Graphene is a rapidly rising star on the horizon of materials science and condensed-matter physics. This strictly two-dimensional material exhibits exceptionally high crystal and electronic quality, and, despite its short history, has already revealed a cornucopia of new physics and potential applications, which are briefly discussed here. Whereas one can be certain of the realness of applications only when commercial products appear, graphene no longer requires any further proof of its importance in terms of fundamental physics. Owing to its unusual electronic spectrum, graphene has led to the emergence of a new paradigm of 'relativistic' condensed-matter physics, where quantum relativistic phenomena, some of which are unobservable in high-energy physics, can now be mimicked and tested in table-top experiments. More generally, graphene represents a conceptually new class of materials that are only one atom thick, and, on this basis, offers new inroads into low-dimensional physics that has never ceased to surprise and continues to provide a fertile ground for applications.

The rise of graphene

This article reviews the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations. The Dirac electrons can be controlled by application of external electric and magnetic fields, or by altering sample geometry and/or topology. The Dirac electrons behave in unusual ways in tunneling, confinement, and the integer quantum Hall effect. The electronic properties of graphene stacks are discussed and vary with stacking order and number of layers. Edge (surface) states in graphene depend on the edge termination (zigzag or armchair) and affect the physical properties of nanoribbons. Different types of disorder modify the Dirac equation leading to unusual spectroscopic and transport properties. The effects of electron-electron and electron-phonon interactions in single layer and multilayer graphene are also presented.

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The electronic properties of graphene

抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

We measured the elastic properties and intrinsic breaking strength of free-standing monolayer graphene membranes by nanoindentation in an atomic force microscope. The force-displacement behavior is interpreted within a framework of nonlinear elastic stress-strain response, and yields second- and third-order elastic stiffnesses of 340 newtons per meter (N m(-1)) and -690 Nm(-1), respectively. The breaking strength is 42 N m(-1) and represents the intrinsic strength of a defect-free sheet. These quantities correspond to a Young's modulus of E = 1.0 terapascals, third-order elastic stiffness of D = -2.0 terapascals, and intrinsic strength of sigma(int) = 130 gigapascals for bulk graphite. These experiments establish graphene as the strongest material ever measured, and show that atomically perfect nanoscale materials can be mechanically tested to deformations well beyond the linear regime.

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Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene

Graphene is a wonder material with many superlatives to its name. It is the thinnest known material in the universe and the strongest ever measured. Its charge carriers exhibit giant intrinsic mobility, have zero effective mass, and can travel for micrometers without scattering at room temperature. Graphene can sustain current densities six orders of magnitude higher than that of copper, shows record thermal conductivity and stiffness, is impermeable to gases, and reconciles such conflicting qualities as brittleness and ductility. Electron transport in graphene is described by a Dirac-like equation, which allows the investigation of relativistic quantum phenomena in a benchtop experiment. This review analyzes recent trends in graphene research and applications, and attempts to identify future directions in which the field is likely to develop.

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Graphene: Status and Prospects

In this paper we report studies of the luminescence from photoexcited poly(p-phenylene vinylene) [PPV]. A strong decrease in the yield and lifetime is observed as the extent of unsaturation is increased by thermal conversion from the precursor to fully converted PPV. Such behaviour can be explained by non-radiative recombination processes that compete with the luminescence and which become increasingly efficient as the conjugation length increases. The non-radiative decay is separated into monomolecular and bimolecular components both of which are seen to increase with conjugation length; with the latter of greater relative importance for the more highly converted samples. The monomolecular component appears consistent with recent theoretical treatments whilst the origin of the bimolecular component is at present unclear.

Radiative and Non-radiative Recombination Processes in Photoexcited Poly(p-phenylene vinylene)

Precursor-route syntheses of conjugated polymers are of considerable interest on account of the flexibility of sample preparation that they impart. The sulphonium polyelectrolyte route to poly(p-phenylene vinylene) [PPV] is one such synthesis that allows samples of PPV to be prepared in a variety of forms. In this paper we report the results of investigations of crystallinity at various stages in the conversion of unoriented films from the precursor to fully converted PPV. In partially converted unoriented samples, as is also the case for oriented films, crystallisation appears to be hindered by the presence of residual sulphur-containing moieties. However, upon full conversion the X-ray diffraction shows sharp Debye-Scherrer rings indicating an isotropic polycrystalline structure. In addition to characterisation of the state of order we have investigated its effect upon charge transfer doping. It is proposed that the difficulties experienced by other workers with iodine doping relate to the crystallinity of the samples.

Control of the State of Order in Poly(p-phenylene vinylene) and Its Effect on Iodine Doping

SbF5-doped polyacetylene was studied on samples with dopant concentrations ranging from 0.1 to 8.4 mol%, using 121Sb Mossbauer spectroscopy. The spectra reveal the presence of SbF3, SbF5, and SbF-6, respectively. From the relative intensities of the well-separated subspectra we could determine the relative fractions of the three molecular species as a function of dopant concentration.

https://hal.archives-ouvertes.fr/jpa-00222698/document

MÖSSBAUER STUDY OF SbF5- DOPED POLYACETYLENE

The influence of sulfur addition on the production of SWCNTs by the arc‐discharge method with Fe/Y catalysts was investigated. It was found that the yield of SWCNTs is strongly influenced by the presence of sulfur. The dependence of the SWCNTs yield on the concentration of sulfur in the anode reaches its maximum around 1.5 at%. The yield of SWCNTs was estimated by thermal gravimetry and by optical absorption.

S. Roth

Papers

Radiative and Non-radiative Recombination Processes in Photoexcited Poly(p-phenylene vinylene)

Control of the State of Order in Poly(p-phenylene vinylene) and Its Effect on Iodine Doping

MÖSSBAUER STUDY OF SbF5- DOPED POLYACETYLENE

The Influence of Sulfur Promoter on the Production of SWCNTs by the Arc‐Discharge Process

Time resolved fluorescence and solvatochromism in donor-substituted bianthrones