A facile and efficient approach for pore-opening detection of anodic aluminum oxide membranes

The well aligned porous anodic aluminum oxide (AAO) membrane is fabricated by a two-step anodization method. The oxide barrier layer of AAO membrane must be removed to get through-hole membrane for synthesizing nanowires and nanotubes of metals, semiconductors and conducting polymers. Removal of the barrier layer of oxide and pore-extending is of significant importance for the preparation of AAO membrane with through-hole pore morphology and desired pore diameter. The conventional method for pore opening is that AAO membrane after removing of aluminum substrate is immersed in chemical etching solution, which is completely empirical and results in catastrophic damage for AAO membrane frequently. A very simple and efficient approach based on capillary action for detecting pore opening of AAO membrane is introduced in this paper, this method can achieve the detection for pore opening visually and control the pore diameter precisely to get desired morphology and the pore diameter of AAO membrane. Two kinds of AAO membranes with different pore shape were obtained by different pore opening methods. In addition, one-dimensional gradient gold nanowires are also fabricated by electrodeposition based on AAO membranes.

► We introduce a simple and efficient approach for removal of oxide barrier layer of AAO membranes. ► Pore diameter and morphology of AAO membranes can be precisely controlled by this novel approach. ► Shape of AAO membrane pore prepared by tradition method is truncated cone shaped. ► Pore shape of AAO membrane fabricated by novel method is cylindrical. ► Truncated cone shaped pores of AAO templates can be used to fabricate one-dimensional gradient metal nanowires.