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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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Fluorescence-Enabled Self-Reporting for Redox Flow Batteries

Monitoring battery health is challenging. Self-reporting enables the rapid health assessment of redox flow batteries (RFBs) and provides insight into degradation mechanisms of electrochemically active molecules (redoxmers). In this study, we introduce fluorescence as an orthogonal property to probe this chemistry in situ. An established anolyte redoxmer, 2,1,3-benzothiadiazole, is rendered an efficient blue-green fluorophore through minimalistic derivatization. One of the derivatives is electrochemically reversible with a long lifetime and cycling stability in the charged state. Spectroscopic measurements on this new redoxmer reveal strong effects of the electrolyte cation on the fluorescence that are useful for probing the solvent microenvironment. Using this probe, we demonstrate proof-of-concept in situ crossover sensing and characterize the effects of electrolyte composition on this crossover. In this way, real-time tracing of redoxmers in a flow cell is demonstrated, paving the way to include still more self-reporting functions into the redoxmers.

25 ENERGY STORAGE↗
DOE OSTI2015

Localizing Exciton Recombination Sites in Conformationally Distinct Single Conjugated Polymers by Super-resolution Fluorescence Imaging

To thoroughly elucidate how molecular conformation and photophysical properties of conjugated polymers (CPs) are related requires simultaneous probing of both. Here, previous efforts used fluorescence imaging with one nanometer accuracy (FIONA) to image CPs, which allowed simultaneous estimation of molecular conformation and probing of fluorescence intensity decay. We show that calculating the molecular radius of gyration for putative folded and unfolded poly(2-methoxy-5-(2'-ethylhexyloxy)1,4-phenylenevinylene) (MEH-PPV) molecules using FIONA underestimates molecular extension by averaging over emitters during localization. In contrast, employing algorithms based on single molecule high resolution imaging with photobleaching (SHRImP), including an approach we term all-frames SHRImP, allows localization of individual emitters. SHRImP processing corroborates that compact MEH-PPV molecules have distinct photophysical properties from extended ones. Estimated radii of gyration for isolated 168 kDa MEH-PPV molecules immobilized in polystyrene and exhibiting either stepwise or continuous intensity decays are found to be 12.6 and 25.3 nm, respectively, while the distance between exciton recombination sites is estimated to be ~10 nm independent of molecular conformation.

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

Developing Fluorescence-Based Sensors to Support Rare Earth Element Separation

Rare earth elements (REEs) are essential to most renewable energy technologies. Unfortunately, as we transition to sustainable energy production, the demand for REEs is rapidly growing well beyond current rates of production. As a result, novel means of efficient, scalable, and easily adaptable methods for processing primary and recycle feedstocks are needed. Development and integration of sensors for highly selective in-line monitoring can support more efficient design and testing of such novel separation processes, as well as more cost-effective deployment of those separation flowsheets. Work here will explore the application of fluorescence spectroscopy, a highly sensitive and selective technique, to quantify multiple lanthanides in complex mixtures including known interferents or quenching agents. Results include identification of the optimal excitation wavelength and the limit of detection of various rare earth elements as well as the performance of data-science-based quantification approaches in streams where “unknowns” are present. Overall, the data science tools in conjunction with optical sensor data were able to quantify analytes in the presence of other lanthanides which can be anticipated in the actual industrial stream. Here we include characterization of lanthanides in a microfluidic device similar to those used in new process development. This study demonstrates the capability of utilizing fluorescence spectroscopy to quantify analytes in a complicated solution matrix, suggesting this is a successful approach for in-line monitoring to optimize the separation efficiency in an industrial stream.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Representation of Leaf-to-Canopy Radiative Transfer Processes Improves Simulation of Far-Red Solar-Induced Chlorophyll Fluorescence in the Community Land Model Version 5

Recent advances in satellite observations of solar-induced chlorophyll fluorescence (SIF) provide a new opportunity to evaluate and constrain the simulation of terrestrial gross primary productivity (GPP). Accurate representation of the processes driving SIF emission and the radiative transfer of SIF to remote sensing sensors is an essential prerequisite for the evaluation and data assimilation. Recently, SIF simulations have been incorporated into several land surface models, but the scaling of SIF from leaf-level to canopy level is usually not well-represented. In this work, we incorporate the simulation of far-red SIF observed at nadir into the Community Land Model version 5 (CLM5). An efficient and accurate method based on escape probability is developed to scale SIF from leaf-level to top-of-canopy while taking clumping and the radiative transfer processes into account. SIF simulated by CLM5 and a canopy-level model agreed well at sites except one in needle leaf forest (R2>0.91, root-mean-square error < 0.19W m -2 sr -1 um -1 ), and captured the day-to-day variation of tower-measured SIF at temperate forest sites (R 2 >0.68). At the global scale, simulated SIF generally captured the spatial and seasonal pat37 terns of satellite-observed SIF (R2 > 0.76 except for tropical forest). Factors including the fluorescence emission model, clumping, bidirectional effect, and canopy properties (leaf optical properties and leaf area index) had considerable impacts on SIF simulation, and the discrepancies between simulated and observed SIF varied with plant functional type. By improving the representation of radiative transfer for SIF simulation, our model allows better comparisons between simulated and observed SIF towards constraining and evaluating GPP simulations.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Smallest near-infrared fluorescent protein evolved from cyanobacteriochrome as versatile tag for spectral multiplexing

From a single domain of cyanobacteriochrome (CBCR) we developed a near-infrared (NIR) fluorescent protein (FP), termed miRFP670nano, with excitation at 645 nm and emission at 670 nm. This is the first CBCR-derived NIR FP evolved to efficiently bind endogenous biliverdin chromophore and brightly fluoresce in mammalian cells. miRFP670nano is a monomer with molecular weight of 17 kDa that is 2-fold smaller than bacterial phytochrome (BphP)-based NIR FPs and 1.6-fold smaller than GFP-like FPs. Crystal structure of the CBCR-based NIR FP with biliverdin reveals a molecular basis of its spectral and biochemical properties. Unlike BphP-derived NIR FPs, miRFP670nano is highly stable to denaturation and degradation and can be used as an internal protein tag. miRFP670nano is an effective FRET donor for red-shifted NIR FPs, enabling engineering NIR FRET biosensors spectrally compatible with GFP-like FPs and blue–green optogenetic tools. miRFP670nano unlocks a new source of diverse CBCR templates for NIR FPs.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Design and applications of a clamp for Green Fluorescent Protein with picomolar affinity

Green fluorescent protein (GFP) fusions are pervasively used to study structures and processes. Specific GFP-binders are thus of great utility for detection, immobilization or manipulation of GFP-fused molecules. We determined structures of two designed ankyrin repeat proteins (DARPins), complexed with GFP, which revealed different but overlapping epitopes. Here in this paper we show a structure-guided design strategy that, by truncation and computational reengineering, led to a stable construct where both can bind simultaneously: by linkage of the two binders, fusion constructs were obtained that “wrap around” GFP, have very high affinities of about 10–30 pM, and extremely slow off-rates. They can be natively produced in E. coli in very large amounts, and show excellent biophysical properties. Their very high stability and affinity, facile site-directed functionalization at introduced unique lysines or cysteines facilitate many applications. As examples, we present them as tight yet reversible immobilization reagents for surface plasmon resonance, as fluorescently labelled monomeric detection reagents in flow cytometry, as pull-down ligands to selectively enrich GFP fusion proteins from cell extracts, and as affinity column ligands for inexpensive large-scale protein purification. We have thus described a general design strategy to create a “clamp” from two different high-affinity repeat proteins, even if their epitopes overlap.

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

PBT2 acts through a different mechanism of action than other 8-hydroxyquinolines: an X-ray fluorescence imaging study

8-Hydroxyquinolines (8HQs) comprise a family of metal-binding compounds that have been used or tested for use in numerous medicinal applications, including as treatments for bacterial infection, Alzheimer's disease, and cancer. Two key 8HQs, CQ (5-chloro-7-iodo-8-hydroxyquinoline) and PBT2 (2-(dimethylamino)methyl-5,7-dichloro-8-hydroxyquinoline), have drawn considerable interest and have been the focus of many studies investigating their in vivo properties. These drugs have been described as copper and zinc ionophores because they do not cause metal depletion, as would be expected for a chelation mechanism, but rather cellular accumulation of these ions. In studies of their anti-cancer properties, CQ has been proposed to elicit toxic intracellular copper accumulation and to trigger apoptotic cancer cell death through several possible pathways. In this study we used synchrotron X-ray fluorescence imaging, in combination with biochemical assays and light microscopy, to investigate 8HQ-induced alterations to metal ion homeostasis, as well as cytotoxicity and cell death. We used the bromine fluorescence from a bromine labelled CQ congener (5,7-dibromo-8-hydroxyquinoline; B2Q) to trace the intracellular localization of B2Q following treatment and found that B2Q crosses the cell membrane. We also found that 8HQ co-treatment with Cu(ii) results in significantly increased intracellular copper and significant cytotoxicity compared with 8HQ treatments alone. PBT2 was found to be more cytotoxic, but a weaker Cu(ii) ionophore than other 8HQs. Moreover, treatment of cells with copper in the presence of CQ or B2Q resulted in copper accumulation in the nuclei, while PBT2-guided copper was distributed near to the cell membrane. Furthermore, these results suggest that PBT2 may be acting through a different mechanism than that of other 8HQs to cause the observed cytotoxicity.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Robust fluorescent calcium coordination polymers as Cu 2+ sensors with high sensitivity and fast response

A three-dimensional (3D) and highly fluorescent calcium-based coordination polymer (Ca-CP) has been synthesized and structurally characterized. Furthermore, built on a strongly fluorescent (FL) chromophore ligand, [Ca(H 2 tcbpe)(H 2 O) 2 ] (1) (H 4 tcbpe = 4',4''',4''''',4'''''''-(ethene-1,1,2,2-tetrayl)tetrakis(([1,1'-biphenyl]-4-carboxylic acid))) is highly luminescent. Photoluminescence (PL) studies indicate that 1 undergoes a bathochromic shift in emission energy from blue to green color upon outgassing or under mechanic force. Notably, 1 exhibits selective FL sensing for Cu 2+ ions with a detection limit (LOD) of 0.064 ppm, far below the U.S. WHO and EPA standard for drinking water. Detailed investigation of the sensing mechanism reveals that uncoordinated COO– groups in 1 play a major role in recognizing Cu 2+ ions.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Th IV –Desferrioxamine: characterization of a fluorescent bacterial probe

Diversifying our ability to guard against emerging pathogenic threats is essential for keeping pace with global health challenges, including those presented by drug-resistant bacteria. Some modern diagnostic and therapeutic innovations to address this challenge focus on targeting methods that exploit bacterial nutrient sequestration pathways, such as the desferrioxamine (DFO) siderophore used by Staphylococcus aureus (S. aureus) to sequester Fe III . Building on recent studies that have shown DFO to be a versatile vehicle for chemical delivery, we show proof-of-principle that the Fe III sequestration pathway can be used to deliver a potential radiotherapeutic. Our approach replaces the FeIII nutrient sequestered by H 4 DFO + with Th IV and made use of a common fluorophore, FITC, which we covalently bonded to DFO to provide a combinatorial probe for simultaneous chelation paired with imaging and spectroscopy, H 3 DFO_FITC. Combining insight provided from FITC-based imaging with characterization by NMR spectroscopy, we demonstrated that the fluorescent DFO_FITC conjugate retained the Th IV chelation properties of native H4DFO+. Fluorescence microscopy with both [Th(DFO_FITC)] and [Fe(DFO_FITC)] complexes showed similar uptake by S. aureus and increased intercellular accumulation as compared to the FITC and unchelated H 3 DFO_FITC controls. Collectively, these results demonstrate the potential for the newly developed H 3 DFO_FITC conjugate to be used as a targeting vector and bacterial imaging probe for S. aureus. The results presented within provide a framework to expand H 4 DFO + and H 3 DFO_FITC to relevant radiotherapeutics (like 227Th).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Ruby and Sm:YAG fluorescence pressure gauges up to 120 GPa and 700 K

Diamond anvil cell (DAC) technique relies on pressure determination based on use of pressure gauges. Fluorescence-based gauges, such as ruby and Sm doped yttrium aluminum garnet (Sm:YAG), are frequently used in the high pressure research. Here we present the results of DAC experiments which allowed extending calibration curves of the fluorescence frequency versus pressure up to 120 GPa at high temperatures up to 700 K for both for ruby and Sm:YAG. Cubic boron nitride was used as the reference gauge.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Precise Measurement of the Absolute Fluorescence Yield

We present preliminary results of the absolute yield of fluorescence emission in atmospheric gases. Measurements were performed at the Fermilab Test Beam Facility with a variety of beam particles and gases. Absolute calibration of the fluorescence yield to 5% level was achieved by comparison with two known light sources - the Cherenkov light emitted by the beam particles, and a calibrated nitrogen laser. The uncertainty of the energy scale of current Ultra-High Energy Cosmic Rays experiments will be significantly improved by the AIRFLY measurement.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Nondestructive identification of isotopes using nuclear resonance fluorescence

Nondestructive identification of heavy isotopes concealed in a thick iron box has been demonstrated by using nuclear resonance fluorescence. A quasi-monochromatic photon beam produced by the collision of laser quanta with high energy electrons was used for resonant excitation of nuclear levels in {sup 206}Pb and {sup 208}Pb. By measuring the resonant {gamma} rays emitted from {sup 206}Pb and {sup 208}Pb, each of these isotopes were clearly identified. The ratio of the effective thickness, i.e., concentration distribution, of these isotopes was deduced from the relative intensities of the measured nuclear resonance fluorescence strengths.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Time-resolved Hyperspectral Fluorescence Spectroscopy using Frequency Modulated Excitation

An intensity-modulated excitation light source is used together with a micro channel plate intensified CCD (ICCD) detector gated at a slightly different frequency to generate a beat frequency from a fluorescent sample. The addition of a spectrograph produces a hyperspectral time-resolved data product where the resulting beat frequency is detected with a low frame rate camera. Measuring the beat frequency of the spectrum as a function of time allows separation of the excited fluorescence from ambient constant light sources. The excitation and detector repetition rates are varied over a range of discrete frequencies, and the phase shift of the beat wave maps out the emission decay rate(s).

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Digital optical phase conjugation of fluorescence in turbid tissue

We demonstrate a method for phase conjugating fluorescence. Our method, called reference free digital optical phase conjugation, can conjugate extremely weak, incoherent optical signals. It was used to phase conjugate fluorescent light originating from a bead covered with 0.5 mm of light-scattering tissue. The phase conjugated beam refocuses onto the bead and causes a local increase of over two orders of magnitude in the light intensity. Potential applications are in imaging, optical trapping, and targeted photochemical activation inside turbid tissue.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2012

A versatile detector for total fluorescence and electron yield experiments

The combination of a non-coated silicon photodiode with electron repelling meshes makes a versatile detector for total fluorescence yield and electron yield techniques highly suitable for x-ray absorption spectroscopy. In particular, a copper mesh with a bias voltage allows to suppress or transmit the electron yield signal. The performance of this detection scheme has been characterized by near edge x-ray absorption fine structure studies of thermal oxidized silicon and sapphire. The results show that the new detector probes both electron yield and for a bias voltage exceeding the maximum photon energy the total fluorescence yield.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Monte Carlo simulation applied in total reflection x-ray fluorescence: Preliminary results

The X-ray Fluorescence (XRF) analysis is a technique for the qualitative and quantitative determination of chemical constituents in a sample. This method is based on detection of the characteristic radiation intensities emitted by the elements of the sample, when properly excited. A variant of this technique is the Total Reflection X-ray Fluorescence (TXRF) that utilizes electromagnetic radiation as excitation source. In total reflection of X-ray, the angle of refraction of the incident beam tends to zero and the refracted beam is tangent to the sample support interface. Thus, there is a minimum angle of incidence at which no refracted beam exists and all incident radiation undergoes total reflection. In this study, we evaluated the influence of the energy variation of the beam of incident x-rays, using the MCNPX code (Monte Carlo NParticle) based on Monte Carlo method.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Suppression and enhancement of coexisting super-fluorescence and multi-wave mixing processes in sodium vapor

Different aspects of the properties of the coexisting super-fluorescence (SFL), multi-wave mixing with the fluorescence signal in the sodium vapor are studied both theoretically and experimentally. First, by scanning the dressed-state, the properties of these coexisting processes, such as the SFL signal modulated by using the dark and bright states, the interplay between dressed-states, are observed for the first time. Then, by scanning the probe field, the interplay between the one-photon and two-photon processes of the coexisting signals is obtained with or without the external dressing fields. Such control on each process in such coexisting system has an important potential application in quantum communication.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

2-dimensional ion velocity distributions measured by laser-induced fluorescence above a radio-frequency biased silicon wafer

The dynamics of ions traversing sheaths in low temperature plasmas are important to the formation of the ion energy distribution incident onto surfaces during microelectronics fabrication. Ion dynamics have been measured using laser-induced fluorescence (LIF) in the sheath above a 30 cm diameter, 2.2 MHz-biased silicon wafer in a commercial inductively coupled plasma processing reactor. The velocity distribution of argon ions was measured at thousands of positions above and radially along the surface of the wafer by utilizing a planar laser sheet from a pulsed, tunable dye laser. Velocities were measured both parallel and perpendicular to the wafer over an energy range of 0.4–600 eV. The resulting fluorescence was recorded using a fast CCD camera, which provided resolution of 0.4 mm in space and 30 ns in time. Data were taken at eight different phases during the 2.2 MHz cycle. The ion velocity distributions (IVDs) in the sheath were found to be spatially non-uniform near the edge of the wafer and phase-dependent as a function of height. Several cm above the wafer the IVD is Maxwellian and independent of phase. Experimental results were compared with simulations. The experimental time-averaged ion energy distribution function as a function of height compare favorably with results from the computer model.

36 MATERIALS SCIENCE↗