Electrospun poly(vinyl alcohol)/reduced graphene oxide nanofibrous scaffolds for skin tissue engineering

Graphene is composed of a two-dimensional (2D) layer of carbon atoms arranged in a honeycomb lattice configuration. In this paper, we adopted a green synthetic method of producing reduced graphene oxide using glucose as a reducing and stabilizing agent. We also investigated the fabrication of electrospun nanofibers of glucose-reduced graphene oxide (GRGO) (0-1.0 wt%) reinforced with polyvinyl alcohol (PVA) as (PG) scaffolds, and chemically crosslinked with acidic glutaraldehyde (GA) in acetone medium to mimic the extracellular matrix (ECM) for skin tissue engineering applications. These PG scaffolds were evaluated for morphology, mechanical strength, surface wettability, thermal properties, hemocompatibility, and biocompatibility. Field emission-scanning electron microscopy (FE-SEM) revealed an increase in the thickness of nanofibers in PG scaffolds with an increase in the concentration of GRGO. X-ray diffraction and attenuated total reflectance-infrared and Raman spectra showed the GRGO was incorporated in the PVA nanofibrous matrix. As the concentration of GRGO was increased in PG scaffolds, tensile strengths and elongations at break decreased, whereas thermal properties increased. The biological activities of PG scaffolds were evaluated using in vitro hemolysis, using CCD-986Sk (a human skin fibroblast cell line) viability and proliferation assays, and by live/dead cell imaging. Results showed GRGO inclusion in PVA nanofibers caused a slight hydrophilic to hydrophobic shift. PG scaffolds did not cause hemolysis of red blood cells even at a GRGO loading of 1.0 wt%, and PG-1.0 scaffold (with a GRGO loading of 1.0 wt%) exhibited excellent compatibility with fibroblasts and significantly increased metabolic activity after culture for 21 days as compared with PG-0 controls. DAPI staining and live/dead imaging assays showed that all PG scaffolds increased fibroblast proliferation and viability, indicating the potential for skin tissue engineering applications.

Thermally reduced mesoporous manganese MOF @reduced graphene oxide nanocomposite as bifunctional electrocatalyst for oxygen reduction and evolution

Oxygen electrocatalysis plays a crucial role in harnessing energy from modern renewable energy technologies like fuel cells and metal–air batteries. But high cost and stability issues of noble metal catalysts call for research on tailoring novel metal–organic framework (MOF) based architectures which can bifunctionally catalyze O₂ reduction and evolution reactions (ORR & OER). In this work, we report a novel manganese MOF @rGO nanocomposite synthesized using a facile self-templated solvothermal method. The nanocomposite is superior to commercial Pt/C catalyst both in material resource and effectiveness in application. A more positive cathodic peak (E_pc = 0.78 V vs. RHE), onset (E_onset = 1.09 V vs. RHE) and half wave potentials (E_1/2 = 0.98 V vs. RHE) for the ORR and notable potential to achieve the threshold current density (E_{@10 mA cm⁻²}= 1.84 V vs. RHE) for OER are features promising to reduce overpotentials during ORR and OER. Small Tafel slopes, methanol tolerance and acceptable short term stability augment the electrocatalytic properties of the as-prepared nanocomposite. Remarkable electrocatalytic features are attributed to the synergistic effect from the mesoporous 3D framework and transition metal–organic composition. Template directed growth, tunable porosities, novel architecture and excellent electrocatalytic performance of the manganese MOF @rGO nanocomposite make it an excellent candidate for energy applications.

Oxygen electrocatalysis plays a crucial role in harnessing energy from modern renewable energy technologies like fuel cells and metal–air batteries.

Preparation of Ultrahigh Molecular Weight Polyethylene/Graphene Nanocomposite In situ Polymerization via Spherical and Sandwich Structure Graphene/Sio2 Support

Reduced graphene oxide/SiO₂ (RGO/SiO₂) serving as a novel spherical support for Ziegler-Natta (Z-N) catalyst is reported. The surface and interior of the support has a porous architecture formed by RGO/SiO₂ sandwich structure. The sandwich structure is like a brick wall coated with a graphene layer of concreted as skeleton which could withstand external pressures and endow the structure with higher support stabilities. After loading the Z-N catalyst, the active components anchor on the surface and internal pores of the supports. When the ethylene molecules meet the active centers, the molecular chains grow from the surface and internal catalytic sites in a regular and well-organized way. And the process of the nascent molecular chains filled in the sandwich structure polymerization could ensure the graphene disperse uniformly in the polymer matrix. Compared with traditional methods, the porous spherical graphene support of this strategy has far more advantages and could maintain an intrinsic graphene performance in the nanocomposites.

Facile synthesis of TiO2-RGO composite with enhanced performance for the photocatalytic mineralization of organic pollutants

Current research reports the synthesis of reduced graphene oxide (RGO)-TiO2 nanocomposite by in-situ redox method and graphene oxide by modified hummers method. The ratio of RGO and TiO2 in the composite was optimized to show best photocatalytic activity for the degradation of targeted pollutants. Optimized (1:10) RGO-TiO2 nanocomposite was characterized by various techniques viz. X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller surface area (BET), Raman and diffuse reflectance spectroscopy (DRS) technique confirming successful formation of nanocomposite. XRD results confirm the presence of anatase phase in RGO-TiO2. Uniform dispersion of TiO2 nanoparticles on RGO could be seen from TEM images. The obtained results of (1:10) RGO-TiO2 showed five-fold and two-fold enhancement for the visible light and UV light, respectively, for the photocatalytic mineralization of methylene blue dye as compared to commercial Aeroxide P25 TiO2. The excellent photocatalytic mineralization activity of (1:10) RGO-TiO2 could be attributed to the enhanced surface area of composite as well as to its good electron sink capability. (1:10) RGO-TiO2 could be recycled easily and was found to be equally efficient even after the fourth cycle for the photocatalytic mineralization of methylene blue dye. The non-selectivity of synthesized composite was checked by the mineralization studies of oxalic acid.

Nitrogen-doped porous carbon foams prepared from mesophase pitch through graphitic carbon nitride nanosheet templates

A scalable and facile method was developed to synthesize nitrogen-doped porous carbon foams (NPCFs) using graphitic carbon nitride (g-C₃N₄) nanosheets as hard templates through the calcination of mesophase pitch.

Nonaqueous lithium-ion capacitors with high energy densities using trigol-reduced graphene oxide nanosheets as cathode-active material

One HEC of a material: The use of trigol-reduced graphene oxide nanosheets as cathode material in hybrid lithium-ion electrochemical capacitors (Li-HECs) results in an energy density of 45 Wh kg(-1) ; much enhanced when compared to similar devices. The mass loading of the active materials is optimized, and the devices show good cycling performance. Li-HECs employing these materials outperform other supercapacitors, making them attractive for use in power sources.

Solid-phase electrochemical reduction of graphene oxide films in alkaline solution

Graphene oxide (GO) film was evaporated onto graphite and used as an electrode to produce electrochemically reduced graphene oxide (ERGO) films by electrochemical reduction in 6 M KOH solution through voltammetric cycling. Fourier transformed infrared and Raman spectroscopy confirmed the presence of ERGO. Electrochemical impedance spectroscopy characterization of ERGO and GO films in ferrocyanide/ferricyanide redox couple with 0.1 M KCl supporting electrolyte gave results that are in accordance with previous reports. Based on the EIS results, ERGO shows higher capacitance and lower charge transfer resistance compared to GO.

Hierarchically nanoperforated graphene as a high performance electrode material for ultracapacitors

High performance is reported for a symmetric ultracapacitor (UC) cell made up of hierarchically perforated graphene nanosheets (HPGN) as an electrode material with excellent values of energy density (68.43 Wh kg⁻¹) and power density (36.31 kW kg⁻¹). Perforations are incorporated in the graphite oxide (GO) and graphene system at room temperature by using silica nanoparticles as template. The symmetric HPGN-based UC cell exhibits excellent specific capacitance (Cs) of 492 F g⁻¹ at 0.1 A g⁻¹ and 200 F g⁻¹ at 20 A g⁻¹ in 1 M H₂SO₄ electrolyte. This performance is further highlighted by galvanostatic charge-discharge study at 2 A g⁻¹ over a large number (1000) of cycles exhibiting 93% retention of the initial Cs. These property features are far superior as compared to those of symmetric UC cells made up of only graphene nanosheets (GNs), i.e. graphene sheets without perforations. The latter exhibit Cs of only 158 F g⁻¹ at 0.1 A g⁻¹ and the cells is not stable at high current density.

Recent advances in the efficient reduction of graphene oxide and its application as energy storage electrode materials

Efficient reduction of graphene oxide (GO) by chemical, thermal, electrochemical, and photo-irradiation techniques has been reviewed. Particular emphasis has been directed towards the proposed reduction mechanisms of GO by different reducing agents and techniques. The advantages of using different kinds of reducing agents on the basis of their availability, cost-effectiveness, toxicity, and easy product isolation processes have also been studied extensively. We provide a detailed description of the improvement in physiochemical properties of reduced GO (RGO) compared to pure GO. For example, the electrical conductivity and electrochemical performance of electrochemically obtained RGO are much better than those of chemically or thermally RGO materials. We provide examples of how RGO has been used as supercapacitor electrode materials. Specific capacitance of GO increases after reduction and the value has been reported to be 100-300 F g(-1). We conclude by proposing new environmentally friendly types of reducing agents that can efficiently remove oxygen functionalities from the surface of GO.