-state theory explains this attraction as a sum of cohesive and depletion forces that originate from the interelectrolyte ion and electrolyte–ion–nanoparticle positional correlations. Our work provides fundamental insights into the effect of ionic correlations in the salting-out mechanism and suggests new routes for the crystallization of colloids and proteins using concentrated salts.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS); Energy Frontier Research Centers (EFRC) (United States). Center for Bio-Inspired Energy Science (CBES); Northwestern Univ., Evanston, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); US Air Force Office of Scientific Research (AFOSR); National Science Foundation (NSF)
• Grant/Contract Number: AC02-06CH11357; SC0000989; FA9550-11-1-0275; DMR-1121262
• OSTI ID: 1245329
• Alternate ID(s): OSTI ID: 1470465
• Journal Information: ACS Central Science, Journal Name: ACS Central Science Vol. 2 Journal Issue: 4; ISSN 2374-7943
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
59 BASIC BIOLOGICAL SCIENCES
Metal nanoparticles
Genetics
Nanoparticles
Ions
Electrolytes