Macroporous Graphene Foam Research Articles

Core/Satellite Structured Fe3O4/Au Nanocomposites Incorporated with Three-Dimensional Macroporous Graphene Foam as a High-Performance Anode for Microbial Fuel Cells

The development of advanced anode materials is a significant step to improve the performance of microbial fuel cells (MFCs). Here, a core/satellite structured Fe3O4/Au nanocomposite-incorporated th...

In-situ mechanics of 3D graphene foam based ultra-stiff and flexible metallic metamaterial

A 3D macroporous graphene foam based ultra-lightweight, stiff and fatigue-resistant mechanical metamaterial is developed in this study. In-situ indentation of the 3D graphene framework reveals an extraordinary spring constant of ∼15 N/m and an upward of 70% recoverable deformation. The brilliant stiffness and superelasticity of graphene foam is exploited to fabricate Aluminum-based Graphene/Metal Metamaterial by electron beam evaporation. In-situ cyclic indentation inside SEM up to 50 cycles revealed long-distance stress-transfer due to the interconnected network of branches, having spring-like mechanical energy storage ability. The structure is highly fatigue-resistant, with more than 98% of displacement recovery at the end of each loading/unloading cycle. In-situ tensile investigation reveals shearing-type failure with dual-strengthening mechanisms, where stress transfer from Aluminum layer to graphene scaffold enhances the overall load bearing ability and the Aluminum deposit on graphene foam provides a structural backbone that restricts brittle failure. A modified scaling law is proposed for modeling the mechanical strength of cellular metamaterials that takes into consideration the hollow anatomy of graphene frameworks, thereby bridging the current gap in theoretical and experimental foam mechanics. The 3D metamaterial developed in this study can be a game-changing candidate for developing flyweight metallic structures with unprecedented elasticity, stiffness and fatigue-resistance.

Highly Efficient Exosome Isolation and Protein Analysis by an Integrated Nanomaterial-Based Platform.

Exosomes play important roles in mediating intercellular communication and regulating a variety of biological processes, but clear understanding of their functions and biogenesis has not been achieved, due to the high technical difficulties involved in analysis of small vesicular structures that contain a high proportion of membrane structures. Herein, we designed a novel approach to integrate two nanomaterials carrying varied surface properties, the hydrophilic, macroporous graphene foam (GF) and the amphiphilic periodic mesoporous organosilica (PMO), for efficient exosome isolation from human serum and effective protein profiling. The high specific surface area of GF, after modification with the antibody against the exosomal protein marker, CD63, allowed highly specific isolation of exosomes from complex biological samples with high recovery. Since the organic solvent, methanol, turned out to be the most effective lysis solution for releasing the exosomal proteins, the amphiphilic PMO was employed to rapidly recover the exosomal proteins, including the highly hydrophobic membrane proteins. The fine pores of PMO also acted as the nanoreactors to accelerate protein digestion that produced peptides subject to liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. A total of 334 proteins with 111 membrane proteins [31% of these contained >2 transmembrane domains (TMD)] were identified using the integrated GF/PMO platform. In contrast, with the commercial exosome isolation kit and the in-solution protein digestion method, only 151 proteins were found, with 28 being membrane proteins (only one contained three TMDs). Our results support that the integrated GF/PMO platform is of great value to facilitate the comprehensive characterization of exosomal proteins for better understanding of their functions and for identification of more exosome-based disease markers.

Three-Dimensional Graphene Foam Induces Multifunctionality in Epoxy Nanocomposites by Simultaneous Improvement in Mechanical, Thermal, and Electrical Properties.

Three-dimensional (3D) macroporous graphene foam based multifunctional epoxy composites are developed in this study. Facile dip-coating and mold-casting techniques are employed to engineer microstructures with tailorable thermal, mechanical, and electrical properties. These processing techniques allow capillarity-induced equilibrium filling of graphene foam branches, creating epoxy/graphene interfaces with minimal separation. Addition of 2 wt % graphene foam enhances the glass transition temperature of epoxy from 106 to 162 °C, improving the thermal stability of the polymer composite. Graphene foam aids in load-bearing, increasing the ultimate tensile strength by 12% by merely 0.13 wt % graphene foam in an epoxy matrix. Digital image correlation (DIC) analysis revealed that the graphene foam cells restrict and confine the deformation of the polymer matrix, thereby enhancing the load-bearing capability of the composite. Addition of 0.6 wt % graphene foam also enhances the flexural strength of the pure epoxy by 10%. A 3D network of graphene branches is found to suppress and deflect the cracks, arresting mechanical failure. Dynamic mechanical analysis (DMA) of the composites demonstrated their vibration damping capability, as the loss tangent (tan δ) jumps from 0.1 for the pure epoxy to 0.24 for ∼2 wt % graphene foam-epoxy composite. Graphene foam branches also provide seamless pathways for electron transfer, which induces electrical conductivity exceeding 450 S/m in an otherwise insulator epoxy matrix. The epoxy-graphene foam composite exhibits a gauge factor as high as 4.1, which is twice the typical gauge factor for the most common metals. Simultaneous improvement in thermal, mechanical, and electrical properties of epoxy due to 3D graphene foam makes epoxy-graphene foam composite a promising lightweight and multifunctional material for aiding load-bearing, electrical transport, and motion sensing in aerospace, automotive, robotics, and smart device structures.

Rapid Enrichment and Sensitive Detection of Multiple Metal Ions Enabled by Macroporous Graphene Foam.

Nanomaterials have shown great promise in advancing biomedical and environmental analysis because of the unique properties originated from their ultrafine dimensions. In general, nanomaterials are separately applied to either enhance detection by producing strong signals upon target recognition or to specifically extract analytes taking advantage of their high specific surface area. Herein, we report a dual-functional nanomaterial-based platform that can simultaneously enrich and enable sensitive detection of multiple metal ions. The macroporous graphene foam (GF) we prepared displays abundant phosphate groups on the surface and can extract divalent metal ions via metal-phosphate coordination. The enriched metal ions then activate the metal-responsive DNAzymes and produce the fluorescently labeled single-stranded DNAs that are adsorbed and quenched by the GF. The resultant fluorescence reduction can be used for metal quantitation. The present work demonstrated duplexed detection of Pb2+ and Cu2+ using the Pb- and Cu-responsive DNAzymes, achieving a low detection limit of 50 pM and 0.6 nM, respectively. Successful quantification of Pb2+ and Cu2+ in human serum and river water were achieved with high metal recovery. Since the phosphate-decorated GF can enrich diverse types of divalent metal cations, this dual-functional GF-DNAzyme platform can serve as a simple and cost-effective tool for rapid and accurate metal quantification in determination of human metal exposure and inspection of environmental contamination.

Facile fabrication of TiO2/Graphene composite foams with enhanced photocatalytic properties

A self-supporting macroporous graphene foam was prepared by template method. This foam which was fabricated by reduced graphene oxide (rGO) has good conductivity, and it also has large surface both in the foam interior and outside surface. The surface can offer a good platform to introduce active materials into the foam. TiO2 nanorods were grown on the foam framework using hydrothermal synthesized method. Due to a well-ordered macroporous structure and high conductivity of the reduced graphene oxide scaffold, the light utilizing in the composite TiO2/rGO foam will increase, and the photoinduced electron also transports quickly to the substrate. These advantages resulted in a better photocurrent response. Furthermore, the well photo induced electron transports will also lead to better photocatalytic degradation property. The enhanced absorption performance, photocurrent response, photocatalytic degradation property of composite TiO2/rGO foam will make this foam a promising material for practical applications in the environmental protection field.

Hierarchical NiMoO4 nanowire arrays supported on macroporous graphene foam as binder-free 3D anodes for high-performance lithium storage.

Novel three-dimensional (3D) NiMoO4 nanowire arrays (NWAs) grown directly onto the surface of macroporous graphene foams (GF) with robust adhesion were synthesized via a facile chemical vapor deposition (CVD) and subsequent hydrothermal route. The as-prepared NiMoO4 nanowires are composed of ultra-small nanoparticles (∼5 nm) with a diameter of 70-150 nm and are several micrometers in length. Such as-grown NiMoO4 NWA/3DGF composites are then evaluated as monolithic electrodes for lithium-ion batteries (LIBs) without the need of binders or metal-based current collectors. Benefitting from the unique three-dimensional arrayed architecture and characteristics with a high specific surface area and more active sites which facilitate fast electron and ionic transport within the electrode, the NiMoO4 NWA/GF composites deliver a high reversible specific capacity of 1088.02 mA h g(-1) at a current density of 200 mA g(-1) and 867.86 mA h g(-1) after 150 cycles (79.77% retention of the second cycle), and excellent rate capability. With the advantages of excellent electrochemical performance and a facile synthesis method, the NiMoO4 nanowire arrays supported on 3DGF exhibit great potential as anode materials for LIBs.

Three-dimensional electrochemical immunosensor for sensitive detection of carcinoembryonic antigen based on monolithic and macroporous graphene foam

A high performance three-dimensional (3D) electrochemical immunosensor was developed for sensitive detection of the tumor biomarker, carcinoembryonic antigen (CEA). Monolithic and macroporous graphene foam grown by chemical vapor deposition (CVD) served as the scaffold of the free-standing 3D electrode. Immuno-recognition interface was fabricated via simple and non-covalent immobilization of antibody using lectin-mediated strategy. Briefly, the well-known lectin macromolecule (concanavalin A, Con A) monolayer was functionalized on 3D graphene (3D-G) using in-situ polymerized polydopamine as the linker. Then the widely used horseradish peroxidase (HRP)-labeled antibody (anti-CEA) in immunoassays was efficiently immobilized to demonstrate the recognition interface via the biospecific affinity of lectin with sugarprotein. The 3D immunosensor is able to detect CEA with a wide linear range (0.1–750.0ngml−1), low detection limit (~90pgml−1 at a signal-to-noise ratio of 3), and short incubation time (30min). Furthermore, this biosensor was used for the detection of the CEA level in real serum samples.

Three-Dimensional Macroporous Graphene Foam Filled with Mesoporous Polyaniline Network for High Areal Capacitance

Bicontinuous macroporous graphene foam composed of few-layered graphene sheets provides a highly conductive platform on which to deposit mesoporous polyaniline via incorporation of electrodeposition and inkjet techniques. The experimental results exhibit that the coating polyaniline thin layer on the surface of three-dimensional graphene foam via electrodeposition is of importance for changing the hydrophobic surface to a hydrophilic one and for the subsequent filling of the mesoporous polyaniline network into the macroporous graphene foam. The porous polyaniline network with high pseudocapacitance is highly efficient for adjusting the pore structure and capacitive properties of graphene foam. When used as electrode materials for supercapacitors, the resulted graphene foam–polyaniline network with high porosity renders a large areal capacitance of over 1700 mF cm–2, which is over two times the enhancement in comparison with the pure graphene foam and polyaniline thin layer coated one. The ultrahigh areal capacitance benefits from the synergistic effect of the good conductive graphene backbone and high pseudocapacitive polyaniline.

Non-enzymatic detection of hydrogen peroxide using a functionalized three-dimensional graphene electrode

A novel three-dimensional (3D) electrochemical sensor was developed for highly sensitive detection of hydrogen peroxide (H2O2). Monolithic and macroporous graphene foam grown by chemical vapor deposition (CVD) served as the electrode scaffold. Using in-situ polymerized polydopamine as the linker, the 3D electrode was functionalized with thionine molecules which can efficiently mediate the reduction of H2O2 at close proximity to the electrode surface. Such stable non-enzymatic sensor is able to detect H2O2 with a wide linear range (0.4 to 660μM), high sensitivity (169.7μAmM−1), low detection limit (80nM), and fast response (reaching 95% of the steady current within 3s). Furthermore, this sensor was used for real-time detection of dynamic release of H2O2 from live cancer cells in response to a pro-inflammatory stimulant.

Macroporous foam of reduced graphene oxides prepared by lyophilization

In this study, we demonstrate that water-soluble grafted polymer polyfluorene-grafted-poly(sulfobetainemetahcrylate) (PF-g-PSBMA) allows chemically reduced GO sheets dispersed in aqueous solution due to its ability to stably disperse hydrophobic rGO sheets. Based on the stable rGO/PF-g-PSBMA dispersion, macroporous graphene foam can be simply obtained by lyophilization process (freeze-drying). The resulting composite foam exhibits three-dimensional macroporous structure with high specific surface area and can easily re-dissolve into water. Also, the stable rGO/PF-g-PSBMA dispersion allows solution-based fabrication of thin-film graphene devices. Moreover, PF-g-PSBMA can be removed from rGO foam or film by thermal annealing, and the conductivity of rGO film can be greatly enhanced likely due to its annealing ability.