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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.

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At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Tuning the fluid wetting dynamics on gold microstructures using photoactive compounds

This work demonstrates how photoactive compounds can be used to tune the surface chemistry, surface free energy, and the wetting velocity of fluids on Spiropyran functionalized surfaces with different surface microstructures. Evidence of this photowetting effect is based on data showing: (1) the cyclic changes in the static, advancing, and receding contact angles $\theta$ CA for multiple UV$\rightleftarrows$vis photoswitching cycles with both smooth and microstructured surfaces and (2) the changes in the fluid wicking velocity (via UV$\rightleftarrows$vis photoswitching) on different Spiropyran functionalized hemiwicking surfaces. X-ray photoelectron spectroscopy is used to determine the efficiency of photoswitching caused by the quality of the Spiropyran functionalization. Reversible photoisomerization of Spiropyran generates a gradient in surface free energy, resulting in a similar change in contact angle ($\theta$ CA ) in the photoswitchable surfaces. In conclusion, by incorporating these changes into the Owens-Wendt and Van Oss surface energy models, the energy of smooth Au surfaces can also be predicted for both UV and visible light irradiations, where reversible contact angle variations of $\Delta$$\theta$ CA ≈ 5–10° are achieved with both water and water-ethanol mixtures due to the conversion of SP to merocyanine, which corresponds to a total free energy change of ~13% on the photoswitchable surface.

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

Impact of wildfires on regional ozone and PM 2.5 : Considering the light absorption of Brown carbon

The influence of wildfire brown carbon (BrC) in moderating the formation of O 3 and fine particulate matter (PM 2.5 ) due to its absorption of ultraviolet (UV) radiation is, for the first time, investigated using a modified community multiscale air quality (CMAQ) model. The wavelength-dependent imaginary refractive index of the organic carbon from wildfires, which are needed by the CMAQ model for its inline photolysis rate calculation, are generated experimentally from wood burning aerosols from a combustion chamber. On high emission days of the Bastrop County Complex fire in Texas in early September 2011, BrC UV absorption reduces the daytime average NO 2 photolysis rate by up to 38% in the core region of the wildfire plume compared to the base scenario that does not consider BrC absorption. Consequently, O 3 production in the smoke plume is suppressed compared to the base scenario due to reduced HO x radical concentrations. Further, in the core region, the predicted O 3 increase due to wildfire reaches as high as 47–123 ppb without considering BrC absorption, the predicted increase of O 3 is 5–15% lower when BrC absorption is considered. Similarly, considering the BrC UV absorption leads to approximately 1% (or ~2–3 µgm -3 ) lower estimation of the wildfire emissions’ impact on total PM 2.5 . This change is small because secondary aerosols, which are the components affected by BrC absorption, only account for a small fraction of the total PM 2.5 in wildfire impacted regions in this study. In addition, our study shows that assumptions about aerosol mixing state (core-shell vs. homogeneous) in the inline photolysis rate calculation would not significantly affect out assessment of the impact of wildfire BrC light absorption on O 3 and PM 2.5 .

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

In situ investigation of conducting interface formation in $\mathrm{LaAlO_3}$/$\mathrm{SrTiO_3}$ heterostructure

The high-mobility conducting interface (CI) between LaAlO 3 (LAO) and SrTiO 3 (STO) has revealed many fascinating phenomena, including exotic magnetism and superconductivity. But, the formation mechanism of the CI has not been conclusively explained. Here, using in situ angle-resolved photoemission spectroscopy, we elucidated the mechanisms for the CI formation. In as-grown samples, we observed a built-in potential (V bi ) proportional to the polar LAO thickness starting from the first unit cell (UC) with CI formation appearing above 3 UCs. However, we found that the V bi is removed by synchrotron ultraviolet (UV)-irradiation; The built-in potential is recovered by oxygen gas (O 2 (g))-exposure. Furthermore, after UV-irradiation, the CI appears even below 3UC of LAO. Here, our results demonstrate not only the V bi -driven CI formation in as-grown LAO/STO, but also a new route to control of the interface state by UV lithographic patterning or other surface modification.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Analysis of persistent contaminants and personal care products by dispersive liquid-liquid microextraction using hydrophobic magnetic deep eutectic solvents

Here, in this work, hydrophobic magnetic deep eutectic solvents (HMDESs) were used in the development of a simple and rapid dispersive liquid-liquid microextraction (DLLME) approach coupled to high performance liquid chromatography with UV detection (HPLC-UV) for the determination of ten organic contaminants including five polycyclic aromatic hydrocarbons, four UV filters, and a pesticide from water at trace levels. The HMDESs were prepared by mixing a hydrogen bond acceptor, metal halide salt, and hydrogen bond donor in suitable molar ratios. Two HMDESs, 2 tetraoctylammonium bromide ([N 8888 + ][Br - ]): cobalt chloride (CoCl 2 ): 4 octanoic acid (OA) and 3 trioctylphosphine oxide (TOPO): neodymium chloride (NdCl 3 ): 3 OA, offered the highest analyte extraction efficiency overall and were chosen as suitable solvents for validation of the microextraction method. Under optimized extraction conditions, the method required 30 µL of HMDES as extraction solvent, acetone (87.5 µL) as disperser solvent, a NaCl concentration of 30% (w/v), and an extraction time of 120 s at 20°C. Enrichment factors of the analytes ranged from 44.6 for 3-(4-methylbenzylindene) camphor to 66.0 for 2-ethylhexyl-4-(dimethyl)aminobenzoate. The method provided low limits of detection (LODs) ranging from 0.5 to 4.5 µg L -1 , and acceptable precision, with RSD values lower than 9.6%. Furthermore, the validated method was successfully applied for tap and lake water analysis, resulting in relative recoveries of spiked samples ranging between 94.7 and 119.2%.

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

Origin of the isotopic composition of natural perchlorate: Experimental results for the impact of reaction pathway and initial ClO x reactant

Natural perchlorate (ClO 4 - ) exists in many places on Earth, in lunar regolith, meteorites, and on the surface of Mars. Terrestrial natural ClO 4 - has widely variable Cl and O stable isotopic compositions (δ 37 Cl, δ 18 O, Δ 17 O). The δ 18 O and Δ 17 O values of ClO 4 - from the most hyper-arid locations co-vary. ClO 4 - from less arid areas has relatively little 17 O excess and poor Δ 17 O-δ 18 O correlation. ClO 4 - from the Atacama Desert has unusually low δ 37 Cl (<-10‰) and exhibits a positive correlation between δ 37 Cl and δ 18 O, while the δ 37 Cl of ClO 4 - from all other locations varies between -5 and +7‰ with no δ 37 Cl-δ 18 O covariation. To evaluate the impact of different precursors (ClO x ) and reaction pathways on the isotopic composition of ClO 4 - , we measured the isotopic composition of ClO 4 - produced in the laboratory by UV or O 3 mediated aqueous oxidation of Cl-, OCl-, ClO2-, and ClO2° as well as O 3 mediated oxidation of dry NaCl. ClO x oxidation in aqueous or dry systems enriched in O 3 produced ClO 4 - with Δ 17 O values that generally increased with the number of O atoms required and included evidence that the site-specific 17 O anomaly in O 3 was preferentially transferred to ClO 4 - . Based on the inferred number of O atoms sourced from O 3 , and known Cl and O reaction pathways, it appears that ClO 2 ° and ClO 3 * were required intermediates in the production of ClO 4 - in the O 3 experiments. ClO x aqueous oxidation by UV irradiation produced ClO 4 - with a large range of δ 18 O values and little or no 17 O anomaly. ClO 3 - was produced to a much greater extent than ClO 4 - in all experiments except dry oxidation of NaCl by O 3 . The isotopic composition of ClO 3 - was distinct from that of ClO 4 - produced from the same initial reactants. Combined results of O 3 and UV mediated reactions largely bracketed the range of natural ClO 4 - δ 18 O and Δ 17 O values as well as δ 37 Cl values of non-Atacama natural samples, but no conditions produced the low δ 37 Cl values of Atacama ClO 4 - . Finally, our results indicate that variation in production mechanisms, possibly combined with isotopically variable precursors, could be responsible for much of the observed isotopic variation in natural ClO 4 - and ClO 3 - .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Delivering laser performance conditions to enable fusion ignition, and beyond at the National Ignition Facility

On December 5th, 2022, controlled fusion ignition was demonstrated for the first time at the National Ignition Facility (NIF), a major achievement in the field of Inertial Confinement Fusion (ICF) requiring a multi-decadal effort involving broad national and international collaborations. To drive the fusion ignition reaction with the compressed fuel capsule, that yielded 3.15 MJ of nuclear energy [1], the NIF laser delivered a high-precision pulse shape with 2.05 MJ of ultra-violet (UV) laser energy and a peak power of 440 TW. This laser energy was an increase of ~8 % compared to that delivered on the previous “threshold of ignition” record yield experiment (1.37 MJ of yield for 1.89 MJ of laser energy) on August 8th, 2021. Here we explain how the results of our extensive research in laser technology and UV optics damage mitigation led to major improvements in the NIF laser, enabling this energy increase along with additional accuracy, precision, and power balance enhancements. Furthermore, we will discuss on-going efforts that have enabled operations at 2.2 MJ of UV energy as well as potential new initiatives to push the laser performance –accuracy and delivered energy– to even higher levels in the future as previously demonstrated on a small subset of NIF beams.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Effects of carbon treating on piperazine oxidation in pilot plant testing of PZAS™

From February to June 2019, a pilot plant campaign was run for 2100 h at the National Carbon Capture Center (NCCC) using moderately degraded 5 m PZ with simulated flue gas equivalent to a 0.64 MW natural gas combined cycle. Piperazine with the Advanced Stripper™ (PZAS™) and a baghouse were used, and N 2 sparging was applied at the bottom of the absorber. A carbon bed was activated and showed beneficial effects in removing degradation products and reducing the oxidation rate. The cumulative NH 3 production was 180 mmol/k, indicating a PZ oxidation rate of 0.07 mmol/kg/h (0.3 kg PZ/tonne of CO 2 ). The total formate before turning on the carbon bed was 41 mmol/kg, and the total Fe was 0.1 mmol/kg. Carbon treating reduced NH3 production from 0.1 mmol/kg/h to 0.056 mmol/kg/h after 400 h of operation, reduced the UV-Vis absorbance of the samples at 320 nm, and caused a decrease of dissolved Cr. Bench-scale experiments were performed using the NCCC solvent and the same type of carbon. In bench-scale experiments, the UV-Vis absorbance and the concentration of Fe, Mn, and Cr all decreased. Finally, a linear equilibrium relationship was observed between the UV-Vis absorbance and the carbon loading.

03 NATURAL GAS↗
DOE OSTI2021

Striking luminescence phenomena of carbon dots and their applications as a double ratiometric fluorescence probes for H2S detection

Here, we report some new observations on the luminescence of carbon dots (CDs) that are passivated with polyethylene glycol, and explored them, for the first time, as highly sensitive H2S detection probe. The as-prepared CDs have an ultraviolet (UV) emission at 350 nm and a green emission at 540 nm when excited at 270 nm, but they have only a green emission at 523 nm when excited at 365 nm. As Na2S is added to the CDs, the UV emission decreases gradually, while the green emission increases slightly, and interestingly a new emission appears at 455 nm is increased linearly in intensity with the increase of Na2S concentration. The blue emission at 455 nm is from the intrinsic core of CDs, and the green emissions at 540 or 523 nm are from their surface states, while the UV emission at 350 nm is from the anchored PEG. Both the emission intensity ratios of F-450/F-350 and F-455/F-523 show an excellent linear relationship with the Na2S concentration in the range of 0-800 mu M, and the detection limit estimated from both of them is approximately 7.0 nM, indicating our method is the most sensitive H2S CDs based detection method reported thus far. Furthermore, the detection was tested successfully for H2S imaging in live cells. We propose that the interactions of H2S with the CDs and the anchored ligands, as well as the energy transfer between the ligands and the CDs, are responsible for the luminescence responses for H2S detection. Our studies enrich the world of carbon dots with plenty of potential applications. (C) 2020 Elsevier Ltd. All rights reserved.

Bioimaging↗
DOE OSTI2020

Characterizing photovoltaic backsheet adhesion degradation using the wedge and single cantilever beam tests, Part II: Accelerated tests

Photovoltaic (PV) backsheets provide critical moisture, mechanical, and electrical insulation to the backside of PV modules, but their continued functionality depends upon their ability to remain well adhered over years of harsh environmental exposure. A study of adhesive strength was conducted on several PV backsheet types exposed to indoor accelerated weathering. Two adhesion tests – the wedge test and single cantilever beam test – were used to measure adhesion energy in four backsheets: two with fluoropolymer-based outer (airside) layers – polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF) – and two with non-fluoropolymer-based outer layers–polyamide (PA) and polyethylene terephthalate (PET). The effects of changes in temperature, ultraviolet (UV) irradiance, relative humidity, and a periodic water spray were studied. The PET-, PVF- and PVDF-based backsheets all showed instances of debonding in an adhesive layer, which is commonly reported. Furthermore, for the PA-, PET-, and PVDF-based backsheets, adhesion energy dropped fairly rapidly with exposure, reaching very low levels by 4000 h. The PVF-based backsheet was relatively robust to weathering. Pull-off of an outer chalking layer in the PA- and PET-based backsheets suggested a sensitivity to UV. Adhesion in these two backsheets was also highly sensitive to changes in moisture level. Changes in UV irradiance and temperature did not show a statistically significant effect on adhesion loss for the exposure levels used. The present work is part of a two-part adhesion study on both field-weathered and indoor-exposed backsheets, and forms a basis for understanding adhesion degradation across a variety of backsheet types and degradation factors.

14 SOLAR ENERGY↗
DOE OSTI2022

Rapid photooxidation and removal of As(III) from drinking water using Fe-Mn composite oxide

Fe-Mn composite oxide (FMO) is widely applied to the oxidation and removal of As(III) from water. However, As(III) can directly reduce manganese oxides, decreasing the oxidation capacity or reusability and thereby greatly limiting the applicability of FMO. Here, the oxidation capacity and reusability of FMO for As(III) were efficiently improved by light radiation, and the effect of typical coexisting ions (SO 4 2– and Ca 2+ ) on the removal of As(III) was also studied. O 2 •– produced from excited manganese oxide and ligand-to-metal charge transfer in iron oxide-As(III) complex enhanced As(III) oxidation and removal under light radiation. At an initial As(III) concentration of 1000 μg L –1 , the total As concentration was respectively decreased to 11.5, 1.5 and 4.4 μg L –1 under darkness, UV light and sunlight at 180 min, and could be reduced to below the guideline limitation of drinking water (10 μg L –1 ) within 40 and 60 min under UV light and sunlight, respectively. SO 4 2– exhibited negligible effect on As removal efficiency because FMO had obviously lower adsorption capacity and selectivity for SO 4 2– than for As(V). The adsorption of coexisting Ca 2+ on manganese oxide decreased the negative charge on the FMO surface, thereby improving As(III) adsorption and oxidation. FMO exhibited excellent reusability, and a total As removal efficiency of 99.1% was still maintained after five cycles of an adsorption-desorption process under UV light. Finally, this work elucidates the photochemical oxidation and removal mechanism of FMO for As(III), and proposes a low-cost and efficient method for the detoxification of As(III)-contaminated drinking water.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Smaller Is Better: The Case for Lower-Order Iodoplumbate Species Dominating MAPbI 3 /Dimethylformamide Solutions

Here, using complementary experimental measurements and computational predictions of spectroscopic measurements (EXAFS, XANES, and UV–vis), we have determined the identity of the most stable iodoplumbate species in dilute lead halide perovskite precursor solutions. We have determined which species are most likely to be thermodynamically stable compared to others that are unstable or metastable. Condensed phase ab initio models were constructed, and the resulting ensembles were used to directly compare the computed signals to the experimental results of the EXAFS, XANES, and UV–vis spectra of PbI 2 :MAI in DMF. The results of this study suggest that only Pb 2+ , PbI + , and PbI 2 are dominant in the dilute lead perovskite precursor solutions as thermodynamically stable entities. Our interpretation of the relative stability of iodoplumbate species in solution, based on an analysis of EXAFS and XANES spectra, provides critically important new insight into the species most likely to be responsible for crystal nucleation and growth in these materials. This insight will have a significant consequence on the broad scientific community and will necessitate the reinterpretation of peaks in the UV–vis spectra of lead halide perovskite precursor solutions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Synthesis, Redox, and Spectroscopic Properties of Pd(II) 10,10-Dimethylisocorrole Complexes Prepared via Bromination of Dimethylbiladiene Oligotetrapyrroles

Two brominated 10,10-dimethylisocorrole (10-DMIC) derivatives containing Pd(II) centers have been prepared and characterized. These compounds were prepared via bromination of 10,10-dimethylbiladiene-based oligotetrapyrroles. Bromination of free base 10,10-dimethylbiladiene (DMBil1) followed by metalation with Pd(OAc) 2 , as well as bromination of the corresponding Pd(II) dimethylbiladiene complex (Pd[DMBil1]) provide routes to Pd(II) hexabromo-10,10-dimethyl-5,15-bis(pentafluorophenyl)-isocorrole (Pd[10-DMIC-Br 6 ]) and Pd(II) octabromo-10,10-dimethyl-5,15-bis(pentafluorophenyl)-isocorrole (Pd[10-DMIC-Br 8 ]). The solid-state structures of the two brominated isocorrole complexes are presented, as is that for a new decabrominated dimethylbiladiene derivative (DMBil-Br 10 ). The electronic and spectroscopic properties of the brominated biladiene and isocorrole derivatives were probed using a combination of voltammetric methods and steady-state UV–vis absorption and emission experiments. Data obtained from these experiments allow the properties of the brominated biladiene and isocorrole derivatives to be compared to previously studied biladiene derivatives (i.e., DMBil1 and Pd[DMBil1]). CV and DPV experiments demonstrate that Pd[10-DMIC-Br 6 ] and Pd[10-DMIC-Br 8 ] support well-behaved multielectron redox chemistry, similar to that which has been observed for other nonaromatic tetrapyrroles containing sp 3 -hybridized meso-carbons. Here, spectroscopic experiments reveal that bromination of the dimethylbiladiene core shifts this system’s UV–vis absorption profile to lower energy and that the dimethylisocorrole complexes support panchromatic absorption profiles that extend across the UV–vis and into the near-IR region. Photosensitization experiments demonstrate that unlike previously studied Pd(II) biladiene constructs, DMBil-Br 10 , Pd[10-DMIC-Br 6 ], and Pd[10-DMIC-Br 8 ] support limited triplet excited state chemistry with O 2 , indicating that the novel nonaromatic tetrapyrrole derivatives described in this work may be best suited for applications other than singlet oxygen sensitization.

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

Photochemistry of Hypervalent Iodoazide Derivatives

The photochemical properties and reaction mechanisms of a series of hypervalent iodoazide compounds (R–IN3) were investigated, with substituents (−CH 3 , −H, −CF 3 ) tuning the electronic density of the phenyl ring. With the help of UV irradiation, ultrafast time-resolved spectroscopy, and density functional theory (DFT) calculations, we elucidated the mechanisms of azide radical (N 3 • ) release and its subsequent reactivity. UV–vis spectroscopy reveals that the photoconversion rates follow the trend CH3 > H > CF3, aligning with DFT-calculated ΔG values for ring-opening transitions. Homolytic cleavage of the I–N bond is identified as the dominant pathway for N3• generation upon UV irradiation, occurring within 400 fs. The released azide radicals react with the solvent molecules, while the iodo radical R–I C • fragments undergo a thermodynamically uphill lactone ring-opening (RO) reaction and subsequent hydrogen atom abstraction from the solvent to form carboxylic acids R–I–COOH, as validated by NMR and IR spectroscopy. The study also highlights the role of substituents in influencing reaction kinetics and intermediate stability, with electron-donating groups accelerating the release of the N 3 • species. This work bridges experimental observations with computational predictions, offering a foundation for future advancements in azide-based reactions and materials.

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

Bismuth-Polyoxocation Coordination Networks: Controlling Nuclearity and Dimension-Dependent Photocatalysis

Bismuth-oxocluster nodes for metal–organic frameworks (MOFs) and coordination networks/polymers are less prolific than other families featuring zinc, zirconium, titanium, lanthanides, etc. However, Bi 3+ is non-toxic, it readily forms polyoxocations, and its oxides are exploited in photocatalysis. This family of compounds provides opportunity in medicinal and energy applications. Here, we show that Bi node nuclearity depends on solvent polarity, leading to a family of Bi x -sulfonate/carboxylate coordination networks with x = 1–38. Larger nuclearity-node networks were obtained from polar and strongly coordinating solvents, and we attribute the solvent’s ability to stabilize larger species in solution. Here, the strong role of the solvent and the lesser role of the linker in defining node topologies differ from other MOF syntheses, and this is due to the Bi 3+ intrinsic lone pair that leads to weak node–linker interactions. We describe this family by single-crystal X-ray diffraction (eleven structures), obtained in pure forms and high yields. Ditopic linkers include NDS (1,5-naphthalenedisulfonate), DDBS (2,2'-[biphenyl-4,4'-diylchethane-2,1-diyl] dibenzenesulphonate), and NH 2 -benzendicarboxylate (BDC). While the BDC and NDS linkers yield more open-framework topologies that resemble those obtained by carboxylate linkers, topologies with DDBS linkers appear to be in part driven by association between DDBS molecules. An in situ small-angle X-ray scattering study of Bi 38 -DDBS reveals stepwise formation, including Bi 38 -assembly, pre-organization in solution, followed by crystallization, confirming the less important role of the linker. We demonstrate photocatalytic hydrogen (H 2 ) generation with select members of the synthesized materials without the benefit of a co-catalyst. Band gap determination from X-ray photoelectron spectroscopy (XPS) and UV–vis data suggest the DDBS linker effectively absorbs in the visible range with ligand-to-Bi-node charge transfer. In addition, materials containing more Bi (larger Bi 38 -nodes or Bi 6 inorganic chains) exhibit strong UV absorption, also contributing to effective photocatalysis by a different mechanism. All tested materials became black with extensive UV–vis exposure, and XPS, transmission electron microscopy, and X-ray scattering of the black Bi 38 -framework suggest that Bi o is formed in situ, without phase segregation. This evolution leads to enhanced photocatalytic performance, perhaps due to increased light absorption.

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

Structure–Activity Relationships for Ethanol Dehydrogenation to Acetaldehyde by Silica-Supported Zinc Oxide Catalysts

Silica-supported ZnO efficiently catalyzes the nonoxidative dehydrogenation of ethanol to acetaldehyde, which is relevant for production of 1,3-butadiene from bioethanol. Characterization with in situ spectroscopies under dehydrated conditions (high sensitivity-low energy ion scattering (HS-LEIS), diffuse reflectance (DR) UV–vis, X-ray absorption spectroscopy (XAS), diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), inelastic neutron scattering (INS), and UV Raman), and ammonia adsorption probed by temperature-programmed desorption followed by DRIFTS and mass spectrometry (DRIFTS-MS NH 3 -TPD), and DFT calculations revealed that the supported ZnO x phase was present as isolated surface ZnO x sites on SiO 2 , with the vast majority coordinated by two siloxane bonds and one silicon atom with two nonbridging oxygens ((≡SiO) 2 Zn 2+ O 2 Si=), anchored at 4-, 5-, and 6-membered siloxane rings. A minor fraction of surface ZnO x sites possessed Lewis acidity, and even fewer sites possessed a Bro̷nsted acidic Zn(OH) + Si moiety. Ethanol temperature-programmed surface reaction-mass spectrometry (TPSR-MS) with various oxidative or ethanol reaction pretreatments indicated that only sites with Lewis and Bro̷nsted acidic character (Zn(OH) + Si) were active for ethanol dehydrogenation, while the majority surface (≡SiO) 2 Zn 2+ O 2 Si= sites were inactive. Greater heterogeneity among all surface ZnO x sites, as assessed by in situ DR UV–vis spectroscopy, was associated with a greater number of ZnO x sites that were active for ethanol dehydrogenation as well as lower enthalpic barriers for acetaldehyde production among the most active surface ZnO x sites. Turnover frequencies and the apparent activation energy for ethanol dehydrogenation were determined from steady-state kinetics. Together, these findings suggested that anchoring inactive surface (≡SiO) 2 Zn 2+ O 2 Si= sites on the silica support caused a greater number of active surface ZnO x sites to adopt a more strained configuration, promoting ethanol dehydrogenation catalysis. Pretreatments and catalysts that promoted desorption of ethanol during TPSR, taken as a marker of surface dehydroxylation, were associated with an increased number of the most active surface (Zn(OH) + Si) sites. Such findings suggested that inactive surface ZnO x sites were activated for ethanol dehydrogenation by dehydroxylation of the support and/or decreased coordination to hemilabile siloxane ligands.

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

Multiphase Processing of the Water-Soluble and Insoluble Phases of Biomass Burning Organic Aerosol

Biomass burning is one of the most significant sources of organic aerosol in the atmosphere. Biomass burning organic aerosol (BBOA) has been observed to undergo liquid– liquid phase separation (LLPS) to give core–shell morphology with the hydrophobic phase encapsulating the hydrophilic phase, potentially impacting the evolution of light-absorbing components, i.e., brown carbon (BrC), through multiphase processes. Here, we demonstrate how multiphase processing differs between the watersoluble (i.e., hydrophilic) and insoluble (i.e., hydrophobic) phases of BBOA in terms of reactive uptake of ozone in a coated-wall flow tube. Effects of relative humidity (RH) and ultraviolet (UV) irradiation were investigated. Experimental timeseries were used to inform simulations using multilayer kinetic modeling. Among non-irradiated thin films, the uptake coefficient was greatest for the water-soluble phase at 75% RH (3 × 10 –5 , corresponding to a diffusion coefficient of BrC, D BrC , of 3 × 10 –9 cm 2 s –1 ) and least for the same phase at 0% RH (1 × 10 –5 , corresponding to D BrC of 1 × 10 –10 cm 2 s –1 ). The uptake coefficient for the water-insoluble phase fell between these two (about 1.5 × 10 –5 ), regardless of RH, and the corresponding D BrC increased only slightly (8 × 10 –10 cm 2 s –1 at 0% RH to 9 × 10 –10 cm 2 s –1 at 75% RH). The uptake coefficients of both phases at 0% RH decreased significantly after UV irradiation, consistent with a transition from viscous liquid to solid and supported by qualitative microscopy observations. Modeling multiphase ozone oxidation of primary BrC components in the atmosphere demonstrated, first, that LLPS may extend the lifetime of water-soluble BBOA encapsulated by water-insoluble species by a factor of 1.5 at moderate to high RH and, also, that UV irradiation may extend the lifetime of both phases by more than a factor of 2.5.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

The complex circumstellar environment of supernova 2023ixf

The early evolution of a supernova (SN) can reveal information about the environment and the progenitor star. When a star explodes in vacuum, the first photons to escape from its surface appear as a brief, hours-long shock-breakout flare, followed by a cooling phase of emission. However, for stars exploding within a distribution of dense, optically thick circumstellar material (CSM), the first photons escape from the material beyond the stellar edge and the duration of the initial flare can extend to several days, during which the escaping emission indicates photospheric heating. Early serendipitous observations that lacked ultraviolet (UV) data were unable to determine whether the early emission is heating or cooling and hence the nature of the early explosion event. Here, in this study, we report UV spectra of the nearby SN 2023ixf in the galaxy Messier 101 (M101). Using the UV data as well as a comprehensive set of further multiwavelength observations, we temporally resolve the emergence of the explosion shock from a thick medium heated by the SN emission. We derive a reliable bolometric light curve that indicates that the shock breaks out from a dense layer with a radius substantially larger than typical supergiants.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Evaluating changes in growth and pigmentation of Cladosporium cladosporioides and Paecilomyces variotii in response to gamma and ultraviolet irradiation

Abstract Melanin-containing fungi (black molds) have the capacity to thrive under extreme environmental conditions such as the elevated radiation levels inside the former Chernobyl reactors. These fungi have been hypothesized to grow toward and use gamma radiation as an energy source, but the literature does not clearly address which energies of the electromagnetic spectrum, if any, positively affect fungal growth. The goal of this work was to characterize the response of non-melanized and melanized fungi to two distinct electromagnetic wavelengths, i.e., ultraviolet (UV) and gamma ray, keeping absorption and other potentially confounding variables constant. Exposure to UV or gamma radiation induced significant changes in fungi pigmentation, but not growth rate of Cladosporium cladosporioides and Paecilomyces variotii . Specifically, increased pigmentation of both fungi was observed in samples exposed to UV, while decreased pigmentation was observed for gamma-irradiated samples. These results provide new insights into the role of electromagnetic energies on growth of fungi and provide an impetus to examine additional energies and types of radiation to develop a fundamental understanding of this phenomenon.

59 BASIC BIOLOGICAL SCIENCES↗