Reactions In Aqueous Environments Research Articles

Dendrite-free Zn anodes enabled by interface engineering for non-alkaline Zn-air and Zn-ion batteries

Aqueous zinc-metal batteries hold immense promise for large-scale energy storage applications due to their cost-effectiveness and superior safety features. However, uncontrolled dendrite growth, corrosion and side reactions in aqueous environments destabilize the electrode/electrolyte, leading to Zn plating/striping irreversibility. Herein, a low-cost, non-toxic functional electrolyte additive, tetraethyl ammonium bromide (TEAB), addresses this challenge. The preferential adsorption of TEAB on the surface of the Zn anode endows the Zn/electrolyte interface with an optimized electric field distribution and abundant active sites for the uniform and dendrite-free Zn2+ deposition. Moreover, TEAB disrupts the H-bond network between the electrolytes, effectively suppressing water-induced side reactions and corrosion. Consequently, a Zn||Zn symmetric battery achieves a long cycle life of 4,950 h at 1 mA cm-2, and the average coulombic efficiency of the Zn||Cu battery reaches as high as 99.5%. Additionally, even after 2,000 cycles at 3 A g-1, the capacity retention of the Zn||MnO2 battery remains at 91.22%. The non-alkaline full Zn||air batteries deliver remarkable cycling stability up to 270 h.

Enzymatic one-step synthesis of natural 2-pyrones and new-to-nature derivatives from coenzyme A esters

The 2-pyrone moiety is present in a wide range of structurally diverse natural products with various biological activities. The plant biosynthetic routes towards these compounds mainly depend on the activity of either type III polyketide synthase-like 2-pyrone synthases or hydroxylating 2-oxoglutarate dependent dioxygenases. In the present study, the substrate specificity of these enzymes is investigated by a systematic screening using both natural and artificial substrates with the aims of efficiently forming (new) products and understanding the underlying catalytic mechanisms. In this framework, we focused on the in vitro functional characterization of a 2-pyrone synthase Gh2PS2 from Gerbera x hybrida and two dioxygenases AtF6’H1 and AtF6’H2 from Arabidopsis thaliana using a set of twenty aromatic and aliphatic CoA esters as substrates. UHPLC-ESI-HRMSn based analyses of reaction intermediates and products revealed a broad substrate specificity of the enzymes, enabling the facile "green" synthesis of this important class of natural products and derivatives in a one-step/one-pot reaction in aqueous environment without the need for halogenated or metal reagents and protective groups. Using protein modeling and substrate docking we identified amino acid residues that seem to be important for the observed product scope.

Supervised AI and Deep Neural Networks to Evaluate High-Entropy Alloys as Reduction Catalysts in Aqueous Environments.

Competitive surface adsorption energies on catalytic surfaces constitute a fundamental aspect of modeling electrochemical reactions in aqueous environments. The conventional approach to this task relies on applying density functional theory, albeit with computationally intensive demands, particularly when dealing with intricate surfaces. In this study, we present a methodological exposition of quantifying competitive relationships within complex systems. Our methodology leverages quantum-mechanical-guided deep neural networks, deployed in the investigation of quinary high-entropy alloys composed of Mo-Cr-Mn-Fe-Co-Ni-Cu-Zn. These alloys are under examination as prospective electrocatalysts, facilitating the electrochemical synthesis of ammonia in aqueous media. Even in the most favorable scenario for nitrogen fixation identified in this study, at the transition from O and OH coverage to surface hydrogenation, the probability of N2 coverage remains low. This underscores the fact that catalyst optimization alone is insufficient for achieving efficient nitrogen reduction. In particular, these insights illuminate that system consideration with oxygen- and hydrogen-repelling approaches or high-pressure solutions would be necessary for improved nitrogen reduction within an aqueous environment.

Proof of Principle of Wastewater Treatment using Plasma Discharge to Reduce the Amount of Methylparaben

Synthetic substances like many pharmaceuticals, preservatives or other chemical compounds are actually very difficult to handle in sewage treatment. These compounds are very stable in aqueous solution and their degradation reactions are insufficient. Therefore, to eliminate these substances from wastewater additional afford is necessary. Extreme conditions like pH value, redox potential, chemical or physical energy need to be present. With our study we try to show that the use of plasma discharge could be a solution to this problem. Using the example of methylparaben, a preservative, we could show, that the physical energy of plasma discharge is able to initialize the degradation reaction in aqueous environment. The concentration was reduced by up to 70 percent in our setting depending on the treatment duration. Overall, the system showed potential to optimize wastewater treatment. Further examinations are necessary for example regarding undesirable by-products. Keywords: wastewater treatment, plasma discharge, high voltage, degradation

Plasmon-Mediated Selective Chemical Reaction of Aromatic Molecules with Amino and Nitro Functional Groups

The plasmon-mediated chemical reaction (PMCR) of aromatic molecules with different functional groups is the frontier topic in the photochemistry area. In this work, two typical Ag-plasmon-catalyzed reactions in aqueous environments are studied, in which the selective reduction reactions of 2-amino-5-nitrobenzenethiol (2A-5NBT) molecules to 3,3′-dimercapto-4,4′-diaminoazobenzene (M1) and the reduction of M1 to 2,5-aminobenzenethiol (M2) by NaBH4 are observed. The mechanism of these two reactions is discussed combined with the calculated Raman spectra. These results demonstrate that 2A-5NBT molecules are selectively catalyzed to M1 in aqueous environments and M1 can be reduced to form M2 in the presence of NaBH4 as a reducing agent. Furthermore, the kinetics of the reduction reaction are analyzed based on surface-enhanced Raman spectroscopy (SERS), which conforms to the first-order kinetic process. This work provides a new perspective on the modulation of selective surface-catalyzed coupling reactions on 2A-5NBT molecules and facilitates the broadening of the research field of in situ monitoring of PMCRs by SERS technology.

Chemoenzymatic Cascade Reaction for the Valorization of the Lignin Depolymerization Product G-C2-Dioxolane Phenol.

Combining solid acid catalysts with enzyme reactions in aqueous environments is challenging because either very acidic conditions inactivate the enzymes, or the solid acid catalyst is neutralized. In this study, Amberlyst-15 encapsulated in polydimethylsiloxane (Amb-15@PDMS) is used to deprotect the lignin depolymerization product G-C2 dioxolane phenol in a buffered system at pH 6.0. This reaction is directly coupled with the biocatalytic reduction of the released homovanillin to homovanillyl alcohol by recombinant horse liver alcohol dehydrogenase, which is subsequently acylated by the promiscuous acyltransferase/hydrolase PestE_I208A_L209F_N288A in a one-pot system. The deprotection catalyzed with Amb-15@PDMS attains up to 97 % conversion. Overall, this cascade enables conversions of up to 57 %.

Templated Generation of a Bcl-xL Inhibitor by Isomer-Free SPAAC Based on Azacyclonon-5-yne.

High-affinity inhibitors of large protein-protein interactions often have a high molecular weight, which compromises their cell permeability and oral bioavailability. We recently presented isomer-free, strain-promoted azide-alkyne cycloaddition (iSPAAC) as a method by which to generate large, chemically uniform bioactive molecules inside living cells from two smaller components with higher cell permeability. Here, we present the synthesis of Fmoc-protected azacyclonon-5-yne (Fmoc-ACN) as the first cyclononyne suitable for iSPAAC. ACN facilitated the structure-guided development of a single-digit micromolar triazole inhibitor of the protein-protein interaction domain of the antiapoptotic protein Bcl-xL . Inhibitor formation in aqueous buffer at 37 °C, templated by the target protein Bcl-xL , proceeded 2800 times faster than the reaction between Fmoc-ACN and benzyl azide under standard conditions in acetonitrile. Our data demonstrate the utility of cyclononynes for iSPAAC and their potential for achieving vastly accelerated templated reactions in aqueous environments.

Electrochemical Synthesis of Hypervalent Iodine Oxidants

Hypervalent iodine compounds are well established, environmentally benign and highly selective oxidants used in organic synthesis. Their chemical synthesis is based on oxidation of iodobenzenes and it usually involves handling toxic or at least potentially unstable oxidants (e.g. bromate, chlorine, persulfate or percarboxylic acids) making the procedure unsuitable for a larger scale production. Obvious alternative in this case represents electrochemical synthesis where the need for application of oxidants is obviated by oxidation of iodobenzenes at the electrode surface. Indeed, this field has developed quickly within last few years. Majority of published electrochemical works focuses on synthesis of l3-iodanes (iodosylbenzenes and diaryliodonium salts). In addition to that, the use of environmentally unfriendly solvents such as fluorinated alcohols is very common. A number of publications describing electrochemical synthesis of l5-iodanes (iodyl compounds) is very limited. In the present contribution, a short summary of the hypervalent iodine oxidants electrochemical synthesis development achieved in our group will be given. At the beginning we have investigated anodic oxidation of 2-iodobenzoic acid in aqueous environment using boron-doped diamond anode. It was shown that both 2-iodosylbenzoic acid as well as 2-iodylbenzoic acid (IBX) can be obtained with high yields especially in acidic environment [1, 2]. Though, the practical applicability of this very reaction in aqueous environment is limited by solubility of the involved compounds being approximately 1 mM, this “key finding” provided solid base for further development of the electrochemical process of iodanes synthesis.We applied two different strategies to solve the problem of limited solubility. The first was modification of the iodobenzene-based precursor structure by appropriate solubilising groups in order to increase its solubility in aqueous systems. This allowed synthesising various l3- and l5-iodanes in practically relevant concentrations. The second approach was to work in non-aqueous environment such as anhydrous acetic acid, in which solubility of majority of iodobenzenes is sufficiently high. Morover, it represents cheap and environmentally friendly solvent allowing efficient anodic oxidation of iodobenzenes to corresponding l3-iodanes, in particular iodosylbenzene (di)acetates. The electrosynthetic process was operated with high yields and fair current efficiencies in batch and flow electrolysers. In some cases, the products could be separated, others exist only in the solution and decompose upon any attempt for isolation.Beside electrosynthesis, we also investigated kinetics and mechanism of iodobenzenes oxidation be combining experiments with advanced density functional theory calculations. This approach allowed, for example, relating oxidation peak potentials of iodobenzene and iodobenzoic acids to their structure. Unexpectedly low peak potential of 2-iodobenzoic acid was explained by interaction of carboxylic group and iodine atom leading to stabilisation of the formed radical cation. [3] In summary, electrochemical synthesis of hypervalent iodine oxidants in environmentally friendly solvents was shown to interesting and in numerous occasions beneficial what compared to classical chemical route.[1] T. Bystron, A. Horbenko, K. Syslova, K.K. Hii, K. Hellgardt, G. Kelsall, 2-Iodoxybenzoic Acid Synthesis by Oxidation of 2-Iodobenzoic Acid at a Boron-Doped Diamond Anode, ChemElectroChem, 5 (2018) 1002-1005.[2] B. Devadas, J. Svoboda, M. Krupička, T. Bystron, Electrochemical and spectroscopic study of 2-iodobenzoic acid and 2-iodosobenzoic acid anodic oxidation in aqueous environment, Electrochimica Acta, 342 (2020) 136080.[3] T. Bystron, B. Devadas, K. Bouzek, J. Svoboda, V. Kolarikova, J. Kvicala, Anodic Oxidation of Iodobenzene and Iodobenzoic Acids in Acetic Acid Environment – Electrochemical Investigation and Density Functional Theory Study, ChemElectroChem, 8 (2021) 3755-3761.The work was supported from European Regional development Fund-Project "Organic redox couple based batteries for energetics of traditional and renewable resources (ORGBAT)" No. CZ.02.1.01/0.0/0.0/16_025/0007445. Figure 1

Thermodynamic Analysis of the Temperature Effect on Calcite Surface Reactions in Aqueous Environments

Reactive transport models for subsurface applications, particularly those for modified salinity waterflooding (MSW) in carbonates, have to be equipped with thermodynamic models that can reliably predict/describe adsorption phenomena at variable temperature conditions. To advance the understanding of the calcite reactivity at high temperatures, combining experimental and modeling studies is required. Therefore, we used a surface complexation model (SCM) to describe the reactivity at the calcite–water interface and obtained the enthalpies of the surface reactions by fitting the SCM either to high-temperature electrokinetic data obtained through streaming potential measurements on limestone samples or to the effluent concentration from single-phase flooding experiments. We assumed that the equilibrium constants of the surface reactions follow a temperature dependence according to van’t Hoff equation. Our calculations suggest that calcite protonation is more exothermic compared to other minerals (e.g., silica, hematite) and that the adsorption of Ca2+, Mg2+, and SO42– are all endothermic, with SO42– having the highest reaction enthalpy. We further show that the inferred enthalpies were in agreement with enthalpy changes from published microcalorimetry experiments. Despite the consistency with microcalorimetry data, the obtained enthalpies are not undisputable, and additional data are necessary to unequivocally constrain the temperature effect on the calcite surface reactivity.

Recent Advances in the Synthesis and Application of Polymer Compartments for Catalysis.

Catalysis is one of the most important processes in nature, science, and technology, that enables the energy efficient synthesis of essential organic compounds, pharmaceutically active substances, and molecular energy sources. In nature, catalytic reactions typically occur in aqueous environments involving multiple catalytic sites. To prevent the deactivation of catalysts in water or avoid unwanted cross-reactions, catalysts are often site-isolated in nanopockets or separately stored in compartments. These concepts have inspired the design of a range of synthetic nanoreactors that allow otherwise unfeasible catalytic reactions in aqueous environments. Since the field of nanoreactors is evolving rapidly, we here summarize—from a personal perspective—prominent and recent examples for polymer nanoreactors with emphasis on their synthesis and their ability to catalyze reactions in dispersion. Examples comprise the incorporation of catalytic sites into hydrophobic nanodomains of single chain polymer nanoparticles, molecular polymer nanoparticles, and block copolymer micelles and vesicles. We focus on catalytic reactions mediated by transition metal and organocatalysts, and the separate storage of multiple catalysts for one-pot cascade reactions. Efforts devoted to the field of nanoreactors are relevant for catalytic chemistry and nanotechnology, as well as the synthesis of pharmaceutical and natural compounds. Optimized nanoreactors will aid in the development of more potent catalytic systems for green and fast reaction sequences contributing to sustainable chemistry by reducing waste of solvents, reagents, and energy.

Electron affinity of liquid water

Understanding redox and photochemical reactions in aqueous environments requires a precise knowledge of the ionization potential and electron affinity of liquid water. The former has been measured, but not the latter. We predict the electron affinity of liquid water and of its surface from first principles, coupling path-integral molecular dynamics with ab initio potentials, and many-body perturbation theory. Our results for the surface (0.8 eV) agree well with recent pump-probe spectroscopy measurements on amorphous ice. Those for the bulk (0.1–0.3 eV) differ from several estimates adopted in the literature, which we critically revisit. We show that the ionization potential of the bulk and surface are almost identical; instead their electron affinities differ substantially, with the conduction band edge of the surface much deeper in energy than that of the bulk. We also discuss the significant impact of nuclear quantum effects on the fundamental gap and band edges of the liquid.

Lab-on-a-micromotor: catalytic Janus particles as mobile microreactors for tailored synthesis of nanoparticles.

Catalytic Janus micromotors encapsulating Cd2+ or citrate are used here as mobile microreactors for "on the fly" CdS quantum dot and gold nanoparticle synthesis. Micromotor navigation in microliter "reagent solutions" results in the generation of the corresponding nanoparticles inside the micromotor body with high yield and negligible waste generation. Nanoparticle generation can be attributed to convective diffusion of reagents into the moving reactor body. "On-demand" modulation of nanoparticle size and catalytic activities can be achieved by judicious control of the motion behavior of the microreactor. The use of confined reagents in connection with such enhanced movement allows for efficient operation in very low (less than 800 μL) volumes. The new microreactors developed here hold considerable promise for reactions in aqueous environments for novel synthetic schemes in different sites along with multiplexed capabilities for a myriad of catalytic reactions.

Getting the Right Answers for the Right Reasons: Toward Predictive Molecular Simulations of Water with Many-Body Potential Energy Functions.

The central role played by water in fundamental processes relevant to different disciplines, including chemistry, physics, biology, materials science, geology, and climate research, cannot be overemphasized. It is thus not surprising that, since the pioneering work by Stillinger and Rahman, many theoretical and computational studies have attempted to develop a microscopic description of the unique properties of water under different thermodynamic conditions. Consequently, numerous molecular models based on either molecular mechanics or ab initio approaches have been proposed over the years. However, despite continued progress, the correct prediction of the properties of water from small gas-phase clusters to the liquid phase and ice through a single molecular model remains challenging. To large extent, this is due to the difficulties encountered in the accurate modeling of the underlying hydrogen-bond network in which both number and strength of the hydrogen bonds vary continuously as a result of a subtle interplay between energetic, entropic, and nuclear quantum effects. In the past decade, the development of efficient algorithms for correlated electronic structure calculations of small molecular complexes, accompanied by tremendous progress in the analytical representation of multidimensional potential energy surfaces, opened the doors to the design of highly accurate potential energy functions built upon rigorous representations of the many-body expansion (MBE) of the interaction energies. This Account provides a critical overview of the performance of the MB-pol many-body potential energy function through a systematic analysis of energetic, structural, thermodynamic, and dynamical properties as well as of vibrational spectra of water from the gas to the condensed phase. It is shown that MB-pol achieves unprecedented accuracy across all phases of water through a quantitative description of each individual term of the MBE, with a physically correct representation of both short- and long-range many-body contributions. Comparisons with experimental data probing different regions of the water potential energy surface from clusters to bulk demonstrate that MB-pol represents a major step toward the long-sought-after "universal model" capable of accurately describing the molecular properties of water under different conditions and in different environments. Along this path, future challenges include the extension of the many-body scheme adopted by MB-pol to the description of generic solutes as well as the integration of MB-pol in an efficient theoretical and computational framework to model acid-base reactions in aqueous environments. In this context, given the nontraditional form of the MB-pol energy and force expressions, synergistic efforts by theoretical/computational chemists/physicists and computer scientists will be critical for the development of high-performance software for many-body molecular dynamics simulations.

Low friction properties of Ti3AlC2/SiC tribo-pair in sea water environment

In this paper, the tribological property of Ti3AlC2/SiC tribo-pair in sea water was investigated. For comparison, the tribological property in deionized water was studied as well. The results revealed that the Ti3AlC2/SiC tribo-pair displayed better lubricating effect in the two aqueous liquids. The friction coefficient and wear rate decreased with the increment of reciprocating frequency. Herein, a layer of soft hydrated tribo-film, which was caused by tribo-chemical reaction in aqueous environment, was easily sheared and conceived to be liable for the lubricating effect. The lubrication and wear mechanism were boundary lubrication and tribo-chemical wear, respectively. When the soft hydrated tribo-film was exposed in air, the tribo-film could contract and yield rimose tribo-film on account of the loss of water.

Selective plasmon-driven catalysis for para-nitroaniline in aqueous environments.

The plasmon-driven oxidation of amine (−NH2) groups and the reduction of nitro (−NO2) groups on a nanostructured metal surface in an aqueous environment have been reported experimentally and theoretically. The question of which process occurs first in the aqueous environment is an interesting question in the field of plasmon-related photochemistry. Para-nitroaniline (PNA), with both nitro (−NO2) and amine (−NH2) groups, is the best candidate for studying the priority of the plasmon-driven oxidation and the reduction reactions in an aqueous environment. Using surface-enhanced Raman scattering (SERS) spectroscopy, our experimental results and theoretical simulations reveal that PNA is selectively catalyzed to 4,4′-diaminoazobenzene (DAAB) through the plasmon-assisted dimerization of the nitro (−NO2) group into an azo group in an aqueous environment. This indicates that the plasmon-driven reduction of the nitro (−NO2) group clearly occurs before the oxidation of the amine (−NH2) group in an aqueous environment. The plasmon-driven reduction of PNA to DAAB is a selective surface catalytic reduced reaction in aqueous environment.

Effect of aqueous and ambient atmospheric environments on plasmon-driven selective reduction reactions.

We successfully realised plasmon-driven selective reduction reactions of 2-amino-5-nitrobenzenethiol (2A-5-NBT) to 3,3’-dimercapto-4,4’-diaminoazobenzene , an azobenzene derivative, using surface-enhanced Raman scattering (SERS) spectroscopy, and supported by the theoretical calculations. The SERS spectra demonstrated that two 5-nitro groups of 2A-5-NBTs were selectively reduced to the –N=N– chemical bond of 3,3’-dimercapto-4,4’-diaminoazobenzene, whereas the 2-amine group of 2A-5-NBT remained unchanged. Our experimental results revealed that aqueous environments were preferable to ambient atmospheric environments for this selective reduction reaction. The product is very stable in aqueous environments. However, in ambient atmosphere environments, the product is not stable and can revert back to 2A-5-NBT, where the –N=N– chemical bond can be broken by plasmon scissors. The plasmon-induced catalytic reactions in aqueous environments could be used for the efficient synthesis of aromatic azobenzene derivative compounds, which are valuable chemicals that are widely used in the chemical industry as dyes, food additives and drugs.

ChemInform Abstract: Asymmetric Catalysis with Short‐Chain Peptides

AbstractReview: 43 refs.

"Clickable" Polymeric Nanofibers through Hydrophilic-Hydrophobic Balance: Fabrication of Robust Biomolecular Immobilization Platforms.

Fabrication of hydrophilic polymeric nanofibers that undergo facile and selective functionalization through metal catalyst-free Diels-Alder "click" reaction in aqueous environment is outlined. Electrospinning of copolymers containing an electron-rich furan moiety, hydrophobic methyl methacrylate units and hydrophilic poly(ethylene glycol)s as side chains provide specifically functionalizable yet antibiofouling fibers that remain stable in aqueous media due to appropriate hydrophobic hydrophilic balance. Efficient functionalization of these nanofibers is accomplished through the Diels-Alder reaction by exposing them to maleimide-containing molecules and ligands. Diels-Alder conjugation based functionalization is demonstrated through attachment of fluorescein-maleimide and a maleimide tethered biotin ligand. Biotinylated nanofibers were utilized to mediate immobilization of the protein streptavidin, as well as streptavidin coated quantum dots. Facile fabrication from readily available polymers and their effective functionalization under mild and reagent-free conditions in aqueous media make these "clickable" nanofibers attractive candidates as functionalizable scaffolds for various biomedical applications.

Controlled Oxygen Release from Pyridone Endoperoxides Promotes Cell Survival under Anoxic Conditions

In tissue engineering, survival of larger constructs remains challenging due to limited supply of oxygen caused by a lack of early vascularization. Controlled release of oxygen from small organic molecules represents a possible strategy to prevent cell death under anoxic conditions. A comprehensive study of methylated pyridone-derived endoperoxides has led to the development of water-soluble molecules that undergo retro-Diels-Alder reactions in aqueous environment releasing oxygen in high yield and with half-lives of up to 13 h. These molecules in combination with vitamin C as singlet oxygen quencher significantly improved survival of 3T3 fibroblasts and rat smooth muscle cells challenged with oxygen-depleted conditions.

All‐Oxide Raman‐Active Traps for Light and Matter: Probing Redox Homeostasis Model Reactions in Aqueous Environment

Core-shell colloidal crystals can act as very efficient traps for light and analytes. Here it is shown that Raman-active probes can be achieved using SiO2-TiO2 core-shell beads. These systems are successfully tested in monitoring of glutathione redox cycle at physiological concentration in aqueous environment, without need of any interfering enhancers. These materials represent a promising alternative to conventional, metal-based SERS probes for investigating chemical and biochemical reactions under real working conditions.