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S. Roth

Bio: S. Roth is an academic researcher from Max Planck Society. The author has contributed to research in topics: Carbon nanotube & Polyacetylene. The author has an hindex of 44, co-authored 281 publications receiving 25195 citations.


Papers
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Book ChapterDOI
01 Jan 1985
TL;DR: Pulsed photoconductivity measurements in polyacetylene and s-carotene (an oligomer with eleven conjugated double bonds) are reported in this paper, where the lifetime of photoexcited carriers in these two systems is studied.
Abstract: Pulsed photoconductivity measurements in polyacetylene and s-carotene (an oligomer with eleven conjugated double bonds) are reported. Since both polyacetylene and s-carotene show light-induced conductivity, we have studied the lifetime of photoexcited carriers in these two systems. Some measurements were done in the picosecond regime to study the carrier motion before trapping,as well as in the micro- and millisecond regime to investigate the relaxation of carriers hopping between localized states. The experimental configuration is pointed out,and some of the difficulties connected with such experiments are discussed.
01 Jan 1990
TL;DR: In this paper, the authors describe the Langmuir-Blodgett-technique (LB) method to transfer ordered molecules on the interface water-air and to transfer these ordered films to solid substrates.
Abstract: in molecular electronics1 . They are regarded as molecular wires, which connect other molecular switching elements. If this molecular wire is modified by attaching donor and accep­ tor groups to the ends of the polyene chain, optical excita­ tion of the donor group at a selected photon energy is accom­ panied by a transfer of charge from the donor group to the acceptor group via the polyene chain. In a chemical view this is expressed by shifting the positions of the double-bonds by one c-atom. This optically - induced change of the molecular dipole moment can also be discussed in terms of sOlitons2 . The Langmuir-Blodgett-technique (LB)3 is a method to or­ der molecules on the interface water-air and to transfer these ordered films to solid substrates. Amphiphilic mole­ cules, consisting of a hydrophilic headgroup and a hydrophob­ ic 'tail' are spread on a clean water surface. The molecules lying on the surface form a two-dimensional gas. On reducing the covered surface, the mean area per molecule [A2 /mol] is reduced until the interaction of the molecules induces a phase transition into a liquid-analogous state. This phase transition is characterized by a change of slope in the sur­ face-pressure/area (a/F)-diagram. Further reduction of the phase induces a second transition into 2D-solid state. This face is comparable to a smectic-b phase, all molecules stand­ ing perpendicular to the water surface. In this solid-analo­ gous state the ordered film can be transferred to a solid substrate. The film is held under constant pressure and the
Journal ArticleDOI
TL;DR: In this article, a thermally activated relaxation process has been found in the anelastic spectrum of HiPco carbon nanotubes at 25 K. The activation energy obtained by the peak shift with frequency is E a ǫ = 54.7 Ã 0 Ã −1 Ã 1 Ã 2 Ã 3 Ã 4 Ã 5 Ã 6 Ã 7 Ã 11 Ã 12 Ã 14 Ã 15 Ã 16 Ã 17 Ã 18 Ã 19 Ã 20 Ã 21 Ã 22 Ã 24
Book ChapterDOI
01 Jan 1992
TL;DR: For more detailed information on the correlation between the mean conjugation length and the EPR linewidth in standard and new polyacetylene defined concentrations of breaking defects were incorporated in these materials by chemical methods as mentioned in this paper.
Abstract: For more detailed information on the correlation between the mean conjugation length and the EPR linewidth in “standard” and “new” polyacetylene defined concentrations of conjugation breaking defects were incorporated in these materials by chemical methods.
Journal ArticleDOI
TL;DR: In this article, the first mechanical spectroscopy experiments in HiPco carbon nanotubes from room temperature to 3 K revealed a thermally activated relaxation process at about 25 K for frequencies in the kHz range.
Abstract: The first mechanical spectroscopy experiments in HiPco carbon nanotubes from room temperature to 3 K revealed a thermally activated relaxation process at about 25 K for frequencies in the kHz range. The peak is due to the presence of a very mobile species performing about 103 jumps per second at the peak temperature. The activation energy obtained by the peak shift with frequency is Ea = 54.7 meV; the value of the pre-exponential factor of the Arrhenius law for the relaxation time, τ0 = 10-14 s, which is typical of point defect relaxation and suggests that the process is originated by the dynamics of hydrogen or by H complexes. The peak is much broader than a single Debye relaxation process, indicating the presence of intense elastic interactions in the highly disordered bundle structure. There are indications that the relaxation process is governed by a quantum mechanism.

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Journal ArticleDOI
TL;DR: 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 can now be mimicked and tested in table-top experiments.
Abstract: 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.

35,293 citations

Journal ArticleDOI
TL;DR: In this paper, the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations, are discussed.
Abstract: 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.

20,824 citations

28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组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�ly.
Abstract: 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。

18,940 citations

Journal ArticleDOI
Changgu Lee1, Xiaoding Wei1, Jeffrey W. Kysar1, James Hone1, James Hone2 
18 Jul 2008-Science
TL;DR: Graphene is established as the strongest material ever measured, and atomically perfect nanoscale materials can be mechanically tested to deformations well beyond the linear regime.
Abstract: 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.

18,008 citations

Journal ArticleDOI
19 Jun 2009-Science
TL;DR: This review analyzes recent trends in graphene research and applications, and attempts to identify future directions in which the field is likely to develop.
Abstract: 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.

12,117 citations