Molecular simulation of interaction between passivated gold nanoparticles in supercritical CO2

Abstract

Molecular dynamics simulations have been performed to study the potential of mean force (PMF) between passivated gold nanoparticles (NPs) in supercritical CO(2) (scCO(2)). The nanoparticle model consists of a 140 atom gold nanocore and a surface self-assembled monolayer, in which two kinds of fluorinated alkanethiols were considered. The molecular origin of the thermodynamics interaction and the solvation effect has been comprehensively studied. The simulation results demonstrate that increasing the solvent density and ligand length can enhance the repulsive feature of the free energy between the passivated Au nanoparticles in scCO(2), which is in good agreement with previous experimental results. The interaction forces between the two passivated NPs have been decomposed to reveal various contributions to the free energy. It was revealed that the interaction between capping ligands and the interaction between the capping ligands and scCO(2) solvent molecules cooperatively determine the total PMF. A thermodynamic entropy-energy analysis for each PMF contribution was used to explain the density dependence of PMF in scCO(2) fluid. Our simulation study is expected to provide a novel microscopic understanding of the effect of scCO(2) solvent on the interaction between passivated Au nanoparticles, which is helpful to the dispersion and preparation of functional metal nanoparticles in supercritical fluids.

Gold nanoparticles protected by fluorinated ligands: Syntheses, properties and applications

“…Theoretical investigations confirmed these data and revealed that increasing the length of the fluorous ligands could provide a strategy to devise more easily dispersible systems in Sc CO 2 [20]. Supercritical CO 2 also proved to be a good solvent for fluorous nanoparticles synthesis by using suitable organometallic precursors and hydrogen as reducing agent [21,22].…”

Modeling Solvation in Supercritical CO2

“…[73,74] The organization of the solvent around the solute and its influence on the solution structural and dynamic properties were investigated by means of MD for small solutes, [75][76][77][78][79][80][81][82][83][84] polymers [85,86] and proteins, [87] and passivated gold nanoparticles. [88] Some work based on Car-Parrinello MD was also performed. [89] Among the physicalp roperties of the solvated system,t he calculation of solubilities and the free energieso fs olvation is particularly important for the CO 2 medium, for which an enhancement of the solvation power represents ar eal challenge.…”

Molecular dynamics simulations on the effect of size and shape on the interactions between negative Au18(SR)14, Au102(SR)44 and Au144(SR)60 nanoparticles in physiological saline

“…[1, 2, 3, 4] Experimental studies performed on large NPs (100 nm) have shown that aspherical shapes require a smaller salt concentration to aggregate, due to the larger contact areas between them;[5, 6] while smaller sizes require larger salt concentrations to aggregate, due to the weaker van der Waals forces of attraction. [7, 8] Such small-sized NPs have presented novel challenges to traditional colloid science theories such as Derjaguin-Landau-Verwey-Overbeak (DLVO).…”