Structures of Se chains encapsulated in single-walled carbon nanotubes

In this study, the structures of two Se chains confined inside single-walled carbon nanotubes (SWCNTs), which were denoted as Se@SWCNT, were investigated by extended X-ray absorption fine structure analysis and transmission electron microscopy. The Se chains were linear and parallel to each other in the SWCNTs. The covalent bond length of Se@SWCNT was shorter than that of trigonal Se (t-Se), whereas the force constant was larger, thereby suggesting that the covalent bond was stronger for Se@SWCNT than that for t-Se. The interchain interaction originated from the overlap of lone-pair and antibonding orbitals on adjacent chains, so the disappearance of the overlap in the encapsulated Se chains strengthened the covalent bonds.