New nanotubes expand and contract, catching and releasing buckyballs

Ars Technica : A new, nonrigid form of nanotube has been created that could be used as a medicine delivery system. Myongsoo Lee and his colleagues at Seoul National University in South Korea combined benzene and pyridine molecules to form V-shaped structures that, when dissolved in water, formed loose hexagonal rings. The rings spontaneously stacked into tubes, trapping water inside the molecular structure. Heating the tubes caused the water molecules to evaporate, which allowed the V-shaped molecules to fit together more tightly, thereby reducing the cross-sectional area of the tubes by almost 50%. The process could be reversed simply by cooling the tubes, and the entire sequence could be repeated. The researchers also filled the tubes with carbon nanospheres called buckyballs, which were then released and recaptured by the contracting and expanding of the tubes. The ability to release molecules on demand could be a major step in the attempt to deliver medicines directly to their targets.