The preparation of gold nanoparticles in triton N-42 reverse micelles after preliminary concentration from acid sulfate-chloride solutions

The distribution of Au(III) between an acid (3 mol/l HCl) aqueous phase and a micellar Triton N-42 solution in n-decane was studied as a function of the concentration of Na₂SO₄ (0–3.55 mol/l). The high distribution coefficients (200–500) allow 50-fold absolute concentration to be performed at a 90% extraction. Au⁰ nanoparticles were obtained by the injection solubilization of a reducing agent (hydrazine) into micellar extracts. At low solubilization capacities (≤1 vol %) and high reducing agent concentrations (≥0.2 mol/l) in Triton N-42 micelles, stable systems of Au⁰ nanoparticles suitable for the spectrophotometric determination of gold were obtained. At high solubilization capacities and low hydrazine concentrations, reduction was accompanied by coagulation and sedimentation processes. These processes were studied by spectrophotometry and the static and dynamic light scattering methods.