Surface Of Reduced Graphene Oxide Sheets Research Articles

Ag nanoparticles decorated MnO2/reduced graphene oxide as advanced electrode materials for supercapacitors

Abstract A ternary nanocomposite of Ag/MnO 2 /RGO, in which reduced graphene oxide (RGO) sheets are decorated with Ag and MnO 2 nanoparticles, is synthesized by in situ growth of MnO 2 nanoparticles on graphene oxide (GO) sheets, following by co-reduction of Ag + and GO. The in situ formed Ag and MnO 2 nanoparticles with sizes of several nanometers are homogeneously distributed on the surface of RGO sheets. The composites as electrode materials for supercapacitors are investigated. It is found that the Ag/MnO 2 /RGO nanocomposites exhibit excellent capacitive performance with a specific capacitance as high as 467.5 F g −1 at the scan rate of 5 mV s −1 , which is much higher than that of MnO 2 /RGO nanocomposites (293.2 F g −1 ). Moreover, the specific capacitance of Ag/MnO 2 /RGO does not show any obvious degeneration after 1000 cycles at the scan rate of 80 mV s −1 , indicating that the Ag/MnO 2 /RGO composites possess an excellent cycle life. The greatly enhanced capacitive performance of the Ag/MnO 2 /RGO nanocomposites is mainly attributed to the introduction of Ag nanoparticles, which can increase the electrical conductivities of the nanocomposites, and promote the electron transfer between the active components. This study suggests that graphene-based ternary nanocomposites are a promising class of electrode materials for high performance energy storage applications.

A facile and general route for the synthesis of semiconductor quantum dots on reduced graphene oxide sheets

Owing to its unique graphitized basal plane nanostructure and intriguing physicochemical properties, graphene is considered as an ideal support for developing nanocomposites for various applications. In this study, a facile and general method was developed for the first time to synthesize a variety of semiconductor quantum dots (SQDs) supported on reduced graphene oxide (RGO) sheets, including RGO/metal oxide and RGO/metal sulfide nanocomposites. The as-prepared nanocomposites were investigated by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectra, X-ray photoelectron spectroscopy and transmission electron microscopy. It was found that by using octadecylamine (ODA) as both reductive and dispersing agent, the resulting metal oxide and sulfide SQDs were all homogeneously decorated on the surface of RGO sheets. The optical properties of the as-synthesized RGO/SQDs nanocomposites were studied through ultraviolet-visible and photoluminescence spectroscopy. To demonstrate one potential application, the RGO/NiO nanocomposites were used as electrode materials for electrochemical supercapacitors, which exhibit enhanced capacitive performance and long cycle life. It is expected that our prepared RGO/SQDs nanocomposites could serve as promising candidates for power source, catalysis, optical sensitizer and optoelectronic applications.

One-step hydrothermal synthesis of anatase TiO2/reduced graphene oxide nanocomposites with enhanced photocatalytic activity

• TiO 2 /RGO nanocomposites were prepared by a facile one-step hydrothermal method. • Using Ti(SO 4 ) 2 and GO as precursors and ethanol/water solvent as reducing agent. • TiO 2 /RGO exhibit superior photocatalytic performance compared to bare TiO 2 . • Mechanism was studied using PL spectrum and photocurrent response measurement. A facile and efficient one-step hydrothermal approach has been developed to synthesize chemically bonded TiO 2 /reduced graphene oxide (RGO) nanocomposites with Ti(SO 4 ) 2 and graphene oxide (GO) as precursors and ethanol/water solvent as a reducing agent. This approach aims to realize a partial reduction of GO and a growth of anatase TiO 2 nanoparticles on RGO sheets simultaneously. The morphology and microstructure characterizations of TiO 2 /RGO nanocomposites reveal that this method leads to close interfacial contact of TiO 2 /RGO and efficient dispersion of TiO 2 nanocrystals on the surface of RGO sheets. The TiO 2 /RGO nanocomposites exhibit superior photocatalytic activity compared to bare TiO 2 nanoparticles and a mechanical mixing TiO 2 + RGO sample in the degradation of Rhodamine B. Based on the photoluminescence spectrum and photocurrent response measurements, the enhanced photocatalytic activity of TiO 2 /RGO is mainly attributed to the excellent electron trapping and transportation properties of RGO.

A novel reduced graphene oxide/Ag/CeO2 ternary nanocomposite: Green synthesis and catalytic properties

The incorporation of two or more active components onto graphene with uniform distribution is expected to facilitate wider applications of graphene-based materials. In this study, a three-component composite composed of reduced graphene oxide (RGO), CeO2 and Ag nanoparticles was designed and synthesized by a facile and environmentally friendly strategy for the first time. It is shown that Ag and CeO2 nanoparticles are uniformly deposited on the surface of RGO sheets. The catalytic properties of the RGO/Ag/CeO2 ternary hybrid nanomaterials were evaluated with the reduction of p-nitrophenol by NaBH4 as a model reaction. The results reveal that the presence of CeO2 not only has a great influence on the size of the Ag nanoparticles formed on RGO, but also can significantly improve the catalytic activity and stability of them. Possible mechanisms for the reduced size of Ag nanoparticles and the enhanced catalytic performance of RGO/Ag nanocomposites after combining with CeO2 were proposed. The facile synthesis of RGO/Ag/CeO2 nanomaterials together with their superior catalytic performance provides a potentially new approach for the design and construction of graphene-based ternary nanostructured composites with various functions.

Ammonia Gas Sensor Based on Aniline Reduced Graphene Oxide

Here we demonstrate a promising gas sensor based on aniline reduced graphene oxide (RGO), which is fabricated through drop drying RGO nanosheets suspension between the electrode arrays to create conductive networks. RGO, as the sensing materials, which is prepared via the chemical reduction of graphene oxide (GO) by aniline, has been characterized by infrared spectroscopy, UV-Vis spectroscopy, transmittance electron microscopy and scanning electron microscopy. The sensing properties of RGO have also been studied, and the results show that RGO reduced from aniline (RGO-A) exhibits an excellent response to ammonia gas (NH3). Comparing with the RGO reduced from hydrazine (RGO-H) and polyaniline (PANI) nanofiber, the RGO-A exhibits a much better response to NH3 gas. The response of the sensor based on RGO-A to 50 ppm NH3 gas exhibits about 9.2 times and 3.5 times higher than those of the device based RGO-H and PANI nanofiber respectively. In addition, the RGO-A sensor exhibits an excellent repeatability and selectivity to NH3 gas. The oxidized aniline, i.e., polyaniline, which is attached on the surface of RGO sheets through π–π interaction, plays important roles in the final sensing performance of the device, and benefits for the application of the sensor in the field of NH3 gas detection.

Development of poly(isobutylene-co-isoprene)/reduced graphene oxide nanocomposites for barrier, dielectric and sensingapplications

Conducting poly(isobutylene-co-isoprene) (IIR)/reduced graphene oxide (RGO)/expanded graphite (EG) composites have been fabricated with high barrier, dielectric and sensing properties, making them suitable in modern electronics (robotic) and electric power systems. The dielectric permittivity increased 10-fold at 10−2Hz for RGO compared to EG filled composites at 5wt% loading while preserving low dielectric loss due to reducing polarization process to screen charge movement. The piezoresistance of RGO and EG filled rubber composites under uniaxial pressure was studied and significant sensing property of RGO is established. The vast surface of RGO sheets improves interaction of nanofiller/elastomer at the interface and provides efficient barrier to the organic vapor. Scanning electron microscopy and X-ray diffraction spectroscopy data give evidences for the high level dispersion state of EG and RGOs inIIR.

ZnO micro-flowers assembled on reduced graphene sheets with high photocatalytic activity for removal of pollutants

In this paper, a simple and efficient strategy was developed for preparing flower-shaped ZnO doped reduced graphene oxide (RGO) composite material by simultaneous crystal growth (of ZnO) and reduction (of graphene oxide) using hydrothermal process. Several analytical techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), FT-IR spectroscopy, Raman spectroscopy, and photoluminescence spectroscopy have been used to characterize the resulting ZnO/RGO photocatalyst. Results showed that highly crystalline ZnO nano-flowers were effectively doped on the surface of RGO sheets. The unique properties of RGO sheets not only provide the decreased rate of electron–hole separation in ZnO but also prevent from the loss of photocatalyst during recovery due to the fixed attachment of ZnO NPs on the surface of high aspect ratio graphene sheets. Therefore, as-synthesized composite is an economically and environmentally friendly photocatalyst.

Enhanced electrocatalytic performance of Pt-based nanoparticles on reduced graphene oxide for methanol oxidation

Pt-based materials have been widely used as electrocatalysts in direct methanol fuel cells (DMFCs) due to their significant activity for methanol oxidation and the superior poison tolerance. In this study, several Pt-based catalysts (PtSn, PtW, and PtMo) supported on reduced graphene oxide (RGO) are successfully synthesized in an ethylene glycol (EG)-water system for the first time. The microstructure and morphology of the synthesized materials are investigated by X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. It is shown that highly dispersed PtM (M=Sn, W, and Mo) nanoparticles with a size of 2–3nm are homogeneously deposited on the surface of RGO sheets. Their electrocatalytic performances in methanol oxidation are investigated by cyclic voltammetry and amperometric method. The RGO/PtM catalysts exhibit much higher catalytic activity and stability than the RGO/Pt nanocomposites. Among these RGO/PtM catalysts, RGO/PtSn nanocomposites show the best catalytic performance. It is proposed that the addition of a second element, which creates much more Pt active sites for methanol oxidation, is responsible for the improved catalytic performance. These results imply that the prepared RGO/PtM nanocomposites could be promising electrocatalysts for high-performance DMFCs applications.

Polyelectrolyte-assisted one-step hydrothermal synthesis of Ag-reduced graphene oxide composite and its antibacterial properties

We demonstrate an effective one-pot hydrothermal route for the synthesis of Poly (diallyldimethylammonium chloride) (PDDA)-protected reduced graphene oxide (RGO) sheets-silver (Ag) nanocomposite in the absence of any seeds and surfactants. In this method, PDDA, an ordinary and water-soluble polyelectrolyte, acts as both a reducing and a stabilizing agent. More importantly, the incorporation of PDDA as a “glue” molecule successfully turns RGO into general platforms for in situ growth of Ag. Small Ag nanoparticles with average height of 4nm are distributed on the surface of RGO sheets. It is also found that the antibacterial activity of Ag nanoparticles is retained in the composite, suggesting that it can be used as RGO-based biomaterial.

Reduced Graphene Oxide-Hierarchical ZnO Hollow Sphere Composites with Enhanced Photocurrent and Photocatalytic Activity

The reduced graphene oxide (RGO)-hierarchical ZnO hollow sphere composites are prepared through a simple ultrasonic treatment of the solution containing graphene oxide (GO), Zn(CH3COO)2, DMSO, and H2O. The GO is reduced to RGO effectively, and the ZnO hollow spheres consisting of nanoparticles are uniformly dispersed on the surface of RGO sheets during the ultrasonic process. The optimum synergetic effect of RGO-ZnO composites is found at a RGO mass ratio of 3.56%, and the photocurrent and photodegradation efficiency on methylene blue of RGO-ZnO composites are improved by five times and 67%, respectively, compared with those of pure ZnO hollow spheres. The enhancements of photocurrent and photocatalytic activity can be attributed to the suppression of charge carriers recombination resulting from the interaction between ZnO and RGO.

Reduced graphene oxide–polyaniline hybrid: Preparation, characterization and its applications for ammonia gas sensing

Here we present a useful ammonia (NH3) gas sensor based on reduced graphene oxide (RGO)–polyaniline (PANI) hybrids. PANI nanoparticles were successfully anchored on the surface of RGO sheets by using RGO–MnO2 hybrids as both of the templates and oxidants for aniline monomer during the process of polymerization. The resultant RGO–PANI hybrids were characterized by transmittance electron microscopy, infrared spectroscopy, Raman spectroscopy, UV-Vis spectroscopy, and scanning electron microscopy. The NH3 gas sensing performance of the hybrids was also investigated and compared with those of the sensors based on bare PANI nanofibers and bare RGO sheets. It was revealed that the synergetic behavior between both of the candidates allowed excellent sensitivity and selectivity to NH3 gas. The RGO–PANI hybrid device exhibited much better (3.4 and 10.4 times, respectively, with the concentration of NH3 gas at 50 ppm) response to NH3 gas than those of the bare PANI nanofiber sensor and bare graphene device. The combination of the RGO sheets and PANI nanoparticles facilitated the enhancement of the sensing properties of the final hybrids, and pave a new avenue for the application of RGO–PANI hybrids in the gas sensing field.

Synthesis of PNIPAM polymer brushes on reduced graphene oxide based on click chemistry and RAFT polymerization

AbstractPreparation and characterization of poly(N‐isopropylacrylamide) (PNIPAM) polymer brushes on the surfaces of reduced graphene oxide (RGO) sheets based on click chemistry and reversible addition‐fragmentation chain transfer (RAFT) polymerization was reported. RGO sheets prepared by thermal reduction were modified by diazonium salt of propargyl p‐aminobenzoate, and alkyne‐functionalized RGO sheets were obtained. RAFT chain transfer agent (CTA) was grafted to the surfaces of RGO sheets by click reaction. PNIPAM on RGO sheets was prepared by RAFT polymerization. Fourier transform‐infrared spectroscopy, thermogravimetric analysis, X‐ray photoelectron spectroscopy, and transmission electron microscopy (TEM) results all demonstrated that RAFT CTA and PNIPAM were successfully produced on the surfaces of RGO sheets. Nanosized PNIPAM domains on RGO sheets were observed on TEM. Micro‐DSC result indicated that in aqueous solution PNIPAM on RGO sheets presented a lower critical solution temperature at 33.2 °C. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012