抄録
We review our recent progress on the fabrication of artificial one-dimensional (1D) conductors using the carbon nanotube-template method. We demonstrate that carbon nanotubes (CNTs) have the ability to stabilize previously-unobserved 1D crystals of chalcogen elements inside their quasi-1D channels. Most importantly, we found by experiment and theory that 1D sulfur crystals, which consist of monatomic zigzag or linear conformations, exhibit a metallic character inside CNTs. Despite the fact that both sulfur and selenium show similar molecular structures in the bulk phase, selenium forms double-helices inside double-wall CNTs. Our theoretical calculations predict that selenium double-helices have a very small bandgap energy, compared to that of the bulk selenium chain. We foresee a new branch of fundamental metal-insulator transitions caused by the nanospace, thus paving the way toward future applications of non-metallic sulfur and/or selenium as a conducting nanowire.
