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Issue 9, 2014
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Interaction between functionalized gold nanoparticles in physiological saline

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Abstract

The interactions between functionalized noble-metal particles in an aqueous solution are central to applications relying on controlled equilibrium association. Herein, we obtain the potentials of mean force (PMF) for pair-interactions between functionalized gold nanoparticles (AuNPs) in physiological saline. These results are based upon >1000 ns experiments in silico of all-atom model systems under equilibrium and non-equilibrium conditions. Four types of functionalization are built by coating each globular Au144 cluster with 60 thiolate groups: GS–AuNP (glutathionate), PhS–AuNP (thiophenol), CyS–AuNP (cysteinyl), and p-APhS–AuNP (para-amino-thiophenol), which are, respectively, negatively charged, hydrophobic (neutral-nonpolar), hydrophilic (neutral-polar), and positively charged at neutral pH. The results confirm the behavior expected of neutral (hydrophilic or hydrophobic) particles in a dilute aqueous environment, however the PMF curves demonstrate that the charged AuNPs interact with one another in a unique way—mediated by H2O molecules and an electrolyte (Na+, Cl)—in a physiological environment. In the case of two GS–AuNPs, the excess, neutralizing Na+ ions form a mobile (or ‘dynamic’) cloud of enhanced concentration between the like-charged GS–AuNPs, inducing a moderate attraction (∼25 kT) between them. Furthermore, to a lesser degree, for a pair of p-APhS–AuNPs, the excess, neutralizing Cl ions (less mobile than Na+) also form a cloud of higher concentration between the two like-charged p-APhS–AuNPs, inducing weaker yet significant attractions (∼12 kT). On combining one GS– with one p-APhS–AuNP, the direct, attractive Coulombic force is completely screened out while the solvation effects give rise to moderate repulsion between the two unlike-charged AuNPs.

Graphical abstract: Interaction between functionalized gold nanoparticles in physiological saline

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Publication details

The article was received on 24 Oct 2013, accepted on 25 Nov 2013 and first published on 26 Nov 2013


Article type: Communication
DOI: 10.1039/C3CP54503B
Citation: Phys. Chem. Chem. Phys., 2014,16, 3909-3913
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    Interaction between functionalized gold nanoparticles in physiological saline

    S. A. Alsharif, L. Y. Chen, A. Tlahuice-Flores, R. L. Whetten and M. J. Yacaman, Phys. Chem. Chem. Phys., 2014, 16, 3909
    DOI: 10.1039/C3CP54503B

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