Water-dispersible and magnetically separable gold nanoparticles supported on a magnetite/s-graphene nanocomposite and their catalytic application in the Ullmann coupling of aryl iodides in aqueous media

Water-dispersible sulfonated graphene (s-G) was synthesized by anchoring sulfonic acid groups on graphene sheets. Subsequently, magnetically separable Fe3O4/s-G was synthesized from the Fe3O4 nanoparticles decorated on s-G sheets by the co-precipitation method of iron ions. Finally, Fe3O4/s-G was successfully decorated with gold nanoparticles in a facile route by reducing chloroauric acid in the presence of sodium dodecyl sulfate, which is used as both a surfactant and reducing agent. The obtained Au/Fe3O4/s-G nanocomposite remained soluble in water, but could be easily separated from reaction solutions by an external magnetic field and then used as a heterogeneous catalyst for the Ullmann coupling reaction in water. The catalytic activity reduction was not significant even after five consecutive reaction runs due to the efficient magnetic separation, the high dispersion and stability of the catalyst in aqueous solution.