By introducing the UV beam into our homemade chemical vapor deposition system, we had obtained a well aligned SWNT array on an ST-cut quartz substrate. After transfer onto a SiO(2)/Si substrate, the SWNT array was detected by Raman spectroscopy and electrical measurement, which showed that over 95% of the SWNTs were semiconducting ones. It is proposed that the selection process took place at the very beginning of the SWNT formation rather than destroying the metallic SWNTs after growth. This approach has solved one of the most important problems in SWNT application.

It is generally accepted that the hydrophilic property of graphene can be affected by the underlying substrate. However, the role of intrinsic vs substrate contributions and the related mechanisms are vividly debated. Here, we show that the intrinsic hydrophilicity of graphene can be intimately connected to the position of its Fermi level, which affects the interaction between graphene and water molecules. The underlying substrate, or dopants, can tune hydrophilicity by modulating the Fermi level of graphene. By shifting the Fermi level of graphene away from its Dirac point, via either chemical or electrical voltage doping, we show enhanced hydrophilicity with experiments and first principle simulations. Increased vapor condensation on graphene, induced by a simple shifting of its Fermi level, exemplifies applications in the area of interfacial transport phenomena.

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The high-energy lithium ion battery is an ideal power source for electric vehicles and grid-scale energy storage applications. Germanium is a promising anode material for lithium ion batteries due to its high specific capacity, but still suffers from poor cyclability. Here, we report a facile preparation of a germanium-graphene nanocomposite using a low-pressure thermal evaporation approach, by which crystalline germanium particles are uniformly deposited on graphene surfaces or embedded into graphene sheets. The nanocomposite exhibits a high Coulombic efficiency of 80.4% in the first cycle and a capacity retention of 84.9% after 400 full cycles in a half cell, along with high utilization of germanium in the composite and high rate capability. These outstanding properties are attributed to the monodisperse distribution of high-quality germanium particles in a flexible graphene framework.This preparation approach can be extended to other active elements that can be easily evaporated (e.g., sulfur, phosphorus) for the preparation of graphene-based composites for lithium ion battery applications.

Due to its unique electronic properties and wide spectrum of promising applications, graphene has attracted much attention from scientists in various fields. Control and engineering of graphene's semiconducting properties is considered to be key to its applications in electronic devices. Here, we report a novel method to prepare in situ nitrogen-doped graphene by microwave plasma assisted chemical vapor deposition (CVD) using PDMS (polydimethylsiloxane) as a solid carbon source. Based on this approach, the concentration of nitrogen-doping can be easily controlled via the flow rate of nitrogen during the CVD process. X-ray photoelectron spectroscopy results indicated that the nitrogen atoms doped into the graphene lattice were mainly in the forms of pyridinic and pyrrolic structures. Moreover, first-principles calculations show that the incorporated nitrogen atoms can lead to p-type doping of graphene. This in situ approach provides a promising strategy to prepare graphene with controlled electronic properties.

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