Search Results (3)

Molybdenum trioxide shows many attractive properties, such as a wide electronic band gap and a high relative permittivity. Monolayers of this material are particularly important, as they offer new avenues in optoelectronic devices, e.g., to alter the properties of graphene electrodes. Nanoscale electrical characterization is essential for potential applications of monolayer molybdenum trioxide. We present a conductive atomic force microscopy study of an epitaxially grown 2D molybdenum oxide layer on a graphene-like substrate, such as highly oriented pyrolytic graphite (HOPG). Monolayers were also investigated using X-ray photoelectron spectroscopy, atomic force microscopy (semi-contact and contact mode), Kelvin probe force microscopy, and lateral force microscopy. We demonstrate mobility of the unpinned island under slight mechanical stress as well as shaping and detachment of the material with applied electrical stimulation. Non-stoichiometric MoO_3-x monolayers show heterogeneous behavior in terms of electrical conductivity, which can be related to the crystalline domains and defects in the structure. Different regions show various I–V characteristics, which are correlated with their susceptibility to electrodegradation. In this work, we cover the existing gap regarding nanomanipulation and electrical nanocharacterization of the MoO₃ monolayer. Full article

The electrochemical stability of ceftriaxone (CFTX), belonging to the third generation of cephalosporin antibiotics, was studied by electrochemical measurements recorded on a platinum electrode (Pt) in aqueous solutions containing sodium halides. The electrochemical behavior of ceftriaxone was investigated by cyclic voltammetry (CV) and constant current density electrolysis assisted by UV-Vis spectrophotometry. Cyclic voltammetry highlighted that the addition of CFTX in sodium halide solutions leads to significant changes in the hysteresis characteristics due to specific interactions with active species from electrolytes, as well as with the platinum electrode surface. After CV, when an exterior electric stimulus in short time (40 s) was applied, the UV-Vis spectra illustrated that CFTX is stable in the presence of F⁻ ions, it is electro(degraded/transformed) in the presence of Cl⁻ and Br⁻ ions and interacts instantly with I⁻ species. Electrolysis at constant current density confirms the results obtained from cyclic voltammetry, showing that (i) in the presence of fluoride ions CFTX gradually decomposes, but not completely, in about 60 min, without identifying a reaction product; (ii) chloride and bromide ions determine the almost complete CFTX electro(degradation/transformation) in 10 and 5 min, respectively, with completion of the electro-transformation reaction after 60 and 30 min, respectively; (iii) instantaneous interactions between CFTX and the iodide ions occurred. Full article

Perfluorooctanoic acid (PFOA), C₇F₁₅COOH, has been widely employed over the past fifty years, causing an environmental problem because of its dispersion and low biodegradability. Furthermore, the high stability of this molecule, conferred by the high strength of the C-F bond makes it very difficult to remove. In this work, electrochemical techniques are applied for PFOA degradation in order to study the influence of the cathode on defluorination. For this purpose, boron-doped diamond (BDD), Pt, Zr, and stainless steel have been tested as cathodes working with BDD anode at low electrolyte concentration (3.5 mM) to degrade PFOA at 100 mg/L. Among these cathodic materials, Pt improves the defluorination reaction. The electro-degradation of a PFOA molecule starts by a direct exchange of one electron at the anode and then follows a complex mechanism involving reaction with hydroxyl radicals and adsorbed hydrogen on the cathode. It is assumed that Pt acts as an electrocatalyst, enhancing PFOA defluorination by the reduction reaction of perfluorinated carbonyl intermediates on the cathode. The defluorinated intermediates are then more easily oxidized by HO^• radicals. Hence, high mineralization (x_TOC: 76.1%) and defluorination degrees (x_F⁻: 58.6%) were reached with Pt working at current density j = 7.9 mA/cm². This BDD-Pt system reaches a higher efficiency in terms of defluorination for a given electrical charge than previous works reported in literature. Influence of the electrolyte composition and initial pH are also explored. Full article