The photocatalytic wastewater hydrogen production process with superior performance to the overall water splitting.

The utilization of a cost-free sacrificial agent is a novel approach to significantly enhance the efficiency of photocatalytic hydrogen (H2) production by water splitting. Wastewater contains various organic pollutants, which have the potential to be used as hole sacrificial agents to promote H2 production. Our studies on different pollutants reveals that not all pollutants can effectively promote H2 production. However, when using the same pollutants, not all photocatalysts achieved a higher H2 evolution rate than pure water. Only when the primary oxidizing active species of the photocatalyst are •OH radicals, which are generated by photogenerated holes, and when the pollutants are easily attacked and degraded by •OH radicals, can the production of H2 be effectively promoted. It is noteworthy that the porous brookite TiO2 photocatalyst exhibits a significantly higher H2 evolution rate in Reactive Red X-3B and Congo Red, reaching as high as 26.46 mmol⋅g-1⋅h-1 and 32.85 mmol⋅g-1 ⋅h-1, respectively, which is 2-3 times greater than that observed in pure water and is 10 times greater than most reported studies. The great significance of this work lies in the potential for efficient H2 production through the utilization of wastewater.

Ozonolysis of ketoprofen in polluted water: Reaction pathways, kinetics, removal efficiency, and health effects.

Ketoprofen (KET), as a non-steroidal anti-inflammatory drug frequently detected in aqueous environments, is a threat to human health due to its accumulation and low biodegradability, which requires the transformation and degradation of KET in aqueous environments. In this paper, the reaction process of ozone-initiated KET degradation in water was investigated using density functional theory (DFT) method at the M06-2X/6-311++g(3df,2p)//M06-2X/6-31+g(d,p) level. The detailed reaction path of KET ozonation is proposed. The thermodynamic results show that ozone-initiated KET degradation is feasible. Under ultraviolet irradiation, the reaction of ozone with water can also produce OH radicals (HO·) that can react with KET. The degradation reaction of KET caused by HO· was further studied. The kinetic calculation illustrates that the reaction rate (1.99 × 10-1 (mol/L)-1 sec-1) of KET ozonation is relatively slow, but the reaction rate of HO· reaction is relatively high, which can further improve the degradation efficiency. On this basis, the effects of pollutant concentration, ozone concentration, natural organic matter, and pH value on degradation efficiency under UV/O3 process were analyzed. The ozonolysis reaction of KET is not sensitive to pH and is basically unaffected. Finally, the toxicity prediction of oxidation compounds produced by degradation reaction indicates that most of the degradation products are harmless, and a few products containing benzene rings are still toxic and have to be concerned. This study serves as a theoretical basis for analyzing the migration and transformation process of anti-inflammatory compounds in the water environment.

Light-Driven Site-Selective Glycosylation of Native Carbohydrates.

Carbohydrates constitute the largest source of biomass on Earth, but their synthetic modification is highly challenging due to their high content of oxygen functionalities. The site- and stereoselective modification of native sugars is a definitive goal of glycochemistry research. Recent efforts to bypass the need for protecting groups, leveraging selective activation through photochemical mechanisms for site-selective C-C bond formation from native sugars, are likely to largely impact all glycochemistry-related areas. Davis, Koh, and co-workers have recently presented their use of photocatalysis to develop a "cap and glycosylate" approach for the site- and stereoselective C-glycosylation of native sugars. The modernization of a direct radical functionalization of in situ formed thioglycoside using photocatalysis was used in the synthetic manipulation of unprotected carbohydrates. This allowed reaching complex saccharides, and post-translational modification of proteins.

Phytochemical Profiling and Bioactive Properties of Essential Oils from Endemic Palestinian Satureja thymbrifolia.

Despite several studies on the Satureja L. genus, the chemical composition and biological activities of the traditional medicinal plant Satureja thymbrifolia (White Thyme), a Palestinian endemic species, are still unknown. It grows in arid regions and is used by Bedouins as a traditional medicinal herb. This study aimed to investigate S. thymbrifolia essential oils (EOs), mainly from its phytochemical pattern and biological properties. The GC-MS study identified p-cymene (48.53%) and thymol (23.27%) as the leading EOs components. Compared to Trolox, the EOs showed potential anti-DPPH free radical activity and had broad-spectrum antimicrobial potentials, with MIC values ranging from 0.13 ± 0.05 to 25 ± 0.00 µL/mL. They were most effective against Candida albicans species. The S. thymbrifolia EOs most effectively eliminated cancer cells when tested against CaCo-2 and HeLa cell lines (IC50 values of 192.15 ± 2.47 and 194.80 ± 1.87 µg/mL, respectively). The present investigation is the first documented study of S. thymbrifolia EOs' phytochemical composition and bioactivities. The results revealed that S. thymbrifolia EOs have potential antioxidant, antimicrobial, and cytotoxic effects. These outcomes emphasized S. thymbrifolia EO's potential dietary, pharmacological, and cosmetic applications.

Dual-Activated Photoacoustic Probe for Reliably Detecting Hydroxyl Radical in Ischemic Cardiovascular Disease in Mouse and Human Samples.

Cardiovascular disease (CVD) is a chronic disease characterized by the accumulation of lipids and fibrous tissue within the arterial walls, potentially leading to vascular obstruction and an increased risk of heart disease and stroke. Hydroxyl radicals play a significant role in the formation and progression of CVD as they can instigate lipid peroxidation, resulting in cellular damage and inflammatory responses. However, precisely detecting hydroxyl radicals in CVD lesions presents significant challenges due to their high reactivity and short lifespan. Herein, we present the development and application of a novel activatable optical probe, Cy-OH-LP, designed to detect hydroxyl radicals in lipid-rich environments specifically. Built on the Cy7 molecular skeleton, Cy-OH-LP exhibits near-infrared absorption and fluorescence characteristics, and its specific response to hydroxyl radicals enables a turn-on signal in both photoacoustic and fluorescence spectra. The probe demonstrated excellent selectivity and stability in various tests. Furthermore, Cy-OH-LP was successfully applied in an in vivo model to detect hydroxyl radicals in mouse models, providing a potential tool for diagnosing and monitoring AS. The biosafety of Cy-OH-LP was also verified, showing low cytotoxicity and no significant organ damage in mice. The findings suggest that Cy-OH-LP is a promising tool for the specific detection of hydroxyl radicals in lipid-rich environments, providing new possibilities for research and clinical applications in the field of oxidative stress-related diseases.

Off-site production of plasma-activated water for efficient disinfection: The crucial role of high valence NOx and new chemical pathways.

Efficient disinfection of pathogens is a critical concern for environmental disinfection and clinical anti-infective treatment. Plasma-activated water (PAW) is a promising alternative to chemical disinfectants and antibiotics for its strong disinfection ability and not inducing any acute toxicity. Previous plasma sources are commonly placed near or fully in contact with water as possible for more efficient activation, but the risk of electrode corrosion and metal particle contamination of water threatens the safety and stability of PAW. In this work, plasma-activated gas (PAG) rich in high-valence NOx is generated by a hybrid plasma configuration and introduced into water for off-site PAW production. It is found that plasma-generated O3 dominates the gas-phase reactions for the formation of high-valence NOx. With the time-evolution of O3 concentration, the gaseous NO3 radicals are produced behind N2O5 formation, but will be decomposed before N2O5 quenching. By decoupling the roles of gaseous NO3, N2O5, and O3 in the water activation, results show that short-lived aqueous species induced by gaseous NO3 radicals play the most crucial role in PAW disinfection, and the acidic environment induced by N2O5 is also beneficial for microbial inactivation. Moreover, SEM photographs and biomacromolecule leakage assays demonstrate that PAW disrupts the cell membranes of bacteria and thus achieves inactivation. In real-life applications, an integrated device for off-site PAW production with a yield of 2 L/h and a bactericidal efficiency of >99.9 % is developed. The PAW of 50 mL produced in 3 min using this device is more effective in disinfection than 0.5 % NaClO and 3 % H2O2 with the same bacterial contact time. Overall, this work provides new avenues for efficient PAW production and deepens insights into the fundamental chemical processes that govern the reactive chemistry in PAW for environmental and biomedical applications.

Biodegradation of organic micropollutants by anoxic denitrification: Roles of extracellular polymeric substance adsorption, enzyme catalysis, and reactive oxygen species oxidation.

The control of organic micropollutants (OMPs) in water environments have received significant attention. Denitrification was reported to exhibit good efficiency to remove OMPs, and the mechanisms involved in are too intricate to be well illustrated. In this study, we selected nitrobenzene [NB] and bisphenol A [BPA] as model pollutants and aimed to unravel the mechanisms of Paracoccus Denitrificans in the removal of OMPs, with a specific emphasis on aerobic behavior during denitrification processes. We demonstrated the formation of extracellular superoxide radicals, i.e., extracellular •O2-, using a chemiluminescence probe and found that extracellular polymeric substance adsorption, extracellular •O2-, and microbial assimilation contributed approximately 40 %, 10 %, and 50 % to OMPs removal, respectively. Transcriptome analysis further revealed the high expression and enrichment of several pathways, such as drug metabolism-other enzymes, of which a typical aerobic enzyme of polyphenol oxidase [PPO] participates in the degradation of NB and BPA. Importantly, all the immediate products showed a significant decrease in toxicity during the aerobic activity-related OMPs degradation process based on the proposed degradation pathways. This study demonstrates the formation of extracellular •O2- and the mechanisms of extracellular •O2-- and PPO-mediated OMPs biodegradation, and offers new insights into OMPs control in widely-used denitrification treatment processes.

Focused starvation of tumor cells using glucose oxidase: A comprehensive review.

Starvation therapy targets the high metabolic demand of tumor cells. It primarily leans over the consumption of intracellular glucose and simultaneous blockade of alternative metabolic pathways. The strategy involves the use of glucose oxidase (GOx) for catalyzing the conversion of glucose into gluconic acid and hydrogen peroxide. Under these conditions, metabolic re-programming of tumor cells enables the utilization of substrates such as amino acids, fatty acids and lipids. This can be overcome by co-administration of chemo-, photo- and immuno-therapeutics together with glucose oxidase. Targeted delivery of glucose oxidase at tumor site can be enabled with the use of nanoformulations. In this review, we highlight that the outcomes of starvation therapy can be improved using rationally developed nano-formulations. It is possible to load synergistically acting bioactives in these formulations and deliver in site-specific manner and hence achieve the elimination of tumors cells with greater efficacy.

Vitamin B12 in Photocatalysis - An Underexplored Frontier in Cooperative Catalysis.

Vitamin B12 (VB12) is a flexible and sustainable catalyst both in nature and the reaction flask, facilitating varied organic transformations of high value to both enzymatic processes and synthetic chemists. Key to this value is the breadth of reactivity it possesses, capable of both ionic, 2 electron chemistry, and radical, 1 electron chemistry. In particular, the ability to generate carbon-centered radical intermediates via photolysis of organocobalt intermediates formed from alkyl electrophiles opens the door to powerful new radical transformations challenging to achieve using classical photoredox or ligand-to-metal charge transfer (LMCT) catalysis. While this unique photocatalytic reactivity of VB12 has been increasingly leveraged in monocatalytic schemes, recent reports have demonstrated VB12 is able to function as the photocatalytic component in cooperative schemes, driving diverse reactivity including remote elimination of alkyl halides, regioselective epoxide arylation, and regioselective epoxide reduction. This concept briefly overviews the enabling photochemical properties of VB12 and recent applications in cooperative catalysis, providing a framework for the continued development of new cooperative catalyst systems using this powerful photoactive complex.

Degradation of ambroxol by UV/chloramine process: Kinetics, degradation pathway, and control of the risk of highly toxic disinfection by-products.

Ambroxol (AMB) is a commonly used bromine-containing organic compound in medical applications and has been frequently found in water environments, which might pose risks of forming brominated disinfection by-products (Br-DBPs) in water treatment systems. The degradation kinetics as well as the degradation mechanism of AMB in the UV/chloramine process were investigated in this study. It was determined that reactive chlorine species (RCS) and the reactive nitrogen species (RNS) were the dominant free radicals for AMB degradation. Debromination occurred mainly in the initial stage of the degradation process, with a debromination rate of 34.5% at 10 min. Four possible degradation pathways of AMB were proposed based on liquid chromatography mass spectrometry (LC-MS) analysis as well as density functional theory (DFT) calculations, meanwhile the ECOSAR model was used to predict the toxicity risk of AMB and its degradation intermediates. Furthermore, after assessing the formation of DBPs during the UV/chloramine pre-oxidation process and conducting a toxicity risk analysis based on the results, it has been verified that this method can effectively remove AMB while reducing the formation potential of DBPs in the water environment. This suggests that the UV/chloramine process shows promise for treating bromine-containing organic compounds in real-world water treatment applications.

Spontaneous Production of H2O2 at the Liquid-Ice Interface: A Potential Source of Atmospheric Oxidants.

We present experimental evidence for the spontaneous production of hydrogen peroxide (H2O2) at the liquid-ice interface during the freezing of dilute salt solutions. Specifically, sample solutions containing NaCl, NaBr, NH4Cl, and NaI at concentrations between 10-6 and 10-1 M were subjected to freezing-melting cycles and then analyzed for H2O2 content. The relationship between the production rate of H2O2 and the salt concentration follows that of the Workman-Reynolds freezing potential (WRFP) values as a function of the salt concentration. Our results suggest that H2O2 is formed at the liquid-ice interface from the self-recombination of hydroxyl radicals (OH·), produced from the oxidation of hydroxide anions due to the high electric field generated at the aqueous-ice interface under the WRFP effect. Furthermore, the involvement of O2 likely acting as an electron capturer could promote to produce more OH radicals and hydroperoxyl radicals (HO2·), thus enhancing the production of H2O2 at the liquid-ice interface. Overall, this study suggests a novel mechanism of H2O2 formation in ice via its spontaneous production at the liquid-ice interface, induced by the Workman-Reynolds effect.

Crystallization-Induced Dimerization and Solution-Phase Bond Dissociation of Stable Dibenzoolympicenyl Radicals.

Crystallization of organic materials can lead to different assembly structure with different reactivity, but this phenomenon is rarely observed for delocalized hydrocarbon radicals. This report introduces a crystallization-induced radical-radical coupling reaction, which employs a series of stable nonplanar organic π-radicals as reactants. Six stable radical congeners are synthesized, resulting in radical-radical coupling at the allenyl radical site during crystallization to produce close-shell dimers. This coupling reaction is absent in the solution phase, which highlights the importance of preorganization in the lattice. Remarkably, the attempts of cocrystallization of different congeners yielded homocoupling products instead of cross-coupling products. In specific cases, two distinct polymorphs are observed and their reactivity is different according to the distance of the reaction sites. Theoretical calculations indicate that the transition from a metastable preorganized monomer to a dimer is barrierless and spontaneous. The dimer could regenerate free radicals by heating or photoirradiation in the solution phase. This discovery may lead to controllable molecular switches.

Hydrogen-Bond-Assisted Electrocatalytic Semi-Oxidation of 5-Hydroxymethylfurfural into 2,5-Diformylfuran by Operando Dissociated N-Oxyl Mediator.

The conversion of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) is a promising approach for enhancing biomass utilization. Nevertheless, traditional methods using noble metal catalysts face challenges due to high costs and poor selectivity towards DFF. Herein, we developed a novel catalytic electrode integrating N-hydroxyphthalimide (NHPI) into a metal-organic framework on a hydrophilic carbon cloth. This design significantly enhances the selective adsorption of HMF due to stronger hydrogen-bond interaction between the electrode's hydrophilic surface and the C(sp3)-OH group in HMF compared to the C(sp2)=O in DFF. Additionally, the electro-driven dissociation of the NHPI-linker generates stabilized N-Oxyl radicals that promote selective semi-oxidation of HMF under neutral conditions. As a result, this approach achieves a high yield rate of 138.2 mol molcat-1 h-1 with a selectivity of 96.7% for the HMF-to-DFF conversion. This work introduces a novel strategy for designing catalytic electrodes with stabilized N-Oxyl radicals, and offers a promising method for electrocatalytic DFF synthesis, leveraging hydrogen-bond interaction between electrode surface and HMF.

Oxidative stress disrupts vascular microenvironmental homeostasis affecting the development of atherosclerosis.

Atherosclerosis is primarily an inflammatory reaction of the cardiovascular system caused by endothelial damage, leading to progressive thickening and hardening of the vessel walls, as well as extensive necrosis and fibrosis of the surrounding tissues, the most necessary pathological process causing cardiovascular disease. When the body responds to harmful internal and external stimuli, excess oxygen free radicals are produced causing oxidative stress to occur in cells and tissues. Simultaneously, the activation of inflammatory immunological processes is followed by an elevation in oxygen free radicals, which directly initiates the release of cytokines and chemokines, resulting in a detrimental cycle of vascular homeostasis abnormalities. Oxidative stress contributes to the harm inflicted upon vascular endothelial cells and the decrease in nitric oxide levels. Nitric oxide is crucial for maintaining vascular homeostasis and is implicated in the development of atherosclerosis. This study examines the influence of oxidative stress on the formation of atherosclerosis, which is facilitated by the vascular milieu. It also provides an overview of the pertinent targets and pharmaceutical approaches for treating this condition.

Enantioconvergent Cross-Nucleophile Coupling: Copper-Catalyzed Deborylative Cyanation.

Organoboron compounds are widely utilized in organic synthesis for their diverse reactivity, modular preparation, and stability compared to other classes of organometallic reagents. While organoboron species are commonly employed as nucleophiles in cross-coupling reactions, their potential as racemic building blocks in enantioconvergent transformations remains largely untapped. Herein, we demonstrate the direct utilization of alkylboronic pinacol esters in intermolecular enantioconvergent transformations. Specifically, this work describes the development and mechanistic study of an enantioconvergent deborylative cyanation enabled by Cu catalysis. This method imparts a high degree of enantioselectivity and tolerates a wide range of common functional groups and heterocycles. The reaction is proposed to proceed through a radical-relay mechanism. Aniline-assisted homolysis of the carbon-boron bond results in prochiral alkyl radicals that are functionalized by in situ generated Cu(II)(CN)2 species in an enantioselective fashion. The Cu(II)(CN)2 intermediate was characterized by electron paramagnetic resonance (EPR) spectroscopy, and its electronic structure was probed using density functional theory (DFT) calculations. Computational studies were carried out to corroborate the proposed radical-relay mechanism.

Photoinduced Pd-Catalyzed Direct Sulfonylation of Allylic C-H Bonds.

Allylic sulfones are valuable motifs due to their medicinal and biological significance and their versatile chemical reactivities. While direct allylic C-H sulfonylation represents a straightforward and desirable approach, these methods are primarily restricted to terminal alkenes, leaving the engagement of the internal counterparts a formidable challenge. Herein we report a photocatalytic approach that accommodates both cyclic and acyclic internal alkenes with diverse substitution patterns and electronic properties. Importantly, the obtained allylic sulfones can be readily diversified into a wide range of products, thus enabling formal alkene transposition and all-carbon quaternary center formation through the sequential C-H functionalization.

Hydroxyl radicals dominated the reduction of antibiotic resistance genes by inactivating Gram-negative bacteria during soil electrokinetic treatment.

Antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are emerging contaminants that widely exist in the environment. Effective reduction of ARB and ARGs from soil and water could be achieved by electrokinetic remediation (EKR) technology. In water, hydroxyl radicals (·OH) are proved to play a major role in the EKR process; while the reduction mechanism of ARB and ARGs is still unclear in soil. In this study, different concentrations of hydroxyl radical scavengers (salicylic acid) were added to the EKR system to explore the possible role of ·OH in the reduction of ARB and ARGs. The results showed that generally, ·OH played a more vital role in the reduction of ARB (65.24-72.46%) compared to the reduction of total cultivable bacteria (57.50%). And ·OH contributed to a higher reduction of sul genes (60.94%) compared to tet genes (47.71%) and integrons (36.02%). It was found that the abundance of Gram-negative bacteria (Chloroflexi, Acidobacteria and norank_c_Acidobacteria) was significantly reduced, and the correlation between norank_f_Gemmatimonadaceae and sul1 was weakened in the presence of ·OH. Correlation analysis indicated that the abundance of ARGs (especially sul1) was closely related to the Gram-negative bacteria (Proteobacteria, Acidobacteria, and Gemmatimonadetes) in the soil EKR treatment. Moreover, changes in bacterial community structure affected the abundance of ARB and ARGs indirectly. Overall, this study revealed the reduction mechanism of ARB and ARGs by ·OH in the soil EKR system for the first time. These findings provide valuable support for soil remediation efforts focusing on controlling antibiotic resistance.

Unveiling chlorine's role: How it shapes the formation and light-activated oxygen dynamics of chlorophenol-derived environmental persistent free radicals.

Environmental persistent free radicals (EPFRs) derived from chlorophenols, triggered by light or heat exposure, pose significant ecological concerns, yet the impact of chlorine substituents on EPFRs formation and reactivity remains inadequately understood. Through an intentional synthesis of chlorophenol-derived EPFRs with varying chlorine contents and positioning, we elucidated the role of chlorine in the photoactivation of molecular oxygen. Our combined experimental and theoretical analysis reveals that these EPFRs are primarily oxygen-centered phenoxy radicals, establishing a direct link between chlorine substitution patterns and their ability to activate molecular oxygen under visible light. Increased chlorine content enhances EPFRs formation by elevating the positive charge on the phenolic hydroxyl group's hydrogen atom, facilitating its removal. Moreover, the capability of EPFRs to activate molecular oxygen was directly correlated with chlorine content, with 2,3,5,6-tetrachlorophenol-derived EPFRs showcasing the highest activity. This activity is attributed to their structural propensity for TCSQ·- species generation. Furthermore, our study established a significant correlation between the toxicity and activity of EPFRs, emphasizing the critical role of halogen substituents in determining the reactivity of EPFRs. These insights contribute to our understanding of their environmental and toxicological ramifications, underscoring the imperative for continued research aimed at mitigating their detrimental impacts.

The mechanism of UV accelerated aging of polyvinyl chloride in marine environment: The role of free radicals.

This study systematically investigated the photo-aging of polyvinyl chloride (PVC) in deionized water, estuary water, and seawater. As the concentration of Cl- increases, the carbonyl index (CI) of PVC during photo aging also increases, indicating that Cl- plays a dominant role in PVC photoaging in the environment, which enhance carbonyl index and •OH radical accumulation. Unlike previous studies, this study discovered that halogen radicals were also generated during PVC aging. Compared to •OH radicals, halogen radicals exhibit stronger selectivity and are more conducive to the photo aging of PVC. Additionally, it was found that PVC shows specific toxicity to Paramecia caudatum at various concentrations both before and after aging, affecting the reproduction process of Paramecia caudatum. This study elucidates the mechanism by which anions in natural water bodies affect the rate of PVC aging, providing a scientific basis for understanding the photodegradation of MPs in the ocean.

Recent Applications of Sulfonium Salts in Synthesis and Catalysis.

The use of sulfonium salts in organic synthesis has experienced a dramatic increase during the last years that can arguably be attributed to three main factors; the development of more direct and efficient synthetic methods that make easily available sulfonium reagents of a wide structural variety, their intrinsic thermal stability, which facilitates their structural modification, handling and purification even on large scale, and the recognition that their reactivity resembles that of hypervalent iodine compounds and therefore, they can be used as replacement of such reagents for most of their uses. This renewed interest has led to the improvement of already existing reactions, as well as to the discovery of unprecedented transformations; in particular, by the implementation of photocatalytic protocols. This review aims to summarize the most recent advancements on the area focusing on the work published during and after 2020. The scope of the methods developed will be highlighted and their limitations critically evaluated.