Fabrication and characterization of TiO₂nanotube arrays having nanopores in their walls by double-template-assisted sol–gel

We present herein a simple method named the double-template-assisted sol–gel method for preparing TiO2 nanotube arrays with nanopores on their walls. Poly(ethylene glycol) dissolved in TiO2 sol was used as a soft template to form nanopores on the walls of TiO2 nanotube arrays, which were templated from ZnO nanorod hard templates by a dip-coating technique. The microstructure of nanoporous TiO2 nanotube arrays can change from end-opened to end-closed by increasing the dip-coating cycle number. In addition, the essential parameters of nanoporous TiO2 nanotube arrays are determined by the growth conditions of ZnO nanorod templates. This paper gives a simple and universal way to produce nanopores on the walls of TiO2 nanotube arrays to increase the specific surface area.