Organic Electron Research Articles

Photocatalytic production of H2O2 from water and dioxygen only under visible light using organic polymers: Systematic study of the effects of heteroatoms

The photocatalytic production of H2O2 that needs dioxygen, water, and light only has been proposed and investigated. However, most of the studies employed organic electron donors. In this work, organic photocatalysts that can produce H2O2 without organic electron donors are designed with a bottom-up approach. Although the heptazine-based g-C3N4 cannot induce water oxidation, a different kind of organic polymer (CN) obtained from the condensation of s-triazine and pyrimidine can produce H2O2 via dioxygen reduction coupled with water oxidation. The incorporation of O and P elements in CN structure (CNO, CNP, CNOP) increases the visible light absorption and hinders the photodecomposition of H2O2, respectively. The C-O and P-O bonds act as the charge trapping sites and also the preferred adsorption sites of a key intermediate, •OOH. As a result, the CNOP exhibits the highest production of H2O2 using dioxygen, water, and visible light only.

Reduction of nitrates in a photocatalytic membrane reactor in the presence of organic acids

The present study explores the capability of the Photocatalytic Membrane Reactor (PMR) technology to remove nitrates from drinking water sources in the presence of organic electron donors. A systematic investigation was performed in a laboratory-pilot PMR, employing a hybrid TiO2/UV-A catalysis–ultrafiltration process, using formic acid as the most favorable hole scavenger for nitrate reduction. The naturally occurring humic acid as well as the cheaper and harmless acetic acid were also tested as sacrificial electron donors. The performance of the PMR system was evaluated in respect of nitrate and Total Organic Carbon (TOC) percentage removal. The results demonstrate the superiority of formic acid regarding nitrate reduction, followed by acetic acid and humic acid, as well as the negligible effect of nitrates on organic mineralization. Formic acid was further used to assess the effects of molar organic/nitrate ratio, catalyst dosage and power of irradiation per unit volume (PR) on nitrate reduction. With the present laboratory-pilot, the near optimum nitrate removal was ~60 % and the TOC reduction ~85 %; selectivity to dinitrogen was in the range 65–90 %. Key issues for improving this synergistic process and related R&D directions are discussed.

Screening of multiple acyl-CoA dehydrogenase deficiency in newborns and follow-up of patients.

To investigate the incidence rate, clinical and gene mutation characteristics of multiple acyl-CoA dehydrogenase deficiency (MADD) in newborns in Zhejiang province. A total of 3 896 789 newborns were screened for MADD using tandem mass spectrometry in Zhejiang Neonatal Screening Center during January 2009 and December 2020. Patients of MADD were confirmed by urine organic acid and electron transferring flavoprotein (or electron transferring flavoprotein dehydrogenase () gene detection. MADD patients were given diet and life management, supplemented with L-carnitine, riboflavin and coenzyme Q 10 treatment, and their growth and intellectual development were evaluated during the followed up.Thirteen patients with MADD were diagnosed, with an incidence of 1/299 753. One patient was type Ⅱ, and the rest were type Ⅲ. Patients were followed up for 1 case died, 4 cases had acute metabolic disorders with hypoglycemia as the main manifestation due to infection, 1 case had hypotonia, and the rest 7 cases developed well. Patients had raised levels of C4-C18:1 acylcarnitines in the initial screening. Thirteen children were genetically tested, 1 case with compound heterozygous mutation in the gene, 1 case with homozygous mutation in the gene, 1 case with compound heterozygous mutation in the gene, 8 cases with compound heterozygous mutation and 1 case with homozygous mutation in the gene, 1 case that only 1 locus of gene was detected. The c.250G>A was the hotspot mutation in this study.The clinical manifestations of MADD are highly heterogeneous. The neonatal-onset form is serious, and late onset form usually has no obvious clinical symptoms. C4-C18:1 acylcarnitines usually increased in the initial screening, and the hotspot gene mutation is c.250G>A.

Carbon & boron substituted-Dibenzo[1,4]azaborinine as a quantum dot-based organic molecular single-electron device for high switching speed applications

The present work investigates the carbon & boron substituted-Dibenzo[1,4]azaborinine molecule as an island or quantum dot(QD) of an organic molecular single electron device(SED). The ‘carbon & boron substituted-Dibenzo[1,4]azaborinine(C13H9BN) as a QD’ is a modified variant of the acene group organic molecule ‘anthracene(C14H10)’, where boron atom are substitution of dangling hydrogens of middle honeycomb and nitrogen substitution of its parent molecule anthracene. Similar to anthracene, the carbon & boron substituted-Dibenzo[1,4]azaborinine is also made up of three linearly fused benzene rings, and has a planar structure with aromatic character. The carbon & boron substituted-Dibenzo[1,4]azaborinine molecule is considered as a QD owing to its impressive stability and conductance that originate from the aromaticity, making it ideal for low power electronic and high switching speed device applications. The calculations have been carried out using the tools AtomisticToolkit-Virtual Nanolab(ATK-VNL) and Gaussian09 packages, which is based on density functional theory (DFT), non-equilibrium green’s function (NEGF) formalisms and ab-initio approach. The charging energies in both isolated and SED conditions, total energy, and the charge stability diagram (CSD) as a function of bias potentials have been used to evaluate the device's efficiency. In comparison to anthracene based SED and its other acene organic molecular derivative SEDs, the proposed ‘carbon & boron substituted-Dibenzo[1,4]azaborinine as a quantum dot based organic molecular SED’ has high switching speed and power efficiency.

Switching from Single to Simultaneous Free-Radical and Anionic Polymerization with Enamine-Based Organic Electron Donors.

Although most monomers can polymerize through different propagation pathways, polymerization-initiating systems that can switch from one mode to another are rare. In this study, we demonstrate that enamine-based organic electron donors (OEDs) constitute the first systems able to initiate either free-radical or anionic polymerization under simple, mild, and safe conditions. While direct electron-transfer reduction of monomers by OEDs results in the initiation of anionic chain-growth polymerization, introduction of a competing oxidant with a higher reduction potential than the monomer switches the former anionic propagation to a clean radical-propagation process. The benefit of this dual-mode activator is highlighted in the synthesis of an interpenetrating polymer network through simultaneous initiation of radical and anionic propagation processes.

Switching from Single to Simultaneous Free‐Radical and Anionic Polymerization with Enamine‐Based Organic Electron Donors

AbstractAlthough most monomers can polymerize through different propagation pathways, polymerization‐initiating systems that can switch from one mode to another are rare. In this study, we demonstrate that enamine‐based organic electron donors (OEDs) constitute the first systems able to initiate either free‐radical or anionic polymerization under simple, mild, and safe conditions. While direct electron‐transfer reduction of monomers by OEDs results in the initiation of anionic chain‐growth polymerization, introduction of a competing oxidant with a higher reduction potential than the monomer switches the former anionic propagation to a clean radical‐propagation process. The benefit of this dual‐mode activator is highlighted in the synthesis of an interpenetrating polymer network through simultaneous initiation of radical and anionic propagation processes.

Photocatalytic production of hydrogen peroxide over Z-scheme Mn3O4/Co9S8 with p-n heterostructure

Photocatalytic production of H2O2 is a green and sustainable technique, which exposes the cost and environment issues with the dependence on organic electron donors and pure O2 before it is put into practice. Herein, we construct a p-n heterojunction of Z-scheme from the p-type Mn3O4 and n-type Co9S8 semiconductors for photocatalytic H2O2 production. Mn3O4/Co9S8 composites with the regulable morphology and structure exhibit improved photogenerated electrons transportability and e−-h+ pairs separation ability. An optimal photocatalyst obtains 1.6 mM of H2O2 for 6 h in alkaline medium without using electron donors and pure O2. The Z-scheme contribution is that the electrons in conduction band of Co9S8 are responsible for the major two-electron reduction of O2, while the holes in valence band of Mn3O4 achieve the OH generation as another channel for H2O2 production. The photogenerated H2O2 can be efficiently used as an in situ oxidant to accomplish dyes degradation.

Tuning the LUMO Levels of Z-Shaped Perylene Diimide via Stepwise Cyanation.

The central dogma in constructing organic electron acceptors is to attach electron-withdrawing groups to polycyclic aromatic hydrocarbons. Yet, the full potentials of many organic acceptors were never realized due to synthetic obstacles. By combining the Wittig-Knoevenagel benzannulation, the Pd(0)-catalyzed cyanation, and nucleophilic addition/oxidation cyanation, six polynitrile Z-shaped perylene diimide were synthesized. These stable and soluble electron acceptors possess LUMO energy levels comparable with those of benchmark compounds. Electrochemical investigation reveals that each additional nitrile group reduces the LUMO energy by 0.2 eV.

Basic Study on Organic Electron Transfer Reactions by Electrochemistry Combined with Quantum Chemical Calculations

This review summarizes the results of the author's basic research on organic electrochemistry conducted at Gifu Pharmaceutical University over about 40 years. After completing graduate school, the author became a research associate in Prof. Tanekazu Kubota's laboratory and started research on molecular spectroscopy in 1983. After Prof. Kubota retired in 1989, the author continued investigations in the field of organic electrochemistry as an independent researcher. At that time, a research environment in which ab initio molecular orbital calculations can be used as an analytical tool for experimental research was developed, and the author commenced research on organic electrochemistry combined with quantum chemical calculations as a lifework. The author's research topics were basic research on the molecular theory of redox potentials of organic molecules, molecular design of functional molecules, intermolecular interactions of organic molecules involving electron transfers and electron transfer systems composed of bioactive quinones, and analytical application research based on the basic electrochemistry. In this review article, the essence of the research results is introduced while reflecting on the existing situation at the time of the research. The author concludes the review by expressing gratitude to all colleagues for supporting the research in the author's laboratory.

Modulating the Pro-Apoptotic Activity of Cytochrome C at a Biomimetic Electrified Liquid|Liquid Interface

Programmed cell death via apoptosis is a natural defence against excessive cell division, crucial at all stages of life from foetal development to maintenance of homeostasis and elimination of precancerous and senescent cells.In this presentation, an electrified liquid|liquid bio-interface is demonstrated that replicates the molecular machinery of the inner mitochondrial membrane at the onset of apoptosis. By mimicking in vivo cytochrome c (Cyt c) interactions with cell membranes, our platform allows us to modulate the conformational plasticity of the protein by simply varying the electrochemical environment at an aqueous|organic interface. Our experimental findings supported by molecular modelling show that adsorption, orientation, restructuring, and pro-apoptotic peroxidase activity of Cyt c can all be precisely manipulated. Remarkably, we observe interfacial electron transfer between an organic electron donor decamethylferrocene and O2, electrocatalysed by Cyt c. This interfacial reaction requires partial Cyt c unfolding, mimicking Cyt c in vivo peroxidase activity.Our electrified liquid|liquid bio-interface motivates development of biomimetic electrochemical platforms to identify drug molecules that can potentially downregulate Cyt c and protect against uncontrolled neuronal cell death in Alzheimer’s and other neurodegenerative diseases. As proof-of-concept, we demonstrate that bifonazole, predicted to target the heme pocket, inhibits the electrocatalytic activity of Cyt c and switches off O2 reduction. Figure 1

Tandem photoelectrochemical and photoredox catalysis for efficient and selective aryl halides functionalization by solar energy

Tandem photoelectrochemical and photoredox catalysis for efficient and selective aryl halides functionalization by solar energy

Bis(Iminophosphorano)-Substituted Pyridinium Ions and their Corresponding Bispyridinylidene Organic Electron Donors.

Optimized synthetic procedures for pyridinium ions featuring iminophosphorano (-N=PR3 ; R=Ph, Cy) π-donor substituents in the 2- and 4- positions are described. Crystallographic and theoretical studies reveal that the strongly donating substituents severely polarize the π-electrons of the pyridyl ring at the expense of aromaticity. Moreover, the pyridinium ions are readily deprotonated to generate powerful bispyridinylidene (BPY) organic electron donors. Electrochemical studies show exceptionally low redox potentials for the two-electron BPY/BPY2+ couples, ranging from -1.71 V vs the saturated calomel electrode for 3PhPh (with four Ph3 P=N- groups) to -1.85 V for 3CyCy (with four Cy3 P=N- groups). These new compounds represent the most reducing neutral organic electron donors (OEDs) currently known. Some preliminary reductions involving 3CyCy showed enhanced capability owing to its low redox potential, such as the thermally activated reduction of an aryl chloride, but purification challenges were often encountered.

Methanotrophs: Discoveries, Environmental Relevance, and a Perspective on Current and Future Applications.

Methane is the final product of the anaerobic decomposition of organic matter. The conversion of organic matter to methane (methanogenesis) as a mechanism for energy conservation is exclusively attributed to the archaeal domain. Methane is oxidized by methanotrophic microorganisms using oxygen or alternative terminal electron acceptors. Aerobic methanotrophic bacteria belong to the phyla Proteobacteria and Verrucomicrobia, while anaerobic methane oxidation is also mediated by more recently discovered anaerobic methanotrophs with representatives in both the bacteria and the archaea domains. The anaerobic oxidation of methane is coupled to the reduction of nitrate, nitrite, iron, manganese, sulfate, and organic electron acceptors (e.g., humic substances) as terminal electron acceptors. This review highlights the relevance of methanotrophy in natural and anthropogenically influenced ecosystems, emphasizing the environmental conditions, distribution, function, co-existence, interactions, and the availability of electron acceptors that likely play a key role in regulating their function. A systematic overview of key aspects of ecology, physiology, metabolism, and genomics is crucial to understand the contribution of methanotrophs in the mitigation of methane efflux to the atmosphere. We give significance to the processes under microaerophilic and anaerobic conditions for both aerobic and anaerobic methane oxidizers. In the context of anthropogenically influenced ecosystems, we emphasize the current and potential future applications of methanotrophs from two different angles, namely methane mitigation in wastewater treatment through the application of anaerobic methanotrophs, and the biotechnological applications of aerobic methanotrophs in resource recovery from methane waste streams. Finally, we identify knowledge gaps that may lead to opportunities to harness further the biotechnological benefits of methanotrophs in methane mitigation and for the production of valuable bioproducts enabling a bio-based and circular economy.

Long‐Persistent Luminescence from an Exciplex‐Based Organic Light‐Emitting Diode

Organic long-persistent luminescent systems (OLPLs) exhibiting long-lasting emission after photoexcitation consist of organic electron donors and acceptors, that are widely used in organic light-emitting diodes (OLEDs). Although OLPLs and OLEDs include very similar excitonic processes, long-lasting emission has never been observed in OLEDs. This study confirms the presence of long-persistent luminescence (LPL) under electrical excitation.

Organic Electron Donors and Terminal Electron Acceptors Structure Anaerobic Microbial Communities and Interactions in a Permanently Stratified Sulfidic Lake.

The extent to which nutrients structure microbial communities in permanently stratified lakes is not well understood. This study characterized microbial communities from the anoxic layers of the meromictic and sulfidic Fayetteville Green Lake (FGL), NY, United States, and investigated the roles of organic electron donors and terminal electron acceptors in shaping microbial community structure and interactions. Bacterial communities from the permanently stratified layer below the chemocline (monimolimnion) and from enrichment cultures inoculated by lake sediments were analyzed using 16S rRNA gene sequencing. Results showed that anoxygenic phototrophs dominated microbial communities in the upper monimolimnion (21 m), which harbored little diversity, whereas the most diverse communities resided at the bottom of the lake (∼52 m). Organic electron donors explained 54% of the variation in the microbial community structure in aphotic cultures enriched on an array of organic electron donors and different inorganic electron acceptors. Electron acceptors only explained 10% of the variation, but were stronger drivers of community assembly in enrichment cultures supplemented with acetate or butyrate compared to the cultures amended by chitin, lignin or cellulose. We identified a range of habitat generalists and habitat specialists in both the water column and enrichment samples using Levin’s index. Network analyses of interactions among microbial groups revealed Chlorobi and sulfate reducers as central to microbial interactions in the upper monimolimnion, while Syntrophaceae and other fermenting organisms were more important in the lower monimolimnion. The presence of photosynthetic microbes and communities that degrade chitin and cellulose far below the chemocline supported the downward transport of microbes, organic matter and oxidants from the surface and the chemocline. Collectively, our data suggest niche partitioning of bacterial communities via interactions that depend on the availability of different organic electron donors and terminal electron acceptors. Thus, light, as well as the diversity and availability of chemical resources drive community structure and function in FGL, and likely in other stratified, meromictic lakes.

Binary-mixed organic electron transport layers for planar heterojunction perovskite solar cells with high efficiency and thermal reliability

The optimal electron transport layer (ETL) is a crucial component in the inverted perovskite solar cells (PSCs) for achieving high photovoltaic performance and device stability. We herein address the alloy ETL strategy, which incorporates a non-fullerene small molecule, ITIC-4F, into the fullerene-based ETL to optimize the electron-selective interfacial properties of CH3NH3PbI3-based inverted PSCs. The alloy ETL exhibited tailored energy level alignment at the interface of perovskite and ETL, so the electron-extraction/recombination behavior is greatly improved. Also, the hydrophobic surface of the alloy ETL effectively impedes not only moisture invasion but also morphological deterioration under continuous operation, so the resultant CH3NH3PbI3-based inverted device modified with the alloy ETL exhibited superior power conversion efficiency (PCE) up to 19.99%, with a negligible hysteresis. The alloy ETL-based PSCs also achieves 25.1% efficiency under indoor lighting condition, which promises a feasible design strategy of interfacial optimization in high-performance PSCs using organic semiconductors.

Highly efficient photosynthesis of hydrogen peroxide in ambient conditions

Photosynthesis of hydrogen peroxide (H2O2) in ambient conditions remains neither cost effective nor environmentally friendly enough because of the rapid charge recombination. Here, a photocatalytic rate of as high as 114 μmol⋅g-1⋅h-1 for the production of H2O2 in pure water and open air is achieved by using a Z-scheme heterojunction, which outperforms almost all reported photocatalysts under the same conditions. An extensive study at the atomic level demonstrates that Z-scheme electron transfer is realized by improving the photoresponse of the oxidation semiconductor under visible light, when the difference between the Fermi levels of the two constituent semiconductors is not sufficiently large. Moreover, it is verified that a type II electron transfer pathway can be converted to the desired Z-scheme pathway by tuning the excitation wavelengths. This study demonstrates a feasible strategy for developing efficient Z-scheme photocatalysts by regulating photoresponses.

Quantification of photocatalytically-generated hydrogen peroxide in the presence of organic electron donors: Interference and reliability considerations

Photocatalytic H2O2 production is an innovative on-site H2O2 synthesis method to treat organic pollutants through Fenton-like reactions, avoiding the need and potential liability of H2O2 storage and transportation. Accurate quantification of H2O2 is crucial to explore the mechanism of photocatalytic H2O2 production and optimize reaction parameters. In this work, three common H2O2 quantification methods (i.e., titration with potassium permanganate (KMnO4), and colorimetry with ammonium metavanadate (NH4VO3) or N,N-diethylp-phenylenediamine-horseradish peroxidase (DPD-POD)) were compared and their susceptibility to interference by seven types of representative organics were considered. Interference mechanisms were explored based on the electron-donating (Egap) and electron-accepting (ELUMO) ability of the present organics. The accuracy of the KMnO4 titration method is greatly compromised by aromatic compounds even at 0.1 mM due to the increased KMnO4 consumption by direct oxidation. The presence of p-benzoquinone that directly reacts with NH4VO3 and DPD compromises these colorimetric methods, especially DPD-POD colorimetry at concentrations as low as 0.1 mM. The DPD-POD method should also be scrutinized in the presence of phenols due to significant disturbance by oxidation byproducts (e.g. hydroquinone inducing immediate color disappearance). A flowchart was generated to provide guidelines for selecting an appropriate H2O2 quantification method for different water matrices treated by Fenton-like reactions.

Metagenomic analysis of facilitation mechanism for azo dye reactive red 2 degradation with the dosage of ferroferric oxide

Biological degradation of azo dyes and their intermediates requires a relatively long reaction duration due to their refractory characteristics. To enhance the azo dye degradation, the effects of ferroferric oxide (Fe3O4) on organic carbon metabolism, azo dye degradation, and microbial community structures were investigated through metagenomic analysis. Microorganisms possessing the azo dye-degradation ability changed from Bacillus, Aeromonas, and Lysobacter to Acinetobacter and Desulfovibrio when the Fe3O4 dosage increased from 0 g/L to 15 g/L. Geobacter and Staphylococcus were the most important bacteria involving in organic carbon metabolism, electron transfer, and azo dye degradation, and the dosage of Fe3O4 could enrich both microorganisms and enhance system performance. The facilitation mechanism with the dosage of Fe3O4 could be attributed to the increase of extracellular electron transfer rate and the enrichment of functional microorganisms.

Power of an Organic Electron Acceptor in Modulation of Intracellular Mitochondrial Reactive Oxygen Species: Inducing JNK- and Caspase-Dependent Apoptosis of Cancer Cells.

Here, we demonstrate an interesting strategy of modulating mitochondrial reactive oxygen species (ROS) using the organic electron acceptor molecule carbonyl-bridged bithiazole attached with bis-trifluoroacetophenone (BBT). This molecule was found to affect complex I activity. It has the propensity to bind close to the flavin mononucleotide site of complex I of mitochondria where it traps electron released from nicotinamide adenine dinucleotide (NADH) and elevates intracellular ROS, which suggests that the bridged carbonyl in BBT plays a crucial role in the acceptance of electron from NADH. We understand that the potential of the NADH/NAD+ redox couple and low-lying LUMO energy level of BBT are compatible with each other, thus favoring its entrapment of released electrons in complex I. This effect of BBT in ROS generation activates JNK and p38 stress-dependent pathways and resulted in mitochondrial-dependent apoptotic cell death with the reduction in expression of several important cyto-protecting factors (Hsp27 and NFκB), indicating its potential in inhibition of cancer cell relapse. Intriguingly, we found that BBT is not a P-glycoprotein substrate, which further reveals its excellent anticancer potential. This study enlightens us on how the power of electron acceptor ability became an emerging strategy for modulation of intracellular function.