scholarly journals Ready Access to Molecular Rotors Based on Boron Dipyrromethene Dyes-Coumarin Dyads Featuring Broadband Absorption

Molecules ◽  
2020 ◽  
Vol 25 (4) ◽  
pp. 781
Author(s):  
Ernesto Enríquez-Palacios ◽  
Teresa Arbeloa ◽  
Jorge Bañuelos ◽  
Claudia I. Bautista-Hernández ◽  
José G. Becerra-González ◽  
...  
Keyword(s):  
Molecular Rotors ◽  
Fluorescence Signal ◽  
Access Method ◽  
Broadband Absorption ◽  
Boron Dipyrromethene ◽  
Conformational Freedom ◽  
Meso Position ◽  
Photophysical Study ◽  
Ready Access

Herein we report on a straightforward access method for boron dipyrromethene dyes (BODIPYs)-coumarin hybrids linked through their respective 8- and 6- positions, with wide functionalization of the coumarin fragment, using salicylaldehyde as a versatile building block. The computationally-assisted photophysical study unveils broadband absorption upon proper functionalization of the coumarin, as well as the key role of the conformational freedom of the coumarin appended at the meso position of the BODIPY. Such free motion almost suppresses the fluorescence signal, but enables us to apply these dyads as molecular rotors to monitor the surrounding microviscosity.

scholarly journals Спектральное исследование фотодинамических процессов в системе C-=SUB=-60-=/SUB=--(н-метилпирролидон)-кислород

2021 ◽  
Vol 129 (12) ◽  
pp. 1493
Author(s):  
И.М. Кисляков ◽  
И.М. Белоусова ◽  
В.М. Киселев ◽  
И.В. Багров ◽  
А.М. Стародубцев ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Singlet Oxygen ◽  
Transient Absorption ◽  
Rapid Quenching ◽  
Quenching Rate ◽  
Broadband Absorption ◽  
Laser Pumping ◽  
Time Dependencies ◽  
Quenching Rate Constant

The processes of photoexcitation and energy transfer in an air-saturated solution of fullerene C60 in n-methylpyrrolidone are studied. With femtosecond laser pumping at a wavelength л(p) = 520 nm, transient absorption spectra were obtained in the range 470-750 nm. Broadband absorption is observed at л > 650 nm as a result of aggregation of fullerene molecules, characterized by a short decay time of the picosecond scale. The analysis of the time dependencies indicates the presence of several processes. Within the proposed interpretation, we state a remarkable reduction in the time of singlet-triplet intersystem crossing with an increase of nanocluster size while the rapid quenching of the singlet state varies only slightly. The quantum yield of the triplet state can therefore increase, reaching 0.14. The phosphorescence spectra of singlet oxygen with a maximum at л = 1276 nm were measured with LED excitation at various wavelengths in the range 370-625 nm. The lifetime and quenching rate constant of singlet oxygen in n-methylpyrrolidone are determined. The combined quantum yield of triplet fullerene and singlet oxygen in n-methylpyrrolidone is estimated as 0.74. The efficiency spectra of the singlet oxygen photosensibilization in the C60-(n-methylpyrrolidone)-oxygen system are obtained, indicating the increasing role of large nanoclusters in this process during aging of the solution.

scholarly journals Broadband Microwave Absorption by Logarithmic Spiral Metasurface

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Shubo Wang ◽  
Bo Hou ◽  
Che Ting Chan
Keyword(s):  
Electromagnetic Wave ◽  
Scale Invariance ◽  
Logarithmic Spiral ◽  
Unit Cell ◽  
Scale Invariant ◽  
Archimedean Spiral ◽  
Broadband Absorption ◽  
Fabry Perot ◽  
Classical Waves

Abstract Metamaterials have enabled the design of electromagnetic wave absorbers with unprecedented performance. Conventional metamaterial absorbers usually employ multiple structure components in one unit cell to achieve broadband absorption. Here, a simple metasurface microwave absorber is proposed that has one metal-backed logarithmic spiral resonator as the unit cell. It can absorb >95% of normally incident microwave energy within the frequency range of 6 GHz–37 GHz as a result of the scale invariant geometry and the Fabry-Perot-type resonances of the resonator. The thickness of the metasurface is 5 mm and approaches the Rozanov limit of an optimal absorber. The physics underlying the broadband absorption is discussed. A comparison with Archimedean spiral metasurface is conducted to uncover the crucial role of scale invariance. The study opens a new direction of electromagnetic wave absorption by employing the scale invariance of Maxwell equations and may also be applied to the absorption of other classical waves such as sound.

scholarly journals Methylglyoxal-Induced Retinal Angiogenesis in Zebrafish Embryo: A Potential Animal Model of Neovascular Retinopathy

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Ying Li ◽  
Yantao Zhao ◽  
Shengmin Sang ◽  
TinChung Leung
Keyword(s):  
Control Group ◽  
Diabetic Patients ◽  
Fluorescence Signal ◽  
Zebrafish Model ◽  
Treatment Groups ◽  
Vegf Signaling ◽  
Vascular Area ◽  
Glycation End Products ◽  
Retinal Angiogenesis

Methylglyoxal (MG) is an intermediate of glucose metabolism and the precursor of advanced glycation end products (AGEs) found in high levels in blood or tissue of diabetic patients. MG and AGEs are thought to play a major role in the pathogenesis of diabetic retinopathy. In order to determine if zebrafish is valuable to help us understand more about retinopathy, we evaluate if MG induces abnormal vascular change and angiogenesis in zebrafish in a short incubation period. We also used an inhibitor of VEGFR (PTK787) to explore the mechanistic role of VEGF in MG-induced pathogenesis. A transgenic Tg(flk1:GFP) zebrafish line was used, and the embryos were incubated with MG solution and in combination with glucose (to mimic hyperglycemia). Retinal vascular structure visible with fluorescence signal was imaged using fluorescence microscopy. The percentage of vascular area was calculated and found elevated in the MG treatment groups than that in the control group (p<0.01) which indicated increased angiogenesis induced by MG treatment. PTK787 blocked the proangiogenic effects of MG treatment. This study suggests that MG has a potential proangiogenic effect via VEGF signaling in the retina of zebrafish embryos. Therefore, this zebrafish model may be used to study neovascular retinopathy.

scholarly journals Silicon Meets Graphene for a New Family of Near-Infrared Schottky Photodetectors

2019 ◽  
Vol 9 (18) ◽  
pp. 3677 ◽  
Author(s):  
Maurizio Casalino
Keyword(s):  
Near Infrared ◽  
Infrared Photodetectors ◽  
Strong Light ◽  
Broadband Absorption ◽  
New Family ◽  
High Carrier Mobility ◽  
Light Matter Interaction ◽  
High Carrier ◽  
Schottky Junctions

In recent years, graphene has attracted much interest due to its unique properties of flexibility, strong light-matter interaction, high carrier mobility and broadband absorption. In addition, graphene can be deposited on many substrates including silicon with which is able to form Schottky junctions, opening the path to the realization of near-infrared photodetectors based on the internal photoemission effect where graphene plays the role of the metal. In this work, we review the very recent progress of the near-infrared photodetectors based on Schottky junctions involving graphene. This new family of device promises to overcome the limitations of the Schottky photodetectors based on metals showing the potentialities to compare favorably with germanium photodetectors currently employed in silicon photonics.

Two new polymorphic forms of combretastatin A-4, an antitumour agent

2020 ◽  
Vol 76 (10) ◽  
pp. 958-964
Author(s):  
Anita M. Grześkiewicz ◽  
Tomasz Stefański ◽  
Zbigniew Dutkiewicz ◽  
Daria Buśko ◽  
Maciej Kubicki
Keyword(s):  
Weak Interactions ◽  
Topological Analysis ◽  
Monoclinic Form ◽  
Colchicine Binding Site ◽  
Biological Studies ◽  
Antitumour Agent ◽  
Conformational Freedom ◽  
Polymorphic Forms

Two new polymorphic forms of combretastatin A-4 {systematic name: 2-methoxy-5-[(E)-2-(3,4,5-trimethoxyphenyl)ethenyl]phenol, C18H20O5, CA-4}, an inhibitor of tubulin polymerization at the colchicine binding site, were identified. A number of crystallization attempts led to the orthorhombic form, with two molecules in the asymmetric part of the unit cell; obtaining a different form required the experiment to be moved to another laboratory. None of the attempts resulted in the monoclinic form described earlier. The three different forms contain molecules of significantly different geometries, which can be related to conformational freedom, postulated as the result of biological studies. In addition, the packing modes in all three forms are basically different. The structural differences at both the molecular and the supramolecular level have also been studied via calculations of energies and a topological analysis of the electron density. The results confirm the role of weak interactions in the determination of crystal architecture and additionally hint at an explanation for the results of crystallization attempts: the new monoclinic form has significantly lower energy than the form reported earlier.

Photophysical study of a charge transfer oxazole dye in micelles: Role of surfactant headgroups

2015 ◽  
Vol 163 ◽  
pp. 21-27 ◽  
Author(s):  
Jyotirmay Maiti ◽  
Yeasmin Sarkar ◽  
Partha Pratim Parui ◽  
Sandipan Chakraborty ◽  
Suman Biswas ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Photophysical Study ◽  
A Charge

The Aramaic Bible in the East

2019 ◽  
Vol 17 (1) ◽  
pp. 39-66
Author(s):  
Philip S. Alexander
Keyword(s):  
Systematic Study ◽  
Religious Identity ◽  
The West ◽  
Jewish Communities ◽  
Bible Translation ◽  
The Bible ◽  
History Of ◽  
Ready Access

Abstract This article challenges the assumption that insofar as the Jewish communities of Babylonia were a ‘people of the book’, their book was a Hebrew Bible. Functionally the Bible that most people would have known was the Aramaic Targum of Onqelos and Jonathan. The Bible’s content—its law, narrative, and prophecy—was culturally mediated through Aramaic. Even in Rabbinic communities, where some had competence in Hebrew that gave them ready access to the original, the lack of formal and systematic study of Miqra may have made the Targum the tradition of first resort for understanding the Hebrew. The situation in the Aramaic-speaking east may not, then, have been all that different from the west, where a Greek Bible shaped the religious identity of the Greek-speaking Jewish communities. This essay is offered as a contribution to the neglected study of the role of Bible translation in the history of Judaism.

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