Ether Formation Research Articles

Solvothermal synthesis and characterization of monoclinic WO3 nanoplatelets: investigation of their photocatalytic performance

A facile and original approach based on a one-pot non-aqueous sol–gel solvothermal process was developed to synthesize 2D Tungsten trioxide (WO3) nanoplatelets with an average size ranging from 30 to 50 nm, and a correspondingly high surface area. The structural, morphological, functional group, optical properties of the materials, and the properties of the adsorption surfaces were all investigated; the degree of surface hydroxyls (–OH groups) has been examined. Nuclear Magnetic Resonance Spectroscopy techniques indicated the formation of di-hexyl ether as a result of the solvothermal reaction. The optical absorption, measured using UV–Vis Diffuse Reflectance Spectroscopy, revealed a narrow bandgap (Eg = 2.18 and 2.48 eV for WO3-24 and WO3-48, respectively) compared to that of for bulk WO3 (2.7 eV), attributable to oxygen vacancies. The as-prepared WO3 nanoplatelets displayed excellent photocatalytic performance for degrading Rhodamine B under visible light-emitting diode light with up 99% degradation rate that was achieved in 120 min. Thus, the enhanced Rhodamine B photodegradation in the presence of WO3-24 along with H2O2 was assigned to the reactive oxygen species such as ·OH and RhB*+, involving in the strong synergistic effect between WO3 and H2O2, effectively separating of photocarriers and, as a consequence, boosting the photocatalytic efficiency.

Investigation of the dynamics of the chemical composition of fermented apple juices in the process of acetic acid fermentation

The article presents the results of a study aimed at a deep and comprehensive study of the factors that determine the effectiveness of the biochemical oxidation process, the study of the dynamics of the chemical composition of apple materials in the process of acetic acid fermentation. At the first stage of the study, a study of the chemical composition of apple juices was conducted. The pH, the content of solids, titrated acids, volatile acids, extract, sugars, nitrogenous substances, phenolic substances and carbohydrates were determined in the studied juice samples. At the second stage, a study of the chemical composition of apple materials was carried outduring fermentation. Fermentation of apple juice was carried out on a pure culture of yeast Apple-7. Fermentation was carried out at a temperature of 20-22⁰C. The finished fermented juice was alcoholized to 9% by volume and stored before use. Further, acetic acid fermentation was carried out in a deep way. The main technological and biochemical parameters were determined in fresh apple juice, fermented alcoholic juice and vinegar. As a result of determining the fractional composition of nitrogenous, phenolic substances and carbohydrates of apple juices, it was found that the chemical composition of apple juices depends on the method of processing apples and their varietal characteristics In the process of acetic acid fermentation of apple materials, a change in nitrogenous and phenolic substances is observed. At the same time, the carbohydrate composition practically does not change. When apple materials are oxidized by acetic acid bacteria, the processes of aldehyde formation and ether formation are significantly intensified. Thus, the data obtained indicate a variety of chemical composition of apple materials and vinegar obtained from them. In general, the chemical composition of apple materials and vinegar depends on the quality of processed raw materials and technological conditions of production.

Formation, Reactivity and Decomposition of Aryl Phospha-Enolates.

Two lithium phospha-enolates [RP=C(Sii Pr3 )OLi]2 were prepared by reaction of triisopropyl silyl phosphaethynolate, i Pr3 SiPCO, with aryl lithium reagents LiR (R=Mes: 1,3,5-trimethyl phenyl; or Mes*: 1,3,5,-tri-tertbutyl phenyl). Monomer/dimer aggregation of the enolates can be modulated by addition of 12-crown-4. Substitution of lithium for a heavier alkali metal was achieved through initial formation of a silyl enol ether, followed by reaction with KOt Bu to form the corresponding potassium phospha-enolate [MesP=C(Sii Pr3 )OK]2 . On addition of water, the enolates are protonated to afford RP=C(Sii Pr3 )(OH). For the sterically less demanding system (R=Mes), this phospha-enol rapidly tautomerises to the corresponding acyl phosphine MesP(H)C(Sii Pr3 )(O), which on heating extrudes CO. In contrast, bulkier phospha-enol (R=Mes*) is stable to rearrangement at room temperature and thermally decomposes to RH and i Pr3 SiPCO.

Ethanol Oxidation on Gold Nanowire Containing Oxygen Impurities: A Study by Ab Initio Molecular Dynamics Simulations

Linear atomic chain (LAC) gold nanowires (Au-NWs) containing oxygen impurities are materials that could be used as supports to stimulate chemical reactions. Its peculiar structural characteristics, such as abnormal Au-Au bonds, make it interesting to explore the chemical reactions of this material at a theoretical level. This work investigated the chemical reaction of ethanol supported on Au-NW containing two oxygen impurities. Using <em>ab initio</em> molecular dynamics simulations, it was shown that the presence of oxygen impurity in the LAC conditions the minimum energy paths (MEP) that ethanol will follow in its chemical transformation. When the structure of the LAC contains two oxygen impurities, the formation of acetaldehyde and acetic acid as reaction products were observed. Specifically, the presence of two oxygen impurities in the LAC favors the migration of hydrogens of the -CH<sub>2</sub>- and -OH groups of ethanol towards the LAC. In addition, it was observed that the formation of the C-O bond was favored, which implies an additional reaction intermediate that leads to a total of two different reaction paths in ethanol oxidation.

Plant homocysteine, a methionine precursor and plant's hallmark of metabolic disorders.

Homocysteine (Hcy) is a sulfur-containing non-proteinogenic amino acid, which arises from redox-sensitive methionine metabolism. In plants, Hcy synthesis involves both cystathionine β-lyase and S-adenosylhomocysteine hydrolase activities. Thus, Hcy itself is crucial for de novo methionine synthesis and S-adenosylmethionine recycling, influencing the formation of ethylene, polyamines, and nicotianamine. Research on mammalian cells has shown biotoxicity of this amino acid, as Hcy accumulation triggers oxidative stress and the associated lipid peroxidation process. In addition, the presence of highly reactive groups induces Hcy and Hcy derivatives to modify proteins by changing their structure and function. Currently, Hcy is recognized as a critical, independent hallmark of many degenerative metabolic diseases. Research results indicate that an enhanced Hcy level is also toxic to yeast and bacteria cells. In contrast, in the case of plants the metabolic status of Hcy remains poorly examined and understood. However, the presence of the toxic Hcy metabolites and Hcy over-accumulation during the development of an infectious disease seem to suggest harmful effects of this amino acid also in plant cells. The review highlights potential implications of Hcy metabolism in plant physiological disorders caused by environmental stresses. Moreover, recent research advances emphasize that recognizing the Hcy mode of action in various plant systems facilitates verification of the potential status of Hcy metabolites as bioindicators of metabolism disorders and thus may constitute an element of broadly understood biomonitoring.

Non-waste energy and resource-saving heterogeneous catalytic methods of obtaining and transformation of cyclic acetalies and gem-dichlorocyclopropanes

New methods and ways of using heterogeneous zeolite catalysts – H-Y, H-Beta, H-MOR, H-ZSM-5 and micro- meso-porous – H-Ymmm and others in organic synthesis were studied. Using the example of available petrochemical compounds such as polyols, olefins, and dienes, the possibilities of carrying out cyclization and condensation reactions in the presence of zeolites of various structural types are shown. It has been established that the H-Beta zeolite catalyst provides a quantitative yield of ethers and esters during the interaction of olefins – substituted vinyl-gem-dichlorocyclopropanes – with linear alcohols and acids, respectively. It has been determined that the condensation of styrene and an equimolar mixture of 4-hydroxymethyl-1,3-dioxolane and 5-hydroxy-1,3-dioxane in the presence of the H-Beta catalyst proceeds with the formation of ethers, while the ratio of 5 and 6-membered isomeric products = 1.2:1. Multicomponent condensations successfully proceed in one stage in the presence of wide-pore zeolites.

Selectivity of Ethanol Conversion on Al/Zr/Ce Mixed Oxides: Dehydration and Dehydrogenation Pathways Based on Surface Acidity Properties

AbstractZirconia‐alumina mixed oxides (Zr+Ce)O2−Al2O3 with various mol. ratios (5, 10, 20, 50, and 75 % alumina) were prepared using the sol‐gel method. The catalysts were characterised via XRD, SEM, DTA/TG, BET, and FT‐IR spectroscopy. The acidities of the catalysts were measured through the absorption of anthraquinone and pyridine probe molecules using EPR and IR spectroscopy, respectively. Catalytic activity and selectivity were investigated for ethanol conversion to acetaldehyde, ethylene, and diethyl ether, which were used as model reactions to identify surface‐active sites. The relationship between the surface structure and the dehydration/dehydrogenation activity was evaluated. Diethyl ether formation is promoted by the presence of the ZrO2 tetragonal phase at a low ZrO2/Al2O3 ratio in the sample composition, at which the Lewis acid site has an aluminum‐oxygen environment. The reaction mechanism was also discussed. In the low‐temperature reaction region, dehydrogenation competes with dehydration; ethylene and acetaldehyde share a common reactive intermediate.

Ion irradiation triggers the formation of the precursors of complex organics in space

Context. Cosmic rays and solar energetic particles induce changes in the composition of compounds frozen onto dust grains in the interstellar medium (ISM), in comets, and on the surfaces of atmosphere-less small bodies in the outer Solar System. This induces the destruction of pristine compounds and triggers the formation of various species, including the precursors of complex organics. Aims. We investigate the role of energetic ions in the formation of formaldehyde (H2CO) and acetaldehyde (CH3CHO), which are observed in the ISM and in comets, and which are thought to be the precursors of more complex compounds such as hexamethylenete-tramine (HMT), which is found in carbonaceous chondrites and in laboratory samples produced after the irradiation and warm-up of astrophysical ices. Methods. We performed ion irradiation of water, methanol, and ammonia mixtures at 14–18 K. We bombarded frozen films with 40–200 keV H+ that simulate solar energetic particles and low-energy cosmic rays. Samples were analysed by infrared transmission spectroscopy. Results. Among other molecules, we observe the formation of H2CO and CH3CHO, and we find that their abundance depends on the dose and on the stoichiometry of the mixtures. We find that the H2CO abundance reaches the highest value after a dose of 10 eV/16u and then it decreases as the dose increases. Conclusions. The data suggest that surfaces exposed to high doses are depleted in H2CO. This explains why the amount of HMT in organic residues and that formed after irradiation of ices depends on the dose deposited in the ice. Because the H2CO abundance decreases at doses higher than 10 eV/16u, a lower quantity of H2CO is available to form HMT during the subsequent warm-up. The H2CO abundances caused by ion bombardment are insufficient to explain the ISM abundances, but ion bombardment can account for the abundance of CH3CHO towards the ISM and comets.

Integration of Transcriptome and Metabolome Analyses Reveals the Mechanistic Basis for Cadmium Accumulation in Maize.

Cadmium (Cd) pollution in soil has become a major environmental issue worldwide. However, the underlying molecular mechanism of low grain-Cd accumulation (GCA) in maize is still largely unknown. Herein, we report the mechanistic basis for low GCA in maize by a multiomics approach. The low GCA genotype L63 showed normal vacuolar formation and a lower capacity of xylem loading of Cd than the high-accumulator L42 under Cd stress. Transcriptomic sequencing identified 84 low-GCA-associated genes which are mainly involved in the S-adenosylmethionine (SAM) cycle, metal transport, and vacuolar sequestration. A metabolome analysis revealed that L63 plants had a more active SAM cycle and a greater capacity for terpenoid synthesis and phenylalanine metabolism than L42. Combining the analysis of transcriptome and metabolome characterized several genes as key genes involved in the determination of Cd accumulation. Our study identifies a mechanistic basis for low Cd accumulation in maize grains and provides candidate genes for genetic improvement of crops.

The effects of oxygen index on soot formation of ethylene, propane and their mixtures in coflow diffusion flames

Oxygen index (OI) effects on soot formation and oxidation of ethylene, propane and their mixtures were investigated in coflow diffusion flames. Experimental results show that the peak soot volume fraction (SVF) firstly increases and then reaches the plateau region as OI increases from 0.21 to 0.42 in ethylene and 90%ethylene/10%propane mixture flames. However, the peak SVF firstly increases and then decreases with the increase of OI in propane flame. All these three cases present a consistent trend in terms of maximum soot yield which increases first and then decreases as OI increases. Synergistic effect was captured in ethylene/propane mixtures while it was firstly enhanced and then mitigated when OI increases in the investigated OI range. Numerical simulations were also conducted. A significant relationship was found among flame temperature, O2 mole fraction and SVF in terms of their spatial gradients. The non-linear trends of SVF and soot yield with OI can be attributed to the competition between soot formation and oxidation. Such competition was also indicated from polycyclic aromatic hydrocarbons (PAHs) growth. Numerical analyses revealed that small radicals including O, CH2 and C6H5 contribute to the non-linear changes of PAHs in the synergistic effect.

Water-soluble β-cyclodextrin based turn-on amplifying fluorescent probes for sensitive and selective detection of Hg2+/Hg+ ions

In this work, fluorescent β- cyclodextrin (β-CD) based probes containing naphthalimide group were synthesized to realize the specific recognition of Hg2+/Hg+ in aqueous system. Firstly, three small fluorescent molecules (N1, N2 and N3) with -NH2 groups were synthesized from 4-bromo-1, 8-naphthalene anhydride. Secondly, CHCCH2- group was introduced into β-CD by Williamson ether formation reaction. Finally, the target probes (β-CD-PI, β-CD-PY and β-CD-TP) were obtained by Amino-Yne click reaction. These probes can efficiently recognize Hg2+/Hg+. β-CD-PI emits bright yellow fluorescence after binding with Hg2+/Hg+, which is a turn-on fluorescent probe. When the Hg2+/Hg+ concentration exceeds 26 μM, the fluorescence intensity amplifies sharply (20 folds). The hydrophobic parts of the probes aggregated together to form a micelle-like structure due to complexation with Hg2+/Hg+, resulting in special micelle-sensitizing properties. Meanwhile, the HOMO-LUMO energy levels of the probes were calculated by cyclic voltammetry (CV). The probe is expected to be used for the detection of Hg2+/Hg+ in aqueous solutions without any organic solvents.

Increasing the Distance of Adjacent Palladium Atoms for Configuration Matching in Selective Hydrogenation.

Precisely tailoring the distance between adjacent metal sites to match adsorption configurations of key species for the targeted reaction pathway is a great challenge in heterogeneous catalysis. Here, we report a proof-of-concept study on the atomically sites-tailored pathway in Pd-catalyzed acetylene hydrogenation, i.e., increasing the distance of adjacent Pd atoms (dPd-a-Pd ) for configuration matching in acetylene semi-hydrogenation against coupling. dPd-a-Pd is identified as a structural descriptor for describing the competitiveness for reaction pathways, and the increased dPd-a-Pd prefers the semi-hydrogenation pathway due to simultaneously promoted C2 H4 desorption and the destabilized transition state of the C2 H3 * coupling. Spectroscopic, kinetics and electronic structure studies reveal that increasing dPd-a-Pd to 3.31 Å delivers superior selectivity and stability due to energy matching and appropriate hybridization of Pd 4d with In 2s and, especially, 2p orbitals.

Possible Fine-Tuning of Methane Activation toward C2 Oxygenates by 3d-Transition Metal-Ions Doped Nano-Ceria-Zirconia.

In this work, we demonstrate a simple sol-gel technique to prepare metal-ion(s)-doped ceria-zirconia solid solution for efficient catalytic methane activation. The cation-depicting formula units are Ce0.80Zr0.20 (CZ), Ce0.79Zr0.20M0.01 (CZM), and Ce0.79Zr0.20M0.005M10.005 (CZMM1) (M and M1 = V, Mn, Fe, Co, and Cu), employed for undoped, mono-metal-ion-doped, and bi-metal-ion-doped solid solutions, respectively. Methane activation with Mn, Fe, Cu mono-metal-ion-doped CZ favors the C1 product, while CZCo assists C-C coupling with the formation of acetaldehyde. On the other hand, the Co- and Fe-doped bi-metal-ion combination catalyst (CZCoFe) shows significant ethanol but predominant formic acid formation. This is further promoted by the Co + V bi-metal-ion combination (CZCoV) catalyst, and it shows ethanol as the major product along with methyl hydrogen peroxide, methanol, and formic acid as minor products. An impressive ethanol yield of 93 μmol/g h with 76% selectivity obtained with the CZCoV catalyst is at par with that obtained with noble-metal-based catalysts under comparable reaction conditions. When Co and V content was increased two and four times from 0.005 to 0.01 and 0.02, ethanol yield increased at the expense of formic acid. The 213 μmol/g h ethanol yield (86% selectivity) observed with Ce0.76Zr0.20Co0.02V0.02 is probably the highest observed. The partial oxidation of CH4 in Co-based bi-metal combinations (Co + V or Co + Fe) suggests the synergistic effect of doped metal ions owing to the heterogeneous near-neighbor environment. The present results are attributed to the surface heterogeneity between the host and the dopants, which selectively promotes methane activation as well as C-C coupling. This indicates a large scope to tune the activity of partial oxidation of methane and product selectivity with different metal-ion(s) combinations.

Probing O2 dependence of hydroperoxy-butyl reactions via isomer-resolved speciation

Degenerate chain-branching mechanisms of n-alkanes are centered on the formation of hydroperoxy-alkyl radicals (̇QOOH), formed via ̇R + O2 reactions, and the ensuing competition between unimolecular decomposition and second-O2-addition. Quantitative measurements of partially oxidized intermediates formed via reactions of ̇QOOH provide critical constraints that are required for accurate modeling of combustion chemistry. To examine the influence of temperature and oxygen concentration on intermediates from unimolecular decomposition of ̇QOOH, isomer-resolved speciation measurements were conducted on n-butane oxidation at 835 Torr in a jet-stirred reactor (JSR) from 500 – 900 K. Resulting from negative-temperature coefficient behavior, cyclic ether formation peaked at two temperatures, 650 K and 800 K, which were selected for separate experiments to quantify the O2-dependence of species profiles using O2 concentrations of 4.2 · 1017 – 1.1 · 1019 molecules cm–3.Utilizing vacuum-ultraviolet absorption spectroscopy and electron-impact mass spectrometry, cyclic ether isomers were quantified separately, including explicit resolution of cis- and trans- isomers of 2,3-dimethyloxirane. Stereoisomers of 2-butene were also quantified explicitly. For all cyclic ethers, a common trend in O2-dependence emerged: species concentrations reach a maximum near 3.0 · 1018 molecules cm–3 (equivalence ratio of 0.5). Although quantitative disparities are evident, chemical kinetics modeling qualitatively reproduces the O2 dependence of species at 650 K. However, at 800 K, weak dependence on O2 is predicted, which is in contrast with the measurements. Two carbonyls, diacetyl and methyl vinyl ketone, were also quantified and follow similar dependence on [O2] and temperature as the cyclic ethers, which indicates some fraction forms via ̇QOOH-mediated reactions. The discrepancies between the measured and model-predicted species profiles indicate that sub-mechanisms for important intermediates may require additional elementary reactions, including stereochemical-specific reactions, to improve the fidelity of n-alkane combustion modeling.

TRANSESTERIFICATION OF TRIGLYCERIDES WITH PROPAN-2-OL CATALYSED BY SULFURIC ACID

Transesterification of sunflower oil triglycerides with propan-2-ol catalyzed by sulfuric acid has been studied. The effect of the homogeneous acid catalyst content and the triglycerides of sunflower oil : propan-2-ol molar ratio on the reagents conversion, selectivity of diisopropyl ether formation, the acid number and the color of reactions products on the iodine scale was determined. It was established that an increase in the sulfuric acid content from 1 wt. % up to 3 wt. % leads to a slight increase in the triglycerides conversion and a significant increase in the propan-2-ol conversion. A further increase in the acid catalyst content causes a decrease in the conversion of both triglycerides and alcohol. Comparison of the obtained results with the data on the reaction products composition allowed us to conclude that a significant increase in the propan-2-ol conversion with an increase in the sulfuric acid content to 3–4 wt. % due to the increase in the diisopropyl ether selectivity formation from 5% by an acid catalyst content of 1 wt. % to almost 65% by a sulfuric acid content of 4 wt. %. It is shown that an increase in the sulfuric acid content in the reaction mixture also leads to a significant increase in the reaction product's color according to the iodine scale - almost 5 times, which also indicates the course of side condensation reactions with the double bonds of higher fatty acids participation, which are part of triglycerides composition. It is established that the reaction product's acid number regularly increases with an increase in the acid catalyst content in the reaction mixture. It is shown that the reaction products acid number value is determined by the amount of acid catalyst used. It is established that the activity of the sulfuric acid in the sunflower oil triglycerides transesterification reaction is slightly lower than the activity of cation exchange resin KU-2-8. The cation exchange resin under the same conditions provides more than 15% higher triglycerides conversion with a lower reaction product's color on the iodine scale value and the absence of a diisopropyl ether formation side reaction. It is concluded that using sulfuric acid as a catalyst for triglyceride transesterification by propan-2-ol is entirely possible.

Kinetic regularities and mechanism of acetylene hydrogenation over PdMn catalyst

Kinetic analysis of acetylene hydrogenation over Pd-Mn/Al2O3 catalyst has been performed. Based on a set of data of stationary catalytic process and non-stationary experiments at 303–323 K, a reaction mechanism scheme is proposed. The overall process is found to proceed by two paths: the initial one comprises formation of an intermediate of C2H4Z2 type that may release C2H4 by acetylene attack (main reaction) or form ethane by hydrogen attack (minor reaction). The main and minor reactions are parallel ones. The second stage comprises consecutive C2H4 attack of adsorbed hydrogen with formation of C2H5Z species and their hydrogenation to ethane. This conclusive stage takes place at acetylene conversions higher than 75%. Kinetic description of two stages of acetylene hydrogenation has been developed and reaction constants are calculated. The activation energy of ethylene formation E2 equals to 64.9 kJ/mol. For conclusive stage of acetylene hydrogenation, the kinetic model developed gave rise to equation for description of selectivity-conversion dependence SC2H4 = f(XC2H2) up to XC2H2 = 100%. General factors for achieving high selectivity to ethylene have been formulated.

Theoretical study on pyrolysis mechanism of decabromodiphenyl ether (BDE-209) using DFT method

Decabromodiphenyl ether (BDE-209), as a brominated flame retardant (BFR), is widely applied to various consumer products due to its superior performance and affordable pricing to improve the flame resistance of materials. To better comprehend the pyrolysis behavior of BDE-209 and the evolution process of main pyrolysis products, the thermal degradation mechanism of BDE-209 was studied using density functional theory (DFT) method at the theoretical level of M06/cc-pVDZ, and thermodynamic parameters were calculated in this paper. Unimolecular degradation was dominated by cleavage of the ether linkage, which results in a high yield of hexabromobenzene, and fission of the ortho-position C–Br bond is the main competitive reaction channel. In the system of BDE-209 + H, the pyrolysis reaction is majorly characterized by debromination, leading to the formation of considerable HBr and low-brominated diphenyl ethers. Additionally, the hydrogen-derived splitting of the ether bond acts as a mainly competitive channel, which is the source of polybromophenols and polybromobenzenes. The formation of polybrominated dibenzofuran (PBDF) derives from the cyclization reaction of ortho-phenyl-type radicals, which are readily generated through the ortho-position Br atom abstraction by H radical. The formation of polybrominated dibenzo-p-dioxin (PBDD) involves the ortho-C-O coupling reaction of polybromophenoxy radicals, debromination reaction, and cyclization reaction. And the total yield of PBDD/Fs was significantly increased when H was involved. Results presented in this work will provide the helpful information for the treatment and reuse of BDE-209-containing waste plastics through using pyrolysis technology.

Theoretical study of the side reactions of ethanol-to-butadiene conversion on MgO catalyst: formation of diethyl ether, ethyl acetal, 1,3-butanediol, methyl ethyl ketone, n-butanol, butanal, and acetone

Theoretical study of the side reactions of ethanol-to-butadiene conversion on MgO catalyst: formation of diethyl ether, ethyl acetal, 1,3-butanediol, methyl ethyl ketone, n-butanol, butanal, and acetone

(Digital Presentation) Electrodeposition of Free-Standing Porous Cu Frameworks for Energy Applications

Recently, a convenient method has been suggested to produce a highly porous metal structure such as Cu using a single-step electrodeposition method [1]. In this approach, hydrogen bubbles are used as dynamic templates during the metal electrodeposition process to create the micro-porous structure. However, the pore walls of the porous layers often grow in ramified dendritic structure, which results in limited mechanical stability and creates challenged for applications in compact devices.In this contribution, a novel approach will be discussed to improve the mechanical stability of these porous structures by employing a second electrodeposition step. This process greatly reduces the number of dendrites within the pore walls making the porous layer more compact and thus improving the mechanical stability significantly. Furthermore, a complete separation of the porous layer from the flat substrate can be achieved by ultrasonication to obtain a free-standing porous Cu framework. Some parameters such as the layer thicknesses and pore sizes can be tuned easily by changing the current density and the electrodeposition time, respectively.The use of thus prepared free-standing porous Cu frameworks will be discussed for photoelectrochemical (PEC) water splitting and CO2 reduction. For the PEC water splitting application, a photoactive Cu2O layer is electrodeposited on the free-standing porous Cu framework. A homogenous coating of the Cu2O can be achieved and the PEC performance shows a significant increase of photocurrents by more than 80 % at 0 V vs. RHE in comparison to the Cu2O planar substrate [2]. For the CO2 reduction application, a large sample with10 cm2 geometric surface area was successfully prepared. The sample was used in a custom-made electrochemical cell with a cation exchange membrane as a separator. CO2 gas in a high humidity environment is transported to the free-standing porous Cu working electrode via a membrane pump in a closed-loop system. Our preliminary results show formation of ethylene and ethane gas using gas chromatography which indicates a successful reduction reaction of the CO2.[1] H.C. Shin., M. Liu. Chem Mater 16:5460–5464 2004. Doi:10.1021/cm048887b[2] M. Kurniawan, M. Stich, M. Marimon, M. Camargo, R. Peipmann, T. Hannappel, A. Bund, J. Mater. Sci. 2021, Doi:10.1007/s10853-021-06058-y

Comparison of composition, sensory properties and aroma compounds of kefir produced from donkey milk and cow milk

In this study, donkey milk and cow milk used for kefir production and the kefir samples were characterised based on compositional and microbiological properties, volatile aroma compounds, amino acid composition, and sensory analyses during storage for 21 days at 5 °C. Compared to cow milk kefir (CMK), donkey milk kefir (DMK) had lower contents of total solids, fat, and protein. Using donkey milk resulted in a weaker body characteristic in the kefir sample due to its low total solids content and the low ratio of casein. Acetaldehyde and acetic acid formation were at a remarkable level in DMK. Besides, the high lactose content of donkey milk caused more ethanol production in the kefir. Tyrosine, valine, and arginine were the primary amino acids in DMK. Donkey milk kefir was evaluated as acceptable in the aspect of sensorial properties such as taste and odour. Based on the present results, it could be concluded that a probiotic fermented beverage can be produced from donkey milk.