Minimizing the shuttle effect by constraining polysulfides to the cathode compartment and activating the passive layer between cathode and separator are highly important for improving the Li-S cell performance, Coulombic efficiency, and cycle life. Here, we report a submicron thin coating of permselective sulfonated poly(ether ether ketone) (SPEEK) composite layer on the separator that would reduce polysulfide crossover, imparting a significant improvement in cycle life. It is observed that SPEEK increases the stability, and adding Nafion improves the capacity value. Among different ratios of Nafion and SPEEK (25:75, 50:50, and 75:25), the composite with a SPEEK/Nafion ratio of 50:50 showed a controlled shuttle effect with a stable cell capacity of 600 mA h g up to 300 cycles. This modified separator with permselective coatings not only reduces the polysulfide shuttle but also improves the wettability and interfacial contact, which results in an improvement in average cell potential and lithium diffusivity. It is demonstrated here that the combination of functional (ionomer coating on separator) and nonfunctional (extra cathode layer) physical barriers effectively suppresses the polysulfide crossover and improves the electrochemical performance of Li-S batteries. The cell shows an initial capacity of 1300 mA h g and a capacity retention of 650 mA h g over 500 cycles with a 6 mg/cm sulfur loading.

Doping of Ni into Fe 2 O 3 lattices has been achieved by co-precipitation followed by thermal decomposition method. The structural, morphological, and magnetic properties of the fabricated samples were investigated by X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared (FT-IR) spectroscopy, UV-visible absorption (UV-vis) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The results reveal that the Ni is well doped within the lattices of Fe 2 O 3 . The Ni dopant suppresses the formation of more stable a-Fe 2 O 3 at higher calcination temperature. Further, the Ni-doped Fe 2 O 3 nanoparticles were used to fabricate an electrochemical sensor (Ni-Fe 2 O 3 /GCE) for the detection of uric acid (UA) in biological conditions by cyclic voltammetry (CV) and chronoamperometry (CA). It was found that 5%Ni-Fe 2 O 3 /GCE exhibits best response towards UA with less positive potential and larger current response. Furthermore, the sensor gives good linear current response in the concentration range of 6.6 to 112.4 mM with the higher sensitivity of 0.849 mA (mM cm 2 ) À1 . Such fabricated sensors are appropriate for newly emerging non-enzymatic electrochemical nanobiosensors.

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Sensing of biogenic amines is important for packed/fermented foods. It reveals the quality of food being consumed.

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Ni 0 /NiO (nickel/nickel oxide) core-shell nanostructures were synthesized through a facile combustible redox reaction. Remarkably, the hetero-phase boundary with different crystalline orientations offered dual properties, which helped in bifunctional catalysis. Presence of a metallic Ni phase changed physicochemical properties and some emerging applications (magnetic properties, optical conductivity, electrochemical sensitivity, catalytic behaviour) could be foreseen. Moreover, formation of a NiO layer on metal surface prevented magnetism-induced aggregation, arrested further oxidation by hindering oxygen diffusion, and acted as a good sorbent to enhance the surface adsorption of the analyte.Hexagonal Ni/NiO nanostructures manifested well-defined ferromagnetic behavior and the catalyst could be collected easily at the end of the catalytic reduction. Ni/NiO core-shell catalysts at the nanoscale had outstanding catalytic performance (reduction of 4-nitrophenol to 4-aminophenol) compared with pure NiO catalysts beyond a reaction time of $9 min. The estimated sensitivity, limit of detection and limit of quantification towards the electrochemical sensing of serotonin were 0.185, 0.43 and 1.47 mM mA À1 , respectively. These results suggest that a bifunctional Ni/NiO nanostructure could be a suitable catalyst for electrochemical detection of serotonin and reduction of 4-nitrophenol.

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