Gold nanostructures-nanowires and nanosheets-are reported to have been prepared from the gold salt HAuCl4 in a solid bulk phase of a block copolymer. The Figure shows a SEM image of nanosheets formed by thermal reduction at 70 degreesC. If water is included in the initial mixture and the reduction occurs by UV irradiation, predominantly nanowires are produced. Reasons for this distinction are.