Use Of Graphene-based Materials Research Articles

Layer-Point Structure of Si3N4-NH2@GO for Improving Corrosion and Wear Resistance of Waterborne Epoxy Coating.

The use of graphene-based materials as anticorrosion coatings to protect metals is always a topic of discussion. In this work, silicon nitride (Si3N4) was aminated to improve its water dispersibility. Then it is attached to the graphene oxide (GO) surface to improve compatibility with epoxy (EP) resin as well as conductivity. The results of Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and zeta potentials test analyses indicated that Si3N4-NH2@GO with a layer-point structure has been successfully prepared. The corrosion resistance of the composite coatings was characterized by electrochemical impedance spectroscopy (EIS) and polarization curve analysis, and the wear resistance of the composite coatings was tested by friction and wear tests. The results showed that 1.0% Si3N4-NH2@GO has excellent corrosion and wear resistance. The use of Si3N4-NH2@GO layer point structures in this study broadens the way for GO applications.

Computational assessment of the use of graphene-based nanosheets as PtII chemotherapeutics delivery systems.

Graphene is the newest form of elemental carbon and it is becoming rapidly a potential candidate in the framework of nano-bio research. Many reports confirm the successful use of graphene-based materials as carriers of anticancer drugs having relatively high loading capacities compared with other nanocarriers. Here, the outcomes of a systematic study of the adsorption behavior of FDA approved PtII drugs cisplatin, oxaliplatin, and carboplatin on surface models of pristine, holey, and nitrogen-doped holey graphene are reported. DFT investigations in water solvent have been carried out considering several initial orientations of the drugs with respect to the surfaces. Adsorption free energies, calculated including basis set superposition error (BSSE) corrections, result to be significantly negative for many of the drug@carrier adducts indicating that tested layers could be used as potential carriers for the delivery of anticancer PtII drugs. The reduced density gradient (RDG) analysis allows to show that many kinds of non-covalent interactions, including canonical H-bond, are responsible for the stabilization of the formed adducts.

Investigating tribological properties of electrophoretically deposited graphene nanoplatelets coatings on mild steel

The use of graphene-based materials to enhance the tribological properties of metal surfaces has garnered increasing interest in recent years. In fact, various studies have demonstrated that graphene-related materials, such as graphene nanoplatelets (GNPs), hold promise as solid lubricants. Electrophoretical deposition (EPD) is an interesting coating method to obtain a deposition of particles such as graphene as it is a simple, cheap and effective process with a low environmental impact. This study focusses on investigating the tribological properties of GNPs coatings obtained through anodic EPD on mild steel. Specifically, a combination of GNPs and deionized water as the deposition medium is introduced, allowing a cost-effective process with reduced environmental impact.Deposition time (5, 10 and 20 min) and concentration in the bath (0.5, 1 and 1.5 g/l) were varied in a full factorial plan to highlight their effects on coating performance. The coatings achieved demonstrated good adhesion with scratch break loads above 10 N and excellent tribological performances, with a friction coefficient of above 0.1. The results showed how concentration and process duration have two opposing effects on the adhesion and tribological characteristics of the coatings. The presence of an intermediate optimal condition, with 10 min deposition and a GNP concentration of 1 g/l, leading to an improvement in anti-wear properties of approximately 85 % and a coating break distance of over 80 m. An ANOVA analysis was developed to confirm the statistical significance of the process parameters in adhesion and tribology of the coatings.

Functionalization of graphene oxide as a way to increase biocompatibility

Introduction. Now, one of the most promising areas for the use of graphene-based materials, in particular graphene oxide, is biomedicine. Due to the wide variety of functional groups and the possibility of chemical modification of graphene oxide, the creation of composite materials for biomedical use is promising. These nanomaterials have a unique structure and properties, which determines their use for creating targeted drug delivery systems, in tissue engineering, bioimaging, as well as for creating new materials with antimicrobial and antiviral properties.The objective was to perform synthesis and identification of graphene oxide and its conjugate with glycine, and to study the biocompatibility of the obtained nanomaterials: the effect on haemolysis and platelet aggregation, genotoxicity and cytotoxicity.Methods and materials. Graphene oxide was synthesized from graphite using the modified Hummers and Offeman method, after which the graphene oxide-glycine conjugate was also obtained. Identification was carried out using nuclear magnetic resonance spectroscopy. Estimation of biocompatibility of the obtained nanomaterials included the study of their hemolytic activity, effect on collagen-induced platelet aggregation, cyto- and genotoxicity.Results. Graphene oxide and its conjugate with glycine were synthesized. Identification with using nuclear magnetic resonance spectroscopy confirmed the structure and composition of the substances. The study of the biocompatibility of the obtained nanomaterials showed the absence of hemolytic activity (the degree of hemolysis did not exceed 2.5% at the studied concentration range); the presence of antiplatelet properties (at C=10–100 mg·ml–1); the absence of geno- and cytotoxicity (graphene oxide at C=0.25–25 mg·L–1 does not affect the viability of HEK293 cells; in turn, the conjugate with glycine at C=100–200 mg·L–1 causes a dose-dependent increase proliferation of HEK293 cells).Conclusion. The study demonstrates that functionalization of the graphene surface with oxygen-containing groups and amino acids leads to increased hemocompatibility, as well as to the production of nanomaterials that do not exhibit genoand cytotoxicity.

Applications of graphene-based nanomaterials in drug design: The good, the bad and the ugly

ABSTRACT Introduction Graphene-based materials (GBMs) have unique physicochemical properties that make them extremely attractive as platforms for the design of new drugs. Indeed, their bidimensional (2D) morphology, high surface area, mechanical and optical properties, associated to different possibilities for functionalization of their surface, provides opportunities for their use as nanomedicines for drug delivery and/or phototherapies. Areas covered This opinion paper provides an overview of the current status of GBMs in drug design, with a focus on their therapeutic applications, potential environmental and health risks, and some controversial results. The authors discuss the chemical modifications of GBMs for the treatment of various diseases. The potential toxicity associated with some GBMs is also presented, along with a safe-by-design approach to minimize the risks. Finally, the authors address some issues associated to the use of GBMs in the biomedical field, such as contradictory antibacterial effects, fluorescence quenching and imprecise chemical functionalization. Expert opinion GBMs are a promising and exciting area of research in drug delivery. It is however important that responsible and safe use of these materials is ensured to fully exploit their advantages and overcome their drawbacks.

Impact of physico-chemical properties on the toxicological potential of reduced graphene oxide in human bronchial epithelial cells

The increasing use of graphene-based materials (GBM) requires their safety evaluation, especially in occupational settings. The same physico-chemical (PC) properties that confer GBM extraordinary functionalities may affect the potential toxic response. Most toxicity assessments mainly focus on graphene oxide and rarely investigate GBMs varying only by one property. As a novelty, the present study assessed the in vitro cytotoxicity and genotoxicity of six reduced graphene oxides (rGOs) with different PC properties in the human bronchial epithelial 16HBE14o − cell line. Of the six materials, rGO1-rGO4 only differed in the carbon-to-oxygen (C/O) content, whereas rGO5 and rGO6 were characterized by different lateral size and number of layers, respectively, but similar C/O content compared with rGO1. The materials were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, laser diffraction and dynamic light scattering, and Brunauer-Emmett-Teller analysis. Cytotoxicity (Luminescent Cell Viability and WST-8 assays), the induction of reactive oxygen species (ROS; 2′,7′-dichlorofluorescin diacetate-based assay), the production of cytokines (enzyme-linked immunosorbent assays) and genotoxicity (comet and micronucleus assays) were evaluated. Furthermore, the internalization of the materials in the cells was confirmed by laser confocal microscopy. No relationships were found between the C/O ratio or the lateral size and any of the rGO-induced biological effects. However, rGO of higher oxygen content showed higher cytotoxic and early ROS-inducing potential, whereas genotoxic effects were observed with the rGO of the lowest density of oxygen groups. On the other hand, a higher number of layers seems to be associated with a decreased potential for inducing cytotoxicity and ROS production.

Reduced Graphene Oxide Aerogels Cartridges for Solid Phase Extraction of Benzotriazoles

UV-benzotriazoles have been identified as water micropollutants that cause serious problems for human health and the environment. Their low concentration in water bodies complicates their detection by direct water analysis, slowing the corrective actions to avoid bioaccumulation. In this regard, the use of graphene-based materials with a high affinity for non-polar molecules has been demonstrated to be a potential tool for the optimal separation and concentration of this type of molecules in solid phase extraction (SPE) processes. This work evaluates the potential of novel reduced graphene oxide aerogels (rGO) as extractants of mixtures of three UV-benzotriazoles in water at low concentrations. These rGO aerogels incorporate graphenic domains into a tough structure of polymeric chains by adding graphene oxide during the synthesis of resorcinol-formaldehyde gels. Aerogels with a different content and ordering of graphenic domains were obtained and characterized using Raman, XRD, SEM and nitrogen adsorption isotherms (-196 °C). The rGO aerogels that performed better as solid phase extractants were those containing 60% rGO. Aerogels with lower rGO contents (40%) required a high-temperature (2000 °C) treatment to render competitive results. The SPE methodology using selected rGO aerogels was optimized by varying the elution solvent, elution time and volume. The best performances, i.e., recoveries of 80-100% and enrichment factors of 12.5-50, were accomplished when using 0.8 mL of tetrahydrofuran (THF) as an elution solvent. As a result, a fast (10 min) and simple extraction method of UV-benzotriazoles in water was attained, achieving a detection limit of 1 ng mL-1. Selected aerogels were finally tested for the SPE of spiked samples of river waters, showing a similar performance to that observed with synthetic mixtures.

Using Graphene-Based Materials for Stiff and Strong Poly(ethylene glycol) Hydrogels.

Blood-contacting devices are increasingly important for the management of cardiovascular diseases. Poly(ethylene glycol) (PEG) hydrogels represent one of the most explored hydrogels to date. However, they are mechanically weak, which prevents their use in load-bearing biomedical applications (e.g., vascular grafts, cardiac valves). Graphene and its derivatives, which have outstanding mechanical properties, a very high specific surface area, and good compatibility with many polymer matrices, are promising candidates to solve this challenge. In this work, we propose the use of graphene-based materials as nanofillers for mechanical reinforcement of PEG hydrogels, and we obtain composites that are stiffer and stronger than, and as anti-adhesive as, neat PEG hydrogels. Results show that single-layer and few-layer graphene oxide can strengthen PEG hydrogels, increasing their stiffness up to 6-fold and their strength 14-fold upon incorporation of 4% w/v (40 mg/mL) graphene oxide. The composites are cytocompatible and remain anti-adhesive towards endothelial cells, human platelets and Staphylococcus aureus, similar to neat hydrogels. To the best of our knowledge, this is the first work to report such an increase of the tensile properties of PEG hydrogels using graphene-based materials as fillers. This work paves the way for the exploitation of PEG hydrogels as a backbone material for load-bearing applications.

A short review on RT-PCR and graphene-based materials in COVID detection

The global pandemic of COVID-19 made all the earth's inhabitants acknowledge the importance of health care and human life. All the countries allocate millions and millions on military and defense, which are in vain today as real soldiers are doctors and health workers waging a war face to face with the invisible Coronavirus. Researchers and companies in Chemistry, Pharmacy, and Biomedical sciences collaborate with technology to fight against COVID-19 and support bringing analyzers for detection and vaccines for eradication. Graphene, a wonder material, is still playing a lead role and exhibiting its multiple astonishing properties. Graphene-enhanced batteries, sensors, biosensors, and photo detectors are available in the market A great deal of research is carried out by many researchers. The present review paper focuses on the use of Graphene-based materials in the COVID pandemic.

Graphene-Based Materials Prove to Be a Promising Candidate for Nerve Regeneration Following Peripheral Nerve Injury.

Peripheral nerve injury is a common medical condition that has a great impact on patient quality of life. Currently, surgical management is considered to be a gold standard first-line treatment; however, is often not successful and requires further surgical procedures. Commercially available FDA- and CE-approved decellularized nerve conduits offer considerable benefits to patients suffering from a completely transected nerve but they fail to support neural regeneration in gaps > 30 mm. To address this unmet clinical need, current research is focused on biomaterial-based therapies to regenerate dysfunctional neural tissues, specifically damaged peripheral nerve, and spinal cord. Recently, attention has been paid to the capability of graphene-based materials (GBMs) to develop bifunctional scaffolds for promoting nerve regeneration, often via supporting enhanced neural differentiation. The unique features of GBMs have been applied to fabricate an electroactive conductive surface in order to direct stem cells and improve neural proliferation and differentiation. The use of GBMs for nerve tissue engineering (NTE) is considered an emerging technology bringing hope to peripheral nerve injury repair, with some products already in preclinical stages. This review assesses the last six years of research in the field of GBMs application in NTE, focusing on the fabrication and effects of GBMs for neurogenesis in various scaffold forms, including electrospun fibres, films, hydrogels, foams, 3D printing, and bioprinting.

Density functional theory study of adsorption and diffusion of potassium atoms on zigzag graphene nanoribbons with different terminal groups

Despite the extensive use of graphene-based materials in K-ion batteries, the effects of various edge morphologies of graphene on K atom adsorption and diffusion are unclear. In this study, the effects of K atom adsorption and diffusion on zigzag graphene nanoribbons (ZGNRs) with hydrogen (−H), ketone (=O), hydroxyl (−OH), and carboxyl (−COOH) terminal groups were investigated by density functional theory calculations. ZGNRs terminating with −H, =O and −COOH promote K atom adsorption, whereas those terminating with −OH suppress it. The −H, =O, −OH and −COOH terminations have a negligible effect on K atom diffusion in the inner region of ZGNRs. In the edge region, the diffusion barriers are nearly unchanged for −H and −OH terminations; however, they are increased for =O and −COOH terminations in the edge region compared to those in the inner region. All the terminal groups hinder K atom diffusion from the edge region toward the inner region. Our results suggest that −H termination enhances K atom adsorption and has a negligible effect on the diffusion barrier of K atom in the edge region. Therefore, the ZGNR with −H termination could be a promising candidate for K-ion batteries.

Antibacterial Activity of Reduced Graphene Oxide

The increasing biological use of graphene-based materials has prompted research inquiries on their effects on microorganisms. The work herein reported different types of microbiological activity of reduced graphene oxide (RGO). At relatively high concentrations (200 and 400 μg/mL), RGO exhibited antibacterial activity on the model bacterium Escherichia coli, while at lower concentrations (10 and 50 μg/mL), interestingly, no antibacterial effect was observed. Instead, an increase in the viable population after exposure at lower concentrations was observed, verified by colony counting and fluorescence microscopy. Further investigation ruled out the possibility of nutrient release from RGO being responsible for this growth-enhancing effect, whereby a comparable number of viable cells were found in the particle-free RGO leachate systems relative to the control. A before and after exposure X-ray photoelectron spectroscopy (XPS) analysis of the RGO detected less presence of C-C bond on the particle surface, suggesting the ability of the bacterium for the use of the carbon-based materials for growth. This potential RGO-cell interaction is further supported by the observed emergence of C-N bond on the particle surface, the nitrogen moieties most likely of bacterial (cell envelope) origins. Although still an early evidence, such RGO-cell interactions could explain the viable cell increase observed at the lower concentration RGO systems. The present study highlights the concentration-dependent microbiological effects of RGO, clarifying the contradicting reports on the growth enhancing versus antibacterial effect of graphene-based materials. The knowledge is important not only for the antibacterial formulation of carbon-based materials but also when assessing their environmental impact.

How macrophages respond to two-dimensional materials: a critical overview focusing on toxicity

With wider use of graphene-based materials and other two-dimensional (2 D) materials in various fields, including electronics, composites, biomedicine, etc., 2 D materials can trigger undesired effects at cellular, tissue and organ level. Macrophages can be found in many organs. They are one of the most important cells in the immune system and they are relevant in the study of nanomaterials as they phagocytose them. Nanomaterials have multi-faceted effects on phagocytic immune cells like macrophages, showing signs of inflammation in the form of pro-inflammatory cytokine or reactive oxidation species production, or upregulation of activation markers due to the presence of these foreign bodies. This review is catered to researchers interested in the potential impact and toxicity of 2 D materials, particularly in macrophages, focusing on few-layer graphene, graphene oxide, graphene quantum dots, as well as other promising 2 D materials containing molybdenum, manganese, boron, phosphorus and tungsten. We describe applications relevant to the growing area of 2 D materials research, and the possible risks of ions and molecules used in the production of these promising 2 D materials, or those produced by the degradation and dissolution of 2 D materials.

Graphene‐Based Nanotechnology in Neurodegenerative Disorders

Graphene‐based materials (GBMs) demonstrate unique electrochemical, mechanical, thermal, and optical properties rendering them attractive candidates for numerous biomedical applications. Since graphene's discovery, GBMs have been at the forefront of biomedical research offering innovative solutions for numerous diseases, including neurodegenerative disorders (NDs). There are numerous reviews in which synthesis and functionalization methods of GBMs are discussed. However, this review focuses specifically on the recent research advances of GBMs for NDs, and more specifically, on sensing and therapeutic applications. After a short description of NDs’ main characteristics, significant attention is given to the functionalization strategies used to improve the biomedical properties of GBMs, and recent applications for Alzheimer's disease, Parkinson's disease, Huntington's disease, multiple sclerosis, and amyotrophic lateral sclerosis. A description of the use of GBMs and neural stem cell technology and known toxicity issues, followed by several limitations that current GBMs need to overcome, completes this review.

Molecular Control of Interfacial Fibronectin Structure on Graphene Oxide Steers Cell Fate.

The use of graphene-based materials (GBMs) for tissue-engineering applications has been growing exponentially because of the seemingly endless multifunctional and tunable physicochemical properties of graphene that can be exploited to influence cellular behavior. Despite many demonstrations wherein cell physiology has been modulated on different GBMs, a clear mechanism connecting the different physicochemical properties of GBMs to cell fate has remained elusive. In this work, we demonstrate how different GBMs can be used to bias cell fate in a multiscale study-starting from serum protein (fibronectin) adsorption and its molecular scale morphology, structure, and bioactivity and ending with stem cell response. Using heat to chemically reduce graphene oxide without changing physical properties, we show that graphene chemistry controls surface-adsorbed molecular conformation and morphology, epitope presentation, and stem cell attachment. Moreover, this subtle change in the protein structure was found to drive increased bone differentiation of stem cells, suggesting that the physicochemical properties of graphene biases cell fate by directly influencing the adsorbed protein structure and subsequent biochemical activity.

Graphene-Based Kinetic Promotion of Gas Hydrate Formation.

Gas hydrate technology holds great potential in energy and environmental fields, and achieving efficient gas hydrate formation is critical for its industrial application. Graphene is a novel carbon-based nanostructured material with excellent thermal conductivity and a large specific surface area. Therefore, the use of graphene-based materials for the promotion of gas hydrate formation might be feasible and has aroused a lot of interests. Accordingly, to evaluate the current research on graphene-based promotion of gas hydrate formation, this work presents a review of existing studies involving graphene-based promoters of gas hydrate formation. Here, the studies applying various types of graphene-based promoters for gas hydrate formation are listed and detailed, the peculiar properties of graphene-based promoters are discussed, and the promotion mechanisms are analyzed. Through this review, comprehensive insight into graphene-based promotion of gas hydrate formation can be obtained, which can guide the design and applications of novel graphene-based promoters and might contribute to achieving efficient gas hydrate formation.

Poorly conductive electrochemically reduced graphene oxide films modified with alkyne chains to avoid the corrosion-promoting effect of graphene-based materials on carbon steel

Recently, the discovery of the corrosion-promoting effect of graphene has hindered the progress in the use of graphene-based materials as anticorrosive coatings. This work proposes to avoid the corrosion-promoting effect by the introduction of favorable defects to electrochemically reduced graphene oxide (ErGO), which consisted in the hydrogenation of sp2 domains during the removal of O-groups in graphene oxide, favoring sp3 domains and low conductivity. The ErGO films were subsequently modified with 4-pentyonate chains to obtain films with lower conductivity and enhanced hydrophobicity (HrGO). The alkyne chains were bonded to the remaining sp2 domains in ErGO by a simple electrochemical process. Both films were characterized by FT-IR, XPS, Raman spectroscopy and electrochemical methods. As anticorrosive coating, the HrGO film achieved a 4-times decrease in the corrosion current and showed a longer lifetime in comparison to the ErGO film, and an 18-times decrease compared to the bare carbon steel. According to the galvanic current measurements, neither of the films presented a corrosion-promoting effect, which was attributed to their low conductivity, 13 and 1.3 S cm−1 for ErGO and HrGO, respectively. These results show that the corrosion promoting effect of graphene can be avoided using correctly engineering ErGO with adequate defects.

Keratinocytes are capable of selectively sensing low amounts of graphene-based materials: Implications for cutaneous applications

Skin provides the first interface between body and environment, representing one of the most feasible exposure routes to graphene-based materials (GBMs). However, interactions of GBMs with the skin are poorly understood. In particular, low-concentration effects have not been investigated. Here we explored the ability of endotoxin-free, few-layer graphene (FLG) and dehydrated graphene oxide (d-GO) to initiate an inflammatory response at the cutaneous level by using human HaCaT keratinocytes. HaCaT cell exposure to low concentrations (0.01–1.0 μg/mL) of FLG or d-GO did not affect cell viability. FLG triggered the secretion of pro-inflammatory tumor necrosis factor-α (TNF-α), interleukin (IL)-1α, and IL-6, while d-GO, and to a lesser extent FLG, prompted IL-8 (CXCL8) production. However, conditioned medium from HaCaT cells exposed to FLG or d-GO had no effect on THP-1 monocyte activation. Moreover, co-culture experiments did not show any effect of FLG- or d-GO-treated HaCaT cells on THP-1 cell migration. These results suggest that while GBMs are able to initiate an inflammatory response in keratinocytes, this does not necessarily lead to activation of monocytes. The present findings are relevant for potential dermal exposures to GBMs in occupational settings as well as the use of GBMs for cutaneous applications such as in wearable sensors.

Graphene-Based Catalysts for Ozone Processes to Decontaminate Water.

The use of graphene-based materials as catalysts in both ozone and ozone/radiation processes is creating interest among researchers devoted to the study of advanced oxidation processes (AOPs) for the degradation of organic pollutants in water. In this review, detailed explanations of catalytic and photocatalytic ozonation processes mediated by graphene-based materials are presented, focusing on aspects related to the preparation and characterization of catalysts, the nature of the water pollutants treated, the type of reactors and radiation sources applied, the influence of the main operating variables, catalyst activity and stability, and kinetics and mechanisms.

Graphene-Based Membranes for CO2/CH4 Separation: Key Challenges and Perspectives

Increasing demand to strengthen energy security has increased the importance of natural gas sweetening and biogas upgrading processes. Membrane-based separation of carbon dioxide (CO2) and methane (CH4) is a relatively newer technology, which offers several competitive advantages, such as higher energy-efficiency and cost-effectiveness, over conventional technologies. Recently, the use of graphene-based materials to elevate the performance of polymeric membranes have attracted immense attention. Herein, we do not seek to provide the reader with a comprehensive review of this topic but rather highlight the key challenges and our perspectives going ahead. We approach the topic by evaluating three mainstream membrane designs using graphene-based materials: (1) nanoporous single-layer graphene, (2) few- to multi-layered graphene-based stacked laminates, and (3) mixed-matrix membranes. At present, each design faces different challenges, including low scalability, high production cost, limited performance enhancement, and the lack of robust techno-economic review and systematic membrane design optimization. To help address these challenges, we have mapped out a technology landscape of the current graphene-based membrane research based on the separation performance enhancement, commercial viability, and production cost. Accordingly, we contend that future efforts devoted to advancing graphene-based membranes must be matched by progress in these strategic areas so as to realize practical and commercially relevant graphene-based membranes for CO2/CH4 separation and beyond.