Electron Acceptor Research Articles

Assessing Lanthanide-Dependent Methanol Dehydrogenase Activity: The Assay Matters.

Artificial dye-coupled assays have been widely adopted as a rapid and convenient method to assess the activity of methanol dehydrogenases (MDH). Lanthanide(Ln)-dependent XoxF-MDHs are able to incorporate different lanthanides (Lns) in their active site. Dye-coupled assays showed that the earlier Lns exhibit a higher enzyme activity than the late Lns. Despite widespread use, there are limitations: oftentimes a pH of 9 and activators are required for the assay. Moreover, Ln-MDH variants are not obtained by isolation from the cells grown with the respective Ln, but by incubation of an apo-MDH with the Ln. Herein, we report the cultivation of Ln-dependent methanotroph Methylacidiphilum fumariolicum SolV with nine different Lns, the isolation of the respective MDHs and the assessment of the enzyme activity using the dye-coupled assay. We compare these results with a protein-coupled assay using its physiological electron acceptor cytochrome cGJ (cyt cGJ ). Depending on the assay, two distinct trends are observed among the Ln series. The specific enzyme activity of La-, Ce- and Pr-MDH, as measured by the protein-coupled assay, exceeds that measured by the dye-coupled assay. This suggests that early Lns also have a positive effect on the interaction between XoxF-MDH and its cyt cGJ thereby increasing functional efficiency.

Ultra-thin carbon nitride activated periodate for efficient tetracycline degradation with the assistance of visible light

This study developed a novel activated periodate (PI, IO4−) system mediated by ultra-thin carbon nitride (UCN) and visible light (Vis), and investigated its efficiency and kinetics of tetracycline hydrochloride (TC) degradation in water. UCN/PI/Vis system could remove 96% TC within 16 min through the mixed radical/non-radical pathway dominated by IO3•, 2.3 times higher than that of polymerized carbon nitride (PCN)/PI/Vis system. This gap was attributed to UCN having a greater specific surface area, more active sites, and a shorter charge transfer path. The UCN/PI/Vis system has outstanding recyclability, attractive pH adaptability, and remarkable tolerance to co-existing substances and natural water bodies. The fascinating degradation efficiency was ascribed to the synergistic effect among UCN that produced photoelectrons, TC as an electron donor, and PI as an electron acceptor. The quantum confinement effect of the ultra-thin structure improved the band gap and enhanced the redox capacity of photogenerated carriers, which greatly improved the photocatalytic activation of PI by UCN.

Anaerobic methane oxidation is quantitatively important in deeper peat layers of boreal peatlands: Evidence from anaerobic incubations, in situ stable isotopes depth profiles, and microbial communities

Boreal peatlands store most of their carbon in layers deeper than 0.5 m under anaerobic conditions, where carbon dioxide and methane are produced as terminal products of organic matter degradation. Since the global warming potential of methane is much greater than that of carbon dioxide, the balance between the production rates of these gases is important for future climate predictions. Herein, we aimed to understand whether anaerobic methane oxidation (AMO) could explain the high CO2/CH4 anaerobic production ratios that are widely observed for the deeper peat layers of boreal peatlands. Furthermore, we quantified the metabolic pathways of methanogenesis to examine whether hydrogenotrophic methanogenesis is a dominant methane production pathway for the presumably recalcitrant deeper peat. To assess the CH4 cycling in deeper peat, we combined laboratory anaerobic incubations with a pathway-specific inhibitor, in situ depth patterns of stable isotopes in CH4, and 16S rRNA gene amplicon sequencing for three representative boreal peatlands in Western Siberia. We found up to a 69 % reduction in CH4 production due to AMO, which largely explained the high CO2/CH4 anaerobic production ratios and the in situ depth-related patterns of δ13C and δD in methane. The absence of acetate accumulation after inhibiting acetotrophic methanogenesis and the presence of sulfate- and nitrate-reducing anaerobic acetate oxidizers in the deeper peat indicated that these microorganisms use SO42− and NO3− as electron acceptors. Acetotrophic methanogenesis dominated net CH4 production in the deeper peat, accounting for 81 ± 13 %. Overall, anaerobic oxidation is quantitatively important for the methane cycle in the deeper layers of boreal peatlands, affecting both methane and its main precursor concentrations.

Unveil of the role of fungal taxa in iron(III) reduction in paddy soil.

Hitherto, research on iron(III)-reduction has mainly focused on bacteria rather than fungal communities. To acquire insight into fungi involved in iron(III) reduction, typical organic matters (containing cellulose, glucose, lactate, and acetate) and ferrihydrite were used as electron donors and acceptors, respectively, in the presence of antibiotics. After antibiotic addition, microbial iron(III) reduction was still detected at quite high rates. In comparison, rates of iron(III) reduction were significantly lower in cellulose-amended groups than those with glucose, lactate, and acetate under the antibiotic-added condition. Patterns of intermediate (e.g., acetate, pyruvate, glucose) turnover were markedly different between treatments with and without antibiotics during organic degradation. A total of 20 genera of potential respiratory and fermentative iron(III)-reducing fungi were discovered based on ITS sequencing and genome annotation. This study provided an insight into the diversity of iron(III)-reducing fungi, indicating the underestimated contribution of fungi to iron and the coupled carbon biogeochemical cycling in environments.

An all-electron acceptor-based semiconducting polymer nanoprobe for in vivo high brightness NIR-II fluorescence imaging

In vivo fluorescence imaging within the second near-infrared window (NIR-II, 1000−1700 nm) has advantages of a higher spatial resolution, and deeper tissue penetration depth than that in traditional near-infrared (NIR-I, 750−950 nm). However, currently reported most of imaging materials showed very low fluorescence quantum yield. Here, we developed a new all-acceptor strategy to design and synthesize a new diketopyrrolopyrrole-based semiconducting polymer nanoparticles (PDP NPs) with high quantum yield (∼1.3 %–0.13 %) by Stille reaction of weak and moderate electron acceptor. Such high fluorescence quantum yield may be attributed to the all-acceptor strategy effectively reducing the polymeric intrachain charge-transfer effect. The fluorescence quantum yield (0.13 %) of PDP NPs was higher than currently reported most of semiconducting polymer nanoparticles. Thus, the PDP NPs-enhanced NIR-II imaging exhibited clear microvascular networks in living mice as well as xenograft 4T1 tumor with high signal-to-background ratio and spatial resolution. This study not only introduced an all-acceptor strategy to fabricate diketopyrrolopyrrole-based semiconducting polymer nanoparticles, but also provided a convenient and effective approach to amplify the effectiveness of imaging in vivo.

Extremely long-lived charge separation and related carrier spin excitation in CsPbBr3 perovskite quantum dots with an electron acceptor benzoquinone

Extremely long-lived charge separation and related carrier spin excitation in CsPbBr3 perovskite quantum dots with an electron acceptor benzoquinone

Sensitive photochemical detection of Pb2+ based on the "on-off-on" strategy coupled with adsorption

A photoelectrochemical (PEC) sensor, utilizing the semiconductor BiVO4 and gold nanoparticles (AuNPs) modified with glutathione (GSH), was successfully fabricated for the sensitive detection of Pb2+ ions. The calcinated BiVO4-modified indium tin oxide (ITO) electrode (ITO/BiVO4) generated a low cathodic photocurrent response under light irradiation. The photocurrent at ITO/BiVO4/AuNPs photoelectrode increased significantly due to the plasmon enhancement of AuNPs and the electron transfer. This enhancement photocurrent intensity was largely suppressed by introducing GSH to form ITO/BiVO4/AuNPs/GSH. It minimized the base photocurrent of the photoelectrode. Upon the addition of Pb2+ ions in the cell, they were adsorbed on the electrode surface through the interaction with the two carboxyl groups in GSH. Subsequently, Pb2+ ions, serving as electron acceptors, underwent reduction under light irradiation, leading to increase in photocurrent intensity again. Therefore, a signal "on-off-on" PEC sensor was developed for the detection of Pb2+ ions. The concentration of Pb2+ ions show a good linearity between 0.1 pM and 10 μM with a detection limit of 0.08 pM (S/N = 3). The prepared PEC sensor shows high sensitivity, a wide linear range, and good selectivity. This work provides a promising platform for the analytical detection of heavy metal ions.

The influence of montmorillonite on the mineralogical and magnetic changes in magnetite and maghemite during microbial iron reduction

Magnetic iron minerals, such as magnetite (Fe3O4) and maghemite (γ-Fe2O3), are widely distributed in sediments, holding significant potential for reconstructing paleoenvironments through their magnetic properties. However, the impact of microbial iron reduction on the physicochemical and magnetic characteristics of Fe(III)-containing magnetic minerals has recently been recognized as a crucial but often overlooked factor in paleoenvironmental reconstructions. Although magnetic iron minerals are frequently associated with clay minerals in sedimentary settings, our understanding of the influence of clay minerals on the microbial reduction of Fe(III) in magnetic minerals remains limited. To address this knowledge gap, a series of bioreduction experiments were conducted in a non-growth medium, in which lactate acted as the electron donor, magnetite or maghemite nanoparticles (NPs) served as the electron acceptor, and a typical iron-reducing bacterium, Shewanella oneidensis strain MR-1, acted as the reaction mediator, in the presence or absence of montmorillonite (STx-1b). Our results demonstrated that the addition of montmorillonite STx-1b significantly enhanced the dispersion of magnetite and maghemite NPs, thereby increasing the final extent of microbial iron reduction. Moreover, the degree of microbial iron reduction impacted the crystallography and magnetic properties of magnetite and maghemite. Upon bioreduction, the lattice constant, magnetic susceptibility, and the 10-K magnetic coercivity of these magnetic iron minerals exhibited an increase, accompanied by the presence of more structural defects. Specifically, maghemite-magnetite solid solutions were formed in the maghemite-amended biosystems. These findings highlight the influence of clay minerals in natural settings during microbial iron reduction on the magnetic properties of magnetic iron minerals used for paleoenvironmental reconstructions.

Iodinated Electron Acceptor with Significantly Extended Exciton Diffusion Length for Efficient Organic Photovoltaic Cells.

Iodination has unlocked new potentials in organic photovoltaics (OPVs). A newly designed and synthesized iodinated non-fullerene acceptor, BO-4I, showcases exceptional excitation delocalization property with the exciton diffusion length increased to 80 nm. The enhanced electron delocalization property is attributed to the larger atomic radius and electron orbit of the iodine atom, which facilitates the formation of intra-moiety excitations in the acceptor phase. This effectively circumvents the charge transfer state-related recombination mechanisms, leading to a substantial reduction in non-radiative energy loss (ΔEnr ). As a result, OPV cell based on PBDB-TF : BO-4I achieves an impressive efficiency of 18.9 % with a notable ΔEnr of 0.189 eV, markedly surpassing their fluorinated counterparts. This contribution highlights the pivotal role of iodination in reducing energy loss, thereby affirming its potential as a key strategy in the development of advanced next-generation OPV cells.

Iodinated Electron Acceptor with Significantly Extended Exciton Diffusion Length for Efficient Organic Photovoltaic Cells

AbstractIodination has unlocked new potentials in organic photovoltaics (OPVs). A newly designed and synthesized iodinated non‐fullerene acceptor, BO‐4I, showcases exceptional excitation delocalization property with the exciton diffusion length increased to 80 nm. The enhanced electron delocalization property is attributed to the larger atomic radius and electron orbit of the iodine atom, which facilitates the formation of intra‐moiety excitations in the acceptor phase. This effectively circumvents the charge transfer state‐related recombination mechanisms, leading to a substantial reduction in non‐radiative energy loss (ΔEnr). As a result, OPV cell based on PBDB‐TF : BO‐4I achieves an impressive efficiency of 18.9 % with a notable ΔEnr of 0.189 eV, markedly surpassing their fluorinated counterparts. This contribution highlights the pivotal role of iodination in reducing energy loss, thereby affirming its potential as a key strategy in the development of advanced next‐generation OPV cells.

The novel thermally activated delayed fluorescence compounds based on trifluoromethylpyridine were synthesized for blue OLEDs

Seeking efficient blue thermally activated delayed fluorescence (TADF) luminous materials with a simple structure and applying them to organic light-emitting diodes (OLEDs) is still an urgent challenge. Herein, two novel D-π-A type blue TADF emitters with simple molecular structure, namely p-AcBPyCF3 and m-AcBPyCF3, featuring a trifluoromethylpyridine (PyCF3) as acceptor moiety, 9,9-dimethyl-tetrahydroacridine (Ac) as donor unit and benzene (B) as π-bridge, respectively, are first developed and compared in parallel. The analysis of single crystal reveals that p-AcBPyCF3 possesses clearly twisted geometry between the donor and acceptor units, as well as expanded molecular rigidity, thus leading to a smaller singlet-triplet energy difference and greatly improved emission efficiency. The p-AcBPyCF3 exhibits a photoluminescence quantum yield (PLQY) of 28.80 %, surpassing the PLQY value of 18.70 % for the m-AcBPyCF3. Compared to m-AcBPyCF3, the TADF-OLEDs based on p-AcBPyCF3 demonstrated exceptional properties, which suppresses the rotation of molecular conformation and can achieve high PLQY by reducing non radiative transformation processes, resulting in a maximum external quantum efficiency (EQE) of 9.26 % with peak at 470 nm and blue color coordinates of (0.18, 0.25). This work highlights that the simple PyCF3 group can be a promising electron acceptor moiety for the design of blue TADF materials.

NO3− as an electron acceptor elevates antibiotic resistance gene and human bacterial pathogen risks in managed aquifer recharge (MAR): A comparison with O2

Managed aquifer recharge (MAR) stands out as a promising strategy for ensuring water resource sustainability. This study delves into the comparative impact of nitrate (NO3−) and oxygen (O2) as electron acceptors in MAR on water quality and safety. Notably, NO3−, acting as an electron acceptor, has the potential to enrich denitrifying bacteria, serving as hosts for antibiotic resistance genes (ARGs) and enriching human bacterial pathogens (HBPs) compared to O2. However, a direct comparison between NO3− and O2 remains unexplored. This study assessed risks in MAR effluent induced by NO3− and O2, alongside the presence of the typical refractory antibiotic sulfamethoxazole. Key findings reveal that NO3− as an electron acceptor resulted in a 2 times reduction in dissolved organic carbon content compared to O2, primarily due to a decrease in soluble microbial product production. Furthermore, NO3− significantly enriched denitrifying bacteria, the primary hosts of major ARGs, by 747%, resulting in a 66% increase in the overall abundance of ARGs in the effluent of NO3− MAR compared to O2. This escalation was predominantly attributed to horizontal gene transfer mechanisms, as evidenced by a notable 78% increase in the relative abundance of mobile ARGs, alongside a minor 27% rise in chromosomal ARGs. Additionally, the numerous denitrifying bacteria enriched under NO3− influence also belong to the HBP category, resulting in a significant 114% increase in the abundance of all HBPs. The co-occurrence of ARGs and HBPs was also observed to intensify under NO3− influence. Thus, NO3− as an electron acceptor in MAR elevates ARG and HBP risks compared to O2, potentially compromising groundwater quality and safety.

Self-Assembled Nanotubes Based on Chiral H8-BINOL Modified with 1,2,3-Triazole to Recognize Bi3+ Efficiently by ICT Mechanism.

A novel fluorescent "off" probe R-β-D-1 containing a 1,2,3-triazole moiety was obtained by the Click reaction with azidoglucose using H8-BINOL as a substrate, and the structure was characterized by 1H NMR and 13C NMR and ESI-MS analysis. The fluorescence properties of R-β-D-1 in methanol were investigated, and it was found that R-β-D-1 could be selectively fluorescently quenched by Bi3+ in the recognition of 19 metal ions and basic cations. The recognition process of Bi3+ by R-β-D-1 was also investigated by fluorescence spectroscopy, SEM, AFM, etc. The complex pattern of R-β-D-1 with Bi3+ was determined by Job's curve as 1 + 1, and the binding constant Ka of R-β-D-1 and Bi3+ was valued by the Benesi-Hildebrand equation as 1.01 × 104 M-1, indicating that the binding force of R-β-D-1 and Bi3+ was medium. The lowest detection limit (LOD) of the self-assembled H8-BINOL derivative for Bi3+ was up to 0.065 µM. The mechanism for the recognition of Bi3+ by the sensor R-β-D-1 may be the intramolecular charge transfer effect (ICT), which was attributed to the fact that the N-3 of the triazole readily serves as an electron acceptor while the incorporation of Bi3+ serves as an electron donor, and the two readily undergo coordination leading to the quenching of fluorescence. The recognition mechanism and recognition site could be verified by DFT calculation and CDD (Charge Density Difference).

Precisely Manipulating Molecular Packing via Tuning Alkyl Side‐Chain Topology Enabling High‐Performance Nonfused‐Ring Electron Acceptors

AbstractIn the development of high‐performance organic solar cells (OSCs), the self‐organization of organic semiconductors plays a crucial role. This study focuses on the precisely manipulation of molecular assemble via tuning alkyl side‐chain topology in a series of low‐cost nonfused‐ring electron acceptors (NFREAs). Among the three NFREAs investigated, DPA‐4, which possesses an asymmetric alkyl side‐chain length, exhibits a tight packing in the crystal and high crystallinity in the film, contributing to improved electron mobility and favorable film morphology for DPA‐4. As a result, the OSC device based on DPA‐4 achieves an excellent power conversion efficiency of 16.67 %, ranking among the highest efficiencies for NFREA‐based OSCs.

Pyridine Iodine(I) Cations: Kinetic Trapping as a Sulfonate Complexes.

Seven pyridine iodine(I) sulfonate complexes were prepared and isolated at low temperatures and characterized by X-ray diffraction analysis. The inherently instable pyridine iodine(I) cations are stabilized by an oxygen of sulfonate anions via the I⋅⋅⋅O halogen bond. In these complexes, the iodine atom of the pyridine iodine(I) cation acts as an electron acceptor and the sulfonate oxygen as the electron donor. These complexes are stable enough in the crystalline state, yet decompose rapidly under ambient conditions, also being unstable in solution. The (pyridine)N-I bond lengths [2.140(3)-2.197(2) Å] and the I⋅⋅⋅O halogen bonds [2.345(6)-2.227(3) Å] are analogous to (imide)N-I⋅⋅⋅O-N-pyridine uncharged halogen-bonded complexes formed from N-haloimides and pyridine N-oxides, thus confirming the existence of elusive pyridine iodine(I) cation.

Rational design of a donor-acceptor structured poly(3-bromothiophene) modified g-C3N4 for enhanced photocatalytic degradation of 2-mercaptobenzothiazole

Donor-acceptor (D-A) structure has gained momentous attention due to its controllable optical band gap and impressive carrier separation performance. The intramolecular charge transfer within photocatalysts could be modulated by constructing a D-A structure, thereby enhancing their performance in degrading pollutants. In our recent research, using poly(3-bromothiophene) (PTh-Br) and dicyandiamide (DCD) as precursors, a series of D-A structures (CN-PTh-Br(x)) based on polythiophene donors and carbon nitride acceptors were obtained by one-pot synthesis for first-time. The density functional theory calculations further demonstrate that PTh-Br segment (an electron donor) donates electrons to tri-s-triazine rings (an electron acceptor). The introduction of electron-rich polythiophene groups and electron-withdrawing Br atoms on carbon nitride skeleton can propel the transfer and separation of holes and electrons. Moreover, the polythiophene groups with high conjugation length can optimize the optical absorption of CN-PTh-Br(x) at 450–600 nm, thus markedly heightening the visible-light utilization efficiency of the materials. The photocatalytic performance of CN-PTh-Br(x) was assessed through the photodegradation of 2-mercaptobenzothiazole (MBT) under visible-light illumination. The photodegradation performance of CN-PTh-Br(0.5) stood out among all the samples, demonstrating a remarkable ability to remove 99.8% of MBT within 45 min.

Vitamin C-regulated CoAl- layered double hydroxide with oxygen vacancies to efficiently activate peroxydisulfate for sulfamethoxazole removal triggered via reactive oxygen and high-valent cobalt species

In this study, a vitamin C-regulated CoAl-layered double hydroxide with abundant oxygen vacancies was synthesized via a simple hydrothermal process. The resulting CoAl-layered double hydroxide was employed to activate peroxydisulfate for removal of sulfamethoxazole. The effect of the experimental parameters such as pH, catalyst dose and peroxydisulfate concentration on sulfamethoxazole removal was investigated. The current system exhibited excellent catalytic performance for sulfamethoxazole removal in a broad pH range (i.e., pH 3.0–11.0). Under the optimized condition, 94.2% of sulfamethoxazole was degraded within 15 min, accompanied by a 67.6% reduction in chemical oxygen demand. The effective sulfamethoxazole degradation could be attributed to four pathways. Firstly, the ≡ Co2+ in catalyst reacted with peroxydisulfate to generate reactive species, including SO4•−, •OH, O2•− and 1O2, which could degrade sulfamethoxazole. Secondly, the oxygen vacancies could modulate intrinsic electrons, resulted in the surface activation of catalyst and accelerated charge transfer, which was favorable for the degradation of sulfamethoxazole. Thirdly, the presence of vitamin C not only promoted the formation of oxygen vacancies but also expanded the interlayer spacing of layered double hydroxide. A large interlayer spacing facilitated the diffusion of peroxydisulfate and pollutants in the interlayer and improved the utilization efficiency of the active site. Lastly, the high-valent cobalt species exhibited excellent oxidation ability and enhanced the catalyst performance through continuously being employed as an electron acceptor. This study provided a valuable insight for the design and application of Co-based catalysts in peroxydisulfate-based advanced oxidation processes.

Precisely Manipulating Molecular Packing via Tuning Alkyl Side-Chain Topology Enabling High-Performance Nonfused-Ring Electron Acceptors.

In the development of high-performance organic solar cells (OSCs), the self-organization of organic semiconductors plays a crucial role. This study focuses on the precisely manipulation of molecular assemble via tuning alkyl side-chain topology in a series of low-cost nonfused-ring electron acceptors (NFREAs). Among the three NFREAs investigated, DPA-4, which possesses an asymmetric alkyl side-chain length, exhibits a tight packing in the crystal and high crystallinity in the film, contributing to improved electron mobility and favorable film morphology for DPA-4. As a result, the OSC device based on DPA-4 achieves an excellent power conversion efficiency of 16.67 %, ranking among the highest efficiencies for NFREA-based OSCs.

Interdisciplinary Research on Electrons and Biofilms

Interdisciplinary research on electrons and biofilms is being carried out by Assistant Professor Dr Yoshihide Tokunou, Faculty of Life and Environmental Sciences, University of Tsukuba, Japan. His work is aimed at gaining a deeper understanding of the role of electrons in bacterial society and exploring the process of bacterial extracellular electron transfer (EET) in biofilms. By combining microbiology and electrochemistry, Dr Tokunou is developing EET-based biotechnologies and improving our understanding of the physiological importance of EET in bacterial society. To achieve this, he is collaborating with various experts such as microbiologists, chemists, and engineers, including Professor Dr Nobuhiko Nomura. His current interest is in the EET process that terminates with soluble electron acceptors. By regulating the EET in biofilms respiring with oxygen, he is trying to control various biofilm-related phenomena such as host-bacteria interaction, antibiotic resistance of biofilms, biochemical production from biofilms, etc.

Theoretical examination of nuclear spin diffusion in light-induced spin coherences in photosystem I

Microsecond coherence times are predicted in spin dynamics calculations of a donor–acceptor electron spin pair P+A1A− created upon light excitation of photosystem I (PSI). The effects of nuclear spin diffusion (NSD) due to the anisotropic protein environment on the predicted coherence times TM are studied. Closely positioned pairs and triples of protons located 5–8 Å from the electron spin are shown to largely control TM. Knowledge of the crystal structure of PSI allows for spin dynamics calculations where specific cofactors and amino acid residues are removed or replaced and the identification of anisotropic environmental features controlling electronic decoherence. Finally, we show that NSD alone cannot explain the >3× shorter experimentally observed coherence times and suggest that methyl groups at key protein sites may explain this discrepancy.