Enhanced ammonia nitration by Bio-Electrochemical systems with constructed wetlands.

The insufficient abundance of electron acceptors for ammonia during electron transfer in constructed wetlands (CWs) results in low nitrification rates. This study developed a green, low-carbon CWs enhanced by a bio-electrochemical systems (BESs-CWs) to achieve efficient ammonia (NH4+-N) removal. Electrode enhancement significantly promoted NH4+-N removal. Compared with traditional CWs, the average removal efficiency of NH4+-N in the BESs-CWs increased from 62.9 % to 90.6 %. The intermittent voltage driven by the photovoltaic power system caused minimal plant stress. However, electrode enhancement significantly affected microbial communities involved in short-path nitrification and denitrification within the biofilm. Specifically, the removal rate of NH4+-N by BESs-CWs under electrode enhancement was increased by 27.7 % compared to traditional CWs, enhancing the electron output of NH4+-N in the BESs-CWs. This system provides a method of ammonia nitration for CWs under poor electron acceptor conditions.

Synthesis and characterization of 1,2,3,4-naphthalene and anthracene diimides.

We report the synthesis and characterization of naphthalene and anthracene scaffolds end-capped by cyclic imides. The solid-state structures of the N-phenyl derivatives, determined by X-ray crystallography, reveal changes in packing preference based on the number of aromatic rings in the core. The optical and electronic properties of the title compounds compare favorably with other previously described isomers and expand the toolbox of electron-deficient aromatic compounds available to organic materials chemists.

Anaerobic oxidation of methane driven by different electron acceptors: A review.

Methane, the most significant reduced form of carbon on Earth, acts as a crucial fuel and greenhouse gas. Globally, microbial methane sinks encompass both aerobic oxidation of methane (AeOM), conducted by oxygen-utilizing methanotrophs, and anaerobic oxidation of methane (AOM), performed by anaerobic methanotrophs employing various alternative electron acceptors. These electron acceptors involved in AOM include sulfate, nitrate/nitrite, humic substances, and diverse metal oxides. The known anaerobic methanotrophic pathways comprise the internal aerobic oxidation pathway found in NC10 bacteria and the reverse methanogenesis pathway utilized by anaerobic methanotrophic archaea (ANME). Diverse anaerobic methanotrophs can perform AOM independently or in cooperation with symbiotic partners through several extracellular electron transfer (EET) pathways. AOM has been documented in various environments, including seafloor methane seepages, coastal wetlands, freshwater lakes, soils, and even extreme environments like hydrothermal vents. The environmental activities of AOM processes, driven by different electron acceptors, primarily depend on the energy yields, availability of electron acceptors, and environmental adaptability of methanotrophs. It has been suggested that different electron acceptors driving AOM may occur across a wider range of habitats than previously recognized. Additionally, it is proposed that methanotrophs have evolved flexible metabolic strategies to adapt to complex environmental conditions. This review primarily focuses on AOM, driven by different electron acceptors, discussing the associated reaction mechanisms and the habitats where these processes are active. Furthermore, it emphasizes the pivotal role of AOM in mitigating methane emissions.

Water-Stable, Eight-electron Acceptor Drives Anion∙∙∙Water Assisted Tunable Ionic Self-Assembly and Proton Conduction.

Organic π-scaffolds are being envisaged for new-age electron- and ion-responsive materials that can accumulate electrons as well as transport proton. However, such systems are extremely rare as electron-deficient scaffolds are unstable in aqueous solution. Here we detail the synthesis of a water-stable core-naphthalenediimide-nitrobenzyl-viologen based tetra-cation, which accumulates up to eight-electrons within an exceptionally narrow potential window of +0.05 V and -1.12 V. The supramolecular interactions and the ensuing ionic framework are tunable based on the three anions, e.g., Cl-, Br- and PF6-, that are investigated in this work. The ionic framework is formed and supported by a range of H-bonds, in which, the nitro benzyl groups act as pillars connecting the 1D water-tapes and the halide anions. The water molecules are hydrogen-bonded with the halide anions and bestow a facile pathway for the proton conduction, with proton conductivity up to 3.19 x 10-3 S cm-1. In contrast, the ionic assembly formed by the lipophilic PF6- anions do not host the water tapes and consequently the proton conductivity is found to be four orders of magnitude lower. This is a unique example, whereby proton conductivity is realized and is tunable within a highly electron-deficient, eight-electron acceptor, water-stable ionic supramolecular system.

Covalently Linked 5,6,11,12-Tetraazanaphthacene Dimer and Its Triptycene-Capped Derivatives as Electron Acceptors.

The development of electron transport and n-type materials is still largely dominated by a limited number of organic semiconductors, with fullerenes at the forefront. In contrast, substantial progress has been made in developing hole transport and p-type materials. Therefore, expanding the range of electron acceptors, making them solution-processable, and elucidating their structural arrangement by X-ray crystallography is essential. We synthesised 2,2'-bi-(5,6,11,12-tetraazanaphthacene) (bi-TANC) and its triptycene end-capped derivative, 2,2'-bi(8,13-dihydro-8,13-[1,2]benzenonaphtho-5,6,15,16-tetraazanaphthacene) (bi-TpTANC), as electron acceptors. Bi-TANC exhibits a herringbone-like crystal packing with intermolecular π-π overlap, which is observed in typical organic n-type semiconductors. However, it showed poor solubility, similar to larger acenes. In contrast, bi-TpTANC exhibited favourable solubility, and its electrochemistry in solution was investigated. In the cyclic voltammogram of bi-TpTANC, reversible redox waves corresponding to 3-step/4-electron transfer were observed at -0.795 V (1e-), -0.927 V (1e-), and -1.44 V (2e-) as half-wave potentials. The redox wave associated with the two-electron transfer on the negative low-potential side indicates the presence of through-bond charge delocalisation in the monoanionic state. Furthermore, the LUMO level of bi-TpTANC is -4.1 eV, which indicates its potential as a promising air-stable n-type material.

Cyclization Engineering of Electron-Deficient Maleimide Unit for Nonfused Ring Electron Acceptors Enables Efficient Organic Solar Cells.

Nonfused ring electron acceptors (NFREAs) have emerged as promising materials for commercial applications in organic solar cells due to their straightforward synthesis process and cost-effectiveness. The rational design of their structural frameworks is crucial for enhancing device efficiency. In this study, we explore the use of maleimide and thiophene as key building blocks, employing cyclization engineering techniques. Additionally, cyclopentanedithiophene was chosen as the bridging unit, coupled with fluorinated terminals, to fabricate NFREAs, namely, PI-DTS and DPI-DTS. DPI-DTS demonstrated superior molecular planarity and an upshifted lowest unoccupied molecular orbital energy level. Moreover, DPI-DTS-based blend films display enhanced π-π interactions and crystallinity, alongside a predominantly face-on orientation. Consequently, DPI-DTS-based devices displayed enhanced and more balanced carrier mobility, reduced bimolecular recombination, and trap-assisted recombination, leading to improved charge transfer efficiency. Ultimately, this led to an excellent efficiency of 10.48%, with an open-circuit voltage as high as 0.914 V. These findings highlight the significant promise of aromatic imides in constructing NFREAs, and the established structure-performance relationship provides a theoretical basis for the design of high performance NFREAs.

Precisely Regulating Intermolecular Interactions and Molecular Packing of Nonfused-Ring Electron Acceptors via Halogen Transposition for High-Performance Organic Solar Cells.

The structure of molecular aggregates is crucial for charge transport and photovoltaic performance in organic solar cells (OSCs). Herein, the intermolecular interactions and aggregated structures of nonfused-ring electron acceptors (NFREAs) are precisely regulated through a halogen transposition strategy, resulting in a noteworthy transformation from a 2D-layered structure to a 3D-interconnected packing network. Based on the 3D electron transport pathway, the binary and ternary devices deliver outstanding power conversion efficiencies (PCEs) of 17.46 % and 18.24 %, respectively, marking the highest value for NFREA-based OSCs.

Machine learning assisted designing of non-fullerene electron acceptors: A quest for lower exciton binding energy.

The designing of acceptors materials for the organic solar cells is a hot topic. The normal experimental methods are tedious and expensive for large screening. Machine learning guided exploration is more suitable solution. Bagging regression, random forest regression, gradient boosting regression, and linear regression are trained to predict exciton binding energy. Breaking Retrosynthetically Interesting Chemical Substructures (BRICS) methodology has utilized for designing of new non-fullerene acceptors (NFAs). The predicted values were used to select the designed NFAs. On the selected NFAs, clustering and chemical similarity analyses are also performed. Chemical fingerprints are used for this purpose, and the synthetic accessibility score of the new NFAs is also investigated.30 NFAs have selected with low exciton binding energy values. This approach will allow for the rapid screening of NFAs for organic solar cells. Our proposed framework stands out as a valuable tool for strategically selecting the most effective NFAs for organic solar cells and offers a streamlined approach for material discovery.

Advancing Integration of Direct C-H Arylation-Derived Star-Shaped Oligomers as Second Acceptors for Ternary Organic Solar Cells.

Organic solar cells (OSCs) could benefit from the ternary bulk heterojunction (BHJ), a method that allows for fine-tuning of light capture, cascade energy levels, and film shape, in order to increase their power conversion efficiency (PCE). In this work, the third components of PM6:Y6 and PM6:BTP-eC9 BHJs are a set of four star-shaped unfused ring electron acceptors (SSUFREAs), i.e., BD-IC, BFD-IC, BD-2FIC, and BFD-2FIC, that are facilely synthesized by direct C-H arylation. The four SSUFREAs all show complete complementary absorption with PM6, Y6, and BTP-eC9, which facilitates light harvesting and exciton collection. When BFD-2FIC is added as a third component, the PCEs of PM6:Y6 and PM6:BTP-eC9 binary BHJs are able to be improved from 15.31% to 16.85%, and from 16.23% to 17.23%, respectively, showing that BFD-2FIC is useful for most effective ternary OSCs in general, and increasing short circuit current (JSC) and better film morphology are two additional benefits. The ternary PM6:Y6:BFD-2FIC exhibits a 9.7% percentage of increase in PCE compared to the PM6:Y6 binary BHJ, which is one of the highest percentage increases among the reported ternary BHJs, showing the huge potential of BFD-2FIC for ternary BHJ OSCs.

Polymerizing M-Series Acceptors for Efficient Polymer Solar Cells: Effect of the Molecular Shape.

Currently, high-performance polymerized small-molecule acceptors (PSMAs) based on ADA-type SMAs are still rare and greatly demanded for polymer solar cells (PSCs). Herein, two novel regioregular PSMAs (PW-Se and PS-Se) are designed and synthesized by using centrosymmetric (linear-shaped) and axisymmetric (banana-shaped) ADA-type SMAs as the main building blocks, respectively. It is demonstrated that photovoltaic performance of the PSMAs can be significantly improved by optimizing the configuration of ADA-type SMAs. Compared to the axisymmetric SMA-based polymer (PS-Se), PW-Se using a centrosymmetric SMA as the main building block exhibits better backbone coplanarity thereby resulting in bathochromically shifted absorption with a higher absorption coefficient, tighter interchain π-π stacking, and more favorable blend film morphology. As a result, enhanced and more-balanced charge transport, better exciton dissociation, and reduced charge recombination are achieved for PW-Se-based devices with PM6 as polymer donor. Benefiting from these positive factors, the optimal PM6:PW-Se-based device exhibits a higher power conversion efficiency (PCE) of 15.65% compared to the PM6:PS-Se-based device (8.90%). Furthermore, incorporation of PW-Se as a third component in the binary active layer of PM6:M36 yields ternary devices with an outstanding PCE of 18.0%, which is the highest value for PSCs based on ADA-type SMAs, to the best of the knowledge.

Structure-Property Relationships for Potential Inversion From Electron Acceptors Based on Thiophene-Fused Triptycene Quinones, 1,4-Diketones and Their Malononitrile Adducts.

The synthesis and properties of a series of 11,11,12,12-tetracyano-9,10-anthraquinodimethane (TCAQ) inspired electron acceptors based on thiophene-fused quinone and triptycene motifs is presented. This has yielded insights into structure-property relationships for establishing and modulating simultaneous two-electron reduction processes in TCAQ analogues. These new compounds were synthesised using a Friedel-Crafts acylation between triptycene and thiophene-3,4-dicarbonyl chloride. Isomeric para-quinones featuring a [c]-fused thiophene on one side and a ß,ß- or α,ß-fused triptycene on the other were isolated alongside a thiophene-3,4-diketone which bears two triptycene fragments. Knoevenagel condensation of these products with malononitrile produced a quinoidal bis(dicyanomethylene), an oxo-dicyanomethylene and an acyclic bis(dicyanomethylene). This series of new electron accepting molecules has been studied using X-ray crystallography and the implications of their 3D structures on NMR and UV/vis absorbance spectroscopy and cyclic voltammetry results have been ascertained with conclusions underpinned by computational methods.

Optimizing Molecular Crystallinity and Suppressing Electron-Phonon Coupling in Completely Non-Fused Ring Electron Acceptors for Organic Solar Cells.

High open-circuit voltage (Voc) organic solar cells (OSCs) have received increasing attention because of their promising application in tandem devices and indoor photovoltaics. However, the lack of a precise correlation between molecular structure and stacking behaviors of wide band gap electron acceptors has greatly limited its development. Here, we adopted an asymmetric halogenation strategy (AHS) and synthesized two completely non-fused ring electron acceptors (NFREAs), HF-BTA33 and HCl-BTA33. The results show that AHS significantly enhances the molecular dipoles and suppresses electron-phonon coupling, resulting in enhanced intramolecular/intermolecular interactions and decreased nonradiative decay. As a result, PTQ10 : HF-BTA33 realizes a power conversion efficiency (PCE) of 11.42 % with a Voc of 1.232 V, higher than that of symmetric analogue F-BTA33 (PCE=10.02 %, Voc=1.197 V). Notably, PTQ10 : HCl-BTA33 achieves the highest PCE of 12.54 % with a Voc of 1.201 V due to the long-range ordered π-π packing and enhanced surface electrostatic interactions thereby facilitating exciton dissociation and charge transport. This work not only proves that asymmetric halogenation of completely NFREAs is a simple and effective strategy for achieving both high PCE and Voc, but also provides deeper insights for the precise molecular design of low cost completely NFREAs.

Fate of sulfamethoxazole in wetland sediment under controlled redox conditions.

Redox condition is an important controlling factor for contaminant removal in constructed wetlands; however, the redox-sensitivity of antibiotic removal in wetland sediments under controlled conditions with specific electron acceptors remains unclear. Here, using a 14C radioactive tracer, we explored fate of sulfamethoxazole (SMX) in a wetland sediment slurry under oxic, nitrate-reducing, iron-reducing, and methanogenic conditions. In the sterile treatment, unlike the comparable SMX dissipation from the water phase under four redox conditions, non-extractable residues (NERs) of SMX was highest formed in the sediment under oxic condition, mainly in sequestered and ester/amide-linked forms. Microorganisms markedly promoted SMX transformation in the slurry. The dissipation rate of SMX and its transformation products (TPs) followed the order: oxic ≈ iron-reducing > methanogenic >> nitrate-reducing conditions, being consistent with the dynamics of microbial community in the sediment, where microbial diversity was greater and networks connectivity linking dominant bacteria to SMX transformation were more complex under oxic and iron-reducing conditions. Kinetic modeling indicated that the transformation trend of SMX and its TPs into the endpoint pool NERs depended on the redox conditions. Addition of wetland plant exudates and sediment dissolved organic matter at environmental concentrations affected neither the abiotic nor the biotic transformation of SMX. Overall, the iron-reducing condition was proven the most favorable and eco-friendly for SMX transformation, as it resulted in a high rate of SMX dissipation from water without an increase in toxicity and subsequent formation of significant stable NERs in sediment. Our study comprehensively revealed the abiotic and biotic transformation processes of SMX under controlled redox conditions and demonstrated iron-reducing condition allowing optimal removal of SMX in constructed wetlands.

Screening novel candidates of ZL003-based organic dyes for dye-sensitized solar cells by modifying auxiliary electron acceptors: A theoretical study.

In this work, a series of ZL003-based free-metal sensitizers with the donor-acceptor-π- conjugated spacer-acceptor (D-A-π-A) structure were designed by modifying auxiliary electron acceptors for the potential application in dye-sensitized solar cells. The energy levels of frontier molecular orbitals, absorption spectra, electronic transition, and photovoltaic parameters for all studied dyes were systematically evaluated using density functional theory (DFT)/time-dependent DFT calculations. Results illustrated that thienopyrazine (TPZ), selenadiazolopyridine (SDP), and thiadiazolopyridine (TDP) are excellent electron acceptors, and dye sensitizers functionalized by these acceptors have smaller HOMO-LUMO gaps, obviously red-shifted absorption bands and stronger light harvesting. The present study revealed that the photoelectric conversion efficiency (PCE) of ZL003 is around 13.42 % with a JSC of 20.21 mA·cm-2, VOC of 966 mV and FF of 0.688 under the AM 1.5G sun exposure, in good agreement with its experimental value (PCE = 13.6 ± 0.2 %, JSC = 20.73 ± 0.20 mA·cm-2, VOC = 956 ± 5 mV, and FF = 0.685 ± 0.005.). With the same procedure, the PCE values for M4, M6, and M7 were estimated to be as high as 19.93 %, 15.38 %, and 15.80 % respectively. Hence, these three dyes are expected to be highly efficient organic sensitizers applied in practical DSSCs.

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.