Synthesis of Gold Nanoparticles Using Au(OH)₃ as a Precursor in Aqueous Media

With the advance of nanotechnology, gold nanoparticles (AuNPs) with interesting optical and chemical properties are attracting attention. The reduction reaction of soluble Au precursors such as chloroauric acid (HAuCl₄ ) in an aqueous solution is widely used as the synthetic route of AuNPs. However, coexisting ionic species, especially Cl−, can negatively affect the application of AuNPs, so an additional removal process is necessary. Herein, we report the synthesis of AuNPs using almost insoluble gold hydroxide (Au(OH)₃ ) as the Au precursor in aqueous media. AuNPs were successfully synthesized under mild conditions (pH ～7, 60℃ and 80℃) in the presence of a non-toxic triblock copolymer acting as a reducing and stabilizing agent. The sizes of the AuNPs were 39.3±11.7 nm and 51.0±12.9 nm at 60℃ and 80℃, respectively. The resulting colloidal dispersions of the AuNPs obtained under neutral conditions and without the influence of coexisting the ionic species are expected to apply to catalytic and biological applications where surface activity plays an important role.