GO Surface Research Articles

P-Type Charge Transfer Doping of Graphene Oxide with (NiCo)1-y Fey Ox for Air-Stable, All-Inorganic CsPbIBr2 Perovskite Solar Cells.

The precise regulation of interfacial charge distribution highly determines the power conversion efficiency of perovskite solar cells (PSCs). Herein, inorganic (NiCo)1-y Fey Ox nanoparticle decorated graphene oxide (GO) is successfully demonstrated as a hole booster for all-inorganic CsPbIBr2 PSC free of precious metal electrode. Arising from the spontaneous electron transfer induced p-type doping of GO from edged oxygen-containing functional groups to (NiCo)1-y Fey Ox , the best all-inorganic CsPbIBr2 PSC achieves an efficiency of 10.95 % under one standard sun owing to the eliminated paradox between charge extraction and charge localization in GO surface. Furthermore, the champion device exhibits an excellent long-term stability at 10 % relative humidity without encapsulation over 70 days because of the suppressed ions migration.

Oxidation degree dependent adsorption of ssDNA onto graphene-based surface* *Project supported by the National Natural Science Foundation of China (Grant Nos. 11305237 and 11974366), the Fundamental Research Funds for the Central Universities, China, the Natural Science Foundation of Shanghai, China (Grant No. 19ZR1463200), and the Key Research Program of Chinese Academy of Sciences (Grant No. QYZDJ-SSW-SLH053).

DNA/GO composite plays a significant role in the research field of biotechnology and nanotechnology, and attracts a great deal of interest. However, it is still unclear how the oxidation degree of the graphene-based surface affects the adsorption process of single-strand DNA (ssDNA). In this paper, based on the molecular dynamics simulations, we find that ssDNA molecule is absorbed on the GO surface in the most stable state with the oxidation degree around 15%. The microscopic mechanism is attributed to the van Der Walls and the electrostatic interactions between the ssDNA molecule and the graphene-based surface, which is accompanied with the π–π stacking and hydrogen bond formation. The number of π–π stacking between ssDNA and GO reaches the maximum value when the oxidation degree is around 15% among all the GO surfaces. Our simulation results also reveal the coexistence of stretched and curved configurations as well as the adsorption orientation of ssDNA on the GO surface. Furthermore, it is found that the absorbed ssDNA molecules are more likely to move on the graphene-based surface of low oxidation degree, especially on pristine graphene. Our work provides the physics picture of ssDNA’s physisorption dynamics onto graphene-based surface and it is helpful in designing DNA/GO nanomaterials.

Anchoring nanoscale iron sulfide onto graphene oxide for the highly efficient immobilization of uranium (VI) from aqueous solutions

Uranium is one of the most important radioactive elements using in the nuclear technology application, but it is hazardous for environment and human health because of its high mobility and toxicity. Hence, designing effective materials for uranium immobilization is highly desirable. In this paper, a novel adsorbent of GO/FeS prepared using a simple and convenient manner, by anchoring graphene oxide on nanoscale FeS was investigated for the immobilization of U(VI) from aqueous solutions. The mechanism of U(VI) immobilized onto GO/FeS was unveiled by X-ray photoelectron spectroscopy (XPS). The results revealed that FeS nanoparticles were successfully anchored onto GO surface, resulting in more reactive sites than pristine FeS or GO. Impressively, it was found that GO/FeS can enhance the immobilization of U(VI), leading to high adsorption capacity up to 347.2 mg/g. The kinetics of U(VI) immobilization was in accordance with the pseudo-second order kinetic model, and the isotherm of U(VI) immobilization was described by the D–R model, indicating chemical interaction mainly contributed to U(VI) immobilization on GO/FeS. The synergy between surface adsorption and reduction/precipitation mainly accounted for the immobilization mechanisms of U(VI) on GO/FeS, making GO/FeS to be as potential materials for remediation of U(VI)-contaminated wastewater.

Biologically reduced graphene oxide as a green and easily available photocatalyst for degradation of organic dyes

The disposal of untreated textile industrial wastewater having unmanageable pollutants is a global issue. Eco-friendly remediation technology is needed for the removal of environmental contaminants. In this study, a simple hydrothermal method is adapted to synthesis reduced graphene oxide (PErGO) using Phyllanthus emblica fruits extract and used as a photocatalyst for the degradation of synthetic toxic dyes. The physicochemical properties of green synthesized PErGO are confirmed using UV–Vis spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction. The ID/IG ratio is found as 1.02 for GO which is improved to 1.15 for PErGO, which confirms the existence of unrepaired defects after the elimination of negatively charged O2 moieties from the surface of GO. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis show well-exploited PErGO morphology. The photocatalytic removal of methylene blue (MB) and methyl orange (MO) dyes is confirmed using UV–vis spectrophotometer. PErGO shows about 92% of MO and 91% of MB degradation within 90 min of sunlight exposure while carried out as a mixed dye degradation. The sustainability of this catalyst is confirmed by testing it for five subsequent degradation cycles and noticed a stable and significant degradation activity. Outcomes from this study suggest that eco-friendly PErGO can be used as an alternate sustainable material to treat a large volume of wastewater from various dye industries.

Facile synthesis of reduced graphene oxide using Acalypha indica and Raphanus sativus extracts and their in vitro cytotoxicity activity against human breast (MCF-7) and lung (A549) cancer cell lines.

In the present study, an eco-friendly approach is adapted for the synthesis of reduced graphene oxide (rGO's) by a simple hydrothermal reaction using two plant extracts namely Acalypha indica and Raphanus sativus. After the hydrothermal reaction, GO turns into a black color from brown color, which indicates the successful reduction of graphene oxide. Further, various characterization techniques such as UV-Vis spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction is used to confirm the physicochemical properties of synthesized rGO's. Raman analysis confirms the reduction of GO by noticing an increase in the ID/IG ratio significantly. Field emission scanning electron microscopy and transmission electron microscopy clearly show the morphology and crystalline nature of rGO's. FT-IR spectrum confirms that the bioactive molecules of the plant extract (i.e. polyphenols, flavonoids, terpenoids, etc.) playing a key role in the elimination of oxygen groups from the GO surface. Further, the synthesized rGO's are tested for their potential against human lung and breast cancer cell lines. A significant cancer cell inhibition activity is obtained even in the less concentration of rGO's with IC50 values for lung cancer cell lines are 38.46µg/mL and 26.69µg/mL for AIrGO and RSrGO, respectively. Similarly, IC50 values for breast cancer cell lines are 35.97µg/mL and 33.22µg/mL for AIrGO and RSrGO, respectively.

Synergistic effect of anion and cation in oxalic acid for graphene surface engineering and its enhanced pseudocapacitance performance

The reduced graphene oxide (rGO-oxalic) with rich carbonyl and hydroxyl groups was prepared by using oxalic acid as reducing agent, and the structure of rGO-oxalic was characterized by XRD, Raman, TEM, AFM, XPS and BET. The anion and cation in oxalic acid play an important role in the removal of oxygen groups on GO surface, but the chemical reaction and mechanism are different. The further study indicated that the GO was reduced rapidly and effectively in the initial stage of reaction, and it is selective reduction in the middle and final stage of the reaction, showing that more carbonyl and hydroxyl groups were retained. The supercapacitor with rGO-oxalic as electrode material exhibited the superior specific capacitance (301.1 F·g−1 and 217.0 F·g−1 at 1 A·g−1 in three- and two-electrode systems, respectively). Meanwhile, the capacitance retention was as high as 89.5% after 10,000 cycles at 5 A·g−1 for the symmetric supercapacitor. The research on the reduction mechanism of rGO-oxalic is beneficial to its potential application in energy storage and other fields.

Non-enzymatic electrochemical sensor for nitrite based on a graphene oxide–polyaniline–Au nanoparticles nanocomposite

Although non-enzymatic electrochemical methods are advantageous for the detection of nitrite, a highly toxic pollutant, improved sensitivity is required for practical applications. Herein, a graphene oxide–polyaniline–Au nanoparticles (GO-PANI-AuNPs) nanocomposite prepared by a hydrothermal synthesis method was used to fabricate a novel electrochemical nitrite sensor. Structural and morphological characterisation of the nanocomposite using transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy revealed that PANI formed a network structure on the GO surface and that a large amount of AuNPs were uniformly connected to the active sites of GO-PANI. Electrochemical investigations showed that the fabricated GO-PANI-AuNPs sensor exhibited excellent catalytic performance for the oxidation of nitrite. The sensor showed good selectivity for nitrite with linear ranges of 0.5 μM–0.24 mM and 0.24 mM–2.58 mM and a detection limit of 0.17 μM (signal-to-noise ratio of 3). This developed sensor was successfully applied to the detection of nitrite ions in tap water and sewage, and the recovery rate was 97%–105%. Therefore, the GO-PANI-AuNPs nanocomposite offers a reliable electrochemical strategy for the detection of NO2−, which has important theoretical and practical significance for environmental monitoring applications.

Self-assembled monolayers modified and further silanized graphene nanosheets reinforced silicone rubber with highly mechanical performance

Self-assembled monolayer (SAM) modified graphene oxide SAM-rGO (AGO) has been prepared and works as the template for further fabricated silanized 2D AGO-TEOS nanosheets with tetraethyl orthosilicate (TEOS), which can effectively prevent the agglomeration of GO and well-dispersed in the silicone rubber (SR). Compared with the popular method of synthesizing silica nanoparticles on the surface of GO, the polysiloxane chains directly interact with AGO-TEOS without using silica as a medium, therefore it can produce a stronger interface interaction with SR, and greatly improves the mechanical strength of SR. When 5 wt% AGO-TEOS are added, the strength of SR is increased to 6.30 MPa, which is 1575% of unfilled SR, while the elongation at break is 99.31%.

Enhanced electrochemical detection of dopamine by graphene oxide/tungsten trioxide nanocomposite

Dopamine plays a vital role in neurotransmission and dopamine level detection in body fluid is very essential for diagnosis of neurological diseases. Finding a novel material, which enhances the electrochemical detection of dopamine is necessary in the present scenario. The Graphene oxide/tungsten trioxide (GO/WO3) nanocomposite were prepared by two-step procedure; modified Hummer's method for GO synthesis, followed by co-precipitation method for the preparation of WO3 with GO. The structural, chemical compositional and surface functional properties of as-synthesized GO/WO3 composite were systematically characterized. The WO3 nanocube shaped particles with an average diameter of 100–200 nm, completely covered the GO surface, during the in-situ growth process. Glassy carbon electrode (GCE) modified with prepared GO/WO3 nanocomposite was used as working electrode and analysed its selective and sensitive detection of dopamine by means of electrochemical measurements. The chronoamperometric results revealed that, GCE has wide linear range of (0.3 μM–1245 μM) of dopamine detection with outstanding selective performances. The limit of detection to 0.306 μM and sensitivity 0.392 μA μM−1cm−1 of electrode was calculated. The as-prepared GCE towards the detection of dopamine was tested in real samples (human urine), the measured results established the great dopamine sensing abilities with high selectivity and good stability in real samples.

Rapid synthesis and characterization of silver-loaded graphene oxide nanomaterials and their antibacterial applications.

With the promising potential application of Ag/graphene-based nanomaterials in medicine and engineering materials, the large-scale production has attracted great interest of researchers on the basis of green synthesis. In this study, water-soluble silver/graphene oxide (Ag/GO) nanomaterials were synthesized under ultrasound-assisted conditions. The structural characteristics of Ag/GO were confirmed by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy and energy dispersion spectroscopy, respectively. The results showed the silver particles (AgNPs) obtained by reduction were attached to the surface of GO, and there was a strong interaction between AgNPs and GO. The antibacterial activity was primarily evaluated by the plate method and hole punching method. Antibacterial tests indicated that Ag/GO could inhibit the growth of Gram-negative and Gram-positive bacteria, special for the Staphylococcus aureus.

Magnetically Recyclable Graphene Oxide Demulsifier Adapting Wide pH Conditions on Detachment of Oil in the Crude Oil-in-Water Emulsion.

In the present work, an amphiphilic and magnetically recyclable graphene oxide (MR-GO) demulsifier was devised and synthesized by graft of magnetic nanoparticles (Fe3O4@SiO2-APTES) and ethylenediamine on the GO surface. The wettability and surface charges of MR-GO under various pH conditions can be regulated via adjusting the contents and species of surface functional groups (such as amino, carboxyl, and hydroxyl). In the demulsificaition test, MR-GO displayed favorable demulsification performance for crude oil-in-water (O/W) emulsion under pH of 2.0-10.0, thusly greatly improving the application scope of common demulsifier. The optimal dosage of MR-GO was 200 mg/L and the demulsification efficiency attained a maximum value of 99.7% for crude O/W emulsion with pH of 6.0. What's more, owing to its magnetic response performance, the MR-GO can be reused and the demulsification efficiency remained above 91.0% after six cycles. Based on the strong interfacial activity, MR-GO can arrive to the crude oil-water interface. With the synergy effects of interfacial adsorption (π-π/n-π) interactions and electrostatic attraction of demulsifier and interfacial films, and the aid of external mechanical forces, the interfacial films stabilized the emulsion were disrupted. Therefore, the oil droplets coated on the water droplets were gathered rapidly to form oily flocs and then migrated to the water surface to accomplish the demulsification of crude O/W emulsion.

Durable superhydrophobic PVDF/FEVE/GO@TiO2 composite coating with excellent anti-scaling and UV resistance properties

Biomimetic superhydrophobic surfaces with excellent self-cleaning, antifouling and anticorrosion properties often suffer from mechanical damage and stop functioning when exposed to corrosive solutions or UV light in practical applications. In this study, a robust superhydrophobic PVDF/FEVE/GO@TiO2 composite coating with a high water contact angle of 158 ± 1.6° and low sliding angle of 6 ± 0.5° has been successfully fabricated via the combination of hydrothermal synthesis and spraying techniques. The GO@TiO2 composite particles were synthesized by in-situ growth of TiO2 on the GO surface through chemical condensation with the active sites of GO under hydrothermal conditions. Owing to the interfacial enhancement of GO@TiO2 and the adhesion enhancement of FEVE, the prepared superhydrophobic coating demonstrated excellent mechanical durability and retained its superhydrophobicity after 1000 abrasion cycles. Moreover, due to the orientation of lamellar GO, TiO2 was evenly distributed on the coating surface to construct uniform micro-/nanostructures, which can capture stable air film to prevent the permeation of H+, Cl−, OH− from water and simultaneously absorb more UV irradiation. Thus, the prepared coating demonstrated outstanding chemical stability under strong acidic and alkaline conditions for 7 days and after exposure to UV radiation (300 W) for 20 days. Furthermore, under the cooperative effect of the air film and hierarchical structures, the prepared superhydrophobic coating can inhibit the nucleation of CaCO3 scale and induce the formation of unstable needle-like CaCO3 on the coating surface. Therefore, it is anticipated that this durable superhydrophobic coating will be an excellent candidate for technological applications, such as anti-scaling, antifouling, and self-cleaning materials.

Facile synthesis of lanthanum hydroxide doped graphene oxide for scavenged of radioactive and heavy elements from water

Lanthanum hydroxide nanoparticles doped graphene oxide (GO-La(OH)3) was facile synthesized by sol–gel process and analyzed by spectroscopy and microscopy techniques including Fourier transform infrared (FT-IR), X-ray photoelectron (XPS), X-ray diffraction (XRD) spectroscopy and scanning electron microscopy equipped with energy-dispersive X-ray (SEM-EDX) spectroscopy. The prepared material exhibited high adsorption capacities of 78.82 and 71.42 mg g−1 for U(VI) and Pb(II), respectively. Batch studies confirmed that the adsorption was altered when conditions such as aqueous solution pH, dosage, and system temperature were varied, which indicates that the adsorption process comprises of chemical surface complexation. Further, it was conferred from the 2-pKa diffusion model fitting was well explained the adsorption process. The main and novel observations from the doping of GO surface with La can be termed as La-composites (such as La oxide and La(OH)3) are the alteration of the GO adsorption efficiency, enhancing of adsorbent separation rate from the aqueous solutions, and increases stability of the composite. In addition, the adsorption capacity was increased with the reaction temperature. The overall results have been indicating that the simple preparation of material having easy recovery and reliable adsorption efficiency for radioactive and heavy metals treatment applications.

Graphene oxide nanofilm and chicken embryo extract decrease the invasiveness of HepG2 liver cancer cells

BackgroundThe extracellular matrix (ECM) is a mosaic of various structural and functional proteins that cooperate with the cell, regulate adhesion, and consequently manage its further fate. Liver destruction is accompanied by a disruption of the physicochemical properties of the ECM which deregulates the cell–ECM interaction and can lead to uncontrolled proliferation and neoplastic transformation of cells. Therefore, it can be assumed that ECM modification and restoration of its characteristics for healthy tissue may counteract uncontrolled cell proliferation. The purpose of the presented research model was to optimise the physical characteristics of ECM by introducing a graphene oxide plane/nanofilm (nfGO) and enriching the cell environment with potentially missing proteins by adding a functional protein cocktail (chicken embryo liver extract) and determine the impact of these factors on cell–ECM cooperation and its consequences on adhesion, proliferation, and cell phase, which are factors of the invasiveness of cancer cells.ResultsExperiments were performed with non-cancer HS-5 cells and liver cancer cells HepG2 and C3A. The cells were divided into four groups: (1) control, (2) cultured on nfGO, (3) cultured with the addition of chicken embryo liver extract (CELE) and (4) cultured on the nfGO with the addition of CELE. CELE contained 1735 proteins; the top 57 of these proteins have been presented. The use of nfGO as well as CELE and nfGO + CELE reduced the proliferation of HepG2 cancer cells to the greatest extent; this is in contrast to non-cancer cells and also to C3A cancer cells. Furthermore, the combined use of the CELE protein cocktail and GO substrate effectively resulted in a decrease in the population of HepG2 cells in the G0/G1 phase and an increase of the population in G2/M. Molecular analysis of HepG2 cancer cells also showed an increase in the expression of genes responsible for adhesion such as focal adhesion kinase (fak), e-cadherin, and n-cadherin and a decrease in β-catenin, which is considered a proto-oncogene.ConclusionsStudies have shown that both the GO surface structure on which the cells are grown as well as the presence of a multi-component natural cocktail of regulatory proteins, can modify the expression of integrins, increase adhesion and, as a consequence, proliferation and the cell cycle—entering the resting phase. For the first time, it has been documented that hepatic cancer cells of the HepG2 line under the influence of stimuli derived from mimic ECM (graphene oxide) in interaction with a unique protein complex derived from chicken liver embryo decreased of the invasiveness of cancer cells.

Graphene oxide as a pesticide carrier for enhancing fungicide activity against Magnaporthe oryzae

GO can cause the cell damage by cutting cell wall and oxidative stress, and the drug absorbed on the surface of GO were released precisely.

Preparation and characterization of polythiophene/graphene oxide/epoxy nanocomposite coatings with advanced properties

In this paper, polythiophene–graphene oxide (PTh–GO) hybrids-filled epoxy (0–2 wt%) coatings with enhanced mechanical and anti-corrosion properties applied as an advanced coating. The chemical structure, morphology, toughness, adhesion to the substrate and anticorrosive properties of these coatings were studied. FTIR analysis and morphological investigations (XRD, SEM and TEM) confirmed that PTh synthesized in the presence of GO and PTh nanoparticles located on the surface of GO and exfoliated structure were obtained. Potentiodynamic polarization, EIS and OCP analysis confirmed better anti-corrosion properties of PTh–GO hybrids-filled epoxy coatings than neat epoxy and GO- or PTh-filled epoxy. Adhesion analysis results demonstrated that epoxy/PTh–GO nanocomposites better adhesion to the mild steel and only 5% of the coating was removed during analysis. Izod test shows that addition of 0.5 wt% PTh–GO to epoxy lead to 61% improvement of impact strength of epoxy coating.

A novel method to synthesize BiSI uniformly coated with rGO by chemical bonding and its application as a supercapacitor electrode material

Bismuth cations are uniformly anchored on the surface of GO and the size of GO can determine the final size of rGO coated BiSI composite.

A proof of concept for cooperation from the quinone groups adjacent to N sites during the metal-free oxidation of glycerol by nitrogen-rich graphene oxide

A catalytic active site already present in an organic molecule was chemically tagged on the GO surface to prove the role of quinone groups adjacent to N sites in nitrogen-rich carbon materials for the metal-free oxidation of glycerol.

Rapid Effective Reduction by Microwave-Irradiated Thermal Reaction for Large-Scale Production of High-Quality Reduced Graphene Oxide

ABSTACT In this study, we suggest a simple and effective one-pot hybrid reduction process for the mass production of high-quality reduced graphene oxide (rGO) by simultaneously doing deoxygenation and healing reactions. During the microwave-irradiated thermal reduction, intercalated benzene in the GO easily generates acetylene by pyrolysis; the released acetylene react with surrounding defect sites in the GO surface to successfully form new C–C bonds. As a result of the newly formed sp2-hybridized C–C bond in the rGO surface, the defect-repaired rGO (rGO-B) shows remarkably enhanced crystallinity (ID/IG ratio: rGO-B, 0.63; rGO-T, 1.08), thermal stability, and electrical properties over that of rGO prepared without a carbon-source supplement (rGO-T). Especially, compared to the rGO-T, the rGO-B had 4.4 times more carrier density and 18 times increased carrier mobility because of the restoration of defect sites in the rGO-B surface. The rGO-B exhibited six times higher electrical conductivity than did rGO-T because of the improved carrier mobility. These results obviously suggest that the reduction of GO by means of microwave-irradiated thermal reduction with a carbon-source supplement could be a powerful approach for commercial mass production of high-quality rGO because of its easy manufacturing approach.

Porous BMTTPA-CS-GO nanocomposite for the efficient removal of heavy metal ions from aqueous solutions.

In this study, a stable, cost-effective and environmentally friendly porous 2,5-bis(methylthio)terephthalaldehyde–chitosan–grafted graphene oxide (BMTTPA–CS–GO) nanocomposite was synthesized by covalently grafting BMTTPA–CS onto the surfaces of graphene oxide and used for removing heavy metal ions from polluted water. According to well-established Hg2+–thioether coordination chemistry, the newly designed covalently linked stable porous BMTTPA–CS–GO nanocomposite with thioether units on the pore walls greatly increases the adsorption capacity of Hg2+ and does not cause secondary pollution to the environment. The results of sorption experiments and inductively coupled plasma mass spectrometry measurements demonstrate that the maximum adsorption capacity of Hg2+ on BMTTPA–CS–GO at pH 7 is 306.8 mg g−1, indicating that BMTTPA–CS–GO has excellent adsorption performance for Hg2+. The experimental results show that this stable, environmentally friendly, cost-effective and excellent adsorption performance of BMTTPA–CS–GO makes it a potential nanocomposite for removing Hg2+ and other heavy metal ions from polluted water, and even drinking water. This study suggests that covalently linked crucial groups on the surface of carbon-based materials are essential for improving the adsorption capacity of adsorbents for heavy metal ions.