O2 Generation Rate Research Articles

Highly efficient Bi2Fe4O9-ZnIn2S4 Z-scheme heterojunction for piezo-photocatalytic overall water splitting under near-infrared light up to 1200 nm

Photocatalytic overall water splitting is considered as a sustainable and appealing strategy to solve the issues of energy supply and conversion. However, a critical hurdle to applying photocatalytic overall water splitting is the restricted light absorption and sluggish mobility of light-induced charge carriers in catalysts. Herein, a near-infrared light-responsive Bi2Fe4O9-ZnIn2S4 Z-scheme piezoelectric photocatalyst with a Fe-S bonded interface is constructed. This ingenious design synergistically utilizes the advantages of the Z-scheme, strong coupling interfaces, and piezoelectric field. The Bi2Fe4O9-ZnIn2S4 Z-scheme heterojunction significantly suppresses photogenerated carriers' recombine and extends photocatalytic response to the infrared light region, achieving highly efficient piezo-photocatalytic activity. Consequently, the optimized Bi2Fe4O9-ZnIn2S4 heterojunction displays an unprecedented piezo-photocatalytic H2 and O2 generation rate of 1862 and 927 μmol h−1 g−1 under sunlight illumination. This rate is approximately 4.9 and 10.0 times greater than that of photocatalysis and piezocatalysis alone. This study lays novel groundwork for developing future heterojunctions for photocatalytic water splitting.

Nature of Li2O2 and its relationship to the mechanisms of discharge/charge reactions of lithium-oxygen batteries.

Lithium-air batteries (LABs) are considered one of the most promising energy storage devices because of their large theoretical energy density. However, low cyclability caused by battery degradation prevents its practical use. Thus, to realize practical LABs, it is essential to improve cyclability significantly by understanding how the degradation processes proceed. Here, we used online mass spectrometry for real-time monitoring of gaseous products generated during charging of lithium-oxygen batteries (LOBs), which was operated with pure oxygen not air, with 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) tetraethylene glycol dimethyl ether (TEGDME) electrolyte solution. Linear voltage sweep (LVS) and voltage step modes were employed for charge instead of constant current charge so that the energetics of the product formation during the charge process can be understood more quantitatively. The presence of two distinctly different types of Li2O2, one being decomposed in a wide range of relatively low cell voltages (2.8-4.16 V) (l-Li2O2) and the other being decomposed at higher cell voltages than ca. 4.16 V (h-Li2O2), was confirmed by both LVS and step experiments. H2O generation started when the O2 generation rate reached a first maximum and CO2 generation took place accompanied by the decomposition of h-Li2O2. Based on the above results and the effects of discharge time and the use of isotope oxygen during discharge on product distribution during charge, the generation mechanism of O2, H2O, and CO2 during charging is discussed in relation to the reactions during discharge.

Cyano-Regulated Organic Polymers for Highly Efficient Photocatalytic H2 O2 Production in Various Actual Water Bodies.

Photocatalytic production of H2 O2 has drawn significant attention in recent years, but the yield rate of current photocatalytic systems is still unsatisfactory. Moreover, the presence of various components in actual water bodies will consume the photogenerated charges and deactivate the catalyst, severely limiting the real applications of photocatalytic H2 O2 production. Herein, a cyano-modified polymer photocatalyst is synthesized by Knoevenagel condensation with subsequent thermal polymerization. The introduction of cyano group and sulfer (S), oxygen (O) elements modulates the microstructure and energy band of the polymer catalyst, and the cyano group sites can effectively adsorb and activate O2 , realizing the generation of H2 O2 in the two-step single-electron oxygen reduction process. The reported system achieves high H2 O2 generation rate up to 1119.2µmol g-1 h-1 in various water bodies including tap water, river water, seawater, and secondary effluent. This simple and readily available catalyst demonstrates good anti-interference performance and pH adaptability in photocatalytic H2 O2 production in actual water bodies, and its photodegradation and sterilization applications are also demonstrated. This study offers new insights in developing polymer catalysts for efficient photocatalytic production of H2 O2 in various water bodies for practical application.

C-doped Bi3O4X nanosheets with self-induced internal electric fields for pyrene degradation: Effects of carbon and halogen element type on photocatalytic activity

A series of C-doped Bi3O4X (X = Cl, Br, I) photocatalysts with layer-stacked structure was synthesized using glucose as carbon source, and the carbon doping and halogen species on harvesting broader solar spectrum and promoting charge carrier separation were systematically investigated. For pyrene photolysis, the photodegradation rate of pristine materials followed the order of Bi3O4I > Bi3O4Br > Bi3O4Cl, which was attributed to the difference in electronegativity of the halogen elements. The doped carbon boosted photocatalytic performance and the optimal C/Bi3O4I achieved 100% pyrene removal within 20 min, which primarily benefited from the dramatic improvement of the internal electric field (IEF). The improved IEF further increased the separation and transfer efficiency of photogenerated charge carriers. XRD and XPS characterizations confirmed that the doped carbon implanted into the lattice of [X] layers, and mainly affected the X np states. The X np orbitals contributed to the valence band (VB) of Bi3O4X, thus the local occupied states induced by doped carbon formed above VB and significantly decreased the VB potential. Meanwhile, the doped carbon narrowed the band gap and greatly improved visible light utilization. The O2−, h+ and OH were identified as dominant active species for pyrene degradation, and the generation rate of O2− and OH was further measured by the probe technique. Moreover, the photodegradation pathways of pyrene were proposed and the ecotoxicity of intermediates was assessed. This study reveals the effect of halogen species on photocatalytic activity and provides guidance for enhancing IEF by doping inorganic element.

Construction of a Novel Cascade Electrolysis-Heterocatalysis System by Using Zeolite-Encaged Ultrasmall Palladium Catalysts for H2 O2 Generation.

In situ generation of hydrogen peroxide (H2 O2 ) has attracted extensive attention, especially in water treatment. However, traditional anthraquinones can only produce high-concentration H2 O2 and its transportation and storage are not convenient and dangerous. Herein, an in situ and on-demand strategy to produce H2 O2 by using a cascade water electrolysis together with a heterocatalysis system is provided. Beginning with water, H2, and O2 can be generated via electrolysis and then react with each other to produce H2 O2 immediately on efficient zeolite-encaged ultrasmall Pd catalysts. Significantly, the H2 O2 generation rate in the optimized cascade system reaches up to 0.85mol L-1 h-1 gPd -1 , overcoming most of the state-of-the-art catalysts in previous literature. The confinement effect of zeolites is not only beneficial to the formation of highly dispersed metal species, promoting the H2 O2 generation, but also inhibits the H2 O2 decomposition, enhancing the production yield of H2 O2 . In addition, the effect of electrolytes, sizes of Pd species, as well as zeolite acidity are also systematically studied. This work provides a new avenue for H2 O2 generation via a highly efficient cascade electrolysis-heterocatalysis system by using zeolite-supported metal catalysts. The high catalytic efficiency and green process for H2 O2 generation make it very promising for further practical applications.

B2, an abscisic acid mimic, improves salinity tolerance in winter wheat seedlings via improving activity of antioxidant enzymes.

Salinity severely inhibits growth and reduces yield of salt-sensitive plants like wheat, and this effect can be alleviated by plant growth regulators and phytohormones, among which abscisic acid (ABA) plays a central role in response to various stressful environments. ABA is highly photosensitive to light disruption, which this limits its application. Here, based on pyrabactin (a synthetic ABA agonist), we designed and synthesized a functional analog of ABA and named B2, then evaluated its role in salt resistance using winter wheat seedlings. The phenotypes showed that B2 significantly improved the salt tolerance of winter wheat seedlings by elevating the biomass. The physiological analysis found that B2 treatment reduced the generation rate of O2–, electrolyte leakage, the content of proline, and the accumulation of malonaldehyde (MDA) and H2O2 and also significantly increased the contents of endogenous hormones zeatin riboside (ZA) and gibberellic acid (GA). Further biochemical analysis revealed that the activities of various antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX), were enhanced by B2, and the activities of antioxidase isozymes SOD3, POD1/2, and APX1/2 were particularly increased, largely resembling ABA treatment. The abiotic stress response-related gene TaSOS1 was significantly upregulated by B2, while the TaTIP2;2 gene was suppressed. In conclusion, an ABA analog B2 was capable to enhance salt stress tolerance in winter wheat seedlings by stimulating the antioxidant system, providing a novel regulator for better survival of crops in saline soils and improving crop yield.

SiP Nanosheets: A Metal-Free Two-Dimensional Photocatalyst for Visible-Light Photocatalytic H2 Production and Nitrogen Fixation.

Two-dimensional (2D) semiconductors for photocatalysis are more advantageous than the other photocatalytic materials since the 2D semiconductors generally have large specific surface area and abundant active sites. Phosphorus silicon (SiP), with an indirect bandgap in bulk and a direct bandgap in the monolayer, has recently emerged as an attractive 2D material because of its anisotropic layered structure, tunable bandgap, and high charge carrier mobility. However, the utilization of SiP as a photocatalyst for photocatalysis has been scarcely studied experimentally. Herein, we reported the synthesis of SiP nanosheets (SiP NSs) prepared from bulk SiP by an ultrasound-assisted liquid-phase exfoliation approach which can act as a metal-free, efficient, and visible-light-responsive photocatalyst for photocatalytic H2 production and nitrogen fixation. In a half-reaction system, the maximal H2 and NH3 generation rate under visible light irradiation achieves 528 and 35 μmol·h-1·g-1, respectively. Additionally, the apparent quantum yield for H2 production at 420 nm reaches 3.56%. Furthermore, a Z-scheme photocatalytic overall water-splitting system was successfully constructed by using Pt-loaded SiP NSs as the H2-evolving photocatalyst, Co3O4/BiVO4 as the O2-evolving photocatalyst, and Co(bpy)33+/2+ as an electron mediator. Notably, the highest H2 and O2 generation rate with respect to Pt/SiP NSs achieves 71 and 31 μmol·h-1·g-1, respectively. This study explores the potential application of 2D SiP as a metal-free visible-light-responsive photocatalyst for photocatalysis.

Iodide-Induced Fragmentation of Polymerized Hydrophilic Carbon Nitride for High-Performance Quasi-Homogeneous Photocatalytic H2 O2 Production.

Polymeric carbon nitride (PCN) as a class of two-electron oxygen reduction reaction (2 e- ORR) photocatalyst has attracted much attention for H2 O2 production. However, the low activity and inferior selectivity of 2 e- ORR greatly restrict the H2 O2 production efficiency. Herein, we develop a new strategy to synthesize hydrophilic, fragmented PCN photocatalyst by the terminating polymerization (TP-PCN) effect of iodide ions. The obtained TP-PCN with abundant edge active sites (AEASs), which can form quasi-homogeneous photocatalytic system, exhibits superior H2 O2 generation rate (3265.4 μM h-1 ), far surpassing PCN and other PCN-based photocatalysts. DFT calculations further indicate that TP-PCN is more favorable for electron transiting from β spin-orbital to the π* orbitals of O2 , which optimizes O2 activation and reduces the energy barrier of H2 O2 formation. This work provides a new concept for designing functional photocatalysts and understanding the mechanism of O2 activation in ORR for H2 O2 production.

The role of antioxidant mechanism in photosynthesis under heavy metals Cd or Zn exposure in tobacco leaves

ABSTRACT We examined the effects of Cd and Zn exposure on the photosynthetic function and the tolerant mechanisms of ROS metabolism in tobacco leaves. The results showed that the photosynthesis inhibition caused by Cd exposure was due to the limitation of both stomatal and non-stomatal factors, while Zn exposure only showed a significant effect on the Gs of tobacco leaves. Cd increased the generation rate of O2•– and the content of H2O2, but Zn did not lead to the ROS burst. Cd enhanced the POD activity, but inhibited SOD and CAT activities. The activities of SOD and POD significantly increased under Zn exposure. Cd inhibited the activity and expression of APX. The up regulation of GPX, GR and GST expression and the increase of their activities also play a positive role in the adaptation to Cd. Although Zn inhibited the activities of APX and GPX, it had little effect on other enzyme activities and protein expression in AsA-GSH cycle. TPX and TrxR activities, Trx-Prx pathway-related proteins are very sensitive to Cd. However, only PrxQ and 2-Cys Prx BAS1, which are located in chloroplast, and Trx-HFC164 were significantly down-regulated in Trx-Prx pathway under Zn exposure.

Spermidine Enhanced Free Polyamine Levels and Expression of Polyamine Biosynthesis Enzyme Gene in Rice Spikelets under Heat Tolerance before Heading

High temperatures (HT) before heading strongly inhibit the development of spikelets in rice. Spermidine (Spd) can improve rice’s resistance to HT stress; however, the mechanism underlying this effect has not been elucidated. This study investigated several parameters, including yield, superoxide anion (O2.-), protective enzyme activities, and polyamine content, in a heat-sensitive genotype, Shuanggui 1. The yield and yield components decreased dramatically when subjected to HT stress, while this reduction could be partially recovered by exogenous Spd. Spd also slowed the generation rate of O2.- and increased protective enzyme, superoxide dismutase (SOD) and catalase (CAT) activities both under normal and high temperatures, which suggested that Spd may participate in the antioxidant system. Furthermore, genes involved in polyamine synthesis were analyzed. The results show that HT before heading significantly increased the expression of arginine decarboxylase OsADC1, Spd synthase OsSPDS1 and OsSPDS3 and had little effect on the expression of the S-adenosylmethionine decarboxylase OsSAMDC2 and ornithine decarboxylase OsODC1. In addition, exogenous Spd considerably reduced the expression of OsSAMDC2, OsSPDS1 and OsSPDS3 under HT but not the expression of OsADC1. The above mentioned results indicate that the exogenous Spd could help young rice spikelets to resist HT stress by reducing the expression of OsSAMDC2, OsSPDS1 and OsSPDS3, resulting in higher levels of endogenous Spd and Spm, which were also positively correlated with yield. In conclusion, the adverse effect of HT stress on young spikelets seems to be alleviated by increasing the amounts of Spd and Spm, which provides guidance for adaptation to heat stress during rice production.

TiO2 nanocrystalline for enhanced hydrogen and oxygen generation of thin film photocatalyst: from catalytic mechanism and microstructural analysis

Anatase TiO2 nanocrystalline film prepared by using sol–gel method was assembled on TiO2 nanotubes to produce composite thin film photocatalyst and investigated as interfacial layer for the catalytic performance of Ti/TNT/N–P/NaTaO3:La (the nanostructures is Ti/TiO2 nanotubes/TiO2 nanocrystalline film/NiO film/NaTaO3:La) photocatalyst to generate hydrogen and oxygen under UV irradiation. The as-synthesized samples were characterized by FESEM, XRD, Element Mapping, UV–Vis, PL, I–V, and EIS. Characteristic analyses show that the interface between the TNT layer (TiO2 nanotubes) and P layer (NiO film) can be optimized by adjusting the number of N layers (TiO2 nanocrystalline film), thus affecting the efficiency of the photocatalyst. Compared with unformed TiO2 film, the Ti/TNT/N–P/NaTaO3:La photocatalyst with four TiO2 layers enhanced the H2 and O2 generation rate from 43.7 to 87.1 μmol/h which realized almost 2.0 times. The enhanced photocatalytic performance can be attributed to the low defect density and the effective separation of photo-generated electron–hole pairs. Furthermore, the performance stability of thin film photocatalyst was favorably showcased through multiple water splitting reactions, and the rational mechanism of improved photocatalytic property was interpreted systematically. In summary, such results have certain guiding effect on solving the weakness of composite film catalyst of interface defects and carrier recombination.

High quantum efficiency of photocatalytic water oxidation over the TiO2/MMO nanocomposite under visible-light irradiation

The titanium dioxide/ZnAl-layered double hydroxide (TiO2/ZnAl-LDH) nanocomposite was first prepared using the co-precipitation method, and the TiO2/metal mixed oxide (TiO2/MMO) was then fabricated by annealing the TiO2/ZnAl-LDH nanocomposite at 430 °C. The obtained materials were characterized by means of techniques, such as field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV–visible diffuse reflectance spectroscopy (DRS), and N2 adsorption-desorption (BET). Photocatalytic activities of the TiO2/MMO nanocomposite was evaluated for O2 generation from aqueous solutions in the presence of AgNO3 (1 mmol) as the sacrificial agent at neutral pH and room temperature under visible-light irradiation. It is found that photocatalytic activity of the TiO2/MMO sample was better than that of the TiO2/ZnAl-LDH sample, which could be attributed to the reduction in bandgap energy, low electron-hole recombination, and high surface area. An O2 generation rate of 371 μmol/(g h) was achieved over 20 mg of the TiO2/MMO nanocomposite photocatalyst, and the quantum efficiency for O2 generation was 84% at 400 nm. Such a quantum efficiency was the highest value obtained over the TiO2/MMO sample under visible-light illumination. This study presents a novel approach for water oxidation using the visible-light-responsive TiO2/MMO nanocomposite photocatalyst, which might be applied as a promising candidate in solar energy conversion and environmental science for highly efficient O2 generation.

A new photocatalyst based on Co(CO3)0.5(OH)·0.11H2O/Bi2WO6 nanocomposites for high-efficiency cocatalyst-free O2 evolution

The practical application of photocatalytic water splitting is essentially limited by the slow kinetic nature of the water oxidation process. Therefore, it is highly desirable but challenging to explore a low-cost and high-efficiency water oxidation catalyst for the aim of commercialization and industrialization. We herein report the first-time synthesis of a novel and high-efficiency visible-light-driven photocatalyst composed of flower-like Co(CO3)0.5(OH)·0.11H2O (CCO) nanowires and Bi2WO6 (BWO) nanosheets, i.e. CCO/BWO nanocomposite, via a facile hydrothermal method. Without utilizing any additional cocatalyst, the composite of CCO/BWO in 30% weight ratio exhibits extraordinarily high photoactivity and photostability towards O2 evolution, achieving an average O2 generation rate of 953 µmol h−1 g−1 under visible-light irradiation (λ > 420 nm).

Construction of Au/CuO/Co3O4 Tricomponent Heterojunction Nanotubes for Enhanced Photocatalytic Oxygen Evolution under Visible Light Irradiation

Semiconductor-metal heterojunctions are widely used in the design of photocatalyst for water splitting and organic compound degradation. In this work we introduced the design and fabrication of Au/CuO/Co3O4 tricomponent heterojunction to produce oxygen efficiently through photocatalysis of water. A facile and universal strategy was employed to prepare Au/CuO/Co3O4 tricomponent nanotubes. The CuO/Co3O4 nanotubes were first synthesized by electrospinning technique and subsequent thermal treatment. Upon visible light excitation, the CuO/Co3O4 nanotubes in the presence of HAuCl4.4H2O readily transformed into Au/CuO/Co3O4 heterojunction nanotubes. These tricomponent heterostructures demonstrated high O2 generation rate of 2.92 mmol h–1g–1 during the photocatalytic process, a value much larger than that of CuO/Co3O4 nanotube control. The work suggests that the design of tricomponent heterojunctions integrating semiconductor-semiconductor and semiconductor-metal heterojunctions could be an effective route to rai...

In Situ Synthesis of Bi2O3 Nanoparticles on ZincMe (Me=Al or Cr) Layered Double Hydroxide Frameworks for Photocatalytic Oxygen Evolution from Water under Solar‐Light Activation

AbstractA key target to boost solar‐to‐chemical conversion processes is to fabricate an efficient solar‐light‐responsive photocatalyst. Herein, we report the in situ synthesis of nanoparticles (NPs) of Bi2O3 directly on Zn‐based layered double hydroxide (LDHs) frameworks. The in situ synthesis of Bi2O3NPs is done at room temperature, is ligand free and explores the ability of calcined ZnMeLDHs to reconstruct their layered structures in Bi(NO3)3 aqueous solution. The in situ formation of Bi2O3NPs on ZnMeLDHs is assessed by transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), powder X‐ray diffraction (XRD), and UV/Vis spectroscopy and compared with the features of a corresponding Bi2O3NPs/LDH prepared by the conventional impregnation route. The rapid photocatalytic response of the Bi2O3NPs/ZnMeLDH (Me=Al, Cr) heterostructures is confirmed by O2 generation from water under solar‐light irradiation. The rate of O2 generation increases by a factor of approximately 2 for the ZnCrLDH based catalysts as compared to that of the family of ZnAlLDH catalysts. Further, the presence of the bismuth phase and its nano‐dimension leads to increased efficiency for the in situ prepared Bi2O3NPs/LDHs as compared to that of impregnated Bi2O3/LDH and the pristine LDHs.

Effects of p-hydroxybenzoic acid and phloroglucinol on mitochondria function and root growth in cotton (Gossypium hirsutum L.) seedling roots.

With early-maturing cotton cultivar CCRI-50 widely grown in China as experimental material, water culture experiment was conducted to study the effects of p-hydroxybenzoic acid and phloroglucinol with different concentrations (0.8, 4.0, and 20.0 mmol·L-1) on generation rate of reactive oxygen, changes of antioxidant enzyme activities and mitochondria function of cotton roots. Results showed that p-hydroxybenzoic acid and phloroglucinol treatments inhibited the cotton root growth, reduced SOD, POD, CAT and H+-ATPase activities in root mitochondria, increased the generation rate of O2-· and H2O2 content. In addition, they also increased the opening of mitochondrial permeability transition pores (MPTP), decreased the membrane fluidity and cytochrome c/a (Cyt c/a). Difference of mitochondria function between p-hydroxybenzoic acid and phloroglucinol treatments was minor at concentration of 0.8 mmol·L-1, while the inhibition to root growth and mitochondria function under treatment of p-hydroxybenzoic acid at concentration of 4.0 and 20.0 mmol·L-1 was stronger than that of phloroglucinol. Above all, p-hydroxybenzoic acid and phloroglucinol inhibited antioxidant enzyme activity and mitochondrial function in cotton seedling roots, and the inhibition depended on dose of phenolic acids. The inhibition to root growth and mitochondria function between p-hydroxybenzoic acid and phloroglucinol treatment was different, and p-hydroxybenzoic acid had stronger inhibition than phloroglucinol at the concentration more than 4.0 mmol·L-1.

Enhanced photoelectrochemical water splitting and photocatalytic water oxidation of Cu2O nanocube-loaded BiVO4 nanocrystal heterostructures

Reducing the fast recombination of photogenerated electron-hole pairs of semiconductor photocatalyst is very important to improve its photocatalysis. In this paper we fabricate Cu2O nanocube-decorated BiVO4 nanocrystal (denoted as BiVO4@Cu2O nanocrystal@nanocube) heterostructure photocatalyst by coupling n-type BiVO4 with p-type Cu2O. The BiVO4@Cu2O nanocrystal@nanocube photocatalysts show superior photocatalytic activities in photoelectrochemical (PEC) activity and photocatalytic water oxidation to BiVO4 photocatalysts under visible light illumination. The BiVO4@Cu2O nanocrystal@nanocube heterostructure electrode achieves the highest photocurrent density of ∼ 10 μA cm−2 at 0 V versus Ag/AgCl, 5 times higher than that of BiVO4 nanocrystal electrode (∼ 2 μA cm−2). The light induced evolution rate of O2 generation for BiVO4@Cu2O nanocrystal@nanocube heterostructures is as high as 150 μmol h−1100 mg cat−1, more than 3 times higher than that (48 μmol h−1100 mg cat−1) of BiVO4 nanocrystals. The enhanced photocatalysis activities of the BiVO4@Cu2O nanocrystal@nanocube photocatalysts are attributed to the efficient separation of the photoexcited electron-hole pairs caused by inner electronic field (IEF) of p-n junction. This study opens up new opportunities in designing photoactive materials with highly enhanced performance for solar energy conversion.

Two-tier vessel for photoautotrophic high-density cultures

Two-tier vessels, developed for culturing of microalgae and cyanobacteria at high cell density on a shaken platform, were assembled from a flat lower chamber to be filled with a CO2 buffer and an upper flat sterile chamber for the culture that was separated from the lower chamber by a porous polypropylene membrane. Diffusive gas exchange with the atmosphere was controlled by the O2 outlet channel. Referred to surface area, rates of CO2 transfer to a shaken weakly alkaline buffer solution across the membrane were higher than those reached on the conventional pathway through the free upper liquid surface. Membrane-mediated CO2 supply enabled rapid growth of Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 7002 up to ultrahigh cell density. The biomass (dry weight) concentration of Synechococcus cultures reached more than 30 g L−1 on a buffered medium with adequate concentrations of mineral nutrients. An increase of 15 to 20 g L−1 was observed during repeated two-day cycles. Separate pathways for CO2 supply and oxygen outlet prevented significant loss of CO2. Convective gas flow through the oxygen outlet channel enabled the estimation of the O2 generation rate. The permeability of the channel for diffusive O2/N2 exchange limited the O2 concentration to a moderate value. It is concluded that shaken flat cultures using CO2 supply through a porous hydrophobic membrane and diffusive release of O2 through a separate pathway are promising for research on microalgae and cyanobacteria.

Design of Hybrid MnO2‐Polymer‐Lipid Nanoparticles with Tunable Oxygen Generation Rates and Tumor Accumulation for Cancer Treatment

Manganese dioxide (MnO2) nanoparticles (NPs) were discovered in previous work to be effective in improving tumor oxygenation (hypoxia) and reducing H2O2 and acidity in the tumor microenvironment (TME) via local injection. To develop MnO2 formulations useful for clinical application, hybrid NPs are designed with tailored hydrophobicity and structure suitable for intravenous injection, with good blood circulation, biocompatibility, high tumor accumulation, and programmable oxygen generation rate. Two different hybrid NPs are constructed by embedding polyelectrolyte‐MnO2 (PMD) in hydrophilic terpolymer/protein‐MnO2 (TMD) or hydrophobic polymer/lipid‐MnO2 (LMD) matrices. The in vitro reactivity of the MnO2 toward H2O2 is controlled by matrix material and NP structure and dependent on pH with up to two‐fold higher O2 generation rate at acidic (tumor) pH than at systemic pH. The hybrid NPs are found to be safe to cells in vitro and organs in vivo and effectively decrease tumor hypoxia and hypoxia‐inducible‐factor‐1alpha through local or systemic administration. Fast acting TMD reduces tumor hypoxia by 70% in 0.5 h by local injection. Slow acting LMD exhibits superior tumor accumulation and retention through the systemic administration and decreased hypoxia by 45%. These findings encourage a broader use of hybrid MD NPs to overcome TME factors for cancer treatment.

Exogenous glutathione confers high temperature stress tolerance in mung bean (Vigna radiata L.) by modulating antioxidant defense and methylglyoxal detoxification system

The present study investigates the role of exogenous glutathione (GSH) in conferring high temperature stress (HT, 42°C) tolerance in mung bean (Vigna radiata L. cv. Binamoog-1) seedlings by modulating the antioxidant defense and methylglyoxal (MG) detoxification systems. Six-day-old seedlings were exposed to HT stress with or without exogenous GSH (0.5mM for 24h as pretreatment) for 24 and 48h. Heat stress at any duration significantly increased lipid peroxidation (MDA), H2O2, MG, and Proline (Pro) content, generation rate of O2− and lipoxygenase (LOX) activity; decreased leaf chlorophyll (chl) and leaf relative water content (RWC), and the level of ascorbate (AsA); increased endogenous GSH and GSSG (glutathione disulfide); decreased the GSH/GSSG ratio. For both treatment durations, activities of ascorbate peroxidase (APX), glutathione reductase (GR), glutathione-S-transferase (GST) increased; the activities of monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), glutathione peroxidase (GPX), catalase (CAT) and glyoxalase I (Gly I) decreased; the activity of glyoxalase II (Gly II) increased at 48h. Mung bean seedlings pretreated with exogenous GSH under HT improved chl and leaf RWC; increased APX (only after 24h), MDHAR, DHAR, GR, GPX, GST (increased only after 24h), CAT, Gly I and Gly II activities; improved endogenous GSH content and the GSH/GSSG ratio; lowered GSSG content. Glutathione supplementation with drought stress significantly decreased MDA, H2O2 and MG content, O2− generation rate and LOX activity. Pretreatment with GSH resulted in better physiological performance, improved antioxidant and glyoxalase systems, and reduced MG and oxidative stress under 24h of HT stress, compared with that of 48h. The results suggest that exogenous GSH enhances mung bean seedling tolerance of short-term HT stress by modulating the antioxidant and glyoxalase systems and by improving physiological adaptation.