Synthesis of graphene soluble in organic solvents by simultaneous ether-functionalization with octadecane groups and reduction

Octadecane-functionalized graphene (OD-G) soluble in organic solvents was produced by combining the Hummers process for graphite oxidation and a simultaneous ether-functionalization and reduction approach with 1-bromooctadecane in pyridine and dimethylformamide (DMF). The exfoliated OD-Gs were testified to be monolayer sheets by transmission electron microscope (TEM) and atomic force microscopy (AFM). The functionalization with octadecane (OD) groups and the effective deoxygenation of graphene oxide (GO) were confirmed by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). It is proved that the effective reduction and functionalization of GO could be simultaneously completed during the refluxing process. The functionalization with OD groups can effectively prevent the aggregation of GO during the reduction.     

Synthesis and characterization of Rosebengal/folicacid-functionalized multiwall carbon nanotubes

Multiwall carbon nanotubes (MWCNTs) were functionalized with a photosensitizer, rosebengal (RB), and folicacid (FA), an anti-cancer drug simultaneously and individually, which was characterized with various analytical instruments like Fourier Transform Iinfrared (FTIR) spectroscopy, UV–Vis spectroscopy, Thermogravimetric analysis (TGA), Photoluminescence (PL) spectroscopy, X-ray photoelectron spectroscopy (XPS), and Transmission electron microscopy (TEM). FTIR spectra confirmed the chemical modification of MWCNT. The chemical functionalization of MWCNT with RB was further supported by UV–Vis and PL spectra.     

The synthesis and fluorescence quenching properties of well soluble hybrid graphene material covalently functionalized with indolizine

Chemically functionalized graphene-indolizine functionalized graphene (IMG) sheets, which can be well dispersed in different organic solvents over four months without obvious aggregation, are obtained through a 1,3-dipolar cycloaddition to graphene with pyridinium ylide. The properties of IMG sheets are investigated using a thorough set of measurements including UV-visible spectroscopy, Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL), transmission electron microscopy (TEM), atomic force microscopy (AFM) and cyclic voltammetry (CV), and a tagging technique has exhibited the distribution of functional groups on the graphene surface. The IMG sheets show very strong quenching by a factor of ～ 93.4% to that of indolizine, which is attributed to the fluorescence resonance energy transfer (FRET) from indolizine molecules to few-layer graphene sheets. The CV method also proved the catalytic properties of IMG sheets in some redox systems.     

Synthesis and characterization of stable aqueous dispersions of graphene

A stable aqueous dispersion (5 mg ml^?1) of graphene was synthesized by a simple protocol based on three-step reduction of graphene oxide (GO) dispersion synthesized using the modified version of Hummers and Offeman method. Reduction of GO was carried out using sodium borohydride, hydrazine hydrate and dimethyl hydrazine as reducing agents. The chemically synthesized graphene was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–visible absorption spectroscopy, Fourier transform infrared (FTIR) and Raman spectroscopy, thermogravimetric analysis (TGA), optical microscopy. The stability of aqueous dispersions of graphene was confirmed through zeta potential measurements and the negative zeta potentials of 55–60 mV were obtained indicating the high stability of aqueous graphene dispersions.     

Crystallization,mechanical performance and hydrolytic degradation of poly(butylene succinate)/graphene oxide nanocomposites obtained via in situ polymerization

Poly(butylene succinate) (PBS)/graphene oxide (GO) nanocomposites were fabricated via in situ polymerization with very low GO content (from 0.03 to 0.5 wt%). The microstructures of the nanocomposites were characterized with Raman spectroscopy, fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), sedimentation experiments and atomic force microscopy (AFM). The results showed that PBS chains have been successfully grafted onto GO sheets during in-situ polymerization, accompanied by the thermo-reduction from GO to graphene. The grafted GO displayed a great nucleating effect on PBS crystallization, resulting in largely improved crystallization temperature and decreased spherules size. A simultaneous enhancement in tensile strength and elongation was achieved for PBS/GO nanocomposites fiber. Meanwhile, increase in hydrolytic degradation rate was also observed for these nanohybrids. Our result indicates that using very low content GO is a simple way to achieve good dispersion yet with remarkable property enhancement for polymer/GO nanocomposites.     

Graphene oxide‐ellagic acid nanocomposite as effective anticancer and antimicrobial agent

In this study, ellagic acid (ELA), a skin anticancer drug, is capped on the surface(s) of functionalised graphene oxide (GO) nano‐sheets through electrostatic and π–π staking interactions. The prepared ELA‐GO nanocomposite have been thoroughly characterised by using eight techniques: Fourier‐transform infrared spectroscopy (FTIR), zeta potential, X‐ray diffraction (XRD), thermogravimetric analysis (TGA), Raman spectroscopy, atomic force microscopy (AFM) topographic imaging, transmission electron microscopy (TEM), and surface morphology via scanning electron microscopy (SEM). Furthermore, ELA drug loading and release behaviours from ELA‐GO nanocomposite were studied. The ELA‐GO nanocomposite has a uniform size distribution averaging 88 nm and high drug loading capacity of 30 wt.%. The in vitro drug release behaviour of ELA from the nanocomposite was investigated by UV–Vis spectrometry at a wavelength of λ _max 257 nm. The data confirmed prolonged ELA release over 5000 min at physiological pH (7.4). Finally, the IC ₅₀ of this ELA‐GO nanocomposite was found to be 6.16 µg/ml against B16 cell line; ELA and GO did not show any cytotoxic effects up to 50 µg/ml on the same cell lines.     

Temperature dependence of graphene oxide reduced by hydrazine hydrate

Graphene oxide (GO) was successfully prepared by a modified Hummer's method. The reduction effect and mechanism of the as-prepared GO reduced with hydrazine hydrate at different temperatures and time were characterized by x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), x-ray diffractions (XRD), Raman spectroscopy and thermo-gravimetric analysis (TGA). The results showed that the reduction effect of GO mainly depended on treatment temperature instead of treatment time. Desirable reduction of GO can only be obtained at high treatment temperature. Reduced at 95?°C for 3 h, the C/O atomic ratio of GO increased from 3.1 to 15.1, which was impossible to obtain at low temperatures, such as 80, 60 or 15?°C, even for longer reduction time. XPS, 13C NMR and FTIR results show that most of the epoxide groups bonded to graphite during the oxidation were removed from GO and form the sp(2) structure after being reduced by hydrazine hydrate at high temperature (>60?°C), leading to the electric conductivity of GO increasing from 1.5 × 10(-6) to 5 S cm(-1), while the hydroxyls on the surface of GO were not removed by hydrazine hydrate even at high temperature. Additionally, the FTIR, XRD and Raman spectrum indicate that the GO reduced by hydrazine hydrate can not be entirely restored to the pristine graphite structures. XPS and FTIR data also suggest that carbonyl and carboxyl groups can be reduced by hydrazine hydrate and possibly form hydrazone, but not a C = C structure.     

Triethylenetetramine/hydroxyethyl cellulose-functionalized graphene oxide monoliths for the removal of copper and arsenate ions

Nitrogen-doped graphene oxide monoliths (GOMs) were readily constructed by crosslinking graphene oxide (GO) using triethylenetetramine (TETA) and hydroxyethyl cellulose (HEC). The addition of HEC was beneficial to the formation of a network structure compared to that in the absence of HEC. The generated monoliths have shown various morphologies with different d spacing, layer thickness, and micropore size. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses provided evidences for the formation of covalent C–N bonds and some nitrogen-containing heterocyclic composition inside the graphene oxide sheet, indicating that the interaction of GO with the amine crosslinker involved the crosslinking reaction between GO epoxides and amine groups. HEC was also involved in the N-doping reaction via the partial reduction of oxygen in HEC molecules. Analysis of X-ray diffraction (XRD) results indicated that the lattice distance between GO sheets increased after TETA/HEC crosslinking. Thermogravimetric analysis (TGA) confirmed the successful incorporation of crosslinker moieties on the surface of GO sheets. The fabricated GOMs could be used to efficiently adsorb metal ions and arsenate by the introduced polar functional groups on GO sheets and porous structures based on hydrogen bonds, whose morphologies and compositions were confirmed via XRD, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS).     

Excellent photocatalytic performance under visible-light irradiation of ZnS/rGO nanocomposites synthesized by a green method

ZnS/graphene nanocomposites with different graphene concentrations (5, 10 and 15 wt.%) were synthesized using L-cysteine as surfactant and graphene oxide (GO) powders as graphene source. Excellent performance for nanocomposites to remove methylene blue (MB) dye and hexavalent chromium (Cr(VI)) under visible-light illumination was revealed. TEM images showed that ZnS NPs were decorated on GO sheets and the GO caused a significant decrease in the ZnS diameter size. XRD patterns, XPS and FTIR spectroscopy results indicated that GO sheets changed into reduced graphene oxide (rGO) during the synthesis process. Photocurrent measurements under a visiblelight source indicated a good chemical reaction between ZnS NPs and rGO sheets.     

Nylon-6/Graphene composites modified through polymeric modification of graphene

The covalent functionalization of graphene oxide (GO) with poly(vinyl alcohol) (PVA) via ester linkages (GO-es-PVA) as well as the characterization of modified graphene based Nylon-6 (PA6) composite prepared by solution mixing techniques was examined. The anchoring of PVA chains on GO sheets was confirmed by XPS and FTIR measurements. The resulting functionalized sample became soluble in formic acid, allowing solution-phase processing for preparation of PA6/GO composites. Answering to the efficient polymer-chain grafting, a homogeneously dispersion of GO sheets in PA6 matrix and a dramatic improvement of interface adhesion between nanosheets and matrix were observed in PA6/GO-es-PVA composites by SEM and TEM. The depressed crystallization of PA6 chains in PA6/GO-es-PVA composites was investigated by their DSC and XRD results.     

Synthesis of polymer-protected graphene by solvent-assisted thermal reduction process

Polyvinylpyrrolidone-protected (PVP-protected) graphene was synthesized by refluxing graphene oxide (GO) in dimethylformamide (DMF), using PVP as the dispersant. The structure and stability of this composite (DMF-rGO) were characterized using UV-vis spectroscopy, atomic force microscopy (AFM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD) and thermogravimetric analysis (TGA). The results confirm the presence of a single sheet of DMF-rGO with PVP of 42%. This kind of chemically reduced GO has a greater solubility in water and also is more biocompatible than rGO reduced by hydrazine hydrate. This method is simple, environmentally friendly and the composite has potential applications in biology and polymer nanocomposites.     

Radical addition of perfluorinated alkyl iodides to multi-layered graphene and single-walled carbon nanotubes

A simple one-pot reaction that serves to functionalize graphite nanosheets (graphene) and single-walled carbon nanotubes (SWNTs) with perfluorinated alkyl groups is reported. Free radical addition of 1-iodo-1H,1H,2H, 2H-perfluorododecane to ortho-dichlorobenzene suspensions of the carbon nanomaterial is initiated by thermal decomposition of benzoyl peroxide. Similarly, UV photolysis of 1-iodo-perfluorodecane serves to functionalize the carbon materials. Perfluorododecyl-SWNTs, perfluorododecyl-graphene, and perfluorodecyl-graphene are characterized by infrared (IR) and Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and atomic force microscopy (AFM). The products show enhanced dispersability in CHCl₃ as compared to unfunctionalized starting materials. The advantage of this one-pot functionalization procedure lies in the use of pristine graphite as starting material thereby avoiding the use of harsh oxidizing conditions.     

Synthesis of tin oxide-coated gold nanostars and evaluation of their surface-enhanced Raman scattering activities

Tin oxide-coated gold nanostar hybrid nanostructures are prepared by first synthesizing gold nanostars (ca. 400 nm), then introducing Na₂SnO₃ precursor followed by its hydrolysis and formation of a tin oxide layer on nanoparticle surface. The synthesized hybrid structures have been characterized by combination of UV–Vis spectroscopy, transmission electron microscope (TEM), energy-dispersive X-ray studies, scanning electron microscope (SEM), X-Ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The TEM and SEM analyses showed that gold nanostars have a coating with an approximate thickness of 15 nm. The tin (IV) oxide coating on the gold nanostars was identified by XRD and XPS analyses and confirmed by FTIR spectroscopy. Surface-enhanced Raman scattering (SERS) spectroscopy was performed on tin oxide-coated and uncoated gold nanostars with crystal violet as a probe molecule. The SERS studies revealed field enhancement properties of Au nanostars, thus their strong SERS activity remained after tin oxide coating.     

Structural,morphological, optical and electrical properties of spray deposited zinc doped copper oxide thin films

Nanostructured spray deposited zinc (Zn) doped copper oxide (CuO) thin films were characterized by employing X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), atomic force microscopy (AFM) and ultraviolet–visible–near infrared (UV–Vis–NIR) spectroscopy. XRD patterns of CuO and Zn doped CuO thin films indicated monoclinic structure with the preferred orientation along \(\left( {\bar 111} \right)\) plane. Maximum value of crystallite size is found about 28.24 nm for 5 at% Zn doped CuO thin film. In FESEM images, nanoparticles were observed around the nucleation center. EDX analysis confirms the presence of all component elements in CuO and Zn doped CuO thin films. Analysis by AFM of CuO and Zn doped CuO thin films figured out decrease of surface roughness due to Zn doping. UV–Vis–NIR spectroscopy showed that CuO and Zn doped CuO thin films are highly transparent in the NIR region. Optical band gap of CuO thin films decreased with substrate temperature and that of Zn doped CuO thin films increased with Zn concentration. Refractive index of CuO and Zn doped CuO thin films raised with photon wavelength and became constant in the NIR region. 5 at% Zn doped CuO thin film showed the highest optical conductivity and the lowest electrical resistivity at room temperature.     

Synthesis of Ag-AgBr/Al-MCM-41 nanocomposite and its application in photocatalytic oxidative desulfurization of dibenzothiophene

A series of Ag-AgBr/Al-MCM-41 nanocomposites were synthesized by dispersion of Ag-AgBr on mesoporous silica Al-MCM-41 obtained from natural bentonite. The synthesized Ag-AgBr/Al-MCM-41 composites with Ag nanoparticles growing on the surface of Al-MCM-41 were used for photocatalytic oxidative desulfurization of dibenzothiophene. The physical properties of Ag-AgBr/Al-MCM-41 were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Ultraviolet–visible diffuse reflection spectroscopy (UV–Vis DRS), photoluminescence (PL) emission spectra, and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity results showed that in the presence of 40% Ag-AgBr/Al-MCM-41 photocatalyst the oxidative desulfurization of dibenzothiophene reached the maximum efficiency at 99.22% and the photocatalytic activity still keeps high level after four cycles.     

Structural and textural evolution of dimethyl-modified silica xerogels

A series of dimethyl-modified silica xerogels with different dimethyl contents were prepared by one-step hydrolysis and co-condensation from tetraethyloxysilane (TEOS) and dimethyldiethoxysilane (DEOS) containing precursor. The structural and textural evolution was traced by FT-IR spectroscopy, nitrogen absorption, scanning electron microscopy (SEM), transmittance electrical microscope (TEM), UV–Vis spectroscopy and thermogravimetric analysis (TGA). The addition of dimethyl groups can greatly reduce the pore size distribution of the resulted sample, while the 30% DEOS–70% TEOS sample is the most textural compact and therefore the most optical transparent. FT-IR and TGA results show that the samples are less hydroxygen containing owing to the hydrophobicity of the dimethyl groups.     

Preparation of covalently functionalized graphene using residual oxygen-containing functional groups

When fabricated by thermal exfoliation, graphene can be covalently functionalized more easily by applying a direct ring-opening reaction between the residual epoxide functional groups on the graphene and the amine-bearing molecules. Investigation by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy (TEM) all confirm that these molecules were covalently grafted to the surface of graphene. The resulting dispersion in an organic solvent demonstrated a long-term homogeneous stability of the products. Furthermore, comparison with traditional free radical functionalization shows the extent of the defects characterized by TEM and Raman spectroscopy and reveals that direct functionalization enables graphene to be covalently functionalized on the surface without causing any further damage to the surface structure. Thermogravmetric analysis (TGA) shows that the nondestroyed graphene structure provides greater thermal stability not only for the grafted molecules but also, more importantly, for the graphene itself, compared to the free-radical grafting method.     

液相制备石墨烯/硫复合材料及其在锂硫电池正极中的应用

采用氧化石墨烯(grapheneoxide,GO)作为制备石墨烯的前驱体,通过液相还原自组装过程与硫纳米颗粒进行复合,获得了高性能的还原氧化石墨烯/硫(r GO/S)复合正极材料。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射仪(XRD)、拉曼光谱、X射线光电子能谱分析(XPS)等对材料微观形貌与结构进行表征。结果表明:硫纳米颗粒均匀分布在石墨烯片层间,并且硫纳米颗粒被石墨烯片层有效地封装,硫在35-r GO/S复合物中的质量分数高达83.6%。该35-r GO/S复合正极在0.2C电流密度下初始放电容量可达1197.3mAh·g^-1,经过200次循环后容量仍保持在730mAh·g^-1左右,表现出优异的循环性能。     

Ozone-Mediated Functionalization of Multi-Walled Carbon Nanotubes and Their Activities for Oxygen Reduction Reaction

The functionalization of multi-walled carbon nanotubes(MWCNTs)by ozone treatment has been systematically investigated by using Raman spectroscopy,transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),organic elemental analysis(OEA)and Boehm titration.The results showed that the functionalization process occurred at defective sites(opened mouths,tube caps,debris,etc.)before opening caps and truncating walls,and finally the graphitic structure was deteriorated.The surface oxygen content first increased with the treatment time but kept at around 8.0 wt%after 5 h.The analysis of the distribution of oxygen-containing groups revealed that phenolic hydroxyl was gradually converted to carboxyl and lactone.The carboxyl was found to play a pivotal role to reduce the over-potentials when we used the functionalized MWCNTs as the catalyst for oxygen reduction reaction(ORR).     

Synthesis,characterization, optical and electrical properties of novel highly dendritic polythiophene nanocomposites with silver and/or gold

Novel highly dendritic polythiophene/gold PT/Au and polythiophene/silver PT/Ag nanocomposites have been successfully prepared. Polythiophene PT has been also prepared for comparison. The obtained polymers have been characterized via scanning electron microscopy SEM, transmission electron microscopy TEM, UV–Vis absorption spectroscopy, Fourier transform infrared spectroscopy FT-IR and thermo gravimetric analysis TGA. Optical as well as electrical properties have been also investigated. It was found that the highly dendritic structure of the nanocomposites resulted in high improvements in the optical and electrical properties for the nanocomposites rather than that of pure PT.