Influence of Gold Content on Colloidal Structure of Gold Nanoparticles Capped with Arabinogalactan

We studied the nanobiocomposites obtained by reduction of gold ions with water-soluble polysaccharide arabinogalactan. The influence of the gold content on the structure of the nanocomposite colloids was investigated. The size of gold nanoparticles (AuNPs) determined by transmission electron microscopy (TEM) was found to increase with the gold content in accord with the Ostwald ripening theory. Simultaneously, the anisotropic self-assembly of AuNPs, observed by TEM and extinction spectroscopy, increased due to the oriented attachment of AuNPs. The AuNP dimers were found to be mainly responsible for both scattered light depolarization and bimodal correlation time distributions determined by dynamic light scattering (MS). Rotational and translational diffusion coefficients obtained by DLS corresponded to the spherical form of the colloids. Comparison of colloidal hydrodynamic radii and the radii of AuNPs showed that the colloidal shell was composed from the monolayer of arabinogalactan macromolecules.