Non-aqueous Media Research Articles

Effect of sulfidation on ethaline-assisted electrodeposited iron sulfide-based electrocatalyst for efficient saline water splitting

This study investigated the synthesis of ethaline-assisted iron sulfide on nickel foam (NF) using the electrodeposition method to facilitate saline water splitting. The oxidization of iron and the formation of Fe(OH)3 on the cathode surface pose challenges for the electrodeposition of iron sulfide from aqueous solutions. To tackle these issues, deep eutectic solvent-assisted electrodeposition and ethaline-assisted sulfidation methods have been investigated for synthesizing FeS2. These approaches aim to enhance the efficiency of the iron sulfide electrode by preventing unwanted oxidation and ensuring the formation of high-quality coatings. Sulfidation in non-aqueous media was performed at varying durations, revealing that sulfur content significantly impacts the morphology of the prepared electrode. The optimum FeS2/NF catalyst offers the lowest overpotential of 194 mV at 10 mA cm−2 for oxygen evolution reaction (OER) and 176 mV at 10 mA cm−2 for hydrogen evolution reaction (HER) in saline water splitting. The enhanced catalytic activity is attributed to the formation of multiphasic components in the catalyst. The electrodes exhibited stability in saline water conditions for approximately 10 h for both OER and HER. Moreover, FeS2/NF exhibited stability for 50 h in OER and 20 h in HER when applied to pure water splitting. The investigation explores the unique synthesis of FeS2 in non-aqueous media and examines its catalytic activity in saline water electrolysis.

Fluorescence sensing of water in various organic solvents based on a novel cyclic polymer

A sensor capable of sensing of water in various organic solvents ranging from water-soluble to water-miscible solvents is still a challenging task. In this research, a cyclic polymer fluorescence chemosensor (CPFC) has been developed for sensing of water by turn-on model in 9 organic solvents and turn-off model in DMA, where the broadest concentration range and the lowest detection limit was obtained for water in DMA (10 %–90 %) and dioxane (0.011 %), respectively. The sensing mechanism is explored by theory calculation and experimental investigation. The amphiphilic nature endows the polymer probe with great potential for measuring various contaminants from aqueous and nonaqueous mediums. Furthermore, the present search highlights the potential applications of cyclic polymer as fluorescence probes in the field of sensing.

Potentiometric Application of CeFeMoP and CeAlMoP in Zr(IV) Ions Analysis: A Comparative Study

Two cerium-based ionophores Cerium(III) ironmolybdophosphate (CeFeMoP) and Cerium(III) aluminomolybdophosphate (CeAlMoP), were synthesised, having ion exchange capacities of 5.76±0.1 and 5.6±0.2 meq/gm respectively. Electroanalytical studies of synthesised heteropolyacid salts have been done using epoxy resin as binder material to form membranes of variable compositions. The potentiometric observation supports the behaviour of 40% membrane in both cases. CeFeMoP-based electrode showed a linear range from concentration 1x10-6 to 1x10-1 M and a limit of detection 6.31×10-7 M. In contrast, these parameters in the case of CeAlMoP are of linear range from 1x10-7 M to 1x10-1 M, response time 22 seconds and a limit of detection 5.01 × 10-7 M. Membranes yielded a rapid response time of 15 seconds in the case of CeFeMoP. The membranes performed very well in the case of internal concentration variations of the same solution and several other types of non-aqueous media. The FIM method proves the selectivity of the electrode even in the presence of interfering ions. CeFeMoP based sensor performed over a constant potential behaviour in pH values ranging between 3.32-8.26 while CeAlMoP based electrode worked in the pH range of 3.25-10.54 for a constant internal concentration of Zr(IV) ions. The two sensors also performed well as indicator electrodes as well as in real-time sample analysis. Hence, it is concluded that these sensors derived from CeFeMoP and CeAlMoP are quite effective in analyzing the Zr(IV) ions in various samples with quick response time and a lifetime of around 8 and 7 months respectively. A real field study was also performed by using an ICP-MS analyzer.

Solvent Tolerance Improvement of Lipases Enhanced Their Applications: State of the Art.

Lipases, crucial catalysts in biochemical synthesis, find extensive applications across industries such as food, medicine, and cosmetics. The efficiency of lipase-catalyzed reactions is significantly influenced by the choice of solvents. Polar organic solvents often result in a decrease, or even loss, of lipase activity. Conversely, nonpolar organic solvents induce excessive rigidity in lipases, thereby affecting their activity. While the advent of new solvents like ionic liquids and deep eutectic solvents has somewhat improved the activity and stability of lipases, it fails to address the fundamental issue of lipases' poor solvent tolerance. Hence, the rational design of lipases for enhanced solvent tolerance can significantly boost their industrial performance. This review provides a comprehensive summary of the structural characteristics and properties of lipases in various solvent systems and emphasizes various strategies of protein engineering for non-aqueous media to improve lipases' solvent tolerance. This study provides a theoretical foundation for further enhancing the solvent tolerance and industrial properties of lipases.

The Effect of Weakly Coordinating Solvent and Counter Anion on Diphosphine‐Palladium(II) Catalytic Reactivity for Copolymerization of 1‐Butene with Carbon Monoxide in Aqueous Media

AbstractWater soluble bis(acetonitrile) diphospalladium (II) complexes cis‐[Pd(L1–L5)(NCCH3)2][BF4]2 (C1–C5) were obtained by the reaction [Pd(NCCH3)4][BF4]2 with diphosphines ligands L1–L5 (CH2(CH2PR2)2: where R=(CH2)nP(O)(OEt)2, n=2–4, n=6 and n=8)) in dichloromethane–acetonitrile. The isolated complexes were characterized by elemental analysis, FTIR, 1H‐ and 31P‐NMR spectroscopy. The complexes were applied as catalysts for the copolymerization of 1‐butene with carbon monoxide in aqueous media. The present work emphasized on the effect of weakly coordinated solvent and counterion on the catalytic behavior of cis‐[Pd(L1–L5)(NCCH3)2][BF4]2 complexes compared to previously prepared cis‐[ Pd(L1–L5)(OAc)2] (A1–A5). The exchange of π‐bonding NCCH3 ligand with π‐bonding CO and alkene was more favored than the exchange of σ‐bonding OAc− as reflected by the much higher catalytic activity (TON) of the former compared to the latter. In order to compare the catalytic efficiency of water soluble complexes with the performance of a standard, the water insoluble complex, cis‐[Pd(CH2(CH2P(CH2CH3)2)2(NCCH3)2][BF4]2, C6, was prepared and incorporated in the investigations. The isolated alternating 1‐butene/CO copolymer exhibits glass transition temperature of Tg=−3–−15 °C, which is in the range desirable for latex emulsion application. The solid content is up to 21 % with high molecular weight (Mw=4×104 g mol−1) and narrow polydispersities (Mw/Mn=2–3). The C5 complex was found to be fourteen times more active in aqueous polymerization medium (6369 mol substr. mol Pd−1 h−1) than C6 complex in nonaqueous medium (441 mol substr. mol Pd−1 h−1).

Biocatalysts engineering by varying the binary CNTs-silica composition and the physicochemical characteristics of adsorbents for the immobilization of recombinant T. lanuginosus lipase

Biocatalytic engineering was carried out by varying monotonically the binary CNTs-silica composition and, accordingly, the physicochemical characteristics of adsorbents developed for immobilization of recombinant T. lanuginosus lipase (rPichia/lip). The adsorbents based on composite carbon-silica materials (CCSMs) were produced by impregnating finely dispersed multi-walled carbon nanotubes with silica hydrosol followed by calcination in argon at 350°C; the mass ratio of the hydrophobic and the hydrophilic components varied over a wide range. Biocatalysts (BCs) for green low-temperature synthesis of various esters in a non-aqueous medium of organic solvents were prepared by adsorption of rPichia/lip with subsequent drying under ambient conditions. The characteristics of the CCSMs and BCs were characterized by thermogravimetry, nitrogen porosimetry and electron microscopy. The catalytic properties of BCs, such as enzymatic activity, substrate conversion and specificity, as well we their operational stability depending on the chemical composition of CCSMs were extensively studied in the esterification of saturated monocarboxylic acids (C4, C7, C18) and primary aliphatic alcohols (C2, C4, C16) in hexane at 20°C. It was found that the esterifying activity manyfold decreased with increasing the silica content primarily due to a decrease in adsorption ability of CCSMs toward rPichia/lip. The substrate specificity and operational stability of the lipase-active BCs did not greatly depend on the composition of CCSMs. Biocatalysts retained more than half of their initial esterifying activity after 10 reaction cycles.

Understanding the Droplet Diffusion in Ionic Liquid Microemulsions.

Ionic liquids (ILs) as polar components in nonaqueous microemulsions are complex formulations that have interesting transport and structural properties, and offer broader applicability of ILs in areas such as drug delivery and cleaning technology. The phase behavior, electrical conductivity, and nanostructures of these formulations have been investigated for quite some time, but the characteristics of the diffusion of nanodroplets were rarely explored─ and hence little understood. This work investigates the droplet diffusion processes in a series of IL-microemulsions containing 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim]BF4) by means of viscosity and depolarized dynamic light scattering (DDLS) measurements. The intensity correlation functions are strikingly similar to polymeric solutions in nonaqueous media and aqueous microemulsions containing block copolymers─having bimodal relaxations that are separated by three to four decades of correlation delay times. The "faster" diffusion process is likely a collective process characterizing the correlated motions of droplets in droplet clusters. The collective diffusion coefficient Dcol values are quite comparable to aqueous microemulsions. The "slower" diffusion is likely due to the "caging" effect caused by nearby clusters and/or bulk solvent─this mode may be linked to the microemulsion bulk viscosity. Interestingly, the Dcol variations on increasing [C4mim]BF4 concentration are strongly correlated to the microemulsion viscosity changes as well as locations of these compositions on the microemulsion phase diagram.

Electrochemical Properties and Determination of Serotonin with Graphene/Coal Tar Pitch/Pencil Graphite Sensor Electrode using Square Wave Adsorptive Stripping Voltammetry Technique

In the present work, electrochemical and spectroelectrochemical behaviors of Serotonin (5-HT) were studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. Cyclic voltammetric experiments of 5-HT on graphene/coal tar pitch/pencil graphite electrode (GR/CTP/PGE) were carried out between 0.0 V and 1.8 V potential range at a scan rate of 100 mV s-1 with 20 cycles in non-aqueous media. Surface characterizations were performed using CV, EIS and scanning electron microscope (SEM). Effect of different pH values was investigated by square wave voltammetry (SWV) for determination of 5-HT. Optimization of accumulation time was determined using square wave adsorptive stripping voltammetry (SWAdSV) within potential range of -0.2 to +0.6 V. 5-HT standard solutions changing from 75 µM to 1.0 µM were prepared and the corresponding peak currents were measured. From the obtained data calibration equation was derived Ip = 0.0329C5-HT + 0.1511 with correlation coefficient (R2) 0.9958. LOD was 3.51x10-7 M and LOQ was 1.05x10-6 M.

Graphene Oxide-Induced Prototropism and Enhancement of Fluorescence Yield of Organic Molecules in Solutions: Recent Advances.

Till date, humankind has mainly acknowledged the quenching phenomenon of graphene oxide (GO). From a fundamental science standpoint, the unique and dynamic prospects of graphene oxide have been showcased in a brief but concise manner. Worldwide research studies have proven that graphene oxide has tremendous potentiality in showcasing breakthroughs in the fields of both basic science and innovative applications. In this Perspective, the fact that, apart from the very common fluorescence quenching phenomenon, graphene oxide can also enhance fluorescence intensity, promote prototropism, demonstrate aggregation-induced emission, and itself exhibit photoluminescence properties in nonaqueous media has been highlighted. It draws attention to the fact regarding unveiling the unknown properties of graphene oxide that might be useful to scientific communities in upcoming years.

Vanadium oxides nanostructures for adsorption of Methylene blue, vehicle exhaust and soot of ink as low carbon applications

In this study, V2O5 nanoparticles were synthesized via facile method by annealing ammonium meta vanadate at 450 °C for 1 h. The resulting nanoparticles were analyzed using X-ray diffractometer, scanning electron microscopy, and transmission electron microscopy to investigate their structural and morphological properties. The optical properties of the prepared samples were examined using UV–VIS spectrophotometry. The XRD measurements indicated an orthorhombic V2O5 structure with an average crystallite size of 21.34 nm as calculated using the Debye-Scherrer formula. The synthesized V2O5 nanoparticles showed a plate like rod structure with an average size around 55 nm through TEM and HRTEM analysis. The Urbach energy (Eu) of V2O5 was calculated to be 1.07ev. The V2O5 nano-adsorbents were tested for their effectiveness in the selective removal of MB from an aqueous medium, as well vehicle exhaust and soot of ink from non-aqueous media. During the adsorption process, the impact of several factors including time, adsorbent dose, and different initial concentrations were investigated. Equilibrium adsorption isotherms were evaluated using Langmuir and Freundlich equations. The Langmuir model was found to be a better fit for the adsorption equilibrium, with correlation coefficients of 0.915, 0.904, and 0.912 for MB, vehicle exhaust, and soot of ink, respectively. The experimental kinetic results of V2O5 were found to fit the pseudo-second-order model for both aqueous and non-aqueous media with a higher correlation factor indicating chemisorption during the adsorption process.

Stabilizing BiVO4 Photoanode in Bicarbonate Electrolyte for Efficient Photoelectrocatalytic Alcohol Oxidation.

In order to expand the application of bismuth vanadate (BiVO4) to the field of photoelectrochemistry, researchers have explored the potential of BiVO4 in catalyzing or degrading organic substances, potentially presenting a green and eco-friendly solution. A study was conducted to investigate the impact of electrolytes on the photocatalysis of benzyl alcohol by BiVO4. The research discovered that, in an acetonitrile electrolyte (pH 9) with sodium bicarbonate, BiVO4 catalyzed benzyl alcohol by introducing saturated V5+. This innovation addressed the issue of benzyl alcohol being susceptible to catalysis in an alkaline setting, as V5+ was prone to dissolution in pH 9 on BiVO4. The concern of the photocorrosion of BiVO4 was mitigated through two approaches. Firstly, the incorporation of a non-aqueous medium inhibited the formation of active material intermediates, reducing the susceptibility of the electrode surface to photocorrosion. Secondly, the presence of saturated V5+ further deterred the leaching of V5+. Concurrently, the production of carbonate radicals by bicarbonate played a vital role in catalyzing benzyl alcohol. The results show that, in this system, BiVO4 has the potential to oxidize benzyl alcohol by photocatalysis.

Towards environmental protection and safety coloration process in wool fibers: Role of disperse reactive dyes structure

Traditional wool fibers dyeing uses a huge amount of water and energy, and relies on lots of chemicals, which produces huge amounts of lower-biodegradable wastewater, and poses a great threat to the water environment. Here, to investigate the role of disperse reactive dyes structure on the dyeing properties, a sustainable waterless dyeing of wool fibers was investigated with four synthesized disperse reactive dyes by using supercritical CO2 as a non-aqueous dyeing medium. The effects of dyeing time, pressure, temperature and dye concentration on the dyeing properties were discussed. The results showed that K/S values up to 5.5 under the optimal dyeing condition of 383.15 K, 23 MPa, and 70 min were obtained, indicating shorter reaction time and higher K/S values compared to similar studies. Moreover, excellent colorfastness to soaping and rubbing up to 4–5 was displayed since nucleophilic substitution reaction occurs between the C atom on the triazine group of disperse reactive dyes and -NH2 on the cysteine of fiber macromolecules. This study provides an environmental protection and safety coloration process to produce high-quality wool fiber products by establishing the relationship between structure of disperse reactive dyes and dyeing properties of wool.

Electroreduction mechanisms of meso-Tetraphenylphlorin cation in strongly acidic media of benzonitrile

In nonaqueous media free-base porphyrins are easily protonated by strong proton donors to form the diprotonated porphyrins. The two-electron reduction of these species leads to phlorin cation species. To investigate the electroreduction products that follow the formation of these species, we evaluate the effect of increasing amounts of HClO4 on the electroreduction mechanism of the phlorin cation of meso-tetraphenyl porphyrin. We demonstrate that the phlorin cation undergoes a reversible protonation reaction to form a porphodimethene, which is further reduced to yield the chlorin-phlorin cation, a 4-electron reduced phlorin macrocycle with a hydrogenated pyrrolic Cβ = Cβ double bond. This undergoes further protonation and a 2-electron reduction to form a phlorin macrocycle, the bacteriochlorin-phlorin cation, wherein two pyrrole rings are hydrogenated. All these reduction processes occur at similar potential values, yet we managed to selectively form the 2-, 4- or 6- electron reduced product by a strict control of the number of protons in the medium. To the best of our knowledge, this is the first report of the electrochemical reduction of Cβ = Cβ bonds of pyrrolic rings. Thus, a new pathway for the electrochemical reduction of porphyrins is proposed.

Voltammetric Detection of Singlet Oxygen Enabled by Nanogap Scanning Electrochemical Microscopy.

Despite the significance of singlet oxygen (1O2) in several biological, chemical, and energy storage systems, its voltammetric reduction at an electrode remains unreported. We address this issue using nanogap scanning electrochemical microscopy (SECM) in substrate-generation/tip-collection mode. Our investigation reveals a reductive process on the SECM tip at -1.0 V (vs Fc+/Fc) during the breakdown of the Li2CO3 substrate in deuterated acetonitrile. Notably, this value is approximately 0.9 V more positive than the reduction potential of triplet oxygen (3O2), consistent with thermodynamic estimates for the energy of the formation of 1O2. This finding holds significant implications for understanding the reaction mechanisms involving 1O2 in nonaqueous media.

3D printing by stereolithography using thermal initiators

Additive manufacturing technologies based on stereolithography rely on initiating spatial photopolymerization by using photoinitiators activated by UV-visible light. Many applications requiring printing in water are limited since water-soluble photoinitiators are scarce, and their price is skyrocketing. On the contrary, thermal initiators are widely used in the chemical industry for polymerization processes due to their low cost and simplicity of initiation by heat at low temperatures. However, such initiators were never used in 3D printing technologies, such as vat photopolymerization stereolithography, since localizing the heat at specific printing voxels is impossible. Here we propose using a thermal initiator for 3D printing for localized polymerization processes by near-infrared and visible light irradiation without conventional photoinitiators. This is enabled by using gold nanorods or silver nanoparticles at very low concentrations as photothermal converters in aqueous and non-aqueous mediums. Our proof of concept demonstrates the fabrication of hydrogel and polymeric objects using stereolithography-based 3D printers, vat photopolymerization, and two-photon printing.

(Diazomethyl)dimethylphosphine Oxide - A Diazoalkane Reagent for [3+2] Cycloadditions.

A safe and efficient method for the in-situ preparation of (diazomethyl)dimethylphosphine oxide - a hereto unexplored diazoalkane reagent - is developed. The method is based on the diazotization of the corresponding P(O)Me2-substituted amine (readily available in multigram quantities) in non-aqueous media. The protocol provides the target product as ca. 1.5 M CHCl3 solution which is stable at -18 °C. The utility of the synthesized diazoalkane is illustrated by its [3+2] cycloaddition with electron-poor alkynes and alkenes providing the corresponding P(O)Me2-substituted pyrazoles and pyrazolines with moderate to good efficiency. In this view, the title compound represents and an important extension of medicinally relevant phosphine oxide reagents.

Flow synthesis development and photocatalytic activity optimization of copper oxide nanoparticles using design of experiments

Many studies have focused on reducing the impact of carbon dioxide (CO2) on climate change. A promising approach for CO2 utilization is to use a photocatalyst to activate CO2 and generate valuable chemical compounds. One of the most commonly synthetized photocatalysts is cuprous oxide (Cu2O); however, low efficiency and fast deactivation still limit its industrial application. Here, a batch synthesis in nonaqueous media of Cu2O containing small amounts of metallic copper (Cu0) is investigated. By adjusting the ratio between Cu2O and Cu0 an enhanced photocatalytic efficiency is obtained. To overcome the deactivation limitations of Cu2O, a flow synthesis is developed that continuously supplies fresh photocatalysts to the reaction environment. The flow synthesis has the potential to allow the separate evaluation of the intrinsic reaction kinetic from the photocatalyst deactivation. This work optimizes the flow synthesis using a design of experiments (DOE) approach coupled with response surface methodology (RSM). The obtained surface responses for the measured factors were highly significant (p-value < 0.01 and R2 > 0.95). This novel methodology makes it possible to identify the optimum process conditions to simultaneously improve photocatalytic performance of the obtained material and reaction productivity. This approach enabled us to obtain in flow a combination of Cu2O/Cu0 photocatalyst and to propose a reaction mechanism and kinetic model for the Cu2O formation. The optimization procedure for flow synthesis proposed here provides an efficient path that can be extended to flow synthesis of a wide range of nanoparticles for photocatalytic applications.

Unusual Structural Insights Revealed by Rheo-SAXS Studies of Nonaqueous Crystalline Gels.

Glycerol is a nonaqueous polar solvent and is of interest in many industrial areas due to its beneficial properties, such as green production and biocompatibility. Our previous works have shown the presence of a fibrillar phase on the microscale that consists of lamellar sodium dodecyl sulfate (SDS) crystals containing interstitial glycerol on the nanoscale. The phase is gel-like at room temperature and demonstrates shear-thinning behavior upon application of a shear. Initially, small-angle X-ray scattering coupled with rheology (rheo-SAXS) measurements were performed to elucidate the structural transition of the gel phase under an applied shear, but it became clear that the aging process of the gel has a profound impact on both the gel nanostructure and also the mechanical properties. For younger gels, both the dissolution of SDS crystallites and the alignment of the fibrillar phase were seen. However, in the aged gels, an unexpected foam was formed at shear rates > 700 s-1. The microscopic structure of the foam phase was imaged using polarizing light microscopy and brightfield and darkfield optical microscopy. The nanostructure of the foam phase was investigated using rheo-SAXS. The foam phase was shown to be stabilized by the presence of SDS crystallites at the air-liquid interface, and the stability of the foam is high with foam persisting even t = 3 months after formation. These results highlight the importance of investigating green nonaqueous media and the gel aging process, both of which are interesting not only on a fundamental level but also for a range of industrial applications, from personal care products and cosmetics to food science.

Correlation between dye structure with dyeing properties in anhydrous dyeing systems: Insights from Crystallographic, DFT, kinetic, and thermodynamic analyses

The dyeing performance of different disperse dyes in D5 non-aqueous media dyeing varies greatly, and dye structure is closely related to dyeing performance. Therefore, in this paper, the influence of dye molecular structure on the dyeing properties in D5 non-aqueous media was studied by incorporating X-ray crystal diffraction analysis, density functional theory (DFT), and dyeing experiments. The results showed that cyano group on the azo component increased the coplanarity of the aromatic ring, forming a stronger π-π stacking. Meanwhile, introducing a smaller steric effect substituent on the coupling component also facilitated the formation of tighter molecular arrangements. The thermodynamic and kinetic parameters of dyeing showed that the close molecular stacking and arrangement could effectively increase the adsorption amount of disperse dye on the polyester fabric but reduce the diffusion in the fiber, which helped to improve the dyeing uptake. These results helped us understand the relationship between dye structure, molecular stacking, and dyeing performance in D5 non-aqueous medium dyeing and provided a theoretical basis for screening and optimizing D5 dyeing system-specific dyes.

Biocatalysis for the Synthesis of Active Pharmaceutical Ingredients in Deep Eutectic Solvents: State-of-the-Art and Prospects

Biocatalysis holds immense potential for pharmaceutical development as it enables synthetic routes to various chiral building blocks with unparalleled selectivity. Therein, solvent and water use account for a large contribution to the environmental impact of the reactions. In the spirit of Green Chemistry, a transition from traditional highly diluted aqueous systems to intensified non-aqueous media to overcome limitations (e.g., water shortages, recalcitrant wastewater treatments, and low substrate loadings) has been observed. Benefiting from the spectacular advances in various enzyme stabilization techniques, a plethora of biotransformations in non-conventional media have been established. Deep eutectic solvents (DESs) emerge as a sort of (potentially) greener non-aqueous medium with increasing use in biocatalysis. This review discusses the state-of-the-art of biotransformations in DESs with a focus on biocatalytic pathways for the synthesis of active pharmaceutical ingredients (APIs). Representative examples of different enzyme classes are discussed, together with a critical vision of the limitations and discussing prospects of using DESs for biocatalysis.