Three-dimensional Graphene Foam Research Articles

Novel Biocompatible Amino Acids-Functionalized Three-dimensional Graphene Foams: As the Attractive and Promising Cisplatin Carriers for Sustained Release Goals.

Application of amino acids-immobilized porous materials for drug delivery studies has been attracted a lot of attention in the recent years. In this study, amino acids-grafted graphene foams were prepared by anchoring of Alanine (Ala), Cysteine (Cys) and Glycine (Gly) amino acids on the surface of graphene oxide (GO) nanostructures and used as the novel biocompatible carriers to control releasing of the cisplatin as the cytotoxic anticancer drug. The characterization of prepared compounds was done by the FT-IR, Raman, TGA, N2 adsorption-desorption isotherms, SEM, and TEM techniques. Adsorption and in vitro release behavior of amino acids-functionalized foams were studied using ICP standard method. The results show that the drug loading amount and the drug releasing rate are significantly enhanced upon functionalization process. The Ala-Foam sample with the larger surface area and pore volume showed a higher loading content (4.53%) than other samples. In addition, the MTT test on the two MCF-7 and HepG2 human cancer cell lines exhibited an acceptable biocompatibility and sustainable drug releasing from the carriers up to 48h, leading to the dosage frequency decrease and the patient compliance improvement.

Nitrogen-Doped Graphene Foam as a Metal-Free Catalyst for Reduction Reactions under a High Gravity Field

Herein, we report on the effect of a high gravity field on metal-free catalytic reduction, taking the nitrobenzene (NB) reduction and methylene blue (MB) degradation as model reactions in a high-gravity rotating tube reactor packed with three-dimensional (3D) nitrogen-doped graphene foam (NGF) as a metal-free catalyst. The apparent rate constant (kapp) of the metal-free catalytic reduction of NB in the rotating tube reactor under a high gravity level of 6484g (g = 9.81 m·s−2) was six times greater than that in a conventional stirred reactor (STR) under gravity. Computational fluid dynamics (CFD) simulations indicated that the improvement of the catalytic efficiency was attributed to the much higher turbulent kinetic energy and faster surface renewal rate in the high-gravity tube reactor in comparison with those in a conventional STR. The structure of the 3D metal-free catalysts was stable during the reaction process under a high gravity field, as confirmed by X-ray photoelectron spectroscopy (XPS) and Raman spectra. In the other model reaction, the rate of MB degradation also increased as the high gravity level increased gradually, which aligns with the result for the NB catalytic reduction system. These results demonstrate the potential to use a high-gravity rotating packed tube reactor for the process intensification of metal-free catalytic reduction reactions.

Ionic Liquid Gating Enhanced Photothermoelectric Conversion in Three-Dimensional Microporous Graphene.

The photothermoelectric (PTE) effect can effectively convert light into electricity through photothermal and thermoelectric processes and has great potential applications in light energy harvesting and bandgap-independent photodetection. It is particularly applicable for the terahertz (THz) range featuring low photon energy but has not been well established due to lack of high-performance PTE materials in this range. Three-dimensional microporous graphene (3DMG) foam possesses ultrahigh THz absorptivity and outstanding photothermal conversion and can serve as a promising candidate. Here, enhancement of the THz PTE response of 3DMG foam by fine-tuning its thermoelectric properties using the ionic liquid electric double layer (EDL) technique was demonstrated. Continuous and reversible control of the Seebeck coefficient of 3DMG highlights the effectiveness of EDL gating in manipulating the electronic structures of such bulk and porous material. An approximate 1 order of magnitude enhancement in the Seebeck coefficient as well as the PTE responsivity was observed. In addition, a double-cell 3DMG EDL device with a p-n junction like channel configuration enabled further improvement of the photoresponse. This work opens a new avenue to optimize the PTE performance of 2D nanosheet-assembled 3D porous materials for highly efficient energy harvesting and detection of THz radiation.

Development of foamy-like 3-dimensional graphene networks decorated with iron oxide nanoparticles for strontium adsorption

ABSTRACT Three-dimensional magnetic graphene foam (3D-MGF) was improved for removal of strontium ions. Chemical Vapor Deposition (CVD) method and hydrothermal method were used to obtained 3D-MGFs, respectively. Central Composite Design (CCD) method was conducted to establish the optimum conditions for adsorption of strontium ions on 3D-MGFs. At the optimum conditions, the maximum adsorption capacity was calculated 39.68 mg/g. Freundlich isotherm model showed that a multilayer formation occurred in the 3D-MGF’s surface. Moreover, the adsorption process was endothermic, and recycle experiments showed there was about 25% loss in the adsorption capacity of 3D-MGFs for strontium ions after 5 times reuse.

Sustainable production of value-added carbon nanomaterials from biomass pyrolysis

The production of renewable energy and chemicals from biomass can be performed sustainably using pyrolysis, but the production costs associated with biomass pyrolysis hinder its wider application. The use of renewable precursors and waste heat to fabricate high-quality functional carbon nanomaterials can considerably improve the sustainability and economic viability of this process. Here, we propose a method to maximize the economic benefits and the sustainability of biomass pyrolysis by utilizing waste pyrolysis gases and waste heat to prepare high-quality three-dimensional graphene foams (3DGFs). The resulting 3DGFs exhibit excellent performance in environmental and energy-storage applications. On the basis of a life-cycle assessment, the overall life-cycle impacts of the present synthetic route on human health, ecosystems and resources are less than those of the conventional chemical vapour deposition (CVD) process. Overall, incorporating the pyrolytic route for fabricating functional carbonaceous materials into the biomass pyrolysis process improves the sustainability and economic viability of the process and can support wider commercial application of biomass pyrolysis. Biomass pyrolysis for renewable energy and chemicals offers sustainability advantages but is expensive. This study shows a route to improve both the sustainability and economic viability of biomass pyrolysis by using pyrolytic gases and waste heat to fabricate high-quality carbon nanomaterials.

Nonlinear free vibration of rectangular plates reinforced with 3D graphene foam: Approximate analytical solution

This paper investigates nonlinear free vibration of three-dimensional graphene foam skeleton reinforced rectangular plates. The three-dimensional graphene foam skeleton can distribute in different patterns along the thickness direction of the plate. According to the mixing rule, the effective Poisson’s ratio, mass density and elastic modulus of three-dimensional graphene foam reinforced (3D-GFR) plates are described. In the framework of the von Kármán nonlinear plate theory, Hamilton’s principle is utilized to derive equations of motion. Then, analytical nonlinear frequencies of 3D-GFR plates are solved by using the Galerkin method and the harmonic balance method. Results show that 3D-GFR plates exhibit hardening nonlinearity. The effect of porosity coefficient on nonlinear vibration depends on the foam skeleton distribution. In addition, the nonlinear frequencies of 3D-GFR plates increase as the skeleton weight fraction rises.

ZnS Nanosphere Arrays/Graphene Foam for Voltammetric Sensing of Dopamine in the Presence of Uric Acid

Graphene foam (GF) was prepared by chemical vapor deposition (CVD) using nickel foam (NF) as sacrificial template. Afterward, ZnS nanosphere arrays (ZnS NSAs) were grown in situ on GF by hydrothermal synthesis. The ZnS NSAs/GF was used as sensing electrode to detect dopamine (DA) in the presence of uric acid (UA). The results show that ZnS NSAs with the diameter of ~500 nm are uniformly distributed on the three-dimensional GF. Ultrasensitive voltammetric response of the ZnS NSAs/GF electrode to DA, such as high sensitivity of 2.99 $\mu \text {A}\cdot \mu \text {M}^{-\textsf {1}} \cdot \text {cm}^{-\textsf {2}}$ and low limit of detection (LOD) of 0.04 $\mu \text{M}$ (at S/N = 3). In addition, it also shows good reproducibility and long-term stability, which is expected to be applied to the detection of DA in clinical practice.

Electrodeposition-Assisted Rapid Preparation of Pt Nanocluster/3D Graphene Hybrid Nanozymes with Outstanding Multiple Oxidase-Like Activity for Distinguishing Colorimetric Determination of Dihydroxybenzene Isomers.

Here, we demonstrate a facile bottom-up strategy to fabricate Pt nanoclusters (Pt NCs) grafted onto three-dimensional graphene foam (3D GF) assisted by cetyltrimethyl ammonium bromide (CTAB) using the electrodeposition method. The homogeneous grafting of Pt NC onto 3D GF is due to the formation of hemimicelles above some CTAB concentration. With the unique nanocluster structure and the high content of Pt0, the Pt NC/3D GF nanohybrid exhibits extremely high activity and shows higher reusability and stability. Apart from the intrinsic oxidase-like activity with 3,3',5,5'-tetramethylbenzidine (TMB) as the substrate, the Pt NC/3D GF nanohybrid can act simultaneously as an effective polyphenol oxidase (PPO) mimic, such as tyrosinase, catechol oxidase, and laccase. More importantly, utilizing intrinsic catechol oxidase-like activity and the oxidase-like activity with TMB as the substrate of the nanohybrid, distinguishing colorimetric determination of dihydroxybenzene isomers (catechol and hydroquinone) is performed. Distinguishing colorimetric analysis of dihydroxybenzene isomers was first developed using nanozymes. The present work provides a simple bottom-up approach for the reasonable fabrication of various nanostructured nanozymes with excellent performance using the electrodeposition method assisted with surfactants.

Study of the effect of chemical composition on the surface wettability of three-dimensional graphene foams

The chemical composition obviously affects the surface wettability of a three-dimensional (3D) graphene material apart from its surface energy and microstructure. In the hydrothermal preparation, the heteroatom doping changes the chemical composition and wettability of the 3D graphene material. To realize the controllable surface wettability of graphene materials, aminobenzene sulfonic acid (ABSA) was selected as a typical doping agent for the preparation of nitrogen and sulfur co-doped 3D graphene foam (SNGF) using a hydrothermal method. Different from using o-ABSA or p-ABSA as the dopant, SNGF with tunable surface wettability is obtained only when m-ABSA is used. This result indicates that the substituent position of -SO3H group in the benzene ring of ABSA is rather important for the tunable wettability. This work provides some theoretical foundations for dopant selection and some new insights in manipulating the properties of 3D graphene foams by adjusting the configuration of dopants.

Ultraviolet-to-microwave room-temperature photodetectors based on three-dimensional graphene foams

Highly sensitive broadband photodetection is of critical importance for many applications. However, it is a great challenge to realize broadband photodetection by using a single device. Here we report photodetectors (PDs) based on three-dimensional (3D) graphene foam (GF) photodiodes with asymmetric electrodes, which show an ultra-broadband photoresponse from ultraviolet to microwave for wavelengths ranging from 10 2 to 10 6 nm . Moreover, the devices exhibit a high photoresponsivity of 10 3 A · W − 1 , short response time of 43 ms, and 3 dB bandwidth of 80 Hz. The high performance of the devices can be attributed to the photothermoelectric (PTE, also known as the Seebeck) effect in 3D GF photodiodes. The excellent optical, thermal, and electrical properties of 3D GFs offer a superior basis for the fabrication of PTE-based PDs. This work paves the way to realize ultra-broadband and high-sensitivity PDs operated at room temperature.

Synthesis of nitrogen-superdoped and graphene fiber-supported three-dimensional graphene foam for supercapacitors

Nitrogen-doped three-dimensional (3D) graphene foam (GF) has aroused tremendous interest for the supercapacitors (SCs) applications because of its unique properties. However, it is still confronting the challenges of facile preparation and the high N-doping level. Here, by rolling a part of graphene planes into the fiber-like scaffold to support other graphene sheets, we obtain high-quality 3D GF. Followed by fluorination and N-doping, N-superdoped GF (NGF) with N content as high as 15.7 at.% was successfully prepared. The combination of fiber-supported 3D structure and high N-level facilitate forming GF with large surface area, low internal resistance, good wettability, and sufficient active sites, which results in high-performance SCs: The prepared NGF electrode has a high specific capacitance (320.0 F g−1 and 303.5 F g−1 in three- and two-electrode system, respectively), and a long cycle life (92.8% retention after 1000 cycles), as well, the NGF SC device has a high energy density (42.1 Wh kg−1 at 250 W kg−1).

A cost-effective and green-reduced graphene oxide/polyurethane foam electrode for electrochemical applications

Three-dimensional graphene foams with interconnected and macroporous structure, high surface area and excellent electrochemical behavior are noticeably used as a substrate for other nanomaterials in electrochemical applications. Herein, a three-dimensional green reduced graphene oxide/polyurethane (3DrGO/PU) foam with a facile and cost-effective synthesis method has been developed. Accordingly, after coating the polyurethane foam by graphene oxide (GO), boiling ascorbic acid (AA) was used for GO reduction. Analytical tools and electrochemical investigations were applied for characterization and evaluation of the electrochemical behavior of the resulted electrode. Acceptable energy density in the range of supercapacitors (0.33 W h kg−1) and long-term stability during 1000 electrochemical cycles were observed for the 3DrGO/PU electrode. Finally, it was demonstrated that the gold nanoparticles (with about 300 nm diameter) can be easily electrodeposited on the 3DrGO/PU electrode. This work proposes a simple and green-produced 3D structure, which can be used as a nanohybrid electrode for future studies, including electrochemical sensors/biosensors and supercapacitors.

Three-Dimensional Graphene Enhances Neural Stem Cell Proliferation Through Metabolic Regulation.

Graphene consists of two-dimensional sp2-bonded carbon sheets, a single or a few layers thick, which has attracted considerable interest in recent years due to its good conductivity and biocompatibility. Three-dimensional graphene foam (3DG) has been demonstrated to be a robust scaffold for culturing neural stem cells (NSCs) in vitro that not only supports NSCs growth, but also maintains cells in a more active proliferative state than 2D graphene films and ordinary glass. In addition, 3DG can enhance NSCs differentiation into astrocytes and especially neurons. However, the underlying mechanisms behind 3DG's effects are still poorly understood. Metabolism is the fundamental characteristic of life and provides substances for building and powering the cell. Metabolic activity is tightly tied with the proliferation, differentiation, and self-renewal of stem cells. This study focused on the metabolic reconfiguration of stem cells induced by culturing on 3DG. This study established the correlation between metabolic reconfiguration metabolomics with NSCs cell proliferation rate on different scaffold. Several metabolic processes have been uncovered in association with the proliferation change of NSCs. Especially, culturing on 3DG triggered pathways that increased amino acid incorporation and enhanced glucose metabolism. These data suggested a potential association between graphene and pathways involved in Parkinson's disease. Our work provides a very useful starting point for further studies of NSC fate determination on 3DG.

Functional nanostructure-loaded three-dimensional graphene foam as a non-enzymatic electrochemical sensor for reagentless glucose detection

Non-enzymatic and reagentless electrochemical sensors for convenient and sensitive detection of glucose are highly desirable for prevention, diagnosis and treatment of diabetes owing to their unique merits of simplicity and easy operation. Facile fabrication of a three-dimensional (3D) sensing interface with non-enzymatic recognition groups and an immobilized electrochemical probe remains challenge. Herein, a novel non-enzymatic electrochemical sensor was developed for the sensitive and reagentless detection of glucose by loading functional nanostructure on 3D graphene. Monolithic and macroporous 3D graphene (3DG) foam grown by chemical vapor deposition (CVD) served as the electrode scaffold. Prussian blue (PB) and gold nanoparticles (AuNPs) were first co-electrodeposited on 3DG (3DG/PB-AuNPs) as immobilized signal indicator and electron conductor. After a polydopamine (PDA) layer was introduced on 3DG/PB-AuNPs via facile self-polymerization of dopamine to stabilize internal PB probes and offer chemical reducibility, the second layer of AuNPs was in situ formed to assemble the recognition ligand, mercaptobenzoboric acid (MPBA). Owing to the high stability of PB and good affinity between MPBA and glucose, the non-enzymatic sensor was able to be used in reagentless detection of glucose with high selectivity, wide linear range (5 μM–65 μM) and low detection limit (1.5 μM). Furthermore, the sensor was used for the detection of glucose level in human serum samples.

Preparation of three-dimensional graphene foam with controllable defects by closed-environment chemical vapor deposition method and composite electrode electrochemical performance

Three-dimensional graphene provides a promising approach to developing high-energy-density electrodes. Compared with two-dimensional (2D) graphene, three-dimensional (3D) graphene has a three-dimensional conductive network, which greatly improves the ability of lithium ions and electron to transport and can tolerate the changes of structural and volume in the cycling process. In this paper, 3D graphene with controllable defects is prepared by using an innovative low-pressure closed chemical vapor deposition method, through using nickel foam as the template and polymethyl methacrylate as a solid carbon source. The effects of the amount of carbon source addition, reaction time and hydrogen content on the morphology and structure of graphene foam are analyzed. The experimental results indicate that the amount of carbon source added, the reaction time, and the hydrogen content have significant effects on the morphology and structure of graphene. The defect density and the number of layers of as-prepared graphene are directly proportional to the amount of carbon source added. There is a threshold for the reaction time. After reaching a certain reaction time, graphene with good structure and morphology can be formed. The optimal reaction time is about 20 min. The hydrogen content promotes the high-temperature pyrolysis of solid carbon source. The sample has a highest defect density at 0.5 kPa hydrogen content. In summary, the low-pressure closed CVD method has strong safety and can synthesize 3D graphene with excellent controllable structure and defects. The 3D graphene foam with a complete structure of 2–5 layers can be prepared under the conditions of 1000 ℃, 500 μL carbon source addition, 20 min reaction time and 0.5 kPa hydrogen content, displaying the best physical chemistry performance. The graphene foam prepared in this experiment has the characteristics of convenient and controllable defect density, light weight and stable chemical properties. When ZnO/GF electrode prepared with 3D GF as a conductive frame and active carrier is used as an anode, the lithium ion battery has a high specific capacity of 851.5 mA·h·g<sup>–1</sup> after 200 cycles, which exhibites high reversible capacity and good cycling performance. Although ZnO/GF electrode displays excellent lithium storage performance, the GF prepared based on the 3D Ni foam has a low spatial structure density and the surface loading of the ZnO/GF composite electrode is still low, resulting in a low energy density. Therefore, the following researchers should focus on the structural design of 3D graphene host/current collector to obtain a 3D graphene frame with high conductivity and high loading capacity.

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 grown hollow Fe3O4 onto graphene foam nanocomposites with high EMI shielding effectiveness and thermal conductivity

With the increasing packaging density and multi-functionality, thermal management and electromagnetic pollution in electronic devices are crucial. In this work, we propose a novel method to in-situ grow hollow Fe3O4 sphere (h-Fe3O4, inner and outer diameter of 870 nm and 975 nm, respectively) onto three-dimensional graphene foam (GF) surface and then filled it with polydimethylsiloxane (PDMS) to fabricate nanocomposites with high electromagnetic interference shielding effectiveness (70.37 dB from 8.2 to 12.4 GHz) and thermal conductivity (28.12 ± 1.212 W m−1 K−1) at room temperature. Moreover, conductive networks inside composites show super-flexible performance with high electrical conductivity (84.02 ± 8.385 S cm−1). The effect of in-situ growth hollow Fe3O4 spheres in the enhancement of EMI SE has been demonstrated via comparing with different contents, morphologies and preparation processing. Besides, the mechanism of thermal conductivity has been investigated by FEM simulation and theoretical modeling. Finally, the usage of GF/h-Fe3O4/PDMS composites as thermal interface materials (TIMs) for chip cooling is proved to be successful, and the corresponding temperature under usage power density is accurately predicted. These comprehensive properties of GF/h-Fe3O4/PDMS composite open a potential application for next-generation TIMs in chip packaging.

On the use of Chebyshev polynomials in the Rayleigh-Ritz method for vibration and buckling analyses of circular cylindrical three-dimensional graphene foam shells

This study aims to perform free vibration and buckling analyses of circular cylindrical shells made of three-dimensional (3D) graphene foam. Three kinds of porosity distribution are considered including two kinds of symmetrical distribution and uniform distribution. The Kirchhoff-Love shell theory is utilized to establish the mathematical model of 3D graphene foam (3D-GF) shells. Natural frequencies and buckling loads of the shells under various boundary conditions are obtained via the Rayleigh-Ritz method in conjunction with Chebyshev polynomials. Results show that the mechanical characteristics of the 3D-GF shells are significantly affected by the porosity coefficient and porosity distribution. Moreover, the effect of porosity coefficient is closely related to boundary conditions of the shells. It is also shown that as the porosity coefficient increases, the porosity distribution effect on the mechanical characteristics of 3D-GF shells becomes increasingly significant.

A non-enzymatic sensor based on three-dimensional graphene foam decorated with Cu-xCu2O nanoparticles for electrochemical detection of glucose and its application in human serum.

In the present study, a porous structure consisting of three-dimensional graphene (3DG) decorated with Cu-based nanoparticles (NPs) (Cu or Cu-Cu2O) was synthesized in order to develop an enzyme-free electrochemical glucose sensor. Moreover, the effects of Cu-based nanoparticle concentrations on electrochemical properties and glucose detection were evaluated by cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry. Cu-based NPs@3DG showed markedly better electrochemical performance in glucose oxidation in alkaline solution compared to 3DG foam. Moreover, Cu-Cu2O NPs@3DG foam with the lowest concentration of Cu precursor showed excellent performance in glucose detection. A high sensitivity of 230.86 μA mM-1 cm-2 was obtained for this electrode in a linear range of 0.8-10 mM (R2 = 0.9951) and a detection limit of 16 μM. This sensor also showed good repeatability (relative standard deviation of 1.02%) and high selectivity (no observation of significant interference by interfering species such as ascorbic acid, dopamine, urea, and acetaminophen). The results confirmed that this electrode could be applied as a feasible and inexpensive non-enzymatic electrochemical glucose sensor.

Non-enzymatic reusable graphene-based electrodes by a simple scalable preparation method and superior electrochemical property

Simple, applicable electrodes are the main features of electrochemical biosensors. Production of such electrodes using a time-consuming and non-expensive method was the aim of this study. According to this purpose, three-dimensional graphene foam (3DGF) was produced successively as an interconnected porous network of the high intrinsic surface area via a self-assembly method. Using Ag pastes as substrate, free-standing 3DGF electrodes as well as other graphene-based electrodes were prepared simply with high conductivity and desired electrochemical features. Any kind of additives including enzymes or functional groups or even, other nanomaterials as a hybrid was not used in the electrodes provided longer stability and less preparation time. A low cathodic current of −4.3 mA was measured in cyclic voltammograms (CV) of such small 3DGF electrodes (100 times less than previously reported glassy carbon (GC)-based electrodes). Non-enzymatic detection of H2O2 was clearly illustrated by a remarkable drop of the cathodic current, about 1.2 mA. Besides, the amperometric response of the 3DGF electrode certified the excellent reduction toward hydrogen peroxide with a correlation coefficient of more than 98%. The reusability of the 3DGF electrode was confirmed by less than 3% deviation in the cathodic current of particular electrodes after washing and repetitive use.