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Sample records for 1o2 quantum yields

  1. Ru(II) complexes of new tridentate ligands: unexpected high yield of sensitized 1O2.

    PubMed

    Liu, Yao; Hammitt, Richard; Lutterman, Daniel A; Joyce, Lauren E; Thummel, Randolph P; Turro, Claudia

    2009-01-05

    Ru(II) complexes possessing new tridentate ligands with extended pi systems, pydppx (3-(pyrid-2'-yl)-11,12-dimethyl-dipyrido[3,2-a:2',3'-c]phenazine) and pydppn (3-(pyrid-2'-yl)-4,5,9,16-tetraaza-dibenzo[a,c]naphthacene), were synthesized and characterized. The investigation of the photophysical properties of the series [Ru(tpy)(n)(L)(2-n)](2+) (L = pydppx, pydppn, n = 0-2) reveals markedly different excited state behavior among the complexes. The Ru(II) complexes possessing the pydppx ligand are similar to the pydppz (3-(pyrid-2'-yl)dipyrido[3,2-a:2',3'-c]phenazine) systems, with a lowest energy metal-to-ligand charge transfer excited state with lifetimes of 1-4 ns. In contrast, the lowest energy excited state in the [Ru(tpy)(n)(pydppn)(2-n)](2+) (n = 0, 1) complexes is a ligand-centered (3)pipi* localized on the pydppn ligand with lifetimes of approximately 20 mus. The [Ru(tpy)(n)(pydppn)(2-n)](2+) (n = 0, 1) complexes are able to generate (1)O(2) with approximately 100% efficiency. Both [Ru(tpy)(pydppn)](2+) and [Ru(pydppn)(2)](2+) bind to DNA, however, the former exhibits a approximately 10-fold greater DNA binding constant than the latter. Efficient DNA photocleavage is observed for [Ru(tpy)(pydppn)](2+), owing to its ability to photosensitize the production of (1)O(2), which can mediate the reactivity. Such high quantum yields of (1)O(2) photosensitization of transition metal complexes may be useful in the design of new systems with long-lived excited states for photodynamic therapy.

  2. Cobalt(II), Nickel(II) and Copper(II) complexes of a tetradentate Schiff base as photosensitizers: Quantum yield of 1O2 generation and its promising role in anti-tumor activity.

    PubMed

    Pradeepa, S M; Bhojya Naik, H S; Vinay Kumar, B; Indira Priyadarsini, K; Barik, Atanu; Ravikumar Naik, T R

    2013-01-15

    In the present investigation, a Schiff base N'1,N'3-bis[(E)-(5-bromo-2-hydroxyphenyl)methylidene]benzene-1,3-dicarbohydrazide and its metal complexes have been synthesized and characterized. The DNA-binding studies were performed using absorption spectroscopy, emission spectra, viscosity measurements and thermal denatuaration studies. The experimental evidence indicated that, the Co(II), Ni(II) and Cu(II) complexes interact with calf thymus DNA through intercalation with an intrinsic binding constant Kb of 2.6×10(4) M(-1), 5.7×10(4) M(-1) and 4.5×10(4) M(-1), respectively and they exhibited potent photodamage abilities on pUC19 DNA, through singlet oxygen generation with quantum yields of 0.32, 0.27 and 0.30 respectively. The cytotoxic activity of the complexes resulted that they act as a potent photosensitizers for photochemical reactions.

  3. Cobalt(II), Nickel(II) and Copper(II) complexes of a tetradentate Schiff base as photosensitizers: Quantum yield of 1O2 generation and its promising role in anti-tumor activity

    NASA Astrophysics Data System (ADS)

    Pradeepa, S. M.; Bhojya Naik, H. S.; Vinay Kumar, B.; Indira Priyadarsini, K.; Barik, Atanu; Ravikumar Naik, T. R.

    2013-01-01

    In the present investigation, a Schiff base N'1,N'3-bis[(E)-(5-bromo-2-hydroxyphenyl)methylidene]benzene-1,3-dicarbohydrazide and its metal complexes have been synthesized and characterized. The DNA-binding studies were performed using absorption spectroscopy, emission spectra, viscosity measurements and thermal denatuaration studies. The experimental evidence indicated that, the Co(II), Ni(II) and Cu(II) complexes interact with calf thymus DNA through intercalation with an intrinsic binding constant Kb of 2.6 × 104 M-1, 5.7 × 104 M-1 and 4.5 × 104 M-1, respectively and they exhibited potent photodamage abilities on pUC19 DNA, through singlet oxygen generation with quantum yields of 0.32, 0.27 and 0.30 respectively. The cytotoxic activity of the complexes resulted that they act as a potent photosensitizers for photochemical reactions.

  4. The effect of axial ligands on the quantum yield of singlet oxygen of new silicon phthalocyanine

    NASA Astrophysics Data System (ADS)

    Lv, Huafei; Zhang, Xuemei; Yu, Xinxin; Pan, Sujuan; Xie, Shusen; Yang, Hongqin; Peng, Yiru

    2016-10-01

    The singlet oxygen (1O2) production abilitity is an important factor to assess their potential as effective of photosensitizers. In this paper, the 1O2 production rate, production rate constant and quantum yield of silicon(IV) phthalocyanine axially bearing 1-3 generation dendritic substituents were evaluated by a high performance liquid chromatographic method. The results show that the 1O2 production rate and production rate constant of these compounds increase gradually with dendritic generations increase. And the 1O2 quantum yield of silicon(IV) phthalocyanine with first generation dendritic ligand was the highest. This may be due to the isolation effect of the dendritic ligands on the phthalocyanine core. The parameters of the observed 1O2 production properties will provide valuable data for these dendrimer phthalocyanines as promising photosensitizer in PDT application.

  5. Correlations between dissolved organic matter optical properties and quantum yields of singlet oxygen and hydrogen peroxide.

    PubMed

    Dalrymple, Renée M; Carfagno, Amy K; Sharpless, Charles M

    2010-08-01

    Various aquatic dissolved organic matter (DOM) samples produce singlet oxygen (1O2) and hydrogen peroxide (H2O2) with quantum yields of 0.59 to 4.5% (1O2 at 365 nm) and 0.017 to 0.053% (H2O2, 300-400 nm integrated). The two species' yields have opposite pH dependencies and strong, but opposite, correlations with the E2/E3 ratio (A254 divided by A365). Linear regressions allow prediction of both quantum yields from E2/E3 in natural water samples with errors ranging from -3% to 60%. Experimental evidence and kinetic calculations indicate that less than six percent of the H2O2 is produced by reaction between 1O2 and DOM. The inverse relationship between the 1O2 and H2O2 yields is thus best explained by a model in which precursors to these species are populated competitively. A model is presented, which proposes that important precursors to H2O2 may be either charge-transfer or triplet states of DOM.

  6. Absolute quantum yield measurement of powder samples.

    PubMed

    Moreno, Luis A

    2012-05-12

    Measurement of fluorescence quantum yield has become an important tool in the search for new solutions in the development, evaluation, quality control and research of illumination, AV equipment, organic EL material, films, filters and fluorescent probes for bio-industry. Quantum yield is calculated as the ratio of the number of photons absorbed, to the number of photons emitted by a material. The higher the quantum yield, the better the efficiency of the fluorescent material. For the measurements featured in this video, we will use the Hitachi F-7000 fluorescence spectrophotometer equipped with the Quantum Yield measuring accessory and Report Generator program. All the information provided applies to this system. Measurement of quantum yield in powder samples is performed following these steps: 1. Generation of instrument correction factors for the excitation and emission monochromators. This is an important requirement for the correct measurement of quantum yield. It has been performed in advance for the full measurement range of the instrument and will not be shown in this video due to time limitations. 2. Measurement of integrating sphere correction factors. The purpose of this step is to take into consideration reflectivity characteristics of the integrating sphere used for the measurements. 3. Reference and Sample measurement using direct excitation and indirect excitation. 4. Quantum Yield calculation using Direct and Indirect excitation. Direct excitation is when the sample is facing directly the excitation beam, which would be the normal measurement setup. However, because we use an integrating sphere, a portion of the emitted photons resulting from the sample fluorescence are reflected by the integrating sphere and will re-excite the sample, so we need to take into consideration indirect excitation. This is accomplished by measuring the sample placed in the port facing the emission monochromator, calculating indirect quantum yield and correcting the direct

  7. Acetylene bridged porphyrin-monophthalocyaninato ytterbium(III) hybrids with strong two-photon absorption and high singlet oxygen quantum yield.

    PubMed

    Ke, Hanzhong; Li, Wenbin; Zhang, Tao; Zhu, Xunjin; Tam, Hoi-Lam; Hou, Anxin; Kwong, Daniel W J; Wong, Wai-Kwok

    2012-04-21

    Several acetylene bridged porphyrin-monophthalocyaninato ytterbium(III) hybrids, PZn-PcYb, PH(2)-PcYb and PPd-PcYb, have been prepared and characterized by (1)H and (31)P NMR, mass spectrometry, and UV-vis spectroscopy. Their photophysical and photochemical properties, especially the relative singlet oxygen ((1)O(2)) quantum yields and the two-photon absorption cross-section (σ(2)), were investigated. These three newly synthesized compounds exhibited very large σ(2) values and substantial (1)O(2) quantum yields upon photo-excitation, making them potential candidates as one- and two-photon photodynamic therapeutic agents.

  8. Influence of excitonic effects on luminescence quantum yield in silicon

    NASA Astrophysics Data System (ADS)

    Sachenko, A. V.; Kostylyov, V. P.; Vlasiuk, V. M.; Sokolovskyi, I. O.; Evstigneev, M.

    2017-03-01

    Nonradiative exciton lifetime in silicon is determined by comparison of the experimental and theoretical curves of bulk minority charge carriers lifetime on doping and excitation levels. This value is used to analyze the influence of excitonic effects on internal luminescence quantum yield at room temperature, taking into account both nonradiative and radiative exciton lifetimes. A range of Shockley-Hall-Reed lifetimes is found, where excitonic effects lead to an increase of internal luminescence quantum yield.

  9. Measurement of the fluorescence quantum yield of bis-MSB

    NASA Astrophysics Data System (ADS)

    Ding, Xue-Feng; Wen, Liang-Jian; Zhou, Xiang; Ding, Ya-Yun; Ye, Xing-Chen; Zhou, Li; Liu, Meng-Chao; Cai, Hao; Cao, Jun

    2015-12-01

    The fluorescence quantum yield of bis-MSB, a widely used liquid scintillator wavelength shifter, was measured to study the photon absorption and re-emission processes in a liquid scintillator. The re-emission process affects the photoelectron yield and distribution, especially in a large liquid scintillator detector, thus must be understood to optimize the liquid scintillator for good energy resolution and to precisely simulate the detector with Monte Carlo. In this study, solutions of different bis-MSB concentration were prepared for absorption and fluorescence emission measurements to cover a broad range of wavelengths. Harmane was used as a standard reference to obtain the absolution fluorescence quantum yield. For the first time we measured the fluorescence quantum yield of bis-MSB up to 430 nm as inputs required by Monte Carlo simulation, which is 0.926±0.053 at λex=350 nm. Supported by National Natural Science Foundation of China (11205183, 11225525, 11390381)

  10. Quantum Yield Heterogeneity among Single Nonblinking Quantum Dots Revealed by Atomic Structure-Quantum Optics Correlation.

    PubMed

    Orfield, Noah J; McBride, James R; Wang, Feng; Buck, Matthew R; Keene, Joseph D; Reid, Kemar R; Htoon, Han; Hollingsworth, Jennifer A; Rosenthal, Sandra J

    2016-02-23

    Physical variations in colloidal nanostructures give rise to heterogeneity in expressed optical behavior. This correlation between nanoscale structure and function demands interrogation of both atomic structure and photophysics at the level of single nanostructures to be fully understood. Herein, by conducting detailed analyses of fine atomic structure, chemical composition, and time-resolved single-photon photoluminescence data for the same individual nanocrystals, we reveal inhomogeneity in the quantum yields of single nonblinking "giant" CdSe/CdS core/shell quantum dots (g-QDs). We find that each g-QD possesses distinctive single exciton and biexciton quantum yields that result mainly from variations in the degree of charging, rather than from volume or structure inhomogeneity. We further establish that there is a very limited nonemissive "dark" fraction (<2%) among the studied g-QDs and present direct evidence that the g-QD core must lack inorganic passivation for the g-QD to be "dark". Therefore, in contrast to conventional QDs, ensemble photoluminescence quantum yield is principally defined by charging processes rather than the existence of dark g-QDs.

  11. On the photoelectric quantum yield of small dust particles

    NASA Astrophysics Data System (ADS)

    Kimura, Hiroshi

    2016-07-01

    Photoelectron emission is crucial to electric charging of dust particles around main-sequence stars and gas heating in various dusty environments. An estimate of the photoelectric processes contains an ill-defined parameter called the photoelectric quantum yield, which is the total number of electrons ejected from a dust particle per absorbed photon. Here we revisit the so-called small particle effect of photoelectron emission and provide an analytical model to estimate photoelectric quantum yields of small dust particles in sizes down to nanometers. We show that the small particle effect elevates the photoelectric quantum yields of nanoparticles up to by a factor of 103 for carbon, water ice, and organics, and a factor of 102 for silicate, silicon carbide, and iron. We conclude the surface curvature of the particles is a quantity of great importance to the small particle effect, unless the particles are submicrometers in radius or larger.

  12. Light propagation and fluorescence quantum yields in liquid scintillators

    NASA Astrophysics Data System (ADS)

    Buck, C.; Gramlich, B.; Wagner, S.

    2015-09-01

    For the simulation of the scintillation and Cherenkov light propagation in large liquid scintillator detectors a detailed knowledge about the absorption and emission spectra of the scintillator molecules is mandatory. Furthermore reemission probabilities and quantum yields of the scintillator components influence the light propagation inside the liquid. Absorption and emission properties are presented for liquid scintillators using 2,5-Diphenyloxazole (PPO) and 4-bis-(2-Methylstyryl)benzene (bis-MSB) as primary and secondary wavelength shifter. New measurements of the quantum yields for various aromatic molecules are shown.

  13. Unity quantum yield of photogenerated charges and band-like transport in quantum-dot solids.

    PubMed

    Talgorn, Elise; Gao, Yunan; Aerts, Michiel; Kunneman, Lucas T; Schins, Juleon M; Savenije, T J; van Huis, Marijn A; van der Zant, Herre S J; Houtepen, Arjan J; Siebbeles, Laurens D A

    2011-09-25

    Solid films of colloidal quantum dots show promise in the manufacture of photodetectors and solar cells. These devices require high yields of photogenerated charges and high carrier mobilities, which are difficult to achieve in quantum-dot films owing to a strong electron-hole interaction and quantum confinement. Here, we show that the quantum yield of photogenerated charges in strongly coupled PbSe quantum-dot films is unity over a large temperature range. At high photoexcitation density, a transition takes place from hopping between localized states to band-like transport. These strongly coupled quantum-dot films have electrical properties that approach those of crystalline bulk semiconductors, while retaining the size tunability and cheap processing properties of colloidal quantum dots.

  14. New Ru(II) complexes for dual photoreactivity: ligand exchange and (1)O2 generation.

    PubMed

    Knoll, Jessica D; Albani, Bryan A; Turro, Claudia

    2015-08-18

    Uncovering the factors that govern the electronic structure of Ru(II)-polypyridyl complexes is critical in designing new compounds for desired photochemical reactions, and strategies to tune excited states for ligand dissociation and (1)O2 production are discussed herein. The generally accepted mechanism for photoinduced ligand dissociation proposes that population of the dissociative triplet ligand field ((3)LF) state proceeds through thermal population from the vibrationally cooled triplet metal-to-ligand charge transfer ((3)MLCT) state; however, temperature-dependent emission spectroscopy provides varied activation energies using the emission and ligand exchange quantum yields for [Ru(bpy)2(L)2](2+) (bpy = 2,2'-bipyridine; L = CH3CN or py). This suggests that population of the (3)LF state proceeds from the vibrationally excited (3)MLCT state. Because the quantum yield of ligand dissociation for nitriles is much more efficient than that for py, steric bulk was introduced into the ligand set to distort the pseudo-octahedral geometry and lower the energy of the (3)LF state. The py dissociation quantum yield with 500 nm irradiation in a series of [Ru(tpy)(NN)(py)](2+) complexes (tpy = 2,2':6',2″-terpyridine; NN = bpy, 6,6'-dimethyl-2,2'-bipyridine (Me2bpy), 2,2'-biquinoline (biq)) increases by 2-3 orders of magnitude with the sterically bulky Me2bpy and biq ligands relative to bpy. Ultrafast transient absorption spectroscopy reveals population of the (3)LF state within 3-7 ps when NN is bulky, and density functional theory calculations support stabilized (3)LF states. Dual activity via ligand dissociation and (1)O2 production can be achieved by careful selection of the ligand set to tune the excited-state dynamics. Incorporation of an extended π system in Ru(II) complexes such as [Ru(bpy)(dppn)(CH3CN)2](2+) (dppn = benzo[i]dipyrido[3,2-a:2',3'-c]phenazine) and [Ru(tpy)(Me2dppn)(py)](2+) (Me2dppn = 3,6-dimethylbenzo[i]dipyrido[3,2-a:2',3'-c]phenazine) introduces

  15. New Ru(II) Complexes for Dual Photoreactivity: Ligand Exchange and 1O2 Generation

    PubMed Central

    Knoll, Jessica D.; Albani, Bryan A.; Turro, Claudia

    2016-01-01

    CONSPECTUS Uncovering the factors that govern the electronic structure of Ru(II)–polypyridyl complexes is critical in designing new compounds for desired photochemical reactions, and strategies to tune excited states for ligand dissociation and 1O2 production are discussed herein. The generally accepted mechanism for photoinduced ligand dissociation proposes that population of the dissociative triplet ligand field (3LF) state proceeds through thermal population from the vibrationally cooled triplet metal-to-ligand charge transfer (3MLCT) state; however, temperature-dependent emission spectroscopy provides varied activation energies using the emission and ligand exchange quantum yields for [Ru(bpy)2(L)2]2+ (bpy = 2,2′-bipyridine; L = CH3CN or py). This suggests that population of the 3LF state proceeds from the vibrationally excited 3MLCT state. Because the quantum yield of ligand dissociation for nitriles is much more efficient than that for py, steric bulk was introduced into the ligand set to distort the pseudo-octahedral geometry and lower the energy of the 3LF state. The py dissociation quantum yield with 500 nm irradiation in a series of [Ru(tpy)(NN)(py)]2+ complexes (tpy = 2,2′:6′,2″-terpyridine; NN = bpy, 6,6′-dimethyl-2,2′-bipyridine (Me2bpy), 2,2′-biquinoline (biq)) increases by 2–3 orders of magnitude with the sterically bulky Me2bpy and biq ligands relative to bpy. Ultrafast transient absorption spectroscopy reveals population of the 3LF state within 3–7 ps when NN is bulky, and density functional theory calculations support stabilized 3LF states. Dual activity via ligand dissociation and 1O2 production can be achieved by careful selection of the ligand set to tune the excited-state dynamics. Incorporation of an extended π system in Ru(II) complexes such as [Ru(bpy)(dppn)(CH3CN)2]2+ (dppn = benzo[i]dipyrido[3,2-a:2′,3′-c]phenazine) and [Ru(tpy)(Me2dppn)(py)]2+ (Me2dppn = 3,6-dimethylbenzo[i]dipyrido[3,2-a:2′,3

  16. Photosynthetic quantum yield dynamics: from photosystems to leaves.

    PubMed

    Hogewoning, Sander W; Wientjes, Emilie; Douwstra, Peter; Trouwborst, Govert; van Ieperen, Wim; Croce, Roberta; Harbinson, Jeremy

    2012-05-01

    The mechanisms underlying the wavelength dependence of the quantum yield for CO(2) fixation (α) and its acclimation to the growth-light spectrum are quantitatively addressed, combining in vivo physiological and in vitro molecular methods. Cucumber (Cucumis sativus) was grown under an artificial sunlight spectrum, shade light spectrum, and blue light, and the quantum yield for photosystem I (PSI) and photosystem II (PSII) electron transport and α were simultaneously measured in vivo at 20 different wavelengths. The wavelength dependence of the photosystem excitation balance was calculated from both these in vivo data and in vitro from the photosystem composition and spectroscopic properties. Measuring wavelengths overexciting PSI produced a higher α for leaves grown under the shade light spectrum (i.e., PSI light), whereas wavelengths overexciting PSII produced a higher α for the sun and blue leaves. The shade spectrum produced the lowest PSI:PSII ratio. The photosystem excitation balance calculated from both in vivo and in vitro data was substantially similar and was shown to determine α at those wavelengths where absorption by carotenoids and nonphotosynthetic pigments is insignificant (i.e., >580 nm). We show quantitatively that leaves acclimate their photosystem composition to their growth light spectrum and how this changes the wavelength dependence of the photosystem excitation balance and quantum yield for CO(2) fixation. This also proves that combining different wavelengths can enhance quantum yields substantially.

  17. Biexciton quantum yield of single semiconductor nanocrystals from photon statistics

    PubMed Central

    Nair, Gautham; Zhao, Jing; Bawendi, Moungi G

    2012-01-01

    Biexciton properties strongly affect the usability of a light emitter in quantum photon sources and lasers but are difficult to measure for single fluorophores at room temperature due to luminescence intermittency and bleaching at the high excitation fluences usually required. Here, we observe the biexciton (BX) to exciton (X) to ground photoluminescence cascade of single colloidal semiconductor nanocrystals (NCs) under weak excitation in a g(2) photon correlation measurement and show that the normalized amplitude of the cascade feature is equal to the ratio of the BX to X fluorescence quantum yields. This imposes a limit on the attainable depth of photon antibunching and provides a robust means to study single emitter biexciton physics. In NC samples, we show that the BX quantum yield is considerably inhomogeneous, consistent with the defect sensitivity expected of the Auger nonradiative recombination mechanism. The method can be extended to study X,BX spectral and polarization correlations. PMID:21288042

  18. High quantum yield ZnO quantum dots synthesizing via an ultrasonication microreactor method.

    PubMed

    Yang, Weimin; Yang, Huafang; Ding, Wenhao; Zhang, Bing; Zhang, Le; Wang, Lixi; Yu, Mingxun; Zhang, Qitu

    2016-11-01

    Green emission ZnO quantum dots were synthesized by an ultrasonic microreactor. Ultrasonic radiation brought bubbles through ultrasonic cavitation. These bubbles built microreactor inside the microreactor. The photoluminescence properties of ZnO quantum dots synthesized with different flow rate, ultrasonic power and temperature were discussed. Flow rate, ultrasonic power and temperature would influence the type and quantity of defects in ZnO quantum dots. The sizes of ZnO quantum dots would be controlled by those conditions as well. Flow rate affected the reaction time. With the increasing of flow rate, the sizes of ZnO quantum dots decreased and the quantum yields first increased then decreased. Ultrasonic power changed the ultrasonic cavitation intensity, which affected the reaction energy and the separation of the solution. With the increasing of ultrasonic power, sizes of ZnO quantum dots first decreased then increased, while the quantum yields kept increasing. The effect of ultrasonic temperature on the photoluminescence properties of ZnO quantum dots was influenced by the flow rate. Different flow rate related to opposite changing trend. Moreover, the quantum yields of ZnO QDs synthesized by ultrasonic microreactor could reach 64.7%, which is higher than those synthesized only under ultrasonic radiation or only by microreactor.

  19. Quantum Yield of Single Surface Plasmons Generated by a Quantum Dot Coupled with a Silver Nanowire.

    PubMed

    Li, Qiang; Wei, Hong; Xu, Hongxing

    2015-12-09

    The interactions between surface plasmons (SPs) in metal nanostructures and excitons in quantum emitters (QEs) lead to many interesting phenomena and potential applications that are strongly dependent on the quantum yield of SPs. The difficulty in distinguishing all the possible exciton recombination channels hinders the experimental determination of SP quantum yield. Here, we experimentally measured for the first time the quantum yield of single SPs generated by the exciton-plasmon coupling in a system composed of a single quantum dot and a silver nanowire (NW). By utilizing the SP guiding property of the NW, the decay rates of all the exciton recombination channels, i.e., direct free space radiation channel, SP generation channel, and nonradiative damping channel, are quantitatively obtained. It is determined that the optimum emitter-NW coupling distance for the largest SP quantum yield is about 10 nm, resulting from the different distance-dependent decay rates of the three channels. These results are important for manipulating the coupling between plasmonic nanostructures and QEs and developing on-chip quantum plasmonic devices for potential nanophotonic and quantum information applications.

  20. Kok Effect and the Quantum Yield of Photosynthesis 1

    PubMed Central

    Sharp, Robert E.; Matthews, Mark A.; Boyer, John S.

    1984-01-01

    The linear response of photosynthesis to light at low photon flux densities is known to change abruptly in the vicinity of the light compensation point so that the quantum yield seems to decrease as radiation increases. We studied this `Kok effect' in attached sunflower (Helianthus annuus L. cv IS894) leaves using gas exchange techniques. The effect was present even though respiration was constant in the dark. It was observed at a similar photon flux density (7 to 11 micromole photons per square meter per second absorbed photosynthetically active radiation) despite a wide range of light compensation points as well as rates of photosynthesis. The effect was not apparent when photorespiration was inhibited at low pO2 (1 kilopascal), but this result was complicated because dark respiration was quite O2-sensitive and was partially suppressed under these conditions. The Kok effect was observed at saturating pCO2 and, therefore, could not be explained by a change in photorespiration. Instead, the magnitude of the effect varied as dark respiration varied in a single leaf, and was minimized when dark respiration was minimized, indicating that a partial suppression of dark respiration by light is responsible. Quantum yields measured at photon flux densities between 0 and 7 to 11 micromole photons per square meter per second, therefore, represent the combined yields of photosynthesis and of the suppression of a component of dark respiration by light. This leads to an overestimate of the quantum yield of photosynthesis. In view of these results, quantum yields of photosynthesis must be measured (a) when respiration is constant in the dark, and (b) when dark respiration has been inhibited either at low pO2 to eliminate most of the light-induced suppression of dark respiration or at photon flux densities above that required to saturate the light-induced suppression of dark respiration. Significant errors in quantum yields of photosynthesis can result in leaves exhibiting this

  1. Interpretation of quantum yields exceeding unity in photoelectrochemical systems

    SciTech Connect

    Szklarczyk, M.; Allen, R.E.

    1986-10-20

    In photoelectrochemical systems involving light shining on a semiconductor interfaced with an electrolyte, the quantum yield as a function of photon frequency ..nu.. is observed to exhibit a peak at h..nu..roughly-equal2E/sub g/, where E/sub g/ is the band gap of the semiconductor. The maximum in this peak is sometimes found to exceed unity. We provide an interpretation involving surface states and inelastic electron-electron scattering. The theory indicates that the effect should be observable for p-type semiconductors, but not n-type.

  2. Photoacoustic analysis of proteins: volumetric signals and fluorescence quantum yields.

    PubMed Central

    Kurian, E; Prendergast, F G; Small, J R

    1997-01-01

    A series of proteins has been examined using time-resolved, pulsed-laser volumetric photoacoustic spectroscopy. Photoacoustic waveforms were collected to measure heat release for calculation of fluorescence quantum yields, and to explore the possibility of photoinduced nonthermal volume changes occurring in these protein samples. The proteins studied were the green fluorescent protein (GFP); intestinal fatty acid binding protein (IFABP), and adipocyte lipid-binding protein (ALBP), each labeled noncovalently with 1-anilinonaphthalene-8-sulfonate (1,8-ANS) and covalently with 6-acryloyl-2-(dimethylamino)naphthalene (acrylodan); and acrylodan-labeled IFABP and ALBP with added oleic acid. Of this group of proteins, only the ALBP labeled with 1,8-ANS showed significant nonthermal volume changes at the beta = 0 temperature (approximately 3.8 degrees C) for the buffer used (10 mM Tris-HCI, pH 7.5) (beta is the thermal cubic volumetric expansion coefficient). For all of the proteins except for acrylodan-labeled IFABP, the fluorescence quantum yields calculated assuming simple energy conservation were anomalously high, i.e., the apparent heat signals were lower than those predicted from independent fluorescence measurements. The consistent anomalies suggest that the low photoacoustic signals may be characteristic of fluorophores buried in proteins, and that photoacoustic signals derive in part from the microenvironment of the absorbing chromophore. Images FIGURE 1 PMID:9199809

  3. New Ru(II) Complex for Dual Activity: Photoinduced Ligand Release and (1)O2 Production.

    PubMed

    Loftus, Lauren M; White, Jessica K; Albani, Bryan A; Kohler, Lars; Kodanko, Jeremy J; Thummel, Randolph P; Dunbar, Kim R; Turro, Claudia

    2016-03-07

    The new complex [Ru(pydppn)(biq)(py)](2+) (1) undergoes both py photodissociation in CH3CN with Φ500 =0.0070(4) and (1)O2 production with ΦΔ =0.75(7) in CH3 OH from a long-lived (3) ππ* state centered on the pydppn ligand (pydppn=3-(pyrid-2-yl)benzo[i]dipyrido[3,2-a:2',3'-c]phenazine; biq = 2,2'-biquinoline; py=pyridine). This represents an order of magnitude decrease in the Φ500 compared to the previously reported model compound [Ru(tpy)(biq)(py)](2+) (3) (tpy=2,2':6',2''-terpyridine) that undergoes only ligand exchange. The effect on the quantum yields by the addition of a second deactivation pathway through the low-lying (3) ππ* state necessary for dual reactivity was investigated using ultrafast and nanosecond transient absorption spectroscopy, revealing a significantly shorter (3) MLCT lifetime in 1 relative to that of the model complex 3. Due to the structural similarities between the two compounds, the lower values of Φ500 and ΦΔ compared to that of [Ru(pydppn)(bpy)(py)](2+) (2) (bpy=2,2'-bipyridine) are attributed to a competitive excited state population between the (3) LF states involved in ligand dissociation and the long-lived (3) ππ* state in 1. Complex 1 represents a model compound for dual activity that may be applied to photochemotherapy.

  4. Synthesis of Luminescent Graphene Quantum Dots with High Quantum Yield and Their Toxicity Study

    PubMed Central

    Jiang, Dan; Chen, Yunping; Li, Na; Li, Wen; Wang, Zhenguo; Zhu, Jingli; Zhang, Hong; Liu, Bin; Xu, Shan

    2015-01-01

    High fluorescence quantum yield graphene quantum dots (GQDs) have showed up as a new generation for bioimaging. In this work, luminescent GQDs were prepared by an ameliorative photo-Fenton reaction and a subsequent hydrothermal process using graphene oxide sheets as the precursor. The as-prepared GQDs were nanomaterials with size ranging from 2.3 to 6.4 nm and emitted intense green luminescence in water. The fluorescence quantum yield was as high as 24.6% (excited at 340 nm) and the fluorescence was strongest at pH 7. Moreover, the influences of low-concentration (12.5, 25 μg/mL) GQDs on the morphology, viability, membrane integrity, internal cellular reactive oxygen species level and mortality of HeLa cells were relatively weak, and the in vitro imaging demonstrated GQDs were mainly in the cytoplasm region. More strikingly, zebrafish embryos were co-cultured with GQDs for in vivo imaging, and the results of heart rate test showed the intake of small amounts of GQDs brought little harm to the cardiovascular of zebrafish. GQDs with high quantum yield and strong photoluminescence show good biocompatibility, thus they show good promising for cell imaging, biolabeling and other biomedical applications. PMID:26709828

  5. Quantum Yield Enhancement of Cd/Se Colloidal Quantum Dots by Variation of Surface Ligands

    DTIC Science & Technology

    2013-01-01

    a solvent and a ligand, and oleic acid , which also serves as a ligand. The second used more complex ligands, octadecylphosphonic acid , and oleyamine...outgassed for another 30 min. To prepare the Cd precursor 26 mg of cadmium oxide (CdO) powder was mixed with 1.2 ml of oleic acid (OA) and 9.0 ml ODE...Acronyms Ar argon Cd cadmium CdO cadmium oxide OA oleic acid ODE octadecene QD quantum dots QY quantum yield Rh6G rhodamine 6G Se selenium NO. OF

  6. Film quantum yields of EUV& ultra-high PAG photoresists

    SciTech Connect

    Hassanein, Elsayed; Higgins, Craig; Naulleau, Patrick; Matyi, Richard; Gallatin, Greg; Denbeaux, Gregory; Antohe, Alin; Thackery, Jim; Spear, Kathleen; Szmanda, Charles; Anderson, Christopher N.; Niakoula, Dimitra; Malloy, Matthew; Khurshid, Anwar; Montgomery, Cecilia; Piscani, Emil C.; Rudack, Andrew; Byers, Jeff; Ma, Andy; Dean, Kim; Brainard, Robert

    2008-01-10

    Base titration methods are used to determine C-parameters for three industrial EUV photoresist platforms (EUV-2D, MET-2D, XP5496) and twenty academic EUV photoresist platforms. X-ray reflectometry is used to measure the density of these resists, and leads to the determination of absorbance and film quantum yields (FQY). Ultrahigh levels ofPAG show divergent mechanisms for production of photo acids beyond PAG concentrations of 0.35 moles/liter. The FQY of sulfonium PAGs level off, whereas resists prepared with iodonium PAG show FQY s that increase beyond PAG concentrations of 0.35 moles/liter, reaching record highs of 8-13 acids generatedlEUV photons absorbed.

  7. Sensitivity of quantum yield for O(/sup 1/D) production from ozone photolysis

    SciTech Connect

    Wuebbles, D.J.; Tarp, R.L.

    1980-06-01

    Recent laboratory studies have indicated that the quantum yield for O(/sup 1/D) production from photolysis of ozone may be less than unity at wavelengths shorter than 300 nm (below the fall off region). Previously it had been assumed that the quantum yield was unity at these wavelengths. Based on the recent work of Brock and Watson (who measured the quantum yield at 266 nm), the effect of assuming a quantum yield of 0.9 for O(/sup 1/D) production at wavelengths less than 300 nm in the LLL 1-d model was tested. Since measurements of the quantum yield fall off at longer wavelength also assume unity quantum yield below the fall off region, we also multiplied the O(/sup 1/D) quantum yield through this region by 0.9. The remaining quantum yield from the photolysis reaction is assumed to produce O(/sup 3/P) at all wavelengths so that the total quantum yield is unity.

  8. Near-unity photoluminescence quantum yield in MoS₂.

    PubMed

    Amani, Matin; Lien, Der-Hsien; Kiriya, Daisuke; Xiao, Jun; Azcatl, Angelica; Noh, Jiyoung; Madhvapathy, Surabhi R; Addou, Rafik; KC, Santosh; Dubey, Madan; Cho, Kyeongjae; Wallace, Robert M; Lee, Si-Chen; He, Jr-Hau; Ager, Joel W; Zhang, Xiang; Yablonovitch, Eli; Javey, Ali

    2015-11-27

    Two-dimensional (2D) transition metal dichalcogenides have emerged as a promising material system for optoelectronic applications, but their primary figure of merit, the room-temperature photoluminescence quantum yield (QY), is extremely low. The prototypical 2D material molybdenum disulfide (MoS2) is reported to have a maximum QY of 0.6%, which indicates a considerable defect density. Here we report on an air-stable, solution-based chemical treatment by an organic superacid, which uniformly enhances the photoluminescence and minority carrier lifetime of MoS2 monolayers by more than two orders of magnitude. The treatment eliminates defect-mediated nonradiative recombination, thus resulting in a final QY of more than 95%, with a longest-observed lifetime of 10.8 ± 0.6 nanoseconds. Our ability to obtain optoelectronic monolayers with near-perfect properties opens the door for the development of highly efficient light-emitting diodes, lasers, and solar cells based on 2D materials.

  9. Near-unity quantum yields from chloride treated CdTe colloidal quantum dots.

    PubMed

    Page, Robert C; Espinobarro-Velazquez, Daniel; Leontiadou, Marina A; Smith, Charles; Lewis, Edward A; Haigh, Sarah J; Li, Chen; Radtke, Hanna; Pengpad, Atip; Bondino, Federica; Magnano, Elena; Pis, Igor; Flavell, Wendy R; O'Brien, Paul; Binks, David J

    2015-04-01

    Colloidal quantum dots (CQDs) are promising materials for novel light sources and solar energy conversion. However, trap states associated with the CQD surface can produce non-radiative charge recombination that significantly reduces device performance. Here a facile post-synthetic treatment of CdTe CQDs is demonstrated that uses chloride ions to achieve near-complete suppression of surface trapping, resulting in an increase of photoluminescence (PL) quantum yield (QY) from ca. 5% to up to 97.2 ± 2.5%. The effect of the treatment is characterised by absorption and PL spectroscopy, PL decay, scanning transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. This process also dramatically improves the air-stability of the CQDs: before treatment the PL is largely quenched after 1 hour of air-exposure, whilst the treated samples showed a PL QY of nearly 50% after more than 12 hours.

  10. Near-Unity Quantum Yields from Chloride Treated CdTe Colloidal Quantum Dots

    PubMed Central

    Page, Robert C; Espinobarro-Velazquez, Daniel; Leontiadou, Marina A; Smith, Charles; Lewis, Edward A; Haigh, Sarah J; Li, Chen; Radtke, Hanna; Pengpad, Atip; Bondino, Federica; Magnano, Elena; Pis, Igor; Flavell, Wendy R; O'Brien, Paul; Binks, David J

    2015-01-01

    Colloidal quantum dots (CQDs) are promising materials for novel light sources and solar energy conversion. However, trap states associated with the CQD surface can produce non-radiative charge recombination that significantly reduces device performance. Here a facile post-synthetic treatment of CdTe CQDs is demonstrated that uses chloride ions to achieve near-complete suppression of surface trapping, resulting in an increase of photoluminescence (PL) quantum yield (QY) from ca. 5% to up to 97.2 ± 2.5%. The effect of the treatment is characterised by absorption and PL spectroscopy, PL decay, scanning transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. This process also dramatically improves the air-stability of the CQDs: before treatment the PL is largely quenched after 1 hour of air-exposure, whilst the treated samples showed a PL QY of nearly 50% after more than 12 hours. PMID:25348200

  11. New RuII Complex for Dual Activity: Photoinduced Ligand Release and 1O2 Production

    PubMed Central

    Loftus, Lauren M.; White, Jessica K.; Albani, Bryan A.; Kohler, Lars; Kodanko, Jeremy J.; Thummel, Randolph P.

    2016-01-01

    The new complex [Ru(pydppn)(biq)(py)]2+ (1) undergoes both py photodissociation in CH3CN with Φ500=0.0070(4) and 1O2 production with ΦΔ=0.75(7) in CH3OH from a long-lived 3ππ* state centered on the pydppn ligand (pydppn=3-(pyrid-2-yl)benzo[i]dipyrido[3,2-a:2′,3′-c]phenazine; biq = 2,2′-biquinoline; py= pyridine). This represents an order of magnitude decrease in the Φ500 compared to the previously reported model compound [Ru(tpy)(biq)(py)]2+ (3) (tpy=2,2′:6′,2″-terpyridine) that undergoes only ligand exchange. The effect on the quantum yields by the addition of a second deactivation pathway through the low-lying 3ππ* state necessary for dual reactivity was investigated using ultrafast and nanosecond transient absorption spectroscopy, revealing a significantly shorter 3MLCT lifetime in 1 relative to that of the model complex 3. Due to the structural similarities between the two compounds, the lower values of Φ500 and ΦΔ compared to that of [Ru(pydppn)(bpy)(py)]2+ (2) (bpy=2,2′-bipyridine) are attributed to a competitive excited state population between the 3LF states involved in ligand dissociation and the long-lived 3ππ* state in 1. Complex 1 represents a model compound for dual activity that may be applied to photochemotherapy. PMID:26715085

  12. Local Density Fluctuations Predict Photoisomerization Quantum Yield of Azobenzene-Modified DNA.

    PubMed

    Kingsland, Addie; Samai, Soumyadyuti; Yan, Yunqi; Ginger, David S; Maibaum, Lutz

    2016-08-04

    Azobenzene incorporated into DNA has a photoisomerization quantum yield that depends on the DNA sequence near the azobenzene attachment site. We use Molecular Dynamics computer simulations to elucidate which physical properties of the modified DNA determine the quantum yield. We show for a wide range of DNA sequences that the photoisomerization quantum yield is strongly correlated with the variance of the number of atoms in close proximity to the outer phenyl ring of the azobenzene group. We infer that quantum yield is controlled by the availability of fluctuations that enable the conformational change. We demonstrate that these simulations can be used as a qualitative predictive tool by calculating the quantum yield for several novel DNA sequences, and confirming these predictions using UV-vis spectroscopy. Our results will be useful for the development of a wide range of applications of photoresponsive DNA nanotechnology.

  13. Absolute 1* quantum yields for the ICN A state by diode laser gain versus absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Hess, Wayne P.; Leone, Stephen R.

    1987-01-01

    Absolute I* quantum yields were measured as a function of wavelength for room temperature photodissociation of the ICN A state continuum. The temperature yields are obtained by the technique of time-resolved diode laser gain-versus-absorption spectroscopy. Quantum yields are evaluated at seven wavelengths from 248 to 284 nm. The yield at 266 nm is 66.0 +/- 2% and it falls off to 53.4 +/- 2% and 44.0 +/- 4% at 284 and 248 respectively. The latter values are significantly higher than those obtained by previous workers using infrared fluorescence. Estimates of I* quantum yields obtained from analysis of CN photofragment rotational distributions, as discussed by other workers, are in good agreement with the I* yields. The results are considered in conjunction with recent theoretical and experimental work on the CN rotational distributions and with previous I* yield results.

  14. Creating high yield water soluble luminescent graphene quantum dots via exfoliating and disintegrating carbon nanotubes and graphite flakes.

    PubMed

    Lin, Liangxu; Zhang, Shaowei

    2012-10-21

    We have developed an effective method to exfoliate and disintegrate multi-walled carbon nanotubes and graphite flakes. With this technique, high yield production of luminescent graphene quantum dots with high quantum yield and low oxidization can be achieved.

  15. Fluorescence quantum yield measurement in nanoparticle-fluorophore systems by thermal lens spectroscopy

    NASA Astrophysics Data System (ADS)

    Ferreira, M.; Piscitelli, V.

    2016-04-01

    Metallic nanoparticles have been used as a way to tailor the fluorescence properties like quantum yield, but regular fluorescence quantum yield measurements have to counter the reflection and dispersion of a sample for an accurate result. Thermal lens spectroscopy is a good alternative to resolve this problem because doesn't measure the fluorescence intensity but the heat generated by absorption. We studied the changes induced by silver nanoparticles, generated by laser ablation, in the fluorescence peak and quantum yield of Rhodamine B. We fund that the silver nanoparticles lowered the fluorescence peak and quenched the fluorescence of the Rhodamine B and how much is quenched also depends on its concentration.

  16. Colloidal Spherical Quantum Wells with Near-Unity Photoluminescence Quantum Yield and Suppressed Blinking.

    PubMed

    Jeong, Byeong Guk; Park, Young-Shin; Chang, Jun Hyuk; Cho, Ikjun; Kim, Jai Kyeong; Kim, Heesuk; Char, Kookheon; Cho, Jinhan; Klimov, Victor I; Park, Philip; Lee, Doh C; Bae, Wan Ki

    2016-10-02

    Thick inorganic shell endows colloidal nanocrystals (NCs) with enhanced photochemical stability and suppression of photoluminescence intermittency (also known as blinking). However, the progress of using thick-shell heterostructure NCs in applications has been limited, due to low photoluminescence quantum yield (PL QY  60%) at room temperature. Here, we demonstrate thick-shell NCs with CdS/CdSe/CdS seed/spherical quantum well/shell (SQW) geometry that exhibit near-unity PL QY at room temperature and suppression of blinking. In SQW NCs, the lattice mismatch is diminished between the emissive CdSe layer and the surrounding CdS layers as a result of coherent strain, which suppresses the formation of misfit defects and consequently permits ~ 100% PL QY for SQW NCs with thick CdS shell (≥ 5 nm). High PL QY of thick-shell SQW NCs are preserved even in concentrated dispersion and in film under thermal stress, which makes them promising candidates for applications in solid-state lightings and luminescent solar concentrators.

  17. Gradient CdSe/CdS Quantum Dots with Room Temperature Biexciton Unity Quantum Yield.

    PubMed

    Nasilowski, Michel; Spinicelli, Piernicola; Patriarche, Gilles; Dubertret, Benoît

    2015-06-10

    Auger recombination is a major limitation for the fluorescent emission of quantum dots (QDs). It is the main source of QDs fluorescence blinking at the single-particle level. At high-power excitation, when several charge carriers are formed inside a QD, Auger becomes more efficient and severely decreases the quantum yield (QY) of multiexcitons. This limits the efficiency and the use of colloidal QDs in applications where intense light output is required. Here, we present a new generation of thick-shell CdSe/CdS QDs with dimensions >40 nm and a composition gradient between the core and the shell that exhibits 100% QY for the emission of both the monoexciton and the biexciton in air and at room temperature for all the QDs we have observed. The fluorescence emission of these QDs is perfectly Poissonian at the single-particle level at different excitation levels and temperatures, from 30 to 300 K. In these QDs, the emission of high-order (>2) multiexcitons is quite efficient, and we observe white light emission at the single-QD level when high excitation power is used. These gradient thick shell QDs confirm the suppression of Auger recombination in gradient core/shell structures and help further establish the colloidal QDs with a gradient shell as a very stable source of light even under high excitation.

  18. DETERMINATION OF APPARENT QUANTUM YIELD SPECTRA FOR THE FORMATION OF BIOLOGICALLY LABILE PHOTOPRODUCTS

    EPA Science Inventory

    Quantum yield spectra for the photochemical formation of biologically labile photoproducts from dissolved organic matter (DOM) have not been available previously, although they would greatly facilitate attempts to model photoproduct formation rates across latitudinal, seasonal, a...

  19. Ensemble brightening and enhanced quantum yield in size-purified silicon nanocrystals

    DOE PAGES

    Miller, Joseph B.; Van Sickle, Austin R.; Anthony, Rebecca J.; ...

    2012-07-18

    Here, we report on the quantum yield, photoluminescence (PL) lifetime and ensemble photoluminescent stability of highly monodisperse plasma-synthesized silicon nanocrystals (SiNCs) prepared though density-gradient ultracentrifugation in mixed organic solvents. Improved size uniformity leads to a reduction in PL line width and the emergence of entropic order in dry nanocrystal films. We find excellent agreement with the anticipated trends of quantum confinement in nanocrystalline silicon, with a solution quantum yield that is independent of nanocrystal size for the larger fractions but decreases dramatically with size for the smaller fractions. We also find a significant PL enhancement in films assembled from themore » fractions, and we use a combination of measurement, simulation and modeling to link this ‘brightening’ to a temporally enhanced quantum yield arising from SiNC interactions in ordered ensembles of monodisperse nanocrystals. Using an appropriate excitation scheme, we exploit this enhancement to achieve photostable emission.« less

  20. Ensemble brightening and enhanced quantum yield in size-purified silicon nanocrystals

    SciTech Connect

    Miller, Joseph B.; Van Sickle, Austin R.; Anthony, Rebecca J.; Kroll, Daniel M.; Kortshagen, Uwe R.; Hobbie, Erik K.

    2012-07-18

    Here, we report on the quantum yield, photoluminescence (PL) lifetime and ensemble photoluminescent stability of highly monodisperse plasma-synthesized silicon nanocrystals (SiNCs) prepared though density-gradient ultracentrifugation in mixed organic solvents. Improved size uniformity leads to a reduction in PL line width and the emergence of entropic order in dry nanocrystal films. We find excellent agreement with the anticipated trends of quantum confinement in nanocrystalline silicon, with a solution quantum yield that is independent of nanocrystal size for the larger fractions but decreases dramatically with size for the smaller fractions. We also find a significant PL enhancement in films assembled from the fractions, and we use a combination of measurement, simulation and modeling to link this ‘brightening’ to a temporally enhanced quantum yield arising from SiNC interactions in ordered ensembles of monodisperse nanocrystals. Using an appropriate excitation scheme, we exploit this enhancement to achieve photostable emission.

  1. Wavelength dependence of the fluorescence and singlet oxygen quantum yields of new photosensitizers

    NASA Astrophysics Data System (ADS)

    Lavi, Adina; Johnson, Fred M.; Ehrenberg, Benjamin

    1994-12-01

    The photophysical properties of Mg and Zn tetrabenzoporphyrins and Cd-texaphyrin are presented. These sensitizers have strong absorption bands in the red and near-IR regions that make them good candidates for biological photosensitization. Singlet oxygen quantum yields which were determined in an absolute manner, in several solvents, are reported. We show an unusual behavior regarding adherence to Kasha's and Vavilov's rules: upon excitation to different electronic states, different values of singlet oxygen quantum yields were obtained. We also show an unusual wavelength dependence of singlet oxygen and fluorescence yields upon excitation to different vibrational levels within the same electronic state.

  2. Superhydrophobic Photosensitizers. Mechanistic Studies of 1O2 Generation in the Plastron and Solid/Liquid Droplet Interface

    PubMed Central

    Aebisher, David; Bartusik, Dorota; Liu, Yang; Zhao, Yuanyuan; Barahman, Mark; Xu, QianFeng; Lyons, Alan M.; Greer, Alexander

    2014-01-01

    We describe here a physical-organic study of the first triphasic superhydrophobic sensitizer for photooxidations in water droplets. Control of synthetic parameters enables the mechanistic study of “borderline” two- and three-phase superhydrophobic sensitizer surfaces where 1O2 is generated in compartments that are wetted, partially wetted, or remain dry in the plastron (i.e., air layer beneath the droplet). The superhydrophobic surface is synthesized by partially embedding silicon phthalocyanine (Pc) sensitizing particles to specific locations on polydimethylsiloxane (PDMS) posts printed in a square array (1 mm tall posts on 0.5 mm pitch). In the presence of red light and oxygen, singlet oxygen is formed on the superhydrophobic surface and reacts with 9,10-anthracene dipropionate dianion (1) within a freestanding water droplet to produce an endoperoxide in 54–72% yields. Control of the 1O2 chemistry was achieved by the synthesis of superhydrophobic surfaces enriched with Pc particles either at the PDMS end-tips or at PDMS post bases. Much of the 1O2 that reacts with anthracene 1 in the droplets was generated by the sensitizer “wetted” at the Pc particle/water droplet interface and gave the highest endoperoxide yields. About 20% of the 1O2 can be introduced into the droplet from the plastron. The results indicate that the superhydrophobic sensitizer surface offers a unique system to study 1O2 transfer routes where a balance of gas and liquid contributions of 1O2 is tunable within the same superhydrophobic surface. PMID:24295210

  3. Variation in Quantum Yield for CO2 Uptake among C3 and C4 Plants 1

    PubMed Central

    Ehleringer, James; Pearcy, Robert W.

    1983-01-01

    The quantum yield for CO2 uptake was measured on a number of C3 and C4 monocot and dicot species. Under normal atmospheric conditions (330 microliters per liter CO2, 21% O2) and a leaf temperature of 30°C, the average quantum yields (moles CO2 per einstein) were as follows: 0.052 for C3 dicots, 0.053 for C3 grasses, 0.053 for NAD-malic enzyme type C4 dicots, 0.060 for NAD-malic enzyme type C4 grasses, 0.064 for phosphoenolpyruvate carboxykinase type C4 grasses, 0.061 for NADP-malic enzyme C4 dicots, and 0.065 for NADP-malic enzyme type C4 grasses. The quantum yield under normal atmospheric conditions was temperature dependent in C3 species, but apparently not in C4 species. Light and temperature conditions during growth appeared not to influence quantum yield. The significance of variation in the quantum yields of C4 plants was discussed in terms of CO2 leakage from the bundle sheath cells and suberization of apoplastic regions of the bundle sheath cells. PMID:16663257

  4. Fluorescence quantum yield of Yb3+-doped tellurite glasses determined by thermal lens spectroscopy

    NASA Astrophysics Data System (ADS)

    Lima, S. M.; Souza, A. K. R.; Langaro, A. P.; Silva, J. R.; Costa, F. B.; Moraes, J. C. S.; Figueiredo, M. S.; Santos, F. A.; Baesso, M. L.; Nunes, L. A. O.; Andrade, L. H. C.

    2017-01-01

    In this work, the combination of three different thermal lens spectroscopic methodologies was used to better determine the fluorescence quantum yield and to observe the concentration quenching in Yb3+-doped binary tellurite glasses (in mol%, 80TeO2 - 20Li2O and 80TeO2 - 20WO3). The samples were synthesized by the conventional melt-quenching method and then studied using optical spectroscopy and thermal lens spectroscopy (TLS). These characterizations enabled investigation of the radiative and nonradiative processes involved in the ytterbium doped systems. High fluorescence quantum yield was obtained for low Yb3+ doping (>90%), and in both glasses the Yb3+ presented concentration quenching mainly caused by impurities, host-ion interaction and OH- vibrations. The observations suggested that there is a possibility of doping the glasses with higher Yb concentration (>1.6 × 1021 ions/cm3) with low reduction of the quantum yield.

  5. Quantum Yield Measurements of Fluorophores in Lipid Bilayers Using a Plasmonic Nanocavity.

    PubMed

    Schneider, Falk; Ruhlandt, Daja; Gregor, Ingo; Enderlein, Jörg; Chizhik, Alexey I

    2017-03-20

    Precise knowledge of the quantum yield is important for many fluorescence-spectroscopic techniques, for example, for Förster resonance energy transfer. However, to measure it for emitters in a complex environment and at low concentrations is far from being trivial. Using a plasmonic nanocavity, we measure the absolute quantum yield value of lipid-conjugated dyes incorporated into a supported lipid bilayer. We show that for both hydrophobic and hydrophilic molecules the quantum yield of dyes inside the lipid bilayer strongly differs from its value in aqueous solution. This finding is of particular importance for all fluorescence-spectroscopic studies involving lipid bilayers, such as protein-protein or protein-lipid interactions in membranes or direct fluorescence-spectroscopic measurements of membrane physical properties.

  6. Optomechanical Control of Quantum Yield in Trans-Cis Ultrafast Photoisomerization of a Retinal Chromophore Model.

    PubMed

    Valentini, Alessio; Rivero, Daniel; Zapata, Felipe; García-Iriepa, Cristina; Marazzi, Marco; Palmeiro, Raúl; Fdez Galván, Ignacio; Sampedro, Diego; Olivucci, Massimo; Frutos, Luis Manuel

    2017-03-27

    The quantum yield of a photochemical reaction is one of the most fundamental quantities in photochemistry, as it measures the efficiency of the transduction of light energy into chemical energy. Nature has evolved photoreceptors in which the reactivity of a chromophore is enhanced by its molecular environment to achieve high quantum yields. The retinal chromophore sterically constrained inside rhodopsin proteins represents an outstanding example of such a control. In a more general framework, mechanical forces acting on a molecular system can strongly modify its reactivity. Herein, we show that the exertion of tensile forces on a simplified retinal chromophore model provokes a substantial and regular increase in the trans-to-cis photoisomerization quantum yield in a counterintuitive way, as these extension forces facilitate the formation of the more compressed cis photoisomer. A rationale for the mechanochemical effect on this photoisomerization mechanism is also proposed.

  7. A graphene quantum dot photodynamic therapy agent with high singlet oxygen generation

    NASA Astrophysics Data System (ADS)

    Ge, Jiechao; Lan, Minhuan; Zhou, Bingjiang; Liu, Weimin; Guo, Liang; Wang, Hui; Jia, Qingyan; Niu, Guangle; Huang, Xing; Zhou, Hangyue; Meng, Xiangmin; Wang, Pengfei; Lee, Chun-Sing; Zhang, Wenjun; Han, Xiaodong

    2014-08-01

    Clinical applications of current photodynamic therapy (PDT) agents are often limited by their low singlet oxygen (1O2) quantum yields, as well as by photobleaching and poor biocompatibility. Here we present a new PDT agent based on graphene quantum dots (GQDs) that can produce 1O2 via a multistate sensitization process, resulting in a quantum yield of ~1.3, the highest reported for PDT agents. The GQDs also exhibit a broad absorption band spanning the UV region and the entire visible region and a strong deep-red emission. Through in vitro and in vivo studies, we demonstrate that GQDs can be used as PDT agents, simultaneously allowing imaging and providing a highly efficient cancer therapy. The present work may lead to a new generation of carbon-based nanomaterial PDT agents with overall performance superior to conventional agents in terms of 1O2 quantum yield, water dispersibility, photo- and pH-stability, and biocompatibility.

  8. A graphene quantum dot photodynamic therapy agent with high singlet oxygen generation.

    PubMed

    Ge, Jiechao; Lan, Minhuan; Zhou, Bingjiang; Liu, Weimin; Guo, Liang; Wang, Hui; Jia, Qingyan; Niu, Guangle; Huang, Xing; Zhou, Hangyue; Meng, Xiangmin; Wang, Pengfei; Lee, Chun-Sing; Zhang, Wenjun; Han, Xiaodong

    2014-08-08

    Clinical applications of current photodynamic therapy (PDT) agents are often limited by their low singlet oxygen ((1)O2) quantum yields, as well as by photobleaching and poor biocompatibility. Here we present a new PDT agent based on graphene quantum dots (GQDs) that can produce (1)O2 via a multistate sensitization process, resulting in a quantum yield of ~1.3, the highest reported for PDT agents. The GQDs also exhibit a broad absorption band spanning the UV region and the entire visible region and a strong deep-red emission. Through in vitro and in vivo studies, we demonstrate that GQDs can be used as PDT agents, simultaneously allowing imaging and providing a highly efficient cancer therapy. The present work may lead to a new generation of carbon-based nanomaterial PDT agents with overall performance superior to conventional agents in terms of (1)O2 quantum yield, water dispersibility, photo- and pH-stability, and biocompatibility.

  9. Control of the external photoluminescent quantum yield of emitters coupled to nanoantenna phased arrays

    SciTech Connect

    Guo, Ke; Verschuuren, Marc A.; Lozano, Gabriel

    2015-08-21

    Optical losses in metals represent the largest limitation to the external quantum yield of emitters coupled to plasmonic antennas. These losses can be at the emission wavelength, but they can be more important at shorter wavelengths, i.e., at the excitation wavelength of the emitters, where the conductivity of metals is usually lower. We present accurate measurements of the absolute external photoluminescent quantum yield of a thin layer of emitting material deposited over a periodic nanoantenna phased array. Emission and absorptance measurements of the sample are performed using a custom-made setup including an integrating sphere and variable angle excitation. The measurements reveal a strong dependence of the external quantum yield on the angle at which the optical field excites the sample. Such behavior is attributed to the coupling between far-field illumination and near-field excitation mediated by the collective resonances supported by the array. Numerical simulations confirm that the inherent losses associated with the metal can be greatly reduced by selecting an optimum angle of illumination, which boosts the light conversion efficiency in the emitting layer. This combined experimental and numerical characterization of the emission from plasmonic arrays reveals the need to carefully design the illumination to achieve the maximum external quantum yield.

  10. THE QUANTUM YIELD OF OXYGEN PRODUCTION BY CHLOROPLASTS SUSPENDED IN SOLUTIONS CONTAINING FERRIC OXALATE

    PubMed Central

    French, C. S.; Rabideau, G. S.

    1945-01-01

    1. The quantum yield of oxygen liberation by spinach and Tradescantia chloroplasts suspended in solutions containing ferric oxalate and potassium ferricyanide varied from 0.013 to 0.080. 2. It was concluded that the nature of this oxygen liberation reaction is not fundamentally different from the formation of oxygen in normal photosynthesis, with respect to its light efficiency. PMID:19873423

  11. Control of the external photoluminescent quantum yield of emitters coupled to nanoantenna phased arrays

    NASA Astrophysics Data System (ADS)

    Guo, Ke; Lozano, Gabriel; Verschuuren, Marc A.; Gómez Rivas, Jaime

    2015-08-01

    Optical losses in metals represent the largest limitation to the external quantum yield of emitters coupled to plasmonic antennas. These losses can be at the emission wavelength, but they can be more important at shorter wavelengths, i.e., at the excitation wavelength of the emitters, where the conductivity of metals is usually lower. We present accurate measurements of the absolute external photoluminescent quantum yield of a thin layer of emitting material deposited over a periodic nanoantenna phased array. Emission and absorptance measurements of the sample are performed using a custom-made setup including an integrating sphere and variable angle excitation. The measurements reveal a strong dependence of the external quantum yield on the angle at which the optical field excites the sample. Such behavior is attributed to the coupling between far-field illumination and near-field excitation mediated by the collective resonances supported by the array. Numerical simulations confirm that the inherent losses associated with the metal can be greatly reduced by selecting an optimum angle of illumination, which boosts the light conversion efficiency in the emitting layer. This combined experimental and numerical characterization of the emission from plasmonic arrays reveals the need to carefully design the illumination to achieve the maximum external quantum yield.

  12. Optimum doping achieves high quantum yields in GaAs photoemitters

    NASA Technical Reports Server (NTRS)

    Sonnenberg, H.

    1971-01-01

    Experimental data indicate that optimum doping exists. Measured quantum yield curves indicate optimum overall response is obtained in GaAs emitters with doping in high 10 to the 18th power per cu cm range. Doping for optimum response is not necessarily in this range.

  13. Variations in fluorescence quantum yield of basic fuchsin with silver nanoparticles prepared by femtosecond laser ablation.

    PubMed

    Pathrose, Bini; Sahira, H; Nampoori, V P N; Radhakrishnan, P; Mujeeb, A

    2014-07-15

    Nano structured noble metals have very important applications in diverse fields such as photovoltaics, catalysis, electronic and magnetic devices, etc. In the present work, the application of dual beam thermal lens technique is employed for the determination of the absolute fluorescence quantum yield of the triaminotriphenylmethane dye, basic fuchsin in the presence of silver sol is studied. Silver sol is prepared by femtosecond laser ablation. It is observed that the presence of silver sol decreases the fluorescence quantum efficiency. The observed results are in line with the conclusion that the reduction in quantum yield in the quenching region is essentially due to the non-radiative relaxation of the absorbed energy. It is also observed that the presence of silver sol enhances the thermal lens signal which makes its detection easier at any concentration.

  14. Picosecond Lifetimes with High Quantum Yields from Single-Photon-Emitting Colloidal Nanostructures at Room Temperature.

    PubMed

    Bidault, Sébastien; Devilez, Alexis; Maillard, Vincent; Lermusiaux, Laurent; Guigner, Jean-Michel; Bonod, Nicolas; Wenger, Jérôme

    2016-04-26

    Minimizing the luminescence lifetime while maintaining a high emission quantum yield is paramount in optimizing the excitation cross-section, radiative decay rate, and brightness of quantum solid-state light sources, particularly at room temperature, where nonradiative processes can dominate. We demonstrate here that DNA-templated 60 and 80 nm diameter gold nanoparticle dimers, featuring one fluorescent molecule, provide single-photon emission with lifetimes that can fall below 10 ps and typical quantum yields in a 45-70% range. Since these colloidal nanostructures are obtained as a purified aqueous suspension, fluorescence spectroscopy can be performed on both fixed and freely diffusing nanostructures to quantitatively estimate the distributions of decay rate and fluorescence intensity enhancements. These data are in excellent agreement with theoretical calculations and demonstrate that millions of bright fluorescent nanostructures, with radiative lifetimes below 100 ps, can be produced in parallel.

  15. Quantum yield regeneration: influence of neutral ligand binding on photophysical properties in colloidal core/shell quantum dots.

    PubMed

    Shen, Yi; Tan, Rui; Gee, Megan Y; Greytak, Andrew B

    2015-03-24

    This article describes an experiment designed to identify the role of specific molecular ligands in maintaining the high photoluminescence (PL) quantum yield (QY) observed in as-synthesized CdSe/CdZnS and CdSe/CdS quantum dots (QDs). Although it has been possible for many years to prepare core/shell quantum dots with near-unity quantum yield through high-temperature colloidal synthesis, purification of such colloidal particles is frequently accompanied by a reduction in quantum yield. Here, a recently established gel permeation chromatography (GPC) technique is used to remove weakly associated ligands without a change in solvent: a decrease in ensemble QY and average PL lifetime is observed. Minor components of the initial mixture that were removed by GPC are then added separately to purified QD samples to determine whether reintroduction of these components can restore the photophysical properties of the initial sample. We show that among these putative ligands trioctylphosphine and cadmium oleate can regenerate the initial high QY of all samples, but only the "L-type" ligands (trioctyphosphine and oleylamine) can restore the QY without changing the shapes of the optical spectra. On the basis of the PL decay analysis, we confirm that quenching in GPC-purified samples and regeneration in ligand-introduced samples are associated chiefly with changes in the relative population fraction of QDs with different decay rates. The reversibility of the QY regeneration process has also been studied; the introduction and removal of trioctylphosphine and oleylamine tend to be reversible, while cadmium oleate is not. Finally, isothermal titration calorimetry has been used to study the relationship between the binding strength of the neutral ligands to the surface and photophysical property changes in QD samples to which they are added.

  16. Quantum yield for carbon monoxide production in the 248 nm photodissociation of carbonyl sulfide (OCS)

    NASA Technical Reports Server (NTRS)

    Zhao, Z.; Stickel, R. E.; Wine, P. H.

    1995-01-01

    Tunable diode laser absorption spectroscopy has been coupled with excimer laser flash photolysis to measure the quantum yield for CO production from 248 nm photodissociation of carbonyl sulfide (OCS) relative to the well-known quantum yield for CO production from 248 nm photolysis of phosgene (Cl2CO2). The temporal resolution of the experiments was sufficient to distinguish CO formed directly by photodissociation from that formed by subsequent S((sup 3)P(sub J)) reaction with OCS. Under the experimental conditions employed, CO formation via the fast S((sup 1)D(sub 2)) + OCS reaction was minimal. Measurements at 297K and total pressures from 4 to 100 Torr N2 + N2O show the CO yield to be greater than 0.95 and most likely unity. This result suggests that the contribution of OCS as a precursor to the lower stratospheric sulfate aerosol layer is somewhat larger than previously thought.

  17. Absolute I(asterisk) quantum yields for the ICN A state by diode laser gain-vs-absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Hess, Wayne P.; Leone, Stephen R.

    1987-01-01

    Absolute I(asterisk) quantum yields have been measured as a function of wavelength for room temperature photodissociation of the ICN A state continuum. The yields are obtained by the technique of time-resolved diode laser gain-vs-absorption spectroscopy. Quantum yields are evaluated at seven wavelengths from 248 to 284 nm. The yield at 266 nm is 66.0 + or - 2 percent and it falls off to 53.4 + or - 2 percent and 44.0 + or - 4 percent at 284 and 248 nm, respectively. The latter values are significantly higher than those obtained by previous workers using infrared fluorescence. Estimates of I(asterisk) quantum yields obtained from analysis of CN photofragment rotational distributions, as discussed by other workers, are in good agreement with the I(asterisk) yields reported here. The results are considered in conjunction with recent theoretical and experimental work on the CN rotational distributions and with previous I(asterisk) quantum yield results.

  18. Fluorescence Quantum Yield Measurements of Fluorescent Proteins: A Laboratory Experiment for a Biochemistry or Molecular Biophysics Laboratory Course

    ERIC Educational Resources Information Center

    Wall, Kathryn P.; Dillon, Rebecca; Knowles, Michelle K.

    2015-01-01

    Fluorescent proteins are commonly used in cell biology to assess where proteins are within a cell as a function of time and provide insight into intracellular protein function. However, the usefulness of a fluorescent protein depends directly on the quantum yield. The quantum yield relates the efficiency at which a fluorescent molecule converts…

  19. Photophysical investigation of (D-π-A) DMHP dye: Dipole moments, photochemical quantum yield and fluorescence quantum yield, by solvatochromic shift methods and DFT studies

    NASA Astrophysics Data System (ADS)

    Asiri, Abdullah M.; Sobahi, Tariq R.; Osman, Osman I.; Khan, Salman A.

    2017-01-01

    (2E)-3-(3,4-dimethoxyphenyl)-1-(2-hydroxyphenyl)prop-2-en-1-one (DMHP) was synthesized by the reaction of 3,4-dimethoxy benzaldehyde with 1-(2-hydroxyphenyl) ethanone under microwave irradiation. The structure of DMHP was established experimentally by EI-MS, FT-IR, 1H and 13C NMR spectral studies and elemental analysis and theoretically. Electronic absorption and emission spectra of DMHP were studied in different solvents on the basis of polarities, and the obtain data were used to determine the solvatochromic properties such as extinction coefficient, oscillator strength, transition dipole moment, stokes shift, fluorescence quantum yield and photochemical quantum yield. The absorption and emission maxima were red-shifted when the polarity of the solvent was increased from dioxan to DMSO; in excellent agreement the DFT findings. The DMHP experimental intramolecular charge transfer (ICT) was complemented by a natural bond orbital (NBO) analysis. Fluorescence intensities of DMHP were increase and decrease in presence of CTAB and SDS, so DMHP was used to find out the critical micelle concentration (CMC) of CTAB and SDS.

  20. Structural Basis for Near Unity Quantum Yield Core/Shell Nanostructures

    SciTech Connect

    McBride, James; Treadway, Joe; Pennycook, Stephen J; Rosenthal, Sandra

    2006-01-01

    Aberration-corrected Z-contrast scanning transmission electron microscopy of core/shell nanocrystals shows clear correlations between structure and quantum efficiency. Uniform shell coverage is obtained only for a graded CdS/ZnS shell material and is found to be critical to achieving near 100% quantum yield. The sublattice sensitivity of the images confirms that preferential growth takes place on the anion-terminated surfaces. This explains the three-dimensional "nanobullet" shape observed in the case of core/shell nanorods.

  1. Excitation of biomolecules with incoherent light: quantum yield for the photoisomerization of model retinal.

    PubMed

    Tscherbul, T V; Brumer, P

    2014-05-01

    Cis-trans isomerization in retinal, the first step in vision, is often computationally studied from a time-dependent viewpoint. Motivation for such studies lies in coherent pulsed laser experiments that explore the isomerization dynamics. However, such biological processes take place naturally in the presence of incoherent light, which is expected to excite a nonevolving mixture of stationary states. Here the isomerization problem is considered from the latter viewpoint and applied to a standard two-state, two-mode linear vibronic coupling model of retinal that explicitly includes a conical intersection between the ground and first excited electronic states. The calculated quantum yield at 500 nm agrees well with both the previous time-dependent calculations of Hahn and Stock (0.63) [ J. Phys. Chem. B 2000, 104, 1146-1149 ] and with experiment (0.65 ± 0.01), as does its wavelength dependence. Significantly, the effects of environmental relaxation on the quantum yield in this well-established model are found to be negligible. The results make clear the connection of the photoisomerization quantum yield to properties of stationary eigenstates, providing alternate insights into conditions for yield optimization.

  2. Photodissociation of quantum state-selected diatomic molecules yields new insight into ultracold chemistry

    NASA Astrophysics Data System (ADS)

    McDonald, Mickey; McGuyer, Bart H.; Lee, Chih-Hsi; Apfelbeck, Florian; Zelevinsky, Tanya

    2016-05-01

    When a molecule is subjected to a sufficiently energetic photon it can break apart into fragments through a process called ``photodissociation''. For over 70 years this simple chemical reaction has served as a vital experimental tool for acquiring information about molecular structure, since the character of the photodissociative transition can be inferred by measuring the 3D photofragment angular distribution (PAD). While theoretical understanding of this process has gradually evolved from classical considerations to a fully quantum approach, experiments to date have not yet revealed the full quantum nature of this process. In my talk I will describe recent experiments involving the photodissociation of ultracold, optical lattice-trapped, and fully quantum state-resolved 88Sr2 molecules. Optical absorption images of the PADs produced in these experiments reveal features which are inherently quantum mechanical in nature, such as matter-wave interference between output channels, and are sensitive to the quantum statistics of the molecular wavefunctions. The results of these experiments cannot be predicted using quasiclassical methods. Instead, we describe our results with a fully quantum mechanical model yielding new intuition about ultracold chemistry.

  3. Preparation of carbon quantum dots with a high quantum yield and the application in labeling bovine serum albumin

    NASA Astrophysics Data System (ADS)

    Liu, Pengpeng; Zhang, Changchang; Liu, Xiang; Cui, Ping

    2016-04-01

    An economic and green approach of manufacturing carbon quantum dots (CQDs) with a high quantum yield (denoted with HQY-CQDs) and the application in labeling bovine serum albumin (BSA) were described in detail in this work. Firstly, the cheap resources of citric acid and glycine were pyrolysed in drying oven for preparing the CQDs. Then the product was immersed in tetrahydrofuran for 8 h. HQY-CQDs were obtained by removing tetrahydrofuran from the supernate and were evaluated that they possessed a much higher quantum yield compared with that without dealing with tetrahydrofuran and a wonderful photo-bleaching resistance. Such HQY-CQDs could be functionalized by N-hydroxysuccinimide and successively combined with BSA covalently. Thus fluorescent labeling on BSA was realized. The HQY-CQDs were demonstrated with transmission electron microscopy and the chemical modification with N-hydroxysuccinimide was proved by infrared and X-ray photoelectron spectra. Labeling BSA with the HQY-CQDs was confirmed by gel electrophoresis and fluorescence imaging.

  4. Quantum yield and excitation rate of single molecules close to metallic nanostructures.

    PubMed

    Holzmeister, Phil; Pibiri, Enrico; Schmied, Jürgen J; Sen, Tapasi; Acuna, Guillermo P; Tinnefeld, Philip

    2014-11-05

    The interaction of dyes and metallic nanostructures strongly affects the fluorescence and can lead to significant fluorescence enhancement at plasmonic hot spots, but also to quenching. Here we present a method to distinguish the individual contributions to the changes of the excitation, radiative and non-radiative rate and use this information to determine the quantum yields for single molecules. The method is validated by precisely placing single fluorescent dyes with respect to gold nanoparticles as well as with respect to the excitation polarization using DNA origami nanostructures. Following validation, measurements in zeromode waveguides reveal that suppression of the radiative rate and enhancement of the non-radiative rate lead to a reduced quantum yield. Because the method exploits the intrinsic blinking of dyes, it can generally be applied to fluorescence measurements in arbitrary nanophotonic environments.

  5. Fluorescence lifetimes and quantum yields of rhodamine derivatives: new insights from theory and experiment.

    PubMed

    Savarese, Marika; Aliberti, Anna; De Santo, Ilaria; Battista, Edmondo; Causa, Filippo; Netti, Paolo A; Rega, Nadia

    2012-07-19

    Although lifetimes and quantum yields of widely used fluorophores are often largely characterized, a systematic approach providing a rationale of their photophysical behavior on a quantitative basis is still a challenging goal. Here we combine methods rooted in the time-dependent density functional theory and fluorescence lifetime imaging microscopy to accurately determine and analyze fluorescence signatures (lifetime, quantum yield, and band peaks) of several commonly used rhodamine and pyronin dyes. We show that the radiative lifetime of rhodamines can be correlated to the charge transfer from the phenyl toward the xanthene moiety occurring upon the S(0) ← S(1) de-excitation, and to the xanthene/phenyl relative orientation assumed in the S(1) minimum structure, which in turn is variable upon the amino and the phenyl substituents. These findings encourage the synergy of experiment and theory as unique tool to design finely tuned fluorescent probes, such those conceived for modern optical sensors.

  6. Determining the Photoisomerization Quantum Yield of Photoswitchable Molecules in Solution and in the Solid State

    PubMed Central

    Stranius, K.; Börjesson, K.

    2017-01-01

    Photoswitchable molecules are able to isomerize between two metastable forms through light stimuli. Originally being studied by photochemists, this type of molecule has now found a wide range of applications within physics, chemistry and biology. The extensive usage of photochromic molecules is due to the two isomers having fundamentally different physical and chemical properties. The most important attribute of a photoswitch is the photoisomerization quantum yield, which defines the efficiency of the photoisomerization event. Here we show how to determine the photoisomerization quantum yield in the solid state and in solution when taking thermal processes into account. The described method together with provided software allows for rapid and accurate determination of the isomerization process for this important class of molecules. PMID:28117426

  7. Determining the Photoisomerization Quantum Yield of Photoswitchable Molecules in Solution and in the Solid State

    NASA Astrophysics Data System (ADS)

    Stranius, K.; Börjesson, K.

    2017-01-01

    Photoswitchable molecules are able to isomerize between two metastable forms through light stimuli. Originally being studied by photochemists, this type of molecule has now found a wide range of applications within physics, chemistry and biology. The extensive usage of photochromic molecules is due to the two isomers having fundamentally different physical and chemical properties. The most important attribute of a photoswitch is the photoisomerization quantum yield, which defines the efficiency of the photoisomerization event. Here we show how to determine the photoisomerization quantum yield in the solid state and in solution when taking thermal processes into account. The described method together with provided software allows for rapid and accurate determination of the isomerization process for this important class of molecules.

  8. A quantum yield determination of O/1D/ production from ozone via laser flash photolysis

    NASA Technical Reports Server (NTRS)

    Philen, D. L.; Davis, D. D.; Watson, R. T.

    1977-01-01

    The quantum yield of electronically excited atomic oxygen produced from ozone photolysis was measured at 298 K from wavelengths of 293.0 to 316.5 nm. The reaction of the atomic oxygen with N2O to form excited NO2 was used to monitor the O production; a frequency-doubled flashlamp-pumped dye laser which provided tunable ultraviolet in the desired spectral region with 0.1-nm linewidth served as the photolysis source. The atomic oxygen quantum yield was found to be constant below 300 nm, with a sharp decrease centered at 308 nm and a diminution to less than one tenth of the constant value by 313.5 nm.

  9. Photo-dissociation quantum yields of mammalian oxyhemoglobin investigated by a nanosecond laser technique

    SciTech Connect

    Yang Ningli; Zhang Shuyi . E-mail: zhangsy@nju.edu.cn; Kuo Paokuang; Qu Min; Fang Jianwen; Li Jiahuang; Hua Zichun

    2007-02-23

    The photo-dissociations of oxyhemoglobin of several mammals, such as human, bovine, pig, horse, and rabbit, have been studied. By means of optical pump-probe technique, the quantum yields for photo-dissociation of these oxyhemoglobin have been determined at pH 7 and 20 {sup o}C. A nanosecond laser at 532 nm is used as the pumping source, and a xenon lamp through a monochrometer provides a probe light at 432 nm. The experimental results show that the quantum yields of these mammalian oxyhemoglobin are different from each other, especially for that of rabbit. By analyzing the amino acid sequences and tetramer structures as well as the flexibility and hydrophobicity of the different hemoglobin, possible explanations for the differences are proposed.

  10. Sample-Averaged Biexciton Quantum Yield Measured by Solution-Phase Photon Correlation

    PubMed Central

    Beyler, Andrew P.; Bischof, Thomas S.; Cui, Jian; Coropceanu, Igor; Harris, Daniel K.; Bawendi, Moungi G.

    2015-01-01

    The brightness of nanoscale optical materials such as semiconductor nanocrystals is currently limited in high excitation flux applications by inefficient multiexciton fluorescence. We have devised a solution-phase photon correlation measurement that can conveniently and reliably measure the average biexciton-to-exciton quantum yield ratio of an entire sample without user selection bias. This technique can be used to investigate the multiexciton recombination dynamics of a broad scope of synthetically underdeveloped materials, including those with low exciton quantum yields and poor fluorescence stability. Here, we have applied this method to measure weak biexciton fluorescence in samples of visible-emitting InP/ZnS and InAs/ZnS core/shell nanocrystals, and to demonstrate that a rapid CdS shell growth procedure can markedly increase the biexciton fluorescence of CdSe nanocrystals. PMID:25409496

  11. Analysis of wavelength-dependent photoisomerization quantum yields in bilirubins by fitting two exciton absorption bands

    NASA Astrophysics Data System (ADS)

    Mazzoni, M.; Agati, G.; Troup, G. J.; Pratesi, R.

    2003-09-01

    The absorption spectra of bilirubins were deconvoluted by two Gaussian curves of equal width representing the exciton bands of the non-degenerate molecular system. The two bands were used to study the wavelength dependence of the (4Z, 15Z) rightarrow (4Z, 15E) configurational photoisomerization quantum yield of the bichromophoric bilirubin-IXalpha (BR-IX), the intrinsically asymmetric bile pigment associated with jaundice and the symmetrically substituted bilirubins (bilirubin-IIIalpha and mesobilirubin-XIIIalpha), when they are irradiated in aqueous solution bound to human serum albumin (HSA). The same study was performed for BR-IX in ammoniacal methanol solution (NH4OH/MeOH). The quantum yields of the configurational photoprocesses were fitted with a combination function of the two Gaussian bands normalized to the total absorption, using the proportionality coefficients and a scaling factor as parameters. The decrease of the (4Z, 15Z) rightarrow (4Z, 15E) quantum yield with increasing wavelength, which occurs for wavelengths longer than the most probable Franck-Condon transition of the molecule, did not result in a unique function of the exciton absorptions. In particular we found two ranges corresponding to different exciton interactions with different proportionality coefficients and scaling factors. The wavelength-dependent photoisomerization of bilirubins was described as an abrupt change in quantum yield as soon as the resulting excitation was strongly localized in each chromophore. The change was correlated to a variation of the interaction between the two chromophores when the short-wavelength exciton absorption became vanishingly small. With the help of the circular dichroism (CD) spectrum of BR-IX in HSA, a small band was resolved in the bilirubin absorption spectrum, delivering part of the energy required for the (4Z, 15Z) rightarrow (4Z, 15E) photoisomerization of the molecule.

  12. Convenient determination of luminescence quantum yield using a combined electronic absorption and emission spectrometer

    SciTech Connect

    Prakash, John; Mishra, Ashok Kumar

    2016-01-15

    It is possible to measure luminescence quantum yield in a facile way, by designing an optical spectrometer capable of obtaining electronic absorption as well as luminescence spectra, with a setup that uses the same light source and detector for both the spectral measurements. Employment of a single light source and single detector enables use of the same correction factor profile for spectral corrections. A suitable instrumental scaling factor is used for adjusting spectral losses.

  13. Luminescent carbon quantum dots with high quantum yield as a single white converter for white light emitting diodes

    SciTech Connect

    Feng, X. T.; Zhang, Y.; Liu, X. G.; Zhang, F.; Wang, Y. L.; Yang, Y. Z.

    2015-11-23

    Carbon quantum dots (CQDs) with high quantum yield (51.4%) were synthesized by a one-step hydrothermal method using thiosalicylic acid and ethylenediamine as precursor. The CQDs have the average diameter of 2.3 nm and possess excitation-independent emission wavelength in the range from 320 to 440 nm excitation. Under an ultraviolet (UV) excitation, the CQDs aqueous solutions emit bright blue fluorescence directly and exhibit broad emission with a high spectral component ratio of 67.4% (blue to red intensity to total intensity). We applied the CQDs as a single white-light converter for white light emitting diodes (WLEDs) using a UV-LED chip as the excitation light source. The resulted WLED shows superior performance with corresponding color temperature of 5227 K and the color coordinates of (0.34, 0.38) belonging to the white gamut.

  14. Excitation-emission spectra and fluorescence quantum yields for fresh and aged biogenic secondary organic aerosols.

    PubMed

    Lee, Hyun Ji Julie; Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey A

    2013-06-04

    Certain biogenic secondary organic aerosols (SOA) become absorbent and fluorescent when exposed to reduced nitrogen compounds such as ammonia, amines, and their salts. Fluorescent SOA may potentially be mistaken for biological particles by detection methods relying on fluorescence. This work quantifies the spectral distribution and effective quantum yields of fluorescence of water-soluble SOA generated from two monoterpenes, limonene and α-pinene, and two different oxidants, ozone (O3) and hydroxyl radical (OH). The SOA was generated in a smog chamber, collected on substrates, and aged by exposure to ∼100 ppb ammonia in air saturated with water vapor. Absorption and excitation-emission matrix (EEM) spectra of aqueous extracts of aged and control SOA samples were measured, and the effective absorption coefficients and fluorescence quantum yields (∼0.005 for 349 nm excitation) were determined from the data. The strongest fluorescence for the limonene-derived SOA was observed for λexcitation = 420 ± 50 nm and λemission = 475 ± 38 nm. The window of the strongest fluorescence shifted to λexcitation = 320 ± 25 nm and λemission = 425 ± 38 nm for the α-pinene-derived SOA. Both regions overlap with the EEM spectra of some of the fluorophores found in primary biological aerosols. Despite the low quantum yield, the aged SOA particles may have sufficient fluorescence intensities to interfere with the fluorescence detection of common bioaerosols.

  15. Excitation-emission spectra and fluorescence quantum yields for fresh and aged biogenic secondary organic aerosols

    SciTech Connect

    Lee, Hyun Ji; Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey A.

    2013-05-10

    Certain biogenic secondary organic aerosols (SOA) become absorbent and fluorescent when exposed to reduced nitrogen compounds such as ammonia, amines and their salts. Fluorescent SOA may potentially be mistaken for biological particles by detection methods relying on fluorescence. This work quantifies the spectral distribution and effective quantum yields of fluorescence of SOA generated from two monoterpenes, limonene and a-pinene, and two different oxidants, ozone (O3) and hydroxyl radical (OH). The SOA was generated in a smog chamber, collected on substrates, and aged by exposure to ~100 ppb ammonia vapor in air saturated with water vapor. Absorption and excitation-emission matrix (EEM) spectra of aqueous extracts of aged and control SOA samples were measured, and the effective absorption coefficients and fluorescence quantum yields (~0.005 for 349 nm excitation) were determined from the data. The strongest fluorescence for the limonene-derived SOA was observed for excitation = 420+- 50 nm and emission = 475 +- 38 nm. The window of the strongest fluorescence shifted to excitation = 320 +- 25 nm and emission = 425 +- 38 nm for the a-pinene-derived SOA. Both regions overlap with the excitation-emission matrix (EEM) spectra of some of the fluorophores found in primary biological aerosols. Our study suggests that, despite the low quantum yield, the aged SOA particles should have sufficient fluorescence intensities to interfere with the fluorescence detection of common bioaerosols.

  16. Acetone photolysis at 248 nm revisited: pressure dependence of the CO and CO2 quantum yields.

    PubMed

    Somnitz, H; Ufer, T; Zellner, R

    2009-10-14

    Pressure dependent CO and CO2 quantum yields in the laser pulse photolysis of acetone at 248 nm and T = 298 K have been measured directly using quantitative infrared diode laser absorption. The experiments cover the pressure range from 50 to 900 mbar. It is found that the quantum yields show a significant dependence on total pressure, with Phi(CO) decreasing from around 0.5 at 20 mbar to approximately 0.3 at 900 mbar. The corresponding CO2 yields as observed when O2 exists in the reaction mixture, exhibit exactly the opposite behaviour. For the sum of both a value of 1.05(-0.05)(+0.02) independent of pressure is obtained, showing that the sum of (Phi(CO) + Phi(CO2)) is a measure for the primary quantum yield in the photolysis of acetone. In addition, CO quantum yields and corresponding pressure dependences were measured in experiments using different bath gases including He, Ar, Kr, SF6, and O2 as third body colliders. The theoretical framework in which we discuss these data is based on our previous findings that the pressure dependence of the CO yield is a consequence of a stepwise fragmentation mechanism during which acetone decomposes initially into methyl and a vibrationally 'hot' acetyl radical, with the latter being able to decompose promptly into methyl plus CO. The pressure dependence of the CO yield then originates from the second step and is modelled quantitatively via statistical dynamical calculations using a combination of RRKM theory with a time-dependent master equation (ME) approach. From a comparison of experiment with theory the amount of excess energy in the vibrationally hot acetyl radicals (E* approximately 65 kJ mol(-1)) as well as the characteristic collision parameters for interaction of acetyl with the different bath gases were derived. Values of 90, 280, 310, 545, 550 and 1800 cm(-1) for the average energy transferred per downward collision for the bath gases He, Ar, Kr, O2, N2, and SF6, respectively, are obtained. The calculations also

  17. Cu(2+) inhibits photosystem II activities but enhances photosystem I quantum yield of Microcystis aeruginosa.

    PubMed

    Deng, Chunnuan; Pan, Xiangliang; Wang, Shuzhi; Zhang, Daoyong

    2014-08-01

    Responses of photosystem I and II activities of Microcystis aeruginosa to various concentrations of Cu(2+) were simultaneously examined using a Dual-PAM-100 fluorometer. Cell growth and contents of chlorophyll a were significantly inhibited by Cu(2+). Photosystem II activity [Y(II)] and electron transport [rETRmax(II)] were significantly altered by Cu(2+). The quantum yield of photosystem II [Y(II)] decreased by 29 % at 100 μg L(-1) Cu(2+) compared to control. On the contrary, photosystem I was stable under Cu(2+) stress and showed an obvious increase of quantum yield [Y(I)] and electron transport [rETRmax(I)] due to activation of cyclic electron flow (CEF). Yield of cyclic electron flow [Y(CEF)] was enhanced by 17 % at 100 μg L(-1) Cu(2+) compared to control. The contribution of linear electron flow to photosystem I [Y(II)/Y(I)] decreased with increasing Cu(2+) concentration. Yield of cyclic electron flow [Y(CEF)] was negatively correlated with the maximal photosystem II photochemical efficiency (F v/F m). In summary, photosystem II was the major target sites of toxicity of Cu(2+), while photosystem I activity was enhanced under Cu(2+) stress.

  18. Spectroscopy of colloidal semiconductor core/shell nanoplatelets with high quantum yield.

    PubMed

    Tessier, M D; Mahler, B; Nadal, B; Heuclin, H; Pedetti, S; Dubertret, B

    2013-07-10

    Free standing two-dimensional materials appear as a novel class of structures. Recently, the first colloidal two-dimensional heterostructures have been synthesized. These core/shell nanoplatelets are the first step toward colloidal quantum wells. Here, we study in detail the spectroscopic properties of this novel generation of colloidal nanoparticles. We show that core/shell CdSe/CdZnS nanoplatelets with 80% quantum yield can be obtained. The emission time trace of single core/shell nanoplatelets exhibits reduced blinking compared to core nanoplatelets with a two level emission time trace. At cryogenic temperatures, these nanoplatelets have a quantum yield close to 100% and a stable emission time trace. A solution of core/shell nanoplatelets has emission spectra with a full width half-maximum close to 20 nm, a value much lower than corresponding spherical or rod-shaped heterostructures. Using single particle spectroscopy, we show that the broadening of the emission spectra upon the shell deposition is not due to dispersity between particles but is related to an intrinsic increased exciton-phonon coupling in the shell. We also demonstrate that optical spectroscopy is a relevant tool to investigate the presence of traps induced by shell deposition. The spectroscopic properties of the core/shell nanoplatelets presented here strongly suggest that this new generation of objects will be an interesting alternative to spherical or rod-shaped nanocrystals.

  19. Photoluminescence quantum yield of PbS nanocrystals in colloidal suspensions

    SciTech Connect

    Greben, M.; Fucikova, A.; Valenta, J.

    2015-04-14

    The absolute photoluminescence (PL) quantum yield (QY) of oleic acid-capped colloidal PbS quantum dots (QDs) in toluene is thoroughly investigated as function of QD size, concentration, excitation photon energy, and conditions of storage. We observed anomalous decrease of QY with decreasing concentration for highly diluted suspensions. The ligand desorption and QD-oxidation are demonstrated to be responsible for this phenomenon. Excess of oleic acid in suspensions makes the QY values concentration-independent over the entire reabsorption-free range. The PL emission is shown to be dominated by surface-related recombinations with some contribution from QD-core transitions. We demonstrate that QD colloidal suspension stability improves with increasing the concentration and size of PbS QDs.

  20. Quantum yield for carbon monoxide production in the 248 nm photodissociation of carbonyl sulfide (OCS)

    SciTech Connect

    Zhao, Z.; Stickel, R.E.; Wine, P.H.

    1995-03-01

    Tunable diode laser absorption spectroscopy has been coupled with excimer laser flash photolysis to measure the quantum yield for CO production from 248 nm photodissociation of carbonyl sulfide (OCS) relative to the well known quantum yield for CO production from 248 nm photolysis of phosgene (Cl{sub 2}CO). The temporal resolution of the experiments was sufficient to distinguish CO formed directly by photodissociation from that formed by subsequent S({sup 3}P{sub j}) reaction with OCS. Under the experimental conditions employed, CO formation via the fast S({sup 1}D{sub 2})+OCS reaction was minimal. Measurements at 297K and total pressures from 4 to 100 Torr N{sub 2}+N{sub 2}O show the CO yield to be greater than 0.95 and most likely unity. This result suggests that the contribution of OCS as a precursor to the lower stratospheric sulfate aerosol layer is somewhat larger than previously thought. 25 refs., 1 fig., 2 tabs.

  1. A general quantitative pH sensor developed with dicyandiamide N-doped high quantum yield graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Wu, Zhu Lian; Gao, Ming Xuan; Wang, Ting Ting; Wan, Xiao Yan; Zheng, Lin Ling; Huang, Cheng Zhi

    2014-03-01

    A general quantitative pH sensor for environmental and intracellular applications was developed by the facile hydrothermal preparation of dicyandiamide (DCD) N-doped high quantum yield (QY) graphene quantum dots (GQDs) using citric acid (CA) as the carbon source. The obtained N-doped GQDs have excellent photoluminesence (PL) properties with a relatively high QY of 36.5%, suggesting that N-doped chemistry could promote the QY of carbon nanomaterials. The possible mechanism for the formation of the GQDs involves the CA self-assembling into a nanosheet structure through intermolecular H-bonding at the initial stage of the reaction, and then the pure graphene core with many function groups formed through the dehydration between the carboxyl and hydroxyl of the intermolecules under hydrothermal conditions. These N-doped GQDs have low toxicity, and are photostable and pH-sensitive between 1.81 to 8.96, giving a general pH sensor with a wide range of applications from real water to intracellular contents.A general quantitative pH sensor for environmental and intracellular applications was developed by the facile hydrothermal preparation of dicyandiamide (DCD) N-doped high quantum yield (QY) graphene quantum dots (GQDs) using citric acid (CA) as the carbon source. The obtained N-doped GQDs have excellent photoluminesence (PL) properties with a relatively high QY of 36.5%, suggesting that N-doped chemistry could promote the QY of carbon nanomaterials. The possible mechanism for the formation of the GQDs involves the CA self-assembling into a nanosheet structure through intermolecular H-bonding at the initial stage of the reaction, and then the pure graphene core with many function groups formed through the dehydration between the carboxyl and hydroxyl of the intermolecules under hydrothermal conditions. These N-doped GQDs have low toxicity, and are photostable and pH-sensitive between 1.81 to 8.96, giving a general pH sensor with a wide range of applications from real water

  2. The relationship between photooxidation defects and quantum yield loss in a liquid crystalline oligofluorene

    NASA Astrophysics Data System (ADS)

    Wesely, E. Jane; Rothberg, Lewis; Geng, Yanhou; Chen, Shaw

    2004-03-01

    We have studied the photophysics of a liquid crystalline oligofluorene which emits blue light with a quantum efficiency of forty-nine percent.( Y. Geng, S. Culligan, A. Trajkovska, J. Wallace and S. Chen, Chem. Mater; 2003, 15, 542-549.) The fluorescent yield is reduced when the film has been exposed to ultra-violet light and air. The resulting photooxidation creates luminescent defects that have previously been observed in some polyfluorenes.( E. J. W. List, R. Guentner, P. Scanducci de Freitas, and U. Scherf, Adv Mater., 2002, 14, 374-378.) The defects decrease the overall fluorescent yield because they divert energy away from the blue-emitting chromophores and emit at longer wavelengths with low efficiency. In contrast with previous studies of photooxidized polyfluorenes, we observe two emission peaks associated with defects that have distinct intensity dependence and decay dynamics.

  3. A general quantitative pH sensor developed with dicyandiamide N-doped high quantum yield graphene quantum dots.

    PubMed

    Wu, Zhu Lian; Gao, Ming Xuan; Wang, Ting Ting; Wan, Xiao Yan; Zheng, Lin Ling; Huang, Cheng Zhi

    2014-04-07

    A general quantitative pH sensor for environmental and intracellular applications was developed by the facile hydrothermal preparation of dicyandiamide (DCD) N-doped high quantum yield (QY) graphene quantum dots (GQDs) using citric acid (CA) as the carbon source. The obtained N-doped GQDs have excellent photoluminesence (PL) properties with a relatively high QY of 36.5%, suggesting that N-doped chemistry could promote the QY of carbon nanomaterials. The possible mechanism for the formation of the GQDs involves the CA self-assembling into a nanosheet structure through intermolecular H-bonding at the initial stage of the reaction, and then the pure graphene core with many function groups formed through the dehydration between the carboxyl and hydroxyl of the intermolecules under hydrothermal conditions. These N-doped GQDs have low toxicity, and are photostable and pH-sensitive between 1.81 to 8.96, giving a general pH sensor with a wide range of applications from real water to intracellular contents.

  4. pH-responsive silica nanoparticles for controllable 1O2 generation

    NASA Astrophysics Data System (ADS)

    Li, Zhaobo; Wang, Jianguang; Chen, Jingrong; Lei, Wanhua; Wang, Xuesong; Zhang, Baowen

    2010-03-01

    pH-responsive 1O2 photosensitizing systems may serve as selective photodynamic therapy (PDT) agents by targeting the acidic interstitial fluid of many kinds of tumors. In this work, we present a pH-responsive nanoparticle-based platform for controllable 1O2 generation, in which a hydrophobic 1O2 photosensitizer (meso-tetraphenylporphyrin, TPP) and a pH indicator (Bromocresol Purple, BCP, or Bromothymol Blue, BTB) are simultaneously encapsulated in organically modified silica nanoparticles (OSNP). In basic conditions, the pH indicator absorbs light competitively and thus restricts sensitizer excitation. In acidic solution, the blue shifted absorption of the pH indicator allows the efficient excitation of the sensitizer. The pH indicator serves as an 'inner filter' to modulate effectively the excitation of the sensitizer and thus the 1O2 generation efficiency.

  5. Investigation of the CO2 Dependence of Quantum Yield and Respiration in Eucalyptus pauciflora

    PubMed Central

    Kirschbaum, Miko U. F.; Farquhar, Graham D.

    1987-01-01

    In leaves of C3 plants, the rate of nonphotorespiratory respiration appears to be higher in darkness than in the light. This change from a high to a low rate of carbon loss with increasing photon flux density leads to an increase in the apparent quantum yield of photosynthetic CO2 assimilation at low photon flux densities (Kok effect). The mechanism of this suppression of nonphotorespiratory respiration is not understood, but biochemical evidence and the observation that a Kok effect is often not observed under low O2, has led to the suggestion that photorespiration might be involved in some way. This hypothesis was tested with snowgum (Eucalyptus pauciflora Sieb. ex Spreng.) using gas exchange methods. The test was based on the assumption that if photorespiration were involved, then it would be expected that the intercellular partial pressure of CO2 would also have an influence on the Kok effect. Under normal atmospheric levels of CO2 and O2, a Kok effect was found. Changing the intercellular partial pressure of CO2, however, did not affect the estimate of nonphotorespiratory respiraton, and it was concluded that its decrease with increasing photon flux density did not involve photorespiration. Concurrent measurements showed that the quantum yield of net assimilation of CO2 increased with increasing intercellular partial pressure of CO2, and this increase agreed closely with predictions based on recent models of photosynthesis. PMID:16665319

  6. Functionalization of quinoxalines by using TMP bases: preparation of tetracyclic heterocycles with high photoluminescene quantum yields.

    PubMed

    Nafe, Julia; Herbert, Simon; Auras, Florian; Karaghiosoff, Konstantin; Bein, Thomas; Knochel, Paul

    2015-01-12

    Tetracyclic heterocycles that exhibit high photoluminescence quantum yields were synthesized by anellation reactions of mono-, di-, and trifunctionalized 2,3-dichloroquinoxalines. Thus, treatment of 2,3-dichloroquinoxaline with TMPLi (TMP = 2,2,6,6-tetramethylpiperidyl) allows a regioselective lithiation in position 5. Quenching with various electrophiles (iodine, (BrCl2 C)2 , allylic bromide, acid chloride, aryl iodide) leads to 5-functionalized 2,3-dichloroquinoxalines. Further functionalization in positions 6 and 8 can be achieved by using TMPLi or TMPMgCl⋅LiCl furnishing a range of new di- and tri-functionalized 2,3-dichloroquinoxalines. The chlorine atoms are readily substituted by anellation with 1,2-diphenols or 1,2-dithiophenols leading to a series of new tetracyclic compounds. These materials exhibit strong, tunable optical absorption and emission in the blue and green spectral region. The substituted O-heterocyclic compounds exhibit particularly high photoluminescence quantum yields of up to 90%, which renders them interesting candidates for fluorescence imaging applications.

  7. Structure-guided evolution of cyan fluorescent proteins towards a quantum yield of 93%

    PubMed Central

    Goedhart, Joachim; von Stetten, David; Noirclerc-Savoye, Marjolaine; Lelimousin, Mickaël; Joosen, Linda; Hink, Mark A.; van Weeren, Laura; Gadella, Theodorus W.J.; Royant, Antoine

    2012-01-01

    Cyan variants of green fluorescent protein are widely used as donors in Förster resonance energy transfer experiments. The popular, but modestly bright, Enhanced Cyan Fluorescent Protein (ECFP) was sequentially improved into the brighter variants Super Cyan Fluorescent Protein 3A (SCFP3A) and mTurquoise, the latter exhibiting a high-fluorescence quantum yield and a long mono-exponential fluorescence lifetime. Here we combine X-ray crystallography and excited-state calculations to rationalize these stepwise improvements. The enhancement originates from stabilization of the seventh β-strand and the strengthening of the sole chromophore-stabilizing hydrogen bond. The structural analysis highlighted one suboptimal internal residue, which was subjected to saturation mutagenesis combined with fluorescence lifetime-based screening. This resulted in mTurquoise2, a brighter variant with faster maturation, high photostability, longer mono-exponential lifetime and the highest quantum yield measured for a monomeric fluorescent protein. Together, these properties make mTurquoise2 the preferable cyan variant of green fluorescent protein for long-term imaging and as donor for Förster resonance energy transfer to a yellow fluorescent protein. PMID:22434194

  8. Mathematical optimization approach for estimating the quantum yield distribution of a photochromic reaction in a polymer

    NASA Astrophysics Data System (ADS)

    Tanaka, Mirai; Yamashita, Takashi; Sano, Natsuki; Ishigaki, Aya; Suzuki, Tomomichi

    2017-01-01

    The convolution of a series of events is often observed for a variety of phenomena such as the oscillation of a string. A photochemical reaction of a molecule is characterized by a time constant, but materials in the real world contain several molecules with different time constants. Therefore, the kinetics of photochemical reactions of the materials are usually observed with a complexity comparable with those of theoretical kinetic equations. Analysis of the components of the kinetics is quite important for the development of advanced materials. However, with a limited number of exceptions, deconvolution of the observed kinetics has not yet been mathematically solved. In this study, we propose a mathematical optimization approach for estimating the quantum yield distribution of a photochromic reaction in a polymer. In the proposed approach, time-series data of absorbances are acquired and an estimate of the quantum yield distribution is obtained. To estimate the distribution, we solve a mathematical optimization problem to minimize the difference between the input data and a model. This optimization problem involves a differential equation constrained on a functional space as the variable lies in the space of probability distribution functions and the constraints arise from reaction rate equations. This problem can be reformulated as a convex quadratic optimization problem and can be efficiently solved by discretization. Numerical results are also reported here, and they verify the effectiveness of our approach.

  9. Carbon dots with high fluorescence quantum yield: the fluorescence originates from organic fluorophores

    NASA Astrophysics Data System (ADS)

    Shi, Lei; Yang, Jian Hai; Zeng, Hai Bo; Chen, Yong Mei; Yang, Sheng Chun; Wu, Chao; Zeng, Hao; Yoshihito, Osada; Zhang, Qiqing

    2016-07-01

    In this contribution, we have shown that the organic fluorophores, 5-oxo-3,5-dihydro-2H-thiazolo [3,2-a] pyridine-3,7-dicarboxylic acid (TPDCA) and 5-oxo-3,5-dihydro-2H-thiazolo [3,2-a] pyridine-7-carboxylic acid (TPCA), are the main ingredients and fluorescence origins of N,S-CDs via systematic analyses. It inspires us to deeply analyze and understand the fluorescence origins of carbon dots with high fluorescence quantum yields, which will expand their applications.In this contribution, we have shown that the organic fluorophores, 5-oxo-3,5-dihydro-2H-thiazolo [3,2-a] pyridine-3,7-dicarboxylic acid (TPDCA) and 5-oxo-3,5-dihydro-2H-thiazolo [3,2-a] pyridine-7-carboxylic acid (TPCA), are the main ingredients and fluorescence origins of N,S-CDs via systematic analyses. It inspires us to deeply analyze and understand the fluorescence origins of carbon dots with high fluorescence quantum yields, which will expand their applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00451b

  10. Solvent effect on the relative quantum yield and fluorescence quenching of 2DAM

    NASA Astrophysics Data System (ADS)

    Nagaraja, D.; Melavanki, R. M.; Patil, N. R.; Kusanur, R. A.

    2014-09-01

    The relative quantum yield of diethyl 2-acetamido-2-((3-oxo-3H-benzo[f]chromen-1-yl)methyl) malonate [2DAM] is estimated using single point method with quinine sulfate as standard reference. The quantum yield varies between 0.1161 and 0.3181 depending on the nature of the solvent. The rates of radiative and non radiative decay constants are also calculated. The fluorescence quenching of [2DAM] by aniline is studied at room temperature, by steady state, in five different solvents namely acetonitrile (AN), 1,4 dioxane (DX), 1,2 dichloroethane (DCE), tetrahydrofuran (THF) and toluene (TOL), in order to explore various possible quenching mechanisms. The experimental results show a positive deviation in Stern Volmer plots for all solvents. Various parameters for the quenching process are determined by ground state complex, sphere of action static quenching model and finite sink approximation model. The magnitudes of these rate parameters indicate that positive deviation in the Stern Volmer (SV) plot is due to both static and dynamic processes. Further, finite sink approximation model is used to check whether these bimolecular reactions were diffusion limited or not. The values of distance parameter R‧ and diffusion co efficient D are determined and then compared with the values of encounter distance R and diffusion coefficient D calculated using Stokes-Einstein equation.

  11. Photoisomerization dynamics of a rhodopsin-based molecule (potential molecular switch) with high quantum yields

    NASA Astrophysics Data System (ADS)

    Allen, Roland; Jiang, Chen-Wei; Zhang, Xiu-Xing; Fang, Ai-Ping; Li, Hong-Rong; Xie, Rui-Hua; Li, Fu-Li

    2015-03-01

    It is worthwhile to explore the detailed reaction dynamics of various candidates for molecular switches, in order to understand, e.g., the differences in quantum yields and switching times. Here we report density-functional-based simulations for the rhodopsin-based molecule 4-[4-Methylbenzylidene]-5-p-tolyl-3,4-dihydro-2H-pyrrole (MDP), synthesized by Sampedro et al. We find that the photoisomerization quantum yields are remarkably high: 82% for cis-to-trans, and 68% for trans-to-cis. The lifetimes of the S1 excited state in cis-MDP in our calculations are in the range of 900-1800 fs, with a mean value of 1270 fs, while the range of times required for full cis-to-trans isomerization are 1100-2000 fs, with a mean value of 1530 fs. In trans-MDP, the calculated S1 excited state lifetimes are 860-2140 fs, with a mean value of 1330 fs, and with the full trans-to-cis isomerization completed about 200 fs later. In both cases, the dominant reaction mechanism is rotation around the central C =C bond (connected to the pyrroline ring), and de-excitation occurs at an avoided crossing between the ground state and the lowest singlet state, near the midpoint of the rotational pathway. Research Fund for the Doctoral Program of Higher Education of China; Fundamental Research Funds for the Central Universities; Robert A. Welch Foundation; National Natural Science Foundation of China.

  12. Photoisomerization dynamics of a rhodopsin-based molecule (potential molecular switch) with high quantum yields

    NASA Astrophysics Data System (ADS)

    Jiang, Chen-Wei; Zhang, Xiu-Xing; Fang, Ai-Ping; Li, Hong-Rong; Xie, Rui-Hua; Li, Fu-Li; Allen, Roland E.

    2015-02-01

    It is worthwhile to explore the detailed reaction dynamics of various candidates for molecular switches, in order to understand, e.g., the differences in quantum yields and switching times. Here we report density-functional-based simulations for the rhodopsin-based molecule 4-[4-methylbenzylidene]-5-p-tolyl-3,4-dihydro-2H-pyrrole (MDP), synthesized by Sampedro et al We find that the photoisomerization quantum yields are remarkably high: 82% for cis-to-trans, and 68% for trans-to-cis. The lifetimes of the S1 excited state in cis-MDP in our calculations are in the range of 900-1800 fs, with a mean value of 1270 fs, while the range of times required for full cis-to-trans isomerization are 1100-2000 fs, with a mean value of 1530 fs. In trans-MDP, the calculated S1 excited state lifetimes are 860-2140 fs, with a mean value of 1330 fs, and with the full trans-to-cis isomerization completed about 200 fs later. In both cases, the dominant reaction mechanism is rotation around the central C=C bond (connected to the pyrroline ring), and de-excitation occurs at an avoided crossing between the ground state and the lowest singlet state, near the midpoint of the rotational pathway. Perhaps remarkably, but apparently because of electrostatic repulsion, the direction of rotation is the same for both reactions.

  13. Quantum-yield-optimized fluorophores for site-specific labeling and super-resolution imaging.

    PubMed

    Grunwald, Christian; Schulze, Katrin; Giannone, Gregory; Cognet, Laurent; Lounis, Brahim; Choquet, Daniel; Tampé, Robert

    2011-06-01

    Single-molecule applications, saturated pattern excitation microscopy, and stimulated emission depletion (STED) microscopy demand bright as well as highly stable fluorescent dyes. Here we describe the synthesis of quantum-yield-optimized fluorophores for reversible, site-specific labeling of proteins or macromolecular complexes. We used polyproline-II (PPII) helices as sufficiently rigid spacers with various lengths to improve the fluorescence signals of a set of different trisNTA-fluorophores. The improved quantum yields were demonstrated by steady-state and fluorescence lifetime analyses. As a proof of principle, we characterized the trisNTA-PPII-fluorophores with respect to in vivo protein labeling and super-resolution imaging at synapses of living neurons. The distribution of His-tagged AMPA receptors (GluA1) in spatially restricted synaptic clefts was imaged by confocal and STED microscopy. The comparison of fluorescence intensity profiles revealed the superior resolution of STED microscopy. These results highlight the advantages of biocompatible and, in particular, small and photostable trisNTA-PPII-fluorophores in super-resolution microscopy.

  14. Accuracy of quantum sensors measuring yield photon flux and photosynthetic photon flux

    NASA Technical Reports Server (NTRS)

    Barnes, C.; Tibbitts, T.; Sager, J.; Deitzer, G.; Bubenheim, D.; Koerner, G.; Bugbee, B.; Knott, W. M. (Principal Investigator)

    1993-01-01

    Photosynthesis is fundamentally driven by photon flux rather than energy flux, but not all absorbed photons yield equal amounts of photosynthesis. Thus, two measures of photosynthetically active radiation have emerged: photosynthetic photon flux (PPF), which values all photons from 400 to 700 nm equally, and yield photon flux (YPF), which weights photons in the range from 360 to 760 nm according to plant photosynthetic response. We selected seven common radiation sources and measured YPF and PPF from each source with a spectroradiometer. We then compared these measurements with measurements from three quantum sensors designed to measure YPF, and from six quantum sensors designed to measure PPF. There were few differences among sensors within a group (usually <5%), but YPF values from sensors were consistently lower (3% to 20%) than YPF values calculated from spectroradiometric measurements. Quantum sensor measurements of PPF also were consistently lower than PPF values calculated from spectroradiometric measurements, but the differences were <7% for all sources, except red-light-emitting diodes. The sensors were most accurate for broad-band sources and least accurate for narrow-band sources. According to spectroradiometric measurements, YPF sensors were significantly less accurate (>9% difference) than PPF sensors under metal halide, high-pressure sodium, and low-pressure sodium lamps. Both sensor types were inaccurate (>18% error) under red-light-emitting diodes. Because both YPF and PPF sensors are imperfect integrators, and because spectroradiometers can measure photosynthetically active radiation much more accurately, researchers should consider developing calibration factors from spectroradiometric data for some specific radiation sources to improve the accuracy of integrating sensors.

  15. SU-E-T-191: First Principle Calculation of Quantum Yield in Photodynamic Therapy

    SciTech Connect

    Abolfath, R; Guo, F; Chen, Z; Nath, R

    2014-06-01

    Purpose: We present a first-principle method to calculate the spin transfer efficiency in oxygen induced by any photon fields especially in MeV energy range. The optical pumping is mediated through photosensitizers, e.g., porphyrin and/or ensemble of quantum dots. Methods: Under normal conditions, oxygen molecules are in the relatively non-reactive triplet state. In the presence of certain photosensitizer compounds such as porphyrins, electromagnetic radiation of specific wavelengths can excite oxygen to highly reactive singlet state. With selective uptake of photosensitizers by certain malignant cells, photon irradiation of phosensitized tumors can lead to selective killing of cancer cells. This is the basis of photodynamic therapy (PDT). Despite several attempts, PDT has not been clinically successful except in limited superficial cancers. Many parameters such as photon energy, conjugation with quantum dots etc. can be potentially combined with PDT in order to extend the role of PDT in cancer management. The key quantity for this optimization is the spin transfer efficiency in oxygen by any photon field. The first principle calculation model presented here, is an attempt to fill this need. We employ stochastic density matrix description of the quantum jumps and the rate equation methods in quantum optics based on Markov/Poisson processes and calculate time evolution of the population of the optically pumped singlet oxygen. Results: The results demonstrate the feasibility of our model in showing the dependence of the optical yield in generating spin-singlet oxygen on the experimental conditions. The adjustable variables can be tuned to maximize the population of the singlet oxygen hence the efficacy of the photodynamic therapy. Conclusion: The present model can be employed to fit and analyze the experimental data and possibly to assist researchers in optimizing the experimental conditions in photodynamic therapy.

  16. Effect of capsid proteins to ICG mass ratio on fluorescent quantum yield of virus-resembling optical nano-materials

    NASA Astrophysics Data System (ADS)

    Gupta, Sharad; Ico, Gerardo; Matsumura, Paul; Rao, A. L. N.; Vullev, Valentine; Anvari, Bahman

    2012-03-01

    We recently reported construction of a new type of optical nano-construct composed of genome-depleted plant infecting brome mosaic virus (BMV) doped with Indocyanine green (ICG), an FDA-approved chromophore. We refer to these constructs as optical viral ghosts (OVGs) since only the capsid protein (CP) subunits of BMV remain to encapsulate ICG. To utilize OVGs as effective nano-probes in fluorescence imaging applications, their fluorescence quantum yield needs to be maximized. In this study, we investigate the effect of altering the CP to ICG mass ratio on the fluorescent quantum yield of OVGs. Results of this study provide the basis for construction of OVGs with optimal amounts of CP and ICG to yield maximal fluorescence quantum yield.

  17. Fluorescence quantum yield measurements of fluorescent proteins: a laboratory experiment for a biochemistry or molecular biophysics laboratory course.

    PubMed

    Wall, Kathryn P; Dillon, Rebecca; Knowles, Michelle K

    2015-01-01

    Fluorescent proteins are commonly used in cell biology to assess where proteins are within a cell as a function of time and provide insight into intracellular protein function. However, the usefulness of a fluorescent protein depends directly on the quantum yield. The quantum yield relates the efficiency at which a fluorescent molecule converts absorbed photons into emitted photons and it is necessary to know for assessing what fluorescent protein is the most appropriate for a particular application. In this work, we have designed an upper-level, biochemistry laboratory experiment where students measure the fluorescence quantum yields of fluorescent proteins relative to a standard organic dye. Four fluorescent protein variants, enhanced cyan fluorescent protein (ECFP), enhanced green fluorescent protein (EGFP), mCitrine, and mCherry, were used, however the methods described are useful for the characterization of any fluorescent protein or could be expanded to fluorescent quantum yield measurements of organic dye molecules. The laboratory is designed as a guided inquiry project and takes two, 4 hr laboratory periods. During the first day students design the experiment by selecting the excitation wavelength, choosing the standard, and determining the concentration needed for the quantum yield experiment that takes place in the second laboratory period. Overall, this laboratory provides students with a guided inquiry learning experience and introduces concepts of fluorescence biophysics into a biochemistry laboratory curriculum.

  18. Film quantum yields of EUV and ultra-high PAG photoresists

    NASA Astrophysics Data System (ADS)

    Hassanein, Elsayed; Higgins, Craig; Naulleau, Patrick; Matyi, Richard; Gallatin, Gregg; Denbeaux, Gregory; Antohe, Alin; Thackeray, Jim; Spear, Kathleen; Szmanda, Charles; Anderson, Christopher N.; Niakoula, Dimitra; Malloy, Matthew; Khurshid, Anwar; Montgomery, Cecilia; Piscani, Emil C.; Rudack, Andrew; Byers, Jeff; Ma, Andy; Dean, Kim; Brainard, Robert

    2008-03-01

    Base titration methods are used to determine C-parameters for three industrial EUV photoresist platforms (EUV- 2D, MET-2D, XP5496) and twenty academic EUV photoresist platforms. X-ray reflectometry is used to measure the density of these resists, and leads to the determination of absorbance and film quantum yields (FQY). Ultrahigh levels of PAG show divergent mechanisms for production of photoacids beyond PAG concentrations of 0.35 moles/liter. The FQY of sulfonium PAGs level off, whereas resists prepared with iodonium PAG show FQYs that increase beyond PAG concentrations of 0.35 moles/liter, reaching record highs of 8-13 acids generated/EUV photons absorbed.

  19. Surface structures for enhancement of quantum yield in broad spectrum emission nanocrystals

    DOEpatents

    Schreuder, Michael A.; McBride, James R.; Rosenthal, Sandra J.

    2014-07-22

    Disclosed are inorganic nanoparticles comprising a body comprising cadmium and/or zinc crystallized with selenium, sulfur, and/or tellurium; a multiplicity of phosphonic acid ligands comprising at least about 20% of the total surface ligand coverage; wherein the nanocrystal is capable of absorbing energy from a first electromagnetic region and capable of emitting light in a second electromagnetic region, wherein the maximum absorbance wavelength of the first electromagnetic region is different from the maximum emission wavelength of the second electromagnetic region, thereby providing a Stokes shift of at least about 20 nm, wherein the second electromagnetic region comprises an at least about 100 nm wide band of wavelengths, and wherein the nanoparticle exhibits has a quantum yield of at least about 10%. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present invention.

  20. 183W NMR Study of Peroxotungstates Involved in the Disproportionation of Hydrogen Peroxide into Singlet Oxygen ((1)O(2), (1)Delta(g)) Catalyzed by Sodium Tungstate in Neutral and Alkaline Water.

    PubMed

    Nardello, V.; Marko, J.; Vermeersch, G.; Aubry, J. M.

    1998-10-19

    The disproportionation of aqueous hydrogen peroxide catalyzed by sodium tungstate has been investigated with regard to the multiplicity of the oxygen molecules released. Trapping experiments and detection of the IR luminescence of (1)O(2) have shown that the yield of (1)O(2) is virtually quantitative. The mono-, di-, and tetraperoxotungstate intermediates W(O(2))(n)()O(4)(-)(n)()(2)(-) (n = 1, 2, 4) have been characterized by UV and (183)W NMR spectroscopies. The diperoxo species is proposed as the precursor of (1)O(2).

  1. Yield Enhancement of a Double-Quantum Filter Sequence Designed for the Edited Detection of GABA

    NASA Astrophysics Data System (ADS)

    Wilman, Alan H.; Allen, Peter S.

    1995-11-01

    To overcome limitations in the signal to noise ratio (S/N) of previously proposed multiple-quantum filters (MQFs), designed for editing the GABA A2multiplet from the creatine (Cr) singlet in proton spectroscopy of brain, a new double-quantum filter is proposed which significantly enhancesS/N(thereby making it comparable with the spin-echo difference editing technique) while maintaining the superior Cr suppression and zero vulnerability to subtraction errors of previously proposed MQFs. TheS/Nenhancement results primarily from a significant reduction in transverse-relaxation losses, achieved by shortening the filter sequence by ∼70%, first by altering the criterion that determines the initial evolution period and, second, by effectively eliminating the refocusing time prior to the start of acquisition. The altered evolution time criterion also leads to an increase in the intrinsic yield of the filter from 25 to 39%. The analysis of the filter design was verifiedin vitroon phantoms of GABA in D2O, and the maintenance of editing capability, i.e., Cr suppression by more than 1600, was demonstrated on rat brain extracts.

  2. Quantum yield in blue-emitting anthracene derivatives: vibronic coupling density and transition dipole moment density.

    PubMed

    Uejima, Motoyuki; Sato, Tohru; Yokoyama, Daisuke; Tanaka, Kazuyoshi; Park, Jong-Wook

    2014-07-21

    A theoretical design principle for enhancement of the quantum yield of light-emitting molecules is desired. For the establishment of the principle, we focused on the S1 states of blue-emitting anthracene derivatives: 2-methyl-9,10-di(2'-naphthyl)anthracene (MADN), 4,9,10-bis(3',5'-diphenylphenyl)anthracene (MAM), 9-(3',5'-diphenylphenyl)-10-(3'',5''-diphenylbiphenyl-4''-yl) anthracene (MAT), and 9,10-bis(3''',5'''-diphenylbiphenyl-4'-yl) anthracene (TAT) [Kim et al., J. Mater. Chem., 2008, 18, 3376]. The vibronic coupling constants and transition dipole moments were calculated and analyzed by using the concepts of vibronic coupling density (VCD) and transition dipole moment density (TDMD), respectively. It is found that the driving force of the internal conversions and vibrational relaxations originate mainly from the anthracenylene group. On the other hand, fluorescence enhancement results from the large torsional distortion of the side groups in the S1 state. The torsional distortion is caused by the diagonal vibronic coupling for the lowest-frequency mode in the Franck-Condon (FC) S1 state, which originates from a small portion of the electron density difference on the side groups. These findings lead to the following design principles for anthracene derivatives with a high quantum yield: (1) reduction in the electron density difference and overlap density between the S0 and S1 states in the anthracenylene group to suppress vibrational relaxation and radiationless transitions, respectively; (2) increase in the overlap density in the side group to enhance the fluorescence.

  3. The Determination of Quantum Yield in the Fluoresence Spectra of Porphyrins

    NASA Astrophysics Data System (ADS)

    ćati, Odeta; Kristo, Kejda; Spiro, Marenglen; Xhuvani, Emil; Babani, Fatbardha; Tafa, Dentila

    2010-01-01

    The porphyrins, natural macromolecules, and especially the glycosylated ones, are recently used in the photodynamic therapy of different kinds of tumor cells. The porphyrins are injected through intravenous way in the human body. Under appropriate radiation of tumor zone with light in UV region, oxidation processes of the porphyrins occur through different mechanizms. As a result, inside the tumor, is producing oxygen in singlet state which is lethal for the tumor cells. The spectroscopic study of the porphyrins, both the absorbtion and the fluoresence spectroscopy, reveals some properties of the porphyrins which are ralated with their eventual application in the photodynamic therapy. So, from the value of the quantum yield, which is an important quantity that derives from the measurement of fluoresence of porphyrins, one can judge, through which mechanizm, the oxidation process does occurs. This suggest how the porphyrin should be used in the therapy, as monomers or as aggregates. The porphyrins are sinthetised in the Laboratory of Chemistry of Natural Compaunds, in the University of Limoges. The spectra has been taken by means of a photospectrometer, in the University of Tirana. The fluoresence spectra of the "protected" and "unprotected" porphyrins are studied. The determination of the quantum yield has been done through the comparison of porphyrins spectra, with them of Rhodamine B, which has a large fluoresence, in the same region of spectrum where does occurr the fluoresence of porphyrins. In order to do that, the calculations of the surface under the fluoresence spectra and under the Rhodamine one, is necessary. Also, the extintion of the fluoresence of some "protected" porphyrins, in polar solution, has been detected. These extintion of fluoresence has to do with the formation of agregates, of dimers, which can be confirmed from the absorbtion spectra.

  4. Quantum yield variation across the three pathways of photosynthesis: not yet out of the dark.

    PubMed

    Skillman, John B

    2008-01-01

    The convergent quantum yield hypothesis (CQY) assumes that thermodynamics and natural selection jointly limit variation in the maximum energetic efficiency of photosynthesis in low light under otherwise specified conditions (e.g. temperature and CO(2) concentration). A literature survey of photosynthetic quantum yield (phi) studies in terrestrial plants from C(3), C(4), and CAM photosynthetic types was conducted to test the CQY hypothesis. Broad variation in phi values from C(3) plants could partially be explained by accounting for whether the measuring conditions were permissive or restrictive for photorespiration. Assimilatory quotients (AQ), calculated from the CO(2) phi:O(2) phi ratios, indicated that 49% and 29% of absorbed light energy was allocated to carbon fixation and photorespiration in C(3) plants, respectively. The unexplained remainder (22%) may represent diversion to various other energy-demanding processes (e.g. starch synthesis, nitrogen assimilation). Individual and cumulative effects of these other processes on photosynthetic efficiency are poorly quantified. In C(4) plants, little variation in phi values was observed, consistent with the fact that C(4) plants exhibit little photorespiration. As before, AQ values indicate that 22% of absorbed light energy cannot be accounted for by carbon fixation in C(4) plants. Among all three photosynthetic types, the phi of photosynthesis in CAM plants is the least studied, appears to be highly variable, and may present the greatest challenge to the CQY hypothesis. The high amount of energy diverted to processes other than carbon fixation in C(3) and C(4) plants and the poor characterization of photosynthetic efficiency in CAM plants are significant deficiencies in our otherwise robust understanding of the energetics of terrestrial photoautotrophy.

  5. Quantum yields for the photolysis of glyoxal below 350 nm and parameterisations for its photolysis rate in the troposphere.

    PubMed

    Salter, Robert J; Blitz, Mark A; Heard, Dwayne E; Kovács, Tamás; Pilling, Michael J; Rickard, Andrew R; Seakins, Paul W

    2013-04-14

    The formation of HCO and of H in the photolysis of glyoxal have been investigated over the wavelength ranges 310-335 nm for HCO and 193-340 nm for H. Dye laser photolysis was coupled with cavity ring-down spectroscopy for HCO, and with laser induced fluorescence spectroscopy for H. Absolute quantum yields were determined using actinometers based on (a) Cl2 photolysis and the Cl + HCHO reaction for HCO and (b) N2O photolysis (and O(1)D + H2) and CH2CO photolysis (and CH2 + O2) for H. The quantum yields were found to be pressure independent in this wavelength region. Quantum yields for all product channels under atmospheric conditions were calculated and compared with literature values. Differences between this work and previously published work and their atmospheric implications are discussed.

  6. Quantum yield measurements of light-induced H₂ generation in a photosystem I-[FeFe]-H₂ase nanoconstruct.

    PubMed

    Applegate, Amanda M; Lubner, Carolyn E; Knörzer, Philipp; Happe, Thomas; Golbeck, John H

    2016-01-01

    The quantum yield for light-induced H2 generation was measured for a previously optimized bio-hybrid cytochrome c 6-crosslinked PSI(C13G)-1,8-octanedithiol-[FeFe]-H2ase(C97G) (PSI-H2ase) nanoconstruct. The theoretical quantum yield for the PSI-H2ase nanoconstruct is 0.50 molecules of H2 per photon absorbed, which equates to a requirement of two photons per H2 generated. Illumination of the PSI-H2ase nanoconstruct with visible light between 400 and 700 nm resulted in an average quantum yield of 0.10-0.15 molecules of H2 per photon absorbed, which equates to a requirement of 6.7-10 photons per H2 generated. A possible reason for the difference between the theoretical and experimental quantum yield is the occurrence of non-productive PSI(C13G)-1,8-octanedithiol-PSIC13G (PSI-PSI) conjugates, which would absorb light without generating H2. Assuming the thiol-Fe coupling is equally efficient at producing PSI-PSI conjugates as well as in producing PSI-H2ase nanoconstructs, the theoretical quantum yield would decrease to 0.167 molecules of H2 per photon absorbed, which equates to 6 photons per H2 generated. This value is close to the range of measured values in the current study. A strategy that purifies the PSI-H2ase nanoconstructs from the unproductive PSI-PSI conjugates or that incorporates different chemistries on the PSI and [FeFe]-H2ase enzyme sites could potentially allow the PSI-H2ase nanoconstruct to approach the expected theoretical quantum yield for light-induced H2 generation.

  7. The effect of varying short-chain alkyl substitution on the molar absorptivity and quantum yield of cyanine dyes.

    PubMed

    Chapman, Gala; Henary, Maged; Patonay, Gabor

    2011-01-01

    The effect of varying short-chain alkyl substitution of the indole nitrogens on the spectroscopic properties of cyanine dyes was examined. Molar absorptivities and fluorescence quantum yields were determined for a set of pentamethine dyes and a set of heptamethine dyes for which the substitution of the indole nitrogen was varied. For both sets of dyes, increasing alkyl chain length resulted in no significant change in quantum yield or molar absorptivity. These results may be useful in designing new cyanine dyes for analytical applications and predicting their spectroscopic properties.

  8. Ultraviolet photolysis of HCHO: absolute HCO quantum yields by direct detection of the HCO radical photoproduct.

    PubMed

    Carbajo, Paula Gorrotxategi; Smith, Shona C; Holloway, Anne-Louise; Smith, Carina A; Pope, Francis D; Shallcross, Dudley E; Orr-Ewing, Andrew J

    2008-12-04

    Absolute quantum yields for the radical (H + HCO) channel of HCHO photolysis, Phi(HCO), have been measured for the tropospherically relevant range of wavelengths (lambda) between 300 and 330 nm. The HCO photoproduct was directly detected by using a custom-built, combined ultra-violet (UV) absorption and cavity ring down (CRD) detection spectrometer. This instrument was previously employed for high-resolution (spectral resolution approximately 0.0035 nm) measurements of absorption cross-sections of HCHO, sigma(HCHO)(lambda), and relative HCO quantum yields. Absolute Phi(HCO) values were measured at seven wavelengths, lambda = 303.70, 305.13, 308.87, 314.31, 320.67, 325.59, and 329.51 nm, using an independent calibration technique based on the simultaneous UV photolysis of HCHO and Cl(2). These Phi(HCO) measurements display greater variability as a function of wavelength than the current NASA-JPL recommendations for Phi(HCO). The absolute Phi(HCO)(lambda) determinations and previously measured sigma(HCHO)(lambda) were used to scale an extensive set of relative HCO yield measurements. The outcome of this procedure is a full suite of data for the product of the absolute radical quantum yield and HCHO absorption cross-section, Phi(HCO)(lambda)sigma(HCHO)(lambda), at wavelengths from 302.6 to 331.0 nm with a wavelength resolution of 0.005 nm. This product of photochemical parameters is combined with high-resolution solar photon flux data to calculate the integrated photolysis rate of HCHO to the radical (H + HCO) channel, J(HCO). Comparison with the latest NASA-JPL recommendations, reported at 1 nm wavelength resolution, suggests an increased J(HCO) of 25% at 0 degrees solar zenith angle (SZA) increasing to 33% at high SZA (80 degrees). The differences in the calculated photolysis rate compared with the current HCHO data arise, in part, from the higher wavelength resolution of the current data set and highlight the importance of using high-resolution spectroscopic

  9. ABSORBANCE, ABSORPTION COEFFICIENT, AND APPARENT QUANTUM YIELD: A COMMENT ON AMBIGUITY IN THE USE OF THESE OPTICAL CONCEPTS

    EPA Science Inventory

    Several important optical terms such as "absorbance" and "absorption coefficient" are frequently used ambiguously in the current peer-reviewed literature. Since they are important terms that are required to derive other quantities such as the "apparent quantum yield" of photoprod...

  10. Effects of inter-nanocrystal distance on luminescence quantum yield in ensembles of Si nanocrystals

    SciTech Connect

    Valenta, J. Greben, M.; Gutsch, S.; Hiller, D.; Zacharias, M.

    2014-12-15

    The absolute photoluminescence (PL) quantum yield (QY) of multilayers of Silicon nanocrystals (SiNCs) separated by SiO{sub 2} barriers were thoroughly studied as function of the barrier thickness, excitation wavelength, and temperature. By mastering the plasma-enhanced chemical vapor deposition growth, we produce a series of samples with the same size-distribution of SiNCs but variable interlayer barrier distance. These samples enable us to clearly demonstrate that the increase of barrier thickness from ∼1 to larger than 2 nm induces doubling of the PL QY value, which corresponds to the change of number of close neighbors in the hcp structure. The temperature dependence of PL QY suggests that the PL QY changes are due to a thermally activated transport of excitation into non-radiative centers in dark NCs or in the matrix. We estimate that dark NCs represent about 68% of the ensemble of NCs. The PL QY excitation spectra show no significant changes upon changing the barrier thickness and no clear carrier multiplication effects. The dominant effect is the gradual decrease of the PL QY with increasing excitation photon energy.

  11. White carbon: Fluorescent carbon nanoparticles with tunable quantum yield in a reproducible green synthesis

    PubMed Central

    Meiling, Till T.; Cywiński, Piotr J.; Bald, Ilko

    2016-01-01

    In this study, a new reliable, economic, and environmentally-friendly one-step synthesis is established to obtain carbon nanodots (CNDs) with well-defined and reproducible photoluminescence (PL) properties via the microwave-assisted hydrothermal treatment of starch and Tris-acetate-EDTA (TAE) buffer as carbon sources. Three kinds of CNDs are prepared using different sets of above mentioned starting materials. The as-synthesized CNDs: C-CND (starch only), N-CND 1 (starch in TAE) and N-CND 2 (TAE only) exhibit highly homogenous PL and are ready to use without need for further purification. The CNDs are stable over a long period of time (>1 year) either in solution or as freeze-dried powder. Depending on starting material, CNDs with PL quantum yield (PLQY) ranging from less than 1% up to 28% are obtained. The influence of the precursor concentration, reaction time and type of additives on the optical properties (UV-Vis absorption, PL emission spectrum and PLQY) is carefully investigated, providing insight into the chemical processes that occur during CND formation. Remarkably, upon freeze-drying the initially brown CND-solution turns into a non-fluorescent white/slightly brown powder which recovers PL in aqueous solution and can potentially be applied as fluorescent marker in bio-imaging, as a reduction agent or as a photocatalyst. PMID:27334409

  12. Determination of Dacarbazine Φ-Order Photokinetics, Quantum Yields, and Potential for Actinometry.

    PubMed

    Maafi, Mounir; Lee, Lok-Yan

    2015-10-01

    The characterization of drugs' photodegradation kinetics is more accurately achieved by means of the recently developed Φ-order kinetics than by the zero-, first-, and/or second-order classical treatments. The photodegradation of anti-cancer dacarbazine (DBZ) in ethanol has been investigated and found to obey Φ-order kinetics when subjected to continuous and monochromatic irradiation of various wavelengths. Its photochemical efficiency was proven to be wavelength dependent in the 220-350 nm range, undergoing a 50-fold increase. Albeit this variation was well defined by a sigmoid pattern, the overall photoreactivity of DBZ was proven to depend also on the contributions of reactants and experimental attributes. The usefulness of DBZ to serve as a drug-actinometer has been investigated using the mathematical framework of Φ-order kinetics. It has been shown that DBZ in ethanol can represent a good candidate for reliable actinometry in the range 270-350 nm. A detailed and easy-to-implement procedure has been proposed for DBZ actinometry. This procedure could advantageously be implemented prior to the determination of the photodegradation quantum yields. This approach might be found useful for the development of many drug actinometers as alternatives to quinine hydrochloride.

  13. Integrated semiconductor quantum dot scintillation detector: Ultimate limit for speed and light yield

    SciTech Connect

    Oktyabrsky, Serge; Yakimov, Michael; Tokranov, Vadim; Murat, Pavel

    2016-03-30

    Here, a picosecond-range timing of charged particles and photons is a long-standing challenge for many high-energy physics, biophysics, medical and security applications. We present a design, technological pathway and challenges, and some properties important for realization of an ultrafast high-efficient room-temperature semiconductor scintillator based on self-assembled InAs quantum dots (QD) embedded in a GaAs matrix. Low QD density (<; 1015 cm-3), fast (~5 ps) electron capture, luminescence peak redshifted by 0.2-0.3 eV from GaAs absorption edge with fast decay time (0.5-1 ns) along with the efficient energy transfer in the GaAs matrix (4.2 eV/pair) allows for fabrication of a semiconductor scintillator with the unsurpassed performance parameters. The major technological challenge is fabrication of a large volume (> 1 cm3 ) of epitaxial QD medium. This requires multiple film separation and bonding, likely using separate epitaxial films as waveguides for improved light coupling. Compared to traditional inorganic scintillators, the semiconductor-QD based scintillators could have about 5x higher light yield and 20x faster decay time, opening a way to gamma detectors with the energy resolution better than 1% and sustaining counting rates MHz. Picosecond-scale timing requires segmented low-capacitance photodiodes integrated with the scintillator. For photons, the proposed detector inherently provides the depth-of-interaction information.

  14. Integrated semiconductor quantum dot scintillation detector: Ultimate limit for speed and light yield

    DOE PAGES

    Oktyabrsky, Serge; Yakimov, Michael; Tokranov, Vadim; ...

    2016-03-30

    Here, a picosecond-range timing of charged particles and photons is a long-standing challenge for many high-energy physics, biophysics, medical and security applications. We present a design, technological pathway and challenges, and some properties important for realization of an ultrafast high-efficient room-temperature semiconductor scintillator based on self-assembled InAs quantum dots (QD) embedded in a GaAs matrix. Low QD density (<; 1015 cm-3), fast (~5 ps) electron capture, luminescence peak redshifted by 0.2-0.3 eV from GaAs absorption edge with fast decay time (0.5-1 ns) along with the efficient energy transfer in the GaAs matrix (4.2 eV/pair) allows for fabrication of a semiconductormore » scintillator with the unsurpassed performance parameters. The major technological challenge is fabrication of a large volume (> 1 cm3 ) of epitaxial QD medium. This requires multiple film separation and bonding, likely using separate epitaxial films as waveguides for improved light coupling. Compared to traditional inorganic scintillators, the semiconductor-QD based scintillators could have about 5x higher light yield and 20x faster decay time, opening a way to gamma detectors with the energy resolution better than 1% and sustaining counting rates MHz. Picosecond-scale timing requires segmented low-capacitance photodiodes integrated with the scintillator. For photons, the proposed detector inherently provides the depth-of-interaction information.« less

  15. Quantum Yields and Rate Constants of Photochemical and Nonphotochemical Excitation Quenching (Experiment and Model).

    PubMed Central

    Laisk, A.; Oja, V.; Rasulov, B.; Eichelmann, H.; Sumberg, A.

    1997-01-01

    Sunflower (Helianthus annuus L.), cotton (Gossypium hirsutum L.), tobacco (Nicotiana tabacum L.), sorghum (Sorghum bicolor Moench.), amaranth (Amaranthus cruentus L.), and cytochrome b6f complex-deficient transgenic tobacco leaves were used to test the response of plants exposed to differnt light intensities and CO2 concentrations before and after photoinhibition at 4000 [mu]mol photons m-2 s-1 and to thermoinhibition up to 45[deg]C. Quantum yields of photochemical and nonphotochemical excitation quenching (YP and YN) and the corresponding relative rate constants for excitation capture from the antenna-primary radical pair equilibrium system (k[prime]P and k[prime]N) were calculated from measured fluorescence parameters. The above treatments resulted in decreases in YP and K[prime]P and in approximately complementary increases in YN and K[prime]N under normal and inhibitory conditions. The results were reproduced by a mathematical model of electron/proton transport and O2 evolution/CO2 assimilation in photosynthesis based on budget equations for the intermediates of photosynthesis. Quantitative differences between model predictions and experiments are explainable, assuming that electron transport is organized into domains that contain relatively complete electron and proton transport chains (e.g. thylakoids). With the complementation that occurs between the photochemical and nonphotochemical excitation quenching, the regulatory system can constantly maintain the shortest lifetime of excitation necessary to avoid the formation of chlorophyll triplet states and singlet oxygen. PMID:12223845

  16. White carbon: Fluorescent carbon nanoparticles with tunable quantum yield in a reproducible green synthesis

    NASA Astrophysics Data System (ADS)

    Meiling, Till T.; Cywiński, Piotr J.; Bald, Ilko

    2016-06-01

    In this study, a new reliable, economic, and environmentally-friendly one-step synthesis is established to obtain carbon nanodots (CNDs) with well-defined and reproducible photoluminescence (PL) properties via the microwave-assisted hydrothermal treatment of starch and Tris-acetate-EDTA (TAE) buffer as carbon sources. Three kinds of CNDs are prepared using different sets of above mentioned starting materials. The as-synthesized CNDs: C-CND (starch only), N-CND 1 (starch in TAE) and N-CND 2 (TAE only) exhibit highly homogenous PL and are ready to use without need for further purification. The CNDs are stable over a long period of time (>1 year) either in solution or as freeze-dried powder. Depending on starting material, CNDs with PL quantum yield (PLQY) ranging from less than 1% up to 28% are obtained. The influence of the precursor concentration, reaction time and type of additives on the optical properties (UV-Vis absorption, PL emission spectrum and PLQY) is carefully investigated, providing insight into the chemical processes that occur during CND formation. Remarkably, upon freeze-drying the initially brown CND-solution turns into a non-fluorescent white/slightly brown powder which recovers PL in aqueous solution and can potentially be applied as fluorescent marker in bio-imaging, as a reduction agent or as a photocatalyst.

  17. White carbon: Fluorescent carbon nanoparticles with tunable quantum yield in a reproducible green synthesis.

    PubMed

    Meiling, Till T; Cywiński, Piotr J; Bald, Ilko

    2016-06-23

    In this study, a new reliable, economic, and environmentally-friendly one-step synthesis is established to obtain carbon nanodots (CNDs) with well-defined and reproducible photoluminescence (PL) properties via the microwave-assisted hydrothermal treatment of starch and Tris-acetate-EDTA (TAE) buffer as carbon sources. Three kinds of CNDs are prepared using different sets of above mentioned starting materials. The as-synthesized CNDs: C-CND (starch only), N-CND 1 (starch in TAE) and N-CND 2 (TAE only) exhibit highly homogenous PL and are ready to use without need for further purification. The CNDs are stable over a long period of time (>1 year) either in solution or as freeze-dried powder. Depending on starting material, CNDs with PL quantum yield (PLQY) ranging from less than 1% up to 28% are obtained. The influence of the precursor concentration, reaction time and type of additives on the optical properties (UV-Vis absorption, PL emission spectrum and PLQY) is carefully investigated, providing insight into the chemical processes that occur during CND formation. Remarkably, upon freeze-drying the initially brown CND-solution turns into a non-fluorescent white/slightly brown powder which recovers PL in aqueous solution and can potentially be applied as fluorescent marker in bio-imaging, as a reduction agent or as a photocatalyst.

  18. Excitation power dependent population pathways and absolute quantum yields of upconversion nanoparticles in different solvents.

    PubMed

    Würth, C; Kaiser, M; Wilhelm, S; Grauel, B; Hirsch, T; Resch-Genger, U

    2017-03-23

    The rational design of brighter upconversion nanoparticles (UCNPs) requires a better understanding of the radiationless deactivation pathways in these materials. Here, we demonstrate the potential of excitation power density (P)-dependent studies of upconversion (UC) luminescence intensities, slope factors, and absolute quantum yields (ΦUC) of popular β-NaYF4:20% Yb(3+),2% Er(3+) UCNPs of different surface chemistries in organic solvents, D2O, and water as a tool to gain deeper insight into the UC mechanism including population and deactivation pathways particularly of the red emission. Our measurements, covering a P regime of three orders of magnitude, reveal a strong difference of the P-dependence of the ratio of the green and red luminescence bands (Ig/r) in water and organic solvents and P-dependent population pathways of the different emissive energy levels of Er(3+). In summary, we provide experimental evidence for three photon processes in UCNPs, particularly for the red emission. Moreover, we demonstrate changes in the excited population dynamics via bi- and triphotonic processes dependent on the environment, surface chemistry, and P, and validate our findings theoretically.

  19. CDOM Sources and Photobleaching Control Quantum Yields for Oceanic DMS Photolysis.

    PubMed

    Galí, Martí; Kieber, David J; Romera-Castillo, Cristina; Kinsey, Joanna D; Devred, Emmanuel; Pérez, Gonzalo L; Westby, George R; Marrasé, Cèlia; Babin, Marcel; Levasseur, Maurice; Duarte, Carlos M; Agustí, Susana; Simó, Rafel

    2016-12-20

    Photolysis is a major removal pathway for the biogenic gas dimethylsulfide (DMS) in the surface ocean. Here we tested the hypothesis that apparent quantum yields (AQY) for DMS photolysis varied according to the quantity and quality of its photosensitizers, chiefly chromophoric dissolved organic matter (CDOM) and nitrate. AQY compiled from the literature and unpublished studies ranged across 3 orders of magnitude at the 330 nm reference wavelength. The smallest AQY(330) were observed in coastal waters receiving major riverine inputs of terrestrial CDOM (0.06-0.5 m(3) (mol quanta)(-1)). In open-ocean waters, AQY(330) generally ranged between 1 and 10 m(3) (mol quanta)(-1). The largest AQY(330), up to 34 m(3) (mol quanta)(-1)), were seen in the Southern Ocean potentially associated with upwelling. Despite the large AQY variability, daily photolysis rate constants at the sea surface spanned a smaller range (0.04-3.7 d(-1)), mainly because of the inverse relationship between CDOM absorption and AQY. Comparison of AQY(330) with CDOM spectral signatures suggests there is an interplay between CDOM origin (terrestrial versus marine) and photobleaching that controls variations in AQYs, with a secondary role for nitrate. Our results can be used for regional or large-scale assessment of DMS photolysis rates in future studies.

  20. Action spectra of photosystems II and I and quantum yield of photosynthesis in leaves in State 1.

    PubMed

    Laisk, Agu; Oja, Vello; Eichelmann, Hillar; Dall'Osto, Luca

    2014-02-01

    The spectral global quantum yield (YII, electrons/photons absorbed) of photosystem II (PSII) was measured in sunflower leaves in State 1 using monochromatic light. The global quantum yield of PSI (YI) was measured using low-intensity monochromatic light flashes and the associated transmittance change at 810nm. The 810-nm signal change was calibrated based on the number of electrons generated by PSII during the flash (4·O2 evolution) which arrived at the PSI donor side after a delay of 2ms. The intrinsic quantum yield of PSI (yI, electrons per photon absorbed by PSI) was measured at 712nm, where photon absorption by PSII was small. The results were used to resolve the individual spectra of the excitation partitioning coefficients between PSI (aI) and PSII (aII) in leaves. For comparison, pigment-protein complexes for PSII and PSI were isolated, separated by sucrose density ultracentrifugation, and their optical density was measured. A good correlation was obtained for the spectral excitation partitioning coefficients measured by these different methods. The intrinsic yield of PSI was high (yI=0.88), but it absorbed only about 1/3 of quanta; consequently, about 2/3 of quanta were absorbed by PSII, but processed with the low intrinsic yield yII=0.63. In PSII, the quantum yield of charge separation was 0.89 as detected by variable fluorescence Fv/Fm, but 29% of separated charges recombined (Laisk A, Eichelmann H and Oja V, Photosynth. Res. 113, 145-155). At wavelengths less than 580nm about 30% of excitation is absorbed by pigments poorly connected to either photosystem, most likely carotenoids bound in pigment-protein complexes.

  1. Biosolar cells: global artificial photosynthesis needs responsive matrices with quantum coherent kinetic control for high yield.

    PubMed

    Purchase, R L; de Groot, H J M

    2015-06-06

    This contribution discusses why we should consider developing artificial photosynthesis with the tandem approach followed by the Dutch BioSolar Cells consortium, a current operational paradigm for a global artificial photosynthesis project. We weigh the advantages and disadvantages of a tandem converter against other approaches, including biomass. Owing to the low density of solar energy per unit area, artificial photosynthetic systems must operate at high efficiency to minimize the land (or sea) area required. In particular, tandem converters are a much better option than biomass for densely populated countries and use two photons per electron extracted from water as the raw material into chemical conversion to hydrogen, or carbon-based fuel when CO2 is also used. For the average total light sum of 40 mol m(-2) d(-1) for The Netherlands, the upper limits are many tons of hydrogen or carbon-based fuel per hectare per year. A principal challenge is to forge materials for quantitative conversion of photons to chemical products within the physical limitation of an internal potential of ca 2.9 V. When going from electric charge in the tandem to hydrogen and back to electricity, only the energy equivalent to 1.23 V can be stored in the fuel and regained. A critical step is then to learn from nature how to use the remaining difference of ca 1.7 V effectively by triple use of one overpotential for preventing recombination, kinetic stabilization of catalytic intermediates and finally generating targeted heat for the release of oxygen. Probably the only way to achieve this is by using bioinspired responsive matrices that have quantum-classical pathways for a coherent conversion of photons to fuels, similar to what has been achieved by natural selection in evolution. In appendix A for the expert, we derive a propagator that describes how catalytic reactions can proceed coherently by a convergence of time scales of quantum electron dynamics and classical nuclear dynamics. We

  2. Adaptation to high CO2 concentration in an optimal environment: radiation capture, canopy quantum yield and carbon use efficiency

    NASA Technical Reports Server (NTRS)

    Monje, O.; Bugbee, B.

    1998-01-01

    The effect of elevated [CO2] on wheat (Triticum aestivum L. Veery 10) productivity was examined by analysing radiation capture, canopy quantum yield, canopy carbon use efficiency, harvest index and daily C gain. Canopies were grown at either 330 or 1200 micromoles mol-1 [CO2] in controlled environments, where root and shoot C fluxes were monitored continuously from emergence to harvest. A rapidly circulating hydroponic solution supplied nutrients, water and root zone oxygen. At harvest, dry mass predicted from gas exchange data was 102.8 +/- 4.7% of the observed dry mass in six trials. Neither radiation capture efficiency nor carbon use efficiency were affected by elevated [CO2], but yield increased by 13% due to a sustained increase in canopy quantum yield. CO2 enrichment increased root mass, tiller number and seed mass. Harvest index and chlorophyll concentration were unchanged, but CO2 enrichment increased average life cycle net photosynthesis (13%, P < 0.05) and root respiration (24%, P < 0.05). These data indicate that plant communities adapt to CO2 enrichment through changes in C allocation. Elevated [CO2] increases sink strength in optimal environments, resulting in sustained increases in photosynthetic capacity, canopy quantum yield and daily C gain throughout the life cycle.

  3. A Reactive 1O2 - Responsive Combined Treatment System of Photodynamic and Chemotherapy for Cancer

    NASA Astrophysics Data System (ADS)

    Wang, Xiaojun; Meng, Guoqing; Zhang, Song; Liu, Xinli

    2016-07-01

    The development of reactive oxygen species (ROS)-responsive drug delivery and drug release has gradually attracted much attention in recent years as a promising therapeutic strategy. Singlet oxygen (1O2) as the major ROS species is widely used in photodynamic therapy (PDT) of cancer. In the present study, we introduce a combined treatment using ROS-sensitive thioketal (TK) linkage as a linker between upconversion nanoparticles (UNs)-based PDT and doxorubicin (DOX)-based chemotherapy. UNs can not only play a role in PDT, but can also be used as a nanocarrier for drug delivery of DOX. Moreover, the products of 1O2 during PDT are able to cleave TK linker inducing the release of DOX which can further achieve the goal of chemotherapy. By using this 1O2-responsive nanocarrier delivery system, DOX can easily reach the tumor site and be accumulated in the nuclei to effectively kill the cancer cells, and therefore decreasing the side effects of chemotherapy on the body. Thus, PDT also has the function of controlling drug release in this combination treatment strategy. Compared with monotherapy, the combination of PDT with chemotherapy also possesses excellent drug loading capability and anticancer efficiency.

  4. A Reactive 1O2 - Responsive Combined Treatment System of Photodynamic and Chemotherapy for Cancer

    PubMed Central

    Wang, Xiaojun; Meng, Guoqing; Zhang, Song; Liu, Xinli

    2016-01-01

    The development of reactive oxygen species (ROS)-responsive drug delivery and drug release has gradually attracted much attention in recent years as a promising therapeutic strategy. Singlet oxygen (1O2) as the major ROS species is widely used in photodynamic therapy (PDT) of cancer. In the present study, we introduce a combined treatment using ROS-sensitive thioketal (TK) linkage as a linker between upconversion nanoparticles (UNs)-based PDT and doxorubicin (DOX)-based chemotherapy. UNs can not only play a role in PDT, but can also be used as a nanocarrier for drug delivery of DOX. Moreover, the products of 1O2 during PDT are able to cleave TK linker inducing the release of DOX which can further achieve the goal of chemotherapy. By using this 1O2-responsive nanocarrier delivery system, DOX can easily reach the tumor site and be accumulated in the nuclei to effectively kill the cancer cells, and therefore decreasing the side effects of chemotherapy on the body. Thus, PDT also has the function of controlling drug release in this combination treatment strategy. Compared with monotherapy, the combination of PDT with chemotherapy also possesses excellent drug loading capability and anticancer efficiency. PMID:27443831

  5. Alternating layer addition approach to CdSe/CdS core/shell quantum dots with near-unity quantum yield and high on-time fractions

    PubMed Central

    Allen, Peter M.; Liu, Wenhao; Zhao, Jing; Young, Elizabeth R.; Popović, Zoran; Walker, Brian

    2014-01-01

    We report single-particle photoluminescence (PL) intermittency (blinking) with high on-time fractions in colloidal CdSe quantum dots (QD) with conformal CdS shells of 1.4 nm thickness, equivalent to approximately 4 CdS monolayers. All QDs observed displayed on-time fractions > 60% with the majority > 80%. The high-on-time-fraction blinking is accompanied by fluorescence quantum yields (QY) close to unity (up to 98% in an absolute QY measurement) when dispersed in organic solvents and a monoexponential ensemble photoluminescence (PL) decay lifetime. The CdS shell is formed in high synthetic yield using a modified selective ion layer adsorption and reaction (SILAR) technique that employs a silylated sulfur precursor. The CdS shell provides sufficient chemical and electronic passivation of the QD excited state to permit water solubilization with greater than 60% QY via ligand exchange with an imidazole-bearing hydrophilic polymer. PMID:24932403

  6. Quantum-orbit analysis for yield and ellipticity of high order harmonic generation with elliptically polarized laser field.

    PubMed

    Li, Yang; Zhu, Xiaosong; Zhang, Qingbin; Qin, Meiyan; Lu, Peixiang

    2013-02-25

    We perform a quantum-orbit analysis for the dependence of high-order-harmonic yield on the driving field ellipticity and the polarization properties of the generated high harmonics. The electron trajectories responsible for the emission of particular harmonics are identified. It is found that, in elliptically polarized driving field, the electrons have ellipticity-dependent initial velocities, which lead to the decrease of the ionization rate. Thus the harmonic yield steeply decreases with laser ellipticity. Besides, we show that the polarization properties of the harmonics are related to the complex momenta of the electron. The physical origin of the harmonic ellipticity is interpreted as the consequence of quantum-mechanical uncertainty of the electron momentum. Our results are verified with the experimental results as well as the numerical solutions of the time dependent Schrödinger equation from the literature.

  7. Rigidifying Fluorescent Linkers by Metal-Organic Framework Formation for Fluorescence Blue Shift and Quantum Yield Enhancement

    SciTech Connect

    Wei, ZW; Gu, ZY; Arvapally, RK; Chen, YP; McDougald, RN; Ivy, JF; Yakovenko, AA; Feng, DW; Omary, MA; Zhou, HC

    2014-06-11

    We demonstrate that rigidifying the structure of fluorescent linkers by structurally constraining them in metal-organic frameworks (MOFs) to control their conformation effectively tunes the fluorescence energy and enhances the quantum yield. Thus, a new tetraphenylethylene-based zirconium MOF exhibits a deep-blue fluorescent emission at 470 nm with a unity quantum yield (99.9 +/- 0.5%) under Ar, representing ca. 3600 cm(-1) blue shift and doubled radiative decay efficiency vs the linker precursor. An anomalous increase in the fluorescence lifetime and relative intensity takes place upon heating the solid MOF from cryogenic to ambient temperatures. The origin of these unusual photoluminescence properties is attributed to twisted linker conformation, intramolecular hindrance, and framework rigidity.

  8. Rigidifying Fluorescent Linkers by Metal–Organic Framework Formation for Fluorescence Blue Shift and Quantum Yield Enhancement

    SciTech Connect

    Wei, Zhangwen; Gu, Zhi-Yuan; Arvapally, Ravi K.; Chen, Ying-Pin; Ivy, Joshua F.; Yakovenko, Andrey A.; Feng, Dawei; Omary, Mohammad A.; Zhou, Hong-Cai

    2014-06-11

    We demonstrate that rigidifying the structure of fluorescent linkers by structurally constraining them in metal–organic frameworks (MOFs) to control their conformation effectively tunes the fluorescence energy and enhances the quantum yield. Thus, a new tetraphenylethylene-based zirconium MOF exhibits a deep-blue fluorescent emission at 470 nm with a unity quantum yield (99.9 ± 0.5%) under Ar, representing ca. 3600 cm⁻¹ blue shift and doubled radiative decay efficiency vs the linker precursor. An anomalous increase in the fluorescence lifetime and relative intensity takes place upon heating the solid MOF from cryogenic to ambient temperatures. The origin of these unusual photoluminescence properties is attributed to twisted linker conformation, intramolecular hindrance, and framework rigidity.

  9. Laser flash photolysis of ozone - O/1D/ quantum yields in the fall-off region 297-325 nm

    NASA Technical Reports Server (NTRS)

    Brock, J. C.; Watson, R. T.

    1980-01-01

    The wavelength dependence of the quantum yield for O(1D) production from ozone photolysis has been determined between 297.5 nm and 325 nm in order to resolve serious discrepancies among previous studies. The results of this investigation are compared to earlier work by calculating atmospheric production rate constants for O(1D). It is found that for the purpose of calculating this rate constant, there is now good agreement among three studies at 298 K. Furthermore, it appears that previous data on the temperature dependence of the O(1D) quantum yield fall-off is adequate for determining the vertical profile of the O(1D) production rate constant. Several experimental difficulties associated with using NO2(asterisk) chemiluminescence to monitor O(1D) have been identified.

  10. Calculated quantum yield of photosynthesis of phytoplankton in the Marine Light-Mixed Layers (59 deg N, 21 deg W)

    NASA Technical Reports Server (NTRS)

    Carder, K. L.; Lee, Z. P.; Marra, John; Steward, R. G.; Perry, M. J.

    1995-01-01

    The quantum yield of photosynthesis (mol C/mol photons) was calculated at six depths for the waters of the Marine Light-Mixed Layer (MLML) cruise of May 1991. As there were photosynthetically available radiation (PAR) but no spectral irradiance measurements for the primary production incubations, three ways are presented here for the calculation of the absorbed photons (AP) by phytoplankton for the purpose of calculating phi. The first is based on a simple, nonspectral model; the second is based on a nonlinear regression using measured PAR values with depth; and the third is derived through remote sensing measurements. We show that the results of phi calculated using the nonlinear regreesion method and those using remote sensing are in good agreement with each other, and are consistent with the reported values of other studies. In deep waters, however, the simple nonspectral model may cause quantum yield values much higher than theoretically possible.

  11. Challenge to the Charging Model of Semiconductor-Nanocrystal Fluorescence Intermittency from Off-State Quantum Yields and Multiexciton Blinking

    NASA Astrophysics Data System (ADS)

    Zhao, Jing; Nair, Gautham; Fisher, Brent R.; Bawendi, Moungi G.

    2010-04-01

    Semiconductor nanocrystals emit light intermittently; i.e., they “blink,” under steady illumination. The dark periods have been widely assumed to be due to photoluminescence (PL) quenching by an Auger-like process involving a single additional charge present in the nanocrystal. Our results challenge this long-standing assumption. Close examination of exciton PL intensity time traces of single CdSe(CdZnS) core(shell) nanocrystals reveals that the dark state PL quantum yield can be 10 times less than the biexciton PL quantum yield. In addition, we observe spectrally resolved multiexciton emission and find that it also blinks with an on/off ratio greater than 10∶1. These results directly contradict the predictions of the charging model.

  12. Challenge to the Charging Model of Semiconductor-Nanocrystal Fluorescence Intermittency from Off-State Quantum Yields and Multiexciton Blinking

    PubMed Central

    Zhao, Jing; Nair, Gautham; Fisher, Brent R.; Bawendi, Moungi G.

    2012-01-01

    Semiconductor nanocrystals emit light intermittently; i.e., they “blink,” under steady illumination. The dark periods have been widely assumed to be due to photoluminescence (PL) quenching by an Auger-like process involving a single additional charge present in the nanocrystal. Our results challenge this long-standing assumption. Close examination of exciton PL intensity time traces of single CdSe(CdZnS) core (shell) nanocrystals reveals that the dark state PL quantum yield can be 10 times less than the biexciton PL quantum yield. In addition, we observe spectrally resolved multiexciton emission and find that it also blinks with an on/off ratio greater than 10:1. These results directly contradict the predictions of the charging model. PMID:20482016

  13. Challenge to the charging model of semiconductor-nanocrystal fluorescence intermittency from off-state quantum yields and multiexciton blinking.

    PubMed

    Zhao, Jing; Nair, Gautham; Fisher, Brent R; Bawendi, Moungi G

    2010-04-16

    Semiconductor nanocrystals emit light intermittently; i.e., they "blink," under steady illumination. The dark periods have been widely assumed to be due to photoluminescence (PL) quenching by an Auger-like process involving a single additional charge present in the nanocrystal. Our results challenge this long-standing assumption. Close examination of exciton PL intensity time traces of single CdSe(CdZnS) core(shell) nanocrystals reveals that the dark state PL quantum yield can be 10 times less than the biexciton PL quantum yield. In addition, we observe spectrally resolved multiexciton emission and find that it also blinks with an on/off ratio greater than 10:1. These results directly contradict the predictions of the charging model.

  14. Quantum yields for OH production from 193 and 248 nm photolysis of HNO3 and H2O2

    NASA Astrophysics Data System (ADS)

    Schiffman, A.; Nelson, D. D., Jr.; Nesbitt, D. J.

    1993-05-01

    Flash kinetic spectroscopy in a flow tube is used to measure at room temperature the absolute yields for OH production from 193 and 248 nm photolysis of HNO3 and H2O2. The OH radicals are produced by excimer laser photolysis and probed via direct absorption of high resolution tunable IR laser light. The results indicate quantum yields for both precursors at both wavelengths which are less than the maximum possible values of 1 for H2O2. The present measurements are discussed in light of contrasting results suggested from other work.

  15. Quantum yield of chlorine-atom formation in the photodissociation of chlorine peroxide (ClOOCl) at 308 nm

    NASA Technical Reports Server (NTRS)

    Molina, M. J.; Colussi, A. J.; Molina, L. T.; Schindler, R. N.; Tso, T.-L.

    1990-01-01

    The production of Cl atoms in the laser flash photolysis of ClOOCl at 308 nm has been investigated by time-resolved atomic resonance fluorescence at 235 K. A value of phi = 1.03 +/-0.12 has been obtained for the primary quantum yield based on an absorption cross section ratio sigma(245)/phi(308) = 22 for ClOOCl at 245 and 308 nm.

  16. Laboratory study of nitrate photolysis in Antarctic snow. I. Observed quantum yield, domain of photolysis, and secondary chemistry

    SciTech Connect

    Meusinger, Carl; Johnson, Matthew S.; Berhanu, Tesfaye A.; Erbland, Joseph; Savarino, Joel

    2014-06-28

    Post-depositional processes alter nitrate concentration and nitrate isotopic composition in the top layers of snow at sites with low snow accumulation rates, such as Dome C, Antarctica. Available nitrate ice core records can provide input for studying past atmospheres and climate if such processes are understood. It has been shown that photolysis of nitrate in the snowpack plays a major role in nitrate loss and that the photolysis products have a significant influence on the local troposphere as well as on other species in the snow. Reported quantum yields for the main reaction spans orders of magnitude – apparently a result of whether nitrate is located at the air-ice interface or in the ice matrix – constituting the largest uncertainty in models of snowpack NO{sub x} emissions. Here, a laboratory study is presented that uses snow from Dome C and minimizes effects of desorption and recombination by flushing the snow during irradiation with UV light. A selection of UV filters allowed examination of the effects of the 200 and 305 nm absorption bands of nitrate. Nitrate concentration and photon flux were measured in the snow. The quantum yield for loss of nitrate was observed to decrease from 0.44 to 0.003 within what corresponds to days of UV exposure in Antarctica. The superposition of photolysis in two photochemical domains of nitrate in snow is proposed: one of photolabile nitrate, and one of buried nitrate. The difference lies in the ability of reaction products to escape the snow crystal, versus undergoing secondary (recombination) chemistry. Modeled NO{sub x} emissions may increase significantly above measured values due to the observed quantum yield in this study. The apparent quantum yield in the 200 nm band was found to be ∼1%, much lower than reported for aqueous chemistry. A companion paper presents an analysis of the change in isotopic composition of snowpack nitrate based on the same samples as in this study.

  17. Enhanced Hypsochromic Shifts, Quantum Yield, and π-π Interactions in a meso,β-Heteroaryl-Fused BODIPY.

    PubMed

    Zhao, Ning; Xuan, Sunting; Fronczek, Frank R; Smith, Kevin M; Vicente, M Graça H

    2017-03-10

    We report the synthesis and investigation of an unprecedented 8-heteroaryl-fused BODIPY 4. This compound exhibits enhanced π-π stacking in the solid state, unusually large blue-shifts in the absorbance and emission spectra, and higher fluorescence quantum yield than its unfused precursor; DFT calculations suggest a small energy gap for 4 and strong electronic communication between the 8-OPh and the BODIPY core.

  18. Laboratory study of nitrate photolysis in Antarctic snow. I. Observed quantum yield, domain of photolysis, and secondary chemistry.

    PubMed

    Meusinger, Carl; Berhanu, Tesfaye A; Erbland, Joseph; Savarino, Joel; Johnson, Matthew S

    2014-06-28

    Post-depositional processes alter nitrate concentration and nitrate isotopic composition in the top layers of snow at sites with low snow accumulation rates, such as Dome C, Antarctica. Available nitrate ice core records can provide input for studying past atmospheres and climate if such processes are understood. It has been shown that photolysis of nitrate in the snowpack plays a major role in nitrate loss and that the photolysis products have a significant influence on the local troposphere as well as on other species in the snow. Reported quantum yields for the main reaction spans orders of magnitude - apparently a result of whether nitrate is located at the air-ice interface or in the ice matrix - constituting the largest uncertainty in models of snowpack NOx emissions. Here, a laboratory study is presented that uses snow from Dome C and minimizes effects of desorption and recombination by flushing the snow during irradiation with UV light. A selection of UV filters allowed examination of the effects of the 200 and 305 nm absorption bands of nitrate. Nitrate concentration and photon flux were measured in the snow. The quantum yield for loss of nitrate was observed to decrease from 0.44 to 0.003 within what corresponds to days of UV exposure in Antarctica. The superposition of photolysis in two photochemical domains of nitrate in snow is proposed: one of photolabile nitrate, and one of buried nitrate. The difference lies in the ability of reaction products to escape the snow crystal, versus undergoing secondary (recombination) chemistry. Modeled NOx emissions may increase significantly above measured values due to the observed quantum yield in this study. The apparent quantum yield in the 200 nm band was found to be ∼1%, much lower than reported for aqueous chemistry. A companion paper presents an analysis of the change in isotopic composition of snowpack nitrate based on the same samples as in this study.

  19. Quantum yields of OH, HO2 and NO3 in the UV photolysis of HO2NO2.

    PubMed

    Jiménez, Elena; Gierczak, Tomasz; Stark, Harald; Burkholder, James B; Ravishankara, A R

    2005-01-21

    Quantum yields, phi, of OH and HO2 in the ultraviolet photolysis of HO2NO2 (peroxynitric acid, PNA) at 193 and 248 nm and that of NO3 at 193, 248 and 308 nm are reported. Quantum yields were measured using pulsed excimer laser photolysis combined with pulsed laser induced fluorescence (PLIF) detection of OH radicals and cavity ring-down (CRD) detection of NO3 radicals. HO2 radicals were quantified by converting them to OH via the HO2 + NO --> OH + NO2 reaction and detecting OH. The quantum yields obtained at 296 K are: phi193 nm(OH) = 0.21 +/- 0.12, phi248 nm(OH) = 0.085 +/- 0.08, phi193 nm(HO2) = 0.56 +/- 0.09, phi248 nm(HO2) = 0.89 +/- 0.26, phi193 nm(NO3) = 0.35 +/- 0.09, phi248 nm(NO3) = 0.08 +/- 0.04 and phi308 nm(NO3) = 0.05 +/- 0.02. The quoted uncertainties are 2sigma (95% confidence level) and include estimated systematic errors. Our results are compared with the previous quantum yield measurements of OH (MacLeod et al., J. Geophys. Res., 1988, 93, 3813) and NO2 (Roehl et al., 2001, J. Phys. Chem., 105, 1592) at 248 nm and the discrepancies are discussed. The rate coefficients at 298 K for reactions of OH with HO2NO2, H2O2, HNO3 and NO are also reported.

  20. Quantum yields lower than unity in photo- induced dissociative electron transfers: the reductive cleavage of carbon tetrachloride.

    PubMed

    Pause, L; Robert, M; Savéant, J M

    2000-12-15

    It has been shown recently that the electrochemical reduction of carbon tetrachloride in N,N'-dimethylformamide follows a mechanism in which electron transfer and bond cleavage are concerted. We report here results concerning photoinduced electron transfer from the singlet excited state of two aromatic molecules, 2-ethyl-9,10-dimethoxyanthracene and perylene, to CCl4 , which is characterised by a quantum yield of complete quenching fragmentation ranging from 0.7 to 0.8. It is shown that a quantum yield below unity is compatible with a dissociative mechanism and arises from partitioning of the system at the intersection of the product- and ground-state potential energy surfaces. This phenomenon predominates over back electron transfer from the clustered fragments state. The photoinduced reductive cleavage of CCl4 thus provides a clear illustration of the recent theoretical prediction, that photoinduced dissociative electron transfers are not necessarily endowed with a unity quantum yield. This offers an opportunity to estimate the magnitude of the electronic matrix element that couples the fragmented product state and the ground reactant state.

  1. Photobleaching of astaxanthin and canthaxanthin. Quantum-yields dependence of solvent, temperature, and wavelength of irradiation in relation to packaging and storage of carotenoid pigmented salmonoids.

    PubMed

    Christophersen, A G; Jun, H; Jørgensen, K; Skibsted, L H

    1991-05-01

    The quantum yield for the photobleaching of astaxanthin (the carotenoid of wild salmonoids) and of canthaxanthin (the closely related carotenoid used as a feeding additive for farmed salmonoids) has been determined for monochromatic light at different wavelengths and in different solvents. Astaxanthin is less sensitive to light than canthaxanthin. The photobleaching is strongly wavelength dependent, and the quantum yield for astaxanthin dissolved in chloroform at 22 degrees C is 3.2 x 10(-1) mol.Einstein-1 at 254 nm, 3.1 x 10(-2) at 313 nm, and 1.6 x 10(-6) at 436 nm, respectively. The quantum yields are less dependent on the nature of the solvent and show no simple correlation with oxygen solubility, i.e. for 366 nm excitation of astaxanthin the quantum yields are 6.1 x 10(-5) mol.Einstein-1 in acetone, 1.2 x 10(-4) in saturated vegetable oil, 1.9 x 10(-4) in chloroform, and 3.4 x 10(-4) solubilized in water, respectively. The photobleaching quantum yield provides an objective measure of the light sensitivity of the carotenoids in relation to the discolouration of carotenoid-pigmented salmonoids. The quantum yield was also found to be independent of the carotenoid concentration and, in a homogenous solution, of light intensities. For astaxanthin solubilized in water, the quantum yield increases for low light intensities. Excitation of astaxanthin solubilized in water using visible light shows that the photobleaching quantum yield is independent of temperature, while excitation at 313 nm shows an increase in the quantum yield with increasing temperatures, corresponding to an energy of activation of 28 kJ.mol-1.(ABSTRACT TRUNCATED AT 250 WORDS)

  2. Photophysics of a new photosensitizer with high quantum yield of singlet oxygen generation and its application to stereo-selective synthesis of (+)-deoxoartemisinin

    NASA Astrophysics Data System (ADS)

    Wang, Kang-Kyun; Choi, Kyoung-Hoon; Shin, Hee-Won; Kim, Bong-Jin; Im, Ji-Eun; Oh, Seung-Lim; Park, Nam-Soo; Jung, Mankil; Oh, Jae-Buem; Lee, Myung-Jun; Kim, Hwan-Kyu; Kim, Yong-Rok

    2009-11-01

    A new photo-catalyst of [5,10,15-triphenyl-20-(4-methoxycarbonylphenyl)-porphyrin] platinum was synthesized and its photophysical study revealed that it had a high quantum yield of singlet oxygen generation. As an application study, a stereo-specific synthesis of (+)-deoxoartemisinin was performed. The induced high triplet quantum yield (0.96 ± 0.03) of [5,10,15-triphenyl-20-(4-methoxycarbonylphenyl)-porphyrin] resulted the high singlet oxygen quantum yield of 0.90 ± 0.04. The photo-catalytic effect was compared with that of methylene blue (MB) which was generally used as a photo-catalyst for these types of stereo-specific syntheses of organic compounds. The yield of synthesized (+)-deoxoartemisinin was correlated with singlet oxygen quantum yield.

  3. Biosolar cells: global artificial photosynthesis needs responsive matrices with quantum coherent kinetic control for high yield

    PubMed Central

    Purchase, R. L.; de Groot, H. J. M.

    2015-01-01

    This contribution discusses why we should consider developing artificial photosynthesis with the tandem approach followed by the Dutch BioSolar Cells consortium, a current operational paradigm for a global artificial photosynthesis project. We weigh the advantages and disadvantages of a tandem converter against other approaches, including biomass. Owing to the low density of solar energy per unit area, artificial photosynthetic systems must operate at high efficiency to minimize the land (or sea) area required. In particular, tandem converters are a much better option than biomass for densely populated countries and use two photons per electron extracted from water as the raw material into chemical conversion to hydrogen, or carbon-based fuel when CO2 is also used. For the average total light sum of 40 mol m−2 d−1 for The Netherlands, the upper limits are many tons of hydrogen or carbon-based fuel per hectare per year. A principal challenge is to forge materials for quantitative conversion of photons to chemical products within the physical limitation of an internal potential of ca 2.9 V. When going from electric charge in the tandem to hydrogen and back to electricity, only the energy equivalent to 1.23 V can be stored in the fuel and regained. A critical step is then to learn from nature how to use the remaining difference of ca 1.7 V effectively by triple use of one overpotential for preventing recombination, kinetic stabilization of catalytic intermediates and finally generating targeted heat for the release of oxygen. Probably the only way to achieve this is by using bioinspired responsive matrices that have quantum–classical pathways for a coherent conversion of photons to fuels, similar to what has been achieved by natural selection in evolution. In appendix A for the expert, we derive a propagator that describes how catalytic reactions can proceed coherently by a convergence of time scales of quantum electron dynamics and classical nuclear dynamics

  4. Measurement of the triplet lifetime and the quantum yield of triplet formation of phthalazine by the time-resolved thermal lens method

    NASA Astrophysics Data System (ADS)

    Terazima, Masahide; Azumi, Tohru

    1987-11-01

    The time-resolved thermal lens technique is used to determine the quantum yield of the triplet formation and the triplet lifetime of phthalazine in a polar and a non-polar solvent. The quantum yields of phthalazine in ethanol and benzene are 0.44 and 0.49, respectively. Very short triplet lifetimes of phthalazine (2.7 μ;s) in benzene at room temperature are reported.

  5. In cellulo evaluation of phototransformation quantum yields in fluorescent proteins used as markers for single-molecule localization microscopy.

    PubMed

    Avilov, Sergiy; Berardozzi, Romain; Gunewardene, Mudalige S; Adam, Virgile; Hess, Samuel T; Bourgeois, Dominique

    2014-01-01

    Single-molecule localization microscopy of biological samples requires a precise knowledge of the employed fluorescent labels. Photoactivation, photoblinking and photobleaching of phototransformable fluorescent proteins influence the data acquisition and data processing strategies to be used in (Fluorescence) Photoactivation Localization Microscopy ((F)-PALM), notably for reliable molecular counting. As these parameters might depend on the local environment, they should be measured in cellulo in biologically relevant experimental conditions. Here, we measured phototransformation quantum yields for Dendra2 fused to actin in fixed mammalian cells in typical (F)-PALM experiments. To this aim, we developed a data processing strategy based on the clustering optimization procedure proposed by Lee et al (PNAS 109, 17436-17441, 2012). Using simulations, we estimated the range of experimental parameters (molecular density, molecular orientation, background level, laser power, frametime) adequate for an accurate determination of the phototransformation yields. Under illumination at 561 nm in PBS buffer at pH 7.4, the photobleaching yield of Dendra2 fused to actin was measured to be (2.5 ± 0.4) × 10(-5), whereas the blinking-off yield and thermally-activated blinking-on rate were measured to be (2.3 ± 0.2) × 10(-5) and 11.7 ± 0.5 s-1, respectively. These phototransformation yields differed from those measured in poly-vinyl alcohol (PVA) and were strongly affected by addition of the antifading agent 1,4-diazabicyclo[2.2.2]octane (DABCO). In the presence of DABCO, the photobleaching yield was reduced 2-fold, the blinking-off yield was decreased more than 3-fold, and the blinking-on rate was increased 2-fold. Therefore, DABCO largely improved Dendra2 photostability in fixed mammalian cells. These findings are consistent with redox-based bleaching and blinking mechanisms under (F)-PALM experimental conditions. Finally, the green-to-red photoconversion quantum yield of Dendra

  6. In cellulo Evaluation of Phototransformation Quantum Yields in Fluorescent Proteins Used As Markers for Single-Molecule Localization Microscopy

    PubMed Central

    Avilov, Sergiy; Berardozzi, Romain; Gunewardene, Mudalige S.; Adam, Virgile; Hess, Samuel T.; Bourgeois, Dominique

    2014-01-01

    Single-molecule localization microscopy of biological samples requires a precise knowledge of the employed fluorescent labels. Photoactivation, photoblinking and photobleaching of phototransformable fluorescent proteins influence the data acquisition and data processing strategies to be used in (Fluorescence) Photoactivation Localization Microscopy ((F)-PALM), notably for reliable molecular counting. As these parameters might depend on the local environment, they should be measured in cellulo in biologically relevant experimental conditions. Here, we measured phototransformation quantum yields for Dendra2 fused to actin in fixed mammalian cells in typical (F)-PALM experiments. To this aim, we developed a data processing strategy based on the clustering optimization procedure proposed by Lee et al (PNAS 109, 17436–17441, 2012). Using simulations, we estimated the range of experimental parameters (molecular density, molecular orientation, background level, laser power, frametime) adequate for an accurate determination of the phototransformation yields. Under illumination at 561 nm in PBS buffer at pH 7.4, the photobleaching yield of Dendra2 fused to actin was measured to be (2.5±0.4)×10−5, whereas the blinking-off yield and thermally-activated blinking-on rate were measured to be (2.3±0.2)×10−5 and 11.7±0.5 s−1, respectively. These phototransformation yields differed from those measured in poly-vinyl alcohol (PVA) and were strongly affected by addition of the antifading agent 1,4-diazabicyclo[2.2.2]octane (DABCO). In the presence of DABCO, the photobleaching yield was reduced 2-fold, the blinking-off yield was decreased more than 3-fold, and the blinking-on rate was increased 2-fold. Therefore, DABCO largely improved Dendra2 photostability in fixed mammalian cells. These findings are consistent with redox-based bleaching and blinking mechanisms under (F)-PALM experimental conditions. Finally, the green-to-red photoconversion quantum yield of Dendra2 was

  7. Solvent dependence of laser-synthesized blue-emitting Si nanoparticles: Size, quantum yield, and aging performance

    NASA Astrophysics Data System (ADS)

    Xin, Yunzi; Kitasako, Takumi; Maeda, Makoto; Saitow, Ken-ichi

    2017-04-01

    Pulsed-laser ablation of silicon (Si) was conducted in six different organic solvents using a nanosecond laser. Si nanoparticles (Si-NPs) that exhibited blue photoluminescence (PL) were generated in all the solvents, but a significant solvent dependence emerged: particle size, PL spectra, and PL quantum yield (QY). The results of solvent dependence were well characterized using an atomic ratio in a solvent molecule. The highest QY was observed for the smallest Si-NPs (ca. 2 nm) synthesized in 1-octyne. The QY was enhanced by aging in 1-octyne, and its mechanism was attributed to alkyl passivation of dangling bonds on the Si-NPs.

  8. Synthesis of 1-O-(2'-acetoxy)benzoyl-alpha-D-2-deoxyglucopyranose, a novel aspirin prodrug.

    PubMed

    Truelove, J E; Hussain, A A; Kostenbauder, H B

    1980-02-01

    The synthesis and characterization of 1-O-(2'-acetoxy)benzoyl-alpha-D-2-deoxyglucopyranose, a novel aspirin prodrug, are described. 3,4,6-Tri-O-benzyl-alpha-D-2-deoxyglucopyranose was synthesized by methylating the anomeric hydroxyl group of 2-deoxyglucose, benzylating the 3-, 4-, and 6-hydroxy functional grups, and cleaving hydrolytically the anomeric methyl group. Reaction of the tribenzylated sugar with the acid chloride of aspirin and subsequent hydrogenolysis of the benzyl groups resulted in the prodrug, mp 128 degrees. The compound was further characterized by elemental analysis and PMR and 13C-NMR spectroscopy. In vitro, the compound cleaved to aspirin with a half-life of 7 min at 37 degrees. Prodrug cleavage was independent of pH over the pH 3--9 range.

  9. Effects of Bleaching by Nitrogen Deficiency on the Quantum Yield of Photosystem II in Synechocystis sp. PCC 6803 Revealed by Chl Fluorescence Measurements.

    PubMed

    Ogawa, Takako; Sonoike, Kintake

    2016-03-01

    Estimation of photosynthesis by Chl fluorescence measurement of cyanobacteria is always problematic due to the interference from respiratory electron transfer and from phycocyanin fluorescence. The interference from respiratory electron transfer could be avoided by the use of DCMU or background illumination by blue light, which oxidizes the plastoquinone pool that tends to be reduced by respiration. On the other hand, the precise estimation of photosynthesis in cells with a different phycobilisome content by Chl fluorescence measurement is difficult. By subtracting the basal fluorescence due to the phycobilisome and PSI, it becomes possible to estimate the precise maximum quantum yield of PSII in cyanobacteria. Estimated basal fluorescence accounted for 60% of the minimum fluorescence, resulting in a large difference between the 'apparent' yield and 'true' yield under high phycocyanin conditions. The calculated value of the 'true' maximum quantum yield of PSII was around 0.8, which was similar to the value observed in land plants. The results suggest that the cause of the apparent low yield reported in cyanobacteria is mainly ascribed to the interference from phycocyanin fluorescence. We also found that the 'true' maximum quantum yield of PSII decreased under nitrogen-deficient conditions, suggesting the impairment of the PSII reaction center, while the 'apparent' maximum quantum yield showed a marginal change under the same conditions. Due to the high contribution of phycocyanin fluorescence in cyanobacteria, it is essential to eliminate the influence of the change in phycocyanin content on Chl fluorescence measurement and to evaluate the 'true' photosynthetic condition.

  10. In vivo characterization of hair and skin derived carbon quantum dots with high quantum yield as long-term bioprobes in zebrafish

    NASA Astrophysics Data System (ADS)

    Zhang, Jing-Hui; Niu, Aping; Li, Jing; Fu, Jian-Wei; Xu, Qun; Pei, De-Sheng

    2016-11-01

    Carbon quantum dots (CDs) were widely investigated because of their tunable fluorescence properties and low toxicity. However, so far there have been no reports on in vivo functional studies of hair and skin derived CDs. Here, hair derived CDs (HCDs) and skin derived CDs (SCDs) were produced by using human hair and pig skin as precursors. The quantum yields (QYs) of HCDs and SCDs were quite high, compared to citric acid derived CDs (CCDs). HCDs and SCDs possess optimal photostability, hypotoxicity and biocompatibility in zebrafish, indicating that HCDs and SCDs possess the capacity of being used as fluorescence probes for in vivo biological imaging. The long-time observation for fluorescence alternation of CDs in zebrafish and the quenching assay of CDs by ATP, NADH and Fe3+ ions demonstrated that the decaying process of CDs in vivo might be induced by the synergistic effect of the metabolism process. All results indicated that large batches and high QYs of CDs can be acquired by employing natural and nontoxic hair and skin as precursors. To our knowledge, this is the first time to report SCDs, in vivo comparative studies of HCDs, SCDs and CCDs as bioprobes, and explore their mechanism of photostability in zebrafish.

  11. In vivo characterization of hair and skin derived carbon quantum dots with high quantum yield as long-term bioprobes in zebrafish

    PubMed Central

    Zhang, Jing-Hui; Niu, Aping; Li, Jing; Fu, Jian-Wei; Xu, Qun; Pei, De-Sheng

    2016-01-01

    Carbon quantum dots (CDs) were widely investigated because of their tunable fluorescence properties and low toxicity. However, so far there have been no reports on in vivo functional studies of hair and skin derived CDs. Here, hair derived CDs (HCDs) and skin derived CDs (SCDs) were produced by using human hair and pig skin as precursors. The quantum yields (QYs) of HCDs and SCDs were quite high, compared to citric acid derived CDs (CCDs). HCDs and SCDs possess optimal photostability, hypotoxicity and biocompatibility in zebrafish, indicating that HCDs and SCDs possess the capacity of being used as fluorescence probes for in vivo biological imaging. The long-time observation for fluorescence alternation of CDs in zebrafish and the quenching assay of CDs by ATP, NADH and Fe3+ ions demonstrated that the decaying process of CDs in vivo might be induced by the synergistic effect of the metabolism process. All results indicated that large batches and high QYs of CDs can be acquired by employing natural and nontoxic hair and skin as precursors. To our knowledge, this is the first time to report SCDs, in vivo comparative studies of HCDs, SCDs and CCDs as bioprobes, and explore their mechanism of photostability in zebrafish. PMID:27886267

  12. Freestanding carbon nanodots/poly (vinyl alcohol) films with high photoluminescent quantum yield realized by inverted-pyramid structure

    NASA Astrophysics Data System (ADS)

    Pang, Linna; Ba, Lixiang; Pan, Wei; Shen, Wenzhong

    2017-02-01

    Carbon nanodots (C-dots) have attracted great attention for their biocompatibility and strong tunable photoluminescence (PL). However, aggregation-induced PL quenching blocks their practical application in solid-state optoelectronics. Here, we report a luminescent C-dots freestanding film with a substantially enhanced high quantum yield (QY) of 72.3%. A facile template method, rather than complicate lithography and etching technique is proposed to fabricate the C-dots composite films with large-area (8 inch × 8 inch) ordered micro-scale inverted-pyramid patterns on the surface. The control experiment and theoretical analysis demonstrate the key success to QY enhancement lies in the separation of C-dots and the pattern of surface inverted-pyramid structure. This work realizes the QY enhancement simply by geometrical optics, not the chemical treatment of luminescent particles. It provides a general approach to fabricate large-area freestanding luminescent composite film with high QY.

  13. Hydrogen quantum yields in the 360 nm photolysis of Eu/2+/ solutions and their relationship to photochemical fuel formation

    NASA Technical Reports Server (NTRS)

    Ryason, P. R.

    1977-01-01

    Water decomposition by a cyclic photoredox process is discussed in general terms. Thermodynamics determines the wavelength of the charge-transfer band corresponding to electron transfer to or from water of hydration of a cation. These relationships indicate that it is unlikely that a photoreduction reaction resulting in water decomposition will occur in the sea-level solar range of wavelengths. Such is not the case for photooxidation, and an example is known: the photolysis of Eu(2+) in aqueous solution. Hydrogen quantum yields have been determined for this reaction. They are sufficiently high (about 0.3) as to offer encourangement for the further exploration of photoredox reactions as a means of solar energy conversion.

  14. Freestanding carbon nanodots/poly (vinyl alcohol) films with high photoluminescent quantum yield realized by inverted-pyramid structure.

    PubMed

    Pang, Linna; Ba, Lixiang; Pan, Wei; Shen, Wenzhong

    2017-02-24

    Carbon nanodots (C-dots) have attracted great attention for their biocompatibility and strong tunable photoluminescence (PL). However, aggregation-induced PL quenching blocks their practical application in solid-state optoelectronics. Here, we report a luminescent C-dots freestanding film with a substantially enhanced high quantum yield (QY) of 72.3%. A facile template method, rather than complicate lithography and etching technique is proposed to fabricate the C-dots composite films with large-area (8 inch × 8 inch) ordered micro-scale inverted-pyramid patterns on the surface. The control experiment and theoretical analysis demonstrate the key success to QY enhancement lies in the separation of C-dots and the pattern of surface inverted-pyramid structure. This work realizes the QY enhancement simply by geometrical optics, not the chemical treatment of luminescent particles. It provides a general approach to fabricate large-area freestanding luminescent composite film with high QY.

  15. Kinetically Stable Lanthanide Complexes Displaying Exceptionally High Quantum Yields upon Long-Wavelength Excitation: Synthesis, Photophysical Properties, and Solution Speciation.

    PubMed

    Routledge, Jack D; Jones, Michael W; Faulkner, Stephen; Tropiano, Manuel

    2015-04-06

    We demonstrate how highly emissive, kinetically stable complexes can be prepared using the macrocyclic scaffold of DO3A bearing coordinating aryl ketones as highly effective sensitizing chromophores. In the europium complexes, high quantum yields (up to 18% in water) can be combined with long-wavelength excitation (370 nm). The behavior in solution upon variation of pH, studied by means of UV-vis absorption, emission, and NMR spectroscopies, reveals that the nature of the chromophore can give rise to pH-dependent behavior as a consequence of deprotonation adjacent to the carbonyl group. Knowledge of the molecular speciation in solution is therefore critical when assessing the luminescence properties of such complexes.

  16. Diurnal changes of photosynthetic quantum yield in the intertidal macroalga Sargassum thunbergii under simulated tidal emersion conditions

    NASA Astrophysics Data System (ADS)

    Yu, Yong Qiang; Zhang, Quan Sheng; Tang, Yong Zheng; Li, Xue Meng; Liu, Hong Liang; Li, Li Xia

    2013-07-01

    In this study, a three-way factorial experimental design was used to investigate the diurnal changes of photosynthetic activity of the intertidal macroalga Sargassum thunbergii in response to temperature, tidal pattern and desiccation during a simulated diurnal light cycle. The maximum (Fv/Fm) and effective (ΦPSII) quantum yields of photosystem II (PSII) were estimated by chlorophyll fluorescence using a pulse amplitude modulated fluorometer. Results showed that this species exhibited sun-adapted characteristics, as evidenced by the daily variation of Fv/Fm and ΦPSII. Both yield values decreased with increasing irradiance towards noon and recovered rapidly in the afternoon suggesting a dynamic photoinhibition. The photosynthetic quantum yield of S. thunbergii thalli varied significantly with temperature, tidal pattern and desiccation. Thalli were more susceptible to light-induced damage at high temperature of 25 °C and showed complete recovery of photosynthetic activity only when exposed to 8 °C. In contrast with the mid-morning low tide period, although there was an initial increase in photosynthetic yield during emersion, thalli showed a greater degree of decline at the end of emersion and remained less able to recover when low tide occurred at mid-afternoon. Short-term air exposure of 2 h did not significantly influence the photosynthesis. However, when exposed to moderate conditions (4 h desiccation at 15 °C or 6 h desiccation at 8 °C), a significant inhibition of photosynthesis was followed by partial or complete recovery upon re-immersion in late afternoon. Only extreme conditions (4 h desiccation at 25 °C or 6 h desiccation at 15 °C or 25 °C) resulted in the complete inhibition, with little indication of recovery until the following morning, implying the occurrence of chronic PSII damage. Based on the magnitude of effect, desiccation was the predominant negative factor affecting the photosynthesis under the simulated daytime irradiance period. These

  17. Phosphorescent Iridium(III) Complexes Bearing Fluorinated Aromatic Sulfonyl Group with Nearly Unity Phosphorescent Quantum Yields and Outstanding Electroluminescent Properties.

    PubMed

    Zhao, Jiang; Yu, Yue; Yang, Xiaolong; Yan, Xiaogang; Zhang, Huiming; Xu, Xianbin; Zhou, Guijiang; Wu, Zhaoxin; Ren, Yixia; Wong, Wai-Yeung

    2015-11-11

    A series of heteroleptic functional Ir(III) complexes bearing different fluorinated aromatic sulfonyl groups has been synthesized. Their photophysical features, electrochemical behaviors, and electroluminescent (EL) properties have been characterized in detail. These complexes emit intense yellow phosphorescence with exceptionally high quantum yields (ΦP > 0.9) at room temperature, and the emission maxima of these complexes can be finely tuned depending upon the number of the fluorine substituents on the pendant phenyl ring of the sulfonyl group. Furthermore, the electrochemical properties and electron injection/transporting (EI/ET) abilities of these Ir(III) phosphors can also be effectively tuned by the fluorinated aromatic sulfonyl group to furnish some desired characters for enhancing the EL performance. Hence, the maximum luminance efficiency (ηL) of 81.2 cd A(-1), corresponding to power efficiency (ηP) of 64.5 lm W(-1) and external quantum efficiency (ηext) of 19.3%, has been achieved, indicating the great potential of these novel phosphors in the field of organic light-emitting diodes (OLEDs). Furthermore, a clear picture has been drawn for the relationship between their optoelectronic properties and chemical structures. These results should provide important information for developing highly efficient phosphors.

  18. Developing a diagnostic model for estimating terrestrial vegetation gross primary productivity using the photosynthetic quantum yield and Earth Observation data.

    PubMed

    Ogutu, Booker O; Dash, Jadunandan; Dawson, Terence P

    2013-09-01

    This article develops a new carbon exchange diagnostic model [i.e. Southampton CARbon Flux (SCARF) model] for estimating daily gross primary productivity (GPP). The model exploits the maximum quantum yields of two key photosynthetic pathways (i.e. C3 and C4 ) to estimate the conversion of absorbed photosynthetically active radiation into GPP. Furthermore, this is the first model to use only the fraction of photosynthetically active radiation absorbed by photosynthetic elements of the canopy (i.e. FAPARps ) rather than total canopy, to predict GPP. The GPP predicted by the SCARF model was comparable to in situ GPP measurements (R(2)  > 0.7) in most of the evaluated biomes. Overall, the SCARF model predicted high GPP in regions dominated by forests and croplands, and low GPP in shrublands and dry-grasslands across USA and Europe. The spatial distribution of GPP from the SCARF model over Europe and conterminous USA was comparable to those from the MOD17 GPP product except in regions dominated by croplands. The SCARF model GPP predictions were positively correlated (R(2)  > 0.5) to climatic and biophysical input variables indicating its sensitivity to factors controlling vegetation productivity. The new model has three advantages, first, it prescribes only two quantum yield terms rather than species specific light use efficiency terms; second, it uses only the fraction of PAR absorbed by photosynthetic elements of the canopy (FAPARps ) hence capturing the actual PAR used in photosynthesis; and third, it does not need a detailed land cover map that is a major source of uncertainty in most remote sensing based GPP models. The Sentinel satellites planned for launch in 2014 by the European Space Agency have adequate spectral channels to derive FAPARps at relatively high spatial resolution (20 m). This provides a unique opportunity to produce global GPP operationally using the Southampton CARbon Flux (SCARF) model at high spatial resolution.

  19. Bacterial Inactivation by a Singlet Oxygen Bubbler: Identifying Factors Controlling the Toxicity of 1O2 Bubbles

    PubMed Central

    Bartusik, Dorota; Aebisher, David; Lyons, Alan

    2013-01-01

    A microphotoreactor device was developed to generate bubbles (sized: 1.4 mm diameter, 90 μL) containing singlet oxygen at levels toxic to bacteria and fungus. As singlet oxygen decays rapidly to triplet oxygen, the bubbles leave behind no waste or by-products other than O2. From a comparative study in deaerated, air saturated, and oxygenated solutions, it was reasoned that the singlet oxygen bubbles inactivate Escherichia coli and Aspergillus fumigatus, mainly by an oxygen gradient inside and outside of the bubble such that singlet oxygen is solvated and diffuses through the aqueous solution until it reacts with the target organism. Thus, singlet oxygen bubble toxicity was inversely proportional to the amount of dissolved oxygen in solution. In a second mechanism, singlet oxygen interacts directly with E. coli that accumulate at the gas-liquid interface although this mechanism operates at a rate approximately 10 times slower. Due to encapsulation in the gaseous core of the bubble and a 0.98 ms lifetime, the bubbles can traverse relatively long 0.39 mm distances carrying 1O2 far into the solution; by comparison the diffusion distance of 1O2 fully solvated in H2O is much shorter (~150 nm). Bubbles that reached the outer air/water interface contained no 1O2. The mechanism by which 1O2 deactivated organisms was explored through the addition of detergent molecules and Ca2+ ions. Results indicate that the preferential accumulation of E. coli at the air-water interface of the bubble leads to enhanced toxicity of bubbles containing 1O2. The singlet oxygen device offers intriguing possibilities for creating new types of disinfection strategies based on photodynamic (1O2) bubble carriers. PMID:23075418

  20. Electronic structure of Rh-based CuRh0.9Mg0.1O2 oxide thermoelectrics

    NASA Astrophysics Data System (ADS)

    Vilmercati, P.; Martin, E.; Cheney, C. Parks; Bondino, F.; Magnano, E.; Parmigiani, F.; Sasagawa, T.; Mannella, N.

    2013-03-01

    The electronic structure of the Rh-based CuRh0.9Mg0.1O2 oxide thermoelectric compound has been studied with a multitechnique approach consisting of photoemission, x-ray absorption, and x-ray emission spectroscopies. The data indicate that the region of the valence band in the proximity of the Fermi level is dominated by Rh-derived states. These findings outline the importance of the electronic structure of the Rh ions for the large thermoelectric power in CuRh0.9Mg0.1O2 at high temperature.

  1. Total integral reactive cross sections for F + H2 yielding HF + H - Comparison of converged quantum, quasiclassical trajectory and experimental results

    NASA Technical Reports Server (NTRS)

    Neuhauser, Daniel; Judson, Richard S.; Jaffe, Richard L.; Baer, Michael; Kouri, Donald J.

    1991-01-01

    The paper reports converged quantum total integral reactive cross sections for the reaction F + H2 yielding HF + H, for initial rotational states j sub i = 0 and 1, using a time-dependent method. The results are compared to classical results and to the experimental results of Neumark et al. (1985). Strong quantum effects are found in the threshold region for both initial states (i.e., in the dependence of the reaction on initial state for low energies). The classical results agree better with experiment than do the quantum results; this appears to be due to errors in the potential used.

  2. Enhanced hydrogen production by doping Pr into Ce0.9Hf0.1O2 for thermochemical two-step water-splitting cycle

    NASA Astrophysics Data System (ADS)

    Meng, Qing-Long; Tamaura, Yutaka

    2014-03-01

    We synthesized (Ce0.9Hf0.1)1-xPrxO2-δ (x=0, 0.05 and 0.1) using the polymerized complex method. The synthesized samples, as well as the samples after thermochemical two-step water-splitting cycles have a fluorite structure and Pr exists in the solid solutions with both trivalent and tetravalent states, as suggested by powder X-ray Diffraction (XRD) Patterns. The reduction fraction of Ce4+ in redox cycles (oxidation step in air) and two-step water-splitting cycles (oxidation step in steam) indicates that the addition of Pr into Ce-Hf oxide solid solution cannot improve the reduction fraction of Ce4+ during the redox cycles but both the reduction fraction of Ce4+ and H2 yield are significantly enhanced during two-step water-splitting cycles. The chemical composition of 10 mol% Pr doped Ce0.9Hf0.1O2 exhibits the highest reactivity for hydrogen production in H2-generation step by yielding an average amount of 5.72 ml g-1 hydrogen gas, which is much higher than that evolved by Ce0.9Hf0.1O2 (4.50 ml g-1). The enhancement effect of doping Pr on the performance during two-step water-splitting cycles is because of the multivalent properties of Pr, which can: (1) reduce the amount of Ce3+ oxidized by contamination air (contamination air eliminated by partial oxidation of Pr3+ to Pr4+) in H2-generation step; (2) enhance the reaction rate in H2-generation step by improving the ionic conductivity (extrinsic oxygen vacancies created by the substitution of Ce4+ by Pr3+).

  3. Quantum wave packet study of nonadiabatic effects in O({sup 1}D) + H{sub 2} {yields} OH + H

    SciTech Connect

    Gray, S.K.; Petrongolo, C.; Drukker, K.; Schatz, G.C.

    1999-11-25

    The authors develop a wave packet approach to treating the electronically nonadiabatic reaction dynamics of O({sup 1}D) + H{sub 2} {yields} OH + H, allowing for the 1{sup 1}A{prime} and 2{sup 1}A{prime} potential energy surfaces and couplings, as well as the three internal nuclear coordinates. Two different systems of coupled potential energy surfaces are considered, a semiempirical diatomics-in-molecules (DIM) system due to Kuntz, Niefer, and Sloan, and a recently developed ab initio system due to Dobbyn and Knowles (DK). Nonadiabatic quantum results, with total angular momentum J = 0, are obtained and discussed. Several single surface calculations are carried out for comparison with the nonadiabatic results. Comparisons with trajectory surface hopping (TSH) calculations, and with approximate quantum calculations, are also included. The electrostatic coupling produces strong interactions between the 1{sup 1}A{prime} and 2{sup 1}A{prime} states at short range (where these states have a conical intersection) and weak but, interestingly, nonnegligible interactions between these states at longer range. The wave packet results show that if the initial state is chosen to be effectively the 1A{prime} state (for which insertion to form products occurs on the adiabatic surface), then there is very little difference between the adiabatic and coupled surface results. In either case the reaction probability is a relatively flat function of energy, except for resonant oscillations. However, the 2A{prime} reaction, dynamics (which involves a collinear transition state) is strongly perturbed by nonadiabatic effects in two distinct ways. At energies above the transition state barrier, the diabatic limit is dominant, and the 2A{prime} reaction probability is similar to that for 1A{double{underscore}prime}, which has no coupling with the other surfaces. At energies below the barrier, the authors find a significant component of the reaction probability from long range electronic

  4. Room-temperature and gram-scale synthesis of CsPbX3 (X = Cl, Br, I) perovskite nanocrystals with 50-85% photoluminescence quantum yields.

    PubMed

    Wei, Song; Yang, Yanchun; Kang, Xiaojiao; Wang, Lan; Huang, Lijian; Pan, Daocheng

    2016-05-26

    All inorganic CsPbX3 (X = Cl, Br, I) perovskite nanocrystals (PNCs) with 50-85% photoluminescence quantum yields and tunable emission in the range of 440-682 nm have been successfully synthesized at room temperature in open air. This facile strategy enables us to prepare gram-scale CsPbBr3 NCs with a PLQY approaching 80%.

  5. Molar Absorptivity and Concentration-Dependent Quantum Yield of Fe(II) Photo-Formation for the Aqueous Solutions of Fe(III)-Dicarboxylate Complexes

    NASA Astrophysics Data System (ADS)

    Hitomi, Y.; Arakaki, T.

    2009-12-01

    Redox cycles of iron in the aquatic environment affect formation of reactive oxygen species such as hydrogen peroxide and hydroxyl radicals, which in turn determines lifetimes of many organic compounds. Although aqueous Fe(III)-dicarboxylate complexes are considered to be important sources of photo-formed Fe(II), molar absorptivity and quantum yield of Fe(II) formation for individual species are not well understood. We initiated a study to characterize Fe(II) photo-formation from Fe(III)-dicarboxylates with the concentration ranges that are relevant to the natural aquatic environment. The Visual MINTEQ computer program was used to calculate the equilibrium concentrations of individual Fe(III)-dicarboxylate species. The molar absorptivity of Fe(III)-dicarboxylate species was obtained by UV-VIS spectrophotometer, and the product of the quantum yield and the molar absorptivity of Fe(III)-dicarboxylate species were obtained from photochemical experiments. These experimental data were combined with the calculated equilibrium Fe(III)-dicarboxylate concentrations to determine individual molar absorptivity and quantum yield of Fe(II) photo-formation for a specific Fe(III)-dicarboxylate species. We used initial concentrations of less than 10 micromolar Fe(III) to study the photochemical formation of Fe(II). Dicarboxylate compounds studied include oxalate, malonate, succinate, malate, and phthalate. We report molar absorptivity and concentration-dependent quantum yields of Fe(II) photo-formation of individual Fe(III)-dicarboxylates.

  6. Synthesis and formation mechanistic investigation of nitrogen-doped carbon dots with high quantum yields and yellowish-green fluorescence

    NASA Astrophysics Data System (ADS)

    Hou, Juan; Wang, Wei; Zhou, Tianyu; Wang, Bo; Li, Huiyu; Ding, Lan

    2016-05-01

    Heteroatom doped carbon dots (CDs) have received increasing attention due to their unique properties and related applications. However, previously reported CDs generally show strong emission only in the blue-light region, thus restricting their further applications. And the fundamental investigation on the preparation process is always neglected. Herein, we have developed a simple and solvent-free synthetic strategy to fabricate nitrogen-doped CDs (N-CDs) from citric acid and dicyandiamide. The as-prepared N-CDs exhibited a uniform size distribution, strong yellowish-green fluorescence emission and a high quantum yield of 73.2%. The products obtained at different formation stages were detailedly characterized by transmission electron microscopy, X-ray diffraction spectrometer, X-ray photoelectron spectroscopy and UV absorbance spectroscopy. A possible formation mechanism has thus been proposed including dehydration, polymerization and carbonization. Furthermore, the N-CDs could serve as a facile and label-free probe for the detection of iron and fluorine ions with detection limits of 50 nmol L-1 and 75 nmol L-1, respectively.Heteroatom doped carbon dots (CDs) have received increasing attention due to their unique properties and related applications. However, previously reported CDs generally show strong emission only in the blue-light region, thus restricting their further applications. And the fundamental investigation on the preparation process is always neglected. Herein, we have developed a simple and solvent-free synthetic strategy to fabricate nitrogen-doped CDs (N-CDs) from citric acid and dicyandiamide. The as-prepared N-CDs exhibited a uniform size distribution, strong yellowish-green fluorescence emission and a high quantum yield of 73.2%. The products obtained at different formation stages were detailedly characterized by transmission electron microscopy, X-ray diffraction spectrometer, X-ray photoelectron spectroscopy and UV absorbance spectroscopy. A

  7. Photosensitized electron transfer processes in SiO2 colloids and sodium lauryl sulfate micellar systems: Correlation of quantum yields with interfacial surface potentials

    PubMed Central

    Laane, Colja; Willner, Itamar; Otvos, John W.; Calvin, Melvin

    1981-01-01

    The effectiveness of negatively charged colloidal SiO2 particles in controlling photosensitized electron transfer reactions has been studied and compared with that of the negatively charged sodium lauryl sulfate (NaLauSO4) micellar system. In particular, the photosensitized reduction of the zwitterionic electron acceptor propylviologen sulfonate (PVS0) with tris(2,2′-bipyridinium)ruthenium(II) [Ru(bipy)32+] as the sensitizer and triethanolamine as the electron donor is found to have a quantum yield of 0.033 for formation of the radical anion (PVS[unk]) in the SiO2 colloid compared with 0.005 in the homogeneous system and 0.0086 in a NaLauSO4 micellar solution. The higher quantum yields obtained with the SiO2 colloidal system are attributed to substantial stabilization against back reaction of the intermediate photoproducts—i.e., Ru(bipy)33+ and PVS[unk]—by electrostatic repulsion of the reduced electron acceptor from the negatively charged particle surface. The binding properties of the SiO2 particles and NaLauSO4 micelles were investigated by flow dialysis. The results show that the sensitizer binds to both interfaces and that the SiO2 interface is characterized by a much higher surface potential than the micellar interface (≈-170 mV vs. -85 mV). The effect of ionic strength on the surface potential was estimated from the Gouy-Chapman theory, and the measured quantum yields of photosensitized electron transfer were correlated with surface potential at different ionic strengths. This correlation shows that the quantum yield is not affected by surface potentials smaller than ≈-40 mV. At larger potentials, the quantum yield increases rapidly. The quantum yield obtained in the micellar system at different strengths fits nicely on the correlation curve for the colloid SiO2 system. These results indicate that the surface potential is the dominant factor in the quantum yield improvement for PVS0 reduction. PMID:16593095

  8. Binding of 3O2 and 1O2 to dyes used in photodynamic therapy in gas phase and aqueous media

    NASA Astrophysics Data System (ADS)

    Kushwaha, P. S.; Mishra, P. C.

    Density functional theory (DFT) was employed at the B3LYP/6-31+G* level to study complexes of 1O2 and 3O2 with the dye molecules proflavine, methylene blue, and acridine orange, which are useful in photodynamic therapy. It was found that the most stable complex between 1O2 and proflavine are formed when 1O2 is located above the central ring, while the most stable complex between 1O2 and methylene blue is formed when 1O2 is located above the molecular plane, but not above any of the rings, near the sulfur atom. 1O2 can make a stable complex with acridine orange, as it is located above the outer ring of the dye. The binding energies of the complexes of 1O2 with all three dyes are enhanced considerably in going from gas phase to aqueous media. The complexes of 3O2 with the dyes will be unstable in all cases, while those of 1O2 with the same will be quite stable and will not be dissociated due to thermal fluctuations at room temperature. In the complexes of 1O2 and 3O2 with the dyes, charge transfer occurs from the dyes to the O2 moiety, the amount of charge transfer being much more to 1O2 than to 3O2 in each case.

  9. Measurement procedure for absolute broadband infrared up-conversion photoluminescent quantum yields: Correcting for absorption/re-emission

    SciTech Connect

    MacDougall, Sean K. W.; Ivaturi, Aruna; Marques-Hueso, Jose; Richards, Bryce S.

    2014-06-15

    The internal photoluminescent quantum yield (iPLQY) – defined as the ratio of emitted photons to those absorbed – is an important parameter in the evaluation and application of luminescent materials. The iPLQY is rarely reported due to the complexities in the calibration of such a measurement. Herein, an experimental method is proposed to correct for re-emission, which leads to an underestimation of the absorption under broadband excitation. Although traditionally the iPLQY is measured using monochromatic sources for linear materials, this advancement is necessary for nonlinear materials with wavelength dependent iPLQY, such as the application of up-conversion to solar energy harvesting. The method requires an additional measurement of the emission line shape that overlaps with the excitation and absorption spectra. Through scaling of the emission spectrum, at the long wavelength edge where an overlap of excitation does not occur, it is possible to better estimate the value of iPLQY. The method has been evaluated for a range of nonlinear material concentrations and under various irradiances to analyze the necessity and boundary conditions that favor the proposed method. Use of this refined method is important for a reliable measurement of iPLQY under a broad illumination source such as the Sun.

  10. A comparative study of maximal quantum yield of photosystem II to determine nitrogen and phosphorus limitation on two marine algae

    NASA Astrophysics Data System (ADS)

    Qi, Hongju; Wang, Jiangtao; Wang, Zhaoyu

    2013-07-01

    We studied the effects of nitrogen and phosphorus supply on Fv/Fm (maximal quantum yield of photosystem II) in the diatom Chaetoceros debilis and dinoflagellate Scrippsiella trochoidea in nitrogen (N) and phosphorus (P) depleted cultures to determine whether this parameter could be used to monitor N or P limitation. In the nutrient depleted experiments, no obvious decrease of cell density and chlorophyll concentration was observed except in N-depleted incubation of S. trochoidea. For C. debilis, Fv/Fm decreased quickly in periods of N- and P-depletion and re-supply of N and P induced a quick recovery of Fv/Fm. However, in S. trochoidea culture, Fv/Fm remained unchanged in N- and P-depleted conditions and addition of sufficient N and P to N- and P-depleted cultures did not affect Fv/Fm. Therefore, Fv/Fm is insensitive to N and/or P limitation in growth of S. trochoidea. The results suggested that Fv/Fm was not a robust diagnostic for nutrient limitation in dinoflagellates. The differences in the sensitivity of Fv/Fm to nutrient limitation may result from different nutrient storage abilities among algal species.

  11. Low cost 3D-printing used in an undergraduate project: an integrating sphere for measurement of photoluminescence quantum yield

    NASA Astrophysics Data System (ADS)

    Tomes, John J.; Finlayson, Chris E.

    2016-09-01

    We report upon the exploitation of the latest 3D printing technologies to provide low-cost instrumentation solutions, for use in an undergraduate level final-year project. The project addresses prescient research issues in optoelectronics, which would otherwise be inaccessible to such undergraduate student projects. The experimental use of an integrating sphere in conjunction with a desktop spectrometer presents opportunities to use easily handled, low cost materials as a means to illustrate many areas of physics such as spectroscopy, lasers, optics, simple circuits, black body radiation and data gathering. Presented here is a 3rd year undergraduate physics project which developed a low cost (£25) method to manufacture an experimentally accurate integrating sphere by 3D printing. Details are given of both a homemade internal reflectance coating formulated from readily available materials, and a robust instrument calibration method using a tungsten bulb. The instrument is demonstrated to give accurate and reproducible experimental measurements of luminescence quantum yield of various semiconducting fluorophores, in excellent agreement with literature values.

  12. Controls of the quantum yield and saturation light of isoprene emission in different-aged aspen leaves.

    PubMed

    Niinemets, Ülo; Sun, Zhihong; Talts, Eero

    2015-12-01

    Leaf age alters the balance between the use of end-product of plastidic isoprenoid synthesis pathway, dimethylallyl diphosphate (DMADP), in prenyltransferase reactions leading to synthesis of pigments of photosynthetic machinery and in isoprene synthesis, but the implications of such changes on environmental responses of isoprene emission have not been studied. Because under light-limited conditions, isoprene emission rate is controlled by DMADP pool size (SDMADP ), shifts in the share of different processes are expected to particularly strongly alter the light dependency of isoprene emission. We examined light responses of isoprene emission in young fully expanded, mature and old non-senescent leaves of hybrid aspen (Populus tremula x P. tremuloides) and estimated in vivo SDMADP and isoprene synthase activity from post-illumination isoprene release. Isoprene emission capacity was 1.5-fold larger in mature than in young and old leaves. The initial quantum yield of isoprene emission (αI ) increased by 2.5-fold with increasing leaf age primarily as the result of increasing SDMADP . The saturating light intensity (QI90 ) decreased by 2.3-fold with increasing leaf age, and this mainly reflected limited light-dependent increase of SDMADP possibly due to feedback inhibition by DMADP. These major age-dependent changes in the shape of the light response need consideration in modelling canopy isoprene emission.

  13. Facile Synthesis of pH-sensitive Germanium Nanocrystals with High Quantum Yield for Intracellular Acidic Compartment Imaging.

    PubMed

    Li, Feng; Wang, Jing; Sun, Shuqing; Wang, Hai; Tang, Zhiyong; Nie, Guangjun

    2015-04-24

    A green-light emitting germanium nanocrystal-based biosensor to monitor lysosomal pH changes is developed. The Ge nanocrystals are synthesized in an aqueous solution with a significantly enhanced photoluminescence quantum yield of 26%. This synthesis involves a facile solution based route which avoided the use of toxic or environmentally unfriendly agents. Importantly, the photoluminescence intensity of the synthesized Ge nanocrystals is particularly sensitive to changes in pH between 5 and 6. When incubated with cultured cells, the nanocrystals are internalized and subsequently translocated via the lysosomal pathway, and the Ge nanocrystals' fluorescence are greatly enhanced, even when the lysosomal pH is only slightly increased. These results reveal that the Ge nanocrystals possess high pH sensitivity compared to a commercially available dye, LysoSensor Green DND-189. The fluorescent properties of the Ge nanocrystals are demonstrated to be dependent on both the crystal form and their surface chemistry. The superior fluorescence properties and bioapplicability of the Ge nanocrystals makes them a promising intracellular bioimaging probe for monitoring various pH-sensitive processes in cells.

  14. Accounting for the decrease of photosystem photochemical efficiency with increasing irradiance to estimate quantum yield of leaf photosynthesis.

    PubMed

    Yin, Xinyou; Belay, Daniel W; van der Putten, Peter E L; Struik, Paul C

    2014-12-01

    Maximum quantum yield for leaf CO2 assimilation under limiting light conditions (Φ CO2LL) is commonly estimated as the slope of the linear regression of net photosynthetic rate against absorbed irradiance over a range of low-irradiance conditions. Methodological errors associated with this estimation have often been attributed either to light absorptance by non-photosynthetic pigments or to some data points being beyond the linear range of the irradiance response, both causing an underestimation of Φ CO2LL. We demonstrate here that a decrease in photosystem (PS) photochemical efficiency with increasing irradiance, even at very low levels, is another source of error that causes a systematic underestimation of Φ CO2LL. A model method accounting for this error was developed, and was used to estimate Φ CO2LL from simultaneous measurements of gas exchange and chlorophyll fluorescence on leaves using various combinations of species, CO2, O2, or leaf temperature levels. The conventional linear regression method under-estimated Φ CO2LL by ca. 10-15%. Differences in the estimated Φ CO2LL among measurement conditions were generally accounted for by different levels of photorespiration as described by the Farquhar-von Caemmerer-Berry model. However, our data revealed that the temperature dependence of PSII photochemical efficiency under low light was an additional factor that should be accounted for in the model.

  15. Photolysis of CH₃CHO at 248 nm: evidence of triple fragmentation from primary quantum yield of CH₃ and HCO radicals and H atoms.

    PubMed

    Morajkar, Pranay; Bossolasco, Adriana; Schoemaecker, Coralie; Fittschen, Christa

    2014-06-07

    Radical quantum yields have been measured following the 248 nm photolysis of acetaldehyde, CH3CHO. HCO radical and H atom yields have been quantified by time resolved continuous wave Cavity Ring Down Spectroscopy in the near infrared following their conversion to HO2 radicals by reaction with O2. The CH3 radical yield has been determined using the same technique following their conversion into CH3O2. Absolute yields have been deduced for HCO radicals and H atoms through fitting of time resolved HO2 profiles, obtained under various O2 concentrations, to a complex model, while the CH3 yield has been determined relative to the CH3 yield from 248 nm photolysis of CH3I. Time resolved HO2 profiles under very low O2 concentrations suggest that another unknown HO2 forming reaction path exists in this reaction system besides the conversion of HCO radicals and H atoms by reaction with O2. HO2 profiles can be well reproduced under a large range of experimental conditions with the following quantum yields: CH3CHO + hν(248nm) → CH3CHO*, CH3CHO* → CH3 + HCO ϕ(1a) = 0.125 ± 0.03, CH3CHO* → CH3 + H + CO ϕ(1e) = 0.205 ± 0.04, CH3CHO*[Formula: see text]CH3CO + HO2 ϕ(1f) = 0.07 ± 0.01. The CH3O2 quantum yield has been determined in separate experiments as ϕ(CH₃) = 0.33 ± 0.03 and is in excellent agreement with the CH3 yields derived from the HO2 measurements considering that the triple fragmentation (R1e) is an important reaction path in the 248 nm photolysis of CH3CHO. From arithmetic considerations taking into account the HO2 and CH3 measurements we deduce a remaining quantum yield for the molecular pathway: CH3CHO* → CH4 + CO ϕ(1b) = 0.6. All experiments can be consistently explained with absence of the formerly considered pathway: CH3CHO* → CH3CO + H ϕ(1c) = 0.

  16. Upconverting core-shell nanocrystals with high quantum yield under low irradiance: On the role of isotropic and thick shells

    SciTech Connect

    Fischer, Stefan; Goldschmidt, Jan Christoph; Johnson, Noah J. J.; Pichaandi, Jothirmayanantham; Veggel, Frank C. J. M. van

    2015-11-21

    Colloidal upconverter nanocrystals (UCNCs) that convert near-infrared photons to higher energies are promising for applications ranging from life sciences to solar energy harvesting. However, practical applications of UCNCs are hindered by their low upconversion quantum yield (UCQY) and the high irradiances necessary to produce relevant upconversion luminescence. Achieving high UCQY under practically relevant irradiance remains a major challenge. The UCQY is severely limited due to non-radiative surface quenching processes. We present a rate equation model for migration of the excitation energy to show that surface quenching does not only affect the lanthanide ions directly at the surface but also many other lanthanide ions quite far away from the surface. The average migration path length is on the order of several nanometers and depends on the doping as well as the irradiance of the excitation. Using Er{sup 3+}-doped β-NaYF{sub 4} UCNCs, we show that very isotropic and thick (∼10 nm) β-NaLuF{sub 4} inert shells dramatically reduce the surface-related quenching processes, resulting in much brighter upconversion luminescence at simultaneously considerably lower irradiances. For these UCNCs embedded in poly(methyl methacrylate), we determined an internal UCQY of 2.0% ± 0.2% using an irradiance of only 0.43 ± 0.03 W/cm{sup 2} at 1523 nm. Normalized to the irradiance, this UCQY is 120× higher than the highest values of comparable nanomaterials in the literature. Our findings demonstrate the important role of isotropic and thick shells in achieving high UCQY at low irradiances from UCNCs. Additionally, we measured the additional short-circuit current due to upconversion in silicon solar cell devices as a proof of concept and to support our findings determined using optical measurements.

  17. The enhancement of fluorescence quantum yields of anilino naphthalene sulfonic acids by inclusion of various cyclodextrins and cucurbit[7]uril.

    PubMed

    Sueishi, Yoshimi; Fujita, Tomonori; Nakatani, Shinichiro; Inazumi, Naoya; Osawa, Yoshihiro

    2013-10-01

    The association constants (K) for the inclusion complexation of four kinds of cyclodextrins (CDs (β- and γ-), 2,6-di-O-methylated β-CD, and 2,3,6-tri-O-methylated β-CD) and cucurbit[7]uril (CB[7]) with 1,8- and 2,6-anilinonaphthalene sulfonic acids (ANSs) were determined from fluorescence spectra enhanced by inclusion. Various CDs and CB[7] form stable 1:1 inclusion complexes with 1,8- and 2,6-ANSs: K=80-11700 M(-1) for 2,6-ANS and 50-195 M(-1) for 1,8-ANS. The high stability of the inclusion complexes of 2,6-ANS with CB[7] and 2,6-di-O-methylated β-CD is shown. Further, we determined the fluorescence quantum yields (Φ values) for the inclusion complexes of ANSs by using a fluorescence spectrophotometer equipped with a half-moon unit. The Φ values of 1,8- and 2,6-ANSs were largely enhanced by the inclusion of methylated β-CDs and did not correlate with the degree of stability (K) of the inclusion complexes. We characterized the structures of the inclusion complexes by 2D ROESY-NMR measurements. In addition, the microenvironmental polarity inside the hydrophobic CD and CB[7] cavities was evaluated using the fluorescence probe 2,6-ANS. Based on the emission mechanism and the aspect of inclusion in a hydrophobic cavity, we have suggested that the microenvironmental polarity and viscosity for the excited state of ANS plays an important role for the Φ values of inclusion complexes.

  18. Photosynthetic maximum quantum yield increases are an essential component of the Southern Ocean phytoplankton response to iron.

    PubMed

    Hiscock, Michael R; Lance, Veronica P; Apprill, Amy M; Bidigare, Robert R; Johnson, Zackary I; Mitchell, B Greg; Smith, Walker O; Barber, Richard T

    2008-03-25

    It is well established that an increase in iron supply causes an increase in total oceanic primary production in many regions, but the physiological mechanism driving the observed increases has not been clearly identified. The Southern Ocean iron enrichment experiment, an iron fertilization experiment in the waters closest to Antarctica, resulted in a 9-fold increase in chlorophyll (Chl) concentration and a 5-fold increase in integrated primary production. Upon iron addition, the maximum quantum yield of photosynthesis (phi(m)) rapidly doubled, from 0.011 to 0.025 mol C.mol quanta(-1). Paradoxically, this increase in light-limited productivity was not accompanied by a significant increase in light-saturated productivity (P(max)(b)). P(max)(b), maximum Chl normalized productivity, was 1.34 mg C.mg Chl(-1).h(-1) outside and 1.49 mg C.mg Chl(-1).h(-1) inside the iron-enriched patch. The importance of phi(m) as compared with P(max)(b) in controlling the biological response to iron addition has vast implications for understanding the ecological response to iron. We show that an iron-driven increase in phi(m) is the proximate physiological mechanism affected by iron addition and can account for most of the increases in primary production. The relative importance of phi(m) over P(max)(b) in this iron-fertilized bloom highlights the limitations of often-used primary productivity algorithms that are driven by estimates of P(max)(b) but largely ignore variability in phi(m) and light-limited productivity. To use primary productivity models that include variability in iron supply in prediction or forecasting, the variability of light-limited productivity must be resolved.

  19. Accurate quantum yields by laser gain vs absorption spectroscopy - Investigation of Br/Br(asterisk) channels in photofragmentation of Br2 and IBr

    NASA Technical Reports Server (NTRS)

    Haugen, H. K.; Weitz, E.; Leone, S. R.

    1985-01-01

    Various techniques have been used to study photodissociation dynamics of the halogens and interhalogens. The quantum yields obtained by these techniques differ widely. The present investigation is concerned with a qualitatively new approach for obtaining highly accurate quantum yields for electronically excited states. This approach makes it possible to obtain an accuracy of 1 percent to 3 percent. It is shown that measurement of the initial transient gain/absorption vs the final absorption in a single time-resolved signal is a very accurate technique in the study of absolute branching fractions in photodissociation. The new technique is found to be insensitive to pulse and probe laser characteristics, molecular absorption cross sections, and absolute precursor density.

  20. Quantum yield for O-atom production in the VUV photodissociation of CO2 using the time-sliced velocity-mapped imaging (TS-VMI) method

    NASA Astrophysics Data System (ADS)

    Jackson, William M.

    2016-10-01

    VUV photodissociation above 10.5 eV is considered the primary region for photochemical destruction of CO2 by solar radiation. There is enough photon energy in this region so that in addition to ground state O(3PJ) and CO(1Σ +) that can be produced during photodissociation excited species such as atomic oxygen O(1D) and O(1S), as well as excited carbon monoxide CO(a3Π, a'3Σ+) also can be formed. Electronic excited oxygen atom and carbon monoxide are the species that are responsible for the airglows in atmospheres of the solar planets and comets. Therefore, detail photodissociation quantum yields for these excited species from CO2 are critical in interpreting the chemistry in these solar system bodies. We have previously shown that the time-sliced velocity-mapped imaging (TS-VMI) technique can provide detailed branching ratio information about photodissociation of diatomic molecules.1, 2 However, to date we have not been able to show how this technique can be use to determine absolute quantum yields for the products produced in the VUV photodissociation of CO2. In this talk we will describe how the known quantum yields for the photodissociation O2 to O(3P2), O(3P1), O(3P0) and O(1D) can be used to determine quantum yields of similar products in the photodissociation of CO2.[1] Yu Song, Hong Gao, Yih Chung Chang, D. Hammouténe, H. Ndome, M. Hochlaf, William M. Jackson, and C. Y. Ng, Ap. J., 819:23 (13pp), 2016; doi:10.3847/0004-637X/819/1/23.[2] Hong Gao, Yu Song, William M. Jackson and C. Y. Ng, J. Chem. Phys, 138, 191102, 2013.

  1. Near-Infrared Fluorescent Probe with High Quantum Yield and Its Application in the Selective Detection of Glutathione in Living Cells and Tissues.

    PubMed

    Xie, Jun-Ying; Li, Chun-Yan; Li, Yong-Fei; Fei, Junjie; Xu, Fen; Ou-Yang, Juan; Liu, Juan

    2016-10-04

    Glutathione (GSH), cysteine (Cys), and homocysteine (Hcy) are small-molecular biothiols that play key roles in various biological systems. Among these biothiols, GSH is the most abundant intracellular thiol. Until now, a small number of the near-infrared (NIR) fluorescent probes have been designed for the detection of GSH. Unfortunately, most of these NIR probes are based on cyanine dyes, which generally suffer low fluorescence quantum yield (Φ < 0.25), which are not suitable for bioimaging. In addition, some probes are difficult to effectively distinguish GSH from Cys and Hcy. In this work, an NIR fluorescent probe with high fluorescence quantum yield is developed by introducing a rigid coplanar structure such as rhodamine dyes, and the NIR probe (CyR) with spirolactam structure is first synthesized and used to recognize GSH. The characteristics of this NIR probe are as follows: (1) probe CyR exhibits high fluorescence quantum yield (Φ = 0.43) after the addition of GSH and high sensitivity toward GSH with 75-fold fluorescence enhancement. (2) The probe is highly selective, which will not interfere with the other biological thiols (Cys, Hcy) and amino acids. (3) A possible reaction mechanism of the NIR probe CyR and GSH (Cys, Hcy) can be proposed and proved by (1)H NMR, (13)C NMR, and MS (mass spectra). (4) The NIR probe displays selective detection of GSH in biological samples such as living cells and tissues.

  2. Molar Absorptivity and Quantum Yield of Fe(II) Photo-formation for the Aqueous Solutions of Fe(III)-Dicarboxylate Comlexes

    NASA Astrophysics Data System (ADS)

    Hitomi, Y.; Arakaki, T.

    2009-04-01

    Fe(III)/Fe(II) cycle in the environment affects formation of active oxygen species such as hydrogen peroxide and hydroxyl radicals, which in turn determines lifetimes of many organic compounds. Although aqueous Fe(III)-dicarboxylate complexes are considered to be an important source of photo-chemically formed Fe(II), molar absorptivity and quantum yield of Fe(II) formation for individual species are not well understood. The Visual MINTEQ computer program was used to calculate the equilibrium concentrations of individual Fe(III)-dicarboxylate species in the aqueous solutions of Fe(III)-dicarboxylate complexes. The molar absorptivity and the product of the quantum yield and the molar absorptivity of Fe(III)-dicarboxylate species were obtained by UV-VIS spectrophotometer and photochemical experiments, and these experimental data were combined with the calculated equilibrium Fe(III)-dicarboxylate concentrations to determine individual molar absorptivity and quantum yield of Fe(II) photo-formation for a specific Fe(III)-dicarboxylate species. Dicarboxylate compounds studied were oxalate, malonate, succinate, malate, and phthalate.

  3. The role of Cercospora zeae-maydis homologs of Rhodobacter sphaeroides 1O2-resistance genes in resistance to the photoactivated toxin cercosporin.

    PubMed

    Beseli, Aydin; Goulart da Silva, Marilia; Daub, Margaret E

    2015-01-01

    The photosynthetic bacterium Rhodobacter sphaeroides and plant pathogenic fungus Cercospora nicotianae have been used as models for understanding resistance to singlet oxygen ((1)O(2)), a highly toxic reactive oxygen species. In Rhodobacter and Cercospora, (1)O(2) is derived, respectively, from photosynthesis and from the (1)O(2)-generating toxin cercosporin which the fungus produces to parasitize plants. We identified common genes recovered in transcriptome studies of putative (1)O(2)-resistance genes in these two systems, suggesting common (1)O(2)-resistance mechanisms. To determine if the Cercospora homologs of R. sphaeroides (1)O(2)-resistance genes are involved in resistance to cercosporin, we expressed the genes in the cercosporin-sensitive fungus Neurospora crassa and assayed for increases in cercosporin resistance. Neurospora crassa transformants expressing genes encoding aldo/keto reductase, succinyl-CoA ligase, O-acetylhomoserine (thiol) lyase, peptide methionine sulphoxide reductase and glutathione S-transferase did not have elevated levels of cercosporin resistance. Several transformants expressing aldehyde dehydrogenase were significantly more resistant to cercosporin. Expression of the transgene and enzyme activity did not correlate with resistance, however. We conclude that although the genes tested in this study are important in (1)O(2) resistance in R. sphaeroides, their Cercospora homologs are not involved in resistance to (1)O(2) generated from cercosporin.

  4. High yield and ultrafast sources of electrically triggered entangled-photon pairs based on strain-tunable quantum dots

    NASA Astrophysics Data System (ADS)

    Zhang, Jiaxiang; Wildmann, Johannes S.; Ding, Fei; Trotta, Rinaldo; Huo, Yongheng; Zallo, Eugenio; Huber, Daniel; Rastelli, Armando; Schmidt, Oliver G.

    2015-12-01

    Triggered sources of entangled photon pairs are key components in most quantum communication protocols. For practical quantum applications, electrical triggering would allow the realization of compact and deterministic sources of entangled photons. Entangled-light-emitting-diodes based on semiconductor quantum dots are among the most promising sources that can potentially address this task. However, entangled-light-emitting-diodes are plagued by a source of randomness, which results in a very low probability of finding quantum dots with sufficiently small fine structure splitting for entangled-photon generation (~10-2). Here we introduce strain-tunable entangled-light-emitting-diodes that exploit piezoelectric-induced strains to tune quantum dots for entangled-photon generation. We demonstrate that up to 30% of the quantum dots in strain-tunable entangled-light-emitting-diodes emit polarization-entangled photons. An entanglement fidelity as high as 0.83 is achieved with fast temporal post selection. Driven at high speed, that is 400 MHz, strain-tunable entangled-light-emitting-diodes emerge as promising devices for high data-rate quantum applications.

  5. High yield and ultrafast sources of electrically triggered entangled-photon pairs based on strain-tunable quantum dots

    PubMed Central

    Zhang, Jiaxiang; Wildmann, Johannes S.; Ding, Fei; Trotta, Rinaldo; Huo, Yongheng; Zallo, Eugenio; Huber, Daniel; Rastelli, Armando; Schmidt, Oliver G.

    2015-01-01

    Triggered sources of entangled photon pairs are key components in most quantum communication protocols. For practical quantum applications, electrical triggering would allow the realization of compact and deterministic sources of entangled photons. Entangled-light-emitting-diodes based on semiconductor quantum dots are among the most promising sources that can potentially address this task. However, entangled-light-emitting-diodes are plagued by a source of randomness, which results in a very low probability of finding quantum dots with sufficiently small fine structure splitting for entangled-photon generation (∼10−2). Here we introduce strain-tunable entangled-light-emitting-diodes that exploit piezoelectric-induced strains to tune quantum dots for entangled-photon generation. We demonstrate that up to 30% of the quantum dots in strain-tunable entangled-light-emitting-diodes emit polarization-entangled photons. An entanglement fidelity as high as 0.83 is achieved with fast temporal post selection. Driven at high speed, that is 400 MHz, strain-tunable entangled-light-emitting-diodes emerge as promising devices for high data-rate quantum applications. PMID:26621073

  6. Diffusion-enhanced Förster resonance energy transfer and the effects of external quenchers and the donor quantum yield.

    PubMed

    Jacob, Maik H; Dsouza, Roy N; Ghosh, Indrajit; Norouzy, Amir; Schwarzlose, Thomas; Nau, Werner M

    2013-01-10

    effective FRET rate and the recovered donor-acceptor distance depend on the quantum yield, most strongly in the absence of diffusion, which has to be accounted for in the interpretation of distance trends monitored by FRET.

  7. LASERS IN MEDICINE: Quantum efficiency of the laser-excited singlet-oxygen-sensitised delayed fluorescence of the zinc complex of tetra(4-tert-butyl)phthalocyanine

    NASA Astrophysics Data System (ADS)

    Bashtanov, M. E.; Drozdova, N. N.; Krasnovskii, A. A.

    1999-12-01

    An investigation was made of the ratios of the intensity Idf of the singlet-oxygen(1O2)-sensitised delayed fluorescence of the zinc complex of tetra(4-tert-butyl)phthalocyanine (ZnTBPc), with the maximum at λ = 685 nm, to the intensity I1270 of the photosensitised phosphorescence of 1O2 with the maximum at λ = 1270 nm in deuterated benzene when excited with λ = 337 nm nitrogen-laser pulses. Depending on the energy density of the laser radiation (0.25 — 0.7 mJ cm-2) and on the concentration of ZnTBPc (0.06 — 3.4 μM), the ratio of the zero-time intensities of the delayed fluorescence of ZnTBPc and of the singlet-oxygen phosphorescence Idf0/I12700 varied from 0.01 to 0.2 in air-saturated solutions of ZnTBPc. The intensity Idf0 decreased fivefold as a result of saturation with oxygen of air-saturated solutions. The quantum efficiency of the delayed fluorescence was represented by the coefficient α =(Idf0/I12700)kr/(γf[1O2]0[ZnTBPc]), where [1O2]0 is the zero-time concentration of 1O2 after a laser shot; kr is the rate constant of radiative deactivation of 1O2 in the investigated solvent; γf is the quantum yield of the ZnTBPc fluorescence. It was established that in the case of air-saturated solutions of ZnTBPc this coefficient was approximately 200 times less than for metal-free tetra(4-tert-butyl)phthalocyanine and its absolute value was ~2 × 1011 M-2 s-1.

  8. Electrochemical, Spectroscopic, and 1O2 Sensitization Characteristics of 10,10-Dimethylbiladiene Complexes of Zinc and Copper

    PubMed Central

    2015-01-01

    The synthesis, electrochemistry, and photophysical characterization of a 10,10-dimethylbiladiene tetrapyrrole bearing ancillary pentafluorophenyl groups at the 5- and 15-meso positions (DMBil1) is presented. This nonmacrocyclic tetrapyrrole platform is robust and can serve as an excellent ligand scaffold for Zn2+ and Cu2+ centers. X-ray diffraction studies conducted for DMBil1 along with the corresponding Zn[DMBil1] and Cu[DMBil1] complexes show that this ligand scaffold binds a single metal ion within the tetrapyrrole core. Additionally, electrochemical experiments revealed that all three of the aforementioned compounds display an interesting redox chemistry as the DMBil1 framework can be both oxidized and reduced by two electrons. Spectroscopic and photophysical experiments carried out for DMBil1, Zn[DMBil1], and Cu[DMBil1] provide a basic picture of the electronic properties of these platforms. All three biladiene derivatives strongly absorb light in the visible region and are weakly emissive. The ability of these compounds to sensitize the formation of 1O2 at wavelengths longer than 500 nm was probed. Both the free base and Zn2+ 10,10-dimethylbiladiene architectures show modest efficiencies for 1O2 sensitization. The combination of structural, electrochemical, and photophysical data detailed herein provides a basis for the design of additional biladiene constructs for the activation of O2 and other small molecules. PMID:25187099

  9. Measuring a 10,000-fold enhancement of singlet molecular oxygen (1O2*) concentration on illuminated ice relative to the corresponding liquid solution

    NASA Astrophysics Data System (ADS)

    Bower, Jonathan P.; Anastasio, Cort

    2013-08-01

    Much attention has focused on the highly reactive hydroxyl radical in the oxidation of trace organic compounds on snow and ice (and subsequent release of volatile organics to the atmospheric boundary layer) but other oxidants are likely also important in this processing. Here we examine the ice chemistry of singlet molecular oxygen (1O2*), which can be significant in atmospheric water drops but has not been examined in ice or snow. To examine 1O2* on ice we illuminate laboratory ices containing Rose Bengal (RB) as the source of 1O2*, furfuryl alcohol (FFA) as the probe, and Na2SO4 to control the total solute concentration. We find that the 1O2*-mediated loss of FFA (and, thus, the 1O2* concentration) is up to 11,000 times greater on ice than in the equivalent liquid sample at the same photon flux. We attribute this large increase in the 1O2* steady-state concentration to the freeze-concentration of solutes into liquid-like regions (LLRs) in/on ice: compared to the initial solution, in the LLRs of ice the sources for 1O2* are highly concentrated, while the concentration of the dominant sink for 1O2* (i.e., water) remains largely unchanged. Similar to results expected in liquid solution, rates of FFA loss in ice depend on both the initial sensitizer concentration and temperature, providing evidence that these reactions occur in LLRs. However, we find that the enhancement in 1O2* concentrations on ice does not follow predictions from freezing-point depression, likely because experiments were conducted below the eutectic temperature for sodium sulfate, where all of the salt should have precipitated. We also explore a method for separating 1O2* and rad OH contributions to FFA oxidation in laboratory ices and show its application to two natural snow samples. We find that 1O2* concentrations in these snows are approximately 100 times higher than observed in polluted, mid-latitude fog waters, showing that the enhancement of 1O2* on ice is environmentally relevant and that

  10. Near-Unity Quantum Yields of Biexciton Emission from CdSe=CdS Nanocrystals Measured Using Single-Particle Spectroscopy

    SciTech Connect

    Park, Young-Shin; Malko, Anton V.; Vela, Javier; Chen, Yongfen; Ghosh, Yagnaseni; Garcia-Santamaria, Florencio; Hollingsworth, Jennifer A.; Klimov, Victor I.; Htoon, Han

    2011-05-03

    Biexciton photoluminescence (PL) quantum yields (Q2X) of individual CdSe/CdS core-shell nanocrystal quantum dots with various shell thicknesses are derived from independent PL saturation and two-photon correlation measurements. We observe a near-unity Q{sub 2X} for some nanocrystals with an ultrathick 19-monolayer shell. High Q2X’s are, however, not universal and vary widely among nominally identical nanocrystals indicating a significant dependence of Q2X upon subtle structural differences. Interestingly, our measurements indicate that high Q2X’s are not required to achieve complete suppression of PL intensity fluctuations in individual nanocrystals.

  11. Effect of silver nano particles on the fluorescence quantum yield of Rhodamine 6G determined using dual beam thermal lens method.

    PubMed

    Santhi, A; Umadevi, M; Ramakrishnan, V; Radhakrishnan, P; Nampoori, V P N

    2004-04-01

    Nano structured noble metals have very important applications in diverse fields as photovoltaics, catalysis, electronic and magnetic devices, etc. Here, we report the application of dual beam thermal lens technique for the determination of the effect of silver sol on the absolute fluorescence quantum yield (FQY) of the laser dye rhodamine 6G. A 532 nm radiation from a diode pumped solid state laser was used as the excitation source. It has been observed that the presence of silver sol decreases the fluorescence quantum efficiency. This is expected to have a very important consequence in enhancing Raman scattering which is an important spectrochemical tool that provides information on molecular structures. We have also observed that the presence of silver sol can enhance the thermal lens signal which makes the detection of the signal easier at any concentration.

  12. A water-soluble ESIPT fluorescent probe with high quantum yield and red emission for ratiometric detection of inorganic and organic palladium.

    PubMed

    Gao, Tang; Xu, Pengfei; Liu, Meihui; Bi, Anyao; Hu, Pengzhi; Ye, Bin; Wang, Wei; Zeng, Wenbin

    2015-05-01

    A novel fluorescent probe with a high quantum yield (0.41), large Stokes shifts (255 nm), and red emission (635 nm) was designed to detect all typical oxidation states of palladium species (0, +2, +4) by palladium-mediated terminal propargyl ethers cleavage reaction in water solution without any organic media. The probe showed a high selectivity and excellent sensitivity for palladium species, with a detection as low as 57 nM (6.2 μg L(-1)).

  13. Cl2O photochemistry: ultraviolet/vis absorption spectrum temperature dependence and O(3P) quantum yield at 193 and 248 nm.

    PubMed

    Papanastasiou, Dimitrios K; Feierabend, Karl J; Burkholder, James B

    2011-05-28

    The photochemistry of Cl(2)O (dichlorine monoxide) was studied using measurements of its UV/vis absorption spectrum temperature dependence and the O((3)P) atom quantum yield, Φ(Cl(2)O)(O)(λ), in its photolysis at 193 and 248 nm. The Cl(2)O UV/vis absorption spectrum was measured over the temperature range 201-296 K between 200 and 500 nm using diode array spectroscopy. Cl(2)O absorption cross sections, σ(Cl(2)O)(λ,T), at temperatures <296 K were determined relative to its well established room temperature values. A wavelength and temperature dependent parameterization of the Cl(2)O spectrum using the sum of six Gaussian functions, which empirically represent transitions from the ground (1)A(1) electronic state to excited states, is presented. The Gaussian functions are found to correlate well with published theoretically calculated vertical excitation energies. O((3)P) quantum yields in the photolysis of Cl(2)O at 193 and 248 nm were measured using pulsed laser photolysis combined with atomic resonance fluorescence detection of O((3)P) atoms. O((3)P) quantum yields were measured to be 0.85 ± 0.15 for 193 nm photolysis at 296 K and 0.20 ± 0.03 at 248 nm, which was also found to be independent of temperature (220-352 K) and pressure (17 and 28 Torr, N(2)). The quoted uncertainties are at the 2σ (95% confidence) level and include estimated systematic errors. ClO radical temporal profiles obtained following the photolysis of Cl(2)O at 248 nm, as reported previously in Feierabend et al. [J. Phys. Chem. A 114, 12052, (2010)], were interpreted to establish a <5% upper-limit for the O + Cl(2) photodissociation channel, which indicates that O((3)P) is primarily formed in the three-body, O + 2Cl, photodissociation channel at 248 nm. The analysis also indirectly provided a Cl atom quantum yield of 1.2 ± 0.1 at 248 nm. The results from this work are compared with previous studies where possible.

  14. Oxalyl chloride, ClC(O)C(O)Cl: UV/vis spectrum and Cl atom photolysis quantum yields at 193, 248, and 351 nm

    SciTech Connect

    Ghosh, Buddhadeb; Papanastasiou, Dimitrios K.; Burkholder, James B.

    2012-10-28

    Oxalyl chloride, (ClCO){sub 2}, has been used as a Cl atom photolytic precursor in numerous laboratory kinetic and photochemical studies. In this study, the UV/vis absorption spectrum of (ClCO){sub 2} and the Cl atom quantum yields in its photolysis at 193, 248, and 351 nm are reported. The UV/vis spectrum was measured between 200 and 450 nm at 296 K using diode array spectroscopy in conjunction with an absolute cross section obtained at 213.9 nm. Our results are in agreement with the spectrum reported by Baklanov and Krasnoperov [J. Phys. Chem. A 105, 97-103 (2001)], which was obtained at 11 discrete wavelengths between 193.3 and 390 nm. Cl atom quantum yields, {Phi}({lambda}), were measured using pulsed laser photolysis coupled with time resolved atomic resonance fluorescence detection of Cl. The UV photolysis of (ClCO){sub 2} has been shown in previous studies to occur via an impulsive three-body dissociation mechanism, (COCl){sub 2}+ hv{yields} ClCO*+ Cl + CO (2), where the excited ClCO radical, ClCO*, either dissociates or stabilizes ClCO*{yields} Cl + CO (3a), {yields} ClCO (3b). ClCO is thermally unstable at the temperatures (253-298 K) and total pressures (13-128 Torr) used in our experiments ClCO + M {yields} Cl + CO + M (4) leading to the formation of a secondary Cl atom that was resolvable in the Cl atom temporal profiles obtained in the 248 and 351 nm photolysis of (ClCO){sub 2}. {Phi}(193 nm) was found to be 2.07 {+-} 0.37 independent of bath gas pressure (25.8-105.7 Torr, N{sub 2}), i.e., the branching ratio for channel 2a or the direct formation of 2Cl + 2CO in the photolysis of (ClCO){sub 2} is >0.95. At 248 nm, the branching ratio for channel 2a was determined to be 0.79 {+-} 0.15, while the total Cl atom yield, i.e., following the completion of reaction (4), was found to be 1.98 {+-} 0.26 independent of bath gas pressure (15-70 Torr, N{sub 2}). {Phi}(351 nm) was found to be pressure dependent between 7.8 and 122.4 Torr (He, N{sub 2}). The low

  15. Fluorescence of tryptophan in designed hairpin and Trp-cage miniproteins: measurements of fluorescence yields and calculations by quantum mechanical molecular dynamics simulations.

    PubMed

    McMillan, Andrew W; Kier, Brandon L; Shu, Irene; Byrne, Aimee; Andersen, Niels H; Parson, William W

    2013-02-14

    The quantum yield of tryptophan (Trp) fluorescence was measured in 30 designed miniproteins (17 β-hairpins and 13 Trp-cage peptides), each containing a single Trp residue. Measurements were made in D(2)O and H(2)O to distinguish between fluorescence quenching mechanisms involving electron and proton transfer in the hairpin peptides, and at two temperatures to check for effects of partial unfolding of the Trp-cage peptides. The extent of folding of all the peptides also was measured by NMR. The fluorescence yields ranged from 0.01 in some of the Trp-cage peptides to 0.27 in some hairpins. Fluorescence quenching was found to occur by electron transfer from the excited indole ring of the Trp to a backbone amide group or the protonated side chain of a nearby histidine, glutamate, aspartate, tyrosine, or cysteine residue. Ionized tyrosine side chains quenched strongly by resonance energy transfer or electron transfer to the excited indole ring. Hybrid classical/quantum mechanical molecular dynamics simulations were performed by a method that optimized induced electric dipoles separately for the ground and excited states in multiple π-π* and charge-transfer (CT) excitations. Twenty 0.5 ns trajectories in the tryptophan's lowest excited singlet π-π* state were run for each peptide, beginning by projections from trajectories in the ground state. Fluorescence quenching was correlated with the availability of a CT or exciton state that was strongly coupled to the π-π* state and that matched or fell below the π-π* state in energy. The fluorescence yields predicted by summing the calculated rates of charge and energy transfer are in good accord with the measured yields.

  16. Determination of apparent quantum yield spectra of DMS photo-degradation in an in situ iron-induced Northeast Pacific Ocean bloom

    NASA Astrophysics Data System (ADS)

    Bouillon, René-Christian; Miller, William L.

    2004-03-01

    The wavelength dependence of the photochemical removal efficiency for DMS was studied for samples from an iron-induced bloom in the Northeastern Pacific Ocean. In July 2002, a 64 km2 patch of ocean was iron-fertilized near Ocean Station Papa (50°12'N 144°45'W). Only small changes in pseudo-first-order apparent quantum yield (AQY*DMS(λ)) were observed outside the iron-patch. However, inside the patch, AQY*DMS(λ) decreased considerably over the two weeks following the initial iron injection. A positive strong correlation was found between pseudo-first-order apparent quantum yield determined at 330 nm (AQY*DMS(330 nm)) and NO3- concentrations. We propose that NO3--photolysis has a substantial influence on DMS photo-degradation rates in oceanic waters. This finding demonstrates that in addition to control DMS production, marine phytoplankton could indirectly influence the DMS photochemical loss rate via its control on NO3- distribution.

  17. A methacrylate-based polymeric imidazole ligand yields quantum dots with low cytotoxicity and low nonspecific binding

    PubMed Central

    Johnson, Colin M.; Pate, Kayla M.; Shen, Yi; Viswanath, Anand; Tan, Rui; Benicewicz, Brian C.; Moss, Melissa A.; Greytak, Andrew B.

    2016-01-01

    This paper assesses the biocompatibility for fluorescence imaging of colloidal nanocrystal quantum dots (QDs) coated with a recently-developed multiply-binding methacrylate-based polymeric imidazole ligand. The QD samples were purified prior to ligand exchange via a highly repeatable gel permeation chromatography (GPC) method. A multi-well plate based protocol was used to characterize nonspecific binding and toxicity of the QDs toward human endothelial cells. Nonspecific binding in 1% fetal bovine serum was negligible compared to anionically-stabilized QD controls, and no significant toxicity was detected on 24 h exposure. The nonspecific binding results were confirmed by fluorescence microscopy. This study is the first evaluation of biocompatibility in QDs initially purified by GPC and represents a scalable approach to comparison among nanocrystal-based bioimaging scaffolds. PMID:26247382

  18. Oxalyl chloride, ClC(O)C(O)Cl: UV/vis spectrum and Cl atom photolysis quantum yields at 193, 248, and 351 nm.

    PubMed

    Ghosh, Buddhadeb; Papanastasiou, Dimitrios K; Burkholder, James B

    2012-10-28

    Oxalyl chloride, (ClCO)(2), has been used as a Cl atom photolytic precursor in numerous laboratory kinetic and photochemical studies. In this study, the UV/vis absorption spectrum of (ClCO)(2) and the Cl atom quantum yields in its photolysis at 193, 248, and 351 nm are reported. The UV∕vis spectrum was measured between 200 and 450 nm at 296 K using diode array spectroscopy in conjunction with an absolute cross section obtained at 213.9 nm. Our results are in agreement with the spectrum reported by Baklanov and Krasnoperov [J. Phys. Chem. A 105, 97-103 (2001)], which was obtained at 11 discrete wavelengths between 193.3 and 390 nm. Cl atom quantum yields, Φ(λ), were measured using pulsed laser photolysis coupled with time resolved atomic resonance fluorescence detection of Cl. The UV photolysis of (ClCO)(2) has been shown in previous studies to occur via an impulsive three-body dissociation mechanism, (COCl)(2) + hv → ClCO* + Cl + CO (2), where the excited ClCO radical, ClCO*, either dissociates or stabilizes ClCO* → Cl + CO (3a), → ClCO (3b). ClCO is thermally unstable at the temperatures (253-298 K) and total pressures (13-128 Torr) used in our experiments ClCO + M → Cl + CO + M (4) leading to the formation of a secondary Cl atom that was resolvable in the Cl atom temporal profiles obtained in the 248 and 351 nm photolysis of (ClCO)(2). Φ(193 nm) was found to be 2.07 ± 0.37 independent of bath gas pressure (25.8-105.7 Torr, N(2)), i.e., the branching ratio for channel 2a or the direct formation of 2Cl + 2CO in the photolysis of (ClCO)(2) is >0.95. At 248 nm, the branching ratio for channel 2a was determined to be 0.79 ± 0.15, while the total Cl atom yield, i.e., following the completion of reaction (4), was found to be 1.98 ± 0.26 independent of bath gas pressure (15-70 Torr, N(2)). Φ(351 nm) was found to be pressure dependent between 7.8 and 122.4 Torr (He, N(2)). The low-pressure limit of the total Cl atom quantum yield, Φ(0)(351 nm), was 2

  19. Deep tissue optical imaging of upconverting nanoparticles enabled by exploiting higher intrinsic quantum yield through use of millisecond single pulse excitation with high peak power.

    PubMed

    Liu, Haichun; Xu, Can T; Dumlupinar, Gökhan; Jensen, Ole B; Andersen, Peter E; Andersson-Engels, Stefan

    2013-10-21

    We have accomplished deep tissue optical imaging of upconverting nanoparticles at 800 nm, using millisecond single pulse excitation with high peak power. This is achieved by carefully choosing the pulse parameters, derived from time-resolved rate-equation analysis, which result in higher intrinsic quantum yield that is utilized by upconverting nanoparticles for generating this near infrared upconversion emission. The pulsed excitation approach thus promises previously unreachable imaging depths and shorter data acquisition times compared with continuous wave excitation, while simultaneously keeping the possible thermal side-effects of the excitation light moderate. These key results facilitate means to break through the general shallow depth limit of upconverting-nanoparticle-based fluorescence techniques, necessary for a range of biomedical applications, including diffuse optical imaging, photodynamic therapy and remote activation of biomolecules in deep tissues.

  20. Slow-Injection Growth of Seeded CdSe/CdS Nanorods with Unity Fluorescence Quantum Yield and Complete Shell to Core Energy Transfer.

    PubMed

    Coropceanu, Igor; Rossinelli, Aurelio; Caram, Justin R; Freyria, Francesca S; Bawendi, Moungi G

    2016-03-22

    A two-step process has been developed for growing the shell of CdSe/CdS core/shell nanorods. The method combines an established fast-injection-based step to create the initial elongated shell with a second slow-injection growth that allows for a systematic variation of the shell thickness while maintaining a high degree of monodispersity at the batch level and enhancing the uniformity at the single-nanorod level. The second growth step resulted in nanorods exhibiting a fluorescence quantum yield up to 100% as well as effectively complete energy transfer from the shell to the core. This improvement suggests that the second step is associated with a strong suppression of the nonradiative channels operating both before and after the thermalization of the exciton. This hypothesis is supported by the suppression of a defect band, ubiquitous to CdSe-based nanocrystals after the second growth.

  1. Measuring solid-state quantum yields: The conversion of a frequency-doubled Nd:YAG diode laser pointer module into a viable light source.

    PubMed

    Daglen, Bevin C; Harris, John D; Dax, Clifford D; Tyler, David R

    2007-07-01

    This article outlines the difficulties associated with measuring quantum yields for solid-state samples using a high-pressure mercury arc lamp as the irradiation source. Details are given for the conversion of an inexpensive frequency-doubled neodymium-doped yttrium aluminum garnet (Nd:YAG) diode laser pointer module into a viable irradiation source. The modified Nd:YAG laser was incorporated into a computer-controlled system, which allowed for the simultaneous irradiation and spectroscopic monitoring of the sample. The data obtained with the Nd:YAG diode laser system show far less scatter than data obtained with a high-pressure Hg arc lamp, and consequently the degradation rates obtained with the laser system could be calculated with far greater accuracy.

  2. Photochemistry of UV-excited trifluoroacetylacetone and hexafluoroacetylacetone II: Quantum yield and rate constants of hydrogen fluoride photoelimination forming fluorinated methylfuranones

    NASA Astrophysics Data System (ADS)

    Disselkoen, Kyle R.; Alsum, Joel R.; Thielke, Timothy A.; Muyskens, Mark A.

    2017-03-01

    The photochemistry of gas-phase 1,1,1-trifluoroacetylacetone (TFAA) and 1,1,1,5,5,5-hexafluoroacetylacetone (HFAA) excited with ultraviolet light involves a significant photoelimination channel producing HF and difluoromethylfuranone or pentafluoromethylfuranone, respectively. We report collisional self-quenching of the experimentally-determined relative quantum yield, and determine rate constants of 0.27 ± 0.03 and 0.33 ± 0.04 μs-1, for HFAA and TFAA respectively. A strong collision model is consistent with the observed quenching. The data suggest that this elimination is the primary photochemical fate at low pressure in both cases. The TFAA rate constant is larger than that for HFAA, in spite of TFAA having half as many fluorine atoms as HFAA.

  3. A DPF Analysis Yields Quantum Mechanically Accurate Analytic Potential Energy Functions for the a ^1Σ^+ and X ^1Σ^+ States of NaH

    NASA Astrophysics Data System (ADS)

    Le Roy, Robert J.; Walji, Sadru; Sentjens, Katherine

    2013-06-01

    Alkali hydride diatomic molecules have long been the object of spectroscopic studies. However, their small reduced mass makes them species for which the conventional semiclassical-based methods of analysis tend to have the largest errors. To date, the only quantum-mechanically accurate direct-potential-fit (DPF) analysis for one of these molecules was the one for LiH reported by Coxon and Dickinson. The present paper extends this level of analysis to NaH, and reports a DPF analysis of all available spectroscopic data for the A ^1Σ^+-X ^1Σ^+ system of NaH which yields analytic potential energy functions for these two states that account for those data (on average) to within the experimental uncertainties. W.C. Stwalley, W.T. Zemke and S.C. Yang, J. Phys. Chem. Ref. Data {20}, 153-187 (1991). J.A. Coxon and C.S. Dickinson, J. Chem. Phys. {121}, 8378 (2004).

  4. Biexciton quantum yield heterogeneities in single CdSe(CdS) core(shell) nanocrystals and its correlation to exciton blinking

    PubMed Central

    Zhao, Jing; Chen, Ou; Strasfeld, David B.

    2012-01-01

    We explore biexciton (BX) non-radiative recombination processes in single semiconductor nanocrystals (NCs) using confocal fluorescence microscopy and second-order photon intensity correlation. More specifically, we measure the photoluminescence blinking and BX quantum yields (QYs), and study the correlation between these two measurements for single core(shell) CdSe(CdS) nanocrystals (NCs). We find that NCs with a high “on” time fraction are significantly more likely to have a high BX QY than NCs with a low “on” fraction, even though the BX QYs of NCs with a high “on” fraction vary dramatically. The BX QYs of single NCs are also weakly dependent upon excitation wavelength. The weak correlation between exciton “on” fractions and BX QYs suggests that multiple recombination processes are involved in the BX recombination. To explain our results, we propose a model that combines both trapping and an Auger mechanism for BX recombination. PMID:22871126

  5. Absorption and Quantum Yield of Single Conjugated Polymer Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) Molecules

    PubMed Central

    2017-01-01

    We simultaneously measured the absorption and emission of single conjugated polymer poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) molecules in a poly(methyl methacrylate) (PMMA) matrix using near-critical xenon to enhance the photothermal contrast for direct absorption measurements. We directly measured the number of monomers and the quantum yield of single conjugated polymer molecules. Simultaneous absorption and emission measurements provided new insight into the photophysics of single conjugated polymers under optical excitation: quenching in larger molecules is more efficient than in smaller ones. Photoinduced traps and defects formed under prolonged illumination lead to decrease of both polymer fluorescence and absorption signals with the latter declining slower. PMID:28221806

  6. A Time-Dependent Quantum Dynamics Study of the H2 + CH3 yields H + CH4 Reaction

    NASA Technical Reports Server (NTRS)

    Wang, Dunyou; Kwak, Dochan (Technical Monitor)

    2002-01-01

    We present a time-dependent wave-packet propagation calculation for the H2 + CH3 yields H + CH4 reaction in six degrees of freedom and for zero total angular momentum. Initial state selected reaction probability for different initial rotational-vibrational states are presented in this study. The cumulative reaction probability (CRP) is obtained by summing over initial-state-selected reaction probability. The energy-shift approximation to account for the contribution of degrees of freedom missing in the 6D calculation is employed to obtain an approximate full-dimensional CRP. Thermal rate constant is compared with different experiment results.

  7. Study on the Ultrahigh Quantum Yield of Fluorescent P,O-g-C3 N4 Nanodots and its Application in Cell Imaging.

    PubMed

    Rong, Mingcong; Cai, Zhixiong; Xie, Lei; Lin, Chunshui; Song, Xinhong; Luo, Feng; Wang, Yiru; Chen, Xi

    2016-06-27

    Graphitic carbon nitride nanodots (g-C3 N4 nanodots), as a new kind of heavy-metal-free quantum dots, have attracted considerable attention because of their unique physical and chemical properties. Although various methods to obtain g-C3 N4 nanodots have been reported, it is still a challenge to synthesize g-C3 N4 nanodots with ultrahigh fluorescence quantum yield (QY). In this study, highly fluorescent phosphorus/oxygen-doped graphitic carbon nitride (P,O-g-C3 N4 ) nanodots were prepared by chemical oxidation and hydrothermal etching of bulk P-g-C3 N4 derived from the pyrolysis of phytic acid and melamine. The as-prepared P,O-g-C3 N4 nanodots showed strong blue fluorescence and a relatively high QY of up to 90.2 %, which can be ascribed to intrinsic phosphorus/oxygen-containing groups, and surface-oxidation-related fluorescence enhancement. In addition, the P,O-g-C3 N4 nanodots were explored for cell imaging with excellent stability and biocompatibility, which suggest that they have great potential in biological applications.

  8. Luminescent pincer platinum(II) complexes with emission quantum yields up to almost unity: photophysics, photoreductive C-C bond formation, and materials applications.

    PubMed

    Chow, Pui-Keong; Cheng, Gang; Tong, Glenna So Ming; To, Wai-Pong; Kwong, Wai-Lun; Low, Kam-Hung; Kwok, Chi-Chung; Ma, Chensheng; Che, Chi-Ming

    2015-02-09

    Luminescent pincer-type Pt(II)  complexes supported by C-deprotonated π-extended tridentate RC^N^NR' ligands and pentafluorophenylacetylide ligands show emission quantum yields up to almost unity. Femtosecond time-resolved fluorescence measurements and time-dependent DFT calculations together reveal the dependence of excited-state structural distortions of [Pt(RC^N^NR')(CC-C6 F5 )] on the positional isomers of the tridentate ligand. Pt complexes [Pt(R-C^N^NR')(CC-Ar)] are efficient photocatalysts for visible-light-induced reductive CC bond formation. The [Pt(R-C^N^NR')(CC-C6 F5 )] complexes perform strongly as phosphorescent dopants for green- and red-emitting organic light-emitting diodes (OLEDs) with external quantum efficiency values over 22.1 %. These complexes are also applied in two-photon cellular imaging when incorporated into mesoporous silica nanoparticles (MSNs).

  9. Arbuscular mycorrhizal symbiosis ameliorates the optimum quantum yield of photosystem II and reduces non-photochemical quenching in rice plants subjected to salt stress.

    PubMed

    Porcel, Rosa; Redondo-Gómez, Susana; Mateos-Naranjo, Enrique; Aroca, Ricardo; Garcia, Rosalva; Ruiz-Lozano, Juan Manuel

    2015-08-01

    Rice is the most important food crop in the world and is a primary source of food for more than half of the world population. However, salinity is considered the most common abiotic stress reducing its productivity. Soil salinity inhibits photosynthetic processes, which can induce an over-reduction of the reaction centres in photosystem II (PSII), damaging the photosynthetic machinery. The arbuscular mycorrhizal (AM) symbiosis may improve host plant tolerance to salinity, but it is not clear how the AM symbiosis affects the plant photosynthetic capacity, particularly the efficiency of PSII. This study aimed at determining the influence of the AM symbiosis on the performance of PSII in rice plants subjected to salinity. Photosynthetic activity, plant gas-exchange parameters, accumulation of photosynthetic pigments and rubisco activity and gene expression were also measured in order to analyse comprehensively the response of the photosynthetic processes to AM symbiosis and salinity. Results showed that the AM symbiosis enhanced the actual quantum yield of PSII photochemistry and reduced the quantum yield of non-photochemical quenching in rice plants subjected to salinity. AM rice plants maintained higher net photosynthetic rate, stomatal conductance and transpiration rate than nonAM plants. Thus, we propose that AM rice plants had a higher photochemical efficiency for CO2 fixation and solar energy utilization and this increases plant salt tolerance by preventing the injury to the photosystems reaction centres and by allowing a better utilization of light energy in photochemical processes. All these processes translated into higher photosynthetic and rubisco activities in AM rice plants and improved plant biomass production under salinity.

  10. Photoluminescence quantum yields of PbSe and PbS QDs in the range of 1000 nm to 2000 nm (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Beard, Matthew C.; Semonin, Octavi E.; Johnson, Justin C.; Marshall, Ashley; Zhang, Jianbing; Chernomordik, Boris D.

    2016-03-01

    PbS and PbSe quantum dots (QDs) are promising strong infrared emitters. We have developed several synthetic routes to producing PbS and PbSe QDs with a variety of sizes such that the bandgap can be continuously tuned from 2000 to 1000 nm. We provide a simple and accurate synthetic route to reproducibly produce PbS QDs with a narrow size-distribution and high chemical yield. The different synthetic routes lead to differences in their surface chemistry and to differences in their air stability and photoluminescence quantum yields (PLQY). To characterize the PLQY we directly measured the PLQY IR-26 (a standard IR emitting organic dye) at a range of concentrations as well as the PLQY of PbS and PbSe QDs for a range of sizes. We find that the PLQY of IR-26 has a weak concentration dependence due to reabsorption, with a PLQY of 0:048_0:002% for low concentrations, lower than previous reports by a full order of magnitude. We also find a dramatic size dependence for both PbS and PbSe QDs, with the smallest dots exhibiting a PLQY in excess of 60% while larger dots fall below 3%. A model, including nonradiative transition between electronic states and energy transfer to ligand vibrations, appears to explain this size dependence. These findings provide both a better characterization of photoluminescence for near infrared emitters. Halogen surface passivation provides both a larger PLQY (~ 30% improvement) as well as increased air stability.

  11. Origin of the Photoluminescence Quantum Yields Enhanced by Alkane-Termination of Freestanding Silicon Nanocrystals: Temperature-Dependence of Optical Properties

    PubMed Central

    Ghosh, Batu; Takeguchi, Masaki; Nakamura, Jin; Nemoto, Yoshihiro; Hamaoka, Takumi; Chandra, Sourov; Shirahata, Naoto

    2016-01-01

    On the basis of the systematic study on temperature dependence of photoluminescence (PL) properties along with relaxation dynamics we revise a long-accepted mechanism for enhancing absolute PL quantum yields (QYs) of freestanding silicon nanocrystals (ncSi). A hydrogen-terminated ncSi (ncSi:H) of 2.1 nm was prepared by thermal disproportination of (HSiO1.5)n, followed by hydrofluoric etching. Room-temperature PL QY of the ncSi:H increased twentyfold only by hydrosilylation of 1-octadecene (ncSi-OD). A combination of PL spectroscopic measurement from cryogenic to room temperature with structural characterization allows us to link the enhanced PL QYs with the notable difference in surface structure between the ncSi:H and the ncSi-OD. The hydride-terminated surface suffers from the presence of a large amount of nonradiative relaxation channels whereas the passivation with alkyl monolayers suppresses the creation of the nonradiative relaxation channels to yield the high PL QY. PMID:27830771

  12. Origin of the Photoluminescence Quantum Yields Enhanced by Alkane-Termination of Freestanding Silicon Nanocrystals: Temperature-Dependence of Optical Properties

    NASA Astrophysics Data System (ADS)

    Ghosh, Batu; Takeguchi, Masaki; Nakamura, Jin; Nemoto, Yoshihiro; Hamaoka, Takumi; Chandra, Sourov; Shirahata, Naoto

    2016-11-01

    On the basis of the systematic study on temperature dependence of photoluminescence (PL) properties along with relaxation dynamics we revise a long-accepted mechanism for enhancing absolute PL quantum yields (QYs) of freestanding silicon nanocrystals (ncSi). A hydrogen-terminated ncSi (ncSi:H) of 2.1 nm was prepared by thermal disproportination of (HSiO1.5)n, followed by hydrofluoric etching. Room-temperature PL QY of the ncSi:H increased twentyfold only by hydrosilylation of 1-octadecene (ncSi-OD). A combination of PL spectroscopic measurement from cryogenic to room temperature with structural characterization allows us to link the enhanced PL QYs with the notable difference in surface structure between the ncSi:H and the ncSi-OD. The hydride-terminated surface suffers from the presence of a large amount of nonradiative relaxation channels whereas the passivation with alkyl monolayers suppresses the creation of the nonradiative relaxation channels to yield the high PL QY.

  13. Depopulation of highly excited singlet states of DNA model compounds: quantum yields of 193 and 245 nm photoproducts of pyrimidine monomers and dinucleoside monophosphates.

    PubMed

    Gurzadyan, G G; Görner, H

    1996-02-01

    Formation of uracil and orotic acid photodimers, uridine and 5'-UMP photohydrates, TpT photodimers and (6-4)photoproducts, dCpT photohydrates and (6-4)photoproducts and UpU, CpC and CpU photohydrates were studied in neutral deoxygenated aqueous solution at room temperature upon irradiation at either 193 or 254 nm. The photoproducts were identified and quantified and the contribution from photoionization to substrate decomposition, using lambda irr = 193 nm, was separated. The ratio of the quantum yields of respective stable products, eta = phi 193/phi 254, is indicative of the yield of internal conversion from the second to the first excited singlet state, S2-->S1. For the observed photodimers eta decreases from 0.94 for uracil to 0.7 for TpT and further to 0.55 for orotic acid. For the (6-4)photoproducts of TpT and dCpT eta = 0.5-0.8 and for the photohydrates in the cases of UpU, CpC, CpU and dCpT eta ranges from 0.55 to 1.

  14. 2,5-disubstituted oxazole research: fluorescence quantum yields and laser conversion efficiencies of 2-(p-italic-biphenyl)-5-phenyl oxazole and its 5-p-italic-substituted derivatives

    SciTech Connect

    Yu Peifeng

    1986-03-01

    The fluorescence quantum yield and laser conversion efficiency of 2-(p-italic-biphenyl)-5-phenyl-oxazole and thirteen 5-substituted phenyl derivatives are measured. A brief discussion is also given on the relation between the subtituent effects and spectral properties of the compounds.

  15. Predawn and high intensity application of supplemental blue light decreases the quantum yield of PSII and enhances the amount of phenolic acids, flavonoids, and pigments in Lactuca sativa.

    PubMed

    Ouzounis, Theoharis; Razi Parjikolaei, Behnaz; Fretté, Xavier; Rosenqvist, Eva; Ottosen, Carl-Otto

    2015-01-01

    To evaluate the effect of blue light intensity and timing, two cultivars of lettuce [Lactuca sativa cv. "Batavia" (green) and cv. "Lollo Rossa" (red)] were grown in a greenhouse compartment in late winter under natural light and supplemental high pressure sodium (SON-T) lamps yielding 90 (±10) μmol m(-2) s(-1) for up to 20 h, but never between 17:00 and 21:00. The temperature in the greenhouse compartments was 22/11°C day/night, respectively. The five light-emitting diode (LED) light treatments were Control (no blue addition), 1B 06-08 (Blue light at 45 μmol m(-2) s(-1) from 06:00 to 08:00), 1B 21-08 (Blue light at 45 μmol m(-2) s(-1) from 21:00 to 08:00), 2B 17-19 (Blue at 80 μmol m(-2) s(-1) from 17:00 to 19:00), and 1B 17-19 (Blue at 45 μmol m(-2) s(-1) from 17:00 to 19:00). Total fresh and dry weight was not affected with additional blue light; however, plants treated with additional blue light were more compact. The stomatal conductance in the green lettuce cultivar was higher for all treatments with blue light compared to the Control. Photosynthetic yields measured with chlorophyll fluorescence showed different response between the cultivars; in red lettuce, the quantum yield of PSII decreased and the yield of non-photochemical quenching increased with increasing blue light, whereas in green lettuce no difference was observed. Quantification of secondary metabolites showed that all four treatments with additional blue light had higher amount of pigments, phenolic acids, and flavonoids compared to the Control. The effect was more prominent in red lettuce, highlighting that the results vary among treatments and compounds. Our results indicate that not only high light level triggers photoprotective heat dissipation in the plant, but also the specific spectral composition of the light itself at low intensities. However, these plant responses to light are cultivar dependent.

  16. Predawn and high intensity application of supplemental blue light decreases the quantum yield of PSII and enhances the amount of phenolic acids, flavonoids, and pigments in Lactuca sativa

    PubMed Central

    Ouzounis, Theoharis; Razi Parjikolaei, Behnaz; Fretté, Xavier; Rosenqvist, Eva; Ottosen, Carl-Otto

    2015-01-01

    To evaluate the effect of blue light intensity and timing, two cultivars of lettuce [Lactuca sativa cv. “Batavia” (green) and cv. “Lollo Rossa” (red)] were grown in a greenhouse compartment in late winter under natural light and supplemental high pressure sodium (SON-T) lamps yielding 90 (±10) μmol m−2 s−1 for up to 20 h, but never between 17:00 and 21:00. The temperature in the greenhouse compartments was 22/11°C day/night, respectively. The five light-emitting diode (LED) light treatments were Control (no blue addition), 1B 06-08 (Blue light at 45 μmol m−2 s−1 from 06:00 to 08:00), 1B 21-08 (Blue light at 45 μmol m−2 s−1 from 21:00 to 08:00), 2B 17-19 (Blue at 80 μmol m−2 s−1 from 17:00 to 19:00), and 1B 17-19 (Blue at 45 μmol m−2 s−1 from 17:00 to 19:00). Total fresh and dry weight was not affected with additional blue light; however, plants treated with additional blue light were more compact. The stomatal conductance in the green lettuce cultivar was higher for all treatments with blue light compared to the Control. Photosynthetic yields measured with chlorophyll fluorescence showed different response between the cultivars; in red lettuce, the quantum yield of PSII decreased and the yield of non-photochemical quenching increased with increasing blue light, whereas in green lettuce no difference was observed. Quantification of secondary metabolites showed that all four treatments with additional blue light had higher amount of pigments, phenolic acids, and flavonoids compared to the Control. The effect was more prominent in red lettuce, highlighting that the results vary among treatments and compounds. Our results indicate that not only high light level triggers photoprotective heat dissipation in the plant, but also the specific spectral composition of the light itself at low intensities. However, these plant responses to light are cultivar dependent. PMID:25767473

  17. Dynamics of cover, UV-protective pigments, and quantum yield in biological soil crust communities of an undisturbed Mojave Desert shrubland

    USGS Publications Warehouse

    Belnap, J.; Phillips, S.L.; Smith, S.D.

    2007-01-01

    Biological soil crusts are an integral part of dryland ecosystems. We monitored the cover of lichens and mosses, cyanobacterial biomass, concentrations of UV-protective pigments in both free-living and lichenized cyanobacteria, and quantum yield in the soil lichen species Collema in an undisturbed Mojave Desert shrubland. During our sampling time, the site received historically high and low levels of precipitation, whereas temperatures were close to normal. Lichen cover, dominated by Collema tenax and C. coccophorum, and moss cover, dominated by Syntrichia caninervis, responded to both increases and decreases in precipitation. This finding for Collema spp. at a hot Mojave Desert site is in contrast to a similar study conducted at a cool desert site on the Colorado Plateau in SE Utah, USA, where Collema spp. cover dropped in response to elevated temperatures, but did not respond to changes in rainfall. The concentrations of UV-protective pigments in free-living cyanobacteria at the Mojave Desert site were also strongly and positively related to rainfall received between sampling times (R2 values ranged from 0.78 to 0.99). However, pigment levels in the lichenized cyanobacteria showed little correlation with rainfall. Quantum yield in Collema spp. was closely correlated with rainfall. Climate models in this region predict a 3.5-4.0 ??C rise in temperature and a 15-20% decline in winter precipitation by 2099. Based on our data, this rise in temperature is unlikely to have a strong effect on the dominant species of the soil crusts. However, the predicted drop in precipitation will likely lead to a decrease in soil lichen and moss cover, and high stress or mortality in soil cyanobacteria as levels of UV-protective pigments decline. In addition, surface-disturbing activities (e.g., recreation, military activities, fire) are rapidly increasing in the Mojave Desert, and these disturbances quickly remove soil lichens and mosses. These stresses combined are likely to lead to

  18. A Brown Mesoporous TiO2-x /MCF Composite with an Extremely High Quantum Yield of Solar Energy Photocatalysis for H2 Evolution.

    PubMed

    Xing, Mingyang; Zhang, Jinlong; Qiu, Bocheng; Tian, Baozhu; Anpo, Masakazu; Che, Michel

    2015-04-24

    A brown mesoporous TiO2-x /MCF composite with a high fluorine dopant concentration (8.01 at%) is synthesized by a vacuum activation method. It exhibits an excellent solar absorption and a record-breaking quantum yield (Φ = 46%) and a high photon-hydrogen energy conversion efficiency (η = 34%,) for solar photocatalytic H2 production, which are all higher than that of the black hydrogen-doped TiO2 (Φ = 35%, η = 24%). The MCFs serve to improve the adsorption of F atoms onto the TiO2 /MCF composite surface, which after the formation of oxygen vacancies by vacuum activation, facilitate the abundant substitution of these vacancies with F atoms. The decrease of recombination sites induced by high-concentration F doping and the synergistic effect between lattice Ti(3+)-F and surface Ti(3+)-F are responsible for the enhanced lifetime of electrons, the observed excellent absorption of solar light, and the photocatalytic production of H2 for these catalysts. The as-prepared F-doped composite is an ideal solar light-driven photocatalyst with great potential for applications ranging from the remediation of environmental pollution to the harnessing of solar energy for H2 production.

  19. Synthesis and characterization of (3-Aminopropyl)trimethoxy-silane (APTMS) functionalized Gd2O3:Eu(3+) red phosphor with enhanced quantum yield.

    PubMed

    Jain, Akhil; Hirata, G A; Farías, M H; Castillón, F F

    2016-02-12

    We report the surface modification of nanocrystalline Gd2O3:Eu(3+) phosphor by (3-Aminopropyl)trimethoxysilane (APTMS). The nanoparticles were first coated with silica using the Stöber process, and then annealed at 650 °C for 2 h. Afterwards, APTMS was functionalized onto the silica layer to obtain Gd2O3:Eu(3+) nanoparticles bearing amine groups on the surface. The effect of silica coating, and the subsequent annealing process on the crystallization of the nanophosphor were analyzed by x-ray diffraction (XRD). High-resolution transmission electron microscopy (HR-TEM) confirmed the presence of a silica layer of ∼45 nm thickness. X-ray photoelectron (XPS) and Fourier transform infrared (FTIR) spectroscopy confirmed the presence of silica and the amine groups. Photoluminescence (PL) analysis demonstrated an increased emission after functionalization of nanoparticles. Absolute quantum yield (QY) measurements revealed an 18% enhancement in QY in functionalized nanoparticles compared with unmodified nanoparticles, which is of great importance for their biomedical applications.

  20. Synthesis and characterization of (3-Aminopropyl)trimethoxy-silane (APTMS) functionalized Gd2O3:Eu3+ red phosphor with enhanced quantum yield

    NASA Astrophysics Data System (ADS)

    Jain, Akhil; Hirata, G. A.; Farías, M. H.; Castillón, F. F.

    2016-02-01

    We report the surface modification of nanocrystalline Gd2O3:Eu3+ phosphor by (3-Aminopropyl)trimethoxysilane (APTMS). The nanoparticles were first coated with silica using the Stöber process, and then annealed at 650 °C for 2 h. Afterwards, APTMS was functionalized onto the silica layer to obtain Gd2O3:Eu3+ nanoparticles bearing amine groups on the surface. The effect of silica coating, and the subsequent annealing process on the crystallization of the nanophosphor were analyzed by x-ray diffraction (XRD). High-resolution transmission electron microscopy (HR-TEM) confirmed the presence of a silica layer of ∼45 nm thickness. X-ray photoelectron (XPS) and Fourier transform infrared (FTIR) spectroscopy confirmed the presence of silica and the amine groups. Photoluminescence (PL) analysis demonstrated an increased emission after functionalization of nanoparticles. Absolute quantum yield (QY) measurements revealed an 18% enhancement in QY in functionalized nanoparticles compared with unmodified nanoparticles, which is of great importance for their biomedical applications.

  1. A Facile and Low-Cost Method to Enhance the Internal Quantum Yield and External Light-Extraction Efficiency for Flexible Light-Emitting Carbon-Dot Films

    PubMed Central

    Jiang, Z. C.; Lin, T. N.; Lin, H. T.; Talite, M. J.; Tzeng, T. T.; Hsu, C. L.; Chiu, K. P.; Lin, C. A. J.; Shen, J. L.; Yuan, C. T.

    2016-01-01

    Solution-processed, non-toxic carbon dots (CDs) have attracted much attention due to their unique photoluminescence (PL) properties. They are promising emissive layers for flexible light-emitting devices. To this end, the CDs in pristine aqueous solutions need to be transferred to form solid-state thin films without sacrificing their original PL characteristics. Unfortunately, solid-state PL quenching induced by extra non-radiative (NR) energy transfer among CDs would significantly hinder their practical applications in optoelectronics. Here, a facile, low-cost and effective method has been utilized to fabricate high-performance CD/polymer light-emitting flexible films with submicron-structured patterns. The patterned polymers can serve as a solid matrix to disperse and passivate CDs, thus achieving high internal quantum yields of 61%. In addition, they can act as an out-coupler to mitigate the waveguide-mode losses, approximately doubling the external light-extraction efficiency. Such CD/polymer composites also exhibit good photo-stability, and thus can be used as eco-friendly, low-cost phosphors for solid-state lighting. PMID:26822337

  2. Host-Guest Chemistry between Perylene Diimide (PDI) Derivatives and 18-Crown-6: Enhancement in Luminescence Quantum Yield and Electrical Conductivity.

    PubMed

    Lasitha, P; Prasad, Edamana

    2016-07-18

    Perylene diimide (PDI) derivatives exhibit a high propensity for aggregation, which causes the aggregation-induced quenching of emission from the system. Host-guest chemistry is one of the best-known methods for preventing aggregation through the encapsulation of guest molecules. Herein we report the use of 18-crown-6 (18-C-6) as a host system to disaggregate suitably substituted PDI derivatives in methanol. 18-C-6 formed complexes with amino-substituted PDIs in methanol, which led to disaggregation and enhanced emission from the systems. Furthermore, the embedding of the PDI⋅18-C-6 complexes in poly(vinyl alcohol) (PVA) films generated remarkably high emission quantum yields (60-70 %) from the PDI derivatives. More importantly, the host-guest systems were tested for their ability to conduct electricity in PVA films. The electrical conductivities of the self-assembled systems in PVA were measured by electrochemical impedance spectroscopy (EIS) and the highest conductivity observed was 2.42×10(-5)  S cm(-1) .

  3. Measurement of Quantum Yield and Upconversion Brightness in Red, Blue and Green on NIR Excited M2O2S:Yb/Er/Ho/Tm Phosphors

    NASA Astrophysics Data System (ADS)

    Beeks, Ivan; Kumar, Ajith G.; Sardar, Dhiraj K.

    2015-03-01

    A series of broadly color tunable upconversion phosphors were synthesized from M2O2S (M=Y,Gd,La) using a flux fusion method. We investigate their upconversion properties as a function of the dopant concentrations and excitation power density. The phosphor compositions were determined for their upconversion characteristics under 800, 980 and 1550 nm excitations. By measuring the quantum yield and luminous brightness, we investigate their potential applications in biomedical imaging as well as NIR display applications. Results are compared with the well-known upconversion phosphor NaYF4:Yb/Er/Ho/Tm and found that the M2O2S phosphor systems are more efficient compared to NaYF4. By adopting various synthesis protocols, we were able to examine M2O2S in the size range of 10 nm to 10 μm. This research is supported by the National Science Foundation Partnerships for Research and Education in Materials (NSF-PREM) Grant N0-DMR-0934218.

  4. Luminescence, lifetime, and quantum yield studies of redispersible Eu3+-doped GdPO4 crystalline nanoneedles: Core-shell and concentration effects

    NASA Astrophysics Data System (ADS)

    Yaiphaba, N.; Ningthoujam, R. S.; Singh, N. Shanta; Vatsa, R. K.; Singh, N. Rajmuhon; Dhara, Sangita; Misra, N. L.; Tewari, R.

    2010-02-01

    Crystalline nanoneedles of Eu3+-doped GdPO4 and Eu3+-doped GdPO4 covered with GdPO4 shell (core shell) have been prepared at relatively low temperature of 150 °C in ethylene glycol medium. From luminescence study, asymmetric ratio of Eu3+ emission at 612 nm (electric dipole transition) to 592 nm (magnetic dipole transition) is found to be less than one. Maximum luminescence was observed from the nanoparticles with Eu3+ concentration of 5 at. %. For a fixed concentration of Eu3+ doping, there is an improvement in emission intensity for core-shell nanoparticles compared to that for core. This has been attributed to effective removal of surface inhomogeneities around Eu3+ ions present on the surface of core as well as the passivation of inevitable surface states, defects or capping ligand (ethylene glycol) of core nanoparticles by bonding to the shell. Lifetime for D50 level of Eu3+ was found to increase three times for core-shell nanoparticles compared to that for core confirming the more Eu3+ ions with symmetry environment in core shell. For 5 at. % Eu3+-doped GdPO4, quantum yield of 19% is obtained. These nanoparticles are redispersible in water, ethanol, or chloroform and thus will be useful in biological labeling. The dispersed particles are incorporated in polymer-based films that will be useful in display devices.

  5. Design of weak-donor alkyl-functionalized push-pull pyrene dyes exhibiting enhanced fluorescence quantum yields and unique on/off switching properties.

    PubMed

    Niko, Yosuke; Sasaki, Shunsuke; Kawauchi, Susumu; Tokumaru, Katsumi; Konishi, Gen-Ichi

    2014-07-01

    We designed, synthesized, and evaluated environmentally responsive solvatochromic fluorescent dyes by incorporating weak push-pull moieties. The quantum yields of the push (alkyl)-pull (formyl) pyrene dyes were dramatically enhanced by the introduction of alkyl groups into formylpyrene (1-formylpyrene: Φ(F) =0.10; 3,6,8-tri-n-butyl-1-formylpyrene: Φ(F) =0.90; in MeOH). The new dyes exhibited unique sensitivity to solvent polarity and hydrogen-bond donor ability, and specific fluorescence turn-on/off properties (e.g., 3,6,8-tri-n-butyl-1-formylpyrene: Φ(F) =0.004, 0.80, 0.37, and 0.90 in hexane, chloroform, DMSO, and MeOH, respectively). Here, the alkyl groups act as weak donors to suppress intersystem crossing by destabilizing the HOMOs of 1-formylpyrene while maintaining weak intramolecular charge-transfer properties. By using alkyl groups as weak donors, environmentally responsive, and in particular, pH-responsive fluorescent materials may be developed in the future.

  6. Constructing Solid-Gas-Interfacial Fenton Reaction over Alkalinized-C3N4 Photocatalyst To Achieve Apparent Quantum Yield of 49% at 420 nm.

    PubMed

    Li, Yunxiang; Ouyang, Shuxin; Xu, Hua; Wang, Xin; Bi, Yingpu; Zhang, Yuanfang; Ye, Jinhua

    2016-10-03

    Efficient generation of active oxygen-related radicals plays an essential role in boosting advanced oxidation process. To promote photocatalytic oxidation for gaseous pollutant over g-C3N4, a solid-gas interfacial Fenton reaction is coupled into alkalinized g-C3N4-based photocatalyst to effectively convert photocatalytic generation of H2O2 into oxygen-related radicals. This system includes light energy as power, alkalinized g-C3N4-based photocatalyst as an in situ and robust H2O2 generator, and surface-decorated Fe(3+) as a trigger of H2O2 conversion, which attains highly efficient and universal activity for photodegradation of volatile organic compounds (VOCs). Taking the photooxidation of isopropanol as model reaction, this system achieves a photoactivity of 2-3 orders of magnitude higher than that of pristine g-C3N4, which corresponds to a high apparent quantum yield of 49% at around 420 nm. In-situ electron spin resonance (ESR) spectroscopy and sacrificial-reagent incorporated photocatalytic characterizations indicate that the notable photoactivity promotion could be ascribed to the collaboration between photocarriers (electrons and holes) and Fenton process to produce abundant and reactive oxygen-related radicals. The strategy of coupling solid-gas interfacial Fenton process into semiconductor-based photocatalysis provides a facile and promising solution to the remediation of air pollution via solar energy.

  7. Au/Ce0.72Zr0.18Pr0.1O2 nanodisperse catalyst for oxidation of carbon monoxide

    NASA Astrophysics Data System (ADS)

    Liberman, E. Yu.; Naumkin, A. V.; Mikhailichenko, A. I.; Batrakova, M. K.; Maslakov, K. I.; Revina, A. A.; Papkova, M. V.; Kon'kova, T. V.; Grunskii, V. N.; Gasparyan, M. D.; Karpovich, A. L.; Lizunova, A. A.

    2016-01-01

    The nanodisperse Au/Ce0.72Zr0.18Pr0.1O2 catalysts for low-temperature oxidation of carbon monoxide were synthesized. The compounds were identified by XRD, XPS, TEM, ISP-MS, and gas chromatography. The samples containing gold nanoparticles obtained by radiation chemical reduction in reverse micellar dispersion exhibited higher activity than the catalysts obtained by deposition-precipitation (DP) despite the higher content of the active component.

  8. Adiabatically implementing quantum gates

    SciTech Connect

    Sun, Jie; Lu, Songfeng Liu, Fang

    2014-06-14

    We show that, through the approach of quantum adiabatic evolution, all of the usual quantum gates can be implemented efficiently, yielding running time of order O(1). This may be considered as a useful alternative to the standard quantum computing approach, which involves quantum gates transforming quantum states during the computing process.

  9. X-ray induced singlet oxygen generation by nanoparticle-photosensitizer conjugates for photodynamic therapy: determination of singlet oxygen quantum yield

    NASA Astrophysics Data System (ADS)

    Clement, Sandhya; Deng, Wei; Camilleri, Elizabeth; Wilson, Brian C.; Goldys, Ewa M.

    2016-01-01

    Singlet oxygen is a primary cytotoxic agent in photodynamic therapy. We show that CeF3 nanoparticles, pure as well as conjugated through electrostatic interaction with the photosensitizer verteporfin, are able to generate singlet oxygen as a result of UV light and 8 keV X-ray irradiation. The X-ray stimulated singlet oxygen quantum yield was determined to be 0.79 ± 0.05 for the conjugate with 31 verteporfin molecules per CeF3 nanoparticle, the highest conjugation level used. From this result we estimate the singlet oxygen dose generated from CeF3-verteporfin conjugates for a therapeutic dose of 60 Gy of ionizing radiation at energies of 6 MeV and 30 keV to be (1.2 ± 0.7) × 108 and (2.0 ± 0.1) × 109 singlet oxygen molecules per cell, respectively. These are comparable with cytotoxic doses of 5 × 107-2 × 109 singlet oxygen molecules per cell reported in the literature for photodynamic therapy using light activation. We confirmed that the CeF3-VP conjugates enhanced cell killing with 6 MeV radiation. This work confirms the feasibility of using X- or γ- ray activated nanoparticle-photosensitizer conjugates, either to supplement the radiation treatment of cancer, or as an independent treatment modality.

  10. X-ray induced singlet oxygen generation by nanoparticle-photosensitizer conjugates for photodynamic therapy: determination of singlet oxygen quantum yield

    PubMed Central

    Clement, Sandhya; Deng, Wei; Camilleri, Elizabeth; Wilson, Brian C.; Goldys, Ewa M.

    2016-01-01

    Singlet oxygen is a primary cytotoxic agent in photodynamic therapy. We show that CeF3 nanoparticles, pure as well as conjugated through electrostatic interaction with the photosensitizer verteporfin, are able to generate singlet oxygen as a result of UV light and 8 keV X-ray irradiation. The X-ray stimulated singlet oxygen quantum yield was determined to be 0.79 ± 0.05 for the conjugate with 31 verteporfin molecules per CeF3 nanoparticle, the highest conjugation level used. From this result we estimate the singlet oxygen dose generated from CeF3-verteporfin conjugates for a therapeutic dose of 60 Gy of ionizing radiation at energies of 6 MeV and 30 keV to be (1.2 ± 0.7) × 108 and (2.0 ± 0.1) × 109 singlet oxygen molecules per cell, respectively. These are comparable with cytotoxic doses of 5 × 107–2 × 109 singlet oxygen molecules per cell reported in the literature for photodynamic therapy using light activation. We confirmed that the CeF3-VP conjugates enhanced cell killing with 6 MeV radiation. This work confirms the feasibility of using X- or γ- ray activated nanoparticle-photosensitizer conjugates, either to supplement the radiation treatment of cancer, or as an independent treatment modality. PMID:26818819

  11. Fluorescent properties of DNA base analogue tC upon incorporation into DNA — negligible influence of neighbouring bases on fluorescence quantum yield

    PubMed Central

    Sandin, Peter; Wilhelmsson, L. Marcus; Lincoln, Per; Powers, Vicki E. C.; Brown, Tom; Albinsson, Bo

    2005-01-01

    The quantum yield of the fluorescent tricyclic cytosine analogue, 1,3-diaza-2-oxophenothiazine, tC, is high and virtually unaffected by incorporation into both single- and double-stranded DNA irrespective of neighbouring bases (0.17–0.24 and 0.16–0.21, respectively) and the corresponding fluorescence decay curves are all mono-exponential, properties that are unmatched by any base analogue so far. The fluorescence lifetimes increase when going from tC free in solution (3.2 ns) to single- and double-stranded DNA (on average 5.7 and 6.3 ns, respectively). The mono-exponential decays further support previous NMR results where it was found that tC has a well-defined position and geometry within the DNA helix. Furthermore, we find that the oxidation potential of tC is 0.4 V lower than for deoxyguanosine, the natural base with the lowest oxidation potential. This suggests that tC may be of interest in charge transfer studies in DNA as an electron hole acceptor. We also present a novel synthetic route to the phosphoramidite form of tC. The results presented here together with previous work show that tC is a very good C-analogue that induces minimal perturbation to the native structure of DNA. This makes tC unique as a fluorescent base analogue and is thus highly interesting in a range of applications for studying e.g. structure, dynamics and kinetics in nucleic acid systems. PMID:16147985

  12. A chlorophyll fluorescence analysis of photosynthetic efficiency, quantum yield and photon energy dissipation in PSII antennae of Lactuca sativa L. leaves exposed to cinnamic acid.

    PubMed

    Hussain, M Iftikhar; Reigosa, Manuel J

    2011-11-01

    This study investigated the effects of cinnamic acid (CA) on growth, biochemical and physiological responses of Lactuca sativa L. CA (0.1, 0.5, 1.0 and 1.5 mM) treatments decreased plant height, root length, leaf and root fresh weight, but it did not affect the leaf water status. CA treatment (1.5 mM) significantly reduced F(v), F(m), photochemical efficiency of PSII (F(v)/F(m)) and quantum yield of PSII (ΦPSII) photochemistry in L. sativa. The photochemical fluorescence quenching (qP) and non-photochemical quenching (NPQ) were reduced after treatment with 1.5 mM CA. Fraction of photon energy absorbed by PS II antennae trapped by "open" PS II reaction centers (P) was reduced by CA (1.5 mM) while, portion of absorbed photon energy thermally dissipated (D) and photon energy absorbed by PSII antennae and trapped by "closed" PSII reaction centers (E) was increased. Carbon isotope composition ratios (δ(13)C) was less negative (-27.10) in CA (1.5 mM) treated plants as compared to control (-27.61). Carbon isotope discrimination (Δ(13)C) and ratio of intercellular CO(2) concentration (ci/ca) from leaf to air were also less in CA treated plants. CA (1.5 mM) also decreased the leaf protein contents of L. sativa as compared to control.

  13. Nitryl chloride (ClNO2): UV/vis absorption spectrum between 210 and 296 K and O(3P) quantum yield at 193 and 248 nm.

    PubMed

    Ghosh, Buddhadeb; Papanastasiou, Dimitrios K; Talukdar, Ranajit K; Roberts, James M; Burkholder, James B

    2012-06-21

    Recent studies have shown that the UV/vis photolysis of nitryl chloride (ClNO2) can be a major source of reactive chlorine in the troposphere. The present work reports measurements of the ClNO2 absorption spectrum and its temperature dependence between 210 and 296 K over the wavelength range 200–475 nm using diode array spectroscopy. The room temperature spectrum obtained in this work was found to be in good agreement with the results from Ganske et al. (J. Geophys. Res. 1992, 97, 7651) over the wavelength range common to both studies (200–370 nm) but differs systematically from the currently recommended spectrum for use in atmospheric models. The present results lead to a decrease in the calculated atmospheric ClNO2 photolysis rate by 30%. Including the temperature dependence of the ClNO2 spectrum decreases the calculated atmospheric photolysis rate at lower temperatures (higher altitudes) even further. A parametrization of the wavelength and temperature dependence of the ClNO2 spectrum is presented. O(3P) quantum yields, Φ(ClNO2)(O), in the photolysis of ClNO2 at 193 and 248 nm were measured at 296 K using pulsed laser photolysis combined with atomic resonance fluorescence detection of O(3P) atoms. Φ(ClNO2)(O)(λ) was found to be 0.67 ± 0.12 and 0.15 ± 0.03 (2σ error limits, including estimated systematic errors) at 193 and 248 nm, respectively, indicating that multiple dissociation channels are active in the photolysis of ClNO2 at these wavelengths. The Φ(ClNO2)(O)(λ) values obtained in this work are discussed in light of previous ClNO2 photodissociation studies and the differences are discussed.

  14. X-ray induced singlet oxygen generation by nanoparticle-photosensitizer conjugates for photodynamic therapy: determination of singlet oxygen quantum yield.

    PubMed

    Clement, Sandhya; Deng, Wei; Camilleri, Elizabeth; Wilson, Brian C; Goldys, Ewa M

    2016-01-28

    Singlet oxygen is a primary cytotoxic agent in photodynamic therapy. We show that CeF3 nanoparticles, pure as well as conjugated through electrostatic interaction with the photosensitizer verteporfin, are able to generate singlet oxygen as a result of UV light and 8 keV X-ray irradiation. The X-ray stimulated singlet oxygen quantum yield was determined to be 0.79 ± 0.05 for the conjugate with 31 verteporfin molecules per CeF3 nanoparticle, the highest conjugation level used. From this result we estimate the singlet oxygen dose generated from CeF3-verteporfin conjugates for a therapeutic dose of 60 Gy of ionizing radiation at energies of 6 MeV and 30 keV to be (1.2 ± 0.7) × 10(8) and (2.0 ± 0.1) × 10(9) singlet oxygen molecules per cell, respectively. These are comparable with cytotoxic doses of 5 × 10(7)-2 × 10(9) singlet oxygen molecules per cell reported in the literature for photodynamic therapy using light activation. We confirmed that the CeF3-VP conjugates enhanced cell killing with 6 MeV radiation. This work confirms the feasibility of using X- or γ- ray activated nanoparticle-photosensitizer conjugates, either to supplement the radiation treatment of cancer, or as an independent treatment modality.

  15. Using the quantum yields of photosystem II and the rate of net photosynthesis to monitor high irradiance and temperature stress in chrysanthemum (Dendranthema grandiflora).

    PubMed

    Janka, Eshetu; Körner, Oliver; Rosenqvist, Eva; Ottosen, Carl-Otto

    2015-05-01

    Under a dynamic greenhouse climate control regime, temperature is adjusted to optimise plant physiological responses to prevailing irradiance levels; thus, both temperature and irradiance are used by the plant to maximise the rate of photosynthesis, assuming other factors are not limiting. The control regime may be optimised by monitoring plant responses, and may be promptly adjusted when plant performance is affected by extreme microclimatic conditions, such as high irradiance or temperature. To determine the stress indicators of plants based on their physiological responses, net photosynthesis (Pn) and four chlorophyll-a fluorescence parameters: maximum photochemical efficiency of PSII [Fv/Fm], electron transport rate [ETR], PSII operating efficiency [F'q/F'm], and non-photochemical quenching [NPQ] were assessed for potted chrysanthemum (Dendranthema grandiflora Tzvelev) 'Coral Charm' under different temperature (20, 24, 28, 32, 36 °C) and daily light integrals (DLI; 11, 20, 31, and 43 mol m(-2) created by a PAR of 171, 311, 485 and 667 μmol m(-2) s(-1) for 16 h). High irradiance (667 μmol m(-2) s(-1)) combined with high temperature (>32 °C) significantly (p < 0.05) decreased Fv/Fm. Under high irradiance, the maximum Pn and ETR were reached at 24 °C. Increased irradiance decreased the PSII operating efficiency and increased NPQ, while both high irradiance and temperature had a significant effect on the PSII operating efficiency at temperatures >28 °C. Under high irradiance and temperature, changes in the NPQ determined the PSII operating efficiency, with no major change in the fraction of open PSII centres (qL) (indicating a QA redox state). We conclude that 1) chrysanthemum plants cope with excess irradiance by non-radiative dissipation or a reversible stress response, with the effect on the Pn and quantum yield of PSII remaining low until the temperature reaches 28 °C and 2) the integration of online measurements to monitor photosynthesis and PSII

  16. Electrophilic arene hydroxylation and phenol O-H oxidations performed by an unsymmetric μ-η(1):η(1)-O2-peroxo dicopper(II) complex.

    PubMed

    Garcia-Bosch, Isaac; Ribas, Xavi; Costas, Miquel

    2012-02-13

    Reactions of the unsymmetric dicopper(II) peroxide complex [Cu(II)(2)(μ-η(1):η(1)-O(2))(m-XYL(N3N4))](2+) (1 O(2), where m-XYL is a heptadentate N-based ligand), with phenolates and phenols are described. Complex 1 O(2) reacts with p-X-PhONa (X = MeO, Cl, H, or Me) at -90 °C performing tyrosinase-like ortho-hydroxylation of the aromatic ring to afford the corresponding catechol products. Mechanistic studies demonstrate that reactions occur through initial reversible formation of metastable association complexes [Cu(II)(2)(μ-η(1):η(1)-O(2))(p-X-PhO)(m-XYL(N3N4))](+) (1 O(2)⋅X-PhO) that then undergo ortho-hydroxylation of the aromatic ring by the peroxide moiety. Complex 1 O(2) also reacts with 4-X-substituted phenols p-X-PhOH (X = MeO, Me, F, H, or Cl) and with 2,4-di-tert-butylphenol at -90 °C causing rapid decay of 1 O(2) and affording biphenol coupling products, which is indicative that reactions occur through formation of phenoxyl radicals that then undergo radical C-C coupling. Spectroscopic UV/Vis monitoring and kinetic analysis show that reactions take place through reversible formation of ground-state association complexes [Cu(II)(2)(μ-η(1):η(1)-O(2))(X-PhOH)(m-XYL(N3N4))](2+) (1 O(2)⋅X-PhOH) that then evolve through an irreversible rate-determining step. Mechanistic studies indicate that 1 O(2) reacts with phenols through initial phenol binding to the Cu(2)O(2) core, followed by a proton-coupled electron transfer (PCET) at the rate-determining step. Results disclosed in this work provide experimental evidence that the unsymmetric 1 O(2) complex can mediate electrophilic arene hydroxylation and PCET reactions commonly associated with electrophilic Cu(2)O(2) cores, and strongly suggest that the ability to form substrate⋅Cu(2)O(2) association complexes may provide paths to overcome the inherent reactivity of the O(2)-binding mode. This work provides experimental evidence that the presence of a H(+) completely determines the

  17. Simultaneous Rapid Detection and Serotyping of Cronobacter sakazakii Serotypes O1, O2, and O3 by Using Specific Monoclonal Antibodies

    PubMed Central

    Scharinger, Eva J.; Dietrich, Richard; Kleinsteuber, Ina; Märtlbauer, Erwin

    2016-01-01

    Cronobacter sakazakii is a foodborne pathogen associated with rare but often lethal infections in neonates. Powdered infant formula (PIF) represents the most frequent source of infection. Out of the identified serotypes (O1 to O7), O1, O2, and O3 are often isolated from clinical and PIF samples. Serotype-specific monoclonal antibodies (MAbs) suitable for application in enzyme immunoassays (EIAs) for the rapid detection of C. sakazakii have not yet been developed. In this study, we created specific MAbs with the ability to bind to C. sakazakii of serotypes O1, O2, and O3. Characterization by indirect EIAs, immunofluorescence, motility assays, and immunoblotting identified lipopolysaccharide (LPS) and exopolysaccharide (EPS) as the antigenic determinants of the MAbs. The established sandwich EIAs were highly sensitive and were able to detect between 2 × 103 and 9 × 106 CFU/ml. Inclusivity tests confirmed that 93% of serotype O1 strains, 100% of O2 strains, and 87% of O3 strains were detected at low cell counts. No cross-reactivity with >100 strains of Cronobacter spp. and other Enterobacteriaceae was observed, except for that with C. sakazakii serotype O3 and Cronobacter muytjensii serotype O1. Moreover, the sandwich EIAs detected C. sakazakii in PIF samples artificially contaminated with 1 to 10 bacterial cells per 10 g of sample after 15 h of preenrichment. The use of these serotype-specific MAbs not only allows the reliable detection of C. sakazakii strains but also enables simultaneous serotyping in a simple sandwich EIA method. PMID:26850303

  18. Photolysis of CH{sub 3}CHO at 248 nm: Evidence of triple fragmentation from primary quantum yield of CH{sub 3} and HCO radicals and H atoms

    SciTech Connect

    Morajkar, Pranay; Schoemaecker, Coralie; Fittschen, Christa; Bossolasco, Adriana

    2014-06-07

    Radical quantum yields have been measured following the 248 nm photolysis of acetaldehyde, CH{sub 3}CHO. HCO radical and H atom yields have been quantified by time resolved continuous wave Cavity Ring Down Spectroscopy in the near infrared following their conversion to HO{sub 2} radicals by reaction with O{sub 2}. The CH{sub 3} radical yield has been determined using the same technique following their conversion into CH{sub 3}O{sub 2}. Absolute yields have been deduced for HCO radicals and H atoms through fitting of time resolved HO{sub 2} profiles, obtained under various O{sub 2} concentrations, to a complex model, while the CH{sub 3} yield has been determined relative to the CH{sub 3} yield from 248 nm photolysis of CH{sub 3}I. Time resolved HO{sub 2} profiles under very low O{sub 2} concentrations suggest that another unknown HO{sub 2} forming reaction path exists in this reaction system besides the conversion of HCO radicals and H atoms by reaction with O{sub 2}. HO{sub 2} profiles can be well reproduced under a large range of experimental conditions with the following quantum yields: CH{sub 3}CHO + hν{sub 248nm} → CH{sub 3}CHO{sup *}, CH{sub 3}CHO{sup *} → CH{sub 3} + HCO ϕ{sub 1a} = 0.125 ± 0.03, CH{sub 3}CHO{sup *} → CH{sub 3} + H + CO ϕ{sub 1e} = 0.205 ± 0.04, CH{sub 3}CHO{sup *}→{sup o{sub 2}}CH{sub 3}CO + HO{sub 2} ϕ{sub 1f} = 0.07 ± 0.01. The CH{sub 3}O{sub 2} quantum yield has been determined in separate experiments as ϕ{sub CH{sub 3}} = 0.33 ± 0.03 and is in excellent agreement with the CH{sub 3} yields derived from the HO{sub 2} measurements considering that the triple fragmentation (R1e) is an important reaction path in the 248 nm photolysis of CH{sub 3}CHO. From arithmetic considerations taking into account the HO{sub 2} and CH{sub 3} measurements we deduce a remaining quantum yield for the molecular pathway: CH{sub 3}CHO{sup *} → CH{sub 4} + CO ϕ{sub 1b} = 0.6. All experiments can be

  19. Relative quantum yield of I-asterisk(2P1/2) in the tunable laser UV photodissociation of i-C3F7I and n-C3F7I - Effect of temperature and exciplex emission

    NASA Technical Reports Server (NTRS)

    Smedley, J. E.; Leone, S. R.

    1983-01-01

    Wavelength-specific relative quantum yields of metastable I from pulsed laser photodissociation of i-C3F7I and n-C3F7I in the range 265-336 nm are determined by measuring the time-resolved infrared emission from the atomic I(P-2(1/2) P-2(3/2) transition. It is shown that although this yield appears to be unity from 265 to 298 nm, it decreases dramatically at longer wavelengths. Values are also reported for the enhancement of emission from metastable I due to exciplex formation at several temperatures. The exciplex formation emission increases linearly with parent gas pressure, but decreases with increasing temperature. Absorption spectra of i- and n-C3F7I between 303 and 497 K are presented, and the effect of temperature on the quantum yields at selected wavelengths greater than 300 nm, where increasing the temperature enhances the absorption considerably, are given. The results are discussed in regard to the development of solar-pumped iodine lasers.

  20. Acclimation of tobacco leaves to high light intensity drives the plastoquinone oxidation system--relationship among the fraction of open PSII centers, non-photochemical quenching of Chl fluorescence and the maximum quantum yield of PSII in the dark.

    PubMed

    Miyake, Chikahiro; Amako, Katsumi; Shiraishi, Naomasa; Sugimoto, Toshio

    2009-04-01

    Responses of the reduction-oxidation level of plastoquinone (PQ) in the photosynthetic electron transport (PET) system of chloroplasts to growth light intensity were evaluated in tobacco plants. Plants grown in low light (150 micromol photons m-2 s-1) (LL plants) were exposed to a high light intensity (1,100 micromol photons m-2 s-1) for 1 d. Subsequently, the plants exposed to high light (LH plants) were returned back again to the low light condition: these plants were designated as LHL plants. Both LH and LHL plants showed higher values of non-photochemical quenching of Chl fluorescence (NPQ) and the fraction of open PSII centers (qL), and lower values of the maximum quantum yield of PSII in the dark (Fv/Fm), compared with LL plants. The dependence of qL on the quantum yield of PSII [Phi(PSII)] in LH and LHL plants was higher than that in LL plants. To evaluate the effect of an increase in NPQ and decrease in Fv/Fm on qL, we derived an equation expressing qL in relation to both NPQ and Fv/Fm, according to the lake model of photoexcitation of the PSII reaction center. As a result, the heat dissipation process, shown as NPQ, did not contribute greatly to the increase in qL. On the other hand, decreased Fv/Fm did contribute to the increase in qL, i.e. the enhanced oxidation of PQ under photosynthesis-limited conditions. Thylakoid membranes isolated from LH plants, having high qL, showed a higher tolerance against photoinhibition of PSII, compared with those from LL plants. We propose a 'plastoquinone oxidation system (POS)', which keeps PQ in an oxidized state by suppressing the accumulation of electrons in the PET system in such a way as to regulate the maximum quantum yield of PSII.

  1. Enhanced quantum yield of yellow photoluminescence of Dy{sup 3+} ions in nonlinear optical Ba{sub 2}TiSi{sub 2}O{sub 8} nanocrystals formed in glass

    SciTech Connect

    Maruyama, N.; Honma, T.; Komatsu, T.

    2009-02-15

    Transparent crystallized glasses consisting of nonlinear optical Ba{sub 2}TiSi{sub 2}O{sub 8} nanocrystals (diameter: {approx}100 nm) are prepared through the crystallization of 40BaO-20TiO{sub 2}-40SiO{sub 2}-0.5Dy{sub 2}O{sub 3} glass (in the molar ratio), and photoluminescence quantum yields of Dy{sup 3+} ions in the visible region are evaluated directly by using a photoluminescence spectrometer with an integrating sphere. The incorporation of Dy{sup 3+} ions into Ba{sub 2}TiSi{sub 2}O{sub 8} nanocrystals is confirmed from the X-ray diffraction analyses. The total quantum yields of the emissions at the bands of {sup 4}F{sub 9/2}{yields}{sup 6}H{sub 15/2} (blue: 484 nm), {sup 4}F{sub 9/2}{yields}{sup 6}H{sub 13/2} (yellow: 575 nm), and {sup 4}F{sub 9/2}{yields}{sup 6}H{sub 11/2} (red: 669 nm) in the crystallized glasses are {approx}15%, being about four times larger compared with the precursor glass. It is found that the intensity of yellow (575 nm) emissions and the branching ratio of the yellow (575 nm)/blue (484 nm) intensity ratio increase largely due to the crystallization. It is suggested from Judd-Ofelt analyses that the site symmetry of Dy{sup 3+} ions in the crystallized glasses is largely distorted, giving a large increase in the yellow emissions. It is proposed that Dy{sup 3+} ions substitute Ba{sup 2+} sites in Ba{sub 2}TiSi{sub 2}O{sub 8} nanocrystals. - Grapical abstract: This figure shows the photoluminescence spectra of Dy{sup 3+} ions in the range of 450-700 nm obtained in the quantum field measurements for the precursor BTS and crystallized (at 770 and 790 deg. C, for 30 min) glasses. The wavelength of the excitation light was 352 nm. By incorporating into Ba{sub 2}TiSi{sub 2}O{sub 8} nanocrystals, the emission intensity of the yellow band of Dy{sup 3+} ions is largely enhanced. This would give an impact in the science and technology of photoluminescence materials.

  2. Step-like increase of quantum yield of 1.5 μm Er-related emission in SiO{sub 2} doped with Si nanocrystals

    SciTech Connect

    Saeed, S.; Jong, E. M. L. D. de; Gregorkiewicz, T.

    2015-02-14

    We investigate the excitation dependence of the efficiency of the Si nanocrystals-mediated photoluminescence from Er{sup 3+} ions embedded in a SiO{sub 2} matrix. We show that the quantum yield of this emission increases in a step-like manner with excitation energy. The subsequent thresholds of this characteristic dependence are approximately given by the sum of the Si nanocrystals bandgap energy and multiples of 0.8 eV, corresponding to the energy of the first excited state of Er{sup 3+} ions. By comparing differently prepared materials, we explicitly demonstrate that the actual values of the threshold energies and the rate of the observed increase of the external quantum yield depend on sample characteristics—the size, the optical activity and the concentration of Si nanocrystals as well Er{sup 3+} ions to Si nanocrystals concentration ratio. In that way, detailed insights into the efficient excitation of Er{sup 3+} ions are obtained. In particular, the essential role of the hot-carrier-mediated Er excitation route is established, with a possible application perspective for highly efficient future-generation photovoltaics.

  3. A new homologous series Sr n-1 Cu n+1 O 2 n found in the SrOCuO system treated under high pressure

    NASA Astrophysics Data System (ADS)

    Hiroi, Z.; Azuma, M.; Takano, M.; Bando, Y.

    1991-11-01

    A new homologous series of high-pressure phases, Sr n-1 Cu n+1 O 2 n ( n = 3, 5, …), were found in the SrOCuO system treated at 6 GPa and 1373-1573 K. These crystallize in orthorhombic structures of space group Cmmm with unit-cell parameters of a ˜ 3.9 Å, b ˜ n × a, and c ˜ 3.5 Å. Along the c-axis Cu 1+ {1}/{n}O 2 sheets alternate with Sr1- {1}/{n} sheets without oxygen. Within the CuO sheets, CuO double chains made of corner- and edge-sharing CuO 4 squares are intergrown with a corner-sharing CuO 4 network; the distance between the double chains is {b}/{2}. The serial chemical composition and structure are interpreted as resulting from a shear operation upon the high-pressure form of SrCuO 2 ( n = ∞).

  4. Decay kinetics and quantum yields of fluorescence in photosystem I from Synechococcus elongatus with P700 in the reduced and oxidized state: are the kinetics of excited state decay trap-limited or transfer-limited?

    PubMed Central

    Byrdin, M; Rimke, I; Schlodder, E; Stehlik, D; Roelofs, T A

    2000-01-01

    Transfer and trapping of excitation energy in photosystem I (PS I) trimers isolated from Synechococcus elongatus have been studied by an approach combining fluorescence induction experiments with picosecond time-resolved fluorescence measurements, both at room temperature (RT) and at low temperature (5 K). Special attention was paid to the influence of the oxidation state of the primary electron donor P700. A fluorescence induction effect has been observed, showing a approximately 12% increase in fluorescence quantum yield upon P700 oxidation at RT, whereas at temperatures below 160 K oxidation of P700 leads to a decrease in fluorescence quantum yield ( approximately 50% at 5 K). The fluorescence quantum yield for open PS I (with P700 reduced) at 5 K is increased by approximately 20-fold and that for closed PS I (with P700 oxidized) is increased by approximately 10-fold, as compared to RT. Picosecond fluorescence decay kinetics at RT reveal a difference in lifetime of the main decay component: 34 +/- 1 ps for open PS I and 37 +/- 1 ps for closed PS I. At 5 K the fluorescence yield is mainly associated with long-lived components (lifetimes of 401 ps and 1.5 ns in closed PS I and of 377 ps, 1.3 ns, and 4.1 ns in samples containing approximately 50% open and 50% closed PS I). The spectra associated with energy transfer and the steady-state emission spectra suggest that the excitation energy is not completely thermally equilibrated over the core-antenna-RC complex before being trapped. Structure-based modeling indicates that the so-called red antenna pigments (A708 and A720, i.e., those with absorption maxima at 708 nm and 720 nm, respectively) play a decisive role in the observed fluorescence kinetics. The A720 are preferentially located at the periphery of the PS I core-antenna-RC complex; the A708 must essentially connect the A720 to the reaction center. The excited-state decay kinetics turn out to be neither purely trap limited nor purely transfer (to the trap

  5. High Throughput, High Yield Fabrication of High Quantum Efficiency Back-Illuminated Photon Counting, Far UV, UV, and Visible Detector Arrays

    NASA Technical Reports Server (NTRS)

    Nikzad, Shouleh; Hoenk, M. E.; Carver, A. G.; Jones, T. J.; Greer, F.; Hamden, E.; Goodsall, T.

    2013-01-01

    In this paper we discuss the high throughput end-to-end post fabrication processing of high performance delta-doped and superlattice-doped silicon imagers for UV, visible, and NIR applications. As an example, we present our results on far ultraviolet and ultraviolet quantum efficiency (QE) in a photon counting, detector array. We have improved the QE by nearly an order of magnitude over microchannel plates (MCPs) that are the state-of-the-art UV detectors for many NASA space missions as well as defense applications. These achievements are made possible by precision interface band engineering of Molecular Beam Epitaxy (MBE) and Atomic Layer Deposition (ALD).

  6. Dopamine-quantum dot conjugate: a new kind of photosensitizers for photodynamic therapy of cancers

    NASA Astrophysics Data System (ADS)

    Chou, Kai-Liang; Meng, He; Cen, Yan; Li, Lei; Chen, Ji-Yao

    2013-01-01

    The thiol-capped CdTe quantum dots (QDs) with the average size of 3.5 nm were linked to dopamines (DAs) forming DA-QD conjugates, with the characteristics of red-shifted photoluminescence (PL) peak and remarkably reduced PL lifetime. The QDs in the conjugates readily accept the electron from DAs when excited by the visible light, resulting in the oxidation of DAs and the production of singlet oxygen (1O2) with the yield comparable to that of sulfonated aluminum phthalocyanine (AlPcS), a popularly used photosensitizer. The DA-QD conjugate can quickly penetrate into human nasopharyngeal carcinoma (KB) cells and seriously destroy cells under the irradiation of visible lights, showing the potential to become a new kind of photosensitizers.

  7. The effects of side-chain-induced disorder on the emission spectra and quantum yields of oligothiophene nano-aggregates. A combined experimental and MD-TDDFT study

    SciTech Connect

    Hong, Jiyun; Jeon, SuKyung; Kim, Janice J.; Devi, Diane; Chacon-Madrid, Kelly; Lee, Wynee; Koo, Seung Moh; Wildeman, Jurjen; Sfeir, Matthew Y.; Peteanu, Linda A.; Wen, Jin; Ma, Jing

    2014-07-24

    Oligomeric thiophenes are commonly-used components in organic electronics and solar cells. These molecules stack and/or aggregate readily under the processing conditions used to form thin films for these applications, significantly altering their optical and charge-transport properties. To determine how these effects depend on the substitution pattern of the thiophene main chains, nano-aggregates of three sexi-thiophene (6T) oligomers having different alkyl substitution patterns were formed using solvent poisoning techniques and studied using steady-state and time-resolved emission spectroscopy. The results indicate the substantial role played by the side-chain substituents in determining the emissive properties of these species. Both the measured spectral changes and their dependence on substitution are well modeled by combined quantum chemistry and molecular dynamics simulations. The simulations connect the side-chain-induced disorder, which determines the favorable chain packing configurations within the aggregates, with their measured electronic spectra.

  8. Decay kinetics of the excited S{sub 1} state of the cyanine dye Cy{sup +}I{sup -} (thiacarbocyanine iodide): The computation of quantum yields for different pathways

    SciTech Connect

    Odinokov, A. V.; Basilevsky, M. V.; Petrov, N. Kh.

    2011-10-14

    This work explains the unordinary solvent effect which was observed in the photochemical decay kinetics for the cyanine dye thiacarbocyanine iodide (Cy{sup +}I{sup -}) in binary solvent mixtures toluene/dimethylsulfoxide. The interpretation is formulated in terms of the probability density F(R) describing the distribution of interionic distances R in the ion pair Cy{sup +}I{sup -} and depending on the solvent composition. The proper normalization of this distribution is expressed via the degree of association {alpha} for the ion pair in a given solvent mixture. The {alpha} values are, in turn, extracted by means of the mass action law from the ionic association constants computed in a separate publication. The detailed kinetic scheme includes the empirical parametrization of the R-dependent kinetic constants for different decay channels. The multiparameter fitting procedure represents, with the reasonable parameter values, the dependence of the observed quantum yields on the solvent composition.

  9. Time-dependent quantum wave packet study of the Ar+H{sub 2}{sup +}{yields}ArH{sup +}+H reaction on a new ab initio potential energy surface for the ground electronic state (1{sup 2}A Prime )

    SciTech Connect

    Hu Mei; Liu Xinguo; Tan Ruishan; Li Hongzheng; Xu Wenwu

    2013-05-07

    A new global potential energy surface for the ground electronic state (1{sup 2}A Prime ) of the Ar+H{sub 2}{sup +}{yields}ArH{sup +}+H reaction has been constructed by multi-reference configuration interaction method with Davidson correction and a basis set of aug-cc-pVQZ. Using 6080 ab initio single-point energies of all the regions for the dynamics, a many-body expansion function form has been used to fit these points. The quantum reactive scattering dynamics calculations taking into account the Coriolis coupling (CC) were carried out on the new potential energy surface over a range of collision energies (0.03-1.0 eV). The reaction probabilities and integral cross sections for the title reaction were calculated. The significance of including the CC quantum scattering calculation has been revealed by the comparison between the CC and the centrifugal sudden approximation calculation. The calculated cross section is in agreement with the experimental result at collision energy 1.0 eV.

  10. Ce(0.6)Zr(0.3)Y(0.1)O(2) nanorod supported gold and palladium alloy nanoparticles: high-performance catalysts for toluene oxidation.

    PubMed

    Tan, Wei; Deng, Jiguang; Xie, Shaohua; Yang, Huanggen; Jiang, Yang; Guo, Guangsheng; Dai, Hongxing

    2015-05-14

    The Ce0.6Zr0.3Y0.1O2 (CZY) nanorods and their supported gold and palladium alloy (zAuxPdy/CZY; z = 0.80-0.93 wt%; x or y = 0, 1, 2) nanoparticles (NPs) were prepared using the cetyltrimethyl ammonium bromide-assisted hydrothermal and polyvinyl alcohol-protected reduction methods, respectively. Physicochemical properties of the samples were characterized by means of numerous analytical techniques, and their catalytic activities were evaluated for the oxidation of toluene. It is shown that the CZY in zAuxPdy/CZY was cubic in crystal structure, surface areas of CZY and zAuxPdy/CZY were in the range 68-77 m(2) g(-1), and the Au-Pd NPs with a size of 4.6-5.6 nm were highly dispersed on the surface of CZY nanorods. Among all the samples, 0.90Au1Pd2/CZY possessed the highest adsorbed oxygen concentration and the best low-temperature reducibility, and performed the best: T50% and T90% (temperatures required for achieving toluene conversions of 50 and 90%) were 190 and 218 °C at a space velocity of 20 000 mL (g h)(-1), respectively. The partial deactivation due to water vapor introduction was reversible. The active sites might be the surface oxygen vacancies on CZY, oxidized noble metal NPs, and/or interfaces between noble metal NPs and CZY. The apparent activation energies (37-43 kJ mol(-1)) obtained over 0.90-0.93AuxPdy/CZY were much lower than that (88 kJ mol(-1)) obtained over CZY for toluene oxidation. It is concluded that the excellent catalytic performance of 0.90Au1Pd2/CZY was associated with its high adsorbed oxygen species concentration, good low-temperature reducibility, and strong interaction between Au-Pd NPs and CZY nanorods as well as good dispersion of Au-Pd NPs.

  11. The effects of side-chain-induced disorder on the emission spectra and quantum yields of oligothiophene nano-aggregates. A combined experimental and MD-TDDFT study

    DOE PAGES

    Hong, Jiyun; Jeon, SuKyung; Kim, Janice J.; ...

    2014-07-24

    Oligomeric thiophenes are commonly-used components in organic electronics and solar cells. These molecules stack and/or aggregate readily under the processing conditions used to form thin films for these applications, significantly altering their optical and charge-transport properties. To determine how these effects depend on the substitution pattern of the thiophene main chains, nano-aggregates of three sexi-thiophene (6T) oligomers having different alkyl substitution patterns were formed using solvent poisoning techniques and studied using steady-state and time-resolved emission spectroscopy. The results indicate the substantial role played by the side-chain substituents in determining the emissive properties of these species. Both the measured spectral changesmore » and their dependence on substitution are well modeled by combined quantum chemistry and molecular dynamics simulations. The simulations connect the side-chain-induced disorder, which determines the favorable chain packing configurations within the aggregates, with their measured electronic spectra.« less

  12. Quantum-chemical calculations of the metallofullerene yields in the X@C{sub 74}, L@C{sub 74}, and Z@C{sub 82} series

    SciTech Connect

    Uhlík, Filip; Slanina, Zdeněk; Nagase, Shigeru

    2015-01-22

    The contribution reports computations for Al@C{sub 82}, Sc@C{sub 82}, Y@C{sub 82} and La@C{sub 82} based on encapsulation into the IPR (isolated pentagon rule) C{sub 2ν} C{sub 82} cage and also on Mg@C{sub 74}, Ca@C{sub 74}, Sr@C{sub 74} and Ba@C{sub 74} based on encapsulation into the only C{sub 74} IPR cage as well as for three selected lanthanoids La@C{sub 74}, Yb@C{sub 74}, and Lu@C{sub 74}. Their structural and energetic characteristics are used for evaluations of the relative production yields, using the encapsulation Gibbs-energy and saturated metal pressures. It is shown that the results can be well related to the ionization potentials of the free metal atoms.

  13. Determination of the D{sup 0}{yields}K{sup -}{pi}{sup +}{pi}{sup 0} and D{sup 0}{yields}K{sup -}{pi}{sup +}{pi}{sup +}{pi}{sup -} coherence factors and average strong-phase differences using quantum-correlated measurements

    SciTech Connect

    Lowrey, N.; Mehrabyan, S.; Selen, M.; Wiss, J.; Mitchell, R. E.; Shepherd, M. R.; Besson, D.; Pedlar, T. K.; Cronin-Hennessy, D.; Gao, K. Y.; Hietala, J.; Kubota, Y.; Klein, T.; Poling, R.; Scott, A. W.; Zweber, P.; Dobbs, S.; Metreveli, Z.; Seth, K. K.; Tan, B. J. Y.

    2009-08-01

    The first measurements of the coherence factors (R{sub K{pi}}{sub {pi}{sup 0}} and R{sub K3{pi}}) and the average strong-phase differences ({delta}{sub D}{sup K{pi}}{sup {pi}{sup 0}} and {delta}{sub D}{sup K3{pi}}) for D{sup 0}{yields}K{sup -}{pi}{sup +}{pi}{sup 0} and D{sup 0}{yields}K{sup -}{pi}{sup +}{pi}{sup +}{pi}{sup -} are presented. These parameters can be used to improve the determination of the unitarity triangle angle {gamma} in B{sup -}{yields}DK{sup -} decays, where D is a D{sup 0} or D{sup 0} meson decaying to the same final state. The measurements are made using quantum-correlated, fully reconstructed D{sup 0}D{sup 0} pairs produced in e{sup +}e{sup -} collisions at the {psi}(3770) resonance. The measured values are: R{sub K{pi}}{sub {pi}{sup 0}}=0.84{+-}0.07, {delta}{sub D}{sup K{pi}}{sup {pi}{sup 0}}=(227{sub -17}{sup +14}) deg., R{sub K3{pi}}=0.33{sub -0.23}{sup +0.20}, and {delta}{sub D}{sup K3{pi}}=(114{sub -23}{sup +26}) deg. These results indicate significant coherence in the decay D{sup 0}{yields}K{sup -}{pi}{sup +}{pi}{sup 0}, whereas lower coherence is observed in the decay D{sup 0}{yields}K{sup -}{pi}{sup +}{pi}{sup +}{pi}{sup -}. The analysis also results in a small improvement in the knowledge of other D-meson parameters, in particular, the strong-phase difference for D{sup 0}{yields}K{sup -}{pi}{sup +}, {delta}{sub D}{sup K{pi}}, and the mixing parameter y.

  14. Short-Term Responses in Maximum Quantum Yield of PSII (Fv/Fm) to ex situ Temperature Treatment of Populations of Bryophytes Originating from Different Sites in Hokkaido, Northern Japan

    PubMed Central

    Jägerbrand, Annika K.; Kudo, Gaku

    2016-01-01

    There is limited knowledge available on the thermal acclimation processes for bryophytes, especially when considering variation between populations or sites. This study investigated whether short-term ex situ thermal acclimation of different populations showed patterns of site dependency and whether the maximum quantum yield of PSII (Fv/Fm) could be used as an indicator of adaptation or temperature stress in two bryophyte species: Pleurozium schreberi (Willd. ex Brid.) Mitt. and Racomitrium lanuginosum (Hedw.) Brid. We sought to test the hypothesis that differences in the ability to acclimate to short-term temperature treatment would be revealed as differences in photosystem II maximum yield (Fv/Fm). Thermal treatments were applied to samples from 12 and 11 populations during 12 or 13 days in growth chambers and comprised: (1) 10/5 °C; (2) 20/10 °C; (3) 25/15 °C; (4) 30/20 °C (12 hours day/night temperature). In Pleurozium schreberi, there were no significant site-dependent differences before or after the experiment, while site dependencies were clearly shown in Racomitrium lanuginosum throughout the study. Fv/Fm in Pleurozium schreberi decreased at the highest and lowest temperature treatments, which can be interpreted as a stress response, but no similar trends were shown by Racomitrium lanuginosum. PMID:27135242

  15. An Acoustic Charge Transport Imager for High Definition Television Applications: Reliability Modeling and Parametric Yield Prediction of GaAs Multiple Quantum Well Avalanche Photodiodes. Degree awarded Oct. 1997

    NASA Technical Reports Server (NTRS)

    Hunt, W. D.; Brennan, K. F.; Summers, C. J.; Yun, Ilgu

    1994-01-01

    Reliability modeling and parametric yield prediction of GaAs/AlGaAs multiple quantum well (MQW) avalanche photodiodes (APDs), which are of interest as an ultra-low noise image capture mechanism for high definition systems, have been investigated. First, the effect of various doping methods on the reliability of GaAs/AlGaAs multiple quantum well (MQW) avalanche photodiode (APD) structures fabricated by molecular beam epitaxy is investigated. Reliability is examined by accelerated life tests by monitoring dark current and breakdown voltage. Median device lifetime and the activation energy of the degradation mechanism are computed for undoped, doped-barrier, and doped-well APD structures. Lifetimes for each device structure are examined via a statistically designed experiment. Analysis of variance shows that dark-current is affected primarily by device diameter, temperature and stressing time, and breakdown voltage depends on the diameter, stressing time and APD type. It is concluded that the undoped APD has the highest reliability, followed by the doped well and doped barrier devices, respectively. To determine the source of the degradation mechanism for each device structure, failure analysis using the electron-beam induced current method is performed. This analysis reveals some degree of device degradation caused by ionic impurities in the passivation layer, and energy-dispersive spectrometry subsequently verified the presence of ionic sodium as the primary contaminant. However, since all device structures are similarly passivated, sodium contamination alone does not account for the observed variation between the differently doped APDs. This effect is explained by the dopant migration during stressing, which is verified by free carrier concentration measurements using the capacitance-voltage technique.

  16. Evaluation of the absolute photoluminescence quantum yields of molecularly doped organic composite films and the electroluminescence efficiencies of molecular light-emitting devices containing oligoheterocycles as efficient emission centers

    NASA Astrophysics Data System (ADS)

    Kushto, Gary P.; Hill, Ian G.; Mitschke, Ullrich; Baeuerle, Peter; Kafafi, Zakya H.

    2001-02-01

    The absolute photoluminescence quantum yields ((Phi) PL) of three end-capped oligothiophene derivatives dispersed in N,N'-((alpha) -naphthyl)-N,N'-diphenyl-1,1'-biphenyl ((alpha) -NPD) have been evaluated and the most efficient of the emitters was used as a dopant in molecular organic LEDs. Composite films of 2,5-bis [5-(4,5,6,7- tetrahydrobenzo[b]thien-2-yl) thien-2-yl]-furan (EC5FUR); 2,5-bis [5-(4,5,6,7- tetrahydrobenzo[b]thien-2-yl) thien-2-yl]-oxazole (EC5OXZ) and 2,5-bis [5-(4,5,6,7- tetrahydrobenzo[b]thien-2-yl)thien-2-yl]-1,3,4- oxadiazole (EC5OXD) doped into (alpha) -NPD were found to have (Phi) PL values of 78, 62 and 28%, respectively. MOLED devices were fabricated using an EC5FUR/(alpha) -NPD composite as the emitting layer and the external quantum efficiencies ((eta) EL) of these devices were evaluated. The results of the device characterization show that the inclusion of EC5FUR in the NPD hole transport layer increases the device (eta) EL to 1.45% at a current density of 10 mA/cm2. In addition, the concentration dependence of the (eta) EL on the EC5FUR dopant in certain device structures when considered in conjunction with the current results of ultraviolet photoemission spectroscopic experiments suggests that this dopant species may be acting as both a hole and electron trap in the (alpha) -NPD host.

  17. Quantum phase slip noise

    NASA Astrophysics Data System (ADS)

    Semenov, Andrew G.; Zaikin, Andrei D.

    2016-07-01

    Quantum phase slips (QPSs) generate voltage fluctuations in superconducting nanowires. Employing the Keldysh technique and making use of the phase-charge duality arguments, we develop a theory of QPS-induced voltage noise in such nanowires. We demonstrate that quantum tunneling of the magnetic flux quanta across the wire yields quantum shot noise which obeys Poisson statistics and is characterized by a power-law dependence of its spectrum SΩ on the external bias. In long wires, SΩ decreases with increasing frequency Ω and vanishes beyond a threshold value of Ω at T →0 . The quantum coherent nature of QPS noise yields nonmonotonous dependence of SΩ on T at small Ω .

  18. Nd1.8Ce0.2CuO4+δ:Ce0.9Gd0.1O2-δ as a composite cathode for intermediate-temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Khandale, A. P.; Bhoga, S. S.

    2014-12-01

    The (100 - x)Nd1.8Ce0.2CuO4+δ:(x)Ce0.9Gd0.1O2-δ (x = 00, 10, 20 and 30 vol.%) composite systems are obtained by impregnating a stoichiometric solution of cerium and gadolinium nitrates followed by sintering at 900 °C for 4 h. Impregnating the Ce0.9Gd0.1O2-δ not only inhibits the growth of the host Nd1.8Ce0.2CuO4+δ grains during sintering but also enlarges the oxygen reduction reaction zone by introducing a nanosized phase that is ionically conductive, which significantly decreases the electrode polarization resistance of the composite cathode. A minimum polarization resistance value of 0.23 ± 0.02 Ω cm2 is obtained at 700 °C for a (80)Nd1.8Ce0.2CuO4+δ:(20)Ce0.9Gd0.1O2-δ composite cathode, and this value is attributed to the optimal dispersion into the porous Nd1.8Ce0.2CuO4+δ matrix. The impedance spectra are modeled using an electrical equivalent model that consists of a mid-frequency ZR1 -CPE circuit (parallel combination of R1 and constant phase element (CPE)) and a low-frequency Gerischer impedance. The Gerischer impedance decreases significantly when Ce0.9Gd0.1O2-δ infiltrates the Nd1.8Ce0.2CuO4+δ matrix. The oxygen partial pressure-dependent polarization study suggests a medium-frequency response, which is due to charge transfer step; however, the low-frequency response corresponds to the non-charge transfer oxygen adsorption-desorption and the diffusion process during the overall oxygen reduction reaction process.

  19. HYPERSENSITIVE TO HIGH LIGHT1 Interacts with LOW QUANTUM YIELD OF PHOTOSYSTEM II1 and Functions in Protection of Photosystem II from Photodamage in Arabidopsis[C][W][OPEN

    PubMed Central

    Jin, Honglei; Liu, Bing; Luo, Lujun; Feng, Dongru; Wang, Peng; Liu, Jun; Da, Qingen; He, Yanming; Qi, Kangbiao; Wang, Jinfa; Wang, Hong-Bin

    2014-01-01

    Under high-irradiance conditions, plants must efficiently protect photosystem II (PSII) from damage. In this study, we demonstrate that the chloroplast protein HYPERSENSITIVE TO HIGH LIGHT1 (HHL1) is expressed in response to high light and functions in protecting PSII against photodamage. Arabidopsis thaliana hhl1 mutants show hypersensitivity to high light, drastically decreased PSII photosynthetic activity, higher nonphotochemical quenching activity, a faster xanthophyll cycle, and increased accumulation of reactive oxygen species following high-light exposure. Moreover, HHL1 deficiency accelerated the degradation of PSII core subunits under high light, decreasing the accumulation of PSII core subunits and PSII–light-harvesting complex II supercomplex. HHL1 primarily localizes in the stroma-exposed thylakoid membranes and associates with the PSII core monomer complex through direct interaction with PSII core proteins CP43 and CP47. Interestingly, HHL1 also directly interacts, in vivo and in vitro, with LOW QUANTUM YIELD OF PHOTOSYSTEM II1 (LQY1), which functions in the repair and reassembly of PSII. Furthermore, the hhl1 lqy1 double mutants show increased photosensitivity compared with single mutants. Taken together, these results suggest that HHL1 forms a complex with LQY1 and participates in photodamage repair of PSII under high light. PMID:24632535

  20. Photocatalytic activity of transition-metal-ion-doped coordination polymer (CP): photoresponse region extension and quantum yields enhancement via doping of transition metal ions into the framework of CPs.

    PubMed

    Xu, Xin-Xin; Cui, Zhong-Ping; Gao, Xin; Liu, Xiao-Xia

    2014-06-21

    To improve photocatalytic activity of a coordination polymer (CP) in the visible light region, five different transition metal ions (Fe(3+), Cr(3+), Ru(3+), Co(2+) and Ni(2+)) were introduced into its framework through an ion-exchange process. Among all the resulting transition metal ion doped coordination polymers (TMI/CPs), the one doped with Fe(3+) took on the most excellent photocatalytic activity and the highest quantum yields in the visible light region, decomposing 94% Rhodamine B (RhB) in 8 hours. It can be attributed to the doping of Fe(3+), which reduced the band gap (Eg) of the original CP, facilitating photocatalysis of the obtained polymer. Compared with the coordination polymer with Fe(3+) as a dopant, products doped with other metal ions presented weaker photocatalytic activities in the visible light region, while under the irradiation of ultraviolet light, they showed favorable photocatalytic properties. The results suggest that to dope transition metal ions into the framework of CPs would be an ideal option for enhancing the photocatalytic activity of coordination polymers.

  1. Quantum computing of semiclassical formulas.

    PubMed

    Georgeot, B; Giraud, O

    2008-04-01

    We show that semiclassical formulas such as the Gutzwiller trace formula can be implemented on a quantum computer more efficiently than on a classical device. We give explicit quantum algorithms which yield quantum observables from classical trajectories, and which alternatively test the semiclassical approximation by computing classical actions from quantum evolution. The gain over classical computation is in general quadratic, and can be larger in some specific cases.

  2. Quantum Turbulence

    NASA Astrophysics Data System (ADS)

    Tsubota, Makoto

    2008-11-01

    The present article reviews the recent developments in the physics of quantum turbulence. Quantum turbulence (QT) was discovered in superfluid 4He in the 1950s, and the research has tended toward a new direction since the mid 90s. The similarities and differences between quantum and classical turbulence have become an important area of research. QT is comprised of quantized vortices that are definite topological defects, being expected to yield a model of turbulence that is much simpler than the classical model. The general introduction of the issue and a brief review on classical turbulence are followed by a description of the dynamics of quantized vortices. Then, we discuss the energy spectrum of QT at very low temperatures. At low wavenumbers, the energy is transferred through the Richardson cascade of quantized vortices, and the spectrum obeys the Kolmogorov law, which is the most important statistical law in turbulence; this classical region shows the similarity to conventional turbulence. At higher wavenumbers, the energy is transferred by the Kelvin-wave cascade on each vortex. This quantum regime depends strongly on the nature of each quantized vortex. The possible dissipation mechanism is discussed. Finally, important new experimental studies, which include investigations into temperature-dependent transition to QT, dissipation at very low temperatures, QT created by vibrating structures, and visualization of QT, are reviewed. The present article concludes with a brief look at QT in atomic Bose-Einstein condensates.

  3. Correlation of oxygen non-stoichiometry to the instabilities and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 utilized in lithium ion battery

    NASA Astrophysics Data System (ADS)

    Bi, Yujing; Yang, Wenchao; Du, Rui; Zhou, Jingjing; Liu, Meng; Liu, Yang; Wang, Deyu

    2015-06-01

    In this work, we investigate the influence of oxygen non-stoichiometry on the characteristics of LiNi0.8Co0.1Mn0.1O2 cathode material. Among the investigated samples, the level of Ni/Li disorder in the bulk and the thickness of auto-generated layer on the surface share the same trend as the amount of oxygen loss in LiNi0.8Co0.1Mn0.1O2 materials. It indicates that the aforementioned key structural instabilities should be tightly related to the oxygen defects and the induced structural relaxation. As a consequence of structural entirety, the sample with the least defects presents the highest discharge capacity (192.9 mAhg-1 at 0.1C), the best rate capability (160.1 mAhg-1 at 5C), and the most stable cyclibility (89.9% at 200th). Our results demonstrate that oxygen deficiency plays a key role to determine the electrochemical performance of high-nickel cathode materials.

  4. Improved cycle stability of high-capacity Ni-rich LiNi0.8Mn0.1Co0.1O2 at high cut-off voltage by Li2SiO3 coating

    NASA Astrophysics Data System (ADS)

    Zhao, Enyue; Chen, Minmin; Hu, Zhongbo; Chen, Dongfeng; Yang, Limei; Xiao, Xiaoling

    2017-03-01

    A high cut-off voltage is pretty pivotal for the improvement of the energy density of cathode materials. Unfortunately, high-capacity Ni-rich cathode materials usually show serious capacity attenuation at high cut-off voltage. Herein, we propose a Li2SiO3-surface modification strategy to highly improve the cycle performance of the Ni-rich LiNi0.8Mn0.1Co0.1O2 material at high voltage. The capacity retention of the pristine and Li2SiO3-coated electrodes is 57.6 and 77.7%, respectively, at the cut-off voltage of 4.6 V after 50 cycles. Meanwhile, the problems of polarization and voltage reduction of LiNi0.8Mn0.1Co0.1O2 are also alleviated. Our results show that Li2SiO3-surface modification is a very effective strategy for improving the cycle stability of Ni-rich cathode materials and can be used for other high capacity electrode materials.

  5. Quantum Approach to Informatics

    NASA Astrophysics Data System (ADS)

    Stenholm, Stig; Suominen, Kalle-Antti

    2005-08-01

    An essential overview of quantum information Information, whether inscribed as a mark on a stone tablet or encoded as a magnetic domain on a hard drive, must be stored in a physical object and thus made subject to the laws of physics. Traditionally, information processing such as computation occurred in a framework governed by laws of classical physics. However, information can also be stored and processed using the states of matter described by non-classical quantum theory. Understanding this quantum information, a fundamentally different type of information, has been a major project of physicists and information theorists in recent years, and recent experimental research has started to yield promising results. Quantum Approach to Informatics fills the need for a concise introduction to this burgeoning new field, offering an intuitive approach for readers in both the physics and information science communities, as well as in related fields. Only a basic background in quantum theory is required, and the text keeps the focus on bringing this theory to bear on contemporary informatics. Instead of proofs and other highly formal structures, detailed examples present the material, making this a uniquely accessible introduction to quantum informatics. Topics covered include: * An introduction to quantum information and the qubit * Concepts and methods of quantum theory important for informatics * The application of information concepts to quantum physics * Quantum information processing and computing * Quantum gates * Error correction using quantum-based methods * Physical realizations of quantum computing circuits A helpful and economical resource for understanding this exciting new application of quantum theory to informatics, Quantum Approach to Informatics provides students and researchers in physics and information science, as well as other interested readers with some scientific background, with an essential overview of the field.

  6. Quantum focusing conjecture

    NASA Astrophysics Data System (ADS)

    Bousso, Raphael; Fisher, Zachary; Leichenauer, Stefan; Wall, Aron C.

    2016-03-01

    We propose a universal inequality that unifies the Bousso bound with the classical focusing theorem. Given a surface σ that need not lie on a horizon, we define a finite generalized entropy Sgen as the area of σ in Planck units, plus the von Neumann entropy of its exterior. Given a null congruence N orthogonal to σ , the rate of change of Sgen per unit area defines a quantum expansion. We conjecture that the quantum expansion cannot increase along N . This extends the notion of universal focusing to cases where quantum matter may violate the null energy condition. Integrating the conjecture yields a precise version of the Strominger-Thompson quantum Bousso bound. Applied to locally parallel light-rays, the conjecture implies a novel inequality, the quantum null energy condition, a lower bound on the stress tensor in terms of the second derivative of the von Neumann entropy. We sketch a proof of the latter relation in quantum field theory.

  7. Cold-acclimation limits low temperature induced photoinhibition by promoting a higher photochemical quantum yield and a more effective PSII restoration in darkness in the Antarctic rather than the Andean ecotype of Colobanthus quitensis Kunt Bartl (Cariophyllaceae)

    PubMed Central

    2012-01-01

    Background Ecotypes of Colobanthus quitensis Kunt Bartl (Cariophyllaceae) from Andes Mountains and Maritime Antarctic grow under contrasting photoinhibitory conditions, reaching differential cold tolerance upon cold acclimation. Photoinhibition depends on the extent of photodamage and recovery capability. We propose that cold acclimation increases resistance to low-temperature-induced photoinhibition, limiting photodamage and promoting recovery under cold. Therefore, the Antarctic ecotype (cold hardiest) should be less photoinhibited and have better recovery from low-temperature-induced photoinhibition than the Andean ecotype. Both ecotypes were exposed to cold induced photoinhibitory treatment (PhT). Photoinhibition and recovery of photosystem II (PSII) was followed by fluorescence, CO2 exchange, and immunoblotting analyses. Results The same reduction (25%) in maximum PSII efficiency (Fv/Fm) was observed in both cold-acclimated (CA) and non-acclimated (NA) plants under PhT. A full recovery was observed in CA plants of both ecotypes under dark conditions, but CA Antarctic plants recover faster than the Andean ecotype. Under PhT, CA plants maintain their quantum yield of PSII, while NA plants reduced it strongly (50% and 73% for Andean and Antarctic plants respectively). Cold acclimation induced the maintenance of PsaA and Cyt b6/f and reduced a 41% the excitation pressure in Antarctic plants, exhibiting the lowest level under PhT. xCold acclimation decreased significantly NPQs in both ecotypes, and reduced chlorophylls and D1 degradation in Andean plants under PhT. NA and CA plants were able to fully restore their normal photosynthesis, while CA Antarctic plants reached 50% higher photosynthetic rates after recovery, which was associated to electron fluxes maintenance under photoinhibitory conditions. Conclusions Cold acclimation has a greater importance on the recovery process than on limiting photodamage. Cold acclimation determined the kinetic and extent of

  8. Sm0.5Sr0.5CoO3-δ infiltrated Ce0.9Gd0.1O2-δ composite cathodes for high performance protonic ceramic fuel cells

    NASA Astrophysics Data System (ADS)

    Zhao, Ling; Li, Geng; Chen, Kongfa; Ling, Yihan; Cui, Yuexiao; Gui, Liangqi; He, Beibei

    2016-11-01

    Sm0.5Sr0.5CoO3-δ (SSC) infiltrated Ce0.9Gd0.1O2-δ (GDC) composite cathodes are developed for protonic ceramic fuel cells (PCFCs). Although the SSC infiltrated GDC cathodes make little contribute to expending the reaction sites of water formation, it can significantly improve the oxygen reduction dynamics among the whole electrochemical reaction. The symmetric half cell and single cell testing results demonstrate the high electrochemical activity of SSC infiltrated GDC cathodes. Moreover, the single cell is stable at 600 °C for 120 h in humidified H2 and humidified H2sbnd CO. The encouraging results indicate that the SSC infiltrated GDC could be the promising composite cathodes for application in PCFCs.

  9. Pd-substituted (La,Sr)CrO3-δ-Ce0.9Gd0.1O2-δ solid oxide fuel cell anodes exhibiting regenerative behavior

    NASA Astrophysics Data System (ADS)

    Bierschenk, David M.; Potter-Nelson, Elizabeth; Hoel, Cathleen; Liao, Yougui; Marks, Laurence; Poeppelmeier, Kenneth R.; Barnett, Scott A.

    2011-03-01

    Composite anodes consisting of Pd-substituted (La,Sr)CrO3-δ mixed with 50 wt% Ce0.9Gd0.1O2-δ were tested in La0.9Sr0.1Ga0.8Mg0.2O3-δ-electrolyte supported fuel cells at 800 °C with humidified H2 fuel. Low anode polarization resistance was observed during the first several hours of operation, explained by the nucleation of Pd nano-particles on perovskite particle surfaces. Anode performance then degraded gradually before stabilizing. Redox cycling repeatedly restored the anodes to their initial peak performance, followed again by degradation. This regenerative behavior was explained by the observation that the Pd nano-particles were removed by oxidation, and then re-nucleated upon reduction.

  10. Raising yield potential in wheat: increasing photosynthesis capacity and efficiency

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increasing wheat yields to help to ensure food security is a major challenge. Meeting this challenge requires a quantum improvement in the yield potential of wheat. Past increases in yield potential have largely resulted from improvements in harvest index not through increased biomass. Further large...

  11. Intrinsic Origins of Crack Generation in Ni-rich LiNi0.8Co0.1Mn0.1O2 Layered Oxide Cathode Material

    NASA Astrophysics Data System (ADS)

    Lim, Jin-Myoung; Hwang, Taesoon; Kim, Duho; Park, Min-Sik; Cho, Kyeongjae; Cho, Maenghyo

    2017-01-01

    Ni-rich LiNi0.8Co0.1Mn0.1O2 layered oxide cathodes have been highlighted for large-scale energy applications due to their high energy density. Although its specific capacity is enhanced at higher voltages as Ni ratio increases, its structural degradation due to phase transformations and lattice distortions during cycling becomes severe. For these reasons, we focused on the origins of crack generation from phase transformations and structural distortions in Ni-rich LiNi0.8Co0.1Mn0.1O2 using multiscale approaches, from first-principles to meso-scale phase-field model. Atomic-scale structure analysis demonstrated that opposite changes in the lattice parameters are observed until the inverse Li content x = 0.75 then, structure collapses due to complete extraction of Li from between transition metal layers. Combined-phase investigations represent the highest phase barrier and steepest chemical potential after x = 0.75, leading to phase transformations to highly Li-deficient phases with an inactive character. Abrupt phase transformations with heterogeneous structural collapse after x = 0.81 (~220 mAh g‑1) were identified in the nanodomain. Further, meso-scale strain distributions show around 5% of anisotropic contraction with lower critical energy release rates, which cause not only micro-crack generations of secondary particles on the interfaces between the contracted primary particles, but also mechanical instability of primary particles from heterogeneous strain changes.

  12. Intrinsic Origins of Crack Generation in Ni-rich LiNi0.8Co0.1Mn0.1O2 Layered Oxide Cathode Material

    PubMed Central

    Lim, Jin-Myoung; Hwang, Taesoon; Kim, Duho; Park, Min-Sik; Cho, Kyeongjae; Cho, Maenghyo

    2017-01-01

    Ni-rich LiNi0.8Co0.1Mn0.1O2 layered oxide cathodes have been highlighted for large-scale energy applications due to their high energy density. Although its specific capacity is enhanced at higher voltages as Ni ratio increases, its structural degradation due to phase transformations and lattice distortions during cycling becomes severe. For these reasons, we focused on the origins of crack generation from phase transformations and structural distortions in Ni-rich LiNi0.8Co0.1Mn0.1O2 using multiscale approaches, from first-principles to meso-scale phase-field model. Atomic-scale structure analysis demonstrated that opposite changes in the lattice parameters are observed until the inverse Li content x = 0.75; then, structure collapses due to complete extraction of Li from between transition metal layers. Combined-phase investigations represent the highest phase barrier and steepest chemical potential after x = 0.75, leading to phase transformations to highly Li-deficient phases with an inactive character. Abrupt phase transformations with heterogeneous structural collapse after x = 0.81 (~220 mAh g−1) were identified in the nanodomain. Further, meso-scale strain distributions show around 5% of anisotropic contraction with lower critical energy release rates, which cause not only micro-crack generations of secondary particles on the interfaces between the contracted primary particles, but also mechanical instability of primary particles from heterogeneous strain changes. PMID:28045118

  13. Quantum State Smoothing

    NASA Astrophysics Data System (ADS)

    Guevara, Ivonne; Wiseman, Howard

    2015-10-01

    Smoothing is an estimation method whereby a classical state (probability distribution for classical variables) at a given time is conditioned on all-time (both earlier and later) observations. Here we define a smoothed quantum state for a partially monitored open quantum system, conditioned on an all-time monitoring-derived record. We calculate the smoothed distribution for a hypothetical unobserved record which, when added to the real record, would complete the monitoring, yielding a pure-state "quantum trajectory." Averaging the pure state over this smoothed distribution yields the (mixed) smoothed quantum state. We study how the choice of actual unraveling affects the purity increase over that of the conventional (filtered) state conditioned only on the past record.

  14. Quantum State Smoothing.

    PubMed

    Guevara, Ivonne; Wiseman, Howard

    2015-10-30

    Smoothing is an estimation method whereby a classical state (probability distribution for classical variables) at a given time is conditioned on all-time (both earlier and later) observations. Here we define a smoothed quantum state for a partially monitored open quantum system, conditioned on an all-time monitoring-derived record. We calculate the smoothed distribution for a hypothetical unobserved record which, when added to the real record, would complete the monitoring, yielding a pure-state "quantum trajectory." Averaging the pure state over this smoothed distribution yields the (mixed) smoothed quantum state. We study how the choice of actual unraveling affects the purity increase over that of the conventional (filtered) state conditioned only on the past record.

  15. Quantum plasmonic sensing

    DOE PAGES

    Fan, Wenjiang; Lawrie, Benjamin J.; Pooser, Raphael C.

    2015-11-04

    Surface plasmon resonance (SPR) sensors can reach the quantum noise limit of the optical readout field in various configurations. We demonstrate that two-mode intensity squeezed states produce a further enhancement in sensitivity compared with a classical optical readout when the quantum noise is used to transduce an SPR sensor signal in the Kretschmann configuration. The quantum noise reduction between the twin beams when incident at an angle away from the plasmonic resonance, combined with quantum noise resulting from quantum anticorrelations when on resonance, results in an effective SPR-mediated modulation that yields a measured sensitivity 5 dB better than that withmore » a classical optical readout in this configuration. Furthermore, the theoretical potential of this technique points to resolving particle concentrations with more accuracy than is possible via classical approaches to optical transduction.« less

  16. Quantum plasmonic sensing

    SciTech Connect

    Fan, Wenjiang; Lawrie, Benjamin J.; Pooser, Raphael C.

    2015-11-04

    Surface plasmon resonance (SPR) sensors can reach the quantum noise limit of the optical readout field in various configurations. We demonstrate that two-mode intensity squeezed states produce a further enhancement in sensitivity compared with a classical optical readout when the quantum noise is used to transduce an SPR sensor signal in the Kretschmann configuration. The quantum noise reduction between the twin beams when incident at an angle away from the plasmonic resonance, combined with quantum noise resulting from quantum anticorrelations when on resonance, results in an effective SPR-mediated modulation that yields a measured sensitivity 5 dB better than that with a classical optical readout in this configuration. Furthermore, the theoretical potential of this technique points to resolving particle concentrations with more accuracy than is possible via classical approaches to optical transduction.

  17. Yield Advances in Peanut

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Average yields of peanut in the U.S. set an all time record of 4,695 kg ha-1 in 2012. This far exceeded the previous record yield of 3,837 kg ha-1 in 2008. Favorable weather conditions undoubtedly contributed to the record yields in 2012; however, these record yields would not have been achievable...

  18. Magnetic Order and Frustrated Dynamics in Li (Ni0.8Co0.1Mn0.1)O2: A Study by μ+SR and SQUID Magnetometry

    NASA Astrophysics Data System (ADS)

    Wikberg, J. Magnus; Månsson, Martin; Dahbi, Mohammed; Kamazawa, Kazuya; Sugiyama, Jun

    Recently, the mixed transition metal oxides of the form Li (Ni1-y-zCoyMnz)O2, havebecome the center of attention as promising candidates for novel battery material. These materials have also revealed very interesting magnetic properties due to the alternate stacking of planes of metal oxides on a 2D triangular lattice and the Li-layers. The title compound, Li (Ni0.8Co0.1Mn0.1) O2, has been investigated by both magnetometry and measurements and μ+SR. We find the evolution of localized magnetic moments with decreasing temperature below 70 K. The magnetic ground state (T = 2K) is, however, shown to be a frustrated system in 3D, followed by a transition into a possible 2D spin-glass above 22 K.With further increasing temperature the compound show the presence of remaining correlations with increasing effective dimensionality all the way up to the ferrimagnetic transition at TC = 70 K.

  19. A new LaCo0.71(1)V0.29(1)O2.97(3) perovskite containing vanadium in octahedral sites: synthesis and structural and magnetic characterization.

    PubMed

    Fuertes, V C; Blanco, M C; Franco, D G; Ceppi, S; Sánchez, R D; Fernández-Díaz, M T; Tirao, G; Carbonio, R E

    2015-06-21

    In the course of an investigation to prepare the hypothetic new double perovskite La(3)Co(2)VO(9) with Co(2+) and V(5+) in octahedral sites, we obtained the new simple perovskite LaCo(0.71(1))V(0.29(1))O(2.97(3)) as the main phase. The pure compound was then synthesized by the citrate decomposition method. The crystal structure was studied by X-ray (PXRD) and powder neutron diffraction (PND). Physical properties were characterized by X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and thermogravimetric analysis (TGA). Rietveld refinements were performed in the orthorhombic space group Pnma (#62). Refined cell parameters were a = 5.4762(2) Å, b = 7.7609(2) Å and c = 5.5122(1) Å. Magnetization measurements showed that this perovskite is an antiferromagnet with a Neel temperature of 15 K. At high T the magnetization follows the Curie-Weiss law corrected by temperature independent paramagnetism (TIP) showing an effective magnetic moment of 3.03μ(B) well described by the contribution of Co(2+) (HS), Co(3+) (IS), V(3+) and V(4+) ions. The crystallographic formula was refined by PND and oxidation state distribution was determined by the combination of PND, XAS, TGA and magnetic measurements.

  20. Optimization of the electrochemical performance of a Ni/Ce0.9Gd0.1O2-δ-impregnated La0.57Sr0.15TiO3 anode in hydrogen

    NASA Astrophysics Data System (ADS)

    Xia, Tian; Brüll, Annelise; Grimaud, Alexis; Fourcade, Sébastien; Mauvy, Fabrice; Zhao, Hui; Grenier, Jean-Claude; Bassat, Jean-Marc

    2014-09-01

    A-site deficient perovskite La0.57Sr0.15TiO3 (LSTO) materials are synthesized by a modified polyacrylamide gel route. X-ray diffraction pattern of LSTO indicates an orthorhombic structure. The thermal expansion coefficient of LSTO is 10.0 × 10-6 K-1 at 600 °C in 5%H2/Ar. LSTO shows an electrical conductivity of 2 S cm-1 at 600 °C in 3%H2O/H2. A new composite material, containing the porous LSTO backbone impregnated with small amounts of Ce0.9Gd0.1O2-δ (CGO) (3.4-8.3 wt.%) and Ni/Cu (2.0-6.3 wt.%), is investigated as an alternative anode for solid oxide fuel cells (SOFCs). Because of the substantial electro-catalytic activity of the fine and well-dispersed Ni particles on the surface of the ceramic framework, the polarization resistance of 6.3%Ni-8.3%CGO-LSTO anode reaches 0.73 Ω cm2 at 800 °C in 3%H2O/H2. In order to further improve the anodic performance, corn starch and carbon black are used as pore-formers to optimize the microstructure of anodes.

  1. Machine learning for precise quantum measurement.

    PubMed

    Hentschel, Alexander; Sanders, Barry C

    2010-02-12

    Adaptive feedback schemes are promising for quantum-enhanced measurements yet are complicated to design. Machine learning can autonomously generate algorithms in a classical setting. Here we adapt machine learning for quantum information and use our framework to generate autonomous adaptive feedback schemes for quantum measurement. In particular, our approach replaces guesswork in quantum measurement by a logical, fully automatic, programable routine. We show that our method yields schemes that outperform the best known adaptive scheme for interferometric phase estimation.

  2. Quantum Mechanics in Insulators

    SciTech Connect

    Aeppli, G.

    2009-08-20

    Atomic physics is undergoing a large revival because of the possibility of trapping and cooling ions and atoms both for individual quantum control as well as collective quantum states, such as Bose-Einstein condensates. The present lectures start from the 'atomic' physics of isolated atoms in semiconductors and insulators and proceed to coupling them together to yield magnets undergoing quantum phase transitions as well as displaying novel quantum states with no classical analogs. The lectures are based on: G.-Y. Xu et al., Science 317, 1049-1052 (2007); G. Aeppli, P. Warburton, C. Renner, BT Technology Journal, 24, 163-169 (2006); H. M. Ronnow et al., Science 308, 392-395 (2005) and N. Q. Vinh et al., PNAS 105, 10649-10653 (2008).

  3. Quantum Criticality and Black Holes

    SciTech Connect

    Sachdev, Subir

    2007-08-22

    I will describe the behavior of a variety of condensed matter systems in the vicinity of zero temperature quantum phase transitions. There is a remarkable analogy between the hydrodynamics of such systems and the quantum theory of black holes. I will show how insights from this analogy have shed light on recent experiments on the cuprate high temperature superconductors. Studies of new materials and trapped ultracold atoms are yielding new quantum phases, with novel forms of quantum entanglement. Some materials are of technological importance: e.g. high temperature superconductors. Exact solutions via black hole mapping have yielded first exact results for transport coefficients in interacting many-body systems, and were valuable in determining general structure of hydrodynamics. Theory of VBS order and Nernst effect in cuprates. Tabletop 'laboratories for the entire universe': quantum mechanics of black holes, quark-gluon plasma, neutrons stars, and big-bang physics.

  4. Quantum Criticality and Black Holes

    ScienceCinema

    Sachdev, Subir [Harvard University, Cambridge, Massachusetts, United States

    2016-07-12

    I will describe the behavior of a variety of condensed matter systems in the vicinity of zero temperature quantum phase transitions. There is a remarkable analogy between the hydrodynamics of such systems and the quantum theory of black holes. I will show how insights from this analogy have shed light on recent experiments on the cuprate high temperature superconductors. Studies of new materials and trapped ultracold atoms are yielding new quantum phases, with novel forms of quantum entanglement. Some materials are of technological importance: e.g. high temperature superconductors. Exact solutions via black hole mapping have yielded first exact results for transport coefficients in interacting many-body systems, and were valuable in determining general structure of hydrodynamics. Theory of VBS order and Nernst effect in cuprates. Tabletop 'laboratories for the entire universe': quantum mechanics of black holes, quark-gluon plasma, neutrons stars, and big-bang physics.

  5. Exact quantum dynamics study of the O{sup +}+H{sub 2}(v=0,j=0){yields}OH{sup +}+H ion-molecule reaction and comparison with quasiclassical trajectory calculations

    SciTech Connect

    Martinez, Rodrigo; Lucas, Josep M.; Gimenez, Xavier; Aguilar, Antonio; Gonzalez, Miguel

    2006-04-14

    The close-coupling hyperspherical (CCH) exact quantum method was used to study the title barrierless reaction up to a collision energy (E{sub T}) of 0.75 eV, and the results compared with quasiclassical trajectory (QCT) calculations to determine the importance of quantum effects. The CCH integral cross section decreased with E{sub T} and, although the QCT results were in general quite similar to the CCH ones, they presented a significant deviation from the CCH data within the 0.2-0.6 eV collision energy range, where the QCT method did not correctly describe the reaction probability. A very good accord between both methods was obtained for the OH{sup +} vibrational distribution, where no inversion of population was found. For the OH{sup +} rotational distributions, the agreement between the CCH and QCT results was not as good as in the vibrational case, but it was satisfactory in many conditions. The kk{sup '} angular distribution showed a preferential forward character, and the CCH method produced higher forward peaks than the QCT one. All the results were interpreted considering the potential energy surface and plots of a representative sampling of reactive trajectories.

  6. Loop Quantum Gravity.

    PubMed

    Rovelli, Carlo

    2008-01-01

    The problem of describing the quantum behavior of gravity, and thus understanding quantum spacetime, is still open. Loop quantum gravity is a well-developed approach to this problem. It is a mathematically well-defined background-independent quantization of general relativity, with its conventional matter couplings. Today research in loop quantum gravity forms a vast area, ranging from mathematical foundations to physical applications. Among the most significant results obtained so far are: (i) The computation of the spectra of geometrical quantities such as area and volume, which yield tentative quantitative predictions for Planck-scale physics. (ii) A physical picture of the microstructure of quantum spacetime, characterized by Planck-scale discreteness. Discreteness emerges as a standard quantum effect from the discrete spectra, and provides a mathematical realization of Wheeler's "spacetime foam" intuition. (iii) Control of spacetime singularities, such as those in the interior of black holes and the cosmological one. This, in particular, has opened up the possibility of a theoretical investigation into the very early universe and the spacetime regions beyond the Big Bang. (iv) A derivation of the Bekenstein-Hawking black-hole entropy. (v) Low-energy calculations, yielding n-point functions well defined in a background-independent context. The theory is at the roots of, or strictly related to, a number of formalisms that have been developed for describing background-independent quantum field theory, such as spin foams, group field theory, causal spin networks, and others. I give here a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.

  7. Cloning of a quantum measurement

    SciTech Connect

    Bisio, Alessandro; D'Ariano, Giacomo Mauro; Perinotti, Paolo; Sedlak, Michal

    2011-10-15

    We analyze quantum algorithms for cloning of a quantum measurement. Our aim is to mimic two uses of a device performing an unknown von Neumann measurement with a single use of the device. When the unknown device has to be used before the bipartite state to be measured is available we talk about 1{yields}2 learning of the measurement, otherwise the task is called 1{yields}2 cloning of a measurement. We perform the optimization for both learning and cloning for arbitrary dimension d of the Hilbert space. For 1{yields}2 cloning we also propose a simple quantum network that achieves the optimal fidelity. The optimal fidelity for 1{yields}2 learning just slightly outperforms the estimate and prepare strategy in which one first estimates the unknown measurement and depending on the result suitably prepares the duplicate.

  8. Quantum ontologies

    SciTech Connect

    Stapp, H.P.

    1988-12-01

    Quantum ontologies are conceptions of the constitution of the universe that are compatible with quantum theory. The ontological orientation is contrasted to the pragmatic orientation of science, and reasons are given for considering quantum ontologies both within science, and in broader contexts. The principal quantum ontologies are described and evaluated. Invited paper at conference: Bell's Theorem, Quantum Theory, and Conceptions of the Universe, George Mason University, October 20-21, 1988. 16 refs.

  9. Quantum Computer Games: Quantum Minesweeper

    ERIC Educational Resources Information Center

    Gordon, Michal; Gordon, Goren

    2010-01-01

    The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical…

  10. Quantum computation for quantum chemistry

    NASA Astrophysics Data System (ADS)

    Aspuru-Guzik, Alan

    2010-03-01

    Numerically exact simulation of quantum systems on classical computers is in general, an intractable computational problem. Computational chemists have made progress in the development of approximate methods to tackle complex chemical problems. The downside of these approximate methods is that their failure for certain important cases such as long-range charge transfer states in the case of traditional density functional theory. In 1982, Richard Feynman suggested that a quantum device should be able to simulate quantum systems (in our case, molecules) exactly using quantum computers in a tractable fashion. Our group has been working in the development of quantum chemistry algorithms for quantum devices. In this talk, I will describe how quantum computers can be employed to carry out numerically exact quantum chemistry and chemical reaction dynamics calculations, as well as molecular properties. Finally, I will describe our recent experimental quantum computation of the energy of the hydrogen molecule using an optical quantum computer.

  11. Yield Improvement in Steel Casting (Yield II)

    SciTech Connect

    Richard A. Hardin; Christoph Beckermann; Tim Hays

    2002-02-18

    This report presents work conducted on the following main projects tasks undertaken in the Yield Improvement in Steel Casting research program: Improvement of Conventional Feeding and Risering Methods, Use of Unconventional Yield Improvement Techniques, and Case Studies in Yield Improvement. Casting trials were conducted and then simulated using the precise casting conditions as recorded by the participating SFSA foundries. These results present a statistically meaningful set of experimental data on soundness versus feeding length. Comparisons between these casting trials and casting trials performed more than forty years ago by Pellini and the SFSA are quite good and appear reasonable. Comparisons between the current SFSA feeding rules and feeding rules based on the minimum Niyama criterion reveal that the Niyama-based rules are generally less conservative. The niyama-based rules also agree better with both the trials presented here, and the casting trails performed by Pellini an d the SFSA years ago. Furthermore, the use of the Niyama criterion to predict centerline shrinkage for horizontally fed plate sections has a theoretical basis according to the casting literature reviewed here. These results strongly support the use of improved feeding rules for horizontal plate sections based on the Niyama criterion, which can be tailored to the casting conditions for a given alloy and to a desired level of soundness. The reliability and repeatability of ASTM shrinkage x-ray ratings was investigated in a statistical study performed on 128 x-rays, each of which were rated seven different times. A manual ''Feeding and Risering Guidelines for Steel Castings' is given in this final report. Results of casting trials performed to test unconventional techniques for improving casting yield are presented. These use a stacked arrangement of castings and riser pressurization to increase the casting yield. Riser pressurization was demonstrated to feed a casting up to four time s the

  12. Atmospheric Nitrogen Fluorescence Yield

    NASA Technical Reports Server (NTRS)

    Adams, J. H., Jr.; Christl, M. J.; Fountain, W. F.; Gregory, J. C.; Martens, K. U.; Sokolsky, Pierre; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Several existing and planned experiments estimate the energies of ultra-high energy cosmic rays from air showers using the atmospheric nitrogen fluorescence. The nitrogen fluorescence yield from air shower electrons depends on the atmospheric composition. We will discuss the uncertainties in the fluorescence yield form electrons in the real atmosphere and describe a concept for a small balloon payload to measure the atmospheric fluorescence yield as a function of attitude.

  13. Quantum memristors

    SciTech Connect

    Pfeiffer, P.; Sanz, M.

    2016-07-06

    Technology based on memristors, resistors with memory whose resistance depends on the history of the crossing charges, has lately enhanced the classical paradigm of computation with neuromorphic architectures. However, in contrast to the known quantized models of passive circuit elements, such as inductors, capacitors or resistors, the design and realization of a quantum memristor is still missing. Here, we introduce the concept of a quantum memristor as a quantum dissipative device, whose decoherence mechanism is controlled by a continuous-measurement feedback scheme, which accounts for the memory. Indeed, we provide numerical simulations showing that memory effects actually persist in the quantum regime. Our quantization method, specifically designed for superconducting circuits, may be extended to other quantum platforms, allowing for memristor-type constructions in different quantum technologies. As a result, the proposed quantum memristor is then a building block for neuromorphic quantum computation and quantum simulations of non-Markovian systems.

  14. Quantum memristors

    PubMed Central

    Pfeiffer, P.; Egusquiza, I. L.; Di Ventra, M.; Sanz, M.; Solano, E.

    2016-01-01

    Technology based on memristors, resistors with memory whose resistance depends on the history of the crossing charges, has lately enhanced the classical paradigm of computation with neuromorphic architectures. However, in contrast to the known quantized models of passive circuit elements, such as inductors, capacitors or resistors, the design and realization of a quantum memristor is still missing. Here, we introduce the concept of a quantum memristor as a quantum dissipative device, whose decoherence mechanism is controlled by a continuous-measurement feedback scheme, which accounts for the memory. Indeed, we provide numerical simulations showing that memory effects actually persist in the quantum regime. Our quantization method, specifically designed for superconducting circuits, may be extended to other quantum platforms, allowing for memristor-type constructions in different quantum technologies. The proposed quantum memristor is then a building block for neuromorphic quantum computation and quantum simulations of non-Markovian systems. PMID:27381511

  15. Application of an InGaAsP diode laser to probe photodissociation dynamics - I(asterisk) quantum yields from n- and i-C3F7I and CH3I by laser gain vs absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Hess, W. P.; Kohler, S. J.; Haugen, H. K.; Leone, S. R.

    1986-01-01

    Initial measurements on I-asterisk yields of alkyl iodides at 266 nm are reported using gain vs. absorption spectroscopy with an InGaAsP diode probe laser. The results are 102 percent + or - 4 percent, 102 percent + or - 7 percent, and 73 percent + or - 4 percent for n-C3F7I, i-C3F7I, and CH3I respectively. Future prospects for the development of diode laser systems and for their use in dynamical studies are discussed.

  16. Quantum yields of decomposition and homo-dimerization of solid L-alanine induced by 7.2 eV Vacuum ultraviolet light irradiation: an estimate of the half-life of L-alanine on the surface of space objects.

    PubMed

    Izumi, Yudai; Nakagawa, Kazumichi

    2011-08-01

    One of the leading hypotheses regarding the origin of prebiotic molecules on primitive Earth is that they formed from inorganic molecules in extraterrestrial environments and were delivered by meteorites, space dust and comets. To evaluate the availability of extraterrestrial amino acids, it is necessary to examine their decomposition and oligomerization rates as induced by extraterrestrial energy sources, such as vacuum ultraviolet (VUV) and X-ray photons and high energy particles. This paper reports the quantum yields of decomposition ((8.2 ± 0.7) × 10(-2) photon(-1)) and homo-dimerization ((1.2 ± 0.3) × 10(-3) photon(-1)) and decomposition of the dimer (0.24 ± 0.06 photon(-1)) of solid L-alanine (Ala) induced by VUV light with an energy of 7.2 eV. Using these quantum yields, the half-life of L-Ala on the surface of a space object in the present earth orbit was estimated to be about 52 days, even when only photons with an energy of 7.2 eV emitted from the present Sun were considered. The actual half-life of solid L-Ala on the surface of a space object orbit around the present day Earth would certainly be much shorter than our estimate, because of the added effect of photons and particles of other energies. Thus, we propose that L-Ala needs to be shielded from solar VUV in protected environments, such as the interior of a meteorite, within a time scale of days after synthesis to ensure its arrival on the primitive Earth.

  17. Quantum robots and quantum computers

    SciTech Connect

    Benioff, P.

    1998-07-01

    Validation of a presumably universal theory, such as quantum mechanics, requires a quantum mechanical description of systems that carry out theoretical calculations and systems that carry out experiments. The description of quantum computers is under active development. No description of systems to carry out experiments has been given. A small step in this direction is taken here by giving a description of quantum robots as mobile systems with on board quantum computers that interact with different environments. Some properties of these systems are discussed. A specific model based on the literature descriptions of quantum Turing machines is presented.

  18. Quantum guidebooks

    NASA Astrophysics Data System (ADS)

    Crease, Robert P.

    2012-06-01

    Fresh from his appearance on the latest Physics World podcast, which examined the enduring popularity of books about quantum mechanics, Robert P Crease surveys the many tour guides to the quantum world.

  19. Quantum Darwinism

    SciTech Connect

    Zurek, Wojciech H

    2008-01-01

    Quantum Darwinism - proliferation, in the environment, of multiple records of selected states of the system (its information-theoretic progeny) - explains how quantum fragility of individual state can lead to classical robustness of their multitude.

  20. Quantum memristors

    DOE PAGES

    Pfeiffer, P.; Egusquiza, I. L.; Di Ventra, M.; ...

    2016-07-06

    Technology based on memristors, resistors with memory whose resistance depends on the history of the crossing charges, has lately enhanced the classical paradigm of computation with neuromorphic architectures. However, in contrast to the known quantized models of passive circuit elements, such as inductors, capacitors or resistors, the design and realization of a quantum memristor is still missing. Here, we introduce the concept of a quantum memristor as a quantum dissipative device, whose decoherence mechanism is controlled by a continuous-measurement feedback scheme, which accounts for the memory. Indeed, we provide numerical simulations showing that memory effects actually persist in the quantummore » regime. Our quantization method, specifically designed for superconducting circuits, may be extended to other quantum platforms, allowing for memristor-type constructions in different quantum technologies. As a result, the proposed quantum memristor is then a building block for neuromorphic quantum computation and quantum simulations of non-Markovian systems.« less

  1. Adaptive schemes for incomplete quantum process tomography

    SciTech Connect

    Teo, Yong Siah; Englert, Berthold-Georg; Rehacek, Jaroslav; Hradil, Zdenek

    2011-12-15

    We propose an iterative algorithm for incomplete quantum process tomography with the help of quantum state estimation. The algorithm, which is based on the combined principles of maximum likelihood and maximum entropy, yields a unique estimator for an unknown quantum process when one has less than a complete set of linearly independent measurement data to specify the quantum process uniquely. We apply this iterative algorithm adaptively in various situations and so optimize the amount of resources required to estimate a quantum process with incomplete data.

  2. Quantum Transport.

    DTIC Science & Technology

    1994-08-15

    Notre Dame was concerned with a variety of quantum transport in mesoscopic structures. This research was funded by the Air Force Office of Scientific...Research under Grant No. AFOSR-91-0211. The major issues examined included quantum transport in high magnetic fields and modulated channels, Coulomb...lifetimes in quasi-1D structures, quantum transport experiments in metals, the mesoscopic photovoltaic effect, and new techniques for fabricating quantum structures in semiconductors.

  3. Probing deformed quantum commutators

    NASA Astrophysics Data System (ADS)

    Rossi, Matteo A. C.; Giani, Tommaso; Paris, Matteo G. A.

    2016-07-01

    Several quantum gravity theories predict a minimal length at the order of magnitude of the Planck length, under which the concepts of space and time lose their physical meaning. In quantum mechanics, the insurgence of such a minimal length can be described by introducing a modified position-momentum commutator, which in turn yields a generalized uncertainty principle, where the uncertainty on position measurements has a lower bound. The value of the minimal length is not predicted by theories and must be estimated experimentally. In this paper, we address the quantum bound to the estimability of the minimal uncertainty length by performing measurements on a harmonic oscillator, which is analytically solvable in the deformed algebra induced by the deformed commutation relations.

  4. Argentina corn yield model

    NASA Technical Reports Server (NTRS)

    Callis, S. L.; Sakamoto, C.

    1984-01-01

    A model based on multiple regression was developed to estimate corn yields for the country of Argentina. A meteorological data set was obtained for the country by averaging data for stations within the corn-growing area. Predictor variables for the model were derived from monthly total precipitation, average monthly mean temperature, and average monthly maximum temperature. A trend variable was included for the years 1965 to 1980 since an increasing trend in yields due to technology was observed between these years.

  5. Argentina wheat yield model

    NASA Technical Reports Server (NTRS)

    Callis, S. L.; Sakamoto, C.

    1984-01-01

    Five models based on multiple regression were developed to estimate wheat yields for the five wheat growing provinces of Argentina. Meteorological data sets were obtained for each province by averaging data for stations within each province. Predictor variables for the models were derived from monthly total precipitation, average monthly mean temperature, and average monthly maximum temperature. Buenos Aires was the only province for which a trend variable was included because of increasing trend in yield due to technology from 1950 to 1963.

  6. Argentina soybean yield model

    NASA Technical Reports Server (NTRS)

    Callis, S. L.; Sakamoto, C.

    1984-01-01

    A model based on multiple regression was developed to estimate soybean yields for the country of Argentina. A meteorological data set was obtained for the country by averaging data for stations within the soybean growing area. Predictor variables for the model were derived from monthly total precipitation and monthly average temperature. A trend variable was included for the years 1969 to 1978 since an increasing trend in yields due to technology was observed between these years.

  7. Quantum cheques

    NASA Astrophysics Data System (ADS)

    Moulick, Subhayan Roy; Panigrahi, Prasanta K.

    2016-06-01

    We propose the idea of a quantum cheque scheme, a cryptographic protocol in which any legitimate client of a trusted bank can issue a cheque, that cannot be counterfeited or altered in anyway, and can be verified by a bank or any of its branches. We formally define a quantum cheque and present the first unconditionally secure quantum cheque scheme and show it to be secure against any no-signalling adversary. The proposed quantum cheque scheme can been perceived as the quantum analog of Electronic Data Interchange, as an alternate for current e-Payment Gateways.

  8. Quantum frames

    NASA Astrophysics Data System (ADS)

    Brown, Matthew J.

    2014-02-01

    The framework of quantum frames can help unravel some of the interpretive difficulties i the foundation of quantum mechanics. In this paper, I begin by tracing the origins of this concept in Bohr's discussion of quantum theory and his theory of complementarity. Engaging with various interpreters and followers of Bohr, I argue that the correct account of quantum frames must be extended beyond literal space-time reference frames to frames defined by relations between a quantum system and the exosystem or external physical frame, of which measurement contexts are a particularly important example. This approach provides superior solutions to key EPR-type measurement and locality paradoxes.

  9. Quantum Darwinism

    NASA Astrophysics Data System (ADS)

    Zurek, Wojciech Hubert

    2009-03-01

    Quantum Darwinism describes the proliferation, in the environment, of multiple records of selected states of a quantum system. It explains how the quantum fragility of a state of a single quantum system can lead to the classical robustness of states in their correlated multitude; shows how effective `wave-packet collapse' arises as a result of the proliferation throughout the environment of imprints of the state of the system; and provides a framework for the derivation of Born's rule, which relates the probabilities of detecting states to their amplitudes. Taken together, these three advances mark considerable progress towards settling the quantum measurement problem.

  10. Quantum graph as a quantum spectral filter

    SciTech Connect

    Turek, Ondrej; Cheon, Taksu

    2013-03-15

    We study the transmission of a quantum particle along a straight input-output line to which a graph {Gamma} is attached at a point. In the point of contact we impose a singularity represented by a certain properly chosen scale-invariant coupling with a coupling parameter {alpha}. We show that the probability of transmission along the line as a function of the particle energy tends to the indicator function of the energy spectrum of {Gamma} as {alpha}{yields}{infinity}. This effect can be used for a spectral analysis of the given graph {Gamma}. Its applications include a control of a transmission along the line and spectral filtering. The result is illustrated with an example where {Gamma} is a loop exposed to a magnetic field. Two more quantum devices are designed using other special scale-invariant vertex couplings. They can serve as a band-stop filter and as a spectral separator, respectively.

  11. Quantum games as quantum types

    NASA Astrophysics Data System (ADS)

    Delbecque, Yannick

    In this thesis, we present a new model for higher-order quantum programming languages. The proposed model is an adaptation of the probabilistic game semantics developed by Danos and Harmer [DH02]: we expand it with quantum strategies which enable one to represent quantum states and quantum operations. Some of the basic properties of these strategies are established and then used to construct denotational semantics for three quantum programming languages. The first of these languages is a formalisation of the measurement calculus proposed by Danos et al. [DKP07]. The other two are new: they are higher-order quantum programming languages. Previous attempts to define a denotational semantics for higher-order quantum programming languages have failed. We identify some of the key reasons for this and base the design of our higher-order languages on these observations. The game semantics proposed in this thesis is the first denotational semantics for a lambda-calculus equipped with quantum types and with extra operations which allow one to program quantum algorithms. The results presented validate the two different approaches used in the design of these two new higher-order languages: a first one where quantum states are used through references and a second one where they are introduced as constants in the language. The quantum strategies presented in this thesis allow one to understand the constraints that must be imposed on quantum type systems with higher-order types. The most significant constraint is the fact that abstraction over part of the tensor product of many unknown quantum states must not be allowed. Quantum strategies are a new mathematical model which describes the interaction between classical and quantum data using system-environment dialogues. The interactions between the different parts of a quantum system are described using the rich structure generated by composition of strategies. This approach has enough generality to be put in relation with other

  12. Improved constructions for quantum maximum distance separable codes

    NASA Astrophysics Data System (ADS)

    Qian, Jianfa; Zhang, Lina

    2017-01-01

    In this work, we further improve the distance of the quantum maximum distance separable (MDS) codes of length n=q^2+1/10. This yields new families of quantum MDS codes. We also construct a family of new quantum MDS codes with parameters [[q^2-1/3, q^2-1/3-2d+2, d

  13. Quantum flywheel

    NASA Astrophysics Data System (ADS)

    Levy, Amikam; Diósi, Lajos; Kosloff, Ronnie

    2016-05-01

    In this work we present the concept of a quantum flywheel coupled to a quantum heat engine. The flywheel stores useful work in its energy levels, while additional power is extracted continuously from the device. Generally, the energy exchange between a quantum engine and a quantized work repository is accompanied by heat, which degrades the charging efficiency. Specifically when the quantum harmonic oscillator acts as a work repository, quantum and thermal fluctuations dominate the dynamics. Quantum monitoring and feedback control are applied to the flywheel in order to reach steady state and regulate its operation. To maximize the charging efficiency one needs a balance between the information gained by measuring the system and the information fed back to the system. The dynamics of the flywheel are described by a stochastic master equation that accounts for the engine, the external driving, the measurement, and the feedback operations.

  14. Quantifying Quantumness

    NASA Astrophysics Data System (ADS)

    Braun, Daniel; Giraud, Olivier; Braun, Peter A.

    2010-03-01

    We introduce and study a measure of ``quantumness'' of a quantum state based on its Hilbert-Schmidt distance from the set of classical states. ``Classical states'' were defined earlier as states for which a positive P-function exists, i.e. they are mixtures of coherent states [1]. We study invariance properties of the measure, upper bounds, and its relation to entanglement measures. We evaluate the quantumness of a number of physically interesting states and show that for any physical system in thermal equilibrium there is a finite critical temperature above which quantumness vanishes. We then use the measure for identifying the ``most quantum'' states. Such states are expected to be potentially most useful for quantum information theoretical applications. We find these states explicitly for low-dimensional spin-systems, and show that they possess beautiful, highly symmetric Majorana representations. [4pt] [1] Classicality of spin states, Olivier Giraud, Petr Braun, and Daniel Braun, Phys. Rev. A 78, 042112 (2008)

  15. Hybrid structures based on quantum dots and graphene nanobelts

    NASA Astrophysics Data System (ADS)

    Reznik, I. A.; Gromova, Yu. A.; Zlatov, A. S.; Baranov, M. A.; Orlova, A. O.; Moshkalev, S. A.; Maslov, V. G.; Baranov, A. V.; Fedorov, A. V.

    2017-01-01

    Luminescence and photoelectric properties of hybrid structures based on CdSe/ZnS quantum dots (QDs) and multilayer graphene have been investigated. A correlation between the luminescence quantum yield of QDs and their photoelectric properties in hybrid structures is established. It is shown that a decrease in the QD luminescence quantum yield due to adsorption of 1-(2-pyridylazo)-2-naphtol azo dye molecules onto the QD surface and a photoinduced increase in the QD luminescence quantum yield are accompanied by a symbate change in the hybrid structure photoconductivity.

  16. Quantum Metaphotonics

    DTIC Science & Technology

    2016-03-24

    This included optimizing the MBE growth conditions of a near-surface quantum wells with emission around 1500nm and fabrication of arrays of various...antennas and near-surface quantum-confined structures. This included optimizing the molecular beam epitaxy growth conditions of a near-surface quantum...due to the single process epitaxial growth , increases the interaction. Low densities of indium islands have been shown to increase the

  17. Quantum seismography

    NASA Astrophysics Data System (ADS)

    Lanzagorta, Marco; Jitrik, Oliverio; Uhlmann, Jeffrey; Venegas, Salvador

    2016-05-01

    A major scientific thrust from recent years has been to try to harness quantum phenomena to increase the performance of a wide variety of information processing devices. In particular, quantum radar has emerged as an intriguing theoretical concept that could revolutionize electromagnetic standoff sensing. In this paper we will discuss how the techniques developed for quantum radar could also be used towards the design of novel seismographs able to detect small ground vibrations., We use a hypothetical earthquake warning system in order to compare quantum seismography with traditional seismographic techniques.

  18. Quantum Dots

    NASA Astrophysics Data System (ADS)

    Tartakovskii, Alexander

    2012-07-01

    Part I. Nanostructure Design and Structural Properties of Epitaxially Grown Quantum Dots and Nanowires: 1. Growth of III/V semiconductor quantum dots C. Schneider, S. Hofling and A. Forchel; 2. Single semiconductor quantum dots in nanowires: growth, optics, and devices M. E. Reimer, N. Akopian, M. Barkelid, G. Bulgarini, R. Heeres, M. Hocevar, B. J. Witek, E. Bakkers and V. Zwiller; 3. Atomic scale analysis of self-assembled quantum dots by cross-sectional scanning tunneling microscopy and atom probe tomography J. G. Keizer and P. M. Koenraad; Part II. Manipulation of Individual Quantum States in Quantum Dots Using Optical Techniques: 4. Studies of the hole spin in self-assembled quantum dots using optical techniques B. D. Gerardot and R. J. Warburton; 5. Resonance fluorescence from a single quantum dot A. N. Vamivakas, C. Matthiesen, Y. Zhao, C.-Y. Lu and M. Atature; 6. Coherent control of quantum dot excitons using ultra-fast optical techniques A. J. Ramsay and A. M. Fox; 7. Optical probing of holes in quantum dot molecules: structure, symmetry, and spin M. F. Doty and J. I. Climente; Part III. Optical Properties of Quantum Dots in Photonic Cavities and Plasmon-Coupled Dots: 8. Deterministic light-matter coupling using single quantum dots P. Senellart; 9. Quantum dots in photonic crystal cavities A. Faraon, D. Englund, I. Fushman, A. Majumdar and J. Vukovic; 10. Photon statistics in quantum dot micropillar emission M. Asmann and M. Bayer; 11. Nanoplasmonics with colloidal quantum dots V. Temnov and U. Woggon; Part IV. Quantum Dot Nano-Laboratory: Magnetic Ions and Nuclear Spins in a Dot: 12. Dynamics and optical control of an individual Mn spin in a quantum dot L. Besombes, C. Le Gall, H. Boukari and H. Mariette; 13. Optical spectroscopy of InAs/GaAs quantum dots doped with a single Mn atom O. Krebs and A. Lemaitre; 14. Nuclear spin effects in quantum dot optics B. Urbaszek, B. Eble, T. Amand and X. Marie; Part V. Electron Transport in Quantum Dots Fabricated by

  19. Dissipative quantum computing with open quantum walks

    SciTech Connect

    Sinayskiy, Ilya; Petruccione, Francesco

    2014-12-04

    An open quantum walk approach to the implementation of a dissipative quantum computing scheme is presented. The formalism is demonstrated for the example of an open quantum walk implementation of a 3 qubit quantum circuit consisting of 10 gates.

  20. Multipartite asymmetric quantum cloning

    SciTech Connect

    Iblisdir, S.; Gisin, N.; Acin, A.; Cerf, N.J.; Filip, R.; Fiurasek, J.

    2005-10-15

    We investigate the optimal distribution of quantum information over multipartite systems in asymmetric settings. We introduce cloning transformations that take N identical replicas of a pure state in any dimension as input and yield a collection of clones with nonidentical fidelities. As an example, if the clones are partitioned into a set of M{sub A} clones with fidelity F{sup A} and another set of M{sub B} clones with fidelity F{sup B}, the trade-off between these fidelities is analyzed, and particular cases of optimal N{yields}M{sub A}+M{sub B} cloning machines are exhibited. We also present an optimal 1{yields}1+1+1 cloning machine, which is an example of a tripartite fully asymmetric cloner. Finally, it is shown how these cloning machines can be optically realized.

  1. Quantum Transition State Theory

    NASA Astrophysics Data System (ADS)

    Waalkens, Holger

    2009-03-01

    The main idea of Wigner's transition state theory (TST) is to compute reaction rates from the flux through a dividing surface placed between reactants and products. In order not to overestimate the rate the dividing surface needs to have the no- recrossing property, i.e. reactive trajectories cross the dividing surface exactly once, and nonreactive trajectories do not cross it at all. The long standing problem of how to construct such a diving surface for multi-degree-of-freedom systems was solved only recently using ideas from dynamical systems theory. Here a normal form allows for a local decoupling of the classical dynamics which leads to the explicit construction of the phase space structures that govern the reaction dynamics through transition states. The dividing surface is spanned by a normally hyperbolic manifold which is the mathematical manifestation of the transition state as an unstable invariant subsystem of one degree of freedom less than the full system. The mere existence of a quantum version of TST is discussed controversially in the literature. The key isssue is the presence of quantum mechanical tunneling which prohibits the existence of a local theory analogous to the classical case. Various approaches have been devloped to overcome this problem by propagating quantum wavefunctions through the transition state region. These approaches have in common that they are computationally very expensive which seriously limits their applicability. In contrast the approach by Roman Schubert, Stephen Wiggins and myself is local in nature. A quantum normal form allows us to locally decouple the quantum dynamics to any desired order in Planck's constant. This yields not only the location of the scattering and resonance wavefunctions relative to the classical phase space structures, but also leads to very efficient algorithms to compute cumulative reaction probabilities and Gamov-Siegert resonances which are the quantum imprints of the transition state.

  2. Atmospheric Fluorescence Yield

    NASA Technical Reports Server (NTRS)

    Adams, James H., Jr.; Christl, M. J.; Fountain, W. F.; Gregory, J. C.; Martens, K.; Sokolsky, P.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Several existing and planned experiments estimate the energies of ultra-high energy cosmic rays from air showers using the atmospheric fluorescence from these showers. Accurate knowledge of the conversion from atmospheric fluorescence to energy loss by ionizing particles in the atmosphere is key to this technique. In this paper we discuss a small balloon-borne instrument to make the first in situ measurements versus altitude of the atmospheric fluorescence yield. The instrument can also be used in the lab to investigate the dependence of the fluorescence yield in air on temperature, pressure and the concentrations of other gases that present in the atmosphere. The results can be used to explore environmental effects on and improve the accuracy of cosmic ray energy measurements for existing ground-based experiments and future space-based experiments.

  3. Quantum Algorithms

    NASA Technical Reports Server (NTRS)

    Abrams, D.; Williams, C.

    1999-01-01

    This thesis describes several new quantum algorithms. These include a polynomial time algorithm that uses a quantum fast Fourier transform to find eigenvalues and eigenvectors of a Hamiltonian operator, and that can be applied in cases for which all know classical algorithms require exponential time.

  4. Quantum metrology

    NASA Technical Reports Server (NTRS)

    Lee, H.; Kok, P.; Dowling, J. P.

    2002-01-01

    This paper addresses the formal equivalence between the Mach-Zehnder interferometer, the Ramsey spectroscope, and a specific quantum logical gate. Based on this equivalence we introduce the quantum Rosetta Stone, and we describe a projective measurement scheme for generating the desired correlations between the interferometric input states in order to achieve Heisenberg-limited sensitivity.

  5. Quantum Finance

    NASA Astrophysics Data System (ADS)

    Baaquie, Belal E.

    2004-11-01

    Financial mathematics is currently almost completely dominated by stochastic calculus. Presenting a completely independent approach, this book applies the mathematical and conceptual formalism of quantum mechanics and quantum field theory (with particular emphasis on the path integral) to the theory of options and to the modeling of interest rates. Many new results, accordingly, emerge from the author's perspective.

  6. Theory of smeared quantum phase transitions.

    PubMed

    Hoyos, José A; Vojta, Thomas

    2008-06-20

    We present an analytical strong-disorder renormalization group theory of the quantum phase transition in the dissipative random transverse-field Ising chain. For Ohmic dissipation, we solve the renormalization flow equations analytically, yielding asymptotically exact results for the low-temperature properties of the system. We find that the interplay between quantum fluctuations and Ohmic dissipation destroys the quantum critical point by smearing. We also determine the phase diagram and the behavior of observables in the vicinity of the smeared quantum phase transition.

  7. Quantum teleportation with continuous measurements

    NASA Astrophysics Data System (ADS)

    Greplova, Eliska; Mølmer, Klaus; Andersen, Christian Kraglund

    2016-10-01

    We propose a scheme for quantum teleportation between two qubits, coupled sequentially to a cavity field. An implementation of the scheme is analyzed with superconducting qubits and a transmission line resonator, where measurements are restricted to continuous probing of the field leaking from the resonator rather than instantaneous projective Bell state measurement. We show that the past quantum state formalism S. Gammelmark, B. Julsgaard, and K. Mølmer, Phys. Rev. Lett. 111, 160401 (2013), 10.1103/PhysRevLett.111.160401 can be successfully applied to estimate what would have been the most likely Bell measurement outcome conditioned on our continuous signal record. This information determines which local operation on the target qubit yields the optimal teleportation fidelity. Our results emphasize the significance of applying a detailed analysis of quantum measurements in feedforward protocols in nonideal leaky quantum systems.

  8. Low quantum defect laser performance

    NASA Astrophysics Data System (ADS)

    Bowman, Steven R.

    2017-01-01

    Low quantum defect lasers are possible using near-resonant optical pumping. This paper examines the laser material performance as the quantum defect of the laser is reduced. A steady-state model is developed, which incorporates the relevant physical processes in these materials and predicts extraction efficiency and waste heat generation. As the laser quantum defect is reduced below a few percent, the impact of fluorescence cooling must be included in the analysis. The special case of a net zero quantum defect laser is examined in detail. This condition, referred to as the radiation balance laser (RBL), is shown to provide two orders of magnitude lower heat generation at the cost of roughly 10% loss in extraction efficiency. Numerical examples are presented with the host materials Yb:YAG and Yb:Silica. The general conditions, which yield optimal laser efficiency, are derived and explored.

  9. Bifurcation-based adiabatic quantum computation with a nonlinear oscillator network

    PubMed Central

    Goto, Hayato

    2016-01-01

    The dynamics of nonlinear systems qualitatively change depending on their parameters, which is called bifurcation. A quantum-mechanical nonlinear oscillator can yield a quantum superposition of two oscillation states, known as a Schrödinger cat state, via quantum adiabatic evolution through its bifurcation point. Here we propose a quantum computer comprising such quantum nonlinear oscillators, instead of quantum bits, to solve hard combinatorial optimization problems. The nonlinear oscillator network finds optimal solutions via quantum adiabatic evolution, where nonlinear terms are increased slowly, in contrast to conventional adiabatic quantum computation or quantum annealing, where quantum fluctuation terms are decreased slowly. As a result of numerical simulations, it is concluded that quantum superposition and quantum fluctuation work effectively to find optimal solutions. It is also notable that the present computer is analogous to neural computers, which are also networks of nonlinear components. Thus, the present scheme will open new possibilities for quantum computation, nonlinear science, and artificial intelligence. PMID:26899997

  10. Bifurcation-based adiabatic quantum computation with a nonlinear oscillator network

    NASA Astrophysics Data System (ADS)

    Goto, Hayato

    2016-02-01

    The dynamics of nonlinear systems qualitatively change depending on their parameters, which is called bifurcation. A quantum-mechanical nonlinear oscillator can yield a quantum superposition of two oscillation states, known as a Schrödinger cat state, via quantum adiabatic evolution through its bifurcation point. Here we propose a quantum computer comprising such quantum nonlinear oscillators, instead of quantum bits, to solve hard combinatorial optimization problems. The nonlinear oscillator network finds optimal solutions via quantum adiabatic evolution, where nonlinear terms are increased slowly, in contrast to conventional adiabatic quantum computation or quantum annealing, where quantum fluctuation terms are decreased slowly. As a result of numerical simulations, it is concluded that quantum superposition and quantum fluctuation work effectively to find optimal solutions. It is also notable that the present computer is analogous to neural computers, which are also networks of nonlinear components. Thus, the present scheme will open new possibilities for quantum computation, nonlinear science, and artificial intelligence.

  11. Bifurcation-based adiabatic quantum computation with a nonlinear oscillator network.

    PubMed

    Goto, Hayato

    2016-02-22

    The dynamics of nonlinear systems qualitatively change depending on their parameters, which is called bifurcation. A quantum-mechanical nonlinear oscillator can yield a quantum superposition of two oscillation states, known as a Schrödinger cat state, via quantum adiabatic evolution through its bifurcation point. Here we propose a quantum computer comprising such quantum nonlinear oscillators, instead of quantum bits, to solve hard combinatorial optimization problems. The nonlinear oscillator network finds optimal solutions via quantum adiabatic evolution, where nonlinear terms are increased slowly, in contrast to conventional adiabatic quantum computation or quantum annealing, where quantum fluctuation terms are decreased slowly. As a result of numerical simulations, it is concluded that quantum superposition and quantum fluctuation work effectively to find optimal solutions. It is also notable that the present computer is analogous to neural computers, which are also networks of nonlinear components. Thus, the present scheme will open new possibilities for quantum computation, nonlinear science, and artificial intelligence.

  12. Quantum Chaos

    NASA Astrophysics Data System (ADS)

    Casati, Giulio; Chirikov, Boris

    1995-04-01

    Preface; Acknowledgments; Introduction: 1. The legacy of chaos in quantum mechanics G. Casati and B. V. Chirikov; Part I. Classical Chaos and Quantum Localization: 2. Stochastic behaviour of a quantum pendulum under a periodic perturbation G. Casati, B. V. Chirikov, F. M. Izrailev and J. Ford; 3. Quantum dynamics of a nonintegrable system D. R. Grempel, R. E. Prange and S. E. Fishman; 4. Excitation of molecular rotation by periodic microwave pulses. A testing ground for Anderson localization R. Blümel, S. Fishman and U. Smilansky; 5. Localization of diffusive excitation in multi-level systems D. K. Shepelyansky; 6. Classical and quantum chaos for a kicked top F. Haake, M. Kus and R. Scharf; 7. Self-similarity in quantum dynamics L. E. Reichl and L. Haoming; 8. Time irreversibility of classically chaotic quantum dynamics K. Ikeda; 9. Effect of noise on time-dependent quantum chaos E. Ott, T. M. Antonsen Jr and J. D. Hanson; 10. Dynamical localization, dissipation and noise R. F. Graham; 11. Maximum entropy models and quantum transmission in disordered systems J.-L. Pichard and M. Sanquer; 12. Solid state 'atoms' in intense oscillating fields M. S. Sherwin; Part II. Atoms in Strong Fields: 13. Localization of classically chaotic diffusion for hydrogen atoms in microwave fields J. E. Bayfield, G. Casati, I. Guarneri and D. W. Sokol; 14. Inhibition of quantum transport due to 'scars' of unstable periodic orbits R. V. Jensen, M. M. Sanders, M. Saraceno and B. Sundaram; 15. Rubidium Rydberg atoms in strong fields G. Benson, G. Raithel and H. Walther; 16. Diamagnetic Rydberg atom: confrontation of calculated and observed spectra C.-H. Iu, G. R. Welch, M. M. Kash, D. Kleppner, D. Delande and J. C. Gay; 17. Semiclassical approximation for the quantum states of a hydrogen atom in a magnetic field near the ionization limit M. Y. Kuchiev and O. P. Sushkov; 18. The semiclassical helium atom D. Wintgen, K. Richter and G. Tanner; 19. Stretched helium: a model for quantum chaos

  13. Quantum Chaos

    NASA Astrophysics Data System (ADS)

    Casati, Giulio; Chirikov, Boris

    2006-11-01

    Preface; Acknowledgments; Introduction: 1. The legacy of chaos in quantum mechanics G. Casati and B. V. Chirikov; Part I. Classical Chaos and Quantum Localization: 2. Stochastic behaviour of a quantum pendulum under a periodic perturbation G. Casati, B. V. Chirikov, F. M. Izrailev and J. Ford; 3. Quantum dynamics of a nonintegrable system D. R. Grempel, R. E. Prange and S. E. Fishman; 4. Excitation of molecular rotation by periodic microwave pulses. A testing ground for Anderson localization R. Blümel, S. Fishman and U. Smilansky; 5. Localization of diffusive excitation in multi-level systems D. K. Shepelyansky; 6. Classical and quantum chaos for a kicked top F. Haake, M. Kus and R. Scharf; 7. Self-similarity in quantum dynamics L. E. Reichl and L. Haoming; 8. Time irreversibility of classically chaotic quantum dynamics K. Ikeda; 9. Effect of noise on time-dependent quantum chaos E. Ott, T. M. Antonsen Jr and J. D. Hanson; 10. Dynamical localization, dissipation and noise R. F. Graham; 11. Maximum entropy models and quantum transmission in disordered systems J.-L. Pichard and M. Sanquer; 12. Solid state 'atoms' in intense oscillating fields M. S. Sherwin; Part II. Atoms in Strong Fields: 13. Localization of classically chaotic diffusion for hydrogen atoms in microwave fields J. E. Bayfield, G. Casati, I. Guarneri and D. W. Sokol; 14. Inhibition of quantum transport due to 'scars' of unstable periodic orbits R. V. Jensen, M. M. Sanders, M. Saraceno and B. Sundaram; 15. Rubidium Rydberg atoms in strong fields G. Benson, G. Raithel and H. Walther; 16. Diamagnetic Rydberg atom: confrontation of calculated and observed spectra C.-H. Iu, G. R. Welch, M. M. Kash, D. Kleppner, D. Delande and J. C. Gay; 17. Semiclassical approximation for the quantum states of a hydrogen atom in a magnetic field near the ionization limit M. Y. Kuchiev and O. P. Sushkov; 18. The semiclassical helium atom D. Wintgen, K. Richter and G. Tanner; 19. Stretched helium: a model for quantum chaos

  14. Scattering of quantum wave packets by shallow potential islands: a quantum lens.

    PubMed

    Goussev, Arseni; Richter, Klaus

    2013-05-01

    We consider the problem of quantum scattering of a localized wave packet by a weak Gaussian potential in two spatial dimensions. We show that, under certain conditions, this problem bears close analogy with that of focusing (or defocusing) of light rays by a thin optical lens: Quantum interference between straight paths yields the same lens equation as for refracted rays in classical optics.

  15. Deterministic quantum teleportation with atoms.

    PubMed

    Riebe, M; Häffner, H; Roos, C F; Hänsel, W; Benhelm, J; Lancaster, G P T; Körber, T W; Becher, C; Schmidt-Kaler, F; James, D F V; Blatt, R

    2004-06-17

    Teleportation of a quantum state encompasses the complete transfer of information from one particle to another. The complete specification of the quantum state of a system generally requires an infinite amount of information, even for simple two-level systems (qubits). Moreover, the principles of quantum mechanics dictate that any measurement on a system immediately alters its state, while yielding at most one bit of information. The transfer of a state from one system to another (by performing measurements on the first and operations on the second) might therefore appear impossible. However, it has been shown that the entangling properties of quantum mechanics, in combination with classical communication, allow quantum-state teleportation to be performed. Teleportation using pairs of entangled photons has been demonstrated, but such techniques are probabilistic, requiring post-selection of measured photons. Here, we report deterministic quantum-state teleportation between a pair of trapped calcium ions. Following closely the original proposal, we create a highly entangled pair of ions and perform a complete Bell-state measurement involving one ion from this pair and a third source ion. State reconstruction conditioned on this measurement is then performed on the other half of the entangled pair. The measured fidelity is 75%, demonstrating unequivocally the quantum nature of the process.

  16. Photodestruction Quantum Yield of Adenine in Aqueous Solution.

    ERIC Educational Resources Information Center

    Rivera, Mercedes

    1989-01-01

    In this article, background information on the photochemical properties of nucleic acids is provided and an experiment to illustrate this concept is presented. Sample preparation, procedures, and data analysis are discussed. Sample UV absorption spectra are included. (CW)

  17. The Quantum Yield of NO3 from Peroxyacetyl Nitrate Photolysis

    NASA Technical Reports Server (NTRS)

    Mazely, Troy L.; Friedl, Randall R.; Sander, Stanley P.

    1997-01-01

    Peroxyacetyl nitrate (PAN) vapor was photolyzed at 248nm and the NO3 photoproduct was detected by laser induced fluorescence. The excited state flourescence contributions were investigated and a data analysis methodology was established to minimize their effects.

  18. Quantum Computers

    DTIC Science & Technology

    2010-03-04

    1227–1230 (2009). 31. Olmschenk, S. et al. Quantum teleportation between distant matter qubits. Science 323, 486–489 (2009). 32. Dür, W., Briegel, H...REVIEWS Quantum computers T. D. Ladd1{, F. Jelezko2, R. Laflamme3,4,5, Y. Nakamura6,7, C. Monroe8,9 & J. L. O’Brien10 Over the past several decades... quantum information science has emerged to seek answers to the question: can we gain some advantage by storing, transmitting and processing

  19. Regular and chaotic quantum dynamics in atom-diatom reactive collisions

    SciTech Connect

    Gevorkyan, A. S.; Nyman, G.

    2008-05-15

    A new microirreversible 3D theory of quantum multichannel scattering in the three-body system is developed. The quantum approach is constructed on the generating trajectory tubes which allow taking into account influence of classical nonintegrability of the dynamical quantum system. When the volume of classical chaos in phase space is larger than the quantum cell in the corresponding quantum system, quantum chaos is generated. The probability of quantum transitions is constructed for this case. The collinear collision of the Li + (FH) {sup {yields}}(LiF) + H system is used for numerical illustration of a system generating quantum (wave) chaos.

  20. Observable measure of quantum coherence in finite dimensional systems.

    PubMed

    Girolami, Davide

    2014-10-24

    Quantum coherence is the key resource for quantum technology, with applications in quantum optics, information processing, metrology, and cryptography. Yet, there is no universally efficient method for quantifying coherence either in theoretical or in experimental practice. I introduce a framework for measuring quantum coherence in finite dimensional systems. I define a theoretical measure which satisfies the reliability criteria established in the context of quantum resource theories. Then, I present an experimental scheme implementable with current technology which evaluates the quantum coherence of an unknown state of a d-dimensional system by performing two programmable measurements on an ancillary qubit, in place of the O(d2) direct measurements required by full state reconstruction. The result yields a benchmark for monitoring quantum effects in complex systems, e.g., certifying nonclassicality in quantum protocols and probing the quantum behavior of biological complexes.

  1. Revisiting the quantum Szilard engine with fully quantum considerations

    SciTech Connect

    Li, Hai; Zou, Jian; Li, Jun-Gang; Shao, Bin; Wu, Lian-Ao

    2012-12-15

    By considering level shifting during the insertion process we revisit the quantum Szilard engine (QSZE) with fully quantum consideration. We derive the general expressions of the heat absorbed from thermal bath and the total work done to the environment by the system in a cycle with two different cyclic strategies. We find that only the quantum information contributes to the absorbed heat, and the classical information acts like a feedback controller and has no direct effect on the absorbed heat. This is the first demonstration of the different effects of quantum information and classical information for extracting heat from the bath in the QSZE. Moreover, when the well width L{yields}{infinity} or the temperature of the bath T{yields}{infinity} the QSZE reduces to the classical Szilard engine (CSZE), and the total work satisfies the relation W{sub tot}=k{sub B}Tln2 as obtained by Sang Wook Kim et al. [S.W. Kim, T. Sagawa, S. De Liberato, M. Ueda, Phys. Rev. Lett. 106 (2011) 070401] for one particle case. - Highlights: Black-Right-Pointing-Pointer For the first time analyze the QSZE by considering energy level shifts. Black-Right-Pointing-Pointer Find different roles played by classical and quantum information in the QSZE. Black-Right-Pointing-Pointer The amount of work extracted depends on the cyclic strategies of the QSZE. Black-Right-Pointing-Pointer Verify that the QSZE will reduce to the CSZE in the classical limits.

  2. Quantum computers.

    PubMed

    Ladd, T D; Jelezko, F; Laflamme, R; Nakamura, Y; Monroe, C; O'Brien, J L

    2010-03-04

    Over the past several decades, quantum information science has emerged to seek answers to the question: can we gain some advantage by storing, transmitting and processing information encoded in systems that exhibit unique quantum properties? Today it is understood that the answer is yes, and many research groups around the world are working towards the highly ambitious technological goal of building a quantum computer, which would dramatically improve computational power for particular tasks. A number of physical systems, spanning much of modern physics, are being developed for quantum computation. However, it remains unclear which technology, if any, will ultimately prove successful. Here we describe the latest developments for each of the leading approaches and explain the major challenges for the future.

  3. Quantum Locality?

    NASA Astrophysics Data System (ADS)

    Stapp, Henry P.

    2012-05-01

    Robert Griffiths has recently addressed, within the framework of a `consistent quantum theory' that he has developed, the issue of whether, as is often claimed, quantum mechanics entails a need for faster-than-light transfers of information over long distances. He argues that the putative proofs of this property that involve hidden variables include in their premises some essentially classical-physics-type assumptions that are not entailed by the precepts of quantum mechanics. Thus whatever is proved is not a feature of quantum mechanics, but is a property of a theory that tries to combine quantum theory with quasi-classical features that go beyond what is entailed by quantum theory itself. One cannot logically prove properties of a system by establishing, instead, properties of a system modified by adding properties alien to the original system. Hence Griffiths' rejection of hidden-variable-based proofs is logically warranted. Griffiths mentions the existence of a certain alternative proof that does not involve hidden variables, and that uses only macroscopically described observable properties. He notes that he had examined in his book proofs of this general kind, and concluded that they provide no evidence for nonlocal influences. But he did not examine the particular proof that he cites. An examination of that particular proof by the method specified by his `consistent quantum theory' shows that the cited proof is valid within that restrictive version of quantum theory. An added section responds to Griffiths' reply, which cites general possibilities of ambiguities that might make what is to be proved ill-defined, and hence render the pertinent `consistent framework' ill defined. But the vagaries that he cites do not upset the proof in question, which, both by its physical formulation and by explicit identification, specify the framework to be used. Griffiths confirms the validity of the proof insofar as that pertinent framework is used. The section also shows

  4. Drilling ban yields verdict

    SciTech Connect

    Nation, L.M.

    1992-01-01

    This paper briefly reviews a lawsuit which is under appeal by the State of Michigan regarding a takings claim filed over a petroleum exploration site. The dispute arose as a result of a 1987 decision by the Michigan Department of Natural Resources forbidding the property owners from developing the mineral rights leased to Miller Brothers in the Huron/Manistee National Forest. This area is bisected by a trend of Silurian Niagaran reef complexes which has a known production history throughout the State. The dunes area of the national forest has been deemed a wilderness area. As a result of the State's decision, the courts have awarded a sum of 71 million dollars to the developer to cover damages and lost resources. The reserve estimates were taken from adjacent areas which showed that the Niagaran reefs are relatively consistent in their yield.

  5. Quantum technology: the second quantum revolution.

    PubMed

    Dowling, Jonathan P; Milburn, Gerard J

    2003-08-15

    We are currently in the midst of a second quantum revolution. The first quantum revolution gave us new rules that govern physical reality. The second quantum revolution will take these rules and use them to develop new technologies. In this review we discuss the principles upon which quantum technology is based and the tools required to develop it. We discuss a number of examples of research programs that could deliver quantum technologies in coming decades including: quantum information technology, quantum electromechanical systems, coherent quantum electronics, quantum optics and coherent matter technology.

  6. Quantum correlations and distinguishability of quantum states

    NASA Astrophysics Data System (ADS)

    Spehner, Dominique

    2014-07-01

    A survey of various concepts in quantum information is given, with a main emphasis on the distinguishability of quantum states and quantum correlations. Covered topics include generalized and least square measurements, state discrimination, quantum relative entropies, the Bures distance on the set of quantum states, the quantum Fisher information, the quantum Chernoff bound, bipartite entanglement, the quantum discord, and geometrical measures of quantum correlations. The article is intended both for physicists interested not only by collections of results but also by the mathematical methods justifying them, and for mathematicians looking for an up-to-date introductory course on these subjects, which are mainly developed in the physics literature.

  7. Quantum Mechanics

    NASA Astrophysics Data System (ADS)

    Commins, Eugene D.

    2014-10-01

    Preface; 1. Introduction; 2. Mathematical preliminaries; 3. The rules of quantum mechanics; 4. The connection between the fundamental rules and wave mechanics; 5. Further illustrations of the rules of quantum mechanics; 6. Further developments in one-dimensional wave mechanics; 7. The theory of angular momentum; 8. Wave mechanics in three dimensions: hydrogenic atoms; 9. Time-independent approximations for bound state problems; 10. Applications of static perturbation theory; 11. Identical particles; 12. Atomic structure; 13. Molecules; 14. The stability of matter; 15. Photons; 16. Interaction of non-relativistic charged particles and radiation; 17. Further topics in perturbation theory; 18. Scattering; 19. Special relativity and quantum mechanics: the Klein-Gordon equation; 20. The Dirac equation; 21. Interaction of a relativistic spin 1/2 particle with an external electromagnetic field; 22. The Dirac field; 23. Interaction between relativistic electrons, positrons, and photons; 24. The quantum mechanics of weak interactions; 25. The quantum measurement problem; Appendix A: useful inequalities for quantum mechanics; Appendix B: Bell's inequality; Appendix C: spin of the photon: vector spherical waves; Works cited; Bibliography; Index.

  8. Exciton-plasmon coupling of a single quantum dot and a metal nanowire

    NASA Astrophysics Data System (ADS)

    Wei, Hong

    2016-11-01

    The interactions between surface plasmons in metal nanostructures and excitons in quantum emitters lead to many interesting phenomena that are strongly dependent on the quantum yield of surface plasmons. The experimental measurement of this quantum yield is hindered due to the difficulty in distinguishing all the possible exciton recombination channels. By utilizing the propagation of surface plasmons, we experimentally measured the decay rates of all exciton recombination channels, and thus obtained the quantum yield of single surface plasmons generated by a quantum dot coupled with a silver nanowire.

  9. Quantum Particles From Quantum Information

    NASA Astrophysics Data System (ADS)

    Görnitz, T.; Schomäcker, U.

    2012-08-01

    Many problems in modern physics demonstrate that for a fundamental entity a more general conception than quantum particles or quantum fields are necessary. These concepts cannot explain the phenomena of dark energy or the mind-body-interaction. Instead of any kind of "small elementary building bricks", the Protyposis, an abstract and absolute quantum information, free of special denotation and open for some purport, gives the solution in the search for a fundamental substance. However, as long as at least relativistic particles are not constructed from the Protyposis, such an idea would remain in the range of natural philosophy. Therefore, the construction of relativistic particles without and with rest mass from quantum information is shown.

  10. Rebuilding mathematics on a quantum logical foundation

    NASA Astrophysics Data System (ADS)

    DeJonghe, Richard J., III

    We construct a rich first-order quantum logic which generalizes the standard classical predicate logic used in the development of virtually all of modern mathematics, and we use this quantum logic to build the foundations of a new quantum mathematics. First, we prove both soundness and completeness for the quantum logic we develop, and also prove a powerful new completeness result which heretofore had been known to hold for classical, but not quantum, first-order logic. We then use our quantum logic to develop multiple areas of mathematics, including abstract algebra, axiomatic set theory, and arithmetic. In some preliminary investigations into quantum mathematics, Dunn found that the Peano axioms for arithmetic yield the same theorems using either classical or quantum logic. We prove a similar result for certain classes of abstract algebras, and then show that Dunn's result is not generic by presenting examples of quantum monoids, groups, lattices, vector spaces, and operator algebras, all which differ from their classical counterparts. Moreover, we find natural classes of quantum lattices, vector spaces, and operator algebras which all have a beautiful inter-relationship, and make some preliminary investigations into using these structures as a basis for a new mathematical formulation of quantum mechanics. We also develop a quantum set theory (equivalent to ZFC under classical logic) which is far more tractable than quantum set theory previously developed. We then use this set theory to construct a quantum version of the natural numbers, and develop an arithmetic of these numbers based upon an alternative to Peano's axioms (which avoids Dunn's theorem). Surprisingly, we find that these "quantum natural numbers" satisfy our arithmetical axioms if and only if the underlying truth values form a modular lattice, giving a new arithmetical characterization of this important lattice-theoretic property. Finally, we show that these numbers have a natural interpretation as

  11. Quantum Computing for Quantum Chemistry

    DTIC Science & Technology

    2010-09-01

    random walks as the decoherence became strong. Recent experiments on photosynthetic light -harvesting complexes observed long-lived excitonic coherences...by the light -harvesting complex. In Environment-assisted quantum walks in energy transfer of photosynthetic complexes, J. Chem. Phys. 129 (2008...a decohered quantum walk. Motivated by the experiments on the Fenna-Matthews-Olson (FMO) light -harvesting complex of green sulfur bacteria, we

  12. Hiking Over Quantum Control Landscapes

    NASA Astrophysics Data System (ADS)

    Rabitz, Herschel

    2008-03-01

    Seeking the best control over a posed quantum dynamic objective entails climbing over the associated control landscape, which is defined as the quantum mechanical observable as a function of the controls. The topology and general structure of quantum control landscapes as input output maps dictate the final attainable yield, the efficiency of the search for an effective control, the possible existence of multiple dynamically equivalent controls, and the robustness of any viable control solution. Normal optimization problems in virtually any area of engineering and science typically have landscape topologies that remain a mystery. Quantum mechanics appears out to be quite special in that the topology of quantum control landscapes can be established generically based on minimal physical assumptions. Various features of these landscapes will be discussed and illustrated for circumstances where the controls are either an external field or the time independent portions of the Hamiltonian; the latter circumstance corresponds to subjecting the material or molecules to systematic variation and hence viewed in the context of being controls. Both theoretical and experimental findings on control landscapes and their consequences will be discussed, including issues of robustness to noise, search algorithm efficiency, existence of multiple control solutions, prospects for identifying reduced sets of control variables, simultaneous control of multiple quantum systems (optimal dynamic discrimination (ODD)), and mechanism analysis.

  13. Introduction to Quantum Simulation

    NASA Technical Reports Server (NTRS)

    Williams, Colin P.

    2005-01-01

    This viewgraph presentation addresses the problem of efficiently simulating the evolution of a quantum system. The contents include: 1) Quantum Simulation; 2) Extracting Answers from Quantum Simulations; 3) Quantum Fourier Transform; 4) Eigenvalue Estimation; 5) Fermionic Simulations.

  14. Quantum Transmemetic Intelligence

    NASA Astrophysics Data System (ADS)

    Piotrowski, Edward W.; Sładkowski, Jan

    The following sections are included: * Introduction * A Quantum Model of Free Will * Quantum Acquisition of Knowledge * Thinking as a Quantum Algorithm * Counterfactual Measurement as a Model of Intuition * Quantum Modification of Freud's Model of Consciousness * Conclusion * Acknowledgements * References

  15. Quantum Physics for Beginners.

    ERIC Educational Resources Information Center

    Strand, J.

    1981-01-01

    Suggests a new approach for teaching secondary school quantum physics. Reviews traditional approaches and presents some characteristics of the three-part "Quantum Physics for Beginners" project, including: quantum physics, quantum mechanics, and a short historical survey. (SK)

  16. Yield enhancement with DFM

    NASA Astrophysics Data System (ADS)

    Paek, Seung Weon; Kang, Jae Hyun; Ha, Naya; Kim, Byung-Moo; Jang, Dae-Hyun; Jeon, Junsu; Kim, DaeWook; Chung, Kun Young; Yu, Sung-eun; Park, Joo Hyun; Bae, SangMin; Song, DongSup; Noh, WooYoung; Kim, YoungDuck; Song, HyunSeok; Choi, HungBok; Kim, Kee Sup; Choi, Kyu-Myung; Choi, Woonhyuk; Jeon, JoongWon; Lee, JinWoo; Kim, Ki-Su; Park, SeongHo; Chung, No-Young; Lee, KangDuck; Hong, YoungKi; Kim, BongSeok

    2012-03-01

    A set of design for manufacturing (DFM) techniques have been developed and applied to 45nm, 32nm and 28nm logic process technologies. A noble technology combined a number of potential confliction of DFM techniques into a comprehensive solution. These techniques work in three phases for design optimization and one phase for silicon diagnostics. In the DFM prevention phase, foundation IP such as standard cells, IO, and memory and P&R tech file are optimized. In the DFM solution phase, which happens during ECO step, auto fixing of process weak patterns and advanced RC extraction are performed. In the DFM polishing phase, post-layout tuning is done to improve manufacturability. DFM analysis enables prioritization of random and systematic failures. The DFM technique presented in this paper has been silicon-proven with three successful tape-outs in Samsung 32nm processes; about 5% improvement in yield was achieved without any notable side effects. Visual inspection of silicon also confirmed the positive effect of the DFM techniques.

  17. Shortcomings in wheat yield predictions

    NASA Astrophysics Data System (ADS)

    Semenov, Mikhail A.; Mitchell, Rowan A. C.; Whitmore, Andrew P.; Hawkesford, Malcolm J.; Parry, Martin A. J.; Shewry, Peter R.

    2012-06-01

    Predictions of a 40-140% increase in wheat yield by 2050, reported in the UK Climate Change Risk Assessment, are based on a simplistic approach that ignores key factors affecting yields and hence are seriously misleading.

  18. Quantum hydrodynamics

    NASA Astrophysics Data System (ADS)

    Tsubota, Makoto; Kobayashi, Michikazu; Takeuchi, Hiromitsu

    2013-01-01

    Quantum hydrodynamics in superfluid helium and atomic Bose-Einstein condensates (BECs) has been recently one of the most important topics in low temperature physics. In these systems, a macroscopic wave function (order parameter) appears because of Bose-Einstein condensation, which creates quantized vortices. Turbulence consisting of quantized vortices is called quantum turbulence (QT). The study of quantized vortices and QT has increased in intensity for two reasons. The first is that recent studies of QT are considerably advanced over older studies, which were chiefly limited to thermal counterflow in 4He, which has no analog with classical traditional turbulence, whereas new studies on QT are focused on a comparison between QT and classical turbulence. The second reason is the realization of atomic BECs in 1995, for which modern optical techniques enable the direct control and visualization of the condensate and can even change the interaction; such direct control is impossible in other quantum condensates like superfluid helium and superconductors. Our group has made many important theoretical and numerical contributions to the field of quantum hydrodynamics of both superfluid helium and atomic BECs. In this article, we review some of the important topics in detail. The topics of quantum hydrodynamics are diverse, so we have not attempted to cover all these topics in this article. We also ensure that the scope of this article does not overlap with our recent review article (arXiv:1004.5458), “Quantized vortices in superfluid helium and atomic Bose-Einstein condensates”, and other review articles.

  19. Quantum walk computation

    SciTech Connect

    Kendon, Viv

    2014-12-04

    Quantum versions of random walks have diverse applications that are motivating experimental implementations as well as theoretical studies. Recent results showing quantum walks are “universal for quantum computation” relate to algorithms, to be run on quantum computers. We consider whether an experimental implementation of a quantum walk could provide useful computation before we have a universal quantum computer.

  20. Crop yield gaps in Cameroon.

    PubMed

    Yengoh, Genesis T; Ardö, Jonas

    2014-03-01

    Although food crop yields per hectare have generally been increasing in Cameroon since 1961, the food price crisis of 2008 and the ensuing social unrest and fatalities raised concerns about the country's ability to meet the food needs of its population. This study examines the country's potential for increasing crop yields and food production to meet this food security challenge. Fuzzy set theory is used to develop a biophysical spatial suitability model for different crops, which in turn is employed to ascertain whether crop production is carried out in biophysically suited areas. We use linear regression to examine the trend of yield development over the last half century. On the basis of yield data from experimental stations and farmers' fields we assess the yield gap for major food crops. We find that yields have generally been increasing over the last half century and that agricultural policies can have significant effects on them. To a large extent, food crops are cultivated in areas that are biophysically suited for their cultivation, meaning that the yield gap is not a problem of biophysical suitability. Notwithstanding, there are significantly large yield gaps between actual yields on farmers' farms and maximum attainable yields from research stations. We conclude that agronomy and policies are likely to be the reasons for these large yield gaps. A key challenge to be addressed in closing the yield gaps is that of replenishing and properly managing soil nutrients.

  1. Quantum turbulence

    NASA Astrophysics Data System (ADS)

    Skrbek, L.

    2011-12-01

    We review physical properties of quantum fluids He II and 3He-B, where quantum turbulence (QT) has been studied experimentally. Basic properties of QT in these working fluids are discussed within the phenomenological two-fluid model introduced by Landau. We consider counterflows in which the normal and superfluid components flow against each other, as well as co-flows in which the direction of the two fluids is the same. We pay special attention to the important case of zero temperature limit, where QT represents an interesting and probably the simplest prototype of three-dimensional turbulence in fluids. Experimental techniques to explore QT such as second sound attenuation, Andreev reflection, NMR, ion propagation are briefly introduced and results of various experiments on so-called Vinen QT and Kolmogorov QT both in He II and 3He are discussed, emphasizing similarities and differences between classical and quantum turbulence.

  2. Quantum dice

    NASA Astrophysics Data System (ADS)

    Sassoli de Bianchi, Massimiliano

    2013-09-01

    In a letter to Born, Einstein wrote [42]: "Quantum mechanics is certainly imposing. But an inner voice tells me that it is not yet the real thing. The theory says a lot, but does not really bring us any closer to the secret of the 'old one.' I, at any rate, am convinced that He does not throw dice." In this paper we take seriously Einstein's famous metaphor, and show that we can gain considerable insight into quantum mechanics by doing something as simple as rolling dice. More precisely, we show how to perform measurements on a single die, to create typical quantum interference effects, and how to connect (entangle) two identical dice, to maximally violate Bell's inequality.

  3. Quantum Spring

    NASA Astrophysics Data System (ADS)

    Feng, Chao-Jun; Li, Xin-Zhou

    In this paper, we will give a short review on quantum spring, which is a Casimir effect from the helix boundary condition that proposed in our earlier works. The Casimir force parallel to the axis of the helix behaves very much like the force on a spring that obeys the Hooke's law when the ratio r of the pitch to the circumference of the helix is small, but in this case, the force comes from a quantum effect, so we would like to call it quantum spring. On the other hand, the force perpendicular to the axis decreases monotonously with the increasing of the ratio r. Both forces are attractive and their behaviors are the same in two and three dimensions.

  4. Universal quantum computation with a nonlinear oscillator network

    NASA Astrophysics Data System (ADS)

    Goto, Hayato

    2016-05-01

    We theoretically show that a nonlinear oscillator network with controllable parameters can be used for universal quantum computation. The initialization is achieved by a quantum-mechanical bifurcation based on quantum adiabatic evolution, which yields a Schrödinger cat state. All the elementary quantum gates are also achieved by quantum adiabatic evolution, in which dynamical phases accompanying the adiabatic evolutions are controlled by the system parameters. Numerical simulation results indicate that high gate fidelities can be achieved, where no dissipation is assumed.

  5. Complementarity of quantum discord and classically accessible information

    SciTech Connect

    Zwolak, Michael P.; Zurek, Wojciech H.

    2013-05-20

    The sum of the Holevo quantity (that bounds the capacity of quantum channels to transmit classical information about an observable) and the quantum discord (a measure of the quantumness of correlations of that observable) yields an observable-independent total given by the quantum mutual information. This split naturally delineates information about quantum systems accessible to observers – information that is redundantly transmitted by the environment – while showing that it is maximized for the quasi-classical pointer observable. Other observables are accessible only via correlations with the pointer observable. In addition, we prove an anti-symmetry property relating accessible information and discord. It shows that information becomes objective – accessible to many observers – only as quantum information is relegated to correlations with the global environment, and, therefore, locally inaccessible. Lastly, the resulting complementarity explains why, in a quantum Universe, we perceive objective classical reality while flagrantly quantum superpositions are out of reach.

  6. Complementarity of quantum discord and classically accessible information

    DOE PAGES

    Zwolak, Michael P.; Zurek, Wojciech H.

    2013-05-20

    The sum of the Holevo quantity (that bounds the capacity of quantum channels to transmit classical information about an observable) and the quantum discord (a measure of the quantumness of correlations of that observable) yields an observable-independent total given by the quantum mutual information. This split naturally delineates information about quantum systems accessible to observers – information that is redundantly transmitted by the environment – while showing that it is maximized for the quasi-classical pointer observable. Other observables are accessible only via correlations with the pointer observable. In addition, we prove an anti-symmetry property relating accessible information and discord. Itmore » shows that information becomes objective – accessible to many observers – only as quantum information is relegated to correlations with the global environment, and, therefore, locally inaccessible. Lastly, the resulting complementarity explains why, in a quantum Universe, we perceive objective classical reality while flagrantly quantum superpositions are out of reach.« less

  7. Quantum Finance

    NASA Astrophysics Data System (ADS)

    Baaquie, Belal E.

    2007-09-01

    Foreword; Preface; Acknowledgements; 1. Synopsis; Part I. Fundamental Concepts of Finance: 2. Introduction to finance; 3. Derivative securities; Part II. Systems with Finite Number of Degrees of Freedom: 4. Hamiltonians and stock options; 5. Path integrals and stock options; 6. Stochastic interest rates' Hamiltonians and path integrals; Part III. Quantum Field Theory of Interest Rates Models: 7. Quantum field theory of forward interest rates; 8. Empirical forward interest rates and field theory models; 9. Field theory of Treasury Bonds' derivatives and hedging; 10. Field theory Hamiltonian of forward interest rates; 11. Conclusions; Appendix A: mathematical background; Brief glossary of financial terms; Brief glossary of physics terms; List of main symbols; References; Index.

  8. Quantum Foam

    SciTech Connect

    Lincoln, Don

    2014-10-24

    The laws of quantum mechanics and relativity are quite perplexing however it is when the two theories are merged that things get really confusing. This combined theory predicts that empty space isn’t empty at all – it’s a seething and bubbling cauldron of matter and antimatter particles springing into existence before disappearing back into nothingness. Scientists call this complicated state of affairs “quantum foam.” In this video, Fermilab’s Dr. Don Lincoln discusses this mind-bending idea and sketches some of the experiments that have convinced scientists that this crazy prediction is actually true.

  9. Quantum Uniqueness

    NASA Astrophysics Data System (ADS)

    Sych, Denis; Leuchs, Gerd

    2015-12-01

    Classical physics allows for the existence of pairs of absolutely identical systems. Pairwise application of identical measurements to each of those systems always leads to exactly alike results irrespectively of the choice of measurements. Here we ask a question how the picture looks like in the quantum domain. Surprisingly, we get a counterintuitive outcome. Pairwise application of identical (but a priori unknown) measurements cannot always lead to exactly alike results. We interpret this as quantum uniqueness—a feature that has no classical analog.

  10. Brightness-equalized quantum dots

    PubMed Central

    Lim, Sung Jun; Zahid, Mohammad U.; Le, Phuong; Ma, Liang; Entenberg, David; Harney, Allison S.; Condeelis, John; Smith, Andrew M.

    2015-01-01

    As molecular labels for cells and tissues, fluorescent probes have shaped our understanding of biological structures and processes. However, their capacity for quantitative analysis is limited because photon emission rates from multicolour fluorophores are dissimilar, unstable and often unpredictable, which obscures correlations between measured fluorescence and molecular concentration. Here we introduce a new class of light-emitting quantum dots with tunable and equalized fluorescence brightness across a broad range of colours. The key feature is independent tunability of emission wavelength, extinction coefficient and quantum yield through distinct structural domains in the nanocrystal. Precise tuning eliminates a 100-fold red-to-green brightness mismatch of size-tuned quantum dots at the ensemble and single-particle levels, which substantially improves quantitative imaging accuracy in biological tissue. We anticipate that these materials engineering principles will vastly expand the optical engineering landscape of fluorescent probes, facilitate quantitative multicolour imaging in living tissue and improve colour tuning in light-emitting devices. PMID:26437175

  11. Quantum effects in warp drives

    NASA Astrophysics Data System (ADS)

    Finazzi, Stefano

    2013-09-01

    Warp drives are interesting configurations that, at least theoretically, provide a way to travel at superluminal speed. Unfortunately, several issues seem to forbid their realization. First, a huge amount of exotic matter is required to build them. Second, the presence of quantum fields propagating in superluminal warp-drive geometries makes them semiclassically unstable. Indeed, a Hawking-like high-temperature flux of particles is generated inside the warp-drive bubble, which causes an exponential growth of the energy density measured at the front wall of the bubble by freely falling observers. Moreover, superluminal warp drives remain unstable even if the Lorentz symmetry is broken by the introduction of regulating higher order terms in the Lagrangian of the quantum field. If the dispersion relation of the quantum field is subluminal, a black-hole laser phenomenon yields an exponential amplification of the emitted flux. If it is superluminal, infrared effects cause a linear growth of this flux.

  12. Brightness-equalized quantum dots.

    PubMed

    Lim, Sung Jun; Zahid, Mohammad U; Le, Phuong; Ma, Liang; Entenberg, David; Harney, Allison S; Condeelis, John; Smith, Andrew M

    2015-10-05

    As molecular labels for cells and tissues, fluorescent probes have shaped our understanding of biological structures and processes. However, their capacity for quantitative analysis is limited because photon emission rates from multicolour fluorophores are dissimilar, unstable and often unpredictable, which obscures correlations between measured fluorescence and molecular concentration. Here we introduce a new class of light-emitting quantum dots with tunable and equalized fluorescence brightness across a broad range of colours. The key feature is independent tunability of emission wavelength, extinction coefficient and quantum yield through distinct structural domains in the nanocrystal. Precise tuning eliminates a 100-fold red-to-green brightness mismatch of size-tuned quantum dots at the ensemble and single-particle levels, which substantially improves quantitative imaging accuracy in biological tissue. We anticipate that these materials engineering principles will vastly expand the optical engineering landscape of fluorescent probes, facilitate quantitative multicolour imaging in living tissue and improve colour tuning in light-emitting devices.

  13. Blind Quantum Signature with Blind Quantum Computation

    NASA Astrophysics Data System (ADS)

    Li, Wei; Shi, Ronghua; Guo, Ying

    2017-04-01

    Blind quantum computation allows a client without quantum abilities to interact with a quantum server to perform a unconditional secure computing protocol, while protecting client's privacy. Motivated by confidentiality of blind quantum computation, a blind quantum signature scheme is designed with laconic structure. Different from the traditional signature schemes, the signing and verifying operations are performed through measurement-based quantum computation. Inputs of blind quantum computation are securely controlled with multi-qubit entangled states. The unique signature of the transmitted message is generated by the signer without leaking information in imperfect channels. Whereas, the receiver can verify the validity of the signature using the quantum matching algorithm. The security is guaranteed by entanglement of quantum system for blind quantum computation. It provides a potential practical application for e-commerce in the cloud computing and first-generation quantum computation.

  14. Blind Quantum Signature with Blind Quantum Computation

    NASA Astrophysics Data System (ADS)

    Li, Wei; Shi, Ronghua; Guo, Ying

    2016-12-01

    Blind quantum computation allows a client without quantum abilities to interact with a quantum server to perform a unconditional secure computing protocol, while protecting client's privacy. Motivated by confidentiality of blind quantum computation, a blind quantum signature scheme is designed with laconic structure. Different from the traditional signature schemes, the signing and verifying operations are performed through measurement-based quantum computation. Inputs of blind quantum computation are securely controlled with multi-qubit entangled states. The unique signature of the transmitted message is generated by the signer without leaking information in imperfect channels. Whereas, the receiver can verify the validity of the signature using the quantum matching algorithm. The security is guaranteed by entanglement of quantum system for blind quantum computation. It provides a potential practical application for e-commerce in the cloud computing and first-generation quantum computation.

  15. Electron quantum optics as quantum signal processing

    NASA Astrophysics Data System (ADS)

    Roussel, B.; Cabart, C.; Fève, G.; Thibierge, E.; Degiovanni, P.

    2017-03-01

    The recent developments of electron quantum optics in quantum Hall edge channels have given us new ways to probe the behavior of electrons in quantum conductors. It has brought new quantities called electronic coherences under the spotlight. In this paper, we explore the relations between electron quantum optics and signal processing through a global review of the various methods for accessing single- and two-electron coherences in electron quantum optics. We interpret electron quantum optics interference experiments as analog signal processing converting quantum signals into experimentally observable quantities such as current averages and correlations. This point of view also gives us a procedure to obtain quantum information quantities from electron quantum optics coherences. We illustrate these ideas by discussing two mode entanglement in electron quantum optics. We also sketch how signal processing ideas may open new perspectives for representing electronic coherences in quantum conductors and understand the properties of the underlying many-body electronic state.

  16. Quantum memory for images: A quantum hologram

    SciTech Connect

    Vasilyev, Denis V.; Sokolov, Ivan V.; Polzik, Eugene S.

    2008-02-15

    Matter-light quantum interface and quantum memory for light are important ingredients of quantum information protocols, such as quantum networks, distributed quantum computation, etc. [P. Zoller et al., Eur. Phys. J. D 36, 203 (2005)]. In this paper we present a spatially multimode scheme for quantum memory for light, which we call a quantum hologram. Our approach uses a multiatom ensemble which has been shown to be efficient for a single spatial mode quantum memory. Due to the multiatom nature of the ensemble and to the optical parallelism it is capable of storing many spatial modes, a feature critical for the present proposal. A quantum hologram with the fidelity exceeding that of classical hologram will be able to store quantum features of an image, such as multimode superposition and entangled quantum states, something that a standard hologram is unable to achieve.

  17. Quantum renewal equation for the first detection time of a quantum walk

    NASA Astrophysics Data System (ADS)

    Friedman, H.; Kessler, D. A.; Barkai, E.

    2017-01-01

    We investigate the statistics of the first detected passage time of a quantum walk. The postulates of quantum theory, in particular the collapse of the wave function upon measurement, reveal an intimate connection between the wave function of a process free of measurements, i.e. the solution of the Schrödinger equation, and the statistics of first detection events on a site. For stroboscopic measurements a quantum renewal equation yields basic properties of quantum walks. For example, for a tight binding model on a ring we discover critical sampling times, diverging quantities such as the mean time for first detection, and an optimal detection rate. For a quantum walk on an infinite line the probability of first detection decays like {{≤ft(\\text{time}\\right)}-3} with a superimposed oscillation, critical behavior for a specific choice of sampling time, and vanishing amplitude when the sampling time approaches zero due to the quantum Zeno effect.

  18. Bifurcation-based adiabatic quantum computation with a nonlinear oscillator network

    NASA Astrophysics Data System (ADS)

    Goto, Hayato

    The dynamics of nonlinear systems qualitatively change depending on their parameters, which is called bifurcation. A quantum-mechanical nonlinear oscillator can yield a quantum superposition of two oscillation states, known as a Schrödinger cat state, via its bifurcation with a slowly varying parameter. Here we propose a quantum computer comprising such quantum nonlinear oscillators, instead of quantum bits, to solve hard combinatorial optimization problems. The nonlinear oscillator network finds optimal solutions via quantum adiabatic evolution, where nonlinear terms are increased slowly, in contrast to conventional adiabatic quantum computation or quantum annealing. To distinguish them, we refer to the present approach as bifurcation-based adiabatic quantum computation. Our numerical simulation results suggest that quantum superposition and quantum fluctuation work effectively to find optimal solutions.

  19. Quantum learning without quantum memory.

    PubMed

    Sentís, G; Calsamiglia, J; Muñoz-Tapia, R; Bagan, E

    2012-01-01

    A quantum learning machine for binary classification of qubit states that does not require quantum memory is introduced and shown to perform with the minimum error rate allowed by quantum mechanics for any size of the training set. This result is shown to be robust under (an arbitrary amount of) noise and under (statistical) variations in the composition of the training set, provided it is large enough. This machine can be used an arbitrary number of times without retraining. Its required classical memory grows only logarithmically with the number of training qubits, while its excess risk decreases as the inverse of this number, and twice as fast as the excess risk of an "estimate-and-discriminate" machine, which estimates the states of the training qubits and classifies the data qubit with a discrimination protocol tailored to the obtained estimates.

  20. Quantum learning without quantum memory

    NASA Astrophysics Data System (ADS)

    Sentís, G.; Calsamiglia, J.; Muñoz-Tapia, R.; Bagan, E.

    2012-10-01

    A quantum learning machine for binary classification of qubit states that does not require quantum memory is introduced and shown to perform with the minimum error rate allowed by quantum mechanics for any size of the training set. This result is shown to be robust under (an arbitrary amount of) noise and under (statistical) variations in the composition of the training set, provided it is large enough. This machine can be used an arbitrary number of times without retraining. Its required classical memory grows only logarithmically with the number of training qubits, while its excess risk decreases as the inverse of this number, and twice as fast as the excess risk of an ``estimate-and-discriminate'' machine, which estimates the states of the training qubits and classifies the data qubit with a discrimination protocol tailored to the obtained estimates.

  1. Quantum Speedup by Quantum Annealing

    NASA Astrophysics Data System (ADS)

    Somma, Rolando D.; Nagaj, Daniel; Kieferová, Mária

    2012-08-01

    We study the glued-trees problem from A. M. Childs, R. Cleve, E. Deotto, E. Farhi, S. Gutmann, and D. Spielman, in Proceedings of the 35th Annual ACM Symposium on Theory of Computing (ACM, San Diego, CA, 2003), p. 59. in the adiabatic model of quantum computing and provide an annealing schedule to solve an oracular problem exponentially faster than classically possible. The Hamiltonians involved in the quantum annealing do not suffer from the so-called sign problem. Unlike the typical scenario, our schedule is efficient even though the minimum energy gap of the Hamiltonians is exponentially small in the problem size. We discuss generalizations based on initial-state randomization to avoid some slowdowns in adiabatic quantum computing due to small gaps.

  2. Topological Characterization of Extended Quantum Ising Models.

    PubMed

    Zhang, G; Song, Z

    2015-10-23

    We show that a class of exactly solvable quantum Ising models, including the transverse-field Ising model and anisotropic XY model, can be characterized as the loops in a two-dimensional auxiliary space. The transverse-field Ising model corresponds to a circle and the XY model corresponds to an ellipse, while other models yield cardioid, limacon, hypocycloid, and Lissajous curves etc. It is shown that the variation of the ground state energy density, which is a function of the loop, experiences a nonanalytical point when the winding number of the corresponding loop changes. The winding number can serve as a topological quantum number of the quantum phases in the extended quantum Ising model, which sheds some light upon the relation between quantum phase transition and the geometrical order parameter characterizing the phase diagram.

  3. Adaptive Quantum State Detection through Repetitive Mapping

    NASA Astrophysics Data System (ADS)

    Hume, David; Rosenband, Till; Wineland, David; Bergquist, Jim

    2007-06-01

    State detection plays an important role in quantum information processing and quantum-limited metrology. In some quantum systems direct detection is impossible or inefficient. This can be overcome by coupling the primary quantum system to an ancillary system used for measurement [1]. The measurement process consists of mapping the primary state to the ancilla followed by ancilla detection. If the measurement does not affect the projected populations of the primary system, it may be repeated yielding higher fidelity. Using two trapped ion species (^27Al^+ and ^9Be^+) as the primary and ancillary systems, we demonstrate high-fidelity measurement despite imperfect information transfer and ancilla detection. An adaptive measurement strategy allows for multiple qubit state discrimination with one ancilla. This opens the way for several applications in quantum information processing and advances our optical clock effort. [1] P.O. Schmidt, et. al. Science 309 749 (2005)

  4. Quantum rendering

    NASA Astrophysics Data System (ADS)

    Lanzagorta, Marco O.; Gomez, Richard B.; Uhlmann, Jeffrey K.

    2003-08-01

    In recent years, computer graphics has emerged as a critical component of the scientific and engineering process, and it is recognized as an important computer science research area. Computer graphics are extensively used for a variety of aerospace and defense training systems and by Hollywood's special effects companies. All these applications require the computer graphics systems to produce high quality renderings of extremely large data sets in short periods of time. Much research has been done in "classical computing" toward the development of efficient methods and techniques to reduce the rendering time required for large datasets. Quantum Computing's unique algorithmic features offer the possibility of speeding up some of the known rendering algorithms currently used in computer graphics. In this paper we discuss possible implementations of quantum rendering algorithms. In particular, we concentrate on the implementation of Grover's quantum search algorithm for Z-buffering, ray-tracing, radiosity, and scene management techniques. We also compare the theoretical performance between the classical and quantum versions of the algorithms.

  5. Quantum dice

    SciTech Connect

    Sassoli de Bianchi, Massimiliano

    2013-09-15

    In a letter to Born, Einstein wrote [42]: “Quantum mechanics is certainly imposing. But an inner voice tells me that it is not yet the real thing. The theory says a lot, but does not really bring us any closer to the secret of the ‘old one.’ I, at any rate, am convinced that He does not throw dice.” In this paper we take seriously Einstein’s famous metaphor, and show that we can gain considerable insight into quantum mechanics by doing something as simple as rolling dice. More precisely, we show how to perform measurements on a single die, to create typical quantum interference effects, and how to connect (entangle) two identical dice, to maximally violate Bell’s inequality. -- Highlights: •Rolling a die is a quantum process admitting a Hilbert space representation. •Rolling experiments with a single die can produce interference effects. •Two connected dice can violate Bell’s inequality. •Correlations need to be created by the measurement, to violate Bell’s inequality.

  6. Quantum Interferometry

    NASA Technical Reports Server (NTRS)

    Dowling, Jonathan P.

    2000-01-01

    Recently, several researchers, including yours truly, have been able to demonstrate theoretically that quantum photon entanglement has the potential to also revolutionize the entire field of optical interferometry, by providing many orders of magnitude improvement in interferometer sensitivity. The quantum entangled photon interferometer approach is very general and applies to many types of interferometers. In particular, without nonlocal entanglement, a generic classical interferometer has a statistical-sampling shot-noise limited sensitivity that scales like 1/Sqrt[N], where N is the number of particles (photons, electrons, atoms, neutrons) passing through the interferometer per unit time. However, if carefully prepared quantum correlations are engineered between the particles, then the interferometer sensitivity improves by a factor of Sqrt[N] (square root of N) to scale like 1/N, which is the limit imposed by the Heisenberg Uncertainty Principle. For optical (laser) interferometers operating at milliwatts of optical power, this quantum sensitivity boost corresponds to an eight-order-of-magnitude improvement of signal to noise. Applications are to tests of General Relativity such as ground and orbiting optical interferometers for gravity wave detection, Laser Interferometer Gravity Observatory (LIGO) and the European Laser Interferometer Space Antenna (LISA), respectively.

  7. Quantum wormholes

    SciTech Connect

    Visser, M. )

    1991-01-15

    This paper presents an application of quantum-mechanical principles to a microscopic variant of the traversable wormholes recently introduced by Morris and Thorne. The analysis, based on the surgical grafting of two Reissner-Nordstroem spacetimes, proceeds by using a minisuperspace model to approximate the geometry of these wormholes. The thin shell'' formalism is applied to this minisuperspace model to extract the effective Lagrangian appropriate to this one-degree-of-freedom system. This effective Lagrangian is then quantized and the wave function for the wormhole is explicitly exhibited. A slightly more general class of wormholes---corresponding to the addition of some dust'' to the wormhole throat---is analyzed by recourse to WKB techniques. In all cases discussed in this paper, the expectation value of the wormhole radius is calculated to be of the order of the Planck length. Accordingly, though these quantum wormholes are of considerable theoretical interest they do not appear to be useful as a means for interstellar travel. The results of this paper may also have a bearing on the question of topological fluctuations in quantum gravity. These calculations serve to suggest that topology-changing effects might in fact be {ital suppressed} by quantum-gravity effects.

  8. Quantum gravity.

    NASA Astrophysics Data System (ADS)

    Maślanka, K.

    A model of reality based on quantum fields, but with a classical treatment of gravity, is inconsistent. Finding a solution has proved extremely difficult, possibly due to the beauty and conceptual simplicity of general relativity. There is a variety of approaches to a consistent theory of quntum gravity. At present, it seems that superstring theory is the most promising candidate.

  9. Teleportation-induced correlated quantum channels.

    PubMed

    Caruso, F; Giovannetti, V; Palma, G M

    2010-01-15

    Quantum teleportation of an n-qubit state performed using as an entangled resource a general bipartite state of 2n qubits instead of n Bell states is equivalent to a correlated Pauli channel. This yields a new characterization of such channels in terms of many-body correlation functions of the teleporting media. It provides a relatively simple method for determining whether a correlated quantum channel is able to reliably convey quantum messages by studying the entanglement properties of the teleportation mediating system. Our model is then generalized to the continuous-variable case.

  10. Quantum theory of light propagation - Linear medium

    NASA Astrophysics Data System (ADS)

    Abram, I.

    1987-06-01

    A quantum-mechanical formalism has been developed which permits the treatment of light propagation within the conceptual framework of quantum optics. The formalism rests on the calculation of the momentum operator for the radiation field, and yields directly a description for the spatial progression of the electromagnetic waves. In this paper, a quantum-mechanical treatment for refraction and reflection is given by applying the formalism to propagation through a linear dielectric. The fidelity with which this formalism reproduces all results known from classical optics demonstrates its validity.

  11. Quantum Search and Beyond

    DTIC Science & Technology

    2008-07-02

    solution of certain problems for which the communication needs do not dominate. A similar situation prevails in the quantum world. Quantum teleportation and...REPORT Quantum Search and Beyond 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: Ten years ago, the quantum search algorithm was designed to provide a way...P.O. Box 12211 Research Triangle Park, NC 27709-2211 15. SUBJECT TERMS quantum searching - partial quantum searching, fixed-point quantum

  12. Efficient quantum walk on a quantum processor

    NASA Astrophysics Data System (ADS)

    Qiang, Xiaogang; Loke, Thomas; Montanaro, Ashley; Aungskunsiri, Kanin; Zhou, Xiaoqi; O'Brien, Jeremy L.; Wang, Jingbo B.; Matthews, Jonathan C. F.

    2016-05-01

    The random walk formalism is used across a wide range of applications, from modelling share prices to predicting population genetics. Likewise, quantum walks have shown much potential as a framework for developing new quantum algorithms. Here we present explicit efficient quantum circuits for implementing continuous-time quantum walks on the circulant class of graphs. These circuits allow us to sample from the output probability distributions of quantum walks on circulant graphs efficiently. We also show that solving the same sampling problem for arbitrary circulant quantum circuits is intractable for a classical computer, assuming conjectures from computational complexity theory. This is a new link between continuous-time quantum walks and computational complexity theory and it indicates a family of tasks that could ultimately demonstrate quantum supremacy over classical computers. As a proof of principle, we experimentally implement the proposed quantum circuit on an example circulant graph using a two-qubit photonics quantum processor.

  13. Efficient quantum walk on a quantum processor

    PubMed Central

    Qiang, Xiaogang; Loke, Thomas; Montanaro, Ashley; Aungskunsiri, Kanin; Zhou, Xiaoqi; O'Brien, Jeremy L.; Wang, Jingbo B.; Matthews, Jonathan C. F.

    2016-01-01

    The random walk formalism is used across a wide range of applications, from modelling share prices to predicting population genetics. Likewise, quantum walks have shown much potential as a framework for developing new quantum algorithms. Here we present explicit efficient quantum circuits for implementing continuous-time quantum walks on the circulant class of graphs. These circuits allow us to sample from the output probability distributions of quantum walks on circulant graphs efficiently. We also show that solving the same sampling problem for arbitrary circulant quantum circuits is intractable for a classical computer, assuming conjectures from computational complexity theory. This is a new link between continuous-time quantum walks and computational complexity theory and it indicates a family of tasks that could ultimately demonstrate quantum supremacy over classical computers. As a proof of principle, we experimentally implement the proposed quantum circuit on an example circulant graph using a two-qubit photonics quantum processor. PMID:27146471

  14. Quantum Secure Dialogue with Quantum Encryption

    NASA Astrophysics Data System (ADS)

    Ye, Tian-Yu

    2014-09-01

    How to solve the information leakage problem has become the research focus of quantum dialogue. In this paper, in order to overcome the information leakage problem in quantum dialogue, a novel approach for sharing the initial quantum state privately between communicators, i.e., quantum encryption sharing, is proposed by utilizing the idea of quantum encryption. The proposed protocol uses EPR pairs as the private quantum key to encrypt and decrypt the traveling photons, which can be repeatedly used after rotation. Due to quantum encryption sharing, the public announcement on the state of the initial quantum state is omitted, thus the information leakage problem is overcome. The information-theoretical efficiency of the proposed protocol is nearly 100%, much higher than previous information leakage resistant quantum dialogue protocols. Moreover, the proposed protocol only needs single-photon measurements and nearly uses single photons as quantum resource so that it is convenient to implement in practice.

  15. Efficient quantum walk on a quantum processor.

    PubMed

    Qiang, Xiaogang; Loke, Thomas; Montanaro, Ashley; Aungskunsiri, Kanin; Zhou, Xiaoqi; O'Brien, Jeremy L; Wang, Jingbo B; Matthews, Jonathan C F

    2016-05-05

    The random walk formalism is used across a wide range of applications, from modelling share prices to predicting population genetics. Likewise, quantum walks have shown much potential as a framework for developing new quantum algorithms. Here we present explicit efficient quantum circuits for implementing continuous-time quantum walks on the circulant class of graphs. These circuits allow us to sample from the output probability distributions of quantum walks on circulant graphs efficiently. We also show that solving the same sampling problem for arbitrary circulant quantum circuits is intractable for a classical computer, assuming conjectures from computational complexity theory. This is a new link between continuous-time quantum walks and computational complexity theory and it indicates a family of tasks that could ultimately demonstrate quantum supremacy over classical computers. As a proof of principle, we experimentally implement the proposed quantum circuit on an example circulant graph using a two-qubit photonics quantum processor.

  16. Quantum to classical randomness extractors

    NASA Astrophysics Data System (ADS)

    Wehner, Stephanie; Berta, Mario; Fawzi, Omar

    2013-03-01

    The goal of randomness extraction is to distill (almost) perfect randomness from a weak source of randomness. When the source yields a classical string X, many extractor constructions are known. Yet, when considering a physical randomness source, X is itself ultimately the result of a measurement on an underlying quantum system. When characterizing the power of a source to supply randomness it is hence a natural question to ask, how much classical randomness we can extract from a quantum system. To tackle this question we here introduce the notion of quantum-to-classical randomness extractors (QC-extractors). We identify an entropic quantity that determines exactly how much randomness can be obtained. Furthermore, we provide constructions of QC-extractors based on measurements in a full set of mutually unbiased bases (MUBs), and certain single qubit measurements. As the first application, we show that any QC-extractor gives rise to entropic uncertainty relations with respect to quantum side information. Such relations were previously only known for two measurements. As the second application, we resolve the central open question in the noisy-storage model [Wehner et al., PRL 100, 220502 (2008)] by linking security to the quantum capacity of the adversary's storage device.

  17. Nearly deterministic Bell measurement using quantum communication bus

    NASA Astrophysics Data System (ADS)

    Wang, Jia-Ming; Zhu, Meng-zheng; Wang, Dong; Ye, Liu

    2017-03-01

    We present a scheme to implement Bell states measurement for an arbitrary number of photons by using robust continuous variable coherent modes, called as quantum communication bus (qubus) and weak cross-Kerr nonlinearities. Remarkably, the success probability of our scheme is close to unity, and our scheme does not require any ancillary resource entanglement. Our scheme is likely to yield versatile applications for quantum computation and quantum teleportation.

  18. Luminescent properties of cadmium selenide quantum dots in fluorophosphate glasses

    NASA Astrophysics Data System (ADS)

    Lipatova, Zh. O.; Kolobkova, E. V.; Babkina, A. N.

    2016-11-01

    The optical properties of fluorophosphate glasses with CdSe quantum dots are studied. Secondary heat treatment at a temperature exceeding the glass transition temperature resulted in the formation of quantum dots with sizes of 3.7-6.2 nm. The influence of the semiconductor component concentration on the spectral-luminescent characteristics of glasses is shown. It is experimentally demonstrated that glasses with a lower CdSe concentration have a higher absolute luminescence quantum yield.

  19. Noncommuting observables in quantum detection and estimation theory

    NASA Technical Reports Server (NTRS)

    Helstrom, C. W.

    1971-01-01

    In quantum detection theory, the optimum detection operators must commute; admitting simultaneous approximate measurement of noncommuting observables cannot yield a lower Bayes cost. In addition, the lower bounds on mean square errors of parameter estimates, predicted by the quantum mechanical Cramer-Rao inequality, cannot be reduced by such means.

  20. Noncommunting observables in quantum detection and estimation theory

    NASA Technical Reports Server (NTRS)

    Helstrom, C. W.

    1971-01-01

    In quantum detection theory the optimum detection operators must commute; admitting simultaneous approximate measurement of noncommuting observables cannot yield a lower Bayes cost. The lower bounds on mean square errors of parameter estimates predicted by the quantum-mechanical Cramer-Rao inequality can also not be reduced by such means.

  1. Quantum decision tree classifier

    NASA Astrophysics Data System (ADS)

    Lu, Songfeng; Braunstein, Samuel L.

    2013-11-01

    We study the quantum version of a decision tree classifier to fill the gap between quantum computation and machine learning. The quantum entropy impurity criterion which is used to determine which node should be split is presented in the paper. By using the quantum fidelity measure between two quantum states, we cluster the training data into subclasses so that the quantum decision tree can manipulate quantum states. We also propose algorithms constructing the quantum decision tree and searching for a target class over the tree for a new quantum object.

  2. Quantum gate decomposition algorithms.

    SciTech Connect

    Slepoy, Alexander

    2006-07-01

    Quantum computing algorithms can be conveniently expressed in a format of a quantum logical circuits. Such circuits consist of sequential coupled operations, termed ''quantum gates'', or quantum analogs of bits called qubits. We review a recently proposed method [1] for constructing general ''quantum gates'' operating on an qubits, as composed of a sequence of generic elementary ''gates''.

  3. Quantum simulated annealing

    NASA Astrophysics Data System (ADS)

    Boixo, Sergio; Somma, Rolando; Barnum, Howard

    2008-03-01

    We develop a quantum algorithm to solve combinatorial optimization problems through quantum simulation of a classical annealing process. Our algorithm combines techniques from quantum walks and quantum phase estimation, and can be viewed as the quantum analogue of the discrete-time Markov Chain Monte Carlo implementation of classical simulated annealing.

  4. Quantum oligopoly

    NASA Astrophysics Data System (ADS)

    Lo, C. F.; Kiang, D.

    2003-12-01

    Based upon a modification of Li et al.'s "minimal" quantization rules (Phys. Lett. A306(2002) 73), we investigate the quantum version of the Cournot and Bertrand oligopoly. In the Cournot oligopoly, the profit of each of the N firms at the Nash equilibrium point rises monotonically with the measure of the quantum entanglement. Only at maximal entanglement, however, does the Nash equilibrium point coincide with the Pareto optimal point. In the Bertrand case, the Bertrand Paradox remains for finite entanglement (i.e., the perfectly competitive stage is reached for any N>=2), whereas with maximal entanglement each of the N firms will still have a non-zero shared profit. Hence, the Bertrand Paradox is completely resolved. Furthermore, a perfectly competitive market is reached asymptotically for N → ∞ in both the Cournot and Bertrand oligopoly.

  5. Quantum nonlocality

    SciTech Connect

    Stapp, H.P.

    1988-04-01

    It is argued that the validity of the predictions of quantum theory in certain spin-correlation experiments entails a violation of Einstein's locality idea that no causal influence can act outside the forward light cone. First, two preliminary arguments suggesting such a violation are reviewed. They both depend, in intermediate stages, on the idea that the results of certain unperformed experiments are physically determinate. The second argument is entangled also with the problem of the meaning of physical reality. A new argument having neither of these characteristics is constructed. It is based strictly on the orthodox ideas of Bohr and Heisenberg, and has no realistic elements, or other ingredients, that are alien to orthodox quantum thinking.

  6. Quantum Foam

    ScienceCinema

    Lincoln, Don

    2016-07-12

    The laws of quantum mechanics and relativity are quite perplexing however it is when the two theories are merged that things get really confusing. This combined theory predicts that empty space isn’t empty at all – it’s a seething and bubbling cauldron of matter and antimatter particles springing into existence before disappearing back into nothingness. Scientists call this complicated state of affairs “quantum foam.” In this video, Fermilab’s Dr. Don Lincoln discusses this mind-bending idea and sketches some of the experiments that have convinced scientists that this crazy prediction is actually true.

  7. Relaxation in quantum glasses

    NASA Astrophysics Data System (ADS)

    Ancona Torres, Carlos E.

    The Ising model in transverse field provides the simplest description of a quantum glass. I study two systems that are realizations of the Ising model in transverse field, LiHoxY1-- xF4 and Rb1-- x(NH4)xH2PO 4. In the spin glass LiHoxY1-- xF4, applying a magnetic field Ht transverse to the Ising direction introduces tunneling between the bare Ising eigenstates. In addition, the coupling between the transverse dipolar interaction and the transverse field introduces entanglement or tunable random fields depending on the concentration. By comparing the classical and quantum transitions in LiHo0.198Y0.802F4 and LiHo 0.167Y0.833F4, I characterize the crossover from random field dominated behavior in the 19.8% sample to entanglement dominated behavior in the 16.7% sample. The quantum transition in the 19.8% sample is dominated by the limit on its correlation length caused by the random fields, while the dominant effect in the 16.7% sample is the enhanced tunneling rate introduced by entanglement. The proton glass Rb1--x(NH 4)xH2PO4 relaxes through tunneling of protons in the hydrogen bonds of the crystal, yielding an effective Ising model in transverse field. Since this field cannot be tuned directly, I combine bulk dielectric susceptibility measurements with neutron Compton scattering measurements of the local tunneling potential in two different concentrations, x = 35% and 72%. I find that tunneling drives the fastest relaxation processes at temperatures as high as 20 K and explicitly calculate the tunneling rate from the tunneling potential of the hydrogen bond. Moreover, the structural mechanism for the glassy relaxation allows a real-space picture of the relaxation dynamics to be correlated to the free energy description of aging. I find that the glassy relaxation is driven by the sequential diffusion of defects called Takagi configurations with a classical to quantum crossover in the relaxation at 3 K. I relate the relaxation rate to the quantum action of tunneling

  8. Quantum Computing

    DTIC Science & Technology

    1998-04-01

    information representation and processing technology, although faster than the wheels and gears of the Charles Babbage computation machine, is still in...the same computational complexity class as the Babbage machine, with bits of information represented by entities which obey classical (non-quantum...nuclear double resonances Charles M Bowden and Jonathan P. Dowling Weapons Sciences Directorate, AMSMI-RD-WS-ST Missile Research, Development, and

  9. Quantum Mechanics

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    A development of quantum theory that was initiated in the 1920s by Werner Heisenberg (1901-76) and Erwin Schrödinger (1887-1961). The theory drew on a proposal made in 1925 Prince Louis de Broglie (1892-1987), that particles have wavelike properties (the wave-particle duality) and that an electron, for example, could in some respects be regarded as a wave with a wavelength that depended on its mo...

  10. Incorporating phenology into yield models

    NASA Astrophysics Data System (ADS)

    Gray, J. M.; Friedl, M. A.

    2015-12-01

    Because the yields of many crops are sensitive to meteorological forcing during specific growth stages, phenological information has potential utility in yield mapping and forecasting exercises. However, most attempts to explain the spatiotemporal variability in crop yields with weather data have relied on growth stage definitions that do not change from year-to-year, even though planting, maturity, and harvesting dates show significant interannual variability. We tested the hypothesis that quantifying temperature exposures over dynamically determined growth stages would better explain observed spatiotemporal variability in crop yields than statically defined time periods. Specifically, we used National Agricultural and Statistics Service (NASS) crop progress data to identify the timing of the start of the maize reproductive growth stage ("silking"), and examined the correlation between county-scale yield anomalies and temperature exposures during either the annual or long-term average silking period. Consistent with our hypothesis and physical understanding, yield anomalies were more correlated with temperature exposures during the actual, rather than the long-term average, silking period. Nevertheless, temperature exposures alone explained a relatively low proportion of the yield variability, indicating that other factors and/or time periods are also important. We next investigated the potential of using remotely sensed land surface phenology instead of NASS progress data to retrieve crop growth stages, but encountered challenges related to crop type mapping and subpixel crop heterogeneity. Here, we discuss the potential of overcoming these challenges and the general utility of remotely sensed land surface phenology in crop yield mapping.

  11. Brazil soybean yield covariance model

    NASA Technical Reports Server (NTRS)

    Callis, S. L.; Sakamoto, C.

    1984-01-01

    A model based on multiple regression was developed to estimate soybean yields for the seven soybean-growing states of Brazil. The meteorological data of these seven states were pooled and the years 1975 to 1980 were used to model since there was no technological trend in the yields during these years. Predictor variables were derived from monthly total precipitation and monthly average temperature.

  12. Rx for low cash yields.

    PubMed

    Tobe, Chris

    2003-10-01

    Certain strategies can offer not-for-profit hospitals potentially greater investment yields while maintaining stability and principal safety. Treasury inflation-indexed securities can offer good returns, low volatility, and inflation protection. "Enhanced cash" strategies offer liquidity and help to preserve capital. Stable value "wrappers" allow hospitals to pursue higher-yielding fixed-income securities without an increase in volatility.

  13. Efficient Quantum Information Processing via Quantum Compressions

    NASA Astrophysics Data System (ADS)

    Deng, Y.; Luo, M. X.; Ma, S. Y.

    2016-01-01

    Our purpose is to improve the quantum transmission efficiency and reduce the resource cost by quantum compressions. The lossless quantum compression is accomplished using invertible quantum transformations and applied to the quantum teleportation and the simultaneous transmission over quantum butterfly networks. New schemes can greatly reduce the entanglement cost, and partially solve transmission conflictions over common links. Moreover, the local compression scheme is useful for approximate entanglement creations from pre-shared entanglements. This special task has not been addressed because of the quantum no-cloning theorem. Our scheme depends on the local quantum compression and the bipartite entanglement transfer. Simulations show the success probability is greatly dependent of the minimal entanglement coefficient. These results may be useful in general quantum network communication.

  14. Peptide-Decorated Tunable-Fluorescence Graphene Quantum Dots.

    PubMed

    Sapkota, Bedanga; Benabbas, Abdelkrim; Lin, Hao-Yu Greg; Liang, Wentao; Champion, Paul; Wanunu, Meni

    2017-03-22

    We report here the synthesis of graphene quantum dots with tunable size, surface chemistry, and fluorescence properties. In the size regime 15-35 nm, these quantum dots maintain strong visible light fluorescence (mean quantum yield of 0.64) and a high two-photon absorption (TPA) cross section (6500 Göppert-Mayer units). Furthermore, through noncovalent tailoring of the chemistry of these quantum dots, we obtain water-stable quantum dots. For example, quantum dots with lysine groups bind strongly to DNA in solution and inhibit polymerase-based DNA strand synthesis. Finally, by virtue of their mesoscopic size, the quantum dots exhibit good cell permeability into living epithelial cells, but they do not enter the cell nucleus.

  15. Role of the Active Site Guanine in the glmS Ribozyme Self-Cleavage Mechanism: Quantum Mechanical/Molecular Mechanical Free Energy Simulations

    PubMed Central

    2015-01-01

    The glmS ribozyme catalyzes a self-cleavage reaction at the phosphodiester bond between residues A-1 and G1. This reaction is thought to occur by an acid–base mechanism involving the glucosamine-6-phosphate cofactor and G40 residue. Herein quantum mechanical/molecular mechanical free energy simulations and pKa calculations, as well as experimental measurements of the rate constant for self-cleavage, are utilized to elucidate the mechanism, particularly the role of G40. Our calculations suggest that an external base deprotonates either G40(N1) or possibly A-1(O2′), which would be followed by proton transfer from G40(N1) to A-1(O2′). After this initial deprotonation, A-1(O2′) starts attacking the phosphate as a hydroxyl group, which is hydrogen-bonded to deprotonated G40, concurrent with G40(N1) moving closer to the hydroxyl group and directing the in-line attack. Proton transfer from A-1(O2′) to G40 is concomitant with attack of the scissile phosphate, followed by the remainder of the cleavage reaction. A mechanism in which an external base does not participate, but rather the proton transfers from A-1(O2′) to a nonbridging oxygen during nucleophilic attack, was also considered but deemed to be less likely due to its higher effective free energy barrier. The calculated rate constant for the favored mechanism is in agreement with the experimental rate constant measured at biological Mg2+ ion concentration. According to these calculations, catalysis is optimal when G40 has an elevated pKa rather than a pKa shifted toward neutrality, although a balance among the pKa’s of A-1, G40, and the nonbridging oxygen is essential. These results have general implications, as the hammerhead, hairpin, and twister ribozymes have guanines at a similar position as G40. PMID:25526516

  16. Quantum Locality?

    SciTech Connect

    Stapp, Henry

    2011-11-10

    Robert Griffiths has recently addressed, within the framework of a ‘consistent quantum theory’ (CQT) that he has developed, the issue of whether, as is often claimed, quantum mechanics entails a need for faster-than-light transfers of information over long distances. He argues, on the basis of his examination of certain arguments that claim to demonstrate the existence of such nonlocal influences, that such influences do not exist. However, his examination was restricted mainly to hidden-variable-based arguments that include in their premises some essentially classical-physics-type assumptions that are fundamentally incompatible with the precepts of quantum physics. One cannot logically prove properties of a system by attributing to the system properties alien to that system. Hence Griffiths’ rejection of hidden-variable-based proofs is logically warranted. Griffiths mentions the existence of a certain alternative proof that does not involve hidden variables, and that uses only macroscopically described observable properties. He notes that he had examined in his book proofs of this general kind, and concluded that they provide no evidence for nonlocal influences. But he did not examine the particular proof that he cites. An examination of that particular proof by the method specified by his ‘consistent quantum theory’ shows that the cited proof is valid within that restrictive framework. This necessary existence, within the ‘consistent’ framework, of long range essentially instantaneous influences refutes the claim made by Griffiths that his ‘consistent’ framework is superior to the orthodox quantum theory of von Neumann because it does not entail instantaneous influences. An added section responds to Griffiths’ reply, which cites a litany of ambiguities that seem to restrict, devastatingly, the scope of his CQT formalism, apparently to buttress his claim that my use of that formalism to validate the nonlocality theorem is flawed. But the

  17. Trotter-based simulation of quantum-classical dynamics.

    PubMed

    Kernan, Dónal Mac; Ciccotti, Giovanni; Kapral, Raymond

    2008-01-17

    Quantum rate processes in condensed phase systems are often computed by combining quantum and classical descriptions of the dynamics. An algorithm for simulating the quantum-classical Liouville equation, which describes the dynamics of a quantum subsystem coupled to a classical bath, is presented in this paper. The algorithm is based on a Trotter decomposition of the quantum-classical propagator, in conjunction with Monte Carlo sampling of quantum transitions, to yield a surface-hopping representation of the dynamics. An expression for the nonadiabatic propagator that is responsible for quantum transitions and associated bath momentum changes is derived in a form that is convenient for Monte Carlo sampling and exactly conserves the total energy of the system in individual trajectories. The expectation values of operators or quantum correlation functions can be evaluated by initial sampling of quantum states and use of quantum-classical Liouville dynamics for the time evolution. The algorithm is tested by calculations on the spin-boson model, for which exact quantum results are available, and is shown to reproduce the exact results for stronger nonadiabatic coupling and much longer times using fewer trajectories than other schemes for simulating quantum-classical Liouville dynamics.

  18. Full-colour quantum dot displays fabricated by transfer printing

    NASA Astrophysics Data System (ADS)

    Kim, Tae-Ho; Cho, Kyung-Sang; Lee, Eun Kyung; Lee, Sang Jin; Chae, Jungseok; Kim, Jung Woo; Kim, Do Hwan; Kwon, Jang-Yeon; Amaratunga, Gehan; Lee, Sang Yoon; Choi, Byoung Lyong; Kuk, Young; Kim, Jong Min; Kim, Kinam

    2011-03-01

    Light-emitting diodes with quantum dot luminophores show promise in the development of next-generation displays, because quantum dot luminophores demonstrate high quantum yields, extremely narrow emission, spectral tunability and high stability, among other beneficial characteristics. However, the inability to achieve size-selective quantum dot patterning by conventional methods hinders the realization of full-colour quantum dot displays. Here, we report the first demonstration of a large-area, full-colour quantum dot display, including in flexible form, using optimized quantum dot films, and with control of the nano-interfaces and carrier behaviour. Printed quantum dot films exhibit excellent morphology, well-ordered quantum dot structure and clearly defined interfaces. These characteristics are achieved through the solvent-free transfer of quantum dot films and the compact structure of the quantum dot networks. Significant enhancements in charge transport/balance in the quantum dot layer improve electroluminescent performance. A method using plasmonic coupling is also suggested to further enhance luminous efficiency. The results suggest routes towards creating large-scale optoelectronic devices in displays, solid-state lighting and photovoltaics.

  19. Decoding the quantum horizon

    NASA Astrophysics Data System (ADS)

    Hayden, Patrick; Myers, Robert

    2017-01-01

    Patrick Hayden and Robert Myers describe how the study of “qubits”, quantum bits of information, may hold the key to uniting quantum theory and general relativity into a unified theory of quantum gravity

  20. Quantum probability and quantum decision-making.

    PubMed

    Yukalov, V I; Sornette, D

    2016-01-13

    A rigorous general definition of quantum probability is given, which is valid not only for elementary events but also for composite events, for operationally testable measurements as well as for inconclusive measurements, and also for non-commuting observables in addition to commutative observables. Our proposed definition of quantum probability makes it possible to describe quantum measurements and quantum decision-making on the same common mathematical footing. Conditions are formulated for the case when quantum decision theory reduces to its classical counterpart and for the situation where the use of quantum decision theory is necessary.

  1. Quantum maximum-entropy principle for closed quantum hydrodynamic transport within a Wigner function formalism

    SciTech Connect

    Trovato, M.; Reggiani, L.

    2011-12-15

    By introducing a quantum entropy functional of the reduced density matrix, the principle of quantum maximum entropy is asserted as fundamental principle of quantum statistical mechanics. Accordingly, we develop a comprehensive theoretical formalism to construct rigorously a closed quantum hydrodynamic transport within a Wigner function approach. The theoretical formalism is formulated in both thermodynamic equilibrium and nonequilibrium conditions, and the quantum contributions are obtained by only assuming that the Lagrange multipliers can be expanded in powers of ({h_bar}/2{pi}){sup 2}. In particular, by using an arbitrary number of moments, we prove that (1) on a macroscopic scale all nonlocal effects, compatible with the uncertainty principle, are imputable to high-order spatial derivatives, both of the numerical density n and of the effective temperature T; (2) the results available from the literature in the framework of both a quantum Boltzmann gas and a degenerate quantum Fermi gas are recovered as a particular case; (3) the statistics for the quantum Fermi and Bose gases at different levels of degeneracy are explicitly incorporated; (4) a set of relevant applications admitting exact analytical equations are explicitly given and discussed; (5) the quantum maximum entropy principle keeps full validity in the classical limit, when ({h_bar}/2{pi}){yields}0.

  2. Delivering quantum dots to cells: bioconjugated quantum dots for targeted and nonspecific extracellular and intracellular imaging.

    PubMed

    Biju, Vasudevanpillai; Itoh, Tamitake; Ishikawa, Mitsuru

    2010-08-01

    Bioconjugated nanomaterials offer endless opportunities to advance both nanobiotechnology and biomedical technology. In this regard, semiconductor nanoparticles, also called quantum dots, are of particular interest for multimodal, multifunctional and multiplexed imaging of biomolecules, cells, tissues and animals. The unique optical properties, such as size-dependent tunable absorption and emission in the visible and NIR regions, narrow emission and broad absorption bands, high photoluminescence quantum yields, large one- and multi-photon absorption cross-sections, and exceptional photostability are the advantages of quantum dots. Multimodal imaging probes are developed by interfacing the unique optical properties of quantum dots with magnetic or radioactive materials. Besides, crystalline structure of quantum dots adds scope for high-contrast X-ray and TEM imaging. Yet another unique feature of a quantum dot is its spacious and flexible surface which is promising to integrate multiple ligands and antibodies and construct multi-functional probes for bioimaging. In this critical review, we will summarize recent advancements in the preparation of biocompatible quantum dots, bioconjugation of quantum dots, and applications of quantum dots and their bioconjugates for targeted and nonspecific imaging of extracellular and intracellular proteins, organelles and functions (181 references).

  3. Quantum Error Correction

    DTIC Science & Technology

    2005-07-06

    many families of quantum MDS codes. 15. SUBJECT TERMS Quantum Information Science , Quantum Algorithms, Quantum Cryptography 16. SECURITY...separable codes over alphabets of arbitrary size,” a preprint, 2005; to be presented at ERATO conference on quantum information science , Tokyo, Japan...β, γ〉〉 = 1. Due to the Chinese remainder theorem, we have one more equivalent ∗ERATO Conference on Quantum Information Science , 2005 †jkim

  4. Quantum algorithms: an overview

    NASA Astrophysics Data System (ADS)

    Montanaro, Ashley

    2016-01-01

    Quantum computers are designed to outperform standard computers by running quantum algorithms. Areas in which quantum algorithms can be applied include cryptography, search and optimisation, simulation of quantum systems and solving large systems of linear equations. Here we briefly survey some known quantum algorithms, with an emphasis on a broad overview of their applications rather than their technical details. We include a discussion of recent developments and near-term applications of quantum algorithms.

  5. Relativistic quantum cryptography

    SciTech Connect

    Molotkov, S. N.

    2011-03-15

    A new protocol of quantum key distribution is proposed to transmit keys through free space. Along with quantum-mechanical restrictions on the discernibility of nonorthogonal quantum states, the protocol uses additional restrictions imposed by special relativity theory. Unlike all existing quantum key distribution protocols, this protocol ensures key secrecy for a not strictly one-photon source of quantum states and an arbitrary length of a quantum communication channel.

  6. Decomposing global crop yield variability

    NASA Astrophysics Data System (ADS)

    Ben-Ari, Tamara; Makowski, David

    2014-11-01

    Recent food crises have highlighted the need to better understand the between-year variability of agricultural production. Although increasing future production seems necessary, the globalization of commodity markets suggests that the food system would also benefit from enhanced supplies stability through a reduction in the year-to-year variability. Here, we develop an analytical expression decomposing global crop yield interannual variability into three informative components that quantify how evenly are croplands distributed in the world, the proportion of cultivated areas allocated to regions of above or below average variability and the covariation between yields in distinct world regions. This decomposition is used to identify drivers of interannual yield variations for four major crops (i.e., maize, rice, soybean and wheat) over the period 1961-2012. We show that maize production is fairly spread but marked by one prominent region with high levels of crop yield interannual variability (which encompasses the North American corn belt in the USA, and Canada). In contrast, global rice yields have a small variability because, although spatially concentrated, much of the production is located in regions of below-average variability (i.e., South, Eastern and South Eastern Asia). Because of these contrasted land use allocations, an even cultivated land distribution across regions would reduce global maize yield variance, but increase the variance of global yield rice. Intermediate results are obtained for soybean and wheat for which croplands are mainly located in regions with close-to-average variability. At the scale of large world regions, we find that covariances of regional yields have a negligible contribution to global yield variance. The proposed decomposition could be applied at any spatial and time scales, including the yearly time step. By addressing global crop production stability (or lack thereof) our results contribute to the understanding of a key

  7. Grapevine canopy reflectance and yield

    NASA Technical Reports Server (NTRS)

    Minden, K. A.; Philipson, W. R.

    1982-01-01

    Field spectroradiometric and airborne multispectral scanner data were applied in a study of Concord grapevines. Spectroradiometric measurements of 18 experimental vines were collected on three dates during one growing season. Spectral reflectance, determined at 30 intervals from 0.4 to 1.1 microns, was correlated with vine yield, pruning weight, clusters/vine, and nitrogen input. One date of airborne multispectral scanner data (11 channels) was collected over commercial vineyards, and the average radiance values for eight vineyard sections were correlated with the corresponding average yields. Although some correlations were significant, they were inadequate for developing a reliable yield prediction model.

  8. Quantum Correlations Evolution Asymmetry in Quantum Channels

    NASA Astrophysics Data System (ADS)

    Li, Meng; Huang, Yun-Feng; Guo, Guang-Can

    2017-03-01

    It was demonstrated that the entanglement evolution of a specially designed quantum state in the bistochastic channel is asymmetric. In this work, we generalize the study of the quantum correlations, including entanglement and quantum discord, evolution asymmetry to various quantum channels. We found that the asymmetry of entanglement and quantum discord only occurs in some special quantum channels, and the behavior of the entanglement evolution may be quite different from the behavior of the quantum discord evolution. To quantum entanglement, in some channels it decreases monotonously with the increase of the quantum channel intensity. In some other channels, when we increase the intensity of the quantum channel, it decreases at first, then keeps zero for some time, and then rises up. To quantum discord, the evolution becomes more complex and you may find that it evolutes unsmoothly at some points. These results illustrate the strong dependence of the quantum correlations evolution on the property of the quantum channels. Supported by the National Natural Science Foundation of China under Grant Nos. 61327901, 61490711, 61225025, 11474268, and the Fundamental Research Funds for the Central Universities under Grant No. WK2470000018

  9. Yield surfaces for anisotropic plates

    NASA Astrophysics Data System (ADS)

    Walker, J. D.; Thacker, B. H.

    2000-04-01

    Aerospace systems are incorporating composite materials into their structures. The composite materials are often anisotropic in mechanical response due to their geometric layout. For many years, the failure surfaces of anisotropic materials were thought to be characterizable by a quadratic function in the stress, referred to as a Tsai-Wu yield surface, or, in a more restrictive form, a Tsai-Hill yield surface. Such a representation does not work for materials that are strong in two directions and weak in one direction, which is the case of most interest since it represents fiber/epoxy composite plates. This paper demonstrates the impossibility of modeling the failure surface with either the Tsai-Wu or Tsai-Hill failure surfaces. A yield surface is presented based on the lemniscate, which is quartic in the stress. This new yield surface addresses the case of strong in two directions and weak in one.

  10. Quantum Universe

    NASA Astrophysics Data System (ADS)

    Mukhanov, V. F.

    2016-10-01

    In March 2013, following an accurate processing of available measurement data, the Planck Scientific Collaboration published the highest-resolution photograph ever of the early Universe when it was only a few hundred thousand years old. The photograph showed galactic seeds in sufficient detail to test some nontrivial theoretical predictions made more than thirty years ago. Most amazing was that all predictions were confirmed to be remarkably accurate. With no exaggeration, we may consider it established experimentally that quantum physics, which is normally assumed to be relevant on the atomic and subatomic scale, also works on the scale of the entire Universe, determining its structure with all its galaxies, stars, and planets.

  11. Yield Surfaces for Anisotropic Plates

    NASA Astrophysics Data System (ADS)

    Walker, J. D.; Thacker, B. H.

    1999-06-01

    Modern aerospace systems are incorporating composite materials into their structures. Often, the composite materials are anisotropic in their mechanical response due to the geometric layout of fibers. For many years, the failure surfaces of anisotropic materials were thought to be characterizable by a quadratic function in the stress, often referred to as a Tsai-Wu yield surface, or, in a more restrictive form, a Tsai-Hill yield surface. Such a representation does not work for materials that are strong in two directions and weak in one direction, which, unfortunately, is the case of most interest since it represents most composite plates. This paper demonstrates the impossibility of modeling the failure surface with both the Tsai-Wu and Tsai-Hill failure surfaces. We then present a yield surface based on the lemniscate, which is quartic in the stress. This new yield surface addresses the case of strong in two directions and weak in one. Calculations with a fragment impacting a composite plate modeled with the new yield surface are presented. Modifications of the yield surface are presented to allow, in a limited way, materials that are both anisotropic and have differing strengths in tension and compression.

  12. Fission yield measurements at IGISOL

    NASA Astrophysics Data System (ADS)

    Lantz, M.; Al-Adili, A.; Gorelov, D.; Jokinen, A.; Kolhinen, V. S.; Mattera, A.; Moore, I.; Penttilä, H.; Pomp, S.; Prokofiev, A. V.; Rakopoulos, V.; Rinta-Antila, S.; Simutkin, V.; Solders, A.

    2016-06-01

    The fission product yields are an important characteristic of the fission process. In fundamental physics, knowledge of the yield distributions is needed to better understand the fission process. For nuclear energy applications good knowledge of neutroninduced fission-product yields is important for the safe and efficient operation of nuclear power plants. With the Ion Guide Isotope Separator On-Line (IGISOL) technique, products of nuclear reactions are stopped in a buffer gas and then extracted and separated by mass. Thanks to the high resolving power of the JYFLTRAP Penning trap, at University of Jyväskylä, fission products can be isobarically separated, making it possible to measure relative independent fission yields. In some cases it is even possible to resolve isomeric states from the ground state, permitting measurements of isomeric yield ratios. So far the reactions U(p,f) and Th(p,f) have been studied using the IGISOL-JYFLTRAP facility. Recently, a neutron converter target has been developed utilizing the Be(p,xn) reaction. We here present the IGISOL-technique for fission yield measurements and some of the results from the measurements on proton induced fission. We also present the development of the neutron converter target, the characterization of the neutron field and the first tests with neutron-induced fission.

  13. Quantum teleportation of optical quantum gates.

    PubMed

    Bartlett, Stephen D; Munro, William J

    2003-03-21

    We show that a universal set of gates for quantum computation with optics can be quantum teleported through the use of EPR entangled states, homodyne detection, and linear optics and squeezing operations conditioned on measurement outcomes. This scheme may be used for fault-tolerant quantum computation in any optical scheme (qubit or continuous-variable). The teleportation of nondeterministic nonlinear gates employed in linear optics quantum computation is discussed.

  14. Quantum Hamilton mechanics: Hamilton equations of quantum motion, origin of quantum operators, and proof of quantization axiom

    SciTech Connect

    Yang, C.-D. . E-mail: cdyang@mail.ncku.edu.tw

    2006-12-15

    This paper gives a thorough investigation on formulating and solving quantum problems by extended analytical mechanics that extends canonical variables to complex domain. With this complex extension, we show that quantum mechanics becomes a part of analytical mechanics and hence can be treated integrally with classical mechanics. Complex canonical variables are governed by Hamilton equations of motion, which can be derived naturally from Schroedinger equation. Using complex canonical variables, a formal proof of the quantization axiom p {sup {yields}} p = -ih{nabla}, which is the kernel in constructing quantum-mechanical systems, becomes a one-line corollary of Hamilton mechanics. The derivation of quantum operators from Hamilton mechanics is coordinate independent and thus allows us to derive quantum operators directly under any coordinate system without transforming back to Cartesian coordinates. Besides deriving quantum operators, we also show that the various prominent quantum effects, such as quantization, tunneling, atomic shell structure, Aharonov-Bohm effect, and spin, all have the root in Hamilton mechanics and can be described entirely by Hamilton equations of motion.

  15. Acid soil infertility effects on peanut yields and yield components

    SciTech Connect

    Blamey, F.P.C.

    1983-01-01

    The interpretation of soil amelioration experiments with peanuts is made difficult by the unpredictibility of the crop and by the many factors altered when ameliorating acid soils. The present study was conducted to investigate the effects of lime and gypsum applications on peanut kernel yield via the three first order yield components, pods per ha, kernels per pod, and kernel mass. On an acid medium sandy loam soil (typic Plinthustult), liming resulted in a highly significant kernel yield increase of 117% whereas gypsum applications were of no significant benefit. As indicated by path coefficient analysis, an increase in the number of pods per ha was markedly more important in increasing yield than an increase in either the number of kernels per pod or kernel mass. Furthermore, exch. Al was found to be particularly detrimental to pod number. It was postulated that poor peanut yields resulting from acid soil infertility were mainly due to the depressive effect of exch. Al on pod number. Exch. Ca appeared to play a secondary role by ameliorating the adverse effects of exch. Al.

  16. Sensitive chemical compass assisted by quantum criticality

    NASA Astrophysics Data System (ADS)

    Cai, C. Y.; Ai, Qing; Quan, H. T.; Sun, C. P.

    2012-02-01

    A radical-pair-based chemical reaction might be used by birds for navigation via the geomagnetic direction. The inherent physical mechanism is that the quantum coherent transition from a singlet state to triplet states of the radical pair could respond to a weak magnetic field and be sensitive to the direction of such a field; this then results in different photopigments to be sensed by the avian eyes. Here, we propose a quantum bionic setup, inspired by the avian compass, as an ultrasensitive probe of a weak magnetic field based on the quantum phase transition of the environments of the two electrons in the radical pair. We prove that the yield of the chemical products via recombination from the singlet state is determined by the Loschmidt echo of the environments with interacting nuclear spins. Thus quantum criticality of environments could enhance the sensitivity of detection of weak magnetic fields.

  17. A quantum approach to homomorphic encryption

    PubMed Central

    Tan, Si-Hui; Kettlewell, Joshua A.; Ouyang, Yingkai; Chen, Lin; Fitzsimons, Joseph F.

    2016-01-01

    Encryption schemes often derive their power from the properties of the underlying algebra on the symbols used. Inspired by group theoretic tools, we use the centralizer of a subgroup of operations to present a private-key quantum homomorphic encryption scheme that enables a broad class of quantum computation on encrypted data. The quantum data is encoded on bosons of distinct species in distinct spatial modes, and the quantum computations are manipulations of these bosons in a manner independent of their species. A particular instance of our encoding hides up to a constant fraction of the information encrypted. This fraction can be made arbitrarily close to unity with overhead scaling only polynomially in the message length. This highlights the potential of our protocol to hide a non-trivial amount of information, and is suggestive of a large class of encodings that might yield better security. PMID:27658349

  18. A quantum approach to homomorphic encryption

    NASA Astrophysics Data System (ADS)

    Tan, Si-Hui; Kettlewell, Joshua A.; Ouyang, Yingkai; Chen, Lin; Fitzsimons, Joseph F.

    2016-09-01

    Encryption schemes often derive their power from the properties of the underlying algebra on the symbols used. Inspired by group theoretic tools, we use the centralizer of a subgroup of operations to present a private-key quantum homomorphic encryption scheme that enables a broad class of quantum computation on encrypted data. The quantum data is encoded on bosons of distinct species in distinct spatial modes, and the quantum computations are manipulations of these bosons in a manner independent of their species. A particular instance of our encoding hides up to a constant fraction of the information encrypted. This fraction can be made arbitrarily close to unity with overhead scaling only polynomially in the message length. This highlights the potential of our protocol to hide a non-trivial amount of information, and is suggestive of a large class of encodings that might yield better security.

  19. A quantum approach to homomorphic encryption.

    PubMed

    Tan, Si-Hui; Kettlewell, Joshua A; Ouyang, Yingkai; Chen, Lin; Fitzsimons, Joseph F

    2016-09-23

    Encryption schemes often derive their power from the properties of the underlying algebra on the symbols used. Inspired by group theoretic tools, we use the centralizer of a subgroup of operations to present a private-key quantum homomorphic encryption scheme that enables a broad class of quantum computation on encrypted data. The quantum data is encoded on bosons of distinct species in distinct spatial modes, and the quantum computations are manipulations of these bosons in a manner independent of their species. A particular instance of our encoding hides up to a constant fraction of the information encrypted. This fraction can be made arbitrarily close to unity with overhead scaling only polynomially in the message length. This highlights the potential of our protocol to hide a non-trivial amount of information, and is suggestive of a large class of encodings that might yield better security.

  20. Hot Hole Transfer Increasing Polaron Yields in Hybrid Conjugated Polymer/PbS Blends.

    PubMed

    Strein, Elisabeth; deQuilettes, Dane W; Hsieh, Stephen T; Colbert, Adam E; Ginger, David S

    2014-01-02

    We use quasi-steady-state photoinduced absorption (PIA) to study charge generation in blends of poly(3-hexylthiophene-2,5-diyl) (P3HT) with PbS nanocrystal quantum dots as a function of excitation energy. We find that, per photon absorbed, the yield of photogenerated holes present on the conjugated polymer increases with pump energy, even at wavelengths where only the quantum dots absorb. We interpret this result as direct evidence for transfer of hot holes in these conjugated polymer/quantum dot blends. These results help understand the operation of hybrid organic/inorganic photovoltaics.

  1. Quantum Steganography and Quantum Error-Correction

    ERIC Educational Resources Information Center

    Shaw, Bilal A.

    2010-01-01

    Quantum error-correcting codes have been the cornerstone of research in quantum information science (QIS) for more than a decade. Without their conception, quantum computers would be a footnote in the history of science. When researchers embraced the idea that we live in a world where the effects of a noisy environment cannot completely be…

  2. Quantum Hall effect in quantum electrodynamics

    SciTech Connect

    Penin, Alexander A.

    2009-03-15

    We consider the quantum Hall effect in quantum electrodynamics and find a deviation from the quantum-mechanical prediction for the Hall conductivity due to radiative antiscreening of electric charge in an external magnetic field. A weak dependence of the universal von Klitzing constant on the magnetic field strength, which can possibly be observed in a dedicated experiment, is predicted.

  3. Production yield of rare-earth ions implanted into an optical crystal

    SciTech Connect

    Kornher, Thomas Xia, Kangwei; Kolesov, Roman; Reuter, Rolf; Villa, Bruno; Wrachtrup, Jörg; Kukharchyk, Nadezhda; Wieck, Andreas D.; Siyushev, Petr; Stöhr, Rainer; Schreck, Matthias; Becker, Hans-Werner

    2016-02-01

    Rare-earth (RE) ions doped into desired locations of optical crystals might enable a range of novel integrated photonic devices for quantum applications. With this aim, we have investigated the production yield of cerium and praseodymium by means of ion implantation. As a measure, the collected fluorescence intensity from both implanted samples and single centers was used. With a tailored annealing procedure for cerium, a yield up to 53% was estimated. Praseodymium yield amounts up to 91%. Such high implantation yield indicates a feasibility of creation of nanopatterned rare-earth doping and suggests strong potential of RE species for on-chip photonic devices.

  4. Quantum Error Correction

    NASA Astrophysics Data System (ADS)

    Lidar, Daniel A.; Brun, Todd A.

    2013-09-01

    Prologue; Preface; Part I. Background: 1. Introduction to decoherence and noise in open quantum systems Daniel Lidar and Todd Brun; 2. Introduction to quantum error correction Dave Bacon; 3. Introduction to decoherence-free subspaces and noiseless subsystems Daniel Lidar; 4. Introduction to quantum dynamical decoupling Lorenza Viola; 5. Introduction to quantum fault tolerance Panos Aliferis; Part II. Generalized Approaches to Quantum Error Correction: 6. Operator quantum error correction David Kribs and David Poulin; 7. Entanglement-assisted quantum error-correcting codes Todd Brun and Min-Hsiu Hsieh; 8. Continuous-time quantum error correction Ognyan Oreshkov; Part III. Advanced Quantum Codes: 9. Quantum convolutional codes Mark Wilde; 10. Non-additive quantum codes Markus Grassl and Martin Rötteler; 11. Iterative quantum coding systems David Poulin; 12. Algebraic quantum coding theory Andreas Klappenecker; 13. Optimization-based quantum error correction Andrew Fletcher; Part IV. Advanced Dynamical Decoupling: 14. High order dynamical decoupling Zhen-Yu Wang and Ren-Bao Liu; 15. Combinatorial approaches to dynamical decoupling Martin Rötteler and Pawel Wocjan; Part V. Alternative Quantum Computation Approaches: 16. Holonomic quantum computation Paolo Zanardi; 17. Fault tolerance for holonomic quantum computation Ognyan Oreshkov, Todd Brun and Daniel Lidar; 18. Fault tolerant measurement-based quantum computing Debbie Leung; Part VI. Topological Methods: 19. Topological codes Héctor Bombín; 20. Fault tolerant topological cluster state quantum computing Austin Fowler and Kovid Goyal; Part VII. Applications and Implementations: 21. Experimental quantum error correction Dave Bacon; 22. Experimental dynamical decoupling Lorenza Viola; 23. Architectures Jacob Taylor; 24. Error correction in quantum communication Mark Wilde; Part VIII. Critical Evaluation of Fault Tolerance: 25. Hamiltonian methods in QEC and fault tolerance Eduardo Novais, Eduardo Mucciolo and

  5. Quantum Walk Schemes for Universal Quantum Computation

    NASA Astrophysics Data System (ADS)

    Underwood, Michael S.

    Random walks are a powerful tool for the efficient implementation of algorithms in classical computation. Their quantum-mechanical analogues, called quantum walks, hold similar promise. Quantum walks provide a model of quantum computation that has recently been shown to be equivalent in power to the standard circuit model. As in the classical case, quantum walks take place on graphs and can undergo discrete or continuous evolution, though quantum evolution is unitary and therefore deterministic until a measurement is made. This thesis considers the usefulness of continuous-time quantum walks to quantum computation from the perspectives of both their fundamental power under various formulations, and their applicability in practical experiments. In one extant scheme, logical gates are effected by scattering processes. The results of an exhaustive search for single-qubit operations in this model are presented. It is shown that the number of distinct operations increases exponentially with the number of vertices in the scattering graph. A catalogue of all graphs on up to nine vertices that implement single-qubit unitaries at a specific set of momenta is included in an appendix. I develop a novel scheme for universal quantum computation called the discontinuous quantum walk, in which a continuous-time quantum walker takes discrete steps of evolution via perfect quantum state transfer through small 'widget' graphs. The discontinuous quantum-walk scheme requires an exponentially sized graph, as do prior discrete and continuous schemes. To eliminate the inefficient vertex resource requirement, a computation scheme based on multiple discontinuous walkers is presented. In this model, n interacting walkers inhabiting a graph with 2n vertices can implement an arbitrary quantum computation on an input of length n, an exponential savings over previous universal quantum walk schemes. This is the first quantum walk scheme that allows for the application of quantum error correction

  6. Optimal quantum cloning via spin networks

    SciTech Connect

    Chen Qing; Cheng Jianhua; Wang Kelin; Du Jiangfeng

    2006-09-15

    In this paper we demonstrate that optimal 1{yields}M phase-covariant cloning quantum cloning is available via free dynamical evolution of spin networks. By properly designing the network and the couplings between spins, we show that optimal 1{yields}M phase-covariant cloning can be achieved if the initial state is prepared as a specific symmetric state. Especially, when M is an odd number, the optimal phase-covariant cloning can be achieved without ancillas. Moreover, we demonstrate that the same framework is capable for optimal 1{yields}2 universal cloning.

  7. Efficient quantum computing using coherent photon conversion.

    PubMed

    Langford, N K; Ramelow, S; Prevedel, R; Munro, W J; Milburn, G J; Zeilinger, A

    2011-10-12

    Single photons are excellent quantum information carriers: they were used in the earliest demonstrations of entanglement and in the production of the highest-quality entanglement reported so far. However, current schemes for preparing, processing and measuring them are inefficient. For example, down-conversion provides heralded, but randomly timed, single photons, and linear optics gates are inherently probabilistic. Here we introduce a deterministic process--coherent photon conversion (CPC)--that provides a new way to generate and process complex, multiquanta states for photonic quantum information applications. The technique uses classically pumped nonlinearities to induce coherent oscillations between orthogonal states of multiple quantum excitations. One example of CPC, based on a pumped four-wave-mixing interaction, is shown to yield a single, versatile process that provides a full set of photonic quantum processing tools. This set satisfies the DiVincenzo criteria for a scalable quantum computing architecture, including deterministic multiqubit entanglement gates (based on a novel form of photon-photon interaction), high-quality heralded single- and multiphoton states free from higher-order imperfections, and robust, high-efficiency detection. It can also be used to produce heralded multiphoton entanglement, create optically switchable quantum circuits and implement an improved form of down-conversion with reduced higher-order effects. Such tools are valuable building blocks for many quantum-enabled technologies. Finally, using photonic crystal fibres we experimentally demonstrate quantum correlations arising from a four-colour nonlinear process suitable for CPC and use these measurements to study the feasibility of reaching the deterministic regime with current technology. Our scheme, which is based on interacting bosonic fields, is not restricted to optical systems but could also be implemented in optomechanical, electromechanical and superconducting

  8. Approaches to Quantum Gravity

    NASA Astrophysics Data System (ADS)

    Oriti, Daniele

    2009-03-01

    Preface; Part I. Fundamental Ideas and General Formalisms: 1. Unfinished revolution C. Rovelli; 2. The fundamental nature of space and time G. 't Hooft; 3. Does locality fail at intermediate length scales R. Sorkin; 4. Prolegomena to any future quantum gravity J. Stachel; 5. Spacetime symmetries in histories canonical gravity N. Savvidou; 6. Categorical geometry and the mathematical foundations of quantum gravity L. Crane; 7. Emergent relativity O. Dreyer; 8. Asymptotic safety R. Percacci; 9. New directions in background independent quantum gravity F. Markopoulou; Questions and answers; Part II: 10. Gauge/gravity duality G. Horowitz and J. Polchinski; 11. String theory, holography and quantum gravity T. Banks; 12. String field theory W. Taylor; Questions and answers; Part III: 13. Loop Quantum Gravity T. Thiemann; 14. Covariant loop quantum gravity? E. LIvine; 15. The spin foam representation of loop quantum gravity A. Perez; 16. 3-dimensional spin foam quantum gravity L. Freidel; 17. The group field theory approach to quantum gravity D. Oriti; Questions and answers; Part IV. Discrete Quantum Gravity: 18. Quantum gravity: the art of building spacetime J. Ambjørn, J. Jurkiewicz and R. Loll; 19. Quantum Regge calculations R. Williams; 20. Consistent discretizations as a road to quantum gravity R. Gambini and J. Pullin; 21. The causal set approach to quantum gravity J. Henson; Questions and answers; Part V. Effective Models and Quantum Gravity Phenomenology: 22. Quantum gravity phenomenology G. Amelino-Camelia; 23. Quantum gravity and precision tests C. Burgess; 24. Algebraic approach to quantum gravity II: non-commutative spacetime F. Girelli; 25. Doubly special relativity J. Kowalski-Glikman; 26. From quantum reference frames to deformed special relativity F. Girelli; 27. Lorentz invariance violation and its role in quantum gravity phenomenology J. Collins, A. Perez and D. Sudarsky; 28. Generic predictions of quantum theories of gravity L. Smolin; Questions and

  9. Security of counterfactual quantum cryptography

    SciTech Connect

    Yin Zhenqiang; Li Hongwei; Chen Wei; Han Zhengfu; Guo Guangcan

    2010-10-15

    Recently, a 'counterfactual' quantum-key-distribution scheme was proposed by T.-G. Noh [Phys. Rev. Lett. 103, 230501 (2009)]. In this scheme, two legitimate distant peers may share secret keys even when the information carriers are not traveled in the quantum channel. We find that this protocol is equivalent to an entanglement distillation protocol. According to this equivalence, a strict security proof and the asymptotic key bit rate are both obtained when a perfect single-photon source is applied and a Trojan horse attack can be detected. We also find that the security of this scheme is strongly related to not only the bit error rate but also the yields of photons. And our security proof may shed light on the security of other two-way protocols.

  10. Quantum algorithms for quantum field theories.

    PubMed

    Jordan, Stephen P; Lee, Keith S M; Preskill, John

    2012-06-01

    Quantum field theory reconciles quantum mechanics and special relativity, and plays a central role in many areas of physics. We developed a quantum algorithm to compute relativistic scattering probabilities in a massive quantum field theory with quartic self-interactions (φ(4) theory) in spacetime of four and fewer dimensions. Its run time is polynomial in the number of particles, their energy, and the desired precision, and applies at both weak and strong coupling. In the strong-coupling and high-precision regimes, our quantum algorithm achieves exponential speedup over the fastest known classical algorithm.

  11. Quantum Information Science

    DTIC Science & Technology

    2012-02-01

    for constructing quantum gates. In [Miller11b] we detailed the use of multiplexing to simulate quantum teleportation . One alternative to multiplexing...LABORATORY INFORMATION DIRECTORATE QUANTUM INFORMATION SCIENCE FEBRUARY 2012 FINAL TECHNICAL REPORT  ROME, NY...YYYY) FEB 2012 2. REPORT TYPE Final Technical Report 3. DATES COVERED (From - To) OCT 2009 – SEP 2011 4. TITLE AND SUBTITLE QUANTUM INFORMATION

  12. Advanced quantum communication systems

    NASA Astrophysics Data System (ADS)

    Jeffrey, Evan Robert

    Quantum communication provides several examples of communication protocols which cannot be implemented securely using only classical communication. Currently, the most widely known of these is quantum cryptography, which allows secure key exchange between parties sharing a quantum channel subject to an eavesdropper. This thesis explores and extends the realm of quantum communication. Two new quantum communication protocols are described. The first is a new form of quantum cryptography---relativistic quantum cryptography---which increases communication efficiency by exploiting a relativistic bound on the power of an eavesdropper, in addition to the usual quantum mechanical restrictions intrinsic to quantum cryptography. By doing so, we have observed over 170% improvement in communication efficiency over a similar protocol not utilizing relativity. A second protocol, Quantum Orienteering, allows two cooperating parties to communicate a specific direction in space. This application shows the possibility of using joint measurements, or projections onto an entangled state, in order to extract the maximum useful information from quantum bits. For two-qubit communication, the maximal fidelity of communication using only separable operations is 73.6%, while joint measurements can improve the efficiency to 78.9%. In addition to implementing these protocols, we have improved several resources for quantum communication and quantum computing. Specifically, we have developed improved sources of polarization-entangled photons, a low-loss quantum memory for polarization qubits, and a quantum random number generator. These tools may be applied to a wide variety of future quantum and classical information systems.

  13. Increasing crude tall oil yield

    SciTech Connect

    Gupta, J.

    1983-10-01

    In the kraft pulping process for softwoods and hardwood, tall oil recovery is an important part of making profit. During the past 10 years, crude tall oil (CTO) production in the U.S. and Canada has dropped. Estimated CTO yield from fresh Canadian pine is 36-40 lb/a.d. ton and from Southern U.S. 70-80 lb/a.d. ton, while the average yield of CTO is approximately 40% of available tall oil in pine wood. Besides low yield, many pulp mills fail to achieve a CTO quality that lives up to market expectations. The moisture content of CTO is reported to vary widely (1.5-3.5%), whereas it should not exceed 1.5% for marketable quality. The acid number of CTO varies in the range of 135 to 150, whereas industry standards are 145-150. At present the average sale price of CTO is approximately $150/ton. By upgrading existing plants, the yield can be increased, resulting in additional revenues. Thus, if a batch acidulation plant is replaced by a continuous acidulation plant, the yield will increase by approximately 15-50%. The capital required for installing a continuous system is approximately $1.1-1.5 million for a 500-a.d. ton/day pulp mill, requiring a payback period of approximatley 5-7 years. 7 references.

  14. A short process for the efficient utilization of transition-metal chlorides in lithium-ion batteries: A case of Ni0.8Co0.1Mn0.1O1.1 and LiNi0.8Co0.1Mn0.1O2

    NASA Astrophysics Data System (ADS)

    Li, Tao; Li, Xinhai; Wang, Zhixing; Guo, Huajun

    2017-02-01

    A short process for the efficient utilization of transition-metal chlorides in lithium-ion batteries (LIBs) is proposed. A uniformly dispersed tri-component nanocomposite of Ni0.8Co0.1Mn0.1O1.1 microspheres with a porous structure has been prepared from the solution of transition-metal chlorides via spray pyrolysis. When evaluated as anode for LIBs, the Ni0.8Co0.1Mn0.1O1.1 nanocomposite exhibits a reversible capacity of 1180 mAh g-1 after 120 cycles. More strikingly, the nanoparticles-assembled Ni0.8Co0.1Mn0.1O1.1 precursor has its unique advantages in synthesizing well-ordered layered LiNi0.8Co0.1Mn0.1O2, owning to its excellent atomic uniformity, porous structure and Ni3+-rich surface. The as-prepared cathode material shows excellent structural stability. Discharge capacities of 173 mAh g-1 after 100 cycles at 1 C (1 C = 180 mA g-1) between 2.8 and 4.3 V are consistently obtained, corresponding to 95.6% capacity retention. These outstanding electrochemical results are obtained with minimal process optimization, indicating that spray pyrolysis is an efficient, robust synthesis technique for the production of Ni-rich layered cathode from solution of transition-metal chlorides.

  15. Exploring constrained quantum control landscapes

    NASA Astrophysics Data System (ADS)

    Moore, Katharine W.; Rabitz, Herschel

    2012-10-01

    The broad success of optimally controlling quantum systems with external fields has been attributed to the favorable topology of the underlying control landscape, where the landscape is the physical observable as a function of the controls. The control landscape can be shown to contain no suboptimal trapping extrema upon satisfaction of reasonable physical assumptions, but this topological analysis does not hold when significant constraints are placed on the control resources. This work employs simulations to explore the topology and features of the control landscape for pure-state population transfer with a constrained class of control fields. The fields are parameterized in terms of a set of uniformly spaced spectral frequencies, with the associated phases acting as the controls. This restricted family of fields provides a simple illustration for assessing the impact of constraints upon seeking optimal control. Optimization results reveal that the minimum number of phase controls necessary to assure a high yield in the target state has a special dependence on the number of accessible energy levels in the quantum system, revealed from an analysis of the first- and second-order variation of the yield with respect to the controls. When an insufficient number of controls and/or a weak control fluence are employed, trapping extrema and saddle points are observed on the landscape. When the control resources are sufficiently flexible, solutions producing the globally maximal yield are found to form connected "level sets" of continuously variable control fields that preserve the yield. These optimal yield level sets are found to shrink to isolated points on the top of the landscape as the control field fluence is decreased, and further reduction of the fluence turns these points into suboptimal trapping extrema on the landscape. Although constrained control fields can come in many forms beyond the cases explored here, the behavior found in this paper is illustrative of

  16. Bohmian quantum mechanics with quantum trajectories

    NASA Astrophysics Data System (ADS)

    Jeong, Yeuncheol

    The quantum trajectory method in the hydrodynamical formulation of Madelung-Bohm-Takabayasi quantum mechanics is an example of showing the cognitive importance of scientific illustrations and metaphors, especially, in this case, in computational quantum chemistry and electrical engineering. The method involves several numerical schemes of solving a set of hydrodynamical equations of motion for probability density fluids, based on the propagation of those probability density trajectories. The quantum trajectory method gives rise to, for example, an authentic quantum electron transport theory of motion to, among others, classically-minded applied scientists who probably have less of a commitment to traditional quantum mechanics. They were not the usual audience of quantum mechanics and simply choose to use a non-Copenhagen type interpretation to their advantage. Thus, the metaphysical issues physicists had a trouble with are not the main concern of the scientists. With the advantages of a visual and illustrative trajectory, the quantum theory of motion by Bohm effectively bridges quantum and classical physics, especially, in the mesoscale domain. Without having an abrupt shift in actions and beliefs from the classical to the quantum world, scientists and engineers are able to enjoy human cognitive capacities extended into the quantum mechanical domain.

  17. A quantum-quantum Metropolis algorithm.

    PubMed

    Yung, Man-Hong; Aspuru-Guzik, Alán

    2012-01-17

    The classical Metropolis sampling method is a cornerstone of many statistical modeling applications that range from physics, chemistry, and biology to economics. This method is particularly suitable for sampling the thermal distributions of classical systems. The challenge of extending this method to the simulation of arbitrary quantum systems is that, in general, eigenstates of quantum Hamiltonians cannot be obtained efficiently with a classical computer. However, this challenge can be overcome by quantum computers. Here, we present a quantum algorithm which fully generalizes the classical Metropolis algorithm to the quantum domain. The meaning of quantum generalization is twofold: The proposed algorithm is not only applicable to both classical and quantum systems, but also offers a quantum speedup relative to the classical counterpart. Furthermore, unlike the classical method of quantum Monte Carlo, this quantum algorithm does not suffer from the negative-sign problem associated with fermionic systems. Applications of this algorithm include the study of low-temperature properties of quantum systems, such as the Hubbard model, and preparing the thermal states of sizable molecules to simulate, for example, chemical reactions at an arbitrary temperature.

  18. Engineered semiconductor nanocrystals with enhanced carrier multiplication yields

    NASA Astrophysics Data System (ADS)

    Klimov, Victor

    2014-03-01

    Carrier multiplication (CM) is a process whereby absorption of a single photon results in multiple electron-hole pairs (excitons). This process could benefit a number of solar-energy conversion technologies, most notably photocatalysis and photovoltaics. This presentation overviews recent progress in understanding the CM process in semiconductor nanocrystals, motivated by an outstanding challenge in this field - the lack of capability to predict the CM performance of nanocrystals based on their known photophysical properties or documented parameters of parental bulk solids. Here, we present a possible solution to this problem by showing that, using biexciton Auger lifetimes and intraband relaxation rates inferred from ultrafast spectroscopic studies, we can rationalize relative changes in CM yields as a function of nanocrystal composition, size and shape. Further, guided by this model, we demonstrate a two-fold enhancement in multiexciton yields in PbSe nanorods vs. quantum dots attributed to enhanced Coulomb interactions. We also explore the control of competing intra-band cooling for increasing multiexciton production. Specifically, we design a new type of hetero-structured PbSe/CdSe quantum dots with reduced rates of intra-band relaxation and demonstrate a four-fold boost in the multiexciton yield. These studies provide useful guidelines for future efforts to achieve the ultimate, energy-conservation-defined CM efficiencies.

  19. Uncertainty under quantum measures and quantum memory

    NASA Astrophysics Data System (ADS)

    Xiao, Yunlong; Jing, Naihuan; Li-Jost, Xianqing

    2017-04-01

    The uncertainty principle restricts potential information one gains about physical properties of the measured particle. However, if the particle is prepared in entanglement with a quantum memory, the corresponding entropic uncertainty relation will vary. Based on the knowledge of correlations between the measured particle and quantum memory, we have investigated the entropic uncertainty relations for two and multiple measurements and generalized the lower bounds on the sum of Shannon entropies without quantum side information to those that allow quantum memory. In particular, we have obtained generalization of Kaniewski-Tomamichel-Wehner's bound for effective measures and majorization bounds for noneffective measures to allow quantum side information. Furthermore, we have derived several strong bounds for the entropic uncertainty relations in the presence of quantum memory for two and multiple measurements. Finally, potential applications of our results to entanglement witnesses are discussed via the entropic uncertainty relation in the absence of quantum memory.

  20. Quantum signatures of chaos or quantum chaos?

    NASA Astrophysics Data System (ADS)

    Bunakov, V. E.

    2016-11-01

    A critical analysis of the present-day concept of chaos in quantum systems as nothing but a "quantum signature" of chaos in classical mechanics is given. In contrast to the existing semi-intuitive guesses, a definition of classical and quantum chaos is proposed on the basis of the Liouville-Arnold theorem: a quantum chaotic system featuring N degrees of freedom should have M < N independent first integrals of motion (good quantum numbers) specified by the symmetry of the Hamiltonian of the system. Quantitative measures of quantum chaos that, in the classical limit, go over to the Lyapunov exponent and the classical stability parameter are proposed. The proposed criteria of quantum chaos are applied to solving standard problems of modern dynamical chaos theory.

  1. Secure quantum signatures using insecure quantum channels

    NASA Astrophysics Data System (ADS)

    Amiri, Ryan; Wallden, Petros; Kent, Adrian; Andersson, Erika

    2016-03-01

    Digital signatures are widely used in modern communication to guarantee authenticity and transferability of messages. The security of currently used classical schemes relies on computational assumptions. We present a quantum signature scheme that does not require trusted quantum channels. We prove that it is unconditionally secure against the most general coherent attacks, and show that it requires the transmission of significantly fewer quantum states than previous schemes. We also show that the quantum channel noise threshold for our scheme is less strict than for distilling a secure key using quantum key distribution. This shows that "direct" quantum signature schemes can be preferable to signature schemes relying on secret shared keys generated using quantum key distribution.

  2. Optimal Blind Quantum Computation

    NASA Astrophysics Data System (ADS)

    Mantri, Atul; Pérez-Delgado, Carlos A.; Fitzsimons, Joseph F.

    2013-12-01

    Blind quantum computation allows a client with limited quantum capabilities to interact with a remote quantum computer to perform an arbitrary quantum computation, while keeping the description of that computation hidden from the remote quantum computer. While a number of protocols have been proposed in recent years, little is currently understood about the resources necessary to accomplish the task. Here, we present general techniques for upper and lower bounding the quantum communication necessary to perform blind quantum computation, and use these techniques to establish concrete bounds for common choices of the client’s quantum capabilities. Our results show that the universal blind quantum computation protocol of Broadbent, Fitzsimons, and Kashefi, comes within a factor of (8)/(3) of optimal when the client is restricted to preparing single qubits. However, we describe a generalization of this protocol which requires exponentially less quantum communication when the client has a more sophisticated device.

  3. Quantum key management

    DOEpatents

    Hughes, Richard John; Thrasher, James Thomas; Nordholt, Jane Elizabeth

    2016-11-29

    Innovations for quantum key management harness quantum communications to form a cryptography system within a public key infrastructure framework. In example implementations, the quantum key management innovations combine quantum key distribution and a quantum identification protocol with a Merkle signature scheme (using Winternitz one-time digital signatures or other one-time digital signatures, and Merkle hash trees) to constitute a cryptography system. More generally, the quantum key management innovations combine quantum key distribution and a quantum identification protocol with a hash-based signature scheme. This provides a secure way to identify, authenticate, verify, and exchange secret cryptographic keys. Features of the quantum key management innovations further include secure enrollment of users with a registration authority, as well as credential checking and revocation with a certificate authority, where the registration authority and/or certificate authority can be part of the same system as a trusted authority for quantum key distribution.

  4. Randomness: Quantum versus classical

    NASA Astrophysics Data System (ADS)

    Khrennikov, Andrei

    2016-05-01

    Recent tremendous development of quantum information theory has led to a number of quantum technological projects, e.g. quantum random generators. This development had stimulated a new wave of interest in quantum foundations. One of the most intriguing problems of quantum foundations is the elaboration of a consistent and commonly accepted interpretation of a quantum state. Closely related problem is the clarification of the notion of quantum randomness and its interrelation with classical randomness. In this short review, we shall discuss basics of classical theory of randomness (which by itself is very complex and characterized by diversity of approaches) and compare it with irreducible quantum randomness. We also discuss briefly “digital philosophy”, its role in physics (classical and quantum) and its coupling to the information interpretation of quantum mechanics (QM).

  5. Status of fission yield data

    SciTech Connect

    England, T.R.; Blachot, J.

    1988-01-01

    In this paper we summarize the current status of the recent US evaluation for 34 fissioning nuclides at one or more neutron incident energies and for spontaneous fission. Currently there are 50 yields sets, and for each we have independent and cumulative yields and uncertainties for approximately 1100 fission products. When finalized the recommended data will become part of Version VI of the US ENDF/B. Other major evaluations in progress that are included in a recently formed IAEA Coordinated Research Program are also summarized. In a second part we review two empirical models in use to estimate independent yields. Comparison of model estimates with measured data is presented, including a comparison with some recent data obtained from Lohengrin (Cf-249 T). 18 refs., 13 figs., 3 tabs.

  6. Yield statistics of interpolated superoscillations

    NASA Astrophysics Data System (ADS)

    Katzav, Eytan; Perlsman, Ehud; Schwartz, Moshe

    2017-01-01

    Yield optimized interpolated superoscillations have been recently introduced as a means for possibly making the use of the phenomenon of superoscillation practical. In this paper we study how good is a superoscillation that is not optimal. Namely, by how much is the yield decreased when the signal departs from the optimal one. We consider two situations. One is the case where the signal strictly obeys the interpolation requirement and the other is when that requirement is relaxed. In the latter case the yield can be increased at the expense of deterioration of signal quality. An important conclusion is that optimizing superoscillations may be challenging in terms of the precision needed, however, storing and using them is not at all that sensitive. This is of great importance in any physical system where noise and error are inevitable.

  7. [Theoretical analysis and experimental measurement for secondary electron yield of microchannel plate in extreme ultraviolet region].

    PubMed

    Li, Min; Ni, Qi-liang; Dong, Ning-ning; Chen, Bo

    2010-08-01

    Photon counting detectors based on microchannel plate have widespread applications in astronomy. The present paper deeply studies secondary electron of microchannel plate in extreme ultraviolet. A theoretical model describing extreme ultraviolet-excited secondary electron yield is presented, and the factor affecting on the secondary electron yields of both electrode and lead glass which consist of microchannel plate is analyzed according to theoretical formula derived from the model. The result shows that the higher secondary electron yield is obtained under appropriate condition that the thickness of material is more than 20 nm and the grazing incidence angle is larger than the critical angle. Except for several wavelengths, the secondary electron yields of both electrode and lead glass decrease along with the increase in the wavelength And also the quantum efficiency of microchannel plate is measured using quantum efficiency test set-up with laser-produced plasmas source as an extreme ultraviolet radiation source, and the result of experiment agrees with theoretical analysis.

  8. Diagrammatic quantum mechanics

    NASA Astrophysics Data System (ADS)

    Kauffman, Louis H.; Lomonaco, Samuel J.

    2015-05-01

    This paper explores how diagrams of quantum processes can be used for modeling and for quantum epistemology. The paper is a continuation of the discussion where we began this formulation. Here we give examples of quantum networks that represent unitary transformations by dint of coherence conditions that constitute a new form of non-locality. Local quantum devices interconnected in space can form a global quantum system when appropriate coherence conditions are maintained.

  9. Do Quantum Dice Remember?

    NASA Astrophysics Data System (ADS)

    Durt, Thomas

    2014-03-01

    We shall present certain experiments aimed at testing the Markovian nature of the quantum statistical distributions and comment their results, which confirmed the standard quantum interpretation. We shall also show how certain sophisticated experiments that were realized in the framework of quantum optics during the last decade in order to test fundamental effects such as quantum non-locality also lead us to eliminate certain (non-Markovian and non-local) alternatives to the standard quantum theory.

  10. Quantum Virtual Machine (QVM)

    SciTech Connect

    McCaskey, Alexander J.

    2016-11-18

    There is a lack of state-of-the-art HPC simulation tools for simulating general quantum computing. Furthermore, there are no real software tools that integrate current quantum computers into existing classical HPC workflows. This product, the Quantum Virtual Machine (QVM), solves this problem by providing an extensible framework for pluggable virtual, or physical, quantum processing units (QPUs). It enables the execution of low level quantum assembly codes and returns the results of such executions.

  11. Quantum Information, Computation and Communication

    NASA Astrophysics Data System (ADS)

    Jones, Jonathan A.; Jaksch, Dieter

    2012-07-01

    Part I. Quantum Information: 1. Quantum bits and quantum gates; 2. An atom in a laser field; 3. Spins in magnetic fields; 4. Photon techniques; 5. Two qubits and beyond; 6. Measurement and entanglement; Part II. Quantum Computation: 7. Principles of quantum computing; 8. Elementary quantum algorithms; 9. More advanced quantum algorithms; 10. Trapped atoms and ions; 11. Nuclear magnetic resonance; 12. Large scale quantum computers; Part III. Quantum Communication: 13. Basics of information theory; 14. Quantum information; 15. Quantum communication; 16. Testing EPR; 17. Quantum cryptography; Appendixes; References; Index.

  12. The yield of N/2D/ atoms in the dissociative recombination of NO/+/

    NASA Technical Reports Server (NTRS)

    Kley, D.; Lawrence, G. M.; Stone, E. J.

    1977-01-01

    The quantum yield or branching ratio of N(2D) atoms formed in the reaction e + NO(+) yields N + O was measured to be 76% plus or minus 6%. Photoionization of buffered nitric oxide by a flash lamp was studied using time-resolved atomic absorption. Atoms were produced both by direct photodissociation and by dissociative recombination, and these two effects were separated by means of SF6 as an electron scavenger.

  13. Satellite-Based Quantum Communications

    SciTech Connect

    Hughes, Richard J; Nordholt, Jane E; McCabe, Kevin P; Newell, Raymond T; Peterson, Charles G

    2010-09-20

    Single-photon quantum communications (QC) offers the attractive feature of 'future proof', forward security rooted in the laws of quantum physics. Ground based quantum key distribution (QKD) experiments in optical fiber have attained transmission ranges in excess of 200km, but for larger distances we proposed a methodology for satellite-based QC. Over the past decade we have devised solutions to the technical challenges to satellite-to-ground QC, and we now have a clear concept for how space-based QC could be performed and potentially utilized within a trusted QKD network architecture. Functioning as a trusted QKD node, a QC satellite ('QC-sat') could deliver secret keys to the key stores of ground-based trusted QKD network nodes, to each of which multiple users are connected by optical fiber or free-space QC. A QC-sat could thereby extend quantum-secured connectivity to geographically disjoint domains, separated by continental or inter-continental distances. In this paper we describe our system concept that makes QC feasible with low-earth orbit (LEO) QC-sats (200-km-2,000-km altitude orbits), and the results of link modeling of expected performance. Using the architecture that we have developed, LEO satellite-to-ground QKD will be feasible with secret bit yields of several hundred 256-bit AES keys per contact. With multiple ground sites separated by {approx} 100km, mitigation of cloudiness over any single ground site would be possible, potentially allowing multiple contact opportunities each day. The essential next step is an experimental QC-sat. A number of LEO-platforms would be suitable, ranging from a dedicated, three-axis stabilized small satellite, to a secondary experiment on an imaging satellite. to the ISS. With one or more QC-sats, low-latency quantum-secured communications could then be provided to ground-based users on a global scale. Air-to-ground QC would also be possible.

  14. Fission Reaction Event Yield Algorithm

    SciTech Connect

    Hagmann, Christian; Verbeke, Jerome; Vogt, Ramona; Roundrup, Jorgen

    2016-05-31

    FREYA (Fission Reaction Event Yield Algorithm) is a code that simulated the decay of a fissionable nucleus at specified excitation energy. In its present form, FREYA models spontaneous fission and neutron-induced fission up to 20 MeV. It includes the possibility of neutron emission from the nuclear prior to its fussion (nth chance fission).

  15. Quantum Cosmology

    NASA Astrophysics Data System (ADS)

    Bojowald, Martin

    The universe, ultimately, is to be described by quantum theory. Quantum aspects of all there is, including space and time, may not be significant for many purposes, but are crucial for some. And so a quantum description of cosmology is required for a complete and consistent worldview. At any rate, even if we were not directly interested in regimes where quantum cosmology plays a role, a complete physical description could not stop at a stage before the whole universe is reached. Quantum theory is essential in the microphysics of particles, atoms, molecules, solids, white dwarfs and neutron stars. Why should one expect this ladder of scales to end at a certain size? If regimes are sufficiently violent and energetic, quantum effects are non-negligible even on scales of the whole cosmos; this is realized at least once in the history of the universe: at the big bang where the classical theory of general relativity would make energy densities diverge. 1.Lachieze-Rey, M., Luminet, J.P.: Phys. Rept. 254,135 (1995), gr-qc/9605010 2.BSDeWitt1967Phys. Rev.160511131967PhRv..160.1113D0158.4650410.1103/PhysRev.160.1113DeWitt, B.S.: Phys. Rev. 160(5), 1113 (1967) 3.Wiltshire, D.L.: In: Robson B., Visvanathan N., Woolcock W.S. (eds.) Cosmology: The Physics of the Universe, pp. 473-531. World Scientific, Singapore (1996

  16. Quantum optics, cavity QED, and quantum optomechanics

    NASA Astrophysics Data System (ADS)

    Meystre, Pierre

    2013-05-01

    Quantum optomechanics provides a universal tool to achieve the quantum control of mechanical motion. It does that in devices spanning a vast range of parameters, with mechanical frequencies from a few Hertz to GHz, and with masses from 10-20 g to several kilos. Its underlying ideas can be traced back to the study of gravitational wave antennas, quantum optics, cavity QED and laser cooling which, when combined with the recent availability of advanced micromechanical and nanomechanical devices, opens a path to the realization of macroscopic mechanical systems that operate deep in the quantum regime. At the fundamental level this development paves the way to experiments that will lead to a more profound understanding of quantum mechanics; and from the point of view of applications, quantum optomechanical techniques will provide motion and force sensing near the fundamental limit imposed by quantum mechanics (quantum metrology) and significantly expand the toolbox of quantum information science. After a brief summary of key historical developments, the talk will give a broad overview of the current state of the art of quantum optomechanics, and comment on future prospects both in applied and in fundamental science. Work supported by NSF, ARO and the DARPA QuASAR and ORCHID programs.

  17. Quantum leadership: the implication for Iranian nursing leaders.

    PubMed

    Dargahi, Hossein

    2013-07-13

    Quantum organizations are referred where stakeholders know how to access the infinite potential of the quantum field. Viewing healthcare organizations from perspective of quantum theory suggest new approaches into management techniques for effective and efficient delivery of healthcare services. This research is aimed to determine the quantum skills, quantum leadership characteristics and functions of Tehran University of Medical Sciences hospitals' nursing administrators. A cross-sectional, descriptive and analytical study was conducted among 25 nursing administrators of Tehran University of Medical Sciences (TUMS) hospitals, Tehran, Iran. The research tool for data collection was a self-constructed questionnaire that measured the quantum skills, quantum leadership characteristics and functions of TUMS hospitals' nursing administrators. The validity of questionnaire was confirmed by 5 management science experts and its reliability was performed by using test-retest method yielded a Cronbach's alpha coefficient of 0.90. Data were collected and analyzed by SPSS software and t-test statistical methods. The results of this research showed that all respondents had desired quantum skills (75.71±5.98), quantum leadership characteristics (82.01±6.77), and quantum leadership functions (78.57±6.28) and total quantum leadership (78.76±4.50). Also, passing management training courses of the respondents was significantly correlated with their quantum leadership. Iranian healthcare organizations require quantum leadership that provides an important resource to advance Iranian nursing leadership to the organizational excellence. We hope Iranian hospitals' nursing leaders who have quantum skills potentially, present a highly developed sense of self and the ability to improve nursing care outcomes in these hospitals.

  18. Multi-junction-solar-cell designs and characterizations based on detailed-balance principle and luminescence yields

    NASA Astrophysics Data System (ADS)

    Akiyama, Hidefumi; Zhu, Lin; Yoshita, Masahiro; Kim, Changsu; Chen, Shaoqiang; Mochizuki, Toshimitsu; Kanemitsu, Yoshihiko

    2015-03-01

    We developed a straightforward method based on detailed balance relations to analyze individual subcells in multi-junction solar cells via measuring absolute electroluminescence quantum yields. This method was applied to characterization of a InGaP/GaAs/Ge 3-junction solar cell for satellite use. In addition to subcell I-V characteristics and internal luminescence yields, we derived balance sheets of energy and carriers, which revealed respective subcell contributions of radiative and nonradiative recombination losses, junction loss, and luminescence coupling. These results provide important diagnosis and feedback to fabrications. We calculated conversion-efficiency limit and optimized bandgap energy in 2-, 3-, and 4-junction tandem solar cells, including finite values of sub-cell internal luminescence quantum yields to account for realistic material qualities in sub-cells. With reference to the measured internal luminescence quantum yields, the theoretical results provide realistic targets of efficiency limits and improved design principles of practical tandem solar cells.

  19. Comparison of the Photosynthetic Yield of Cyanobacteria and Green Algae: Different Methods Give Different Answers.

    PubMed

    Schuurmans, R Milou; van Alphen, Pascal; Schuurmans, J Merijn; Matthijs, Hans C P; Hellingwerf, Klaas J

    2015-01-01

    The societal importance of renewable carbon-based commodities and energy carriers has elicited a particular interest for high performance phototrophic microorganisms. Selection of optimal strains is often based on direct comparison under laboratory conditions of maximal growth rate or additional valued features such as lipid content. Instead of reporting growth rate in culture, estimation of photosynthetic efficiency (quantum yield of PSII) by pulse-amplitude modulated (PAM) fluorimetry is an often applied alternative method. Here we compared the quantum yield of PSII and the photonic yield on biomass for the green alga Chlorella sorokiniana 211-8K and the cyanobacterium Synechocystis sp. PCC 6803. Our data demonstrate that the PAM technique inherently underestimates the photosynthetic efficiency of cyanobacteria by rendering a high F0 and a low FM, specifically after the commonly practiced dark pre-incubation before a yield measurement. Yet when comparing the calculated biomass yield on light in continuous culture experiments, we obtained nearly equal values for both species. Using mutants of Synechocystis sp. PCC 6803, we analyzed the factors that compromise its PAM-based quantum yield measurements. We will discuss the role of dark respiratory activity, fluorescence emission from the phycobilisomes, and the Mehler-like reaction. Based on the above observations we recommend that PAM measurements in cyanobacteria are interpreted only qualitatively.

  20. Comparison of the Photosynthetic Yield of Cyanobacteria and Green Algae: Different Methods Give Different Answers

    PubMed Central

    Schuurmans, R. Milou; van Alphen, Pascal; Schuurmans, J. Merijn; Matthijs, Hans C. P.; Hellingwerf, Klaas J.

    2015-01-01

    The societal importance of renewable carbon-based commodities and energy carriers has elicited a particular interest for high performance phototrophic microorganisms. Selection of optimal strains is often based on direct comparison under laboratory conditions of maximal growth rate or additional valued features such as lipid content. Instead of reporting growth rate in culture, estimation of photosynthetic efficiency (quantum yield of PSII) by pulse-amplitude modulated (PAM) fluorimetry is an often applied alternative method. Here we compared the quantum yield of PSII and the photonic yield on biomass for the green alga Chlorella sorokiniana 211-8K and the cyanobacterium Synechocystis sp. PCC 6803. Our data demonstrate that the PAM technique inherently underestimates the photosynthetic efficiency of cyanobacteria by rendering a high F0 and a low FM, specifically after the commonly practiced dark pre-incubation before a yield measurement. Yet when comparing the calculated biomass yield on light in continuous culture experiments, we obtained nearly equal values for both species. Using mutants of Synechocystis sp. PCC 6803, we analyzed the factors that compromise its PAM-based quantum yield measurements. We will discuss the role of dark respiratory activity, fluorescence emission from the phycobilisomes, and the Mehler-like reaction. Based on the above observations we recommend that PAM measurements in cyanobacteria are interpreted only qualitatively. PMID:26394153

  1. Expected number of quantum channels in quantum networks.

    PubMed

    Chen, Xi; Wang, He-Ming; Ji, Dan-Tong; Mu, Liang-Zhu; Fan, Heng

    2015-07-15

    Quantum communication between nodes in quantum networks plays an important role in quantum information processing. Here, we proposed the use of the expected number of quantum channels as a measure of the efficiency of quantum communication for quantum networks. This measure quantified the amount of quantum information that can be teleported between nodes in a quantum network, which differs from classical case in that the quantum channels will be consumed if teleportation is performed. We further demonstrated that the expected number of quantum channels represents local correlations depicted by effective circles. Significantly, capacity of quantum communication of quantum networks quantified by ENQC is independent of distance for the communicating nodes, if the effective circles of communication nodes are not overlapped. The expected number of quantum channels can be enhanced through transformations of the lattice configurations of quantum networks via entanglement swapping. Our results can shed lights on the study of quantum communication in quantum networks.

  2. Reliable quantum communication over a quantum relay channel

    SciTech Connect

    Gyongyosi, Laszlo; Imre, Sandor

    2014-12-04

    We show that reliable quantum communication over an unreliable quantum relay channels is possible. The coding scheme combines the results on the superadditivity of quantum channels and the efficient quantum coding approaches.

  3. The Forbidden Quantum Adder

    NASA Astrophysics Data System (ADS)

    Alvarez-Rodriguez, U.; Sanz, M.; Lamata, L.; Solano, E.

    2015-07-01

    Quantum information provides fundamentally different computational resources than classical information. We prove that there is no unitary protocol able to add unknown quantum states belonging to different Hilbert spaces. This is an inherent restriction of quantum physics that is related to the impossibility of copying an arbitrary quantum state, i.e., the no-cloning theorem. Moreover, we demonstrate that a quantum adder, in absence of an ancillary system, is also forbidden for a known orthonormal basis. This allows us to propose an approximate quantum adder that could be implemented in the lab. Finally, we discuss the distinct character of the forbidden quantum adder for quantum states and the allowed quantum adder for density matrices.

  4. Evaluation of a cotton stripper yield monitor

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this work was to evaluate the accuracy of a microwave sensor based yield monitor for measuring yield on a cotton stripper harvester and determine if the yield monitor can discriminate differences in yield to the same level as a reference scale system. A new yield monitor was instal...

  5. Quantum junction solar cells.

    PubMed

    Tang, Jiang; Liu, Huan; Zhitomirsky, David; Hoogland, Sjoerd; Wang, Xihua; Furukawa, Melissa; Levina, Larissa; Sargent, Edward H

    2012-09-12

    Colloidal quantum dot solids combine convenient solution-processing with quantum size effect tuning, offering avenues to high-efficiency multijunction cells based on a single materials synthesis and processing platform. The highest-performing colloidal quantum dot rectifying devices reported to date have relied on a junction between a quantum-tuned absorber and a bulk material (e.g., TiO(2)); however, quantum tuning of the absorber then requires complete redesign of the bulk acceptor, compromising the benefits of facile quantum tuning. Here we report rectifying junctions constructed entirely using inherently band-aligned quantum-tuned materials. Realizing these quantum junction diodes relied upon the creation of an n-type quantum dot solid having a clean bandgap. We combine stable, chemically compatible, high-performance n-type and p-type materials to create the first quantum junction solar cells. We present a family of photovoltaic devices having widely tuned bandgaps of 0.6-1.6 eV that excel where conventional quantum-to-bulk devices fail to perform. Devices having optimal single-junction bandgaps exhibit certified AM1.5 solar power conversion efficiencies of 5.4%. Control over doping in quantum solids, and the successful integration of these materials to form stable quantum junctions, offers a powerful new degree of freedom to colloidal quantum dot optoelectronics.

  6. Single molecule study of silicon quantum dots

    NASA Astrophysics Data System (ADS)

    So, Woong Young; Li, Qi; Jin, Rongchao; Peteanu, Linda

    2016-09-01

    Recently, fluorescent Silicon (Si) Quantum Dots (QDs) have attracted much interest due to their high quantum yield, use of non-toxic and environmentally-benign chemicals, and water-solubility. However, more research is necessary to understand the energy level characteristics and single molecule behavior to enable their development for imaging applications. Therefore, single molecule time-resolved fluorescence spectroscopy of fluorescent Si QDs (cyan, green, and yellow) is needed. A rigorous analysis of time-resolved photon correlation spectroscopy and fluorescence lifetime data on single Si QDs at room temperature is presented.

  7. Interfacing external quantum devices to a universal quantum computer.

    PubMed

    Lagana, Antonio A; Lohe, Max A; von Smekal, Lorenz

    2011-01-01

    We present a scheme to use external quantum devices using the universal quantum computer previously constructed. We thereby show how the universal quantum computer can utilize networked quantum information resources to carry out local computations. Such information may come from specialized quantum devices or even from remote universal quantum computers. We show how to accomplish this by devising universal quantum computer programs that implement well known oracle based quantum algorithms, namely the Deutsch, Deutsch-Jozsa, and the Grover algorithms using external black-box quantum oracle devices. In the process, we demonstrate a method to map existing quantum algorithms onto the universal quantum computer.

  8. Quantum Estimation Methods for Quantum Illumination

    NASA Astrophysics Data System (ADS)

    Sanz, M.; Las Heras, U.; García-Ripoll, J. J.; Solano, E.; Di Candia, R.

    2017-02-01

    Quantum illumination consists in shining quantum light on a target region immersed in a bright thermal bath with the aim of detecting the presence of a possible low-reflective object. If the signal is entangled with the receiver, then a suitable choice of the measurement offers a gain with respect to the optimal classical protocol employing coherent states. Here, we tackle this detection problem by using quantum estimation techniques to measure the reflectivity parameter of the object, showing an enhancement in the signal-to-noise ratio up to 3 dB with respect to the classical case when implementing only local measurements. Our approach employs the quantum Fisher information to provide an upper bound for the error probability, supplies the concrete estimator saturating the bound, and extends the quantum illumination protocol to non-Gaussian states. As an example, we show how Schrödinger's cat states may be used for quantum illumination.

  9. Quantum Estimation Methods for Quantum Illumination.

    PubMed

    Sanz, M; Las Heras, U; García-Ripoll, J J; Solano, E; Di Candia, R

    2017-02-17

    Quantum illumination consists in shining quantum light on a target region immersed in a bright thermal bath with the aim of detecting the presence of a possible low-reflective object. If the signal is entangled with the receiver, then a suitable choice of the measurement offers a gain with respect to the optimal classical protocol employing coherent states. Here, we tackle this detection problem by using quantum estimation techniques to measure the reflectivity parameter of the object, showing an enhancement in the signal-to-noise ratio up to 3 dB with respect to the classical case when implementing only local measurements. Our approach employs the quantum Fisher information to provide an upper bound for the error probability, supplies the concrete estimator saturating the bound, and extends the quantum illumination protocol to non-Gaussian states. As an example, we show how Schrödinger's cat states may be used for quantum illumination.

  10. Quantum thermodynamics of general quantum processes.

    PubMed

    Binder, Felix; Vinjanampathy, Sai; Modi, Kavan; Goold, John

    2015-03-01

    Accurately describing work extraction from a quantum system is a central objective for the extension of thermodynamics to individual quantum systems. The concepts of work and heat are surprisingly subtle when generalizations are made to arbitrary quantum states. We formulate an operational thermodynamics suitable for application to an open quantum system undergoing quantum evolution under a general quantum process by which we mean a completely positive and trace-preserving map. We derive an operational first law of thermodynamics for such processes and show consistency with the second law. We show that heat, from the first law, is positive when the input state of the map majorizes the output state. Moreover, the change in entropy is also positive for the same majorization condition. This makes a strong connection between the two operational laws of thermodynamics.

  11. Open Quantum Walks and Dissipative Quantum Computing

    NASA Astrophysics Data System (ADS)

    Petruccione, Francesco

    2012-02-01

    Open Quantum Walks (OQWs) have been recently introduced as quantum Markov chains on graphs [S. Attal, F. Petruccione, C. Sabot, and I. Sinayskiy, E-print: http://hal.archives-ouvertes.fr/hal-00581553/fr/]. The formulation of the OQWs is exclusively based upon the non-unitary dynamics induced by the environment. It will be shown that OQWs are a very useful tool for the formulation of dissipative quantum computing and quantum state preparation. In particular, it will be shown how to implement single qubit gates and the CNOT gate as OQWs on fully connected graphs. Also, OQWS make possible the dissipative quantum state preparation of arbitrary single qubit states and of all two-qubit Bell states. Finally, it will be shown how to reformulate efficiently a discrete time version of dissipative quantum computing in the language of OQWs.

  12. Quantum finance

    NASA Astrophysics Data System (ADS)

    Schaden, Martin

    2002-12-01

    Quantum theory is used to model secondary financial markets. Contrary to stochastic descriptions, the formalism emphasizes the importance of trading in determining the value of a security. All possible realizations of investors holding securities and cash is taken as the basis of the Hilbert space of market states. The temporal evolution of an isolated market is unitary in this space. Linear operators representing basic financial transactions such as cash transfer and the buying or selling of securities are constructed and simple model Hamiltonians that generate the temporal evolution due to cash flows and the trading of securities are proposed. The Hamiltonian describing financial transactions becomes local when the profit/loss from trading is small compared to the turnover. This approximation may describe a highly liquid and efficient stock market. The lognormal probability distribution for the price of a stock with a variance that is proportional to the elapsed time is reproduced for an equilibrium market. The asymptotic volatility of a stock in this case is related to the long-term probability that it is traded.

  13. Quantum information causality.

    PubMed

    Pitalúa-García, Damián

    2013-05-24

    How much information can a transmitted physical system fundamentally communicate? We introduce the principle of quantum information causality, which states the maximum amount of quantum information that a quantum system can communicate as a function of its dimension, independently of any previously shared quantum physical resources. We present a new quantum information task, whose success probability is upper bounded by the new principle, and show that an optimal strategy to perform it combines the quantum teleportation and superdense coding protocols with a task that has classical inputs.

  14. Counterfactual quantum cryptography.

    PubMed

    Noh, Tae-Gon

    2009-12-04

    Quantum cryptography allows one to distribute a secret key between two remote parties using the fundamental principles of quantum mechanics. The well-known established paradigm for the quantum key distribution relies on the actual transmission of signal particle through a quantum channel. In this Letter, we show that the task of a secret key distribution can be accomplished even though a particle carrying secret information is not in fact transmitted through the quantum channel. The proposed protocols can be implemented with current technologies and provide practical security advantages by eliminating the possibility that an eavesdropper can directly access the entire quantum system of each signal particle.

  15. Estimates on Functional Integrals of Quantum Mechanics and Non-relativistic Quantum Field Theory

    NASA Astrophysics Data System (ADS)

    Bley, Gonzalo A.; Thomas, Lawrence E.

    2017-01-01

    We provide a unified method for obtaining upper bounds for certain functional integrals appearing in quantum mechanics and non-relativistic quantum field theory, functionals of the form {E[{exp}(A_T)]} , the (effective) action {A_T} being a function of particle trajectories up to time T. The estimates in turn yield rigorous lower bounds for ground state energies, via the Feynman-Kac formula. The upper bounds are obtained by writing the action for these functional integrals in terms of stochastic integrals. The method is illustrated in familiar quantum mechanical settings: for the hydrogen atom, for a Schrödinger operator with {1/|x|^2} potential with small coupling, and, with a modest adaptation of the method, for the harmonic oscillator. We then present our principal applications of the method, in the settings of non-relativistic quantum field theories for particles moving in a quantized Bose field, including the optical polaron and Nelson models.

  16. Quantum Darwinian Evolution Implies Tumor Origination

    NASA Astrophysics Data System (ADS)

    Cooper, W. Grant

    2011-03-01

    Quantum uncertainty limits operating on metastable amino DNA protons drive the arrangement, keto-amino ? enol-imine, which contributes to time-dependent stochastic mutations. Product enol-imine protons participate in coupled quantum oscillations at frequencies of about 1013 s-1 until ``measured by'' an evolutionarily selected quantum reader, the transcriptase. This introduces entanglement states between coherent protons and transcriptase components, which ultimately yield an ensemble of decohered, non-reequilibrated enol and imine isomers that participate in ``molecular clock'' base substitutions at G'-C' and *G-*C sites. This introduces a quantum Darwinian evolution model which (a) simulates incidence of cancer data and (b) implies insight into quantum origins of evolutionary extinction. Data identify an inherited ``genetic space,'' s, which is initially mutation-free and satisfies the inequality, 1 = s = 0.97. When accumulated stochastic mutations cause s-values to approach their evolutionarily allowed threshold limit, s 0.97 + e, age-related degenerative disease is manifested. This implies a gain in evolutionary advantage which protects the gene pool against acquiring unsafe levels of mutation. Data requiring coherent states imply that classical duplex DNA contains an embedded microphysical subset of electron lone-pairs and hydrogen bonded protons that govern time-dependent genetic specificity in terms of quantum probability laws.

  17. Positioning of quantum dots on metallic nanostructures.

    PubMed

    Kramer, R K; Pholchai, N; Sorger, V J; Yim, T J; Oulton, R; Zhang, X

    2010-04-09

    The capability to position individual emitters, such as quantum dots, near metallic nanostructures is highly desirable for constructing active optical devices that can manipulate light at the single photon level. The emergence of the field of plasmonics as a means to confine light now introduces a need for high precision and reliability in positioning any source of emission, which has thus far been elusive. Placing an emission source within the influence of plasmonic structures now requires accuracy approaching molecular length scales. In this paper we report the ability to reliably position nanoscale functional objects, specifically quantum dots, with sub-100-nm accuracy, which is several times smaller than the diffraction limit of a quantum dot's emission light. Electron beam lithography-defined masks on metallic surfaces and a series of surface chemical functionalization processes allow the programmed assembly of DNA-linked colloidal quantum dots. The quantum dots are successfully functionalized to areas as small as (100 nm)(2) using the specific binding of thiolated DNA to Au/Ag, and exploiting the streptavidin-biotin interaction. An analysis of the reproducibility of the process for various pattern sizes shows that this technique is potentially scalable to the single quantum dot level with 50 nm accuracy accompanied by a moderate reduction in yield.

  18. Quantum Kolmogorov complexity and bounded quantum memory

    SciTech Connect

    Miyadera, Takayuki

    2011-04-15

    The effect of bounded quantum memory in a primitive information protocol has been examined using the quantum Kolmogorov complexity as a measure of information. We employed a toy two-party protocol in which Bob, by using a bounded quantum memory and an unbounded classical memory, estimates a message that was encoded in qubits by Alice in one of the bases X or Z. Our theorem gave a nontrivial effect of the memory boundedness. In addition, a generalization of the uncertainty principle in the presence of quantum memory has been obtained.

  19. Work and quantum phase transitions: quantum latency.

    PubMed

    Mascarenhas, E; Bragança, H; Dorner, R; França Santos, M; Vedral, V; Modi, K; Goold, J

    2014-06-01

    We study the physics of quantum phase transitions from the perspective of nonequilibrium thermodynamics. For first-order quantum phase transitions, we find that the average work done per quench in crossing the critical point is discontinuous. This leads us to introduce the quantum latent work in analogy with the classical latent heat of first order classical phase transitions. For second order quantum phase transitions the irreversible work is closely related to the fidelity susceptibility for weak sudden quenches of the system Hamiltonian. We demonstrate our ideas with numerical simulations of first, second, and infinite order phase transitions in various spin chain models.

  20. Quantum optics. Gravity meets quantum physics

    SciTech Connect

    Adams, Bernhard W.

    2015-02-27

    Albert Einstein’s general theory of relativity is a classical formulation but a quantum mechanical description of gravitational forces is needed, not only to investigate the coupling of classical and quantum systems but simply to give a more complete description of our physical surroundings. In this issue of Nature Photonics, Wen-Te Liao and Sven Ahrens reveal a link between quantum and gravitational physics. They propose that in the quantum-optical effect of superradiance, the world line of electromagnetic radiation is changed by the presence of a gravitational field.