Controlled fabrication of hierarchically branched nanopores, nanotubes, and nanowires

PNAS Meng et al. 10.1073/pnas.0502098102.

Supporting Information

Files in this Data Supplement:

Supporting Table 1
Supporting Figure 5
Supporting Figure 6
Supporting Figure 7
Supporting Figure 8

Supporting Figure 5

Fig. 5. SEM images show complex hierarchically branched nanotube architectures of 1

3
2 structure. At each of the junctions (locations of white arrows), the stems split into three and two branches, respectively. High-magnification images at Right show the close-up of the corresponding two 1
3
2 structures. Junctions are highlighted with white line contours for clarity. (Scale bars: 100 nm for Right.)

Supporting Figure 6

Fig. 6. SEM images from complex 1

2
4 nanotube architectures. Arrays of nanotubes show two generations of branching (indicated with the white arrows). At each of the junctions, stems split into two and four nanotube branches, respectively (seen at higher magnification in Right), giving the 1
2
4 structures. Junctions are highlighted by white line contours for clarity. (Right, scale bars: 100 nm.)

Supporting Figure 7

Fig. 7. SEM images showing hierarchically branched Ni nanowire arrays fabricated inside of complex nanochannels in AAO using electrodeposition, as described in Methods. Shown are 1

2
2 (A) and 1
4 (B); junctions are highlighted with white line contours for clarity. (Scale bars: 200 nm.)

Supporting Figure 8

Fig. 8. TransmissionEM images showing different junctions in hierarchically branched nanotubes that have been fabricated inside complex nanochannels of AAO templates. (A and B) Ys having different diameters. (C) One tube branching into three tubes. (D) One tube gradually (not abruptly) changing into eight branches (some rough morphology is seen on the tube walls due to roughness in the pores resulting from instabilities in anodizing current). (E) One tube becoming two and each of those two becoming four. (F) An array of larger tubes turning into multiple small branches (>10). The junctions formed by these various tubes and branches are clearly seen in the micrographs. (All scale bars: 100 nm.)

Table 1. Diameter ratios of the nanotube architectures fabricated (final branches to main stem)

Architectures	Measured from SEM*	Calculated from anodizing voltage
1 2	48.3/66.2 = 0.73	0.70
1 2 2	36.4/66.2 = 0.55	0.49
1 2 2 2	23.4/66.2 = 0.35	0.34
1 2 2 2 2	16.6/66.2 = 0.25	0.24
1 4	41.7/83.3 = 0.50	0.50
1 8^†	31.2/120 = 0.26	0.35
1 16^†	28.0/130 = 0.22	0.25
1 3 3^†	33.0/150 = 0.22	0.33
1 4 4	15.0/60 = 0.25	0.24
1 2 3^†	27.8/69.4 = 0.40	0.42
1 2 4^†	30.0/83.3 = 0.36	0.34
1 3 2^†	40.9/95 = 0.43	0.40
1 2 6^†	30.8/102.6 = 0.30	0.30