scholarly journals Electron-Deficient Heteroacenes that Contain Two Boron Atoms: Near-Infrared Fluorescence Based on a Push–Pull Effect

2021 ◽  
Author(s):  
Masato Ito, ◽  
Mika Sakai ◽  
Naoki Ando ◽  
Shigehiro Yamaguchi
Keyword(s):  
Near Infrared ◽  
Narrow Band ◽  
Crystallographic Analysis ◽  
X Ray ◽  
Reversible Redox ◽  
Nir Emission ◽  
Intense Absorption ◽  
Reduction And Oxidation ◽  
Franck Condon

Electron-deficient heteroacenes that contain two tricoordinate boron atoms in their acene skeletons and planarized phenyl ether moieties at their periphery were synthesized via the borylation of the corresponding silicon-bridged precursors. X-ray crystallographic analysis revealed quinoidal structures, which give rise to two-step reversible redox processes for both the reduction and oxidation. These compounds exhibit intense absorption and sharp fluorescence bands with vibronic structures in the near-infrared (NIR) region. These properties originate from the push–pull effect along the long axis of the molecule derived from the electron-donating ether moiety and the electron-accepting boron moieties. Of particular note is the NIR emission of the thienothiophene-centered heteroacene, which has a maximum at 952 nm with a narrow band width of 309 cm–1 in cyclohexane. A Franck–Condon analysis revealed the crucial role of the sterically less-hindered thienothiophene spacer in achieving this sharp emission band.

scholarly journals Electron-Deficient Heteroacenes that Contain Two Boron Atoms: Near-Infrared Fluorescence Based on a Push–Pull Effect

2021 ◽  
Author(s):  
Masato Ito, ◽  
Mika Sakai ◽  
Naoki Ando ◽  
Shigehiro Yamaguchi
Keyword(s):  
Near Infrared ◽  
Narrow Band ◽  
Crystallographic Analysis ◽  
X Ray ◽  
Reversible Redox ◽  
Nir Emission ◽  
Intense Absorption ◽  
Reduction And Oxidation ◽  
Franck Condon

Electron-deficient heteroacenes that contain two tricoordinate boron atoms in their acene skeletons and planarized phenyl ether moieties at their periphery were synthesized via the borylation of the corresponding silicon-bridged precursors. X-ray crystallographic analysis revealed quinoidal structures, which give rise to two-step reversible redox processes for both the reduction and oxidation. These compounds exhibit intense absorption and sharp fluorescence bands with vibronic structures in the near-infrared (NIR) region. These properties originate from the push–pull effect along the long axis of the molecule derived from the electron-donating ether moiety and the electron-accepting boron moieties. Of particular note is the NIR emission of the thienothiophene-centered heteroacene, which has a maximum at 952 nm with a narrow band width of 309 cm–1 in cyclohexane. A Franck–Condon analysis revealed the crucial role of the sterically less-hindered thienothiophene spacer in achieving this sharp emission band.

Near-Infrared Quantum Cutting Nanophosphors for Solar Cells

2011 ◽  
Vol 366 ◽  
pp. 173-176 ◽  
Author(s):  
Su Wen Li
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Solar Cells ◽  
Near Infrared ◽  
Photoluminescence Spectra ◽  
X Ray ◽  
Transmission Electron ◽  
Nir Emission ◽  
Quantum Cutting ◽  
Scanning Electron

An efficient near-infrared (NIR) quantum cutting (QC) nanophospors with Ce3+, Yb3+ codoped in CaF2 had been synthesized by hydrothermal method and characterized by X-ray powder diffraction, scanning electron microscope, transmission electron microscopy, photoluminescence spectra and decay dynamics. The nanoparticles were uniform and monodisperse. Under the excitation of 5d level of Ce3+, an intense NIR emission at 900-1050nm was observed which match to the energy of Si band gap of Si - based solar cells. In the Ce3+, Yb3+ codoped CaF2, the lifetime of Ce3+ decreases Superscript textand the quantum efficiency (QE) increases with increasing Yb3+ concentration.

Near-Infrared Downconversion in LuPO4: Tm3+, Yb3+ Phosphors

2016 ◽  
Vol 16 (4) ◽  
pp. 3511-3516 ◽  
Author(s):  
Li Li ◽  
Yongjie Wang ◽  
Jun Shen ◽  
Wenxuan Chang ◽  
Tianting Jin ◽  
...  
Keyword(s):  
Tetragonal Phase ◽  
Diffuse Reflectance ◽  
Near Infrared ◽  
Luminescent Properties ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Good Crystallinity ◽  
Nir Emission ◽  
Co Precipitation

Tm3+ and Yb3+ codoped LuPO4 phosphors were synthesized by the reverse-strike co-precipitation method. The obtained LuPO4:Tm3+, Yb3+ phosphors were characterized by X-ray diffraction (XRD), diffuse reflectance spectra, photoluminescence (PL) spectra, and decay lifetime to understand the observed near-infrared downconversion (DC) phenomena. The XRD results show that all the prepared phosphors can be readily indexed to the pure tetragonal phase of LuPO4 and exhibit good crystallinity. The experimental results showed that the strong visible emission around 649 nm from Tm3+(1G4 → 3F4) and near-infrared (NIR) emission around 1003 nm from Yb3+(2F5/2 → 2F7/2) of LuPO4:Tm3+, Yb3+ phosphors were observed under 468 nm excitation, respectively. The Yb3+ concentration dependence of luminescent properties and lifetimes of both the visible and NIR emissions have also been investigated. The quenching concentration of Yb3+ ions approaches 30 mol%. The DC mechanism is also discussed in detail.

scholarly journals The beamed jet and quasar core of the distant blazar 4C 71.07

2019 ◽  
Vol 489 (2) ◽  
pp. 1837-1849 ◽  
Author(s):  
C M Raiteri ◽  
M Villata ◽  
M I Carnerero ◽  
J A Acosta-Pulido ◽  
D O Mirzaqulov ◽  
...  
Keyword(s):  
Near Infrared ◽  
High Redshift ◽  
Spectral Energy Distribution ◽  
Dilution Effect ◽  
Polarization Degree ◽  
Spectral Energy ◽  
Polarization Angle ◽  
X Ray ◽  
Hydrogen Column Density

ABSTRACT The object 4C 71.07 is a high-redshift blazar whose spectral energy distribution shows a prominent big blue bump and a strong Compton dominance. We present the results of a 2-yr multiwavelength campaign led by the Whole Earth Blazar Telescope (WEBT) to study both the quasar core and the beamed jet of this source. The WEBT data are complemented by ultraviolet and X-ray data from Swift, and by γ-ray data by Fermi. The big blue bump is modelled by using optical and near-infrared mean spectra obtained during the campaign, together with optical and ultraviolet quasar templates. We give prescriptions to correct the source photometry in the various bands for the thermal contribution, in order to derive the non-thermal jet flux. The role of the intergalactic medium absorption is analysed in both the ultraviolet and X-ray bands. We provide opacity values to deabsorb ultraviolet data, and derive a best-guess value for the hydrogen column density of $N_{\rm H}^{\rm best}=6.3 \times 10^{20} \rm \, cm^{-2}$ through the analysis of X-ray spectra. We estimate the disc and jet bolometric luminosities, accretion rate, and black hole mass. Light curves do not show persistent correlations among flux changes at different frequencies. We study the polarimetric behaviour and find no correlation between polarization degree and flux, even when correcting for the dilution effect of the big blue bump. Similarly, wide rotations of the electric vector polarization angle do not seem to be connected with the source activity.

Preparation and Photoluminescent Properties of Ce3+, Yb3+ Co-Doped YF3 Nanophosphors for Solar Cells

2014 ◽  
Vol 508 ◽  
pp. 26-29 ◽  
Author(s):  
Su Wen Li ◽  
Ming Yue
Keyword(s):  
Solar Cells ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Near Infrared ◽  
Photoluminescence Spectra ◽  
X Ray ◽  
Nir Emission ◽  
Quantum Cutting ◽  
Co Doped ◽  
Scanning Electron

An efficient near-infrared (NIR) quantum cutting (QC) nanophospors with Ce3+, Yb3+ co-doped in YF3 had been prepared by hydrothermal method and characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), photoluminescence spectra and decay dynamics. The obtained nanorods were uniform and monodisperse. Under the excitation of 5d level of Ce3+, an intense NIR emission at 900 1100 nm was observed which match to the energy of Si band gap of Si - based solar cells. In the Ce3+, Yb3+ codoped YF3, the lifetime of Ce3+ decreases and the quantum efficiency (QE) increases with increasing Yb3+ concentration.

scholarly journals Expression, purification, crystallization and preliminary X-ray analysis of theD-alanyl carrier protein DltC fromStaphylococcus epidermidis

2012 ◽  
Vol 68 (7) ◽  
pp. 810-812
Author(s):  
Chi-Hung Huang ◽  
Chao-Hung Kao ◽  
Chia-Shin Yang ◽  
Chi-Huang Chang ◽  
Sheng-Chia Chen ◽  
...  
Keyword(s):  
Staphylococcus Epidermidis ◽  
Crystallographic Analysis ◽  
Diffusion Method ◽  
Carrier Protein ◽  
X Ray ◽  
Cell Parameters ◽  
Gram Positive Bacteria ◽  
Cation Homeostasis ◽  
Shed Light

The D-alanyl lipoteichoic acids (D-alanyl LTAs) present in the cell walls of Gram-positive bacteria play crucial roles in autolysis, cation homeostasis and biofilm formation. The alanylation of LTAs requires the D-alanyl carrier protein DltC to transfer D-Ala onto a membrane-associated LTA. Here, DltC fromStaphylococcus epidermidis(SeDltC) was purified and crystallized using the sitting-drop vapour-diffusion method. The crystals diffracted to a resolution of 1.83 Å and belonged to space groupP2, with unit-cell parametersa= 66.26,b = 53.28,c= 88.05 Å, β = 98.22°. The results give a preliminary crystallographic analysis ofSeDltC and shed light on the functional role of DltC in the alanylation of LTAs.

Near-Infrared Quantum Cutting in Yb3+ Doped SrMoO4 Phosphors

2016 ◽  
Vol 16 (4) ◽  
pp. 3494-3499 ◽  
Author(s):  
Xiaobing Luo ◽  
Jun Shen ◽  
He Huang ◽  
Lu Xu ◽  
Zhixiang Wang ◽  
...  
Keyword(s):  
Diffuse Reflectance ◽  
Near Infrared ◽  
Luminescent Properties ◽  
Solid State Reaction Method ◽  
X Ray Diffraction ◽  
Reaction Method ◽  
X Ray ◽  
Good Crystallinity ◽  
Nir Emission ◽  
Quantum Cutting

Efficient near-infrared (NIR) quantum cutting (QC) has been demonstrated in Yb3+ doped SrMoO4 phosphors synthesized by the high-temperature solid-state reaction method. The obtained SrMoO4:Yb3+ phosphors were characterized by X-ray diffraction (XRD), diffuse reflectance spectra, photoluminescence (PL) spectra and decay lifetime to understand the observed near-infrared quantum cutting phenomena. The XRD results show that all the prepared phosphors can be readily indexed to the pure tetragonal phase of SrMoO4 and exhibit good crystallinity. The experimental results showed that the strong visible molybdate (MoO2−24 emission around 493 nm and near-infrared (NIR) emission around 1000 nm from Yb3+(2F5/2 → 2F7/2) of SrMoO4:Yb3+ phosphors were observed under ultraviolet (290 nm) excitation. The Yb3+ concentration dependence of luminescent properties and lifetimes of both the visible and NIR emissions have also been investigated. The quenching concentration of Yb3+ ions approaches as high as 10 mol%. The cooperative energy transfer (CET) mechanism was also discussed in detail. The broadband NIR QC phosphors may possibly have potential application in enhancing the conversion efficiency of solar cells.

A Novel 3D Salen Neodymium Framework with Near-Infrared (NIR) Properties

2017 ◽  
Vol 70 (3) ◽  
pp. 265
Author(s):  
Shushen Chi ◽  
Hongfeng Li ◽  
Peng Chen ◽  
Ting Gao ◽  
Yu Yang ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Solid State ◽  
Near Infrared ◽  
3D Structure ◽  
Lanthanide Complex ◽  
Crystallographic Analysis ◽  
X Ray ◽  
Bridging Ligand ◽  
Hydrogen Bond Interactions ◽  
Counter Ions

The reaction of N,N′-bis(3-hydroxy)ethylene-1,2-diamine (H2salen) with Nd(NO3)3·6H2O and NdCl3·6H2O yields a novel lanthanide complex, namely, Nd(salen)2(NO3)2Cl (1). X-ray crystallographic analysis revealed that H2salen effectively functions as a bridging ligand forming a kind of novel 3D structure complex which is constructed by Salen ligands and mixed lanthanide counter-ions without π–π stacking and hydrogen bond interactions. This is the first Salen-type 3D lanthanide complex to be constructed in this way. The near-infrared (NIR) properties of 1 in the solid state were also studied.

Quaternary structure of Limulus polyphemus hemocyanin

1978 ◽  
Vol 36 (2) ◽  
pp. 176-177
Author(s):  
T. Wichertjes ◽  
E.J. Kwak ◽  
E.F.J. Van Bruggen
Keyword(s):  
Electron Microscopy ◽  
Functional Properties ◽  
Horseshoe Crab ◽  
Temperature Jump ◽  
Quaternary Structure ◽  
Crystallographic Analysis ◽  
Limulus Polyphemus ◽  
Oxygen Binding ◽  
X Ray ◽  
Intact Molecule

Hemocyanin of the horseshoe crab (Limulus polyphemus) has been studied in nany ways. Recently the structure, dissociation and reassembly was studied using electron microscopy of negatively stained specimens as the method of investigation. Crystallization of the protein proved to be possible and X-ray crystallographic analysis was started. Also fluorescence properties of the hemocyanin after dialysis against Tris-glycine buffer + 0.01 M EDTA pH 8.9 (so called “stripped” hemocyanin) and its fractions II and V were studied, as well as functional properties of the fractions by NMR. Finally the temperature-jump method was used for assaying the oxygen binding of the dissociating molecule and of preparations of isolated subunits. Nevertheless very little is known about the structure of the intact molecule. Schutter et al. suggested that the molecule possibly consists of two halves, combined in a staggered way, the halves themselves consisting of four subunits arranged in a square.

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