Non-aqueous Media Research Articles

A thermostable organic solvent-tolerant lipase from Brevibacillus sp.: production and integrated downstream processing using an alcohol-salt-based aqueous two-phase system.

Lipases are used for the synthesis of different compounds in the chemical, pharmaceutical, and food industries. Most of the reactions are carried out in non-aqueous media and often at elevated temperature, requiring the use of organic solvent-tolerant thermostable lipases. However, most known lipases are not stable in the presence of organic solvents and at elevated temperature. In this study, an organic solvent-tolerant thermostable lipase was obtained from Brevibacillus sp. SHI-160, a moderate thermophile isolated from a hot spring in the East African Rift Valley. The enzyme was optimally active at 65°C and retained over 90% of its activity after 1 h of incubation at 70°C. High lipase activity was measured in the pH range of 6.5 to 9.0 with an optimum pH of 8.5. The enzyme was stable in the presence of both polar and non-polar organic solvents. The stability of the enzyme in the presence of polar organic solvents allowed the development of an efficient downstream processing using an alcohol-salt-based aqueous two-phase system (ATPS). Thus, in the presence of 2% salt, over 98% of the enzyme partitioned to the alcohol phase. The ATPS-recovered enzyme was directly immobilized on a solid support through adsorption and successfully used to catalyze a transesterification reaction between paranitrophenyl palmitate and short-chain alcohols in non-aqueous media. This shows the potential of lipase SHI-160 to catalyze reactions in non-aqueous media for the synthesis of valuable compounds. The integrated approach developed for enzyme production and cheap and efficient downstream processing using ATPS could allow a significant reduction in enzyme production costs. The results also show the potential of extreme environments in the East African Rift Valley as sources of valuable microbial genetic resources for the isolation of novel lipases and other industrially important enzymes.

Origin of electrochemical activation on vanadium hexacyanoferrate cathode for aqueous zinc-ion battery

Herein, we investigate the phase evolution and reactions of vanadium hexacyanoferrate (VHCF) cathode in aqueous Zn-ion battery. X-ray diffraction, in situ Raman spectroscopy, scanning electron microscopy, time-of-flight secondary-ion mass spectrometry, and electrochemical methods reveal electrochemical activation of VHCF electrode in multiple charge–discharge cycles that eventually converts VHCF into zinc hexacyanoferrate and vanadium oxides (VOx). The emerging VOx redox behavior enhances the specific capacity of the electrode from 77 to 165 mAh g−1. Operando UV–vis absorption spectra of the electrolyte in the vicinity of the electrode during electrochemical reaction verifies the presence of decavanadate anion — the intermediate of VHCF transformation into the electrochemically active vanadium oxide. Analysis of the electrodes under various electrochemical conditions and experiments in aqueous and non-aqueous media demonstrate that vanadium of VHCF is redox inactive in the pristine material but products of VHCF transformation start to contribute to the specific capacity of the electrode upon the formation of vanadium oxide.

Multi-spectroscopic, TD-DFT and bio-imaging studies of new Schiff base optical probe for the detection of CN− and Al(III) ions

The selective and sensitive dual channel assay of CN− and fluorescence assay of Al(III) are reported using a simple organic probe (VDP1) in aqueous and non-aqueous media. The binding behaviours of these ionic analytes with VDP1 were studied using UV–Vis, fluorescence, (1H, 13C & 27Al) NMR and mass spectral techniques. VDP1 showed a highly selective change of colour and fluorescence enhancement with CN− ion immediately without interference from other anions. The experimental results revealed that the mechanism of CN− detection involves deprotonation of the phenolic -OH group followed by nucleophilic addition at the imine C-atom. The addition of Al(III) was found to enhance the fluorescence of VDP1 significantly through chelation-enhanced fluorescence effect (CHEF) by forming a 1:1 octahedral complex [Al(VDP1)(NO3)3(H2O)]. The Density Functional Theory (DFT) and Time-dependent Density Functional Theory (TD-DFT) based theoretical calculations confirmed that the weak fluorescence of VDP1 is due to the charge transfer (CT) character of the transition in which non-radiative decay dominates. The theoretically computed optical properties matched well with that of experimental observations. The limits of detection (LOD) of these ionic analytes were also calculated and found to be much lower than the corresponding recommended limit set by the World Health Organization (WHO). MTT assay indicated that VDP1 is less toxic to HeLa cells and could detect intracellular CN− and Al(III) ions by bioimaging.

Solvation number, thermochemical parameter, and viscosity study of sweeteners in aqueous and non-aqueous media through ultrasonic measurements

Solvation number, thermochemical parameter, and viscosity study of sweeteners in aqueous and non-aqueous media through ultrasonic measurements

A crystalline aluminium-carbon-based ambiphile capable of activation and catalytic transfer of ammonia in non-aqueous media.

Despite recent achievements in the field of frustrated Lewis pairs (FLPs) for small molecule activations, the reversible activation and catalytic transformations of N-H-activated ammonia remain a challenge. Here we report on a rare combination of an aluminium Lewis acid and a carbon Lewis base. A so-called hidden FLP consisting of a phosphorus ylide featuring an aluminium fragment in the ortho position of a phenyl ring scaffold is introduced. Although the formation of the Lewis acid/base adduct is observed in the solid state, which at first glance leads to formally quenched FLP reactivity, we show that the title compound readily reacts with non-aqueous ammonia thermoneutrally and splits the N-H bond reversibly at ambient temperature. In addition, NH3 transfer reactions mediated by a main-group catalyst are presented. This proof-of-principle study is expected to initiate further activities in utilizing N-H-activated ammonia as a readily available, atom-economical nitrogen source.

Recent advances in the production, properties and applications of haloextremozymes protease and lipase from haloarchaea.

Proteases and lipases are significant groups of enzymes for commercialization at the global level. Earlier, the industries depended on mesophilic proteases and lipases, which remain nonfunctional under extreme conditions. The discovery of extremophilic microorganisms, especially those belonging to haloarchaea, paved a new reserve of industrially competent extremozymes. Haloarchaea or halophilic archaea are polyextremophiles of domain Archaea that grow at high salinity, elevated temperature, pH range (pH 6-12), and low aw. Interestingly, haloarchaeal proteolytic and lipolytic enzymes also perform their catalytic function in the presence of 4-5M NaCl in vivo and in vitro. Also, they are of great interest to study due to their capacity to function and are active at elevated temperatures, tolerance to pH extremes, and in non-aqueous media. In recent years, advances have been achieved in various aspects of genomic/molecular expression methods involving homologous and heterologous processes for the overproduction of these extremozymes and their characterization from haloarchaea. A few protease and lipase extremozymes have been successfully expressed in prokaryotic systems, especially E.coli, and enzyme modification techniques have improved the catalytic properties of the recombinant enzymes. Further, in-silico methods are currently applied to elucidate the structural and functional features of salt-stable protease and lipase in haloarchaea. In this review, the production and purification methods, catalytic and biochemical properties and biotechnological applications of haloextremozymes proteases and lipases are summarized along with recent advancements in overproduction and characterization of these enzymes, concluding with the directions for further in-depth research on proteases and lipases from haloarchaea.

Immobilization of Lipases on Chitosan Hydrogels Improves Their Stability in the Presence of the Products of Triglyceride Oxidation.

A significant bottleneck for the industrial application of lipases stems from their poor stability in the presence of commercial triglycerides. This is mainly due to the inactivating effect of the products of triglyceride oxidation (PTO), which are usually produced when oils and fats, being imported from far countries, are stored for long periods. In this study, the immobilization of a lipase from Candida rugosa on chitosan hydrogels has been carried out following two alternative approaches based on the enzyme adsorption and entrapment to increase the lipase stability under the operating conditions that are typical of oleochemical transformations. The effect of model compounds representing different classes of PTO on a lipase has been studied to optimize the enzyme immobilization method. Particular attention has been devoted to the characterization of the inactivating effect of PTO in nonaqueous media, which are adopted for most industrial applications of lipases.

Chromogenic, specific cascade detection of fluoride and alkaline earth metal ions

A salen-based colorimetric chemosensor (MM) has been designed and synthesized to selectively recognize F− and alkaline earth metal ions in solution and solid phase, respectively. A ratiometric UV–visible absorption spectral change with a colorimetric visualization from yellow to pink is observed in the presence of F− ions. The detection of F− ions is fully reversible in alkaline earth metal ions. The limit of detection (LOD) of F− ions by our as-prepared MM could be possible down to the μM range. A paper strips-based test kit has been fabricated to detect F− ions selectively by the naked eye. A smartphone-based assay analysis is also successfully performed to identify F− ions in the non-aqueous media. Such a dual ions sensing system with excellent reversibility and repeatability prompted us to consider probe MM a viable choice for fabricating molecular logic circuits and set-reset memorized molecular devices.

Enhancing lipases reactivity in benzylic acetates hydrolysis: impact of kosmotropic salts under non-conventional conditions

The effect of four kosmotropic salts additives, namely Na2CO3, Na2SO4, Na2HPO4, and NaCl, on the reactivity and selectivity of immobilized Candida antarctica lipase B (CAL-B) and a free lipase of Pseudomonas cepacia (PCL) during the hydrolysis of rac-4-(1-methoxyphenyl) ethyl and rac − 1-phenyl ethyl acetates (1a-2a) was investigated in this study. The study was carried out in two different mediums: non-aqueous conditions and in low water content media. The impact of the anionic counter-ions was examined in four solvents: nonpolar, semipolar, protic, and aprotic, with and without the aforementioned salts. In non-aqueous media, the addition of Na2CO3 significantly enhanced CAL-B hydrolysis rates, resulting in a conversion of 50% for 1a and 44% for 2a, with high enantioselectivities (E > 200). These effects were independent of the solvent hydrophobicity. In contrast, PCL required the presence of external water for effective hydrolysis of both acetates. The addition of salt additives had an adverse impact on PCL activity during the hydrolysis of 1a in hexane, toluene, and TBME solvents. However, when 2M2B was used, the inclusion of salt additives had a notable positive effect on the conversion rates, except for NaCl, which resulted in a lower conversion rate with a value of 15.5%. The presence of Na2CO3 improved the conversion rate during the hydrolysis of 2a in both hexane and TBME. Na2HPO4 further enhanced the conversion rate, reaching 44% in TBME. However, in 2M2B solvent, the addition of Na2HPO4 significantly reduced the enantioselectivity.

Synthesis of NiO/Fe2VO4 nano-hybrid structures via sonication induced approach for electrochemical energy storage in non-aqueous medium

The design of scalable electrode materials has been the subject of research in energy storage for the advancement of the field. Herewith, we report on the metal oxide-based nanomaterials which were synthesized via facile sonication strategy and calcination by forming nano-hybrid material, NiO/Fe2VO4 (VFN) with a size of 5–10 nm. Activated carbon (AC) based nanocomposite electrodes with VFN (5–15 %) were produced having excellent physicochemical properties and better conductivity. The nanocomposite electrodes showed promising electrochemical performance with anhydrous glycerol/KOH gel electrolyte in supercapacitor application. The device with C/VFN15 electrodes in symmetric cell configuration displayed an excellent specific capacitance of 290 F g−1 at a current density of 1 A g−1 and specific energy of 40 Wh kg−1 at a power of 250 W kg−1 with non-aqueous electrolyte. The material exhibited promising cyclic stability up to 10,000 cycles retaining 90 % of its initial capacitance. In addition, a device with C/VFN15 was assembled and exhibited better performance and lighting a RGB LED under various angles.

Peculiarities of the Electrochemical Behavior of Chlorophenoxy-Substituted Phthalocyanines of Cobalt and Copper in Non-Aqueous Media

Peculiarities of the Electrochemical Behavior of Chlorophenoxy-Substituted Phthalocyanines of Cobalt and Copper in Non-Aqueous Media

Potential-Dependent Competitive Adsorption of Electrolytes Kinetically Inhibits High-Current Hydrogen Oxidation in Non-Aqueous Media

Performing electrochemical transformations in non-aqueous media can unlock new reactivities and selectivities unattainable in aqueous media. For instance, non-aqueous media (e.g. acetonitrile (MeCN), dimethylformamide (DMF), dimethylsulfoxide (DMSO)) allow the dissolution of organic compounds and enable water-incompatible organic electrosynthesis reactions. On the other hand, the lithium-mediated nitrogen reduction reaction (NRR) carried out electrochemically in tetrahydrofuran (THF) is one of the most promising routes towards electrifying the Haber-Bosch reaction and thus eliminating the need for hundreds of atmospheres of pressure and high temperatures. However, many cathodic non-aqueous electrochemical reactions either do not operate with well-defined anodic reactions (e.g. unproductive solvent and/or electrolyte oxidation) or are often coupled with the sacrificial oxidation of a dissolving metal electrode (e.g. magnesium, zinc). Hence, the development of a non-sacrificial anodic reaction is essential for engineering practical, sustainable non-aqueous electrochemical transformations. In this study, we investigate the hydrogen oxidation reaction (HOR) in a variety of non-aqueous solvents (MeCN, DMF, DMSO, THF) and buffers (AcO-/AcOH, Cl-/HCl, etc.) whose base serves as the proton acceptor for HOR. The reason why HOR can be sustainable is because it produces protons, which can be paired with a number of proton-demanding electro-reductions such as NRR, carbon dioxide reduction (CDR) to form oxalic acid or carboxylic acids, and more. Hydrogen is also stoichiometrically cheaper and less greenhouse-emitting than sacrificial metals, making HOR both cheaper and greener. First, we demonstrate a fabricated gas diffusion electrode (GDE) architecture that supports high H2 transport-limited current densities in non-aqueous solvents at ambient pressure. We find that the maximum HOR current density obtained is not H2 transport-limited but instead depends on the kinetics influenced by the pKa and steric profile of the buffer electrolytes present. By also varying the buffer electrolyte concentration and H2 partial pressure and conducting voltametric studies in the absence of H2, we demonstrate that the HOR current density reaches a maximum due to a competitive adsorption mechanism of the buffer electrolytes, limiting the surface concentration of adsorbed hydrogen atoms from H2 dissociative adsorption and thus inhibiting HOR. Based on these findings, we outline strategies for mitigating HOR inhibition via this competitive adsorption mechanism to unlock higher HOR current densities.

A “Green” Reaction Cycle Pathway for Synthesizing Metal Oxide Quantum Dots

Synthesis of highly stable quantum dots (QDs) is always a challenge for researchers in nanomaterial community because of involved complexities of the process time and steps. In the past few years, we have demonstrated a simple and single step synthesis process for a range of metal oxide (MO) QDs using plasma-induced non-equilibrium electrochemistry (PiNE).1 , 2 , 3 PiNE is a new and emerging technique based on electrochemical process taking place in liquids from plasma interaction.4 This method is rapid and produces highly stable QDs starting from a metal foil and ethanol as electrolyte. As MO QDs semiconductors in general are a promising candidate for energy harvesting application mainly from their nanoscale effects.5 , 6 In this work, we will present the general applicability of this method for a range of metal oxides and the provide more an in-depth case study for CuO QDs providing details of the reaction mechanisms. An extensive analysis of the solution along with the quantum dots was carried out with nuclear magnetic resonance (NMR) spectroscopy and gas chromatography-mass (GC-MS) spectroscopy, Fourier transform infra-red spectroscopy (FTIR) and ultraviolet-visible (UV-Vis) spectroscopy, pH and the plasma-ethanol interface using optical emission spectroscopy. Thus, the study discloses important aspects of plasma interactions with a non-aqueous medium particularly the trace products and QD purity shows the entire process is a ‘green’ synthesis cycle.7 Reference (1) Ni, C.; Carolan, D.; Rocks, C.; Hui, J.; Fang, Z.; Padmanaban, D. B.; Ni, J.; Xie, D.; Maguire, P.; Irvine, J. T. S.; Mariotti, D. Microplasma-Assisted Electrochemical Synthesis of Co 3 O 4 Nanoparticles in Absolute Ethanol for Energy Applications. Green Chem. 2018, 20 (9), 2101–2109. https://doi.org/10.1039/C8GC00200B.(2) Ni, C.; Carolan, D.; Hui, J.; Rocks, C.; Padmanaban, D.; Ni, J.; Xie, D.; Fang, Z.; Irvine, J.; Maguire, P.; Mariotti, D. Evolution of Anodic Product from Molybdenum Metal in Absolute Ethanol and Humidity Sensing under Ambient Conditions. Cryst. Growth Des. 2019, 19 (9), 5249–5257. https://doi.org/10.1021/acs.cgd.9b00646.(3) Chakrabarti, S.; Carolan, D.; Alessi, B.; Maguire, P.; Svrcek, V.; Mariotti, D. Microplasma-Synthesized Ultra-Small NiO Nanocrystals, a Ubiquitous Hole Transport Material. Nanoscale Adv. 2019. https://doi.org/10.1039/C9NA00299E.(4) Mariotti, D.; Patel, J.; Švrček, V.; Maguire, P. Plasma-Liquid Interactions at Atmospheric Pressure for Nanomaterials Synthesis and Surface Engineering. Plasma Process. Polym. 2012, 9 (11–12), 1074–1085. https://doi.org/10.1002/ppap.201200007.(5) Velusamy, T.; Liguori, A.; Macias-Montero, M.; Padmanaban, D. B.; Carolan, D.; Gherardi, M.; Colombo, V.; Maguire, P.; Svrcek, V.; Mariotti, D. Ultra-Small CuO Nanoparticles with Tailored Energy-Band Diagram Synthesized by a Hybrid Plasma-Liquid Process. Plasma Process. Polym. 2017, 14 (7), 1600224. https://doi.org/10.1002/ppap.201600224.(6) McGlynn, R.; Chakrabarti, S.; Alessi, B.; Moghaieb, H. S.; Maguire, P.; Singh, H.; Mariotti, D. Plasma-Induced Non-Equilibrium Electrochemistry Synthesis of Nanoparticles for Solar Thermal Energy Harvesting. Sol. Energy 2020, 203 (April), 37–45. https://doi.org/10.1016/j.solener.2020.04.004.(7) Padmanaban, D. B.; McGlynn, R.; Byrne, E.; Velusamy, T.; Swadźba-Kwaśny, M.; Maguire, P.; Mariotti, D. Understanding Plasma–Ethanol Non-Equilibrium Electrochemistry during the Synthesis of Metal Oxide Quantum Dots. Green Chem. 2021, 23 (11), 3983–3995. https://doi.org/10.1039/D0GC03291C.

Intercalation of Potassium Ions in Molybdenum Sulfide as Catalyst for CO2 Reduction

The increasing CO2 emission during the last decades highly contributed to global warming and as a consequence, we are facing the disruption of nature and more and more extreme weather conditions nowadays [1]. One way of dealing with the emitted excess CO2 is to create a synthetic carbon cycle, where the emitted CO2 is captured and turned into fuel using electrocatalysis and green energy. However, in order to achieve this, the exploration of new electrocatalysts is needed for the sake of cost and process efficiency and environmental friendliness.Two dimensional materials have a promising future as catalysts due to their high surface-to-volume ratio. A potential catalyst material for CO2 reduction is molybdenite (MoS2), a cheap, layered semiconductor which already showed selectivity towards CO2 reduction in non-aqueous media [2,3]. Its layered structure allows not only to have a high specific surface area but also makes the intercalation of different ions possible. These features enable us to enhance the conductivity of the material via electron donation by the intercalated species [4]. The improved conductivity and the changed band gap can contribute to a higher efficiency of electrochemical processes.Our research investigates the intercalation mechanism of potassium ions into MoS2 layers and the effects of the intercalated potassium on the CO2 reduction efficiency. The intercalation process is studied experimentally through electrochemical impedance spectroscopy (EIS) and confirmed by X-ray diffraction (XRD). Furthermore, the Gibbs free energy profile of the intercalation is obtained by Molecular Dynamics (MD) simulations using umbrella sampling. The electronic properties are measured with X-ray photoelectron spectroscopy (XPS) and the products of the CO2 reduction reaction is measured with gas chromatography (GC). The results suggest that the potassium intercalation improves the conductivity of the MoS2 and consequently the CO2 reduction efficiency.[1] McCrystall et al. New climate models reveal faster and larger increases in Arctic precipitation than previously projected. Nat. Commun. 12:6765, 2021.[2] Asadi et al. Robust carbon dioxide reduction on molybdenum disulphide edges. Nature Communications, 5(1), 2014.[3] Asadi et al. Nanostructured transition metal dichalcogenide electrocatalysts for CO2 reduction in ionic liquid. Science, 353(6298):467–470, 2016.[4] Wang et al. Atomic-scale clarification of structural transition of MoS2 upon sodium intercalation. ACS Nano, 8(11):11394– 11400, 2014.

A hydrazine-based unsymmetrical bis-imine-Schiff base as a chemosensor for turn-off fluorescence and naked-eye detection of Cu2+ ion: Application in aqueous media using test strips

A new hydrazine-based unsymmetrical bis-imine-Schiff base 1-((((5-bromothiophen-2-yl)methylene)hydrazono)methyl)naphthalen-2-ol (L1) was synthesized and characterized with FT-IR, 1H NMR, 13C NMR, UV–visible spectroscopy, ESI-MS, and elemental analysis. The solution of L1 in dichloromethane/methanol (9.8:0.2,v/v) mixture shows a rapid change in color from yellow to yellowish brown in the presence of Cu2+ ions. In addition, L1 displays “turn-off” fluorescence preferentially for Cu2+ ions which was attributed to the Chelation Enhanced Quenching (CHEQ) effect caused due to the reversible binding of L1 to paramagnetic Cu2+ in a 2:1 stoichiometric ratio. No interference was caused in the sensing process by other metal ions such as Ag+, Na+, Ni2+, Co2+, Hg2+, Cr3+ Ba2+, Ca2+, Cd2+, Pb2+, Sn2+, Zn2+, Fe3+, Al3+, K+, and Sr2+. The limit of detection was determined to be 2.809 µM. Furthermore, the test strips coated with L1 show a change in color from pale yellow to brownish-yellow in the presence of Cu2+ions in the aqueous medium, and the limit of visual detection was found to be 15 µM, which is well under the maximum recommended limit (31.5 µM) of Cu2+ for drinking water as per WHO guidelines. These observations establish L1 as an efficient reversible chemosensor for sensing Cu2+ in both aqueous and non-aqueous media with high sensitivity and selectivity.

Thermodynamic Insights of the Molecular Interactions of Dopamine (Neurotransmitter) with Anionic Surfactant in Non-Aqueous Media.

This study was aimed at establishing the interactions prevailing in an anionic surfactant, sodium dodecyl sulfate, and dopamine hydrochloride in an alcoholic (ethanol) media by using volumetric, conductometric, and tensiometric techniques. Various methods were utilized to estimate the critical micelle concentration (cmc) values at different temperatures. The entire methods yielded the same cmc values. The corresponding thermodynamic parameters viz. the standard free energy of micellization (Gmico), enthalpy of micellization (Hmico), and entropy of micellization (Smico) were predicted by applying the pseudo-phase separation model. The experimental density data at different temperatures (298.15 K, 303.15 K, 308.15 K, and 313.15 K) were utilized to estimate the apparent molar volumes (Vϕo) at an infinite dilution, apparent molar volumes (Vφcmc) at the critical micelle concentration, and apparent molar volumes (ΔVφm) upon micellization. Various micellar and interfacial parameters, for example, the surface excess concentration (Γmax), standard Gibbs free energy of adsorption at the interface (ΔGoad), and the minimum surface area per molecule (Amin), were appraised using the surface tension data. The results were used to interpret the intermolecular interactions prevailing in the mixed systems under the specified experimental conditions.

Design and construction of fluorine-free, cost-effective and robust superhydrophobic coatings using nanosilica with highly covalently bonded octadecyl ligands

Low surface energy and rough structure are two key factors in achieving superhydrophobicity. Currently, one of the common routes to acquire low surface energy is via the hydrolytic modification of organosilanes. However, due to steric hindrance, self-condensation of hydrolyzed silanes predominates, whereby the resulting products are mainly physically adsorbed or attached to the substrate by few bonds, resulting in the formed superhydrophobic surfaces susceptible to damage by external forces, which significantly inhibits their practical application and long-term service. Herein, we prepared a novel functionalized nanosilica with highly chemically grafted octadecyl ligands in a non-aqueous medium. The covalent bond structure of the product (ODS@SiO2) is approved, and an average grafting density of 10 chains nm−2 was calculated. The ODS@SiO2 has a crystal structure and displays superior thermal and chemical resistance. ODS@SiO2 can be homogeneously dispersed in n-hexane and then applied to various substrates pre-coated with an adhesive by directly spraying or dip-coating to create superhydrophobic coatings. Studies demonstrate that the aggregation of the ODS@SiO2 with high grafting octadecyl ligands on a substrate not only provides a stable low-surface energy layer but also creates multi-level hierarchical structures and microspheres, thus strengthening the robustness of the coating. The coatings exhibit excellent water repellency and self-cleaning ability while maintaining superhydrophobicity after multiple cycles of mechanical abrasion and exposure to harsh environmental conditions. We convince that the fluorine-free, cost-effective and robust superhydrophobic coating has potential applications in various fields.

C-H···π interactions disrupt electrostatic interactions between non-aqueous electrolytes to increase solubility.

Grid-scale energy storage applications, such as redox flow batteries, rely on the solubility of redox-active organic molecules. Although redox-active pyridiniums exhibit exceptional persistence in multiple redox states at low potentials (desirable properties for energy storage applications), their solubility in non-aqueous media remains low, and few practical molecular design strategies exist to improve solubility. Here we convey the extent to which discrete, attractive interactions between C-H groups and π electrons of an aromatic ring (C-H···π interactions) can describe the solubility of N-substituted pyridinium salts in a non-aqueous solvent. We find a direct correlation between the number of C-H···π interactions for each pyridinium salt and its solubility in acetonitrile. The correlation presented in this work highlights a consequence of disrupting strong electrostatic interactions with weak dispersion interactions, showing how minimal structural change can dramatically impact pyridinium solubility.

Nitrogen Electrocatalysis: Electrolyte Engineering Strategies to Boost Faradaic Efficiency.

The electrochemical activation of dinitrogen at ambient temperature and pressure for the synthesis of ammonia has drawn increasing attention. The Faradaic Efficiency (FE) as well as ammonia yield in the electrochemical synthesis is far from reaching the requirement of industrial scale production. In aqueous electrolytes, the electron stealing hydrogen evolution reaction (HER) and poor solubility of nitrogen are the two major bottlenecks. As the electrochemical reduction of nitrogen involves proton-coupled electron transfer reaction, the rationally engineered electrolytes are required to boost FE and ammonia yield. In this review, we comprehensively summarize various electrolyte engineering strategies to boost the FE in aqueous and non-aqueous medium and suggest possible approach to further improve the performance. In aqueous medium, the performance can be improved by modulating the electrolyte pH, transport velocity of proton, and water activity. The other strategies involve the use of hybrid and water-in-salt electrolytes, ionic liquids, and non-aqueous electrolytes. The existing aqueous electrolytes are not ideal for industrial scale production. Suppression of HER and enhanced nitrogen solubility have been observed with hybrid and non-aqueous electrolytes. The engineered electrolytes are very promising though the electrochemical activation has several challenges. The outcome of lithium-mediated NRR with engineered non-aqueous electrolyte is highly encouraging.

DEVELOPMENT AND VALIDATION OF THE QUANTITATIVE DETERMINATION METHOD FOR A NEW BIOLOGICALLY ACTIVE COMPOUND N-[2-[4-OXO-3(4Н)-QINAZOLINYL]PROPIONYL]-GUANIDINE BY THE METHOD OF TITRATION IN A NON-AQUEOUS MEDIUM

Relevance. Due to the wide spread of diseases of the cardiovascular system, the development and study of drugs aimed at the treatment of diseases of the circulatory system is relevant. A new biologically active compound (BAC) is synthesized at the Department of Pharmaceutical and Toxicological Chemistry of the Volgograd State Medical University – a derivative of quinazoline: N-[2-[4-oxo-3(4H)-quinazolinyl] propionyl]-guanidine (VMA-13-15), which at the stage of preclinical studies confirmed the prospects for use in medical practice as a cardioprotective and neuroprotective drug. The aim of the study is to develop and validate a method for the quantitative determination of N-[2-[4-oxo-3(4H)-quinazolinyl]propionyl]-guanidine (VMA-13-15). Material and methods. The objects of study are laboratory samples of N-[2-[4-oxo-3(4H)-quinazolinyl]propionyl]-guanidine (VMA-13-15, series 2019, 2020 and 2021). A laboratory sample VMA-13-15 twice recrystallized from methanol and dried to constant weight is used as a standard sample (RS). Quantitative determination is carried out by acid-base titration in a non-aqueous medium. The end of the titration is fixed potentiometrically. Results. The ionization constants VMA-13-15 are determined. A procedure is developed for the quantitative determination of N-[2-[4-oxo-3(4H)-quinazolinyl]propionyl]guanidine by acid-base titration in a solvent medium of glacial acetic acid with the establishment of an equivalence point using a potentiometer. The developed method is validated according to the main characteristics: specificity, linearity, correctness, convergence and analytical area. The validation analysis of the developed method confirms that it is suitable for the quantitative determination of the main substance content in the VMA-13-15 substance. Conclusions. A technique for potentiometric titration of N-[2-[4-oxo-3(4H)-quinazolinyl]propionyl]guanidine in a non-aqueous medium is developed and validated.