Poly(propylene imine) dendrimer as reducing agent for chloroauric acid to fabricate and stabilize gold nanoparticles

Abstract

Gold nanoparticles (AuNPs) are among the most important metal nanoparticles with unique size-dependent properties, and they have been applied in various fields including as catalysts, biomarkers, and in drug delivery. Various methods have been utilized to synthesize AuNPs, but chemical methods are the most commonly employed for preparing AuNPs from chloroauric acid (HAuCl4) as a precursor. Amine compounds are attractive as reducing agents for use in the synthesis of AuNPs because it is possible to control the growth rate of AuNPs and to tune their optical properties. Among the various amine compounds, dendrimers may be effective reducing agents because of their peripheral primary amine groups. In this study, we used a 5th generation poly(propylene imine) (PPI) dendrimer (G5A) with ethylenediamine (EDA) core as simultaneous reducing and stabilizing agent to synthesize AuNPs produced from HAuCl4. Different amounts of aqueous G5A solution were added to the aqueous gold salt solution and a reduction reaction was performed under mild conditions. The results showed that reducing HAuCl4 with the dendrimer molecules yielded low stable colloidal nanoparticles because the electrostatic repulsion between the AuNPs was affected by the neutral pH of the final medium. In addition, the results confirmed that the dendrimer molecules were deposited on the surfaces of the AuNPs to stabilize the colloidal nanoparticles.