Gold particle stabilization by Cape aloe active components

Biosynthesis of metallic nanoparticles is reported as a clean, non toxic and environmentally acceptable route, using different plant extracts [1, 2], bacteria, yeast or fungi [3, 4]. These reports mainly describe nanoparticle formation as a consequence of the Au(III) to Au(0) reduction within plant tissues or cells. In this context we have wondered if could exist any specific metal-plant active component adduct during the nanoparticle biosynthesis. For this purpose, we have chosen to use two active components, extracted from the Cape aloe plant, aloin A and aloesin, as stabilizing agents for gold and silver nanoparticles. Varying the reaction conditions (temperature, reaction time and reducing agent) stabile, water soluble particles of different sizes (4-45 nm) and shape (spherical, triangular and hexagonal) have been prepared. In particular the use of citric acid (1 M) as reducing agent led to a mixture of differently shaped aloin A or aloesin coated gold nanoparticles. The mixture consisted of spherical (50 nm) and large triangular or truncated triangular nanoparticles. Prior to characterization, the aloin A and aloesin coated gold particles were purified of excess ligand by dialysis, in the case of small-sized particles (