Alumina Membrane with Hour-Glass Shaped Nanochannels: Tunable Ionic Current Rectification Device Modulated by Ions Gradient
Figure 2
The cross-sectional SEM images of (a–e) the Al2O3 nanotube layers with different second-step anodized time, which would be regulated from 7 h, 8 h, 8.5 h, and 9 h to 9.2 h, respectively. The thickness of Al2O3 nanotube layers increased when the anodized time increased, while the thickness of Al substrate decreased. When the anodization time was 9.2 h, the Al substrate was completely anodized. The double-layer alumina nanotubes were fabricated and the boundary between the two nanotube layers became vague after 30 min in situ pore opening process (f). Scale bar is 25 μm.
