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Sample records for dot cl hydrogen

  1. Effects of Shannon entropy and electric field on polaron in RbCl triangular quantum dot

    NASA Astrophysics Data System (ADS)

    M, Tiotsop; A, J. Fotue; S, C. Kenfack; N, Issofa; H, Fotsin; L, C. Fai

    2016-04-01

    In this paper, the time evolution of the quantum mechanical state of a polaron is examined using the Pekar type variational method on the condition of the electric-LO-phonon strong-coupling and polar angle in RbCl triangular quantum dot. We obtain the eigenenergies, and the eigenfunctions of the ground state, and the first excited state respectively. This system in a quantum dot can be treated as a two-level quantum system qubit and the numerical calculations are performed. The effects of Shannon entropy and electric field on the polaron in the RbCl triangular quantum dot are also studied.

  2. Computation of energy states of hydrogenic quantum dot with two-electrons

    NASA Astrophysics Data System (ADS)

    Yakar, Y.; Özmen, A.; ćakır, B.

    2016-03-01

    In this study we have investigated the electronic structure of the hydrogenic quantum dot with two electrons inside an impenetrable potential surface. The energy eigenvalues and wavefunctions of the ground and excited states of spherical quantum dot have been calculated by using the Quantum Genetic Algorithm (QGA) and Hartree-Fock Roothaan (HFR) method, and the energies are investigated as a function of dot radius. The results show that as dot radius increases, the energy of quantum dot decreases.

  3. Dynamic [Cl-]i measurement with chloride sensing quantum dots nanosensor in epithelial cells

    NASA Astrophysics Data System (ADS)

    Wang, Yuchi; Mao, Hua; Wong, Lid B.

    2010-02-01

    We have synthesized a chloride sensing quantum dots (QD) nanosensor, Cl-QD, for the dynamic measurements of chloride ion concentration in the millimolar range, a sensitivity that is applicable to most physiological intracellular chloride ion concentration ([Cl-]i) measurements in epithelial cells. The Cl-QD is synthesized by conjugating an anion receptor, 1-(2-mercapto-ethyl)-3-phenyl-thiourea (MEPTU) to a water soluble CdSe/ZnS QD at an emission wavelength of 620 nm. Upon binding of chloride ions to the Cl-QD, a photo-induced electron transfer mechanism caused the fluorescence of the QD to quench. This resulted in an inversely proportional relationship between the chloride ion concentration and the fluorescence intensity of the Cl-QD. We have utilized this Cl-QD to measure [Cl-]i in T84 and CF-PAC cultured cells, with either the C1C-2 or CFTR chloride channels being manipulated by pharmacological chloride channel activators and inhibitors. Activations of C1C-2 and CFTR chloride channels in T84 by the respective lubiprostone and genistein caused predictive increases in the fluorescence of the Cl-QD, i.e., a decrease of [Cl-]i. Conversely, glibenclamide, a chloride channel inhibitor, applied to the CF-PAC cells caused a predictable decrease in the fluorescence of Cl-QD due to the increase of [Cl-]i. These are the first data in using QD-based chloride ion sensors for dynamic measurements of intracellular chloride ion concentrations in epithelial cells.

  4. Solvothermal method to prepare graphene quantum dots by hydrogen peroxide

    NASA Astrophysics Data System (ADS)

    Tian, Renbing; Zhong, Suting; Wu, Juan; Jiang, Wei; Shen, Yewen; Jiang, Wei; Wang, Tianhe

    2016-10-01

    Graphene quantum dots (GQDs) have been synthesized by different chemical methods in recent years. For conventional chemical methods, it is inevitable to introduce a large amount of impurities in the preparation process. Long time of dialysis process increases the time cost extremely. Herein, we report a one-step solvothermal method for synthesizing GQDs with the application of hydrogen peroxide in N, N-Dimethylformamide (DMF) environment, which completely avoids the use of concentrated sulphuric acid and nitric acid to treat raw material and introduces no impurity in whole preparation process simultaneously for the first time. Pure GQDs can be obtained after evaporation/redissolution and filtration process with a strong blue emission at 15% quantum yield. This solvothermal method, not requiring dialysis process and complicated equipments, exhibits simple, eco-friendly and low time-cost properties. Besides high quantum yields, the as-prepared GQDs also show good photoluminescence stability in different pH conditions. The optical properties, morphology and structure of GQDs were studied by various equipments, implying potential application in biomedical fields and electronic device.

  5. Computation of hyperfine energies of hydrogen, deuterium and tritium quantum dots

    NASA Astrophysics Data System (ADS)

    Çakır, Bekir; Özmen, Ayhan; Yakar, Yusuf

    2016-01-01

    The hyperfine energies and hyperfine constants of the ground and excited states of hydrogen, deuterium and tritium quantum dots(QDs) are calculated. Quantum genetic algorithm (QGA) and Hartree-Fock-Roothaan (HFR) methods are employed to calculate the unperturbed wave functions and energy eigenvalues. The results show that in the medium and strong confinement regions the hyperfine energy and hyperfine constant are strongly affected by dot radius, impurity charge, electron spin orientation, impurity spin and impurity magnetic moment. Besides, in all dot radii, the hyperfine splitting and hyperfine constant of the confined hydrogen and tritium atoms are approximately equivalent to each other and they are greater than the confined deuterium atom.

  6. Quantum-dot-sensitized TiO2 inverse opals for photoelectrochemical hydrogen generation.

    PubMed

    Cheng, Chuanwei; Karuturi, Siva Krishna; Liu, Lijun; Liu, Jinping; Li, Hongxing; Su, Liap Tat; Tok, Alfred Iing Yoong; Fan, Hong Jin

    2012-01-01

    A new nanoarchitecture photoelectrode design comprising CdS quantum-dot-sensitized, optically and electrically active TiO(2) inverse opals is developed for photoelectrochemical water splitting. The photoelectrochemical performance shows high photocurrent density (4.84 mA cm(-2) at 0 V vs. Ag/AgCl) under simulated solar-light illumination. PMID:22009604

  7. Quantum-dot-sensitized TiO2 inverse opals for photoelectrochemical hydrogen generation.

    PubMed

    Cheng, Chuanwei; Karuturi, Siva Krishna; Liu, Lijun; Liu, Jinping; Li, Hongxing; Su, Liap Tat; Tok, Alfred Iing Yoong; Fan, Hong Jin

    2012-01-01

    A new nanoarchitecture photoelectrode design comprising CdS quantum-dot-sensitized, optically and electrically active TiO(2) inverse opals is developed for photoelectrochemical water splitting. The photoelectrochemical performance shows high photocurrent density (4.84 mA cm(-2) at 0 V vs. Ag/AgCl) under simulated solar-light illumination.

  8. Enhancement of electrochemical hydrogen storage in NiCl2-FeCl3-PdCl2-graphite intercalation compound effected by chemical exfoliation

    NASA Astrophysics Data System (ADS)

    Skowroński, J. M.; Rozmanowski, T.; Krawczyk, P.

    2013-06-01

    In the present work, a quaternary NiCl2-FeCl3-PdCl2-graphite intercalation compound (NiCl2-FeCl3-PdCl2-GIC) was successfully synthesized by molten salts method. A part of this compound was subsequently subjected to chemical exfoliation to obtain expanded compound (NiCl2-FeCl3-PdCl2-EGIC). The changes created in crystalline structure, morphology and chemical composition of GIC due to exfoliation were examined by XRD, SEM and EDS techniques and then related to electrochemical behaviour of electrodes made of the original and exfoliated compound. The results of electrochemical studies carried out by the cyclic voltammetry (CV) method in 6 M KOH solution showed that current charges of all the cathodic and anodic peaks recorded for NiCl2-FeCl3-PdCl2-EGIC are considerably higher already in the first two cycles as compared to those observed for the original NiCl2-FeCl3-PdCl2-GIC. This improvement is ascribed to chemical exfoliation leading to a tremendous development of surface area of the compound due to the splitting and wrinkling of graphite flakes followed by easier access of hydroxyl ions of the electrolyte to active species of intercalates preserved between the graphene interspaces as well as expelled from the graphite interspacing. A large anodic peak was recorded on CV curves after the potentiostatic polarization of electrodes at the potential of -1.2 V where the reaction of hydrogen sorption/evolution occurs and intercalates highly dispersed in the graphite matrix are reduced to a metal form. This peak mainly corresponding to the recovery of hydrogen stored in the electrode appeared to be over five times higher for electrode made of exfoliated compound. This significant enhancement of the hydrogen storage capacity is attributed to electrochemically active Pd nanoparticles highly dispersed in porous structure of exfoliated compound and likely functioning in synergy with Ni/Fe clusters.

  9. Cooperatively enhanced ionic hydrogen bonds in Cl-(CH3OH)(1-3)Ar clusters.

    PubMed

    Beck, Jordan P; Lisy, James M

    2010-09-23

    Infrared predissociation (IRPD) spectra of Cl−(CH3OH)1-3Ar and Cl-(CH3OD)1-3Ar were obtained in the OH and CH stretching regions. The use of methanol-d1 was necessary to distinguish between CH stretches and hydrogen-bonded OH features. The spectra of Cl-(CH3OH)2-3Ar show intense features at frequencies lower than the CH stretches, indicating structures with very strong hydrogen bonds. These strong hydrogen bonds arise from structures in which a Cl-···methanol ionic hydrogen bond is cooperatively enhanced by the presence of a second shell and, in the case of Cl-(CH3OH)3Ar, a third shell methanol. The strongest hydrogen bond is observed in the Cl-(CH3OH)3Ar spectrum at 2733 cm-1, shifted a remarkable -948 cm-1 from the neutral, gas-phase methanol value. Harmonic, ab initio frequency calculations are not adequate in describing these strong hydrogen bonds. Therefore, we describe a simple computational approach to better approximate the hydrogen bond frequencies. Overall, the results of this study indicate that high-energy isomers are very efficiently trapped using our experimental method of introducing Cl- into neutral, cold methanol-argon clusters.

  10. EVALUATION OF RADIOLYSIS INDUCED HYDROGEN GENERATION IN DOT 6M DRUMS FROM INTEC

    SciTech Connect

    Vinson, D

    2007-06-18

    Three DOT 6M 30-gallon drums are scheduled to be shipped from the Idaho Nuclear Technology Engineering Center (INTEC) at the Idaho National Laboratory (INL) to L-Area at the Savannah River Site (SRS). These three drums contain radioactive materials that resulted from the material recovery effort following a small explosion that had occurred in the Idaho Chemical Processing Plant (ICPP) hot chemistry laboratory (HCL). In support of the shipment and subsequent storage of the three DOT 6M drums, an evaluation of the potential for molecular hydrogen production in the drums has been completed and documented herein. The potential sources of hydrogen evaluated in the current report include radiolytic decomposition of polymeric materials in the DOT 6M drums No.3031 and No.3598 and the radiolytic decomposition of water in drum No.20102. No other potential sources have been identified based upon reported drum contents and packaging configuration. A parametric approach was used to evaluate the maximum quantity of molecular hydrogen that can be expected to evolve in two DOT 6M 30-gallon drums in support of receipt and subsequent interim storage prior to canyon processing. These drums are two of three drums scheduled for shipment from INTEC to SRS as part of the decommissioning effort of the INTEC facility. The three DOT 6M drums will be received at L-Area in SRS and stored for up to 13-years prior to final disposition at HB-Line in 2020. Results of the current analysis do not include parametric analysis of drum No.20102 containing 114/133 SAL (salvage) which contains UO{sub 3} powder. This drum has not been identified as containing polymeric materials and a conservative calculation indicates that the maximum gross molecular hydrogen production due to the radiolysis of adsorbed moisture would yield a production rate of 5.1-cm{sup 3}/yr, driven primarily by the large surface are to volume ratio of the oxide powder. The remaining two drums, No.3031 and No.3598 contain polymer

  11. Atmospheric chemistry of the reaction ClO + O2 reversible reaction ClO (center dot) O2: Where it stands, what needs to be done, and why?

    NASA Technical Reports Server (NTRS)

    Prasad, Sheo S.; Lee, Timothy J.

    1994-01-01

    Possible existence and chemistry of ClO (center dot) O2 was originally proposed to explain the Norrish-Neville effect that O2 suppresses chlorine photosensitized loss of ozone. It was also thought that ClO (center dot) O2 might have some atmospheric chemistry significance. Recently, doubts have been cast on this proposal, because certain laboratory data seem to imply that the equilibrium constant of the title reaction is so small that ClO (center dot) O2 may be too unstable to matter. However, those data create only a superficial illusion to that effect, because on a closer analysis they do not disprove a moderately stable and chemically significant ClO (center dot) O2. Furthermore, our state-of-the-science accurate computational chemistry calculations also suggest that ClO (center dot) O2 may be a weakly bound ClOOO radical with a reactive (2)A ground electronic state. There is therefore a need to design and perform definitive experimental tests of the existence and chemistry of the ClO (center dot) O2 species, which we discuss and which have the potential to mediate the chlorine-catalyzed stratospheric ozone depletion.

  12. Anionic complexes of F- and Cl- with substituted methanes: Hydrogen, halogen, and tetrel bonds

    NASA Astrophysics Data System (ADS)

    Del Bene, Janet E.; Alkorta, Ibon; Elguero, José

    2016-07-01

    Ab initio MP2/aug‧-cc-pVTZ calculations have been carried out to investigate the anionic complexes X-:CX(FnH3-n), for X = F, Cl, and n = 0-3. These complexes are stabilized by tetrel, hydrogen, and halogen bonds. Hydrogen-bonded complexes are the most stable complexes and halogen-bonded complexes are the least stable, with one exception. Charge-transfer across intermolecular bonds stabilizes all complexes, and occurs from the anion lone-pair to a σ∗ orbital of the substituted methane. EOM-CCSD spin-spin coupling constants 1tJ(X-C) across intermolecular tetrel bonds, 2hJ(C-X) across hydrogen bonds, and 1xJ(Cl-Cl) and 2xJ(C-Cl) across halogen bonds correlate with intermolecular distances.

  13. Investigation of the hydrogenation of SiCl4

    NASA Technical Reports Server (NTRS)

    Mui, J. Y. P.; Seyferth, D.

    1981-01-01

    A laboratory scale pressure reactor was constructed to study the 3 SiCl + 2H2 + Si yields 4 SiHCl3 reaction at pressures up to 500 psig. Reaction kinetic measurements were carried out as a function of reactor pressure, reaction temperature and H2/SiCl4 feed ratio. Based on the reaction kinetic data, the hydroclorination of SiCl4 and m.g. silicon metal is found to be an efficient process to produce SiHCl3 in good conversions and in high yields. Copper is an effective catalyst. Results of the corrosion study show that conventional nickel chromium alloys are suitable material of construction for the hydrochlorination reactor. The hydrochlorination reaction is relatively insensitive to external process parameters such as silicon particle size distribution and the impurities in the m.g. silicon metal.

  14. Carbon quantum dots coated BiVO{sub 4} inverse opals for enhanced photoelectrochemical hydrogen generation

    SciTech Connect

    Nan, Feng; Shen, Mingrong; Fang, Liang E-mail: lfang@suda.edu.cn; Kang, Zhenhui E-mail: lfang@suda.edu.cn; Wang, Junling

    2015-04-13

    Carbon quantum dots (CQDs) coated BiVO{sub 4} inverse opal (io-BiVO{sub 4}) structure that shows dramatic improvement of photoelectrochemical hydrogen generation has been fabricated using electrodeposition with a template. The io-BiVO{sub 4} maximizes photon trapping through slow light effect, while maintaining adequate surface area for effective redox reactions. CQDs are then incorporated to the io-BiVO{sub 4} to further improve the photoconversion efficiency. Due to the strong visible light absorption property of CQDs and enhanced separation of the photoexcited electrons, the CQDs coated io-BiVO{sub 4} exhibit a maximum photo-to-hydrogen conversion efficiency of 0.35%, which is 6 times higher than that of the pure BiVO{sub 4} thin films. This work is a good example of designing composite photoelectrode by combining quantum dots and photonic crystal.

  15. Carbon quantum dots coated BiVO4 inverse opals for enhanced photoelectrochemical hydrogen generation

    NASA Astrophysics Data System (ADS)

    Nan, Feng; Kang, Zhenhui; Wang, Junling; Shen, Mingrong; Fang, Liang

    2015-04-01

    Carbon quantum dots (CQDs) coated BiVO4 inverse opal (io-BiVO4) structure that shows dramatic improvement of photoelectrochemical hydrogen generation has been fabricated using electrodeposition with a template. The io-BiVO4 maximizes photon trapping through slow light effect, while maintaining adequate surface area for effective redox reactions. CQDs are then incorporated to the io-BiVO4 to further improve the photoconversion efficiency. Due to the strong visible light absorption property of CQDs and enhanced separation of the photoexcited electrons, the CQDs coated io-BiVO4 exhibit a maximum photo-to-hydrogen conversion efficiency of 0.35%, which is 6 times higher than that of the pure BiVO4 thin films. This work is a good example of designing composite photoelectrode by combining quantum dots and photonic crystal.

  16. The Interplay of Quantum Confinement and Hydrogenation in Amorphous Silicon Quantum Dots.

    PubMed

    Askari, Sadegh; Svrcek, Vladmir; Maguire, Paul; Mariotti, Davide

    2015-12-22

    Hydrogenation in amorphous silicon quantum dots (QDs) has a dramatic impact on the corresponding optical properties and band energy structure, leading to a quantum-confined composite material with unique characteristics. The synthesis of a-Si:H QDs is demonstrated with an atmospheric-pressure plasma process, which allows for accurate control of a highly chemically reactive non-equilibrium environment with temperatures well below the crystallization temperature of Si QDs.

  17. Electromagnetically induced transparency in a spherical quantum dot with hydrogenic impurity in the external magnetic field

    NASA Astrophysics Data System (ADS)

    Pavlović, Vladan; Stevanović, Ljiljana

    2016-04-01

    In this paper we analyzed the realization of the electromagnetically induced transparency (EIT) effect in the spherical quantum dot with on-center hydrogenic impurity under the influence of the external magnetic field. Three energy levels of hydrogen impurity 1s0, 2p-1, and 3d-2, together with the probe and control laser fields, which induce σ- transitions between the given states, form a ladder configuration. Optical Bloch equations for such a system are solved in a stationary regime. Dependence of the susceptibility for such a system on the Rabi frequency of the control field, intensity of the external magnetic field, detuning of the control field, and decay rates coefficients are then discussed in detail. Finally, the explanation in dressed state picture is given.

  18. Carbon quantum dots as novel sensitizers for photoelectrochemical solar hydrogen generation and their size-dependent effect

    NASA Astrophysics Data System (ADS)

    Yu, Xuelian; Liu, Rongji; Zhang, Guangjin; Cao, Hongbin

    2013-08-01

    As a result of global energy needs, much research has been devoted to the conversion of solar energy to various usable forms, such as chemical energy in the form of hydrogen via water splitting. To make the conversion methods efficient, economically practical, and industrially scalable, sensitizers capable of utilizing visible and near infrared (IR) light need to be developed. Herein, water-soluble, colloidally stable carbon quantum dots (CQDs) are successfully synthesized by a facile one-step alkali-assisted electrochemical method. Owing to their broad visible light absorption, upconversion luminescence properties and efficient electron injection to TiO2, these CQDs can be used as the sensitizer for photoelectrochemical cells and show an optimized photocurrent of 1.2 mA cm-2 at 0 V versus Ag/AgCl under 100 mW cm-2 simulated sunlight. The above results indicate that the elementally abundant and environmentally friendly CQDs, as a novel sensitizer, can surely be employed to make full use of the visible spectrum of sunlight for their application in photovoltaic devices.

  19. 40 CFR 266.107 - Standards to control hydrogen chloride (HCl) and chlorine gas (Cl2) emissions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 26 2010-07-01 2010-07-01 false Standards to control hydrogen chloride... Industrial Furnaces § 266.107 Standards to control hydrogen chloride (HCl) and chlorine gas (Cl2) emissions. (a) General. The owner or operator must comply with the hydrogen chloride (HCl) and chlorine...

  20. 40 CFR 266.107 - Standards to control hydrogen chloride (HCl) and chlorine gas (Cl2) emissions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 27 2014-07-01 2014-07-01 false Standards to control hydrogen chloride... Industrial Furnaces § 266.107 Standards to control hydrogen chloride (HCl) and chlorine gas (Cl2) emissions. (a) General. The owner or operator must comply with the hydrogen chloride (HCl) and chlorine...

  1. 40 CFR 266.107 - Standards to control hydrogen chloride (HCl) and chlorine gas (Cl2) emissions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 27 2011-07-01 2011-07-01 false Standards to control hydrogen chloride... Industrial Furnaces § 266.107 Standards to control hydrogen chloride (HCl) and chlorine gas (Cl2) emissions. (a) General. The owner or operator must comply with the hydrogen chloride (HCl) and chlorine...

  2. 40 CFR 266.107 - Standards to control hydrogen chloride (HCl) and chlorine gas (Cl2) emissions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 28 2012-07-01 2012-07-01 false Standards to control hydrogen chloride... Industrial Furnaces § 266.107 Standards to control hydrogen chloride (HCl) and chlorine gas (Cl2) emissions. (a) General. The owner or operator must comply with the hydrogen chloride (HCl) and chlorine...

  3. 40 CFR 266.107 - Standards to control hydrogen chloride (HCl) and chlorine gas (Cl2) emissions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 28 2013-07-01 2013-07-01 false Standards to control hydrogen chloride... Industrial Furnaces § 266.107 Standards to control hydrogen chloride (HCl) and chlorine gas (Cl2) emissions. (a) General. The owner or operator must comply with the hydrogen chloride (HCl) and chlorine...

  4. Photoluminescence of MoS2 quantum dots quenched by hydrogen peroxide: A fluorescent sensor for hydrogen peroxide

    NASA Astrophysics Data System (ADS)

    Gan, Zhixing; Gui, Qingfeng; Shan, Yun; Pan, Pengfei; Zhang, Ning; Zhang, Lifa

    2016-09-01

    By cutting MoS2 microcrystals to quantum dots (QDs) of sizes below 10 nm, the photoluminescence (PL) at ca. 450 nm can be detected easily due to the quantum confinement effects across the 2D planes. The PL is stable under continuous irradiation of UV light but gradually quenches when treated with an increasing concentration of hydrogen peroxide. Time-resolved PL and Raman spectra imply that H2O2 causes the partial oxidation of MoS2 QDs. First-principles calculations reveal that the MoS2 QDs with oxygen impurity are of indirect bandgap structures showing no notable PL. And absorption spectra verify that the PL of MoS2 QDs quenched by H2O2 is attributed to the oxidation. The integrated PL intensity and H2O2 concentration show an exponential relationship in the range of 2-20 μM, suggesting that MoS2 QDs are potential fluorescent probes for hydrogen peroxide sensing in a physiological environment.

  5. Hydrolysis of CuCl{sub 2} in the Cu-Cl thermochemical cycle for hydrogen production : experimental studies using a spray reactor with an ultrasonic atomizer.

    SciTech Connect

    Ferrandon, M. S.; Lewis, M. A.; Alvarez, F.; Shafirovich, E.; Chemical Sciences and Engineering Division; Univ. of Texas at El Paso

    2010-03-01

    The Cu-Cl thermochemical cycle is being developed as a hydrogen production method. Prior proof-of-concept experimental work has shown that the chemistry is viable while preliminary modeling has shown that the efficiency and cost of hydrogen production have the potential to meet DOE's targets. However, the mechanisms of CuCl{sub 2} hydrolysis, an important step in the Cu-Cl cycle, are not fully understood. Although the stoichiometry of the hydrolysis reaction, 2CuCl{sub 2} + H{sub 2}O {leftrightarrow} Cu{sub 2}OCl{sub 2} + 2HCl, indicates a necessary steam-to-CuCl{sub 2} molar ratio of 0.5, a ratio as high as 23 has been typically required to obtain near 100% conversion of the CuCl{sub 2} to the desired products at atmospheric pressure. It is highly desirable to conduct this reaction with less excess steam to improve the process efficiency. Per Le Chatelier's Principle and according to the available equilibrium-based model, the needed amount of steam can be decreased by conducting the hydrolysis reaction at a reduced pressure. In the present work, the experimental setup was modified to allow CuCl{sub 2} hydrolysis in the pressure range of 0.4-1 atm. Chemical and XRD analyses of the product compositions revealed the optimal steam-to-CuCl{sub 2} molar ratio to be 20-23 at 1 atm pressure. The experiments at 0.4 atm and 0.7 atm showed that it is possible to lower the steam-to-CuCl{sub 2} molar ratio to 15, while still obtaining good yields of the desired products. An important effect of running the reaction at reduced pressure is the significant decrease of CuCl concentration in the solid products, which was not predicted by prior modeling. Possible explanations based on kinetics and residence times are suggested.

  6. Organic Polymer Dots as Photocatalysts for Visible Light-Driven Hydrogen Generation.

    PubMed

    Wang, Lei; Fernández-Terán, Ricardo; Zhang, Lei; Fernandes, Daniel L A; Tian, Lei; Chen, Hong; Tian, Haining

    2016-09-26

    For the first time, organic semiconducting polymer dots (Pdots) based on poly[(9,9'-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1',3} thiadiazole)] (PFBT) and polystyrene grafting with carboxyl-group-functionalized ethylene oxide (PS-PEG-COOH) are introduced as a photocatalyst towards visible-light-driven hydrogen generation in a completely organic solvent-free system. With these organic Pdots as the photocatalyst, an impressive initial rate constant of 8.3 mmol h(-1)  g(-1) was obtained for visible-light-driven hydrogen production, which is 5-orders of magnitude higher than that of pristine PFBT polymer under the same catalytic conditions. Detailed kinetics studies suggest that the productive electron transfer quench of the excited state of Pdots by an electron donor is about 40 %. More importantly, we also found that the Pdots can tolerate oxygen during catalysis, which is crucial for further application of this material for light-driven water splitting. PMID:27604393

  7. Charge Transfer Dynamics in Semiconductor Quantum Dots Relevant to Solar Hydrogen Production

    NASA Astrophysics Data System (ADS)

    Krauss, Todd

    Artificial conversion of sunlight to chemical fuels has attracted attention for several decades as a potential source of clean, renewable energy. For example, in light-driven proton reduction to molecular hydrogen, a light-absorbing molecule (the photosensitizer) rapidly transfers a photoexcited electron to a catalyst for reducing protons. We recently found that CdSe quantum dots (QDs) and simple aqueous Ni2+ salts in the presence of a sacrificial electron donor form a highly efficient, active, and robust system for photochemical reduction of protons to molecular hydrogen. To understand why this system has such extraordinary catalytic behavior, ultrafast transient absorption (TA) spectroscopy studies of electron transfer (ET) processes from the QDs to the Ni catalysts were performed. CdSe QDs transfer photoexcited electrons to a Ni-dihydrolipoic acid (Ni-DHLA) catalyst complex extremely fast and with high efficiency. Even under high fluence, the relative fraction of TA signal due to ET remains well over 80%, and depopulation from exciton-exciton annihilation is minimal (6%). We also found that increasing QD size and/or shelling the core CdSe QDs with a shell of CdS slowed the ET rate, in agreement with the relative efficiency of photochemical H2 generation. The extremely fast ET provides a fundamental explanation for the exceptional photocatalytic H2 activity of the CdSe QD/Ni-DHLA system and guides new directions for further improvements.

  8. Enhanced photoelectric performance of PbS/CdS quantum dot co-sensitized solar cells via hydrogenated TiO2 nanorod arrays.

    PubMed

    Chen, Yanli; Tao, Qiang; Fu, Wuyou; Yang, Haibin; Zhou, Xiaoming; Su, Shi; Ding, Dong; Mu, Yannan; Li, Xue; Li, Minghui

    2014-08-28

    The enhanced photoelectric performance of quantum dot sensitized solar cells via hydrogenated TiO2 is proposed. The best energy conversion efficiency is 1.5 times higher than cells without hydrogen treatment. We demonstrated that introducing oxygen vacancies by hydrogenation is an effective and feasible method for enhanced photoelectric performance.

  9. Efficient and limiting reactions in aqueous light-induced hydrogen evolution systems using molecular catalysts and quantum dots.

    PubMed

    Gimbert-Suriñach, Carolina; Albero, Josep; Stoll, Thibaut; Fortage, Jérôme; Collomb, Marie-Noëlle; Deronzier, Alain; Palomares, Emilio; Llobet, Antoni

    2014-05-28

    Hydrogen produced from water and solar energy holds much promise for decreasing the fossil fuel dependence. It has recently been proven that the use of quantum dots as light harvesters in combination with catalysts is a valuable strategy to obtain photogenerated hydrogen. However, the light to hydrogen conversion efficiency of these systems is reported to be lower than 40%. The low conversion efficiency is mainly due to losses occurring at the different interfacial charge-transfer reactions taking place in the multicomponent system during illumination. In this work we have analyzed all the involved reactions in the hydrogen evolution catalysis of a model system composed of CdTe quantum dots, a molecular cobalt catalyst and vitamin C as sacrificial electron donor. The results demonstrate that the electron transfer from the quantum dots to the catalyst occurs fast enough and efficiently (nanosecond time scale), while the back electron transfer and catalysis are much slower (millisecond and microsecond time scales). Further improvements of the photodriven proton reduction should focus on the catalytic rate enhancement, which should be at least in the hundreds of nanoseconds time scale.

  10. Reduction of hazards from copper(I) chloride in a Cu-Cl thermochemical hydrogen production plant.

    PubMed

    Ghandehariun, Samane; Wang, Zhaolin; Rosen, Marc A; Naterer, Greg F

    2012-08-30

    The copper-chlorine cycle of thermochemical water splitting, using various heat sources, is a promising technology for hydrogen production. The chemical hazards accompanying the new technology affect significantly the industrialization of the cycle, but have scarcely been examined. This paper addresses this need by examining the copper(I) chloride (CuCl) hazards that may be generated in the cycle. Regardless of the variations of Cu-Cl cycle, copper(I) chloride is always present, serving as an intermediate compound that may cause health concerns. In this paper, the CuCl hazards are quantified for each process from the generation source of the hazards along with the paths where the CuCl may be present. The processes of greatest relevance include oxygen production, heat recovery, solidification, and dissolution. The options for reducing the CuCl hazards in a Cu-Cl thermochemical hydrogen production plant are evaluated from the perspectives of variations of the Cu-Cl cycle, process integration, heat recovery, and equipment design. It is concluded that using the intake reactant Cu(2)OCl(2) for the oxygen production step to absorb CuCl vapor is the most preferable option compared with other alternatives such as absorbing CuCl vapor with water or CuCl(2), building additional structures inside the oxygen production reactor, and cooling the exiting gas at the outlet of the oxygen reactor.

  11. Brightly Luminescent and Color-Tunable Colloidal CH3NH3PbX3 (X = Br, I, Cl) Quantum Dots: Potential Alternatives for Display Technology.

    PubMed

    Zhang, Feng; Zhong, Haizheng; Chen, Cheng; Wu, Xian-gang; Hu, Xiangmin; Huang, Hailong; Han, Junbo; Zou, Bingsuo; Dong, Yuping

    2015-04-28

    Organometal halide perovskites are inexpensive materials with desirable characteristics of color-tunable and narrow-band emissions for lighting and display technology, but they suffer from low photoluminescence quantum yields at low excitation fluencies. Here we developed a ligand-assisted reprecipitation strategy to fabricate brightly luminescent and color-tunable colloidal CH3NH3PbX3 (X = Br, I, Cl) quantum dots with absolute quantum yield up to 70% at room temperature and low excitation fluencies. To illustrate the photoluminescence enhancements in these quantum dots, we conducted comprehensive composition and surface characterizations and determined the time- and temperature-dependent photoluminescence spectra. Comparisons between small-sized CH3NH3PbBr3 quantum dots (average diameter 3.3 nm) and corresponding micrometer-sized bulk particles (2-8 μm) suggest that the intense increased photoluminescence quantum yield originates from the increase of exciton binding energy due to size reduction as well as proper chemical passivations of the Br-rich surface. We further demonstrated wide-color gamut white-light-emitting diodes using green emissive CH3NH3PbBr3 quantum dots and red emissive K2SiF6:Mn(4+) as color converters, providing enhanced color quality for display technology. Moreover, colloidal CH3NH3PbX3 quantum dots are expected to exhibit interesting nanoscale excitonic properties and also have other potential applications in lasers, electroluminescence devices, and optical sensors. PMID:25824283

  12. Characterisation of potential barriers in a donor quantum dot defined by hydrogen resist lithography

    NASA Astrophysics Data System (ADS)

    Fuhrer, Andreas; Pascher, Nikola

    We use a four terminal donor quantum dot (QD) to characterize potential barriers between degenerately doped nanoscale contacts. The QD is fabricated by hydrogen resist lithography on Si(001) in combination with n-type doping from the gas-phase. The four contacts have different separations (d = 9, 12, 16 and 29 nm) to a central 6 nm x 6 nm island, leading to different tunnel- and capacitive coupling. We use cryogenic transport measurements in the Coulomb blockade regime to simultaneously probe current flow in the four terminals for various voltage configurations. The magnitude of the measured tunnelling currents as a function of applied bias and contact separation sets a limit of about 15 nm for tunnelling contacts and shows a strong increase of the barrier transmission with applied bias. Using a constant interaction picture we extract the mutual capacitances between the QD and the four contacts which are found to be in excellent agreement with numerically calculated values. Our results contribute to a better understanding of tunnelling barriers and gate electrodes in planar dopant devices and pave the way towards reliable quantum device fabrication at the atomic scale. Support from EU grants PAMS, SiSpin, SiAM and from Swiss NCCR QSIT is gratefully acknowledged.

  13. Nanoparticles based on quantum dots and a luminol derivative: implications for in vivo imaging of hydrogen peroxide by chemiluminescence resonance energy transfer.

    PubMed

    Lee, Eun Sook; Deepagan, V G; You, Dong Gil; Jeon, Jueun; Yi, Gi-Ra; Lee, Jung Young; Lee, Doo Sung; Suh, Yung Doug; Park, Jae Hyung

    2016-03-18

    Overproduction of hydrogen peroxide is involved in the pathogenesis of inflammatory diseases such as cancer and arthritis. To image hydrogen peroxide via chemiluminescence resonance energy transfer in the near-infrared wavelength range, we prepared quantum dots functionalized with a luminol derivative. PMID:26857551

  14. New amide-chloride phases in the Li-Al-N-H-Cl system: formation and hydrogen storage behaviour.

    PubMed

    Fernández Albanesi, L; Garroni, S; Enzo, S; Gennari, F C

    2016-04-01

    New amide-chloride phases were successfully synthesized by mechanical milling of the LiNH2-AlCl3 mixture at a molar ratio of 1 : 0.11 and further heating at 150 °C under argon (0.1 MPa) or under hydrogen pressure (0.7 MPa). Powder X-ray diffraction measurements as a function of milling time increase revealed that the milling of the LiNH2-0.11AlCl3 mixture results in the formation of a FCC solid solution with an excess of LiNH2. Subsequent heating of the LiNH2-0.11AlCl3 sample ball milled for 5 hours at 150 °C under argon or under hydrogen induces the appearance of an amide-chloride phase isostructural with cubic Li4(NH2)3Cl. This Li-Al-N-H-Cl phase transforms progressively into the trigonal phase after prolonged heating at 300 °C under hydrogen pressure. The thermal behaviour of the amide-chloride without and with LiH addition displays dissimilar decomposition pathways. The decomposition of amide-chloride alone involves the formation of ammonia and hydrogen from 120 to 300 °C. Conversely, the amide-chloride material in the presence of LiH only releases hydrogen avoiding the emission of ammonia. The resultant material is able to be rehydrogenated under moderate conditions (300 °C, 0.7 MPa H2), providing a new reversible hydrogen storage system.

  15. Diamagnetic susceptibility of a hydrogenic donor in a group IV-VI quantum dot-quantum well heterostructure

    NASA Astrophysics Data System (ADS)

    Saravanamoorthy, S. N.; Peter, A. John

    2016-05-01

    Electronic properties of a hydrogenic donor impurity in a CdSe/Pb0.8Cd0.2Se/CdSe quantum dot quantum well system are investigated for various radii of core with shell materials. Confined energies are obtained taking into account the geometrical size of the system and thereby the donor binding energies are found. The diamagnetic susceptibility is estimated for a confined shallow donor in the well system. The results show that the diamagnetic susceptibility strongly depends on core and shell radii and it is more sensitive to variations of the geometrical size of the well material.

  16. Effect of Rasbha spin-orbit interaction on the ground state energy of a hydrogenic D{sup 0} complex in a Gaussian quantum dot

    SciTech Connect

    Boda, Aalu Kumar, D. Sanjeev; Chatterjee, Ashok; Mukhopadhyay, Soma

    2015-06-24

    The ground state energy of a hydrogenic D{sup 0} complex trapped in a three-dimensional GaAs quantum dot with Gaussian confinement is calculated variationally incorporating the effect of Rashba spin-orbit interaction. The results are obtained as a function of the quantum dot size and the Rashba spin-orbit interaction. The results show that the Rashba interaction reduces the ground state energy of the system.

  17. Si quantum dots embedded in an amorphous SiC matrix: nanophase control by non-equilibrium plasma hydrogenation.

    PubMed

    Cheng, Qijin; Tam, Eugene; Xu, Shuyan; Ostrikov, Kostya Ken

    2010-04-01

    Nanophase nc-Si/a-SiC films that contain Si quantum dots (QDs) embedded in an amorphous SiC matrix were deposited on single-crystal silicon substrates using inductively coupled plasma-assisted chemical vapor deposition from the reactive silane and methane precursor gases diluted with hydrogen at a substrate temperature of 200 degrees C. The effect of the hydrogen dilution ratio X (X is defined as the flow rate ratio of hydrogen-to-silane plus methane gases), ranging from 0 to 10.0, on the morphological, structural, and compositional properties of the deposited films, is extensively and systematically studied by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Raman spectroscopy, Fourier-transform infrared absorption spectroscopy, and X-ray photoelectron spectroscopy. Effective nanophase segregation at a low hydrogen dilution ratio of 4.0 leads to the formation of highly uniform Si QDs embedded in the amorphous SiC matrix. It is also shown that with the increase of X, the crystallinity degree and the crystallite size increase while the carbon content and the growth rate decrease. The obtained experimental results are explained in terms of the effect of hydrogen dilution on the nucleation and growth processes of the Si QDs in the high-density plasmas. These results are highly relevant to the development of next-generation photovoltaic solar cells, light-emitting diodes, thin-film transistors, and other applications.

  18. Towards visible light hydrogen generation: quantum dot-sensitization via efficient light harvesting of hybrid-TiO2.

    PubMed

    Kim, Kwanghyun; Kim, Myeong-Jong; Kim, Sun-I; Jang, Ji-Hyun

    2013-01-01

    We report pronounced enhancement of photoelectrochemical hydrogen generation of a quantum dot-sensitized hybrid-TiO2 (QD/H-TiO2) electrode that is composed of a mesoporous TiO2 layer sandwiched by a double sided energy harvesting layer consisting of a surface-textured TiO2 inverse opals layer on the bottom and a patterned mesoporous TiO2 layer on the top. CdSe/H-TiO2 exhibits a maximum photocurrent density of ~16.2 mA/cm(2), which is 35% higher than that of the optimized control sample (CdSe/P25), achieved by matching of the bandgap of quantum dot-sensitization with the wavelength where light harvesting of H-TiO2 is observed. Furthermore, CdSe/H-TiO2 under filtered exposure conditions recorded current density of ~14.2 mA/cm(2), the greatest value in the visible range. The excellent performance of the quantum dot-sensitized H-TiO2 suggests that alteration of the photoelectrodes to suitable nanostructures with excellent light absorption may offer optimal strategies for attaining maximum efficiency in a variety of photoconversion systems. PMID:24270426

  19. Towards Visible Light Hydrogen Generation: Quantum Dot-Sensitization via Efficient Light Harvesting of Hybrid-TiO2

    NASA Astrophysics Data System (ADS)

    Kim, Kwanghyun; Kim, Myeong-Jong; Kim, Sun-I.; Jang, Ji-Hyun

    2013-11-01

    We report pronounced enhancement of photoelectrochemical hydrogen generation of a quantum dot-sensitized hybrid-TiO2 (QD/H-TiO2) electrode that is composed of a mesoporous TiO2 layer sandwiched by a double sided energy harvesting layer consisting of a surface-textured TiO2 inverse opals layer on the bottom and a patterned mesoporous TiO2 layer on the top. CdSe/H-TiO2 exhibits a maximum photocurrent density of ~16.2 mA/cm2, which is 35% higher than that of the optimized control sample (CdSe/P25), achieved by matching of the bandgap of quantum dot-sensitization with the wavelength where light harvesting of H-TiO2 is observed. Furthermore, CdSe/H-TiO2 under filtered exposure conditions recorded current density of ~14.2 mA/cm2, the greatest value in the visible range. The excellent performance of the quantum dot-sensitized H-TiO2 suggests that alteration of the photoelectrodes to suitable nanostructures with excellent light absorption may offer optimal strategies for attaining maximum efficiency in a variety of photoconversion systems.

  20. In situ growth of surfactant-free gold nanoparticles on nitrogen-doped graphene quantum dots for electrochemical detection of hydrogen peroxide in biological environments.

    PubMed

    Ju, Jian; Chen, Wei

    2015-02-01

    In this work, we report a green and simple strategy for the in situ growth of surfactant-free Au nanoparticles (Au NPs) on nitrogen-doped graphene quantum dots (Au NPs-N-GQDs). The formation of hybrid was achieved by just mixing the N-GQDs and HAuCl4·4H2O without addition of any other reductant and surfactant. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) characterizations clearly showed the formation of Au nanoparticles with predominantly exposed (111) facets which can provide more adsorption sites. Such nonsurfactant-capped Au NPs can provide naked catalytic surface with highly electrocatalytic activity. The Au NPs-N-GQDs exhibit high sensitivity and selectivity for electrochemical detection of hydrogen peroxide (H2O2) with a low detection limit of 0.12 μM and sensitivity of 186.22 μA/mM cm(2). Importantly, the Au NPs-N-GQDs-based electrochemical biosensor has shown great potential applications for detection of H2O2 levels in human serum samples and that released from human cervical cancer cells with satisfactory results. The present study demonstrates that such novel Au NPs-N-GQDs nanocomposite is promising for fabrication of nonenzymatic H2O2 biosensors. PMID:25533846

  1. ZnO-dotted porous ZnS cluster microspheres for high efficient, Pt-free photocatalytic hydrogen evolution

    PubMed Central

    Wu, Aiping; Jing, Liqiang; Wang, Jianqiang; Qu, Yang; Xie, Ying; Jiang, Baojiang; Tian, Chungui; Fu, Honggang

    2015-01-01

    The Pt-free photocatalytic hydrogen evolution (PHE) has been the focus in the photocatalysis field. Here, the ZnO-dotted porous ZnS cluster microsphere (PCMS) is designed for high efficient, Pt-free PHE. The PCMS is designed through an easy “controlling competitive reaction” strategy by selecting the thiourea as S2− source and Zn(Ac)2·2H2O as Zn source in ethylene glycol medium. Under suitable conditions, one of the PCMS, named PCMS-1, with high SBET specific area of 194 m2g−1, microsphere size of 100 nm and grain size of 3 nm can be obtained. The formation of PCMS is verified by TEM, XAES, XPS, Raman and IR methods. Importantly, a series of the experiments and theoretical calculation demonstrate that the dotting of ZnO not only makes the photo-generated electrons/hole separate efficiently, but also results in the formation of the active catalytic sites for PHE. As a result, the PCMS-1 shows the promising activity up to 367 μmol h−1 under Pt-free condition. The PHE activity has no obvious change after addition 1 wt.% Pt, implying the presence of active catalytic sites for hydrogen evolution in the PCMS-1. The easy synthesis process, low preparation cost of the PCMS makes their large potential for Pt-free PHE. PMID:25748688

  2. Nano-design of quantum dot-based photocatalysts for hydrogen generation using advanced surface molecular chemistry.

    PubMed

    Yu, Weili; Noureldine, Dalal; Isimjan, Tayirjan; Lin, Bin; Del Gobbo, Silvano; Abulikemu, Mutalifu; Hedhili, Mohamed Nejib; Anjum, Dalaver H; Takanabe, Kazuhiro

    2015-01-14

    Efficient photocatalytic hydrogen generation in a suspension system requires a sophisticated nano-device that combines a photon absorber with effective redox catalysts. This study demonstrates an innovative molecular linking strategy for fabricating photocatalytic materials that allow effective charge separation of excited carriers, followed by efficient hydrogen evolution. The method for the sequential replacement of ligands with appropriate molecules developed in this study tethers both quantum dots (QDs), as photosensitizers, and metal nanoparticles, as hydrogen evolution catalysts, to TiO2 surfaces in a controlled manner at the nano-level. Combining hydrophobic and hydrophilic interactions on the surface, CdSe-ZnS core-shell QDs and an Au-Pt alloy were attached to TiO2 without overlapping during the synthesis. The resultant nano-photocatalysts achieved substantially high-performance visible-light-driven photocatalysis for hydrogen evolution. All syntheses were conducted at room temperature and in ambient air, providing a promising route for fabricating visible-light-responsive photocatalysts.

  3. Selective conversion of polyenes to monoenes by RuCl(3) -catalyzed transfer hydrogenation: the case of cashew nutshell liquid.

    PubMed

    Perdriau, Sébastien; Harder, Sjoerd; Heeres, Hero J; de Vries, Johannes G

    2012-12-01

    Cardanol, a constituent of cashew nutshell liquid (CNSL), was subjected to transfer hydrogenation catalyzed by RuCl(3) using isopropanol as a reductant. The side chain of cardanol, which is a mixture of a triene, a diene, and a monoene, was selectively reduced to the monoene. Surprisingly, it is the C8-C9 double bond that is retained with high selectivity. A similar transfer hydrogenation of linoleic acid derivatives succeeded only if the substrate contained an aromatic ring, such as a benzyl ester. TEM and a negative mercury test showed that the catalyst was homogeneous. By using ESI-MS, ruthenium complexes were identified that contained one, two, or even three molecules of substrate, most likely as allyl complexes. The interaction between ruthenium and the aromatic ring determines selectivity in the hydrogenation reaction.

  4. Photocatalytic hydrogen evolution from glycerol and water over nickel-hybrid cadmium sulfide quantum dots under visible-light irradiation.

    PubMed

    Wang, Jiu-Ju; Li, Zhi-Jun; Li, Xu-Bing; Fan, Xiang-Bing; Meng, Qing-Yuan; Yu, Shan; Li, Cheng-Bo; Li, Jia-Xin; Tung, Chen-Ho; Wu, Li-Zhu

    2014-05-01

    Natural photosynthesis offers the concept of storing sunlight in chemical form as hydrogen (H2), using biomass and water. Herein we describe a robust artificial photocatalyst, nickel-hybrid CdS quantum dots (Nih-CdS QDs) made in situ from nickel salts and CdS QDs stabilized by 3-mercaptopropionic acid, for visible-light-driven H2 evolution from glycerol and water. With visible light irradiation for 20 h, 403.2 μmol of H2 was obtained with a high H2 evolution rate of approximately 74.6 μmol h(-1)  mg(-1) and a high turnover number of 38 405 compared to MPA-CdS QDs (mercaptopropionic-acid-stabilized CdS quantum dots). Compared to CdTe QDs and CdSe QDs, the modified CdS QDs show the greatest affinity toward Ni(2+) ions and the highest activity for H2 evolution. X-ray photoelectron spectroscopy (XPS), inductively-coupled plasma atomic emission spectrometry (ICP-AES), and photophysical studies reveal the chemical nature of the Nih-CdS QDs. Electron paramagnetic resonance (EPR) and terephthalate fluorescence measurements clearly demonstrate water splitting to generate ⋅OH radicals. The detection of DMPO-H and DMPO-C radicals adduct in EPR also indicate that ⋅H radicals and ⋅C radicals are the active species in the catalytic cycle. PMID:24692310

  5. A highly efficient noble metal free photocatalytic hydrogen evolution system containing MoP and CdS quantum dots.

    PubMed

    Yin, Shengming; Han, Jianyu; Zou, Yinjun; Zhou, Tianhua; Xu, Rong

    2016-08-14

    We report the construction of a highly efficient noble metal free photocatalytic hydrogen (H2) evolution system using CdS quantum dots as the light absorber and metallic MoP as the cocatalyst. MoP can be prepared by a facile temperature programmed reduction method and small clusters of MoP nanoparticles sized 10-30 nm were obtained by probe ultrasonication. The effect of synthesis conditions on the electrocatalytic and photocatalytic H2 evolution activity of MoP was investigated. The highest H2 evolution rate of 1100 μmol h(-1) can be achieved by the optimized system under visible light (λ≥ 420 nm), which is comparable to that when Pt was used as the cocatalyst. A high quantum efficiency of 45% is obtained at 460 nm irradiation. PMID:27406067

  6. Effects of the large distribution of CdS quantum dot sizes on the charge transfer interactions into TiO2 nanotubes for photocatalytic hydrogen generation.

    PubMed

    González-Moya, Johan R; Garcia-Basabe, Yunier; Rocco, Maria Luiza M; Pereira, Marcelo B; Princival, Jefferson L; Almeida, Luciano C; Araújo, Carlos M; David, Denis G F; da Silva, Antonio Ferreira; Machado, Giovanna

    2016-07-15

    Hydrogen fuels generated by water splitting using a photocatalyst and solar irradiation are currently gaining the strength to diversify the world energy matrix in a green way. CdS quantum dots have revealed a hydrogen generation improvement when added to TiO2 materials under visible-light irradiation. In the present paper, we investigated the performance of TiO2 nanotubes coupled with CdS quantum dots, by a molecular bifunctional linker, on photocatalytic hydrogen generation. TiO2 nanotubes were obtained by anodization of Ti foil, followed by annealing to crystallize the nanotubes into the anatase phase. Afterwards, the samples were sensitized with CdS quantum dots via an in situ hydrothermal route using 3-mercaptopropionic acid as the capping agent. This sensitization technique permits high loading and uniform distribution of CdS quantum dots onto TiO2 nanotubes. The XPS depth profile showed that CdS concentration remains almost unchanged (homogeneous), while the concentration relative to the sulfate anion decreases by more than 80% with respect to the initial value after ∼100 nm in depth. The presence of sulfate anions is due to the oxidation of sulfide and occurs in greater proportion in the material surface. This protection for air oxidation inside the nanotubular matrix seemingly protected the CdS for photocorrosion in sacrificial solution leading to good stability properties proved by long duration, stable photocurrent measurements. The effect of the size and the distribution of sizes of CdS quantum dots attached to TiO2 nanotubes on the photocatalytic hydrogen generation were investigated. The experimental results showed three different behaviors when the reaction time of CdS synthesis was increased in the sensitized samples, i.e. similar, deactivation and activation effects on the hydrogen production with regard to TiO2 nanotubes. The deactivation effect was related to two populations of sizes of CdS, where the population with a shorter band gap acts as a

  7. Effects of the large distribution of CdS quantum dot sizes on the charge transfer interactions into TiO2 nanotubes for photocatalytic hydrogen generation

    NASA Astrophysics Data System (ADS)

    González-Moya, Johan R.; Garcia-Basabe, Yunier; Rocco, Maria Luiza M.; Pereira, Marcelo B.; Princival, Jefferson L.; Almeida, Luciano C.; Araújo, Carlos M.; David, Denis G. F.; Ferreira da Silva, Antonio; Machado, Giovanna

    2016-07-01

    Hydrogen fuels generated by water splitting using a photocatalyst and solar irradiation are currently gaining the strength to diversify the world energy matrix in a green way. CdS quantum dots have revealed a hydrogen generation improvement when added to TiO2 materials under visible-light irradiation. In the present paper, we investigated the performance of TiO2 nanotubes coupled with CdS quantum dots, by a molecular bifunctional linker, on photocatalytic hydrogen generation. TiO2 nanotubes were obtained by anodization of Ti foil, followed by annealing to crystallize the nanotubes into the anatase phase. Afterwards, the samples were sensitized with CdS quantum dots via an in situ hydrothermal route using 3-mercaptopropionic acid as the capping agent. This sensitization technique permits high loading and uniform distribution of CdS quantum dots onto TiO2 nanotubes. The XPS depth profile showed that CdS concentration remains almost unchanged (homogeneous), while the concentration relative to the sulfate anion decreases by more than 80% with respect to the initial value after ˜100 nm in depth. The presence of sulfate anions is due to the oxidation of sulfide and occurs in greater proportion in the material surface. This protection for air oxidation inside the nanotubular matrix seemingly protected the CdS for photocorrosion in sacrificial solution leading to good stability properties proved by long duration, stable photocurrent measurements. The effect of the size and the distribution of sizes of CdS quantum dots attached to TiO2 nanotubes on the photocatalytic hydrogen generation were investigated. The experimental results showed three different behaviors when the reaction time of CdS synthesis was increased in the sensitized samples, i.e. similar, deactivation and activation effects on the hydrogen production with regard to TiO2 nanotubes. The deactivation effect was related to two populations of sizes of CdS, where the population with a shorter band gap acts as a

  8. Effects of the large distribution of CdS quantum dot sizes on the charge transfer interactions into TiO2 nanotubes for photocatalytic hydrogen generation.

    PubMed

    González-Moya, Johan R; Garcia-Basabe, Yunier; Rocco, Maria Luiza M; Pereira, Marcelo B; Princival, Jefferson L; Almeida, Luciano C; Araújo, Carlos M; David, Denis G F; da Silva, Antonio Ferreira; Machado, Giovanna

    2016-07-15

    Hydrogen fuels generated by water splitting using a photocatalyst and solar irradiation are currently gaining the strength to diversify the world energy matrix in a green way. CdS quantum dots have revealed a hydrogen generation improvement when added to TiO2 materials under visible-light irradiation. In the present paper, we investigated the performance of TiO2 nanotubes coupled with CdS quantum dots, by a molecular bifunctional linker, on photocatalytic hydrogen generation. TiO2 nanotubes were obtained by anodization of Ti foil, followed by annealing to crystallize the nanotubes into the anatase phase. Afterwards, the samples were sensitized with CdS quantum dots via an in situ hydrothermal route using 3-mercaptopropionic acid as the capping agent. This sensitization technique permits high loading and uniform distribution of CdS quantum dots onto TiO2 nanotubes. The XPS depth profile showed that CdS concentration remains almost unchanged (homogeneous), while the concentration relative to the sulfate anion decreases by more than 80% with respect to the initial value after ∼100 nm in depth. The presence of sulfate anions is due to the oxidation of sulfide and occurs in greater proportion in the material surface. This protection for air oxidation inside the nanotubular matrix seemingly protected the CdS for photocorrosion in sacrificial solution leading to good stability properties proved by long duration, stable photocurrent measurements. The effect of the size and the distribution of sizes of CdS quantum dots attached to TiO2 nanotubes on the photocatalytic hydrogen generation were investigated. The experimental results showed three different behaviors when the reaction time of CdS synthesis was increased in the sensitized samples, i.e. similar, deactivation and activation effects on the hydrogen production with regard to TiO2 nanotubes. The deactivation effect was related to two populations of sizes of CdS, where the population with a shorter band gap acts as a

  9. Effects of the large distribution of CdS quantum dot sizes on the charge transfer interactions into TiO2 nanotubes for photocatalytic hydrogen generation

    NASA Astrophysics Data System (ADS)

    González-Moya, Johan R.; Garcia-Basabe, Yunier; Rocco, Maria Luiza M.; Pereira, Marcelo B.; Princival, Jefferson L.; Almeida, Luciano C.; Araújo, Carlos M.; David, Denis G. F.; Ferreira da Silva, Antonio; Machado, Giovanna

    2016-07-01

    Hydrogen fuels generated by water splitting using a photocatalyst and solar irradiation are currently gaining the strength to diversify the world energy matrix in a green way. CdS quantum dots have revealed a hydrogen generation improvement when added to TiO2 materials under visible-light irradiation. In the present paper, we investigated the performance of TiO2 nanotubes coupled with CdS quantum dots, by a molecular bifunctional linker, on photocatalytic hydrogen generation. TiO2 nanotubes were obtained by anodization of Ti foil, followed by annealing to crystallize the nanotubes into the anatase phase. Afterwards, the samples were sensitized with CdS quantum dots via an in situ hydrothermal route using 3-mercaptopropionic acid as the capping agent. This sensitization technique permits high loading and uniform distribution of CdS quantum dots onto TiO2 nanotubes. The XPS depth profile showed that CdS concentration remains almost unchanged (homogeneous), while the concentration relative to the sulfate anion decreases by more than 80% with respect to the initial value after ∼100 nm in depth. The presence of sulfate anions is due to the oxidation of sulfide and occurs in greater proportion in the material surface. This protection for air oxidation inside the nanotubular matrix seemingly protected the CdS for photocorrosion in sacrificial solution leading to good stability properties proved by long duration, stable photocurrent measurements. The effect of the size and the distribution of sizes of CdS quantum dots attached to TiO2 nanotubes on the photocatalytic hydrogen generation were investigated. The experimental results showed three different behaviors when the reaction time of CdS synthesis was increased in the sensitized samples, i.e. similar, deactivation and activation effects on the hydrogen production with regard to TiO2 nanotubes. The deactivation effect was related to two populations of sizes of CdS, where the population with a shorter band gap acts as a

  10. The chemistry of boron and titanium diboride formation: Decomposition of TiCl{sub 4} and BCl{sub 3} in hydrogen and helium

    SciTech Connect

    Osterheld, T.H.; Allendorf, M.D.

    1995-12-01

    Measurements of the decomposition of mixtures of boron trichloride (BCl{sub 3}), titanium tetrachloride (TiCl{sub 4}), and hydrogen at elevated temperatures are presented. The decomposition of BCl{sub 3} with hydrogen appears to drive the chemistry in this system. The species depositing boron on the surface contains at least 2 chlorine atoms. Once deposited, the surface chlorine is removed by reaction with hydrogen to form HCl and, presumably, surface B-H bonds.

  11. Hydrogen Sulfide Inhibits the Development of Atherosclerosis with Suppressing CX3CR1 and CX3CL1 Expression

    PubMed Central

    Wu, Duojiao; Zhang, Alian; Gu, Ting; Wang, Liansheng; Wang, Changqian

    2012-01-01

    Hydrogen sulfide, as a novel gaseous mediator, has been suggested to play a key role in atherogenesis. However, the precise mechanisms by which H2S affects atherosclerosis remain unclear. Therefore, the present study aimed to investigate the potential role of H2S in atherosclerosis and the underlying mechanism with respect to chemokines (CCL2, CCL5 and CX3CL1) and chemokine receptors (CCR2, CCR5, and CX3CR1) in macrophages. Mouse macrophage cell line RAW 264.7 or mouse peritoneal macrophages were pre-incubated with saline or NaHS (50 µM, 100 µM, 200 µM), an H2S donor, and then stimulated with interferon-γ (IFN-γ) or lipopolysaccharide (LPS). It was found that NaHS dose-dependently inhibited IFN-γ or LPS-induced CX3CR1 and CX3CL1 expression, as well as CX3CR1-mediated chemotaxis in macrophages. Overexpression of cystathionine γ-lyase (CSE), an enzyme that catalyzes H2S biosynthesis resulted in a significant reduction in CX3CR1 and CX3CL1 expression as well as CX3CR1-mediated chemotaxis in stimulated macrophages. The inhibitory effect of H2S on CX3CR1 and CX3CL1 expression was mediated by modulation of proliferators-activated receptor-γ (PPAR-γ) and NF-κB pathway. Furthermore, male apoE−/− mice were fed a high-fat diet and then randomly given NaHS (1 mg/kg, i.p., daily) or DL-propargylglycine (PAG, 10 mg/kg, i.p., daily). NaHS significantly inhibited aortic CX3CR1 and CX3CL1 expression and impeded aortic plaque development. NaHS had a better anti-atherogenic benefit when it was applied at the early stage of atherosclerosis. However, inhibition of H2S formation by PAG increased aortic CX3CR1 and CX3CL1 expression and exacerbated the extent of atherosclerosis. In addition, H2S had minimal effect on the expression of CCL2, CCL5, CCR2 and CCR5 in vitro and in vivo. In conclusion, these data indicate that H2S hampers the progression of atherosclerosis in fat-fed apoE−/− mice and downregulates CX3CR1 and CX3CL1 expression on macrophages and in lesion

  12. A highly efficient noble metal free photocatalytic hydrogen evolution system containing MoP and CdS quantum dots

    NASA Astrophysics Data System (ADS)

    Yin, Shengming; Han, Jianyu; Zou, Yinjun; Zhou, Tianhua; Xu, Rong

    2016-07-01

    We report the construction of a highly efficient noble metal free photocatalytic hydrogen (H2) evolution system using CdS quantum dots as the light absorber and metallic MoP as the cocatalyst. MoP can be prepared by a facile temperature programmed reduction method and small clusters of MoP nanoparticles sized 10-30 nm were obtained by probe ultrasonication. The effect of synthesis conditions on the electrocatalytic and photocatalytic H2 evolution activity of MoP was investigated. The highest H2 evolution rate of 1100 μmol h-1 can be achieved by the optimized system under visible light (λ >= 420 nm), which is comparable to that when Pt was used as the cocatalyst. A high quantum efficiency of 45% is obtained at 460 nm irradiation.We report the construction of a highly efficient noble metal free photocatalytic hydrogen (H2) evolution system using CdS quantum dots as the light absorber and metallic MoP as the cocatalyst. MoP can be prepared by a facile temperature programmed reduction method and small clusters of MoP nanoparticles sized 10-30 nm were obtained by probe ultrasonication. The effect of synthesis conditions on the electrocatalytic and photocatalytic H2 evolution activity of MoP was investigated. The highest H2 evolution rate of 1100 μmol h-1 can be achieved by the optimized system under visible light (λ >= 420 nm), which is comparable to that when Pt was used as the cocatalyst. A high quantum efficiency of 45% is obtained at 460 nm irradiation. Electronic supplementary information (ESI) available: SEM image with EDS, XPS survey spectrum, XRD and TEM images of MoP samples prepared under different conditions; XRD, TEM, UV-vis and photoluminescence spectra of CdS QDs; H2 evolution activity comparison for different MoP/CdS samples; the effect of pH value on H2 evolution activity of a MoP/CdS system; the XPS spectrum of MoP/CdS after photoreaction; table of literature studies on H2 evolution activity by different noble metal free photocatalytic systems

  13. Single layer of silicon quantum dots in silicon oxide matrix: Investigation of forming gas hydrogenation on photoluminescence properties and study of the composition of silicon rich oxide layers

    NASA Astrophysics Data System (ADS)

    Aliberti, P.; Shrestha, S. K.; Li, Ruoyu; Green, M. A.; Conibeer, G. J.

    2011-07-01

    Structures consisting of a single layer of silicon quantum dots in a SiO 2 matrix show interesting optoelectronic properties and potential use as energy selective filters, which are a crucial component for the realization of the hot carrier solar cell. In this work single layer silicon quantum dots in SiO 2 have been realized using a magnetron sputtering technique. Quantum dots are formed by annealing of a silicon rich oxide layer deposited between a thermally grown SiO 2 layer and a sputtered SiO 2 layer. The effects of a forming gas post-hydrogenation process on the photoluminescence of the single layer of quantum dots have been investigated in order to understand the photoluminescence mechanism. It was found that for sputtered silicon quantum dots in SiO 2 matrix the photoemission mechanisms are primarily due to quantum confinement and does not strongly rely on matrix defects. In addition, physical and optical properties of several thick silicon rich oxide layers, with different chemical compositions, have been investigated in order to optimize the stoichiometry of silicon rich oxide in the single layers.

  14. Intercalation of aliphatic amines into the layered structure of vanadyl(IV) hydrogen phosphate hemihydrate (VOHPO[sub 4][center dot]0. 5H[sub 2]O)

    SciTech Connect

    Guliants, V.V.; Benziger, J.B.; Sundaresan, S. )

    1994-04-01

    The vanadyl(IV) hydrogen phosphate hemihydrate, VOHPO[sub 4][center dot]0.5H[sub 2]O, is a pyrolytic precursor of the vanadyl(IV) pyrophosphate phase, (VO)[sub 2]P[sub 2]O[sub 7], generally believed to be the active phase in the selective oxidation of n-butane into maleic anhydride. Pyrolytic transformation into the pyrophosphate phase occurs with conservation of a morphology of the material. VOHPO[sub 4][center dot]0.5H[sub 2]O is a layered hydrogen phosphate, where -POH groups form interlayer hydrogen bonds with the water molecules shared by two face-linked vanadyl octahedra. The structure of the hemihydrate is similar to that of [alpha]-zirconium hydrogen phosphate ([alpha]-ZrP), where hydrogen bonds are within the same layer and -POH groups are also pointed into the interlayer space. In contrast to [alpha]-ZrP, where extensive data exist, intercalation chemistry of the layered vanadyl(IV) hydrogen phosphate hemihydrate at present is a terra incognita. This paper reports the results of the first systematic study of VOHPO[sub 4][center dot]0.5H[sub 2]O intercalation with aliphatic amines as a new route to novel vanadyl(IV) phosphate phases. N-Alkylamines have been commonly known as excellent intercalation agents for testing the intracrystalline reactivity of layered oxides. Intercalated alkylamines may also facilitate introduction of thermostable guest molecules, or [open quotes]pillars[close quotes], by ion exchange producing microporous materials which can modify catalytic and sorptive properties. 9 refs., 6 figs., 2 tabs.

  15. Diphosphine- and CO-Induced Fragmentation of Chloride-bridged Dinuclear Complex and Cp*Ir(mu-Cl)(3)Re(CO)(3) and Attempted Synthesis of Cp*Ir(mu-Cl)(3)Mn(CO)(3): Spectroscopic Data and X-ray Diffraction Structures of the Pentamethylcyclopentadienyl Compounds [Cp*IrCl{(Z)-Ph2PCH = CHPPh2}][Cl]center dot 2CHCl(3) and Cp*Ir(CO)Cl-2

    SciTech Connect

    Hammons, Casey; Wang, Xiaoping; Nesterov, Vladimir; Richmond, Michael G.

    2010-01-01

    The confacial bioctahedral compound Cp*Ir(mu-Cl)(3)Re(CO)(3) (1) undergoes rapid fragmentation in the presence of the unsaturated diphosphine ligand (Z)-Ph2PCH = CHPPh2 to give the mononuclear compounds [Cp*IrCl {(Z)-Ph2PCH = CHPPh2}][Cl] (2) and fac-ClRe(CO)(3)[(Z)-Ph2PCH = CHPPh2] (3). 2 has been characterized by H-1 and P-31 NMR spectroscopy and X-ray diffraction analysis. 2 center dot 2CHCl(3) crystallizes in the monoclinic space group C2/c, a = 35.023 (8) angstrom, b = 10.189 (2) angstrom, c = 24.003 (6) angstrom, b = 103.340 (3), V = 8,335 (3) angstrom 3, Z = 8, and d(calc) = 1.647 Mg/m(3); R = 0.0383, R-w = 0.1135 for 8,178 reflections with I> 2 sigma(I). The Ir(III) center in 2 exhibits a six-coordinate geometry and displays a chelating diphosphine group. Compound 1 reacts with added CO with fragmentation to yield the known compounds Cp*Ir(CO)Cl-2 (4) and ClRe(CO)(5) (5) in near quantitative yield by IR spectroscopy. Using the protocol established by our groups for the synthesis of 1, we have explored the reaction of [Cp*IrCl2](2) with ClMn(CO)(5) as a potential route to Cp*Ir(mu-Cl)(3)Mn(CO)(3); unfortunately, 4 was the only product isolated from this reaction. The solid-state structure of 4 was determined by X-ray diffraction analysis. 4 crystallizes in the triclinic space group P-1, a = 7.4059 (4) angstrom, b = 7.8940 (4) angstrom, c = 11.8488 (7) angstrom, alpha = 80.020 (1), beta = 79.758 (1), gamma = 68.631 (1), V = 630.34 (6) angstrom(3), Z = 2, and d(calc) = 2.246 Mg/m(3); R = 0.0126, R-w = 0.0329 for 2,754 reflections with I> 2 sigma(I). The expected three-legged piano-stool geometry in 4 has been crystallographically confirmed.

  16. Integration of epitaxially-grown InGaAs/GaAs quantum dot lasers with hydrogenated amorphous silicon waveguides on silicon.

    PubMed

    Yang, Jun; Bhattacharya, Pallab

    2008-03-31

    The monolithic integration of epitaxially-grown InGaAs/GaAs self-organized quantum dot lasers with hydrogenated amorphous silicon (a:Si-H) waveguides on silicon substrates is demonstrated. Hydrogenated amorphous silicon waveguides, formed by plasma-enhanced-chemical-vapor deposition (PECVD), exhibit a propagation loss of approximately 10 dB/cm at a wavelength of 1.05 microm. The laser-waveguide coupling, with coupling coefficient of 22%, is achieved through a 3.2 microm-width groove etched by focused-ion-beam (FIB) milling which creates high-quality etched GaAs facets.

  17. Hydrogen and oxygen isotope fractionation between brucite and aqueous NaCl solutions from 250 to 450°C

    USGS Publications Warehouse

    Saccocia, Peter J.; Seewald, Jeffrey S.; Shanks, Wayne C.

    1998-01-01

    Hydrogen and oxygen isotope fractionation factors between brucite and aqueous NaCl solutions (1000lnαbr-sw) have been calibrated by experiment from 250 to 450°C at 0.5 Kb. For D/H fractionation, 1000lnα br-sw values are as follows: −32 ± 6‰ (250°C, 3.2 wt% NaCl), −21 ± 2‰ (350°C, 10.0 wt% NaCl), and −22 ± 2‰ (450°C, 3.2 wt% NaCl), indicating that brucite is depleted in D relative to coexisting aqueous NaCl solutions. These results are in good agreement with previous D/H fractionation factors determined in the brucite-water system, indicating that any effects of dissolved salt on D/H fractionation are relatively small, particularly in solutions with near seawater salinity. The maximum salt effect (+4‰) was observed in 10.0 wt% NaCl solutions at 350°C, suggesting that the addition of dissolved NaCl increases the amount of deuterium fractionated into mineral structures. For 18O/16O fractionation, 1000lnαbr-sw values in 3.0 wt% NaCl solutions are −6.0 ± 1.3‰, −5.6 ± 0.7‰ and −4.1 ± 0.2‰, at 250, 350, and 450°C, respectively, and −5.8 ± 0.6‰ in 10.0 wt % NaCl at 350°C. These data indicate that brucite is depleted in 18O relative to coexisting aqueous NaCl solutions and that the degree of depletion decreases slightly with increasing temperature and is not strongly dependent on salinity. We calculated 18O/16O brucite-water fractionation factors from available calibrations of the salt-effect on 18O/16O fractionation between coexisting phases. The resulting values were fit to the following equation that is valid from 250 to 450°C 1000ln αbr-w = 9.54 × 106T−2 − 3.53 × 104T−1 + 26.58 where T is temperature in Kelvins. These new data have been used to improve the prediction of 18O/16O fractionation factors in the talc-water and serpentine-water systems by modifying existing empirical bond-water models. The results of this analysis indicate that the δ18O composition of talc-brucite and serpentine

  18. Functionalization of TiO2 with graphene quantum dots for efficient photocatalytic hydrogen evolution

    NASA Astrophysics Data System (ADS)

    Hao, Xuqiang; Jin, Zhiliang; Xu, Jing; Min, Shixiong; Lu, Gongxuan

    2016-06-01

    Graphene quantum dots (GQDs) serve as a novel solid-state electron transfer reagent anchored on TiO2 by in situ photo-assisted strategy and greatly enhanced photocatalytic H2 evolution activity in methanol aqueous solution without the noble mental cocatalyst. The excellent photocatalytic activities were ascribed to the GQDs which act as an excellent electron transporters and acceptors, as well as photosensitizer. GQDs not only acted as efficient electron reservoirs and a solid-state electron transfer reagent from the conduction band of TiO2 to GQDs, but also acted as an excellent photosensitizer to sensitize TiO2, in which the photoinduced electrons transfer from excited GQDs to TiO2 to produce H2. In addition, GQDs is nanoscale fragments of graphene which can provide a larger active surface and greatly increase the contact area with the TiO2, which is conducive to rapidly transfer photo-generated electrons due to the large specific area and high carrier mobility of GQDs. Thus, GQDs improved the photocatalytic activity for H2 evolution.

  19. In situ photochemical synthesis of fluorescent carbon dots for optical sensing of hydrogen peroxide and antioxidants.

    PubMed

    Costas-Mora, Isabel; Romero, Vanesa; Lavilla, Isela; Bendicho, Carlos

    2015-11-01

    A new synthesis approach for obtaining fluorescent carbon dots (CDs) based on UV irradiation of carbohydrates was developed. The photochemical synthesis pathway allows the formation of water soluble CDs of analytical usefulness within one min. CDs obtained by photochemical treatment from the sucrose/NaOH/poly(ethylene glycol) system are monodisperse with an average size of 8 nm as determined by transmission electron microscopy. A dramatic increase in the CDs fluorescence (turn on) is observed when H2O2 is added. The decrease in CDs size occurring by the action of highly oxidant OH radicals gives rise to confinement of emissive energy traps and, in turn, to fluorescence enhancement. Antioxidants such as ascorbic acid and glutathione inhibit the photochemical reaction giving rise to a decrease in fluorescence of the CDs/H2O2 system (turn on-off). The detection limit was 5 µM H2O2 and the repeatability expressed as the relative standard deviation was 3.8% (N=7). The photochemical synthesis of CDs allows building a green, low-cost, safe and fast assay for the detection of H2O2 and antioxidants. An application of the novel fluorescent nanoprobe to H2O2 detection in contact lens cleaning solutions is performed.

  20. Life cycle assessment of nuclear-based hydrogen production via thermochemical water splitting using a copper-chlorine (Cu-Cl) cycle

    NASA Astrophysics Data System (ADS)

    Ozbilen, Ahmet Ziyaettin

    The energy carrier hydrogen is expected to solve some energy challenges. Since its oxidation does not emit greenhouse gases (GHGs), its use does not contribute to climate change, provided that it is derived from clean energy sources. Thermochemical water splitting using a Cu-Cl cycle, linked with a nuclear super-critical water cooled reactor (SCWR), which is being considered as a Generation IV nuclear reactor, is a promising option for hydrogen production. In this thesis, a comparative environmental study is reported of the three-, four- and five-step Cu-Cl thermochemical water splitting cycles with various other hydrogen production methods. The investigation uses life cycle assessment (LCA), which is an analytical tool to identify and quantify environmentally critical phases during the life cycle of a system or a product and/or to evaluate and decrease the overall environmental impact of the system or product. The LCA results for the hydrogen production processes indicate that the four-step Cu-Cl cycle has lower environmental impacts than the three- and five-step Cu-Cl cycles due to its lower thermal energy requirement. Parametric studies show that acidification potentials (APs) and global warming potentials (GWPs) for the four-step Cu-Cl cycle can be reduced from 0.0031 to 0.0028 kg SO2-eq and from 0.63 to 0.55 kg CO2-eq, respectively, if the lifetime of the system increases from 10 to 100 years. Moreover, the comparative study shows that the nuclear-based S-I and the four-step Cu-Cl cycles are the most environmentally benign hydrogen production methods in terms of AP and GWP. GWPs of the S-I and the four-step Cu-Cl cycles are 0.412 and 0.559 kg CO2-eq for reference case which has a lifetime of 60 years. Also, the corresponding APs of these cycles are 0.00241 and 0.00284 kg SO2-eq. It is also found that an increase in hydrogen plant efficiency from 0.36 to 0.65 decreases the GWP from 0.902 to 0.412 kg CO 2-eq and the AP from 0.00459 to 0.00209 kg SO2-eq for the

  1. Effects of Pauli, Rashba and Dresselhaus spin-orbit interactions on electronic states in 2D circular hydrogenic anti-dot

    NASA Astrophysics Data System (ADS)

    Abuali, Z.; Golshan, M. M.; Davatolhagh, S.

    2016-09-01

    The present work is concerned with a report on the effects of Pauli, Rashba and Dresselhaus spin-orbit interactions (SOI) on the energy levels of a 2D circular hydrogenic quantum anti-dot(QAD). To pursue this aim, we first present a brief review on the analytical solutions to the Schrödinger equation of electronic states in a quantum anti-dot when a hydrogenic donor is placed at the center, revealing the degeneracies involved in the ground, first and second excited states. We then proceed by adding the aforementioned spin-orbit interactions to the Hamiltonian and treat them as perturbation, thereby, calculating the energy shifts to the first three states. As we show, the Rashba spin-orbit interaction gives rise to a shift in the energies of the ground and second excited states, while it partially lifts the degeneracy of the first excited state. Our calculations also indicate that the Dresselhaus effect, while keeping the degeneracy of the ground and second excited states intact, removes the degeneracy of the first excited state in the opposite sense. The Pauli spin-orbit interaction, on the other hand, is diagonal in the appropriate bases, and thus its effect is readily calculated. The results show that degeneracy of ℓ = 0 (prevailing in the ground and second excited state) remains but the degeneracy of ℓ = 1 (prevailing in the first excited state) is again partially lifted. Moreover, we present the energy corrections due to the three spin-orbit interactions as functions of anti-dot's radius, Rashba and Dresselhaus strengths discussing how they affect the corresponding states. The material presented in the article conceives the possibility of generating spin currents in the hydrogenic circular anti-dots.

  2. Theoretical Study of Intramolecular, CH [Formula: see text] X (X = N, O, Cl), Hydrogen Bonds in Thiazole Derivatives.

    PubMed

    Castro, Miguel; Nicolás-Vázquez, Inés; Zavala, Jesús I; Sánchez-Viesca, F; Berros, Martha

    2007-05-01

    CH [Formula: see text] X (X = N, O, or Cl) hydrogen bonds formed intramolecularly in 2-methyl-4-(2-chloro-4,5-dimethoxyphenyl)thiazole (Ia), 2-amino-4-(2-chloro-4,5-dimethoxy phenyl)thiazole (Ib), 2-amino-4-(2,4,5-trimethoxyphenyl)thiazole (Ic), and 2-methyl-4-(2,4,5-trimethoxyphenyl)thiazole (Id) were studied by means of all-electron calculations performed with the B3LYP/6-311++G(d,p) method. Computed ground states, in the gas phase, show the presence of a single H-bond, CH [Formula: see text] Cl, in each Ia and Ib moiety, and two H-bonds, CH [Formula: see text] N and CH [Formula: see text] O, for each Ic and Id molecule. H [Formula: see text] Cl, H [Formula: see text] N, and H [Formula: see text] O distances are shorter than the sum of the X and H van der Waals radii. H-bond energies of ≅2.0 kcal/mol were estimated for Ia and Ib and ≅4.0 kcal/mol for Ic and Id. These results agree with those of the theory of atoms in molecules, since bond critical points were found for these H [Formula: see text] X bonds. Finally, the chemical shifts in the (1)H NMR were calculated by the GIAO method; in Ia and Ib they are merely due to the different topological positions of the H atoms. But in Ic and Id the shifts of H [Formula: see text] N and H [Formula: see text] O have signatures of H-bond formations.

  3. Hydrogenic impurity, external electric and magnetic fields effects on the nonlinear optical properties of a multi-layer spherical quantum dot

    NASA Astrophysics Data System (ADS)

    Tanhaei, M. H.; Rezaei, G.

    2016-10-01

    In this work, effects of an on-center hydrogenic impurity, external electric and magnetic fields on the optical rectification coefficient (ORC), second and third harmonic generations (SHG and THG) of a multi-layer spherical quantum dot (MLSQD) are studied. Energy eigenvalues and eigenvectors are calculated using the direct matrix diagonalization method and optical properties are obtained using the compact density matrix approach. Our results reveal that the hydrogenic impurity and external fields have a great influence on these optical quantities. Hydrogenic impurity reduces the magnitude of the resonant peaks and shifts them to the higher energies. An increase in the magnetic (electric) field, leads to increase (decrease) the interval energies and the dipole moment matrix elements. Therefore, resonant peaks of these optical quantities find an obvious blue (red) shift and their magnitudes enhance (diminish) with increasing the external magnetic (electric) field.

  4. The effects of temperature, hydrostatic pressure and size on optical gain for GaAs spherical quantum dot laser with hydrogen impurity

    NASA Astrophysics Data System (ADS)

    Owji, Erfan; Keshavarz, Alireza; Mokhtari, Hosein

    2016-10-01

    In this paper, the effects of temperature, hydrostatic pressure and size on optical gain for GaAs spherical quantum dot laser with hydrogen impurity are investigated. For this purpose, the effects of temperature, pressure and quantum dot size on the band gap energy, effective mass, and dielectric constant are studied. The eigenenergies and eigenstates for valence and conduction band are calculated by using Runge-Kutta numerical method. Results show that changes in the temperature, pressure and size lead to the alteration of the band gap energy and effective mass. Also, increasing the temperature redshifts the optical gain peak and at special temperature ranges lead to increasing or decreasing of it. Further, by reducing the size, temperature-dependent of optical gain is decreased. Additionally, enhancing of the hydrostatic pressure blueshifts the peak of optical gain, and its behavior as a function of pressure which depends on the size. Finally, increasing the radius rises the redshifts of the peak of optical gain.

  5. Enhancement of periodate-hydrogen peroxide chemiluminescence by nitrogen doped carbon dots and its application for the determination of pyrogallol and gallic acid.

    PubMed

    Shah, Syed Niaz Ali; Li, Haifang; Lin, Jin-Ming

    2016-06-01

    A new sensitized chemiluminescence (CL) was developed to broaden the analytical application of KIO4-H2O2 system. The nitrogen doped carbon dots (N-CDs) dramatically boosted the CL intensity of KIO4-H2O2 system which was further enriched by basic medium. In light of EPR analysis, free radical scavenging studies and CL spectra the detail mechanism for the enhancement was conferred in the presence of N-CDs and NaOH. The results suggested that CL of KIO4-H2O2 system in the presence and absence of N-CDs and NaOH proceeds via radical pathway. The enhanced CL was used for the determination of pyrogallol and gallic acid in range of 1.0×10(-4)-1.0×10(-7)M with 4.6×10(-8) and 6.1×10(-8)M limit of detection respectively. The relative standard deviation (RSD) at a concentration of 10(-5) for gallic acid and pyrogallol was 1.4% and 2.3% respectively (n=11). The attained results unveil that the present method is sensitive, faster, simpler and less costly compared to other methods and could be applied to determine polyphenols in real samples.

  6. Stereo-specificity for pro-(R) hydrogen of NAD(P)H during enzyme-catalyzed hydride transfer to CL-20.

    PubMed

    Bhushan, Bharat; Halasz, Annamaria; Hawari, Jalal

    2005-12-01

    A dehydrogenase from Clostridium sp. EDB2 and a diaphorase from Clostridium kluyveri were reacted with CL-20 to gain insights into the enzyme-catalyzed hydride transfer to CL-20, and the enzyme's stereo-specificity for either pro-R or pro-S hydrogens of NAD(P)H. Both enzymes biotransformed CL-20 at rates of 18.5 and 24nmol/h/mg protein, using NADH and NADPH as hydride-source, respectively, to produce a N-denitrohydrogenated product with a molecular weight of 393Da. In enzyme kinetics studies using reduced deuterated pyridine nucleotides, we found a kinetic deuterium isotopic effect of 2-fold on CL-20 biotransformation rate using dehydrogenase enzyme against (R)NADD as a hydride-source compared to either (S)NADD or NADH. Whereas, in case of diaphorase, the kinetic deuterium isotopic effect of about 1.5-fold was observed on CL-20 biotransformation rate using (R)NADPD as hydride-source. In a comparative study with LC-MS, using deuterated and non-deuterated NAD(P)H, we found a positive mass-shift of 1Da in the N-denitrohydrogenated product suggesting the involvement of a deuteride (D(-)) transfer from NAD(P)D. The present study thus revealed that both dehydrogenase and diaphorase enzymes from the two Clostridium species catalyzed a hydride transfer to CL-20 and showed stereo-specificity for pro-R hydrogen of NAD(P)H. PMID:16225844

  7. Photoluminescence properties and crystallization of silicon quantum dots in hydrogenated amorphous Si-rich silicon carbide films

    SciTech Connect

    Wen, Guozhi; Zeng, Xiangbin Wen, Xixin; Liao, Wugang

    2014-04-28

    Silicon quantum dots (QDs) embedded in hydrogenated amorphous Si-rich silicon carbide (α-SiC:H) thin films were realized by plasma-enhanced chemical vapor deposition process and post-annealing. Fluorescence spectroscopy was used to characterize the room-temperature photoluminescence properties. X-ray photoelectron spectroscopy was used to analyze the element compositions and bonding configurations. Ultraviolet visible spectroscopy, Raman scattering, and high-resolution transmission electron microscopy were used to display the microstructural properties. Photoluminescence measurements reveal that there are six emission sub-bands, which behave in different ways. The peak wavelengths of sub-bands P1, P2, P3, and P6 are pinned at about 425.0, 437.3, 465.0, and 591.0 nm, respectively. Other two sub-bands, P4 is red-shifted from 494.6 to 512.4 nm and P5 from 570.2 to 587.8 nm with temperature increasing from 600 to 900 °C. But then are both blue-shifted, P4 to 500.2 nm and P5 to 573.8 nm from 900 to 1200 °C. The X-ray photoelectron spectroscopy analysis shows that the samples are in Si-rich nature, Si-O and Si-N bonds consumed some silicon atoms. The structure characterization displays that a separation between silicon phase and SiC phase happened; amorphous and crystalline silicon QDs synthesized with increasing the annealing temperature. P1, P2, P3, and P6 sub-bands are explained in terms of defect-related emission, while P4 and P5 sub-bands are explained in terms of quantum confinement effect. A correlation between the peak wavelength shift, as well as the integral intensity of the spectrum and crystallization of silicon QDs is supposed. These results help clarify the probable luminescence mechanisms and provide the possibility to optimize the optical properties of silicon QDs in Si-rich α-SiC: H materials.

  8. Influence of the image charge effect on the hydrogen-like impurity-bound polaron in a spherical quantum dot in the presence of an electric field

    NASA Astrophysics Data System (ADS)

    Vartanian, Arshak L.; Vardanyan, Lyudvig A.

    2016-01-01

    We have investigated the influence of an external electric field on the binding energies and polaronic shifts of the ground and some first few excited states of a hydrogenic impurity in a spherical quantum dot by taking into account the image charge effect. By using Landau-Pekar variational method the general analytical expression is obtained for the impurity bound-polaron energies. It has been numerically identified the conditions (electric field, nominal radius of quantum dot, etc.) in which the bound-polaron states can be existence in GaAs quantum dot. We have shown that the polaronic shifts in the binding energy of 1s-like state are the same in cases with and without image charge effect while they for 2s-like state are not coincide and have different monotonic behavior versus confinement potential. Electron-phonon interaction lifts the degeneracy of the 2px-, 2py-, and 2pz-like states of a donor impurity and reduces their binding energies.

  9. Chloride–hydrogen antiporters ClC-3 and ClC-5 drive osteoblast mineralization and regulate fine-structure bone patterning in vitro

    PubMed Central

    Larrouture, Quitterie C; Nelson, Deborah J; Robinson, Lisa J; Liu, Li; Tourkova, Irina; Schlesinger, Paul H; Blair, Harry C

    2015-01-01

    Osteoblasts form an epithelium-like layer with tight junctions separating bone matrix from extracellular fluid. During mineral deposition, calcium and phosphate precipitation in hydroxyapatite liberates 0.8 mole of H+ per mole Ca+2. Thus, acid export is needed for mineral formation. We examined ion transport supporting osteoblast vectorial mineral deposition. Previously we established that Na/H exchangers 1 and 6 are highly expressed at secretory osteoblast basolateral surfaces and neutralize massive acid loads. The Na/H exchanger regulatory factor-1 (NHERF1), a pdz-organizing protein, occurs at mineralizing osteoblast basolateral surfaces. We hypothesized that high-capacity proton transport from matrix into osteoblast cytosol must exist to support acid transcytosis for mineral deposition. Gene screening in mineralizing osteoblasts showed dramatic expression of chloride–proton antiporters ClC-3 and ClC-5. Antibody localization showed that ClC-3 and ClC-5 occur at the apical secretory surface facing the bone matrix and in membranes of buried osteocytes. Surprisingly, the Clcn3−/− mouse has only mildly disordered mineralization. However, Clcn3−/− osteoblasts have large compensatory increases in ClC-5 expression. Clcn3−/− osteoblasts mineralize in vitro in a striking and novel trabecular pattern; wild-type osteoblasts form bone nodules. In mesenchymal stem cells from Clcn3−/− mice, lentiviral ClC-5 shRNA created Clcn3−/−, ClC-5 knockdown cells, validated by western blot and PCR. Osteoblasts from these cells produced no mineral under conditions where wild-type or Clcn3−/− cells mineralize well. We conclude that regulated acid export, mediated by chloride–proton exchange, is essential to drive normal bone mineralization, and that CLC transporters also regulate fine patterning of bone. PMID:26603451

  10. Chloride-hydrogen antiporters ClC-3 and ClC-5 drive osteoblast mineralization and regulate fine-structure bone patterning in vitro.

    PubMed

    Larrouture, Quitterie C; Nelson, Deborah J; Robinson, Lisa J; Liu, Li; Tourkova, Irina; Schlesinger, Paul H; Blair, Harry C

    2015-11-01

    Osteoblasts form an epithelium-like layer with tight junctions separating bone matrix from extracellular fluid. During mineral deposition, calcium and phosphate precipitation in hydroxyapatite liberates 0.8 mole of H(+) per mole Ca(+2). Thus, acid export is needed for mineral formation. We examined ion transport supporting osteoblast vectorial mineral deposition. Previously we established that Na/H exchangers 1 and 6 are highly expressed at secretory osteoblast basolateral surfaces and neutralize massive acid loads. The Na/H exchanger regulatory factor-1 (NHERF1), a pdz-organizing protein, occurs at mineralizing osteoblast basolateral surfaces. We hypothesized that high-capacity proton transport from matrix into osteoblast cytosol must exist to support acid transcytosis for mineral deposition. Gene screening in mineralizing osteoblasts showed dramatic expression of chloride-proton antiporters ClC-3 and ClC-5. Antibody localization showed that ClC-3 and ClC-5 occur at the apical secretory surface facing the bone matrix and in membranes of buried osteocytes. Surprisingly, the Clcn3(-/-) mouse has only mildly disordered mineralization. However, Clcn3(-/-) osteoblasts have large compensatory increases in ClC-5 expression. Clcn3(-/-) osteoblasts mineralize in vitro in a striking and novel trabecular pattern; wild-type osteoblasts form bone nodules. In mesenchymal stem cells from Clcn3(-/-) mice, lentiviral ClC-5 shRNA created Clcn3(-/-), ClC-5 knockdown cells, validated by western blot and PCR. Osteoblasts from these cells produced no mineral under conditions where wild-type or Clcn3(-/-) cells mineralize well. We conclude that regulated acid export, mediated by chloride-proton exchange, is essential to drive normal bone mineralization, and that CLC transporters also regulate fine patterning of bone.

  11. Chloride-hydrogen antiporters ClC-3 and ClC-5 drive osteoblast mineralization and regulate fine-structure bone patterning in vitro.

    PubMed

    Larrouture, Quitterie C; Nelson, Deborah J; Robinson, Lisa J; Liu, Li; Tourkova, Irina; Schlesinger, Paul H; Blair, Harry C

    2015-11-01

    Osteoblasts form an epithelium-like layer with tight junctions separating bone matrix from extracellular fluid. During mineral deposition, calcium and phosphate precipitation in hydroxyapatite liberates 0.8 mole of H(+) per mole Ca(+2). Thus, acid export is needed for mineral formation. We examined ion transport supporting osteoblast vectorial mineral deposition. Previously we established that Na/H exchangers 1 and 6 are highly expressed at secretory osteoblast basolateral surfaces and neutralize massive acid loads. The Na/H exchanger regulatory factor-1 (NHERF1), a pdz-organizing protein, occurs at mineralizing osteoblast basolateral surfaces. We hypothesized that high-capacity proton transport from matrix into osteoblast cytosol must exist to support acid transcytosis for mineral deposition. Gene screening in mineralizing osteoblasts showed dramatic expression of chloride-proton antiporters ClC-3 and ClC-5. Antibody localization showed that ClC-3 and ClC-5 occur at the apical secretory surface facing the bone matrix and in membranes of buried osteocytes. Surprisingly, the Clcn3(-/-) mouse has only mildly disordered mineralization. However, Clcn3(-/-) osteoblasts have large compensatory increases in ClC-5 expression. Clcn3(-/-) osteoblasts mineralize in vitro in a striking and novel trabecular pattern; wild-type osteoblasts form bone nodules. In mesenchymal stem cells from Clcn3(-/-) mice, lentiviral ClC-5 shRNA created Clcn3(-/-), ClC-5 knockdown cells, validated by western blot and PCR. Osteoblasts from these cells produced no mineral under conditions where wild-type or Clcn3(-/-) cells mineralize well. We conclude that regulated acid export, mediated by chloride-proton exchange, is essential to drive normal bone mineralization, and that CLC transporters also regulate fine patterning of bone. PMID:26603451

  12. The linear optical properties of a multi-shell spherical quantum dot of a parabolic confinement for cases with and without a hydrogenic impurity

    NASA Astrophysics Data System (ADS)

    Şahin, Mehmet; Köksal, Koray

    2012-12-01

    Throughout this work, we aim to explore the linear optical properties of a semiconductor multi-shell spherical quantum dot with and without a hydrogenic donor impurity. The core and well layers are defined by the parabolic electronic potentials in the radial direction. The energy levels and corresponding wavefunctions of the structure are calculated by using the shooting technique in the framework of the effective-mass approximation. We investigate the intersublevel absorption coefficients of a single electron and the hydrogenic donor impurity comparatively as a function of the photon energy. In addition, we carry out the effect of a donor impurity and the layer thickness on the oscillator strengths and magnitude and position of absorption coefficient peaks. We illustrate the electron probability distribution and variation of the energy levels in cases with and without the impurity for different thicknesses of layers. This kind of structure gives an opportunity to tune and control the absorption coefficient of the system by changing three different thickness parameters. Also it provides a possibility to separate 0s and 1p electrons in different regions of the quantum dot.

  13. Probing temperature effects on the hydrogen bonding network of the Cl{sup {minus}}(H{sub 2}O){sub 2} cluster

    SciTech Connect

    Dorsett, H.E.; Watts, R.O.; Xantheas, S.S.

    1999-05-06

    The authors have incorporated the flexible RWK2 water potential into the parameterization of a chloride-water interaction potential from first principles calculations and used it to investigate the temperature effects in the infrared (IR) spectrum of Cl{sup {minus}}(H{sub 2}O){sub 2}. They have found that spectral signatures of hydrogen bonding between the two water molecules in the cluster disappear with increasing temperature, a consequence of the weak water-water interaction in the cluster.

  14. Vectorial electron transfer for improved hydrogen evolution by mercaptopropionic-acid-regulated CdSe quantum-dots-TiO2 -Ni(OH)2 assembly.

    PubMed

    Yu, Shan; Li, Zhi-Jun; Fan, Xiang-Bing; Li, Jia-Xin; Zhan, Fei; Li, Xu-Bing; Tao, Ye; Tung, Chen-Ho; Wu, Li-Zhu

    2015-02-01

    A visible-light-induced hydrogen evolution system based on a CdSe quantum dots (QDs)-TiO2 -Ni(OH)2 ternary assembly has been constructed under an ambient environment, and a bifunctional molecular linker, mercaptopropionic acid, is used to facilitate the interaction between CdSe QDs and TiO2 . This hydrogen evolution system works effectively in a basic aqueous solution (pH 11.0) to achieve a hydrogen evolution rate of 10.1 mmol g(-1)  h(-1) for the assembly and a turnover frequency of 5140 h(-1) with respect to CdSe QDs (10 h); the latter is comparable with the highest value reported for QD systems in an acidic environment. X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and control experiments demonstrate that Ni(OH)2 is an efficient hydrogen evolution catalyst. In addition, inductively coupled plasma optical emission spectroscopy and the emission decay of the assembly combined with the hydrogen evolution experiments show that TiO2 functions mainly as the electron mediator; the vectorial electron transfer from CdSe QDs to TiO2 and then from TiO2 to Ni(OH)2 enhances the efficiency for hydrogen evolution. The assembly comprises light antenna CdSe QDs, electron mediator TiO2 , and catalytic Ni(OH)2 , which mimics the strategy of photosynthesis exploited in nature and takes us a step further towards artificial photosynthesis.

  15. Supramolecular arrangement promoted in trans-[PdCl2(HONC10H14O)2]·2H2O by hydrogen bonding

    NASA Astrophysics Data System (ADS)

    Galvão, Adelino M.; Carvalho, M. Fernanda N. N.; Grilo, António L.

    2014-05-01

    Palladium(II) complexes trans-[PdCl2(3-HONC10H14O)2]ṡ2H2O and trans-[PdCl2(2-HONC10H16)2] with similar formulations and molecular geometries display considerably different supramolecular arrangements due to hydrogen bonding involving the oxime substituent (NOH) of the camphor ligand, the halide co-ligand of adjacent molecules and H2O outer-sphere molecules in the case of trans-[PdCl2(3-HONC10H14O)2]ṡ2H2O. The discussion is based on data collected by X-ray diffraction analysis and DFT calculations.

  16. Density functional study of hydrogen bond formation between methanol and organic molecules containing Cl, F, NH2, OH, and COOH functional groups.

    PubMed

    Kolev, Stefan K; St Petkov, Petko; Rangelov, Miroslav A; Vayssilov, Georgi N

    2011-12-01

    Various hydrogen-bonded complexes of methanol with different proton accepting and proton donating molecules containing Cl, F, NH(2), OH, OR, and COOH functional groups have been modeled using DFT with hybrid B3LYP and M05-2X functionals. The latter functional was found to provide more accurate estimates of the structural and thermodynamic parameters of the complexes of halides, amines, and alcohols. The characteristics of these complexes are influenced not only by the principle hydrogen bond of the methanol OH with the proton acceptor heteroatom, but also by additional hydrogen bonds of a C-H moiety with methanol oxygen as a proton acceptor. The contribution of the former hydrogen bond in the total binding enthalpy increases in the order chlorides < fluorides < alcohols < amines, while the contribution of the second type of hydrogen bond increases in the reverse order. A general correlation was found between the binding enthalpy of the complex and the electrostatic potential at the hydrogen center participating in the formation of the hydrogen bond. The calculated binding enthalpies of different complexes were used to clarify which functional groups can potentially form a hydrogen bond to the 2'-OH hydroxyl group in ribose, which is strong enough to block it from participation in the intramolecular catalytic activation of the peptide bond synthesis. Such blocking could result in inhibition of the protein biosynthesis in the living cell if the corresponding group is delivered as a part of a drug molecule in the vicinity of the active site in the ribosome. According to our results, such activity can be accomplished by secondary or tertiary amines, alkoxy groups, deprotonated carboxyl groups, and aliphatic fluorides, but not by the other modeled functional groups. PMID:21992409

  17. Intramolecular N-H···Cl hydrogen bonds in the outer coordination sphere of a bipyridyl bisurea-based ligand stabilize a tetrahedral FeLCl2 complex.

    PubMed

    Gavette, Jesse V; Klug, Christina M; Zakharov, Lev N; Shores, Matthew P; Haley, Michael M; Johnson, Darren W

    2014-07-11

    A bipyridyl-based anion receptor is utilized as a ligand in a tetrahedral FeCl2 complex and demonstrates secondary coordination sphere influence through intramolecular hydrogen bonding to the chloride ligands as evidenced by X-ray crystallography.

  18. Dielectric barrier discharge-assisted one-pot synthesis of carbon quantum dots as fluorescent probes for selective and sensitive detection of hydrogen peroxide and glucose.

    PubMed

    He, Duhong; Zheng, Chengbin; Wang, Qiang; He, Chunlin; Lee, Yong-Ill; Wu, Li; Hou, Xiandeng

    2015-09-01

    In this work, we proposed a dielectric barrier discharge (DBD)-assisted one-pot strategy to fabricate carbon quantum dots (CQDs) using only one reagent N, N-dimethylformamide (DMF) at atmospheric pressure and room temperature. The experimental conditions were carefully investigated, and the prepared CQDs were characterized by using UV-vis spectrophotometer, fluorescence spectrophotometer, Fourier transform infrared (FTIR) spectrometer, transmission electron microscopy (TEM) and X-ray photoelectron spectrometer (XPS). The CQDs have an average size of 3.6 nm in diameter with narrow size distribution, and can be used as highly selective and sensitive fluorescence probes for hydrogen peroxide and glucose, with limits of detection of 3.8 μM and 3.5 μM, respectively.

  19. Infrared absorption of 1-chloro-2-methyl-2-propyl [ṡC(CH3)2CH2Cl] and 2-chloro-2-methylpropyl [ṡCH2C(CH3)2Cl] radicals produced in the addition reactions of Cl with isobutene (i-C4H8) in solid para-hydrogen

    NASA Astrophysics Data System (ADS)

    Chou, Ching-Yin; Lee, Yuan-Pern

    2016-10-01

    The addition reactions of chlorine atom with isobutene (i-C4H8) in solid para-hydrogen (p-H2) were investigated with infrared (IR) absorption spectra. When a p-H2 matrix containing Cl2 and isobutene was irradiated with ultraviolet light at 365 nm, intense lines in a set at 534.5, 1001.0, 1212.9, 1366.0, 2961.6, and 2934.7 cm-1, and several weaker others due to the 1-chloro-2-methyl-2-propyl radical, ṡC(CH3)2CH2Cl, and those in a second set including intense ones at 642.7, 799.2, 1098.2, 1371.8, and 3027.3 cm-1 due to the 2-chloro-2-methylpropyl radical, ṡCH2C(CH3)2Cl, appeared; the ratio of ṡC(CH3)2CH2Cl to ṡCH2C(CH3)2Cl was approximately (3 ± 1):1. The observed wavenumbers and relative intensities agree with the vibrational wavenumbers and IR intensities predicted with the B3PW91/aug-cc-pVTZ method. That the Cl atom adds to both carbons of the C=C bond of isobutene with the terminal site slightly favored is consistent with the energies of products predicted theoretically, but is in contrast to the reaction of Cl + propene in solid p-H2 in which the addition of Cl to mainly the central C atom was previously reported. The role of the p-H2 matrix in affecting the reaction paths is discussed. Absorption lines of the complex i-C4H8ṡCl2 and the dichloro-product anti-1,2-dichloro-2-methylpropane, a-CH2ClCCl(CH3)2, are also characterized.

  20. A comparative study of the chalcogen bond, halogen bond and hydrogen bond S⋯O/Cl/H formed between SHX and HOCl.

    PubMed

    Fang, Yi; Li, An Yong; Ma, Fei Yan

    2015-03-01

    Ab initio quantum chemistry methods were used to analyze the noncovalent interactions between HOCl and SHX (X = F, CN, NC, Cl, Br, NO2, CCH, CH3, H). Three energetic minimal configurations were characterized for each case, where the S center acts as a Lewis acid interacting with O to form a chalcogen bond, as well as a Lewis base interacting with Cl or H of HOCl to form halogen bond and hydrogen bond, respectively. An electronegative substituent such as F, CN, NC and NO2 tends to form a stronger chalcogen bond, while an electropositive substituent such as CCH, CH3 and H is inclined to form a more stable H-bonded complex. The chalcogen-bonded, halogen-bonded and H-bonded complexes are stabilized by charge transfers from Lp(O) to σ*(SX), from Lp(S) to σ*(ClO), and from Lp(S) to σ*(HO), respectively. As a result, the SHX unit becomes positively charged in halogen-bonded and hydrogen-bonded complexes but negatively charged in chalcogen-bonded complexes. Theory of atoms in molecules, natural bond orbital analysis, molecular electrostatic potential and localized molecular orbital energy decomposition analysis were applied to investigate these noncovalent bonds.

  1. Hydrogen Interaction with Metal Halides: the Nuclear Quadrupole Coupling Constant of Gold in the {p}{-H}_2{-AuCl} Complex and Trends in the Other Hydrogen-Coinage Metal Halide Interactions

    NASA Astrophysics Data System (ADS)

    Obenchain, Daniel A.; Grubbs, G. S. Grubbs, Ii; Pickett, Herbert M.; Novick, Stewart E.

    2013-06-01

    The rotational spectrum of p-H_2-AuCl has been measured using a laser ablation equipped FTMW cavity spectrometer. The predicted structure, using a 60 electron core potential and an aug-cc-pVQZ at the MP2 level of theory, shows that H_2 has an r_e = 0.91Å. A predicted value for the eQq(χ_{aa}) of gold required a semi-empirical method using the results of previous AuCl complexes in the gas phase. Transitions have been measured across multiple J levels, and have been used to determine the rotational constants, centrifugal distortion constants, and nuclear quadrupole coupling constants of multiple isotopologues. The o-H_2-AuCl has also been observed. While the monomer value of the eQq of ^{197}Au was determined to be 9.63112(13) MHz in ^{197}Au^{35}Cl, we observed a significant change in the eQq of ^{197}Au in p-H_2-^{197}Au^{35}Cl to a value of -817.9983(36) MHz [0.02728556(12) cm^{-1}], giving rise to a Au hyperfine component splittings of approximately 220 MHz [0.007 cm^{-1}] and suggesting a change in electronic structure with the interaction of H_2. We will present a summary of the hydrogen-coinage metal halide talks given at this conference, including trends in eQq and hydrogen metal halide dissociation energies. D. Figgen, G. Rauhut, M. Dolh, H. Stoll J. Chem. Phys. 311(2005) 227. K. A. Peterson, C. Puzzarini, Theor. Chem. Acc. 114 (2005) 283. C. J. Evans, C. L. Gerry J. Mol. Spectrosc. 203 (2000) 105.

  2. Electric field induced optical gain of a hydrogenic impurity in a Cd{sub 0.8}Zn{sub 0.2}Se/ZnSe parabolic quantum dot

    SciTech Connect

    Jasmine, P. Christina Lily; Peter, A. John

    2015-06-24

    The dependence of electric field on the electronic and optical properties is investigated in a Cd{sub 0.8}Zn{sub 0.2}Se/ZnSe quantum dot. The hydrogenic binding energy, in the presence of electric field, is calculated with the spatial confinement effect. The electric field dependent optical gain with the photon energy is found using compact density matrix method. The results show that the electric field has a great influence on the optical properties of II-VI semiconductor quantum dot.

  3. Plasmonic silver quantum dots coupled with hierarchical TiO2 nanotube arrays photoelectrodes for efficient visible-light photoelectrocatalytic hydrogen evolution

    PubMed Central

    Lian, Zichao; Wang, Wenchao; Xiao, Shuning; Li, Xin; Cui, Yingying; Zhang, Dieqing; Li, Guisheng; Li, Hexing

    2015-01-01

    A plasmonic Ag/TiO2 photocatalytic composite was designed by selecting Ag quantum dots (Ag QDs) to act as a surface plasmon resonance (SPR) photosensitizer for driving the visible-light driven photoelectrocatalytic hydrogen evolution. Vertically oriented hierarchical TiO2 nanotube arrays (H-TiO2-NTAs) with macroporous structure were prepared through a two-step method based on electrochemical anodization. Subsequently, Ag QDs, with tunable size (1.3-21.0 nm), could be uniformly deposited on the H-TiO2 NTAs by current pulsing approach. The unique structure of the as-obtained photoelectrodes greatly improved the photoelectric conversion efficiency. The as-obtained Ag/H-TiO2-NTAs exhibited strong visible-light absorption capability, high photocurrent density, and enhanced photoelectrocatalytic (PEC) activity toward photoelectrocatalytic hydrogen evolution under visible-light irradiation (λ > 420 nm). The enhancement in the photoelectric conversion efficiency and activity was ascribed to the synergistic effects of silver and the unique hierarchical structures of TiO2 nanotube arrays, strong SPR effect, and anti-shielding effect of ultrafine Ag QDs. PMID:26067850

  4. Plasmonic silver quantum dots coupled with hierarchical TiO2 nanotube arrays photoelectrodes for efficient visible-light photoelectrocatalytic hydrogen evolution.

    PubMed

    Lian, Zichao; Wang, Wenchao; Xiao, Shuning; Li, Xin; Cui, Yingying; Zhang, Dieqing; Li, Guisheng; Li, Hexing

    2015-01-01

    A plasmonic Ag/TiO2 photocatalytic composite was designed by selecting Ag quantum dots (Ag QDs) to act as a surface plasmon resonance (SPR) photosensitizer for driving the visible-light driven photoelectrocatalytic hydrogen evolution. Vertically oriented hierarchical TiO2 nanotube arrays (H-TiO2-NTAs) with macroporous structure were prepared through a two-step method based on electrochemical anodization. Subsequently, Ag QDs, with tunable size (1.3-21.0 nm), could be uniformly deposited on the H-TiO2 NTAs by current pulsing approach. The unique structure of the as-obtained photoelectrodes greatly improved the photoelectric conversion efficiency. The as-obtained Ag/H-TiO2-NTAs exhibited strong visible-light absorption capability, high photocurrent density, and enhanced photoelectrocatalytic (PEC) activity toward photoelectrocatalytic hydrogen evolution under visible-light irradiation (λ>420 nm). The enhancement in the photoelectric conversion efficiency and activity was ascribed to the synergistic effects of silver and the unique hierarchical structures of TiO2 nanotube arrays, strong SPR effect, and anti-shielding effect of ultrafine Ag QDs. PMID:26067850

  5. The Synthesis and Structural Properties of Crystalline Silicon Quantum Dots upon Thermal Annealing of Hydrogenated Amorphous Si-Rich Silicon Carbide Films

    NASA Astrophysics Data System (ADS)

    Wen, Guozhi; Zeng, Xiangbin; Li, Xianghu

    2016-08-01

    Silicon quantum dots (QDs) embedded in non-stoichiometric hydrogenated silicon carbide (SiC:H) thin films have been successfully synthesized by plasma-enhanced chemical vapor deposition and post-annealing. The chemical composition analyses have been carried out by x-ray photoelectron spectroscopy (XPS). The bonding configurations have been deduced from Fourier transform infrared absorption measurements (FTIR). The evolution of microstructure with temperature has been characterized by glancing incident x-ray diffraction (XRD) and Raman diffraction spectroscopy. XPS and FTIR show that it is in Si-rich feature and there are a few hydrogenated silicon clusters in the as-grown sample. XRD and Raman diffraction spectroscopy show that it is in amorphous for the as-grown sample, while crystalline silicon QDs have been synthesized in the 900°C annealed sample. Silicon atoms precipitation from the SiC matrix or silicon phase transition from amorphous SiC is enhanced with annealing temperature increase. The average sizes of silicon QDs are about 5.1 nm and 5.6 nm, the number densities are as high as 1.7 × 1012 cm-2 and 3.2 × 1012 cm-2, and the crystalline volume fractions are about 58.3% and 61.3% for the 900°C and 1050°C annealed samples, respectively. These structural properties analyses provide an understanding about the synthesis of silicon QDs upon thermal annealing for applications in next generation optoelectronic and photovoltaic devices.

  6. CB-TE2A(+)·Cl(-)·3H2O: a short intermolecular hydrogen bond between zwitterionic bicyclo[6.6.2]tetraamine macrocycles.

    PubMed

    Jurek, Paul; Reibenspies, Joseph H; Kiefer, Garry E

    2016-02-01

    1,4,8,11-Tetraazabicyclo[6.6.2]hexadecane-4,11-diacetic acid (CB-TE2A) is of much interest in nuclear medicine for its ability to form copper complexes that are kinetically inert, which is beneficial in vivo to minimize the loss of radioactive copper. The structural chemistry of the hydrated HCl salt of CB-TE2A, namely 11-carboxymethyl-1,8-tetraaza-4,11-diazoniabicyclo[6.6.2]hexadecane-4-acetate chloride trihydrate, C16H31N4O4(+)·Cl(-)·3H2O, is described. The compound crystallized as a positively charged zwitterion with a chloride counter-ion. Two of the amine groups in the macrocyclic ring are protonated. Formally, a single negative charge is shared between two of the carboxylic acid groups, while one chloride ion balances the charge. Two intramolecular hydrogen bonds are observed between adjacent pairs of N atoms of the macrocycle. Two intramolecular hydrogen bonds are also observed between the protonated amine groups and the pendant carboxylate groups. A short intermolecular hydrogen bond is observed between two partially negatively charged O atoms on adjacent macrocycles. The result is a one-dimensional polymeric zigzag chain that propagates parallel to the crystallographic a direction. A second intermolecular interaction is a hydrogen-bonding network in the crystallographic b direction. The carbonyl group of one macrocycle is connected through the three water molecules of hydration to the carbonyl group of another macrocycle. PMID:26846499

  7. Binding energy of the ground and first few excited states of hydrogenic donor impurity in a rectangular GaAs quantum dot in the presence of electric field

    NASA Astrophysics Data System (ADS)

    Wang, Sheng; Kang, Yun; Li, Xian-Li

    2014-12-01

    Within the quasi-one-dimensional effective potential model and effective mass approximation, we calculate the ground and the first 9 excited-state binding energies of a hydrogenic donor impurity in a rectangular quantum dot (RQD) in the presence of electric field. The analytical form of the quasi-one-dimensional effective potential replacing the three-dimensional Coulomb potential in our model is derived by Fourier transforms. We discuss detailedly dependence of the binding energies on the impurity positions and electric fields. For the ground-state binding energy, our results qualitatively agree with that of Mendoza et al. (2005) in which they only calculated the ground-state binding energies in cubic quantum dots by variational method. However, for first 9 excited-state binding energies, such dependence has complex manner since there are two or three peaks in the electronic probability density distribution curves. The strengths and positions of these peaks in RQD affect the interaction potential between electron and impurity, which appears to be the critical control on the binding energies of impurity. The applied electric field pushes the positions of these peaks downwards, and the strengths of peaks located at the upper half of RQD increase while the strengths of lower peaks firstly decrease, then increase with increasing electric field. The high peak strength can lead to increase of the binding energy while the large distance between the position of peak and impurity center results in reduce of the energy, which is an interesting competition. This competition is more obvious for excited-state binding energies of off-central impurity.

  8. Electronic structure of a spherical quantum dot: Effects of the Kratzer potential, hydrogenic impurity, external electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Dehyar, A.; Rezaei, G.; Zamani, A.

    2016-10-01

    In the present work, we have investigated the simultaneous effects of external electric and magnetic fields on the energy spectrum of an electron bound to an impurity confined in a spherical quantum dot with Kratzer potential. To this end, energy eigenvalues are obtained using the asymptotic iteration method. The energy dependencies upon the confinement potential and external fields are reported. Our results indicate that the confinement potential, external electric and magnetic fields have a great influence on the energy eigenvalues of the system. We found that, an increase in the magnetic field increases the energy eigenvalues of the states with positive magnetic quantum number, m ≽ 0 . While, the states with negative m decrease, reaching to their minimum values and increase again, with increasing the magnetic field. Moreover, an increase in electric field strength leads to decrease the confinement effects and energy eigenvalues of the system.

  9. Crystalline Al1 - x Ti x phases in the hydrogen cycled NaAlH4 + 0.02TiCl3 system

    NASA Astrophysics Data System (ADS)

    Pitt, M. P.; Vullum, P. E.; Sørby, M. H.; Emerich, H.; Paskevicius, M.; Buckley, C. E.; Gray, E. MacA.; Walmsley, J. C.; Holmestad, R.; Hauback, B. C.

    2013-03-01

    The hydrogen (H) cycled planetary milled (PM) NaAlH4 + 0.02TiCl3 system has been studied by high resolution synchrotron X-ray diffraction and transmission electron microscopy during the first 10 H cycles. After the first H absorption, we observe the formation of four nanoscopic crystalline (c-) Ti-containing phases embedded on the NaAlH4 surface, i.e. Al2Ti, Al3Ti, Al82Ti18 and Al89Ti11, with 100% of the originally added Ti atoms accounted for. Al2Ti and Al3Ti are observed morphologically as a mechanical couple on the NaAlH4 surface, with a moderately strained interface. Electron diffraction shows that the Al82Ti18 phase retains some ordering from the L12 structure type, with the observation of forbidden (100) ordering reflections in the fcc Al82Ti18 lattice. After 2 H cycles the NaAlH4 + 0.02TiCl3 system displays only two crystalline Ti-containing phases, Al3Ti and Al89Ti11. After 10 H cycles, the Al89Ti11 is completely converted to Al85Ti15. Al89Ti11, Al85Ti15 and Al3Ti do not display any ordering reflections, and they are modeled in the A1 structure type. Quantitative phase analysis indicates that the Al3Ti proportion continues to increase with further H cycles. The formation of Ti-poor Al1 - x Ti x (x < 0.25) phases in later H cycles is detrimental to hydrogenation kinetics, compared to the starting Ti-richer near-surface Al2Ti/NaAlH4 interface present during the first absorption of hydrogen.

  10. Estimating the hydrogen ion concentration in concentrated NaCl and Na{sub 2}SO{sub 4} electrolytes

    SciTech Connect

    Rai, D.; Felmy, A.R.; Juracich, S.P.; Rao, F.

    1995-06-01

    Combination glass electrodes were tested for determining H{sup +} concentrations in concentrated pure and mixed NaCl and Na{sub 2}SO{sub 4} solutions, as well as natural brine systems. NaCl, Na{sub 2}SO{sub 4}, and mixtures of NaCl and Na{sub 2}SO{sub 4} solutions were analyzed. Correction factors for estimating pC{sub H}{sup +} (negative logarithm of H{sup +} concentration) were determined from measured/observed pH values. Required Gran-type titrations were done with HCl and/or NaOH. The titration method is described and a step-by-step procedure provided; it has been used previously for determining pC{sub H}{sup +} values of synthetic chloride-dominated brines. Precautions are required to determine correction factors for electrolytes that react with H{sup +} or OH{sup {minus}} [sulfate brines for titration with acid; magnesium brines for titration with base because of precipitation of Mg(OH)2]. Correction factors A (pC{sub H}{sup +} = pH{sub ob} + A) from HCl titrations were similar to those from NaOH titrations where the concentration of free H{sup +} was calculated using a thermodynamic model. These values should be applicable to solns with a very large range in measured pH values (2 to 12). Because a large number of solns were titrated with HCl and the A values are similar for HCl and NaOH titrations, the A values for NaCl and Na2SO4 solns were fit as a function of molality to allow extrapolation. For NaCl solns 0 to 6.0 M, A can be obtained by multiplying the molality by 0.159. For Na2SO4 solns 0 to 2.0 M, the values of A can be obtained from (0.221 {minus} 0.549X + 0.201X{sup 2}), where X is the molality of Na{sub 2}SO{sub 4}. Orion-Ross electrode evaluations indicated that the A values did not differ significantly for different electrodes. Results suggest that the data in this report can be used to estimate A values for different NaCl and Na{sub 2}SO{sub 4} solns even for noncalibrated electrodes.

  11. Hydrogen bonding interaction between HO2 radical and selected organic acids, RCOOH (R = CH3, H, Cl and F)

    NASA Astrophysics Data System (ADS)

    Joshi, Ravi; Ghanty, Tapan K.

    2013-10-01

    A systematic study on the H-bonding interaction of hydroperoxyl radical with formic, acetic, chloroformic and fluoroformic acids has been carried out using B3LYP/6-311++G(2df,2p) and MP2/aug-cc-pVTZ methods. Several possible geometries have been considered, and the calculated global minima of RCOOH-HO2 have been found to be planar cyclic structure with two hydrogen bonds. A definite trend has been found between the electron donating character of the R group with calculated bond lengths, binding energies and vibrational frequencies. The most stable complex of RCOOH-HO2 with H2O has been found to be associated with a planar cyclic structure involving three hydrogen bonds.

  12. Image Charge and Electric Field Effects on Hydrogen-like Impurity-bound Polaron Energies and Oscillator Strengths in a Quantum Dot

    NASA Astrophysics Data System (ADS)

    Vardanyan, L. A.; Vartanian, A. L.; Asatryan, A. L.; Kirakosyan, A. A.

    2016-11-01

    By using Landau-Pekar variational method, the ground and the first excited state energies and the transition frequencies between the ground and the first excited states of a hydrogen-like impurity-bound polaron in a spherical quantum dot (QD) have been studied by taking into account the image charge effect (ICE). We employ the dielectric continuum model to describe the phonon confinement effects. The oscillator strengths (OSs) of transitions from the 1 s-like state to excited states of 2 s, 2 p x , and 2 p z symmetries are calculated as functions of the applied electric field and strength of the confinement potential. We have shown that with and without image charge effect, the increase of the strength of the parabolic confinement potential leads to the increase of the oscillator strengths of 1 s - 2 p x and 1 s - 2 p z transitions. This indicates that the energy differences between 1 s- and 2 p x - as well as 1 s- and 2 p z -like states have a dominant role determining the oscillator strength. Although there is almost no difference in the oscillator strengths for transitions 1 s - 2 p x and 1 s -2 p z when the image charge effect is not taken into account, it becomes significant with the image charge effect.

  13. Absolute rate of the reaction of Cl(p-2) with molecular hydrogen from 200 - 500 K

    NASA Technical Reports Server (NTRS)

    Whytock, D. A.; Lee, J. H.; Michael, J. V.; Payne, W. A.; Stief, L. J.

    1976-01-01

    Rate constants for the reaction of atomic chlorine with hydrogen are measured from 200 - 500 K using the flash photolysis-resonance fluorescence technique. The results are compared with previous work and are discussed with particular reference to the equilibrium constant for the reaction and to relative rate data for chlorine atom reactions. Theoretical calculations, using the BEBO method with tunneling, give excellent agreement with experiment.

  14. Cadmium sulfide quantum dots supported on gallium and indium oxide for visible-light-driven hydrogen evolution from water.

    PubMed

    Pan, Yun-xiang; Zhuang, Huaqiang; Hong, Jindui; Fang, Zheng; Liu, Hai; Liu, Bin; Huang, Yizhong; Xu, Rong

    2014-09-01

    In this work, CdS quantum dots (QDs) supported on Ga2O3 and In2O3 are applied for visible-light-driven H2 evolution from aqueous solutions that contain lactic acid. With Pt as the cocatalyst, the H2 evolution rates on CdS/Pt/Ga2O3 and CdS/Pt/In2O3 are as high as 995.8 and 1032.2 μmol h(-1), respectively, under visible light (λ>420 nm) with apparent quantum efficiencies of 43.6 and 45.3% obtained at 460 nm, respectively. These are much higher than those on Pt/CdS (108.09 μmol h(-1)), Pt/Ga2O3 (0.12 μmol h(-1)), and Pt/In2O3 (0.05 μmol h(-1)). The photocatalysts have been characterized thoroughly and their band structures and photocurrent responses have been measured. The band alignment between the CdS QDs and In2O3 can lead to interfacial charge separation, which cannot occur between the CdS QDs and Ga2O3. Among the various possible factors that contribute to the high H2 evolution rates on CdS/Pt/oxide, the surface properties of the metal oxides play important roles, which include (i) the anchoring of CdS QDs and Pt nanoparticles for favorable interactions and (ii) the efficient trapping of photogenerated electrons from the CdS QDs because of surface defects (such as oxygen defects) based on photoluminescence and photocurrent studies.

  15. Exogenous hydrogen peroxide, nitric oxide and calcium mediate root ion fluxes in two non-secretor mangrove species subjected to NaCl stress.

    PubMed

    Lu, Yanjun; Li, Niya; Sun, Jian; Hou, Peichen; Jing, Xiaoshu; Zhu, Huipeng; Deng, Shurong; Han, Yansha; Huang, Xuxin; Ma, Xujun; Zhao, Nan; Zhang, Yuhong; Shen, Xin; Chen, Shaoliang

    2013-01-01

    Using 3-month-old seedlings of Bruguiera gymnorrhiza (L.) Savigny and Kandelia candel (L.) Druce, we compared species differences in ionic homeostasis control between the two non-secretor mangrove species. A high salinity (400 mM NaCl, 4 weeks) resulted in a decline of the K(+)/Na(+) ratio in root and leaf tissues, and the reduction was more pronounced in K. candel (41-66%) as compared with B. gymnorrhiza (5-36%). Salt-altered flux profiles of Na(+), K(+), H(+) and Ca(2+) in roots and effects of exogenous hydrogen peroxide (H(2)O(2)), nitric oxide (NO) and Ca(2+) on root ion fluxes were examined in seedlings that were hydroponically treated short term with 100 mM NaCl (ST, 24 h) and long term with 200 mM NaCl (LT, 7 days). Short term and LT salinity resulted in Na(+) efflux and a correspondingly increased H(+) influx in roots of both species, although a more pronounced effect was observed in B. gymnorrhiza. The salt-enhanced exchange of Na(+) with H(+) was obviously inhibited by amiloride (a Na(+)/H(+) antiporter inhibitor) or sodium orthovanadate (a plasma membrane H(+)-ATPase inhibitor), indicating that the Na(+) efflux resulted from active Na(+) exclusion across the plasma membrane. Short term and LT salinity accelerated K(+) efflux in the two species, but K. candel exhibited a higher flux rate. The salt-induced K(+) efflux was markedly restricted by the K(+) channel blocker, tetraethylammonium chloride, indicating that the K(+) efflux is mediated by depolarization-activated channels, e.g., KORCs (outward rectifying K(+) channels) and NSCCs (non-selective cation channels). Exogenous H(2)O(2) application (10 mM) markedly increased the apparent Na(+) efflux and limited K(+) efflux in ST-treated roots, although H(2)O(2) caused a higher Na(+) efflux in B. gymnorrhiza roots. CaCl(2) (10 mM) reduced the efflux of K(+) in salinized roots of the two mangroves, but its enhancement of Na(+) efflux was found only in B. gymnorrhiza. Under ST treatment, sodium nitroprusside

  16. The vibration characterization of synthetic crystalline lead hydrogen arsenite chloride precipitates Pb2(HAsO3)Cl2-implications of solidification of As (III) and Pb (II).

    PubMed

    Liu, Juan; Jia, Ru; Liu, Jing

    2014-01-01

    The lead hydrogen arsenite chloride precipitates (Pb2(HAsO3)Cl2) are synthesized hydrothermally due to its structure trap for lead and arsenic. The synthetic precipitates have well-developed crystalline. The crystals of lead hydrogen arsenite chloride have a series of obvious IR bands at 790, 721, 645, 589 and 554 cm(-1). These bands are assigned to the Ag mode of As-O stretching vibration (790), the antisymmetric stretch of As-OH (721), Ag modes (554 and 589) and E1g (645) of the symmetric deformation (ν1 and ν3) of AsO3 unit. The Raman bands at 782, 723, 586, 559 cm(-1) are attributed to As-O stretching vibration (ν1) and the symmetric deformation (ν1 and ν3), of which the positions and assignments display in accordance with IR result. The most intense Raman band is found in 814 cm(-1) and is attributed to the Ag mode of ν1 symmetric stretching vibration of AsO3 unit, which is not active in IR. The SEM image shows that the precipitates have needle morphology.

  17. Ion hydration and associated defects in hydrogen bond network of water: Observation of reorientationally slow water molecules beyond first hydration shell in aqueous solutions of MgCl 2

    NASA Astrophysics Data System (ADS)

    Baul, Upayan; Vemparala, Satyavani

    2015-01-01

    Effects of the presence of ions, at moderate to high concentrations, on dynamical properties of water molecules are investigated through classical molecular dynamics simulations using two well-known nonpolarizable water models. Simulations reveal that the presence of magnesium chloride (MgCl2) induces perturbations in the hydrogen bond network of water leading to the formation of bulklike domains with ``defect sites'' on boundaries of such domains: water molecules at such defect sites have less number of hydrogen bonds than those in bulk water. Reorientational autocorrelation functions for dipole vectors of such defect water molecules are computed at different concentrations of ions and compared with system of pure water. Earlier experimental and simulation studies indicate significant differences in reorientational dynamics for water molecules in the first hydration shell of many dissolved ions. Results of this study suggest that defect water molecules, which are beyond the first hydration shells of ions, also experience significant slowing of reorientation times as a function of concentration in the case of MgCl2. However, addition of cesium chloride (CsCl) to water does not perturb the hydrogen bond network of water significantly even at higher concentrations. This difference in behavior between MgCl2 and CsCl is consistent with the well-known Hofmeister series.

  18. Ion hydration and associated defects in hydrogen bond network of water: observation of reorientationally slow water molecules beyond first hydration shell in aqueous solutions of MgCl2.

    PubMed

    Baul, Upayan; Vemparala, Satyavani

    2015-01-01

    Effects of the presence of ions, at moderate to high concentrations, on dynamical properties of water molecules are investigated through classical molecular dynamics simulations using two well-known nonpolarizable water models. Simulations reveal that the presence of magnesium chloride (MgCl(2)) induces perturbations in the hydrogen bond network of water leading to the formation of bulklike domains with ''defect sites'' on boundaries of such domains: water molecules at such defect sites have less number of hydrogen bonds than those in bulk water. Reorientational autocorrelation functions for dipole vectors of such defect water molecules are computed at different concentrations of ions and compared with system of pure water. Earlier experimental and simulation studies indicate significant differences in reorientational dynamics for water molecules in the first hydration shell of many dissolved ions. Results of this study suggest that defect water molecules, which are beyond the first hydration shells of ions, also experience significant slowing of reorientation times as a function of concentration in the case of MgCl(2). However, addition of cesium chloride (CsCl) to water does not perturb the hydrogen bond network of water significantly even at higher concentrations. This difference in behavior between MgCl(2) and CsCl is consistent with the well-known Hofmeister series.

  19. Structural investigations of phosphorus-nitrogen compounds. 7. Relationships between physical properties, electron densities, reaction mechanisms and hydrogen-bonding motifs of N3P3Cl(6 - n)(NHBu(t))n derivatives.

    PubMed

    Bartlett, Stewart W; Coles, Simon J; Davies, David B; Hursthouse, Michael B; Ibişoglu, Hanife; Kiliç, Adem; Shaw, Robert A; Un, Ilker

    2006-04-01

    A series of compounds of the N3P3Cl(6 - n)(NHBu(t))n family (where n = 0, 1, 2, 4 and 6) are presented, and their molecular parameters are related to trends in physical properties, which provides insight into a potential reaction mechanism for nucleophilic substitution. The crystal structures of N3P3Cl5(NHBu(t)) and N3P3Cl2(NHBu(t))4 have been determined at 120 K, and those of N3P3Cl6 and N3P3Cl4(NHBu(t))2 have been redetermined at 120 K. These are compared with the known structure of N3P3(NHBu(t))6 studied at 150 K. Trends in molecular parameters [phosphazene ring, P-Cl and P-N(HBu(t)) distances, PCl2 angles, and endo- and exocyclic phosphazene ring parameters] across the series are observed. Hydrogen-bonding motifs are identified, characterized and compared. Both the molecular and the hydrogen-bonding parameters are related to the electron distribution in bonds and the derived basicities of the cyclophosphazene series of compounds. These findings provide evidence for a proposed mechanism for nucleophilic substitution at a phosphorus site bearing a PCl(NHBu(t)) group.

  20. 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

  1. Rotationally adiabatic pair interactions of para- and ortho-hydrogen with the halogen molecules F2, Cl2, and Br2

    NASA Astrophysics Data System (ADS)

    Berg, Matthias; Accardi, Antonio; Paulus, Beate; Schmidt, Burkhard

    2014-08-01

    The present work is concerned with the weak interactions between hydrogen and halogen molecules, i.e., the interactions of pairs H2-X2 with X = F, Cl, Br, which are dominated by dispersion and quadrupole-quadrupole forces. The global minimum of the four-dimensional (4D) coupled cluster with singles and doubles and perturbative triples (CCSD(T)) pair potentials is always a T shaped structure where H2 acts as the hat of the T, with well depths (De) of 1.3, 2.4, and 3.1 kJ/mol for F2, Cl2, and Br2, respectively. MP2/AVQZ results, in reasonable agreement with CCSD(T) results extrapolated to the basis set limit, are used for detailed scans of the potentials. Due to the large difference in the rotational constants of the monomers, in the adiabatic approximation, one can solve the rotational Schrödinger equation for H2 in the potential of the X2 molecule. This yields effective two-dimensional rotationally adiabatic potential energy surfaces where pH2 and oH2 are point-like particles. These potentials for the H2-X2 complexes have global and local minima for effective linear and T-shaped complexes, respectively, which are separated by 0.4-1.0 kJ/mol, where oH2 binds stronger than pH2 to X2, due to higher alignment to minima structures of the 4D-pair potential. Further, we provide fits of an analytical function to the rotationally adiabatic potentials.

  2. The Role of Vibrational Excitation on the Dynamics of the F(^2P) + HCl → FH + Cl(2P) Hydrogen-Transfer Reaction

    NASA Astrophysics Data System (ADS)

    Ray, Sara E.; Vissers, G. W. M.; McCoy, Anne B.

    2010-06-01

    Recently, open-shell systems have gained interest in experimental and theoretical science. What proves interesting about these open-shell systems is that the potential energy surfaces often contain a van der Waals well in the reactant or product channel that allows researchers to probe the pre-reactive species. Here we present the results of time-dependent quantum wave packet calculations on the asymmetric hydrogen-transfer reaction of F(^SUP>2P) + HCl. In these calculations, the reaction is initiated by vibrationally exciting the HCl stretching motion of the pre-reactive F\\cdotsHCl complex in the van der Waals well. The wave packet is propagated on a three-dimensional, fully coupled potential energy surface that has been constructed based on electronic energies calculated at the multi-reference configuration interation+Davidson correction (MRCI+Q) level of theory with an aug-cc-pVnZ (n=2,3,4) basis. Product state distributions were calculated for reactions initiated in the first three vibrationally excited states of HCl, v=1, 2, and 3. Specifically, we analyzed the final electronic, vibrational, and rotational distributions. Previous studies on the hydrogen-transfer reaction of the Cl(^2P) + HCl system focused on whether vibrational excitation of the HCl stretch would promote the reaction and if so, how the reaction dynamics reflect the coupling among the diabatic potential surfaces that describe this system. We also compare our F(^2P) + HCl results to those of this related system. M. P. Deskevich, M. Y. Hayes, K. Takahashi, R. T. Skodje, and D. J. Nesbitt J. Chem. Phys., 124(22) 224303 (2006) G. W. M. Vissers and A. B. McCoy J. Phys Chem. A, 110 5978 (2006)

  3. Strong, positive-ion hydrogen bonds: The binary complexes formed from NH3, OH2, FH, PH3, SH2, and ClH

    NASA Astrophysics Data System (ADS)

    Desmeules, Peter J.; Allen, Leland C.

    1980-05-01

    A systematic, ab initio electronic structure analysis of the strong, positive-ion hydrogen bond is reported. Energies and wave functions have been obtained at the 4-31G level for the twenty-one complexes, (BṡṡṡH-A)+, where A,B=NH3, OH2, FH, PH3, SH2, ClH. The A-H bond length (r1), the BṡṡṡA separation (R(, and the angle (ϑ) measured relative to the symmetry axis of B have been optimized. Calculated dimerization energies ED are found to be in reasonable agreement with experiment. Charge density difference plots of these complexes exhibit a remarkable similarity to the pattern of alternating charge gain and loss known for the neutral H-bonded dimers. The proton donor is characterized by a charge gain region between A and the proton and charge loss on the proton; the electron donor by a charge loss between B and the proton. Four of the complexes (HFṡṡṡHṡṡṡFH)+, (H2OṡṡṡHṡṡṡOH2)+, (HClṡṡṡHṡṡṡClH)+, (HClṡṡṡHṡṡṡFH)+, have unusually short internuclear separations and show large charge gain around the protons. This is the first theoretical evidence of a transition from predominantly electrostatic to predominantly covalent binding in hydrogen bonding and it corroborates a recent experimental X-N study. An estimate of the amount of charge lost from the proton, ΔqH, has been obtained from the difference plots and is found to bear a linear relation with the dimerization energy ED for a series of complexes with a single proton donor. The inverse relation between ED and the difference in monomer proton affinities, ΔPA, reported in the literature for substituted pyridinium ions, is shown to hold as well for all A and B. Our calculated results also give a quantitative demonstration of the recently proposed inverse relationship between proton position and ΔPA. Several useful new organizing principles have been found: (a) R varies linearly with r2, the BṡṡṡH distance. Covalent bonding in the four complexes noted

  4. Oxygen and hydrogen isotope fractionation by hydration complexes of Li +, Na +, K +, Mg 2+, F -, Cl -, and Br -: a theoretical study

    NASA Astrophysics Data System (ADS)

    Driesner, T.; Ha, T.-K.; Seward, T. M.

    2000-09-01

    Hydration complexes of the ions Li +, Na +, Mg 2+, F -, Cl -, and Br - that are expected to occur in natural brines, hydrothermal solutions, or volcanic vapors were studied theoretically using quantum mechanical methods, in particular density functional theory. The normal modes of vibration were calculated for minimum energy configurations obtained with the BLYP and B3LYP functionals in combination with the 6-31G∗∗ and 6-311G∗∗ basis sets. Enthalpies of dissociation for Li +, Na +, and Cl - hydrates calculated from these vibrational spectra are in good agreement with experimental values. From the theoretical normal modes of vibration, the reduced partition function ratios for D/H and 18O/ 16O substitution in the hydration complexes as well as the isotope fractionation between the complexes and monomeric water vapor were calculated. Following a scheme introduced by Bopp et al. (1974) we used the gas-phase results to model isotope salt effects in aqueous solutions. Good agreement with measured results was obtained for both oxygen and hydrogen isotope effects caused by cations, whereas anion results are less satisfactory, probably due to first shell-second shell interactions, which are not properly accounted for by the calculations. However, the calculations for the gas-phase cation hydration complexes can be utilized to gain insight into the nature of isotope "salt effects" in aqueous electrolyte solutions. Hydration-related "salt effects" are quantitatively dominated by the changes of O-H stretching frequencies due to the presence of the ions. Lower frequencies such as those related to the ion-water bonds are of minor importance. The distance up to which measurable effects on the O-H frequencies (and hence on the reduced partition function ratios) are induced is shown to be limited to the first hydration shell. These results may also be relevant for a better theoretical understanding of isotope fractionation involving clay minerals, adsorption of water on

  5. Kinetics of NiO and NiCl2 Hydrogen Reduction as Precursors and Properties of Produced Ni/Al2O3 and Ni-Pd/Al2O3 Catalysts

    PubMed Central

    Sokić, Miroslav; Kamberović, Željko; Nikolić, Vesna; Marković, Branislav; Korać, Marija; Anđić, Zoran; Gavrilovski, Milorad

    2015-01-01

    The objects of this investigation were the comparative kinetic analysis of the NiO and NiCl2 reduction by hydrogen during an induction period and elimination of the calcination during the synthesis of Ni/Al2O3 catalysts. The effect of temperature and time on NiO and NiCl2 reduction degrees was studied. Avrami I equation was selected as the most favorable kinetic model and used to determine activation energy of the NiO and NiCl2 reduction for the investigated temperature range (623–923 K) and time intervals (1–5 minutes). The investigation enabled reaching conclusions about the reaction ability and rate of the reduction processes. Afterward, Ni/Al2O3 catalysts were obtained by using oxide and chloride precursor for Ni. The catalysts were supported on alumina-based foam and prepared via aerosol route. Properties of the samples before and after low-temperature hydrogen reduction (633 K) were compared. Obtained results indicated that the synthesis of Ni/Al2O3 catalysts can be more efficient if chloride precursor for Ni is directly reduced by hydrogen during the synthesis process, without the calcination step. In addition, Ni-Pd/Al2O3 catalysts with different metal content were prepared by using chloride precursors. Lower reduction temperature was utilized and the chlorides were almost completely reduced at 533 K. PMID:25789335

  6. Anticooperativity of FHF hydrogen bonds in clusters of the type F- × (HF)n, RF × (HF)n and XF × (HF)n, R = alkyl and X = H, Br, Cl, F

    NASA Astrophysics Data System (ADS)

    Kucherov, S. Yu.; Bureiko, S. F.; Denisov, G. S.

    2016-02-01

    Properties of twenty five hydrogen-bonded complexes, namely, F- × (HF)n (n = 1-6), RF × (HF)n (R = t-Bu, i-Pr, Et, Me; n = 1-3), XF × (HF)n (X = H, Br, Cl; n = 1-2), and FF…HF with the hydrogen bond energy varying in a wide range have been calculated using ab initio methods at the MP2/6-31++G** level. For the first time, the energies, geometrical parameters and vibrational frequencies are obtained for the series of clusters, where the bonding character changes from covalent to van der Waals on the variation of proton-acceptor ability of the base, and the energies are in the range of 45-1 kcal/mol. The mutual influence of multiple hydrogen bonds of F…HF type in clusters, in which a fluorine anion or an atom participates in hydrogen bond formation as the acceptor, is systematically investigated. The relative changes in the values of the considered parameters on the sequential addition of an HF molecule (anticooperativity) were determined. It was shown that non-additivity of the interaction is most strongly pronounced in the energy and vibrational frequency values, geometrical parameters of hydrogen bonds are less sensitive to the mutual influence. The anticooperative effect is more pronounced on the hydrogen bridge length R(F...F) than on the geometry of proton donor r(HF). The hydrogen bond formation and the increase of the number n of ligands lead to successive lengthening of the r(XF) bond adjacent to the hydrogen bridge. The length of an XF bond changes stronger on formation of each hydrogen bond than the HF bond length.

  7. Hydrogen-bond-directed assemblies of [La(18-crown-6)(H2O)4](BiCl6)·3H2O and [Nd(18-crown-6)(H2O)4](BiCl6)·3.5H2O regulated by different symmetries

    NASA Astrophysics Data System (ADS)

    Zhang, Shi-Yong; Li, Jian; Zeng, Ying; Wen, He-Rui; Du, Zi-Yi

    2016-12-01

    The reactions of La2O3 or Nd2O3 with BiCl3 and 18-crown-6 in the presence of excessive hydrochloric acid afforded two ion-pair compounds, namely [La(18-crown-6)(H2O)4](BiCl6)·3H2O (1) and [Nd(18-crown-6)(H2O)4](BiCl6)·3.5H2O (2). Although these two compounds contain similar building blocks, they exhibit two distinct hydrogen-bonded networks, which are mainly induced by the slightly different geometries of their large-sized cationic [Ln(18-crown-6)(H2O)4]3+ components.

  8. Impact of deformation energy on the hydrogen bonding interactions in gas phase 3-X catechol ⋯ H2O complexes (X = H, F, Cl, Br): The effect of approach of a water molecule

    NASA Astrophysics Data System (ADS)

    Deb, Debojit Kumar; Sarkar, Biplab

    2016-06-01

    The conformations and nature of hydrogen bonding interactions for 3-X catechol ⋯ H2O (X = H, F, Cl, Br) has been investigated by ab initio MP2, CCSD(T), and density functional B3LYP, wB97XD and M06-2X methods. The changes in interaction energies due to deformation of the structures has been studied in detail. The intra- and intermolecular hydrogen bonding interactions due to the different direction of approach of water molecule have been discussed. A detailed natural bond orbital (NBO) analysis and the symmetry-adapted perturbation theory (SAPT) based energy decomposition analysis has been carried out to elucidate interaction strength and properties in these hydrogen bonded systems. The charge transfer percentage (CTP) has been derived which will be universally useful for correlating binding energy, deformation energy and the geometrical parameters such as angles, bond lengths, etc. for other systems as well.

  9. Organically-Templated Zinc Hydrogen Phosphites: Syntheses, Structures and Properties of {alpha}- and {Beta}-ZnHOP{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4}

    SciTech Connect

    HARRISON,WILLIAM T.A.; PHILLIPS,MARK L.F.; STANCHFIELD,JESSE; NENOFF,TINA M.

    2000-07-14

    The syntheses, crystal structures and some properties of {alpha}- and {beta}-ZnHPO{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4} are reported. These two polymorphs are the first organically-templated hydrogen phosphites. They are built up from vertex-sharing HPO{sub 3} pseudo pyramids and ZnO{sub 3}N tetrahedra, where the Zn-N bond represents a direct link between zinc and the neutral 2-cyanoguanidine template. {alpha}-ZnHPO{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4} is built up from infinite layers of vertex-sharing ZnO{sub 3}N and HPO{sub 3} groups forming 4-rings and 8-rings. {beta}-ZnHPO{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4} has strong one-dimensional character, with the polyhedral building units forming 4-ring ladders. Similarities and differences to related zinc phosphates are discussed. Crystal data: {alpha}-ZnHPO{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4}, M{sub r} = 229.44, monoclinic, P2{sub 1}/c, a = 9.7718 (5) {angstrom}, b = 8.2503 (4) {angstrom}, c = 9.2491 (5) {angstrom}, {beta} = 104.146 (1){sup 0}, V = 723.1 (1) {angstrom}{sup 3}, R(F) = 2.33%, wR(F) = 2.52%. {beta}-ZnHPO{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4}, M{sub r} = 229.44, monoclinic, C2/c, a = 14.5092 (9) {angstrom}, b = 10.5464 (6) {angstrom}, c = 10.3342 (6) {angstrom}, {beta} = 114.290 (1){sup 0}, V = 1441.4 (3) {angstrom}{sup 3}, R(F) = 3.01%, wR(F) = 3.40%.

  10. Second sphere coordination complexes via hydrogen bonding: Synthesis, spectroscopic characterisation of [ trans-Co(en) 2Cl 2]CdX 4 (X=Br or I) and single crystal X-ray structure determination of [ trans-Co(en) 2Cl 2]CdBr 4

    NASA Astrophysics Data System (ADS)

    Sharma, Raj Pal; Sharma, Rajni; Bala, Ritu; Salas, Juan M.; Quiros, Miguel

    2006-08-01

    In an effort to explore [ trans-Co(en) 2Cl 2] + as anion receptor for tetrabromocadmate and tetraiodocadmate ion, green coloured single crystals of [ trans-Co(en) 2Cl 2]CdBr 4I and [ trans-Co(en) 2Cl 2]CdI 4II have been obtained by slowly mixing the separately dissolved trans-dichlorobis(ethylenediamine)cobalt(III) chloride with potassium tetrabromocadmate and tetraiodocadmate in aqueous medium in 2:1 molar ratio. The newly synthesized complex salt was characterized on the basis of elemental analysis and spectroscopic techniques (IR, UV/visible, 1H and 13C NMR). Single crystal X-ray structure determination of [ trans-Co(en) 2Cl 2] 2CdBr 4 revealed that it crystallizes in the orthorhombic space group Pbca with a=18.6201(10), b=12.0872(6), c=24.0877(12) Å, V=5421.3(5) Å 3, Z=8, R=0.0727. Supramolecular hydrogen bonding networks between ionic groups: bromide ions of tetrabromocadmate group and NH groups of coordinated ethylenediamine molecules, i.e. N-H⋯Br - interactions by second sphere coordination besides electrostatic forces of attraction have been observed. This suggests that [ trans-Co(en) 2Cl 2] + is a promising anion receptor for the tetrabromocadmate.

  11. Selective recognition of dysprosium(III) ions by enhanced chemiluminescence CdSe quantum dots.

    PubMed

    Hosseini, Morteza; Ganjali, Mohammad R; Vaezi, Zahra; Faridbod, Farnoush; Arabsorkhi, Batool; Sheikhha, Mohammad H

    2014-01-01

    The intensity of emitted light from CdSe quantum dots (QDs)-H2O2 is described as a novel chemiluminescence (CL) reaction for determination of dysprosium. This reaction is based on the catalytic effect of Dy(3+) ions, causing a significant increase in the light emission, as a result of the reaction of quantum dots (QDs) with hydrogen peroxide. In the optimum conditions, this method was satisfactorily described by linear calibration curve in the range of 8.3×10(-7)-5.0×10(-6)M, the detection limit of 6.0×10(-8)M, and the relative standard deviation for five determinations of 2.5×10(-6)M Dy(3+) 3.2%. The main experimental advantage of the proposed method is its selective to Dy(3+) ions compared with common coexisting cations, therefore, it was successfully applied for the determination of dysprosium ions in water samples.

  12. Infrared identification of the {sigma}-complex of Cl-C{sub 6}H{sub 6} in the reaction of chlorine atom and benzene in solid para-hydrogen

    SciTech Connect

    Bahou, Mohammed; Witek, Henryk; Lee, Yuan-Pern

    2013-02-21

    The reaction of a chlorine atom with benzene (C{sub 6}H{sub 6}) is important in organic chemistry, especially in site-selective chlorination reactions, but its product has been a subject of debate for five decades. Previous experimental and theoretical studies provide no concrete conclusion on whether the product is a {pi}- or {sigma}-form of the Cl-C{sub 6}H{sub 6} complex. We took advantage of the diminished cage effect of para-hydrogen (p-H{sub 2}) to produce Cl in situ to react with C{sub 6}H{sub 6} (or C{sub 6}D{sub 6}) upon photolysis of a Cl{sub 2}/C{sub 6}H{sub 6} (or C{sub 6}D{sub 6})/p-H{sub 2} matrix at 3.2 K. The infrared spectrum, showing intense lines at 1430.5, 833.6, 719.8, 617.0, and 577.4 cm{sup -1}, and several weaker ones for Cl-C{sub 6}H{sub 6}, and the deuterium shifts of observed new lines unambiguously indicate that the product is a 6-chlorocyclohexadienyl radical, i.e., the {sigma}-complex of Cl-C{sub 6}H{sub 6}. Observation of the {sigma}-complex rather than the {pi}-complex indicates that the {sigma}-complex is more stable in solid p-H{sub 2} at 3.2 K. The spectral information is crucial for further investigations of the Cl + C{sub 6}H{sub 6} reaction either in the gaseous or solution phase.

  13. Infrared spectroscopy and ab initio study of hydrogen bonded Cl3CD·N(CH3)3 complex in the gas phase

    NASA Astrophysics Data System (ADS)

    Rutkowski, K. S.; Melikova, S. M.; Linok, O. V.; Czarnik-Matusewicz, B.; Rospenk, M.

    2015-02-01

    FTIR spectra of the gas phase Cl3CD + TMA mixture have been studied at room temperature in ∼800-4000 cm-1 frequency domain. The formation of the H-bonded Cl3CD…TMA complex has been detected. Spectroscopic parameters of the band ascribed to the complex were evaluated. MP2 frozen core ab initio calculations have been carried out with the Pople-type 6-311++G(d,p) basis set. The equilibrium geometries and harmonic vibrational frequencies of the complex were obtained using CP-corrected gradient techniques. The ''freq = anharm'' option has been tested for Cl3CD monomer and Cl3CD…TMA complex to examine possible anharmonic effects on the vibrations localized on the proton donor. The effects of Darling-Dennison and Fermi resonances on the frequency of the stretching vibration of the CH proton donor were analyzed.

  14. An ab initio molecular dynamics study of the liquid-vapor interface of an aqueous NaCl solution: inhomogeneous density, polarity, hydrogen bonds, and frequency fluctuations of interfacial molecules.

    PubMed

    Choudhuri, Jyoti Roy; Chandra, Amalendu

    2014-11-21

    We have presented a first principles simulation study of the structural and dynamical properties of a liquid-vapor interfacial system of a concentrated (5.3 M) aqueous NaCl solution. We have used ab initio molecular dynamics to examine the structural and dynamical properties of the bulk and interfacial regions. The structural aspects of the system that have been considered here include the inhomogeneous density profiles of ions and water molecules, hydrogen bond distributions, orientational profiles, and also vibrational frequency distributions in the bulk and interfacial regions. It is found that the sodium ions are mostly located in the interior, while the chloride anions occupy a significant portion of the interface of the slab. The water dipoles at the interface prefer to orient parallel to the surface. The dynamical aspects of the interfaces are investigated in terms of diffusion, orientational relaxation, hydrogen bond dynamics, and vibrational spectral diffusion. The results of the interfacial dynamics are compared with those of the corresponding bulk region. It is observed that the interfacial molecules exhibit faster diffusion and orientational relaxation with respect to the bulk. However, the interfacial molecules are found to have longer hydrogen bond lifetimes than those of the bulk. We have also investigated the correlations of hydrogen bond relaxation with the vibrational frequency fluctuations of interfacial water molecules.

  15. Hydrogen Bonding, Hydration of Species, Ion Pairing and Clusterization in H2O-NaCl-CaCl2-CO2-NaHCO3-Na2CO3 Fluids: Molecular Dynamics Simulation of the Effects of Temperature, Pressure and Composition

    NASA Astrophysics Data System (ADS)

    Kalinichev, A. G.; Kirkpatrick, R. J.; Wang, J.

    2004-12-01

    Molecular computer simulation is an especially valuable tool to study the structural and dynamic properties of carbon-bearing aqueous fluids on the fundamental atomic time- and length- scale because these fluids are not readily studied experimentally using conventional X-ray or EXAFS methods. In this case, experimental methods can produce ambiguous results, because the carbon and oxygen atoms of the solute species are not easily distinguishable from the oxygen atoms of solvent water. Systematic molecular dynamics (MD) computer simulation studies of several fluid compositions - H2O-CO2, H2O-CO2-NaCl, H2O-NaHCO3, and H2O-Na2CO3 - were performed to study the effects of temperature, pressure (fluid density) and concentration on the structural, energetic, spectroscopic and dynamic properties of these solutions characterized on the atomic scale via the statistical parameters of individual hydrogen bonds and H-bonding networks, local hydration structures of dissolved species, and ion pair formation. Similar molecular-level characteristics of pure water and H2O-NaCl and H2O-CaCl2 solutions are calculated and used for comparison with the properties of carbon-bearing fluids. H2O-rich and CO2-rich compositions of the ternary H2O-CO2-NaCl system demonstrate strikingly different structural and dynamic behavior at about the same average density. In dense CO2-rich fluids, dissolved H2O molecules exhibit a high degree of hydrogen bonding and form relatively stable H-bonded clusters structurally similar to those observed in supercritical water at a much lower density. In contrast, CO2 molecules dissolved in water-rich fluids occur in clathrate-like cages formed by surrounding H-bonded water molecules. The hydration shells of carbonate and bicarbonate ions both contain approximately 10 water molecules, but the water structure around the carbonate ion is much more pronounced due to the higher anion charge. This also leads to the formation of very stable ion pairs and larger ionic

  16. Rate constants for aqueous-phase reactions of hydroxyl radical ({center_dot}OH) with aldehydes and ketones

    SciTech Connect

    Allen, J.M.; Allen, S.K.

    1995-12-31

    A wide variety of aldehydes and ketones are formed in the troposphere by the gas-phase oxidation of hydrocarbons. These compounds are expected to readily partition into cloud, fog, and aquated aerosol drops where they can participate in a variety of aqueous-phase reactions. It has been previously demonstrated by other researchers that aqueous-phase photochemical reactions involving aromatic aldehydes and ketones may lead to the formation of hydrogen peroxide. Hydrogen peroxide is an important oxidant for S(IV) and is also an {center_dot}OH precursor. Aldehydes and ketones may also participate in other aqueous-phase reactions within atmospheric water drops including reactions with {center_dot}OH. Rate constants for reactions involving {center_dot}OH in aqueous solutions have been reported for only a limited number of tropospheric aldehydes and ketones. The authors have measured the rate constants for aqueous-phase reactions of {center_dot}OH with several tropospheric aldehydes and ketones by the technique of competition kinetics. Hydroxyl radicals were generated by continuous illumination at 313 nm of an aqueous acidified solution containing Fe(ClO{sub 4}){sub 3}, an {center_dot}OH scavenger, the aldehyde or ketone whose rate constant was to be measured, and a standard for which the rate constant for reaction with {center_dot}OH is well known. Nitrobenzene was used as the standard in all experiments. Loss of the aldehyde or ketone and the standard were monitored by HPLC. Losses attributable to direct photolysis and dark reactions were minimal.

  17. Substitutional impurity in the graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Sierański, K.; Szatkowski, J.

    2015-09-01

    The process of formation of the localized defect states due to substitutional impurity in sp2-bonded graphene quantum dot is considered using a simple tight-binding-type calculation. We took into account the interaction of the quantum dot atoms surrounding the substitutional impurity from the second row of elements. To saturate the external dangling sp2 orbitals of the carbon additionally 18 hydrogen atoms were introduced. The chemical formula of the quantum dot is H18C51X, where X is the symbol of substitutional atom. The position of the localized levels is determined relative to the host-atoms (C) εp energies. We focused on the effect of substitutional doping by the B, N and O on the eigenstate energies and on the total energy change of the graphene dots including for O the effect of lattice distorsion. We conclude that B, N, and O can form stable substitutional defects in graphene quantum dot.

  18. Improving the accuracy of carbon-to-hydrogen ratio determination for P, N, S, O, Cl, and Br-containing organic compounds using atomic emission detection.

    PubMed

    Chernetsova, Elena S; Revelsky, Alexander I; Durst, Dupont; Sobolevsky, Tim G; Revelsky, Igor A

    2005-05-01

    The objective of this work was to investigate the dependence of atomic emission detector C and H response on microwave-induced plasma conditions and to improve the accuracy of carbon-to-hydrogen ratio determination for trialkylphosphates, herbicides, chlorophenols, and sulfur-containing organic compounds. Compounds which differed structurally from the analytes were used as reference compounds. It was found that when the oxygen concentration in the helium was the maximum for the instrument (9%) relative errors in carbon-to-hydrogen ratio determination were 3-8%, irrespective of analyte and reference compound structure, whereas when working in the mode of operation recommended by the manufacturer of the instrument (1.5% oxygen in helium) the respective errors were 10-20% or higher. This improvement in the accuracy of carbon-to-hydrogen ratio determination was accompanied by a factor of ten decrease in sensitivity. PMID:15688154

  19. Influence of solvent composition on the kinetics of cyclooctene epoxidation by hydrogen peroxide catalyzed by iron(III) [tetrakis(pentafluorophenyl)] porphyrin chloride [(F20TPP)FeCl].

    PubMed

    Stephenson, Ned A; Bell, Alexis T

    2006-03-20

    The epoxidation of cyclooctene catalyzed by iron(III) [tetrakis(pentafluorophenyl)] porphyrin chloride [(F20TPP)FeCl] was investigated in alcohol/acetonitrile solutions in order to determine the effects of the alcohol composition on the reaction kinetics. It was observed that alcohol composition affects both the observed rate of hydrogen peroxide consumption (the limiting reagent) and the selectivity of hydrogen peroxide utilization to form cyclooctene epoxide. The catalytically active species are formed only in alcohol-containing solvents as a consequence of (F(20)TPP)FeCl dissociation into [(F20TPP)Fe(ROH)]+ cations and Cl- anions. The observed reaction kinetics are analyzed in terms of a proposed mechanism for the epoxidation of the olefin and the decomposition of H2O2. The first step in this scheme is the reversible coordination of H2O2 to [(F20TPP)Fe(ROH)]+. The O-O bond of the coordinated H2O2 then undergoes either homolytic or heterolytic cleavage. The rate of homolytic cleavage is found to be independent of alcohol composition, whereas the rate of heterolytic cleavage increases with alcohol acidity. Heterolytic cleavage is envisioned to form iron(IV) pi-radical cations, whereas homolytic cleavage forms iron(IV) hydroxo cations. The iron(IV) radical cations are active for olefin epoxidation, whereas the iron(IV) cations catalyze the decomposition of H2O2. Reaction of iron(IV) pi-radical cations with H2O2 to form iron(IV) hydroxo cations is also included in the mechanism, a process that is favored by alcohols with a high charge density on the O atoms. The proposed mechanism describes successfully the effects of H2O2, cyclooctene, and porphyrin concentrations, as well as the effects of alcohol concentration.

  20. Efficient catalysis by MgCl2 in hydrogen generation via hydrolysis of Mg-based hydride prepared by hydriding combustion synthesis.

    PubMed

    Zhao, Zelun; Zhu, Yunfeng; Li, Liquan

    2012-06-01

    Magnesium chloride efficiently catalyzed the hydrolysis of Mg-based hydride prepared by hydriding combustion synthesis. Hydrogen yield of 1635 mL g(-1) was obtained (MgH(2)), i.e. with 96% conversion in 30 min at 303 K.

  1. Improved activity and thermo-stability of the horse radish peroxidase with graphene quantum dots and its application in fluorometric detection of hydrogen peroxide

    NASA Astrophysics Data System (ADS)

    Xiaoyan, Zhou; Yuanyuan, Jiang; Zaijun, Li; Zhiguo, Gu; Guangli, Wang

    2016-08-01

    Graphene quantum dots (GQDs) have received extensive concern in many fields such as optical probe, bioimaging and biosensor. However, few reports refer on the influence of GQDs on enzyme performance. The paper reports two kinds of graphene quantum dots (termed as GO-GQDs and N,S-GQDs) that were prepared by cutting of graphene oxide and pyrolysis of citric acid and L-cysteine, and their use for the horse radish peroxidase (HRP) modification. The study reveals that GO-GQDs and N,S-GQDs exhibit an opposite effect on the HRP performance. Only HRP modified with GO-GQDs offers an enhanced activity (more than 1.9 times of pristine enzyme) and thermo-stability. This is because GO-GQDs offer a larger conjugate rigid plane and fewer hydrophilic groups compared to N,S-GQDs. The characteristics can make GO-GQDs induce a proper conformational change in the HRP for the catalytic performance, improving the enzyme activity and thermo-stability. The HRP modified with green luminescent GO-GQDs was also employed as a biocatalyst for sensing of H2O2 by a fluorometric sensor. The colorless tetramethylbenzidine (TMB) is oxidized into blue oxidized TMB in the presence of H2O2 by the assistance of HRP/GO-GQDs, leading to an obvious fluorescence quenching. The fluorescence intensity linearly decreases with the increase of H2O2 concentration in the range from 2 × 10 - 9 to 2 × 10 - 4 M with the detection limit of 6.8 × 10 - 10 M. The analytical method provides the advantage of sensitivity, stability and accuracy compared with present H2O2 sensors based on the pristine HRP. It has been successfully applied in the determination of H2O2 in real water samples. The study also opens a new avenue for modification of enzyme activity and stability that offers great promise in applications such as biological catalysis, biosensing and enzyme engineering.

  2. Improved activity and thermo-stability of the horse radish peroxidase with graphene quantum dots and its application in fluorometric detection of hydrogen peroxide.

    PubMed

    Xiaoyan, Zhou; Yuanyuan, Jiang; Zaijun, Li; Zhiguo, Gu; Guangli, Wang

    2016-08-01

    Graphene quantum dots (GQDs) have received extensive concern in many fields such as optical probe, bioimaging and biosensor. However, few reports refer on the influence of GQDs on enzyme performance. The paper reports two kinds of graphene quantum dots (termed as GO-GQDs and N,S-GQDs) that were prepared by cutting of graphene oxide and pyrolysis of citric acid and l-cysteine, and their use for the horse radish peroxidase (HRP) modification. The study reveals that GO-GQDs and N,S-GQDs exhibit an opposite effect on the HRP performance. Only HRP modified with GO-GQDs offers an enhanced activity (more than 1.9 times of pristine enzyme) and thermo-stability. This is because GO-GQDs offer a larger conjugate rigid plane and fewer hydrophilic groups compared to N,S-GQDs. The characteristics can make GO-GQDs induce a proper conformational change in the HRP for the catalytic performance, improving the enzyme activity and thermo-stability. The HRP modified with green luminescent GO-GQDs was also employed as a biocatalyst for sensing of H2O2 by a fluorometric sensor. The colorless tetramethylbenzidine (TMB) is oxidized into blue oxidized TMB in the presence of H2O2 by the assistance of HRP/GO-GQDs, leading to an obvious fluorescence quenching. The fluorescence intensity linearly decreases with the increase of H2O2 concentration in the range from 2×10-9 to 2×10-4M with the detection limit of 6.8×10-10M. The analytical method provides the advantage of sensitivity, stability and accuracy compared with present H2O2 sensors based on the pristine HRP. It has been successfully applied in the determination of H2O2 in real water samples. The study also opens a new avenue for modification of enzyme activity and stability that offers great promise in applications such as biological catalysis, biosensing and enzyme engineering. PMID:27116472

  3. Fluorescent carbon dot (C-dot) nanoclusters.

    PubMed

    Wang, Guan; Pan, Xiaoyong; Gu, Liuqun; Ren, Wei; Cheng, Weiren; Kumar, Jatin N; Liu, Ye

    2014-09-19

    Fluorescent carbon dot (C-dot) nanoclusters composed of C-dot-loaded hollow silica spheres are obtained via the dehydration of mannose, which is adsorbed onto hollow silica spheres or poly(ethylene glycol)-graft-hollow silica spheres (PEG-g-hollow silica). The structure of C-dot nanoclusters are confirmed using 1H NMR, FTIR, TEM and TGA. C-dot nanoclusters show a redshifted fluorescence emission with an increased excitation wavelength. Passivation with PEG diamines improve the quantum yields to ∼2%. Confocal laser scanning microscopy (CLSM) results reflect the fact that C-dot nanoclusters can provide good cytoplasm imaging of live Hep G2 cells and live MCF-7 cells, and the imaging obtained is brighter and more even than those from free C-dots. With their combination of good photostability and low cytotoxicity, C-dot nanoclusters are promising for the production of higher quality bioimaging.

  4. Competition between hydrogen abstraction and halogen displacement in the reaction of Br with CH3I, CH3Br, and CH3Cl.

    PubMed

    Irikura, Karl K; Francisco, Joseph S

    2007-07-26

    Sudden ozone depletion events in the marine boundary layer are associated with jumps in the CH3Br mixing ratio, but current models of atmospheric chemistry explain neither the ozone depletion nor the CH3Br spikes. We have used ab initio theory to predict the forward and reverse rate constants for the competing hydrogen abstraction and homolytic substitution (SH2) channels of the title reactions. Including the spin-orbit stabilization of the transition structures increases the rate constants by factors between 1.3 and 49. For the atmospherically relevant case of CH3I, our findings suggest that the hydrogen abstraction and homolytic substitution reactions are competitive. The predicted branching fraction to CH3Br is about 13%.

  5. Ternary Isothermal Diffusion Coefficients of NaCl-MgCl2-H2O at 25 C. 7. Seawater Composition

    SciTech Connect

    Miller, D G; Lee, C M; Rard, J A

    2007-02-12

    The four diffusion coefficients D{sub ij} of the ternary system NaCl-MgCl{sub 2}-H{sub 2}O at the simplified seawater composition 0.48877 mol {center_dot} dm{sup -3} NaCl and 0.05110 mol {center_dot} dm{sup -3} MgCl{sub 2} have been remeasured at 25 C. The diffusion coefficients were obtained using both Gouy and Rayleigh interferometry with the highly precise Gosting diffusiometer. The results, which should be identical in principle, are essentially the same within or very close to their combined 'realistic' errors. This system has a cross-term D{sub 12} that is larger than the D{sub 22} main-term, where subscript 1 denotes NaCl and 2 denotes MgCl{sub 2}. The results are compared with earlier, less-precise measurements. Recommended values for this system are (D{sub 11}){sub V} = 1.432 x 10{sup -9} m{sup 2} {center_dot} sec{sup -1}, (D{sub 12}){sub V} = 0.750 x 10{sup -9} m{sup 2} {center_dot} sec{sup -1}, (D{sub 21}){sub V} = 0.0185 x 10{sup -9} m{sup 2} {center_dot} sec{sup -1}, and (D{sub 22}){sub V} = 0.728 x 10{sup -9} m{sup 2} {center_dot} sec{sup -1}.

  6. 1D and 2D assembly structures by imidazole···chloride hydrogen bonds of iron(II) complexes [Fe(II)(HL(n-Pr))3]Cl·Y (HL(n-Pr) = 2-methylimidazol-4-yl-methylideneamino-n-propyl; Y = AsF6, BF4) and their spin states.

    PubMed

    Fujinami, Takeshi; Nishi, Koshiro; Matsumoto, Naohide; Iijima, Seiichiro; Halcrow, Malcolm A; Sunatsuki, Yukinari; Kojima, Masaaki

    2011-12-01

    Two Fe(II) complexes fac-[Fe(II)(HL(n-Pr))(3)]Cl·Y (Y = AsF(6) (1) and BF(4) (2)) were synthesized, where HL(n-Pr) is 2-methylimidazole-4-yl-methylideneamino-n-propyl. Each complex-cation has the same octahedral N(6) geometry coordinated by three bidentate ligands and assumes facial-isomerism, fac-[Fe(II)(HL(n-Pr))(3)](2+) with Δ- and Λ-enantiomorphs. Three imidazole groups per Δ- or Λ-fac-[Fe(II)(HL(n-Pr))(3)](2+) are hydrogen-bonded to three Cl(-) ions or, from the viewpoint of the Cl(-) ion, one Cl(-) ion is hydrogen-bonded to three neighbouring fac-[Fe(II)(HL(n-Pr))(3)](2+) cations. The 3 : 3 NH···Cl(-) hydrogen bonds between Δ- or Λ-fac-[Fe(II)(HL(n-Pr))(3)](2+) and Cl(-) generate two kinds of assembly structures. The directions of the 3 : 3 NH···Cl(-) hydrogen bonds and hence the resulting assembly structures are determined by the size of the anion Y, though Y is not involved into the network structure and just accommodated in the cavity. Compound 1 has a 1D ladder structure giving a larger cavity, in which the Δ- and Λ-fac-[Fe(II)(HL(n-Pr))(3)](2+) enantiomorphs are bridged by two NH···Cl(-) hydrogen bonds. Compound 2 has a 2D network structure with a net unit of a cyclic trimer of {fac-[Fe(II)(HL(n-Pr))(3)](2+)···Cl(-)}(3) giving a smaller cavity, in which Δ- or Λ-fac-[Fe(II)(HL(n-Pr))(3)](2+) species with the same chirality are linked by NH···Cl(-) hydrogen bonds to give a homochiral 2D network structure. Magnetic susceptibility and Mössbauer spectral measurements demonstrated that compound 1 showed an abrupt one-step spin crossover with 4.0 K thermal hysteresis of T(c↓) = 125.5 K and T(c↑) = 129.5 K and compound 2 showed no spin transition and stayed in the high-spin state over the 5-300 K temperature range.

  7. Solvation Thermodynamic Properties of Hydrogen Sulfide in [C4mim][PF6], [C4mim][BF4], and [C4mim][Cl] Ionic Liquids, Determined by Molecular Simulations.

    PubMed

    Sánchez-Badillo, Joel; Gallo, Marco; Alvarado, Sandra; Glossman-Mitnik, Daniel

    2015-08-20

    Removal of hydrogen sulfide (H2S) and acid gases from natural gas is accomplished by absorption processes using a solvent. The gas solubility in a liquid can be used to measure the degree of removal of the gas and is quantified by the Henry's constant, the free energy of solvation at infinite dilution, or the excess chemical potential. In this work, Henry's constants and thermodynamic properties of solvation of H2S were calculated in three ionic liquids: [C4mim][PF6], [C4mim][BF4], and [C4mim][Cl] ([C4mim], 1-butyl-3-methyl imidazolium). The first step in this work was the evaluation of the force fields for the gas and condensed phases in order to obtain accurate values for the excess chemical potential for H2S on each ionic liquid using free energy perturbation techniques. In the H2S-[C4mim][PF6] and H2S-[C4mim][BF4] systems, the results obtained by molecular simulation agree with the experimental values reported in the literature. However, the solvation free energy calculated for the H2S-[C4mim][Cl] system can be considered predictive because of the lack of experimental data at the simulated conditions. Based on these results, the best solvent for removing H2S is [C4mim][Cl] because it has the highest affinity for this species (lowest value of the Henry's constant). Also, solvation thermodynamic properties such as enthalpy and entropy were calculated in order to evaluate their contribution to the free energy of solvation.

  8. Free radical hydrogen atom abstraction from saturated hydrocarbons: A crossed-molecular-beams study of the reaction Cl + C{sub 3}H{sub 8} {yields} HCl + C{sub 3}H{sub 7}

    SciTech Connect

    Blank, D.A.; Hemmi, N.; Suits, A.G.; Lee, Y.T.

    1997-04-01

    The abstraction of hydrogen atoms from saturated hydrocarbons are reactions of fundamental importance in combustion as well as often being the rate limiting step in free radical substitution reactions. The authors have begun studying these reactions under single collision conditions using the crossed molecular beam technique on beamline 9.0.2.1, utilizing VUV undulator radiation to selectively ionize the scattered hydrocarbon free radical products (C{sub x}H{sub 2x+1}). The crossed molecular beam technique involves two reactant molecular beams fixed at 90{degrees}. The molecular beam sources are rotatable in the plane defined by the two beams. The scattered neutral products travel 12.0 cm where they are photoionized using the VUV undulator radiation, mass selected, and counted as a function of time. In the authors initial investigations they are using halogen atoms as protypical free radicals to abstract hydrogen atoms from small alkanes. Their first study has been looking at the reaction of Cl + propane {r_arrow} HCl + propyl radical. In their preliminary efforts the authors have measured the laboratory scattering angular distribution and time of flight spectra for the propyl radical products at collision energies of 9.6 kcal/mol and 14.9 kcal/mol.

  9. Is It Homogeneous or Heterogeneous Catalysis Derived from [RhCp*Cl2]2? In Operando-XAFS, Kinetic and Crucial Kinetic Poisoning Evidence for Subnanometer Rh4 Cluster-Based Benzene Hydrogenation Catalysis

    SciTech Connect

    Bayram, Ercan; Linehan, John C.; Fulton, John L.; Roberts, John A.; Szymczak, Nathaniel; Smurthwaite, Tricia D.; Ozkar, Saim; Balasubramanian, Mahalingam; Finke, Richard G.

    2011-11-23

    Determining the true, kinetically dominant catalytically active species, in the classic benzene hydrogenation system pioneered by Maitlis and co-workers 34 years ago starting with [RhCp*Cl2]2 (Cp* = [{eta}5-C5(CH3)5]), has proven to be one of the most challenging case studies in the quest to distinguish single-metal-based 'homogeneous' from polymetallic, 'heterogeneous' catalysis. The reason, this study will show, is the previous failure to use the proper combination of (i) operando spectroscopy to determine the dominant form(s) of the precatalyst's mass under catalysis (i.e., operating) conditions, plus then and crucially also (ii) the previous lack of the necessary kinetic studies, catalysis being a 'wholly kinetic phenomenon' as J. Halpern long ago noted. An important contribution from this study will be to reveal the power of quantitiative kinetic poisoning experiments for distinguishing single-metal, or in this case subnanometer Rh4 cluster-based catalysis from larger, polymetallic Rh(0)n nanoparticle catalysis, at least under favorable conditions. The combined operando-XAFS (X-ray absorption fine structure) spectroscopy and kinetic evidences provide a compelling case for Rh4-based, with average stoichiometry 'Rh4Cp*2.4Cl4Hc', benzene hydrogenation catalysis in 2-propanol with added Et3N and at 100 C and 50 atm initial H2 pressure. The results also reveal, however, that if even ca. 1.4% of the total soluble Rh(0)n had formed nanoparticles, then those Rh(0)n nanoparticles would have been able to account for all the observed benzene hydrogenation catalytic rate (using commercial, ca. 2 nm, polyethyleneglycol-dodecylether hydrosol stabilized Rh(0)n nanoparticles as a model system). The results 'especially the poisoning methodology developed and employed' are of significant, broader interest since determining the nature of the true catalyst continues to be a central, often vexing issue in any and all catalytic reactions. The results are also of fundamental

  10. Is it homogeneous or heterogeneous catalysis derived from [RhCp*Cl2]2? In operando XAFS, kinetic, and crucial kinetic poisoning evidence for subnanometer Rh4 cluster-based benzene hydrogenation catalysis.

    PubMed

    Bayram, Ercan; Linehan, John C; Fulton, John L; Roberts, John A S; Szymczak, Nathaniel K; Smurthwaite, Tricia D; Özkar, Saim; Balasubramanian, Mahalingam; Finke, Richard G

    2011-11-23

    Determining the true, kinetically dominant catalytically active species, in the classic benzene hydrogenation system pioneered by Maitlis and co-workers 34 years ago starting with [RhCp*Cl(2)](2) (Cp* = [η(5)-C(5)(CH(3))(5)]), has proven to be one of the most challenging case studies in the quest to distinguish single-metal-based "homogeneous" from polymetallic, "heterogeneous" catalysis. The reason, this study will show, is the previous failure to use the proper combination of: (i) in operando spectroscopy to determine the dominant form(s) of the precatalyst's mass under catalysis (i.e., operating) conditions, and then crucially also (ii) the previous lack of the necessary kinetic studies, catalysis being a "wholly kinetic phenomenon" as J. Halpern long ago noted. An important contribution from this study will be to reveal the power of quantitiative kinetic poisoning experiments for distinguishing single-metal, or in the present case subnanometer Rh(4) cluster-based catalysis, from larger, polymetallic Rh(0)(n) nanoparticle catalysis, at least under favorable conditions. The combined in operando X-ray absorption fine structure (XAFS) spectroscopy and kinetic evidence provide a compelling case for Rh(4)-based, with average stoichiometry "Rh(4)Cp*(2.4)Cl(4)H(c)", benzene hydrogenation catalysis in 2-propanol with added Et(3)N and at 100 °C and 50 atm initial H(2) pressure. The results also reveal, however, that if even ca. 1.4% of the total soluble Rh(0)(n) had formed nanoparticles, then those Rh(0)(n) nanoparticles would have been able to account for all the observed benzene hydrogenation catalytic rate (using commercial, ca. 2 nm, polyethyleneglycol-dodecylether hydrosol stabilized Rh(0)(n) nanoparticles as a model system). The results--especially the poisoning methodology developed and employed--are of significant, broader interest since determining the nature of the true catalyst continues to be a central, often vexing issue in any and all catalytic reactions

  11. Dot-immunobinding assay (Dot-Iba).

    PubMed

    Surendran, Sumi; Mathai, Annamma; Radhakrishnan, Vishnampet Venkataraman

    2015-01-01

    Dot-immunobinding assay (Dot-Iba) is a simple and highly reproducible immunodiagnostic method. Antibody or antigen is dotted directly onto nitrocellulose membrane (NCM) discs. The diagnostic material to be checked can be incubated on this disc. Presence of antigen-antibody complex in NCM discs can be directly demonstrated with enzyme-conjugated antiglobulins and substrate. Development of a purple-pink colored, insoluble substrate product in the nitrocellulose membrane will be considered a positive result in the assay. This assay allows the processing of multiple specimens at a time and the entire operational procedures required only 4-6 h. Dot-IBA is rapid and the technical steps involved in the assay are much simpler than the other immunoassays such as enzyme-linked immunosorbent assay in detecting circulating antigen and antibody in clinical samples. The Dot-Iba showed an overall sensitivity of 60 % for tuberculous meningitis diagnosis and no false positive results were encountered. Hence this assay is highly specific for the diagnosis of paucibacillary diseases like extrapulmonary tuberculosis. Dot-Iba is best suited to laboratories in developing world where there are constraints in laboratory resources.

  12. Spectroscopic and theoretical evidence for the cooperativity between red-shift hydrogen bond and blue-shift hydrogen bond in DMSO aqueous solutions.

    PubMed

    Li, Qingzhong; An, Xiulin; Gong, Baoan; Cheng, Jianbo

    2008-01-01

    The cooperativity between red-shifted hydrogen bond and blue-shifting hydrogen bond in dimethyl sulfoxide aqueous solutions was studied by methods of quantum chemical calculations and infrared spectroscopy. The water molecule plays a different role in two types of hydrogen bonds: proton-donor in red-shifted hydrogen bond and proton-acceptor in blue-shifting hydrogen bond. The cooperativity is not prominent if the ring structure is formed through the OHcdots, three dots, centeredOS H-bond and CHcdots, three dots, centeredO(w) H-bond. However, if the methyl groups in the above ring structure participate in second CHcdots, three dots, centeredO(w) H-bond, the cooperativity is increased. The second CHcdots, three dots, centeredO(w) H-bond enhances OHcdots, three dots, centeredOS H-bond and weakens the first CHcdots, three dots, centeredO(w) H-bond.

  13. Decimetric radio dot emissions

    NASA Astrophysics Data System (ADS)

    Mészárosová, H.; Karlický, M.; Sawant, H. S.; Fernandes, F. C. R.; Cecatto, J. R.; de Andrade, M. C.

    2008-11-01

    Context: We study a rare type of solar radio bursts called decimetric dot emissions. Aims: In the period 1999-2001, 20 events of decimetric dot emissions observed by the Brazilian Solar Spectroscope (BSS) in the frequency range 950-2640 MHz are investigated statistically and compared with radio fine structures of zebras and fibers. Methods: For the study of the spectral characteristics of the dot emissions we use specially developed Interactive Data Language (IDL) software called BSSView and basic statistical methods. Results: We have found that the dm dot emissions, contrary to the fine structures of the type IV bursts (i.e. zebras, fibers, lace bursts, spikes), are not superimposed on any background burst emission. In the radio spectrum, in most cases the dot emissions form chains that appear to be arranged in zebra patterns or fibers. Because some zebras and fibers, especially those observed with high time and high spectral resolutions, also show emission dots (but superimposed on the background burst emission), we compared the spectral parameters of the dot emissions with the dots being the fine structure of zebras and fibers. For both these dots, similar spectral characteristics were found. Some similarities of the dot emissions can be found also with the lace bursts and spikes. For some events the dot emissions show structural evolution from patterns resembling fibers to patterns resembling zebras and vice versa, or they evolve into fully chaotic patterns. Conclusions: For the first time, we present decimetric dot emissions that appear to be arranged in zebra patterns or fibers. We propose that these emissions are generated by the plasma emission mechanism at the locations in the solar atmosphere where the double resonance condition is fulfilled.

  14. Oxophily of gadolinium(III) and synthesis of dissymmetric di(Schiff bases) and dissymmetric dinuclear compounds. Crystal structure of [Cu[sub 2]L[prime](OH)](ClO[sub 4])[sub 2][center dot]H[sub 2]O with L[prime] = 2-[N-(2-pyridylethyl)formimidoyl]-6-[N-((dimethylamino)propyl)formimidoyl]phenolato

    SciTech Connect

    Andruh, M.; Kahn, O.; Sainton, J. ); Dromzee, Y.; Jeannin, S. )

    1993-04-28

    The strong oxophilic character of the Gd(III) ion has been utilized to protect one of the carbonyl functions of 2,6-diformyl-4-methylphenol, which has allowed the quantitative synthesis of mono(Schiff bases), then dissymmetric di(Schiff bases). The synthetic process is as follows: the reaction of 2,6-diformyl-4-methylphenol with a primary amine RNH[sub 2] in the presence of Gd(III) affords a complex in which Gd(III) is coordinated to two mono(Schiff bases) through their carbonyl and phenolic oxygen atoms. The mono(Schiff base) may be isolated by precipitation of Gd(III) in the form of gadolinium(III) oxalate. The reaction of another primary amine, R[prime]NH[sub 2], on this mono(Schiff base) affords a dissymmetric di(Schiff base), from which dissymmetric dinuclear compounds can be synthesized. For example, this reaction has been carried out with RNH[sub 2] = 2-(2-aminoethyl)pyridine and R[prime]NH[sub 2] = N,N-dimethylpropylenediamine. The mono(Schiff base) 2-formyl-6-(N-(2-pyridylethyl)formimidoyl)-4-methylphenol (HL) and the di(Schiff base) 2-[N-(2-pyridylethyl)formimidoyl]-6-[N-((dimethylamino)propyl)formimidoyl]-4-methylphenol (HL[prime]) have been unambiguously characterized from their [sup 1]H NMR spectra. The copper(II) dinuclear compound [CuL[prime](OH)](ClO[sub 4])[sub 2][center dot]H[sub 2]O obtained from this di(Schiff base) has been synthesized, and its crystal structure has been solved. 36 refs., 2 figs., 5 tabs.

  15. Quantum Dots: Theory

    SciTech Connect

    Vukmirovic, Nenad; Wang, Lin-Wang

    2009-11-10

    This review covers the description of the methodologies typically used for the calculation of the electronic structure of self-assembled and colloidal quantum dots. These are illustrated by the results of their application to a selected set of physical effects in quantum dots.

  16. Quantum Dot Solar Cells

    NASA Technical Reports Server (NTRS)

    Raffaelle, Ryne P.; Castro, Stephanie L.; Hepp, Aloysius; Bailey, Sheila G.

    2002-01-01

    We have been investigating the synthesis of quantum dots of CdSe, CuInS2, and CuInSe2 for use in an intermediate bandgap solar cell. We have prepared a variety of quantum dots using the typical organometallic synthesis routes pioneered by Bawendi, et. al., in the early 1990's. However, unlike previous work in this area we have also utilized single-source precursor molecules in the synthesis process. We will present XRD, TEM, SEM and EDS characterization of our initial attempts at fabricating these quantum dots. Investigation of the size distributions of these nanoparticles via laser light scattering and scanning electron microscopy will be presented. Theoretical estimates on appropriate quantum dot composition, size, and inter-dot spacing along with potential scenarios for solar cell fabrication will be discussed.

  17. A computational mechanistic investigation of hydrogen production in water using the [Rh(III)(dmbpy)2Cl2](+)/[Ru(II)(bpy)3](2+)/ascorbic acid photocatalytic system.

    PubMed

    Kayanuma, Megumi; Stoll, Thibaut; Daniel, Chantal; Odobel, Fabrice; Fortage, Jérôme; Deronzier, Alain; Collomb, Marie-Noëlle

    2015-04-28

    We recently reported an efficient molecular homogeneous photocatalytic system for hydrogen (H2) production in water combining [Rh(III)(dmbpy)2Cl2](+) (dmbpy = 4,4'-dimethyl-2,2'-bipyridine) as a H2 evolving catalyst, [Ru(II)(bpy)3](2+) (bpy = 2,2'-bipyridine) as a photosensitizer and ascorbic acid as a sacrificial electron donor (Chem. - Eur. J., 2013, 19, 781). Herein, the possible rhodium intermediates and mechanistic pathways for H2 production with this system were investigated at DFT/B3LYP level of theory and the most probable reaction pathways were proposed. The calculations confirmed that the initial step of the mechanism is a reductive quenching of the excited state of the Ru photosensitizer by ascorbate, affording the reduced [Ru(II)(bpy)2(bpy˙(-))](+) form, which is capable, in turn, of reducing the Rh(III) catalyst to the distorted square planar [Rh(I)(dmbpy)2](+) species. This two-electron reduction by [Ru(II)(bpy)2(bpy˙(-))](+) is sequential and occurs according to an ECEC mechanism which involves the release of one chloride after each one-electron reduction step of the Rh catalyst. The mechanism of disproportionation of the intermediate Rh(II) species, much less thermodynamically favoured, cannot be barely ruled out since it could also be favoured from a kinetic point of view. The Rh(I) catalyst reacts with H3O(+) to generate the hexa-coordinated hydride [Rh(III)(H)(dmbpy)2(X)](n+) (X = Cl(-) or H2O), as the key intermediate for H2 release. The DFT study also revealed that the real source of protons for the hydride formation as well as the subsequent step of H2 evolution is H3O(+) rather than ascorbic acid, even if the latter does govern the pH of the aqueous solution. Besides, the calculations have shown that H2 is preferentially released through an heterolytic mechanism by reaction of the Rh(III)(H) hydride and H3O(+); the homolytic pathway, involving the reaction of two Rh(III)(H) hydrides, being clearly less favoured. In parallel to this

  18. 29 CFR 1910.103 - Hydrogen.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...—Regulations of the Department of Transportation published in 49 CFR Chapter I. (vi) DOT regulations—See § 1910... 29 Labor 5 2014-07-01 2014-07-01 false Hydrogen. 1910.103 Section 1910.103 Labor Regulations... OCCUPATIONAL SAFETY AND HEALTH STANDARDS Hazardous Materials § 1910.103 Hydrogen. (a) General—(1)...

  19. 29 CFR 1910.103 - Hydrogen.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...—Regulations of the Department of Transportation published in 49 CFR Chapter I. (vi) DOT regulations—See § 1910... 29 Labor 5 2012-07-01 2012-07-01 false Hydrogen. 1910.103 Section 1910.103 Labor Regulations... OCCUPATIONAL SAFETY AND HEALTH STANDARDS Hazardous Materials § 1910.103 Hydrogen. (a) General—(1)...

  20. 29 CFR 1910.103 - Hydrogen.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...—Regulations of the Department of Transportation published in 49 CFR Chapter I. (vi) DOT regulations—See § 1910... 29 Labor 5 2013-07-01 2013-07-01 false Hydrogen. 1910.103 Section 1910.103 Labor Regulations... OCCUPATIONAL SAFETY AND HEALTH STANDARDS Hazardous Materials § 1910.103 Hydrogen. (a) General—(1)...

  1. 29 CFR 1910.103 - Hydrogen.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...—Regulations of the Department of Transportation published in 49 CFR Chapter I. (vi) DOT regulations—See § 1910... 29 Labor 5 2011-07-01 2011-07-01 false Hydrogen. 1910.103 Section 1910.103 Labor Regulations... OCCUPATIONAL SAFETY AND HEALTH STANDARDS Hazardous Materials § 1910.103 Hydrogen. (a) General—(1)...

  2. 75 FR 27665 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2C10 (Regional Jet Series 700, 701 & 702...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-18

    .... Model CL-600-2C10 (Regional Jet Series 700, 701 & 702), Model CL-600-2D15 (Regional Jet Series 705), and Model CL-600-2D24 (Regional Jet Series 900) Airplanes AGENCY: Federal Aviation Administration (FAA), DOT... Series Regional Jet Aircraft Maintenance Manual (AMM), CSP B-001, Revision 28, dated January 20,...

  3. 76 FR 61633 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2C10 (Regional Jet Series 700, 701, & 702...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-05

    ..., Inc. Model CL-600-2C10 (Regional Jet Series 700, 701, & 702), CL-600-2D15 (Regional Jet Series 705), and CL-600-2D24 (Regional Jet Series 900) Airplanes AGENCY: Federal Aviation Administration (FAA), DOT... proposed AD. Discussion On June 28, 2006, we issued AD 2006-14-05, Amendment 39-14676 (71 FR 38979, July...

  4. A quantum dot-lucigenin probe for Cl-.

    PubMed

    Ruedas-Rama, Maria Jose; Hall, Elizabeth A H

    2008-11-01

    In this work, the first chloride ion sensor based on QD-lucigenin nanoparticles is reported. The mechanism uses the ability of semiconductor QDs to engage in short range exchange processes, leading to fluorescence changes. An acridinium dication (lucigenin) which is an electron acceptor, was self-assembled on the surface of negative charged QDs (capped with mercaptopropionic acid). Mutual quenching of the lucigenin and QD were observed. From a sphere of action, Perrin-type model, exchange was estimated to occur over a range of the order of 2 nm. The possibility of spin-orbit coupling (SOC) or electron transfer between the QD and the lucigenin dication (Luc(2+)) is discussed. The radical cation Luc(+*) was not identified, but electron transfer from the QD conduction band to the Luc(2+), then electron transfer back, from the Luc(+*) to the QD valence band, could lead to mutual quenching, without build up of Luc(+*) . SOC between the QD and lucigenin, with or without charge transfer being involved, can also account for the results obtained. Lucigenin is also a chloride-sensitive indicator dye, with a sensing mechanism based on SOC. In the QD-MPA-lucigenin conjugate luminescence is restored by adding chloride ion. Thus, the presence of chloride is transduced into an enhancement of the luminescence of QDs. Using this operating principle, a chloride ion sensor based on CdSe-ZnS core-shell QD nanoparticles, showed a very good linearity in the range 1-250 mM, with a detection limit 0.29 mM and a RSD of 2.5% (n = 10). In a study of interferences, the chloride sensitive QDs showed good selectivity to most of the other anions tested. The versatility of the system was also demonstrated in terms of fluorescent emission wavelength, which could be selected across a wide range through choice of QDs. Examples are shown for lambda(max) = 500, 540 and 620 nm. The results from samples mimicking physiological conditions suggested very good applicability in the determination of chloride ion in physiological samples.

  5. Highly sensitive humidity sensing properties of carbon quantum dots films

    SciTech Connect

    Zhang, Xing; Ming, Hai; Liu, Ruihua; Han, Xiao; Kang, Zhenhui; Liu, Yang; Zhang, Yonglai

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► A humidity sensing device was fabricated based on carbon quantum dots (CQDs) films. ► The conductivity of the CQDs films shows a linear and rapid response to atmosphere humidity. ► The humidity sensing property was due to the hydrogen bonds between the functional groups on CQDs. -- Abstract: We reported the fabrication of a humidity sensing device based on carbon quantum dots (CQDs) film. The conductivity of the CQDs film has a linear and rapid response to relative humidity, providing the opportunity for the fabrication of humidity sensing devices. The mechanism of our humidity sensor was proposed to be the formation of hydrogen bonds between carbon quantum dots and water molecules in the humidity environment, which significantly promote the electrons migration. In a control experiment, this hypothesis was confirmed by comparing the humidity sensitivity of candle soot (i.e. carbon nanoparticles) with and without oxygen containing groups on the surfaces.

  6. Dots and Cubes

    ERIC Educational Resources Information Center

    Eaton, Bryan L.

    1974-01-01

    Illustrated is the mathematical analysis of a three-dimensional game using techniques from the calculus of finite differences. This game is an analog of the familiar two-dimensional game, Dots and Squares. (JP)

  7. Density functional calculation of the structural and electronic properties of germanium quantum dots

    SciTech Connect

    Anas, M. M.; Gopir, G.

    2015-04-24

    We apply first principles density functional computational methods to study the structures, densities of states (DOS), and higher occupied molecular orbital (HOMO) – lowest unoccupied molecular orbital (LUMO) gaps of selected free-standing Ge semiconductor quantum dots up to 1.8nm. Our calculations are performed using numerical atomic orbital approach where linear combination of atomic orbital was applied. The surfaces of the quantum dots was passivized by hydrogen atoms. We find that surface passivation does affect the electronic properties associated with the changes of surface state, electron localization, and the energy gaps of germanium nanocrystals as well as the confinement of electrons inside the quantum dots (QDs). Our study shows that the energy gaps of germanium quantum dots decreases with the increasing dot diameter. The size-dependent variations of the computed HOMO-LUMO gaps in our quantum dots model were found to be consistent with the effects of quantum confinement reported in others theoretical and experimental calculation.

  8. Notizen: Raman-Spektroskopische Untersuchungen der Systeme ASCl3/Cl2-AlCl3 und AsCl3 /Cl2-GaCl3/ Raman Spectra of the Systems AsCl3/Cl2—AlCl3 and AsCl3/Cl2-GaCl3

    NASA Astrophysics Data System (ADS)

    Demircan, B.; Brockner, W.

    1983-07-01

    In the systems investigated only the compounds AsAlCl8 and AsGaCl8 g are found. Raman spectra were recorded for the solid and molten compounds and for mixtures with excess ASCl3 + CL2 and AlCl3 and GaCl3 , respectively. The observed frequencies are assigned to tetrahedral AsCl4+, AlCl4- and GaCl4- units. Melting of AsCl4AlCl 4 and AsCl4GaCl4 causes a decomposition into AsCl3 , Cl2 and AlCl3 and GaCl3 , respectively.

  9. Nanoscale and Single-Dot Patterning of Colloidal Quantum Dots.

    PubMed

    Xie, Weiqiang; Gomes, Raquel; Aubert, Tangi; Bisschop, Suzanne; Zhu, Yunpeng; Hens, Zeger; Brainis, Edouard; Van Thourhout, Dries

    2015-11-11

    Using an optimized lift-off process we develop a technique for both nanoscale and single-dot patterning of colloidal quantum dot films, demonstrating feature sizes down to ~30 nm for uniform films and a yield of 40% for single-dot positioning, which is in good agreement with a newly developed theoretical model. While first of all presenting a unique tool for studying physics of single quantum dots, the process also provides a pathway toward practical quantum dot-based optoelectronic devices.

  10. Synthesis and characterization of copper(II)-bis(pyridin-2-carbonyl)amine (pyca)-pseudohalide complexes: 2D superstructure formation through C sbnd H⋯O hydrogen bond and π⋯π interaction in [Cu(pyca)Cl(NCO)

    NASA Astrophysics Data System (ADS)

    Chowdhury, Habibar; Rahaman, Sk Hafijur; Ghosh, Rajarshi; Sarkar, Sajal Kumar; Fun, Hoong-Kun; Ghosh, Barindra Kumar

    2007-01-01

    Three copper(II) complexes of type [Cu(pyca)(Cl)(Y)] ( 1- 3) [pyca = bis(pyridin-2-carbonyl)amine; Y = NCO -, N 3-, NCS -] have been synthesized and characterized on the basis of microanalytical, spectroscopic, magnetic, electrochemical, and other physicochemical properties. X-ray diffraction study in [Cu(pyca)(Cl)(NCO)] ( 1) reveals copper(II) center in a distorted trigonal bipyramidal environment through coordination by two pyridine N atoms, and one amine N atom of the tridentate ligand, one Cl -, and N atom of terminal NCO -. The mononuclear units in 1 are engaged in intermolecular C sbnd H⋯O hydrogen bonding leading to 1D chain, which are interlocked through face-to-face π⋯π interactions resulting in a 2D sheet. The complexes 1- 3 exhibit solvatochromism as evidenced from UV-Vis study in different solvent media. They display high-energy intraligand 1(π-π ∗) fluorescence at room temperature and intraligand 3(π-π ∗) phosphorescence in glassy solutions (MeOH at 77 K) and solid states. Electrochemical electron transfer study in MeOH solutions shows a reductive response presumably due to copper(II)-copper(I) couple.

  11. PREFACE: Quantum Dot 2010

    NASA Astrophysics Data System (ADS)

    Taylor, Robert A.

    2010-09-01

    These conference proceedings contain the written papers of the contributions presented at Quantum Dot 2010 (QD2010). The conference was held in Nottingham, UK, on 26-30 April 2010. The conference addressed topics in research on: 1. Epitaxial quantum dots (including self-assembled and interface structures, dots defined by electrostatic gates etc): optical properties and electron transport quantum coherence effects spin phenomena optics of dots in cavities interaction with surface plasmons in metal/semiconductor structures opto-electronics applications 2. Novel QD structures: fabrication and physics of graphene dots, dots in nano-wires etc 3. Colloidal quantum dots: growth (shape control and hybrid nanocrystals such as metal/semiconductor, magnetic/semiconductor) assembly and surface functionalisation optical properties and spin dynamics electrical and magnetic properties applications (light emitting devices and solar cells, biological and medical applications, data storage, assemblers) The Editors Acknowledgements Conference Organising Committee: Maurice Skolnick (Chair) Alexander Tartakovskii (Programme Chair) Pavlos Lagoudakis (Programme Chair) Max Migliorato (Conference Secretary) Paola Borri (Publicity) Robert Taylor (Proceedings) Manus Hayne (Treasurer) Ray Murray (Sponsorship) Mohamed Henini (Local Organiser) International Advisory Committee: Yasuhiko Arakawa (Tokyo University, Japan) Manfred Bayer (Dortmund University, Germany) Sergey Gaponenko (Stepanov Institute of Physics, Minsk, Belarus) Pawel Hawrylak (NRC, Ottawa, Canada) Fritz Henneberger (Institute for Physics, Berlin, Germany) Atac Imamoglu (ETH, Zurich, Switzerland) Paul Koenraad (TU Eindhoven, Nethehrlands) Guglielmo Lanzani (Politecnico di Milano, Italy) Jungil Lee (Korea Institute of Science and Technology, Korea) Henri Mariette (CNRS-CEA, Grenoble, France) Lu Jeu Sham (San Diego, USA) Andrew Shields (Toshiba Research Europe, Cambridge, UK) Yoshihisa Yamamoto (Stanford University, USA) Artur

  12. Colloidal Double Quantum Dots

    PubMed Central

    2016-01-01

    Conspectus Pairs of coupled quantum dots with controlled coupling between the two potential wells serve as an extremely rich system, exhibiting a plethora of optical phenomena that do not exist in each of the isolated constituent dots. Over the past decade, coupled quantum systems have been under extensive study in the context of epitaxially grown quantum dots (QDs), but only a handful of examples have been reported with colloidal QDs. This is mostly due to the difficulties in controllably growing nanoparticles that encapsulate within them two dots separated by an energetic barrier via colloidal synthesis methods. Recent advances in colloidal synthesis methods have enabled the first clear demonstrations of colloidal double quantum dots and allowed for the first exploratory studies into their optical properties. Nevertheless, colloidal double QDs can offer an extended level of structural manipulation that allows not only for a broader range of materials to be used as compared with epitaxially grown counterparts but also for more complex control over the coupling mechanisms and coupling strength between two spatially separated quantum dots. The photophysics of these nanostructures is governed by the balance between two coupling mechanisms. The first is via dipole–dipole interactions between the two constituent components, leading to energy transfer between them. The second is associated with overlap of excited carrier wave functions, leading to charge transfer and multicarrier interactions between the two components. The magnitude of the coupling between the two subcomponents is determined by the detailed potential landscape within the nanocrystals (NCs). One of the hallmarks of double QDs is the observation of dual-color emission from a single nanoparticle, which allows for detailed spectroscopy of their properties down to the single particle level. Furthermore, rational design of the two coupled subsystems enables one to tune the emission statistics from single

  13. Synthesis of highly fluorescent nitrogen and phosphorus doped carbon dots for the detection of Fe(3+) ions in cancer cells.

    PubMed

    Chandra, Soumen; Laha, Dipranjan; Pramanik, Arindam; Ray Chowdhuri, Angshuman; Karmakar, Parimal; Sahu, Sumanta Kumar

    2016-02-01

    Highly fluorescent nitrogen and phosphorus-doped carbon dots with a quantum yield 59% have been successfully synthesized from citric acid and di-ammonium hydrogen phosphate by single step hydrothermal method. The synthesized carbon dots have high solubility as well as stability in aqueous medium. The as-obtained carbon dots are well monodispersed with particle sizes 1.5-4 nm. Owing to a good tunable fluorescence property and biocompatibility, the carbon dots were applied for intercellular sensing of Fe(3+) ions as well as cancer cell imaging.

  14. Multinuclear magnetic resonance studies of the 2Feter dot 2S sup * ferredoxin from Anabaena species strain PCC 7120. 1. Sequence-specific hydrogen-1 resonance assignments and secondary structure in solution of the oxidized form

    SciTech Connect

    Oh, Byung-Ha; Markley, J.L. )

    1990-04-24

    Complete sequence-specific assignments were determined for the diamagnetic {sup 1}H resonances from Anabaena 7120 ferredoxin. A novel assignment procedure was followed whose first step was the identification of the {sup 13}C spin systems of the amino acids by a {sup 13}C({sup 13}C) double quantum correlation experiment. Then, the {sup 1}H spin systems of the amino acids were identified from the {sup 13}C spin systems by means of direct and relayed {sup 1}H({sup 13}C) single-bond correlations. The sequential resonance assignments were based mainly on conventional interresidue {sup 1}H{sup {alpha}}{sub i}-{sup 1}H{sup N}{sub i+1} NOE connectivities. Resonances from 18 residues were not resolved in two-dimensional {sup 1}H NMR spectra. When these residues were mapped onto the X-ray crystal structure of the homologous ferredoxin from Spirulina platensis, it was found that they correspond to amino acids close to the paramagnetic 2Fe{center dot}2S cluster. Cross peaks in two-dimensional homonuclear {sup 1}H NMR spectra were not observed for any protons closer than about 7.8 {angstrom} to both iron atoms. Secondary structural features identified in solution include two antiparallel {beta}-sheets, one parallel {beta}-sheet, and one {alpha}-helix.

  15. Molecular dynamics simulations of carbon dioxide hydrate growth in electrolyte solutions of NaCl and MgCl2

    NASA Astrophysics Data System (ADS)

    Yi, Lizhi; Liang, Deqing; Zhou, Xuebing; Li, Dongliang; Wang, Jianwei

    2014-12-01

    Molecular dynamics simulations are performed to study the growth of carbon dioxide (CO2) hydrate in electrolyte solutions of NaCl and MgCl2. The kinetic behaviour of the hydrate growth is examined in terms of cage content, density profile, and mobility of ions and water molecules, and how these properties are influenced by added NaCl and MgCl2. Our simulation results show that both NaCl and MgCl2 inhibit the CO2 hydrate growth. With a same mole concentration or ion density, MgCl2 exhibits stronger inhibition on the growth of CO2 hydrate than NaCl does. The growth rate of the CO2 hydrate in NaCl and MgCl2 solutions decreases slightly with increasing pressure. During the simulations, the Na+, Mg2+, and Cl- ions are mostly excluded by the growing interface front. We find that these ions decrease the mobility of their surrounding water molecules, and thus reduce the opportunity for these water molecules to form cage-like clusters toward hydrate formation. We also note that during the growth processes, several 51263 cages appear at the hydrate/solution interface, although they are finally transformed to tetrakaidecahedral (51262) cages. Structural defects consisting of one water molecule trapped in a cage with its hydrogen atoms being attracted by two Cl- ions have also been observed.

  16. 75 FR 69030 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2C10 (Regional Jet Series 700, 701, & 702...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-10

    ... springs, P/N 670-93465-1, were installed in production aeroplanes serial number 10266 (CL-600-2C10) and... rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and 3. Will... Series 700, 701, & 702) airplanes, serial numbers 10003 and subsequent; and Model CL-600-2D15...

  17. GaN quantum dots as optical transducers for chemical sensors

    SciTech Connect

    Weidemann, O.; Jegert, G.; Stutzmann, M.; Kandaswamy, P. K.; Monroy, E.

    2009-03-16

    GaN/AlN quantum dots were investigated as optical transducers for field effect chemical sensors. The structures were synthesized by molecular-beam epitaxy and covered by a semitransparent catalytic Pt top contact. Due to the thin (3 nm) AlN barriers, the variation of the quantum dot photoluminescence with an external electric field along the [0001] axis is dominated by the tunneling current rather than by the quantum confined Stark effect. An increasing field results in a blueshift of the luminescence and a decreasing intensity. This effect is used to measure the optical response of quantum dot superlattices upon exposure to molecular hydrogen.

  18. Hydrogen sensor

    DOEpatents

    Duan, Yixiang; Jia, Quanxi; Cao, Wenqing

    2010-11-23

    A hydrogen sensor for detecting/quantitating hydrogen and hydrogen isotopes includes a sampling line and a microplasma generator that excites hydrogen from a gas sample and produces light emission from excited hydrogen. A power supply provides power to the microplasma generator, and a spectrometer generates an emission spectrum from the light emission. A programmable computer is adapted for determining whether or not the gas sample includes hydrogen, and for quantitating the amount of hydrogen and/or hydrogen isotopes are present in the gas sample.

  19. Quantum Dots as Cellular Probes

    SciTech Connect

    Alivisatos, A. Paul; Gu, Weiwei; Larabell, Carolyn

    2004-09-16

    Robust and bright light emitters, semiconductor nanocrystals[quantum dots (QDs)] have been adopted as a new class of fluorescent labels. Six years after the first experiments of their uses in biological applications, there have been dramatic improvements in understanding surface chemistry, biocompatibility, and targeting specificity. Many studies have shown the great potential of using quantum dots as new probes in vitro and in vivo. This review summarizes the recent advances of quantum dot usage at the cellular level, including immunolabeling, cell tracking, in situ hybridization, FRET, in vivo imaging, and other related technologies. Limitations and potential future uses of quantum dot probes are also discussed.

  20. Self-assembly drives quantum dot photoluminescence.

    PubMed

    Plain, J; Sonnefraud, Y; Viste, P; Lérondel, G; Huant, S; Royer, P

    2009-03-01

    Engineering the spectral properties of quantum dots can be achieved by a control of the quantum dots organization on a substrate. Indeed, many applications of quantum dots as LEDs are based on the realization of a 3D architecture of quantum dots. In this contribution, we present a systematic study of the quantum dot organization obtained on different chemically modified substrates. By varying the chemical affinity between the quantum dots and the substrate, the quantum dot organization is strongly modified from the 2D monolayer to the 3D aggregates. Then the photoluminescence of the different obtained samples has been systematically studied and correlated with the quantum dot film organization. We clearly show that the interaction between the substrate and the quantum dot must be stronger than the quantum dot-quantum dot interaction to avoid 3D aggregation and that these organization strongly modified the photoluminescence of the film rather than intrinsic changes of the quantum dot induced by pure surface chemistry.

  1. 29 CFR 1910.103 - Hydrogen.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...—Regulations of the Department of Transportation published in 49 CFR Chapter I. (vi) DOT regulations—See § 1910..., threaded, socket, or compression fittings. Gaskets and thread sealants shall be suitable for hydrogen...) Joints in piping and tubing shall preferably be made by welding or brazing; flanged, threaded, socket,...

  2. Extracting inter-dot tunnel couplings between few donor quantum dots in silicon

    NASA Astrophysics Data System (ADS)

    Gorman, S. K.; Broome, M. A.; Keizer, J. G.; Watson, T. F.; Hile, S. J.; Baker, W. J.; Simmons, M. Y.

    2016-05-01

    The long term scaling prospects for solid-state quantum computing architectures relies heavily on the ability to simply and reliably measure and control the coherent electron interaction strength, known as the tunnel coupling, t c. Here, we describe a method to extract the t c between two quantum dots (QDs) utilising their different tunnel rates to a reservoir. We demonstrate the technique on a few donor triple QD tunnel coupled to a nearby single-electron transistor (SET) in silicon. The device was patterned using scanning tunneling microscopy-hydrogen lithography allowing for a direct measurement of the tunnel coupling for a given inter-dot distance. We extract {t}{{c}}=5.5+/- 1.8 {{GHz}} and {t}{{c}}=2.2+/- 1.3 {{GHz}} between each of the nearest-neighbour QDs which are separated by 14.5 nm and 14.0 nm, respectively. The technique allows for an accurate measurement of t c for nanoscale devices even when it is smaller than the electron temperature and is an ideal characterisation tool for multi-dot systems with a charge sensor.

  3. Benzen and Ethylene Binding to Copper(I)-Ziconium(IV) Chloride Materials: The Crystal Structure and Solid-State Reactivity of ((bz)2Cu)2Zr2Cl10.bz

    SciTech Connect

    Dattelbaum,A.; Martin, J.

    2006-01-01

    The solvothermal reaction of Cu{sub 2}ZrCl{sub 6} and ZrCl{sub 4} in benzene is shown to yield the molecular species ((bz){sub 2}Cu){sub 2}Zr{sub 2}Cl{sub 10} {center_dot} bz(1), which is characterized by single crystal X-ray diffraction. The structure consists of edge-shared dimers of zirconium chloride octahedra whose axial chlorides are bridged by bis-benzene chlorocuprate fragments. The Cu{sub 2}Zr{sub 2} tetramers are linked in the crystal lattice by edge-to-face {pi}-stacking of the coordinated and lattice benzene molecules, as well as benzene-to-chloride hydrogen bonding. Benzene is lost from this material in a stepwise fashion resulting in what are described to be chain, ((bz)Cu){sub 2}Zr{sub 2}Cl{sub 10} (3). The desolvated materials, 2 and 3, reversibly sorb ethylene, as characterized by sorption isotherms, in situ pressure-resolved synchrotron X-ray diffraction and UV/Vis diffuse reflectance spectroscopy.

  4. Pressure-Induced Phase Transition in Guanidinium Perchlorate: A Supramolecular Structure Directed by Hydrogen Bonding and Electrostatic Interactions

    SciTech Connect

    Li, Shourui; Li, Qian; Wang, Kai; Tan, Xiao; Zhou, Mi; Li, Bing; Liu, Bingbing; Zou, Guangtian; Zou, Bo

    2012-01-20

    In situ Raman spectroscopy and synchrotron X-ray diffraction (XRD) experiments have been performed to investigate the response of guanidinium perchlorate (C(NH{sub 2}){sub 3}{sup +} {center_dot} ClO{sub 4}{sup -}, GP) to high pressures of {approx}11 GPa. GP exhibits a typical supramolecular structure of two-dimensional (2D) hydrogen-bonded ionic networks at ambient conditions. A subtle phase transition, accompanied by the symmetry transformation from R3m to C2, has been confirmed by obvious changes in both Raman and XRD patterns at 4.5 GPa. The phase transition is attributed to the competition between hydrogen bonds and close packing of the supramolecular structure at high pressure. Hydrogen bonds have been demonstrated to evolve into a distorted state through the phase transition, accompanied by the reduction in separation of oppositely charged ions in adjacent sheet motifs. A detailed mechanism of the phase transition, as well as the cooperativity between hydrogen bonding and electrostatic interactions, is discussed by virtue of the local nature of the structure.

  5. Finding Areas on Dot Paper

    ERIC Educational Resources Information Center

    Pagni, David L.

    2007-01-01

    This article contains investigative activities to assist students in constructing formulas out of an understanding of the area of geometric shapes. Included with this article are a "Finding Areas on Square Dot Paper Activity Sheet" and a "Finding Areas on Triangle Dot Paper Activity Sheet." (Contains 1 table and 11 figures.)

  6. Isopiestic Determination of the Osmotic and Activity Coefficients of NaCl + SrCl2 + H2O at 298.15 K, and Representation with an Extended Ion-Interaction Model

    SciTech Connect

    Clegg, S L; Rard, J A; Miller, D G

    2004-11-09

    Isopiestic vapor-pressure measurements were made at 298.15 K for aqueous NaCl + SrCl{sub 2} solutions, using NaCl(aq) as the reference standard. The measurements for these ternary solutions were made at NaCl ionic strength fractions of y{sub 1} = 0.17066, 0.47366, and 0.82682 for the water activity range 0.9835 {ge} a{sub w} {ge} 0.8710. Our results, and those from two previous isopiestic studies, were combined and used with previously determined parameters for NaCl(aq) and those for SrCl{sub 2}(aq) determined here to evaluate the mixing parameters{sup S}{Theta}{sub Na,Sr} = (0.0562 {+-} 0.0007) kg {center_dot} mol{sup -1} and {Psi}{sub Na,Sr,Cl} = -(0.00705 {+-} 0.00017) kg{sup 2} {center_dot} mol{sup -2} for an extended form of Pitzer's ion-interaction model. These model parameters are valid for ionic strengths of I {le} 7.0 mol {center_dot} kg{sup -1}, where higher-order electrostatic effects have been included in the mixture model. If the fitting range is extended to the saturated solution molalities, then {sup S}{Theta}{sub Na,Sr} = (0.07885 {+-} 0.00195) kg {center_dot} mol{sup -1} and {Psi}{sub Na,Sr,Cl} = -(0.01230 {+-} 0.00033) kg{sup 2} {center_dot} mol{sup -2}. The extended ion-interaction model parameters obtained from available isopiestic data for SrCl{sub 2}(aq) at 298.15 K yield recommended values of the water activities and osmotic and activity coefficients.

  7. The development of a fullerene based hydrogen storage system

    SciTech Connect

    Brosha, E.L.; Davey, J.R.; Garzon, F.H.; Gottesfeld, S.

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The project objective was to evaluate hydrogen uptake by fullerene substrates and to probe the potential of the hydrogen/fullerene system for hydrogen fuel storage. As part of this project, the authors have completed and tested a fully automated, computer controlled system for measuring hydrogen uptake that is capable of handling both a vacuum of 1 x 10{sup -6} torr and pressures greater than 200 bars. The authors have first established conditions for significant uptake of hydrogen by fullerenes. Subsequently, hydrogenation and dehydrogenation of pure and catalyst-doped C60 was further studied to probe suitability for hydrogen storage applications. C60 {center_dot} H18.7 was prepared at 100 bar H2 and 400 C, corresponding to hydrogen uptake of 2.6 wt%. Dehydrogenation of C60 {center_dot} H18.7 was studied using thermogravimetric and powder x-ray diffraction analysis. The C60 {center_dot} H18.7 molecule was found to be stable up to 430 C in Ar, at which point the release of hydrogen took place simultaneously with the collapse of the fullerene structure. X-ray diffraction analysis performed on C60 {center_dot} H18.7 samples dehydrogenated at 454 C, 475 C, and 600 C showed an increasing volume fraction of amorphous material due to randomly oriented, single-layer graphine sheets. Evolved gas analysis using gas chromatography and mass spectroscopy confirmed the presence of both H{sub 2} and methane upon dehydrogenation, indicating decomposition of the fullerene. The remaining carbon could not be re-hydrogenated. These results provide the first complete evidence for the irreversible nature of fullerene hydrogenation and for limitations imposed on the hydrogenation/dehydrogenation cycle by the limited thermal stability of the molecular crystal of fullerene.

  8. High-enthalpy hydrogen adsorption in cation-exchanged variants of the microporous metal-organic framework Mn3[(Mn4Cl)3(BTT)8(CH3OH)10]2.

    PubMed

    Dinca, Mircea; Long, Jeffrey R

    2007-09-12

    Exchange of the guest Mn2+ ions in Mn3[(Mn4Cl)3(BTT)8(CH3OH)10]2 (1-Mn2+; BTT=1,3,5-benzenetristetrazolate) with selected cations results in the formation of isostructural framework compounds 1-M (M=Li+, Cu+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+). Similar to the parent compound, the new microporous materials are stable to desolvation and exhibit a high H2 storage capacity, ranging from 2.00 to 2.29 wt % at 77 K and 900 torr. Measurements of the isosteric heat of adsorption at zero coverage reveal a difference of 2 kJ/mol between the weakest and strongest H2-binding materials, which is attributed to variations in the strength of interaction between H2 molecules and unsaturated metal centers within each framework. The Co2+-exchanged compound, 1-Co2+, exhibits an initial enthalpy of adsorption of 10.5 kJ/mol, the highest yet observed for a microporous metal-organic framework.

  9. Quantum dot cascade laser

    PubMed Central

    2014-01-01

    We demonstrated an unambiguous quantum dot cascade laser based on InGaAs/GaAs/InAs/InAlAs heterostructure by making use of self-assembled quantum dots in the Stranski-Krastanow growth mode and two-step strain compensation active region design. The prototype generates stimulated emission at λ ~ 6.15 μm and a broad electroluminescence band with full width at half maximum over 3 μm. The characteristic temperature for the threshold current density within the temperature range of 82 to 162 K is up to 400 K. Moreover, our materials show the strong perpendicular mid-infrared response at about 1,900 cm-1. These results are very promising for extending the present laser concept to terahertz quantum cascade laser, which would lead to room temperature operation. PACS 42.55.Px; 78.55.Cr; 78.67.Hc PMID:24666965

  10. Visualization Dot Com

    SciTech Connect

    Bethel, Wes

    2000-02-09

    In this article, we explore the seemingly well-worn subject of distance-based, or remote visualization. Current practices in remote visualization tend to clump into two broad categories. One approach, which we'll call render-remote, is to render an image remotely, then transmit the data to the user. Another option, render-local, transfers raw data to the user, where it is then visualized and rendered on the local workstation. With advances in networking and graphics technology, we can explore a class of approaches from a new, third category. With this third category, which we'll called shared, or ''dot com'' visualization, we stand to reap the best of both worlds; minimized data transfers and workstation-accelerated rendering. We will describe a prototype system called Visapult currently under development at Lawrence Berkeley National Laboratory (LBNL) that strikes such a balance, achieving a blended, scalable visualization tool. ''Dot com'' visualization means that remote and local resources collaborate and negotiate, combining capabilities to produce a final product.

  11. Association quotients of aluminum sulphate complexes in NaCl media from 50 to 125 C: Results of a potentiometric and solubility study

    SciTech Connect

    Ridley, M.K.; Kettler, R.M.; Wesolowski, D.J.; Palmer, D.A.

    1999-02-01

    The speciation and molal formation quotients for the complexation of aluminum with sulphate were measured based on potentiometric and solubility experiments. Potentiometric titrations, utilizing a hydrogen-electrode concentration cell, were performed from 50 to 125 C at ionic strengths of 0.1, 0.3 and 1.0 molal in aqueous NaCl media. Two aluminum-sulphate species, AlSO{sub 4}{sup +} and Al(SO{sub 4}){sub 2}{sup {minus}}, were identified from the titration data and the formation quotients for these species were modeled by empirical equations to describe their temperature and ionic strength dependencies. Thermodynamic parameters for the complexation reactions were obtained by differentiating the empirical equations with respect to temperature. The thermodynamic quantities obtained for the formation of AlSO{sub 4}{sup +} at 50 C and infinite dilution are: logK{sub 1} = 3.7 {+-} 0.4, {Delta}H{sub 1}{degree} = {minus}10 {+-} 30 kJ/mol, {Delta}S{sub 1}{degree} = 40 {+-} 100 J/K{center_dot}mol and {Delta}C{sub p 1}{degree} = 1900 {+-} 800 J/K{center_dot}mol; whereas the values for Al(SO{sub 4}){sub 2}{sup {minus}} are: logK{sub 2} = 5.6 {+-} 0.7, {Delta}H{sub 2}{degree} = 10 {+-} 50 kJ/mol, {Delta}S{sub 2}{degree} = 100 {+-} 100 J/K{center_dot}mol and {Delta}C{sub p 2}{degree} = 2800 {+-} 800 J/K{center_dot}mol. A solubility study, which was undertaken to verify the 50 C potentiometric data, was performed by reacting powdered gibbsite (Al(OH){sub 3}) with sulphate solutions at 10{sup {minus}3.5} and 10{sup {minus}4} molal H{sup +}, total sulphate concentrations from 0.005 to 0.080 molal, and 0.1 and 1.0 molal ionic strength in aqueous NaCl media. The results of the solubility study are in good agreement with the potentiometric data and establish that Al-sulphate complexation substantially enhances the equilibrium solubility of gibbsite.

  12. Quantum Dot Light-Emitting Diodes Based on Inorganic Perovskite Cesium Lead Halides (CsPbX3 ).

    PubMed

    Song, Jizhong; Li, Jianhai; Li, Xiaoming; Xu, Leimeng; Dong, Yuhui; Zeng, Haibo

    2015-11-25

    Novel quantum-dot light-emitting diodes based on all-inorganic perovskite CsPbX3 (X = Cl, Br, I) nanocrystals are reported. The well-dispersed, single-crystal quantum dots (QDs) exhibit high quantum yields, and tunable light emission wavelength. The demonstration of these novel perovskite QDs opens a new avenue toward designing optoelectronic devices, such as displays, photodetectors, solar cells, and lasers.

  13. Lighting Up Enzymes for Solar Hydrogen Production (Fact Sheet)

    SciTech Connect

    Not Available

    2011-02-01

    Scientists at the National Renewable Energy Laboratory (NREL) have combined quantum dots, which are spherical nanoparticles that possess unique size-tunable photophysical properties, with the high substrate selectivity and fast turnover of hydrogenase enzymes to achieve light-driven hydrogen (H2) production. They found that quantum dots of cadmium telluride coated in carboxylic acids easily formed highly stable complexes with the hydrogenase and that these hybrid assemblies functioned to catalyze H2 production using the energy of sunlight.

  14. Illusory movement of dotted lines

    PubMed Central

    Ito, Hiroyuki; Anstis, Stuart; Cavanagh, Patrick

    2013-01-01

    When oblique rows of black and white dots drifted horizontally across a mid-grey surround, the perceived direction of motion was shifted to be almost parallel to the dotted lines and was often nearly orthogonal to the real motion. The reason is that the black/white contrast signals between adjacent dots along the length of the line are stronger than black/grey or white/grey contrast signals across the line, and the motion is computed as a vector sum of local contrast-weighted motion signals. PMID:19911636

  15. Local Effects in the X-ray Absorption Spectrum of CaCl2, MgCl2, and NaCl Solutions

    SciTech Connect

    Kulik, H J; Correa Tedesco, A A; Schwegler, E; Prendergast, D; Galli, G

    2010-04-12

    Both first principles molecular dynamics and theoretical X-ray absorption spectroscopy have been used to investigate the aqueous solvation of cations in 0.5 M MgCl{sub 2}, CaCl{sub 2}, and NaCl solutions. We focus here on the species-specific effects that Mg{sup 2+}, Ca{sup 2+}, and Na{sup +}, have on the X-ray absorption spectrum of the respective solutions. For the divalent cations, we find that the hydrogen bonding characteristics of the more rigid magnesium first shell water molecules differ from those in the more flexible solvation shell surrounding calcium. In particular, the first solvation shell water molecules of calcium are accessible to forming acceptor hydrogen bonds, and this results in an enhancement of a post-edge peak near 540 eV. The absence of acceptor hydrogen bonds for magnesium first shell water molecules provides an explanation for the experimental and theoretical observation of a lack of enhancement at the post-main-edge peak. For the sodium monovalent cation we find that the broad tilt angle distribution results in a broadening of post-edge features, despite populations in donor-and-acceptor configurations consistent with calcium. We also present the re-averaged spectra of the MgCl{sub 2}, CaCl{sub 2}, and NaCl solutions and show that trends apparent with increasing concentration (0.5 M, 2.0 M, 4.0 M) are consistent with experiment. Finally, we examine more closely both the effect that cation coordination number has on the hydrogen bonding network and the relative perturbation strength of the cations on lone pair oxygen orbitals.

  16. Dependence of heavy hole exciton binding energy and the strain distribution in GaAs1-xBix/GaAs finite spherical quantum dots on Bi content in the material

    NASA Astrophysics Data System (ADS)

    Das, Subhasis; Sharma, Akant Sagar; Das, T. D.; Dhar, S.

    2015-10-01

    The ground state binding energy of heavy hole excitons confined in GaAs1-xBix/GaAs spherical quantum dots is calculated as a function of dot radius and the Bi content using a Variational method based on 1-s hydrogenic wave functions with effective mass approximation. The parameter shows strong dependence on the Bi mole fraction x, particularly at smaller values of the dot radii. The strain associated with the quantum dot is found to decrease exponentially with increase in dot radius and shows a linear increase with Bi composition.

  17. Hydrogen Production

    SciTech Connect

    2014-09-01

    This 2-page fact sheet provides a brief introduction to hydrogen production technologies. Intended for a non-technical audience, it explains how different resources and processes can be used to produce hydrogen. It includes an overview of research goals as well as “quick facts” about hydrogen energy resources and production technologies.

  18. Quantum dots: Rethinking the electronics

    NASA Astrophysics Data System (ADS)

    Bishnoi, Dimple

    2016-05-01

    In this paper, we demonstrate theoretically that the Quantum dots are quite interesting for the electronics industry. Semiconductor quantum dots (QDs) are nanometer-scale crystals, which have unique photo physical, quantum electrical properties, size-dependent optical properties, There small size means that electrons do not have to travel as far as with larger particles, thus electronic devices can operate faster. Cheaper than modern commercial solar cells while making use of a wider variety of photon energies, including "waste heat" from the sun's energy. Quantum dots can be used in tandem cells, which are multi junction photovoltaic cells or in the intermediate band setup. PbSe (lead selenide) is commonly used in quantum dot solar cells.

  19. Surfactant-induced hydrogen production in cyanobacteria

    SciTech Connect

    Famiglietti, M.; Luisi, P.L. ); Hochkoeppler, A. . Dept. di Biologia)

    1993-10-01

    Addition of Tween 85 to aqueous suspensions of Anabaena variabilis induced photosynthetic evolution of hydrogen over a time span of several weeks: as much as 148 nmol H[sub 2]/h [center dot] mg dry weight was produced in the first week by a suspension containing 4.2 mg dry weight of cells and 77 mM Tween 85. The chemical structure of Tween 85 was a necessary prerequisite for inducing hydrogen production, as compounds such as Tween 20, 60, and 80 had a quite different effect. There was a coupling between photosynthetic oxygen evolution and hydrogen evolution: Hydrogen evolution started to be effective only when oxygen evolution subdued. The presence of heterocysts in A. variabilis was also required for the Tween-induced hydrogen production. Based on these observations, possible mechanisms for the photosynthetic effect of Tween 85 are advanced and discussed.

  20. Quantum Dots in Cell Biology

    PubMed Central

    Barroso, Margarida M.

    2011-01-01

    Quantum dots are semiconductor nanocrystals that have broad excitation spectra, narrow emission spectra, tunable emission peaks, long fluorescence lifetimes, negligible photobleaching, and ability to be conjugated to proteins, making them excellent probes for bioimaging applications. Here the author reviews the advantages and disadvantages of using quantum dots in bioimaging applications, such as single-particle tracking and fluorescence resonance energy transfer, to study receptor-mediated transport. PMID:21378278

  1. Heterogeneous Reaction of ClONO2(g) + NaCl(s) to Cl2(g) + NaNO3(s)

    NASA Technical Reports Server (NTRS)

    Timonen, Raimo S.; Chu, Liang T.; Leu, Ming-Taun; Keyser, Leon F.

    1994-01-01

    The heterogeneous reaction of ClON02 + NaCl yields Cl2 + NaNO3 (eq 1) was investigated over a temperature range 220-300 K in a flow-tube reactor interfaced with a differentially pumped quadrupole mass spectrometer. Partial pressures of ClON02 in the range 10(exp -8) - 10(exp -5) Torr were used. Granule sizes and surface roughness of the NaCl substrates were determined by using a scanning electron microscope, and in separate experiments, surface areas of the substrates were measured by using BET analysis of gas-adsorption isotherms. For dry NaCl substrates, both the decay rates of ClON02 and the growth rates Of C12 were used to obtain reaction probabilities, gamma(sub l) = (4.6 +/- 3.0) x 10(exp -3) at 296 K and (6.7 +/- 3.2) x 10(exp -1) at 225 K, after considering the internal surface area, The error bars represent 1 standard deviation. The Cl2 yield based on the ClONO2 reacted was measured to be 1.0 +/- 0.2. In order to mimic the conditions encountered in the lower stratosphere, the effect of water vapor pressures between 5 x 10(exp -5) and 3 x 10(exp -4) Torr on reaction 1 was also studied. With added H20, reaction probabilities, gamma = (4.1 +/- 2.1) x 10(exp -3) at 296 K and (4.7 +/- 2.9) x 10(exp -3) at 225 K, were obtained. A trace of HOCl, the reaction product from the ClON02 + H20 yield HOCl + HN03 reaction, was observed in addition to the C12 product from reaction 1. The implications of this result for the enhancement of hydrogen chloride in the stratosphere after the El Chichon volcanic eruption and for the marine troposphere are discussed.

  2. Single to quadruple quantum dots with tunable tunnel couplings

    SciTech Connect

    Takakura, T.; Noiri, A.; Obata, T.; Yoneda, J.; Yoshida, K.; Otsuka, T.; Tarucha, S.

    2014-03-17

    We prepare a gate-defined quadruple quantum dot to study the gate-tunability of single to quadruple quantum dots with finite inter-dot tunnel couplings. The measured charging energies of various double dots suggest that the dot size is governed by the gate geometry. For the triple and quadruple dots, we study the gate-tunable inter-dot tunnel couplings. For the triple dot, we find that the effective tunnel coupling between side dots significantly depends on the alignment of the center dot potential. These results imply that the present quadruple dot has a gate performance relevant for implementing spin-based four-qubits with controllable exchange couplings.

  3. High efficiency stationary hydrogen storage

    SciTech Connect

    Hynek, S.; Fuller, W.; Truslow, S.

    1995-09-01

    Stationary storage of hydrogen permits one to make hydrogen now and use it later. With stationary hydrogen storage, one can use excess electrical generation capacity to power an electrolyzer, and store the resultant hydrogen for later use or transshipment. One can also use stationary hydrogen as a buffer at fueling stations to accommodate non-steady fueling demand, thus permitting the hydrogen supply system (e.g., methane reformer or electrolyzer) to be sized to meet the average, rather than the peak, demand. We at ADL designed, built, and tested a stationary hydrogen storage device that thermally couples a high-temperature metal hydride to a phase change material (PCM). The PCM captures and stores the heat of the hydriding reaction as its own heat of fusion (that is, it melts), and subsequently returns that heat of fusion (by freezing) to facilitate the dehydriding reaction. A key component of this stationary hydrogen storage device is the metal hydride itself. We used nickel-coated magnesium powder (NCMP) - magnesium particles coated with a thin layer of nickel by means of chemical vapor deposition (CVD). Magnesium hydride can store a higher weight fraction of hydrogen than any other practical metal hydride, and it is less expensive than any other metal hydride. We designed and constructed an experimental NCM/PCM reactor out of 310 stainless steel in the form of a shell-and-tube heat exchanger, with the tube side packed with NCMP and the shell side filled with a eutectic mixture of NaCL, KCl, and MgCl{sub 2}. Our experimental results indicate that with proper attention to limiting thermal losses, our overall efficiency will exceed 90% (DOE goal: >75%) and our overall system cost will be only 33% (DOE goal: <50%) of the value of the delivered hydrogen. It appears that NCMP can be used to purify hydrogen streams and store hydrogen at the same time. These prospects make the NCMP/PCM reactor an attractive component in a reformer-based hydrogen fueling station.

  4. Alkyl Chlorides as Hydrogen Bond Acceptors

    SciTech Connect

    Nadas, Janos I; Vukovic, Sinisa; Hay, Benjamin

    2012-01-01

    To gain an understanding of the role of an alkyl chloride as a hydrogen bond acceptor, geometries and interaction energies were calculated at the MP2/aug-cc-pVDZ level of theory for complexes between ethyl chloride and representative hydrogen donor groups. The results establish that these donors, which include hydrogen cyanide, methanol, nitrobenzene, pyrrole, acetamide, and N-methylurea, form X-H {hor_ellipsis} Cl hydrogen bonds (X = C, N, O) of weak to moderate strength, with {Delta}E values ranging from -2.8 to -5.3 kcal/mol.

  5. Hydrogen Spectrum

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    The series of absorption or emission lines that are characteristic of the hydrogen atom. According to the Bohr theory of the hydrogen atom, devised by Danish physicist Neils Bohr (1885-1962) in 1913, the hydrogen atom can be envisaged as consisting of a central nucleus (a proton) around which a single electron revolves. The electron is located in one of a number of possible permitted orbits, each...

  6. Microwave Spectra and Structures of H_2S-CuCl and H_2O-CuCl.

    NASA Astrophysics Data System (ADS)

    Walker, N. R.; Wheatley, D. E.; Stephens, S. L.; Roberts, F. J.; Mikhailov, V. A.; Legon, A. C.

    2010-06-01

    A Balle-Flygare FT-MW spectrometer coupled to a laser ablation source has been used to measure the pure rotational spectra of H2S-CuCl and H2O-CuCl. Both molecules are generated via laser ablation (532 nm) of a metal rod in the presence of CCl4, argon, a low partial pressure of H2S or H2O and are stabilized by supersonic expansion. Rotational constants and centrifugal distortion constants have been measured for eight isotopologues of H2S-CuCl with substitutions available at the copper, chlorine and hydrogen atoms. Transitions in the spectra of nine isotopologues of H2O-CuCl have been measured with isotopic substitutions achieved for every atom. The spectra of both H2S-CuCl and H2O-CuCl are consistent with a linear arrangement of sulphur or oxygen, metal and chlorine atoms. The structure of H2S-CuCl is pyramidal with CS symmetry. The structure of H2O-CuCl is either C2v planar at equilibrium or CS pyramidal but with a low potential-energy barrier to planarity such that the v=0 and 1 states associated with the motion that inverts the configuration at the O atom are well separated. Nuclear quadrupole coupling constants have been measured for the chlorine and copper atoms in each molecule. Nuclear spin-rotation constants have been determined for the copper atom.

  7. Coal hydrogenation

    SciTech Connect

    Sinor, J.E.

    1981-01-06

    Disclosure is made of a method and apparatus for reacting carbonaceous material such as pulverized coal with heated hydrogen to form hydrocarbon gases and liquids suitable for conversion to fuels wherein the reaction involves injection of pulverized coal entrained in a minimum amount of gas and mixing the entrained coal at ambient temperature with a separate source of heated hydrogen. The heated hydrogen and entrained coal are injected through a rocket engine type injector device. The coal particles are reacted with hydrogen in a reaction chamber downstream of the injector. The products of reaction are rapidly quenched as they exit the reaction chamber and are subsequently collected.

  8. Impurity-modulated Aharonov-Bohm oscillations and intraband optical absorption in quantum dot-ring nanostructures

    NASA Astrophysics Data System (ADS)

    Barseghyan, M. G.; Manaselyan, A. Kh.; Laroze, D.; Kirakosyan, A. A.

    2016-07-01

    In this work we study the electronic states in quantum dot-ring complex nanostructures with an on-center hydrogenic impurity. The influence of the impurity on Aharonov-Bohm energy spectra oscillations and intraband optical absorption is investigated. It is shown that in the presence of a hydrogenic donor impurity the Aharonov-Bohm oscillations in quantum dot-ring structures become highly tunable. Furthermore, the presence of the impurity drastically changes the intraband absorption spectra due to the strong controllability of the electron localization type.

  9. Dynamic observing tonometry (DOT)

    NASA Astrophysics Data System (ADS)

    Kanngiesser, Hartmut E.; Robert, Yves C.

    1999-06-01

    To help improve early detection of vascular eye diseases, a method, named Dynamic Observing Tonometry (DOT), for measuring the intra-ocular pressure (IOP) has been developed, which allows for simultaneous ophthalmoscopy and dynamic tonometry of the human eye. Material and Method. A system for the application of this method is presented, consisting of a transducer to be placed on the corneal surface and of a stand-alone base unit. The latter can be connected to a personal computer for further data processing and storage. The transducer consists of a Goldmann-type contact lens modified by implementing means for transparent pressure-measurement of IOP. A small flat membrane in the center of the lens applanates the cornea. A liquid transmits the applanation pressure from the opposite side of this membrane to a pressure sensor located outside the optical pathway. Time-dependent IOP's are transmitted telemetrically to the base unit for processing. Results. Current initial tests provide evidence for the viability of the concept and have demonstrated the performance of the system. Typical time dependent IOP measurements obtained with an experimental device are presented. Clinical trials with two prototypes are underway. Conclusion: The proposed device allows the ophthalmology to perform the ordinary slit-lamp fundus examinations combined with simultaneous dynamic tonometry. It offers for the first time easy and precise analysis of cardiac and respiratory- modulated intra-ocular pressure while directly observing the choroid and the papilla, as well as the analysis of heart rate variability and inspection of the iridocorneal angle at varying applied pressure. Moreover, dynamic observing tonometry gives easy access to examination procedures such as tonography and ophthalmodynamometry, which have been rarely performed despite their potential diagnostic value due to the complexity of experimental protocols hitherto used.

  10. 75 FR 6862 - Airworthiness Directives; Bombardier, Inc. Model CL-600-1A11 (CL-600), CL-600-2A12 (CL-601), CL...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-12

    ...- 104 and 2770571-105, were installed in production on the following aircraft: CL-600-1A11 , CL-600-2A12... Policies and Procedures (44 FR 11034, February 26, 1979); and 3. Will not have a significant economic...), and (c)(3) of this AD. (1) Model CL-600-1A11 (CL-600) airplanes, serial numbers 1004 through...

  11. Cl- sensitive biosensor used electrolyte-solution-gate diamond FETs.

    PubMed

    Song, Kwang-Soup; Sakai, Toshikatsu; Kanazawa, Hirofumi; Araki, Yuta; Umezawa, Hitoshi; Tachiki, Minoru; Kawarada, Hiroshi

    2003-11-15

    We have investigated the electrolyte-solution-gate field effect transisitors (SGFETs) used hydrogen terminated (H-terminated) or partially oxygen terminated (O-terminated) polycrystalline diamond surface in the Cl- and Br- ionic solutions. The H-terminated channel SGFETs are insensitive to pH values in electrolyte solutions. The threshold voltages of the diamond SGFETs shift according to the density of Cl- and Br- ions about 30 mV/decade. One of the attractive biomedical applications for the Cl- sensitive SGFETs is the detection of chloride density in blood or in sweat especially in the case of cystic fibrosis. The sensitivities of Cl- and Br- ions have been lost on the partially O-terminated diamond surface. These phenomena can be explained by the polarity of surface change on the H-terminated and the O-terminated surface.

  12. 49 CFR 178.345 - General design and construction requirements applicable to Specification DOT 406 (§ 178.346), DOT...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... applicable to Specification DOT 406 (§ 178.346), DOT 407 (§ 178.347), and DOT 412 (§ 178.348) cargo tank....345 General design and construction requirements applicable to Specification DOT 406 (§ 178.346), DOT 407 (§ 178.347), and DOT 412 (§ 178.348) cargo tank motor vehicles....

  13. Optical Fiber Sensing Using Quantum Dots

    PubMed Central

    Jorge, Pedro; Martins, Manuel António; Trindade, Tito; Santos, José Luís; Farahi, Faramarz

    2007-01-01

    Recent advances in the application of semiconductor nanocrystals, or quantum dots, as biochemical sensors are reviewed. Quantum dots have unique optical properties that make them promising alternatives to traditional dyes in many luminescence based bioanalytical techniques. An overview of the more relevant progresses in the application of quantum dots as biochemical probes is addressed. Special focus will be given to configurations where the sensing dots are incorporated in solid membranes and immobilized in optical fibers or planar waveguide platforms.

  14. Biosynthesis of luminescent quantum dots in an earthworm.

    PubMed

    Stürzenbaum, S R; Höckner, M; Panneerselvam, A; Levitt, J; Bouillard, J-S; Taniguchi, S; Dailey, L-A; Ahmad Khanbeigi, R; Rosca, E V; Thanou, M; Suhling, K; Zayats, A V; Green, M

    2013-01-01

    The synthesis of designer solid-state materials by living organisms is an emerging field in bio-nanotechnology. Key examples include the use of engineered viruses as templates for cobalt oxide (Co(3)O(4)) particles, superparamagnetic cobalt-platinum alloy nanowires and gold-cobalt oxide nanowires for photovoltaic and battery-related applications. Here, we show that the earthworm's metal detoxification pathway can be exploited to produce luminescent, water-soluble semiconductor cadmium telluride (CdTe) quantum dots that emit in the green region of the visible spectrum when excited in the ultraviolet region. Standard wild-type Lumbricus rubellus earthworms were exposed to soil spiked with CdCl(2) and Na(2)TeO(3) salts for 11 days. Luminescent quantum dots were isolated from chloragogenous tissues surrounding the gut of the worm, and were successfully used in live-cell imaging. The addition of polyethylene glycol on the surface of the quantum dots allowed for non-targeted, fluid-phase uptake by macrophage cells.

  15. Biosynthesis of luminescent quantum dots in an earthworm

    NASA Astrophysics Data System (ADS)

    Stürzenbaum, S. R.; Höckner, M.; Panneerselvam, A.; Levitt, J.; Bouillard, J.-S.; Taniguchi, S.; Dailey, L.-A.; Khanbeigi, R. Ahmad; Rosca, E. V.; Thanou, M.; Suhling, K.; Zayats, A. V.; Green, M.

    2013-01-01

    The synthesis of designer solid-state materials by living organisms is an emerging field in bio-nanotechnology. Key examples include the use of engineered viruses as templates for cobalt oxide (Co3O4) particles, superparamagnetic cobalt-platinum alloy nanowires and gold-cobalt oxide nanowires for photovoltaic and battery-related applications. Here, we show that the earthworm's metal detoxification pathway can be exploited to produce luminescent, water-soluble semiconductor cadmium telluride (CdTe) quantum dots that emit in the green region of the visible spectrum when excited in the ultraviolet region. Standard wild-type Lumbricus rubellus earthworms were exposed to soil spiked with CdCl2 and Na2TeO3 salts for 11 days. Luminescent quantum dots were isolated from chloragogenous tissues surrounding the gut of the worm, and were successfully used in live-cell imaging. The addition of polyethylene glycol on the surface of the quantum dots allowed for non-targeted, fluid-phase uptake by macrophage cells.

  16. Hydrogen Bibliography

    SciTech Connect

    Not Available

    1991-12-01

    The Hydrogen Bibliography is a compilation of research reports that are the result of research funded over the last fifteen years. In addition, other documents have been added. All cited reports are contained in the National Renewable Energy Laboratory (NREL) Hydrogen Program Library.

  17. 14 CFR 323.13 - DOT actions.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false DOT actions. 323.13 Section 323.13... REGULATIONS TERMINATIONS, SUSPENSIONS, AND REDUCTIONS OF SERVICE § 323.13 DOT actions. (a) If an objection has been filed under this part, DOT will dispose of the objection by order. (b) If no objection has...

  18. 49 CFR 199.5 - DOT procedures.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false DOT procedures. 199.5 Section 199.5 Transportation... DOT procedures. The anti-drug and alcohol programs required by this part must be conducted according to the requirements of this part and DOT Procedures. Terms and concepts used in this part have...

  19. Hydrogen energy.

    PubMed

    Edwards, P P; Kuznetsov, V L; David, W I F

    2007-04-15

    The problem of anthropogenically driven climate change and its inextricable link to our global society's present and future energy needs are arguably the greatest challenge facing our planet. Hydrogen is now widely regarded as one key element of a potential energy solution for the twenty-first century, capable of assisting in issues of environmental emissions, sustainability and energy security. Hydrogen has the potential to provide for energy in transportation, distributed heat and power generation and energy storage systems with little or no impact on the environment, both locally and globally. However, any transition from a carbon-based (fossil fuel) energy system to a hydrogen-based economy involves significant scientific, technological and socio-economic barriers. This brief report aims to outline the basis of the growing worldwide interest in hydrogen energy and examines some of the important issues relating to the future development of hydrogen as an energy vector.

  20. Reversible Photoswitching of Carbon Dots

    PubMed Central

    Khan, Syamantak; Verma, Navneet Chandra; Gupta, Abhishek; Nandi, Chayan Kanti

    2015-01-01

    We present a method of reversible photoswitching in carbon nanodots with red emission. A mechanism of electron transfer is proposed. The cationic dark state, formed by the exposure of red light, is revived back to the bright state with the very short exposure of blue light. Additionally, the natural on-off state of carbon dot fluorescence was tuned using an electron acceptor molecule. Our observation can make the carbon dots as an excellent candidate for the super-resolution imaging of nanoscale biomolecules within the cell. PMID:26078266

  1. Toxicity of Oxidatively Degraded Quantum Dots

    PubMed Central

    Wiecinski, Paige N.; Metz, Kevin M.; King Heiden, Tisha C.; Louis, Kacie M.; Mangham, Andrew N.; Hamers, Robert J.; Heideman, Warren; Peterson, Richard E.; Pedersen, Joel A.

    2014-01-01

    Once released into the environment, engineered nanoparticles (eNPs) are subjected to processes that may alter their physical or chemical properties, potentially altering their toxicity vis-à-vis the as-synthesized materials. We examined the toxicity to zebrafish embryos of CdSecore/ZnSshell quantum dots (QDs) before and after exposure to an in vitro chemical model designed to simulate oxidative weathering in soil environments based on a reductant-driven Fenton’s reaction. Exposure to these oxidative conditions resulted in severe degradation of the QDs: the Zn shell eroded, Cd2+ and selenium were released, and amorphous Se-containing aggregates were formed. Weathered QDs exhibited higher potency than did as-synthesized QDs. Morphological endpoints of toxicity included pericardial, ocular and yolk sac edema, non-depleted yolk, spinal curvature, tail malformations, and craniofacial malformations. To better understand the selenium-like toxicity observed in QD exposures, we examined the toxicity of selenite, selenate and amorphous selenium nanoparticles (SeNPs). Selenite exposures resulted in high mortality to embryos/larvae while selenate and SeNPs were non-toxic. Co-exposures to SeNPs + CdCl2 resulted in dramatic increase in mortality and recapitulated the morphological endpoints of toxicity observed with weathered QD exposures. Cadmium body burden was increased in larvae exposed to weathered QDs or SeNP + CdCl2 suggesting the increased potency of weathered QDs was due to selenium modulation of cadmium toxicity. Our findings highlight the need to examine the toxicity of eNPs after they have undergone environmental weathering processes. PMID:23815598

  2. Chlorine doped graphene quantum dots: Preparation, properties, and photovoltaic detectors

    SciTech Connect

    Zhao, Jianhong; Xiang, Jinzhong; Tang, Libin Ji, Rongbin Yuan, Jun; Zhao, Jun; Yu, Ruiyun; Tai, Yunjian; Song, Liyuan

    2014-09-15

    Graphene quantum dots (GQDs) are becoming one of the hottest advanced functional materials because of the opening of the bandgap due to quantum confinement effect, which shows unique optical and electrical properties. The chlorine doped GQDs (Cl-GQDs) have been fabricated by chemical exfoliation of HCl treated carbon fibers (CFs), which were prepared from degreasing cotton through an annealing process at 1000 °C for 30 min. Raman study shows that both G and 2D peaks of GQDs may be redshifted (softened) by chlorine doping, leading to an n-type doping. The first vertical (Cl)-GQDs based photovoltaic detectors have been demonstrated, both the light absorbing and electron-accepting roles for (Cl)-GQDs in photodetection have been found, resulting in an exceptionally big ratio of photocurrent to dark current as high as ∼10{sup 5} at room temperature using a 405 nm laser irradiation under the reverse bias voltage. The study expands the application of (Cl)-GQDs to the important optoelectronic detection devices.

  3. Chlorine doped graphene quantum dots: Preparation, properties, and photovoltaic detectors

    NASA Astrophysics Data System (ADS)

    Zhao, Jianhong; Tang, Libin; Xiang, Jinzhong; Ji, Rongbin; Yuan, Jun; Zhao, Jun; Yu, Ruiyun; Tai, Yunjian; Song, Liyuan

    2014-09-01

    Graphene quantum dots (GQDs) are becoming one of the hottest advanced functional materials because of the opening of the bandgap due to quantum confinement effect, which shows unique optical and electrical properties. The chlorine doped GQDs (Cl-GQDs) have been fabricated by chemical exfoliation of HCl treated carbon fibers (CFs), which were prepared from degreasing cotton through an annealing process at 1000 °C for 30 min. Raman study shows that both G and 2D peaks of GQDs may be redshifted (softened) by chlorine doping, leading to an n-type doping. The first vertical (Cl)-GQDs based photovoltaic detectors have been demonstrated, both the light absorbing and electron-accepting roles for (Cl)-GQDs in photodetection have been found, resulting in an exceptionally big ratio of photocurrent to dark current as high as ˜105 at room temperature using a 405 nm laser irradiation under the reverse bias voltage. The study expands the application of (Cl)-GQDs to the important optoelectronic detection devices.

  4. Quantum Dots for Molecular Pathology

    PubMed Central

    True, Lawrence D.; Gao, Xiaohu

    2007-01-01

    Assessing malignant tumors for expression of multiple biomarkers provides data that are critical for patient management. Quantum dot-conjugated probes to specific biomarkers are powerful tools that can be applied in a multiplex manner to single tissue sections of biopsies to measure expression levels of multiple biomarkers. PMID:17251330

  5. Inhibition in Dot Comparison Tasks

    ERIC Educational Resources Information Center

    Clayton, Sarah; Gilmore, Camilla

    2015-01-01

    Dot comparison tasks are commonly used to index an individual's Approximate Number System (ANS) acuity, but the cognitive processes involved in completing these tasks are poorly understood. Here, we investigated how factors including numerosity ratio, set size and visual cues influence task performance. Forty-four children aged 7-9 years completed…

  6. Reading Comprehension Strategy: Rainbow Dots

    ERIC Educational Resources Information Center

    Moore, Claire; Lo, Lusa

    2008-01-01

    An action research study was conducted using the Rainbow Dots strategy to evaluate its effectiveness on reading comprehension skills in a third-grade class with students both with and without a specific learning disability. Results of the study indicated that students' overall performances in reading comprehension have increased. Students also…

  7. Vertical asymmetric double quantum dots

    NASA Astrophysics Data System (ADS)

    Roßbach, R.; Reischle, M.; Beirne, G. J.; Schweizer, H.; Jetter, M.; Michler, P.

    2007-01-01

    Two layers of differently sized self-assembled InP-quantum dots (QDs) separated by a GaInP spacer layer with varying thickness were grown by metal organic vapor phase epitaxy (MOVPE). Photoluminescence measurements of the QD ensembles and of individual asymmetric double QDS show coupling due to the tunnelling of carriers.

  8. Designing quantum dots for solotronics

    PubMed Central

    Kobak, J.; Smoleński, T.; Goryca, M.; Papaj, M.; Gietka, K.; Bogucki, A.; Koperski, M.; Rousset, J.-G.; Suffczyński, J.; Janik, E.; Nawrocki, M.; Golnik, A.; Kossacki, P.; Pacuski, W.

    2014-01-01

    Solotronics, optoelectronics based on solitary dopants, is an emerging field of research and technology reaching the ultimate limit of miniaturization. It aims at exploiting quantum properties of individual ions or defects embedded in a semiconductor matrix. It has already been shown that optical control of a magnetic ion spin is feasible using the carriers confined in a quantum dot. However, a serious obstacle was the quenching of the exciton luminescence by magnetic impurities. Here we show, by photoluminescence studies on thus-far-unexplored individual CdTe dots with a single cobalt ion and CdSe dots with a single manganese ion, that even if energetically allowed, nonradiative exciton recombination through single-magnetic-ion intra-ionic transitions is negligible in such zero-dimensional structures. This opens solotronics for a wide range of as yet unconsidered systems. On the basis of results of our single-spin relaxation experiments and on the material trends, we identify optimal magnetic-ion quantum dot systems for implementation of a single-ion-based spin memory. PMID:24463946

  9. 75 FR 43882 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2C10 (Regional Jet Series 700, 701, & 702...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-27

    ...), and CL-600-2D24 (Regional Jet Series 900) Airplanes AGENCY: Federal Aviation Administration (FAA), DOT.... List of Subjects in 14 CFR Part 39 Air transportation, Aircraft, Aviation safety, Incorporation by... TRANSPORTATION Federal Aviation Administration 14 CFR Part 39 RIN 2120-AA64 Airworthiness Directives;...

  10. 76 FR 4264 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2C10 (Regional Jet Series 700, 701, & 702...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-25

    ...), and CL-600-2D24 (Regional Jet Series 900) Airplanes AGENCY: Federal Aviation Administration (FAA), DOT... Part 39 Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. The Proposed... TRANSPORTATION Federal Aviation Administration 14 CFR Part 39 RIN 2120-AA64 Airworthiness Directives;...

  11. High (36)Cl/Cl ratios in Chernobyl groundwater.

    PubMed

    Roux, Céline; Le Gal La Salle, Corinne; Simonucci, Caroline; Van Meir, Nathalie; Fifield, L Keith; Diez, Olivier; Bassot, Sylvain; Simler, Roland; Bugai, Dmitri; Kashparov, Valery; Lancelot, Joël

    2014-12-01

    After the explosion of the Chernobyl Nuclear Power Plant in April 1986, contaminated material was buried in shallow trenches within the exclusion zone. A (90)Sr plume was evidenced downgradient of one of these trenches, trench T22. Due to its conservative properties, (36)Cl is investigated here as a potential tracer to determine the maximal extent of the contamination plume from the trench in groundwater. (36)Cl/Cl ratios measured in groundwater, trench soil water and leaf leachates are 1-5 orders of magnitude higher than the theoretical natural (36)Cl/Cl ratio. This contamination occurred after the Chernobyl explosion and currently persists. Trench T22 acts as an obvious modern point source of (36)Cl, however other sources have to be involved to explain such contamination. (36)Cl contamination of groundwater can be explained by dilution of trench soil water by uncontaminated water (rainwater or deep groundwater). With a plume extending further than that of (90)Sr, radionuclide which is impacted by retention and decay processes, (36)Cl can be considered as a suitable tracer of contamination from the trench in groundwater provided that modern release processes of (36)Cl from trench soil are better characterized. PMID:25128774

  12. High (36)Cl/Cl ratios in Chernobyl groundwater.

    PubMed

    Roux, Céline; Le Gal La Salle, Corinne; Simonucci, Caroline; Van Meir, Nathalie; Fifield, L Keith; Diez, Olivier; Bassot, Sylvain; Simler, Roland; Bugai, Dmitri; Kashparov, Valery; Lancelot, Joël

    2014-12-01

    After the explosion of the Chernobyl Nuclear Power Plant in April 1986, contaminated material was buried in shallow trenches within the exclusion zone. A (90)Sr plume was evidenced downgradient of one of these trenches, trench T22. Due to its conservative properties, (36)Cl is investigated here as a potential tracer to determine the maximal extent of the contamination plume from the trench in groundwater. (36)Cl/Cl ratios measured in groundwater, trench soil water and leaf leachates are 1-5 orders of magnitude higher than the theoretical natural (36)Cl/Cl ratio. This contamination occurred after the Chernobyl explosion and currently persists. Trench T22 acts as an obvious modern point source of (36)Cl, however other sources have to be involved to explain such contamination. (36)Cl contamination of groundwater can be explained by dilution of trench soil water by uncontaminated water (rainwater or deep groundwater). With a plume extending further than that of (90)Sr, radionuclide which is impacted by retention and decay processes, (36)Cl can be considered as a suitable tracer of contamination from the trench in groundwater provided that modern release processes of (36)Cl from trench soil are better characterized.

  13. Systematic safety evaluation on photoluminescent carbon dots

    NASA Astrophysics Data System (ADS)

    Wang, Kan; Gao, Zhongcai; Gao, Guo; Wo, Yan; Wang, Yuxia; Shen, Guangxia; Cui, Daxiang

    2013-03-01

    Photoluminescent carbon dots (C-dots) were prepared using the improved nitric acid oxidation method. The C-dots were characterized by tapping-mode atomic force microscopy, and UV-vis absorption spectroscopy. The C-dots were subjected to systematic safety evaluation via acute toxicity, subacute toxicity, and genotoxicity experiments (including mouse bone marrow micronuclear test and Salmonella typhimurium mutagenicity test). The results showed that the C-dots were successfully prepared with good stability, high dispersibility, and water solubility. At all studied C-dot dosages, no significant toxic effect, i.e., no abnormality or lesion, was observed in the organs of the animals. Therefore, the C-dots are non-toxic to mice under any dose and have potential use in fluorescence imaging in vivo, tumor cell tracking, and others.

  14. Dot-ELISA in diagnosis of schistosomiasis.

    PubMed

    Madwar, M A; Hassan, M M

    1989-12-01

    One microliter of S. mansoni egg antigen was dotted directly on the nitrocellulose paper sheet acting as the adsorbent surface (9 dots/paper). The sera of 25 Egyptian patients and 15 healthy persons (2 microliters of each) were dotted over the antigen dots, then 2 ml of each of the blocking, washing, HRP-conjugated IgG and DAB adding procedures, were added over the nitrocellulose paper in the petri-dish at room temperature. An intact brown circle (by naked-eye) indicates a positive in Dot-ELISA. There is an insignificant dot colour intensities in different clinical stages of S. mansoni infected Egyptians whereas, a direct relation was obtained between egg count and the colour intensity of the dots. The test had 100% sensitivity and 86% specificity thus it appears to be useful for both laboratory and field studies. PMID:2794577

  15. Modeling of the quantum dot filling and the dark current of quantum dot infrared photodetectors

    SciTech Connect

    Ameen, Tarek A.; El-Batawy, Yasser M.; Abouelsaood, A. A.

    2014-02-14

    A generalized drift-diffusion model for the calculation of both the quantum dot filling profile and the dark current of quantum dot infrared photodetectors is proposed. The confined electrons inside the quantum dots produce a space-charge potential barrier between the two contacts, which controls the quantum dot filling and limits the dark current in the device. The results of the model reasonably agree with a published experimental work. It is found that increasing either the doping level or the temperature results in an exponential increase of the dark current. The quantum dot filling turns out to be nonuniform, with a dot near the contacts containing more electrons than one in the middle of the device where the dot occupation approximately equals the number of doping atoms per dot, which means that quantum dots away from contacts will be nearly unoccupied if the active region is undoped.

  16. Photoluminescence, chemiluminescence and anodic electrochemiluminescence of hydrazide-modified graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Dong, Yongqiang; Dai, Ruiping; Dong, Tongqing; Chi, Yuwu; Chen, Guonan

    2014-09-01

    Single-layer graphene quantum dots (SGQDs) were refluxed with hydrazine (N2H4) to prepare hydrazide-modified SGQDs (HM-SGQDs). Compared with SGQDs, partial oxygen-containing groups have been removed from HM-SGQDs. At the same time, a lot of hydrazide groups have been introduced into HM-SGQDs. The introduced hydrazide groups provide HM-SGQDs with a new kind of surface state, and give HM-SGQDs unique photoluminescence (PL) properties such as blue-shifted PL emission and a relatively high PL quantum yield. More importantly, the hydrazide-modification made HM-SGQDs have abundant luminol-like units. Accordingly, HM-SGQDs exhibit unique and excellent chemiluminescence (CL) and anodic electrochemiluminescence (ECL). The hydrazide groups of HM-SGQDs can be chemically oxidized by the dissolved oxygen (O2) in alkaline solutions, producing a strong CL signal. The CL intensity is mainly dependent on the pH value and the concentration of O2, implying the potential applications of HM-SGQDs in pH and O2 sensors. The hydrazide groups of HM-SGQDs can also be electrochemically oxidized in alkaline solutions, producing a strong anodic ECL signal. The ECL intensity can be enhanced sensitively by hydrogen peroxide (H2O2). The enhanced ECL intensity is proportional to the concentration of H2O2 in a wide range of 3 μM to 500 μM. The detection limit of H2O2 was calculated to be about 0.7 μM. The results suggest the great potential applications of HM-SGQDs in the sensors of H2O2 and bio-molecules that are able to produce H2O2 in the presence of enzymes.Single-layer graphene quantum dots (SGQDs) were refluxed with hydrazine (N2H4) to prepare hydrazide-modified SGQDs (HM-SGQDs). Compared with SGQDs, partial oxygen-containing groups have been removed from HM-SGQDs. At the same time, a lot of hydrazide groups have been introduced into HM-SGQDs. The introduced hydrazide groups provide HM-SGQDs with a new kind of surface state, and give HM-SGQDs unique photoluminescence (PL) properties such

  17. The stability of sodalite in the system NaAlSiO sub 4 -NaCl

    SciTech Connect

    Sharp, Z.D. ); Helffrich, G.R. ); Bohlen, S.R. ); Essene, E.J. )

    1989-08-01

    The reaction sodalite = {beta}-nepheline + NaCl (s) was reversed in solid-medium apparatus and the reaction sodalite = carnegieite + NaCl (l) was reversed at 1 bar (1,649-1,652 K). The experimental reversals between 923 K and 973 K can be fit with a dP/dT of {minus}11 bar/K, suggesting that the excess entropy for sodalite is present only above 923 K. A phase diagram for the NaAlSiO{sub 4}-NaCl system that is consistent with the measured thermochemical data and the experiments between 973 and 1,650 K can be generated if the 61.7 J/mol{center dot}K entropy contribution is included in the S{sup 0}{sub 298} of sodalite. This entropy contribution must be removed below 973 K for the experiments to fit with calculations. Previously unreported thermodynamic data estimated in this study are {Delta}G{sup 0}{sub 298} for sodalite ({minus}12,697 kJ/mol) and carnegieite (NaAlSiO{sub 4}) ({minus}1,958 kJ/mol), S{sup 0}{sub 298} of carnegieite (129.6 J/mol{center dot}K) and compressibility of NaCl{sub liquid} (V{sup P}{sub 298} (cm{sup 3}) = 31.6{center dot}(1 - 24.7{center dot}10{sup {minus}3}{center dot}P + 800{center dot}10{sup {minus}6}{center dot}P{sup 2}))(T in K; P in kbar). Sodalite is a high-temperature, low-pressure phase, stable well above the solidus in sodic silica-undersaturated magmas enriched in NaCl, and its presence constrains NaCl activities in magmas. Estimates of minimum NaCl (l) activities in the Mont St-Hilaire sodalite syenites are 0.05 at 1,073 K and 0.13 at 1,273 K. Density calculations are consistent with the field observations that sodalite phenocrysts will float in a nepheline syenite liquid. This explains the enrichment of sodalite in the upper levels of the sodalite syenites at Mont St.Hilaire and elsewhere.

  18. Hydrogen Effect against Hydrogen Embrittlement

    NASA Astrophysics Data System (ADS)

    Murakami, Yukitaka; Kanezaki, Toshihiko; Mine, Yoji

    2010-10-01

    The well-known term “hydrogen embrittlement” (HE) expresses undesirable effects due to hydrogen such as loss of ductility, decreased fracture toughness, and degradation of fatigue properties of metals. However, this article shows, surprisingly, that hydrogen can have an effect against HE. A dramatic phenomenon was found in which charging a supersaturated level of hydrogen into specimens of austenitic stainless steels of types 304 and 316L drastically improved the fatigue crack growth resistance, rather than accelerating fatigue crack growth rates. Although this mysterious phenomenon has not previously been observed in the history of HE research, its mechanism can be understood as an interaction between hydrogen and dislocations. Hydrogen can play two roles in terms of dislocation mobility: pinning (or dragging) and enhancement of mobility. Competition between these two roles determines whether the resulting phenomenon is damaging or, unexpectedly, desirable. This finding will, not only be the crucial key factor to elucidate the mechanism of HE, but also be a trigger to review all existing theories on HE in which hydrogen is regarded as a dangerous culprit.

  19. Synthesis of palm-based polyurethane-LiClO{sub 4} via prepolymerization

    SciTech Connect

    Sien, Jason Wong Chee; Badri, Khairiah Haji; Su’ait, Mohd Sukor; Hassan, Nurul Izzati

    2015-09-25

    Palm-based polyurethane (pPU) with varying lithium salt (LiClO{sub 4}) content was synthesized. Higher loading percentage of LiClO{sub 4} in the pPU led to the inhibition of prepolymerization process from taking place. Hydrogen bonded C=O was detected in the FTIR spectrum indicating the hydrogen bonding between the urethane bonds. Ordered complexed C=O was observed in the FTIR spectrum confirming the complex formation between urethane bond and Li{sup +} ion. DSC thermogram showed the increase in the LiClO{sub 4} content could increase the glass transition temperature. SEM micrographs exhibited that more bubbles were formed when the LiClO{sub 4} increased from 10 to 30wt% indicating the reaction between free isocyanate groups with moisture presence in the salt due to the hygroscopic properties of LiClO{sub 4}.

  20. Color-switchable, emission-enhanced fluorescence realized by engineering C-dot@C-dot nanoparticles.

    PubMed

    Guo, Zhen; Zhang, Zhiqiang; Zhang, Wei; Zhou, Lianqun; Li, Haiwen; Wang, Hongmei; Andreazza-Vignolle, Caroline; Andreazza, Pascal; Zhao, Dongxu; Wu, Yihui; Wang, Quanlong; Zhang, Tao; Jiang, Keming

    2014-12-10

    This paper reports the preparation and properties of color-switchable fluorescent carbon nanodots (C-dots). C-dots that emit dark turquoise and green-yellow fluorescence under 365 nm UV illumination were obtained from the hydrothermal decomposition of citric acid. Dark green fluorescent C-dots were obtained by conjugating prepared C-dots to form C-dot@C-dot nanoparticles. After successful conjugation of the C-dots, the fluorescence emission undergoes a blue-shift of nearly 20 nm (∼0.15 eV) under UV excitation at 370 nm. The C-dots emit goldenrod, green-yellow, and gold light under excitation at 455 nm, which shows that the prepared C-dots are color-switchable. Furthermore, conjugation of the C-dots results in enhanced, red-shifted absorption of the π-π* transition of the aromatic sp(2) domains due to the conjugated π-electron system. N incorporation in the carbon structure leads to a degree of dipoles for all the aromatic sp(2) bonds. The enhanced absorption in a wide range from 226 to 601 nm indicates extended conjugation in the C-dot@C-dot structure. The time-resolved average lifetimes for the three different types of C-dots prepared in this study are 7.10, 7.65, and 4.07 ns. The radiative rate (reduced decay lifetime) increases when the C-dots are conjugated in the C-dot@C-dot nanoparticles, leading to the enhanced fluorescence emission. The fluorescence emission of the C-dot@C-dot nanoparticles can be used in applications such as flow cytometry and cell imaging.

  1. Color-switchable, emission-enhanced fluorescence realized by engineering C-dot@C-dot nanoparticles.

    PubMed

    Guo, Zhen; Zhang, Zhiqiang; Zhang, Wei; Zhou, Lianqun; Li, Haiwen; Wang, Hongmei; Andreazza-Vignolle, Caroline; Andreazza, Pascal; Zhao, Dongxu; Wu, Yihui; Wang, Quanlong; Zhang, Tao; Jiang, Keming

    2014-12-10

    This paper reports the preparation and properties of color-switchable fluorescent carbon nanodots (C-dots). C-dots that emit dark turquoise and green-yellow fluorescence under 365 nm UV illumination were obtained from the hydrothermal decomposition of citric acid. Dark green fluorescent C-dots were obtained by conjugating prepared C-dots to form C-dot@C-dot nanoparticles. After successful conjugation of the C-dots, the fluorescence emission undergoes a blue-shift of nearly 20 nm (∼0.15 eV) under UV excitation at 370 nm. The C-dots emit goldenrod, green-yellow, and gold light under excitation at 455 nm, which shows that the prepared C-dots are color-switchable. Furthermore, conjugation of the C-dots results in enhanced, red-shifted absorption of the π-π* transition of the aromatic sp(2) domains due to the conjugated π-electron system. N incorporation in the carbon structure leads to a degree of dipoles for all the aromatic sp(2) bonds. The enhanced absorption in a wide range from 226 to 601 nm indicates extended conjugation in the C-dot@C-dot structure. The time-resolved average lifetimes for the three different types of C-dots prepared in this study are 7.10, 7.65, and 4.07 ns. The radiative rate (reduced decay lifetime) increases when the C-dots are conjugated in the C-dot@C-dot nanoparticles, leading to the enhanced fluorescence emission. The fluorescence emission of the C-dot@C-dot nanoparticles can be used in applications such as flow cytometry and cell imaging. PMID:25408428

  2. Trace Analysis of Sinomenine Hydrochloride Using CdTe/CdS Quantum Dots-enhanced Chemiluminescence.

    PubMed

    Wu, Kegang; Han, Suqin

    2015-01-01

    A novel flow-injection chemiluminescence (FI-CL) method was described for the determination of sinomenine hydrochloride (SIN). The method was based on the inhibitory effect of SIN on the CL reaction of luminol and K3Fe(CN)6 in an alkaline solution, which was sensitized by CdTe/CdS quantum dots (QDs). Under the optimized conditions, the linear range for the determination of SIN was 1.0 × 10(-8) to 1.4 × 10(-6) mol/L. The detection limit was 7.5 × 10(-9) mol/L, and the relative standard deviation was 2.47% (n = 11). The current CL method was applied to determine SIN in pharmaceutical formulations and biological fluids with satisfactory results. The possible CL reaction mechanism was discussed briefly. PMID:26656813

  3. Two-center three-electron bonding in ClNH3 revealed via helium droplet infrared laser Stark spectroscopy: Entrance channel complex along the Cl + NH3 → ClNH2 + H reaction

    NASA Astrophysics Data System (ADS)

    Moradi, Christopher P.; Xie, Changjian; Kaufmann, Matin; Guo, Hua; Douberly, Gary E.

    2016-04-01

    Pyrolytic dissociation of Cl2 is employed to dope helium droplets with single Cl atoms. Sequential addition of NH3 to Cl-doped droplets leads to the formation of a complex residing in the entry valley to the substitution reaction Cl + NH3 → ClNH2 + H. Infrared Stark spectroscopy in the NH stretching region reveals symmetric and antisymmetric vibrations of a C3v symmetric top. Frequency shifts from NH3 and dipole moment measurements are consistent with a ClNH3 complex containing a relatively strong two-center three-electron (2c-3e) bond. The nature of the 2c-3e bonding in ClNH3 is explored computationally and found to be consistent with the complexation-induced blue shifts observed experimentally. Computations of interconversion pathways reveal nearly barrierless routes to the formation of this complex, consistent with the absence in experimental spectra of two other complexes, NH3Cl and Cl-HNH2, which are predicted in the entry valley to the hydrogen abstraction reaction Cl + NH3 → HCl + NH2.

  4. Two-center three-electron bonding in ClNH3 revealed via helium droplet infrared laser Stark spectroscopy: Entrance channel complex along the Cl + NH3 → ClNH2 + H reaction.

    PubMed

    Moradi, Christopher P; Xie, Changjian; Kaufmann, Matin; Guo, Hua; Douberly, Gary E

    2016-04-28

    Pyrolytic dissociation of Cl2 is employed to dope helium droplets with single Cl atoms. Sequential addition of NH3 to Cl-doped droplets leads to the formation of a complex residing in the entry valley to the substitution reaction Cl + NH3 → ClNH2 + H. Infrared Stark spectroscopy in the NH stretching region reveals symmetric and antisymmetric vibrations of a C3v symmetric top. Frequency shifts from NH3 and dipole moment measurements are consistent with a ClNH3 complex containing a relatively strong two-center three-electron (2c-3e) bond. The nature of the 2c-3e bonding in ClNH3 is explored computationally and found to be consistent with the complexation-induced blue shifts observed experimentally. Computations of interconversion pathways reveal nearly barrierless routes to the formation of this complex, consistent with the absence in experimental spectra of two other complexes, NH3Cl and Cl-HNH2, which are predicted in the entry valley to the hydrogen abstraction reaction Cl + NH3 → HCl + NH2. PMID:27131544

  5. Two-Center Three-Electron Bonding in ClNH3 Revealed via Helium Droplet Infrared Spectroscopy: Entrance Channel Complex Along the cl + NH3 → ClNH2 + H Reaction

    NASA Astrophysics Data System (ADS)

    Franke, Peter R.; Moradi, Christopher P.; Kaufmann, Matin; Xie, Changjian; Guo, Hua; Douberly, Gary E.

    2016-06-01

    Pyrolytic dissociation of Cl2 is employed to dope helium droplets with single Cl atoms. Sequential addition of NH3 to Cl-doped droplets leads to the formation of a complex residing in the entry valley to the substitution reaction, Cl + NH3 → ClNH2 + H. Infrared Stark spectroscopy in the NH stretching region reveals symmetric and antisymmetric vibrations of a C3v symmetric top. Frequency shifts from NH3 and dipole moment measurements are consistent with a ClNH3 complex containing a relatively strong two-center three-electron (2c-3e) bond. The nature of the 2c-3e bonding in ClNH3 is explored computationally and found to be consistent with the complexation-induced blue shifts observed experimentally. Computations of interconversion pathways reveal nearly barrierless routes to the formation of this complex, consistent with the absence of two other complexes, NH3Cl and Cl-HNH2, which are predicted in the entry valley to the hydrogen abstraction reaction, Cl + NH3 → HCl + NH2

  6. Energy spectrum of D{sup 0} centre in a spherical Gaussian quantum dot

    SciTech Connect

    Boda, Aalu Chatterjee, Ashok

    2015-05-15

    The properties of a neutral hydrogenic donor (D{sup 0}) centres have been studied for a GaAs semiconductor quantum dot with the Gaussian confinement potential. The energy levels of the ground state (n = 1) and the excited states of both the first excited (n = 2) and second excited (n = 3) configurations have been calculated by variational method. It has been shown that the excited states of the (D{sup 0}) centre in quantum dot are bound for sufficiently strong confinement potential. The conditions of binding for the ground state as well as excited states have been determined as functions of the potential strength and quantum dot radius. The ground state electron energy is compared with those available in the literature.

  7. Fluctuating defect density probed with noise spectroscopy in hydrogenated amorphous silicon

    SciTech Connect

    Verleg, P.A.W.E.; Uca, O.; Dijkhuis, J.I.

    1997-07-01

    Resistance fluctuations have been studied in hydrogenated amorphous silicon in the temperature range between 300 K and 450 K. The primary noise source has a power spectrum of approximately 1/f and is ascribed to hydrogen motion. Hopping of weakly bound hydrogen is thermally activated at such low temperatures with an average activation energy of 0.85 eV. The attempt rate amounts to 7 {center_dot} 10{sup 12} s{sup {minus}1}.

  8. Structures of Three Dehydration Products of Bischofite from in situ Synchrotron Powder Diffraction Data(MgCL2*nH2O;n=1,2,4)

    SciTech Connect

    Sugimoto,K.; Dinnebeir, R.; Hanson, J.

    2007-01-01

    High-quality in situ synchrotron powder diffraction data have been used to investigate the decomposition products of bischofite in the temperature range 298 {<=} T {<=} 873 K. At least eight phases could be identified: MgCl{sub 2}{center_dot}nH{sub 2}O (n = 1, 2, 4 and 6), MgOHCl{center_dot}nH{sub 2}O (0 {<=} n {<=} 1.0), MgCl{sub 2} and MgO. The crystal structures of three magnesium chloride hydrates MgCl{sub 2}{center_dot}nH{sub 2}O (n = 1, 2, 4) were determined ab initio, replacing published Rietveld refinements from low-quality powder diffraction data based on similarity criteria. MgCl{sub 2}{center_dot}4H{sub 2}O was found to be disordered and has been correctly determined for the first time. The crystal structures of bishcofite and MgCl{sub 2}4H{sub 2}O consist of discrete Mg(H{sub 2}O){sub 6} and MgCl{sub 2}(H{sub 2}O){sub 4} octahedra, respectively. The crystal structure of MgCl{sub 2}{center_dot}2H{sub 2}O is formed by single chains of edge-sharing MgCl{sub 2}(H{sub 2}O){sub 4} octahedra, while in the case of MgCl{sub 2}H{sub 2}O double chains of edge-sharing MgCl(H{sub 2}O){sub 5} octahedra are found. The phases in the system MgCl{sub 2}-H{sub 2}O are intermediates in the technologically important process of MgO and subsequently Mg production. The same phases were recently found to be of key importance in the understanding of cracks in certain magnesia concrete floors.

  9. Low temperature synthesis of silicon quantum dots with plasma chemistry control in dual frequency non-thermal plasmas.

    PubMed

    Sahu, Bibhuti Bhusan; Yin, Yongyi; Han, Jeon Geon; Shiratani, Masaharu

    2016-06-21

    The advanced materials process by non-thermal plasmas with a high plasma density allows the synthesis of small-to-big sized Si quantum dots by combining low-temperature deposition with superior crystalline quality in the background of an amorphous hydrogenated silicon nitride matrix. Here, we make quantum dot thin films in a reactive mixture of ammonia/silane/hydrogen utilizing dual-frequency capacitively coupled plasmas with high atomic hydrogen and nitrogen radical densities. Systematic data analysis using different film and plasma characterization tools reveals that the quantum dots with different sizes exhibit size dependent film properties, which are sensitively dependent on plasma characteristics. These films exhibit intense photoluminescence in the visible range with violet to orange colors and with narrow to broad widths (∼0.3-0.9 eV). The observed luminescence behavior can come from the quantum confinement effect, quasi-direct band-to-band recombination, and variation of atomic hydrogen and nitrogen radicals in the film growth network. The high luminescence yields in the visible range of the spectrum and size-tunable low-temperature synthesis with plasma and radical control make these quantum dot films good candidates for light emitting applications. PMID:27226277

  10. Hydrogen from renewable resources monthly progress report

    SciTech Connect

    Rocheleau, R.E.

    1995-02-01

    During February, we achieved two significant results in our hydrogen storage activates. Reversible hydrogen uptake and release was measured at room temperature, near ambient pressure on the (IrClH{sub 2}(H{sub 2})Pr{sup i}{sub 3}) complex. Dr. Jensen also observed that certain polyhydzide complexes catalyze the low temperature, reversible dehydrogenation of cycloalkanes to aromatic hydrocarbons at temperatures as low as 130{degrees}C. This discovery may represent a breakthrough in chemical storage of hydrogen as all other cycloalkane dehydrogenation systems require temperatures in excess of 300{degrees}C.

  11. Storing Hydrogen

    SciTech Connect

    Kim, Hyun Jeong; Karkamkar, Abhijeet J.; Autrey, Thomas; Chupas, Peter; Proffen, Thomas E.

    2010-05-31

    Researchers have been studying mesoporous materials for almost two decades with a view to using them as hosts for small molecules and scaffolds for molding organic compounds into new hybrid materials and nanoparticles. Their use as potential storage systems for large quantities of hydrogen has also been mooted. Such systems that might hold large quantities of hydrogen safely and in a very compact volume would have enormous potential for powering fuel cell vehicles, for instance. A sponge-like form of silicon dioxide, the stuff of sand particles and computer chips, can soak up and store other compounds including hydrogen. Studies carried out at the XOR/BESSRC 11-ID-B beamline at the APS have revealed that the nanoscopic properties of the hydrogenrich compound ammonia borane help it store hydrogen more efficiently than usual. The material may have potential for addressing the storage issues associated with a future hydrogen economy. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  12. Dot-in-Well Quantum-Dot Infrared Photodetectors

    NASA Technical Reports Server (NTRS)

    Gunapala, Sarath; Bandara, Sumith; Ting, David; Hill, cory; Liu, John; Mumolo, Jason; Chang, Yia Chung

    2008-01-01

    Dot-in-well (DWELL) quantum-dot infrared photodetectors (QDIPs) [DWELL-QDIPs] are subjects of research as potentially superior alternatives to prior QDIPs. Heretofore, there has not existed a reliable method for fabricating quantum dots (QDs) having precise, repeatable dimensions. This lack has constituted an obstacle to the development of uniform, high-performance, wavelength-tailorable QDIPs and of focal-plane arrays (FPAs) of such QDIPs. However, techniques for fabricating quantum-well infrared photodetectors (QWIPs) having multiple-quantum- well (MQW) structures are now well established. In the present research on DWELL-QDIPs, the arts of fabrication of QDs and QWIPs are combined with a view toward overcoming the deficiencies of prior QDIPs. The longer-term goal is to develop focal-plane arrays of radiationhard, highly uniform arrays of QDIPs that would exhibit high performance at wavelengths from 8 to 15 m when operated at temperatures between 150 and 200 K. Increasing quantum efficiency is the key to the development of competitive QDIP-based FPAs. Quantum efficiency can be increased by increasing the density of QDs and by enhancing infrared absorption in QD-containing material. QDIPs demonstrated thus far have consisted, variously, of InAs islands on GaAs or InAs islands in InGaAs/GaAs wells. These QDIPs have exhibited low quantum efficiencies because the numbers of QD layers (and, hence, the areal densities of QDs) have been small typically five layers in each QDIP. The number of QD layers in such a device must be thus limited to prevent the aggregation of strain in the InAs/InGaAs/GaAs non-lattice- matched material system. The approach being followed in the DWELL-QDIP research is to embed In- GaAs QDs in GaAs/AlGaAs multi-quantum- well (MQW) structures (see figure). This material system can accommodate a large number of QD layers without excessive lattice-mismatch strain and the associated degradation of photodetection properties. Hence, this material

  13. Quantum Dot Light Emitting Diode

    SciTech Connect

    Kahen, Keith

    2008-07-31

    The project objective is to create low cost coatable inorganic light emitting diodes, composed of quantum dot emitters and inorganic nanoparticles, which have the potential for efficiencies equivalent to that of LEDs and OLEDs and lifetime, brightness, and environmental stability between that of LEDs and OLEDs. At the end of the project the Recipient shall gain an understanding of the device physics and properties of Quantum-Dot LEDs (QD-LEDs), have reliable and accurate nanocrystal synthesis routines, and have formed green-yellow emitting QD-LEDs with a device efficiency greater than 3 lumens/W, a brightness greater than 400 cd/m{sup 2}, and a device operational lifetime of more than 1000 hours. Thus the aim of the project is to break the current cost-efficiency paradigm by creating novel low cost inorganic LEDs composed of inorganic nanoparticles.

  14. 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

  15. Quantum Dot Light Emitting Diode

    SciTech Connect

    Keith Kahen

    2008-07-31

    The project objective is to create low cost coatable inorganic light emitting diodes, composed of quantum dot emitters and inorganic nanoparticles, which have the potential for efficiencies equivalent to that of LEDs and OLEDs and lifetime, brightness, and environmental stability between that of LEDs and OLEDs. At the end of the project the Recipient shall gain an understanding of the device physics and properties of Quantum-Dot LEDs (QD-LEDs), have reliable and accurate nanocrystal synthesis routines, and have formed green-yellow emitting QD-LEDs with a device efficiency greater than 3 lumens/W, a brightness greater than 400 cd/m2, and a device operational lifetime of more than 1000 hours. Thus the aim of the project is to break the current cost-efficiency paradigm by creating novel low cost inorganic LEDs composed of inorganic nanoparticles.

  16. Microwave Spectra and Structures of H_2O-AgCl and H_3N-AgCl.

    NASA Astrophysics Data System (ADS)

    Walker, N. R.; Mikhailov, V. A.; Harris, S. J.; Roberts, F. J.; Legon, A. C.

    2010-06-01

    A Balle-Flygare FT-MW spectrometer coupled to a laser ablation source has been used to measure the pure rotational spectra of H2O-AgCl and H3N-AgCl. Both molecules are generated via laser ablation (532 nm) of a metal rod in the presence of CCl4, argon, a low partial pressure of H2O or NH3 and are stabilized by supersonic expansion. Rotational constants and centrifugal distortion constants have been measured for eight isotopologues of H2O-AgCl with substitutions at the silver, chlorine, oxygen and hydrogen atoms. B0 and C0 have been independently determined for six isotopologues and the spectra are consistent with a linear arrangement of oxygen, silver and chlorine atoms. The structure is either C2v planar at equilibrium or CS pyramidal but with a low potential-energy barrier to planarity such that the v=0 and 1 states associated with the motion that inverts the configuration at the O atom are well separated. Preliminary data from a study of H3N-AgCl will also be presented. Several transitions have been observed and tentatively assigned to hyperfine components of the 202-101, 303-202 and 404-303 transitions of H3N-107Ag35Cl and H3N-109Ag35Cl. These data are consistent with a C3v structure.

  17. Hydrogen program overview

    SciTech Connect

    Gronich, S.

    1997-12-31

    This paper consists of viewgraphs which summarize the following: Hydrogen program structure; Goals for hydrogen production research; Goals for hydrogen storage and utilization research; Technology validation; DOE technology validation activities supporting hydrogen pathways; Near-term opportunities for hydrogen; Market for hydrogen; and List of solicitation awards. It is concluded that a full transition toward a hydrogen economy can begin in the next decade.

  18. A quantum dot in topological insulator nanofilm.

    PubMed

    Herath, Thakshila M; Hewageegana, Prabath; Apalkov, Vadym

    2014-03-19

    We introduce a quantum dot in topological insulator nanofilm as a bump at the surface of the nanofilm. Such a quantum dot can localize an electron if the size of the dot is large enough, ≳5 nm. The quantum dot in topological insulator nanofilm has states of two types, which belong to two ('conduction' and 'valence') bands of the topological insulator nanofilm. We study the energy spectra of such defined quantum dots. We also consider intraband and interband optical transitions within the dot. The optical transitions of the two types have the same selection rules. While the interband absorption spectra have multi-peak structure, each of the intraband spectra has one strong peak and a few weak high frequency satellites.

  19. The Blue Dots Initiative and Roadmapping Exercise

    NASA Astrophysics Data System (ADS)

    Coudé du Foresto, V.

    2010-10-01

    The Blue Dots initiative (a grassroot effort to build a scientific community in Europe around the exoplanet theme) is introduced. The Blue Dots activities include the elaboration of a roadmap towards the spectroscopic characterization of habitable exoplanets, a summary of which is presented here. While the roadmap will need to be updated regularly, it is expected that the methodology developed within Blue Dots will provide a durable framework for the elaboration of future revisions.

  20. Recognition-Mediated Assembly of Quantum Dot Polymer Conjugates with Controlled Morphology

    PubMed Central

    Nandwana, Vikas; Subramani, Chandramouleeswaran; Eymur, Serkan; Yeh, Yi-Cheun; Tonga, Gulen Yesilbag; Tonga, Murat; Jeong, Youngdo; Yang, Boqian; Barnes, Michael D.; Cooke, Graeme; Rotello, Vincent M.

    2011-01-01

    We have demonstrated a polymer mediated “bricks and mortar” method for the self-assembly of quantum dots (QDs). This strategy allows QDs to self-assemble into structured aggregates using complementary three-point hydrogen bonding. The resulting nanocomposites have distinct morphologies and inter-particle distances based on the ratio between QDs and polymer. Time resolved photoluminescence measurements showed that the optical properties of the QDs were retained after self-assembly. PMID:22016664

  1. An electrochemical hydrogen meter for measuring hydrogen in sodium using a ternary electrolyte mixture

    NASA Astrophysics Data System (ADS)

    Sridharan, R.; Mahendran, K. H.; Nagaraj, S.; Gnanasekaran, T.; Periaswami, G.

    2003-01-01

    An electrochemical sensor for measuring hydrogen concentration in liquid sodium that is based on a ternary mixture of LiCl, CaCl 2 and CaHCl as the electrolyte has been developed. DSC experiments showed the eutectic temperature of this ternary system to be ˜725 K. Impedance spectroscopic analysis of the electrolyte indicated ionic conduction through a molten phase at ˜725 K. Two electrochemical hydrogen sensors were constructed using the ternary electrolyte of composition 70 mol% LiCl:16 mol% CaHCl:14 mol% CaCl 2 and tested at 723 K in a mini sodium loop and at hydrogen levels of 60-250 ppb in sodium. The sensors show linear response in this concentration range and are capable of detecting a change of 10 ppb hydrogen in sodium over a background level of 60 ppb. Identification of this electrolyte system and its use in a sensor for measuring hydrogen in sodium are described in this paper.

  2. Charge state hysteresis in semiconductor quantum dots

    SciTech Connect

    Yang, C. H.; Rossi, A. Lai, N. S.; Leon, R.; Lim, W. H.; Dzurak, A. S.

    2014-11-03

    Semiconductor quantum dots provide a two-dimensional analogy for real atoms and show promise for the implementation of scalable quantum computers. Here, we investigate the charge configurations in a silicon metal-oxide-semiconductor double quantum dot tunnel coupled to a single reservoir of electrons. By operating the system in the few-electron regime, the stability diagram shows hysteretic tunnelling events that depend on the history of the dots charge occupancy. We present a model which accounts for the observed hysteretic behaviour by extending the established description for transport in double dots coupled to two reservoirs. We demonstrate that this type of device operates like a single-electron memory latch.

  3. Quantum dot enabled high color gamut LCDs

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Kan, Shihai; Lee, Ernie; Gensler, Steve; Hartlove, Jason

    2015-03-01

    Quantum dots are a new generation of phosphor material that have high photon conversion efficiency, narrow spectral line-widths and can be continuously tuned in their emission wavelengths. Since 2013, quantum dots have been adopted by the consumer electronics industry into LCDs to significantly increase their color performance. Compared to the OLED solution, quantum dot LCDs have higher energy efficiency, larger color gamut, longer lifetime, and are offered at a fraction of the cost of OLED panels. In this paper, we demonstrate that quantum-dot based LCDs can achieve more than 90% coverage of the ultra-wide color gamut, Rec. 2020, which is the new color standard for UHDTV.

  4. Thermoelectric energy harvesting with quantum dots.

    PubMed

    Sothmann, Björn; Sánchez, Rafael; Jordan, Andrew N

    2015-01-21

    We review recent theoretical work on thermoelectric energy harvesting in multi-terminal quantum-dot setups. We first discuss several examples of nanoscale heat engines based on Coulomb-coupled conductors. In particular, we focus on quantum dots in the Coulomb-blockade regime, chaotic cavities and resonant tunneling through quantum dots and wells. We then turn toward quantum-dot heat engines that are driven by bosonic degrees of freedom such as phonons, magnons and microwave photons. These systems provide interesting connections to spin caloritronics and circuit quantum electrodynamics.

  5. Magnesium chloride tetrahydrate, MgCl2·4H2O.

    PubMed

    Schmidt, Horst; Hennings, Erik; Voigt, Wolfgang

    2012-01-01

    The title compound, MgCl(2)·4H(2)O, was crystallized at 403 K and its structure determined at 200 K. The structure is built up from MgCl(2)(H(2)O)(4) octahedra with a trans configuration. Each complex is situated on a crystallographic twofold axis, with the rotation axis aligned along one H(2)O-Mg-OH(2) axis. They are connected by a complex network of O-H···Cl hydrogen bonds. The structure contains two-dimensional sections that are essentially identical to those in the reported tetrahydrates of CrCl(2), FeCl(2), FeBr(2) and CoBr(2), but they are stacked in a different manner in MgCl(2)·4H(2)O compared with the transition metal structures.

  6. Hydrogen sulfide

    Integrated Risk Information System (IRIS)

    Hydrogen sulfide ; 7783 - 06 - 4 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effec

  7. Hydrogen chloride

    Integrated Risk Information System (IRIS)

    Hydrogen chloride ; CASRN 7647 - 01 - 0 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogeni

  8. Hydrogen technologies

    SciTech Connect

    Not Available

    1992-05-01

    To the non-nonsense engineer, any talk of a hydrogen economy may seem like so much hot air. This paper reports that as legislative, safety and environmental issues continue to tighten, they're promoting hydrogen's chances as an energy source and, more immediately, its prospects as a chemical feedstock. Paradoxically, the environmental demands that are stimulating hydrogen demand are also inhibiting the gas's production. Previously, gasoline was made with benzene, which means that H{sub 2} was rejected. But now that the laws mandate lower aromatic and higher oxygenate levels in gasolines, there's less H{sub 2} available as byproduct. At the same time, H{sub 2} demand is rising in hydrodesulfurization units, since the same laws require refiners to cut sulfur levels in fuels. Supplementary sources for the gas are also shrinking. In the chlor-alkali industry, H{sub 2} output is dropping, as demand for its coproduct chlorine weakens. At the same time, H{sub 2} demand for the making of hydrogen peroxide is growing, as that environmentally safer bleach gains chlorine's market share.

  9. Analytical investigation of AlCl[3]/SO[2]Cl[2] catholyte materials for secondary fuze reserve batteries.

    SciTech Connect

    Butler, Paul Charles; Rodriguez, Mark Andrew; Segall, Judith M.; Malizia, Louis A., Jr.; Cherry, Brian Ray; Andrews, Nicholas L.; Clark, Nancy H.; Alam, Todd Michael; Ingersoll, David T.; Tallant, David Robert; Simpson, Regina Lynn; Boyle, Timothy J.; Garcia, Manuel Joseph

    2004-05-01

    Exploration of the fundamental chemical behavior of the AlCl{sub 3}/SO{sub 2}Cl{sub 2} catholyte system for the ARDEC Self-Destruct Fuze Reserve Battery Project under accelerated aging conditions was completed using a variety of analytical tools. Four different molecular species were identified in this solution, three of which are major. The relative concentrations of the molecular species formed were found to depend on aging time, initial concentrations, and storage temperature, with each variable affecting the kinetics and thermodynamics of this complex reaction system. We also evaluated the effect of water on the system, and determined that it does not play a role in dictating the observed molecular species present in solution. The first Al-containing species formed was identified as the dimer [Al({mu}-Cl)Cl{sub 2}]{sub 2}, and was found to be in equilibrium with the monomer, AlCl{sub 3}. The second species formed in the reaction scheme was identified by single crystal X-ray diffraction studies as [Cl{sub 2}Al({mu}-O{sub 2}SCl)]{sub 2} (I), a scrambled AlCl{sub 3}{center_dot}SO{sub 2} adduct. The SO{sub 2}(g) present, as well as CL{sub 2}(g), was formed through decomposition of SO{sub 2}CL{sub 2}. The SO{sub 2}(g) generated was readily consumed by AlCl{sub 3} to form the adduct 1 which was experimentally verified when 1 was also isolated from the reaction of SO{sub 2}(g) and AlCl {sub 3}. The third species found was tentatively identified as a compound having the general formula {l_brace}[Al(O)Cl{sub 2}][OSCl{sub 2}]{r_brace}{sub n}. This was based on {sup 27}Al NMR data that revealed a species with tetrahedrally coordinated Al metal centers with increased oxygen coordination and the fact that the precipitate, or gel, that forms over time was shown by Raman spectroscopic studies to possess a component that is consistent with SOCl{sub 2}. The precursor to the precipitate should have similar constituents, thus the assignment of {l_brace}[Al(O)Cl{sub 2}][OSCl{sub 2

  10. Metallic Hydrogen

    NASA Astrophysics Data System (ADS)

    Silvera, Isaac; Zaghoo, Mohamed; Salamat, Ashkan

    2015-03-01

    Hydrogen is the simplest and most abundant element in the Universe. At high pressure it is predicted to transform to a metal with remarkable properties: room temperature superconductivity, a metastable metal at ambient conditions, and a revolutionary rocket propellant. Both theory and experiment have been challenged for almost 80 years to determine its condensed matter phase diagram, in particular the insulator-metal transition. Hydrogen is predicted to dissociate to a liquid atomic metal at multi-megabar pressures and T =0 K, or at megabar pressures and very high temperatures. Thus, its predicted phase diagram has a broad field of liquid metallic hydrogen at high pressure, with temperatures ranging from thousands of degrees to zero Kelvin. In a bench top experiment using static compression in a diamond anvil cell and pulsed laser heating, we have conducted measurements on dense hydrogen in the region of 1.1-1.7 Mbar and up to 2200 K. We observe a first-order phase transition in the liquid phase, as well as sharp changes in optical transmission and reflectivity when this phase is entered. The optical signature is that of a metal. The mapping of the phase line of this transition is in excellent agreement with recent theoretical predictions for the long-sought plasma phase transition to metallic hydrogen. Research supported by the NSF, Grant DMR-1308641, the DOE Stockpile Stewardship Academic Alliance Program, Grant DE-FG52-10NA29656, and NASA Earth and Space Science Fellowship Program, Award NNX14AP17H.

  11. A ketone/alcohol polymer for cycle of electrolytic hydrogen-fixing with water and releasing under mild conditions

    NASA Astrophysics Data System (ADS)

    Kato, Ryo; Yoshimasa, Keisuke; Egashira, Tatsuya; Oya, Takahiro; Oyaizu, Kenichi; Nishide, Hiroyuki

    2016-09-01

    Finding a safe and efficient carrier of hydrogen is a major challenge. Recently, hydrogenated organic compounds have been studied as hydrogen storage materials because of their ability to stably and reversibly store hydrogen by forming chemical bonds; however, these compounds often suffer from safety issues and are usually hydrogenated with hydrogen at high pressure and/or temperature. Here we present a ketone (fluorenone) polymer that can be moulded as a plastic sheet and fixes hydrogen via a simple electrolytic hydrogenation at -1.5 V (versus Ag/AgCl) in water at room temperature. The hydrogenated alcohol derivative (the fluorenol polymer) reversibly releases hydrogen by heating (80 °C) in the presence of an aqueous iridium catalyst. Both the use of a ketone polymer and the efficient hydrogen fixing with water as a proton source are completely different from other (de)hydrogenated compounds and hydrogenation processes. The easy handling and mouldable polymers could suggest a pocketable hydrogen carrier.

  12. Effects of Lewis acid catalysts on the hydrogenation and cracking of two-ring aromatic and hydroaromatic structures related to coal

    SciTech Connect

    Salim, Sadie S.; Bell, Alexis T.

    1982-08-01

    Little is known about the hydrogenation of fused aromatic nuclei during the liquefaction of coal under the influence of Lewis acid catalysts. For this paper, this study was conducted to establish the effects of catalyst acidity on the activity and selectivity of Lewis acid catalysts, the sources of hydrogen involved in hydrogenation and cracking, and the relations between reactant structure and reactivity. Two-ring aromatic and hydroaromatic compounds were used to simulate some of the structural units present in coal. The catalysts examined were ZnCl2 and AlCl3. ZnCl2 is less active than AlCl3 for both hydrogenation and cracking but it does not promote the formation of tars via Scholl condensation: Methyl or hydroxyl substitution of the reactants greatly enhances their reactivity towards hydrogenation and cracking. The source of hydrogen consumed during hydrogenation depends on the choice of catalyst. In the presence of AlCl3, Scholl condensation of aromatic nuclei serves as the principal source of hydrogen. Molecular hydrogen is used exclusively, though, when hydrogenation is catalysed by ZnCl2. The formation of reaction products and the trends in reactant reactivity can be interpreted on the basis of carbonium ion mechanisms. Finally, the results of this study provide a basis for assessing the extent of hydrogenation occurring during the liquefaction of coal using ZnCl2 or AlCl3.

  13. Nitrogen-Doped Carbon Dots for "green" Quantum Dot Solar Cells.

    PubMed

    Wang, Hao; Sun, Pengfei; Cong, Shan; Wu, Jiang; Gao, Lijun; Wang, Yun; Dai, Xiao; Yi, Qinghua; Zou, Guifu

    2016-12-01

    Considering the environment protection, "green" materials are increasingly explored for photovoltaics. Here, we developed a kind of quantum dots solar cell based on nitrogen-doped carbon dots. The nitrogen-doped carbon dots were prepared by direct pyrolysis of citric acid and ammonia. The nitrogen-doped carbon dots' excitonic absorption depends on the N-doping content in the carbon dots. The N-doping can be readily modified by the mass ratio of reactants. The constructed "green" nitrogen-doped carbon dots solar cell achieves the best power conversion efficiency of 0.79 % under AM 1.5 G one full sun illumination, which is the highest efficiency for carbon dot-based solar cells.

  14. Single-dot optical emission from ultralow density well-isolated InP quantum dots

    SciTech Connect

    Ugur, A.; Hatami, F.; Masselink, W. T.; Vamivakas, A. N.; Lombez, L.; Atatuere, M.

    2008-10-06

    We demonstrate a straightforward way to obtain single well-isolated quantum dots emitting in the visible part of the spectrum and characterize the optical emission from single quantum dots using this method. Self-assembled InP quantum dots are grown using gas-source molecular-beam epitaxy over a wide range of InP deposition rates, using an ultralow growth rate of about 0.01 atomic monolayers/s, a quantum-dot density of 1 dot/{mu}m{sup 2} is realized. The resulting isolated InP quantum dots embedded in an InGaP matrix are individually characterized without the need for lithographical patterning and masks on the substrate. Such low-density quantum dots show excitonic emission at around 670 nm with a linewidth limited by instrument resolution. This system is applicable as a single-photon source for applications such as quantum cryptography.

  15. Pathways for the OH + Cl2 → HOCl + Cl and HOCl + Cl → HCl + ClO Reactions.

    PubMed

    Wang, Hongyan; Qiu, Yudong; Czakó, Gábor; Schaefer, Henry F

    2015-07-16

    High level coupled-cluster theory, with spin-orbit coupling evaluated via the Breit-Pauli operator in the interacting-states approach, is used to investigate the OH radical reaction with Cl2 and the subsequent reaction HOCl + Cl. The entrance complex, transition state, and exit complex for both reactions have been determined using the CCSD(T) method with correlation consistent basis sets up to cc-pV6Z. Also reported are CCSDT computations. The OH + Cl2 reaction is predicted to be endothermic by 2.2 kcal/mol, compared to the best experiments, 2.0 kcal/mol. The above theoretical results include zero-point vibrational energy corrections and spin-orbit contributions. The activation energy (Ea) of the OH + Cl2 reaction predicted here, 2.3 kcal/mol, could be as much as 1 kcal/mol too high, but it falls among the four experimental Ea values, which span the range 1.1-2.5 kcal/mol. The exothermicity of the second reaction HOCl + Cl → HCl + ClO is 8.4 kcal/mol, compared to experiment 8.7 kcal/mol. The activation energy for latter reaction is unknown experimentally, but predicted here to be large, 11.5 kcal/mol. There are currently no experiments relevant to the theoretical entrance and exit complexes predicted here. PMID:25965106

  16. Rapid DOTS expansion in India.

    PubMed Central

    Khatri, G. R.; Frieden, Thomas R.

    2002-01-01

    Since late 1998 the coverage of the DOTS strategy in India has been expanded rapidly. In both 2000 and 2001 the country probably accounted for more than half the global increase in the number of patients treated under DOTS and by early 2002 more than a million patients were being treated in this way in India. As a result, nearly 200 000 lives were saved. The lessons learnt relate to the importance of the following elements of the programme: (1) getting the science right and ensuring technical excellence; (2) building commitment and ensuring the provision of funds and flexibility in their utilization; (3) maintaining focus and priorities; (4) systematically appraising each area before starting service delivery; (5) ensuring an uninterrupted drug supply; (6) strengthening the established infrastructure and providing support for staff; (7) supporting the infrastructure required in urban areas; (8) ensuring full-time independent technical support and supervision, particularly during the initial phases of implementation; (9) monitoring intensively and giving timely feedback; and (10) continuous supervision. Tuberculosis (TB) control still faces major challenges in India. To reach its potential, the control programme needs to: continue to expand so as to cover the remaining half of the country, much of which has a weaker health infrastructure than the areas already covered; increase its reach in the areas already covered so that a greater proportion of patients is treated; ensure sustainability; improve the patient-friendliness of services; confront TB associated with human immunodeficiency virus (HIV) infection. It is expected that HIV will increase the number of TB cases by at least 10% and by a considerably higher percentage if HIV becomes much more widespread. India's experience shows that DOTS can achieve high case-detection and cure rates even with imperfect technology and often with an inadequate public health infrastructure. However, this can only happen if the

  17. Diamond LED substrate and novel quantum dots.

    PubMed

    Sung, James C; Sung, Michael

    2009-02-01

    Nitride LED (e.g., GaN) has become the mainstream of blue light source. The blue light can be converted to white light by exciting a phosphor (e.g., Nichia's YAG or Osram's TAG) with the complementary yellow emission. However, GaN is typically deposited on sapphire (Al2O3) substrates formed by crystal pulling or hexagonal (e.g., 4 H or 6 H) SiC wafers condensed from SiC vapor. In either case, the nitride lattice is ridden (e.g., 10(9)/cm2) with dislocations. The high dislocation density with sapphire is due to the large (>13%) lattice mismatch; and with hexagonal SiC, because of intrinsic defects. Cubic (beta) SiC may be deposited epitaxially using a CVD reactor onto silicon wafer by diffusing the interface and by chemical gradation. A reactive echant (e.g., hydrogen or fluorine) can be introduced periodically to gasify mis-aligned atoms. In this case, large single crystal wafers would be available for the manufacture of high bright LED with superb electro-optical efficiency. The SiC wafer may be coated with diamond film that can eliminate heat in real time. As a result of lower temperature, the nitride LED can be brighter and it will last longer. The blue light of GaN LED formed on SiC on Diamond (SiCON) LED may also be scattered by using novel quantum dots (e.g., 33 atom pairs of CdSe) to form a broad yellow light that blend in with the original blue light to form sunlight-like white light. This would be the ideal source for general illumination (e.g., for indoor) or backlighting (e.g., for LCD). PMID:19441383

  18. Diamond LED substrate and novel quantum dots.

    PubMed

    Sung, James C; Sung, Michael

    2009-02-01

    Nitride LED (e.g., GaN) has become the mainstream of blue light source. The blue light can be converted to white light by exciting a phosphor (e.g., Nichia's YAG or Osram's TAG) with the complementary yellow emission. However, GaN is typically deposited on sapphire (Al2O3) substrates formed by crystal pulling or hexagonal (e.g., 4 H or 6 H) SiC wafers condensed from SiC vapor. In either case, the nitride lattice is ridden (e.g., 10(9)/cm2) with dislocations. The high dislocation density with sapphire is due to the large (>13%) lattice mismatch; and with hexagonal SiC, because of intrinsic defects. Cubic (beta) SiC may be deposited epitaxially using a CVD reactor onto silicon wafer by diffusing the interface and by chemical gradation. A reactive echant (e.g., hydrogen or fluorine) can be introduced periodically to gasify mis-aligned atoms. In this case, large single crystal wafers would be available for the manufacture of high bright LED with superb electro-optical efficiency. The SiC wafer may be coated with diamond film that can eliminate heat in real time. As a result of lower temperature, the nitride LED can be brighter and it will last longer. The blue light of GaN LED formed on SiC on Diamond (SiCON) LED may also be scattered by using novel quantum dots (e.g., 33 atom pairs of CdSe) to form a broad yellow light that blend in with the original blue light to form sunlight-like white light. This would be the ideal source for general illumination (e.g., for indoor) or backlighting (e.g., for LCD).

  19. STED nanoscopy with fluorescent quantum dots

    PubMed Central

    Hanne, Janina; Falk, Henning J.; Görlitz, Frederik; Hoyer, Patrick; Engelhardt, Johann; Sahl, Steffen J.; Hell, Stefan W.

    2015-01-01

    The widely popular class of quantum-dot molecular labels could so far not be utilized as standard fluorescent probes in STED (stimulated emission depletion) nanoscopy. This is because broad quantum-dot excitation spectra extend deeply into the spectral bands used for STED, thus compromising the transient fluorescence silencing required for attaining super-resolution. Here we report the discovery that STED nanoscopy of several red-emitting commercially available quantum dots is in fact successfully realized by the increasingly popular 775 nm STED laser light. A resolution of presently ∼50 nm is demonstrated for single quantum dots, and sub-diffraction resolution is further shown for imaging of quantum-dot-labelled vimentin filaments in fibroblasts. The high quantum-dot photostability enables repeated STED recordings with >1,000 frames. In addition, we have evidence that the tendency of quantum-dot labels to blink is largely suppressed by combined action of excitation and STED beams. Quantum-dot STED significantly expands the realm of application of STED nanoscopy, and, given the high stability of these probes, holds promise for extended time-lapse imaging. PMID:25980788

  20. STED nanoscopy with fluorescent quantum dots

    NASA Astrophysics Data System (ADS)

    Hanne, Janina; Falk, Henning J.; Görlitz, Frederik; Hoyer, Patrick; Engelhardt, Johann; Sahl, Steffen J.; Hell, Stefan W.

    2015-05-01

    The widely popular class of quantum-dot molecular labels could so far not be utilized as standard fluorescent probes in STED (stimulated emission depletion) nanoscopy. This is because broad quantum-dot excitation spectra extend deeply into the spectral bands used for STED, thus compromising the transient fluorescence silencing required for attaining super-resolution. Here we report the discovery that STED nanoscopy of several red-emitting commercially available quantum dots is in fact successfully realized by the increasingly popular 775 nm STED laser light. A resolution of presently ~50 nm is demonstrated for single quantum dots, and sub-diffraction resolution is further shown for imaging of quantum-dot-labelled vimentin filaments in fibroblasts. The high quantum-dot photostability enables repeated STED recordings with >1,000 frames. In addition, we have evidence that the tendency of quantum-dot labels to blink is largely suppressed by combined action of excitation and STED beams. Quantum-dot STED significantly expands the realm of application of STED nanoscopy, and, given the high stability of these probes, holds promise for extended time-lapse imaging.

  1. Thick-shell nanocrystal quantum dots

    DOEpatents

    Hollingsworth, Jennifer A.; Chen, Yongfen; Klimov, Victor I.; Htoon, Han; Vela, Javier

    2011-05-03

    Colloidal nanocrystal quantum dots comprising an inner core having an average diameter of at least 1.5 nm and an outer shell, where said outer shell comprises multiple monolayers, wherein at least 30% of the quantum dots have an on-time fraction of 0.80 or greater under continuous excitation conditions for a period of time of at least 10 minutes.

  2. STED nanoscopy with fluorescent quantum dots.

    PubMed

    Hanne, Janina; Falk, Henning J; Görlitz, Frederik; Hoyer, Patrick; Engelhardt, Johann; Sahl, Steffen J; Hell, Stefan W

    2015-05-18

    The widely popular class of quantum-dot molecular labels could so far not be utilized as standard fluorescent probes in STED (stimulated emission depletion) nanoscopy. This is because broad quantum-dot excitation spectra extend deeply into the spectral bands used for STED, thus compromising the transient fluorescence silencing required for attaining super-resolution. Here we report the discovery that STED nanoscopy of several red-emitting commercially available quantum dots is in fact successfully realized by the increasingly popular 775 nm STED laser light. A resolution of presently ∼ 50 nm is demonstrated for single quantum dots, and sub-diffraction resolution is further shown for imaging of quantum-dot-labelled vimentin filaments in fibroblasts. The high quantum-dot photostability enables repeated STED recordings with >1,000 frames. In addition, we have evidence that the tendency of quantum-dot labels to blink is largely suppressed by combined action of excitation and STED beams. Quantum-dot STED significantly expands the realm of application of STED nanoscopy, and, given the high stability of these probes, holds promise for extended time-lapse imaging.

  3. Hydrogen scavengers

    SciTech Connect

    Carroll, David W.; Salazar, Kenneth V.; Trkula, Mitchell; Sandoval, Cynthia W.

    2002-01-01

    There has been invented a codeposition process for fabricating hydrogen scavengers. First, a .pi.-bonded allylic organometallic complex is prepared by reacting an allylic transition metal halide with an organic ligand complexed with an alkali metal; and then, in a second step, a vapor of the .pi.-bonded allylic organometallic complex is combined with the vapor of an acetylenic compound, irradiated with UV light, and codeposited on a substrate.

  4. ADVANCED HYDROGEN TRANSPORT MEMBRANES FOR VISION 21 FOSSIL FUEL PLANTS

    SciTech Connect

    Shane E. Roark; Anthony F. Sammells; Richard Mackay; Scott R. Morrison; Sara L. Rolfe; U. Balachandran; Richard N. Kleiner; James E. Stephen; Frank E. Anderson; Shandra Ratnasamy; Jon P. Wagner; Clive Brereton

    2004-01-30

    The objective of this project is to develop an environmentally benign, inexpensive, and efficient method for separating hydrogen from gas mixtures produced during industrial processes, such as coal gasification. Currently, this project is focusing on four basic categories of dense membranes: (1) mixed conducting ceramic/ceramic composites, (2) mixed conducting ceramic/metal (cermet) composites, (3) cermets with hydrogen permeable metals, and (4) layered composites with hydrogen permeable alloys. The primary technical challenge in achieving the goals of this project will be to optimize membrane composition to enable practical hydrogen separation rates and chemical stability. Other key aspects of this developing technology include catalysis, ceramic processing methods, and separation unit design operating under high pressure. To achieve these technical goals, Eltron Research Inc. has organized a consortium consisting of CoorsTek, Sued Chemie, Inc. (SCI), Argonne National Laboratory (ANL), and NORAM. Hydrogen permeation rates in excess of 50 mL {center_dot} min{sup -1} {center_dot} cm{sup 2} at {approx}440 C were routinely achieved under less than optimal experimental conditions using a range of membrane compositions. Factors that limit the maximum permeation attainable were determined to be mass transport resistance of H{sub 2} to and from the membrane surface, as well as surface contamination. Mass transport resistance was partially overcome by increasing the feed and sweep gas flow rates to greater than five liters per minute. Under these experimental conditions, H2 permeation rates in excess of 350 mL {center_dot} min{sup -1} {center_dot} cm{sup 2} at {approx}440 C were attained. These results are presented in this report, in addition to progress with cermets, thin film fabrication, catalyst development, and H{sub 2} separation unit scale up.

  5. Biocompatible Quantum Dots for Biological Applications

    SciTech Connect

    Rosenthal, Sandra; Chang, Jerry; Kovtun, Oleg; McBride, James; Tomlinson, Ian

    2011-01-01

    Semiconductor quantum dots are quickly becoming a critical diagnostic tool for discerning cellular function at the molecular level. Their high brightness, long-lasting, size-tunable, and narrow luminescence set them apart from conventional fluorescence dyes. Quantum dots are being developed for a variety of biologically oriented applications, including fluorescent assays for drug discovery, disease detection, single protein tracking, and intracellular reporting. This review introduces the science behind quantum dots and describes how they are made biologically compatible. Several applications are also included, illustrating strategies toward target specificity, and are followed by a discussion on the limitations of quantum dot approaches. The article is concluded with a look at the future direction of quantum dots.

  6. Model-based clustered-dot screening

    NASA Astrophysics Data System (ADS)

    Kim, Sang Ho

    2006-01-01

    I propose a halftone screen design method based on a human visual system model and the characteristics of the electro-photographic (EP) printer engine. Generally, screen design methods based on human visual models produce dispersed-dot type screens while design methods considering EP printer characteristics generate clustered-dot type screens. In this paper, I propose a cost function balancing the conflicting characteristics of the human visual system and the printer. By minimizing the obtained cost function, I design a model-based clustered-dot screen using a modified direct binary search algorithm. Experimental results demonstrate the superior quality of the model-based clustered-dot screen compared to a conventional clustered-dot screen.

  7. Photoluminescence of a quantum-dot molecule

    SciTech Connect

    Kruchinin, Stanislav Yu.; Rukhlenko, Ivan D.; Baimuratov, Anvar S.; Leonov, Mikhail Yu.; Turkov, Vadim K.; Baranov, Alexander V.; Fedorov, Anatoly V.; Gun'ko, Yurii K.

    2015-01-07

    The coherent coupling of quantum dots is a sensitive indicator of the energy and phase relaxation processes taking place in the nanostructure components. We formulate a theory of low-temperature, stationary photoluminescence from a quantum-dot molecule composed of two spherical quantum dots whose electronic subsystems are resonantly coupled via the Coulomb interaction. We show that the coupling leads to the hybridization of the first excited states of the quantum dots, manifesting itself as a pair of photoluminescence peaks with intensities and spectral positions strongly dependent on the geometric, material, and relaxation parameters of the quantum-dot molecule. These parameters are explicitly contained in the analytical expression for the photoluminescence differential cross section derived in the paper. The developed theory and expression obtained are essential in interpreting and analyzing spectroscopic data on the secondary emission of coherently coupled quantum systems.

  8. Photophysical properties gallium octacarboxy phthalocyanines conjugated to CdSe@ZnS quantum dots.

    PubMed

    Tshangana, Charmaine; Nyokong, Tebello

    2015-01-01

    L-Glutathione (GSH) capped core CdSe (2.3 nm) and core shell CdSe@ZnS quantum dots (QDs) (3.0 nm and 3.5 nm) were coordinated to gallium octacarboxy phthalocyanine (ClGaPc(COOH)8) to form ClGaPc(COOH)8-QDs conjugates. An efficient transfer of energy from the QDs to the Pcs was demonstrated through Förster resonance energy transfer (FRET), the FRET efficiencies in all cases was above 50%. The photophysical parameters (triplet state and fluorescence quantum yields and lifetimes) were also determined for the conjugates. There was a decrease in the fluorescence lifetimes of ClGaPc(COOH)8 in the presence of all the QDs, due to the heavy atom effect. The triplet quantum yields increased in the conjugates. The lifetimes also became longer for the conjugates compared to Pc alone.

  9. Transition energies and magnetic properties of a neutral donor complex in a Gaussian GaAs quantum dot

    NASA Astrophysics Data System (ADS)

    Boda, Aalu; Chatterjee, Ashok

    2016-09-01

    The problem of a neutral hydrogenic donor (D0) centre located at the centre of a GaAs quantum dot with Gaussian confinement is studied in the presence of an external magnetic field. The ground and the first excited state energies and the corresponding binding energies are obtained as functions of the potential strength, quantum dot radius and the magnetic field using a variational method. It is suggested that the first excited state of the D0 centre is bound for sufficiently strong confinement potential. The 1 s - 2p- transition energy and the magnetic susceptibilities for the ground and the first excited states are also determined.

  10. Blood Compatibility Evaluations of Fluorescent Carbon Dots.

    PubMed

    Li, Sha; Guo, Zhong; Zhang, Yi; Xue, Wei; Liu, Zonghua

    2015-09-01

    Because of their unique advantages, fluorescent carbon dots are gaining popularity in various biomedical applications. For these applications, good biosafety is a prerequisite for their use in vivo. Studies have reported the preliminary biocompatibility evaluations of fluorescent carbon dots (mainly cytotoxicity); however, to date, little information is available about their hemocompatibility, which could impede their development from laboratory to bedside. In this work, we evaluated the hemocompatibility of fluorescent carbon dots, which we prepared by hydrothermal carbonization of α-cyclodextrin. The effects of the carbon dots on the structure and function of key blood components were investigated at cellular and molecular levels. In particular, we considered the morphology and lysis of human red blood cells, the structure and conformation of the plasma protein fibrinogen, the complement activation, platelet activation, and in vitro and in vivo blood coagulation. We found that the carbon dots have obvious concentration-dependent effects on the blood components. Overall, concentrations of the fluorescent carbon dots at ≤0.1 mg/mL had few adverse effects on the blood components, but at higher doses, the carbon dots impair the structure and function of the blood components, causing morphological disruptions and lysis of red blood cells, interference in the local microenvironments of fibrinogen, activation of the complement system, and disturbances in the plasma and whole blood coagulation function in vitro. However, the carbon dots tend to activate platelets only at low concentrations. Intravenous administration of the carbon dots at doses up to 50 mg/kg did not impair the blood coagulation function. These results provide valuable information for the clinical application of fluorescent carbon dots.

  11. A DFT study of the extractive desulfurization mechanism by [BMIM](+)[AlCl4](-) ionic liquid.

    PubMed

    Li, Hongping; Chang, Yonghui; Zhu, Wenshuai; Jiang, Wei; Zhang, Ming; Xia, Jiexiang; Yin, Sheng; Li, Huaming

    2015-05-14

    In this work, the interaction nature between [BMIM](+)[AlCl4](-) ionic liquid (IL) and aromatic sulfur compounds (thiophene, benzothiophene, and dibenzothiophene) has been studied by means of density functional theory (M06-2X functional) combined with an implicit solvation model. Although [BMIM](+)[AlCl4](-) is a metal-containing IL, its extractive desulfurization mechanism is different from other metal-containing ILs but similar to non-metal-containing ILs. Important reactions involved in extractive desulfurization (EDS) were systematically studied. Our results have demonstrated that both the cation and the anion play important roles in EDS. On the basis of the structure analysis, reduced density gradient analaysis (RDG), and energy decomposition analysis, [BMIM](+) cation affords a π-π interaction while [AlCl4](-) anion provides a hydrogen bonding interaction. Electrostatic potential analysis implies the dominant π-π interaction and hydrogen bonding interaction are driven by electrostatic interaction between IL and aromatic sulfur compounds. Interaction energy between [BMIM](+)[AlCl4](-) and thiophene (TH), benzothiophene (BT), and dibenzothiophene (DBT) follows the order TH < BT < DBT. Moreover, Al-containing IL with a high molar ratio of AlCl3 ([BMIMCl]/2[AlCl3]) has also been studied. Results show that [Al2Cl7](-) species will be formed with excess AlCl3. However, the [Al2Cl7](-)-based IL cannot improve the EDS performance. Improvement of EDS performance with a high molar ratio of AlCl3 is credited to the Lewis acidity of AlCl3. Charge analysis reveals that there is no obvious charge transfer during the reaction, which is different from Fe-containing ILs as well as solid sorbents. In addition, CH-π interaction is not important for the current system.

  12. Chiral quantum dot based materials

    NASA Astrophysics Data System (ADS)

    Govan, Joseph; Loudon, Alexander; Baranov, Alexander V.; Fedorov, Anatoly V.; Gun'ko, Yurii

    2014-05-01

    Recently, the use of stereospecific chiral stabilising molecules has also opened another avenue of interest in the area of quantum dot (QD) research. The main goal of our research is to develop new types of technologically important quantum dot materials containing chiral defects, study their properties and explore their applications. The utilisation of chiral penicillamine stabilisers allowed the preparation of new water soluble white emitting CdS quantum nanostructures which demonstrated circular dichroism in the band-edge region of the spectrum. It was also demonstrated that all three types of QDs (D-, L-, and Rac penicillamine stabilised) show very broad emission bands between 400 and 700 nm due to defects or trap states on the surfaces of the nanocrystals. In this work the chiral CdS based quantum nanostructures have also been doped by copper metal ions and new chiral penicilamine stabilized CuS nanoparticles have been prepared and investigated. It was found that copper doping had a strong effect at low levels in the synthesis of chiral CdS nanostructures. We expect that this research will open new horizons in the chemistry of chiral nanomaterials and their application in biotechnology, sensing and asymmetric synthesis.

  13. Hydrogen environment embrittlement

    NASA Technical Reports Server (NTRS)

    Gray, H. R.

    1972-01-01

    Hydrogen embrittlement is classified into three types: internal reversible hydrogen embrittlement, hydrogen reaction embrittlement, and hydrogen environment embrittlement. Characteristics of and materials embrittled by these types of hydrogen embrittlement are discussed. Hydrogen environment embrittlement is reviewed in detail. Factors involved in standardizing test methods for detecting the occurrence of and evaluating the severity of hydrogen environment embrittlement are considered. The effect of test technique, hydrogen pressure, purity, strain rate, stress concentration factor, and test temperature are discussed. Additional research is required to determine whether hydrogen environment embrittlement and internal reversible hydrogen embrittlement are similar or distinct types of embrittlement.

  14. Charge induced enhancement of adsorption for hydrogen storage materials

    NASA Astrophysics Data System (ADS)

    Sun, Xiang

    2009-12-01

    The rising concerns about environmental pollution and global warming have facilitated research interest in hydrogen energy as an alternative energy source. To apply hydrogen for transportations, several issues have to be solved, within which hydrogen storage is the most critical problem. Lots of materials and devices have been developed; however, none is able to meet the DOE storage target. The primary issue for hydrogen physisorption is a weak interaction between hydrogen and the surface of solid materials, resulting negligible adsorption at room temperature. To solve this issue, there is a need to increase the interaction between the hydrogen molecules and adsorbent surface. In this study, intrinsic electric dipole is investigated to enhance the adsorption energy. The results from the computer simulation of single ionic compounds with hydrogen molecules to form hydrogen clusters showed that electrical charge of substances plays an important role in generation of attractive interaction with hydrogen molecules. In order to further examine the effects of static interaction on hydrogen adsorption, activated carbon with a large surface area was impregnated with various ionic salts including LiCl, NaCl, KCl, KBr, and NiCl2 and their performance for hydrogen storage was evaluated by using a volumetric method. Corresponding computer simulations have been carried out by using DFT (Density Functional Theory) method combined with point charge arrays. Both experimental and computational results prove that the adsorption capacity of hydrogen and its interaction with the solid materials increased with electrical dipole moment. Besides the intrinsic dipole, an externally applied electric field could be another means to enhance hydrogen adsorption. Hydrogen adsorption under an applied electric field was examined by using porous nickel foil as electrodes. Electrical signals showed that adsorption capacity increased with the increasing of gas pressure and external electric voltage

  15. Carbon-dot-decorated TiO₂ nanotube arrays used for photo/voltage-induced organic pollutant degradation and the inactivation of bacteria.

    PubMed

    Feng, Lingyan; Sun, Hanjun; Ren, Jinsong; Qu, Xiaogang

    2016-03-18

    Photoluminescent carbon dots (c-dots) have recently attracted growing interest as a new member of the carbon-nanomaterial family. Here, we report for the first time that c-dot-decorated TiO2 nanotube arrays (c-dot/TiNTs) exhibit highly enhanced abilities regarding photo/voltage-induced organic pollutant degradation and bacterial inactivation. By applying UV irradiation (365 nm) or an electrochemical potential over 3 V (versus Ag/AgCl), an organic dye and a herbicide were efficiently degraded. Moreover, the inactivation of Gram-positive S. aureus and Gram-negative E. coli bacteria was realized on a c-dot/TiNT film. The c-dots were able to absorb light efficiently resulting in multiple exciton generation and also a reduction in the recombination of the e(-)/h(+) pair produced in c-dot/TiNT film during photo/voltage-induced degradation. It was also possible to readily regenerate the surface using ultraviolet light irradiation, leaving the whole film structure undamaged and with high reproducibility and stability.

  16. Carbon-dot-decorated TiO2 nanotube arrays used for photo/voltage-induced organic pollutant degradation and the inactivation of bacteria

    NASA Astrophysics Data System (ADS)

    Feng, Lingyan; Sun, Hanjun; Ren, Jinsong; Qu, Xiaogang

    2016-03-01

    Photoluminescent carbon dots (c-dots) have recently attracted growing interest as a new member of the carbon-nanomaterial family. Here, we report for the first time that c-dot-decorated TiO2 nanotube arrays (c-dot/TiNTs) exhibit highly enhanced abilities regarding photo/voltage-induced organic pollutant degradation and bacterial inactivation. By applying UV irradiation (365 nm) or an electrochemical potential over 3 V (versus Ag/AgCl), an organic dye and a herbicide were efficiently degraded. Moreover, the inactivation of Gram-positive S. aureus and Gram-negative E. coli bacteria was realized on a c-dot/TiNT film. The c-dots were able to absorb light efficiently resulting in multiple exciton generation and also a reduction in the recombination of the e-/h+ pair produced in c-dot/TiNT film during photo/voltage-induced degradation. It was also possible to readily regenerate the surface using ultraviolet light irradiation, leaving the whole film structure undamaged and with high reproducibility and stability.

  17. Reaction rates for O3 + HCl yielding O + O2 + HCl, Cl + O3 yielding ClO + O2, and HCl + O yielding OH + Cl at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Park, C.

    1977-01-01

    Ozone and a much greater quantity of hydrogen chloride, slightly diluted by oxygen and argon, were heated by a shock wave process to temperatures in the range 480-1300 K at pressures from four to eight atmospheres. From variations in ozone concentration, determined by the attentuation of 2537-A radiation, the rate coefficient for the reaction O3 + HCl yielding O + O2 + HCl was determined to be k1 = (4.0 plus or minus 1.5) x 10 to the minus 10 exp(-10,408/T)cm3/s for temperatures of 480-720 K. From the concentration of ClO remaining at the end of ozone decomposition the rate coefficients for the reactions Cl + O3 yielding ClO + O2 and HCl + O yielding OH + Cl were also deduced for a temperature of about 1100 K.

  18. Hydrogen detector

    DOEpatents

    Kanegae, Naomichi; Ikemoto, Ichiro

    1980-01-01

    A hydrogen detector of the type in which the interior of the detector is partitioned by a metal membrane into a fluid section and a vacuum section. Two units of the metal membrane are provided and vacuum pipes are provided independently in connection to the respective units of the metal membrane. One of the vacuum pipes is connected to a vacuum gauge for static equilibrium operation while the other vacuum pipe is connected to an ion pump or a set of an ion pump and a vacuum gauge both designed for dynamic equilibrium operation.

  19. Metamorphic quantum dots: Quite different nanostructures

    SciTech Connect

    Seravalli, L.; Frigeri, P.; Nasi, L.; Trevisi, G.; Bocchi, C.

    2010-09-15

    In this work, we present a study of InAs quantum dots deposited on InGaAs metamorphic buffers by molecular beam epitaxy. By comparing morphological, structural, and optical properties of such nanostructures with those of InAs/GaAs quantum dot ones, we were able to evidence characteristics that are typical of metamorphic InAs/InGaAs structures. The more relevant are: the cross-hatched InGaAs surface overgrown by dots, the change in critical coverages for island nucleation and ripening, the nucleation of new defects in the capping layers, and the redshift in the emission energy. The discussion on experimental results allowed us to conclude that metamorphic InAs/InGaAs quantum dots are rather different nanostructures, where attention must be put to some issues not present in InAs/GaAs structures, namely, buffer-related defects, surface morphology, different dislocation mobility, and stacking fault energies. On the other hand, we show that metamorphic quantum dot nanostructures can provide new possibilities of tailoring various properties, such as dot positioning and emission energy, that could be very useful for innovative dot-based devices.

  20. Quantum Dots in Gated Nanowires and Nanotubes

    NASA Astrophysics Data System (ADS)

    Churchill, Hugh Olen Hill

    This thesis describes experiments on quantum dots made by locally gating one-dimensional quantum wires. The first experiment studies a double quantum dot device formed in a Ge/Si core/shell nanowire. In addition to measuring transport through the double dot, we detect changes in the charge occupancy of the double dot by capacitively coupling it to a third quantum dot on a separate nanowire using a floating gate. We demonstrate tunable tunnel coupling of the double dot and quantify the strength of the tunneling using the charge sensor. The second set of experiments concerns carbon nanotube double quantum dots. In the first nanotube experiment, spin-dependent transport through the double dot is compared in two sets of devices. The first set is made with carbon containing the natural abundance of 12C (99%) and 13C (1%), the second set with the 99% 13C and 1% 12C. In the devices with predominantly 13C, we find evidence in spin-dependent transport of the interaction between the electron spins and the 13C nuclear spins that was much stronger than expected and not present in the 12C devices. In the second nanotube experiment, pulsed gate experiments are used to measure the timescales of spin relaxation and dephasing in a two-electron double quantum dot. The relaxation time is longest at zero magnetic field and goes through a minimum at higher field, consistent with the spin-orbit-modified electronic spectrum of carbon nanotubes. We measure a short dephasing time consistent with the anomalously strong electron-nuclear interaction inferred from the first nanotube experiment.

  1. Rate constant for the reaction Cl + HO2NO2 yielding products. [in stratospheric chemistry

    NASA Technical Reports Server (NTRS)

    Simonaitis, R.; Leu, M. T.

    1985-01-01

    The rates for the reaction of Cl atoms iwth HO2NO2 were calculated from data obtained by the use of the discharge flow/resonance fluorescence (DF/RF) and the discharge flow/mass spectrometric (DF/MS) techniques. The total rate constant, k1, for the overall reaction: 1a (Cl + HO2NO2 yielding HCl + NO2 +O2), 1b (yielding HO2 + ClNO2), and the two possible additional channels was found to be less than 1.0 x 10 to the -13th cu cm/s at 296 K. The value of (k1a + k1b) was found to be 3.4 + or - 1.4) x 10 to the -14th cu cm/s. Thus, the reaction of Cl with peroxynitric acid is too slow, by a factor of 100, to contribute significantly to the hydrogen abstraction by Cl in the stratosphere.

  2. Extracellular biosynthesis of CdTe quantum dots by the fungus Fusarium oxysporum and their anti-bacterial activity

    NASA Astrophysics Data System (ADS)

    Syed, Asad; Ahmad, Absar

    2013-04-01

    The growing demand for semiconductor [quantum dots (Q-dots)] nanoparticles has fuelled significant research in developing strategies for their synthesis and characterization. They are extensively investigated by the chemical route; on the other hand, use of microbial sources for biosynthesis witnessed the highly stable, water dispersible nanoparticles formation. Here we report, for the first time, an efficient fungal-mediated synthesis of highly fluorescent CdTe quantum dots at ambient conditions by the fungus Fusarium oxysporum when reacted with a mixture of CdCl2 and TeCl4. Characterization of these biosynthesized nanoparticles was carried out by different techniques such as Ultraviolet-visible (UV-Vis) spectroscopy, Photoluminescence (PL), X-ray Diffraction (XRD), X-ray Photoelectron spectroscopy (XPS), Transmission Electron Microscopy (TEM) and Fourier Transformed Infrared Spectroscopy (FTIR) analysis. CdTe nanoparticles shows antibacterial activity against Gram positive and Gram negative bacteria. The fungal based fabrication provides an economical, green chemistry approach for production of highly fluorescent CdTe quantum dots.

  3. Fluorescent Quantum Dots for Biological Labeling

    NASA Technical Reports Server (NTRS)

    McDonald, Gene; Nadeau, Jay; Nealson, Kenneth; Storrie-Lomardi, Michael; Bhartia, Rohit

    2003-01-01

    Fluorescent semiconductor quantum dots that can serve as "on/off" labels for bacteria and other living cells are undergoing development. The "on/off" characterization of these quantum dots refers to the fact that, when properly designed and manufactured, they do not fluoresce until and unless they come into contact with viable cells of biological species that one seeks to detect. In comparison with prior fluorescence-based means of detecting biological species, fluorescent quantum dots show promise for greater speed, less complexity, greater sensitivity, and greater selectivity for species of interest. There are numerous potential applications in medicine, environmental monitoring, and detection of bioterrorism.

  4. Magnon-driven quantum dot refrigerators

    NASA Astrophysics Data System (ADS)

    Wang, Yuan; Huang, Chuankun; Liao, Tianjun; Chen, Jincan

    2015-12-01

    A new model of refrigerator consisting of a spin-splitting quantum dot coupled with two ferromagnetic reservoirs and a ferromagnetic insulator is proposed. The rate equation is used to calculate the occupation probabilities of the quantum dot. The expressions of the electron and magnon currents are obtained. The region that the system can work in as a refrigerator is determined. The cooling power and coefficient of performance (COP) of the refrigerator are derived. The influences of the magnetic field, applied voltage, and polarization of two leads on the performance are discussed. The performances of two different magnon-driven quantum dot refrigerators are compared.

  5. Clocking an Array of Quantum Dots

    NASA Astrophysics Data System (ADS)

    Khatun, Mahfuza; Mandell, Eric

    2000-10-01

    Preferred Session: Condensed Matter Physics Clocking an Array of Quantum Dots* Eric Mandell and M. Khatun, Ball State University. We report a theoretical analysis of the time-dependent electric field due to a line of charged rods. The effects of both the real and image charge are taken into account. The rods are biased electrostatically to study the dynamical behavior of an array of quantum dots. The barrier heights between the quantum dots are controlled by the electric field. *Supported in part by the Indiana Academy of Science, Center for Energy Research/Education/Services(CERES) and the Office of Academic Research and Sponsored Programs, Ball State University.

  6. Nanometer distance measurements between multicolor quantum dots.

    PubMed

    Antelman, Josh; Wilking-Chang, Connie; Weiss, Shimon; Michalet, Xavier

    2009-05-01

    Quantum dot dimers made of short double-stranded DNA molecules labeled with different color quantum dots at each end were imaged using multicolor stage-scanning confocal microscopy. This approach eliminates chromatic aberration and color registration issues usually encountered in other multicolor imaging techniques. We demonstrate nanometer accuracy in individual distance measurement by suppression of quantum dot blinking and thoroughly characterize the contribution of different effects to the variability observed between measurements. Our analysis opens the way to accurate structural studies of biomolecules and biomolecular complexes using multicolor quantum labeling.

  7. Quantum Dots Investigated for Solar Cells

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila G.; Castro, Stephanie L.; Raffaelle, Ryne P.; Hepp, Aloysius F.

    2001-01-01

    The NASA Glenn Research Center has been investigating the synthesis of quantum dots of CdSe and CuInS2 for use in intermediate-bandgap solar cells. Using quantum dots in a solar cell to create an intermediate band will allow the harvesting of a much larger portion of the available solar spectrum. Theoretical studies predict a potential efficiency of 63.2 percent, which is approximately a factor of 2 better than any state-of-the-art devices available today. This technology is also applicable to thin-film devices--where it offers a potential four-fold increase in power-to-weight ratio over the state of the art. Intermediate-bandgap solar cells require that quantum dots be sandwiched in an intrinsic region between the photovoltaic solar cell's ordinary p- and n-type regions (see the preceding figure). The quantum dots form the intermediate band of discrete states that allow sub-bandgap energies to be absorbed. However, when the current is extracted, it is limited by the bandgap, not the individual photon energies. The energy states of the quantum dot can be controlled by controlling the size of the dot. Ironically, the ground-state energy levels are inversely proportional to the size of the quantum dots. We have prepared a variety of quantum dots using the typical organometallic synthesis routes pioneered by Ba Wendi et al., in the early 1990's. The most studied quantum dots prepared by this method have been of CdSe. To produce these dots, researchers inject a syringe of the desired organometallic precursors into heated triocytlphosphine oxide (TOPO) that has been vigorously stirred under an inert atmosphere (see the following figure). The solution immediately begins to change from colorless to yellow, then orange and red/brown, as the quantum dots increase in size. When the desired size is reached, the heat is removed from the flask. Quantum dots of different sizes can be identified by placing them under a "black light" and observing the various color differences in

  8. Electronic Structure of Few-Electron Quantum Dot Molecules

    NASA Astrophysics Data System (ADS)

    Popsueva, V.; Hansen, J. P.; Caillat, J.

    2007-12-01

    We present a study of strongly correlated few-electron quantum dots, exploring the spectra of various few-electron quantum dot molecules: a double (diatomic) structure a quadruple two-electron quantum dot, and a three-electron double dot. Electron energy spectra are computed for different values of dot separation. All spectra show clear band structures and can be understood from asymptotical properties of the system.

  9. High-resolution photocurrent microscopy using near-field cathodoluminescence of quantum dots

    NASA Astrophysics Data System (ADS)

    Yoon, Heayoung P.; Lee, Youngmin; Bohn, Christopher D.; Ko, Seung-Hyeon; Gianfrancesco, Anthony G.; Steckel, Jonathan S.; Coe-Sullivan, Seth; Talin, A. Alec; Zhitenev, Nikolai B.

    2013-06-01

    We report a fast, versatile photocurrent imaging technique to visualize the local photo response of solar energy devices and optoelectronics using near-field cathodoluminescence (CL) from a homogeneous quantum dot layer. This approach is quantitatively compared with direct measurements of high-resolution Electron Beam Induced Current (EBIC) using a thin film solar cell (n-CdS / p-CdTe). Qualitatively, the observed image contrast is similar, showing strong enhancement of the carrier collection efficiency at the p-n junction and near the grain boundaries. The spatial resolution of the new technique, termed Q-EBIC (EBIC using quantum dots), is determined by the absorption depth of photons. The results demonstrate a new method for high-resolution, sub-wavelength photocurrent imaging measurement relevant for a wide range of applications.

  10. Instability-driven quantum dots

    NASA Astrophysics Data System (ADS)

    Aqua, Jean-Noël; Frisch, Thomas

    2015-10-01

    When a film is strained in two dimensions, it can relax by developing a corrugation in the third dimension. We review here the resulting morphological instability that occurs by surface diffusion, called the Asaro-Tiller-Grinfel'd instability (ATG), especially on the paradigmatic silicon/germanium system. The instability is dictated by the balance between the elastic relaxation induced by the morphological evolution, and its surface energy cost. We focus here on its development at the nanoscales in epitaxial systems when a crystal film is coherently deposited on a substrate with a different lattice parameter, thence inducing epitaxial stresses. It eventually leads to the self-organization of quantum dots whose localization is dictated by the instability long-time dynamics. In these systems, new effects, such as film/substrate wetting or crystalline anisotropy, come into play and lead to a variety of behaviors. xml:lang="fr"

  11. Quantum dots and prion proteins

    PubMed Central

    Sobrova, Pavlina; Blazkova, Iva; Chomoucka, Jana; Drbohlavova, Jana; Vaculovicova, Marketa; Kopel, Pavel; Hubalek, Jaromir; Kizek, Rene; Adam, Vojtech

    2013-01-01

    A diagnostics of infectious diseases can be done by the immunologic methods or by the amplification of nucleic acid specific to contagious agent using polymerase chain reaction. However, in transmissible spongiform encephalopathies, the infectious agent, prion protein (PrPSc), has the same sequence of nucleic acids as a naturally occurring protein. The other issue with the diagnosing based on the PrPSc detection is that the pathological form of prion protein is abundant only at late stages of the disease in a brain. Therefore, the diagnostics of prion protein caused diseases represent a sort of challenges as that hosts can incubate infectious prion proteins for many months or even years. Therefore, new in vivo assays for detection of prion proteins and for diagnosis of their relation to neurodegenerative diseases are summarized. Their applicability and future prospects in this field are discussed with particular aim at using quantum dots as fluorescent labels. PMID:24055838

  12. Detecting collinear dots in noise.

    PubMed

    Tripathy, S P; Mussap, A J; Barlow, H B

    1999-01-01

    We estimated the sensitivity for detecting a row of collinear target elements (usually dots) by measuring the maximum density of randomly positioned noise elements that allowed 75% correct detection of the orientation of alignment (binary choice: horizontal versus vertical) of the target elements. We varied the number of target elements, their mode of generation, and their accuracy of positioning. As reported previously (Moulden (1994) Higher-order processing in the visual system. Ciba Foundation Symposium 184. Chichester: Wiley), target detection improved rapidly until the number of target elements reached about seven, and then improved more slowly beyond this point. However, this break was reduced (and often removed entirely) when the target array was formed by repositioning pre-existing noise elements lying close to the target location, rather than by superimposition of additional target elements onto the noise array. This almost linear slope of improvement, coupled with the observation that target detection was disrupted more by random jitter of target elements at right angles to their axis of alignment than by jittering along this axis, argues against a two-stage process of perceptual grouping (Moulden, 1994) and supports instead an explanation based on the operation of a single mechanism. This single mechanism explanation is further supported by the observation that intrinsic positional uncertainty (estimated from the results of jitter experiments) was independent of target element number. Additional experiments showed that target detection is facilitated by aperiodic noise dots that fall close to the target axis. The results are discussed in relation to alternative explanations of perceptual grouping.

  13. Energies and wave functions of an off-centre donor in hemispherical quantum dot: Two-dimensional finite difference approach and ritz variational principle

    NASA Astrophysics Data System (ADS)

    Nakra Mohajer, Soukaina; El Harouny, El Hassan; Ibral, Asmaa; El Khamkhami, Jamal; Assaid, El Mahdi

    2016-09-01

    Eigenvalues equation solutions of a hydrogen-like donor impurity, confined in a hemispherical quantum dot deposited on a wetting layer and capped by an insulating matrix, are determined in the framework of the effective mass approximation. Conduction band alignments at interfaces between quantum dot and surrounding materials are described by infinite height barriers. Ground and excited states energies and wave functions are determined analytically and via one-dimensional finite difference approach in case of an on-center donor. Donor impurity is then moved from center to pole of hemispherical quantum dot and eigenvalues equation is solved via Ritz variational principle, using a trial wave function where Coulomb attraction between electron and ionized donor is taken into account, and by two-dimensional finite difference approach. Numerical codes developed enable access to variations of donor total energy, binding energy, Coulomb correlation parameter, spatial extension and radial probability density with respect to hemisphere radius and impurity position inside the quantum dot.

  14. Mechanochemical hydrogenation of coal

    DOEpatents

    Yang, Ralph T.; Smol, Robert; Farber, Gerald; Naphtali, Leonard M.

    1981-01-01

    Hydrogenation of coal is improved through the use of a mechanical force to reduce the size of the particulate coal simultaneously with the introduction of gaseous hydrogen, or other hydrogen donor composition. Such hydrogen in the presence of elemental tin during this one-step size reduction-hydrogenation further improves the yield of the liquid hydrocarbon product.

  15. Nanomaterials: Earthworms lit with quantum dots

    NASA Astrophysics Data System (ADS)

    Tilley, Richard D.; Cheong, Soshan

    2013-01-01

    Yeast, bacteria and fungi have been used to synthesize a variety of nanocrystals. Now, the metal detoxification process in the gut of an earthworm is exploited to produce biocompatible cadmium telluride quantum dots.

  16. Luminescence blinking of a reacting quantum dot.

    PubMed

    Routzahn, Aaron L; Jain, Prashant K

    2015-04-01

    Luminescence blinking is an inherent feature of optical emission from individual fluorescent molecules and quantum dots. There have been intense efforts, although not with complete resolution, toward the understanding of the mechanistic origin of blinking and also its mitigation in quantum dots. As an advance in our microscopic view of blinking, we show that the luminescence blinking of a quantum dot becomes unusually heavy in the temporal vicinity of a reactive transformation. This stage of heavy blinking is a result of defects/dopants formed within the quantum dot on its path to conversion. The evolution of blinking behavior along the reaction path allows us to measure the lifetime of the critical dopant-related intermediate in the reaction. This work establishes luminescence blinking as a single-nanocrystal level probe of catalytic, photocatalytic, and electrochemical events occurring in the solid-state or on semiconductor surfaces.

  17. Quantum dots: A charge for blinking

    NASA Astrophysics Data System (ADS)

    Krauss, Todd D.; Peterson, Jeffrey J.

    2012-01-01

    No accepted description of luminescent blinking in quantum dots is currently available. Now, experiments probing the connection between charge and fluorescence intensity fluctuations unveil an unexpected source of blinking, significantly advancing our fundamental understanding of this baffling phenomenon.

  18. Teleportation on a quantum dot array.

    PubMed

    de Pasquale, F; Giorgi, G; Paganelli, S

    2004-09-17

    We present a model of quantum teleportation protocol based on a double quantum dot array. The unknown qubit is encoded using a pair of quantum dots, with one excess electron, coupled by tunneling. It is shown how to create a maximally entangled state using an adiabatically increasing Coulomb repulsion between different dot pairs. This entangled state is exploited to perform teleportation again using an adiabatic coupling between itself and the incoming unknown state. Finally, a sudden separation of Bob's qubit allows a time evolution of Alice's, which amounts to a modified version of standard Bell measurement. A transmission over a long distance could be obtained by considering the entangled state of a chain of N coupled double quantum dots. The system is shown to be increasingly robust with N against decoherence due to phonons.

  19. Etude structurale et vibrationnelle d’un nouveau composé complexe de cobalt: [Co(imidazole)4Cl]Cl

    PubMed Central

    Derbel, Amira; Mhiri, Tahar; Graia, Mohsen

    2015-01-01

    In the title complex, chlorido­tetra­kis­(1H-imidazole-κN 3)cobalt(II) chloride, [CoCl(C3H4N2)4]Cl, the CoII cation has a distorted square-pyramidal coordination environment. It is coordinated by four N atoms of four imidazole (Im) groups in the basal plane, and by a Cl atom in the apical position. It is isostructural with [Cu(Im)4Cl]Cl [Morzyk-Ociepa et al. (2012 ▸). J. Mol. Struct. 1028, 49–56] and [Cu(Im)4Br]Br [Hossaini Sadr et al. (2004 ▸). Acta Cryst. E60, m1324–m1326]. In the crystal, the [CoCl(C3H4N2)4]+ cations and Cl− anions are linked via N—H⋯Cl hydrogen bonds, forming layers parallel to (010). These layers are linked via C—H⋯Cl hydrogen bonds and C—H⋯π and π–π [inter-centroid distance = 3.794 (2) Å] inter­actions, forming a three-dimensional framework. The IR spectrum shows vibrational bands typical for imidazol groups. The monoclinic unit cell of the title compound emulates an ortho­rhom­bic cell as its β angle is close to 90°. The crystal is twinned, with the refined ratio of twin components being 0.569 (1):0.431 (1). PMID:26594402

  20. Exploring Extragalactic Emission: The Hα Dot Survey

    NASA Astrophysics Data System (ADS)

    Rampalli, Rayna; Salzer, John Joseph

    2016-01-01

    The Hα Dot Survey was established as a result of finding point sources of strong line emission in the data obtained for the ALFALFA Hα Survey (Van Sistine et al. 2015). In the latter survey, broad-band R and narrow-band Hα filters were used to examine target galaxies from the ALFALFA blind HI survey (Giovanelli et al. 2005, Haynes et al. 2011). In the process of reducing the ALFALFA Hα Survey data the "Hα Dots" were discovered (Kellar et al. 2008, 2012). Using specialized image analysis tools, a large population of dots has already been detected in the more than 1500 ALFALFA Hα narrow-band images taken with the 0.9m WIYN and 2.1m KPNO telescopes. Follow-up spectra of over 200 Hα Dots discovered from the 0.9m images reveal that these objects are a mix of nearby low-luminosity star-forming galaxies, compact starbursts and Seyfert 2 galaxies at intermediate redshifts, and high-redshift QSOs. Here we present the first list of Hα Dots detected using 2.1m telescope data. The 2.1m images yield a sample of Dots that average almost two magnitudes fainter than those detected with the 0.9m. The current REU project is designed to characterize the set of Hα Dots detected in the deeper 2.1m telescope images, while the broad goals of the Hα Dot Survey include the desire to understand better the chemical evolution of galaxies over cosmic time. This project was supported in part by the NSF REU grant 1358980, by the Maria Mitchell Association (Nantucket, MA), and by the Massachusetts Space Grant Consortium.

  1. First principle thousand atom quantum dot calculations

    SciTech Connect

    Wang, Lin-Wang; Li, Jingbo

    2004-03-30

    A charge patching method and an idealized surface passivation are used to calculate the single electronic states of IV-IV, III-V, II-VI semiconductor quantum dots up to a thousand atoms. This approach scales linearly and has a 1000 fold speed-up compared to direct first principle methods with a cost of eigen energy error of about 20 meV. The calculated quantum dot band gaps are parametrized for future references.

  2. Renormalization in Periodically Driven Quantum Dots.

    PubMed

    Eissing, A K; Meden, V; Kennes, D M

    2016-01-15

    We report on strong renormalization encountered in periodically driven interacting quantum dots in the nonadiabatic regime. Correlations between lead and dot electrons enhance or suppress the amplitude of driving depending on the sign of the interaction. Employing a newly developed flexible renormalization-group-based approach for periodic driving to an interacting resonant level we show analytically that the magnitude of this effect follows a power law. Our setup can act as a non-Markovian, single-parameter quantum pump. PMID:26824557

  3. Electron Spin Dynamics in Semiconductor Quantum Dots

    SciTech Connect

    Marie, X.; Belhadj, T.; Urbaszek, B.; Amand, T.; Krebs, O.; Lemaitre, A.; Voisin, P.

    2011-07-15

    An electron spin confined to a semiconductor quantum dot is not subject to the classical spin relaxation mechanisms known for free carriers but it strongly interacts with the nuclear spin system via the hyperfine interaction. We show in time resolved photoluminescence spectroscopy experiments on ensembles of self assembled InAs quantum dots in GaAs that this interaction leads to strong electron spin dephasing.

  4. Hydrogenation of GaSb/GaAs quantum rings

    SciTech Connect

    Hodgson, P. D. Hayne, M.; Zhuang, Q. D.; Ahmad Kamarudin, M.; Birindelli, S.; Capizzi, M.

    2014-08-25

    We present the results of photoluminescence measurements on hydrogenated type-II GaSb/GaAs quantum dot/ring (QD/QR) samples at temperatures ranging from 4.2 K to 400 K. Hydrogenation is found to suppress optically induced charge depletion (associated with the presence of carbon acceptors in this system). A redshift of the QD\\QR emission energy of a few tens of meV is observed at temperatures ≥300 K, consistent with a reduction in average occupancy by ∼1 hole. These effects are accompanied by a reduction in PL intensity post-hydrogenation. We conclude that although hydrogenation may have neutralized the carbon acceptors, multiple hole occupancy of type-II GaSb/GaAs QD/QRs is very likely a precondition for intense emission, which would make extending the wavelength significantly beyond 1300 nm at room temperature difficult.

  5. Investigation of the Hydrochlorination of SiCl4

    NASA Technical Reports Server (NTRS)

    Mui, J. Y. P.

    1983-01-01

    The hydrochlorination of silicon tetrachloride with hydrogen and metallurgical grade (m.g.) silicon metal, 3 SiCl4 + 2 H2 + Si yields 4 SiHCl3 was shown to be an efficient process to produce trichlorosilane. A research and development program was carried out to study the hydrochlorination reaction over a wide range of reaction conditions. Equilibrium constant and reaction kinetics measurements were made to provide the basis for a theoretical study on the hydrochlorination process. Thermodynamic properties of the hydrochlorination reaction were also measured. The effects of temperature, pressure, and concentration on the equilibrium constant, K sub p, were studied.

  6. Hydrogen peroxide poisoning

    MedlinePlus

    ... peroxide is used in these products: Hydrogen peroxide Hair bleach Some contact lens cleaners Note: Household hydrogen peroxide ... it contains 97% water and 3% hydrogen peroxide. Hair bleaches are stronger. They usually have a concentration of ...

  7. DEVELOPMENT OF A CL-IMPREGNATED ACTIVATED CARBON FOR ENTRAINED-FLOW CAPTURE OF ELEMENTAL MERCURY

    EPA Science Inventory

    Efforts to discern the role of an activated carbon's surface functional groups on the adsorption of elemental mercury [Hg(0)] and mercuric chloride demonstrated that chlorine (Cl) impregnation of a virgin activated carbon using dilute solutions of hydrogen chloride leads to incre...

  8. Luminescent Quantum Dots as Ultrasensitive Biological Labels

    NASA Astrophysics Data System (ADS)

    Nie, Shuming

    2000-03-01

    Highly luminescent semiconductor quantum dots have been covalently coupled to biological molecules for use in ultrasensitive biological detection. This new class of luminescent labels is considerably brighter and more resistant againt photobleaching in comparison with organic dyes. Quantum dots labeled with the protein transferrin undergo receptor-mediated endocytosis (RME) in cultured HeLa cells, and those dots that were conjugated to immunomolecules recognize specific antibodies or antigens. In addition, we show that DNA functionalized quantum dots can be used to target specific genes by hybridization. We expect that quantum dot bioconjugates will have a broad range of biological applications, such as ligand-receptor interactions, real-time monitoring of molecular trafficking inside living cells, multicolor fluorescence in-situ hybridization (FISH), high-sensitivity detection in miniaturized devices (e.g., DNA chips), and fluorescent tagging of combinatorial chemical libraries. A potential clinical application is the use of quantum dots for ultrasensitive viral RNA detection, in which as low as 100 copies of hepatitis C and HIV viruses per ml blood should be detected.

  9. Electrical control of quantum dot spin qubits

    NASA Astrophysics Data System (ADS)

    Laird, Edward Alexander

    This thesis presents experiments exploring the interactions of electron spins with electric fields in devices of up to four quantum dots. These experiments are particularly motivated by the prospect of using electric fields to control spin qubits. A novel hyperfine effect on a single spin in a quantum dot is presented in Chapter 2. Fluctuations of the nuclear polarization allow single-spin resonance to be driven by an oscillating electric field. Spin resonance spectroscopy revealed a nuclear polarization built up inside the quantum dot device by driving the resonance. The evolution of two coupled spins is controlled by the combination of hyperfine interaction, which tends to cause spin dephasing, and exchange, which tends to prevent it. In Chapter 3, dephasing is studied in a device with tunable exchange, probing the crossover between exchange-dominated and hyperfine-dominated regimes. In agreement with theoretical predictions, oscillations of the spin conversion probability and saturation of dephasing are observed. Chapter 4 deals with a three-dot device, suggested as a potential qubit controlled entirely by exchange. Preparation and readout of the qubit state are demonstrated, together with one out of two coherent exchange operations needed for arbitrary manipulations. A new readout technique allowing rapid device measurement is described. In Chapter 5, an attempt to make a two-qubit gate using a four-dot device is presented. Although spin qubit operation has not yet been possible, the electrostatic interaction between pairs of dots was measured to be sufficient in principle for coherent qubit coupling.

  10. Formation and ordering of epitaxial quantum dots

    NASA Astrophysics Data System (ADS)

    Atkinson, Paola; Schmidt, Oliver G.; Bremner, Stephen P.; Ritchie, David A.

    2008-10-01

    Single quantum dots (QDs) have great potential as building blocks for quantum information processing devices. However, one of the major difficulties in the fabrication of such devices is the placement of a single dot at a pre-determined position in the device structure, for example, in the centre of a photonic cavity. In this article we review some recent investigations in the site-controlled growth of InAs QDs on GaAs by molecular beam epitaxy. The method we use is ex-situ patterning of the GaAs substrate by electron beam lithography and conventional wet or dry etching techniques to form shallow pits in the surface which then determine the nucleation site of an InAs dot. This method is easily scalable and can be incorporated with marker structures to enable simple post-growth lithographic alignment of devices to each site-controlled dot. We demonstrate good site-control for arrays with up to 10 micron spacing between patterned sites, with no dots nucleating between the sites. We discuss the mechanism and the effect of pattern size, InAs deposition amount and growth conditions on this site-control method. Finally we discuss the photoluminescence from these dots and highlight the remaining challenges for this technique. To cite this article: P. Atkinson et al., C. R. Physique 9 (2008).

  11. Silicon quantum dots for optical applications

    NASA Astrophysics Data System (ADS)

    Wu, Jeslin J.

    Luminescent silicon quantum dots (SiQDs) are emerging as attractive materials for optoelectronic devices, third generation photovoltaics, and bioimaging. Their applicability in the real world is contingent on their optical properties and long-term environmental stability; and in biological applications, factors such as water solubility and toxicity must also be taken into consideration. The aforementioned properties are highly dependent on the QDs' surface chemistry. In this work, SiQDs were engineered for the respective applications using liquid-phase and gas-phase functionalization techniques. Preliminary work in luminescent downshifting for photovoltaic systems are also reported. Highly luminescent SiQDs were fabricated by grafting unsaturated hydrocarbons onto the surface of hydrogen-terminated SiQDs via thermal and photochemical hydrosilylation. An industrially attractive, all gas-phase, nonthermal plasma synthesis, passivation (aided by photochemical reactions), and deposition process was also developed to reduce solvent waste. With photoluminescence quantum yields (PLQYs) nearing 60 %, the alkyl-terminated QDs are attractive materials for optical applications. The functionalized SiQDs also exhibited enhanced thermal stability as compared to their unfunctionalized counterparts, and the photochemically-hydrosilylated QDs further displayed photostability under UV irradiation. These environmentally-stable SiQDs were used as luminescent downshifting layers in photovoltaic systems, which led to enhancements in the blue photoresponse of heterojunction solar cells. Furthermore, the QD films demonstrated antireflective properties, improving the coupling efficiency of sunlight into the cell. For biological applications, oxide, amine, or hydroxyl groups were grafted onto the surface to create water-soluble SiQDs. Luminescent, water-soluble SiQDs were produced in by microplasma treating the QDs in water. Stable QYs exceeding 50 % were obtained. Radical-based and

  12. 49 CFR 40.227 - May employers use the ATF for non-DOT tests, or non-DOT forms for DOT tests?

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 1 2010-10-01 2010-10-01 false May employers use the ATF for non-DOT tests, or non-DOT forms for DOT tests? 40.227 Section 40.227 Transportation Office of the Secretary of..., Equipment and Supplies Used in Alcohol Testing § 40.227 May employers use the ATF for non-DOT tests, or...

  13. Novel cookie-with-chocolate carbon dots displaying extremely acidophilic high luminescence.

    PubMed

    Lu, Siyu; Zhao, Xiaohuan; Zhu, Shoujun; Song, Yubin; Yang, Bai

    2014-11-21

    A fluorescent carbon dot with a cookie-with-chocolate film structure (about 5 × 5 μm(2)) showed a high fluorescence quantum yield (61.12%) at low pH. It was hydrothermally synthesized from l-serine and l-tryptophan. The formation mechanism of the film with carbon dots (CDs) was investigated. The film structure was formed by hydrogen bonding and π-π stacking interactions between aromatic rings. The strong blue fluorescence of the CDs increased under strong acidic conditions owing to the changes in the N-groups. These cookie-like CDs are attractive for their potential use as effective fluorescent probes for the sensitive detection of aqueous H(+) and Fe(3+).

  14. Laser driven impurity states in two-dimensional quantum dots and quantum rings

    NASA Astrophysics Data System (ADS)

    Laroze, D.; Barseghyan, M.; Radu, A.; Kirakosyan, A. A.

    2016-11-01

    The hydrogenic donor impurity states in two-dimensional GaAs/Ga0.7Al0.3As quantum dot and quantum ring have been investigated under the action of intense laser field. A laser dressed effect on both electron confining and electron-impurity Coulomb interaction potentials has been considered. The single electron energy spectrum and wave functions have been found using the effective mass approximation and exact diagonalization technique. The accidental degeneracy of the impurity states have been observed for different positions of the impurity and versus values of the laser field parameter. The obtained theoretical results indicate a novel opportunity to tune the performance of quantum dots and quantum rings and to control their specific properties by means of laser field.

  15. Photo-driven autonomous hydrogen generation system based on hierarchically shelled ZnO nanostructures

    SciTech Connect

    Kim, Heejin; Yong, Kijung

    2013-11-25

    A quantum dot semiconductor sensitized hierarchically shelled one-dimensional ZnO nanostructure has been applied as a quasi-artificial leaf for hydrogen generation. The optimized ZnO nanostructure consists of one dimensional nanowire as a core and two-dimensional nanosheet on the nanowire surface. Furthermore, the quantum dot semiconductors deposited on the ZnO nanostructures provide visible light harvesting properties. To realize the artificial leaf, we applied the ZnO based nanostructure as a photoelectrode with non-wired Z-scheme system. The demonstrated un-assisted photoelectrochemical system showed the hydrogen generation properties under 1 sun condition irradiation. In addition, the quantum dot modified photoelectrode showed 2 mA/cm{sup 2} current density at the un-assisted condition.

  16. Thermochemical cycles for the production of hydrogen

    DOEpatents

    Steinberg, M.; Dang, V.D.

    Two-step processes for the preparation of hydrogen are described: CrCl/sub 3/(g) ..-->.. CrCl/sub 2/(g) + 1/2Cl/sub 2/(g) and CrCl/sub 2/(s) + HCl(g) reversible CrCl/sub 3/(s) + 1/2H/sub 2/(g); UCl/sub 4/(g) ..-->.. UCl/sub 3/(g) + 1/2Cl/sub 2/(g) and UCl/sub 3/(s) + HCl(g) ..-->.. UCl/sub 4/(s) + 1/2H/sub 2/(g); and CaSO/sub 4/(s) ..-->.. CaO(s) + SO/sub 2/(g) + 1/2O/sub 2/(g) and CaO(s) + SO/sub 2/(g) + H/sub 2/O(l) ..-->.. CaSO/sub 4/(s) + H/sub 2/(g). The high temperature available from solar collectors, high temperature gas reactors or fusion reactors is utilized in the first step in which the reaction is endothermic. The efficiency is at least 60% and with process heat recovery, the efficiency may be increased up to 74.4%. An apparatus fr carrying out the process in conjunction with a fusion reactor, is described.

  17. Electronic spectrum of non-tetrahedral acceptors in CdTe:Cl and CdTe:Bi,Cl single crystals

    NASA Astrophysics Data System (ADS)

    Krivobok, V. S.; Nikolaev, S. N.; Bagaev, V. S.; Pruchkina, A. A.; Onishchenko, E. E.; Kolosov, S. A.; Klevkov, Yu. V.; Skorikov, M. L.

    2016-02-01

    The electronic spectra of complex acceptors in compensated CdTe:Cl, CdTe:Ag,Cl, and CdTe:Bi,Cl single crystals are studied using low-temperature photoluminescence (PL) measurements under both nonresonant and resonant excitation of distant donor-acceptor pairs (DAP). The wavelength modulation of the excitation source combined with the analysis of the differential PL signal is used to enhance narrow spectral features obscured because of inhomogeneous line broadening and/or excitation transfer for selectively excited DAPs. For the well-known tetrahedral (TD) AgCd acceptor, the energies of four excited states are measured, and the values obtained are shown to be in perfect agreement with the previous data. Moreover, splitting between the 2P3/2 (D8) and 2S3/2 (D8) states is clearly observed for AgCd centers located at a short distance (5-7 nm) from a hydrogen-like donor (ClTe). This splitting results from the reduction of the TD symmetry taking place when the acceptor is a member of a donor-acceptor pair. For the Cl-related complex acceptor with an activation energy of ˜121 meV (A-center), the energies of eight excited states are measured. It is shown that this defect produces low-symmetry central-cell correction responsible for the strong splitting of S-like TD shells. The energy spectrum of the Bi-related shallow acceptor with an activation energy of ˜36 meV is measured as well. The spectrum obtained differs drastically from the hydrogen-like set of levels, which indicates the existence of repulsive low-symmetry perturbation of the hydrogen-like Coulomb potential. It is also shown that the spectra of selectively excited PL recorded for a macroscopic ensemble of distant donor-acceptor pairs allow one to detect the low symmetry of acceptors of a given type caused by their complex nature or by the Jahn-Teller distortion. This method does not require any additional (external) field and is applicable to acceptors in diverse zinc-blende compound semiconductors.

  18. Chloride ion conduction without water coordination in the pore of ClC protein.

    PubMed

    Ko, Youn Jo; Jo, Won Ho

    2010-02-01

    In the present work, we have found by an atomistic molecular dynamics simulation that hydrogen atoms originating from the residues of a prokaryotic ClC protein (EcClC) stabilize the chloride ion without water molecules in the pore of ClC protein. When the chloride ion conduction is simulated by pulling a chloride ion along the pore axis, the free energy barrier for chloride ion conduction is calculated to be low (4 kcal/mol), although the chloride ion is stripped of its hydration shell as it passes through the dehydrated pore region. The calculation of the number of hydrogen atoms surrounding the chloride ion reveals that water molecules hydrating the chloride ion are replaced by polar and non-polar hydrogen atoms protruding from the protein residues. From the analysis of the pair interaction energy between the chloride ion and these hydrogen atoms, it is realized that the hydrogen atoms from the protein residues stabilize the chloride ion at the dehydrated region instead of water molecules, by which the energetic penalty for detaching water molecules from the permeating ion is compensated.

  19. Low Gate Voltage Operated Multi-emitter-dot H+ Ion-Sensitive Gated Lateral Bipolar Junction Transistor

    NASA Astrophysics Data System (ADS)

    Yuan, Heng; Zhang, Ji-Xing; Zhang, Chen; Zhang, Ning; Xu, Li-Xia; Ding, Ming; Patrick, J. Clarke

    2015-02-01

    A low gate voltage operated multi-emitter-dot gated lateral bipolar junction transistor (BJT) ion sensor is proposed. The proposed device is composed of an arrayed gated lateral BJT, which is driven in the metal-oxide-semiconductor field-effect transistor (MOSFET)-BJT hybrid operation mode. Further, it has multiple emitter dots linked to each other in parallel to improve ionic sensitivity. Using hydrogen ionic solutions as reference solutions, we conduct experiments in which we compare the sensitivity and threshold voltage of the multi-emitter-dot gated lateral BJT with that of the single-emitter-dot gated lateral BJT. The multi-emitter-dot gated lateral BJT not only shows increased sensitivity but, more importantly, the proposed device can be operated under very low gate voltage, whereas the conventional ion-sensitive field-effect transistors cannot. This special characteristic is significant for low power devices and for function devices in which the provision of a gate voltage is difficult.

  20. Porous palladium coated conducting polymer nanoparticles for ultrasensitive hydrogen sensors.

    PubMed

    Lee, Jun Seop; Kim, Sung Gun; Cho, Sunghun; Jang, Jyongsik

    2015-12-28

    Hydrogen, a clean-burning fuel, is of key importance to various industrial applications, including fuel cells and in the aerospace and automotive industries. However, hydrogen gas is odorless, colorless, and highly flammable; thus appropriate safety protocol implementation and monitoring are essential. Highly sensitive hydrogen leak detection and surveillance sensor systems are needed; additionally, the ability to maintain uniformity through repetitive hydrogen sensing is becoming increasingly important. In this report, we detail the fabrication of porous palladium coated conducting polymer (3-carboxylate polypyrrole) nanoparticles (Pd@CPPys) to detect hydrogen gas. The Pd@CPPys are produced by means of facile alkyl functionalization and chemical reduction of a pristine 3-carboxylate polypyrrole nanoparticle-contained palladium precursor (PdCl(2)) solution. The resulting Pd@CPPy-based sensor electrode exhibits ultrahigh sensitivity (0.1 ppm) and stability toward hydrogen gas at room temperature due to the palladium sensing layer.

  1. Porous palladium coated conducting polymer nanoparticles for ultrasensitive hydrogen sensors.

    PubMed

    Lee, Jun Seop; Kim, Sung Gun; Cho, Sunghun; Jang, Jyongsik

    2015-12-28

    Hydrogen, a clean-burning fuel, is of key importance to various industrial applications, including fuel cells and in the aerospace and automotive industries. However, hydrogen gas is odorless, colorless, and highly flammable; thus appropriate safety protocol implementation and monitoring are essential. Highly sensitive hydrogen leak detection and surveillance sensor systems are needed; additionally, the ability to maintain uniformity through repetitive hydrogen sensing is becoming increasingly important. In this report, we detail the fabrication of porous palladium coated conducting polymer (3-carboxylate polypyrrole) nanoparticles (Pd@CPPys) to detect hydrogen gas. The Pd@CPPys are produced by means of facile alkyl functionalization and chemical reduction of a pristine 3-carboxylate polypyrrole nanoparticle-contained palladium precursor (PdCl(2)) solution. The resulting Pd@CPPy-based sensor electrode exhibits ultrahigh sensitivity (0.1 ppm) and stability toward hydrogen gas at room temperature due to the palladium sensing layer. PMID:26598964

  2. Novel cookie-with-chocolate carbon dots displaying extremely acidophilic high luminescence

    NASA Astrophysics Data System (ADS)

    Lu, Siyu; Zhao, Xiaohuan; Zhu, Shoujun; Song, Yubin; Yang, Bai

    2014-10-01

    A fluorescent carbon dot with a cookie-with-chocolate film structure (about 5 × 5 μm2) showed a high fluorescence quantum yield (61.12%) at low pH. It was hydrothermally synthesized from l-serine and l-tryptophan. The formation mechanism of the film with carbon dots (CDs) was investigated. The film structure was formed by hydrogen bonding and π-π stacking interactions between aromatic rings. The strong blue fluorescence of the CDs increased under strong acidic conditions owing to the changes in the N-groups. These cookie-like CDs are attractive for their potential use as effective fluorescent probes for the sensitive detection of aqueous H+ and Fe3+.A fluorescent carbon dot with a cookie-with-chocolate film structure (about 5 × 5 μm2) showed a high fluorescence quantum yield (61.12%) at low pH. It was hydrothermally synthesized from l-serine and l-tryptophan. The formation mechanism of the film with carbon dots (CDs) was investigated. The film structure was formed by hydrogen bonding and π-π stacking interactions between aromatic rings. The strong blue fluorescence of the CDs increased under strong acidic conditions owing to the changes in the N-groups. These cookie-like CDs are attractive for their potential use as effective fluorescent probes for the sensitive detection of aqueous H+ and Fe3+. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03965c

  3. Lateral Quantum Dots for Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    House, Matthew Gregory

    The possibility of building a computer that takes advantage of the most subtle nature of quantum physics has been driving a lot of research in atomic and solid state physics for some time. It is still not clear what physical system or systems can be used for this purpose. One possibility that has been attracting significant attention from researchers is to use the spin state of an electron confined in a semiconductor quantum dot. The electron spin is magnetic in nature, so it naturally is well isolated from electrical fluctuations that can a loss of quantum coherence. It can also be manipulated electrically, by taking advantage of the exchange interaction. In this work we describe several experiments we have done to study the electron spin properties of lateral quantum dots. We have developed lateral quantum dot devices based on the silicon metal-oxide-semiconductor transistor, and studied the physics of electrons confined in these quantum dots. We measured the electron spin excited state lifetime, which was found to be as long as 30 ms at the lowest magnetic fields that we could measure. We fabricated and characterized a silicon double quantum dot. Using this double quantum dot design, we fabricated devices which combined a silicon double quantum dot with a superconducting microwave resonator. The microwave resonator was found to be sensitive to two-dimensional electrons in the transistor channel, which we measured and characterized. We developed a new method for extracting information from random telegraph signals, which are produced when we observe thermal fluctuations of electrons in quantum dots. The new statistical method, based on the hidden Markov model, allows us to detect spin-dependent effects in such fluctuations even though we are not able to directly observe the electron spin. We use this analysis technique on data from two experiments involving gallium arsenide quantum dots and use it to measure spin-dependent tunneling rates. Our results advance the

  4. Hydrogen bonding in 1-butyl- and 1-ethyl-3-methylimidazolium chloride ionic liquids.

    PubMed

    Skarmoutsos, Ioannis; Dellis, Dimitris; Matthews, Richard P; Welton, Tom; Hunt, Patricia A

    2012-04-26

    A detailed investigation of hydrogen bonding in the pure ionic liquids [C4C1im]Cl and [C2C1im]Cl has been carried out using primarily molecular dynamics techniques. Analyses of the individual atom-atom pair radial distribution functions, and in particular those for C···Cl(-), have revealed that hydrogen bonding to the first methylene or methyl units of the substituent groups is important. Multiple geometric criteria for defining a hydrogen bond have been applied, and in particular the choice of the cutoff angle has been carefully examined. The interpretation of hydrogen bonding within these ionic liquids is highly angle dependent, and justification is provided for why it may be appropriate to employ a wider angle criteria than the 30° used for water or alcohol systems. The different types of hydrogen bond formed are characterized, and "top" conformations where the Cl anion resides above (or below) the imidazolium ring are investigated. The number of hydrogen bonds undertaken by each hydrogen atom (and the chloride anion) is quantified, and the propensity to form zero, one, or two hydrogen bonds is established. The effects of an increase in temperature on the static hydrogen bonding are also briefly examined.

  5. Tribology in Gaseous Hydrogen

    NASA Astrophysics Data System (ADS)

    Sawae, Yoshinori; Sugimura, Joich

    Hydrogen is expected as a clean and renewable energy carrier for future environment-friendly society. Many machine elements in hydrogen energy systems should be operating within hydrogen gas and tribological behavior, such as friction and wear, of bearings and seals are affected by the hydrogen environment through some interactions between material surfaces and gaseous hydrogen, i.e., physisorption of hydrogen molecules and following chemisorptions of dissociated atoms on metal surfaces, formation of metal hydride and reduction of metal oxide layer by hydrogen atoms diffused into bulk. Therefore, friction and wear characteristics of tribomaterials in the hydrogen environment should be appropriately understood to establish a design guideline for reliable hydrogen utilizing systems. This paper reviews the current knowledge about the effect of hydrogen on friction and wear of materials, and then describes our recent progress of hydrogen research in the tribology field.

  6. (In,Mn)As multilayer quantum dot structures

    SciTech Connect

    Bouravleuv, Alexei; Sapega, Victor; Nevedomskii, Vladimir; Khrebtov, Artem; Samsonenko, Yuriy; Cirlin, George

    2014-12-08

    (In,Mn)As multilayer quantum dots structures were grown by molecular beam epitaxy using a Mn selective doping of the central parts of quantum dots. The study of the structural and magneto-optical properties of the samples with three and five layers of (In,Mn)As quantum dots has shown that during the quantum dots assembly, the out-diffusion of Mn from the layers with (In,Mn)As quantum dots can occur resulting in the formation of the extended defects. To produce a high quality structures using the elaborated technique of selective doping, the number of (In,Mn)As quantum dot layers should not exceed three.

  7. Submonolayer Quantum Dot Infrared Photodetector

    NASA Technical Reports Server (NTRS)

    Ting, David Z.; Bandara, Sumith V.; Gunapala, Sarath D.; Chang, Yia-Chang

    2010-01-01

    A method has been developed for inserting submonolayer (SML) quantum dots (QDs) or SML QD stacks, instead of conventional Stranski-Krastanov (S-K) QDs, into the active region of intersubband photodetectors. A typical configuration would be InAs SML QDs embedded in thin layers of GaAs, surrounded by AlGaAs barriers. Here, the GaAs and the AlGaAs have nearly the same lattice constant, while InAs has a larger lattice constant. In QD infrared photodetector, the important quantization directions are in the plane perpendicular to the normal incidence radiation. In-plane quantization is what enables the absorption of normal incidence radiation. The height of the S-K QD controls the positions of the quantized energy levels, but is not critically important to the desired normal incidence absorption properties. The SML QD or SML QD stack configurations give more control of the structure grown, retains normal incidence absorption properties, and decreases the strain build-up to allow thicker active layers for higher quantum efficiency.

  8. Comparison of two methods for selegiline determination: A flow-injection chemiluminescence method using cadmium sulfide quantum dots and corona discharge ion mobility spectrometry

    NASA Astrophysics Data System (ADS)

    Khataee, Alireza; Lotfi, Roya; Hasanzadeh, Aliyeh; Iranifam, Mortaza; Zarei, Mahmoud; Joo, Sang Woo

    2016-01-01

    Two analytical approaches including chemiluminescence (CL) and corona discharge ionization ion mobility spectrometry (CD-IMS) were developed for sensitive determination of selegiline (SG). We found that the CL intensity of the KMnO4-Na2S2O3 CL system was significantly enhanced in the presence of L-cysteine capped CdS quantum dots (QDs). A possible CL mechanism for this CL reaction is proposed. In the presence of SG, the enhanced CL system was inhibited. Based on this inhibition, a simple and sensitive flow-injection CL method was proposed for the determination of SG. Under optimum experimental conditions, the decreased CL intensity was proportional to SG concentration in the range of 0.01 to 30.0 mg L- 1. The detection limit (3σ) was 0.004 mg L- 1. Also, SG was determined using CD-IMS, and under optimum conditions of CD-IMS, calibration curves were linear in the range of 0.15 to 42.0 mg L- 1, with a detection limit (3σ) of 0.03 mg L- 1. The precision of the two methods was calculated by analyzing samples containing 5.0 mg L- 1 of SG (n = 11). The relative standard deviations (RSDs%) of the flow-injection CL and CD-IMS methods are 2.17% and 3.83%, respectively. The proposed CL system exhibits a higher sensitivity and precision than the CD-IMS method for the determination of SG.

  9. Chlorine transfer out of a very low permeability clay sequence (Paris Basin, France): 35Cl and 37Cl evidence

    NASA Astrophysics Data System (ADS)

    Lavastre, Véronique; Jendrzejewski, Nathalie; Agrinier, Pierre; Javoy, Marc; Evrard, Marc

    2005-11-01

    The marine Callovo-Oxfordian clay formation is found at a depth around 410m in the eastern part of the Paris Basin (France). It is a very low permeability formation investigated by the French agency for nuclear waste management (ANDRA) to study the feasibility of a radioactive waste disposal. Examining hydrogeological and geochemical characteristics of the clay sequence may test confinement properties of this formation. This study uses chlorine isotopes to investigate long-term transport processes which may carry chemical elements out of the clay layer to the surrounding rocks. Detailed chlorine concentration and δ 37Cl depth profiles are examined using pore waters and aquifer waters sampled in the clay formation and its surrounding aquifers (the Dogger at the bottom and the Oxfordian/Kimmeridgian/Tithonian unit at the top). They are discussed in terms of chlorine budget and hydrogeological processes. Clay pore waters and aquifer waters show strong chlorine concentration depletion (<3000 mg/L) relative to the original marine interstitial water (˜19000 mg/L). This probably results from an early dilution by meteoric water in limestones (as also indicated by oxygen and hydrogen isotopes). A steep Cl-concentration gradient from the Dogger at ˜500m in depth (˜2500 mg/L) to the Oxfordian/Kimmeridgian/Tithonian aquifer near the surface (≈ 10 mg/L) is associated to a 'v-shaped' profile of the δ 37Cl values. Modelling Cl transport shows that a hydrodynamic dispersion process explains Cl concentration and δ 37Cl profiles in Oxfordian Limestone. This process implies a mean upward flux of chloride in the 2.6 10 -8-8.2 10 -8 mole/m 2/yr range from the clay formation towards upper limestones where a westward advective flow disperses the chloride. The modelling and knowledge of underground water transfer suggest a maximum effective Cl-hydrodynamic vertical dispersion coefficient (= vertical Cl-transport coefficient) of ˜7.6 10 -10 m 2/s. Chlorine transfer through the

  10. Cl atom initiated oxidation of 1-alkenes under atmospheric conditions

    NASA Astrophysics Data System (ADS)

    Walavalkar, M.; Sharma, A.; Alwe, H. D.; Pushpa, K. K.; Dhanya, S.; Naik, P. D.; Bajaj, P. N.

    2013-03-01

    In view of the importance of the oxidation pathways of alkenes in the troposphere, and the significance of Cl atom as an oxidant in marine boundary layer (MBL) and polluted industrial atmosphere, the reactions of four 1-alkenes (C6-C9) with Cl atoms are investigated. The rate coefficients at 298 K are measured to be (4.0 ± 0.5), (4.4 ± 0.7), (5.5 ± 0.9) and (5.9 ± 1.7) × 10-10 cm3 molecule-1 s-1 for 1-hexene, 1-heptene, 1-octene and 1-nonene, respectively. The quoted errors include the experimental 2σ, along with the error in the reference rate coefficients. From the systematic increase in the rate coefficients with the number of carbon atoms, an approximate value for the average rate coefficient for hydrogen abstraction per CH2 group in alkenes is estimated to be (4.9 ± 0.3) × 10-11 cm3 molecule-1 s-1. Based on these rate coefficients, the contribution of Cl atom reactions towards the degradation of these molecules is found to be comparable to that of OH radical reactions, under MBL conditions. The products identified in gas phase indicate that Cl atom addition occurs mainly at the terminal carbon, leading to the formation of 1-chloro-2-ketones and 1-chloro-2-ols. The major gas phase products from the alkenyl radicals (formed by H atom abstraction) are different positional isomers of long chain enols and enones. A preference for dissociation leading to an allyl radical, resulting in aldehydes, lower by three carbon atoms, is indicated. The observed relative yields suggest that in general, the increased contribution of the reactions of Cl atoms towards degradation of 1-alkenes in NOx free air does not result in an increase in the generation of small aldehydes (carbon number < 4), including chloroethanal, as compared to that in the reaction of 1-butene.

  11. NQR application to the study of hydrogen dynamics in hydrogen-bonded molecular dimers

    NASA Astrophysics Data System (ADS)

    Asaji, Tetsuo

    2016-12-01

    The temperature dependences of 1H NMR as well as 35Cl NQR spin-lattice relaxation times T 1 were investigated in order to study the hydrogen transfer dynamics in carboxylic acid dimers in 3,5-dichloro- and 2,6-dichlorobenzoic acids. The asymmetry energy A/ k B and the activation energy V/ k B for the hydrogen transfer were estimated to be 240 K and 900 K, and 840 K and 2500 K, respectively, for these compounds. In spite of a large asymmetric potential the quantum nature of hydrogen transfer is recognized in the slope of the temperature dependence of T 1 on the low-temperature side of the T 1 minimum. The NQR T 1 measurements was revealed to be a good probe for the hydrogen transfer dynamics.

  12. Understanding electronic systems in semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Ciftja, Orion

    2013-11-01

    Systems of confined electrons are found everywhere in nature in the form of atoms where the orbiting electrons are confined by the Coulomb attraction of the nucleus. Advancement of nanotechnology has, however, provided us with an alternative way to confine electrons by using artificial confining potentials. A typical structure of this nature is the quantum dot, a nanoscale system which consists of few confined electrons. There are many types of quantum dots ranging from self-assembled to miniaturized semiconductor quantum dots. In this work we are interested in electrostatically confined semiconductor quantum dot systems where the electrostatic confining potential that traps the electrons is generated by external electrodes, doping, strain or other factors. A large number of semiconductor quantum dots of this type are fabricated by applying lithographically patterned gate electrodes or by etching on two-dimensional electron gases in semiconductor heterostructures. Because of this, the whole structure can be treated as a confined two-dimensional electron system. Quantum confinement profoundly affects the way in which electrons interact with each other, and external parameters such as a magnetic field. Since a magnetic field affects both the orbital and the spin motion of the electrons, the interplay between quantum confinement, electron-electron correlation effects and the magnetic field gives rise to very interesting physical phenomena. Thus, confined systems of electrons in a semiconductor quantum dot represent a unique opportunity to study fundamental quantum theories in a controllable atomic-like setup. In this work, we describe some common theoretical models which are used to study confined systems of electrons in a two-dimensional semiconductor quantum dot. The main emphasis of the work is to draw attention to important physical phenomena that arise in confined two-dimensional electron systems under various quantum regimes.

  13. Advancements in the Field of Quantum Dots

    NASA Astrophysics Data System (ADS)

    Mishra, Sambeet; Tripathy, Pratyasha; Sinha, Swami Prasad.

    2012-08-01

    Quantum dots are defined as very small semiconductor crystals of size varying from nanometer scale to a few micron i.e. so small that they are considered dimensionless and are capable of showing many chemical properties by virtue of which they tend to be lead at one minute and gold at the second minute.Quantum dots house the electrons just the way the electrons would have been present in an atom, by applying a voltage. And therefore they are very judiciously given the name of being called as the artificial atoms. This application of voltage may also lead to the modification of the chemical nature of the material anytime it is desired, resulting in lead at one minute to gold at the other minute. But this method is quite beyond our reach. A quantum dot is basically a semiconductor of very tiny size and this special phenomenon of quantum dot, causes the band of energies to change into discrete energy levels. Band gaps and the related energy depend on the relationship between the size of the crystal and the exciton radius. The height and energy between different energy levels varies inversely with the size of the quantum dot. The smaller the quantum dot, the higher is the energy possessed by it.There are many applications of the quantum dots e.g. they are very wisely applied to:Light emitting diodes: LEDs eg. White LEDs, Photovoltaic devices: solar cells, Memory elements, Biology : =biosensors, imaging, Lasers, Quantum computation, Flat-panel displays, Photodetectors, Life sciences and so on and so forth.The nanometer sized particles are able to display any chosen colour in the entire ultraviolet visible spectrum through a small change in their size or composition.

  14. Advanced Electrochemical Technologies for Hydrogen Production by Alternative Thermochemical Cycles

    SciTech Connect

    Lvov, Serguei; Chung, Mike; Fedkin, Mark; Lewis, Michele; Balashov, Victor; Chalkova, Elena; Akinfiev, Nikolay; Stork, Carol; Davis, Thomas; Gadala-Maria, Francis; Stanford, Thomas; Weidner, John; Law, Victor; Prindle, John

    2011-01-06

    Hydrogen fuel is a potentially major solution to the problem of climate change, as well as addressing urban air pollution issues. But a key future challenge for hydrogen as a clean energy carrier is a sustainable, low-cost method of producing it in large capacities. Most of the world's hydrogen is currently derived from fossil fuels through some type of reforming processes. Nuclear hydrogen production is an emerging and promising alternative to the reforming processes for carbon-free hydrogen production in the future. This report presents the main results of a research program carried out by a NERI Consortium, which consisted of Penn State University (PSU) (lead), University of South Carolina (USC), Tulane University (TU), and Argonne National Laboratory (ANL). Thermochemical water decomposition is an emerging technology for large-scale production of hydrogen. Typically using two or more intermediate compounds, a sequence of chemical and physical processes split water into hydrogen and oxygen, without releasing any pollutants externally to the atmosphere. These intermediate compounds are recycled internally within a closed loop. While previous studies have identified over 200 possible thermochemical cycles, only a few have progressed beyond theoretical calculations to working experimental demonstrations that establish scientific and practical feasibility of the thermochemical processes. The Cu-Cl cycle has a significant advantage over other cycles due to lower temperature requirements – around 530 °C and below. As a result, it can be eventually linked with the Generation IV thermal power stations. Advantages of the Cu-Cl cycle over others include lower operating temperatures, ability to utilize low-grade waste heat to improve energy efficiency, and potentially lower cost materials. Another significant advantage is a relatively low voltage required for the electrochemical step (thus low electricity input). Other advantages include common chemical agents and

  15. Highly Sensitive and Fast Anion-Selective InN Quantum Dot Electrochemical Sensors

    NASA Astrophysics Data System (ADS)

    Hassan Alvi, Naveed ul; Rodriguez, Paul E. D. Soto; Gómez, Victor J.; Kumar, Praveen; Willander, Magnus; Nötzel, Richard

    2013-11-01

    Epitaxial InN quantum dots (QDs) are demonstrated as ion-selective electrode for potentiometric anion concentration measurements. The sensor reveals high sensitivity above 90 mV/decade for the detection of chlorine and hydroxyl ions in sodium chloride (NaCl), calcium chloride (CaCl2), and sodium hydroxide (NaOH) solutions. The response time is less than two seconds after which the signal is very stable and repeatable. The sensitivity for the InN QDs is about two times that for a reference InN thin film and the response time is about five times shorter. In pH buffer solutions the sensor reveals no clear response to cations. A model is presented for the high sensitivity, fast response, and ion selectivity based on the unique electronic properties of the InN surface together with the zero-dimensional nature of the QDs.

  16. Composition for absorbing hydrogen

    DOEpatents

    Heung, Leung K.; Wicks, George G.; Enz, Glenn L.

    1995-01-01

    A hydrogen absorbing composition. The composition comprises a porous glass matrix, made by a sol-gel process, having a hydrogen-absorbing material dispersed throughout the matrix. A sol, made from tetraethyl orthosilicate, is mixed with a hydrogen-absorbing material and solidified to form a porous glass matrix with the hydrogen-absorbing material dispersed uniformly throughout the matrix. The glass matrix has pores large enough to allow gases having hydrogen to pass through the matrix, yet small enough to hold the particles dispersed within the matrix so that the hydrogen-absorbing particles are not released during repeated hydrogen absorption/desorption cycles.

  17. Composition for absorbing hydrogen

    DOEpatents

    Heung, L.K.; Wicks, G.G.; Enz, G.L.

    1995-05-02

    A hydrogen absorbing composition is described. The composition comprises a porous glass matrix, made by a sol-gel process, having a hydrogen-absorbing material dispersed throughout the matrix. A sol, made from tetraethyl orthosilicate, is mixed with a hydrogen-absorbing material and solidified to form a porous glass matrix with the hydrogen-absorbing material dispersed uniformly throughout the matrix. The glass matrix has pores large enough to allow gases having hydrogen to pass through the matrix, yet small enough to hold the particles dispersed within the matrix so that the hydrogen-absorbing particles are not released during repeated hydrogen absorption/desorption cycles.

  18. Photoluminescence of carbon dots from mesoporous silica

    NASA Astrophysics Data System (ADS)

    Nelson, D. K.; Razbirin, B. S.; Starukhin, A. N.; Eurov, D. A.; Kurdyukov, D. A.; Stovpiaga, E. Yu; Golubev, V. G.

    2016-09-01

    Photophysical properties of carbon dots were investigated under various excitation conditions and over a wide temperature region - from room to liquid helium temperatures. The carbon dots (CDs) were synthesized using mesoporous silica particles as a reactor and (3-aminopropyl)triethoxysilane (APTES) as a precursor. The photoluminescence spectra of CDs exhibit a strong dependence on the excitation wavelength and demonstrate a significant inhomogeneous broadening. Lowering sample temperature reveals the doublet structure of the spectra, which is associated with the vibronic structure of radiative transitions. The vibration energy ∼1200 cm-1 is close to the energy of Csbnd O stretching vibration. Long-lived phosphorescence of carbon dots with its decay time ∼0.2 s at T = 80 K was observed. The fluorescence and phosphorescence spectra are shown to be spectrally separated. The long-lived component of the emission was ascribed to optically forbidden triplet-singlet transitions. The value of the singlet-triplet splitting was found to be about 0.3 eV. Photo-induced polarization of the luminescence of carbon dots was revealed. The degree of the linear polarization is dependent on the wavelengths of both excitation and emitted light. The effect indicates a hidden anisotropy of optical dipole transitions in the dots and demonstrates the loss of the dipole orientation during the electron energy relaxation.

  19. Low severity coal conversion by ionic hydrogenation

    SciTech Connect

    Larsen, J.W.; Maioriello, J.; Cheng, J.C.

    1990-08-17

    The work accomplished in this project will be reported in two parts. Part one will focus on the development of catalytic ionic hydrogenation reactions utilizing a transition metal-H{sub 2} complex as the hydride donor and BF{sub 3}:H{sub 2}O as proton donor. This part reports the results of prelimiary work leading to the development of a new catalytic ionic hydrogenation system (MeCN){sub 2}PtCl{sub 2}/H{sub 2}/BF{sub 3}: H{sub 2}O. The results from some of this work have been published and the paper is included as the appendix. The second part focuses on the newly developed catalytic and other well characterized ionic hydrogenation reactions applied to lignites (Beulah-Zap), sub-bitumiuous (Wyodak), and bituminous coals (Pittsburgh {number sign}8). 19 refs., 10 tabs.

  20. Crystal structure and explosive performance of a new CL-20/caprolactam cocrystal

    NASA Astrophysics Data System (ADS)

    Guo, Changyan; Zhang, Haobin; Wang, Xiaochuan; Xu, Jinjiang; Liu, Yu; Liu, Xiaofeng; Huang, Hui; Sun, Jie

    2013-09-01

    Co-crystallization is an effective way to improve performance of the high explosive 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (CL-20). A new CL-20/caprolactam (CPL) cocrystal has been prepared by a rapid solvent evaporation method, and the crystal structure investigations show that the cocrystal is formed by strong intermolecular hydrogen bond interaction. The cocrystal can only be prepared with low moisture content of the air, because water in the air has a profound effect on the cocrystal formation, and it can lead to crystal form conversion of CL-20, but not the formation of cocrystal. The CL20/CPL explosive possess very low sensitivity, and may be used as additive in explosives formulation to desensitize other high explosives.

  1. Equilibrium constant for the reaction ClO + ClO ↔ ClOOCl between 250 and 206 K.

    PubMed

    Hume, Kelly L; Bayes, Kyle D; Sander, Stanley P

    2015-05-14

    The chlorine peroxide molecule, ClOOCl, is an important participant in the chlorine-catalyzed destruction of ozone in the stratosphere. Very few laboratory measurements have been made for the partitioning between monomer ClO and dimer ClOOCl at temperatures lower than 250 K. This paper reports absorption spectra for both ClO and ClOOCl when they are in equilibrium at 1 atm and temperatures down to 206 K. The very low ClO concentrations involved requires measuring and calibrating a differential cross section, ΔσClO, for the 10-0 band of ClO. A third law fit of the new results gives Keq = [(2.01 ± 0.17) 10–27 cm3 molecule–1] e(8554∓21)K/T, where the error limits reflect the uncertainty in the entropy change. The resulting equilibrium constants are slightly lower than currently recommended. The slope of the van’t Hoff plot yields a value for the enthalpy of formation of ClOOCl at 298 K, ΔHfo, of 129.8 ± 0.6 kJ mol–1. Uncertainties in the absolute ultraviolet cross sections of ClOOCl and ClO appear to be the limiting factors in these measurements. The new Keq parameters are consistent with the measurements of Santee et al.42 in the stratosphere. PMID:25560546

  2. Equilibrium constant for the reaction ClO + ClO ↔ ClOOCl between 250 and 206 K.

    PubMed

    Hume, Kelly L; Bayes, Kyle D; Sander, Stanley P

    2015-05-14

    The chlorine peroxide molecule, ClOOCl, is an important participant in the chlorine-catalyzed destruction of ozone in the stratosphere. Very few laboratory measurements have been made for the partitioning between monomer ClO and dimer ClOOCl at temperatures lower than 250 K. This paper reports absorption spectra for both ClO and ClOOCl when they are in equilibrium at 1 atm and temperatures down to 206 K. The very low ClO concentrations involved requires measuring and calibrating a differential cross section, ΔσClO, for the 10-0 band of ClO. A third law fit of the new results gives Keq = [(2.01 ± 0.17) 10–27 cm3 molecule–1] e(8554∓21)K/T, where the error limits reflect the uncertainty in the entropy change. The resulting equilibrium constants are slightly lower than currently recommended. The slope of the van’t Hoff plot yields a value for the enthalpy of formation of ClOOCl at 298 K, ΔHfo, of 129.8 ± 0.6 kJ mol–1. Uncertainties in the absolute ultraviolet cross sections of ClOOCl and ClO appear to be the limiting factors in these measurements. The new Keq parameters are consistent with the measurements of Santee et al.42 in the stratosphere.

  3. Determination of Hydrogen Bond Structure in Water versus Aprotic Environments To Test the Relationship Between Length and Stability

    SciTech Connect

    Sigala, Paul A.; Ruben, Eliza A.; Liu, Corey W.; Piccoli, Paula M. B.; Hohenstein, Edward G.; Martinez, Todd J.; Schultz, Arthur J.; Herschiag, Daniel

    2015-05-06

    Hydrogen bonds profoundly influence the architecture and activity of biological macromolecules. Deep appreciation of hydrogen bond contributions to biomolecular function thus requires a detailed understanding of hydrogen bond structure and energetics and the relationship between these properties. Hydrogen bond formation energies (Delta G(f)) are enormously more favorable in aprotic solvents than in water, and two classes of contributing factors have been proposed to explain this energetic difference, focusing respectively on the isolated and hydrogen-bonded species: (I) water stabilizes the dissociated donor and acceptor groups much better than aprotic solvents, thereby reducing the driving force for hydrogen bond formation; and (II) water lengthens hydrogen bonds compared to aprotic environments, thereby decreasing the potential energy within the hydrogen bond. Each model has been proposed to provide a dominant contribution to Delta G(f), but incisive tests that distinguish the importance of these contributions are lacking. Here we directly test the structural basis of model II. Neutron crystallography, NMR spectroscopy, and quantum mechanical calculations demonstrate that O-H center dot center dot center dot O hydrogen bonds in crystals, chloroform, acetone, and water have nearly identical lengths and very similar potential energy surfaces despite Delta G(f) differences >8 kcal/mol across these solvents. These results rule out a substantial contribution from solvent-dependent differences in hydrogen bond structure and potential energy after association (model II) and thus support the conclusion that differences in hydrogen bond Delta G(f) are predominantly determined by solvent interactions with the dissociated groups (model I). These findings advance our understanding of universal hydrogen-bonding interactions and have important implications for biology and engineering.

  4. Chlorine monoxide radical, ozone, and hydrogen peroxide: stratospheric measurements by microwave limb sounding

    SciTech Connect

    Waters, J.W.; Hardy, J.C.; Jarnot, R.F.; Pickett, H.M.

    1981-10-02

    Profiles of stratospheric ozone and chlorine monoxide radical (ClO) were obtained from balloon measurements of atmospheric limb thermal emission at millimeter wavelengths. The ClO measurements, important for assessing the predicted depletion of stratospheric ozone by chlorine from industrial sources, are in close agreement with present theory. The predicted decrease of ClO at sunset was measured. A tentative value for the stratospheric abundance of hydrogen peroxide was also determined.

  5. Chlorine monoxide radical, ozone, and hydrogen peroxide - Stratospheric measurements by microwave limb sounding

    NASA Technical Reports Server (NTRS)

    Waters, J. W.; Hardy, J. C.; Jarnot, R. F.; Pickett, H. M.

    1981-01-01

    Profiles of stratospheric ozone and chlorine monoxide radical (ClO) have been obtained from balloon measurements of atmospheric limb thermal emission at millimeter wavelengths. The ClO measurements, important for assessing the predicted depletion of stratospheric ozone by chlorine from industrial sources, are in close agreement with present theory. The predicted decrease of ClO at sunset was measured. A tentative value for the stratospheric abundance of hydrogen peroxide was also determined.

  6. 49 CFR 15.15 - SSI disclosed by DOT.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... document issued by DOT. (2) Security background check. Prior to providing SSI to a person under paragraph... the Secretary of DOT, a security background check. (e) Other conditional disclosure. The Secretary...

  7. 49 CFR 15.15 - SSI disclosed by DOT.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... document issued by DOT. (2) Security background check. Prior to providing SSI to a person under paragraph... the Secretary of DOT, a security background check. (e) Other conditional disclosure. The Secretary...

  8. 49 CFR 15.15 - SSI disclosed by DOT.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... document issued by DOT. (2) Security background check. Prior to providing SSI to a person under paragraph... the Secretary of DOT, a security background check. (e) Other conditional disclosure. The Secretary...

  9. 49 CFR 15.15 - SSI disclosed by DOT.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... document issued by DOT. (2) Security background check. Prior to providing SSI to a person under paragraph... the Secretary of DOT, a security background check. (e) Other conditional disclosure. The Secretary...

  10. 49 CFR 15.15 - SSI disclosed by DOT.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... document issued by DOT. (2) Security background check. Prior to providing SSI to a person under paragraph... the Secretary of DOT, a security background check. (e) Other conditional disclosure. The Secretary...

  11. Origins and optimization of entanglement in plasmonically coupled quantum dots

    NASA Astrophysics Data System (ADS)

    Otten, Matthew; Larson, Jeffrey; Min, Misun; Wild, Stefan M.; Pelton, Matthew; Gray, Stephen K.

    2016-08-01

    A system of two or more quantum dots interacting with a dissipative plasmonic nanostructure is investigated in detail by using a cavity quantum electrodynamics approach with a model Hamiltonian. We focus on determining and understanding system configurations that generate multiple bipartite quantum entanglements between the occupation states of the quantum dots. These configurations include allowing for the quantum dots to be asymmetrically coupled to the plasmonic system. Analytical solution of a simplified limit for an arbitrary number of quantum dots and numerical simulations and optimization for the two- and three-dot cases are used to develop guidelines for maximizing the bipartite entanglements. For any number of quantum dots, we show that through simple starting states and parameter guidelines, one quantum dot can be made to share a strong amount of bipartite entanglement with all other quantum dots in the system, while entangling all other pairs to a lesser degree.

  12. Surface treatment of nanocrystal quantum dots after film deposition

    DOEpatents

    Sykora, Milan; Koposov, Alexey; Fuke, Nobuhiro

    2015-02-03

    Provided are methods of surface treatment of nanocrystal quantum dots after film deposition so as to exchange the native ligands of the quantum dots for exchange ligands that result in improvement in charge extraction from the nanocrystals.

  13. Growing InAs/GaAs quantum dots by droplet epitaxy under MOVPE conditions

    NASA Astrophysics Data System (ADS)

    Surnina, M. A.; Akchurin, R. Kh.; Marmalyuk, A. A.; Bagaev, T. A.; Sizov, A. L.

    2016-07-01

    Results of studying the formation of InAs quantum dots (QDs) on GaAs(100) substrates by droplet epitaxy using trimethylindium and arsine (AsH3) as precursors are presented. The growth process was carried out at temperatures within 230-400°C in a horizontal reactor for metalorganic vapor phase epitaxy (MOVPE) using high-purity hydrogen as the carrier gas. Data on the influence of process temperature on the QD size and the density of QD array and results of investigation of the low-temperature photoluminescence of obtained samples are presented.

  14. [Development and perspectives of community DOTS].

    PubMed

    Narita, Tomoyo; Kobayashi, Noriko

    2009-04-01

    The Japanese version of DOTS seems to have established itself. However, there is criticism that the primary purpose of DOTS expansion has often been supplanted by pressure to meet a quota. In this symposium, we returned to the starting point of DOTS, i.e., seeking a total cure of TB patients, and rededicated ourselves to our ultimate goal--TB elimination. In order to promote community DOTS more effectively, we should endeavor to build a community DOTS network with unified related information systems backed by government commitments. In so doing, we must continue to provide patients with support while respecting their rights and emphasizing their improved quality of life. 1. Achievements and challenges of DOTS conference: Yukiko SAITO (Fukujuji Hospital, JATA). We conduct face-to-face DOTS for all patients from the time of their admission until the time they are discharged. The DOTS conference is a place where hospitals and public health centers can share patient information, linking hospital DOTS with community DOTS. This meeting is an indispensable process in order to prevent patients' defaulting and irregular treatment. The ultimate goal of DOTS is treatment completion of tuberculosis patients, and in order to achieve that goal, a partnership among clinical, public health, and social services is crucial. The DOTS conference provides an opportunity for several public health centers to come together and share information. Conducting hospital DOTS and the DOTS conference in parallel facilitates providing comprehensive patient support. Continuing to hold regular DOTS conferences is both a sign of achievement of DOTS and a challenge for the future. 2. Achievements and challenges of cohort meeting in the TB control program in Kobe: Noriko TANAKA (Kobe City Public Health Office) The TB control program of Kobe City is based on the Second Five-Year TB strategy targeting the reduction of the TB incidence rate. It has five policy pillars, prevention and IEC, early case

  15. TOPICAL REVIEW: Polar and nonpolar GaN quantum dots

    NASA Astrophysics Data System (ADS)

    Daudin, Bruno

    2008-11-01

    Growth, structural and optical properties of GaN quantum dots are reviewed, with a special emphasis on plasma-assisted molecular beam epitaxy. The versatility of this technique makes it particularly adapted to growth of quantum dots, either polar (c-plane) or nonpolar (a-plane and m-plane). After describing in detail the growth process and analyzing the morphology of the dots, we review the optical properties of these nanostructures and discuss the properties of single dots.

  16. Easy methods to study the smart energetic TNT/CL-20 co-crystal.

    PubMed

    Li, Huarong; Shu, Yuanjie; Gao, Shijie; Chen, Ling; Ma, Qing; Ju, Xuehai

    2013-11-01

    2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) is a high-energy nitramine explosive with high mechanical sensitivity. 2,4,6-trinitrotoluene (TNT) is insensitive but by no means a high performance explosive. To reveal the significant importance and smart-material functionality of the energetic-energetic co-crystals, the stability, mechanical and explosive properties TNT/CL-20 co-crystal, TNT crystal and CL-20 crystal were studied. Non-hydrogen bonded non-covalent interactions govern the structures of energetic-energetic co-crystals. However, it is very difficult to accurately calculate the non-covalent intermolecular interaction energies. In this paper, the local conformation and the intricate non-covalent interactions were effectively mapped and analyzed from the electron density (ρ) and its derivatives. The results show that the two components TNT and CL-20 are connected mainly by nitro-aromatic interactions, and nitro-nitro interactions. The steric interactions in TNT/CL-20 could not be confronted with the attractive interactions. Moreover, the scatter graph of TNT crystal reveals the reason why TNT is brittle. The detailed electrostatic potential analysis predicted that the detonation velocities (D) and impact sensitivity for the compounds both increase in the sequence of CL-20 > TNT/CL-20 co-crystal > TNT. Additionally, TNT/CL-20 co-crystal has better malleability than its pure components. This demonstrates the capacity and the feasibility of realizing explosive smart materials by co-crystallization, even if strong hydrogen bonding schemes are generally lacking in energetic materials. PMID:24043545

  17. Slow electron cooling in colloidal quantum dots.

    PubMed

    Pandey, Anshu; Guyot-Sionnest, Philippe

    2008-11-01

    Hot electrons in semiconductors lose their energy very quickly (within picoseconds) to lattice vibrations. Slowing this energy loss could prove useful for more efficient photovoltaic or infrared devices. With their well-separated electronic states, quantum dots should display slow relaxation, but other mechanisms have made it difficult to observe. We report slow intraband relaxation (>1 nanosecond) in colloidal quantum dots. The small cadmium selenide (CdSe) dots, with an intraband energy separation of approximately 0.25 electron volts, are capped by an epitaxial zinc selenide (ZnSe) shell. The shell is terminated by a CdSe passivating layer to remove electron traps and is covered by ligands of low infrared absorbance (alkane thiols) at the intraband energy. We found that relaxation is markedly slowed with increasing ZnSe shell thickness.

  18. PRISM3 DOT1 Atlantic Basin Reconstruction

    USGS Publications Warehouse

    Dowsett, Harry; Robinson, Marci; Dwyer, Gary; Chandler, Mark; Cronin, Thomas

    2006-01-01

    PRISM3 DOT1 (Pliocene Research, Interpretation and Synoptic Mapping 3, Deep Ocean Temperature 1) provides a three-dimensional temperature reconstruction for the mid-Pliocene Atlantic basin, the first of several regional data sets that will comprise a global mid-Pliocene reconstruction. DOT1 is an alteration of modern temperature values for the Atlantic Ocean in 4 degree x 5 degree cells in 13 depth layers for December 1 based on Mg/Ca-derived BWT estimates from seventeen DSDP and ODP Sites and SST estimates from the PRISM2 reconstruction (Dowsett et al., 1999). DOT1 reflects a vaguely modern circulation system, assuming similar processes of deep-water formation; however, North Atlantic Deep Water (NADW) production is increased, and Antarctic Bottom Water (AABW) production is decreased. Pliocene NADW was approximately 2 degreesC warmer than modern temperatures, and Pliocene AABW was approximately 0.3 degreesC warmer than modern temperatures.

  19. Quantum Dot-Based Cell Motility Assay

    SciTech Connect

    Gu, Weiwei; Pellegrino, Teresa; Parak Wolfgang J; Boudreau,Rosanne; Le Gros, Mark A.; Gerion, Daniele; Alivisatos, A. Paul; Larabell, Carolyn A.

    2005-06-06

    Because of their favorable physical and photochemical properties, colloidal CdSe/ZnS-semiconductor nanocrystals (commonly known as quantum dots) have enormous potential for use in biological imaging. In this report, we present an assay that uses quantum dots as markers to quantify cell motility. Cells that are seeded onto a homogeneous layer of quantum dots engulf and absorb the nanocrystals and, as a consequence, leave behind a fluorescence-free trail. By subsequently determining the ratio of cell area to fluorescence-free track area, we show that it is possible to differentiate between invasive and noninvasive cancer cells. Because this assay uses simple fluorescence detection, requires no significant data processing, and can be used in live-cell studies, it has the potential to be a powerful new tool for discriminating between invasive and noninvasive cancer cell lines or for studying cell signaling events involved in migration.

  20. Low Frequency Noise in Mesoscopic Magnetic Dots

    NASA Astrophysics Data System (ADS)

    Dahlberg, E. Dan

    2014-03-01

    Measurements of random telegraph noise (RTN) in individual mesoscopic sized NiFe alloy dots will be presented; the dots dimensions are as small as 200nm x 200nm x 10nm. The temperature and magnetic field dependence of the RTN are explained by the energy landscape in the dots; the energy landscape RTN was independently measured [Appl. Phys. Lett. 103, 042409 (2013)]. The research was motivated by questions raised in understanding magnetic noise in magnetic tunnel junctions and giant magnetoresistance devices [Appl. Phys. Lett. 95, 062512 (2009) and Phys. Rev. B 88, 014409 (2013)]. This work was supported primarily by ONR Grant N00014-11-1-0850 and the MRSEC Program of the NSF under Grant No. DMR-0819885. Additional support for work done using the University of Minnesota Nanofabrication Center and Characterization Facility was provided by the NSF NNIN network. Reseach performed in collaboration with Dan Endean, Feng Guo, C. T. Weigelt and R. H. Victora.

  1. Isotopically enhanced triple-quantum-dot qubit.

    PubMed

    Eng, Kevin; Ladd, Thaddeus D; Smith, Aaron; Borselli, Matthew G; Kiselev, Andrey A; Fong, Bryan H; Holabird, Kevin S; Hazard, Thomas M; Huang, Biqin; Deelman, Peter W; Milosavljevic, Ivan; Schmitz, Adele E; Ross, Richard S; Gyure, Mark F; Hunter, Andrew T

    2015-05-01

    Like modern microprocessors today, future processors of quantum information may be implemented using all-electrical control of silicon-based devices. A semiconductor spin qubit may be controlled without the use of magnetic fields by using three electrons in three tunnel-coupled quantum dots. Triple dots have previously been implemented in GaAs, but this material suffers from intrinsic nuclear magnetic noise. Reduction of this noise is possible by fabricating devices using isotopically purified silicon. We demonstrate universal coherent control of a triple-quantum-dot qubit implemented in an isotopically enhanced Si/SiGe heterostructure. Composite pulses are used to implement spin-echo type sequences, and differential charge sensing enables single-shot state readout. These experiments demonstrate sufficient control with sufficiently low noise to enable the long pulse sequences required for exchange-only two-qubit logic and randomized benchmarking. PMID:26601186

  2. Three-terminal quantum-dot refrigerators

    NASA Astrophysics Data System (ADS)

    Zhang, Yanchao; Lin, Guoxing; Chen, Jincan

    2015-05-01

    Based on two capacitively coupled quantum dots in the Coulomb-blockade regime, a model of three-terminal quantum-dot refrigerators is proposed. With the help of the master equation, the transport properties of steady-state charge current and energy flow between two quantum dots and thermal reservoirs are revealed. It is expounded that such a structure can be used to construct a refrigerator by controlling the voltage bias and temperature ratio. The thermodynamic performance characteristics of the refrigerator are analyzed, including the cooling power, coefficient of performance (COP), maximum cooling power, and maximum COP. Moreover, the optimal regions of main performance parameters are determined. The influence of dissipative tunnel processes on the optimal performance is discussed in detail. Finally, the performance characteristics of the refrigerators operated in two different cases are compared.

  3. A hybrid double-dot in silicon

    SciTech Connect

    Gonzalez-Zalba, M. F.; Heiss, D.; Ferguson, A. J.

    2013-12-04

    We report electrical measurements of a single arsenic dopant atom in the tunnel barrier of a silicon single-electron transistor (SET). In addition to performing the electrical characterisation of the individual dopants, we study the series electrical transport through the dopant and SET. We measure the bias triangles of this hybrid double-dot and show that we can tune the electrostatic coupling between the two sub-systems. Additionally, we measured SET in which an additional plunger gate allows the reduction of the electron number in the SET down to the few-electron regime where the dot presents well-defined spin configurations. Finally, we discuss the challenges of operating a dopant-dot hybrid system in the few-electron regime.

  4. Isotopically enhanced triple-quantum-dot qubit

    PubMed Central

    Eng, Kevin; Ladd, Thaddeus D.; Smith, Aaron; Borselli, Matthew G.; Kiselev, Andrey A.; Fong, Bryan H.; Holabird, Kevin S.; Hazard, Thomas M.; Huang, Biqin; Deelman, Peter W.; Milosavljevic, Ivan; Schmitz, Adele E.; Ross, Richard S.; Gyure, Mark F.; Hunter, Andrew T.

    2015-01-01

    Like modern microprocessors today, future processors of quantum information may be implemented using all-electrical control of silicon-based devices. A semiconductor spin qubit may be controlled without the use of magnetic fields by using three electrons in three tunnel-coupled quantum dots. Triple dots have previously been implemented in GaAs, but this material suffers from intrinsic nuclear magnetic noise. Reduction of this noise is possible by fabricating devices using isotopically purified silicon. We demonstrate universal coherent control of a triple-quantum-dot qubit implemented in an isotopically enhanced Si/SiGe heterostructure. Composite pulses are used to implement spin-echo type sequences, and differential charge sensing enables single-shot state readout. These experiments demonstrate sufficient control with sufficiently low noise to enable the long pulse sequences required for exchange-only two-qubit logic and randomized benchmarking. PMID:26601186

  5. A Few Facts about Hydrogen [and] Hydrogen Bibliography.

    ERIC Educational Resources Information Center

    Hinds, H. Roger

    Divided into two sections, this publication presents facts about and the characteristics of hydrogen and a bibliography on hydrogen. The first section lists nine facts on what hydrogen is, four on where hydrogen is found, nine on how hydrogen is used, nine on how hydrogen can be used, and 14 on how hydrogen is made. Also included are nine…

  6. 75 FR 37994 - Airworthiness Directives; Bombardier, Inc. Model CL-600-1A11 (CL-600), CL-600-2A12 (CL-601), CL...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-01

    ... hydraulic accumulator screw cap or end cap failure have been experienced on CL-600-2B19 (CRJ) aircraft, resulting in loss of the associated hydraulic system and high-energy impact damage to adjacent systems and..., resulting in impact damage causing loss of both hydraulic systems No. 2 and No. 3, with consequent loss...

  7. Carbon dots-decorated multiwalled carbon nanotubes nanocomposites as a high-performance electrochemical sensor for detection of H2O2 in living cells.

    PubMed

    Bai, Jing; Sun, Chunhe; Jiang, Xiue

    2016-07-01

    A novel enzyme-free hydrogen peroxide sensor composed of carbon dots (CDs) and multi-walled carbon nanotubes (MWCNTs) was prepared. It was found that the carbon dots-decorated multi-walled carbon nanotubes nanocomposites (CDs/MWCNTs) modified glassy carbon (GC) electrode (CDs/MWCNTs/GCE) exhibited a significant synergistic electrocatalytic activity towards hydrogen peroxide reduction as compared to carbon dots or multi-walled carbon nanotubes alone, and the CDs/MWCNTs/GCE has shown a low detection limit as well as excellent stability, selectivity, and reproducibility. These remarkable analytical advantages enable the practical application of CDs/MWCNTs/GCE for the real-time tracking of hydrogen peroxide (H2O2) released from human cervical cancer cells with satisfactory results. The enhanced electrochemical activity can be assigned to the edge plane-like defective sites and lattice oxygen in the CDs/MWCNTs nanocomposites due to the small amount of decoration of carbon dots on the multi-walled carbon nanotubes. Based on a facile preparation method and with good electrochemical properties, the CDs/MWCNTs nanocomposites represent a new class of carbon electrode for electrochemical sensor applications. Graphical Abstract CDs/MWCNTs exhibited good electrocatalytic activity and stability to H2O2 reduction and can be used for real-time detection of H2O2 released from living cells.

  8. Crystal structures of Ca(ClO4)2·4H2O and Ca(ClO4)2·6H2O.

    PubMed

    Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang

    2014-12-01

    The title compounds, calcium perchlorate tetra-hydrate and calcium perchlorate hexa-hydrate, were crystallized at low temperatures according to the solid-liquid phase diagram. The structure of the tetra-hydrate consists of one Ca(2+) cation eightfold coordinated in a square-anti-prismatic fashion by four water mol-ecules and four O atoms of four perchlorate tetra-hedra, forming chains parallel to [01-1] by sharing corners of the ClO4 tetra-hedra. The structure of the hexa-hydrate contains two different Ca(2+) cations, each coordinated by six water mol-ecules and two O atoms of two perchlorate tetra-hedra, forming [Ca(H2O)6(ClO4)]2 dimers by sharing two ClO4 tetra-hedra. The dimers are arranged in sheets parallel (001) and alternate with layers of non-coordinating ClO4 tetra-hedra. O-H⋯O hydrogen bonds between the water mol-ecules as donor and ClO4 tetra-hedra and water mol-ecules as acceptor groups lead to the formation of a three-dimensional network in the two structures. Ca(ClO4)2·6H2O was refined as a two-component inversion twin, with an approximate twin component ratio of 1:1 in each of the two structures. PMID:25552974

  9. The PZP Domain of AF10 Senses Unmodified H3K27 to Regulate DOT1L-Mediated Methylation of H3K79.

    PubMed

    Chen, Shoudeng; Yang, Ze; Wilkinson, Alex W; Deshpande, Aniruddha J; Sidoli, Simone; Krajewski, Krzysztof; Strahl, Brian D; Garcia, Benjamin A; Armstrong, Scott A; Patel, Dinshaw J; Gozani, Or

    2015-10-15

    AF10, a DOT1L cofactor, is required for H3K79 methylation and cooperates with DOT1L in leukemogenesis. However, the molecular mechanism by which AF10 regulates DOT1L-mediated H3K79 methylation is not clear. Here we report that AF10 contains a "reader" domain that couples unmodified H3K27 recognition to H3K79 methylation. An AF10 region consisting of a PHD finger-Zn knuckle-PHD finger (PZP) folds into a single module that recognizes amino acids 22-27 of H3, and this interaction is abrogated by H3K27 modification. Structural studies reveal that H3 binding triggers rearrangement of the PZP module to form an H3(22-27)-accommodating channel and that the unmodified H3K27 side chain is encased in a compact hydrogen-bond acceptor-lined cage. In cells, PZP recognition of H3 is required for H3K79 dimethylation, expression of DOT1L-target genes, and proliferation of DOT1L-addicted leukemic cells. Together, our results uncover a pivotal role for H3K27-via readout by the AF10 PZP domain-in regulating the cancer-associated enzyme DOT1L.

  10. Fluorescence correlation spectroscopy using quantum dots: advances, challenges and opportunities.

    PubMed

    Heuff, Romey F; Swift, Jody L; Cramb, David T

    2007-04-28

    Semiconductor nanocrystals (quantum dots) have been increasingly employed in measuring the dynamic behavior of biomacromolecules using fluorescence correlation spectroscopy. This poses a challenge, because quantum dots display their own dynamic behavior in the form of intermittent photoluminescence, also known as blinking. In this review, the manifestation of blinking in correlation spectroscopy will be explored, preceded by an examination of quantum dot blinking in general.

  11. Experimental and theoretical rationalization of the growth mechanism of silicon quantum dots in non-stoichiometric SiN x : role of chlorine in plasma enhanced chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Mon-Pérez, E.; Salazar, J.; Ramos, E.; Santoyo Salazar, J.; López Suárez, A.; Dutt, A.; Santana, G.; Marel Monroy, B.

    2016-11-01

    Silicon quantum dots (Si-QDs) embedded in an insulator matrix are important from a technological and application point of view. Thus, being able to synthesize them in situ during the matrix growth process is technologically advantageous. The use of SiH2Cl2 as the silicon precursor in the plasma enhanced chemical vapour deposition (PECVD) process allows us to obtain Si-QDs without post-thermal annealing. Foremost in this work, is a theoretical rationalization of the mechanism responsible for Si-QD generation in a film including an analysis of the energy released by the extraction of HCl and the insertion of silylene species into the terminal surface bonds. From the results obtained using density functional theory (DFT), we propose an explanation of the mechanism responsible for the formation of Si-QDs in non-stoichiometric SiN x starting from chlorinated precursors in a PECVD system. Micrograph images obtained through transmission electron microscopy confirmed the presence of Si-QDs, even in nitrogen-rich (N-rich) samples. The film stoichiometry was controlled by varying the growth parameters, in particular the NH3/SiH2Cl2 ratio and hydrogen dilution. Experimental and theoretical results together show that using a PECVD system, along with chlorinated precursors it is possible to obtain Si-QDs at a low substrate temperature without annealing treatment. The optical property studies carried out in the present work highlight the prospects of these thin films for down shifting and as an antireflection coating in silicon solar cells.

  12. Biodegradation of the nitramine explosive CL-20.

    PubMed

    Trott, Sandra; Nishino, Shirley F; Hawari, Jalal; Spain, Jim C

    2003-03-01

    The cyclic nitramine explosive CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane) was examined in soil microcosms to determine whether it is biodegradable. CL-20 was incubated with a variety of soils. The explosive disappeared in all microcosms except the controls in which microbial activity had been inhibited. CL-20 was degraded most rapidly in garden soil. After 2 days of incubation, about 80% of the initial CL-20 had disappeared. A CL-20-degrading bacterial strain, Agrobacterium sp. strain JS71, was isolated from enrichment cultures containing garden soil as an inoculum, succinate as a carbon source, and CL-20 as a nitrogen source. Growth experiments revealed that strain JS71 used 3 mol of nitrogen per mol of CL-20. PMID:12620886

  13. Polymeric gamma-MgCl2 Nanoribbons

    SciTech Connect

    Vittadello,M.; Stallworth, P.; Alamgir, F.; Suarez, S.; Abbrent, S.; Drain, C.; Di Noto, V.; Greenbaum, S.

    2006-01-01

    {delta}-MgCl{sub 2} has relevant applications in the field of electrochemical energy storage and Ziegler-Natta catalysis. Here, we clarify the short-range structural peculiarities that make the disordered phase {delta}-MgCl{sub 2} extremely chemically active relative to the higher lattice energy phases, {alpha}-MgCl{sub 2} and {beta}-MgCl{sub 2}. X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS) and nuclear magnetic resonance (NMR) results are included. These findings, demonstrate the existence of [MgCl{sub 2}]{sub n} nanoribbons and active nanosurfaces in {delta}-MgCl{sub 2} and provide new insight about the nature of the bonding in the allotropic forms of MgCl{sub 2}.

  14. Biodegradation of the Nitramine Explosive CL-20

    PubMed Central

    Trott, Sandra; Nishino, Shirley F.; Hawari, Jalal; Spain, Jim C.

    2003-01-01

    The cyclic nitramine explosive CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane) was examined in soil microcosms to determine whether it is biodegradable. CL-20 was incubated with a variety of soils. The explosive disappeared in all microcosms except the controls in which microbial activity had been inhibited. CL-20 was degraded most rapidly in garden soil. After 2 days of incubation, about 80% of the initial CL-20 had disappeared. A CL-20-degrading bacterial strain, Agrobacterium sp. strain JS71, was isolated from enrichment cultures containing garden soil as an inoculum, succinate as a carbon source, and CL-20 as a nitrogen source. Growth experiments revealed that strain JS71 used 3 mol of nitrogen per mol of CL-20. PMID:12620886

  15. Local structures and the dissolving behavior of aqueous ammonia and its KCl and NH4Cl solutions: A Raman spectroscopy and X-ray scattering study

    NASA Astrophysics Data System (ADS)

    Li, Shenyu; Yuan, Junsheng; Li, Fei; Liu, Ziyu

    2016-06-01

    The aqueous ammonia (5%-15%) and its KCl and NH4Cl solutions have been studied by Raman spectroscopy and X-ray scattering. The microscopic structures in these solutions were proposed. The addition of KCl reinforced the hydrogen bond between NH3 and H2O. On contrary, NH4Cl destroyed this interaction by forming hydrogen bond NH4+-NH3. This study gave an interpretation of the different dissolving behavior of KCl and NH4Cl in aqueous ammonia, which may have important implications in the separation of potassium and ammonium salt during the industrial production.

  16. Resonant tunneling in graphene pseudomagnetic quantum dots.

    PubMed

    Qi, Zenan; Bahamon, D A; Pereira, Vitor M; Park, Harold S; Campbell, D K; Neto, A H Castro

    2013-06-12

    Realistic relaxed configurations of triaxially strained graphene quantum dots are obtained from unbiased atomistic mechanical simulations. The local electronic structure and quantum transport characteristics of y-junctions based on such dots are studied, revealing that the quasi-uniform pseudomagnetic field induced by strain restricts transport to Landau level- and edge state-assisted resonant tunneling. Valley degeneracy is broken in the presence of an external field, allowing the selective filtering of the valley and chirality of the states assisting in the resonant tunneling. Asymmetric strain conditions can be explored to select the exit channel of the y-junction.

  17. Potential clinical applications of quantum dots

    PubMed Central

    Medintz, Igor L; Mattoussi, Hedi; Clapp, Aaron R

    2008-01-01

    The use of luminescent colloidal quantum dots in biological investigations has increased dramatically over the past several years due to their unique size-dependent optical properties and recent advances in biofunctionalization. In this review, we describe the methods for generating high-quality nanocrystals and report on current and potential uses of these versatile materials. Numerous examples are provided in several key areas including cell labeling, biosensing, in vivo imaging, bimodal magnetic-luminescent imaging, and diagnostics. We also explore toxicity issues surrounding these materials and speculate about the future uses of quantum dots in a clinical setting. PMID:18686776

  18. Bilayer graphene quantum dot defined by topgates

    SciTech Connect

    Müller, André; Kaestner, Bernd; Hohls, Frank; Weimann, Thomas; Pierz, Klaus; Schumacher, Hans W.

    2014-06-21

    We investigate the application of nanoscale topgates on exfoliated bilayer graphene to define quantum dot devices. At temperatures below 500 mK, the conductance underneath the grounded gates is suppressed, which we attribute to nearest neighbour hopping and strain-induced piezoelectric fields. The gate-layout can thus be used to define resistive regions by tuning into the corresponding temperature range. We use this method to define a quantum dot structure in bilayer graphene showing Coulomb blockade oscillations consistent with the gate layout.

  19. Ambipolar quantum dots in intrinsic silicon

    SciTech Connect

    Betz, A. C. Gonzalez-Zalba, M. F.; Podd, G.; Ferguson, A. J.

    2014-10-13

    We electrically measure intrinsic silicon quantum dots with electrostatically defined tunnel barriers. The presence of both p- and n-type ohmic contacts enables the accumulation of either electrons or holes. Thus, we are able to study both transport regimes within the same device. We investigate the effect of the tunnel barriers and the electrostatically defined quantum dots. There is greater localisation of charge states under the tunnel barriers in the case of hole conduction, leading to higher charge noise in the p-type regime.

  20. Improved dot size uniformity and luminescense of InAs quantum dots on InP substrate

    NASA Technical Reports Server (NTRS)

    Qiu, Y.; Uhl, D.

    2002-01-01

    InAs self-organized quantum dots have been grown in InGaAs quantum well on InP substrates by metalorganic vapor phase epitaxy. Atomic Force Microscopy confirmed of quantum dot formation with dot density of 3X10(sup 10) cm(sup -2). Improved dot size uniformity and strong room temperature photoluminescence up to 2 micron were observed after modifying the InGaAs well.

  1. Hydrogen energy systems studies

    SciTech Connect

    Ogden, J.M.; Kreutz, T.G.; Steinbugler, M.

    1996-10-01

    In this report the authors describe results from technical and economic assessments carried out during the past year with support from the USDOE Hydrogen R&D Program. (1) Assessment of technologies for small scale production of hydrogen from natural gas. Because of the cost and logistics of transporting and storing hydrogen, it may be preferable to produce hydrogen at the point of use from more readily available energy carriers such as natural gas or electricity. In this task the authors assess near term technologies for producing hydrogen from natural gas at small scale including steam reforming, partial oxidation and autothermal reforming. (2) Case study of developing a hydrogen vehicle refueling infrastructure in Southern California. Many analysts suggest that the first widespread use of hydrogen energy is likely to be in zero emission vehicles in Southern California. Several hundred thousand zero emission automobiles are projected for the Los Angeles Basin alone by 2010, if mandated levels are implemented. Assuming that hydrogen vehicles capture a significant fraction of this market, a large demand for hydrogen fuel could evolve over the next few decades. Refueling a large number of hydrogen vehicles poses significant challenges. In this task the authors assess near term options for producing and delivering gaseous hydrogen transportation fuel to users in Southern California including: (1) hydrogen produced from natural gas in a large, centralized steam reforming plant, and delivered to refueling stations via liquid hydrogen truck or small scale hydrogen gas pipeline, (2) hydrogen produced at the refueling station via small scale steam reforming of natural gas, (3) hydrogen produced via small scale electrolysis at the refueling station, and (4) hydrogen from low cost chemical industry sources (e.g. excess capacity in refineries which have recently upgraded their hydrogen production capacity, etc.).

  2. Hydrogen Diffusion Behavior in Titanium-Chromium Hydrides with Laves Structures

    SciTech Connect

    Bowman Jr., R.C.; Craft, B.D.; Attalla, A.; Johnson, J.R.

    1981-03-31

    Extensive NMR measurements of the proton relaxation times have been performed on low (i.e., alpha-phase) and intermediate (i.e., alpha'-phase) hydrogen concentrations in TiCr{sub}2H{sub}x with both the hexagonal Cl4 and cubic Cl5 Laves structures. The relaxation times indicate rapid diffusion rates above 200 K for all the TiCr{sub}2H{sub}x phases; however, large differences in the diffusion activation energies are observed. This behavior is associated with the hydrogen interstitial site occupancies and diffusion pathways becoming restricted in the Cl4 structure.

  3. CNN pincer ruthenium catalysts for hydrogenation and transfer hydrogenation of ketones: experimental and computational studies.

    PubMed

    Baratta, Walter; Baldino, Salvatore; Calhorda, Maria José; Costa, Paulo J; Esposito, Gennaro; Herdtweck, Eberhardt; Magnolia, Santo; Mealli, Carlo; Messaoudi, Abdelatif; Mason, Sax A; Veiros, Luis F

    2014-10-13

    Reaction of [RuCl(CNN)(dppb)] (1-Cl) (HCNN=2-aminomethyl-6-(4-methylphenyl)pyridine; dppb=Ph2 P(CH2 )4 PPh2 ) with NaOCH2 CF3 leads to the amine-alkoxide [Ru(CNN)(OCH2 CF3 )(dppb)] (1-OCH2 CF3 ), whose neutron diffraction study reveals a short RuO⋅⋅⋅HN bond length. Treatment of 1-Cl with NaOEt and EtOH affords the alkoxide [Ru(CNN)(OEt)(dppb)]⋅(EtOH)n (1-OEt⋅n EtOH), which equilibrates with the hydride [RuH(CNN)(dppb)] (1-H) and acetaldehyde. Compound 1-OEt⋅n EtOH reacts reversibly with H2 leading to 1-H and EtOH through dihydrogen splitting. NMR spectroscopic studies on 1-OEt⋅n EtOH and 1-H reveal hydrogen bond interactions and exchange processes. The chloride 1-Cl catalyzes the hydrogenation (5 atm of H2 ) of ketones to alcohols (turnover frequency (TOF) up to 6.5×10(4) h(-1) , 40 °C). DFT calculations were performed on the reaction of [RuH(CNN')(dmpb)] (2-H) (HCNN'=2-aminomethyl-6-(phenyl)pyridine; dmpb=Me2 P(CH2 )4 PMe2 ) with acetone and with one molecule of 2-propanol, in alcohol, with the alkoxide complex being the most stable species. In the first step, the Ru-hydride transfers one hydrogen atom to the carbon of the ketone, whereas the second hydrogen transfer from NH2 is mediated by the alcohol and leads to the key "amide" intermediate. Regeneration of the hydride complex may occur by reaction with 2-propanol or with H2 ; both pathways have low barriers and are alcohol assisted. PMID:25195979

  4. A flow injection chemiluminescence method for determination of nalidixic acid based on KMnO4-morin sensitized with CdS quantum dots

    NASA Astrophysics Data System (ADS)

    Khataee, Alireza; Lotfi, Roya; Hasanzadeh, Aliyeh; Iranifam, Mortaza; Joo, Sang Woo

    2016-02-01

    A simple and sensitive flow injection chemiluminescence (CL) method was developed for determination of nalidixic acid by application of CdS quantum dots (QDs) in KMnO4-morin CL system in acidic medium. Optical and structural features of L-cysteine capped CdS quantum dots which were synthesized via hydrothermal approach were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), and ultraviolet-visible (UV-Vis) spectroscopy. Moreover, the potential mechanism of the proposed CL method was described using the results of the kinetic curves of CL systems, the spectra of CL, PL and UV-Vis analyses. The CL intensity of the KMnO4-morin-CdS QDs system was considerably increased in the presence of nalidixic acid. Under the optimum condition, the enhanced CL intensity was linearly proportional to the concentration of nalidixic acid in the range of 0.0013 to 21.0 mg L- 1, with a detection limit of (3σ) 0.003 mg L- 1. Also, the proposed CL method was utilized for determination of nalidixic acid in environmental water samples, and commercial pharmaceutical formulation to approve its applicability. Furthermore, corona discharge ionization ion mobility spectrometry (CD-IMS) method was utilized for determination of nalidixic acid and the results of real sample analysis by two proposed methods were compared. Comparison the analytical features of these methods represented that the proposed CL method is preferable to CD-IMS method for determination of nalidixic acid due to its high sensitivity and precision.

  5. Concentration of Hydrogen Peroxide

    NASA Technical Reports Server (NTRS)

    Parrish, Clyde F. (Inventor)

    2006-01-01

    Methods for concentrating hydrogen peroxide solutions have been described. The methods utilize a polymeric membrane separating a hydrogen peroxide solution from a sweep gas or permeate. The membrane is selective to the permeability of water over the permeability of hydrogen peroxide, thereby facilitating the concentration of the hydrogen peroxide solution through the transport of water through the membrane to the permeate. By utilizing methods in accordance with the invention, hydrogen peroxide solutions of up to 85% by volume or higher may be generated at a point of use without storing substantial quantities of the highly concentrated solutions and without requiring temperatures that would produce explosive mixtures of hydrogen peroxide vapors.

  6. A study of the lunisolar secular resonance 2dot{ω}+dot{Ω}=0

    NASA Astrophysics Data System (ADS)

    Celletti, Alessandra; Gales, Catalin

    2016-03-01

    The dynamics of small bodies around the Earth has gained a renewed interest, since the awareness of the problems that space debris can cause in the nearby future. A relevant role in space debris is played by lunisolar secular resonances, which might contribute to an increase of the orbital elements, typically of the eccentricity. We concentrate our attention on the lunisolar secular resonance described by the relation 2dot{ω}+dot{Ω}=0, where ω and Ω denote the argument of perigee and the longitude of the ascending node of the space debris. We introduce three different models with increasing complexity. We show that the growth in eccentricity, as observed in space debris located in the MEO region at the inclination about equal to 56°, can be explained as a natural effect of the secular resonance 2dot{ω}+dot{Ω}=0, while the chaotic variations of the orbital parameters are the result of interaction and overlapping of nearby resonances.

  7. Hydrogen-bonding alterations of the protonated Schiff base and water molecule in the chloride pump of Natronobacterium pharaonis.

    PubMed

    Shibata, Mikihiro; Muneda, Norikazu; Sasaki, Takanori; Shimono, Kazumi; Kamo, Naoki; Demura, Makoto; Kandori, Hideki

    2005-09-20

    Halorhodopsin is a light-driven chloride ion pump. Chloride ion is bound in the Schiff base region of the retinal chromophore, and unidirectional chloride transport is probably enforced by the specific hydrogen-bonding interaction with the protonated Schiff base and internal water molecules. In this article, we study hydrogen-bonding alterations of the Schiff base and water molecules in halorhodopsin of Natronobacterium pharaonis (pHR) by assigning their N-D and O-D stretching vibrations in D(2)O, respectively. Highly accurate low-temperature Fourier transform infrared spectroscopy revealed that hydrogen bonds of the Schiff base and water molecules are weak in the unphotolyzed state, whereas they are strengthened upon retinal photoisomerization. Halide dependence of the stretching vibrations enabled us to conclude that the Schiff base forms a direct hydrogen bond with Cl(-) only in the K intermediate. Hydrogen bond of the Schiff base is further strengthened in the L(1) intermediate, whereas the halide dependence revealed that the acceptor is not Cl(-), but presumably a water molecule. Thus, it is concluded that the hydrogen-bonding interaction between the Schiff base and Cl(-) is not a driving force of the motion of Cl(-). Rather, the removal of its hydrogen bonds with the Schiff base and water(s) makes the environment around Cl(-) less polar in the L(1) intermediate, which presumably drives the motion of Cl(-) from its binding site to the cytoplasmic domain.

  8. Development of cadmium-free quantum dot for intracellular labelling through electroporation or lipid-calcium-phosphate

    NASA Astrophysics Data System (ADS)

    Liu, Ying-Feng; Hung, Wei-Ling; Hou, Tzh-Yin; Huang, Hsiu-Ying; Lin, Cheng-An J.

    2016-04-01

    Traditional fluorescent labelling techniques has severe photo-bleaching problem such as organic dyes and fluorescent protein. Quantum dots made up of traditional semiconductor (CdSe/ZnS) material has sort of biological toxicity. This research has developed novel Cd-free quantum dots divided into semiconductor (Indium phosphide, InP) and noble metal (Gold). Former has lower toxicity compared to traditional quantum dots. Latter consisting of gold (III) chloride (AuCl3) and toluene utilizes sonochemical preparation and different stimulus to regulate fluorescent wavelength. Amphoteric macromolecule surface technology and ligand Exchange in self-Assembled are involved to develop hydrophilic nanomaterials which can regulate the number of grafts per molecule of surface functional groups. Calcium phosphate (CaP) nanoparticle (NP) with an asymmetric lipid bilayer coating technology developed for intracellular delivery and labelling has synthesized Cd-free quantum dots possessing high brightness and multi-fluorescence successfully. Then, polymer coating and ligand exchange transfer to water-soluble materials to produce liposome nanomaterials as fluorescent probes and enhancing medical applications of nanotechnology.

  9. Photoluminescence Imaging of Focused Ion Beam Induced Individual Quantum Dots

    SciTech Connect

    Lee, Jieun; Saucer, Timothy W.; Martin, Andrew J.; Tien, Deborah; Millunchick, Joanna M.; Sih, Vanessa

    2011-02-08

    We report on scanning microphotoluminescence measurements that spectrally and spatially resolve emission from individual InAs quantum dots that were induced by focused ion beam patterning. Multilayers of quantum dots were spaced 2 μm apart, with a minimum single dot emission line width of 160 μeV, indicating good optical quality for dots patterned using this technique. Mapping 16 array sites, at least 65% were occupied by optically active dots and the spectral inhomogeneity was within 30 meV.

  10. Hydrogen for X-group exchange in CH3X, X = Cl, Br, I, OMe and NMe2 byMonomeric [1,2,4-(Me3C)3C5H2]2CeH: Experimental and Computational Support for a Carbenoid Mechanism

    SciTech Connect

    Werkema, Evan; Andersen, Richard; Yahia, Ahmed; Maron, Laurent; Eisenstein, Odile

    2009-05-15

    The reaction between [1,2,4-(Me3C)3C5H2]2CeH, referred to as Cp'2CeH, andCH3X where X is Cl, Br, I, OMe and NMe2, are described. The reactions fall intothree distinct classes. Class a, where X = Cl, Br and I rapidly form Cp'2CeX and CH4without formation of identifiable intermediates in the 1H NMR spectra. Class b, whereX = OMe proceeds rapidly to Cp'2Ce(eta2-CH2OMe) and H2 and then to Cp'2CeOMeand CH4. The methoxymethyl derivative is sufficiently stable to be isolated andcharacterized and it is rapidly converted to Cp'2CeOMe in presence of BPh3. Class c,where X = NMe2 does not result in formation of Cp'2CeNMe2, but deuterium labelingexperiments show that H for D exchange occurs in NMe3. Density functionalcalculations DFT(B3PW91) on the reaction of (C5H5)2CeH, referred to as Cp2CeH,and CH3X show that the barrier for alpha-CH activation, resulting in formation ofCp2Ce(eta2-CH2X), proceeds with a relatively low activation barrier (DeltaG++) but thesubsequent ejection of CH2 and trapping by H2 has a higher barrier; the height of thesecond barrier lies in the order F, Cl, Br, I< OMe<< NMe2, consistent with theexperimental studies. The DFT calculations also show that the two-step reaction,which proceeds through a carbenoid intermediate, has a lower barrier than a directone-step sigma bond metathesis mechanism. The reaction of Cp2CeCH2OMe and BPh3 is calculated to be a low barrier process and the ylide, CH2(+)BPh3(-), is a transition state and not an intermediate.

  11. Synthesis of CdSe quantum dots for quantum dot sensitized solar cell

    SciTech Connect

    Singh, Neetu Kapoor, Avinashi; Kumar, Vinod; Mehra, R. M.

    2014-04-24

    CdSe Quantum Dots (QDs) of size 0.85 nm were synthesized using chemical route. ZnO based Quantum Dot Sensitized Solar Cell (QDSSC) was fabricated using CdSe QDs as sensitizer. The Pre-synthesized QDs were found to be successfully adsorbed on front ZnO electrode and had potential to replace organic dyes in Dye Sensitized Solar Cells (DSSCs). The efficiency of QDSSC was obtained to be 2.06 % at AM 1.5.

  12. Amphoteric CdSe nanocrystalline quantum dots.

    PubMed

    Islam, Mohammad A

    2008-06-25

    The nanocrystal quantum dot (NQD) charge states strongly influence their electrical transport properties in photovoltaic and electroluminescent devices, optical gains in NQD lasers, and the stability of the dots in thin films. We report a unique electrostatic nature of CdSe NQDs, studied by electrophoretic methods. When we submerged a pair of metal electrodes, in a parallel plate capacitor configuration, into a dilute solution of CdSe NQDs in hexane, and applied a DC voltage across the pair, thin films of CdSe NQDs were deposited on both the positive and the negative electrodes. Extensive characterizations including scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) and Raman studies revealed that the films on both the positive and the negative electrodes were identical in every respect, clearly indicating that: (1) a fraction (<1%) of the CdSe NQDs in free form in hexane solution are charged and, more importantly, (2) there are equal numbers of positive and negative CdSe NQDs in the hexane solution. Experiments also show that the number of deposited dots is at least an order of magnitude higher than the number of initially charged dots, indicating regeneration. We used simple thermodynamics to explain such amphoteric nature and the charging/regeneration of the CdSe NQDs.

  13. Applications of quantum dots in cell biology

    NASA Astrophysics Data System (ADS)

    Barroso, Margarida; Mehdibeigi, Roshanak; Brogan, Louise

    2006-02-01

    Quantum dots promise to revolutionize the way fluorescence imaging is used in the Cell Biology field. The unique fluorescent spectral characteristics, high photostability, low photobleaching and tight emission spectra of quantum dots, position them above traditional dyes. Here we will address the ability of EviTags, which are water stabilized quantum dot products from Evident Technologies, to behave as effective FRET donors in cells. EviTag-Hops Yellow (HY; Emission 566nm; Donor) conjugated to biotin were bound to stretapvidin-Alexa568 (Acceptor) conjugates. These HYbiotin-streptavidin-Alexa568 FRET EviTag conjugates were then internalized by fluid-phase into non-polarized MDCK cells. Confocal microscopy detects these FRET EviTag conjugates in endocytic compartments, suggesting that EviTags can be used to track fluid-phase internalization and trafficking. EviTags are shown here to be effective FRET donors when internalized into cells. Upon pairing with the appropriate acceptor dyes, quantum dots will reduce the laborious data processing that is required to compensate for bleed through contamination between organic dye donor and acceptor pair signals. The EviTag technology will simplify and expand the use of FRET in the analysis of cellular processes that may involve protein-protein interactions and other complex cellular processes.

  14. Nonequilibrium dephasing in Coulomb blockaded quantum dots.

    PubMed

    Altland, Alexander; Egger, Reinhold

    2009-01-16

    We present a theory of zero-bias anomalies and dephasing rates for a Coulomb-blockaded quantum dot, driven out of equilibrium by coupling to voltage biased source and drain leads. We interpret our results in terms of the statistics of voltage fluctuations in the system.

  15. Resistance to Black Dot in Potato

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Black dot fungus can colonize tubers on the surface, in the stolon end, or in a combination of both.On the surface the fungus is prevalent as sclerotia, and in the stolon end the fungus colonizes the vascular tissuesas hyphae. The fungus is introduced to non-infested soils mostly by infected potato ...

  16. Small bright charged colloidal quantum dots.

    PubMed

    Qin, Wei; Liu, Heng; Guyot-Sionnest, Philippe

    2014-01-28

    Using electrochemical charge injection, the fluorescence lifetimes of negatively charged core/shell CdTe/CdSe QDs are measured as a function of core size and shell thickness. It is found that the ensemble negative trion lifetimes reach a maximum (∼4.5 ns) for an intermediate shell thickness. This leads to the smallest particles (∼4.5 nm) with the brightest trion to date. Single dot measurements show that the negative charge suppresses blinking and that the trion can be as bright as the exciton at room temperature. In contrast, the biexciton lifetimes remain short and exhibit only a monotonous increase with shell thickness, showing no correlation with the negative trion decays. The suppression of the Auger process in small negatively charged CdTe/CdSe quantum dots is unprecedented and a significant departure from prior results with ultrathick CdSe/CdS core/shell or dot-in-rod structures. The proposed reason for the optimum shell thickness is that the electron-hole overlap is restricted to the CdTe core while the electron is tuned to have zero kinetic energy in the core for that optimum shell thickness. The different trend of the biexciton lifetime is not explained but tentatively attributed to shorter-lived positive trions at smaller sizes. These results improve our understanding of multiexciton recombination in colloidal quantum dots and may lead to the design of bright charged QDs for more efficient light-emitting devices.

  17. 14 CFR 302.18 - DOT decisionmaker.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... shall render a recommended decision to the senior career official, who shall have all of the powers set... International Affairs is the DOT decisionmaker. The Assistant Secretary shall have all of the powers set forth in § 302.17(a)(1) and those additional powers delegated by the Secretary. The Assistant Secretary...

  18. Saturating optical resonances in quantum dots

    NASA Astrophysics Data System (ADS)

    Nair, Selvakumar V.; Rustagi, K. C.

    Optical bistability in quantum dots, recently proposed by Chemla and Miller, is studied in a two-resonance model. We show that for such classical electromagnetic resonances the applicability of a two-resonance model is far more restrictive than for those in atoms.

  19. Producing Quantum Dots by Spray Pyrolysis

    NASA Technical Reports Server (NTRS)

    Banger, Kulbinder; Jin, Michael H.; Hepp, Aloysius

    2006-01-01

    An improved process for making nanocrystallites, commonly denoted quantum dots (QDs), is based on spray pyrolysis. Unlike the process used heretofore, the improved process is amenable to mass production of either passivated or non-passivated QDs, with computer control to ensure near uniformity of size.

  20. Grating image with desired shaped dots

    NASA Astrophysics Data System (ADS)

    Honma, Hideaki; Toda, Toshiki; Takahashi, Susumu; Sawamura, Chikara; Iwata, Fujio

    2000-03-01

    A new type of Grating Image we dominate as `Sparklegram' is presented. The Sparklegram is characterized because it provides high quality and better design flexibility. These features are achieved by constructing it with shaped dots as desired. Each dot can be designed as an individual shape, for example, a star or a triangle. As dot shapes, we can use not only geometric patterns, but also some kind of symbols. Not only flexibility of each consists dot shape, but also the quality of reconstructed image is remarkably increased too. Because of these features, the constructed image with the new type of Grating Image, Sparklegram has high quality and high flexibility. It can be applied to security use, for example on credit-cards, tickets, etc., and also can be applied to the package of software products, CDs, videos and other kind of items requiring security. And with these features of flexibility and high quality, Sparklegram has also advantages to be applied to other use, for example amusement use, comics and game characters' goods and packages.

  1. Quantum-dot infrared photodetectors: a review

    NASA Astrophysics Data System (ADS)

    Stiff-Roberts, Adrienne D.

    2009-04-01

    Quantum-dot infrared photodetectors (QDIPs) are positioned to become an important technology in the field of infrared (IR) detection, particularly for high-temperature, low-cost, high-yield detector arrays required for military applications. High-operating temperature (>=150 K) photodetectors reduce the cost of IR imaging systems by enabling cryogenic dewars and Stirling cooling systems to be replaced by thermo-electric coolers. QDIPs are well-suited for detecting mid-IR light at elevated temperatures, an application that could prove to be the next commercial market for quantum dots. While quantum dot epitaxial growth and intraband absorption of IR radiation are well established, quantum dot non-uniformity remains as a significant challenge. Nonetheless, state-of-the-art mid-IR detection at 150 K has been demonstrated using 70-layer InAs/GaAs QDIPs, and QDIP focal plane arrays are approaching performance comparable to HgCdTe at 77 K. By addressing critical challenges inherent to epitaxial QD material systems (e.g., controlling dopant incorporation), exploring alternative QD systems (e.g., colloidal QDs), and using bandgap engineering to reduce dark current and enhance multi-spectral detection (e.g. resonant tunneling QDIPs), the performance and applicability of QDIPs will continue to improve.

  2. Inter-dot strain field effect on the optoelectronic properties of realistic InP lateral quantum-dot molecules

    SciTech Connect

    Barettin, Daniele Auf der Maur, Matthias; De Angelis, Roberta; Prosposito, Paolo; Casalboni, Mauro; Pecchia, Alessandro

    2015-03-07

    We report on numerical simulations of InP surface lateral quantum-dot molecules on In{sub 0.48}Ga{sub 0.52 }P buffer, using a model strictly derived by experimental results by extrapolation of the molecules shape from atomic force microscopy images. Our study has been inspired by the comparison of a photoluminescence spectrum of a high-density InP surface quantum dot sample with a numerical ensemble average given by a weighted sum of simulated single quantum-dot spectra. A lack of experimental optical response from the smaller dots of the sample is found to be due to strong inter-dot strain fields, which influence the optoelectronic properties of lateral quantum-dot molecules. Continuum electromechanical, k{sup →}·p{sup →} bandstructure, and optical calculations are presented for two different molecules, the first composed of two dots of nearly identical dimensions (homonuclear), the second of two dots with rather different sizes (heteronuclear). We show that in the homonuclear molecule the hydrostatic strain raises a potential barrier for the electrons in the connection zone between the dots, while conversely the holes do not experience any barrier, which considerably increases the coupling. Results for the heteronuclear molecule show instead that its dots do not appear as two separate and distinguishable structures, but as a single large dot, and no optical emission is observed in the range of higher energies where the smaller dot is supposed to emit. We believe that in samples of such a high density the smaller dots result as practically incorporated into bigger molecular structures, an effect strongly enforced by the inter-dot strain fields, and consequently it is not possible to experimentally obtain a separate optical emission from the smaller dots.

  3. Annealing-induced change in quantum dot chain formation mechanism

    NASA Astrophysics Data System (ADS)

    Park, Tyler D.; Colton, John S.; Farrer, Jeffrey K.; Yang, Haeyeon; Kim, Dong Jun

    2014-12-01

    Self-assembled InGaAs quantum dot chains were grown using a modified Stranski-Krastanov method in which the InGaAs layer is deposited under a low growth temperature and high arsenic overpressure, which suppresses the formation of dots until a later annealing process. The dots are capped with a 100 nm GaAs layer. Three samples, having three different annealing temperatures of 460°C, 480°C, and 500°C, were studied by transmission electron microscopy. Results indicate two distinct types of dot formation processes: dots in the 460°C and 480°C samples form from platelet precursors in a one-to-one ratio whereas the dots in the sample annealed at 500°C form through the strain-driven self-assembly process, and then grow larger via an additional Ostwald ripening process whereby dots grow into larger dots at the expense of smaller seed islands. There are consequently significant morphological differences between the two types of dots, which explain many of the previously-reported differences in optical properties. Moreover, we also report evidence of indium segregation within the dots, with little or no indium intermixing between the dots and the surrounding GaAs barrier.

  4. Annealing-induced change in quantum dot chain formation mechanism

    SciTech Connect

    Park, Tyler D.; Colton, John S.; Farrer, Jeffrey K.; Yang, Haeyeon; Kim, Dong Jun

    2014-12-15

    Self-assembled InGaAs quantum dot chains were grown using a modified Stranski-Krastanov method in which the InGaAs layer is deposited under a low growth temperature and high arsenic overpressure, which suppresses the formation of dots until a later annealing process. The dots are capped with a 100 nm GaAs layer. Three samples, having three different annealing temperatures of 460°C, 480°C, and 500°C, were studied by transmission electron microscopy. Results indicate two distinct types of dot formation processes: dots in the 460°C and 480°C samples form from platelet precursors in a one-to-one ratio whereas the dots in the sample annealed at 500°C form through the strain-driven self-assembly process, and then grow larger via an additional Ostwald ripening process whereby dots grow into larger dots at the expense of smaller seed islands. There are consequently significant morphological differences between the two types of dots, which explain many of the previously-reported differences in optical properties. Moreover, we also report evidence of indium segregation within the dots, with little or no indium intermixing between the dots and the surrounding GaAs barrier.

  5. Language, visual working memory, and dot subtraction: What counts?

    PubMed

    Briere, Jennifer L; Campbell, Jamie I D

    2016-03-01

    To investigate cognitive factors affecting subtraction of visual objects, we adapted the dot subtraction task developed by Pica, Lemer, Izard, and Dehaene (2004), who used it to investigate calculation by the Mundurukú, an indigene group in Brazil that has a limited number word vocabulary. In the dot subtraction task, briefly displayed arrays of moving dots are used to represent the quantities for subtraction. We tested 40 Canadian university students' dot enumeration, Arabic digit subtraction, visual working memory, and performance on the dot subtraction task with dot display durations of 2, 1.5, 1, and .5 s. In the 2 s condition, error rates were uniformly low, whereas in the .5 s condition, error rates increased sharply as the minuend increased from 4 to 8, as was observed with the Mundurukú. Individual differences in dot subtraction accuracy were predicted by dot enumeration skill with longer dot display durations but were predicted by visual working memory efficiency with shorter durations. Pica et al. (2004) attributed the Mundurukú participants' very poor subtraction to the absence of counting words, but our results show that a shift to reliance on visual working memory is a nonlinguistic factor that comes into play in the dot subtraction task when time to encode the dot arrays is limited.

  6. Optical properties of quantum-dot-doped liquid scintillators

    PubMed Central

    Aberle, C.; Li, J.J.; Weiss, S.; Winslow, L.

    2014-01-01

    Semiconductor nanoparticles (quantum dots) were studied in the context of liquid scintillator development for upcoming neutrino experiments. The unique optical and chemical properties of quantum dots are particularly promising for the use in neutrinoless double-beta decay experiments. Liquid scintillators for large scale neutrino detectors have to meet specific requirements which are reviewed, highlighting the peculiarities of quantum-dot-doping. In this paper, we report results on laboratory-scale measurements of the attenuation length and the fluorescence properties of three commercial quantum dot samples. The results include absorbance and emission stability measurements, improvement in transparency due to filtering of the quantum dot samples, precipitation tests to isolate the quantum dots from solution and energy transfer studies with quantum dots and the fluorophore PPO. PMID:25392711

  7. Hydrogen production by Cyanobacteria

    PubMed Central

    Dutta, Debajyoti; De, Debojyoti; Chaudhuri, Surabhi; Bhattacharya, Sanjoy K

    2005-01-01

    The limited fossil fuel prompts the prospecting of various unconventional energy sources to take over the traditional fossil fuel energy source. In this respect the use of hydrogen gas is an attractive alternate source. Attributed by its numerous advantages including those of environmentally clean, efficiency and renew ability, hydrogen gas is considered to be one of the most desired alternate. Cyanobacteria are highly promising microorganism for hydrogen production. In comparison to the traditional ways of hydrogen production (chemical, photoelectrical), Cyanobacterial hydrogen production is commercially viable. This review highlights the basic biology of cynobacterial hydrogen production, strains involved, large-scale hydrogen production and its future prospects. While integrating the existing knowledge and technology, much future improvement and progress is to be done before hydrogen is accepted as a commercial primary energy source. PMID:16371161

  8. Hydrogen transport membranes

    DOEpatents

    Mundschau, Michael V.

    2005-05-31

    Composite hydrogen transport membranes, which are used for extraction of hydrogen from gas mixtures are provided. Methods are described for supporting metals and metal alloys which have high hydrogen permeability, but which are either too thin to be self supporting, too weak to resist differential pressures across the membrane, or which become embrittled by hydrogen. Support materials are chosen to be lattice matched to the metals and metal alloys. Preferred metals with high permeability for hydrogen include vanadium, niobium, tantalum, zirconium, palladium, and alloys thereof. Hydrogen-permeable membranes include those in which the pores of a porous support matrix are blocked by hydrogen-permeable metals and metal alloys, those in which the pores of a porous metal matrix are blocked with materials which make the membrane impervious to gases other than hydrogen, and cermets fabricated by sintering powders of metals with powders of lattice-matched ceramic.

  9. Si quantum dots in silicon nitride: Quantum confinement and defects

    SciTech Connect

    Goncharova, L. V. Karner, V. L.; D'Ortenzio, R.; Chaudhary, S.; Mokry, C. R.; Simpson, P. J.; Nguyen, P. H.

    2015-12-14

    Luminescence of amorphous Si quantum dots (Si QDs) in a hydrogenated silicon nitride (SiN{sub x}:H) matrix was examined over a broad range of stoichiometries from Si{sub 3}N{sub 2.08} to Si{sub 3}N{sub 4.14}, to optimize light emission. Plasma-enhanced chemical vapor deposition was used to deposit hydrogenated SiN{sub x} films with excess Si on Si (001) substrates, with stoichiometry controlled by variation of the gas flow rates of SiH{sub 4} and NH{sub 3} gases. The compositional and optical properties were analyzed by Rutherford backscattering spectroscopy, elastic recoil detection, spectroscopic ellipsometry, photoluminescence (PL), time-resolved PL, and energy-filtered transmission electron microscopy. Ultraviolet-laser-excited PL spectra show multiple emission bands from 400 nm (3.1 eV) to 850 nm (1.45 eV) for different Si{sub 3}N{sub x} compositions. There is a red-shift of the measured peaks from ∼2.3 eV to ∼1.45 eV as Si content increases, which provides evidence for quantum confinement. Higher N content samples show additional peaks in their PL spectra at higher energies, which we attribute to defects. We observed three different ranges of composition where Tauc band gaps, PL, and PL lifetimes change systematically. There is an interesting interplay of defect luminescence and, possibly, small Si QD luminescence observed in the intermediate range of compositions (∼Si{sub 3}N{sub 3.15}) in which the maximum of light emission is observed.

  10. Si quantum dots in silicon nitride: Quantum confinement and defects

    NASA Astrophysics Data System (ADS)

    Goncharova, L. V.; Nguyen, P. H.; Karner, V. L.; D'Ortenzio, R.; Chaudhary, S.; Mokry, C. R.; Simpson, P. J.

    2015-12-01

    Luminescence of amorphous Si quantum dots (Si QDs) in a hydrogenated silicon nitride (SiNx:H) matrix was examined over a broad range of stoichiometries from Si3N2.08 to Si3N4.14, to optimize light emission. Plasma-enhanced chemical vapor deposition was used to deposit hydrogenated SiNx films with excess Si on Si (001) substrates, with stoichiometry controlled by variation of the gas flow rates of SiH4 and NH3 gases. The compositional and optical properties were analyzed by Rutherford backscattering spectroscopy, elastic recoil detection, spectroscopic ellipsometry, photoluminescence (PL), time-resolved PL, and energy-filtered transmission electron microscopy. Ultraviolet-laser-excited PL spectra show multiple emission bands from 400 nm (3.1 eV) to 850 nm (1.45 eV) for different Si3Nx compositions. There is a red-shift of the measured peaks from ˜2.3 eV to ˜1.45 eV as Si content increases, which provides evidence for quantum confinement. Higher N content samples show additional peaks in their PL spectra at higher energies, which we attribute to defects. We observed three different ranges of composition where Tauc band gaps, PL, and PL lifetimes change systematically. There is an interesting interplay of defect luminescence and, possibly, small Si QD luminescence observed in the intermediate range of compositions (˜Si3N3.15) in which the maximum of light emission is observed.

  11. Photocatalytic Hydrogen Generation by CdSe/CdS Nanoparticles.

    PubMed

    Qiu, Fen; Han, Zhiji; Peterson, Jeffrey J; Odoi, Michael Y; Sowers, Kelly L; Krauss, Todd D

    2016-09-14

    The photocatalytic hydrogen (H2) production activity of various CdSe semiconductor nanoparticles was compared including CdSe and CdSe/CdS quantum dots (QDs), CdSe quantum rods (QRs), and CdSe/CdS dot-in-rods (DIRs). With equivalent photons absorbed, the H2 generation activity orders as CdSe QDs ≫ CdSe QRs > CdSe/CdS QDs > CdSe/CdS DIRs, which is surprisingly the opposite of the electron-hole separation efficiency. Calculations of photoexcited surface charge densities are positively correlated with the H2 production rate and suggest the size of the nanoparticle plays a critical role in determining the relative efficiency of H2 production. PMID:27478995

  12. Hydrogen Technologies Safety Guide

    SciTech Connect

    Rivkin, C.; Burgess, R.; Buttner, W.

    2015-01-01

    The purpose of this guide is to provide basic background information on hydrogen technologies. It is intended to provide project developers, code officials, and other interested parties the background information to be able to put hydrogen safety in context. For example, code officials reviewing permit applications for hydrogen projects will get an understanding of the industrial history of hydrogen, basic safety concerns, and safety requirements.

  13. Solar hydrogen generator

    NASA Technical Reports Server (NTRS)

    Sebacher, D. I.; Sabol, A. P. (Inventor)

    1977-01-01

    An apparatus, using solar energy to manufacture hydrogen by dissociating water molecules into hydrogen and oxygen molecules is described. Solar energy is concentrated on a globe containing water thereby heating the water to its dissociation temperature. The globe is pervious to hydrogen molecules permitting them to pass through the globe while being essentially impervious to oxygen molecules. The hydrogen molecules are collected after passing through the globe and the oxygen molecules are removed from the globe.

  14. Disposable Hydrogen Generator.

    PubMed

    Brewer, J H; Allgeier, D L

    1965-02-26

    A convenient means of producing hydrogen gas for anaerobe jars or other situations where 2 liters of hydrogen will suffice is described. Hydrogen gas is produced by the chemical action of magnesium metal, zinc chloride, sodium chloride, and water within a unique plastic and aluminum foil envelope. That there is no excessive buildup of hydrogen greatly reduces the hazard of explosion. The gas-producing units are simple to activate and may be discarded after use.

  15. The structure evolution mechanism of electrodeposited porous Ni films on NH4Cl concentration

    NASA Astrophysics Data System (ADS)

    Yu, Xiangtao; Wang, Mingyong; Wang, Zhi; Gong, Xuzhong; Guo, Zhancheng

    2016-01-01

    NH4Cl was an important component for the electrodeposition of porous metal films through hydrogen bubble template approach. The effects of NH4Cl concentrations on pore formation and structure evolution of the electrodeposited porous Ni films were studied. It was found that Ni films electrodeposited from solutions with 0.25-0.35 M NH4Cl were compact. When NH4Cl concentrations were 0.4-0.75 M and 0.85-3 M, porous Ni films with dish-like and honeycomb-like pores were electrodeposited, respectively. To form porous structure, the critical amounts of Ni in mass deposited onto the electrode must be achieved. However, at lower NH4Cl concentration, Ni electrodeposition was interrupted after about 15 s due to Ni2+ hydrolysis. The critical amounts of Ni in mass were not reached, and compact Ni films were obtained. When NH4Cl concentrations exceeded 0.4 M, Ni2+ hydrolysis was inhibited due to the enhanced buffer ability of solution and Ni(NH3)n2+ (2 ≤ n ≤ 6) complexes became the discharged ions. Ni electrodeposition proceeded continuously and reached the critical amounts of Ni in mass, and porous Ni films were formed. At higher NH4Cl concentration, hydrogen was produced mainly by the electrochemical reduction of NH4+. pH near cathode was hardly changed, and Ni2+ ions with low overpotential were reduced. The rough Ni films were formed, which led to smaller break-off diameter of bubbles. Therefore, the pore sizes of Ni films were decreased.

  16. Three-dimensional Si/Ge quantum dot crystals.

    PubMed

    Grützmacher, Detlev; Fromherz, Thomas; Dais, Christian; Stangl, Julian; Müller, Elisabeth; Ekinci, Yasin; Solak, Harun H; Sigg, Hans; Lechner, Rainer T; Wintersberger, Eugen; Birner, Stefan; Holý, Vaclav; Bauer, Günther

    2007-10-01

    Modern nanotechnology offers routes to create new artificial materials, widening the functionality of devices in physics, chemistry, and biology. Templated self-organization has been recognized as a possible route to achieve exact positioning of quantum dots to create quantum dot arrays, molecules, and crystals. Here we employ extreme ultraviolet interference lithography (EUV-IL) at a wavelength of lambda = 13.5 nm for fast, large-area exposure of templates with perfect periodicity. Si(001) substrates have been patterned with two-dimensional hole arrays using EUV-IL and reactive ion etching. On these substrates, three-dimensionally ordered SiGe quantum dot crystals with the so far smallest quantum dot sizes and periods both in lateral and vertical directions have been grown by molecular beam epitaxy. X-ray diffractometry from a sample volume corresponding to about 3.6 x 10(7) dots and atomic force microscopy (AFM) reveal an up to now unmatched structural perfection of the quantum dot crystal and a narrow quantum dot size distribution. Intense interband photoluminescence has been observed up to room temperature, indicating a low defect density in the three-dimensional (3D) SiGe quantum dot crystals. Using the Ge concentration and dot shapes determined by X-ray and AFM measurements as input parameters for 3D band structure calculations, an excellent quantitative agreement between measured and calculated PL energies is obtained. The calculations show that the band structure of the 3D ordered quantum dot crystal is significantly modified by the artificial periodicity. A calculation of the variation of the eigenenergies based on the statistical variation in the dot dimensions as determined experimentally (+/-10% in linear dimensions) shows that the calculated electronic coupling between neighboring dots is not destroyed due to the quantum dot size variations. Thus, not only from a structural point of view but also with respect to the band structure, the 3D ordered

  17. Liquid metal hydrogen barriers

    DOEpatents

    Grover, George M.; Frank, Thurman G.; Keddy, Edward S.

    1976-01-01

    Hydrogen barriers which comprise liquid metals in which the solubility of hydrogen is low and which have good thermal conductivities at operating temperatures of interest. Such barriers are useful in nuclear fuel elements containing a metal hydride moderator which has a substantial hydrogen dissociation pressure at reactor operating temperatures.

  18. Purification of Hydrogen

    DOEpatents

    Newton, A S

    1950-12-05

    Disclosed is a process for purifying hydrogen containing various gaseous impurities by passing the hydrogen over a large surface of uranium metal at a temperature above the decomposition temperature of uranium hydride, and below the decomposition temperature of the compounds formed by the combination of the uranium with the impurities in the hydrogen.

  19. Flash hydrogenation of coal

    DOEpatents

    Manowitz, Bernard; Steinberg, Meyer; Sheehan, Thomas V.; Winsche, Warren E.; Raseman, Chad J.

    1976-01-01

    A process for the hydrogenation of coal comprising the contacting of powdered coal with hydrogen in a rotating fluidized bed reactor. A rotating fluidized bed reactor suitable for use in this process is also disclosed. The coal residence time in the reactor is limited to less than 5 seconds while the hydrogen contact time is not in excess of 0.2 seconds.

  20. Sensitive hydrogen leak detector

    DOEpatents

    Myneni, G.R.

    1999-08-03

    A sensitive hydrogen leak detector system is described which uses passivation of a stainless steel vacuum chamber for low hydrogen outgassing, a high compression ratio vacuum system, a getter operating at 77.5 K and a residual gas analyzer as a quantitative hydrogen sensor. 1 fig.

  1. Sensitive hydrogen leak detector

    DOEpatents

    Myneni, Ganapati Rao

    1999-01-01

    A sensitive hydrogen leak detector system using passivation of a stainless steel vacuum chamber for low hydrogen outgassing, a high compression ratio vacuum system, a getter operating at 77.5 K and a residual gas analyzer as a quantitative hydrogen sensor.

  2. Biological hydrogen photoproduction

    SciTech Connect

    Nemoto, Y.

    1995-09-01

    Following are the major accomplishments of the 6th year`s study of biological hydrogen photoproduction which were supported by DOE/NREL. (1) We have been characterizing a biological hydrogen production system using synchronously growing aerobically nitrogen-fixing unicellular cyanobacterium, Synechococcus sp. Miami BG 043511. So far it was necessary to irradiate the cells to produce hydrogen. Under darkness they did not produce hydrogen. However, we found that, if the cells are incubated with oxygen, they produce hydrogen under the dark. Under 80% argon + 20% oxygen condition, the hydrogen production activity under the dark was about one third of that under the light + argon condition. (2) Also it was necessary so far to incubate the cells under argon atmosphere to produce hydrogen in this system. Argon treatment is very expensive and should be avoided in an actual hydrogen production system. We found that, if the cells are incubated at a high cell density and in a container with minimum headspace, it is not necessary to use argon for the hydrogen production. (3) Calcium ion was found to play an important role in the mechanisms of protection of nitrogenase from external oxygen. This will be a clue to understand the reason why the hydrogen production is so resistant to oxygen in this strain. (4) In this strain, sulfide can be used as electron donor for the hydrogen production. This result shows that waste water can be used for the hydrogen production system using this strain.

  3. Energy levels and mean lives of Cl II to Cl VII.

    NASA Technical Reports Server (NTRS)

    Bashkin, S.; Martinson, I.

    1971-01-01

    Investigation of the spectra of chlorine between 500 and 2800 A using the beam-foil technique. Over 200 multiplets have been observed, many of which had not been reported earlier. A number of such transitions could be classified, and several new term values are proposed for Cl IV, Cl V, Cl VI , and Cl VII. Mean lives of various excited levels were measured for Cl II to Cl VII. The results are compared with theoretical calculations and other measurements in appropriate isoelectronic systems.

  4. Comparative Study of Cl-Atom Reactions in Solution Using Time-Resolved Vibrational Spectroscopy.

    PubMed

    Shin, Jae Yoon; Case, Amanda S; Crim, F Fleming

    2016-04-28

    A Cl atom can react with 2,3-dimethylbutane (DMB), 2,3-dimethyl-2-butene (DMBE), and 2,5-dimethyl-2,4-hexadiene (DMHD) in solution via a hydrogen-abstraction reaction. The large exoergicity of the reaction between a Cl atom and alkenes (DMBE and DMHD) makes vibrational excitation of the HCl product possible, and we observe the formation of vibrationally excited HCl (v = 1) for both reactions. In CCl4, the branching fractions of HCl (v = 1), Γ (v = 1), for the Cl-atom reactions with DMBE and DMHD are 0.14 and 0.23, respectively, reflecting an increased amount of vibrational excitation in the products of the more exoergic reaction. In addition, Γ (v = 1) for both reactions is larger in the solvent CDCl3, being 0.23 and 0.40, as the less viscous solvent apparently dampens the vibrational excitation of the nascent HCl less effectively. The bimolecular reaction rates for the Cl reactions with DMB, DMBE, and DMHD in CCl4 are diffusion limited (having rate constants of 1.5 × 10(10), 3.6 × 10(10), and 17.5 × 10(10) M(-1) s(-1), respectively). In fact, the bimolecular reaction rate for Cl + DMHD exceeds a typical diffusion-limited reaction rate, implying that the attractive intermolecular forces between a Cl atom and a C═C bond increase the rate of favorable encounters. The 2-fold increase in the reaction rate of the Cl + DMBE reaction from that of the Cl + DMB reaction likely reflects the effect of the C═C bond, while both the number of C═C bonds and the molecular geometry likely play a role in the large reaction rate of the Cl + DMHD reaction.

  5. Isostructural crystal packing and hydrogen bonding in alkylammonium tin(IV) chloride compounds.

    PubMed

    Lemmerer, Andreas; Billing, David G; Reisinger, Sandra A

    2007-03-01

    The three isostructural compounds butylammonium hexachloridotin(IV), pentylammonium hexachloridotin(IV) and hexylammonium hexachloridotin(IV), (C(n)H(2n+1)NH(3))(2)[SnCl(6)], with n = 4, 5 and 6, respectively, crystallize as inorganic-organic hybrids. As such, the structures consist of layers of [SnCl(6)](2-) octahedra, separated by hydrocarbon layers of interdigitated butylammonium, pentylammonium or hexylammonium cations. Corrugated layers of cations alternate with tin(IV) chloride layers. The asymmetric unit in each compound consists of an anionic component comprising one Sn and two Cl atoms on a mirror plane, and two Cl atoms in general positions; the two cations lie on another mirror plane. Application of the mirror symmetry generates octahedral coordination around the Sn atom. All compounds exhibit bifurcated and simple hydrogen-bonding interactions between the ammonium groups and the Cl atoms, with little variation in the hydrogen-bonding geometries. PMID:17339715

  6. Determination of berberine in pharmaceutical preparations using acidic hydrogen peroxide-nitrite chemiluminescence system.

    PubMed

    Liang, Yao-Dong; Yu, Chun-Xia

    2013-03-01

    A stronger chemiluminescence (CL) was observed when hydrogen peroxide was mixed with nitrite and berberine in sulfuric acid solution. The stronger CL originated from peroxidation of berberine by peroxynitrous acid that was synthesized online by the mixing of acidic hydrogen peroxide solution with nitrite solution in a flow system. The emitting species was excited state oxyberberine, a peroxidized product of berberine. Based on the stronger CL, a flow injection CL method for the determination of berberine was proposed. Under optimum experimental conditions, the stronger CL intensity was linearly related to the concentration of berberine over the range of 2.0 × 10(-7) -2.0 × 10(-5) mol L(-1) . The limit of detection (s/n = 3) was 6.2 × 10(-8) mol L(-1) . The proposed method has been evaluated by analyzing berberine in pharmaceutical preparations.

  7. Osmium pyme complexes for fast hydrogenation and asymmetric transfer hydrogenation of ketones.

    PubMed

    Baratta, Walter; Ballico, Maurizio; Del Zotto, Alessandro; Siega, Katia; Magnolia, Santo; Rigo, Pierluigi

    2008-01-01

    The osmium compound trans,cis-[OsCl2(PPh3)2(Pyme)] (1) (Pyme=1-(pyridin-2-yl)methanamine), obtained from [OsCl2(PPh3)3] and Pyme, thermally isomerizes to cis,cis-[OsCl2(PPh3)(2)(Pyme)] (2) in mesitylene at 150 degrees C. Reaction of [OsCl2(PPh3)3] with Ph2P(CH2)(4)PPh2 (dppb) and Pyme in mesitylene (150 degrees C, 4 h) leads to a mixture of trans-[OsCl2(dppb)(Pyme)] (3) and cis-[OsCl2(dppb)(Pyme)] (4) in about an 1:3 molar ratio. The complex trans-[OsCl2(dppb)(Pyet)] (5) (Pyet=2-(pyridin-2-yl)ethanamine) is formed by reaction of [OsCl2(PPh3)3] with dppb and Pyet in toluene at reflux. Compounds 1, 2, 5 and the mixture of isomers 3/4 efficiently catalyze the transfer hydrogenation (TH) of different ketones in refluxing 2-propanol and in the presence of NaOiPr (2.0 mol %). Interestingly, 3/4 has been proven to reduce different ketones (even bulky) by means of TH with a remarkably high turnover frequency (TOF up to 5.7 x 10(5) h(-1)) and at very low loading (0.05-0.001 mol %). The system 3/4 also efficiently catalyzes the hydrogenation of many ketones (H2, 5.0 atm) in ethanol with KOtBu (2.0 mol %) at 70 degrees C (TOF up to 1.5 x 10(4) h(-1)). The in-situ-generated catalysts prepared by the reaction of [OsCl2(PPh3)3] with Josiphos diphosphanes and (+/-)-1-alkyl-substituted Pyme ligands, promote the enantioselective TH of different ketones with 91-96 % ee (ee=enantiomeric excess) and with a TOF of up to 1.9 x 10(4) h(-1) at 60 degrees C.

  8. Hydrogen separation process

    DOEpatents

    Mundschau, Michael; Xie, Xiaobing; Evenson, IV, Carl; Grimmer, Paul; Wright, Harold

    2011-05-24

    A method for separating a hydrogen-rich product stream from a feed stream comprising hydrogen and at least one carbon-containing gas, comprising feeding the feed stream, at an inlet pressure greater than atmospheric pressure and a temperature greater than 200.degree. C., to a hydrogen separation membrane system comprising a membrane that is selectively permeable to hydrogen, and producing a hydrogen-rich permeate product stream on the permeate side of the membrane and a carbon dioxide-rich product raffinate stream on the raffinate side of the membrane. A method for separating a hydrogen-rich product stream from a feed stream comprising hydrogen and at least one carbon-containing gas, comprising feeding the feed stream, at an inlet pressure greater than atmospheric pressure and a temperature greater than 200.degree. C., to an integrated water gas shift/hydrogen separation membrane system wherein the hydrogen separation membrane system comprises a membrane that is selectively permeable to hydrogen, and producing a hydrogen-rich permeate product stream on the permeate side of the membrane and a carbon dioxide-rich product raffinate stream on the raffinate side of the membrane. A method for pretreating a membrane, comprising: heating the membrane to a desired operating temperature and desired feed pressure in a flow of inert gas for a sufficient time to cause the membrane to mechanically deform; decreasing the feed pressure to approximately ambient pressure; and optionally, flowing an oxidizing agent across the membrane before, during, or after deformation of the membrane. A method of supporting a hydrogen separation membrane system comprising selecting a hydrogen separation membrane system comprising one or more catalyst outer layers deposited on a hydrogen transport membrane layer and sealing the hydrogen separation membrane system to a porous support.

  9. 76 FR 41653 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2A12 (CL-601) and CL-600-2B16 (CL-601-3A...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-15

    ... products. That NPRM was published in the Federal Register on January 5, 2011 (76 FR 477). That NPRM...; 2. Is not a ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034.... Functional Test of the Leading Edge Thermal Switches. (h) For all tasks identified in paragraph (g) of...

  10. 77 FR 56525 - Special Conditions: Bombardier, Model CL-600-2B16 Airplane (CL-601-3A, CL-601-3R, and CL-604...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-13

    ... external view, the EFVS image is a monochrome, two-dimensional display. Many, but not all, of the depth... April 11, 2000 (65 FR 19477-19478), as well as at http://DocketsInfo.dot.gov/ . Docket: Background... with a crew of two. It is powered by two General Electric engines and has a maximum takeoff weight...

  11. Hydrogen effects in dilute III-N-V alloys: From defect engineering to nanostructuring

    SciTech Connect

    Pettinari, G.; Felici, M.; Capizzi, M.; Polimeni, A.; Trotta, R.

    2014-01-07

    The variation of the band gap energy of III-N-V semiconductors induced by hydrogen incorporation is the most striking effect that H produces in these materials. A special emphasis is given here to the combination of N-activity passivation by hydrogen with H diffusion kinetics in dilute nitrides. Secondary ion mass spectrometry shows an extremely steep (smaller than 5 nm/decade) forefront of the H diffusion profile in Ga(AsN) under appropriate hydrogenation conditions. This discovery prompts the opportunity for an in-plane nanostructuring of hydrogen incorporation and, hence, for a modulation of the material band gap energy at the nanoscale. The properties of quantum dots fabricated by a lithographically defined hydrogenation are presented, showing the zero-dimensional character of these novel nanostructures. Applicative prospects of this nanofabrication method are finally outlined.

  12. Air-Stable and Efficient PbSe Quantum-Dot Solar Cells Based upon ZnSe to PbSe Cation-Exchanged Quantum Dots.

    PubMed

    Kim, Sungwoo; Marshall, Ashley R; Kroupa, Daniel M; Miller, Elisa M; Luther, Joseph M; Jeong, Sohee; Beard, Matthew C

    2015-08-25

    We developed a single step, cation-exchange reaction that produces air-stable PbSe quantum dots (QDs) from ZnSe QDs and PbX2 (X = Cl, Br, or I) precursors. The resulting PbSe QDs are terminated with halide anions and contain residual Zn cations. We characterized the PbSe QDs using UV-vis-NIR absorption, photoluminescence quantum yield spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Solar cells fabricated from these PbSe QDs obtained an overall best power conversion efficiency of 6.47% at one sun illumination. The solar cell performance without encapsulation remains unchanged for over 50 days in ambient conditions; and after 50 days, the National Renewable Energy Laboratory certification team certified the device at 5.9%.

  13. Safe venting of hydrogen

    SciTech Connect

    Stewart, W.F.; Dewart, J.M.; Edeskuty, F.J.

    1990-01-01

    The disposal of hydrogen is often required in the operation of an experimental facility that contains hydrogen. Whether the vented hydrogen can be discharged to the atmosphere safely depends upon a number of factors such as the flow rate and atmospheric conditions. Calculations have been made that predict the distance a combustible mixture can extend from the point of release under some specified atmospheric conditions. Also the quantity of hydrogen in the combustible cloud is estimated. These results can be helpful in deciding of the hydrogen can be released directly to the atmosphere, or if it must be intentionally ignited. 15 refs., 5 figs., 2 tabs.

  14. Quantum dot-sized organic fluorescent dots for long-term cell tracing

    NASA Astrophysics Data System (ADS)

    Li, Kai; Tang, Ben Zhong; Liu, Bin

    2014-03-01

    Fluorescence techniques have been extensively employed to develop non-invasive methodologies for tracking and understanding complex biological processes both in vitro and in vivo, which is of high importance in modern life science research. Among a variety of fluorescent probes, inorganic semiconductor quantum dots (QDs) have shown advantages in terms of better photostability, larger Stokes shift and more feasible surface functionalization. However, their intrinsic toxic heavy metal components and unstable fluorescence at low pH greatly impede the applications of QDs in in vivo studies. In this work, we developed novel fluorescent probes that can outperform currently available QD based probes in practice. Using conjugated oligomer with aggregation-induced emission characteristics as the fluorescent domain and biocompatible lipid-PEG derivatives as the encapsulation matrix, the obtained organic dots have shown higher brightness, better stability in biological medium and comparable size and photostability as compared to their counterparts of inorganic QDs. More importantly, unlike QD-based probes, the organic fluorescent dots do not blink, and also do not contain heavy metal ions that could be potentially toxic when applied for living biosubstrates. Upon surface functionalization with a cell-penetrating peptide, the organic dots greatly outperform inorganic quantum dots in both in vitro and in vivo long-term cell tracing studies, which will be beneficial to answer crucial questions in stem cell/immune cell therapies. Considering the customized fluorescent properties and surface functionalities of the organic dots, a series of biocompatible organic dots will be developed to serve as a promising platform for multifarious bioimaging tasks in future.

  15. Multi-Color Emission of Hybrid Block Copolymer-Quantum Dot Microspheres by Controlled Quantum Dot Spatial Isolation

    NASA Astrophysics Data System (ADS)

    Ku, Kang; Kim, Minsoo; Paek, Kwanyeol; Shin, Jae; Chung, Sunhaeng; Jang, Se; Chae, Weon-Sik; Yi, Gi-Ra; Kim, Bumjoon; Se Gyu Jang Collaboration; Weon-Sik Chae Collaboration; Gi-Ra Yi Collaboration

    2013-03-01

    Fluorescent quantum dots (QDs) are promising candidates for multi-color or white light-emitting systems, however, most current systems involve undesired Forster resonance energy transfer (FRET) between QDs. Herein, we developed multi-color emitting hybrid microspheres with block copolymers (BCPs) and QDs through control of the locations of different-colored QDs in BCP micelles. Hydrogen interaction assisted method was exploited to confine QDs within the BCP spheres without sacrificing any quantum yield efficiency. BCP microspheres with raspberry-like surface structures were prepared by an evaporation-induced self-assembly from an emulsion. When different-colored QDs were independently incorporated into isolated micelles, FRET was completely suppressed because the size of the protective micellar corona was greater than the Forster radius. In contrast, FRET was observed when QDs were concurrently incorporated into the same micelle cores. This spatial control of QDs in microsphere was confirmed by TEM, EDX, PL, and FLIM measurements. Through the isolated BCP micelles, ratiometric control of different colored QDs can display a wide range of colors

  16. An AAAA-DDDD quadruple hydrogen-bond array

    NASA Astrophysics Data System (ADS)

    Blight, Barry A.; Hunter, Christopher A.; Leigh, David A.; McNab, Hamish; Thomson, Patrick I. T.

    2011-03-01

    Secondary electrostatic interactions between adjacent hydrogen bonds can have a significant effect on the stability of a supramolecular complex. In theory, the binding strength should be maximized if all the hydrogen-bond donors (D) are on one component and all the hydrogen-bond acceptors (A) are on the other. Here, we describe a readily accessible AAAA-DDDD quadruple hydrogen-bonding array that exhibits exceptionally strong binding for a small-molecule hydrogen-bonded complex in a range of different solvents (Ka > 3 × 1012 M-1 in CH2Cl2, 1.5 × 106 M-1 in CH3CN and 3.4 × 105 M-1 in 10% v/v DMSO/CHCl3). The association constant in CH2Cl2 corresponds to a binding free energy (ΔG) in excess of -71 kJ mol-1 (more than 20% of the thermodynamic stability of a carbon-carbon covalent bond), which is remarkable for a supramolecular complex held together by just four intercomponent hydrogen bonds.

  17. An AAAA–DDDD quadruple hydrogen-bond array.

    PubMed

    Blight, Barry A; Hunter, Christopher A; Leigh, David A; McNab, Hamish; Thomson, Patrick I T

    2011-03-01

    Secondary electrostatic interactions between adjacent hydrogen bonds can have a significant effect on the stability of a supramolecular complex. In theory, the binding strength should be maximized if all the hydrogen-bond donors (D) are on one component and all the hydrogen-bond acceptors (A) are on the other. Here, we describe a readily accessible AAAA–DDDD quadruple hydrogen-bonding array that exhibits exceptionally strong binding for a small-molecule hydrogen-bonded complex in a range of different solvents (K(a) > 3 × 10(12) M(-1) in CH2Cl2, 1.5 × 10(6) M(-1) in CH3CN and 3.4 × 10(5) M(-1) in 10% v/v DMSO/CHCl3). The association constant in CH2Cl2 corresponds to a binding free energy (ΔG) in excess of –71 kJ mol(-1) (more than 20% of the thermodynamic stability of a carbon–carbon covalent bond), which is remarkable for a supramolecular complex held together by just four intercomponent hydrogen bonds.

  18. Spin transport measurements in gallium arsenide quantum dots

    NASA Astrophysics Data System (ADS)

    Folk, Joshua Alexander

    This thesis presents a series of measurements investigating the spin physics of lateral quantum dots, defined electrostatically in the 2-D electron gas at the interface of a GaAs/AlGaAs heterostructure. The experiments span a range from open dots, where the leads of the dot carry at least one fully transmitting mode, to closed dots, where the leads are set to be tunnel barriers. For open dots, spin physics is inferred from measurements of conductance fluctuations; the effects of spin degeneracy in the orbital levels as well as a spin-orbit interaction are observed. In the closed dot measurements, ground state spin transitions as electrons are added to the dot may be determined from the motion of Coulomb blockade peaks in an in-plane magnetic field. In addition, this thesis demonstrates for the first time a direct measurement of the spin polarization of current emitted from a quantum dot, or a quantum point contact, during transport. These experiments make use of a spin-sensitive focusing geometry in which a quantum point contact serves as a spin analyzer for the mesoscopic device under test. Measurements are presented both in the open dot regime, where good agreement with theory is found, as well as the closed dot regime, where the data defies a simple theoretical explanation.

  19. Photobiological hydrogen production.

    PubMed

    Asada, Y; Miyake, J

    1999-01-01

    The principles and recent progress in the research and development of photobiological hydrogen production are reviewed. Cyanobacteria produce hydrogen gas using nitrogenase and/or hydrogenase. Hydrogen production mediated by native hydrogenases in cyanobacteria occurs under in the dark under anaerobic conditions by degradation of intracellular glycogen. In vitro and in vivo coupling of the cyanobacterial photosynthetic system with a clostridial hydrogenase via cyanobacterial ferredoxin was demonstrated in the presence of light. Genetic transformation of Synechococcus PCC7942 with the hydrogenase gene from Clostridium pasteurianum was successful; the active enzyme was expressed in PCC7942. The strong hydrogen producers among photosynthetic bacteria were isolated and characterized. Coculture of Rhodobacter and Clostriudium was applied for hydrogen production from glucose. A mutant strain of Rhodobacter sphaeroides RV whose light-harvesting proteins were altered was obtained by UV irradiation. Hydrogen productivity by the mutant was improved when irradiated with monochromatic light of some wavelengths. The development of photobioreactors for hydrogen production is also reviewed.

  20. Al/Cl2 molten salt battery

    NASA Technical Reports Server (NTRS)

    Giner, J.

    1972-01-01

    Molten salt battery has been developed with theoretical energy density of 5.2 j/kg (650 W-h/lb). Battery, which operates at 150 C, can be used in primary mode or as rechargeable battery. Battery has aluminum anode and chlorine cathode. Electrolyte is mixture of AlCl3, NaCl, and some alkali metal halide such as KCl.

  1. Cl2O4 in the Stratosphere

    ERIC Educational Resources Information Center

    Whisnant, David M.; Lever, Lisa; Howe, Jerry

    2005-01-01

    A comprehensive project in which the students use computational chemistry to investigate a larger chlorine oxide, Cl2O4 is described. The students start the project by reading a scenario and then follow a series of hyperlinks to develop, along with their colleagues, a better understanding of the implications of the presence of Cl2O4 in the…

  2. Hydrogen storage methods.

    PubMed

    Züttel, Andreas

    2004-04-01

    Hydrogen exhibits the highest heating value per mass of all chemical fuels. Furthermore, hydrogen is regenerative and environmentally friendly. There are two reasons why hydrogen is not the major fuel of today's energy consumption. First of all, hydrogen is just an energy carrier. And, although it is the most abundant element in the universe, it has to be produced, since on earth it only occurs in the form of water and hydrocarbons. This implies that we have to pay for the energy, which results in a difficult economic dilemma because ever since the industrial revolution we have become used to consuming energy for free. The second difficulty with hydrogen as an energy carrier is its low critical temperature of 33 K (i.e. hydrogen is a gas at ambient temperature). For mobile and in many cases also for stationary applications the volumetric and gravimetric density of hydrogen in a storage material is crucial. Hydrogen can be stored using six different methods and phenomena: (1) high-pressure gas cylinders (up to 800 bar), (2) liquid hydrogen in cryogenic tanks (at 21 K), (3) adsorbed hydrogen on materials with a large specific surface area (at T<100 K), (4) absorbed on interstitial sites in a host metal (at ambient pressure and temperature), (5) chemically bonded in covalent and ionic compounds (at ambient pressure), or (6) through oxidation of reactive metals, e.g. Li, Na, Mg, Al, Zn with water. The most common storage systems are high-pressure gas cylinders with a maximum pressure of 20 MPa (200 bar). New lightweight composite cylinders have been developed which are able to withstand pressures up to 80 MPa (800 bar) and therefore the hydrogen gas can reach a volumetric density of 36 kg.m(-3), approximately half as much as in its liquid state. Liquid hydrogen is stored in cryogenic tanks at 21.2 K and ambient pressure. Due to the low critical temperature of hydrogen (33 K), liquid hydrogen can only be stored in open systems. The volumetric density of liquid hydrogen

  3. Hydrogen storage methods

    NASA Astrophysics Data System (ADS)

    Züttel, Andreas

    Hydrogen exhibits the highest heating value per mass of all chemical fuels. Furthermore, hydrogen is regenerative and environmentally friendly. There are two reasons why hydrogen is not the major fuel of today's energy consumption. First of all, hydrogen is just an energy carrier. And, although it is the most abundant element in the universe, it has to be produced, since on earth it only occurs in the form of water and hydrocarbons. This implies that we have to pay for the energy, which results in a difficult economic dilemma because ever since the industrial revolution we have become used to consuming energy for free. The second difficulty with hydrogen as an energy carrier is its low critical temperature of 33 K (i.e. hydrogen is a gas at ambient temperature). For mobile and in many cases also for stationary applications the volumetric and gravimetric density of hydrogen in a storage material is crucial. Hydrogen can be stored using six different methods and phenomena: (1) high-pressure gas cylinders (up to 800 bar), (2) liquid hydrogen in cryogenic tanks (at 21 K), (3) adsorbed hydrogen on materials with a large specific surface area (at T<100 K), (4) absorbed on interstitial sites in a host metal (at ambient pressure and temperature), (5) chemically bonded in covalent and ionic compounds (at ambient pressure), or (6) through oxidation of reactive metals, e.g. Li, Na, Mg, Al, Zn with water. The most common storage systems are high-pressure gas cylinders with a maximum pressure of 20 MPa (200 bar). New lightweight composite cylinders have been developed which are able to withstand pressures up to 80 MPa (800 bar) and therefore the hydrogen gas can reach a volumetric density of 36 kg.m-3, approximately half as much as in its liquid state. Liquid hydrogen is stored in cryogenic tanks at 21.2 K and ambient pressure. Due to the low critical temperature of hydrogen (33 K), liquid hydrogen can only be stored in open systems. The volumetric density of liquid hydrogen is

  4. Spectrophotometric and electrochemical study of neptunium ions in molten NaCl-CsCl eutectic

    NASA Astrophysics Data System (ADS)

    Uehara, Akihiro; Nagai, Takayuki; Fujii, Toshiyuki; Shirai, Osamu; Yamana, Hajimu

    2013-06-01

    The chemical oxidation states of NpO2+, Np4+ and Np3+ in NaCl-CsCl eutectic were controlled by using Cl2, O2, H2 and Ar gas mixtures, the redox behavior and electronic absorption properties of their Np ions were studied. The Np4+ was prepared from NpO2Cl by bubbling Cl2 gas into the melt in the presence of carbon rod. Np3+ was quantitatively prepared by bubbling H2-Ar gas mixture. The molar absorptivities of NpO2+, Np4+ and Np3+ were determined in molten NaCl-CsCl eutectic at 923 K and hypersensitive transitions of Np4+ and Np3+ ions were assigned. Since the polarizing ability of the cations in the NaCl-CsCl eutectic is lower than that in some other melts, it has been shown that the coordination symmetry of the Np-Cl complex is higher. In the electrochemical measurement of Np4+, the cathodic current for the reduction of Np4+ was found to be controlled by the diffusion of Np4+. The temperature dependence of the diffusion coefficient between 823 and 923 K was formulated to be lnD=-4304/T-6.172. The formal redox potential of the Np4+|Np3+ couple depended on the temperature, this dependence was formulated as ENp|Np∘'=-1.313+6.210×10-4T V (vs. Cl2|Cl-).

  5. ADVANCED HYDROGEN TRANSPORT MEMBRANES FOR VISION 21 FOSSIL FUEL PLANTS

    SciTech Connect

    Shane E. Roark; Anthony F. Sammells; Richard Mackay; Stewart R. Schesnack; Scott R. Morrison; Thomas F. Barton; Sara L. Rolfe; U. Balachandran; Richard N. Kleiner; James E. Stephan; Frank E. Anderson; Aaron L. Wagner; Jon P. Wagner

    2003-10-30

    Eltron Research Inc. and team members CoorsTek, Sued Chemie, Argonne National Laboratory, and NORAM are developing an environmentally benign, inexpensive, and efficient method for separating hydrogen from gas mixtures produced during industrial processes, such as coal gasification. This project was motivated by the National Energy Technology Laboratory (NETL) Vision 21 initiative, which seeks to economically eliminate environmental concerns associated with the use of fossil fuels. Over the past 12 months, this project has focused on four basic categories of dense membranes: (1) mixed conducting ceramic/ceramic composites, (2) mixed conducting ceramic/metal (cermet) composites, (3) cermets with hydrogen permeable metals, and (4) layered composites containing hydrogen permeable alloys. Ultimately, these materials must enable hydrogen separation at practical rates under ambient and high-pressure conditions, without deactivation in the presence of feedstream components such as carbon dioxide, water, and sulfur. The ceramic/ceramic composites demonstrate the lowest hydrogen permeation rates, with a maximum of approximately 0.1 mL/min/cm{sup 2} for 0.5-mm thick membranes at 800 to 950 C. Under equivalent conditions, cermets achieve a hydrogen permeation rate near 1 mL/min/cm{sup 2}, and the metal phase also improves structural stability and surface catalysis for hydrogen dissociation. Furthermore, if metals with high hydrogen permeability are used in cermets, permeation rates near 4 mL/min/cm{sup 2} are achievable with relatively thick membranes. Layered composite membranes have by far the highest permeation rates with a maximum flux in excess of 200 mL {center_dot} min{sup -1} {center_dot} cm{sup -2}. Moreover, these permeation rates were achieved at a total pressure differential across the membrane of 450 psi. Based on these results, effort during the next year will focus on this category of membranes. This report contains long-term hydrogen permeation data over eight

  6. Relationship of the DOT`s regulations to the UN recommendations and international regulations

    SciTech Connect

    Saltzman, S.C.

    1994-12-31

    International, regional and national hazardous materials transportation regulations, including those of the US Department of Transportation, or DOT, are all being harmonized (i.e., made more uniform) by becoming fully based on the United Nations Recommendations on the Transport of Dangerous Goods. Effective last October, DOT`s regulations, Title 49 of the US Code of Federal Regulations, started requiring UN classification, marking, labeling, placarding and documentation. Full use of UN packaging in the US will be required by October 1996. Canada and Australia already adopted the UN Recommendations ahead of DOT; Mexico is in the process of doing so right now, and international air and ocean transport codes have required UN packaging for hazardous materials since 1990. European regional hazardous materials transportation regulations will also be harmonized with UN by 1995. Understanding how the international system is structured and the process by which it works will help to understand why and how the DOT regulations are changing, as well as the occasional differences between regulations. More importantly, this understanding allows one to anticipate changes, and either prepare for them, or try to head them off if there is the belief that they will be harmful to one`s industry.

  7. DotKnot: pseudoknot prediction using the probability dot plot under a refined energy model

    PubMed Central

    Sperschneider, Jana; Datta, Amitava

    2010-01-01

    RNA pseudoknots are functional structure elements with key roles in viral and cellular processes. Prediction of a pseudoknotted minimum free energy structure is an NP-complete problem. Practical algorithms for RNA structure prediction including restricted classes of pseudoknots suffer from high runtime and poor accuracy for longer sequences. A heuristic approach is to search for promising pseudoknot candidates in a sequence and verify those. Afterwards, the detected pseudoknots can be further analysed using bioinformatics or laboratory techniques. We present a novel pseudoknot detection method called DotKnot that extracts stem regions from the secondary structure probability dot plot and assembles pseudoknot candidates in a constructive fashion. We evaluate pseudoknot free energies using novel parameters, which have recently become available. We show that the conventional probability dot plot makes a wide class of pseudoknots including those with bulged stems manageable in an explicit fashion. The energy parameters now become the limiting factor in pseudoknot prediction. DotKnot is an efficient method for long sequences, which finds pseudoknots with higher accuracy compared to other known prediction algorithms. DotKnot is accessible as a web server at http://dotknot.csse.uwa.edu.au. PMID:20123730

  8. WNK protein kinases modulate cellular Cl- flux by altering the phosphorylation state of the Na-K-Cl and K-Cl cotransporters.

    PubMed

    Kahle, Kristopher T; Rinehart, Jesse; Ring, Aaron; Gimenez, Ignacio; Gamba, Gerardo; Hebert, Steven C; Lifton, Richard P

    2006-10-01

    Precise control of cellular Cl(-) transport is necessary for many fundamental physiological processes. For example, the intracellular concentration of Cl(-), fine-tuned through the coordinated action of cellular Cl(-) influx and efflux mechanisms, determines whether a neuron's response to GABA is excitatory or inhibitory. In epithelia, synchrony between apical and basolateral Cl(-) flux, and transcellular and paracellular Cl(-) transport, is necessary for efficient transepithelial Cl(-) reabsorption or secretion. In cells throughout the body, coordination of Cl(-) entry and exit mechanisms help defend against changes in cell volume. The Na-K-Cl and K-Cl cotransporters of the SLC12 gene family are important molecular determinants of Cl(-) entry and exit, respectively, in these systems. The WNK serine-threonine kinase family, members of which are mutated in an inherited form of human hypertension, are components of a signaling pathway that coordinates Cl(-) influx and efflux through SLC12 cotransporters to dynamically regulate intracellular Cl(-) activity. PMID:16990453

  9. Mesoscopic cavity quantum electrodynamics with quantum dots

    SciTech Connect

    Childress, L.; Soerensen, A.S.; Lukin, M.D.

    2004-04-01

    We describe an electrodynamic mechanism for coherent, quantum-mechanical coupling between spatially separated quantum dots on a microchip. The technique is based on capacitive interactions between the electron charge and a superconducting transmission line resonator, and is closely related to atomic cavity quantum electrodynamics. We investigate several potential applications of this technique which have varying degrees of complexity. In particular, we demonstrate that this mechanism allows design and investigation of an on-chip double-dot microscopic maser. Moreover, the interaction may be extended to couple spatially separated electron-spin states while only virtually populating fast-decaying superpositions of charge states. This represents an effective, controllable long-range interaction, which may facilitate implementation of quantum information processing with electron-spin qubits and potentially allow coupling to other quantum systems such as atomic or superconducting qubits.

  10. Scanning photoluminescent spectroscopy of bioconjugated quantum dots

    NASA Astrophysics Data System (ADS)

    Chornokur, G.; Ostapenko, S.; Oleynik, E.; Phelan, C.; Korsunska, N.; Kryshtab, T.; Zhang, J.; Wolcott, A.; Sellers, T.

    2009-04-01

    We report on the application of the bio-conjugated quantum dots (QDs) for a "sandwich" enzyme-linked immunosorbent assay (ELISA) cancer testing technique. Quantum dot ELISA detection of the cancer PSA antigen at concentrations as low as 0.01 ng/ml which is ˜50 times lower than the classic "sandwich" ELISA was demonstrated. Scanning photoluminescence (PL) spectroscopy was performed on dried ELISA wells and the results compared with the same QD samples dried on a solid substrate. We confirmed a "blue" up to 37 nm PL spectral shift in a case of QDs conjugated to PSA antibodies. Increasing of the "blue" spectral shift was observed at lower PSA antigen concentrations. The results can be used to improve sensitivity of "sandwich" ELISA cancer antigen detection.

  11. Separability and dynamical symmetry of Quantum Dots

    SciTech Connect

    Zhang, P.-M.; Zou, L.-P.; Horvathy, P.A.; Gibbons, G.W.

    2014-02-15

    The separability and Runge–Lenz-type dynamical symmetry of the internal dynamics of certain two-electron Quantum Dots, found by Simonović et al. (2003), are traced back to that of the perturbed Kepler problem. A large class of axially symmetric perturbing potentials which allow for separation in parabolic coordinates can easily be found. Apart from the 2:1 anisotropic harmonic trapping potential considered in Simonović and Nazmitdinov (2013), they include a constant electric field parallel to the magnetic field (Stark effect), the ring-shaped Hartmann potential, etc. The harmonic case is studied in detail. -- Highlights: • The separability of Quantum Dots is derived from that of the perturbed Kepler problem. • Harmonic perturbation with 2:1 anisotropy is separable in parabolic coordinates. • The system has a conserved Runge–Lenz type quantity.

  12. Entangling distant quantum dots using classical interference

    NASA Astrophysics Data System (ADS)

    Busch, Jonathan; Kyoseva, Elica S.; Trupke, Michael; Beige, Almut

    2008-10-01

    We show that it is possible to employ reservoir engineering to turn two distant and relatively bad cavities into one good cavity with a tunable spontaneous decay rate. As a result, quantum computing schemes, which would otherwise require the shuttling of atomic qubits in and out of an optical resonator, can now be applied to distant quantum dots. To illustrate this we transform a recent proposal to entangle two qubits via the observation of macroscopic fluorescence signals [J. Metz , Phys. Rev. Lett. 97, 040503 (2006)] to the electron-spin states of two semiconductor quantum dots. Our scheme requires neither the coherent control of qubit-qubit interactions nor the detection of single photons. Moreover, the scheme is relatively robust against spin-bath couplings, parameter fluctuations, and the spontaneous emission of photons.

  13. Lifetime blinking in nonblinking nanocrystal quantum dots

    NASA Astrophysics Data System (ADS)

    Galland, Christophe; Ghosh, Yagnaseni; Steinbrück, Andrea; Hollingsworth, Jennifer A.; Htoon, Han; Klimov, Victor I.

    2012-06-01

    Nanocrystal quantum dots are attractive materials for applications as nanoscale light sources. One impediment to these applications is fluctuations of single-dot emission intensity, known as blinking. Recent progress in colloidal synthesis has produced nonblinking nanocrystals; however, the physics underlying blinking suppression remains unclear. Here we find that ultra-thick-shell CdSe/CdS nanocrystals can exhibit pronounced fluctuations in the emission lifetimes (lifetime blinking), despite stable nonblinking emission intensity. We demonstrate that lifetime variations are due to switching between the neutral and negatively charged state of the nanocrystal. Negative charging results in faster radiative decay but does not appreciably change the overall emission intensity because of suppressed nonradiative Auger recombination for negative trions. The Auger process involving excitation of a hole (positive trion pathway) remains efficient and is responsible for charging with excess electrons, which occurs via Auger-assisted ionization of biexcitons accompanied by ejection of holes.

  14. Lifetime blinking in nonblinking nanocrystal quantum dots.

    PubMed

    Galland, Christophe; Ghosh, Yagnaseni; Steinbrück, Andrea; Hollingsworth, Jennifer A; Htoon, Han; Klimov, Victor I

    2012-06-19

    Nanocrystal quantum dots are attractive materials for applications as nanoscale light sources. One impediment to these applications is fluctuations of single-dot emission intensity, known as blinking. Recent progress in colloidal synthesis has produced nonblinking nanocrystals; however, the physics underlying blinking suppression remains unclear. Here we find that ultra-thick-shell CdSe/CdS nanocrystals can exhibit pronounced fluctuations in the emission lifetimes (lifetime blinking), despite stable nonblinking emission intensity. We demonstrate that lifetime variations are due to switching between the neutral and negatively charged state of the nanocrystal. Negative charging results in faster radiative decay but does not appreciably change the overall emission intensity because of suppressed nonradiative Auger recombination for negative trions. The Auger process involving excitation of a hole (positive trion pathway) remains efficient and is responsible for charging with excess electrons, which occurs via Auger-assisted ionization of biexcitons accompanied by ejection of holes.

  15. Quantum dot molecular beacons for DNA detection.

    PubMed

    Cady, Nathaniel C

    2009-01-01

    Molecular beacons have become an important fluorescent probe for sequence-specific DNA detection. To improve the sensitivity and robustness of molecular beacon assays, fluorescent semiconductor quantum dots (QDs) are now being used as the fluorescent moiety for molecular beacon synthesis. Multiple linkage strategies can be used for attaching molecular beacon DNA to QDs, and multiple quenchers, including gold particles, can be used for fluorescence quenching. Covalent attachment of QDs to DNA can be achieved through amide linkage, and affinity-based attachment can be achieved with streptavidin-biotin linkage. We have shown that these linkage strategies can be used to successfully create quantum dot molecular beacons that can be used in DNA detection assays with high specificity.

  16. Influence of delta-doping on the hole capture probability in Ge/Si quantum dot mid-infrared photodetectors

    PubMed Central

    2014-01-01

    We study the effect of delta-doping on the hole capture probability in ten-period p-type Ge quantum dot photodetectors. The boron concentration in the delta-doping layers is varied by either passivation of a sample in a hydrogen plasma or by direct doping during the molecular beam epitaxy. The devices with a lower doping density is found to exhibit a lower capture probability and a higher photoconductive gain. The most pronounced change in the trapping characteristics upon doping is observed at a negative bias polarity when the photoexcited holes move toward the δ-doping plane. The latter result implies that the δ-doping layers are directly involved in the processes of hole capture by the quantum dots. PMID:25249825

  17. Neutralization of Hydroxide Ion in Melt-Grown NaCl Crystals

    NASA Technical Reports Server (NTRS)

    Otterson, Dumas A.

    1961-01-01

    Many recent studies of solid-state phenomena, particularly in the area of crystal imperfections, have involved the use of melt-grown NaCl single crystals. Quite often trace impurities in these materials have had a prominent effect on these phenomena. Trace amounts of hydroxide ion have been found in melt-grown NaCl crystals. This paper describes a nondestructive method of neutralizing the hydroxide ion in such crystals. Crystals of similar hydroxide content are maintained at an elevated temperature below the melting point of NaCl in a flowing atmosphere containing. dry hydrogen chloride. Heat treatment is continued until an analysis of the test specimens shows no excess hydroxide ion. A colorimetric method previously described4 is used for this analysis.

  18. Genotoxic and mutagenic effects of lipid-coated CdSe/ZnS quantum dots.

    PubMed

    Aye, Mélanie; Di Giorgio, Carole; Berque-Bestel, Isabelle; Aime, Ahissan; Pichon, Benoit P; Jammes, Yves; Barthélémy, Philippe; De Méo, Michel

    2013-01-20

    We proposed to evaluate the genotoxicity and mutagenicity of a new quantum dots (QDs) nanoplatform (QDsN), consisting of CdSe/ZnS core-shell QDs encapsulated by a natural fusogenic lipid (1,2-di-oleoyl-sn-glycero-3-phosphocholine (DOPC)) and functionalized by a nucleolipid N-[5'-(2',3'-di-oleoyl) uridine]-N',N',N'-trimethylammoniumtosylate (DOTAU). This QDs nanoplatform may represent a new therapeutic tool for the diagnosis and treatment of human cancers. The genotoxic, mutagenic and clastogenic effects of QDsN were compared to those of cadmium chloride (CdCl(2)). Three assays were used: (1) the Salmonella/microsome assay with four tester strains, (2) the comet assay and (3) the micronucleus test on CHO cells. The contribution of simulated sunlight was studied in the three assays while oxidative events were only explored in the comet assay in aliquots pretreated with the antioxidant l-ergothioneine. We found that QDsN could enter CHO-K1 cells and accumulate in cytoplasmic vesicles. It was not mutagenic in the Salmonella/mutagenicity test whereas CdCl(2) was weakly positive. In the dark, both the QDsN and CdCl(2) similarly induced dose-dependent increases in single-strand breaks and micronuclei. Exposure to simulated sunlight significantly potentiated the genotoxic activities of both QDsN and CdCl(2), but did not significantly increase micronucleus frequencies. l-Ergothioneine significantly reduced but did not completely suppress the DNA-damaging activity of QDsN and CdCl(2). The present results clearly point to the genotoxic properties and the risk of long-term adverse effects of such a nanoplatform if used for human anticancer therapy and diagnosis in the future.

  19. The Cl-36 in the stratosphere

    NASA Technical Reports Server (NTRS)

    Deck, Bruce; Wahlen, Martin; Weyer, Harley; Kubik, Peter; Sharma, Pankaj; Gove, Harry

    1991-01-01

    Initial measurements of the cosmogenic radionuclide, Cl-36, in the lower stratosphere were made by accelerator mass spectrometry. Samples were obtained using the large volume LASL air sampling pods on a NASA WB-57F aircraft. Untreated (for collection of particulates only) and tetrabutyl ammonium hydroxide treated (for collection of particulates and HCl) IPC-1478 filters were flown on three flights in the lower stratosphere. Chlorine (Cl) and Cl compounds are important trace constituents for stratospheric chemistry, in particular with respect to O3 destruction. Stratospheric Cl chemistry has recently received increased attention with the observation of strong O3 depletion in the Antarctic winter vortex and in the weaker and more complex Arctic winter vortices. Cosmogenic (Cl-36) is produced by spallation reactions from Ar mainly in the stratosphere, and has had several applications as a geochemical tracer. The large amounts of Cl-36 introduced by nuclear weapon testing have been removed from the stratosphere by now, and measurements in the stratosphere to obtain cosmogenic production rates and concentration distributions is now possible. The use of cosmogenic Cl-36 as a tracer for stratospheric Cl chemistry and for stratospheric/tropospheric exchange processes is investigated. A first attempt to determine stratospheric and tropospheric production rates, the partitioning of Cl-36 among particulate and gaseous Cl compounds, and the respective inventories and removal rates is being made. Results from a flight at 13.7 km, 30-33 degrees N, 97-107 degrees W, and from a second flight at 17.7 km, 43-45-36 degrees N, 92-94 degrees W, for the untreated and treated filters respectively are presented.

  20. Hydrogen Filling Station

    SciTech Connect

    Boehm, Robert F; Sabacky, Bruce; Anderson II, Everett B; Haberman, David; Al-Hassin, Mowafak; He, Xiaoming; Morriseau, Brian

    2010-02-24

    Hydrogen is an environmentally attractive transportation fuel that has the potential to displace fossil fuels. The Freedom CAR and Freedom FUEL initiatives emphasize the importance of hydrogen as a future transportation fuel. Presently, Las Vegas has one hydrogen fueling station powered by natural gas. However, the use of traditional sources of energy to produce hydrogen does not maximize the benefit. The hydrogen fueling station developed under this grant used electrolysis units and solar energy to produce hydrogen fuel. Water and electricity are furnished to the unit and the output is hydrogen and oxygen. Three vehicles were converted to utilize the hydrogen produced at the station. The vehicles were all equipped with different types of technologies. The vehicles were used in the day-to-day operation of the Las Vegas Valley Water District and monitoring was performed on efficiency, reliability and maintenance requirements. The research and demonstration utilized for the reconfiguration of these vehicles could lead to new technologies in vehicle development that could make hydrogen-fueled vehicles more cost effective, economical, efficient and more widely used. In order to advance the development of a hydrogen future in Southern Nevada, project partners recognized a need to bring various entities involved in hydrogen development and deployment together as a means of sharing knowledge and eliminating duplication of efforts. A road-mapping session was held in Las Vegas in June 2006. The Nevada State Energy Office, representatives from DOE, DOE contractors and LANL, NETL, NREL were present. Leadership from the National hydrogen Association Board of Directors also attended. As a result of this session, a roadmap for hydrogen development was created. This roadmap has the ability to become a tool for use by other road-mapping efforts in the hydrogen community. It could also become a standard template for other states or even countries to approach planning for a hydrogen

  1. Effect of salts addition on hydrogen production by C. acetobutylicum.

    PubMed

    Alshiyab, H; Kalil, M S; Hamid, A A; Wan Yusoff, W M

    2008-09-15

    The objective of this study is to investigate the effect of salts addition to fermentation medium on hydrogen production, under anaerobic batch culture system. In this study, batch experiments were conducted to investigate the inhibitory effect of both NaCl and sodium acetate on hydrogen production. The optimum pH and temperature for hydrogen production were at initial pH of 7.0 and 30 degrees C. Enhanced production of hydrogen, using glucose as substrate was achieved. In the absence of Sodium Chloride and Sodium Acetate enhanced hydrogen yield (Y(P/S)) from 350 mL g(-1) glucose utilized to 391 mL g(-1) glucose utilized with maximum hydrogen productivity of 77.5 ml/L/h. Results also show that sodium chloride and sodium acetate in the medium adversely affect growth. Hydrogen yield per biomass (Y(P/X)) of 254 ml/L/g, biomass per substrate utilized (Y(X/S)) of 0.268 and (Y(H2/S) of 0.0349. The results suggested that Sodium at any concentration resulted to inhibit the bacterial productivity of hydrogen.

  2. Ultrafine hydrogen storage powders

    DOEpatents

    Anderson, Iver E.; Ellis, Timothy W.; Pecharsky, Vitalij K.; Ting, Jason; Terpstra, Robert; Bowman, Robert C.; Witham, Charles K.; Fultz, Brent T.; Bugga, Ratnakumar V.

    2000-06-13

    A method of making hydrogen storage powder resistant to fracture in service involves forming a melt having the appropriate composition for the hydrogen storage material, such, for example, LaNi.sub.5 and other AB.sub.5 type materials and AB.sub.5+x materials, where x is from about -2.5 to about +2.5, including x=0, and the melt is gas atomized under conditions of melt temperature and atomizing gas pressure to form generally spherical powder particles. The hydrogen storage powder exhibits improved chemcial homogeneity as a result of rapid solidfication from the melt and small particle size that is more resistant to microcracking during hydrogen absorption/desorption cycling. A hydrogen storage component, such as an electrode for a battery or electrochemical fuel cell, made from the gas atomized hydrogen storage material is resistant to hydrogen degradation upon hydrogen absorption/desorption that occurs for example, during charging/discharging of a battery. Such hydrogen storage components can be made by consolidating and optionally sintering the gas atomized hydrogen storage powder or alternately by shaping the gas atomized powder and a suitable binder to a desired configuration in a mold or die.

  3. Hydrogen interactions with metals

    NASA Technical Reports Server (NTRS)

    Mclellan, R. B.; Harkins, C. G.

    1975-01-01

    Review of the literature on the nature and extent of hydrogen interactions with metals and the role of hydrogen in metal failure. The classification of hydrogen-containing systems is discussed, including such categories as covalent hydrides, volatile hydrides, polymeric hydrides, and transition metal hydride complexes. The use of electronegativity as a correlating parameter in determining hydride type is evaluated. A detailed study is made of the thermodynamics of metal-hydrogen systems, touching upon such aspects as hydrogen solubility, the positions occupied by hydrogen atoms within the solvent metal lattice, the derivation of thermodynamic functions of solid solutions from solubility data, and the construction of statistical models for hydrogen-metal solutions. A number of theories of hydrogen-metal bonding are reviewed, including the rigid-band model, the screened-proton model, and an approach employing the augmented plane wave method to solve the one-electron energy band problem. Finally, the mechanism of hydrogen embrittlement is investigated on the basis of literature data concerning stress effects and the kinetics of hydrogen transport to critical sites.

  4. Hydrogen energy systems studies

    SciTech Connect

    Ogden, J.M.; Steinbugler, M.; Kreutz, T.

    1998-08-01

    In this progress report (covering the period May 1997--May 1998), the authors summarize results from ongoing technical and economic assessments of hydrogen energy systems. Generally, the goal of their research is to illuminate possible pathways leading from present hydrogen markets and technologies toward wide scale use of hydrogen as an energy carrier, highlighting important technologies for RD and D. Over the past year they worked on three projects. From May 1997--November 1997, the authors completed an assessment of hydrogen as a fuel for fuel cell vehicles, as compared to methanol and gasoline. Two other studies were begun in November 1997 and are scheduled for completion in September 1998. The authors are carrying out an assessment of potential supplies and demands for hydrogen energy in the New York City/New Jersey area. The goal of this study is to provide useful data and suggest possible implementation strategies for the New York City/ New Jersey area, as the Hydrogen Program plans demonstrations of hydrogen vehicles and refueling infrastructure. The authors are assessing the implications of CO{sub 2} sequestration for hydrogen energy systems. The goals of this work are (a) to understand the implications of CO{sub 2} sequestration for hydrogen energy system design; (b) to understand the conditions under which CO{sub 2} sequestration might become economically viable; and (c) to understand design issues for future low-CO{sub 2} emitting hydrogen energy systems based on fossil fuels.

  5. Quantum-dot optical temperature probes

    NASA Astrophysics Data System (ADS)

    Walker, Glen W.; Sundar, Vikram C.; Rudzinski, Christina M.; Wun, Aetna W.; Bawendi, Moungi G.; Nocera, Daniel G.

    2003-10-01

    The steady-state photoluminescence (PL) properties of cadmium selenide quantum dots (QDs) with a zinc sulfide overlayer [(CdSe)ZnS] can be strongly dependent on temperature in the range from 100 to 315 K. The PL intensity from 50 to 55 Å (CdSe)ZnS QDs in poly(lauryl methacrylate) matrices increases by a factor of ˜5 when the temperature is decreased from 315 to 100 K, and the peak of the emission band is blueshifted by 20 nm over the same range. The change in PL intensity is appreciable, linear, and reversible (-1.3% per °C) for temperatures close to ambient conditions. These properties of (CdSe)ZnS dots are retained in a variety of matrices including polymer and sol-gel films, and they are independent of excitation wavelength above the band gap. The significant temperature dependence of the luminescence combined with its insensitivity to oxygen quenching establishes (CdSe)ZnS dots as optical temperature indicators for temperature-sensitive coatings.

  6. Blinking statistics of silicon quantum dots.

    PubMed

    Bruhn, Benjamin; Valenta, Jan; Sangghaleh, Fatemeh; Linnros, Jan

    2011-12-14

    The blinking statistics of numerous single silicon quantum dots fabricated by electron-beam lithography, plasma etching, and oxidation have been analyzed. Purely exponential on- and off-time distributions were found consistent with the absence of statistical aging. This is in contrast to blinking reports in the literature where power-law distributions prevail as well as observations of statistical aging in nanocrystal ensembles. A linear increase of the switching frequency with excitation power density indicates a domination of single-photon absorption processes, possibly through a direct transfer of charges to trap states without the need for a bimolecular Auger mechanism. Photoluminescence saturation with increasing excitation is not observed; however, there is a threshold in excitation (coinciding with a mean occupation of one exciton per nanocrystal) where a change from linear to square-root increase occurs. Finally, the statistics of blinking of single quantum dots in terms of average on-time, blinking frequency and blinking amplitude reveal large variations (several orders) without any significant correlation demonstrating the individual microscopic character of each quantum dot.

  7. Theory of the Quantum Dot Hybrid Qubit

    NASA Astrophysics Data System (ADS)

    Friesen, Mark

    2015-03-01

    The quantum dot hybrid qubit, formed from three electrons in two quantum dots, combines the desirable features of charge qubits (fast manipulation) and spin qubits (long coherence times). The hybridized spin and charge states yield a unique energy spectrum with several useful properties, including two different operating regimes that are relatively immune to charge noise due to the presence of optimal working points or ``sweet spots.'' In this talk, I will describe dc and ac-driven gate operations of the quantum dot hybrid qubit. I will analyze improvements in the dephasing that are enabled by the sweet spots, and I will discuss the outlook for quantum hybrid qubits in terms of scalability. This work was supported in part by ARO (W911NF-12-0607), NSF (PHY-1104660), the USDOD, and the Intelligence Community Postdoctoral Research Fellowship Program. The views and conclusions contained in this presentation are those of the authors and should not be interpreted as representing the official policies or endorsements, either expressed or implied, of the US government.

  8. Quantum dot spectroscopy using a single phosphorus donor

    NASA Astrophysics Data System (ADS)

    Büch, Holger; Fuechsle, Martin; Baker, William; House, Matthew G.; Simmons, Michelle Y.

    2015-12-01

    Using a deterministic single P donor placed with atomic precision accuracy next to a nanoscale silicon quantum dot, we present a way to analyze the energy spectrum of small quantum dots in silicon by tunnel-coupled transport measurements. The energy-level structure of the quantum dot is observed as resonance features within the transport bias triangles when the donor chemical potential is aligned with states within the quantum dot as confirmed by a numeric rate equation solver SIMON. This technique allows us to independently extract the quantum dot level structure irrespective of the density of states in the leads. Such a method is useful for the investigation of silicon quantum dots in the few-electron regime where the level structure is governed by an intricate interplay between the spin- and the valley-orbit degrees of freedom.

  9. Dynamic and static behavior of hydrogen bonds of the X-H···π type (X = F, Cl, Br, I, RO and RR'N; R, R' = H or Me) in the benzene π-system, elucidated by QTAIM dual functional analysis.

    PubMed

    Sugibayashi, Yuji; Hayashi, Satoko; Nakanishi, Waro

    2015-11-21

    Dynamic and static behavior of the X-H-*-π interactions in X-H-*-π(C6H6) (X = F, Cl, Br, I, HO, MeO, H2N, MeHN and Me2N) is elucidated by QTAIM-DFA (QTAIM dual functional analysis), which we proposed recently, as the first step to clarify various types of X-H-*-π interactions. The asterisk * emphasizes the existence of the bond critical point (BCP) on the interaction in question. Total electron energy densities (H(b)(r(c))) are plotted versus H(b)(r(c)) - V(b)(r(c))/2 [=(ℏ(2)/8m)∇(2)ρ(b)(r(c))] at BCPs in QTAIM-DFA, where V(b)(r(c)) are potential energy densities at BCPs. In our treatment, data for the perturbed structures around the fully optimized ones are employed, in addition to those for the fully optimized structures. Data from the fully optimized structures are analyzed by the polar coordinate (R, θ) representation. Each plot for an interaction, containing data from the perturbed structures, shows a specific curve, which provides important information. The plot is expressed by (θ(p), κ(p)): θ(p) corresponds to the tangent line of the plot and κ(p) is the curvature. θ and θ(p) are measured from the y-axis and the y-direction, respectively. While (R, θ) correspond to the static nature, (θ(p), κ(p)) represent the dynamic nature of interactions. The nature of the X-H-*-π(C6H6) interactions is well specified by (R, θ) and (θ(p), κ(p)). All interactions, examined in this work, are classified by the pure closed shell interactions and predicted to have the van der Waals nature.

  10. Determination of 2-methoxyestradiol by chemiluminescence based on luminol-KMnO4-CdTe quantum dots system

    NASA Astrophysics Data System (ADS)

    Du, Bin; Wang, Tiantian; Han, Shuping; Cao, Xiaohui; Qu, Tiantian; Zhao, Feifei; Guo, Xinhong; Yao, Hanchun

    2015-02-01

    In this study, water-soluble CdTe quantum-dots (QDs) capped with glutathione (GSH) was synthesized. It was found that CdTe QDs could greatly enhance the chemiluminescence (CL) emission from the luminol-KMnO4 system in alkaline medium, and 4 nm CdTe QDs was used as catalysts to enhance the reaction sensitivity. The CL intensity of CdTe QDs-luminol-KMnO4 was strongly inhibited in the presence of 2-methoxyestradiol (2-ME) and the relative CL intensity was in linear correlation with the concentration of 2-ME. Based on this inhibition, a novel CL method with a lower detection limit and wider linear range was developed for the determination of 2-ME. The detection limit of plasma samples was 3.07 × 10-10 g mL-1 with a relative standard deviation of 0.24% for 8.0 × 10-9 g mL-1 2-ME. The method was successfully applied for determination of 2-ME in plasma samples. The possible CL reaction mechanism was also discussed briefly.

  11. Thermodynamic evaluation of the NaCl-MgCl 2-UCl 3-PuCl 3 system

    NASA Astrophysics Data System (ADS)

    Beneš, O.; Konings, R. J. M.

    2008-04-01

    A full thermodynamic description of the quaternary NaCl-MgCl 2-UCl 3-PuCl 3 system, a Molten Salt Fast Breeder Fuel, is presented. The binary phase diagrams have been assessed in this study and the data were used to extrapolate the higher order systems. To optimize the excess parameters of the liquid phase the modified quasi chemical model has been used, while for the solid solution the classical polynomial model has been applied. From the obtained results a possible fuel composition for the Molten Salt Reactor has been evaluated.

  12. CL-20 photodecomposition: ab initio foundations for identification of products.

    PubMed

    Kholod, Yana; Kosenkov, Dmytro; Okovytyy, Sergiy; Gorb, Leonid; Qasim, Mohammad; Leszczynski, Jerzy

    2008-11-01

    1,5-Dihydrodiimidazo[4,5-b:4'5'e]pyrazine, 1H-imidazo[4,5-b]pyrazine, and 1H-imidazole were considered as possible products of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) photodecomposition. Since we took as a reference the product obtained after CL-20 irradiation in methanol solution, the nature of intermolecular bonds between heterocycles under study and methanol molecules was analyzed in detail. Existing hydrogen bonds were found to be quite strong, so dependence of calculations results on an influence of solvent was taken into account using both the polarizable continuum model (PCM) and the supermolecular approach. Electronic spectra of 1,5-dihydrodiimidazo[4,5-b:4'5'e]pyrazine, 1H-imidazo[4,5-b]pyrazine and 1H-imidazole were simulated using time dependent density functional theory (TD-DFT) and single-excitation configuration interaction (CIS) method. We observed that TD-DFT excitation energies are lower if compared to corresponding values obtained by the CIS method. Results of calculations with PCM and the supermolecular approach are very close. It was found that differences between calculated gas phase excitation energies and those values obtained by applying solvent models increases when the number of conjugated bonds in a molecule increases. Oscillator strengths of UV bands of the considered molecules are higher in the gas phase than in modeled methanol solutions. We found that the predicted spectrum of 1H-imidazole is in close agreement with the experimental UV spectrum of the CL-20 photolysis product. PMID:18262832

  13. CL-20 photodecomposition: Ab initio foundations for identification of products

    NASA Astrophysics Data System (ADS)

    Kholod, Yana; Kosenkov, Dmytro; Okovytyy, Sergiy; Gorb, Leonid; Qasim, Mohammad; Leszczynski, Jerzy

    2008-11-01

    1,5-Dihydrodiimidazo[4,5-b:4'5'e]pyrazine, 1H-imidazo[4,5-b]pyrazine, and 1H-imidazole were considered as possible products of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) photodecomposition. Since we took as a reference the product obtained after CL-20 irradiation in methanol solution, the nature of intermolecular bonds between heterocycles under study and methanol molecules was analyzed in detail. Existing hydrogen bonds were found to be quite strong, so dependence of calculations results on an influence of solvent was taken into account using both the polarizable continuum model (PCM) and the supermolecular approach. Electronic spectra of 1,5-dihydrodiimidazo[4,5-b:4'5'e]pyrazine, 1H-imidazo[4,5-b]pyrazine and 1H-imidazole were simulated using time dependent density functional theory (TD-DFT) and single-excitation configuration interaction (CIS) method. We observed that TD-DFT excitation energies are lower if compared to corresponding values obtained by the CIS method. Results of calculations with PCM and the supermolecular approach are very close. It was found that differences between calculated gas phase excitation energies and those values obtained by applying solvent models increases when the number of conjugated bonds in a molecule increases. Oscillator strengths of UV bands of the considered molecules are higher in the gas phase than in modeled methanol solutions. We found that the predicted spectrum of 1H-imidazole is in close agreement with the experimental UV spectrum of the CL-20 photolysis product.

  14. Sulfur X-Ray Absorption And Vibrational Spectroscopic Study of Sulfur Dioxide, Sulfite, And Sulfonate Solutions And of the Substituted Sulfonate Ions X(3)CSO(3-)(X = H, Cl, F)

    SciTech Connect

    Risberg, E.Damian; Eriksson, L.; Mink, J.; Pettersson, L.G.M.; Skripkin, M.Yu.; Sandstrom, M.

    2009-06-02

    Sulfur K-edge X-ray absorption near-edge structure (XANES) spectra have been recorded and the S(1s) electron excitations evaluated by means of density functional theory-transition potential (DFT-TP) calculations to provide insight into the coordination, bonding, and electronic structure. The XANES spectra for the various species in sulfur dioxide and aqueous sodium sulfite solutions show considerable differences at different pH values in the environmentally important sulfite(IV) system. In strongly acidic (pH < {approx}1) aqueous sulfite solution the XANES spectra confirm that the hydrated sulfur dioxide molecule, SO{sub 2}(aq), dominates. The theoretical spectra are consistent with an OSO angle of {approx}119{sup o} in gas phase and acetonitrile solution, while in aqueous solution hydrogen bonding reduces the angle to {approx}116{sup o}. The hydration affects the XANES spectra also for the sulfite ion, SO{sub 3}{sup 2-}. At intermediate pH (4) the two coordination isomers, the sulfonate (HSO{sub 3{sup -}}) and hydrogen sulfite (SO{sub 3}H{sup -}) ions with the hydrogen atom coordinated to sulfur and oxygen, respectively, could be distinguished with the ratio HSO{sub 3{sup -}}:SO{sub 3}H{sup -} about 0.28:0.72 at 298 K. The relative amount of HSO{sub 3{sup -}} increased with increasing temperature in the investigated range from 275 to 343 K. XANES spectra of sulfonate, methanesulfonate, trichloromethanesulfonate, and trifluoromethanesulfonate compounds, all with closely similar S-O bond distances in tetrahedral configuration around the sulfur atom, were interpreted by DFT-TP computations. The energy of their main electronic transition from the sulfur K-shell is about 2478 eV. The additional absorption features are similar when a hydrogen atom or an electron-donating methyl group is bonded to the -SO{sub 3} group. Significant changes occur for the electronegative trichloromethyl (Cl{sub 3}C-) and trifluoromethyl (F{sub 3}C-) groups, which strongly affect the

  15. The distribution of meteoric 36Cl/Cl in the United States: A comparison of models

    USGS Publications Warehouse

    Moysey, S.; Davis, S.N.; Zreda, M.; Cecil, L.D.

    2003-01-01

    The natural distribution of 36Cl/Cl in groundwater across the continental United States has recently been reported by Davis et al. (2003). In this paper, the large-scale processes and atmospheric sources of 36Cl and chloride responsible for controlling the observed 36Cl/Cl distribution are discussed. The dominant process that affects 36Cl/Cl in meteoric groundwater at the continental scale is the fallout of stable chloride from the atmosphere, which is mainly derived from oceanic sources. Atmospheric circulation transports marine chloride to the continental interior, where distance from the coast, topography, and wind patterns define the chloride distribution. The only major deviation from this pattern is observed in northern Utah and southern Idaho where it is inferred that a continental source of chloride exists in the Bonneville Salt Flats, Utah. In contrast to previous studies, the atmospheric flux of 36Cl to the land surface was found to be approximately constant over the United States, without a strong correlation between local 36Cl fallout and annual precipitation. However, the correlation between these variables was significantly improved (R 2=0.15 to R 2=0.55) when data from the southeastern USA, which presumably have lower than average atmospheric 36Cl concentrations, were excluded. The total mean flux of 36Cl over the continental United States and total global mean flux of 36Cl are calculated to be 30.5??7.0 and 19.6??4.5 atoms m-2 s-1, respectively. The 36Cl/Cl distribution calculated by Bentley et al. (1996) underestimates the magnitude and variability observed for the measured 36Cl/Cl distribution across the continental United States. The model proposed by Hainsworth (1994) provides the best overall fit to the observed 36Cl/Cl distribution in this study. A process-oriented model by Phillips (2000) generally overestimates 36Cl/Cl in most parts of the country and has several significant local departures from the empirical data.

  16. Photoluminescence polarization of single InP quantum dots

    SciTech Connect

    Zwiller, Valery; Jarlskog, Linda; Pistol, Mats-Erik; Pryor, Craig; Castrillo, Pedro; Seifert, Werner; Samuelson, Lars

    2001-06-15

    The linear polarization dependence of photoluminescence emission was measured on single self-assembled InP quantum dots. The dots were obtained by Stranski-Krastanow growth on Ga{sub 0.5}In{sub 0.5}P. The highest-intensity emission occurred for light polarized parallel to the elongation of the dots in agreement with theoretical calculations. The excitation intensity was varied to obtain the polarization dependence of higher (state-filled) levels.

  17. Gallium arsenide-based long-wavelength quantum dot lasers

    NASA Astrophysics Data System (ADS)

    Park, Gyoungwon

    2001-09-01

    GaAs-based long-wavelength quantum dot lasers have long been studied for applications to optical interconnects. The zero-dimensional confinement potential of quantum dots opens possibility of novel devices. Also, the quantum dot itself shows very interesting characteristics. This dissertation describes the development of GaAs-based 1.3 μm quantum dot lasers and the research on the unique characteristics of quantum dot ensemble. InGaAs quantum dots grown using molecular beam epitaxy in submonolayer deposition have extended wavelength around 1.3 μm and well resolved energy levels that can be described by three-dimensional harmonic oscillator model assuming parabolic confining potential. Lasing transitions from various InGaAs quantum dot energy levels are obtained from edge-emitting lasers. With optimized quantum dot active region and device structure, continuous-wave, room-temperature lasing operation around 1.3 μm is achieved with very low threshold current. Lateral confinement of carriers and photons in the cavity with AlxO y using wet-oxidation technique results in low waveguide loss, which lowers the threshold further. InGaAs quantum dot lasers have almost temperature- insensitive lasing threshold below ~200 K with very low threshold current density close to transparency current density. The rapid increase of threshold current along with temperature above ~200 K is due to thermal excitation of carriers into the higher energy levels and increase of non-radiative recombination. Quasi- equilibrium model for carrier dynamics shows that the optical gain of quantum dot ensemble is strongly temperature dependent, and that the separation between quantum dot energy levels plays an important role in the temperature dependence of the device characteristics. Several predictions of the model are compared with the experimental results. Lasing operation with less temperature-sensitivity is achieved from InAs quantum dot lasers with increased level separation.

  18. Recent advances in carbon-based dots for electroanalysis.

    PubMed

    Yulong, Ying; Xinsheng, Peng

    2016-04-25

    Carbon-based dots represent a new type of quantum dot with unique and well-defined properties owing to their quantum confinement and edge effects, which are widely employed in sensing, light-emitting diodes, nanomedicine, photocatalysis, electrocatalysis, bioimaging, etc. In this review, we update the latest research results of carbon-based dots in this rapidly evolving field of electroanalysis, place emphases on their applications as sensors and give future perspectives for developing more smart sensors.

  19. Polarization anisotropic luminescence of tunable single lateral quantum dot molecules

    NASA Astrophysics Data System (ADS)

    Hermannstädter, C.; Witzany, M.; Heldmaier, M.; Hafenbrak, R.; Jöns, K. D.; Beirne, G. J.; Michler, P.

    2012-03-01

    We investigate the photoluminescence polarization anisotropy of self-assembled individual lateral InGaAs/GaAs quantum dot molecules. In contrast to similarly grown single quantum dots, the dot molecules exhibit a remarkable degree of linear polarization, which remains almost unchanged when a lateral electric field is applied to tune the exciton wave function and, thus, the luminescence spectral properties. We discuss the nature of this polarization anisotropy and suggest possible causes based on the system's symmetry and heterostructure alloy composition.

  20. Quantum dot blueing and blinking enables fluorescence nanoscopy.

    PubMed

    Hoyer, Patrick; Staudt, Thorsten; Engelhardt, Johann; Hell, Stefan W

    2011-01-12

    We demonstrate superresolution fluorescence imaging of cells using bioconjugated CdSe/ZnS quantum dot markers. Fluorescence blueing of quantum dot cores facilitates separation of blinking markers residing closer than the diffraction barrier. The high number of successively emitted photons enables ground state depletion microscopy followed by individual marker return with a resolving power of the size of a single dot (∼12 nm). Nanoscale imaging is feasible with a simple webcam.

  1. Aerial measurement error with a dot planimeter: Some experimental estimates

    NASA Technical Reports Server (NTRS)

    Yuill, R. S.

    1971-01-01

    A shape analysis is presented which utilizes a computer to simulate a multiplicity of dot grids mathematically. Results indicate that the number of dots placed over an area to be measured provides the entire correlation with accuracy of measurement, the indices of shape being of little significance. Equations and graphs are provided from which the average expected error, and the maximum range of error, for various numbers of dot points can be read.

  2. AAA-DDD triple hydrogen bond complexes.

    PubMed

    Blight, Barry A; Camara-Campos, Amaya; Djurdjevic, Smilja; Kaller, Martin; Leigh, David A; McMillan, Fiona M; McNab, Hamish; Slawin, Alexandra M Z

    2009-10-01

    Experiment and theory both suggest that the AAA-DDD pattern of hydrogen bond acceptors (A) and donors (D) is the arrangement of three contiguous hydrogen bonding centers that results in the strongest association between two species. Murray and Zimmerman prepared the first example of such a system (complex 3*2) and determined the lower limit of its association constant (K(a)) in CDCl(3) to be 10(5) M(-1) by (1)H NMR spectroscopy (Murray, T. J. and Zimmerman, S. C. J. Am. Chem. Soc. 1992, 114, 4010-4011). The first cationic AAA-DDD pair (3*4(+)) was described by Bell and Anslyn (Bell, D. A. and Anslyn, E. A. Tetrahedron 1995, 51, 7161-7172), with a K(a) > 5 x 10(5) M(-1) in CH(2)Cl(2) as determined by UV-vis spectroscopy. We were recently able to quantify the strength of a neutral AAA-DDD arrangement using a more chemically stable AAA-DDD system, 6*2, which has an association constant of 2 x 10(7) M(-1) in CH(2)Cl(2) (Djurdjevic, S., Leigh, D. A., McNab, H., Parsons, S., Teobaldi, G. and Zerbetto, F. J. Am. Chem. Soc. 2007, 129, 476-477). Here we report on further AA(A) and DDD partners, together with the first precise measurement of the association constant of a cationic AAA-DDD species. Complex 6*10(+)[B(3,5-(CF(3))(2)C(6)H(3))(4)(-)] has a K(a) = 3 x 10(10) M(-1) at RT in CH(2)Cl(2), by far the most strongly bound triple hydrogen bonded system measured to date. The X-ray crystal structure of 6*10(+) with a BPh(4)(-) counteranion shows a planar array of three short (NH...N distances 1.95-2.15 A), parallel (but staggered rather than strictly linear; N-H...N angles 165.4-168.8 degrees), primary hydrogen bonds. These are apparently reinforced, as theory predicts, by close electrostatic interactions (NH-*-N distances 2.78-3.29 A) between each proton and the acceptor atoms of the adjacent primary hydrogen bonds.

  3. Increasing Efficiency in Photoelectrochemical Hydrogen Production

    SciTech Connect

    Warren, S.; Turner, J.

    2002-01-01

    Photoelectrochemical hydrogen production promises to be a renewable, clean, and efficient way of storing the sun's energy for use in hydrogen-powered fuel cells. We use p-type Ga.51In.49P semiconductor (henceforth as GaInP2) to absorb solar energy and produce a photocurrent. When the semiconductor is immersed in water, the photocurrent can break down water into hydrogen and oxygen. However, before the GaInP2 can produce hydrogen and oxygen, the conduction band and the Fermi level of the semiconductor must overlap the water redox potentials. In an unmodified system, the conduction band and Fermi level of GaInP2 do not overlap the water redox potentials. When light shines on the semiconductor, electrons build up on the surface, shifting the bandedges and Fermi level further away from overlap of the water redox potentials. We report on surface treatments with metallated porphyrins and transition metals that suppress bandedge migration and allow bandedge overlap to occur. Coating ruthenium octaethylporphyrin carbonyl (RuOEP CO) on the GaInP2 surface shifted bandedges in the positive direction by 270 mV on average, allowing the bandedges to frequently overlap the water redox potentials. Coating the GaInP2 surface with RuCl3 catalyzed charge transfer from the semiconductor to the water, lessening bandedge migration under light irradiation. Future work will focus on the long-term surface stability of these new treatments and quantitative applications of porphyrins.

  4. On the nature of blueshifting hydrogen bonds.

    PubMed

    Mo, Yirong; Wang, Changwei; Guan, Liangyu; Braïda, Benoît; Hiberty, Philippe C; Wu, Wei

    2014-07-01

    The block-localized wave function (BLW) method can derive the energetic, geometrical, and spectral changes with the deactivation of electron delocalization, and thus provide a unique way to elucidate the origin of improper, blueshifting hydrogen bonds versus proper, redshifting hydrogen bonds. A detailed analysis of the interactions of F(3)CH with NH(3) and OH(2) shows that blueshifting is a long-range phenomenon. Since among the various energy components contributing to hydrogen bonds, only the electrostatic interaction has long-range characteristics, we conclude that the contraction and blueshifting of a hydrogen bond is largely caused by electrostatic interactions. On the other hand, lengthening and redshifting is primarily due to the short-range n(Y)→σ*(X-H) hyperconjugation. The competition between these two opposing factors determines the final frequency change direction, for example, redshifting in F(3)CH⋅⋅⋅NH(3) and blueshifting in F(3)CH⋅⋅⋅OH(2). This mechanism works well in the series F(n)Cl(3)-n CH⋅⋅⋅Y (n=0-3, Y=NH(3), OH(2), SH(2)) and other systems. One exception is the complex of water and benzene. We observe the lengthening and redshifting of the O-H bond of water even with the electron transfer between benzene and water completely quenched. A distance-dependent analysis for this system reveals that the long-range electrostatic interaction is again responsible for the initial lengthening and redshifting.

  5. A novel LiCl-BaCl2:Eu2+ eutectic scintillator for thermal neutron detection

    NASA Astrophysics Data System (ADS)

    Wu, Yuntao; Lukosi, Eric D.; Zhuravleva, Mariya; Lindsey, Adam C.; Melcher, Charles L.

    2015-10-01

    A natLiCl-BaCl2:Eu2+ eutectic scintillator was synthesized by the vertical Bridgman method aiming at the application of thermal neutron detection. The molar ratio of LiCl and BaCl2 was 75.1/24.9, which corresponds to the eutectic composition in the LiCl-BaCl2 system. The grown eutectic showed a periodic microstructure of BaCl2:Eu2+ and LiCl phases with 2-3 μm thickness. The α-particle induced radioluminescence spectrum of the scintillator showed an intense emission peak at 406 nm due to the Eu2+ 5d1→4f emission from the BaCl2:Eu2+ phase and an additional weak emission peak at 526 nm. The scintillation decay time was 412 ns. LiCl-BaCl2:Eu2+ eutectic samples exhibited non-correlated neutron detection efficiency and light yield as a function of crystal length, suggesting material non-uniformities within the boule. The relative light yield was equal to or greater than that of Nucsafe lithium glass. Gamma-ray exposures indicate that gamma/neutron threshold discrimination for higher energy gamma-rays will be limited.

  6. Analysis of hydrogen isotope mixtures

    DOEpatents

    Villa-Aleman, Eliel

    1994-01-01

    An apparatus and method for determining the concentrations of hydrogen isotopes in a sample. Hydrogen in the sample is separated from other elements using a filter selectively permeable to hydrogen. Then the hydrogen is condensed onto a cold finger or cryopump. The cold finger is rotated as pulsed laser energy vaporizes a portion of the condensed hydrogen, forming a packet of molecular hydrogen. The desorbed hydrogen is ionized and admitted into a mass spectrometer for analysis.

  7. Unbound states of (32)Cl andthe (31)S(p,gamma)(32)Cl reaction rate

    SciTech Connect

    Matos, M.; Blackmon, Jeff C; Linhardt, Laura; Bardayan, Daniel W; Nesaraja, Caroline D; Clark, Jason; Diebel, C.; O'Malley, Patrick; Parker, P.D.

    2011-01-01

    The {sup 31}S(p,{gamma}){sup 32}Cl reaction is expected to provide the dominant break-out path from the SiP cycle in novae and is important for understanding enrichments of sulfur observed in some nova ejecta. We studied the {sup 32}S(3He,t){sup 32}Cl charge-exchange reaction to determine properties of proton-unbound levels in {sup 32}Cl that have previously contributed significant uncertainties to the {sup 31}S(p,{gamma}){sup 32}Cl reaction rate. Measured triton magnetic rigidities were used to determine excitation energies in {sup 32}Cl. Proton-branching ratios were obtained by detecting decay protons from unbound {sup 32}Cl states in coincidence with tritons. An improved {sup 31}S(p,{gamma}){sup 32}Cl reaction rate was calculated including robust statistical and systematic uncertainties.

  8. Porous palladium coated conducting polymer nanoparticles for ultrasensitive hydrogen sensors

    NASA Astrophysics Data System (ADS)

    Lee, Jun Seop; Kim, Sung Gun; Cho, Sunghun; Jang, Jyongsik

    2015-12-01

    Hydrogen, a clean-burning fuel, is of key importance to various industrial applications, including fuel cells and in the aerospace and automotive industries. However, hydrogen gas is odorless, colorless, and highly flammable; thus appropriate safety protocol implementation and monitoring are essential. Highly sensitive hydrogen leak detection and surveillance sensor systems are needed; additionally, the ability to maintain uniformity through repetitive hydrogen sensing is becoming increasingly important. In this report, we detail the fabrication of porous palladium coated conducting polymer (3-carboxylate polypyrrole) nanoparticles (Pd@CPPys) to detect hydrogen gas. The Pd@CPPys are produced by means of facile alkyl functionalization and chemical reduction of a pristine 3-carboxylate polypyrrole nanoparticle-contained palladium precursor (PdCl2) solution. The resulting Pd@CPPy-based sensor electrode exhibits ultrahigh sensitivity (0.1 ppm) and stability toward hydrogen gas at room temperature due to the palladium sensing layer.Hydrogen, a clean-burning fuel, is of key importance to various industrial applications, including fuel cells and in the aerospace and automotive industries. However, hydrogen gas is odorless, colorless, and highly flammable; thus appropriate safety protocol implementation and monitoring are essential. Highly sensitive hydrogen leak detection and surveillance sensor systems are needed; additionally, the ability to maintain uniformity through repetitive hydrogen sensing is becoming increasingly important. In this report, we detail the fabrication of porous palladium coated conducting polymer (3-carboxylate polypyrrole) nanoparticles (Pd@CPPys) to detect hydrogen gas. The Pd@CPPys are produced by means of facile alkyl functionalization and chemical reduction of a pristine 3-carboxylate polypyrrole nanoparticle-contained palladium precursor (PdCl2) solution. The resulting Pd@CPPy-based sensor electrode exhibits ultrahigh sensitivity (0.1 ppm

  9. A composite of borohydride and super absorbent polymer for hydrogen generation

    NASA Astrophysics Data System (ADS)

    Li, Z. P.; Liu, B. H.; Liu, F. F.; Xu, D.

    To develop a hydrogen source for underwater applications, a composite of sodium borohydride and super absorbent polymer (SAP) is prepared by ball milling sodium borohydride powder with SAP powder, and by dehydrating an alkaline borohydride gel. When sodium polyacrylate (NaPAA) is used as the SAP, the resulting composite exhibits a high rate of borohydride hydrolysis for hydrogen generation. A mechanism of hydrogen evolution from the NaBH 4-NaPAA composite is suggested based on structure analysis by X-ray diffraction and scanning electron microscopy. The effects of water and NiCl 2 content in the precursor solution on the hydrogen evolution behavior are investigated and discussed.

  10. Realizing Rec. 2020 color gamut with quantum dot displays.

    PubMed

    Zhu, Ruidong; Luo, Zhenyue; Chen, Haiwei; Dong, Yajie; Wu, Shin-Tson

    2015-09-01

    We analyze how to realize Rec. 2020 wide color gamut with quantum dots. For photoluminescence, our simulation indicates that we are able to achieve over 97% of the Rec. 2020 standard with quantum dots by optimizing the emission spectra and redesigning the color filters. For electroluminescence, by optimizing the emission spectra of quantum dots is adequate to render over 97% of the Rec. 2020 standard. We also analyze the efficiency and angular performance of these devices, and then compare results with LCDs using green and red phosphors-based LED backlight. Our results indicate that quantum dot display is an outstanding candidate for achieving wide color gamut and high optical efficiency.

  11. Power-law photoluminescence decay in quantum dots

    SciTech Connect

    Král, Karel; Menšík, Miroslav

    2014-05-15

    Some quantum dot samples show a long-time (power-law) behavior of their luminescence intensity decay. This effect has been recently explained as being due to a cooperation of many tunneling channels transferring electrons from small quantum dots with triplet exciton to quantum dots at which the electrons can recombine with the holes in the valence band states. In this work we show that the long-time character of the sample luminescence decay can also be caused by an intrinsic property of a single dot, namely, by a non-adiabatic effect of the electron occupation up-conversion caused by the electron-phonon multiple scattering mechanism.

  12. Imaging ligand-gated ion channels with quantum dots

    NASA Astrophysics Data System (ADS)

    Tomlinson, I. D.; Orndorff, Rebecca L.; Gussin, Hélène; Mason, John N.; Blakely, Randy D.; Pepperberg, David R.; Rosenthal, Sandra J.

    2007-02-01

    In this paper we report two different methodologies for labeling ligand-gated receptors. The first of these builds upon our earlier work with serotonin conjugated quantum dots and our studies with pegilated quantum dots to reduce non specific binding. In this approach a pegilated derivative of muscimol was synthesized and attached via an amide linkage to quantum dots coated in an amphiphillic polymer derivative of poly acrylamide. These conjugates were used to image the GABA C receptor in oocytes. An alternative approach was used to image tissue sections to study nicotinic acetylcholine receptors in the neuro muscular junction with biotinylated Bungerotoxin and streptavidin coated quantum dots.

  13. Silver-enhanced fluorescence emission of single quantum dot nanocomposites.

    PubMed

    Fu, Yi; Zhang, Jian; Lakowicz, Joseph R

    2009-01-21

    A novel plasmon-coupled quantum dot (QD) nanocomposite via covalently interfacing the QD surfaces with silver nanoparticles was developed with greatly reduced blinking and enhanced emission fluorescence.

  14. Terahertz transmission through rings of quantum dots-nanogap

    NASA Astrophysics Data System (ADS)

    Tripathi, Laxmi-Narayan; Bahk, Young-Mi; Choi, Geunchang; Han, Sanghoon; Park, Namkyoo; Kim, Dai-Sik

    2016-03-01

    We report resonant funneling of terahertz (THz) waves through (9 ± 1) nm wide quantum dots-nanogap of cadmium selenide quantum dots silver nanogap metamaterials. We observed a giant THz intensity enhancement (∼104) through the quantum dots-nanogap at the resonant frequency. We, further report the experimentally measured effective mode indices for these metamaterials. A finite difference time domain simulation of the nanogap enabled by the quantum dots supports the experimentally measured THz intensity enhancement across the nanogap. We propose that these low effective mode index terahertz resonators will be useful as bio/chemical sensors, gain-enhanced antennas, and wave guides.

  15. Non-Markovian full counting statistics in quantum dot molecules.

    PubMed

    Xue, Hai-Bin; Jiao, Hu-Jun; Liang, Jiu-Qing; Liu, Wu-Ming

    2015-03-10

    Full counting statistics of electron transport is a powerful diagnostic tool for probing the nature of quantum transport beyond what is obtainable from the average current or conductance measurement alone. In particular, the non-Markovian dynamics of quantum dot molecule plays an important role in the nonequilibrium electron tunneling processes. It is thus necessary to understand the non-Markovian full counting statistics in a quantum dot molecule. Here we study the non-Markovian full counting statistics in two typical quantum dot molecules, namely, serially coupled and side-coupled double quantum dots with high quantum coherence in a certain parameter regime. We demonstrate that the non-Markovian effect manifests itself through the quantum coherence of the quantum dot molecule system, and has a significant impact on the full counting statistics in the high quantum-coherent quantum dot molecule system, which depends on the coupling of the quantum dot molecule system with the source and drain electrodes. The results indicated that the influence of the non-Markovian effect on the full counting statistics of electron transport, which should be considered in a high quantum-coherent quantum dot molecule system, can provide a better understanding of electron transport through quantum dot molecules.

  16. Reconfigurable quadruple quantum dots in a silicon nanowire transistor

    NASA Astrophysics Data System (ADS)

    Betz, A. C.; Tagliaferri, M. L. V.; Vinet, M.; Broström, M.; Sanquer, M.; Ferguson, A. J.; Gonzalez-Zalba, M. F.

    2016-05-01

    We present a reconfigurable metal-oxide-semiconductor multi-gate transistor that can host a quadruple quantum dot in silicon. The device consists of an industrial quadruple-gate silicon nanowire field-effect transistor. Exploiting the corner effect, we study the versatility of the structure in the single quantum dot and the serial double quantum dot regimes and extract the relevant capacitance parameters. We address the fabrication variability of the quadruple-gate approach which, paired with improved silicon fabrication techniques, makes the corner state quantum dot approach a promising candidate for a scalable quantum information architecture.

  17. Terahertz hot electron bolometric detectors based on graphene quantum dots

    NASA Astrophysics Data System (ADS)

    El Fatimy, A.; Myers-Ward, R. L.; Boyd, A. K.; Daniels, K. M.; Gaskill, D. K.; Barbara, P.

    2015-03-01

    We study graphene quantum dots patterned from epitaxial graphene on SiC with a resistance strongly dependent on temperature. The combination of weak electron-phonon coupling and small electronic heat capacity in graphene makes these quantum dots ideal hot-electron bolometers. We measure and characterize the THz optical response of devices with different dot sizes, at operating temperatures from 2.5K to 80K. The high responsivity, the potential for operation above 80 K and the process scalability show great promise towards practical applications of graphene quantum dot THz detectors. This work was sponsored by the U.S. Office of Naval Research (Award Number N000141310865).

  18. Polarized quantum dot emission in electrohydrodynamic jet printed photonic crystals

    SciTech Connect

    See, Gloria G.; Xu, Lu; Nuzzo, Ralph G.; Sutanto, Erick; Alleyne, Andrew G.; Cunningham, Brian T.

    2015-08-03

    Tailored optical output, such as color purity and efficient optical intensity, are critical considerations for displays, particularly in mobile applications. To this end, we demonstrate a replica molded photonic crystal structure with embedded quantum dots. Electrohydrodynamic jet printing is used to control the position of the quantum dots within the device structure. This results in significantly less waste of the quantum dot material than application through drop-casting or spin coating. In addition, the targeted placement of the quantum dots minimizes any emission outside of the resonant enhancement field, which enables an 8× output enhancement and highly polarized emission from the photonic crystal structure.

  19. Emission switching in carbon dots coated CdTe quantum dots driving by pH dependent hetero-interactions

    SciTech Connect

    Dai, Xiao; Wang, Hao; Yi, Qinghua; Wang, Yun; Cong, Shan; Zhao, Jie; Sun, Yinghui; Zou, Guifu E-mail: jiexiong@uestc.edu.cn; Qian, Zhicheng; Huang, Jianwen; Xiong, Jie E-mail: jiexiong@uestc.edu.cn; Luo, Hongmei

    2015-11-16

    Due to the different emission mechanism between fluorescent carbon dots and semiconductor quantum dots (QDs), it is of interest to explore the potential emission in hetero-structured carbon dots/semiconducting QDs. Herein, we design carbon dots coated CdTe QDs (CDQDs) and investigate their inherent emission. We demonstrate switchable emission for the hetero-interactions of the CDQDs. Optical analyses indicate electron transfer between the carbon dots and the CdTe QDs. A heterojunction electron process is proposed as the driving mechanism based on N atom protonation of the carbon dots. This work advances our understanding of the interaction mechanism of the heterostructured CDQDs and benefits the future development of optoelectronic nanodevices with new functionalities.

  20. Hydrogen powered bus

    ScienceCinema

    None

    2016-07-12

    Take a ride on a new type of bus, fueled by hydrogen. These hydrogen taxis are part of a Department of Energy-funded deployment of hydrogen powered vehicles and fueling infrastructure at nine federal facilities across the country to demonstrate this market-ready advanced technology. Produced and leased by Ford Motor Company , they consist of one 12- passenger bus and one nine-passenger bus. More information at: http://go.usa.gov/Tgr