Functionalized graphene nanoribbons via anionic polymerization initiated by alkali metal-intercalated carbon nanotubes.

The preparation of polymer-functionalized graphene nanoribbons (PF-GNRs) in a one-pot synthesis is described. Multiwalled carbon nanotubes (MWCNTs) were intercalated by potassium under vapor- or liquid-phase conditions, followed by the addition of vinyl or epoxide monomers, resulting in PF-GNRs. Scanning electron microscopy, thermogravimetric mass spectrometry, and X-ray photoelectron spectroscopy were used to characterize the PF-GNRs.

Graphene nanoribbons as an advanced precursor for making carbon fiber.

Graphene oxide nanoribbons (GONRs) and chemically reduced graphene nanoribbons (crGNRs) were dispersed at high concentrations in chlorosulfonic acid to form anisotropic liquid crystal phases. The liquid crystal solutions were spun directly into hundreds of meters of continuous macroscopic fibers. The relationship of fiber morphology to coagulation bath conditions was studied.

Graphene oxide for effective radionuclide removal.

Here we show the efficacy of graphene oxide (GO) for rapid removal of some of the most toxic and radioactive long-lived human-made radionuclides from contaminated water, even from acidic solutions (pH < 2). The interaction of GO with actinides including Am(III), Th(IV), Pu(IV), Np(V), U(VI) and typical fission products Sr(II), Eu(III) and Tc(VII) were studied, along with their sorption kinetics. Cation/GO coagulation occurs with the formation of nanoparticle aggregates of GO sheets, facilitating their removal.

Graphene: powder, flakes, ribbons, and sheets.

Graphene's unique physical and electrical properties (high tensile strength, Young's modulus, electron mobility, and thermal conductivity) have led to its nickname of "super carbon." Graphene research involves the study of several different physical forms of the material: powders, flakes, ribbons, and sheets and others not yet named or imagined. Within those forms, graphene can include a single layer, two layers, or ≤10 sheets of sp² carbon atoms.

3-Dimensional graphene carbon nanotube carpet-based microsupercapacitors with high electrochemical performance.

In this research, 3-dimensional (3D) graphene/carbon nanotube carpets (G/CNTCs)-based microsupercapacitors (G/CNTCs-MCs) were fabricated in situ on nickel electrodes. The G/CNTCs-MCs show impedance phase angle of -81.5° at a frequency of 120 Hz, comparable to commercial aluminum electrolytic capacitors (AECs) for alternating current (ac) line filtering applications.

Graphene oxide. Origin of acidity, its instability in water, and a new dynamic structural model.

The existing structural models of graphene oxide (GO) contradict each other and cannot adequately explain the acidity of its aqueous solutions. Inadequate understanding of chemical structure can lead to a misinterpretation of observed experimental phenomena. Understanding the chemistry and structure of GO should enable new functionalization protocols while explaining GO's limitations due to its water instability.

Calculating the hydrodynamic volume of poly(ethylene oxylated) single-walled carbon nanotubes and hydrophilic carbon clusters.

Poly(ethylene glycol) (PEG) functionalization of carbon nanotubes (CNTs) is widely used to render CNTs suitable as vectors for targeted drug delivery. One recently described PEGylated version uses an oxidized single-walled carbon nanotube called a hydrophilic carbon cluster (HCC). The resulting geometric dimension of the hybrid PEG-CNT or PEG-HCC is an important factor determining its ability to permeate the cellular membrane and to maintain its blood circulation.

Three-dimensional metal-graphene-nanotube multifunctional hybrid materials.

Graphene was grown directly on porous nickel films, followed by the growth of controlled lengths of vertical carbon nanotube (CNT) forests that seamlessly emanate from the graphene surface. The metal-graphene-CNT structure is used to directly fabricate field-emitter devices and double-layer capacitors. The three-dimensional nanostructured hybrid materials, with better interfacial contacts and volume utilization, can stimulate the development of several energy-efficient technologies.

Synthesis and single-molecule imaging of highly mobile adamantane-wheeled nanocars.

The synthesis and single-molecule imaging of two inherently fluorescent nanocars equipped with adamantane wheels is reported. The nanocars were imaged using 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) as the chromophore, which was rigidly incorporated into the nanocar chassis via Sonogashira cross-coupling chemistry that permitted the synthesis of nanocars having different geometries. In particular, studied here were four- and three-wheeled nanocars with adamantane wheels.

A seamless three-dimensional carbon nanotube graphene hybrid material.

Graphene and single-walled carbon nanotubes are carbon materials that exhibit excellent electrical conductivities and large specific surface areas. Theoretical work suggested that a covalently bonded graphene/single-walled carbon nanotube hybrid material would extend those properties to three dimensions, and be useful in energy storage and nanoelectronic technologies. Here we disclose a method to bond graphene and single-walled carbon nanotubes seamlessly during the growth stage.

Synthesis of dispersible ferromagnetic graphene nanoribbon stacks with enhanced electrical percolation properties in a magnetic field.

Iron-intercalated and tetradecyl-edge-functionalized graphene nanoribbon stacks (Fe@TD-GNRs) can be made from commercially available carbon nanotubes by a facile synthesis. The physical properties of the Fe@TD-GNRs were analyzed by transmission electron microscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, evolved gas analysis, Raman spectroscopy, and scanning electron microscopy. By the intercalation of iron, the alignment of the Fe@TD-GNRs in a magnetic field was enabled.

Large-area Bernal-stacked bi-, tri-, and tetralayer graphene.

Few-layer graphene, with Bernal stacking order, is of particular interest to the graphene community because of its unique tunable electronic structure. A synthetic method to produce such large area graphene films with precise thickness from 2 to 4 layers would be ideal for chemists and physicists to explore the promising electronic applications of these materials. Here, large-area uniform Bernal-stacked bi-, tri-, and tetralayer graphene films were successfully synthesized on a Cu surface in selective growth windows, with a finely tuned total pressure and CH(4)/H(2) gas ratio.

Highly transparent nonvolatile resistive memory devices from silicon oxide and graphene.

Transparent electronic memory would be useful in integrated transparent electronics. However, achieving such transparency produces limits in material composition, and hence, hinders processing and device performance. Here we present a route to fabricate highly transparent memory using SiO(x) as the active material and indium tin oxide or graphene as the electrodes.

Toward the synthesis of wafer-scale single-crystal graphene on copper foils.

In this research, we constructed a controlled chamber pressure CVD (CP-CVD) system to manipulate graphene's domain sizes and shapes. Using this system, we synthesized large (~4.5 mm(2)) single-crystal hexagonal monolayer graphene domains on commercial polycrystalline Cu foils (99.

Effect of Tether Conductivity on the Efficiency of Photoisomerization of Azobenzene-Functionalized Molecules on Au{111}.

We establish the role of tether conductivity on the photoisomerization of azobenzene-functionalized molecules assembled as isolated single molecules in well-defined decanethiolate self-assembled monolayer matrices on Au{111}. We designed the molecules so as to tune the conductivity of the tethers that separate the functional moiety from the underlying Au substrate. By employing surface-enhanced Raman spectroscopy, time-course measurements of surfaces assembled with azobenzene functionalized with different tether conductivities were independently studied under constant UV light illumination.

Design of poly(ethylene glycol)-functionalized hydrophilic carbon clusters for targeted therapy of cerebrovascular dysfunction in mild traumatic brain injury.

Traumatic brain injury (TBI) involves the elaboration of oxidative stress that causes cerebrovascular dysfunction, including impairment of autoregulation of cerebral blood flow. Currently, there is no clinically effective antioxidant treatment for these pathologies. Most currently available antioxidants act through mechanisms in which the antioxidant either transfers the radical or requires regeneration, both of which are impaired in the toxic post-TBI environment.

New routes to graphene, graphene oxide and their related applications.

Recent research has focused upon the growth of the graphene, with a concentration on the synthesis of graphene and related materials using both solution processes and high temperature chemical vapor and solid growth methods. Protocols to prepare high aspect ratio graphene nanoribbons from multi-walled carbon nanotubes have been developed as well as techniques to grow high quality graphene for electronics and other applications where high quality is needed. Graphene materials have been manipulated and modified for use in applications such as transparent electrodes, field effect transistors, thin film transistors and energy storage devices.

Spin dynamics and relaxation in graphene nanoribbons: electron spin resonance probing.

Here we report the results of a multifrequency (~9, 20, 34, 239.2, and 336 GHz) variable-temperature continuous wave (cw) and X-band (~9 GHz) pulse electron spin resonance (ESR) measurement performed at cryogenic temperatures on potassium split graphene nanoribbons (GNRs). Important experimental findings include the following: (a) The multifrequency cw ESR data infer the presence of only carbon-related paramagnetic nonbonding states, at any measured temperature, with the g value independent of microwave frequency and temperature.

Nonlinear photoluminescence imaging of isotropic and liquid crystalline dispersions of graphene oxide.

We report a visible-range nonlinear photoluminescence (PL) from graphene oxide (GO) flakes excited by near-infrared femtosecond laser light. PL intensity has nonlinear dependence on the laser power, implying a multiphoton excitation process, and also strongly depends on a linear polarization orientation of excitation light, being at maximum when it is parallel to flakes. We show that PL can be used for a fully three-dimensional label-free imaging of isotropic, nematic, and lamellar liquid crystalline dispersions of GO flakes in water.

Reversible formation of ammonium persulfate/sulfuric acid graphite intercalation compounds and their peculiar Raman spectra.

Graphite intercalation compounds (GICs) can be considered stacks of individual doped graphene layers. Here we demonstrate a reversible formation of sulfuric acid-based GICs using ammonium persulfate as the chemical oxidizing agent. No covalent chemical oxidation leading to the formation of graphite oxide occurs, which inevitably happens when other compounds such as potassium permanganate are used to charge carbon layers.

Antioxidant carbon particles improve cerebrovascular dysfunction following traumatic brain injury.

Injury to the neurovasculature is a feature of brain injury and must be addressed to maximize opportunity for improvement. Cerebrovascular dysfunction, manifested by reduction in cerebral blood flow (CBF), is a key factor that worsens outcome after traumatic brain injury (TBI), most notably under conditions of hypotension. We report here that a new class of antioxidants, poly(ethylene glycol)-functionalized hydrophilic carbon clusters (PEG-HCCs), which are nontoxic carbon particles, rapidly restore CBF in a mild TBI/hypotension/resuscitation rat model when administered during resuscitation--a clinically relevant time point.

Graphene-Ni-α-MnO2 and -Cu-α-MnO2 nanowire blends as highly active non-precious metal catalysts for the oxygen reduction reaction.

Graphene-like carbon-Ni-α-MnO(2) and -Cu-α-MnO(2) blends can serve as effective catalysts for the oxygen reduction reaction with activities comparable to Pt/C.

Quantitative analysis of structure and bandgap changes in graphene oxide nanoribbons during thermal annealing.

Graphene oxide nanoribbons (GONRs) are wide bandgap semiconductors that can be reduced to metallic graphene nanoribbons. The transformation of GONRs from their semiconductive to the metallic state by annealing has attracted significant interest due to its simplicity. However, the detailed process by which GONRs transform from wide-bandgap semiconductors to semimetals with a near zero bandgap is unclear.

Closed-edged graphene nanoribbons from large-diameter collapsed nanotubes.

The diameter dependence of the collapse of single- and double-walled carbon nanotubes to two- and four-walled graphene nanoribbons with closed edges (CE(x)GNRs) has been experimentally determined and compared to theory. TEM and AFM were used to characterize nanotubes grown from preformed 4.0 nm diameter aluminum-iron oxide particles.

Terahertz and infrared spectroscopy of gated large-area graphene.

We have fabricated a centimeter-size single-layer graphene device with a gate electrode, which can modulate the transmission of terahertz and infrared waves. Using time-domain terahertz spectroscopy and Fourier-transform infrared spectroscopy in a wide frequency range (10-10 000 cm(-1)), we measured the dynamic conductivity change induced by electrical gating and thermal annealing. Both methods were able to effectively tune the Fermi energy, E(F), which in turn modified the Drude-like intraband absorption in the terahertz as well as the "2E(F) onset" for interband absorption in the mid-infrared.