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

Single-layer metal dichalcogenides are two-dimensional semiconductors that present strong potential for electronic and sensing applications complementary to that of graphene.

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Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.

We present a detailed investigation of pulse width and spectral dynamics of an E1 3+ -doped soliton fiber ring laser, mode-locked by a carbon-nanotube-polymer composite. The laser is stable and produces ∼ 650 fs pulses at fundamental repetition rate of 20.8 MHz. The carbon nanotube saturable absorber has a low saturation intensity of ∼ 18.9 MW/cm 2 and a 16.9% reduction in absorption (due to saturation) at high pulse intensity (∼ 270 MW/cm 2 ). Spectral and transient effects confirm the soliton operation of the laser.

Soliton fiber laser mode‐locked by a single‐wall carbon nanotube‐polymer composite

Abstract We report on a Q-switched Yb-doped all-fiber laser based on a solution-processed Ag nanoplates saturable absorber. Optical deposition procedure is implemented to transfer the Ag nanoplates onto the fiber core area through the thermal effect. The saturable absorber is sandwiched between two fiber connectors, providing simplicity, flexibility, and easy integration into the laser oscillator. The modulation depth and saturation incident fluence are measured to be ~5.8% and ~106.36 μJ/cm2 at 1-μm region, respectively. Self-started stable Q-switched operation is achieved for a threshold pump power of 180 mW. The repetition rates of the pulse trains range from 66.6 to 184.8 kHz when the pump power scales from 210 to 600 mW. The maximum average output power is 10.77 mW, corresponding to the single-pulse energy of 58.3 nJ and minimum pulse duration of ~1.01 μs. To the best of our knowledge, it is the first time that the Ag nanoplates saturable absorbers are utilized in the 1-μm Yb-doped Q-switched fiber laser.

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Passively Q-switched Yb-doped all-fiber laser based on Ag nanoplates as saturable absorber

Recent Progress on Metal-Based Nanomaterials: Fabrications, Optical Properties, and Applications in Ultrafast Photonics

Plasmon sensing and enhancement of laser prepared silver colloidal nanoplates

Improvement on the stability and loading of unfunctionalized single wall carbon nanotubes (SWNTs) in amide solvents is necessary to enhance the performances of SWNT-polymer composites used for optical applications (e.g., as non-linear saturable absorbers). We show that polyvinylpyrrolidone (PVP) can not only increase the stability of ultrasonically dispersed HiPco SWNTs in pure N-methyl-2-pyrrolidone (NMP), but also improve the photoluminescence emission signals from SWNTs even after 1 month of incubation. Compared to two non-ionic surfactants (Igepal DM-970 and Pluronic F-98), we find that PVP-aided SWNT dispersions in NMP can improve the SWNT loading by at least four times. Unlike surfactant-aided dispersions, the PVP-aided dispersions remain completely stable by close visual inspection even after 6 months of incubation.

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Vittorio Scardaci

Papers

Soliton fiber laser mode‐locked by a single‐wall carbon nanotube‐polymer composite

Passively Q-switched Yb-doped all-fiber laser based on Ag nanoplates as saturable absorber

Recent Progress on Metal-Based Nanomaterials: Fabrications, Optical Properties, and Applications in Ultrafast Photonics

Plasmon sensing and enhancement of laser prepared silver colloidal nanoplates

Dispersibility and stability improvement of unfunctionalized nanotubes in amide solvents by polymer wrapping