Issue 46, 2022

Self-assembly of a CTAB surfactant on gold nanoparticles: a united-atom molecular dynamics study

Abstract

Self-assembly of a cetyltrimethyl ammonium bromide (CTAB) surfactant on gold nanoparticles (AuNPs) is studied using united-atom molecular dynamics (MD) simulations. For AuNPs in the size range of 1–3 nm, CTAB self-assembles such that the tail groups adsorb on the AuNP surface while the ionic head group is exposed to water, giving a net negative charge to the AuNPs. Near the AuNP surface, water molecules are depleted. The fraction of adsorbed CTAB molecules increased with AuNP size, while packing density decreased with size. Binding free energy also increased with AuNP size. The microscopic structural aspects of CTAB on AuNP and water-AuNP correlations are obtained from radial distribution functions. Contrary to the bilayer model proposed in the literature, the present simulations show the formation of a monolayer at CTAB concentrations equivalent to AuNP synthesis conditions. Even immobilizing bromide ions on the AuNP surface did not facilitate bilayer formation. Our simulation studies show that for very small nanoparticles, bilayer formation is unfavorable and instead a single monolayer of CTAB is formed around AuNPs.

Graphical abstract: Self-assembly of a CTAB surfactant on gold nanoparticles: a united-atom molecular dynamics study

Supplementary files

Article information

Article type
Paper
Submitted
15 May 2022
Accepted
23 Oct 2022
First published
01 Nov 2022

Phys. Chem. Chem. Phys., 2022,24, 28353-28361

Self-assembly of a CTAB surfactant on gold nanoparticles: a united-atom molecular dynamics study

P. Kalipillai, E. Raghuram, S. Bandyopadhyay and E. Mani, Phys. Chem. Chem. Phys., 2022, 24, 28353 DOI: 10.1039/D2CP02202H

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