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Preparing the low-cost nanomaterials for electrocatalytic processes is still a big challenge. Mesoporous cobalt hydroxide and cobalt oxide nanoparticles were prepared through simple soft chemistry as high-performance materials for durable electrocatalyst for OER and supercapacitive applications. The synthesis method is used to prepare nanoring particles in neither emulsion nor template-directed method. The final nanoparticles display mesoporous hexagonal nanoring morphology. The physio-chemical properties of the as-synthesized nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and nitrogen adsorption-desorption techniques. The TEM characterizations prove that NPs retain the topotactical relationship in their structure during the conversion process. The BET measurements prove the mesoporous nature of the nanorings, having good specific surface area and pore volume. Finally, the electrochemical performance toward water splitting and supercapacitor applications were investigated by electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and cyclic voltammetry (CV) techniques. The Co 3 O 4 NPs exhibits better catalytic properties than Co(OH) 2 NPs when applied as electrocatalyst in an alkaline medium for water splitting and supercapacitor measurements. The enhanced electrocatalytic performance attributed to the mesoporous structure along with high pore volume, which provides more active boundary sites for the electrochemical process, resulted in the enhanced exchange of the intermediates and more efficient electron transfer. This synthetic methodology, with the advantages of inexpensive/non-complicated experimental setup and high electrochemical performance, could shed light on the development of non-expensive electrocatalysts for clean energy production and storage. Image 1 • Cobalt hydroxide/oxide nanorings are synthesized by a facile approach. • NPs show excellent catalytic activity for oxygen production. • NPs exhibit superior electrochemical cyclic stability. • The superior performance of NPs mainly related to mesoporous structure. [ABSTRACT FROM AUTHOR]

[Display omitted] NiO and NiO-Ni nanoparticles were synthesized via a low-cost and simple procedure using solvothermal-calcination method. Our preparation method is a facile and green chemicals process without using toxic/hazardous chemicals or any template. The nanoparticles were used to fabricate a sensor by drop-casting of its solution on a surface of a cleaned glassy carbon electrode. The effectiveness for the electrochemical determination of Metronidazole was confirmed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The modified electrode represented an electrocatalytic response for the analyte with a considerable decrease of overvoltage as well as an enhancing of the peak current in comparison with the bare electrode. The represented sensors showed linear behavior to metronidazole in the concentration range of 0.01–1.44 μmol L−1 (NiO-Ni) and 0.8–3.8 μmol L−1 (NiO) in CV and 0.01–1.63 μmol L−1 (NiO-Ni) and 0.01–0.47 μmol L−1 (NiO) in DPV techniques. The detection limits were found to be 0.007 (CV) and 0.006 (DPV) μmol L−1 for NiO-Ni and 0.4 (CV) and 0.008 μmol L−1 (DPV) for NiO modified electrodes, respectively. Additionally, the modified electrodes have significant benefits such as low cost, convenient preparation, fast response time, good stability, acceptable repeatability, high sensitivity, wide concentration range, and low detection limit. [ABSTRACT FROM AUTHOR]

The application of silica coated quantum dots (QDs@SiO2) in glucose detection in combination with glucose oxidase is reported. The high specific surface area of such particles can be exploited to immobilise a greater amount of the enzyme on a modified electrode. In addition to this electrochemical method, we report here an indirect optical technique based on the photoluminescence quenching of QDs by hydrogen peroxide produced during glucose oxidation. The results obtained with these two different detection methodologies are compared. [ABSTRACT FROM AUTHOR]