Taking Advantage of Potential Coincidence Region: Insights into Gas Production Behavior in Advanced Self-Activated Hydrazine-Assisted Alkaline Seawater Electrolysis.

Water electrolysis assisted by hydrazine has emerged as a prospective energy conversion method for achieving efficient hydrogen generation. Due to the potential coincidence region (PCR) between the hydrogen evolution reaction (HER) and the electro-oxidation of hydrazine, the hydrazine oxidation reaction (HzOR) offers distinct advantages in terms of strategy amalgamation, device architecture, and the broadening of application horizons. Herein, we report a bifunctional electrocatalyst of interfacial heterogeneous Fe2P/Co2P microspheres supported on Ni foam (FeCoP/NF). Benefiting from the strong interfacial coupling effect between Fe2P and Co2P and the three-dimensional microsphere structure, FeCoP/NF exhibits outstanding bifunctional electrocatalytic performance, achieving 10 mA cm-2 with low overpotentials of 10 and 203 mV for HER and HzOR, respectively. Utilizing FeCoP/NF for both electrodes in HzOR-assisted water electrolysis results in significantly reduced potentials of 820 mV for 1 A cm-2 in contrast to the electro-oxidation of alternative chemical substrates. The presence of a potential coincidence region makes the application of self-activated seawater electrolysis realistic. The gas production behavior at different current densities in this interesting hydrogen production system is discussed, and some rules that are distinguished from conventional water electrolysis are summarized. Furthermore, a new self-powered hydrogen production system with a direct hydrazine fuel cell, rechargeable Zn-hydrazine battery, and hydrazine-assisted seawater electrolysis is proposed, emphasizing the distinct benefits of HzOR and its potential role in electrochemical energy conversion technologies powered by renewable sources.

Synthesis of paeonol hydrazone derivatives and their anti-oomycete, anti-fungal, and nematicidal activities.

BACKGROUND: The natural product paeonol is a rich and sustainable natural bioresource, and its derivatives have various unique biological efficacy. As is well known, Schiff bases are a class of organic compounds with a wide range of biological activities, including anti-fungal, insecticidal, anti-viral, and nematicidal. RESULTS: To discover biorational natural product-based pesticides, nine intermediates (2-10), 12 sulfonylhydrazones (11a-11c, 12a-12c, 13a-13c, and 14a-14c) and 20 benzylidene hydrazones (18a-18r, 19a, and 20a) were synthesized by structural modification of paeonol, and their structures were characterized by proton nuclear magnetic resonance (1H NMR), carbon-13 (13C) NMR, and high-resolution mass spectrometry (HRMS). The stereochemical configurations of compounds 14a, 18d, and 18r were unambiguously confirmed by single-crystal X-ray diffraction. Furthermore, bioactivities of these compounds as anti-oomycete, anti-fungal, and nematicidal agents against three serious agricultural pests, Phytophthora capsici, Fusarium graminearum, and Heterodera glycines were evaluated. Among all tested compounds: (i) compound 7 exhibited promising anti-oomycete against Phytophthora capsici, with a half maximal effective concentration (EC50) value of 15.81 mg L-1; (ii) compounds 2, 7, 10, and 19a displayed promising anti-fungal against F. graminearum, with EC50 values of 12.22, 14.72, 23.39, and 33.10 mg L-1, respectively; (iii) ten compounds (12a-12c, 14c, 18g-18j, 18m, and 19a) showed significant nematicidal activity against H. glycines, with median lethal concentration (LC50) values all less than 30.00 mg L-1. Especially for compound 18g, its LC50 value is the smallest, at 12.65 mg L-1. CONCLUSION: The research results indicate that introducing nitro groups at the C5 position of paeonol, or introducing halogens at both C5 and C3 positions, can significantly enhance its biological activity against Phytophthora capsici, F. graminearum, and H. glycines. © 2024 Society of Chemical Industry.

Data on the temporal changes in soil properties at the emergency crash site of the launch vehicle 'Soyuz-FG' in Kazakhstan.

On October 11, 2018, in the Ulytau region of the Republic of Kazakhstan, the Soyuz-FG launch vehicle carrying a crewed MS-10 spacecraft failed, creating two areas where rocket propellants spilled and soil condition was monitored in 2018, 2019, 2022 and 2023. This article presents data on the content of pollutants, namely unsymmetrical dimethylhydrazine (UDMH), nitrosodimethylamine (NDMA) and total petroleum hydrocarbons (TPH), total N, organic carbon, exchangeable Ca and Mg, water-soluble NO3-, NO2-, HCO3-, CO3 2-, SO4 2-, Cl-, K +, Na+, pH values, cation exchange capacity and electrical conductivity of the water extract in disturbed and background Aridisols (more than 200 samples in total). This data set contains information on interseasonal (autumn 2022 and spring 2023) differences in the content and vertical differentiation of some soil properties in Aridisols in Central Kazakhstan. In autumn, the content of TPH, water-soluble Cl- and SO4 2- and alkalinity from CO3 2- is 1.4, 235, 201, and 2 times higher, respectively, and the content of total N and water-soluble NO3 - and NO2 -, alkalinity from HCO3 - is 2.4, 1.4, 6.4 and 1.9 times lower, respectively (p < 0.05). In spring and autumn, the content of exchangeable Ca and Mg, cation exchange capacity did not differ significantly. The presented materials can be used to optimize restoration of disturbed arid ecosystems and future monitoring work at sites of regular landing of the first stages and emergency crash sites of launch vehicles.

Fluorescence Recognition of Hydrazine Driven by Neighboring Group Participation.

Hydrazine (N2H4) has toxic effects on the environment. Although a variety of reactive probes have been used to identify hydrazine, practical applications required continuous development of hydrazine fluorescent probes with improved performance. Here, we applied the neighboring group participation (NGP) to the design of a fluorescent probe for hydrazine. The probe exhibited a rapid response to N2H4 and strong anti-interference ability, with detection limited to 0.031 µmol/L. Theoretical calculation showed that the energy barrier could be reduced by NGP. The cyclic intermediate formed by the indole ring and the α-ester carbonyl group significantly reduced the activation energy of the reaction. Practically, the probe could detect hydrazine in actual water samples.

Pt-decorated spinel MnCo2O4 nanosheets enable ampere-level hydrazine assisted water electrolysis.

Coupling hydrazine oxidation reaction (HzOR) with hydrogen evolution reaction (HER) has been widely concerned for high efficiency of green hydrogen preparation with low energy consumption. However, the lacking of bifunctional electrodes with ampere-level performance severely limits its industrialization. Herein, we put forward an efficient active site anchored strategy for MnCo2O4 nanosheet arrays on nickel foam (NF) by introducing Pt species (denoted as Pt-MnCo2O4/NF), which is standing for excellent bifunctional electrodes. The Pt-MnCo2O4/NF delivers ultralow potentials of -195 mV and 350 mV at 1000 mA cm-2 as well as robust stability for HzOR and HER, respectively. The study of in-situ Raman and reaction kinetics reveal that the formation of key adsorbed *NH2 and *N2H4 intermediates and the rapidly oxidization of intermediates with a fast interfacial charge transfer on Pt-MnCo2O4/NF. Remarkably, the Pt-MnCo2O4/NF assembled two-electrode hydrazine assisted water electrolyzer realizes current density of 100 mA cm-2 and 1000 mA cm-2 at 0.16 V and 0.62 V with over 80 h stability. This work provides a promising way to design efficient electrodes for energy-saving H2 generation under ampere-level current density.

Induced genetic diversity through mutagenesis in wheat gene pool and significant use of SCoT markers to underpin key agronomic traits.

BACKGROUND: This research explores the efficacy of mutagenesis, specifically using sodium azide (SA) and hydrazine hydrate (HZ) treatments, to introduce genetic diversity and enhance traits in three wheat (Triticum aestivum L.) genotypes. The experiment entails subjecting the seeds to different doses of SA and HZ and cultivating them in the field for two consecutive generations: M1 (first generation) and M2 (second generation). We then employed selective breeding techniques with Start Codon Targeted (SCoT) markers to select traits within the wheat gene pool. Also, the correlation between SCoT markers and specific agronomic traits provides insights into the genetic mechanisms underlying mutagenesis-induced changes in wheat. RESULTS: In the study, eleven genotypes were derived from parent varieties Sids1, Sids12, and Giza 168, and eight mutant genotypes were selected from the M1 generation and further cultivated to establish the M2 generation. The results revealed that various morphological and agronomical characteristics, such as plant height, spikes per plant, spike length, spikelet per spike, grains per spikelet, and 100-grain weight, showed increases in different genotypes from M1 to M2. SCoT markers were employed to assess genetic diversity among the eleven genotypes. The bioinformatics analysis identified a correlation between SCoT markers and the transcription factors ABSCISIC ACID INSENSITIVE3 (ABI3) and VIVIPAROUS1 (VP1), crucial for plant development, growth, and stress adaptation. A comprehensive examination of genetic distance and the function identification of gene-associated SCoT markers may provide valuable insights into the mechanisms by which SA and HZ act as mutagens, enhancing wheat agronomic qualities. CONCLUSIONS: This study demonstrates the effective use of SA and HZ treatments to induce gene diversity through mutagenesis in the wheat gene pool, resulting in the enhancement of agronomic traits, as revealed by SCoT markers. The significant improvements in morphological and agronomical characteristics highlight the potential of mutagenesis techniques for crop improvement. These findings offer valuable information for breeders to develop effective breeding programs to enhance wheat quality and resilience through increased genetic diversity.

A Julolidine Aldehyde Dansyl Hydrazine Schiff Base as Fluorescence Chemosensor for Zn2+ ions Recognition and its Application.

The Schiff base fluorescent probe (Dz-Jul), containing julolidine aldehyde and dansyl hydrazine, was derived using a simple condensation. This chemosensor showed high selectivity towards Zn2+ and quick response (170 s) in DMSO/H2O solutions (8/2, v/v, pH 7.2 buffer). A fluorometric titration determined that Dz-Jul-Zn2+ has a binding ratio of 1:1, and the association constant (Ka) is 1.03 × 105 M-1. The Dz-Jul detection limit of Zn2+ ions was 15 nM, much lower than the WHO standard (76.0 nM). DFT, ESI mass, and FTIR spectral demonstrated a plausible complexation mode between Dz-Jul and Zn2+ ions. In actual water samples, Zn2+ has been detected with good detection performance using Dz-Jul. Additionally, Dz-Jul-coated test strips allowed for rapid and qualitative monitoring of Zn2+ ions in a visible manner.

Electrocatalysis Using Cobalt Porphyrin Covalently Linked with Multi-Walled Carbon Nanotubes: Hydrazine Sensing and Hydrazine-Assisted Green Hydrogen Synthesis.

Acid-treated multi-walled carbon nanotube (MWCNT) covalently functionalized with cobalt triphenothiazine porphyrin (CoTriPTZ-OH) A3B type porphyrin, containing three phenothiazine moieties (represented as MWCNT-CoTriPTZ) is synthesized and characterized by various spectroscopic and microscopic techniques. The nanoconjugate, MWCNT-CoTriPTZ, exhibits a pair of distinct redox peaks due to the Co2+/Co3+ redox process in 0.1 M pH 7.0 phosphate buffer. Further, it electrocatalytically oxidizes hydrazine at a low overpotential with a high current. This property is advantageously utilized for the sensitive determination of hydrazine. The developed electrochemical sensor exhibits high sensitivity (0.99 µAµM-1cm-2), a low limit of detection (4.5 ppb), and a broad linear calibration range (0.1 µM to 3.0 mM) for the determination of hydrazine. Further, MWCNT-CoTriPTZ is exploited for hydrazine-assisted green hydrogen synthesis. The high efficiency of hydrazine oxidation is confirmed by the low onset potential (0.45 V (vs RHE)) and 0.60 V (vs RHE) at the current density of 10 mA.cm-2. MWCNT-CoTriPTZ displays a high current density (77.29 mA.cm-2) at 1.45 V (vs RHE).

A Pyrazine-Based Chromophore Photophysical Properties and its Detection for Hydrazine and Acid Vapors.

Designed and synthesized linear pyrazine-based D-π-A-π-A probe is investigated to study the colorimetric and emission properties with different polarity index solvents. Their molar extinction coefficients were estimated for each solvent. This TLP probe was investigated in THF/water binary solution aggregates, and a redshifted AIE was observed reaching a water fraction of 70%. Also, this TLP probe was applied to the multifunctional, rapid, sensitive and selective detection of acid-base (TFA/TEA) and hydrazine (N2H4) in colorimetric and fluorimetric sensors. The pyrazine unit probe demonstrated an acidochromic effect and explored the acid-sensing behavior. The TLP probe containing malononitrile functional groups has extensively detected hazardous hydrazine species due to nucleophilic attack of hydrazine at the α-position of dicyano. This TLP probe allowed the quick and fast-sensitive detection of hydrazine hydride with a low detection limit of 1.08 nM. According to the results, the mechanism was confirmed by UV-Vis, PL, NMR and MS spectra for the detection of hydrazine, and further evidence of the protonation-deprotonation process in added TFA/TEA was made by titration studies by 1H NMR. Therefore, this work can be used for test strip kits for multifunction applications.

Phenanthroimidazole-based fluorescence probe for discriminative detecting of hydrazine and bisulfite and its applications in environmental samples.

Hydrazine (N2H4) and bisulfite (HSO3-) detection methods are urgently needed due to its harmful to the human health and environment safety. Herein, we reported a dual-response fluorescence probe EPC, which is capable of sequential detection of N2H4 and HSO3- by two different fluorescence signals. The probe EPC itself showed yellow florescence. In presence of N2H4, probe EPC exhibited an obviously fluorescence change (from yellow to green). However, a new addition product came into being after probe EPC mixed with HSO3-, followed with weak yellow emission. More important, probe EPC exhibited excellent fluorescence response properties for N2H4 and HSO3-, such as high sensitivity (0.182 µM for N2H4, 0.093 µM for HSO3-), rapid response (55 s for N2H4, 45 s for HSO3-), excellent selectivity and anti-interference performance. The sensing mechanisms for N2H4 and HSO3- were proved by 1H NMR and MS spectra. Practical applications were studied. EPC based test paper can be utilized for quantitative detecting N2H4 in actual water samples. And, probe EPC has been successfully applied to recognize N2H4 contaminant in soil samples. Moreover, EPC has great potential to be used to detect HSO3- in real food samples.

Iodophor-Catalyzed Disulfenylation of Amino Naphthalenes with Aryl Sulfonyl Hydrazines.

An iodophor-catalyzed direct disulfenylation of amino naphthalenes with aryl sulfonyl hydrazines in water was developed. A series of aryl sulfides were obtained in moderate to excellent yields. The advantages of this green protocol were the simple reaction conditions (metal-free, water as the solvent, under air), the odorless and easily available sulfur reagent, the broad substrate scope, and gram-scale synthesis. Moreover, the potential application of aryl sulfides was exemplified by further transformations.

A water-soluble red-emitting fluorescence probe for detecting hazardous hydrazine in environmental waters and biosystems.

Hydrazine (N2H4), a crucial chemical raw material, enhances people's lives and fosters human progress. Hydrazine usage or leakage has caused environmental contamination, affecting water, soil, and living beings. Hydrazine simultaneously presents a possible risk to human health due to its carcinogenic properties. Thus, quick and precise detection of hydrazine is crucial in environmental studies and biological contexts. We prepared a red-emitting fluorescence turn-on probe (XT-HZ) to detect hydrazine specifically. The probe has a low detecting limit for hydrazine (63 nM) with excitation wavelength at 570 nm and emission wavelength at 625 nm. Besides, the probe XT-HZ had excellent water solubility, high selectivity, and good sensitivity for detecting hydrazine. Finally, probe XT-HZ was applied in the imaging of N2H4 in living cells, zebrafish and environmental water samples.

Hydrogen peroxide enhanced glow-type chemiluminescence of hydrazine hydrate modified carbon quantum dots-potassium persulfate system.

Most known chemiluminescence (CL) systems are flash-type that generate weak luminescence and decline quickly after dozens of seconds, while the glow-type CL systems have stable emission for an extended period to achieve accurate quantitation. In this work, a long-term CL system based on hydrazine-hydrate (N2H4·H2O) modified carbon quantum dots (N-CQDs) as a luminescent probe, with K2S2O8 and H2O2 as co-reactants, was proposed. The CL emission enhanced by H2O2 increased 18-fold more than that of N-CQDs and K2S2O8 direct reaction, and decayed by 5% of the maximum intensity over 700 s. In the reaction system, K2S2O8 and H2O2 co-reactants can promote each other to continuously generate corresponding radicals (•OH, O2•-, 1O2), which in turn trigger the CL emission of N-CQDs. This phenomenon was identified as the primary cause for the production of persistent CL. In addition, a stable and selective CL sensor based on the N-CQDs-K2S2O8-H2O2 CL enhancing system was developed for ascorbic acid quantitation in the linear range from 0.1 to 10.0 mM with a detection limit of 0.036 mM. The method has been applied to the analysis of tablet samples and holds potential in pharmaceutical analysis field.

Fabrication of Curcumin-Based Electrochemical Nanosensors for the Detection of Environmental Pollutants: 1,4-Dioxane and Hydrazine.

This work reports the development of novel curcuminoid-based electrochemical sensors for the detection of environmental pollutants from water. In this study, the first set of electrochemical experiments was carried out using curcumin-conjugated multi-walled carbon nanotubes (MWCNT-CM) for 1,4-dioxane detection. The MWCNT-CM/GCE showed good sensitivity (103.25 nA nM-1 cm-2 in the linear range 1 nM to 1 µM), with LOD of 35.71 pM and LOQ of 108.21 pM. The second set of electrochemical experiments was carried out with bisdemethoxy curcumin analog quantum dots (BDMCAQD) for hydrazine detection. The BDMCAQD/GCE exhibited good sensitivity (74.96 nA nM-1 cm-2 in the linear range 100 nM to 1 µM), with LOD of 10 nM and LOQ of 44.93 nM. Thus, this work will serve as a reference for the fabrication of metal-free electrochemical sensors using curcuminoids as the redox mediator for the enhanced detection of environmental pollutants.

Practical Synthesis of 7-Bromo-4-chloro-1H-indazol-3-amine: An Important Intermediate to Lenacapavir.

7-Bromo-4-chloro-1H-indazol-3-amine is a heterocyclic fragment used in the synthesis of Lenacapavir, a potent capsid inhibitor for the treatment of HIV-1 infections. In this manuscript, we describe a new approach to synthesizing 7-bromo-4-chloro-1H-indazol-3-amine from inexpensive 2,6-dichlorobenzonitrile. This synthetic method utilizes a two-step sequence including regioselective bromination and heterocycle formation with hydrazine to give the desired product in an overall isolated yield of 38-45%. The new protocol has been successfully demonstrated on hundred-gram scales without the need for column chromatography purification. This new synthesis provides a potential economical route to the large-scale production of this heterocyclic fragment of Lenacapavir.

Sonochemical decomposition effects of nickelocene aiming for low-temperature and dispersant-free synthesis of nickel fine particle.

Sonochemical decomposition effects of nickelocene, which sublimates easily were investigated to synthesize dispersant-free nickel fine particles at low temperature. In a hydrazine monohydrate and 2-propanol mixed solvent, the reduction of nickelocene was promoted by ultrasound irradiation, and nickel fine particles were synthesized while precluding the sublimation of nickelocene. Unlike the common hydrazine reduction of nickel salts, which requires multiple-step reactions, nickelocene was reduced directly without forming intermediates. The effect of the water-bath temperature (20-60 °C) was investigated, where larger fine particles were synthesized using a higher water-bath temperature (60 °C). When irradiated at 20 °C, the reduction rate of nickelocene was low, leading to the formation of nickel fine particles and organic nanoparticles via the reduction and decomposition of nickelocene. The ultrasound frequency was also investigated, where fine nickel particles were synthesized using low-frequency ultrasound irradiation. The formation of high-temperature hotspots led to the diffusion and growth of nickel on the surface of the nickel fine particles; therefore, raspberry-like nickel fine particles were synthesized. In this study, the difficult-to-handle nature of nickelocene, owing to its sublimation properties, was easily overcome by ultrasound irradiation. Instantaneous and localized reactions at hotspots contributed to inhibiting particle growth. Furthermore, Ni fine particles were synthesized via a direct reduction pathway, which differs from previous reactions. This method represents a new, dispersant-free, low-temperature process for synthesizing Ni fine particles.

Enhancement of hydrazine accumulation in anammox bioreactors.

The role of hydrazine (N2H4) in anammox metabolism has been widely studied; however, studies on N2H4 biosynthesis by anammox bacteria are limited in the literature. In this context, the current research aims to investigate the enhancement of biological N2H4 production in the anammox process in a long-term manner. The experimental studies started with the optimization of the operating conditions to achieve maximum N2H4 accumulation. Under favorable conditions (pH = 8.97 ± 0.08; T = 35.5 ± 0.5 °C; initial hydroxylamine dose = 1.46 ± 0.01 mM), 17.16 ± 0.64 mg L-1 of N2H4 accumulated in the batch systems. The continuity of N2H4 bioproduction was then evaluated by long-term observations. A continuous flow bioreactor was operated in four consecutive manipulated periods under optimized conditions. In the long-term operated bioreactor, 55.10 ± 0.30 mg L-1 N2H4 was accumulated at optimal conditions, which was 2.5 times higher than reported in the literature. Although manipulation of the bioreactor operating conditions initially resulted in a significant increase in N2H4 bioaccumulation, it subsequently caused a severe deterioration in anammox activity. However, this could be mitigated by increasing the biomass concentration in the anammox systems. In addition, the relative abundance of Candidatus Kuenenia decreased by 1.88% throughout the long-term operation.

Synthesis and Antitumor Activities of Novel 5-amino-3-(halophenyl)- 1- phenyl-1H-pyrazole-4-carbonitriles.

In this work, a series of novel 3-(halophenyl)-1-phenyl-1H-pyrazole moieties have been synthesized. Their structures were characterized by IR, NMR, and MS spectroscopy, and the corresponding antitumor properties were also studied. OBJECTIVES: This study aimed to synthesize a series of new 3-(halophenyl)-1-phenyl-1Hpyrazole moieties and survey the antitumor properties of these compounds. MATERIALS AND METHODS: 3-(halophenyl)-1-phenyl-1H-pyrazoles (4a-j) were prepared by reaction of phenyl hydrazine (3) with different halogen aromatic aldehydes (1a-j) and malononitrile (2) in C2H5OH and piperidine. The reaction took place under microwave irradiation settings for two minutes at140°C. RESULTS: Three human cancer cell lines were used as in vitro test subjects for compounds 4a - j. Three cell lines from mammals HeLa (a cell line for human cervical cancer), MCF-7 (a cell line for human breast cancer), and PC-3 (a cell line for human prostate cancer), all with 5- fluorouracil as the standard reference drug were used. CONCLUSION: A series of novel 3-(halophenyl)-1-phenyl-1H-pyrazoles were synthesized in this work. All substances had their anticancer properties assessed.

Facile room temperature synthesis of size-controlled spherical silica from silicon metal via simple sonochemical process.

The waterglass or St o¨ ber method is commonly used to synthesize spherical colloidal silica; however, these methods have some disadvantages, such as complicated processes for the removal of sodium ions and expensive and energy-consuming raw materials such as tetraethoxysilane (TEOS). In this study, size-controlled spherical colloidal silica was synthesized from silicon metal at room temperature using an ultrasound process with hydrazine monohydrate as the solvent. Silicon metal dissolves easily in hydrazine monohydrate under ultrasound irradiation, and spherical colloidal silica can be synthesized by adding alcohol to this precursor solution. By changing the concentration or type of alcohol, size-controlled colloidal silica 20-200 nm in size could be easily obtained. In addition, finer and more monodisperse particles were produced by low-frequency ultrasound irradiation, which had a higher stirring effect at the particle formation stage. The present method is effective because size-controlled colloidal silica can be synthesized at room temperature using only silicon metal, hydrazine, and alcohol as raw materials, without complicated processes or expensive and energy-consuming raw materials such as TEOS or tetramethoxysilane (TMOS).

Ferroheme/Ferriheme Directly Involved in the Synthesis and Decomposition of Hydrazine as an Electron Carrier during Anammox.

Anammox bacteria performed the reaction of NH4+ and NO with hydrazine synthase to produce N2H4, followed by the decomposition of N2H4 with hydrazine dehydrogenase to generate N2. Ferroheme/ferriheme, which serves as the active center of both hydrazine synthase and hydrazine dehydrogenase, is thought to play a crucial role in the synthesis and decomposition of N2H4 during Anammox due to its high redox activity. However, this has yet to be proven and the exact mechanisms by which ferroheme/ferriheme is involved in the Anammox process remain unclear. In this study, abiotic and biological assays confirmed that ferroheme participated in NH4+ and NO reactions to generate N2H4 and ferriheme, and the produced N2H4 reacted with ferriheme to generate N2 and ferroheme. In other words, the ferroheme/ferriheme cycle drove the continuous reaction between NH4+ and NO. Raman, ultraviolet-visible spectroscopy, and X-ray absorption fine structure spectroscopy confirmed that ferroheme/ferriheme is involved in the synthesis and decomposition of N2H4 via the core FeII/FeIII cycle. The mechanism of ferroheme/ferriheme participation in the synthesis and decomposition of N2H4 was proposed by density functional theory calculations. These findings revealed for the first time the heme electron transfer mechanisms, which are of great significance for deepening the understanding of Anammox.