Graphene Oxide Composite Hydrogels Research Articles

Adhesive, self-healing polydopamine/reduced graphene oxide composite hydrogel for self-powered application

ABSTRACT Graphene-based hydrogels have a broad application prospect in various fields due to their excellent adsorption, electrical conductivity, water retention, flexibility, etc. In this work, polydopamine/reduced graphene oxide (PDA/rGO) composite hydrogel was prepared using water bath heating. The prepared PDA/rGO hydrogel has high swelling ratio, good adhesiveness, and self-healing ability. Furthermore, the generation of electric current was observed when pressure was applied to the PDA/rGO hydrogel filled with NaCl solution, indicating the self-powered property of the hydrogel. The PDA/rGO hydrogel is self-powered because the negative groups on the hydrogel matrix attract cations from the NaCl solution, leaving mobile negative ions in the solution. The pressure-induced flow of liquid in the hydrogel' s nanochannels drives the migration of mobile ions through the channels, generating a net ionic flow. These properties of PDA/rGO hydrogel suggest that the material would be promising for power sources of wearable devices by harvesting ambient mechanical energy.

Exploring the effect of polyacrylamide/graphene oxide composite hydrogel on the synthesis and application of ZSM-5 molecular sieves

Herein, we demonstrate the synthesis of coffin-shaped ZSM-5 molecular sieves in polyacrylamide (PAM)/graphene oxide (GO) composite hydrogel using the hydrothermal method. The as-synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS), and Thermogravimetry analyses (TGA). The effect of PAM and GO addition on the morphology and structure of ZSM-5 was investigated. The results indicated that the introduction of PAM and GO promoted the growth of the ZSM-5 (101) plane. Moreover, samples synthesized in the PAM/GO hydrogel exhibited a longer c-axis and a more pronounced coffin-shaped morphology compared to samples synthesized solely in PAM hydrogel. The Si/Al ratio decreased with the addition of GO, possibly due to interface effects leading to the formation of ZSM-5 precursors with a higher Al content. TG, FT-IR, and XPS characterization revealed hydrogen bonding interactions between PAM and GO, and the addition of GO likely restricted the movement of polymers, improving cross-linking between monomers and forming a more uniform network structure. The sample G-15 (P-5) exhibited higher mesopore volume and average pore diameter, contributing to enhanced catalytic performance. However, with increasing GO content, the average pore diameter decreased, potentially due to functional groups on the surfaces of graphene oxide and polyacrylamide forming a more uniform and structurally stable three-dimensional network structure. This allowed for controlled modulation of the molecular sieve morphology and pore size. The introduction of PAM/GO hydrogel resulted in a moderate amount of weak acid and an increased amount of strong acid, both shifting to lower temperatures. The ZSM-5 molecular sieves synthesized in the PAM/GO composite hydrogel demonstrated outstanding MTO catalytic performance, exhibiting high selectivity for light olefins and an extended catalytic lifespan. This work is expected to provide new ideas and methods for developing efficient ZSM-5 catalysts.

Electrogelated drug-embedded silk/gelatin/rGO degradable electrode for anti-inflammatory applications in brain-implant systems.

Implantable electrodes have raised great interest over the last years with the increasing incidence of neurodegenerative disorders. For brain implant devices, some key factors resulting in the formation of glial scars, such as mechanical mismatch and acute injury-induced inflammation, should be considered for material design. Therefore, in this study, a new biocompatible flexible electrode (e-SgG) with arbitrary shapes on a positive electrode was developed via electrogelation by applying a direct electrical voltage on a silk fibroin/gelatin/reduced graphene oxide composite hydrogel. The implantable flexible e-SgG-2 film with 1.23% rGO content showed high Young's modulus (11-150 MPa), which was sufficient for penetration under dried conditions but subsequently became a biomimetic brain tissue with low Young's modulus (50-3200 kPa) after insertion in the brain. At the same time, an anti-inflammatory drug (DEX) incorporated into the e-SgG-2 film can be electrically stimulated to exhibit two-stage release to overcome tissue inflammation during cyclic voltammetry via degradation by applying an AC field. The results of cell response to the SF/gelatin/rGO/DEX composite film showed that the released DEX could interrupt astrocyte growth to reduce the inflammatory response but showed non-toxicity toward neurons, which demonstrated a great potential for the application of the biocompatible and degradable e-SgG-D electrodes in the improvement of nerve tissue repair.

High-performance supercapacitors based on compact graphene composite hydrogels

Because of its ultra-high specific surface area and outstanding electrochemical performance, graphene has become a study focus of electrode materials for supercapacitors. However, severe agglomeration and poor volumetric electrochemical properties greatly reduce its potential for practical applications. Here, we proposed a simple hydrothermal strategy to synthesize L-glutamic acid functionalized nanocellulose/reduced graphene oxide composite hydrogels (GNGHs) with compact porous structures and plentiful heteroatom functional groups. In the hydrothermal process, a high concentration of graphene oxide solution (GO) was employed to boost the packing density of the samples. Nanocellulose (NC) and the molecular chains of L-glutamic acid were used as spacers to modulate the porous structure of GNGHs. At the same time, NC and heteroatomic groups can also boost the surface wettability of GNGHs, thereby increasing their ion-available specific surface area. The GNGH-15 based symmetric aqueous supercapacitors (SASC) deliver high gravimetric (282.0 F g−1) and volumetric (329.9 F cm−3) specific capacitance, remarkable rate capacity, and good cycling durability. Moreover, the all-solid-state flexible supercapacitors (ASSC) assembled by GNGH-15 also exhibit prominent specific capacitance (154.7 F g−1) and good rate performance. These brilliant electrochemical properties make GNGHs a strong contender for electrode materials of energy storage devices.

Efficient degradation of ciprofloxacin by 3D oxygen-doped MoS2/polyacrylamide/graphene oxide composite hydrogel co-catalytic Fenton reaction

In this work, we prepared a novel recyclable 3D oxygen-doped MoS2/polyacrylamide (PAM)/graphene oxide (GO) composite hydrogel (O-MoS2-CH) and constructed an O-MoS2-CH co-catalytic Fenton system (O-MoS2-CH/Fenton) to enhance ciprofloxacin (CIP) degradation. The degradation efficiency of CIP reached 92% in O-MoS2-CH/Fenton under suitable conditions ([FeSO4·7 H2O] = 10 mg/L, [H2O2] = 0.6 mM, pH = 4.21, one O-MoS2-CH), and the degradation rate constant of O-MoS2-CH/Fenton was 1.4 times that of MoS2-CH/Fenton. Additionally, the Fe2+ content of this system was 1.5 times higher than that of MoS2-CH/Fenton. Various instrumental characterizations and density functional theory (DFT) calculations proved that O-MoS2-CH contained 2 H/1 T mixed-phase MoS2, which had a stronger ability to transfer electrons and adsorb Fe3+. The Fe3+/Fe2+ cycle was driven by the exposed Mo4+ and S2- active sites on the O-MoS2-CH surface, which further enhanced the activation of H2O2. Electron paramagnetic resonance (EPR) tests and quenching experiments verified that·OH and 1O2 were dominant ROS for CIP degradation. Notably, O-MoS2-CH/Fenton could tolerate high concentrations of Cl- and NO3- (even up to 3000 mg/L). O-MoS2-CH structure kept unchanged and the co-catalytic activity decreased slightly after five cycles, and the maximum leaching of Mo was less than 0.88 mg/L. This study provides a theoretical basis and technical support for 3D O-MoS2-CH co-catalytic Fenton technology and its application in degrading residual antibiotics in water.

Three-dimensional nitrogen-doped graphene quantum dots/reduced graphene oxide composite hydrogels as binder-free electrodes for symmetric supercapacitors

Herein, nitrogen-doped graphene quantum dots/reduced graphene oxide composite hydrogels (N-GQDs/rGOs) were prepared via a hydrothermal approach from graphene oxide (GO) aqueous solution. During the preparation of the samples, ammonia water was used as reducing agent, pH regulator and nitrogen dopant, and graphene quantum dots (GQDs) were used as spacer between graphene sheets. Benefiting from their three-dimensional porous structures, large specific surface area, large number of heteroatom functional groups (N, O) on the surface, and the synergistic effect between GQDs and graphene sheets, the synthesized samples exhibit excellent electrochemical performance. Particularly, the N-GQDs/rGO-20 sample based binder-free symmetric supercapacitor show a high specific capacitance of 277.8 F g−1 at 0.3 A g−1, and this value can still maintain at 220.9 F g−1 even at 10 A g−1 in 6 M KOH electrolyte. Moreover, the capacitance retention rate of the symmetric supercapacitor can reach 92.7% after 10,000 cycles at 10 A g−1, indicating its excellent cycle stability.

Enhanced growth and differentiation of neural stem cells on alginate/collagen/reduced graphene oxide composite hydrogel incorporated with lithium chloride.

Cell transplantation with hydrogel-based carriers is one of the advanced therapeutics for challenging diseases, such as spinal cord injury. Electrically conductive hydrogel has received much attention for its effect on nerve outgrowth and differentiation. Besides, a load of neuroprotective substances, such as lithium chloride can promote the differentiation properties of the hydrogel. In this study, alginate/collagen/reduced graphene oxide hydrogel loaded with lithium chloride (AL/CO/rGO Li+) was prepared as an injectable cell delivery system for neural tissue regeneration. After determining the lithium-ion release profile, an MTT assay was performed to check neural viability. In the next step, real-time PCR was performed to evaluate the expression of cell adhesion and neurogenic markers. Our results showed that the combination of collagen fibers and rGO with alginates increased cell viability and the gene expression of collagen-binding receptor subunits such as integrin α1, and β1. Further, rGO contributed to the controlled release of lithium-ion hydrogel in terms of its plenty of negatively charged functional groups. The continuous culture of NSCs on AL/CO/rGO Li+ hydrogel increased neurogenic genes' expressions of nestin (5.9 fold), NF200 (36.8 fold), and synaptophysin (13.2 fold), as well as protein expression of NF200 and synaptophysin after about 14 days. The simultaneous ability of electrical conduction and lithium-ion release of AL/CO/rGO Li+ hydrogel could provide a favorable microenvironment for NSCs by improving their survival, maintaining cell morphology, and expressing the neural marker. It may be potentially used as a therapeutic approach for stem cell transplantation in a spinal cord injury.

Graphene oxide composite hydrogels for wearable devices

For graphene oxide (GO) composite hydrogels, a two-dimensional GO material is introduced into them, whose special structure is used to improve their properties. GO contains abundant oxygen-containing functional groups, which can improve the mechanical properties of hydrogels and support the application needs. Especially, the unique-conjugated structure of GO can endow or enhance the stimulation response of hydrogels. Therefore, GO composite hydrogels have a great potential in the field of wearable devices. We referred to the works published in recent years, and reviewed from these aspects: (a) structure of GO; (b) factors affecting the mechanical properties of the composite hydrogel, including hydrogen bond, ionic bond, coordination bond and physical crosslinking; (c) stimuli and signals; (d) challenges. Finally, we summarized the research progress of GO composite hydrogels in the field of wearable devices, and put forward some prospects.

Nanocellulose/Reduced Graphene Oxide Composite Hydrogels for High-Volumetric Performance Symmetric Supercapacitors

Nanocellulose/Reduced Graphene Oxide Composite Hydrogels for High-Volumetric Performance Symmetric Supercapacitors

Effects of in situ cross-linked graphene oxide-containing gelatin methacrylate anhydride hydrogel on wound vascularization of full-thickness skin defect in mice

Effects of in situ cross-linked graphene oxide-containing gelatin methacrylate anhydride hydrogel on wound vascularization of full-thickness skin defect in mice

Tromethamine functionalized nanocellulose/reduced graphene oxide composite hydrogels with ultrahigh gravimetric and volumetric performance for symmetric supercapacitors

Due to poor pseudocapacitive properties and low packing density, pristine graphene-based supercapacitors have always exhibited inferior gravimetric and volumetric electrochemical performance. Herein, tromethamine functionalized nanocellulose/reduced graphene oxide composites hydrogels (TNGHs) with dense porous structure and high packing density are produced using a one-pot hydrothermal technique. During the reaction, a high-concentration of graphene oxide (GO) solution is used to increase the compactness of the sample. At the same time, tromethamine is used as reducing agent, nitrogen dopant and structure regulator. Furthermore, nanocellulose (NC) can not only be employed as spacers to constrain the extreme agglomeration of graphene, but also be used as reservoirs to boost the diffusion efficiency of electrolytes in the sample. Benefitting from the dense porous structure, pseudocapacitive behavior of the highly-enriched heteroatom functional groups and high packing density, the binder-free symmetric supercapacitors based on TNGH-40 displays ultrahigh gravimetric specific capacitance (342.5 F g−1) and volumetric specific capacitance (339.1 F cm−3) at 0.3 A g−1. This innovative strategy makes TNGHs a potential candidate for miniaturized and compact energy storage devices.

Study of capacitance type flexible electronic devices based on polyacrylamide and reduced graphene oxide composite hydrogel

Flexible electronic devices can transform various external stimuli into electrical signals, and have broad prospects in wearable devices, soft machines, artificial intelligence and other fields. However, the flexible electronic materials based on hydrogel lack mechanical strength and stability. Meanwhile, the electrodes in hydrogels are also easily corroded by electrolytes. In this work, the capacitive sensor based on polyacrylamide-rGO (PAM-rGO) composite hydrogel was studied to solve these problems. Due to the effect of hydrogen bonds, the reduced graphene oxide (rGO) can greatly enhance the mechanical strength of hydrogels. At the same time, the hydrogel is encapsulated in the capacitor, and the stability of the capacitor increases due to the decrease of the water loss of the hydrogel. The PAM-rGO composite hydrogel did not contain free anion and cation, the corrosion of the electrode decreased and the service life was prolonged. The wearable device of PAM-rGO composite hydrogel sensor performed well in tensile and compression stimulation tests, and the linear relationship reached 0.998 and 0.992 in turn, showing potential applications in the field of flexible electronic devices.

Corn Stalk-Based Carbon Microsphere/Reduced Graphene Oxide Composite Hydrogels for High-Performance Symmetric Supercapacitors

Corn Stalk-Based Carbon Microsphere/Reduced Graphene Oxide Composite Hydrogels for High-Performance Symmetric Supercapacitors

Removal of humic acid from aqueous solution by a carbon nanotubes/reduced graphene oxide composite hydrogel

Removal of humic acid from aqueous solution by a carbon nanotubes/reduced graphene oxide composite hydrogel

Strong and tough cellulose–graphene oxide composite hydrogels by multi-modulus components strategy as photothermal antibacterial platform

Biomacromolecule-derived hydrogels have gained increased attention owing to their favorable hydrophilicity, flexibility, biocompatibility, and biodegradability. However, enhancing the mechanical strength of these hydrogels, while simultaneously improving their toughness remains a challenging task. Herein, a strategy of using multi-modulus components is proposed to fabricate strong and tough cellulose–graphene oxide (GO) composite hydrogels. The GO nanosheet content, molar ratio of the GO crosslinker to anhydroglucose units of cellulose, and ethanol concentration are shown to be critical parameters for achieving cellulose–GO nanosheet composite hydrogels with high strength and high toughness; the highest stress and work of fracture of the as-prepared composite hydrogels reached 13.6 MPa and 1.47 MJ/m3, respectively, in the compressive mode, and 2.8 MPa and 1.40 MJ/m3, respectively, in the tensile mode. The strengthening and toughening mechanism of the hydrogels composed of multi-modulus components is discussed. Moreover, the composite hydrogels exhibited excellent photothermal antibacterial properties against Escherichia coli and Staphylococcus aureus under near-infrared irradiation. We anticipate that the strategy of using multi-modulus components will inspire new design principles toward the development of high-strength and high-toughness biomacromolecule-derived hydrogels for biomedical devices, flexible bioelectronics, and others.

Facile Synthesis of Polypyrrole/Reduced Graphene Oxide Composite Hydrogel for Cr(VI) Removal

Facile Synthesis of Polypyrrole/Reduced Graphene Oxide Composite Hydrogel for Cr(VI) Removal

The composite hydrogel with “2D flexible crosslinking point” of reduced graphene oxide for strain sensor

AbstractIntelligent hydrogels with excellent flexibility, biocompatibility, and stimulus responsivity can mimic the functions of the skin to detect human motions. However, the low mechanical strength limits its application in the field of biomimetic materials. In this work, polyacrylamide‐reduced graphene oxide (PAM‐rGO) composite hydrogels were prepared by the combination of PAM and partially rGO, and their biomimetic strain sensors were studied. The rGO played the role of “2D flexible crosslinking point” in the composite hydrogel. Through the H‐bonds between rGO and hydrogels, the toughness and strength of the composite hydrogel were enhanced. The maximum strain of the hydrogel changed from 751% to 1097%, and the maximum stress changed from 0.065 to 0.20 MPa. On the other hand, the interaction between the PAM backbone and the rGO provided a credible resistance response to the stimulation of strain. The better linear relationship between resistance and length was built, with R2 of 0.992. Furthermore, the composite hydrogels were assembled into wearable devices to monitor human‐motion, including fingers bending, elbows bending and walking. The experimental results showed that the PAM‐rGO composite hydrogel had great potential in the field of bionic skin.

Efficient Electrode Material based on Carbon Cloth Supported Polyaniline/Reduced Graphene Oxide Composites for Supercapacitor Application

Nowadays, world energy infrastructure is being stretched due to imbalance between energy production and energy consumption; renewable & sustainable energy storage and conversion techniques could resolve this issue. Thus global energy requirements, limited availability of fossil fuels and environmental crisis drive the expansion of alternative or non- conventional energy sources with high energy and power densities. Electrochemical capacitors or supercapacitors, with a combined form of high power density and energy density, have acquired a stunning acceptance towards the field of electrochemical energy storage. Supercapacitors are used in electric vehicles, mobile phones, digital cameras, wearable devices, portable devices and uninterruptible power supplies (UPS) etc. Here, we have reported the binder free carbon cloth supported polyaniline/reduced graphene oxide (PRGO) composite hydrogel as a high performance supercapacitor electrode synthesized by a facile chemical polymerization method using phytic acid (PA). The electrochemical performance of binder free carbon cloth based PRGO composite hydrogel electrode has been analysed using cyclic voltammetry (CV), and galvanostatic charge-discharge (GCD) techniques. The high specific capacitance (C S ) ~ 235.32 F g -1 has been obtained for the PRGO composite hydrogel @cc in 1 M H 2 SO 4 . The electrochemical results show that the binder free carbon cloth based PRGO composite hydrogel electrode is a promising candidate for supercapacitors.

BiVO4 and reduced graphene oxide composite hydrogels for solar-driven steam generation and decontamination of polluted water

In this report, we demonstrate composite hydrogels obtained from BiVO4 and reduced graphene oxide (rGO) (BiVO4-rGO) for enhanced solar-driven steam generation and decontamination of polluted water. The BiVO4-rGO composite hydrogel is obtained via a facile yet effective hydrothermal reduction of graphene oxide with the presence of the BiVO4 nanoparticles. We show that with the composite hydrogel floating on the water surface, an evaporative rate of ~1.6 kg/m2 h and solar-thermal conversion efficiency of 87% under 1 sun illumination can be achieved, which can be attributed to the highly porous structures and the interfacial heating characteristics. Additionally, when simulated polluted water is used as the source water for the freshwater production, the BiVO4-rGO composite hydrogel also exhibits an outstanding photo-decontamination performance of the toxic organic dyes in the underlying source water, such as rhodamine B (RhB) and methyl orange (MO). We anticipate that this multifunctional BiVO4-rGO hydrogel could be promising in the freshwater generation and decontamination of polluted water and will contribute to sustainable development.

Facile fabrication of sodium carboxymethyl cellulose/reduced graphene oxide composite hydrogel and its application for Pb(II) removal

The sodium carboxymethyl cellulose/reduced graphene oxide (rGO-CMC) composite hydrogel was fabricated via environmental friendly one-step hydrothermal reduction method. The morphology, pore structure and surface properties of the as-prepared sample were characterized by scanning electron microscopy, Brunauer–Emmett–Teller surface area measurement and zeta potential analyser, respectively. To investigate the adsorption behaviour of rGO-CMC for Pb(II), effects of contact time, temperature, initial concentration and pH were studied in detail. The rGO-CMC composite before and after adsorption of Pb(II) was analysed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy to further explore adsorption mechanism. Compared with rGO, the adsorption capacities of rGO-CMC-3 composite for heavy metals including Pb(II), Cu(II), Ni(II), Mn(II), Co(II) were increased to 156.85, 35.70, 21.40, 20.85 and 15.80 mg g−1, respectively. In addition, the rGO-CMC composite formed a complete aerogel after freeze-drying, which confirms its great potential as an easily separable adsorbent to remove heavy metals in aqueous solutions.