Oxygen Yield Research Articles

The Catalytic Mechanism of a Highly Active Cobalt Chlorin Complex for Photocatalytic Water Oxidation.

Highly active catalysts for electrocatalytic and photocatalytic water oxidation are strongly demanded to realize artificial photosynthesis. A cobalt complex with a chlorin derivative ligand (CoII(Ch)) exhibited high activity for electrocatalytic water oxidation with an overpotential of 0.45 V at pH 9.0. Spectroelectrochemistry (UV-vis) unveiled the formation of two intermediates by successive one-electron oxidations. Also, the Pourbaix diagram depicted by the pH dependence of redox potentials indicated that the water oxidation proceeded after the oxidation of both the central cobalt ion and chlorin ligand with proton-coupled electron transfer (PCET). Then, the photocatalytic activity of CoII(Ch) was examined for water oxidation using [RuII(bpy)3]2+ (bpy: 2,2'-bipyridine) and S2O82- as a photosensitizer and a sacrificial electron acceptor, respectively. The turnover number, turnover frequency, and oxygen yield reached as high as 980, 5.2 s-1, and 98%, respectively, under optimized conditions. The O2-evolution rates increased in proportion to the square of the catalyst concentration in the reaction solution, suggesting that the formation of the O-O bond regarded as the rate-determining step of water oxidation proceeded by the interaction of two metal centers (I2M) mechanism in which two molecules of high-valent metal oxo or oxyl radical species react with each other.

Disulfide-Bridged Cationic Dinuclear Ir(III) Complex with Aggregation-Induced Emission and Glutathione-Consumption Properties for Elevating Photodynamic Therapy.

The ability of photosensitizers (PSs) to generate reactive oxygen species (ROS) is crucial for photodynamic therapy (PDT). However, many traditional PSs face the drawbacks that aggregation-caused quenching (ACQ) and highly expressed glutathione (GSH) in the tumor microenvironment seriously limit their ROS generation ability. Herein, we report two cationic dinuclear iridium complexes, Ir-C-C-Ir and Ir-S-S-Ir, which possess aggregation-induced emission (AIE). Ir-S-S-Ir was constructed for GSH consumption by introducing a disulfide linkage between the two auxiliary ligands with imine units. Quantum chemical calculations revealed that Ir-C-C-Ir and Ir-S-S-Ir possess many degenerate states, which provide more channels for singlet-to-triplet exciton transitions, and then the intersystem crossing rate is increased due to the heavy atom effect of the iridium and sulfur atoms. The ROS production experiments indicated that the singlet oxygen yield of Ir-S-S-Ir was 33 times more than that of the ACQ mononuclear iridium complex Ir-C. Most importantly, Ir-S-S-Ir consumed GSH through a thiol-disulfide exchange reaction, as demonstrated by mass spectrometry and high-performance liquid chromatography. Cell experiments testified that Ir-S-S-Ir consumes GSH in tumor cells, possesses good ROS production capacity, and exhibits an extraordinary PDT effect. This is the first report of an AIE dinuclear iridium complex with a GSH-consuming function.

Quantitative Conversion of Sulfate Oxygen for High-Precision Triple Oxygen Isotope Analysis.

Triple oxygen isotope composition (Δ'17O) of sulfate carries information on the sulfur cycle as well as signatures of atmospheric O2, O3, and surface water of the geological past. However, existing analytical techniques can only achieve a partial oxygen yield during the conversion from sulfate to the analyte O2, which results in isotope fractionation and impedes the Δ'17O comparison with other oxygen-bearing compounds (e.g., H2O) on the VSMOW-SLAP scale. Here, we present an analytical method involving high-temperature graphite reduction, CO discharge, and Pt-catalyzed CO2-O2 isotope exchange, the R-D-E method, that achieves ∼100% conversion of sulfate oxygen to CO2. Compared with the widely used CO2-laser-fluorination technique, our R-D-E method has a better Δ'17O precision (9 per meg) and requires a smaller sample amount, as low as 4 μmol of sulfate (equivalent to 1 mg BaSO4), with both Δ'17O and δ18O being determined simultaneously. Using this method, we report the triple oxygen isotope compositions of three international reference materials (NBS-127, IAEA-SO-5, and IAEA-SO-6) and three in-house references on the VSMOW-SLAP scale. We found that the sulfate Δ'17O values measured on the partially yielded O2 from the fluorination technique are 10-200 per meg higher than those obtained by our R-D-E method, depending on the oxidant used (e.g., F2 or BrF5). Incomplete conversion of sulfate oxygen during the high-temperature graphite reduction would result in lower δ18O and higher Δ'17O values. This work highlights the needs for recalibration and reinterpretation of the published sulfate Δ'17O data when sulfate Δ'17O values of interest are small.

Substituent-Modulated Excited Triplet States and Activities of Ruthenium Complexes for Dual Photodynamic/Sonodynamic Therapy to Cisplatin-Resistant Non-Small Cell Lung Cancer.

Six polypyridyl Ru(II) complexes were designed for single-molecule photodynamic and sonodynamic therapy (PDT/SDT) synergistic multimodal anticancer toward cisplatin-resistant NSCLC. They demonstrated lowest 3ES with distinct intraligand transition nature, which is beneficial for singlet oxygen generation. Remarkable quantum yields of both singlet oxygen and superoxide anion under either 808 nm laser irradiation or ultrasonic treatment and could induce apoptosis and ferroptosis of A549R cells. Cytotoxicity experiments clearly demonstrated a synergistic effect between PDT and SDT. The relationship between the structures of these complexes and their cellular biological mechanisms has been explored in detail. Using a single-molecule sensitizer to achieve synergistic PDT/SDT may provide valuable insights for the treatment of drug-resistant tumors that located deeply and in hypoxic microenvironment.

TME-Activated MnO2/Pt Nanoplatform of Hydroxyl Radical and Oxygen Generation to Synergistically Promote Radiotherapy and MR Imaging of Glioblastoma.

Radiotherapy (RT) is currently recognized as an important treatment for glioblastoma (GBM), however, it is associated with several challenges. One of these challenges is the radioresistance caused by hypoxia, whereas the other is the low conversion efficiency of the strongly oxidized hydroxyl radical (•OH), which is produced by the decomposition of water due to high-energy X-ray radiation. These factors significantly limit the clinical effectiveness of radiotherapy. To address these limitations, we developed a highly stable and efficient nanoplatform (MnO2/Pt@BSA). Compared to MnO2@BSA, this platform demonstrates high stability, a high yield of oxygen (O2), enhanced production of •OH, and reduced clearance of •OH. The system exhibited increased O2 production in vitro and significantly improved oxygen production efficiency within 100 s at the Pt loading of 38.7%. Furthermore, compared with MnO2, the expression rate of hypoxia-inducible factor (HIF-1α) in glioma cells treated with MnO2/Pt decreased by half. Additionally, the system promotes •OH generation and consumes glutathione (GSH), thereby inhibiting the clearance of •OH and enhancing its therapeutic effect. Moreover, the degradation of the nanoplatform produces Mn2+, which serves as a magnetic resonance imaging (MRI) contrast agent with a T1-weighted enhancement effect at the tumor site. The nanoplatform exhibited excellent biocompatibility and performed multiple functions related to radiotherapy, with simpler components. In U87 tumor bearing mice model, we utilized MnO2/Pt nanocatalysis to enhance the therapeutic effect of radiotherapy on GBM. This approach represents a novel and effective strategy for enhancing radiotherapy in gliomas, thereby advancing the field of catalytic radiotherapy and glioma treatment.

Preparation of cysteine-functionalized graphene quantum dots – Zinc phthalocyanines supramolecular hybrid system and their sono-photochemical studies

Current PDT agents often suffer from low singlet oxygen quantum yields, photobleaching, and poor biocompatibility. To address these issues, we propose novel PDT agents that combine the synthesized phthalocyanines with cysteine-functionalized graphene quantum dots (cys-GQDs) for the first time. This combination aims to enhance singlet oxygen production and improve solubility in biological media. In this way, new zinc phthalocyanines with halogen substituents were synthesized for potential use in photodynamic therapy (PDT). Specifically, 2-Bromo-4-methylphenol zinc (II) phthalocyanine (2a) and 2-chloro-4-methylphenol zinc(II) phthalocyanine (2b) and their graphene quantum dots derivatives were synthesized and characterized. The photochemical, sonochemical, and sono-photochemical properties of these compounds were analyzed, focusing on their efficiency in singlet oxygen production. Our studies of the 2a@cys-GQDs and 2b@cys-GQDs conjugates demonstrated higher singlet oxygen yields, suggesting their enhanced potential for clinical applications.

Simultaneous production of singlet oxygen and superoxide anion by thiocarbonyl coumarin for photodynamic therapy

Photodynamic therapy (PDT) is a medical treatment that kills target cells through reactive oxygen species (ROS) generated by photosensitizers (PS) and surrounding oxygen under the stimulus of light. Despite of its popularity in cancer treatment, PDT relys on oxygen and therefore suffers from long response time and low efficiency under low-oxygen situations such as tumor hypoxia. Herein, to improve the usage of oxygen and increase ROS yield, we synthesized six potential PSs termed DC-O, DC-S, DC-BrO, DC-BrS, DC-IO, and DC-IS, by modifying coumarins with thiocarbonyl and bromine/iodine. We found that the thiocarbonyl group induces a significant bathochromic shift of the absorption spectra. In addition, the ROS production was significantly improved, likely because these PSs can simultaneously generate singlet oxygen (1O2) and superoxide anions (O2•−) through different pathways. Among these compounds, DC-BrS produces largest amount of ROS and exhibits strongest cytotoxicity towards cells, the survival rate of B16-F10 cells incubated with DC-BrS was only 20.7 % after irradiation at 460 nm for 10 min, indicating DC-BrS as a strong candidate for photodynamic therapy. Most importantly, this work provides an important direction for the design of PSs in the future.

Novel cyanide-containing porphyrins: Unleashing in vitro photodynamic therapy potential

Porphyrins, a class of four-pyrrole nitrogen heterocyclic compounds, have been used in photodynamic cancer therapy. In this study, three distinct pyridine cationic porphyrin photosensitizers were synthesized, each possessing unique side chains containing cyanide groups (H2-P1∼H2-P3). These photosensitizers were prepared using innovative synthetic methods. Subsequently, their theoretical photophysical properties were investigated using density functional theory (DFT). Notably, this research revealed that H2-P2 exhibits the smallest band gap (2.3548 eV) and the lowest energy gap (ΔEST = 0.67 eV). Simultaneously, it was confirmed that these three photosensitizers could indeed produce singlet oxygen under illumination using DPBF as a singlet oxygen probe. Additionally, TPP was uesed as a reference to calculate the singlet oxygen yield for all three compounds, with H2-P2 demonstrating the highest yield (ΦΔ = 0.74). The experimental results aligned with the theoretical predictions. The phototoxicity and dark toxicity of the three photosensitizers were further evaluated using the MTT test. Remarkably, H2-P2 exhibited the highest phototoxicity toward HepG2 cancer cells (IC50=41.8 nM), while the lowest dark toxicity toward HUVEC cells (IC50>10 μM). These findings were supported by additional experiments involving cell staining and measurement of reactive oxygen species.

Triad photosensitizers based on iodo-aza-Bodipy and naphthalenediimides (NDI) with broadband absorption: Study of resonance energy transfer and electron transfer

Two organic photosensitizers based on resonance energy transfer (A-1 and A-2) are prepared. Naphthalenediimides was used as intramolecular energy donor and iodo-aza-Bodipy was used as intramolecular energy acceptor/spin converter. A-1 (ε = 42,800 at 618 nm and ε = 59,600 at 674 nm) and A-2 (ε = 33,300 at 514 nm and ε = 68,300 at 674 nm) give the two strong absorption band and both of them show broadband absorption in visible region. The photophysical properties of the compounds were studied with steady state and time-resolved spectroscopy in detail. With steady state and time-resolved spectroscopy, we found that photoexcitation into the energy donor was followed by singlet energy transfer, then via the intersystem crossing (ISC) of the energy acceptor. By nanosecond time-resolved transient absorption spectroscopy and DFT calculation, triplet excited state is localized on the iodo-aza-Bodipy moiety. Quantum yield of singlet oxygen of A-1 and A-2 is 39.7 % and 40.9 %, respectively. Based on fluorescence lifetime quenching, the efficiency of intramolecular energy transfer is estimated to be 15.9 % and 27.7 % for A-1 and A-2. And PET is responsible for the relatively low efficiency, which is identified by the calculation of kcs/kFRET and the Gibbs free energy change (△G0cs). A-1 and A-2 were used for singlet oxygen (1O2) mediated photooxidation of 1,5-dihydroxylnaphthalene and the photosensitizing ability are more efficient than the triplet photosensitizers with the mono-chromophore photosensitizer.

Controlled Photooxidation via Singlet Oxygen Generation by Triplet Harvesting in a Heavy Atom Free Pure Organic Dithienylethene-Naphthalene Diimide.

Noninvasive control over the reversible generation of singlet oxygen (1O2) has found the enormous practical implications in the field of biomedical science. However, metal-free pure organic emitters, connected with a photoswitch, capable of generating "on-demand" 1O2 via triplet harvesting remain exceedingly rare; therefore, the utilization of these organic materials for the reversible control of singlet oxygen production remains at its infancy. Herein, an ambient triplet mediated emission in quinoline-dithienylethene (DTE)-core-substituted naphthalene diimide (cNDI) derivative is unveiled via delayed fluorescence. The quinoline-DTE-cNDI triad displayed enhanced photoswitching efficiency via double FRET mechanism. It was found to have direct utilization in controlled photosensitized organic transformations via efficient generation of singlet oxygen (yield ΦΔ~0.55 in DCM and 0.73 in methanol). The designed molecule exhibits a long-lived emission (τ∼1.1 μs) and very small singlet-triplet splitting (ΔEST) of 0.13 eV empowering it to display delayed fluorescence. Comprehensive steady state and time-resolved emission spectroscopy (TRES) analyses along with DFT calculations offer detailed understandings into the excited-state manifolds of organic compound and energy transfer (ET) pathways involved in 1O2 generation.

Turning Microenvironments of Porous Co─N─C Catalysts Enable Efficient Fenton-Like Reaction.

Metal nitrogen carbon (MNC)-based Fenton reactions leveraged with robust peroxymonosulfate (PMS) interaction effectively guarantee the elimination of refractory contaminants, yet the precise design of local microenvironment of MNC to couple with the multiple PMS activation pose major challenges. Herein, a porous Co single-atom catalyst (SAC) with nitrogen defects (Nv) (MCo/NC-6) is fabricated to initiate PMS oxidation reaction. The weaker but richer coordination between Co and N in the precursor facilitates the formation of Nv and porous structure during pyrolysis, achieving simultaneously electronic structure and spatial distribution tuning. Compared with the Co SAC (ZCo/NC-6), the optimized MCo/NC-6 significantly increase the bisphenol A (BPA) reactivity (k = 0.63 min-1), PMS utilization (78%), and singlet oxygen (1O2) yield (100%) by 15.3, 2.4, and 2.6 times, respectively. Experimental analyses and theoretical calculations reveal that the Co─N─C coordination regulated by both micro space and neighboring Nv is endowed high-mobility electrons, thus synergistically facilitating rapid generation and efficient utilization of 1O2. This work promises new opportunities for the design of local microenvironments-regulated SACs, and charts new trajectories in complex Fenton-like systems.

The (un)known issue with using rose bengal as a standard of singlet oxygen photoproduction.

Rose bengal (RB) is a widely used photosensitizer for determining quantum yields of singlet oxygen generation. While it is known to aggregate in polar environments at concentrations above 2 μM, the relationship between RB concentration and singlet oxygen photogeneration remains unclear. This study investigates the shift from monomeric to dimeric RB with increasing concentration and its impact on singlet oxygen generation in D2O-based solutions and DMPC liposomes. Absorbance maxima for RB were observed at 514 nm (dimer) and 549 nm (monomer), with ionic environments influencing aggregation rates. Singlet oxygen phosphorescence showed non-linear dependency above 2 μM, indicating the effects of aggregation. Results suggest that RB concentrations should be kept at 1 μM or lower in photochemical studies to avoid aggregation-related discrepancies in singlet oxygen yield determination. These findings highlight the importance of considering RB aggregation in photochemical research and medical applications.

Monomeric and Dimeric Boron (III) Subphthalocyanines Functionalized with 4-Hydroxy-Benzoic Acid as Potential Photosensitizers and Photocatalysts in Sulfoxidation.

Axial modification of boron (III) subphthalocyanine bromides with 4-hydroxy-benzoic acid successfully led to the formation of the macrocycles with anchored 4-carboxyphenoxy group [RsPcPHBA] (R=tBu, H) in the axial position and to a new dimer [sPcPHBAsPc] as minor product. Tri-tert-butyl and unsubstituted subphthalocyanines bearing benzoate ([tBusPcBA], [sPcBA]), phenoxy-group ([tBusPcOPh], [sPcOPh])) in the axial position, have been also investigated as well as control sPcs. All compounds were characterized by NMR, IR, UV-Vis and mass spectrometry. The electrochemical properties were studied using cyclic voltammetry (CV) and square wave voltammetry (SWV). Singlet oxygen generation was systematically measured for all synthesized [RsPcX] by kinetic method of chemical trap decomposition (DPBF) and by determination of phosphorescence of singlet oxygen (at 1270 nm). Axially modified subphthalocyanines exhibit high quantum yields of singlet oxygen (1O2) generation (0.47-0.62). The observed exceptional photostability in oxygen-saturated ethanol or toluene solutions and high 1O2 quantum yields allows to use [tBusPcPHBA] as photocatalysts of selective oxidative transformations of organic sulfides to sulfoxides. Loading the catalyst to 9.7 ⋅ 10-2 mol % made it possible to achieve complete conversion of the substrate (TON up to 1700).

Amino-rich silicon quantum dots as efficient activator with intrinsic chemiluminescence for the detection of peroxydisulfate

The specific detection of peroxydisulfate (S2O82−, PDS) is significant and challenging due to the rapid development of PDS-related technologies and their widespread application in multiple fields. However, traditional analytical methods are mainly based on their strong oxidizing properties, making it difficult to simultaneously achieve specific identification and high sensitivity for PDS detection in complex water environments. Here, we purposely prepared amino-rich SiQDs (N-SiQDs) as an effective catalyst and introduced H2O2 acts as a co-reactant for PDS activation and determination with strong intrinsic chemiluminescence (CL) emission. High yield of reactive active oxygen (mainly O2˙− and ˙OH) were generated during CL process, which trigger electron-hole annihilation between the N-SiQDs˙+ and N-SiQDs˙− accounted for extraordinary CL emission. On this basis, a new CL assay for PDS detection was fabricated with broad linear range of 5 × 10−7M-5 × 10−5 M and low detection limit (3.2 × 10−7 M). Due to the absence of SO4˙− involvement during CL emission, the sensing platform is sensitive enough, satisfactory selectivity and does not respond to transition-metal ions and inorganic anions that have interferences in the PDS CL sensors reported before. This work not only deepens insight into the mechanisms of nanomaterials assisted PDS activation but also provides a new perspective on the modified metal-free QDs CL probe for chemical species detection.

Specifically Targeting Capture and Photoinactivation of Viruses through Phosphatidylcholine-Ganglioside Vesicles with Photosensitizer.

Herein, we performed a simple virus capture and photoinactivation procedure using visible light on phosphatidylcholine vesicles. l-α-Phosphatidylcholine vesicles were enriched by viral receptors, GT1b gangliosides, and the nonpolar photosensitizer 5,10,15,20-tetraphenylporphyrin. These vesicles absorb in the blue region of visible light with a high quantum yield of antiviral singlet oxygen, O2 (1Δg). Through the successful incorporation of gangliosides into the structure of vesicles and the encapsulation of photosensitizers in their photoactive and monomeric state, the photogeneration of O2(1Δg) was achieved with high efficiency on demand; this process was triggered by light, and specifically targeting/inactivating viruses were captured on ganglioside receptors due to the short lifetime (3.3 μs) and diffusion pathway (approximately 100 nm) of O2(1Δg). Time-resolved and steady-state luminescence as well as absorption spectroscopy were used to monitor the photoactivity of the photosensitizer and the photogeneration of O2(1Δg) on the surface of the vesicles. The capture of model mouse polyomavirus and its inactivation were achieved using immunofluorescence methods, and loss of infectivity toward mouse fibroblast 3T6 cells was detected.

Pt/Pd dual-modified porphyrin metal-organic frameworks for NIR-II photothermal-enhanced photodynamic/catalytic therapy

Photodynamic therapy (PDT) and catalytic therapy were promising treatment modes, but tumor hypoxia and poor catalytic activity severely limited their efficacies. Herein, using a porphyrin metal–organic framework (PCN-224) as nanocarrier, a platinum/palladium (Pt/Pd) dual-modified PCN-224 nanoprobe (PCN-224-Pt@Pd) with strong peroxidase (POD)/catalase (CAT)-like activities was developed, achieving photothermal-promoted PDT/catalytic therapy. Compared with single ultrasmall Pt modifying, CAT-like activity of Pt/Pd dual-modifying increased oxygen concentration from 6.24 to 9.35 mg/L, which improved singlet oxygen (1O2) yield from 63.8 % to 82.9 %. Moreover, POD-like activity of Pt/Pd dual-modifying significantly accelerated hydroxyl radicals (·OH) generation. Importantly, PCN-224-Pt@Pd possessed near-infrared II (NIR-II) photothermal effect with a high efficiency (55.6 %), which further promoted ·OH production. Under combined therapy of PCN-224-Pt@Pd, the cell survival rate greatly reduced to 5.8 %, and the tumors were cured, suggesting NIR-II photothermal-enhanced PDT/catalytic therapy.

Synergy of pore confinement and co-catalytic effects in Peroxymonosulfate activation for persistent and selective removal of contaminants

The activation of peroxymonosulfate (PMS) through nanoconfinement and co-catalytic effects has demonstrated considerable promise in environmental remediation. Nevertheless, the attainment of persistent efficiency and specificity for pollutant degradation remains a formidable obstacle. Herein, we proposed a solvent-free molten approach to convert a mixture of zeolitic imidazolate frameworks (ZIFs) and MoS2 into 3D integrated cobalt-molybdenum bimetallic nitrogen-doped porous carbon foam with catalytic/co-catalytic performance (MC@NCF). The integrated materials exhibited exceptional efficiency in degrading contaminants based on the synergy of pore confinement and co-catalytic effects, achieving almost 100 % tetracycline degradation in 10 min with a k-value as high as 112.44 min−1·M−1, which was superior to the existing catalysts reported so far. The experimental findings revealed that the structural adjustment of MC@NCF significant accelerated the mass transfer through the formation of interfacial Mo-S/O-Co and Mo-N-Co/C bonds electron-tuning bridges between pore-confined micro-units, leading to the increased singlet oxygen (1O2) yield. Therefore, the MC@NCF exhibited more remarkable stability without interference from coexisting inorganic ions and cations, humic acid, and water matrices. Moreover, a flow-through nanoreactor was constructed and acquired efficient reactivity with negligible biotoxicity, and easy nanocatalyst recycling after continuous operation. The possible reactivity mechanism was identified by Frontier molecular orbital theory HOMO-LUMO, Fukui function, LC-MS, EPR, in-situ ATR-FTIR, and Raman analyses. Our results will guide integrated “catalytic/co-catalytic” nanoconfined MOF derivatives design to further enhance deep water purification technology.

A Highly Charged Positive Cage Causes Simultaneous Enhancement of Type‐II and O2‐Independent‐Type‐I Photodynamic Therapy via One‐/Two‐Photon Stimulation and Tumor Immunotherapy via PANoptosis and Ferroptosis

To solve the oxygen dependence problem of photodynamic therapy (PDT), it is critical to explore photosensitizers that do not rely on O2 molecule to generate reactive oxygen species (ROS). Herein, a stable cationic metal‐organic cage [Pd6(RuLoz3)8](BF4)28 (MOC‐88) that possesses high +28 charges is designed. The cage‐confined positive microenvironment enables efficient generation of hydroxyl radicals and improved yield of the singlet oxygen under one‐/two‐photon excitation, showing excellent performance to concurrently enhance Type‐II and O2‐independent‐Type‐I PDT. Moreover, the effective ROS production and robust lipid peroxidation trigger a series of signaling pathways (inflammasome, cyclic guanosine monophosphate–adenosine monophosphate synthase stimulator of interferon genes, and NF‐κB) to evoke PANoptosis and ferroptosis in tumor cells, enabling MOC‐88 to simultaneously cause the loss of cell membrane integrity, release a series of inflammatory cytokines and damage‐associated molecular patterns, stimulate the maturation and antigen presentation ability of dendritic cells, and ultimately activate T‐cell‐dependent adaptive immunity in vivo to inhibit tumor growth.

A Comprehensive Metallicity Analysis of J0332−3557: Establishing a z ∼ 4 Anchor for Direct Gas Metallicity and C/O Abundance Investigations

We provide one of the most comprehensive metallicity studies at z ∼ 4 by analyzing the UV/optical Hubble Space Telescope photometry and rest-frame Very Large Telescope (VLT)/FORS2 UV and VLT/XSHOOTER optical spectra of J0332−3557, a gravitationally lensed galaxy magnified by a factor of 20. With a 5σ detection of the auroral O iii] λ1666 line, we are able to derive a direct gas metallicity estimate for our target. We find Z gas =12+log(O/H)=8.26±0.06 , which is compatible with an increase of both the gas fraction and the outflow metal loading factor from z ∼ 0 to z ∼ 4. J0332−3557 is the most metal-rich individual galaxy at z ∼ 4 for which the C/O ratio has been measured. We derive a low log(C/O) = −1.02 ± 0.2, which suggests that J0332−3557 is in the early stages of interstellar medium carbon enrichment driven mostly by massive stars. The low C/O abundance also indicates that J0332−3557 is characterized by a low star formation efficiency, higher yields of oxygen, and longer burst duration. We find that EWC III]1906,9 is as low as ∼3 Å, and the main drivers of the low EWC III]1906,9 are the higher gas metallicity and the low C/O abundance. J0332−3557 is characterized by one diffuse and two more compact regions ∼1 kpc in size. We find that the carbon emission mostly originates in the compact knots. Our study on J0332−3557 serves as an anchor for studies investigating the evolution of metallicity and C/O abundance across different redshifts.

Synthesis and evaluation of novel mitochondria-targeted, water-soluble phenoxazine-porphyrins for efficient photodynamic therapy

In this study, we use cationic imidazole as the targeting group and phenoxazine as the electron donor, attaching phenoxazine to porphyrin via two different linking methods to synthesize two phenoxazine-porphyrin photosensitizers (PSs), P1 and P2, intended for photodynamic therapy (PDT) applications. Additionally, we synthesized a molecule, P3, that does not contain the cationic imidazole group, to serve as a control PS. We comprehensively evaluate the performance of P1 and P2 through steady-state and transient spectroscopy analysis, theoretical calculations, photooxidation experiments, and in vitro cell experiments. The results showed that P1 and P2 exhibit excellent water solubility, longer triplet state lifetimes (P1 at 200 μs, P2 at 170 μs), outstanding photostability, higher photooxidation rates and quantum yields of singlet oxygen (1O2). Notably, in the photooxidation experiment, P1's photooxidation rate is 1.1 times that of P2, and 1.5 times that of tetraphenyl zinc porphyrin (ZnTPP) without phenothiazine. This may be due to the larger Gibbs free energy difference between the singlet and triplet excited states in P1 (ΔGS-T of P1 is 0.87 eV, compared to 0.83 eV for P2), which results in a greater driving force for intersystem crossing (ISC) in P1 than in P2. The introduction of the cationic imidazole group in P1 and P2 significantly enhances water solubility and tumor cell uptake compared to P3, particularly showing higher intracellular accumulation and 1O2 generation capabilities in HepG2 tumor cells. Flow cytometry test results further confirmed the significant photocytotoxicity of P1 and P2, with a marked decrease in survival rates after light exposure, where the survival rate of P1 nanoparticles (NPs) dropped to 41.7 %, P2 NPs to 35.1 %, and P3 NPs to 75.0 %. The findings of this study provide crucial theoretical support for the design of new PSs.