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Defect‐engineering is a viable strategy to improve the activity of nanocatalysts for the oxygen evolution reaction (OER), whose slow kinetics still strongly limits the broad market penetration of electrochemical water splitting as a sustainable technology for large‐scale hydrogen production. High‐entropy spinel oxides (HESOs) are in focus due to their great potential as low‐cost OER electrocatalysts. In this work, electrospun HESO nanofibers (NFs), based on (Cr,Mn,Fe,Co,Ni), (Cr,Mn,Fe,Co,Zn) and (Cr,Mn,Fe,Ni,Zn) combinations, with granular architecture and oxygen‐deficient surface are produced by calcination at low temperature (600 or 500 °C), characterized by a combination of benchtop analytical techniques and evaluated as electrocatalysts for OER in alkaline medium. The variation of HESO composition and calcination temperature produces complex and interdependent changes in the morphology of the fibers, crystallinity and inversion degree of the spinel oxide, concentration of the oxygen‐vacancies, cation distribution in the lattice, which mirror on different electrochemical properties of the fibers. The best electrocatalytic performance (overpotential and Tafel slope at 10 mA cm−2: 360 mV and 41 mV dec−1, respectively) pertains to (Cr1/5Mn1/5Fe1/5Co1/5Ni1/5)3O4 NFs calcined at 500 °C and results from the lower outer 3d‐electron number, eg filling closer to its optimal value and higher occupation of 16d sites by the most redox‐active species. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor for the determination of nitrites based on the modified screen‐printed electrode (SPCE) by Zn‐bidentate Schiff base complexes (ZnLX2) is presented. ZnLX2 complexes have been synthesized and characterized using several morphological and microstructural techniques such as scanning electron microscopy (SEM), X‐ray powder diffraction (XRD), and fourier transformed‐infrared (FT‐IR) spectroscopy. Cyclic voltammetry (CVs) proved the good electrochemical performances of the ZnLX2/SPCE for nitrite ions determination. The influence of pH, scan rate, nitrite concentration, and interfering ions was investigated. After optimization of the operating parameters, the developed ZnLX2/SPCE sensor displayed two linear relationships between response current and nitrite concentration in the overall range 2–4838 μM and a lower detection limit estimated to be 0.78 μM based on 3σ/m. Finally, the analytical application of the developed sensor was evaluated to quantify nitrite in a real sample of mineral water. Results obtained demonstrate that the ZnLX2/SPCE electrochemical sensor provided an effective tool for the detection of nitrite ions. [ABSTRACT FROM AUTHOR]

In this article, the electrochemical monitoring of phenol (Ph) in water by using a nanostructured MnO2-modified screen-printed carbon electrode (MnO2-SPCE) is reported. MnO2 nanoparticles were synthesized by the redox-precipitation method. Morphological, textural, and microstructural characteristics were investigated by scanning electron microscopy (SEM), X-ray diffraction, Raman, Brunauer–Emmett–Teller (BET) surface area, and pore volume analyses. Electrochemical properties of the modified MnO2-SPCE electrode have been investigated by cyclic voltammetry and linear sweep voltammetry. The detection of Ph in water by the developed sensor was exploited using square wave voltammetry and chronoamperometry. The sensor showed good characteristics, such as simple fabrication, low cost, good sensitivity, stability, reproducibility, and selectivity, against inorganic analytes and other phenolic compounds. The reported results demonstrated the great potential of nanostructured MnO2 in developing high performances electrochemical sensors to be utilized in the field of environmental pollution monitoring. [ABSTRACT FROM AUTHOR]

This article describes a simple though extremely effective sensor for acetone monitoring in the breath. The sensor is capable of monitoring the presence of acetone at parts per million (ppm) concentrations, thus being suitable for a diabetes diagnosis. It has a dimension of $3 {\,\,\mathrm {mm}} \times 6 {\,\,\mathrm {mm}}$ and a cost of less than one dollar. The small dimensions allow one to greatly limit the power required to increase its temperature, and its high selectivity with respect to other gases present in the breath reduces the risk of false-positive responses. The sensor is based on a thin alumina substrate on which platinum strips are deposited on both faces. A thin Nb2O5 layer with a nanometric thickness provides the required sensitivity and selectivity. Sensor prototypes have been characterized by field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) and proved an inherent linear response up to a few ppm of acetone. [ABSTRACT FROM AUTHOR]

Fast, selective and low-cost sensors for nitric oxide (NO) detection are highly desirable due to the harmful effects of this gas. Low temperature NO detection is challenging, requiring selective and effective catalytic processes. Here, we present an experimentally based CuO-NO interaction model in the 50–400 °C temperature range and a promising NO chemoresistive sensing device working at 50 °C based on CuO nanoparticles (NPs) produced by pulsed laser ablation in liquid environment (PLAL). Ligand-free Cu/Cu 2 O nanostructures produced by PLAL were converted into 35 ± 12 nm CuO NPs by 400 °C annealing, and analysed by X-Ray Diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray techniques. The chemoresistive sensor is produced by drop-casting the CuO NPs suspension onto an interdigitated electrode and tested in a flow-controlled test chamber. Below 250 °C, oxidation behavior is recorded, while above 350 °C reduction takes place, with a peculiar transient regime observed at 300 °C. A full model of CuO-NO interaction is proposed, based on Langmuir adsorption theory and kinetics barriers extracted by response curves in the 50–400 °C temperature range. A peculiar catalytic activity of CuO NPs emerges in combination with oxygen species absorbed at different temperature, leading to effective NO detection. The ease and scalability of CuO NPs production by PLAL and the reported fast and selective NO sensor working at 50 °C open promising routes towards exploitation for massive and affordable harmful gas detection. [Display omitted] • Synthesis of CuO ligand-free nanoparticles by pulsed laser ablation in liquid. • Fabrication of chemoresistive CuO-based sensor of gas phase NO. • The CuO-based sensor showed low LoD, high sensitivity and selectivity to NO at 50 °C. • The sensor presents good stability and very short response and recovery times. • The sensing mechanism is analyzed and described. [ABSTRACT FROM AUTHOR]