Fast scanning growth of high-quality graphene films on Cu foils fueled by dimeric carbon precursor

Carbon source precursor is a critical factor governing chemical vapor deposition growth of graphene films.Methane(CH4),has been the most commonly used precursor in the last decade,but it presents challenges in terms of decomposition efficiency and growth rate.Here we thoroughly evaluated acetylene(C2H_(2)),a precursor that is probably for providing carbon dimer(C2)species,for fast growth of large-scale graphene films.We find that the graphene growth behaviors fueled by C2H_(2) exhibit unconventional localized growth behavior with significant advantages in terms of high growth rate,which mainly ascribe to the as-decomposed C2 species.Therefore,a C2-fueled scanning growth strategy is proposed,and the fast scanning growth rate of 40 cm/min was experimentally demonstrated.This growth strategy is compatible with the approach of unidirectional growth of single-crystal graphene films,and the as-grown graphene films are of high-quality.This work demonstrates a reliable and promising strategy for the rapid synthesis of high-quality graphene film and may pave the avenue to cost-effective mass production of graphene materials in the roll-to-roll system.

Large-scale fabrication of re duce d graphene oxide-sulfur composite films for flexible lithium-sulfur batteries

The rapid development of flexible electronic devices requires the design of flexible energy-storage devices. Lithium-sulfur(Li-S) batteries are attracting much interest due to their high energy density. Therefore, flexible Li-S batteries with high areal capacity are desired. Herein, we fabricated freestanding reduced graphene oxide-sulfur(RGO@S) composite films with a cross-linked structure using a blade coating technique, followed by a subsequent chemical reduction. The porous cross-linked structure endows the composite films with excellent electrochemical performance. The batteries based on RGO@S composite films could exhibit a high discharge capacity of 1381 m Ah/g at 0.1 C and excellent cycle stability. Furthermore, the freestanding composite film possesses excellent conductivity and high mechanical strength. Therefore, they can be used as the cathodes of flexible Li-S batteries. As a proof of concept, soft-packaged Li-S batteries were assembled and remained stable electrochemical performance under different bending states.

Highly Sensitive Flexible Pressure Sensors based on Graphene/Graphene Scrolls Multilayer Hybrid Films

In recent years,flexible pressure sensors have attracted much attention owing to their potential applications in motion detection and wearable electronics.As a result,important innovations have been reported in both conductive materials and the underlying substrates,which are the two crucial components of a pressure sensor.1D materials like nanowires are being widely used as the conductive materials in flexible pressure sensors,but such sensors usually exhibit low performances mainly due to the lack of strong interfacial interactions between the substrates and 1D materials.In this paper,we report the use of graphene/graphene scrolls hybrid multilayers films as the conductive material and a microstructured polydimethylsiloxane substrate using Epipremnum aureum leaf as the template to fabricate highly sensitive pressure sensors.The 2D structure of graphene allows to strongly anchor the scrolls to ensure the improved adhesion between the highly conductive hybrid films and the patterned substrate.We attribute the increased sensitivity(3.5 k Pa^-1),fast response time(<50 ms),and the good reproducibility during 1000 loading-unloading cycles of the pressure sensor to the synergistic effect between the 1D scrolls and 2D graphene films.Test results demonstrate that these sensors are promising for electronic skins and motion detection applications.

Mechanically flexible reduced graphene oxide/carbon composite films for high-performance quasi-solid-state lithium-ion capacitors

Practical applications of diverse flexible wearable electronics require electrochemical energy storage(EES)devices with multiple configurations.Moreover,to fabricate flexible EES devices with high energy density and stability,organic integration from electrode design to device assembly is required.To address these challenges,a free-standing reduced graphene oxide(rGO)/carbon film with a unique sandwich structure has been designed via the assistance of vacuum-assistant filtration for lithium-ion capacitors(LICs).The graphene acts as not only a binder to construct a three-dimensional conductive network but also an active material to provide additional capacitive lithium storage sites,thus enabling fast ion/electron transport and improving the capacity.The designed rGO/hard carbon(rGO/HC)and rGO/activated carbon(rGO/AC)free-standing films exhibit enhanced specific capacities(513.7 mA h g^(-1)for rGO/HC and 102.8 mA h g^(-1)for rGO/AC)and excellent stability.Moreover,the integrated flexible quasi-solid-state rGO/AC//rGO/HC LIC devices possess a maximum energy density of 138.3 Wh kg^(-1),a high power density of 11 kW kg^(-1),and improved cycling performance(84.4%capacitance maintained after 10,000 cycles),superior to the AC//HC LIC(43.5%retention).Such a strategy enlightens the development of portable flexible LICs.

Direct fabrication of flexible tensile sensors enabled by polariton energy transfer based on graphene nanosheet films

A fundamental problem in the direct manufacturing of flexible devices is the low melting temperature of flexible substrates,which hinders the development of flexible electronics.Proposed here is an electron-cyclotron-resonance sputtering system that can batch-fabricate devices directly on flexible substrates under a low temperature by virtue of the polariton energy transfer between the plasma and the material.Flexible graphene nanosheet-embedded carbon(F-GNEC)films are manufactured directly on polyimide,polyethylene terephthalate,and polydimethylsiloxane,and how the substrate bias(electron energy),microwave power(plasma flux and energy),and magnetic field(electron flux)affect the nanostructure of the F-GNEC films is investigated,indicating that electron energy and flux contribute to the formation of standing graphene nanosheets in the film.The films have good uniformity of distribution in a large size(17 mm×17 mm),and tensile and angle sensors with a high gauge factor(0.92)and fast response(50 ms)for a machine hand are obtained by virtue of the unique nanostructure of the F-GNEC film.This work sheds light on the quantum manufacturing of carbon sensors and its applications for intelligent machine hands and virtual-reality technology.

Electrochemical study and application on rutin at chitosan/graphene films modified glassy carbon electrode

Graphene（G） was dispersed into 0.5% chitosan（Chit） solution,then the composite films were coated on glassy carbon electrode（GCE）,the electrochemical behavior of rutin on a Chit/G modified GCE was investigated and the electrochemical parameters of rutin were calculated.Rutin effectively accumulated on the Chit/G/GCE and caused a pair of redox peaks at around 408 mV and 482 mV（vs.SCE） in 0.1M phosphate buffer solution（pH 4.0）.Under optimized conditions,the anodic peak current was linear to the rutin concentration in the range of 5×107-1.04×105M.The regression equation was：y 9.9219x-0.0025,r=0.9958.The proposed method was successfully used for the determination of rutin content in tablet samples with satisfactory results.

Room-Temperature Humidity Sensing Using Graphene Oxide Thin Films

In this article, we report on a room-temperature humidity sensing device using graphene oxide (GO) thin films synthesized by chemical exfoliation. Changes in the device conductivity are measured for varying relative humidity in the experimental chamber. Experiments are carried out for relative humidity varying from 30% to 95%. We observe a difference in the results obtained for low relative humidity (50%), and propose a sensing mechanism to explain this difference. Although the sensor exhibits some hysteresis at high relative humidities, a method to “reset” the sensor is also proposed. The sensing device has high sensitivity and fast response time.

Preparation and Characterization of Co_(3)O_(4)/Graphene/Cellulose Nanofiber Composite Films

Nanocellulose has served as an eye-catching nanomaterial for constructing advanced functional devices with renewability,light weight,flexibility,and environmental friendliness.In this study,Co_(3)O_(4)/graphene/cellulose nanofiber(CNF)flexible composite films,in which the CNF acted as a spacer for the graphene,were prepared via a facile and scalable vacuum filtration method.The effects of the CNF on the microstructure,hydrophilicity,thermal stability,tensile strength,surface resistance,and electrochemical performance of the Co_(3)O_(4)/graphene/CNF composite films were systematically investigated.The results showed that the synergistic interaction of the CNF and graphene substantially improved the overall properties of the Co_(3)O_(4)/graphene/CNF composite films,particularly their hydrophilicity and tensile strength.Meanwhile,Co_(3)O_(4)/graphene/CNF composite films with a CNF content of 4%appeared to have the optimal electrochemical performance,with an area specific capacitance of 56 mF/cm^(2) and prominent capacitance retention of 95.6%at a current density of 1 A/g after 1000 cycles.This work demonstrated that the prepared Co_(3)O_(4)/graphene/CNF flexible composite films have great application potential in the field of flexible energy storage devices.

Electrochemical Preparation of Polypyrrole/Graphene Films on Titanium Mesh as Active Materials for Supercapacitors

Films of polypyrrole/graphene on titanium mesh were prepared by electrochemical reduction of the fresh dried foam films of graphene oxide followed by an electrochemical polymerization of pyrrole. The as-obtained composite had highly surface area, conductivity, and could be used as the electrode for supercapacitors, especially directly used as the active materials in free of binders while the Ti mesh worked as the collector. Plenty of polypyrrole nanoparticles formed on the surface of reduced graphene film, and some fiber-like aggregates could be formed during the polymerization, which worked as the material for pseudo-capacitance. The specific capacitance of the supercapacitor reached 400 F/g and showed high stability with retaining capacitance of 82% after 5000 cycles, indicating that the nanocomposite is a suitable active material for supercapacitors.

High-Quality Bi_2Te_3 Single Crystalline Films on Flexible Substrates and Bendable Photodetectors

Recently, great efforts have been made in the fabrication of arbitrary warped devices to satisfy the requirement of wearable and lightweight electronic products. Direct growth of high crystalline quality films on flexible substrates is the most desirable method to fabricate flexible devices owing to the advantage of simple and compatible preparation technology with current semiconductor devices, while it is a very challenging work, and usually amorphous, polycrystalline or discontinuous single crystalline films are achieved. Here we demonstrate the direct growth of high-quality Bi2 Te3 single crystalline films on flexible polyimide substrates by the modified hot wall epitaxy technique. Experimental results reveal that adjacent crystallites are coherently coalesced to form a continuous film, although amounts of disoriented crystallites are generated due to fast growth rate. By inserting a quartz filter into the growth tube, the number density of disoriented crystallites is effectively reduced owing to the improved spiral interaction. Furthermore, flexible Bi2 Te3 photoconductors are fabricated and exhibit strong near-infrared photoconductive response under different degrees of bending, which also confirms the obtained fexible films suitable for electronic applications.

Preparation of High-Quality Poly-Si Films by a Solid Phase Crystallizing Method

A solid phase crystallizing method has been developed to grow a Si crystal at tem-peratures as low as 550 ℃. Using this method, a high-quality thin-film polycrystalline silicon (Poly-Si) was obtained. The largest grain size, examined with X-ray diffraction spectroscopy and scanning electron microscopy images of recrystallized samples, is approximately 1 /μm for substrate temperature at 300 ℃ and annealed at 550℃ for 3 hours.

Growth of High-Quality Superconducting FeSe0.5Te0.5 Thin Films Suitable for Angle-Resolved Photoemission Spectroscopy Measurements via Pulsed Laser Deposition

High-quality superconducting FeSe0.5 Te0.5 films are epitaxiMly grown on different substrates by using the pulsed laser deposition method. By measuring the transport properties and surface morphology of films grown on single- crystal substrates of Al2O3 （0001）, SrTiO3 （001）, and MgO （001）, as well as monitoring the real-time growth process on MgO substrates with reflection high energy electron diffraction, we find the appropriate parameters for epitaxial growth of high-quality FeSe0.5 Te0.5 thin films suitable for angle-resolved photoemission spectroscopy measurements. We further report the angle-resolved photoemission spectroscopy characterization of the super- conducting films. The clearly resolved Fermi surfaces and the band structure suggest a sample quality that is as good as that of high-quality single-crystals, demonstrating that the pulsed laser deposition method can serve as a promising technique for in situ preparation and manipulation of iron-based superconducting thin films, which may bring new prosperity to angle-resolved photoemission spectroscopy research on iron-based superconductors.

New Insight into the Graphene Based Films Prepared from Carbon Fibers

In this work, ultrathin sections from longitudinal polyacrylonitrile (PAN) based T700 and T300 carbon fibers were prepared by ultramicrotomy, a promising graphene based thin films were developed in one step at ambient temperature. It is investigated that the network-graphene planes composed with carbon atoms are partly straight and partly twisted in the thin films prepared from T700 carbon fibers, the distance between the carbon atoms of network-graphene plane decreases, the order design of graphene in the films prepared from T700 carbon fibers is denser and its arrangement shows a preferred orientation along the drawing direction, its consistency of the neighboring graphene based planes is better, moreover, the relative content of the forming SP2-hybridized orbit of carbon atoms in the films prepared from T700 carbon fibers is higher, in the other words, the fact of the graphene based film prepared from carbon fibers without having the characteristic of skin-core structure has been verified.

Electron Emission of Graphene-Diamond Hybrid Films Using Paraffin Wax as Diamond Seeding Source

We present a scalable, reproducible and economic process for the fabrication of diamond and diamond-graphene hybrid films using paraffin wax as a seeding source for diamond. The films were characterized using Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron energy loss spectroscopy (EELS). Raman spectra show the characteristic band of diamond at 1332 cm-1 and the D, G, and 2D bands of graphene at 1360, 1582 and 2709 cm-1, respectively. Electron microscopy confirms the microcrystalline nature of the diamond films with crystal size in the range of 0.5 μm to 1.0 μm, and the hybrid film consists of microcrystalline diamond attached to thin, semi-transparent graphene flakes. The graphene-diamond hybrid films exhibit a turn-on field of about 3.6 V/μm with a prolonged current stability of at least 135 h.

Materials for Spintronics: Magnetic and Transport Properties of Ultrathin (Monolayer Graphene)/MnO(001) and MnO(001) Films

Results of investigations of band structure, Fermi surface and effective masses of charge carriers in the ultrathin (monolayer graphene)/MnO(001) and MnO(001) films are presented using the method of the density functional theory. Features of spin states of valence band and Fermi level as well as an interatomic interaction in these systems are discussed. A magnetic moment at Mn atom is estimated and an effect of spin polarization at atoms of oxygen and carbon has been revealed which natures are discussed. By calculations of structural energies for 2D (monolayer graphene)/MnO(001) and 2D MnO(001) a stability of these systems has been ascertained. In the 2D (monolayer graphene)/MnO(001) and 2D MnO(001) systems the band structure calculations for the 2D systems mentioned above point out that tensor components of effective masses of both electrons and holes are in the ranges of (0.15 - 0.54) m0 and (0.38 - 1.27) m0 respectively. Mobility estimations of two-dimensional charge carriers for a 2D (monolayer graphene)/MnO(001)AF2 heterostructure have been performed.

Synthesis and Characterization of Graphene Oxide and Reduced Graphene Oxide Thin Films Deposited by Spray Pyrolysis Method

Graphene Oxide (GO) was chemically synthesized from Natural Flake Graphite (NFG). The GO was chemically reduced to Reduced Graphene Oxide (RGO) using hydrazine monohydrate. Thin films of GO and RGO were also deposited on sodalime glass substrate using spray pyrolysis technique (SPT). The samples were characterized using Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray (EDS) facility attached to it, UV-Visible Spectrometry and Four-Point probe. The FTIR spectra showed the addition of oxygen functionality groups in GO while such groups was drastically reduced in RGO. SEM micrograph of GO thin film showed a porous sponge-like structure while the micrograph of RGO thin film showed evenly distributed and well connected graphene structure. The EDX spectrum of RGO showed that there was decrease in oxygen content and increase in carbon content of RGO when compared to GO. The optical analysis of the GO and RGO thin films gave a direct energy bandgap of 2.7 eV and 2.2 eV respectively. The value of sheet resistance of GO and RGO films was determined to be 22.9 × 106Ω/sq and 4.95 × 106Ω/sq respectively.

Progress and roadmap for graphene films in electromagnetic interference shielding

Graphene films(GFs)featured with exceptional electrical property and macroscopic ultrathin two-dimensional structure demonstrate infinite potentials for electromagnetic interference shielding applications.By retrospect-ing the advanced achievements of GF-type shielding materials over the past decades,this review aims to provide a roadmap driven by the great progress and inspire future disruptive innovations.The fabrication methods of GFs are systematically discussed,with a particular emphasis on creative approaches.Strategies to optimize the shielding performance are elaborated in terms of manufacturing methods,shielding efficiency and properties,corresponding mechanisms,challenges and perspectives.Likewise,advancements of multifunctional GFs simul-taneously satisfying electromagnetic shielding with thermal dissipation or transparent requirements are outlined.Using history as a mirror,a clear insight into this rapidly growing field is given,and corresponding current chal-lenges and future opportunities in the fabrication and application of GF-family shielding materials are highlighted and envisioned.We hope this review can encourage further innovations in this exciting branch of research and inspire scientists from both academia and industry to promote revolutionary breakthroughs in GF-shields for next-generation shielding applications.

Graphene film for thermal management:A review

Thermal conductivity and thermal dissipation are of great importance for modern electronics due to the increased transistor density and operation frequency of contemporary integrated circuits.Due to its exceptionally high thermal conductivity,graphene has drawn considerable interests worldwide for heat spreading and dissipation.However,maintaining high thermal conductivity in graphene laminates(the basic technological unit)is a significant technological challenge.Aiming at highly thermal conductive graphene films(GFs),this prospective review outlines the most recent progress in the production of GFs originated from graphene oxide due to its great convenience in film processing.Additionally,we also consider such issues as film assembly,defect repair and mechanical compression during the post-treatment.We also discuss the thermal conductivity in in-plane and through-plane direction and mechanical properties of GFs.Further,the current typical applications of GFs are presented in thermal management.Finally,perspectives are given for future work on GFs for thermal management.

Self-assembled activated carbon sandwiched graphene film for symmetrical supercapacitors

Activated carbon(AC)particles sandwiched reduced graphene oxide sheets(rGO)film has been successfully fabricated via a facile self-assemble approach.The as-formed AC/rGO film is self-standing,flexible and mechanically robust,allowing to be transferred to any substrate on demand without rupture.Since AC particles effectively suppressed the restacking of the rGO sheet,AC/rGO film exhibits loose layer-by-layer stacking structures with various gaps between AC particles and rGO sheets,which is different from compact structures of pure graphene films.The as-formed gaps provide fast diffusion channels for electrolyte ions and enhanced accessible surface area of rGO.Therefore,the AC/rGO electrode delivers improved electrochemical performance over the voltage range of 0.0−3.0 V.This work offers a promising strategy to design free-standing supercapacitor electrodes based on traditional nanocarbon materials.

Computer simulation of the bombardment of a copper film on graphene with argon clusters

The process of graphene cleaning of a copper film by bombarding it with Ar_（13） clusters is investigated by the molecular dynamics method.The kinetic energies of the clusters are 5,10,20,and 30 eV and the incident angles are θ= 90°,75°,60°,45°,and 0°.It is obtained that the cluster energy should be in the interval 20 eV-30 eV for effective graphene cleaning.There is no cleaning effect at vertical incidence（θ =0°） of Ar_（13） clusters.The bombardments at 45° and 90° incident angles are the most effective on a moderate and large amount of deposited copper,respectively.