Spherulitic Growth of Gold Particles Precipitated from Aqueous Solution

Spherical gold particles were formed by reduction of auric acid with ascorbic acid in both spontaneous precipitation and seeded experiments. Micron-sized gold polycrystalline sea urchin-like particles were generated at lower pH conditions with and without a polymeric stabilizer. The fact that growth was depending on the surface area of the seeds and at the same time was not significantly affected by stabilizing polymers illustrates that the underlying particle enlargement mechanism is crystal growth and not an assembly of already nucleated nano-crystals by aggregation as usually claimed in the literature. When the seed surface area was reduced, nucleation of new gold nanoparticles was observed, and these particles did not show any tendency to aggregate. Based on this understanding it was demonstrated how the morphology of the micron-sized particles can be controlled.