Synthesis of positively charged gold nanoparticles using a stainless-steel mesh

A novel, rapid, one-pot, and facile approach was developed to synthesize positively charged gold nanoparticles [(+) AuNPs] by employing an aqueous solution of HAuCl₄ ·3H₂O as a precursor at 30 °C and a stainless-steel mesh as a reducing agent. The penetration of Cl^- ions into the stainlesssteel surface results in corrosion on the stainless-steel surface and excretion of electrons which are used for reduction of Au³⁺ → Au⁰. As a result, (+) AuNPs 5-20 nm in size, mostly monodispersed, were synthesized within 3 h. The as-synthesized AuNPs were charaterized by UV-vis, DLS, XRD, TEM, HR-TEM, EDX and SAED. The utilization of non-toxic chemicals and easily available materials, and the non-requirement of energy input, make this methodology easy, inexpensive, and efficient. The new findings about the role of the stainless-steel mesh, which provides electrons in the presence of Cl^- ions, for the reduction of Au³⁺ → Au⁰, makes it a novel material for (+) AuNPs synthesis.