Abstract
We report the growth of ultralong ZnO nanowires on silicon (100) substrates via the gold-catalyzed vapor transport approach. An ample supply of zinc vapor generated through carbothermal reduction of ZnO powder at 917°C and a suitable amount of oxygen facilitate the rapid growth of nanowires. These ZnO nanowires are extremely long with lengths of 85-100 μm, and exhibit an overall vertical orientation. The nanowires have largely diameters of 250-400 nm. Crystal structure analysis indicates typical ZnO nano wire growth along the [0001] direction. The band gap of these nanowires was determined to be 3.22 eV. These nanowires show a relatively weak near-band-edge emission peak at 390 nm, and a significant oxygen vacancy-related emission band at 495 nm. Good photocatalytic activity of these nanowires on substrates toward the photodegradation of rhodamine B and 4-chlorophenol was demonstrated. Furthermore, we showed that these nanowires on substrates can serve as effective and convenient recyclable photocatalysts. Only a slight decrease in the photodecomposition rate was observed after 10 cycles of the photocatalysis experiment. The photocatalysts also work well under natural sunlight. © 2007 American Chemical Society.