Covalent Functionalization Of Graphene Oxide Research Articles

Fabrication of amine functionalized graphene oxide – AgNPs nanocomposite with improved dispersibility for reduction of 4-nitrophenol

In the present work, graphene oxide (GO) was synthesized through modified Hummer's method and the covalent functionalization of GO was achieved via amino moiety using N,N′-dicyclohexylcarbodiimide (DCC) as coupling agent and ethylenediamine (EDA) & 1,3-diaminopropane (DAP) as amino precursors. The amino functionalized GO served as nucleation and growth sites for silver nanoparticles. These two amino functionalized graphene oxide-AgNPs were compared based on the chain length of the alkyl-diamine and metal loading capacity. Further, these two nanocomposites were characterized using FTIR, UV, Raman, XPS and TEM analyses. We reported that these alkyl-diamine-functionalized graphene oxides had superior dispersibility in different polar solvents with reduced agglomeration of Ag nanoparticles and had control over the size of Ag nanoparticles in the range of 5–10 nm. The catalytic efficiency of these two types of amine functionalized GO-AgNPs nanocomposite were assessed based on the reduction of 4-nitrophenol. The reduction outcomes revealed that the kobs value for DAP functionalized AgNPs (7.548 × 10−4 s−1) was comparatively superior than GO-EDA-AgNPs (3.345 × 10−4 s−1) due to the variation in chain length. Optimization of parameters like [substrate], [NaBH4] and catalyst load was also investigated and found to possess influence on kobs values.

Water dispersible magnetite graphene oxide anchored sulfonic acid hybrid for mechanical enhancement of waterborne epoxy nanocomposites

The Fe3O4-functionalized graphene oxide (Fe3O4@GO-SO3H) and waterborne epoxy (WEP) nanocomposites (WEP/Fe3O4@GO-SO3H) were fabricated via co-precipitation followed by sulfonation, and the effects of modified GO on mechanical behaviors of the WEP nanocomposites were further examined. The synthesized Fe3O4@GO-SO3H hybrid was analyzed and confirmed by FTIR, Raman, XRD, and TGA. It was convinced from the FESEM and the related analyses that the covalent functionalization of graphene oxide with Fe3O4 nanoparticles followed by sulfonation with 3-mercaptopropyl trimethoxysilane was encouraging to equal distribution in the WEP system. Meanwhile, the tight mutual sharing interfaces amid WEP and Fe3O4@GO-SO3H promote the stress transfer. As the content of Fe3O4@GO-SO3H increases, the tensile strength of WEP increases, but the totaling more than 0.2 wt% Fe3O4@GO-SO3H yields unfavorable results. When the filler content of Fe3O4@GO-SO3H arises to 0.2 wt%, the tensile strength of the nanocomposites was found to be 257% higher than that of the blank group. Besides, the DMA shows that the storage modulus and tanδ of the WEP/Fe3O4@GO-SO3H was remarkably enhanced due to the strong interactions between Fe3O4@GO-SO3H and WEP. The improved thermal stability and conductivity of the WEP nanocomposites was also achieved. It could be concluded that the appropriate quantity of Fe3O4@GO-SO3H toting up can significantly improve the mechanical properties of WEP/Fe3O4@GO-SO3H nanocomposites.

Covalent Decoration of Cortical Membranes with Graphene Oxide as a Substrate for Dental Pulp Stem Cells.

(1) Background: The aim of this study was to optimize, through a cheap and facile protocol, the covalent functionalization of graphene oxide (GO)-decorated cortical membrane (Lamina®) in order to promote the adhesion, the growth and the osteogenic differentiation of DPSCs (Dental Pulp Stem Cells); (2) Methods: GO-coated Laminas were fully characterized by Scannsion Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) analyses. In vitro analyses of viability, membrane integrity and calcium phosphate deposition were performed; (3) Results: The GO-decorated Laminas demonstrated an increase in the roughness of Laminas, a reduction in toxicity and did not affect membrane integrity of DPSCs; and (4) Conclusions: The GO covalent functionalization of Laminas was effective and relatively easy to obtain. The homogeneous GO coating obtained favored the proliferation rate of DPSCs and the deposition of calcium phosphate.

Modular Preparation of Graphene-Based Functional Architectures through Two-Step Organic Reactions: Towards High-Performance Energy Storage.

Graphene-based materials have recently attracted much attention due to their extraordinary physical and chemical properties, which make them attractive candidates for many technological applications in sensing, optoelectronics, catalysis, and energy storage. Their chemical functionalization is key to tuning their properties. Herein, a novel two-step synthetic approach, which enables a high degree of covalent functionalization of graphene oxide (GO) is devised, thereby making the facile attachment of various robust functional molecules possible. Such a process relies initially on the grafting of an ethylenediamine linker followed by a second step consisting of the condensation reaction between aldehyde and amine groups to form imine bonds. As test beds, two kinds of graphene-based functional systems, namely, porphyrin-modified GO and ferrocene-modified GO, are prepared. Such hybrid systems are characterized by various spectroscopic and microscopic techniques. The degree of functionalization is quantified as the attachment of one porphyrin or ferrocene unit to every 34 or 77 carbon atoms of the GO scaffold, respectively, which is much higher than that of values obtained upon using various established chemical approaches to functionalize GO, such as condensation, cycloaddition, or coupling reactions. For the first time, the reduced form of ferrocene-modified GO was employed as an electrode material in supercapacitors, showing a specific capacitance of 127 F g-1 at a current density of 1 A g-1 , with capacitance retention of about 93 % after 5000 cycles at the same current density; this demonstrates great potential for application in high-performance energy-storage devices.

Covalent functionalization of graphene oxide with d-mannose: evaluating the hemolytic effect and protein corona formation.

In this work, graphene oxide (GO) was covalently functionalized with d-mannose (man-GO) using mannosylated ethylenediamine. XPS (C1s and N1s) confirmed the functionalization of GO through the binding energies at 288.2 eV and 399.8 eV, respectively, which are attributed to the amide bond. ATR-FTIR spectroscopy showed an increase in the amine bond intensity, at 1625 cm-1 (stretching C[double bond, length as m-dash]O), after the functionalization step. Furthermore, the man-GO toxicity to human red blood cells (hemolysis) and its nanobiointeractions with human plasma proteins (hard corona formation) were evaluated. The mannosylation of GO drastically reduced its toxicity to red blood cells. SDS-PAGE analysis showed that the mannosylation process of GO also drastically reduced the amount of the proteins in the hard corona. Additionally, proteomics analysis by LC-MS/MS revealed 109 proteins in the composition of the man-GO hard corona. Finally, this work contributes to future biomedical applications of graphene-based materials functionalized with active biomolecules.

Aryl fluoride functionalized graphene oxides for excellent room temperature ammonia sensitivity/selectivity.

Herein, we report the covalent functionalization of graphene oxide (GO) through ‘‘click’’ reaction and its applications towards ammonia sensing. This inimitable method of covalent functionalization involves linking GO with azide moiety and click coupling of different derivatives of aryl propargyl ether, which enhances the sensitivity towards ammonia. The functionalized GO were characterized using NMR, XRD, SEM, FT-IR, Raman, UV-Vis, TGA and DSC. Compared to pristine GO, the GO functionalized with Ar samples (GO-Ar) exhibit excellent room temperature ammonia sensing properties with good response/recovery characteristics. It has been observed that 2,3-difluoro and 2,3,4-trifluoro substituted aryl propargyl ether functionalized GO (GO-Ar2 and GO-Ar3) shows superior ammonia sensing with response/recovery of 63%/∼90% and 60%/100%, respectively at 20 ppm. The GO-Ar3 exhibits high sensitivity towards ammonia at 20–100 ppm. Computational studies supports the high sensitivity of GO-Ar towards ammonia due to its high adsorption energy.

Covalent functionalization of graphene oxide with molybdenum-carboxylate complexes: New reusable catalysts for the epoxidation of olefins

New graphene oxide (GO) and reduced graphene oxide (rGO) supported molybdenum catalysts were designed for the epoxidation of olefins. First, the surfaces of GO and rGO were functionalized with appropriate carboxylic acid ligands. Complexation of the supported carboxylic acid ligands with bis(acetylacetonato)dioxomolybdenum(VI) resulted in the formation of desired heterogeneous molybdenum catalysts. Characterization of the prepared catalysts was performed with various techniques such as Fourier transform infrared (FT-IR) and inductively coupled plasma optical emission (ICP-OES) spectroscopies, X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), and N2 adsorption-desorption analysis which confirmed the successful immobilization of molybdenum-carboxylate complexes on the surfaces of GO and rGO. The obtained catalysts showed high catalytic activities in the selective epoxidation of olefins with tert-butylhydroperoxide (TBHP). Also, the heterogeneous catalysts were recycled without remarkable decrease in catalytic efficiencies under five successive runs.

Synthesis and characterization of reinforced acrylate photosensitive resin by 2-hydroxyethyl methacrylate-functionalized graphene nanosheets for 3D printing

The acrylate photosensitive resin hybrids containing 2-hydroxyethyl methacrylate-functionalized graphene oxide (HEMA-g-GO/PRFRPCP) were prepared. 2-Hydroxyethyl methacrylate-grafted graphene oxide (HEMA-g-GO) was synthesized by in situ covalent functionalization of graphene oxide (GO) with 2-hydroxyethyl methacrylate (HEMA). The effects of HEMA-g-GO on the properties of the photosensitive resin were evaluated through evaluating the variation in viscosity and gel rate. Compared with GO, HEMA-g-GO addition doesn’t more markedly increase the viscosity and also doesn’t reduce the gel rate until the addition amount of HEMA-g-GO reaches 0.06 wt% in the resin. The best result of 3.6% volume shrinkage for the nanocomposite cured with UV irradiation from the resin hybrid HEMA-g-GO/PRFRPCP containing 0.06 wt% HEMA-g-GO was obtained. The nanocomposites show the enhancement in mechanical properties and thermal properties even with very small HEMA-g-GO additions (0.01–0.06 wt%). Furthermore, the behaviors of the nanocomposites under dynamic thermal conditions were examined with dynamic thermomechanical analysis, confirming that there is the excellent interfacial adhesion between HEMA-g-GO and the resin matrix which is responsible for the enhanced properties of the nanocomposites.

A Schiff base/quaternary ammonium salt bifunctional graphene oxide as an efficient adsorbent for removal of Th(IV)/U(VI)

A novel approach for facile covalent functionalization of graphene oxide (GO) was proposed in the present study in order to effectively avoid necessary anhydrous conditions and the usage of harsh reagents during the chemical functionalization of GO. Herein, a GO derivative that was functionalized with a primary amine derivative bearing a positively charged quaternary ammonium group, GO-S, was synthesized through a Schiff base condensation reaction between the amine groups of the primary amine derivative and the aldehyde groups of GO. The introduction of the quaternary ammonium groups can prevent GO from stacking and improve the dispersibility of GO after modification. The formation of imine bonds (NCH) between the primary amine and GO has been confirmed by Fourier transform infrared and X-ray photoelectron spectroscopy. The GO-S demonstrated good dispersion stability in aqueous medium and also exhibited better adsorption performance than GO for Th(IV) and U(VI), with a maximum thorium adsorption capacity of 2.22mmol/g and a maximum uranium adsorption capacity of 0.83mmol/g, suggesting a great potential for the application of graphene oxide-based materials for facilitating the removal of Th(IV) and U(VI) from nuclear waste solutions.

Elucidation of siRNA complexation efficiency by graphene oxide and reduced graphene oxide

Gene therapy has attracted tremendous attention as a promising method for the treatment of many diseases. Graphene oxide (GO), the oxidized form of graphene, is showing lot of potential in this field. Indeed, the polar GO oxygenated functional groups make this material highly hydrophilic, leading to a good dispersibility in water. Until now, the interaction of small interference RNA (siRNA) with graphene materials has not been elucidated. The main goal of this work was to develop a novel platform to complex siRNA molecules and to rationalize the supramolecular interactions between GO surface and the double strand RNA. Our study focused first on green and facile methods such as hydrothermal or vitamin C treatments to prepare graphene oxides at various percentage of oxygen. Epoxidation was also explored to reintroduce epoxide groups on reduced GO for further functionalization. Subsequently, we performed the covalent functionalization of GO with triethyleneglycoldiamine (TEG) and with low molecular weight polyethyleneimine (PEI) via the epoxy ring opening reaction. Finally, by gel electrophoresis, we were able to correlate the GO complexation ability with the graphene surface chemistry. In addition, ozonated GO functionalized with PEI showed a high complexing capacity for siRNA, proving to be a promising candidate for gene silencing.

Selenium-Functionalized Graphene Oxide That Can Modulate the Balance of Reactive Oxygen Species.

Graphene oxide (GO) is an important two-dimensional material since it is water-soluble and can be functionalized to adapt to different applications. However, the current covalent functionalization methods usually require hash conditions, long duration, and sometimes even multiple steps, while noncovalent functionalization is inevitably unstable, especially under a physiological environment where competing species exist. Diselenide bond is a dynamic covalent bond and can respond to both redox conditions and visible light irradiation in a sensitive manner. Thus, in this work by combining the stimuli response of diselenide bond and the oxidative/radical attackable nature of GO, we achieved the in situ covalent functionalization of GO simply by stirring GO with diselenide-containing molecules in aqueous solution. The covalent functionalization was proved by Fourier transform infrared, time-of-flight secondary ion mass spectrometry, atomic force microscopy, thermogravimetric analysis, and so forth, and the functionalization mechanism was deduced to involve both redox reaction and radical addition reaction according to the X-ray photoelectron spectrscopy, atomic emission spectroscopy, and Raman spectroscopy. Moreover, we modified GO with a biocompatible diselenide-containing polymer (mPEGSe)2 and found selenium-functionalized GO could modulate the balance of reactive oxygen species (ROS). GOSe could decrease ROS level by accelerating the reduction of peroxides when the ROS concentration is high while boosting the ROS level by in situ generating ROS when its concentration is relatively low.

Ultrafast Dye Removal Using Ionic Liquid–Graphene Oxide Sponge

A methylimidazolium ionic-liquid-functionalized graphene oxide (mimGO) sponge was prepared by facile amidation reaction followed by freeze-drying. Covalent functionalization of graphene oxide (GO) was confirmed by SEM, XRD, XPS, FT-IR, Raman and TGA. The mimGO sponge was employed to remove direct red 80 (DR80) dye from aqueous solutions. Results showed exceptional affinity for adsorption of azo dye direct red 80 (DR80) due to the charge-induced adsorption aided by protonated amine and cationic methylimidazolium ionic liquid pendant groups. Detailed adsorption characteristics of mimGO sponge including operational parameters, adsorption kinetics and adsorption isotherms were investigated. Adsorption on the mimGO sponge followed pseudo-second-order kinetic model, and the equilibrium capacity was described by the Langmuir adsorption model. An ultrahigh adsorption rate of 588.2 mg/(g·min) and equilibrium adsorption capacity of 501.3 mg/g for DR80 were observed for the mimGO sponge, which is much higher than th...

Electrocatalytic properties of [FeFe]-hydrogenases models and visible-light-driven hydrogen evolution efficiency promotion with porphyrin functionalized graphene nanocomposite

Five tolyl-functionalized monophosphine substituted diiron complexes [Fe2(CO)5(L){μ-SC6H3(CH3)S}] (L=PPh3, 2; Ph2PCH2Ph, 3; Ph2PCH2CH2CH3, 4; Ph2P(2-C5H4N), 5; P(4-C6H4OCH3)3, 6), which could be regarded as the active site models of [FeFe]-hydrogenases, have been successfully synthesized from parent complex [Fe2(CO)6{μ-SC6H3(CH3)S}] (1). The influence of the different phosphine ligands on the reduction potentials of the models has been evaluated by cyclic voltammetry (CV). According to the result of the electrochemical analysis, complexes 1, 2 and 5 were chosen to carry out the photocatalytic experiments. Meanwhile, tetraphenylporphyrin (TPP) covalently functionalized graphene oxide (GO) nanocomposite (TPP-GO) and cystine were applied as the photosensitizer and the electron-donor respectively in the [FeFe]-hydrogenases bionic photocatalytic system. The result of light-driven hydrogen (H2) evolution in aqueous ethanol solution demonstrated that the efficiency of H2 production is affected by following factors: the participation of GO or cystine, the covalent functionalization of GO by TPP and the hetero-atom on the phosphine ligand substituent of [FeFe]-hydrogenases models. Ultraviolet-visible (UV–vis) absorption, fluorescence emission and time-resolved fluorescence were used to analyze and compare the efficiency of electron transferring in the process of photocatalytic H2 production. And a possible mechanism for the light-driven H2 evolution of the photocatalytic system containing TPP-GO was proposed.

Covalent functionalization of graphene oxide with porphyrin and porphyrin incorporated polymers for optical limiting.

Porphyrin-graphene composites have attracted increasing attention due to a number of intriguing functions, and their photoelectrical and catalytic performances are expected to be modulated through different approaches. In the present study, a designed polymer based on phenyl sulfone, (p-amino)phenylhydroquinone, and a symmetrical dinaphthylporphyrin were covalently attached to a graphene oxide (GO) sheet. The formation of the nanohybrid was characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and Raman, ultraviolet-visible (UV-vis) absorption, steady and transient fluorescence spectroscopy techniques. The nonlinear optical and optical limiting performances of the hybrid were investigated using Z-scan measurements at 532 nm and 1064 nm. For comparison, a porphyrin functionalized GO hybrid was synthesized as a reference. At the same linear transmittance, the polymer functionalized GO exhibited a stronger optical limiting response and a larger nonlinear extinction coefficient than the individual GO, porphyrinated polymer, and porphyrin functionalized GO hybrid analogue, and its intrinsic photophysical mechanism was discussed in detail. More importantly, further improvement of its nonlinear optical properties can be achieved by the chemical reduction of the hybrid. The enhanced nonlinear optical performance originated from the effective combination of nonlinear scattering, reverse saturable absorption, and a possible photo-induced electron/energy transfer mechanism from donor porphyrin moieties in the polymer backbone to acceptor graphene. Our result might provide a new avenue for the development of graphene-porphyrin materials in the field of photocatalysis, nonlinear optics, and optoelectronic devices.

Hybrid formation of graphene oxide–POSS and their effect on the dielectric properties of poly(aryl ether ketone) composites

Covalent functionalization of graphene oxide with aminopropylisobutyl polyhedral oligomeric silsesquioxane efficiently reduced the dielectric constant of the polymer matrix.

Surface functionalization of graphene oxide with poly(2-hydroxyethyl methacrylate)-graft-poly(ε-caprolactone) and its electrospun nanofibers with gelatin

This article describes covalent functionalization of graphene oxide (GO) with poly(2-hydroxyethyl methacrylate)-graft-poly(e-caprolactone) [P(HEMA-g-CL)] via ‘living’ polymerization techniques and preparation of its electrospun nanofibers with gelatin. For this purpose, the GO was synthesized by oxidizing pristine graphite powder and then acetyl chloride was incorporated into the GO to afford an atom transfer radical polymerization (ATRP) macroinitiator (GO-Cl). The synthesized macroinitiator was employed for HEMA polymerization via ATRP technique to produce GO-g-PHEMA. Afterward, CL was graft copolymerized from the hydroxyl groups of the PHEMA via ring-opening polymerization approach to afford GO-g-[P(HEMA-g-CL)] nanocomposite. The solutions of the GO-g-[P(HEMA-g-CL)] and gelatin were electrospun to fabricate uniform, conductive, and biocompatible nanofibers. The morphology, in vitro degradability, biocompatibility, hydrophilicity, and conductivity of the GO-g-[P(HEMA-g-CL)]/gelatin electrospun nanofibers were investigated. It is expected that the prepared nanofibers find application as a scaffolding biomaterial for regenerative medicine, mainly due to their biocompatibility, degradability, and electrical conductivity.

Amino acids functionalized graphene oxide for enhanced hydrophilicity and antifouling property of poly(vinylidene fluoride) membranes

Herein, functionalized graphene oxide (GO) was prepared by the covalent functionalization with amino acids (lysine, glycine, glutamic acid and tyrosine) in this study. Zeta potential results demonstrated that covalent functionalization of GO with amino acids was favourable for their homogeneous dispersion in water and organic solvents. Based on the higher absolute value of zeta potential and the better dipersion stability of GO-lysine, the PVDF/GO-lysine hybrid membranes were then prepared via the phase inversion induced by immersion precipitation technique. SEM images showed a better pore diameter and porosity distribution on the PVDF/GO-lysine membrane surface. The zeta potential absolute value of the PVDF/GO-lysine membrane surface was higher than that of the virgin PVDF membrane. Furthermore, the PVDF/GO-lysine membranes surface exhibited good hydrophilicity. The water flux of PVDF/GO-lysine membranes can reach two times of that of the virgin PVDF membrane. And the BSA adsorbed amount on PVDF/GO-lysine surface was decreased to 0.82 mg/cm2 for PVDF/GO-lysine-8% membrane. Filtration experiment results indicated that the fouling resistance was significantly improved for the PVDF/GO-lysine membranes. As a result, lysine functionalized GO will provide a promising method to fabricate graphene oxide based hybrid membranes with effective antifouling property and hydrophilicity.

Solution-processable graphenes by covalent functionalization of graphene oxide with polymeric monoamines

We develop here a simple wet chemistry to prepare covalent functionalized graphenes (FGs) through epoxide aminolysis especially under alkaline aqueous condition. Remarkably, a series of typical monoamines, such as industrial Huntsman Jeffamine® M-2070 and M-2005 polymer with hydrophilic or hydrophobic polyetheramine chains, positively-charged 2-amino-N,N,Ntrimethylpropanaminium, negatively-charged sulfanilic acid, even oligopeptide sequence, can be effectively grafted on the platelets of graphene oxide precursor with covalent functionalization and partially reduced features. This strategy provides the researchers a facile and convenient approach to design and synthesize solution processable, biocompatible and functionalized graphenes for the potent applications in electronic inks, drug carriers and biomedicines. Expansion of the current study is actively ongoing in our laboratory.

Solvent-free one-step covalent functionalization of graphene oxide and nanodiamond with amines

Solvent-free covalent functionalization of graphene oxide and nanodiamond with amines was performed in one step at 150–180 °C.

Graphene oxide nanohybrid that photoreleases nitric oxide.

We report herein a photoresponsive nanoplatform that delivers nitric oxide (NO) on demand, achieved by the covalent functionalization of graphene oxide (GO) with an amino-terminated nitric oxide (NO) photodonor (NOP1). The resulting GO-NOP1 hybrid nanomaterial is dispersible in water, is very stable in the dark and has been thoroughly characterized by SEM, TEM, AFM, XRD, FTIR and UV-Vis absorption spectroscopy. Photolysis experiments demonstrate that the photodecomposition of the NO photoreleaser integrated into the GO scaffold occurs with an efficiency similar to that observed for a free model compound, ruling out any significant quenching effect (i.e. photoinduced energy/electron transfer) and accounting for the excellent preservation of its photochemical properties upon grafting. A combination of direct amperometric detection and indirect measurements based on a fluorometric assay prove that the remote-controlled release of NO from the GO-NOP1 nanoplatform is exclusively regulated by visible light stimuli.