Advantages Of Graphene Research Articles

Mediating coherent acoustic phonon oscillation of a 2D semiconductor/3D dielectric heterostructure by interfacial engineering

Abstract Coherent acoustic phonon (CAP) oscillation of 2D layered semiconductor/3D dielectric heterostructure generated by femtosecond laser pulse excitation can realize ultrafast photoacoustic conversion, while the photoacoustic conversion efficiency suffers from interfacial phonon scatterings of simultaneously laser-induced lattice heat. Here, taking advantage of graphene’s high thermal conductivity and large acoustic impedance, we demonstrate that phonon scatterings can be markedly mediated in a MoS$_2$/graphene/glass heterostructure via femtosecond laser pump-probe measurements. Equilibrium temperatures of MoS$_2$ lattice have been cooled down by about 45 %. As a benefit, both lifetime of CAP oscillations and pump pulse-picosecond acoustic pulse energy conversion efficiency have been enhanced by a factor of about 2. Our results constitute insights into CAP manipulations via interfacial engineering, that are fundamentally important for ultrafast photoacoustics based on 2D layered semiconductors.

Electrochemical Biosensors Composed of Polyethylenimine (PEI) and Graphene Derivatives for Rapid Detection of Alzheimer’s Disease

Graphene materials can be used as nanofillers in polymers to take advantage of graphene's suitable properties. Graphene-PEI composites are materials that combine the unique properties of graphene and PEI. These composites are made by combining graphene with PEI through physical or chemical method. The resulting material is characterized by enhanced mechanical properties, improved electrical conductivity and increased stability. By incorporating graphene into biosensor platforms, it can improve overall’s performance, including sensitivity, specificity and response. In this work, the detection of anti-βA40 biomarker was tested. Beta-amyloid peptide (βA1-40) was incorporated into liposomes of Dipalmitoyl Phosphatidylglycerol (DPPG) and was immobilized using Layer-by-Layer self-assembling technique on PEI_graphene derivatives composites. To obtain these composites it was utilized graphene oxide (GO) from Hummers’ method, it’s thermally reduced form (rGO) and also electrochemically exfoliated graphene (EEG). MilliQ water was added to the PEI to obtain a concentration of 2mg/mL and stirred for 30 min at room temperature for complete dissolution of the PEI. Then EEG, GO and rGO were added to PEI solution and subjected to ultrasonication in a Hielscher UP400ST sonicator, using the H14 probe for 30 minutes to obtain a homogeneous and stable dispersion.Carbon microelectrodes modified with PEI-graphene derivatives composites and (DPPG +Aβ-40) were used as biosensors platforms to detect anti-Aβ40 related to Alzheimer's disease. The assembly of the biosensors is shown in Figure 1. Cyclic Voltammetry was performed in three cycles, at a potential of -0.6 V to 0.6 V and scan rate of 0.05 V s-1 to evaluate the sensory response. The electrochemical measurements were performed with saline phosphate buffer solution (PBS). The morphology of PEI and PEI_graphene oxide can be seen in Figure 2. The large surface area of graphene allows for increased binding sites for bioreceptors, which may favor the adsorption of Aβ-40 peptide, improving signal transduction and sensitivity of the biosensor. The wettability of the composites was obtained through measurements of the static contact angle using the Ramé-Hart Contact Angle Goniometer (model 100-25-A). Figure 3 presents the contact angle for a film layer of the composites. All PEI_graphene derivative composites showed hydrophilic behavior (θ < 90°), PEI_EEG composite stood out as less hydrophilic (θ = 68°) among all composites. Hydrophilicity is essential in biosensors because it affects the interactions between the biological recognition elements and the target analytes, as well as the overall stability and reliability of the biosensor. Figure 4 presents the calibration curves using the normalized area obtained from cyclic voltammetry of the biosensors manufactured with 2 bilayers (PEI_graphene derivative/DPPG+Aβ40) and anti-Aβ40 biomarker in concentrations ranging from 1 ng mL to 5 µg mL-1. Among the tested PEI_graphene derivatives composites, the ones with EEG and RGO stood out in relation to pure PEI. Table 1 presents the adjusted R-square of the data in Figure 4. All composites, except PEI_GO, showed excellent linear fit, adjusted R-square close to 1 in the detection range between 1 and 1000 ng mL-1. The PEI_graphene oxide composite can be used in biosensors to enable rapid and efficient transduction of the binding signal, leading to improved detection performance. Figure 1

Molybdenum disulfide polymeric nanoarchitectures and applications: A review

AbstractThe advent of nanotechnology has escalated the quest for novel 2‐D nanomaterials (NMs) with the capability of surpassing all known advantages of graphene (GN), and more, resulting in the recent discovery of molybdenum disulfide (MoS2). MoS2 is a 2‐D sheet‐like NM, possessing unique layered “sandwich” architecture, in addition to chemical, electronic, and optical features similar to those of GN, thereby expanding their scope of applications for transistors, solar cells, catalysts, sensors, and so on. The embedment of MoS2 inside polymeric substrates (PP, PEG, epoxy, and so on), have resulted in the construction of MoS2 polymer nanoarchitectures exhibiting superior mechanical, thermal, and flame retardant features with multifunctional and versatile applications. Hence, this elucidation discusses recently emerging research activities in MoS2 polymeric nanoarchitectures and multifaceted applications.

Fabrication of Graphene‐cuprous Oxide Hybrid Paste Electrodes for Capillary Electrophoretic Measurement of Polyhydroxy Compounds

AbstractAn alkaline mixture containing copper(II) spices, graphene oxide and glucose was heated by far infrared radiations to synthesize graphene‐cuprous oxide hybrid. The hybrid was blended with mineral oil and packed into tubes to fabricate paste electrodes. The electrodes were coupled with capillary electrophoresis for the detection of polyhydroxy compounds. The sensitivities of them on the hybrid electrodes were significantly enhanced by taking advantages of graphene and cuprous oxide. The contents of polyhydroxy compounds in tobacco method was determined by the electrodes with satisfactory assay results.

PVA-Based MMMs for Ethanol Dehydration via Pervaporation: A Comparison Study between Graphene and Graphene Oxide

Two different types of 2D nanosheets, including hydrophobic graphene (GR) and hydrophilic graphene oxide (GO), were filled into poly (vinyl alcohol) (PVA) polymers to prepare mixed matrix membranes (MMMs) for ethanol dehydration via pervaporation. The relationship between the physical/chemical properties of graphene and pervaporation performance of MMMs was investigated by a comparison of GR/PVA and GO/PVA MMMs in microstructure and PV performance. The incorporation of GO nanosheets into PVA reduced PVA crystallinity and enhanced the membrane hydrophilicity, while the incorporation of GR into PVA led to the opposite results. The incorporation of GR/GO into PVA depressed the PVA membrane swelling degree, and the incorporation of GR showed a more obvious depression effect. GR/PVA MMMs showed a much higher separation factor than GO/PVA MMMs, while they exhibited a much lower permeation flux than GO/PVA MMMs and pristine PVA membranes. The huge difference in microstructure and performance between GO/PVA and GR/PVA MMMs was strongly associated with the oxygen-containing groups on graphene lamellae. The higher permeation flux of GO/PVA MMMs was ascribed to the facilitated transport of water molecules induced by oxygen-containing groups and exclusive channels provided by GO lamellae, while the much lower permeation flux and higher separation factor GR/PVA MMMs was resulted from the smaller GR interplanar spacing (0.33 nm) and hydrophobicity as well as barrier effect of GR lamellae on the sorption and diffusion of water molecules. It was presumed that graphene intercalated with an appropriate number of oxygen-containing groups might be a good choice to prepare PVA-based MMMs for ethanol dehydration, which would combine the advantages of GR’s high interlayer diffusion selectivity and GO’s high permeation properties. The investigation might open a door to achieve both of high permeation flux and separation factor of PVA-based MMMs by tuning the microstructure of graphene.

Study on Graphene Field Effect Tube Photoelectric Sensor

As a special device that converts the measured physical quantity into electrical signal or other signal output according to specific rules, the sensor becomes the nerve ending connecting the natural world and the electronic world. Photoelectric sensors, as an important branch of sensors, play a central role in applications such as optical communication, imaging and detection, as electronic systems perceive external eyes. At present, the main sensor products in the market have defects such as limited detection wavelength, low responsivity and complex structure. In view of these problems and practical needs, combined with the advantages of graphene with wide detection wavelength range, high influence and high electron mobility, this paper proposes a graphene field effect tube photoelectric sensor with silicon nitride protective layer, and its preparation process, environmental stability test and photoelectric response characteristics are studied and analyzed. The results have potential application value. Graphene field effect transistor photoelectric sensor has many excellent characteristics, such as wide detection band, high response, good environmental stability and easy preparation and integration. It provides a new research idea for MEMS photoelectric sensor and has a very broad application prospect.

Opportunities Offered by Graphene Nanoparticles for MicroRNAs Delivery for Amyotrophic Lateral Sclerosis Treatment.

Amyotrophic lateral sclerosis (ALS) is characterized by the degeneration and death of motor neurons. This neurodegenerative disease leads to muscle atrophy, paralysis, and death due to respiratory failure. MicroRNAs (miRNAs) are small non-coding ribonucleic acids (RNAs) with a length of 19 to 25 nucleotides, participating in the regulation of gene expression. Different studies have demonstrated that miRNAs deregulation is critical for the onset of a considerable number of neurodegenerative diseases, including ALS. Some studies have underlined how miRNAs are deregulated in ALS patients and for this reason, design therapies are used to correct the aberrant expression of miRNAs. With this rationale, delivery systems can be designed to target specific miRNAs. Specifically, these systems can be derived from viral vectors (viral systems) or synthetic or natural materials, including exosomes, lipids, and polymers. Between many materials used for non-viral vectors production, the two-dimensional graphene and its derivatives represent a good alternative for efficiently delivering nucleic acids. The large surface-to-volume ratio and ability to penetrate cell membranes are among the advantages of graphene. This review focuses on the specific pathogenesis of miRNAs in ALS and on graphene delivery systems designed for gene delivery to create a primer for future studies in the field.

Effects of Field-Effect and Schottky Heterostructure on p-Type Graphene-Based Gas Sensor Modified by n-Type In2O3 and Phenylenediamine

Over the past decade, advantages of graphene in high-performance gas sensing have been demonstrated, especially for single- or few-layered graphene wherein the theoretical and technical advances are mature. Owing to the complexity of multi-layered graphene (MLG) sensors and the increasing demand for practical applications, there is an urgent need to comprehensively understand the correlation between MLG and its derivatives for developing next-generation gas sensors. Herein, theoretical and empirical strategies for obtaining better gas sensors are developed. These approaches can be divided into three categories: 1) building devices with Fermi level near the Dirac point (EF,Dirac), 2) enhancing the adsorption probability f(x) and driving force (gap between as-prepared and saturated Fermi levels), and 3) accelerating mobility. A device employing p-type reduced graphene oxide (rGO) decorated with n-type indium oxide and phenylenediamine (GIP) was designed and fabricated by adopting approaches 1 and 2 (EF,Dirac and f(x) enhancement). The resulting hole-compensated GIP displayed a remarkable response to formaldehyde (HCHO), which was 66.3 times higher than rGO, with faster response/recovery. GIP also exhibited higher selectivity for HCHO than for ammonia and trimethylamine. We believe that the classification will untangle the complex role of graphene in sensing, helping to design next-generation advanced gas sensors.

Computational screening toward quantum capacitance of transition-metals and vacancy doped/co-doped graphene as electrode of supercapacitors

It is of importance to explore electrode materials with high specific capacitance, improving energy density of supercapacitors. Generally, the composition and structure of electrode materials determines its function. Despite many advantages of graphene, low intrinsic capacitance limits its application in the electrode of supercapacitors. Herein, quantum capacitance of 56 kinds of 3d, 4d and 5d transition-metal and vacancy doped/co-doped graphene, named as TM@G and TM@VG, are screened by density functional theory. We concluded that quantum capacitance (Cq) and density of surface charge (Qsc) of graphene-based electrodes can be effectively enhanced with transition-metal and vacancy co-doping, which can be related to shift and/or enhancement of DOS near the Fermi level. Calculated stability (ΔEb) and Qsc imply that Y@G, Ta@VG, Au@VG and Ni@VG are suitable for anode in aqueous systems, while Sc@VG, Y@VG, Fe@VG and Zn@VG for cathode. Cu@VG and Re@VG are more potential for symmetric supercapacitors. Besides, the capacitive performance of graphene can also be enhanced by transition-metal and vacancy co-doping in ionic/organic systems. Noteworthily, in aqueous/ionic/organic systems, Sc@VG and Y@VG are good cathode materials, when Y@G, Ta@VG and Au@VG are superior candidates for anode materials. Therefore, the selection of electrode materials will hold an instructional significance in the development of suporcapacitors.

Dirac fermion metagratings in graphene

We theoretically demonstrate a Dirac fermion metagrating which is an artificially engineered material in graphene. Although its physics mechanism is different from that of optical metagrating, both of them can deliver waves to one desired diffraction order. Here we design the metagrating as a linear array of bias-tunable quantum dots to engineer electron beams to travel along the -1st-order transmission direction with unity efficiency. Equivalently, electron waves are deflected by an arbitrary large-angle ranging from 90° to 180° by controlling the bias. The propagation direction changes abruptly without the necessity of a large transition distance. This effect is irrelevant to complete band gaps and thus the advantages of graphene with high mobility are not destroyed. This can be attributed to the whispering-gallery modes, which evolve with the angle of incidence to completely suppress the other diffraction orders supported by the metagrating and produce unity-efficiency beam deflection by enhancing the -1st transmitted diffraction order. The concept of Dirac fermion metagratings opens up a new paradigm in electron beam steering and could be applied to achieve two-dimensional electronic holography.

Tunable Graphene Phononic Crystal.

In the field of phononics, periodic patterning controls vibrations and thereby the flow of heat and sound in matter. Bandgaps arising in such phononic crystals (PnCs) realize low-dissipation vibrational modes and enable applications toward mechanical qubits, efficient waveguides, and state-of-the-art sensing. Here, we combine phononics and two-dimensional materials and explore tuning of PnCs via applied mechanical pressure. To this end, we fabricate the thinnest possible PnC from monolayer graphene and simulate its vibrational properties. We find a bandgap in the megahertz regime within which we localize a defect mode with a small effective mass of 0.72 ag = 0.002 mphysical. We exploit graphene’s flexibility and simulate mechanical tuning of a finite size PnC. Under electrostatic pressure up to 30 kPa, we observe an upshift in frequency of the entire phononic system by ∼350%. At the same time, the defect mode stays within the bandgap and remains localized, suggesting a high-quality, dynamically tunable mechanical system.

Progress in Photocatalytic Degradation of Organic Wastewater by Graphene Binary Composites

Graphene composites not only have most advantages of graphene, but also have the characteristics of easy regulation, morphology and so on. Among many applications, graphene composite photocatalytic degradation of organic wastewater is one of the most likely graphene technologies. At present, the most studied graphene complexes include graphene monophyletic complex, graphene binary complex and graphene ternary complex. In this paper, the preparation of graphene binary complex and the research status of photocatalytic degradation of organic wastewater are summarized, and the existing problems are analyzed in order to provide a reference for the further research and application of graphene complex photocatalytic degradation of organic wastewater.

3D printing of graphene oxide composites with well controlled alignment

As a super-anisotropic material, graphene possesses unprecedented strength, Young’s modulus and electrical/thermal conductivity in its plane direction, while extremely weak properties along perpendicular direction. In order to fully take the advantage of graphene, its alignment in 3D polymer based structure is extremely important, yet still a daunting task. Here, we report a universal strategy of aligning graphene oxide (GO) in large scale without any modification of GO. This approach consists of laminating GO nanosheets with polymer (polylactic acid (PLA) for the demonstration) thin film, scrolling and then 3D printed by filament fused deposition technique. In printed filament, GO nanosheets are aligned in the filament axial direction, based on which GO orientation can be easily controlled via the path of filament fused deposition. We show that PLA/GO scrolled fibers and printed fibers with graphene content of 0.4 wt% exhibit outstanding mechanical properties with strength increase about 32.7% and 35.2%, respectively, which is significantly higher than similar nanocomposites with random graphene distribution, indicating much improved polymer reinforcement efficiency. The proposed scrolled fiber with 3D printing framework could be broadly applicable for various 2D materials and structural composites.

Facile Fabrication of Flexible Graphene-Based Micro-Supercapacitors with Ultra-High Areal Performance

Micro-supercapacitors (MSCs) with high performance and flexibility could meet the demand of miniaturized electronic devices. The advantages of graphene and reduced graphene oxide (rGO), such as hig...

Monolayer Conveyor for Stably Trapping and Transporting Sub‐1 nm Particles

AbstractEfficient manipulation of nanoparticles and single molecules has always been of great interest and potential in nanotechnology. However, many challenges still remain in effectively functionalizing structures for this purpose. In this work, taking advantage of graphene's Dirac plasmon for its extreme confinement and tunability, a monolayer conveyor along which the position of optical potential well can be dynamically controlled is theoretically proposed. It is shown that by tuning a single voltage, one can manipulate the resonance along the graphene nanoribbon by changing graphene's effective surface plasmons wavelength. A configuration of monolayer graphene conveyor is proposed and Langevin dynamics reveals that a prototypical nanoparticle (1 nm size) can be effectively confined and transported along the device with proper external bias voltage. Hence, this work successfully proposes a promising avenue toward reconfigurable nanomanipulation of sub‐1 nm nanoparticles, and goes beyond the current state‐of‐the‐art of optical micrometer/nanometer‐sized particles manipulation with optical tweezers and nanoplasmonic tweezers.

Highly efficient electrochemical detection of lead ion using metal-organic framework and graphene as platform based on DNAzyme

Abstract Based on the electrode modified by the carboxyl-functionalized graphene, a highly sensitive electrochemical sensor for Pb2+ detection was proposed by using 8–17 DNAzyme as the recognition element and the reaction of H2O2 catalyzed by Fe-MIL-101 as the signal probe. Due to the high selectivity of the 8–17 DNAzyme to Pb2+, the excellent catalytic ability of Fe-MIL-101 and the advantages of graphene, the proposed electrochemical sensor exhibited an excellent sensing performance with a wide linear range of 10−13 to10−7 mol·L−1, a lower detection limit of 1.74 × 10−14 mol·L−1 and high selectivity to Pb2+. Tap water and river water were analyzed by the developed sensor with satisfying recoveries and RSD, demonstrating a promising practicability for the determination of Pb2+ in the real sample analysis. Furthermore, the proposed strategy could be extended to the determination of other metal ions just by changing the specific DNAzymes.

Growing quality graphene at low temperatures

To build devices that take advantage of graphene’s unique electrical properties, researchers need large sheets of the material. It’s typically grown by chemical vapor deposition (CVD) on pieces of copper heated to about 1,000 °C, then transferred to another surface, such as a silicon wafer or a plastic film. Ideally, researchers would grow the material right where it’s needed, but the high temperatures necessary to grow high-quality graphene are too extreme, melting other substrates. By designing and building a specialized plasma-blowing device, researchers led by Jaeho Kim and Hiromoto Itagaki at the National Institute of Advanced Industrial Science and Technology (AIST) have overcome this challenge. The new growth technique could make it possible to directly grow the ultrathin electronic material on plastic, silicon circuits, and other surfaces for use in high-performance or flexible electronics (Nano Lett. 2019, DOI: 10.1021/acs.nanolett.8b03769). A process called plasma-enhanced CVD, which uses microw...

2D Schottky Junction between Graphene Oxide and Transition‐Metal Dichalcogenides: Photoresponsive Properties and Electrocatalytic Performance

Abstract2D graphene is conductor and not a semiconductor. 2D transition—metal dichalcogenides (TMD) is a semiconductor and not a conductor. Preparing 2D composite material that simultaneously possesses both advantages of graphene and TMD has proven to be challenging. In this work, both 2D‐WS2/2D‐GO and 2D‐MoS2/2D‐GO composites with few layer thickness are synthesized. The electronic structure indicates a high content of Mo4+ 3d5/2 and W4+4f7/2 with lower binding energy in the 2D composite, which is ascribed to partial loss of surface sulfur atoms in 2D composites and the newly formed heteroatomic bond of CWS and CMoS. The Schottky junction between 2D‐GO and 2D‐TMD (2D G‐T junction) is established and exhibits obvious photoelectric responses. Superior electrocatalytic properties of the two 2D‐composites are attributable to the 2D Schottky Junction between 2D‐TMDs and 2D‐GO. Interlayer electronic coupling in 2D Schottky Junction (2D G‐T junction) activates inert sites on the 2D surface of 2D‐TMDs or GO. The power conversion efficiency of dye‐sensitized solar cells (DSCs) based on 2D‐WS2/2D‐GO is 9.54% under standard solar illumination intensity (AM1.5, 100 mW cm−2). The value is one of the highest reported efficiencies for DSCs based on Pt‐free counter electrodes. Finally, 2D‐WS2/2D‐GO composites exhibit excellent stability as counter electrode of DSCs.

Estimation of intrinsic and extrinsic capacitances of graphene self-switching diode using conformal mapping technique

Due to a very high carrier concentration and low band gap, graphene based self-switching diodes do not demonstrate a very high rectification ratio. Despite that, it takes the advantage of graphene’s high carrier mobility and has been shown to work at very high microwave frequencies. However, the AC component of these devices is hidden in the very linear current–voltage characteristics. Here, we extract and quantitatively study the device capacitance that determines the device nonlinearity by implementing a conformal mapping technique. The estimated value of the nonlinear component or curvature coefficient from DC results based on Shichman–Hodges model predicts the rectified output voltage, which is in good agreement with the experimental RF results.

Facile fabrication of carbon brush with reduced graphene oxide (rGO) for decreasing resistance and accelerating pollutants removal in bio-electrochemical systems

Low electrode resistance is crucial for achieving efficient reactions in bio-electrochemical system (BES), especially considering the factors of BES scaling-up and microbial effects. Graphene has revealed a cornucopia of potential applications due to its high conductivity and extraordinary electrochemical properties. Here, significant reduction of electrode resistance and increment of electrochemical activity were achieved by fabricating the three-dimensional carbon brush using reduced graphene oxide (rGO/carbon brush) through one-step electro-deposition without any binder. The rGO/carbon brush was employed as cathode in BES equipped with bio-anode for azo compound (AO7) removal. The charge transfer resistances of cathode part and whole cell were decreased by 89% and 65%, respectively. The reactor showed quickly start-up within 48 h with peak cycle current six fold increase relative to the control. AO7 decolorization efficiency reached 91.1 ± 0.1% at 4 h and 97.6 ± 0.4% at 6 h. Effective decolorization of AO7 was at rate up to 650.7 g AO7/m3·h. The results indicated that the advantages of graphene and three-dimensional carbon brush successfully improved the overall performance of BES and enhanced refractory pollutants removal when applied to specific wastewater.