Amorphous Co₂B Grown on CoSe₂ Nanosheets as a Hybrid Catalyst for Efficient Overall Water Splitting in Alkaline Medium

In this work, we synthesized a novel hybrid catalyst (Co₂B/CoSe₂) by growing amorphous Co₂B on the surface of CoSe₂ nanosheets. Benefiting from the prominent coupled effects between Co₂B and CoSe₂ nanosheets, an efficient oxygen evolution reaction catalyst Co₂B/CoSe₂ exhibits a very low overpotential of 320 mV @ 10 mA cm^–2 with a Tafel slope of 56.0 mV dec^–1 in alkaline medium. An overpotential of 300 mV can also be achieved by Co₂B/CoSe₂ at the same condition for hydrogen evolution reaction. Notably, at the applied potential of 1.73 V, the electrocatalyst Co₂B/CoSe₂ demonstrates a current density of 10 mA cm^–2 for overall water splitting and displays an outstanding long-term stability. The faradaic efficiencies of Co₂B/CoSe₂ for both hydrogen and oxygen evolution are close to 100%

Introducing Ratiometric Fluorescence to MnO₂ Nanosheet-Based Biosensing: A Simple, Label-Free Ratiometric Fluorescent Sensor Programmed by Cascade Logic Circuit for Ultrasensitive GSH Detection

Glutathione (GSH) plays crucial roles in various biological functions, the level alterations of which have been linked to varieties of diseases. Herein, we for the first time expanded the application of oxidase-like property of MnO₂ nanosheet (MnO₂ NS) to fluorescent substrates of peroxidase. Different from previously reported fluorescent quenching phenomena, we found that MnO₂ NS could not only largely quench the fluorescence of highly fluorescent Scopoletin (SC) but also surprisingly enhance that of nonfluorescent Amplex Red (AR) via oxidation reaction. If MnO₂ NS is premixed with GSH, it will be reduced to Mn²⁺ and lose the oxidase-like property, accompanied by subsequent increase in SC’s fluorescence and decrease in AR’s. On the basis of the above mechanism, we construct the first MnO₂ NS-based ratiometric fluorescent sensor for ultrasensitive and selective detection of GSH. Notably, this ratiometric sensor is programmed by the cascade logic circuit (an INHIBIT gate cascade with a 1 to 2 decoder). And a linear relationship between ratiometric fluorescent intensities of the two substrates and logarithmic values of GSH’s concentrations is obtained. The detection limit of GSH is as low as 6.7 nM, which is much lower than previous ratiometric fluorescent sensors, and the lowest MnO₂ NS-based fluorescent GSH sensor reported so far. Furthermore, this sensor is simple, label-free, and low-cost; it also presents excellent applicability in human serum samples