Functionalization Of Graphene Research Articles

Antibacterial Properties of Ethacridine Lactate and Sulfmethoxazole Loaded Functionalized Graphene Oxide Nanocomposites.

The emergence of drug-resistant bacterial strains that reduce the effectiveness of antimicrobial agents has become a major ongoing health concern in recent years. It is therefore necessary to find new antibacterials with broad-spectrum activity against both Gram-positive and Gram-negative bacteria, and/or to use nanotechnology to boost the potency of already available medications. In this research, we examined the antibacterial efficacy of sulfamethoxazole and ethacridine lactate loaded two-dimensional glucosamine functionalized graphene-based nanocarriers against a range of bacterial isolates. Graphene oxide was first functionalized with glucosamine, which as a carbohydrate moiety can render hydrophilic and biocompatible characters to the GO surface, and subsequently loaded with ethacridine lactate and sulfamethoxazole. The resulting nanoformulations had distinct, controllable physiochemical properties. By analyzing the formulation using Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (PXRD), a thermogravimetric analysis (TGA), zetasizer, and a morphological analysis using Scanning Electron Microscopy and Atomic Force Microscopy, researchers were able to confirm the synthesis of nanocarriers. Both nanoformulations were tested against Gram-negative bacteria, including Escherichia coli K1, Serratia marcescens, Pseudomonas aeruginosa, Salmonella enterica, as well as Gram-positive bacteria, including Bacillus cereus, Streptococcus pyogenes, and Streptococcus pneumoniae. Importantly, ethacridine lactate and its nanoformulations exhibited significant antibacterial properties against all bacteria tested in this study. When tested for minimum inhibitory concentration (MIC), the results were remarkable and revealed that ethacridine lactate presented MIC90 at 9.7 µg/mL against S. enteric, and MIC90 at 6.2 µg/mL against B. cereus. Notably, ethacridine lactate and its nanoformulations showed limited toxicity effects against human cells using lactate dehydrogenase assays. Overall, the results revealed that ethacridine lactate and its nanoformulations possess antibacterial activities against various Gram-negative and Gram-positive bacteria and that nanotechnology can be employed for the targeted delivery of effective drugs without harming the host tissue.

Prospective features of functional 2D nanomaterial graphene oxide in the wound healing process

Prospective features of functional 2D nanomaterial graphene oxide in the wound healing process

Direct mask-free fabrication of patterned hierarchical graphene electrode for on-chip micro-supercapacitors

• Functionalized membrane with customized pattern is prepared by fast laser carving. • Selective permeable membrane complemented with vacuum filtration is used to develop intact interdigital thin film. • Macroscopic assembly based on size effect rationally guide the structural design and precise fabrication of flexible electrode with expected high performances. • Flexible high-performance on-chip micro-supercapacitors with planar arbitrary shape are fabricated. Graphene-based electrodes with rational structural design have shown extraordinary prospect for enhanced electrical double-layer capacitance of micro-supercapacitors (MSCs). Herein, a facile fabrication method for flexible planar MSCs based on hierarchical graphene was demonstrated by using a laser-treated membrane for electrode patterning, complemented with hierarchical electrode configuration taking full advantages of size-determined functional graphene. The in-plane interdigital shape of MSCs was defined through vacuum filtration with the assistance of the functionalized polypropylene (PP) membrane. The hierarchical graphene films were built by macroscopic assembly based on size effect of different lateral sized graphene sheets (rGO-LSL). The sample of MSCs based on rGO-LSL (MSCs-LSL) exhibited excellent volumetric capacitance of 6.7 F cm −3 and high energy density of 0.37 mWh cm −3 . The MSCs-LSL presented superb flexibility and cycling stability with no capacitance deteroriated after 2000 cycles. This newly developed fabrication strategy is of good scalability and designability to manufacture flexible electrode for MSCs with customized shapes, while the construction of hierarchical graphene can enlighten the structural design of analogous two-dimensional materials for potential advanced electronics. A facile mask-free filtration approach is developed for the fabrication of patterned onchip micro-supercapacitors based on hierarchical graphene. The use of the functionalized membrane complemented with macroscopic assembly based on size effect provides the control over the planar configuration of micro-supercapacitors, and rationally guide the structural design of flexible electrode with expected high performances.

Bottom-up synthesis of mesoscale nanomeshes of graphene nanoribbons on germanium

The synthesis of functional graphene nanostructures on Ge(001) provides an attractive route toward integrating graphene-based electronic devices onto complementary metal oxide semiconductor-compatible platforms. In this study, we leverage the phenomenon of the anisotropic growth of graphene nanoribbons from rationally placed graphene nanoseeds and their rotational self-alignment during chemical vapor deposition to synthesize mesoscale graphene nanomeshes over areas spanning several hundred square micrometers. Lithographically patterned nanoseeds are defined on a Ge(001) surface at pitches ranging from 50 to 100 nm, which serve as starting sites for subsequent nanoribbon growth. Rotational self-alignment of the nanoseeds followed by anisotropic growth kinetics causes the resulting nanoribbons to be oriented along each of the equivalent, orthogonal Ge⟨110⟩ directions with equal probability. As the nanoribbons grow, they fuse, creating a continuous nanomesh. In contrast to nanomesh synthesis via top-down approaches, this technique yields nanomeshes with atomically faceted edges and covalently bonded junctions, which are important for maximizing charge transport properties. Additionally, we simulate the electrical characteristics of nanomeshes synthesized from different initial nanoseed-sizes, size-polydispersities, pitches, and device channel lengths to identify a parameter-space for acceptable on/off ratios and on-conductance in semiconductor electronics. The simulations show that decreasing seed diameter and pitch are critical to increasing nanomesh on/off ratio and on-conductance, respectively. With further refinements in lithography, nanomeshes obtained via seeded synthesis and anisotropic growth are likely to have superior electronic properties with tremendous potential in a multitude of applications, such as radio frequency communications, sensing, thin-film electronics, and plasmonics.

Spin-lattice relaxation time in water/graphene-oxide dispersion.

We present the results of the calculations of the spin-lattice relaxation time of water in contact with graphene oxide by means of all-atom molecular dynamics simulations. We fully characterized the water-graphene oxide interaction through the calculation of the relaxation properties of bulk water and of the contact angle as a function of graphene oxide oxidation state and comparing them with the available experimental data. We then extended the calculation to investigate how graphene oxide alters the dynamical and relaxation properties of water in different conditions and concentrations. We show that, despite the diamagnetic nature of the graphene oxide, the confining effects of the bilayers strongly affect the longitudinal relaxation properties of interfacial water, which presents a reduced dynamics due to hydrogen bonds with oxygen groups on graphene oxide. This property makes graphene oxide an interesting platform to investigate water dynamics in confined geometries and an alternative contrast-agent for magnetic resonance imaging applications, especially in view of the possibility to functionalize graphene oxide from theranostic perspectives.

Marine macroalgae-derived multielement-doped porous biochars for efficient removal of sulfamethoxazole from aqueous solution: Sorption performance and governing mechanisms

Marine macroalgae are promising biomass resources due to their fast growth, high yield and special composition and urgently need to be developed. Pyrolytic conversion of marine macroalgae into stable and multifunctional biochars is an extremely feasible strategy, but there are few related studies, especially on further decontamination applications and performance. In this study, the green tide-derived marine macroalga Enteromorpha prolifera was used to prepare multielement-doped porous biochars (MPBs) and applied to remove a typical antibiotic, sulfamethoxazole (SMX), from aqueous solution for the first time. The MPBs possess a porous structure, and the specific surface area and pore volume are as high as 134 m2 g−1 and 0.030 cm3 g−1, respectively. The surface N, O, S and Cl contents of the MPBs are high. An abundant ash content, O-containing surface functional groups and graphene structure also exist in the MPBs. These excellent properties contribute to a high sorption quantity, up to 30 mg g−1. Pore filling, n/π-π stacking, cation bridging interactions, electrostatic attraction, hydrogen bonding and partitioning are the potential sorption mechanisms. Moreover, the sorption is controlled by physical processes; monolayer sorption is relevant for low carbonization temperature-derived MPBs, and multilayer sorption is relevant for high carbonization temperature-derived MPBs. In addition, the removal capacity of SMX changed slightly after 4 cycles. The findings suggest that marine macroalgae can be deemed excellent precursors for the preparation of MPBs-based sorbents for organic pollutants.

Electrically switchable and tunable infrared light modulator based on functional graphene metasurface

Abstract Graphene is emerging as an ideal material for new-generation optoelectronic devices. In this paper, a novel graphene metasurface-based electrically switchable and tunable infrared light modulator has been proposed and theoretically studied. The functional modulator comprises a monolayer graphene sheet sandwiched in a Fabry–Perot (FP) like nanostructure consisting of a metal reflector, a dielectric spacer, and an ellipse patterned anisotropy antenna layer. As a result of the photon localization effect of the guided-mode resonance (GMR) in the FP structure, the graphene electroabsorption can be significantly enhanced to enable a high-performance light modulator. By fine-tuning the Fermi energy (E f) of graphene via controlling its bias-gate voltage, the proposed modulator can switch between a perfect absorber and a reflective polarization converter of high conversion efficiency (i.e., >90%) at 1550 nm. The conversion mechanism and the geometric dependences of the infrared light modulator have been investigated. We further demonstrated the tunability of the highly-efficient polarization converter over a broad spectrum by adjusting the real dispersion of E f. Our design concept provides an effective strategy for customizing novel optoelectronic devices by combining an electrically-tunable 2D material with a functional metasurface.

Signatures of hot carriers and hot phonons in the re-entrant metallic and semiconducting states of Moiré-gapped graphene

Stacking of graphene with hexagonal boron nitride (h-BN) can dramatically modify its bands from their usual linear form, opening a series of narrow minigaps that are separated by wider minibands. While the resulting spectrum offers strong potential for use in functional (opto)electronic devices, a proper understanding of the dynamics of hot carriers in these bands is a prerequisite for such applications. In this work, we therefore apply a strategy of rapid electrical pulsing to drive carriers in graphene/h-BN heterostructures deep into the dissipative limit of strong electron-phonon coupling. By using electrical gating to move the chemical potential through the “Moiré bands”, we demonstrate a cyclical evolution between metallic and semiconducting states. This behavior is captured in a self-consistent model of non-equilibrium transport that considers the competition of electrically driven inter-band tunneling and hot-carrier scattering by strongly non-equilibrium phonons. Overall, our results demonstrate how a treatment of the dynamics of both hot carriers and hot phonons is essential to understanding the properties of functional graphene superlattices.

Auxetic effects in the large deflection bending characteristics of FG GRMMC shallow arches

Shallow arches are ubiquitous in long-span buildings, bridge structures, and tunnels. Uniform loading can cause large deflections characterized by snap-through, which can ultimately lead to structural failure. In this work, nonlinear bending of functional graded graphene reinforced metal matrix composite (GRMMC) shallow arches with auxetic properties is studied using higher order shear constitutive equations based on the von Kármán nonlinear theory of beam. Asymptotic solutions for an arch with simply and clamped supported ends are derived using a two-perturbation approach. The results show that the the initial thermal stress-induced deformation of the members increases with increasing environmental temperature. The generated auxetic effect in the structures due to Negative Poisson's Ratio (NPR) will act to resist bending deformation. This strengthening effect is more noticeable with increase in the deflection, especially in the first snap-through. In addition, the elastic foundation increases the global stiffness of the arch, thus enhancing its bending stiffness. The current work not only provides a theoretical foundation for understanding the interrelationship between the auxetic effect and mechanical performance of structures but also offers guidance for designing metamaterial structures.

Study on NO2 Barrier Properties of RTV Silicone Rubber by Incorporation of Functional Graphene Oxide.

In this study, functional graphene oxide (f-GO) nanosheets were prepared to enhance the NO2 resistibility of room-temperature-vulcanized (RTV) silicone rubber. A nitrogen dioxide (NO2) accelerated aging experiment was designed to simulate the aging process of nitrogen oxide produced by corona discharge on a silicone rubber composite coating, and then electrochemical impedance spectroscopy (EIS) was used to test the process of conductive medium penetration into silicone rubber. After exposure to the same concentration (115 mg·L-1) of NO2 for 24 h, at an optimal filler content of 0.3 wt.%, the impedance modulus of the composite silicone rubber sample was 1.8 × 107 Ω·cm2, which is an order of magnitude higher than that of pure RTV. In addition, with an increase in filler content, the porosity of the coating decreases. When the content of the nanosheet increases to 0.3 wt.%; the porosity reaches a minimum value 0.97 × 10-4%, which is 1/4 of the porosity of the pure RTV coating, indicating that this composite silicone rubber sample has the best resistance to NO2 aging.

Semi-empirical infrared spectra simulation of pyrene-like molecules insight for simple analysis of functionalization graphene quantum dots

The Infrared (IR) spectra usually assume the samples are 3D materials. Thus, it is difficult to identify functional groups in 2D materials at the edge and the center of the 2D surface. Therefore, it is crucial to introduce analysis methods that enable the investigation of 2D carbon materials such as graphene and its derivatives using IR spectra. This study calculates the infrared spectra of pyrene-like molecules as an insight for a simple analysis of graphene quantum dots using a semi-empirical method. These IR spectra were correlated to the electronic transition and charge distribution associated with functional groups. The IR spectra analysis focuses on comparing the pristine and functionalized molecule at the wavenumber 1400–2000 cm−1, especially to identify the C=C stretching mode and 3000–3500 cm−1 for C–H and OH stretching. Moreover, the determination of excitation spectra was carried out to analyze the electronic transition of the molecules in the ultraviolet–visible region (200–900 nm) calculated using ZINDO method. The investigation of the pyrene-like GQD permitted the identification of the edge and center surface functionalization in 2D carbon materials.

Functional Graphene for Peritumoral Brain Microenvironment Modulation Therapy in Glioblastoma.

Peritumoral brain invasion is the main target to cure glioblastoma. Chemoradiotherapy and targeted therapies fail to combat peritumoral relapse. Brain inaccessibility and tumor heterogeneity explain this failure, combined with overlooking the peritumor microenvironment. Reduce graphene oxide (rGO) provides a unique opportunity to modulate the local brain microenvironment. Multimodal graphene impacts are reported on glioblastoma cells in vitro but fail when translated in vivo because of low diffusion. This issue is solved by developing a new rGO formulation involving ultramixing during the functionalization with polyethyleneimine (PEI) leading to the formation of highly water-stable rGO-PEI. Wide mice brain diffusion and biocompatibility are demonstrated. Using an invasive GL261 model, an anti-invasive effect is observed. A major unexpected modification of the peritumoral area is also observed with the neutralization of gliosis. In vitro, mechanistic investigations are performed using primary astrocytes and cytokine array. The result suggests that direct contact of rGO-PEIUT neutralizes astrogliosis, decreasing several proinflammatory cytokines that would explain a bystander tumor anti-invasive effect. rGO also significantly downregulates several proinvasive/protumoral cytokines at the tumor cell level. The results open the way to a new microenvironment anti-invasive nanotherapy using a new graphene nanomaterial that is optimized for in vivo brain delivery.

Extraction of selected benzothiazoles, benzotriazoles and benzenesulfonamides from environmental water samples using a home-made sol-gel silica-based mixed-mode zwitterionic sorbent modified with graphene

A novel sol-gel silica-based mixed-mode zwitterionic sorbent modified with graphene microparticles was synthesized. Thanks to the inclusion of multiple functional groups and graphene microparticles to exert a wide range of intermolecular/interionic interactions including dipole-dipole interactions, ion-exchange interactions and π-π interactions, the sorbent showed high retention in the solid-phase extraction (SPE) of benzothiazoles, benzotriazoles and benzenesulfonamides.The SPE protocol was optimized in terms of pH, sample loading volume and elution conditions using liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS). The method based on SPE followed by LC-HRMS was validated. Apparent recoveries at two levels of concentration were in the range from 48 to 85% (in most cases) in matrices such as influent wastewater, matrix effect was lower than ±30% in most cases, method detection and quantification limits being lower than 20 ng/L and repeatability and reproducibility between days were lower than 18% (n = 4).River, effluent and influent wastewaters samples were analyzed, obtaining concentrations ranging from 3 to 175 ng/L in river samples, from 12 to 499 ng/L in effluent samples and from 15 to 632 ng/L in influent samples, when the compounds were above the method quantification limits.

ZrN6 -Doped Graphene for Ammonia Synthesis: A Density Functional Theory Study.

Considering the pivotal role of ammonia in the modern chemical industry, designing effective catalysts for the N2 -to-NH3 conversion stimulates great research enthusiasms. In this work, by means of density functional theory calculations, we systematically investigated the electrocatalysis of six-coordinated transition metal atom anchored graphene for nitrogen fixation. The free energy analysis shows that the ZrN6 configuration has a good activity toward ammonia synthesis under overpotential of 0.51 V. According to the electron transfer analysis, ZrN6 site plays a bridging role in charge transfer between the functional graphene and the reactant. Furthermore, the presence of N6 coordination increases the electron accumulation on the NNHx intermediates, which weakens the intermolecular N-N bond, reducing the thermodynamic barrier of protonation process. This work provides a basic understanding of the interaction between transition metal and the adjacent coordination in tuning the reactivity.

Ultraclean and Facile Patterning of CVD Graphene by a UV-Light-Assisted Dry Transfer Method

The synthesis of large-area graphene by the chemical vapor deposition (CVD) method is a mature technology; however, a transfer procedure is required to integrate CVD-grown graphene into a functional device. The reported methods for transferring graphene films cause different degrees of defects (cracking, rupture) and ion/polymer residues, which deteriorate or alter the electrical properties of as-grown graphene. Developing a reliable and fast transfer method that can maintain high-quality graphene remains a challenge. In this work, we employed UV light release tape (UV-RT) as the support layer to replace the frequently used thermal release tape (TRT) in a typical roll-to-roll dry transfer process. In this process, we used an easier-to-remove polymer as an adhesion layer to greatly reduce the strain and defects that occur during the transfer process. The cleanliness of graphene transferred by this method is above 99%, and the carrier mobility is 1.6 and 1.1 times higher than that obtained with conventional wet transfer and TRT transfer methods, respectively. UV illumination leads to facile and uniform release of the graphene film onto the target substrate, achieving one-step and selective patterning of graphene (feature size of <100 μm). The UV-assisted decomposition of the polymer molecular structure into small molecules enables a residue-free and ultraclean graphene surface. This proposed transfer method enables facile patterning of graphene and 2D films while maintaining high quality, which paves the way for versatile functional graphene applications.

STRUCTURAL AND THERMAL STABILITY OF FUNCTIONALIZED GRAPHENE INCORPORATED POLYURETHANE NANOCOMPOSITE FOAM

The thermal stability and morphology of polyurethane nanocomposite foams reinforced with chemically modified Fenton graphene (FG), graphene oxide (GO), or reduced graphene oxide (rGO) were investigated. The polyurethane (PU) polymeric nanocomposite foams having 0.5 to 2.0 wt.&amp;#37; were prepared using a thermo-reversible solution method involving a supramolecular self-assembly process. The effect of edge and surface oxidization morphology of functionalized graphene/PU foams was characterized by scanning electron microscopy and X-ray diffraction methods. The thermal stability of the polyurethane nanocomposite foam was investigated by thermo-gravimetric analysis (TGA). The thermal stability of 0.5 wt.&amp;#37; FG-based nanocomposite foam was more as compared to 0.5 wt.&amp;#37; of GO and rGO-based nanocomposite foam.

Preparation of functional groups-rich graphene oxide for high-performance lithium–sulfur batteries

Lithium–sulfur (Li–S) battery has promising application prospect owing to the high energy density. Yet, its cycling life and Coulombic efficiency are always low due to shuttle effect of the mid-product, Li2Sn (4 ≤ n ≤ 8), on the cathode. Herein, oxygen-containing functional groups rich/defect-rich graphene oxide (D-GO) with large size and porous network structure is developed, which exhibits outstanding adsorption ability to S and Li2Sn. S can be uniformly deposited onto the D-GO (S@D-GO), and the proportion of S is as high as 89.5 wt% in the composite. As cathode of Li–S batteries, the S@D-GO can deliver a high capacity of 1370 mAh/g at 0.05 C. The capacity is still as high as 1011 mAh/g at 1 C, and 95% of the initial value is remained after 400 cycles' cycling, exhibiting good rate performance and cycling stability. Meanwhile, the Coulombic efficiency is close to 100% during the whole test, suggesting that the D-GO can inhibit the shuttle of polysulfide effectively. Most important, with a high loading amount of 14.8 mg/cm2 for the S@D-GO, areal capacity of the cathode still can reach 14.85 mAh/cm2 at 0.1 C, indicating high practical and commercial value in energy storage field.

Artificial Intelligence-Based Rapid Design of Grease with Chemically Functionalized Graphene and Carbon Nanotubes as Lubrication Additives

Rapid chemical functionalization of additives and efficient determination of their optimum concentrations are important for designing high-performance lubricants, especially under multi-additive conditions. Herein, chemically functionalized graphene (FGR) and carbon nanotubes (FCNTs) were rapidly prepared by microwave-assisted ball milling and subsequently introduced into grease as additives. The tribological properties of the additives in grease at different concentrations and ratios were measured using a four-ball test. A reliable artificial neural network (ANN) model was established according to a few test results. Subsequently, the optimal concentration of multiple additives in the grease was predicted using a genetic algorithm and experimentally validated. The results indicated that the introduction of FGR (0.14 wt %) and FCNT (0.16 wt %) improved the antifriction and anti-wear performance of the base grease by 25.66 and 29.34%, respectively. The results of the ANN model analysis and friction interface characterization indicate that such performance is principally attributed to the synergistic lubrication of the FGR and FCNT.

Mechanism of ethanol/water reverse separation through a functional graphene membrane: a molecular simulation investigation

Mechanism of ethanol/water reverse separation through a functional graphene membrane: a molecular simulation investigation

A New Support Film for Cryo Electron Microscopy Protein Structure Analysis Based on Covalently Functionalized Graphene.

Protein adsorption at the air-water interface is a serious problem in cryogenic electron microscopy (cryoEM) as it restricts particle orientations in the vitrified ice-film and promotes protein denaturation. To address this issue, the preparation of a graphene-based modified support film for coverage of conventional holey carbon transmission electron microscopy (TEM) grids is presented. The chemical modification of graphene sheets enables the universal covalent anchoring of unmodified proteins via inherent surface-exposed lysine or cysteine residues in a one-step reaction. Langmuir-Blodgett (LB) trough approach is applied for deposition of functionalized graphene sheets onto commercially available holey carbon TEM grids. The application of the modified TEM grids in single particle analysis (SPA) shows high protein binding to the surface of the graphene-based support film. Suitability for high resolution structure determination is confirmed by SPA of apoferritin. Prevention of protein denaturation at the air-water interface and improvement of particle orientations is shown using human 20S proteasome, demonstrating the potential of the support film for structural biology.