Simple one-step synthesis of water and organic media soluble gold nanoparticles with various shapes and sizes

Gold nanoparticles with an average diameter in the range 1–100 nm have been synthesized from hydrogen tetrachloroaureate (III) hydrate (HAuCl4·3H2O) in didodecyldimethyl ammonium bromide (DDAB) aqueous solutions at room temperature. The particle size could be controlled by the concentration of DDAB and HAuCl4·3H2O, and reaction temperature. An increase in DDAB concentration caused a change in the particle shape from spherical to triangular, rectangular or various shapes. Until critical concentration of DDAB, where the size of gold nanoparticles seemed to prevent particle growth from aggregation, and resulted in small particle size and narrow size distribution. And DDAB-coated nanoparticles can be dispersed well in both water and organic solvent with high colloidal stability.