Precision synthesis of a one-dimensional single chain polymorph of Sb2Te3 within single-walled carbon nanotubes

The discovery and synthesis of atomically precise low-dimensional inorganic solids has led to numerous unusual structural motifs and nascent physical properties. However, access to low-dimensional van der Waals (vdW)-bound analogues of bulk crystals is often limited by chemical considerations arising from structural factors like atomic radii, bonding or coordination, and electronegativity. Using single-walled carbon nanotubes (SWCNTs) as confinement templates, we demonstrate the synthesis of a new 0.67 eV gap quasi-one-dimensional (q-1D) chain polymorph of Sb2Te3 ([Sb4Te6]n) that is structurally and electronically distinct from its 2D counterpart. We found that the q-1D chain polymorph has both three- and five-coordinate Sb atoms covalently bonded to Te and is thermodynamically stabilized by the electrostatic interaction between the encapsulated chain and the model SWCNT. These complementary results demonstrate the synthetic advantage of vdW nanotube confinement in the discovery of low-dimensional polytypes with drastically altered physical properties and potential applications in energy conversion processes.