OH Radicals Research Articles

Study on the photocatalytic properties of the ternary ZnO/MgAl-LDH/FeOOH composite photocatalyst with a Type-II and S-scheme linked carrier migration mechanism in degrading TC solution

The synthesis of high-performance photocatalysts represents a pivotal aspect of research into photocatalytic degradation technology. In order to address this need, a novel ZnO/MgAl-LDH/FeOOH ternary composite photocatalyst has been synthesized via a multi-step process involving the hydrothermal, calcination and ultrasonic-assisted wet impregnation methods. The ternary composite photocatalyst was observed to demonstrate effective separation of photogenerated carriers in photocatalysis, following a Type-II and S-scheme linked carrier migration mechanism. An examination of the photocatalytic characteristics of the composite photocatalyst in the degradation of a tetracycline (TC) solution revealed that the reduction of •O2- radicals and the oxidation of •OH radicals resulted in the effective degradation of the TC solution. The degradation efficiency of the TC solution under the photocatalysis of the ternary composite photocatalyst was observed to be 1.54, 1.11 and 3.15 times that of the single-component samples of ZnO, MgAl-LDH and FeOOH, respectively, in 30 min. Moreover, the degradation pathway of TC molecules under the photocatalysis of the composite has been elucidated. The research findings provide a foundation for further investigation into this composite photocatalyst.

The design of a combustion chamber operated in MILD regime — Numerical modeling of hydrogen combustion in oxygen–steam mixtures

The goal of the current work is to develop a combustion chamber that can operate on recirculated steam produced by burning hydrogen in oxygen under conditions of Moderate or Intense oxygen Dilution (MILD) in atmospheric and stoichiometric conditions. The study investigates several configurations of combustor with nozzles, taking into account the overall temperature, OH radicals, and heat release rate distribution throughout the combustor’s domain. Thermal power variations of the steam generator (5 to 20 kW) were examined in conjunction with different oxygen dilutions with steam, down to 3% of O2 (by mol.). The outcomes reveal that a rise in dilution degree promotes a drop in the mean temperature across every case and reagents’ recirculation with homogeneous temperature field, suggesting the presence of MILD combustion. The highest temperature values were observed at the stoichiometric mixture fraction. Higher dilution degree revealed more efficient heat release across the domain with low fluctuations from the reference MILD combustion data. Of the two combustion models studied, the Partially Stirred Reactor model did not show flame extinction at the highest dilution degrees, unlike the Eddy Dissipation model. The selected final design of the combustion chamber was used for constructing the actual combustor dedicated for lab-scale operation.

Antimicrobial and antioxidant study of combined essential oils of Anethum Sowa Kurz. and Trachyspermum ammi (L.) along with quality determination, comparative histo-anatomical features, GC‒MS and HPTLC chemometrics

Spices played crucial and variable roles in traditions, culture, history, religious ceremonials and festivals along with fetching food flavor and microbial protection globally due to presence of structurally unique and multi-natured chemotypes. Their existence in dishes portrayed key roles in improving shelf life by regulating spoilage of cuisine with different synergistic mechanism. Histo-anatomically (A) sowa exhibited distinguished cellular attributes which created remarkable differences with T. ammi. HPTLC chemometrics of both fruits revealed several peaks for active metabolomics with unique isocratic combination of menstruum. GC-MS study of hydro-distillate exhibited presence of monoterpenic cyclic and aromatic hydrocarbons, alcoholic and ketonic groups along with phenolic derivative that covers majorly 90% of total metabolites. Combined essential oils (EOs 1 + 2) of both fruits showed excellent antimicrobial activity against various clinical pathogenic strains such as K. pneumoniae at 10 µL/mL, S. aureus at 2.5 µL/mL, E. coli and E. faecalis at 1.25 µL/mL, and MRSA and Bcereus at 0.625 µL/mL and (C) albicans at 0.312 µL/mL as the MIC. The antioxidant study of (EOs 1 + 2) with maximum inhibition percentage to DPPH assay was 84.02 ± 1.05 at 100 µg/mL, and minimal inhibition was 72.31 ± 0.63 at 5 µg/mL with IC50 value 4.69 ± 0.22 µg/mL, while ABTS assay extreme was 79.15 ± 2.14 µg/mL and minimal was 67 ± 1.34 with the IC50 value of 18.37 ± 0.15 µg/mL, in superoxide assay uppermost inhibition was 81.03 ± 0.27 µg/mL and lowest was at 65.16 ± 3.15 with the IC50 value 16.46 ± 0.54, and H2O2 radical scavenging activity, predominant value was 78.01 ± 0.47 and least was 64.1 ± 2.01 with IC50 15.58 ± 0.34. These comparative key diagnostic features and synergistic effect of multicomponent natural antimicrobials will provide profound intellect of ancient utility and further scientists to explore their multiple mechanistic modality and application in food and beverages industry.

Cavity-enhanced Faraday rotation spectroscopy for interference-free measurement of OH radical at 2.8 μm

An instrument based on cavity-enhanced Faraday rotation spectroscopy (CE-FRS) operating at 2.8 μm has been developed for interference-free measurement of OH radicals in the laboratory. By off-axis coupling of a continuous-wave laser into a high finesse optical cavity, FRS signal is obtained from balanced detection of time-integrated light intensity leaking out of the cavity in the presence of magnetic field. Radio-frequency white noise (5–520 MHz) was injected into laser current which reduced intensity fluctuations in cavity transmission, thus improved the signal-to-noise ratio of the spectroscopic signal by a factor of 2. The setup provides a simple and robust spectroscopic instrument for in-situ and highly-selective detection of paramagnetic species. We demonstrated the instrument’s capabilities using OH radical with concentration in the range of 1012 molecule.cm−3, generated by microwave discharge of water vapor at low pressure. The CE-FRS instrument exhibited a limit of detection of ∼ 1010 molecule.cm−3 in an integration time of 20 s, which is enhanced by a factor of 2.5 compared to cavity-enhanced wavelength modulation spectroscopy involving an off-axis integrated cavity output spectroscopy approach. A time-resolved FRS signal was recorded in a pulsed microwave discharge regime, giving a millisecond time resolution for the measurement of OH concentration profile. The developed instrument provides a potential analytical tool for the measurement of OH concentration for chemical kinetic study in reactor cells.

Uncovering Metal-Decorated TiO2 Photocatalysts for Ciprofloxacin Degradation-A Combined Experimental and DFT Study.

Optimization of the efficiency of the photocatalytic degradation of organic and pharmaceutical pollutants represents a matter of fundamental and practical interest. The present experimental and DFT study deals with evaluation of OH radical binding energy as a simple computational descriptor of the catalytic activity of d-metal-decorated TiO2 photocatalysts for the photodegradation of the widely used antibiotic ciprofloxacin. Five d-metals commonly used in catalytic materials (Zr, Pt, Pd, Fe, and Cu) were deposited on the TiO2 surface, and the obtained photocatalysts were characterized experimentally (XRPD, ICP-OES, and SEM) and theoretically (DFT). Attention was also paid to the mechanistic insights and degradation byproducts (based on UV-Vis spectrometry and LC/MS analysis) in order to obtain systematic insight into their structure/performance relationships and confirm the proposed model of the degradation process based on OH radical reactivity.

Design of MgO/graphene nanocomposites for photocatalytic reduction of 4-nitrophenol and electrocatalytic oxidation of Methylene blue dye

The present study deals with the combustion synthesis of MgO/Graphene (MG) nanocomposites and investigates their photocatalytic, electrocatalytic, and photo-electrocatalytic properties for efficient redox reactions. Techniques such as FT-IR, XRD, SEM, HR-TEM, EDX, BET, and UV–vis-DRS were used to characterize MG nanocomposites. Both the photocatalytic degradation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) and the electrocatalytic results of the MG2 nanocomposite were studied under visible light. The results showed that the MG2 nanocomposite catalyst achieved 99.07% degradation of MB dye and kinetic degradation rates of 0.114 min−1 after 40 min, compared to the catalytic activity of MG0. Thus, facile modification can effectively improve the photocatalytic reduction (toxic 4-NP to beneficial 4-AP) and electrocatalytic degradation (MB) abilities of MG0. The functions of active species in the catalytic process were investigated using various scavengers. The ·OH radicals are the reactive species responsible for the 4-NP reduction, and a possible mechanism for improved catalytic activities was also provided. Incorporating graphene under visible light boosted the MG’s activity and confirmed it to be the most effective method for handling MB dye.

Systematic study on the hydrogen abstraction reactions from oxygenated compounds by H and HO2

AbstractTo extend the rule‐based approach for hydrogen abstraction reactions from oxygenated compounds, a systematic investigation was performed to examine the reactivity of gas‐phase hydrogen abstraction reactions from alkyl groups (methyl and ethyl groups) bound to oxygen atoms in five types of oxygenated compounds (alcohols, ethers, formate esters, acetate esters, and carbonate esters) by H atoms and HO2 radicals comprehensively considering rotational conformers. Quantum chemical calculations were conducted at the CBS‐QB3 level for stationary points. Rate constants were determined employing conventional transition state theory (TST). For hydrogen abstraction reactions by H, the rotational conformer distribution partition function was employed to approximate partition functions, owing to the similarity in vibrational energy‐level structures among conformers. In hydrogen abstraction reactions by HO2, the vibrational structures of transition‐state (TS) conformers varied significantly due to the hydrogen bonding, leading to an inappropriate evaluation of rate constants when using the lowest‐energy conformer as a representative. Therefore, the rate constants were calculated by the multi‐structural TST. It was revealed that the differences in functional groups containing O atoms mainly affect the bond dissociation energies of the C–H bonds and the activation energies of hydrogen abstraction reactions only when the C atoms are adjacent to the O atoms. Additionally, it was found that hydrogen bonds formed in the TSs show minor effect on rate parameters for the overall rate constants, apart from the reduction of the pre‐exponential factors for the H‐abstraction reactions from the methylene position of ethyl groups. The comparison with the rate constants from previous studies showed reasonable results, indicating that the rate constants in this study, which thoroughly consider rotational conformers, can be the current best estimates.

Mechanistic studies on the oxidation reaction of n-pentane

The oxidation reaction mechanism of n-pentane is investigated using density functional theory and transition state theory as a case study to elucidate the combustion characteristics of liquids with low boiling points. This study divides the oxidation reaction of n-pentane into four steps. First, n-pentane decomposes to form n-pentyl radicals C5H11 and H, CH3 and C4H9, and C2H5 and C3H7 radicals. Second, n-pentane primarily undergoes H-abstraction reactions with H, CH3, C2H5, and C3H7 radicals to form the C5H11 radicals. Subsequently, C5H11 radicals react with O2 in an addition reaction to form n-pentyl peroxy radicals ROO. Finally, ROO radical undergoes internal H-atom transfer to form hydroperoxy pentyl radicals QOOH, which then undergoes cyclization and bond scission to produce cyclic ethers, alkenes, aldehydes, OH radicals, and HO2 radicals. Results indicate that n-pentane readily decomposes into C2H5 and C3H7 radicals, with a bond dissociation energy of 367.1 KJ/mol. The H-abstraction reactions involving H and CH3 radicals have the fastest rates, which require the lowest energy barriers of 21.6 and 41.9 KJ/mol, respectively. The reaction between C5H11 and O2 is a barrierless addition reaction. The oxidation of n-pentane, which leads to the formation of 2-methyloxirane and OH radicals, exhibits the fastest reaction rate.

The removal mechanism of tetracycline by environmentally friendly modified sepiolite activated peroxymonosulfate

Sepiolite (SEP), a naturally abundant and environmentally friendly clay mineral, possesses various active sites and a large specific surface area. In this work, peroxymonosulfate (PMS) was activated to remove tetracycline (TC) using modified Sepiolite (MSEP), which was synthesized by ball milling and calcination techniques. According to the findings, MSEP efficiently stimulated PMS to produce 1O2 and ·OH radicals for the degradation of TC, with 1O2 being a key component of this process. The findings demonstrated that the carbonate on the MSEP surface encouraged the production of singlet oxygen. (1O2). Under the conditions of pH 6.5, 0.2 g/L MSEP, 2 mmol/L PMS and 25 °C, a 10 mg/L TC concentration was reduced by 93.3 % after 30 min. The presence of Cl− and NO3− did not inhibit TC degradation, while HCO3− promoted it, and H2PO4− exhibited an inhibitory effect. This work offers a novel method for using clay minerals to activate PMS and degrade organic contaminant without secondary pollution.

Stabilize the oxygen vacancies in ZnO via altering local electronic structure by Co and Ni doping: A novel strategy for achieving durable visible light driven photo-Fenton degradation of chloramphenicol

The build-up of antibiotics, harmful pollutants, and pharmaceutical products has led to the significant contamination of environmental water bodies. Hence, the advancement of oxidation methods such as light-induced photo-Fenton degradation has proven crucial for efficiently desolating these harmful pollutants. Herein, we report a novel photo Fenton catalyst, Co and Ni co-doped ZnO (Zn1-x-yCoxNiyO) nanorods (NRs) for enhanced photocatalytic degradation of chloramphenicol (CAP) under visible light irradiation. The NRs were synthesized via the ultrasonication-assisted solvothermal method. Among the different Co and Ni doping concentrations, Zn0.96Co0.03Ni0.01O NRs showed superior photodegradation efficiency of 94.2%. Here, •OH radicals were identified as predominant reactive oxygen species in photocatalytic degradation by electron spin resonance (ESR) analysis and scavenging assay. The effect of various environmental parameters such as nanoparticle dosage, CAP concentration, pH, and ions were investigated to understand the impact of these parameters on the degradation of CAP. Further, Zn0.96Co0.03Ni0.01O NRs were stable for six consecutive photodegradation cycles, which showed their excellent efficiency and reusability for prolonged usage. Photostability was further confirmed by XPS and XRD analysis of the used photocatalyst. Also, the photodegradation pathway of CAP was predicted by identifying the intermediate compounds via GC-MS analysis. This approach holds promise for the efficient visible-light-driven degradation of pharmaceutical pollutants including CAP and contributes to the advancement of sustainable water treatment technologies.

Five novel Pb/Zn/Co metal-organic frameworks using 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene and carboxylate ligands: Synthesis, characterization, DFT calculation and catalytic PMS degradation of RhB

Five new metal-organic frameworks (MOFs), namely {Pb(atpt)(3-bpd)0.5}n (1); {Co(cbz)2(3-bpd)(H2O)2·2H2O}n (2); {Co(imdc)(3-bpd)(H2O)·H2O}n (3); {Co(tdca)(3-bpd)(H2O)2·DMF}n (4); {Zn(tdca)(3-bpd)(H2O)2·DMF}n (5), were assembled with metal ions Pb²⁺, Zn²⁺, and Co²⁺ using 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene (3-bpd) as the main ligand, combined with 2-aminoterephthalic acid (H2atpt), 4-cyanobenzoic acid (Hcbz), 4,5-imidazoledicarboxylic acid (H2imdc), and thiophene-2,5-dicarboxylic acid (H2tdca) as auxiliary ligands via hydro/solvothermal methods. Their molecular structures were analyzed by single-crystal X-ray diffraction and characterized by FT-IR and PXRD. Complex 1 has a three-dimensional structure with a hepta-coordinated, semi-directed {PbNO6} metal center. The central metal ions in complexes 2–5 exhibit a six-coordinated {MN2O4} (M = Co or Zn) octahedral geometry. In complex 2, the carboxylate ligand does not function as a bridging ligand, resulting in a 1D chain structure, while complexes 3- 5 extend into 2D layered structures. Thermogravimetric analysis indicates good thermal stability for complexes 1–5. Then, the prepared complexes were used as catalysts to degrade Rhodamine B (RhB) during the monopersulfate (PMS) activation. Complexes 3 and 4 demonstrated significant efficiency, achieving degradation rates of 93.61 % and 98.56 % within 10 min. Radical scavenging experiments and EPR analysis identified that the activation of PMS for dye degradation by the two catalysts occurs through both radical and non-radical pathways, with SO4•− and •OH radicals being the dominant species. Density functional theory (DFT) calculations explained the superior catalytic performance of complex 4 compared to complex 3.

Insights into flame flashback phenomenon utilizing a Strut-Cavity flame holder inside scramjet combustor

Understanding upstream flame propagation in scramjets is challenging, particularly concerning flame flashback in a combustor with a novel strut-cavity flame holder. Two-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) simulations were performed to investigate how Mach number and wall divergence affect flame behavior. The utility of the strut-cavity flame holder was highlighted through a study of its non-reacting flow characteristics. Flow dynamics are significantly altered as the shear layer above the cavity interacts with the downstream hydrogen jet. Shear layer dynamics and fuel-air mixing are improved through key factors such as shock-train behavior, cavity oscillations, and transverse fuel injection. The submerged fuel jet is less exposed to supersonic flow and demonstrates reduced entropy rise, achieving a 16% increase in mixing efficiency compared to standalone struts and a 46% improvement over transverse injection without a flame holder. Thermal choking shifts the shock train upstream, facilitating interactions with the shear layer and enhancing vortex formation, which decreases flow speed and promotes upstream flame propagation. The presence of OH radicals indicates that flame flashback follows a periodic pattern with an initial gradual slope, suggesting effective anchoring. Stability and flashback likelihood are affected by low-speed zones, vortex merging, and wall divergence. At Mach 3, combustion efficiency improves without wall divergence due to increased heat release, while wall divergence prevents flame flashback by sustaining supersonic core flow and managing flow-flame interactions. At higher core flow velocities, flame stabilization occurs at the cavity's separation corner, despite a tendency for upstream propagation, with validation of the URANS results achieved through two-dimensional large eddy simulations.

Photocatalytic degradation of cetirizine hydrochloride using polypyrrole decorated zinc ferrite nanohybrids under visible light irradiation.

The present work reports photocatalytic degradation of cetirizine hydrochloride (CTZ-HCl) utilizing polypyrrole (PPy) nanohybrids with ZnFe2O4 (ZnFe) nanoparticles. The synthesized materials were characterized using UV-visible spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) spectroscopy, BET, and scanning electron microscopy (SEM) techniques. UV diffuse reflectance studies (UV-DRS) revealed that the band gap was found to decrease with increase in the loading of PPy and Kubelka-Munk plots confirmed the bandgap values to be 2.14eV for ZnFe, 1.94eV for 1% PPy/ZnFe, 1.66eV for 3% PPy/ZnFe, and 1.38eV for 5% PPy/ZnFe. The photocatalytic performance against CTZ-HCl degradation was performed under visible light irradiation for 60min. The effect of catalyst dosage and the effect of drug concentration were investigated to confirm degradation behavior of the PPy/ZnFe photocatalysts. The degradation followed the pseudo-first-order kinetics model. Maximum photocatalytic degradation was observed to be 98% within 60min using 5% PPy/ZnFe as the photocatalyst. The recyclability tests revealed that the 5% PPy/ZnFe photocatalyst was reusable up to 4 cycles. Radical scavenging studies confirmed the generation of ●OH radicals that were responsible for the drug degradation. The degraded fragments were analyzed using LCMS technique and the tentative mechanism of degradation was proposed.

Fabrication of novel S-type In2S3/Ag2S heterostructures with superior photocatalytic and electrochemical characteristics for remediation of organic contaminants in water

In the present report, In2S3/Ag2S heterojunctions were created hydrothermally and characterized for their crystalline structure, morphology, composition, optical characteristics, charges reunification and property of charge by standard analytical techniques. Synthesized nanomaterials were utilized for the decontamination of organic pollutants such as Rhodamine B (RhB) dye and antibiotic ciprofloxacin (CP) by using visible light radiance. Calculated photocatalytic removal efficacy for RhB and CP over In2S3/Ag2S nanocomposite was 99.95 % in 40 min and 99.49 % in 140 min respectively which is 1.98 and 1.21 times greater than In2S3 alone. Maximum removal efficiency was achieved for In2S3/Ag2S (3 wt%) composition. The enhanced activity is attributed to the greater absorption of visible light and construction of S-type heterojunction which are more efficient for light induced charge separation and therefore decrease the reunification of hole-electron carriers. Density functional theory (DFT) analysis also supported that the nanocomposite is energetically favorable, stable and show significantly electronic and photocatalytic properties. In2S3/Ag2S (3 wt%) nanocomposite achieved excellent photocatalytic stability towards the removal of RhB and CP even after five runs. In2S3/Ag2S (3 wt%) nanocomposites showed maximum photocatalytic activity in acidic medium. Effect of trapping agents towards removal of CP and RhB were conducted and results showed that.O2− radical play dominant role as active species in comparison to ⋅OH radical and holes. Plausible mechanism of transfer of charge in In2S3/Ag2S and removal of pollutants is also represented. Owing to their unique features, novel In2S3/Ag2S heterojunctions exhibits as an exceptionally effective photocatalyst for removal of pollutants and it would display the promising utilization towards wastewater treatment.

Correlation between temperature distribution and changes in self-organized luminous pattern in an atmospheric pressure DC glow discharge with sheath gas flow

Abstract The self-organized luminous patterns observed above the anode surface in atmospheric-pressure DC glow discharges were changed by the composition of the gas flow. The patterns were observed not only with liquid anodes but also with metal anodes. Various pattern structures were observed by changing the helium gas flow rate in the core and the ambient oxygen gas flow rate supplied during the discharge. When the pattern formation was observed, the emission spectra and the radial spread of the positive column changed, and the voltage–current characteristic also changed. These results suggest that not only the anode surface but the entire discharge affects the pattern formation. Comparing the results for the liquid and metal anodes, the trends in the pattern formation and voltage–current characteristics were almost identical. The gas temperature in the discharge was also investigated in two different ways, by the laser-induced fluorescence spectroscopy of OH radicals and by Rayleigh scattering, showing in good agreement between both methods. Under the condition where the pattern formed, the gas temperature in the discharge was approximately 2500–3000 K and higher than that of the discharge without the pattern formation. Focusing on the gradient of the temperature distribution, the discharge with the pattern formation had a steeper gradient than that of the discharge without the pattern formation. It is suggested that not only the high temperature of the discharge but also the large gradient of the temperature change plays an important role in the pattern formation. The role of oxygen gas in the pattern formation may be the effect of increasing the temperature and altering the temperature gradient in the discharge rather than generating negative ions in the discharge.

Photocatalyzed oxidation of water on oxygen pretreated rutile TiO2(110)

The oxygen evolution reaction (OER) is the bottleneck in the overall photocatalytic splitting of water. The active sites (terminal titanium or bridging oxygen) and active species (molecular or dissociative water) of the initial step of the photocatalyzed OER on the prototypical photocatalyst TiO2, remain debatable. Herein, the photocatalytic chemistry of monolayer water on oxygen-pretreated TiO2(110) (o-TiO2(110)) and reduced TiO2(110) (r-TiO2(110)) surfaces initiated by 400 nm light illumination was investigated by time-dependent two-photon photoemission spectroscopy (TD-2PPE). The photoinduced reduction of the H2O/o-TiO2(110) interface rather than the H2O/r-TiO2(110) interface was detected by TD-2PPE. The difference in 2PPE originated from the presence of the terminal hydroxyl anions (OHt¯) on H2O/o-TiO2(110), as identified by X-ray photoelectron spectroscopy and temperature-programmed desorption. Therefore, the evolution of the electronic structure of H2O/o-TiO2(110) was attributed to the photocatalyzed oxidation of the terminal hydroxyl anions, which most likely formed gaseous •OH radicals, reducing the interface. This work suggested that the oxidation of hydroxyl anions on top of the terminal titanium ions on TiO2, which were excluded previously in solution, need to be considered in the mechanistic studies of the photocatalyzed OER.

Design of Lignin-Based TiO2 Composite for Enhanced Photocatalytic Activity and its Applications

Lignin with TiO2 necessitates careful consideration of the organic-to-inorganic ratio in order to achieve the desired functional characteristics. This study synthesized a Lignin-TiO2 hybrid material through a single-step process utilizing the Taguchi design, which significantly enhanced photocatalytic efficiency under visible light. The Lignin-TiO2 composite demonstrated improved dispersion, negative surface charge, lower bandgap energy, and reduced charge carrier recombination compared to the controls, resulting in a 2.2-fold increase in photocatalytic efficiency for the removal of methylene blue (MB) dye relative to pure TiO2. Additionally, lignin was found to be an effective inhibitor of photo-corrosion, significantly enhancing the stability of Lignin-TiO2 during 690minutes of irradiation. The role of OH radicals in MB photodegradation was confirmed by the degradation of coumarin to 7-hydroxycoumarin (7-OHC). Moreover, Lignin-TiO2 displayed antimicrobial activity against S. aureus and showed potential as a filler in polyvinyl alcohol (PVA), extending the shelf life of cherry tomatoes by up to 7 days. This study presents a promising approach to enhancing visible light-active photocatalysts using renewable materials while highlighting the practical applications of the composite in environmental remediation and the preservation of agricultural products.

CF3H production from the ozonolysis of HCFOs: E- and Z-CF3CH=CHCl

As part of the green transition new technologies and chemical compounds are being introduced with lower climate impact. One example is the replacement of halogenated compounds with high global warming potentials (GWPs) using compounds with low GWPs. Halogenated olefins are a family of chemicals that has been developed as alternatives to high GWP hydrofluorocarbons (HFCs). The olefinic double bond provides a reaction site for atmospheric OH radicals, lowering the atmospheric lifetime and climate impact. There is interest in the possible production of trifluoromethane (CF3H, GWP=14,600) (IPCC, 2021) from atmospheric photolysis of CF3CHO, an oxidation product from several hydrofluoroolefins (HFOs). In addition to reaction with OH, the double bond in HFOs is reactive towards other atmospheric oxidants, including chlorine and ozone. The production of CF3H from the ozonolysis of different commercially relevant fluorinated olefins has been reported (McGillen et al, PNAS, 120, e2312714120, 2023). If CF3H is formed in the ozonolysis of HFOs, it is plausible that it would also be formed in other halogenated olefins with a CF3CH= moiety. HCFO-1233zd (CF3CH=CHCl) is a widely used hydrochlorofluoroolefin (HCFO). We report the formation of CF3H in molar yields of (6.1±0.9) % and (6.4±1.0) % in the ozonolysis of E- and Z-CF3CH=CHCl, respectively. This finding is discussed in the context of the contribution of halogenated olefins to the radiative forcing of climate change.

A straightforward strategy to modulate ROS generation of AIE photosensitizers for type-I PDT

Type-I photodynamic therapy (PDT), valued for its reduced oxygen requirement, generates highly cytotoxic •OH radicals. However, conventional strategies for developing type-I photosensitizers (PSs) are complex and involve intricate organic synthesis. Herein, we present a novel strategy to alter the generation of reactive oxygen species (ROS) by simply manipulating the twisting degree of donor–acceptor (D−A) type aggregation-induced emission (AIE) PSs. Specifically, natural saturated fatty acids are employed to modulate the twisting state of AIE PSs, with higher doping ratios yielding more twisted structures and increased type-I ROS generation. In contrast, fatty acids with higher crystallinity promote planar structures and type-II ROS generation. Theoretical calculations suggest that AIE PSs with highly twisted structures lead to a prominent reduction in ΔEST and effective separation of electron−hole pairs, thereby favoring efficient intersystem crossing and charge transfer. The PDT system primarily driven by type-I ROS exhibits efficient bactericidal activity against clinically drug-resistant bacteria, which remarkably accelerates the recovery of bacteria-infected wounds in mice. This study demonstrates the first example of modulating ROS generation type by manipulating the twisting degree of D−A type AIE PSs, eliminating the need for intricate molecular design and organic synthesis. The proposed strategy opens up new avenues for advancing PDT applications.

Hydroxyl radical oxidation of chemical contaminants on indoor surfaces and dust

Humans are widely exposed to semivolatile organic contaminants in indoor environments. Many contaminants have long lifetimes following partitioning to the large surface reservoirs present indoors, which leads to long exposure times to gas-phase oxidants and multiphase chemistry. Studies have shown selective multiphase oxidation of organics on indoor surfaces, but the presence of hydroxyl radicals with nonselective reactivity and evidence of multiphase OH radical reactivity toward common indoor contaminants indicates that there may be additional unknown transformation chemistry indoors. We screened genuine indoor samples for 60 OH radical oxidation products of the common plasticizer and endocrine-disrupting contaminant bis(2-ethylhexyl) phthalate (DEHP) identified in laboratory experiments using nontargeted high-resolution mass spectrometry. At least 30 and 10 of these products are observed in indoor dust and DEHP films exposed to ambient indoor conditions, respectively, indicating that multiphase OH reactions occur indoors. Using the PROTEX model and a multimedia indoor chemical fate model, we demonstrate that these products have long indoor lifetimes and cause a higher potential for human exposure than DEHP. Some of these products are more active endocrine disruptors than DEHP itself, but most have unknown toxicities. Coexposure to all oxidation products will likely have an additive effect, leading to higher human health risks from indoor organic contaminants than previously thought. Due to the nonselective reactivity of OH radicals, it is likely that most indoor contaminants follow similar chemistry, and further study is needed to understand the prevalence and human health implications of such multiphase chemistry.