We have successfully fabricated an asymmetric supercapacitor with high energy and power densities using graphene hydrogel (GH) with 3D interconnected pores as the negative electrode and vertically aligned MnO(2) nanoplates on nickel foam (MnO(2)-NF) as the positive electrode in a neutral aqueous Na(2)SO(4) electrolyte. Because of the desirable porous structure, high specific capacitance and rate capability of GH and MnO(2)-NF, complementary potential window of the two electrodes, and the elimination of polymer binders and conducting additives, the asymmetric supercapacitor can be cycled reversibly in a wide potential window of 0-2.0 V and exhibits an energy density of 23.2 Wh kg(-1) with a power density of 1.0 kW kg(-1). Energy density of the asymmetric supercapacitor is significantly improved in comparison with those of symmetric supercapacitors based on GH (5.5 Wh kg(-1)) and MnO(2)-NF (6.7 Wh kg(-1)). Even at a high power density of 10.0 kW kg(-1), the asymmetric supercapacitor can deliver a high energy density of 14.9 Wh kg(-1). The asymmetric supercapacitor also presents stable cycling performance with 83.4% capacitance retention after 5000 cycles.

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We report a facile one-step ultrasonication-assisted electrochemical method to synthesize nanocomposites of graphene and PtNi alloy nanoparticles (NPs) and their uses for highly selective nonenzymatic glucose detection. We have demonstrated that the obtained nanocomposites exhibit a collection of unique features including well-dispersed NPs with alloy features, high NP loading, and effective reduction of graphene oxide (GO). And the resulting nanoelectrocatalyst shows significantly improved electrochemical performance in nonenzymatic amperometric glucose detection, compared to a number of control electrode materials including the PtNi NP-chemically reduced GO nanocomposites fabricated in two steps (chemical reduction of GO followed by the electrodeposition of metal NPs). Under the physiological condition, the response current of the sensor is linear to glucose concentration up to 35 mM with a sensitivity of 20.42 μA cm(-2) mM(-1) at a substantially negative potential (i.e., -0.35 V). Operation under this potential eliminates the impact from the oxidation of common interfering species. This sensor with excellent sensitivity and selectivity also allows for reproducible detection of glucose in human urine samples.

We report the design of all-solid-state asymmetric supercapacitors based on free-standing carbon nanotube/graphene (CNTG) and Mn(3)O(4) nanoparticles/graphene (MG) paper electrodes with a polymer gel electrolyte of potassium polyacrylate/KCl. The composite paper electrodes with carbon nanotubes or Mn(3)O(4) nanoparticles uniformly intercalated between the graphene nanosheets exhibited excellent mechanical stability, greatly improved active surface areas, and enhanced ion transportation, in comparison with the pristine graphene paper. The combination of the two paper electrodes with the polymer gel electrolyte endowed our asymmetric supercapacitor of CNTG//MG an increased cell voltage of 1.8 V, a stable cycling performance (capacitance retention of 86.0% after 10,000 continuous charge/discharge cycles), more than 2-fold increase of energy density (32.7 Wh/kg) compared with the symmetric supercapacitors, and importantly a distinguished mechanical flexibility.

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01761188.

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We have developed a new type of flexible electrodes based on Cu nanocube-decorated free-standing graphene paper (GP) using a facile electrodeposition method. The Cu nanocubes− graphene paper (Cu−GP) hybrid electrode processes remarkable electrocatalytic activity with an onset potential of −0.10 V toward hydrazine oxidation in alkaline solutions and can serve as the catalyst layer for direct hydrazine fuel cells. One interesting finding is that a copper hydroxide/oxide layer in situ formed on Cu nanocube surfaces plays an important role in enhancing the electrocatalytic activity and durability of the electrocatalyst. A totally irreversible and diffusion-controlled oxidation of hydrazine occurs on the electrocatalyst, eventually leading to environmentally friendly products such as nitrogen and water.

The solubilities of two polymorphs of glycine (α-form and γ-form) in different aqueous solvent mixtures were measured by using the analytical gravimetric method. Based on the measured solubility data in pure water, the relative stability and the enthalpy and entropy of dissolution of the two forms were determined using van’t Hoff plots. The solubilities of forms α and γ were also investigated in aqueous solutions containing methanol or polyethylene glycol (PEG200) at 20 °C. It was shown that the solubilities of both forms decreased with increasing concentration of methanol and PEG200. The pH dependence of solubility of the γ-form was measured in the pH range of (0.35 to 13.7) at temperatures of (20 and 25) °C. The solubility profiles show a U-shape with pronounced changes at pH below 3.0 or above 10.0.