Synthesis and stabilization of gold nanoparticles by inverse reduction method using sodium citrate and sodium boro hydride as reducing agent

In recent decades, observed focus largely on the preparation of nano metallic elements, including the gold because of its unique properties and many applications. In most of these researches, the Turkevich' method has been adopted. This method is based on the reduction of gold ion Au3+ to the nano gold Au0 by the addition of a reducing agent to the gold salt H[AuCl4].3H2O. In this research, a novel simple and cost-effective technique is enhanced via the addition of the gold ion (Au3+) to the decreasing agent in opposite to the previous method. This is the cause to call it "The inverse method". In this inverse method one can control the amount of gold salt solution that add and stop this addition by observing the formation of the red color, which indicates the formation of gold nanoparticles(GNPs).Many reactions were conducted to prepare stable gold nanoparticles by usingchemical reducing agents such as (sodium tri-citrate, sodium borohydride),The reactions to prepare GNPs using these reducing agents were done at temperature of 60 – 80 °C.The resulted GNPs were characterized by UV- Vis spectra, zeta potential, atomic force microscope(AFM), scanning electron microscope(SEM), and transmission electron microscope(TEM).The absorption spectrum of the red GNPs solution appeared at the range of 520-540 nm. The gold nanoparticles which formed from various reactions have different shapes but the most prominent form is the spherical, and the sizes have also been different and appeared at the range of 14.5- 44 nm, which are consistent with published researches.