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Quantum ring

Nannan Jian, Kai Qu, Hua Gu, Lie Zou, Ximei Liu, Faqi Hu, Jingkun Xu, Yan Yu, Baoyang Lu
Conjugated fluorophores have been extensively used for fluorescence sensing of various substances in the field of life processes and environmental science, due to their noninvasiveness, sensitivity, simplicity and rapidity. Most existing conjugated fluorophores exhibit excellent light-emitting performance in dilute solutions, but their properties substantially decrease or even completely vanish due to severe aggregation quenching in the solid state. Herein, we synthesize a series of triazolopyridine-thiophene donor-acceptor-donor (D-A-D) type conjugated molecules with high absolute fluorescence quantum yields (ΦF) ranging from 80% to 89% in solution...
March 19, 2019: Physical Chemistry Chemical Physics: PCCP
Kazumasa Funabiki, Yuki Saito, Takashi Kikuchi, Kazutaka Yagi, Yasuhiro Kubota, Toshiyasu Inuzuka, Yohei Miwa, Michiyuki Yoshida, Osamu Sakurada, Shoichi Kutsumizu
We have developed a novel aromatic fluorine-induced one-pot synthesis of ring-perfluorinated trimethine cyanine dye without the use of a pyridine by reacting hexafluorobenzoindolenine with 5 equiv. of methyl trifluoromethanesulfonate in mixed solvents of DMF and toluene. The thus-obtained ring-perfluorinated trimethine cyanine dye shows much better fluorescence properties, including intensity, quantum yield, and lifetime, than the non-fluorinated dye, not only in CH2Cl2 solution and PMMA film, but also in powder...
March 19, 2019: Journal of Organic Chemistry
Wenzhe Li, Kaitlyn S Morgan, Yuan Li, J Keith Miller, Graham White, Richard J Watkins, Eric G Johnson
Beams with fast and continuously-tunable orbital angular momentum (OAM) have potential applications in classical and quantum optical communications, sensing, and in the study of beam propagation through turbulence. An acousto-optical deflector (AOD) is a sophisticated, well-studied device that continuously and rapidly tunes the deflection angle of an output beam. The log-polar HOBBIT setup can generate beams with OAM by wrapping elliptically shaped Gaussian beams with linear phase tilt to a ring. By combining the linear tilted output from the AOD with the OAM generation capabilities of the HOBBIT system, the generated OAM modes become continuously tunable at high speeds measured on the order of 400 kHz...
February 18, 2019: Optics Express
Patricia Saura, Ville R I Kaila
Complex I functions as an initial electron acceptor in aerobic respiratory chains that reduces quinone and pumps protons across a biological membrane. This remarkable charge transfer process extends ca. 300 Å and it is initiated by a poorly understood proton-coupled electron transfer (PCET) reaction between NADH and a protein-bound flavin (FMN) cofactor. We combine here large-scale density functional theory (DFT) calculations and quantum/classical (QM/MM) models with atomistic molecular dynamics (MD) simulations to probe the energetics and dynamics of the NADH-driven PCET reaction in complex I...
March 15, 2019: Journal of the American Chemical Society
Amanda N Oehrlein, Antonio Sanchez-Diaz, Philip C Goff, Miquel Planells, Neil Robertson, David A Blank, Wayne L Gladfelter
Oligothiophene dyes with two to five thiophene units were anchored to oleate-capped, quantum-confined zinc oxide nanocrystals (ZnO NCs) through a cyanoacrylate functional group. While the fluorescence of the bithiophene derivative was too weak for meaningful quenching studies, the fluorescence of the dyes with three, four and five thiophene rings was quenched upon binding to the NCs. Ultrafast pump-probe spectroscopy was used to observe the singlet excited states of the free dyes dissolved in dichloromethane as well as attached to a ZnO NC dispersed in the same solvent...
March 14, 2019: Physical Chemistry Chemical Physics: PCCP
Krešimir Molčanov, Biserka Kojić-Prodić
The first systematic study of π interactions between non-aromatic rings, based on the authors' own results from an experimental X-ray charge-density analysis assisted by quantum chemical calculations, is presented. The landmark (non-aromatic) examples include quinoid rings, planar radicals and metal-chelate rings. The results can be summarized as: (i) non-aromatic planar polyenic rings can be stacked, (ii) interactions are more pronounced between systems or rings with little or no π-electron delocalization ( e...
March 1, 2019: IUCrJ
Atsushi Kobayashi, Momoko Fujii, Yasuhiro Shigeta, Masaki Yoshida, Masako Kato
The luminescent Cu(I) coordination polymers [Cu2 I2 ( m, m'-bpy)] n (CuI- m; m, m'-bpy = m, m'-bipyridine; m = 3, 4) were successfully synthesized by the solvent-free thermal reaction of the metal salt CuI with the organic linkers m, m'-bpy. Powder X-ray diffraction analysis revealed that CuI-3 was immediately formed when a mixture of CuI and 3,3'-bpy was ground in a mortar at room temperature (20 °C). In contrast, a temperature >120 °C was required to synthesize the CuI-4 isomer, probably because of the higher melting point of the 4,4'-bpy linker...
March 13, 2019: Inorganic Chemistry
Jiang-Huan Ke, Li-Sha Zhang, Shi-Xin Chen, Sheng-Nan Shen, Tian Zhang, Chang-Xin Zhou, Jian-Xia Mo, Li-Gen Lin, Li-She Gan
Fourteen acetylbenzofuran derivatives, including three undescribed carbon skeletons with a newly formed hexane or benzene ring on the other side of the benzofuran ring, (±)-eupatonin A (1), (±)-eupatonin B (2), and eupatonin C (3), two new benzofurans (-)-12β-hydroxygynunone (4) and (+)-12-hydroxyl-13-noreuparin (5), as well as 9 known ones (6-14), were isolated from 95% ethanol extract of the roots of Eupatorium chinense. Their structures were determined by spectroscopic methods and quantum chemical DFT and TDDFT calculations of the NMR chemical shifts and ECD spectra, which helped in the determination of the relative configurations of 1 and 2 and the absolute configurations of 4 and 5, respectively...
March 8, 2019: Fitoterapia
Noah D Bronstein, Marissa Martinez, Daniel M Kroupa, Márton Vörös, Haipeng Lu, Nicholas P Brawand, Arthur J Nozik, Alan Sellinger, Giulia Galli, Matthew C Beard
We present a combined experimental and theoretical study of ligand-ligand cooperativity during X-type carboxylate-to-carboxylate ligand exchange reactions on PbS quantum dot surfaces. We find that the ligand dipole moment (varied through changing the substituents on the benzene ring of cinnamic acid derivatives) impacts the ligand-exchange isotherms; in particular, ligands with large electron withdrawing character result in a sharper transition from an oleate-dominated ligand shell to a cinnamate-dominated ligand shell...
March 11, 2019: ACS Nano
Marin Neykov Marinov, Emilia Dimitrova Naydenova, Georgi Tsvetanov Momekov, Rumyana Yordanova Prodanova, Nadezhda Vasileva Markova, Yulian Tenchev Voynikov, Neyko Marinov Stoyanov
BACKGROUND: The 1,8-Naphthalimides constitute an important class of biologically active, DNA-binding compounds. There are no available data on the synthesis of 1,8-naphthalimide derivatives with non-protein amino acids and their biological activity. The aims of this paper are to synthesis, structural characterization and cytotoxic activity of new 1-(1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)cycloalkane-1-carboxylic acids with 5-, 6-, 7-, 8- and 12-membered rings as well as 2-(1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)adamantane-2-carboxylic acid and 1-(1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)-1,2,3,4-tetrahydronaphthalene-1-carboxylic acid...
March 6, 2019: Anti-cancer Agents in Medicinal Chemistry
Sirous Yourdkhani, Michał Chojecki, Tatiana Korona
Despite massive efforts to pinpoint the substituent effects in the so-called cationπ systems, no consensus has been yet reached on how substituents exercise their effects in the interaction of the aromatic molecule with the metal ion. The π-polarization (the Hunter model) and the direct local effect (the Wheeler-Houk model) are two lines of thought applied to this problem, but the justification of both approaches is based on insufficiently proven assumptions and approximations. In order to shed more light on this issue we propose a new approach which enables us to gauge directly the energetic trends resulting from the interaction of the ring with the cation...
March 6, 2019: Physical Chemistry Chemical Physics: PCCP
Hsin-Yang Chang, Tzu-Ping Ko, Yu-Ching Chang, Kai-Fa Huang, Cheng-Yung Lin, Hong-Yun Chou, Cheng-Yi Chiang, Huai-Jen Tsai
Chromoproteins are a good source of engineered biological tools. We previously reported the development of a blue fluorescent protein, termed shBFP, which was derived from a purple chromoprotein shCP found in the sea anemone Stichodacyla haddoni. shBFP contains a Leu63 -Leu64 -Gly65 tri-peptide chromophore, and shows maximum excitation and emission wavelengths at 401 nm and 458 nm, along with a high quantum yield. How this chromophore endows shBFP with the unique fluorescence property in the absence of a hydroxyphenyl ring remained unclear...
March 2, 2019: International Journal of Biological Macromolecules
Filipa Mandim, Vânia C Graça, Ricardo C Calhelha, Isabel L F Machado, Luis F V Ferreira, Isabel C F R Ferreira, Paulo F Santos
In this work, several benzothiazole-based aminosquaraine dyes, displaying strong absorption within the so-called phototherapeutic window (650⁻800 nm), were synthesized. The ability, of all the new dyes, to generate singlet oxygen was assessed by determining the correspondent phosphorescence emission and through the comparison with a standard. The quantum yields of singlet oxygen generation were determined and exhibited to be strongly dependent on the nature of the amino substituents introduced in the squaric ring...
February 28, 2019: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Sumit Kumar Panja, Boumediene Haddad, Mansour Debdab, Johannes Kiefer, Yassine Chaker, Serge Bresson, Annalisa Paolone
Several recent studies of hydroxyl-functionalized ionic liquids (ILs) have shown that cation-cation interactions can be dominating these materials at the molecular level when the anion involved is weakly interacting. The hydrogen bonds between the like ions led to the formation of interesting chain-like, ring-like, or distinct dimeric (i.e. two ion pairs) supermolecular clusters. In the present work, vibrational spectroscopy (ATR-IR and Raman) and quantum chemical theory (DFT) of the hydroxyl-functionalized imidazolium ionic liquid C2OHmimCl indicate that anion-cation hydrogen bonding interactions are dominating and lead to the formation of distinct dimeric ion pair clusters...
March 1, 2019: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Sergei Aksenov, V V Val'kov, Maxim Yu Kagan
Taking into account an inner structure of the arms of the Aharonov-Bohm ring (AB ring) we have analyzed the transport features related to the topological phase transition which is induced in a superconducting wire (SC wire) with strong spin-orbit interaction (SOI). The SC wire acts as a bridge connecting the arms. The in-plane magnetic-field dependence of linear-response conductance obtained using the nonequilibrium Green's functions in the tight-binding approximation revealed the Breit-Wigner and Fano resonances (FRs) if the wire is in the nontrivial phase...
February 28, 2019: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Eline Bartolami, Dimitris Basagiannis, Lili Zong, Rémi Martinent, Yasunori Okamoto, Quentin Laurent, Thomas R Ward, Marcos Gonzalez-Gaitan, Naomi Sakai, Stefan Matile
Cyclic oligochalcogenides are emerging as powerful tools to penetrate cells. With disulfide ring tension maximized, selenium chemistry had to be explored next to enhance speed and selectivity of dynamic covalent exchange on the way into the cytosol. We show that diseleno lipoic acid (DiSeL) delivers a variety of relevant substrates. DiSeL-driven uptake of artificial metalloenzymes enables bioorthogonal fluorophore uncaging within cells. Binding of a bicyclic peptide, phalloidin, to actin fibers evinces targeted delivery to the cytosol...
February 28, 2019: Chemistry: a European Journal
Yasser Saleem, Luis Najera Baldo, Alain Delgado, Ludmila Marta Szulakowska, Pawel Hawrylak
We determine here the evolution of the bandgap energy with size in graphene quantum dots (GQDs). 
 We find oscillatory behaviour of the bandgap and explain its
 origin in terms of armchair and zigzag edges.
 The electronic energy spectra of GQDs are
 computed using both the tight binding model and {\it ab-initio} density functional
 methods. The results of the tight binding model are analyzed by dividing zigzag graphene
 quantum dots into concentric rings. For each ring, the energy spectra,
 the wave functions and the bandgap are obtained analytically...
February 27, 2019: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Iryna V Omelchenko, Oleg V Shishkin, Przemyslaw Dopieralskie, Zdzislaw Latajka
Aromaticity and structural features of the isolated symm-triaminotrinitrobenzene (TATB) were examined using the non-empirical ab initio quantum chemical method and molecular dynamics at the Car-Parrinello level. Different criteria of the aromaticity were combined with the study of conformational flexibility of molecule and analysis of the electron density distribution. It was found that cooperative effect of the resonance-assisted hydrogen bonds results in the ultimate decreasing aromaticity of the benzene ring in TATB...
February 27, 2019: Journal of Physical Chemistry. A
Harikrishnan Vijayamohanan, Parth Bhide, Dante Boyd, Zhe Zhou, Edmund F Palermo, Chaitanya K Ullal
We study the effect of the microenvironment on writing chemical patterns into spirothiopyran monolayers over large areas in a single step with light. Surfaces functionalized with photoresponsive spirothiopyran are fabricated by chemically modify-ing amine terminated monolayers. The merocyanine isomer selectively participates in a Thiol-Michael addition reaction with maleimide functionalized molecules, rendering these surfaces ideal for fast, mask-less direct writing. The local microenvi-ronment of spirothiopyran is found to strongly influence the kinetics of photoswitching...
February 26, 2019: Langmuir: the ACS Journal of Surfaces and Colloids
S Bellissima, M Neumann, U Bafile, D Colognesi, F Barocchi, E Guarini
We report the results of a ring polymer molecular dynamics study of the Kubo velocity autocorrelation function of a quantum fluid as para-hydrogen aimed at the comparison with its classical counterpart. Quite different density conditions were considered for both the classical and quantum cases, in order to compare the two systems before and after the dynamical crossover typically undergone by the velocity autocorrelation function (VAF) of fluids at densities around the triple point, where the shape of the function changes from a monotonic to an oscillatory behavior with a negative minimum...
February 21, 2019: Journal of Chemical Physics
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