Figure 7.

SEM images of Nb2O5 nanotubes with a smaller diameter (approximately 200 nm). These nanotubes products were obtained with the same etching route. Red circles in Figure 7c and d indicate the hollow section of nanotubes.

Liu et al. Nanoscale Research Letters 2011 6:138   doi:10.1186/1556-276X-6-138
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