Surface Chemistry Of Graphene Oxide Research Articles

Electrochemical Fine-Tuning of the Chemoresponsiveness of Langmuir-Blodgett Graphene Oxide Films.

Graphene oxide has been widely deployed in electrical sensors for monitoring physical, chemical, and biological processes. The presence of abundant oxygen functional groups makes it an ideal substrate for integrating biological functional units to assemblies. However, the introduction of this type of defects on the surface of graphene has a deleterious effect on its electrical properties. Therefore, adjusting the surface chemistry of graphene oxide is of utmost relevance for addressing the immobilization of biomolecules, while preserving its electrochemical integrity. Herein, we describe the direct immobilization of glucose oxidase onto graphene oxide-based electrodes prepared by Langmuir-Blodgett assembly. Electrochemical reduction of graphene oxide allowed to control its surface chemistry and, by this, regulate the nature and density of binding sites for the enzyme and the overall responsiveness of the Langmuir-Blodgett biofilm. X-ray photoelectron spectroscopy, surface plasmon resonance, and electrochemical measurements were used to characterize the compositional and functional features of these biointerfaces. Covalent binding between amine groups on glucose oxidase and epoxy and carbonyl groups on the surface of graphene oxide was successfully used to build up stable and active enzymatic assemblies. This approach constitutes a simple, quick, and efficient route to locally address functional proteins at interfaces without the need for additives or complex modifiers to direct the adsorption process.

Physicochemical transformation of graphene oxide during heat treatment at 110–200 °C

Graphene oxide (GO) was subjected to different heating pathways to investigate water removal at 110°C (GO-110), water removal followed by removal of surface groups at 140°C or 200°C (GO-110-140 or GO-110-200), and simultaneous removal of water and surface groups at 140°C or 200°C (GO-140 or GO-200). Physicochemical characteristics of GO samples at each stage were determined to quantify and understand the impact of each treatment pathway on porosity development, physical structure, or surface chemistry of GO. Surface elemental composition showed the following order for C/O ratio: GO-140-200 > GO-110-200 > GO-200, suggesting that a two-step heat treatment results in more oxygen removal from the surface, and FTIR profiles confirmed the lowest intensities of all functionalities for GO-140-200. Proton NMR spectra of as-received and heat-treated GO samples confirmed near complete removal of water and hydroxyl groups for samples treated at 200°C. XRD results showed that the interlayer spacing of GO reduced from 0.792 nm to the lowest values of 0.371 nm for GO-200 and 0.367 nm for GO-110-200. Porosity characterization revealed that only two pathways, GO-200 and GO-110-200, created a porous structure. Further analysis of data suggested that exfoliation is primarily triggered by decomposition of surface functionalities and release of a substantial volume of CO2/CO, but water vapor release helps to enhance the exfoliation. These results demonstrate that direct and rapid heat treatment of GO at 200°C (or higher temperatures) is the most effective option for developing a porous structure.

Topographic Manipulation of Graphene Oxide by Polyaniline Nanocone Arrays Enables High‐Performance Solar‐Driven Water Evaporation

AbstractTuning the surface topography of solar evaporators is of significance for boosting light absorption and enhancing solar‐to‐vapor efficiency. Herein, a novel strategy to manipulate the surface topography of graphene oxide (GO) via electrostatic assembly coupled with in situ polymerizations of aniline is reported. The GO surface is fully hybridized with the polyaniline (PANI) nanocone arrays, manifesting periodic structures with highly foldable configurations. Additionally, the PANI arrays tune the surface chemistry of GO and retard the redispersion of GO into water, thus enabling corresponding composite (PG) robust structural durability. Featuring these intriguing attributes, when applied as an evaporator in pure water, the PG delivers an improved evaporation performance of 1.42 kg m−2h−1and a high evaporation efficiency of 96.6% under one sun illumination. Further investigations reveal that the periodically conical structures of PANI over GO surface strengthen light absorption via multiple reflections and facilitate heat localization. Desalination test substantiates the reliability of PG for practical freshwater production. The numerical simulations and optical microscopy observation exhibit the surface topography‐strengthened vapor generation effect. This study sheds new light on the rational manipulation of surface topography of photothermal materials for high‐efficiency solar evaporation.

Development of graphene oxide-based nano-delivery system for natural chemotherapeutic agent (Caffeic Acid)

In this work, a graphene oxide-based nano-delivery system was designed for a sustainable release of caffeic acid. The graphene oxide (GO) nanocarrier was prepared by employing the modified Hummers method. Furthermore, the natural chemotherapeutic agent caffeic acid with different weight proportions was successfully loaded on GO. The 2D nano-morphology, structure and surface chemistry of GO, GO-CA nanocomposite were further investigated via various characterization techniques. The maximum loading efficiency of GO was found as 40 %. A sustainable release of CA from GO-CA nanocomposite was observed with 66 % as the maximum amount of release in 72 h and followed the pseudo-second-order kinetic model.

A combined experimental and molecular dynamics simulation study on customizing surface chemistry of graphene oxide toward high‐performance natural rubber composites

AbstractModification of fillers and enhancement of the dispersion and compatibility of fillers in a rubber matrix is an effective way to improve the comprehensive performance of rubber. In this work, graphene oxide (GO) was modified with each of polyvinylpyrrolidone, 1‐allyl‐3‐methylimidazole hydrochloride and 1‐butyl‐3‐methylimidazole hexafluorophosphate. Then, modified GO/natural rubber (NR) composites were fabricated using a latex‐mixing method. By combining experiments and molecular simulation, we investigated the relationship between the microstructures and properties of the modified GO/NR composites. Results showed that the polyvinylpyrrolidone‐modified GO/NR composite had the smallest fractional free volume and mean square displacement, which led to excellent solvent resistance, and dynamic and physical mechanical properties. This study provides new insights into the design of high‐performance GO/NR composites at the molecular level. © 2022 Society of Industrial Chemistry.

Tough, Strong, and Conductive Graphene Fibers by Optimizing Surface Chemistry of Graphene Oxide Precursor

AbstractGraphene fibers with integrated mechanical and multifunctional properties are highly required for various potential applications. However, it remains a challenge to efficiently produce high‐performance graphene fibers because of the imperfect structures and harsh graphitization conditions. Herein, a scalable additive‐free wet‐spinning methodology is demonstrated for producing strong, tough, and conductive pristine graphene fibers by optimizing the surface chemistry of graphene oxide (GO) sheets and controlling their spinning and assembly behavior. Benefiting from GO with fewer surface terminations and low structural defects (f‐GO), the pristine f‐GO fibers possess a compact and ordered microstructure and strong interlayer interactions, giving a record high tensile strength of 791.7 MPa and high toughness of 24.0 MJ m−3 due to the stretching‐induced toughening behavior. After the mild chemical reduction, reduced f‐GO fibers inherit the optimized microstructure and present an outstanding tensile strength of 875.9 MPa and high toughness of 13.3 MJ m−3. Furthermore, the repairable structural defects on the f‐GO sheets allow the instant restoration of intrinsic conjugated structures, affording a superb electrical conductivity of 1.06 × 105 S m−1. Therefore, this study provides a facile, efficient, and scalable methodology for the fabrication of high‐performance and multifunctional graphene fibers and flexible wearable devices.

Graphene oxide interaction with Lemna minor: Root barrier strong enough to prevent nanoblade-morphology-induced toxicity

The production of graphene oxide (GO) along with its applications in various aquatic environments is vastly increasing thanks to its rapidly expanding range of new GO-based environmental technologies. Therefore, the fate of GO in aquatic environments is an important issue, as it could become an environmental challenge if its potential toxic mechanism is not addressed properly. Number of studies reporting the toxicity of GO to various aquatic organisms is still increasing. However, research data on the possible toxic mechanism of GO towards aquatic plants have yet to be collected, especially regarding GO's surface chemistry. Here, we studied the interaction of three differently oxidized GO systems with model aquatic plant Lemna minor. We found that although none of the three GOs caused lethal phytotoxicity to Lemna after 7 days, the mechanism of action was dependent on the GO's surface oxidation. Based on the amount of functional surface groups, the GO was able to directly interact with the Lemna's root through its edges. However, in this case in contrast to algae and crustaceans, the interaction did not lead to a mechanical damage. Therefore, our results showed that GO is not hazardous to Lemna minor even at very high concentrations (up to 25 mg/L), because the root barrier proved to be strong enough to prevent GO's penetration and its consequent toxicity.

Influence of the Surface Chemistry of Graphene Oxide on the Structure-Property Relationship of Waterborne Poly(urethane urea) Adhesive.

Small amounts—0.04 wt.%—graphene oxide derivatives with different surface chemistry (graphene oxide—GO-, amine-functionalized GO—A-GO-, reduced GO—r-GO) were added during prepolymer formation in the synthesis of waterborne poly(urethane urea) dispersions (PUDs). Covalent interactions between the surface groups on the graphene oxide derivatives and the end NCO groups of the prepolymer were created, these interactions differently altered the degree of micro-phase separation of the PUDs and their structure–properties relationships. The amine functional groups on the A-GO surface reacted preferentially with the prepolymer, producing new urea hard domains and higher percentage of soft segments than in the PUD without GO derivative. All GO derivatives were well dispersed into the PU matrix. The PUD without GO derivative showed the most noticeable shear thinning and the addition of the GO derivative reduced the extent of shear thinning differently depending on its functional chemistry. The free urethane groups were dominant in all PUs and the addition of the GO derivative increased the percentage of the associated by hydrogen bond urethane groups. As a consequence, the addition of GO derivative caused a lower degree of micro-phase separation. All PUs containing GO derivatives exhibited an additional thermal decomposition at 190–206 °C which was ascribed to the GO derivative-poly(urethane urea) interactions, the lowest temperature corresponded to PU+A-GO. The PUs exhibited two structural relaxations, their temperatures decreased by adding the GO derivative, and the values of the maximum of tan delta in PU+r-GO and PU+A-GO were significantly higher than in the rest. The addition of the GO derivative increased the elongation-at-break, imparted some toughening, and increased the adhesion of the PUD. The highest T-peel strength values corresponded to the joints made with PUD+GO and PUD+r-GO, and a rupture of the substrate was obtained.

Influence of Oxidation Degree of Graphene Oxide on Its Nuclear Relaxivity and Contrast in MRI.

Graphene oxide (GO) serves as a versatile platform for various applications, with the oxygen content of GO playing an important role in governing its properties. In the present study, different GO types covering a wide range of oxidation degree were prepared using our newly developed two-step method involving ball milling of graphite followed by its oxidation to GO. In addition to the variations in their physicochemical properties, the different GO types exhibited differences in proton relaxivity due to their paramagnetic nature. Nuclear magnetic resonance spectroscopy studies showed that the degree of oxidation of GO perturbs its nuclear relaxation properties and, together with intercalated Mn2+ ions, provides large contrast variation in magnetic resonance imaging (MRI). The study for the first time reveals that the surface chemistry of GO affects its relaxivity and opens up new avenues for developing tunable GO-based contrast agents in magnetic resonance imaging for diagnostics and therapies.

Controlling the surface chemistry of graphene oxide: Key towards efficient ZnO-GO photocatalysts

Graphene oxide (GO) and related materials are widely reported to enhance the photocatalytic activity of zinc oxide. However, the origin of the observed performance improvements remains elusive and studies contributing to a deeper understanding of this critical issue are largely missing. In this work, we have prepared a set of benchmark ZnO-GO hybrid materials in order to systematically put under closer scrutiny the influence of the surface chemistry of GO on the photocatalytic degradation of methylene blue. The set of ZnO-GO hybrids has been synthesized in an ultrasonication process involving ZnO nanoparticles obtained in a microwave synthesis process and GO with three distinct oxidation degrees, employed in three different loading fractions. Structural and physical-chemical characterization by XRD, FTIR, Raman, UV–vis, photoluminescence and spectroscopy and XPS, consistently demonstrate the importance of the surface chemistry of GO for establishing photo-induced charge-transfer interface interactions with ZnO, facilitating the enhancement of the catalytic activity of the ZnO-GO catalyst. Optimized interface interactions thus enabled the design of a ZnO-GO catalyst exhibiting a conversion rate of 80% obtained in a time of 70 min and at a catalyst concentration of only 0.045 mg/mL.

Tuning the Surface Chemistry of Graphene Oxide for Enhanced Dielectric and Actuated Performance of Silicone Rubber Composites

The influence of reduction temperature on the electromechanical properties and actuation behavior of polydimethylsiloxane (PDMS) dielectric elastomer containing the thermally reduced graphene oxide (rGO) with different surface chemistry has been systematically investigated. A set of rGO nanosheets was prepared by thermal reduction of graphene oxide (GO) at four temperatures (150, 200, 300, and 400 °C). The dielectric permittivity, dielectric loss, and elastic modulus of PDMS composites were increased, while the electrical breakdown strength of composites was decreased with an increase of the reduction temperature of GO. A thermodynamic model applied for studying the electromechanical deformation and stability of PDMS/GO(rGO-x) dielectric elastomer composites showed that the optimum value of the break-point was observed in PDMS/rGO-300. It is shown for the first time that the variation of electromechanical instability and recovery behavior are attributed to the surface chemistry of rGOs. A critical reducti...

Quantifying Graphene Oxide Reduction Using Spectroscopic Techniques: A Chemometric Analysis.

The surface chemistry of graphene oxide (GO) can be modified by the chemical reduction of oxygen-containing groups using L-ascorbic acid (L-AA). Being able to "tune" the surface hydrophobicity of GO in a controlled manner, with a well-defined level of reduction, provides a valuable tool for understanding and controlling interactions with hydrophobic surfaces. Numerous analytical and chemical methods have been used to determine the extent of reduction in chemically reduced graphene oxide (CRGO) samples. However, many of these methods are limited by their laborious nature, cost, or lack of sensitivity in resolving oxygen content in samples that have only been reduced for short periods of time, making them inappropriate for rapid use with multiple samples. Here, we have used ultraviolet (UV), Raman, and attenuated total reflection infrared (ATR-IR) spectroscopy to monitor the chemical reduction of GO. These three techniques are simple, rapid, nondestructive, accurate, and widely available. The data set from each technique has been correlated and modeled against a reference data set (carbon to oxygen ratio obtained from elemental analysis) using partial least squares regression (PSLR). Using this approach, the chemical reduction of GO was quantified from UV (r2 = 0.983, RMSECV = 0.049), Raman (r2 = 0.961, RMSECV = 0.073) and ATR-IR (r2 = 0.993, RMSECV = 0.032) data. ATR-IR enabled identification of the different oxygen-containing groups on GO, and coupled with chemometric modeling, provides an excellent approach for the routine quantitative analysis of the chemical reduction of GO.

The Role of Water in Mediating Interfacial Adhesion and Shear Strength in Graphene Oxide.

Graphene oxide (GO), whose highly tunable surface chemistry enables the formation of strong interfacial hydrogen-bond networks, has garnered increasing interest in the design of devices that operate in the presence of water. For instance, previous studies have suggested that controlling GO's surface chemistry leads to enhancements in interfacial shear strength, allowing engineers to manage deformation pathways and control failure mechanisms. However, these previous reports have not explored the role of ambient humidity and only offer extensive chemical modifications to GO's surface as the main pathway to control GO's interfacial properties. Herein, through atomic force microscopy experiments on GO-GO interfaces, the adhesion energy and interfacial shear strength of GO were measured as a function of ambient humidity. Experimental evidence shows that adhesion energy and interfacial shear strength can be improved by a factor of 2-3 when GO is exposed to moderate (∼30% water weight) water content. Furthermore, complementary molecular dynamics simulations uncovered the mechanisms by which these nanomaterial interfaces achieve their properties. They reveal that the strengthening mechanism arises from the formation of strongly interacting hydrogen-bond networks, driven by the chemistry of the GO basal plane and intercalated water molecules between two GO surfaces. In summary, the methodology and findings here reported provide pathways to simultaneously optimize GO's interfacial and in-plane mechanical properties, by tailoring the chemistry of GO and accounting for water content, in engineering applications such as sensors, filtration membranes, wearable electronics, and structural materials.

Simultaneously ‘pushing’ and ‘pulling’ graphene oxide into low-polar solvents through a designed interface

Dispersing graphene oxide (GO) in low-polar solvents can realize a perfect self-assembly with functional molecules and application in removal of organic impurities that only dissolve in low-polar solvents. The surface chemistry of GO plays an important role in its dispersity in these solvents. The direct transfer of hydrophilic GO into low-polar solvents, however, has remained an experimental challenge. In this study, we design an interface to transfer GO by simultaneously ‘pushing and pulling’ the nanosheets into low-polar solvents. Our approach is outstanding due to the ability to obtain monolayers of chemically reduced GO (CRGO) with designed surface properties in the organic phase. Using the transferred GO or CRGO dispersions, we have fabricated GO/fullerene nanocomposites and assessed the ability of CRGOs for dye adsorption. We hope our work can provide a universal approach for the phase transfer of other nanomaterials.

The effect of pH on lateral size and surface chemistry of graphene oxide

In recent times, single layer graphene oxide (GO) has been of intense interest for a broad spectrum of applications. Size and surface charge of GO sheets are two key factors in the most of these fields. These structural properties can be tuned by adjusting pH manipulating the content of oxygen-containing groups. Furthermore, the pH value extremely affects on the surface chemistry and functional groups of GO sheets which are crucial in providing a high stable solution and chemical activity of particles. In this study, Graphene oxide is synthesized by improved hummer method and characterized by XRD, AFM, FTIR, DLS and zeta potential. pH value can be tuned trough titration with NaOH and HCl and effect of pH on GO dispersion stability and optical properties is investigated.

Systematic study of the correlation between surface chemistry, conductivity and electrocatalytic properties of graphene oxide nanosheets

A main advantage of graphene oxide (GO) over other materials is the high tunability of its surface functional groups and of its electric conductivity. However, the complex chemical composition of GO renders difficult to unravel the correlation between structural and electric properties. Here, we use a combination of electron spectroscopy and electrochemistry to correlate the surface chemistry of GO to its electrical conductivity and electrocatalytic properties with respect to two molecules of high biological interest: β-nicotinamide adenine dinucleotide (NADH) and vitamin C. We demonstrate that the electrocatalytic properties of the material are due to hydroxyl, carbonyl and carboxyl groups residues that, even if already present on pristine GO, become electroactive only upon GO reduction.The results of this study demonstrate the advantages in the use of GO in amperometric biosensing and in enzymatic biofuel cells: it allows the oxidation of the target molecules at low potential values, with a sensitivity >15 times higher with respect to standard, carbon-based electrode materials.Finally, we demonstrate that the right amount of chemical groups to achieve such high performance can be obtained also by direct electrochemical exfoliation of bulk graphite, without passing through GO production, thus rendering this approach suitable for cheap, large-scale applications.

Graphene-Based Electrocatalysts to Boost Electrocatalytic Reduction of Oxygen in Bioelectrochemical Systems

Microbial fuel cells (MFCs) can be considered as an efficient and flexible platform for integrated waste treatment and energy recovery [1]. The extensive research work devoted to this technology over the past decade demonstrates the promising outlook of MFCs, but practical application is still limited by the high costs associated to the materials used for device assembly, such as cathode materials which accounts for over 50% of the overall MFC capital cost. The sluggish kinetics of oxygen reduction reaction (ORR) has led to the use of expensive catalysts, such as platinum, which is not suitable to be applied to sustainable technologies. Hence, a great variety of materials have been developed for MFC cathodes, including nitrogen-doped activated carbons and non platinum group metal catalysts. Such materials allow achieving ORR rate comparable to Pt, the morphology and structure of the catalysts playing an important role on the efficiency and durability of ORR active sites [2,3]. The development of new carbon nanostructures with highly tunable morphology and structure has led to the use of graphene for several applications, including as component for MFC cathodes [4,5]. However, challenges, such as complexity in synthesis and costs, still limit the applicability of graphene as cathode component of MFCs. Therefore, a facile and efficient approach to develop graphene based catalysts can be considered a promising direction to achieve sustainable wastewater treatment and bioenergy production by BESs. In this work, we report a facile method for large-scale preparation of ORR catalysts based on graphene oxide (GO) obtained by electrochemical oxidation of graphite in aqueous solutions of inorganic salts. We developed different strategies to include nitrogen functionalities in GO structure, including post treatments based on annealing with ammonia gas and one-step nitrogen-doping of GO. By combining the use of atomic force microscopy with electrochemical and spectroscopic techniques, we correlated the different morphology and surface chemistry of GO with catalytic activity towards ORR. Differences in catalytic activity obtained by supporting iron on GO surface were also elucidated, investigating the nature of ORR active sites. The applicability of GO-based materials as ORR cathodes of MFCs was evaluated by assembling single chamber air-cathodes MFCs operating with sodium acetate in phosphate buffer solution. Coulombic efficiency, polarization and power density curves, and voltage generation cycles over time were acquired. The body of results demonstrated the potential ability of GO electrocatalysts to substitute platinum for ORR in MFCs. Acknowledgements. The present work was carried out with the support of the “European Union's Horizon 2020 research and innovation programme” (under H2020-FTIPilot-2015-1, Grant Agreement n. 720367-GREENERNET), the University of Rome Tor Vergata (under the Research Call “Consolidate the Foundations”, project name: BEST WATER), and CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico, Brazil. References. [1] A. Rinaldi, B. Mecheri, V. Garavaglia, S. Licoccia, P. Di Nardo, E.Traversa. Energ. Environ. Sci., 1 (2008) 417-429. [2] C. Santoro, A. Serov, L. Stariha, M. Kodali, J. Gordon, S. Babanova, O. Bretschger, K. Artyushkova, P. Atanassov, Energ. Environ. Sci. 9 (2016) 2346-2353. [3] A. Iannaci, B. Mecheri, A. D'Epifanio, M. J. Lázaro Elorri, S. Licoccia. Int J Hydrogen Energ. 41 (2016) 19637-19644. [4] H. Yuan, Z. He. Nanoscale 7 (2015) 7022-7029. [5] K. Parvez, S. Yang, Y. Hernandez, A. Winter, A. Turchanin, X. Feng, K. Müllen. ACS Nano. 6 (2012) 9541-9550.

Differential cytotoxicity and internalization of graphene family nanomaterials in myocardial cells

Given the well-known physical properties of graphene oxide (GO), numerous applications for this novel nanomaterial have been recently envisioned to improve the performance of biomedical devices. However, the toxicological assessment of GO, which strongly depends on the used material and the studied cell line, is a fundamental task that needs to be performed prior to its use in biomedical applications. Therefore, the toxicological characterization of GO is still ongoing. This study contributes to this, aiming to synthesize and characterize GO particles and thus investigate their toxic effects in myocardial cells. Herein, GO particles were produced from graphite using the Tour method and subsequent mild reduction was carried out to obtain low-reduced GO (LRGO) particles. A qualitative analysis of the viability, cellular uptake, and internalization of particles was carried out using GO (~54% content of oxygen) and LRGO (~37% content of oxygen) and graphite. GO and LRGO reduce the viability of cardiac cells at IC50 of 652.1±1.2 and 129.4±1.2μg/mL, respectively. This shows that LRGO particles produce a five-fold increase in cytotoxicity when compared to GO. The cell uptake pattern of GO and LRGO particles demonstrated that cardiac cells retain a similar complexity to control cells. Morphological alterations examined with electron microscopy showed that internalization by GO and LRGO-treated cells (100μg/mL) occurred affecting the cell structure. These results suggest that the viability of H9c2 cells can be associated with the surface chemistry of GO and LRGO, as defined by the amount of oxygen functionalities, the number of graphitic domains, and the size of particles. High angle annular dark-field scanning transmission electron microscopy, dynamic light-scattering, Fourier-transform infrared, Raman, and X-ray photoelectron spectroscopies were used to characterize the as-prepared materials.

Quantifying the Tunable Conjugated Area of Graphene Oxide by Using Pyrene as a Fluorescent Probe.

The determination of oxygenous groups, conjugated area ratio, and reduction efficiency of graphene oxide (GO) is a difficult task because of its heterogeneous structure. Herein, a novel approach is described for a detailed understanding of the surface chemistry of GO by using pyrene as a fluorescent probe through π-π stacking interactions.

Poly(methyl methacrylate) nanocomposites based on graphene oxide: a comparative investigation of the effects of surface chemistry on properties and foaming behavior

The effects of oxygen functional groups and alkyl chains at the surface of graphene oxide (GO) on the thermal stability, mechanical properties and foaming behavior of poly(methyl methacrylate) (PMMA) nanocomposites were investigated. Alkyl‐functionalized GO (GO‐ODA) was prepared by grafting octadecylamine (ODA) on the surface of GO. PMMA/GO and PMMA/GO‐ODA nanocomposite were obtained by solution blending and were foamed using supercritical carbon dioxide (scCO2). GO‐ODA, with the presence of alkyl chains, showed a better dispersion capability in PMMA matrix than GO with a large amount of oxygen functional groups. In addition, the good dispersion capability increased thermal stability and mechanical strength. In comparison with PMMA/GO samples foamed at 70 °C, PMMA/GO‐ODA nanocomposite foams displayed improved cell structures with higher cell density, smaller cell size and more homogeneous cell size distribution, which results from the strong heterogeneous nucleation due to alkyl chains on the GO surface. The foaming behaviors became more complicated at 80 °C as the GO might be intercalated and exfoliated with the aid of scCO2, thus further enhancing the heterogeneous nucleation during the foaming process. The results indicated that the surface chemistry of GO was closely related to the properties and foaming behavior of the nanocomposites. © 2016 Society of Chemical Industry