Surface Functionalization Of Graphene Oxide Research Articles

In situ exfoliation and surface functionalization of graphene oxide for epoxy composites with improved thermal and mechanical properties

AbstractWet mixing and solvent evaporation were used to prepare in situ exfoliation and surface functionalization of graphene oxide (GO). The structure and composition of diglycidyl 7‐oxabicyclo[4.1.0]heptane‐3,4‐dicarboxylate (TDE85) functionalized GO (TDE85‐GO) were characterized. A thorough investigation was done into how surface functionalization affected the shape and dispersion of GO as well as the mechanical and thermal performance of the TDE85‐GO/epoxy composites. TDE85‐GO was evenly distributed throughout the matrix as a result of the special preparation method and excellent interfacial interaction between the functionalized GO and epoxy. By incorporating 0.5 wt% of TDE85‐GO, the molecular weight between crosslinks decreased from 435.1 to 182.0 g/mol, and the glass transition temperature significantly increased by 45.7°C from 148.8 to 194.5°C. The tensile strength, Young's modulus, and elongation at break increased by 18.3%, 3.7%, and 29.9%, respectively. Moreover, thermomechanical and water resistance properties have also been improved. This approach is a workable one to produce high‐performance structural composites. This approach represents a practical strategy for developing high‐performance structural composites.Highlights In situ exfoliation and surface functionalization of graphene oxide. Glass transition temperature increased by 45.7°C with 0.5 wt% of TDE85‐GO. Tensile, thermomechanical, and water resistance properties were improved.

Surface Functionalization of Graphene Oxide with Polystyrene Sulfonic Acid Brushes to Fabricate Hierarchical Ag and Au Microstructures as SERS Substrates

AbstractIn this work, we reported the spontaneous growth of Ag and Au microstructures on the surface of the graphene oxide‐grafted‐polystyrene sulfonic acid brushes (GO‐g‐PSSA) in Ag(NH3)2OH solution and HAuCl4 solution, respectively. The influences of reaction time and temperature on the morphology and size of Ag (Au) particles were investigated. By optimizing reaction conditions, Ag nanosheet‐assembled microstructures and sea urchin‐like Au microspheres were obtained. These hierarchical Ag (Au) microstructures with highly nanotextured topographies could provide many “hot spots” for surface‐enhanced Raman spectroscopy (SERS). The as‐prepared GO‐g‐PSSA/Ag (Au) composites exhibited excellent SERS performances using Rhodamine 6G (R6G) as the probe molecules and the detection limit of R6G was up to 10−12 m.

Surface Functionalization of Graphene Oxide with Silver Nanoparticles Using Phyto Extract and its Antimicrobial Properties Against Biological Contaminants

Surface Functionalization of Graphene Oxide with Silver Nanoparticles Using Phyto Extract and its Antimicrobial Properties Against Biological Contaminants

Surface functionalization of graphene oxide with tannic acid: Covalent vs non-covalent approaches

Graphene oxide (GO) is gaining a lot of interest in material science, biomedicine and biotechnology due to its outstanding physical properties, combined with its surface functionalization capacity, processability in aqueous media and biocompatibility. However, van der Waals forces among GO layers result in aggregation, yet its dispersion, large-scale production, and reinforcing efficiency remain challenging. Herein, simple and environmentally friendly methods via covalent and non-covalent routes have been developed to exfoliate and prepare surface-functionalized GO nanosheets with tannic acid (TA), a biological macromolecule with antioxidant activity. Four esterification strategies were tested: direct, carbodiimide activated, oxalyl chloride acylation and via an acid-functionalized GO intermediate. The resulting samples have been extensively characterized to get knowledge on the GO-TA interactions and the degree of grafting, as well as their surface topography, level of hydrophilicity, solubility/dispersibility, thermal and antibacterial properties. The covalent grafting of TA renders the GO surface more hydrophobic, resulting in improved dispersion in organic solvents. Besides, TA acts as a crosslinker between the GO nanosheets, leading to higher thermal resistance. A synergistic effect of both GO and TA on inhibiting bacterial growth has also been found. The esterification via carbodiimide leads to the highest grafting degree, the best thermal stability and the most effective antibacterial activity. This work not only highlights the great potential of TA for both exfoliation and surface functionalization of GO, but also extends its applications in biomedicine and for the development of green nanocomposites.

Surface Functionalization of Graphene Oxide with Hyperbranched Polyamide-Amine and Microcrystalline Cellulose for Efficient Adsorption of Heavy Metal Ions.

Graphene oxide (GO)-based adsorbents have received attention in the removal of heavy metal ions in wastewater due to its large specific surface area and oxygen-containing functional groups, which can enhance the interaction between GO and heavy metal ions. Many researchers are seeking economical and effective strategies to further improve the adsorption capacity of GO. In this study, hyperbranched polymers and cellulose were used to surface functionalize GO for the efficient adsorption of heavy metal ions. First, hyperbranched polyamide-amine (HPAMAM) functionalized GO was fabricated by the formation of an amide bond between the carboxyl group of GO and the amino group of HPAMAM, increasing the active groups on the GO surface and enhancing the affinity with heavy metal ions. Then, dialdehyde cellulose (DAC) obtained through the oxidation of microcrystalline cellulose was grafted onto GO/HPAMAM by forming a Schiff-based structure between the amino group of HPAMAM and aldehyde group of DAC. Interestingly, DAC formed micro/nano bumps on GO, which was beneficial to increase the hydroxyl number and contact area with heavy metal ions. The Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) results confirmed the successful synthesis of GO/HPAMAM/DAC. The obtained GO/HPAMAM/DAC adsorbent exhibited strong adsorption capacity and good cycle stability for heavy metal ions. The maximum adsorption capacities of Pb(II), Cd(II), and Cu(II) were 680.3, 418.4, and 280.1 mg/g at 298 K, which were better than those of most adsorbents reported. A pseudo-second-order kinetic model could well-describe the Pb(II), Cd(II), and Cu(II) adsorption onto GO/HPAMAM/DAC, and the equilibrium data fitted well with the Langmuir isotherm model. The adsorption of Pb(II), Cd(II), and Cu(II) was mainly attributed to the chelation or complexation of nitrogen- and oxygen-containing groups on the GO/HAPAMAM/DAC adsorbent. This study may provide a novel strategy for improving the adsorption performance of GO with hyperbranched polymers and cellulose.

Surface functionalization of graphene oxide by sulfonation method to catalyze the synthesis of furfural from sugarcane bagasse

Surface functionalization of graphene oxide by sulfonation method to catalyze the synthesis of furfural from sugarcane bagasse

Efficient reinforcement of epoxy resin with amine‐rich rigid short‐chain grafted graphene oxide

AbstractFor improving the mechanical properties of epoxy resin (EP), it is an effective strategy to utilize surface‐modified graphene oxide (GO) as a reinforcement. However, there is nearly no report on surface modification using rigid short‐chain grafted GO, especially with multiple reactive sites. In this work, a novel surface functionalization of GO with an amine‐rich rigid short‐chain was successfully prepared and applied as a filler for EP with simultaneously high toughness and mechanical strength. Superior toughness and mechanical strength of the resultant epoxy nanocomposite can be obtained by grafting amine‐rich rigid short‐chain onto GO (DHN‐GO) owing to the enhanced interface binding ability with the EP and the optimized dispersibility in the matrix. Compared with the pure EP, the epoxy nanocomposites at an extremely low loading (0.75 wt‰) of DHN‐GO showed excellent mechanical properties. The tensile strength, elongation at break, and bending strength are increased by 28%, 37%, and 29%, respectively. This work is expected to provide more inspiration for the preparation of GO/EP composites with high toughness and mechanical strength.

Surface Functionalization of Graphene Oxide with Polymer Brushes for Improving Thermal Properties of the Polymer Matrix

In this work, polymethyl methacrylate (PMMA) and polystyrene (PS) with controlled structures would be grafted on graphene material. The hybrid materials were prepared by coating graphene oxide (GO) with polydopamine (PDA) as a reactive underlayer and reducing agent, subsequently, surface-initiated polymerization of monomers (methyl methacrylate, styrene) based on the activators regenerated electron transfer atom transfer radical polymerization (ARGET-ATRP) technique. The polymer brush-modified graphene materials were then incorporated into the PMMA or PS matrix to get polymer nanocomposites with better thermal properties. The results of Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermal gravimetric analysis (TGA) demonstrated that PMMA and PS chains were successfully anchored on the surfaces of functionalized GO sheets. The influence of the grafted polymer brush-modified GO on thermal stability of PMMA and PS was investigated by a simultaneous thermal analyzer. Thermal conductivity of the polymer nanocomposite was determined by a conductive calorimeter. The results showed that thermal stability, glass transition temperature ( T g ), and thermal conductivity of the polymer nanocomposites were obviously improved compared with pure PMMA or PS.

Enhanced mechanical properties of epoxy nanocomposites with mildly surface-functionalized graphene oxide by tuned amine species

The surface functionalization of graphene oxide (GO) is always attractive in modulating the interfacial characteristics, improving the interfacial bonds and mechanical properties of epoxy-based nanocomposites. In this contribution, amine functionalized graphene oxide (AGO) samples were prepared through the surface functionalization of GO using m-xylylenediamine (m-XDA) and polyetheramine D230, respectively. Simultaneously, weakly oxidized and normally oxidized GO samples were both functionalized to obtain AGO samples with low and high amine grafting density. AGO/epoxy nanocomposites were fabricated and their mechanical properties at room temperature (RT) and liquid nitrogen temperature (LNT) were investigated. Interfacial characteristics of the nanocomposites were revealed through experimental and molecular dynamics (MD) simulation methods. It was found that m-XDA grafted GO (MAGO) showed better dispersion in the matrix and prominently higher efficiency in enhancing the mechanical properties of epoxy resin than D230 grafted GO (DAGO). MAGO nanocomposites exhibited tensile strength 18.1% and 11.3% higher than neat epoxy at RT and LNT, respectively. The result was highly consistent with the enhanced interfacial interaction energy between MAGO and epoxy compared to that between DAGO and epoxy as revealed by MD simulation. However, nanocomposites modified by AGO with improved amine grafting density didn’t show enhanced mechanical properties as expected from MD simulation.

Enhanced thermal and energetic properties of NC-based nanocomposites with silane functionalized GO.

The surface functionalization of graphene oxide (GO) is always attractive in improving certain properties of the polymer. In this study, 3-aminopropyltriethoxysilane (APTES) and 3-mercaptopropyl-trimethoxysilane (SPTES) have been used to make silane functionalized graphene oxides (SiGOs). The APTES-grafted GO (NH-SiGO), SPTES-grafted GO (SH-SiGO) and pure GO have been separately introduced into the nitrocellulose (NC) matrix. The morphology, thermal properties and energetic properties of the prepared nanocomposites (NH-SiGO and SH-SiGO) were investigated comprehensively. It is shown that the presence of GO and SiGOs have different influences on the thermal reactivity of NC with various contents, and NH-SiGO with 0.5 wt% content showed better catalytic performance on the thermal decomposition of NC than others and showed prominently higher efficiency in improving its heat of combustion. Adding 0.5 wt% of NH-SiGO to NC may decrease its decomposition temperature from 202.1 °C to 196.6 °C, and the residue was decreased from 10.61 wt% to 3.95 wt%, respectively. One isoconversional kinetic method was exploited to determine the kinetic parameters of NC and its nanocomposites. It was found that NH-SiGO had a strong catalytic action on the thermal decomposition of NC-based nanocomposites for which the activation energy and the pre-exponential factor were considerably lowered, while SH-SiGO exhibited an inverse effect. The heat of combustion from NC/GO/0.5, NC/NH-SiGO/0.5 and NC/SH-SiGO/0.5 were determined as 11 249.5, 11 675.1 and 11 491.5 J g-1, respectively, which are higher than that of the pure NC (10 908.4 J g-1). From the combustion process of NC/NH-SiGO/0.5, it was shown that the nanocomposite was combusted completely.

On the Effect of Ultralow Loading of Microwave-Assisted Bifunctionalized Graphene Oxide in Stereolithographic 3D-Printed Nanocomposites.

Surface functionalization of graphene oxide (GO) is one of the best ways to achieve homogeneous dispersions of GO within polymeric matrices and composites. Nonetheless, studies regarding how the level of GO functionalization affects the macroscopic properties of three-dimensional (3D) printed nanocomposites are still few. Furthermore, the bifunctionalization of GO with the NH2/NH3+ groups to obtain improved thermomechanical macroscopic properties at ultralow loads has not been reported. In this paper, fast and straightforward surface bifunctionalization of GO with a controlled ratio of NH2/NH3+ groups at low, medium, and high functionalization levels (AGOL, AGOM, and AGOH) in a one-step microwave-assisted synthesis is reported for the first time. The functionalization mechanism was disclosed, wherein three graft densities (Gφ) were obtained. A plateau of maximum functionalization (Gφ = 4.9 μmol/m2 = 2.9 molecules/nm2) was reached, suggesting that full coverage of the GO surface is achievable. Also, an increase in the exfoliation of functionalized layers was obtained, ranging from d002 = 8.6 Å up to d002 = 15.8 Å. X-ray photoelectron spectroscopy (XPS) reveals the successful functionalization of GO, as well as an atomic relationship NH2/NH3+ of about 50/50% in all functionalized samples. Stereolithographic (SLA) 3D-printed nanocomposites (AGOL/R, AGOM/R, and AGOH/R) were obtained using ultralow loads (0.01 wt %) of each bifunctionalized material. This ultralow amount was sufficient to enhance thermal stability (up to 4 °C) and a significant increase in the glass transition temperature (93 °C ≤ Tg ≤ 120 °C). Interestingly, we found that low and medium grafting density promotes a ductile material (ε > 5%); meanwhile, a high graft density produces brittle materials. Also, we observe that the toughness can be tuned as a function of the graft density (AGOH: 24 MPa, AGOM: 342 MPa, AGOL: 562 MPa) at ultralow loadings. The 3D-printed nanocomposites using GO with low graft density (AGOL) increase their tensile strain by 90% in comparison with the control sample (without filler). Finally, the underlying mechanisms were discussed to explain the findings.

Embedding of L–Arginine into graphene oxide (GO) for endotoxin removal from water: Modeling and optimization approach

Endotoxin, also called lipopolysaccharides (LPS), has strong biological effects, even at a very low concentration in humans. In this study, surface functionalization of graphene oxide (GO) with L–Arginine amino acid was successfully prepared using epichlorohydrin as a coupling agent (GO–EPI–L–Arg) for endotoxin removal from water. Characterization of Novel GO–EPI–L–Arg was confirmed by an analytical technique. The model was optimized using response surface methodology (RSM) via various input parameters. The effect of concomitant anions was also investigated to establish and simulate competitive endotoxin adsorption in real hemodialysis water supply. The pH and endotoxin concentration had an antagonistic effect on the quadratic model. The endotoxin adsorption process was better fitted by pseudo-second-order model with Qmax value of 139.47 EU/mg, while the equilibrium followed the Langmuir isotherm with the maximum monolayer adsorption capacity of 154.85 EU/mg. The coefficient of determination (R2=0.9761), non–significant lack of fit (p > 0.05), and p–value with low probability (<5.596 × 10–11) revealed a regression model with a good fit with input variables. The GO–EPI–L–Arg nanocomposite could be regenerated more than four times based on their adsorption-desorption cycles, with a slight loss in adsorption capacity. The results suggested that the GO–EPI–L–Arg can be applied as an effective adsorbent for endotoxin removal from water.

Application of deep eutectic solvent for conjugation of magnetic nanoparticles onto graphene oxide for lead(II) and methylene blue removal

Abstract Deep eutectic solvents (DESs) have emerged as a substitute for ionic liquids with lower cost and enhanced biodegradability. The most common class of DES refers to a mixture of a quaternary ammonium or phosphonium salt and a hydrogen bond donor (e.g., carboxylic acid) with a melting point lower than that of individual components. DESs have recently shown promise for surface modification of graphene oxide (GO) nanosheets with different functional groups. We hypothesize that such surface functionalization of GO (and other carbon nanomaterials) with DESs can provide a new route to conjugate metallic nanoparticles onto GO surfaces (and similar). Here, we used a typical DES, based on choline chloride and urea, for the conjugation of pre-synthesized Fe3O4 nanoparticles onto GO nanosheets at different GO:Fe3O4 ratios. Physicochemical characterization not only confirmed the ability of DES to prepare DES/GO-Fe3O4 nanohybrids successfully, but also evidenced the influence of DES on the homogeneity and size distribution of Fe3O4 nanoparticles in these nanohybrids. DES/GO-Fe3O4 nanohybrids can perform better than both GO and Fe3O4 as adsorbents for organic dyes (methylene blue, MB) and heavy metals (Lead (II)). However, depending on the contaminant type, the contaminant removal performance varied differently for DES/GO-Fe3O4 nanohybrids with different ratios.

Surface functionalization of graphene oxide using amino silane magnetic nanocomposite for Chromium (VI) removal and bacterial treatment

Amino silane magnetic nanocomposite decorated on graphene oxide (GO-Fe3O4-APTES) was successfully prepared by organic transformation reaction followed by co-precipitation method. The nanocomposite was characterised by using FT-IR, XRD, FE-SEM, TEM, EDS mapping, VSM, Raman spectroscopy, BET surface area analyzer, Zeta potential and UV-visible spectrophotometer. From TEM results we observed that 8 nm sized particles successfully modified on GO surface. The surface area of GO-Fe3O4-APTES was 57.9 m2 g−1. The magnetic Saturation value of GO-Fe3O4-APTES was 30.6 emu g−1 and the S-like magnetization of all the samples shows super paramagnetic in nature. Due to magnetic nature adsorbent, it could be easily separated from aqueous solution. GO-Fe3O4-APTES material was highly selective for Chromium (VI) removal from aqueous solution. About 91% of Chromium (VI) was removed at pH 3, 160 rpm of shaking speed, 0.3 g l−1 of adsorbent dose and 10 h of contact time. The adsorption process of Chromium (VI) on GO-Fe3O4-APTES follows Pseudo-second-order kinetic and Langmuir isotherm model because of high coefficient of determination value (R2 = 0.99). The maximum adsorption capacity (qm) of GO-Fe3O4- APTES was observed at 60.53 mg g−1. The synthesized material was desorbed with 0.5 M NaOH and recycled up to five cycles. After five cycles, the removal efficiency of Chromium (VI) possesses high efficacy towards GO-Fe3O4-APTES. Mechanistically, adsorption of Chromium (VI) follows strong electrostatic attraction between adsorbate and adsorbent. GO-Fe3O4-APTES has potential adsorbent for the adsorption of Chromium (VI) in waste water treatment. Furthermore, the GO-Fe3O4-APTES were tested for antibacterial properties against gram negative (Escherichia coli) and gram positive (Bacillus subtilis) bacterial strain. The synthesized material responds positively towards antibacterial activity.

Direct surface functionalization of graphene oxide with ionic liquid through gamma ray irradiation induced radical polymerization with remarkable enhanced adsorption capacity

Abstract A facile one-step synthesis method based on Gamma ray irradiation induced radical polymerization was proposed for the first time for preparation of graphene oxide-ionic liquid composites (GO@IL) using 3-n-Hexadecyl-1-vinylimidazolium bromide ([C16VIm+] [Br−]) as the monomer. The GO@IL composites were utilized as adsorbents for adsorption and separation of Sunset Yellow (SY) and chromium (Cr, VI) ions from the stock solution. The maximum adsorption capacities of prepared GO@IL to adsorb SY and Cr (VI) were observed in the acidic media at room temperature, with the maximum adsorption capacities of 169.6 and 75.8 mg g−1, respectively. Various adsorption kinetics and isotherm models were employed to fit adsorption data to better understand the adsorption process and behavior of contaminants onto GO@IL surfaces. The value of ΔG0 and ΔH0 implied the adsorption were initiative and endothermic nature for SY and Cr (VI). The electrostatic and π − π stacking interactions were expected to be involved in the adsorption for SY and Cr (VI) onto the functionalized graphene oxide composite. These data illuminate that the adsorption performance of graphene oxides has enhanced remarkable after polymerization with [C16VIm+] [Br−] on their surface. Considering the regeneration ability, the easily synthetic GO@IL composites with great promise applications for wastewater treatment and purification.

Most suitable amino silane molecules for surface functionalization of graphene oxide toward hexavalent chromium adsorption

Adsorption is a simple and effective method for the removal of hexavalent chromium (Cr(VI)) from contaminated water. Several amino silane–graphene oxide (GO) composites with different species of amino groups (pN-GO, psN-GO, and pssN-GO; p: primary, s: secondary, N: amine) were evaluated to investigate their adsorption capacity and the effects of primary and secondary amines on Cr(VI) adsorption. We conducted a quantitative analysis to reveal the difference between primary and secondary amines in terms of Cr(VI) removal efficiency. A synergic effect was observed between the neighboring secondary amines in pssN-GO. From the Langmuir model prediction, we found that the composite with pssN-GO exhibited the highest maximum adsorption capacity (260.74 mg/g), followed by those with psN-GO (208.22 mg/g) and pN-GO (189.47 mg/g). Monolayer adsorption was more dominant when using pssN-GO, with the pseudo-second-order model best fitting the kinetic experiment results, whereas multilayer adsorption was dominant when using psN-GO and pN-GO.

New mixed matrix PEI nanofiltration membrane decorated by glycidyl-POSS functionalized graphene oxide nanoplates with enhanced separation and antifouling behaviour: Heavy metal ions removal

Surface functionalization of graphene oxide (GO) nanoplates was performed by glycidyl polyhedral oligosilsesquioxane (POSS), and was used to fabrication of polyetherimide (PEI) based nanofiltration membranes by phase inversion method. The prepared membranes characterized by Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray spectrometry (EDX) and atomic force microscopy (AFM) analysis. The effect of different concentrations of glycidyl POSS-GO (PG) in membrane matrix on separation performance and antifouling property of blended membranes was investigated by contact angle measurement, pure water flux, Na2SO4, Pb(NO3)2, CrSO4 and Cu(NO3)2 rejection and flux recovery ratio. The blended PEI/PG membranes showed significant separation performance and antifouling properties compared with neat PEI and PEI/GO membranes. The highest pure water flux measured 74.77 (L/m2·h) for the blended membrane with 0.001 wt% of PG whereas it was 51.06 (L/m2·h) for the PEI/GO membrane and 17.63 (L/m2·h) for pristine membrane at 4.5 bar pressure. The blended PEI/PG membranes showed outstanding Na2SO4 and Pb(NO3)2, CrSO4, and Cu(NO3)2 rejection compared to blended PEI/GO membranes and neat PEI ones. Furthermore, the highest flux recover ratio (FRR) value was obtained (96%) for the blended [PEI/0.1 %wt PG] membrane whereas FRR was (40%) for PEI/GO and (33%) for the neat PEI membranes.

Surface functionalization of graphene oxide by disodium guanosine 5′-monophosphate and its excellent performance for lipase immobilization

Abstract In order to solve the toxic and hazardous issues of the agents in the chemical reduction process of graphene oxide (GO), disodium guanosine 5′-monophosphate (GMP-2Na) was used as an ideal reducing agent for the synthesis of functionalized GO (FGO) for lipase immobilization. At the condition of low amount adsorption of GMP-2Na indicated by the N1s spectra of X-ray photoelectron spectroscopy (XPS), the C/O atomic ratio of the FGO increased from 2.09 to 3.12, indicating the reduction of GO. As the amount of GMP-2Na increased, the intensity of the characteristic peak of GO in the XRD pattern decreased, and the I D /I G peak intensity of Raman spectra increased during the functionalization process. It was found that when the concentration of GMP-2Na is 0.20 mg/mL, the degree of hydrophobicity of FGO is conducive to the formation of optimal conformation of lipase. After immobilization, the activity of the immobilized enzyme reaches twice the value of free enzyme. At the same time, the protein loading reaches to 600 mg/g. The immobilized enzyme showed enhanced durability since no obvious decrease was observed after incubation for 8 h at pH 6.0 and pH 7.0. After storage for 35 days, the activity of GO-G@ enzyme was 54.47% higher than that of free enzyme. GO reduced by GMP-2Na provides a possibility to obtain a highly efficient lipase immobilization carrier.

Surface functionalization of graphene oxide with DBU as electrode materials for supercapacitors

Nitrogen-containing groups functionalized graphene has been synthesized via the reaction of graphene oxide with 1, 8-diazoicyclo (5, 4, 0) undecene-7, trimethylamine (DBU) through epoxide-ring-open reaction without high temperatures. Samples were analyzed by x-ray diffraction spectroscopy, Raman, N2 adsorption-desorption, transmission electron microscope, galvanostatic charge/discharge, and cyclic voltammetrys. Results show that the amount of added DBU has great influence on the structure and properties of the resultant graphene. The DBU modified graphene with appropriate N content and low charge transfer resistance exhibits 190 F g−1 at 5 mV s−1 in 6 M KOH aqueous solution. This will also provide a new strategy for configuring nitrogen-containing groups functionalized graphene electrode materials for supercapacitors and other energy storage devices.

Simultaneous reduction and surface functionalization of graphene oxide by cystamine dihydrochloride for rubber composites

The simultaneous reduction and functionalization of graphene oxide (GO) was achieved through a chemical grafting reaction with cystamine dihydrochloride (CDHC), a novel functional agent with dynamic disulfide bond. CDHC-reduced GO (CGO) can be uniformly and stably dispersed in the aqueous phase. Furthermore, CGO reinforced styrene-butadiene rubber (SBR) composites with highly filled silica content were prepared by a latex mixing and coagulation process. TEM confirmed both CGO and silica can be uniformly dispersed in the rubber matrix. The dynamic disulfide bonds of the grafted CDHC in the CGO can participate in the subsequent vulcanization of SBR rubber through disulfide exchange reactions, thereby forming a tight interaction between GO and rubber. Compared with normally reduced GO system, the mechanical and thermal properties of CGO-containing rubber nanocomposites were significantly improved. The results show that CGO is effective to reinforce rubber composites, which has the potential to be used for tire rubber materials.