Solution-based production of graphene nano-platelets containing extremely low amounts of heteroatoms

We developed a new route for scalable production of graphene-based nano-platelets containing extremely low amounts of heteroatoms via treatment of graphene oxide suspensions with ammonia borane at low temperatures without further thermal annealing. The C/O atomic ratio measured by combustion-based elemental analysis is the highest value among published data on graphene-based nano-platelets using solution processes. Resulting materials showed a very high electrical conductivity.     

Solvothermal reduction of graphene oxide in dimethylformamide

The reduction of graphene oxide (G-O) is one of the most promising methods for the large scale production of graphene-based materials. In this paper, we report a simple and non-toxic method to produce reduced graphene oxide (rG-O) by refluxing G-O in N, N-dimethylformamide without the aid of a reducing agent. The rG-O materials with high degrees of reduction are prepared and the levels of reduction are controlled using reflux time. Successful reduction is confirmed by combustion-based elemental analysis and X-ray photoelectron and Fourier transform infrared spectroscopy.     

Introduction of CdO nanoparticles into graphene and graphene oxide nanosheets for increasing adsorption capacity of Cr from wastewater collected from petroleum refinery

Graphene and graphene oxide nanocomposites are promising and fascinating types of nanocomposites because of their fast kinetics, unique affinity for heavy metals, and greater specific area. Initially, in this study, a green, cost-effective and facile method was utilized to prepare G, GO, CdO, G-CdO, and CdO-GO nanocomposites by Azadirachta indica and then analyzed using UV–vis spectroscopy, Fourier-transform spectroscopy, Raman, X-ray diffraction and scanning electron microscope. The synthesized nanocomposites were explored for chromium elimination from wastewater collected from a petroleum refinery. CdO-GO, G-CdO nanocomposites showed remarkable adsorption capability of 699 and 430 mg g^?1 which was higher than G (80 mg g^?1), GO (65 mg g^?1), and CdO (400 mg g^?1). Based on the R² (correlation coefficient) values, the kinetic statistics of Cr (VI) onto the G, GO, CdO, G-CdO, and CdO-GO were effectively obeyed by pseudo-second-order than by all other models. The R² values for the five nano-bioadsorbents were extraordinarily high (R² greater than 0.990) which ensured the chemisorption. This study ensured that the adsorptive removal rate of Cr (VI) is still greater than 85 % after repeated five cycles, suggesting that the produced nanomaterials are adsorbents with strong recyclability.     

功能化氧化石墨烯的细胞相容性

采用改进的Hummers方法制备了纳米尺度的氧化石墨烯.对氧化石墨烯的表面进行羧基化,并连接上聚乙二醇(PEG)使其在细胞培养液中可溶并能稳定保存.采用透射电镜(TEM)、傅里叶变换红外(FTIR)光谱和zeta电位测量等对修饰后的氧化石墨烯的结构和功能进行了表征.体外细胞实验表明PEG修饰的氧化石墨烯在水中具有良好的可溶性,对A549细胞没有明显的毒性,在生物医药领域具有潜在的应用价值.     

Self-assembly of graphene oxide nanosheets in t-butanol/water medium under gamma-ray radiation

Graphene oxide (GO) nanosheets dispersed in strong acidic t-butanol/water medium can be reduced and self-assembled into a self-standing graphene hydrogel under γ-ray radiation, providing a facile and economical preparation method for hydroxylalkylated graphene-based aerogel.     

Synthesis of multifunctional fluorescent magnetic graphene oxide hybrid materials

Fluorescent magnetic graphene oxide hybrid materials have been fabricated by a multistep method. X-ray diffraction, transmission and scanning electron microscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, vibration sample magnetometry, and energy dispersive spectroscopy were used to characterize the resulting material. The results showed that the materials have a saturation magnetization value of 22.0 emu/g at room temperature and exhibit a symmetrical and narrow emission peak at 544 nm. The resultant materials are able to carry an anti-cancer drug, 5-fluorouracil, with a load capacity of 0.24 mg/mg.     

Defect and doping concentration study with series and shunt resistance influence on graphene modified perovskite solar cell: A numerical investigation in SCAPS-1D framework

Perovskite solar cells (PSCs) have the potential to be highly efficient, low-cost next-generation solar cells. By raising open circuit voltage (V_oc), the interfacial recombination kinetics can further improve device performance. In this study, we used simulation concept to elucidate the influence of using graphene as a surface passivation material in perovskite solar cells. Graphene works well as an interlayer to promote hole extraction and reduce interfacial recombination. In order to evaluate the effect of graphene in PSCs, the simulation was done in the SCAPS-1D framework to compare the performance of a device with and without graphene. Three interface layers were included to the model: TiO₂/MAPbI₃, MAPbI₃/Graphene, and Graphene/Spiro-OMeTAD, in order to account for the impacts of interface defect density on device performance. The impacts of absorber doping concentration, absorber defect density, ETL doping concentration, HTL doping concentration, series resistance, and shunt resistance were also evaluated for the modelled PSC. Without any optimization, the control device with power conversion efficiency (PCE) of 20.677% was outperformed by the graphene-modified device with PCE of 20.911%. This difference is mostly due to the lower recombination losses and more effective suppression of interfacial non-radiative recombination. With optimization, the modified graphene-based device has a PCE of 26.667%. This result shows an enhancement of ∼1.28 times over that of the pristine graphene-based device. The outcomes have opened the way for the development of cost-effective and comparable state-of-the-art, high-efficiency perovskite solar cells with graphene interlayer by eliminating defects and managing non-radiative recombination.     

Dispersion of graphene oxide and its flame retardancy effect on epoxy nanocomposites

Graphene oxide was prepared by ultrasonication of completely oxidized graphite and used to improve the flame retardancy of epoxy.The epoxy/graphene oxide nanocomposite was studied in terms of exfoliation/dispersion,thermal stability and flame retardancy.X-ray diffraction and transmission electron microscopy confirmed the exfoliation of the graphene oxide nanosheets in epoxy matrix.Cone calorimeter measurements showed that the time to ignition of the epoxy/graphene oxide nanocomposite was longer than that of neat epoxy.The heat release rate curve of the nanocomposite was broadened compared to that of neat epoxy and the peak heat release rate decreased as well.     

氧化石墨烯-石墨烯纳米复合物传感器检测 对乙酰氨基酚和对氨基苯酚

本文通过简单超声法制备了氧化石墨烯-石墨烯(GO-Gr)碳复合材料,通过扫描电镜和电化学方法进行表征。将其修饰在玻碳电极表面,成功构建了用于对乙酰氨基苯酚(APAP)和对氨基苯酚(PAP)检测的电化学传感器。采用差分脉冲伏安法(DPV)测定APAP和PAP,线性检测范围为0.1～70μmol/L和0.3～60μmol/L,检出限为0.02 和0.1μmol/ L。同时,构建的传感器还表现出良好的稳定性和抗干扰能力,可用于实际样品的检测。     

Polarised infrared microspectroscopy of edge-oriented graphene oxide papers

We have performed FTIR transmission microspectroscopy on graphene oxide papers oriented with the nominal lattice planes parallel to the infrared optical axis. By polarising the IR light for samples of this geometry, spectral contributions of oriented oxide species are isolated from broad convoluted bands. Analysing the data alongside previous works, including experiments where samples were perturbed by reduction, dehydration and deuteration, we tabulate the most likely assignments for the observed spectral bands.     

Multifunctional nanocomposites based on tetraethylenepentamine-modified graphene oxide/epoxy

Composites based on epoxy/graphene were investigated for thermal-mechanical performance. Initially, few-layer graphene oxide (GO) was modified with tetraethylenepentamine (GO-TEPA) in a reaction assisted by microwave radiation. GO and GO-TEPA samples were characterized for their structure and morphology. Composites containing 0.1, 0.3 and 0.5 wt.% of GO and GO-TEPA were prepared, and the effect of fillers on the morphology of cryofractured regions of epoxy matrix was observed through electron microscopy images. Dynamic mechanical thermal analysis (DMA) tests revealed increases of approximately 20 °C in glass transition. Moreover, when compared to neat polymer, composites containing 0.5 wt.% of GO-TEPA gained up to 103% in thermal conductivity (obtained by flash laser). Finally, nanoindentation analyses showed increases of 72% in Young's modulus and 143% in hardness for the same sample. The system is characterized as multifunctional nanocomposites because of the simultaneous gains in thermal and mechanical properties. The best results of the multifunctional composites were strongly associated with the chemical modification of the GO by TEPA.     

Photovoltaic properties of graphene oxide sheets beaded with ZnO nanoparticles

A hybrid material of graphene oxide (GO) sheets beaded with ZnO nanoparticles was prepared. The material extends over a few hundred square nanometers, in which the ZnO nanoparticles (average diameter (∼5 nm)) are dispersed evenly on the GO sheet. Both the surface photovoltage or surface photocurrent intensity for the material are much stronger than for pure ZnO nanoparticles, meaning that the free charge carriers can effectively be transferred from ZnO nanoparticles to GO sheets, which can serve as a probe to monitor the electron transfer from excited ZnO to GO. Anchoring ZnO nanoparticles on two dimensional carbon nanostructures such as GO can pave a way towards the design of ordered nanostructure assemblies that can harvest light energy efficiently.     

Size separation of graphene oxide using preparative free‐flow electrophoresis

Graphene oxide nanosheets often bear a wide size distribution. However, it is critical to have nanosheets with narrow size distribution for their unique size‐dependent physiochemical properties, and nanosheets with a narrow size distribution are the cornerstones for application. Therefore, efficient separation methods of graphene nanosheets have been given considerable attention in many scientific areas recently. Free‐flow electrophoresis is extensively used in the separation and purification of biological molecules with continuous flow separation. The charged graphene oxide nanosheets to some extent are very close in size to biological molecules and share similarity in motion behavior in an electric field. Thus, in the present work, we present a new and simple means to separate graphene oxide nanosheets into more mono‐dispersed size groups by using the free‐flow electrophoresis technique. By optimizing the separation conditions, we were able to obtain graphene oxide sheets with narrow size distribution. The separated samples were characterized by atomic force microscopy, and the size measurements were made by using the software “Image Pro Plus.” In addition, a brief discussion is also given into the theoretic background of the separation of graphene oxide according to the size by the technique of preparative free‐flow electrophoresis.     

Robust curcumin-mustard oil emulsions for pro to anti-oxidant modulation of graphene oxide

The compositional flexibility of emulsions, via surfactant and additive choice, has been the major reason for their recognition as tuneable delivery sources for a variety of drugs. In particular, the kinetically stable nanoemulsions (NE) are preferred to minimize the toxicity extents of several poorly hydrophobic drugs through variation in their delivered extents. Inspired by these specialties, we have optimized our curcumin (curc) loaded sodium dodecylsulpahte (SDS) and dodecyl trimethylammonium bromide (DTAB) stabilized mustard oil microemulsions (ME) which catalyzed the pro-oxidant (with ethanol only) to antioxidant graphene oxide (GO) structural expression. The GO was synthesized using wet chemical approach, using ubiquitous graphite flakes as raw material. GO was loaded into 1:1 mixtures of (separately made) SDS and DTAB curc loaded formulations (CLFs). Henceforth, the resultant formulation contained 60% (1:1 SDS and DTAB) CLF mixture and ethanol dispersed GO (@ 1 mg/mL) as the other component. Compared to an insignificant (~47%) free state (while being dispersed in ethanol) DPPH free radical scavenging, the GO dispersed in CLFs enabled (62.47–100.96)% increments in DPPH scavenging, with 94.45% as maximum neutralization extent. The (493.57–3154.95)% particle size increments and (40.64–92.70)% PDI decrements for GO supplemented formulation over SDS and DTAB CLF mixtures, have inferred a wider curc distribution, through the larger GO surface area (SA) and its augmented oxygen enhanced chemical controls. In support, the physicochemical variations, characterized by (1.77–21.23)% γ decrements, (63.56–98.08%) and (68.90–163.22)% η and σ increments, have complemented the dispersion enhancing GO activities. Considering the bioactive nature of curc, these observations predict a prevalence of native curc structure or its enhanced non-covalent interaction controls with GO. Edible nature of mustard oil alongwith frequent inclusion of SDS and DTAB in routine gadgets, propel our formulations as robust media for attaining desired structural activities of functionalized GO derivatives.     

An electrochemical ascorbic acid sensor based on palladium nanoparticles supported on graphene oxide

In this study, an electrochemical ascorbic acid (AA) sensor was constructed based on a glassy carbon electrode modified with palladium nanoparticles supported on graphene oxide (PdNPs-GO). PdNPs with a mean diameter of 2.6 nm were homogeneously deposited on GO sheets by the redox reaction between PdCl₄²⁻ and GO. Cyclic voltammetry and amperometric methods were used to evaluate the electrocatalytic activity towards the oxidation of AA in neutral media. Compared to a bare GC or a Pd electrode, the anodic peak potential of AA (0.006 V) at PdNPs-GO modified electrode was shifted negatively, and the large anodic peak potential separation (0.172 V) of AA and dopamine (DA), which could contribute to the synergistic effect of GO and PdNPs, was investigated. A further amperometric experiment proved that the proposed sensor was capable of sensitive and selective sensing of AA even in the presence of DA and uric acid. The modified electrode exhibited a rapid response to AA within 5 s and the amperometric signal showed a good linear correlation to AA concentration in a broad range from 20 μM to 2.28 mM with a correlation coefficient of R = 0.9991. Moreover, the proposed sensor was applied to the determination of AA in vitamin C tablet samples. The satisfactory results obtained indicated that the proposed sensor was promising for the development of novel electrochemical sensing for AA determination.     

A facile synthesis of cellulose acetate reinforced graphene oxide nanosheets as proton exchange membranes for fuel cell applications

In this work, for the first time, a simple casting process is used to create an efficient and highly stable cellulose acetate (CA) based membrane with dispersive graphene oxide nanosheets (GO). The successful preparation of GO and its integration into the polymer matrix was verified by structural and morphological characterization using FTIR, TEM, SEM, and XRD. Furthermore, the impact of GO nanosheets and their content on the composite membranes' physicochemical properties is investigated. The water uptake increased up to 24% as the concentration of GO increased, while the ion exchange capacity increased threefold compared to the blank CA membrane. Additionally, increasing GO loading also enhanced the proton conductivity and the tensile strength of the developed membranes. The homogeneous CA/GO nanocomposite membranes with GO filler amounts ranging from 0.3 to 0.8 wt% were found to have excellent proton conductivity varying from 9.2 to 15.5 mS/cm compared to 6.94 mS/cm for Nafion 212. Further, as systematically studied and compared in membrane performance, the overall power density of the membrane electrode assembly (MEA) with GO content was increased up to 519 mW/cm² compared to 401 mW/cm² for Nafion 212 with significantly lower cost. The encouraging outcomes of this study pave the way for a simple, environmentally friendly, and cost-effective approach for developing nanocomposite membranes for application in PEMFCs.     

Facile synthesis and excellent catalytic activity of gold nanoparticles on graphene oxide

For the first time,Au nanoparticles on graphene oxide（GO-AuNPs） were successfully fabricated without applying any additional reductants,just by the redox reaction between AuCl₄^-1 and GO.Their structure was characterized by transmission electron microscopy and X-ray powder diffraction.The results show that flower-like AuNPs were successfully dispersed on GO surface.Importantly,they showed a high catalytic activity for the Suzuki-Miyaura coupling reaction in an aqueous medium.     

Synthesis of Ferrosoferric Oxide‐graphene Oxide Nanocomposite by Isoelectric Point Method for the Detection of Catechol

Ferrosoferric oxide functionalized graphene oxide nanocomposite with layer by layer structure was synthesized by isoelectric point method in this work. The prepared material was characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. Then the material was used to modify a glassy carbon electrode to fabricate an electrochemical sensor for the detection of catechol. The electrochemical sensor exhibited excellent electrochemical performance towards the detection of catechol with a linear response in the range of 5–205 μM and a detection limit of 2.32 μM. Furthermore, the electrochemical sensor showed excellent selectivity, stability and repeatability. These results revealed ferrosoferric oxide functionalized graphene oxide nanocomposite has potential applications in the fabrication of electrochemical sensors.     

Number of graphene layers exhibiting an influence on oxidation of DNA bases: Analytical parameters

This article investigates the analytical performance of double-, few- and multi-layer graphene upon oxidation of adenine and guanine. We observed that the sensitivity of differential pulse voltammetric response of guanine and adenine is significantly higher at few-layer graphene surface than single-layer graphene. We use glassy carbon electrode as substrate coated with graphenes. Our findings shall have profound influence on construction of graphene based genosensors.     

Light-responsive nanocomposites combining graphene oxide with POSS based on host-guest chemistry

A facile methodology has been proposed to construct lightresponsive nanocomposites composed of GO and POSS based on host-guest inclusion of CD/Azo. Through manipulating photo-irradiation conditions, GO and POSS moieties in GO-POSS exhibited impressive and reversible supramolecular assembly/disassembly behaviors and had remarkable effect on oxygen barrier property of PVA-coated films, which would have potential application for smart gas barrier materials in packaging.