Research Article

Alumina Membrane with Hour-Glass Shaped Nanochannels: Tunable Ionic Current Rectification Device Modulated by Ions Gradient

Figure 3

SEM images from the top opening side, bottom opening side, and the cross-sectional viewing of (a–c) the double-layer Al2O3 nanotubes and (d–f) hour-glass shaped alumina nanochannels, respectively. Both the nanotube and the nanochannel have the pore diameters at top and bottom opening sides about 45 nm. At the center of the nanotube membrane, two barrier layers closely contact and the ion transportation would be blocked. With the in situ barrier layer etching for about 30 min, hour-glass shaped nanochannel was fabricated, which has a small pore at the central region of channel with the diameter of about 15 nm. Scale bar is 200 nm.
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