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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Dye laser traveling wave amplifier

Injection locking was applied to a cavity-dumped coaxial flashlamp pumped dye laser in an effort to obtain nanosecond duration pulses which have both high energy and narrow-linewidth. In the absence of an injected laser pulse, the cavity-dumped dye laser was capable of generating high energy (approx. 60mJ) nanosecond duration output pulses. These pulses, however, had a fixed center wavelength and were extremely broadband (approx. 6nm FWHM). Experimental investigations were performed to determine if the spectral properties of these outputs could be improved through the use of injection-locking techniques. A parametric study to determine the specific conditions under which the laser could be injection-locked was also carried out. Significant linewidth reduction to 0.0015nm) of the outputs was obtained through injection-locking but only at wavelengths near the peak lasing wavelength of the dye. It was found, however; that by inserting weakly dispersive tuning elements in the laser cavity, these narrow-linewidth outputs could be obtained over a wide (24nm) tuning range. Since the tuning elements had low insertion losses, the tunability of the output was obtained without sacrificing output pulse energy.

Davidson, F.↗
NASA NTRS1986

Linewidth characteristics of Raman-shifted dye laser output at 720 and 940 nm

A compact and simple simultaneous multi-wavelength dye laser cavity was developed for a differential absorption technique. Dielectric multilayer interference filters were inserted inside the cavities as tuning elements, and two types of a DIAL system were constucted by using the dye laser tuned with dielectric multilayer filters to measure NO2 concentration. The usefulness of this dye laser was clarified for the differential absoroption technique in outdoor experiments. Some basic designs of the laser cavity with these filters to get simultaneously multi-wavelength output are summarized.

Grossmann, B. E.↗
NASA NTRS1991

Reactive Fluorescent Dyes For Urethane Coatings

Molecules of fluorescent dyes chemically bound in urethane conformal-coating materials to enable nondestructive detection of flaws in coats through inspection under ultraviolet light, according to proposal. Dye-bonding technique prevents outgassing of dyes, making coating materials suitable for use where flaw-free coats must be assured in instrumentation or other applications in which contamination by outgassing must be minimized.

Willis, Paul B.↗
NASA NTRS2003

Dye-Sensitized Solar Cells for Space Power

During the course of this grant, dye-sensitized solar cells were prepared and characterized. The solar cells were prepared using materials (dyes, electrolytes, transparent conductive oxide coated glass, nanocrystalline TiO2) entirely prepared in-house, as well as prepared using materials available commercially. Complete cells were characterized under simulated AM0 illumination. The best cell prepared at NASA had an AM0 efficiency of 1.22% for a 1.1 sq cm cell. Short circuit current (Isc), open circuit voltage (Voc) and fill factor (FF) for the cell were 6.95 mA, 618 mV and 42.8%, respectively. For comparison purposes, two commercially prepared dye-sensitized solar cells were obtained from Solaronix SA, Aubonne, Switzerland. The Solaronix cells were also characterized under simulated AM0 illumination. The best cell from Solaronix had an active area of 3.71 sq cm and measured an AM0 efficiency of 3.16%. with Isc, Voc and FF of 45.80 mA, 669.6 mV and 52.3%, respectively. Both cells from Solaronix were rapid thermal cycled between -80 C and 80 C. Thermal cycling led to a 4.6% loss of efficiency in one of the cells and led to nearly a complete failure in the second cell.

Harris, Jerry D.↗
NASA NTRS2007

Bench-Top Antigen Detection Technique that Utilizes Nanofiltration and Fluorescent Dyes which Emit and Absorb Light in the Near Infrared

This article discusses the development of a bench-top technique to detect antigens in fluids. The technique involves the use of near infrared NIR fluorescent dyes conjugated to antibodies, centrifugation, nanofilters, and spectrometry. The system used to detect the antigens utilizes a spectrometer, fiber optic cables, NIR laser, and laptop computer thus making it portable and ideally suited for desk top analysis. Using IgM as an antigen and the secondary antibody, anti-IgM conjugated to the near infrared dye, IRDye (trademark) 800, for detection, we show that nanofiltration can efficiently and specifically separate antibody-antigen complexes in solution and that the complexes can be detected by a spectrometer and software using NIR laser excitation at 778 nm and NIR dye offset emission at 804 nm. The peak power detected at 778 nm for the excitation emission and at 804 nm for the offset emission is 879 pW (-60.06 dBm) and 35.7 pW (-74.5 dBm), respectively.

Varaljay-Spence, Vanessa A.↗
NASA NTRS2007

Use of dye to distinguish salt and protein crystals under microcrystallization conditions

An improved method of screening crystal growth conditions is provided wherein molecules are crystallized from solutions containing dyes. These dyes are selectively incorporated or associated with crystals of particular character thereby rendering crystals of particular character colored and improving detection of the dyed crystals. A preferred method involves use of dyes in protein solutions overlayed by oil. Use of oil allows the use of small volumes of solution and facilitates the screening of large numbers of crystallization conditions in arrays using automated devices that dispense appropriate solutions to generate crystallization trials, overlay crystallization trials with an oil, provide appropriate conditions conducive to crystallization and enhance detection of dyed (colored) or undyed (uncolored) crystals that result.

Cosenza, Larry↗
NASA NTRS2015

Particle Image Velocimetry Applications Using Fluorescent Dye-Doped Particles

Polystyrene latex sphere particles are widely used to seed flows for velocimetry techniques such as Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV). These particles may be doped with fluorescent dyes such that signals spectrally shifted from the incident laser wavelength may be detected via Laser Induced Fluorescence (LIF). An attractive application of the LIF signal is achieving velocimetry in the presence of strong interference from laser scatter, opening up new research possibilities very near solid surfaces or at liquid/gas interfaces. Additionally, LIF signals can be used to tag different fluid streams to study mixing. While fluorescence-based PIV has been performed by many researchers for particles dispersed in water flows, the current work is among the first in applying the technique to micron-scale particles dispersed in a gas. A key requirement for such an application is addressing potential health hazards from fluorescent dyes; successful doping of Kiton Red 620 (KR620) has enabled the use of this relatively safe dye for fluorescence PIV for the first time. In this paper, basic applications proving the concept of PIV using the LIF signal from KR620-doped particles are exhibited for a free jet and a twophase flow apparatus. Results indicate that while the fluorescence PIV techniques are roughly 2 orders of magnitude weaker than Mie scattering, they provide a viable method for obtaining data in flow regions previously inaccessible via standard PIV. These techniques have the potential to also complement Mie scattering signals, for example in multi-stream and/or multi-phase experiments.

Petrosky, Brian J.↗
NASA NTRS2016

Dye Penetrant Crack Detectability in External Corners in Presence of Fillet Radius

NASA uses special dye penetrant nondestructive evaluation process to provide reliable detection of very small cracks. Typically the surface crack lengths sizes are 0.030' and 0.050' for special dye penetrant process. Qualification requires demonstration of crack detection on a set of cracks with average crack size smaller than or equal to the qualification crack size. The demonstration is called point estimate demonstration. A set of corner cracks can be used to determine reliably detectable corner crack using the point estimate demonstration method. However, dye penetrant demonstration on surface cracks can be used to assess reliably detectable corner crack sizes by using similarity in the penetrant process. The paper provides similarity analysis approach for determining the reliably detectable corner crack sizes for given a point estimate demonstrated surface crack size.

Koshti, Ajay M.↗
DOE OSTI2013

Dye-sensitized solar cell employing zinc oxide aggregates grown in the presence of lithium

Provided are a novel ZnO dye-sensitized solar cell and method of fabricating the same. In one embodiment, deliberately added lithium ions are used to mediate the growth of ZnO aggregates. The use of lithium provides ZnO aggregates that have advantageous microstructure, morphology, crystallinity, and operational characteristics. Employing lithium during aggregate synthesis results in a polydisperse collection of ZnO aggregates favorable for porosity and light scattering. The resulting nanocrystallites forming the aggregates have improved crystallinity and more favorable facets for dye molecule absorption. The lithium synthesis improves the surface stability of ZnO in acidic dyes. The procedures developed and disclosed herein also help ensure the formation of an aggregate film that has a high homogeneity of thickness, a high packing density, a high specific surface area, and good electrical contact between the film and the fluorine-doped tin oxide electrode and among the aggregate particles.

14 SOLAR ENERGY↗
DOE OSTI2018

Small molecule dye for molecular imaging and photothermal therapy

Disclosed is a small molecule dye for use in imaging in the near-infrared window, namely between 1000 nm-1700 nm wavelength. The present dyes are also useful for photoacoustic imaging and photothermal therapy. The dyes have a structure of a D-A-D (donor-acceptor-donor) fluorescent compound core and side chains rendering the compounds water soluble and easily conjugated to hydrophilic polymers and/or targeting ligands. Further disclosed is compound, CH1055 that can be PEGylated, conjugated to a targeting ligand, or conjugated to taurine. Key steps utilized to assemble the core structure of the target included a cross-Suzuki coupling reaction, iron reduction and N-thionylaniline induced ring closure. Four carboxylic acid groups were introduced into the donor-acceptor-donor (D-A-D) type fluorescent compound to impart a certain aqueous solubility and to allow facile conjugation to targeting ligands.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Small molecule dye for molecular imaging and photothermal therapy

Disclosed is a small molecule dye for use in imaging in the near-infrared window, namely between 1000 nm-1700 nm wavelength. The present dyes are also useful for photoacoustic imaging and photothermal therapy. The dyes have a structure of a D-A-D (donor-acceptor-donor) fluorescent compound core and side chains rendering the compounds water soluble and easily conjugated to hydrophilic polymers and/or targeting ligands. Further disclosed is compound, CH1055 that can be PEGylated, conjugated to a targeting ligand, or conjugated to taurine. Key steps utilized to assemble the core structure of the target included a cross-Suzuki coupling reaction, iron reduction and N-thionylaniline induced ring closure. Four carboxylic acid groups were introduced into the donor-acceptor-donor (D-A-D) type fluorescent compound to impart a certain aqueous solubility and to allow facile conjugation to targeting ligands.

Cheng, Zhen↗
DOE OSTI2026

Probing the External Surface Chemistry of Imine-Based Covalent Organic Frameworks Using Reactive Organic Dyes

The external surfaces of covalent organic frameworks (COFs) are presumably composed of free terminal functional groups from their constituent monomers. These terminal groups have been utilized to immobilize molecules onto COF surfaces for a variety of studies and potential applications. Despite the utility of these latent functional groups for COF functionalization and composite formation, the surface chemistry of the COFs has not been quantitatively investigated and is not well understood. In this work, fluorescent organic dyes bearing reactive amine and aldehyde functional groups are used to probe the surface chemistry of representative two-dimensional (2D) imine-based COFs. Furthermore, systematic dye binding and displacement experiments provide new insights into the characteristics of COF surfaces and the reactivity of different molecules with the surface groups on the COF crystallites.

COFs↗
DOE OSTI2018

Dye-sensitized photoelectrochemical water oxidation through a buried junction

Water oxidation has long been a challenge in artificial photosynthetic devices that convert solar energy into fuels. Water-splitting dye-sensitized photoelectrochemical cells (WS-DSPECs) provide a modular approach for integrating light-harvesting molecules with water-oxidation catalysts on metal-oxide electrodes. Despite recent progress in improving the efficiency of these devices by introducing good molecular water-oxidation catalysts, WS-DSPECs have poor stability, owing to the oxidation of molecular components at very positive electrode potentials. Here we demonstrate that a solid-state dye-sensitized solar cell (ss-DSSC) can be used as a buried junction for stable photoelectrochemical water splitting. A thin protecting layer of TiO 2 grown by atomic layer deposition (ALD) stabilizes the operation of the photoanode in aqueous solution, although as a solar cell there is a performance loss due to increased series resistance after the coating. With an electrodeposited iridium oxide layer, a photocurrent density of 1.43 mA cm −2 was observed in 0.1 M pH 6.7 phosphate solution at 1.23 V versus reversible hydrogen electrode, with good stability over 1 h. We measured an incident photon-to-current efficiency of 22% at 540 nm and a Faradaic efficiency of 43% for oxygen evolution. While the potential profile of the catalyst layer suggested otherwise, we confirmed the formation of a buried junction in the as-prepared photoelectrode. The buried junction design of ss-DSSs adds to our understanding of semiconductor–electrocatalyst junction behaviors in the presence of a poor semiconducting material.

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

Scalable Graphene Oxide Hollow Fiber Membranes for Dye Desalination Enabled by Multi‐Purpose Polyamine Functionalization

2D nanosheets such as graphene oxide (GO) can be stacked to construct membranes with fine-tuned nanochannels to achieve molecular sieving ability. These membranes are often thin to achieve high water permeance, but their fabrication with consistent nanostructures on a large scale presents an enormous challenge. Herein, GO-based hollow fiber membranes (HFMs) are developed for dye desalination by synergistically combining chemical etching to form in-plane nanopores (10–30 nm) to increase water permeance and polyamine functionalization to improve underwater stability and enable facile large-scale production using existing membrane manufacturing processes. HFM modules with areas of 88 cm 2 and GO layer thicknesses of ≈500 nm are fabricated, and they exhibited a stable dye water permeance of 75 L m −2 h −1 bar −1 , rejection of >99.5% for Direct red and Congo red, and Na 2 SO 4 /dye separation factor of 300–500, superior to state-of-the-art commercial membranes. Furthermore, the versatility of this approach is also demonstrated using different short polyamines and porous substrates. This study reveals a scalable way of designing 2D materials into high-performance robust membranes for practical applications.

amine functionalization↗
DOE OSTI2018

Lasing of Some Red Laser Dyes in Annealed Silica Xerogel

The spectral and energy characteristics of generation in the red spectral region 650–720 nm were measured and analyzed for three laser dyes in preliminarily annealed SiO{sub 2} xerogel matrices under laser excitation λ{sub p} = 588 nm in a nonselective cavity. The specific laser-energy output for two of them (LK678 and Ox170) in the matrices was 10–13% higher than in MeOH. NBA dye in the matrix generated two laser radiation bands in the 700–720 nm region with pumping E{sub p} ≥ 80 mJ whereas its generation threshold in MeOH exceeded the maximum pumping energy of 140 mJ so that NBA generation was not observed. Laser emission spectra of the studied matrices in a nonselective cavity were red-shifted by ~1000 cm{sup –1} from the fluorescence maximum. Such a shift could improve the characteristics of biosensors based on these matrices.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Iterative Method to Obtain Raman Spectra of Organic Dyes by Their Chaotic Generation in Multiple-Scattering Media

An iterative method is developed to obtain vibrational spectra of laser organic dyes from their secondary radiation spectra in multiple-scattering media, which manifests as a result of coupled process of chaotic generation (CG) and stimulated Raman scattering (SRS). The developed method increases significantly the capability to detect weak Raman lines by using batch processing of a set of experimental SRS-CG spectra, which makes it possible to optimize the deconvolution of these spectra and to average vibrational spectra obtained from the set of experimental SRS-CG spectra. The method is tested on spectra of the SRS-CG laser dye pyrromethene 597 in a vesicular film. The obtained results agree well with Raman spectra calculated by the Hartree–Fock method.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Poly(N,N-dimethylacrylamide-co-acrylamide) Grafted Hydroxyethyl Cellulose Hydrogel: A Useful Congo Red Dye Remover

Composite hydrogel was prepared by cross-link copolymerization of a mixture of acrylamide, and N,N-dimethylacrylamide using N,N′-methylene-bis-acrylamide as a cross-linking agent onto hydroxyethyl cellulose backbone. Several hydrogels (H{sub 1}–H{sub 5}) were prepared by varying the amount of acrylamide and N,N-dimethylacrylamide. Swelling characteristics in water of all the hydrogels were evaluated to identify the hydrogel having highest water swelling property. The hydrogel showing highest water swelling performance (H{sub 3}) was characterized by FTIR spectroscopy, XRD and SEM studies. Swelling and deswelling kinetic studies of the hydrogel (H{sub 3}) were also carried out. The hydrogel (H{sub 3}) was used for the removal of congo red (CR), a toxic azo dye from its aqueous solution. Adsorption dynamics, kinetics and isotherms were also evaluated. The adsorption follows a pseudo second order kinetics, and the sorption data were well fitted with Langmuir adsorption isotherm. The hydrogel (H{sub 3}) showed a high monolayer adsorption capacity (Q{sub m} = 102.4 mg g{sup −1}) for the CR dye adsorption. Graphical Abstract: .

36 MATERIALS SCIENCE↗
DOE OSTI2019

Investigation into the Role of Surface Modification of Cellulose Nanocrystals with Succinic Anhydride in Dye Removal

Herein, the effect of surface modification of cellulose nanocrystals (CNC) on the sorption of dyes from waste textile effluent (methylene blue as a model) was achieved. The esterification of the isolated CNC from wood sawdust by acid hydrolysis was performed through melting with succinic anhydride (SA). At using 1:3–1:9 as the feeding ratios of CNC to SA, the succinylated CNC (CNC-SA) was obtained with degree of substitution of 1.6–2.2 and carboxylic content of 286.8–381.7 mmol/kg. Both of diameter size and zeta potential of the prepared CNC-SA were gradually enlarged by increasing the reactant feed ratio, indicating the successful modification of CNC surface with highly stable particles via increasing the negative charges on the outer surface. FTIR and XRD affirmed the change in the chemical structure as well as crystallinity of CNC after succinylation reaction. The prepared succinylated CNC was applied in the removal of methylene blue (MB) dye and the data showed that the sorption capacity is a direct proportional linear relation with the contents of carboxylic group. Within 120 min contact time, the sorption capacity was enlarged from 64.1 mg/g for CNC to 84.1 mg/g for CNC-SA3. The sorption data was fitted well to the first order kinetic model. Due to the esterification, the rate of sorption reaction is accelerated by double factor. These findings will maximize the benefit of esterified CNC in water treatment.

36 MATERIALS SCIENCE↗