Magnetic impurities in graphene

Hu, Fengming; Ma, Tianxing; Lin, Hai–Qing; Gubernatis, J. E.

doi:10.1103/physrevb.84.075414

Cited by 132 publications

(170 citation statements)

References 34 publications

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“…The presence of residual metallic impurities in graphene is a known problem, and many of these impurities are able to dramatically alter the electronic and electrochemical properties of graphene (26)(27)(28). It is often falsely assumed in the graphene community that these impurities are sufficiently removed during the conversion of graphite to RGOs and that they have little or no effect on the final material's properties.…”

mentioning

confidence: 99%

Synthetic routes contaminate graphene materials with a whole spectrum of unanticipated metallic elements

Wong

Sofer²,

Kubešová

et al. 2014

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

145

118

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The synthesis of graphene materials is typically carried out by oxidizing graphite to graphite oxide followed by a reduction process. Numerous methods exist for both the oxidation and reduction steps, which causes unpredictable contamination from metallic impurities into the final material. These impurities are known to have considerable impact on the properties of graphene materials. We synthesized several reduced graphene oxides from extremely pure graphite using several popular oxidation and reduction methods and tracked the concentrations of metallic impurities at each stage of synthesis. We show that different combinations of oxidation and reduction introduce varying types as well as amounts of metallic elements into the graphene materials, and their origin can be traced to impurities within the chemical reagents used during synthesis. These metallic impurities are able to alter the graphene materials' electrochemical properties significantly and have wide-reaching implications on the potential applications of graphene materials.

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mentioning

confidence: 99%

Synthetic routes contaminate graphene materials with a whole spectrum of unanticipated metallic elements

Wong

Sofer²,

Kubešová

et al. 2014

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

145

118

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“…It was shown by theoretical modeling that the interaction of transition metal impurities with graphene may alter its electronic properties dramatically (35,36). We recently demonstrated that metallic impurities present in synthetic graphite still remain and significantly interfere with the electrochemistry of related graphene materials produced by means of thermal reduction/exfoliation of graphite oxide (37).…”

mentioning

confidence: 99%

Chemically reduced graphene contains inherent metallic impurities present in parent natural and synthetic graphite

Ambrosi

Chua

Khezri

et al. 2012

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

207

168

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Graphene-related materials are in the forefront of nanomaterial research. One of the most common ways to prepare graphenes is to oxidize graphite (natural or synthetic) to graphite oxide and exfoliate it to graphene oxide with consequent chemical reduction to chemically reduced graphene. Here, we show that both natural and synthetic graphite contain a large amount of metallic impurities that persist in the samples of graphite oxide after the oxidative treatment, and chemically reduced graphene after the chemical reduction. We demonstrate that, despite a substantial elimination during the oxidative treatment of graphite samples, a significant amount of impurities associated to the chemically reduced graphene materials still remain and alter their electrochemical properties dramatically. We propose a method for the purification of graphenes based on thermal treatment at 1,000°C in chlorine atmosphere to reduce the effect of such impurities on the electrochemical properties. Our findings have important implications on the whole field of graphene research.electrochemistry | synthesis G raphene and graphene-derived materials have recently attracted enormous attention from the scientific community because of their extraordinary physical, chemical, and mechanical features (1, 2). Graphene materials can be used in several applications-including electronics (3), composite materials (4, 5), sensing (6), energy storage (7,8), and medicine (9)-with expected or known advantages over conventional materials.In general, there are two routes leading to the production of graphene: (i) a bottom-up approach, consisting of growing single/ bilayered graphene onto a catalytic surface through chemical vapor deposition (CVD) technique (10, 11); and (ii) a top-down approach, starting from graphite to obtain single/few-layered graphene sheets by an exfoliation procedure (12, 13). Because exfoliation in the liquid phase is hardly achieved directly on graphitic materials because of the highly cohesive van der Waals forces between the graphene sheets (14), a chemical treatment is generally performed to oxidize graphite to graphite oxide (GO). The oxidation helps to increase the graphene interlayer distance for an easy exfoliation, which is then followed by the removal of the oxygen functionalities to give single/few-layered graphene (12). The second approach received particularly huge attention because it is suitable for large-scale production of graphene materials and is cost-effective, although the graphene produced presents significant structural defects and lower carrier mobility properties (12). Natural graphite is the preferred starting material for this method of preparation because it is available in great quantities and at a low cost. Alternatively, synthetic graphite is also widely adopted as a starting material. It is important to highlight the differences between these two graphitic materials with particular focus on the content of metallic impurities and possible sources of contamination.Natural graphite is mined using standard ...

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“…the local moment of impurity 37,42 , the Kondo effect 43 and the interaction between localized moments 43,44 , etc.. Recently, the HFQMC technique is applied to study the magnetic properties of Ander-son impurities in dilute magnetic semiconductors 45 and graphene 46 . The paper is organized as follows.…”

Section: Introductionmentioning

confidence: 99%

Spin-spin interaction in the bulk of topological insulators

2014

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We apply mean-field theory and Hirsch-Fye quantum Monte Carlo method to study the spinspin interaction in the bulk of three-dimensional topological insulators. We find that the spin-spin interaction has three different components: the longitudinal, the transverse and the transverse Dzyaloshinskii-Moriya-like terms. When the Fermi energy is located in the bulk gap of topological insulators, the spin-spin interaction decays exponentially due to Bloembergen-Rowland interaction. The longitudinal correlation is antiferromagnetic and the transverse correlations are ferromagnetic. When the chemical potential is in the conduction or valence band, the spin-spin interaction follows power law decay, and isotropic ferromagnetic interaction dominates in short separation limit.

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Magnetic impurities in graphene

Cited by 132 publications

References 34 publications

Synthetic routes contaminate graphene materials with a whole spectrum of unanticipated metallic elements

Synthetic routes contaminate graphene materials with a whole spectrum of unanticipated metallic elements

Chemically reduced graphene contains inherent metallic impurities present in parent natural and synthetic graphite

Spin-spin interaction in the bulk of topological insulators

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