Radical Yield Research Articles

Coupling Probiotics with CaO2 Nanoparticle-Loaded CoFeCe-LDH Nanosheets to Remodel the Tumor Microenvironment for Precise Chemodynamic Therapy.

Chemodynamic therapy (CDT) has become an emerging cancer treatment strategy with advantages of tumor-specificity, high selectivity, and low systemic toxicity. However, it usually suffers from low therapeutic efficacy. This is caused by low hydroxyl radical (·OH) yield arising because of the relatively high pH, overexpressed glutathione, and low H2O2 concentration in the tumor microenvironment (TME). Herein, a probiotic metabolism-initiated pH reduction and H2O2 supply-enhanced CDT strategy is reported to eradicate tumors by generating ·OH, in which Lactobacillus acidophilus is coupled with CoFeCe-layered double hydroxide nanosheets loaded with CaO2 nanoparticles (NPs) as a chemodynamic platform for high-efficiency CDT (CaO2/LDH@L. acidophilus). Owing to the hypoxia tropism of L. acidophilus, CaO2/LDH@L. acidophilus exhibits increased accumulation at tumor sites compared with the CaO2/LDH. The CaO2 NPs loaded on CoFeCe-LDH nanosheets are decomposed into H2O2 in the TME. L. acidophilus metabolite-induced pH reduction (<5.5) and CaO2-mediated in situ H2O2 generation synergistically boost ·OH generation activity of the CoFeCe-LDH nanosheets, effectively damaging cancer cells and ablating tumors with a tumor inhibition rate of 96.4%, 2.32-fold higher than that of CaO2/LDH. This work demonstrates that probiotics can function as a tumor-targeting platform to remodel the TME and amplify ROS generation for highly efficient and precise CDT.

Enhanced peracetic acid activation under Far-UVC Radiation: Micropollutant degradation and radical assessment

Traditional ultraviolet/peracetic acid process (UV/PAA) was limited by energy utilization. Herein, an efficient advanced oxidation process (AOP) for activating PAA by the far-ultraviolet of 222 nm (UV222/PAA) was established for micropollutant degradation. UV222/PAA system can effectively degrade various kinds of micropollutants, and the degradation rate of naproxen (NAP) in UV222/PAA system were about 2.61, 3.50 and 4.92 times higher than that in UV222/H2O2, UV222 and UV254/PAA systems within 300 s, respectively. The innate quantum yields of molecular state PAA (PAA0) and dissociated state PAA (PAA−) photolysis under UV222 irradiation were determined to be 0.51 and 0.84 mol Einstein−1 at pH 5.0 and pH 9.6, respectively. Based on an established kinetic model, the second-order rate constants of acetylperoxyl radical (CH3(O)OO•) and acetyloxyl radical (CH3(O)O•) with NAP were determined to be 1.74 × 107 and 1.08 × 106 M−1s−1, respectively. UV222, hydroxyl radical (HO•) and CH3(O)OO• were mainly responsible for the degradation of NAP, and their relative contributions were 33.00 %, 8.15 %, and 58.83 %, respectively. The increase of pH showed a promoting effect on NAP degradation, and the steady-state concentration of radicals increased with the increase of pH in UV222/PAA system. Cl– and HCO3– have inconspicuous impact on NAP degradation, while HA inhibits the degradation of NAP. The degradation pathway of NAP was proposed on the basis of product identification and theoretical calculation analysis. Finally, the effectiveness of the UV222/PAA system for NAP degradation was also verified in real water. This work develops an efficient PAA activation AOP with high radical yield for micropollutant degradation in practical applications.

3D printed lanthanide-doped Ti4O7 reactive membrane for efficient electrochemical disinfection and degradation of antibiotic resistance genes

Simultaneous removal of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) is absolutely imperative to prevent the spread of antibiotic resistance in the environment. Herein, suitable dopants of Ti4O7 anode from the lanthanide elements were firstly selected to boost Ti4O7 electrooxidation ability according to density functional theory simulation. 3D printing technology was further adopted to prepare 3D printed lanthanide-doped reactive electrochemical membrane (REM) electrodes, which could efficiently avoid the problem of membrane clogging in the electrochemical filtration operation and increase the hydroxyl radical yield by 56–442 % compared to Ti4O7 REM. We found that complete inactivation (>8.0-log inactivation) of antibiotic resistant Escherichia coli (AR E. coli) was achieved during Nd-Ti4O7 REM (1 wt% Nd) treatment in a single pass at 4 mA cm−2, indicating significant improvement of disinfection efficiency than Ti4O7 REM (3.3-log inactivation) operated in same conditions occurred. Morphology characterization results of treated AR E. coli revealed that cytoplasmic leakage in cell membrane perforation was the main inactivation mechanism. In addition, Nd-Ti4O7 REM also exhibited better electrooxidation efficiency for ARGs removal, thereby eliminating the spread risk of antibiotic resistance. These findings greatly promoted the preparation and application of Ti4O7 REM with highly efficient electrooxidation ability in the treatment of wastewater containing an abundance of antibiotic resistant bacteria.

Surface and morphology modulated adsorption-activation of trace concentration hydrogen peroxide with multiple electron transfer pathways and sustained Fenton reactions

To promote mass transfer and activation of hydrogen peroxide (H2O2) in Fenton-like reactions, a novel MOFs-derived Fe2O3 was tailor-designed through surface sulfur modification and morphology tuning for degrading a group of persistent micropollutants, i.e., sulfamethoxazole, enrofloxacin, and ofloxacin. The introduction of Ca2+ and Mg2+ modulated the growth of crystal clusters to prevent aggregation of Fe2O3 nanoparticles and provide more reaction sites. Likewise, the abundant acid sites (–SO3H) promote the chemisorption of even trace-concentration H2O2 (S–O bonding), whereas the S–Fe bonding accelerates electron transfer to promote the Fe3+/Fe2+ cycle and thus the H2O2 utilization. More interestingly, surface-adsorbed H2O is found to be activated to form •OH, due to electron-poor Fe sites formed after detachment of –SO3H, demonstrating a sustained radical yield for the micropollutant degradation. This study opens new perspectives in catalyst design to ultimately realize the utilization of trace-concentration H2O2 and even H2O in Fenton-like systems.

Synergistic Degradation of Methylene Blue by Hydrodynamic Cavitation Combined with Hydrogen Peroxide/Vitamin C System.

In this study, a new combined process of hydrodynamic cavitation (HC) and a hydrogen peroxide/vitamin C (H2O2/Vc) system was proposed for the degradation of methylene blue (MB) in wastewater. An impact-jet hydraulic cavitator was used as the cavitation generation equipment, and H2O2/Vc was selected as a homogeneous oxidation system. The degradation characteristics of MB were investigated. The results showed that the degradation effect of HC in combination with the H2O2/Vc system was more effective than that of the individual HC or H2O2/Vc system. A maximum degradation rate of 87.8% was achieved under the following conditions: H2O2 concentration of 0.03 mol/L, Vc concentration of 0.021 mol/L, inlet pressure of 0.3 MPa, initial solution concentration of 4 μmol/L, solution volume of 150 mL, and reaction time of 10 min. The synergy index was 1.615, indicating a synergistic effect between the HC and H2O2/Vc system. The data of the hydroxyl radical (·OH) yield under the conditions of HC, the H2O2/Vc system, and the HC + H2O2/Vc system were fitted and analyzed. A correlation equation for ·OH yield was established, further revealing the synergistic mechanism of the HC and H2O2/Vc system. The intermediate products of MB degradation were detected based on LC-MS, and three possible degradation pathways of MB degradation were proposed. The combined process of HC and H2O2/Vc systems exhibited relatively low energy efficiency and operating cost, indicating that it was in line with the development direction of wastewater treatment.

Computational study of the supramolecular complexation of azocompounds with cucurbit[7]uril: effects on the production and release of free radicals.

An inclusion complex between 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH), a widely employed azocompound, and cucurbit[7]util (CB[7]), has shown an increased yield of radicals derived from the homolytic cleavage of the azo bond. Aimed to get insights about the formation of complexes and their effect on the yield of radicals production, complexes of CB[7] with seven azocompounds were studied by computational methods. Molecular electrostatic surfaces and structural analysis showed that the inclusion of symmetrical azocompounds inside of CB[7] depends mainly on the charge density and position of the functional groups at the main chain of the azoderivative. Analysis of non-covalent interactions and thermodynamic outcomes revealed that positively charged azocompounds with amidinium or imidazolium groups presented strong favorable interactions (multiple hydrogen bonds) with the oxygens of CB[7] portals. Additionally, carbon-centered radicals generated from the complexes (azocompounds@CB[7]) were corroborated using the electron localization function (ELF). Results evidenced that the strength of the interactions and the level of inclusion (partial or complete) between the azocompound and CB[7] determined the final orientation of the radicals (located out- or inside of the CB[7] cavity). Obtained results could be employed to design new supramolecular systems based on the properties of azocomplound@CB[7] complexes for new scientific or industrial applications. First-principles calculations at B3LYP-D3BJ/6-311g(d,p) level theory in the gas phase and in solvent (PCM, water) were performed in Gaussian 16 software package. The dispersion energy correction was included through the Grimme's dispersion with Becke-Johnson damping D3(BJ). Thermodynamical data and the minimum character of all structures were obtained from vibrational frequency calculations. NBO, Multiwfn, Chemcraft, and NCIPLOT software were used to perform population analysis, analyze outcomes, visualize data, and display non-covalent interactions respectively.

Constructing novel metal-free HCOF-Ph@g-C3N4 heterojunctions through molecular expansion to enhance photogenerated carrier involved molecular oxygen activation and photocatalytic hydrogen evolution

Modification of covalent organic frameworks (COFs) have exceptional stability as well as tunable structures is the key to efficient photocatalysts. In this study, hyper-crosslinked COF-Ph was constructed with g-C3N4 to obtain a novel HCOF-Ph@g-C3N4 heterojunction, and the lamellar mesoporous of g-C3N4 was successfully embedded into the pores of 3D HCOF-Ph. The synthetic strategy greatly enhanced the photocatalytic properties and molecular oxygen activation capability of the catalyst. 10 mg of HCOF-Ph@g-C3N4 heterojunction could completely degrade 30 mg/L of tetracycline (TC) within 14 min, and the rate of hydrogen generation reached 9214.69 μmol g−1 h−1. The active species in this process of photocatalysis were verified through tests with free radical trapping and ESR spectra. In addition, the molecular oxygen activation capacity of heterojunction interface and the yield of superoxide radicals were examined by 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation and degradation of nitrotetrazolium nlue chloride (NBT) experiments, respectively. We found that the molecular expansion strategy can change molecule energy band structure to improve absorption of sunlight, and the efficient segregation of the photogenerated charge were ensured by the complementary energy band structure between g-C3N4 and HCOF-Ph. This study created an efficient molecular expansion method for the synthesis of COF-based catalysts with potential uses in the energy and environmental fields.

Contact-Electro-Catalysis Through Electret Behavior to Facilitate Electron Transfer.

Contact-electro-catalysis (CEC) usually uses polymer dielectrics as its catalysts under mechanical stimulation conditions, which although has a decent catalytic dye degradation effect still warrants performance improvement. A carrier separation promotion strategy based on an internal electric field by polarization can effectively improve ferroelectric material performance in photocatalysis and piezocatalysis. Therefore, carrier separation as a necessary process of CEC also can be promoted and is largely expected to improve CEC performance theoretically. However, the carrier separation enhancement by the internal electric field strategy has not been achieved in the CEC experiment yet, because of the difficulty of building an internal electric field in an inert polymer dielectric. Herein, a polytetrafluoroethylene (PTFE) dielectric was charged through an electret process, which was believed to establish an internal electric field for CEC catalysts proved by KPFM, XPS, and triboelectric nanogenerator voltage output analysis. The fastest degradation rate of methyl orange reached over 90% at 1.5 h, while the hydroxyl free radical (•OH) yield of the PTFE electret was nearly three times that of the original PTFE. Density functional theory (DFT) calculations verified that the potential barrier of interatomic electron transfer between PTFE and H2O was reduced by 37% under the internal electric field. The electret strategy used herein to optimize the PTFE catalyst provides a base for the use of other general plastics in CEC and facilitates the production of easily prepared, easily recyclable, and inexpensive polymer dielectric catalysts that can promote large-scale pollutant degradation via CEC.

Electro-activated periodate for organic contaminants degradation: Insights into the pH-dependent mechanism of active species

Although electro-activated periodate (PI) has demonstrated significant efficiency in degrading emerging contaminants (ECs), there has been limited research investigating the pH-dependence of active species generation and pollutant degradation. A graphite felt-based electrochemical system (GF-PI) was chosen to deeply explored. It exhibited significant differences in contaminants removal under different pH conditions. Notably, an interesting result is found that the GF-PI system at pH=3 exhibited exceptional removal performance specifically for phenolic contaminants, such as bisphenol A (BPA) and acetaminophen (ACT), whereas it displayed poor efficiency for other compounds, including sulfamethoxazole (SMX), carbamazepine (CBZ), benzoic acid (BA), and atrazine (ATZ). However, there is no selectivity for contaminants removal in pH=4, 7, and 9 system. The experiment of probe capture and quenching are conducted to thoroughly investigate the variety of reactive oxygen species (ROSs) generated. It has been proven that hypoiodous acid (HOI) is the main active species in the system with pH=3. In addition, the system with pH=4 exhibits the highest degradation efficiency and TOC removal efficiency, despite the low yield of hydroxyl radical (·OH), indicating that the iodate radical (IO3·) plays a pivotal role. Under neutral and alkaline conditions, ·OH, IO3·, and singlet oxygen (1O2) are the main active species. Moreover, the system exhibits remarkable stability, anti-interference capabilities, and cost-effectiveness, indicating the superiority for treatment of authentic wastewater. Additionally, the degradation intermediates and biotoxicity of SMX are evaluated through multiple measures. A comprehensive understanding of pH is indispensable in electro-activated PI system for treatment of emerging organic contaminants.

Optimizing Ultrasonic‐Assisted Extraction for Enhanced Yield of Phenolic Compounds and Antioxidant Activity in Cold Brew Coffee

ABSTRACTThis study aimed to identify the best conditions for ultrasonic‐assisted extraction (UAE) of DPPH and phenolic compounds from cold brew coffee using Box‐Behnken Design (BBD) and Response Surface Methodology (RSM). It explored the effects of solid‐liquid ratio (5%–15%), extraction time (40–50 min), and ultrasonic power (70%–80%) on these compounds, finding that all factors significantly influenced the outcomes. Statistical analysis showed the data fit a quadratic polynomial model well, with R2 values of 0.9981 for phenolic compounds and 0.9799 for DPPH radicals. Using 3D surface and contour plots from these models, the optimal extraction conditions for these compounds from cold brew coffee were determined. The highest yields of total phenolic compounds and DPPH radical were obtained when samples were extracted at a 10% solid–liquid ratio, 45 min extraction time, and 75% ultrasonic power. Under these optimal conditions, total phenolic compounds and DPPH radical were 64.10 ± 0.31 gGAE/mL and 61.90 ± 0.14%, respectively, with a maximum caffeine content of 213.13 ± 0.23 mg/L. Gamma irradiation at kGy also reduced cold brew coffee's microbial content. This research may be a new alternative for producing cold brew coffee that will save time and help extend the shelf life.

Quantification of Free Radicals from Vaping Electronic Cigarettes Containing Nicotine Salt Solutions with Different Organic Acid Types and Concentrations.

Electronic (e-) cigarette formulations containing nicotine salts from a range of organic acid conjugates and pH values have dominated the commercial market. The acids in the nicotine salt formulations may alter the redox environment in e-cigarettes, impacting free radical formation in e-cigarette aerosol. Here, the generation of aerosol mass and free radicals from a fourth-generation e-cigarette device was evaluated at 2 wt % nicotine salts (pH 7, 30:70 mixture propylene glycol to vegetable glycerin) across eight organic acids used in e-liquids: benzoic acid (BA), salicylic acid (SLA), lactic acid (LA), levulinic acid (LVA), succinic acid (SA), malic acid (MA), tartaric acid (TA), and citric acid (CA). Furthermore, 2 wt % BA nicotine salts were studied at the following nicotine to acid ratios: 1:2 (pH 4), 1:1 (pH 7), and 2:1 (pH 8), in comparison with freebase nicotine (pH 10). Radical yields were quantified by spin-trapping and electron paramagnetic resonance (EPR) spectroscopy. The EPR spectra of free radicals in the nicotine salt aerosol matched those generated from the Fenton reaction, which are primarily hydroxyl (OH) radicals and other reactive oxygen species (ROS). Although the aerosol mass formation was not significantly different for most of the tested nicotine salts and acid concentrations, notable ROS yields were observed only from BA, CA, and TA under the study conditions. The e-liquids with SLA, LA, LVA, SA, and MA produced less ROS than the 2 wt % freebase nicotine e-liquid, suggesting that organic acids may play dual roles in the production and scavenging of ROS. For BA nicotine salts, it was found that the ROS yield increased with a higher acid concentration (or a lower nicotine to acid ratio). The observation that BA nicotine salts produce the highest ROS yield in aerosol generated from a fourth-generation vape device, which increases with acid concentration, has important implications for ROS-mediated health outcomes that may be relevant to consumers, manufacturers, and regulatory agencies.

Critical Role of Mineral Fe(IV) Formation in Low Hydroxyl Radical Yields during Fe(II)-Bearing Clay Mineral Oxygenation.

In subsurface environments, Fe(II)-bearing clay minerals can serve as crucial electron sources for O2 activation, leading to the sequential production of O2•-, H2O2, and •OH. However, the observed •OH yields are notably low, and the underlying mechanism remains unclear. In this study, we investigated the production of oxidants from oxygenation of reduced Fe-rich nontronite NAu-2 and Fe-poor montmorillonite SWy-3. Our results indicated that the •OH yields are dependent on mineral Fe(II) species, with edge-surface Fe(II) exhibiting significantly lower •OH yields compared to those of interior Fe(II). Evidence from in situ Raman and Mössbauer spectra and chemical probe experiments substantiated the formation of structural Fe(IV). Modeling results elucidate that the pathways of Fe(IV) and •OH formation respectively consume 85.9-97.0 and 14.1-3.0% of electrons for H2O2 decomposition during oxygenation, with the Fe(II)edge/Fe(II)total ratio varying from 10 to 90%. Consequently, these findings provide novel insights into the low •OH yields of different Fe(II)-bearing clay minerals. Since Fe(IV) can selectively degrade contaminants (e.g., phenol), the generation of mineral Fe(IV) and •OH should be taken into consideration carefully when assessing the natural attenuation of contaminants in redox-fluctuating environments.

Experimental and chemical kinetics study on the flammability limit of CO2/C3H6 mixture working fluid at variable initial temperature

CO2/C3H6 mixture has a wide range of applications in refrigeration systems, heat pumps and Organic Rankine Cycle (ORC) systems, but its flammability safety needs to be considered. An experimental and computational investigation has been conducted on the determination of the flammability limits of CO2/C3H6 and on the understanding of associated limit phenomena in general. We tested the flammable zone of CO2/C3H6 at variable initial temperature. The accuracy of the prediction model of calculation adiabatic flame temperature were verified based on the experimental data. Meanwhile, a high-speed camera was used to record the process of CO2 suppression of flame propagation near flammability limit. Furthermore, based on kinetic numerical calculation, the effect of CO2 chemical and thermal on the flammability limit of C3H6 were analyzed. The results show that the thermal effect of CO2 is greater than that of chemical effect near the flammability limit. The theory of chemical reactivity inhibition reduces the yield and molar ratio of key radicals. The addition of CO2 can inhibit the activity of the dominant chain and increase the activity of the dominant chain termination reaction in the global combustion kinetics. Results of this study provide theoretical guidance for the safe application of CO2/C3H6 mixture.

Unusual enhancement of the radical production in the X-ray irradiated aqueous-organic systems containing W(VI) in homogeneous and nanoparticle forms

The metal and oxide nanoparticles (NPs) containing various elements with high atomic number (Z) are considered as prospective sensitizers for the production of radicals upon X-ray irradiation of aqueous solutions, which can be used for different applications in medical treatment and material modification. The common basis for the sensitizing effect in oxygen-free systems is concerned with increase of the absorbed dose due to the presence of high-Z atoms (known as physical enhancement, relatively insensitive to the NP size). In this work we report the first experimental evidence for extra enhancement of the radical yield in a model oxygen-free aqueous organic system irradiated with X-rays (45 kVp) in the presence of W(VI) compounds, both in homogeneous solutions of Na2WO4 and in the form of ultra-small NPs of WO3. Meanwhile, in the case of larger WO3 NPs the radical yield is consistent with physical enhancement mechanism. In the case of systems containing HfO2 NPs only physical enhancement was observed, independent of the NP size. Unusually large enhancement of radical production and size effect for W(VI) in homogeneous and NP forms was tentatively attributed to the radiation-chemical processes involving intermediate formation of metastable W(V) due to reactions of hydrated electron.

Cyclodextrin-boosted photocatalytic oxidation for efficient bisphenol A removal

Wastewater contains various high-risk trace organic pollutants, such as antibiotics and endocrine disruptors, which seriously restrict wastewater reuse. Cyclodextrin-based functional materials show great potential in the removal of trace pollutants because of their adsorption catalytic synergy. Clarifying the synergistic mechanism of cyclodextrin in oxidation is the key issue in confined catalytic oxidation process design. In this work, we fabricated a BiOIO3@BiOBr/β-CD heterojunction photocatalyst to study the synergistic mechanism of cyclodextrin in the photocatalytic oxidation process. The synergistic mechanism of cyclodextrin was investigated by combining radical chemistry, electrochemistry, spectroscopy, and time-dependent density functional theory. Results showed that the excited intermediate free radicals played an important role in promoting the photocatalytic degradation process. The heterojunction photocatalyst loaded with β-cyclodextrin (β-CD) at the electronic end (C[Cat.] = 0.2 mg/mL) removed about 97% of bisphenol A (BPA) within 30 min, and the first-order kinetic constant (kCDBIB = 0.112 min−1) was about twice that of the unloaded β-CD (kBIB = 0.057 min−1). Cyclodextrin loading improved the photocatalytic performance of the heterojunction and stimulated the intermediate to increase the free radical yield and regulate the reaction path.

Multiscale Modeling of Plutonium Radiation Chemistry in Nitric Acid Solutions. 1. Cobalt-60 Gamma Irradiation of Pu(IV).

Careful manipulation of the plutonium oxidation states is essential in the study and utilization of its rich redox chemistry. To achieve this level of control, a comprehensive mechanistic understanding of radiation-induced plutonium redox chemistry is critical due to the unavoidable exposure of plutonium to ionizing radiation fields, both inherent and from in-process applications. To this end, we have developed an experimentally evaluated multiscale computer model for the prediction of gamma radiation-induced Pu(IV) redox chemistry in concentrated nitric acid solutions (1.0, 3.0, and 6.0 M). Under these acidic, aqueous solution conditions, cobalt-60 gamma irradiation afforded marginal net conversion of Pu(IV) to Pu(VI), the extent of which was dependent on the concentration of HNO3 and absorbed gamma dose. Multiscale calculations, which are in excellent agreement with experimental data, indicate that this observation is due to a combination of inherent plutonium disproportionation reactions and several radiation-induced processes, including redox cycling between Pu(IV) and Pu(III), as achieved by the reduction of Pu(IV) by nitrous acid and hydrogen peroxide, the oxidation of Pu(III) by nitrate and hydroxyl radicals, and the sequential oxidation of Pu(IV) to Pu(V) and Pu(VI) by the remaining available yield of nitrate radicals.

Degradation mechanisms of antibiotics in UV222/H2O2 and UV222/persulfate systems: Dual roles of inorganic anions

Advanced oxidation processes based on KrCl* excimer lamps (UV222-AOPs) have recently received widespread attention in water treatment due to their high radical yields. In this investigation, the degradation of two typical antibiotics, florfenicol (FLO) and ciprofloxacin (CIP), by UV222 and its combination with hydrogen peroxide (H2O2) or persulfate (PDS) were studied, respectively. The dual effects of inorganic anions on the degradation performance of UV222/UV222-AOPs were determined. It was found that NO3– significantly enhanced the photolysis of CIP, and the degradation rate constants increased from 1.03 × 10-4 mJ−1 cm2 (without NO3–) to 2.56 × 10-4 mJ−1 cm2 (with 1 mM NO3–). However, NO3– markedly inhibited the photolysis of FLO, leading to a decrease in the degradation rate constants from 1.18 × 10-3 mJ−1 cm2 (without NO3–) to 5.27 × 10-4 mJ−1 cm2 (with 1 mM NO3–). HCO3– was found to have a certain promoting effect on the photolysis of FLO and CIP, and SO42- has a negligible effect on the photolysis of both antibiotics. The above three inorganic ions decelerated the degradation of CIP and FLO in UV222-AOP, where NO3– exerted the most inhibition. Through LC-MS analysis and ECOSAR model, the main transformation products were individually determined and evaluated for toxicity. In addition, the performance of UV222-AOPs and UV254-AOPs in reclaimed wastewater (RWW) treatment were compared, and the steady-state concentration of radicals was measured. This study provided novel insight into the application of UV222-AOPs in RWW treatment.

Quantum Control of Radical-Pair Dynamics beyond Time-Local Optimization

We realize arbitrary-wave-form-based control of spin-selective recombination reactions of radical pairs in the low-magnetic-field regime. To this end, we extend the gradient-ascent pulse engineering (GRAPE) paradigm to allow for optimizing reaction yields. This overcomes drawbacks of previously suggested time-local optimization approaches for the reaction control of radical pairs, which were limited to high biasing fields. We demonstrate how efficient time-global optimization of the recombination yields can be realized by gradient-based methods augmented by time blocking, sparse sampling of the yield, and evaluation of the central single time-step propagators and their Fréchet derivatives using iterated Trotter-Suzuki splittings. Results are shown for both a toy model, previously used to demonstrate coherent control of radical-pair reactions in the simpler high-field scenario and, furthermore, for a realistic exciplex-forming donor-acceptor system comprising 16 nuclear spins. This raises prospects for the spin control of actual radical-pair systems in ambient magnetic fields, by suppressing or boosting radical reaction yields using purpose-specific radio-frequency wave forms, paving the way for reaction-yield-dependent quantum magnetometry and potentially applications of quantum control to biochemical radical-pair reactions. We demonstrate the latter aspect for two radical pairs implicated in quantum biology. Published by the American Physical Society 2024

Computational modeling of a surfatron mode microwave plasma in NH3/N2 for remote radical generation in a silicon native oxide cleaning process

Plasma-produced NxHy radicals facilitate the removal of native oxide layers in a semiconductor wafer surface. A remote microwave excited plasma with a NH3–N2 feed gas is used commonly to produce the active radicals. We perform a three-dimensional modeling of a microwave excited plasma operating in a surfatron mode. The device consists of a rectangular waveguide intersecting a quartz tube through which the feed gas flows. We discuss the propagation of a polarized 2.45 GHz microwave from the waveguide into the quartz tube where power is deposited into the plasma. The plasma–wave interaction is found to be highly three dimensional, with a propagating surface mode of the wave established along the dielectric tube plasma interface. Significant heating occurs on the side of the tube that directly faces the incident wave. As the flow carries the plasma-produced species down the tube, species radial profiles become increasingly diffusion controlled and axisymmetric. The dominant radicals that exit the tube are H2 and NH2, with nearly complete conversion of the feed gases to product species. The gas temperature rises above this inlet feed gas temperature and increases with increasing wave power. However, the gas temperature increase is not consequential to the overall radical yield from the plasma. The parametric study with changing pressure and input power illustrates the role of specific chemical reactions in the overall remote plasma process.

Electron-catalytic conversion of carbon dioxide into formaldehyde and methanol

Since the mid-19th century, there has been a steady increase in the amount of CO2 in the atmosphere, leading to global warming due to the greenhouse effect. CO2 can be utilized to obtain a large number of organic compounds. The formation of these compounds depends on the methods of CO2 processing, which include biological, thermal conversion, photochemical, and plasma methods. Most of these methods involve the use of catalysts. One of the plasma methods is the electron-catalytic method using a barrier discharge. Studies on the catalytic conversion of CO2 into methanol and formaldehyde were carried out on a laboratory setup consisting of two sources of low-temperature plasma – dischargers, one of which contains a heterogeneous catalyst. Water vapor was used as the source of hydrogen. The formation of methanol and formaldehyde was investigated under different operating modes of the setup. The effect of sample aging for a day was determined. As a result, there is an increase in the concentration of methanol in the sample from 5.8% to 49.74% and formaldehyde from 4.1% to 50.01% for different operating modes of the setup. The observed results are explained by a sharp increase in the yield of oxygen-containing radicals and , which are formed by the interaction of ozone, formed from CO2 in the discharge zone, with aqueous solutions.