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A facile one-pot method for the formation of MoO 2 /RGO has been established using Mo particles as both the reductant for graphene oxide (GO) and as the Mo source. The Mo powder efficiently reduced the GO under acidic conditions to give reduced GO (RGO) and Mo ions. These ions were then transformed into MoO 2 and MoO 2 /RGO composites were formed by tuning the pH of the solution. Other variables such as reaction time and Mo:GO weight ratio were also investigated. The MoO 2 /RGO composite prepared at 3:1 (Mo:GO, called MoO 2 /RGO 3 ) had the best electrochemical performance for the oxygen reduction reaction (ORR) in alkaline medium. The ORR reaction at the MoO 2 /RGO 3 electrode mainly proceeded via a four-electron pathway and the electrode displayed superior catalytic activity and good stability. These results indicate that MoO 2 /RGO 3 could be a promising noble metal-free electrocatalyst for fuel cells. [ABSTRACT FROM AUTHOR]

At present, low-cost and efficient electrocatalysts for accelerating the oxygen reduction reaction in fuel cells are highly desired. In this work, we report a facile approach to fabricate nanostructured CuFeS2 that is supported on nitrogen/sulfur dual-doped reduced graphene oxide (NS-rGO). The chemical composition and surface morphology of CuFeS2/NS-rGO are characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. Cyclic voltammetry, linear sweep voltammetry and chronoamperometry are used to evaluate the electrochemical activity and durability of the CuFeS2/NS-rGO catalysts in alkaline media. CuFeS2/NS-rGO-2 (CuFeS2/GO theoretical mass ratio is 2.8) shows much superior methanol tolerance and better stability than the commercial Pt/C catalyst. The catalyzed reaction follows a desirable four-electron pathway in alkaline electrolytes. Therefore, CuFeS2/NS-rGO-2 can be used as a promising low cost nonprecious metal electrocatalyst for fuel cells and metal–air batteries in future. [ABSTRACT FROM AUTHOR]

Fabrication of low-cost and efficient electrocatalyst for oxygen reduction reaction (ORR) is highly desirable. Herein, Zinc ferrite/reduced graphene oxide (ZnFe 2 O 4 /rGO) is prepared by a quite simple and environmentally benign approach and applied as a high performance ORR electrocatalyst for the first time. The surface morphology and chemical composition of ZnFe 2 O 4 /rGO are characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis and Fourier transform infrared spectroscopy. Cyclic voltammetry, linear sweep voltammetry and chronoamperometry are used to evaluate the electrochemical activities and stabilities of ZnFe 2 O 4 /rGO catalysts in alkaline media. Among ZnFe 2 O 4 /rGO with different mass ratios, the catalyst with 69.8 wt% ZnFe 2 O 4 (called ZnFe 2 O 4 /rGO (3)) has the best catalytic activities and it shows much superior methanol tolerance and better durability than the commercial Pt/C catalyst. Due to the synergistic effect, the ZnFe 2 O 4 /rGO (3) nanohybrid exhibits high ORR catalytic performance and durability, which follows a desirable four electron transfer mechanism in alkaline media. Therefore, it may be a highly competitive catalyst for fuel cells and metal-air batteries. [ABSTRACT FROM AUTHOR]

This paper demonstrates a novel strategy for the construction of a graphene hybrid composites film, which was fabricated by electrodeposited reduced graphene oxide (ERGO) incorporating polymerization of l -lysine (PLL) onto glassy carbon electrode (GCE). Here we show that graphene films can be prepared on electrodes directly from GO dispersions by one-step electrodeposition technique based on electropolymerized PLL as a positively charged polymer interface to adsorb negatively charged GO nanosheets through electrostatic attraction. The thickness of graphene film can be easily controlled by using the electrodeposition technique, a distinct advantage over previously developed methods. The electrochemically reduced process of GO and electropolymerization of l -lysine were investigated by cyclic voltammetry with a wide potential range. The surface morphology of the modified electrode was characterized by scanning electron microscopy. The ERGO/PLL/GCE shows conducive to electron transfer kinetics for Fe(CN) 6 3 − /Fe(CN) 6 4 − redox probes, compared with bare GCE, PLL/GCE and ERGO/GCE. The electrochemical behaviors of ascorbic acid (AA), dopamine (DA) and uric acid (UA) at ERGO/PLL/GCE were investigated by cyclic voltammetry, and the results suggest that the modified electrode exhibits enhanced electrocatalytic activity toward these important molecules. Under physiological condition and in the co-existence system of AA, DA and UA, the ERGO/PLL/GCE showed linear voltammetric responses in the concentration of 100 μM–1200 μM for AA, 2.0 μM–60 μM for DA and 20 μM–200 μM for UA, and with the detection limits (S/N = 3) of 2.0 μM, 0.10 μM and 0.15 μM for AA, DA and UA, respectively. The developed method has been applied to simultaneous determination of AA, DA and UA in human urine with satisfactory recoveries of 104.2%, 95.4% and 99.9%, respectively. This work demonstrates that the attractive features of ERGO/PLL provide promising applications in simultaneous determination of AA, DA and UA in physiological and pathological studies. [ABSTRACT FROM AUTHOR]

This work presents a sensitive voltammetric method for determination of curcumin by using a electrochemically reduced graphene oxide (ERGO) modified glass carbon electrode (GCE) in 100 mM KCl-10 mM sodium phosphate buffer solution (pH 7.40). The electrochemical behaviors of curcumin at ERGO/GCE were investigated by cyclic voltammetry, suggesting that the ERGO/GCE exhibits excellent electrocatalytic activity towards curcumin, compared with bare GCE and GO/GCE electrodes. The electrochemical reaction mechanisms of curcumin, demethoxycurcumin and bisdemethoxycurcumin at the ERGO/GCE were also investigated and discussed systematically. Under physiological condition, the modified electrode showed linear voltammetric response from 0.2 μM to 60.0 μM for curcumin, with the detection limit of 0.1 μm. This work demonstrates that the graphene-modified electrode is a promising strategy for electrochemical determination of biological important phenolic compounds. [ABSTRACT FROM AUTHOR]

This work presents a sensitive voltammetric method for determination of folic acid by adsorbing methylene blue onto electrodeposited reduced graphene oxide film modified glassy carbon electrode (MB/ERGO/GCE) in 100 mM KCl-10 mM sodium phosphate buffer solution (pH 7.40). The surface morphology of the MB/ERGO/GCE modified electrode was characterized using scanning electron microscopy, displays that both MB and ERGO distributed homogeneously on the surface of GCE. The MB/ERGO/GCE modified electrode shows more favorable electron transfer kinetics for potassium ferricyanide and potassium ferrocyanide probe molecules, which are important electroactive compounds, compared with bare GCE, MB/GCE, and ERGO/GCE. The electrochemical behaviors of folic acid at MB/ERGO/GCE were investigated by cyclic voltammetry, suggesting that the modified electrode exhibited excellent electrocatalytic activity towards folic acid compared with other electrodes. Under physiological condition, the MB/ERGO/GCE modified electrode showed a linear voltammetric response from 4.0 μM to 167 μM for folic acid, and with the detection limit of 0.5 μM (S/N=3). The stability, reproducibility and anti-interference ability of the modified electrode were examined. The developed method has been successfully applied to determination of FA in tablets with a satisfactory recovery from 96 % to 100 %. The work demonstrated that the electroactive MB adsorbing onto graphene modified electrode showed an enhanced electron transfer property and a high resolution capacity to FA. [ABSTRACT FROM AUTHOR]

Abstract: Bimetallic palladium–silver nanoparticles (NPs) supported on reduced oxide graphene (RGO) with different Pd/Ag ratios (Pd–Ag/RGO) were prepared by an easy green method which did not use any additional reducing agents or a dispersing agent. During the process, simultaneous redox reactions between AgNO3, K2PdCl4 and graphene oxide (GO) led to bimetallic Pd–Ag NPs. The morphology and composition of the Pd–Ag/RGO were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis and Raman spectroscopy. Cyclic voltammetry and chronoamperometry were used to investigate the electrochemical activities and stabilities of these Pd–Ag/RGO catalysts for the electro-oxidation of methanol and ethanol in alkaline media. Among the different Pd/Ag ratios, the Pd–Ag (1:1)/RGO had the best catalytic activities and stability. So it is a promising catalyst for direct alcohol fuel cell applications. [Copyright &y& Elsevier]

This paper demonstrates a novel strategy for real-time monitoring of cellular small biomolecules based on graphene hybrid composites film, which was fabricated by one step electrodeposited reduced graphene oxide (ERGO) incorporating adsorption of electroactive methylene blue (MB) onto glassy carbon electrode (GCE). UV–visible spectroscopy, FT-IR spectroscopy, electrochemistry and scanning electron microscopy were employed for systematical characterization of GO-MB adsorptive nanostructure. The ERGO-MB/GCE shows more favorable electron transfer kinetics for potassium ferricyanide and potassium ferrocyanide probe molecules, which are important electroactive compounds, compared with bare GCE, MB/GCE and ERGO/GCE. The electrochemical behaviors of dissolved oxygen and hydrogen peroxide (H 2 O 2 ) at ERGO-MB/GCE were investigated by cyclic voltammetry, suggesting that the modified electrode exhibits enhanced electrocatalytic activity toward H 2 O 2 . Under physiological condition, the ERGO-MB/GCE showed a linear amperometric response from 0.5 μM to 11.68 mM for H 2 O 2 , with the detection limit of 60 nM (S/N = 3), and also showed high sensitivity (10.2 μA mM − 1 cm − 2 ) and short response time within 2 s for H 2 O 2 detection. Besides, the reproducibility, stability and anti-interference ability of the proposed nonenzymatic H 2 O 2 biosensor were also proved. The developed method has been successfully applied to determination of H 2 O 2 released from living cells, which could be clearly distinguished cancer cells including Hep3B, HepG2 and HeLa cells from normal cells HEK 293. This assay shows great potential for nonenzymatic determination of H 2 O 2 in physiological and pathological investigations. [ABSTRACT FROM AUTHOR]

Palladium–copper nanoparticles (Pd–Cu NPs) supported on reduced graphene oxide (RGO) with different Pd/Cu ratios (Pd–Cu/RGO) were prepared by a two step method. The Pd–Cu/RGO hybrids were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction and thermogravimetric analyses. Cyclic voltammetry and chronoamperometry were used to investigate the electrochemical activities and stabilities of the Pd–Cu/RGO catalysts for the electro-oxidation of methanol and ethanol in alkaline media. The Pd–Cu/RGO catalysts exhibited high catalytic activities and good stabilities. This is because the catalysts have a bimetallic structure consisting of a small Pd–Cu core surrounded by a thin Pd-rich shell which improves the catalytic activities of the Pd–Cu/RGO hybrids. Thus they should be useful in direct methanol and ethanol fuel cells. [ABSTRACT FROM AUTHOR]