Covalent Functionalization Of Graphene Oxide Research Articles

Covalent functionalization of graphene oxide

Covalent functionalization of graphene oxide

Covalent functionalization of graphene oxide

Covalent functionalization of graphene oxide

Covalent functionalization of graphene oxide with l-lysine for highly sensitive and selective simultaneous electrochemical detection of rifampicin and acetaminophen

Covalent functionalization of graphene oxide with l-lysine for highly sensitive and selective simultaneous electrochemical detection of rifampicin and acetaminophen

Graphene Oxide-BODIPY Conjugates as Highly Fluorescent Materials.

Covalent functionalization of graphene oxide (GO) with boron dipyrromethenes (BODIPYs) was achieved through a facile synthesis, affording two different GO-BODIPY conjugates where the main difference lies in the nature of the spacer and the type of bonds between the two components. The use of a long but flexible spacer afforded strong electronic GO-BODIPY interactions in the ground state. This drastically altered the light absorption of the BODIPY structure and impeded its selective excitation. In contrast, the utilisation of a short, but rigid spacer based on boronic esters resulted in a perpendicular geometry of the phenyl boronic acid BODIPY (PBA-BODIPY) with respect to the GO plane, which enables only minor electronic GO-BODIPY interactions in the ground state. In this case, selective excitation of PBA-BODIPY was easily achieved, allowing to investigate the excited state interactions. A quantitative ultrafast energy transfer from PBA-BODIPY to GO was observed. Furthermore, due to the reversible dynamic nature of the covalent GO-PBA-BODIPY linkage, some PBA-BODIPY is free in solution and, hence, not quenched from GO. This resulted in a weak, but detectable fluorescence from the PBA-BODIPY that will allow to exploit GO-PBA-BODIPY for slow release and imaging purposes.

Synthesis of Graphene oxide/Porphyrin Nanocomposite for Photocatalytic Degradation of Crystal Violet Dye

AbstractA novel nanocomposite was synthesized by covalent functionalization of graphene oxide (GO) with 5,10,15,20‐tetrakis(4‐hydroxyphenyl)porphyrinatoiron (III) chloride (Fe−THPP) via an ester linkage. The synthesized nanocomposite was characterized by various techniques such as XPS, Raman spectroscopy, BET, IR, UV‐Visible, TGA, SEM, and EDX. The synthesized nanocomposite exhibited appreciable interaction with crystal violet (CV) dye with a detection limit of 2.6×10−6 μg/mL and binding constant of 35.93×103 ppm−1 which ensured the high concentration of CV dye on the surface of synthesized photocatalyst. The nanocomposite was effectively utilized in the photo‐degradation of CV dye under visible light irradiation. The photo‐degradation efficiency was remarkably high (93.45 %) with a low catalytic dosage of 0.4 mg/L within 80 minutes. The nanocomposite exhibited good stability and reusability and thereby can be used in the photocatalytic degradation processes to treat wastewater.

Study of the water-oil interfacial activity of amino-modified graphene oxide

The interfacial properties of Graphene oxide (GO) based materials have been widely studied in emulsification processes. The 2D chemical structure and high reactivity of Graphene Oxide (GO) allows the properties modification as wettability and dispersibility. Furthermore, the functionalized GO has been tested as a surfactant agent; however, little or nothing is known about its mechanism of action. Here, we investigated the interfacial activity of amine-modified GO in a water-toluene system. To consider the effect of the aliphatic chain length, GO was functionalized by amidation reaction and nucleophilic substitutions with n-propylamine (GO@3 C) and n-dodecylamine (GO@12 C). The covalent functionalization of GO was confirmed by FTIR spectroscopy, Raman spectroscopy, XPS spectroscopy, XRD and their morphology were observed by Scanning Electron microscopy. Results showed that the chemical modification of GO with n-alkylamines can decrease the Interfacial Tension (IFT) of the water-toluene system as the nanomaterial concentration increase, like a molecular surfactant that obey the Traube´s rule. Wettability of the materials it was also determined by the sessile drop method, revealing that the GO hydrophobicity increases as the length of the aliphatic chain becomes longer. Characteristics of the emulsion droplets were determined by micrograph analysis, and it was revealed that the diameter size, stability, and kind of emulsion can be changed depending on the type of GO functionalization.

The effects of functionalized graphene oxide on the thermal and mechanical properties of liquid crystalline polymers.

Herein, we report a robust approach for the selective covalent functionalization of graphene oxide (GO) with 4-hydroxybenzoic acid (HBA) for developing polymeric nanocomposites based on liquid crystalline polymers (LCPs). The functionalization of GO with HBA was confirmed by Raman spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD) spectroscopy. The surface morphology of GO and functionalized GO (FGO) was studied using field emission scanning electron microscopy (FE-SEM). Furthermore, the interactions between FGO and LCPs have been investigated by FT-IR spectroscopy, whereas dispersion of GO and FGO in the LCP matrix was analyzed by FE-SEM. The better dispersion of FGO can be attributed to the hydrogen bonding and π-π stacking interactions between FGO and LCPs. Our results showed that even the addition of 5 wt% FGO in the LCP matrix significantly enhances the tensile strength and storage modulus of the pristine LCPs by 84% and 78% respectively. Compared to neat LCPs, FGO incorporated composites also demonstrate an improvement in the melting temperature (Tm) by 11 °C and glass transition temperature (Tg) by 12 °C. Furthermore, thermogravimetric analysis (TGA) was performed to evaluate the thermal stability of the composite. The 5 and 50% decomposition temperature for the LCP/FGO nanocomposites (containing 5 wt% FGO) increased by 75 °C and 107 °C respectively.

Advancing the boundaries of the covalent functionalization of graphene oxide

The synthesis of a derivatized graphene oxide with a particularly high degree of functionalization is achieved through a facile wet‑chemistry procedure. Graphene oxide is a highly reactive graphene derivative, especially with nucleophiles or dipolarophiles. However the reductive action of nucleophiles, as well as of other reactants or solvents usually prevails over functionalization. Therefore, the reactions of graphene oxide lead almost exclusively into reduced graphene derivatives with low functionalization degree. Here we report that tuning the reaction conditions during functionalization can alter the competition outcome of the two simultaneous reactions in a 1,3 dipolar cycloaddition on graphene oxide. Under these conditions, the cycloaddition pathway was dramatically favoured against the unspecific reduction/oxygen elimination side reactions, affording a selectively and densely functionalized graphene oxide. This property can be exploited for enhancing the interactions with target molecules (very effective immobilization of pharmaceutic compounds, as demonstrated here), as well as in other applications such as in preparing catalysts with high content of active sites by coordinating metal nanoparticles or atoms.

Covalent Functionalization of Graphene Oxide with Fructose, Starch, and Micro-Cellulose by Sonochemistry.

In this work, we report the synthesis of graphene oxide (GO) nanohybrids with starch, fructose, and micro-cellulose molecules by sonication in an aqueous medium at 90 °C and a short reaction time (30 min). The final product was washed with solvents to extract the nanohybrids and separate them from the organic molecules not grafted onto the GO surface. Nanohybrids were chemically characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy and analyzed by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray diffraction (XRD). These results indicate that the ultrasound energy promoted a chemical reaction between GO and the organic molecules in a short time (30 min). The chemical characterization of these nanohybrids confirms their covalent bond, obtaining a grafting percentage above 40% the weight in these nanohybrids. This hybridization creates nanometric and millimetric nanohybrid particles. In addition, the grafted organic molecules can be crystallized on GO films. Interference in the ultrasound waves of starch hybrids is due to the increase in viscosity, leading to a partial hybridization of GO with starch.

A novel composite based on pyrene thiazole grafted on graphene oxide:physico-chemical characterization and electrochemical investigations

We report the obtaining of a new composite starting from pyrene thiazole, a compound certified by nuclear magnetic resonance and its covalent grafting on the surface of graphene oxide. Novel material was synthesized in two stages: the first involving transformation of carboxyl groups of graphene oxide into acid chlorides and the second the amide reaction between acid chloride and amine group of pyrene thiazole (PTC). Numerous characterization methods have been used to certify this material, such as: Raman spectroscopy, fluorescence, infrared spectroscopy and X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. Their results show the successful covalent functionalization of graphene oxide with pyrene thiazole through the formation of amide bonds. The electrochemical investigation consisted of evaluating the redox behavior of the carbon screen printed electrodes modified with the new composite (GO-PTC) using caffeic acid, as analyte. From analytical point of view, it is relevant to be able to quantify the presence of caffeic acid and for such reason we used as analytical method the square wave voltammetry. The results showed that the GO-PTC modified carbon screen printed electrodes were able to detect the caffeic acid over more than one order of magnitude (linear working range: 0.005–0.1 mM) and GO-PTC modified electrodes can be considered promising for other analytical investigations.

Innovative Hyperbranched Polybenzoxazine-Based Graphene Oxide-Poly(amidoamines) Nanomaterials.

The covalent functionalization of graphene oxide (GO) surface with hyperbranched benzoxazine (BZ) structures has been achieved using poly(amidoamine) dendrimers (PAMAM) of different generations. By increasing the PAMAM generation, multiple benzoxazine rings were synthesized decorating the GO layers. The polymerization process and the exfoliation behavior were investigated. The novel BZ-functionalized GO hybrid materials were characterized by a combination of techniques such as FT-IR, XPS, and 1H-NMR for the confirmation of benzoxazine formation onto the GO layer surfaces. Raman and XRD investigation showed that the GO stacking layers are highly disintegrated upon functionalization with hyperbranched benzoxazine monomers, the exfoliation being more probably to occur when lower PAMAM generation (G) is involved for the synthesis of hybrid GO-BZ nanocomposites. The polymerization of BZ rings may occur either between the BZ units from the same dendrimer molecule or between BZ units from different dendrimer molecules, thus influencing the intercalation/exfoliation of GO. DSC data showed that the polymerization temperature strongly depends on the PAMAM generation and a significant decrease of this value occurred for PAMAM of higher generation, the polymerization temperature being reduced with ~10 °C in case of GO-PAMAM(G2)-BZ. Moreover, the nanoindentation measurements showed significant mechanical properties improvement in case of GO-PAMAM(G2)-BZ comparing to GO-PAMAM(G0)-BZ in terms of Young modulus (from 0.536 GPa to 1.418 GPa) and stiffness (from 3617 N/m to 9621 N/m).

Fabrication and properties for novel graphene oxide powder with extra large interlayer spacing and high reactivity

Exfoliation and preparation of large interlayer spacing and reactive graphene oxide (GO) powder are of crucial importance and neck technologies for their applications in polymer composites. Herein, we reported an innovative approach to prepare a large interlayer spacing reactive NCO-GO powder by covalent functionalization of GO with 4,4’-diphenylmethane diisocyanate (MDI). The morphology, microstructure, interlayer spacing, dispersion, and thermal stability of the NCO-GO powder were seriously investigated by FT-IR, XPS, XRD, TEM, TG, and Raman. Interlayer spacing of NCO-GO nanosheets was successfully expanded from 0.83 nm to 2.43 nm after modification, the NCO-GO powder showed better dispersion stability than GO in polar solvents and higher decomposition temperature. The fabricated novel NCO-GO powder showed a great prospect in the future to prepare graphene-based PU composites with significantly enhanced electrical conductivity and mechanical properties of PU elastomer.

Effects of solvent-free amine functionalization of graphene oxide and nanodiamond on bacterial growth

We studied the effect of covalent functionalization of graphene oxide (GO) and nanodiamond (ND) with octadecylamine (ODA) on bacterial growth (a series of experiments was performed also with pristine single-walled carbon nanotubes [SWNTs] for comparison). The bacteria tested were Escherichia coli and Staphylococcus aureus, which represent Gram-positive and Gram-negative types, respectively, and are of importance for the environment and human health. We found that pristine GO is the most toxic nanomaterial in both bacteria species, which exhibits a dose-dependent behavior. SWNTs show toxicity only against S. aureus at the higher concentrations of 1.0 and 10 mg/mL. Pristine ND, as expected, was found to be the least toxic against both species of bacteria, and in the experiments with S. aureus it even showed a viability amplifier activity at 10 mg/mL concentration. The use of ODA-functionalized nanomaterials generally changed the toxicity behavior, neutralizing the antibacterial effect of GO (for both S. aureus and E. coli), but making ODA-functionalized ND more toxic as compared to pristine material (with respect to S. aureus).

Amino Borate-Functionalized Reduced Graphene Oxide Further Functionalized with Copper Phthalocyanine Nanotubes for Reducing Friction and Wear

Covalent functionalization of graphene oxide (GO) was performed by 2-aminoethyl diphenyl borate (ADB) to overcome the demerits of plain GO/reduced GO (rGO) during lubrication such as the agglomerat...

Hydroxamic acid-functionalized graphene thin films as nanocatalysts towards organophosphate degradation

Herein we describe the covalent functionalization of graphene oxide with hydroxamic acid groups (GOHD) anchored directly on the carboxylate groups. The functionalization was confirmed by several characterization techniques, such as infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and Raman spectroscopy. The anchored groups have many potential applications, but we focused on its catalytic activity towards organophosphate (OPs) degradation, a serious environmental and health worldwide issue. The material was applied as nanocatalysts towards the degradation of the organophosphate of diethyl 2,4-dinitrophenyl phosphate and the real-life pesticide dimethyl 4-nitrophenyl phosphate (Paraoxon). High catalytic increments were obtained up to 108 fold (Paraoxon). Thus, reactions that would take over millions of years are reduced to a couple of days. Overall, the nanocatalyst shows potential as efficient detoxifying agents to eliminate chemical warfare stocks and pesticides by employing a practical material that can be deposited on any substrate and even over large areas.

SiO2-GO nanofillers enhance the corrosion resistance of waterborne polyurethane acrylic coatings

Corrosion to metal is a great challenge to major industries. Anticorrosive coatings can effectively prevent metal corrosion. In this study, we propose a novel method to prepare silica nanoparticles-covered graphene oxide (SiO2-GO) nanohybrids and anticorrosion SiO2-GO/waterborne polyurethane acrylic (WPUA) coatings. Firstly, we obtained silane-functionalized graphene oxide (A-GO) via a simple covalent functionalization of graphene oxide (GO) with 3-aminopropyltriethoxysilane. Secondly, SiO2-GO was synthesized by a simple sol–gel method with tetraethoxysilane in water–alcohol solution. Finally, the obtained SiO2-GO nanofillers were added into WPUA to prepare SiO2-GO/WPUA coatings. GO, A-GO, and SiO2-GO nanohybrids could be confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectra, and transmission electron microscope. SiO2-GO nanohybrids showed small size compared with the unfunctionalized GO. Meanwhile, GO, A-GO, and SiO2-GO nanofillers were added into WPUA. The electrochemical impedance spectroscopy and field emission scanning electron microscope indicate that SiO2-GO nanohybrids can be homogeneously dispersed in the WPUA coatings at 0.4% loading level and the SiO2-GO/WPUA film exhibits excellent anticorrosion performance. SiO2-GO nanoparticles can effectively utilize in the area of anticorrosive nanofiller industry. This study provides a convenient method of anticorrosive coating production.

Covalent functionalization of graphene oxide with hyperbranched lanthanum phthalocyanines for improving optical limiting

Abstract Two graphene oxide (GO)-based nanohybrid materials possessing axially covalent linkages to lanthanum phthalocyanines (LaPc-GO) and hyperbranched lanthanum phthalocyanines (HBLaPc-GO) were prepared. Significant fluorescence quenching demonstrates electron transfer between lanthanum phthalocyanine precursors and GO. At the identical mass concentration of 0.1 mg mL−1, all the hybrids show stronger nonlinear optical (NLO) performance than the individual components, ascribed to a combination of nonlinear scattering and two-photon absorption with reverse saturable absorption and the photoinduced electron or energy transfer from the electron donor phthalocyanine moiety to the acceptor graphene. Due to the better dispersion and the more flexible electron/energy transfer, the HBLaPc-GO exhibits a stronger optical limiting response (the normalized transmittances decrease to 49%) and a larger nonlinear extinction coefficient (1.48 cm GW−1) than that of LaPc-GO hybrid.

Surface-Induced in Situ Sonothermodynamically Controlled Functionalized Graphene Oxide for in Vitro Cytotoxicity and Antioxidant Evaluations.

Graphene oxide-based advanced functional materials offer an ultimate solution for wider biomedical applications. In situ thermodynamically ultrasound-assisted direct covalent functionalization of graphene oxide (GO) with sulfanilamide (SA) has synthesized f-(SA)GO. Raman spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy, selected area electron diffraction pattern, scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) have analyzed the f-(SA)GO structure for functional activities, expressed through synergistic impact of heteroatomic domains (SIHAD). The TGA of GO and f-(SA)GO demonstrates their total weight losses of 82.0 and 61.1%, respectively. Enhanced thermal stability of f-(SA)GO infers an exothermic behavior obtained with DSC. The surface-induced in situ thermodynamically controlled nonspontaneous reaction for f-(SA)GO has facilitated calculations for activation energy (Ea) = – 2.65 × 103 kJ mol–1 and Gibbs free energy (ΔG) = 8.3741 kJ mol–1, energetics for biological activities with sulforhodamine B assay on MCF-7 and Vero cell lines and antioxidant potential by free radical scavenging activity with DPPH (2,2-diphenyl-1-picrylhydrazyl). Cell viabilities are >89.8% for Vero and >90.1% for MCF-7 with f-(SA)GO over 10 to 80 μg mL–1. Its cytocompatibility infers establishment of a new material. The morphological effect on MCF-7 and Vero cell lines confirm its structurally stable biocompatibility. The SIHAD of f-(SA)GO scavenges radical activity, and its heteroatomic structure causes valuable physiochemical activities. f-(SA)GO could emerge as an advanced functional biomaterial for structurally and thermally stable biocompatible nanocoatings.

Covalent Functionalization of Graphene Oxide with a Presynthesized Metal-Organic Framework Enables a Highly Stable Electrochemical Sensing.

This paper reports the covalent functionalization of graphene oxide (GO) by a presynthesized metal-organic framework NH2-MIL-101(Fe) via ultrasonication of the two components. The formation of Fe-O covalent bonding in the NH2-MIL-101(Fe)-GO nanohybrid is clearly evidenced, and the covalent bonding still remains after electrochemical reduction. The morphology and structure of the nanohybrid are characterized via scanning electron microscopy, transmission electron microscopy, UV-vis spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectroscopy. The electrode based on electrochemically reduced NH2-MIL-101(Fe)-GO shows ultrastable and high-sensitive performance in simultaneous electrochemical sensing of three purine metabolic derivatives (uric acid, xanthine, and hypoxanthine); in particular, no signal fading is seen even after running for 120 times. The covalent bonding within the nanohybrid is obviously the key to maintain such a stability.

Functionalization of graphene oxide with poly(ε-caprolactone) for enhanced interfacial adhesion in polyamide 6 nanocomposites

Because interfacial adhesion between polymer chains and a nanofiller strongly influences the properties of polyamide nanocomposites, various approaches have been described to improve it. Here, we investigate the covalent functionalization of graphene oxide (GO) with poly(ε-caprolactone) and its application for the in situ synthesis of polyamide 6 nanocomposites. For the functionalization, GO moieties were used to initiate the polymerization of ε-caprolactone, which was followed by the separation of ungrafted polymer chains. TGA and FTIR confirmed covalent bonding between the GO and poly(ε-caprolactone). The synthesis of the nanocomposites was carried out by the in situ polymerization of ε-caprolactam containing either untreated or functionalized GO. TEM and AFM images of the nanocomposites containing the functionalized GO revealed the presence of single exfoliated nanofiller layers. DMA showed that the functionalized GO had a higher reinforcing effect than the untreated one. Thus, the obtained results suggest that our method is simple and effective for enhancing the interfacial adhesion between GO and polyamide 6.