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Plasmonic materials are promising photocatalysts as they are well suited to convert light into hot carriers and heat. Hot electron transfer is suggested as the driving force in many plasmon-driven reactions. However, to date, there are no direct molecular measures of the rate and yield of plasmon-to-molecule electron transfer or energy of these electrons on the timescale of plasmon decay. Here, we use ultrafast and spectroelectrochemical surface-enhanced Raman spectroscopy to quantify electron transfer from a plasmonic substrate to adsorbed methyl viologen molecules. We observe a reduction yield of 2.4 to 3.5% on the picosecond timescale, with plasmon-induced potentials ranging from -3.1 to -4.5 mV. Excitingly, some of these reduced species are stabilized and persist for tens of minutes. This work provides concrete metrics toward optimizing material-molecule interactions for efficient plasmon-driven photocatalysis. [ABSTRACT FROM AUTHOR]

Bacterial small laccases (SLAC) are promising industrial biocatalysts due to their ability to oxidize a broad range of substrates with exceptional thermostability and tolerance for alkaline pH. Electron transfer between substrate, copper centers, and O2 is one of the key steps in the catalytic turnover of SLAC. However, limited research has been conducted on the electron transfer pathway of SLAC and SLAC-catalyzed reactions, hindering further engineering of SLAC to produce tunable biocatalysts for novel applications. Herein, the combinational use of electron paramagnetic resonance (EPR) and ultravioletevisible (UV evis) spectroscopic methods coupled with redox titration were employed to monitor the electron transfer processes and obtain further insights into the electron transfer pathway in SLAC. The reduction potentials for type 1 copper (T1Cu), type 2 copper (T2Cu) and type 3 copper (T3Cu) were determined to be 367 ± 2 mV, 378 ± 5 mV and 403 ± 2 mV, respectively. Moreover, the reduction potential of a selected substrate of SLAC, hydroquinone (HQ), was determined to be 288 mV using cyclic voltammetry (CV). In this way, an electron transfer pathway was identified based on the reduction potentials. Specifically, electrons are transferred from HQ to T1Cu, then to T2Cu and T3Cu, and finally to O2. Furthermore, superhyperfine splitting observed via EPR during redox titration indicated a modification in the covalency of T2Cu upon electron uptake, suggesting a conformational alteration in the protein environment surrounding the copper sites, which could potentially influence the reduction potential of the copper sites during catalytic processes. The results presented here not only provide a comprehensive method for analyzing the electron transfer pathway in metalloenzymes through reduction potential measurements, but also offer valuable insights for further engineering and directed evolution studies of SLAC in the aim for biotechnological and industrial applications. [ABSTRACT FROM AUTHOR]

Bioelectrochemical systems hold the promise of enabling sustainable microbial‐mediated energy interconversion between electrical and chemical energy. Herein, it is demonstrated how a single conjugated polymer can be used to enhance bidirectional extracellular electron transfer through forming self‐assembled coatings on individual cells. Specifically, the n‐type conjugated polyelectrolyte p(cNDI‐gT2) exhibits a reduction potential window between −0.1 and −0.8 V (vs Ag/AgCl), thereby driving thermodynamically favored electron transfer in both directions across the abiotic‐biotic interface that involves the outer membrane cytochromes and flavins of Shewanella oneidensis MR‐1. Electrochemical tests show that injection from an external electrode into Shewanella oneidensis MR‐1 is enabled at negative potentials (−0.6 V), while electron extraction is possible at positive potentials (0.2 V). Relative to controls, the biohybrid shows a sixfold increase in biocurrent generation and a 35‐fold increase in current uptake for the bioelectrosynthesis of succinate from fumarate. This demonstrated abiotic‐biotic synergy provides new strategies for designing multifunctional biohybrids. [ABSTRACT FROM AUTHOR]

A series of chemically and biologically relevant N‐(arylthio)phthalimides is synthesized and its electrochemical reduction investigated. The results of the electrochemical study are analysed through application of Savéant's dissociative electron transfer theory and with the assistance of theoretical calculations. Reduction of all investigated N‐(arylthio)phthalimides leads to the corresponding radical anions, followed by the ejection of the phthalimide anion resulting from the dissociation of the N−S chemical bond. This stepwise electron transfer mechanism is evidenced by the electrochemical data which allow determination of the standard reduction potentials of all compounds. In the formation of the N‐(arylthio)phthalimide radical anions, the theoretical calculations show that the incoming electron, is hosted by the phthalimidyl group indicating a homolytic dissociation mechanism. The dissociation rate constants of the radical anions are deduced and show that upon changing the substituent from the MeO, to Me, H, F, Cl and Br the dissociation becomes faster. A good correlation with the Hammett substituent constants is also obtained. Application of Savéant's theory through determination of the associated driving force and the intrinsic barrier energies help rationalize the observed results and show that the change in the dissociation rate constant depends mainly on the standard reduction potential of the parent compounds. [ABSTRACT FROM AUTHOR]

Flavodoxins are enzymes that contain the redox-active flavin mononucleotide (FMN) cofactor and play a crucial role in numerous biological processes, including energy conversion and electron transfer. Since the redox characteristics of flavodoxins are significantly impacted by the molecular environment of the FMN cofactor, the evaluation of the interplay between the redox properties of the flavin cofactor and its molecular surroundings in flavoproteins is a critical area of investigation for both fundamental research and technological advancements, as the electrochemical tuning of flavoproteins is necessary for optimal interaction with redox acceptor or donor molecules. In order to facilitate the rational design of biomolecular devices, it is imperative to have access to computational tools that can accurately predict the redox potential of both natural and artificial flavoproteins. In this study, we have investigated the feasibility of using non-equilibrium thermodynamic integration protocols to reliably predict the redox potential of flavodoxins. Using as a test set the wild-type flavodoxin from Clostridium Beijerinckii and eight experimentally characterized single-point mutants, we have computed their redox potential. Our results show that 75% (6 out of 8) of the calculated reaction free energies are within 1 kcal/mol of the experimental values, and none exceed an error of 2 kcal/mol, confirming that non-equilibrium thermodynamic integration is a trustworthy tool for the quantitative estimation of the redox potential of this biologically and technologically significant class of enzymes. [ABSTRACT FROM AUTHOR]

Coenzyme F430 is a nickel‐containing tetrapyrrole, serving as the prosthetic group of methyl‐coenzyme M reductase in methanogenic and methanotrophic archaea. During coenzyme F430 biosynthesis, the tetrapyrrole macrocycle is reduced by the nitrogenase‐like CfbC/D system consisting of the reductase component CfbC and the catalytic component CfbD. Both components are homodimeric proteins, each carrying a [4Fe‐4S] cluster. Here, the ligands of the [4Fe‐4S] clusters of CfbC2 and CfbD2 were identified revealing an all cysteine ligation of both clusters. Moreover, the midpoint potentials of the [4Fe‐4S] clusters were determined to be −256 mV for CfbC2 and −407 mV for CfbD2. These midpoint potentials indicate that the consecutive thermodynamically unfavorable 6 individual "up‐hill" electron transfers to the organic moiety of the Ni2+‐sirohydrochlorin a,c‐diamide substrate require an intricate interplay of ATP‐binding, hydrolysis, protein complex formation and release to drive product formation, which is a common theme in nitrogenase‐like systems. [ABSTRACT FROM AUTHOR]

The anaerobic region of the gastrointestinal (GI) tract has been replicated in the anaerobic chamber of a microbial fuel cell (MFC). Electroactive biomolecules released by the facultative anaerobes (Providencia rettgeri) under anoxic conditions have been studied for their potential role for redox balance. MALDI study reveals the presence of vitamin B9 (folate), 6-methylpterin, para-aminobenzoic acid (PABA) and pteroic acid called pterin pool. ATR-FTIR studies further confirm the presence of the aromatic ring and side chains of folate, 6-methylpterin and PABA groups. The photoluminescence spectra of the pool exhibit the maximum emission at 420, 425, 440, and 445 nm when excited by 310, 325, 350, and 365 nm wavelengths (day 20 sample) highlighting the presence of tunable bands. The cyclic voltammetric studies indicate the active participation of pterin pool molecules in the transfer of electrons with redox potentials at − 0.2 V and − 0.4 V for p-aminobenzoate and pterin groups, respectively. In addition, it is observed that under prolonged conditions of continuous oxidative stress (> 20 days), quinonoid tetrahydrofolate is formed, leading to temporary storage of charge. The results of the present study may potentially be useful in designing effective therapeutic strategies for the management of various GI diseases by promoting or blocking folate receptors. [ABSTRACT FROM AUTHOR]

Simple Summary: Many biological systems contain iron–sulfur clusters, which are typically found as components of electron transport proteins. Continuum electrostatic calculations were used to investigate the effect of protein environment on the redox properties of the three iron–sulfur clusters in the cyanobacterial photosystem I. Our results show a good correlation between the estimated and the measured reduction potential. Moreover, the results indicate that the low potential of FX is shown to be due to the interactions with the surrounding residues and ligating sulfurs. Our results will help in understanding the electron transfer reaction in photosystem I. Photosystem I is a light-driven electron transfer device. Available X-ray crystal structure from Thermosynechococcus elongatus showed that electron transfer pathways consist of two nearly symmetric branches of cofactors converging at the first iron–sulfur cluster FX, which is followed by two terminal iron–sulfur clusters FA and FB. Experiments have shown that FX has lower oxidation potential than FA and FB, which facilitates the electron transfer reaction. Here, we use density functional theory and Multi-Conformer Continuum Electrostatics to explain the differences in the midpoint E m potentials of the FX, FA and FB clusters. Our calculations show that FX has the lowest oxidation potential compared to FA and FB due to strong pairwise electrostatic interactions with surrounding residues. These interactions are shown to be dominated by the bridging sulfurs and cysteine ligands, which may be attributed to the shorter average bond distances between the oxidized Fe ion and ligating sulfurs for FX compared to FA and FB. Moreover, the electrostatic repulsion between the 4Fe-4S clusters and the positive potential of the backbone atoms is lowest for FX compared to both FA and FB. These results agree with the experimental measurements from the redox titrations of low-temperature EPR signals and of room temperature recombination kinetics. [ABSTRACT FROM AUTHOR]

Biocatalysts are widely used in industry, but few examples of the use of oxidoreductases, in which enzymatic function often requires electrons, have been reported. NADPH is a cofactor that supplies an electron to oxidoreductases, but is consequently inactivated and no longer able to act as an electron donor. NADP+ can not receive electrons from electrodes through straightforward electrochemistry owing to its complicated three-dimensional structure. This study reports that bipyridines effectively mediate electron transfer between an electrode and NADP+, allowing them to serve as electron mediators for NADPH production. Using bipyridines, quinones, and anilines, which have negative oxidation–reduction potentials, an electrochemical investigation was conducted into whether electrons were transferred to NADP+. Only bipyridines with a reduction potential near -1.0 V exhibited electron transfer. Furthermore, the NADPH production level was measured using spectroscopy. NADPH was efficiently produced using bipyridines, such as methyl viologen and ethyl viologen, in which the bipyridyl 1- and 1'-positions bear small substituents. However, methyl viologen caused a dehydrogenation reaction of NADPH, making it unsuitable as an electron mediator for NADPH production. The dehydrogenation reaction did not occur using ethyl viologen. These results indicated that NADP+ can be reduced more effectively using substituents that prevent a dehydrogenation reaction at the bipyridyl 1- and 1'-positions while maintaining the reducing power. [ABSTRACT FROM AUTHOR]

Extracellular electron transfer (EET) is a bioelectrochemical process performed by electrochemically active bacteria (EAB) found in host-associated environments, including plant and animal ecosystems and fermenting plant- and animal-derived foods. Through direct or mediated electron transfer pathways, certain bacteria use EET to enhance ecological fitness with host-impacting effects. In the plant rhizosphere, electron acceptors support the growth of EAB such as Geobacter , cable bacteria, and some clostridia that can result changing iron and heavy metal uptake by plants. In animal microbiomes, EET is associated with diet-derived iron in the intestines of soil-dwelling termites, earthworms, and beetle larvae. EET is also associated with the colonization and metabolism of some bacteria in human and animal microbiomes, such as Streptococcus mutans in the mouth, Enterococcus faecalis and Listeria monocytogenes in the intestine, and Pseudomonas aeruginosa in the lungs. During the fermentation of plant tissues and bovine milk, lactic acid bacteria like Lactiplantibacillus plantarum and Lactococcus lactis may use EET to increase their growth and food acidification, as well as decrease environmental oxidation–reduction potential. Thus, EET is likely an important metabolic pathway for host-associated bacteria and has implications for ecosystem function, health and disease, and biotechnological applications. [ABSTRACT FROM AUTHOR]

Sediment microbial fuel cell (SMFC) is a type of MFC without a proton exchange membrane. However, SMFC have had problems with low-power production performance. In this paper, the effects of native bacteria (K1) in oily sludge and their electro-oil-induced domestication on the power generation and oil removal performance of SMFC were studied. The results showed that K1 belonged to Ochrobactrum intermedium. During the domestication process, an upward trend was shown in the OD600 and ORP values in the culture medium, and it grown best at 0.7 V. Ochrobactrum intermedium K1 significantly increased the average output voltage, electromotive force, and maximum power density of SMFC and reduced the apparent internal resistance of the battery. The maximum power density was 169.43 mW/m3, which was 8.59 times higher than that of the control group. Ochrobactrum intermedium K1 improved the degradation of crude oil by SMFC. Ochrobactrum intermedium K1 enhanced the degradation of high-carbon alkanes and even-carbon alkanes in n-alkanes. Cyclic voltammetry and chronoamperometry tests showed that after acclimation, Ochrobactrum intermedium K1 improved the extracellular electron transfer efficiency (EET) mediated by c-Cyts and flavin by increasing the surface protein redox potential. [ABSTRACT FROM AUTHOR]

A ternary arrow down dual S-scheme nano photocatalyst ZnIn2S4/Bi2O2CO3/ZnFe2O4 composed of microspheres of ZnIn2S4, layered Bi2O2CO3, and magnetic ZnFe2O4 has been prepared for RhB degradation. The ZnIn2S4/Bi2O2CO3/ZnFe2O4 degraded 99.8% of RhB in 90 min, and its photocatalytic activity toward RhB degradation was highest as compared to pure ZnIn2S4 (36.38%), Bi2O2CO3 (19.56%), ZnFe2O4 (16.65%) and binary Bi2O2CO3/ZnFe2O4 (43.82%) composite. The Langmuir–Hinshelwood kinetics model was found for RhB degradation for all photocatalysts. The rate constant of the ZnIn2S4/Bi2O2CO3/ZnFe2O4 hybrid photocatalyst was 0.177 min−1, which is 12.73, 29.84, and 38.06 times greater than pure ZnIn2S4, Bi2O2CO3, and ZnFe2O4, respectively. UV–Vis, EIS, and PL measurements indicate that the synergistic effect is brought on by an expanded range of light absorption, lower charge separation resistance, and decreased recombination of e−/h+ pairs. The significant decrease in photocatalytic activity with radical scavengers established that •O2−, •OH, and h+ were the active free radicals, and •O2− was the leading one during the degradation of RhB. The dual S-scheme electron transfer mechanism has been proposed because lesser energy electrons and holes were destroyed, and charge carriers with higher redox potentials were retained. The photocatalysts' good magnetic separation and photostability were confirmed after four reuse cycles and maintained 87% degradation efficiency. [ABSTRACT FROM AUTHOR]

Cyanoarene-based photocatalysts (PCs) have attracted significant interest owing to their superior catalytic performance for radical anion mediated photoredox catalysis. However, the factors affecting the formation and degradation of cyanoarene-based PC radical anion (PC•‒) are still insufficiently understood. Herein, we therefore investigate the formation and degradation of cyanoarene-based PC•‒ under widely-used photoredox-mediated reaction conditions. By screening various cyanoarene-based PCs, we elucidate strategies to efficiently generate PC•‒ with adequate excited-state reduction potentials (Ered*) via supra-efficient generation of long-lived triplet excited states (T1). To thoroughly investigate the behavior of PC•‒ in actual photoredox-mediated reactions, a reductive dehalogenation is carried out as a model reaction and identified the dominant photodegradation pathways of the PC•‒. Dehalogenation and photodegradation of PC•‒ are coexistent depending on the rate of electron transfer (ET) to the substrate and the photodegradation strongly depends on the electronic and steric properties of the PCs. Based on the understanding of both the formation and photodegradation of PC•‒, we demonstrate that the efficient generation of highly reducing PC•‒ allows for the highly efficient photoredox catalyzed dehalogenation of aryl/alkyl halides at a PC loading as low as 0.001 mol% with a high oxygen tolerance. The present work provides new insights into the reactions of cyanoarene-based PC•‒ in photoredox-mediated reactions. Cyanoarene-based photocatalysts are widely used due to their catalytic performance, but the formation of the active species and its potential degradation pathways are poorly understood. Here, the authors investigate these pathways under commonly-used photoredox-mediated reaction conditions. [ABSTRACT FROM AUTHOR]

During extracellular electron transfer, Geobacter sulfurreducens constitutively expresses the bc‐cytochrome CbcL, yet cells containing only this menaquinone oxidase fail to respire above −0.1 V vs. SHE. By identifying mutations within cbcL that permit growth at higher potentials, we provide evidence that this cytochrome is regulated by redox potential. Strains expressing only CbcLV205A, CbcLV205G, and CbcLF525Y were capable of growth with high potential electron acceptors including Fe(III) citrate, Mn(IV) oxides, and electrodes poised at +0.1 V vs. SHE. Electrochemical characterization of wild type CbcL revealed oxidative inactivation of electron transfer above −0.1 V, while CbcLV205A, CbcLV205G, and CbcLF525Y remained active. Growth yields of CbcLV205A, CbcLV205G, and CbcLF525Y were only 50 % of WT, consistent with CbcL‐dependent electron transfer conserving less energy. These data support the hypothesis that CbcL has evolved to rapidly shut off in response to redox potential, in order to divert electrons to higher yield oxidases that coexist in the Geobacter membrane. [ABSTRACT FROM AUTHOR]

Nitrate (NO3−-N) and nitrites (NO2−-N) are common pollutants in various water bodies causing serious threats not only to aquatic, but also to animals and human beings. In this study, we developed a strategy for efficiently reducing nitrates in microbial fuel cells (MFCs) powered by a granular activated carbon (GAC)-biocathode. GAC was developed by acclimatizing and enriching denitrifying bacteria under a redox potential (0.3 V) generated from MFCs. Thus, using the formed GAC-biocathode we continued to study their effect on denitrification with different cathode materials and circulation speeds in MFCs. The GAC-biocathode with its excellent capacitive property can actively reduce nitrate for over thirty days irrespective of the cathode material used. The stirring speed of GAC in the cathode showed a steady growth in potential generation from 0.25 V to 0.33 V. A rapid lag phase was observed when a new carbon cathode was used with enriched GAC. While a slow lag phase was seen when a stainless-steel cathode was replaced. These observations showed that effective storage and supply of electrons to the GAC plays a crucial role in the reduction process in MFCs. Electrochemical analysis of the GAC properties studied using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and zeta potential showed distinct properties with different abiotic and biocathode conditions. We found that the enrichment of electrotrophic bacteria on GAC facilitates the direct electron transfer in the cathode chamber for reducing NO3−-N in MFCs as observed by scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Photo-induced charge separation, which is terminated by electron transfer from the primary quinone QA to the secondary quinone QB, provides the driving force for O2 evolution in photosystem II (PSII). However, the backward charge recombination using the same electron-transfer pathway leads to the triplet chlorophyll formation, generating harmful singlet-oxygen species. Here, we investigated the molecular mechanism of proton-mediated QA·- stabilization. Quantum mechanical/molecular mechanical (QM/MM) calculations show that in response to the loss of the bicarbonate ligand, a low-barrier H-bond forms between D2-His214 and QA·-. The migration of the proton from D2-His214 toward QA·- stabilizes QA·-. The release of the bicarbonate ligand from the binding Fe2+ site is an energetically uphill process, whereas the bidentate-to-monodentate reorientation is almost isoenergetic. These suggest that the bicarbonate protonation and decomposition may be a basis of the mechanism of photoprotection via QA-/QAH· stabilization, increasing the QA redox potential and activating a charge-recombination pathway that does not generate the harmful singlet oxygen. [ABSTRACT FROM AUTHOR]

Ferredoxin (Fdx) is regarded as the main electron carrier in biological electron transfer and acts as an electron donor in metabolic pathways of many organisms. Here, we screened a self-sufficient P450-derived reductase PRF with promising production yield of 9OHAD (9α-hydroxy4-androstene-3,17-dione) from AD, and further proved the importance of [2Fe–2S] clusters of ferredoxin-oxidoreductase in transferring electrons in steroidal conversion. The results of truncated Fdx domain in all oxidoreductases and mutagenesis data elucidated the indispensable role of [2Fe–2S] clusters in the electron transfer process. By adding the independent plant-type Fdx to the reaction system, the AD (4-androstene-3,17-dione) conversion rate have been significantly improved. A novel efficient electron transfer pathway of PRF + Fdx + KshA (KshA, Rieske-type oxygenase of 3-ketosteroid-9-hydroxylase) in the reaction system rather than KshAB complex system was proposed based on analysis of protein–protein interactions and redox potential measurement. Adding free Fdx created a new conduit for electrons to travel from reductase to oxygenase. This electron transfer pathway provides new insight for the development of efficient exogenous Fdx as an electron carrier. [ABSTRACT FROM AUTHOR]

Predicting the redox behavior of organic contaminants and heavy metals in soils is challenging because there are few soil redox potential (E h) models. In particular, current aqueous and suspension models usually show a significant deviation for complex laterites with few Fe(II). Here, we measured the E h of simulated laterites over a range of soil conditions (2450 tests). The impacts of soil pH, organic carbon, and Fe speciation on the Fe activity were quantified as Fe activity coefficients, respectively, using a two-step Universal Global Optimization method. Integrating these Fe activity coefficients and electron transfer terms into the formula significantly improved the correlation of measured and modeled E h values (R 2 = 0.92), and the estimated E h values closely matched the relevant measured E h values (accuracy R 2 = 0.93). The developed model was further verified with natural laterites, presenting a linear fit and accuracy R 2 of 0.89 and 0.86, respectively. These findings provide compelling evidence that integrating Fe activity into the Nernst formula could accurately calculate the E h if the Fe(III)/Fe(II) couple does not work. The developed model could help to predict the soil E h toward controllable and selective oxidation-reduction of contaminants for soil remediation. [Display omitted] • Soil pH, organic carbon, and Fe speciation impacted Fe activities were quantified. • An E h model of red soils was established with the integration of Fe activity. • The model showed high linear fit and accuracy correlation coefficients (R 2 > 0.90). • The established model presented high applicability for natural red soils. [ABSTRACT FROM AUTHOR]

[Display omitted] • Promotion or inhibition of sludge AD by HAs depended on their redox potentials. • HAs presence and ORP influenced microbial activity, but not to microbial community. • HAs with lower ORP have stronger capability in interspecies and intracellular electron transfers. • A novel mechanism of HAs influence mediated by their ORP on sludge AD was proposed. Thermal hydrolysis pretreatment has been widely employed to improve sludge anaerobic digestion (AD), but also results in excessive releases of humic acids (HAs) from sludge. The influences of HAs on sludge AD recently have resulted in ever-increasing concerns, but those reported results are not consistent and sometimes even contradictory. The results in the present study indicated whether HAs promote or inhibit sludge AD mainly depends on their redox potentials. Generally, the HAs derived from sludge with low redox potentials were seemingly facilitative to sludge AD, whereas commercial HAs with high redox potentials presented inhibitory effects. In fact, the influences of HAs on each stage of sludge AD, namely hydrolysis, acidification and methanogenesis, were also quite different, and mostly the differences were related to HAs redox potentials. Mechanism analysis indicated HAs with different redox potentials did not evidently influence microbial community profile, but resulted in noticeable changes in microbial activities. Protease and α-glucosidase activities were substantially inhibited by HAs, which became more pronounced as HAs redox potentials decreased from 154 to −238 mV. The relative activity of F 420 was shifted to 89.1 %, 104.1 %, 121.3 %, 92.4 % and 73.2 % with the additions of HAs at redox potentials of 154, −63, −392, −419 and −458 mV, respectively. Furthermore, the presence of HAs accelerated interspecies electron transfer and assisted ferredoxin (Fd) in intracellular electron transfer of methanogens. HAs with too high (≫ −398 mV) or too low (≪ −398 mV) redox potentials were not conducive to methanogenesis. The findings of this study could forcefully clarify those contradictory results reported recently about the influences of HAs on sludge AD. Overall, all the findings in this present study indicate that it is of great necessity to regulate sludge thermal hydrolysis based on the redox potentials of released HAs. [ABSTRACT FROM AUTHOR]

In comparison to metal complexes, organic photosensitive dyes employed in photocatalytic hydrogen production exhibit promising developmental prospects. Utilizing the organic dye molecule TA+0 as the foundational structure, a series of innovative organic dyes, denoted as TA1-1 to TA2-6, were systematically designed. Employing first-principles calculations, we methodically explored the modifying effects of diverse electron-donating groups on the R1 and R2 positions to assess their application potential. Our findings reveal that, relative to the experimentally synthesized TATA+03, the TA2-6 molecule boasts a spatial structure conducive to intramolecular electron transfer, showcasing the most negative reduction potential (Ered = -2.11 eV) and the maximum reaction driving force (ΔG02 = -1.26 eV). This configuration enhances its compatibility with the reduction catalyst, thereby facilitating efficient hydrogen evolution. The TA2-6 dye demonstrates outstanding photophysical properties and a robust solar energy capture capacity. Its maximum molar extinction coefficient (ε) stands at 2.616 x 104 M-1·cm-1, representing a remarkable 292.8% improvement over TATA+03. In conclusion, this research underscores the promising potential of the TA2-6 dye as an innovative organic photosensitizer, positioning it as an efficacious component in homogeneous photocatalytic systems. [ABSTRACT FROM AUTHOR]

Geobacter sulfurreducens utilizes extracellular electron acceptors such as Mn(IV), Fe(III), syntrophic partners, and electrodes that vary from +0.4 to −0.3 V versus standard hydrogen electrode (SHE), representing a potential energy span that should require a highly branched electron transfer chain. Here we describe CbcBA, a bc‐type cytochrome essential near the thermodynamic limit of respiration when acetate is the electron donor. Mutants‐lacking cbcBA ceased Fe(III) reduction at −0.21 V versus SHE, could not transfer electrons to electrodes between −0.21 and −0.28 V, and could not reduce the final 10%–35% of Fe(III) minerals. As redox potential decreased during Fe(III) reduction, cbcBA was induced with the aid of the regulator BccR to become one of the most highly expressed genes in G. sulfurreducens. Growth yield (CFU/mM Fe(II)) was 112% of WT in ∆cbcBA, and deletion of cbcL (an unrelated bc‐cytochrome essential near −0.15 V) in ΔcbcBA increased yield to 220%. Together with ImcH, which is required at high redox potentials, CbcBA represents a third cytoplasmic membrane oxidoreductase in G. sulfurreducens. This expanding list shows how metal‐reducing bacteria may constantly sense redox potential to adjust growth efficiency in changing environments. [ABSTRACT FROM AUTHOR]

Despite the oxidation mechanism of antimonite (Sb(Ⅲ)) by biosynthesized iron nanoparticles (Fe NPs) has been reported, the impact of coexisting components in acid mine drainage (AMD) on the Sb(III) oxidation by Fe NPs is unknown. Herein, how the coexisting components in AMD affect Sb(Ⅲ) oxidation by Fe NPs was investigated. Firstly, Fe NPs achieved complete oxidation of Sb(Ⅲ) (100%), while only 65.0% of Sb(Ⅲ) was oxidized when As(Ⅲ) was added, due to competitive oxidation between As(Ⅲ) and Sb(Ⅲ), which was verified by characterization analysis. Secondly, the decline in solution pH improved Sb(Ⅲ) oxidation from 69.5% (pH 4) to 100% (pH 2), which could be attributed to the rise of Fe3+ in solution promoting the electron transfer between Sb(Ⅲ) and Fe NPs. Thirdly, the oxidation efficiencies of Sb(Ⅲ) fell by 14.9 and 44.2% following the addition of oxalic and citric acid, respectively, resulting from the fact that these two acids reduced the redox potential of Fe NPs, thereby inhibiting Sb(Ⅲ) oxidation by Fe NPs. Finally, the interference effect of coexisting ions was studied, where PO 4 3− significantly reduced Sb(Ⅲ) oxidation efficiency due to the occupation of the surface-active sites on Fe NPs. Overall, this study has significant implications for the prevention of Sb contamination in AMD. [Display omitted] • Impact of coexisting ions in AMD on the Sb(Ⅲ) oxidation was investigated. • Competitive oxidation between As(Ⅲ) and Sb(Ⅲ) was observed. • Organic acids inhibited oxidation of Sb(Ⅲ). • PO 4 3− significantly reduced Sb(Ⅲ) oxidation efficiency. [ABSTRACT FROM AUTHOR]

Cytochrome P450 reductase (CYPOR) provides electrons to all human microsomal cytochrome P450s (cyt P450s). The length and sequence of the "140s" FMN binding loop of CYPOR has been shown to be a key determinant of its redox potential and activity with cyt P450s. Shortening the "140s loop" by deleting glycine-141(ΔGly141) and by engineering a second mutant that mimics flavo-cytochrome P450 BM3 (ΔGly141/Glu142Asn) resulted in mutants that formed an unstable anionic semiquinone. In an attempt to understand the molecular basis of the inability of these mutants to support activity with cyt P450, we expressed, purified, and determined their ability to reduce ferric P450. Our results showed that the ΔGly141 mutant with a very mobile loop only reduced ~7% of cyt P450 with a rate similar to that of the wild type. On the other hand, the more stable loop in the ΔGly141/Glu142Asn mutant allowed for ~55% of the cyt P450 to be reduced ~60% faster than the wild type. Our results reveal that the poor activity of the ΔGly141 mutant is primarily accounted for by its markedly diminished ability to reduce ferric cyt P450. In contrast, the poor activity of the ΔGly141/Glu142Asn mutant is presumably a consequence of the altered structure and mobility of the "140s loop". [ABSTRACT FROM AUTHOR]

The non-classical bacterial peroxidase from Escherichia coli, YhjA, is proposed to deal with peroxidative stress in the periplasm when the bacterium is exposed to anoxic environments, defending it from hydrogen peroxide and allowing it to thrive under those conditions. This enzyme has a predicted transmembrane helix and is proposed to receive electrons from the quinol pool in an electron transfer pathway involving two hemes (NT and E) to accomplish the reduction of hydrogen peroxide in the periplasm at the third heme (P). Compared with classical bacterial peroxidases, these enzymes have an additional N-terminal domain binding the NT heme. In the absence of a structure of this protein, several residues (M82, M125 and H134) were mutated to identify the axial ligand of the NT heme. Spectroscopic data demonstrate differences only between the YhjA and YhjA M125A variant. In the YhjA M125A variant, the NT heme is high-spin with a lower reduction potential than in the wild-type. Thermostability was studied by circular dichroism, demonstrating that YhjA M125A is thermodynamically more unstable than YhjA, with a lower TM (43 °C vs. 50 °C). These data also corroborate the structural model of this enzyme. The axial ligand of the NT heme was validated to be M125, and mutation of this residue was proven to affect the spectroscopic, kinetic, and thermodynamic properties of YhjA. [ABSTRACT FROM AUTHOR]

Quinones play important roles in biological electron transfer reactions in almost all organisms, with specific roles in many physiological processes and chemotherapy. Quinones participate in two-electron, two-proton reactions in aqueous solution at equilibrium near neutral pH, but protons often lag behind the electron transfers. The relevant reactions in proteins are often sequential one electron redox processes without involving protons. Here we report the aprotic electrochemistry of the two half-couples, Q/Q.- and Q.−/Q=, of 11 parent quinones and 118 substituted 1,4-benzoquinones, 91 1,4-naphthoquinones, and 107 9,10-anthraquinones. The measured redox potentials are fit quite well with the Hammett para sigma (σ para) parameter. Occasional exceptions can involve important groups, such as methoxy substituents in ubiquinone and hydroxy substituents in therapeutics. These can generally be explained by reasonable conjectures involving steric clashes and internal hydrogen bonds. We also provide data for 25 other quinones, 2 double quinones and 15 non-quinones, all measured under similar conditions. • In aprotic solvents quinones are reduced to stable semiquinones (Q−) and to Q=. • Substituents effects on related quinone E m s generally follow Hammett predictions. • The ubiquinone E m is anomalous due to steric crowding of the methoxy groups. • α-Hydroxyquinone E m s are anomalous due to hydrogen bonding to the quinone oxygens. [ABSTRACT FROM AUTHOR]

2D/2D semimetal 1T′ phase MoS 2 /ZnIn 2 S 4 (1T′-MoS 2 /ZnIn 2 S 4) S-Scheme heterojunction has been prepared by a simple hydrothermal method. The 1T′-MoS 2 /ZnIn 2 S 4 2D/2D S-Scheme heterojunction presents excellent photocatalytic activity for hydrogen production without the addition of noble metal co-catalysts. [Display omitted] Heterojunction engineering is an effective strategy to improve photocatalytic performance. Two-dimensional (2D)/2D semimetal 1T′ phase molybdenum sulfide/zinc indium sulfide (1T′-MoS 2 /ZnIn 2 S 4) S-scheme heterojunctions with tight and stable interfaces were synthesized by a simple hydrothermal synthesis method. Under the optimal 1T′-MoS 2 loading ratio (5 wt%), the hydrogen production rate of 1T′-MoS 2 /ZnIn 2 S 4 composites reaches 11.42 mmol h−1 g−1, which is 3.1 and 1.4 times higher than that of pure ZnIn 2 S 4 (2.9 mmol h−1 g−1) and ZnIn 2 S 4 /Pt (8.01 mmol h−1 g−1), and the apparent quantum efficiency (AQE) reaches 53.17 % (λ = 370 nm). Semimetal 1T′ phase MoS 2 on ZnIn 2 S 4 broadens the light absorption range, enhances the light absorption ability, promotes electron transfer, and offers abundant active sites. The establishment of S-scheme heterojunctions achieves the spatial separation of photogenerated charges and increases the reduction potential. This work provides insights for the design of novel photocatalysts. [ABSTRACT FROM AUTHOR]

Samarium diiodide is a versatile single electron transfer (SET) agent with various applications in organic chemistry. Lewis structures regularly insinuate the existence of a ketyl radical when samarium diiodide binds a carbonyl group. The study presented here investigates this electron transfer by the means of computational chemistry. All electron CASPT2 calculations with the inclusion of scalar relativistic effects predict an endotherm electron transfer from samarium diiodide to acetone. Energies calculated with the PBE0-D3(BJ) functional and a small core pseudopotential are in good agreement with CASPT2. The calculations confirm the experimentally measured increase of the samarium diiodide reduction potential through the addition of hexamethylphosphoramide also known as HMPA. [ABSTRACT FROM AUTHOR]

The preparation of Fe-MMT/WO 3 composites by the hydrothermal method has been explored in this study for the construction of a chemical and photocatalytic catalyst for the reduction of U (VI). This research found that the visible light absorption and reduction potential of the Fe-MMT/WO 3 composites were relatively superior compared to Fe-MMT and WO 3 alone. Based on an evaluation of the performance of the Fe-MMT/WO 3 composites under visible light irradiation, it was discovered that they had greater uranium extraction capacity, where the maximum extraction capacity of U (VI) was determined to be 1862.69 mg g−1, with removal efficiency reaching 93.32%. To investigate the electron transfer and U (VI) to U (IV) reduction mechanisms after the composite, XPS and DFT calculations were conducted. Results showed that Fe (II) is converted to a higher state Fe (III) and WO 3 produce photoelectrons which together reduce U (VI) to U (IV). Moreover, the photoelectrons partially transferred to Fe-MMT with low reduction potential to reduce Fe (III) to Fe (II), allowing iron cycling during uranium extraction to be achieved. [Display omitted] • Fe-MMT/WO 3 showed the excellent U extraction performance without sacrificial agents. • Fe-MMT/WO 3 extract uranium through a chemical-photocatalytic reduction process. • Fe-MMT/WO 3 produces photoelectrons for iron cycling and uranium reduction. • The extraction capacity of 1862.69 mg g−1 with an efficiency over 93.36% was achieved. [ABSTRACT FROM AUTHOR]

Exoelectrogenic microorganisms are in the spotlight due to their unique respiratory mechanisms and potential applications in distinct biotechnological fields, including bioremediation, bioenergy production and microbial electrosynthesis. These applications rely on the capability of these microorganisms to perform extracellular electron transfer, a mechanism that allows the bacteria to transfer electrons to the cell's exterior by establishing functional interfaces between different multiheme cytochromes at the inner membrane, periplasmic space, and outer membrane. The multiheme cytochrome CbcL from Geobacter sulfurreducens is associated to the inner membrane and plays an essential role in the transfer of electrons to final electron acceptors with a low redox potential, as Fe(III) oxides and electrodes poised at −100 mV. CbcL has a transmembranar di-heme b -type cytochrome domain with six helices, linked to a periplasmic cytochrome domain with nine c -type heme groups. The complementary usage of ultraviolet-visible, circular dichroism and nuclear magnetic resonance permitted the structural and functional characterization of CbcL's periplasmic domain. The protein was found to have a high percentage of disordered regions and its nine hemes are low-spin and all coordinated by two histidine residues. The apparent midpoint reduction potential of the CbcL periplasmic domain was determined, suggesting a thermodynamically favorable transfer of electrons to the putative redox partner in the periplasm − the triheme cytochrome PpcA. The establishment of a redox complex between the two proteins was confirmed by probing the electron transfer reaction and the molecular interactions between CbcL and PpcA. The results obtained show for the first time how electrons are injected into the periplasm of Geobacter sulfurreducens for subsequent transfer to the cell's exterior. [ABSTRACT FROM AUTHOR]

Microbial extracellular reduction of insoluble compounds requires soluble electron shuttles that diffuse in the environment, freely diffusing cytochromes, or direct contact with cellular conductive appendages that release or harvest electrons to assure a continuous balance between cellular requirements and environmental conditions. In this work, we produced and characterized the three cytochrome domains of PgcA, an extracellular triheme cytochrome that contributes to Fe(III) and Mn(IV) oxides reduction in Geobacter sulfurreducens. The three monoheme domains are structurally homologous, but their heme groups show variable axial coordination and reduction potential values. Electron transfer experiments monitored by NMR and visible spectroscopy show the variable extent to which the domains promiscuously exchange electrons while reducing different electron acceptors. The results suggest that PgcA is part of a new class of cytochromes - microbial heme-tethered redox strings - that use low-complexity protein stretches to bind metals and promote intra- and intermolecular electron transfer events through its cytochrome domains. [ABSTRACT FROM AUTHOR]

Cytochrome b561 proteins (CYB561s) are integral membrane proteins with six trans-membrane domains, two heme-b redox centers, one on each side of the host membrane. The major characteristics of these proteins are their ascorbate reducibility and trans-membrane electron transferring capability. More than one CYB561 can be found in a wide range of animal and plant phyla and they are localized in membranes different from the membranes participating in bioenergization. Two homologous proteins, both in humans and rodents, are thought to participate—via yet unidentified way—in cancer pathology. The recombinant forms of the human tumor suppressor 101F6 protein (Hs_CYB561D2) and its mouse ortholog (Mm_CYB561D2) have already been studied in some detail. However, nothing has yet been published about the physical-chemical properties of their homologues (Hs_CYB561D1 in humans and Mm_CYB561D1 in mice). In this paper we present optical, redox and structural properties of the recombinant Mm_CYB561D1, obtained based on various spectroscopic methods and homology modeling. The results are discussed in comparison to similar properties of the other members of the CYB561 protein family. [ABSTRACT FROM AUTHOR]

Periodontitis is a chronic disease caused by bacteria (e.g. Porphyromonas gingivalis, P.gingivalis) that currently lacks effective non-invasive treatment options. Sonodynamic therapy (SDT) is an emerging non-invasive antimicrobial therapeutic strategy. Since ultrasonic tooth cleaning is widely used in dental treatments, SDT has significant potential for the facile implementation of treat periodontitis. However, hypoxia in periodontitis severely limits the effectiveness of traditional sonosensitizers. To address this issue, we have developed a new sonosensitizer termed as TPP-TeV, which combines the traditional sonosensitizer tetraphenylporphyrin (TPP) with a new photosensitizer telluroviologen (TeV). Under ultrasound radiation, TPP-TeV can produce numerous cationic free radicals (TPP-TeV•), which subsequently generate ROS free radicals (O 2 •−, •OH) efficiently via electron transfer mechanism, resulting in the effective killing of anaerobic P.gingivalis both in vivo and in vitro. As a result, the dental environment is improved, and the inhibition rate of alveolar bone loss reaches 80 %. The introduction of tellurium into the viologen molecule induces changes in its reduction potential, resulting in increased rigidity of the molecule. This modification systematically reduces the biotoxicity of our novel sonosensitizer by 75 % at 50 μM based on bacterial experiments. These promising findings could potentially establish new options for sonodynamic therapy (SDT) in periodontitis clinical treatments. A novel sonosensitizer, TPP-TeV, has been discovered to efficiently generate telluroviologen cationic radicals via electron transfer mechanism upon US radiation, forming ROS (O 2 •-, •OH), which can effectively kill anaerobic P.gingivalis both in vitro and in vivo. This finding suggests that ultrasonic tooth cleaning, a common dental treatment, may also serve as a periodontitis treatment. Additionally, by comparing the biotoxicity of TPP-V and TPP-TeV, it was found that the introduction of tellurium atoms into the viologen molecule reduced its reduction potential and increased its molecular rigidity, leading to reduced molecular toxicity. This work provides a new strategy to the design of new sonosensitizers for periodontitis sonodynamic therapy. [Display omitted] [ABSTRACT FROM AUTHOR]

• The fermi level difference forms electric field to drive photo generated electrons. • The PDA modification decreased the overall fouling rate of the membrane. • The ternary heterojunction increases the proportion of reversible fouling. • After three cycles, the flux of the prepared membrane decreased only slightly. • The prepared membrane can remove sulfamethazine and inhibit bacterial growth. The development of multifunctional membranes with anti-fouling and self-cleaning properties holds significant research importance in the field of wastewater purification as membrane fouling has long been a scientific challenge in the treatment of organic wastewater. Using polydopamine-modified polyvinylidene fluoride as the carrier and a CeO 2 @Ag/Ag 2 MoO 4 ternary heterojunction as the core, a photocatalytic membrane system is built in this work. By sacrificing the reduction potential of the photoinduced electrons in the heterojunction, the gradient Fermi level is designed to drive the photogenerated electrons from Ag 2 MoO 4 and CeO 2 towards Ag, thereby increasing the production of oxidizing radicals •OH. This rational design has broad-spectrum anti-fouling capabilities against membrane pollutants, including organic molecules, proteins and bacteria, and can efficiently suppress the recombination of photogenerated electrons and holes. We examine the self-cleaning and anti-fouling characteristics of the photocatalytic membrane using bovine serum albumin as a model pollutant. The flux recovery rate of the CeO 2 @Ag/Ag 2 MoO 4 -polydopamine/polyvinylidene fluoride photocatalytic membrane increases by 27.8 % in comparison to pure polyvinylidene fluoride, while its irreversible fouling rate decreases from 32.0 % to 3.8 %. Simultaneously, the membrane demonstrates remarkable photocatalytic activity for sulfamethazine, achieving a removal rate surpassing 95.4 % in less than 80 min. Upon testing four distinct strains of Gram-positive/negative bacteria, the photocatalytic membrane demonstrates over 80 % antibacterial effectiveness. This study therefore provides a new method for creating effective and multipurpose photocatalytic membranes. [ABSTRACT FROM AUTHOR]

[Display omitted] Photocatalytic technology is of great significance in environmental purification due to its eco-friendly and cost-effective operations. However, low charge-transfer efficiency restricts the photocatalytic activity of the catalyst. Herein, we report Cs 2 SnBr 6 /C 3 N 4 composite catalysts that exhibit a robust interfacial electron exchange thereby enhancing photocatalytic nitric oxide (NO) oxidation. A comprehensive study has demonstrated the S-scheme electron transfer mechanism. Benefiting from the interfacial internal electric field, the C-Br bond serves as a direct electron transfer channel, resulting in enhanced charge separation. Furthermore, the S-scheme heterojunction effectively traps high redox potential electrons and holes, leading to the production of abundant reactive oxygen radicals that enhance photocatalytic NO abatement. The NO removal rate of the Cs 2 SnBr 6 /C 3 N 4 heterogeneous system can reach 86.8 %, which is approximately 3-fold and 18-fold that of pristine C 3 N 4 and Cs 2 SnBr 6 , respectively. The comprehensive understanding of the electron transfer between heterojunction atomic interfaces will provide a novel perspective on efficient environmental photocatalysis. [ABSTRACT FROM AUTHOR]

Photosystem I is a key component of primary energy conversion in oxygenic photosynthesis. Electron transfer reactions in Photosystem I take place across two parallel electron transfer chains that converge after a few electron transfer steps, sharing both the terminal electron acceptors, which are a series of three iron–sulphur (Fe-S) clusters known as F X , F A , and F B , and the terminal donor, P 700 . The two electron transfer chains show kinetic differences which are, due to their close geometrical symmetry, mainly attributable to the tuning of the physicochemical reactivity of the bound cofactors, exerted by the protein surroundings. The factors controlling the rate of electron transfer between the terminal Fe-S clusters are still not fully understood due to the difficulties of monitoring these events directly. Here we present a discussion concerning the driving forces associated with electron transfer between F X and F A as well as between F A and F B , employing a tunnelling-based description of the reaction rates coupled with the kinetic modelling of forward and recombination reactions. It is concluded that the reorganisation energy for F X − oxidation shall be lower than 1 eV. Moreover, it is suggested that the analysis of mutants with altered F A redox properties can also provide useful information concerning the upstream phylloquinone cofactor energetics. [ABSTRACT FROM AUTHOR]

On the basis of first-principles calculations and non-adiabatic molecular dynamics (NAMD) simulations, we explore the photocatalytic water splitting properties of PtSSe/ζ-Phosphorene heterostructure. This heterostructure possess semiconducting nature with high carrier mobility (≈ 103 cm2V− 1s− 1). The calculated high value of electron-hole recombination rate as compared to electron transfer rate and hole transfer rate, establish the Type-II mechanism more favorable for PtSSe/ζ-Phosphorene heterostructure. Further, the calculated value of solar-to-hydrogen (STH) conversion efficiency of PtSSe/ζ-Phosphorene exceeds to 10%, which makes it the potential candidate for commercial production of hydrogen for industrial use. STH conversion efficiency is further tunable on rotating one monolayer over other with specific angles in the heterostructure. Our study demonstrates PtSSe/ζ-Phosphorene heterostructure to be efficient Type II-scheme photocatalyst for water splitting. [ABSTRACT FROM AUTHOR]

The combination of micron zero-valent iron (mZVI) and microorganisms is an effective method for trichloroethylene (TCE) degradation, but electron transfer efficiency needs improvement. A new chem-bio hybrid process using a composite material (S-ZVI@biochar) was developed, consisting of sulfurized mZVI and biochar as a chemical remover, and Shewanella oneidensis MR-1 and dechlorinating bacteria (DB) as a biological agent for TCE degradation. S-ZVI@biochar showed improved stability, biocompatibility, and TCE removal compared to ZVI and S-ZVI. The hybrid system DB + MR-1 + S-ZVI@biochar exhibited the highest TCE removal efficiency at 96.5% after 30 days, which was 3.7 times higher than that of bare ZVI. The study revealed that the enhanced dechlorination performance was due to improved electron transfer efficiency, adjustment of microbial community structure, and iron recycling. S-ZVI@biochar constructed electron transport channels in the composite system, improving the overall dechlorination capacity. This system shows promise for long-term TCE removal in anaerobic environments. [ABSTRACT FROM AUTHOR]

Background: Nitrogen (N) is a crucial element for increasing photosynthesis and crop yields. The study aims to evaluate the photosynthetic regulation and yield formation mechanisms of different nodulating peanut varieties with N fertilizer application. Method: The present work explored the effect of N fertilizer application rates (N0, N45, N105, and N165) on the photosynthetic characteristics, chlorophyll fluorescence characteristics, dry matter, N accumulation, and yield of four peanut varieties. Results: The results showed that N application increased the photosynthetic capacity, dry matter, N accumulation, and yield of peanuts. The measurement of chlorophyll a fluorescence revealed that the K-phase, J-phase, and I-phase from the OJIP curve decreased under N105 treatment compared with N0, and WOI, ET0/CSM, RE0/CSM, ET0/RC, RE0/RC, φPo, φEo, φRo, and Ψ0 increased, whereas VJ, VI, WK, ABS/RC, TR0/RC, DI0/RC, and φDo decreased. Meanwhile, the photosystem activity and electron transfer efficiency of nodulating peanut varieties decreased with an increase in N (N165). However, the photosynthetic capacity and yield of the non-nodulating peanut variety, which highly depended on N fertilizer, increased with an increase in N. Conclusion: Optimized N application (N105) increased the activity of the photosystem II (PSII) reaction center, improved the electron and energy transfer performance in the photosynthetic electron transport chain, and reduced the energy dissipation of leaves in nodulating peanut varieties, which is conducive to improving the yield. Nevertheless, high N (N165) had a positive effect on the photosystem and yield of non-nodulating peanut. The results provide highly valuable guidance for optimizing peanut N management and cultivation measures. [ABSTRACT FROM AUTHOR]

Conventional advanced oxidation processes (AOPs) require significant external energy consumption to eliminate emerging contaminants (ECs) with stable structures. Herein, a catalyst consisting of nanocube BiCeO particles (BCO‐NCs) prepared by an impregnation‐hydrothermal process is reported for the first time, which is used for removing ECs without light/electricity or any other external energy input in water and simultaneous in situ generation of H2O2. A series of characterizations and experiments reveal that dual reaction centers (DRC) which are similar to the valence band/conducting band structure are formed on the surface of BCO‐NCs. Under natural conditions without any external energy consumption, the BCO‐NCs self‐purification system can remove more than 80% of ECs within 30 min, and complete removal of ECs within 30 min in the presence of abundant electron acceptors, the corresponding second‐order kinetic constant is increased to 3.62 times. It is found that O2 can capture electrons from ECs through the Bi─O─Ce bond bridge during the reaction process, leading to the in situ production of H2O2. This work will be a key advance in reducing energy consumption for deep wastewater treatment and generating important chemical raw materials. [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]

Biochar can facilitate Cr(VI) bioreduction, but it is still undetermined which biochar property control this process. We observed that the apparent Cr(VI) bioreduction by Shewanella oneidensis MR-1 could be identified as a fast and a relatively slow processes. The fast-bioreduction rates (r f0) were 2–15 times higher than the slow-bioreduction rates (r s0). In this study, we investigated the kinetics and efficiency of biochar in promoting Cr(VI) reduction by S. oneidensis MR-1 in the neutral solution using a "dual-process model" (fast and slow processes), and analyzed the mechanisms of biochar concentration, conductivity, particle size and other properties on these two processes. The correlation analysis of these rate constants and biochar properties was carried out. The fast-bioreduction rates were associated with higher conductivity and smaller particle sizes of biochar, which facilitated the direct electron transfer from Shewanella oneidensis MR-1 to Cr(VI). The Cr(VI) slow-bioreduction rates (r s0) were mainly determined by the electron donating capability of biochar and independent of the cell concentration. Our results suggested that Cr(VI) bioreduction was mediated by both electron conductivity and redox potential of biochar. This result is instructive for biochar production. Manipulating biochar properties to control fast and slow Cr(VI) reduction may be helpful to effectively remove or detoxify Cr(VI) in the environment. [Display omitted] • Biochar conductivity and size dominate the Cr(VI) fast-bioreduction process. • EDC of biochar dominates the Cr(VI) slow-bioreduction process. • Biochar could improve the slow-bioreduction rates by the detoxification effect. [ABSTRACT FROM AUTHOR]

Dual strategies on energy band modulation and surface charge utilization have been employed to fundamentally actualize the photocatalytic CO 2 reduction performance of Bi 4 MoO 9 materials. Herein, N-doped carbon quantum dots (N-CQDs) decorated Bi 4 MoO 9 nanoparticles was successfully synthesized, in which N -CQDs advanced the CO 2 molecule adsorption capacity as well as the excited carriers' separation efficiency. After 5h light irradiation, N-CQDs/Bi 4 MoO 9 -2 composite exhibited more than 3 times higher CO yield rate than pure Bi 4 MoO 9 nanoparticles. [Display omitted] Owing to the exorbitant CO 2 activation energy and unsatisfactory photogenerated charge separation efficiency, CO 2 photoconversion still faces enormous challenges. In this study, a directional electron transfer channel has been established by decorating N-doped carbon quantum dots (N-CQDs) on the surface of Bi 4 MoO 9 nanoparticles to ensure that more active electrons can participate in the CO 2 reduction. The conduction band of Bi 4 MoO 9 nanoparticles is calculated to be −1.55 eV versus the normal hydrogen electrode (NHE), pH = 7, which is negative enough to attain the photocatalytic CO 2 reduction potential of −0.53 eV versus NHE, pH = 7. CO 2 adsorption curves and in situ Fourier transform infrared spectra reveal that N-CQDs facilitate surface CO 2 adsorption and activation, as well as CO desorption. In addition, steady-state photoluminescence and photoelectrochemical tests prove that the charge separation efficiency can be greatly enhanced by constructing N-CQDs/Bi 4 MoO 9 composites. In the presence of pure water, N-CQDs/Bi 4 MoO 9 -2 composite achieved a CO yield of 16.22 μmol g−1 after 5 h Xe light illumination, which was 3.24 times higher than that of pure Bi 4 MoO 9 (4.98 μmol g−1). This study offers a distinctive approach to the optimization of Bi 4 MoO 9 photocatalysts and their application in energy conversion. [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 growing energy consumption and the need for a circular economy have driven considerable interest in the anaerobic digestion (AD) of organic waste, offering potential solutions through biogas and digestate production. AD processes not only have the capability to reduce greenhouse gas emissions but also contribute to the production of renewable methane. This comprehensive review aims to consolidate prior research on AD involving different feedstocks. The principles of AD are explored and discussed, including both chemical and biological pathways and the microorganisms involved at each stage. Additionally, key variables influencing system performance, such as temperature, pH, and C/N ratio are also discussed. Various pretreatment strategies applied to enhance biogas generation from organic waste in AD are also reviewed. Furthermore, this review examines the conversion of generated digestate into biochar through pyrolysis and its utilization to improve AD performance. The addition of biochar has demonstrated its efficacy in enhancing metabolic processes, microorganisms (activity and community), and buffering capacity, facilitating Direct Interspecies Electron Transfer (DIET), and boosting CH4 production. Biochar also exhibits the ability to capture undesirable components, including CO2, H2S, NH3, and siloxanes. The integration of digestate-derived biochar into the circular economy framework emerges as a vital role in closing the material flow loop. Additionally, the review discusses the environmental benefits derived from coupling AD with pyrolysis processes, drawing on life cycle assessment investigations. Techno-economic assessment (TEA) studies of the integrated processes are also discussed, with an acknowledgment of the need for further TEA to validate the viability of integrating the biochar industry. Furthermore, this survey examines the techno-economic and environmental impacts of biochar production itself and its potential application in AD for biogas generation, aiming to establish a more cost-effective and sustainable integrated system. [ABSTRACT FROM AUTHOR]

The key factors in achieving high energy efficiency for proton exchange membrane fuel cells are reducing overpotential and increasing the oxygen reduction rate. Based on first-principles calculations, we induce H atom adsorption on 4 × 4 × 1 monolayer MoSe2 to induce spin polarization, thereby improving the catalytic performance. In the calculation of supercells, the band unfolding method is used to address the band folding effect in doped systems. Furthermore, it is evident from analyzing the unique energy band configuration of MoSe2 that a higher valley splitting value has better catalytic effects on the oxygen reduction reaction. We believe that the symmetries of the distinct adsorption site result in different overpotentials. In addition, when an even number of hydrogen atoms is adsorbed, the monolayer MoSe2 has no spin polarization. The spin can affect the electron transfer process and alter the hybrid energy with the reaction products, thereby regulating its catalytic performance. [ABSTRACT FROM AUTHOR]

The use of non–precious metals for electrocatalytic hydrogen reaction (HER) is particularly important for energy conservation and environmental protection. In this work, three new cobalt corroles containing o−, m−, and p−nitrobenzyl (1, 2, 3) at the meso 10−position of the corrole macrocycle were synthesized, and their electrocatalytic hydrogen evolution reaction in organic and neutral aqueous systems was also investigated. The results show that these three cobalt corroles have significant catalytic HER activity in both systems, and the catalytic efficiency follows 1 > 3 > 2, which indicates that the position of the nitro group can affect the catalytic property of the complexes. In the organic phase, when using trifluoroacetic acid or p−toluenesulfonic acid as the proton source, the electrocatalytic HER may undergo an EECC (E: electron transfer, C: proton coupling) pathway. In a neutral aqueous system, the HER turnover frequency value of 1 is up to 137.4 h−1 at 938 mV overpotential. [ABSTRACT FROM AUTHOR]

Photoactive supramolecular porphyrin assemblies are attractive molecules for light‐harvesting applications. This is due to their relatively non‐toxicity, biological activities and charge and energy exchange characteristics. However, the extreme cost associated with their synthesis and requirements for toxic organic solvents during purification pose a challenge to the sustainability characteristics of their applications. This work presents the first report on the sustainable synthesis, spectroscopic and photophysical characterizations of a near‐infrared (NIR) absorbing Ca(II)‐meso‐tetrakis (4‐hydroxyphenyl)porphyrin using an electrolyzed pyrrole solution. The latter was obtained by cycling the pyrrole solution across the silver nanodumbbell particle surface at room temperature. The electrolyzed solution condensed readily with acidified p‐hydroxybenzaldehyde, producing the targeted purple porphyrin. The non‐electrolyzed pyrrole solution formed a green substance with significantly different optical properties. Remarkable differences were observed in the voltammograms of the silver nanodumbbell particles and those of the conventional gold electrode during the pyrrole cycling, suggesting different routes of porphyrin formation. The rationale behind these formations and the associated mechanisms were extensively discussed. Metalation with aqueous Ca2+ ion caused a Stokes shift of 38.75 eV. The current study shows the advantage of the electrochemical method towards obtaining sustainable light‐harvesting porphyrin at room temperature without the need for high‐energy‐dependent conventional processes. [ABSTRACT FROM AUTHOR]

In the design of photoelectrocatalytic cells, a key element is effective photogeneration of electron‐hole pairs to drive redox activation of catalysts. Despite recent progress in photoelectrocatalysis, experimental realization of a high‐performance photocathode for multi‐electron reduction of chemicals, such as nitrate reduction to ammonia, has remained a challenge due to difficulty in obtaining efficient electrode configurations for extraction of high‐throughput electrons from absorbed photons. This work describes a new design for catalytic photoelectrodes using chromophore assembly‐functionalized covalent networks for boosting eight‐electron reduction of nitrate to ammonia. Upon sunlight irradiation, the photoelectrode stores a mass of reducing equivalents at the photoexcited chromophore assembly for multielectron reduction of a copper catalyst, enabling efficient nitrate reduction to ammonia. By introducing the new photoelectrode structure, it is demonstrated that the electronic interplay between charge photo‐accumulating assembly and multi‐electron redox catalysts can be optimized to achieve proper balance between electron transfer dynamics and thermodynamic output of photoelectrocatalytic systems. [ABSTRACT FROM AUTHOR]

The genome—the source of life and platform of evolution—is continuously exposed to harmful factors, both extra- and intra-cellular. Their activity causes different types of DNA damage, with approximately 80 different types of lesions having been identified so far. In this paper, the influence of a clustered DNA damage site containing imidazolone (Iz) or oxazolone (Oz) and 7,8-dihydro-8-oxo-2′-deoxyguanosine (OXOdG) on the charge transfer through the double helix as well as their electronic properties were investigated. To this end, the structures of oligo-Iz, d[A1Iz2A3OXOG4A5]*d[T5C4T3C2T1], and oligo-Oz, d[A1Oz2A3OXOG4A5]*d[T5C4T3C2T1], were optimized at the M06-2X/6-D95**//M06-2X/sto-3G level of theory in the aqueous phase using the ONIOM methodology; all the discussed energies were obtained at the M06-2X/6-31++G** level of theory. The non-equilibrated and equilibrated solvent–solute interactions were taken into consideration. The following results were found: (A) In all the discussed cases, OXOdG showed a higher predisposition to radical cation formation, and B) the excess electron migration toward Iz and Oz was preferred. However, in the case of oligo-Oz, the electron transfer from Oz2 to complementary C4 was noted during vertical to adiabatic anion relaxation, while for oligo-Iz, it was settled exclusively on the Iz2 moiety. The above was reflected in the charge transfer rate constant, vertical/adiabatic ionization potential, and electron affinity energy values, as well as the charge and spin distribution. It can be postulated that imidazolone moiety formation within the CDL ds-oligo structure and its conversion to oxazolone can significantly influence the charge migration process, depending on the C2 carbon hybridization sp2 or sp3. The above can confuse the single DNA damage recognition and removal processes, cause an increase in mutagenesis, and harm the effectiveness of anticancer therapy. [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]