Presence Of Graphene Oxide Nanosheets Research Articles

Preparation and characterization of Cu-GO and Cu-GO-YSZ nanocomposite coating by electrochemical deposition for improved mechanical and anti-corrosion properties

Graphene oxide (GO) and yttria-stabilized zirconia (YSZ) nanoparticle reinforced copper (Cu) matrix nanocomposite coatings were successfully fabricated via direct current electroplating from a copper sulfate electrolyte. Influences of particle concentration (GO/YSZ) in electrolyte, electrodeposition time and applied current density on composition, microstructural and anti-corrosion performance of Cu-GO and Cu-GO-YSZ composite coatings were explored. The corrosion behaviors were evaluated by electrochemical measurement. Results indicated the composite coatings exhibit a uniform and compact surface which was made up of stacked granules, exhibiting morphologies that nanoflake-like structures dispersed on the pyramid-like copper matrix granule clusters network. The crystallite sizes of Cu-GO first increased and then decreased as GO, time and current density increased, while it varied little for Cu-GO-YSZ composite coating. The preferred orientation of Cu matrix composite coating was oriented (220) texture. The content of incorporated GO increased with the introduction of YSZ into the Gu-GO matrix. The Gu-GO coating contains 93.3 wt% Cu and 5.5 GO, and the Gu-GO-YSZ coating contains 91.7 wt% Cu and 7.6 wt% GO. The average roughness Ra of Cu-GO and Cu-GO-YSZ were 240 ± 7 nm and 236 ± 40 nm, respectively. The addition of GO nanosheets could improve the microhardness and decrease the COF of Cu matrix. Both self-lubrication effect and load-bearing capability were improved by introducing GO and YSZ together in the Cu matrix. Deposits obtained at 30 mA cm−2, 30 min, 0.1 g L−1 GO and 10 g L−1 YSZ particles own the optimal corrosion resistance with the maximum Rp. It reveals that corrosion resistance was enhanced by the presence of GO nanosheets in Cu matrix for physical isolation effect of GO and the preferred orientation (220) plane, which benefited the formation of passive film.

Effects of graphene oxide nanosheets in the polychaete Hediste diversicolor: Behavioural, physiological and biochemical responses

Numerous applications exist for graphene-based materials, such as graphene oxide (GO) nanosheets. Increased concentrations of GO nanosheets in the environment have the potential to have a large negative effect on the aquatic environment, with consequences for benthic organisms, such as polychaetes. The polychaete Hediste diversicolor mobilises the sediments, hence altering the availability of contaminants and the nutrients biogeochemical cycle. As such, this study proposes to assess the effects of different GO nanosheet concentrations on the behaviour, feeding activity, mucus production, regenerative capacity, antioxidant status, biochemical damage and metabolism of H. diversicolor. This study evidenced that H. diversicolor exposed to GO nanosheets had a significantly lower ability to regenerate their bodies, took longer to feed and burrow into the sediment and produced more mucus. Membrane oxidative damage (lipid peroxidation) increased in exposed specimens. The increased metabolic rate (ETS) evidenced a higher energy expenditure in exposed organisms (high use of ready energy sources – soluble sugars) to fight the toxicity induced by GO nanosheets, such as SOD activity. The increase in SOD activity was enough to reduce reactive oxygen species (ROS) induced by GO on cytosol at the lowest concentrations, avoiding the damage on proteins (lower PC levels), but not on membranes (LPO increase). This study revealed that the presence of GO nanosheets, even at the lower levels tested, impaired behavioural, physiological, and biochemical traits in polychaetes, suggesting that the increase of this engineered nanomaterial in the environment can disturb these benthic organisms, affecting the H. diversicolor population. Moreover, given the important role of this group of organisms in coastal and estuarine food webs, the biogeochemical cycle of nutrients, and sediment oxygenation, there is a real possibility for repercussions into the estuarine community.

Microfluidic investigation of the effect of graphene oxide on mechanical properties of cell and actin cytoskeleton networks: experimental and theoretical approaches

Biomechanical and morphological analysis of the cells is a novel approach for monitoring the environmental features, drugs, and toxic compounds’ effects on cells. Graphene oxide (GO) has a broad range of medical applications such as tissue engineering and drug delivery. However, the effects of GO nanosheets on biological systems have not been completely understood. In this study, we focused on the biophysical characteristics of cells and their changes resulting from the effect of GO nanosheets. The biophysical properties of the cell population were characterized as follows: cell stiffness was calculated by atomic force microscopy, cell motility and invasive properties were characterized in the microfluidic chip in which the cells are able to visualize cell migration at a single-cell level. Intracellular actin was stained to establish a quantitative picture of the intracellular cytoskeleton. In addition, to understand the molecular interaction of GO nanosheets and actin filaments, coarse-grained (CG) molecular dynamics (MD) simulations were carried out. Our results showed that GO nanosheets can reduce cell stiffness in MCF7 cells and MDA-MB-231 cell lines and highly inhibited cell migration (39.2%) in MCF-7 and (38.6%) in MDA-MB-231 cell lines through the GO nanosheets-mediated disruption of the intracellular cytoskeleton. In the presence of GO nanosheets, the cell migration of both cell lines, as well as the cell stiffness, significantly decreased. Moreover, after GO nanosheets treatment, the cell actin network dramatically changed. The experimental and theoretical approaches established a quantitative picture of changes in these networks. Our results showed the reduction of the order parameter in actin filaments was 23% in the MCF7 cell line and 20.4% in the MDA-MB-231 cell line. The theoretical studies also showed that the GO nanosheet–actin filaments have stable interaction during MD simulation. Moreover, the 2D free energy plot indicated the GO nanosheet can induce conformational changes in actin filaments. Our findings showed that the GO nanosheets can increase the distance of actin-actin subunits from 3.22 to 3.5 nm and in addition disrupt native contacts between two subunits which lead to separate actin subunits from each other in actin filaments. In this study, the biomechanical characteristics were used to explain the effect of GO nanosheets on cells which presents a novel view of how GO nanosheets can affect the biological properties of cells without cell death. These findings have the potential to be applied in different biomedical applications.

Graphene oxide/silver nanostructure as a green anti-biofouling composite toward controlling the microbial corrosion

Microbiologically influenced corrosion is a serious problem in the oil and gas industry, which leads to both economical losses and environmental pollutions. To control biocorrosion and prevent the problems, using biocides is the main solution. Recently, nanomaterials have been introduced as a new generation of biocides to control the biocorrosion. In this study, graphene oxide/silver nanostructure was synthetized, and its biocidal effect was evaluated by a dose–response test. The response surface methodology in the Design-Expert software was used to analyze the result, and to determine the optimum concentration of nanostructure to inhibit sulfate reducing bacteria, which was 80 mg/L. The corrosion morphology and the composition of the formed corrosion products were studied using surface analysis methods. The result illustrated the uniform corrosion and significantly reduced amount of iron sulfide in the presence of nanostructure, due to the inhibition of sulfate reducing bacteria. In comparison, the pitting corrosion was observed on the surface of the exposed coupon to the bacteria, and the high presence of iron sulfide in the corrosion products. The corrosion behavior of steel in the presence of the bacteria and the nanostructure was investigated via electrochemical impedance spectroscopy and Tafel polarization techniques. Corrosion test result indicated that the addition of the nanostructure increased the charge transfer resistance, resulting in the reduction in corrosion rate. This is attributed to preventing the production of biofilm by the nanostructure and the formation of a protective film in the presence of graphene oxide nanosheets.

Effect of crystallinity, crystal polymorphism, and graphene oxide nanosheets on the barrier properties of poly (l-lactic acid)

In this study, the effects of crystallinity, crystal polymorphism, and graphene oxide nanosheets (GONS) on the oxygen and water vapor permeability of PLLA were investigated. It was revealed that for the pristine PLLA with a crystallinity degree of 40%, the oxygen and water vapor permeability decreased by about 48% and 30%, respectively. Also, by changing the crystal form from α′ to α in a constant crystallinity ratio, the oxygen and water vapor permeability decreased by about 10% and 28%, respectively. PLLA/GO nanocomposites with various compositions were prepared by solution coagulation. Results of the permeability analysis on nanocomposites showed that in the presence of 1 wt% GONS, the oxygen and water vapor permeability of PLLA films decreased by about 80% and 30% respectively. In addition, the simultaneous effect of crystallinity and the presence of GONS was investigated, demonstrating that the simultaneous presence of crystalline structures with nanosheets caused the gas pathways to prolong immensely, and for the sample containing 1 wt% nanosheets with about 35% of crystallinity, the rate of oxygen permeation and water vapor transmission decreases by about 90% and 60%, respectively. The Nielsen, Bharadwaj, Duan & Thomas, and Tan & Thomas models were used for comparing these results.

Development of three-dimensional piezoelectric polyvinylidene fluoride-graphene oxide scaffold by non-solvent induced phase separation method for nerve tissue engineering

In this work, non-solvent induced phase separation method was applied to develop polyvinylidene fluoride (PVDF)/graphene oxide (GO) scaffold for nerve tissue engineering. Furthermore, the effects of GO concentration (0, 0.5, 1, 3 and 5 wt%) on the electrical, mechanical, physical and biological properties of scaffolds were also evaluated. Results demonstrated that, incorporation of GO nanosheets in the PVDF matrix decreased water contact angle, while enhanced the hydrophilicity, water absorption and water flux of the scaffolds. Moreover, mechanical properties of the nanocomposite scaffolds improved in the presence of GO nanosheets. Significantly, increasing GO content up to 3 wt% enhanced tensile modulus and strength of PVDF scaffold from 8.1 ± 1.4 and 0.8 ± 0.2 MPa to 17.0 ± 3.7 and 1.4 ± 0.4 MPa, respectively. Incorporation of GO nanosheets into the PVDF scaffold simultaneously enhanced β phase fraction, piezoelectricity and electrical conductivity of all nanocomposite scaffolds. Furthermore, PVDF-GO scaffolds significantly promoted cell proliferation, compared to PVDF scaffold, depending on the GO content. Finally, PVDF-GO scaffold could easily be converted in to a nerve guidance conduit with 4 internal longitudinally aligned channels making it appropriate for the nerve regeneration applications.

Preparation of binary and hybrid epoxy nanocomposites containing graphene oxide and rubber nanoparticles: Fracture toughness and mechanical properties

ABSTRACTBinary and hybrid epoxy nanocomposites modified with graphene oxide (GO) and core–shell rubbers (CSR) were synthesized via the solvent‐exchange method. X‐ray diffraction analysis and scanning electron microscopy of the samples showed a homogeneous dispersion of GO and CSR in the epoxy matrix. The tensile modulus and tensile strength of the samples modified with CSR decreased continuously with increasing CSR content; however, with the addition of only 0.05 phr GO to the neat epoxy and rubber‐modified epoxy, these properties significantly increased. The use of GO and CSR individually improved the fracture toughness, but the impact of GO was greater. The simultaneous use of GO and CSR improved both the fracture toughness and the mechanical properties. Our investigation of the toughening mechanism indicated that crack deflection–bifurcation, crack pinning, and particle debonding–pullout in the presence of GO nanosheets and limited rubber particle cavitation contributed to fracture toughness improvement in the hybrid systems. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46988.

A Study of Calcium-Silicate-Hydrate/Polymer Nanocomposites Fabricated Using the Layer-By-Layer Method.

Calcium-silicate-hydrate (CSH)/polymer nanocomposites were synthesized with the layer-by-layer (LBL) method, and their morphology and mechanical properties were investigated using atomic force microscopy (AFM) imaging and AFM nanoindentation. Different sets of polymers were used to produce CSH/polymer nanocomposites. The effect of different factors including dipping time, calcium to silicate ratios (C/S ratios) and pH on morphology was investigated. CSH/polymer nanocomposites made with different sets of polymers showed variation in morphologies. However, the Young’s modulus did not seem to reveal significant differences between the nanocomposites studied here. In nanocomposites containing graphene oxide (GO) nanosheet, an increase in the density of CSH particles was observed on the GO nanosheet compared to areas away from the GO nanosheet, providing evidence for improved nucleation of CSH in the presence of GO nanosheets. An increase in roughness and a reduction in the packing density in nanocomposites containing GO nanosheets was observed.

Graphene oxide incorporated ZnO nanostructures as a powerful ultraviolet composite detector

In this study, ultraviolet (UV) photodetection performance of graphene oxide (GO) incorporated ZnO composites with different contents of GO (0.25, 0.5, 1.0, and 2.0 wt%) is investigated. The presence of graphene oxide nanosheets in the composites is confirmed by microscopic images and spectroscopic tools. Scanning electron microscopy images showed a uniform distribution of GO nanosheets between ZnO nanostructures. Uniform dispersion of GO nanosheets between ZnO nanostructures was also approved by transmission electron microscopy. Based on X-ray diffraction spectra, it was found that GO nanosheets could be considered as seeds for inhomogeneous nucleation of ZnO nanoparticles. According to Raman spectroscopy, the number layers of graphene oxide nanosheets was calculated to be around 4–6. Finally, UV-detection measurements showed that 1.0 wt% of GO into ZnO nanopowder was accounted as optimal point. However, increasing the GO concentration gave rise to a substantial reduction in the responsivity of the samples. Indeed, we believe, in the sample whose GO concentration is more than 1.0 wt%, graphene sheets play as obstacles which decrease the amount of UV light absorbed by ZnO nanostructures.

Structural, mechanical and thermal behaviors of novolac/graphene oxide nanocomposite aerogels

Main microstructural properties of organic aerogels dictate the thermal degradation of these materials. Incorporating of nanomaterials into the structure of organic aerogels can result in controlling and engineering the microstructural characteristics and as a result, the thermal degradation of organic aerogels. Here, the role of graphene oxide (GO) presence on the microstructure and morphology of novolac/GO nanocomposite aerogels is investigated. Although, the presence of GO nanosheets results in an enhancement of the density, but the specific surface area of aerogels increased with the contents of loaded-nanosheets, due to the high available surface area of GO nanosheets. The sol-gel polymerization of novolac resin in the presence of GO nanosheets results in formation of colloidal nanoparticles on the surface of GO nanosheets. Chemical characterizations confirm that the reason behind this phenomenon is the formation of covalent interactions between polymer chains and GO surface. Moreover, the thermal degradation and thermal conductivity behaviors of novolac/GO nanocomposite aerogels are studied here, to investigate the influences of GO presence on the heat-transfer mechanism through the aerogel. Thermal studies approve that the heat transfer depends strongly on the reduction of GO nanosheets, as well as on the contents of loaded-GO. As the contents of loaded-GO reach a percolation threshold, the structural characteristics, and consequently, the mechanism of thermal degradation throughout aerogel structure, change.

Electrospun PU/P(AMPS-GO) nanofibrous membrane with dual-mode hydrophobic–hydrophilic properties for protective clothing applications

Bi-functional nanofibrous membrane composed of polyurethane in one face and poly(2-acryloylamido-2-methylpropanesulfonic acid)-graphene oxide (PAMPS-GO) in another face has been fabricated using two opposite-nozzle electrospinning set-up. The effect of graphene oxide addition on morphology of PAMPS nanofibers and performance of membrane were investigated. Besides structure of graphene oxide layers, electrospun nanofibers were studied using TEM, X-ray, FTIR, and FE-SEM methods. To evaluate the nanofibrous membrane performance, their tensile strength, water vapor permeability, and contact angle were measured. An average diameter of 500 nm and 83 nm were obtained for PU and PAMPS nanofibers, respectively, through the optimized electrospinning process. Results show that PAMPS nanofiber diameters together with pore sizes of its mat decrease by increasing the graphene oxide content. Also, the dimensional stability of electrospun fibers against water vapor was strengthened in the presence of graphene oxide nanosheets. An improvement in tensile strength of PAMPS nanofibers was observed by the addition of graphene oxide up to 0.2 wt.%, while more addition caused a negative change. Studying water vapor permeability of PAMPS nanofibers showed that increasing the graphene oxide content, the water vapor permeability increases. However, it decreases by increasing the surface density of nanofibers. From a hydrophobic–hydrophilic perspective, an excellent dual-mode behavior on two opposite faces was observed that is already proper for water proof-breathable protective clothing and wound dressing applications.

Graphene oxide-enriched poly(ε-caprolactone) electrospun nanocomposite scaffold for bone tissue engineering applications

Tissue engineering aims at fabricating biological substitutes to improve, repair, and regenerate failing human tissues or organs. Designing a nanocomposite scaffolds with tailored properties that enhance the development of functional tissue can be an appropriate approach to achieve this purpose. In this study, the uniform and bead-free nanofibers of poly(ε-caprolactone) composited with different graphene oxide nanosheet contents (ranging from 0.5 to 2 wt%) were successfully fabricated through electrospinning process. A decrease in the average diameter of poly(ε-caprolactone) nanofibers was observed with the addition of graphene oxide nanosheets. Moreover, the nanocomposite scaffolds containing 2 wt% of graphene oxide nanosheets exhibited superior mechanical properties compared to that of pure poly(ε-caprolactone). Compared with pure poly(ε-caprolactone) scaffold, the degradation rate of poly(ε-caprolactone)-graphene oxide nanosheet nanofibers was enhanced, while the integrity of fibers was preserved. The presence of graphene oxide nanosheets in poly(ε-caprolactone) fibers promoted in vitro biomineralization, indicating bioactive features of the nanocomposite scaffolds. Compared to the pure one, nanocomposite fibers also showed better ability in protein adsorption. The in vitro cell culture studies showed that the addition of graphene oxide nanosheets did not diminish the biocompatibility of the electrospun poly(ε-caprolactone) nanofiber. Furthermore, the adhesion and proliferation of MG63 cells were increased. Altogether, the results demonstrated that electrospun poly(ε-caprolactone)-graphene oxide nanosheet nanofiber may be a suitable candidate for tissue engineering scaffold applications.

Polystyrene/graphene oxide nanocomposites synthesized via Pickering polymerization

Abstract The synthesis of graphene oxide (GO)—based nanocomposite materials, as environment-friendly nanostructures suitable for novel applications, has received significant attention in recent years. In this paper, a series of GO have been successfully fabricated utilizing the modified Hummers’ method. GO was characterized by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (RS), X-ray diffraction analysis (XRD), Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM) respectively. The characterization results showed that GO nanosheets have hydrophilic oxygen-containing functional groups and were well exfoliated. The graphene oxide/polystyrene (PSt) nanocomposite emulsion was synthesized via Pickering emulsion polymerization in the presence of GO nanosheets as a sole emulsifier. TEM, SEM and XRD results all suggested the successful preparation of GO-stabilized PSt colloidal particles. The Pickering emulsion products showed that the average diameter of nanocomposite particles can be well controlled from 240 to 320 nm by variation of the GO content. The GO layer was wrapped on the surface of PSt microspheres. PSt/GO nanocomposites have higher crystallinity and better thermal stability than pure PSt. Graphene oxide was not only being used as an effective solid stabilizer for Pickering emulsion, but also dispersed homogeneously into the production of polystyrene as highly effective nanofiller.

Graphene oxide nanosheets-catalyzed synthesis of novel benzylbarbiturocoumarin derivatives under green conditions

An efficient tricomponent reaction between barbituric acid (or N,N-dimethylbarbituric acid), 4-hydroxycoumarin, and a wide range of aryl aldehydes to obtain novel benzylbarbiturocoumarins is described. Starting materials were successfully condensed via three C–C bond formation by graphene oxide nanosheets as an efficient, metal-free, environmentally safe, and recyclable nanocatalyst to obtain target products. The target products were obtained with high selectivities and yields (80–88 %) in H2O/EtOH (1:1) in the presence of graphene oxide nanosheets (0.005 g) at 80 °C.

A simple way to prepare reduced graphene oxide nanosheets/Fe2O3-Pd/N-doped carbon nanosheets and their application in catalysis

The catalysts with Pd and γ-Fe2O3 nanoparticles embedded between reduced graphene oxide nanosheets (rGS) and N-doped carbon nanosheets (NCS) were prepared through a two-step method. Firstly, graphene oxide nanosheets (GS)/prussian blue (PB)-Pd/polypyrrole (PPy) composites were synthesized by using pyrrole monomer as reductant, K3Fe(CN)6 and PdCl2 as oxidants in the presence of GS via a redox reaction. Subsequently, the as-obtained GS/PB-Pd/PPy composites were calcinated in N2 atmosphere. During the heat-treatment, carbonization of PPy to NCS, conversion of nonmagnetic PB to magnetic γ-Fe2O3 nanoparticles, and reduction of GS to rGS were finished, simultaneously. rGS/Fe2O3-Pd/NCS composites exhibited good catalytic activity toward reduction of 4-nitrophenol. The rate constant k and turnover frequency were calculated and compared with recent reports. Owing to γ-Fe2O3 nanoparticles, the rGS/Fe2O3-Pd/NCS composites could be quickly separated by magnet and reused without obvious decrease in activity.

Assembly of Polypyrrole-Graphene Oxide Hydrogel Nanocomposites and Their Swelling Properties

An effective one-step strategy for the static assembly of hydrogels from polypyrrole (PPy) and graphene oxide (GO) is demonstrated. The static polymerization of pyrrole monomer was carried out in the presence of GO nanosheets, leading to the formation of PPy-GO hydrogels. During the static polymerization process, gelation takes place simultaneously by supramolecular interactions. The well-dispersed GO nanosheets in the polymer networks resulted in a significant improvement in water absorbencies. With only a very low loading of GO in the PPy-GO hydrogels, they exhibited significantly larger water uptake compared to a PPy hydrogel. Even in saline solutions, PPy-GO hydrogels also showed obvious water absorbency. Moreover, the PPy-GO hydrogels exhibited a better water retention ability compared with the control under the same conditions. This method is believed to provide possibilities to combine the extraordinary performances of GO with the multifunctional properties of conducting polymers, thus holding great potential for technical applications in the future.

Crystallization behavior, thermal property and enzymatic degradation of PVP/amylose in the presence of graphene oxide nanosheets

The PVP/amylose composite films with different amounts of graphene oxide (GO) were prepared by means of a solution casting method. The solution of PVP/amylose/GO was exposed to ultrasonic irradiation (10, 30, 50, and 70 W) and then prepared for casting. The crystallization behavior, thermal stability and enzymatic degradation of PVP/amylose were investigated with differential scanning calorimetry (DSC), X-Ray diffraction (XRD), scanning electron microscopy (SEM), and FTIR spectroscopy. XRD patterns monitored that the addition of GO induced a layered structure to the PVP/amylose composite films. This result indicated that GO nanosheets were uniformly dispersed into the composite network. The thermal properties measured by DSC showed that the glass transition temperature (Tg) was shifted to a lower temperature with the humidity percent increasing. DSC thermograms for PVP/amylose/GO showed an endothermic reaction and reduction in peak temperature, revealing that GO increased the thermal stability of PVP/amylose composite films. FTIR analysis suggests that PVP/amylose composites become more resilient to enzymatic attacks as the content of GO reaches higher, being related to the reduction of Amylose–Amylose interactions in the presence of GO nanosheets. These results indicate that this approach is an efficient method to improve the properties of PVP/amylose.

The effect of concentration on transient pool boiling heat transfer of graphene-based aqueous nanofluids

Transient pool boiling experiments were performed by quenching of stainless steel spheres in dilute aqueous nanofluids in the presence of graphene oxide nanosheets (GONs) at various concentrations (by weight) up to 0.1 wt.%. All the experiments were performed for saturated boiling at atmospheric pressure. Quenching and boiling curves were obtained for the nanofluids in comparison to the baseline case of pure water. It was shown that quenching is accelerated upon increasing the concentration of GONs. The enhanced boiling heat transfer by the nanofluids was interpreted in relation to the modified surface properties, including morphology, wettability, and roughness, on the quenched surfaces. Unlike the findings in available relevant studies that point to surface wettability change, however, the primary cause of critical heat flux (CHF) enhancement was observed to be related to the increased surface roughness serving as paths to facilitate solid−liquid contacts. The increases of both nucleation site density and liquid agitation intensity as a result of the presence of porous structures at relatively high concentrations were also found to be responsible for the enhanced CHF.

Physicochemical and biological properties of electrodeposited graphene oxide/chitosan films with drug-eluting capacity

In this study, novel graphene oxide/chitosan nanocomposite coatings with long term drug-eluting potential are presented. The coatings are fabricated by the facile and reproducible electrophoretic deposition technique. Analysis of the prepared films shows that the graphene oxide nanosheets are exfoliated in the chitosan matrix. Fourier-transform infrared spectrometry reveals polymer attachment to the carboxylic bonds of graphene oxide, providing a strong interaction and exfoliation of the nanolayers. In vitro viability assay by human osteosarcoma cells (MG-63) demonstrates that the nanocomposite films are highly biocompatible up to 30wt% graphene oxide, but at higher concentrations a slight cytotoxicity is noticed. Alkaline phosphates enzyme assay also reveals that the presence of graphene oxide nanosheets moderately hampers osteogenesis of the cultured cells. It is shown that vancomycin-loaded nanocomposite coatings gradually release the drug macromolecules for relatively long period of time (up to 4weeks). The electrodeposited films also exhibit a high bactericidal potential against Gram-positive Staphylococcus aureus. Effects of graphene oxide nanosheets on the physicochemical, biological, antimicrobial and drug-eluting properties of electrodeposited chitosan films are presented and discussed. It is shown that the GO/CS films support the initial attachment, proliferation and growth of osteoblast-like cells.

Fabrication of highly dispersed palladium/graphene oxide nanocomposites and their catalytic properties for efficient hydrogenation of p-nitrophenol and hydrogen generation

In this report, graphene oxide (GO) nanosheets decorated with ultrafine Pd nanoparticles (Pd NPs) have been successfully fabricated through a reaction between [Pd2(μ-CO)2Cl4]2− and water in the presence of GO nanosheets without any surfactant or other reductant. The as-synthesized small Pd NPs with average diameter of about 4.4 nm were well-dispersed on the surface of GO nanosheets. The Pd/GO nanocomposites show remarkable catalytic activity toward the hydrogenation of p-nitrophenol at room temperature. The kinetic apparent rate constant (kapp) could reach about 34.3 × 10−3 s−1. Furthermore, the as-prepared Pd/GO nanocomposites could also be used as an efficient and stable catalyst for hydrogen production from hydrolytic dehydrogenation of ammonia borane (AB). The catalytic activity is much higher than the conventional Pd/C catalysts.