Templating rare-earth hybridization via ultrahigh vacuum annealing of ErCl3nanowires inside carbon nanotubes

Abstract

Here we report on controlling the effective hybridization and charge transfer of rare-earth elements inside a carbon nanotube (CNT) nanoreactor. The tubular space inside CNTs can encapsulate one-dimensional (1D) crystals such as ErCl 3 , which we have used as a starting material. Applying a thermochemical reaction in ultrahigh vacuum, we obtain elemental Er nanowires still encapsulated in the CNTs. The hybridization degree and the effective charge changes were directly accessed across the Er 4d and 3d edges by high-energy spectroscopy. It was found that Er is trivalent but the effective valence is reduced for the Er-filled tube, which strongly suggests an increased hybridization between the nanotube π states and the Er 5d orbitals. This was also evidenced by the conduction band response determined in C1s-x-ray absorption spectroscopy (XAS). These results have significant implications for the 1D electronic and magnetic properties of these and similar rare-earth nanowire hybrids.

One-Dimensional Crystals inside Single-Walled Carbon Nanotubes: Growth, Structure and Electronic Properties

“…As a consequence of the increased electron doping of the outer tubes by the encapsulated cerium chains, the Fermi level upshift is observed . Another approach was implemented for rare-earth nanowires within the SWNTs (Ayala et al, 2011). Quantum ErCl 3 nanowires templated inside carbon nanotubes tailored under high temperature and vacuum, were studied within a combined XAS and resonant photoemission approach.…”

Advances in tailoring the electronic properties of single-walled carbon nanotubes

“…Authors of reports [49,256,304] observed the shift, broadening and increase in asymmetry of the C 1s peak of filled SWCNTs, which were assigned to the charge transfer. In case of the SWCNTs filled with halogenides of silver [306], copper [307], iron [310], nickel [312], manganese [313], zinc [314,317] and cadmium [316,317], cobalt bromide [311], terbium chloride [317], thulium chloride [315] and gallium selenide [315,328] the C 1s spectra were separated into several components.…”

“…This tendency was explained by the downshift of the SWCNT Fermi level as result of the charge transfer from the nanotube walls to the incorporated zinc bromide [314]. Acceptor doping effect on the SWCNTs was also proven by the valence band spectra measurements for endohedral fullerene Gd@C 82 [49,256], erbium chloride [304], copper halogenides [307] and fullerene С 60 [240]. Media [314].…”

“…That is why the conclusions about the direction of charge transfer in later reports [306,307,[310][311][312][313][314][315][316][317]328] were no longer exclusively drawn from Raman spectroscopy ( Table 2). The charge transfer from the nanotube walls to the incorporated substances and shift of the SWCNT Fermi level was determined as a result of analysis of the C 1s Xray photoelectron spectra of nanotubes filled with Gd@C 82 molecules [49,256], erbium chloride [304], halogenides of silver [306], cadmium [316,317], copper [307], iron [310], nickel [312], manganese [313], zinc [314,317], cobalt bromide [311], terbium chloride [317], thulium chloride [315] and gallium selenide [315,328], and comparison of the spectra of filled nanotubes with the spectrum of pristine SWCNTs, which is a 98 narrow peak with the maximum at 284.65 eV binding energy and the FWHM of 0.4 eV [79] ( Table 2).…”

Orbital and spin magnetic moments of transforming one-dimensional iron inside metallic and semiconducting carbon nanotubes

“…The magnetization of purified empty SWCNT was measured and found to be much lower than in ErCl 3 nanowires grown into the SWCNT where the magnetization values are the same as the bulk anhydrous ErCl 3 . 12,30 In recent years, metallocene filled and especially ferrocene filled carbon nanotubes (FeCp 2 @SWCNT) have been widely studied both experimentally and theoretically. Their electronic properties can be modified via filling followed by the transformation of the molecules inside into inner tubes and cementite clusters 14,31 utilizing a nanochemical reaction.…”