Nanomaterials confined within the inner space of carbon nanotubes (CNTs) exhibit unusual behavior that differs from that of bulk materials; extensive research has been thus carried out on the encapsulation of various molecules in the inner space of CNTs in order to discover new properties of the nanomaterials. The chemically and mechanically stable pseudo-1D confined nanospace of CNTs can serve as an ideal environment for the template assembly of various nanomaterials. Since the confined nanospace of a CNT prevents molecules from reacting, as it impedes their movement, it can potentially be utilized for stable storage of various reactive materials.
In this work by Keita Kobayashi et al. at the National Institute of Advanced Industrial Science and Technology (Japan), the authors compare the crystal growth of Sn, Pb, Ag, and Au within CNTs, and discuss the impact of the confined nanospace on the growth of molten metal. Molten Sn, Pb, Ag, and Au are encapsulated within the nanotubes by capillary action and the structure of the encapsulated metals is observed by high-resolution transmission electron microscopy. Although dominant crystallization of Ag and Au within the CNTs is observed, Sn and Pb are found to be in a pseudo liquid state at room temperature. Using associated thermodynamic calculations, the authors conclude that nucleation for crystal growth of low-melting-point metals is unable to occur within the confined nanospace of CNTs.