Vertically aligned carbon nanotubes (VACNTs) possess the advantages of a high degree of order, good controllability, and easy manipulation. Thus, their synthesis, properties, and potential for applications have been intensively investigated. [1][2][3][4][5] VACNTs are usually grown by chemical vapor deposition (CVD) on substrates with pre-deposited catalysts. Due to the rigorous CVD synthesis conditions, substrates employed for VACNT growth should be thermally and chemically stable materials, such as SiO 2 /Si, Al 2 O 3 , or quartz. A problem thus arising is that these substrates are usually insulators, which hampers the direct application of VACNTs in those areas that require desirable integrated electrical and thermal conductivities. [ 6 ] For example, a mismatching problem often emerges when assembling devices based on VACNTs due to the rigidity and poor conductivity of the substrates. To solve this problem, some researchers have developed multiform but complicated methods to transfer VACNTs from the insulating substrates to conducting substrates by post-synthesis processing, which facilitates the application of VACNTs in some electronic devices, such as fi eld emitters. [ 7,8 ] On the other hand, Tatsuki et al. reported direct growth of VACNTs on Ni-based alloy foils. [ 9 ] Although excellent fi eld emission homogeneity was demonstrated, the 30 nm thick alumina buffer layer deposited between the metal substrate and catalyst fi lm weakens the electrical contact and mechanical adhesion between the VACNTs and the metal substrate. The incompatible thermal expansion coeffi cients of alumina and metal may also lead to detaching of the VACNTs and the alumina buffer layer from the metal substrate.Graphene is a newly discovered 2D carbon material with excellent conductivity, mechanical properties, [ 10,11 ] and more importantly, compatibility with CNTs. Therefore, graphene can be an ideal substrate for VACNT growth. Recently, Lee et al. demonstrated the growth of VACNTs on a ∼ 7 nm thick reduced graphene fi lm supported by silicon wafer. The VACNT/ graphene hybrid fi lm infi ltrated with a poly(dimethyl siloxane) (PDMS) elastomer displayed good mechanical properties, electrical conductivity, and fi eld emission performance. [ 12 ] Nitrogendoped VACNTs grown on mechanically compliant graphene fi lm for a fl exible fi eld emitter were also demonstrated by Lee et al. [ 13 ] Jeong et al. reported a flexible room temperature NO 2 gas sensor consisting of a VACNT/reduced graphene hybrid film supported by a polyimide substrate. [ 14 ] Paul et al. prepared a 3D pillared graphene nanostructure comprising graphene and aligned carbon nanotubes by a one-step CVD method. [ 15 ] Zhang et al. demonstrated desirable visible light photocatalytic performance for a 3D pillared CNT/reduced graphene oxide composite material. [ 16 ] Fan et al. prepared a 3D CNT/graphene sandwich with short CNT pillars ( ∼ 100 nm in length) grown between graphene layers or by ultrasonicating purifi ed, shortcut CNTs in a graphene oxide suspension followed b...

Currently, the performances of thin film solar cells are limited by poor light absorption and carrier collection. In this research, large, broadband, and polarization-insensitive light absorption enhancement was realized via integrating with unique metallic nanogratings. Through simulation, three possible mechanisms were identified to be responsible for such an enormous enhancement. A test for totaling the absorption over the solar spectrum shows an up to approximately 30% broadband absorption enhancement when comparing to bare thin film cells.

We demonstrate stable 70 ns pulse generation from a Yb-doped fiber laser passively Q-switched by a graphene-based saturable absorber mirror in a short linear cavity. The maximum output power was 12 mW and the highest single pulse energy was 46 nJ. The repetition rate of the fiber laser can be widely tuned from 140 to 257 kHz along with the increase of the pump power. To the best of our knowledge, this is the first report for passively Q-switched sub-100-ns pulse operation of a graphene-based saturable absorber in a Yb-doped fiber laser.

We demonstrated the femtosecond erbium-doped all-fiber lasers mode-locked with graphene oxide, which can be conveniently obtained from natural graphite by simple oxidation and ultra-sonication process. With proper dispersion management in an all-fiber ring cavity, the laser directly generated 200 fs pulses at a repetition rate of 22.9 MHz and the average output power was 5.8 mW. With the variation of net cavity dispersion, output pulses with pulse width of 0.2~3 ps were obtained at a repetition rate of 22.9~0.93 MHz. These results are comparable with those of graphene saturable absorbers and the superiority of easy fabrication and hydrophilic property of graphene oxide will facilitate its potential applications for ultrafast photonics.

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A strong solid/liquid interfacial interaction is found between porous alumina and graphene oxide (GO) aqueous dispersion, which promotes a fast enrichment of GO on the alumina surface and results in the formation of a GO hydrogel.

Graphene and its derivatives are emerging as a class of novel but versatile templates for the controlled preparation and functionalization of materials. In this paper a conceptual review on graphene-based templates is given, highlighting their versatile roles in materials preparation. Graphene is capable of acting as a low-dimensional hard template, where its two-dimensional morphology directs the formation of novel nanostructures. Graphene oxide and other functionalized graphenes are amphiphilic and may be seen as soft templates for formatting the growth or inducing the controlled assembly of nanostructures. In addition, nanospaces in restacked graphene can be used for confining the growth of sheet-like nanostructures, and assemblies of interlinked graphenes can behave either as skeletons for the formation of composite materials or as sacrificial templates for novel materials with a controlled network structure. In summary, flexible graphene and its derivatives together with an increasing number of assembled structures show great potentials as templates for materials production. Many challenges remain, for example precise structural control of such novel templates and the removal of the non-functional remaining templates.