Electronic Structure of Polymerized C<sub>60</sub> Phases

Schulte, Joachim; Böhm, Michael; Schedel‐Niedrig, Th.; Schlögl, Robert

doi:10.1002/bbpc.199700017

Cited by 5 publications

(2 citation statements)

References 51 publications

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“…They suggest that the final product is amorphous carbon with a graphite-like local structure. Theoretical investigations of different polymeric phases of C 60 [23] in- dicate that the relatively strong changes in the valence-band of our C 60 polymer are mainly due to the polymerization to higher polymers. An additional contribution to the broadening may be oxidation.…”

Section: Resultsmentioning

confidence: 98%

X-ray photoelectron spectroscopy and near-edge X-ray-absorption fine structure of C 60 polymer films

Ramm¹,

Ata²,

Groß

et al. 2000

Applied Physics A: Materials Science & Processing

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We report core-level and valence-band X-ray photoelectron spectroscopy (XPS) and carbon K near-edge X-ray-absorption fine structure spectroscopy (NEXAFS) results of plasma-polymerized C 60 . In comparison with evaporated C 60 the C 1s peak is broader and asymmetric for the C 60 polymer and its shake-up satellites diminished. Furthermore, the features of the valence-band as well as the features of the π * antibonding orbitals of the C 60 polymer are broader and reduced in intensity. Changes in the electronic structure are attributed to the polymerization of C 60 , the post-plasma functionalization of the surface by oxygen after exposure to atmosphere, and the occurrence of amorphous carbon. PACS: 73.61.Wp; 68.35.-p; 82.35.+t The fullerene C 60 can be polymerized by different routes including: photo-polymerization [1], hydrostatic pressure [2], charge transfer from alkali-metal dopants to the C 60 molecules [3], plasma [4], and electrochemical process [5].A [2 + 2] cycloaddition via electronically excited triplet states is considered to be the most likely pathway of the polymerization in the photopolymer [1] and subsequent highpressure-high-temperature-(HPHT) induced polymer [6]. The [2 + 2] cycloaddition reaction results in the formation of a cyclobutane ring requiring a sp 2 − sp 3 rehybridization at the 6 − 6 double bonds of C 60 , which form the intermolecular C−C bonds. The formation of the intermolecular bonds leads to a reduced molecular symmetry.In this study, C 60 was polymerized using the plasma deposition technique. The application of radio-frequency (rf) plasma has increased greatly in materials and device processing. However, the physics of the rf plasma and the chemical mechanisms of deposition are not understood in whole, which makes a controlled deposition difficult.Very little is known explicitly about the structure of plasma-polymerized C 60 . In the plasma, various interactions between the vaporized fullerenes and the plasma particles (energetic neutrals, ions, electrons) and photons as well as the already-deposited material occur. The effects of these interactions are dependent on the geometry and the process parameters. Besides the polymerization reaction, undesirable processes such as fullerene fragmentation, substrate heating, re-emission and sputtering of the deposited material, and process gas incorporation have to be considered.Various experimental techniques have been used to characterize the structure of fullerene polymers. In particular, Raman spectroscopy has been widely used [7]. Near-edge X-ray-absorption fine structure spectroscopy (NEXAFS) has proven to be especially useful in examining the electronic structure of carbon materials because it gives a deep insight into the π * and σ * antibonding orbitals and distinguishes between sp 2 and sp 3 bonding with similar sensitivity [8,9].We performed core-level and valence-band X-ray photoelectron spectroscopy (XPS) and C K near-edge X-rayabsorption fine structure spectroscopy to investigate the polymerization and to characterize the chan...

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Section: Resultsmentioning

confidence: 98%

X-ray photoelectron spectroscopy and near-edge X-ray-absorption fine structure of C 60 polymer films

Ramm¹,

Ata²,

Groß

et al. 2000

Applied Physics A: Materials Science & Processing

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“…A C K-edge NEXAFS study was also performed on polymerized C 60 molecules . In a similar, building blocks approach, the main resonances of pristine C 60 are also observed in a cross-linked 2D structure of C 60 molecules, including both the π* (284−290 eV) and σ* (292−303 eV) structure .…”

Section: Introductionmentioning

confidence: 99%

Oxygen-Containing Functional Groups on Single-Wall Carbon Nanotubes: NEXAFS and Vibrational Spectroscopic Studies

et al. 2001

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Single-walled nanotubes (SWNTs) produced by plasma laser vaporization (PLV) and containing oxidized surface functional groups have been studied for the first time with NEXAFS. Comparisons are made to SWNTs made by catalytic synthesis over Fe particles in high-pressure CO, called HiPco material. The results indicate that the acid purification and cutting of single-walled nanotubes with either HNO3/H2SO4 or H2O2/H2SO4 mixtures produces the oxidized groups (O/C = 5.5-6.7%), which exhibit both pi*(CO) and sigma*(CO) C K-edge NEXAFS resonances. This indicates that both carbonyl (C=O) and ether C-O-C functionalities are present. Upon heating in a vacuum to 500-600 K, the pi*(CO) resonances are observed to decrease in intensity; on heating to 1073 K, the sigma*(CO) resonances disappear as the C-O-C functional groups are decomposed. Raman spectral measurements indicate that the basic tubular structure of the SWNTs is not perturbed by heating to 1073 K, based on the invariance of the ring breathing modes upon heating. The NEXAFS studies agree well with infrared studies which show that carboxylic acid groups are thermally destroyed first, followed by the more difficult destruction of ether and quinone groups. Single-walled nanotubes produced by the HiPco process, and not treated with oxidizing acids, exhibit an O/C ratio of 1.9% and do not exhibit either pi*(CO) or sigma*(CO) resonances at the detection limit of NEXAFS. It is shown that heating (to 1073 K) of the PLV-SWNTs containing the functional groups produces C K-edge NEXAFS spectra very similar to those seen for the HiPco material. The NEXAFS spectra are calibrated against spectra measured for a number of fused-ring aromatic hydrocarbon molecules containing various types of oxidized functional groups present on the oxidized SWNTs.

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Highly ordered iron oxide-mesoporous fullerene nanocomposites for oxygen reduction reaction and supercapacitor applications

Benzigar

Joseph

Saianand

et al. 2019

Microporous and Mesoporous Materials

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Electronic Structure of Polymerized C₆₀ Phases

Cited by 5 publications

References 51 publications

X-ray photoelectron spectroscopy and near-edge X-ray-absorption fine structure of C 60 polymer films

X-ray photoelectron spectroscopy and near-edge X-ray-absorption fine structure of C 60 polymer films

Oxygen-Containing Functional Groups on Single-Wall Carbon Nanotubes: NEXAFS and Vibrational Spectroscopic Studies

Highly ordered iron oxide-mesoporous fullerene nanocomposites for oxygen reduction reaction and supercapacitor applications

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Electronic Structure of Polymerized C60 Phases

Cited by 5 publications

References 51 publications

X-ray photoelectron spectroscopy and near-edge X-ray-absorption fine structure of C 60 polymer films

X-ray photoelectron spectroscopy and near-edge X-ray-absorption fine structure of C 60 polymer films

Oxygen-Containing Functional Groups on Single-Wall Carbon Nanotubes: NEXAFS and Vibrational Spectroscopic Studies

Highly ordered iron oxide-mesoporous fullerene nanocomposites for oxygen reduction reaction and supercapacitor applications

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Electronic Structure of Polymerized C₆₀ Phases