| 1. |
- Briones-Leon, Antonio, et al.
(author)
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Orbital and spin magnetic moments of ferrocene encapsulated in metallicity sorted single-walled carbon nanotubes
- 2012
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In: Physica status solidi. B, Basic research. - : Wiley-VCH Verlag Berlin. - 0370-1972 .- 1521-3951. ; 249:12, s. 2424-2427
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Journal article (peer-reviewed)abstract
- The nature of the electronic and local magnetic properties of ferrocene (FeCp2) filled single-walled carbon nanotubes (SWCNT) has been investigated by X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD). Metallic, semiconducting, and unsorted ferrocene-filled tubes have been studied in different conditions of temperature and magnetic field. XMCD signal becomes evident with the application of a magnetic field at low temperature. We find that the molecular states of ferrocene interact with SWCNT of different metallicities. A paramagnetic behavior of encapsulated ferrocene is observed from the magnetic field dependent XMCD measurements which is consistent with theoretical predictions.
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| 2. |
- Briones-Leon, Antonio, et al.
(author)
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Orbital and spin magnetic moments of transforming one-dimensional iron inside metallic and semiconducting carbon nanotubes
- 2013
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In: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 87:19
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Journal article (peer-reviewed)abstract
- The orbital and spin magnetic properties of iron inside metallic and semiconducting carbon nanotubes are studied by means of local x-ray magnetic circular dichroism (XMCD) and bulk superconducting quantum interference device (SQUID). The iron-nanotube hybrids are initially ferrocene filled single-walled carbon nanotubes (SWCNT) of different metallicities. We show that the ferrocene's molecular orbitals interact differently with the SWCNT of different metallicities with no significant XMCD response. At elevated temperatures the ferrocene molecules react with each other to form cementite nanoclusters. The XMCD at various magnetic fields reveal that the orbital and/or spin magnetic moments of the encapsulated iron are altered drastically as the transformation to the 1D clusters takes place. The orbital and spin magnetic moments are both found to be larger in filled semiconducting nanotubes than in the metallic sample. This could mean that the magnetic polarization of the encapsulated material depends on the metallicity of the tubes. From a comparison between the iron 3d magnetic moments and the bulk magnetism measured by SQUID, we conclude that the delocalized magnetisms dominate the magnetic properties of these 1D hybrid nanostructures.
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| 3. |
- Kharlamova, Marianna V., et al.
(author)
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Inner tube growth properties and electronic structure of ferrocene-filled large diameter single-walled carbon nanotubes
- 2013
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In: Physica status solidi. B, Basic research. - : Wiley-VCH Verlag. - 0370-1972 .- 1521-3951. ; 250:12, s. 2575-2580
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Journal article (peer-reviewed)abstract
- We study the filling of single-walled carbon nanotubes (SW- CNTs) with ferrocene molecules. Using e-DIPS SWCNTs with a mean diameter of 1.7nm, we obtain a filling factor as high as 90%. At elevated temperatures in high vacuum the filled SWCNTs are transformed to double-walled carbon nanotubes (DWCNTs). Temperature dependence of inner tube growth is investigated by Raman spectroscopy. The electronic properties of the obtained nanostructures are studied by X-ray photoelectron spectroscopy and near edge X-ray absorption fine structure spectroscopy. It is found that the growth temperature is higher for larger diameter inner tubes. It is demonstrated that ferrocene filling leads to electron doping of SWCNTs.
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| 4. |
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| 5. |
- Rohringer, Philip, et al.
(author)
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Purification, separation and extraction of inner tubes from double-walled carbon nanotubes by tailoring density gradient ultracentrifugation using optical probes
- 2014
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In: Carbon. - : Elsevier. - 0008-6223 .- 1873-3891. ; 74, s. 282-290
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Journal article (peer-reviewed)abstract
- We studied the effect of varying sonication and centrifugation parameters on double-walled carbon nanotubes (DWCNT) by measuring optical absorption and photoluminescence (PL) of the samples. We found that by using a low sonication intensity before applying density gradient ultracentrifugation (DGU), only inner tube species with a diameter less than= 0.8 nm can be identified in absorption measurements. This is in stark contrast to the result after sonicating at higher intensities, where also bigger inner tubes can be found. Furthermore, by comparing PL properties of samples centrifugated either with or without a gradient medium, we found that applying DGU greatly enhances the PL intensity, whereas centrifugation at even higher speeds but without a gradient medium results in lower intensities. This can be explained by extraction of inner tubes from their host outer tubes in a two-stage process: the different shearing forces from the sonication treatments result in some DWCNT to be opened, whereas others stay uncut. A subsequent application of DGU leads to the extraction of the inner tubes or not if the host nanotube stayed uncut or no gradient medium was used. This work shows a pathway to avoid this phenomenon to unravel the intrinsic PL from inner tubes of DWCNT.
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| 6. |
- Sauer, Markus, et al.
(author)
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Tailoring the electronic properties of single-walled carbon nanotubes via filling with nickel acetylacetonate
- 2015
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In: Physica Status Solidi. B: Basic Research. - : Wiley. - 0370-1972. ; 252:11, s. 2546-2550
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Journal article (peer-reviewed)abstract
- Although chemical functionalization of single-walled carbon nanotubes was extensively studied, in many cases detailed information about the influence of the nanotube metallicity and diameter is missing. Here, we present an X-ray photoemission and absorption spectroscopy study of endohedrally functionalized carbon nanotubes with different diameters, where Ni(II) acetylacetonate molecules are reacted to tailor the nanotubes' electronic properties. The filling factor is found to be dependent on the SWCNT base material used. We trace the reaction process of the filling material at several annealing steps and reveal their dependence on annealing temperature, which allows doping of nanotubes to be controlled. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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