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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Torsionally Responsive C[subscript 3]-Symmetric Azo Dyes: Azo−Hydrazone Tautomerism, Conformational Switching, and Application for Chemical Sensing

An efficient triple azo coupling reaction between anilines and phloroglucinol furnished a series of C{sub 3}-symmetric molecules 7-9 supporting multiple conjugation pathways that converge at the molecular core. A combination of {sup 1}H/{sup 13}C NMR spectroscopy, X-ray crystallography, and density functional theory computational studies provided a coherent picture of the [n,{pi}]-conjugated molecular core, which is best described as the tris(hydrazone) [rather than tris(azo)] tautomer stabilized by resonance-assisted hydrogen bonding. For a homologous series of compounds, an increase in the torsional angles between the planar molecular core and the peripheral aryl groups results in a systematic blue shift in the low-energy electronic transitions (7, 523 nm; 8, 505 nm; 9, 445 nm in CHCl{sub 3}) that qualitatively correlates with the shrinkage of effective conjugation through structural distortion. Similar spectral shifts could also be induced by amine substrates that interact with the intramolecular hydrogen-bonding network to trigger bond-twisting motions. Specifically, a brief exposure of a thin film of 7 to vapor samples of butyl-, hexyl-, diethyl-, and diisopropylamine resulted in a rapid and reversible color change from pink to dark-orange. Under similar conditions, however, triethylamine did not elicit any detectable color change, despite the fact that it has a significantly higher vapor pressure than n-hexylamine. These findings implicate that the hydrogen-bonding donor ability is a key requirement for the binding-induced conformational switching, which allows for direct naked-eye detection of volatile amines under ambient conditions.

08 HYDROGEN↗
DOE OSTI2015

Synthesis and characterization of BiFeO{sub 3} for photocatalytic degradation of azo dye

A novel approach is reported to synthesize single phase BiFeO{sub 3} via. sol-gel auto combustion method using glycine as fuel. Synthesized powder was subjected to annealing at different temperatures, i.e. 400 °C, 450 °C, 500 °C, 550 °C, and 600°C. Crystal structure of BiFeO{sub 3} samples examined by X-ray diffraction indicates that the samples were single-phased with different particle sizes, as particle sizes are temperature dependent and crystallized in rhombohedral structure. As the temperature was increased, the diffraction peak intensity of BiFeO3 in the XRD spectra gradually enhanced and the diffraction peaks became sharper. The optical properties of the resultant BiFeO{sub 3} were characterized using UV-Vis spectrophotometer over the range of 350-800 nm. UV-vis spectra of all the samples indicate that optical band gap lies in the visible region in the range of 2.2-2.07 eV at all temperatures. Moreover, photocatalytic properties of the BiFeO{sub 3} powders were investigated by the photodegradation of Reactive Black-5 (RB-5)

36 MATERIALS SCIENCE↗
DOE OSTI2015

Theoretical investigation on dye sensitizer solar cell: Spin-forbidden transition

We studied spin-forbidden transitions of metal polypyridyl sensitizers by two-component relativistic time-dependent density functional theory with the spin-orbit interaction based on Tamm-Dancoff approximation. The singlet-to-triplet transition, which is assigned to a metal-to-ligand charge-transfer type excitation, appears for a phosphine-coordinated Ru(II), DX1. Absorption spectra of the modified DX1 molecules, whose Ru is replaced with Fe and Os, were also calculated for examining the effects of metals on the spin-orbit interaction.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

An organic dye with very large Stokes-shift and broad tunability of fluorescence: Potential two-photon probe for bioimaging and ultra-sensitive solid-state gas sensor

Light-emitting nonlinear optical molecules, especially those with large Stokes shifts and broad tunability of their emission wavelength, have attracted considerable attention for various applications including biomedical imaging and fluorescent sensors. However, most fluorescent chromophores have only limited potential for such applications due to small Stokes shifts, narrow tunability of fluorescence emissions, and small optical nonlinearity in highly polar solvents. In this work, we demonstrate that a two-photon absorbing stilbene chromophore exhibits a large two-photon absorption action cross-section (ηδ = 320 GM) in dimethylsulfoxide (DMSO) and shows broad fluorescence tunability (125 nm) by manipulating the polarity of the surrounding medium. Importantly, a very large Stokes shift of up to 227 nm is achieved in DMSO. Thanks to these features, this chromophore can be utilized as a two-photon probe for bioimaging applications and in an ultrasensitive solid-state gas detector.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Fe{sub 3}O{sub 4}/CuO/ZnO/Nano graphene platelets (Fe{sub 3}O{sub 4}/CuO/ZnO/NGP) composites prepared by sol-gel method with enhanced sonocatalytic activity for the removal of dye

In this study, an attempt has been made to synthesize nanographene platelets coupled with Fe3O4/CuO/ZnO (Fe3O4/CuO/ZnO/NGP) with various ZnO loadings using a two step methods, sol-gel followed by hydrothermal method. Characterization was carried out by X-ray diffraction, energy-dispersive X-ray spectroscopy and vibrating sample magnetometer. The sonocatalytic performance was evaluated by degradation of methylene blue under ultrasonic irradiation.The Fe3O4/CuO/ZnO/NGP showed superior sonocatalytic activity than the Fe3O4/CuO/ZnO materials. They also showed high stability and can be easily separated from the reaction system for recycling process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Synergy effect in sonodegradation of organic dye using graphene based magnetite composite materials

Owing to the unique physical properties, nanographene platelets could act as a good recombination inhibitor for functional materials. In this study, various concentrations of nanographene platelets are introduced to ferromagnetic Fe{sub 3}O{sub 4} nanoparticles to remove methylene blue in aqueous solution under ultrasonic irradiation. The coupling of nanographene platelets with Fe{sub 3}O{sub 4} nanoparticles is formed using hydrothermal method. Compared to pure Fe{sub 3}O{sub 4} nanoparticles, Fe{sub 3}O{sub 4}–nanographene platelets (Fe{sub 3}O{sub 4}–NGP) composites exhibited higher catalytic efficiency for methylene blue removal under ultrasonic irradiation. The catalytic efficiency increase with increasing nanographene platelets loading from 1 wt.% until 5 wt% and further decreased. From the scavenger technique, it is revealed that hole plays an important key role in sonocatalytic processes. The degradation efficiency decreased only 12% after 4 cycled.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Nanorods and nanoparticles of titanium dioxide and their use in dye sensitized solar cells

Mesoporous TiO{sub 2} nanorods/nanorods were successfully synthesized by hydrothermal process at 170 °C for 72 hr. The powder X-ray diffraction pattern shows large fraction of anatase phase with good crystalline behavior of the prepared materials. The specific surface area and pore volume of the synthesized material are about 84.83 m{sup 2}/g and 0.1316 cc/g respectively. The morphological results show that the TiO{sub 2} nanorods had diameter of ~ 25 nm and the length of ~ 80 nm. The nanoparticles have 20 nm in size. The current-voltage curve shows that the synthesized TiO{sub 2} nanostructure results in 36.7 % higher solar cell efficiency than commercial P25.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Electroluminescence from completely horizontally oriented dye molecules

A complete horizontal molecular orientation of a linear-shaped thermally activated delayed fluorescent guest emitter 2,6-bis(4-(10Hphenoxazin-10-yl)phenyl)benzo[1,2-d:5,4-d′] bis(oxazole) (cis-BOX2) was obtained in a glassy host matrix by vapor deposition. The orientational order of cis-BOX2 depended on the combination of deposition temperature and the type of host matrix. Complete horizontal orientation was obtained when a thin film with cis-BOX2 doped in a 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) host matrix was fabricated at 200 K. The ultimate orientation of guest molecules originates from not only the kinetic relaxation but also the kinetic stability of the deposited guest molecules on the film surface during film growth. Utilizing the ultimate orientation, a highly efficient organic light-emitting diode with the external quantum efficiency of 33.4 ± 2.0% was realized. The thermal stability of the horizontal orientation of cis-BOX2 was governed by the glass transition temperature (T{sub g}) of the CBP host matrix; the horizontal orientation was stable unless the film was annealed above T{sub g}.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Phototoxic effect of conjugates of plasmon-resonance nanoparticles with indocyanine green dye on Staphylococcus aureus induced by IR laser radiation

The effect of IR laser radiation ({lambda} = 805 - 808 nm) on the bacteria of the strain Staphylococcus aureus 209 P, incubated in indocyanine green solutions, is studied, as well as that of colloid gold nanoshells, nanocages and their conjugates with indocyanine green. It is found that the S. aureus 209 P cells are equally subjected to the IR laser radiation ({lambda} = 805 nm) after preliminary sensitisation with indocyanine green and gold nanoparticles separately and with conjugates of nanoparticles and indocyanine green. The enhancement of photodynamic and photothermal effects by 5 % is observed after 30 min of laser illumination ({lambda} = 808 nm) of bacteria, treated with conjugates of indocyanine green and nanocages. (optical technologies in biophysics and medicine)

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1993

Optimization of the First and Second Hyperpolarizabilities of Organic Dyes (abstract)

We have been attempting to correlate hyperpolarizabilities with bond-length alteration (BLA), which is defined as the difference in the average length between adjacent carbon-carbon bonds in a polymethine [(CH)(sub n)] Polyenes have alternating double and single bonds (bond length equal to 1.34 Sand 1.45 U respectively), and thus show a high degree of bond-length alteration (BLA = -0.11 u.

organic dyes carbon-carbon bonds hyperpolarizabili↗
DOE OSTI2019

Energy Transfer Induced by Dye Encapsulation in a Hybrid Nanoparticle‐Purple Membrane Reversible Assembly

Abstract The purple membrane (PM) isolated from the bacteria Halobacterium salinarum ( H. salinarum ) arranges the transmembrane proton pump bacteriorhodopsin (bR) in a 2D hexagonal crystalline lattice. Here, PM sheets containing native bR bend into tube‐like structures with open edges under acidic pH conditions. When decorated with gold nanoparticles (AuNPs), these same PM sheets yield a sealed tube assembly. Upon Rhodamine B (Rh B) sequestration inside the sealed tube, a dramatic decrease in Rh B fluorescence lifetime (τ f ) from 1.5 ns (unencapsulated) to 14 ps (encapsulated) is observed. The dramatic decrease in lifetime is attributed to energy transfer between AuNPs and Rh B. Subsequent release from the AuNP–PM capsules triggered by an increase in pH shows that 93% of Rh B is recovered (τ = 14 min) due to the capsules' unfolding. The hybrid AuNP–PM material highlights the utility of multicomponent ensembles (i.e., lipid bilayer, protein array, and NPs) by demonstrating that complex, multistimuli 3D responses can lead to multiplexed functions such as controlling energy transfer in the confined, encapsulated state and breaking the energy pair via molecular release in response to a change in pH.

de Q. Silveira, Gleiciani↗