Electron Donor Research Articles

Capturing wastewater nitrogen through METs-assisted dissimilatory nitrate reduction to ammonium (DNRA) using various electron donors: Recent Trends, challenges, and future directions

Capturing wastewater nitrogen through METs-assisted dissimilatory nitrate reduction to ammonium (DNRA) using various electron donors: Recent Trends, challenges, and future directions

Charge-Transfer Interactions Between Antibiotics and Small Organic Acids: Spectroscopic Characterization and Computational Investigation

Six new charge-transfer complexes using ofloxacin (OFL) and sulfamethazine (SMR) as electron donors and coumaric acid (COA), cinnamic acid (CNA), and salicylic acid (SAA) as acceptors via equimolar mixture have been synthesized. The experiment used UV-vis spectroscopy to determine the formation of the complex in methanol through the presence of a new broad absorption band with a maximum wavelength in the 200-400 nm range. The molecular composition of the charge-transfer complexes was determined by the spectrophotometric titration method and found to be 1:1 (donor: acceptor). These complexes have been characterized by infrared (FTIR) and scanning electron microscopy (SEM). In the FTIR spectra, the CT complexes showed a wavelength shift compared to the reactants. The complexes exhibited various morphologies by SEM, including spherical particles, short rods, and flattened shapes. Additionally, quantum chemical calculations at the DFT/B3LYP level of theory investigated the complexes' steady-state structures, energies, and charge densities. The intermolecular binding energies was negative, indicating that the reactions of the six complexes proceeded spontaneously. There was strong van der Waals forces and hydrogen bonds between the donor and acceptor, which contributed to the complexes' strong molecular stability. The C-N and N-H groups in the donor molecule, and the -COOH group in the acceptor molecule, played key roles in the complexation process. DFT calculation results were appropriate to support our experimental results. This study highlights the molecular mechanisms of donor and acceptor action in charge-transfer interactions, providing a theoretical basis for the synthesis of antibiotic complexes and the removal of antibiotics.

Influence mechanism of divalent metals in the laminates of M2+Al-layered double hydroxides on peroxymonosulfate activation reaction pathway: Radical vs nonradical

Radical and nonradical reaction pathways have been commonly validated in peroxymonosulfate (PMS) based advanced oxidation progresses (AOPs) using layered double hydroxides (LDHs) as catalysts, but achieving efficient and selective degradation of organic pollutants remains challenging due to the unclear regulatory mechanism of laminate M2+ in PMS activation. Here, the d-orbital electrons configuration of M2+ was found to influence the degree of overlap between M−OH and O of PMS, which results in the selective dissociation of PMS to form reactive oxygen species (ROS) or achieve electron transfer pathway. Further analysis revealed that Co(II, 3d7) and Ni(II, 3d8) with filled 3d orbital electrons can serve as electron donors for PMS, leading to the cleavage of O–O bond and the efficient generation of radical-based ROS. In contrast, Mg(II, 3d0) with unfilled 3d orbital electrons and Zn(II, 3d10) with full filled 3d orbital electrons tend to act as electron shuttles, and the outermost orbitals substantially overlap with the O of PMS to form metastable complexes. Consequently, MgAl-LDH interacts with PMS to selectively degrade quinolones as electron donor through electron transfer pathway, and its performance was not inhibited by common anions and organic matter in actual water. The above results provide a basis for optimizing the design of LDH-based catalysts according to the type of laminate M2+ to achieve high selectivity and efficiency of PMS-AOPs in water purification applications.

A water-soluble aggregation-induced emission luminogen for NIR-I/NIR-II fluorescence imaging of breast cancer bone metastases

Advanced breast cancer is prone to bone metastasis, which is the most common bone metastatic tumor. Current clinical methods for diagnosing breast cancer bone metastases rely on serological markers, computed tomography and magnetic resonance imaging. However, these technologies cannot meet patients' needs due to the delayed screening, complex procedures and expensive equipment. Optical imaging currently exhibits inexhaustible and vigorous vitality in the field of diagnosis thanks to its advantages of simplicity, good controllability and high resolution. Nevertheless, the development of prominent chromophores for the diagnosis of breast cancer bone metastases is an appealing yet significantly challenging task. In this contribution, we rationally designed and synthesized three water-soluble aggregation-induced emission (AIE) luminogens, named PEGTPA-BTD, PEGTPA-NTD, and PEGTPA-NSD, by introducing different moieties as electron acceptors and PEGylated triphenylamine derivatives as electron donors and hydrophilic moieties. In vitro experiments showed that PEGTPA-NSD has a longer absorption and emission wavelength, where the emission wavelength can extend into NIR-II region. Besides, PEGTPA-NSD could self-assemble into stable nanoparticles in aqueous solution. Cell experiments showed that PEGTPA-NSD had no obvious dark toxicity to tumor cells or normal cells, and were easily taken in by tumor cells for cell imaging. What's more, PEGTPA-NSD NPs possessed excellent fluorescence imaging performance and biocompatibility in vivo for breast cancer bone metastases in NIR-I and NIR-II region, respectively. In summary, PEGTPA-NSD is the first reported aggregation-induced emission luminogens (AIEgens) that can self-assemble to nanoparticles in aqueous solution for NIR-I/NIR-II fluorescence imaging of breast cancer bone metastases. These findings would provide new strategies for optical diagnostic imaging of breast cancer bone metastases to better advance clinical technology development.

Electronic and Magnetic Properties of Cobalt Clusters on Pristine and Divacancy Graphene

Using ab initio calculations we investigate the adsorption of Co atoms, dimers and small cobalt clusters of 5 and 13 atoms on pristine graphene and graphene with a double vacancy. We report the atomic, electronic, magnetic and energetic properties of these systems. Stable adsorption configurations tend to maximize the number of cobalt-carbon bonds. On graphene, the adsorption energy of the clusters is only about 0.4 to 1 eV, and the clusters are relatively mobile on graphene. Interestingly, for different adsorbed Co13 isomers on graphene it is found that they converge to the same atomic structure. On graphene with a divacancy, the Co clusters bind in the divacancy site and isomerisation also occurs for the Co5 cluster system as well as for Co13. Co atoms and clusters can be effectively immobilized on the divacancy with corresponding adsorption energy being significantly enhanced by about 5 to 7 eV. All clusters act as electron donors in the interaction with the graphene/divacancy systems, and the amount of electron charge transfer increases with cluster size. Finite magnetic moments occur for all systems, where upon adsorption, the magnetic moment of the isolated Co atom (3μB) is significantly reduced due to electron transfer and bonding, resulting in values varying from ≈0.9-2.2 μB per Co atom. For the pristine graphene substrate, the total induced magnetic moments on the carbon atoms are negligible, while on the divacancy system, they are of the order of 0.1-0.3 μB. The attractive physical properties of these hybrid systems could find applications in catalysis and materials science.

Redox-active molecules in bacterial cultivation media produce photocurrent.

Renewable energy concepts such as microbial fuel cells (MFCs) present a promising, yet intrinsically complex electrochemical approach for utilizing bacteria as an electron source. In this work, we show that just the cultivation media for bacterial growth, which is based on yeast extract, is sufficient for generating electrical current in a bio-electrochemical cell (BEC). We apply cyclic voltammetry and 2-dimensional fluorescence spectroscopy to identify redox active molecules such as NADH, NAD+, and flavines that may play key roles in electron donation. Finally, we show that upon illumination, current production is enhanced 2-fold. This photocurrent is generated by a variety of metabolites capable of photochemical reduction, enabling them to donate electrons at the anode of the BEC.

On-Demand Metal-to-Metal Electron Donation during Zr–Ru Heterodinuclear-Catalyzed Amine–Borane Dehydrogenation

On-Demand Metal-to-Metal Electron Donation during Zr–Ru Heterodinuclear-Catalyzed Amine–Borane Dehydrogenation

Nitrogen-doped hierarchically porous carbon derived from biomass for efficient capture of iodine

Effectively capturing radioactive iodine formed during nuclear energy utilization is crucial for environment protection and human health. Herein, we present a facile and effective strategy to synthesize a nitrogen-doped hierarchically porous carbon from corn stalks for iodine capture in gaseous and liquid environment. The as-prepared carbon material possesses a hierarchically micro/mesopore structure with highly developed mesopores, a large specific surface area (1892.99 m2 g−1), and suitable nitrogen-doping (2.32 at.%). As a result, the carbon material exhibits efficient iodine capture performance, showing a large capture capacity of 3.14 g g−1 at 80 °C for iodine vapor and a fast removal rate of ∼97 % within 5 min for iodine aqueous solution, outperforming most of carbon-based materials for iodine capture reported in literatures. Thermodynamic and kinetic analyses reveal that the adsorption of iodine vapor conforms to the Langmuir model and pseudo-second-order model, respectively. Density functional theory calculation results indicate that the doped-nitrogen heteroatoms strengthen the interaction between iodine molecules and carbon, which can enhance the affinity for iodine molecules by forming a donor–acceptor complex through the donation of lone-pair electrons, thereby facilitating effective capture of iodine. This work develops a biomass-based porous carbon with potential to efficiently capture radioactive iodine.

Introducing electron-rich thiophene bridges in hot exciton emitter for efficient non-Doped near-infrared OLEDs with low turn-on voltages

The development of near-infrared (NIR) luminescent materials featuring high photoluminescence quantum yield (ΦPL) at aggregated state is of great significance for achieving highly efficient non-doped organic light-emitting diodes (OLEDs) but remains formidable challenging. Herein, a design strategy of introducing electron-rich thiophene groups between electron acceptor and donor is proposed for efficient NIR luminescent materials, and a tailored D-π-A-π-D type emitter, namely, 4,4′-(benzo[c][1,2,5]thiadiazole-4,7-diylbis(thiophene-5,2-diyl))bis(N,N-diphenylaniline) (TPATBT), is designed and prepared. The photophysical investigation and density functional theory analysis disclose that TPATBT is a hot exciton emitter feature with hybridized local and charge-transfer state. Additionally, TPATBT demonstrates aggregation-induced emission characteristic, prefers high thermal stability, and exhibits a strong emission at 692 nm with a decent ΦPL of 20 % in the neat film. The non-doped device based on TPATBT neat film presents a maximum external quantum efficiency (ηext,max) of 1.22 % with electroluminescence peak at 718n m. Moreover, we first try to use interlayer sensitization to sensitize non-doped devices, which achieves better ηext,max of 1.34 % with low turn-on voltage of 3.2 V. The proposed molecular design strategy in this work is promising for exploring robust NIR luminescent materials for high-performance OLEDs.

Enhanced charge transfer kinetics across the graphdiyne-metal sulfide ohmic interface for boosting photocatalytic hydrogen evolution

The design and construction of photocatalysts are the crucial step for solar-driven hydrogen evolution. Herein, a new type of graphdiyne (CnH2n-2)-based photocatalyst, which was prepared by one pot method, was used to promote hydrogen evolution reaction by constructing GDY/VS2 ohmic junction with S sites anchoring on the surface. Actually, the unique two-dimensional conjugated carbon network of GDY can maintain the structural stability. The uneven surface facilitates the flow of electrons, which makes GDY a good electron donor. In addition, the expanded interlayer spacing of VS2 exposes more hydrogen evolution active sites. The increase in surface electronegativity of composite catalysts enhances their redox ability and charge transfer kinetics. The band edge of the graphdiyne-metal sulfide Ohmic contact interface is bent, allowing electrons to flow into the co catalyst without resistance. These synergistic effects lead to the robust hydrogen production of GDY/VS2, which was increased by nearly 10.3 times compared with that of pure GDY. Finally, charge migration at the interface of graphdiyne-metal sulfide heterojunction was proposed and further verified combining in situ XPS and theory calculation. This research marks a significant stride for enhance the efficiency of photocatalytic hydrogen evolution by designing and constructing composite heterojunction materials.

Determination of pKa of triazolo[5,1-c][1,2,4]triazines in non-aqueous media by potentiometric titration

In this work, for the first time, an approach was suggested for determining the pKa of triazolo[5,1-c][1,2,4]triazine compounds in N,N-dimethylformamide using potentiometric titration. It was noted that change in system potential in the titration curves of triazolo[5,1-с][1,2,4]triazine are observed for compounds containing either H+ located at the nitrogen atom in position 1 or an –NH2 group. The calculated pKa values of the studied molecules correspond to the pKa values of moderately strong acids and are in the range of 2–8. The relationship was established between the acidity of the heterocyclic fragment and the presence of electron donor substituents. The obtained pKa values of the compounds correlate with the calculated possible deprotonation centers of the molecule. It was found that determining the acidity constants of substances is useful for clarifying the mechanisms of their transformations. The possibility of establishing a relationship between the structure of the compound, pKa, and probable biological activity was shown.

Novel sulfide-driven denitrification methane oxidation (SDMO) system based on SBR-MBfR and EGSB-MBfR

Traditional denitrification process consumes external organic carbon leading to an increase in treatment costs and carbon emission. A novel sulfide-driven denitrification methane oxidation (SDMO) system, which could simultaneously utilize CH4 and H2S in biogas as electron donors for denitrification to reduce the cost and carbon emission, has been successfully operated in two kinds of reactors SBR-MBfR and EGSB-MBfR for ∼ 200 days in this study. The performance and microbial community were explored meanwhile machine learning approach have been used for predicting the complex effects on SDMO’s denitrification efficiency. Result shows SBR-MBfR’s superior performance with the maximum nitrate removal efficiency > 90 % while the denitrification rates and biological activity were also better than EGSB-MBfR. The autotrophic denitrification (Auto-D) contributed 5 % much more for nitrate removal in SBR-MBfR than EGSB-MBfR while denitrification anaerobic methane oxidation (DAMO) was more prominent in EGSB-MBfR. Nineteen machine learning models were used for operation data training and random forest regressor was demonstrated to be the optimal model for predicting nitrate removal efficiency in SDMO. According to random forest regressor’s analysis, HRT presented the highest importance in affecting SDMO nitrate removal efficiency. After the introduction of biogas for domestication, Auto-D bacteria Thiobacillus was the dominant bacteria in both systems occupying > 20 % and the abundance would increase gradually from ∼ 20 % to ∼ 60 % as H2S content rising. A hidden positive correlation between DAMO bacteria Candidatus Methylomirabilis and Thiobacillus was uncovered by mantel test analysis here, implying the integrating of Auto-D and DAMO process for nitrate removal. This study not only provides insights into the novel SDMO technology but also offers a potential advancement in simultaneously low-carbon wastewater treatment and biogas utilization.

Synthesized CuO-PEI-JE with 3D open-cell structure as an efficient heterogeneous activator of peroxodisulfate for phenol degradation

The core of heterogeneous catalytic systems is to design high-performance heterogeneous catalysts. In the present study, CuO-PEI-JE was synthesized via in situ precipitation of CuO on the 3D structure of PEI-JE prepared by a cross-linking method. It possessed a macro-size and 3D open-cell structure, being easily separated and having super-performance for PDS activation. Compared to PDS alone (0.0017 min-1), the CuO-PEI-JE+PDS+NaHCO3 system increased the kobs (0.3526 min-1) by a factor of 207 with 100% phenol degradation within 20 min and 87% TOC removal at 30 min. It outperformed many other published heterogeneous persulfate systems in phenol degradation. Meanwhile, the developed system displayed a good anti-interference ability in the coexistence of anions or different water matrixes. After five successive cycles, the degradation rate still kept 100%, exhibiting the excellent reusability of CuO-PEI-JE. Furthermore, the preparation of CuO-PEI-JE had the advantages with moderate preparation conditions (60 °C) and readily available raw materials. The activation mechanism was mainly involved in the formation of active PDS and its further decomposition into ·OHads, SO4·-ads, O2·- and 1O2. Surface functional groups and phenol acted as electron donors for active PDS. Phenol was first degraded into hexadienedioic acid, then oxidized to propane diacid and oxalic acid, and finally mineralized into CO2 and H2O. This work provides a new strategy for preparing effective heterogeneous persulfate activators and has high potential for the treatment of phenol-containing wastewater.

Synergistic effect of indium doping on thermoelectric performance of cubic GeTe-based thin films

Germanium Telluride (GeTe) has been widely explored as a promising lead-free thermoelectric material in its rhombohedral and cubic phases. However, the structural transition between these two phases at ∼700 K causes an abrupt change of thermal expansion coefficient, challenging its broader practical applications. Also, as characterized by multi-valence bands and strong anharmonic interaction, the high-temperature cubic phase exhibits a higher power factor, lower thermal conductivity, and ultimately superior thermoelectric performance than its rhombohedral counterpart. Prompted by these, in this work, the cubic phase of Ge0.9Sb0.1Te (presented as GeSbTe in the following content) nanocrystalline thin film is successfully realized by RF sputtering followed by post-annealing treatment. Additionally, Indium, as an electron donor to the germanium site and an effective scattering center, further moderates carrier concentration, enhances the Seebeck coefficient and reduces thermal conductivity. The optimal composition achieves an estimated peak of ∼1.95 and an estimated average of ∼ 1.11 within the temperature range of 300 K to 575 K, showcasing GeTe as a compelling candidate for applications close to room temperature.

Novel mixotrophic denitrification biofilter for efficient nitrate removal using dual electron donors of polycaprolactone and thiosulfate

Novel mixotrophic denitrification biofilter for efficient nitrate removal using dual electron donors of polycaprolactone and thiosulfate

CuO/Cu(OH)2@g-C3N4 derived from CuBTC/g-C3N4 for two channel photocatalytic hydrogen peroxide production

Photocatalytic production of H2O2 is indeed a safe, sustainable and cost-effective technology, offering an environmentally friendly solution to the energy crisis through solar photocatalysis. However, it still faces challenges such as reliance on organic electron donors and pure O2, as well as inefficiencies in hole utilization. To overcome these limitations, a dual-channel photocatalytic system has been developed. In this study, we showcase the efficiency of the CuO/Cu(OH)2@g-C3N4 composite, derived from CuBTC/g-C3N4 via NaOH treatment, as a high-performance dual-channel photocatalyst for H2O2 production. Under visible light (λ ≥ 420 nm), this composite achieves a H2O2 yield of 1354 μmol/L in 120 min without any sacrificial agent, outperforming g-C3N4 by 8.4 times, CuO by 13.6 times and CuO@g-C3N4 by 1.9 times. Quenching experiments and electron paramagnetic resonance spectra confirmed that HO• and O2•− are intermediate products in the photocatalytic process, following a two-step single-electron reaction pathway. The superior activity of CuO/Cu(OH)2@g-C3N4 in H2O2 generation can be attributed to the synergistic effects of OH bonds on the CuO@g-C3N4 Z-type heterojunction and Cu(OH)2. This research presents a straightforward and promising approach for developing highly efficient photocatalysts for energy conversion.

ZnO Nanowires/Self-Assembled Monolayer Mediated Selective Detection of Hydrogen.

We are proposing a novel self-assembled monolayer (SAM) functionalized ZnO nanowires (NWs)-based conductometric sensor for the selective detection of hydrogen (H2). The modulation of the surface electron density of ZnO NWs due to the presence of negatively charged terminal amine groups (-NH2) of monolayers leads to an enhanced electron donation from H2 to ZnO NWs. This, in turn, increases the relative change in the conductance (response) of functionalized ZnO NWs as compared to bare ones. In contrast, the sensing mechanism of bare ZnO NWs is determined by the chemisorbed oxygen ions. The functionalized ZnO NWs exhibit an eight times higher response compared to bare ZnO NWs at an optimal working temperature of 200 °C. Finally, in comparison to studies in the literature involving strategies to enhance the sensing performance of metal oxides toward H2, like decoration with metal nanoparticles, heterostructures, and functionalization with a metal-organic framework, etc., SAM functionalization showed superior sensing results.

Enrichment of acid-tolerant sulfide-producing microbes from an acidic pit lake.

High concentrations of harmful metal(loid)s and extreme acidity are persistent environmental concerns in acidic pit lakes. In this study, we examine Cueva de la Mora (CM), a meromictic pit lake in the Iberian Pyrite Belt, Spain, as a model system. Our research aims to explore potential bioremediation strategies to mitigate the impacts of metal(loid)s and acidity in such environments. The major strategy applied in this research is to biologically stimulate sulfate reduction (i.e., biosulfidogenesis) in the deep layer of the lake to promote the formation of low-solubility sulfide minerals. Previous omics-based studies of CM have shown that several sulfate-reducing bacteria (SRB) taxa are present in the deep layer. However, their activities are likely limited by the availability of electron donors for sulfide production. Therefore, different amendments (glycerol, elemental sulfur, and glycerol + elemental sulfur) were tested to promote sulfide production and enrich acid-tolerant sulfide-producing microbes. Our results showed that glycerol stimulated dissimilatory sulfate reduction much faster than elemental sulfur alone, suggesting that electron donor limitations control sulfide production. Furthermore, the combined addition of glycerol and elemental sulfur (S(0)) resulted in the highest level of sulfide production. This indicates that S(0) can play a significant role as an electron acceptor in further promoting sulfide production when a suitable electron donor is present. Microbial community analysis revealed that Desulfosporosinus acididurans, a previously discovered acid-tolerant SRB, was enriched and became the dominant species in incubations with glycerol only (~76-96% abundance) or the combination of glycerol and S(0) (~93-99% abundance).

Enhanced water molecule sensitivity on defective WS2 monolayers through (ZnO)12 spherical nanocages decoration: A theoretical study

The adsorption of water molecules on sulfur vacancies (VS and V2S2) and gold atoms embedded in the sulfur vacancies (AuS) of tungsten disulfide (WS2) monolayers (ML) decorated with zinc-oxide (ZnO)12 nanocages were studied using dispersion-corrected density functional theory. Since the WS2 monolayer is predominantly inert, the introduction of defect states into the mid-bandgap region is significant due to its chemical and physical implications. The possibility of turning from an electron acceptor (p-type) to an electron donor (n-type) semiconductor character, when the sulfur vacancy density is varied or if the sulfur vacancies are filled with gold atoms, was demonstrated. The binding energy of the Au atom forming the AuS defect and the diffusion energy barrier from the VS defect to an adjacent site for Au were determined as 2.99 and 2.16 eV, respectively. Consequently, the substitutional defect AuS remains attached to the ML. The adsorption energy showed that the water molecule is chemisorbed on AuS defect on WS2 (n-type). Also, the density of states suggests a clear response as the chemiresistive sensor. Besides, how zinc-oxide spherical nanocages behave as sensors for different relative humidity levels was discussed. The response to water molecules was significantly enhanced by the chemisorption of the (ZnO)12 spherical nanocage on WS2-AuS. These composed systems formed WS2-ZnO heterojunctions with differences in the electronic structure. The study provides a comprehensive outlook on analyte interactions with WS2 (n-type) and WS2-ZnO surfaces, which have been utilized in the design of semiconductor gas sensors.

Identification of Five Robust Novel Ene-Reductases from Thermophilic Fungi

Ene-reductases (ERs) are enzymes known for catalyzing the asymmetric hydrogenation of activated alkenes. Among these, old yellow enzyme (OYE) ERs have been the most extensively studied for biocatalytic applications due to their dependence on NADH or NADPH as electron donors. These flavin-containing enzymes are highly enantio- and stereoselective, making them attractive biocatalysts for industrial use. To discover novel thermostable OYE-type ERs, we explored genomes of thermophilic fungi. Five genes encoding ERs were selected and expressed in Escherichia coli, namely AtOYE (from Aspergillus thermomutatus), CtOYE (from Chaetomium thermophilum), LtOYE (from Lachancea thermotolerans), OpOYE (from Ogatae polymorpha), and TtOYE (from Thermothielavioides terrestris). Each enzyme was purified as a soluble FMN-containing protein, allowing detailed characterization. All ERs exhibited a preference for NADPH, with AtOYE showing the broadest substrate range. Moreover, all the enzymes showed activity toward maleimide and p-benzoquinone, with TtOYE presenting the highest catalytic efficiency. The optimal pH for enzyme activity was between 6 and 7 and the enzymes displayed notable solvent tolerance and thermostability, with CtOYE and OpOYE showing the highest stability (Tm > 60 °C). Additionally, all enzymes converted R-carvone into (R,R)-dihydrocarvone. In summary, this study contributes to expanding the toolbox of robust ERs.