Graphene Hybrid Films Research Articles

Graphene/protamine assembled hybrid paper with antibacterial activity

Integrating graphene with other kinds of biochemical molecules is an effective way to improve the properties of graphene film. Proteins are promising candidates for graphene hybridization. We create an effective method to prepare multifunctional graphene hybrid film by incorporation of antibacterial protamine. Protamine could be stably adsorbed on the surface of GO as both a reductant and an antibiotic to realize antimicrobial protamine/RGO conjugates. The presence of decorated protein layers makes it possible to adjust the physical performance of the composite. The obtained hybrid papers show improved hydrophilic property of reduced GO paper. These freestanding papers have a reversible humidity response shape-memory effect and great antibacterial property. The facile strategy possesses a promising way to develop multifunctional antibacterial materials.

In situ mechanical characterization of silver nanowire/graphene hybrids films for flexible electronics

ABSTRACT Flexible transparent conductive films are indispensable for nowadays wearable electronic devices with various applications. However, existing solutions such as ITO and metal mesh were limited by their poor intrinsic stretching ability. In this work, we designed and fabricated silver nanowires (AgNWs) on graphene hybrid films for enhanced mechanical and electrical performance. In situ TEM characterizations show that, beside conductive paths, silver nanowire network, can also contribute to the toughening mechanisms of the hybrid films. Furthermore, bending and electrical tests were applied to examine the corresponding flexible electronics’ performance. Finally, we showed that the fabrication of our AgNW/graphene hybrid films could be scaled up for large film applications and extended to other 1D/2D hybrid systems.

Characterization of a Ferroelectric-Gated Graphene Memory Device Fabricated on a Flexible Substrate by Transfer Process.

The mechanical flexibility of both ferroelectric polymer and graphene provides the possibility for the memory device based on ferroelectric polymer and grapheme to operate on flexible substrate. Here, a memory device was fabricated on flexible substrate through the continuous transfer process of the two units with the ferroelectric polymer and the graphene hybrid film as one unit, and characterized. In particular, characteristics were maintained even with repetitive bending. The transfer process demonstrated in this paper is useful for implementing a memory device on a large-area substrate by consuming a very small amount of graphene.

Controlled Growth of an Mo₂C-Graphene Hybrid Film as an Electrode in Self-Powered Two-Sided Mo₂C-Graphene/Sb₂S0.42Se2.58/TiO₂ Photodetectors.

The monotonic work function of graphene makes it difficult to meet the electrode requirements of every device with different band structures. Two-dimensional (2D) transition metal carbides (TMCs), such as carbides in MXene, are considered good candidates for electrodes as a complement to graphene. Carbides in MXene have been used to make electrodes for use in devices such as lithium batteries. However, the small lateral size and thermal instability of carbides in MXene, synthesized by the chemically etching method, limit its application in optoelectronic devices. The chemical vapor deposition (CVD) method provides a new way to obtain high-quality ultrathin TMCs without functional groups. However, the TMCs film prepared by the CVD method tends to grow vertically during the growth process, which is disadvantageous for its application in the transparent electrode. Herein, we prepared an ultrathin Mo2C—graphene (Mo2C—Gr) hybrid film by CVD to solve the above problem. The work function of Mo2C—Gr is between that of graphene and a pure Mo2C film. The Mo2C—Gr hybrid film was selected as a transparent hole-transporting layer to fabricate novel Mo2C—Gr/Sb2S0.42Se2.58/TiO2 two-sided photodetectors. The Mo2C—Gr/Sb2S0.42Se2.58/TiO2/fluorine-doped tin oxide (FTO) device could detect light from both the FTO side and the Mo2C—Gr side. The device could realize a short response time (0.084 ms) and recovery time (0.100 ms). This work is believed to provide a powerful method for preparing Mo2C—graphene hybrid films and reveals its potential applications in optoelectronic devices.

Highly Flexible and Durable Graphene Hybrid Film Electrode Modified with Aminated β-Cyclodextrin for Supercapacitor

The aminated beta-cyclodextrin (β-CD-N) molecules were first used to modify graphene for fabricating the hybrid film electrode (G/β-CD-N) using a method combining mild water bath heat-treatment and vacuum filtration. As compared with pure graphene film (G) and beta-cyclodextrin (β-CD) modified graphene film (G/β-CD), the prepared G/β-CD-N hybrid film exhibits better hydrophilic property, thermal stability and higher mechanical flexibility. Particularly, the G/β-CD-N hybrid film has a remarkably high areal specific capacitance (614 mF cm−2 at 0.5 mA cm−2), good mechanical flexibility (maintaining 98.2% for 1000 bending/unbending cycles) and long-term cycle stability (maintaining 96.8% for 10000 charge/discharge cycles). Moreover, the assembled G/β-CD-N based flexible and symmetric all-solid-state supercapacitor shows an excellent volumetric specific capacitance of 22.53 F cm−3 at 0.5 mA cm−2 and a high energy density of 3.13 mWh cm−3 at a power density of 0.014 W cm−3. The high comprehensive performances of the developed hybrid film electrodes can be ascribed to the combined effects of β-CD molecules and the amination process. This work provides a new approach for the fabrication of flexible supercapacitor with high performance.

Scalable fabrication of ultrathin free-standing graphene nanomesh films for flexible ultrafast electrochemical capacitors with AC line-filtering performance

The commercialized aluminum electrolytic capacitors (AECs) currently used for alternating current (AC) line-filtering have low specific capacitances, making them usually the largest components in electronic circuits. Herein, an ultrathin free-standing graphene nanomesh film (GMF) with uniform and dense nanoholes has been successfully fabricated by an in-situ carbothermal reduction strategy on the basis of spontaneously assembled graphene hybrid film. Due to the carbothermal reduction reaction between carbon atoms of graphene and the metal oxide nanoparticles in-situ generated during assembly process, in-plane nanopores are generated within graphene film. The pore size and density of GMF can be conveniently tuned by annealing temperature. With large ion-accessible surface area, efficient ion diffusion and electron transport pathways, the typical GMF-based electrochemical capacitor (EC) exhibits a high volumetric capacitance of up to 7.6 F cm−3 at 120 Hz, unprecedented power density of up to 3000 W cm−3, ultrafast frequency response with a phase angle of −82.3°, and a short resistor-capacitor time constant of 0.32 ms at 120 Hz, as well as long-term cycling stability. The performances of these ECs are superior to those of the state-of-the-art carbon-based ECs for this purpose; thus, it is promising to replace commercialized AECs for AC line-filtering in future electronics.

Development of 3D MoO3/graphene aerogel and sandwich-type polyaniline decorated porous MnO2−graphene hybrid film based high performance all-solid-state asymmetric supercapacitors

A new flexible all-solid-state asymmetric supercapacitor with very high energy density has been fabricated by adopting a 3D heterogeneous composite based on polyaniline (PANI) and graphene and enlarging its operating voltage window. This novel supercapacitor is based on the 3D molybdenum oxide/graphene aerogel (MoO3/GF) composite as the negative electrode and the sandwich-type PANI decorated 3D porous manganese dioxide/reduced graphene oxide hybrid film (PANI/(MnO2−RGO)/PANI) as the positive electrode material. Polyvinyl alcohol/potassium hydroxide (PVA/KOH) was used as the gel electrolyte. The self-assembled 3D MoO3/GF was synthesized by hydrothermal route followed by heat treatment in a furnace. For the positive electrode, a facile novel 3D MnO2−RGO porous film was first fabricated by vacuum filtration of MnO2 and GO suspension, followed by hydrothermal chemical reduction. Then, PANI nanofibers were grown on top of the hybrid film. The fabrication steps show a facile formation of the 3D sandwich-type PANI/(MnO2−RGO)/PANI porous hybrid film. The asymmetric supercapacitor (MoO3/GF//PANI/(MnO2−RGO)/PANI) showed a high energy density of 51.91 Wh kg−1 at a power density of 0.838 kW kg−1. The asymmetric cells were flexible, and three cells connected in series could illuminate a green-LED for 62 s.

Large-area self-assembled reduced graphene oxide/electrochemically exfoliated graphene hybrid films for transparent electrothermal heaters

Graphene shows great promise as a high-efficiency electrothermal film for flexible transparent defoggers/defrosters. However, it remains a great challenge to achieve a good balance between the production cost and the properties of graphene films. Here, we proposed a cost-effective self-assembly method to fabricate high-performance, large-area graphene oxide/electrochemically exfoliated graphene hybrid films for heater applications. The self-assembled graphene hybrid films with the area of 20 × 20 cm2 could be transferred onto arbitrary substrates with nonplanar surfaces and simply patterned with the hard mask. After reduction by hydrogen iodide vapor followed by 800 °C thermal treatment, the hybrid films with the transmittance of 76.2% exhibit good heating characteristics and defogging performance, which reach a saturation temperature of up to 127.5 °C when 40 V was applied for 60 s.

One‐Step Growth of Graphene/Carbon Nanotube Hybrid Films on Soda‐Lime Glass for Transparent Conducting Applications

AbstractThe direct growth of graphene on low‐cost soda‐lime glass has attracted widespread attention for its potential to promote the development of high‐value‐added graphene‐based products. For its most promising application as a transparent electrode, a relatively low sheet resistance is highly desired for the derived graphene glass. However, obtaining this result is still a challenge owing to the low catalytic activity of the glass surface, the small domain size of the resultant graphene, and the limited film continuity. Carbon nanotubes (CNT), which have similar structural and electronic properties to those of graphene, have been proposed to bridge/offset the grain boundaries and defects of graphene to improve electron transfer and reduce the sheet resistance. To achieve this, the one‐batch synthesis of highly conductive graphene and multiwalled CNT (MWCNT) hybrid films on soda‐lime glass using a molten‐bed chemical vapor deposition (CVD) method is designed. The thus‐obtained glass exhibits excellent conductivity, transmittance, and outstanding thermal and chemical stability. This highly conductive hybrid material is then employed as a high‐performance liquid‐crystal‐based switchable window. In short, this work is believed to enhance the versatile applications of highly conductive graphene/MWCNT‐hybrid‐coated glass as well as its mass production, considering its compatibility with current glass production techniques.

Transparent Conducting Graphene Hybrid Films To Improve Electromagnetic Interference (EMI) Shielding Performance of Graphene.

Conducting graphene-based hybrids have attracted considerable attention in recent years for their scientific and technological significance in many applications. In this work, conductive graphene hybrid films, consisting of a metallic network fully encapsulated between monolayer graphene and quartz-glass substrate, were fabricated and characterized for their electromagnetic interference shielding capabilities. Experimental results show that by integration with a metallic network the sheet resistance of graphene was significantly suppressed from 813.27 to 5.53 Ω/sq with an optical transmittance at 91%. Consequently, the microwave shielding effectiveness (SE) exceeded 23.60 dB at the Ku-band and 13.48 dB at the Ka-band. The maximum SE value was 28.91 dB at 12 GHz. Compared with the SE of pristine monolayer graphene (3.46 dB), the SE of graphene hybrid film was enhanced by 25.45 dB (99.7% energy attenuation). At 94% optical transmittance, the sheet resistance was 20.67 Ω/sq and the maximum SE value was 20.86 dB at 12 GHz. Our results show that hybrid graphene films incorporate both high conductivity and superior electromagnetic shielding comparable to existing ITO shielding modalities. The combination of high conductivity and shielding along with the materials' earth-abundant nature, and facile large-scale fabrication, make these graphene hybrid films highly attractive for transparent EMI shielding.

Simple and Reliable Lift-Off Patterning Approach for Graphene and Graphene-Ag Nanowire Hybrid Films.

We present a simple, ultrasonic vibration-assisted lift-off-based patterning approach for graphene and graphene-Ag nanowire (NW) hybrid films. A 20 μm width pattern with uniform and smooth pattern edges was neatly defined on various rigid and flexible substrates. The patterned graphene-Ag NW electrodes showed a low sheet resistance of 19 Ω/sq with a high transmittance of 93% at 550 nm, a robust stability against oxidation, and a high reliability under a bending test. The electrodes also exhibited markedly higher performance than that of commercial fluorine-doped tin oxide electrodes for dye-sensitized solar cells. Given its low-cost, high throughput, and nondamaging effect, this simple and reliable patterning approach stimulates the practical applications of graphene-based flexible transparent electrodes in soft electronic and optoelectronic devices.

Carbon nanotubes/holey graphene hybrid film as binder-free electrode for flexible supercapacitors

The practical application of graphene (GR) has still been hindered because of its unsatisfied physical and chemical properties resulting from the irreversible agglomerates. Preparation of GR-based materials with designed porosities is essential for its practical application. In this work, a facile and scalable method is developed to synthesize carbon nanotubes/holey graphene (CNT/HGR) flexible film using functional CNT and HGR as precursors. Owing to the existence of the small amount CNT, the CNT-5/HGR flexible film with a 3D conductive interpenetrated architecture exhibit significantly improved ion diffusion rate compared to that of the HGR. Moreover, CNT-5/HGR flexible film can be used as binder-free supercapacitor electrodes with ultrahigh specific capacitances of 268Fg−1, excellent rate capabilities, and superior cycling stabilities. CNT-5/HGR flexible film could be used to fabricate high-performance flexible supercapacitors electrodes.

Electrophoretic Deposition of SnFe2O4–Graphene Hybrid Films as Anodes for Lithium Ion Batteries

Binder-free SnFe2O4–submillimetre (hundreds of micrometres)-sized reduced graphene oxide (SnFe2O4–srGO) hybrid films were synthesized through electrophoretic deposition and subsequent carbonization treatment. Scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy results revealed that SnFe2O4–srGO hybrid films exhibit both horizontal and vertical channels. SnFe2O4–srGO hybrid films were used as binder-free anodes for lithium ion half-cells and revealed a high capacity of ~1018.5 mA h g−1 at 0.1 A g−1 after 200 cycles. During rate performance tests, a high capacity of 464.1 mA h g−1 (~61.2 % retention) was maintained at a current density of 4 A g−1, indicating an excellent structural stability of SnFe2O4–srGO hybrid films at high current densities.

Electrostatically driven scalable synthesis of MoS2–graphene hybrid films assisted by hydrophobins

Green synthesis of MoS2/biofunctionalized graphene hybrid films assisted by Vmh2 hydrophobin for applications in biosensing and photodetection.

Enhanced oxidation resistance and electrical conductivity copper nanowires–graphene hybrid films for flexible strain sensors

Enhanced oxidation resistance and electrical conductivity copper nanowires–graphene hybrid films were fabricated and which exhibited high sensitivity as flexible strain sensors to monitor human motions.

Graphene-carbon nanotube hybrid films for high-performance flexible photodetectors

Graphene is being actively explored as a candidate material for flexible and stretchable devices. However, the development of graphene-based flexible photonic devices, i.e. photodetectors, is hindered by the low absorbance of the single layer of carbon atoms. Recently, van der Waals bonded carbon nanotube and graphene hybrid films have demonstrated excellent photoresponsivity, and the use of vein-like carbon nanotube networks resulted in significantly higher mechanical strength. Here, we report for the first time, a flexible photodetector with a high photoresponsivity of ~ 51 A/W and a fast response time of ~ 40 ms over the visible range, revealing the unique potential of this emerging all-carbon hybrid films for flexible devices. In addition, the device exhibits good robustness against repetitive bending, suggesting its applicability in large-area matrix-array flexible photodetectors.

Seamless Three-Dimensional Carbon Nanotubes-Grown Graphene Hybrid Films Modified with Heme for Electrochemical Biosensing with High Stability and Sensitivity

INTRODUCTION Seamless three-dimensional (3D) sp2 carbon-based nanomaterials, such as foam-like graphene and carbon nanotubes-grown graphene (CNTs/G) hybrid films, are one of the promising candidates as new electrode materials because of their high electrical conductivity and electroactive surface area per unit planar/footprint area. In particular, charge carriers are movable in all three dimensions without significant contact resistance. Seamless 3D sp2 carbon-based nanomaterials would therefore be applied to highly sensitive sensors and high power fuel cells. The determination of H2O2 using heme-containing proteins, such as horseradish peroxidase (HRP), has widely been employed for pharmaceutical and environmental analyses and immunoassay. Although HRP exhibits high catalytic activity, its stability is low. Meanwhile, hemin, which is one of the heme molecules and the active site of peroxidase, exhibits low catalytic activity, but high stability because of their simple structure without long chain polypeptide, compared with HRP. Even if the catalytic activity per one molecule of hemin is low, the surface coverage of hemin would be significantly enhanced because of its small molecular size, reflecting that the total catalytic activity at the CNTs/G film surface should be improved. In the present work, we therefore constructed seamless 3D CNTs/G film-coated electrodes modified with hemin toward the development of not only highly stable but also highly sensitive electrochemical biosensors. By comparing with seamless two-dimensional graphene film-coated electrodes modified with hemin, we confirmed the superiority of the hemin-modified CNTs/G film in electrochemical biosensing. EXPERIMENTAL The graphene film was prepared on a copper foil in an electric tubular furnace at 1030 ˚C under flowing argon, hydrogen, and methane. After the decoration of iron film at the graphene-formed copper foil by e-beam evaporator, the resultant copper foil was further annealed at 750 ˚C under flowing argon, hydrogen, and acetylene to obtain the seamless 3D CNTs/G film. After the removal of the copper foil and iron film in both FeCl3 and HCl aqueous solutions completely, CNTs/G or graphene films were transferred to the glassy carbon electrode surface. Hemin and HRP were immobilized at each surface of CNTs/G and graphene electrodes via 1-pyrenebutytic acid N-hydroxysuccinimide ester (hemin/CNTs/G, hemin/G, HRP/CNTs/G, and HRP/G electrodes). The H2O2 reduction at hemin-modified CNTs/G and graphene electrodes was evaluated by amperometry. After the working electrode was polarized at +150 mV vs. Ag|AgCl and steady-state current was obtained, H2O2 solution was added into phosphate buffer (pH 7.4) as an electrolyte and steady-state current was monitored. RESULTS AND DISCUSSION Cyclic voltammetry was performed at the hemin/CNTs/G, hemin/G, HRP/CNTs/G, and HRP/G electrodes in deaerated phosphate buffer. Redox peaks appeared at hemin/CNTs/G and hemin/G electrodes at approximately -310 mV, corresponding to (P)Fe2+/3+ (P = porphyrin ring), whereas no redox peaks were clearly observed at HRP/CNTs/G and HRP/G electrodes probably due to deeply embedded redox site in insulating polypeptide. We therefore used hemin/CNTs/G and hemin/G electrodes for further studies. The redox peak current for both electrodes was proportional to the scan rate below at least 500 mV s-1, indicating that the redox reaction was a surface controlled process. In addition, the redox peak current at the hemin/CNTs/G electrode was approximately six-folds larger than that at the hemin/G electrode. This is attributed to the larger electroactive surface area of the CNTs/G film because of 3D structure. Based on the relationship between redox peak currents and scan rate, the surface coverage of hemin at the CNTs/G film was determined to be about ~10-10 mol cm-2. This value was about six times larger than that at the graphene electrode and two orders of magnitude larger than the theoretical value of monolayer HRP (ca. ~10-12 mol cm-2) at the flat surface. We next measured cathodic current responses to H2O2 at CNTs/G and graphene electrodes, on which hemin was immobilized. The response at both electrodes increased with increasing H2O2 up to about 1 mM and then leveled off. Since the current response was not influenced when the electrolyte solution was stirred, the catalytic cathodic currents obtained here were kinetically controlled. All electroactive hemin molecules should therefore contribute to the current. The cathodic current for the hemin/CNTs/G electrode was about six-folds lager than that for the hemin/graphene electrode, reflecting that the surface coverage of electroactive hemin at the CNT/G electrode was about six times larger than that at the graphene electrode, as mentioned above. Thus, the CNTs/G film modified with hemin would be applicable to highly stable and sensitive electrochemical biosensors to H2O2.

Highly conductive natural rubber–graphene hybrid films prepared by solution casting and in situ reduction for solvent-sensing application

High-performance solvent sensors have extensive applications in many fields. In this work, we report a quite efficient method to fabricate electrically conductive natural rubber (NR)-reduced graphene oxide (RGO) hybrid films for solvent-sensing application. The RGO/NR hybrid films with three-dimensional continuous RGO networks were prepared by blending graphene oxide suspension with rubber latex, followed by solution casting and then in situ hydroiodic acid reduction. The electrical conductivity of hybrid film was as high as 49.3 S/m when filled with 5.00 vol% RGO, and the film exhibited an extremely low percolation threshold of 0.31 vol%. The solvent-sensitive properties were evaluated by detecting the variation in electrical resistance due to the swelling of NR matrix. It was noted that the RGO/NR hybrid films exhibited exceptional stimuli responses for organic solvents, however, with different sensing responses for different solvents. Due to the reconstruction of continuous RGO networks after solvent evaporation, the hybrid films performed an excellent repeatability for solvent sensitivity. Therefore, as intelligent materials, the conductive RGO/NR hybrid films have great potential applications in sensing fields.

Organic Dye Graphene Hybrid Structures with Spectral Color Selectivity

This study characterizes a hybrid structure formed between graphene and organic dye molecules for use in photodetectors with spectral color selectivity. Rhodamine‐based organic dye molecules with red, green, or blue light absorption profiles are deposited onto a graphene surface by dip‐coating. UV–vis absorption spectroscopy, charge transport measurements, and density functional theory based calculations reveal that the photoresponses of the dye graphene hybrid films are governed by the light absorption of the dye molecules and also by the photo‐excited‐charge‐transfer‐induced photocurrent gain. The hybrid films respond only to photons with an energy exceeding the band gap of the immobilized dye. Dye‐Graphene charge transfer is affected by the distance and direction of the dipole moment between the two layers. The resulting hybrid films exhibit spectral color selectivities with responsivities of ≈103 A W−1 and specific detectivities of ≈1010 Jones. This study demonstrates the successful operation of photodetectors with a full‐color optical bandwidth using hybrid graphene structures coated with a mixture of dyes. The strategy of building a simple hybrid photodetector can further offer many opportunities to be also tuned for other optical functionalities using a variety of commercially available dye molecules.

Enhanced power factor of poly (3,4-ethyldioxythiophene):poly (styrene sulfonate) (PEDOT:PSS)/RTCVD graphene hybrid films

The thermoelectric generator has been an attractive alternative power source to operate a wireless sensor node. Usually, inorganic compounds are most often used in thermoelectric devices, and hence, are extensively studied due to their superior thermoelectric performance. We have investigated a novel interfacial technique to fabricate a hybrid film of highly conductive PEDOT:PSS (poly 3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) and graphene. Organic materials PEDOT doped with PSS exhibits outstanding electrical properties due to its high conductivity, low bandgap, and energy migration. Furthermore, we utilized graphene fabricated by rapid thermal chemical vapor deposition (RTCVD) as a thermoelectric material. Our results show that the interfacial technique between substrate and hybrid film could be clearly improved due to the UV plasma treatment. The thermoelectric hybrid film of PEDOT:PSS and RTCVD graphene (P/RTG) exhibited an enhanced power factor of 56.28 μW m−1 K−2 with a Seebeck coefficient of 54.0 μV K−1.