Reaction of molecular oxygen with C<sub>60</sub>: spectroscopic studies

Werner, Harald; Schedel‐Niedrig, Th.; Wohlers, M.; Herein, Daniel; Herzog, Bernd; Schlögl, Robert; Keil, Matthias; Bradshaw, Alexander M.; Kirschner, J.

doi:10.1039/ft9949000403

Cited by 76 publications

(41 citation statements)

References 20 publications

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“…3A). The concentration of oxygen in C 60 exposed to atmospheric conditions drops when heated in vacuum at 400 K, reaching near-pristine levels by 450 K (40). The magnetism at Sc/C 60 interfaces follows this deoxygenation trend, with increased magnetization after 300 400 500 600 700 800 900 1000 0.5 heating to 400-500 K. At higher temperatures, the C 60 is desorbed from the metallic substrate, leading to a reduced magnetization (Fig.…”

Section: Systemmentioning

confidence: 89%

Emergent magnetism at transition-metal–nanocarbon interfaces

Ma’Mari

Rogers

Alghamdi

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Charge transfer at metallo-molecular interfaces may be used to design multifunctional hybrids with an emergent magnetization that may offer an eco-friendly and tunable alternative to conventional magnets and devices. Here, we investigate the origin of the magnetism arising at these interfaces by using different techniques to probe 3d and 5d metal films such as Sc, Mn, Cu, and Pt in contact with fullerenes and rf-sputtered carbon layers. These systems exhibit small anisotropy and coercivity together with a high Curie point. Low-energy muon spin spectroscopy in Cu and Sc-C 60 multilayers show a quick spin depolarization and oscillations attributed to nonuniform local magnetic fields close to the metallo-carbon interface. The hybridization state of the carbon layers plays a crucial role, and we observe an increased magnetization as sp 3 orbitals are annealed into sp 2 −π graphitic states in sputtered carbon/copper multilayers. X-ray magnetic circular dichroism (XMCD) measurements at the carbon K edge of C 60 layers in contact with Sc films show spin polarization in the lowest unoccupied molecular orbital (LUMO) and higher π*-molecular levels, whereas the dichroism in the σ*-resonances is small or nonexistent. These results support the idea of an interaction mediated via charge transfer from the metal and dz-π hybridization. Thin-film carbon-based magnets may allow for the manipulation of spin ordering at metallic surfaces using electrooptical signals, with potential applications in computing, sensors, and other multifunctional magnetic devices. emergent magnetism | molecular spintronics | interfacial magnetism | charge transfer | nanocarbon I nterfaces are critical in quantum physics, and therefore we must explore the potential for designer hybrid materials that profit from promising combinatory effects. In particular, the fine-tuning of spin polarization at metallo-organic interfaces opens a realm of possibilities, from the direct applications in molecular spintronics and thin-film magnetism to biomedical imaging or quantum computing. This interaction at the surface can control the spin polarization in magnetic field sensors, generate magnetization spin-filtering effects in nonmagnetic electrodes, or even give rise to a spontaneous spin ordering in nonmagnetic elements such as diamagnetic copper and paramagnetic manganese (1-11).The impact of carbon-based molecules on adjacent ferromagnets is not limited to spin filtering and electronic transport, but extends to induced changes in the metal anisotropy, magnetization, coercivity, and bias (12-14). Charge transfer and d(metal)-π(carbon) orbital coupling at the interface may change the density of states, spin population, and exchange of metallocarbon interfaces (4,15,16). The interaction between the molecule and the metal depends strongly on the morphology and specific molecular geometry (17, 18). It may lead to a change in the density of states at the Fermi energy DOS(E F ) and/or the exchange-correlation integral (I s ) as described by the Stoner criterion for ferr...

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Section: Systemmentioning

confidence: 89%

Emergent magnetism at transition-metal–nanocarbon interfaces

Ma’Mari

Rogers

Alghamdi

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…The O K-edge NEXAFS data are comparable to the results, published in Refs. [2,7] on a fullerite film, heat-treated in oxygen at 500 K. The C K-edge absorption and emission lines are broadened and relative intensities, corresponding to different molecular orbitals, are to some extent redistributed. The spectra still retain the C 60 spectral profile, which indicates that C 60 cages have not been broken.…”

Section: Discussionmentioning

confidence: 99%

“…4 orders of magnitude) increase in the resistivity of C 60 upon oxygen exposure (intercalation), followed by a slight decrease after a heating cycle in vacuum to 630 K to desorb the oxygen. However, when annealing a C 60 sample, the de-intercalation of the contained oxygen competes with further reaction of oxygen with the fullerite, which ultimately leads to the opening and breaking of the C 60 cages [2,20]. The processes are similar when the sample is exposed to UV-light [3,21,22] instead of heating.…”

Section: Introductionmentioning

confidence: 93%

Study of oxygen-C 60 compound formation by NEXAFS and RIXS

Käämbre

Rubensson

et al. 2001

The European Physical Journal D

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The interaction of oxygen with C60 molecules was studied on a C60 film which had been exposed simultaneously to oxygen and UV-light for 190 hours, producing an approximately C60O1 stoichiometry in the bulk of the sample. C K-edge and O K-edge NEXAFS (using total fluorescence yield detection) and resonant X-ray inelastic scattering (RIXS) spectra from the sample film were measured and the C K-edge data were compared to the spectra from pristine C60 as reference. The C K-edge absorption and emission spectral profiles of the oxygen-doped sample are similar to those of the C60 reference, suggesting that cage breaking of C60 under these conditions, if any, is negligible. However, the redistribution of intensities in the spectra indicates changes in the occupancies of different molecular orbitals, possibly due to changes in electron density upon reaction. Similarities of the O K-edge soft X-ray emission (SXES) spectra to several small oxygen-containing molecules is being discussed in terms of bonding models.PACS. 73.61.Wp Fullerenes and related materials -33.50.Dq Fluorescence and phosphorescence spectra -33.20.Rm X-ray spectra

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“…Fullerenes do not react readily with molecular oxygen in the absence of energetic electromagnetic radiation [7][8][9][10][11][12]. However, their oxides form as byproducts of fullerene synthesis in the carbon-arc process or in oxygen-starved combustion of hydrocarbons.…”

Section: Sources and Purification Of Oxides And Ozonidesmentioning

confidence: 96%