Modified Graphene Oxide Research Articles

Chemically modified graphene oxide with fatty alcohol as antiwear, antifriction and rheology modifier for lubricating oil

Chemically modified graphene oxide with fatty alcohol as antiwear, antifriction and rheology modifier for lubricating oil

Graphene oxide-reinforced alginate/gelatin hydrogel via Schiff-base bond and thiol-Michael addition for bone regeneration

The poor mechanical properties of hydrogels limit their application as scaffolds to provide support for bone regeneration. Inspired by the superior mechanical properties of nanocomposites-reinforced hydrogels and the double network (DN) structure of hydrogels, the current study investigated the fabrication of graphene oxide (GO) reinforced DN hydrogels for bone regeneration. To this regard, aldehyde methylene sodium alginate (AMSA), amino gelatin ( amino G), and dithiothreitol modified graphene oxide (DGO) were initially synthesized, and subsequently were employed in the preparation of AMSA/ amino G (AG) and DGO/AMSA/ amino G (GSG) DN-hydrogels, while imposing different mass ratios of the reacting components. The physicochemical and biological properties of the prepared hydrogels were subsequently assessed using several tests such as Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, nuclear magnetic resonance, cell compatibility and in vivo experiments. The compressive strengths of the prepared AG and GSG hydrogels were conversely correlated with their porosity characteristics. This study showed that although AG and GSG hydrogels had favorable cell viability and cell proliferation characteristics, GSG hydrogels presented an improved osteogenic capacity compared to AG hydrogels. This study was, therefore, able to demonstrate the functionality of employing novel GSG hydrogels in tissue engineering via their use as scaffolds for mechanical support and cell proliferation to promote bone regeneration.

Plasma surface modification of graphene oxide nanosheets for the synthesis of GO/PES nanocomposite ultrafiltration membrane for enhanced oily separation

AbstractIn this study, two different monomers, namely hexafluorobutyl acrylate (HFBA) and diethylaminoethyl methacrylate (DEAEMA) were individually used to modify graphene oxide (GO) nanosheets via environmentally friendly plasma enhanced chemical vapor deposition (PECVD) method. The results from instrumental analyses confirmed the successful deposition of respective functional material onto the nanomaterials. Modified GOs were used as the nano‐fillers to develop composite polyethersulfone (PES) ultrafiltration (UF) membrane with improved surface properties for oily solution treatment. All the developed membranes were characterized with a series of analytical instruments to support the findings of membrane filtration performance. The results indicated that the membrane incorporated with DEAEMA‐GOs (coated with hydrophilic polymer) could achieve better results in terms of oil rejection, antifouling resistance and water recovery rate than the membrane incorporated with HFBA‐GOs (coated with hydrophobic polymer). This is due to the reduced agglomeration between modified GOs as well as better interaction of hydrophilic‐coated GOs with polymer membrane. Compared to the pure water flux of the membrane incorporated with unmodified GO, the membrane incorporated with DEAEMA‐GO achieve approximately 85% higher value with oil removal rate remained almost unchanged (98.94% rejection).

Charge modifications of graphene oxide enhance the inhibitory effect on insulin amyloid fibrillation based on electrostatic interactions

Graphene oxide (GO) is a biocompatible nanomaterial that has an inhibitory effect on insulin amyloid fibrillation. In order to enhance the inhibitory effect of GO and explore the rules of electrostatic interactions on the inhibitory effect, carboxyl group, PEI and PEG were coupled to the GO nanoplatelet surface to prepare inhibitors of different surface electrical properties. The effects of surface electrical properties of inhibitors on insulin fibrillation were investigated. The results showed that GO, carboxyl group modified GO (GO-COOH), PEI modified GO (GO-PEI), and PEG modified GO (GO-PEG) inhibited insulin fibrillation in a dose-dependent manner. Compared with GO, positive charge-modified GO-PEI and negative charge-modified GO-COOH enhanced the inhibitory effect, while uncharged polymer-modified GO-PEG weakened the inhibitory effect. The inhibitory effect of the inhibitors increased with the increase of surface charge density. The difference in inhibitory effect between GO-PEI and GO-COOH was due to the different electrostatic interactions between inhibitors and insulin, and the different inhibition mechanisms. In addition, inhibitors mainly interact with insulin during the nucleation phase to hinder insulin fibrillation. The charge modifications of graphene oxide enhanced the inhibitory effect on insulin fibrillation based on electrostatic interactions, which will provide new thoughts for the development of anti-amyloid fibrillation drugs.

High thermal storage ability and photothermal conversion capacity phase change capsule with graphene oxide covalently grafted silica shell

Preparation of phase change materials with energy collection, conversion and storage functions is considered to be an important way to solve the energy shortage problem. Hence, a novel phase change capsule (EP@MGO) with photothermal conversion function was innovatively designed. In the process of preparing EP@MGO, the modified graphene oxide (MGO) layer was covalently anchored on the surface of the phase change capsule encapsulated by silica shell (EP) through Si-O-Si bonds, in which MGO was obtained by modifying GO nanosheets with isocyanate propyl triethoxysilane. The as-prepared EP@MGO microcapsule presents favorable latent heat storage capacity, with enthalpy of 139.8 J/g and high encapsulation efficiency of 83.6%. Besides, the thermal stability, leakage-proof property, durability, and thermal reliability of EP@MGO were enhanced significantly due to the physical protection effect provided by the SiO2-MGO double-layer shell. Moreover, the covalently MGO-grafted silica shell endows EP@MGO with high thermal conductivity (1.603 W/m·K), which improves its thermal management efficiency. More importantly, EP@MGO exhibits the potential ability to effectively utilize ultraviolet and visible light. In detail, the absorbance of EP@MGO increased by ∼192% in the ultraviolet and visible light region (200–800 nm), and the photothermal conversion efficiency under near infrared (NIR) region as high as 64.4%, which has negligible change (64.2%) even after 50 times heating-cooling cycle. Therefore, the phase change capsule EP@MGO provides a new idea for realizing efficient utilization of solar energy, and exhibits the application potential in biomedical treatment, smart textiles, and solar thermal collector.

Bovine serum albumin functional graphene oxide membrane for effective chiral separation

An efficient chiral separation membrane was fabricated from bovine serum albumin (BSA) modified graphene oxide (GO), BSA was linked with GO through EDC/NHS coupling chemistry. This BSA modified membrane can successfully separate Phe racemate, and the excess enantiomer (ee) in osmotic solution was up to 96.1% under the optimal conditions. We found that the addition of BSA not only enlarged the spacing but also formed chiral channels in the membrane to selective transport of L-Phe, enabling the chiral membrane to have both high flux and high selectivity. Further, we confirmed that the microstructure of BSA plays an important role in the chiral separation performance of the membrane. When the helical structure and globular three-dimensional structure of BSA are unfolding due to temperature rise, the chiral separation performance of the membrane will be weakened or even disappear. Addition, molecular docking simulation experiments also proved the reliability of this conclusion.

Highly-efficient and selective adsorption of phenols by GO-BT composite in the presence of rare earth elements

Recently, industrial activities have produced large quantities of wastewater containing metal ions (such as rare earth elements) or organic contaminants (such as phenols), which are difficult to be degraded or recycled. Carbon nanocomposites have been considered to be a kind of effective adsorbent for the separation/enrichment of organic substances or metal ions from aqueous solutions. To selectively adsorb/remove these contaminants, 2-bis(2-hydroxyethyl)amino-2-(hydroxymethyl)− 1,3-propanediol was utilized as a functional component to modify graphene oxide (GO) by a facile one-step coupling method. The fabricated GO-BT composite was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, specific surface area analysis, thermogravimetric analysis and Zeta potential analysis. The equilibrium adsorption capacities of GO-BT composite for Y3+, Yb3+, Eu3+, Sm3+, Nd3+, La3+, Er3+, Pr3+, p-chlorophenol (PCP), p-methylphenol (PMP), phenol and aniline were tested to be 24.89, 28.13, 18.77, 57.46, 26.25, 33.12, 22.64, 6.529, 486.5, 391.8, 268.0 and 60.34 µmol g−1, respectively. The selectivity coefficient of GO-BT composite toward Y3+ against phenol was 0.2999, confirming its excellent adsorption selectivity for organic phenols rather than rare earth elemental (REE) ions. After 10 times of adsorption-desorption cycles, GO-BT composite maintained 80% removal rate and considerable recycling performance. The adsorption process could be better described by the pseudo-second order kinetic model and the non-linear Langmuir isothermal model. Adsorption thermodynamic studies demonstrated a non-spontaneous and exothermic process with decreasing randomness. This work can provide some references for fabricating GO-based adsorbents for selective removal of organic reagents in the flotation separation of REE ores.

Vancomycin modified graphene oxide as carriers to load phthalocyanine for synergistic phototherapy of vancomycin-resistant bacteria

Vancomycin modified graphene oxide as carriers to load phthalocyanine for synergistic phototherapy of vancomycin-resistant bacteria

Light Response and Switching Behavior of Graphene Oxide Membranes Modified with Azobenzene Compounds.

Here, we report on the fabrication of light-switchable and light-responsive membranes based on graphene oxide (GO) modified with azobenzene compounds. Azobenzene and para-aminoazobenzene were grafted onto graphene oxide layers by covalent attachment/condensation reaction prior to the membranes' assembly. The modification of GO was proven by the UV-vis, IR, Raman and photoelectron spectroscopy. The membrane's light-responsive properties were investigated in relation to the permeation of permanent gases and water vapors under UV and IR irradiation. Light irradiation does not influence the permeance of permanent gases, while it strongly affected that of water vapors. Both switching and irradiation-induced water permeance variation is described, and they were attributed to over 20% of the initial permeance. According to in situ diffraction studies, the effect is ascribed to the change to the interlayer distance between the graphene oxide nanoflakes, which increases under UV irradiation to ~1.5 nm while it decreases under IR irradiation to ~0.9 nm at 100% RH. The last part occurs due to the isomerization of grafted azobenzene under UV irradiation, pushing apart the GO layers, as confirmed by semi-empirical modelling.

Silver nanoparticles based on sulfobutylether-β-cyclodextrin functionalized graphene oxide nanocomposite: Synthesized, characterization, and antibacterial activity

In this work, an effective method was explored to prepare silver nanoparticles/graphene oxide-sulfobutylether-β-cyclodextrin (AgNPs/GO-SBE-β-CD) antibacterial nanocomposite. Dopamine (DA) was used as a green and mild reductant to directly in situ reduce silver nitrate on Sulfobutylether-β-cyclodextrin (SBE-β-CD) modified graphene oxide (GO-SBE-β-CD). Its synthesized, antibacterial properties and biocompatibility were studied. Results showed that silver nanoparticles with an average size of 73 nm were uniformly distributed on the GO-SBE-β-CD sheets. In addition, AgNPs/GO-SBE-β-CD were proved an effective antibacterial material against both gram-negative and gram-positive, reduced the viability of E. coli and S. aureus by 90 % at 40 µg/mL. At the same time, AgNPs/GO-SBE-β-CD co-cultured with L929 cells did not show cytotoxicity. In vivo experiment, AgNPs/GO-SBE-β-CD showed good biocompatibility. Collectively, AgNPs/GO-SBE-β-CD is a promising material to prevent bacterial infection, expecting to be applied in wound healing.

Cancer cell membrane camouflaged biomimetic nanosheets for enhanced chemo-photothermal-starvation therapy and tumor microenvironment remodeling

Tumor microenvironment (TME) featured by dense extracellular matrix (ECM), high interstitial pressure, hypoxia, and immunosuppression hinders the infiltration of nanoparticles (NPs) into tumors, impairing the efficacy of chemotherapy or phototherapy. To overcome these obstacles, we propose a novel biomimetic nano-carrier, B16F10 cell membrane camouflaged heparin-3-bromopyruvate conjugate modified graphene oxide (GOHep-3BP@membrane, GBM), for the targeted delivery of etoposide (EPT). EPT/GBM accumulates in tumor tissue and is internalized into B16F10 cells relying on homologous targeting ability. GO-mediated hyperthermia could accelerate the release of EPT, destruct ECM, dilate blood vessels, increase oxygen supply, and induce immunogenic cell death (ICD). The acylhydrazone bond-conjugated 3BP is released in acidic environment, suppressing glycolysis for starvation therapy, and reducing lactate efflux to alleviate immunosuppression. The released EPT entered the cell nuclei to exert a chemotherapeutic effect and downregulated the expression of programmed death ligand 1 (PD-L1) by inhibiting epithelial-mesenchymal transition (EMT)/β-catenin/STT3/PD-L1 signaling. EPT/GBM plus near infrared (NIR) laser treatment activated T lymphocytes and downregulated M2 tumor-associated macrophage (TAM), showing significant efficacy against primary tumors, abscopal tumors and lung metastases. In summary, this study presented a novel combinational strategy that integrated PTT, chemotherapy, starvation therapy and immunotherapy in one system, providing a new perspective for targeted-therapy of melanoma.

Alginate foam gel modified by graphene oxide for wound dressing

Recently, hydrogel dressings have been rapidly developed for wound healing. However, it is still a huge challenge to endow hydrogel wound dressings with excellent hemostatic performance. Here, a new wound treatment material, foam gel wound dressing, is reported, which possesses rapid hemostasis and antibacterial properties. The foam gel dressing is composed of chitooligosaccharide modified graphene oxide (CG) nanocomposites and calcium alginate foam substrate. In this system, CG has a strong interaction with platelets, which is helpful for rapid hemostasis. So the wound dressing could stop bleeding quickly within 10 s. Meanwhile, CG also provides excellent antibacterial properties to dressings, which is conducive to wound healing. Full-thickness wound healing experiments showed that compared with blank control and CG-free foam gel dressings, CG-loaded foam gel dressings shows better healing properties, and the wounds covered with them are almost completely healed within 12 days. In addition, histological morphology analysis displays CG-loaded wound dressing could significantly accelerate wound healing by reducing the inflammatory response and promoting vascular remodeling. This unique strategy provides a simple and practical method for the clinical application of the next generation of wound dressings.

Thermally Conductive and Antistatic Properties of Silicone Rubber Reinforced by the Modified Graphene Oxide.

Silicone rubber (SR)/vinyl-graphene oxide (vinyl-GO) nanocomposites were prepared through the hydrosilylation reaction of silicon hydrogen polydimethylsiloxane (H-PDMS) with vinyl polydimethylsiloxane (vinyl-PDMS), in which vinyl-GO was used as a nano filler. The thermally conductive and antistatic properties of the nanocomposites, and their tensile strength and thermal stability were evaluated. The thermally conductive and antistatic properties increased naturally when the nanocomposites had eight to nine parts of vinyl-GO. The addition of 9 parts of vinyl-GO increased the thermal conductivity to 0.44 from 0.17 W/m-1·K-1 of neat SR and the surface resistance value to 108 from 1014 Ω of neat SR. Vinyl-GO is effective in improving the tensile strength and toughness of the nanocomposites. The tensile strength and elongation at break of the nanocomposites were much higher than that of neat SR, especially for 10 parts of vinyl-GO in the nanocomposite, and the tensile strength was 1.84 MPa and the elongation at break was 314.1%. Additionally, compared with neat SR, the nanocomposites had a much higher thermal stability. For eight parts of vinyl-GO in the nanocomposites, H-PDMS with the selected silicon hydrogen content and vinyl-PDMS with the selected vinyl content could offer an appropriate cross-linking degree that suits the character of GO. When the nanocomposite had eight parts of vinyl-GO, its scanning electron microscope exhibited a monolayer GO with folded, twisted, and local surface folds. However, there was a certain amount of multilayer aggregation of GO for 10 parts of vinyl-GO in the nanocomposite.

Graphene Oxide Modified Microtubular ZnO Antibacterial Agents for a Photocatalytic Filter in a Facial Mask

Graphene Oxide Modified Microtubular ZnO Antibacterial Agents for a Photocatalytic Filter in a Facial Mask

Engineering CO2-philic pathway via grafting poly(ethylene glycol) on graphene oxide for mixed matrix membranes with high CO2 permeance

The introduction of two-dimensional (2D) nanofillers into thin-film (<1 μm thickness) mixed-matrix membranes (MMMs) remains challenging because of the interfacial issues that lead to Knudsen diffusion, thereby causing a loss of selectivity. Herein, we describe a surface modification technique that involves the application of an epoxy group ring opening process and free-radical polymerization to the graphene oxide (GO) surface to enable the grafting of CO2-philic poly(ethylene glycol) (PEG) chains. The use of functional groups to achieve the PEG modification of GO increases the interlayer spacing between the 2D GO layers. Specifically, the abundant PEG domain between the layers provides an effective CO2-philic pathway and minimizes the occurrence of polymer matrix/GO filler interfacial defects, resulting in excellent CO2 permeance and selectivity. The MMM consisting of GO-glycidyl methacrylate grafted with poly(oxyethylene methacrylate) achieved the highest performance, with a CO2 permeance of 3169 GPU, CO2/N2 selectivity of 37.4, and CO2/CH4 selectivity of 15.8. These results indicate the suitability of the as-prepared materials for commercial applications.

Study on friction properties of silver/polydopamine modified graphene oxide nanocomposites as lubricant additive

According to the redox ability of dopamine in a weak alkaline environment, silver nanoparticles were uniformly loaded on the surface of polydopamine-modified graphene oxide (Ag/PGO). The results show that the base oil containing Ag/PGO nanoparticles exhibits a better tribological property than base oil. The maximum decrease in wear rate and friction coefficient at different temperatures amounted to 68% and 53.6%, respectively. The tribofilm containing C, O, N, and Ag exists and plays an important role in reducing friction and increasing wear resistance. Molecular dynamics simulations show that the microscopic oil film composed of Ag/PGO and n-hexadecane has low shear deformation during the shearing process, and the oil film has low interaction energy with the upper and lower shear walls.

Advances in atom transfer radical polymerization of modified grain

Atom transfer radical polymerization (ATRP) is a kind of controllable reactive radical polymerization method with potential application value. The modification of graphene oxide (GO) by ATRP reaction can effectively control various graft polymer molecules Chain length and graft density, giving GO different functionality, such as good solvent dispersibility, environmental sensitive stimulus responsiveness, biocompatibility, and the like. In this paper, ATRP reaction and GO surface non-covalent bonding ATRP polymer molecular chain were directly initiated from GO surface immobilization initiator. The ATRP reaction modified GO was reviewed, and the process conditions and research methods of ATRP modification reaction were summarized, as well as pointed out the functional characteristics and application prospect of GO functionalized composites.

Advances and outlook in modified graphene oxide (GO)/epoxy composites for mechanical applications

Advances and outlook in modified graphene oxide (GO)/epoxy composites for mechanical applications

Photothermal self-healing polyurethane/graphene oxide composites based on diselenide bond

The polymer PCL-MDI-SeSe-PU polyurethane was synthesized by the reaction of PCL, diisocyanate and a diselenide bond-containing chain extender, and a certain amount of diisocyanate-modified graphene oxide NCO-GO was doped into polyurethane to obtain the PCL-MDI-SeSe-PU/NCO-GO composite. Benefitting from the thermal stimulated dynamic properties of diselenide bond and the photothermal effects of NCO-GO, the composite exhibited efficient self-healing behaviors upon exposure to infrared irradiation. As a result, the polymer PCL-MDI-SeSe-PU has good self-healing properties with 95.4% self-healing efficiency at 80 °C for 3 h. After doping modified graphene oxide, the elongation at break of the polymer is greatly improved and reveals the excellent photothermal effect, the surface temperature can reach 148 °C and the maximum self-healing efficiency of 88.3% can be maintained under 60 s of infrared laser irradiation.

Synthesis of a nanocomposite based on the modification of graphene oxide with cysteamine-capped gold nanoparticles and investigation of its use as anode catalyst in ethylene glycol fuel cells

• A nanocomposite was synthesized using cysteamine-capped Au nanoparticles and rGO. • Cysteamine behaved as a linker, a stabilizer and a reducing agent in the synthesis. • Au/Cys@rGO was tested as a catalyst layer for the first time in EG fuel cells. • Au/Cys@rGO showed high activity towards the electrochemical oxidation of EG. • The stability of Au/Cys@rGO was much higher than that of Au@rGO. In this study, cysteamine-capped Au nanoparticles (Au/Cys) were used for the first time for the modification of graphene oxide (GO) to form a nanocomposite (Au/Cys@rGO) that could be used in ethylene glycol (EG) fuel cells. The Cys has three important functions in the preparation of the targeted nanocomposite; i) preventing the aggregation of Au nanoparticles as a stabilizer, ii) presenting N and S heteroatoms for doping of rGO, iii) enabling the reduction of GO to form rGO. The Au nanoparticles modified rGO (Au@rGO) was also prepared for comparison. The characterization studies showed that the presence of Cys allowed the homogeneous and uniform distribution of Au nanoparticles on rGO. The average particle sizes of Au nanoparticles in Au/Cys@rGO and Au@rGO were calculated as 10.36 (±3.21) and 54.80 (±30.13) nm, respectively. The amounts of Au loaded to Au/Cys@rGO and Au@rGO were measured as 38.19% and 41.72%, respectively. The cyclic voltammograms of EG showed that the activity of Au/Cys@rGO in the oxidation of EG is 37.33 times higher than that of Au@rGO, showing the prominent effect of Cys. The high activity and stability of Au/Cys@rGO over Au@rGO demonstrates the potential of this nanocomposite to be used in EG fuel cells.