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Pulsed discharge nozzles (PDNs) have been successfully used for decades to produce rotationally cold (Trot ∼ 20 K) radicals and ions of astrophysical interest and to characterize these species spectroscopically. In this work, an evolution of the PDN, the piezostack pulsed discharge nozzle (P2DN), is used for the first time to investigate the characteristics of the still poorly understood supersonic plasma expansion. The P2DN allows for a better control of the reservoir pressure of which an accurate measurement is required to characterize the plasma expansion. This new source, thus, gives the opportunity to further optimize the plasma conditions and extend its use to new target species. The spatial distribution of an argon plasma and the effect of the supersonic flow for different pressures are studied by combining a two-dimensional extended fluid model (extFM) and a direct simulation Monte Carlo (DSMC) method. The combined simulation is validated with experimental results obtained through emission spectroscopy associated with a group-code collisional-radiative model to retrieve the plasma parameters. The validated numerical approach (DSMC-extFM) allows for an accurate characterization of the plasma structure in our typical experimental conditions (a reservoir pressure ranging from 90 to 905 mbar). Thus, this simulation will be used in future studies to improve the plasma conditions to favor the synthesis of (transient) hydrocarbon species as found in space, by seeding the argon gas with a suitable precursor, such as acetylene. [ABSTRACT FROM AUTHOR]

Co‐precipitated biotic CoFe2O4 nanoparticles from the leaves of the Hibiscus rosa sinensis plant were used to produce bio‐reductant nanoparticles. The CoFe2O4 biomolecules were analyzed using EDX analysis to identify their structure through XRD, FTIR, UV, VSM, and SEM characterization. The cubic phase and crystallite size of biotic CoFe2O4 nanoparticles were determined using XRD analysis. The FTIR spectroscopy was used to confirm Cation migration and Co−Fe−O interaction. Using SEM, TEM, and EDX, it was confirmed that spherical biosynthesized CoFe2O4 nanoparticles and the material they were made were present. VSM analysis confirmed the super‐paramagnetic nature of the CoFe2O4 nanoparticles and magnetic pulse. Biosynthetic CoFe2O4 nanoparticles were used to eliminate organic(MB dye) and bacterial(S. aureus, B.Substils, and E. coli bacterial strains) pollutants. Spinel ferrite biosynthetic CoFe2O4 nanoparticles are capable of generating radical superoxide ions. [ABSTRACT FROM AUTHOR]

Back electron transfer (BET) in eosin Y (EY) photoredox catalysis was visualized via the fluorescence of single EYs. BET between the radical ion pair formed in photoinduced electron transfer (PET) induced photoblinking of single EYs under constant photoexcitation. Commonly used quenchers, alkyl bromides and a tertiary amine, were studied. BET was observed in alkyl bromides, but not in the tertiary amine. The findings helped explain the mechanism of EY-catalyzed photoinduced atom transfer radical polymerizations. The method can be applied to studying BET on photo-emissive catalysts. [ABSTRACT FROM AUTHOR]

The etch rate uniformity in photoresist etching was monitored using multi-channel optical emission spectroscopy (OES) and a spatially resolved etch rate model incorporating radical and ion etching characteristics. The F radical densities at various locations were estimated using 8-channel OES and applied to a radical-spontaneous etch rate model to examine the impact of radicals on the etch rate. The ion fluxes were measured using a scanning floating harmonic probe for an ion-enhanced etch rate model to investigate the effect of ions on the etch rate. A combined etch rate model was proposed to explain the effects on both radical and ion etching characteristics, and the etch rates and etch rate uniformities predicted by the model were quantitatively compared with the measured values. The calculated R-squared score (R2) and the mean absolute percentage error (MAPE) of the etch rates predicted by the model were 0.99 and 1.3%, respectively. The etch rate uniformities predicted by the model showed good accuracy with R2 of 0.99 and MAPE of 12.0% compared to the measured values, and the combined etch rate model also successfully predicted the distribution of the etch rate. This study demonstrates that multi-channel OES and the developed model can quantitatively predict the etch rate distribution of plasma etching processes. [ABSTRACT FROM AUTHOR]

Highlights: A flow-bed water purification system with an asymmetric solar-thermal and catalytic membrane is designed for synergistic solar-thermal desalination of seawater/brine and catalytic degradation of organic pollutants. The hydrogen bonding networks can be regulated by the abundant surface –OH groups and the in situ generated ions and radicals during the degradation process for promoting solar-driven steam generation. The de-solvation of solvated Na+ and subsequent nucleation/growth of NaCl are effectively inhibited by SO42−/HSO5− ions. Although solar steam generation strategy is efficient in desalinating seawater, it is still challenging to achieve continuous solar-thermal desalination of seawater and catalytic degradation of organic pollutants. Herein, dynamic regulations of hydrogen bonding networks and solvation structures are realized by designing an asymmetric bilayer membrane consisting of a bacterial cellulose/carbon nanotube/Co2(OH)2CO3 nanorod top layer and a bacterial cellulose/Co2(OH)2CO3 nanorod (BCH) bottom layer. Crucially, the hydrogen bonding networks inside the membrane can be tuned by the rich surface –OH groups of the bacterial cellulose and Co2(OH)2CO3 as well as the ions and radicals in situ generated during the catalysis process. Moreover, both SO42− and HSO5− can regulate the solvation structure of Na+ and be adsorbed more preferentially on the evaporation surface than Cl−, thus hindering the de-solvation of the solvated Na+ and subsequent nucleation/growth of NaCl. Furthermore, the heat generated by the solar-thermal energy conversion can accelerate the reaction kinetics and enhance the catalytic degradation efficiency. This work provides a flow-bed water purification system with an asymmetric solar-thermal and catalytic membrane for synergistic solar thermal desalination of seawater/brine and catalytic degradation of organic pollutants. [ABSTRACT FROM AUTHOR]

The incorporation of cationic groups onto electron‐poor compounds is a viable strategy for achieving potent electron acceptors, as evidenced by reports of air‐stable radical forms of large aromatic diimides such as naphthalene and perylene diimides. These ions have also been observed to exhibit anion–π interaction tendencies of interest in molecular recognition applications. The benefits of phosphonium incorporation, however, have not yet been extended to the smallest benzene diimides. Here, we report that dibrominated pyromellitic diimide and mellophanic diimide both readily undergo substitution reactions with phosphine sources to yield bisphosphonium compounds. In the single crystalline form, these dications display anion‐π interactions and, in the case of mellophanic diimide, the stabilization of a bromide–water H−bonding ring pattern. The reaction of these dications with chemical reductants readily provides the singly and doubly reduced redox states, which were characterized by UV‐vis spectroscopy and found to exhibit intense absorptions extending into the near‐IR region. Taken together, this work demonstrates that phosphonium incorporation onto congested aromatic diimide scaffolds is synthetically viable and produces unusual electron‐poor compounds. [ABSTRACT FROM AUTHOR]

Living cell‐mediated polymerization offers promising applications in biomaterials, yet its further biological utilization is hindered by the need for metal ions or radical initiators with available methods. In this study, we introduce a living cell‐mediated polymerization that leverages the intrinsic metabolic activities of living cells to initiate and sustain free radical polymerization of zwitterionic methacrylates. The polymerization proceeded in the absence of transition metal catalysts, radical initiators, or light sources. The conversion of zwitterionic methacrylate strongly correlated with cellular activities and achieved a maximum conversion of 98 % within 48 hours. Living cells efflux redox power across membranes through metabolism and that terminal electron fluxes are captured by zwitterionic methacrylates pre‐assembled on the living cell surface to initiate radical polymerization reactions. The polymerization caused significant changes to the cell membrane surface and synthesized hydrogels with tailored mechanical properties. The polymer hydrogel obtained via probiotic E. coli Nissle 1917 was able to release the in situ encapsulated molecules, which demonstrated living cell‐mediated polymer hydrogel as a vehicle for the delivery of both cellular and molecular therapeutic agents. This research offered a green and efficient method for synthesizing bioactive materials and advancing the field of cellular therapeutics and drug delivery. [ABSTRACT FROM AUTHOR]

As antibiotics including the Sulfa drugs (SDs) have been found in aquatic environments, their derivatives and structural analogs have attracted increasing concern as pollutants. In this study, the density functional theory (DFT) and B3LYP method to investigate the direct and indirect photo-decomposition mechanisms of Sulfachloropyridazine (SC) a representative of SDs. The direct Photo-decomposition mechanisms were investigated with two pathways. In the initiation step an intermediate product (IP) was obtained with the computed activation energy (Ea), equal to 4.598 kcal.mol-1. The IP further leaded the path–I and path–II, in which two different products were obtained along with the SO2 as common product. However, the path–I was observed as the main pathway due to its low Ea value and influences of two metal ions (Mg2+ and Na+) on this pathway were investigated. Both the metal ions promoted direct-photo-decomposition of the SC by decreasing Ea the main pathway. Further, the role of •OH radical on the decomposition of the SC was investigated as the indirect photo-decomposition of the SC with three different decomposition schemes. A variety of decomposed products of the SC were obtained in the three schemes with different energy pathways and their calculated activation energies were detected in the range of 2.311 to 18.306, 0.6 to 16.43, and 0.037 to 23.177 Kcal.mol-1 respectively. [ABSTRACT FROM AUTHOR]

Houttuynia cordata Thunb. (H.cordata), as a traditional Chinese medicinal herb and food, has been used to treat various diseases because of rich content in flavonoids. Here, an ultra-high performance liquid chromatography with triple quadrupole tandem mass spectrometry (UPLC-TQ-MS/MS) method was proposed for the determination of flavonoids profiling in H.cordata. Single factor experiment and response surface methodology were used to optimize the pretreatment process of H.cordata samples. The optimal conditions were as follows: ultrasonic temperature: room temperature (25 °C); ultrasonic time: 5 min; solid-liquid ratio: 1:40 and concentration of ethanol: 60%. The method showed the good linearity (r ≥ 0.9855), the satisfactory intra-day (RSD%≤10.94%) and inter-day precision (RSD% ≤ 11.2%) and low limit of quantification (< 0.01 µg/mL). The content of flavonoids in flowers and leaves was much higher than in roots and stems. The flavonoids in the leaves of H.cordata from Chongqing was the highest (9.22 mg/g), and that in the flowers of H.cordata from Hubei province was the highest (6.69 mg/g). In addition, the antioxidant activity of the extracts of H.cordata was evaluated using the scavenging effect of the extracts on five free radicals and the iron ion reducing ability. The best antioxidant activity was observed in scavenging DPPH free radicals with EC50 value of 295.16 µg/mL. The scavenging of ABTS•+ free radicals and PTIO• free radicals was also effective with EC50 values of 818.82 µg/mL and 685.43 685.43 µg/mL, respectively. Thus, this study will be helpful to the development and utilization of flavonoids from H.cordata in food and pharmaceutical industries. [ABSTRACT FROM AUTHOR]

Aminoacetonitrile (AAN), also known as glycinenitrile, has been suggested as a possible precursor of glycine and adenine in the interstellar medium. Here, we present the chemical modelling of AAN and its isomers in hot cores using the three-phase chemical model NAUTILUS with the addition of over 300 chemical reactions of the three AAN isomers and related species. Our models predicted a peak gas-phase abundance of AAN reaching the order of 10 |$^{-8}$|⁠ , which is consistent with observation towards Sgr B2(N). Regarding the reaction pathways of AAN and its isomers, we found that AAN is primarily formed via free radical reactions on grain surfaces during the early evolutionary stages. Subsequently, it is thermally desorbed into the gas phase as the temperature rises and is then destroyed by positive ions and radicals in gas phase. The isomers of AAN are formed through the hydrogenation reaction of CH |$_3$| NCN on the grain surface and via electron recombination reactions of ion C |$_2$| H |$_5$| N |$_2^+$| in gas phase. We speculate that there is a possibility for NCCN and AAN to react with each other, eventually leading to the formation of adenine in hot cores. However, further investigation is required to understand the efficiency of grain surfaces in adenine formation, through theoretical calculations or laboratory experiments in future research. [ABSTRACT FROM AUTHOR]

The combination of continuous wave electron paramagnetic resonance (cw‐EPR) with electrochemistry is highly attractive as it allows a clean in‐situ generation and the subsequent spectroscopic characterisation of radical ions, which are important intermediates in many photocatalytic cycles as well as light‐induced processes occurring in biological systems or optoelectronic devices. Although commercial setups for spectroelectrochemical EPR are available, they are often expensive and tailored to a particular spectroscopic setup. Here we present a design for a low‐cost electrochemical EPR cell that can be used in combination with any commercial cw‐EPR instrumentation. The cell design is compared to existing setups and the performance of the cell is evaluated by comparison of EPR spectra obtained by chemical and electrochemical oxidation of a graphene fragment. [ABSTRACT FROM AUTHOR]

Cu-doped Bi4O5Br2 photocatalyst was synthesized via a solvothermal method, and the influence of Cu doping on its structure, morphology, and photoelectric characteristics was comprehensively investigated by adopting various characterization techniques. Furthermore, the photocatalytic performance of the material was assessed through the degradation of ciprofloxacin (CIP) under visible light. The characterization results demonstrated that compared to the intrinsic Bi4O5Br2, the introduction of Cu resulted in a decreased bandgap, an expanded visible light absorption range, an enhanced visible light absorption intensity, and improved separation efficiency of electrons and holes, thereby enhancing the photocatalytic activity. In the ciprofloxacin degradation experiment, 3%Cu-Bi4O5Br2 exhibited superior performance, achieving a degradation rate of 80.1%, which was more than twice as high as the intrinsic Bi4O5Br2 (53.2%). Moreover, it maintained excellent stability even after undergoing five cycling experiments. The free radical capture experiments indicated that h+, •O2− and •OH played a dominant role in the photodegradation reactions of ciprofloxacin. Finally, this study discussed the possible photocatalytic mechanism and deduced three degradation pathways of ciprofloxacin on the basis of the 8 intermediate products detected by LCMS. In summary, Cu-Bi4O5Br2 demonstrated remarkable photocatalytic performance and stability under visible light response, positioning it as a promising catalyst for future sunlight-based removal of diverse pollutants. The doping of Cu enhances the absorption of visible light by Bi4O5Br2, improving its photocatalytic performance. The photocatalytic degradation mechanism of Cu-doped Bi4O5Br2 photocatalyst mainly includes three approaches. The holes can interact with electrons in ciprofloxacin (CIP), thereby directly oxidizing it. Next, photogenerated electrons combine with dissolved oxygen to form superoxide negative ions, and some of these are further oxidized to produce hydroxyl radicals. Both superoxide negative ions and hydroxyl radicals participate in the degradation of CIP. Last, Cu2+ captures photogenerated electrons and transforms into Cu+, which promotes the reduction of dissolved oxygen molecules to generate superoxide radicals (•O2-), accelerating the degradation of CIP. Meanwhile, Cu+ can be oxidized back to Cu2+. This conversion is dynamic and continuously cycles as long as the illumination persists [ABSTRACT FROM AUTHOR]

Chemical (molecular, quantum) machine learning relies on representing molecules in unique and informative ways. Here, we present the matrix of orthogonalized atomic orbital coefficients (MAOC) as a quantum-inspired molecular and atomic representation containing both structural (composition and geometry) and electronic (charge and spin multiplicity) information. MAOC is based on a cost-effective localization scheme that represents localized orbitals via a predefined set of atomic orbitals. The latter can be constructed from such small atom-centered basis sets as pcseg-0 and STO-3G in conjunction with guess (non-optimized) electronic configuration of the molecule. Importantly, MAOC is suitable for representing monatomic, molecular, and periodic systems and can distinguish compounds with identical compositions and geometries but distinct charges and spin multiplicities. Using principal component analysis, we constructed a more compact but equally powerful version of MAOC—PCX-MAOC. To test the performance of full and reduced MAOC and several other representations (CM, SOAP, SLATM, and SPAHM), we used a kernel ridge regression machine learning model to predict frontier molecular orbital energy levels and ground state single-point energies for chemically diverse neutral and charged, closed- and open-shell molecules from an extended QM7b dataset, as well as two new datasets, N-HPC-1 (N-heteropolycycles) and REDOX (nitroxyl and phenoxyl radicals, carbonyl, and cyano compounds). MAOC affords accuracy that is either similar or superior to other representations for a range of chemical properties and systems. [ABSTRACT FROM AUTHOR]

Free radicals and metal ions are key factors causing coal spontaneous combustion. In order to effectively suppress coal spontaneous combustion, experiments were conducted using luteolin as an inhibitor, luteolin is abbreviated as LUT. The influence of different concentrations of LUT on the spontaneous combustion heat characteristics of coal was tested using a C600 high-precision microcalorimeter, and the inhibition mechanism was inferred by FTIR. The experimental results show that LUT is an effective coal oxygen inhibitor, under the same action conditions, different concentrations of LUT can absorb heat to different degrees, delay the initial exothermic temperature of coal, prolong the heat absorption phase of coal. Compared with raw coal, 6 wt% LUT absorbs the most heat, the starting exothermic temperature is delayed by 46°C, and the activation energy is increased by 47.89 kJ/mol, the functional group -OH content decreased by 43.4%, -CH3 decreased by 32.1%, -CH2-decreased by 37.76%. Based on this, the mechanism of inhibition is inferred, LUT not only removes free radicals (ROO•) during the chain initiation stage and captures free radicals (•OH) in the reaction chain but also chelates metal ions to inhibit the catalytic effect of metal ions during the free radical reaction, which can play a dual role in preventing free radical generation and interrupting the free radical chain reaction. The results of the study can provide a novel, environmentally friendly and effective way to prevent the spontaneous combustion of coal. [ABSTRACT FROM AUTHOR]

We present a hollow-core fiber (HCF) based transient absorption experiment, with capabilities beyond common titanium:sapphire based setups. By spectral filtering of the HCF spectrum, we provide pump pulses centered at 425 nm with several hundred nJ of pulse energy at the sample position. By employing the red edge of the HCF output for seeding CaF2, we obtain smooth probing spectra in the range between 320 and 900 nm. We demonstrate the capabilities of our experiment by following the ultrafast relaxation dynamics of a radical cationic photocatalyst to prove its pre-association with an arene substrate, a phenomenon that was not detectable previously by steady-state spectroscopic techniques. The detected preassembly rationalizes the successful participation of radical ionic photocatalysts in single electron transfer reactions, a notion that has been subject to controversy in recent years. [ABSTRACT FROM AUTHOR]

Stable organic radicals generated by photo‐excitation hold applications in molecular switching devices and information storage. It remains challenging to develop photo‐generated radical materials with rapid response and air stability in the solid state. Here, we report a structure based on 1,3,6,8‐tetraphenylpyrene derivative (Py‐TTAc) displaying photo‐induced radicals with air stability in the solid state. Photo‐induced electron transfer, exposed to a 365 nm ultraviolet lamp for 1 minute, affords radicals in Py‐TTAc powder as confirmed by electron paramagnetic resonance (EPR) spectroscopy. The maximum radical concentration reaches 2.21 % after continuous irradiation for 1 hour and recurs more than 10 times without any chemical degradation. The mechanistic study according to the femtosecond transient absorption (fsTA) and X‐ray technology suggests that the radicals are derived from photo‐induced symmetry‐breaking charge separation (SB‐CS) and stabilized through non‐covalent interactions. The photo‐generated stable radical system is employed in anti‐counterfeiting paper and optoelectronic device applications. This study will provide insights into the development of photoactive organic radical materials. [ABSTRACT FROM AUTHOR]

Fluorination of heterocyclic compounds accompanied by molecular rearrangements is an area of synthesis experiencing rapid advances. One of the characteristics of electrophilic and oxidative fluorination is the involvement of carbocations, radicals, and radical ions which can undergo rearrangements. Such rearrangements expand the range of fluorinated products, which are sometimes difficult to access by direct fluorination of heterocyclic compounds. The purpose of this review is to systematize and analyze the literature data published over the past decade on fluorination of heterocyclic compounds accompanied by molecular rearrangements. Particular attention is paid to the analysis of reaction mechanisms and the problem of selectivity. [ABSTRACT FROM AUTHOR]

The use of non thermal plasma (NTP) to improve indoor air quality (IAQ) has grown considerably in recent years. This paper demonstrates the advantage of NTP for IAQ improvement in terms of particulate matter (PM) removal. The PM removal mechanism using active air ions and radicals has been investigated. From the developed dielectric barreir discharge (DBD) air plasma reactor, the total PM removal efficiency of 61.72% has been achieved at an optimised concentration of negative and positive air ions in 2 hours of continuous operation. Due to the utilised sensor's limit of quantification (LOQ), PM 2.5 and PM 10 have been reduced to a certain value. The findings revealed that DBD air plasma can be effectively used for PM removal in an enclosed environment. [ABSTRACT FROM AUTHOR]

In order to create Pyrrolo pyrimidine derivatives, multicomponent reactions involving butanoates, aldehydes, guanidine, activated acetylenic compounds, and ethyl bromopyruvate were carried out in water at room temperature with catalytic amounts of Cu@KF/CP NPs as a high-performance catalyst. Additionally, experiments involving the reducing power of ferric ions and radical trapping by DPPH were conducted to investigate the antioxidant capacity. As a result, the produced compounds exhibit excellent DPPH radical trapping and good ferric ion reduction capacity. The current method offers advantages including good reaction yield, green media, and simple product and catalyst separation. The pyrimidine ring is an aza-aromatic scaffold that can be found in many molecules of biological or pharmaceutical interest. Multicomponent reactions (MCRs) are a more interesting type of reaction due to mixing three or more reactants in one-pot and generating one product. They are also more economically useful and environmentally secure than multi-step methods. Carrying out the synthesis of organic compounds in water media is very interesting because water is a cheap solvent more readily available in large amounts. [ABSTRACT FROM AUTHOR]

Mashing is a decisive brewing step, affecting wort quality. Critical mashing parameters include time, temperature, pH, mash density and oxygen uptake. While the pH-dependent biochemical changes during mashing have been researched, the oxidative processes remain unclear. This work explores the impact of pH conditions during mashing on the biochemical composition and oxidative properties of wort. In laboratory trials, mashing was conducted at different mashing-in pH (4.5, 5.0, 5.2, 5.4, 6.0). The sweet worts were analyzed for extract, fermentable sugars, limit dextrins, amino acids, soluble proteins, polyphenols, color, aldehydes, transition metals, reducing potential, and rate of radical formation. Differences were found in enzymatic activities (particularly proteolysis), color, aldehydes, transition metal ions, the rate of radical formation and the rate of oxygen consumption. Notably, when adjusting the pH at mashing-in, the obtained wort tends to gravitate toward the pH of the unadjusted wort, underscoring its buffering capacity. This was reflected by similar properties of the produced worts, indicating pH playing a lesser role during mashing compared to time/temperature. However, under extreme acidified conditions (pH 4.5 at mashing-in), the produced wort markedly deviates. An intriguing negative correlation between the reducing potential and the content of transition metal ions with the rate of radical formation is discussed. [ABSTRACT FROM AUTHOR]

The aim of this study was to prepare and characterize stable non−covalent ternary complexes based on pea protein (PP, 0.5%), hyaluronic acid (HA, 0.125%), and chlorogenic acid (CA, 0~0.03%). The ternary complexes were comprehensively evaluated for physicochemical attributes, stability, emulsifying capacities, antioxidant properties, and antimicrobial efficacy. PP-HA binary complexes were first prepared at pH 7, and then CA was bound to the binary complexes, as verified by fluorescence quenching. Molecular docking elucidated that PP interacted with HA and CA through hydrogen bonding, hydrophobic and electrostatic interactions. The particle size of ternary complexes initially decreased, then increased with CA concentration, peaking at 0.025%. Ternary complexes demonstrated good stability against UV light and thermal treatment. Emulsifying activity of complexes initially decreased and then increased, with a turning point of 0.025%, while emulsion stability continued to increase. Complexes exhibited potent scavenging ability against free radicals and iron ions, intensifying with higher CA concentrations. Ternary complexes effectively inhibited Staphylococcus aureus and Escherichia coli, with inhibition up to 0.025%, then decreasing with CA concentration. Our study indicated that the prepared ternary complexes at pH 7 were stable and possessed good functionality, including emulsifying properties, antioxidant activity, and antibacterial properties under certain concentrations of CA. These findings may provide valuable insights for the targeted design and application of protein-polysaccharide-polyphenol complexes in beverages and dairy products. [ABSTRACT FROM AUTHOR]

A quasi‐planar N, N, N',N'‐tetraphenyl‐para‐phenylenediamine, where all the phenyl rings are tethered by four oxygen atoms to embed quasi‐planar triphenylamine moieties into the molecular skeleton, was prepared and characterized to evaluate the impact by incorporating the structural rigidity. The monocationic and dicationic species could be selectively generated, depending on the type of oxidizing agents used. Spectroscopic and X‐ray diffraction analyses revealed the radical cation was in a unique charge/spin delocalized class III mixed‐valence state due to an exquisite balance between the electronic effect by the oxygen‐bridges and the rigidity of molecular framework. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Herein, we report an efficient and practical protocol for the photoinduced dehalocyclization of ortho‐halophenylacrylamides with formate by the engagement of a CO2 radical anion to access substituted oxindoles. This method proceeds smoothly under mild conditions and exhibits a wide range of substrate as well as remarkable functional group compatibility. [ABSTRACT FROM AUTHOR]

Primary excitation energy transfer and charge separation in photosystem I (PSI) from the extremophile desert green alga Chlorella ohadii grown in low light were studied using broadband femtosecond pump-probe spectroscopy in the spectral range from 400 to 850 nm and in the time range from 50 fs to 500 ps. Photochemical reactions were induced by the excitation into the blue and red edges of the chlorophyll Qy absorption band and compared with similar processes in PSI from the cyanobacterium Synechocystis sp. PCC 6803. When PSI from C. ohadii was excited at 660 nm, the processes of energy redistribution in the light-harvesting antenna complex were observed within a time interval of up to 25 ps, while formation of the stable radical ion pair P700+A1− was kinetically heterogeneous with characteristic times of 25 and 120 ps. When PSI was excited into the red edge of the Qy band at 715 nm, primary charge separation reactions occurred within the time range of 7 ps in half of the complexes. In the remaining complexes, formation of the radical ion pair P700+A1− was limited by the energy transfer and occurred with a characteristic time of 70 ps. Similar photochemical reactions in PSI from Synechocystis 6803 were significantly faster: upon excitation at 680 nm, formation of the primary radical ion pairs occurred with a time of 3 ps in ~30% complexes. Excitation at 720 nm resulted in kinetically unresolvable ultrafast primary charge separation in 50% complexes, and subsequent formation of P700+A1− was observed within 25 ps. The photodynamics of PSI from C. ohadii was noticeably similar to the excitation energy transfer and charge separation in PSI from the microalga Chlamydomonas reinhardtii; however, the dynamics of energy transfer in C. ohadii PSI also included slower components. [ABSTRACT FROM AUTHOR]

Classical photochemistry requires nanosecond excited-state lifetimes for diffusion-controlled reactions. Excited radicals with picosecond lifetimes have been implied by numerous photoredox studies, and controversy has arisen as to whether they can actually be catalytically active. We provide direct evidence for the elusive pre-association between radical ions and substrate molecules, enabling photoinduced electron transfer beyond the diffusion limit. A strategy based on two distinct light absorbers, mimicking the natural photosystems I and II, is used to generate excited radicals, unleashing extreme reduction power and activating C(sp2)―Cl and C(sp2)―F bonds. Our findings provide a long-sought mechanistic understanding for many previous synthetically-oriented works and permit more rational future photoredox reaction development. The newly developed excitation strategy pushes the current limits of reactions based on multi-photon excitation and very short-lived but highly redox active species. Classical photochemistry requires nanosecond excited-state lifetimes for diffusion-controlled reactions. Here the authors provide direct evidence for the elusive pre-association between radical ions and substrate molecules, enabling photoinduced electron transfer beyond the diffusion limit. [ABSTRACT FROM AUTHOR]

The objective of this study was to optimize the extraction process of total sterols from wild Pyracantha fortuneana leaves (WPFL), and explore their antioxidant and whitening activities. The yield of total sterols (WPFLTPS) was used as indicator, and the single factor experiment was used to investigate the effects of extraction solvent, solid-liquid ratio, ultrasonic temperature and ultrasonic time on the yield of WPFLTPS. Based on this, the orthogonal experimental design was used to optimize the extraction conditions. The DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] and nitrite methods were used to evaluate the antioxidant activity of WPFLTPS in vitro. The whitening activity was evaluated by the inhibitory effect on tyrosinase. The results showed that for optimal extraction process of WPFLTPS, the extraction solvent was absolute ethanol, ultrasonic temperature was 50 °C, solid-liquid ratio was 1:16 g/mL, and ultrasonic time was 25 minutes. Under these conditions, the yield of WPFLTPS was (11.00± 0.03) mg/g. In the range of 0.5~5 mg/mL, WPFLTPS had strong scavenging effects on DPPH radicals, ABTS+ radicals and nitrite ions, as well as a strong inhibitory effect on tyrosinase, demonstrating a good dose-response relationship. This extraction process was stable and reliable for extracting WPFLTPS. The WPFLTPS can be used as a new, natural antioxidant and tyrosinase inhibitor in functional foods. [ABSTRACT FROM AUTHOR]

The first ππ* transition for protonated 2-, 3-, and 4-formylpyridine (FPH+) (m/z 108) is investigated by mass spectrometry coupled with photodissociation action spectroscopy at room temperature and 10 K. The photoproduct ions are detected over 35 000–43 000 cm−1, and the major product channel for 3-FPH+ and 4-FPH+ is the loss of CO forming protonated pyridine at m/z 80. For 2-FPH+, the CO loss product is present but a more abundant photoproduct arises from the loss of CH2O to form m/z 78. Plausible potential energy pathways that lead to dissociation are mapped out and comparisons are made to products arising from collision-induced dissociation. Although, in all cases, the elimination of CO is the overwhelming thermodynamically preferred pathway, the protonated 2-FPH+ results suggest that the CH2O product is kinetically driven and competitive with CO loss. In addition, for each isomer, radical photoproduct ions are detected at lower abundances. SCS-CC2/aug-cc-pVTZ Franck–Condon simulations assist with the assignment of vibrionic structure and adiabatic energies (0–0) for 2-FPH+ at 36 560 cm−1, 37 430 cm−1 for 3-FPH+, and 36 140 cm−1 for 4-FPH+, yielding an accurate prediction, on average, within 620 cm−1. [ABSTRACT FROM AUTHOR]

Tin contamination of the collector mirror surface remains one of the crucial issues of EUV (Extreme Ultraviolet) sources, directly impacting the availability of the tool. Hydrogen plasma-based tin removal processes employ hydrogen radicals and ions to interact with tin deposits to form gaseous tin hydride (SnH4), which can be removed through pumping. An annular surface wave plasma (SWP) source developed at the University of Illinois—Urbana Champaign is integrated into the cone and perimeter of the collection mirror for in situ tin removal. The SWP is characterized by high ion and radical densities, low electron temperature, and local generation where etching is needed. This method has the potential to significantly reduce downtime and increase mirror lifetime. Radical probe measurements show hydrogen radical densities in the order of 1019 m−3, while Langmuir probe measurements show electron temperatures of up to 6 eV and plasma densities on the order of 1017–18 m−3. The generated ions are essential to the tin cleaning and have sufficiently low energy to cause no damage to the collector capping layer. Tin etch rates of up to 270 nm/min were observed in a variety of experimental conditions, including various powers, pressures, flowrates, and temperatures. The high etch rates demonstrated in this study exceed the expected contamination rate of the EUV source. [ABSTRACT FROM AUTHOR]

Thermally activated delayed fluorescence (TADF) assisted fluorescence organic light‐emitting devices (TAF‐OLEDs), also known as hyperfluorescence OLEDs, sometimes have limited operational lifetimes, making them unsuitable for industrial applications. Although, this limitation is believed to originate from the irreversible degradation of constituent materials, the chemical processes underlying this degradation remain elusive. This study enables to better understand the chemical origins of the degradation processes by identifying key degradation intermediates in emission layers comprising 2,8‐di‐tert‐butyl‐5,11‐bis(4‐tert‐butylphenyl)‐6,12‐diphenyltetracene (TBRb) as the fluorescent emitter and 1,4‐azaborin‐based molecules exhibiting multi‐resonance (MR) TADF behaviors, 5,9‐diphenyl‐5,9‐diaza‐13b‐boranaphtho[3,2,1‐de]anthracene (DABNA‐1) and 9‐([1,1′‐biphenyl]‐3‐yl)‐N,N,5,11‐tetraphenyl‐5,9‐dihydro‐5,9‐diaza‐13b‐boranaphtho[3,2,1‐de]anthracen‐3‐amine (DABNA‐2), as exciton sensitizers. Despite the sensitizers facilitating energy transfer to TBRb, they also reduce the device's longevity. While the singlet and triplet excitons of TBRb, as well as excitons of the sensitizers, prove to be relatively stable, the radical ions of the sensitizers prove to be the key limit to device longevity. Comparisons with donor–acceptor‐type TADF exciton sensitizers, 2,4,5,6‐tetrakis(9H‐carbazol‐9‐yl)benzene‐1,3‐dicarbonitrile (4CzIPN), 10,10′‐(sulfonyldi‐4,1‐phenylene)bis[9,10‐dihydro‐9,9‐dimethylacridine] (DMAC‐DPS), and 10‐[4‐(4,6‐diphenyl‐1,3,5‐triazin‐2‐yl)phenyl]‐9,10‐dihydro‐9,9‐dimethylacridine (DMAC‐TRZ), corroborate the findings, pointing to radical ions as primary degradation intermediates. This knowledge is essential for enhancing the durability of TAF‐OLEDs in future designs. [ABSTRACT FROM AUTHOR]

Advanced organoboron dyes, incorporating tetra‐boron difluoride (tetra‐BF2) moieties, are developed, demonstrating efficient electrochemiluminescence (ECL) emissions in the green to orange regions through direct ion annihilation. By introducing diverse alkyl modifications in the molecules, luminescence color tuning is achieved via alterations in conjugation and bending angle. A photoluminescence quantum yield of 100% in dilute solutions is successfully achieved. Notably, the introduction of alkyl groups to the methine side stabilizes the radical ionic state, resulting in a high ECL efficiency of 74% through an efficient radical‐ion annihilation pathway. The key factor is that the energy of the annihilation reaction exceeds the S1 energy required for luminescence. Spin density calculations further elucidate the substituent effects on the radical ions of complexes. Moreover, the lasing properties of these materials in the solution‐processed blend films are investigated, revealing a low amplified spontaneous emission (ASE) threshold (Eth) of 6.40 ± 0.24 µJ cm−2, which is notably lower among organic laser materials. This is attributed to their large Stokes shifts and high quantum yield. The excellent ECL and ASE performances establish these materials as a valuable addition to the existing library of organoboron dyes, offering fresh insights into the development of organic solid‐state lasers. [ABSTRACT FROM AUTHOR]

We have synthesized a quinone‐incorporated bistriarylamine donor‐acceptor‐donor (D–A–D) semiconductor 1 by B(C6F5)3 (BCF) catalyzed C−H/C−H cross coupling via radical ion pair intermediates. Coordination of Lewis acids BCF and Al(ORF)3 (RF=C(CF3)3) to the semiconductor 1 afforded diradical zwitterions 2 and 3 by integer electron transfer. Upon binding to Lewis acids, the LUMO energy of 1 is significantly lowered and the band gap of the semiconductor is significantly narrowed from 1.93 eV (1) to 1.01 eV (2) and 1.06 eV (3). 2 and 3 are rare near‐infrared (NIR) diradical dyes with broad absorption both centered around 1500 nm. By introducing a photo BCF generator, 2 can be generated by light‐dependent control. Furthermore, the integer electron transfer process can also be reversibly regulated via the addition of CH3CN. In addition, the temperature of 2 sharply increased and reached as high as 110 °C in 10 s upon the irradiation of near‐infrared‐II (NIR‐II) laser (1064 nm, 0.7 W cm−2), exhibiting a fast response to laser. It displays excellent photothermal stability with a photothermal (PT) conversion efficiency of 62.26 % and high‐quality PT imaging. [ABSTRACT FROM AUTHOR]

Diarsene [L(MeO)GaAs]2 (L=HC[C(Me)N(Ar)]2, Ar=2,6‐iPr2C6H3, 4) reacts with MeOTf and MeNHC (MeNHC=1,3,4,5‐tetra‐methylimidazol‐2‐ylidene) to the diarsene [L(TfO)GaAs]2 (5) and the carbene‐coordinated diarsene [L(MeO)GaAsAs(MeNHC)Ga(OMe)L] (6). The NHC‐coordination results in an inversion of the redox properties of the diarsene 4, which shows only a reversible reduction event at E1/2=−2.06 V vs Fc0/+1, whereas the carbene‐coordinated diarsene 6 shows a reversible oxidation event at E1/2=−1.31 V vs Fc0/+1. Single electron transfer reactions of 4 and 6 yielded [K[2.2.2.]cryp][L(MeO)GaAs]2 (8) and [L(MeO)GaAsAs(MeNHC)‐Ga(OMe)L][B(C6F5)4] (9) containing the radical anion [L(MeO)GaAs]2⋅− (8⋅−) and the NHC‐coordinated radical cation [L(MeO)GaAsAs(MeNHC)Ga(OMe)L]⋅+ (9⋅+), respectively, while the salt‐elimination reaction of the triflate‐coordinated diarsene 5 with Na[B(C6F5)4] gave [LGaAs]2[B(C6F5)4]2 (11) containing the dication [LGaAs]22+ (112+). Compounds 1–11 were characterized by 1H and 13C NMR, EPR (8, 9), IR, and UV‐Vis spectroscopy and by single crystal X‐ray diffraction (sc‐XRD). DFT calculations provided a detailed understanding of the electronic nature of the diarsenes (4, 6) and the radical ions (8⋅−, 9⋅+), respectively. [ABSTRACT FROM AUTHOR]

Ar ions with controlled energy and doses, along with radicals in CF4 plasma, were irradiated separately onto a Si (111) 7 × 7 surface by using a plasma beam reactor. The crystal structure and the chemical bonds on the surface were analyzed by scanning tunneling microscopy, atomic force microscopy, and x-ray photoelectron spectroscopy without air exposure of the samples. The SiF layer formed by F radical irradiation was completely removed by a desorption reaction induced by heating at 600 °C, resulting in an atomically flat surface that maintained the crystal structure. The 7 × 7 structure, which was reconstructed by each irradiation process alone, was not reconstructed because of the synergistic effects of F radicals and Ar ions in the cyclic CF4/Ar plasma used to simulate an atomic layer etching process. The cyclic CF4/Ar plasma process inhibited the reconstruction of the crystal structure by forming a mixture region that included Si, F, and C atoms. [ABSTRACT FROM AUTHOR]

In this work, a series of novel 2,5‐bis(het)aryl and 2,5‐bis‐thienyl substituted thiophenes have been synthesized and characterized by ultraviolet‐visible‐near infrared (UV‐Vis‐NIR) absorption and fluorescence spectroscopy as well as cyclic voltammetry. From the electron paramagnetic resonance (EPR)/UV‐Vis‐NIR spectroelectrochemical data, information about the optical and magnetic properties of the charged species of these compounds have been provided. The spin distributions in the electrochemically generated radical ions were estimated experimentally and compared with theoretical data. [ABSTRACT FROM AUTHOR]

Developing Type‐I photosensitizers provides an attractive approach to solve the dilemma of inadequate efficacy of photodynamic therapy (PDT) caused by the inherent oxygen consumption of traditional Type‐II PDT and anoxic tumor microenvironment. The challenge for the exploration of Type‐I PSs is to facilitate the electron transfer ability of photosensitization molecules for transforming oxygen or H2O to reactive oxygen species (ROS). Herein, we propose an electronic acceptor‐triggered photoinduced electron transfer (a‐PET) strategy promoting the separation of electron‐hole pairs by marriage of two organic semiconducting molecules of a non‐fullerene scaffold‐based photosensitizer and a perylene diimide that significantly boost the Type‐I PDT pathway to produce plentiful ROS, especially, inducing 3.5‐fold and 2.5‐fold amplification of hydroxyl (OH⋅) and superoxide (O2−⋅) generation. Systematic mechanism exploration reveals that intermolecular electron transfer and intramolecular charge separation after photoirradiation generate a competent production of radical ion pairs that promote the Type‐I PDT process by theoretical calculation and ultrafast femtosecond transient absorption (fs‐TA) spectroscopy. By complementary tumor diagnosis with photoacoustic imaging and second near‐infrared fluorescence imaging, this as‐prepared nanoplatform exhibits fabulous photocytotoxicity in harsh hypoxic conditions and terrific cancer revoked abilities in living mice. We envision that this work will broaden the insight into high‐efficiency Type‐I PDT for cancer phototheranostics. [ABSTRACT FROM AUTHOR]

The electrochemical oxidative dearomatizing methoxylation of phenols and naphthols was developed. It provides an alternative route for the preparation of methoxycyclohexadienones, important and versatile synthetic intermediates, that eliminates the need for stoichiometric high‐energy chemical oxidants and generates hydrogen as a sole by‐product. The reaction proceeds in a simple constant current mode, in an undivided cell, and it employs standardized instrumentation. A collection of methoxycyclohexadienones derived from various 2,4,6‐tri‐substituted phenols and 1‐substituted‐2‐naphthols was obtained in moderate to excellent yields. These include a complex derivative of estrone, as well as methoxylated dearomatized 1,1′‐bi‐2‐naphthols (BINOLs). The mechanism of the reaction was subject to profound investigations using density functional theory calculations. In particular, the reactivity of two key intermediates, phenoxyl radical and phenoxenium ion, was carefully examined. The obtained results shed light on the pathway leading to the desired product and rationalize experimentally observed selectivities regarding a side benzylic methoxylation and the preference for the functionalization at the para over the ortho position. They also uncover the structure‐selectivity relationship, inversely correlating the steric bulk of the substrate with its propensity to undergo the side‐reaction. Moreover, the loss of stereochemical information from enantiopure BINOL substrates during the reaction is rationalized by the computations. [ABSTRACT FROM AUTHOR]

A sequential process via photoredox catalysis and Lewis acid mediation for C−F bond transformation of the CF2 unit in perfluoroalkyl groups has been achieved to transform perfluoroalkylarenes into complex fluoroalkylated compounds. A phenothiazine‐based photocatalyst promotes the defluoroaminoxylation of perfluoroalkylarenes with (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) under visible light irradiation, affording the corresponding aminoxylated products. These products undergo a further defluorinative transformation with various organosilicon reagents mediated by AlCl3 to provide highly functionalized perfluoroalkyl alcohols. Our novel phenothiazine catalyst works efficiently in the defluoroaminoxylation. Transient absorption spectroscopy revealed that the catalyst regeneration step is crucial for the photocatalytic aminoxylation. [ABSTRACT FROM AUTHOR]

Accurate binding energies of molecules to water clusters are relevant for understanding intermolecular interactions and various chemical applications. They enter models of interstellar chemical processes, as binding to icy grains influences surface reactions and thus affects calculated gas-phase abundances. Unfortunately, many astrochemical molecules (especially radicals and ions) are incompletely characterised in these models. To address this, we report computational searches for optimal structures and benchmark binding and condensation energies for sets of neutral, radical, cationic, and anionic molecules of astrochemical relevance with clusters of $ N=1{\rm -}4 $ N = 1 − 4 water molecules. These calculations utilised reliable density functionals for geometry optimisation, and coupled cluster (CCSD(T)) single point calculations with large basis sets. Four energetic binding motifs (weak, intermediate, strong or covalently bonded) were observed depending on the chemical nature of the guest molecule. Neutral closed and open-shell molecules with strong dipoles and a greater potential for hydrogen bonding are more tightly bound to water clusters compared to non-polar ones. For closed-shell cationic and anionic species, barrier-less reactions with water clusters occur, which reveals radical-free routes to molecular processing in the gas phase and on amorphous ice surfaces. [ABSTRACT FROM AUTHOR]

Radio-frequency capacitively coupled plasmas (CCPs) are one of the key technologies enabling the latest etching processes in 3D NAND and FinFET manufacturing. These processes rely crucially on the precise control of the uniformity of ion/radical fluxes and ion angular and energy distribution function (IAEDF) in CCPs. The plasma behavior and scaling properties are dependent on the plasma chemistry in these processes, e.g., electro-positive Ar plasmas vs highly electro-negative O2 plasmas. With the large number of process and design parameters influencing the plasma properties, computational modeling has become an important tool in conjunction with experimental diagnostics in understanding the intricate physical mechanisms in CCPs. In this paper, a 2D particle-in-cell plasma model is used to study the kinetic behavior of low-pressure (<5 Pa) CCPs in two different representative chemistries: Ar and O2. The low-frequency RF source is at 1.356 MHz while 27.12 MHz is used for the high frequency. Simulations show a shift of the peak in the plasma density from the center of the chamber to the edge as the pressure increases from 0.3 to 2.6 Pa. The computed magnitude and spatial profile of electron density compare reasonably with experimental measurements over a range of pressure. Comparison between electro-positive and electro-negative plasmas are discussed. Modeling results for the dual frequency CCP highlight the effect of plasma uniformity on the IAEDF, especially near the outer edge of the electrodes. Collisions in the sheath increase the population of low-energy ions as the pressure is increased to 2.6 Pa. [ABSTRACT FROM AUTHOR]

Ultrafine semiconductor fabrication by lithography has undergone a significant transition from deep ultraviolet (DUV) to extreme ultraviolet (EUV) processes, which presents new challenges. Specifically, the damage caused to components utilized in an EUV system, such as multilayer mirrors, reticles, and pellicles within lithography equipment, owing to EUV-induced H2 plasma, is a critical issue that directly affects the process yield and equipment lifespan. To address these issues, it is crucial to establish an environment similar to that of EUV-induced plasma and develop a method to evaluate the resulting damage. Accordingly, an evaluation method is developed for assessing the material damage caused by hydrogen radicals and ions in inductively coupled H2 plasma. In these systems, the electron density ranged from 5 × 108 to 3.5 × 1010 cm−3, the electron temperature ranged from 1 to 4 eV, and the ion energy ranged from several to tens of eV; these conditions closely align with the environment of an EUV-induced H2 plasma. The damage to Mo2C, a potential EUV pellicle material, is quantitatively analyzed by measuring the fraction of the pore area and examining the chemical characteristics after exposing the samples to various plasma conditions, including electron density, gas pressure, and exposure time. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: The electrophilic addition to an alkene with an electrophile has been widely studied and applied in organic synthesis. The organic chemistry textbook describes the classical reaction between an alkene and an iodine electrophile (such as elemental iodine and N‐iodosuccinimide (NIS)) as a typical ionic reaction, in which an iodonium ion is formed and then attacked by a nucleophile. However, in this article, we report a new and unusual reaction mode between an alkene and NIS; that is, a single electron transfer (SET) process occurs between these two reactants by forming an electron‐donor acceptor complex. Not only does this unusual single electron transfer reaction between an alkene and NIS add fundamentally important knowledge to organic chemistry, it also provides a valuable synthetic method as the new SET reaction mode with opposite regioselectivity as compared with the traditional ionic mode. [ABSTRACT FROM AUTHOR]

This work presents the results of developing a set of electronic and chemical reactions for a plasma discharge in octafluoropropane (C3F8). Electronic reactions were obtained using the most relevant set of cross sections at the moment, taking into account experimentally known dissociation and ionization channels. Based on the dissociation products obtained during electronic reactions, a set of chemical reactions was adapted by analogy with the C4F8 reaction scheme from the literature. Next, the resulting complete set of reactions was tested against published experimental data on the concentration of electrons, negative ions, and electronegativity in a capacitive plasma discharge at different gas pressures and discharge input powers. For this purpose, a one-dimensional hydrodynamic drift-diffusion model was used. Reasonable agreement was obtained between the model and experimental data on electronegativity. Eventually, the resulting set of reactions was adapted for a two-dimensional hydrodynamic drift-diffusion model of an ICP discharge. The results of the calculations are two-dimensional distributions of radicals and ions, radical and ion composition of fluxes onto the substrate under conditions typical for industrial reactors. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: The electrophilic addition to an alkene with an electrophile has been widely studied and applied in organic synthesis. The organic chemistry textbook describes the classical reaction between an alkene and an iodine electrophile (such as elemental iodine and N‐iodosuccinimide (NIS)) as a typical ionic reaction, in which an iodonium ion is formed and then attacked by a nucleophile. However, in this article, we report a new and unusual reaction mode between an alkene and NIS; that is, a single electron transfer (SET) process occurs between these two reactants by forming an electron‐donor acceptor complex. Not only does this unusual single electron transfer reaction between an alkene and NIS add fundamentally important knowledge to organic chemistry, it also provides a valuable synthetic method as the new SET reaction mode with opposite regioselectivity as compared with the traditional ionic mode. [ABSTRACT FROM AUTHOR]

Photosystem II (PSII) is the pigment–protein complex driving the photoinduced oxidation of water and reduction of plastoquinone in all oxygenic photosynthetic organisms. Excitations in the antenna chlorophylls are photochemically trapped in the reaction center (RC) producing the chlorophyll–pheophytin radical ion pair P+ Pheo−. When electron donation from water is inhibited, the oxidized RC chlorophyll P+ acts as an excitation quencher, but knowledge on the kinetics of quenching is limited. Here, we used femtosecond transient absorption spectroscopy to compare the excitation dynamics of PSII with neutral and oxidized RC (P+). We find that equilibration in the core antenna has a major lifetime of about 300 fs, irrespective of the RC redox state. Two-dimensional electronic spectroscopy revealed additional slower energy equilibration occurring on timescales of 3–5 ps, concurrent with excitation trapping. The kinetics of PSII with open RC can be described well with previously proposed models according to which the radical pair P+ Pheo− is populated with a main lifetime of about 40 ps, which is primarily determined by energy transfer between the core antenna and the RC chlorophylls. Yet, in PSII with oxidized RC (P+), fast excitation quenching was observed with decay lifetimes as short as 3 ps and an average decay lifetime of about 90 ps, which is shorter than the excited-state lifetime of PSII with open RC. The underlying mechanism of this extremely fast quenching prompts further investigation. [ABSTRACT FROM AUTHOR]

Ion regulation strategy is regarded as a promising pathway for designing transition metal oxide‐based electrocatalysts for oxygen evolution reaction (OER) with improved activity and stability. Precise anion conditioning can accurately change the anionic environment so that the acid radical ions (SO42−, PO32−, SeO42−, etc.), regardless of their state (inside the catalyst, on the catalyst surface, or in the electrolyte), can optimize the electronic structure of the cationic active site and further increase the catalytic activity. Herein, we report a new approach to encapsulate S atoms at the tetrahedral sites of the NaCl‐type oxide NiO to form a tetraoxo‐tetrahedral coordination structure (S‐O4) inside the NiO (S‐NiO ‐I). Density functional theory (DFT) calculations and operando vibrational spectroscopy proves that this kind of unique structure could achieve the S‐O4 and Ni‐S stable structure in S‐NiO‐I. Combining mass spectroscopy characterization, it could be confirmed that the S‐O4 structure is the key factor for triggering the lattice oxygen exchange to participate in the OER process. This work demonstrates that the formation of tetraoxygen tetrahedral structure is a generalized key for boosting the OER performances of transition metal oxides. [ABSTRACT FROM AUTHOR]

The present work deals with precipitation followed by the hydrothermal method for the synthesis of cerium vanadate decorated nitrogen doped reduced graphene oxide (CeV/NRGO) nanocomposite. The crystallographic and Raman spectroscopic characterization confirm the formation of CeV/NRGO nanocomposite. A computational study on crystal structure using Material Studio, confirms the presence of zircon‐like CeV with VO4 tetrahedra sharing corners and edges with CeO8 dodecahedra in CeV/NRGO nanocomposite. X‐ray photoelectron spectroscopic (XPS) analysis supports the presence of Ce in +3 and +4 oxidation state. The optical characterization shows the decreased bandgap in CeV/NRGO nanocomposite (2.03 eV) compared to pristine CeV (2.35 eV). Enhanced photocatalytic activity is observed towards hydrogen evolution in CeV/NRGO (15 124 μmol) compared to CeV (7215 μmol) and NRGO (2034 μmol). In addition, CeV/NRGO, CeV, and NRGO are evaluated for degradation of Alizarin Yellow (AY) and Orange G (OG) dyes in presence of visible light. CeV/NRGO managed to degrade 97% and 94% of AY and OG, respectively in 80 min. The electron spin resonance (ESR) studies show superoxide radicals and hydroxyl ions are the active species responsible for photocatalytic reactions. Based on the liquid chromatography–mass spectroscopy (LC–MS) results, a possible photocatalytic mechanism has been discussed. The good stability and reusability of CeV/NRGO nanocomposite could be a choice of material for energy and environmental related research. [ABSTRACT FROM AUTHOR]

Carbonate radical anion (CO3.− ${\mathrm{C}{\mathrm{O}}_{3}}^{.-}$) is generally overlooked in atmospheric chemistry. Our recent work emphasizes the important role of carbonate radicals produced on mineral dust surfaces in fast sulfate production under solar irradiation in the presence of CO2 at specifically low RH and light intensity. Yet so far how CO3.− ${\mathrm{C}{\mathrm{O}}_{3}}^{.-}$ involves and affects secondary sulfate production under diverse RH, light intensity, and complex constituent matrix remains unknown, which essentially limits our comprehensive knowledge of CO3.− ${\mathrm{C}{\mathrm{O}}_{3}}^{.-}$initiated SO2 oxidation scheme in the atmosphere. Herein, we explored the heterogeneous SO2 oxidation over both model and authentic dust and clays in the presence of CO2 at atmospheric relevant RHs and light intensities. Interestingly, we observe that CO2 promotes sulfate yield over authentic dust and clays at atmospheric‐relevant RH and light intensity. This observation relates to the favorable kinetic between SO2 oxidation and CO3.− ${\mathrm{C}{\mathrm{O}}_{3}}^{.-}$ while auto‐quenching of these radical ions is largely minimized due to the sufficient sites of crustal constituents. Furthermore, employing a suite of authentic dust and machine learning strategies, we evaluated the relative importance of each constituent within airborne minerals or clays as well as environmental conditions including relative humidity, light intensity, and CO2 concentration in affecting SO2 uptake capability. On this basis, sulfate formation mediated by dust‐driven pathway, accounting for nearly ∼20.9% of overall contribution by the end of this century during some pollution episodes, even higher than gas‐phase ·OH $\cdot \text{OH}$ (∼16.9%), will be increased by 163% if CO2‐initiated SO2 oxidation scheme is incorporated. Plain Language Summary: How carbonate radical ions involve and affect sulfate formation under different RHs, light intensities, and complex component matrices remains an open question. Secondary sulfate production is facilitated by CO3.− ${\mathrm{C}{\mathrm{O}}_{3}}^{.-}$ over authentic dust particles in atmospheric relevant RH and light intensity. More importantly, this research emphasizes that CO2 is not an inert greenhouse gas that rarely participates in atmospheric chemistry but a strong oxidant precursor that will produce CO3.− ${\mathrm{C}{\mathrm{O}}_{3}}^{.-}$ and subsequently trigger quick SO2 oxidation via chain reactions. This dust‐driven reaction channel mediated by CO3.− ${\mathrm{C}{\mathrm{O}}_{3}}^{.-}$ potentially contributes to nearly ∼1/5 of secondary sulfate production during some pollution hours if the growing intensive anthropogenic activities continue. Key Points: Carbonate radical‐initiated SO2 heterogeneous oxidation is sensitive to RH, CO2 concentration, light intensity, and dust constituentsCarbonate radicals promote atmospheric sulfate production on authentic dust and clay particles at haze‐relevant conditionsThis previously unrecognized scheme will account for ∼20.9% of overall atmospheric sulfate formation by the end of this century [ABSTRACT FROM AUTHOR]

This study aimed to screen the main phytochemical constituents; determine the total amounts of phenolics, flavonoids, and tannins; and evaluate the antimicrobial (against Escherichia coli, Staphylococcus sciuri, Candida glaebosa and Cryptococcus albidus) and antioxidant (against DPPH radical and ferric ion) activities of E. aethiopicum leaves extracts. Methods: Powdered E. aethiopicum leaves were macerated using n-hexane, chloroform, ethyl acetate, ethanol, and methanol. All crude extracts were qualitatively screened for phytochemical identification. The total phenolic, flavonoid, and condensed tannin contents of the chloroform, ethanol, and methanol extracts were determined by UV-Vis spectrophotometry. The n-hexane, chloroform, and methanol extracts were evaluated for their antimicrobial activity against the aforementioned microbes using agar disc diffusion and broth micro-dilution techniques. Chloroform, ethanol, and methanol extracts were also evaluated for antioxidant activity by DPPH and ferric ion reduction antioxidant power (FRAP) assays. Results: Methanol (17.56 ± 16%) and ethanol (16.45 ± 19%) showed better extraction efficiency. Flavonoids, polyphenols, tannins, terpenoids, saponins, and sterols were detected in all extracts. The highest total content of phenolics (22.63 ± 0.69 mgGAE/gDCE), flavonoids (5.38 ± 0.52 mgCE/gDCE) and tannins (39.18 ± 38 mg CE/g DCE), as milligram of gallic acid and catechin per gram of dried crude extract, were recorded in the methanolic extract. The methanolic extract also presented best anti -DPPH strength (IC50, 4.31 μg/mL) and ferric ion reduction power (absorbance of 0.71) though found weak compared to the ascorbic acid (IC50 of 0.49 μg/mL and absorbance of 0.93, respectively). Conclusion: All evaluated extracts displayed antifungal activity against both Cryptococcus albidus and Candida glaebosa strains (minimum inhibitory concentration values of 12.5– 25 mg/mL), whereas they were found to have negligible activity against all tested bacterial strains. This report provides preliminary information for further phytochemical investigation of Erianthemum aethiopicum to isolate potential antioxidant and antifungal compounds. [ABSTRACT FROM AUTHOR]

The hexacyano[3]radialene radical anion (1) is an attractive catholyte material for use in redox flow battery (RFB) applications. The substitution of cyano groups with ester moieties enhances solubility while maintaining redox reversibility and favorable redox potentials. Here we show that these ester‐functionalized, hexasubstituted [3]radialene radical anions dimerize reversibly in water. The dimerization mode is dependent on the substitution pattern and can be switched in solution. Stimuli‐responsive behavior is achieved by exploiting an unprecedented tristate switching mechanism, wherein the radical can be toggled between the free radical, a π‐dimer, and a σ‐dimer‐each with dramatically different optical, magnetic, and redox properties‐by changing the solvent environment, temperature, or salinity. The symmetric, triester‐tricyano[3]radialene (3) forms a solvent‐responsive, σ‐dimer in water that converts to the radical anion with the addition of organic solvents or to a π‐dimer in brine solutions. Diester‐tetracyano[3]radialene (2) exists primarily as a π‐dimer in aqueous solutions and a radical anion in organic solvents. The dimerization behavior of both 2 and 3 is temperature dependent in methanol solutions. Dimerization equilibrium has a direct impact on catholyte stability during galvanostatic charge–discharge cycling in static H‐cells. Specifically, conditions that favor the free radical anion or π‐dimer exhibit significantly enhanced cycling profiles. [ABSTRACT FROM AUTHOR]