Facile preparation and electrochemical characterization of graphene/ZnO nanocomposite for supercapacitor applications

Graphene/ZnO nanocomposites were successfully synthesized by microwave-assisted method. The structure, morphology, optical and composition of the obtained samples were characterized using XRD, FT-IR, laser Raman, UV–Vis spectroscopy and XPS analysis. XRD analysis confirmed the presence of graphene/ZnO nanocomposite. FE-SEM image reveals that the homogenous distribution of ZnO nanoparticles on the graphene nanosheets. The electrochemical properties of the graphene/ZnO electrodes were analyzed by cyclic voltammetry and impedance spectroscopy. The results confirmed that the incorporation of ZnO nanoparticles enhanced the capacitive performance of graphene electrode. Graphene/ZnO nanocomposite electrode showed higher capacitance value of 109 F g⁻¹ at a scan rate of 5 mV s⁻¹ in 1 M KCl solution as compared to the graphene electrodes. These results demonstrated the importance and great potential of graphene based composites in the development of high-performance energy-storage systems.     

Facile one-step synthesis of MnO2 nanowires on graphene under mild conditions for application in supercapacitors

Composites of integrated 1-D MnO₂ nanowires and 2-D graphene sheets at nanoscale are successfully prepared under the mild condition of 100 °C. The fabricated materials are extensively characterized by electron microscopy and X-ray diffraction, and the formation mechanism is investigated. It is of particular note that the graphene sheets in this case play dual roles, both as active reagent to reduce MnO^4? to form 1-D MnO₂ nanowires and as active component of the composites integrated into the 3-D structure. The proof-of-concept demonstration shows that the 3-D composites can be used as active materials for supercapacitors, where the high-surface area 2-D graphene sheets serve as both high-surface area active materials and conductive supports for high-capacity 1-D MnO₂ nanowires.     

Facile preparation of graphene nanoribbon filled silicone rubber nanocomposite with improved thermal and mechanical properties

In the present study, graphene nanoribbon was prepared through unzipping the multi walled carbon nanotubes, and its reinforcing effect as a filler to the silicone rubber was further investigated. The results showed that carbon nanotubes could be unzipped to graphene nanoribbon using strong oxidants like potassium permanganate and sulfuric acid. The prepared graphene nanoribbon could homogeneously disperse within silicone rubber matrix using a simple solution mixing approach. It was also found from the thermogravimetric analysis curves that the thermal stability of the graphene nanoribbon filled silicone rubber nanocomposites improved compared to the pristine silicone rubber. Besides, with the incorporation of the nanofiller, the mechanical properties of the resulting nanocomposites were significantly enhanced, in which both the tensile stress and Young’s modulus increased by 67% and 93% respectively when the mass content of the graphene nanoribbon was 2.0 wt%. Thus it could be expected that graphene nanoribbon had large potentials to be applied as the reinforcing filler to fabricate polymers with increased the thermal and mechanical properties.     

Facile coordinating decoration of salophen Al on graphene nanosheet: Salophen Al complex functionalized graphene nanocomposite with electrochemical properties

Salophen Al complex functionalized graphene (SCFG) nanocomposite was synthesized by simple coordination of phenol functionalized graphene (PFG) and as-prepared salophen Al complex. This process is facile, convenient and high efficient. We also investigated the structure, optical properties and electrochemical properties of the obtained SCFG composites. The results showed that salophen Al conjugated and incorporated onto the graphene sheet surface and the composites maintained the micro-structure of graphene sheets without agglomeration. The photoluminescence of salophen Al was completely quenched by graphene, due to the charge transfer between the salophen Al and the graphene nanosheets. Moreover, a significant electrochemical signal emerged on the SCFG modified electrodes compared with those of the graphene sheets or salophen Al complex. Owing to preliminary results of the excellent electrochemical property, SCFG nanocomposite is a promising electrochemical redox probe material.     

Solution-processed ZnO-chemically converted graphene gas sensor

We report a solution-processed gas sensor based on vertically aligned ZnO nanorods (NRs) on a chemically converted graphene (CCG) film. The prepared sensor device effectively detected 2 ppm of H₂S in oxygen at room temperature. A high sensitivity of the gas sensor resulted from the growth of highly dense vertical ZnO NRs on the CCG film with numerous tiny white dots on its surface, which may provide a sufficient number of sites for the nucleation and growth of the ZnO NRs. The adsorption of oxygen on the surface of the ZnO NRs was found to be crucial for obtaining an excellent gas sensing performance of the ZnO NRs-CCG sensor.     

Facile synthesis of poly(Safranine T)/Reduced graphene oxide nanocomposite for supercapacitors with wide potential window in aqueous neutral electrolyte

A facile method is introduced for incorporating reduced graphene oxide (rGO) into poly(safranine T) (PST) films. First, ST-functionalized GO (ST/GO) was obtained via the absorption of ST on GO in pH 7.0 phosphate buffer solution. Then rGO/PST composite was synthesized by the electropolymerization of ST and the subsequent electrochemical reduction of GO. The as-prepared PST/rGO composite films are characterized using scanning electron microscope, X-ray diffraction, and Fourier transform–infrared spectroscopy. PST/rGO composites possess a microporous structure, which creates enormous amount of pores, and therefore provides larger interfaces for charge carrier. The properties of electrochemical capacitance for PST/rGO composites have also been investigated with cyclic voltammetry (CV) and galvanostatic charge–discharge measurements. The experimental results manifest that the PST/rGO composite showed high capacitance (293.2 F g^?1) at 20-mV s^?1 CV scan and an excellent cycling stability (8.3% drop after 1000 cycles) in 0.1 M Na₂SO₄ electrolyte.     

Facile synthesis of papillae-like polyaniline nanocones on graphene nanosheets for ultracapacitors

Papillae-like polyaniline (PANI) nanocones arrays growing on graphsene nanosheets (GNs) were synthesized in mass at low cost by in situ polymerization with the assistant of ethanol. Scanning electron microscopy and transmission electron microscopy images show that papillae-like PANI nanocones arrays are located uniformly on flexible two-dimensional GNs. Electrochemical properties are tested by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The electrochemical performances of GNs/PANI hybrid are better than those of bare GNs or PANI. GNs/PANI electrode delivered a maximum specific capacitance of 372 F g^?1 at a current density of 0.1 A g^?1 in 1.0 M Na₂SO₄ aqueous solution. And the composite exhibit an excellent cycle life with ~80% specific capacitance retention over 3000 cycles at 1 A g^?1. The GNs/PANI nanocomposites will be one of the most promising flexible electrode materials for high-performance ultracapacitors.     

Facile synthesis of amine-functionalized graphene quantum dots with highly pH-sensitive photoluminescence

Graphene quantum dots (GQDs) as promising materials have gained increasing attention due to their optical and chemical properties, but the complicated synthetic procedures restrict their large-scale application. Here we report a novel one-pot hydrothermal method to synthesize the GQDs with bifunctional groups (-OH and -NH₂) using a polycyclic aromatic hydrocarbon as the precursor, in which 1,5-dinitronaphthalene was graphitized in aqueous ammonium solution. The as-synthesized GQDs with single-layer structures have a size distribution of 1–3 nm and an average value of 1.5 nm. The alkaline species play a crucial role in the formation of amine-functionalized GQDs. More importantly, the as-synthesized GQDs exhibit a distinct pH-sensitive photoluminescence and the fluorescence colors vary from bluish green to yellow with pH value from 5 to 10, which can be attributed to the protonation and deprotonation of the amine-groups in acid or alkaline solution.     

Hydrothermal synthesis of zirconia-based nanocomposite powder reinforced by graphene and its application for bone scaffold with 3D printing

Hydrothermal method is a cheap and green approach for the synthesis of composite powders. In this study, the zirconia (ZrO₂)-based nanocomposite powder was reinforced with reduced graphene oxide (ZrO₂/RGO) and was synthesized in a one-pot as a precursor for bone scaffold applications. Moreover, for the stimulation of osseointegration in bone scaffolds, Hydroxyapatite (HA) was used in 10 wt%. In this regard, the two types of ZrO₂/RGO and ZrO₂/RGO/HA precursors were applied for the fabrication of bone scaffolds via 3D printing and finally, the mechanical and biological properties of scaffolds were evaluated. For characterization, the X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), compress strength, and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide as MTT assay protocol were performed. The results demonstrated that the ZrO₂/RGO scaffolds with a tolerance of compressive stress of 240.11 MPa depicted better mechanical properties compared with ZrO₂/RGO/HA with the compress strength of 141.66 MPa. Moreover, after 7 days of bone scaffolds immersion in simulated body fluid (SBF) the growth of compressive strength began while after 28 days reached 260.15 MPa for ZrO₂/RGO and 192.31 for ZrO₂/RGO/HA. Finally, the cellular response of the scaffolds indicated the lack of cellular toxicity of the scaffolds during MTT assay.     

基于简易微波方法制备高性能MoS2/石墨烯纳米复合材料用于高效析氢反应（英文）

用于析氢反应(HER)的低成本、高效能催化剂对于推进基于清洁氢气的能源工业非常重要.二维二硫化钼(MoS2)具有显著的催化性能,因而已被人们广泛深入研究.然而,大多数现有的合成方法耗时、复杂且效率较低.本文通过超快(60秒)微波引发的方法生产MoS2/石墨烯催化剂.石墨烯的高比表面积和导电性为MoS2纳米片的生长提供了有利的导电网络和快速电荷转移动力.文中制备的MoS2/石墨烯纳米复合材料在酸性介质中对HER表现出优异的电催化活性,具有62 mV的低起始电位,高阴极电流和43.3mV/dec的Tafel斜率.除了优异的催化活性外, MoS2/石墨烯还具有较长的循环稳定性,在250 mV的过电位下阴极电流密度高达1000 mA cm^-2.此外, MoS2/石墨烯催化剂在30–120°C范围内具有出色的HER活性和36.51 kJ mol^-1的低活化能,提供了潜在的大批量生产和制备的机会.     

Facile synthesis of soluble graphene via a green reduction of graphene oxide in tea solution and its biocomposites

The chemical reduction of graphene oxide (GO) typically involves highly toxic reducing agents that are harmful to human health and environment, and complicated surface modification is often needed to avoid aggregation of the reduced GO during reduction process. In this paper, a green and facile strategy is reported for the fabrication of soluble reduced GO. The proposed method is based on the reduction of exfoliated GO in green tea solution by making use of the reducing capability and the aromatic rings of tea polyphenol (TP) that contained in tea solution. The measurements of the resultant graphene confirm the efficient removal of the oxygen-containing groups in GO. The strong interactions between the reduced graphene and the aromatic TPs guarantee the good dispersion of the reduced graphene in both aqueous and a variety of organic solvents. These features endow this green approach with great potential in constructing of various graphene-based materials, especially for high-performance biorelated materials as demonstrated in this study of chitosan/graphene composites.     

Facile synthesis and biosensing application of hybrid zinc nanoparticles

Hybrid zinc nanoparticles were synthesized by adding thioglycolic acid (TGA) into a ZnO-particle synthesis procedure. Compared to the ZnO particles prepared without TGA, the hybrid nanoparticles are markedly different in their morphology, chemical composition, and growth kinetics. Moreover, they display colloidal stability and appropriate surface properties for bioconjugation. To demonstrate their biosensing application, the hybrid nanoparticles were conjugated and applied as biolabels or signal transducers in a sandwich immunoassay for mouse IgG. The immunoassay fluorescence signal was obtained by releasing zinc ions from these nanoparticle labels and further incubating the released zinc ions with zinc-sensitive fluorescence indicator Fluozin-3. The immunoassay presents a dynamic detection range from 10 pM to 1 nM.     

Facile synthesis of three-dimensional porous graphene nanostructures from coordination complexes for supercapacitor electrode

Fabrication of hierarchical nanostructures is an important way for performance improvement and application expansion of nanomaterials. It is still a great challenge to synthesize three dimensional hierarchical graphene nanostructures with controlled secondary structures and primary building units, because it is difficult to realize effective control of graphene layer morphology and necessary arrangement of graphene. In this work, a “complex-directed” strategy has been successfully developed for the synthesis of three dimensional graphene nanostructures. Especially, the obtained three dimensional graphene nanostructures are quite regular in morphology, they can be nanorods or regular particles, composed of hollow graphene nanospheres with different layers. The morphology and the structure of these nanostructures, including primary building units and secondary structures are strongly dependent on the amount of HCl solution. The obtained three-dimensional graphene nanostructure can serve as an excellent candidate for electrode material of electric double layer capacitors (EDLCs) and present outstanding electrochemical behaviors. This is mainly due to the excellent electrical conductivity of graphene hollow nanospheres and the porous structures conducive to ion diffusion and electron transport.     

Functional composite materials based on chemically converted graphene

Graphene, a one-atom layer of graphite, possesses a unique two-dimensional structure and excellent mechanical, thermal, and electrical properties. Thus, it has been regarded as an important component for making various functional composite materials. Graphene can be prepared through physical, chemical and electrochemical approaches. Among them, chemical methods were tested to be effective for producing chemically converted graphene (CCG) from various precursors (such as graphite, carbon nanotubes, and polymers) in large scale and at low costs. Therefore, CCG is more suitable for synthesizing high-performance graphene based composites. In this progress report, we review the recent advancements in the studies of the composites of CCG and small molecules, polymers, inorganic nanoparticles or other carbon nanomaterials. The methodology for preparing CCG and its composites has been summarized. The applications of CCG-based functional composite materials are also discussed.     

In situ synthesis of SnO2/graphene nanocomposite and their application as anode material for lithium ion battery

SnO₂/graphene nanocomposite was prepared via an in situ chemical synthesis method. The nanocomposite was characterized by X-ray diffraction, filed emission scanning electron microscope and transmission electron microscope, which revealed that tiny SnO₂ nanoparticles could be homogeneously distributed on the graphene matrix. The electrochemical performance of the SnO₂/graphene nanocomposite as anode material was measured by galvanostatic charge/discharge cycling. The SnO₂/graphene nanocomposite showed a reversible capacity of 665 mAh/g after 50 cycles and an excellent cycling performance for lithium ion battery, which was ascribed to the three-dimensional architecture of SnO₂/graphene nanocomposite. These results suggest that SnO₂/graphene nanocomposite would be a promising anode material for lithium ion battery.     

Facile one-step transfer process of graphene

Chemical vapour deposition (CVD) is emerging as a popular method for growing large-area graphene on metal substrates. For transferring graphene to other substrates the technique generally used involves deposition of a polymer support with subsequent etching of the metal substrate. Here we report a simpler one-step transfer process. Few-layer graphene (FLG) grown on a Cu substrate were transferred to a silanized wafer by just pressing them together. Hydrogen bonding between the hydroxyl group on FLG and the amine group on silane molecules facilitate the transfer.