Progress in carbon nanotubes filled with foreign substances

The nano-sized quasi-one-dimensional hollow cores of carbon nanotubes make it possible for them to be filled with foreign substances. The physical and chemical properties of the filled carbon nanotubes are closely related to the type., the structure and the composition of the filling materials. Therefore, it is expected that various types of filled-carbon nanotubes can be designed and assembled to meet the application demand. This article reviews the current status of research in this area. Various chemical and physical methods and the possible mechanisms of filling the carbon nanotubes with foreign substances as well as that of encapsulating foreign substances during the preparation process are presented. The promising applications of nanotubes filled with foreign substances in the fields of electronics, information technology, biochemistry and medicine etc., are introduced. Furthermore, some necessary studies in the future, such as the mechanism of the interaction of the carbon nanotubes and the filling substances, the physical properties of the quantum lines and the preparation technique of aligned and filled carbon nanotubes are proposed.