SEARCH · Engineering Papers
Results for “photos”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Alcohol oxidation as alternative anode reactions paired with (photo)electrochemical fuel production reactions
Not Available
Photo-enhanced ionic conductivity across grain boundaries in polycrystalline ceramics
Not provided.
Direct photo-oxidation of methane to methanol over a mono-iron hydroxyl site
Explore the source record for details and available documents.
Photo-actuators via epitaxial growth of microcrystal arrays in polymer membranes
Photomechanical crystals composed of three-dimensionally ordered and densely packed photochromes hold promise for high-performance photochemical actuators. However, bulk crystals with high structural ordering are severely limited in their flexibility, resulting in poor processibility and a tendency to fragment upon light exposure, while previous nano- or microcrystalline composites have lacked global alignment. Here we demonstrate a photon-fuelled macroscopic actuator consisting of diarylethene microcrystals in a polyethylene terephthalate host matrix. These microcrystals survive large deformations and show a high degree of three-dimensional ordering dictated by the anisotropic polyethylene terephthalate, which critically also has a similar stiffness. Overall, these ordered and compliant composites exhibit rapid response times, sustain a performance of over at least hundreds of cycles and generate work densities exceeding those of single crystals. In conclusion, our composites represent the state-of-the-art for photochemical actuators and enable properties unattainable by single crystals, such as controllable, reversible and abrupt jumping (photosalient behaviour).
Unlocking the potential of the formate pathway in the photo-assisted Sabatier reaction
Explore the source record for details and available documents.
Reversible photo control of proton chemistry
Control and drive functional systems with light and metastable state photoacids.
Probe metal binding mode of imine covalent organic frameworks: cycloiridation for (photo)catalytic hydrogen evolution from formate
This study describes cyclometallation as a new metal binding mode for imine-based COFs. The iridacycle decorated COF could be used for catalytic hydrogen evolution from aqueous formate solution with high stability and high efficacy.
Selective photo-excitation of molecules enabled by stimulated Raman pre-excitation
Double resonance excitation, where the energies of vibrational and electronic molecular transitions are combined in a single, sequential excitation process, was introduced in the 1970s but has only been recently applied to microscopy due to the immense progress in Raman spectroscopy. The value of the technique is in combining the chemical selectivity of IR or Raman excitation with the much larger cross-sections of electronic transitions. Recently, it has been shown to be particularly suited for the detection and identification of chromophores at low concentrations and in the presence of spectral crosstalk. However, despite its low quantum yield per pulse sequence, we believe the technique has potential for selective photochemical transformations. There are some cases (e.g., the selective excitation of optogenetic switches) where the low yield may be overcome by repeated excitations to build up biochemically relevant concentrations. Here we show that double resonance excitation using general, non-resonant Raman pre-excitation is a viable candidate for selectively promoting molecules to chemically active energy levels. Further, the use of non-resonant Raman pre-excitation is less constraining than resonant Raman (used in previous double resonance microscopy works) since the choice of Raman pump-Stokes frequencies may be rather freely chosen.
Photo-induced phase-transitions in complex solids
This review highlights the recent experimental and theoretical advances in ultrafast science in the field of ultrafast sciences, particularly photoinduced phase transitions in complex systems.
Time-resolved radioluminescence of the Cu( i ) cluster Cu 4 I 6 2− . Different responses to photo, X-ray, β-ray and α-particle excitation
The temporal response of radioluminescence from crystalline Cu 4 I 6 2− salts displays an initial fast component owing to excited state densities generated by high energy radiation.
Atomic autoionization in the photo-dissociation of super-excited deuterated water molecules fragmenting into D + + O + + D
We present the relaxation dynamics of deuterated water molecules via autoionization, initiated by the absorption of a 61 eV photon, producing the very rare D + + O + + D breakup channel. We employ the COLd target recoil ion momentum spectroscopy method to measure the 3D momenta of the ionic fragments and emitted electrons from the dissociating molecule in coincidence. We interpret the results using the potential energy surfaces extracted from multi-reference configuration interaction calculations. The measured particle energy distributions can be related to a super-excited monocationic state located above the double ionization threshold of D 2 O. The autoionized electron energy shows a sharp distribution centered around 0.5 eV, which is a signature of the atomic oxygen autoionization occurring in the direct and sequential dissociation processes of D 2 O + * at a large internuclear distance. In this way, an O + radical fragment and a low-energy electron are created, both of which can trigger secondary reactions in their environment.
Photo-ejected ligands hyperpolarized by parahydrogen in reversible exchange
Hyperpolarization derived from signal amplification by reversible exchange (SABRE) is a catalytic approach to enhance NMR detection. Here, we introduce light-triggered ejection of heterocyclic ligands to initiate the SABRE process.
Synthesis and characterization of conjugated [3]cumulenes and substitution-dependent photo-switchability
Explore the source record for details and available documents.
Work function lowering of LaB 6 by monolayer hexagonal boron nitride coating for improved photo- and thermionic-cathodes
We report a lowering of work function for lanthanum hexaboride (LaB 6 ) by monolayer hexagonal boron nitride (hBN) coating. Photoemission electron microcopy (PEEM) and thermionic emission electron microscopy (TEEM) both revealed that the hBN coated region of a LaB 6 (100) single crystal has a lower work function compared to the bare (i.e., non-coated) and graphene coated regions. A broad and uniform brighter image of the hBN coated region in PEEM was quantitatively supported by a 0.4 eV decrease in the work function in photoelectron spectra compared to the bare region. TEEM results were consistent in that the hBN coated region exhibited thermionic emission at 905 °C, whereas the bare and graphene coated regions did not. A larger decrease in the work function for hBN coated LaB 6 (100) compared to graphene coated LaB 6 (100) was qualitatively supported by our density functional theory calculations. Adding an oxide layer in the calculations improved consistency between the calculation and experimental results. We followed up our calculations with synchrotron-radiation x-ray photoelectron spectroscopy and confirmed the presence of an oxide layer on our LaB 6 .
Giant exciton-enhanced shift currents and direct current conduction with subbandgap photo excitations produced by many-electron interactions
Significance Shift current, a bulk photovoltaic effect, arises from nonlinear light–matter interaction in a noncentrosymmetric crystal under continuous wave illumination. Although it is a promising mechanism for photocurrent generation without p–n junctions, the short-circuit current (which is related to the power efficiency of a solar cell device) is usually low. It is therefore important to understand the physics of the phenomenon and find materials with strong shift current conductivity. We calculate the shift current conductivity including excitonic effects in a real material (monolayer GeS) from first principles. We show that electron–hole interactions can dramatically enhance and qualitatively change shift current in reduced-dimensional materials. Our results indicate low-dimensional materials are promising candidates for next-generation photovoltaic devices with high efficiencies.
Photo-printing of faceted DNA patchy particles
Patchy particles with shape complementarity can serve as building blocks for assembling colloidal superstructures. Alternatively, encoding information on patches using DNA can direct assembly into a variety of crystalline or other preprogrammed structures. Here, we present a tool where DNA is used both to engineer shape and to encode information on colloidal particles. Two reactive oil emulsions with different but complementary DNA (cDNA) brushes are assembled into CsCl-like crystalline lattices. The DNA brushes are recruited to and ultimately localized at the junctions between neighboring droplets, which gives rise to DNA-encoded faceted patches. The emulsions are then solidified by ultraviolet (UV) polymerization, producing faceted patchy particles. The facet size and DNA distribution are determined by the balance between the DNA binding energy and the elastic deformation energy of droplets. This method leads to a variety of new patchy particles with directional interactions in scalable quantities.