Impermeable barrier films and protective coatings based on reduced graphene oxide

Discrimination of Xylene Isomers by Precisely Tuning the Interlayer Spacing of Reduced Graphene Oxide Membrane

Separating xylene isomers is a challenging task due to their similar physical and chemical properties. In this study, we developed a molecular sieve incorporating a reduced graphene oxide (rGO) membrane for the precise differentiation of xylene isomers. We fabricated GO membranes using a vacuum filtration technique followed by thermal-induced reduction to produce rGO membranes with precisely controllable interlayer spacing. Notably, we could finely tune the interlayer spacing of the rGO membrane from 8.0 to 5.0 Å by simply varying the thermal reduction temperature. We investigated the reverse osmosis separation ability of the rGO membranes for xylene isomers and found that the rGO membrane with an interlayer spacing of 6.1 Å showed a high single component permeance of 0.17 and 0.04 L m-2 h-1 bar-1 for para- and ortho-xylene, respectively, exhibiting clear permselectivity. The separation factor reached 3.4 and 2.8 when 90:10 and 50:50 feed mixtures were used, respectively, with permeance 1 order of magnitude higher than that of current state-of-the-art reverse osmosis membranes. Additionally, the membrane showed negligible permeance and selectivity decay even after continuous operation for more than 5 days, suggesting commendable membrane resistance to solvent swelling and operating pressure.

The biological and therapeutic assessment of a P(3HB-co-4HB)-bioactive glass-graphene composite biomaterial for tissue regeneration

An ideal wound dressing should create a healing environment that relieves pain, protects against infections, maintains moisture, removes debris, and speeds up wound closure and repair. However, conventional options like gauze often fall short in fulfilling these requirements, especially for chronic or nonhealing wounds. Hence there is a critical need for inventive formulations that offer efficient, cost-effective, and eco-friendly alternatives. This study focuses on assessing the innovative formulation based on a microbial-derived copolymer known as poly(3-hydroxybutyrate-co-4-hydroxybutyrate), P(3HB-co-4HB) bioactive glass and graphene particles, and exploring their biological response in vitro and in vivo-to find the best combination that promotes cell adhesion and enhances wound healing. The formulation optimized at concentration of bioactive glass (1 w/w%) and graphene (0.01 w/w%) showed accelerated degradation and enhanced blood vessel formation. Meanwhile biocompatibility was evaluated using murine osteoblasts, human dermal fibroblasts, and standard cell culture assays, demonstrating no adverse effects after 7 days of culture and well-regulated inflammatory kinetics. Whole thickness skin defect using mice indicated the feasibility of the biocomposites for a faster wound closure and reduced inflammation. Overall, this biocomposite appears promising as an ideal wound dressing material and positively influencing wound healing rates.

Enhanced reduction of graphene oxide via laser-dispersion coupling: Towards large-scale, low-defect graphene for crease-free heat-dissipating membranes in advanced flexible electronics

The advancement of flexible electronics demands improved components, necessitating heat dissipation membranes (HDMs) to exhibit high thermal conductivity while maintaining structural integrity and performance stability even after extensive deformation. Herein, we have devised a laser-modulated reduction technique for graphene oxide (GO), enabling the fabrication of high-quality, large-scale, low-defect graphene, which yields high-performance HDMs after orderly deposition. The work underscores the crucial role of the laser wavelength and dispersion liquid's coupling intensity in influencing the morphology and properties of graphene. Optimal coupling effect and energy conversion are realized when a laser of 1064 nm wavelength irradiates a triethylene glycol (TEG)/N,N-Dimethylformamide (DMF) dispersion. This unique synergy generates high transient energy, which facilitates the deprotonation process and ensures a swift, comprehensive GO reduction. In contrast to conventional water-based laser reduction methods, the accelerated reaction magnifies the size of the graphene sheets by mitigating the ablation effect. After membrane construction with an ordered structure, the corresponding membrane exhibits a high thermal conductivity of 1632 W m-1 K-1, requiring only ∼1/10 of the total preparation time required by other reported methods. Remarkably, the resulting HDM demonstrates superior resilience against creasing and folding, maintaining excellent smoothness and negligible reduction in thermal conductivity after violent rubbing. The combination of exceptional flexibility and thermal conductivity in HDMs paves the way for long-term practical use in the flexible electronics industry.

Performance analysis of un-doped and doped titania (TiO 2 ) as an electron transport layer (ETL) for perovskite solar cells

CONTEXT

Density functional theory (DFT) calculations are carried out on pure and doped rutile TiO2 . The bandgap (Eg ) for pristine, S-doped, Fe-doped, and Fe/S co-doped materials is direct, with values of 2.98 eV, 2.18 eV, 1.58 eV, and 1.40 eV. The effective mass of charge carriers (m*) and ratio of effective masses of holes to effective masses of electrons (R) are also investigated, and it is discovered that Fe/S co-doped materials have the lowest charge carrier recombination rate. The Fe/S co-doped material has the highest ε ( ω ) . α ( ω ) of doped materials shifted into the visible range. Due to the high dopant concentration in Fe and Fe/S-doped cases, the Eg is lowered to a relatively small value; hence, only pristine and S-doped materials are verified as electron transport layer (ETL). A solar cell device analysis employing pure and S-doped rutile TiO2 as ETL is completed using DFT-derived parameters in SCAPS-1D modeling software for the first time. For the optimized solar cells, current-voltage (IV) characteristics, quantum efficiency (QE), capacitance-voltage (CV) characteristics, and capacitance-frequency (Cf) characteristics are provided. The aim of the present study is to improve efficiency of perovskite solar cell by doping as well as to improve accuracy of simulation by applying DFT extracted parameters as input. From the analysis, improvement is found in efficiency of doped TiO2 compared to un-doped TiO2 . The efficiency of the PSC with S-doped ETL is 1.418% higher than the PSC with un-doped ETL.

METHOD

Quantumwise Automistic Tool Kit (ATK) is used to extract DFT parameters. Using these DFT parameters as input in SCAPS-1D (Solar Cell Capacitance Simulator), solar cells for doped and un-doped material are simulated. The density functional theory (DFT)-based orthogonalized linear combination of atomic orbital (OLCAO) technique is used. Structural optimization is done using the LBFGS (Limited-memory Broyden-Fletcher-Goldfarb-Shanno). PBESol-GGA (Perdew-Burke-Ernzerhof solid-generalized gradient approximation) is applied as exchange correlation for calculating structural parameters, while MGGA-TB09 (meta-generalized gradient approximation-Tran and Blaha) is applied as exchange correlation for calculating optical and electronic properties.

Orientation of reduced graphene oxide in composite coatings

Composite coatings containing reduced graphene oxide (rGO) and 3-(aminopropyl)triethoxysilane functionalised rGO (APTES-rGO) were prepared by sol-gel technology and deposited on Al 2024 T-3. Covalent functionalisation of GO by APTES occurred by formation of amide bonds, accompanied by GO reduction. The thin sheets were retained. The hydrophilicity of the coating increased when APTES-rGO was added. The opposite was observed when GO was added. A key finding is that the rGO flakes agglomerate and lie in a random orientation in the coating, whereas the APTES-rGO flakes are more evenly distributed in the matrix and appear to lie along the plane of the substrate.

2D Nanomaterials Reinforced Organic Coatings for Marine Corrosion Protection: State of the Art, Challenges, and Future Prospectives

2D nanomaterials, with extraordinary physical and chemical characteristics, have long been regarded as promising nanofillers in organic coatings for marine corrosion protection. The past decade has witnessed the high-speed progress of 2D nanomaterial-reinforced organic composite coatings, and plenty of breakthroughs have been achieved as yet. This review covers an in-depth and all-around outline of the up-to-date advances in 2D nanomaterial-modified organic coatings employed for the marine corrosion protection realm. Starting from a brief introduction to 2D nanomaterials, the preparation strategies and properties are illustrated. Subsequently, diverse protection models based on composite coatings for marine corrosion protection are also introduced, including physical barrier, self-healing, as well as cathodic protection, respectively. Furthermore, computational simulations and critical factors on the corrosion protection properties of composite coatings are clarified in detail. Finally, the remaining challenges and prospects for marine corrosion protection based on 2D nanomaterials reinforced organic coatings are highlighted.

Enhanced gas and plasticizer barrier HTPB composite liner implanted with parallel orientation Fe3O4/RGO nanosheets by an ultrasound/magnet-coassisted method

It is of great significance to prepare liners with excellent inhibition of energetic plasticizer migration and gas barrier properties. Here, we have successfully prepared magnetic iron oxide decorated reduced-graphene-oxide nanosheets (MRGO) by using ultrasound-assisted method. The obtained MRGO nanosheet-fillers were filled into hydroxyl-terminated polybutadiene (HTPB) which was exposed to a magnetic field (200 mT) to achieve ordered orientation of MRGO in the HTPB matrix (Ordered MRGO/HTPB). The laser confocal microscopy demonstrates that MRGO exhibit ordered orientation structure in HTPB matrix with good dispersion, which renders the HTPB composite liners exhibiting high gas and plasticizer barrier capability, with a reduction of 18.9 % in water vapor permeability and a decrease of 14.1 % in dibutyl phthalate (DBP) migration equilibrium concentration as compared with those of random MRGO embedded HTPB composite liners (Random MRGO/HTPB). Moreover, a theoretical model accounting for such enhanced gas/plasticizer barrier performance of HTPB due to the implantation of order aligned MRGO was established, which shows that the effective diffusion pathways of plasticizer/gas for liner penetration would be significantly enhanced when the MRGO nanosheets are oriented within the HTPB matrix. This work provides an effective and facile strategy toward the design and development of composite liners with high plasticizer/gas barrier performance for industrial applications.

Macroscopic assembly of 2D materials for energy storage and seawater desalination

Since the discovery of graphene in 2004, two-dimensional (2D) materials have attracted widespread attention due to their excellent physical and chemical properties in the fields of energy, environment, catalysis, and optoelectronics. However, there are still many key problems in the process of practical application. To further promote the potential of 2D materials for practical applications, macroscopic assembly of 2D materials is crucial for the continued development of 2D materials, especially in the fields of energy storage and seawater desalination. Therefore, this review focuses on the latest progress and current status related to the macroscopic assembly of 2D materials, including 1D fibers, 2D films, and 3D architectures. In addition, the application of macroscopic bodies assembled based on 2D materials in the fields of energy storage and seawater desalination is also introduced. Finally, future directions for the macroscopic assembly of 2D materials and their applications are prospected.

Impermeable Graphene Skin Increases the Heating Efficiency and Stability of an MXene Heating Element

A Joule heater made of emerging 2D nanosheets, i.e., MXene, has the advantage of low-voltage operation with stable heat generation owing to its highly conductive and uniformly layered structure. However, the self-heated MXene sheets easily get oxidized in warm and moist environments, which limits their intrinsic heating efficiencies. Herein, an ultrathin graphene skin is introduced as a surface-regulative coating on MXene to enhance its oxidative stability and Joule heating efficiency. The skin layer is deposited on MXene using a scalable solution-phased layer-by-layer assembly process without deteriorating the excellent electrical conductivity of the MXene. The graphene skin comprises narrow and hydrophobic channels, which results in ≈70 times higher water impermeability of the hybrid film of graphene and MXene (GMX) than that of the pristine MXene. A complementary electrochemical analysis confirms that the graphene skin facilitates longer-lasting protection than conventional polymer coatings owing to its tortuous pathways. In addition, the sp2 planar carbon surface with a low heat loss coefficient improves the heating efficiency of the GMX, indicating that this strategy is promising for developing adaptive heating materials with a tractable voltage range and high Joule heating efficiency.

Solvent Effect on the Nanotextural Formation of Reduced Graphene Oxide Membranes

Solvent is involved in many wet-chemical synthesis and bottom-up assembly processes. Understanding its influence on the nanotextural formation of the resultant assemblies is essential for the design and control of the properties for targeted applications. With wet chemically reduced graphene oxide (rGO) membranes as a materials platform, this study investigates the solvent effect on nanotexture formation in 2D nanomaterial-based membranes through light scattering and electrochemical characterization. Our finding indicates that the nanotexture of the resultant rGO membrane is largely correlated to the dielectric constant of the solvent. Specifically, solvents with higher dielectric constants yield rGO membranes with more wrinkled, loosely stacked, and less graphitized structures. In contrast, solvents with a lower dielectric constant tend to yield densely stacked structures with larger graphitized domains. Our finding underscores the important role of solvents in wet processing and nanoengineering of 2D nanomaterial-based membranes and provides valuable insights for their controlled synthesis and application.

High Moisture-Barrier Performance of Double-Layer Graphene Enabled by Conformal and Clean Transfer

Graphene films that can theoretically block almost all molecules have emerged as promising candidate materials for moisture barrier films in the applications of organic photonic devices and gas storage. However, the current barrier performance of graphene films does not reach the ideal value. Here, we reveal that the interlayer distance of the large-area stacked multilayer graphene is the key factor that suppresses water permeation. We show that by minimizing the gap between the two monolayers, the water vapor transmission rate of double-layer graphene can be as low as 5 × 10-3 g/(m2 d) over an A4-sized region. The high barrier performance was achieved by the absence of interfacial contamination and conformal contact between graphene layers during layer-by-layer transfer. Our work reveals the moisture permeation mechanism through graphene layers, and with this approach, we can tailor the interlayer coupling of manually stacked two-dimensional materials for new physics and applications.

Environmental and health impacts of functional graphenic materials and their ultrasonically altered products

Graphenic materials have excited the scientific community due to their exciting mechanical, thermal, and optoelectronic properties for a potential range of applications. Graphene and graphene derivatives have demonstrated application in areas stretching from composites to medicine; however, the environmental and health impacts of these materials have not been sufficiently characterized. Graphene oxide (GO) is one of the most widely used graphenic derivatives due to a relatively easy and scalable synthesis, and the ability to tailor the oxygen containing functional groups through further chemical modification. In this paper, ecological and health impacts of fresh and ultrasonically altered functional graphenic materials (FGMs) were investigated. Model organisms, specifically Escherichia coli, Bacillus subtilis, and Caenorhabditis elegans, were used to assess the consequences of environmental exposure to fresh and ultrasonically altered FGMs. FGMs were selected to evaluate the environmental effects of aggregation state, degree of oxidation, charge, and ultrasonication. The major findings indicate that bacterial cell viability, nematode fertility, and nematode movement were largely unaffected, suggesting that a wide variety of FGMs may not pose significant health and environmental risks.

Mechanical Mechanism of Ion and Water Molecular Transport through Angstrom-Scale Graphene Derivatives Channels: From Atomic Model to Solid-Liquid Interaction

Ion and water transport at the Angstrom/Nano scale has always been one of the focuses of experimental and theoretical research. In particular, the surface properties of the angstrom channel and the solid-liquid interface interaction will play a decisive role in ion and water transport when the channel size is small to molecular or angstrom level. In this paper, the chemical structure and theoretical model of graphene oxide (GO) are reviewed. Moreover, the mechanical mechanism of water molecules and ions transport through the angstrom channel of GO are discussed, including the mechanism of intermolecular force at a solid/liquid/ion interface, the charge asymmetry effect and the dehydration effect. Angstrom channels, which are precisely constructed by two-dimensional (2D) materials such as GO, provide a new platform and idea for angstrom-scale transport. It provides an important reference for the understanding and cognition of fluid transport mechanism at angstrom-scale and its application in filtration, screening, seawater desalination, gas separation and so on.

Nanoantibiotic effect of carbon-based nanocomposites: epicentric on graphene, carbon nanotubes and fullerene composites: a review

Carbon in many different forms especially, Graphene, Carbon nanotubes (CNTs), and Fullerene is emerging as an important material in the areas of the biomedical field for various applications. This review comprehensively describes the nano antibiotic effect of carbon-based nanocomposites: epicenter on graphene, carbon nanotubes, and fullerene Composites. It summarises the studies conducted to evaluate their antimicrobial applications as they can disrupt the cell membrane of bacteria resulting in cell death. The initial section gives a glimpse of both "Gram"-positive and negative bacteria, which have been affected by Graphene, CNTs, and Fullerene-based nanocomposites. These bacteria include Staphylococcus Aureus, Bacillus Thuringiensis, Enterococcus faecalis, Enterococcus faecium, Bacillus subtilis, Escherichia coli, Klebseilla pneumoniae, Pseudomonas aeroginosa, Pseudomonas syringae , Shigella flexneri,Candida Albicans, Mucor. Another section is dedicated to the insight of Graphene, and its types such as Graphene Oxide (GO), Reduced graphene oxide (rGO), Graphene Nanoplatelets (GNPs), Graphene Nanoribbons (GNRs), and Graphene Quantum Dots (GQDs). Insight into CNT, including both the types SWCNT and MWCNT, studied, followed by understanding fullerene is also reported. Another section is dedicated to the antibacterial mechanism of Graphene, CNT, and Fullerene-based nanocomposites. Further, an additional section is dedicated to a comprehensive review of the antibacterial characteristics of Graphene, CNT, and nanocomposites based on fullerene. Future perspectives and recommendations have also been highlighted in the last section.

Graphene nanoplatelets and other 2D-materials as protective means against the fading of coloured inks, dyes and paints

The present work demonstrates the ability of graphene nanoplatelets (GNPs) and other two-dimensional materials (2DMs) like tungsten disulfide (WS2), molybdenum disulfide (MoS2) and hexagonal boron nitride (hBN) to act as protective barriers against the fading of architectural paints and also inks/paints used in art. The results present a new approach for improving the lightfastness of colours of artworks and painted indoor/outdoor wall surfaces taking advantage of the remarkable properties of 2DMs. As shown herein, commercial inks and architectural paints of different colours doped with graphene nanoplatelets (GNPs), graphene oxide (GO), reduced graphene oxide (rGO) and other 2DMs, exhibit a superior resistance to fading under ultraviolet radiation or even under exposure to visible light. A spectroscopic study on these inks and dyes reveals that the peaks which are characteristic of the colour pigments are less affected from aging/fading when the GNPs and the other 2DMs are present. The protection mechanism for the GNPs and the other 2DMs differs. For GNPs, mainly their high surface area which leads to free radicals scavenging (especially hydroxyl radicals), and secondarily their UV absorption, are responsible for their protection effects, while for GO, a transition to rGO structures and consequently to 'smart' paints can be observed after the performed aging routes. In this way, the paint gets improved by time preventing or slowing its own fading and decolorization. For the other 2DMs, the transition-metal dichalcogenides performed better than hBN, even though they all absorb in the UV region. This can be ascribed to the facts that the formers also absorb in the visible, while hBN does not, while most importantly, they can trap reactive oxygen species (ROS) and corrosive gases in their structure as opposed to hBN. By conducting colorimetric measurements, we have discovered that the lifetime of the as-developed 2DM-doped inks and paints can be extended by up to ∼40%.

Subnanometric Stacking of Two-Dimensional Nanomaterials: Insights from the Nanotexture Evolution of Dense Reduced Graphene Oxide Membranes

Assembling two-dimensional (2D) nanomaterials into laminar membranes with a subnanometer (subnm) interlayer spacing provides a material platform for studying a range of nanoconfinement effects and exploring the technological applications related to the transport of electrons, ions and molecules. However, the strong tendency for 2D nanomaterials to restack to their bulk crystalline-like structure makes it challenging to control their spacing at the subnm scale. It is thus necessary to understand what nanotextures can be formed at the subnm scale and how they can be engineered experimentally. In this work, with dense reduced graphene oxide membranes as a model system, we combine synchrotron-based X-ray scattering and ionic electrosorption analysis to reveal that their subnanometric stacking can result in a hybrid nanostructure of subnm channels and graphitized clusters. We demonstrate that the ratio of these two structural units, their sizes and connectivity can be engineered by stacking kinetics through the reduction temperature to allow the realization of high-performance compact capacitive energy storage. This work highlights the great complexity of subnm stacking of 2D nanomaterials and provides potential methods to engineer their nanotextures at will.

Nonaqueous Interfacial Polymerization-Derived Polyphosphazene Films for Sieving or Blocking Hydrogen Gas

A series of cyclomatrix polyphosphazene films have been prepared by nonaqueous interfacial polymerization (IP) of small aromatic hydroxyl compounds in a potassium hydroxide dimethylsulfoxide solution and hexachlorocyclotriphosphazene in cyclohexane on top of ceramic supports. Via the amount of dissolved potassium hydroxide, the extent of deprotonation of the aromatic hydroxyl compounds can be changed, in turn affecting the molecular structure and permselective properties of the thin polymer networks ranging from hydrogen/oxygen barriers to membranes with persisting hydrogen permselectivities at high temperatures. Barrier films are obtained with a high potassium hydroxide concentration, revealing permeabilities as low as 9.4 × 10^-17 cm³ cm cm^-2 s^-1 Pa^-1 for hydrogen and 1.1 × 10^-16 cm³ cm cm^-2 s^-1 Pa^-1 for oxygen. For films obtained with a lower concentration of potassium hydroxide, single gas permeation experiments reveal a molecular sieving behavior, with a hydrogen permeance of around 10^-8 mol m^-2 s^-1 Pa^-1 and permselectivities of H₂/N₂ (52.8), H₂/CH₄ (100), and H₂/CO₂ (10.1) at 200 °C.

A novel epoxy coating with nanocatalytic anticorrosion performance achieved by single-atom Fe-N-C catalyst

In view of the critical importance of oxygen to corrosion evolution, to starve corrosion via depleting oxygen in coatings is a promising strategy. In this work, a novel nanocatalytic anticorrosion concept is proposed to design new coating with outstanding corrosion resistance. Different from the passive barrier of traditional coatings and self-repair after corrosion of current stimuli-feedback coatings, such coating could spontaneously eliminate internal diffused oxygen and greatly suppress the corrosion process. As a proof of concept, single-atom Fe-N-C electrocatalyst with isolated FeN₄ active sites is synthesized by a simple confined carbonization method, exhibiting excellent oxygen reduction performance (E_1/2 = 0.902 V). In composite coating, the evenly dispersed Fe-N-C compensates for the coating defects and serves as oxygen scavengers, which could actively adsorb and consume ambient oxygen, thereby preventing oxygen penetration to the metal substrate surface, eliminating the oxygen contribution to corrosion and significantly boosting the anticorrosion performance of epoxy coating. This in-situ mediation for oxygen in coating prevents metal substrate from receiving new supply of oxygen, while imparting active anticorrosion property to the coating.

Large-area ultra-thin GO nanofiltration membranes prepared by a pre-crosslinking rod coating technique

In existing separation membranes, it is difficult to quickly produce large-area graphene oxide (GO) nanofiltration membranes with high permeability and high rejection, which is the bottleneck of industrialization. In this study, a pre-crosslinking rod-coating technique is reported. A GO-P-Phenylenediamine (PPD) suspension was obtained by chemically crosslinking GO and PPD for 180 min. After scraping and coating with a Mayer rod, the ultra-thin GO-PPD nanofiltration membrane with an area of 400 cm² and a thickness of 40 nm was prepared in 30 s. The PPD formed an amide bond with GO to improve its stability. It also increased the layer spacing of GO membrane, which could improve the permeability. The prepared GO nanofiltration membrane had a 99 % rejection rate for dyes such as methylene blue, crystal violet, and Congo red. Meanwhile, the permeation flux reached to 42 LMH/bar, which was 10 times that of the GO membrane without PPD crosslinking, and it still maintained excellent stability under strongly acidic and basic conditions. This work successfully solved the problems of GO nanofiltration membranes, including the large-area fabrication, high permeability and high rejection.

Rugged bialkali photocathodes encapsulated with graphene and thin metal film

Protection of free-electron sources has been technically challenging due to lack of materials that transmit electrons while preventing corrosive gas molecules. Two-dimensional materials uniquely possess both of required properties. Here, we report three orders of magnitude increase in active pressure and factor of two enhancement in the lifetime of high quantum efficiency (QE) bialkali photocathodes (cesium potassium antimonide (CsK₂Sb)) by encapsulating them in graphene and thin nickel (Ni) film. The photoelectrons were extracted through the graphene protection layer in a reflection mode, and we achieved QE of ~ 0.17% at ~ 3.4 eV, 1/e lifetime of 188 h with average current of 8.6 nA under continuous illumination, and no decrease of QE at the pressure of as high as ~ 1 × 10^-3 Pa. In comparison, the QE decreased drastically at 10^-6 Pa for bare, non-protected CsK₂Sb photocathodes and their 1/e lifetime under continuous illumination was ~ 48 h. We attributed the improvements to the gas impermeability and photoelectron transparency of graphene.

Tunable Interlayer Interactions in Reduced Graphene Oxide Paper

Free-standing graphene-based paper-like materials have garnered significant interest for various applications because of their tunable physical and chemical properties, along with unique multilayered structures. Because of the layered configuration of graphene paper, characterization of the interactions between graphene sheets is critical for understanding its fundamental properties and applications. We investigate the interlayer cohesion energies in graphene papers using the mode I fracture concept with double cantilever beam specimens. Mechanical separation along the middle of the graphene paper thickness enables the evaluation of interlayer bonding strength in the paper. Starting from graphene oxide paper, the chemical reduction using hydroiodic acid tunes the interlayer cohesion energy from 11.30 ± 0.25 to 4.78 ± 0.18 J/m² as the reduction time increases. The interlayer cohesion energy is correlated with the oxygen content, interlayer spacing, and electrical conductivity of graphene papers. This work provides a fundamental characterization of the interlayer cohesion energy of graphene paper and establishes the potential for tunability of the interlayer interactions in graphene paper.

Carbon Nanostructure Embedded Novel Sensor Implementation for Detection of Aromatic Volatile Organic Compounds: An Organized Review

For field-like environmental gas monitoring and noninvasive illness diagnostics, effective sensing materials with exceptional sensing capabilities of sensitive, quick detection of volatile organic compounds (VOCs) are required. Carbon-based nanomaterials (CNMs), like CNTs, graphene, carbon dots (Cdots), and others, have recently drawn a lot of interest for their future application as an elevated-performance sensor for the detection of VOCs. CNMs have a greater potential for developing selective sensors that target VOCs due to their tunable chemical and surface properties. Additionally, the mechanical versatility of CNMs enables the development of novel gas sensors and places them ahead of other sensing materials for wearable applications. An overview of the latest advancements in the study of CNM-based sensors is given in this comprehensive organized review.

Graphene oxide for photonics, electronics and optoelectronics

Graphene oxide (GO) was initially developed to emulate graphene, but it was soon recognized as a functional material in its own right, addressing an application space that is not accessible to graphene and other carbon materials. Over the past decade, research on GO has made tremendous advances in material synthesis and property tailoring. These, in turn, have led to rapid progress in GO-based photonics, electronics and optoelectronics, paving the way for technological breakthroughs with exceptional performance. In this Review, we provide an overview of the optical, electrical and optoelectronic properties of GO and reduced GO on the basis of their chemical structures and fabrication approaches, together with their applications in key technologies such as solar energy harvesting, energy storage, medical diagnosis, image display and optical communications. We also discuss the challenges of this field, together with exciting opportunities for future technological advances.

Recent Advances in Responsive Membrane Functionalization Approaches and Applications

In recent years, significant advances have been made in the field of functionalized membranes. With the functionalization using various materials, such as polymers and enzymes, membranes can exhibit property changes in response to an environmental stimulation, such as heat, light, ionic strength, or pH. The resulting responsive nature allows for an increased breadth of membrane uses, due to the developed functionalization properties, such as smart-gating filtration for size-selective water contaminant removal, self-cleaning antifouling surfaces, increased scalability options, and highly sensitive molecular detection. In this review, new advances in both fabrication and applications of functionalized membranes are reported and summarized, including temperature-responsive, pH-responsive, light-responsive, enzyme-functionalized, and two-dimensional material-functionalized membranes. Specific emphasis was given to the most recent technological improvements, current limitations, advances in characterization techniques, and future directions for the field of functionalized membranes.

Waterborne Eco-Sustainable Sol-Gel Coatings Based on Phytic Acid Intercalated Graphene Oxide for Corrosion Protection of Metallic Surfaces

In the past few years, corrosion protection of metal materials has become a global challenge, due to its great economic importance. For this reason, various methods have been developed to inhibit the corrosion process, such as surface treatment approaches, by employing corrosion inhibitors through the deposition of opportunely designed functional coatings, employed to preserve from corrosion damages metallic substrates. Recently, among these techniques and in order to avoid the toxic chromate-based pre-treatment coatings, silane-based coatings and films loaded with organic and inorganic corrosion inhibitors have been widely used in corrosion mitigation water-based surface treatment. In this study, the synthetic approach was devoted to create an embedded, hosted, waterborne, and eco-friendly matrix, obtained by use of the sol–gel technique, through the reaction of functional alkoxysilane cross-linking precursors, namely (3-glycidyloxypropyl)trimethoxysilane (GPTMS) and (3-aminopropyl)triethoxysilane (APTES), in the presence of graphene oxide (GO) intercalated with natural and non-toxic phytic acid (PA) molecules. As a matter of fact, all experimental results from FT-IR spectroscopy, UV–Vis analysis, and SEM confirmed that PA molecules were successfully decorated on GO. Furthermore, polarization measurements and a neutral salt spray test were used to evaluate the anticorrosive performance on aluminum and steel substrates, thus showing that the GO-PA nanofiller improved the barrier and corrosion protection properties of the developed functional silane-based coatings.

Recent Advances and Prospects in Design of Hydrogen Permeation Barrier Materials for Energy Applications-A Review

The hydrogen infrastructure involves hydrogen production, storage and delivery for utilization with clean energy applications. Hydrogen ingress into structural materials can be detrimental due to corrosion and embrittlement. To enable safe operation in applications that need protection from hydrogen isotopes, this review article summarizes most recent advances in materials design and performance characterization of barrier coatings to prevent hydrogen isotopes' absorption ingress and permeation. Barriers are crucial to prevent hydride formation and unwanted hydrogen effects to increase safety, materials' lifetime and reduce cost for applications within nuclear and renewable energy. The coating may be applied on a material that requires protection from hydrogen pick-up, transport and hydride formation in hydrogen storage containers, in pipelines, spent nuclear fuel storage or in nuclear reactors. While existing, commercial coatings that have been much in use may be satisfactory for various applications, it is desirable to evaluate whether alternative coating concepts can provide a greater resistance to hydrogen isotope permeation along with other improved properties, such as mechanical strength and thermal resistance. The information presented here is focusing on recent findings within the past 5-7 years of promising hydrogen barriers including oxides, nitrides, carbon, carbide, MAX-phases and metals and their mechanical strength, hydrogen pick-up, radiation resistance and coating manufacturing techniques. A brief introduction to hydrogen permeation is provided. Knowledge gaps were identified to provide guidance for material's research prospects.

Functionalized GO/Hydroxy-Terminated Polybutadiene Composites with High Anti-Migration and Ablation Resistance Performance

The migration of plasticizers such as nitroglycerin seriously affects the storage and working safety of rocket systems. In this work, hydroxy-terminated polybutadiene (HTPB) liner composites with the cross-linked structure were prepared by cross-linking isocyanate functionalized graphene oxide (IGO) with HTPB to prevent the migration of high energy plasticizers in the propellant. IGO was uniformly dispersed in the matrix as reinforcement and cross-linker, providing good migration resistance and ablation resistance for the liner composites. Compared with pure HTPB, the migration resistance of the liner with 0.5 wt% IGO increased by 18.94%, 16.33% and 15.34% at 25 °C, 60 °C and 90 °C, respectively. In addition, the ablation resistance of the HTPB liner was improved by the addition of IGO. The improved anti-migration properties come from the special laminar structure of IGO and the dense molecular chains network of the cross-linked composites.

Conformal Encapsulation of Silver Nanowire Transparent Electrodes by Nanosized Reduced Graphene Oxide Leading to Improved All-Round Stability

Solution-processed silver nanowire (AgNW) networks are promising as next-generation transparent conductive electrodes due to their excellent optoelectronic properties, mechanical flexibility, as well as low material and processing costs. However, AgNWs are prone to thermally induced fragmentation and chemical degradation, necessitating a conformal protective coating typically achieved by low-throughput methods such as sputtering or atomic layer deposition. Herein, we report a facile all-solution-based approach to synthesize a conformally coated AgNW network by nanosized reduced graphene oxide R(nGO). In this method, probe ultrasonication is used to obtain nanosized GO, which is coated on AgNWs by a layer-by-layer approach and then chemically treated to form R(nGO)/AgNW. We show that our transparent electrode has excellent transmittance (85-92%) and sheet resistance (17.5 Ω/sq), combined with outstanding thermal and electrothermal stability, thanks to the conformal nature of the R(nGO) film, and demonstrate its use as a transparent heater with a high maximum temperature. This, in conjunction with improved long-term chemical and mechanical bending stability of R(nGO)/AgNW, indicates that our newly developed process represents an effective and low-cost strategy to improve the overall operational resilience of metal nanowire-based transparent conductive electrodes.

The Optimization of the Transition Zone of the Planar Heterogeneous Interface for High-Performance Seawater Desalination

Reverse osmosis has become the most prevalent approach to seawater desalination. It is still limited by the permeability-selectivity trade-off of the membranes and the energy consumption in the operation process. Recently, an efficient ionic sieving with high performance was realized by utilizing the bi-unipolar transport behaviour and strong ion depletion of heterogeneous structures in 2D materials. A perfect salt rejection rate of 97.0% and a near-maximum water flux of 1529 L m-2 h-1 bar-1 were obtained. However, the energy consumption of the heterogeneous desalination setup is a very important factor, and it remains largely unexplored. Here, the geometric-dimension-dependent ion transport in planar heterogeneous structures is reported. The two competitive ion migration behaviours during the desalination process, ion-depletion-dominated and electric-field-dominated ion transport, are identified for the first time. More importantly, these two ion-transport behaviours can be regulated. The excellent performance of combined high rejection rate, high water flux and low energy consumption can be obtained under the synergy of voltage, pressure and geometric dimension. With the appropriate optimization, the energy consumption can be reduced by 2 orders of magnitude, which is 50% of the industrial energy consumption. These findings provide beneficial insight for the application and optimized design of low-energy-consumption and portable water desalination devices.

Nano-Graphene Layer from Facile, Scalable and Eco-Friendly Liquid Phase Exfoliation Strategy as Effective Barrier Layer for High-Performance and Durable Direct Liquid Alcohol Fuel Cells

Graphene, in spite of exceptional physio-chemical properties, still faces great limitations in its use and industrial scale-up as highly selective membranes (enhanced ratio of proton conductivity to fuel cross-over) in liquid alcohol fuel cells (LAFCs), due to complexity and high cost of prevailing production methods. To resolve these issues, a facile, low-cost and eco-friendly approach of liquid phase exfoliation (bath sonication) of graphite to obtain graphene and spray depositing the prepared graphene flakes, above anode catalyst layer (near the membrane in the membrane electrode assembly (MEA)) as barrier layer at different weight percentages relative to the base membrane Nafion 115 was utilized in this work. The 5 wt.% nano-graphene layer raises 1 M methanol/oxygen fuel cell power density by 38% to 91 mW·cm⁻², compared to standard membrane electrode assembly (MEA) performance of 63 mW·cm⁻², owing to less methanol crossover with mild decrease in proton conductivity, showing negligible voltage decays over 20 h of operation at 50 mA·cm⁻². Overall, this work opens three prominent favorable prospects: exploring the usage of nano-materials prepared by liquid phase exfoliation approach, their effective usage in ion-transport membrane region of MEA and enhancing fuel cell power performance.

High-performance cellulose acetate-based gas barrier films via tailoring reduced graphene oxide nanosheets

Improving the gas molecule barrier performance and structural stability of bio-plastic films dramatically contribute to packaging and protective fields. Herein, we proposed a novel nanocomposite film consisting of cellulose acetate (CA)/polyethyleneimine (PEI)/reduced graphene oxide (rGO)-NiCoFeO_x) with high gas barrier property by applying "molecular glue" and "nano-patching" strategies. Systematical investigations demonstrated that the CA/rGO interfacial interaction was effectively enhanced due to the "molecular glue" role of PEI chains via physical/chemical bonds and the defective regions in rGO plane were nano-patched through hydrophilic interactions between edged oxygen-containing functional groups and ultrafine NiCoFeO_x nanoparticles (~3 nm). As a result, the oxygen and moisture transmission rates of the prepared CA/PEI/rGO-NPs hybrid film were significantly reduced to 0.31 cm³ ∗ μm/(m² ∗ d ∗ kPa) and 314.23 g/m² ∗ 24 h, respectively, which were 99.60% and 54.69% lower than pristine CA films. Meanwhile, the tensile strength of hybrid film was increased from 25.90 MPa to 40.67 MPa. More importantly, the designed nanocomposite film possesses excellent structural stability without obvious GO layer shedding and hydrophobicity attenuation after persistent bending at least 100 times. The exceptional robust and high gas barrier film displays great promising application in food, agriculture, pharmaceuticals and electronic instruments packaging industry.

A Review of In-Service Coating Health Monitoring Technologies: Towards “Smart” Neural-Like Networks for Condition-Based Preventive Maintenance

In line with the recent industrial trends of hyperconnectivity, 5G technology deployment, the Internet of Things (IoT) and Industry 4.0, the ultimate goal of corrosion prevention is the invention of smart coatings that are able to assess their own condition, predict the onset of corrosion and alert users just before it happens. It is of particular interest to tackle corrosion that occurs in non-accessible areas where human inspectors or handheld devices are useless. To accomplish this, a variety of technologies that are embedded or could potentially be embedded into the coatings are being developed to monitor coating condition, which are based, for instance, on the evolution of electrochemical or mechanical properties over time. For these technologies to be fully embedded into the coatings and work remotely, solutions are needed for connectivity and power supply. A paradigm shift from routine prescheduled maintenance to condition-based preventive maintenance could then become a reality. In this work, the technologies that enable the in-service monitoring of organic anticorrosion coatings were compiled. Soon, some of them could be integrated into the sensing elements of autonomous, connected neural-like networks that are capable of remotely assessing the condition of the anticorrosion protection of future infrastructures.

Sulfonated NbS2-based proton-exchange membranes for vanadium redox flow batteries

In this work, novel proton-exchange membranes (PEMs) based on sulfonated poly(ether ether ketone) (SPEEK) and two-dimensional (2D) sulfonated niobium disulphide (S-NbS₂) nanoflakes are synthesized by a solution-casting method and used in vanadium redox flow batteries (VRFBs). The NbS₂ nanoflakes are produced by liquid-phase exfoliation of their bulk counterpart and chemically functionalized with terminal sulfonate groups to improve dimensional and chemical stabilities, proton conductivity (σ) and fuel barrier properties of the as-produced membranes. The addition of S-NbS₂ nanoflakes to SPEEK decreases the vanadium ion permeability from 5.42 × 10^-7 to 2.34 × 10^-7 cm² min^-1. Meanwhile, it increases the membrane σ and selectivity up to 94.35 mS cm^-2 and 40.32 × 10⁴ S min cm^-3, respectively. The cell assembled with the optimized membrane incorporating 2.5 wt% of S-NbS₂ nanoflakes (SPEEK:2.5% S-NbS₂) exhibits high efficiency metrics, i.e., coulombic efficiency between 98.7 and 99.0%, voltage efficiency between 90.2 and 73.2% and energy efficiency between 89.3 and 72.8% within the current density range of 100-300 mA cm^-2, delivering a maximum power density of 0.83 W cm^-2 at a current density of 870 mA cm^-2. The SPEEK:2.5% S-NbS₂ membrane-based VRFBs show a stable behavior over 200 cycles at 200 mA cm^-2. This study opens up an effective avenue for the production of advanced SPEEK-based membranes for VRFBs.

Green modification of graphene dispersion with high nanosheet content, good dispersibility, and long storage stability

In this work, an easy, green, noncovalent surface modification of pristine graphene (GR) was carried out using a single-step method between sodium carboxymethyl cellulose (CMC) and pristine GR, resulting in the formation of a modified CMC-GR (CGR) dispersion with 15% nanosheet content, the first reported in water. Results obtained from thermogravimetry analysis (TGA), Raman spectroscopy, and atomic force microscopy (AFM) confirm that the CMC modifier is successfully decorated on the pristine GR surface. Analyses of transmittance spectrum, zeta potential and transmittance electron microscopy (TEM) images reveal that the modified CGR has a high degree of dispersion. More importantly, the pristine GR is insoluble, while the modified CGR-3, mixed with 1.1 wt% CMC modifier, is easily well dispersed in water and has good flowability, and no sedimentation is observed after more than 3 months.

Two-Dimensional Stacked Composites of Self-Assembled Alkane Layers and Graphene for Transparent Gas Barrier Films with Low Permeability

Self-assembled alkane layers are introduced between graphene layers to physically block nanometer size defects in graphene and lateral gas pathways between graphene layers. A well-defined hexatriacontane (HTC) monolayer on graphene could cover nanometer-size defects because of the flexible nature and strong intermolecular van der Waals interactions of alkane, despite the roughness of graphene. In addition, HTC multilayers between graphene layers greatly improve their adhesion. This indicates that HTC multilayers between graphene layers can effectively block the lateral pathway between graphene layers by filling open space with close-packed self-assembled alkanes. By these mechanisms, alternately stacked composites of graphene and self-assembled alkane layers greatly increase the gas-barrier property to a water vapor transmission rate (WVTR) as low as 1.2 × 10^-3 g/(m² day), whereas stacked graphene layers generally show a WVTR < 0.5 g/(m² day). Furthermore, the self-assembled alkane layers have superior crystallinity and wide bandgap, so they have little effect on the transmittance.

Controlled Release of Molecular Intercalants from Two-Dimensional Nanosheet Films

Solution co-deposition of two-dimensional (2D) nanosheets with chemical solutes yields nanosheet-molecular heterostructures. A feature of these macroscopic layered hybrids is their ability to release the intercalated molecular agent to express chemical functionality on their surfaces or in their near surroundings. Systematic design methods are needed to control this molecular release to match the demand for rate and lifetime in specific applications. We hypothesize that release kinetics are controlled by transport processes within the layered solids, which primarily involve confined molecular diffusion through nanochannels formed by intersheet van der Waals gaps. Here a variety of graphene oxide (GO)/molecular hybrids are fabricated and subject to transient experiments to characterize release kinetics, locations, and mechanisms. The measured release rate profiles can be successfully described by a numerical model of internal transport processes, and the results used to extract effective Z-directional diffusion coefficients for various film types. The diffusion coefficients are found to be 8 orders of magnitude lower than those in free solution due to nanochannel confinement and serpentine path effects, and this retardation underlies the ability of 2D materials to control and extend release over useful time scales. In-plane texturing of the heterostructured films by compressive wrinkling or crumpling is shown to be a useful design tool to control the release rate for a given film type and molecular intercalant. The potential of this approach is demonstrated through case studies on the controlled release of chemical virucidal agents.

Plug-and-play polymer microfluidic chips for hydrated, room temperature, fixed-target serial crystallography

The practice of serial X-ray crystallography (SX) depends on efficient, continuous delivery of hydrated protein crystals while minimizing background scattering. Of the two major types of sample delivery devices, fixed-target devices offer several advantages over widely adopted jet injectors, including: lower sample consumption, clog-free delivery, and the ability to control on-chip crystal density to improve hit rates. Here we present our development of versatile, inexpensive, and robust polymer microfluidic chips for routine and reliable room temperature serial measurements at both synchrotrons and X-ray free electron lasers (XFELs). Our design includes highly X-ray-transparent enclosing thin film layers tuned to minimize scatter background, adaptable sample flow layers tuned to match crystal size, and a large sample area compatible with both raster scanning and rotation based serial data collection. The optically transparent chips can be used both for in situ protein crystallization (to eliminate crystal handling) or crystal slurry loading, with prepared samples stable for weeks in a humidified environment and for several hours in ambient conditions. Serial oscillation crystallography, using a multi-crystal rotational data collection approach, at a microfocus synchrotron beamline (SSRL, beamline 12-1) was used to benchmark the performance of the chips. High-resolution structures (1.3-2.7 Å) were collected from five different proteins - hen egg white lysozyme, thaumatin, bovine liver catalase, concanavalin-A (type VI), and SARS-CoV-2 nonstructural protein NSP5. Overall, our modular fabrication approach enables precise control over the cross-section of materials in the X-ray beam path and facilitates chip adaption to different sample and beamline requirements for user-friendly, straightforward diffraction measurements at room temperature.

An Axially Continuous Graphene-Copper Wire for High-Power Transmission: Thermoelectrical Characterization and Mechanisms

The demand for high-power electrical transmission continues to increase with technical advances in electric vehicles, unmanned drones, portable devices, and deployable military applications. In this study, significantly enhanced electrical properties (i.e., a 450% increase in the current density breakdown limit) are demonstrated by synthesizing axially continuous graphene layers on microscale-diameter wires. To elucidate the underlying mechanisms of the observed enhancements, the electrical properties of pure copper wires and axially continuous graphene-copper (ACGC) wires with three different diameters are characterized while controlling the experimental conditions, including ambient temperature, gases, and pressure. The study reveals that the main mechanism that allows the application of extremely large current densities (>400 000 A cm^-2 ) through the ACGC wires is threefold: the continuous graphene layers considerably improve: 1) surface heat dissipation (224% higher), 2) electrical conductivity (41% higher), and 3) thermal stability (41.2% lower resistivity after thermal cycles up to 450 °C), compared with pure copper wires. In addition, it is observed, through the use of high-speed camera images, that the ACGC wires exhibit very different failure behavior near the current density limit, compared with the pure copper wires.

Interfacial Hydrothermal Assembly of Three-Dimensional Lamellar Reduced Graphene Oxide Aerogel Membranes for Water Self-Purification

Energy-saving membrane separation for water purification is increasingly desired, which requires appropriate nanofiltration membranes enabling to reject undesired solutes efficiently and allows high permeation of water. Herein, we report the fabrication of three-dimensional lamellar reduced graphene oxide (rGO) hydrogel membranes with a one-step, environment-friendly and water/vapor interfacial hydrothermal assembly process and the corresponding aerogel membranes by the freeze-drying method. The structures of the aerogel membranes can be tuned from lamellar to porously interconnected morphologies by controlling the volume of GO suspensions during the hydrothermal process. The rGO aerogel membrane was extremely flexible, which can be bent in liquid nitrogen and boiling water without any deformation, and highly stable in various solvents for at least 2 months. When used as nanofiltration membranes, the rGO aerogel membranes showed ∼100% rejection of organic dyes and a moderate water flux (up to 53 L m^-2 h^-1) only under the gravity of organic dye aqueous solutions of a 30 cm height. This water self-purification property of our flexible and stable aerogel membranes without extra energy consumption provides a possibility to make cheap, portable water purification devices for utilization in emergency and home-used water purification systems in the areas with electricity unavailable or inconvenient.

3D printed silicon-few layer graphene anode for advanced Li-ion batteries

The printing of three-dimensional (3D) porous electrodes for Li-ion batteries is considered a key driver for the design and realization of advanced energy storage systems. While different 3D printing techniques offer great potential to design and develop 3D architectures, several factors need to be addressed to print 3D electrodes, maintaining an optimal trade-off between electrochemical and mechanical performances. Herein, we report the first demonstration of 3D printed Si-based electrodes fabricated using a simple and cost-effective fused deposition modelling (FDM) method, and implemented as anodes in Li-ion batteries. To fulfil the printability requirement while maximizing the electrochemical performance, the composition of the FDM filament has been engineered using polylactic acid as the host polymeric matrix, a mixture of carbon black-doped polypyrrole and wet-jet milling exfoliated few-layer graphene flakes as conductive additives, and Si nanoparticles as the active material. The creation of a continuous conductive network and the control of the structural properties at the nanoscale enabled the design and realization of flexible 3D printed anodes, reaching a specific capacity up to ∼345 mA h g⁻¹ at the current density of 20 mA g⁻¹, together with a capacity retention of 96% after 350 cycles. The obtained results are promising for the fabrication of flexible polymeric-based 3D energy storage devices to meet the challenges ahead for the design of next-generation electronic devices.

Novel 3D printed anodes based on Si and wet-jet milling-exfoliated few-layer graphene are produced by fused diffusion modelling (FDM) technique and used in Li-ion batteries.

Recent Developments in Nanoporous Graphene Membranes for Organic Solvent Nanofiltration: A Short Review

Graphene-based membranes are promising candidates for efficient organic solvent nanofiltration (OSN) processes because of their unique structural characteristics, such as mechanical/chemical stability and precise molecular sieving. Recently, to improve organic solvent permeance and selectivity, nanopores have been fabricated on graphene planes via chemical and physical methods. The nanopores serve as an additional channel for facilitating ultrafast solvent permeation while filtering organic molecules by size exclusion. This review summarizes the recent developments in nanoporous graphene (NG)-based membranes for OSN applications. The membranes are categorized depending on the membrane structure: single-layer NG, multilayer NG, and graphene-based composite membranes hybridized with other porous materials. Techniques for nanopore generation on graphene, as well as the challenges faced and the perspectives required for the commercialization of NG membranes, are also discussed.