H2O2 Production Research Articles

Glucose oxidase-driven self-accelerating drug release nanosystem based on metal-phenolic networks orchestrates tumor chemotherapy and ferroptosis-based therapy.

Nanocarriers responding to tumor microenvironment have been extensively exploited to improve the antitumor outcome of chemotherapeutic drugs. However, selectively and completely releasing drugs within the tumor remains a challenge, thereby limiting the therapeutic effect of drug delivery nanosystem. To tackle this challenge, a metal-phenolic networks (MPNs)-based nanosystem (F-MGD) showing the capability of self-accelerating drug release was originally fabricated in this study. Glucose oxidase (GOx) encapsulated in F-MGD could conduct the glucose transformation in tumor to cause the oxygen consumption and the production of gluconic acid and H2O2. Therefore, F-MGD with acid and hypoxia sensitivities thoroughly disintegrated under the aggravated acidity and hypoxia to achieve a more complete drug release. Besides, the product of H2O2 was readily decomposed into hydroxyl radicals via the iron ion-mediated Fenton reaction, which markedly augmented the oxidative stress in tumor cells and promoted ferroptosis. The results of both in vitro and in vivo assays demonstrated the significant antitumor efficacy of F-MGD. Collectively, this study proposes a strategy to expedite drug release in tumor and improve the tumor treatment effect by combining ferroptosis-based therapy and chemotherapy.

NADPH oxidase 4-SH3 domain-containing YSC84-like 1 complex participates liver inflammation and fibrosis.

There is growing evidence that NADPH oxidase 4 (Nox4) in hepatocytes contributes to liver inflammation and fibrosis during the development of metabolic dysfunction-associated steatohepatitis (MASH). However, how Nox4 is regulated and leads to liver pathogenesis is unclear. Our previous studies showed that the cytosolic protein SH3 domain-containing Ysc84-like 1 (SH3YL1) regulates Nox4 activity. Here, we asked whether SH3YL1 also participates in liver inflammation and fibrosis during MASH development. We generated that whole body SH3YL1 knockout (SH3YL1-/-), Nox4 knockout (Nox4-/-) mice, and the hepatocyte-specific SH3YL1 conditional knockout (Alb-Cre/SH3YL1fl/fl) mice were fed a methionine/choline-deficient (MCD) diet to induce liver inflammation and fibrosis in pathogenesis of MASH. Palmitate-stimulated primary SH3YL1- and Nox4-deficient hepatocytes and hepatic stellate cells (HSCs) did not generate H2O2. While the liver of MCD diet-fed wild type (WT) mice demonstrated elevated 3-nitrotyrosine as a protein oxidation and 4-hydroxynonenal adducts as a lipid oxidation and increased liver inflammation, hepatocyte apoptosis, and liver fibrosis, these events were markedly reduced in SH3YL1-/-, Nox4-/-, and Alb-Cre/SH3YL1fl/fl mice. The MCD diet-fed WT mice also showed elevated hepatocyte expression of SH3YL1 protein. Similarly, liver biopsies from MASH patients demonstrated strong hepatocyte SH3YL1 protein expression, whereas hepatocytes from patients with steatosis weakly expressed SH3YL1 and histologically normal patient hepatocytes exhibited very little SH3YL1 expression. The Nox4-SH3YL1 complex in murine hepatocytes elevates their H2O2 production, which promotes the liver inflammation, hepatocyte apoptosis, and liver fibrosis that characterize MASH. This axis may also participate in MASH in humans.

Polyphenol autoxidation and prooxidative activity induce protein oxidation and protein-polyphenol adduct formation in model systems

Polyphenols are well-known for their antioxidant properties, but their prooxidative activity remain less understood. This study quantitatively examined the formation of hydrogen peroxide (H2O2) during the autooxidation of nine different polyphenols in model systems, investigating how it impacts protein oxidation and protein-polyphenol covalent adduct formation. Polyphenols (4 mM) generated H2O2 in the range of 0.2–242 μM, depending on type of polyphenol, incubation time, temperature, and pH, but no clear relationship between polyphenol structure and H2O2 production was observed. The presence of free amino acids and proteins (bovine serum albumin and β-lactoglobulin) inhibited H2O2 formation, with Cys completely scavenging H2O2. Met was highly susceptible to oxidation with a 25–75 % loss, forming methionine sulfoxide through a two-electron oxidation pathway. Trp and Tyr were oxidized to produce dioxindolyl-L-alanine, kynurenine, 3,4-dihydroxyphenylalanine, N′-formylkynurenine, and 5-hydroxytryptophan in the nmol/mol-mmol/mol amino acid range. Furthermore, autoxidation of polyphenols resulted in >177 distinct amino acid/protein-polyphenol adducts as identified using LC-Orbitrap-MS/MS analysis.

Heterogeneous catalysts for electro-Fenton degradation of cytostatic drug cytarabine

In the present work, a reduced graphene oxide (rGO) modified-Fe3O4 doped bifunctional carbon felt cathode (rGO-Fe3O4/CF) that is capable of generating and converting H2O2 into hydroxyl radicals (•OH) on-site was fabricated, thus removing the need for an external catalyst. In addition, an rGO-modified cathode (rGO/CF) with high H2O2 production efficiency and a heterogeneous Fenton catalyst (CNT-Fe3O4) with magnetic properties were fabricated. The study examined the degradation and mineralization of the cytostatic drug cytarabine (CYT) using two HEF configurations: (i) a bifunctional cathode rGO-Fe3O4/CF and (ii) a combination of the rGO/CF cathode with CNT-Fe3O4 catalyst. The effects of parameters such as catalyst concentration, initial pH, and applied current were studied. HPLC and ion chromatography analyses were used to identify carboxylic acids and inorganic end-products, respectively. The results show that 0.1mM CYT was completely degraded within 18min at an applied current of 300mA in the HEF system with the rGO-Fe3O4/CF bifunctional cathode. Total organic carbon (TOC) analysis revealed that the bifunctional cathode system achieved 98.2% mineralization of CYT after 4h of treatment at 300mA. Using the rGO/CF cathode and CNT-Fe3O4 catalyst cell, total degradation of 0.1mM CYT occurred within 7min, and nearly total mineralization (97.3% TOC removal) was achieved at 300mA after 4h.

Thiophene and acetylene functionalized conjugated organic polymers with hollow nanotube structure toward high-performance photocatalytic H2O2 production

Thiophene and acetylene functionalized conjugated organic polymers with hollow nanotube structure toward high-performance photocatalytic H2O2 production

The paradoxical effects of beneficial bacteria on Solanum lycopersicum under Cd stress.

This study investigated the complex interactions between a novel consortium and tomato seedlings under cadmium (Cd) stress. The consortium consists of two bacteria, Pseudomonas sp. HS4 and Paenarthrobacter sp. AS8, both with proven plant growth-promoting (PGP) properties, isolated from Cd hyperaccumulators. Our research highlights the paradoxical effects of these bacteria, revealing their dual role in reducing Cd uptake while simultaneously inducing oxidative stress in plants. Hydroponic experiments showed that the consortium reduced Cd accumulation in tomato shoots by 52% compared to uninoculated controls. However, this reduction was accompanied by decreased plant biomass and increased oxidative stress, with malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) levels up to 80% and 160% higher, respectively, in inoculated plants. Root H₂O₂ production increased by 38% under 50μM Cd without a corresponding rise in catalase (CAT) activity. Despite Cd exposure, the consortium promoted chlorophyll and carotenoid synthesis, restoring pigment levels to those of unstressed controls. Gene expression analysis revealed a complex impact on stress responses, with inoculation suppressing Sl1 gene expression in roots and upregulating the oxidative stress-related GR-1 gene in shoots. These findings highlight the complex and multifaceted relationship between beneficial bacteria and plant fitness under heavy metal stress, with significant implications for sustainable agriculture. The study raises new questions regarding the broader physiological and ecological impacts of applying hyperaccumulator-associated bacteria in crop management, emphasizing the necessity for deeper mechanistic insights into these interactions to fully harness their potential in improving crop resilience and productivity.

NH2-MIL-125(Ti) and its functional nanomaterials - a versatile platform in the photocatalytic arena.

Titanium (Ti)-based MOFs are promising materials known for their porosity, stability, diverse valence states, and a lower conduction band (CB) than Zr-MOFs. These features support stable ligand-to-metal charge transfer (LMCT) transitions under photoirradiation, enhancing photocatalytic performance. However, Ti-MOF structures remain a challenge owing to the highly volatile and hydrophilic nature of ionic Ti precursors. The discovery of MIL-125 marked a breakthrough in Ti-cluster coordination chemistry. Combining it with NH2 chromophores to form NH2-MIL-125 enhanced its structural design and extended its activity into the visible light region. This review delves into the high-performance photocatalytic properties of NH2-MIL-125, focusing on its applications in H2O2 and H2 production, CO2 and N2 reduction, drug and dye degradation, photocatalytic sensors, and organic transformation reactions. The discussion considers the influence of the Ti precursor, coordination environment, synthesis process, and charge transfer mechanisms. Numerous strategic methods have been discussed to improve the performance of NH2-MIL-125 by incorporating linker modification, metal node modification, encapsulation of active species, and post-modification for enhancing light absorption ability, promoting charge separation, and improving photocatalytic efficiency. Moreover, future perspectives include methods to investigate how the efficiency of NH2-MIL-125-based materials can be planned in promoting research by highlighting their versatility and potential impacts in the area of photocatalysis.

Short-term airborne ultrasound induced cell death in tobacco cells and changed their wall components

The effects of low-intensity ultrasound on plants such as piezoelectric and ultrasonic water baths, on plants have been extensively studied. However, the specific effect of airborne ultrasound on plant cells has yet to be reported. The present study was conducted to elucidate the physiological responses of plant cells to airborne US. Homogeneous suspension-cultured tobacco cells (Nicotiana tabacum L. cv Burley 21) were subjected to airborne US at 24 kHz in two pulsatile and continuous modes for 10 and 20 s. The study’s outcome revealed that airborne US triggered the production of H2O2, elevated internal calcium concentration, and reduced antioxidant capacity upon cavitation. Alteration of covalently bound peroxidase and other wall-modifying enzyme activities was accompanied by reduced cellulose, pectin, and hemicellulose B but increased lignin and hemicellulose A. The biomass and viability of tobacco cells were also significantly decreased by airborne US, which ultimately resulting in PCD and secondary necrosis. The results highlight the potential risks of even short-time exposure to the airborne US on plant physiology and cell wall chemical composition raising significant concerns about its implications.

Pressure-Induced Engineering of Surface Oxygen Vacancies on Metal Oxides for Heterogeneous Photocatalysis.

Oxygen vacancies (OVs) spatially confined on the surface of metal oxide semiconductors are advantageous for photocatalysis, in particular, for O2-involved redox reactions. However, the thermal annealing process used to generate surface OVs often results in undesired bulk OVs within the metal oxides. Herein, a high pressure-assisted thermal annealing strategy has been developed for selectively confining desirable amounts of OVs on the surface of metal oxides, such as tungsten oxide (WO3). Applying a pressure of 1.2 gigapascal (GPa) on WO3 induces significant lattice compression, which would strengthen the W-O bonds and increase the diffusion activation energy for the migration of the O migration. This pressure-induced compression effectively inhibits the formation of bulk OVs, resulting in a high density of surface-confined OVs on WO3. These well-defined surface OVs significantly enhance the photocatalytic activation of O2, facilitating H2O2 production and aerobic oxidative coupling of amines. This strategy holds promise for the defect engineering of other metal oxides, enabling abundant surface OVs for a range of emerged applications.

Hollow TiO2@TpPa S-Scheme Photocatalyst for Efficient H2O2 Production Through 1O2 in Deionized Water Using Phototautomerization.

Hydrogen peroxide (H2O2) production through photocatalytic O2 reduction reaction (ORR) is a mild and cost-efficient alternative to the anthraquinone oxidation strategy. Of note, singlet state oxygen (1O2) plays a crucial role in ORR. Herein, a hollow TiO2@TpPa (TOTP) S-scheme heterojunction by the Schiff base reactions involving 1,3,5-triformylphloroglucinol (Tp) and paraphenylenediamine (Pa) for efficient photocatalytic H2O2 production in deionized water has been developed. Upon irradiation, rapid phototautomerization of TaPa from enol to keto form expands π-electron delocalization, facilitating effective conversion of the triplet excited state and consequent generation of 1O2. This mechanism is supported by time-resolved electron paramagnetic resonance (EPR) spectral analysis. Additionally, density functional theory calculations, in situ irradiated X-ray photoelectron spectroscopy, and femtosecond transient absorption spectroscopy reveal superior separation of photogenerated carriers in the TOTP S-scheme composites. In deionized water, the TOTP2.4 S-scheme heterojunction exhibits exceptional H2O2 production activity, yielding 891 µmol g-1 h-1, underscoring the critical role of 1O2 in the process. This research offers insights into the S-scheme heterojunctions and emphasizes the pivotal role of 1O2 in enhancing H2O2 production efficiency.

Paired Photoproduction of H2O2 and 3,4-Dihydroisoquinoline over Covalent Pyrene-(Thio)urea Frameworks with Electron Push-Pull Effect.

Pairing photocatalytic 1,2,3,4-tetrahydroisoquinoline semi-dehydrogenation reaction (THIQ-SDR) with two-electron oxygen reduction reaction (2e- ORR) is a green solar to chemical strategy by simultaneously utilizing the photo-excited electrons and holes. However, it is still short of high-efficiency photocatalyst to drive two reactions above. In the present work, crystalline pyrene-thiourea/urea covalent organic frameworks (COF-Py-S and -O) were synthesized and demonstrated as high-performance metal-free photocatalysts. In particular, COF-Py-S exhibited higher 2e- ORR to H2O2 yield rate of ~19 mmol g-1 h-1 under visible light and finally solid H2O2 products (Na2CO3•1.5H2O2) was collected after long-time irradiation. Under natural sunlight conditions, the H2O2 production rate over COF-Py-S further increased to ~51 mmol g-1 h-1, among the best organic photocatalysts. COF-Py-S also showed high THIQ-SDR conversion (~100%) with 3,4-dihydroisoquinoline (DHIQ) selectivity of ~92%. Theoretical calculations reveal stronger electron push-pull effect of COF-Py-S than COF-Py-O, enhancing its photoinduced charge carries, and a four-step 2e- ORR mechanism with thiourea as the active sites has been confirmed as well as the mechanism of THIQ-SDR to DHIQ, featuring lower energy barriers for O2 adsorption and *HOOH desorption over thiourea units. This work provides a paired photosynthesis strategy of H2O2 and DHIQ over high-efficiency pyrene-(thio)urea COF photocatalysts with electron push-pull effect.

Paired Photoproduction of H2O2 and 3,4‐Dihydroisoquinoline over Covalent Pyrene‐(Thio)urea Frameworks with Electron Push‐Pull Effect

Pairing photocatalytic 1,2,3,4‐tetrahydroisoquinoline semi‐dehydrogenation reaction (THIQ‐SDR) with two‐electron oxygen reduction reaction (2e‐ ORR) is a green solar to chemical strategy by simultaneously utilizing the photo‐excited electrons and holes. However, it is still short of high‐efficiency photocatalyst to drive two reactions above. In the present work, crystalline pyrene‐thiourea/urea covalent organic frameworks (COF‐Py‐S and ‐O) were synthesized and demonstrated as high‐performance metal‐free photocatalysts. In particular, COF‐Py‐S exhibited higher 2e‐ ORR to H2O2 yield rate of ~19 mmol g‐1 h‐1 under visible light and finally solid H2O2 products (Na2CO3•1.5H2O2) was collected after long‐time irradiation. Under natural sunlight conditions, the H2O2 production rate over COF‐Py‐S further increased to ~51 mmol g‐1 h‐1, among the best organic photocatalysts. COF‐Py‐S also showed high THIQ‐SDR conversion (~100%) with 3,4‐dihydroisoquinoline (DHIQ) selectivity of ~92%. Theoretical calculations reveal stronger electron push‐pull effect of COF‐Py‐S than COF‐Py‐O, enhancing its photoinduced charge carries, and a four‐step 2e‐ ORR mechanism with thiourea as the active sites has been confirmed as well as the mechanism of THIQ‐SDR to DHIQ, featuring lower energy barriers for O2 adsorption and *HOOH desorption over thiourea units. This work provides a paired photosynthesis strategy of H2O2 and DHIQ over high‐efficiency pyrene‐(thio)urea COF photocatalysts with electron push‐pull effect.

Linkage Microenvironment Modulation in Triazine-Based Covalent Organic Frameworks for Enhanced Photocatalytic Hydrogen Peroxide Production.

Covalent organic frameworks (COFs), known for the precise tunability of molecular structures, hold significant promise for photocatalytic hydrogen peroxide (H2O2) production. Herein, by systematically altering the quinoline (QN) linkages in triazine (TA)-based COFs via the multi-component reactions, six R-QN-TA-COFs are synthesized with identical skeletons but different substituents. The fine-tuning of the optoelectronic properties and local microenvironment of COFs is allowed, thereby optimizing charge separation and improving interactions with dissolved oxygen. Consequently, MeO-QN-TA-COF is customized to achieve an impressive rate of H2O2 production up to 7384µmolg⁻1h⁻1 under an air atmosphere in water without any sacrificial agents, surpassing most of the reported COF photocatalysts. Its high stability is demonstrated through five consecutive recycling experiments and the characterization of the recovered COF. The reaction mechanism for the H2O2 production is further investigated using a suite of quenching experiments, in situ spectroscopic analysis, and theoretical calculations. The enhanced photocatalytic H2O2 production over MeO-QN-TA-COF is through 2e⁻ oxygen reduction reaction and water oxidation reaction pathways. Overall, the crucial role of linkage microenvironment modulation in the design of COFs for solar-driven effective photocatalytic H2O2 production.

Internal Nanocavity Regulation of Embedded Rare Earth Up-Conversion Nanoparticles for H2O2 Production Operable at Up to 780 nm.

Semiconductor photocatalysts embedded with rare earth upconversion nanoparticles (REUPs) are a promising strategy to improve their photoresponse range, but their photocatalytic performance within the near-infrared (NIR) region is far from satisfactory. Here, a method is reported to improve the photocatalytic activity by adjusting the nanocavity of upconversion nanoparticles inside a semiconductor. Two types of CdS embedded with NaYF4:Yb,Er photocatalysts with core-shell structure (no cavity) (NYE/CdS) and yolk-shell structure (empty cavity) (NYE@CdS) are synthesized by different methods. Experimental and theoretical analysis indicates that the yolk-shell structure NYE@CdS can enhance the local fluorescence-induced electric field within the hollow cavity, and realize more effective energy transfer from REUPs to CdS. Notably, the H2O2 production performance of NYE@CdS reaches 0.33mmol g-1 h-1 under NIR light irradiation (λ > 780nm), exceeding most of the reported photocatalysts. This research will provide new ideas for the design of high-efficiency photocatalysts for H2O2 production.

AuNPs/GO/Pt microneedle electrochemical sensor for in situ monitoring of hydrogen peroxide in tomato stems in response towounding stimulation.

Hydrogen peroxide (H2O2) is a critical signaling molecule with significant roles in various physiological processes in plants. Understanding its regulation through in situ monitoring could offer deeper insights into plant responses and stress mechanisms. In this study, we developed a microneedle electrochemical sensor to monitor H2O2 in situ, offering deeper insights into plant stress responses. The sensor features a platinum wire (100µm diameter) modified with graphene oxide (GO) and gold nanoparticles (AuNPs) as the working electrode, an Ag/AgCl wire (100µm diameter) as the reference electrode, and an untreated platinum wire (100µm diameter) as the counter electrode. This innovative design enhances sensitivity and selectivity through the high catalytic activity of AuNPs, increased surface area from GO, and the superior conductivity of platinum. Operating at a low potential of -0.2V to minimize interference, the sensor detects H2O2 concentrations from 10 to 1000µM with high accuracy. In situ monitoring of H2O2 dynamics in tomato stems under the wounding stimulation reveals that H2O2 concentration increases as the sensor approaches the wound site, indicating localized production and transport of H2O2. This approach not only improves H2O2 monitoring in plant systems but also paves the way for exploring its generation, transport, and elimination mechanisms.

Observation of O2 Molecules Inserting into Fe-H Bonds in a Ferrous Metal-Organic Framework.

Exploring the interactions between oxygen molecules and metal sites has been a significant topic. Most previous studies concentrated on enzyme-mimicking metal sites interacting with O2 to form M-OO species, leaving the development of new types of O2-activating metal sites and novel adsorption mechanisms largely overlooked. In this study, we reported an Fe(II)-doped metal-organic framework (MOF) [Fe3Zn2H4(bibtz)3] (MAF-203, H2bibtz = 1H,1'H-5,5'-bibenzo[d][1,2,3]triazole), featuring an unprecedented tetrahedral Fe(II)HN3 site. This MOF exhibits selective adsorption behavior for O2 from air, achieving an O2/N2 separation selectivity of up to 67.1. Breakthrough experiments confirmed that MAF-203 can effectively capture O2 from the air even under a high relative humidity of 60%. X-ray absorption spectroscopy, in situ diffuse reflectance infrared Fourier transform spectra, and ab initio molecular dynamics simulations were utilized to monitor the O2 loading process on the Fe(II)HN3 site. Interestingly, O2 molecules could insert into the Fe-H bonds of the tetrahedral FeIIHN3 sites, forming FeIII-OOH species (instead of the commonly observed Fe-OO species) with an ultrahigh adsorption enthalpy of -99.2 kJ mol-1. Consequently, the O2 capture behavior of MAF-203 enables efficient electrochemical 2e- oxygen reduction for the production of H2O2 with air as the feedstock. Specifically, in a solid-state electrolyte electrolyzer without any liquid electrolyte, MAF-203 achieved selective O2 capture and continuous production of medical-grade H2O2 (3.2 wt %) solution without salts for 70 h, with performance comparable to that under pure O2 conditions. The O2 adsorption and activation mechanisms inaugurate a fresh chapter in grasping the interaction between O2 molecules and metal sites.

Noble-metal-free Electrocatalysts for Selective Hydrogen Peroxide Generation via Oxygen Reduction Reaction.

Hydrogen peroxide (H2O2) is a versatile chemical widely used in various industries. The traditional anthraquinone method for H2O2 synthesis has environmental and safety concerns due to the use of organic solvents and hazardous by-products. The direct synthesis of H2O2 from H2 and O2 poses risks of flammability and explosion. Recently, the 2-electron oxygen reduction reaction (2e- ORR) method has emerged as a promising alternative, offering safety, environmental friendliness, and cost-effectiveness. This method utilizes gas diffusion electrodes to efficiently generate H2O2 without the need for additional dilution. In this review, we focus on the recent advancements in noble-metal-free materials for 2e- ORR electrocatalysis, which play a crucial role in the efficient production of H2O2. These materials, including transition metal compounds, macrocyclic complexes, carbon-based catalysts, framework materials, and MXene catalyst, demonstrate significant advantages in enhancing H2O2 yield. The development of these non-precious metal catalysts can reduce costs and improve sustainability and promote the commercialization of related technologies. The review concludes with an outlook on the future trends of 2e- ORR electrocatalysts.

Employing a Zn-air/Photo-Electrochemical Cell for In Situ Generation of H2O2 for Onsite Control of Pollutants.

Industrial production of hydrogen peroxide (H2O2) is energy-intensive and generates unwanted byproducts. Herein, an alternative production strategies of H2O2 are demonstrated in a Zn-air and a photoelectrochemical cell. Employing an optimally produced reduced graphene oxide (rGO) electrocatalyst@air-cathode, an impressive power density of 320 Wmgeo -2 (geo = geometric area) is achieved along with a high H2O2 production rate of 3.17mol mgeo -2h-1 (operating potential = 0.8V). Systematic investigations reveal the critical role of specific functional groups (viz. C─O─C, chemisorbed O2, C≐C) to be responsible for enhancing the yield of H2O2. The in situ generated superoxide (O2˙) and hydroxyl radicals (˙OH) act as oxidants to efficiently degrade onsite, a model textile dye pollutant (viz. rhodamine B) inside the Zn-air cell. Using the identical rGO as the photoelectrode in an H-type cell, the H2O2 production is remarkably enhanced under visible light illumination. Simultaneously, the onsite pollutant degradation occurs five times faster than the Zn-air cell (at the same operating potential = 0.8 V). This work opens a new paradigm for electrosynthesis, wherein an underlying redox can be utilized to synthesize industrial chemicals for onsite control of environmental pollution sustainably.

Effect of FLASH dose-rate and oxygen concentration in the production of H2O2 in cellular-like media versus water: a Monte Carlo track-structure study

Objective. To study the effect of dose-rate in the time evolution of chemical yields produced in pure water versus a cellular-like environment for FLASH radiotherapy research.Approach.A version of TOPAS-nBio with Tau-Leaping algorithm was used to simulate the homogenous chemistry stage of water radiolysis using three chemical models: (1) liquid water model that considered scavenging ofeaq-, H•by dissolved oxygen; (2) Michaels & Hunt model that considered scavenging of•OH,eaq‒, and H•by biomolecules existing in cellular environment; (3) Wardman model that considered model 2) and the non-enzymatic antioxidant glutathione (GSH). H2O2concentrations at conventional and FLASH dose-rates were compared with published measurements. Model 3) was used to estimate DNA single-strand break (SSB) yields and compared with published data. SSBs were estimated from simulated yields of DNA hydrogen abstraction and attenuation factors to account for the scavenging capacity of the medium. The simulation setup consisted of monoenergetic protons (100 MeV) delivered in pulses at conventional (0.2857Gy s-1) and FLASH (500Gy s-1) dose rates. Dose varied from 5-20 Gy, and oxygen concentration from 10µM-1 mM.Main Results.At the steady state, for model (1), H2O2concentration differed by 81.5%± 4.0% between FLASH and conventional dose-rates. For models (2) and (3) the differences were within 8.0%± 4.8%, and calculated SSB yields agreed with published data within 3.8%± 1.2%. A maximum oxygen concentration difference of 60% and 50% for models (2) and (3) between conventional and FLASH dose-rates was found between 2 × 106and 9 × 1013ps for 20 Gy of absorbed dose.Significance.The findings highlight the importance of developing more advanced cellular models to account for both the chemical and biological factors that comprise the FLASH effect. It was found that differences between pure water and cellular environment models were significant and extrapolating results between the two should be avoided. Observed differences call for further experimental investigation.

Constructing Interfacial B-P Bonding Bridge to Promote S-Scheme Charge Migration within Heteroatom-Doped Carbon Nitride Homojunction for Efficient H2O2 Photosynthesis.

The emerging step (S)-scheme heterojunction systems became a powerful strategy in promoting photogenerated charge separation while maintaining their high redox potentials. However, the weak interfacial interaction limits the charge migration rate in S-scheme heterojunctions. Herein, we construct a unique S-scheme carbon nitride (CN) homojunction with boron (B)-doped CN and phosphorus (P)-doped CN (B-CN/P-CN) for hydrogen peroxide (H2O2) photosynthesis. The B-CN/P-CN nanosheet composites revealed extensively tight interfacial contact, improved visible-light harvesting, and reduced carrier lifetime. The structural investigation results also indicate that the interfacial chemical B-P bonding is formed between B-CN and P-CN nanosheets, inducing an accelerated interfacial S-scheme charge migration. Density functional theory calculations further clarify the S-scheme charge transfer mechanism. Consequently, the 2e- oxygen reduction reaction was the predominant pathway of H2O2 production, facilitated by the B-CN/P-CN homojunction. The optimal H2O2 yield rate reached 2199.5 μmol L-1 h-1 over the B-CN/P-CN homojunction (S3) photocatalyst under monochromatic LED irradiation, increasing 2-8 times as against most of the C3N4 photocatalysts. This study highlights the crucial role of interfacial charge transfer between heterojunction/homojunction materials, accompanied by an unveiling reaction mechanism for solar-energy conversions.