Smallest ever square nanotube

Very cool nanotech story and image from PhysOrg.

The image:

An electron microscope image of the smallest reported square-cross-section nanotube. Image courtesy Daniel Ugarte.

 

And from the link:

Scientists have observed the smallest reported nanotube that has a square cross-section. The structure formed spontaneously and unexpectedly when silver nanowires were stretched and is a reminder that scientists still have much more to learn about the nanoscale world.

The study was performed by scientists at two Brazilian institutions, the Laboratorio Nacional de Luz Sıncrotron (the Brazilian Synchrotron Light Laboratory) and the Universidade Estadual de Campinas-UNICAMP.

This research illustrates how material behavior at the nanoscale can be vastly and surprisingly different from the macroscopic scale, particularly in the case of applied mechanical stress. In general, the main differences between the behaviors of nanoscale and bulk materials are due to “surface energy.” In the physics of solid materials, surfaces must be less energetic than the rest of the material, lest surfaces be constantly created until the material become nothing but a single surface.

For nanostructures, surface energy is more powerful because there is such a small amount of the material. Scientists expect to see certain atomic behaviors, such as how the atoms order themselves, based on predictions of surface energy. But this work has shown that the addition of a mechanical stress, such as pulling, can produced unexpected results.