Structure and chemistry of graphene oxide in liquid water from first principles

Nanomaterials-based electrochemical biosensors for diagnosis of COVID-19

Since the outbreak of corona virus disease 2019 (COVID-19), this pandemic has caused severe death and infection worldwide. Owing to its strong infectivity, long incubation period, and nonspecific symptoms, the early diagnosis is essential to reduce risk of the severe illness. The electrochemical biosensor, as a fast and sensitive technique for quantitative analysis of body fluids, has been widely studied to diagnose different biomarkers caused at different infective stages of COVID-19 virus (SARS-CoV-2). Recently, many reports have proved that nanomaterials with special architectures and size effects can effectively promote the biosensing performance on the COVID-19 diagnosis, there are few comprehensive summary reports yet. Therefore, in this review, we will pay efforts on recent progress of advanced nanomaterials-facilitated electrochemical biosensors for the COVID-19 detections. The process of SARS-CoV-2 infection in humans will be briefly described, as well as summarizing the types of sensors that should be designed for different infection processes. Emphasis will be supplied to various functional nanomaterials which dominate the biosensing performance for comparison, expecting to provide a rational guidance on the material selection of biosensor construction for people. Finally, we will conclude the perspective on the design of superior nanomaterials-based biosensors facing the unknown virus in future.

Staggered structural dynamic-mediated selective adsorption of H2O/D2O on flexible graphene oxide nanosheets

Graphene oxide (GO) is the one of the most promising family of materials as atomically thin membranes for water-related molecular separation technologies due to its amphipathic nature and layered structure. Here, we show important aspects of GO on water adsorption from molecular dynamics (MD) simulations, in-situ X-ray diffraction (XRD) measurements, and ex-situ nuclear magnetic resonance (NMR) measurements. Although the MD simulations for GO and the reduced GO models revealed that the flexibility of the interlayer spacing could be attributed to the oxygen-functional groups of GO, the ultra-large GO model cannot well explain the observed swelling of GO from XRD experiments. Our MD simulations propose a realistic GO interlayer structure constructed by staggered stacking of flexible GO sheets, which can explain very well the swelling nature upon water adsorption. The transmission electron microscopic (TEM) observation also supports the non-regular staggered stacking structure of GO. Furthermore, we demonstrate the existence of the two distinct types of adsorbed water molecules in the staggered stacking: water bonded with hydrophilic functional groups and "free" mobile water. Finally, we show that the staggered stacking of GO plays a crucial role in H/D isotopic recognition in water adsorption, as well as the high mobility of water molecules.

Confined and spontaneously transformed oxidation structures due to the intrinsic heterogeneous surface morphology of C3N monolayer

Identifying the oxidation structure of two-dimensional interfaces is crucial to improve surface chemistry and electronic properties. Beyond graphene with only phenyl rings, a novel carbon-nitrogen material, C3N, presents an intrinsic heterogeneous surface morphology where each phenyl ring is encircled by six nitrogen atoms, yet its atomistic oxidation structure remains unclear. Here, combining a series of density functional theory calculations and ab initio molecular dynamics simulations, we demonstrate that thermodynamically favorable oxidation loci are confined to the phenyl ring, and kinetic transformations of oxidation structures are feasible along the phenyl ring, whereas those toward nitrogen atoms are proven to be extremely difficult. These results are attributed to the lower barrier of oxygen atom migration along the phenyl ring, while the significantly high barriers toward nitrogen atoms are due to the heterogeneous potential energy surface for oxygen-C3N interaction. This work highlights the significance of surface morphology on the characteristics of oxidation structure, offering insights into tunable electronic properties via confined interfacial oxidation.

Origin of Oxygen in Graphene Oxide Revealed by 17O and 18O Isotopic Labeling

Wet-chemical oxidation of graphite in a mixture of sulfuric acid with a strong oxidizer, such as potassium permanganate, leads to the formation of graphene oxide with hydroxyl and epoxide groups as the major functional groups. Nevertheless, the reaction mechanism remains unclear and the source of oxygen is a subject of debate. It could theoretically originate from the oxidizer, water, or sulfuric acid. In this study, we employed 18O and 17O labeled reagents to experimentally elucidate the reaction mechanism and, thus, determine the origin of oxo-functional groups. Our findings reveal the multifaceted roles of sulfuric acid, acting as a dispersion medium, a dehydrating agent for potassium permanganate, and an intercalant. Additionally, it significantly acts as a source of oxygen next to manganese oxides. Through 17O solid-state magic-angle spinning (MAS) NMR experiments, we exclude water as a direct reaction partner during oxygenation. With labeling experiments, we conclude on mechanistic insights, which may be exploited for the synthesis of novel graphene derivatives.

Structural Stability and Disorder Level of Moderately Reduced Paper-like Graphene Oxide Investigated with Micro-Raman Analysis

This paper discusses the results of the micro-Raman analysis performed on paper-like graphene oxide (GO) samples consisting of many functionalised graphene layers and annealed at moderate temperatures (≤500 °C) under vacuum conditions (p ≃ 10-4 mbar). The analysis of the standalone samples revealed that the obtained material is characterised by a noticeable disorder level but still stays below the commonly accepted threshold of high or total disorder. GO formed in a simple way showed two spectral bands above 1650 cm-1 recorded very rarely or not at all and their origin has been discussed in detail. The results also confirmed the metastable character of multilayer GO after the annealing process at moderate temperatures as the C/O ratio was kept between 2 and 3 and the spectral features were stable within the annealing temperature range.

ReaxFF molecular dynamics of graphene oxide/NaCl aqueous solution interfaces

In this work, the interaction of NaCl aqueous solution with graphene (G), graphene oxide (GO), and graphite oxide (GTO) is studied using the ReaxFF module of Amsterdam Modeling Suite (AMS) software. We consider four models using the NaCl aqueous solution, containing a graphene sheet (G), a single sheet of GO with epoxide and hydroxyl groups on its surface, 4 layers of GO to model GTO, and a bulk NaCl solution as a reference. The structural and dynamical properties of G, GO, and GTO were quantified by analyzing the functional groups, radial distribution functions, density profiles and diffusivities of water and ions. Due to the reactive force field, the systems underwent spontaneous modification of surface functional groups during the first 750 ps after which the structure stabilizes (the energy stabilizes in less than 400 ps). Pristine graphene in contact with the NaCl solution formed hydroxyl groups on the edges, i.e., converted to partially reduced graphene oxide. The epoxy groups (Oe) on the initial GO were rather unstable, leading to a reduction of their number, however, there was an increase in the number of hydroxyl groups (Oh), mainly at the edges. The interactions of NaCl with the carbon-based sheets are rather weak, including GO and GTO which are decorated with numerous functional groups. Diffusion coefficients of water agree with the available data, but discrepancies in Na+ and Cl- diffusivity compared to other references underscore the need for further development in the dynamic parameters of the reactive force field used. In essence, our research provides specific data previously unreported, laying a foundation for advancing water desalination system design. The study's novelty lies in its realistic approach to graphene/graphene oxide modification, comprehensive characterization, and the application of the reactive force field to explore the graphene oxide-NaCl aqueous interface, contributing to the development of a practical membrane system for water desalination.

Graphene Oxide Nanoparticles and Organoids: A Prospective Advanced Model for Pancreatic Cancer Research

Pancreatic cancer, notorious for its grim 10% five-year survival rate, poses significant clinical challenges, largely due to late-stage diagnosis and limited therapeutic options. This review delves into the generation of organoids, including those derived from resected tissues, biopsies, pluripotent stem cells, and adult stem cells, as well as the advancements in 3D printing. It explores the complexities of the tumor microenvironment, emphasizing culture media, the integration of non-neoplastic cells, and angiogenesis. Additionally, the review examines the multifaceted properties of graphene oxide (GO), such as its mechanical, thermal, electrical, chemical, and optical attributes, and their implications in cancer diagnostics and therapeutics. GO's unique properties facilitate its interaction with tumors, allowing targeted drug delivery and enhanced imaging for early detection and treatment. The integration of GO with 3D cultured organoid systems, particularly in pancreatic cancer research, is critically analyzed, highlighting current limitations and future potential. This innovative approach has the promise to transform personalized medicine, improve drug screening efficiency, and aid biomarker discovery in this aggressive disease. Through this review, we offer a balanced perspective on the advancements and future prospects in pancreatic cancer research, harnessing the potential of organoids and GO.

Performance of graphene oxide as a water-repellent coating nanomaterial to extend the service life of concrete structures

Surface treatments help to protect the built heritage against damage (environmental, accidental, etc.), reducing repair and restitution costs and increasing the useful life of building materials. The use of nanomaterials is currently the most important field of research in surface treatment technology for the preservation of building materials and, more specifically, to improve their durability and prevent their deterioration, extending their useful life. This paper studies the influence of a graphene oxide (GO) suspension as a surface treatment on the properties of concrete. The results indicate that, at best, surface treatment with GO can decrease both the water absorption and capillary absorption of concrete by about 15 %. The increase in the amount of GO deposited as a surface treatment leads to a further reduction in concrete water absorption. It is shown that, at best, GO coating also reduces water penetration at low and high pressures by approximately 20 % and 60 %, respectively. In addition, scanning electron microscopy analysis shows that GO surface treatment facilitates the hydration process and densifies the concrete microstructure. A simple aqueous suspension of GO is revealed as a tool with a high potential to protect concrete surfaces in a fast and cost-effective way, thanks to the easy application by spraying and the small amount of material needed to obtain great results.

A Short Overview on Graphene and Graphene-Related Materials for Electrochemical Gas Sensing

The development of new and high-performing electrode materials for sensing applications is one of the most intriguing and challenging research fields. There are several ways to approach this matter, but the use of nanostructured surfaces is among the most promising and highest performing. Graphene and graphene-related materials have contributed to spreading nanoscience across several fields in which the combination of morphological and electronic properties exploit their outstanding electrochemical properties. In this review, we discuss the use of graphene and graphene-like materials to produce gas sensors, highlighting the most relevant and new advancements in the field, with a particular focus on the interaction between the gases and the materials.

An influence of temperature jump and Navier's slip-on hybrid nano fluid flow over a permeable stretching/shrinking sheet with heat transfer and inclined MHD

This research article, explores the influence of an inclined magnetic field on the fluid flow over a permeable stretching/shrinking surface with heat transfer. The study use water as a conventional base fluid, with graphene oxide (GO) and Aluminum oxide (Al2O3) nanoparticles submerged to create a nanofluid, the system of governing nonlinear partial differential equations converted into ordinary differential equations via suitable similarity conversions. This allow for the unique solution for stretching sheet/shrinking sheets to be obtained, along with the corresponding temperature solution in terms of the hypergeometric function, several parameters are included in the investigation and their contribution is graphically explained to examine physical characteristics such as radiation, inclined magnetic field, solution domain, volume fraction parameter, and temperature jump. Increasing the volume fraction and thermal radiation increases the thermal boundary layer, increasing the magnetic field parameter and inverse Darcy number increases the temperature and decays the velocity profile. The present work has many useful applications in engineering, biological and physical sciences, as well as in cleaning engine lubricants and thrust-bearing technologies.

Exploration of functionalizing graphene and the subsequent impact on PFAS adsorption capabilities via molecular dynamics

Per- and polyfluoroalkyl substances (PFAS) are extremely stable compounds due to their strong C-F bonds. They are used in water and stain proof coatings, aqueous film forming foams for fire suppression, cosmetics, paints, adhesives, etc. PFAS have been found in soils and waterways around the world due to their widespread usage and recalcitrance to degradation. Development of selective adsorbent materials is necessary to effectively capture a vast family of PFAS structures in order to remediate PFAS contamination in the environment. The work herein is focused on extracting design principles from molecular dynamics simulations of PFAS with functionalized graphene materials. Simulations examined how PFBA, PFOA, and PFOS interact with graphene, graphene oxide, nitrogen group-functionalized graphene oxide, partially fluorinated graphene flakes, and fully fluorinated flakes. Five flakes were used in each simulation to examine how interactions between flakes may lead to competitive interactions with respect to PFAS or formation of pores. Our study revealed that both the clustering mechanisms of the flakes and functional groups on the flake play a role in PFAS adsorption. The most effective functionalizations for PFAS adsorption are as follows: pristine graphene ≈ fully fluorinated > graphene oxide ≈ partially fluorinated > amine and amide functionalized graphene oxide flake. Long chain PFAS and sulfonate PFAS had higher propensity to adsorb to the materials compared to short chain PFAS and carboxylic head groups.

First-Principles Study on Out-of-Plane Piezoelectricity of Self-Assembled Ammonia Layers Confined in Two Vertically Stacked Graphene Oxide Nanosheets

Two-dimensional (2D) piezoelectric materials have attracted widespread attention due to their increasingly important niche applications in flexible nanoscale devices. The water-wetted graphene oxide papers exhibit scalable out-of-plane piezoelectricity induced by the hydrogen-bonded network within, and this system can be treated as a potential 2D piezoelectric candidate for future device applications. It triggered our interest to search for more 2D piezoelectric hydrogen-bonded networks. Ammonia (NH3) isoelectronic with water is introduced to generate NH3-wetted graphene oxide papers and realize their out-of-plane piezoelectricity. Their structures and piezoelectricity are investigated using first-principles calculations. They reveal ultrahigh piezoelectricity, compared to the best reported 2D materials. Their piezoelectricity is tuned by varying oxygen-containing functional groups in GO plates, confined NH3 layers, or orientations of NH3 molecules, and it could be applied to fabrication of ammonia sensors. Our study not only enriches the family of 2D piezoelectric nanosystems but also inspires their future experimental exploration.

Decoding the Interplay between Topology and Surface Charge in Graphene Oxide Membranes During Humidity Induced Swelling

Graphene oxide (GO) membranes are known to have a complex morphology that depends on the degree of oxidation of the graphene flake and the membrane preparation technique. In this study, using Grand Canonical Monte Carlo simulations, we investigate the mechanism of swelling of GO membranes exposed to different relative humidity (RH) values and show how this is intimately related to the graphene surface chemistry. We show that the structure of the GO membrane changes while the membrane adsorbs water from the environment and that graphene oxide flakes become charged as the membrane is loaded with water and swells. A detailed comparison between simulation and experimental adsorption data reveals that the flake surface charge drives the water adsorption mechanism at low RH when the membrane topology is still disordered and the internal pores are small and asymmetric. As the membrane is exposed to higher RH (80%), the flake acquires more surface charge as more oxide groups deprotonate, and the pores grow in size, yet maintain their disordered geometry. Only for very high relative humidity (98%) does the membrane undergo structural changes. At this level of humidity, the pores in the membrane become slit-like but the flake surface charge remains constant. Our results unveil a very complex mechanism of swelling and show that a single molecular model cannot fully capture the ever-changing chemistry and morphology of the membrane as it swells. Our computational procedure provides the first atomically resolved insight into the GO membrane structure of experimental samples.

Biocomposites Based on Electrospun Fibers of Poly(3-hydroxybutyrate) and Nanoplatelets of Graphene Oxide: Thermal Characteristics and Segmental Dynamics at Hydrothermal and Ozonation Impact

In order to create new biodegradable nanocomposites for biomedicine, packaging, and environmentally effective adsorbents, ultra-thin composite fibers consisting of poly(3-hydroxybutyrate) (PHB) and graphene oxide (GO) were obtained by electrospinning. Comprehensive studies of ultrathin fibers combining thermal characteristics, dynamic electron paramagnetic resonance (ESR) probe measurements, and scanning electron microscopy (SEM) were carried out. It is shown that at the addition of 0.05, 0.1, 0.3, and 1% OG, the morphology and geometry of the fibers and their thermal and dynamic characteristics depend on the composite content. The features of the crystalline and amorphous structure of the PHB fibers were investigated by the ESR and DSC methods. For all compositions of PHB/GO, a nonlinear dependence of the correlation time of molecular mobility TEMPO probe (τ) and enthalpy of biopolyether melting (ΔH) is observed. The influence of external factors on the structural-dynamic properties of the composite fiber, such as hydrothermal exposure of samples in aqueous medium at 70 °C and ozonolysis, leads to extreme dependencies of τ and ΔH, which reflect two processes affecting the structure in opposite ways. The plasticizing effect of water leads to thermal destruction of the orientation of the pass-through chains in the amorphous regions of PHB and a subsequent decrease in the crystalline phase, and the aggregation of GO nanoplates into associates, reducing the number of GO-macromolecule contacts, thus increasing segmental mobility, as confirmed by decreasing τ values. The obtained PHB/GO fibrillar composites should find application in the future for the creation of new therapeutic and packaging systems with improved biocompatibility and high-barrier properties.

The cytocompatibility of graphene oxide as a platform to enhance the effectiveness and safety of silver nanoparticles through in vitro studies

The increasing emergence of antibiotic-resistant bacteria and the need to reduce the use of antibiotics call for the development of safe alternatives, such as silver nanoparticles. However, their potential cytotoxic effect needs to be addressed. Graphene oxide provides a large platform that can increase the effectiveness and safety of silver nanoparticles. Graphene oxide and silver nanoparticles complex applied as a part of an innovative material might have direct contact with human tissues, such as skin, or might be inhaled from aerosol or exfoliated pieces of the complex. Thereby, the safety of the prepared complex has to be evaluated carefully, employing a range of methods. We demonstrated the high cytocompatibility of graphene oxide and the graphene oxide-silver nanoparticles complex toward human cell lines, fetal foreskin fibroblasts (HFFF2), and lung epithelial cells (A549). The supporting platform of graphene oxide also neutralized the slight toxicity of bare silver nanoparticles. Finally, in studies on Staphylococcus aureus and Pseudomonas aeruginosa, the number of bacteria reduction was observed after incubation with silver nanoparticles and the graphene oxide-silver nanoparticles complex. Our findings confirm the possibility of employing a graphene oxide-silver nanoparticles complex as a safe agent with reduced silver nanoparticles' cytotoxicity and antibacterial properties.

Polycaprolactone/graphene oxide/acellular matrix nanofibrous scaffolds with antioxidant and promyelinating features for the treatment of peripheral demyelinating diseases

Peripheral demyelinating diseases entail damage to axons and Schwann cells in the peripheral nervous system. Because of poor prognosis and lack of a cure, this group of diseases has a global impact. The primary underlying cause of these diseases involves the inability of Schwann cells to remyelinate the damaged insulating myelin around axons, resulting in neuronal death over time. In the past decade, extensive research has been directed in the direction of Schwann cells focusing on their physiological and neuroprotective effects on the neurons in the peripheral nervous system. One cause of dysregulation in the remyelinating function of Schwann cells has been associated with oxidative stress. Tissue-engineered biodegradable scaffolds that can stimulate remyelination response in Schwann cells have been proposed as a potential treatment strategy for peripheral demyelinating diseases. However, strategies developed to date primarily focussed on either remyelination or oxidative stress in isolation. Here, we have developed a multifunctional nanofibrous scaffold with material and biochemical cues to tackle both remyelination and oxidative stress in one matrix. We developed a nanofibrous scaffold using polycaprolactone (PCL) as a foundation loaded with antioxidant graphene oxide (GO) and coated this bioscaffold with Schwann cell acellular matrix. In vitro studies revealed both antioxidant and remyelination properties of the developed bioscaffold. Based on the results, the developed multifunctional bioscaffold approach can be a promising biomaterial approach for treating demyelinating diseases.

Boosting Plant Photosynthesis with Carbon Dots: A Critical Review of Performance and Prospects

Artificially augmented photosynthesis in nano-bionic plants requires tunable nano-antenna structures with physiochemical and optoelectronic properties, as well as unique light conversion capabilities. The use of nanomaterials to promote light capture across photosystems, primarily by carbon dots, has shown promising results in enhancing photosynthesis through tunable uptake, translocation, and biocompatibility. Carbon dots possess the ability to perform both down and up-light conversions, making them effective light promoters for harnessing solar energy beyond visible light wavelengths.This review presents and discusses the recent progress in fabrication, chemistry, and morphology, as well as other properties such as photoluminescence and energy conversion efficiency of nano-antennas based on carbon dots. The performance of artificially boosted photosynthesis is discussed and then correlated with the conversion properties of carbon dots and how they are applied to plant models. The challenges related to the nanomaterial delivery and the performance evaluation practices in modified photosystems, consideration of the reliability of this approach, and the potential avenues for performance improvements through other types of nano-antennas based on alternative nanomaterials are also critically evaluated. It is anticipated that this review will stimulate more high-quality research in plant nano-bionics and provide avenues to enhance photosynthesis for future agricultural applications.

Extreme Ion-Transport Inorganic 2D Membranes for Nanofluidic Applications

Inorganic 2D materials offer a new approach to controlling mass diffusion at the nanoscale. Controlling ion transport in nanofluidics is key to energy conversion, energy storage, water purification, and numerous other applications wherein persistent challenges for efficient separation must be addressed. The recent development of 2D membranes in the emerging field of energy harvesting, water desalination, and proton/Li-ion production in the context of green energy and environmental technology is herein discussed. The fundamental mechanisms, 2D membrane fabrication, and challenges toward practical applications are highlighted. Finally, the fundamental issues of thermodynamics and kinetics are outlined along with potential membrane designs that must be resolved to bridge the gap between lab-scale experiments and production levels.

Ion and water adsorption to graphene and graphene oxide surfaces

Graphene and graphene oxide (GO) are two particularly promising nanomaterials for a range of applications including energy storage, catalysis, and separations. Understanding the nanoscale interactions between ions and water near graphene and GO surfaces is critical for advancing our fundamental knowledge of these systems and downstream application success. This minireview highlights the necessity of using surface-specific experimental probes and computational techniques to fully characterize these interfaces, including the nanomaterial, surrounding water, and any adsorbed ions, if present. Key experimental and simulation studies considering water and ion structures near both graphene and GO are discussed. The major findings are: water forms 1-3 hydration layers near graphene; ions adsorb electrostatically to graphene under an applied potential; the chemical and physical properties of GO vary considerably depending on the synthesis route; and these variations influence water and ion adsorption to GO. Lastly, we offer outlooks and perspectives for these research areas.

Diffusion Dynamics of Water and Ethanol in Graphene Oxide

We utilized the momentum transfer (Q)-dependence of quasi-elastic neutron scattering (QENS) to measure the dynamics of water and ethanol confined in graphene oxide (GO) powder or membranes at different temperatures and in different orientations. We found reduced diffusivities (up to 30% in the case of water) and a depression of dynamic transition temperatures. While water showed near Arrhenius behavior with an almost bulk-like activation barrier in a temperature range of 280-310 K, the diffusivity of ethanol showed little temperature dependence. For both water and ethanol, we found evidence for immobile and mobile fractions of the confined liquid. The mobile fraction exhibited jump diffusion, with a jump length consistent with the expected average spacing of hydroxide groups in the GO surfaces. From anisotropy measurements, we found weak anisotropy in the diffusivity of the mobile species and in the fraction and geometry of immobile species.

Revealing the Chemical Nature of Functional Groups on Graphene Oxide by Integrating Potentiometric Titration and Ab Initio Calculations

A new graphene oxide (GO) model with reasonable functional group types and distribution modes was proposed by integrating potentiometric titrations and ab initio calculations. Due to the complex synthesis mechanism, the atomic structure of GO has been controversial for a long time. Here, we use density functional theory calculations to mimic the oxidation process, and a series of GO fragments (GOFs) were deduced. A new pK_a calculation method (RCDPKA) developed specifically in this work was further used to predict pK_a values of the fragments. Then, we performed potentiometric titrations on four different GO samples to confirm the existence of these GOFs and determine the content of functional groups. Interestingly, different GO samples present the same pK_a values in titration, and the results are consistent with the predicted ones. Based on the evidence from titration and calculation, prominent correlations between functional groups could be found. Groups at the edges are mainly double-interactive carboxyls (pK_a1 ≈ 3.4, pK_a2 ≈ 5.7) and double-adjacent phenolic hydroxyls (pK_a1 ≈ 8.8, pK_a2 ≈ 12.1), while groups on the plane are mainly collocated epoxies and hydroxyls (pK_a1 ≈ 11.1, pK_a2 ≈ 13.8) on both sides of the plane with a meta-positional hydrogen bond interaction. These findings were further validated by multiple characterizations and GO modifications. These results not only stimulate a fundamental understanding of the GO structure but also provide a quantitative analysis method for functional groups on GO.

Chemical and Physical Drivers for Improvement in Permeance and Stability of Linker-Free Graphene Oxide Membranes

Graphene oxide (GO) is a promising membrane material for chemical separations, including water treatment. However, GO has often required postsynthesis chemical modifications, such as linkers or intercalants, to improve either the permeability, performance, or mechanical integrity of GO membranes. In this work, we explore two different feedstocks of GO to investigate chemical and physical differences, where we observe up to a 100× discrepancy in the permeability-mass loading trade-off while maintaining nanofiltration capacity. GO membranes also show structural stability and chemical resilience to harsh pH conditions and bleach treatment. We probe GO and the resulting assembled membranes through a variety of characterization approaches, including a novel scanning-transmission-electron-microscopy-based visualization approach, to connect differences in sheet stacking and oxide functional groups to significant improvements in permeability and chemical stability.

Molecular Understanding of Adhesion of Epoxy Resin to Graphene and Graphene Oxide Surfaces in Terms of Orbital Interactions

The adhesion mechanism of epoxy resin (ER) cured material consisting of diglycidyl ether of bisphenol A (DGEBA) and 4,4'-diaminodiphenyl sulfone (DDS) to pristine graphene and graphene oxide (GO) surfaces is investigated on the basis of first-principles density functional theory (DFT) with dispersion correction. Graphene is often used as a reinforcing filler incorporated into ER polymer matrices. The adhesion strength is significantly improved by using GO obtained by the oxidation of graphene. The interfacial interactions at the ER/graphene and ER/GO interfaces were analyzed to clarify the origin of this adhesion. The contribution of dispersion interaction to the adhesive stress at the two interfaces is almost identical. In contrast, the DFT energy contribution is found to be more significant at the ER/GO interface. Crystal orbital Hamiltonian population (COHP) analysis suggests the existence of hydrogen bonding (H-bonding) between the hydroxyl, epoxide, amine, and sulfonyl groups of the ER cured with DDS and the hydroxyl groups of the GO surface, in addition to the OH-π interaction between the benzene rings of ER and the hydroxyl groups of the GO surface. The H-bond has a large orbital interaction energy, which is found to contribute significantly to the adhesive strength at the ER/GO interface. The overall interaction at the ER/graphene is much weaker due to antibonding type interactions just below the Fermi level. This finding indicates that only dispersion interaction is significant when ER is adsorbed on the graphene surface.

Green and Sustainable Ultrasound-Assisted Anodic Electrochemical Preparation of Graphene Oxide Dispersions and Their Antioxidant Properties

A fast method for preparing aqueous graphene oxide (GO) dispersions by electrochemical oxidation of a graphite anode without preliminary intercalation with oxidizing agents is proposed. Ultrasonic probing was used in the modulation mode of ultrasonic waves (work/rest) for more efficient graphite oxidation-exfoliation. It is shown that the 4/2 s mode of ultrasonic modulation is the most effective due to the probe material's low corrosion while maintaining the optimum synthesis temperature not exceeding 30-35 °C and achieving the best characteristics of the resulting product. Three cases of anodic oxidation of graphite to obtain graphene oxide were considered: (1) a combined cathode-anode compartment, (2) a split cathode-anode salt-bridged compartment, and (3) separated anode compartment with a 3.5 kDa dialysis membrane. It was determined that the approach to synthesis with a divided cathode-anode compartment makes it possible to obtain GO sheets with fewer defects compared to chemical methods or methods with a combined cathode-anode compartment and makes it possible to control the oxidation degree of the material (C:O ratio) by varying the current density. The prepared samples showed good stability for more than six months. The spectral and morphological characteristics were studied. Using chemiluminometry in the luminol/Co(II)/H₂O₂ system, the antioxidant properties concerning three key reactive oxygen species (H₂O₂, superoxide anion radical, and hydroxyl radical) were demonstrated. It was also shown that the prepared GO dispersions do not induce lipid and phospholipid peroxidation.

From nanohole to ultralong straight nanochannel fabrication in graphene oxide with swift heavy ions

Porous architectures based on graphene oxide with precisely tailored nm-sized pores are attractive for biofluidic applications such as molecular sieving, DNA sequencing, and recognition-based sensing. However, the existing pore fabrication methods are complex, suffer from insufficient control over the pore density and uniformity, or are not scalable to large areas. Notably, creating vertical pores in multilayer films appears to be particularly difficult. Here, we show that uniform 6-7 nm-sized holes and straight, vertical nanochannels can be formed by simply irradiating graphene oxide (GO) films with high-energy heavy ions. Long penetration depths of energetic ions in combination with localized energy deposition and effective self-etching processes enable the creation of through pores even in 10 µm-thick GO films. This fully scalable fabrication provides a promising possibility for obtaining innovative GO track membranes.

Development of Nanoscale Graphene Oxide Models for the Adsorption of Biological Molecules

Graphene oxide (GO), a nanomaterial with promising applications that range from water purification to enzyme immobilization, is actively present in scientific research since its discovery. GO studies with computational methodologies such as molecular dynamics are frequently reported in the literature; however, the models used often rely on approximations, such as randomly placing functional groups and the use of generalized force fields. Therefore, it is important to develop new MD models that provide a more accurate description of GO structures and their interaction with an aqueous solvent and other adsorbate molecules. In this paper, we derived new force field non-bonded parameters from linear-scaling density functional theory calculations of nanoscale GO sheets with more than 10,000 atoms through an atoms-in-molecules (AIM) partitioning scheme. The resulting GAFF2-AIM force field, derived from the bonded terms of GAFF2 parameterization, reproduces the solvent structure reported in ab initio MD simulations better than the force field nowadays widely used in the literature. Additionally, we analyzed the effect of the ionic strength of the medium and of the C/O ratio on the distribution of charges surrounding the GO sheets. Finally, we simulated the adsorption of natural amino acid molecules to a GO sheet and estimated their free energy of binding, which compared very favorably to their respective experimental values, validating the force field presented in this work.

Convenient Confinement: Interplay of Solution Conditions and Graphene Oxide Film Structure on Rare Earth Separations

Graphene oxide (GO) membranes are excellent candidates for a range of separation applications, including rare earth segregation and radionuclide decontamination. Understanding nanoscale water and ion behavior near interfacial GO is critical for groundbreaking membrane advances, including improved selectivity and permeability. We experimentally examine the impact of solution conditions on water and lanthanide interactions with interfacial GO films and connect these results to GO membrane performance. The investigation of the confined films at the air-water interface with a combination of surface-specific spectroscopy and X-ray scattering techniques allows us to understand water and ion behaviors separately. Sum frequency generation spectroscopy reveals a dramatic change in interfacial water organization because of graphene oxide film deprotonation. Interfacial X-ray fluorescence measurements show a 17× increase in adsorbed lanthanide to the GO film from subphase pH 3 to pH 9. Liquid surface X-ray reflectivity data show an additional 2.7 e^- per Ų for GO films at pH 9 versus pH 3 as well. These results are connected to GO membrane performance, which show increased selectivity and decreased flux for membranes filtering pH 9 solutions. We posit insoluble lanthanide hydroxides form at higher pHs. Taken together, these results highlight the importance of interfacial experiments on model GO systems.

Insights into the Stability of Graphene Oxide Aqueous Dispersions

Understanding graphene oxide's stability (or lack thereof) in liquid solvents is critical for fine-tuning the material's characteristics and its potential involvement in future applications. In this work, through the use of structural and surface investigations, the alteration of the structural and edge-surface properties of 2D graphene oxide nanosheets was monitored over a period of eight weeks by involving DLS, zeta potential, XRD, XPS, Raman and FT-IR spectroscopy techniques. The samples were synthesized as an aqueous suspension by an original modified Marcano-Tour method centred on the sono-chemical exfoliation of graphite. Based on the acquired experimental results and the available literature, a phenomenological explanation of the two underlying mechanisms responsible for the meta-stability of graphene oxide aqueous dispersions is proposed. It is based on the cleavage of the carbon bonds in the first 3-4 weeks, while the bonding of oxygen functional groups on the carbon lattice occurs, and the transformation of epoxide and hydroxyl groups into adsorbed water molecules in a process driven by the availability of hydrogen in graphene oxide nanosheets.

Effects of Moisture and Synthesis-Derived Contaminants on the Mechanical Properties of Graphene Oxide: A Molecular Dynamics Investigation

This paper reports on the effects of the chemical composition of graphene oxide (GO) sheets on the mechanical properties of bulk GO. Three key factors were analyzed: (i) the oxygenated functional groups' concentration, (ii) the content of intersheet water (moisture), and (iii) the presence of residual contaminants observed from the synthesis of GO. Molecular dynamics simulations using the reactive force field ReaxFF were conducted to model tensile strength, indentation, and shear stress tests. The structural integrity of the carbon basal plane was the primary variable that determined mechanical behavior of GO slabs. Hydrogen-bond networks played an essential role in the tensile fracture mechanism, delaying the onset of fracture whenever strong hydrogen bonds existed in the intersheet space. The presence of interlayer sulfate ion contaminants negatively impacted the tensile strength, stiffness, and toughness of GO. Moreover, it was observed that intersheet sulfate ions improved the resistance to fracture of GO at low sulfur concentrations, while lower fracture strains were observed beyond a critical concentration. Alike the tensile stress findings, the indentation properties were determined by the integrity of the carbon basal plane. Our findings agree with experimental mechanical property measurements and reveal the importance of considering synthesis-derived contaminants in molecular models of GO.

The Role of Oxidation Pattern and Water Content in the Spatial Arrangement and Dynamics of Oxidized Graphene-Based Aqueous Dispersions

In this work, we employ fully atomistic molecular dynamics simulations to elucidate the effects of the oxidation pattern and of the water content on the organization of graphene sheets in aqueous dispersions and on the dynamic properties of the different moieties at neutral pH conditions. Analysis of the results reveals the role of the oxidation motif (peripherally or fully oxidized flakes) in the tendency of the flakes to self-assemble and in the control of key structural characteristics, such as the interlayer distance between the sheets and the average size and the distribution of the formed aggregates. In certain cases, the results are compared to a pertinent experimental system, validating further the relevant computational models. Examination of the diffusional motion of the oxidized flakes shows that different degrees of spatial restriction are imposed upon the decrease in the water content and elucidates the conditions under which a motional arrest of the flakes takes place. At constant water content, the structural differences between the formed aggregates appear to additionally impart distinct diffusional characteristics of a water molecule. A detailed examination of the counterion dynamics describes their interaction with the oxidized flakes and their dependence on the water content and on the oxidation pattern, offering new insight into the expected electrical properties of the dispersions. The detailed information provided by this work will be particularly useful in applications such as molecular sieving, nanofiltration, and in cases where conductive membranes based on oxidized forms of graphene are used.

Photocatalytic aerobic oxidative functionalization (PAOF) reaction of benzyl alcohols by GO-MIL-100(Fe) composite in glycerol/K2CO3 deep eutectic solvent

An MIL-100 (Fe)/graphene oxide (GO) hybrid, a fairly-known composite, was made through a simple one-step procedure and played a highlighted role in the photo-induced oxidative functionalization of the benzylic C–H bond. To identify the given binary composite, various techniques were applied: FT-IR, P-XRD, SEM, nitrogen absorption–desorption analysis, TGA, TEM, and UV–Visible DRS spectra. Proportions of GO used within the structure of the prepared composite differently ranged from low to high amount, and the most optimized ratio met at 38.5% of GO as the most efficient catalyst. Additionally, the reaction ran in Glycerol/K₂CO₃ (2:1) as the optimal solvent. The elemental roles of O₂^·− and OH⁻ were supposed to be the major ones for running a tandem oxidation-Knoevenagel reaction. The heterogeneity and reusability of the catalyst were also examined and confirmed after five successive runs.

Understanding water transport through graphene-based nanochannels via experimental control of slip length

The water transport along graphene-based nanochannels has gained significant interest. However, experimental access to the influence of defects and impurities on transport poses a critical knowledge gap. Here, we investigate the water transport of cation intercalated graphene oxide membranes. The cations act as water-attracting impurities on the channel walls. Via water transport experiments, we show that the slip length of the nanochannels decay exponentially with the hydrated diameter of the intercalated cations, confirming that water transport is governed by the interaction between water molecules and the impurities on the channel wall. The exponential decay of slip length approximates non-slip conditions. This offers experimental support for the use of the Hagen-Poiseuille equation in graphene-based nanochannels, which was previously only confirmed by simulations. Our study gives valuable feedback to theoretical predictions of the water transport along graphene-based channels with water-attracting impurities.

Chitosan-Gelatin Films: Plasticizers/Nanofillers Affect Chain Interactions and Material Properties in Different Ways

Biopolymers, which are biodegradable and inherently functional, have high potential for specialized applications (e.g., disposable and transient systems and biomedical treatment). For this, it is important to create composite materials with precisely defined chain interactions and tailored properties. This work shows that for a chitosan–gelatin material, both glycerol and isosorbide are effective plasticizers, but isosorbide could additionally disrupt the polyelectrolyte complexation (PEC) between the two biopolymers, which greatly impacts the glass transition temperature (T_g), mechanical properties, and water absorption. While glycerol-plasticized samples without nanofiller or with graphene oxide (GO) showed minimal water uptake, the addition of isosorbide and/or montmorillonite (MMT) made the materials hydrolytically unstable, likely due to disrupted PEC. However, these samples showed an opposite trend in surface hydrophilicity, which means surface chemistry is controlled differently from chain structure. This work highlights different mechanisms that control the different properties of dual-biopolymer systems and provides an updated definition of biopolymer plasticization, and thus could provide important knowledge for the future design of biopolymer composite materials with tailored surface hydrophilicity, overall hygroscopicity, and mechanical properties that meet specific application needs.

Effective Method for a Graphene Oxide with Impressive Selectivity in Carboxyl Groups

The development of new applications of graphene oxide in the biomedical field requires the covalent bonding of bioactive molecules to a sheet skeleton. Obtaining a large carboxyl group population over the surface is one of the main targets, as carboxyl group concentration in conventional graphene oxide is low among a majority of non-useful sp3-C-based functionalities. In the present work, we propose a selective method that yields an impressive increase in carboxyl group population using single-layer, thermally reduced graphene oxide as a precursor in a conventional Hummers-Offemann reaction. When starting with a reduced graphene oxide with no interlayer registry, sulfuric acid cannot form a graphite intercalated compound. Then, potassium permanganate attacks in in-plane (vacancies or holes) structural defects, which are numerous over a thermally reduced graphene oxide, as well as in edges, yielding majorly carboxyl groups without sheet cutting and unzipping, as no carbon dot formation was observed. A single-layer precursor with no ordered stacking prevents the formation of an intercalated compound, and it is this mechanism of the potassium permanganate that results in carboxyl group formation and the hydrophilic character of the compound.

Electronic-Level Insight into Interfacial Effects and Their Induced Anisotropic Ion Diffusion and Ion Selectivity in Nanochannels

Osmotic energy conversion features directional ion migration in selective nanochannels, dominated by interfacial effects, temperature, and concentration. Current efforts emphasize membrane modification for superior reliability and durability, whereas the origin and implication of interfacial effects are unclear. This work performs ab initio molecular dynamics simulations for hydrated ion-graphene oxide interfaces by regulating the temperature and concentration. The interfacial effects associated with their induced anisotropic ion diffusion and ion selectivity are revealed. The scientific essence of the interfacial effects is an electron transfer triggered by hydrated ion-functional group interactions. The interfacial effects are clarified to include dynamic solvation structures, interfacial H-bonds, and chemical reactions. Ions possess incomplete hydration shells, and their arrangements vary from ordered to disordered to overlapped. Interfacial H-bonds restrict hydrated ions by constraining water molecules, whereas continuous reactions provide lateral pathways to generate anisotropy. Cation selectivity is further clarified by negative surface charges from hydroxyl deprotonation. Besides, temperature rise induces disordered hydrated ions as well as frequent and violent reactions, enhancing ion diffusion, selectivity, and anisotropy; excessive concentrations produce overlapped hydrated ions, more H-bonds, and inferior reactions, weakening ion diffusion, selectivity, and anisotropy. Finally, the bottom-up concept for osmotic energy conversion is summarized, and elevated temperature combined with low concentration is found to boost ion diffusion and ion selectivity synergistically. This work provides an in-depth understanding of interfacial phenomena and ion behaviors in nanochannels.

First-principles study of CO2 hydrogenation to formic acid on single-atom catalysts supported on SiO2

The hydrogenation of CO₂ into valuable chemical fuels reduces the atmospheric CO₂ content and also has broad economic prospects. Support is essential for catalysts, but many of the reported support materials cannot meet the requirements of accessibility and durability. Herein, we theoretically designed a series of single-atom noble metals anchored on a SiO₂ surface for CO₂ hydrogenation using density functional theory (DFT) calculations. Through theoretical evaluation of the formation energy, hydrogen dissociation capacity, and activity of CO₂ hydrogenation, we found that Ru@SiO₂ is a promising candidate for CO₂ hydrogenation to formic acid. The energy barrier of the rate-determining step of the entire conversion process is 23.9 kcal mol^-1; thus, the reaction can occur under mild conditions. In addition, active and stable origins were revealed through electronic structure analysis. The charge of the metal atom is a good descriptor of the catalytic activity. The Pearson correlation coefficient (PCC) between metal charge and its CO₂ hydrogenation barrier is 0.99. Two solvent models were also used to investigate hydrogen spillover processes and the reaction path was searched by the climbing image nudged-elastic-band (CI-NEB) method. The results indicated that the explicit solvent model could not be simplified into a few solvent molecules, leading to a large difference in the reaction paths. This work will serve as a reference for the future design of more efficient catalysts for CO₂ hydrogenation.

Enhanced aqueous dissolution of hydrophobic apixaban via direct incorporation of hydrophilic nanographene oxide

In this study, we have directly incorporated nanographene oxide (nGO) into a hydrophobic drug for enhanced dissolution performance through an antisolvent technique. Apixaban (APX) drug composites were synthesized with nGO incorporation ranging from 0.8% to 2.0% concentration. It was observed that the nGO was successfully embedded without any changes to the original drug crystal structure or physical properties. Dissolution of the drug composites was evaluated using US Pharmacopeia Paddle Method (USP 42). The time needed to reach a 50% release (T₅₀) reduced from 106 min to 24 min with the integration of 1.96% nGO in APX and the T₈₀ also dropped accordingly. Alternatively, dissolution rate showed promising performance with increase in nGO concentration. Initial dissolution rate increased dramatically from 74 µg/min to 540 µg/min. Further, work done in intestinal media revealed T₅₀ went from not dissolving to 79.0 min. Decreased lipophilicity or logP value and increased aqueous solubility are both accredited to hydrophilic nGO water dispersion, producing a hydrophilic channel into the drug crystal surfaces through intermolecular interaction. Additionally, physical, and chemical characterizations confirm that hydrophobic apixaban was successfully transformed into a hydrophilic composite, showing potential for this technology to improve dissolution rate of a model hydrophobic compound.

Tunable Thermochromic Graphene Metamaterials with Iridescent Color

Thermochromic materials have been widely applied in energy-efficient buildings, aerospace, textiles, and sensors. Conventional thermochromic materials rely on material phase or structure changes upon thermal stimuli, which only enable a few colors, greatly limiting their applicability. Here, we propose and demonstrate the concept of dynamically tunable thermochromic graphene metamaterials (TGMs), which can achieve continuous color tunability (380-800 nm) with fast (<100 ms) response times. The TGMs are composed of an ultrathin graphene oxide (GO) film on a flexible metal substrate. We demonstrated that external thermal energy can dynamically adjust the water contents in the GO film to manipulate the color of TGMs. An impressive thermochromic sensitivity of 1.11 nm/°C covering a large percentage of the color space has been achieved. Prototype applications for a cup and smartphone have been demonstrated. The reversible TGMs promise great potential for practical applications of temperature sensing in optoelectronic devices, environmental monitoring, and dynamic color modulation.

Enhanced nanofluidic transport in activated carbon nanoconduits

Carbon has emerged as a unique material in nanofluidics, with reports of fast water transport, molecular ion separation and efficient osmotic energy conversion. Many of these phenomena still await proper rationalization due to the lack of fundamental understanding of nanoscale ionic transport, which can only be achieved in controlled environments. Here we develop the fabrication of 'activated' two-dimensional carbon nanochannels. Compared with nanoconduits with 'pristine' graphite walls, this enables the investigation of nanoscale ionic transport in great detail. We show that activated carbon nanochannels outperform pristine channels by orders of magnitude in terms of surface electrification, ionic conductance, streaming current and (epi-)osmotic currents. A detailed theoretical framework enables us to attribute the enhanced ionic transport across activated carbon nanochannels to an optimal combination of high surface charge and low friction. Furthermore, this demonstrates the unique potential of activated carbon for energy harvesting from salinity gradients with single-pore power density across activated carbon nanochannels, reaching hundreds of kilowatts per square metre, surpassing alternative nanomaterials.

A computational inspection of the dissociation energy of mid-sized organic dimers

The gas-phase value of the dissociation energy ( D0) is a key parameter employed in both experimental and theoretical descriptions of noncovalent complexes. The D0 data were obtained for a set of mid-sized organic dimers in their global minima which was located using geometry optimizations that applied ample basis sets together with either the conventional second-order Møller–Plesset (MP2) method or several dispersion-corrected density-functional theory (DFT-D) schemes. The harmonic vibrational zero-point (VZP) and deformation energies from the MP2 calculations were combined with electronic energies from the coupled cluster theory with singles, doubles, and iterative triples [CCSD(T)] extrapolated to the complete basis set (CBS) limit to estimate D0 with the aim of inspecting values that were most recently measured, and an analogous comparison was performed using the DFT-D data. In at least one case (namely, for the aniline⋯methane cluster), the D0 estimate that employed the CCSD(T)/CBS energies differed from experiment in the way that could not be explained by a possible deficiency in the VZP contribution. Curiously, one of the DFT-D schemes (namely, the B3LYP-D3/def2-QZVPPD) was able to reproduce all measured D0 values to within 1.0 kJ/mol from experimental error bars. These findings show the need for further measurements and computations of some of the complexes. In order to facilitate such studies, the physical nature of intermolecular interactions in the investigated dimers was analyzed by means of the DFT-based symmetry-adapted perturbation theory.

Graphene/g-carbon nitride (GO/g-C3N4) nanohybrids as a sensor material for the detection of methyl parathion and carbendazim

The widespread use of methyl parathion (MP) and carbendazim (CBZ) as pesticide molecules for controlling pests and protect crops has added pollution issues; excess usage of these can lead to atmospheric pollution through contaminating water and soil sources. In the present study, detection of these compounds at the trace level was achieved by employing graphene oxide (GO) and graphitic carbon nitride (g-C₃N₄) nanohybrid electrode assembly (GO/g-C₃N₄/GCE). The X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), and Atomic Force Microscopy (AFM) techniques were also used to characterize the materials developed to reveal their purity, crystal structure, and morphology. The complete voltammetric behavior of these analytes was investigated using cyclic voltammetic (CV) and square wave voltammetry (SWV) techniques. The influence of pH was studied and it was noticed that electrochemical response was the highest at pH 7.0 for MP and at pH 4.2 for CBZ. Density Functional Theory (DFT) calculations could help us to understand the adsorption behavior of MP and CBZ onto the GO and g-C₃N₄ before their degradation due to the electrochemical reactions. SWV technique was helpful in the trace level detection of MP and CBZ. Linearity plots were obtained in the range of concentration from 8.0 × 10^-8 M to 1.0 × 10^-4 M with a limit of detection 0.824 nM for MP and 1.0 × 10^-8 M to 2.5 × 10^-4 M for CBZ with the detection limit of 2.82 nM. Significance of the developed method in the field of agricultural and environmental domains was successfully investigated by monitoring MP and CBZ in water and soil samples, and the obtained results suggested the selectivity, stability, and reproducibility of the newly developed GO/g-C₃N₄/GCE electrode assembly.

Stability of Graphene Oxide Composite Membranes in an Aqueous Environment from a Molecular Point of View

We used molecular dynamics to investigate the stability of graphene oxide (GO) layers supported on three polymeric materials, namely a polyvinylidene fluoride (PVDF), a pristine and a crosslinked polyamide–imide (PAI and PAI-cr). The membrane configurations consisted of a few layers of GO nanosheets stacked over the specified polymeric supports and submerged in water. We monitored the position, the tilt angle, and the radial distribution function of the individual GO nanosheets in respect to the plane of the supports. We showed that the outermost GO nanosheets were more distorted than those attached directly on the supports. The greatest distortion was observed for the GO nanosheets of the PVDF-supported system. Next, we recorded the density profiles of the water molecules across the distance from the layers to the polymer and discussed the hydrogen bonds between water hydrogens and the oxygen atoms of the GO functional groups.

Electronic properties of graphene oxide: nanoroads towards novel applications

In this work, we suggest an approach to manipulate the electronic properties of graphene oxide in a controllable manner. We study graphene nanoroads paved inside graphene oxide using density functional calculations. We show that this patterning allows transforming an insulator, graphene oxide, into a semiconductor or metal depending on the orientation of the nanoroads and their magnetic state. As a semiconductor, patterned graphene oxide is characterized by notably low effective masses of charge carriers. Additionally, we demonstrate the possibility to force the transition from a semiconducting to a half-metallic state in a controllable manner, by application of an external electric field. We believe that this remarkable opportunity to combine and control the electronic and magnetic properties of a material within a single sheet of graphene oxide paves the way towards new applications of graphene-oxide-based devices in 2D optoelectronics and spintronics.

Graphene Oxide–Protein-Based Scaffolds for Tissue Engineering. Recent Advances and Applications

The field of tissue engineering is constantly evolving as it aims to develop bioengineered and functional tissues and organs for repair or replacement. Due to their large surface area and ability to interact with proteins and peptides, graphene oxides offer valuable physiochemical and biological features for biomedical applications and have been successfully employed for optimizing scaffold architectures for a wide range of organs, from the skin to cardiac tissue. This review critically focuses on opportunities to employ protein–graphene oxide structures either as nanocomposites or as biocomplexes and highlights the effects of carbonaceous nanostructures on protein conformation and structural stability for applications in tissue engineering and regenerative medicine. Herein, recent applications and the biological activity of nanocomposite bioconjugates are analyzed with respect to cell viability and proliferation, along with the ability of these constructs to sustain the formation of new and functional tissue. Novel strategies and approaches based on stem cell therapy, as well as the involvement of the extracellular matrix in the design of smart nanoplatforms, are discussed.