Selenium electrochemistry in choline chloride–urea deep eutectic electrolyte

Electrodeposition in Deep Eutectic Solvents: The "Obvious", the "Unexpected" and the "Wonders"

Deep eutectic solvents (DESs) are attracting considerable attention as non-conventional media for electrodeposition processes. This opinion contribution discusses the debated nature and definition of these solvents as well as some practical considerations of relevance when performing electrodeposition studies in DESs. Using a few illustrative case studies, it is shown that speciation is a key factor determining the electrochemical behaviour of chemical elements in different DESs, and that accounting for the speciation strong similarities can often be found with more conventional or more documented solvents. The need for thermodynamic data is emphasised and it is suggested to expand the composition range of these solvents beyond fixed ratios between the components to exploit the full potentialities of DESs.

Fabrication of UMCM-1 based monolithic and hollow fiber - Metal-organic framework deep eutectic solvents/molecularly imprinted polymers and their use in solid phase microextraction of phthalate esters in yogurt, water and edible oil by GC-FID

In this study, for the first time, hollow fiber and monolithic fiber were fabricated based on metal-organic framework deep eutectic solvents/molecularly imprinted polymers (MOF- DES/MIPs) and were used for microextraction of phthalate esters under termed hollow fiber liquid membrane-protected solid-phase microextraction (HFLMP-SPME) followed by gas chromatography- flame ionization detection. Several parameters influencing extraction recoveries of phthalate esters including adsorption and desorption parameters were investigated and optimized using fabricated MOF- DES/MIPs monolithic fiber. Under optimal conditions, detection limits (S/N = 3) of the method were in a range of 0.008-0.03 µg L^-1 and limits of quantification (S/N = 10) were between 0.028 and 0.12 µg L^-1. RSD (%) for intra-day and inter-day precisions were between 2.4-4.7% and 2.6-3.4%, respectively. Subsequently, this procedure was successfully applied with satisfactory results in the determination of phthalate esters in yogurt, water, and soybean oil samples. The R (%) ranged from 95.5 to 100.0% in different samples.

Electrochemical, Spectroscopic, and Computational Investigations on Redox Reactions of Selenium Species on Galena Surfaces

Despite previous studies investigating selenium (Se) redox reactions in the presence of semiconducting minerals, Se redox reactions mediated by galena (PbS) are poorly understood. In this study, the redox chemistry of Se on galena is investigated over a range of environmentally relevant Eh and pH conditions (+0.3 to −0.6 V vs. standard hydrogen electrode, SHE; pH 4.6) using a combination of electrochemical, spectroscopic, and computational approaches. Cyclic voltammetry (CV) measurements reveal one anodic/cathodic peak pair at a midpoint potential of +30 mV (vs. SHE) that represents reduction and oxidation between HSeO3− and H2Se/HSe−. Two peak pairs with midpoint potentials of −400 and −520 mV represent the redox transformation from Se(0) to HSe− and H2Se species, respectively. The changes in Gibbs free energies of adsorption of Se species on galena surfaces as a function of Se oxidation state were modeled using quantum-mechanical calculations and the resulting electrochemical peak shifts are (−0.17 eV for HSeO3−/H2Se, −0.07 eV for HSeO3−/HSe−, 0.15 eV for Se(0)/HSe−, and −0.15 eV for Se(0)/H2Se). These shifts explain deviation between Nernstian equilibrium redox potentials and observed midpoint potentials. X-ray photoelectron spectroscopy (XPS) analysis reveals the formation of Se(0) potentials below −100 mV and Se(0) and Se(−II) species at potentials below −400 mV.

On the cobalt and cobalt oxide electrodeposition from a glyceline deep eutectic solvent

The electrodeposition of cobalt and cobalt oxides from a glyceline deep eutectic solvent is reported.

A green ultrasonic-assisted liquid-liquid microextraction based on deep eutectic solvent for the HPLC-UV determination of ferulic, caffeic and cinnamic acid from olive, almond, sesame and cinnamon oil

A simple, inexpensive and sensitive ultrasonic-assisted liquid-liquid microextraction method based on deep eutectic solvent (UALLME-DES) was used for the extraction of three phenolic acids (ferulic, caffeic and cinnamic) from vegetable oils. In a typical experiment, deep eutectic solvent as green extraction solvent was added to n-hexane (as a typical oil medium) containing target analytes. Subsequently, the extraction was accelerated by sonication. After the extraction, phase separation (DES rich phase/n-hexane phase) was performed by centrifugation. DES rich phase (lower phase) was withdrawn by a micro-syringe and submitted to isocratic reverse-phase HPLC with UV detection. Under optimum conditions obtained by response surface methodology (RSM) and desirability function (DF), the method has good linear calibration ranges (between 1.30 and 1000 µg L(-1)), coefficients of determination (r(2)>0.9949) and low limits of detection (between 0.39 and 0.63 µg L(-1)). This procedure was successfully applied to the determination of target analytes in olive, almond, sesame and cinnamon oil samples. The relative mean recoveries ranged from 94.7% to 104.6%.

Electrodeposition in Ionic Liquids

Due to their attractive physico-chemical properties, ionic liquids (ILs) are increasingly used as deposition electrolytes. This review summarizes recent advances in electrodeposition in ILs and focuses on its similarities and differences with that in aqueous solutions. The electrodeposition in ILs is divided into direct and template-assisted deposition. We detail the direct deposition of metals, alloys and semiconductors in five types of ILs, including halometallate ILs, air- and water-stable ILs, deep eutectic solvents (DESs), ILs with metal-containing cations, and protic ILs. Template-assisted deposition of nanostructures and macroporous structures in ILs is also presented. The effects of modulating factors such as deposition conditions (current density, current density mode, deposition time, temperature) and electrolyte components (cation, anion, metal salts, additives, water content) on the morphology, compositions, microstructures and properties of the prepared materials are highlighted.

Dispersive micro-solid-phase extraction of dopamine, epinephrine and norepinephrine from biological samples based on green deep eutectic solvents and Fe3O4@MIL-100 (Fe) core–shell nanoparticles grafted with pyrocatechol

DA, EP and NE were determined without interference of ascorbic acid using grafted Fe₃O₄@MIL-100 (Fe) NPs and a green solvent.

Effects of ultrasound and temperature on copper electro reduction in Deep Eutectic Solvents (DES)

This paper concerns a preliminary study for a new copper recovery process from ionic solvent. The aim of this work is to study the reduction of copper in Deep Eutectic Solvent (choline chloride-ethylene glycol) and to compare the influence of temperature and the ultrasound effects on kinetic parameters. Solutions were prepared by dissolution of chloride copper salt CuCl2 (to obtain Copper in oxidation degree II) or CuCl (to obtain Copper in oxidation degree I) and by leaching metallic copper directly in DES. The spectrophotometry UV-visible analysis of the leached solution showed that the copper soluble form obtained is at oxidation degree I (Copper I). Both cyclic voltammetry and linear voltammetry were performed in the three solutions at three temperatures (25, 50 and 80°C) and under ultrasonic conditions (F=20kHz, PT=5.8W) to calculate the mass transfer diffusion coefficient kD and the standard rate coefficient k°. These parameters are used to determine that copper reduction is carried out via a mixed kinetic-diffusion control process. Temperature and ultrasound have the same effect on mass transfer for reduction of Cu(II)/Cu(I). On the other hand, temperature is more beneficial than ultrasound for mass transfer of Cu(I)/Cu. Standard rate constant improvement due to temperature increase is of the same order as that obtained with ultrasound. But, by combining higher temperature and ultrasound (F=20kHz, PT=5.6W at 50°C), reduction limiting current is increased by a factor of 10 compared to initial conditions (T=25°C, silent), because ultrasonic stirring is more efficient in lower viscosity fluid. These values can be considered as key-parameters in the design of copper recovery in global processes using ultrasound.

Cathodic electrodeposition of amorphous elemental selenium from an air- and water-stable ionic liquid

Electrodeposition of selenium from 1-propyl-1-methylpiperidinium bis(trifluoromethylsulfonyl)imide is reported. In situ UV-vis spectroelectrochemistry was used to investigate the reduction of diethyl selenite to form elemental selenium thin films from an ionic liquid-acetonitrile medium. Three reduction peaks of diethyl selenite were observed via cyclic voltammetry and are attributed to the stepwise reduction of the selenium precursor adsorbed on the electrode. The electrodeposition mechanism is influenced by both potential and time. Electrodeposition at -1.7 V vs Pt QRE resulted in the deposition of elemental selenium nanoparticles that with time coalesced to form a continuous film. At reduction potentials more negative than -1.7 V the morphology of the deposit changed significantly due to the reduction of elemental Se to Se(2-). In addition, p-type photoconductivity of the films was observed during the spectroelectrochemical measurements. X-ray diffraction and Raman spectroscopy confirmed that the deposited selenium films were amorphous. X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy confirm the films consisted of pure selenium with minor residual contamination from the precursor and ionic liquid.