Light-Induced Sulfur Transport inside Single-Walled Carbon Nanotubes

Abstract

Filling of single-walled carbon nanotubes (SWCNTs) and extraction of the encapsulated species from their cavities are perspective treatments for tuning the functional properties of SWCNT-based materials. Here, we have investigated sulfur-modified SWCNTs synthesized by the ampoule method. The morphology and chemical states of carbon and sulfur were analyzed by transmission electron microscopy, Raman scattering, thermogravimetric analysis, X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopies. Successful encapsulation of sulfur inside SWCNTs cavities was demonstrated. The peculiarities of interactions of SWCNTs with encapsulated and external sulfur species were analyzed in details. In particular, the donor–acceptor interaction between encapsulated sulfur and host SWCNT is experimentally demonstrated. The sulfur-filled SWCNTs were continuously irradiated in situ with polychromatic photon beam of high intensity. Comparison of X-ray spectra of the samples before and after the treatment revealed sulfur transport from the interior to the surface of SWCNTs bundles, in particular extraction of sulfur from the SWCNT cavity. These results show that the moderate heating of filled nanotubes could be used to de-encapsulate the guest species tuning the local composition, and hence, the functional properties of SWCNT-based materials.

Laser Patterning of Aligned Carbon Nanotubes Arrays: Morphology, Surface Structure, and Interaction with Terahertz Radiation

“…The emergence of iron occurs due to the transport of encapsulated catalyst nanoparticles from the cavities of nanotubes under high-energy exposure. A similar effect was previously obtained for plasma-treated MWCNTs [45], single-walled CNTs filled with sulfur [46], and MWCNTs under femtosecond laser radiation [18]. The XPS C1s spectra are also governed by sp 2 -hybridized carbons (peak C1) with the FWHM of ca.…”

Magnetic Properties of 1D Iron–Sulfur Compounds Formed Inside Single‐Walled Carbon Nanotubes

“…The Fe content in the pristine SWCNTs was estimated to be below 0.3 wt% by AAS. [ 21 ] Filling of nanotubes with sulfur was carried out using two approaches: 1) ampoule method described elsewhere [ 39 ] , which we refer to as HT method, and 2) hot pressing, [ 59–62 ] which we refer to as HTHP method. In brief, in the first approach, mixture of SWCNTs and sulfur with a ratio of 1:4 was heated in a sealed quartz ampoule at 750 °C for 1 h and 600 °C for 14 h. Hot pressing approach was carried out using a split‐sphere multi‐anvil apparatus.…”

“…These nanotubes were continuously heated with sulfur in a sealed ampoule (HT method) followed by the toluene treatment to remove sulfur from the outside of the nanotubes, whereas the sulfur located inside the nanotubes remained intact. [ 39 ] Energy dispersive X‐ray (EDX) spectroscopy revealed ≈12.7 wt% of sulfur, and the content of iron estimated by AAS was about 0.3 wt%. Due to a quite low iron concentration, its visualization using microscopy methods is a rather challenging task.…”

“…The homogeneous filling of nanotubes with sulfur by the ampoule method was also previously demonstrated. [ 39 ] Both TEM and Raman spectra have shown that SWCNTs filled with sulfur keep their integrity (Figure 1a,b); no metallic particles can be seen. However, when sulfur is filling the SWCNTs containing encapsulated residual iron catalyst, iron sulfides are also expected to be formed [ 39 ] as confirmed by an X‐ray diffraction (XRD) analysis (Figure 1c).…”

“…[ 39 ] Both TEM and Raman spectra have shown that SWCNTs filled with sulfur keep their integrity (Figure 1a,b); no metallic particles can be seen. However, when sulfur is filling the SWCNTs containing encapsulated residual iron catalyst, iron sulfides are also expected to be formed [ 39 ] as confirmed by an X‐ray diffraction (XRD) analysis (Figure 1c). One can see the pattern of pyrite FeS 2 , which is one of the most probable compounds to be formed according to the iron–sulfur phase diagram.…”