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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 and graphene-based nanomaterials such as graphene oxide (GO), reduced graphene oxide (rGO) and graphene quantum dots (GQDs) have gained a lot of attention from diverse scientific fields for applications in sensing, catalysis, nanoelectronics, material engineering, energy storage and biomedicine due to its unique structural, optical, electrical and mechanical properties. Graphene-based nanomaterials emerge as a novel class of nanomedicine for cancer therapy for several reasons. Firstly, its structural properties like high surface area and aromaticity enables easy loading of hydrophobic drugs. Secondly, presence of oxygen containing functional groups improve its physiological stability and also act as site for biofunctionalization. Thirdly, its optical absorption in the NIR region enable them to act as photoagents for photothermal and photodynamic therapies of cancer, both in vitro and in vivo. Finally, its intrinsic fluorescence property helps in bioimaging of cancer cells. Overall, graphene-based nanomaterials can act as agents for developing multifunctional theranostic platforms for carrying out more efficient detection and treatment of cancers. This review provides a detailed summary of the different applications of graphene-based nanomaterials in drug delivery, nucleic acid delivery, phototherapy, bioimaging and theranostics.

Effect of irradiation on graphene oxide by sunlight, UV light and KrF excimer laser has been investigated in detail. Both sunlight and ultraviolet light reduce graphene oxide well after prolonged irradiation, but laser irradiation produces graphene with negligible oxygen functionalities within a short time. Laser irradiation is also useful for one-step synthesis of metal particle decorated graphene. Laser irradiation of graphene oxide appears to be an efficient procedure for large-scale synthesis of graphene.

Cross-linked polyvinyl alcohol (PVA) graphene oxide (GO) nanocomposites were prepared by simple solution-mixing route and characterized by Raman, UV–visible and fourier transform infrared (FT-IR) spectroscopy analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The XRD pattern and SEM analysis showed significant changes in the nanocomposite structures, and the FT-IR spectroscopy results confirmed the chemical interaction between the GO filler and the PVA matrix. After these morphological characterizations, PVA-GO-based diodes were fabricated and their electrical properties were characterized using current–voltage (I–V) and impedance-voltage-frequency (Z-V-f) measurements at room temperature. Semilogarithmic I–V characteristics of diode showed a good rectifier behavior. The values of C and G/$\omega$ increased with decreasing frequency due to the surface/interface states (N${}_{\mathrm{\text{ss}}}$) which depend on the relaxation time and the frequency of the signal. The voltage, dependent profiles of N${}_{\mathrm{\text{ss}}}$ and series resistance (R${}_{\mathrm{\text{s}}}$) were obtained from the methods of high-low frequency capacitance and Nicollian and Brews, respectively. The obtained values of N${}_{\mathrm{\text{ss}}}$ and R${}_{\mathrm{\text{s}}}$ were attributed to the use of cross-linked PVA-GO interlayer at the Au/n-Si interface.

The present work investigates the novel impact loading response of two-dimensional graphene oxide (GO) reinforced epoxy nanocomposites at high strain rate. The testing was performed up to 1000s${}^{-1}$ of high strain rate, where maximum damage occurs during the impact loading conditions. The Split Hopkinson Pressure Bar (SHPB) was used for the impact loading of the composite specimen. The nanofiller material GO was synthesized by chemical oxidation of graphite flakes used as the precurser. Synthesized GO was characterized using FTIR, UV-visible, XRD, Raman Spectroscopy and FE-SEM. Solution mixing method was used to fabricate the nanocomposite samples having uniform dispersion of GO as confirmed from the SEM images. Strain gauges mounted on the SHPB showed regular signal of transmitted wave during high strain rate testing on SHPB, confirming the regular dispersion of both the phases. Results of the transmission signal showed that the solution mixing method was effective in the synthesis of almost defect-free nanocomposite samples. The strength of the nanocomposite improved significantly using 0.5wt.% reinforcement of GO in the epoxy matrix at high strain rate loading. The epoxy GO nanocomposite showed a 41% improvement in maximum stress at 815s${}^{-1}$ strain rate loading.

New techniques and materials are called for wastewater treatment due to the shortage of worldwide fresh water and the increasing water demand. As a simple and efficient method, adsorption technique has been extensively applied to remove organic and inorganic pollutants from contaminated water. The application of carbon nanomaterials, such as activated carbon, carbon nanotubes (CNTs), graphenes and their derivatives/analogues, in wastewater treatment has also been investigated due to their unique properties, such as wide availability, porous structure, large surface area, tunable morphology and nontoxicity. This review highlights the recent advances of wastewater treatment utilizing carbon nanomaterial modified composites as adsorbents. The adsorption phenomenon and its mechanism are briefly discussed. Detailed discussions are focused on the selective adsorption of carbon nanomaterial composites to unique pollutants. The remaining challenges are also mentioned.

Graphene, a single layer of hexagonal packed carbon atoms, has attracted increasing attention in recent years. Because of its exceptional electronic, optical, mechanical, and thermal properties, graphene has shown great promises in a wide range of applications. Graphene derivatives, e.g. graphene oxide (GO) and reduced graphene oxide (rGO) sheets, possess surface defects and oxygen functional groups, which make them ideal templates for synthesis of metal and semiconductor nanoparticles (NPs). Enhanced properties are expected in these graphene–NP composites, which arise from the synergic effect of the GO/rGO sheets and the anchored NPs. In this review, after a brief introduction on the properties and synthesis of graphene, we will discuss the fabrication methods of graphene–metal NP and graphene–semiconductor NP composites, as well as their related applications in catalysis, photovoltaic devices, supercapacitors, and so on.

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.

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.

CaMoO₄ nanoparticles/graphene oxide (CaMoO₄/GO) composites are prepared by a facile hydrothermal method. CaMoO₄ nanoparticles are adsorbed on the GO sheets by in situ reduction. Along with the synergistic effect between the CaMoO₄ and GO sheets, the CaMoO₄/GO nanocomposites exhibited high performances as electrodes for supercapacitors. The specific capacity ($Q_s)$ of the CaMoO₄/GO electrodes could be up to 571.82F$\cdot$g${}^{-1}$ at 0.5A$\cdot$g${}^{-1}$. Furthermore, asymmetric supercapacitors (ASCs) are mainly composed of CaMoO₄/GO composite and activated carbon (AC), respectively. The fabricated CaMoO₄/GO//AC devices display an energy density of 25.18W$\cdot$h$\cdot$kg${}^{-1}$ at 1710.3W$\cdot$kg${}^{-1}$. A blue LED is powered using two series-connected two ASC devices. These results indicate the considerable potential of CaMoO₄/GO for use in high-performance energy storage devices.

A sensitive and fast sensor for quantitative detection of organophosphorus pesticides (OPs) is obtained using acetylcholinesterase (AChE) biosensor based on graphene oxide (GO)–chitosan (CS) composite film. This new biosensor is prepared via depositing GO–CS composite film on glassy carbon electrode (GCE) and then assembling AChE on the composite film. The GO–CS composite film shows an excellent biocompatibility with AChE and enhances immobilization efficiency of AChE. GO homogeneously disperses in the GO–CS composite films and exhibits excellent electrocatalytic activity to thiocholine oxidation, which is from acetylthiocholine catalyzed by AChE. The results show that the inhibition of carbaryl/trichlorfon on AChE activity is proportional to the concentration of carbaryl/trichlorfon. The detection of linear range for carbaryl is from 10nM to 100nM and the correlation coefficients of 0.993. The detection limit for carbaryl is calculated to be about 2.5nM. In addition, the detection of linear range for trichlorfon is from 10nM to 60nM and the correlation coefficients of 0.994. The detection limit for trichlorfon is calculated to be about 1.2nM. This biosensor provides a new promising tool for trace organophosphorus pesticide detection.

Recent advances in polymer nanocomposites open a wide range of applications in various industrial sectors. Due to their high potential properties, these materials are replacing the usage of metals for many heavier components in automobile industries. In this experimental work, the tribological performance of Graphene oxide (GO) — Polyamide is investigated against pristine polyamide by fabricating gears for the usage in engineering applications. A gear test rig was developed in-house for analysis to study the specific wear rate and temperature gradient at different conditions of load and speeds. The wear resistance of the polyamide gears with the addition of 0.03wt.% of graphene oxide is better than the pristine polyamide gears and the specific wear rate is reduced significantly. The reduced specific wear rate of these polymer nanocomposite gears is attributed to the superior properties of graphene oxide such as High specific surface area, good adhesion properties and enhanced glass transition temperatures. The GO nanocomposite gear seems to be a potential alternative against conventional gears for engineering applications. Finally, the wear mechanisms and the potential of GO-based polyamide nanocomposite gears were proposed tentatively in the development of transmission gears for engineering applications.

Graphene oxide (GO) concentrated slurry dispersion method was used to prepare the GO epoxy thermal insulation and anti-corrosion coating. Corrosion test was carried out in 3.5% NaCl solution at 50^∘C, and a thermal testing device tested the thermal insulation performance. The results of the electrochemical corrosion test after 456h show that the low-frequency impedance of the coating with 0.5% GO-modified significantly improved, and the corrosion resistance of the coating is better than that of the coating without GO and 1.0% GO-modification. SEM analysis results show that surface morphology of the coating modified with GO 0.5% and 1.0% after 456 h of corrosion, there were no cracks and corrosion products at the substrate interface. In contrast, coatings without GO modification have apparent corrosion damage. Before corrosion testing, the thermal insulation performance of coating modified by 0.5%, 1.0% GO coating was not significantly different from that of the neat epoxy. The bonding strength is also reduced to 3.9, 2.3, and 1.0 MPa. The experimental results show that the coating with 0.5% GO modified is the best for corrosion resistance and insulation.

In the present study, graphene oxide (GO)-reinforced poly (4-styrenesulfonic acid) (PSSA)/polyvinyl alcohol (PVA) blend composite films were prepared using colloidal blending technique at various concentrations of GO (0–3wt.%). The morphological investigations of the prepared composites were carried out using polarized optical microscopy and scanning electron microscopy. The electrical properties of composites were evaluated using an impedance analyzer in the frequency range 50Hz to 20MHz and temperature in the range 40–150${}^{\circ }$C. Morphological studies infer that GO was homogeneously dispersed in the PSSA/PVA blend matrix. Investigations of electrical property indicate that the incorporation of GO into PSSA/PVA blend matrix resulted in the enhancement of the impedance ($Z)$ and the quality factor ($Q$-factor) values. A maximum impedance of about 4.32$\times$10${}^6\mathrm{\Omega }$ was observed at 50Hz and 90${}^{\circ }$C for PSSA/PVA/GO composites with 3wt.% GO loading. The $Q$-factor also increased from 8.37 for PSSA/PVA blend to 59.8 for PSSA/PVA/GO composites with 3wt.% GO loading. These results indicate that PSSA/PVA/GO composites can be used for high-$Q$ capacitor applications.

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.

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.

In this paper, a functional ternary slurry consisting of polyurethane (PU) microspheres, graphene oxide (GO) nano platelets and silicon oxide (SiO₂) abrasives was used to carry out the polishing process on Si face of 4H-SiC wafers. The processing parameters of the slurry include graphene weight fraction in slurry GO1–GO7 (0.1–0.7wt.%), pH value (3–5), and sonication time T5–T15 (5–15min). Polishing process is conducted with two kinds of polishing pads A and B, PU and PC (polycarbonate). Results show that material removal rate (MRR) increases with increasing GO weight fraction up to GO5; besides, MRR also increases with increasing sonication time up to T10, and with increasing pH value. Using PU pad, the GO5-T10-pH5-A slurry leads to highest MRR 102.220nm/h of the polished SiC wafer. On the other hand, surface roughness improvement rate (SRIR) increases with increasing GO weight fraction up to GO5, and increases with increasing sonication time up to T15. But SRIR is not affected by pH value. Regarding effect of pad type, on average the PU pad results in higher MRR and better SRIR compared with the PC pad. Using PC pad, GO5-T10-pH5-B leads to lower MRR of 87.627nm/h. The addition of GO as the ternary slurry demonstrates its better effect on polishing SiC wafers by comparing with the counterpart binary slurry without GO. For example, MRR by the counterpart slurry SiO₂12-pH5-A is 58.411nm/h, which is lower than 102.220nm/h by the ternary slurry GO5-T10-pH5-A. Both XPS and Raman spectra demonstrate that the wafer polished by the functional ternary slurry can effectively produce the softer SiO₂ reactant layer on SiC wafer, and result in better polishing performance.

Graphene has been considered one of the most important materials for many applications due to its unique electronic structure, physical and chemical properties. Graphite flakes are the main source of graphene oxide which can be transformed to graphene after reduction. The effect of irradiation on graphene oxide has been rarely studied, only few studies dealing with the irradiation of graphene oxide with gamma radiation were reported. The effect of irradiation of graphene oxide with gamma ray doses (low linear energy transfer) has been previously studied. It was found that there are no changes in the crystalline structure of graphene oxide after irradiation. Graphene oxide was prepared by modified Hummer’s method. The scanning electron microscopy image of the obtained sample suggests the presence of both single and multilayer graphene oxide sheets. The structural measurements for the graphene oxide samples with high linear energy transfers were carried out after irradiations with different doses of alpha particle (9.30–479.90 Gy). The effect of irradiation on oxygen functional groups of graphene oxide was followed by Fourier transforms infra-red spectrometer. Moreover, the irradiation effect on the lamellar space of graphene oxide layers was measured by X-ray diffraction. It was found that the d-spacing of graphene oxide was decreased after alpha particles irradiation with different doses. The effect of irradiation on dielectric constant and conductivity of graphene oxide samples was measured in the frequency range (200 Hz–1.00 MHz). The dielectric measurements show less dependence on irradiation doses. The graphene oxide sample can be used as radiation dosimeter for $\alpha$-particles in the range of the low irradiation doses.

This study investigated the preparation of graphene oxide from mildly oxidized graphite through ultrasonic exfoliation. Both the original and produced materials were analyzed by ultraviolet–visible spectrophotometer, X-ray diffraction and atomic force microscopy. The results indicated that the exfoliation yield of graphene oxide was proportional to the input ultrasonic energy. In addition, a two-stage exfoliation phenomenon was observed in the exfoliation of mildly oxidized graphite with both ultrasonic homogenizer and cleaner. It also was found that increasing the content of [$O$] in a C–H₂SO₄–[$O$] reaction system was the most simple and direct method to increase the oxidation degree of graphite oxide.

A flexible organic light-emitting device (OLED) was produced using copper nanowire (CuNW) film as anode and Graphene oxide (GO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) film as anode buffer layer. Compared with other transparent conductive films (TCFs), CuNWs are low cost, easy to fabricate, and compatible with flexible substrates over a large area. Due to these advantages, CuNWs are showing greater and greater promise for the next generation of TCF. Modified by PEDOT:PSS, the conductivity and work function of the CuNW film can be dramatically enhanced. However, PEDOT:PSS is highly acidic and easy to corrode the CuNW film, which will reduce maximum luminous brightness and current efficiency of the OLED. In this paper, GO/PEDOT:PSS was used as anode buffer layer to modify the CuNW anode and the composite transparent electrode exhibited excellent optoelectrical properties. The driving voltage of the OLED with CuNW/PEDOT:PSS is 6.2V, and the maximum luminous brightness is 2737.2cd/m². The driving voltage of the OLED with CuNW/GO/PEDOT:PSS anode was reduced to 5.1V, and the maximum luminous brightness was improved to 3007.4cd/m².