Graphite sulphate – a precursor to graphene

Eigler, Siegfried

doi:10.1039/c4cc09381j

Cited by 82 publications

(91 citation statements)

References 33 publications

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“…Methods) to cover a wide range of θ . Figure 1a depicts the schematic representation of these derivatives: pristine CVD graphene (CVD-G), hexylated (hexyl-G)24, mixed functionalised (hexyl/aryl-G)24, reduced oxo-graphene (r-oxo-G)2526, arylated (aryl-G)27 as well as oxo-graphene (oxo-G)2526 (Supplementary note 1). In order to eliminate the impact of the addends on the optoelectronic response, the chemical moieties used were either non-Raman active28 or showed a Raman response far from the dominant graphene peak positions29.…”

Section: Resultsmentioning

confidence: 99%

“…Oxo-graphene (oxo-G) of 50% was synthesized from natural graphite in sulfuric acid with potassium permanganate as oxidant25; for 6% oxo-G the starting material was graphite sulphate26. Arylated CVD graphene (aryl-G): Bis-(4- tert -butylphenyl) iodonium hexafluorophosphate was deposited from solution (CH 2 Cl 2 ) on a monolayer flake.…”

Section: Methodsmentioning

confidence: 99%

“…We selected Raman spectroscopy, including a combined in situ Raman-spectroscopy and dry electrostatic doping method, as a principally non-invasive method for probing the (localized) sp 2 areas of differently functionalised graphene derivatives24252627. Here we show that for monolayer functionalised graphene, the increase in optical response with θ is directly associated with the presence of photoluminescent C(sp 2 ) domains in the material.…”

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confidence: 93%

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Degree of functionalisation dependence of individual Raman intensities in covalent graphene derivatives

Vecera

Eigler

Koleśnik-Gray

et al. 2017

Sci Rep

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Covalent functionalisation of graphene is a continuously progressing field of research. The optical properties of such derivatives attract particular attention. In virtually all optical responses, however, an enhancement in peak intensity with increase of sp3 carbon content, and a vanishing of the peak position shift in monolayer compared to few-layer systems, is observed. The understanding of these seemingly connected phenomena is lacking. Here we demonstrate, using Raman spectroscopy and in situ electrostatic doping techniques, that the intensity is directly modulated by an additional contribution from photoluminescent π-conjugated domains surrounded by sp3 carbon regions in graphene monolayers. The findings are further underpinned by a model which correlates the individual Raman mode intensities to the degree of functionalisation. We also show that the position shift in the spectra of solvent-based and powdered functionalised graphene derivatives originates predominantly from the presence of edge-to-edge and edge-to-basal plane interactions and is by large functionalisation independent.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 93%

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Degree of functionalisation dependence of individual Raman intensities in covalent graphene derivatives

Vecera

Eigler

Koleśnik-Gray

et al. 2017

Sci Rep

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“…A variation in the density of defects up to several % is well known. 31,32 In this work, we use two types of GO: a commercial source of GO from Cheap Tubes (CT-GO) and oxo-functionalized graphene (oxo-G 1 ), which exhibits an average density of defects of only 0.3% within the carbon skeleton (Fig. 3a).…”

Section: Resultsmentioning

confidence: 99%

“…It might reflect the fact that oxo-G 1 possesses lower density in terms of lattice defects in the basal plain compared to CT-GO. 18,31,32,34,42,50 The reaction time is increasing proportionally to CT-GO concentration, for example, from 1.25 min to ca. 7 min upon the change of CT-GO concentration from 0.025 to 0.125 g L −1 under otherwise identical conditions.…”

Section: Indirect Photoreduction Of Go With Acetone/2-prohmentioning

confidence: 99%

High quality reduced graphene oxide flakes by fast kinetically controlled and clean indirect UV-induced radical reduction

et al. 2016

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This work highlights a surprisingly simple and kinetically controlled highly efficient indirect method for the production of high quality reduced graphene oxide (rGO) flakes via UV irradiation of aqueous dispersions of graphene oxide (GO), in which the GO is not excited directly. While the direct photoexcitation of aqueous GO (when GO is the only light-absorbing component) takes several hours of reaction time at ambient temperature (4 h) leading only to a partial GO reduction, the addition of small amounts of isopropanol and acetone (2% and 1%) leads to a dramatically shortened reaction time by more than two orders of magnitude (2 min) and a very efficient and soft reduction of graphene oxide. This method avoids the formation of non-volatile species and in turn contamination of the produced rGO and it is based on the highly efficient generation of reducing carbon centered isopropanol radicals via the reaction of triplet acetone with isopropanol. While the direct photolysis of GO dispersions easily leads to degradation of the carbon lattice of GO and thus to a relatively low electric conductivity of the films of flakes, our indirect photoreduction of GO instead largely avoids the formation of defects, keeping the carbon lattice intact.Mechanisms of the direct and indirect photoreduction of GO have been elucidated and compared.Raman spectroscopy, XPS and conductivity measurements prove the efficiency of the indirect photoreduction in comparison with the state-of-the-art reduction method for GO (hydriodic acid/trifluoroacetic acid). The rapid reduction times and water solvent containing only small amounts of isopropanol and acetone may allow easy process up-scaling for technical applications and low-energy consumption.

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Mechanism of Formation and Chemical Structure of Graphene Oxide

Dimiev¹

2016

Graphene Oxide

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Graphite sulphate – a precursor to graphene

Cited by 82 publications

References 33 publications

Degree of functionalisation dependence of individual Raman intensities in covalent graphene derivatives

Degree of functionalisation dependence of individual Raman intensities in covalent graphene derivatives

High quality reduced graphene oxide flakes by fast kinetically controlled and clean indirect UV-induced radical reduction

Mechanism of Formation and Chemical Structure of Graphene Oxide

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