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https://www.readbyqxmd.com/read/28728100/photophysics-of-a-coumarin-based-schiff-base-in-solvents-of-varying-polarities
#1
Saptarshi Ghosh, Nayan Roy, T Sanjoy Singh, Nitin Chattopadhyay
The present work reports detailed photophysics of a coumarin based Schiff base, namely, (E)-7-(((8-hydroxyquinolin-2-yl)methylene)amino)-4-methyl-2H-chromen-2-one (HMC) in different solvents of varying polarity exploiting steady state absorption, fluorescence and time resolved fluorescence spectroscopy. The dominant photophysical features of HMC are discussed in terms of emission from an intramolecular charge transfer (ICT) excited state. Molecular orbital (MO) diagrams as obtained from DFT based computational analysis confirms the occurrence of charge transfer from 8'-hydroxy quinoline moiety of the molecule to the coumarin part...
July 13, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28726960/robust-triplet-triplet-annihilation-photon-upconversion-by-efficient-oxygen-scavenging
#2
Damir Dzebo, Kasper Moth-Poulsen, Bo Albinsson
We hereby present a simple method for reducing the effect of oxygen quenching in Triplet-Triplet Annihilation Upconversion (TTA-UC) systems. A number of commercially available thioethers and one thiol have been tested as singlet oxygen scavengers. Recording of the upconverted emission from a well-studied PdOEP (sensitizer)-DPA (annihilator/emitter) couple has been made over time with steady-state excitation capturing the steady-state kinetics of the TTA-UC process as the solubilized oxygen is depleted by reaction with the scavengers...
July 20, 2017: Photochemical & Photobiological Sciences
https://www.readbyqxmd.com/read/28726952/porphyra-polysaccharide-derived-carbon-dots-for-non-viral-co-delivery-of-different-gene-combinations-and-neuronal-differentiation-of-ectodermal-mesenchymal-stem-cells
#3
Jiaxin Chen, Qiang Wang, Jie Zhou, Wenwen Deng, Qingtong Yu, Xia Cao, Jianping Wang, Fengxia Shao, Yang Li, Ping Ma, Myron Spector, Jiangnan Yu, Ximing Xu
In this study, multifunctional fluorescent carbon dots (CDs) were synthesized using a one-pot hydrothermal carbonization reaction, with the naturally-occurring porphyra polysaccharide (PPS) serving as a single carbon source for the first time and ethylenediamine (Ed) acting as the surface passivation agent. The resulting CDs enjoyed a high quantum yield (56.3%), excitation-dependent fluorescence, small size (<10 nm), spherical shape, uniform distribution, positive surface charge, low cytotoxicity and excellent ability to condense macromolecular plasmid DNA...
July 20, 2017: Nanoscale
https://www.readbyqxmd.com/read/28726903/reversible-trans-%C3%A2-cis-photoisomerizations-of-re-co-3-ph2phen-stpycn-towards-molecular-machines
#4
Kassio P S Zanoni, Neyde Y Murakami Iha
In our search for light powered molecular devices, a novel fac-[Re(CO)3(ph2phen)(trans-stpyCN)](+) complex was synthesized to show switchable trans-cis configurations of the coordinated stpyCN ligand through efficient and reversible photoassisted isomerizations. Controlled photolyses of acetonitrile solutions led to spectral changes ascribed to reversible trans ⇌ cis photoisomerization processes. A remarkable quantum yield for the back cis-to-trans isomerization was obtained, with the same magnitude of the trans-to-cis photoprocess, and curiously, both trans- and cis-isomers are emissive at room temperature...
July 20, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28726891/frontier-orbitals-of-photosubstitutionally-active-ruthenium-complexes-an-experimental-study-of-the-spectator-ligands-electronic-properties-influence-on-photoreactivity
#5
Hyo Jin Jang, Samantha L Hopkins, Maxime A Siegler, Sylvestre Bonnet
The synthesis and characterization of [Ru(tpy)(R2bpy)(L)](X)n complexes (tpy = 2,2':6',2''-terpyridine, R2bpy = 4,4'-dimethyl-2,2'-bipyridine (dmbpy), or 4,4'-bis(trifluoromethyl)-2,2'-bipyridine (tfmbpy), X = Cl(-) or PF6(-), and n = 1 or 2) are described. The dmbpy and tfmbpy bidentate ligands allow for investigating the effects of electron-donating and electron-withdrawing ligands, respectively, on the frontier orbital energetics as well as the photoreactivity of these ruthenium polypyridyl complexes for five prototypical monodentate ligands L = Cl(-), H2O, CH3CN, 2-(methylthio)ethanol (Hmte), or pyridine...
July 20, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28726885/simulation-of-the-experimental-imaging-results-for-the-oh-chd3-reaction-with-a-simple-and-accurate-theoretical-approach
#6
Laurent Bonnet, Joaquin Espinosa-Garcia
The OH + CHD3 reaction is among the largest one ever studied at the high-resolution level permitted by imaging techniques [B. Zhang et al., J. Phys. Chem. A, 2005, 109, 8989]. This process involves eighteen configuration space coordinates, which are large enough to make exact quantum scattering calculations beyond reach. Moreover, freezing some degrees-of-freedom in order to render these calculations feasible may lead to unrealistic predictions. However, we have found it possible to reproduce for the first time the pair-correlated measurements of Zhang et al...
July 20, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28726866/acyclic-cucurbit-n-uril-conjugated-dextran-for-drug-encapsulation-and-bioimaging
#7
Jiafu Chen, Yamin Liu, Dake Mao, Da Ma
An acyclic cucurbit[n]uril (CB[n]) conjugated dextran is developed as a new biomaterial for drug delivery and bioimaging. This biomaterial retains the host-guest recognition properties of acyclic CB[n]s. It is able to directly encapsulate anti-tumor drugs 5-fluorouracil and temozolomide. This polymeric material can form a supramolecular assembly with polyethyleneimine (PEI). Although there is no conventional chromophore in these supramolecular systems, they exhibit aggregation-induced emission (AIE) in water with a quantum yield of 10%...
July 20, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28726405/fluorescence-enhancement-of-unconstrained-gfp-chromophore-analogues-based-on-the-push-pull-substituent-effect
#8
Meng-Shiue Tsai, Chun-Lin Ou, Chi-Jui Tsai, Yen-Chin Huang, Yuan-Chung Cheng, Shih-Sheng Sun, Jye-Shane Yang
Unlike the high fluorescence quantum yield of the naturally occurring green fluorescence protein (GFP, Φf ∼ 0.8), the GFP chromophore, a benzylidenedimethylimidazolinone (BDI) dye, is nearly nonfluorescent (Φf < 0.001) in common solutions at room temperature. While many efforts have been devoted into the BDI chromophore engineering for fluorescence recovery, limited success has been achieved for structurally unconstrained GFP chromophore analogues (uGFPc). Herein we report a rational design of uGFPc toward an unprecedentedly high fluorescence quantum efficiency of 0...
July 20, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28726387/aryl-substituted-ruthenium-ii-complexes-a-strategy-for-enhanced-photocleavage-and-efficient-dna-binding
#9
Felipe Diógenes Abreu, Tercio de F Paulo, Marcelo H Gehlen, Rômulo A Ando, Luiz G F Lopes, Ana Cláudia S Gondim, Mayron A Vasconcelos, Edson H Teixeira, Eduardo Henrique Silva Sousa, Idalina Maria Moreira de Carvalho
Ruthenium polypyridine complexes have shown promise as agents for photodynamic therapy (PDT) and tools for molecular biology (chromophore-assisted light inactivation). To accomplish these tasks, it is important to have at least target selectivity and great reactive oxygen species (ROS) photogeneration: two properties that are not easily found in the same molecule. To prepare such new agents, we synthesized two new ruthenium complexes that combine an efficient DNA binding moiety (dppz ligand) together with naphthyl-modified (1) and anthracenyl-modified (2) bipyridine as a strong ROS generator bound to a ruthenium complex...
July 20, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28725054/quantifying-magnetic-sensitivity-of-radical-pair-based-compass-by-quantum-fisher-information
#10
Li-Sha Guo, Bao-Ming Xu, Jian Zou, Bin Shao
The radical pair (RP) based compass is considered as one of the principal models of avian magnetoreception. Different from the conventional approach where the sensitivity of RP based compass is described by the singlet yield, we introduce the quantum Fisher information (QFI), which represents the maximum information about the magnetic field's direction extracted from the RP state, to quantify the sensitivity of RP based compass. The consistency between our results and experimental observations suggests that the QFI may serve as a measure to describe the sensitivity of RP based compass...
July 19, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28723895/visible-light-driven-methane-formation-from-co2-with-a-molecular-iron-catalyst
#11
Heng Rao, Luciana C Schmidt, Julien Bonin, Marc Robert
Converting CO2 into fuel or chemical feedstock compounds could in principle reduce fossil fuel consumption and climate-changing CO2 emissions. One strategy aims for electrochemical conversions powered by electricity from renewable sources, but photochemical approaches driven by sunlight are also conceivable. A considerable challenge in both approaches is the development of efficient and selective catalysts, ideally based on cheap and Earth-abundant elements rather than expensive precious metals. Of the molecular photo- and electrocatalysts reported, only a few catalysts are stable and selective for CO2 reduction; moreover, these catalysts produce primarily CO or HCOOH, and catalysts capable of generating even low to moderate yields of highly reduced hydrocarbons remain rare...
July 17, 2017: Nature
https://www.readbyqxmd.com/read/28723213/dual-functional-core-shell-fluorescent-ag2s-carbon-nanostructure-for-selective-assay-of-e-coli-o157-h7-and-bactericidal-treatment
#12
Ning Wang, Xing Wei, An-Qi Zheng, Ting Yang, Ming-Li Chen, Jian-Hua Wang
A dual functional fluorescent core-shell Ag2S@Carbon nanostructure is prepared by a hydrothermally assisted multi-amino synthesis approach with folic acid (FA), polyethylenimine (PEI), and mannoses (Mans) as carbon and nitrogen sources (FA-PEI-Mans-Ag2S nanocomposite shortly as Ag2S@C). The nanostructure exhibits strong fluorescent emission at λex/λem = 340/450 nm with a quantum yield of 12.57 ± 0.52%. Ag2S@C is bound to E. coli O157:H7 via strong interaction with the Mans moiety in Ag2S@C with FimH proteins on the fimbriae tip in E...
March 24, 2017: ACS Sensors
https://www.readbyqxmd.com/read/28722068/photoluminescence-quantum-yield-exceeding-80-in-low-dimensional-perovskite-thin-films-via-passivation-control
#13
Maria-Grazia La-Placa, Giulia Longo, Azin Babaei, Laura Martínez-Sarti, Michele Sessolo, Henk J Bolink
Quasi-2D perovskites with the BA : MA molar ratio equal to 3 : 3 show a remarkable PLQY exceeding 80%, thanks to the use of an electron donor as the passivating agent. These films have been applied in LEDs that exhibit high brightness exceeding 1000 cd m(-2) and current efficiencies >3 cd A(-1).
July 19, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28721419/highly-fluorescent-hyperbranched-bodipy-based-conjugated-polymer-dots-for-cellular-imaging
#14
Rongxin Du, Shuang Cui, Zezhou Sun, Ming Liu, Yong Zhang, Qiong Wu, Changfeng Wu, Fengyun Guo, Liancheng Zhao
The first hyperbranched BODIPY-based conjugated polymer dots (Pdots) were reported. The Pdots showed quantum yields of as high as 22%, which is 40% higher than their linear counterparts. The Pdots were successfully applied in cell-labelling applications. These results demonstrated that hyperbranched polymers are a very promising material for biological imaging and applications.
July 19, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28719213/full-dimensional-excited-state-intramolecular-proton-transfer-dynamics-of-salicylic-acid
#15
Tim Raeker, Bernd Hartke
Not all photodynamical processes are ultrafast processes in the range of 100 fs. Thus, using high-level ab initio methods for systems evolving along deactivation pathways in the excited state for picoseconds is not feasible. We will present full-dimensional photodynamics using the floating-occupation configuration-interaction (FOCI) treatment with single and paired double excitations based on the semiempirical RM1 Hamiltonian. Salicylic acid (SAc) served as our sample system which is a well-studied system both experimentally and theoretically by static calculations...
July 18, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28719191/relationships-between-dissolved-organic-matter-composition-and-photochemistry-in-lakes-of-diverse-trophic-status
#16
Andrew Chapin Maizel, Jing Li, Christina K Remucal
The North Temperate Lakes-Long Term Ecological Research site includes seven lakes in northern Wisconsin that vary in hydrology, trophic status, and landscape position. We examine the molecular composition of dissolved organic matter (DOM) within these lakes using Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) and quantify DOM photochemical activity using probe compounds. Correlations between the relative intensity of individual molecular formulas and reactive species production demonstrate the influence of DOM composition on photochemistry...
July 18, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28719145/preparation-of-carbon-dot-based-ratiometric-fluorescent-probes-for-cellular-imaging-from-curcuma-longa
#17
Zihnil Adha Islamy Mazrad, Eun Bi Kang, Insik In, Sung Young Park
This work derived biocompatible and stable probes based on fluorescent nanoparticles (FNPs) from a natural source, Curcuma longa. The multi-color fluorescence emissions from carbonized Curcuma longa (C-FNPs) obtained through defined dehydration conditions are soluble in water and have a small particle size (~17 nm). The surface passivation with polyethylene glycol (PEG) capped with amine groups in FNPs (P-FNPs) generated a probe with a higher quantum yield and longer fluorescence lifetime than obtained with C-FNPs...
July 18, 2017: Luminescence: the Journal of Biological and Chemical Luminescence
https://www.readbyqxmd.com/read/28718483/resonant-dynamic-stark-shift-as-a-tool-in-strong-field-quantum-control-calculation-and-application-for-selective-multiphoton-ionization-of-sodium
#18
A Bunjac, D B Popović, N S Simonović
A method for determining the resonant dynamic Stark shift (RDSS), based on wave-packet calculations of the populations of quantum states, is presented. It is almost insensitive to variations of the laser pulse profile, and this feature ensures generality in applications. This method is used to determine an RDSS data set for 3s → nl (n ≤ 6) transitions in sodium induced by laser pulses with peak intensities up to 7.9 × 10(12) W cm(-2) and wavelengths in the range from 455.6 to 1139 nm. The data are applied to analyze the photoelectron spectra (electron yield versus excess energy) of the sodium atom interacting with 800 nm laser radiation...
July 18, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28715635/redox-potentials-from-ab-initio-molecular-dynamics-and-explicit-entropy-calculations-application-to-transition-metals-in-aqueous-solution
#19
Miguel A Caro, Olga Lopez-Acevedo, Tomi Laurila
We present a complete methodology to consistently estimate redox potentials strictly from first principles, without any experimental input. The methodology is based on (i) ab initio molecular dynamics (MD) simulations, (ii) all-atom explicit solvation, (iii) the two-phase thermodynamic (2PT) model and (iv) the use of electrostatic potentials as references for the absolute electrochemical scale. We apply the approach presented to compute reduction potentials of the following redox couples: Cr(+2/+3), V(+2/+3), Ru(NH3)6(+2/+3), Sn(+2/+4), Cu(+1/+2), FcMeOH(0/+1) and Fe(+2/+3) (in aqueous solution) and Fc(0/+1) (in acetonitrile)...
July 17, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/28715191/engineering-the-self-assembly-induced-emission-of-cu-nanoclusters-by-au-i-doping
#20
Jiale Liu, Zhennan Wu, Ye Tian, Yanchun Li, Lin Ai, Tingting Li, Haoyang Zou, Yi Liu, Xindong Zhang, Hao Zhang, Bai Yang
Aggregation-induced emission (AIE) and self-assembly induced emission (SAIE) effects have been employed to tune the emission properties of metal nanoclusters (NCs). However, it is still not possible to further enhance the photoluminescence quantum yields (PLQYs) and control the emission colors of the NCs using AIE and SAIE. On the basis of our recent work studying the contribution of Cu(I) defects in the SAIE of Cu NCs, in this article, Au(I) was doped into Cu NC self-assembled nanosheets (NSASs) to construct a more stable Au(I)-centered state...
July 17, 2017: ACS Applied Materials & Interfaces
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