Hydration Shell Water Surrounding Citrate-Stabilised Gold Nanoparticles

Presence of gold nanoparticles in an aqueous dispersion perturbs water molecules in their vicinity. Such water molecules form what is known as hydration shell and possess different vibrational attributes than those in the bulk dispersion. Raman spectroscopy was utilised to study these hydration shell water molecules around citrate-stabilised gold nanoparticles. Aqueous dilution series of three sizes of gold nanoparticle samples were prepared. Hydration shell spectral response, recovered by applying multivariate curve resolution technique, were compared against the spectra of the bulk phase. Once correlated with an increasing aqueous content in the respective samples, it could be inferred from the comparison that the hydration shell contains a less extensive hydrogen-bonding network with a smaller number of hydrogen-bonding interactions being possible than that in bulk. The results also suggest the hydrogen-bonding network in the hydration shells to be structurally more rigid and stronger, if compared against the intermolecular hydrogen-bonding prevalent in bulk.