Construction and analytical characterization of prussian blue-based carbon paste electrodes and their assembly as oxidase enzyme sensors

This paper reports on the development and characterization of Prussian Blue-modified carbon paste electrodes. New methods of matrix modification with Prussian Blue are reported. Two different carbon pastes have been prepared, using mineral oil or solid paraffin, thus obtaining different types of sensors whose behavior toward the electrochemical reduction of hydrogen peroxide has been fully characterized. Results obtained with Prussian Blue-modified electrodes showed a long operational lifetime, an excellent stability in a nide range of pH (3-9), a high sensitivity, and a fast response time. In addition, the coupling of solid carbon paste modified with Prussian Blue and the enzymes glucose oxidase and choline oxidase led to the assembling of biosensors that showed an optimum working range at alkaline pH.[...

Thermodynamic Study of Barium Cerate (BaCeO3) by Knudsen Effusion Mass Spectrometry

Abstract: The vaporization/decomposition of single-phase BaCeO3 samples was studied by the Knudsen Effusion Mass Spectrometry technique in the overall temperature range 1647–1923 K. The partial pressures of the gaseous species BaO(g), CeO2(g) and CeO(g) were monitored as a function of temperature. The formation of reduced form of cerium oxide as a product of the high temperature decomposition of BaCeO3 under the given experimental conditions was suggested by the low value of the measured CeO2(g)/CeO(g) pressure ratio and confirmed by the XRD spectra of the vaporization residues. The equilibrium data were tentatively processed according to various heterogeneous equilibria that may be established in the cell: (i) BaCeO3(s) = BaO(g) + CeO2(s); (ii) BaCeO3(s) + CeO(g) = BaO(g) + Ce2O3(s); (iii) BaCeO3(s) = BaO(g) + CeO2(g). The corresponding enthalpy changes were calculated by the third-law method and the enthalpy of formation of BaCeO3 derived thereafter. The thermodynamic analysis confirms that the decomposition process forming CeO2(s) is very unlikely to occur under the high temperature, high vacuum conditions used in the present study. The analysis of process BaCeO3(s) = BaO(g) + CeO2(g), not involving solid products, was selected as the most reliable and leads to a value for the enthalpy of formation of barium cerate (ΔfH298⁰ (BaCeO3) = –1688.7 ± 6.2 kJ/mol) in agreement with the available calorimetric determinations

Crosslinked organic/inorganic hybrid proton exchange polymeric membranes

A general, efficient and experimentally simple method for the synthesis of covalently crosslinked class II hybrid polymers based on PolyEtherEtherKetone (PEEK) with a high degree of sulfonation (DS = 0.8) was performed. The synthetic strategy foreseen two steps: the first one, direct sulfonation, led to the introduction of sulfonic acid groups and to the formation of sulfone bridges among repeat units. The second step, lithiation and silylation, led to the formation of covalent bonds between the organic backbone and Si(OH)3 moieties. The materials were characterized by 1H NMR Spectroscopy, ATR/FTIR Spectroscopy, Thermogravimetric Analysis (TGA) and Mass Spectrometry. Preliminary proton conduction measurements in dry conditions were performed. The introduction of silicon groups in the system improved thermal stability

Functionalized ORMOSIL-based hybrid membranes for polymer electrolyte membrane fuel cells

Sulfonated poly ether ether ketone (SPEEK) with a high degree of sulfonation (DS = 0.9) was mixed with a modified silane bearing a sulfonic acid function (sulfonated diphenylsilanediole, SDPDO).Homogeneous composite membranes with several SPEEK:SDPDO ratios, were obtained. The addition of the ormosil significantly improved the water uptake and solubility properties of pure SPEEK.The structural and electrochemical characteristics of the composite membranes were investigated by means of thermogravimetric analysis (TG), field emission scanning electron microscopy (FE-SEM), and electrochemical impedance spectroscopy (EIS). The conductivity values of the composites SPEEK/SDPDO demonstrated that they possess good proton transport characteristics, thus being suitable for application in Polymer Electrolyte Fuel Cells operating at intermediate temperature

The Aladin Laser - From Development Challenges to Early In-Orbit Operations

The Aladin instrument is the sole payload on board the European Space Agency’s Aeolus satellite. The purpose of the mission is to measure wind velocities through the Earth’s atmosphere using the Doppler effect in order to provide inputs to numerical weather prediction models and to better understand atmospheric dynamics. To this end, the instrument has two high intensity, Q-switched lasers that emit 20ns pulses at a wavelength of 355nm, with a pulse repetition frequency of 50Hz. The development of these lasers proved to be somewhat longer and more challenging than was first anticipated, with several technology hurdles to be overcome before they could be integrated and tested on the Aladin instrument. This paper will present these, along with the solutions that were eventually implemented for the flight built instrument along with the on-ground verifications which were undertaken to demonstrate fitness for launch. The Aeolus satellite was launched into a sun-synchronous, 320km orbit, from the Guiana Space Center, Kourou, French Guiana, on 22nd August 2018 on an Arianespace Vega rocket. The Aladin instrument, including the FM-A laser transmitter, was switched on 10 days later on 2nd September. The switch-on was successfully performed utilising several discrete energy steps, with intermittent assessments of the laser beam using the imaging mode of the Aladin spectrometers, in order to reduce the risk of laser damage. Full energy operation commenced on 4th September. This, along with an assessment of the early operations of the Aladin laser transmitter during the 3 month in-orbit commissioning phase and the subsequent early in-orbit operations will be described