Search NASA⌕ Search

SEARCH · Search NASA

Results for “oxygen generation”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Triplet-Induced Singlet Oxygen Photobleaches Near-Infrared Dye-Sensitized Upconversion Nanosystems

The rapid photobleaching of near-infrared (NIR) dye-sensitized upconversion nanosystems is one of the crucial problems that has blocked their technological applications. Uncovering the photophysical and photochemical pathways of NIR dyes would help to elucidate the photobleaching mechanism and thereby improve the photostability of the system. Here we investigate the triplet dynamics of NIR dyes and their interaction with triplet oxygen in the typically investigated IR806-sensitized upconversion nanoparticle (UCNP) nanosystem. Low-temperature fluorescence at 77 K provides direct proof of the generation of singlet oxygen ( 1 O 2 ) under 808 nm laser irradiation. Further, mass spectrometry indicates that all three double bonds in the structure of IR806 can be broken in the photochemical process. Coupling IR806 to the surface of UCNPs can accelerate its triplet dynamics, thus producing more 1 O 2 to photocleave IR806. Importantly, we find that the addition of β-carotene can scavenge the generated 1 O 2 , thereby providing a simple method to effectively inhibit photobleaching.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Preparation of 2D Polyaniline/MoO 3– x Superlattice Nanosheets via Intercalation-Induced Morphological Transformation for Efficient Chemodynamic Therapy

Organic intercalation of layered nanomaterials is an attractive strategy to fabricate organic/inorganic superlattices for a wide range of promising applications. However, the synthesis of 2D organic/inorganic superlattice nanosheets remains a big challenge. In this work, the preparation of 2D polyaniline/MoO 3–x (PANI/MoO 3–x ) superlattice nanosheets via intercalation-induced morphological transformation from MoO 3 nanobelts, as efficient Fenton-like reagents for chemodynamic therapy (CDT), is reported. Micrometer-long MoO 3 nanobelts are co-intercalated with Na + /H 2 O followed by the guest exchange with aniline monomer for in situ polymerization to obtain PANI/MoO 3–x nanosheets. Intriguingly, the PANI intercalation can induce the morphological transformation from long MoO 3 nanobelts to 2D PANI/MoO 3–x nanosheets along with the partial reduction of Mo 6+ to Mo 5+ , and generation of rich oxygen vacancies. More importantly, thanks to the PANI intercalation-induced activation, the PANI/MoO 3–x nanosheets exhibit excellent Fenton-like catalytic activity for generation of hydroxyl radical (·OH) by decomposing H 2 O 2 compared with the MoO 3 nanobelts. It is speculated that the good conductivity of PANI can facilitate electron transport during the Fenton-like reaction, thereby enhancing the efficiency of CDT. Thus, the polyvinylpyrrolidone-modified PANI/MoO 3–x nanosheets can function as Fenton-like reagents for highly efficient CDT to kill cancer cells and eradicate tumors.

2D materials↗
DOE OSTI2020

A reactive separation process for pre-combustion CO 2 capture employing oxygen-blown coal gasifier off-gas

In this paper, we present an experimental study of a reactive separation system, consisting of a membrane reactor (MR) and an adsorptive reactor (AR) operating in tandem, with the MR’s reject stream serving as the AR’s feed. We investigates the feasibility of applying this MR-AR system for high-purity H 2 production and simultaneous CO 2 capture via the water gas shift (WGS) reaction in the context of Integrated Gas Combined Cycle (IGCC) power generation employing oxygen-blown gasifier syngas from biomass and coal. We previously studied this MR-AR system for the IGCC process employing air-blown gasifier syngas, for which it demonstrated good performance, attaining high conversion exceeding equilibrium, producing ultra-pure H 2 for power generation, and a CO 2 stream ready for sequestration. In this study, we focus on oxygen-blown gasifier off-gas that contains no N 2 , with composition distinctly different from the air-blown gasifier syngas which has a large N 2 content. We employ a carbon molecular sieve membrane (CMSM), a commercial sour-shift WGS catalyst, and a hydrotalcite (HTC) adsorbent. We carried out experiments to determine membrane performance and to identify promising operating conditions in an IGCC-relevant environment. The CMSM proved robust during a long-term (~344 hr run) experimental run under high temperature and pressure maintaining a high He/N 2 selectivity (~170). Multi-cycle runs were carried out during which the MR-AR system displayed superior performance to that of a PBR, by producing a high purity H 2 product directly usable in power generation. Therefore, the findings from this study demonstrate the ability of the MR-AR system to operate stably for a broad range of gasifier off-gas compositions, and indicate its potential for integration into IGCC plants for power generation with CO 2 capture.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2020

Oxygen Atom Transfer as an Alternative Pathway for Oxygen–Oxygen Bond Formation

Fundamental understanding of catalytic mechanisms of water oxidation is a prerequisite for the design and development of efficient and rugged water oxidation catalysts. In this work, a detailed mechanistic study of the water oxidation mechanism of the [Ru II (npm)(4-pic) 2 (H 2 O)] 2+ (npm = 4-t-butyl-2,6-di(1',8'-naphthyrid-2'-yl)-pyridine, pic = 4-picoline) complex, [Ru II –OH 2 ] 2+ , reveals oxygen atom transfer from highly reactive ruthenium oxo intermediates to noncoordinating nitrogen atoms of the ligand as a novel route for oxygen evolution via storage of oxidizing equivalents as N-oxide groups on the ligand framework. Theoretical calculations show that the initial complex, [RuII–OH 2 ] 2+ , is transformed to a di-N-oxide [Ru II –OH 2 ,(-NO) 2 ] 2+ complex upon oxidation via facile OAT steps from Ru V =O species and that [Ru V =O,(-NO) 2 ] 3+ represents the most likely reactive species for the critical O–O bond formation. Furthermore, a new stepwise mechanism for oxygen evolution is introduced, which proceeds via coupling of Ru–O and N–O moieties producing a peroxide intermediate, [Ru V –OO–N,(-NO)] 3+ , and can compete with the water nucleophilic attack pathway for the oxygen evolution reaction. In this mechanism, a water molecule is oxidatively activated to an “oxygen atom” which is “stored” at a noncoordinating pyridine. Oxidative activation of a second water molecule, facilitated by coordination expansion of the intermediate N-oxide, generates the second oxygen atom required to produce a dioxygen molecule.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Chlamydomonas as a model for reactive oxygen species signaling and thiol redox regulation in the green lineage

While the maintenance of redox balance is important for all organisms, the energy balance in the chloroplast is particularly tightly linked to the overall cellular redox status in photosynthetic organisms. Excess light can cause overreduction of the photosynthetic electron transport chain, which, when unchecked, results in the generation of reactive oxygen species (ROS) that can oxidize cellular components including nucleic acids, proteins, and lipids (Li et al., 2009). A photosynthetic cell possesses multiple layers of defense against oxidative stress, such as antioxidant enzymes (Foyer and Noctor, 2005) and alternative electron transfer pathways (Alric and Johnson, 2017). At the same time, ROS can function as important signals that mediate responses to biotic and abiotic stresses (Apel and Hirt, 2004). Reversibly oxidizable small molecules and proteins can serve as ROS sinks and signals and are re-reduced by multiple mechanisms. For example, the ascorbate–glutathione (GSH) cycle is central in controlling ROS levels and regenerating/reducing oxidized cellular redox agents (Figure 1A; reviewed by Foyer and Noctor, 2011). The functions of many proteins can be regulated by the redox state of cysteine residues, such as the formation or reduction of disulfides by thioredoxins (TRX) (Buchanan, 1991) and glutaredoxins (Michelet et al., 2013b; Figure 1, B and C).

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Generation of a fluorescent short-lifetime oxygen nanosensor by coupling of an exciplex forming dye pair

Typical oxygen-sensitive dyes have lifetimes in the μs-ms regime for sensitive oxygen detection based on molecular quenching. Due to the long triplet-state lifetimes and poor quenching efficiency of these probes, it has been difficult to develop short lifetime probes. We have developed oxygen sensors using a short-lifetime dye (∼30–60 ns) that forms an anthracene-aniline exciplex, which is quenched by molecular oxygen through an excited-state charge transfer mechanism. To achieve measurements in aqueous systems, we have tethered the dyes together via a C3 alkyl linker to facilitate greater exciplex formation at low dye concentration (20 μg mL −1 ) and encapsulated the resulting compound into polymeric nanoparticles to form an aqueous-dispersible short-lifetime oxygen nanosensor. The sensors emit at 420 nm (unfolded dye) and 500 nm (exciplex), and the ratiometric Stern-Volmer Constant is 1.52 ± 0.02 L mol −1 , showing good sensitivity from 0 % to 40 % dissolved oxygen without the tradeoff of a long lifetime needed for direct molecular quenching. In this paper, we characterize this sensor for both lifetime-based measurements using time-correlated single-photon counting and ratiometric intensity-based measurements using the unfolded dye emission as an internal reference peak.

Biological and medical sciences↗
DOE OSTI2022

Photocatalytic Biocidal Coatings Featuring Zr 6 Ti 4 -Based Metal–Organic Frameworks

The world is currently suffering socially, economically, and politically from the recent pandemic outbreak due to the Coronavirus Disease 2019 (COVID-19), and those in hospitals, schools, and elderly nursing homes face enhanced threats. Healthcare textiles, such as masks and medical staff gowns, are susceptible to contamination of various pathogenic microorganisms, including bacteria and viruses. Here, metal–organic frameworks (MOFs) can potentially address these challenges due to their tunable reactivity and ability to be incorporated as porous coatings on textile materials. Here, we report how incorporating titanium into the zirconium-pyrene-based MOF NU-1000, denoted as NU-1012, generates a highly reactive biocidal photocatalyst. This MOF features a rare ligand migration phenomenon, and both the Ti/Zr center and the pyrene linker act synergistically as dual active centers and widen the absorption band for this material that results in enhanced reactive oxygen species (ROS) generation upon visible light irradiation. Additionally, we found the ligand migration process is generally applicable to other csq topology Zr-MOFs. Importantly, NU-1012 can be easily incorporated onto cotton textile cloths as a coating, and the resulting composite material demonstrates fast and potent biocidal activity against Gram-negative bacteria (E. coli), Gram-positive bacteria (S. epidermidis), and T7 bacteriophage virus with up to a 7-log (99.99999%) reduction within one hour under simulated daylight.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Fundamental Insights into Cathode Stability: Linking Compositional Tuning and Local Coordination in Complex Metal Oxides under Aqueous Transformations

Compositional tuning of complex metal oxides in Li-ion battery materials influences their performance as well as their end-of-life behavior, in particular, the tendency to release toxic metal cations in aqueous solution. We modeled ternary variants of a parent LiCoO 2 delafossite structure by varying the metal identity and relative amounts. This yielded ten model formulations of Li(A 4/6 B 1/6 C 1/6 )O 2 , where the material is enriched with the A metal and doped with B and C, with Ni, Mn, Co, Fe, Al, V, and Ti as constituent metals. To assess their stability in aqueous conditions, metal release energetics were calculated using a combination of Density Functional Theory calculations and thermodynamics. Metal release in ternary oxides is dictated by subtle variations in the coordination environment of the leaving group. To identify governing chemical features across diverse compositions with varying local coordination environments, we leverage random forest regression and descriptor importance analysis. A key result is that metal–oxygen orbital hybridization, quantified using a projected density-of-states-derived descriptor, H d/p , provides a physically grounded measure of interaction strength that governs metal release energetics. This refined perspective goes beyond conventional oxidation state considerations and offers more robust insights for materials science. Finally, we model defect surface-bound O 2 dimer formation as a proxy for reactive oxygen species (ROS) generation. The results show that Ni-rich compositions more readily stabilize spin-polarized O 2 dimers, corroborating experimental reports of an increased ROS-driven biological response. In conclusion, our results establish a compositional and electronic basis for metal release and surface oxygen reactivity that form a rationale for complex metal oxide design principles.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Plastoquinone redox status influences carboxysome integrity via a RpaA ‐ and reactive oxygen species‐dependent regulatory network

SUMMARY Carboxysomes are bacterial microcompartments that encapsulate Rubisco and are a core component of the cyanobacterial carbon concentration mechanism (CCM). While carboxysome number, size, and spatial organization vary in different environmental conditions (CO 2 , light availability, redox state, temperature, and light quality), the molecular mechanisms underlying this potentially adaptive process remain elusive. Herein, we observe that mutants of the circadian rhythm/metabolism factor, Regulator of Phycobilisome Association A (RpaA), exhibit a striking breakdown of carboxysomes under certain environmental conditions. We find that conditions leading to overreduction of the plastoquinone (PQ) pool (mixotrophic growth, high irradiance, or chemical inhibition of electron transfer from PQ to the cytochromeb 6 fcomplex) are accompanied by an elevated generation of reactive oxygen species (ROS) and correlate with the loss of carboxysome integrity. Carboxysome breakdown is reversed by environmental conditions or chemical inhibitors that prevent PQ overreduction and accompanying ROS generation. Taken together, our data support a novel link between the redox status of the PQ pool and carboxysome integrity. Our results have implications for the fundamental understanding of cyanobacterial energy‐balancing pathways and may indicate new research directions for understanding how the carboxysome is remodeled in response to changing environments.

Plant Sciences↗
DOE OSTI2021

Understanding the Photochemical Properties of Polythiophene Polyelectrolyte Soft Aggregates with Sodium Dodecyl Sulfate for Antimicrobial Activity

The threat of antibiotic-resistant bacteria is an ever-increasing problem in public health. In this report, we examine the photochemical properties with a proof-of-principle biocidal assay for a novel series of regio-regular imidazolium derivative poly-(3-hexylthiophene)/sodium dodecyl sulfate (P3HT-Im/SDS) materials from ultrafast sub-ps dynamics to μs generation of reactive oxygen species (ROS) and 30 min biocidal reactivity with Escherichia coli (E. coli). This broad series encompassing pure P3HT-Im to cationic, neutral, and anionic P3HT-Im/SDS materials are all interrogated by a variety of techniques to characterize the physical material structure, electronic structure, and antimicrobial activity. Our results show that SDS complexation with P3HT-Im results in aggregate materials with reduced ROS generation and light-induced anti-microbial activity. However, our characterization reveals that the presence of non-aggregated or lightly SDS-covered polymer segments is still capable of ROS generation. Full encapsulation of the P3HT-Im polymer completely deactivates the light killing pathway. High SDS concentrations, near and above critical micelle concentration, further deactivate all anti-microbial activity (light and dark) even though the P3HT-Im regains its electronic properties to generate ROS.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

GmMPK6 Positively Regulates Salt Tolerance through Induction of GmRbohI1 in Soybean

Salt stress is a critical environmental stress that impairs plant growth and development, especially in crop productivity; therefore, understanding the salt response in plants is the basis for their development of salt tolerance. Under salinity, soybean mitogen-activated protein kinase 6 (GmMPK6) is activated and positively regulates reactive oxygen species (ROS) generation. However, it is not yet elucidated how GmMPK6 regulates ROS generation and its role in salt tolerance. Here, we show that GmMPK6, solely activated in NaCl treatment, and gene expression of GmRbohI1 was not only reduced by MPK inhibitor SB202190 in NaCl treatment, but also increased in a GMKK1-expressing protoplast. Furthermore, SB202190 and the NADPH-oxidase inhibitor, diphenyleneiodonium chloride, increased susceptibility to salt stress. The expression of GmRD19A was induced by NaCl treatment, but this expression was compromised by SB202190. Consequently, we revealed that GmMPK6 induces ROS generation through the transcriptional regulation of GmRbohI1 and increases salt tolerance in soybean.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Electrochemical Corrosion and Catalysis Dynamics of Tin Oxide during Water Oxidation

Metal oxide corrosion severely limits anodic electrocatalysis, particularly at high potentials in acidic environments, where degradation pathways remain poorly defined. This study establishes explicit connections between corrosion and electrocatalysis on tin oxide during water oxidation by examining the roles of lattice defects, reactive oxygen species, interfacial pH variations, and speciation of corroded tin in acid. We first demonstrate the presence of structural defects such as oxygen vacancies and substoichiometric Sn(II) species by integrating electron paramagnetic resonance spectroscopy, ultraviolet photoelectron spectroscopy, and Mott–Schottky analysis. Kohn–Sham density functional theory calculations reveal that explicit water structures thermodynamically stabilize reaction intermediates and lower reaction overpotentials. Moreover, we propose that water dissociation leads to hydrogen-bonding networks formed by H* and OH* intermediates, which may span the entire catalyst surface and decrease the interfacial pH to drive corrosion. In contrast, the electrochemical generation of reactive oxygen species is shown to play a minor role in catalyst corrosion during water oxidation using inductively coupled plasma mass spectrometry coupled with selective chemical scavengers. Square-wave voltammetry combined with rotating ring-disk electrodes is used to reveal that under open-circuit conditions, only Sn(IV) cations chemically dissolve from tin oxide, while both Sn(IV) and Sn(II) species electrochemically corrode during water oxidation. Our results unveil a dynamic and complicated interplay between corrosive and catalytic pathways on metal oxide electrocatalysts: a decrease in interfacial pH due to water oxidation exacerbates Sn(II)/Sn(IV) corrosion. Subsequently, the electrochemical corrosion of Sn(II)/Sn(IV) facilitates product formation from lattice oxygen, while the redeposition of corroded Sn(II) as Sn(IV) can enable oxygen exchange with water. By elucidating the roles of defects and interfacial chemistry, this work provides a roadmap for engineering improved electrocatalysts that balance activity and stability, a critical step toward scalable and durable energy technologies.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Air resonance enhanced multiphoton ionization tagging velocimetry

Air resonance enhanced multiphoton ionization (REMPI) tagging velocimetry (ART) was demonstrated in quiescent and supersonic flows. The ART velocimetry method utilizes a wavelength tunable laser beam to resonantly ionize molecular oxygen in air and generate additional avalanche-type ionization of molecular nitrogen. The fluorescence emissions from the first negative and first positive bands of molecular nitrogen are, thus, produced and used for flow tagging. Detailed characterization of ART was conducted, including the effects of oxygen resonance to fluoresce nitrogen, nitrogen fluorescence spectrum, laser energy deposition into quiescent flow showing minimal perturbations in flow, fluorescence lifetime study at various pressures, and line tagging without breakdown. Pointwise velocity measurements within a supersonic flow from a nominal Mach 1.5 nozzle have been conducted and characterized.

Clark, Aleksander↗
DOE OSTI2020

Enhanced visible-light-assisted peroxymonosulfate activation on cobalt-doped mesoporous iron oxide for orange II degradation

Sulfate radical-based advanced oxidation processes (SR-AOP) attracted a lot of attention due to their capability and adaptability in wastewater treatment. Although heterogeneous cobalt-based catalysts have been extensively studied and have emerged superior for peroxymonosulfate (PMS) activation, leaching of cobalt is still a major concern. Herein, we report a photo-assisted PMS activation approach using cobalt doped mesoporous iron oxide with exceptional activity and stability up to 7 cycles with very low cobalt leaching (0.5 ppm). The highest activity was obtained by 1 mol % cobalt doped mesoporous iron oxide. Orange II dye was completely degraded by the reactive oxygen species (ROS) generated under visible light irradiation within 1 min. ROS were evaluated using two distinct techniques (Fluorescence probes and Electron Paramagnetic Resonance (EPR). ROS quenching experiments were also used to highlight the dominant pathway. This study correlates the structural and electronic changes induced with cobalt doping to the exceptional activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Kinetic studies of excited singlet oxygen atom O( 1 D) reactions with ethanol

In this work, themultichannel reaction of excited singlet oxygen atom with ethanol, O( 1 D) + C 2 H 5 OH (1), was studied in a photolysis flow reactor coupled with mid-infrared Faraday rotation spectroscopy (FRS) and UV-IR direct absorption spectroscopy (DAS) at 297 K with reactor pressures of 60, 120, and 150 Torr (bath He). The excited singlet oxygen atom was generated through the photolysis of O 3 at 266 nm. The photon flux and O( 1 D) concentrations were determined by in situ actinometry based on O 3 depletion. Temporal profiles of OH and H 2 O were monitored via DAS signals at ca. 3568.62 and 3568.29 cm –1 , while temporal profiles of HO 2 were measured via FRS signals at ca. 1396.90 cm –1 . The branching ratios of the target reaction (1) were determined by fitting temporal profiles to simulations from an in-house reaction mechanism. Two major reaction channels were identified as CH 3 CHOH + OH and CH 3 O + CH 2 OH, and their branching ratios were determined as 0.46 ± 0.12 and 0.42 ± 0.11, respectively. A specific HO 2 + RO 2 reaction between HO 2 and O 2 CH 2 CH 2 OH (β-RO 2 ) at the low-temperature range is estimated in this work as HO 2 + O 2 CH 2 CH 2 OH → products with a rate constant of 7 × 10 –12 cm 3 molecule –1 s –1 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Marine algae growth and carbon capture augmentation by antioxidant nanozymes

Large scale commercial cultivation of microalgae year-round is limited by seasonal stress conditions. The rapid growth and high CO 2 capture of the marine microalga Picochlorum celeri is largely inhibited under winter stress conditions of low temperature and high light. Herein, we demonstrated a nanotechnology approach to enhance the biomass productivity and CO 2 capture of P. celeri under abiotic stress by interfacing with antioxidant cerium oxide nanozymes (nanoceria). Antioxidant nanoceria catalytically scavenged reactive oxygen species (ROS) generated under stress conditions, reducing damage to the microalgae photosynthetic machinery in chloroplasts. Negatively charged poly-acrylic acid-coated nanoceria (PNC, 10 μM) were biocompatible in microalgae cells and colocalized with chloroplasts. In contrast, positively charged aminated nanoceria (ANC) resulted in microalgae aggregation (>50 μM) and were toxic at all concentrations tested (≥10 μM). PNC reduction of ROS levels in microalgae (78%) and superoxide levels (26%), enhanced microalgae growth (65%), photosynthetic performance (130%), and CO 2 uptake rate (380%) under low-temperature stress (15 °C) and high light (500 μmol/m 2 /s PAR) stress relative to controls without nanoceria. Nanoceria augmentation of microalgae provides a rapid and facile technology to increase algae CO 2 capture and biomass under stress conditions.

09 BIOMASS FUELS↗