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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Hyperspectral and Nanosecond Temporal Resolution Widefield Infrared Photothermal Heterodyne Imaging

Label-free, bond-selective imaging offers new opportunities for fundamental and applied studies in chemistry, biology, and materials science. Preventing its broader application to investigating spectrally congested specimens are issues related to low sensitivity as well as low spatial and temporal resolution. Here, we demonstrate a widefield, mid-infrared (MIR) photothermal imaging technique, called widefield Infrared Photothermal Heterodyne imaging (wIR-PHI), that massively parallelizes acquisition of MIR absorption data through use of a high-speed complementary metal-oxide-semiconductor camera. wIR-PHI possesses notable features that include: spatial resolution significantly below the MIR diffraction limit, hyperspectral imaging capabilities, high sensitivity, and ~100 ns temporal resolution. Here, the first two features are highlighted by hyperspectral imaging of proximally close poly(methyl methacrylate) (PMMA) and polystyrene (PS) nanoparticles where clear, bond-specific imaging of nanoparticles, separated by less than the MIR diffraction limit, is demonstrated. Sensitivity is highlighted by imaging individual PMMA and PS nanoparticles with radii between r = 97-556 nm. This leads to a current, peak absorption cross-section limit-of-detection of σ abs = 1.9× 10 –16 cm 2 . wIR-PHI's 100 ns temporal resolution is simultaneously demonstrated by observing the decay of photothermal contrast on individual nanoparticles on a ~200-6000 ns timescale. In whole, wIR-PHI’s dramatic increase in acquisition speed opens opportunities for future MIR kinetic imaging and spectroscopic studies of important chemical, biological, and material processes.

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

Fast widefield imaging of neuronal structure and function with optical sectioning in vivo

Optical microscopy, owing to its noninvasiveness and subcellular resolution, enables in vivo visualization of neuronal structure and function in the physiological context. Optical-sectioning structured illumination microscopy (OS-SIM) is a widefield fluorescence imaging technique that uses structured illumination patterns to encode in-focus structures and optically sections 3D samples. However, its application to in vivo imaging has been limited. In this study, we optimized OS-SIM for in vivo neural imaging. We modified OS-SIM reconstruction algorithms to improve signal-to-noise ratio and correct motion-induced artifacts in live samples. Incorporating an adaptive optics (AO) module to OS-SIM, we found that correcting sample-induced optical aberrations was essential for achieving accurate structural and functional characterizations in vivo. With AO OS-SIM, we demonstrated fast, high-resolution in vivo imaging with optical sectioning for structural imaging of mouse cortical neurons and zebrafish larval motor neurons, and functional imaging of quantal synaptic transmission at Drosophila larval neuromuscular junctions.

42 ENGINEERING↗
DOE OSTI2022

Computational microscopy for fast widefield deep-tissue fluorescence imaging using a commercial dual-cannula probe

A solid-glass cannula serves as a micro-endoscope that can deliver excitation light deep inside tissue while also collecting emitted fluorescence. Then, we utilize deep neural networks to reconstruct images from the collected intensity distributions. By using a commercially available dual-cannula probe, and training a separate deep neural network for each cannula, we effectively double the field of view compared to prior work. We demonstrated ex vivo imaging of fluorescent beads and brain slices and in vivo imaging from whole brains. We clearly resolved 4 µm beads, with FOV from each cannula of 0.2 mm (diameter), and produced images from a depth of ∼1.2 mm in the whole brain, currently limited primarily by the labeling. Since no scanning is required, fast widefield fluorescence imaging limited primarily by the brightness of the fluorophores, collection efficiency of our system, and the frame rate of the camera becomes possible.

42 ENGINEERING↗
NASA NTRS1995

The Kuiper Widefield Infrared Camera (KWIC)

The Kuiper Widefield Infrared Camera (KWIC) is a wide-field (5.8 arcmin x 5.8 arcmin) imaging spectrometer for use on the KAO in the wavelength range of 18 to 44 micron. Two resolution modes, R = 35 to 200 and R = 2000 to 10,000 are available. Diffraction limited and near background limited images were obtained on the first flights.

Latvakoski, H.↗
NASA NTRS1999

KWIC: A Widefield Mid-Infrared Array Camera/Spectrometer for the KAO

This grant covered a one year data analysis period for the data we obtained with the Kuiper Widefield Infrared Camera (KWIC) on the KAO during CY94 and CY95. A fairly complete list of scientific papers produced, or soon to be produced under this award is contained at the end of this report. Below we summarize some of the highlights of the work we did under this grant. KWIC Imaging of the Orion Nebula. KWIC was successfully developed under the KAO grants program (NASA grant NAG2-800). First funding arrived in November of 1992, and we flew our first two flights in February of 1994 -just 15 months later. These flights were very successful. We imaged the Orion Nebula in the 37.7 micron continuum and [SiII] 35 micron line and imaged M82 and Arp299 in the 37.7 micron continuum. Our Orion image demonstrates that the 37.7 micron continuum arises in the warm dust associated with the photodissociated surfaces (photodissociation regions, or PDRs) of molecular clouds. We use the brightness and color temperature distribution to ascertain the morphology of the Orion PDR. The [SiII] image of Orion encompassed the entire Orion A HII region and its enveloping PDR. Most of the emission in the PDR regions of the map appears to coincide very well with our 37.7 micron continuum map indicating a PDR origin for the [SiII] in agreement with theoretical predictions. The [SiII] line emission is very clumpy in the PDR directly imaging the clump spectrum indirectly ascertained by examining the distribution and flux ratios of [CII] and [0I] far-IR fine structure line, and high J CO emission. We also detected very strong [SiII] line emission from the embedded BN-KL star formation region tracing the morphology and physical conditions of the high velocity shock from these very young stars.

Stacey, Gordon J.↗
NASA NTRS1999

KWIC: A Widefield Mid-Infrared Array Camera/Spectrometer for the KAO

The Kuiper Widefield Infrared Camera (KWIC) is an imaging spectrometer designed for use on the Kuiper Airborne Observator between 18 and 40 microns. The spectral resolution achieving devices are two fully tunable and scanning cryogenic Fabry-Perot interferometers that employ free standing metal mesh as the reflective surfaces. The detective device is a 128 x 128 pixel Si:Sb BIB array manufactured by Rockwell/Boeing for the SIRTF project. The plate scale for KWIC (one pixel subtends 2.73" x 2.73") was chosen so as to more than fully sample the KAO beam (approximately 9" at 31.5 microns), to enable effective image restoration techniques to be applied. Even so, KWIC has a rather large (5.8' x 5.8') field of view. KWIC has both high and low spectral resolution modes that are interchangeable in a few minutes time in flight on the KAO. The high resolution (R = lambda/(delta)lambda = 1000 to 6000) mode is suitable for detecting weak lines in the presence of strong continuum for Galactic sources, and for resolving broad extragalactic lines. The low resolution (R approximately 30 to 100) mode is suitable for imaging in the thermal dust continuum.

Stacey, Gordon J.↗
NASA NTRS1999

Swift: A Widefield Imaging Fabry Perot for Sofia

Contract was to pursue feasibility studies of the SOFIA Widefield Imaging Fabry-Perot (SWIFT). SWIFT was proposed as a two color 18 to 40 microns imaging Fabry-Perot that utilized two Rockwell/Boeing 256 x 256 pixel Si:Sb BIBs as detective devices. The colors were to be split between 26 and 30 microns using a MgO dichroic. The resolution achieving devices were to be a pair of cryogenic fully tunable scanning Fabry-Perot interferometers (FPIs), two in each band. For high resolving powers, a third, fixed FPI is inserted into the beam. The FPI mirrors were to be made of free standing metal mesh. We also proposed to look into a long wavelength (40 to 210 microns) band during the feasibility study period. We produced a proposal to USRA, submitted in July 1997 that substantially refined our ideas. We decided the long wavelength science was compelling, so the baseline wavelength coverage for SWIFT was widened to 17 to 205 microns. Under typical operations, we proposed to simultaneously image in two bands: 22 to 38 microns, and 50 to 205 microns. The bands were to be split by a cold CaF2 dichroic. The short wavelength (SW) band was to employ a 256 x 256 pixel Boeing/Rockwell Si:Sb BIB array, and the long wavelength (LW) band was to employ a Goddard 6 x 32 (upgradable to 32 x 32) element array of monolithic silicon "pop-up" bolometers as detective devices. The two color capability doubled the data taking efficiency, and ensured "perfect" registration between the images obtained in each band. For the SW band, the beam was to be fully sampled (0.7" pixels, 1.4 in. beam) at 17 microns, and over sampled at longer wavelengths. Even so, SWIFT has a very large (3 ft x 3 ft) field of view. To match the SW and LW fields of view (initially in one dimension only, but in 2-dimensions with 32 x 32 upgrade), SWIFT was to under sample at 63 microns (5.6 in pixels, 5.2 in beam) resulting in a 0.56 x 3 in (upgrade to 3 in x 3 in) field of view. Each band has both Lo-Res (R triple bond lambda/Delta(lambda) approx. 30 to 200) and Hi-Res (R approx. 1000 up to 10(exp 5)) modes, that can be changed in less than a minute. Spectral resolution is obtained with four identical cryogenic, fully tunable, scanning FPIS, two in each band, plus a set of fixed order FPI that can be rotated into the beam for good spectral purity at the highest resolving powers. SWIFT was proposed to explore three primary topics of scientific interest: 1. Protostars, Young Stellar Objects, and Protoplanetary Disks. 2. The Galactic Center. 3. External Galaxies.

Stacey, Gordon J.↗
NASA NTRSDate not supplied

Roman-WFI: characterization of widefield chromatic response

Characterization of filter transmission is essential to control systematic chromatic errors in photometric surveys. Widefield surveys employ large filter optics viewed from high angles of incidence. Large optics may have variations in edge wavelength definition across their surface, and their spectral response shifts at high incidence angles. I will describe the characterization of the band definitions for the Wide Field Instrument of the Roman Space Telescope as part of its thermal vacuum test campaigns and through preparatory work. The measurement approach and analysis enable joint retrieval of chromatic response variations across the filter and focal plane. Additional tests probe out-of-band response and thermal straylight paths.

Eric Switzer↗
DOE OSTI2023

Widefield three-dimensional microscopy with a quantum entanglement light source

Devices, systems and methods for widefield three-dimensional (3D) microscopy with a quantum entanglement light source are described. An example method includes generating a first set of photons and a second set of photons, wherein each of the photons in the first set is quantum entangled with a corresponding photon in the second set, directing the second set of photons toward a sample and simultaneously directing the first set of photons toward a first two-dimensional (2D) detector, detecting, from the sample, a plurality of photons at a second 2D detector, analyzing detections from the first and second 2D detectors to determine coincidence information, and determining one or more characteristics associated with at least a three-dimensional (3D) section of the sample based on collective detections at the first and the second 2D detectors.

Bond, Tiziana C.↗
DOE OSTI2023

NIR fluorescence lifetime macroscopic imaging with a novel time-gated SPAD camera

SwissSPAD3 is the latest of a family of widefield time-gated SPAD imagers developed for fluorescence lifetime imaging (FLI) applications. Its distinctive features are (i) the ability to define shorter gates than its predecessors (width W < 1 ns), (ii) support for laser repetition rates up to at least 80 MHz and (iii) a dual-gate architecture providing an effective duty cycle of 100%. We present widefield macroscopic FLI measurements of short lifetime NIR dyes, analyzed using the phasor approach. Furthermore, the results are compared with those previously obtained with SwissSPAD2 and to theoretical predictions.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

NIR fluorescence lifetime macroscopic imaging with a time-gated SPAD camera

The performance of SwissSPAD2 (SS2), a large scale, widefield time-gated CMOS SPAD imager developed for fluorescence lifetime imaging, has recently been described in the context of visible range and fluorescence lifetime imaging microscopy (FLIM) of dyes with lifetimes in the 2.5 – 4 ns range. Here, we explore its capabilities in the NIR regime relevant for small animal imaging, where its sensitivity is lower and typical NIR fluorescent dye lifetimes are much shorter (1 ns or less). We carry out this study in a simple macroscopic imaging setup based on a compact NIR picosecond pulsed laser, an engineered diffuser-based illumination optics, and NIR optimized imaging lens suitable for well-plate or small animal imaging. Because laser repetition rates can vary between models, but the synchronization signal frequency accepted by SS2 is fixed to 20 MHz, we first checked that a simple frequency-division scheme enables data recording for different laser repetition rates. Next, we acquired data using different time gate widths, including gates with duration longer than the laser period, and analyzed the resulting data using both standard nonlinear least-square fit (NLSF) and phasor analysis. We show that the fixed synchronization rate and large gate widths characterizing SS2 (10 ns and over) are not an obstacle to accurately extracting lifetime in the 1 ns range and to distinguishing between close lifetimes. As a result, SS2 and similar very large gated SPAD imagers appear as a versatile alternative to other widefield time-resolved detectors for NIR fluorescence lifetime imaging, including preclinical molecular applications.

FLIM↗
DOE OSTI2025

Print-and-Plate Architected Electrodes for Electrochemical Transformations Under Flow

Flow cell electrodes are typically composed of porous carbon materials, such as papers, felts, and cloths. However, their random architecture hinders the fundamental characterization of electrode structure-performance relationships during in situ operation of porous electrochemical flow systems. This work describes a “print-and-plate” method that combines direct ink writing of micro-periodic lattices with a two-step metal plating process that converts them into highly conductive (sheet resistance 40 mΩ sq -1 ) electrodes. Their operando performance is assessed in an anthraquinone disulfonic acid half-cell using widefield electrochemical fluorescence microscopy, where output current and fluorescence intensity are in excellent agreement. The pressure drop associated with flow through three electrode designs is determined via simulations from which the most efficient design is identified and manufactured via print-and-plate. Confocal fluorescence microscopy is then used to create a 3D map of the state of charge (SOC) inside this print-and-plate electrode. The experimental state of the charge map is in good agreement with computational predictions. The rapid design, simulation, and fabrication of print-and-plate electrodes enable fundamental investigations of how architected porosity affects electrochemical performance under flow.

3D-printing↗
DOE OSTI2023

Measuring photometric redshifts for high-redshift radio source surveys

With the advent of deep, all-sky radio surveys, the need for ancillary data to make the most of the new, high-quality radio data from surveys like the Evolutionary Map of the Universe (EMU), GaLactic and Extragalactic All-sky Murchison Widefield Array survey eXtended, Very Large Array Sky Survey, and LOFAR Two-metre Sky Survey is growing rapidly. Radio surveys produce significant numbers of Active Galactic Nuclei (AGNs) and have a significantly higher average redshift when compared with optical and infrared all-sky surveys. Thus, traditional methods of estimating redshift are challenged, with spectroscopic surveys not reaching the redshift depth of radio surveys, and AGNs making it difficult for template fitting methods to accurately model the source. Machine Learning (ML) methods have been used, but efforts have typically been directed towards optically selected samples, or samples at significantly lower redshift than expected from upcoming radio surveys. This work compiles and homogenises a radio-selected dataset from both the northern hemisphere (making use of Sloan Digital Sky Survey optical photometry) and southern hemisphere (making use of Dark Energy Survey optical photometry). We then test commonly used ML algorithms such as k-Nearest Neighbours (kNN), Random Forest, ANNz, and GPz on this monolithic radio-selected sample. We show that kNN has the lowest percentage of catastrophic outliers, providing the best match for the majority of science cases in the EMU survey. We note that the wider redshift range of the combined dataset used allows for estimation of sources up to z = 3 before random scatter begins to dominate. When binning the data into redshift bins and treating the problem as a classification problem, we are able to correctly identify ≈ 76% of the highest redshift sources—sources at redshift z > 2.51 —as being in either the highest bin (z > 2.51) or second highest (z = 2.25).

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Characterization of mApple as a Red Fluorescent Protein for Cryogenic Single-Molecule Imaging with Turn-Off and Turn-On Active Control Mechanisms

Single-molecule superresolution microscopy is a powerful tool for the study of biological structures on size scales smaller than the optical diffraction limit. Imaging samples at cryogenic temperatures (77 K) reduces the quantum yield of photobleaching for many fluorescent labels, yielding localization precisions below 10 nm. Cryogenic imaging further enables correlation with cryogenic electron tomography. A key limitation in applying methods such as PALM and STORM to samples maintained at 77 K is the limited number of fluorophores known to undergo efficient turn-on and turn-off mechanisms necessary to control the sparsity of active emitters. Here we find that mApple, a red-emitting fluorescent protein, undergoes a novel turn-off mechanism in response to simultaneous illumination with two colors of light. This turn-off mechanism enables localization of many individual molecules in initially bright samples, but the final density of localizable emitters is limited by relatively inefficient turn-on (photoactivation). Bulk excitation and emission spectroscopy shows that mApple has access to two distinct emissive states as well as dark states accessible optically or through changes in pH. The bright and stable emission of mApple enables widefield collection of single-molecule emission spectra, which highlight the complex nature and environmental sensitivity of states observed in red fluorescent proteins.

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

Models and Measurements Quantify Photon Recycling, Charge-Carrier Diffusion and Photon Scattering Contributions to Photoluminescence in InP Nanowire Arrays

Nanowire arrays present many unique advantages for solar-to-chemical energy conversion. One possible advantage is that photon recycling between neighboring nanowires has the potential to increase solar energy conversion efficiencies. Here, in this work, we explore three underlying mechanisms of optical and electronic coupling between neighboring nanowires─incident photon scattering, photon recycling, and charge-carrier transport from the photoexcited nanowire to the neighboring nanowire via the underlying substrate─using single nanowire-level microscopy and spectroscopy measurements. We present a comprehensive analysis of light absorption and emission of a single nanowire at open circuit, and subsequent re-absorption and re-emission by a neighboring nanowire. We developed a novel correlated single nanowire microspectroscopy and widefield imaging methodology to spatially resolve photon communication pathways between neighboring nanowires and selectively image re-emitted and reflected photons. We developed unique multiphysics models to couple wave optics and semiconductor photophysics to especially isolate contributions from photon recycling and electronic transport to photon emission from neighboring nanowires. By systematically varying the morphologies of the nanowires modeled, we identified pathways to maximize photon recycling between neighboring nanowires. We concluded that the measured photoluminescence is more strongly influenced by the diffusion of charge carriers as compared to photon recycling in materials with moderate-to-large charge-carrier mobilities (>10 cm 2 V –1 s –1 ), and that photon recycling dictates photoluminescence intensity only when the charge-carrier mobility is low (<1 cm 2 V –1 s –1 ). The experimental and simulation platforms developed herein for photon management strategies can be leveraged by the semiconductor photocatalysis community to enhance solar-to-chemical conversion efficiencies in semiconductor nanowire arrays.

25 ENERGY STORAGE↗