skip to main content
DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Curvature dependence of the effect of ionic functionalization on the attraction among nanoparticles in dispersion

Abstract

Solubilization of nanoparticles facilitates nanomaterial processing and enables new applications. An effective method to improve dispersibility in water is provided by ionic functionalization. We explore how the necessary extent of functionalization depends on the particle geometry. Using molecular dynamics/umbrella sampling simulations, we determine the effect of the solute curvature on solvent-averaged interactions among ionizing graphitic nanoparticles in aqueous dispersion. We tune the hydrophilicity of molecular-brush coated fullerenes, carbon nanotubes, and graphane platelets by gradually replacing a fraction of the methyl end groups of the alkyl coating by the ionizing –COOK or –NH3Cl groups. To assess the change in nanoparticles’ dispersibility in water, we determine the potential-of-mean-force profiles at varied degrees of ionization. When the coating comprises only propyl groups, the attraction between the hydrophobic particles intensifies from spherical to cylindrical to planar geometry. This is explained by the increasing fraction of surface groups that can be brought into contact and the reduced access to water molecules, both following the above sequence. When ionic groups are added, however, the dispersibility increases in the opposite order, with the biggest effect in the planar geometry and the smallest in the spherical geometry. These results highlight the important role of geometry in nanoparticle solubilizationmore » by ionic functionalities, with about twice higher threshold surface charge necessary to stabilize a dispersion of spherical than planar particles. At 25%–50% ionization, the potential of mean force reaches a plateau because of the counterion condensation and saturated brush hydration. Moreover, the increase in the fraction of ionic groups can weaken the repulsion through counterion correlations between adjacent nanoparticles. High degrees of ionization and concomitant ionic screening gradually reduce the differences among surface interactions in distinct geometries until an essentially curvature-independent dispersion environment is created. Insights into tuning nanoparticle interactions can guide the synthesis of a broad class of nonpolar nanoparticles, where solubility is achieved by ionic functionalization.« less

Authors:
 [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, USA
Publication Date:
Research Org.:
Virginia Commonwealth Univ., Richmond, VA (United States); Univ. of California, Oakland, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1540157
Alternate Identifier(s):
OSTI ID: 1426522
Grant/Contract Number:  
SC0004406; AC02-05CH11231; SC 0004406
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 148; Journal Issue: 22; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
Chemistry; Physics

Citation Formats

Jabes, B. Shadrack, Bratko, Dusan, and Luzar, Alenka. Curvature dependence of the effect of ionic functionalization on the attraction among nanoparticles in dispersion. United States: N. p., 2018. Web. doi:10.1063/1.5017525.
Jabes, B. Shadrack, Bratko, Dusan, & Luzar, Alenka. Curvature dependence of the effect of ionic functionalization on the attraction among nanoparticles in dispersion. United States. doi:10.1063/1.5017525.
Jabes, B. Shadrack, Bratko, Dusan, and Luzar, Alenka. Thu . "Curvature dependence of the effect of ionic functionalization on the attraction among nanoparticles in dispersion". United States. doi:10.1063/1.5017525. https://www.osti.gov/servlets/purl/1540157.
@article{osti_1540157,
title = {Curvature dependence of the effect of ionic functionalization on the attraction among nanoparticles in dispersion},
author = {Jabes, B. Shadrack and Bratko, Dusan and Luzar, Alenka},
abstractNote = {Solubilization of nanoparticles facilitates nanomaterial processing and enables new applications. An effective method to improve dispersibility in water is provided by ionic functionalization. We explore how the necessary extent of functionalization depends on the particle geometry. Using molecular dynamics/umbrella sampling simulations, we determine the effect of the solute curvature on solvent-averaged interactions among ionizing graphitic nanoparticles in aqueous dispersion. We tune the hydrophilicity of molecular-brush coated fullerenes, carbon nanotubes, and graphane platelets by gradually replacing a fraction of the methyl end groups of the alkyl coating by the ionizing –COOK or –NH3Cl groups. To assess the change in nanoparticles’ dispersibility in water, we determine the potential-of-mean-force profiles at varied degrees of ionization. When the coating comprises only propyl groups, the attraction between the hydrophobic particles intensifies from spherical to cylindrical to planar geometry. This is explained by the increasing fraction of surface groups that can be brought into contact and the reduced access to water molecules, both following the above sequence. When ionic groups are added, however, the dispersibility increases in the opposite order, with the biggest effect in the planar geometry and the smallest in the spherical geometry. These results highlight the important role of geometry in nanoparticle solubilization by ionic functionalities, with about twice higher threshold surface charge necessary to stabilize a dispersion of spherical than planar particles. At 25%–50% ionization, the potential of mean force reaches a plateau because of the counterion condensation and saturated brush hydration. Moreover, the increase in the fraction of ionic groups can weaken the repulsion through counterion correlations between adjacent nanoparticles. High degrees of ionization and concomitant ionic screening gradually reduce the differences among surface interactions in distinct geometries until an essentially curvature-independent dispersion environment is created. Insights into tuning nanoparticle interactions can guide the synthesis of a broad class of nonpolar nanoparticles, where solubility is achieved by ionic functionalization.},
doi = {10.1063/1.5017525},
journal = {Journal of Chemical Physics},
number = 22,
volume = 148,
place = {United States},
year = {2018},
month = {6}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 1 work
Citation information provided by
Web of Science

Save / Share:

Works referenced in this record:

Van der Waals heterostructures
journal, July 2013

  • Geim, A. K.; Grigorieva, I. V.
  • Nature, Vol. 499, Issue 7459, p. 419-425
  • DOI: 10.1038/nature12385

Formation of monolayers by the coadsorption of thiols on gold: variation in the head group, tail group, and solvent
journal, August 1989

  • Bain, Colin D.; Evall, Joe; Whitesides, George M.
  • Journal of the American Chemical Society, Vol. 111, Issue 18, p. 7155-7164
  • DOI: 10.1021/ja00200a039