Maximum Redshift Research Articles

Small D-π-A-π-D organic dyes for near-infrared emitting OLEDs with excellent external quantum efficiency

Organic-light emitting diodes (OLEDs) with near-infrared (NIR) emission have an extremely broad range of attractive applications. Compounds containing donor (D) and acceptor (A) fragments are promising materials for use as active emitting layer in OLEDs due to their fast luminescence and because their luminescence properties can be fine-tuned at the synthesis stage. In this work, we synthesized and investigated two D-π-A-π-D NIR-emitting dyes based on a new pyridazine-thiadiazole electron acceptor with two different π linkers. The introduction of π linkers, together with the geometry modification, provides an additional redshift of the emission maximum from 700 to 850 nm. These dyes demonstrate moderate quantum yields up to 15% in chloroform solutions and to 4% in the solid state. Spectroscopic studies were supported by Time Dependent Density Functional Theory (TD-DFT) and multireference (XMCQDPT/CASSCF) calculations. A series of OLEDs with electroluminescence at 700 and 850 nm was fabricated. One of the devices exhibited maximum optical power 76 μW/cm2 and maximum external quantum efficiency (EQE) 1.2%, which is close to the theoretical limit calculated for fluorescent NIR OLEDs based on low band gap small organic molecules.

Xanthene-based polarity-sensitive fluorescent probe with large Stokes shifts for simultaneous two-color visualizing of lipid droplets and lysosomes

Lipid droplets (LDs) and lysosomes interact as important intracellular subcellular organelles in many physiological and pathological processes. Two-color imaging fluorescent probes have become an important tool for studying the interaction between lipid droplets and lysosomes in cells. Based on the variance in polarity between LDs and lysosomes, a polarity-sensitive probe LD-H-Lyso was designed and synthesized with an xanthene fluorophore as the main body, moreover we introduced a morpholine group into the main structure of the probe to enable it targeting lysosomes. The maximum emission wavelengths of LD-H-Lyso in 1,4-dioxane, acetone and dimethyl sulfoxide were 549 nm (yellow wavelength range), 624 nm (red wavelength range) and 661 nm (red wavelength range) respectively under excitation at 405 nm. The maximum redshift of the fluorescence emission was 112 nm and the maximum Stokes shift was 223 nm. Meanwhile, the results of cell imaging showed that LD-H-Lyso was able to visualize both LDs (yellow channel) and lysosomes (red channel) with high specificity, with pearson's correlation coefficient of 0.96 for LDs and 0.97 for lysosomes. Furthermore, staining of HepG2 cells using LD-H-Lyso allowed monitoring a corresponding decrease or increase in the number of LDs that were lit in starved/oleic acid-treated cells, with a weak effect on lysosomes displayed in the red channel. Similarly, chloroquine-treated cells exhibited poorer targeting of the probe to lysosomes compared to normal cells, resulting in reduced lamellar fluorescence in the red channel and less altered fluorescence in the yellow channel. Thus, LD-H-Lyso presented significant potential as a new monitoring tool that can simultaneously label both organelles and enable monitoring of individual organelles to explore the interaction of LDs and lysosomes.

Ion-specific bathochromic shifts: Simultaneous detection of multiple heavy metal pollutants via charge transfer interactions

An anthraimidazoledione-based colorimetric probe (1) has been developed to detect heavy metal pollutants in acetonitrile medium. Adding metal ions, such as Zn2+, Ni2+ and Co2+ induce ion-dependent redshifts in the metal-to-ligand charge transfer (MLCT) band. As a result, the almost colorless solution of1turned into green, yellow and red colors upon adding Zn2+, Ni2+, and Co2+ ions. On the other hand, the blue fluorescence of 1 is slightly quenched in the presence of Zn2+ ions, while the diminution is significant for Ni2+ ions. On the other hand, Co2+ ion results in the red-shift of emission maxima and quenching. Thus, we could observe faint cyan-colored fluorescence with Co2+ ions. The binding affinities for metal ions follow Irving–William’s order. At the same time, the colorimetric responses depend on the ionic radius, hydration enthalpy, coordination number, crystal field stabilization energies of the metal ions, etc. However, in the mixed aqueous environment, the ratiometric response was noticed only with Co2+ ions. Along with ratiometric color change, additions of metal ions result in an increase in both anodic and cathodic peak current along with shifts in the redox potential values. Further, the presence of residual Co2+ was determined in natural water samples.

Effects of rice bran phenolics on the structure of rice bran protein under different degrees of rancidity

To explore the effects of rice bran endogenous phenolics on rice bran protein under rice bran rancidity-induced oxidation, the structure of non-dephenolized and dephenolized rice bran protein with different degrees of rice bran rancidity (rice bran was stored for 0, 1, 3, 5, and 10 d) were investigated. During rice bran storage, dephenolization increased the carbonyl (from 5.32-24.59 to 6.11–26.52 μmol/g) and free sulfhydryl (from 24.41-32.33 to 32.64–45.04 μmol/g) contents of rice bran protein, and decreased disulfide bonds content (from 24.26-26.61 to 21.78–25.42 μmol/g). Meanwhile, endogenous phenolics improved rice bran protein secondary structural flexibility. Moderate oxidation (rice bran was stored for 0 and 1 d) induced by rice bran rancidity unfolded rice bran protein. The increase of maximum fluorescence emission wavelength red shift and the improvement of surface hydrophobicity induced by endogenous phenolics under moderate oxidation indicated rice bran endogenous phenolics further promoted the unfolding of rice bran protein. Excessive oxidation (rice bran was stored for 3, 5, and 10 d) caused protein aggregation. This work demonstrated that endogenous phenolics significantly affected rice bran protein structure under oxidation, especially the synergistic effect of endogenous phenolics and moderate oxidation on protein unfolding state.

Enhanced circularly polarized luminescence in fluoro-substituted N^C^N-coordinating platinum(II) complexes

Two sets of pinene-fused (N^C^N)Pt isocyanide complexes have been prepared and characterized. Complexes (−)-1 and (−)-2 form supramolecular self-assemblies via intermolecular Pt⋯Pt and/or π–π interactions in H2O solution, which is verified by the 1H NMR signals, SEM morphologies and RLS spectra. All the complexes are emissive in solution and show AIE behaviors in mixed MeOH/H2O solutions with emission quantum yield (Φem) up to 43.89%. The introduction of –F in phosphorescent (N^C^N)Pt skeleton would facilitate a high degree of polymerization for the assemblies, inducing a red-shift of emission maximum and an improvement of Φem. Moreover, complex (−)-2 with –F substitute possesses a helical structure with greater helicity, showing more significant CPL activity.

Geometry tailored magneto-optical absorption spectra of elliptically deformed double quantum rings

ABSTRACT We theoretically investigated the effect of the geometry change on the electronic and magneto-optical absorption spectra of GaAs/Ga0.7Al0.3As double quantum rings. The inner ring shape was changed continuously from circular to elliptic. Our numerical results revealed the decrement of the levels energies with the augments of the eccentricity of the internal/external ellipses that limit the inner ring, leading to a blue shift of the maxima in the absorption spectra in the magnetic field absence. Analysing separately the electronic spectra of the inner/outer single rings and of the double quantum rings structure in the magnetic field, we have found that, in the electronic spectra of the double ring, only the energies and the Aharonov–Bohm periodicity of the outer ring are altered by interference, while the Aharonov–Bohm oscillations of the inner ring levels propagate unchanged in the spectra. The magneto-optical spectra of elliptically deformed double quantum rings cover a wider range of energies than those of circular double ring and, at higher magnetic fields, present new peaks corresponding to transitions to higher states. Also, they show superposed peaks of increased absorption for a particular elliptic geometry and a red-shift of low energy maxima at the augment of the magnetic field which is the more pronounced the eccentricity increases. Moreover, the influence of the temperature is stronger than for the symmetrical structure.

Substitution of the sole tryptophan of the cupredoxin, amicyanin, with 5-hydroxytryptophan alters fluorescence properties and energy transfer to the type 1 copper site

Amicyanin is a type 1 copper protein with a single tryptophan residue. Using genetic code expansion, the tryptophan was selectively replaced with the unnatural amino acid, 5-hydroxytryptophan (5-HTP). The 5-HTP substituted amicyanin exhibited absorbance at 300–320 nm, characteristic of 5-HTP and not seen in native amicyanin. The fluorescence emission maximum in 5-HTP substituted amicyanin is redshifted from 318 nm in native amicyanin to 331 nm and to 348 nm in the unfolded protein. The fluorescence quantum yield of 5-HTP substituted amicyanin mutant was much less than that of native amicyanin. Differences in intrinsic fluorescence are explained by differences in the excited states of tryptophan versus 5-HTP and the intraprotein environment. The substitution of tryptophan with 5-HTP did not affect the visible absorbance and redox potential of the copper, which is 10 Å away. In amicyanin and other cupredoxins, an unexplained quenching of the intrinsic fluorescence by the bound copper is observed. However, the fluorescence of 5-HTP substituted amicyanin is not quenched by the copper. It is shown that the mechanism of quenching in native amicyanin is Förster, or fluorescence, resonance energy transfer (FRET). This does not occur in 5-HTP substituted amicyanin because the fluorescence quantum yield is significantly lower and the red-shift of fluorescence emission maximum decreases overlap with the near UV absorbance of copper. Characterization of the distinct fluorescence properties of 5-HTP relative to tryptophan in amicyanin provides a basis for spectroscopic interrogation of the protein microenvironment using 5-HTP, and long-distance interactions with transition metals.

Time-dependent Numerical Model for Studying the Very-high-energy Emissions of Distant Gamma-Ray Burst GRB 201216C

Recently, the MAGIC Collaboration reported a ∼5σ statistical significance of the very-high-energy (VHE) emission from a distant gamma-ray burst (GRB), GRB 201216C. Such distant GRB may be effectively absorbed by the extragalactic background light (EBL). The origin of the VHE emission from such distant objects is still unknown. Here, we propose a numerical model for studying the afterglow emission of this distant GRB. The model solves the continuity equation governing the temporal evolution of electron distribution, and the broadband observed data can be explained by the synchrotron plus synchrotron self-Compton (SSC) radiation of the forward shock. The predicted observed 0.1 TeV flux can reach ∼10−9−10−10 erg cm−2 s−1 at t ∼ 103−104 s, even with strong EBL absorption, such strong sub-teraelectronvolt (sub-TeV) emissions still can be observed by the MAGIC telescope. Using this numerical model, the shock parameters in the modeling are similar to two other sub-TeV GRBs (i.e., GRB 190114C and GRB 180720B), implying that the sub-TeV GRBs have some commonalities: they have energetic burst energy, low circumburst medium density, and a low magnetic equipartition factor. We regard GRB 201216C as a typical GRB, and estimate the maximum redshift of GRB that can be detected by the MAGIC telescope, i.e., z ∼ 1.6. We also find that the VHE photon energy of such distant GRB can only reach ∼0.1 TeV. Improving the low energy sensitivity of the VHE telescope is very important to detect the sub-TeV emissions of these distant GRBs.

CoLoRe: fast cosmological realisations over large volumes with multiple tracers

We present CoLoRe, a public software package to efficiently generate synthetic realisations of multiple cosmological surveys.CoLoRe can simulate the growth of structure with different degrees of accuracy, with the current implementation supporting lognormal fields, first, and second order Lagrangian perturbation theory.CoLoRe simulates the density field on an all-sky light-cone up to a desired maximum redshift, and uses it to generate multiple 2D and 3D maps: galaxy positions and velocities, lensing (shear, magnification, convergence), integrated Sachs-Wolfe effect, line intensity mapping, and line of sight skewers for simulations of the Lyman-α forest. We test the accuracy of the simulated maps against analytical theoretical predictions, and showcase its performance with a multi-survey simulation including DESI galaxies and quasars, LSST galaxies and lensing, and SKA intensity mapping and radio galaxies. We expect CoLoRe to be particularly useful in studies aiming to characterise the impact of systematics in multi-experiment analyses, quantify the covariance between different datasets, and test cross-correlation pipelines for near-future surveys.

Limiting Flux versus Redshift as a Flag of New Physics

Abstract I show that General Relativity sets an absolute upper limit on the energy flux observed from a cosmological source as a function of its redshift. Detecting a brighter source in gravitational waves, neutrinos or light, would flag new physics. The derived flux limit can also be used to determine the maximum redshift possible for any source with an unknown origin.

Optical Study of Solvatochromic Isocyanoaminoanthracene Dyes and 1,5-Diaminoanthracene.

Isocyanoaminoarenes (ICAAr-s) are a novel and versatile group of solvatochromic fluorophores. Despite their versatile applicability, such as antifungals, cancer drugs and analytical probes, they still represent a mostly unchartered territory among intramolecular charge-transfer (ICT) dyes. The current paper describes the preparation and detailed optical study of novel 1-isocyano-5-aminoanthrace (ICAA) and its N-methylated derivatives along with the starting 1,5-diaminoanthracene. The conversion of one of the amino groups of the diamine into an isocyano group significantly increased the polar character of the dyes, which resulted in a significant 50–70 nm (2077–2609 cm−1) redshift of the emission maximum and a broadened solvatochromic range. The fluorescence quantum yield of ICAAs is strongly influenced by the polarity of the solvent. The starting anthracene-diamine is highly fluorescent in every solvent (√f = 12–53%), while the isocyano derivatives are practically nonfluorescent in solvents more polar than dioxane. This phenomenon implies the potential application of ICAAs to probe the polarity of the medium and is favorable in practical applications, such as cell-staining, resulting in a reduced background fluorescence. The ICT character of the emission states of ICAAs are in good agreement with the computational findings presented in TD-DFT calculations and molecular electrostatic potential (MESP) isosurfaces.

Color-tuning and manipulation of the aggregation-induced emission efficiency of o-carborane-tetraphenylethylene dyads through substituted o-carboranes

By changing the 2-R substituents of carborane, absolute solid state fluorescence quantum yields of TPE derivatives ranging from 18% to 91% were obtained. The emission colors show a clear shift from blue to red with a maximum red shift of 239 nm.

CdSe/ZnS quantum dots capped with oleic acid and L-glutathione: Structural properties and application in detection of Hg2+

Two structures of CdSe/ZnS quantum dots (QDs), with different solubility properties, were prepared, characterized, and applied as fluorescent-based probes to detect Hg2+ ions. From oleic acid-capped CdSe/ZnS QDs (CdSe/ZnS/OA), glutathione-capped CdSe/ZnS QDs (CdSe/ZnS/GSH) were obtained by a ligand exchange reaction upon microwave radiation. X-ray diffraction (XRD), Fourier-Transform Infrared (FT-IR), and X-ray Photoelectron Spectroscopy (XPS) were employed to determine crystallinity, structural characteristics, and chemical composition according to the capping agent. Synthesis methodology produced nanocrystals with cubic zinc blende structure. The coordination mode between the carboxylate group of oleic acid (OA) and the thiol group of glutathione (GSH), and the Zn2+ ions of QDs surface was discussed. Ultraviolet-visible (UV–Vis) spectroscopy and photoluminescence (PL) measurements characterized the optical properties of QDs. The replacement of OA by GSH ligands on QDs surface produced a red-shift of the first absorption maximum and the emission band. Photoluminiscence quantum yield (PL QY) improved from 20% (for CdSe/ZnS/OA) to 26% (for CdSe/ZnS/GSH). The fluorescence (FL) quenching of Hg2+ induction was studied considering the solubility properties of the two structures of QDs. Measurements for hydrophobic CdSe/ZnS/OA QDs were realized in a heterogeneous medium composed of toluene and water. While for CdSe/ZnS/GSH, experiments were carried out in an aqueous solution. Hg2+ ions quenched 100% fluorescence of both structures of QDs, displaying high selectivity, rapid response time. The limit of detection (LOD) for CdSe/ZnS/OA was 74.8 nM and for CdSe/ZnS/GSH was 54.8 nM. Results indicate that the two CdSe/ZnS core/shell QDs are candidates for Hg2+ and other metal ions sensing.

In silico modelling of acceptor materials by End-capped and π-linker modifications for High-Performance organic solar Cells: Estimated PCE > 18%

Efficient acceptor materials are of great importance in improving the performance of organic solar cells. Electron transport materials play a crucial role in improving the power conversion efficiency (PCE) of photovoltaic devices. In recent years, great efforts have been made to develop new acceptor materials that can be used in organic solar cells (OSCs). Previous reports have shown the high efficiency of CH1007 as an acceptor material in OSCs application. In this study, we used CH1007 as a reference molecule (R) and developed four new acceptor materials (CF1-CF4) derived from CH1007 based on the tuning of the end-capped and π-linker units within the conjugated framework. Density functional theory calculations (DFT) were performed to determine the structural, optoelectronic, and charge transfer properties of the developed materials. CF1-CF4 exhibited narrow band gaps with a redshift of the absorption maxima compared to R, which will lead to an improvement in the PCE of OSC. Low reorganization energies of holes and electrons were determined for the designed molecules compared to the reference molecule, indicating high charge carrier transport within these molecules. Transition density matrix (TDM) analysis revealed the movement of electron density from the core block to the acceptor moieties via π-linkages. The photovoltaic parameters were investigated and we found a relevant open-circuit voltage (Voc) for the designed molecules. A mixing study was performed for PTB7-Th: CF3, which gave interesting results. Based on the founding results and comparison with R, we found that the designed molecules are promising materials that can be used as acceptors for high-efficiency OSCs.

Optical absorption and morphology of bio-intercalated polyaniline composites

Bio-intercalation based Polyaniline (PANI)-Aloe vera (AV) with Lithium Perchlorate (LiClO4) composites has been synthesized by In-situ chemical reaction method. The composite was employed characterizations with help of Fourier Transform Infrared (FT-IR) Spectroscopy and Scanning Electron Microscopy (SEM) to know the chemical interaction and morphology of the composites. From SEM result it was noticed that morphology became changes significantly with reduce porosity. The Ultra Violet Absorption (UV-Vis) study shows that absorption increases as well as maximum peak shifts and PAL10 red shifts in visible region at 615nm. These results manifest that PANI-AV/LiClO4 (PAL) composites are the promising materials for solar cell, LED’s and electrical applications. Copyright © 2017 VBRI Press

Absorption properties of bromide photo-thermo-refractive glasses doped with Ytterbium

In this work bromide photo-thermo-refractive glasses with different Ytterbium concentration were explored. It is shown that UV irradiation and subsequent heat treatment of samples with Yb 2 mol.% causes significant red-shift absorption line from 410 nm with temperature lower than Tg to 517 nm with temperature Tg +60 °C. For small concentration of Yb (0,1 mol. %) maximum red-shift in plasmon resonance absorption band is shown as 485 nm and it is the same for heat treatment temperatures from Tg +20 °C to Tg +60 °C.

Optical properties of GeO[SiO] and GeO[SiO2] solid alloy layers grown at low temperature

The optical properties of GeO[SiO] and GeO[SiO2] solid alloy films grown on Si(001) substrates were studied using Raman, Fourier transform infrared absorption (FTIR) and photoluminescence (PL) spectroscopies. A PL signal was observed in the infrared region both for as-deposited and annealed germanium silicate suboxide films. Furnace annealing led to an increase of the PL signal and to a redshift of the PL maximum. The PL at ∼1100 nm is most probably due to defect-induced radiative transitions while the PL at ∼1500 nm may be rather caused by amorphous Ge nanoclusters and Ge nanocrystals. Finally, the temperature dependence of the PL was studied. Anomalous quenching of the PL signal is observed which does not follow the classical Arrhenius law. The temperature dependence of the PL intensity is well explained by using a Berthelot model.

Fluorinated phenothiazine derivatives: Photophysical properties, mechanochromism and thermochromism

Three fluorinated phenothiazine compounds (P-1, P-2, P-3) were synthesized and characterized. It was found that all of them displayed significant solvatochromism and aggregation-induced emission behaviors. It was worth noting that P-1 and P-2 exhibited obvious mechanochromic properties compared to P-3. Specifically, P-1 displayed two different colors upon grinding and smashing, and emission bands showed different shift direction. P-2 exhibited polymorphic emission, its powder emitted yellow fluorescence, whereas crystal emitted orange fluorescence. After grinding, these two states had red shifts of 76 nm and 35 nm, respectively. But P-3 only presented a red shift of 10 nm. In addition, P-1 and P-2 also had thermochromic properties. After heating, their maximum emission wavelengths all would red-shift, and the maximum red shift can be up to 71 nm. These results can be explained by wide-angle X-ray diffraction, the differential scanning calorimetry and single crystal diffraction analysis. This work provided a new idea for the preparation of materials with both mechanochromic and thermochromic characteristics.

Tracing Evolution of Angle-Wavelength Spectrum along the 40-m Postfilament in Corridor Air

Postfilamentation channel resulting from filamentation of freely propagating 744-nm, 5-mJ, 110-fs pulse in the corridor air is examined experimentally and in simulations. The longitudinal extension of postfilament was determined to be 55–95 m from the compressor output. Using single-shot angle-wavelength spectra measurements, we observed a series of red-shifted maxima in the spectrum, localized on the beam axis with the divergence below 0.5 mrad. In the range 55–70 m, the number of maxima and their red-shift increase with the distance reaching 1 μm, while the pulse duration measured by the autocorrelation technique is approximately constant. Further on, for distances larger than 70 m and up to 95 m, the propagation is characterized by the suppressed beam divergence and unchanged pulse spectrum. The pulse duration increases due to the normal air dispersion.

Near field spectral dispersion of dipole radiation: The maximum red and blue shifts, and the near and far field boundary

Spectral dispersion of dipole radiation in near field zone is studied. Spectral changes are demonstrated using polychromatic incident light of Gaussian spectral profile as test examples. Both red and blue shifts are possible. The maximum redshift can reach upon −20% of the original peak frequency ω0. It is found that there is a boundary at r=0.175λ0 separates the red and blue shift zones. The dipole radiation can be decomposed in two parts, evanescent and propagating parts. The dispersion is studied for the whole radiation, as well as for evanescent and propagating parts. It is discovered that the boundary separates red and blue shift corresponds to the point where the propagating part becomes dominate. Therefore it is proposed to also call the boundary the near and far field boundary. In addition, the spectral changes are different for different dipole orientations, which can be essential for applications of near field antennas.