Free-standing TiO2 nanotube arrays made by anodic oxidation and ultrasonic splitting

A facile and green method was employed to prepare large-scale free-standing TiO2 nanotube (TNT) arrays, in which as-anodized TiO2 nanotube films prepared in organic electrolytes with thickness ranging from seven to tens of micrometers were then ultrasonicated in a mix solution of ethanol and water. By controlling the ratio of ethanol to water, the time and the power of ultrasonication, large-scale free-standing TiO2 nanotube arrays without any crack could be detached from the Ti substrates. Hydrogen sensing results demonstrated that the free-standing TNT film is more sensitive than a film with Ti substrates when exposed to 1000 ppm hydrogen ambient.