The influence of PEGylated gold nanoparticles on the solidification of alcohols

Abstract

The effects of PEGylated gold nanoparticles (AuNP) colloidally dispersed in ethanol and methanol–ethanol 4 : 1 on solvent solidification induced by hydrostatic pressure are investigated. We have determined the colloid solidification pressure as a function of gold molar concentration in the 0–12 mM range for three nanoparticle sizes. We show that the solvent solidification pressure does not depend on the AuNP size or its specific surface area. It decreases linearly with the total amount of gold up to a 25% reduction of its initial value. Its dependence on the molar concentration of gold in the colloid correlates with the concentration of PEG-SH molecules. On the other hand, Raman spectroscopy shows that the crystalline solid into which AuNP colloids transform under pressure is the same as that into which pure alcohols transform. In addition, the variation of the AuNP plasmonic resonance with pressure allows us to determine the pressure dependence of the density of ethanol in both its liquid and crystalline phases.