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Quantum yield

Liang Zheng, Marie-Christine Van Labeke
The effect of light quality on leaf morphology, photosynthetic efficiency and antioxidant capacity of leaves that fully developed under a specific spectrum was investigated in Chrysanthemum cv. Four light treatments were applied at 100μmolm(-2)s(-1) and a photoperiod of 14h using light-emitting diodes, which were 100% red (R), 100% blue (B), 75% red with 25% blue (RB) and white (W), respectively. Intraspecific variation was investigated by studying the response of eight cultivars. Overall, red light significantly decreased the leaf area while the thinnest leaves were observed for W...
March 11, 2017: Journal of Plant Physiology
Abd Rashid Bin Mohd Yusoff, Aron J Huckaba, Mohammad Khaja Nazeeruddin
The development of transition metal complexes for application in light-emitting devices is currently attracting significant research interest. Among phosphorescent emitters, those involving iridium (III) complexes have proven to be exceedingly useful due to their relatively short triplet lifetime and high phosphorescence quantum yields. The emission wavelength of iridium (III) complexes significantly depends on the ligands, and changing the electronic nature and the position of the ligand substituents can control the properties of the ligands...
April 2017: Topics in Current Chemistry (Journal)
Man-Jin Kim, Su-Ji Jeon, Tae Woog Kang, Jong-Min Ju, DaBin Yim, Hye-In Kim, Jung Hyun Park, Jong-Ho Kim
Modulating the dimensions and phases of transition metal dichalcogenides is of great interest to enhance their intrinsic properties or to create new physicochemical properties. Herein, we report an effective approach to synthesize 2H-WS2 quantum dots (QDs) via the dimension and phase engineering of 1T-WS2 nanosheets. The solvothermal reaction of chemically-exfoliated 1T-WS2 nanosheets in N-methyl-2-pyrrolidone (NMP) under an N2 atmosphere induced their chopping and phase transition at lower temperature to produce 2H-WS2 QDs with a high quantum yield (5...
March 20, 2017: ACS Applied Materials & Interfaces
Christopher Grieco, Kurt F Hirsekorn, Andrew T Heitsch, Alan C Thomas, Mark H McAdon, Britt A Vanchura, Michael M Romanelli, Lora L Brehm, Anne Leugers, Anatoliy Sokolov, John B Asbury
Phosphor-converted light emitting diodes (pcLEDs) produce white light through the use of phosphors that convert blue light emitted from the LED chip into green and red wavelengths. Understanding the mechanisms of degradation of the emission spectra and quantum yields of the phosphors used in pcLEDs is of critical importance to fully realize the potential of solid state lighting as an energy efficient technology. Toward this end, time-resolved photoluminescence spectroscopy was used to identify the mechanistic origins of enhanced stability and luminescence efficiency that can be obtained from a series of carbidonitride red phosphors with varying degree of substitutional carbon...
March 20, 2017: ACS Applied Materials & Interfaces
Yuan-Jun Gao, Xue-Ping Chang, Xiang-Yang Liu, Quan-Song Li, Ganglong Cui, Walter Thiel
The photophysical properties of tetraphenylethene (TPE) compounds may differ widely depending on the substitution pattern, for example with regard to the fluorescence quantum yield phi_f and the propensity to exhibit aggregation-induced emission (AIE). We report combined electronic structure calculations and nonadiabatic dynamics simulations to study the excited-state decay mechanisms of two TPE derivatives with four methyl substituents, either in meta-position (TPE-4mM, phi_f = 0.1%) or in ortho-position (TPE-4oM, phi_f = 64...
March 20, 2017: Journal of Physical Chemistry. A
Raquel Rondão, Ana Frias, Sandra Correia, Lianshe Fu, Verónica de Zea Bermudez, Paulo André, Rute A S Ferreira, Luis D Carlos
Luminescent solar concentrators (LSCs) appear as candidates to enhance the performance of photovoltaic (PV) cells and contribute to reduce the size of PV systems, decreasing, therefore, the amount of material needed, and thus the cost associated with energy conversion. One way to maximize the devices performance is to explore near infrared (NIR)-emitting centers, resonant with the maximum optical response of the most common Si-based PV cells. Nevertheless, very few examples in the literature demonstrate the feasibility of fabricating LSCs emitting in the NIR region...
March 20, 2017: ACS Applied Materials & Interfaces
Laura A Büldt, Oliver S Wenger
Group 6 d6 metal complexes with arylisocyanide ligands are earth-abundant alternatives to photoactive complexes made from precious metals such as Ru(II), Re(I), Os(II), or Ir(III). Some of them have long-lived 3MLCT excited states that exhibit luminescence with good quantum yields combined with nano- to microsecond lifetimes, and they are very strongly reducing. Recent studies have demonstrated that Cr(0), Mo(0), and W(0) arylisocyanides have great potential for application in luminescent devices, photoredox catalysis, and dye-sensitized solar cells...
March 20, 2017: Angewandte Chemie
Zhen Liu, Vinh Son Nguyen, Jeremy Harvey, Jean-François Müller, Jozef Peeters
In this work we identified and theoretically quantified two photolysis mechanisms of HPALDs (hydroperoxy aldehydes) that result from the isomerization of peroxy radicals in the atmospheric oxidation of isoprene at low/moderate NOx. As a first photolysis mechanism, we show that a fraction of the initially excited S1-state HPALDs isomerizes by a near-barrierless 1,5 H-shift at a rate approaching 10(12) s(-1) - competing with the ∼equally fast intersystem crossing to the T2 triplet state - forming an unstable biradical that spontaneously expels an OH (hydroxyl) radical...
March 20, 2017: Physical Chemistry Chemical Physics: PCCP
Fabrizio Araniti, Monica Scognamiglio, Angela Chambery, Rosita Russo, Assunta Esposito, Brigida D'Abrosca, Antonio Fiorentino, Antonio Lupini, Francesco Sunseri, Maria Rosa Abenavoli
In this study, the effects of the allelochemical coumarin through a metabolomic, proteomic and morpho-physiological approach in Arabidopsis adult plants (25days old) were investigated. Metabolomic analysis evidenced an increment of amino acids and a high accumulation of soluble sugars, after 6days of coumarin treatment. This effect was accompanied by a strong decrease on plant fresh and dry weights, as well as on total protein content. On the contrary, coumarin did not affect leaf number but caused a reduction in leaf area...
March 1, 2017: Journal of Plant Physiology
Elisa Viola, Maria Pia Donzello, Fabiola Sciscione, Kous Shah, Claudio Ercolani, Giuseppe Trigiante
The photosensitizing activity of two multiply charged porphyrazine derivatives, i.e. the Zn(II) species [(CH3)8LZn](8+) and the Zn(II)/Pt(II) heterobimetallic complex [(PtCl2)(CH3)6LZn](6+) (neutralized byI(-) ions; L=tetrakis-2,3-[5,6-di(2-pyridyl)pyrazino]porphyrazinato dianion) has been examined in the water medium in the presence of SDS under experimental conditions in which the two species are present exclusively in their monomeric form. The determined quantum yield values (ΦΔ) for both complexes, of interest in photodynamic therapy (PDT), are 2...
March 9, 2017: Journal of Photochemistry and Photobiology. B, Biology
Mikhail Lemeshko
Understanding the behavior of molecules interacting with superfluid helium represents a formidable challenge and, in general, requires approaches relying on large-scale numerical simulations. Here, we demonstrate that experimental data collected over the last 20 years provide evidence that molecules immersed in superfluid helium form recently predicted angulon quasiparticles [Phys. Rev. Lett. 114, 203001 (2015)PRLTAO0031-900710.1103/PhysRevLett.114.203001]. Most important, casting the many-body problem in terms of angulons amounts to a drastic simplification and yields effective molecular moments of inertia as straightforward analytic solutions of a simple microscopic Hamiltonian...
March 3, 2017: Physical Review Letters
Sandra Wiedbrauk, Benjamin Maerz, Elena Samoylova, Peter Mayer, Wolfgang Zinth, Henry Dube
TICT formation in hemithioindigo photoswitches has recently been reported and constitutes a second deexcitation pathway complementary to photoisomerization. Typically this behavior is not found for this type of photoswitches and it takes special geometric and electronic conditions to realize it. Here we present a systematic study that identifies the molecular preconditions leading to TICT formation in donor substituted hemithioindigo, which can thus serve as a frame of reference for other photoswitching systems...
March 17, 2017: Journal of Physical Chemistry Letters
Fuli Zhang, Yuqiao Guan, Xulin Chen, Shuangshuang Wang, Dong Liang, Yafei Feng, Shufen Chen, Suzhi Li, Zhongyi Li, Fuqiang Zhang, Canzhong Lu, Guangxiu Cao, Bin Zhai
Three thermally activated delayed fluorescence cationic cuprous complexes [Cu(POP) (ECAF)]PF6 (1, POP = bis(2-diphenylphosphinophenyl)ether, ECAF = 9,9-bis(9-ethylcarbazol-3-yl)-4,5-diazafluorene), [Cu(POP) (EHCAF)]PF6 (2, EHCAF = 9,9-bis(9-ethylhexylcarbazol-3-yl)-4,5-diazafluorene), and [Cu(POP) (PCAF)]PF6 (3, PCAF = 9,9-bis(9-phenylcarbazaol-3-yl)-4,5-diazafluorene) with bipolar 4,5-diazafluorene ligand substituted by bis-carbazole have been successfully prepared, and their UV absorption, photoluminescent properties, and electrochemical behaviors were investigated...
March 17, 2017: Inorganic Chemistry
Michael T Ruggiero, J Axel Zeitler, Alessandro Erba
The intermolecular anharmonic potential of crystalline purine is probed by means of temperature-dependent terahertz time-domain spectroscopy, low-frequency Raman scattering, X-ray diffraction, and ab initio quasi-harmonic quantum-chemical simulations. As temperature increases, anharmonicity in the intermolecular interactions results in strongly anisotropic thermal expansion - with a negative thermal expansion along the b crystallographic axis - yielding corresponding bulk structural modifications. The observed thermally-induced shifts of most vibrational bands in the terahertz region of the spectra are shown to arise from volume-dependent thermal changes of the hydrogen-bond pattern along the a and b crystallographic axes...
March 17, 2017: Chemical Communications: Chem Comm
Yu Akimov, S Sun
In surface plasmon-polariton enhanced fluorescence, the use of spacers is simply understood to control the distance between the fluorescence dyes and metals to avoid quenching. However, the presence of a spacer layer over the metallic surface not only manipulates the quantum yield, but also affects the surface plasmon-polariton resonance, which in turn modifies the florescence excitation rate as well as the far-field radiation pattern of the emission. This study presents a systematic investigation on the spacer-controlled emission of randomly oriented emitters in the Kretschmann configuration, with the full leverage of the coupled transfer matrix, reciprocity and plane-wave decomposition methods...
March 16, 2017: Physical Chemistry Chemical Physics: PCCP
Regina Bilan, Amagoia Ametzazurra, Kristina Brazhnik, Sergio Escorza, David Fernández, María Uríbarri, Igor Nabiev, Alyona Sukhanova
A novel suspension multiplex immunoassay for the simultaneous specific detection of lung cancer markers in bronchoalveolar lavage fluid (BALF) clinical samples based on fluorescent microspheres having different size and spectrally encoded with quantum dots (QDEM) was developed. The designed suspension immunoassay was validated for the quantitative detection of three lung cancer markers in BALF samples from 42 lung cancer patients and 10 control subjects. Tumor markers were detected through simultaneous formation of specific immune complexes consisting of a capture molecule, the target antigen, and biotinylated recognition molecule on the surface of the different QDEM in a mixture...
March 16, 2017: Scientific Reports
Gaurav Singh, Manish Tiwari, Surendra Pratap Singh, Ruchi Singh, Surendra Singh, Pramod Arvind Shirke, Prabodh K Trivedi, Pratibha Misra
Heat is a major environmental stress factor that confines growth, productivity, and metabolism of plants. Plants respond to such unfavorable conditions through changes in their physiological, biochemical and developmental processes. Withania somnifera, an important medicinal plant, grows in hot and dry conditions, however, molecular mechanisms related to such adaptive properties are not known. Here, we elucidated that members of the SGT gene family play important roles in the survival of W. somnifera under adverse conditions through maintaining the integrity of the membrane...
March 16, 2017: Physiologia Plantarum
K Mouloudakis, I K Kominis
Radical-ion-pair reactions, central for understanding the avian magnetic compass and spin transport in photosynthetic reaction centers, were recently shown to be a fruitful paradigm of the new synthesis of quantum information science with biological processes. We show here that the master equation so far constituting the theoretical foundation of spin chemistry violates fundamental bounds for the entropy of quantum systems, in particular the Ozawa bound. In contrast, a recently developed theory based on quantum measurements, quantum coherence measures, and quantum retrodiction, thus exemplifying the paradigm of quantum biology, satisfies the Ozawa bound as well as the Lanford-Robinson bound on information extraction...
February 2017: Physical Review. E
Juan José Godina-Nava, Gabino Torres-Vega, Germán Octavio López-Riquelme, Eduardo López-Sandoval, Arturo Rodolfo Samana, Fermín García Velasco, Claudia Hernández-Aguilar, Arturo Domínguez-Pacheco
Using the conventional Haberkorn approach, it is evaluated the recombination of the radical pair (RP) singlet spin state to study theoretically the cytoprotective effect of an extremely-low-frequency electromagnetic field (ELF-EMF) on early stages of hepatic cancer chemically induced in rats. The proposal is that ELF-EMF modulates the interconversion rate of singlet and triplet spin states of the RP populations modifying the products from the metabolization of carcinogens. Previously, we found that the daily treatment with ELF-EMF 120 Hz inhibited the number and area of preneoplastic lesions in chemical carcinogenesis...
February 2017: Physical Review. E
Louis-David Arthaut, Nathalie Jourdan, Ali Mteyrek, Maria Procopio, Mohamed El-Esawi, Alain d'Harlingue, Pierre-Etienne Bouchet, Jacques Witczak, Thorsten Ritz, André Klarsfeld, Serge Birman, Robert J Usselman, Ute Hoecker, Carlos F Martino, Margaret Ahmad
Cryptochromes are evolutionarily conserved blue-light absorbing flavoproteins which participate in many important cellular processes including in entrainment of the circadian clock in plants, Drosophila and humans. Drosophila melanogaster cryptochrome (DmCry) absorbs light through a flavin (FAD) cofactor that undergoes photoreduction to the anionic radical (FAD•-) redox state both in vitro and in vivo. However, recent efforts to link this photoconversion to the initiation of a biological response have remained controversial...
2017: PloS One
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