High Graphene Oxide Research Articles

Enhancing Combustion Efficiency: Utilizing Graphene Oxide Nanofluids as Fuel Additives with Tomato Oil Methyl Ester in CI Engines

The research aims to conduct a thorough examination of the combustion, injection, performance, and emission characteristics of a diesel engine below different engine loads, as well as the synthesis of graphene oxide (GO) nano fuels and their utilization in combination with Tomato Oil methyl ester (TOME) and diesel fuel blend. The graphene oxide, plays a vital role in the pre-mixed combustion phase of diesel engines. Addition of graphene oxide nano fuels enhances the high-pressure combustion stage, resulting in increased maximum pressure and heat release rate. TOME (B20GO75) and TOME (B20GO100) exhibit comparable heat release rate to diesel due to improved fuel characteristics and quicker ignition delay duration. While TOME (B20) shows a slight decrease in (BTE) compared to diesel, the addition of graphene oxide improves BTE, with TOME (B20GO50) displaying the highest BTE at full load, indicating enhanced combustion efficiency. Moreover, graphene oxide addition leads to a reduction in carbon monoxide (CO) and hydrocarbon (HC) emissions, with emissions decreasing as the concentration of graphene oxide increases. However, NoX emissions initially decrease with TOME (B20) compared to diesel but increase with higher graphene oxide concentration. Smoke emissions increase with TOME (B20) but decrease with higher graphene oxide dosages. Overall, the incorporation of graphene oxide nano fuels into Tomato Oil methyl ester blends demonstrates potential for improving engine performance and reducing emissions.

Potential advantage of invasive estuarine worms over native species under exposure to relevant concentrations of graphene oxide: Behavioral and biochemical insights

Technological development using graphene oxide (GO) has increased in the last years, leading to the release of this contaminant to final sinks, such as estuaries. Due to their potential to flocculate and deposit when interacting with high ionic strength media, GO poses a threat, especially to benthic organisms like polychaetes. In addition to chemical contamination, estuaries also face a severe threat from invasive species, which can cause irreversible damage to ecosystems. The combination of abiotic and biotic stressors may work together on native species, decreasing their resilience. Thus, this study aims to assess the effects of an abiotic stressor, GO nanosheets (0.001, 0.01, 0.1, 1, 10 mg GO/Kg dw) on Hediste diversicolor (native species) and Arenicola marina (invasive species) through several behavioral assays and biochemical markers. The impact of invasive species A. marina (biotic factor) on H. diversicolor avoidance behavior was also evaluated. Obtained results demonstrated that H. diversicolor fled from lower GO contamination compartments to higher ones and that exposure to increased GO concentrations negatively impacted its burrowing activity. They were unable to escape from higher contamination compartments, but at the highest concentrations, the bioturbation activity was significantly higher, which may indicate that H. diversicolor tended to dwell deeper in the sediment. A. marina showed an escape behavior from compartments with higher GO concentrations. Additionally, this species' bioturbation activity significantly decreased when exposed to GO. Moreover, avoidance tests demonstrated that the presence of A. marina affected the behavior of H. diversicolor. Regarding oxidative stress, H. diversicolor seems to be more impacted than A. marina, since Lipid peroxidation levels were higher in all GO concentrations and Superoxide dismutase activity significantly increased in the lowest GO levels. Overall, H. diversicolor spatial distribution may be severely constrained under abiotic and biotic stress, while A. marina's higher foraging activity may promote its propagation in the estuary. Behavioral tests, combined with biochemical markers have shown to be relevant tools for the development of more environmental-realistic assessment and monitoring frameworks for estuaries.

Improving CO2 adsorption efficiency of an amine-modified MOF-808 through the synthesis of its graphene oxide composites

This research developed a novel composite of MOF-NH2 and graphene oxide (GO) for enhanced CO2 capture. Employing the response surface methodology-central composite design (RSM-CCD) for experiments design, various MOF-NH2/GO samples with GO loadings from 0 to 30 wt% were synthesized. The results of SEM, XRD, EDS, and BET analysis revealed that the materials maintained their MOF crystal structure, confirmed by X-ray diffraction, and exhibited unique texture, high porosity, and oxygen-enriched surface chemistry. The influence of temperature (25–65 °C) and pressure (1–9 bar) on CO2 adsorption capacity was assessed using a volumetric adsorption system. Optimum conditions were obtained at weight percent of 22.6 wt% GO, temperature of 25 °C, and pressure of 9 bar with maximum adsorption capacity of 303.61 mg/g. The incorporation of amino groups enhanced the CO2 adsorption capacity. Isotherm and kinetic analyses indicated that Freundlich and Fractional-order models best described CO2 adsorption behavior. Thermodynamic analysis showed the process was exothermic, spontaneous, and physical, with enthalpy changes of − 16.905 kJ/mol, entropy changes of − 0.030 kJ/mol K, and Gibs changes energy of − 7.904 kJ/mol. Mass transfer diffusion coefficients increased with higher GO loadings. Regenerability tests demonstrated high performance and resilience, with only a 5.79% decrease in efficiency after fifteen cycles. These findings suggest significant potential for these composites in CO2 capture technologies.

Electron beam irradiation developed cinnamon oil- (polyvinyl alcohol/gum tragacanth)/graphene oxide dressing hydrogels: Antimicrobial and healing assessments

This study aimed to develop hydrogel dressings for wound healing composed of gum tragacanth (TG) and polyvinyl alcohol (PVA) loaded with Graphene oxide (GO) and Cinnamon oil (CMO) using electron beam irradiation. The impact of the preparation conditions and the incorporation of GO and CMO on the characteristic properties of the prepared CMO-(PVA/TG)-GO wound dressings was evaluated. The healing-related characteristics were assessed, including fluid absorption and retention, water vapor transmission rate (WVTR), hemolytic assay, and antimicrobial potential. Wound healing efficacy was evaluated using a scratch wound healing assay. FTIR analysis verified the chemical structure, whereas scanning electron microscopy demonstrated an appropriate porosity structure necessary for optimal wound healing. The gel content increases with the initial total polymer concentration and the irradiation dose increases. Higher GO and CMO content improve the gel content and decreases swelling. WVTR decreases with the rise in CMO content. In vitro, cytotoxicity and hemolytic potency assessments confirmed their biocompatibility. The incorporation of GO and CMO enhances the antimicrobial activity and wound-healing capability. Based on the above findings, CMO-(PVA/TG)-GO dressings show promising potential as candidates for wound care.

Raman spectroscopic quantification of graphene oxide in soil: Transport, surficial enrichment and environmental effects

The transport and retention data in environmental media are indispensable for the hazard evaluations of graphene materials. Due to the complexity of soil, the transport of graphene is hard to quantify without isotope labeling. Herein, we developed 2D Raman mapping as a label-free technique to quantify graphene oxide (GO) in soil. After pre-treatment by hydrazine hydrate to quench its fluorescence, the quantification of GO in soil was achieved in the range of 0.1–1000 mg/L by measuring the average G-band intensity. In column transport experiment, the transport and retention of GO in soil depended on the solution chemistry. Lower pH and higher ionic strength hindered the transport of GO. In particular, Ca2+ showed the most obvious retardation on the transport of GO. GO enriched in the surficial soil layer by several folds of the initial concentrations, and higher GO concentration led to more surficial enrichment. The sowing manner of seeds affected the soil enrichment of GO, too. The surficial enrichment of GO reduced its direct contact with seedling roots, resulting in the alleviation of GO toxicity. Our results provided a facile method to study the environmental behaviors of graphene and highlighted the crucial impacts of environmental media on the graphene toxicity.

Straightforward microwave-assisted synthesis of ultrasmall gold nanoparticles acnhored on reduced graphene oxide for enhanced antibacterial application

Graphene derivative materials, such as graphene oxide (GO) and reduced graphene oxide (rGO), have garnered significant attention from scientists for over two decades due to their distinctive characteristics and versatile applications across various fields, particularly in biomedical applications. Incorporating gold nanoparticles (AuNPs) into rGO sheets as rGO-Au nanocomposites further enhances its performance in biomedical applications. This study presents a rapid and efficient method for synthesizing ultrasmall AuNPs anchored on reduced graphene oxide (rGO-Au) using microwave irradiation and ascorbic acid. The optimum microwave treatment was 4 min, ensuring the highest GO reduction degree. Structural characterization by TEM reveals a distinctive architecture with ultrasmall AuNPs (average size of 2.2 nm) distributed on the rGO sheets. Interestingly, while the synthesized rGO-Au did not exhibit any antibacterial activities against both Escherichia coli and Staphylococcus aureus in disk diffusion assays, it demonstrated bacteriostatic effect at remarkably low concentrations when assessed by optical density measurement. The effective concentration of rGO-Au to inhibit E. coli growth was determined to be 2.5 ppm, while for S. aureus, it was 5 ppm, resulting in growth inhibition of 53.1% and 50.0%, respectively. These findings provide a straightforward synthesis route for rGO-Au nanocomposites and underscore the importance of AuNPs’ size and quantity in modulating antibacterial properties.

Rheological study of hybrid aqueous suspension of TEMPO-oxidized cellulose nanofibrils and graphene oxide

The incorporation of graphene oxide (GO) into a nanocellulose matrix has attracted considerable attention due to the unique advantages of both components. This study focuses on investigating the viscoelastic and flow properties of hybrid aqueous suspensions (2.00 w/v%), composed of TEMPO-oxidized cellulose nanofibrils (TOCNF) and GO at different TOCNF/GO weight ratios. To adjust the elastic properties of the hybrid suspensions, calcium ions are introduced, varying the concentration systematically to study their effects on the hybrid network structure. All blends exhibit shear-thinning behaviour and demonstrate elastic, gel-like properties. Notably, in the absence of calcium ions, the enhancement of elastic properties is more pronounced at higher GO fractions. Conversely, with the introduction of calcium ions, the enhancement of elastic properties becomes particularly important at higher TOCNF fractions. For the quantitative evaluation of these enhancements, we employ the logarithmic mixing rule. Significant positive deviations from the predictions of the logarithmic mixing rule are ascribed to the complex, concentration-dependent arrangement of cellulose nanofibrils and GO liquid crystals in the aqueous suspension, coupled with ionic crosslinking induced by calcium ions. The study aims to contribute to the understanding of the rheological behaviour of the TOCNF/GO hydrogel, showing potential advancements in various applications.Graphical abstract

Hybrid graphene oxide-graphene membrane for efficient water desalination: Insights from molecular dynamics simulation

In the field of reverse osmosis (RO) desalination, layer-by-layer assembled graphene oxide (GO) membranes have emerged as a promising innovation. However, the swelling of these membranes remains a critical barrier that affects their performance and long-term stability. To address this challenge, our study investigates the potential of hybrid GO and graphene (G) membranes to reduce swelling and increase overall performance through molecular dynamics simulations. Our findings reveal that the G/GO/G/GO hybrid membrane outperforms others, demonstrating a water permeation rate of 69.2 L/cm2/day/Mpa, exceeding alternatives, and boasting 100 % ion rejection efficiency, with a channel inter-layer distance of 8.77 Å. Moreover, the combination of hydrophobic G sheets and hydrophilic GO sheets reduces swelling compared to pure GO membranes. Furthermore, the analysis of water velocity within the hybrid GO/G membrane reveals that the velocity profile is no longer symmetrical, unlike in the pure G and GO membranes, and the maximum velocity occurs in close proximity to the hydrophobic sheet. Additionally, increasing the mass of G sheets in the hybrid GO/G membrane, enhances water flow, while a higher GO sheet ratio reduces permeation. Our study reveals the distinct characteristics of pure GO and hybrid GO/G membranes and their significant impact on water desalination technology.

Fabrication of 3D porous polyurethane-graphene oxide scaffolds by a sequential two-step processing for non-load bearing bone defects

Bone defects as a common orthopedic disease lead to severe pains over a long period. Scaffolds are novel approaches in tissue engineering to treat bone problems and deal with their challenges. Here, 3D porous polyurethane (PU) scaffolds containing graphene oxide (GO) with different percentages (0, 0.1, 0.3, and 0.5 wt%) were developed through a combination of freeze-drying and salt etching techniques for bone tissue engineering applications. The morphologies of scaffolds, physicochemical properties, the degree of crystallinity, and hydrophilicity were evaluated by SEM, FTIR, XRD, and water contact angle assay, respectively. The porosity, degradation behavior, compressive strength, and elastic modulus of 3D porous scaffolds were also determined. To assess the scaffold bioactivity, the morphology of the deposited calcium phosphate layer on the scaffold with macro-structure was evaluated by SEM images. The viability and adhesion of MG63 osteoblast-like cells cultured on the fabricated scaffolds were examined by MTT assay and SEM images, respectively. The results show that adding GO particles not only had no effect on the interconnectivity and porosity of 3D porous macroscopic structures of neat PU but also smaller and more uniformed microscopically pores were obtained. The crystallinity, water contact angle, and weight loss of scaffolds increased as the higher GO concentrations were employed. Followed by increasing GO contents from 0 to 0.5 wt%, the compressive strength and Young’s modulus were increased by 232% and 245%, respectively. The bioactivity of scaffolds was fostered as GO concentration increased. Although, the MTT assay proved the biocompatibility of PU scaffolds containing 0.1 and 0.3 wt% GO, the samples loaded with 0.5 GO had a negative impact on the viability of MG63 cell lines. In conclusion, the present study demonstrates a high potential of PU scaffolds loaded with 0.1 and 0.3 wt% GO particles in bone tissue engineering applications.

Graphene oxide influences transfer of plasmid-mediated antibiotic resistance genes into plants

As an emerging contaminant, antibiotic resistance genes (ARGs) are raising concerns about its significant threat to public health. Meanwhile, graphene oxide (GO), which also has a potential ecological damage with increasingly entering the environment, has a great influence on the transfer of ARGs. However, little is known about the effects mechanisms of GO on the migration of antibiotic resistance genes (ARGs) from bacteria into plants. In this study, we investigated the influence of GO on the transfer of ARGs carried by RP4 plasmids from Bacillus subtilis into rice plants. Our results showed that the presence of GO at concentrations ranging from 0 to 400 mg L−1 significantly reduced the transfer of ARGs into rice roots by 13–71 %. Moreover, the migration of RP4 from the roots to aboveground parts was significantly impaired by GO. These effects may be attributed to several factors. First, higher GO concentrations led to low pH in the culture solution, resulting in a substantial decrease in the number of antibiotic-resistant bacteria. Second, GO induced oxidative stress in rice, as indicated by enhanced Evans blue dye staining, and elevated levels of malondialdehyde, nitric oxide, and phenylalanine ammonia-lyase activity. The oxidative stress negatively affected plant growth, as demonstrated by the reduced fresh weight and altered lignin content in the rice. Microscopic observations confirmed the entry of GO into root cells but not leaf mesophyll cells. Furthermore, potential recipients of RP4 plasmid strains in rice after co-cultivation experiments were identified, including Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus cereus. These findings clarify the influence of GO on ARGs in the bacteria–plant system and emphasize the need to consider its potential ecological risks.

Lithium–sulfur battery performance enhancement by optimal loading of graphene oxide on separator with MXene/reduced graphene oxide/sulfur cathode

Lithium–sulfur batteries are a compelling choice for next-generation energy storage devices with their high energy density, low cost, and environmental friendliness. This work employs a one-pot route to synthesize a MXene/reduced graphene oxide/S composite with a graphene oxide (GO)-modified separator to overcome the common bottlenecks to successful commercialization of lithium sulfur batteries like fast capacity fade, low electrochemical utilization, and low sulfur loading. The synthesized cathode material was characterized by powder X-ray diffraction, scanning electron microscopy, thermogravimetry, Raman spectroscopy, and X-ray photoelectron spectroscopy. Electrochemical characterization of assembled coin-cells was performed by cyclic voltammetry, galvanostatic cycling as well as by electrochemical impedance spectroscopy. The loading of GO on the separator was varied to probe its effect and a monotonic increase in capacity with increasing GO loading was observed. GO modification of separator also results in lower cell impedance and enhanced Li+ diffusion. The optimized coin cell exhibited an initial specific capacity of 725 mAh/g when cycled at 100 mA/g current density with a capacity fade of 0.14% per cycle. Post-mortem analysis of cycled cells corroborates increased polysulfide trapping with higher GO loading on separator.

Characterization of a Graphene Oxide-Reinforced Whey Hydrogel as an Eco-Friendly Absorbent for Food Packaging.

This study presents a structural analysis of a whey and gelatin-based hydrogel reinforced with graphene oxide (GO) by ultraviolet and visible (UV-VIS) spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The results revealed barrier properties in the UV range for the reference sample (containing no graphene oxide) and the samples with minimal GO content of 0.66×10-3% and 3.33×10-3%, respectively, in the UV-VIS and near-IR range; for the samples with higher GO content, this was 6.67×10-3% and 33.33×10-3% as an effect of the introduction of GO into the hydrogel composite. The changes in the position of diffraction angles 2θ from the X-ray diffraction patterns of GO-reinforced hydrogels indicated a decrease in the distances between the turns of the protein helix structure due to the GO cross-linking effect. Transmission electron spectroscopy (TEM) was used for GO, whilst scanning electron microscopy (SEM) was used for the composite characterization. A novel technique for investigating the swelling rate was presented by performing electrical conductivity measurements, the results of which led to the identification of a potential hydrogel with sensor properties.

Effect of GO Solution Temperature on the Structural, Optical and Electrical Properties of ZnO Nanostructured for Photoanode Function

The purpose of this study is to determine the effect of different graphene oxide (GO) solution immersion temperature on the structural, morphology, optical, and electrical properties of zinc oxide/graphene oxide (ZnO-GO) nanostructures. The ZnO/GO nanostructures prepared at various GO solution immersion temperature from 75-95℃ using solution immersion method. The structural properties of the samples were investigated using X-ray diffraction (XRD), and the recorded patterns revealed that all the samples had a preferred orientation along the (002) plane. The crystallinity of ZnO/GO nanostructures were enhanced with increasing GO solution immersion temperature. The morphology of ZnO/GO nanostructures was determined using field emission scanning electron microscopy (FESEM). Fourier transformation infrared spectroscopy (FTIR) was used to determine the molecular compounds of ZnO/GO nanostructures. The peak intensity of GO with ZnO nanoparticles is shifted at 744 to 1243 cm-1 when the temperature of GO solutions increases. The UV–visible spectrophotometer was used to examine the optical properties of ZnO/GO nanostructures. It is found that the highest transmittance ZnO/GO nanostructures was obtained at the highest GO solution immersion temperature which is 95℃. Based on the current-voltage(I–V) measurement, the electrical properties of ZnO/GO nanostructures increase when the GO solution immersion temperature increases. Thus, by variation of GO solution immersion temperature the structural, morphology, optical, and electrical behaviour were improved.

Double-Reinforced Fish Gelatin Composite Scaffolds for Osteochondral Substitutes

Genipin crosslinked composite blends of fish gelatin/kappa-carrageenan (fG/κC) with different concentrations of graphene oxide (GO) for osteochondral substitutes were prepared by a simple solution-blending method. The resulting structures were examined by micro-computer tomography, swelling studies, enzymatic degradations, compressions tests, MTT, LDH, and LIVE/DEAD assays. The derived findings revealed that genipin crosslinked fG/κC blends reinforced with GO have a homogenous morphology with ideal pore dimensions of 200-500 µm for bones alternative. GO additivation with a concentration above 1.25% increased the blends' fluid absorption. The full degradation of the blends occurs in 10 days and the gel fraction stability increases with GO concentration. The blend compression modules decrease at first until fG/κC GO3, which has the least elastic behavior, then by raising the GO concentration the blends start to regain elasticity. The MC3T3-E1 cell viability reveals less viable cells with the increase of GO concentration. The LDH together with the LIVE/DEAD assays reports a high concentration of live and healthy cells in all types of composite blends and very few dead cells at the higher GO content.

Bactericidal Action and Industrial Dye Degradation of Graphene Oxide and Polyacrylic Acid-Doped SnO2 Quantum Dots: In Silico Molecular Docking Study.

The present work demonstrates the systematic incorporation of different concentrations of graphene oxide (GO) into a fixed amount of polyacrylic acid (PAA)-doped SnO2 quantum dots (QDs) through a co-precipitation approach. The research aimed to evaluate the catalytic and antibacterial actions of GO/PAA-SnO2 QDs. Moreover, optical properties, surface morphologies, crystal structures, elemental compositions, and d-spacings of prepared QDs were examined. X-ray diffraction patterns revealed the tetragonal configuration of SnO2, and the crystallinity of QDs was suppressed upon dopants verified by the SAED patterns. Electronic spectra identified the blue shift by incorporating GO and PAA led to a reduction in band gap energy. Fourier transform infrared spectra showed the existence of rotational and vibrational modes associated with the functional groups during the synthesis process. A drastic increase in the catalytic efficacy of QDs was observed in the neutral medium by including dopants, indicating that GO/PAA-SnO2 is a promising catalyst. GO/PAA-SnO2 showed strong bactericidal efficacy against Escherichia coli (E. coli) at higher GO concentrations. Molecular docking studies predicted the given nanocomposites, i.e., SnO2, PAA-SnO2, and GO/PAA-SnO2, as potential inhibitors of beta-lactamaseE.coli and DNA gyraseE.coli.

Preparation, characterization, and compatibilization of novel rubber nanocomposites for mechanical applications: relationship between electrical properties, morphology, and rheology

In this paper, a novel rubber nanocomposite containing phenyl-vinyl-methyl-polysiloxane (PVMQ) and ethylene propylene diene monomer (EPDM) was produced during a two-roll mill procedure for mechanical applications. For this purpose, ethylene propylene diene monomer-grafted-maleic anhydride compatibilizer (EPDM-g-MAC) and graphene oxide (GO) was used as a compatibilizer and reinforcements to make a uniform composite. To study mechanical and physical characterizations, dynamic mechanical thermal analysis (DMTA), rheology, morphology, and curing characterizations of nanocomposites were investigated, which showed that compatibilizer makes GO dispersion uniformly. An electrical resistivity test was performed to study the electrical conductivity of the nanocomposites. The results indicate that the samples with higher GO content had a response to the electrical current. The curing study indicates that, by increasing the GO nanoparticles in the presence of EPDM-g-MAC, the curing properties are enhanced as well as mechanical properties by improving the bonding among GO, compatibilizer, and matrix [tensile strength (54%), modulus (68%), elongation-at-break (67%), hardness (81%), and fatigue (51%)]. FE-SEM and TEM images demonstrated that, by increasing GO nanoparticles in the presence of compatibilizer, the mean diameter of EPDM decreased in the substrate, which consequently increased the mechanical properties. The changes in surface temperature were investigated with constant voltage (75 V), which indicates that by increasing GO nanoparticles and electrical conductivity, the surface temperature increased significantly. The results of practical experiments showed good agreement with the theoretical results.

Macro-Size Regenerated Cellulose Fibre Embedded with Graphene Oxide with Antibacterial Properties.

Macro-size regenerated cellulose fibres (RCFs) with embedded graphene oxide (GO) were fabricated by dissolving cellulose in a pre-cooled sodium hydroxide (NaOH)/urea solution and regenerated in sulphuric acid (H2SO4) coagulant. Initially, GO was found to disperse well in the cellulose solution due to intercalation with the cellulose; however, this cellulose-GO intercalation was disturbed during the regeneration process, causing agglomeration of GO in the RCF mixture. Agglomerated GO was confirmed at a higher GO content under a Dino-Lite microscope. The crystallinity index (CrI) and thermal properties of the RCFs increased with increasing GO loadings, up to 2 wt.%, and reduced thereafter. Cellulose-GO intercalation was observed at lower GO concentrations, which enhanced the crystallinity and thermal properties of the RCF-GO composite. It was shown that the GO exhibited antibacterial properties in the RCF-GO composite, with the highest bacterial inhibition against E. coli and S. aureus.

Swelling and Antimicrobial Activity Characterization of a GO-Reinforced Gelatin-Whey Hydrogel.

Whey-based hydrogel samples with increasing concentrations of graphene oxide (GO) were studied, against a control sample (M), for swelling behavior in light of nuclear magnetic resonance (NMR) and mathematical models of the diffusion process and for antibacterial activity. Graphene oxide (GO) is an optimal filler for whey-based hydrogels, giving them improved mechanical and swelling properties at low concentrations. Crosslinking induces a certain stiffness of the hydrogels, which is why only the first part of the swelling process (<60%) follows the first-order model, while during the whole time interval, the swelling process follows the second-order diffusion model. The NMR relaxometry results are consistent with the swelling behavior of GO-reinforced whey−gelatin composite hydrogels, showing that higher GO concentrations induce a higher degree of cross-linking and, therefore, lower swelling capacity. Only hydrogel samples with higher GO concentrations demonstrated antibacterial activity.

Synergistic strengthening mechanism of Portland cement paste reinforced by a triple hybrid of graphene oxide, functionalized carbon nanotube, and nano-silica

• Triple hybrid of GO, f-CNT, and NS as a cement composite reinforcement was studied. • Amount of GO was selected as a variable in the triple hybrid. • Optimal ratio of GO for the triple hybrid was found to be 0.04 wt% (of cement) • Dispersion of the triple hybrid depends on the bonds between the nanomaterials. • Hydration and mechanical properties of cement composites are affected by dispersion of the triple hybrid. This study investigates the synergistic strengthening mechanism of graphene oxide (GO), functionalized carbon nanotubes (f-CNT), and nano-silica (NS) triple hybrid-reinforced Portland cement composite. GO was selected as the variable owing to the synergistic effect of GO with both f-CNTs and NS upon dispersion by forming bonds with both nanomaterials. At a low GO dosage (∼0.03 wt% of cement), the bond between GO and NS deteriorated the dispersion in Ca 2+ -rich solution due to the overly attached NS on the GO surface. The highest GO fraction (0.05 wt%) also led to poor dispersion as the excess GO was agglomerated by Ca 2+ ions. However, an optimal amount of GO (0.04 wt%) significantly improved the dispersion quality. The enhanced dispersion of the triple hybrid positively influenced the hydration degree and mechanical performance of the cement paste (133 % and 156 % for compressive and tensile splitting strength compared to OPC) and the pozzolanic reactivity of NS.

Insights into the performance of hybrid graphene oxide/MOFs for CO2 capture at process conditions by molecular simulations

Hybridization of metal organic frameworks (MOFs) with graphene oxide (GO) is used to improve the CO2 adsorption performance of MOFs, but the underlying mechanism of this process is still unclear. This study provides a general framework to understanding the mechanism of CO2 adsorption and separation on GO/CuBTC and GO/UTSA-16 in order to optimize the synthesis of the desired material. For this purpose, molecular models mimicking the experimentally available hybrid materials were developed and studied by molecular simulations. Once the models were validated with available experimental data, a systematic study on the effect of different structure variables was performed, searching for the best hybridization procedure for this application, in a predictive manner. It has been confirmed that the interface between GO and MOFs produces strong interactions with CO2, which, together with the smaller pore sizes, significantly enhances the adsorption performance at low pressures. Moreover, the performance of the most promising hybrid GO/MOFs structures from pure CO2 adsorption isotherms for separating CO2 from nitrogen were predicted by GCMC based on binary mixtures (15CO2:85 N2) and a temperature swing adsorption (TSA) process. Among the different materials/compositions explored, GO/CuBTC with the highest GO content (i.e., 65% wt.) and under the premise of no stacking of GO, shows the best results in terms of key performance indicators: CO2/N2 adsorption selectivity (120 at 313 K), working capacity (1.794 mmol/g at a desorption temperature of 443 K), and a specific energy consumption (0.534 GJ/tonne-CO2) comparable to amine scrubbing.