Showing papers on "Hydrogen peroxide published in 2022"

Molecularly Engineered Covalent Organic Frameworks for Hydrogen Peroxide Photosynthesis

Abstract: Abstract Synthesizing H2O2 from water and air via a photocatalytic approach is ideal for efficient production of this chemical at small‐scale. However, the poor activity and selectivity of the 2 e− water oxidation reaction (WOR) greatly restricts the efficiency of photocatalytic H2O2 production. Herein we prepare a bipyridine‐based covalent organic framework photocatalyst (denoted as COF‐TfpBpy) for H2O2 production from water and air. The solar‐to‐chemical conversion (SCC) efficiency at 298 K and 333 K is 0.57 % and 1.08 %, respectively, which are higher than the current reported highest value. The resulting H2O2 solution is capable of degrading pollutants. A mechanistic study revealed that the excellent photocatalytic activity of COF‐TfpBpy is due to the protonation of bipyridine monomer, which promotes the rate‐determining reaction (2 e− WOR) and then enhances Yeager‐type oxygen adsorption to accelerate 2 e− one‐step oxygen reduction. This work demonstrates, for the first time, the COF‐catalyzed photosynthesis of H2O2 from water and air; and paves the way for wastewater treatment using photocatalytic H2O2 solution.

Pt Decorated Ti3C2Tx MXene with NIR-II Light Amplified Nanozyme Catalytic Activity for Efficient Phototheranostics.

Abstract: The clinical application of photothermal therapy (PTT) is severely limited by the tissue penetration depth of excitation light, and enzyme therapy is hampered by its low therapeutic efficiency. As a two-dimensional ultrathin nanosheet with high absorbance in the near-infrared-II (NIR-II) region, the titanium carbide (Ti3C2) nanosheet can be used as a substrate to anchor functional components, like nanozymes and nanodrugs. Here, we decorate Pt artificial nanozymes on the Ti3C2 nanosheets to synthesize Ti-based MXene nanocomposites (Ti3C2Tx-Pt-PEG). In the tumor microenvironment, the Pt nanoparticles exhibit peroxidase-like (POD-like) activity, which can in situ catalyze hydrogen peroxide to generate hydroxyl radicals (•OH) to induce cell apoptosis and necrosis. Meanwhile, the composite shows a desirable photothermal effect upon NIR-II light irradiation with a low power density (0.75 W cm-2). Especially, the POD-like activity is significantly enhanced by the elevated temperature arising from the photothermal effect of Ti3C2Tx. Therefore, satisfactory synergistic PTT/enzyme therapy has been accomplished, accompanied by an applicable photoacoustic imaging capability to monitor and guide the therapeutic process. This work may provide an approach for hyperthermia-amplified nanozyme catalytic therapy, especially based on metal catalysts and MXene nanocomposites.

Aqueous Iron(IV)–Oxo Complex: An Emerging Powerful Reactive Oxidant Formed by Iron(II)-Based Advanced Oxidation Processes for Oxidative Water Treatment

Abstract: High-valent iron(IV)-oxo complexes are of great significance as reactive intermediates implicated in diverse chemical and biological systems. The aqueous iron(IV)-oxo complex (FeaqIVO2+) is the simplest but one of the most powerful ferryl ion species, which possesses a high-spin state, high reduction potential, and long lifetime. It has been well documented that FeaqIVO2+ reacts with organic compounds through various pathways (hydrogen-atom, hydride, oxygen-atom, and electron transfer as well as electrophilic addition) at moderate reaction rates and show selective reactivity toward inorganic ions prevailing in natural water, which single out FeaqIVO2+ as a superior candidate for oxidative water treatment. This review provides state-of-the-art knowledge on the chemical properties and oxidation mechanism and kinetics of FeaqIVO2+, with special attention to the similarities and differences to two representative free radicals (hydroxyl radical and sulfate radical). Moreover, the prospective role of FeaqIVO2+ in Feaq2+ activation-initiated advanced oxidation processes (AOPs) has been intensively investigated over the past 20 years, which has significantly challenged the conventional recognition that free radicals dominated in these AOPs. The latest progress in identifying the contribution of FeaqIVO2+ in Feaq2+-based AOPs is thereby reviewed, highlighting controversies on the nature of the reactive oxidants formed in several Feaq2+ activated peroxide and oxyacid processes. Finally, future perspectives for advancing the evaluation of FeaqIVO2+ reactivity from an engineering viewpoint are proposed.

Identification of the Highly Active Co–N4 Coordination Motif for Selective Oxygen Reduction to Hydrogen Peroxide

Abstract: Electrosynthesis of hydrogen peroxide (H2O2) through oxygen reduction reaction (ORR) is an environment-friendly and sustainable route for obtaining a fundamental product in the chemical industry. Co–N4 single-atom catalysts (SAC) have sparkled attention for being highly active in both 2e– ORR, leading to H2O2 and 4e– ORR, in which H2O is the main product. However, there is still a lack of fundamental insights into the structure–function relationship between CoN4 and the ORR mechanism over this family of catalysts. Here, by combining theoretical simulation and experiments, we unveil that pyrrole-type CoN4 (Co–N SACDp) is mainly responsible for the 2e– ORR, while pyridine-type CoN4 catalyzes the 4e– ORR. Indeed, Co–N SACDp exhibits a remarkable H2O2 selectivity of 94% and a superb H2O2 yield of 2032 mg for 90 h in a flow cell, outperforming most reported catalysts in acid media. Theoretical analysis and experimental investigations confirm that Co–N SACDp—with weakening O2/HOO* interaction—boosts the H2O2 production.

Engineering the Local Atomic Environments of Indium Single‐Atom Catalysts for Efficient Electrochemical Production of Hydrogen Peroxide

Abstract: The in-depth understanding of local atomic environment-property relationships of p-block metal single-atom catalysts toward the 2 e- oxygen reduction reaction (ORR) has rarely been reported. Here, guided by first-principles calculations, we develop a heteroatom-modified In-based metal-organic framework-assisted approach to accurately synthesize an optimal catalyst, in which single In atoms are anchored by combined N,S-dual first coordination and B second coordination supported by the hollow carbon rods (In SAs/NSBC). The In SAs/NSBC catalyst exhibits a high H2 O2 selectivity of above 95 % in a wide range of pH. Furthermore, the In SAs/NSBC-modified natural air diffusion electrode exhibits an unprecedented production rate of 6.49 mol peroxide gcatalyst-1 h-1 in 0.1 M KOH electrolyte and 6.71 mol peroxide gcatalyst-1 h-1 in 0.1 M PBS electrolyte. This strategy enables the design of next-generation high-performance single-atom materials, and provides practical guidance for H2 O2 electrosynthesis.

Enhanced Chemodynamic Therapy by Cu-Fe Peroxide Nanoparticles: Tumor Microenvironment-Mediated Synergistic Fenton Reaction.

Abstract: An urgent need in chemodynamic therapy (CDT) is to achieve high Fenton catalytic efficiency at small doses of CDT agents. However, simple general promotion of the Fenton reaction increases the risk of damaging normal cells along with the cancer cells. Therefore, a tailored strategy to selectively enhance the Fenton reactivity in tumors, for example, by taking advantage of the characteristics of the tumor microenvironment (TME), is in high demand. Herein, a heterogeneous CDT system based on copper-iron peroxide nanoparticles (CFp NPs) is designed for TME-mediated synergistic therapy. CFp NPs degrade under the mildly acidic conditions of TME, self-supply H2O2, and the released Cu and Fe ions, with their larger portions at lower oxidation states, cooperatively facilitate hydroxyl radical production through a highly efficient catalytic loop to achieve an excellent tumor therapeutic efficacy. This is distinct from previous heterogeneous CDT systems in that the synergism is closely coupled with the Cu+-assisted conversion of Fe3+ to Fe2+ rather than their independent actions. As a result, almost complete ablation of tumors at a minimal treatment dose is demonstrated without the aid of any other therapeutic modality. Furthermore, CFp NPs generate O2 during the catalysis and exhibit a TME-responsive T1 magnetic resonance imaging contrast enhancement, which are useful for alleviating hypoxia and in vivo monitoring of tumors, respectively.

Guiding Transition Metal‐Doped Hollow Cerium Tandem Nanozymes with Elaborately Regulated Multi‐Enzymatic Activities for Intensive Chemodynamic Therapy

Abstract: Clinical applications of nanozyme-initiated chemodynamic therapy (NCDT) have been severely limited by the poor catalytic efficiency of nanozymes, insufficient endogenous hydrogen peroxide (H2 O2 ) content, and its off-target consumption. Herein, the authors developed a hollow mesoporous Mn/Zr-co-doped CeO2 tandem nanozyme (PHMZCO-AT) with regulated multi-enzymatic activities, that is, the enhancement of superoxide dismutase (SOD)-like and peroxidase (POD)-like activities and inhibition of catalase (CAT)-like activity. PHMZCO-AT as a H2 O2 homeostasis disruptor promotes H2 O2 evolution and restrains off-target elimination of H2 O2 to achieve intensive NCDT. PHMZCO-AT with SOD-like activity catalyzes endogenous superoxide anion (O2•- ) into H2 O2 in the tumor region. The suppression of CAT activity and depletion of glutathione by PHMZCO-AT largely weaken the off-target decomposition of H2 O2 to H2 O. Elevated H2 O2 is then catalyzed by the downstream POD-like activity of PHMZCO-AT to generate toxic hydroxyl radicals, further inducing tumor apoptosis and death. T1 -weighted magnetic resonance imaging and X-ray computed tomography imaging are also achieved using PHMZCO-AT due to the existence of paramagnetic Mn2+ and the high X-ray attenuation ability of elemental Zr, permitting in vivo tracking of the therapeutic process. This work presents a typical paradigm to achieve intensive NCDT efficacy by regulating multi-enzymatic activities of nanozymes to perturb the H2 O2 homeostasis.

S-scheme ZnO/WO3 heterojunction photocatalyst for efficient H2O2 production

Abstract: Designing highly efficient photocatalyst for hydrogen peroxide (H2O2) production is an ideal strategy to avoid the shortcomings of traditional H2O2 production and to realize the conversion of solar energy to chemical energy. In this work, a step-scheme (S-scheme) heterojunction photocatalyst composed of ZnO and WO3 is carefully prepared by hydrothermal and calcination method for efficient photocatalytic H2O2 production. The ZW30 composite photocatalysts exhibit enhanced activity with the highest H2O2-production rate of 6788 μmol L−1 h−1. The results show that the photocatalytic H2O2 production process is dominated by a direct two-electron O2 reduction pathway. The enhanced photocatalytic H2O2-production activity is attributed to the formation of interfacial internal electric field (IEF) in the S-scheme heterojunction, which boosts the spatial separation of charge carriers and enables electrons with the strongest reduction power to participate in H2O2 production. This work provides an in-depth insight of the great advantages of S-scheme heterojunction in photocatalytic H2O2 production.

Accelerated Synthesis and Discovery of Covalent Organic Framework Photocatalysts for Hydrogen Peroxide Production

Abstract: A high-throughput sonochemical synthesis and testing strategy was developed to discover covalent organic frameworks (COFs) for photocatalysis. In total, 76 conjugated polymers were synthesized, including 60 crystalline COFs of which 18 were previously unreported. These COFs were then screened for photocatalytic hydrogen peroxide (H2O2) production using water and oxygen. One of these COFs, sonoCOF-F2, was found to be an excellent photocatalyst for photocatalytic H2O2 production even in the absence of sacrificial donors. However, after long-term photocatalytic tests (96 h), the imine sonoCOF-F2 transformed into an amide-linked COF with reduced crystallinity and loss of electronic conjugation, decreasing the photocatalytic activity. When benzyl alcohol was introduced to form a two-phase catalytic system, the photostability of sonoCOF-F2 was greatly enhanced, leading to stable H2O2 production for at least 1 week.

Key Points of Advanced Oxidation Processes (AOPs) for Wastewater, Organic Pollutants and Pharmaceutical Waste Treatment: A Mini Review

Abstract: Advanced oxidation procedures (AOPs) refer to a variety of technical procedures that produce OH radicals to sufficiently oxidize wastewater, organic pollutant streams, and toxic effluents from industrial, hospital, pharmaceutical and municipal wastes. Through the implementation of such procedures, the (post) treatment of such waste effluents leads to products that are more susceptible to bioremediation, are less toxic and possess less pollutant load. The basic mechanism produces free OH radicals and other reactive species such as superoxide anions, hydrogen peroxide, etc. A basic classification of AOPs is presented in this short review, analyzing the processes of UV/H2O2, Fenton and photo-Fenton, ozone-based (O3) processes, photocatalysis and sonolysis from chemical and equipment points of view to clarify the nature of the reactive species in each AOP and their advantages. Finally, combined AOP implementations are favored through the literature as an efficient solution in addressing the issue of global environmental waste management.

Electrochemical Detection of H2O2 Using an Activated Glassy Carbon Electrode

Abstract: Hydrogen peroxide (H2O2) is extensively used for sterilization purposes in the food industries and pharmaceuticals as an antimicrobial agent. According to the Food and Agriculture Organization (FAO), the permissible level of H2O2 in milk is in the range of 0.04 to 0.05% w/v, so it has been prohibited to use as a preservative agent. Herein, we reported the electrochemical sensing of H2O2 in milk samples using an activated glassy carbon electrode (AGCE). For this purpose, activation of GCE was carried out in 0.1 M H2SO4 by continuous potential sweeping between −0.7 to 1.8 V for 25 cycles. The AGCE showed a redox peak at -0.18 V in the neutral medium corresponding to the quinone functional groups present on the electrode surface. AGCE was studied in (pH 7.4) 0.1 M PBS for the electro-catalysis of H2O2. The surface of the activated electrode was analysed by Raman spectroscopy and contact angle measurements. In addition, for the activated surface, the contact angle was found to be 85° which indicated the hydrophilic nature of the surface. The different optimization parameters such as (1) effect of electrolyte ions, (2) electrooxidation cycles, and (3) oxidation potential windows were studied to improve the activation process. Finally, AGCE was used to detect H2O2 from 0.1 to 10 mM and the limit of detection (LOD) was found to be 0.053 mM with a linear correlation coefficient (R2) of 0.9633. The selectivity of the sensor towards H2O2 was carried out in the presence of other interferents. The sensitivity of the AGCE sensor was calculated as 17.16 μA mol cm−2. Finally, the commercial application of the sensor was verified by testing it in milk samples with H2O2 in the recovery range of 95%–98%.

Optimization of the Synthesis of Fungus-Mediated Bi-Metallic Ag-Cu Nanoparticles

Abstract: Bi-metallic nanoparticles (NPs) have appeared to be more efficient as antimicrobials than mono-metallic NPs. The fungus Aspergillus terreus-mediated synthesis of bi-metallic Ag-Cu NPs was optimized using response surface methodology (RSM) to reach the maximum yield of NPs. The optimal conditions were validated using ANOVA. The optimal conditions were 1.5 mM total metal (Ag + Cu) concentration, 1.25 mg fungal biomass, 350 W microwave power, and 15 min reaction time. The structure and shape of the synthesized NPs (mostly 20–30 nm) were characterized using several analytical tools. The biological activities of the synthesized NPs were assessed by studying their antioxidant, antibacterial, and cytotoxic activity in different NP concentrations. A dose-dependent response was observed in each test. Bi-metallic Ag-Cu NPs inhibited three clinically relevant human pathogens: Klebsiella pneumoniae, Enterobacter cloacae, and Pseudomonas aeruginosa. Escherichia coli, Enterococcus faecalis, and Staphylococcus aureus were inhibited less. The DPPH and hydrogen peroxide scavenging activities of the NPs were high, reaching 90% scavenging. Ag-Cu NPs could be studied as antimicrobials in different applications. The optimization procedure using statistical analyses was successful in improving the yield of nanoparticles.

Band alignment of homojunction by anchoring CN quantum dots on g-C3N4 (0D/2D) enhance photocatalytic hydrogen peroxide evolution

Abstract: Polymeric carbon nitride (C3N4) is a very attractive candidate to produce photocatalytic hydrogen peroxide (H2O2) due to its low-cost, metal-free characteristics. However, the low efficiency would limit its development to higher yields because of insufficient light absorption and electron-hole separation. Here, we developed a simple method to anchor CN quantum dots (QDs) onto g-C3N4 nanosheets to form a homojunction structure (HJ-C3N4), which could improve photocatalytic performance largely without introducing metal elements. Its superior efficiency is a result of the band alignment by the homojunction structure providing excellent electron-hole separation and QDs providing suppressed recombination. Simultaneously, the light responsiveness of QDs endows a wide spectrum-responsive adsorption and enhances the adsorption intensity. The H2O2 yield of the HJ-C3N4 reached 115 μmol·L−1·h−1 in pure water by visible light, which has an 8.6x higher production than g-C3N4 nanosheets. The material design of 0D/2D homojunction could be extended to other materials with specific band alignment.

Engineering Multienzyme‐Mimicking Covalent Organic Frameworks as Pyroptosis Inducers for Boosting Antitumor Immunity

Abstract: The engineering of a series of multienzyme-mimicking covalent organic frameworks (COFs), COF-909-Cu, COF-909-Fe, and COF-909-Ni, as pyroptosis inducers, remodeling the tumor microenvironment to boost cancer immunotherapy, is reported. Mechanistic studies reveal that these COFs can serve as hydrogen peroxide (H2 O2 ) homeostasis disruptors to elevate intracellular H2 O2 levels, and they not only exhibit excellent superoxide dismutase (SOD)-mimicking activity and convert superoxide radicals (O2•- ) to H2 O2 to facilitate H2 O2 generation, but also possess outstanding glutathione peroxidase (GPx)-mimicking activity and deplete glutathione (GSH) to alleviate the scavenging of H2 O2 . Meanwhile, the outstanding photothermal therapy properties of these COFs can accelerate the Fenton-like ionization process to facilitate their chemodynamic therapy efficiency. One member, COF-909-Cu, can robustly induce gasdermin E (GSDME)-dependent pyroptosis and remodel the tumor microenvironment to trigger durable antitumor immunity, thus promoting the response rate of αPD-1 checkpoint blockade and successfully restraining tumor metastasis and recurrence.

Polarization Engineering of Covalent Triazine Frameworks for Highly Efficient Photosynthesis of Hydrogen Peroxide from Molecular Oxygen and Water

Abstract: Two‐electron oxygen photoreduction to hydrogen peroxide (H2O2) is seriously inhibited by its sluggish charge kinetics. Herein, a polarization engineering strategy is demonstrated by grafting (thio)urea functional groups onto covalent triazine frameworks (CTFs), giving rise to significantly promoted charge separation/transport and obviously enhanced proton transfer. The thiourea‐functionalized CTF (Bpt‐CTF) presents a substantial improvement in the photocatalytic H2O2 production rate to 3268.1 µmol h−1 g−1 with no sacrificial agents or cocatalysts that is over an order of magnitude higher than unfunctionalized CTF (Dc‐CTF), and a remarkable quantum efficiency of 8.6% at 400 nm. Mechanistic studies reveal the photocatalytic performance is attributed to the prominently enhanced two‐electron oxygen reduction reaction by forming endoperoxide at the triazine unit and highly concentrated holes at the thiourea site. The generated O2 from water oxidation is subsequently consumed by the oxygen reduction reaction (ORR), thereby boosting overall reaction kinetics. The findings suggest a powerful functional‐groups‐mediated polarization engineering method for the development of highly efficient metal‐free polymer‐based photocatalysts.

An Enzyme‐Engineered Nonporous Copper(I) Coordination Polymer Nanoplatform for Cuproptosis‐Based Synergistic Cancer Therapy

Abstract: Cuproptosis, a newly identified form of regulated cell death that is copper‐dependent, offers great opportunities for exploring the use of copper‐based nanomaterials inducing cuproptosis for cancer treatment. Here, a glucose oxidase (GOx)‐engineered nonporous copper(I) 1,2,4‐triazolate ([Cu(tz)]) coordination polymer (CP) nanoplatform, denoted as GOx@[Cu(tz)], for starvation‐augmented cuproptosis and photodynamic synergistic therapy is developed. Importantly, the catalytic activity of GOx is shielded in the nonporous scaffold but can be “turned on” for efficient glucose depletion only upon glutathione (GSH) stimulation in cancer cells, thereby proceeding cancer starvation therapy. The depletion of glucose and GSH sensitizes cancer cells to the GOx@[Cu(tz)]‐mediated cuproptosis, producing aggregation of lipoylated mitochondrial proteins, the target of copper‐induced toxicity. The increased intracellular hydrogen peroxide (H2O2) levels, due to the oxidation of glucose, activates the type I photodynamic therapy (PDT) efficacy of GOx@[Cu(tz)]. The in vivo experimental results indicate that GOx@[Cu(tz)] produces negligible systemic toxicity and inhibits tumor growth by 92.4% in athymic mice bearing 5637 bladder tumors. This is thought to be the first report of a cupreous nanomaterial capable of inducing cuproptosis and cuproptosis‐based synergistic therapy in bladder cancer, which should invigorate studies pursuing rational design of efficacious cancer therapy strategies based on cuproptosis.

Band alignment of homojunction by anchoring CN quantum dots on g-C3N4 (0D/2D) enhance photocatalytic hydrogen peroxide evolution

Abstract: Polymeric carbon nitride (C 3 N 4 ) is a very attractive candidate to produce photocatalytic hydrogen peroxide (H 2 O 2 ) due to its low-cost, metal-free characteristics. However, the low efficiency would limit its development to higher yields because of insufficient light absorption and electron-hole separation. Here, we developed a simple method to anchor CN quantum dots (QDs) onto g-C 3 N 4 nanosheets to form a homojunction structure (HJ-C 3 N 4 ), which could improve photocatalytic performance largely without introducing metal elements. Its superior efficiency is a result of the band alignment by the homojunction structure providing excellent electron-hole separation and QDs providing suppressed recombination. Simultaneously, the light responsiveness of QDs endows a wide spectrum-responsive adsorption and enhances the adsorption intensity. The H 2 O 2 yield of the HJ-C 3 N 4 reached 115 μmol L −1 h −1 in pure water by visible light, which has an 8.6x higher production than g-C 3 N 4 nanosheets. The material design of 0D/2D homojunction could be extended to other materials with specific band alignment. • Homojunction structure via 0D/2D configuration exhibits an excellent e − -h + separation ability. • Type-I band in CN system promotes the full use of wide-spectrum absorption extending the absorption edge to nearly 600 nm. • In pure water by visible light (λ > 400 nm), H 2 O 2 yield increases by 8.6 times reaching 115 μmol L −1 h −1 . • The defect energy levels contributed by oxygen-terminal functional groups in QDs can suppress the carriers recombination.

Electrochemical oxygen reduction to hydrogen peroxide at practical rates in strong acidic media

Abstract: Electrochemical oxygen reduction to hydrogen peroxide (H2O2) in acidic media, especially in proton exchange membrane (PEM) electrode assembly reactors, suffers from low selectivity and the lack of low-cost catalysts. Here we present a cation-regulated interfacial engineering approach to promote the H2O2 selectivity (over 80%) under industrial-relevant generation rates (over 400 mA cm-2) in strong acidic media using just carbon black catalyst and a small number of alkali metal cations, representing a 25-fold improvement compared to that without cation additives. Our density functional theory simulation suggests a "shielding effect" of alkali metal cations which squeeze away the catalyst/electrolyte interfacial protons and thus prevent further reduction of generated H2O2 to water. A double-PEM solid electrolyte reactor was further developed to realize a continuous, selective (∼90%) and stable (over 500 hours) generation of H2O2 via implementing this cation effect for practical applications.

Recent advances in multifunctional nanomaterials for photothermal-enhanced Fenton-based chemodynamic tumor therapy

Abstract: Photothermal (PT)-enhanced Fenton-based chemodynamic therapy (CDT) has attracted a significant amount of research attention over the last five years as a highly effective, safe, and tumor-specific nanomedicine-based therapy. CDT is a new emerging nanocatalyst-based therapeutic strategy for the in situ treatment of tumors via the Fenton reaction or Fenton-like reaction, which has got fast progress in recent years because of its high specificity and activation by endogenous substances. A variety of multifunctional nanomaterials such as metal-, metal oxide-, and metal-sulfide-based nanocatalysts have been designed and constructed to trigger the in situ Fenton or Fenton-like reaction within the tumor microenvironment (TME) to generate highly cytotoxic hydroxyl radicals (•OH), which is highly efficient for the killing of tumor cells. However, research is still required to enhance the curative outcomes and minimize its side effects. Specifically, the therapeutic efficiency of certain CDTs is still hindered by the TME, including low levels of endogenous hydrogen peroxide (H2O2), overexpression of reduced glutathione (GSH), and low catalytic efficacy of Fenton or Fenton-like reactions (pH 5.6-6.8), which makes it difficult to completely cure cancer using monotherapy. For this reason, photothermal therapy (PTT) has been utilized in combination with CDT to enhance therapeutic efficacy. More interestingly, tumor heating during PTT not only causes damage to the tumor cells but can also accelerate the generation of •OH via the Fenton and Fenton-like reactions, thus enhancing the CDT efficacy, providing more effective cancer treatment when compared with monotherapy. Currently, synergistic PT-enhanced CDT using multifunctional nanomaterials with both PT and chemodynamic properties has made enormous progress in cancer theranostics. However, there has been no comprehensive review on this subject published to date. In this review, we first summarize the recent progress in PT-enhanced Fenton-based CDT for cancer treatment. We then discuss the potential and challenges in the future development of PT-enhanced Fenton-based nanocatalytic tumor therapy for clinical application.

Superoxide Radicals in the Execution of Cell Death

Abstract: Superoxide is a primary oxygen radical that is produced when an oxygen molecule receives one electron. Superoxide dismutase (SOD) plays a primary role in the cellular defense against an oxidative insult by ROS. However, the resulting hydrogen peroxide is still reactive and, in the presence of free ferrous iron, may produce hydroxyl radicals and exacerbate diseases. Polyunsaturated fatty acids are the preferred target of hydroxyl radicals. Ferroptosis, a type of necrotic cell death induced by lipid peroxides in the presence of free iron, has attracted considerable interest because of its role in the pathogenesis of many diseases. Radical electrons, namely those released from mitochondrial electron transfer complexes, and those produced by enzymatic reactions, such as lipoxygenases, appear to cause lipid peroxidation. While GPX4 is the most potent anti-ferroptotic enzyme that is known to reduce lipid peroxides to alcohols, other antioxidative enzymes are also indirectly involved in protection against ferroptosis. Moreover, several low molecular weight compounds that include α-tocopherol, ascorbate, and nitric oxide also efficiently neutralize radical electrons, thereby suppressing ferroptosis. The removal of radical electrons in the early stages is of primary importance in protecting against ferroptosis and other diseases that are related to oxidative stress.

Overlooked Formation of H2O2 during the Hydroxyl Radical-Scavenging Process When Using Alcohols as Scavengers.

Abstract: Hydroxyl radical (•OH) is an active species widely reported in studies across many scientific fields, and hence, its reliable analysis is vitally important. Currently, alcohols are commonly used as scavengers for •OH determination. However, the impacts of alcohols on the reliability of •OH detection remain unknown. In this study, we found that adding different types and different amounts of alcohols in water samples treated with ultraviolet irradiation undesirably produced substantial amounts of hydrogen peroxide (H2O2), which is a known •OH precursor. This means that the conventional •OH determination method using alcohols is likely unreliable or even misleading. Through careful investigation, we revealed an overlooked reaction pathway during H2O2 and •OH transformations. Varying oxygen concentrations, pHs, alcohol dosages, and types altered H2O2 formation, which can affect •OH determination accuracy. Among alcohols, n-butanol is the best scavenger because it quenches •OH rapidly but re-forms little H2O2.

Tuning the atomic configuration of Co-N-C electrocatalyst enables highly-selective H2O2 production in acidic media

Abstract: The oxygen reduction reaction (ORR) is essential for both energy conversion devices and green hydrogen peroxide (H2O2) synthesis. Whereas, it remains a challenge to efficiently tune the oxygen reduction selectivity toward the target applications. Herein, we designed two kinds of Co-N-C materials with encapsulated Co nanoparticles (CoNP-N-C) and with atomically dispersed cobalt atoms strongly embedded into nitrogen-doped carbon nanotubes (CoSA-N-CNTs), and successfully realized the ORR pathway transformation from four-electron (4e−) to two-electron (2e−) for high-performance H2O2 production. This tunability is ascribed to the modification of the atomic configuration of the Co-N-C catalyst. Remarkably, when employing CoSA-N-CNTs material as a 2e− ORR catalyst, the assembled electrode exhibits a high H2O2 production rate of approximately 974 ± 25 mmol gcat−1 h−1, along with an ultra-fast organic matter degradation performance. This work provides an efficient strategy for tuning oxygen reduction selectivity via a simple structure tuning of the materials for specific applications.