Surface Modification Of Graphene Oxide Research Articles

Improving the drug delivery characteristics of graphene oxide based polymer nanocomposites through the “one-pot” synthetic approach of single-electron-transfer living radical polymerization

Graphene oxide (GO) based polymer nanocomposites have attracted extensive research interest recently for their outstanding physicochemical properties and potential applications. However, surface modification of GO with synthetic polymers has demonstrated to be trouble for most polymerization procedures are occurred under non-aqueous solution, which will in turn lead to the restacking of GO. In this work, a facile and efficient “one-pot” strategy has been developed for surface modification of GO with synthetic polymers through single-electron-transfer living radical polymerization (SET-LRP). The GO based polymer nanocomposites were obtained via SET-LRP in aqueous solution using poly(ethylene glycol) methyl ether methacrylate (PEGMA) as the monomer and 11-bromoundecanoic acid as the initiator, which could be effectively adsorbed on GO through hydrophobic interaction. The successful preparation of GO based polymer nanocomposites was confirmed by a series of characterization techniques such as 1H nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy and X-ray photoelectron spectroscopy. The resultant products exhibit high water disperisibility, excellent biocompatibility and high efficient drug loading capability, making these PEGylated GO nanocomposites promising candidates for biomedical applications.

Preparation and properties of acrylic resin coating modified by functional graphene oxide

To improve the dispersion and the strength of filler–matrix interface in acrylic resin, the functional graphene oxide (FGO) was obtained by surface modification of graphene oxide (GO) by γ-methacryloxypropyl trimethoxysilane (KH-570) and then the acrylic nanocomposites containing different loadings of GO and FGO were prepared. The structure, morphology and dispersion/exfoliation of the FGO were characterized by XRD, FT-IR, Raman, XPS, SEM and TEM. The results demonstrated that the KH-570 was successfully grafted onto the surface of GO sheets. Furthermore, the corresponding thermal, mechanical and chemical resistance properties of the acrylic nanocomposites filled with the FGO were studied and compared with those of neat acrylic and GO/acrylic nanocomposites. The results revealed that the loading of FGO effectively enhanced various properties of acrylic resin. These findings confirmed that the dispersion and interfacial interaction were greatly improved by incorporation of FGO, which might be the result of covalent bonds between the FGO and the acrylic matrix. This work demonstrates an in situ polymerization method to construct a flexible interphase structure, strong interfacial interaction and good dispersion of FGO in acrylic nanocomposites, which can reinforce the polymer properties and be applied in research and industrial areas.

Interactions between an Aryl Thioacetate‐Functionalized Zn(II) Porphyrin and Graphene Oxide

The surface modification of graphene oxide (GO) is carried out via the supramolecular functionalization route using a Zn(II)‐porphyrin which is soluble in common organic solvents on basis of long alkyl chains present at the exocyclic positions. This acts as a dispersing agent and decorates the surface of the graphene oxide uniformly, giving rise to a new nanohybrid denoted Zn(II)‐porphyrin@GO. The resulting Zn(II)‐porphyrin@GO nanohybrid forms a stable dispersion in ethanol (as characterized by several different spectroscopic techniques such as UV–vis, Fourier transform infrared, Raman). The morphology of Zn(II)‐porphyrin@GO nanohybrid is investigated by atomic force microscopy (AFM) and transmission electron microscope (TEM)/selected area electron diffraction. Both TEM and AFM measurements indicate that the Zn(II)‐porphyrin self‐assemble onto the surface of graphene oxide sheets. Steady‐state and time‐resolved fluorescence emission studies in the dispersed phase, and as a thin film, point toward the strongly quenched fluorescence emission and lifetime decay, suggesting that energy transfer occurs from the singlet excited state of Zn(II)‐porphyrin unit to GO sheets.

Reduced graphene oxide decorated with gold nanoparticle as signal amplification element on ultra-sensitive electrochemiluminescence determination of caspase-3 activity and apoptosis using peptide based biosensor.

Introduction:Growing demands for ultrasensitive biosensing have led to the development of numerous signal amplification strategies. In this report, a novel electrochemiluminescence (ECL) method was developed for the detection and determination of caspase-3 activity based on reduced graphene oxide sheets decorated by gold nanoparticles as signal amplification element and horseradish peroxidase enzyme (HRP) as ECL intensity enhancing agent. Methods: The ECL intensity of the luminol was improved by using the streptavidin coated magnetic beads and HRP in the presence of hydrogen peroxide. The cleavage behavior of caspase-3 was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques using biotinylated peptide (DEVD containing peptide) which was coated on reduced graphene oxide decorated with gold nanoparticle. The surface modification of graphene oxide was successfully confirmed by FTIR, UV-vis and x-ray spectroscopy. Results: ECL based biosensor showed that the linear dynamic range (LDR) and the lower limit of quantification (LLOQ) were 0.5-100 and 0.5 femtomolar (fM), respectively. Finally, the performance of the engineered peptide based biosensor was validated in the A549 cell line as real samples. Conclusion: The prepared peptide based biosensor could be considered as an excellent candidate for early detection of apoptosis, cell turnover, and cancer related diseases.

Preparation of a Fe3O4-Au-GO nanocomposite for simultaneous treatment of oil/water separation and dye decomposition.

A nanocomposite capable of simultaneously controlling multiple water pollutants (soluble organic dye and insoluble chemical solvent) has been obtained. The Au and Fe3O4 nanoparticles (NPs) were modified on a graphene oxide (GO) surface via light reduction and covalent attachment. The obtained Fe3O4-Au-GO nanocomposite has magnetic driving ability and catalytic applications. The nanocomposite can form emulsions after wrapping an insoluble and volatile organic solvent inside; moreover, the multi-layer graphene shell structure may delay volatilization of the solvent, ensuring that the oil droplets are collected efficiently and completely by the Fe3O4-Au-GO nanocomposite. At the same time, the Au NPs on the surface of the composite can effectively catalyze the decomposition of an organic dye in water and the recovery of the nanocomposite catalyst can also be realized using an external magnetic field. The simultaneous treatment of non-soluble oil (organic solvents) and organic dyes in water can be realized by the Fe3O4-Au-GO nanocomposite. Therefore, based on surface modification of GO, one material with two types of water pollution treatment functions was realized. This provides a new way for the simultaneous treatment of oil separation and dye decomposition, and the assembled structure may result in emulsions to give new applications in fuel cells and other fields.

Surface Modification of Graphene Oxide and Investigation of Its Effects on Surface Properties of Aramid Membranes

To manufacture aramid thin-film-composite membrane for desalination application (reverse osmosis) via in situ interfacial polymerization, the different weight percents of modified graphene oxide were applied into the aramid layer during interfacial polymerization. The dispersion of the modified graphene oxide was investigated by X-ray Diffraction (XRD) and Transition Electron Microscopy (TEM) methods. Also, the effect of the modified graphene oxide on the surface chemical composition and surface morphology of aramid membrane was investigated by Attenuated Total Reflectance-Infrared Spectroscopy (ATR-IR), scanning electron microscopy, and atomic force microscopy, respectively. The results showed that in the presence of the modified graphene oxide, the interfacial polymerization reaction is transferred between the nanoparticles so the depth of surface porosity is increased strongly. In addition, the hydrophilic value of aramid layer in the presence of the modified graphene oxide firstly increased up to 0.15 wt% but with an increase in the modified graphene oxide percent at 0.2 wt%, the surface hydrophilicity decreased gradually. As a result, the optimum hydrophilic and morphological properties were observed in samples containing 0.15 wt% of modified graphene oxide.

Achieving significantly enhanced dielectric performance of reduced graphene oxide/polymer composite by covalent modification of graphene oxide surface

In this study, nanocomposite films of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF–HFP) incorporating polyethylenimine (PEI)-covalently modified graphene sheets (rGO–PEI) were prepared by a solution-cast method, and the dielectric properties of the films were studied. Infrared spectroscopy, atom force microscope, X-ray photoelectron spectroscopy, solid state NMR spectroscopy, Raman, thermogravimetry analysis and additional verification experiment indicated that PEI chains were successfully grafted on the surface of graphene oxide (GO). A dielectric constant of 67 (100Hz), which was five times that of pure PVDF–HFP film, was obtained for the composite films when the concentration of rGO–PEI was 8wt% and the dielectric loss was as low as 0.12. A microcapacitor model explained the behavior of the dielectric composites. The effect of the covalent modification was further studied by introducing control experiments using non-covalently prepared N–GO–PEI as the fillers to create the composite films. The results demonstrated that covalent linkages between GO and PEI were indispensable in obtaining composite films with high dielectric constants and low losses.

Surface Modification of Graphene Oxide by Carboxyl-Group: Preparation, Characterization, and Application for Proteins Immobilization

Two-dimensional grapheme offers interesting electronic, thermal, and mechanical properties that are currently being explored for advanced electronics, membranes, and composites. Here we synthesize and explore the biological applications of grapheme oxide. The functionalization chemistry was developed to impart solubility and compatibility of grapheme oxide in biological environments. We found that the global myoglobin (Mb) – grapheme oxide hybrids (Mb-GO) could be successfully prepared by chemical deposition via carboxylic acid modified graphite oxide (GO-COOH) as the intermediate under mild conditions. The functioned grapheme oxide was characterized by many techniques including UV-Vis, FT-IR, Raman, SEM, and TEM. The results indicated that the hydroxyl groups and epoxide groups could be converted to carboxylic acid moieties under strongly basic conditions, and the carboxylic acid modified graphite oxide had increased water solubility and more carboxylic acid groups available for subsequent enzyme immobilization by covalent binding. The average amount of carboxylic acid groups in GO-COOH were determined to be 1.243 mmol in 100 mg GO-COOH by acid-base titration. And the average mole percentage of the carboxylic acid groups on GO-COOH was about 14.9%. The funcitionalization of GO with carboxylic acid groups provided basis for constructing various function materials, including biosensors, enzyme reactors, cellular imaging, and drug delivery.

Covalently-grafted graphene oxide nanosheets to improve barrier and corrosion protection properties of polyurethane coatings

Surface modification of graphene oxide (GO) has been performed by grafting of polyisocyanate (PI) resin. Results obtained from X-ray photo electron spectroscopy, thermal gravimetric analysis and X-ray diffraction analysis revealed that the PI resin chains were successfully attached onto the surface of GO nanosheets through covalent bonding with hydroxyl and carboxylic groups leading to amides and carbamate esters bonds formation. Subsequently, the PI functionalized GO sheets were incorporated into the polyurethane (PU) matrix. The X-ray diffraction analysis showed that surface modification of GO nanosheets with PI enhanced the level of exfoliation of PI–GO in the PU matrix. Scanning electron microscope analysis showed the enhanced interaction between GO and PU matrix after functionalization by PI resin. The electrochemical impedance spectroscopy and salt spray tests were performed to reveal the effects of addition of 0.1wt.% GO and PI–GO nanosheets on the corrosion protection properties of the PU coating. Also, the adhesion loss of the coatings was obtained by pull-off adhesion test after 30days immersion in 3.5wt.% NaCl solution. It was found that incorporation of 0.1wt.% surface modified GO nanosheets into the PU matrix resulted in significant improvement of the coating corrosion protection properties and ionic resistance.

Thermodynamics of the adsorption of nickel ions from aqueous phase using graphene oxide and glycine functionalized graphene oxide

Adsorption capacity of Ni2+ on graphene oxide (GO) and glycine functionalized graphene oxide (GO-G) surfaces was well investigated and elucidated. Amino group was used to functionalizing agent for the surface modification of GO to GO-G. The effect of numerous influential parameters such as contact time, temperature and initial concentration of Ni2+ in the aqueous solution was well illustrated and optimized using batch adsorption study. The optimized values of adsorbent dose, initial concentration of Ni2+, contact time, and pH were found to be 20mg, 15mg/L, 50min, and 6 respectively, ongoing through the impact of temperature it was seen that, when the temperature was increased from 283 to 308K, the removal of Ni2+ by GO surface decreased but the removal of Ni2+ by functionalized GO-G surface decreased until 298K and after that it was increased. Adsorption isotherm study for the adsorption process was carried out using four types of the Langmuir and Freundlich isotherm models. Results clearly depict that adsorption of Ni2+ ions on to the GO adsorbent surface was well fitted and found to be in good agreement with the type (II) Langmuir isotherm model as the obtained regression constant value (R2) is found to be 0.999 while the adsorption of Ni2+ on GO-G surface was found to be in good agreement with the Freundlich isotherm model because the regression constant value (R2) is found to be 0.999.

Preparation and characterization of epoxy nanocomposites containing surface‐modified graphene oxide

ABSTRACTA three‐step grafting procedure has been used to graft the epoxy monomers (DER332) and the curing agents (diamino diphenyl methane (DDM), onto graphene oxide (GO) surface. The surface modification of GO has been performed by grafting of Jeffamine D‐2000, followed with subsequent grafting of DER332 and DDM, respectively. Fourier transform spectroscopy and thermogravimetric analysis indicate successful surface modification. The resulting modified GO, that is, (DED)‐GO, can be well dispersed in the epoxy monomers. The epoxy nanocomposites containing different GO contents can then be prepared through curing processes. The dispersion of GO in the nanocomposites is characterized by transmission electron microscopy. It is found that the tensile strength and elongation at break of epoxy nanocomposite with only 0.2 wt % DED‐GO are increased by 30 and 16% as compared with the neat epoxy resin, respectively. Dynamic mechanical analysis results show that 62% increase in storage modulus and 26°C enhancement in the glass transition temperature of the nanocomposite have been achieved with the incorporation of only 0.2 wt % of DED‐GO into the epoxy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40236.

Green synthesis of thiolated graphene nanosheets by alliin (garlic) and its effect on the deposition of gold nanoparticles

A novel green one-pot approach for surface modification of graphene oxide into organosulfur modified graphene nanosheets (OS-GNS) is being reported. Alliin (garlic phytochemical) mediated organothiol linkages over OS-GNS facilitated one-step attachment of pre-synthesized gold nanoparticles. In absence of alliin treatment, no Au NP attachment was observed.

Surface modification of graphene oxide with thermoresponsive polymers via atom transfer radical polymerization: Transition from LCST to UCST

Graphene oxide-poly(2-N,N-dimethylamino)ethyl methacrylate (GO-PDMAEMA) nanocomposite was synthesized via atom transfer radical polymerization (ATRP) and PDMAEMA chains were grafted on the surface of GO. After quaternization, quaternized GO-PDMAEMA nanocomposite was achieved. GO-PDMAEMA shows a lower critical solution temperature (LCST)-type thermoresponsivity, and the dispersion-aggregation behavior was controlled by changing the temperature of the solution. The hydrophilicity of GO-PDMAEMA decreased with increasing temperature. Conversely, the dispersion and hydrophilicity of quaternized GO-PDMAEMA increased with increasing temperature due to the upper critical solution temperature (UCST)-type thermoresponsivity. So the LCST–UCST transition can be accomplished by the transition of PDMAEMA to quaternized PDMAEMA on the surface of GO.

Simultaneous reduction, functionalization and stitching of graphene oxide with ethylenediamine for composites application

A simple, efficient and cost-effective approach for the simultaneous reduction, surface modification and stitching of graphene oxide (GO) using ethylenediamine is described. The effect of stitched graphene on the mechanical properties of linear low density polyethylene (LLDPE)-based composites was also investigated. Ethylamine was used to produce unstitched graphene, of which structures and properties were compared to those of stitched graphene. The surface modification of GO with ethylamine or ethylenediamine can easily take place under mild conditions. The reduced GO (rGO) shows good crystalline behavior and high electrical conductivity (∼1075 S m−1). The removal of epoxide, carboxyl and hydroxyl groups from GO by ethylamine or ethylenediamine was confirmed by Fourier transform infrared, Raman and photoelectron spectroscopy. The microstructures were analyzed by atomic force microscopy and transmission electron microscopy revealing stitching and crystalline behavior of the rGO. Compared to other reported methods, the reduction of GO with ethylamine and ethylenediamine is a preferable route for large-scale production of functionalized graphene. It was found that the storage modulus of the ethylenediamine functionalized GO (3 wt%)–LLDPE composites is significantly higher than that of pure LLDPE or ethylamine functionalized GO reinforced composites in the studied temperature range (−70 to 90 °C).

Enhancing Stability and Photocatalytic Activity of ZnO Nanoparticles by Surface Modification of Graphene Oxide

This work reports a simple method for the preparation of high-quality GO-ZnO nanocomposite materials. Transmission electron microscopy (TEM) revealed that the ZnO nanoparticles are uniformly distributed on the GO sheets and the diameter of the ZnO nanoparticles falls in 5-8 nm. Further experimental results imply that involving GO sheets into the system could remarkably prevent the aggregation of ZnO nanoparticles compared to pure ZnO. The photocatalytic activity and stability of the prepared GO-ZnO composite for the degradation of Acid Orange 7 (AO 7) under UV light irradiation is significantly enhanced in comparison to the as-synthesized pristine ZnO nanoparticles. Considering the high photocatalytic acitivity and relative stability, this high-quality GO-ZnO nanocomposite is beneficial for the applications in environmental engineering and other fields.

Effect of surface modification of graphene oxide on photochemical stability of poly(vinyl alcohol)/graphene oxide composites

Poly(vinyl alcohol) (PVA)/graphene oxide (GO) composites were prepared to improve the photochemical stability of PVA. The surface of GO was modified by oxyfluorination to introduce the polar functional groups on GO for the stronger interfacial interaction with PVA. The photochemical stability of PVA/oxyfluorinated-GO composites was evaluated by measuring the insoluble gel content after partial photodegradation of PVA under various UV irradiations. PVA/oxyfluorinated-GO composites showed the significant improvement in both the dispersion of GO in PVA matrix and the photochemical stability of PVA as the oxygen content increased in the oxyfluorination. The photochemical stability of composites had a close relation with the uniform distribution of GO in PVA matrix. The proper modification of GO by oxyfluorination showed the better photochemical stability for PVA/GO composites as compared to that of PVA/pristine GO composite.

Preparation and Characterization of Functionalized Graphene/Linear Low Density Polyethylene Nanocomposites

The present work deals with the functionalization of graphene sheet and preparation of functionalized graphene/linier low density polyethylene (LLDPE) nanocomposites by solution-mix techniques. Dodecyl amine (DA) has been used for the surface modification of graphene oxide (GO) and hydrazine as reducing agent. Fourier transform infrared (FTIR) spectra exhibits the appearance of new peaks in the functionalized graphene (DA-G), which suggests the functionalization of graphene by DA. X-ray diffraction (XRD) analysis infers the formation of fully exfoliated DA-G/LLDPE nanocomposites. The tensile strength (TS) and elongation at break (EB) of the composites are higher in comparison to neat LLDPE. The nanocomposites with only 0.5 wt.% of DA-G content results in TS and EB to be 17% and 10% higher compared to neat LLDPE. TGA shows that the thermal stability of the DA-G/LLDPE nanocomposites is higher compared to pure matrix polymer.