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.

Since graphene was discovered, a great deal of research effort has been devoted to finding more and more effective synthetic routes, stimulated by its astounding properties and manifold promising applications. Over the past decade, laser synthesis has been proposed as a viable synthesis method to reduce graphene oxide to graphene as well as to obtain graphene from other carbonaceous sources such as polymers or other natural materials. This review first proposes to discuss the various conditions under which graphene is obtained from the reduction of graphene oxide or is induced from other materials using laser sources. After that, a wide range of applications proposed for the obtained materials are discussed. Finally, conclusions are drawn and the author’s perspectives are given.

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Laser Synthesized Graphene and Its Applications

We demonstrate three types of sensors based on spray-deposited Carbon Nanotube (CNT) networks on flexible substrates: humidity sensors, dew-point sensors and time-temperature indicators. The presence of Sodium Dodecylsulphate (SDS) significantly increases the sensitivity of the film resistance of CNT networks to changes of relative humidity. We observe up to a 3% change in film resistance in the 30–75% range of relative humidity, with a non-linear relationship. When these SDS-impregnated CNT films are cooled to the dew-point of air, with the temperature of the film monitored, the associated increase in sheet resistance can be used to establish the dew-point temperature. We use acid-doped CNT networks as time-temperature indicators, exploiting the de-doping of the CNT networks at higher temperature. We observe an increase in film resistance of such networks at temperatures higher than 50 °C. The rate of the resistance increase follows the Arrhenius law. The extent of the resistance increase ranges from ∼30%at 50 °C to >300% at 100 °C.

Carbon Nanotube network based sensors

Laser scribing, by far proposed as a method for efficiently transforming graphene oxide into reduced graphene, has been employed, using a CW laser beam, to study the modifications of graphene oxide scribed under different controlled atmospheres, including air, N2, Ar, and a 95 : 5 ( ) Ar/H2 mixture. We have found that laser scribing effects, including chemical composition, order degree, and electrical properties, strongly depend upon the atmosphere during the irradiation. The electrical properties of the various materials, obtained in different atmospheres, have been evaluated with respect to the sensing properties towards humidity, the materials produced in pure Argon yielding the highest sensitivity and the fastest response, while related Raman microspectroscopy measurements showed that both Ar and Ar-H2 mixture produce the highest order among the various samples. The results stress the importance and the potentialities of controlling the irradiation atmosphere in order to tune the composition and electrical properties of the laser-scribed graphene oxide materials.

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Vittorio Scardaci

Papers

Laser Synthesized Graphene and Its Applications

Carbon Nanotube network based sensors

Reduction of Graphene Oxide by Laser Scribing in Different Atmospheres and Application in Humidity Sensing

Silver nanoplates paved PMMA cuvettes as a cheap and re-usable plasmonic sensing device

Raman spectroscopy data related to the laser induced reduction of graphene oxide