Nitrilotriacetic acid: a novel reducing agent for synthesizing colloidal gold.

We report for the first time that nitrilotriacetic acid (NTA) is an effective reductant for the preparation of stable dispersions of uniform gold nanoparticles. The method described is capable of generating stable sols with a metal concentration as high as 1.5×10(-3)moldm(-3). The size of gold nanoparticles can be tuned from 10 to 160 nm by adjusting the stoichiometric excess of NTA. For a constant [Au]/[NTA] ratio the temperature affects the reduction kinetics but has little impact on the size of gold nanoparticles. The mechanisms of the reduction of Au(III) species and the formation and stabilization of gold nanoparticles are discussed.