Phenyl isocyanate‐functionalized and hydrazine‐reduced reduced graphene oxide (rG‐O) is treated to produce chlorinated rG‐O (Cl‐rG‐O) platelets. The dielectric constant of the composite film ...containing Cl‐rG‐O shows a 5.5‐fold increase over that of composites of untreated rG‐O and this cyanoethyl‐based polymer, a consequence of the combination of polar and polarizable C–Cl bonds and the increased interfacial polarization.
By combining a graphene layer and aligned multiwalled carbon nanotube (MWNT) sheets in two different configurations, i) graphene on the top of MWNTs and ii) MWNTs on the top of the graphene, it is ...demonstrated that optical, electrical, and electromechanical properties of the resulting hybrid films depend on configurations.
Hybrid films composed of reduced graphene oxide (RG-O) and Cu nanowires (NWs) were prepared. Compared to Cu NW films, the RG-O/Cu NW hybrid films have improved electrical conductivity, oxidation ...resistance, substrate adhesion, and stability in harsh environments. The RG-O/Cu NW films were used as transparent electrodes in Prussian blue (PB)-based electrochromic devices where they performed significantly better than pure Cu NW films.
Polycrystalline graphene grown by chemical vapor deposition (CVD) on metals and transferred onto arbitrary substrates has line defects and disruptions such as wrinkles, ripples, and folding that ...adversely affect graphene transport properties through the scattering of the charge carriers. It is found that graphene assembled with metal nanowires (NWs) dramatically decreases the resistance of graphene films. Graphene/NW films with a sheet resistance comparable to that of the intrinsic resistance of graphene have been obtained and tested as a transparent electrode replacing indium tin oxide films in electrochromic (EC) devices. The successful integration of such graphene/NW films into EC devices demonstrates their potential for a wide range of optoelectronic device applications.
The electrical conductivity and the specific surface area of conductive fillers in conductor‐insulator composite films can drastically improve the dielectric performance of those films through ...changing their polarization density by interfacial polarization. We have made a polymer composite film with a hybrid conductive filler material made of carbon nanotubes grown onto reduced graphene oxide platelets (rG‐O/CNT). We report the effect of the rG‐O/CNT hybrid filler on the dielectric performance of the composite film. The composite film had a dielectric constant of 32 with a dielectric loss of 0.051 at 0.062 wt% rG‐O/CNT filler and 100 Hz, while the neat polymer film gave a dielectric constant of 15 with a dielectric loss of 0.036. This is attributed to the increased electrical conductivity and specific surface area of the rG‐O/CNT hybrid filler, which results in an increase in interfacial polarization density between the hybrid filler and the polymer.
Carbon nanotubes grown on reduced graphene oxide platelets (rG‐O/CNT) hybrid fillers are fabricated and studied to investigate the effect on the dielectric performance of the polymer composite film. The composite film with rG‐O/CNT fillers exhibited a high dielectric performance due to the increased polarization density, which was caused by enhancing the electrical conductivity and specific surface area of hybrid fillers.
Scaling graphene growth using an oven to heat large substrates becomes less energy efficient as system size is increased. We report a route to graphene synthesis in which radio frequency (RF) ...magnetic fields inductively heat metal foils, yielding graphene of quality comparable to or higher than that of current chemical vapor deposition techniques. RF induction heating allows for rapid temperature ramp up/down, with great potential for large scale and rapid manufacturing of graphene with much better energy efficiency. Back-gated field effect transistors on a SiO2/Si substrate showed carrier mobility up to ∼14 000 cm2 V–1 s–1 measured under ambient conditions. Many advantages of RF heating are outlined, and some fundamental aspects of this approach are discussed.
Here, we demonstrate that the assembly of nanostructures with different dimensionalities yields “multicomponent hybrid” transparent conductive films (TCFs) with sheet resistance and optical ...transmittance comparable to that of indium tin oxide (ITO) films. It was shown that sheet resistance of single-component Ag nanowire (NW) films can be further decreased by introducing gold-decorated reduced graphene oxide (RG-O) nanoplatelets that bridge the closely located noncontacting metal NWs. RG-O nanoplatelets can act as a protective and adhesive layer for underneath metal NWs, resulting in better performance of hybrid TCFs compared to single-component TCFs. Additionally, these hybrid TCFs possess antibacterial properties, demonstrating their multifunctional characteristics that might have a potential for biomedical device applications. Further development of this strategy paves a way toward next generation TCFs composed of different nanostructures and characterized by multiple (or additional) functionalities.
We report the reduction of graphene oxide (G-O) films on Al foil using hydrogen as a reducing agent generated during the etching of Al foil in an aqueous solution of hydrochloric acid (HCl). Complete ...etching of the Al substrate results in simultaneous reduction and a free standing film composed of stacked and overlapped reduced graphene oxide (RG-O) platelets. Generation of hydrogen at the G-O/Al interface increases the reduction efficiency of this method that is demonstrated in better electrical conductivity of the obtained films compared to the RG-O films reduced by the similar method but using remote Al foil in HCl solution and hydrazine reduced RG-O films. By transferring the free standing RG-O films onto Ag NW films, hybrid transparent conductive films (TCFs) with opto-electrical properties comparable to that of ITO films were obtained.
We have devised a dielectric film with a chemical vapor deposited graphene interlayer and studied the effect of the graphene interlayer on the dielectric performance. The highly transparent and ...flexible film was a polymer/graphene/polymer ‘sandwich-structure’ fabricated by a one-step transfer method that had a dielectric constant of 51, with a dielectric loss of 0.05 at 1 kHz. The graphene interlayer in the film forms a space charge layer, i.e., an accumulation of polarized charge carriers near the graphene, resulting in an induced space charge polarization and enhanced dielectric constant. The characteristic of the space charge layer for the graphene dielectric film, the sheet resistance of the graphene interlayer, was adjusted through thermal annealing that caused partial oxidation. The dielectric film with higher sheet resistance due to the oxidized graphene interlayer had a significantly lower dielectric constant compared to that with the graphene with lower interlayer sheet resistance. Oxidizing the graphene interlayer yields a smaller and thinner space charge density in the dielectric film, ultimately leading to decreased capacitance. Considering the simplicity of the fabrication process and high dielectric performance, as well as the high transparency and flexibility, this film is promising for applications in plastic electronics.
Studies of the healing of artificial defects in the surface of highly oriented pyrolitic graphite (HOPG) by chemical vapor deposition (CVD) of acetylene show that only single‐layer depth defects ...could be healed completely during the CVD treatment. A promising method is introduced for defect control in surfaces of graphite, graphene, and graphene‐based materials, with important implications for their application.
