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Highly efficient interconversion of different types of energy plays a crucial role in both science and technology. Among them, electrochemiluminescence, an emission of light excited by electrochemical reactions, has drawn attention as a powerful tool for bioassays. Nonetheless, the large differences in timescale among diverse charge-transfer pathways from picoseconds to seconds significantly limit the electrochemiluminescence efficiency and hamper their broad applications. Here, we report a timescale coordination strategy to improve the electrochemiluminescence efficiency of carbon nitrides by engineering shallow electron trap states via Au-N bond functionalization. Quantitative electrochemiluminescence kinetics measurements and theoretic calculations jointly disclose that Au-N bonds endow shallow electron trap states, which coordinate the timescale of the fast electron transfer in the bulk emitter and the slow redox reaction of co-reagent at diffusion layers. The shallow electron trap states ultimately accelerate the rate and kinetics of emissive electron-hole recombination, setting a new cathodic electrochemiluminescence efficiency record of carbon nitrides, and empowering a visual electrochemiluminescence sensor for nitrite ion, a typical environmental contaminant, with superior detection range and limit. Differences in timescales of electron transfer reactions limit the efficiency of electrochemiluminescence. Here, the authors coordinate the timescales using shallow trap states in carbon nitride to achieve high efficiencies applied in nitrite sensing. [ABSTRACT FROM AUTHOR]

In charged water microdroplets, which occur in nature or in the lab upon ultrasonication or in electrospray processes, the thermodynamics for reactive chemistry can be dramatically altered relative to the bulk phase. Here, we provide a theoretical basis for the observation of accelerated chemistry by simulating water droplets of increasing charge imbalance to create redox agents such as hydroxyl and hydrogen radicals and solvated electrons. We compute the hydration enthalpy of OH− and H+ that controls the electron transfer process, and the corresponding changes in vertical ionization energy and vertical electron affinity of the ions, to create OH• and H• reactive species. We find that at ~ 20 − 50% of the Rayleigh limit of droplet charge the hydration enthalpy of both OH− and H+ have decreased by >50 kcal/mol such that electron transfer becomes thermodynamically favorable, in correspondence with the more favorable vertical electron affinity of H+ and the lowered vertical ionization energy of OH−. We provide scaling arguments that show that the nanoscale calculations and conclusions extend to the experimental microdroplet length scale. The relevance of the droplet charge for chemical reactivity is illustrated for the formation of H2O2, and has clear implications for other redox reactions observed to occur with enhanced rates in microdroplets. Redox reactions exhibit different thermodynamics and kinetics in water microdroplets compared to the bulk. Here, the authors use reactive molecular dynamics to show the importance of charged reactive species in explaining reactivity under confinement. [ABSTRACT FROM AUTHOR]

Cephalopods can change their skin color by using high‐speed electron transduction among receptors, neural networks, and pigmentary effectors. However, it remains challenging to realize a neuroelectrical transmission system like that found in cephalopods, where electrons/ions transmit on nanoscale, which is crucial for fast adaptive electrochromic tuning. Inspired by that, hereby an ideal, rapidly responsive, and multicolor electrochromic biomimetic skin is introduced. Specifically, the biomimetic skin comprises W18O49 nanowires (NWs) that are either colorless or blue, Au nanoparticles@polyaniline (Au NPs@PANI) ranging from green to pink, and a flexible conductive substrate. As the applied voltage changes from 0.4 V to ‐0.7 V and back to 0 V, the color of the biomimetic skin transforms from green to blue and ultimately to pink. This color change is attributed to the electrically induced redox reaction of Au NPs@PANI and W18O49 NWs, triggered by the transfer of electrons and ions. Furthermore, the high versatility and adaptability of electrical stimulus enable the creation of a highly interactive electrochromic biomimetic skin system through the integration of sensitive acoustic sensors, providing a perfect environment‐responsive platform. This work provides a biomimetic multicolor electrochromic skin that depends on electron/ion transfer on nanoscale, expands potential uses for camouflage skin. [ABSTRACT FROM AUTHOR]

ABSTRACT Metal–organic framework (MOF) nanozymes have garnered widespread attention in the field of biomimetic catalysis due to their highly controllable porous structure and surface functionalization, enabling them to mimic the catalytic activity and specificity of natural enzymes while offering greater stability and reusability. In recent years, significant progress has been made in the theoretical computation studies of MOF nanozymes' catalytic reactions, providing deep insights into their catalytic and analytical mechanisms. This review comprehensively gathers the latest research progress of theoretical calculation–driven MOF nanozymes on their catalytic mechanisms and applications. First, the methods that can be used for theoretical calculations of MOF nanozymes, especially density functional theory (DFT), are reviewed to help deeply analyze the active site distribution, electron transfer pathways, and adsorption and activation mechanisms of reactants of MOF nanozymes. Subsequently, this review deeply studies the contribution of these theoretical calculation methods to revealing the catalytic reaction mechanism of MOF nanozymes (such as active sites and enzyme‐like activity), especially the specific role of electron transfer and reaction energy changes in key reaction steps. Finally, this review looks forward to the challenges and opportunities in the theoretical computation for the future design and application of MOF nanozymes, especially in accurately predicting catalytic activities, understanding complex reaction mechanisms, and guiding the synthesis of new nanozyme materials. By integrating theoretical calculations with experimental research, the study of MOF nanozymes is expected to forge new avenues in biomimetic catalysis and provide effective strategies for addressing challenges in the fields of sensing, biomedicine, and environmental protection. [ABSTRACT FROM AUTHOR]

Using different precursors (urea, thiourea, and urea-thiourea), the S(step)-scheme hetero system i. e. 2D/2D S-doped g-C 3 N 4 /g-C 3 N 4 was synthesised by in-situ calcination. Samples that had been prepared were evaluated for water splitting to produce hydrogen in aqueous CH 3 OH scavenger under exposure of a 300W Xe light. The system consisting of urea and thiourea (1:1 CN-T + U) has exhibited the highest rate of hydrogen production i. e. 485.51 μmolg−1h−1 with 1.75% apparent quantum efficiency (AQE) at 420 nm light irradiation, which is 1.37 and 1.29 times higher than the CN–U and CN-T systems. The S-type heterojunction formed between S-doped g-C 3 N 4 and g-C 3 N 4 , is responsible for the higher rate of hydrogen evolution because the heterojunction is more efficient than the typical type-II heterojunction for spatial charge separation and redox ability of the system's oxidation and reduction sites. The photocatalytic electron transfer mechanism based on advanced analysis techniques (XRD, UV–Vis, SEM, EDX, PLE, ESR, XPS, SPV, etc.) was also suggested for the investigated system. [Display omitted] • 2D/2D S-doped g-C 3 N 4 /g-C 3 N 4 (CN-T + U) composite synthesised by utilising in-situ combustion. • Physicochemical analyses of the composite confirm the formation of S-scheme heterojunction. • CN-T + U system exhibited the highest H 2 production (485.51 μmolg−1h−1) and 1.75% AQE at 420 nm. • The electron transfer mechanism proposed for the composite. • DFT of CN-T + U system reveal the presence of cation, anion, N-vacancy, and N-substitution defects. [ABSTRACT FROM AUTHOR]

The explosive growth of information and its widespread availability underscores the need for robust encryption and anticounterfeiting measures. In this study, CdS quantum dots are engineered (QDs) to manifest multiple visual responses to a single trigger through strategic ligand design. The surface engineering method allows QDs to transition from yellow to black upon photoexcitation‐induced electron transfer from Cd(II) to Cd(0). Surface ligands desorption under hole injection, leading to an increase in QDs size and resulting in a redshift in photoluminescence. This photoexcitation‐induced redox reaction reveals unprecedented photochromism and photoluminescence phenomena, establishing a foundation for advanced information protection measures. Utilizing these QDs, excellent writing performance under UV irradiation is achieved in solid‐state substrates, while a dual‐mode encryption system is realized in gel matrices, opening up new avenues for information encryption as well as cumulative and interactive information protection. Furthermore, the redox reaction of CdS QDs is employed as ink for 3D printing, enabling for the creation of digitally programmable materials with distinct temporally evolving appearances by controlling the oxygen content in the ink to regulate the rate of photochromism. This advancement also sheds light on the progress in 3D printing technology. [ABSTRACT FROM AUTHOR]

To investigate the separation of Ni(II) impurity and the refining of the electrolyte for magnesium electrolysis, the electrochemical behavior of the Ni(II) impurity in the MgCl2–KCl–NaCl melt at 973 K has been studied using several techniques, including cyclic voltammetry (CV), square wave voltammetry (SWV), and chronoamperometry (CA). Based on the analysis of the CV and SWV curves, it can be inferred that the reduction of Ni(II) in the MgCl2–KCl–NaCl melt at the tungsten electrode exhibits a quasi-reversible reaction. This reaction involves the transfer of a pair of electrons in a single step. The diffusion coefficient was determined at 973 K to be 3.84 × 10−5 cm2 s−1 through the semi-integral method, with the activation energy for diffusion was found to be 45.81 kJ mol−1. The reaction rate constant for the Ni(II) redox reaction was determined to be approximately 10−3 cm s−1 using the Nicholson method. This value suggests that the reaction fall within the quasi-reversible range, as defined by the Matsuda–Ayabe standard. The results obtained from the CA technique have demonstrated that the deposition of nickel on the tungsten electrode occurs through an instantaneous nucleation process, which is primarily controlled by diffusion. [ABSTRACT FROM AUTHOR]

This work examines the electrochemically enhanced production of succinic acid using the bacterium Actinobacillus succinogenes. The principal objective is to enhance the metabolic potential of glucose and CO2 utilization via the C4 pathway in order to synthesize succinic acid. We report on the development of an electro-bioreactor system to increase succinic acid production in a power-2-X approach. The use of activated carbon fibers as electrode surfaces and contact areas allows A. succinogenes to self-initiate biofilm formation. The integration of an electrical potential into the system shifts the redox balance from NAD+ to NADH, increasing the efficiency of metabolic processes. Mediators such as neutral red facilitate electron transfer within the system and optimize the redox reactions that are crucial for increased succinic acid production. Furthermore, the role of carbon nanotubes (CNTs) in electron transfer was investigated. The electro-bioreactor system developed here was operated in batch mode for 48 h and showed improvements in succinic acid yield and concentration. In particular, a run with 100 µM neutral red and a voltage of −600 mV achieved a yield of 0.7 gsuccinate·gglucose−1. In the absence of neutral red, a higher yield of 0.72 gsuccinate·gglucose−1 was achieved, which represents an increase of 14% compared to the control. When a potential of −600 mV was used in conjunction with 500 µg∙L−1 CNTs, a 21% increase in succinate concentration was observed after 48 h. An increase of 33% was achieved in the same batch by increasing the stirring speed. These results underscore the potential of the electro-bioreactor system to markedly enhance succinic acid production. [ABSTRACT FROM AUTHOR]

Heterogeneous interfaces designed rationally in catalysts can induce geometrical, compositional, and electronic effects that can be applied to modulate catalytically active sites and consequently accelerate reaction kinetics. Here, a core‐shell heterostructure catalyst consisting of crystalline molybdenum phosphide (MoP) cores and amorphous tungsten oxide (WOx) shells on porous carbon nanosheets (PCN) is developed for oxidative desulfurization (ODS) of fuels. The strongly coupled core‐shell heterogeneous interface triggers a distinctive atomic permeation effect that induces substantial electron transfer from MoP to WOx and subsequent generation of electron‐rich W sites, consequently optimizing the adsorption of intermediates and substrates. The resulting catalyst (WOx@MoP/PCN) demonstrates a turnover frequency as high as 768.1 h−1 for ODS at 60 °C, exceeding that of almost all the state‐of‐the‐art ODS catalysts by 1–2 orders of magnitude. Moreover, a novel surface oxidation pathway based on direct electron transfer is identified in the WOx@MoP/PCN‐H2O2 system, which bypasses the formation of reactive oxygen species, consequently endowing the system with a moderate redox potential. Thus, WOx@MoP/PCN exhibits unprecedented selectivity, achieving 100% removal of thiophenic sulfides from real diesel with minimal consumption of oxidant. [ABSTRACT FROM AUTHOR]

Regulating appropriate valence states of metal active centers, such as Ce3+/Ce4+ and Mn3+/Mn2+, as well as surface vacancy defects, is crucial for enhancing the catalytic activity of cerium‐based and manganese‐based nanozymes. Drawing inspiration from the efficient substance exchange in rhizobia‐colonized root cells of legumes, we developed a symbiosis nanozyme system with rhizobia‐like CeOx nanoclusters robustly anchored onto root‐like Mn3O4 nanosupports (CeOx/Mn3O4). The process of “substance exchange” between Ce and Mn atoms—reminiscent of electron transfer—not only fine‐tunes the metal active sites to achieve optimal Ce3+/Ce4+ and Mn3+/Mn2+ ratios but also enhances the vacancy ratio through interface defect engineering. Additionally, the confinement anchoring of CeOx on Mn3O4 ensures efficient electron transfer in catalytic reactions. The final CeOx/Mn3O4 nanozyme demonstrates potent catalase‐like (CAT‐like) and superoxide dismutase‐like (SOD‐like) activities, excelling in both chemical settings and cellular environments with high reactive oxygen species (ROS) levels. This research not only unveils a novel material adept at effectively eliminating ROS but also presents an innovative approach for amplifying the efficacy of nanozymes. [ABSTRACT FROM AUTHOR]

The NASICON cathode, Na3V2(PO4)3, has garnered significant attention due to its robust framework with fast Na+ migration. To expand its application scenarios by diversified electronic reaction, the substitution of vanadium with cost‐effective and abundant redox elements is a special research topic. Nevertheless, in terms of reducing toxicity, increasing Na content and widening voltage range, the V4+/5+ redox couple in Na4FeV(PO4)3 often accompanies asymmetric and irreversible electrochemical reactions that pose a dilemma for capacity and structural stability, especially at high currents. Herein, in this work, Na4FeV1/3Ti2/3(PO4)3 (NFVT) has achieved highly reactive of multiple electron transfer (Ti2+/3+, Fe2+/3+, and V3+/4+/5+) by utilizing the redox reaction with quasi‐monophase behavior, and it can reserve great capacity retention after 3,000 cycles. More competitively, its boosting kinetics makes the fast‐charging characteristic, just requiring only 3.63 min to reach 80% state of charge at 2 C. The rapid ion/electron transport dynamics can achieve the decay of only 0.043% per cycle by unlocking the quasi‐monophase behavior in the framework of NFVT full cells. The present study provides a fresh perspective on designing cathode materials with fast‐charging capabilities for sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

Rechargeable magnesium sulfur batteries (MSBs) face issues like polysulfide shuttling, sluggish redox kinetics, and high cost, leading to dissatisfied practical demonstrations. Herein, simple battery configurations utilizing 100% sulfur are proposed on nine collectors and a low‐cost phenolate‐based magnesium complex (PMC) electrolyte to address these problems. Comprehensive studies indicate that the Cu collector is the most conducive to improving battery performance, not only facilitating the generation of magnesium sulfides during discharging but also effectively dissociating Mg─S bonds during charging. Moreover, Cu surfaces can effectively adsorb magnesium polysulfides (MgSx) and induce an insulator‐to‐metal transition of MgS, leading to a more effective suppression of the shuttle effect and the transfer of electrons. MXene interlayers are further introduced between electrodes to inhibit MgSx shuttling and enhance the interfacial electronic conductivity, as reflected by the reinforced high discharge voltage plateau at ≈1.7 V and stable long discharge voltage plateau at ≈1.2 V. The assembled MSBs exhibit the highest reported capacity of 1260 mAh g−1S and an energy density of 1230 Wh kg−1S with a cycle life of over 1000 cycles. This research contributes to the fundamental understanding of rechargeable MSBs and marks a significant advancement in optimizing cell designs for better performance. [ABSTRACT FROM AUTHOR]

In the chloroplast stroma, dynamic pH changes occur from acidic to alkaline in response to fluctuating light conditions. We investigated the pH dependency of the electron transfer reaction of ferredoxin-NADP+ reductase (FNR) with ferredoxin (Fd) isoproteins, Fd1 and Fd2, which are localized in mesophyll cells and bundle sheath cells, respectively, in the leaves of C4 plant maize. The pH-dependent profile of the electron transfer activity with FNR was quite different between Fd1 and Fd2, which was mainly explained by the opposite pH dependency of the K m value of these Fds for FNR. Replacement of the amino acid residue at position of 65 (D65N) and 78 (H78A) between the two Fds conferred different effect on their pH dependency of the K m value. Double mutations of the two residues between Fd1 and Fd2 (Fd1D65N/H78A and Fd2N65D/A78H) led to the mutual exchange of the pH dependency of the electron transfer activity. This exchange was mainly explained by the changes in the pH-dependent profile of the K m values. Therefore, the differences in Asp/Asn at position 65 and His/Ala at position 78 between Fd1 and Fd2 were shown to be the major determinants for their different pH dependency in the electron transfer reaction with FNR. [ABSTRACT FROM AUTHOR]

A rigorous comparison between square-wave voltammetry (SWV) and the recently proposed multi-frequency electrochemical Faradaic spectroscopy (MEFS) is presented for both a quasireversible electrode reaction of a dissolved redox couple at a planar macroscopic electrode and a catalytic regenerative electrode mechanism (EC′ reaction scheme) by means of numerical simulations. MEFS offers fast kinetic characterisation with a minimal set of experiments, as the system is interrogated with a range of SW frequencies in a single experiment. By changing the mid-potential Em, a critical parameter of MEFS, a broad range of standard rate constants for the heterogeneous interfacial electron transfer is accessible, ranging between 0.006 and 0.12 cm s−1. In the case of the EC′ mechanism, features of the current components in both SWV and MEFS reflect the involvement of the follow-up regenerative chemical reaction (i.e. C′ catalytic step). However, for the kinetic characterisation of the EC′ mechanism, the comparative analysis suggests that SWV should be the main operating technique. [ABSTRACT FROM AUTHOR]

[Display omitted] • Developed Me-SeSPAN/SeS electrode with 70 wt% high active material loading. • This electrode features interconnected mesoporous nanoreactors with spatial confinement. • Nanoreactors serve as additional storage spaces for active materials. • Nanoreactors effectively restricts active material cluster sizes within pores. • Spatial confinement boosts Li+ interaction, speeding up the redox reaction. Sulfurized polyacrylonitrile (SPAN), which is recognized as a promising cathode material for lithium-sulfur batteries (Li-SBs), effectively mitigates the shuttle effect resulting from polysulfide dissolution. However, conventional SPAN cathodes typically exhibit sulfur loadings below 40 wt%. While encapsulation of sulfur within pores via a solid electrolyte interface addresses the low sulfur loading issue, the suboptimal kinetics of the solid–solid reactions hinder effective utilization of sulfur within the pores. In this work, Me-SeSPAN/SeS fibrous membranes were successfully synthesized through electrospinning and molten salt-assisted pyrolysis of ZIF-8, which resulted in the formation of spatially confined interconnected mesoporous nanoreactors. These nanoreactors function as supplementary storage spaces, loading and constraining the size of internal active material clusters. The fibrous membranes facilitate Li+ movement through pore spaces and promote adsorption of the discharge product Li 2 S on the pore walls via the spatial confinement effect. Based on density functional theory (DFT) calculations, this process guarantees a supply of electrons and Li+ to the active material, thereby enabling continuous electron transfer during redox reactions. The optimized Me-SeSPAN/SeS electrode, featuring a sulfur and selenium loading of 70 wt%, demonstrates exceptional cycling stability in both coin and pouch cells. This study presents an effective strategy for enhancing the kinetics of active materials encapsulated in SPAN cathodes. [ABSTRACT FROM AUTHOR]

Two‐dimensional conjugated metal–organic frameworks (2D c‐MOFs) have emerged as promising candidates in gas sensing, owing to their tunable porous structure and conductivity. Nevertheless, the reported gas sensing mechanisms heavily relied on electron transfer between metal nodes and gas molecules. Normally, the strong interaction between the metal sites and target gas molecule would result poor recovery and thus bad recycling property. Herein, we propose a redox synergy strategy to overcome this issue by balancing the reactivity of metal sites and ligands. A 2D c‐MOF, Zn3(HHTQ)2, was prepared for nitrogen dioxide (NO2) sensing, which was constructed from active ligands (hexahydroxyltricycloquinazoline, HHTQ) and inactive transition‐metal ions (Zn2+). Substantial characterizations and theoretical calculations demonstrated that by utilizing only the redox interactions between ligands and NO2, not only high sensitivity and selectivity, but also excellent cycling stability in NO2 sensing could be achieved. In contrast, control experiments employing isostructural 2D c‐MOFs with Cu/Ni metal nodes exhibited irreversible NO2 sensing. Our current work provides a new design strategy for gas sensing materials, emphasizing harnessing the redox activity of only ligands to enhance the stability of MOF sensing materials. [ABSTRACT FROM AUTHOR]

As a chemotherapy drug, 5‐fluorouracil (5‐FU) has been used for colon cancer for decades. Excessive levels of 5‐FU in the human body can lead to notable adverse effects, including severe diarrhea, infection, mouth sores, skin peeling, skin inflammation, and ulcers, which are important and relatively common digestive side effects. In addition, 5‐FU is an analog of uracil and also has similarities to pyrimidines. Therefore, it is not easy to separate them. This research presented a sensor capable of detecting drugs in minimal amounts. An alginate‐derived carbon dot (CD) was synthesized by unique optical properties that obey an on–off fluorescence mechanism for 5‐FU sensing. Introducing copper (Cu(I)) to CDs results in fluorescence quenching through electron transfer. However, when 5‐FU is added to the system as an oxidizing agent, a redox reaction occurs on the surface of the CDs, which leads to the restoration of fluorescence as Cu(I) is altered to Cu(II). Experimental results showed a strong linear correlation (R2 = 0.99) in the concentration range of 1.00–45.00 nM, with the following linear regression, and revealed the relative standard deviation (RSD%) and detection limit of 2.57%, and 1.00 nM, respectively. These results validated the excellent detection capability of the proposed method even at low concentrations of 5‐FU and in the presence of other drugs and interfering substances. Also, the recovery of 5‐FU (varies from 100.46% to 113.7%, with RSD equal to 1.89–3.63) in serum samples indicates the absence of matrix interference in the determination of 5‐FU. In summary, this novel approach to developing a cost‐effective and sensitive sensor holds great potential for future applications in healthcare and related fields. [ABSTRACT FROM AUTHOR]

The production of hydrogen through photocatalysis is an effective strategy for creating sustainable and eco-friendly energy. It harnesses solar energy to catalyze the division of water molecules into hydrogen and oxygen. In this method, photocatalysts, which are generally semiconductor materials, capture solar energy to facilitate the necessary oxidation-reduction reactions for the water splitting. Meanwhile, the two-dimensional material known as Ti 3 C 2 T x MXene is emerging as a prominent player among atomic layer nanomaterials. It features tunable structures, a high surface area-to-volume ratio, hydrophilicity, varied surface chemistry, superior electrical conductivity, and a multitude of sites active in redox reactions. MXenes serve as exceptional co-catalysts in the generation of photocatalytic fuels, thanks to their metallic characteristics. When MXenes are integrated with materials possessing an energy band gap, like semiconductors, it enhances the electron transfer efficiency, prolongs the lifespan of charge carriers, and ultimately boosts the hydrogen production via photocatalysis. Concurrently, metal-organic frameworks (MOFs) are being recognized as materials of great potential due to their vast surface area and semiconductor-like properties. The combination of MOFs with Ti 3 C 2 T x may pave the way for the development of composite materials that exhibit enhanced efficiency in solar energy capture. MOFs possess the capability to generate photoinduced electron/hole pairs (e−/h+). These pairs can facilitate the transfer of electrons to MXene through Schottky junctions, thereby aiding in photoredox reactions. The primary aim of this research is to elucidate recent advancements in the domain of Ti 3 C 2 T x /MOF composites and their application in the production of hydrogen. [ABSTRACT FROM AUTHOR]

Herein, we report a Pd‐catalyzed aerobic lactamization of unactivated γ‐C(sp3)−H bonds of aliphatic carboxylic acids and amino acids derivatives. The utilization of Pd(OAc)2 as a catalyst, along with catalytic AgNO2 as an electron transfer mediator, circumvents the need for stoichiometric oxidants and demonstrates significant practicality. [ABSTRACT FROM AUTHOR]

Electron transfer (ET) is the fundamental redox process of life and element cycling. The ET distance is normally as short as nanometers or micrometers in the subsurface. However, the redox gradient in the subsurface is as long as centimeters or even meters. This gap triggers an intriguing question whether directional long-distance ET from reduced to oxidized zones exists along the redox gradient. By using electron-donating capacity variation as a proxy of ET, we show that ET can last over 10 cm along the redox gradient in sediment columns, through a directional long-distance ET chain from reduced to oxidized zones constituted by a series of short-distance electron hopping reactions. Microbial and chemical processes synergistically mediate the long-distance ET chain, with an estimated flux of 6.73 μmol e−/cm2 per day. This directional long-distance ET represents an overlooked but important "remote" source of electrons for local biogeochemical and environmental processes. A directional long-distance ET chain from reduced to oxidized zones occurs in the subsurface, which reaches the distance of over centimeter scale. This implicates an overlooked contribution of "remote" electron sources/sinks for local biogeochemical processes. [ABSTRACT FROM AUTHOR]

The global ecosystem relies on the metabolism of photosynthetic organisms, featuring the ability to harness light as an energy source. The most successful type of photosynthesis utilizes a virtually inexhaustible electron pool from water, but the driver of this oxidation, sunlight, varies on time and intensity scales of several orders of magnitude. Such rapid and steep changes in energy availability are potentially devastating for biological systems. To enable a safe and efficient light-harnessing process, photosynthetic organisms tune their light capturing, the redox connections between core complexes and auxiliary electron mediators, ion passages across the membrane, and functional coupling of energy transducing organelles. Here, microalgal species are the most diverse group, featuring both unique environmental adjustment strategies and ubiquitous protective mechanisms. In this review, we explore a selection of regulatory processes of the microalgal photosynthetic apparatus supporting smooth electron flow in variable environments. [ABSTRACT FROM AUTHOR]

In recent years, the periodic outbreak of green tides in the coastal areas of China, caused by the combined effects of environmental changes and human activities, has been attracting extensive attention due to the serious negative impacts on the coastal marine ecosystem. In the study, the samples of Ulva linza, a green tide species, were cultivated under two light intensities (LL: 80 mmol photons m-2 s-1; HL: 300 mmol photons m-2 s-1) and three stocking densities (LD: 0.2 g L-1; MD:1 g L-1; HD:2 g L-1) to explore the photosynthetic physiological responses and nutrients absorption capacity. The results showed that high light and low density significantly increased the growth rate of U. linza. Under the HLLD, the maximum growth rate of U. linza was 43.13% day-1 and the energy captured per unit reaction center for electron transfer (ET0/RC) was the highest. The higher density significantly decreased the maximum relative electron transfer rate (rETRmax) of U. linza, especially among groups subjected to high-light condition. Under HL condition, HD also significantly decreased light utilization efficiency (a) in U. linza. The contents of chlorophyll a, b and carotenoids of U. linza were significantly lower in HLLD group compared to other treatment groups. The P uptake of U. linza was prominently inhibited by higher density, and the maximum P uptake and minimum P uptake was 17.94 mM g-1 FW day-1 in LLLD group and 2.74 mM g-1 FW day-1 in LLHD group, respectively. Lower density improved N uptake of U. linza, but high light had no effect on it. These results suggest that high light and lower density synergistically promote the growth of U. linza, which is likely due to enhanced photosynthetic efficiency and nutrient uptake. And the inhibitory effects of higher densities on growth, particularly under high-light conditions, may be due to increased competition for light and nutrients. In the late stage of the green tides outbreak, an increase in accumulation density could help to suppress the sustained outbreak of the green tides, particularly in high-light condition. [ABSTRACT FROM AUTHOR]

In enzymatic catalysis, the redox site and Lewis acid are the two main roles played by metal to assist amino acids. However, the reported enzyme mimics only focus on the redox-active metal as redox site, while the redox-inert metal as Lewis acid has, to the best of our knowledge, not been studied, presenting a bottleneck of enzyme mimics construction. Based on this, a series of highly efficient MxV2O5·nH2O peroxidase mimics with vanadium as redox site and alkaline-earth metal ion (M2+) as Lewis acid are reported. Experimental results and theoretical calculations indicate the peroxidase-mimicking activity of MxV2O5·nH2O show a periodic change with the Lewis acidity (ion potential) of M2+, revealing the mechanism of redox-inert M2+ regulating electron transfer of V-O through non-covalent polarization and thus promoting H2O2 adsorbate dissociation. The biomimetic synergetic effect of redox site and Lewis acid is expected to provide an inspiration for design of enzyme mimics. The so far reported enzyme mimics focus on the redox-active metal as a redox site, while the redox-inert metal as Lewis acid has so far not been reported. Here, the authors report efficient MxV2O5·nH2O peroxidase mimics with vanadium as redox site and alkaline-earth metal ion (M2+) as Lewis acid, where the peroxidase-mimicking activity shows a periodic change with the Lewis acidity of the metal. [ABSTRACT FROM AUTHOR]

The hydroxylated carbon nanotubes (CNTs-OH), due to their propensity to trap electrons, are considered in many applications. Despite many case studies, the effect of the electronic structure of the CNT-OH electrode on its oxidation properties has not received in-depth analysis. In the present study, we used Fe(CN)63−/4− and Ru(NH3)63+/2+ as redox probes, which differ in charge. The CNT-OH and CNT electrodes used in the cyclic voltammetry were in the form of freestanding films. The concentration of holes in the CNTs-OH, estimated from the upshift of the Raman G-feature, was 2.9 × 10 13   c m − 2 . The standard rate constant of the heterogeneous electron transfer (HET) between Fe(CN)63−/4− and the CNTs-OH electrode was 25.9 × 10 − 4   c m · s − 1 . The value was more than four times higher than the HET rate on the CNT electrode ( k s = 6.3 × 10 − 4   c m · s − 1 ), which proves excellent boosting of the redox reaction by the holes. The opposite effect was observed for the Ru(NH3)63+/2+ redox couple. While the redox reaction rate constant at the CNT electrode was 1.4 × 10 − 4   c m · s − 1 , there was a significant suppression of the redox reaction at the CNT-OH electrode ( k s < 0.1 × 10 − 4   c m · s − 1 ). Based on the DFT calculations and the Gerischer model, we find that the boosting of the HET from the reduced form of the redox couple to CNT-OH occurs when the reduced forms of the redox couples are negatively charged and the occupied reduced states are aligned with acceptor states of the nanotube electrode. [ABSTRACT FROM AUTHOR]

Li–O2 batteries deliver ultrahigh theoretical specific energy while suffering from low energy efficiency and poor cyclability due to sluggish kinetics of oxygen electrode reactions. Herein, a strategy of engineering interfacial electron structure of MXene‐based composites is presented to boost oxygen electrode reactions for advancing Li–O2 batteries with the cation vacancy‐rich CoSe@MXene (VCo‐CoSe2@MXene) as the case study. The formation of interfacial Co─C bond between VCo‐CoSe2 and Ti3C2 MXene and its enhanced covalency after introducing Co vacancy leads to promoted electron transfer from Ti3C2 MXene to CoSe2 and optimized electronic structure of interfacial Co sites, especially the second Co sites neighboring Co vacancy, which serve as the active centers for oxygen redox reactions. On this basis, VCo‐CoSe2@MXene‐based Li─O2 batteries exhibit low overpotential (0.35 V) and excellent cycling stability (250 cycles at 500 mA g−1). This work proposes an effective strategy to develop MXene‐based electrocatalysts for Li–O2 batteries by tailoring interfacial electron structure. [ABSTRACT FROM AUTHOR]

The covalent organic framework (COF-1) containing triazine group was prepared by solvothermal method, and its structure and morphology were characterized by XRD, BET, FIRT, SEM, TEM, etc. COF-1 was used for the modification of glassy carbon electrodes and subsequently for the detection of dopamine. The experimental results showed that the COF-1 sensor has excellent selectivity, stability, and repeatability for dopamine under optimal conditions. The modified sensor has a good linear relationship to dopamine in the range of 1 to 500 μM with a detection limit of 0.5 μM (S/N = 3). The results show that the electrode reaction process of dopamine on the modified electrode is an adsorption controlled process, and some parameters of the electrochemical process, such as the electron transfer coefficient (α ), the number of transferred electrons (n), and the apparent heterogeneous electron transfer Reaction rate constant k s , has also been calculated. [ABSTRACT FROM AUTHOR]

Porphyrin-based porous organic polymer (POP) with uniformly immobilized platinum nanoparticles (Pt NPs) were designed and synthesized, and it was demonstrated that such nanocomposites (Pt/POP) have oxidase-like activity. Surprisingly, Hg2+ significantly enhanced the oxidase-like activity of Pt/POP. The enhancement was attributed to the capture of Hg2+ by the thioether group in Pt/POP and the subsequent redox reaction of Hg2+ with Pt NPs, accelerating the electron transfer. In the presence of Hg2+, Pt/POP catalyzed the colorless 3,3',5,5'-tetramethylbenzidine (TMB) to turn blue rapidly and changed its absorbance at 652 nm. Based on this, a fast-response colorimetric sensor was constructed for the sensitive detection of Hg2+ with a linear range of 0.2–50 μM and a detection limit of 36.5 nM. Importantly, Pt/POP can be used as an adsorbent for the efficient removal of Hg2+ with a removal efficiency as high as 99.4%. This work provides a valuable strategy for colorimetric detection and efficient removal of Hg2+. [ABSTRACT FROM AUTHOR]

Porphyrin-based porous organic polymer (POP) with uniformly immobilized platinum nanoparticles (Pt NPs) were designed and synthesized, and it was demonstrated that such nanocomposites (Pt/POP) have oxidase-like activity. Surprisingly, Hg2+ significantly enhanced the oxidase-like activity of Pt/POP. The enhancement was attributed to the capture of Hg2+ by the thioether group in Pt/POP and the subsequent redox reaction of Hg2+ with Pt NPs, accelerating the electron transfer. In the presence of Hg2+, Pt/POP catalyzed the colorless 3,3',5,5'-tetramethylbenzidine (TMB) to turn blue rapidly and changed its absorbance at 652 nm. Based on this, a fast-response colorimetric sensor was constructed for the sensitive detection of Hg2+ with a linear range of 0.2–50 μM and a detection limit of 36.5 nM. Importantly, Pt/POP can be used as an adsorbent for the efficient removal of Hg2+ with a removal efficiency as high as 99.4%. This work provides a valuable strategy for colorimetric detection and efficient removal of Hg2+. [ABSTRACT FROM AUTHOR]

Herein, using azo-amine (H2L) and azo-imine (L1–3) ligands, singlet diradical Ni(II) complexes [1] and [2] were synthesized from Ni(0)(COD)2 in THF. In separate reactions, homoleptic NiII complexes, [3a]2+–[3c]2+, were synthesized from [NiII(H2O)6](ClO4)2 and L1–3, respectively. All these complexes were characterized thoroughly. The X-ray structures of [1] and [2] showed that the amine side arm in [1] and the imine side arm in [2] are de-coordinated. The dN–N lengths in these two complexes were found to be ∼1.32 Å, which corresponds to the one-electron reduced azo-bond length. These complexes, [1] and [2], showed 1H NMR signals characteristic of diamagnetic compounds. These studies, along with DFT calculations, indicated that the unpaired spins on ligands coupled antiferromagnetically with the two unpaired spins on NiII to result in s = 0 ground states. Complex [1] showed ligand-based redox-induced dehydrogenation of the distal amine side arm to result in L1. Complexes [3a]2+–[3c]2+ have dN–N lengths of ∼1.27 Å and dC–N lengths of ∼1.28 Å. In cyclic voltammetry, complex [3a]2+ showed four well-resolved reversible reductive waves at 0.5 V to −1.6 V in dichloromethane. The first two waves became irreversible when they were measured in acetonitrile solution. The electron transfer series of [3a]2+ was further characterized by spectro-electrochemistry, EPR, and DFT calculations. These showed that all the reductions were associated with the ligand. It was further probed by redox events in complexes [3b]2+ and [3c]2+. While the electron donor –OMe group on the phenyl ring of the azo moiety in [3b]2+ showed a prominent cathodic shift of the potentials, the –F substitution on the phenyl group on the imine side arm of [3c]2+ has almost no effect. It has to be noted here that the oxidation of [2] by two electrons returns it back to complex [3a]2+. Reduction of [3a]2+ by two electrons also resulted in complex [2], indicating reversible ligand redox-induced hemilability of the imine moiety between [3a]2+ and [2]. Moreover, characterization of the electron transfer series of [3a]2+ and [2] has shown superior redox non-innocent behaviour and coordination ability of the azo-pyridine moiety in nickel(II) complexes over the imino-pyridine moiety of the ligand. [ABSTRACT FROM AUTHOR]

Micropyramid Si/In 2 O 3 /CuO/ZnO photocathode and Ni/BiVO 4 photoanode have been synthesized using a magnetron sputtering method with different conditions and characterized for a photoelectrochemical water-splitting process. The as-designed heterojunction of Si/In 2 O 3 /CuO/ZnO photocathode successfully induces a facile electron transfer to generate hydrogen in 0.5 M H 2 SO 4. Similarly, Ni/BiVO 4 photoanode evolves oxygen in 0.1 M Na 2 B 4 O 7. Both photoreactions are done under concentrated solar-light irradiation (AM 1.5G, 500 mA/cm2). The analysis shows that IPCE values of photocathode and photoanode reached 40 and 60 % at 300 and 400 nm wavelengths, respectively. Furthermore, the ABPE of photocathode and photoanode achieved 14.9% and 0.8% at 0.21 and 1.15 V RHE , respectively. Photoelectrochemical analysis indicates that half cells of the photocathode and photoanode can reach photocurrents of ∼120 and ∼20 mA/cm2 at 0 and 1.23 V RHE , respectively. The outstanding performances indicate a facile charge transfer during redox reactions at the photocathode and photoanode. In addition, combining the photoelectrodes to form a cell configuration of Si/In 2 O 3 /CuO/ZnO//Ni/BiVO 4 with a proton exchange membrane generates an unbiased photocurrent of 0.26 mA/cm2 at 0.55 V RHE. The combined cell has been tested for its stability in splitting water molecules into hydrogen and oxygen, indicating a promising result to overcome energy and environmental issues. [Display omitted] • Micropyramid Si/In 2 O 3 /CuO/ZnO and Ni/BiVO 4 thin-film photoelectrodes are successfully synthesized. • Si/In 2 O 3 /CuO/ZnO photocathode can induce ∼120 mA/cm2 at 0 V RHE under light illumination. • Ni/BiVO 4 photoanode delivers ∼20 mA/cm2 at 1.23 V RHE under light illumination. • The combine cell of Si/In 2 O 3 /CuO/ZnO//Ni/BiVO 4 generates ∼37 mA/cm2 at 1.23 V RHE. • Si/In 2 O 3 /CuO/ZnO//Ni/BiVO 4 cell shows a stability in water-splitting process. [ABSTRACT FROM AUTHOR]

Current industrial use of methane depends mainly on high-temperature conversion, resulting in high energy consumption and catalyst sintering inactivation. In this paper, metal oxide catalysts with different Ni/Cr ratios were obtained by the sol-gel method for the methane activation reaction. The structure-property relationships of the catalysts were investigated by XRD, XPS, H 2 -TPR, TG, N 2 adsorption-desorption, and CV, focusing on the interaction between Ni–Cr in the composite oxide catalysts. The results showed that Ni0–NiCrO 3 /Cr 2 O 3 structure was formed after the Ni–Cr oxides underwent the reduction and calcination process, which provided a structural support for electron transfer between the two metals. The least prone to sintering nickel metal particles and the highest content of high-valent chromium ions were present in Ni 1 Cr 2. XPS confirmed that this counterpart acts as the donor and acceptor for electron transfer in the catalysts, accelerating oxidation-reduction reaction over the catalyst. The catalyst exhibited the most excellent conversion and product selectivity in the methane activation reaction. • The Ni0–NiCrO 3 /Cr 2 O 3 structured catalysts were synthesized. • Ni0 electron rich, easily gives electrons, activation of methane with NiCrO 3. • Highly valent Cr ions are electronegative, attracting electrons from Ni0. • The electron transfer between Ni and Cr accelerated the redox reaction. [ABSTRACT FROM AUTHOR]

The lumen of the endoplasmic reticulum (ER) is usually considered an oxidative environment; however, oxidized thiol-disulfides and reduced pyridine nucleotides occur there parallelly, indicating that the ER lumen lacks components which connect the two systems. Here, we investigated the luminal presence of the thioredoxin (Trx)/thioredoxin reductase (TrxR) proteins, capable of linking the protein thiol and pyridine nucleotide pools in different compartments. It was shown that specific activity of TrxR in the ER is undetectable, whereas higher activities were measured in the cytoplasm and mitochondria. None of the Trx/TrxR isoforms were expressed in the ER by Western blot analysis. Co-localization studies of various isoforms of Trx and TrxR with ER marker Grp94 by immunofluorescent analysis further confirmed their absence from the lumen. The probability of luminal localization of each isoform was also predicted to be very low by several in silico analysis tools. ER-targeted transient transfection of HeLa cells with Trx1 and TrxR1 significantly decreased cell viability and induced apoptotic cell death. In conclusion, the absence of this electron transfer chain may explain the uncoupling of the redox systems in the ER lumen, allowing parallel presence of a reduced pyridine nucleotide and a probably oxidized protein pool necessary for cellular viability. [ABSTRACT FROM AUTHOR]

Olive oil phenols are recognized as molecules with numerous positive health effects, many of which rely on their antioxidative activity, i.e., the ability to transfer hydrogen to radicals. Proton-coupled electron transfer reactions and hydrogen tunneling are ubiquitous in biological systems. Reactions of olive oil phenols, hydroxytyrosol, tyrosol, oleuropein, oleacein, oleocanthal, homovanillyl alcohol, vanillin, and a few phenolic acids with a DPPH• (2,2-diphenyl-1-picrylhydrazyl) radical in a 1,4-dioxane:water = 95:5 or 99:1 v/v solvent mixture were studied through an experimental kinetic analysis and computational chemistry calculations. The highest rate constants corresponding to the highest antioxidative activity are obtained for the ortho-diphenols hydroxytyrosol, oleuropein, and oleacein. The experimentally determined kinetic isotope effects (KIEs) for hydroxytyrosol, homovanillyl alcohol, and caffeic acid reactions are 16.0, 15.4, and 16.7, respectively. Based on these KIEs, thermodynamic activation parameters, and an intrinsic bond orbital (IBO) analysis along the IRC path calculations, we propose a proton-coupled electron transfer mechanism. The average local ionization energy and electron donor Fukui function obtained for the phenolic compounds show that the most reactive electron-donating sites are associated with π electrons above and below the aromatic ring, in support of the IBO analysis and proposed PCET reaction mechanism. Large KIEs and isotopic values of Arrhenius pre-exponential factor AH/AD determined for the hydroxytyrosol, homovanillyl alcohol, and caffeic acid reactions of 0.6, 1.3, and 0.3, respectively, reveal the involvement of hydrogen tunneling in the process. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate that electromerism could be used to regulate the redox reactivity. Electron self‐exchange rates kex were measured for a series of diamagnetic, monocationic CuI complexes with two redox‐active diguanidine ligands and the corresponding paramagnetic, dicationic complexes. The electronic structures of the paramagnetic, dicationic complexes differ. Some complexes are exclusively present as CuII complexes with reduced, neutral diguanidine ligands. In other complexes, an equilibrium is established between the CuII electromer and the CuI electromer with the unpaired electron delocalized on the two partially‐oxidized ligands. For these complexes, the kex values increase with increasing contribution of the CuI electromer. One of the dicationic molecules is exclusively present as CuI complex with radical ligands in dichloromethane at room temperature, and as CuII electromer with neutral ligands at 200 K. Consequently, the electron self‐exchange rate kex is maximal at room temperature, and strongly decreases with decreasing temperature. The temperature effect is much stronger than for similar complexes that remain in the CuII form at all temperatures, demonstrating the use of electromerism to control the redox reactivity on a large scale. [ABSTRACT FROM AUTHOR]

n‐Bu4NI/K2S2O8 mediated transformylation from p‐anisaldehyde to primary amides is reported. The mechanistic studies suggest the reaction occurs via a single electron transfer pathway. Based on the DFT electronic structure calculations of various reaction pathways, the most plausible mechanism involves the formation of a phenyl radical cation and an arenium ion as the key intermediates. It represents the first example where p‐anisaldehyde is employed as a formyl source via a non‐metal mediated Csp2−Csp2 bond cleavage. [ABSTRACT FROM AUTHOR]

Mimicking the enzymatic oxidation of NADH and obtaining mechanistic insight into the electron transfer reaction pertinent to the redox inter-conversion of NADH/NAD+ couple is a long-term challenge in biological and energy-related chemistry. The kinetics and mechanism of the oxidation of NADH by [RuIII(pic)3] (pic– = picolinate anion) has been studied spectrophotometrically and kinetically in aqueous solution at pH 7.0 (MES buffer). The reaction was followed over time at 466 nm (metal to ligand charge transfer band of [RuII(pic)3]–). The rate of NADH oxidation was found to be first-order with respect to Ru(III)-complex concentration. The values of the observed rate constant (kobs) increased linearly with increase in the concentration of NADH. The rate of the reaction was independent of the ionic strength of the reacting solution. Activation parameters (ΔH≠ = 56 ± 1 kJ mol−1 and ΔS≠ = −65 ± 3 J.deg−1 mol−1) were determined from the temperature dependence studies (15-35 °C) of the reaction. Kinetic data and activation parameters are interpreted in terms of a mechanism involving outer-sphere electron transfer. [RuIII(pic)3] (pic− = picolinate anion) effectively oxidizes NADH in an outer-sphere electron transfer pathway. [ABSTRACT FROM AUTHOR]

Rare-earth elements (REEs) are critical to our modern economy, yet their mining from natural ores bears a profound environmental impact. Traditional separation techniques are chemical and energy-intensive because their chemical similarities make REEs very challenging to purify, requiring multiple extraction steps to achieve high purity products. This emphasizes the need for sustainable and straightforward separation methods. Here we introduce a strategy for the direct separation of europium (Eu) from complex mixtures under ambient conditions, leveraging on the redox non innocence of purely inorganic tungsten tetrathiolate (WS42−) ligands. The recovery of Eu is achieved upon reduction of Eu(III) to a Eu(II) coordination polymer, driven by an induced internal electron transfer from the tetrathiotungstate ligand. Applying this strategy to unconventional feedstock such as spent energy-saving lamps allows selective europium recovery with separation factors over 1000 and recovery efficiency as high as 99% without pre-treatment of the waste. Rare-earth elements (REEs) are vital to the modern economy, yet their mining poses both geopolitical and environmental challenges. Here, authors present a highly selective method for the recovery of europium from spent fluorescent lamps using redox active tetrathiotungstate ligands. [ABSTRACT FROM AUTHOR]

Diffusional dynamics of the donor–acceptor distance are responsible for the appearance of a new time scale of diffusion over the distance of electronic tunneling in electron-transfer reactions. The distance dynamics compete with the medium polarization dynamics in the dynamics-controlled electron-transfer kinetics. The pre-exponential factor of the electron-transfer rate constant switches, at the crossover distance, between a distance-independent, dynamics-controlled plateau and exponential distance decay. The crossover between two regimes is controlled by an effective relaxation time slowed down by a factor exponentially depending on the variance of the donor–acceptor displacement. Flexible donor–acceptor complexes must show a greater tendency for dynamics-controlled electron transfer. Energy chains based on electron transport are best designed by placing the redox cofactors near the crossover distance. [ABSTRACT FROM AUTHOR]

Quinones are redox active organic molecules that have been proposed as an alternative choice to metal-based materials in electrochemical energy storage devices. Functionalization allows one to fine tune not only their chemical stability but also the redox potential and kinetics of the electron transfer reaction. However, the reaction rate constant is not only determined by the redox species but also impacted by solvent effects. In this work, we show how the functionalization of benzoquinone with different functional groups impacts the solvent reorganization free energies of electron transfer half-reactions in acetonitrile. The use of molecular density functional theory, whose computational cost for studying the electron transfer reaction is considerably reduced compared to the state-of-the-art molecular dynamics simulations, enables us to perform a systematic study. We validate the method by comparing the predictions of the solvation shell structure and the free energy profiles for electron transfer reaction to the reference classical molecular dynamics simulations in the case of anthraquinone solvated in acetonitrile. We show that all the studied electron transfer half-reactions follow the Marcus theory, regardless of functional groups. Consequently, the solvent reorganization free energy decreases as the molecular size increases. [ABSTRACT FROM AUTHOR]

We report two dinuclear rhenium(V) oxo complexes 1 and 2 types, [ReV(O)(Cl)3(L2−)ReV(O)(Cl)3][NBu4]2 (1, L2− = dianionic 2,5-dihydroxy 1,4-benzoquinone (DBQ2−)) and (2, L2− = dianionic chloranilic acid (CA2−) ligands), as a homogeneous electrocatalyst for water oxidation reactions in the acetonitrile–water mixture. The evolution of dioxygen gas at the anode was confirmed by a GC-TCD study. In controlled potential electrolysis (CPE), oxidation at 1.30 V (vs. Ag/AgCl) at neutral pH, 1 and 2 afforded 1+ [ReVI(O)(Cl)3(DBQ˙3−)ReVI(O)(Cl)3]− and 2+ [ReVI(O)(Cl)3(CA˙3−)ReVI(O)(Cl)3]− ions, respectively, via the redox induced electron transfer (RIET) process. Electrochemically generated species of 1+ and 2+ could be isolated in dry acetonitrile. 1+ and 2+ ions give strong EPR signals in fluid solution as well as under frozen glass conditions due to the [ReVI(O)(Cl)3(L˙3−)ReVI(O)(Cl)3]− ↔ [ReVI(O)(Cl)3(L2−)ReV(O)(Cl)3]− (where L2− = DBQ2− and CA2−) equilibrium. However, the continuation of the CPE study (1.30 V vs. Ag/AgCl) in the presence of acetonitrile–water mixture oxidised the in situ generated species of 1+ and 2+ to higher valent ReVI＝O species. These species (1+ and 2+) bound water through the water nucleophilic attack (WNA) to produce peroxide intermediate species of [ReV(OOH)(Cl)3(DBQ2−)ReV(OOH)(Cl)3] (A1) and [ReV(OOH)(Cl)3(CA2−)ReV(OOH)(Cl)3] (A2) for catalysts 1 and 2, respectively. Interestingly, A1 and A2 were authenticated and analysed by ESI mass spectrometry and infrared spectroscopy and were the active precursors of this water oxidation process. The extent of current generation under similar conditions suggested that complex 1 is superior to complex 2 for the water oxidation reaction. Notably, the maximum turnover frequency (TOFmax) of catalysts 1 and 2 were 2.1 and 1.6 s−1 at 0.27 V and 0.24 V over potential, respectively, which is very significant in WOR. [ABSTRACT FROM AUTHOR]

The antioxidant properties of 21 proteinogenic amino acids (AAs) and 3,4-dioxophenylanine (DOPA) have been studied in implicit water using density functional theory (DFT). All the calculations have been performed according to three oxidation mechanisms: (1) hydrogen-atom transfer (HAT); (2) single electron transfer followed by proton transfer (SET-PT); and (3) sequential proton-loss electron transfer (SPLET). As a result, five AAs with the highest antioxidant capacity have been established: DOPA, selenocysteine (Sec), tyrosine (Tyr), cysteine (Cys), and tryptophan (Trp). Also, global reactivity in terms of hardness/softness has been evaluated, as well as Fukui indices of local reactivity. Trp has been determined as the most reactive molecule, whereas selenium atom of Sec has been established as the most reactive atom. All the findings are in agreement with the recent literature on both experimental and theoretical studies of amino acids antioxidant activity. However, to the best of my knowledge, the calculations for one electron redox reactions of zwitterionic amino acids in implicit water have been performed for the first time. [ABSTRACT FROM AUTHOR]

Contact-electro-catalysis (CEC) is an emerging field that utilizes electron transfer occurring at the liquid–solid and even liquid–liquid interfaces because of the contact-electrification effect to stimulate redox reactions. The energy source of CEC is external mechanical stimuli, and solids to be used are generally organic as well as in-organic materials even though they are chemically inert. CEC has rapidly garnered extensive attention and demonstrated its potential for both mechanistic research and practical applications of mechanocatalysis. This review aims to elucidate the fundamental principle, prominent features, and applications of CEC by compiling and analyzing the recent developments. In detail, the theoretical foundation for CEC, the methods for improving CEC, and the unique advantages of CEC have been discussed. Furthermore, we outline a roadmap for future research and development of CEC. We hope that this review will stimulate extensive studies in the chemistry community for investigating the CEC, a catalytic process in nature. [ABSTRACT FROM AUTHOR]

The low specific capacity determined by the limited electron transfer of p‐type cathode materials is the main obstruction to their application towards high‐performance aqueous zinc‐ion batteries (ZIBs). To overcome this challenge, boosting multi‐electron transfer is essential for improving the charge storage capacity. Here, as a typical heteroaromatic p‐type material, we unveil the unique reversible two‐electron redox properties of phenoxazine in the aqueous electrolytes for the first time. The second oxidation process is stabilized in the aqueous electrolytes, a notable contrast to its less reversibility in the non‐aqueous electrolytes. A comprehensive investigation of the redox chemistry mechanism demonstrates remarkably stable redox intermediates, including a stable cation radical PNO⋅+ characterized by effective electron delocalization and a closed‐shell state dication PNO2+. Meanwhile, the heightened aromaticity contributes to superior structural stability during the redox process, distinguishing it from phenazine, which features a non‐equivalent hybridized sp2‐N motif. Leveraging these synergistic advantages, the PNO electrodes deliver a high capacity of 215 mAh g−1 compared to other p‐type materials, and impressive long cycling stability with 100 % capacity retention over 3500 cycles. This work marks a crucial step forward in advanced organic electrodes based on multi‐electron transfer phenoxazine moieties for high‐performance aqueous ZIBs. [ABSTRACT FROM AUTHOR]

Bimetallic transition metal complexes with site-specific redox properties offer a versatile platform for understanding electron polarization, intramolecular electron transfer processes, and customizing electronic and magnetic properties that might impact reactivity and catalyst design. Inspired by the dissymmetric nickel sites in the Acetyl CoA Synthase (ACS) Active Site, three new bimetallic Ni(N2S2)-Ni(S2C2R2) complexes based on Ni(N2S2) metalloligand donor synthons, Nid, in mimicry of the nickel site distal to the redox-active iron sulfur cluster of ACS, and nickel dithiolene receiver units, designated as Nip, the nickel proximal to the 4Fe4S cluster, were combined to explore the influence of ligand environment on electronic structure and redox properties of each unit. The combination of synthons gave a matrix of three S-bridged dinickel complexes, characterized by X-ray crystallography, and appropriate spectroscopies. Computational modeling is connected to the electronic characteristics of the nickel donor and receiver units. This study demonstrated the intricacies of identifying sites of electrochemical redox processes, within multi-metallic systems containing non-innocent ligands. [ABSTRACT FROM AUTHOR]

Molecularly imprinted polymers (MIPs), functioning as artificial bioreceptors, hold significant promise for biomarker detection in healthcare, disease diagnosis, and addressing drug abuse. In contrast to natural bioreceptors, MIP-based sensors offer numerous advantages, such as high stability, cost-effectiveness, high selectivity, sensitivity, and notably straightforward preparation with customizable binding sites for diverse targets. Conventional MIP sensors often necessitate external redox reagents in analytes to transduce binding events into electrochemical signals for indirect detection, presenting challenges for practical applications in wearables or point-of-care (POC) testing. Redox-active MIP sensors have emerged as a viable alternative, enabling direct and label-free electrochemical detection, with two types developed. The first type utilizes electrocatalytic materials to expedite electron transfer and facilitate a redox reaction between the captured electroactive target and the electrode. The second type incorporates an embedded redox reactive component that allows selective binding of a target to modulate its electron transfer, leading to a change in the electrical signal. This review covers emerging trends and challenges in redox-active MIP sensors for direct electrochemical detection of biomarkers, focusing on sensing mechanisms, synthesis methods, and applications. Additionally, recent progress in wearable and POC redox-active MIP sensors is highlighted. A comprehensive outlook of challenges is further provided, aiming to advance direct biomarker detection for diverse healthcare applications. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs), also named hydrotalcite-like compounds, are anionic clays with a lamellar structure which have been extensively used in the last two decades as electrode modifiers for the design of electrochemical sensors. These materials can be classified into LDHs containing or not containing redox-active centers. In the former case, a transition metal cation undergoing a reversible redox reaction within a proper potential window is present in the layers, and, therefore, it can act as electron transfer mediator, and electrocatalyze the oxidation of an analyte for which the required overpotential is too high. In the latter case, a negatively charged species acting as a redox mediator can be introduced into the interlayer spaces after exchanging the anion coming from the synthesis, and, again, the material can display electrocatalytic properties. Alternatively, due to the large specific surface area of LDHs, molecules with electroactivity can be adsorbed on their surface. In this review, the most significant electroanalytical applications of LDHs as electrode modifiers for the development of voltammetric sensors are presented, grouping them based on the two types of materials. [ABSTRACT FROM AUTHOR]

Lignocellulose flow fuel cells are promising technologies for large scale generation of renewable electricity at low temperature. However, most of them have low electron transfer kinetics and require pre-reaction and redox mediators in anolytes for a liquid-phase catalytic reaction, which leads to low power density, energy consumption and resource waste. Herein, we develop a new low temperature and high-power density lignin flow fuel cell (LFFC) catalyzed by CoMn-LDH electrocatalysts with superhydrophilic intercalation on the anode to efficiently degrade lignin and transfer electrons rapidly. The experiments and DFT calculations show that CoMn-LDH exhibits high adsorption capacity for lignin due to its superhydrophilic intercalation, and has good electrical conductivity due to the greater overlap of antibonding orbitals and high continuity at the Fermi level. Moreover, the abundant oxygen defects of CoMn-LDH can depolymerize lignin effectively. Thus, the prepared CoMn-LDH electrocatalyst enables fast charge transfer and high catalytic efficiency. The power density of the designed LFFC reached 269.3 mW cm−2, and the generated electrical energy is 294.7 mW h based on 1.0 g of lignin, which are obviously higher than those of the reported LFFCs. Furthermore, it can work stably for more than 9 h at 0.3 V and 413.5 mA cm−2, and successfully power a 1.5 V LED pattern with only a 1 cm2 active membrane. It presents a promising approach for developing high-power density LFFCs towards a sustainable society. [ABSTRACT FROM AUTHOR]

The critical role of global electron density transfer (GEDT) in increasing the reaction rate of polar organic reactions has been studied within the framework of Molecular Electron Density Theory (MEDT). To this end, the series of the polar Diels–Alder (P-DA) reactions of cyclopentadiene with cyanoethylene derivatives, for which experimental kinetic data are available, have been chosen. A complete linear correlation between the computed activation Gibbs free energies and the GEDT taking place at the polar transition state structures (TSs) is found; the higher the GEDT at the TS, the lower the activation Gibbs free energy. An interacting quantum atoms energy partitioning analysis allows for establishing a complete linear correlation between the electronic stabilization of the electrophilic ethylene frameworks and the GEDT taking place at the polar TSs. This finding supports Parr's proposal for the definition of the electrophilicity ω index. The present MEDT study establishes the critical role of the GEDT in the acceleration of polar reactions, since the electronic stabilization of the electrophilic framework with the electron density gain is greater than the destabilization of the nucleophilic one, making a net favorable electronic contribution to the decrease in the activation energy. [ABSTRACT FROM AUTHOR]

Seleniivibrio woodruffii strain S4T is an obligate anaerobe belonging to the phylum Deferribacterota. It was isolated for its ability to respire selenate and was also found to respire arsenate. The high-quality draft genome of this bacterium is 2.9 Mbp, has a G+C content of 48%, 2762 predicted genes of which 2709 are protein-coding, and 53 RNA genes. An analysis of the genome focusing on the genes encoding for molybdenum-containing enzymes (molybdoenzymes) uncovered a remarkable number of genes encoding for members of the dimethylsulfoxide reductase family of proteins (DMSOR), including putative reductases for selenate and arsenate respiration, as well as genes for nitrogen fixation. Respiratory molybdoenzymes catalyze redox reactions that transfer electrons to a variety of substrates that can act as terminal electron acceptors for energy generation. Seleniivibrio woodruffii strain S4T also has essential genes for molybdate transporters and the biosynthesis of the molybdopterin guanine dinucleotide cofactors characteristic of the active centers of DMSORs. Phylogenetic analysis revealed candidate respiratory DMSORs spanning nine subfamilies encoded within the genome. Our analysis revealed the untapped potential of this interesting microorganism and expanded our knowledge of molybdoenzyme co-occurrence. [ABSTRACT FROM AUTHOR]

The flavodoxin of Rhodopseudomonas palustris CGA009 (Rp9Fld) supplies highly reducing equivalents to crucial enzymes such as hydrogenase, especially when the organism is iron-restricted. By acquiring those electrons from photodriven electron flow via the bifurcating electron transfer flavoprotein, Rp9Fld provides solar power to vital metabolic processes. To understand Rp9Fld's ability to work with diverse partners, we solved its crystal structure. We observed the canonical flavodoxin (Fld) fold and features common to other long-chain Flds but not all the surface loops thought to recognize partner proteins. Moreover, some of the loops display alternative structures and dynamics. To advance studies of protein-- protein associations and conformational consequences, we assigned the 19F NMR signals of all five tyrosines (Tyrs). Our electrochemical measurements show that incorporation of 3-19F-Tyr in place of Tyr has only a modest effect on Rp9Fld's redox properties even though Tyrs flank the flavin on both sides. Meanwhile, the 19F probes demonstrate the expected paramagnetic effect, with signals from nearby Tyrs becoming broadened beyond detection when the flavin semiquinone is formed. However, the temperature dependencies of chemical shifts and linewidths reveal dynamics affecting loops close to the flavin and regions that bind to partners in a variety of systems. These coincide with patterns of amino acid type conservation but not retention of specific residues, arguing against detailed specificity with respect to partners. We propose that the loops surrounding the flavin adopt altered conformations upon binding to partners and may even participate actively in electron transfer. [ABSTRACT FROM AUTHOR]