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https://www.readbyqxmd.com/read/28813053/copper-ii-benzimidazole-complexes-as-efficient-fluorescent-probes-for-l-cysteine-in-water
#1
Duraiyarasu Maheshwaran, Selvarasu Priyanga, Ramasamy Mayilmurugan
Copper(ii) complexes [Cu(L1)(H2O)2](SO3CF3)21 and [Cu(L2)(H2O)2](SO3CF3)22 based on 2,6-bis(benzimidazolyl)pyridine were synthesized and are reported herein as highly selective "turn-on" optical probes for l-cysteine. The Cu(ii)/Cu(i) redox potential of probe 1 (0.14 V vs. NHE) was lower than that of 2 (0.233 V vs. NHE) in water. The molecular structure of 2 adopted a square pyramidal geometry (τ = 0.2545), with the Cu-Npy bond (1.958 Å) of its middle pyridine unit being shorter than the other two Cu-Nbenzim bonds (Cu-N, 1...
August 16, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28813052/mixed-ligand-iridium-iii-complexes-as-photodynamic-anticancer-agents
#2
Yue Zheng, Liang He, Dong-Yang Zhang, Cai-Ping Tan, Liang-Nian Ji, Zong-Wan Mao
Many phosphorescent iridium complexes are potent candidates as photodynamic therapeutic agents. In this work, a series of mixed-ligand phosphorescent iridium complexes (Ir1: [Ir(L1)(bpy)Cl](PF6)2; Ir2: [Ir(L1)(ppy)Cl](PF6); Ir3: [Ir(L2)(bpy)Cl](PF6)2; Ir4: [Ir(L2)(ppy)Cl](PF6). L1 = 2,6-bis(2-benzimidazolyl)pyridine; bpy = 2,2'-bipyridine; L2 = 2,6-bis(1-methyl-benzimidazol-2-yl)pyridine; ppy = 2-phenylpyridine) have been synthesized and characterized. These complexes display high luminescence quantum yields and long phosphorescence lifetimes...
August 16, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28812351/structural-investigation-of-cesium-lead-halide-perovskites-for-high-efficiency-quantum-dot-light-emitting-diodes
#3
Quyet Van Le, Jong Beom Kim, Soo Young Kim, Byeongdu Lee, Dong Ryeol Lee
In this study, we have intensively investigated the effect of the reaction temperature of hot-injection method on the structural properties of CsPbX3 (X: Br, I, Cl) perovskite nanocrystals (NCs) using the small- and wide-angle X-ray scattering. Furthermore, light emitting diodes (LEDs) performance as well as photoluminescence characteristics for high-efficient LEDs is compared with reaction temperature. It is confirmed that the size of the NCs decreased as the reaction temperature decreased, resulting stronger quantum confinement...
August 16, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28812068/mechanistic-investigations-of-the-2-coumaranone-chemiluminescence
#4
Stefan Schramm, Isabelle Navizet, Durga Prasad Karothu, Pascal Oesau, Veronika Bensmann, Dieter Weiss, Rainer Beckert, Panče Naumov
2-Coumaranones are evolving as a new, efficient, versatile, and synthetically accessible platform for the next generation chemiluminescent probes. Despite the favorable quantum yields, the exact mechanism of their chemiluminescence remains elusive. Here, we analyze the details of the mechanism of the 2-coumaranone chemiluminescence using a combination of experimental and computational methods. By using EPR spectroscopy we show that superoxide radical anions are involved in the reactions, in support of the hypothesis that the mechanism includes a single electron transfer step...
August 16, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28811462/observation-of-hybrid-tamm-plasmon-exciton-polaritons-with-gaas-quantum-wells-and-a-mose2-monolayer
#5
Matthias Wurdack, Nils Lundt, Martin Klaas, Vasilij Baumann, Alexey V Kavokin, Sven Höfling, Christian Schneider
Strong light matter coupling between excitons and microcavity photons, as described in the framework of cavity quantum electrodynamics, leads to the hybridization of light and matter excitations. The regime of collective strong coupling arises, when various excitations from different host media are strongly coupled to the same optical resonance. This leads to a well-controllable admixture of various matter components in three hybrid polariton modes. Here, we study a cavity device with four embedded GaAs quantum wells hosting excitons that are spectrally matched to the A-valley exciton resonance of a MoSe2 monolayer...
August 15, 2017: Nature Communications
https://www.readbyqxmd.com/read/28810799/spin-dependent-charge-recombination-along-para-phenylene-molecular-wires
#6
Thomas P Fay, Alan M Lewis, David E Manolopoulos
We have used an efficient new quantum mechanical method for radical pair recombination reactions to study the spin-dependent charge recombination along PTZ(•+)-Phn-PDI(•-) molecular wires. By comparing our results with the experimental data of Weiss et al. [J. Am. Chem. Soc. 126, 5577 (2004)], we are able to extract the spin-dependent (singlet and triplet) charge recombination rate constants for wires with n = 2-5. These spin-dependent rate constants have not been extracted previously from the experimental data because they require fitting its magnetic field-dependence to the results of quantum spin dynamics simulations...
August 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28810759/lanthanum-mediated-dehydrogenation-of-1-and-2-butynes-spectroscopy-and-formation-of-la-c4h4-isomers
#7
Wenjin Cao, Dilrukshi Hewage, Dong-Sheng Yang
La atom reactions with 1-butyne and 2-butyne are carried out in a laser-vaporization molecular beam source. Both reactions yield the same La-hydrocarbon products from the dehydrogenation and carbon-carbon bond cleavage and coupling of the butynes. The dehydrogenated species La(C4H4) is characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectra of La(C4H4) produced from the two reactions exhibit two identical transitions, each consisting of a strong origin band and several vibrational intervals...
August 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28810229/photodegradation-of-sulfathiazole-under-simulated-sunlight-kinetics-photo-induced-structural-rearrangement-and-antimicrobial-activities-of-photoproducts
#8
Xi-Zhi Niu, Julie Glady-Croué, Jean-Philippe Croué
Photolysis is a core natural process impacting the fate of some sulfonamide antibiotics in sunlit waters. In this study, sunlight-induced phototransformation of sulfathiazole was investigated. A photolytic quantum yield of 0.079 was obtained in buffered water (pH = 8.0). Different natural organic matter isolates inhibited the photolysis of sulfathiazole by light screening effect. A kinetic model was developed to predict the photodegradation rate of sulfathiazole using the light screening correction factor of the water matrix in the wavelength range of 300-350 nm...
August 9, 2017: Water Research
https://www.readbyqxmd.com/read/28809498/bodipy-anthracene-dyads-as-triplet-photosensitizers-effect-of-chromophore-orientation-on-triplet-state-formation-efficiency-and-application-in-triplet-triplet-annihilation-upconversion
#9
Zhijia Wang, Jianzhang Zhao
Bodipy-anthracene dyads with two chromophores assuming orthogonal geometry to enhance the spin-orbital charge-transfer intersystem crossing (SOCT-ISC) were prepared. The photosensitizers show strong absorption of visible light, efficient triplet-state formation (quantum yield 90%), and a long-lived triplet state (85 μs). The dipole moment orientation exerts significant effect on the ISC efficiency. It is also the first time that photosensitizers based on SOCT-ISC were used for triplet-triplet annihilation upconversion...
August 15, 2017: Organic Letters
https://www.readbyqxmd.com/read/28809462/multiple-electronic-and-structural-factors-control-cpd-and-6-4-thymine-thymine-photodimerization-in-dna-duplex
#10
Irene Conti, Lara Martinez Fernandez, Luciana Esposito, Siegfried Hofinger, Artur Nenov, Marco Garavelli, Roberto Improta
The T-T photodimerization paths leading to the formation of cyclobutane pyrimidine dimer (CPD) and 6-4 pyrimidine pyrimidone (64-PP), the two main DNA photolesions, have been resolved for a T-T step in a DNA duplex by two complementary state-of-the art quantum mechanical approaches: QM(CASPT2//CASSCF)/MM and TD-DFT/PCM. Based on the analysis of several different representative structures, we define a new-ensemble of cooperating geometrical and electronic factors (besides the distance between the reacting bonds) ruling T-T photodimerization in DNA...
August 15, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28808095/what-limits-photosynthetic-energy-conversion-efficiency-in-nature-lessons-from-the-oceans
#11
Paul G Falkowski, Hanzhi Lin, Maxim Y Gorbunov
Constraining photosynthetic energy conversion efficiency in nature is challenging. In principle, two yield measurements must be made simultaneously: photochemistry, fluorescence and/or thermal dissipation. We constructed two different, extremely sensitive and precise active fluorometers: one measures the quantum yield of photochemistry from changes in variable fluorescence, the other measures fluorescence lifetimes in the picosecond time domain. By deploying the pair of instruments on eight transoceanic cruises over six years, we obtained over 200 000 measurements of fluorescence yields and lifetimes from surface waters in five ocean basins...
September 26, 2017: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
https://www.readbyqxmd.com/read/28807573/axially-substituted-silicon-iv-phthalocyanine-and-its-quaternized-derivative-as-photosensitizers-towards-tumor-cells-and-bacterial-pathogens
#12
İpek Ömeroğlu, Esra Nur Kaya, Meltem Göksel, Vesselin Kussovski, Vanya Mantareva, Mahmut Durmuş
Axially di-(alpha,alpha-diphenyl-4-pyridylmethoxy) silicon(IV) phthalocyanine (3) and its quaternized derivative (3Q) were synthesized and tested as photosensitizers against tumor and bacterial cells. These new phthalocyanines were characterized by elemental analysis, and different spectroscopic methods such as FT-IR, UV-Vis, MALDI-TOF and (1)H NMR. The photophysical properties such as absorption and fluorescence, and the photochemical properties such as singlet oxygen generation of both phthalocyanines were investigated in solutions...
August 1, 2017: Bioorganic & Medicinal Chemistry
https://www.readbyqxmd.com/read/28806517/from-non-luminescent-cs4pbx6-x-cl-br-i-nanocrystals-to-highly-luminescent-cspbx3-nanocrystals-water-triggered-transformation-through-a-csx-stripping-mechanism
#13
Linzhong Wu, Huicheng Hu, Yong Xu, Shu Jiang, Min Chen, Qixuan Zhong, Di Yang, Qipeng Liu, Yun Zhao, Baoquan Sun, Qiao Zhang, Yadong Yin
We report a novel CsX-stripping mechanism which enables efficient chemical transformation of non-luminescent Cs4PbX6 (X = Cl, Br, I) nanocrystals (NCs) to highly luminescent CsPbX3 NCs. During the transformation, Cs4PbX6 NCs dispersed in a nonpolar solvent are converted into CsPbX3 NCs by stripping CsX through an interfacial reaction with water in a different phase. This process takes advantage of the high solubility of CsX in water as well as the ionic nature and high ion diffusion property of Cs4PbX6 NCs, and produces monodisperse and air-stable CsPbX3 NCs with controllable halide composition, tunable emission wavelength covering the full visible range, narrow emission width, and high photoluminescent quantum yield (up to 75%)...
August 14, 2017: Nano Letters
https://www.readbyqxmd.com/read/28805846/a-photochromic-prototype-based-on-difurylperhydrocyclopentene-with-remarkable-photoswitching-behavior-and-in-vivo-application
#14
Shangshang Wang, Yunyun Zhou, Liangliang Zhu, Junji Zhang, Qi Zou, Tao Zeng, Wenbo Chen
A new strategy has been developed to synthesize difurylperhydrocyclopentene derivatives. The compound displays reversible photochromism in solution and thin-film. The results show that furan is superior to thiophene in terms of strong fluorescence, higher photocyclization conversion and cyclization quantum yield, as well as better fatigue resistance. Owing to the molecule being derived absolutely from C, H, and O atoms, the compound exhibits no cytotoxicity, which enables it to potentially serve as a biodegradable and biorenewable material for in vivo applications...
August 14, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28802828/photolyase-dynamics-and-electron-transfer-mechanisms-of-dna-repair
#15
REVIEW
Meng Zhang, Lijuan Wang, Dongping Zhong
Photolyase, a flavoenzyme containing flavin adenine dinucleotide (FAD) molecule as a catalytic cofactor, repairs UV-induced DNA damage of cyclobutane pyrimidine dimer (CPD) and pyrimidine-pyrimidone (6-4) photoproduct using blue light. The FAD cofactor, conserved in the whole protein superfamily of photolyase/cryptochromes, adopts a unique folded configuration at the active site that plays a critical functional role in DNA repair. Here, we review our comprehensive characterization of the dynamics of flavin cofactor and its repair photocycles by different classes of photolyases on the most fundamental level...
August 9, 2017: Archives of Biochemistry and Biophysics
https://www.readbyqxmd.com/read/28801979/germanium-bridged-2-phenylbenzoheteroles-as%C3%A3-luminophores-exhibiting-highly-efficient-solid-state-fluorescence
#16
Masaki Shimizu, Daiki Ryuse, Takumi Kinoshita
[1]Benzogermolo[3,2-b]indoles, [1]benzogermolo[3,2-b]-benzofuran, [1]benzogermolo[3,2-b]benzothiophene, and [1]benzo-germolo[3,2-b]benzothiophene-S,S-dioxide were synthesized from the corresponding 3-bromo-2-(2-bromophenyl)benzoheteroles and characterized. A comparison of the absorption spectra of the Ph2Ge- and Ph2Si-bridged 2-phenylindoles reveals that the Ge-bridge has the effect of slightly widening the HOMO-LUMO energy gap of the bridged 2-phenylindole π-system with regard to the Si-bridged system. Replacement of the indole ring by benzofuran or benzothiophene rings induces blue-shifts in the absorption spectrum, while the absorption spectrum of the benzothiophene-S,S-dioxide derivative was red-shifted with respect to the indole derivative...
August 11, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28801823/quantification-of-light-screening-by-anthocyanins-in-leaves-of-berberis-thunbergii
#17
Lars Nichelmann, Wolfgang Bilger
Up to 40% of incident light was screened in red Berberis leaves in vivo by anthocyanins, resulting also in up to 40% reduction of light-limited photosynthesis. The biological function of anthocyanins in leaves has been strongly discussed, but the hypothesis of a screening function is favored by most authors. For an evaluation of the function as photoprotective pigments, a quantification of their screening of the mesophyll is important. Here, chlorophyll fluorescence excitation of leaves of a red and a green variety of Berberis thunbergii was used to estimate the extent of screening by anthocyanins at 545 nm and over the whole photosynthetically active wavelength range...
August 11, 2017: Planta
https://www.readbyqxmd.com/read/28801166/nuclear-factor-erythroid-derived-2-like-2-nrf2-drug-discovery-biochemical-toolbox-to-develop-nrf2-activators-by-reversible-binding-of-kelch-like-ech-associated-protein-1-keap1
#18
REVIEW
Alberto Bresciani, Antonino Missineo, Mariana Gallo, Mauro Cerretani, Paola Fezzardi, Licia Tomei, Daniel Oscar Cicero, Sergio Altamura, Alessia Santoprete, Raffaele Ingenito, Elisabetta Bianchi, Robert Pacifici, Celia Dominguez, Ignacio Munoz-Sanjuan, Steven Harper, Leticia Toledo-Sherman, Larry C Park
Mechanisms that activate innate antioxidant responses, as a way to mitigate oxidative stress at the site of action, hold much therapeutic potential in diseases, such as Parkinson's disease, Alzheimer's disease and Huntington's disease, where the use of antioxidants as monotherapy has not yielded positive results. The nuclear factor NRF2 is a transcription factor whose activity upregulates the expression of cell detoxifying enzymes in response to oxidative stress. NRF2 levels are modulated by KEAP1, a sensor of oxidative stress...
August 8, 2017: Archives of Biochemistry and Biophysics
https://www.readbyqxmd.com/read/28801049/a-four-state-parametric-model-for-the-kinetics-of-the-non-photochemical-quenching-in-photosystem-ii
#19
Joris J Snellenburg, Matthew P Johnson, Alexander V Ruban, Rienk van Grondelle, Ivo H M van Stokkum
The phenomenon of non-photochemical quenching (NPQ) was studied in spinach chloroplasts using pulse amplitude modulated (PAM) fluorometry. We present a new analysis method which describes the observed fluorescence quantum yield as the sum of the product of four different states of PsiI and their corresponding quantum yields. These four distinct states are PsiI in the quenched or unquenched state, and with its reaction center either open or closed depending upon the reduction of the QA site. With this method we can describe the dynamics of the NPQ induction and recovery as well as quantify the percentage of photoinactivated RC throughout the measurement...
August 8, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28800107/sequestration-effect-on-the-open-cyclic-switchable-property-of-warfarin-induced-by-cyclodextrin-time-resolved-fluorescence-study
#20
Naji Al-Dubaili, Na'il Saleh
The excited-state lifetimes of the anticoagulant drug warfarin (W) in water and in the absence and presence of methyl-β-cyclodextrins (Me-β-CD) were recorded using time-resolved fluorescence measurements. Selective excitation of the open and cyclic protonated isomers of W were acquired with laser emitting diodes (LED) producing 320 and 280 nm excitation pulses, respectively. Formation of the inclusion complex was checked by UV-visible absorption spectroscopy, and the values of binding constants (2.9 × 10³ M(-1) and 4...
August 11, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
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