Control of the morphology of gold nanoparticles has received considerable attention because the physical and chemical properties of gold depend significantly on its size and shape. A novel route for obtaining 2-D gold nanostructures has been developed in which chloroaurate ions (AuCl4-) are reduced at the 2-D interface between water and chloroform using an amphiphilic polyoxometallate (SiW12O404-)/surfactant (dimethyldioctadecylammonium; DODA) hybrid photocatalyst under UV irradiation at room temperature in air. This simple method can readily produce large single-crystalline gold nanosheets (lateral size, ca. 20 mu m; thickness, ca. 150 nm).