Surface refinement and electronic properties of graphene layers grown on copper substrate: An XPS, UPS and EELS study

Siokou, A.; Ravani, Fotini; Karakalos, Stavros; Frank, Otakar; Kalbáč, Martin; Galiotis, Costas

doi:10.1016/j.apsusc.2011.06.017

Cited by 188 publications

(113 citation statements)

References 24 publications

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“…The higher intensity of the peak at 286.8 eV confirms a considerable oxidation of graphite to graphene oxide. After reduction with hydrazine the peaks related to the oxygeneous functional groups drastically decrease in intensity, confirming the effectiveness of the reduction [9,38,47,48]. The C/O ratio was calculated from the area under the curve of binding energy related to C1s and O1s and the values found for GO and RGO samples corresponded to 0.43 and 2.06, respectively, which are consistent with other results reported in the literature [49].…”

Section: Resultssupporting

confidence: 81%

Long-term behavior of epoxy/graphene-based composites determined by dynamic mechanical analysis

Silva

Ajayan

et al. 2015

J Mater Sci

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Graphene oxide and reduced graphene oxide were obtained from graphite and reduction of graphene oxide, respectively, and functionalized with 4,4 0 -Methylenebis (phenyl isocyanate) isocyanate. Epoxy/graphenebased composites were prepared by dispersing the as-prepared carbon materials in epoxy resin based on diglycidyl ether of bisphenol A followed by curing with triethylenetetramine. The efficiency of the functionalization of the carbon materials was followed by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoeletronic spectroscopy, and atomic force microscopy. The epoxy-based composites were characterized by dynamic mechanical analysis at frequency and temperature sweeps in order to evaluate the long-term behavior of the composites by using the time temperature superposition principles and the master curves of multi frequency. All composites presented better working temperature range and durability as compared with the pure epoxy network.However, those prepared with graphene oxide and its reduced form functionalized with isocyanate groups presented better mechanical performance and long-term durability, probably because of the better filler-matrix interactions achieved in theses system. The results obtained suggest that the presence of isocyanate groups is the key role for achieving good mechanical performance, and the reduction step of graphene oxide is not of paramount importance for achieving good mechanical response.

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Section: Resultssupporting

confidence: 81%

Long-term behavior of epoxy/graphene-based composites determined by dynamic mechanical analysis

Silva

Ajayan

et al. 2015

J Mater Sci

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“…No Ar + sputtering was made to clean up sample surfaces, which were measured as received in order to not disrupt the sp 2 network. 23 In order to explore the evolution of the surface composition on top of, and under the graphene layer, measurements were made at three different take-off angles (10°, 45°and 90°, outside the photoelectron pathway measured from the sample surface), thus changing the explored depth. The core level spectra were fitted using the XPSPeak software package.…”

Section: Methodsmentioning

confidence: 99%

Determination of a refractive index and an extinction coefficient of standard production of CVD-graphene

et al. 2015

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The refractive index and extinction coefficient of chemical vapour deposition grown graphene are determined by ellipsometry analysis. Graphene films were grown on copper substrates and transferred as both monolayers and bilayers onto SiO 2 /Si substrates by using standard manufacturing procedures. The chemical nature and thickness of residual debris formed after the transfer process were elucidated using photoelectron spectroscopy. The real layered structure so deduced has been used instead of the nominal one as the input in the ellipsometry analysis of monolayer and bilayer graphene, transferred onto both native and thermal silicon oxide. The effect of these contamination layers on the optical properties of the stacked structure is noticeable both in the visible and the ultraviolet spectral regions, thus masking the graphene optical response. Finally, the use of heat treatment under a nitrogen atmosphere of the graphene-based stacked structures, as a method to reduce the water content of the sample, and its effect on the optical response of both graphene and the residual debris layer are presented. The Lorentz-Drude model proposed for the optical response of graphene fits fairly well the experimental ellipsometric data for all the analysed graphene-based stacked structures.

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“…All these facts demonstrate that the lower work function of BND compared with those of MWCNTs and BND could be explained in terms of the destabilization of the p-electrons (lower p electronic binding energy of UNDDs) rather than surface groups or the content of sp 2 carbon. 19 Such specific p-electrons may be attributed to the curvature of the graphitic shell. A similar result on the effect of the curvature on the work function in the case of carbon nanotubes has been previously reported.…”

mentioning

confidence: 99%

Insights into the surface chemistry and electronic properties of sp² and sp³-hybridized nanocarbon materials for catalysis

Lin

Feng

et al. 2017

Chem. Commun.

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af Ultra-dispersed nanodiamond and its derivatives (UNDDs), including bucky nanodiamond and onion-like carbon, offer superior catalytic behavior relative to other nanocarbons. However, a systematic study of their unique properties has been rarely achieved. Their surface chemistry and electronic properties are therefore studied to reveal the essential differences of UNDDs compared to other nanocarbons for catalysis.Nanocarbon catalysis has been considered as a potential candidate to meet the goals of sustainable and green chemistry over the past few years. Fig. S1, ESI †). It not only benefits from the remarkable surface properties of graphene-based nanomaterials but also combines the intrinsic characters of a diamond core. Upon increasing the annealing temperature (T Z 1500 1C, Fig. S1, ESI †), BND will further phase transfer into OLC, which is a fascinating non-planar-related material with multiple sp 2 curved closed concentric graphite-like shells.As new members in the carbonous family, UNDDs possess interesting physicochemical properties, such as superior thermal and chemical stability, high surface energy and unique electronic structure. These properties have made UNDDs competitive candidates for catalytic reactions beside conventional metalbased catalysts.5 Moreover, some recent achievements have highlighted that UNDDs exhibit superior catalytic behavior in comparison to other sp 2 -hybridized nanocarbon materials (e.g., nanographite, nanotubes, activated carbon, graphene) for some important catalytic reactions, such as ethylbenzene dehydrogenation and phenolic oxidation. 6-8 It should be pointed out that the essential differences between a UNDD system and conventional sp 2 -hybridized nanocarbons in catalytic reactions have rarely been studied, and the origin of the catalytic behavior remains elusive and controversial. As such, it is therefore highly desirable to clarify the structure-property relationship in more detail in an effort to elucidate their underlying catalytic applications.In this work, we compare the surface chemistry and electronic structures of representative sp 2 -and sp 3 -hybridized nanocarbon materials by using XPS, temperature programmed desorption (TPD) and ultraviolet photoelectron spectroscopy (UPS), and attempt to give insights into the distinct physicochemical properties of UNDDs and other nanocarbons. Moreover, two probe reactions (nitrobenzene reduction and selective oxidation of 2,3,6-trimethylphenol) are used to reveal the direct correlation between the electronic structure and the catalytic activity.By using electron energy loss spectroscopy (EELS), the surface electronic structure and graphitization transformation of UNDDs were firstly studied. As shown in Fig. 1a, the main peaks located at about 292 eV in the carbon K-edge of UNDDs correspond to the characteristic 1s -s* transitions and the shoulder peaks at 285 eV, which are assigned to the 1s -p* transition, indicate the

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Surface refinement and electronic properties of graphene layers grown on copper substrate: An XPS, UPS and EELS study

Cited by 188 publications

References 24 publications

Long-term behavior of epoxy/graphene-based composites determined by dynamic mechanical analysis

Long-term behavior of epoxy/graphene-based composites determined by dynamic mechanical analysis

Determination of a refractive index and an extinction coefficient of standard production of CVD-graphene

Insights into the surface chemistry and electronic properties of sp² and sp³-hybridized nanocarbon materials for catalysis

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Surface refinement and electronic properties of graphene layers grown on copper substrate: An XPS, UPS and EELS study

Cited by 188 publications

References 24 publications

Long-term behavior of epoxy/graphene-based composites determined by dynamic mechanical analysis

Long-term behavior of epoxy/graphene-based composites determined by dynamic mechanical analysis

Determination of a refractive index and an extinction coefficient of standard production of CVD-graphene

Insights into the surface chemistry and electronic properties of sp2 and sp3-hybridized nanocarbon materials for catalysis

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Insights into the surface chemistry and electronic properties of sp² and sp³-hybridized nanocarbon materials for catalysis