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We report the transformation of electronic structures of sp² graphene to sp³ graphene by UV-light-assisted oxidation. Two distinctive oxidation mechanisms were observed during this metal–insulator transition: (i) At low-oxidation regime, p-doping behavior by oxygen species extracting electrons from graphene and (ii) at high-oxidation regime, n-doping behavior by electron-hopping via strongly localized oxide states. We also found that the dominant oxygen-related functional group by UV-light-assisted oxidation was an epoxide group rather than hydroxyl group, which differed from conventional graphite oxide.

The composites of graphene oxide/Fe₂O₃-nanotubes (GO/Fe₂O₃-NTs) have been fabricated through a facile one-step hydrothermal method. Fe₂O₃-NTs crystallines were homogeneously distributed on GO, which have been confirmed by transmission electron microscopy analysis (TEM). The structure, composition and electrochemical properties of GO/Fe₂O₃-NTs composites were investigated by means of selective-area electron diffraction (SAED), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Raman spectra, cyclic voltammogram (CV) curves and galvanostatic charge–discharge curves. GO/Fe₂O₃-NTs composites exhibit a high specific capacitance of 133.2 Fg^-1 in 1 M Li₂SO₄ electrolyte. In addition, the GO/Fe₂O₃-NTs composites electrode shows good long-term cycle stability (only 9% decrease of the specific capacitance is observed after 1000 charge–discharge cycles).

Stable dispersions of reduced graphene oxide (RGO) have been prepared by indole as a previously unreported reducing agent without employing any external stabilizing reagents. The obtained RGO can be individually dispersed in ethanol, N, N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), dimethylsulfoxide (DMSO), tetrahydrofuran (THF) and isopropanol. Several analytical techniques including Atomic force microscopy, X-ray diffraction, UV-Vis spectra, Raman spectroscopy and X-ray photoelectron spectroscopy indicate that a significant fraction of the oxygen-containing functional groups are removed, yields a C/O ratio as high as 7.4. The conductivity of RGO is 21.2 S/m and the thickness of RGO increases to 1.7 nm. Furthermore, this new reducing agent is of low toxicity, which makes the reduction much safer than hydrazine and this method is cost-effective to produce single-layered RGO on a large scale.

Graphene oxide nanosheet is an ideal platform to capture nanoparticles for highly efficient catalysis, electrochemical sensing and biosensing. In this work, we have described a simple synthesis method for preparation graphene oxide–Au nanohybrid. Au nanodots with an average size of 1.6 nm uniformly dispersed on the surface of graphene oxide. The well-defined nanostructure has been characterized by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The nanohybrid also exhibits enhanced catalytic activity toward the reduction of 4-nitrophenol by NaBH₄. Comparing with pure Au nanodots and graphene oxide, graphene oxide–Au nanohybrid shows the highest catalytic activity. This approach not only suggests a wide potential application of graphene oxide nanosheet as a host material for supporting a variety of nanoparticles, but also provides a new approach for the fabrication of graphene-based nanohybrids with multiple physical and chemical properties.

The effects of oxygen-containing functional groups on the surface roughness of graphene oxide are thoroughly studied using three-dimensional atomic force microscopy images, ball-and-stick model and wire-frame view results. Moreover, X-ray diffraction method and Fourier transform infrared spectroscopy are employed for characterizing the structural and chemical behavior of graphene oxide, respectively. Graphene oxide sheets show a clear concavity on one side when the aggregation of functional groups increased on the other side. This behavior could be the main reason for the surface fluctuation of graphene oxide sheets that is observed in microscopic images. In addition, the individual graphene oxide sheet presents greater values of mean roughness compared to multilayered sheets.

Graphene oxide (GO) has attracted much attention as a derivative of graphene. In addition, it appears to have many unique physicochemical properties and has been investigated widely in many areas. Herein, we prepare GOs using flake graphite (FG), expandable graphite (EG) and microcrystalline graphite (MG) as graphite precursors by the modified Hummers method. According to the X-ray diffraction (XRD), Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, we characterize the component, the functional group, the chemical state of the element and the structural disorder of the obtained GOs to reveal their oxidation degree. Besides, we evaluate the hydrophilicity of the obtained GOs with the water contact angle, and observe their microstructures by transmission electron microscopy (TEM). We find that the GO prepared with EG has a higher-degree oxidation and better hydrophilicity, and it will be exfoliated easily and forms a monolayer or quasi-monolayer structure. Finally, based on the structural characteristic of graphite precursor, we build the intercalation and oxidation model to illuminate the phenomenon.

This paper reports a new graphene oxide (GO)/acenaphthenequinone composite as efficient electrode in electrochemical supercapacitors. The nanosheets of GO provide high surface area and conductivity. The microneedle-like acenaphthenequinone contributes convincible specific capacitance. The structure and morphology of GO/acenaphthenequinone composite have been characterized by field-emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR) spectra and Raman spectra. According to the cyclic voltammetry (CV), galvanostatic charge/discharge, impedance spectra and cycling life analyses, the GO/acenaphthenequinone composite exhibits brilliant supercapacitors performance with a specific capacitance of 248.7 F g^-1 at a scan rate of 1 mV s^-1 and enhanced stability of about 82% (147.5 F g^-1) of initial capacitance (179.8 F g^-1) after 500 cycles at a current density of 1 A g^-1.

A synergistic combination of properties between graphene oxide (GO) nanosheets and porphyrin molecules has been accomplished via the entrapment of the latter species within the pore space formed by parallel plates of the carbon material. A hybrid material, synthesized in this manner, would likely lead to the development of efficient photovoltaic cells, given the high capacity of porphyrin molecules to absorb sunlight or radiation of wavelength shorter than 700 nm as well as because of the excellent electron conduction and fine solar energy capture that can be achieved by the graphene substrate. Herein, materials consisting of trapped porphyrin molecules in-between GO plates have been prepared to develop preliminary solar cell devices for an efficient capture of sunlight energy. The hybrid systems created this way can be physicochemically characterized through diverse techniques, which include fluorescence emission to confirm and avail both the presence and manifest luminescent characteristics of the tetrapyrrolic species that are captured and retained in-between GO plates.

Graphene oxide nanosheet (NGO) was covalently functionalized with positively charged, branched polyethylenimine (bPEI) via an amide bond, coated with serum proteins by electrostatic interaction. Operating as a newly fashioned, multifunctional nanocarrier, the processed NGO showed promise for use in combined gene therapy, chemotherapy, photothermal therapy, bioimaging and as a biosensor of cancer cells. Our current research is focused on the systematic studies of mechanisms of cancer cellular uptake, subcellular location, cytotoxicity and the cellular exclusion of the NGO–bPEI nanocarriers. It was observed that NGO–bPEI accumulated in the mitochondria and that long-term retention of NGO–bPEI led to a decrease in mitochondrial membrane potential while levels of reactive oxygen species increased. The mitochondrial effects associated with long-term retention of NGO–bPEI have potential as a synergistic enhancer of the cytotoxic effects of anti-cancer drugs or genes in human lung carcinoma (A549) cells. This work demonstrated the utility of NGO–bPEI-based multifunctional nanocarriers while detailing the mechanism at the cellular level and providing guidance for further research in cancer therapy.

A novel strategy toward one-pot hydrothermal synthesis of copper sulfide nanoplates-decorated reduced graphene oxide (RGO–CuS) composites was developed. CuS nanoplates were successfully loaded onto the surface of RGO in the hydrothermal procedure, which was confirmed by transmission electron microscopy, UV-Vis–NIR and Raman spectroscopy. The as-synthesized RGO–CuS composites showed pronounced enhanced optical absorbance in near infrared (NR) region and higher photothermal conversion efficiency than noncomposite GO and CuS nanoplates. The RGO–CuS materials were used in photothermal ablation of cancer cells with a 980nm laser irradiation and showed improved performance than CuS nanoplates.

In this work, graphene oxide/polyaniline (GO/PANI) nanocomposites were synthesized by an in situ polymerization of aniline monomer in GO aqueous dispersions. The morphology and structure of GO/PANI were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra and Raman spectra. The effects of the concentration of GO/PANI and temperature on the rheological behavior of silicone oil dispersions of GO/PANI nanocomposites were investigated. The results showed that the steady state viscosity of GO/PANI dispersions remarkably increased with the addition of only little GO and the concentrated dispersions showed characteristic shear-thinning behavior. Significantly, a Newtonian-pseudoplastic transition with a critical exponent of 2.2 was observed in silicone oil dispersions of GO/PANI with the increase of nanocomposites concentration. The viscosity of GO/PANI dispersions apparently decreased with increasing temperature, while the temperature showed a certain effect on the thixotropic behavior of concentrated dispersions. In addition, the effect of the GO content on the electrical conductivity of GO/PANI nanocomposites was also explored. It was noted that the GO sheets are effective fillers for improving the rheological behavior and electrical conductivity of PANI matrix. Therefore, the study of rheological behavior and electric property of GO/PANI nanocomposites could shed light on the processing and application of GO/conductive polymer nanocomposites.

The paper was retracted as the authors have submitted the same manuscript to two completely different journals, which is seriously academic fraud and against academic ethics.

A novel conducting copolymer based on amidoxime groups, polypyrrole and graphene oxide was synthesized by in situ copolymerization by usin g two monomers. The monomer, amidoxime-pyrrole, was synthesized by amidoximation of 1-(2-cyanoethyl) pyrrole. The other monomer, GO-pyrrole, was prepared via esterification between –COOH of GO and –NH₂ of 1-(3-aminopropyl) pyrrole. The conductive ability of the copolymer was based on conductive $\pi$-conjugated system of polypyrrole backbone. The copolymer was able to be used as an effective sorption material for the preconcentration and recovery of uranium. The maximum of adsorption capacity for uranyl ion is as high as 149.57mg/g.

The electrodeposition of reduced graphene oxide (rGO) film with preferred vertical orientation was fabricated on a glassy carbon electrode by using pulse potential method in a graphene oxide solution. The rGO film was applied in developing a high-sensitive electrochemical sensor for detection of levodopa (L-dopa). The new electrochemical sensor displayed a significant response to L-dopa because of its excellent electric conductivity and large specific surface area. Moreover, the determination of L-dopa on this modified electrode was not interfered by the coexistence of ascorbic acid (AA) and uric acid (UA). Under the selective conditions, the modified electrode showed a linear voltammetric response to L-dopa within a certain concentration ranging from $5.0\times 10^{-7}$$-1.5\times 10^{-4}$ mol L${}^{-1}$, with the detection limit of $1.0\times 10^{-7}$ mol L${}^{-1}$. Besides, the modified electrode also exhibited an excellent selectivity, stability, reproducibility and repeatability.

In this work, a novel nanocomposite (NC) based on the decoration of Ag nanoparticles (NPs) and W${}_{18}$O${}_{49}$ nanorods (NRs) on the GO surfaces was prepared using combined techniques of solvothermal method and photochemical process. Compared with the Ag-GO NC, the Ag-W${}_{18}$O${}_{49}$-GO NC exhibited enhanced long-term antibacterial activity against the bacterium of Bacillus sp.1NLA3E (Bacillus sp.). The antibacterial mechanisms of both the Ag-GO and Ag-W${}_{18}$O${}_{49}$-GO NCs were distinctly revealed by observation of the direct interaction between the Ag NPs, W${}_{18}$O${}_{49}$ NRs, or GO sheets and the bacterial cells. Results showed that the GO sheets in the NCs mainly acted as supports for trapping or wrapping the bacterial cells, and it was the Ag NPs or W${}_{18}$O${}_{49}$ NRs grown on the GO surfaces that caused direct damage to the cells. The synergistic effects between the Ag NPs or W${}_{18}$O${}_{49}$ NRs and the GO sheets resulted in the prominent long-term antibacterial effect of the Ag-W${}_{18}$O${}_{49}$-GO NC. This work provides in-depth understanding of the mechanism regarding the antibacterial activity of the GO-based NCs.

The pollution of water due to the release of heavy metals are particularly problematic and supplies of clean water have become a major problem worldwide. The heavy metal ions can cause toxicities and serious side effects toward human health; therefore, these metal ions should be removed from water and wastewater. A variety of strategies have been developed for efficient heavy metal removal from waters. Adsorption/ion exchange strategy play a great important role in removing heavy metal ions due to their advantages. Nanomaterials are excellent adsorbents and extensive studies have been performed to remove heavy metals from wastewater by developing and using various nanomaterials. Recent developments for the heavy metals removal by various nanomaterials, mainly including carbon-based nanomaterials, iron-based nanomaterials and photocatalytic nanomaterials in batch and flow systems are described in this review.

Owing to weak interfacial bonding and incompatibility between graphene and polymer, there are several challenges in the fabrication of graphene-based polymer composites with an effective gas barrier. Hence, it is necessary to enhance the affinity between polymers and graphene. We selected graphene oxide (GO) as filler and brominated butyl rubber (BIIR) as a substrate to prepare GO/BIIR composites via the simple latex mixed route. The tortuous path of diffusion of helium molecules is extended after insertion of GO nanosheets, thus improving the gas barrier of composites. GO/BIIR composite with the GO content of 0.3wt.% exhibits favorable barrier efficiency to helium with a helium gas transmission rate of 12.79cm³ cm m${}^{-2}$ day${}^{-1}$ bar${}^{-1}$.

To explore the mechanism of GO acting on PM${}_{2.5}$, a graphene oxide (GO) film was prepared via a spraying method for air purification. The effects of different media, temperature and heat treatment times on the adsorption of PM${}_{2.5}$ on GO film were investigated. The morphology, composition and structure of GO materials were characterized by scanning electron microscopy (SEM), electron spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (FT-IR) and Raman spectroscopy. When the vacuum heat-treatment temperature is below 80^∘C and the atmospheric heat-treatment temperature is below 100^∘C, the air purification performance of the film does not change significantly. With the increase in the vacuum heat-treatment temperature, the removal efficiency of PM${}_{2.5}$ by GO film decreases gradually from 95% to 83%. At different times, the vacuum heat treatment increases with time, and the film removal rate shows a downward trend. As the heat-treatment temperature and time increase, a certain redox reaction occurs in the GO, and the air purification performance decreases. At a temperature of 120^∘C and a time of 8h, the removal rate drops to 81.68%. The adsorption of PM${}_{2.5}$ by GO film mainly relies on the action of oxygen-containing functional groups.

Owing to the hazardness, the sensitive and selective detection of cyanide (CN⁻) in water or water-containing systems has still been a puzzle plaguing scientists all around the world. In this paper, a novel fluorescence probe based on covalently functionalized graphene oxide (GO) by aminocoumarin for highly selective detection of CN⁻ in deionized water was prepared under the action of EDC/NHS. This probe bears aminocoumarin group as the recognition site and fluorophore, and its fluorescence quantum yield is increased by 0.07. Simultaneously, by loading on GO, the dispersibility, selectivity and reversibility were soundly improved, which facilitated the detection process. The fluorescence spectra showed that the probe has high selectivity and sensitivity for cyanide, and has potential application in real water.

Graphene, a single layer of two-dimensional carbon material, has attracted much attention due to its excellent comprehensive properties including high mechanical strength, antibacterial property, excellent thermal and electrical conductivities, high specific surface area, impermeability, etc. In this study, 3-epoxypropyl-5,5-dimethylhydantoin (GH), as a precursor of $N$-halamine, was synthesized and attached onto graphene oxide (GO) for enhanced antibacterial activity. The synthesized GO–GH was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). After chlorination treatment by household bleach solution, the chlorinated graphene oxide-3-epoxypropyl-5,5-dimethylhydantoin (GO–GH–Cl) possessed great antibacterial efficacy. The synthesized GO–GH–Cl was added to chitosan (CS) solution to produce GO–GH–Cl/CS hybrid films via a solution casting method. The as-prepared antimicrobial hybrid films showed excellent antibacterial activity and could kill 100% of S. aureus and 100% of E. coli O157:H7 within 10min and 30min of contact time, respectively.