Alpha-MnO2 nanofibers/nitrogen and sulfur-co-doped reduced graphene oxide for 4.5 V quasi-solid state supercapacitors using ionic liquid-based polymer electrolyte.

α-MnO2 nanofibers combined with nitrogen and sulfur co-doped reduced graphene oxide (α-MnO2/N&S-rGO) were prepared through simple hydrothermal and ball milling processes. Structural characterization results by X-ray diffraction, X-ray photoemission spectroscopy, electron microscopy and Raman spectroscopy demonstrated that α-MnO2 nanofibers with the average diameter of ~40 nm were well dispersed on N&S-rGO nanoflakes. The synthesized material was incorporated into supercapacitor (SC) electrodes and assembled with the quasi-solid-state electrolyte comprising N,N-Diethyl-N-methyl-N-(2-methoxy-ethyl)ammonium bis (trifluoromethyl-sulfonyl)amide [DEME][TFSA]/polyvinylidene fluoride-hexafluoropropylene (PVDF-co-HFP) to produce coin-cell SCs. Electrochemical performances of SCs were measured by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. From the electrochemical data, SC using α-MnO2/N&S-rGO exhibited a good specific capacitance of 165F g-1 at 0.25 A g-1 with a wide potential window of 0-4.5 V, corresponding to a high energy density of 110 Wh kg-1 and a power density of 550 W kg-1. In addition, it exhibited good electrochemical stability with a capacitance retention of 75% after 10,000 cycles at 1 A g-1 and a low self-discharge loss. The attained energy-storage performances indicated that the α-MnO2/N&S-rGO composite could be highly promising for high-performance ionic liquid-based quasi solid-state supercapacitors.

Point-of-care rapid detection of Vibrio parahaemolyticus in seafood using loop-mediated isothermal amplification and graphene-based screen-printed electrochemical sensor.

Vibrio parahaemolyticus is one of the most important foodborne pathogens that cause various life-threatening diseases in human and animals. Here, we present a rapid detection platform for V. parahaemolyticus by combining loop-mediated isothermal amplification (LAMP) and disposable electrochemical sensors based on screen-printed graphene electrodes (SPGEs). The LAMP reactions using primers targeting V. parahaemolyticus toxR gene were optimized at an isothermal temperature of 65 °C, providing specific detection of V. parahaemolyticus within 45 min at the detection limit of 0.3 CFU per 25 g of raw seafood. The LAMP amplicons can be effectively detected using unmodified SPGEs, redox active molecules namely Hoechst-33258 and a portable potentiostat. Therefore, the proposed system is particularly suitable as a point-of-care device for on-site detection of foodborne pathogens.