Electron Donor Research Articles

Combined Experimental and Theoretical Investigation of the Electrochemical Behavior of Hydroxy‐Substituted Anils

AbstractThe present work explored the electrochemical behavior of two organic compounds, o‐hydroxybenzylidene‐orthochloroaniline(Anil‐1) and o‐hydroxynaphthalidene‐orthochloro aniline(Anil‐2) through a series of theoretical and experimental investigations. The vibrational frequencies of two anilswere analyzed experimentally by FTIR and theoretically by DFT studies. A comparison of the frequencies with their unsubstituted analog, o‐hydroxybenzylideneaniline, confirmed the electron‐donating nature of the −Cl and −OH substituents in anils. The hyperconjugative interaction energy obtained from NBO analysis divulged the direction of the electron donation from the donor orbitals to the acceptor orbitals. UV‐visible studies illustrated prominent π→π* electronic transitions with significant oscillator strength(0.10–0.26) and molar extinction coefficient(~104) experimentally. Analysis of the global and local reactive descriptors of anils revealed a lower HOMO‐LUMO energy gap of Anil‐2(4.05 eV) than Anil‐1(4.46 eV), corroborating the order of decreasing reactivity to be Anil‐2>Anil‐1. The Cyclic Voltammetry studies disclosed the involvement of an oxidation process in Anil‐1 and Anil‐2 with a higher oxidation potential of Anil‐1 (1.43 V) than Anil‐2(1.31 V) due to the naphthyl moiety of the latter. However, the absence of a cathodic peak in both cases envisaged the irreversible nature of oxidation. The results demonstrated that both the anils could be suitable optical materials for microelectronics applications.

Enhancing D/A Interactions via Porphyrin Isomerization to Improve Photovoltaic Performance.

The interactions between the electron donors and electron acceptors (D/A) play important roles for the performance of organic solar cells (OSCs).While the isomerization strategy is known to optimize molecular geometries and properties, the impacts of isomerization on the donors or acceptors in D/A interactions have not been extensively investigated.Here in, we innovatively investigated the impacts of donor isomerism on the D/A interactions by synthesizing two small molecule donors m-ph-ZnP2and p-ph-ZnP2by linking two functionalized porphyrins at the meta and para positions of phenyl groups, respectively.Compared with p-ph-ZnP2, m-ph-ZnP2displays reduced self-aggregation but with PC61BM.Consequently, a much higher power conversion efficiency (PCE) of 5.43% is achieved for the m-ph-ZnP2binary OSCs than the p-ph-ZnP2devices with a PCE of 2.03%.The enhanced performance of m-ph-ZnP2-based device can be primarily attributed to the stronger intramolecular charge transfer (ICT), the enhanced D/A interactions, the improved charge transfer, and the suppressed charge recombination.Furthermore, the ternary devices based on m-ph-ZnP2:Y6:PC61BM achieve a PCE of 8.34%. In short, this work elucidates the relationship among the chemical structure, D/A interactions and device performance, providing valuable guidelines for designing efficient OSCs materials.

Precision Control of Amphoteric Doping in Cu x Bi2Se3 Nanoplates.

Copper-doped Bi2Se3 (Cu x Bi2Se3) is of considerable interest for tailoring its electronic properties and inducing exotic charge correlations while retaining the unique Dirac surface states. However, the copper dopants in Cu x Bi2Se3 display complex electronic behaviors and may function as either electron donors or acceptors depending on their concentration and atomic sites within the Bi2Se3 crystal lattice. Thus, a precise understanding and control of the doping concentration and sites is of both fundamental and practical significance. Herein, we report a solution-based one-pot synthesis of Cu x Bi2Se3 nanoplates with systematically tunable Cu doping concentrations and doping sites. Our studies reveal a gradual evolution from intercalative sites to substitutional sites with increasing Cu concentrations. The Cu atoms at intercalative sites function as electron donors while those at the substitutional sites function as electron acceptors, producing distinct effects on the electronic properties of the resulting materials. We further show that Cu0.18Bi2Se3 exhibits superconducting behavior, which is not present in Bi2Se3, highlighting the essential role of Cu doping in tailoring exotic quantum properties. This study establishes an efficient methodology for precise synthesis of Cu x Bi2Se3 with tailored doping concentrations, doping sites, and electronic properties.

Point-Defect Segregation and Space-Charge Potentials at the Σ5(310)[001] Grain Boundary in Ceria

The atomistic structure and point-defect thermodynamics of the model Σ5(310)[001] grain boundary in CeO2 were explored with atomistic simulations. An interface with a double-diamond-shaped structural repeat unit was found to have the lowest energy. Segregation energies were calculated for oxygen vacancies, electron polarons, gadolinium and scandium acceptor cations, and tantalum donor cations. These energies deviate strongly from their bulk values over the same length scale, thus indicating a structural grain-boundary width of approximately 1.5 nm. However, an analysis revealed no unambiguous correlation between segregation energies and local structural descriptors, such as interatomic distance or coordination number. From the segregation energies, the grain-boundary space-charge potential in Gouy–Chapman and restricted-equilibrium regimes was calculated as a function of temperature for dilute solutions of (i) oxygen vacancies and acceptor cations and (ii) electron polarons and donor cations. For the latter, the space-charge potential is predicted to change from negative to positive in the restricted-equilibrium regime. For the former, the calculation of the space-charge potential from atomistic segregation energies is shown to require the inclusion of the segregation energies for acceptor cations. Nevertheless, the space-charge potential in the restricted-equilibrium regime can be described well with an empirical model employing a single effective oxygen-vacancy segregation energy.

Efficient CdIn2S4/MgIn2S4 heterojunction for ultrasensitive detection of lung cancer marker neuron-specific enolase

In this work, a photoelectrochemical (PEC) immunosensor was constructed for the ultrasensitive detection of lung cancer marker neuron-specific enolase (NSE) based on a microflower-like heterojunction of cadmium indium sulfide and magnesium indium sulfide (CdIn2S4/MgIn2S4, CMIS) as photoactive material. Specifically, the well-matched energy level structure and narrow energy level gradients between CdIn2S4 and MgIn2S4 could accelerate the separation of electron-hole (e−-h+) pairs in the CMIS heterojunction to enhance the photocurrent of CMIS, which was increased 5.5 and 80 times compared with that of single CdIn2S4 and MgIn2S4, respectively. Meanwhile, using CMIS as photoactive material, increasing the biocompatibility by dropping Pt NPs on the surface of CMIS to immobilize the antibody through Pt–N bond. Fe3O4-Ab2, acting as the quencher, competitively consumes electron donors and absorbs light, leading to photocurrent quenching. With the increasing of quencher, the photocurrent decreased. Hence, the developed “signal-off” PEC immunosensor realized the trace detection of NSE within the range from 1.0 fg/mL to 10 ng/mL with a low detection limit of 0.34 fg/mL. This strategy provided a new perspective for establishing ternary metal sulfide heterojunction to construct PEC immunosensor for sensitive detection of disease biomarkers.

EDA Complex-Enabled Annulation to Access CF2-Containing Tetralones and Quinazolinones Using Persulfates as Electron Donors.

A photocatalyst-free and EDA complex-enabled radical cascade cyclization reaction of inactive alkenes with bromodifluoroacetamides was reported for the divergent synthesis of fluorine-containing tetralones and quinazolinones. In this transformation, persulfates as electron donors and difluoro bromamide as electron acceptors generate the EDA complex. This is a promising photochemical method with advantages such as mild reaction conditions, simple operation, being metal-free, and excellent functional group tolerance.

3D non-local thermodynamic equilibrium magnesium abundances reveal a distinct halo population

Magnesium is one of the most important elements in stellar physics as an electron donor; in Galactic archaeology, magnesium serves to distinguish different stellar populations. However, previous studies of Mg I and Mg II lines in metal-poor benchmark stars indicate that magnesium abundances inferred from one-dimensional (1D), hydrostatic models of stellar atmospheres, both with and without the local thermodynamic equilibrium (LTE) approximation, can be problematic. Here, we present three-dimensional (3D) non-LTE calculations for magnesium in FG-type dwarfs and provide corrections for 1D-LTE abundances. 3D non-LTE corrections reduce the ionisation imbalances in the benchmark metal-poor stars HD84937 and HD140283 from −0.16 dex and −0.27 dex in 1D LTE to just −0.02 dex and −0.09 dex, respectively. We applied our abundance corrections to 1D LTE literature results for stars in the thin disc, thick disc, α-rich halo, and α-poor halo. We observed that 3D non-LTE results had a richer substructure in [Mg/Fe] − [Fe/H] in the α-poor halo, revealing two sub-populations at the metal-rich end. These two sub-populations also differ in kinematics, supporting the astro-physical origin of the separation. While the more magnesium-poor sub-population is likely to be debris from a massive accreted galaxy, Gaia-Enceladus, the other sub-population may be related to a previously identified group of stars, called Eos. The additional separation in [Mg/Fe] suggests that previous Mg abundance measurements may have been imprecise due to the 1D and LTE approximations, highlighting the importance of 3D non-LTE modelling.

Preparation of MoS2/V2O5 nanocomposites for ciprofloxacin degradation and Cr (VI) reduction

In this study, MoS2/V2O5 nanocomposites are obtained by hydrothermal process, and used for photocatalytic system of Ciprofloxacin (CIP) degradation and Cr (VI) reduction. Owing to its novel characteristics, MoS2/V2O5 heterojunctions are revealed as potential semiconductors in this region. V2O5 photocatalyst acts as a charge acceptor, meantime MoS2 acts as an electron donor, therefore promoting charge carrier separation and enhancing photocatalytic efficiency. The MoS2/V2O5 nanocomposites displayed enhanced photocatalytic CIP (98.7%) and Cr (VI) reduction (98.8%) after 120min and 100min of visible light activity. In contrast, in the first cycle, the photocatalysis capability of the photocatalyst performed in six cycles is 93.8%. The Kapp values of MoS2/ V2O5 nanocomposites displayed about 11.2 and 19.5-times improvement of photocatalytic of CIP degradation and Cr (VI) reduction, respectively. The MoS2/V2O5 nanocomposites exhibited an enhanced photocurrent density of 0.082 μA/cm-2 compared to a pristine MoS2 sample of 0.045 μA/cm-2. The distinguished heterojunction photocatalysis performance is due to the significant migration of interfacial charges and the inhibited recombination rate of electron-hole pairs. CIP Pollutants eventually decay into H2O, CO2, and small molecule intermediates by generating •O2-, •OH, and h+. The influences of reactive radicals follow the order of •O2- radicals > h+ radicals > •OH radicals. Then, the probable structures of intermediates and achievable photodegradation pathways were discussed for the removal of CIP and Cr (VI) reduction using nanocomposite with visible light response.

Biogenic formation of amorphous carbon in anaerobic digestion: Discovery and regulation with exogenous CO2 and zero valent iron

Anaerobic digestion (AD), a pivotal technology for organic waste reduction and biogas production, has recently gained notable attention for its role in CO2 bioconversion. As membrane separation technologies mature, methane separated from biogas is integrated into natural gas grid, while CO2 can be recycled back into AD reactors, promoting methane production. However, the biogenic formation of amorphous carbon from CO2 in AD is scarcely reported. This study confirmed the presence of amorphous carbon in AD and successfully regulated its growth via exogenous CO2 and zero valent scrap iron (ZVSI), proposing a potential method for CO2 fixation in AD. The results indicated that ZVSI promoted amorphous carbon formation, further boosted by CO2 introduction. Reactors with 80 g/L ZVSI exhibited a 31.4 % increase in amorphous carbon content compared to the control. Concurrently, methane production was also enhanced, with reactors containing 40 g/L ZVSI marking an increase between 9.6 % and 29.8 % over the control. This was attributed to the introduced inorganic carbon, which was further enhanced by the electron donors. Isotopic tracing revealed that the majority of the introduced inorganic carbon was channeled into methane, while a portion formed amorphous carbon. An in-depth microbial community analysis associated potential methanogens (Methanobacteriales, Methanosarcinales, and Methanomicrobiales) with the biogenic formation of amorphous carbon. A potential formation pathway of amorphous carbon was proposed according to metagenomic sequencing analysis. Based on the concept of low carbon, this study breathes new life into traditional anaerobic digestion and also identifies novel pathways for biological CO2 fixation.

Visible-Light-Induced Domino Perfluoroalkylation/Cyclization to Access Perfluoroalkylated Quinazolinones by an EDA Complex.

The electron donor-acceptor (EDA) complexes have been extensively studied, which formed an electronically excited state, obviating the need for an exogenous photocatalyst. Herein, we report a mild and efficient strategy for photoinduced radical domino perfluoroalkylation/cyclization using N,N,N',N'-tetramethylethane-1,2-diamine (TMEDA) as an electron donor. This protocol could be well expanded to access various polycyclic quinazolinones containing perfluoroalkyl groups, exhibiting photocatalyst-free, good functional group tolerance, and environmentally friendly features.

Surface Modifications of Heterogeneous Photocatalysts for Photocatalytic Conversion of CO2 by H2O as the Electron Donor

Surface Modifications of Heterogeneous Photocatalysts for Photocatalytic Conversion of CO2 by H2O as the Electron Donor

Metal-free carbon nanotube boosted periodate oxidation towards organic pollutants: Identification of active sites and activation mechanism

Recent studies have indicated that metal-free carbon material-enhanced periodate (PI) oxidation is a promising strategy for mitigating organic pollution in water. However, the complicated physicochemical properties of carbon materials make it challenging to determine the activation mechanism and roles of the active sites. In this study, various metal-free carbon materials (GO, GP, ND, CNF, and MCNT) were used as catalysts for activating PI in the degradation of organic pollutants, with a focus on elucidating the underlying reaction mechanisms. All of these materials were found to be highly effective in PI activation, and MCNT showed the best catalytic performance. Quenching experiments and EPR results show that the MCNT/PI system primarily oxidizes organic contaminants via two non-radical oxidation routes as electron donors and electron mediators, respectively. Specifically, the oxygen-containing groups of MCNT (particularly carbonyl groups) play a crucial role in electron donation to enhance PI oxidation. Moreover, the structural defects of MCNT significantly accelerate electron transfer from the SIZ (target contaminant) to PI. These insights contribute to unveiling the activation of PI using metal-free carbon materials and hold substantial promise for advancing carbon-based catalysts in environmental cleanup efforts.

ZIF-8 derived Ag/ZnO photocatalyst with enriched Ag-ZnO interface for effective oxidation of methane to liquid oxygenates with simultaneous mmol-scale productivity and ∼100 % selectivity

Achieving a high yield of oxygenates and inhibiting overoxidation remain challenging for CH4 photooxidation. Here, we report a catalyst with enriched Ag-ZnO interfaces by using ZIF-8 as the precursor. The resulting Ag/Z-450 photocatalysts show extraordinary efficiency in the photocatalytic oxidation of CH4, a high liquid oxygenate yield of 57.88 mmol·gcat−1 (28.94 mmol·gcat−1·h−1) and a selectivity of ∼100 % were obtained over 3.0Ag/Z-450, with HCHO as the major product (41.04 mmol·gcat−1, ∼71 % selectivity). Mechanistic studies revealed that ZnO and Ag species acted as electron donors and acceptors, respectively, which enhanced charge carriers transfer and separation. CH4 and O2 can be effectively activated to generate •CH3 and reactive oxygen species (ROS), their following reaction led to formation of CH3OOH, which can be further converted to CH3OH and HCHO. This work contributes to the development of a “two-in-one” CH4 photooxidation catalyst system that simultaneously achieves unparallel productivity and selectivity.

Strong interaction between promoter and metal in Pd-Ba/TiO2 catalysts for formaldehyde oxidation

As our previous works found, alkali metals have a common promotion effect on supported noble metals catalysts for formaldehyde (HCHO) oxidation. As second-group elements, alkaline earth metals (AEMs) are neighbors to the first-group elements and share some properties in common. However, detailed investigations into the specific mechanisms underlying AEMs’ effects on HCHO oxidation remain limited. In this study, we found that Ba addition showed a similar promotion effect on HCHO oxidation for Pd/TiO2. Ba species stabilized Pd groups, improved the dispersion, and even caused a large number of monatomic-like Pd sites to appear, which may be attributed to the electronic interaction between promoter and metal (EIPM) between Ba and Pd. Besides, AEM loading had the important effect of increasing the electron density of metallic Pd nanoparticles, which further improved the ability for O2 activation and so enhanced the mobility of chemisorbed oxygen on the catalyst surface. For Pd/TiO2, the HCHO oxidation path is mainly HCHO→HCOOH→HCOO→H2O+CO2. By contrast, for Pd-Ba/TiO2, with more surface-active species, the formate intermediate was more likely to be directly oxidized into H2O and CO2, which is a more effective reaction pathway. The details of the EIPM between Pd and Ba were investigated by GPAW (DFT calculation module) in ASE (Atomic Simulation Environment). The AEM Ba acted as an electron donor and could interact with Pd d orbital electrons through BaO sp orbital electrons. Ba species were highly dispersed on the carrier due to the Ba-Ti interaction. Ba species dispersed over large areas stabilized the Pd particles and donated electrons to Pd. Therefore, adding an AEM is an efficacious strategy to improve the performance of the catalytic oxidation of HCHO.

NH3 gas sensing and NH3-induced anti-counterfeiting based on nontoxic ternary copper halide

Lead-free ternary copper halides are emerging environmentally friendly materials, which have recently received great attention for their favorable optoelectronic properties. However, few attention was paid to their applications in gas sensing and gas-triggered fluorescence anti-counterfeiting. In this work, we demonstrate an effective Cs3Cu2I5 halide for NH3 sensing and NH3-triggered fluorescence anti-counterfeiting applications. The Cs3Cu2I5-based electrical NH3 sensor exhibits exceptional sensing performance, in which a resistance response of 77.8% is achieved at 50 ppm NH3 with a rapid response time (9s). To elucidate the NH3 sensing mechanism, we investigated the NH3-induced optical and structural evolutions including absorption, photoluminescence (PL), and Raman spectra. Our findings suggest that NH3 molecules, acting as electron donors, adsorb on the Cs3Cu2I5 surface, inducing the decomposition of Cs3Cu2I5 into CsCu2I3 and CsI. During this process, the CsCu2I3·NH3 intermediate phase is generated as a shell layer onto the surface of Cs3Cu2I5 grain, leading to an increase in electrical conductivity (or decrease in resistance), and an emission of bright yellow-red fluorescence from CsCu2I3. Inspired by NH3-induced fluorescence emission, we also explored a novel gas-triggered anti-counterfeiting method using Cs3Cu2I5-paper, demonstrating favorable reversibility and convenience, compared to previously reported water-triggered anti-counterfeiting techniques. This work will promote the development of design of Cs3Cu2I5 for gas sensing and gas-triggered fluorescence anti-counterfeiting applications in the future.

New triglycidyl ether triazine as a protective agent for metal: Comprehensive analysis

This study presents the synthesis and characterization of triglycidyl ether triazine (TGET), a novel epoxy resin, designed as a defensive agent for mild steel (C38) in a 1 M HCl environment. The corrosion inhibitory effectiveness of TGET was evaluated by various electrochemical methods and corroborated by surface analysis using surface and theoretical methods. The key findings demonstrate that the protection behavior of TGET rises with its concentration, achieving a maximum of 94.77% at 10-3 mol/L, indicating a highly effective reduction in iron dissolution. Surface analysis confirmed the establishment of a defensive cover on the metal surface. The theoretical studies supported the experimental data, suggesting a strong adsorption of TGET molecules on the steel surface through chemical interaction, primarily via electron donation from the N and O atoms of the TGET to the metal surface. These results establish TGET as a highly effective corrosion inhibitor with potential applications in protecting steel structures in industrial environments characterized by acidic conditions.

In situ anchoring of bimetal (Cu, Fe) sulfides featured by sulfur vacancy and phosphorus doping within porous carbon nanocubes derived from Prussian blue analogs to activate peroxymonosulfate for the efficient degradation of organic pollutants

In this work, Prussian blue analogues (CuFe-PBA) derived copper-iron sulfides/N-doped porous carbon composite (CuFe-NC-SP-x) was prepared as an effective peroxymonosulfate (PMS) activator to degrade sulfadiazine (SDZ). A strategy that kills two birds with one stone was proposed to construct CuFe-SP-NC-x, i.e., S-etched CuFe-PBA (CuFe-PBA-S) was annealed with NaH2PO2 in N2 atmosphere to simultaneously introduce sulfur vacancy (Sv) and phosphorus doping. 40 μM SDZ was completely removed by CuFe-NC-SP-2/PMS in 20 min (0.2 g/L catalyst and 0.5 mM PMS). The kobs value obtained by CuFe-NC-SP-2 (0.48 min−1) was nearly 33 and 17 times higher than that of CuFe-PBA (0.014 min−1) and CuFe-PBA-S (0.028 min−1), respectively. Quenching tests, electron paramagnetic resonance (EPR) analysis indicated that PMS activation in the system involved radical pathway (26.1 % OH and 22.7 % SO4–) and non-radical pathway (17.8 % 1O2 and 33.4 % electron transfer process). OH and SO4– and 1O2 were mainly produced by S enhanced metal sites for PMS activation. The synergistic effect of Sv and P doping enabled the powerful electron transfer mechanism. Electrochemical tests and DFT calculations demonstrated that Sv existing in CuFe-SP-NC-x improved the electron donor ability and increased the adsorption energy toward PMS, and phosphorus doping accelerated the electron transport from SDZ to PMS. This work not only provides a novel strategy to synthesize a high effective PMS activator by introducing Sv and phosphorous doing in one step, but also manages to comprehensively understand the electron transfer activation mechanisms of PMS facilitated by Sv and phosphorous doping.

Manipulating excited states for constructing ultraviolet hybridized local and charge transfer fluorophores and non-doped OLEDs with high color purity

The development of efficient ultraviolet (UV) organic light-emitting materials and devices holds paramount significance for their practical applications. Nonetheless, attaining a short-wavelength electroluminescence peak of less than 390 nm while maintaining high color purity in non-doped devices remains a formidable challenge. In this work, we have successfully designed and synthesized two UV hybridized local and charge transfer fluorophores, specifically 4DBF-CZCN and 2DBF-CZCN, which are comprised of cyanide-modified phenylcarbazole and a weak electron donor dibenzofuran. And the properties of excited state are well regulated through the different linking site of dibenzofuran. The resulting non-doped devices exhibit not only emission peak wavelengths of 390 and 388 nm, accompanied by narrow full-width-at-half-maximums of 42 and 38 nm, respectively, corresponding to color coordinates of (0.164, 0.034) and (0.164, 0.036), but also admirable external quantum efficiencies of 3.00 % and 2.86 % at high luminance levels of 1910 and 1252 cd m−2, respectively.

N-Halosuccinimide-CeCl3 Transient Charge-Transfer Complexes as Semi Heterogeneous Photocatalyst in Cyclization of N-Propargylamides.

In this work, we used photoinert anhydrous cerium(III) chloride, to form a transient charge-transfer (CT) complex with NXS (N-bromosuccinimide or NBS and N-iodosuccinimide or NIS) in acetonitrile. These transient CT complexes acted as a semi-heterogeneous photocatalyst. These complexes allowed the Ce(III) ions to absorb light, turning them into strong electron donors that transferred electrons to NXS. This created halide radicals from NXS radical anions, helping to turn N-propargylamides into oxazole aldehydes. Experiments with DMPO and spin-trapping showed that a radical-based mechanism followed a single electron transfer (SET) pathway. Notably, CeCl3 was reused after the reaction without much decomposition, as it was regenerated and separated through simple filtration.

Cascading sulfur cycling in simulated oil sands pit lake water cap mesocosms transitioning from oxic to euxinic conditions

Base Mine Lake (BML), the first full-scale demonstration of oil sands tailings pit lake reclamation technology, is experiencing expansive, episodic hypolimnetic euxinia resulting in greater sulfur biogeochemical cycling within the water cap. Here, Fluid Fine Tailings (FFT)-water mesocosm experiments simulating the in situ BML summer hypolimnetic oxic-euxinic transition determined sulfur biogeochemical processes and their controlling factors. While mesocosm water caps without FFT amendments experienced limited geochemical and microbial changes during the experimental period, FFT-amended mesocosm water caps evidenced three successive stages of S speciation in ~30 days: (S1) rising expansion of water cap euxinia from FFT to water surface; enabling (S2) rapid sulfate (SO42−) reduction and sulfide production directly within the water column; fostering (S3) generation and subsequent consumption of sulfur oxidation intermediate compounds (SOI). Identified key SOI, elemental S and thiosulfate, support subsequent SOI oxidation, reduction, and/or disproportionation processes in the system. Dominant water cap microbes shifted from methanotrophs and denitrifying/iron-reducing bacteria to functionally versatile sulfur-reducing bacteria (SRB) comprising sulfate-reducing bacteria (Desulfovibrionales) and SOI-reducing/disproportionating bacteria (Campylobacterales and Desulfobulbales). The observed microbial shift is driven by decreasing [SO42−] and organic aromaticity, with putative hydrocarbon-degrading bacteria providing electron donors for SRB. Comparison between unsterile and sterile water treatments further underscores the biogeochemical readiness of the in situ water cap to enhance oxidant depletion, euxinia expansion and establishment of water cap SRB communities aided by FFT migration of anaerobes. Results here identify the collective influence of FFT and water cap microbial communities on water cap euxinia expansion associated with sequential S reactions that are controlled by concentrations of oxidants, labile organic substrates and S species. This emphasizes the necessity of understanding this complex S cycling in assessing BML water cap O2 persistence.