Preparation of Nanotubes for Longitudinal Observation

Vanadium oxide nanotubes on a carbon foil (grey contrast) with large holes.

To observe the longitudinal structure of nanotubes, they are simply dispersed in ethanol, and some droplets are deposited on a holey carbon foil supported on a metal grid.

Carbon nanotubes — CNTs found in a sample that contains no tubes at all.

Attention: TRAP
If you are looking for nanotubes in a sample that contains none, you nevertheless might find some. The amorphous carbon foil on TEM grids is usually prepared by arc-discharge between graphite electrodes under similar conditions that also generate carbon nanotubes (CNTs). Thus, there are frequently some nanotubes and onions of carbon present on the TEM grids. If there is only a small amount of tubular material present in the sample, one has to check thoroughly if this really is the investigated material. There are some examples in the literature, where CNTs are sold as novel nanotubes of a different material!