Controllable preferential-etching synthesis and photocatalytic activity of porous ZnO nanotubes

Porous ZnO nanotubes have been synthesized via a facile hydrothermal method based on a preferential etching strategy. The nanotubes have a nearly homogeneous size with about 250 nm diameter, 40 nm wall thickness, and 500 nm length. Nanoholes with diameters ranging from tens to hundreds of nanometers were created on the side wall of the tubular structure. Formation of the porous ZnO nanotubes resulted from preferential etching along the c axis and relatively slow etching along the radial directions due to the polar feature of the ZnO crystal. Superior photocatalytic activity of the porous ZnO nanotubes in the degradation of methyl orange compared to the other samples has been demonstrated, and the origin is mainly ascribed to the scattered nanoholes on the wall of the porous nanotubes. The influence factors and formation mechanism of the porous ZnO nanotubes were analyzed and discussed.