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Quantum yield

Sidsel B Schmidt, Marta Powikrowska, Ken S Krogholm, Bianca Naumann-Busch, Jan K Schjoerring, Søren Husted, Poul E Jensen, Pai R Pedas
A catalytic manganese (Mn) cluster is required for the oxidation of water in the oxygen-evolving complex (OEC) of photosystem II (PSII) in plants. Despite this essential role of Mn in generating the electrons driving photosynthesis, limited information is available on how Mn deficiency affects PSII functionality. We have here used parameters derived from measurements of fluorescence induction kinetics (OJIP transients), non-photochemical quenching (NPQ) and PSII subunit composition to investigate how latent Mn deficiency changes the photochemistry in two barley genotypes differing in Mn efficiency...
2016: Frontiers in Plant Science
Shousi Lu, Shanshan Guo, Pingxiang Xu, Xiaorong Li, Yuming Zhao, Wei Gu, Ming Xue
Nitrogen-doped carbon dots (N-CDs) were synthesized using a one-pot hydrothermal treatment with citric acid in the presence of polyethylenimine. Transmission electron microscopy analysis revealed that the N-CDs were monodispersed and quasi-spherical with an average size of ~2.6 nm. Under ultraviolet irradiation the N-CDs emitted a strong blue luminescence with a quantum yield as high as 51%. Moreover, the N-CDs exhibited a negligible cytotoxicity and could be applied as efficient nanoprobes for real-time imaging of live cells...
2016: International Journal of Nanomedicine
Stefan Zeller, Maksim Kunitski, Jörg Voigtsberger, Anton Kalinin, Alexander Schottelius, Carl Schober, Markus Waitz, Hendrik Sann, Alexander Hartung, Tobias Bauer, Martin Pitzer, Florian Trinter, Christoph Goihl, Christian Janke, Martin Richter, Gregor Kastirke, Miriam Weller, Achim Czasch, Markus Kitzler, Markus Braune, Robert E Grisenti, Wieland Schöllkopf, Lothar Ph H Schmidt, Markus S Schöffler, Joshua B Williams, Till Jahnke, Reinhard Dörner
Quantum tunneling is a ubiquitous phenomenon in nature and crucial for many technological applications. It allows quantum particles to reach regions in space which are energetically not accessible according to classical mechanics. In this "tunneling region," the particle density is known to decay exponentially. This behavior is universal across all energy scales from nuclear physics to chemistry and solid state systems. Although typically only a small fraction of a particle wavefunction extends into the tunneling region, we present here an extreme quantum system: a gigantic molecule consisting of two helium atoms, with an 80% probability that its two nuclei will be found in this classical forbidden region...
December 6, 2016: Proceedings of the National Academy of Sciences of the United States of America
Zsombor Miskolczy, László Biczók, István Jablonkai
The temperature dependence of the kinetics of flavopereirine inclusion in cucurbit[7]uril (CB7) was studied by a stopped-flow method in water. The substantial blue-shift of the emission band and the ∼4-fold fluorescence quantum yield enhancement upon host-guest binding permitted the monitoring of the formation and dissociation of the flavopereirine-CB7 1 : 1 complex in real time. The competitive binding of the 1-adamantylammonium cation with extremely high affinity was exploited to selectively and very accurately determine the kinetic parameters of the exit of flavopereirine from the CB7 cavity...
December 8, 2016: Physical Chemistry Chemical Physics: PCCP
Suk Hyun Kang, Sungwook Mhin, Hyuksu Han, Kang Min Kim, Jacob L Jones, Jeong Ho Ryu, Ju Seop Kang, Shin Hee Kim, Kwang Bo Shim
Graphene quantum dots (GQDs) have attractive properties and potential applications. However, their various applications are limited by a current synthetic method which requires long processing time. Here, we report a facile and remarkably rapid method for production of GQDs exhibiting excellent optoelectronic properties. We employed the pulsed laser ablation (PLA) technique to exfoliate GQDs from multi-wall carbon nanotube (MWCNTs), which can be referred to as a pulsed laser exfoliation (PLE) process. Strikingly, it takes only 6 min to transform all MWCNTs precursors to GQDs by using PLE process...
December 8, 2016: Scientific Reports
Antonietta De Sio, Filippo Troiani, Margherita Maiuri, Julien Réhault, Ephraim Sommer, James Lim, Susana F Huelga, Martin B Plenio, Carlo Andrea Rozzi, Giulio Cerullo, Elisa Molinari, Christoph Lienau
The optical excitation of organic semiconductors not only generates charge-neutral electron-hole pairs (excitons), but also charge-separated polaron pairs with high yield. The microscopic mechanisms underlying this charge separation have been debated for many years. Here we use ultrafast two-dimensional electronic spectroscopy to study the dynamics of polaron pair formation in a prototypical polymer thin film on a sub-20-fs time scale. We observe multi-period peak oscillations persisting for up to about 1 ps as distinct signatures of vibronic quantum coherence at room temperature...
December 8, 2016: Nature Communications
Ievgen Levchuk, Patrick Herre, Marco Brandl, Andres Osvet, Rainer Hock, Wolfgang Peukert, Peter Schweizer, Erdmann Spiecker, Miroslaw Batentschuk, Christoph J Brabec
Quantum size-confined CH3NH3PbX3 (X = Br and I) perovskite nanoplatelets with remarkably high photoluminescence quantum yield (up to 90%) were synthesized by ligand-assisted re-precipitation. Thickness-tunability was realized by varying the oleylamine and oleic acid ligand ratio. This method allows tailoring the nanoplatelet thickness by adjusting the number of unit cell monolayers. Broadly tunable emission wavelengths (450-730 nm) are achieved via the pronounced quantum size effect without anion-halide mixing...
December 8, 2016: Chemical Communications: Chem Comm
Aquiles Carattino, Veer I P Keizer, Marcel J M Schaaf, Michel Orrit
Metallic nanoparticles have opened the possibility of imaging, tracking, and manipulating biological samples without time limitations. Their low photoluminescence quantum yield, however, makes them hard to detect under high background conditions. In this study we show that it is possible to image gold nanorods by detecting their anti-Stokes emission under resonant excitation. We show that even in the membrane of a cell containing the fluorescent dye Atto 647N, the signal/background of the anti-Stokes emission can be >10, while it is impossible to image the particles with the Stokes emission...
December 6, 2016: Biophysical Journal
Anukul Boonloed, Genevieve L Weber, Kelly M Ramzy, Veronica R Dias, Vincent T Remcho
A centrifugal partition chromatography (CPC) method was developed for the preparative-scale isolation and purification of xylindein from the wood-staining fungi, Chlorociboria aeruginosa. Xylindein, a blue-green pigment naturally secreted from the hyphae and fruiting bodies of the fungus, has great value in the decorative wood industry and textile coloration. Xylindein has great potential for use as a fluorescent labeling agent as well as in organic semiconductor applications. However, a primary limitation of xylindein is its poor solubility in most common HPLC solvents...
November 18, 2016: Journal of Chromatography. A
Cangjie Yang, Xiaochen Wang, Mingfeng Wang, Keming Xu, Chenjie Xu
We report a new class of colloidal nanoparticles called JAGG containing near-infrared fluorescent J-aggregates of pyrrolopyrrole cyanines (PPcys) stabilized by amphiphilic block copolymers in aqueous media. The formation of such JAGG can be tuned by the chemical structure of PPcys, the concentration of the chromophores inside the polymeric nanoparticles and ultrasonic treatment. These JAGG nanoparticles exhibit a narrow emission band at 773 nm, a fluorescence quantum yield comparable to that of indocyanine green, and significantly enhanced photostability that is ideal for long-term bioimaging...
December 5, 2016: Chemistry: a European Journal
Pascale Changenet-Barret, Lajos Kovács, Dimitra Markovitsi, Thomas Gustavsson
Xanthines represent a wide class of compounds closely related to the DNA bases adenine and guanine. Ubiquitous in the human body, they are capable of replacing natural bases in double helices and give rise to four-stranded structures. Although the use of their fluorescence for analytical purposes was proposed, their fluorescence properties have not been properly characterized so far. The present paper reports the first fluorescence study of xanthine solutions relying on femtosecond spectroscopy. Initially, we focus on 3-methylxanthine, showing that this compound exhibits non-exponential fluorescence decays with no significant dependence on the emission wavelength...
December 3, 2016: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Kwan-Ting Yeung, Wai-Pong To, Chenyue Sun, Gang Cheng, Chensheng Ma, Glenna So Ming Tong, Chen Yang, Chi-Ming Che
The synthesis, excited-state dynamics, and applications of two series of air-stable luminescent tungsten(VI) complexes are described. These tungsten(VI) complexes show phosphorescence in the solid state and in solutions with emission quantum yields up to 22 % in thin film (5 % in mCP) at room temperature. Complex 2 c, containing a 5,7-diphenyl-8-hydroxyquinolinate ligand, displays prompt fluorescence (blue-green) and phosphorescence (red) of comparable intensity, which could be used for ratiometric luminescent sensing...
December 5, 2016: Angewandte Chemie
Andrea Zen, Loïc M Roch, Stephen J Cox, Xiao Liang Hu, Sandro Sorella, Dario Alfè, Angelos Michaelides
Clay minerals are ubiquitous in nature, and the manner in which they interact with their surroundings has important industrial and environmental implications. Consequently, a molecular-level understanding of the adsorption of molecules on clay surfaces is crucial. In this regard computer simulations play an important role, yet the accuracy of widely used empirical force fields (FF) and density functional theory (DFT) exchange-correlation functionals is often unclear in adsorption systems dominated by weak interactions...
November 23, 2016: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Vladimir K Ryabchuk, Vyacheslav N Kuznetsov, Alexei V Emeline, Yurii M Artem'ev, Galina V Kataeva, Satoshi Horikoshi, Nick Serpone
This article evokes the futuristic visions of two giants, one a writer, Jules Verne, who foresaw water as the coal of the future, and the other a scientist, Giacomo Ciamician, who foresaw the utilization of solar energy as an energy source with which to drive photochemical and photocatalytic reactions for the betterment of mankind. Specifically, we examine briefly the early work of the 1960s and 1970s on the photosplitting of free water and water adsorbed on solid supports, based mostly on metal oxides, from which both hydrogen and oxygen evolve in the expected stoichiometric ratio of 2 to 1...
November 29, 2016: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Alicia Gomis-Berenguer, Leticia F Velasco, Inmaculada Velo-Gala, Conchi O Ania
The interest in the use of nanoporous carbon materials in applications related to energy conversion and storage, either as catalysts or additives, has grown over recent decades in various disciplines. Since the early studies reporting the benefits of the use of nanoporous carbons as inert supports of semiconductors and as electron acceptors that enhance the splitting of the photogenerated excitons, many researchers have investigated the key role of carbon matrices coupled to all types of photoactive materials...
November 16, 2016: Journal of Colloid and Interface Science
Lucius Chiaraviglio, Yoon-Suk Kang, James E Kirby
Traditional measures of intracellular antimicrobial activity and eukaryotic cell cytotoxicity rely on endpoint assays. Such endpoint assays require several additional experimental steps prior to readout, such as cell lysis, colony forming unit determination, or reagent addition. When performing thousands of assays, for example, during high-throughput screening, the downstream effort required for these types of assays is considerable. Therefore, to facilitate high-throughput antimicrobial discovery, we developed a real-time assay to simultaneously identify inhibitors of intracellular bacterial growth and assess eukaryotic cell cytotoxicity...
November 16, 2016: Journal of Visualized Experiments: JoVE
Markus Gernert, Ulrich Müller, Martin Haehnel, Jens Pflaum, Andreas Steffen
A series of linear and trigonal copper(I) complexes bearing a cyclic alkyl(amino)carbene (CAAC) ligand show surprising photophysical properties when compared to their corresponding N-heterocyclic carbene (NHC) complexes. Whereas the linear NHC complexes [CuX(NHC)] are nearly non-emissive, [CuX(CAAC)] (X = Cl, Br, I) and [Cu(CAAC)2]PF6 show very bright emission from their triplet excited states in the blue to green region displaying quantum yields of up to 65% in the solid state, although the π-acceptor comprises only the carbene C and N atoms with no other π conjugation...
December 2, 2016: Chemistry: a European Journal
Stepan Stehlik, Marian Varga, Martin Ledinsky, Daria Miliaieva, Halyna Kozak, Viera Skakalova, Clemens Mangler, Timothy J Pennycook, Jannik C Meyer, Alexander Kromka, Bohuslav Rezek
Detonation nanodiamonds (DNDs) with a typical size of 5 nm have attracted broad interest in science and technology. Further size reduction of DNDs would bring these nanoparticles to the molecular-size level and open new prospects for research and applications in various fields, ranging from quantum physics to biomedicine. Here we show a controllable size reduction of the DND mean size down to 1.4 nm without significant particle loss and with additional disintegration of DND core agglutinates by air annealing, leading to a significantly narrowed size distribution (±0...
December 2, 2016: Scientific Reports
M F Brandl, M W van Mourik, L Postler, A Nolf, K Lakhmanskiy, R R Paiva, S Möller, N Daniilidis, H Häffner, V Kaushal, T Ruster, C Warschburger, H Kaufmann, U G Poschinger, F Schmidt-Kaler, P Schindler, T Monz, R Blatt
We report on the design of a cryogenic setup for trapped ion quantum computing containing a segmented surface electrode trap. The heat shield of our cryostat is designed to attenuate alternating magnetic field noise, resulting in 120 dB reduction of 50 Hz noise along the magnetic field axis. We combine this efficient magnetic shielding with high optical access required for single ion addressing as well as for efficient state detection by placing two lenses each with numerical aperture 0.23 inside the inner heat shield...
November 2016: Review of Scientific Instruments
E M Zhurikova, L K Ignatova, N N Rudenko, V A Mudrik, D V Vetoshkina, B N Ivanov
The expression of genes of two carbonic anhydrases (CA) belonging to the α-family, α-CA2 and α-CA4 (according to the nomenclature in N. Fabre et al. (2007) Plant Cell Environ., 30, 617-629), was studied in arabidopsis (Arabidopsis thaliana, var. Columbia) leaves. The expression of the At2g28210 gene coding α-CA2 decreased under increase in plant illumination, while the expression of the At4g20990 gene coding α-CA4 increased. Under conditions close to optimal for photosynthesis, in plants with gene At2g28210 knockout, the effective quantum yield of photosystem 2 and the light-induced accumulation of hydrogen peroxide in leaves were lower than in wild type plants, while the coefficient of non-photochemical quenching of leaf chlorophyll a fluorescence and the rate of CO2 assimilation in leaves were higher...
October 2016: Biochemistry. Biokhimii︠a︡
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