Formation and Stability of Gold Nanoflowers by the Seeding Approach: The Effect of Intraparticle Ripening

The seeding approach for preparation of gold nanoflowers in which 25 nm gold nanoparticles were used as the seeds and a mixture of HAuCl4 and hydroxylamine as growth solution was investigated systematically. It is revealed that the formation and stability of the nanoflowers were affected greatly by the intraparticle ripening induced by the chlorine ions that existed in the reaction system. In this seeding approach, hydroxylamine promoted the rapid reduction of HAuCl4 and thus rapid formation of small Au particles with a diameter around 3 nm in the growth solution. The attachment of the small particles on the seed surface contributed to the growth of the nanoflowers. The branch length of the nanoflowers increased with the increased pH of the growth solution due to the suppressed ripening at higher pH. The stability of the nanoflowers can be improved by increasing the pH of the storing solution and/or removal of the chlorine ions.