Surface Modification Of Graphene Research Articles

Effect of Surface-Modified Graphene Addition on In Situ Synthesized Iron-Based Friction Materials

Effect of Surface-Modified Graphene Addition on In Situ Synthesized Iron-Based Friction Materials

Rheological enhancement of fresh polymer-modified cement composites via surface-modified graphene oxide

Polymer-modified cement (PMC) composites are extensively utilized in modern construction, especially in tunneling and structural applications, but their excessive flowability and reduced thixotropy continue to present fundamental rheological challenges. We present a novel approach to improving the rheological performance of PMC via surface-modified graphene oxide (GO), i.e., GOPMC composites. Specifically, the flow behavior of GOPMCs in relation to shear stress–shear strain response and apparent viscosity were investigated. The rheological parameters were analyzed by using Herschel–Bulkley's model. Additionally, zeta potential and dispersion analysis were conducted to investigate interparticle interaction forces. Flow measurement confirmed ∼20 % lower flowability of the GOPMC than the reference PMC. GOPMC composites further displayed higher yield stress of ∼82 % and ∼33 % reduced viscosity with inherent decreased shear-thickening compared to reference PMC composites. The yield stress of the GOPMC composite increased over time, disclosing distinct structural evolution linked to enhanced hydration kinetics by GO. Additionally, GO nanosheets in the GOPMC altered the rheopectic behavior of the redispersible polymer and enhanced the degree of thixotropy by ∼80 %, attributable to the promotion of bridged flocculated structures which produces a rigid system, facilitated by particle interaction forces comprising of van der Waals and steric forces. This latter observation provides a mechanistic framework for the enhanced rheological performance of GOPMC composites aiming at broader civil engineering and construction sector applications beyond tunneling.

Graphene-Based Composites for Biomedical Applications: Surface Modification for Enhanced Antimicrobial Activity and Biocompatibility.

The application of graphene-based materials in medicine has led to significant technological breakthroughs. The remarkable properties of these carbon materials and their potential for functionalization with various molecules and compounds make them highly attractive for numerous medical applications. To enhance their functionality and applicability, extensive research has been conducted on surface modification of graphene (GN) and its derivatives, including modifications with antimicrobials, metals, polymers, and natural compounds. This review aims to discuss recent and relevant studies related to advancements in the formulation of graphene composites, addressing their antimicrobial and/or antibiofilm properties and evaluating their biocompatibility, with a primary focus on their biomedical applications. It was concluded that GN surface modification, particularly with compounds intrinsically active against bacteria (e.g., antimicrobial peptides, silver and copper nanomaterials, and chitosan), has resulted in biomaterials with improved antimicrobial performance. Furthermore, the association of GN materials with non-natural polymers provides composites with increased biocompatibility when interfaced with human tissues, although with slightly lower antimicrobial efficacy. However, it is crucial to highlight that while modified GN materials hold huge potential, their widespread use in the medical field is still undergoing research and development. Comprehensive studies on safety, long-term effects, and stability are essential before their adoption in real-world medical scenarios.

Bias-switchable photoconductance in surface-modified graphene oxide by green synthesized ZnO nanoparticles

This study provides an environmentally friendly method for synthesizing Zinc oxide (ZnO) nanoparticles through Adhatoda vasica extracts as plant-mediated reducing agents. ZnO-GO nanostructures are prepared using microwave irradiation, while a modified Hummer's method was employed for graphene oxide (GO) synthesis. The thorough characterization establishes the purity, phase and structural conformation of the synthesized ZnO-GO NCs. The observation of ZnO nanoparticles accumulating over the GO surface through High-Resolution Transmission Electron Microscopy and Scanning Electron Microscopy validates the formation of nanocomposites. The resulting ZnO-GO nanocomposites displayed remarkable and broad photoresponsivity across various wavelengths. Notably, at 480 nm, photoresponsivity is found to be a maximum of 0.47 mA/W, whereas it is 0.29 mA/W and 0.21 mA/W at 520 nm and 670 nm respectively. We have achieved responsiveness of 0.48 µA/W and detectivity of 13.9 × 106 Jones at 480 nm with biasing voltage of 1 nV which reflects their potential for self-biased optoelectronic devices. Thus, the photodetector demonstrates a positive photoresponse within the voltage range of 5–30 volts while exhibiting a negative photoresponse in the range of 1–100 nanovolts. This aspect introduces a novel and unprecedented characteristic to the device's behavior. Overall, the integration of eco-friendly synthesis methods, comprehensive characterization, and device performance puts this work with promising implications for sustainable and advanced technology development.

Adsorption and sensing performances of air decomposition components (CO, NOx) on Cr modified graphene surface

The adsorption and sensing abilities of air decomposition components such as CO, NO, and NO2 on a Cr-graphene monolayer were investigated using the first principles of density functional theory. Firstly, three possible doping points of Cr atoms on the surface of graphene were studied, and the most stable Cr-graphene monolayer was obtained through modeling and computational analysis. Then, various adsorption structures were constructed and optimized based on the model. The most stable adsorption structure of Cr-graphene monolayer for the three characteristic gases was determined by comparing their adsorption energy and other relevant parameters.Furthermore, state density, differential charge, and molecular orbital theory analyze the gas sensing mechanism and desorption time. The results show that the surface of the pristine graphene has a weak adsorption effect on these gases, and the Cr-graphene monolayer has good adsorption performance for the three gases. Although the calculation results show that Cr-graphene monolayer has strong adsorption and gas sensitivity performance for the three components, the recovery performance of the Cr-graphene monolayer needs to be improved because of the immense adsorption energy of Cr-graphene monolayer for the three components. The calculation can provide a theoretical guidance for gas sensors based on graphene and its modified materials.

Biosensor Based on Graphene Directly Grown by MW-PECVD for Detection of COVID-19 Spike (S) Protein and Its Entry Receptor ACE2.

Biosensors based on graphene field-effect transistors (G-FET) for detecting COVID-19 spike S protein and its receptor ACE2 were reported. The graphene, directly synthesized on SiO2/Si substrate by microwave plasma-enhanced chemical vapor deposition (MW-PECVD), was used for FET biosensor fabrication. The commercial graphene, CVD-grown on a copper substrate and subsequently transferred onto a glass substrate, was applied for comparison purposes. The graphene structure and surface morphology were studied by Raman scattering spectroscopy and atomic force microscope. Graphene surfaces were functionalized by an aromatic molecule PBASE (1-pyrenebutanoic acid succinimidyl ester), and subsequent immobilization of the receptor angiotensin-converting enzyme 2 (ACE2) was performed. A microfluidic system was developed, and transfer curves of liquid-gated FET were measured after each graphene surface modification procedure to investigate ACE2 immobilization by varying its concentration and subsequent spike S protein detection. The directly synthesized graphene FET sensitivity to the receptor ACE2, evaluated in terms of the Dirac voltage shift, exceeded the sensitivity of the transferred commercial graphene-based FET. The concentration of the spike S protein was detected in the range of 10 ag/mL up to 10 μg/mL by using a developed microfluidic system and measuring the transfer characteristics of the liquid-gated G-FETs. It was found that the shift of the Dirac voltage depends on the spike S concentration and was 27 mV with saturation at 10 pg/mL for directly synthesized G-FET biosensor, while for transferred G-FET, the maximal shift of 70 mV was obtained at 10 μg/mL with a tendency of saturation at 10 ng/mL. The detection limit as low as 10 ag/mL was achieved for both G-FETs. The sensitivity of the biosensors at spike S concentration of 10 pg/mL measured as relative current change at a constant gate voltage corresponding to the highest transconductance of the G-FETs was found at 5.6% and 8.8% for directly synthesized and transferred graphene biosensors, respectively. Thus, MW-PECVD-synthesized graphene-based biosensor demonstrating high sensitivity and low detection limit has excellent potential for applications in COVID-19 diagnostics.

Surface-modified graphene oxide-based composites for advanced sequestration of basic blue 41 from aqueous solution

Advanced materials for the efficient treatment of textile wastewater need to be developed for the sustainable growth of the textile industry. In this study, graphene oxide (GO) was modified by the incorporation of natural clay (bentonite) and mixed metal oxide (copper-cobalt oxide) to produce GO-based binary and ternary composites. Two binary composites, GO/bentonite and GO/Cu–Co Ox (oxide), and one ternary composite, GO/bentonite/Cu–Co Ox, were characterized by Fourier transform-infrared spectroscopy (FTIR), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and Brunauer-Emmett-Teller (BET) analysis. The adsorption efficiency of these composites was evaluated against a cationic dye, Basic Blue 41 (BB41). The composites had several surface functional groups, and the ternary composite had tubular porous structures formed by the cross-linking of the bentonite and GO planes. The BET surface area of the ternary composite was 50% higher than that of the GO. The BB41 removals were 92, 89, 80, and 69% for GO/bentonite/Cu–Co oxide, GO/bentonite, GO and GO/Cu–Co oxide, respectively. The pseudo-2nd-order and intraparticle diffusion models best describe the kinetics results, indicating chemisorption and slow pore diffusion-controlled adsorption processes. The Langmuir isotherm-derived adsorption capacity of GO/bentonite/Cu–Co oxide was 351.1 mg/g, which was very close to the measured value. After five consecutive cycles, the ternary composite retained 90% BB41 removal efficiency compared to its 1st cycle. Electrostatic interaction and pore diffusion were predicted to be the controlling mechanisms for the adsorption of the BB41. The GO-based ternary composite can be a feasible and scalable adsorbent for BB41 in wastewater treatment.

A Density Functional Theory (DFT) Perspective on Optical Absorption of Modified Graphene Interacting with the Main Amino Acids of Spider Silk.

We investigated the possible adsorption of each of the main building blocks of spider silk: alanine, glycine, leucine, and proline. This knowledge could help develop new biocompatible materials and favors the creation of new biosensors. We used ab initio density functional theory methods to study the variations in the optical absorption, reflectivity, and band structure of a modified graphene surface interacting with these four molecules. Four modification cases were considered: graphene with vacancies at 5.55% and fluorine, nitrogen, or oxygen doping, also at 5.55%. We found that, among the cases considered, graphene with vacancies is the best candidate to develop optical biosensors to detect C=O amide and differentiate glycine and leucine from alanine and proline in the visible spectrum region. Finally, from the projected density of states, the main changes occur at deep energies. Thus, all modified graphene's electronic energy band structure undergoes only tiny changes when interacting with amino acids.

First-principles investigation of the electronic and Li-ion diffusion properties of LiFePO4 by graphene surface modification

The structural, electronic and Li-ion diffusion properties of LiFePO4 (010) surface modified by graphene have been investigated by first-principles calculation under the DFT + U framework. The calculated formation energy indicates that the LiFePO4 (010) surface modified with graphene is energetically favourable. It is found that strong C–Fe and C–O covalent bonds are formed at the modified interface, and the band gap of LiFePO4 modified with graphene is narrowed, indicating better electronic conductive properties. The energy barrier for the diffusion of Li-ion along the b-channel perpendicular to the (010) surface is calculated using the method of finding the transition state. The results show that the energy barrier of the modified system is reduced, indicating that the surface modification of LiFePO4 by graphene can improve the surface diffusion rate of Li-ions.

Review of the development of graphene and application in photocatalyst

Graphene was originally found as a thin sheet structure. Researchers have expanded their studies to include this 2D carbon structure in recent years. The paper aims to give a review of the development of graphene and its application in photocatalysts based on existing research literature and data. The result shows that, currently, graphene-based nanomaterials for medical applications are a popular research topic. In this paper, the structure, characteristics, synthesis and surface modification of graphene is classified into covalent and non-covalent approaches.

Injectable and Self-Healable Thermoresponsive Hybrid Hydrogel Constructed via Surface-Modified Graphene Oxide Loading Exosomes for Synergistic Promotion of Schwann Cells

Injectable and Self-Healable Thermoresponsive Hybrid Hydrogel Constructed via Surface-Modified Graphene Oxide Loading Exosomes for Synergistic Promotion of Schwann Cells

A strategy of high-sensitivity solar-blind photodetector for fabricating graphene surface modification ZnGa2O4/Ga2O3 core-shell structure nanowire networks

One-dimensional core-shell nanowires are considered the optimal choice for high-performance photodetectors with the ideal interfacial area, well-controlled structure, and better light absorption ability. There are lots of research about Ga2O3 wide band gap semiconductors applied in solar-blind photodetectors. However, the defects such as relatively slow response/recovery time and poor response rate have limited its application in photodetectors. In this work, a GaZn2O4/Ga2O3 core-shell nanostructure is successfully prepared by the CVD (Chemical Vapor Deposition) technique. Then, a strategy of MSM solar blind ultraviolet detector based on graphene surface modification core-shell nanowires is proposed. The device has a characteristic of nanowire network structure, interface heterojunction, and Schottky contact. According to the results, a significant performance of the device with 0.1% graphene surface modified ZnGa2O4/Ga2O3 nanowires is achieved, like, the faster response time (rise/down time, 130 m s/13 m s), and the higher detection capability of the solar-blind ultraviolet detector (responsivity, 64.5 mA/W). Our work provides a facile fabrication procedure to construct a high-performance photodetector.

On the Road to the Frontiers of Lithium-Ion Batteries: A Review and Outlook of Graphene Anodes.

Graphene has long been recognized as a potential anode for next-generation lithium-ion batteries (LIBs). The past decade has witnessed the rapid advancement of graphene anodes, and considerable breakthroughs are achieved so far. In this review, the aim is to provide a research roadmap of graphene anodes toward practical LIBs. The Li storage mechanism of graphene is started withand then the approaches to improve its electrochemical performanceare comprehensively summarized. First, morphologically engineered graphene anodes with porous, spheric, ribboned, defective and holey structures display improved capacity and rate performance owing to their highly accessible surface area, interconnected diffusion channels, and sufficient active sites. Surface-modified graphene anodes with less aggregation, fast electrons/ions transportation, and optimal solid electrolyte interphase are discussed, demonstrating the close connection between the surface structure and electrochemical activity of graphene. Second, graphene derivatives anodes prepared by heteroatom doping and covalent functionalization are outlined, which show great advantages in boosting the Li storage performances because of the additionally introduced defect/active sites for further Li accommodation. Furthermore, binder-free and free-standing graphene electrodes arepresented,exhibiting great prospects for high-energy-density and flexible LIBs. Finally, the remaining challenges and future opportunities of practically available graphene anodes for advanced LIBs are highlighted.

Gas Desorption and Secondary Electron Emission from Graphene Coated Copper Due to E-Beam Stimulation

The gas desorption and secondary electron multiplication induced by electron bombardment tend to induce severe low-pressure discharge effects in space microwave device cavities. Nevertheless, few studies have focused on both secondary electron emission and electron-stimulated gas desorption (ESD). Although the suppression of secondary electrons by graphene was found to be better in our previous study, it is still unclear whether the surface modification of graphene, which brings about different interfacial states, can also be manifested in terms of ESD. The deep mechanism of gas desorption and secondary electron emission from this extremely thin two-dimensional material under electron bombardment still needs further investigation. Therefore, this paper investigates the mechanism of graphene modification on Cu metal surface on the gas release and secondary electron emission properties under electron bombardment. The surface states of graphene-modified Cu were characterized, and the ESD yield and secondary electron yield of Cu/GoCu were investigated using a self-researched platform and analyzed using molecular dynamics simulations and electron Monte Carlo simulations. The results of the study showed that the most released component on the Cu surface under the bombardment of electrons was H2O molecules, while the most released component on the GoCu surface was H2 molecules. The graphene-modified samples showed a significant suppression effect on the secondary electron yield and ESD only in the low-energy region below 400 eV. This study can provide a valuable reference for suppressing low-pressure discharge and multipactor phenomena in space microwave components.

Graphene-interfaced flexible and stretchable micro-nano electrodes: from fabrication to sweat glucose detection.

Flexible and stretchable wearable electronic devices have received tremendous attention for their non-invasive and personal health monitoring applications. These devices have been fabricated by integrating flexible substrates and graphene nanostructures for non-invasive detection of physiological risk biomarkers from human bodily fluids, such as sweat, and monitoring of human physical motion tracking parameters. The extraordinary properties of graphene nanostructures in fully integrated wearable devices have enabled improved sensitivity, electronic readouts, signal conditioning and communication, energy harvesting from power sources through electrode design and patterning, and graphene surface modification or treatment. This review explores advances made toward the fabrication of graphene-interfaced wearable sensors, flexible and stretchable conductive graphene electrodes, as well as their potential applications in electrochemical sensors and field-effect-transistors (FETs) with special emphasis on monitoring sweat biomarkers, mainly in glucose-sensing applications. The review emphasizes flexible wearable sweat sensors and provides various approaches thus far employed for the fabrication of graphene-enabled conductive and stretchable micro-nano electrodes, such as photolithography, electron-beam evaporation, laser-induced graphene designing, ink printing, chemical-synthesis and graphene surface modification. It further explores existing graphene-interfaced flexible wearable electronic devices utilized for sweat glucose sensing, and their technological potential for non-invasive health monitoring applications.

Surface modification of graphene with functionalized carbenes and their applications in the sensing of toxic gases: a DFT study.

Graphene and other 2D materials have gained significant attention in the development of gas sensors. In this study, we employed Density Functional Theory (DFT) to investigate the adsorption properties of diazomethanes (1a-1g) with various functional groups (R = OH (a), OMe (b), OEt (c), OPr (d), CF3 (e), Ph (f)) on pristine graphene. Furthermore, we explored the adsorption behavior of activated carbenes (2a-2g) generated from the decomposition of diazomethanes on graphene, as well as the functionalized graphene derivatives (3a-3g) resulting from [2 + 1] cycloaddition reactions between (2a-2g) and graphene. The interaction between these functionalized derivatives (3a-3g) and toxic gases was also investigated. Our results revealed that carbenes exhibited a stronger affinity for graphene compared to diazomethanes. The adsorption energy of esters (3b, 3c, and 3d) on graphene decreased relative to compound 3a, while 3e exhibited increased adsorption energy due to the electron-withdrawing effect of fluorine atoms. Additionally, the adsorption energy of phenyl and nitrophenyl groups (3f and 3g) decreased due to their π-stacking interaction with graphene. Importantly, all functionalized derivatives (3a-3g) demonstrated favorable interactions with gases. Notably, the derivative 3a, acting as a hydrogen bonding donor, exhibited superior performance. Furthermore, modified graphene derivatives exhibited the highest adsorption energy with NO2 gas, highlighting their potential for selective NO2 sensing applications. These findings contribute to the understanding of gas-sensing mechanisms and the design of novel graphene-based sensor platforms.

Comparative Study of Tribological Properties of Modified and Non-modified Graphene-Oil Nanofluids under Heated and Non-heated Conditions

With the aim of achieving more effective friction and wear reduction in sliding bearing applications, surface-modified graphene, which exhibits better dispersion stability than non-modified graphene, was synthesized and applied in this study using various graphene allotropes, including graphene nanoplatelets (GNP), multiwalled carbon nanotubes (MWCNT) and nanostructured graphite (NSG). Friction and wear tests of each type of graphene allotrope under modified and non-modified conditions were studied using a pin-on-ring tribo tester. In addition, the dynamic viscosity of each synthesized nanofluid sample was measured using a falling-ball viscometer. A series of modified graphene-oil nanofluids and non-modified graphene-oil nanofluids were prepared and heated before their friction and wear performance was investigated at room temperature. Friction and wear behavior, as well as the dynamic viscosity of the heated nanofluids vary insignificantly when compared to those of the non-heated nanofluids. The results showed that the best friction and wear reduction was achieved by modified GNP with friction and wear reduction of 60.5% and 99.4%, respectively.

Pre-post electron transfer regioselectivity at glycine modified graphene electrode interface for voltammetric sensing applications

In the last few years, glycine (GL) showed good experimental evidence as an electron transfer (ET) mediator at the carbon (in particular graphene (GR)) interface. However, ET properties of GL modified GR interface are still not known completely. These can be achieved using density functional theory-based models. Modelling of modified carbon electrode interfaces is essential in electroanalytical chemistry to get insights into their electronic and redox properties. Here we have modelled glycine modified graphene interface to find out its interfacial redox ET properties. Conceptual density functional theory concepts like frontier molecular orbital (FMO) theory and analytical Fukui functions were utilized to predict the ET sites on the modified graphene surface. It is shown that at the glycine-modified graphene interface, amine groups act as additional oxidation sites and carboxylic acid groups as additional reduction sites. Therefore, glycine acts as an ET mediator at the graphene-based electrode interface. The obtained results are well supported by previously published experimental reports.

Recent Progress on Graphene-Based Nanocomposites for Electrochemical Sodium-Ion Storage.

In advancing battery technologies, primary attention is paid to developing and optimizing low-cost electrode materials capable of fast reversible ion insertion and extraction with good cycling ability. Sodium-ion batteries stand out due to their inexpensive price and comparable operating principle to lithium-ion batteries. To achieve this target, various graphene-based nanocomposites fabricate strategies have been proposed to help realize the nanostructured electrode for high electrochemical performance sodium-ion batteries. In this review, the graphene-based nanocomposites were introduced according to the following main categories: graphene surface modification and doping, three-dimensional structured graphene, graphene coated on the surface of active materials, and the intercalation layer stacked graphene. Through one or more of the above strategies, graphene is compounded with active substances to prepare the nanocomposite electrode, which is applied as the anode or cathode to sodium-ion batteries. The recent research progress of graphene-based nanocomposites for SIBs is also summarized in this study based on the above categories, especially for nanocomposite fabricate methods, the structural characteristics of electrodes as well as the influence of graphene on the performance of the SIBs. In addition, the relevant mechanism is also within the scope of this discussion, such as synergistic effect of graphene with active substances, the insertion/deintercalation process of sodium ions in different kinds of nanocomposites, and electrochemical reaction mechanism in the energy storage. At the end of this study, a series of strategies are summarized to address the challenges of graphene-based nanocomposites and several critical research prospects of SIBs that provide insights for future investigations.

Polyaniline/graphene nanocomposite: Effect of the graphene functionalization with a long-chain fatty acid

Polyaniline (PANI)/graphene nanocomposites are expected to be useful in several applications, such as supercapacitors, sensors, corrosion protection, and photocatalysis. The performance of the nanocomposite depended on the interaction between graphene and PANI and the good distribution of the nanomaterial in the polymer matrix. This study investigated the effect of graphene surface modification with a long-chain fatty acid on the nature of the interactions of PANI/graphene nanocomposites. Myristic acid, a long-chain fatty acid with a 13-carbon backbone, was added to the graphene surface to improve the interaction and distribution of the graphene nanoplatelets in the PANI matrix. An innovative mechanochemical route was applied to functionalize the graphene surface with the fatty acid by ball milling. Nanocomposites were prepared through the in situ synthesis of PANI on pristine and functionalized graphene surfaces. The bare and composite materials were characterized by scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, ultraviolet–visible–near infrared spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Summarily, noncovalent graphene functionalization was successfully achieved. The results indicated that the functionalized graphene acted as a template for the uniform growth of PANI. It was concluded that the nature of the interactions with PANI was different for graphene (π–π stacking) and functionalized graphene (electrostatic and hydrophobic attraction). The characterization performed showed that the graphene surface modification allowed the production of a nanocomposite with a uniform distribution, better graphene incorporation, and good electronic properties. We concluded that this nanocomposite is suitable for applications that use redox PANI properties, such as sensors and anticorrosive coatings.