Metallicity-sorted single-walled carbon nanotubes for water treatment

Single-walled carbon nanotubes (SWCNTs) include metallic and semiconducting conductivity types, which depends on their chirality. Metallicity-sorted SWCNTs are promising for water treatment. The aim of this work was the preparation of metallicity-sorted SWCNTs and the investigation of their electronic properties. The preparation procedure of the metallicity-sorted SWCNTs included density gradient ultracentrifugation of the arc-discharge SWCNTs, with a diameter of 1.4 nm. We analyzed the sorted samples by optical absorption spectroscopy and revealed that the sorted fractions of the metallic and semiconducting SWCNTs had high purity. In the metallic fraction, no absorption bands of the semiconducting SWCNTs were observed. In the semiconducting fraction, no traces of the metallic SWCNTs were revealed. The sorted SWCNT fractions were characterized by Raman spectroscopy with laser wavelengths of 458-568 nm (for the semiconducting SWCNTs) and 633 and 647 nm (for the metallic SWCNTs). The high purity of the sorted SWCNTs was proven. The sorted SWCNTs were studied by X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. The C 1s peaks of the metallic and semiconducting SWCNTs had different positions and exhibited asymmetry. The peaks of van Hove singularities were revealed in the valence band spectra of the sorted SWCNTs. The obtained data on the electronic properties of the metallicity-sorted SWCNTs are required for water treatment applications.