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Sample records for centre dot 6h

  1. Ferroelectric phase transition in hydrogen-bonded 2-aminopyridine phosphate (NC sub 4 H sub 4 NH sub 2)centre dot H sub 3 PO sub 4

    CERN Document Server

    Czapla, Z; Waskowska, A

    2003-01-01

    A new crystal of 2-aminopyridine phosphate (NC sub 4 H sub 4 NH sub 2)centre dot H sub 3 PO sub 4 has been grown and its x-ray structure and physical properties were studied. At room temperature the crystals are monoclinic, space group C2/c. The flat 2-aminopyridine cations are hydrogen bonded to the anionic [PO sub 4 ] groups. The interesting feature of the crystal structure is the three-dimensional network of hydrogen bonds including, among others, two strong, symmetrical O centre dot centre dot centre dot H, H centre dot centre dot centre dot O interactions with disordered proton locations. Symmetrically related PO sub 4 anions linked through these protons form infinite (PO sub 4) subinfinity chains along the crystal a-axis. The anomalies in the temperature dependence of the electric permittivity showed that the crystal undergoes ferroelectric phase transition at T sub c = 103.5 K. The spontaneous polarization takes place along the crystal a-axis, being parallel to the chains of the hydrogen-bonded PO sub ...

  2. Incommensurate phases in the improper ferroelastic MgGeF sub 6 centre dot 6H sub 2 O:Mn sup 2 sup + studied by means of EPR

    CERN Document Server

    Skrylnik, P G

    2002-01-01

    The results of an EPR study of the inhomogeneous phases existing in the temperature interval T sub C = 311.0 +- 0.3 K < T < T sub i sub 1 = 403 +- 0.3 K in improper ferroelastic crystals of MgGeF sub 6 centre dot 6H sub 2 O:Mn sup 2 sup + are presented. On the basis of the analysis of the temperature and angle dependences of the experimental parameters and numerical calculations, the conclusion has been drawn that at T sub i sub 1 the crystals considered undergo a transition to a structurally modulated phase and the order parameter of this transition may be the angle of the Mg[H sub 2 O] sub 6 sup 2 sup + octahedra rotation around the crystal C sub 3 -axis. From T sub i sub 1 to T sub C the modes of the modulated phase follow according to a completely classical scenario for incommensurate crystals: the origin of the incommensurate structure with plane-wave modulation at T sub i sub 1 , the appearance of structural phase solitons below T sub i sub 2 = 380 +- 0.3 K and decrease of the soliton density to v...

  3. NMR investigation on isotope effect of glycinium phosphite H sub 3 NCH sub 2 COOH centre dot H sub 2 PO sub 3

    CERN Document Server

    Ishibashi, T

    2003-01-01

    The motions of the phosphite anions and glycinium cations in H sub 3 NCH sub 2 COOH centre dot H sub 2 PO sub 3 (GPI) and its deuterated analogue (DGPI) were investigated by sup 1 H, sup 1 sup 3 C and sup 3 sup 1 P spin-lattice relaxation times T sub 1. For both GPI and DGPI, T sub 1 's of the sup 1 H, sup 1 sup 3 C and sup 3 sup 1 P nuclei reflect the amino rotation, methylene libration and motion of the phosphite anions, respectively. Activation energies obtained from T sub 1 's of sup 1 H, sup 1 sup 3 C and sup 3 sup 1 P nuclei are 28.6(2), 26.0(4) and 26.2(4) kJ/mol for GPI and are 34.9(6), 27(1), 47(2) kJ/mol for DGPI, respectively. The deuterium substitution increases E sub a for the motion influenced by the hydrogen bonding. In all the observed motions, correlation times of DGPI are larger than those of GPI. (author)

  4. A study of the x-irradiated Cs sub 5 H sub 3 (SO sub 4) sub 4 centre dot H sub 2 O crystal by EPR in the 80-415 K temperature range

    CERN Document Server

    Waplak, S; Baranov, A I; Shuvalov, L A

    1997-01-01

    The EPR spectra of the x-irradiated fast proton conductor Cs sub 5 H sub 3 (SO sub 4) sub 4 centre dot H sub 2 O were investigated in the temperature range of 80-415 K. Two kinds of paramagnetic SO sub 4 sup - centres with different proton configurations below about 370 K and freeze-out behaviour of one of them below about 200 K were observed. The role of acid proton dynamics with respect to the glassy-like transition is discussed. (author)

  5. Inversion of spin levels in Ni sup 2 sup + : Zn(BF sub 4) sub 2 centre dot 6H sub 2 O at all -round compression and effect of transition coincidence

    CERN Document Server

    Krygin, I M; Nejlo, G N; Prokhorov, A D

    2001-01-01

    The study of the EPR spectrum of the Ni sup 2 sup + ion, replacing Zn sup 2 sup + in the Zn(BF sub 4) centre dot 6H sub 2 O crystals in the wide temperature range by the all-round compression in the X- and Q-ranges is carried out. The basic changes by varying temperature and pressure occur with the D parameter, characterizing the initial splitting by practically unchanged g-factor. The increase in the temperature is accompanied by the D nonlinear growth. The all-round compression linearly changes the initial splitting and leads to the change in the D-sign, signifying the spin levels inversion by 3.5 kbar. Coincidence of EPR lines, relative to different transitions, leads to the crevasse appearance in the outline of this one, that is connected with cross-relaxation inside the spin system

  6. Theoretical investigation of molecular hydrogen reactions with active centres in B6H5- and AlB6H5- clusters

    International Nuclear Information System (INIS)

    Mebel', A.M.; Charkin, O.P.

    1991-01-01

    Nonempirical calculations of sections of potential surface (PS) along the shortest way of reaction of hydrogen interaction with different active centres in AlB 5 H 5 - cluster were conducted. Mechanisms of reactions of valent-saturated hydrides (BH, AlH) and clusters (B 6 H 5 - , AlB 5 H 5 - ) with molecular hydrogen are correlated. Qualitative model enabling to form an opinion about the presence or the absence of barrier on PS of the shortest way of reactions of breaking σ-bond of H-H type on the active centre of cluster, is suggested. The model is based on analysis of the character of canonical MO reagents and products

  7. Ferroelectric TGS ((NH sub 2 CH sub 2 COOH) sub 3 centre dot H sub 2 SO sub 4) under high pressure

    CERN Document Server

    Kobayashi, Y; Furuta, H; Endo, S; Deguchi, K

    2002-01-01

    The ferroelectric transition temperature T sub c of (NH sub 2 CH sub 2 COOH) sub 3 centre dot H sub 2 SO sub 4 (TGS), which is a typical order-disorder-type ferroelectric, was determined by dielectric constant and Raman scattering measurements under high pressure. T sub c increased, passed through a maximum and then decreased slightly with increasing pressure, and then abruptly dropped at about 2.5 GPa, where a transition to a new high-pressure phase was confirmed to exist. A tentative p-T phase diagram was proposed for TGS.

  8. Flat-topped emission centred at 1 250 nm from quantum dot superluminescent diodes

    Directory of Open Access Journals (Sweden)

    R.A. Hogg

    2010-01-01

    Full Text Available We present a method for tailoring a broadband and flat-topped emission spectrum in quantum dot superluminescent diodes based upon modification of the dots-in-compositionally-modulated-well (DCMWELL technique. We demonstrate flat-topped emission with 95 nm full width at half maximum (FWHM, centred at 1 250 nm, and with output power in excess of 8 mW.

  9. Origin of the ESR spectrum in the Prussian blue analog RbMn[Fe(CN)(6)]center dot H2O

    NARCIS (Netherlands)

    Antal, A.; Janossy, A.; Forro, L.; Vertelman, E. J. M.; van Koningsbruggen, P. J.; van Loosdrecht, P. H. M.

    2010-01-01

    We present an electron spin resonance (ESR) study at excitation frequencies of 9.4 and 222.4 GHz of powders and single crystals of a Prussian blue analog (PBA), RbMn[Fe(CN)(6)]center dot H2O in which Fe and Mn undergoes a charge-transfer transition between 175 and 300 K. The ESR of PBA powders, also

  10. Optical properties of pH-sensitive carbon-dots with different modifications

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Weiguang, E-mail: 11236095@zju.edu.cn [Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Wu, Huizhen, E-mail: hzwu@zju.edu.cn [Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Ye, Zhenyu, E-mail: yzheny@zju.edu.cn [Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Li, Ruifeng, E-mail: hbrook@zju.edu.cn [Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Xu, Tianning, E-mail: xtn9886@zju.edu.cn [Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Department of Science, Zhijiang College of Zhejiang University of Technology, Hangzhou, Zhejiang 310024 (China); Zhang, Bingpo, E-mail: 11006080@zju.edu.cn [Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang 310027 (China)

    2014-04-15

    Carbon dots with unique characters of chemical inertness, low cytotoxicity and good biocompatibility, demonstrate important applications in biology and optoelectronics. In this paper we report the optical properties of pH-sensitive carbon dots with different surface modifications. The as-prepared carbon dots can be well dispersed in water by modifying with acid, alkali or metal ions though they tend to form a suspension when being directly dispersed in water. We find that the carbon dots dispersed in water show a new emission and absorption character which is tunable due to the pH-sensitive nature. It is firstly proved that the addition of bivalent copper ions offers a high color contrast for visual colorimetric assays for pH measurement. The effect of surface defects with different modification on the performances of the carbon dots is also explored with a core–shell model. The hydro-dispersed carbon dots can be potentially utilized for cellular imaging or metal ion probes in biochemistry. -- Highlights: • The dispersibility in water of as-prepared carbon dots is effectively improved by the addition of acid, alkali or metal ions. • The effect of hydrolysis on the optical properties of the carbon dots is studied. • The luminescent carbon dots show a pH-sensitive fluorescence and absorption property. • The addition of bivalent copper ions in the post-treated carbon dots offers a high color contrast for visual colorimetric assays for pH measurement. • The effect of surface defects and ligands on the performances of the carbon dots is also explored.

  11. Structure-guided mutational analysis reveals the functional requirements for product specificity of DOT1 enzymes.

    Science.gov (United States)

    Dindar, Gülcin; Anger, Andreas M; Mehlhorn, Christine; Hake, Sandra B; Janzen, Christian J

    2014-11-12

    DOT1 enzymes are conserved methyltransferases that catalyse the methylation of lysine 79 on histone H3 (H3K79). Most eukaryotes contain one DOT1 enzyme, whereas African trypanosomes have two homologues, DOT1A and DOT1B, with different enzymatic activities. DOT1A mediates mono- and dimethylation of H3K76, the homologue of H3K79 in other organisms, whereas DOT1B additionally catalyses H3K76 trimethylation. However, it is unclear how these different enzymatic activities are achieved. Here we employ a trypanosomal nucleosome reconstitution system and structure-guided homology modelling to identify critical residues within and outside the catalytic centre that modulate product specificity. Exchange of these residues transfers the product specificity from one enzyme to the other, and reveals the existence of distinct regulatory domains adjacent to the catalytic centre. Our study provides the first evidence that a few crucial residues in DOT1 enzymes are sufficient to catalyse methyl-state-specific reactions. These results might also have far-reaching consequences for the functional understanding of homologous enzymes in higher eukaryotes.

  12. Label-Free Carbon-Dots-Based Ratiometric Fluorescence pH Nanoprobes for Intracellular pH Sensing.

    Science.gov (United States)

    Shangguan, Jingfang; He, Dinggeng; He, Xiaoxiao; Wang, Kemin; Xu, Fengzhou; Liu, Jinquan; Tang, Jinlu; Yang, Xue; Huang, Jin

    2016-08-02

    Measuring pH in living cells is of great importance for better understanding cellular functions as well as providing pivotal assistance for early diagnosis of diseases. In this work, we report the first use of a novel kind of label-free carbon dots for intracellular ratiometric fluorescence pH sensing. By simple one-pot hydrothermal treatment of citric acid and basic fuchsin, the carbon dots showing dual emission bands at 475 and 545 nm under single-wavelength excitation were synthesized. It is demonstrated that the fluorescence intensities of the as-synthesized carbon dots at the two emissions are pH-sensitive simultaneously. The intensity ratio (I475 nm/I545 nm) is linear against pH values from 5.2 to 8.8 in buffer solution, affording the capability as ratiometric probes for intracellular pH sensing. It also displays that the carbon dots show excellent reversibility and photostability in pH measurements. With this nanoprobe, quantitative fluorescence imaging using the ratio of two emissions (I475 nm/I545 nm) for the detection of intracellular pH were successfully applied in HeLa cells. In contrast to most of the reported nanomaterials-based ratiometric pH sensors which rely on the attachment of additional dyes, these carbon-dots-based ratiometric probes are low in toxicity, easy to synthesize, and free from labels.

  13. Effect of different uranium compounds on the properties of U-Pt-Y-Ba-O double-perovskite pinning centres in textured Y-Ba-Cu-O superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Sawh, Ravi-Persad; Weinstein, Roy; Parks, Drew; Gandini, Alberto [Beam Particle Dynamics Laboratories, University of Houston, Houston, TX 77204-5005 (United States); Department of Physics, University of Houston, Houston, TX 77204-5005 (United States); Texas Center for Superconductivity and Advanced Materials, University of Houston, Houston, TX 77204-5005 (United States)

    2005-02-01

    An experiment was performed to test the effect of different uranium compounds on the properties of chemical pinning centres. UO{sub 2}, UO{sub 3}, and UO{sub 4}{center_dot}2H{sub 2}O wereadmixed to Y 123+Pt, and textured. Tests of J{sub c} via measurements of trapped field (B{sub trap}) indicate a clear dependence of B{sub trap} on the U compound admixed to create the pinning centres. In all three cases there is a monotonic increase in B{sub trap} as the mass (M{sub U}) of U is increased. However, the magnitude of the increase in B{sub trap} depends on the admixed U compound. The highest increase in B{sub trap} is measured in samples doped with UO{sub 4}{center_dot}2H{sub 2}O, and the lowest is obtained in samples doped with UO{sub 2}. Microstructure studies indicate that the composition of the U-rich pinning deposits is the same in all three cases, i.e. all are the previously identified (U{sub 0.6}Pt{sub 0.4})Y Ba{sub 2}O{sub 6} compound. The primary difference among the three types of samples is that the size of the U-Pt-Y-Ba-O pinning deposits depends on the admixed U compound. While all are in the nanometre domain, the diameter of these deposits was markedly larger in UO{sub 2} doped samples than in UO{sub 3} doped samples, and smallest in UO{sub 4}{center_dot}2H{sub 2}O doped samples. Because some form of poisoning limits the amount of U that can be added to create pinning centres, to M{sub U} {approx}1 wt%, smaller deposits result in a greater number of pinning centres. We conclude that UO{sub 4}{center_dot}2H{sub 2}O is more effective than either UO{sub 3} or UO{sub 2} in the formation of U-Pt-Y-Ba-O pinning centres because of diminished pinning centre size, and consequent increase in pinning centre density.

  14. Ionophore-based optical nanosensors incorporating hydrophobic carbon dots and a pH-sensitive quencher dye for sodium detection.

    Science.gov (United States)

    Galyean, A A; Behr, M R; Cash, K J

    2018-01-21

    Nanosensors present a biological monitoring method that is biocompatible, reversible, and nano-scale, and they offer many advantages over traditional organic indicators. Typical ionophore-based nanosensors incorporate nile-blue derivative pH indicators but suffer from photobleaching while quantum dot alternatives pose a potential toxicity risk. In order to address this challenge, sodium selective nanosensors containing carbon dots and a pH-sensitive quencher molecule were developed based on an ion-exchange theory and a decoupled recognition element from the pH indicator. Carbon dots were synthesized and integrated into nanosensors containing a pH-indicator, an analyte-binding ligand (ionophore), and a charge-balancing additive. These nanosensors are ion-selective against potassium (selectivity coefficient of 0.4) and lithium (selectivity coefficient of 0.9). Reversible nanosensor response to sodium is also demonstrated. The carbon dot nanosensors are resistant to changes in optical properties for at least 12 h and display stable selectivity to physiologically-relevant sodium (alpha = 0.5 of 200 mM NaCl) for a minimum of 6 days.

  15. ESR investigation of the reactions of glutathione, cysteine and penicillamine thiyl radicals: competitive formation of RSOcenter dot, Rcenter dot, RSSRcenter dot-. , and RSScenter dot

    Energy Technology Data Exchange (ETDEWEB)

    Becker, David; Swarts, Steven; Champagne, Mark; Sevilla, M D

    1988-05-01

    The reactions of cysteine, glutathione and penicillamine thiyl radicals with oxygen and their parent thiols in frozen solutions have been elucidated with e.s.r. The major sulfur radicals observed are: (1) thiyl radicals, RS center dot; (2) disulfide radical anions, RSSR anion radicals; (3) perthiyl radicals, RSS center dot and upon introduction of oxygen; (4) sulfinyl radicals, RSO center dot, where R represents the remainder of the cysteine, glutathione or penicillamine moiety. The radical product observed depends on pH, concentration of thiol, and presence or absence of molecular oxygen. The sulfinyl radical is a ubiquitous intermediate, peroxyl radical attack on thiols may lead to sulfinyl radicals. The authors elaborate the observed reaction sequences that lead to sulfinyl radicals and, using /sup 17/O isotopic substitution studies, demonstrate the oxygen atom in sulfinyl radicals originates from dissolved molecular oxygen. The glutathione radical is found to abstract hydrogen from the ..cap alpha..-carbon position on the cysteine residue of glutathione to form a carbon-centred radical.

  16. DOT1L and H3K79 Methylation in Transcription and Genomic Stability.

    Science.gov (United States)

    Wood, Katherine; Tellier, Michael; Murphy, Shona

    2018-02-27

    The organization of eukaryotic genomes into chromatin provides challenges for the cell to accomplish basic cellular functions, such as transcription, DNA replication and repair of DNA damage. Accordingly, a range of proteins modify and/or read chromatin states to regulate access to chromosomal DNA. Yeast Dot1 and the mammalian homologue DOT1L are methyltransferases that can add up to three methyl groups to histone H3 lysine 79 (H3K79). H3K79 methylation is implicated in several processes, including transcription elongation by RNA polymerase II, the DNA damage response and cell cycle checkpoint activation. DOT1L is also an important drug target for treatment of mixed lineage leukemia (MLL)-rearranged leukemia where aberrant transcriptional activation is promoted by DOT1L mislocalisation. This review summarizes what is currently known about the role of Dot1/DOT1L and H3K79 methylation in transcription and genomic stability.

  17. DOT1L and H3K79 Methylation in Transcription and Genomic Stability

    Directory of Open Access Journals (Sweden)

    Katherine Wood

    2018-02-01

    Full Text Available The organization of eukaryotic genomes into chromatin provides challenges for the cell to accomplish basic cellular functions, such as transcription, DNA replication and repair of DNA damage. Accordingly, a range of proteins modify and/or read chromatin states to regulate access to chromosomal DNA. Yeast Dot1 and the mammalian homologue DOT1L are methyltransferases that can add up to three methyl groups to histone H3 lysine 79 (H3K79. H3K79 methylation is implicated in several processes, including transcription elongation by RNA polymerase II, the DNA damage response and cell cycle checkpoint activation. DOT1L is also an important drug target for treatment of mixed lineage leukemia (MLL-rearranged leukemia where aberrant transcriptional activation is promoted by DOT1L mislocalisation. This review summarizes what is currently known about the role of Dot1/DOT1L and H3K79 methylation in transcription and genomic stability.

  18. Quadra-quantum Dots and Related Patterns of Quantum Dot Molecules:

    Directory of Open Access Journals (Sweden)

    Somsak Panyakeow

    2010-10-01

    Full Text Available Abstract Laterally close-packed quantum dots (QDs called quantum dot molecules (QDMs are grown by modified molecular beam epitaxy (MBE. Quantum dots could be aligned and cross hatched. Quantum rings (QRs created from quantum dot transformation during thin or partial capping are used as templates for the formations of bi-quantum dot molecules (Bi-QDMs and quantum dot rings (QDRs. Preferable quantum dot nanostructure for quantum computation based on quantum dot cellular automata (QCA is laterally close-packed quantum dot molecules having four quantum dots at the corners of square configuration. These four quantum dot sets are called quadra-quantum dots (QQDs. Aligned quadra-quantum dots with two electron confinements work like a wire for digital information transmission by Coulomb repulsion force, which is fast and consumes little power. Combination of quadra-quantum dots in line and their cross-over works as logic gates and memory bits. Molecular Beam Epitaxial growth technique called ‘‘Droplet Epitaxy” has been developed for several quantum nanostructures such as quantum rings and quantum dot rings. Quantum rings are prepared by using 20 ML In-Ga (15:85 droplets deposited on a GaAs substrate at 390°C with a droplet growth rate of 1ML/s. Arsenic flux (7–8×10-6Torr is then exposed for InGaAs crystallization at 200°C for 5 min. During droplet epitaxy at a high droplet thickness and high temperature, out-diffusion from the centre of droplets occurs under anisotropic strain. This leads to quantum ring structures having non-uniform ring stripes and deep square-shaped nanoholes. Using these peculiar quantum rings as templates, four quantum dots situated at the corners of a square shape are regrown. Two of these four quantum dots are aligned either or , which are preferable crystallographic directions of quantum dot alignment in general.

  19. Quadra-Quantum Dots and Related Patterns of Quantum Dot Molecules: Basic Nanostructures for Quantum Dot Cellular Automata Application

    Directory of Open Access Journals (Sweden)

    Somsak Panyakeow

    2010-10-01

    Full Text Available Laterally close-packed quantum dots (QDs called quantum dot molecules (QDMs are grown by modified molecular beam epitaxy (MBE. Quantum dots could be aligned and cross hatched. Quantum rings (QRs created from quantum dot transformation during thin or partial capping are used as templates for the formations of bi-quantum dot molecules (Bi-QDMs and quantum dot rings (QDRs. Preferable quantum dot nanostructure for quantum computation based on quantum dot cellular automata (QCA is laterally close-packed quantum dot molecules having four quantum dots at the corners of square configuration. These four quantum dot sets are called quadra-quantum dots (QQDs. Aligned quadra-quantum dots with two electron confinements work like a wire for digital information transmission by Coulomb repulsion force, which is fast and consumes little power. Combination of quadra-quantum dots in line and their cross-over works as logic gates and memory bits. Molecular Beam Epitaxial growth technique called 'Droplet Epitaxy' has been developed for several quantum nanostructures such as quantum rings and quantum dot rings. Quantum rings are prepared by using 20 ML In-Ga (15:85 droplets deposited on a GaAs substrate at 390'C with a droplet growth rate of 1ML/s. Arsenic flux (7'8'10-6Torr is then exposed for InGaAs crystallization at 200'C for 5 min. During droplet epitaxy at a high droplet thickness and high temperature, out-diffusion from the centre of droplets occurs under anisotropic strain. This leads to quantum ring structures having non-uniform ring stripes and deep square-shaped nanoholes. Using these peculiar quantum rings as templates, four quantum dots situated at the corners of a square shape are regrown. Two of these four quantum dots are aligned either or, which are preferable crystallographic directions of quantum dot alignment in general.

  20. KNOWLEDGE AND MISCONCEPTIONS OF PULMONARY TUBERCULOSIS PATIENTS AT DOTS CENTRE, URBAN MEERUT.

    Directory of Open Access Journals (Sweden)

    R Bansal

    2013-06-01

    Full Text Available Background: India is the second most populated country in the world; it has more new TB cases annually than any other country. In 2008, 1.98 million were estimated to have occurred in India, of whom 0.87 million were infectious cases, thus amounting to a fifth of the global burden of TB.With the entire country geographically covered under the DOTS program, research into socioeconomic impact of TB on patients and their households is crucial for providing comprehensive patient-friendly TB services and to document the benefits of DOTS. Objective: The present study was undertaken with the following objectives: (1 To determine the socio-demographic variables of registered patients for DOTS Treatment at Urban Health Training center Meerut. (2 To assess knowledge, awareness and attitude regarding Pulmonary Tuberculosis and its treatment among the patients. Materials and Methods: A cross-sectional study of 200 TB patients was done using a pre-tested semi-quantitative questionnaire in UHTC Meerut Period of Study: During 2010-2012. Results: Knowledge and awareness regarding Pulmonary Tuberculosis in patients at DOTS centre, Urban Meerut was very poor. There is a great need to educate the people about misconceptions like food and utensils as mode of transmission. BCC using the person to person contact in community , at health center and awareness campaigns are crucial in educating the ignorance seen in our field practice area. Conclusion: Poor knowledge and misconceptions concerning tuberculosis was quite concern in the patients. TB control program will remain ineffective unless myths and fears of TB patients are addressed related to causation of tuberculosis, mode of spread, and methods of prevention.

  1. KNOWLEDGE AND MISCONCEPTIONS OF PULMONARY TUBERCULOSIS PATIENTS AT DOTS CENTRE, URBAN MEERUT.

    Directory of Open Access Journals (Sweden)

    R Bansal

    2013-08-01

    Full Text Available Background: India is the second most populated country in the world; it has more new TB cases annually than any other country. In 2008, 1.98 million were estimated to have occurred in India, of whom 0.87 million were infectious cases, thus amounting to a fifth of the global burden of TB.With the entire country geographically covered under the DOTS program, research into socioeconomic impact of TB on patients and their households is crucial for providing comprehensive patient-friendly TB services and to document the benefits of DOTS. Objective: The present study was undertaken with the following objectives: (1 To determine the socio-demographic variables of registered patients for DOTS Treatment at Urban Health Training center Meerut. (2 To assess knowledge, awareness and attitude regarding Pulmonary Tuberculosis and its treatment among the patients. Materials and Methods: A cross-sectional study of 200 TB patients was done using a pre-tested semi-quantitative questionnaire in UHTC Meerut Period of Study: During 2010-2012. Results: Knowledge and awareness regarding Pulmonary Tuberculosis in patients at DOTS centre, Urban Meerut was very poor. There is a great need to educate the people about misconceptions like food and utensils as mode of transmission. BCC using the person to person contact in community , at health center and awareness campaigns are crucial in educating the ignorance seen in our field practice area. Conclusion: Poor knowledge and misconceptions concerning tuberculosis was quite concern in the patients. TB control program will remain ineffective unless myths and fears of TB patients are addressed related to causation of tuberculosis, mode of spread, and methods of prevention.

  2. Quantum Dots

    Science.gov (United States)

    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

  3. Nanodiamond-based nanostructures for coupling nitrogen-vacancy centres to metal nanoparticles and semiconductor quantum dots.

    Science.gov (United States)

    Gong, Jianxiao; Steinsultz, Nat; Ouyang, Min

    2016-06-08

    The ability to control the interaction between nitrogen-vacancy centres in diamond and photonic and/or broadband plasmonic nanostructures is crucial for the development of solid-state quantum devices with optimum performance. However, existing methods typically employ top-down fabrication, which restrict scalable and feasible manipulation of nitrogen-vacancy centres. Here, we develop a general bottom-up approach to fabricate an emerging class of freestanding nanodiamond-based hybrid nanostructures with external functional units of either plasmonic nanoparticles or excitonic quantum dots. Precise control of the structural parameters (including size, composition, coverage and spacing of the external functional units) is achieved, representing a pre-requisite for exploring the underlying physics. Fine tuning of the emission characteristics through structural regulation is demonstrated by performing single-particle optical studies. This study opens a rich toolbox to tailor properties of quantum emitters, which can facilitate design guidelines for devices based on nitrogen-vacancy centres that use these freestanding hybrid nanostructures as building blocks.

  4. A quantum dot-spore nanocomposite pH sensor.

    Science.gov (United States)

    Zhang, Xingya; Li, Zheng; Zhou, Tao; Zhou, Qian; Zeng, Zhiming; Xu, Xiangdong; Hu, Yonggang

    2016-04-01

    A new quantum dot (QD)-based pH sensor design is investigated. The sensor is synthesized based on the self-assembly of green QDs onto treated spores to form QD@spore nanocomposites. The nanocomposites are characterized using laser scanning confocal microscopy, transmission electron microscope, and fluorescence spectroscopy, among others. Fluorescence measurements showed that these nanocomposites are sensitive to pH in a broad pH range of 5.0-10.0. The developed pH sensors have been satisfactorily applied for pH estimation of real samples and are comparable with those of the commercial assay method, indicating the potential practical application of the pH sensors. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Influence of strain in the reduction of the internal electric field in GaN/AlN quantum dots grown on a-plane 6H-SiC

    Energy Technology Data Exchange (ETDEWEB)

    Cros, A.; Budagosky, J.A.; Garcia-Cristobal, A.; Garro, N.; Cantarero, A. [Institut de Ciencia dels Materials, Universitat de Valencia, 46071 Valencia (Spain); Founta, S.; Mariette, H.; Daudin, B. [CEA-CNRS Group ' ' Nanophysique et Semiconducteurs' ' , Departement de Recherche Fondamentale sur la Matiere Condensee, CEA Grenoble, 17 rue des Martyrs, 38054 Grenoble (France)

    2006-06-15

    The strain state of stacks of GaN/AlN quantum dots (QDs) grown on (0001) and (11 anti 20) 6H-SiC has been investigated by means of Raman spectroscopy. Depending on the orientation of the wurtzite axis with respect to the growth direction it is found that the piezoelectric contribution to the electrostatic potential may either reinforce that arising from the spontaneous polarization or oppose it. The experimental results are compared with a theoretical model for the strain and polarization field in QDs of both orientations that allows the calculation of the electrostatic potential in the QDs. Both the experimental results and the theoretical model indicate that the internal electric field and electrostatic potential are strongly reduced in the QDs grown on (11 anti 20) 6H-SiC as compared to those grown along the wurtzite c-axis. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Nanocrystalline-Si-dot multi-layers fabrication by chemical vapor deposition with H-plasma surface treatment and evaluation of structure and quantum confinement effects

    Directory of Open Access Journals (Sweden)

    Daisuke Kosemura

    2014-01-01

    Full Text Available 100-nm-thick nanocrystalline silicon (nano-Si-dot multi-layers on a Si substrate were fabricated by the sequential repetition of H-plasma surface treatment, chemical vapor deposition, and surface oxidation, for over 120 times. The diameter of the nano-Si dots was 5–6 nm, as confirmed by both the transmission electron microscopy and X-ray diffraction analysis. The annealing process was important to improve the crystallinity of the nano-Si dot. We investigated quantum confinement effects by Raman spectroscopy and photoluminescence (PL measurements. Based on the experimental results, we simulated the Raman spectrum using a phenomenological model. Consequently, the strain induced in the nano-Si dots was estimated by comparing the experimental and simulated results. Taking the estimated strain value into consideration, the band gap modulation was measured, and the diameter of the nano-Si dots was calculated to be 5.6 nm by using PL. The relaxation of the q ∼ 0 selection rule model for the nano-Si dots is believed to be important to explain both the phenomena of peak broadening on the low-wavenumber side observed in Raman spectra and the blue shift observed in PL measurements.

  7. 49 CFR Appendix H to Part 40 - DOT Drug and Alcohol Testing Management Information System (MIS) Data Collection Form

    Science.gov (United States)

    2010-10-01

    ..., App. H Appendix H to Part 40—DOT Drug and Alcohol Testing Management Information System (MIS) Data... 49 Transportation 1 2010-10-01 2010-10-01 false DOT Drug and Alcohol Testing Management Information System (MIS) Data Collection Form H Appendix H to Part 40 Transportation Office of the Secretary...

  8. Preparation, optical, and photocatalytic studies of defect pyrochlores: KCr{sub 0.33}W{sub 1.67}O{sub 6} and A{sub x}Cr{sub 0.33}W{sub 1.67}O{sub 6}{center_dot}nH{sub 2}O

    Energy Technology Data Exchange (ETDEWEB)

    Ravi, G.; Veldurthi, Naveen Kumar [Osmania University, Department of Chemistry (India); Prasad, Muvva D. [University of Hyderabad, School of Chemistry (India); Muniratnam, N. R. [Centre for Materials Electronics Technology (C-MET) (India); Prasad, G. [Osmania University, Department of Physics (India); Vithal, M., E-mail: mugavithal@gmail.com [Osmania University, Department of Chemistry (India)

    2013-09-15

    Nano sized defect pyrochlores of compositions KCr{sub 0.33}W{sub 1.67}O{sub 6} and A{sub x}Cr{sub 0.33}W{sub 1.67}O{sub 6}{center_dot}nH{sub 2}O (A = Sn, Ag, Bi, Sm, Eu, and Gd) have been synthesized by sol-gel and ion exchange methods, respectively. These oxides were characterized by thermogravimetric analysis, powder X-ray diffraction, energy dispersive spectra, transmission electron microscopy, UV-Vis diffuse reflectance spectra, Raman spectra, and Fourier transform infrared spectra. Spontaneous exchange of K{sup +} with A ion is accompanied by insertion of water also into the lattice. KCr{sub 0.33}W{sub 1.67}O{sub 6} and A{sub x}Cr{sub 0.33}W{sub 1.67}O{sub 6}{center_dot}nH{sub 2}O crystallize in cubic lattice and isomorphous with KSbWO{sub 6}. The optical properties of Cr{sup 3+} were investigated. Substitution of K{sup +} by A ion leads to a shift of absorption onset to longer wavelengths marginally. The Raman spectra of all the samples are characteristic of defect pyrochlore system. The photocatalytic degradation of methylene blue aqueous solution was investigated using these oxides. The results obtained were fitted with the Langmuir-Hinshelwood model to study the degradation kinetics. Both Sn{sup 2+} and Bi{sup 3+}-doped KCr{sub 0.33}W{sub 1.67}O{sub 6} exhibit higher photoactivity in the degradation of methylene blue. The structure/composition of the photocatalyst remains the same even after fourth cycle of photodegradation.

  9. Crystal structure, hydrogen bonding, and sup 8 sup 1 Br NQR of low-temperature phase of 4-aminopyridinium tetrabromoantimonate (3)

    CERN Document Server

    Hashimoto, M; Fuess, H; Svoboda, I; Ehrenberg, H

    2003-01-01

    The crystal structure of the low-temperature phase (LTP) of the title compound was determined at 220 K (monoclinic, P2 sub 1 sub / sub c). The 4-aminopyridinium cations (4-NH sub 2 C sub 5 H sub 4 NH sup +) were found to be ordered in LTP, while being severely disordered in the room-temperature phase (monoclinic, C2/c). The tetrabromoantimonate anions (SbBr sub 4 sup -) were incorporated into the infinite polyanion chains of irregular SbBr sub 6 octahedra with two-edges sharing. The trans-Br-Sb-Br moiety in the SbBr sub 4 sup - anion was approximately symmetric differing from the asymmetric Br-Sb centre dot centre dot centre dot Br moiety found in LTP of pyridinium tetrabromoantimonate (3). The N-H moieties in both of the pyridine ring and the amino (-NH sub 2) group participate in the formation of N-H centre dot centre dot centre dot Br hydrogen bonds. It was shown that the sup 8 sup 1 Br NQR spectrum of LTP is closely related to the anion structure and the hydrogen bonds. The distinctive anion structures, a...

  10. Carbon dots with strong excitation-dependent fluorescence changes towards pH. Application as nanosensors for a broad range of pH

    Energy Technology Data Exchange (ETDEWEB)

    Barati, Ali [Faculty of Chemistry, Institute for Advanced Studies in Basic Sciences, Zanjan (Iran, Islamic Republic of); Department of Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of); Shamsipur, Mojtaba, E-mail: mshamsipur@yahoo.com [Department of Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of); Abdollahi, Hamid, E-mail: abd@iasbs.ac.ir [Faculty of Chemistry, Institute for Advanced Studies in Basic Sciences, Zanjan (Iran, Islamic Republic of)

    2016-08-10

    In this study, preparation of novel pH-sensitive N-doped carbon dots (NCDs) using glucose and urea is reported. The prepared NCDs present strong excitation-dependent fluorescence changes towards the pH that is a new behavior from these nanomaterials. By taking advantage of this unique behavior, two separated ratiometric pH sensors using emission spectra of the NCDs for both acidic (pH 2.0 to 8.0) and basic (pH 7.0 to 14.0) ranges of pH are constructed. Additionally, by considering the entire Excitation–Emission Matrix (EEM) of NCDs as analytical signal and using a suitable multivariate calibration method, a broad range of pH from 2.0 to 14.0 was well calibrated. The multivariate calibration method was independent from the concentration of NCDs and resulted in a very low average prediction error of 0.067 pH units. No changes in the predicted pH under UV irradiation (for 3 h) and at high ionic strength (up to 2 M NaCl) indicated the high stability of this pH nanosensor. The practicality of this pH nanosensor for pH determination in real water samples was validated with good accuracy and repeatability. - Highlights: • Novel pH-sensitive carbon dots with strong FL changes towards pH are reported. • Ratiometric FL pH-sensors for both acidic and basic ranges of pH are constructed. • Multivariate calibration methods were used to calibrate a broad range of pH. • Using EEM of carbon dots and ANN, pH from 2.0 to 14.0 was well calibrated. • The pH prediction is stable even at high ionic strength up to 2 M NaCl.

  11. Carbon dots with strong excitation-dependent fluorescence changes towards pH. Application as nanosensors for a broad range of pH

    International Nuclear Information System (INIS)

    Barati, Ali; Shamsipur, Mojtaba; Abdollahi, Hamid

    2016-01-01

    In this study, preparation of novel pH-sensitive N-doped carbon dots (NCDs) using glucose and urea is reported. The prepared NCDs present strong excitation-dependent fluorescence changes towards the pH that is a new behavior from these nanomaterials. By taking advantage of this unique behavior, two separated ratiometric pH sensors using emission spectra of the NCDs for both acidic (pH 2.0 to 8.0) and basic (pH 7.0 to 14.0) ranges of pH are constructed. Additionally, by considering the entire Excitation–Emission Matrix (EEM) of NCDs as analytical signal and using a suitable multivariate calibration method, a broad range of pH from 2.0 to 14.0 was well calibrated. The multivariate calibration method was independent from the concentration of NCDs and resulted in a very low average prediction error of 0.067 pH units. No changes in the predicted pH under UV irradiation (for 3 h) and at high ionic strength (up to 2 M NaCl) indicated the high stability of this pH nanosensor. The practicality of this pH nanosensor for pH determination in real water samples was validated with good accuracy and repeatability. - Highlights: • Novel pH-sensitive carbon dots with strong FL changes towards pH are reported. • Ratiometric FL pH-sensors for both acidic and basic ranges of pH are constructed. • Multivariate calibration methods were used to calibrate a broad range of pH. • Using EEM of carbon dots and ANN, pH from 2.0 to 14.0 was well calibrated. • The pH prediction is stable even at high ionic strength up to 2 M NaCl.

  12. InAs/GaAs quantum dots for THz generation

    International Nuclear Information System (INIS)

    Daghestani, N.S.; Cataluna, M.A.; Berry, G.; Rose, M.J.; Ross, G.

    2012-01-01

    We report pulsed terahertz generation from InAs/GaAs quantum-dot based photoconductive devices. For 800 nm optical excitation, the dots act as recombination centres for carriers generated in the GaAs layers. Using photoreflective pump-probe measurements we demonstrate that the photogenerated carrier lifetime decreases when a lateral bias is applied. This can be attributed to an increase in the capture area of the dots when under bias. Two types of antenna metallization were investigated; non-Ohmic, and quasi-Ohmic contacts. Non-Ohmic antennae displayed resilience to Joule heating when operated at a field strength of 46 MV/m. The breakdown field of the devices was 48 MV/m, which is comparable to the breakdown field of bulk GaAs (∝50 MV/m). The maximum estimated infrared-to-THz conversion efficiency is ∝1x10 -5 . (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Influence of pH on luminescence from water-soluble colloidal Mn-doped ZnSe quantum dots capped with different mercaptoacids

    International Nuclear Information System (INIS)

    Hardzei, Maryia; Artemyev, Mikhail

    2012-01-01

    Water-soluble ZnSe/ZnS core–shell quantum dots with ZnSe core doped by manganese ions show different luminescence response to pH changes in aqueous solutions depending on the type of solubilizing agents (thioglycolic acid, mercaptoundecanoic acid, sodium mercaptopropylsulfonate). In the case of long-chain mercaptoundecanoic acid only excitonic emission is affected by pH changes. Short-chain thioglycolic acid brings about equal excitonic/Mn emission variations with pH, while mercaptopropylsulfonate-stabilized quantum dots are insensitive to pH. The mechanism discussed here is based on the competition between different relaxation channels for excited excitons in ZnSe: excitonic radiative recombination, energy transfer to Mn ion and the photogenerated electron trapping due to the presence of protonated carboxyl group. ZnSe:Mn/ZnS quantum dots stabilized with long-chain mercaptoacids may be used as a new type of fluorescence ratiometric pH-sensor or indicator. - Highlights: ► Prepared ZnSe:Mn/ZnS quantum dots capped with different mercaptoacids in water. ► Photoluminescence intensity of ZnSe:Mn/ZnS quantum dots varied with pH. ► Character of luminescence variations depends on the sort of mercaptoacid capping. ► Competition between different excitonic relaxation channels for different caps.

  14. Time-dependent pH sensing phenomena using CdSe/ZnS quantum dots in EIS structure.

    Science.gov (United States)

    Kumar, Pankaj; Maikap, Siddheswar; Prakash, Amit; Tien, Ta-Chang

    2014-04-12

    Time-dependent pH sensing phenomena of the core-shell CdSe/ZnS quantum dot (QD) sensors in EIS (electrolyte insulator semiconductor) structure have been investigated for the first time. The quantum dots are immobilized by chaperonin GroEL protein, which are observed by both atomic force microscope and scanning electron microscope. The diameter of one QD is approximately 6.5 nm. The QDs are not oxidized over a long time and core-shell CdSe/ZnS are confirmed by X-ray photon spectroscopy. The sensors are studied for sensing of hydrogen ions concentration in different buffer solutions at broad pH range of 2 to 12. The QD sensors show improved sensitivity (38 to 55 mV/pH) as compared to bare SiO2 sensor (36 to 23 mV/pH) with time period of 0 to 24 months, owing to the reduction of defects in the QDs. Therefore, the differential sensitivity of the QD sensors with respect to the bare SiO2 sensors is improved from 2 to 32 mV/pH for the time period of 0 to 24 months. After 24 months, the sensitivity of the QD sensors is close to ideal Nernstian response with good linearity of 99.96%. Stability and repeatability of the QD sensors show low drift (10 mV for 10 cycles) as well as small hysteresis characteristics (sensor is very useful for future human disease diagnostics.

  15. C sub 6 sub 0 fullerene and its molecular complexes under axial and shear deformation

    CERN Document Server

    Spitsina, N G; Bashkin, I V; Meletov, K P

    2002-01-01

    We have studied the pristine C sub 6 sub 0 and its molecular complexes with the organic donors bis(ethylenedithio) tetrathiafulvalene (BEDT-TTF or ET) and tetramethyltetraselenafulvalene (TMTSF) by means of ESR and Raman spectroscopy at high pressure. The important changes in the ESR signal of C sub 6 sub 0 were observed under axial pressure combined with shear deformation. It is shown that the treatment at a anisotropic pressure of 4 GPa results in a reduction in the symmetry of the C sub 6 sub 0 molecule and the formation of radicals. Treatment of the molecular complex of (ET) sub 2 centre dot C sub 6 sub 0 at a pressure of approx 4.5 GPa and a temperature of 150 deg. C leads to the formation of C sub 6 sub 0 dimers. The Raman spectra of the molecular complex C sub 6 sub 0 centre dot TMTSF centre dot 2(CS sub 2) were measured in situ at ambient temperature and pressures up to 9.5 GPa. The pressure behaviour of the Raman peaks reveals singularity at 5.0 +- 0.5 GPa related to the softening and splitting of so...

  16. Record Charge Carrier Diffusion Length in Colloidal Quantum Dot Solids via Mutual Dot-To-Dot Surface Passivation.

    Science.gov (United States)

    Carey, Graham H; Levina, Larissa; Comin, Riccardo; Voznyy, Oleksandr; Sargent, Edward H

    2015-06-03

    Through a combination of chemical and mutual dot-to-dot surface passivation, high-quality colloidal quantum dot solids are fabricated. The joint passivation techniques lead to a record diffusion length for colloidal quantum dots of 230 ± 20 nm. The technique is applied to create thick photovoltaic devices that exhibit high current density without losing fill factor. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Emission switching in carbon dots coated CdTe quantum dots driving by pH dependent hetero-interactions

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Xiao; Wang, Hao; Yi, Qinghua; Wang, Yun; Cong, Shan; Zhao, Jie; Sun, Yinghui; Zou, Guifu, E-mail: zouguifu@suda.edu.cn, E-mail: jiexiong@uestc.edu.cn [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Qian, Zhicheng [School of Electronic and Information Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Huang, Jianwen; Xiong, Jie, E-mail: zouguifu@suda.edu.cn, E-mail: jiexiong@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Luo, Hongmei [Department of Chemical and Materials Engineering, New Mexico State University, Las Cruces, New Mexico 88003 (United States)

    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.

  18. pH sensitive quantum dot-anthraquinone nanoconjugates

    Science.gov (United States)

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

    2014-05-01

    Semiconductor quantum dots (QDs) have been shown to be highly sensitive to electron or charge transfer processes, which may alter their optical properties. This feature can be exploited for different sensing applications. Here, we demonstrate that QD-anthraquinone conjugates can function as electron transfer-based pH nanosensors. The attachment of the anthraquinones on the surface of QDs results in the reduction of electron hole recombination, and therefore a quenching of the photoluminescence intensity. For some anthraquinone derivatives tested, the quenching mechanism is simply caused by an electron transfer process from QDs to the anthraquinone, functioning as an electron acceptor. For others, electron transfer and energy transfer (FRET) processes were found. A detailed analysis of the quenching processes for CdSe/ZnS QD of two different sizes is presented. The photoluminescence quenching phenomenon of QDs is consistent with the pH sensitive anthraquinone redox chemistry. The resultant family of pH nanosensors shows pKa ranging ˜5-8, being ideal for applications of pH determination in physiological samples like blood or serum, for intracellular pH determination, and for more acidic cellular compartments such as endosomes and lysosomes. The nanosensors showed high selectivity towards many metal cations, including the most physiologically important cations which exist at high concentration in living cells. The reversibility of the proposed systems was also demonstrated. The nanosensors were applied in the determination of pH in samples mimicking the intracellular environment. Finally, the possibility of incorporating a reference QD to achieve quantitative ratiometric measurements was investigated.

  19. Contribution of dot-blot assay to the diagnosis and management of myositis: a three-year practice at a university hospital centre.

    Science.gov (United States)

    Martel, Clothilde; Vignaud, Guillaume; Liozon, Eric; Magy, Laurent; Gallouedec, Gael; Ly, Kim; Bezanahary, Holly; Cypierre, Anne; Lapébie, François-Xavier; Palat, Sylvain; Gondran, Guillaume; Jauberteau, Marie-Odile; Fauchais, Anne-Laure

    2016-01-01

    Idiopathic inflammatory myopathies (IIM) are heterogeneous autoimmune diseases with wide clinical spectrum that may lead to delayed diagnosis. The aim of this study was to examine the impact of IIM-specific dot-blot assay on diagnostic process of patients presenting with muscular or systemic symptoms evocating of IIM. We collected all the prescriptions of an IIM specific dot-blot assay (8 autoantigens including Jo-1, PL-7, PL-12, SRP, Mi-2, Ku, PM/Scl and Scl-70) over a 38-month period. 316 myositis dot-blot assays (MSD) were performed in 274 patients (156 women, mean age 53±10.6 years) referring for muscular and/or systemic symptoms suggesting IIM. The timing of dot prescription through the diagnostic process was highly variable: without (35%), concomitantly (16%) or after electromyographic studies (35%). Fifty-nine patients (22%) had IIM according to Bohan and Peter's criteria. Among them, 29 (49%) had positive dot (8 Jo-1, 6 PM-Scl, 5 PL-12, 5 SRP, 2 Mi-2, 2 PL-7 and 1 Ku). Various other diagnoses were performed including 35 autoimmune disease or granulomatosis (12%), 19 inflammatory rheumatic disease (7%), 16 non inflammatory muscular disorders (6%), 10 drug-induced myalgia (4%), 11 infectious myositis (4%). Except 11 borderline SRP results and one transient PM-Scl, MSD was positive only in one case of IIM. Dot allowed clinicians to correct diagnosis in 4 cases and improved the diagnosis of IIM subtypes in 4 cases. This study reflects the interest of myositis dot in the rapid diagnosis process of patients with non-specific muscular symptoms leading to various diagnoses including IIM.

  20. A low cytotoxic and ratiometric fluorescent nanosensor based on carbon-dots for intracellular pH sensing and mapping

    International Nuclear Information System (INIS)

    Du Fangkai; Ming Yunhao; Zeng Fang; Yu Changmin; Wu Shuizhu

    2013-01-01

    Intracellular pH plays a critical role in the function of cells, and its regulation is essential for most cellular processes. In this study, we demonstrate a fluorescence resonance energy transfer (FRET)-based ratiometric pH nanosensor with carbon-dot (CD) as the carrier. The sensor was prepared by covalently linking a pH-sensitive fluorescent dye (fluorescein isothiocyanate, FITC) onto carbon-dot. As the FRET donor, the carbon-dot exhibits bright fluorescence emission as well as λ ex -dependent photoluminescence emission, and a suitable excitation wavelength for the donor (CD) can be chosen to match the energy acceptor (fluorescein moiety). The fluorescein moieties on a CD undergo structural and spectral conversion as the pH changes, affording the nanoplatform a FRET-based pH sensor. The CD-based system exhibits a significant change in fluorescence intensity ratio between pH 4 and 8 with a pK a value of 5.69. It also displays excellent water dispersibility, good spectral reversibility, satisfactory cell permeability and low cytotoxicity. Following the living cell uptake, this nanoplatform with dual-chromatic emissions can facilitate real-time visualization of the pH evolution involved in the endocytic pathway of the nanosensor. This reversible and low cytotoxic fluorescent nanoplatform may be highly valuable in a variety of biological studies, such as endocytic trafficking, endosome/lysosome maturation, and pH regulation in subcellular organelles. (paper)

  1. User's guide for shipping Type B quantities of radioactive and fissile material, including plutonium, in DOT-6M specification packaging configurations

    International Nuclear Information System (INIS)

    Kelly, D.L.

    1994-09-01

    The need for developing a user's guide for shipping Type B quantities of radioactive and fissile material, including plutonium, in a US Department of Transportation Specification 6M (DOT-6M) packaging was identified by the US Department of Energy (DOE)-Headquarters, Transportation Management Division (EM-261) because the DOT-6M packaging is widely used by DOE site contractors and the DOE receives many questions about approved packaging configuration. Currently, EM-261 has the authority to approve new DOT-6M packaging configurations for use by the DOE Operations Offices. This user's guide identifies the DOE-approved DOT-6M packaging configurations and explains how to have new configurations approved by the DOE. The packaging configurations described in this guide are approved by the DOE, and satisfy the applicable DOT requirements and the identified DOE restrictions. These packaging configurations are acceptable for transport of Type B quantities of radioactive and fissile material, including plutonium

  2. Safety analysis report for packaging: the ORNL DOT specification 6M - special form package

    Energy Technology Data Exchange (ETDEWEB)

    Schaich, R.W.

    1982-07-01

    The ORNL DOT Specification 6M - Special Form Package was fabricated at the Oak Ridge Nation al Laboratory (ORNL) for the transport of Type B solid non-fissile radioactive materials in special form. The package was evaluated on the basis of tests performed by the Dow Chemical Company, Rocky Flats Division, on the DOT-6M container and special form tests performed on a variety of stainless steel capsules at ORNL by Operations Division personnel. The results of these evaluations demonstrate that the package is in compliance with the applicable regulations for the transport of Type B quantities in special form of non-fissile radioactive materials.

  3. Safety analysis report for packaging: the ORNL DOT specification 6M - special form package

    International Nuclear Information System (INIS)

    Schaich, R.W.

    1982-07-01

    The ORNL DOT Specification 6M - Special Form Package was fabricated at the Oak Ridge Nation al Laboratory (ORNL) for the transport of Type B solid non-fissile radioactive materials in special form. The package was evaluated on the basis of tests performed by the Dow Chemical Company, Rocky Flats Division, on the DOT-6M container and special form tests performed on a variety of stainless steel capsules at ORNL by Operations Division personnel. The results of these evaluations demonstrate that the package is in compliance with the applicable regulations for the transport of Type B quantities in special form of non-fissile radioactive materials

  4. Safety analysis report for packaging: the ORNL DOT specification 6M - tritium trap package

    International Nuclear Information System (INIS)

    DeVore, J.R.

    1984-04-01

    The ORNL DOT Specification 6M--Tritium Trap Package was fabricated at the Oak Ridge National Laboratory (ORNL) for the transport of Type B quantities of tritium as solid uranium tritide. The package was evaluated on the basis of tests performed by the Dow Chemical Company, Rocky Flats Division, on the DOT-6M container, a drop test performed by the ORNL Operations Division, and International Atomic Energy Agency (IAEA) approvals on a similar tritium transport container. The results of these evaluations demonstrate that the package is in compliance with the applicable regulations for the transport of Type B quantities of tritium. 4 references, 8 figures

  5. Study of manganese binding to the ferroxidase centre of human H-type ferritin.

    Science.gov (United States)

    Ardini, Matteo; Howes, Barry D; Fiorillo, Annarita; Falvo, Elisabetta; Sottini, Silvia; Rovai, Donella; Lantieri, Marco; Ilari, Andrea; Gatteschi, Dante; Spina, Gabriele; Chiancone, Emilia; Stefanini, Simonetta; Fittipaldi, Maria

    2018-05-01

    Ferritins are ubiquitous and conserved proteins endowed with enzymatic ferroxidase activity, that oxidize Fe(II) ions at the dimetal ferroxidase centre to form a mineralized Fe(III) oxide core deposited within the apo-protein shell. Herein, the in vitro formation of a heterodimetal cofactor constituted by Fe and Mn ions has been investigated in human H ferritin (hHFt). Namely, Mn and Fe binding at the hHFt ferroxidase centre and its effects on Fe(II) oxidation have been investigated by UV-Vis ferroxidation kinetics, fluorimetric titrations, multifrequency EPR, and preliminary Mössbauer spectroscopy. Our results show that in hHFt, both Fe(II) and Mn(II) bind the ferroxidase centre forming a Fe-Mn cofactor. Moreover, molecular oxygen seems to favour Mn(II) binding and increases the ferroxidation activity of the Mn-loaded protein. The data suggest that Mn influences the Fe binding and the efficiency of the ferroxidation reaction. The higher efficiency of the Mn-Fe heterometallic centre may have a physiological relevance in specific cell types (i.e. glia cells), where the concentration of Mn is the same order of magnitude as iron. Copyright © 2018 Elsevier Inc. All rights reserved.

  6. Thermal decomposition of Cu(NO{sub 3}){sub 2}{center_dot}3H{sub 2}O at reduced pressures

    Energy Technology Data Exchange (ETDEWEB)

    Morozov, I.V.; Znamenkov, K.O.; Korenev, Yu.M.; Shlyakhtin, O.A

    2003-07-28

    Thermolysis of Cu(NO{sub 3}){sub 2}{center_dot}3H{sub 2}O is studied by means of XRD analysis in situ and mass spectral analysis of the gas phase at P=1/10 Pa at low heating rate. It is shown that stage I of the dehydration (40-80 deg. C) results in the consecutive appearance of crystalline Cu(NO{sub 3}){sub 2}{center_dot}2.5H{sub 2}O and Cu(NO{sub 3}){center_dot}H{sub 2}O. Anhydrous Cu(NO{sub 3}){sub 2} formed during further dehydration at 80-110 deg. C is moderately sublimed at 120-150 deg. C. Dehydration is accompanied by thermohydrolysis, leading to the appearance of Cu{sub 2}(OH){sub 3}NO{sub 3} and gaseous H{sub 2}O, HNO{sub 3}, NO{sub 2}, and H{sub 2}O. The higher pressure in the system, the larger amount of thermohydrolysis products is observed. The formation of the crystalline intermediate CuO{sub x}(NO{sub 3}){sub y} was observed by diffraction methods. Final product of thermolysis (CuO) is formed at 200-250 deg. C.

  7. Direct-Bandgap InAs Quantum-Dots Have Long-Range Electron--Hole Exchange Whereas Indirect Gap Si Dots Have Short-Range Exchange

    International Nuclear Information System (INIS)

    Juo, J.W.; Franceschetti, A.; Zunger, A.

    2009-01-01

    Excitons in quantum dots manifest a lower-energy spin-forbidden 'dark' state below a spin-allowed 'bright' state; this splitting originates from electron-hole (e-h) exchange interactions, which are strongly enhanced by quantum confinement. The e-h exchange interaction may have both a short-range and a long-range component. Calculating numerically the e-h exchange energies from atomistic pseudopotential wave functions, we show here that in direct-gap quantum dots (such as InAs) the e-h exchange interaction is dominated by the long-range component, whereas in indirect-gap quantum dots (such as Si) only the short-range component survives. As a result, the exciton dark/bright splitting scales as 1/R 2 in InAs dots and 1/R 3 in Si dots, where R is the quantum-dot radius.

  8. Quantum dots trace lymphatic drainage from the mouse eye

    Energy Technology Data Exchange (ETDEWEB)

    Tam, Alex L C; Gupta, Neeru; Zhang Zhexue; Yuecel, Yeni H, E-mail: yucely@smh.ca [Department of Ophthalmology and Vision Sciences, University of Toronto, M5T 2S8 (Canada)

    2011-10-21

    Glaucoma is a leading cause of blindness in the world, often associated with elevated eye pressure. Currently, all glaucoma treatments aim to lower eye pressure by improving fluid exit from the eye. We recently reported the presence of lymphatics in the human eye. The lymphatic circulation is known to drain fluid from organ tissues and, as such, lymphatics may also play a role in draining fluid from the eye. We investigated whether lymphatic drainage from the eye is present in mice by visualizing the trajectory of quantum dots once injected into the eye. Whole-body hyperspectral fluorescence imaging was performed in 17 live mice. In vivo imaging was conducted prior to injection, and 5, 20, 40 and 70 min, and 2, 6 and 24 h after injection. A quantum dot signal was observed in the left neck region at 6 h after tracer injection into the eye. Examination of immunofluorescence-labelled sections using confocal microscopy showed the presence of a quantum dot signal in the left submandibular lymph node. This is the first direct evidence of lymphatic drainage from the mouse eye. The use of quantum dots to image this lymphatic pathway in vivo is a novel tool to stimulate new treatments to reduce eye pressure and prevent blindness from glaucoma.

  9. Quantum dots trace lymphatic drainage from the mouse eye

    International Nuclear Information System (INIS)

    Tam, Alex L C; Gupta, Neeru; Zhang Zhexue; Yuecel, Yeni H

    2011-01-01

    Glaucoma is a leading cause of blindness in the world, often associated with elevated eye pressure. Currently, all glaucoma treatments aim to lower eye pressure by improving fluid exit from the eye. We recently reported the presence of lymphatics in the human eye. The lymphatic circulation is known to drain fluid from organ tissues and, as such, lymphatics may also play a role in draining fluid from the eye. We investigated whether lymphatic drainage from the eye is present in mice by visualizing the trajectory of quantum dots once injected into the eye. Whole-body hyperspectral fluorescence imaging was performed in 17 live mice. In vivo imaging was conducted prior to injection, and 5, 20, 40 and 70 min, and 2, 6 and 24 h after injection. A quantum dot signal was observed in the left neck region at 6 h after tracer injection into the eye. Examination of immunofluorescence-labelled sections using confocal microscopy showed the presence of a quantum dot signal in the left submandibular lymph node. This is the first direct evidence of lymphatic drainage from the mouse eye. The use of quantum dots to image this lymphatic pathway in vivo is a novel tool to stimulate new treatments to reduce eye pressure and prevent blindness from glaucoma.

  10. Aspects of the historical development of targetry for heavy ions of 0.05-2000 A centre dot MeV at GSI

    CERN Document Server

    Folger, H

    1999-01-01

    The progressively improved GSI accelerators provide beams of heavy ions from energies of 0.05-2000 A centre dot MeV at high particle intensities now. Therefore, a wide variety of common and new heavy-ion target techniques had to be installed and developed during the past 25 years to prepare and characterize self-supported or backed heavy-ion-targets of chemical elements and compounds from hydrogen (as polyethylene) to uranium. The thickness ranged from 2x10 sup - sup 6 to 20 g/cm sup 2 for beam spots of about 5 mm in diameter. Homogeneity, surface structure or individual shape had to be adapted to the needs of each experiment. Special setups were required for targets of poisonous materials, of highly enriched stable isotopes or those of radioactive species in minute amounts. The capability of thin-layer technologies was as well applied to prepare and measure stripper foils or various high-vacuum deposits for experimental or accelerator purposes. The development of different rotating target wheels and control ...

  11. CdTe quantum dots functionalized with 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide as luminescent nanoprobe for the sensitive recognition of bromide ion

    International Nuclear Information System (INIS)

    Adegoke, Oluwasesan; Hosten, Eric; McCleland, Cedric; Nyokong, Tebello

    2012-01-01

    Graphical abstract: A bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) showed a high selectivity and sensitivity for the determination of bromide ion using fluorescence recovery. Highlights: ► Water soluble CdTe quantum dots interact with tetramethylpiperidine-N-oxide. ► Quantum dots fluorescence is quenched by the radical. ► In the presence of bromide ions the fluorescence is restored. ► The sensor is more selective to bromine ions than other common ions. - Abstract: A novel bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) has been developed. Fluorescence quenching of the QDs by 4AT was observed. The functionalized QDs-4AT nanoprobe allowed a highly sensitive determination of bromide ion via analyte-induced change in the photoluminescence (fluorescence recovery) of the modified QDs. A detection limit of 0.6 nM of bromide ion was obtained, while the interfering effect of other inorganic cations and anions was investigated to examine the selectivity of the nanoprobe. The linear range was between 0.01 and 0.13 μM. Combined fluorescence lifetime and electron paramagnetic resonance measurements confirmed electron transfer processes between bromide ion and QDs-4AT.

  12. Ratiometric photoluminescence sensing based on Ti3C2 MXene quantum dots as an intracellular pH sensor.

    Science.gov (United States)

    Chen, Xu; Sun, Xueke; Xu, Wen; Pan, Gencai; Zhou, Donglei; Zhu, Jinyang; Wang, He; Bai, Xue; Dong, Biao; Song, Hongwei

    2018-01-18

    Intracellular pH sensing is of importance and can be used as an indicator for monitoring the evolution of various diseases and the health of cells. Here, we developed a new class of surface-functionalized MXene quantum dots (QDs), Ti 3 C 2 , by the sonication cutting and hydrothermal approach and further explored their intracellular pH sensing. The functionalized Ti 3 C 2 QDs exhibit bright excitation-dependent blue photoluminescence (PL) originating from the size effect and surface defects. Meanwhile, Ti 3 C 2 QDs demonstrate a high PL response induced by the deprotonation of the surface defects. Furthermore, combining the highly pH sensitive Ti 3 C 2 QDs with the pH insensitive [Ru(dpp) 3 ]Cl 2 , we developed a ratiometric pH sensor to quantitatively monitor the intracellular pH values. These novel MXene quantum dots can serve as a promising platform for developing practical fluorescent nanosensors.

  13. Luminescent behavior of cadmium sulfide quantum dots for gallic acid estimation

    Science.gov (United States)

    Singh, Suman; Garg, Sourav; Chahal, Jitender; Raheja, Khushboo; Singh, Deepak; Singla, M. L.

    2013-03-01

    Thioglycolic acid capped cadmium sulfide (CdS/T) quantum dots have been synthesized using wet chemistry and their optical behavior has been investigated using UV-visible absorption and fluorescence spectroscopy. The role of the capping agent, sulfide source concentration, pH and temperature has been studied and discussed. Studies showed that alkaline pH leads to a decrease in the size of quantum dots and reflux temperature above 70 °C resulted in red-shift of emission spectra which is due to narrowing of the bandgap. Further, to reduce the toxicity and photochemical instability of quantum dots, the quantum dots have been functionalized with polyethylene glycol (PEG), which resulted in a 20% enhancement of the fluorescence intensity. The application potential of CdS/T-PEG quantum dots was further studied using gallic acid as a model compound. The sensing is based on fluorescence quenching of quantum dots in the presence of gallic acid, and this study showed linearity in the range from 1.3 × 10-8 to 46.5 × 10-8 mM, with a detection limit of 3.6 × 10-8 mM.

  14. Luminescent behavior of cadmium sulfide quantum dots for gallic acid estimation

    International Nuclear Information System (INIS)

    Singh, Suman; Garg, Sourav; Chahal, Jitender; Raheja, Khushboo; Singla, M L; Singh, Deepak

    2013-01-01

    Thioglycolic acid capped cadmium sulfide (CdS/T) quantum dots have been synthesized using wet chemistry and their optical behavior has been investigated using UV–visible absorption and fluorescence spectroscopy. The role of the capping agent, sulfide source concentration, pH and temperature has been studied and discussed. Studies showed that alkaline pH leads to a decrease in the size of quantum dots and reflux temperature above 70 °C resulted in red-shift of emission spectra which is due to narrowing of the bandgap. Further, to reduce the toxicity and photochemical instability of quantum dots, the quantum dots have been functionalized with polyethylene glycol (PEG), which resulted in a 20% enhancement of the fluorescence intensity. The application potential of CdS/T-PEG quantum dots was further studied using gallic acid as a model compound. The sensing is based on fluorescence quenching of quantum dots in the presence of gallic acid, and this study showed linearity in the range from 1.3 × 10 −8 to 46.5 × 10 −8 mM, with a detection limit of 3.6 × 10 −8 mM. (paper)

  15. Capped CuInS2 quantum dots for H2 evolution from water under visible light illumination

    International Nuclear Information System (INIS)

    Li, Tzung-Luen; Cai, Cheng-Da; Yeh, Te-Fu; Teng, Hsisheng

    2013-01-01

    Highlights: ► Dispersed CuInS 2 quantum dots showed remarkable photosynthetic activity using visible light. ► Photogenerated electrons in CuInS 2 were effective in H 2 production from aqueous solution. ► The bifunctional capping reagent effectively transported photogenerated electrons for reaction. ► Ru-loaded CuInS 2 quantum dots showed a quantum efficiency of 4.7% in H 2 evolution. ► Attaching CuInS 2 to TiO 2 with CdS passivation achieved a quantum efficiency of 41%. - Abstract: This study demonstrates H 2 evolution from water decomposition catalyzed by capped CuInS 2 quantum dots (QDs) that are highly dispersed in a polysulfide aqueous solution. The CuInS 2 QDs, which are obtained from solvothermal synthesis, have a size of 4.3 nm and a band gap of 1.97 eV. For photosynthetic H 2 evolution in the aqueous solution, the QDs are capped with a multidentate ligand (3-mercaptopropionic acid), which has a thiol end for attaching the QDs and a hydrophilic carboxylic end for dispersion in water. The capped QDs exhibit low activity in catalyzing H 2 evolution under visible illumination. After photodepositing 0.5 wt.% Ru, the capped QDs are active in producing H 2 with illumination. This demonstrates that the photogenerated electrons travel through the capping reagent to generate deposited Ru, which subsequently serves as an electron trap for H 2 evolution. A heterostructure formed by attaching the capped QDs on TiO 2 nanoparticles, followed by coating CdS with photodeposition, exhibits a high quantum efficiency of 41% for H 2 evolution from the polysulfide solution. These results demonstrate the potential for photosynthesis and phototherapy in biologic in vivo or microfluidic systems based on this capped QD material.

  16. Stark-shift of impurity fundamental state in a lens shaped quantum dot

    Science.gov (United States)

    Aderras, L.; Bah, A.; Feddi, E.; Dujardin, F.; Duque, C. A.

    2017-05-01

    We calculate the Stark effect and the polarisability of shallow-donor impurity located in the centre of lens shaped quantum dot by a variational method and in the effective-mass approximation. Our theoretical model assumes an infinite confinement to describe the barriers at the dot boundaries and the electric field is considered to be applied in the z-direction. The systematic theoretical investigation contains results with the quantum dot size and the strength of the external field. Our calculations reveal that the interval wherein the polarisability varies depends strongly on the dot size.

  17. A novel chemiluminescence method for determination of bisphenol Abased on the carbon dot-enhanced HCO3−–H2O2 system

    International Nuclear Information System (INIS)

    Amjadi, Mohammad; Manzoori, Jamshid L.; Hallaj, Tooba

    2015-01-01

    A simple and sensitive chemiluminescence (CL) method on the basis of carbon dot (C-dot) enhanced HCO 3 − –H 2 O 2 system, is designed for the determination of bisphenol A (BPA). The very weak CL of the HCO 3 − –H 2 O 2 system is enhanced by a factor of ∼100 in the presence of C-dots. Possible mechanisms that lead to the effect were elucidated by recording fluorescence and CL spectra and studying the effect of some radical scavengers. This enhancement is inhibited by BPA in the concentration range from 1.0 to 100 µg L −1 . This is exploited for its trace determination with a detection limit (3 s) of 0.3 µg L −1 . The established method was applied to the determination of BPA in baby bottle and water samples with satisfactory results. - Highlights: • The effect of carbon dots on HCO 3 − –H 2 O 2 chemiluminescence reaction is studied. • Carbon dots greatly enhance the CL signal of this reaction (∼100 fold). • The new CL system was applied to determination of bisphenol A in real samples

  18. New metal-organic frameworks of [M(C6H5O7)(C6H6O7)(C6H7O7)(H2O)] . H2O (M=La, Ce) and [Ce2(C2O4)(C6H6O7)2] . 4H2O

    International Nuclear Information System (INIS)

    Weng Shengfeng; Wang, Yun-Hsin; Lee, Chi-Shen

    2012-01-01

    Two novel materials, [M(C 6 H 5 O 7 )(C 6 H 6 O 7 )(C 6 H 7 O 7 )(H 2 O)] . H 2 O (M=La(1a), Ce(1b)) and [Ce 2 (C 2 O 4 )(C 6 H 6 O 7 ) 2 ] . 4H 2 O (2), with a metal-organic framework (MOF) were prepared with hydrothermal reactions and characterized with photoluminescence, magnetic susceptibility, thermogravimetric analysis and X-ray powder diffraction in situ. The crystal structures were determined by single-crystal X-ray diffraction. Compound 1 crystallized in triclinic space group P1-bar (No. 2); compound 2 crystallized in monoclinic space group P2 1 /c (No. 14). The structure of 1 is built from a 1D MOF, composed of deprotonated citric ligands of three kinds. Compound 2 contains a 2D MOF structure consisting of citrate and oxalate ligands; the oxalate ligand arose from the decomposition in situ of citric acid in the presence of Cu II ions. Photoluminescence spectra of compounds 1b and 2 revealed transitions between the 5d 1 excited state and two levels of the 4f 1 ground state ( 2 F 5/2 and 2 F 7/2 ). Compounds 1b and 2 containing Ce III ion exhibit a paramagnetic property with weak antiferromagnetic interactions between the two adjacent magnetic centers. - Graphical Abstract: [M(C 6 H 5 O 7 )(C 6 H 6 O 7 )(C 6 H 7 O 7 )(H 2 O)] . H 2 O (M=La(1a), Ce(1b)) and [Ce 2 (C 2 O 4 )(C 6 H 6 O 7 ) 2 ] . 4H 2 O (2)—with 1D and 2D structures were synthesized and characterized. Highlights: ► Two MOF – [M(C 6 H 5 O 7 )(C 6 H 6 O 7 )(C 6 H 7 O 7 )(H 2 O)] . H 2 O (M=La(1a), Ce(1b)) and [Ce 2 (C 2 O 4 )(C 6 H 6 O 7 ) 2 ] . 4H 2 O (2) – with 1D and 2D structures. ► The adjacent chains of the 1D framework were correlated with each other through an oxalate ligand to form a 2D layer structure. ► The source of the oxalate ligand was the decomposition in situ of citric acid oxidized in the presence of Cu II ions.

  19. All-Inorganic Colloidal Quantum Dot Photovoltaics Employing Solution-Phase Halide Passivation

    KAUST Repository

    Ning, Zhijun

    2012-09-12

    A new solution-phase halide passivation strategy to improve the electronic properties of colloidal quantum dot films is reported. We prove experimentally that the approach leads to an order-of-magnitude increase in mobility and a notable reduction in trap state density. We build solar cells having the highest efficiency (6.6%) reported using all-inorganic colloidal quantum dots. The improved photocurrent results from increased efficiency of collection of infrared-generated photocarriers. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. All-Inorganic Colloidal Quantum Dot Photovoltaics Employing Solution-Phase Halide Passivation

    KAUST Repository

    Ning, Zhijun; Ren, Yuan; Hoogland, Sjoerd; Voznyy, Oleksandr; Levina, Larissa; Stadler, Philipp; Lan, Xinzheng; Zhitomirsky, David; Sargent, Edward H.

    2012-01-01

    A new solution-phase halide passivation strategy to improve the electronic properties of colloidal quantum dot films is reported. We prove experimentally that the approach leads to an order-of-magnitude increase in mobility and a notable reduction in trap state density. We build solar cells having the highest efficiency (6.6%) reported using all-inorganic colloidal quantum dots. The improved photocurrent results from increased efficiency of collection of infrared-generated photocarriers. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. CdTe quantum dots functionalized with 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide as luminescent nanoprobe for the sensitive recognition of bromide ion

    Energy Technology Data Exchange (ETDEWEB)

    Adegoke, Oluwasesan [Department of Chemistry, Rhodes University, Grahamstown 6140 (South Africa); Hosten, Eric; McCleland, Cedric [Department of Chemistry, Nelson Mandela Metropolitan University (South Campus), Port Elizabeth 6031 (South Africa); Nyokong, Tebello, E-mail: t.nyokong@ru.ac.za [Department of Chemistry, Rhodes University, Grahamstown 6140 (South Africa)

    2012-04-06

    Graphical abstract: A bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) showed a high selectivity and sensitivity for the determination of bromide ion using fluorescence recovery. Highlights: Black-Right-Pointing-Pointer Water soluble CdTe quantum dots interact with tetramethylpiperidine-N-oxide. Black-Right-Pointing-Pointer Quantum dots fluorescence is quenched by the radical. Black-Right-Pointing-Pointer In the presence of bromide ions the fluorescence is restored. Black-Right-Pointing-Pointer The sensor is more selective to bromine ions than other common ions. - Abstract: A novel bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) has been developed. Fluorescence quenching of the QDs by 4AT was observed. The functionalized QDs-4AT nanoprobe allowed a highly sensitive determination of bromide ion via analyte-induced change in the photoluminescence (fluorescence recovery) of the modified QDs. A detection limit of 0.6 nM of bromide ion was obtained, while the interfering effect of other inorganic cations and anions was investigated to examine the selectivity of the nanoprobe. The linear range was between 0.01 and 0.13 {mu}M. Combined fluorescence lifetime and electron paramagnetic resonance measurements confirmed electron transfer processes between bromide ion and QDs-4AT.

  2. Remanence coercivity of dot arrays of hcp-CoPt perpendicular films

    Energy Technology Data Exchange (ETDEWEB)

    Mitsuzuka, K; Shimatsu, T; Aoi, H [Research Institute of Electrical Communication, Tohoku University, Sendai, 980-8577 (Japan); Kikuchi, N; Okamoto, S; Kitakami, O, E-mail: shimatsu@riec.tohoku.ac.j [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, 980-8577 (Japan)

    2010-01-01

    The remanence coercivity, H{sub r}, of hcp-CoPt dot arrays with various dot thicknesses, {delta}, (3 and 10 nm) and Pt content (20-30at%) were experimentally investigated as a function of the dot diameter, D(30-400 nm). All dot arrays showed a single domain state, even after removal of an applied field equal to H{sub r}. The angular dependence of H{sub r} for the dot arrays indicated coherent rotation of the magnetization during nucleation. H{sub r} increased as Ddecreased in all series of dot arrays with various {delta} and Pt content. Assuming that the nucleation field of a dot is determined by the switching field of a grain having the smallest switching field, we calculated the value of nucleation field H{sub n}{sup cal} taking account of the c-axis distribution and the distribution of the demagnetizing field in the dot. The values of H{sub r} obtained experimentally are in good agreement with those of H{sub n}{sup cal}, taking account of thermal agitation of magnetization. This result suggested that the reversal process of hcp-CoPt dot arrays starts from a nucleation at the center of the dot followed by a propagation process.

  3. Photostable epoxy polymerized carbon quantum dots luminescent thin films and the performance study

    Directory of Open Access Journals (Sweden)

    Chang Zhang

    Full Text Available High photostable epoxy polymerized carbon quantum dots (C-dots luminescent thin films were prepared and their performances were compared with the CdTe quantum dots (QDs. First, water soluble C-dots (λem = 543.60 nm were synthesized. Poly (ethylene glycol diglycidyl ether (PEG and diaminooctane were used as the polymer matrix to make the epoxy resin films. FT-IR spectra showed that there were vibration at 3448 cm−1 and 1644 cm−1 which contributed to -OH and -NH respectively. SEM observations showed that the polymerizations of the films were uniform and there were no structure defects. Mechanical tests showed the tensile modulus of C-dots composite films were 4.6, 4.9, 6.4 and 7.8 MPa respectively with corresponding 0%, 1%, 2% and 5% mass fraction of C-dots, while the tensile modulus of CdTe QDs films were 4.6 MPa under the same mass fraction of CdTe QDs. Compared with semiconductor QDs, the decay of quantum yield were 5% and 10% for the C-dots and CdTe QDs, respectively. The pictures in the continuous irradiation of 48 h showed that the C-dots film was more photostable. This study provides much helpful and profound towards the fluorescent enhancement films in the field of flexible displays. Keywords: Carbon-dots, Waterborne epoxy resin, Luminescent materials, Quantum dots displays

  4. Syntheses of [5-2H]-uracil, [5-2H]-cytosine, [6-2H]-uracil and [6-2H]-cytosine

    International Nuclear Information System (INIS)

    Kiritani, Reiko; Asano, Takeyoshi; Fujita, Shin-ichi; Dohmaru, Takaaki; Kawanishi, Tetsuro

    1986-01-01

    Syntheses of [5- 2 H]-, [6- 2 H]-uracil and [5- 2 H]-, [6- 2 H]-cytosine were investigated. The catalytic reaction of uracil or cytosine with 2 H 2 gas in alkaline media gave rise to [6- 2 H]-compounds almost exclusively. On the other hand, the reaction of 5-bromouracil or 5-bromocytosine with 2 H 2 gas gave rise to a mixture of [5- 2 H]-, [6- 2 H]- and [5- 2 H, 6- 2 H]-compounds depending on the experimental conditions. By controlling the temperature, the pressure of 2 H 2 gas and the amount of catalyst, [5- 2 H]-uracil and [5- 2 H]-cytosine were obtained. The isotopic distribution in each product was measured by 1 H NMR spectroscopy combined with an HPLC method. (author)

  5. Fluorescent graphene quantum dots as traceable, pH-sensitive drug delivery systems

    Directory of Open Access Journals (Sweden)

    Qiu J

    2015-10-01

    Full Text Available Jichuan Qiu,1 Ruibin Zhang,2 Jianhua Li,1 Yuanhua Sang,1 Wei Tang,3 Pilar Rivera Gil,4 Hong Liu1,51Center of Bio and Micro/Nano Functional Materials, State Key Laboratory of Crystal Materials, Shandong University, 2Blood Purification Center, Jinan Central Hospital, 3Department of Pathogenic Biology, Shandong University School of Medicine, Jinan, People’s Republic of China; 4Institute of Chemistry, Rovira i Virgili University, Tarragona, Spain; 5Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, People’s Republic of ChinaAbstract: Graphene quantum dots (GQDs were rationally fabricated as a traceable drug delivery system for the targeted, pH-sensitive delivery of a chemotherapeutic drug into cancer cells. The GQDs served as fluorescent carriers for a well-known anticancer drug, doxorubicin (Dox. The whole system has the capacity for simultaneous tracking of the carrier and of drug release. Dox release is triggered upon acidification of the intracellular vesicles, where the carriers are located after their uptake by cancer cells. Further functionalization of the loaded carriers with targeting moieties such as arginine-glycine-aspartic acid (RGD peptides enhanced their uptake by cancer cells. DU-145 and PC-3 human prostate cancer cell lines were used to evaluate the anticancer ability of Dox-loaded RGD-modified GQDs (Dox-RGD-GQDs. The results demonstrated the feasibility of using GQDs as traceable drug delivery systems with the ability for the pH-triggered delivery of drugs into target cells.Keywords: graphene quantum dots, drug delivery, pH-sensitive, controlled release, traceable

  6. Engineering colloidal quantum dot solids within and beyond the mobility-invariant regime

    KAUST Repository

    Zhitomirsky, David

    2014-05-06

    © 2014 Macmillan Publishers Limited. Colloidal quantum dots are attractive materials for efficient, low-cost and facile implementation of solution-processed optoelectronic devices. Despite impressive mobilities (1-30 cm2V-1 s-1) reported for new classes of quantum dot solids, it is-surprisingly-the much lower-mobility (10-3-10-2 cm2V-1 s-1) solids that have produced the best photovoltaic performance. Here we show that it is not mobility, but instead the average spacing among recombination centres that governs the diffusion length of charges in today\\'s quantum dot solids. In this regime, colloidal quantum dot films do not benefit from further improvements in charge carrier mobility. We develop a device model that accurately predicts the thickness dependence and diffusion length dependence of devices. Direct diffusion length measurements suggest the solid-state ligand exchange procedure as a potential origin of the detrimental recombination centres. We then present a novel avenue for in-solution passivation with tightly bound chlorothiols that retain passivation from solution to film, achieving an 8.5% power conversion efficiency.

  7. 78 FR 48868 - Proposed Cercla Administrative Cost Recovery Settlement; MassDOT, MassDOT Route 1 Right-of-Way...

    Science.gov (United States)

    2013-08-12

    ... Settlement; MassDOT, MassDOT Route 1 Right-of-Way Site, Chelsea, MA AGENCY: Environmental Protection Agency... (``CERCLA''), 42 U.S.C. 9622(h)(1), concerning the MassDOT Route 1 Right-of-Way Site in Chelsea... (OES04-3), Boston, MA 02109-3912 (Telephone No. 617-918-1886) and should refer to: In re: MassDOT Route 1...

  8. Spin storage in quantum dot ensembles and single quantum dots

    International Nuclear Information System (INIS)

    Heiss, Dominik

    2009-01-01

    This thesis deals with the investigation of spin relaxation of electrons and holes in small ensembles of self-assembled quantum dots using optical techniques. Furthermore, a method to detect the spin orientation in a single quantum dot was developed in the framework of this thesis. A spin storage device was used to optically generate oriented electron spins in small frequency selected quantum dot ensembles using circularly polarized optical excitation. The spin orientation can be determined by the polarization of the time delayed electroluminescence signal generated by the device after a continuously variable storage time. The degree of spin polarized initialization was found to be limited to 0.6 at high magnetic fields, where anisotropic effects are compensated. The spin relaxation was directly measured as a function of magnetic field, lattice temperature and s-shell transition energy of the quantum dot by varying the spin storage time up to 30 ms. Very long spin lifetimes are obtained with a lower limit of T 1 =20 ms at B=4 T and T=1 K. A strong magnetic field dependence T 1 ∝B -5 has been observed for low temperatures of T=1 K which weakens as the temperature is increased. In addition, the temperature dependence has been determined with T 1 ∝T -1 . The characteristic dependencies on magnetic field and temperature lead to the identification of the spin relaxation mechanism, which is governed by spin-orbit coupling and mediated by single phonon scattering. This finding is qualitatively supported by the energy dependent measurements. The investigations were extended to a modified device design that enabled studying the spin relaxation dynamics of heavy holes in self-assembled quantum dots. The measurements show a polarization memory effect for holes with up to 0.1 degree of polarization. Furthermore, investigations of the time dynamics of the hole spin relaxation reveal surprisingly long lifetimes T 1 h in the microsecond range, therefore, comparable with

  9. Spin storage in quantum dot ensembles and single quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Heiss, Dominik

    2009-10-15

    This thesis deals with the investigation of spin relaxation of electrons and holes in small ensembles of self-assembled quantum dots using optical techniques. Furthermore, a method to detect the spin orientation in a single quantum dot was developed in the framework of this thesis. A spin storage device was used to optically generate oriented electron spins in small frequency selected quantum dot ensembles using circularly polarized optical excitation. The spin orientation can be determined by the polarization of the time delayed electroluminescence signal generated by the device after a continuously variable storage time. The degree of spin polarized initialization was found to be limited to 0.6 at high magnetic fields, where anisotropic effects are compensated. The spin relaxation was directly measured as a function of magnetic field, lattice temperature and s-shell transition energy of the quantum dot by varying the spin storage time up to 30 ms. Very long spin lifetimes are obtained with a lower limit of T{sub 1}=20 ms at B=4 T and T=1 K. A strong magnetic field dependence T{sub 1}{proportional_to}B{sup -5} has been observed for low temperatures of T=1 K which weakens as the temperature is increased. In addition, the temperature dependence has been determined with T{sub 1}{proportional_to}T{sup -1}. The characteristic dependencies on magnetic field and temperature lead to the identification of the spin relaxation mechanism, which is governed by spin-orbit coupling and mediated by single phonon scattering. This finding is qualitatively supported by the energy dependent measurements. The investigations were extended to a modified device design that enabled studying the spin relaxation dynamics of heavy holes in self-assembled quantum dots. The measurements show a polarization memory effect for holes with up to 0.1 degree of polarization. Furthermore, investigations of the time dynamics of the hole spin relaxation reveal surprisingly long lifetimes T{sub 1}{sup h

  10. Optically Driven Spin Based Quantum Dots for Quantum Computing - Research Area 6 Physics 6.3.2

    Science.gov (United States)

    2015-12-15

    SECURITY CLASSIFICATION OF: This program conducted experimental and theoretical research aimed at developing an optically driven quantum dot quantum ...computer, where, the qubit is the spin of the electron trapped in a self-assembled quantum dot in InAs. Optical manipulation using the trion state...reports. In this reporting period, we discovered the nuclear spin quieting first discovered in 2008 is present in vertically coupled quantum dots but

  11. One-pot and ultrafast synthesis of nitrogen and phosphorus co-doped carbon dots possessing bright dual wavelength fluorescence emission

    Science.gov (United States)

    Sun, Xiangcheng; Brückner, Christian; Lei, Yu

    2015-10-01

    Very brief microwave heating of aniline, ethylene diamine, and phosphoric acid in water at ambient pressure generated nitrogen and phosphorus co-doped carbon dots (N,P-CDs) that exhibit bright dual blue (centred at 450 nm; 51% quantum yield) and green (centred at 510 nm, 38% quantum yield) fluorescence emission bands. The N,P-CDs were characterized using TEM, XRD, XPS, IR, UV-vis, and fluorescence spectroscopy, demonstrating their partially crystalline carbon, partially amorphous structures, and the incorporation of O, N, and P into the carbogenic scaffold. The N,P-CDs demonstrated excitation-dependent and nearly pH-independent emission properties. The unique dual emission properties lay the foundation for the use of N,P-CDs in ratiometric sensing applications.Very brief microwave heating of aniline, ethylene diamine, and phosphoric acid in water at ambient pressure generated nitrogen and phosphorus co-doped carbon dots (N,P-CDs) that exhibit bright dual blue (centred at 450 nm; 51% quantum yield) and green (centred at 510 nm, 38% quantum yield) fluorescence emission bands. The N,P-CDs were characterized using TEM, XRD, XPS, IR, UV-vis, and fluorescence spectroscopy, demonstrating their partially crystalline carbon, partially amorphous structures, and the incorporation of O, N, and P into the carbogenic scaffold. The N,P-CDs demonstrated excitation-dependent and nearly pH-independent emission properties. The unique dual emission properties lay the foundation for the use of N,P-CDs in ratiometric sensing applications. Electronic supplementary information (ESI) available: Detailed experimental section, XRD, FTIR, explosive sensing and the applications results. See DOI: 10.1039/c5nr05549k

  12. Loading Cd0.5Zn0.5S Quantum Dots onto Onion-Like Carbon Nanoparticles to Boost Photocatalytic Hydrogen Generation.

    Science.gov (United States)

    Zhou, Xiaolong; Wang, Xina; Feng, Xi; Zhang, Kun; Peng, Xiaoniu; Wang, Hanbin; Liu, Chunlei; Han, Yibo; Wang, Hao; Li, Quan

    2017-07-12

    Carbon dots (C dots, size < 10 nm) have been conventionally decorated onto semiconductor matrixes for photocatalytic H 2 evolution, but the efficiency is largely limited by the low loading ratio of the C dots on the photocatalyst. Here, we propose an inverse structure of Cd 0.5 Zn 0.5 S quantum dots (QDs) loaded onto the onionlike carbon (OLC) matrix for noble metal-free photocatalytic H 2 evolution. Cd 0.5 Zn 0.5 S QDs (6.9 nm) were uniformly distributed on an OLC (30 nm) matrix with both upconverted and downconverted photoluminescence property. Such an inverse structure allows the full optimization of the QD/OLC interfaces for effective energy transfer and charge separation, both of which contribute to efficient H 2 generation. An optimized H 2 generation rate of 2018 μmol/h/g (under the irradiation of visible light) and 58.6 μmol/h/g (under the irradiation of 550-900 nm light) was achieved in the Cd 0.5 Zn 0.5 S/OLC composite samples. The present work shows that using the OLC matrix in such a reverse construction is a promising strategy for noble metal-free solar hydrogen production.

  13. The first 3D malonate bridged copper [Cu(O{sub 2}C-CH{sub 2}-CO{sub 2}H){sub 2}{center_dot}2H{sub 2}O]: Structure, properties and electronic structure

    Energy Technology Data Exchange (ETDEWEB)

    Seguatni, A., E-mail: seguatni@gmail.com [LBPC-INSERM U 698, Institut Galilee, Universite Paris XIII, 99, avenue J. B. Clement 93430, Villetaneuse (France); Fakhfakh, M. [Unite de recherche UR 12-30, Synthese et Structure de Materiaux Inorganiques, Faculte des Sciences de Bizerte, 7021 Zarzouna (Tunisia); Departement de Chimie, Universite du Quebec a Montreal, C.P. 8888, Succ. Centre-ville, Montreal, Que., H3C 3P8 (Canada); Smiri, L.S. [Unite de recherche UR 12-30, Synthese et Structure de Materiaux Inorganiques, Faculte des Sciences de Bizerte, 7021 Zarzouna (Tunisia); Gressier, P.; Boucher, F. [Institut des Materiaux Jean Rouxel, Universite de Nantes, CNRS, 2 rue de la Houssiniere, BP 32229, 44322 Nantes Cedex 3 (France); Jouini, N. [Departement de Chimie, Universite du Quebec a Montreal, C.P. 8888, Succ. Centre-ville, Montreal, Que., H3C 3P8 (Canada)

    2012-03-15

    A new inorganic-organic compound [Cu(O{sub 2}C-CH{sub 2}-CO{sub 2}H){sub 2}{center_dot}2H{sub 2}O] ([Cumal]) was hydrothermally synthesized and characterized by IR spectroscopy, thermal analysis and single crystal X-ray diffraction. [Cumal] is the first three-dimensional compound existing in the system Cu(II)-malonic acid-H{sub 2}O. Its framework is built up through carboxyl bridged copper where CuO{sub 6} octahedra are elongated with an almost D{sub 4h} symmetry (4+2) due to the Jahn-Teller effect. The magnetic properties were studied by measuring its magnetic susceptibility in the temperature range of 2-300 K indicating the existence of weak ferromagnetic interactions. The electronic structure of [Cumal] was calculated within the density functional theory (DFT) framework. Structural features are well reproduced using DFT structural optimizations and the optical spectra, calculated within the dielectric formalism, explain very well the light blue colour of the compound. It is shown that a GGA+U approach with a U{sub eff} value of about 6 eV is necessary for a better correlation with the experiment. - Graphical abstract: [Cu(O{sub 2}C-CH{sub 2}-CO{sub 2}H){sub 2}{center_dot}2H{sub 2}O]: the first 3D hybrid organic-inorganic compound built up carboxyl groups. The network presents a diamond-like structure achieved via carboxyl. Highlights: Black-Right-Pointing-Pointer A new organic-inorganic material with an unprecedented topology is synthesized. Black-Right-Pointing-Pointer Crystallographic structure is determined using single crystal X-ray diffraction. Black-Right-Pointing-Pointer Electronic structure is obtained from DFT, GGA+U calculation. Black-Right-Pointing-Pointer Framework can be described as formed from CuC{sub 4} tetrahedron sharing four corners. Black-Right-Pointing-Pointer This structure can be classified as an extended diamond structure.

  14. Production of graphene quantum dots by ultrasound-assisted exfoliation in supercritical CO2/H2O medium.

    Science.gov (United States)

    Gao, Hanyang; Xue, Chen; Hu, Guoxin; Zhu, Kunxu

    2017-07-01

    In this research, three kinds of graphene quantum dots (GQDs)-pristine graphene quantum dots (PGQDs), expanded graphene quantum dots (EGQDs) and graphene oxide quantum dots (GOQDs)-were produced from natural graphite, expanded graphite, and oxide graphite respectively in an ultrasound-assisted supercritical CO 2 (scCO 2 )/H 2 O system. The effects of aqueous solution content ratio, system pressure, and ultrasonic power on the yields of different kinds of GQDs were investigated. According to these experiment results, the combination of the intense knocking force generated from high-pressure acoustic cavitation in a scCO 2 /H 2 O system and the superior penetration ability of scCO 2 was considered to be the key to the successful exfoliation of such tiny pieces from bulk graphite. An interesting result was found that, contrary to common experience, the yield of PGQDs from natural graphite was much higher than that of GOQDs from graphite oxide. Based on the experimental analysis, the larger interlayer resistance of natural graphite, which hindered the insertion of scCO 2 molecules, and the hydrophobic property of natural graphite surface, which made the planar more susceptible to the attack of ultrasonic collapsing bubbles, were deduced to be the two main reasons for this result. The differences in characteristics among the three kinds of GQDs were also studied and compared in this research. In our opinion, this low-cost and time-saving method may provide an alternative green route for the production of various kinds of GQDs, especially PGQDs. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Electronic and Optical Properties of Small Hydrogenated Silicon Quantum Dots Using Time-Dependent Density Functional Theory

    Directory of Open Access Journals (Sweden)

    Muhammad Mus-’ab Anas

    2015-01-01

    Full Text Available This paper presents a systematic study of the absorption spectrum of various sizes of small hydrogenated silicon quantum dots of quasi-spherical symmetry using the time-dependent density functional theory (TDDFT. In this study, real-time and real-space implementation of TDDFT involving full propagation of the time-dependent Kohn-Sham equations were used. The experimental results for SiH4 and Si5H12 showed good agreement with other earlier calculations and experimental data. Then these calculations were extended to study larger hydrogenated silicon quantum dots with diameter up to 1.6 nm. It was found that, for small quantum dots, the absorption spectrum is atomic-like while, for relatively larger (1.6 nm structure, it shows bulk-like behavior with continuous plateau with noticeable peak. This paper also studied the absorption coefficient of silicon quantum dots as a function of their size. Precisely, the dependence of dot size on the absorption threshold is elucidated. It was found that the silicon quantum dots exhibit direct transition of electron from HOMO to LUMO states; hence this theoretical contribution can be very valuable in discerning the microscopic processes for the future realization of optoelectronic devices.

  16. Photoemission Studies of Si Quantum Dots with Ge Core: Dots formation, Intermixing at Si-clad/Ge-core interface and Quantum Confinement Effect

    OpenAIRE

    Yudi Darma

    2008-01-01

    Spherical Si nanocrystallites with Ge core (~20nm in average dot diameter) have been prepared by controlling selective growth conditions of low-pressure chemical vapor deposition (LPCVD) on ultrathin SiO2 using alternately pure SiH4 and 5% GeH4 diluted with He. XPS results confirm the highly selective growth of Ge on the pregrown Si dots and subsequently complete coverage by Si selective growth on Ge/Si dots. Compositional mixing and the crystallinity of Si dots with Ge core as a function of ...

  17. Optical spectroscopy of single, planar, self-assembled InAs/InP quantum dots

    International Nuclear Information System (INIS)

    Kim, D.; Williams, R.L.; Lefebvre, J.; Lapointe, J.; Reimer, M.E.; Mckee, J.; Poole, P.J.

    2006-01-01

    We present optical spectra from numerous, single, self-assembled InAs/InP quantum dots. More than 50 individual dots are studied that emit in the 1.1-1.6 mm wavelength range. The dots are of high optical quality as judged by the clean, single exciton emission line at low power, the resolution limited linewidth, and the brightness. Each dot exhibits similar trends in the power evolution spectra, despite large variations in height and diameter. The level splittings in the p -shell increase with decreasing height, which we interpret to be from dot elongation along the [01 anti 1] direction. The evolution of the spectra with increasing power agrees well with predictions from effective bond orbital calculations. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Complex dynamics in planar two-electron quantum dots

    International Nuclear Information System (INIS)

    Schroeter, Sebastian Josef Arthur

    2013-01-01

    Quantum dots play an important role in a wide range of recent experimental and technological developments. In particular they are promising candidates for realisations of quantum bits and further applications in quantum information theory. The harmonically confined Hooke's atom model is experimentally verified and separates in centre-of-mass and relative coordinates. Findings that are contradictory to this separability call for an extension of the model, in particular changing the confinement potential. In order to study effects of an anharmonic confinement potential on spectral properties of planar two-electron quantum dots a sophisticated numerical approach is developed. Comparison between the Helium atom, Hooke's atom and an anharmonic potential model are undertaken in order to improve the description of quantum dots. Classical and quantum features of complexity and chaos are investigated and used to characterise the dynamics of the system to be mixed regular-chaotic. Influence of decoherence can be described by quantum fidelity, which measures the effect of a perturbation on the time evolution. The quantum fidelity of eigenstates of the system depends strongly on the properties of the perturbation. Several methods for solving the time-dependent Schrödinger equation are implemented and a high level of accuracy for long time evolutions is achieved. The concept of offset entanglement, the entanglement of harmonic models in the noninteracting limit, is introduced. This concept explains different questions raised in the literature for harmonic quantum dot models, recently. It shows that only in the groundstate the electrons are not entangled in the fermionic sense. The applicability, validity, and origin of Hund's first rule in general quantum dot models is further addressed. In fact Hund's first rule is only applicable, and in this case also valid, for one pair of singlet and triplet states in Hooke's atom. For more realistic models of two-electron quantum dots an

  19. Transport through overlapping states in quantum dots and double dot molecules

    International Nuclear Information System (INIS)

    Berkovits, R.

    2006-01-01

    Full Text: We shall review the transport properties of interacting quantum dots with overlapping orbitals for which the orthodox Coulomb blockade picture no longer holds. We shall concentrate on he conductance through a serial double dot structure for which the inter-dot tunneling is stronger than the tunneling to the leads. When the dots are occupied by 1 or 3 electrons the usual Kondo peak is observed. For the case in which 2 electrons occupy the molecule a singlet is formed. Nevertheless, the conductance in that case has a constant non-zero value, and might even be equal to the maximum conductance of 2e 2 /h for certain values of the molecule parameters. We show that this is the result of the subtle interplay between the symmetric and anti-symmetric orbitals of the molecule caused by interactions and interference

  20. Complete quantum control of exciton qubits bound to isoelectronic centres.

    Science.gov (United States)

    Éthier-Majcher, G; St-Jean, P; Boso, G; Tosi, A; Klem, J F; Francoeur, S

    2014-05-30

    In recent years, impressive demonstrations related to quantum information processing have been realized. The scalability of quantum interactions between arbitrary qubits within an array remains however a significant hurdle to the practical realization of a quantum computer. Among the proposed ideas to achieve fully scalable quantum processing, the use of photons is appealing because they can mediate long-range quantum interactions and could serve as buses to build quantum networks. Quantum dots or nitrogen-vacancy centres in diamond can be coupled to light, but the former system lacks optical homogeneity while the latter suffers from a low dipole moment, rendering their large-scale interconnection challenging. Here, through the complete quantum control of exciton qubits, we demonstrate that nitrogen isoelectronic centres in GaAs combine both the uniformity and predictability of atomic defects and the dipole moment of semiconductor quantum dots. This establishes isoelectronic centres as a promising platform for quantum information processing.

  1. Experimental and theoretical studies of the C{sub 6}H{sub 5} + C{sub 6}H{sub 6} reaction

    Energy Technology Data Exchange (ETDEWEB)

    Park, J.; Burova, S.; Rodgers, A.S.; Lin, M.C.

    1999-11-11

    The absolute rate constants for the C{sub 6}H{sub 5} + C{sub 6}H{sub 6} and C{sub 6}D{sub 6} reactions have been measured by cavity ringdown spectrometry at temperatures between 298 and 495 K at a constant 40 Torr Ar pressure. The new results, which reveal no detectable kinetic isotopic effect, can be represented by the Arrhenius equation, {kappa}{sub 1} = 10{sup (11.91{+-}0.13)} exp[{minus}(2,102 {+-} 106)/T] cm{sup 3}/(mol s). Low-temperature data for the addition/stabilization process, C{sub 6}H{sub 5} + C{sub 6}H{sub 6} {r{underscore}arrow} C{sub 12}H{sub 11}, can be correlated with those obtained in a low-pressure, high-temperature Knudsen cell study for the addition/displacement reaction, C{sub 6}H{sub 5} + C{sub 6}H{sub 6} {r{underscore}arrow} C{sub 12}H{sub 10} + H, by the RRKM theory using the molecular and transition-state parameters computed at the B3LYP/6-311G(d,p) level of theory. Combination of these two sets of data gives {kappa}{sub 1} = 10{sup (11.98{+-}0.03)} exp[{minus}(2168 {+-} 34)/T] cm{sup 3}/(mol s) covering the temperature range 298--1,330 K. The RRKM theory also correlates satisfactorily the forward reaction data with the high-temperature shock-tube result for the reverse H-for-C{sub 6}H{sub 5} substitution process with 2.7 and 4.7 kcal/mol barriers for the entrance (C{sub 6}H{sub 5} + C{sub 6}H{sub 6}) and reverse (H + C{sub 12}H{sub 10}) reactions, respectively. For modeling applications, the authors have calculated the forward reaction rate constants for the formation of the two competing products, H + C{sub 12}H{sub 10} and C{sub 12}H{sub 11}, at several pressures covering 300 K {lt} T {lt} 2,500 K.

  2. The Influence of Defects on the Electron-Transfer and Magnetic Properties of RbxMn[Fe(CN)6]y·zH2O

    NARCIS (Netherlands)

    Vertelman, Esther J.M.; Maccallini, Enrico; Gournis, Dimitris; Rudolf, Petra; Bakas, Thomas; Luzon, Javier; Broer-Braam, Henderika; Pugzlys, Audrius; Lummen, Tom T.A.; van Loosdrecht, Paul H.M.; van Koningsbruggen, Petronella

    2006-01-01

    The synthesis and detailed characterization of a few samples of the compound RbxMn[Fe(CN)(6)](y)center dot zH(2)O are described. The composition of the materials significantly depends on the applied preparative conditions. Analysis of spectroscopic results (FTIR, Raman, Fe-57 Mossbauer, XPS) and

  3. Red light emitting solid state hybrid quantum dot-near-UV GaN LED devices

    International Nuclear Information System (INIS)

    Song, Hongjoo; Lee, Seonghoon

    2007-01-01

    We produced core-shell (CdSe)ZnSe quantum dots by direct colloidal chemical synthesis and the surface-passivation method-an overcoating of the core CdSe with a larger-bandgap material ZnSe. The (CdSe)ZnSe quantum dots(QDs) play the role of a colour conversion centre. We call these quantum dots nanophosphors. We fabricated red light emitting hybrid devices of (CdSe)ZnSe QDs and a near-UV GaN LED by combining red light emitting (CdSe)ZnSe quantum dots (as a colour conversion centre) with a near-UV(NUV) GaN LED chip (as an excitation source). A few good red phosphors have been known for UV excitation wavelengths, and red phosphors for UV excitation have been sought for a long time. Here we tested the possibility of using (CdSe)ZnSe QDs as red nanophosphors for UV excitation. The fabricated red light emitting hybrid device of (CdSe)ZnSe and a NUV GaN LED chip showed a good luminance. We demonstrated that the (CdSe)ZnSe quantum dots were promising red nanophosphors for NUV excitation and that a red LED made of QDs and a NUV excitation source was a highly efficient hybrid device

  4. High frequency response of open quantum dots

    International Nuclear Information System (INIS)

    Brunner, R.; Meisels, R.; Kuchar, F.; Ferry, D.; Elhassan, M.; Ishibashi, K.

    2002-01-01

    Full text: We investigate the response of the transport through open quantum dots to millimeterwave radiation (up to 55 GHz). In the low-field region ( 11 cm -2 and a mobility of 1.2 10 6 cm 2 /Vs. By applying a sufficiently negative voltage to the gates the 2DES is split into two regions connected only by a dot-like region (about 350 nm diameter) between them. The DC data exhibit backscattering peaks at fields of a few tenth of a Tesla. Shubnikovde- Haas (SdH) oscillations appear above 0.5 T. While the SdH oscillations show the usual temperature dependence, the backscattering peaks are temperature independent up to 2.5 K. The backscattering peak shows a reduction of 10 percent due to the millimeterwave irradiation. However, due to the temperature independence of this peak, this reduction cannot simply be attributed to electron heating. This conclusion is supported by the observation of a strong frequency dependence of the reduction of the peak height. (author)

  5. Ordered Nanopillar Structured Electrodes for Depleted Bulk Heterojunction Colloidal Quantum Dot Solar Cells

    KAUST Repository

    Kramer, Illan J.; Zhitomirsky, David; Bass, John D.; Rice, Philip M.; Topuria, Teya; Krupp, Leslie; Thon, Susanna M.; Ip, Alexander H.; Debnath, Ratan; Kim, Ho-Cheol; Sargent, Edward H.

    2012-01-01

    A bulk heterojunction of ordered titania nanopillars and PbS colloidal quantum dots is developed. By using a pre-patterned template, an ordered titania nanopillar matrix with nearest neighbours 275 nm apart and height of 300 nm is fabricated and subsequently filled in with PbS colloidal quantum dots to form an ordered depleted bulk heterojunction exhibiting power conversion efficiency of 5.6%. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Ordered Nanopillar Structured Electrodes for Depleted Bulk Heterojunction Colloidal Quantum Dot Solar Cells

    KAUST Repository

    Kramer, Illan J.

    2012-03-30

    A bulk heterojunction of ordered titania nanopillars and PbS colloidal quantum dots is developed. By using a pre-patterned template, an ordered titania nanopillar matrix with nearest neighbours 275 nm apart and height of 300 nm is fabricated and subsequently filled in with PbS colloidal quantum dots to form an ordered depleted bulk heterojunction exhibiting power conversion efficiency of 5.6%. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Enhancement effect of CdTe quantum dots-IgG bioconjugates on chemiluminescence of luminol-H2O2 system

    International Nuclear Information System (INIS)

    Kanwal, Shamsa; Traore, Zoumana; Zhao Chunfang; Su Xingguang

    2010-01-01

    In this paper we developed an entirely new and highly sensitive luminol-H 2 O 2 flow injection chemiluminescence system using the enhancement effect of CdTe quantum dots-IgG bioconjugates. Immunoglobulin G (IgG) as a kind of bio-molecule was conjugated to different sized CdTe semiconductor quantum dots (QDs). Using PL spectra and CL intensity profiles, it was found that chemiluminescence resonance energy transfer (CRET) was possibly occurring between CdTe-IgG bioconjugate and luminol. Under optimum conditions, increase of IgG concentration in CdTe-IgG bioconjugate resulted enhancing effect on CL intensity of luminol-H 2 O 2 system. Moreover quenching effects on CL intensity by addition of different proteases can construct turn off biosensor for these proteases with low detection limits and wide linear range. Furthermore, the effects of various organic and inorganic species on CdTe-IgG bioconjugates enhanced luminol-H 2 O 2 CL system were also studied in this paper.

  8. Formaldehyde in the Galactic Centre

    International Nuclear Information System (INIS)

    Cohen, R.J.; Few, R.W.

    1981-01-01

    Formaldehyde 6-cm absorption in the direction of the Galactic Centre has been surveyed using the Jodrell Bank MK II radio telescope (beam-width 10 x 9 arcmin). The observations sample the region - 2 0 = 0 and - 0 0 .5 = 0 .5, with a velocity range of 620 km s -1 , a velocity resolution of 2.1 km s -1 and an rms noise level of approximately 0.03 K. The data are presented as contour maps showing line temperature as a function of latitude and velocity (b-V maps) and as a function of longitude and velocity (l-V maps). Similar maps of the line-to-continuum ratio are also presented. The radial distribution of formaldehyde (H 2 CO) in the Galactic Centre region is derived using two different kinematic models which give similar results. Formaldehyde is strongly concentrated in the Galactic Centre in a layer of latitude extent approximately 0 0 .5 and longitude extent approximately 4 0 which contains one quarter of all the H 2 CO in the Galaxy. The distribution is centred on l approximately 1 0 . The individual H 2 CO features are described in detail. (author)

  9. Intense Visible Luminescence in CdSe Quantum Dots by Efficiency Surface Passivation with H2O Molecules

    Directory of Open Access Journals (Sweden)

    Hyeoung Woo Park

    2012-01-01

    Full Text Available We have investigated the effect of water (H2O cooling and heat treatment on the luminescence efficiency of core CdSe quantum dots (QDs. The photoluminescence (PL quantum yield of the CdSe QDs was enhanced up to ~85%, and some periodic bright points were observed in wide color ranges during the heat treatment of QDs mixed with H2O. The PL enhancement of QDs could be attributed to the recovery of QDs surface traps by unreacted ligands confined within the hydrophilic H2O molecule containers.

  10. DotFETs: MOSFETs strained by a Single SiGE dot in a Low-Temperature ELA Technology

    OpenAIRE

    Biasotto, C.

    2011-01-01

    The work presented in this thesis was performed in the context of the European Sixth Framework Program FP6 project “Disposable Dot Field Effect Transistor for High Speed Si Integrated Circuits”, referred to as the D-DotFET project. The project had the goal of realizing strain-enhanced mobility in CMOS transistors by transferring strain from a self-assembled germanium dot to the channel of a transistor fabricated above the dot. The initial idea was to dispose of the Ge dot underneath the chann...

  11. Complex dynamics in planar two-electron quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Schroeter, Sebastian Josef Arthur

    2013-06-25

    Quantum dots play an important role in a wide range of recent experimental and technological developments. In particular they are promising candidates for realisations of quantum bits and further applications in quantum information theory. The harmonically confined Hooke's atom model is experimentally verified and separates in centre-of-mass and relative coordinates. Findings that are contradictory to this separability call for an extension of the model, in particular changing the confinement potential. In order to study effects of an anharmonic confinement potential on spectral properties of planar two-electron quantum dots a sophisticated numerical approach is developed. Comparison between the Helium atom, Hooke's atom and an anharmonic potential model are undertaken in order to improve the description of quantum dots. Classical and quantum features of complexity and chaos are investigated and used to characterise the dynamics of the system to be mixed regular-chaotic. Influence of decoherence can be described by quantum fidelity, which measures the effect of a perturbation on the time evolution. The quantum fidelity of eigenstates of the system depends strongly on the properties of the perturbation. Several methods for solving the time-dependent Schrödinger equation are implemented and a high level of accuracy for long time evolutions is achieved. The concept of offset entanglement, the entanglement of harmonic models in the noninteracting limit, is introduced. This concept explains different questions raised in the literature for harmonic quantum dot models, recently. It shows that only in the groundstate the electrons are not entangled in the fermionic sense. The applicability, validity, and origin of Hund's first rule in general quantum dot models is further addressed. In fact Hund's first rule is only applicable, and in this case also valid, for one pair of singlet and triplet states in Hooke's atom. For more realistic models of two

  12. Impact of D2O/H2O Solvent Exchange on the Emission of HgTe and CdTe Quantum Dots: Polaron and Energy Transfer Effects.

    Science.gov (United States)

    Wen, Qiannan; Kershaw, Stephen V; Kalytchuk, Sergii; Zhovtiuk, Olga; Reckmeier, Claas; Vasilevskiy, Mikhail I; Rogach, Andrey L

    2016-04-26

    We have studied light emission kinetics and analyzed carrier recombination channels in HgTe quantum dots that were initially grown in H2O. When the solvent is replaced by D2O, the nonradiative recombination rate changes highlight the role of the vibrational degrees of freedom in the medium surrounding the dots, including both solvent and ligands. The contributing energy loss mechanisms have been evaluated by developing quantitative models for the nonradiative recombination via (i) polaron states formed by strong coupling of ligand vibration modes to a surface trap state (nonresonant channel) and (ii) resonant energy transfer to vibration modes in the solvent. We conclude that channel (i) is more important than (ii) for HgTe dots in either solution. When some of these modes are removed from the relevant spectral range by the H2O to D2O replacement, the polaron effect becomes weaker and the nonradiative lifetime increases. Comparisons with CdTe quantum dots (QDs) served as a reference where the resonant energy loss (ii) a priori was not a factor, also confirmed by our experiments. The solvent exchange (H2O to D2O), however, is found to slightly increase the overall quantum yield of CdTe samples, probably by increasing the fraction of bright dots in the ensemble. The fundamental study reported here can serve as the foundation for the design and optimization principles of narrow bandgap quantum dots aimed at applications in long wavelength colloidal materials for infrared light emitting diodes and photodetectors.

  13. Synthesis of yellow fluorescent carbon dots and their application to the determination of chromium(III) with selectivity improved by pH tuning

    International Nuclear Information System (INIS)

    Chang, Melissa May Fung; Ginjom, Irine Runnie; Ng, Sing Muk; Ngu-Schwemlein, Maria

    2016-01-01

    Carbon dots with yellow fluorescence (y-CDs) were synthesized from sucrose by acid carbonization with phosphoric acid as the dehydrating agent. Optimal yield was obtained by heating sucrose in concentrated phosphoric acid to 85 °C for 30 min. The resulting y-CDs under the photo-excitation at 360 nm display an emission band peaking at 560 nm. The fluorescence is independent of pH values in the range from pH 4.0 to 11.4, and at ionic strengths of up to 4.7 M of potassium chloride. We also show that these y-CDs are viable fluorescent probes for the detection of chromium(III). At near neutral pH conditions, several metal ions quench the emission of the y-CDs, but under acidic conditions (pH 4), fluorescence is strongly affected by Cr(III) only. Quenching depends on the concentration of Cr(III) in the range up to 200 μM, and the limit of detection is 24.6 μM. (author)

  14. Photostability and pH sensitivity of CdSe/ZnSe/ZnS quantum dots in living cells

    International Nuclear Information System (INIS)

    Sun, Y H; Liu, Y S; Vernier, P T; Liang, C H; Chong, S Y; Marcu, L; Gundersen, M A

    2006-01-01

    Photophysical properties of semiconductor nanocrystal quantum dots (QDs) are primary determinants of their efficacy as fluorescence probes in biological systems. Our minimally passivated core/shell/shell QDs are smaller than the QDs with thick polymer coats that are often used for cellular probes, permitting less restricted access to intracellular compartments and at the same time a greater sensitivity to environmental conditions. We report here a reversible photoinduced fluorescence enhancement (photoactivation) of endocytosed mercaptoacetic-acid-capped CdSe quantum dots (MAA QDs) and the pH dependence of MAA QD photoluminescence in SKOV-3 human ovarian cancer cells. The fluorescence emission of MAA QDs taken up directly by SKOV-3 cells without the need for extra capping ligands or permeabilization steps remains bright and stable for at least 14 days. These intracellular fluorescent nanocrystals do not colocalize with low-pH lysosomes, and the emission of the MAA QDs in fixed cell preparations is quenched by acidic buffer, suggesting that a low-pH environment in cellular vesicles quenches QD fluorescence. Photoactivation of intracellular MAA QD luminescence is dependent on the excitation energy and is related to the metabolic activity of the cells. These active interactions between cells and nanocrystals demonstrate the potential of MAA QDs as intracellular environmental sensors

  15. Effect of gamma-ray irradiation on the size and properties of CdS quantum dots in reverse micelles

    International Nuclear Information System (INIS)

    Bekasova, O.D.; Revina, A.A.; Rusanov, A.L.; Kornienko, E.S.; Kurganov, B.I.

    2013-01-01

    Cadmium sulfide quantum dots 1.3–5.6 nm in size have been synthesized in sodium bis(2-ethylhexy1)sulfosuccinate (AOT)–water–isooctane micellar solutions with various [H 2 O]/[AOT] molar ratios (w=2.5, 5.0 or 10). Gamma irradiation method has been used to change the size and optical properties of quantum dots. It has been found that γ-irradiation reduces the size polydispersity of quantum dots in the micellar system and alters their fluorescent properties. Fluorescence intensity is enhanced after γ-irradiation. The average fluorescence lifetime of single quantum dots sized 5.2±0.4 nm increases from 5.14 to 6.39 ns after γ-irradiation at a dose of 7.9 kGy. To the best of our knowledge, this is the first report on fluorescence lifetime of single CdS quantum dots in micellar solution. - Highlights: • Gamma irradiation method has been used successfully to change the size and optical properties of CdS quantum dots synthesized in micellar solutions. • γ-Irradiation reduces the size polydispersity of quantum dots in the micellar system. • Fluorescence intensity of CdS quantum dots is enhanced after γ-irradiation. • Fluorescence lifetime of single CdS quantum dots increases after γ-irradiation

  16. Probing Temperature- and pH-Dependent Binding between Quantum Dots and Bovine Serum Albumin by Fluorescence Correlation Spectroscopy

    Directory of Open Access Journals (Sweden)

    Zonghua Wang

    2017-04-01

    Full Text Available Luminescent quantum dots (QDs with unique optical properties have potential applications in bio-imaging. The interaction between QDs and bio-molecules is important to the biological effect of QDs in vivo. In this paper, we have employed fluorescence correlation spectroscopy (FCS to probe the temperature- and pH-dependent interactions between CdSe QDs with carboxyl (QDs-COOH and bovine serum albumin (BSA in buffer solutions. The results have shown that microscopic dissociation constant K′D is in the range of (1.5 ± 0.2 × 10−5 to (8.6 ± 0.1 × 10−7 M, the Hill coefficient n is from 0.4 to 2.3, and the protein corona thickness is from 3.0 to 9.4 nm. Variable-temperature measurements have shown both negative values of ∆H and ∆S for BSA adsorption on QDs-COOH, while pH has a profound effect on the adsorption. Additional, FCS measurement QDs-COOH and proteins in whole mice serum and plasma samples has also been conducted. Finally, simulation results have shown four favored QD binding sites in BSA.

  17. On the diameter of dot-critical graphs

    Directory of Open Access Journals (Sweden)

    Doost Ali Mojdeh

    2009-01-01

    Full Text Available A graph G is \\(k\\-dot-critical (totaly \\(k\\-dot-critical if \\(G\\ is dot-critical (totaly dot-critical and the domination number is \\(k\\. In the paper [T. Burtona, D. P. Sumner, Domination dot-critical graphs, Discrete Math, 306 (2006, 11-18] the following question is posed: What are the best bounds for the diameter of a \\(k\\-dot-critical graph and a totally \\(k\\-dot-critical graph \\(G\\ with no critical vertices for \\(k \\geq 4\\? We find the best bound for the diameter of a \\(k\\-dot-critical graph, where \\(k \\in\\{4,5,6\\}\\ and we give a family of \\(k\\-dot-critical graphs (with no critical vertices with sharp diameter \\(2k-3\\ for even \\(k \\geq 4\\.

  18. Photoemission Studies of Si Quantum Dots with Ge Core: Dots formation, Intermixing at Si-clad/Ge-core interface and Quantum Confinement Effect

    Directory of Open Access Journals (Sweden)

    Yudi Darma

    2008-03-01

    Full Text Available Spherical Si nanocrystallites with Ge core (~20nm in average dot diameter have been prepared by controlling selective growth conditions of low-pressure chemical vapor deposition (LPCVD on ultrathin SiO2 using alternately pure SiH4 and 5% GeH4 diluted with He. XPS results confirm the highly selective growth of Ge on the pregrown Si dots and subsequently complete coverage by Si selective growth on Ge/Si dots. Compositional mixing and the crystallinity of Si dots with Ge core as a function of annealing temperature in the range of 550-800oC has been evaluated by XPS analysis and confirms the diffusion of Ge atoms from Ge core towards the Si clad accompanied by formation of GeOx at the Si clad surface. The first subband energy at the valence band of Si dot with Ge core has been measured as an energy shift at the top of the valence band density of state using XPS. The systematic shift of the valence band maximum towards higher binding energy with progressive deposition in the dot formation indicate the charging effect of dots and SiO2 layer by photoemission during measurements.

  19. Spin interactions in InAs quantum dots and molecules

    Energy Technology Data Exchange (ETDEWEB)

    Doty, M.F.; Ware, M.E.; Stinaff, E.A.; Scheibner, M.; Bracker, A.S.; Ponomarev, I.V.; Badescu, S.C.; Reinecke, T.L.; Gammon, D. [Naval Research Lab, Washington, DC 20375 (United States); Korenev, V.L. [A.F. Ioffe Physical Technical Institute, St. Petersburg 194021 (Russian Federation)

    2006-12-15

    Spin interactions between particles in quantum dots or quantum dot molecules appear as fine structure in the photoluminescence spectra. Using the understanding of exchange interactions that has been developed from single dot spectra, we analyze the spin signatures of coupled quantum dots separated by a wide barrier such that inter-dot interactions are negligible. We find that electron-hole exchange splitting is directly evident. In dots charged with an excess hole, an effective hole-hole interaction can be turned on through tunnel coupling. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Switching field distribution and magnetization reversal process of FePt dot patterns

    Energy Technology Data Exchange (ETDEWEB)

    Ishio, S., E-mail: ishio@gipc.akita-u.ac.jp [Department of Materials Science and Engineering, Akita University, Akita 010-8502 (Japan); Takahashi, S.; Hasegawa, T.; Arakawa, A.; Sasaki, H. [Department of Materials Science and Engineering, Akita University, Akita 010-8502 (Japan); Yan, Z.; Liu, X. [Venture Business Laboratory, Akita University, Tegata Gakuen-machi, Akita 010-8502 (Japan); Kondo, Y.; Yamane, H.; Ariake, J. [Akita Prefectural R and D Center, 4-21 Sanuki, Akita 010-1623 (Japan); Suzuki, M.; Kawamura, N.; Mizumaki, M. [Japan Synchrotron Radiation Research Institute, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan)

    2014-06-01

    The fabrication of FePt nanodots with a high structural quality and the control of their switching fields are key issues in realizing high density bit pattern recording. We have prepared FePt dot patterns for dots with 15–300 nm diameters by electron beam lithography and re-annealing, and studied the relation between magnetization reversal process and structure of FePt nanodots. The switching field (H{sub sw}) of dot patterns re-annealed at 710 °C for 240 min showed a bimodal distribution, where a higher peak was found at 5–6 T, and a lower peak was found at ∼2 T. It was revealed by cross-sectional TEM analysis that the structure of dots in the pattern can be classified into two groups. One group has a high degree of order with well-defined [0 0 1] crystalline growth, and the other group includes structurally-disturbed dots like [1 1 1] growth and twin crystals. This structural inhomogeneity causes the magnetic switching field distribution observed. - Highlights: • FePt dot patterns with 15–100 nm dot diameters were prepared by EB lithography. • Maximum coercivity of 30 kOe was found in the dot pattern with 30 nm in diameter. • Magnetization reversal was studied on the base of TEM analysis and LLG simulation.

  1. Synthetic Developments of Nontoxic Quantum Dots.

    Science.gov (United States)

    Das, Adita; Snee, Preston T

    2016-03-03

    Semiconductor nanocrystals, or quantum dots (QDs), are candidates for biological sensing, photovoltaics, and catalysis due to their unique photophysical properties. The most studied QDs are composed of heavy metals like cadmium and lead. However, this engenders concerns over heavy metal toxicity. To address this issue, numerous studies have explored the development of nontoxic (or more accurately less toxic) quantum dots. In this Review, we select three major classes of nontoxic quantum dots composed of carbon, silicon and Group I-III-VI elements and discuss the myriad of synthetic strategies and surface modification methods to synthesize quantum dots composed of these material systems. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Emergency support centre concept for the enhanced CANDU 6

    International Nuclear Information System (INIS)

    Nadimian, R.M.; Leger, R.

    2013-01-01

    In a two-unit Enhanced CANDU 6 (EC6) design, the overall management of an emergency is by the plant emergency support staff using the Emergency Support Centre (ESC). The ESC is a shared facility between both units and is separate from the plant control rooms. ESC is used to provide support for managing overall emergency response, coordinating radiological and environmental assessments, determining recommended public protective actions, and coordinating emergency response activities with federal, provincial, and municipal agencies. Such a facility provides provisions to protect its occupants from hazards resulting from accident conditions, and applicable natural external hazards. (author)

  3. Internalization of targeted quantum dots by brain capillary endothelial cells in vivo.

    Science.gov (United States)

    Paris-Robidas, Sarah; Brouard, Danny; Emond, Vincent; Parent, Martin; Calon, Frédéric

    2016-04-01

    Receptors located on brain capillary endothelial cells forming the blood-brain barrier are the target of most brain drug delivery approaches. Yet, direct subcellular evidence of vectorized transport of nanoformulations into the brain is lacking. To resolve this question, quantum dots were conjugated to monoclonal antibodies (Ri7) targeting the murine transferrin receptor. Specific transferrin receptor-mediated endocytosis of Ri7-quantum dots was first confirmed in N2A and bEnd5 cells. After intravenous injection in mice, Ri7-quantum dots exhibited a fourfold higher volume of distribution in brain tissues, compared to controls. Immunofluorescence analysis showed that Ri7-quantum dots were sequestered throughout the cerebral vasculature 30 min, 1 h, and 4 h post injection, with a decline of signal intensity after 24 h. Transmission electron microscopic studies confirmed that Ri7-quantum dots were massively internalized by brain capillary endothelial cells, averaging 37 ± 4 Ri7-quantum dots/cell 1 h after injection. Most quantum dots within brain capillary endothelial cells were observed in small vesicles (58%), with a smaller proportion detected in tubular structures or in multivesicular bodies. Parenchymal penetration of Ri7-quantum dots was extremely low and comparable to control IgG. Our results show that systemically administered Ri7-quantum dots complexes undergo extensive endocytosis by brain capillary endothelial cells and open the door for novel therapeutic approaches based on brain endothelial cell drug delivery. © The Author(s) 2015.

  4. CdSe/ZnS quantum dots conjugated with a fluorescein derivative: a FRET-based pH sensor for physiological alkaline conditions.

    Science.gov (United States)

    Kurabayashi, Tomokazu; Funaki, Nayuta; Fukuda, Takeshi; Akiyama, Shinnosuke; Suzuki, Miho

    2014-01-01

    Dual pH-dependent fluorescence peaks from a semiconductor quantum dot (QD) and a pH-dependent fluorescent dye can be measured by irradiating with a single wavelength light, and the pH can be estimated from the ratio of the fluorescent intensity of the two peaks. In this work, ratiometric pH sensing was achieved in an aqueous environment by a fluorescent CdSe/ZnS QD appended with a pH-sensitive organic dye, based on fluorescence resonance energy transfer (FRET). By functionalizing the CdSe/ZnS QD with 5-(and 6)-carboxynaphthofluorescein succinimidyl ester as a pH-dependent fluorescent dye, we succeeded in fabricating sensitive nanocomplexes with a linear response to a broad range of physiological pH levels (7.5-9.5) when excited at 450 nm. We found that a purification process is important for increasing the high-fluorescence intensity ratio of a ratiometric fluorescence pH-sensor, and the fluorescence intensity ratio was improved up to 1.0 at pH 8.0 after the purification process to remove unreacted CdSe/ZnS QDs even though the fluorescence of the dye could not be observed without the purification process. The fluorescence intensity ratio corresponds to the fluorescence intensity of the dye, and this fluorescent dye exhibited pH-dependent fluorescence intensity changes. These facts indicate that the fluorescence intensity ratio linearly increased with increasing pH value of the buffer solution containing the QD and the dye. The FRET efficiencies changed from 0.3 (pH 7.5) to 6.2 (pH 9.5).

  5. Synthesis of highly fluorescent hydrophobic carbon dots by hot injection method using Paraplast as precursor

    International Nuclear Information System (INIS)

    Talib, Abou; Pandey, Sunil; Thakur, Mukeshchand; Wu, Hui-Fen

    2015-01-01

    We have reported synthesis of bright blue colored hydrophobic carbon dots (hC-dots) using highly pure blend of polymers called Paraplast. We developed a hot injection method for making nearly monodispersed hC-dots with a diameter in a range: 5–30 nm as confirmed by high resolution transmission electron microscopy (HRTEM). The involvement of various functional groups was confirmed by Fourier transform infra-red (FTIR) spectroscopy. These hC-dots were incubated with breast cancer stem cells in order to check the entry as well as biological imaging. The cells were analyzed using epifluorescent microscopy. hC-dots showed concentration dependent cytotoxicity (LD 50 : 50 mg/ml) and could be used for bioimaging even at lower concentration (0.5 mg/ml). hC-dots were found to be versatile agents for peeping inside the cells which could also be used for delivery of water insoluble chemotherapeutic agents to variety of solid tumors. - Highlights: • Synthesis of hydrophobic carbon dots from polymer based Paraplast • Deep blue color under the influence of UV light • Typical optical properties used for biological imaging • Biological imaging of breast cancer stem cells revealing potential of carbon dots

  6. Synthesis of highly fluorescent hydrophobic carbon dots by hot injection method using Paraplast as precursor

    Energy Technology Data Exchange (ETDEWEB)

    Talib, Abou [Doctoral Degree Program in Marine Biotechnology, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan (China); Pandey, Sunil [Department of Chemistry, National Sun Yat-Sen University, 70, Lien-Hai Road, Kaohsiung 80424, Taiwan (China); Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, 70, Lien-Hai Road, Kaohsiung 80424, Taiwan (China); Thakur, Mukeshchand [Department of Chemistry, National Sun Yat-Sen University, 70, Lien-Hai Road, Kaohsiung 80424, Taiwan (China); Wu, Hui-Fen, E-mail: hui@faculty.nsysu.edu.tw [Department of Chemistry, National Sun Yat-Sen University, 70, Lien-Hai Road, Kaohsiung 80424, Taiwan (China); Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, 70, Lien-Hai Road, Kaohsiung 80424, Taiwan (China); Doctoral Degree Program in Marine Biotechnology, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan (China); School of Pharmacy, College of Pharmacy, Kaohsiung Medical University, Kaohsiung 800, Taiwan (China); Institute of Medical Science and Technology, National Sun Yat-Sen University, Kaohsiung, 80424, Taiwan (China)

    2015-03-01

    We have reported synthesis of bright blue colored hydrophobic carbon dots (hC-dots) using highly pure blend of polymers called Paraplast. We developed a hot injection method for making nearly monodispersed hC-dots with a diameter in a range: 5–30 nm as confirmed by high resolution transmission electron microscopy (HRTEM). The involvement of various functional groups was confirmed by Fourier transform infra-red (FTIR) spectroscopy. These hC-dots were incubated with breast cancer stem cells in order to check the entry as well as biological imaging. The cells were analyzed using epifluorescent microscopy. hC-dots showed concentration dependent cytotoxicity (LD{sub 50}: 50 mg/ml) and could be used for bioimaging even at lower concentration (0.5 mg/ml). hC-dots were found to be versatile agents for peeping inside the cells which could also be used for delivery of water insoluble chemotherapeutic agents to variety of solid tumors. - Highlights: • Synthesis of hydrophobic carbon dots from polymer based Paraplast • Deep blue color under the influence of UV light • Typical optical properties used for biological imaging • Biological imaging of breast cancer stem cells revealing potential of carbon dots.

  7. Underestimation of glucose turnover measured with [6-3H]- and [6,6-2H]- but not [6-14C]glucose during hyperinsulinemia in humans

    International Nuclear Information System (INIS)

    McMahon, M.M.; Schwenk, W.F.; Haymond, M.W.; Rizza, R.A.

    1989-01-01

    Recent studies indicate that hydrogen-labeled glucose tracers underestimate glucose turnover in humans under conditions of high flux. The cause of this underestimation is unknown. To determine whether the error is time-, pool-, model-, or insulin-dependent, glucose turnover was measured simultaneously with [6-3H]-, [6,6-2H2]-, and [6-14C]glucose during a 7-h infusion of either insulin (1 mU.kg-1.min-1) or saline. During the insulin infusion, steady-state glucose turnover measured with both [6-3H]glucose (8.0 +/- 0.5 mg.kg-1.min-1) and [6,6-2H2]glucose (7.6 +/- 0.5 mg.kg-1.min-1) was lower (P less than .01) than either the glucose infusion rate required to maintain euglycemia (9.8 +/- 0.7 mg.kg-1.min-1) or glucose turnover determined with [6-14C]glucose and corrected for Cori cycle activity (9.8 +/- 0.7 mg.kg-1.min-1). Consequently negative glucose production rates (P less than .01) were obtained with either [6-3H]- or [6,6-2H2]- but not [6-14C]glucose. The difference between turnover estimated with [6-3H]glucose and actual glucose disposal (or 14C glucose flux) did not decrease with time and was not dependent on duration of isotope infusion. During saline infusion, estimates of glucose turnover were similar regardless of the glucose tracer used. High-performance liquid chromatography of the radioactive glucose tracer and plasma revealed the presence of a tritiated nonglucose contaminant. Although the contaminant represented only 1.5% of the radioactivity in the [6-3H]glucose infusate, its clearance was 10-fold less (P less than .001) than that of [6-3H]glucose. This resulted in accumulation in plasma, with the contaminant accounting for 16.6 +/- 2.09 and 10.8 +/- 0.9% of what customarily is assumed to be plasma glucose radioactivity during the insulin or saline infusion, respectively (P less than .01)

  8. Nucleation size of hcp-CoPt dot arrays characterized by time dependence of coercivity

    Energy Technology Data Exchange (ETDEWEB)

    Kikuchi, N; Kitakami, O [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, 980-8577 (Japan); Mitsuzuka, K; Shimatsu, T; Aoi, H, E-mail: kikuchin@tagen.tohoku.ac.j [Research Institute of Electrical Communication, Tohoku University, Sendai, 980-8577 (Japan)

    2010-01-01

    The magnetization reversal process for dot arrays is likely to start from a nucleation followed by propagation process. In this study, we estimated the nucleation diameter D{sub n} for dot arrays made from thin hcp-CoPt perpendicular films (thickness {delta}=3 nm) and Co/Pt multilayered films ({delta}=9 nm), respectively. The dot diameter, D, was varied from 30 to 200 nm for CoPt dot arrays, and from 40 to 80 nm for Co/Pt dot arrays. The remanence coercivity was measured at measurement times t' = 10{sup 3} s and 10{sup -5} s (pulse field), and defined as H{sub r} and H{sub r}{sup P}. The energy barrier {Delta}E was evaluated by fitting H{sub r} and H{sub r}{sup P} to Sharrock's equation. The value of D{sub n} was estimated from {Delta}E, {delta} and the effective magnetic anisotropy of dot arrays including the demagnetizing energy due to the dot shape K{sub u}{sup eff}. D{sub n} was independent of Din both series of dot arrays, and about 17 nm for CoPt dot arrays and about 11 nm for Co/Pt dot arrays. These values were close to both the grain size and the exchange length of these films.

  9. DOT for patients with limited access to health care facilities in a hill district of eastern Nepal.

    Science.gov (United States)

    Wares, D F; Akhtar, M; Singh, S

    2001-08-01

    The hill district in Nepal, where access to health care facilities is difficult. To compare results before and after a decentralised directly observed treatment (DOT) intervention. Prospective study of patients registered in Dhankuta district, Nepal, 1996-1999. Patients received their intensive phase treatment under health worker supervision via one of three DOT options: 1) ambulatory from the peripheral government health facilities; 2) ambulatory from an international non-governmental organisation (INGO) TB clinic in district centre; or 3) resident in INGO TB hostel in district centre. Historical data from 1995-1996, with unsupervised short-course chemotherapy, were used for comparison. Of 307 new cases, respectively 126 (41%), 86 (28%) and 95 (31%) took their intensive phase treatment via options 1, 2 and 3. Smear conversion (at 2 months) and cure rates in new smear-positive pulmonary tuberculosis cases were respectively 81.6% (vs. 58.8% historical, P = 0.001) and 84.9% (vs. 76.7% historical, P = 0.03). Overall costs to the INGO provider fell by 7%, mainly as a result of staffing reductions in the INGO services made possible by rationalisation with government services during the intervention. By offering varied DOT delivery routes, including an in-patient option, satisfactory results are possible with DOT even in areas where access to health care facilities is difficult. Provision of in-patient care via an INGO TB hostel allowed a significant proportion of new cases (31%) to receive their intensive phase treatment who otherwise may have had difficulty accessing treatment, due either to the distance to the nearest health facility or to disease severity. Substitution of government hospital beds or local hotel beds for the INGO hostel beds may allow the model to be reproduced elsewhere in similar geographical conditions in Nepal, but further studies should be performed in a non-INGO supported district beforehand.

  10. Tuning of tantalum alkylidene reactivity with a terdentate arylamine ligand : synthesis, structure and reactivity of [TaCl2{C6H3(CH2NMe2)2-2,6}(CHBu-tert)

    NARCIS (Netherlands)

    Abbenhuis, H.C.L.; Grove, D.M.; Koten, van G.; Sluijs, van der P.; Spek, A.L.

    1990-01-01

    The terdentate aryldiamine ligand in the aryltantalum(V) alkylidene complex [TaCl2{C6H3(CH2NMe2)2-2,6}(CHBut)] (1) controls alkylidene reactivity in a range of metal-mediated Wittig reactions. An X-ray diffraction study of (1) shows that the hexacoordinate tantalum centre has a very irregular ligand

  11. Sol-Gel Chemistry for Carbon Dots.

    Science.gov (United States)

    Malfatti, Luca; Innocenzi, Plinio

    2018-03-14

    Carbon dots are an emerging class of carbon-based nanostructures produced by low-cost raw materials which exhibit a widely-tunable photoluminescence and a high quantum yield. The potential of these nanomaterials as a substitute of semiconductor quantum dots in optoelectronics and biomedicine is very high, however they need a customized chemistry to be integrated in host-guest systems or functionalized in core-shell structures. This review is focused on recent advances of the sol-gel chemistry applied to the C-dots technology. The surface modification, the fine tailoring of the chemical composition and the embedding into a complex nanostructured material are the main targets of combining sol-gel processing with C-dots chemistry. In addition, the synergistic effect of the sol-gel precursor combined with the C-dots contribute to modify the intrinsic chemo-physical properties of the dots, empowering the emission efficiency or enabling the tuning of the photoluminescence over a wide range of the visible spectrum. © 2018 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Solar system astronomy with the 3.6-m DOT and the 4-m ILMT

    Science.gov (United States)

    Ganesh, Shashikiran; Venkataramani, Kumar; Baliyan, Kiran Singh; Joshi, Umesh Chandra

    2018-04-01

    Solar system astronomy would be an important field of study with the 3.6-m Devasthal Optical Telescope (DOT) and the 4-m International Liquid Mirror Telescope (ILMT). In this contribution, we highlight the work that could be done in reaching a better understanding of the Solar system and its constituents - particularly the minor bodies and other smaller objects. There may be a large number of very faint objects in the vicinity of the Earth orbit. In fact only recently a 'second moon' of the Earth has been found and has been designated 2016 H03. This is a quasi-satellite with the same period of revolution around Earth and Sun. There could be many such objects and it is important to have a full characterization and understanding of these potentially hazardous objects. They are generally fainter than 18th magnitude and one would need a lot of telescope time to fully characterize these objects using techniques of spectropolarimetry. In a similar fashion, a deep census of the Kuiper Belt Objects and the TNOs is needed. In this census, the concept of pencil beam surveys could be extended to cylindrical transit imaging technique available with the 4-m ILMT.

  13. Optical detection of organophosphorus compounds based on Mn-doped ZnSe d-dot enzymatic catalytic sensor.

    Science.gov (United States)

    Gao, Xue; Tang, Guangchao; Su, Xingguang

    2012-01-01

    In this paper, we report a sensitive and selective method for detection of organophosphorus compounds (OPs) based on Mn:ZnSe d-dots-enzyme-hydrogen peroxide (H(2)O(2)) fluorescence quenching system. Acetylcholine esterase (AChE) can hydrolyze acetylcholine (ACh) to choline. Subsequently, choline oxidase (ChOx) oxidizes choline to generate H(2)O(2). The enzyme-generated H(2)O(2) can quench the fluorescence of Mn:ZnSe d-dots. When paraoxon are introduced in solution, it can interact with the active centers of AChE and decrease the enzyme activity. This leads to the decrease of the H(2)O(2) production and then the fluorescence quenching rate of Mn:ZnSe d-dots. Experimental results showed that the enzyme inhibition percentage of Mn:ZnSe d-dots-ChOx-AChE-ACh system was proportional to the logarithm of paraoxon in the range 4.84×10(-11) to 4.84×10(-6) mol/L with the detection limit (S/N=3) of 1.31×10(-11) mol/L. The proposed biosensor has been employed for quick determination of paraoxon in tap water and milk samples with satisfactory reproducibility and accuracy. This nano-biosensor was proved to be sensitive, rapid, simple and tolerance of most interfering substances. Copyright © 2012 Elsevier B.V. All rights reserved.

  14. Structure, ferroelectric ordering, and semiempirical quantum calculations of lanthanide based metal-organic framework: [Nd(C4H5O6)(C4H4O6)][3H2O

    Science.gov (United States)

    Ahmad, Bhat Zahoor; Want, Basharat

    2016-04-01

    We investigate the structure and ferroelectric behavior of a lanthanide based metal-organic framework (MOF), [Nd(C4H5O6)(C4H4O6)][3H2O]. X-ray crystal structure analyses reveal that it crystallizes in the P41212 space group with Nd centres, coordinated by nine oxygen atoms, forming a distorted capped square antiprismatic geometry. The molecules, bridged by tartrate ligands, form a 2D chiral structure. The 2D sheets are further linked into a 3D porous framework via strong hydrogen-bonding scheme (O-H…O ≈ 2.113 Å). Dielectric studies reveal two anomalies at 295 K and 185 K. The former is a paraelectric-ferroelectric transition, and the later is attributed to the freezing down of the motion of the hydroxyl groups. The phase transition is of second order, and the spontaneous polarization in low temperature phase is attributed to the ordering of protons of hydroxyl groups. The dielectric nonlinearity parameters have been calculated using Landau- Devonshire phenomenological theory. In addition, the most recent semiempirical models, Sparkle/PM7, Sparkle/RM1, and Sparkle/AM1, are tested on the present system to assay the accuracy of semiempirical quantum approaches to predict the geometries of solid MOFs. Our results show that Sparkle/PM7 model is the most accurate to predict the unit cell structure and coordination polyhedron geometry. The semiempirical methods are also used to calculate different ground state molecular properties.

  15. Study of the unimolecular decompositions of the (C3H6)+2 and (c-C3H6)+2 complexes

    International Nuclear Information System (INIS)

    Tzeng, W.; Ono, Y.; Linn, S.H.; Ng, C.Y.

    1985-01-01

    The major product channels identified in the unimolecular decompositions ofC 3 H + 6 xC 3 H 6 and c-C 3 H + 6 xc-C 3 H 6 in the total energy [neutral (C 3 H 6 ) 2 or (c-C 3 H 6 ) 2 heat of formation plus excitation energy] range of approx.230--450 kcal/mol are C 3 H + 7 +C 3 H 5 , C 4 H + 7 +C 2 H 5 , C 4 H + 8 +C 2 H 4 , and C 5 H + 9 +CH 3 . The measured appearance energy for C 4 H + 7 (9.54 +- 0.04 eV) from (C 3 H 6 ) 2 is equal to the thermochemical threshold for the formation of C 4 H + 7 +C 2 H 5 from (C 3 H 6 ) 2 , indicating that the exit potential energy barrier for the ion--molecule reaction C 3 H + 6 +C 3 H 6 →C 4 H + 7 +C 2 H 5 is negligible. There is evidence that the formations of C 4 H + 7 +C 2 H 4 +H from (C 3 H 6 ) + 2 and (c-C 3 H 6 ) + 2 also proceed with high probabilities when they are energetically allowed. The variations of the relative abundances for C 4 H + 7 ,C 4 H + 8 , and C 5 H + 9 from (C 3 H 6 ) + 2 and (c-C 3 H 6 ) + 2 as a function of ionizing photon energy are in qualitative agreement, suggesting that (C 3 H 6 ) + 2 and (c-C 3 H 6 ) + 2 rearrange to similar C 6 H + 12 isomers prior to fragmentation. The fact that C 6 H + 11 is found to be a primary ion from the unimolecular decomposition of (c-C 3 H 6 ) + 2 but not (C 3 H 6 ) + 2 supports the conclusion that the distribution of C 6 H + 12 collision complexes involved in the C 3 H + 6 +C 3 H 6 reactions is different from that in the cyclopropane ion--molecule reactions

  16. Resonance Raman spectroscopy of 2H-labelled spheroidenes in petroleum ether and in the Rhodobacter sphaeroides reaction centre.

    Science.gov (United States)

    Kok, P; Köhler, J; Groenen, E J; Gebhard, R; van der Hoef, I; Lugtenburg, J; Farhoosh, R; Frank, H A

    1997-03-01

    As a step towards the structural analysis of the carotenoid spheroidene in the Rhodobacter sphaeroides reaction centre, we present the resonance Raman spectra of 14-2H, 15-2H, 15'-2H, 14'-2H, 14,15'-2H2 and 15-15'-2H2 spheroidenes in petroleum ether and, except for 14,15'-2H2 spheroidene, in the Rb. sphaeroides R26 reaction center (RC). Analysis of the spectral changes upon isotopic substitution allows a qualitative assignment of most of the vibrational bands to be made. For the all-trans spheroidenes in solution the resonance enhancement of the Raman bands is determined by the participation of carbon carbon stretching modes in the centre of the conjugated chain, the C9 to C15' region. For the RC-bound 15,15'-cis spheroidenes, enhancement is determined by the participation of carbon-carbon stretching modes in the centre of the molecule, the C13 to C13' region. Comparison of the spectra in solution and in the RC reveals evidence for an out-of-plane distortion of the RC-bound spheroidene in the central C14 to C14' region of the carotenoid. The characteristic 1240 cm-1 band in the spectrum of the RC-bound spheroidene has been assigned to a normal mode that contains the coupled C12-C13 and C13'-C12' stretch vibrations.

  17. Bis(3-acetyl-6-methyl-2-oxo-2H-pyran-4-olatobis(dimethyl sulfoxidenickel(II

    Directory of Open Access Journals (Sweden)

    Amel Djedouani

    2009-10-01

    Full Text Available In the title compound, [Ni(C8H7O42{(CH32SO}2], the NiII atom is located on a crystallographic centre of symmetry and has a distorted octahedral coordination geometry of type MO6. The bidentate dehydroacetic acid (DHA ligands occupy the equatorial plane of the complex in a trans configuration, and the dimethyl sulfoxide (DMSO ligands are weakly coordinated through their O atoms in the axial positions.

  18. Randomized study of initial treatment with radiationter dot MCNU or radiationter dot MCNUter dot interferon-. beta. for malignant glioma

    Energy Technology Data Exchange (ETDEWEB)

    Kiya, Katsuzo; Uozumi, Tohru; Kurisu, Kaoru (Hiroshima Univ. (Japan). School of Medicine) (and others)

    1990-02-01

    The efficacy of radiation{center dot}MCNU (MR group) or radiation{center dot}MCNU{center dot}interferon-{beta} (IMR group) for malignant glioma was studied by a randomized trial at numerous medical facilities. MR group was irradiated with 50{approx}60 Gy and intravenously injected with 2 mg/kg of MCNU on the initial day of irradiation and 6 weeks later. IMR group was also given intravenous administration of interferon-{beta} at the dose of 2x10{sup 6}IU/m{sup 2} for 5 serial-days every eight weeks. There was no difference in background between the two groups. The response rate in MR group and IMR group was 44.4% (4/9) and 30.0% (3/10), respectively, showing no significant difference. The resected tumor volume before the start of these regimens seemed to correlate the response to the treatment in both groups. The major toxicity was myelosuppression, especially using MCNU with interferon-{beta}. These results indicated that this combined therapy is effective for malignant glioma, and should be executed further trials and follow up study. (author).

  19. Gunn's dots in retinal images of 2,286 adolescents

    DEFF Research Database (Denmark)

    Boberg-Ans, Lars C.; Munch, Inger C.; Larsen, Michael

    2017-01-01

    a 6 mm grid centered on the optic disc. Results: One or more Gunn's dots were seen in at least one eye in 82.6% of children. The median number of Gunn's dots per eye was 46 (range 0-482). Most Gunn's dots were found inferior and superior of the optic disc (49.3% and 45.8%, respectively, of the total...... number of Gunn's dots in the population). The odds for having 1 or more Gunn's dots were 3-fold greater in children with dark brown irides compared with children with blue irides (odds ratio 2.99, 95% CI 1.81 to 4.94, P, 0.0001 adjusted for age, sex, retinal nerve fiber layer thickness, refraction...

  20. Opto-electronics of PbS quantum dot and narrow bandgap polymer blends

    NARCIS (Netherlands)

    Kahmann, Simon; Mura, Andrea; Protesescu, Loredana; Kovalenko, Maksym V.; Brabec, Christoph J.; Loi, Maria A.

    2015-01-01

    Here we report on the interaction between the narrow bandgap polymer [2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta-[2,1-b;3,4-b]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) and lead sulphide (PbS) colloidal quantum dots (CQDs) upon photoexcitation. We show that the presence of both materials

  1. GRUNCLE, 1. Collision Source Calculation for Program DOT. DOT-3.5, 2-D Neutron Transport, Gamma Transport Program DOT with New Space-Scaling

    International Nuclear Information System (INIS)

    1996-01-01

    mesh. Anisotropic scattering is treated using a Legendre expansion of arbitrary order. Convergence can be accelerated by several optional schemes, including a pointwise rescaling technique. DOT-3.5/E: Differs from DOT-3.5 in that exponential supplementary equations, as well as the usual diamond and weighted schemes, may be used to find the mesh-centre flux from the fluxes at the faces of the mesh. The model: 1. always gives positive solutions and does not require any fix-up techniques provided that the source is non-negative; 2. improves convergence rate in most neutron deep-penetration problems and, for any practical spatial discretization, always requires CPU times not only smaller than those required by DOT-3 mixed (linear + step fix-up) model, but also shorter (generally 10-20%) than the times required by DOT-3.5 weighted difference model; 3. increasing spatial mesh size supplies solutions which are always reasonable overestimates of the exact solution and its numerical behaviour is more stable and coherent than the mixed mode. Experience up to now from several deep penetration problems in (r,z) and (x,y) geometry shows that, while for neutrons the exponential model almost always works very well, for gamma rays its behaviour may be critical and in some cases there is lack of convergence. C - Restrictions on the complexity of the problem: The total storage requirement is determined by a formula given in the input description. No other restrictions to problem size are applicable

  2. Spin-valley dynamics of electrically driven ambipolar carbon-nanotube quantum dots

    Science.gov (United States)

    Osika, E. N.; Chacón, A.; Lewenstein, M.; Szafran, B.

    2017-07-01

    An ambipolar n-p double quantum dot defined by potential variation along a semiconducting carbon-nanotube is considered. We focus on the (1e,1h) charge configuration with a single excess electron of the conduction band confined in the n-type dot and a single missing electron in the valence band state of the p-type dot for which lifting of the Pauli blockade of the current was observed in the electric-dipole spin resonance (Laird et al 2013 Nat. Nanotechnol. 8 565). The dynamics of the system driven by periodic electric field is studied with the Floquet theory and the time-dependent configuration interaction method with the single-electron spin-valley-orbitals determined for atomistic tight-binding Hamiltonian. We find that the transitions lifting the Pauli blockade are strongly influenced by coupling to a vacuum state with an empty n dot and a fully filled p dot. The coupling shifts the transition energies and strongly modifies the effective g factors for axial magnetic field. The coupling is modulated by the bias between the dots but it appears effective for surprisingly large energy splitting between the (1e,1h) ground state and the vacuum (0e, 0h) state. Multiphoton transitions and high harmonic generation effects are also discussed.

  3. DotFETs : MOSFETs strained by a Single SiGE dot in a Low-Temperature ELA Technology

    NARCIS (Netherlands)

    Biasotto, C.

    2011-01-01

    The work presented in this thesis was performed in the context of the European Sixth Framework Program FP6 project “Disposable Dot Field Effect Transistor for High Speed Si Integrated Circuits”, referred to as the D-DotFET project. The project had the goal of realizing strain-enhanced mobility in

  4. Strong enhancement of the chemiluminescence of the Cu(II)-H2O2 system on addition of carbon nitride quantum dots, and its application to the detection of H2O2 and glucose.

    Science.gov (United States)

    Hallaj, Tooba; Amjadi, Mohammad; Song, Zhenlun; Bagheri, Robabeh

    2017-12-19

    The authors report that carbon nitride quantum dots (CN QDs) exert a strong enhancing effect on the Cu(II)/H 2 O 2 chemiluminescent system. Chemiluminescence (CL) intensity is enhanced by CN QDs by a factor of ~75, while other carbon nanomaterials have a much weaker effect. The possible mechanism of the effect was evaluated by recording fluorescence and CL spectra and by examining the effect of various radical scavengers. Emitting species was found to be excited-state CN QDs that produce green CL peaking at 515 nm. The new CL system was applied to the sensitive detection of H 2 O 2 and glucose (via glucose oxidase-catalyzed formation of H 2 O 2 ) with detection limits (3σ) of 10 nM for H 2 O 2 and 100 nM for glucose. The probe was employed for glucose determination in human plasma samples with satisfactory results. Graphical abstract The effect of carbon nitride quantum dots (CN QDs) on Cu(II)-H 2 O 2 chemiluminescence reaction was studied and the new CL system was applied for sensitive detection of glucose based on the glucose oxidase (GOx)-catalyzed formation of H 2 O 2 .

  5. Facilitated preparation of bioconjugatable zwitterionic quantum dots using dual-lipid encapsulation.

    Science.gov (United States)

    Shrake, Robert; Demillo, Violeta G; Ahmadiantehrani, Mojtaba; Zhu, Xiaoshan; Publicover, Nelson G; Hunter, Kenneth W

    2015-01-01

    Zwitterionic quantum dots prepared through incorporated zwitterionic ligands on quantum dot surfaces, are being paid significant attention in biomedical applications because of their excellent colloidal stability across a wide pH and ionic strength range, antifouling surface, good biocompatibility, etc. In this work, we report a dual-lipid encapsulation approach to prepare bioconjugatable zwitterionic quantum dots using amidosulfobetaine-16 lipids, dipalmitoyl-sn-glycero-3-phosphoethanolamine lipids with functional head groups, and CuInS2/ZnS quantum dots in a tetrahydrofuran/methanol/water solvent system with sonication. Amidosulfobetaine-16 is a zwitterionic lipid and dipalmitoyl-sn-glycero-3-phosphoethanolamine, with its functional head, provides bioconjugation capability. Under sonication, tetrahydrofuran/methanol containing amidosulfobetaine-16, dipalmitoyl-sn-glycero-3-phosphoethanolamine, and hydrophobic quantum dots are dispersed in water to form droplets. Highly water-soluble tetrahydrofuran/methanol in droplets is further displaced by water, which induces the lipid self-assembling on hydrophobic surface of quantum dots and thus forms water soluble zwitterionic quantum dots. The prepared zwitterionic quantum dots maintain colloidal stability in aqueous solutions with high salinity and over a wide pH range. They are also able to be conjugated with biomolecules for bioassay with minimal nonspecific binding. Copyright © 2014 Elsevier Inc. All rights reserved.

  6. Structure, ferroelectric ordering, and semiempirical quantum calculations of lanthanide based metal-organic framework: [Nd(C4H5O6)(C4H4O6)][3H2O

    International Nuclear Information System (INIS)

    Ahmad, Bhat Zahoor; Want, Basharat

    2016-01-01

    We investigate the structure and ferroelectric behavior of a lanthanide based metal-organic framework (MOF), [Nd(C 4 H 5 O 6 )(C 4 H 4 O 6 )][3H 2 O]. X-ray crystal structure analyses reveal that it crystallizes in the P4 1 2 1 2 space group with Nd centres, coordinated by nine oxygen atoms, forming a distorted capped square antiprismatic geometry. The molecules, bridged by tartrate ligands, form a 2D chiral structure. The 2D sheets are further linked into a 3D porous framework via strong hydrogen-bonding scheme (O-H…O ≈ 2.113 Å). Dielectric studies reveal two anomalies at 295 K and 185 K. The former is a paraelectric-ferroelectric transition, and the later is attributed to the freezing down of the motion of the hydroxyl groups. The phase transition is of second order, and the spontaneous polarization in low temperature phase is attributed to the ordering of protons of hydroxyl groups. The dielectric nonlinearity parameters have been calculated using Landau– Devonshire phenomenological theory. In addition, the most recent semiempirical models, Sparkle/PM7, Sparkle/RM1, and Sparkle/AM1, are tested on the present system to assay the accuracy of semiempirical quantum approaches to predict the geometries of solid MOFs. Our results show that Sparkle/PM7 model is the most accurate to predict the unit cell structure and coordination polyhedron geometry. The semiempirical methods are also used to calculate different ground state molecular properties.

  7. Electron Acceptor Materials Engineering in Colloidal Quantum Dot Solar Cells

    KAUST Repository

    Liu, Huan

    2011-07-15

    Lead sulfide colloidal quantum dot (CQD) solar cells with a solar power conversion efficiency of 5.6% are reported. The result is achieved through careful optimization of the titanium dioxide electrode that serves as the electron acceptor. Metal-ion-doped sol-gel-derived titanium dioxide electrodes produce a tunable-bandedge, well-passivated materials platform for CQD solar cell optimization. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. A highly selective fluorescence sensing platform for nanomolar Hg(II) detection based on cytosine derived quantum dot

    Science.gov (United States)

    Luo, Liang; Song, Ting; Wang, Haoqiang; Yuan, Qunhui; Zhou, Shenghai

    2018-03-01

    Inspired by low toxicity and good biocompatibility of biomass derived quantum dot (QD), we herein developed a cytosine derived quantum dot, namely cyt-dot, via a one-step hydrothermal synthesis. The as-prepared cyt-dot emits blue fluorescence (FL) containing abundant oxygen (20.6 at.%) and nitrogen (24.1 at.%) contents. The cyt-dot based sensing platform shows exclusive selectivity for Hg(II) while being insensitive towards Fe(III) and Ag(I), which are important interference that usually cannot be ruled out. The detection limit for Hg(II) is of 11 nM, which is very close to the guideline value of 10 nM allowed by the U.S. Environmental Protection Agency in drinking water. In real water sample analyses, the present sensing platform can fulfil satisfied recoveries ranging from 100% to 108%. Besides, the acidity of solution has almost no effect on the sensing performance of the cyt-dot in a pH range of 5-8, suggesting its potential applications in sensing and bio-imaging.

  9. Nd(III) and Dy(III) coordination compounds based on 1H-tetrazolate-5-acetic acid ligands: Synthesis, crystal structures and catalytic properties

    Energy Technology Data Exchange (ETDEWEB)

    Li Qiaoyun; Chen Dianyu; He Minghua [Jiangsu Laboratory of Advanced Functional Materials, Department of Chemistry and Materials Engineering, Changshu Institute of Technology, Changshu 215500, Jiangsu (China); Yang Gaowen, E-mail: ygwsx@126.com [Jiangsu Laboratory of Advanced Functional Materials, Department of Chemistry and Materials Engineering, Changshu Institute of Technology, Changshu 215500, Jiangsu (China); Shen Lei; Zhai Chun; Shen Wei; Gu Kun; Zhao Jingjing [Jiangsu Laboratory of Advanced Functional Materials, Department of Chemistry and Materials Engineering, Changshu Institute of Technology, Changshu 215500, Jiangsu (China)

    2012-06-15

    Reactions of 1H-tetrazolate-5-acetic acid(H{sub 2}tza) with Nd(NO{sub 3}){sub 3}{center_dot}6H{sub 2}O or Dy(NO{sub 3}){sub 3}{center_dot}6H{sub 2}O with the presence of KOH under solvothermal conditions, produced two new coordination compounds, [M{sub 2}(tza){sub 3}(H{sub 2}O){sub 6}]{center_dot}2H{sub 2}O [M=Nd(1), Dy(2)]. Both compounds were structurally characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Compounds 1 and 2 reveal 1D structures via bridging tza as linker. Furthermore, the compounds 1 and 2 showed a specific and good catalytic behavior for the polymerization of styrene, and the polymerization showed controlled characteristics. - Graphical Abstract: Two new coordination compounds, [M{sub 2}(tza){sub 3}(H{sub 2}O){sub 6}]{center_dot}2H{sub 2}O [M=Nd(1), Dy(2)] have been synthesis. 1 and 2 reveal 1D structures via bridging tza as linker, and showed a specific and good catalytic behavior for the polymerization of styrene. Highlights: Black-Right-Pointing-Pointer we have reported two novel compounds formed by H{sub 2}tza and Nd(III) or Dy(III). Black-Right-Pointing-Pointer Compounds 1 and 2 were found to have catalysis property for the photo-polymerization of styrene. Black-Right-Pointing-Pointer The high molecular weight polymers with narrow molecular weight distributions were obtained.

  10. Bright infrared quantum-dot light-emitting diodes through inter-dot spacing control

    KAUST Repository

    Sun, Liangfeng; Choi, Joshua J.; Stachnik, David; Bartnik, Adam C.; Hyun, Byung-Ryool; Malliaras, George G.; Hanrath, Tobias; Wise, Frank W.

    2012-01-01

    Infrared light-emitting diodes are currently fabricated from direct-gap semiconductors using epitaxy, which makes them expensive and difficult to integrate with other materials. Light-emitting diodes based on colloidal semiconductor quantum dots, on the other hand, can be solution-processed at low cost, and can be directly integrated with silicon. However, so far, exciton dissociation and recombination have not been well controlled in these devices, and this has limited their performance. Here, by tuning the distance between adjacent PbS quantum dots, we fabricate thin-film quantum-dot light-emitting diodes that operate at infrared wavelengths with radiances (6.4 W sr '1 m '2) eight times higher and external quantum efficiencies (2.0%) two times higher than the highest values previously reported. The distance between adjacent dots is tuned over a range of 1.3 nm by varying the lengths of the linker molecules from three to eight CH 2 groups, which allows us to achieve the optimum balance between charge injection and radiative exciton recombination. The electroluminescent powers of the best devices are comparable to those produced by commercial InGaAsP light-emitting diodes. By varying the size of the quantum dots, we can tune the emission wavelengths between 800 and 1,850 nm.© 2012 Macmillan Publishers Limited.

  11. Bright infrared quantum-dot light-emitting diodes through inter-dot spacing control.

    Science.gov (United States)

    Sun, Liangfeng; Choi, Joshua J; Stachnik, David; Bartnik, Adam C; Hyun, Byung-Ryool; Malliaras, George G; Hanrath, Tobias; Wise, Frank W

    2012-05-06

    Infrared light-emitting diodes are currently fabricated from direct-gap semiconductors using epitaxy, which makes them expensive and difficult to integrate with other materials. Light-emitting diodes based on colloidal semiconductor quantum dots, on the other hand, can be solution-processed at low cost, and can be directly integrated with silicon. However, so far, exciton dissociation and recombination have not been well controlled in these devices, and this has limited their performance. Here, by tuning the distance between adjacent PbS quantum dots, we fabricate thin-film quantum-dot light-emitting diodes that operate at infrared wavelengths with radiances (6.4 W sr(-1) m(-2)) eight times higher and external quantum efficiencies (2.0%) two times higher than the highest values previously reported. The distance between adjacent dots is tuned over a range of 1.3 nm by varying the lengths of the linker molecules from three to eight CH(2) groups, which allows us to achieve the optimum balance between charge injection and radiative exciton recombination. The electroluminescent powers of the best devices are comparable to those produced by commercial InGaAsP light-emitting diodes. By varying the size of the quantum dots, we can tune the emission wavelengths between 800 and 1,850 nm.

  12. Bright infrared quantum-dot light-emitting diodes through inter-dot spacing control

    KAUST Repository

    Sun, Liangfeng

    2012-05-06

    Infrared light-emitting diodes are currently fabricated from direct-gap semiconductors using epitaxy, which makes them expensive and difficult to integrate with other materials. Light-emitting diodes based on colloidal semiconductor quantum dots, on the other hand, can be solution-processed at low cost, and can be directly integrated with silicon. However, so far, exciton dissociation and recombination have not been well controlled in these devices, and this has limited their performance. Here, by tuning the distance between adjacent PbS quantum dots, we fabricate thin-film quantum-dot light-emitting diodes that operate at infrared wavelengths with radiances (6.4 W sr \\'1 m \\'2) eight times higher and external quantum efficiencies (2.0%) two times higher than the highest values previously reported. The distance between adjacent dots is tuned over a range of 1.3 nm by varying the lengths of the linker molecules from three to eight CH 2 groups, which allows us to achieve the optimum balance between charge injection and radiative exciton recombination. The electroluminescent powers of the best devices are comparable to those produced by commercial InGaAsP light-emitting diodes. By varying the size of the quantum dots, we can tune the emission wavelengths between 800 and 1,850 nm.© 2012 Macmillan Publishers Limited.

  13. Adjoint administratif (h/f) - Politiques et planification | CRDI - Centre ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    à‑d. les informer au sujet des programmes et des procédures du Centre, des systèmes et des programmes informatiques, organiser des rendez-vous avec des membres clés du personnel du Centre, réacheminer les questions aux personnes-ressources compétentes au Centre, et organiser la création de comptes de ...

  14. Facile synthetic method for pristine graphene quantum dots and graphene oxide quantum dots: origin of blue and green luminescence.

    Science.gov (United States)

    Liu, Fei; Jang, Min-Ho; Ha, Hyun Dong; Kim, Je-Hyung; Cho, Yong-Hoon; Seo, Tae Seok

    2013-07-19

    Pristine graphene quantum dots and graphene oxide quantum dots are synthesized by chemical exfoliation from the graphite nanoparticles with high uniformity in terms of shape (circle), size (less than 4 nm), and thickness (monolayer). The origin of the blue and green photoluminescence of GQDs and GOQDs is attributed to intrinsic and extrinsic energy states, respectively. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Intracellular pH and 42.00 C heat response of CHO cells cultured at pH 6.6

    International Nuclear Information System (INIS)

    Cook, J.A.; Fox, M.H.

    1987-01-01

    The authors previously reported that cells under chronic low pH (6.6) conditions have altered thermotolerance. They further characterized both the doubling time (t/sub d/) and the internal pH (pH/sub 1/) of CHO cells continuously cultured at pH 6.6 for times greater than one year. The following differences were noted: 1) A t/sub d/ of 16 hr compared to a t/sub d/ of 12 hr for cells at normal pH (7.3) and a t/sub d/ of 25 hr for the acute low pH cells (pH = 6.6; incubation time = 4 hr). 2) A pH/sub i/ 0.1-0.15 pH units > normal cells and 0.3 pH units > acute low pH cells. 3) Survival at 42.0 0 C which differed from both normal and acute low pH cells. The chronic culture was still quite sensitive to 42.0 0 C treatments during the first 5 hr, but developed tolerance at a higher level than cells under acute low pH conditions. The pH/sub i/ of the chronic culture responded to 42.0 0 C heating in a manner similar to that for acute low pH cells. Whether this culture represents a normal response to long term low pH exposure, or was the response of a mutant population is at the present unknown

  16. Exciton binding energy in a pyramidal quantum dot

    Indian Academy of Sciences (India)

    A ANITHA

    2018-03-27

    Mar 27, 2018 ... screening function on exciton binding energy in a pyramid-shaped quantum dot of ... tures may generate unique properties and they show .... where Ee is the ground-state energy of the electron in ... Figure 1. The geometry of the pyramidal quantum dot. base and H is the height of the pyramid which is taken.

  17. Inspection, testing, and operating requiremens for the packaging and shipping of uranium trioxide in 55-gallon Department of Transportation (DOT) Specification 6M shipping packagings

    International Nuclear Information System (INIS)

    Toomer, D.V.

    1991-06-01

    This document identifies the inspection, testing and operating requirements for the packaging, loading, and shipping of uranium trioxide (UO 3 ) in 55-gallon DOT Specification 6M shipping packagings from the Idaho Chemical Processing Plant (ICPP). Compliance with this document assures established controls for the purchasing, packaging, loading, and shipping of DOT Specification 6M shipping packagings are maintained in strict accordance with applicable Code of Federal Regulations (CFRs) and Department of Energy (DOE) Orders. 7 refs., 3 figs., 1 tab

  18. DOT/FAA Human Factors Workshop on Aviation (6th). Transcript.

    Science.gov (United States)

    1982-05-01

    This document is a verbatim transcript of the proceedings of the DOT/FAA Sixth Human Factors Workshop on Aviation held at the Mike Monroney Aeronautical Center, Oklahoma City, Oklahoma on July 7-8, 1981. The subject of the workshop was aviation maint...

  19. Perceptual strategies of pigeons to detect a rotational centre--a hint for star compass learning?

    Directory of Open Access Journals (Sweden)

    Bianca Alert

    Full Text Available Birds can rely on a variety of cues for orientation during migration and homing. Celestial rotation provides the key information for the development of a functioning star and/or sun compass. This celestial compass seems to be the primary reference for calibrating the other orientation systems including the magnetic compass. Thus, detection of the celestial rotational axis is crucial for bird orientation. Here, we use operant conditioning to demonstrate that homing pigeons can principally learn to detect a rotational centre in a rotating dot pattern and we examine their behavioural response strategies in a series of experiments. Initially, most pigeons applied a strategy based on local stimulus information such as movement characteristics of single dots. One pigeon seemed to immediately ignore eccentric stationary dots. After special training, all pigeons could shift their attention to more global cues, which implies that pigeons can learn the concept of a rotational axis. In our experiments, the ability to precisely locate the rotational centre was strongly dependent on the rotational velocity of the dot pattern and it crashed at velocities that were still much faster than natural celestial rotation. We therefore suggest that the axis of the very slow, natural, celestial rotation could be perceived by birds through the movement itself, but that a time-delayed pattern comparison should also be considered as a very likely alternative strategy.

  20. Les héros du banc Danajon | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    27 janv. 2011 ... Pourtant, on a salué partout dans le monde les efforts qu'ils ont déployés pour protéger le milieu marin du banc Danajon, au centre des Philippines. En septembre 2006, le Disney Wildlife Conservation Fund (DWCF) a fait de Kamada — le regroupement de pêcheurs du banc Danajon — un héros de la ...

  1. Tuning the electronic and optical properties of hexagonal boron-nitride nanosheet by inserting graphene quantum dots

    Science.gov (United States)

    Ding, Yi-Min; Shi, Jun-Jie; Zhang, Min; Wu, Meng; Wang, Hui; Cen, Yu-Lang; Pan, Shu-Hang; Guo, Wen-Hui

    2018-02-01

    It is difficult to integrate two-dimensional (2D) graphene and hexagonal boron-nitride (h-BN) in optoelectronic nanodevices, due to the semi-metal and insulator characteristic of graphene and h-BN, respectively. Using the state-of-the-art first-principles calculations based on many-body perturbation theory, we investigate the electronic and optical properties of h-BN nanosheet embedded with graphene dots. We find that C atom impurities doped in h-BN nanosheet tend to phase-separate into graphene quantum dots (QD), and BNC hybrid structure, i.e. a graphene dot within a h-BN background, can be formed. The band gaps of BNC hybrid structures have an inverse relationship with the size of graphene dot. The calculated optical band gaps for BNC structures vary from 4.71 eV to 3.77 eV, which are much smaller than that of h-BN nanosheet. Furthermore, the valence band maximum is located in C atoms bonded to B atoms and conduction band minimum is located in C atoms bonded to N atoms, which means the electron and hole wave functions are closely distributed around the graphene dot. The bound excitons, localized around the graphene dot, determine the optical spectra of the BNC hybrid structures, in which the exciton binding energies decrease with increase in the size of graphene dots. Our results provide an important theoretical basis for the design and development of BNC-based optoelectronic nanodevices.

  2. Research of H5N6 Treatment by Comparing with H6N1 and H10N8 by Using Decision Tree and Apriori Algorithm

    Directory of Open Access Journals (Sweden)

    Kim Sunghyun

    2016-01-01

    Full Text Available Since 2003, 608 people in 15 countries have infected with human-infectious AI viruses and 359 of them died. Especially, in China, H6N1 and H10N8 viruses were wide-spread and a lot of people were infected and died. Recently, H5N6 virus emerged in China and the number of patients has been increasing gradually. Therefore, this research compared amino acid strain of Matrix Protein, Hemagglutinin, Neuraminidase and Nucleoprotein of H5N6, H6N1 and H10N8, by using Decision tree and Apriori Algorithm, to figure out their similarity and devise the treatment. In result, Matrix protein and Nucleoprotein sequences of H5N6 were similar with those of H6N1 and H10N8. Therefore, this research concluded that the treatment targeting those proteins of H6N1 and H10N8 will be also effective to H5N6.

  3. Crystal structure of tetraaquabis(1,3-dimethyl-2,6-dioxo-7H-purin-7-ido-κN7cobalt(II

    Directory of Open Access Journals (Sweden)

    Hicham El Hamdani

    2017-09-01

    Full Text Available The title complex, [Co(C7H7N4O22(H2O4], comprises mononuclear molecules consisting of a CoII ion, two deprotonated theophylline ligands (systematic name: 1,3-dimethyl-7H-purine-2,6-dione and four coordinating water molecules. The CoII atom lies on an inversion centre and has a slightly distorted octahedral coordination environment, with two N atoms of two trans-oriented theophylline ligands and the O atoms of four water molecules. An intramolecular hydrogen bond stabilizes this conformation. A three-dimensional supramolecular network structure is formed by intermolecular O—H...O and O—H...N hydrogen bonds.

  4. Highly fluorescent and morphology-controllable graphene quantum dots-chitosan hybrid xerogels for in vivo imaging and pH-sensitive drug carrier

    Energy Technology Data Exchange (ETDEWEB)

    Lv, Ouyang; Tao, Yongxin; Qin, Yong [Advanced Catalysis and Green Manufacturing Collaborative Innovation Center, School of Petrochemical Engineering, Changzhou University, Changzhou 213164 (China); Chen, Chuanxiang [School of Environmental and Chemical Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003 (China); Pan, Yan; Deng, Linhong [Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou 213164 (China); Liu, Li [School of pharmaceutical Engineering & Life Science, Changzhou University, Changzhou 213164 (China); Kong, Yong, E-mail: yzkongyong@126.com [Advanced Catalysis and Green Manufacturing Collaborative Innovation Center, School of Petrochemical Engineering, Changzhou University, Changzhou 213164 (China)

    2016-10-01

    Highly fluorescent graphene quantum dots (GQDs)-chitosan (CS) hybrid xerogels (GQDs-CS) were facilely synthesized, and the morphology of GQDs-CS was controllable by varying the content of GQDs in the xerogel. The GQDs-CS exhibited a porous and three-dimensional (3D) network structure when the content of GQDs reached 43% (wt%) in the xerogel, which was beneficial for drug loading and sustained release. The as-prepared GQDs-CS could also be applied for in vivo imaging since it showed strong blue, green and red luminescence under excitation of varying wavelengths. Moreover, the pH-induced protonation/deprotonation of the –NH{sub 2} groups on CS chains can result in a pH-dependent drug delivery behavior of the GQDs-CS hybrid xerogel. - Graphical abstract: Highly fluorescent and morphology-controllable graphene quantum dots-chitosan hybrid xerogels for in vivo imaging and pH-sensitive drug carrier. Display Omitted - Highlights: • Highly fluorescent GQDs-CS hybrid xerogels were facilely synthesized. • The as-made xerogels exhibited various morphologies with different GQDs contents. • The GQDs-CS exhibited a porous and 3D network when the content of GQDs reached 43%. • The GQDs-CS could be applied for in vivo imaging since it showed strong luminescence. • The protonation/deprotonation of –NH{sub 2} on CS result in a pH-dependent drug delivery.

  5. Highly fluorescent and morphology-controllable graphene quantum dots-chitosan hybrid xerogels for in vivo imaging and pH-sensitive drug carrier

    International Nuclear Information System (INIS)

    Lv, Ouyang; Tao, Yongxin; Qin, Yong; Chen, Chuanxiang; Pan, Yan; Deng, Linhong; Liu, Li; Kong, Yong

    2016-01-01

    Highly fluorescent graphene quantum dots (GQDs)-chitosan (CS) hybrid xerogels (GQDs-CS) were facilely synthesized, and the morphology of GQDs-CS was controllable by varying the content of GQDs in the xerogel. The GQDs-CS exhibited a porous and three-dimensional (3D) network structure when the content of GQDs reached 43% (wt%) in the xerogel, which was beneficial for drug loading and sustained release. The as-prepared GQDs-CS could also be applied for in vivo imaging since it showed strong blue, green and red luminescence under excitation of varying wavelengths. Moreover, the pH-induced protonation/deprotonation of the –NH_2 groups on CS chains can result in a pH-dependent drug delivery behavior of the GQDs-CS hybrid xerogel. - Graphical abstract: Highly fluorescent and morphology-controllable graphene quantum dots-chitosan hybrid xerogels for in vivo imaging and pH-sensitive drug carrier. Display Omitted - Highlights: • Highly fluorescent GQDs-CS hybrid xerogels were facilely synthesized. • The as-made xerogels exhibited various morphologies with different GQDs contents. • The GQDs-CS exhibited a porous and 3D network when the content of GQDs reached 43%. • The GQDs-CS could be applied for in vivo imaging since it showed strong luminescence. • The protonation/deprotonation of –NH_2 on CS result in a pH-dependent drug delivery.

  6. Experimental and theoretical studies of d-dot

    International Nuclear Information System (INIS)

    Ishida, Takekazu; Fujii, Masaki; Abe, Taiji; Yamamoto, Masuo; Miki, Shigehito; Kawamata, Shuichi; Satoh, Kazuo; Yotsuya, Tsutomu; Kato, Masaru; Machida, Masahiko; Koyama, Tomio; Terashima, Takahito; Tsukui, Shigeki; Adachi, Motoaki

    2006-01-01

    We propose the idea of d-dot, where a d-wave superconducting dot is embedded in s-wave matrix. Spontaneous half vortices should appear in the four corners of the d-dot [M. Kato, M. Ako, M. Machida, T. Koyama, T. Ishida, Physica C 412-414 (2004) 352; M. Ako, M. Kato, M. Machida, T. Koyama, T. Ishida, Physica C 412-414 (2004) 544; M. Fujii, T. Abe, H. Yoshikawa, S. Miki, S. Kawamata, K. Satoh, T. Yotsuya, M. Kato, M. Machida, T. Koyama, T. Terashima, S. Tsukui, M. Adachi, T. Ishida, Physica C 426-431 (2005) 104]. Symmetric geometry and the fourfold symmetry of the d-dot would be suitable as a building block for constructing the novel physical systems. The phase dynamics of a closed 0-π junction, which can be realized in a small d x 2 -y 2 -dot, is mapped on a quantum two-level system when the system size is small enough. Using two-component Ginzburg-Landau equation, we study the physical properties of d-dots systematically. We prepare epitaxial YBa 2 Cu 3 O 7 (YBCO) films of thickness 100nm on SrTiO 3 substrates using a laser ablation apparatus. The d-dot is fabricated by a photolithography, electron beam lithography EB and an electron cyclotron resonance (ECR) etching, a focused ion beam microscope, and a lift-off technique. Local vortex profile is investigated using a SQUID microscope when d-dot is cooled in zero field

  7. An Evaluation of Treatment Outcomes in a Cohort of Clients on the DOTS Strategy, 2012-2016.

    Science.gov (United States)

    Tetteh, Ato Kwamena; Agyarko, Edward; Otchere, Joseph; Bimi, Langbong; Ayi, Irene

    2018-01-01

    We present, for the first time, an evaluation of treatment outcomes in a cohort at a TB referral centre in the Central Region of Ghana. Of the 213 clients placed on DOTS, 59.2% (126/213) were sputum smear-positive. An overall cure rate of 90.2% (51.6% cured + 37.6% completed) and a death rate of 8.5% (18/213) were estimated. Of the number of clients who died, 5.7% (12/213) were males ( χ 2 = 2.891, p = 0.699; LR = 3.004, p = 0.699). Deaths were only recorded among clients who were > 19 years old ( χ 2 = 40.319, p = 0.099; LR = 41.244, p = 0.083). Also, 0.9% (2/213) was lost to follow-up, while 1.4% (3/213) had treatment failure. In total, 13.6% (7.0%, 15/213 males, and 6.6%, 14/213 females) of clients who were placed on DOTS were HIV seropositive. Ages of 40-49 years had the highest number, 13/213 (6.1%), infected with HIV, though the difference among the remaining age groups was not statistically significant ( χ 2 = 9.621, p = 0.142). Furthermore, 7.0% (15/213) had TB/HIV coinfection. Out of them, 9 were cured and 5 died at home, while 1 had treatment failure. Tuberculosis/HIV infection prevention advocacy and interventions that address sociodemographic determinants of unfavourable treatment outcomes are urgently required to augment national efforts towards control.

  8. Presence of photoluminescent carbon dots in Nescafe® original instant coffee: applications to bioimaging.

    Science.gov (United States)

    Jiang, Chengkun; Wu, Hao; Song, Xiaojie; Ma, Xiaojun; Wang, Jihui; Tan, Mingqian

    2014-09-01

    The presence of the carbon dots (C-dots) in food is a hotly debated topic and our knowledge about the presence and the use of carbon dots (C-dots) in food is still in its infancy. We report the finding of the presence of photoluminescent (PL) C-dots in commercial Nescafe instant coffee. TEM analysis reveals that the extracted C-dots have an average size of 4.4 nm. They were well-dispersed in water and strongly photoluminescent under the excitation of ultra-violet light with a quantum yield (QY) about 5.5%, which were also found to possess clear upconversion PL properties. X-ray photoelectron spectroscopy characterization demonstrates that the C-dots contain C, O and N three elements with the relative contents ca. 30.1, 62.2 and 7.8%. The X-ray diffraction (XRD) analysis indicates that the C-dots are amorphous. Fourier-transform infrared (FTIR) spectra were employed to characterize the surface groups of the C-dots. The C-dots show a pH independent behavior by varying the pH value from 2 to 11. The cytotoxicity study revealed that the C-dots did not cause any toxicity to cells at a concentration as high as 20 mg/mL. The C-dots have been directly applied in cells and fish imaging, which suggested that the C-dots present in commercial coffee may have more potential biological applications. Copyright © 2014. Published by Elsevier B.V.

  9. Quantum dot-linked immunosorbent assay (QLISA) using orientation-directed antibodies.

    Science.gov (United States)

    Suzuki, Miho; Udaka, Hikari; Fukuda, Takeshi

    2017-09-05

    An approach similar to the enzyme-linked immunosorbent assay (ELISA), with the advantage of saving time and effort but exhibiting high performance, was developed using orientation-directed half-part antibodies immobilized on CdSe/ZnS quantum dots. ELISA is a widely accepted assay used to detect the presence of a target substance. However, it takes time to quantify the target with specificity and sensitivity owing to signal amplification. In this study, CdSe/ZnS quantum dots are introduced as bright and photobleaching-tolerant fluorescent materials. Since hydrophilic surface coating of quantum dots rendered biocompatibility and functional groups for chemical reactions, the quantum dots were modified with half-sized antibodies after partial reduction. The half-sized antibody could be bound to a quantum dot through a unique thiol site to properly display the recognition domain for the core process of ELISA, which is an antigen-antibody interaction. The reducing conditions were investigated to generate efficient conjugates of quantum dots and half-sized antibodies. This was applied to IL-6 detection, as the quantification of IL-6 is significant owing to its close relationships with various biomedical phenomena that cause different diseases. An ELISA-like assay with CdSe/ZnS quantum dot institution (QLISA; Quantum dot-linked immunosorbent assay) was developed to detect 0.05ng/mL IL-6, which makes it sufficiently sensitive as an immunosorbent assay. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Fluorescence biosensor based on CdTe quantum dots for specific detection of H5N1 avian influenza virus

    Science.gov (United States)

    Hoa Nguyen, Thi; Dieu Thuy Ung, Thi; Hien Vu, Thi; Tran, Thi Kim Chi; Quyen Dong, Van; Khang Dinh, Duy; Liem Nguyen, Quang

    2012-09-01

    This report highlights the fabrication of fluorescence biosensors based on CdTe quantum dots (QDs) for specific detection of H5N1 avian influenza virus. The core biosensor was composed of (i) the highly luminescent CdTe/CdS QDs, (ii) chromatophores extracted from bacteria Rhodospirillum rubrum, and (iii) the antibody of β-subunit. This core part was linked to the peripheral part of the biosensor via a biotin-streptavidin-biotin bridge and finally connected to the H5N1 antibody to make it ready for detecting H5N1 avian influenza virus. Detailed studies of each constituent were performed showing the image of QDs-labeled chromatophores under optical microscope, proper photoluminescence (PL) spectra of CdTe/CdS QDs, chromatophores and the H5N1 avian influenza viruses.

  11. Imaging and Manipulating Energy Transfer Among Quantum Dots at Individual Dot Resolution.

    Science.gov (United States)

    Nguyen, Duc; Nguyen, Huy A; Lyding, Joseph W; Gruebele, Martin

    2017-06-27

    Many processes of interest in quantum dots involve charge or energy transfer from one dot to another. Energy transfer in films of quantum dots as well as between linked quantum dots has been demonstrated by luminescence shift, and the ultrafast time-dependence of energy transfer processes has been resolved. Bandgap variation among dots (energy disorder) and dot separation are known to play an important role in how energy diffuses. Thus, it would be very useful if energy transfer could be visualized directly on a dot-by-dot basis among small clusters or within films of quantum dots. To that effect, we report single molecule optical absorption detected by scanning tunneling microscopy (SMA-STM) to image energy pooling from donor into acceptor dots on a dot-by-dot basis. We show that we can manipulate groups of quantum dots by pruning away the dominant acceptor dot, and switching the energy transfer path to a different acceptor dot. Our experimental data agrees well with a simple Monte Carlo lattice model of energy transfer, similar to models in the literature, in which excitation energy is transferred preferentially from dots with a larger bandgap to dots with a smaller bandgap.

  12. DOT 3.5-E (DOT 3.5-E/JEF-1) analysis of the PCA-Replica (H2O/FE) shielding benchmark for the LWR-PV damage prediction

    International Nuclear Information System (INIS)

    Pescarini, M.

    1991-01-01

    The results of a DOT 3.5-E/JEF-1 validation on the (H2O/Fr) PCA-REPLICA (UKAEA-Winfith) low-flux shielding benchmark are presented. The PCA-REPLICA experiments reproduces the excore radial geometry of a PWR and is closely related to LWR safety since it is dedicated to test the accuracy of the calculated neutron exposure parameters (fast fluence and iron displacement rates) in a pressure vessel simulator. The NJOY/THEMIS data processing system is employed to obtain the neutron damage-energy cross sections for the JEF-1 iron file. The SN 1-D ANISN code is used to collapse cross sections from the VITAMIN-J (175 n) shielding library, based on the JEF-1 data, to a 28 group working library for 2-D calculations. A 3-D-equivalent synthesis (X,Y,Z) of 2-D and 1-D DOT 3.5-E SN calculations in a plane geometry, gives the integral and spectral results for comparison with the respective experimental data. The underprediction of the in-vessel dosimeter experimental activities depends probably on an overestimation of the iron inelastic scattering cross section of the JEF-1 file

  13. Community Documentation Centre on Industrial Risk. Bulletin no. 6

    International Nuclear Information System (INIS)

    Gow, H.B.F.

    1992-06-01

    The Directorate-General for Environment, Nuclear Safety and Civil Protection of the Commission of the European Communities is responsible for the effective and harmonized implementation of the Directive 82/501/EEC on the major-accident hazards of certain industrial activities. To this end, the Commission, in collaboration with the Committee of Competent Authorities responsible for the implementation of this Directive in the twelve Member States, carries out a whole range of activities. One of the most essential areas for action identified was the need for a systematic diffusion of information concerning the practical implementation of the Directive in the Member States, including the technical rules and guidelines applied, the safety practices and the lessons learnt from major accidents. Therefore, the Commission decided to set up a Community Documentation Centre on Industrial Risks (CDCIR). This Documentation Centre is run by the European Commission, Joint Research Centre, Institute for Systems Engineering and Informatics (ISEI), at Ispra, Italy, among its support activities on the implementation of the Directive. The Documentation Centre will collect, classify and review technical rules, guidelines and documents concerning the requirements of the Directive, as well as the safety of industrial installations produced by governments, administrative, scientific or technical bodies, national or international organizations and industrial or professional associations. Documents on major accidents in the form of reports, videotapes will also be collected and reviewed. The Centre is accessible to interested visitors, documents which are not covered by copyright and are not restricted can be obtained from the Documentation Centre on request. Periodical volumes which will feature the inventory, including abstracts, of the collected material will be published and made available to all interested parties. The Centre will also publish documents devoted to compare existing

  14. Leaving the street and reconstructing lives: impact of DOTS in empowering homeless people in Tokyo, Japan.

    Science.gov (United States)

    Kawatsu, L; Sato, N; Ngamvithayapong-Yanai, J; Ishikawa, N

    2013-07-01

    Since 2000, the Public Health Centre (PHC) in Shinjuku, an area of Tokyo with one of the largest homeless populations in Japan, has been implementing PHC-based DOTS treatment for homeless tuberculosis (TB) patients, with much epidemiological success. Anecdotal evidence indicates that homeless patients treated under DOTS have experienced various positive changes. However, this experience has not yet been systematically analysed. To explore the changes experienced by homeless TB patients, and to discuss the possible role of PHC-based DOTS treatment in effecting these changes. A qualitative study via in-depth interviews with 18 ex-homeless patients who completed DOTS-based treatment at Shinjuku City PHC. The data were analysed using the interpretive content analysis method. The various changes experienced by the participants were categorised into five sub-categories of empowerment, including improved mental health and interpersonal relationships. Some of these changes were attributable to the participants undergoing PHC-based DOTS, which, by addressing their various emotional needs, helped to trigger patient empowerment. Based on our findings, a model of empowerment using PHC-based DOTS was constructed. PHC-based DOTS not only successfully controlled TB, it also empowered homeless patients by addressing their emotional needs. The interpersonal skills of the nurses played a critical role in this process.

  15. ZnO quantum dot-doped graphene/h-BN/GaN-heterostructure ultraviolet photodetector with extremely high responsivity

    Science.gov (United States)

    Lu, Yanghua; Wu, Zhiqian; Xu, Wenli; Lin, Shisheng

    2016-12-01

    A ZnO quantum dot photo-doped graphene/h-BN/GaN-heterostructure ultraviolet photodetector with extremely high responsivity of more than 1915 A W-1 and detectivity of more than 1.02 × 1013 Jones (Jones = cm Hz1/2 W-1) has been demonstrated. The interfaced h-BN layer increases the barrier height at the graphene/GaN heterojunction, which decreases the dark current and improves the on/off current ratio of the device. The photo-doping effect increases the barrier height and carrier concentration at the graphene/h-BN/GaN heterojunction, thus the responsivity is improved from 1473 A W-1 to 1915 A W-1 and the detectivity is improved from 5.8 × 1012 to 1.0 × 1013 Jones. Moreover, all of the responsivity and detectivity values are the highest values among all the graphene-based ultraviolet photodetectors.

  16. An Evaluation of Treatment Outcomes in a Cohort of Clients on the DOTS Strategy, 2012–2016

    Directory of Open Access Journals (Sweden)

    Ato Kwamena Tetteh

    2018-01-01

    Full Text Available We present, for the first time, an evaluation of treatment outcomes in a cohort at a TB referral centre in the Central Region of Ghana. Of the 213 clients placed on DOTS, 59.2% (126/213 were sputum smear-positive. An overall cure rate of 90.2% (51.6% cured + 37.6% completed and a death rate of 8.5% (18/213 were estimated. Of the number of clients who died, 5.7% (12/213 were males (χ2 = 2.891, p=0.699; LR = 3.004, p=0.699. Deaths were only recorded among clients who were > 19 years old (χ2 = 40.319, p=0.099; LR = 41.244, p=0.083. Also, 0.9% (2/213 was lost to follow-up, while 1.4% (3/213 had treatment failure. In total, 13.6% (7.0%, 15/213 males, and 6.6%, 14/213 females of clients who were placed on DOTS were HIV seropositive. Ages of 40–49 years had the highest number, 13/213 (6.1%, infected with HIV, though the difference among the remaining age groups was not statistically significant (χ2 = 9.621, p=0.142. Furthermore, 7.0% (15/213 had TB/HIV coinfection. Out of them, 9 were cured and 5 died at home, while 1 had treatment failure. Tuberculosis/HIV infection prevention advocacy and interventions that address sociodemographic determinants of unfavourable treatment outcomes are urgently required to augment national efforts towards control.

  17. Solution-Processed Nanocrystal Quantum Dot Tandem Solar Cells

    KAUST Repository

    Choi, Joshua J.; Wenger, Whitney N.; Hoffman, Rachel S.; Lim, Yee-Fun; Luria, Justin; Jasieniak, Jacek; Marohn, John A.; Hanrath, Tobias

    2011-01-01

    Solution-processed tandem solar cells created from nanocrystal quantum dots with size-tuned energy levels are demonstrated. Prototype devices featuring interconnected quantum dot layers of cascaded energy gaps exhibit IR sensitivity and an open circuit voltage, V oc, approaching 1 V. The tandem solar cell performance depends critically on the optical and electrical properties of the interlayer. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Solution-Processed Nanocrystal Quantum Dot Tandem Solar Cells

    KAUST Repository

    Choi, Joshua J.

    2011-06-03

    Solution-processed tandem solar cells created from nanocrystal quantum dots with size-tuned energy levels are demonstrated. Prototype devices featuring interconnected quantum dot layers of cascaded energy gaps exhibit IR sensitivity and an open circuit voltage, V oc, approaching 1 V. The tandem solar cell performance depends critically on the optical and electrical properties of the interlayer. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Densities, viscosities, and refractive indexes for {C2H5CO2(CH2)2CH3+C6H13OH+C6H6} at T=308.15 K

    International Nuclear Information System (INIS)

    Casas, Herminio; Garcia-Garabal, Sandra; Segade, Luisa; Cabeza, Oscar.; Franjo, Carlos; Jimenez, Eulogio

    2003-01-01

    In this work we present densities, kinematic viscosities, and refractive indexes of the ternary system {C 2 H 5 CO 2 (CH 2 ) 2 CH 3 +C 6 H 13 OH+C 6 H 6 } and the corresponding binary mixtures {C 2 H 5 CO 2 (CH 2 ) 2 CH 3 +C 6 H 6 }, {C 2 H 5 CO 2 (CH 2 ) 2 CH 3 +C 6 H 13 OH}, and {C 6 H 13 OH+C 6 H 6 }. All data have been measured at T=308.15 K and atmospheric pressure over the whole composition range. The excess molar volumes, dynamic viscosity deviations, and changes of the refractive index on mixing were calculated from experimental measurements. The results for binary mixtures were fitted to a polynomial relationship to estimate the coefficients and standard deviations. The Cibulka equation has been used to correlate the experimental values of ternary mixtures. Also, the experimental values obtained for the ternary mixture were used to test the empirical methods of Kohler, Jacob and Fitzner, Colinet, Tsao and Smith, Toop, Scatchard et al., and Hillert. These methods predict excess properties of the ternary mixtures from those of the involved binary mixtures. The results obtained for dynamic viscosities of the binary mixtures were used to test the semi-empirical relations of Grunberg-Nissan, McAllister, Auslaender, and Teja-Rice. Finally, the experimental refractive indexes were compared with the predicted results for the Lorentz-Lorenz, Gladstone-Dale, Wiener, Heller, and Arago-Biot equations. In all cases, we give the standard deviation between the experimental data and that calculated with the above named relations

  20. Directeur, administration des subventions (h/f) | CRDI - Centre de ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Diriger l'élaboration de politiques régissant l'administration de projets du Centre ... Tenir à jour un aperçu stratégique des activités de projet du Centre afin d'en .... Gérer le recrutement du personnel de l'administration des subventions dans ...

  1. H{sub 2}-Ar dilution for improved c-Si quantum dots in P-doped SiN{sub x}:H thin film matrix

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jia [Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710119 (China); Zhang, Weijia, E-mail: zwjghx@126.com [Center of Condensed Matter and Material Physics, School of Physics and Nuclear Energy Engineering, Beihang University, Beijing, 100191 (China); Liu, Shengzhong, E-mail: szliu@dicp.ac.cn [Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710119 (China); State key Laboratory of Catalysis, iChEM, Dalian Institute of Chemical Physics, Dalian National Laboratory for Clean Energy, Chinese Academy of Sciences, Dalian 116023 (China)

    2017-02-28

    Highlights: • Phosphorous-doped SiN{sub x}:H thin films containing c-Si QDs were prepared by PECVD in H{sub 2}-Ar mixed dilution under low temperature. • QD density and QD size can be controlled by tuning H{sub 2}/Ar flow ratio. • The sample prepared at the H{sub 2}/Ar flow ratio of 100/100 possesses both wide band gap and excellent conductivity. • Detail discussion has been presented for illustrating the influence of H{sub 2}/Ar mixed dilution on the crystallization process and P-doping. - Abstract: Phosphorus-doped hydrogenated silicon nitride (SiN{sub x}:H) thin films containing crystalline silicon quantum dot (c-Si QD) was prepared by plasma enhanced chemical vapor deposition (PECVD) using hydrogen-argon mixed dilution. The effects of H{sub 2}/Ar flow ratio on the structural, electrical and optical characteristics of as-grown P-doped SiN{sub x}:H thin films were systematically investigated. Experimental results show that crystallization is promoted by increasing the H{sub 2}/Ar flow ratio in dilution, while the N/Si atomic ratio is higher for thin film deposited with argon-rich dilution. As the H{sub 2}/Ar flow ratio varies from 100/100 to 200/0, the samples exhibit excellent conductivity owing to the large volume fraction of c-Si QDs and effective P-doping. By adjusting the H{sub 2}/Ar ratio to 100/100, P-doped SiN{sub x}:H thin film containing tiny and densely distributed c-Si QDs can be obtained. It simultaneously possesses wide optical band gap and high dark conductivity. Finally, detailed discussion has been made to analyze the influence of H{sub 2}-Ar mixed dilution on the properties of P-doped SiN{sub x}:H thin films.

  2. Immobilization of pH-sensitive CdTe Quantum Dots in a Poly(acrylate) Hydrogel for Microfluidic Applications

    Science.gov (United States)

    Franke, M.; Leubner, S.; Dubavik, A.; George, A.; Savchenko, T.; Pini, C.; Frank, P.; Melnikau, D.; Rakovich, Y.; Gaponik, N.; Eychmüller, A.; Richter, A.

    2017-04-01

    Microfluidic devices present the basis of modern life sciences and chemical information processing. To control the flow and to allow optical readout, a reliable sensor material that can be easily utilized for microfluidic systems is in demand. Here, we present a new optical readout system for pH sensing based on pH sensitive, photoluminescent glutathione capped cadmium telluride quantum dots that are covalently immobilized in a poly(acrylate) hydrogel. For an applicable pH sensing the generated hybrid material is integrated in a microfluidic sensor chip setup. The hybrid material not only allows in situ readout, but also possesses valve properties due to the swelling behavior of the poly(acrylate) hydrogel. In this work, the swelling property of the hybrid material is utilized in a microfluidic valve seat, where a valve opening process is demonstrated by a fluid flow change and in situ monitored by photoluminescence quenching. This discrete photoluminescence detection (ON/OFF) of the fluid flow change (OFF/ON) enables upcoming chemical information processing.

  3. ZnO quantum dot-doped graphene/h-BN/GaN-heterostructure ultraviolet photodetector with extremely high responsivity.

    Science.gov (United States)

    Lu, Yanghua; Wu, Zhiqian; Xu, Wenli; Lin, Shisheng

    2016-12-02

    A ZnO quantum dot  photo-doped graphene/h-BN/GaN-heterostructure ultraviolet photodetector with extremely high responsivity of more than 1915 A W -1 and detectivity of more than 1.02 × 10 13 Jones (Jones = cm Hz 1/2 W -1 ) has been demonstrated. The interfaced h-BN layer increases the barrier height at the graphene/GaN heterojunction, which decreases the dark current and improves the on/off current ratio of the device. The photo-doping effect increases the barrier height and carrier concentration at the graphene/h-BN/GaN heterojunction, thus the responsivity is improved from 1473 A W -1 to 1915 A W -1 and the detectivity is improved from 5.8 × 10 12 to 1.0 × 10 13 Jones. Moreover, all of the responsivity and detectivity values are the highest values among all the graphene-based ultraviolet photodetectors.

  4. New borohydride anion B6H7-

    International Nuclear Information System (INIS)

    Kuznetsov, I.Yu.; Vinitskij, D.M.; Solntsev, K.A.

    1985-01-01

    The [Ni(Bipy) 3 ] (B 6 H 7 ) 2 , (Ph 4 P)B 6 H 7 , [Ni(Phen) 3 ](B 6 H 7 ) 2 crystals (where Bipy = bipyridine, Phen = phenathroline, Ph = phenyl) are obtained via the exchange reaction with a subsequent recrystallization from aqua-acetonic and acetonic solutions. The structure is studied of a new borohydride anion B 6 H 7 - possessing a four-valence bond unique for polyhedral borohydride anions. A triangular face of boride skeleton coordinating a hydrogen atom is considerably larger than other faces, and the electron density on this hydrogen atom is evidently much higher than at the end hydride hydrogen atoms. The trend of B 6 H 7 - anion to form statistically disordered structurs testifies to a rather slight effect of the seventh hydrogen atom position on the structure pattern of the ionic crystal lattice

  5. Electronic transport through a quantum dot chain with strong dot-lead coupling

    International Nuclear Information System (INIS)

    Liu, Yu; Zheng, Yisong; Gong, Weijiang; Gao, Wenzhu; Lue, Tianquan

    2007-01-01

    By means of the non-equilibrium Green function technique, the electronic transport through an N-quantum-dot chain is theoretically studied. By calculating the linear conductance spectrum and the local density of states in quantum dots, we find the resonant peaks in the spectra coincides with the eigen-energies of the N-quantum-dot chain when the dot-lead coupling is relatively weak. With the increase of the dot-lead coupling, such a correspondence becomes inaccurate. When the dot-lead coupling exceeds twice the interdot coupling, such a mapping collapses completely. The linear conductance turn to reflect the eigen-energies of the (N-2)- or (N-1)-quantum dot chain instead. The two peripheral quantum dots do not manifest themselves in the linear conductance spectrum. More interestingly, with the further increase of the dot-lead coupling, the system behaves just like an (N-2)- or (N-1)-quantum dot chain in weak dot-lead coupling limit, since the resonant peaks becomes narrower with the increase of dot-lead coupling

  6. Doping of 6H-SiC pn structures by proton irradiation

    International Nuclear Information System (INIS)

    Strel'chuk, Anatoly M.; Lebedev, Alexandre A.; Kozlovski, Vitali V.; Savkina, Natali S.; Davydov, Denis V.; Solov'ev, Viktor V.; Rastegaeva, Marina G.

    1999-01-01

    The influence of proton irradiation on current-voltage characteristics, N d - N a values and parameters of deep centres in 6H-SiC pn structures grown by sublimation epitaxy has been studied. The irradiation was carried out with 8 MeV protons in the range of doses from 10 14 to 10 16 cm -2 . Irradiation with a dose of 3.6x10 14 cm -2 leaves the voltage drop at high forward currents (10 A/cm 2 ) practically unchanged. For higher irradiation dose of 1.8x10 15 cm -2 , the forward voltage drop and the degree of compensation in the samples increased ; partial annealing of the radiation defects and partial recovery of the electrical parameters occurred after annealing at T∼400-800 K. Irradiation with a dose of 5.4x10 15 cm -2 resulted in very high resistance in forward biased pn structures which remained high even after heating to 500 deg. C. It is suggested that proton irradiation causes decreasing of the lifetime and formation of an i- or an additional p-layer

  7. Printer model for dot-on-dot halftone screens

    Science.gov (United States)

    Balasubramanian, Raja

    1995-04-01

    A printer model is described for dot-on-dot halftone screens. For a given input CMYK signal, the model predicts the resulting spectral reflectance of the printed patch. The model is derived in two steps. First, the C, M, Y, K dot growth functions are determined which relate the input digital value to the actual dot area coverages of the colorants. Next, the reflectance of a patch is predicted as a weighted combination of the reflectances of the four solid C, M, Y, K patches and their various overlays. This approach is analogous to the Neugebauer model, with the random mixing equations being replaced by dot-on-dot mixing equations. A Yule-Neilsen correction factor is incorporated to account for light scattering within the paper. The dot area functions and Yule-Neilsen parameter are chosen to optimize the fit to a set of training data. The model is also extended to a cellular framework, requiring additional measurements. The model is tested with a four color xerographic printer employing a line-on-line halftone screen. CIE L*a*b* errors are obtained between measurements and model predictions. The Yule-Neilsen factor significantly decreases the model error. Accuracy is also increased with the use of a cellular framework.

  8. The quantum mechanical description of the dot-dot interaction in ionic colloids

    International Nuclear Information System (INIS)

    Morais, P.C.; Qu, Fanyao

    2007-01-01

    In this study the dot-dot interaction in ionic colloids is systematically investigated by self-consistently solving the coupled Schroedinger and Poisson equations in the frame of finite difference method (FDM). In a first approximation the interacting two-dot system (dimer) is described using the picture of two coupled quantum wells. It was found that the dot-dot interaction changes the colloid characteristic by changing the hopping coefficient (t) and consequently the nanodot surface charge density (σ). The hopping coefficient and the surface charge density were investigated as a function of the dot size and dot-dot distance

  9. Cesium immobilization into potassium magnesium phosphate matrix

    International Nuclear Information System (INIS)

    Sayenko, S.Y.; Shkuropatenko, V.A.; Bereznyak, O.P.; Hodyreva, Y.S.; Tarasov, R.V.; Virych, V.D.; Ulybkina, E.A.; Pylypenko, O.V.; Kholomeev, G.O.; Zykova, A.V.; Wagh, Arun S.

    2017-01-01

    The possibility of isomorphous substitution of potassium ions by cesium ions in the structure of potassium magnesium phosphate KMgPO 4 centred dot 6H 2 O (PMP) was shown. It was established, that the Cs included into the PMP matrix does not transfer to the environment during high temperatures heating process (1176 deg C, 3 hours). Analysis of the IR absorption spectrum of the PMP sample has demonstrated that an increase in the amount of additive of the cesium chloride resulted in the shift of the main bands in the spectrum to the low-frequency region with average shift value 10 cm -1 , which indicates the strengthening of bonds in the crystal lattice of matter. The calculated degree of substitution of potassium by cesium during energy release process in the PMP matrix at the level of vitrified high level wastes is about 4%, i. e. the PMP matrix should correspond to the formula K 0.96 Cs 0.04 MgPO 4 centred dot 6H 2 O.

  10. Surface functionalization of quantum dots with fine-structured pH-sensitive phospholipid polymer chains.

    Science.gov (United States)

    Liu, Yihua; Inoue, Yuuki; Ishihara, Kazuhiko

    2015-11-01

    To add novel functionality to quantum dots (QDs), we synthesized water-soluble and pH-responsive block-type polymers by reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymers were composed of cytocompatible 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer segments, which contain a small fraction of active ester groups and can be used to conjugate biologically active compounds to the polymer, and pH-responsive poly(2-(N,N-diethylamino) ethyl methacrylate (DEAEMA)) segments. One terminal of the polymer chain had a hydrophobic alkyl group that originated from the RAFT initiator. This hydrophobic group can bind to the hydrophobic layer on the QD surface. A fluorescent dye was conjugated to the polymer chains via the active ester group. The block-type polymers have an amphiphilic nature in aqueous medium. The polymers were thus easily bound to the QD surface upon evaporation of the solvent from a solution containing the block-type polymer and QDs, yielding QD/fluorescence dye-conjugated polymer hybrid nanoparticles. Fluorescence resonance energy transfer (FRET) between the QDs (donors) and the fluorescent dye molecules (acceptors) was used to obtain information on the conformational dynamics of the immobilized polymers. Higher FRET efficiency of the QD/fluorescent dye-conjugated polymer hybrid nanoparticles was observed at pH 7.4 as compared to pH 5.0 due to a stretching-shrinking conformational motion of the poly(DEAEMA) segments in response to changes in pH. We concluded that the block-type MPC polymer-modified nanoparticles could be used to evaluate the pH of cells via FRET fluorescence based on the cytocompatibility of the MPC polymer. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Ground and excited states of the [Fe(H2O)6]2+ and [Fe(H2O)6]3+ clusters: Insight into the electronic structure of the [Fe(H2O)6]2+ – [Fe(H2O)6]3+ complex

    Energy Technology Data Exchange (ETDEWEB)

    Miliordos, Evangelos; Xantheas, Sotiris S.

    2015-04-14

    We report the ground and low lying electronically excited states of the [Fe(H2O)6]2+ and [Fe(H2O)6]3+ clusters using multi-configuration electronic structure theory. In particular, we have constructed the Potential Energy Curves (PECs) with respect to the iron-oxygen distance when removing all water ligands at the same time from the cluster minima and established their correlation to the long range dissociation channels. Due to the fact that both the second and third ionization potentials of iron are larger than the one for water, the ground state products asymptotically correlate with dissociation channels that are repulsive in nature at large separations as they contain at least one H2O+ fragment and a positive metal center. The most stable equilibrium structures emanate – via intersections and/or avoided crossings – from the channels consisting of the lowest electronic states of Fe2+(5D; 3d6) or Fe3+(6S; 3d5) and six neutral water molecules. Upon hydration, the ground state of Fe2+(H2O)6 is a triply (5Tg) degenerate one with the doubly (5Eg) degenerate state lying slightly higher in energy. Similarly, Fe3+(H2O)6 has a ground state of 6Ag symmetry under Th symmetry. We furthermore examine a multitude of electronically excited states of many possible spin multiplicities, and report the optimized geometries for several selected states. The PECs for those cases are characterized by a high density of states. Focusing on the ground and the first few excited states of the [Fe(H2O)6]2+ and [Fe(H2O)6]3+ clusters, we studied their mutual interaction in the gas phase. We obtained the optimal geometries of the Fe2+(H2O)6 – Fe3+(H2O)6 gas phase complex for different Fe–Fe distances. For distances shorter than 6.0 Å, the water molecules in the respective first solvation shells located between the two metal centers were found to interact via weak hydrogen bonds. We examined a total of ten electronic states for this complex, including those corresponding to the

  12. L-Cysteine Capped CdSe Quantum Dots Synthesized by Photochemical Route.

    Science.gov (United States)

    Singh, Avinash; Kunwar, Amit; Rath, M C

    2018-05-01

    L-cysteine capped CdSe quantum dots were synthesized via photochemical route in aqueous solution under UV photo-irradiation. The as grown CdSe quantum dots exhibit broad fluorescence at room temperature. The CdSe quantum dots were found to be formed only through the reactions of the precursors, i.e., Cd(NH3)2+4 and SeSO2-3 with the photochemically generated 1-hydroxy-2-propyl radicals, (CH3)2COH radicals, which are formed through the process of H atom abstraction by the photoexcited acetone from 2-propanol. L-Cysteine was found to act as a suitable capping agent for the CdSe quantum dots and increases their biocompatability. Cytotoxicty effects of these quantum dots were evaluated in Chinese Hamster Ovary (CHO) epithelial cells, indicated a significant lower level for the L-cysteine capped CdSe quantum dots as compare to the bare ones.

  13. Quantum dots

    International Nuclear Information System (INIS)

    Kouwenhoven, L.; Marcus, C.

    1998-01-01

    Quantum dots are man-made ''droplets'' of charge that can contain anything from a single electron to a collection of several thousand. Their typical dimensions range from nanometres to a few microns, and their size, shape and interactions can be precisely controlled through the use of advanced nanofabrication technology. The physics of quantum dots shows many parallels with the behaviour of naturally occurring quantum systems in atomic and nuclear physics. Indeed, quantum dots exemplify an important trend in condensed-matter physics in which researchers study man-made objects rather than real atoms or nuclei. As in an atom, the energy levels in a quantum dot become quantized due to the confinement of electrons. With quantum dots, however, an experimentalist can scan through the entire periodic table by simply changing a voltage. In this article the authors describe how quantum dots make it possible to explore new physics in regimes that cannot otherwise be accessed in the laboratory. (UK)

  14. Highly sensitive enzymatic determination of urea based on the pH-dependence of the fluorescence of graphene quantum dots

    International Nuclear Information System (INIS)

    Shao, Taili; Zhang, Ping; Zhuo, Shujuan; Zhu, Changqing; Tang, Lin

    2015-01-01

    We report on a nanoparticle-based fluorescent sensing scheme for urea. It is based on the finding that graphene quantum dots (GQDs) display pH-sensitive green fluorescence if photoexcited at 460 nm. Fluorescence is gradually quenched due to an increase in the local pH value as a result of the hydrolysis of urea as catalyzed by urease. The effect was used to quantify urea in the 0.1–100 mM concentration range, with a limit of detection of 0.01 mM. The method was successfully applied to the determination of urea in human serum samples. The method is simple, effective, and therefore holds promise as a platform for sensing urea in blood. (author)

  15. Raman study of strain in GaN/AlN quantum dot multilayered structures

    Energy Technology Data Exchange (ETDEWEB)

    Cros, A.; Garro, N.; Llorens, J.M.; Garcia-Cristobal, A.; Cantarero, A. [Institut de Ciencia dels Materials, Universitat de Valencia, 46071 Valencia (Spain); Gogneau, N.; Monroy, E.; Daudin, B. [CEA-CNRS Group, ' ' Nanophysique et Semiconducteurs' ' , Departement de la Recherche Fondamentale sur la Matiere Condensee, CEA-Grenoble, 17 rue des Martyrs, 38054-Grenoble Cedex 9 (France)

    2005-05-01

    Raman spectroscopy has been used to investigate self-assembled stacks of GaN/AlN quantum dots with increasing number of periods. The E{sub 2H} phonon modes associated to GaN and AlN are clearly resolved with visible excitation, and their energies allow the simultaneous monitoring of the dot and barrier strain states. The compression of the quantum dots is evidenced by a shift of the E{sub 2H} phonon mode of circa 29 cm{sup -1} to higher energies with respect to its relaxed value. The strain of the AlN spacer is found to be correlated to that of the dot, with an increase in its tensile component for the samples with fewer periods and a partial relaxation for samples over 50 periods. Additionally, resonant effects of the A{sub 1}(LO) phonon mode have been investigated by tuning the excitation over a wide range in the ultra-violet region. A discussion of the strain distribution in quantum dots and spacers as a function of the number of periods is performed by means of a theoretical calculation based on the method of inclusions. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Isolation and structures of sulfonium salts derived from thioethers: [{o-C(6)H(4)(CH(2)SMe)(2)}H][NbF(6)] and [{[9]aneS(3)}H][NbF(6)].

    Science.gov (United States)

    Jura, Marek; Levason, William; Reid, Gillian; Webster, Michael

    2009-10-07

    Two very unusual sulfonium salts, [{o-C(6)H(4)(CH(2)SMe)(2)}H][NbF(6)] and [{[9]aneS(3)}H][NbF(6)], obtained from reaction of the thioethers with NbF(5) in CH(2)Cl(2) solution, are reported and their structures described; the eight-coordinate tetrafluoro Nb(v) cation of the dithioether is obtained from the same reaction.

  17. Hydrothermal synthesis of two photoluminescent nitrogen-doped graphene quantum dots emitted green and khaki luminescence

    International Nuclear Information System (INIS)

    Zhu, Xiaohua; Zuo, Xiaoxi; Hu, Ruiping; Xiao, Xin; Liang, Yong; Nan, Junmin

    2014-01-01

    A simple and effective chemical synthesis of the photoluminescent nitrogen-doped graphene quantum dots (N-GQDs) biomaterial is reported. Using the hydrothermal treatment of graphene oxide (GO) in the presence of hydrogen peroxide (H 2 O 2 ) and ammonia, the N-GQDs are synthesized through H 2 O 2 exfoliating the GO into nanocrystals with lateral dimensions and ammonia passivating the generated active surface. Then, after a dialytic separation, two water-soluble N-GQDs with average size of about 2.1 nm/6.2 nm, which emit green/khaki luminescence and exhibit excitation dependent/independent photoluminescence (PL) behaviors, are obtained. In addition, it is also demonstrated that these two N-GQDs are stable over a broad pH range and have the upconversion PL property, showing this approach provides a simple and effective method to synthesize the functional N-GQDs. - Highlights: • Nitrogen-doped graphene quantum dots (N-GQDs) are prepared by hydrothermal routine. • Two N-GQDs with different size distribution emit green/khaki photoluminescence. • Two N-GQDs exhibit excitation-dependent/independent photoluminescence behaviors

  18. Platelike WO3 sensitized with CdS quantum dots heterostructures for photoelectrochemical dynamic sensing of H2O2 based on enzymatic etching.

    Science.gov (United States)

    Wang, Yanhu; Gao, Chaomin; Ge, Shenguang; Yu, Jinghua; Yan, Mei

    2016-11-15

    A platelike tungsten trioxide (WO3) sensitized with CdS quantum dots (QDs) heterojunction is developed for solar-driven, real-time, and selective photoelectrochemical (PEC) sensing of H2O2 in the living cells. The structure is synthesized by hydrothermally growing platelike WO3 on fluorine doped tin oxide (FTO) and subsequently sensitized with CdS QDs. The as-prepared WO3-CdS QDs heterojunction achieve significant photocurrent enhancement, which is remarkably beneficial for light absorption and charge carrier separation. Based on the enzymatic etching of CdS QDs enables the activation of quenching the charge transfer efficiency, thus leading to sensitive PEC recording of H2O2 level in buffer and cellular environments. The results indicated that the proposed method will pave the way for the development of excellent PEC sensing platform with the quantum dot sensitization. This study could also provide a new train of thought on designing of self-operating photoanode in PEC sensing, promoting the application of semiconductor nanomaterials in photoelectrochemistry. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Effect of small doses of ionizing radiation on motility, rosette formation, and antioxidant state of leukocytes under modification of G-proteins by cholera and pertussis toxins

    International Nuclear Information System (INIS)

    Zhirnov, V.V.; Luik, A.I.; Metelitsa, L.A.; Mogilevich, S.E.; Charochkina, L.L.

    2000-01-01

    The responses of motility and rosette formation of leukocytes to small radioactive doses (from 6 centre dot 10 -10 to 6 centre dot 10 -4 Gy) are studied. The influence of these doses on cell functions and oxidative homeostasis are investigated under the modification of transducing components of membrane signal pathways (adenylate cyclase and polyphosphoinositide cascades) with pertussis and cholera toxins

  20. A highly efficient single-photon source based on a quantum dot in a photonic nanowire

    DEFF Research Database (Denmark)

    Claudon, Julien; Bleuse, Joel; Malik, Nitin Singh

    2010-01-01

    –4 or a semiconductor quantum dot5–7. Achieving a high extraction efficiency has long been recognized as a major issue, and both classical solutions8 and cavity quantum electrodynamics effects have been applied1,9–12. We adopt a different approach, based on an InAs quantum dot embedded in a GaAs photonic nanowire......The development of efficient solid-state sources of single photons is a major challenge in the context of quantum communication,optical quantum information processing and metrology1. Such a source must enable the implementation of a stable, single-photon emitter, like a colour centre in diamond2...

  1. A review on syntheses, properties, characterization and bioanalytical applications of fluorescent carbon dots

    International Nuclear Information System (INIS)

    Zuo, Pengli; Lu, Xiuhua; Sun, Zhigang; Guo, Yuhan; He, Hua

    2016-01-01

    Carbon dots (C-dots) are a kind of fluorescent nanoparticles that are strongly fluorescent, non-blinking, and can be easily synthesized at low cost. Their emission color can be tuned by varying the excitation wavelength. Their properties make them strong competitors to semiconductor quantum dots. Synthetic approaches for C-dots can be classified into two categories, viz. top-down and bottom-up methods. Surface passivated and functionalized C-dots can be utilized to sense pH values, metal ions and organic molecules. Owing to their low cytotoxicity, biocompatibility and impressive photostability, long-term observations become possible. C-dots also show promise as labels and for bioimaging. This review (with 142 refs.) is divided into several sections. The first covers commonly used methods for preparation of C-dots including laser ablation, arc discharge, electrochemical methods, pyrolytic processes, template based methods, microwave assisted methods, chemical oxidation methods, reverse micelle based methods, etc. The first section also covers methods for surface functionalization and passivation. We continue by discussing the spectroscopic properties and other physical and chemical properties of C-dots (fluorescence, up-conversion fluorescence, methods for enhancing photoluminescence, effects of pH value, cytotoxicity, etc.). Another section covers the characterization including TEM and XRD. Applications in biology are summarized and subdivided into in vitro imaging, in vivo imaging, chemical probe, quantitation of biomacromolecules, but also in drug delivery, photoacoustic imaging and anticancer therapy. We finally discuss current challenges and perspectives in this promising field. (author)

  2. The nido-osmaboranes [2,2,2-(CO)(PPh(3))(2)-nido-2-OsB(5)H(9)] and [6,6,6-(CO)(PPh(3))(2)-nido-6-OsB(9)H(13)].

    Science.gov (United States)

    Bould, J; Kennedy, J D; Thomas, R L; Rath, N P; Barton, L

    2001-11-01

    The structural characterization of the osmahexaborane 2-carbonyl-2,2-bis(triphenylphosphine)-nido-2-osmahexaborane(9), [Os(B(5)H(9))(C(18)H(15)P)(2)(CO)], (I), a metallaborane analogue of B(6)H(10), confirms the structure proposed from NMR spectroscopy. The structure of the osmadecaborane 6-carbonyl-6,6-bis(triphenylphosphine)-nido-6-osmadecaborane(13), [Os(B(9)H(13))(C(18)H(15)P)(2)(CO)], (IV), is similarly confirmed. The short basal B-B distance of 1.652 (8) A in (I), not bridged by an H atom, mirrors that in the parent hexaborane(10) [1.626 (4) A].

  3. Nonlinear Dot Plots.

    Science.gov (United States)

    Rodrigues, Nils; Weiskopf, Daniel

    2018-01-01

    Conventional dot plots use a constant dot size and are typically applied to show the frequency distribution of small data sets. Unfortunately, they are not designed for a high dynamic range of frequencies. We address this problem by introducing nonlinear dot plots. Adopting the idea of nonlinear scaling from logarithmic bar charts, our plots allow for dots of varying size so that columns with a large number of samples are reduced in height. For the construction of these diagrams, we introduce an efficient two-way sweep algorithm that leads to a dense and symmetrical layout. We compensate aliasing artifacts at high dot densities by a specifically designed low-pass filtering method. Examples of nonlinear dot plots are compared to conventional dot plots as well as linear and logarithmic histograms. Finally, we include feedback from an expert review.

  4. Group-III vacancy induced InxGa1-xAs quantum dot interdiffusion

    International Nuclear Information System (INIS)

    Djie, H. S.; Wang, D.-N.; Ooi, B. S.; Hwang, J. C. M.; Gunawan, O.

    2006-01-01

    The impact of group-III vacancy diffusion, generated during dielectric cap induced intermixing, on the energy state transition and the inhomogeneity reduction in the InGaAs/GaAs quantum-dot structure is investigated. We use a three-dimensional quantum-dot diffusion model and photoluminescence data to determine the thermal and the interdiffusion properties of the quantum dot. The band gap energy variation related to the dot uniformity is found to be dominantly affected by the height fluctuation. A group-III vacancies migration energy H m for InGaAs quantum dots of 1.7 eV was deduced. This result is similar to the value obtained from the bulk and GaAs/AlGaAs quantum-well materials confirming the role of SiO 2 capping enhanced group-III vacancy induced interdiffusion in the InGaAs quantum dots

  5. Functional Carbon Quantum Dots: A Versatile Platform for Chemosensing and Biosensing.

    Science.gov (United States)

    Feng, Hui; Qian, Zhaosheng

    2018-05-01

    Carbon quantum dot has emerged as a new promising fluorescent nanomaterial due to its excellent optical properties, outstanding biocompatibility and accessible fabrication methods, and has shown huge application perspective in a variety of areas, especially in chemosensing and biosensing applications. In this personal account, we give a brief overview of carbon quantum dots from its origin and preparation methods, present some advance on fluorescence origin of carbon quantum dots, and focus on development of chemosensors and biosensors based on functional carbon quantum dots. Comprehensive advances on functional carbon quantum dots as a versatile platform for sensing from our group are included and summarized as well as some typical examples from the other groups. The biosensing applications of functional carbon quantum dots are highlighted from selective assays of enzyme activity to fluorescent identification of cancer cells and bacteria. © 2018 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Spectroscopic characteristics of carbon dots (C-dots) derived from carbon fibers and conversion to sulfur-bridged C-dots nanosheets.

    Science.gov (United States)

    Vinci, John C; Ferrer, Ivonne M; Guterry, Nathan W; Colón, Verónica M; Destino, Joel F; Bright, Frank V; Colón, Luis A

    2015-09-01

    We synthesized sub-10 nm carbon nanoparticles (CNPs) consistent with photoluminescent carbon dots (C-dots) from carbon fiber starting material. The production of different C-dots fractions was monitored over seven days. During the course of the reaction, one fraction of C-dots species with relatively high photoluminescence was short-lived, emerging during the first hour of reaction but disappearing after one day of reaction. Isolation of this species during the first hour of the reaction was crucial to obtaining higher-luminescent C-dots species. When the reaction proceeded for one week, the appearance of larger nanostructures was observed over time, with lateral dimensions approaching 200 nm. The experimental evidence suggests that these larger species are formed from small C-dot nanoparticles bridged together by sulfur-based moieties between the C-dot edge groups, as if the C-dots polymerized by cross-linking the edge groups through sulfur bridges. Their size can be tailored by controlling the reaction time. Our results highlight the variety of CNP products, from sub-10 nm C-dots to ~200 nm sulfur-containing carbon nanostructures, that can be produced over time during the oxidation reaction of the graphenic starting material. Our work provides a clear understanding of when to stop the oxidation reaction during the top-down production of C-dots to obtain highly photoluminescent species or a target average particle size.

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

    Science.gov (United States)

    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

  8. Efficient colorimetric pH sensor based on responsive polymer-quantum dot integrated graphene oxide.

    Science.gov (United States)

    Paek, Kwanyeol; Yang, Hyunseung; Lee, Junhyuk; Park, Junwoo; Kim, Bumjoon J

    2014-03-25

    In this paper, we report the development of a versatile platform for a highly efficient and stable graphene oxide (GO)-based optical sensor that exhibits distinctive ratiometric color responses. To demonstrate the applicability of the platform, we fabricated a colorimetric, GO-based pH sensor that responds to a wide range of pH changes. Our sensing system is based on responsive polymer and quantum dot (QD) hybrids integrated on a single GO sheet (MQD-GO), with the GO providing an excellent signal-to-noise ratio and high dispersion stability in water. The photoluminescence emissions of the blue and orange color-emitting QDs (BQDs and OQDs) in MQD-GO can be controlled independently by different pH-responsive linkers of poly(acrylic acid) (PAA) (pKa=4.5) and poly(2-vinylpyridine) (P2VP) (pKa=3.0) that can tune the efficiencies of Förster resonance energy transfer from the BQDs to the GO and from the OQDs to the GO, respectively. As a result, the color of MQD-GO changes from orange to near-white to blue over a wide range of pH values. The detailed mechanism of the pH-dependent response of the MQD-GO sensor was elucidated by measurements of time-resolved fluorescence and dynamic light scattering. Furthermore, the MQD-GO sensor showed excellent reversibility and high dispersion stability in pure water, indicating that our system is an ideal platform for biological and environmental applications. Our colorimetric GO-based optical sensor can be expanded easily to various other multifunctional, GO-based sensors by using alternate stimuli-responsive polymers.

  9. Phenylalanine-a biogenic ligand with flexible η6- and η6:κ1-coordination at ruthenium(ii) centres

    KAUST Repository

    Reiner, Thomas; Jantke, Dominik; Miao, Xiaohe; Marziale, Alexander N.; Kiefer, Florian J.; Eppinger, Jö rg

    2013-01-01

    The reaction of (S)-2,5-dihydrophenylalanine 1 with ruthenium(iii) chloride yields the μ-chloro-bridged dimeric η6-phenylalanine ethyl ester complex 3, which can be converted into the monomeric analogue, η6:κ1-phenylalanine ethyl ester complex 12, under basic conditions. Studies were carried out to determine the stability and reactivity of complexes bearing η6- and η6: κ1-chelating phenylalanine ligands under various conditions. Reaction of 3 with ethylenediamine derivatives N-p-tosylethylenediamine or 1,4-di-N-p-tosylethylenediamine results in the formation of monomeric η6:κ1-phenylalanine ethyl ester complexes 14 and 15, which could be saponified yielding complexes 16 and 17 without changing the inner coordination sphere of the metal centre. The structure of η6:κ1-phenylalanine complex 17 and an N-κ1-phenylalanine complex 13 resulting from the reaction of 3 with an excess of pyridine were confirmed by X-ray crystallography. © 2013 The Royal Society of Chemistry.

  10. Nonequilibrium carrier dynamics in self-assembled InGaAs quantum dots

    International Nuclear Information System (INIS)

    Wesseli, M.; Ruppert, C.; Trumm, S.; Betz, M.; Krenner, H.J.; Finley, J.J.

    2006-01-01

    Carrier dynamics in InGaAs/GaAs quantum dots is analyzed with highly sensitive femtosecond transmission spectroscopy. In a first step, measurements on a large ensemble of nanoislands reveal the dynamical electronic filling of quantum dots from the surrounding wetting layer. Most interestingly, we find a spin-preserving phonon mediated scattering into fully localized states within a few picoseconds. Then, individual artificial atoms are isolated with metallic shadow masks. For the first time, a single self-assembled quantum dot is addressed in an ultrafast transmission experiment. We find bleaching signals in the order of 10 -5 that arise from individual interband transitions of one quantum dot. As a result, we have developed an ultrafast optical tool for both manipulation and read-out of a single self-assembled quantum dot. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Patients' costs and cost-effectiveness of tuberculosis treatment in DOTS and non-DOTS facilities in Rio de Janeiro, Brazil.

    Directory of Open Access Journals (Sweden)

    Ricardo Steffen

    2010-11-01

    Full Text Available Costs of tuberculosis diagnosis and treatment may represent a significant burden for the poor and for the health system in resource-poor countries.The aim of this study was to analyze patients' costs of tuberculosis care and to estimate the incremental cost-effectiveness ratio (ICER of the directly observed treatment (DOT strategy per completed treatment in Rio de Janeiro, Brazil.We interviewed 218 adult patients with bacteriologically confirmed pulmonary tuberculosis. Information on direct (out-of-pocket expenses and indirect (hours lost costs, loss in income and costs with extra help were gathered through a questionnaire. Healthcare system additional costs due to supervision of pill-intake were calculated considering staff salaries. Effectiveness was measured by treatment completion rate. The ICER of DOT compared to self-administered therapy (SAT was calculated.DOT increased costs during the treatment phase, while SAT increased costs in the pre-diagnostic phase, for both the patient and the health system. Treatment completion rates were 71% in SAT facilities and 79% in DOT facilities. Costs per completed treatment were US$ 194 for patients and U$ 189 for the health system in SAT facilities, compared to US$ 336 and US$ 726 in DOT facilities. The ICER was US$ 6,616 per completed DOT treatment compared to SAT.Costs incurred by TB patients are high in Rio de Janeiro, especially for those under DOT. The DOT strategy doubles patients' costs and increases by fourfold the health system costs per completed treatment. The additional costs for DOT may be one of the contributing factors to the completion rates below the targeted 85% recommended by WHO.

  12. Specific detection of Vibrio parahaemolyticus by fluorescence quenching immunoassay based on quantum dots.

    Science.gov (United States)

    Wang, Ling; Zhang, Junxian; Bai, Haili; Li, Xuan; Lv, Pintian; Guo, Ailing

    2014-07-01

    In this study, anti-Vibrio parahaemolyticus polyclonal and monoclonal antibodies were prepared through intradermal injection immune and lymphocyte hybridoma technique respectively. CdTe quantum dots (QDs) were synthesized at pH 9.3, 98 °C for 1 h with stabilizer of 2.7:1. The fluorescence intensity was 586.499, and the yield was 62.43%. QD probes were successfully prepared under the optimized conditions of pH 7.4, 37 °C for 1 h, 250 μL of 50 mg/mL EDC · HCl, 150 μL of 4 mg/mL NHS, buffer system of Na2HPO4-citric acid, and 8 μL of 2.48 mg/mL polyclonal antibodies. As gold nanoparticles could quench fluorescence of quantum dots, the concentration of V. parahaemolyticus could be detected through measuring the reduction of fluorescence intensity in immune sandwich reaction composed of quantum dot probe, gold-labeled antibody, and the sample. For pure culture, fluorescence intensity of the system was proportional with logarithm concentration of antigen, and the correlation coefficient was 99.764%. The fluorescence quenching immunoassay based on quantum dots is established for the first time to detect Vibrio parahaemolyticus. This method may be used as rapid testing procedure due to its high simplicity and sensitivity.

  13. Optical rectification in a strained GaAs{sub 0.9}P{sub 0.1}/GaAs{sub 0.6}P{sub 0.4} quantum dot: Simultaneous effects of electric and magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Vinolin, Ada [Dept. of Physics, Madurai Kamaraj University College, Alagarkoil Road, Madurai-625002 (India); Peter, A. John, E-mail: a.john.peter@gmail.com [Dept. of Physics, Government Arts College, Melur-625106, Tamilnadu (India)

    2014-04-24

    Simultaneous effects of electric field and magnetic field on exciton binding energy as a function of dot radius in a cylindrical GaAs{sub 0.9}P{sub 0.1}/GaAs{sub 0.6}P{sub 0.4} strained quantum dot are investigated. The strain contribution includes the strong built-in electric field induced by the spontaneous and piezoelectric polarizations. Numerical calculations are performed using variational procedure within the single band effective mass approximation. Optical rectification in the GaAs{sub 0.9}P{sub 0.1}/GaAs{sub 0.6}P{sub 0.4} quantum dot is computed in the presence of electric and magnetic fields.

  14. Spontaneous polarization and pyroelectric effect in improper ferroelectrics-ferroelastics Gd2(MoO4)3 and Tb2(MoO4)3 at low temperature

    International Nuclear Information System (INIS)

    Matyjasik, S; Shaldin, Yu.V.

    2013-01-01

    Experimental dependencies for spontaneous polarization ΔP s (T) and pyroelectric coefficient γ s (T)for Gd 2 (MoO 4 ) 3 (GMO) and Tb 2 (MoO 4 ) 3 (TMO) reported here differs from those for intrinsic ferroelectrics. We found fundamental distinction in GMO and TMO samples behavior at their repolarization at the fixed temperatures 300 and 4.2 K. In TMO monodomainization temperature does not affect experimental data, while in GMO monodomainization at 4.2 K results in increase of ΔP s (T) by order of magnitude at 85 K and γ s (T) dependence shows well-defined anomalies, reaching a record magnitude of 3 centre dot 10 -4 C/(m 2 centre dot K) at T = 25 K. At T = 200 K the pyroelectric coefficients values are -1.45 centre dot 10 -6 C/(m 2 centre dot K) and-1.8 centre dot 10 -6 C/(m 2 centre dot K). Taking into account our data, results related to transformation of structure in (001) plane and symmetry reasons we suggested crystallographic model of GMO type improper ferroelectric. It is formed by four meso-tetrahedrons constructed of three coordination tetrahedrons MO 4 (a, b and c types). In the framework of this model we discuss the physical meaning of pseudodeviator Q 12 *, coefficient, that initiate the phase transition at T > 433 K from noncentrosymmetric phase (mm2) to another one (4-bar2m).

  15. Graphene quantum dots probed by scanning tunneling microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Morgenstern, Markus; Freitag, Nils; Nent, Alexander; Nemes-Incze, Peter; Liebmann, Marcus [II. Institute of Physics B and JARA-FIT, RWTH Aachen University, Aachen (Germany)

    2017-11-15

    Scanning tunneling spectroscopy results probing the electronic properties of graphene quantum dots are reviewed. After a short summary of the study of squared wave functions of graphene quantum dots on metal substrates, we firstly present data where the Landau level gaps caused by a perpendicular magnetic field are used to electrostatically confine electrons in monolayer graphene, which are probed by the Coulomb staircase revealing the consecutive charging of a quantum dot. It turns out that these quantum dots exhibit much more regular charging sequences than lithographically confined ones. Namely, the consistent grouping of charging peaks into quadruplets, both, in the electron and hole branch, portrays a regular orbital splitting of about 10meV. At low hole occupation numbers, the charging peaks are, partly, additionally grouped into doublets. The spatially varying energy separation of the doublets indicates a modulation of the valley splitting by the underlying BN substrate. We outline that this property might be used to eventually tune the valley splitting coherently. Afterwards, we describe graphene quantum dots with multiple contacts produced without lithographic resist, namely by local anodic oxidation. Such quantum dots target the goal to probe magnetotransport properties during the imaging of the corresponding wave functions by scanning tunneling spectroscopy. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Preparation of carbon quantum dots based high photostability luminescent membranes.

    Science.gov (United States)

    Zhao, Jinxing; Liu, Cui; Li, Yunchuan; Liang, Jiyuan; Liu, Jiyan; Qian, Tonghui; Ding, Jianjun; Cao, Yuan-Cheng

    2017-06-01

    Urethane acrylate (UA) was used to prepare carbon quantum dots (C-dots) luminescent membranes and the resultants were examined with FT-IR, mechanical strength, scanning electron microscope (SEM) and quantum yields (QYs). FT-IR results showed the polyurethane acrylate (PUA) prepolymer -C = C-vibration at 1101 cm -1 disappeared but there was strong vibration at1687cm -1 which was contributed from the-C = O groups in cross-linking PUA. Mechanical strength results showed that the different quantity of C-dots loadings and UV-curing time affect the strength. SEM observations on the cross-sections of the membranes are uniform and have no structural defects, which prove that the C-dots are compatible with the water-soluble PUA resin. The C-dot loading was increased from 0 to 1 g, the maximum tensile stress was nearly 2.67 MPa, but the tensile strain was decreased from 23.4% to 15.1% and 7.2% respectively. QYs results showed that the C-dots in the membrane were stable after 120 h continuous irradiation. Therefore, the C-dots photoluminescent film is the promising material for the flexible devices in the future applications. Copyright © 2016 John Wiley & Sons, Ltd.

  17. Structure, ferroelectric ordering, and semiempirical quantum calculations of lanthanide based metal-organic framework: [Nd(C{sub 4}H{sub 5}O{sub 6})(C{sub 4}H{sub 4}O{sub 6})][3H{sub 2}O

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Bhat Zahoor; Want, Basharat, E-mail: bawant@kashmiruniversity.ac.in [Solid State Research Laboratory, Department of Physics, University of Kashmir, Srinagar 190006 (India)

    2016-04-14

    We investigate the structure and ferroelectric behavior of a lanthanide based metal-organic framework (MOF), [Nd(C{sub 4}H{sub 5}O{sub 6})(C{sub 4}H{sub 4}O{sub 6})][3H{sub 2}O]. X-ray crystal structure analyses reveal that it crystallizes in the P4{sub 1}2{sub 1}2 space group with Nd centres, coordinated by nine oxygen atoms, forming a distorted capped square antiprismatic geometry. The molecules, bridged by tartrate ligands, form a 2D chiral structure. The 2D sheets are further linked into a 3D porous framework via strong hydrogen-bonding scheme (O-H…O ≈ 2.113 Å). Dielectric studies reveal two anomalies at 295 K and 185 K. The former is a paraelectric-ferroelectric transition, and the later is attributed to the freezing down of the motion of the hydroxyl groups. The phase transition is of second order, and the spontaneous polarization in low temperature phase is attributed to the ordering of protons of hydroxyl groups. The dielectric nonlinearity parameters have been calculated using Landau– Devonshire phenomenological theory. In addition, the most recent semiempirical models, Sparkle/PM7, Sparkle/RM1, and Sparkle/AM1, are tested on the present system to assay the accuracy of semiempirical quantum approaches to predict the geometries of solid MOFs. Our results show that Sparkle/PM7 model is the most accurate to predict the unit cell structure and coordination polyhedron geometry. The semiempirical methods are also used to calculate different ground state molecular properties.

  18. PHASE CHANGES ON 4H AND 6H SIC AT HIGH TEMPERATURE OXIDATION

    Directory of Open Access Journals (Sweden)

    Jan Setiawan

    2016-10-01

    Full Text Available ABSTRACT PHASE CHANGES ON 4H AND 6H SIC AT HIGH TEMPERATURE OXIDATION. The oxidation on two silicon carbide contain 6H phase and contains 6H and 4H phases has been done.  Silicon carbide is ceramic non-oxide with excellent properties that potentially used in industry.  Silicon carbide is used in nuclear industry as structure material that developed as light water reactor (LWR fuel cladding and as a coating layer in the high temperature gas-cooled reactor (HTGR fuel.  In this study silicon carbide oxidation simulation take place in case the accident in primary cooling pipe is ruptured.  Sample silicon carbide made of powder that pressed into pellet with diameter 12.7 mm and thickness 1.0 mm, then oxidized at temperature 1000 oC, 1200 oC dan 1400 oC for 1 hour.  The samples were weighted before and after oxidized.  X-ray diffraction con-ducted to the samples using Panalytical Empyrean diffractometer with Cu as X-ray source.  Diffraction pattern analysis has been done using General Structure Analysis System (GSAS software. This software was resulting the lattice parameter changes and content of SiC phases.  The result showed all of the oxidation samples undergoes weight gain.  The 6S samples showed the highest weight change at oxidation temperature 1200 oC, for the 46S samples showed increasing tendency with the oxidation temperature.  X-ray diffraction pattern analysis showed the 6S samples contain dominan phase 6H-SiC that matched to ICSD 98-001-5325 card.  Diffraction pattern on 6S showed lattice parameter, composition and crystallite size changes.  Lattice parameters changes had smaller tendency from the model and before oxidation.  However, the lowest silicon carbide composition or the highest converted into other phases up to 66.85 %, occurred at oxidation temperature 1200 oC.  The 46S samples contains two polytypes silicon car-bide.  The 6H-SiC phases matched by ICSD 98-016-4972 card and 4H-SiC phase matched by ICSD 98

  19. Fabrication and optical properties of type-II InP/InAs nanowire/quantum-dot heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Xin; Zhang, Xia; Li, Junshuai; Wu, Yao; Li, Bang; Ren, Xiaomin [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing, 100876 (China)

    2016-02-15

    The growth and optical properties of InAs quantum dots on a pure zinc blende InP nanowire are investigated. The quantum dots are formed in Stranski-Krastanov mode and exhibit pure zinc blende crystal structure. A substantial blueshift of the dots peak with a cube-root dependence on the excitation power is observed, suggesting a type-II band alignment. The peak position of dots initially red-shifts and then blue-shifts with increasing temperature, which is attributed to the carrier redistribution among the quantum dots. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Biodistribution study of carbogenic dots in cells and in vivo for optical imaging

    International Nuclear Information System (INIS)

    Li Nan; Liang Xiaofei; Wang Lili; Li Zonghai; Li Peiyong; Zhu Yihua; Song Jing

    2012-01-01

    Blue fluorescent carbon dots (C-dots) were synthesized and evaluated for their cytotoxicity and also for their optical imaging performance. The results showed that the C-dots could enter into the Hela cells in 15 min incubation and the uptake increased rapidly from 15 min to 2 h. In cytotoxicity study, C-dots were biocompatible and nontoxic to three human cells including two cancer cells (Hela and SMCC-7721) and one normal cell (HEK 293) in concentrations up to 500 μg/mL. Since the endocytic interference factors, including NaN 3 , MβCD, sucrose, and low temperature, could not play an inhibitory effect on C-dots entering into cells, the direct nonendocytic pathway for C-dots was speculated. The C-dots showed encouraging cell-imaging applications in vitro and in vivo. They entered into cells without any further functionalization, and the fluorescence property of these particles can be used for fluorescence-based cell-imaging applications.

  1. Study on the fluorescence characteristics of carbon dots

    Science.gov (United States)

    Mao, Xiao-Jiao; Zheng, Hu-Zhi; Long, Yi-Juan; Du, Juan; Hao, Jian-Yu; Wang, Ling-Ling; Zhou, Dong-Bo

    2010-02-01

    Herein, we prepared water-soluble fluorescent carbon dots with diameter about 1.5 nm from cheap commercial lampblack. These fluorescent carbon nanoparticles are stable toward photobleaching and stable in water for more than half a year without fluorescence decrease. In order to improve its fluorescence properties, we passivated these nanoparticles with bisamino-terminated polyethylene glycol (PEG 1500N). Therefore, both fluorescence quantum yield and lifetime increased after this progress. In addition, the passivated carbon dots were more inert to solvent than the bare one and showed different responses to pH change.

  2. Aqp5 is a new transcriptional target of Dot1a and a regulator of Aqp2.

    Directory of Open Access Journals (Sweden)

    Hongyu Wu

    Full Text Available Dot1l encodes histone H3 K79 methyltransferase Dot1a. Mice with Dot1l deficiency in renal Aqp2-expressing cells (Dot1l(AC develop polyuria by unknown mechanisms. Here, we report that Aqp5 links Dot1l deletion to polyuria through Aqp2. cDNA array analysis revealed and real-time RT-qPCR validated Aqp5 as the most upregulated gene in Dot1l(AC vs. control mice. Aqp5 protein is barely detectable in controls, but robustly expressed in the Dot1l(AC kidneys, where it colocalizes with Aqp2. The upregulation of Aqp5 is coupled with reduced association of Dot1a and H3 dimethyl K79 with specific subregions in Aqp5 5' flanking region in Dot1l(AC vs. control mice. In vitro studies in IMCD3, MLE-15 and 293Tcells using multiple approaches including real-time RT-qPCR, luciferase reporter assay, cell surface biotinylation assay, colocalization, and co-immunoprecipitation uncovered that Dot1a represses Aqp5. Human AQP5 interacts with AQP2 and impairs its cell surface localization. The AQP5/AQP2 complex partially resides in the ER/Golgi. Consistently, AQP5 is expressed in none of 15 normal controls, but in all of 17 kidney biopsies from patients with diabetic nephropathy. In the patients with diabetic nephropathy, AQP5 colocalizes with AQP2 in the perinuclear region and AQP5 expression is associated with impaired cellular H3 dimethyl K79. Taken together, these data for the first time identify Aqp5 as a Dot1a potential transcriptional target, and an Aqp2 binding partner and regulator, and suggest that the upregulated Aqp5 may contribute to polyuria, possibly by impairing Aqp2 membrane localization, in Dot1l(AC mice and in patients with diabetic nephropathy.

  3. Electro-optical and dielectric properties of CdSe quantum dots and 6CHBT liquid crystals composites

    Energy Technology Data Exchange (ETDEWEB)

    Singh, U. B.; Pandey, M. B., E-mail: mbpandey@gmail.com [Department of Physics, Vikramajit Singh Sanatan Dharama College, Kanpur-208002 (India); Dhar, R; Pandey, A. S. [Centre of Material Sciences, Institute of Interdisciplinary Studies, University of Allahabad, Allahabad-211002 (India); Kumar, S. [Raman Research Institute, C. V. Raman Avenue, Bangalore-560080 (India); Dabrowski, R. [Institute of Applied Sciences and Chemistry, Military University of Technology, 00-908-Warswa (Poland)

    2014-11-15

    We have prepared the composites of a room temperature nematic liquid crystal namely 4-(trans-4-n-hexylcyclohexyl) isothiocyanatobenzoate (6CHBT) and Cadmium Selenide Quantum Dots (CdSe-QDs) and investigated their electro-optical and dielectric properties. Effect of dispersion of CdSe-QDs on various electro-optical and display parameters of host liquid crystalline material have been studied. Physical parameters, such as switching threshold voltage and splay elastic constant have been altered drastically for composites. Dispersion of QDs in a liquid crystals medium destabilizes nematic ordering of the host and decreases the nematic-to-isotropic transition temperature.

  4. Electro-optical and dielectric properties of CdSe quantum dots and 6CHBT liquid crystals composites

    International Nuclear Information System (INIS)

    Singh, U. B.; Pandey, M. B.; Dhar, R; Pandey, A. S.; Kumar, S.; Dabrowski, R.

    2014-01-01

    We have prepared the composites of a room temperature nematic liquid crystal namely 4-(trans-4-n-hexylcyclohexyl) isothiocyanatobenzoate (6CHBT) and Cadmium Selenide Quantum Dots (CdSe-QDs) and investigated their electro-optical and dielectric properties. Effect of dispersion of CdSe-QDs on various electro-optical and display parameters of host liquid crystalline material have been studied. Physical parameters, such as switching threshold voltage and splay elastic constant have been altered drastically for composites. Dispersion of QDs in a liquid crystals medium destabilizes nematic ordering of the host and decreases the nematic-to-isotropic transition temperature

  5. Nido-Carborane building-block reagents. 2. Bulky-substituent (alkyl)2C2B4H6 derivatives and (C6H5)2C2B4H6: synthesis and properties

    International Nuclear Information System (INIS)

    Boyter, H.A. Jr.; Grimes, R.N.

    1988-01-01

    The preparation and chemistry of nido-2,3-R 2 C 2 C 2 B 4 H 6 carboranes in which R is n-butyl, isopentyl, n-hexyl, and phenyl was investigated in order to further assess the steric and electronic influence of the R groups on the properties of the nido-C 2 B 4 cage, especially with respect to metal complexation at the C 2 B 3 face and metal-promoted oxidative fusion. The three dialkyl derivatives were prepared from the corresponding dialkylacetylenes via reaction with B 5 H 9 and triethylamine, but the diphenyl compound could not be prepared in this manner and was obtained instead in a thermal reaction of B 5 H 9 with diphenylacetylene in the absence of amine. All four carboranes are readily bridge-deprotonated by NaH in THF, and the anions of the dialkyl species, on treatment with FeCl 2 and air oxidation, generate the respective R 4 C 4 B 8 H 8 carborane fusion products were R = n-C 4 H 9 , i-C 5 H 11 or n-C 6 H 13 . The diphenylcarborane anion Ph 2 C 2 B 4 H 5 - did not form detectable metal complexes with Fe 2+ , Co 2+ , or Ni 2+ , and no evidence of a Ph 4 C 4 B 8 H 8 fusion product has been found. Treatment of Ph 2 C 2 B 4 H 6 with Cr(CO) 6 did not lead to metal coordination of the phenyl rings, unlike (PhCH 2 ) 2 C 2 B 4 H 6 , which had previously been shown to form mono- and bis(tricarbonylchromium) complexes. However, the reaction of Ph 2 C 2 B 4 H 5 - , CoCl 2 , and (PhPCH 2 ) 2 did give 1,1-(Ph 2 PCH 2 ) 2 -1-Cl-1,2,3-Co(Ph 2 C 2 B 4 H 4 ), the only case in which metal complexation of the diphenylcarborane was observed. 14 references, 3 figures, 3 tables

  6. Sleep inertia during a simulated 6-h on/6-h off fixed split duty schedule.

    Science.gov (United States)

    Hilditch, Cassie J; Short, Michelle; Van Dongen, Hans P A; Centofanti, Stephanie A; Dorrian, Jillian; Kohler, Mark; Banks, Siobhan

    Sleep inertia is a safety concern for shift workers returning to work soon after waking up. Split duty schedules offer an alternative to longer shift periods, but introduce additional wake-ups and may therefore increase risk of sleep inertia. This study investigated sleep inertia across a split duty schedule. Sixteen participants (age range 21-36 years; 10 females) participated in a 9-day laboratory study with two baseline nights (10 h time in bed, [TIB]), four 24-h periods of a 6-h on/6-h off split duty schedule (5-h TIB in off period; 10-h TIB per 24 h) and two recovery nights. Two complementary rosters were evaluated, with the timing of sleep and wake alternating between the two rosters (2 am/2 pm wake-up roster versus 8 am/8 pm wake-up roster). At 2, 17, 32 and 47 min after scheduled awakening, participants completed an 8-min inertia test bout, which included a 3-min psychomotor vigilance test (PVT-B), a 3-min Digit-Symbol Substitution Task (DSST), the Karolinska Sleepiness Scale (KSS), and the Samn-Perelli Fatigue Scale (SP-Fatigue). Further testing occurred every 2 h during scheduled wakefulness. Performance was consistently degraded and subjective sleepiness/fatigue was consistently increased during the inertia testing period as compared to other testing times. Morning wake-ups (2 am and 8 am) were associated with higher levels of sleep inertia than later wake-ups (2 pm and 8 pm). These results suggest that split duty workers should recognise the potential for sleep inertia after waking, especially during the morning hours.

  7. Molecular Evolution of the dotA Gene in Legionella pneumophila

    OpenAIRE

    Ko, Kwan Soo; Hong, Seong Karp; Lee, Hae Kyung; Park, Mi-Yeoun; Kook, Yoon-Hoh

    2003-01-01

    The molecular evolution of dotA, which is related to the virulence of Legionella pneumophila, was investigated by comparing the sequences of 15 reference strains (serogroups 1 to 15). It was found that dotA has a complex mosaic structure. The whole dotA gene of Legionella pneumophila subsp. pneumophila serogroups 2, 6, and 12 has been transferred from Legionella pneumophila subsp. fraseri. A discrepancy was found between the trees inferred from the nucleotide and deduced amino acid sequences ...

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

    Energy Technology Data Exchange (ETDEWEB)

    Nakra Mohajer, Soukaina; El Harouny, El Hassan [Laboratoire de Physique de la Matière Condensée, Département de Physique, Faculté des Sciences, Université Abdelmalek Essaadi, B.P. 2121 M’Hannech II, 93030 Tétouan (Morocco); Ibral, Asmaa [Equipe d’Optique et Electronique du Solide, Département de Physique, Faculté des Sciences, Université Chouaïb Doukkali, B. P. 20 El Jadida Principale, El Jadida (Morocco); Laboratoire d’Instrumentation, Mesure et Contrôle, Département de Physique, Faculté des Sciences, Université Chouaïb Doukkali, B. P. 20 El Jadida Principale, El Jadida (Morocco); El Khamkhami, Jamal [Laboratoire de Physique de la Matière Condensée, Département de Physique, Faculté des Sciences, Université Abdelmalek Essaadi, B.P. 2121 M’Hannech II, 93030 Tétouan (Morocco); and others

    2016-09-15

    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.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    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.

  10. Conjugation of E. coli O157:H7 Antibody to CdSe/ZnS Quantum Dots

    Directory of Open Access Journals (Sweden)

    N. T. Vo

    2015-01-01

    Full Text Available The conjugation of antibody to semiconductor quantum dots plays a very important role in many applications such as bioimaging, biomarking, and biosensing. In this research, we present some results of highly luminescent core/shell structure CdSe/ZnS on which the E. coli antibody was conjugated. The CdSe core was synthesized successfully with chemical “green” method. For biological applications, the capping surfactant, trioctylphosphine oxide, was substituted by a new one, mercaptopropionic acid (MPA, before the antibody attachment step. Finally, the E. coli antibody was attached to quantum dots CdSe/ZnS. Morphology, structure, and optical properties were investigated with PL, UV-Vis, TEM, and XRD methods. The successful ligand substitution and antibody attachment were confirmed by zeta potential measurement, FTIR spectroscopy, and TEM. The results showed quantum dots size of 2.3 nm, uniform distribution, and high luminescence. CdSe/ZnS core/shell structure had better stability and enhanced the luminescence efficiency up to threefold compared with the core CdSe. MPA ligand shifted the initial hydrophobic quantum dots to hydrophilic ones, which helped to dissolve them in organic solvents and attach the antibody.

  11. Reduction of the internal electric field in GaN/AlN quantum dots grown on the a-plane of SiC substrates

    Energy Technology Data Exchange (ETDEWEB)

    Garro, N.; Cros, A.; Budagosky, J.A.; Cantarero, A. [Institut de Ciencia dels Materials, Universitat de Valencia, 46071 Valencia (Spain); Vinattieri, A.; Gurioli, M. [INFM, Dept. of Physics and LENS, Universita di Firenze, Via Sansone 1, 50019 Sesto Fiorentino (Italy); Founta, S.; Mariette, H.; Daudin, B. [CEA-CNRS Group ' ' Nanophysique et Semiconducteurs' ' , Departement de Recherche Fondamentale sur la Matiere Condensee, CEA Grenoble, 17 rue des Martyrs, 38054 Grenoble (France)

    2005-11-01

    We present a study of the emission of a multi-layer stack of self-assembled GaN/AlN quantum dots grown on the a-plane of 6H-SiC. We look for signatures of the internal electric field in the power dependence of the time-integrated and time-resolved photoluminescence spectra. The lack of a dynamical red-shift reveals that internal electric fields are significantly reduced in these dots. A band on the low energy side of the emission is observed whose intensity quenches fast when increasing the temperature. The polarization selection rules of the emission are examined in order to determine the physical nature of this band. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Synthesis of CdSe Quantum Dots Using Fusarium oxysporum

    Directory of Open Access Journals (Sweden)

    Takaaki Yamaguchi

    2016-10-01

    Full Text Available CdSe quantum dots are often used in industry as fluorescent materials. In this study, CdSe quantum dots were synthesized using Fusarium oxysporum. The cadmium and selenium concentration, pH, and temperature for the culture of F. oxysporum (Fusarium oxysporum were optimized for the synthesis, and the CdSe quantum dots obtained from the mycelial cells of F. oxysporum were observed by transmission electron microscopy. Ultra-thin sections of F. oxysporum showed that the CdSe quantum dots were precipitated in the intracellular space, indicating that cadmium and selenium ions were incorporated into the cell and that the quantum dots were synthesized with intracellular metabolites. To reveal differences in F. oxysporum metabolism, cell extracts of F. oxysporum, before and after CdSe synthesis, were compared using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE. The results suggested that the amount of superoxide dismutase (SOD decreased after CdSe synthesis. Fluorescence microscopy revealed that cytoplasmic superoxide increased significantly after CdSe synthesis. The accumulation of superoxide may increase the expression of various metabolites that play a role in reducing Se4+ to Se2− and inhibit the aggregation of CdSe to make nanoparticles.

  13. Graphene quantum dots as enhanced plant growth regulators: effects on coriander and garlic plants.

    Science.gov (United States)

    Chakravarty, Disha; Erande, Manisha B; Late, Dattatray J

    2015-10-01

    We report investigations on the use of graphene quantum dots for growth enhancement in coriander (Coriandrum sativam L.) and garlic (Allium sativum) plants. The as-received seeds of coriander and garlic were treated with 0.2 mg mL(-1) of graphene quantum dots for 3 h before planting. Graphene quantum dots enhanced the growth rate in coriander and garlic plants, including leaves, roots, shoots, flowers and fruits, when the seeds were treated with graphene quantum dots. Our investigations open up the opportunity to use graphene quantum dots as plant growth regulators that can be used in a variety of other food plants for high yield. © 2015 Society of Chemical Industry.

  14. List of publications of Karlsruhe University (T.H.) and Karlsruhe Nuclear Research Centre

    International Nuclear Information System (INIS)

    1977-01-01

    This 19th volume of the list of publications compiled by Karlsruhe University (T.H.) in cooperation with Karlsruhe Nuclear Research Centre and some other institutions closely connected with the university gives the publications of the year 1976 as well as some supplements from 1975. The publications listed are books and journals, articles from journals and symposia, research reports, dissertations and theses for habilitation published by these institutions, their organs and institutes, their staff and scientific personnel, as well as patents. As a rule, theses for diplomas, newspaper articles, book reviews, internal reports and information have been left out. (orig.) [de

  15. The pH-dependent photoluminescence of colloidal CdSe/ZnS quantum dots with different organic coatings

    International Nuclear Information System (INIS)

    Debruyne, David; Locquet, Jean-Pierre; Van Bael, Margriet J; Deschaume, Olivier; Bartic, Carmen; Coutiño-Gonzalez, Eduardo; Hofkens, Johan

    2015-01-01

    The photoluminescence (PL) of colloidal quantum dots (QDs) is known to be sensitive to the solution pH. In this work we investigate the role played by the organic coating in determining the pH-dependent PL. We compare two types of CdSe/ZnS QDs equipped with different organic coatings, namely dihydrolipoic acid (DHLA)-capped QDs and phospholipid micelle-encapsulated QDs. Both QD types have their PL intensity quenched at acidic pH values, but they differ in terms of the reversibility of the quenching process. For DHLA-capped QDs, the quenching is nearly irreversible, with a small reversible component visible only on short time scales. For phospholipid micelle-encapsulated QDs the quenching is notably almost fully reversible. We suggest that the surface passivation by the organic ligands is reversible for the micelle-encapsulated QDs. Additionally, both coatings display pH-dependent spectral shifts. These shifts can be explained by a combination of irreversible processes, such as photo-oxidation and acid etching, and reversible charging of the QD surface, leading to the quantum-confined Stark effect (QCSE), the extent of each effect being coating-dependent. At high ionic strengths, the aggregation of QDs also leads to a spectral (red) shift, which is attributable to the QCSE and/or electronic energy transfer. (paper)

  16. Efficient photocatalytic degradation of rhodamine 6G with a quantum dot-metal organic framework nanocomposite.

    Science.gov (United States)

    Kaur, Rajnish; Vellingiri, Kowsalya; Kim, Ki-Hyun; Paul, A K; Deep, Akash

    2016-07-01

    The hybrid structures of metal organic frameworks (MOFs) and nanoparticles may offer the realization of effective photocatalytic materials due to combined benefits of the porous and molecular sieving properties of MOF matrix and the functional characteristics of encapsulated nanoparticles. In this study, cadmium telluride (CdTe) quantum dots (QD) are conjugated with a europium-MOF for the synthesis of a novel nanocomposite material with photocatalytic properties. Successful synthesis of a QD/Eu-MOF nanocomposite was characterized with various spectroscopic and microscopic techniques. This QD/Eu-MOF is found to be an effective catalyst to complete the degradation of Rhodamine 6G dye within 50 min. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. The synthesis of CdSe quantum dots with carboxyl group and study on their optical characteristics

    International Nuclear Information System (INIS)

    Ye, Chen; Park, Sangjoon; Kim, Jongsung

    2009-01-01

    Quantum dots are nanocrystal semiconductors which attract lots of research interests due to their peculiar optical properties. CdSe/ZnS quantum dots have been synthesized via pyrolysis of organometallic reagents. The color of the quantum dot changes from yellow-green to red as their size increases with reaction time. Photoluminescence quantum efficiency of CdSe quantum dots have been enhanced by passivating the surface of CdSe quantum dots with ZnS layers. Quantum dots are nanocrystal semiconductors which attract lots of research interests due to their peculiar optical properties. CdSe/ZnS quantum dots have been synthesized via pyrolysis of organometallic reagents. The color of the quantum dot changes from yellow-green to red as their size increases with reaction time. Photoluminescence quantum efficiency of CdSe quantum dots have been enhanced by passivating the surface of CdSe quantum dots with ZnS layers. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Compact and highly stable quantum dots through optimized aqueous phase transfer

    Science.gov (United States)

    Tamang, Sudarsan; Beaune, Grégory; Poillot, Cathy; De Waard, Michel; Texier-Nogues, Isabelle; Reiss, Peter

    2011-03-01

    A large number of different approaches for the aqueous phase transfer of quantum dots have been proposed. Surface ligand exchange with small hydrophilic thiols, such as L-cysteine, yields the lowest particle hydrodynamic diameter. However, cysteine is prone to dimer formation, which limits colloidal stability. We demonstrate that precise pH control during aqueous phase transfer dramatically increases the colloidal stability of InP/ZnS quantum dots. Various bifunctional thiols have been applied. The formation of disulfides, strongly diminishing the fluorescence QY has been prevented through addition of appropriate reducing agents. Bright InP/ZnS quantum dots with a hydrodynamic diameter <10 nm and long-term stability have been obtained. Finally we present in vitro studies of the quantum dots functionalized with the cell-penetrating peptide maurocalcine.

  19. Bis(1,3-dimethyl-1H-imidazolium hexafluorosilicate methanol 0.33-solvate

    Directory of Open Access Journals (Sweden)

    Maxim V. Borzov

    2013-08-01

    Full Text Available The title compound, 6C5H9N2+·3SiF62−·CH3OH, (I, was prepared by recrystallization of the crude salt from methanol along with solvent-free 2C5H9N2+·SiF62− (II. Crystals of these solvatomorphs can be separated manually. The solvate (I crystallizes in a rare hexagonal space group P6/mcc. Its asymmetric unit comprises one half of an imidazolium cation bisected by the crystallographic m-plane, one-sixth and one-twelfth of two crystallographically independent SiF62– dianions (Si atoms are located on the 3.2 and 6/m inversion centres, and one-twelfth of a methanol molecule (C atoms are situated on the 622 inversion centres, other atoms are disordered between general positions. In (I, all F atoms of 3.2-located SiF62– dianions participate in the formation of symmetry-equivalent contacts to the H atoms of imidazolium fragments, thus forming rod-type ensembles positioned on the -6 axes. These `pillar' rods are, in turn, F...H interlinked through SiF62– dianions disordered around the 6/m centres. The twelvefold disordered methanol molecules are appended to this array by O—H...F hydrogen bonds to the 6/m located SiF62– dianions. In terms of graph-set notation, the first and second level networks in (I are N1 = C22(7[3R44(14]D22(4 and N2 = D22(5 (C—H...O hydrogen bonds are not considered. After locating all symmetrically independent atoms in the cation and anions, there remained a strong (> 3 e Å−3 residual electron density peak located at the 622 inversion centre. Treatment of this pre-refined model with the SQUEEZE procedure in PLATON [Spek (2009. Acta Cryst. D65, 148–155] revealed two voids per unit cell, indicative of the presence of the solvent methanol molecule disordered about the 622 inversion centre.

  20. Numerical simulation of spin-qubit operation in coupled quantum dots

    International Nuclear Information System (INIS)

    Goto, Daisuke; Eto, Mikio

    2007-01-01

    Electronic states and spin operation in coupled quantum dots are numerically studied, considering realistic shape of quantum dots and electron-electron interaction. (i) We evaluate the spin coupling J between two electron spins, as a function of magnetic field perpendicular to the quantum dots. We observe a transition from antiferromagnetic coupling (J>0) to ferromagnetic coupling (J<0) at magnetic field of a few Tesla. The spin coupling is hardly influenced by the size difference between the quantum dots if the energy levels are matched. (ii) We simulate SWAP gate operations by calculating the time development of two electron spins. We show that a sudden change of tunnel barrier may result in the gate errors. The spin exchange is incomplete in the presence of strong spin-orbit interaction in InGaAs. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Study of InGaN/GaN quantum dot systems by TEM techniques and photoluminescence spectroscopy

    International Nuclear Information System (INIS)

    Kashtiban, R J; Bangert, U; Harvey, A J; Sherliker, B; Halsall, M P

    2010-01-01

    InGaN/GaN multilayer quantum dot structures produced by MOCVD techniques on c-plane sapphire were studied by transmission electron microscopy (TEM) and photoluminescence (PL) techniques. Indium fluctuations ranging from 1-4 nm were observed with both energy filtered TEM (EFTEM) and high angle annular dark field (HAADF) scanning TEM. The existence of V-shaped defects with nucleation centres at the termination of threading dislocation were observed in HAADF images. There was also evidence of the formation of large quantum dots at low densities from lattice HRTEM images. This was further confirmed by PL measurements through the observation of a single sharp line at low power with the typical saturation behaviour at higher power excitation.

  2. Cleanup Verification Package for the 118-H-6:2, 105-H Reactor Ancillary Support Areas, Below-Grade Structures, and Underlying Soils; the 118-H-6:3, 105-H Reactor Fuel Storage Basin and Underlying Soils; the 118-H-6:6 Fuel Storage Basin Deep Zone Side Slope Soils; the 100-H-9, 100-H-10, and 100-H-13 French Drains; the 100-H-11 and 100-H-12 Expansion Box French Drains; and the 100-H-14 and 100-H-31 Surface Contamination Zones

    International Nuclear Information System (INIS)

    Appel, M.J.

    2006-01-01

    This cleanup verification package documents completion of removal actions for the 105-H Reactor Ancillary Support Areas, Below-Grade Structures, and Underlying Soils (subsite 118-H-6:2); 105-H Reactor Fuel Storage Basin and Underlying Soils (118-H-6:3); and Fuel Storage Basin Deep Zone Side Slope Soils. This CVP also documents remedial actions for the following seven additional waste sties: French Drain C (100-H-9), French Drain D (100-H-10), Expansion Box French Drain E (100-H-11), Expansion Box French Drain F (100-H-12), French Drain G (100-H-13), Surface Contamination Zone H (100-H-14), and the Polychlorinated Biphenyl Surface Contamination Zone (100-H-31)

  3. Benefits of starting hypothermia treatment within 6 h vs. 6-12 h in newborns with moderate neonatal hypoxic-ischemic encephalopathy.

    Science.gov (United States)

    Jia, Wen; Lei, Xiaoping; Dong, Wenbin; Li, Qingping

    2018-02-12

    It has been suggested that mild hypothermia treatment of hypoxia-ischemic encephalopathy (HIE) should start within 6 h after HIE, but many children are admitted to the hospital > 6 h, particularly in developing areas. We aimed to determine whether hypothermia treatment could remain effective within 12 h after birth. According to their admission, 152 newborns were enrolled in the newborns received conventional treatment combined with mild head hypothermia therapy, according to our routine clinical practice. Some newborns only received conventional treatment (lacking informed consent). All newborns received amplitude-integrated electroencephalography (aEEG) monitoring for 4 h and neuron-specific enolase (NSE) measurement before and after 3 days of therapy. Compared to the conventional treatment, hypothermia significantly improved the aEEG scores and NSE values in all newborns of the newborns with moderate HIE. Hypothermia treatment seems to have no effect in newborns with severe HIE after 6 h (P > 0.05). Hypothermia improved the rates of neonatal death and 18-month disability (all P newborns with moderate HIE, starting hypothermia therapy < 6 h and 6-12 h after HIE showed curative effects. In those with severe HIE, only starting hypothermia therapy within 6 h showed curative effects.

  4. Gain dynamics of quantum dot devices for dual-state operation

    Energy Technology Data Exchange (ETDEWEB)

    Kaptan, Y., E-mail: yuecel.kaptan@physik.tu-berlin.de; Herzog, B.; Kolarczik, M.; Owschimikow, N.; Woggon, U. [Institut für Optik und Atomare Physik, Technische Universität Berlin, Berlin (Germany); Schmeckebier, H.; Arsenijević, D.; Bimberg, D. [Institut für Festkörperphysik, Technische Universität Berlin, Berlin (Germany); Mikhelashvili, V.; Eisenstein, G. [Technion Institute of Technology, Faculty of Electrical Engineering, Haifa (Israel)

    2014-06-30

    Ground state gain dynamics of In(Ga)As-quantum dot excited state lasers are investigated via single-color ultrafast pump-probe spectroscopy below and above lasing threshold. Two-color pump-probe experiments are used to localize lasing and non-lasing quantum dots within the inhomogeneously broadened ground state. Single-color results yield similar gain recovery rates of the ground state for lasing and non-lasing quantum dots decreasing from 6 ps to 2 ps with increasing injection current. We find that ground state gain dynamics are influenced solely by the injection current and unaffected by laser operation of the excited state. This independence is promising for dual-state operation schemes in quantum dot based optoelectronic devices.

  5. Exchange bias properties of 140 nm-sized dipolarly interacting circular dots with ultrafine IrMn and NiFe layers

    Energy Technology Data Exchange (ETDEWEB)

    Spizzo, F., E-mail: spizzo@fe.infn.it [Dipartimento di Fisica e Scienze della Terra and CNISM, Università di Ferrara, I-44122 Ferrara (Italy); Tamisari, M. [Dipartimento di Fisica e Scienze della Terra and CNISM, Università di Ferrara, I-44122 Ferrara (Italy); Dipartimento di Fisica e Geologia and CNISM, Università di Perugia, I-06123 Perugia (Italy); Chinni, F.; Bonfiglioli, E. [Dipartimento di Fisica e Scienze della Terra and CNISM, Università di Ferrara, I-44122 Ferrara (Italy); Gerardino, A. [Istituto di Fotonica e Nanotecnologie, CNR, I-00156 Roma (Italy); Barucca, G. [Dipartimento SIMAU, Università Politecnica delle Marche, I-60131 Ancona (Italy); Bisero, D.; Fin, S.; Del Bianco, L. [Dipartimento di Fisica e Scienze della Terra and CNISM, Università di Ferrara, I-44122 Ferrara (Italy)

    2016-02-15

    We studied the exchange bias effect in an array of IrMn(3 nm)/NiFe(3 nm) circular dots (size ~140 nm and center-to-center distance ~200 nm, as revealed by microscopy analyses), prepared on a large area (3×3 mm{sup 2}) by electron beam lithography and lift-off, using dc sputtering deposition. Hysteresis loops were measured by SQUID magnetometer at increasing values of temperature T (in the 5–300 K range) after cooling from 300 K down to 5 K in zero field (ZFC mode) and in a saturating magnetic field (FC mode). The exchange bias effect disappears above T~200 K and, at each temperature, the exchange field H{sub EX} measured in ZFC is substantially lower than the FC one. Micromagnetic calculations indicate that, at room temperature, each dot is in high-remanence ground state, but magnetic dipolar interactions establish a low-remanence configuration of the array as a whole. Hence, at low temperature, following the ZFC procedure, the exchange anisotropy in the dot array is averaged out, tending to zero. However, even the FC values of H{sub EX} and of the coercivity H{sub C} are definitely smaller compared to those measured in a reference continuous film with the same stack configuration (at T=5 K, H{sub EX}~90 Oe and H{sub C}~180 Oe in the dots and H{sub EX}~1270 Oe and H{sub C}~860 Oe in the film). Our explanation is based on the proven glassy magnetic nature of the ultrathin IrMn layer, implying the existence of magnetic correlations among the spins, culminating in a collective freezing below T~100 K. We propose, also by the light of micromagnetic simulations, that the small dot size imposes a spatial constraint on the magnetic correlation length among the IrMn spins so that, even at the lowest temperature, their thermal stability, especially at the dot border, is compromised. - Highlights: • Exchange bias in 140 nm-sized IrMn(3 nm)/NiFe(3 nm) dots much weaker than in a film. • Glassy magnetic nature of the IrMn phase and collective spin freezing at T<100 K

  6. Exchange bias properties of 140 nm-sized dipolarly interacting circular dots with ultrafine IrMn and NiFe layers

    International Nuclear Information System (INIS)

    Spizzo, F.; Tamisari, M.; Chinni, F.; Bonfiglioli, E.; Gerardino, A.; Barucca, G.; Bisero, D.; Fin, S.; Del Bianco, L.

    2016-01-01

    We studied the exchange bias effect in an array of IrMn(3 nm)/NiFe(3 nm) circular dots (size ~140 nm and center-to-center distance ~200 nm, as revealed by microscopy analyses), prepared on a large area (3×3 mm"2) by electron beam lithography and lift-off, using dc sputtering deposition. Hysteresis loops were measured by SQUID magnetometer at increasing values of temperature T (in the 5–300 K range) after cooling from 300 K down to 5 K in zero field (ZFC mode) and in a saturating magnetic field (FC mode). The exchange bias effect disappears above T~200 K and, at each temperature, the exchange field H_E_X measured in ZFC is substantially lower than the FC one. Micromagnetic calculations indicate that, at room temperature, each dot is in high-remanence ground state, but magnetic dipolar interactions establish a low-remanence configuration of the array as a whole. Hence, at low temperature, following the ZFC procedure, the exchange anisotropy in the dot array is averaged out, tending to zero. However, even the FC values of H_E_X and of the coercivity H_C are definitely smaller compared to those measured in a reference continuous film with the same stack configuration (at T=5 K, H_E_X~90 Oe and H_C~180 Oe in the dots and H_E_X~1270 Oe and H_C~860 Oe in the film). Our explanation is based on the proven glassy magnetic nature of the ultrathin IrMn layer, implying the existence of magnetic correlations among the spins, culminating in a collective freezing below T~100 K. We propose, also by the light of micromagnetic simulations, that the small dot size imposes a spatial constraint on the magnetic correlation length among the IrMn spins so that, even at the lowest temperature, their thermal stability, especially at the dot border, is compromised. - Highlights: • Exchange bias in 140 nm-sized IrMn(3 nm)/NiFe(3 nm) dots much weaker than in a film. • Glassy magnetic nature of the IrMn phase and collective spin freezing at T<100 K • Confinement of IrMn magnetic

  7. A convenient preparation of 9 H -carbazole-3,6-dicarbonitrile and 9 H -carbazole-3,6-dicarboxylic acid

    KAUST Repository

    Weselinski, Lukasz Jan

    2014-01-23

    A catalytic, high yielding and scalable procedure for the synthesis of 9H-carbazole-3,6-dicarbonitrile has been developed. Subsequent hydrolysis of the dinitrile in the presence of a catalytic copper species (i.e., CuI) yields 9H-carbazole-3,6-dicarboxylic acid. Both compounds are versatile and fine-tunable organic building blocks and therefore offer potential in material science, medicinal and supramolecular chemistry. © Georg Thieme Verlag Stuttgart New York.

  8. Transport in quantum dots

    International Nuclear Information System (INIS)

    Deus, Fernanda; Continetino, Mucio

    2011-01-01

    Full text. In this work we study the time dependent transport in interacting quantum dot. This is a zero-dimensional nano structure system which has quantized electronic states. In our purpose, we are interested in studying such system in a Coulomb blockade regime where a mean-field treatment of the electronic correlations are appropriate. The quantum dot is described by an Anderson type of Hamiltonian where the hybridization term arises from the contact with the leads. We consider a time dependence of both the energy of the localized state in the quantum dot and of the hybridization-like term. These time dependent parameters, under certain conditions, induce a current in the quantum dot even in the absence of difference on the chemical potential of the leads. The approach to this non-equilibrium problem requires the use of a Keldysh formalism. We calculate the non- equilibrium Green's functions and obtain results for the average (equilibrium term) and the non-equilibrium values of the electronic occupation number in the dot. we consider the possibility of a magnetic solution, with different values for the average up and down spins in the quantum dot. Our results allow to obtain, for instance, the tunneling current through the dot. The magnetic nature of the dot, for a certain range of parameters should give rise also to an induced spin current through the dot

  9. The H_6_0Si_6C_5_4 heterofullerene as high-capacity hydrogen storage medium

    International Nuclear Information System (INIS)

    Yong, Yongliang; Zhou, Qingxiao; Li, Xiaohong; Lv, Shijie

    2016-01-01

    With the great success in Si atoms doped C_6_0 fullerene and the well-established methods for synthesis of hydrogenated carbon fullerenes, this leads naturally to wonder whether Si-doped fullerenes are possible for special applications such as hydrogen storage. Here by using first-principles calculations, we design a novel high-capacity hydrogen storage material, H_6_0Si_6C_5_4 heterofullerene, and confirm its geometric stability. It is found that the H_6_0Si_6C_5_4 heterofullerene has a large HOMO-LUMO gap and a high symmetry, indicating it is high chemically stable. Further, our finite temperature simulations indicate that the H_6_0Si_6C_5_4 heterofullerene is thermally stable at 300 K. H_2 molecules would enter into the cage from the Si-hexagon ring because of lower energy barrier. Through our calculation, a maximum of 21 H_2 molecules can be stored inside the H_6_0Si_6C_5_4 cage in molecular form, leading to a gravimetric density of 11.11 wt% for 21H_2@H_6_0Si_6C_5_4 system, which suggests that the hydrogenated Si_6C_5_4 heterofullerene could be suitable as a high-capacity hydrogen storage material.

  10. A novel H6N1 virus-like particle vaccine induces long-lasting cross-clade antibody immunity against human and avian H6N1 viruses.

    Science.gov (United States)

    Yang, Ji-Rong; Chen, Chih-Yuan; Kuo, Chuan-Yi; Cheng, Chieh-Yu; Lee, Min-Shiuh; Cheng, Ming-Chu; Yang, Yu-Chih; Wu, Chia-Ying; Wu, Ho-Sheng; Liu, Ming-Tsan; Hsiao, Pei-Wen

    2016-02-01

    Avian influenza A(H6N1) virus is one of the most common viruses isolated from migrating birds and domestic poultry in many countries. The first and only known case of human infection by H6N1 virus in the world was reported in Taiwan in 2013. This led to concern that H6N1 virus may cause a threat to public health. In this study, we engineered a recombinant H6N1 virus-like particle (VLP) and investigated its vaccine effectiveness compared to the traditional egg-based whole inactivated virus (WIV) vaccine. The H6N1-VLPs exhibited similar morphology and functional characteristics to influenza viruses. Prime-boost intramuscular immunization in mice with unadjuvanted H6N1-VLPs were highly immunogenic and induced long-lasting antibody immunity. The functional activity of the VLP-elicited IgG antibodies was proved by in vitro seroprotective hemagglutination inhibition and microneutralization titers against the homologous human H6N1 virus, as well as in vivo viral challenge analyses which showed H6N1-VLP immunization significantly reduced viral load in the lung, and protected against human H6N1 virus infection. Of particular note, the H6N1-VLPs but not the H6N1-WIVs were able to confer cross-reactive humoral immunity; antibodies induced by H6N1-VLP vaccine robustly inhibited the hemagglutination activities and in vitro replication of distantly-related heterologous avian H6N1 viruses. Furthermore, the H6N1-VLPs were found to elicit significantly greater anti-HA2 antibody responses in immunized mice than H6N1-WIVs. Collectively, we demonstrated for the first time a novel H6N1-VLP vaccine that effectively provides broadly protective immunity against both human and avian H6N1 viruses. These results, which uncover the underlying mechanisms for induction of wide-range immunity against influenza viruses, may be useful for future influenza vaccine development. Copyright © 2015 Elsevier B.V. All rights reserved.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    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

  12. Costs and cost-effectiveness of different DOT strategies for the treatment of tuberculosis in Pakistan. Directly Observed Treatment.

    Science.gov (United States)

    Khan, M A; Walley, J D; Witter, S N; Imran, A; Safdar, N

    2002-06-01

    An economic study was conducted alongside a clinical trial at three sites in Pakistan to establish the costs and effectiveness of different strategies for implementing directly observed treatment (DOT) for tuberculosis. Patients were randomly allocated to one of three arms: DOTS with direct observation by health workers (at health centres or by community health workers); DOTS with direct observation by family members; and DOTS without direct observation. The clinical trial found no statistically significant difference in cure rate for the different arms. The economic study collected data on the full range of health service costs and patient costs of the different treatment arms. Data were also disaggregated by gender, rural and urban patients, by treatment site and by economic categories, to investigate the costs of the different strategies, their cost-effectiveness and the impact that they might have on patient compliance with treatment. The study found that direct observation by health centre-based health workers was the least cost-effective of the strategies tested (US dollars 310 per case cured). This is an interesting result, as this is the model recommended by the World Health Organization and International Union against Tuberculosis and Lung Disease. Attending health centres daily during the first 2 months generated high patient costs (direct and in terms of time lost), yet cure rates for this group fell below those of the non-observed group (58%, compared with 62%). One factor suggested by this study is that the high costs of attending may be deterring patients, and in particular, economically active patients who have most to lose from the time taken by direct observation. Without stronger evidence of benefits, it is hard to justify the costs to health services and patients that this type of direct observation imposes. The self-administered group came out as most cost-effective (164 dollars per case cured). The community health worker sub-group achieved the

  13. 10.6% Certified Colloidal Quantum Dot Solar Cells via Solvent-Polarity-Engineered Halide Passivation.

    Science.gov (United States)

    Lan, Xinzheng; Voznyy, Oleksandr; García de Arquer, F Pelayo; Liu, Mengxia; Xu, Jixian; Proppe, Andrew H; Walters, Grant; Fan, Fengjia; Tan, Hairen; Liu, Min; Yang, Zhenyu; Hoogland, Sjoerd; Sargent, Edward H

    2016-07-13

    Colloidal quantum dot (CQD) solar cells are solution-processed photovoltaics with broad spectral absorption tunability. Major advances in their efficiency have been made via improved CQD surface passivation and device architectures with enhanced charge carrier collection. Herein, we demonstrate a new strategy to improve further the passivation of CQDs starting from the solution phase. A cosolvent system is employed to tune the solvent polarity in order to achieve the solvation of methylammonium iodide (MAI) and the dispersion of hydrophobic PbS CQDs simultaneously in a homogeneous phase, otherwise not achieved in a single solvent. This process enables MAI to access the CQDs to confer improved passivation. This, in turn, allows for efficient charge extraction from a thicker photoactive layer device, leading to a certified solar cell power conversion efficiency of 10.6%, a new certified record in CQD photovoltaics.

  14. Optical transition energy of magneto-polaron in a GaAs{sub 0.9}P{sub 0.1}/GaAs{sub 0.6}P{sub 0.4} quantum dot

    Energy Technology Data Exchange (ETDEWEB)

    Vinolin, Ada [Dept. of Physics, Madurai Kamaraj University College, Alagarkoil Road, Madurai-625002. India (India); Peter, A. John, E-mail: a.john.peter@gmail.com [Dept. of Physics, Govt. Arts College, Melur-625106. Madurai. India (India)

    2015-06-24

    Magneto-LO-polaron in a cylindrical GaAs{sub 0.9} P{sub 0.1} / GaAs{sub 0.6} P{sub 0.4} quantum dot is investigated taking into consideration of geometrical confinement effect. The effects of phonon on the exciton binding energy and the interband emission energy as a function of dot radius are found. The calculations are performed within the single band effective mass approximation using the variational method based on the Lee-Low-Pine LLP transformation.

  15. Refurbishment and modification of existing protective shipping packages (for 30-inch UF{sub 6} cylinders) per USDOT specification No. USA-DOT-21PF-1A

    Energy Technology Data Exchange (ETDEWEB)

    Housholder, W.R. [Nuclear Containers, Incorporated, Elizabethton, TN (United States)

    1991-12-31

    This paper addresses the refurbishment procedures for existing shipping containers for 30-inch diameter UF{sub 6} cylinders in accordance with DOT Specification 21PF-1 and the criteria used to determine rejection when such packages are unsuitable for refurbishment.

  16. Characterization of electronic charged states of P-doped Si quantum dots using AFM/Kelvin probe

    International Nuclear Information System (INIS)

    Makihara, Katsunori; Xu, Jun; Ikeda, Mitsuhisa; Murakami, Hideki; Higashi, Seiichiro; Miyazaki, Seiichi

    2006-01-01

    Phosphorous doping to Si quantum dots was performed by a pulse injection of 1% PH 3 diluted with He during the dot formation on thermally grown SiO 2 from thermal decomposition of pure SiH 4 , and electron charging to and discharging from P-doped Si dots were studied to characterize their electronic charged states using a Kelvin probe technique in atomic force microscopy (AFM). The potential change corresponding to the extraction of one electron from each of the P-doped Si dots was observed after applying a tip bias as low as + 0.2 V while for undoped Si dots, with almost the same size as P-doped Si dots, almost the same amount of the potential change was detectable only when the tip bias was increased to ∼ 1 V. It is likely that, for P-doped Si dots, the electron extraction from the conduction band occurs and results in a positively charged state with ionized P donor

  17. Search for 4H, 5H and 6H nuclei in the 11B-induced reaction on 9Be

    International Nuclear Information System (INIS)

    Belozerov, A.V.; Borcea, C.; Dlouhy, Z.

    1985-01-01

    In the 11 B(88.0 MeV)+ 9 Be reaction the energy spectra of the 14 O, 15 O and 16 O nuclei have been measured to obtain some information about their partners in the exit channel - the neutron-rich hydrogen isotopes 4 H, 5 H and 6 H. The unbound levels in the 4 H and 6 H systems have been observed at excitation energies of 3.5 +- 0.5 MeV (GITA approximately 1 MeV) and 2.6 +- 0.5 MeV (GITA=1.5 +- 0.3 MeV), respectively

  18. Fluorescence properties of 3-amino phenylboronic acid and its interaction with glucose and ZnS:Cu quantum dots.

    Science.gov (United States)

    Kur-Kowalska, Karolina; Przybyt, Małgorzata; Ziółczyk, Paulina; Sowiński, Przemysław; Miller, Ewa

    2014-08-14

    Preliminary results of a study of the interaction between 3-amino phenylboronic acid and glucose or ZnS:Cu quantum dots are presented in this paper. ZnS:Cu quantum dots with mercaptopropionic acid as a capping agent were obtained and characterized. Quenching of 3-amino phenylboronic acid fluorescence was studied by steady-state and timeresolved measurements. For fluorescence quenching with glucose the results of steady-state measurements fulfill Stern-Volmer equation. The quenching constants are increasing with growing pH. The decay of fluorescence is monoexponential with lifetime about 8.4 ns, which does not depend on pH and glucose concentration indicating static quenching. The quenching constant can be interpreted as apparent equilibrium constant of estrification of boronic group with diol. Quantum dots are also quenching 3-amino phenylboronic acid fluorescence. Fluorescence lifetime, in this case, is slightly decreasing with increasing concentration of quantum dots. The quenching constants are increasing slightly with pH's growth. Quenching mechanism of 3-amino phenylboronic acid fluorescence by quantum dots needs further experiments to be fully explained. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Experimental ion mobility measurements in Xe-C2H6

    Science.gov (United States)

    Perdigoto, J. M. C.; Cortez, A. F. V.; Veenhof, R.; Neves, P. N. B.; Santos, F. P.; Borges, F. I. G. M.; Conde, C. A. N.

    2017-10-01

    In this paper we present the results of the ion mobility measurements made in gaseous mixtures of xenon (Xe) with ethane (C2H6) for pressures ranging from 6 to 10 Torr (8-10.6 mbar) and for low reduced electric fields in the 10 Td to 25 Td range (2.4-6.1 kVṡcm-1ṡ bar-1), at room temperature. The time of arrival spectra revealed two peaks throughout the entire range studied which were attributed to ion species with 3-carbons (C3H5+, C3H6+ C3H8+ and C3H9+) and with 4-carbons (C4H7+, C4H9+ and C4H10+). Besides these, and for Xe concentrations above 70%, a bump starts to appear at the right side of the main peak for reduced electric fields higher than 20 Td, which was attributed to the resonant charge transfer of C2H6+ to C2H6 that affects the mobility of its ion products (C3H8+ and C3H9+). The time of arrival spectra for Xe concentrations of 20%, 50%, 70% and 90% are presented, together with the reduced mobilities as a function of the Xe concentration calculated from the peaks observed for the low reduced electric fields and pressures studied.

  20. DOT's CAFE rulemaking analysis.

    Science.gov (United States)

    2013-02-13

    Presentation discusses what DOT needs to consider in setting CAFE standards. How DOT's use of the CAFE Compliance and Effects Modeling System helps to analyze potential CAFE Standards. How DOT might approach the next round of CAFE standards for model...

  1. Dichloridobis[1-(2,4,6-trimethylphenyl-1H-imidazole-κN3]copper(II

    Directory of Open Access Journals (Sweden)

    Yantao Zhang

    2013-11-01

    Full Text Available In the title complex, [CuCl2(C12H14N22], the Cu2+ cation is situated on an inversion centre and is coordinated by two N atoms from symmetry-related 1-mesityl-1H-imidazole ligands and by two chloride anions in a slightly distorted square-planar geometry. In the organic ligand, the dihedral angle between the benzene ring of the mesityl moiety and the imidazole ring is 76.99 (18°. Weak intramolecular C—H...Cl hydrogen-bonding interactions consolidate the molecular conformation.

  2. The singlet-triplet energy gap in divalent three, five and seven-membered cyclic C2H2M, C4H4M and C6H6M (M = C, Si, Ge, Sn AND Pb

    Directory of Open Access Journals (Sweden)

    E. Vessally

    2009-08-01

    Full Text Available Total energy gaps, ∆Et–s, enthalpy gaps, ∆Ht–s, and Gibbs free energy gaps, ∆Gt–s, between singlet (s and triplet (t states were calculated for three, five and seven-membered cyclic C2H2M, C4H4M and C6H6M (M = C, Si, Ge, Sn and Pb at B3LYP/6-311++G**. The singlet-triplet free energy gaps, ∆Gt–s, for C2H2M (M = C, Si, Ge, Sn and Pb are found to be increased in the order: C2H2Si > C2H2C > C2H2Ge > C2H2Sn > C2H2Pb. The ∆Gt–s of C4H4M are found to be increased in the order: C4H4Pb > C4H4Sn > C4H4Ge > C4H4Si > C4H4C. Also, the ∆Gt–s of C6H6M are determined in the order: C6H6Pb > C6H6Ge ≥ C6H6Sn > C6H6Si > C6H6C. The most stable conformers of C2H2M, C4H4M and C6H6M are proposed for both the singlet and triplet states. Nuclear independent chemical shifts (NICS calculations were carried out for determination of aromatic character. The geometrical parameters are calculated and discussed.

  3. Harnessing Sun's Energy with Quantum Dots Based Next Generation Solar Cell.

    Science.gov (United States)

    Halim, Mohammad A

    2012-12-27

    Our energy consumption relies heavily on the three components of fossil fuels (oil, natural gas and coal) and nearly 83% of our current energy is consumed from those sources. The use of fossil fuels, however, has been viewed as a major environmental threat because of their substantial contribution to greenhouse gases which are responsible for increasing the global average temperature. Last four decades, scientists have been searching for alternative sources of energy which need to be environmentally clean, efficient, cost-effective, renewable, and sustainable. One of the promising sustainable sources of energy can be achieved by harnessing sun energy through silicon wafer, organic polymer, inorganic dye, and quantum dots based solar cells. Among them, quantum dots have an exceptional property in that they can excite multiple electrons using only one photon. These dots can easily be synthesized, processed in solution, and incorporated into solar cell application. Interestingly, the quantum dots solar cells can exceed the Shockley - Queisser limit; however, it is a great challenge for other solar cell materials to exceed the limit. Theoretically, the quantum dots solar cell can boost the power conversion efficiency up to 66% and even higher to 80%. Moreover, in changing the size of the quantum dots one can utilize the Sun's broad spectrum of visible and infrared ranges. This review briefly overviews the present performance of different materials-based solar cells including silicon wafer, dye-sensitized, and organic solar cells. In addition, recent advances of the quantum dots based solar cells which utilize cadmium sulfide/selenide, lead sulfide/selenide, and new carbon dots as light harvesting materials has been reviewed. A future outlook is sketched as to how one could improve the efficiency up to 10% from the current highest efficiency of 6.6%.

  4. 1H-indole (6a)

    Indian Academy of Sciences (India)

    -600020, India. bDepartment of Pharmaceutical Chemistry, Mother Theresa Post Graduate and Research Institute of Health Sciences, Puducherry- 605006, India. cBioinformatics Centre, Pondicherry University, Puducherry-605014, India.

  5. Electronic and electrochemical properties of platinum(II) and platinum-mercury-carboxylato complexes containing 2-Me2NCH2C6H4, 2,6-(Me2NCH2)2C6H3- and 2-Me2NC6H4CH2 - ligands

    NARCIS (Netherlands)

    Koten, G. van; Ploeg, A.F.M.J. van der; Schmitz, J.E.J.; Linden, J.G.M. van der

    1982-01-01

    The organoplatinum(II) compounds [{2, 6-(Me{2}NCH{2}){2}C{6}H{3}}PtBr] and cis-[(C-N){2}Pt] (C-N = 2-Me{2}NCH{2}C{6}H{4}, 2-Me{2}NC{6}H{4}CH{2}) can be chemically irreversibly oxidized in the potential range 1.00 to 1.35 V vs. an Ag/AgCl electrode, whereas the organoplatinum@?mercury complexes

  6. Cluster-enhanced X-O-2 photochemistry (X=CH3I, C3H6, C6H12, and Xe)

    NARCIS (Netherlands)

    Baklanov, A.V.; Bogdanchikov, G.A.; Vidma, K.V.; Chestakov, D.A.; Parker, D.H.

    2007-01-01

    The effect of a local environment on the photodissociation of molecular oxygen is investigated in the van der Waals complex X-O-2 (X=CH3I, C3H6, C6H12, and Xe). A single laser operating at wavelengths around 226 nm is used for both photodissociation of the van der Waals complex and simultaneous

  7. Liquid nitrogen-assisted synthesis of fluorescent carbon dots from Blueberry and their performance in Fe3+ detection

    Science.gov (United States)

    Aslandaş, Ayşe Merve; Balcı, Neslihan; Arık, Mustafa; Şakiroğlu, Halis; Onganer, Yavuz; Meral, Kadem

    2015-11-01

    Fluorescent carbon dots (C-dots) were synthesized by a facile method containing liquid N2 treatment and centrifuge processes. The photophysical properties of the C-dots in an aqueous solution were examined at various conditions such as concentration, temperature, pH and excitation wavelength by using UV-vis absorption, fluorescence and time-resolved fluorescence spectroscopies. The C-dots emitted a broad fluorescence between approximately 350-550 nm and their fluorescence was tuned by changing excitation wavelength. The as-prepared C-dots were applied to Fe3+ detection from aqueous solution. Spectroscopic data revealed that the as-prepared C-dots were used to detect Fe3+ in the range of 12.5 μM to 100 μM as a fluorescence sensor.

  8. A calorimetric and equilibrium investigation of the reaction {l_brace}methyl ferulate(aq) + H{sub 2}O(l) = methanol(aq) + ferulic acid(aq){r_brace}

    Energy Technology Data Exchange (ETDEWEB)

    Goldberg, Robert N., E-mail: robert.goldberg@nist.go [Biochemical Science Division, National Institute of Standards and Technology, Gaithersburg, MD 20876 (United States); Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, Baltimore, MD 21250 (United States); Lang, Brian E., E-mail: brian.lang@nist.go [Biochemical Science Division, National Institute of Standards and Technology, Gaithersburg, MD 20876 (United States); Selig, Michael J., E-mail: michael.selig@nrel.go [National Renewable Energy Laboratory, Biosciences Center, 1617 Cole Boulevard, Golden, CO 80401 (United States); Decker, Stephen R., E-mail: steve.decker@nrel.go [National Renewable Energy Laboratory, Biosciences Center, 1617 Cole Boulevard, Golden, CO 80401 (United States)

    2011-03-15

    Microcalorimetry and high-performance liquid chromatography (HPLC) have been used to conduct a thermodynamic investigation of the reaction: {l_brace}methyl ferulate(aq) + H{sub 2}O(l) = methanol(aq) + ferulic acid(aq){r_brace}, as catalyzed by feruloyl esterase. Values of the apparent equilibrium constant K' = (29.6 {+-} 0.7) (T = 298.15 K, citrate buffer at pH 4.98, ionic strength I = 0.39 mol {center_dot} kg{sup -1}) and of the calorimetrically determined enthalpy of reaction {Delta}{sub r}H(cal) = (4.0 {+-} 0.9) kJ {center_dot} mol{sup -1} (T = 298.15 K and citrate buffer at pH 4.81, I = 0.36 mol {center_dot} kg{sup -1}) were measured. A chemical equilibrium model, together with pKs and standard enthalpies of reaction {Delta}{sub r}H{sup 0} for the H{sup +}(aq) binding reactions of the reactants and products, was then used to calculate the values K = (1.89 {+-} 0.06) . 10{sup -4}, {Delta}{sub r}H{sup o} = (7.3 {+-} 1.7) kJ {center_dot} mol{sup -1}, {Delta}{sub r}G{sup o} = (21.25 {+-} 0.07) kJ {center_dot} mol{sup -1}, and {Delta}{sub r}S{sup o} = - (46.8 {+-} 5.7) J {center_dot} K{sup -1} {center_dot} mol{sup -1} for the chemical reference reaction {l_brace}methyl ferulate(aq) + H{sub 2}O(l) = methanol(aq) + ferulic acid{sup -}(aq) + H{sup +}(aq){r_brace}. These values of K and {Delta}{sub r}H{sup o} are similar in magnitude to the corresponding values reported for the reaction {l_brace}propyl gallate(aq) + H{sub 2}O(l) = 3,4,5-trihydroxybenzoic acid{sup -}(aq) + 1-propanol(aq) + H{sup +}(aq){r_brace}. The results obtained in this study can be used in a chemical equilibrium model to calculate how K' and other standard transformed properties such as the standard transformed enthalpy {Delta}{sub r}H'{sup o}, standard transformed Gibbs free energy {Delta}{sub r}G'{sup o}, and the change in binding of H{sup +}(aq), {Delta}{sub r}N(H{sup +}), vary with the independent variables T, pH, and I.

  9. Short-wavelength InAlGaAs/AlGaAs quantum dot superluminescent diodes

    Science.gov (United States)

    Liang, De-Chun; An, Qi; Jin, Peng; Li, Xin-Kun; Wei, Heng; Wu, Ju; Wang, Zhan-Guo

    2011-10-01

    This paper reports the fabrication of J-shaped bent-waveguide superluminescent diodes utilizing an InAlGaAs/AlGaAs quantum dot active region. The emission spectrum of the device is centred at 884 nm with a full width at half maximum of 37 nm and an output power of 18 mW. By incorporating an Al composition into the quantum dot active region, short-wavelength superluminescent diode devices can be obtained. An intersection was found for the light power-injection current curves measured from the straight-waveguide facet and the bent-waveguide facet, respectively. The result is attributed to the conjunct effects of the gain and the additional loss of the bent waveguide. A numerical simulation is performed to verify the qualitative explanation. It is shown that bent waveguide loss is an important factor that affects the output power of J-shaped superluminescent diode devices.

  10. RTEMS Centre - Support and Maintenance Centre to RTEMS Operating System

    Science.gov (United States)

    Silva, H.; Constantino, A.; Freitas, D.; Coutinho, M.; Faustino, S.; Mota, M.; Colaço, P.; Sousa, J.; Dias, L.; Damjanovic, B.; Zulianello, M.; Rufino, J.

    2009-05-01

    RTEMS CENTRE - Support and Maintenance Centre to RTEMS Operating System is a joint ESA/Portuguese Task Force initiative to develop a support and maintenance centre to the Real-Time Executive for Multiprocessor Systems (RTEMS). This paper gives a high level visibility of the progress, the results obtained and the future work in the RTEMS CENTRE [6] and in the RTEMS Improvement [7] projects. RTEMS CENTRE started officially in November 2006, with the RTEMS 4.6.99.2 version. A full analysis of RTEMS operating system was produced. The architecture was analysed in terms of conceptual, organizational and operational concepts. The original objectives [1] of the centre were primarily to create and maintain technical expertise and competences in this RTOS, to develop a website to provide the European Space Community an entry point for obtaining support (http://rtemscentre.edisoft.pt), to design, develop, maintain and integrate some RTEMS support tools (Timeline Tool, Configuration and Management Tools), to maintain flight libraries and Board Support Packages, to develop a strong relationship with the World RTEMS Community and finally to produce some considerations in ARINC-653, DO-178B and ECSS E-40 standards. RTEMS Improvement is the continuation of the RTEMS CENTRE. Currently the RTEMS, version 4.8.0, is being facilitated for a future qualification. In this work, the validation material is being produced following the Galileo Software Standards Development Assurance Level B [5]. RTEMS is being completely tested, errors analysed, dead and deactivated code removed and tests produced to achieve 100% statement and decision coverage of source code [2]. The SW to exploit the LEON Memory Management Unit (MMU) hardware will be also added. A brief description of the expected implementations will be given.

  11. DOT1L inhibitor improves early development of porcine somatic cell nuclear transfer embryos

    DEFF Research Database (Denmark)

    Tao, Jia; Zhang, Yu; Zuo, Xiaoyuan

    2017-01-01

    Incomplete epigenetic reprogramming of the genome of donor cells causes poor early and full-term developmental efficiency of somatic cell nuclear transfer (SCNT) embryos. Previous research indicate that inhibition of the histone H3 K79 methyltransferase DOT1L, using a selective pharmacological...... inhibitor EPZ004777 (EPZ), significantly improved reprogramming efficiency during the generation of mouse induced pluripotent stem cells. However, the roles of DOT1L in porcine nuclear transfer-mediated cellular reprogramming are not yet known. Here we showed that DOT1L inhibition via 0.5 nM EPZ treatment...

  12. Nonplasmonic Hot-Electron Photocurrents from Mn-Doped Quantum Dots in Photoelectrochemical Cells.

    Science.gov (United States)

    Dong, Yitong; Rossi, Daniel; Parobek, David; Son, Dong Hee

    2016-03-03

    We report the measurement of the hot-electron current in a photoelectrochemical cell constructed from a glass/ITO/Al2 O3 (ITO=indium tin oxide) electrode coated with Mn-doped quantum dots, where hot electrons with a large excess kinetic energy were produced through upconversion of the excitons into hot electron hole pairs under photoexcitation at 3 eV. In our recent study (J. Am. Chem. Soc. 2015, 137, 5549), we demonstrated the generation of hot electrons in Mn-doped II-VI semiconductor quantum dots and their usefulness in photocatalytic H2 production reaction, taking advantage of the more efficient charge transfer of hot electrons compared with band-edge electrons. Here, we show that hot electrons produced in Mn-doped CdS/ZnS quantum dots possess sufficient kinetic energy to overcome the energy barrier from a 5.4-7.5 nm thick Al2 O3 layer producing a hot-electron current in photoelectrochemical cell. This work demonstrates the possibility of harvesting hot electrons not only at the interface of the doped quantum dot surface, but also far away from it, thus taking advantage of the capability of hot electrons for long-range electron transfer across a thick energy barrier. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. The inner 300 parsecs of the Milky Way seen by H.E.S.S.: a Pevatron in the Galactic Centre

    Directory of Open Access Journals (Sweden)

    Moulin Emmanuel

    2017-01-01

    Full Text Available The Galactic Centre region has been observed by the High Energy Stereoscopic System (H.E.S.S. array of ground-based Cherenkov telescopes since 2004 leading to the detection of the very-high-energy γ-ray source HESS J1745-290 spatially coincident with the supermassive black hole Sagittarius A*. Diffuse TeV gamma-ray emission has been detected along the Galactic plane, most likely due to hadronic cosmic-ray interactions with the dense gas of the Central Molecular Zone. The rich 2004-2013 dataset permits detailed spectral and morphological studies of the diffuse emission in the inner 300 pc of the Galactic Centre region. The new results provide an important statement regarding the location and origin of the accelerator of PeV protons. The H.E.S.S. observations of the Pevatron are discussed in the context of the origin of Galactic cosmic rays.

  14. Fluorescent determination of graphene quantum dots in water samples

    Energy Technology Data Exchange (ETDEWEB)

    Benítez-Martínez, Sandra; Valcárcel, Miguel, E-mail: qa1meobj@uco.es

    2015-10-08

    This work presents a simple, fast and sensitive method for the preconcentration and quantification of graphene quantum dots (GQDs) in aqueous samples. GQDs are considered an object of analysis (analyte) not an analytical tool which is the most frequent situation in Analytical Nanoscience and Nanotechnology. This approach is based on the preconcentration of graphene quantum dots on an anion exchange sorbent by solid phase extraction and their subsequent elution prior fluorimetric analysis of the solution containing graphene quantum dots. Parameters of the extraction procedure such as sample volume, type of solvent, sample pH, sample flow rate and elution conditions were investigated in order to achieve extraction efficiency. The limits of detection and quantification were 7.5 μg L{sup −1} and 25 μg L{sup −1}, respectively. The precision for 200 μg L{sup −1}, expressed as %RSD, was 2.8%. Recoveries percentages between 86.9 and 103.9% were obtained for two different concentration levels. Interferences from other nanoparticles were studied and no significant changes were observed at the concentration levels tested. Consequently, the optimized procedure has great potential to be applied to the determination of graphene quantum dots at trace levels in drinking and environmental waters. - Highlights: • Development of a novel and simple method for determination of graphene quantum dots. • Preconcentration of graphene quantum dots by solid phase extraction. • Fluorescence spectroscopy allows fast measurements. • High sensitivity and great reproducibility are achieved.

  15. Raman scattering as a tool for the evaluation of strain in GaN/AlN quantum dots: The effect of capping

    Science.gov (United States)

    Cros, A.; Garro, N.; Cantarero, A.; Coraux, J.; Renevier, H.; Daudin, B.

    2007-10-01

    The strain state of GaN/AlN quantum dots grown on 6H-SiC has been investigated as a function of AlN capping thickness by three different techniques. On the one hand, resonant Raman scattering allowed the detection of the A1(LO) quasiconfined mode. It was found that its frequency increases with AlN deposition, while its linewidth did not evolve significantly. Available experiments of multiwavelength anomalous diffraction and diffraction anomalous fine structure on the same samples provided the determination of the wurtzite lattice parameters a and c of the quantum dots. A very good agreement is found between resonant Raman scattering and x-ray measurements, especially concerning the in-plane strain state. The results demonstrate the adequacy of Raman scattering, in combination with the deformation potential and biaxial approximations, to determine quantitatively values of strain in GaN quantum dot layers.

  16. Raman scattering as a tool for the evaluation of strain in GaN/AlN quantum dots: The effect of capping

    International Nuclear Information System (INIS)

    Cros, A.; Cantarero, A.; Garro, N.; Coraux, J.; Daudin, B.; Renevier, H.

    2007-01-01

    The strain state of GaN/AlN quantum dots grown on 6H-SiC has been investigated as a function of AlN capping thickness by three different techniques. On the one hand, resonant Raman scattering allowed the detection of the A 1 (LO) quasiconfined mode. It was found that its frequency increases with AlN deposition, while its linewidth did not evolve significantly. Available experiments of multiwavelength anomalous diffraction and diffraction anomalous fine structure on the same samples provided the determination of the wurtzite lattice parameters a and c of the quantum dots. A very good agreement is found between resonant Raman scattering and x-ray measurements, especially concerning the in-plane strain state. The results demonstrate the adequacy of Raman scattering, in combination with the deformation potential and biaxial approximations, to determine quantitatively values of strain in GaN quantum dot layers

  17. Radioactive particulate release associated with the DOT specification 6M container under hypothetical accident conditions

    International Nuclear Information System (INIS)

    Taylor, J.M.; Raney, P.J.

    1986-02-01

    A testing program was conducted to determine the leakage of depleted uranium dioxide powder (DUO) from the inner containment components of the US Department of Transportation's (DOT) specification 6M container under hypothetical accident conditions. Depleted uranium dioxide was selected as a surrogate for plutonium oxide because of the similarities in the powder characteristics, density and particle size, and because of the special handling and special facilities required for plutonium oxide. The DUO was packaged inside food pack cans in three different configurations inside the 2R vessel of the 6M container. The amount of DUO powder leakage ranged from none detectable ( -7 g) to a high of 1 x 10 -3 g. The combination of gravity, vibration and pressure produced the highest leakage of DUO. Containers that had hermetic seals (leak rates -4 atm cc/min) did not leak any detectable amount ( -7 g) of DUO under the test conditions. Impact forces had no effect on the leakage of particles with the packaging configurations used. 23 refs., 24 figs., 3 tabs

  18. Colloidal Quantum Dot Photovoltaics: A Path Forward

    KAUST Repository

    Kramer, Illan J.; Sargent, Edward H.

    2011-01-01

    spectrum. CQD materials' ease of processing derives from their synthesis, storage, and processing in solution. Rapid advances have brought colloidal quantum dot photovoltaic solar power conversion efficiencies of 6% in the latest reports. These achievements

  19. Phonon impact on optical control schemes of quantum dots: Role of quantum dot geometry and symmetry

    Science.gov (United States)

    Lüker, S.; Kuhn, T.; Reiter, D. E.

    2017-12-01

    Phonons strongly influence the optical control of semiconductor quantum dots. When modeling the electron-phonon interaction in several theoretical approaches, the quantum dot geometry is approximated by a spherical structure, though typical self-assembled quantum dots are strongly lens-shaped. By explicitly comparing simulations of a spherical and a lens-shaped dot using a well-established correlation expansion approach, we show that, indeed, lens-shaped dots can be exactly mapped to a spherical geometry when studying the phonon influence on the electronic system. We also give a recipe to reproduce spectral densities from more involved dots by rather simple spherical models. On the other hand, breaking the spherical symmetry has a pronounced impact on the spatiotemporal properties of the phonon dynamics. As an example we show that for a lens-shaped quantum dot, the phonon emission is strongly concentrated along the direction of the smallest axis of the dot, which is important for the use of phonons for the communication between different dots.

  20. The Silicon:Colloidal Quantum Dot Heterojunction

    KAUST Repository

    Masala, Silvia; Adinolfi, Valerio; Sun, Jon Paul; Del Gobbo, Silvano; Voznyy, Oleksandr; Kramer, Illan J.; Hill, Ian G.; Sargent, Edward H.

    2015-01-01

    A heterojunction between crystalline silicon and colloidal quantum dots (CQDs) is realized. A special interface modification is developed to overcome an inherent energetic band mismatch between the two semiconductors, and realize the efficient collection of infrared photocarriers generated in the CQD film. This junction is used to produce a sensitive near infrared photodetector. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. The Silicon:Colloidal Quantum Dot Heterojunction

    KAUST Repository

    Masala, Silvia

    2015-10-13

    A heterojunction between crystalline silicon and colloidal quantum dots (CQDs) is realized. A special interface modification is developed to overcome an inherent energetic band mismatch between the two semiconductors, and realize the efficient collection of infrared photocarriers generated in the CQD film. This junction is used to produce a sensitive near infrared photodetector. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Lead-Salt Quantum-Dot Ionic Liquids

    KAUST Repository

    Sun, Liangfeng

    2010-03-08

    PbS quantum dots (QDs) are functionalized using ionic liquids with thiol moieties as capping ligands. The resulting amphiphilic QD ionic liquids exhibit fluidlike behavior at room temperature, even in the absence of solvents. The photostability of the QDs is dramatically improved compared to the as-synthesized oleic acid-capped QDs dispersed in toluene. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Density effects on high-n molecular Rydberg states: CH3I and C6H6 in H2 and Ar

    International Nuclear Information System (INIS)

    Asaf, U.; Felps, W.S.; Rupnik, K.; McGlynn, S.P.; Ascarelli, G.

    1989-01-01

    The absorption spectra of high-n Rydberg states of methyl iodide and benzene perturbed by varying number densities of hydrogen or argon, range 0.9x10 20 --10.5x10 20 cm -3 for H 2 and 0.6x10 20 --7.5x10 20 cm -3 for Ar, have been investigated. The high-n molecular states of both absorbers were found to shift linearly with the number density of atomic Ar and molecular H 2 scatterers. The Fermi formula modified by the Alekseev--Sobel'man polarization term provides an excellent fit of the shift data. The electron scattering lengths obtained are: 0.93 a 0 for H 2 and -1.63 a 0 for Ar using the CH 3 I absorber; and 0.99 a 0 for H 2 and -1.57 a 0 for Ar using the C 6 H 6 absorber. The electron scattering lengths for H 2 and Ar agree with the results of an empirical model that correlates scattering lengths and the polarizabilities α(spherical) for inert atoms and α 2 (nonspherical) for H 2 molecule

  4. Directly deposited quantum dot solids using a colloidally stable nanoparticle ink

    KAUST Repository

    Fischer, Armin H.; Rollny, Lisa R.; Pan, Jun; Carey, Graham H.; Thon, Susanna; Hoogland, Sjoerd H.; Voznyy, Oleksandr; Zhitomirsky, David; Kim, Jinyoung; Bakr, Osman; Sargent, E. H.

    2013-01-01

    We develop a photovoltaic colloidal quantum dot ink that allows for lossless, single-step coating of large areas in a manufacturing-compatible process. Our materials strategy involves a solution-phase ligand exchange to transport compatible linkers that yield 1-thioglycerol-capped PbS quantum dots in dimethyl sulfoxide with a photoluminescence quantum yield of 24%. A proof-of-principle solar cell made from the ink exhibits 2.1% power conversion efficiency. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Directly deposited quantum dot solids using a colloidally stable nanoparticle ink

    KAUST Repository

    Fischer, Armin H.

    2013-08-12

    We develop a photovoltaic colloidal quantum dot ink that allows for lossless, single-step coating of large areas in a manufacturing-compatible process. Our materials strategy involves a solution-phase ligand exchange to transport compatible linkers that yield 1-thioglycerol-capped PbS quantum dots in dimethyl sulfoxide with a photoluminescence quantum yield of 24%. A proof-of-principle solar cell made from the ink exhibits 2.1% power conversion efficiency. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Highly fluorescent and morphology-controllable graphene quantum dots-chitosan hybrid xerogels for in vivo imaging and pH-sensitive drug carrier.

    Science.gov (United States)

    Lv, Ouyang; Tao, Yongxin; Qin, Yong; Chen, Chuanxiang; Pan, Yan; Deng, Linhong; Liu, Li; Kong, Yong

    2016-10-01

    Highly fluorescent graphene quantum dots (GQDs)-chitosan (CS) hybrid xerogels (GQDs-CS) were facilely synthesized, and the morphology of GQDs-CS was controllable by varying the content of GQDs in the xerogel. The GQDs-CS exhibited a porous and three-dimensional (3D) network structure when the content of GQDs reached 43% (wt%) in the xerogel, which was beneficial for drug loading and sustained release. The as-prepared GQDs-CS could also be applied for in vivo imaging since it showed strong blue, green and red luminescence under excitation of varying wavelengths. Moreover, the pH-induced protonation/deprotonation of the -NH2 groups on CS chains can result in a pH-dependent drug delivery behavior of the GQDs-CS hybrid xerogel. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Short term inhalation toxicity of a liquid aerosol of glutaraldehyde-coated CdS/Cd(OH)2 core shell quantum dots in rats.

    Science.gov (United States)

    Ma-Hock, L; Farias, P M A; Hofmann, T; Andrade, A C D S; Silva, J N; Arnaud, T M S; Wohlleben, W; Strauss, V; Treumann, S; Chaves, C R; Gröters, S; Landsiedel, R; van Ravenzwaay, B

    2014-02-10

    Quantum dots exhibit extraordinary optical and mechanical properties, and the number of their applications is increasing. In order to investigate a possible effect of coating on the inhalation toxicity of previously tested non-coated CdS/Cd(OH)2 quantum dots and translocation of these very small particles from the lungs, rats were exposed to coated quantum dots or CdCl2 aerosol (since Cd(2+) was present as impurity), 6h/d for 5 consecutive days. Cd content was determined in organs and excreta after the end of exposure and three weeks thereafter. Toxicity was determined by examination of broncho-alveolar lavage fluid and microscopic evaluation of the entire respiratory tract. There was no evidence for translocation of particles from the respiratory tract. Evidence of a minimal inflammatory process was observed by examination of broncho-alveolar lavage fluid. Microscopically, minimal to mild epithelial alteration was seen in the larynx. The effects observed with coated quantum dots, non-coated quantum dots and CdCl2 were comparable, indicating that quantum dots elicited no significant effects beyond the toxicity of the Cd(2+) ion itself. Compared to other compounds with larger particle size tested at similarly low concentrations, quantum dots caused much less pronounced toxicological effects. Therefore, the present data show that small particle sizes with corresponding high surfaces are not the only factor triggering the toxic response or translocation. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  8. Structurally characterized 1,1,3,3-tetramethylguanidine solvated magnesium aryloxide complexes: [Mg(mu-OEt)(DBP)(H-TMG)]2, [Mg(mu-OBc)(DBP)(H-TMG)]2, [Mg(mu-TMBA)(DBP)(H-TMG)]2, [Mg(mu-DPP)(DBP)(H-TMG)]2, [Mg(BMP)2(H-TMG)2], [Mg(O-2,6-Ph2C6H3)2 (H-TMG)2].

    Science.gov (United States)

    Monegan, Jessie D; Bunge, Scott D

    2009-04-06

    The synthesis and structural characterization of several 1,1,3,3-tetramethylguanidine (H-TMG) solvated magnesium aryloxide complexes are reported. Bu(2)Mg was successfully reacted with H-TMG, HOC(6)H(3)(CMe(3))(2)-2,6 (H-DBP), and either ethanol, a carboxylic acid, or diphenyl phosphate in a 1:1 ratio to yield the corresponding [Mg(mu-L)(DBP)(H-TMG)](2) where L = OCH(2)CH(3) (OEt, 1), O(2)CC(CH(3))(3) (OBc, 2), O(2)C(C(6)H(2)-2,4,6-(CH(3))(3)) (TMBA, 3), or O(2)P(OC(6)H(5))(2) (DPP, 4). Bu(2)Mg was also reacted with two equivalents of H-TMG and HOC(6)H(3)(CMe(3))-2-(CH(3))-6 (BMP) or HO-2,6-Ph(2)C(6)H(3) to yield [Mg(BMP)(2)(H-TMG)(2)] (5) and [Mg(O-2,6-Ph(2)C(6)H(3))(2)(H-TMG)(2)] (6). Compounds 1-6 were characterized by single-crystal X-ray diffraction. Polymerization of l- and rac-lactide with 1 was found to generate polylactide (PLA). A discussion concerning the relevance of compounds 2 - 4 to the structure of Mg-activated phosphatase enzymes is also provided. The bulk powders for all complexes were found to be in agreement with the crystal structures based on elemental analyses, FT-IR spectroscopy, and (1)H, (13)C and (31)P NMR studies.

  9. Synthesis of Aqueous CdTe/CdS/ZnS Core/shell/shell Quantum Dots by a Chemical Aerosol Flow Method

    Directory of Open Access Journals (Sweden)

    Chen Dong

    2009-01-01

    Full Text Available Abstract This work described a continuous method to synthesize CdTe/CdS/ZnS core/shell/shell quantum dots. In an integrated system by flawlessly combining the chemical aerosol flow system working at high temperature (200–300°C to generate CdTe/CdS intermediate products and an additional heat-up setup at relatively low temperature to overcoat the ZnS shells, the CdTe/CdS/ZnS multishell structures were realized. The as-synthesized CdTe/CdS/ZnS core/shell/shell quantum dots are characterized by photoluminescence spectra, X-ray diffraction (XRD, energy-dispersive X-ray spectra (EDS, transmission electron microscopy (TEM, and high-resolution transmission electron microscopy (HRTEM. Fluorescence and XRD results confirm that the obtained quantum dots have a core/shell/shell structure. It shows the highest quantum yield above 45% when compared to the rhodamine 6G. The core/shell/shell QDs were more stable via the oxidation experiment by H2O2.

  10. Sub-monolayer dot vertical-cavity surface-emitting lasers

    International Nuclear Information System (INIS)

    Blokhin, S.A.; Maleev, N.A.; Kuz'menkov, A.G.

    2006-01-01

    Vertical-cavity surface-emitting lasers (VCSELs) based on submonolayer InGaAs quantum-dot active region and doped with AlGaAs/GaAs distributed Bragg reflectors were grown by molecular beam epitaxy. 3 μm aperture single-mode VCSELs demonstrate lasing at 980 nm with threshold current of 0.6 mA, maximum output power of 4 mW and external differential efficiency as high as 68%. Ultimately low internal optical losses were measured for these multimode sub-monolayer quantum dot VCSELs [ru

  11. Ara h 6 complements Ara h 2 as an important marker for IgE reactivity to peanut

    NARCIS (Netherlands)

    Koid, Audrey E.; Chapman, Martin D.; Hamilton, Robert G.; van Ree, Ronald; Versteeg, Serge A.; Dreskin, Stephen C.; Koppelman, Stef J.; Wünschmann, Sabina

    2014-01-01

    The similarities of two major peanut allergens, Ara h 2 and Ara h 6, in molecular size, amino acid sequence, and structure have made it difficult to obtain natural Ara h 6 free of Ara h 2. The objectives of this study were to purify natural Ara h 6 that is essentially free of Ara h 2 and to compare

  12. Comparison of IL-6, IL-8 Concentrations in H. pylori- and non-H. pylori-associated Gastritis

    Directory of Open Access Journals (Sweden)

    Gontar Alamsyah Siregar

    2014-12-01

    Full Text Available BACKGROUND: Helicobacter pylori is a non-invasive microorganism causing intense gastric mucosal inflammatory and immune reaction. The gastric mucosal levels of the proinflammatory cytokines Interleukin 6 (IL-6 and IL-8 have been reported to be increased in H. pylori infection, but the serum levels in H. pylori infection is still controversial. The purpose of this study was to investigate the serum levels of IL-6 and IL-8 in H. pylori infection. METHODS: A cross sectional study was done on eighty consecutive gastritis patients admitted to endoscopy units at Adam Malik General Hospital and Permata Bunda Hospital, Medan, Indonesia from May-October 2014. Histopathology was performed for the diagnosis of gastritis. Rapid urease test for diagnosis of H. pylori infection. Serum samples were obtained to determine circulating IL-6 and IL-8. Univariate and bivariate analysis (independent t test were done. RESULTS: There were 41.25% patients infected with H. pylori. Circulatory IL-6 levels were significantly higher in H. pylori-infected patients compared to H. pylori negative, but there were no differences between serum levels of IL-8 in H. pylori positive and negative patients. CONCLUSIONS: The immune response to H. pylori promotes systemic inflammation, which was reflected in an increased level of serum IL-6. Serum levels of IL-8 were not significantly different between H. pylori positive and negative. KEYWORDS: Helicobacter pylori, gastritis, IL-6, IL-8, cytokine.

  13. Designing artificial 2D crystals with site and size controlled quantum dots.

    Science.gov (United States)

    Xie, Xuejun; Kang, Jiahao; Cao, Wei; Chu, Jae Hwan; Gong, Yongji; Ajayan, Pulickel M; Banerjee, Kaustav

    2017-08-30

    Ordered arrays of quantum dots in two-dimensional (2D) materials would make promising optical materials, but their assembly could prove challenging. Here we demonstrate a scalable, site and size controlled fabrication of quantum dots in monolayer molybdenum disulfide (MoS 2 ), and quantum dot arrays with nanometer-scale spatial density by focused electron beam irradiation induced local 2H to 1T phase change in MoS 2 . By designing the quantum dots in a 2D superlattice, we show that new energy bands form where the new band gap can be controlled by the size and pitch of the quantum dots in the superlattice. The band gap can be tuned from 1.81 eV to 1.42 eV without loss of its photoluminescence performance, which provides new directions for fabricating lasers with designed wavelengths. Our work constitutes a photoresist-free, top-down method to create large-area quantum dot arrays with nanometer-scale spatial density that allow the quantum dots to interfere with each other and create artificial crystals. This technique opens up new pathways for fabricating light emitting devices with 2D materials at desired wavelengths. This demonstration can also enable the assembly of large scale quantum information systems and open up new avenues for the design of artificial 2D materials.

  14. Double Tunneling Injection Quantum Dot Lasers for High Speed Operation

    Science.gov (United States)

    2017-10-23

    Double Tunneling-Injection Quantum Dot Lasers for High -Speed Operation The views, opinions and/or findings contained in this report are those of...SECURITY CLASSIFICATION OF: 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13. SUPPLEMENTARY NOTES 12. DISTRIBUTION AVAILIBILITY STATEMENT 6...State University Title: Double Tunneling-Injection Quantum Dot Lasers for High -Speed Operation Report Term: 0-Other Email: asryan@vt.edu Distribution

  15. Passively mode-locked 4.6 and 10.5 GHz quantum dot laser diodes around 1.55 μm with large operating regime

    NARCIS (Netherlands)

    Heck, M.J.R.; Renault, A.; Bente, E.A.J.M.; Oei, Y.S.; Smit, M.K.; Eikema, K.S.E.; Ubachs, W.; Anantathanasarn, S.; Nötzel, R.

    2009-01-01

    Passive mode-locking in two-section InAs/InP quantum dot laser diodes operating at wavelengths around 1.55 µm is reported. For a 4.6-GHz laser, a large operating regime of stable mode-locking, with RF-peak heights of over 40 dB, is found for injection currents of 750 mA up to 1.0 A and for values of

  16. 5-Fluoro-6H,7′H,8′H-spiro[indoline-3,7′-pyrano[3,2-c:5,6-c′]di-1-benzopyran]-2,6′,8′-trione

    Directory of Open Access Journals (Sweden)

    J. Suresh

    2012-03-01

    Full Text Available In the title compound, C26H12FNO6, the central pyran ring and both benzopyran systems are nonplanar, having total puckering amplitudes of 0.139 (2, 0.050 (1 and 0.112 (2 Å, respectively. The central pyran ring adopts a boat conformation. The crystal structure is stabilized by C—H...O, N—H...O, N—H...F and C—H...π interactions.

  17. Detection of nitrite based on fluorescent carbon dots by the hydrothermal method with folic acid

    Science.gov (United States)

    Lin, Haitao; Ding, Liyun; Zhang, Bingyu; Huang, Jun

    2018-05-01

    A fluorescent carbon dots probe for the detection of aqueous nitrite was fabricated by a one-pot hydrothermal method, and the transmission electron microscope, X-ray diffractometer, UV-Vis absorption spectrometer and fluorescence spectrophotometer were used to study the property of carbon dots. The fluorescent property of carbon dots influenced by the concentration of aqueous nitrite was studied. The interaction between the electron-donating functional groups and the electron-accepting nitrous acid could account for the quenching effect on carbon dots by adding aqueous nitrite. The products of the hydrolysis of aqueous nitrite performed a stronger quenching effect at lower pH. The relationship between the relative fluorescence intensity of carbon dots and the concentration of nitrite was described by the Stern-Volmer equation (I0/I - 1 = 0.046[Q]) with a fine linearity (R2 = 0.99). The carbon dots-based probe provides a convenient method for the detection of nitrite concentration.

  18. Realization of electrically tunable single quantum dot nanocavities

    Energy Technology Data Exchange (ETDEWEB)

    Hofbauer, Felix Florian Georg

    2009-03-15

    We investigated the design, fabrication and optical investigation of electrically tunable single quantum dot-photonic crystal defect nanocavities operating in both the weak and strong coupling regimes of the light matter interaction. We demonstrate that the quantum confined Stark effect can be employed to quickly and reversibly switch the dot-cavity coupling, simply by varying a gate voltage. Our results show that exciton transitions from individual dots can be tuned by up to {proportional_to}4 meV relative to the nanocavity mode, before the emission quenches due to carrier tunneling escape from the dots. We directly probe spontaneous emission, irreversible polariton decay and the statistics of the emitted photons from a single-dot nanocavity in the weak and strong coupling regimes. New information is obtained on the nature of the dot-cavity coupling in the weak coupling regime and electrical control of zero dimensional polaritons is demonstrated for the first time. The structures investigated are p-i-n photodiodes consisting of an 180nm thick free-standing GaAs membrane into which a two dimensional photonic crystal is formed by etching a triangular lattice of air holes. Low mode volume nanocavities (V{sub mode}<1.6 ({lambda}/n){sup 3}) are realized by omitting 3 holes in a line to form L3 cavities and a single layer of InGaAs self-assembled quantum dots is embedded into the midpoint of the membrane. The nanocavities are electrically contacted via 35 nm thick p- and n-doped contact layers in the GaAs membrane. In the weak coupling regime, time resolved spectroscopy reveals a {proportional_to}7 x shortening of the spontaneous emission lifetime as the dot is tuned through the nanocavity mode, due to the Purcell effect. Upon strongly detuning the same quantum dot transition from the nanocavity mode we observe an additional {proportional_to}8 x lengthening of the spontaneous emission lifetime. These observations unequivocally highlight two regimes of dot

  19. Enhanced photoresponsive polyethyleneimine/citric acid co-carbonized dots for facile and selective sensing and intracellular imaging of cobalt ions at physiologic pH

    International Nuclear Information System (INIS)

    Zou, Wen-Sheng; Zhao, Qing-Chun; Zhang, Jun; Chen, Xiao-Ming; Wang, Xiu-Fang; Zhao, Lin; Chen, Shao-Hua; Wang, Ya-Qin

    2017-01-01

    Whether as an important biological element or as a radioactive source/medicine, the monitoring of trace levels of cobalt ions (Co) has become a non-negligible factor for human health and green environment. Current technologies for the detection of Co are cost-expensive and time-consuming, and require cumbersome sample pretreatment process. Herein a novel sensing platform has been developed for Co detection based on the quenching of the enhanced fluorescence signal of polyamine functionalized C-dots. Amine groups at the surface of the C-dots can capture Zn"2"+/Cd"2"+ to form coordination compound, which can inhibit the photoinduced electron transfer pathways of C-dots and then induce the fluorescence enhancement of the C-dots by ∼80% margin. Also, Co interacts with these amine groups to form an absorbent complex, which can strongly quench the enhanced fluorescence of C-dots via an inner filter effect. This C-dots-based probe showed a wide linear response to Co with a concentration ranging from 0.012 to 12 μM, and a detection limit of 8.0 nM and RSD of 5.7% (n = 5). Significantly, the C-Dots exhibit excellent properties, such as negligible cytotoxicity, excellent biocompatibility, low-cost and high photostability, etc., which make C-dots favorable for label-free monitoring of Co and then successfully applied to the confocal imaging of intracellular Co. - Highlights: • Polyethyleneimine/citric acid co-carbonized dots were prepared. • Zn"2"+ can enhance fluorescence of C-dots by inhibiting PET pathways. • Co"2"+ can quench the enhanced fluorescence by an inner filter effect. • Bioprobe has been established for intracellular imaging Co.

  20. Next steps towards a Climate Innovation Centre in Ghana. Discussion Paper

    International Nuclear Information System (INIS)

    De Coninck, H.C.; Wuertenberger, L.; Akon-Yamga, G.

    2011-03-01

    A climate innovation centre is an institution aimed at enabling development through catalysing climate technology research, development, market creation and policy. This discussion paper discusses the possibilities, considerations and next steps for a Climate Innovation Centre (CIC) in Ghana based on new insights within the government of Ghana, a mapping of climate innovation in Ghana, new developments in the international climate negotiations and other multilateral processes, and analysis conducted by ECN. The conclusion is that a Climate Innovation Centre can fill significant gaps in climate resilient development in Ghana. It seems important that a Ghana CIC does not become yet another institution that focuses on basic research in the area of climate change. Rather, it should connect the dots of the Ghanaian climate innovation system and act as a knowledge facilitator, also for the private sector. Various models of climate innovation centres exist. Before choices are made for a model or a combination of models for Ghana, it is recommended to allow for a broad stakeholder process. The World Bank's infoDev programme could be a model for such a process. Such stakeholder engagement should be aligned with other policymaking processes on adaptation and low-carbon development, as well as related policy arenas, such as agriculture, transport, waste and energy.

  1. Next steps towards a Climate Innovation Centre in Ghana. Discussion Paper

    Energy Technology Data Exchange (ETDEWEB)

    De Coninck, H.C.; Wuertenberger, L. [ECN Policy Studies, Petten (Netherlands); Akon-Yamga, G. [Science and Technology Policy Research Institute STEPRI, Accra (Guinea)

    2011-03-15

    A climate innovation centre is an institution aimed at enabling development through catalysing climate technology research, development, market creation and policy. This discussion paper discusses the possibilities, considerations and next steps for a Climate Innovation Centre (CIC) in Ghana based on new insights within the government of Ghana, a mapping of climate innovation in Ghana, new developments in the international climate negotiations and other multilateral processes, and analysis conducted by ECN. The conclusion is that a Climate Innovation Centre can fill significant gaps in climate resilient development in Ghana. It seems important that a Ghana CIC does not become yet another institution that focuses on basic research in the area of climate change. Rather, it should connect the dots of the Ghanaian climate innovation system and act as a knowledge facilitator, also for the private sector. Various models of climate innovation centres exist. Before choices are made for a model or a combination of models for Ghana, it is recommended to allow for a broad stakeholder process. The World Bank's infoDev programme could be a model for such a process. Such stakeholder engagement should be aligned with other policymaking processes on adaptation and low-carbon development, as well as related policy arenas, such as agriculture, transport, waste and energy.

  2. Platinum assisted by carbon quantum dots for methanol electro-oxidation

    Science.gov (United States)

    Pan, Dan; Li, Xingwei; Zhang, Aofeng

    2018-01-01

    Various types of fuel cells as clean and portable power sources show a great attraction, especially direct methanol fuel cell (DMFC) having high energy density, low operating temperature and convenient fuel storage. However, the preparation of low-cost Pt-based catalysts with satisfactory catalytic performance still faces many challenges for its commercialization on large scale. Here, Pt catalysts assisted by carbon quantum dots (CQDs) are reported. The synergistic effect of carbon quantum dots and Pt metals is similar to a bi-component catalyst, such as PtRu. First, carbon quantum dots derived from Vulcan XC-72 carbon black are synthesized by mixed acid etching. Then, carbon black (Vulcan XC-72) is soaked in carbon quantum dots solution for several days to obtain carbon black modified by carbon quantum dots (XC-72-CQDs). Finally, Pt catalysts are supported on XC-72-CQDs (Pt/XC-72-CQDs) through a simple chemical reduction method. For methanol electro-oxidation reaction, the catalytic performance of Pt/XC-72-CQDs is compared with commercial PtRu/C (30% Pt + 15% Ru). Results show that a typical product (Pt/XC-72-CQDs5) exhibits a better catalytic activity than PtRu/C. In cyclic voltammetry test, the specific activity of Pt/XC-72-CQDs5 is 1.06 mA cm-2 Pt and 477.6 mA mg-1 Pt, while that of PtRu/C is 0.77 mA cm-2 Pt and 280.6 mA mg-1 Pt.

  3. Harnessing Sun’s Energy with Quantum Dots Based Next Generation Solar Cell

    Science.gov (United States)

    Halim, Mohammad A.

    2012-01-01

    Our energy consumption relies heavily on the three components of fossil fuels (oil, natural gas and coal) and nearly 83% of our current energy is consumed from those sources. The use of fossil fuels, however, has been viewed as a major environmental threat because of their substantial contribution to greenhouse gases which are responsible for increasing the global average temperature. Last four decades, scientists have been searching for alternative sources of energy which need to be environmentally clean, efficient, cost-effective, renewable, and sustainable. One of the promising sustainable sources of energy can be achieved by harnessing sun energy through silicon wafer, organic polymer, inorganic dye, and quantum dots based solar cells. Among them, quantum dots have an exceptional property in that they can excite multiple electrons using only one photon. These dots can easily be synthesized, processed in solution, and incorporated into solar cell application. Interestingly, the quantum dots solar cells can exceed the Shockley-Queisser limit; however, it is a great challenge for other solar cell materials to exceed the limit. Theoretically, the quantum dots solar cell can boost the power conversion efficiency up to 66% and even higher to 80%. Moreover, in changing the size of the quantum dots one can utilize the Sun’s broad spectrum of visible and infrared ranges. This review briefly overviews the present performance of different materials-based solar cells including silicon wafer, dye-sensitized, and organic solar cells. In addition, recent advances of the quantum dots based solar cells which utilize cadmium sulfide/selenide, lead sulfide/selenide, and new carbon dots as light harvesting materials has been reviewed. A future outlook is sketched as to how one could improve the efficiency up to 10% from the current highest efficiency of 6.6%. PMID:28348320

  4. Interactions between N-acetyl-L-cysteine protected CdTe quantum dots and doxorubicin through spectroscopic method

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiupei, E-mail: xiupeiyang@163.com [Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province, Nanchong 637000 (China); College of Chemistry and Chemical Engineering, China West Normal University, Nanchong 637000 (China); Lin, Jia; Liao, Xiulin; Zong, Yingying; Gao, Huanhuan [College of Chemistry and Chemical Engineering, China West Normal University, Nanchong 637000 (China)

    2015-06-15

    Highlights: • CdTe quantum dots with the diameter of 3–5 nm were synthesized in aqueous solution. • The modified CdTe quantum dots showed well fluorescence properties. • The interaction between the CdTe quantum dots and doxorubicin (DR) was investigated. - Abstract: N-acetyl-L-cysteine protected cadmium telluride quantum dots with a diameter of 3–5 nm were synthesized in aqueous solution. The interaction between N-acetyl-L-cysteine/cadmium telluride quantum dots and doxorubicin was investigated by ultraviolet–visible absorption and fluorescence spectroscopy at physiological conditions (pH 7.2, 37 °C). The results indicate that electron transfer has occurred between N-acetyl-L-cysteine/cadmium telluride quantum dots and doxorubicin under light illumination. The quantum dots react readily with doxorubicin to form a N-acetyl-L-cysteine/cadmium telluride-quantum dots/doxorubicin complex via electrostatic attraction between the −NH{sub 3}{sup +} moiety of doxorubicin and the −COO{sup −} moiety of N-acetyl-L-cysteine/cadmium telluride quantum dots. The interaction of N-acetyl-L-cysteine/cadmium telluride-quantum dots/doxorubicin complex with bovine serum albumin was studied as well, showing that the complex might induce the conformation change of bovine serum due to changes in microenvironment of bovine serum.

  5. Interactions between N-acetyl-L-cysteine protected CdTe quantum dots and doxorubicin through spectroscopic method

    International Nuclear Information System (INIS)

    Yang, Xiupei; Lin, Jia; Liao, Xiulin; Zong, Yingying; Gao, Huanhuan

    2015-01-01

    Highlights: • CdTe quantum dots with the diameter of 3–5 nm were synthesized in aqueous solution. • The modified CdTe quantum dots showed well fluorescence properties. • The interaction between the CdTe quantum dots and doxorubicin (DR) was investigated. - Abstract: N-acetyl-L-cysteine protected cadmium telluride quantum dots with a diameter of 3–5 nm were synthesized in aqueous solution. The interaction between N-acetyl-L-cysteine/cadmium telluride quantum dots and doxorubicin was investigated by ultraviolet–visible absorption and fluorescence spectroscopy at physiological conditions (pH 7.2, 37 °C). The results indicate that electron transfer has occurred between N-acetyl-L-cysteine/cadmium telluride quantum dots and doxorubicin under light illumination. The quantum dots react readily with doxorubicin to form a N-acetyl-L-cysteine/cadmium telluride-quantum dots/doxorubicin complex via electrostatic attraction between the −NH 3 + moiety of doxorubicin and the −COO − moiety of N-acetyl-L-cysteine/cadmium telluride quantum dots. The interaction of N-acetyl-L-cysteine/cadmium telluride-quantum dots/doxorubicin complex with bovine serum albumin was studied as well, showing that the complex might induce the conformation change of bovine serum due to changes in microenvironment of bovine serum

  6. In-capillary self-assembly and proteolytic cleavage of polyhistidine peptide capped quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jianhao; Li, Jingyan; Li, Jinchen; Liu, Feifei [School of Pharmaceutical Engineering and Life Science, Changzhou University, Changzhou, Jiangsu, 213164 (China); Zhou, Xiang; Yao, Yi [Changzhou Qianhong Bio-pharma Co. Ltd, Changzhou 213164, Jiangsu (China); Wang, Cheli [School of Pharmaceutical Engineering and Life Science, Changzhou University, Changzhou, Jiangsu, 213164 (China); Qiu, Lin, E-mail: linqiupjj@gmail.com [School of Pharmaceutical Engineering and Life Science, Changzhou University, Changzhou, Jiangsu, 213164 (China); Jiang, Pengju, E-mail: pengju.jiang@gmail.com [School of Pharmaceutical Engineering and Life Science, Changzhou University, Changzhou, Jiangsu, 213164 (China); State Key Laboratory of Pharmaceutical Biotechnology, Nanjing, Jiangsu (China)

    2015-10-01

    A new method using fluorescence coupled capillary electrophoresis (CE-FL) for monitoring self-assembly and proteolytic cleavage of hexahistidine peptide capped quantum dots (QDs) inside a capillary has been developed in this report. QDs and the ATTO 590-labeled hexahistidine peptide (H6-ATTO) were injected into a capillary, sequentially. Their self-assembly inside the capillary was driven by a metal-affinity force which yielded a new fluorescence signal due to Förster resonance energy transfer (FRET). The highly efficient separation of fluorescent complexes and the FRET process were analyzed using CE-FL. The self-assembly of QDs and biomolecules was found to effectively take place inside the capillary. The kinetics of the assembly was monitored by CE-FL, and the approach was extended to the study of proteolytic cleavage of surface conjugated peptides. Being the first in-depth analysis of in-capillary nanoparticle–biomolecule assembly, the novel approach reported here provides inspiration to the development of QD-based FRET probes for biomedical applications. - Highlights: • We examined the self-assembly QDs with H6-ATTO inside a capillary. • We prove CE-FL to be a powerful method to resolve QDs-H6-ATTO complex. • We achieve chromatographic separation of QDs-H6-ATTO complex. • We discovered a novel strategy for the online detection of thrombin. • This technique integrated “injection, mixing, reaction, separation and detection”.

  7. InAs(Sb) quantum dots grown on GaAs by MBE

    International Nuclear Information System (INIS)

    Sallet, V.; Patriarche, G.; Mauguin, O.; Largeau, L.; Travers, L.

    2006-01-01

    The MBE growth of InAs(Sb)/GaAs quantum dots is investigated. Photoluminescence shows a slight red-shift of the emission wavelength from 1.15 to 1.24 μm (InAs 0.95 Sb 0.05 dots). Attempts to incorporate higher concentrations of antimony lead to a poor optical quality and, occasionally, to a blue-shift. Trans-mission electron microscopy observations are discussed considering the surfactant effect of antimony. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Highly luminescent N, S- Co-doped carbon dots and their direct use as mercury(II) sensor

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yu [Key Lab of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Department of Advanced Organic Materials Science and Engineering, Kyungpook National University, Daegu, 702-701 (Korea, Republic of); Kim, Sung-Hoon, E-mail: shokim@knu.ac.kr [Department of Advanced Organic Materials Science and Engineering, Kyungpook National University, Daegu, 702-701 (Korea, Republic of); Feng, Liang, E-mail: fengl@dicp.ac.cn [Key Lab of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China)

    2015-08-26

    Heteroatom doping has been proven as an efficient way to improve the fluorescent efficiency of carbon dots. Co-doping with heteroatoms may introduce more active sites to carbon dots, which would broaden applications of CDs in sensing. In this work, highly luminescent nitrogen and sulfur co-doped carbon dots (NSCDs) were synthesized through a facile one-step microwave assisted method by using citric acid and rubeanic acid as carbon, nitrogen, and sulfur sources. The well-isolated NSCDs not only exhibit an enhanced fluorescent efficiency with a relatively high quantum yield up to 17.6%, but also show potential use as a multi-sensing platform based on their fluorescence “on-off-on” and color changing behaviors. The NSCDs can be directly used for the selective determination of mercury cations without any functionalization. The detection limit is approximately calculated as 0.18 μM and linear range is 0–20 μM. The sensing mechanism is proposed as coordination reaction induced by oligomers upon the carbon core. Furthermore, in the presence of cyanide anions, the fluorescence shows linear recovery associated with the concentration of cyanide, indicating its potential usage for the detection of cyanide ion. The optimized pH range for such fluorescence “on-off-on” sensing system is investigated as pH 6–8, suggesting potential applications in bio-sensing and imaging area. In addition, by adding hydrosulfide anion to NSCDs@Hg{sup 2+} complex, a notable color change could be clearly observed due to the formation of fuscous HgS. In application, a handy test paper for direct and rapid detection of Hg{sup 2+} is manufactured for the evaluation of usage of NSCDs in the real circumstance. - Highlights: • NSCDs were synthesized by using citric acid and rubeanic acid. • NSCDs exhibited an enhanced fluorescent efficiency with high QY up to 17.6%. • NSCDs presented good sensing performance to mercury ions. • NSCDs showed potential use as a multi-sensing platform.

  9. Highly luminescent N, S- Co-doped carbon dots and their direct use as mercury(II) sensor

    International Nuclear Information System (INIS)

    Wang, Yu; Kim, Sung-Hoon; Feng, Liang

    2015-01-01

    Heteroatom doping has been proven as an efficient way to improve the fluorescent efficiency of carbon dots. Co-doping with heteroatoms may introduce more active sites to carbon dots, which would broaden applications of CDs in sensing. In this work, highly luminescent nitrogen and sulfur co-doped carbon dots (NSCDs) were synthesized through a facile one-step microwave assisted method by using citric acid and rubeanic acid as carbon, nitrogen, and sulfur sources. The well-isolated NSCDs not only exhibit an enhanced fluorescent efficiency with a relatively high quantum yield up to 17.6%, but also show potential use as a multi-sensing platform based on their fluorescence “on-off-on” and color changing behaviors. The NSCDs can be directly used for the selective determination of mercury cations without any functionalization. The detection limit is approximately calculated as 0.18 μM and linear range is 0–20 μM. The sensing mechanism is proposed as coordination reaction induced by oligomers upon the carbon core. Furthermore, in the presence of cyanide anions, the fluorescence shows linear recovery associated with the concentration of cyanide, indicating its potential usage for the detection of cyanide ion. The optimized pH range for such fluorescence “on-off-on” sensing system is investigated as pH 6–8, suggesting potential applications in bio-sensing and imaging area. In addition, by adding hydrosulfide anion to NSCDs@Hg 2+ complex, a notable color change could be clearly observed due to the formation of fuscous HgS. In application, a handy test paper for direct and rapid detection of Hg 2+ is manufactured for the evaluation of usage of NSCDs in the real circumstance. - Highlights: • NSCDs were synthesized by using citric acid and rubeanic acid. • NSCDs exhibited an enhanced fluorescent efficiency with high QY up to 17.6%. • NSCDs presented good sensing performance to mercury ions. • NSCDs showed potential use as a multi-sensing platform

  10. Monte Carlo Simulation of Electron Transport in 4H- and 6H-SiC

    International Nuclear Information System (INIS)

    Sun, C. C.; You, A. H.; Wong, E. K.

    2010-01-01

    The Monte Carlo (MC) simulation of electron transport properties at high electric field region in 4H- and 6H-SiC are presented. This MC model includes two non-parabolic conduction bands. Based on the material parameters, the electron scattering rates included polar optical phonon scattering, optical phonon scattering and acoustic phonon scattering are evaluated. The electron drift velocity, energy and free flight time are simulated as a function of applied electric field at an impurity concentration of 1x10 18 cm 3 in room temperature. The simulated drift velocity with electric field dependencies is in a good agreement with experimental results found in literature. The saturation velocities for both polytypes are close, but the scattering rates are much more pronounced for 6H-SiC. Our simulation model clearly shows complete electron transport properties in 4H- and 6H-SiC.

  11. The interaction between d-dot's

    International Nuclear Information System (INIS)

    Hirayama, Masaki; Machida, Masahiko; Koyama, Tomio; Ishida, Takekazu; Kato, Masaru

    2005-01-01

    We investigated the interaction between two square d-dot's. The d-dot is the nano-scaled superconducting composite structure that is made of a d-wave superconducting dot embedded in the s-wave superconducting matrix. In the numerical calculation, using the finite element method, we solved the two-components Ginzburg-Landau equation self-consistently. We obtained two kinds of solutions, which can be considered as ferromagnetic and antiferromagnetic configurations, when two d-dot's are separated parallel and diagonally. Also we discuss the applicability of d-dot's as an artificial spin system where the interactions can be controlled by the fabrication

  12. Highly luminescent S,N co-doped carbon quantum dots-sensitized chemiluminescence on luminol-H2 O2 system for the determination of ranitidine.

    Science.gov (United States)

    Chen, Jianqiu; Shu, Juan; Chen, Jiao; Cao, Zhiran; Xiao, An; Yan, Zhengyu

    2017-05-01

    S,N co-doped carbon quantum dots (N,S-CQDs) with super high quantum yield (79%) were prepared by the hydrothermal method and characterized by transmission electron microscopy, photoluminescence, UV-Vis spectroscopy and Fourier transformed infrared spectroscopy. N,S-CQDs can enhance the chemiluminescence intensity of a luminol-H 2 O 2 system. The possible mechanism of the luminol-H 2 O 2 -(N,S-CQDs) was illustrated by using chemiluminescence, photoluminescence and ultraviolet analysis. Ranitidine can quench the chemiluminescence intensity of a luminol-H 2 O 2 -N,S-CQDs system. So, a novel flow-injection chemiluminescence method was designed to determine ranitidine within a linear range of 0.5-50 μg ml -1 and a detection limit of 0.12 μg ml -1 . The method shows promising application prospects. Copyright © 2016 John Wiley & Sons, Ltd.

  13. Degradation of the fluoroquinolone enrofloxacin by electrochemical advanced oxidation processes based on hydrogen peroxide electrogeneration

    Energy Technology Data Exchange (ETDEWEB)

    Guinea, Elena; Garrido, Jose Antonio; Rodriguez, Rosa Maria; Cabot, Pere-Lluis; Arias, Conchita; Centellas, Francesc [Laboratori d' Electroquimica dels Materials i del Medi Ambient, Departament de Quimica Fisica, Facultat de Quimica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain); Brillas, Enric, E-mail: brillas@ub.ed [Laboratori d' Electroquimica dels Materials i del Medi Ambient, Departament de Quimica Fisica, Facultat de Quimica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain)

    2010-02-15

    Solutions of the veterinary fluoroquinolone antibiotic enrofloxacin in 0.05 M Na{sub 2}SO{sub 4} of pH 3.0 have been comparatively degraded by electrochemical advanced oxidation processes such as anodic oxidation with electrogenerated H{sub 2}O{sub 2} (AO-H{sub 2}O{sub 2}), electro-Fenton (EF), photoelectro-Fenton (PEF) and solar photoelectro-Fenton (SPEF) at constant current density. The study has been performed using an undivided stirred tank reactor of 100 ml and a batch recirculation flow plant of 2.5 l with an undivided filter-press cell coupled to a solar photoreactor, both equipped with a Pt or boron-doped diamond (BDD) anode and a carbon-polytetrafluoroethylene gas diffusion cathode to generate H{sub 2}O{sub 2} from O{sub 2} reduction. In EF, PEF and SPEF, hydroxyl radical (centre dotOH) is formed from Fenton's reaction between added catalytic Fe{sup 2+} and generated H{sub 2}O{sub 2}. Almost total decontamination of enrofloxacin solutions is achieved in the stirred tank reactor by SPEF with BDD. The use of the batch recirculation flow plant showed that this process is the most efficient and can be viable for industrial application, becoming more economic and yielding higher mineralization degree with raising antibiotic content. This is feasible because organics are quickly oxidized with centre dotOH formed from Fenton's reaction and at BDD from water oxidation, combined with the fast photolysis of complexes of Fe(III) with generated carboxylic acids under solar irradiation. The lower intensity of UVA irradiation used in PEF with BDD causes a slower degradation. EF with BDD is less efficient since centre dotOH cannot destroy the most persistent Fe(III)-oxalate and Fe(III)-oxamate complexes. AO-H{sub 2}O{sub 2} with BDD yields the poorest mineralization because pollutants are only removed with centre dotOH generated at BDD. All procedures are less potent using Pt as anode due to the lower production of centre dotOH at its surface. Enrofloxacin

  14. Enhanced photoresponsive polyethyleneimine/citric acid co-carbonized dots for facile and selective sensing and intracellular imaging of cobalt ions at physiologic pH

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Wen-Sheng, E-mail: wszou@ahjzu.edu.cn; Zhao, Qing-Chun; Zhang, Jun; Chen, Xiao-Ming; Wang, Xiu-Fang; Zhao, Lin; Chen, Shao-Hua; Wang, Ya-Qin, E-mail: yqwang@ahjzu.edu.cn

    2017-06-01

    Whether as an important biological element or as a radioactive source/medicine, the monitoring of trace levels of cobalt ions (Co) has become a non-negligible factor for human health and green environment. Current technologies for the detection of Co are cost-expensive and time-consuming, and require cumbersome sample pretreatment process. Herein a novel sensing platform has been developed for Co detection based on the quenching of the enhanced fluorescence signal of polyamine functionalized C-dots. Amine groups at the surface of the C-dots can capture Zn{sup 2+}/Cd{sup 2+} to form coordination compound, which can inhibit the photoinduced electron transfer pathways of C-dots and then induce the fluorescence enhancement of the C-dots by ∼80% margin. Also, Co interacts with these amine groups to form an absorbent complex, which can strongly quench the enhanced fluorescence of C-dots via an inner filter effect. This C-dots-based probe showed a wide linear response to Co with a concentration ranging from 0.012 to 12 μM, and a detection limit of 8.0 nM and RSD of 5.7% (n = 5). Significantly, the C-Dots exhibit excellent properties, such as negligible cytotoxicity, excellent biocompatibility, low-cost and high photostability, etc., which make C-dots favorable for label-free monitoring of Co and then successfully applied to the confocal imaging of intracellular Co. - Highlights: • Polyethyleneimine/citric acid co-carbonized dots were prepared. • Zn{sup 2+} can enhance fluorescence of C-dots by inhibiting PET pathways. • Co{sup 2+} can quench the enhanced fluorescence by an inner filter effect. • Bioprobe has been established for intracellular imaging Co.

  15. Depleted Bulk Heterojunction Colloidal Quantum Dot Photovoltaics

    KAUST Repository

    Barkhouse, D. Aaron R.

    2011-05-26

    The first solution-processed depleted bulk heterojunction colloidal quantum dot solar cells are presented. The architecture allows for high absorption with full depletion, thereby breaking the photon absorption/carrier extraction compromise inherent in planar devices. A record power conversion of 5.5% under simulated AM 1.5 illumination conditions is reported. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Quantum dot spectroscopy

    DEFF Research Database (Denmark)

    Leosson, Kristjan

    1999-01-01

    Semiconductor quantum dots ("solid state atoms") are promising candidates for quantum computers and future electronic and optoelectronic devices. Quantum dots are zero-dimensional electronic systems and therefore have discrete energy levels, similar to atoms or molecules. The size distribution of...

  17. Quantum dot spectroscopy

    DEFF Research Database (Denmark)

    Leosson, Kristjan

    Semiconductor quantum dots ("solid-state atoms") are promising candidates for quantum computers and future electronic and optoelectronic devices. Quantum dots are zero-dimensional electronic systems and therefore have discrete energy levels, similar to atoms or molecules. The size distribution of...

  18. Spin dynamics in SiGe quantum dot lines and ring molecules

    Science.gov (United States)

    Zinovieva, A. F.; Nenashev, A. V.; Dvurechenskii, A. V.

    2016-04-01

    Semiconductor quantum dot (QD) structures can be used as a model for understanding the effect of the microscopic structure, symmetry of crystals, and molecules on their macroscopic properties. In this work, the results of two theoretical approaches demonstrate that the spin dynamics in ordered QD structures depends on the size, spatial configuration, and topology of the object built of QDs. It was shown that the spin dynamics in QD structures with the hopping regime of conductivity significantly differs from the spin dynamics in two-dimensional (2D) and three-dimensional (3D) structures being at the other side of the metal-insulator transition. The special character of the effective magnetic field δ H fluctuations appearing only during tunneling between quantum dots is responsible for the insensitivity of spin relaxation times to the magnitude of the external magnetic field in infinite QD structures (2D square lattice and 1D linear QD chain). In finite QD structures (QD rings and linear chains), an external magnetic field H0 is directly involved in the spin relaxation process and spin is lost due to interaction with a special combination of fields Δ H ˜[H0×δ H ]/δ H that leads to an unusual orientation dependence of ESR linewidth, recently observed for QD chains. It was shown that the ordering of QD structures can be used for the conservation of spin orientation. For 1D finite quantum dot chains, the ordering can provide the stabilization of all spin components Sx,Sy, and Sz, while for ringlike molecules only Sz polarization can be stabilized. The results obtained in this work can be useful for development of novel semiconductor devices and in quantum information processing.

  19. H3PO4 treated surface modified CuS counter electrodes with high electrocatalytic activity for enhancing photovoltaic performance of quantum dot-sensitized solar cells

    Science.gov (United States)

    Panthakkal Abdul Muthalif, Mohammed; Sunesh, Chozhidakath Damodharan; Choe, Youngson

    2018-05-01

    Herein we report a simple synthetic strategy to prepare highly efficient and surface modified CuS counter electrodes (CEs) for quantum dot-sensitized solar cells (QDSSCs) in the presence of phosphoric acid (H3PO4) using the chemical bath deposition method. This is the first report of successful treatment of H3PO4 on the surface of CuS CEs for designing a high-performance QDSSCs with improved photovoltaic properties. After optimization, the 4 ml H3PO4 treated CuS CE-based QDSSC exhibits excellent photovoltaic performance with a conversion efficiency (η) of 4.20% (Voc = 0.592 V, Jsc = 13.35 mA cm-2, FF = 0.532) under one full-sun illumination (100 mW cm-2, AM 1.5 G).

  20. Synthesis of quantum dots

    Science.gov (United States)

    McDaniel, Hunter

    2017-10-17

    Common approaches to synthesizing alloyed quantum dots employ high-cost, air-sensitive phosphine complexes as the selenium precursor. Disclosed quantum dot synthesis embodiments avoid these hazardous and air-sensitive selenium precursors. Certain embodiments utilize a combination comprising a thiol and an amine that together reduce and complex the elemental selenium to form a highly reactive selenium precursor at room temperature. The same combination of thiol and amine acts as the reaction solvent, stabilizing ligand, and sulfur source in the synthesis of quantum dot cores. A non-injection approach may also be used. The optical properties of the quantum dots synthesized by this new approach can be finely tuned for a variety of applications by controlling size and/or composition of size and composition. Further, using the same approach, a shell can be grown around a quantum dot core that improves stability, luminescence efficiency, and may reduce toxicity.

  1. Quantum Dots: Theory

    Energy Technology Data Exchange (ETDEWEB)

    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.

  2. Continuous wave and time resolved spectroscopy of InAsN/GaAsN based quantum dots

    International Nuclear Information System (INIS)

    Taliercio, T.; Valvin, P.; Intartaglia, R.; Guillet, T.; Lefebvre, P.; Bretagnon, T.; Gil, B.; Sallet, V.; Harmand, J.C.

    2005-01-01

    We present a study of the optical properties of quantum dots based on a new family of semiconductors: III-V dilute nitrides such as (In,Ga)(N,As). Continuous wave and time resolved photoluminescence (PL) experiments allowed us to evaluate the impact of N incorporation during the growth of InAs/GaAs quantum dots. Previous work [V. Sallet et al., to be submitted to J. Cryst. Growth (2005); O. Schumann et al., J. Appl. Phys. 96, 2832 (2004)] showed that increasing the flux of N atoms into the growth chamber modifies drastically the size of the dots which leads to a bimodal growth. Two populations of dots with different sizes appear. The quantum dot PL line broadens and a second PL line appears at higher energy. Time resolved PL allows us to identify the nature of this second PL line: second population of quantum dots. A second decay time is observed which we interpret as being the consequence of the perturbation of the electronic states of the quantum dots. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. One-pot synthesis of stable water soluble Mn:ZnSe/ZnS core/shell quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Hao; Gao Xue; Liu Siyu; Su Xingguang, E-mail: suxg@jlu.edu.cn [College of Chemistry, Jilin University, Department of Analytical Chemistry (China)

    2013-06-15

    In this paper, Mn:ZnSe/ZnS core/shell-doped quantum dots (d-dots) with 3-mercaptopropionic acid as the stabilizer are successfully synthesized through a simple one-pot synthesis procedure in aqueous solution. The average diameter of Mn:ZnSe/ZnS core/shell d-dots is about 2.9 nm, which is lager than that of Mn:ZnSe cores (about 1.9 nm). The optical features and structure of the obtained Mn:ZnSe/ZnS core/shell quantum dots have been characterized by UV-Vis and fluorescence spectroscopy, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The photostability against UV irradiation and chemical stability against H{sub 2}O{sub 2} etching have been studied, and the results showed that the prepared Mn:ZnSe/ZnS core/shell d-dots are more stable than CdTe quantum dots prepared in aqueous solution. Finally, the resulting core/shell quantum dots are used as fluorescent label in human osteoblast-like HepG2 cell imaging.

  4. 49 CFR 40.13 - How do DOT drug and alcohol tests relate to non-DOT tests?

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 1 2010-10-01 2010-10-01 false How do DOT drug and alcohol tests relate to non... TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Employer Responsibilities § 40.13 How do DOT drug and... non-DOT drug and alcohol testing programs. This prohibition includes the use of the DOT forms with...

  5. Probing ultrafast carrier tunneling dynamics in individual quantum dots and molecules

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Kai; Bechtold, Alexander; Kaldewey, Timo; Zecherle, Markus; Wildmann, Johannes S.; Bichler, Max; Abstreiter, Gerhard; Finley, Jonathan J. [Walter Schottky Institut and Physik-Department, Technische Universitaet Muenchen, Am Coulombwall 4, 85748, Garching (Germany); Ruppert, Claudia; Betz, Markus [Experimentelle Physik 2, TU Dortmund, 44221, Dortmund (Germany); Krenner, Hubert J. [Lehrstuhl fuer Experimentalphysik 1 and Augsburg Centre for Innovative Technologies (ACIT), Universitaet Augsburg, Universitaetsstr 1, 86159, Augsburg (Germany); Villas-Boas, Jose M. [Instituto de Fisica, Universidade Federal de Uberlandia, 38400-902, Uberlandia, MG (Brazil)

    2013-02-15

    Ultrafast pump-probe spectroscopy is employed to directly monitor the tunneling of charge carriers from single and vertically coupled quantum dots and probe intra-molecular dynamics. Immediately after resonant optical excitation, several peaks are observed in the pump-probe spectrum arising from Coulomb interactions between the photogenerated charge carriers. The influence of few-Fermion interactions in the photoexcited system and the temporal evolution of the optical response is directly probed in the time domain. In addition, the tunneling times for electrons and holes from the QD nanostructure are independently determined. In polarization resolved measurements, near perfect Pauli-spin blockade is observed in the spin-selective absorption spectrum as well as stimulated emission. While electron and hole tunneling from single quantum dots is shown to be well explained by the WKB formalism, for coupled quantum dots pronounced resonances in the electron tunneling rate are observed arising from elastic and inelastic electron tunneling between the different dots. (copyright 2012 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. F6H8 as an Intraoperative Tool and F6H8/Silicone Oil as a Postoperative Tamponade in Inferior Retinal Detachment with Inferior PVR

    Directory of Open Access Journals (Sweden)

    Gian Marco Tosi

    2014-01-01

    Full Text Available Purpose. To evaluate the effectiveness and safety of perfluorohexyloctane (F6H8 for intraoperative flattening of the retina and of F6H8/silicone oil (SO 1000 cSt as a postoperative tamponade for inferior retinal detachment with inferior proliferative vitreoretinopathy. Methods. This is a retrospective review of 22 patients who underwent pars plana vitrectomy using F6H8 as an intraoperative tool to flatten the retina. At the end of the surgery a direct partial exchange between F6H8 and SO 1000 cSt was performed, tamponing the eye with different ratios of F6H8/SO (70/30, 60/40, 50/50, 40/30, and 30/70. Anatomical and functional results and complications were evaluated over the follow-up period (mean 22.63 months. Results. F6H8 was efficacious for intraoperative flattening of the retina. Twenty-one of the 22 patients achieved a complete retinal reattachment. Postoperative visual acuity (VA ranged from light perception to 20/70, with 72% of patients obtaining VA better than 20/400. No emulsification/inflammation was observed whatever the ratio of F6H8/SO used. With higher ratios of F6H8/SO (70/30 and 60/40 cloudiness of the tamponade was observed. A transparent mixture was present with all the other ratios. Conclusions. The surgical technique adopted is very simple and safe. The optimal F6H8/SO ratio seems to be between 50/50 and 30/70.

  7. Synthesis, spectroscopic, structural and thermal characterizations of [(C7H6NO42TeBr6·4H2O

    Directory of Open Access Journals (Sweden)

    S. Smaoui

    2018-02-01

    Full Text Available Tellurium (IV complexes with pyridine-2,6-dicarboxylate ligand were synthesized by slow evaporation from aqueous solutions yielding a new compound: [(C7H6NO42TeBr6·4H2O]. The structure of this compound was solved and refined by single-crystal X-ray diffraction. The compound is centrosymmetric P21/c (N°: 14 with the parameters a = 8.875(5 Å, b = 15.174(5 Å, c = 10.199(5 Å, β = 94.271° (5 and Z = 2. The structure consists of isolated H2O, isolated [TeBr6]2− octahedral anions and (pyridine-2,6-dicarboxylate [C7H6NO4]+ cations. The stability of the structure was ensured by ionic and hydrogen bonding contacts (N–H⋯Br and O–H⋯Br and Van-Der Walls interaction. The thermal decomposition of the compound was studied by thermogravimetric analysis (TGA and differential scanning calorimetry (DSC. The FTIR and Raman spectroscopy at different temperatures confirm the existence of vibrational modes that correspond to the organic, inorganic and water molecular groups. Additionally, the UV–Vis diffuse reflectance spectrum was recorded in order to investigate the band gap nature. The measurements show that this compound exhibits a semiconducting behavior with an optical band gap of 2.66 eV.

  8. Hyperdense dots mimicking microcalcifications : Mammographic findings

    International Nuclear Information System (INIS)

    Kim, Nam Hyeon; Park, Jeong Mi; Goo, Hyun Woo; Bang, Sun Woo

    1996-01-01

    To differentiate fine hyperdense dots mimicking microcalcifications from true microcalcifications on mammography. Mammograms showing hyperdense dots in ten patients (mean age, 59 years) were evaluated. Two radiologists were asked to differentiate with the naked eye the hyperdense dots seen on ten mammograms and proven microcalcifications seen on ten mammograms. Densitometry was also performed for all lesions and the contrast index was calculated. The shape and distribution of the hyperdense dots were evaluated and enquires were made regarding any history of breast disease and corresponding treatment. Biopsies were performed for two patients with hyperdense dots. Two radiologists made correct diagnoses in 19/20 cases(95%). The contrast index was 0.10-0.88 (mean 0.58) for hyperdense dots and 0.02-0.45 (mean 0.17) for true microcalcifications. The hyperdense dots were finer and homogeneously rounder than the microcalcifications. Distribution of the hyperdense dots was more superficial in subcutaneous fat (seven cases) and subareolar area (six cases). All ten patients with hyperdense dots had history of mastitis and abscesses and had been treated by open drainage (six cases) and/or folk remedy (four cases). In eight patients, herb patches had been attached. Biopsies of hyperdense dots did not show any microcalcification or evidence of malignancy. These hyperdense dots were seen mainly in older patients. Their characteristic density, shape, distribution and clinical history makes differential diagnosis from true microcalcifications easy and could reduce unnecessary diagnostic procedures such as surgical biopsy

  9. Vectorization of DOT3.5 code

    International Nuclear Information System (INIS)

    Nonomiya, Iwao; Ishiguro, Misako; Tsutsui, Tsuneo

    1990-07-01

    In this report, we describe the vectorization of two-dimensional Sn-method radiation transport code DOT3.5. Vectorized codes are not only the NEA original version developed at ORNL but also the versions improved by JAERI: DOT3.5 FNS version for fusion neutronics analyses, DOT3.5 FER version for fusion reactor design, and ESPRIT module of RADHEAT-V4 code system for radiation shielding and radiation transport analyses. In DOT3.5, input/output processing time amounts to a great part of the elapsed time when a large number of energy groups and/or a large number of spatial mesh points are used in the calculated problem. Therefore, an improvement has been made for the speedup of input/output processing in the DOT3.5 FNS version, and DOT-DD (Double Differential cross section) code. The total speedup ratio of vectorized version to the original scalar one is 1.7∼1.9 for DOT3.5 NEA version, 2.2∼2.3 fro DOT3.5 FNS version, 1.7 for DOT3.5 FER version, and 3.1∼4.4 for RADHEAT-V4, respectively. The elapsed times for improved DOT3.5 FNS version and DOT-DD are reduced to 50∼65% that of the original version by the input/output speedup. In this report, we describe summary of codes, the techniques used for the vectorization and input/output speedup, verification of computed results, and speedup effect. (author)

  10. Hyperdense dots mimicking microcalcifications : Mammographic findings

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Nam Hyeon; Park, Jeong Mi; Goo, Hyun Woo; Bang, Sun Woo [Asan Medical Center, University of Ulsan College of Medicine, Seoul (Korea, Republic of)

    1996-12-01

    To differentiate fine hyperdense dots mimicking microcalcifications from true microcalcifications on mammography. Mammograms showing hyperdense dots in ten patients (mean age, 59 years) were evaluated. Two radiologists were asked to differentiate with the naked eye the hyperdense dots seen on ten mammograms and proven microcalcifications seen on ten mammograms. Densitometry was also performed for all lesions and the contrast index was calculated. The shape and distribution of the hyperdense dots were evaluated and enquires were made regarding any history of breast disease and corresponding treatment. Biopsies were performed for two patients with hyperdense dots. Two radiologists made correct diagnoses in 19/20 cases(95%). The contrast index was 0.10-0.88 (mean 0.58) for hyperdense dots and 0.02-0.45 (mean 0.17) for true microcalcifications. The hyperdense dots were finer and homogeneously rounder than the microcalcifications. Distribution of the hyperdense dots was more superficial in subcutaneous fat (seven cases) and subareolar area (six cases). All ten patients with hyperdense dots had history of mastitis and abscesses and had been treated by open drainage (six cases) and/or folk remedy (four cases). In eight patients, herb patches had been attached. Biopsies of hyperdense dots did not show any microcalcification or evidence of malignancy. These hyperdense dots were seen mainly in older patients. Their characteristic density, shape, distribution and clinical history makes differential diagnosis from true microcalcifications easy and could reduce unnecessary diagnostic procedures such as surgical biopsy.

  11. From DOT to Dotty

    CERN Multimedia

    CERN. Geneva

    2017-01-01

    - Module types are interfaces, which can be abstracted. In this talk Martin will present DOT, a particularly simple calculus that can express systems following these principles. DOT has been developed as the foundation of the next version of Scala. He will also report on dotty, a new Scala compiler that implements the constructs of DOT in its core data structures and that uses the lessons learned to drive Scala’s evolution.

  12. Supramolecular assemblies in [Cu(L-Arg){sub 2}(H{sub 2}O)]C{sub 2}O{sub 4}·6H{sub 2}O complex – Structural, spectroscopic, magnetic and thermal behavior

    Energy Technology Data Exchange (ETDEWEB)

    Wojciechowska, Agnieszka, E-mail: agnieszka.wojciechowska@pwr.edu.pl [Faculty of Chemistry, Wroclaw University of Technology, Wybrzeze Wyspiańskiego 27, 50-370, Wrocław (Poland); Kochel, Andrzej [Faculty of Chemistry, University of Wroclaw, F. Joliot-Curie 14, 50-383, Wrocław (Poland); Duczmal, Marek [Faculty of Chemistry, Wroclaw University of Technology, Wybrzeze Wyspiańskiego 27, 50-370, Wrocław (Poland)

    2016-10-01

    The reaction of L-arginine and oxalate ions with copper(II) salts yields a new complex with formula of [Cu(L-Arg){sub 2}(H{sub 2}O)]·C{sub 2}O{sub 4}·6H{sub 2}O (1) (where L-Arg = L-arginine). Single crystals of 1 were synthesized by crystallization from aqueous solution. The complex properties were characterized by X-ray diffraction, spectroscopy (FT-IR, FT-Raman, NIR-Vis-UV and EPR) as well as thermal and magnetic methods. The square pyramidal (SP) geometry around Cu(II) ions in [Cu(L-Arg){sub 2}(H{sub 2}O)]{sup 2+} cation complex is formed by two cis-chelated L-arginine zwitterions and a water molecule coordinated in the apex of square pyramid. The trigonality distortion of SP geometry is relatively small, τ = 0.0087. The solid state EPR spectrum showed broad hyperfine splitting with g{sub ⊥} = 2.061 at 77 K. The copper centres distanced at 7.558(5) Å are joined in a single zig-zag structure via a chain based on the combination of Cu−O(5)−H(29)⋯O(2)−C1−O1−Cu hydrogen bonds along the b axis (d (O2⋯O5) = 2.812 Å). Taking into account the structural features, the magnetic susceptibility data were best-fitted, giving the exchange parameter J = −0.16 cm{sup −1}. Complex 1 is thermally stable up to 66 °C, where it was observed to lose the crystallization water molecules with an 11.7% mass loss (calc. 11.5%). - Highlights: • Crystal and molecular structure of [Cu(L-Arg){sub 2}(H{sub 2}O)]C{sub 2}O{sub 4}·6H{sub 2}O crystals have been studied. • The magnetic interactions of Cu(II) centres are assisted by the formation of single zig-zag chain. • Role of oxalate ions in completed relatively small square pyramid distortion is described. • The cis-fashioned L-arginine created the stronger ligand field than trans-configuration.

  13. Energy centre microgrid model

    Energy Technology Data Exchange (ETDEWEB)

    Pasonen, R.

    2011-09-15

    A simulation model of Energy centre microgrid made with PSCAD simulation software version 4.2.1 has been built in SGEM Smart Grids and Energy Markets (SGEM) work package 6.6. Microgrid is an autonomous electric power system which can operate separate from common distribution system. The idea of energy centre microgrid concept was considered in Master of Science thesis 'Community Microgrid - A Building block of Finnish Smart Grid'. The name of energy centre microgrid comes from a fact that production and storage units are concentrated into a single location, an energy centre. This centre feeds the loads which can be households or industrial loads. Power direction flow on the demand side remains same compared to the current distribution system and allows to the use of standard fuse protection in the system. The model consists of photovoltaic solar array, battery unit, variable frequency boost converter, inverter, isolation transformer and demand side (load) model. The model is capable to automatically switch to islanded mode when there is a fault in outside grid and back to parallel operation mode when fault is removed. The modelled system responses well to load changes and total harmonic distortion related to 50Hz base frequency is kept under 1.5% while operating and feeding passive load. (orig.)

  14. Green biosynthesis of biocompatible CdSe quantum dots in living Escherichia coli cells

    International Nuclear Information System (INIS)

    Yan, Zhengyu; Qian, Jing; Su, Yilong; Ai, Xiaoxia; Wu, Shengmei; Gu, Yueqing

    2014-01-01

    A green and efficient biosynthesis method to prepare fluorescence-tunable biocompatible cadmium selenide quantum dots using Escherichia coli cells as biological matrix was proposed. Decisive factors in biosynthesis of cadmium selenide quantum dots in a designed route in Escherichia coli cells were elaborately investigated, including the influence of the biological matrix growth stage, the working concentration of inorganic reactants, and the co-incubation duration of inorganic metals to biomatrix. Ultraviolet-visible, photoluminescence, and inverted fluorescence microscope analysis confirmed the unique optical properties of the biosynthesized cadmium selenide quantum dots. The size distribution of the nanocrystals extracted from cells and the location of nanocrystals foci in vivo were also detected seriously by transmission electron microscopy. A surface protein capping layer outside the nanocrystals was confirmed by Fourier transform infrared spectroscopy measurements, which were supposed to contribute to reducing cytotoxicity and maintain a high viability of cells when incubating with quantum dots at concentrations as high as 2 μM. Cell morphology observation indicated an effective labeling of living cells by the biosynthesized quantum dots after a 48 h co-incubation. The present work demonstrated an economical and environmentally friendly approach to fabricating highly fluorescent quantum dots which were expected to be an excellent fluorescent dye for broad bio-imaging and labeling. (papers)

  15. Facile hydrothermal synthesis of polyhedral Fe{sub 3}O{sub 4} nanocrystals, influencing factors and application in the electrochemical detection of H{sub 2}O{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Yuan Kefeng [College of Chemistry and Materials Science, Anhui Key Laboratory of Functional Molecular Solids, Anhui Normal University, Wuhu 241000 (China); Ni Yonghong, E-mail: niyh@mail.ahnu.edu.cn [College of Chemistry and Materials Science, Anhui Key Laboratory of Functional Molecular Solids, Anhui Normal University, Wuhu 241000 (China); Zhang Li [College of Chemistry and Materials Science, Anhui Key Laboratory of Functional Molecular Solids, Anhui Normal University, Wuhu 241000 (China)

    2012-08-15

    Highlights: Black-Right-Pointing-Pointer Fe{sub 3}O{sub 4} polyhedra had been successfully synthesized by a facile hydrothermal technology. Black-Right-Pointing-Pointer The as-obtained product exhibited the room-temperature ferrimagnetic property. Black-Right-Pointing-Pointer The final product could be prepared into an electrochemical sensor for the detection of H{sub 2}O{sub 2}. - Abstract: Polyhedral Fe{sub 3}O{sub 4} nanocrystals have been successfully synthesized by a facile hydrothermal technique, employing FeSO{sub 4}{center_dot}7H{sub 2}O, N{sub 2}H{sub 4} and NH{sub 3}{center_dot}H{sub 2}O as the reactants without the assistance of any surfactant. The phase of the as-obtained Fe{sub 3}O{sub 4} was characterized by X-ray powder diffraction (XRD) and further proved by Rietveld refinement of XRD data. Energy dispersive spectrometry (EDS) and scanning electron microscopy (SEM) were used for the composition and morphology analyses of the final product. Some factors influencing the formation of polyhedral Fe{sub 3}O{sub 4} nanocrystals were systematically investigated, including the reaction temperature and time, and the original volume ratio of NH{sub 3}{center_dot}H{sub 2}O/N{sub 2}H{sub 4}{center_dot}H{sub 2}O. It was found that the as-prepared Fe{sub 3}O{sub 4} polyhedra exhibited a good electrochemical property in 0.1 M phosphate buffer solution (PBS) with pH 7.0 and could be prepared into an electrochemical sensor for the detection of H{sub 2}O{sub 2}. The linear response range of the sensor was 10.0 Multiplication-Sign 10{sup -6} to 140.0 Multiplication-Sign 10{sup -6} M and a sensitivity was 11.05 {mu}A/mM. Furthermore, the room-temperature magnetic property of the product was also investigated.

  16. From micro- to nanomagnetic dots: evolution of the eigenmode spectrum on reducing the lateral size

    International Nuclear Information System (INIS)

    Carlotti, G; Madami, M; Gubbiotti, G; Tacchi, S; Hartmann, F; Emmerling, M; Kamp, M; Worschech, L

    2014-01-01

    Brillouin light scattering experiments and micromagnetic simulations have been exploited to investigate the spectrum of thermally excited magnetic eigenmodes in 10 nm-thick elliptical Permalloy dots, when the longer axis D is scaled down from about 1000 to 100 nm. It is shown that for D larger than about 200 nm the characteristics of the spin-wave eigenmodes are dominated by dipolar energy, while for D in the range of about 100 to 200 nm exchange energy effects cause qualitative and quantitative differences in the spin-wave spectrum. In this ‘mesoscopic’ regime, the usual classification scheme, involving one fundamental mode with large average magnetization and many other modes collected in families with specific symmetries, no longer holds. Rather, one finds the simultaneous presence of two modes with ‘fundamental’ character, i.e. with a significant and comparable value of the average dynamical magnetization: the former is at larger frequency and has its maximum amplitude at the dot's centre, while the latter occurs at lower frequency and is localized at the dot's edges. Interestingly, the maximum intensity swaps from the higher frequency mode to the lower frequency one, just when the dot size is reduced from about 200 to 100 nm. This is relevant in view of the exploitation of nanodots for the design of nanomagnetic devices with lateral dimensions in the above interval, such as memory cells, logic gates, reading heads and spin-torque oscillators. (paper)

  17. From micro- to nanomagnetic dots: evolution of the eigenmode spectrum on reducing the lateral size

    Science.gov (United States)

    Carlotti, G.; Gubbiotti, G.; Madami, M.; Tacchi, S.; Hartmann, F.; Emmerling, M.; Kamp, M.; Worschech, L.

    2014-07-01

    Brillouin light scattering experiments and micromagnetic simulations have been exploited to investigate the spectrum of thermally excited magnetic eigenmodes in 10 nm-thick elliptical Permalloy dots, when the longer axis D is scaled down from about 1000 to 100 nm. It is shown that for D larger than about 200 nm the characteristics of the spin-wave eigenmodes are dominated by dipolar energy, while for D in the range of about 100 to 200 nm exchange energy effects cause qualitative and quantitative differences in the spin-wave spectrum. In this ‘mesoscopic’ regime, the usual classification scheme, involving one fundamental mode with large average magnetization and many other modes collected in families with specific symmetries, no longer holds. Rather, one finds the simultaneous presence of two modes with ‘fundamental’ character, i.e. with a significant and comparable value of the average dynamical magnetization: the former is at larger frequency and has its maximum amplitude at the dot's centre, while the latter occurs at lower frequency and is localized at the dot's edges. Interestingly, the maximum intensity swaps from the higher frequency mode to the lower frequency one, just when the dot size is reduced from about 200 to 100 nm. This is relevant in view of the exploitation of nanodots for the design of nanomagnetic devices with lateral dimensions in the above interval, such as memory cells, logic gates, reading heads and spin-torque oscillators.

  18. Stark shifting two-electron quantum dot

    International Nuclear Information System (INIS)

    Dineykhan, M.; Zhaugasheva, S.A.; Duysebaeva, K.S.

    2003-01-01

    Advances in modern technology make it possible to create semiconducting nano-structures (quantum dot) in which a finite number of electrons are 'captured' in a bounded volume. A quantum dot is associated with a quantum well formed at the interface, between two finite-size semiconductors owing to different positions of the forbidden gaps on the energy scale in these semiconductors. The possibility of monitoring and controlling the properties of quantum dots attracts considerable attention to these objects, as a new elemental basis for future generations of computers. The quantum-mechanical effects and image potential play a significant role in the description of the formation mechanism quantum dot, and determined the confinement potential in a two-electron quantum dot only for the spherical symmetric case. In the present talk, we considered the formation dynamics of two-electron quantum dot with violation of spherical symmetry. So, we have standard Stark potential. The energy spectrum two-electron quantum dot were calculated. Usually Stark interactions determined the tunneling phenomena between quantum dots

  19. Hydrogenic impurity in double quantum dots

    International Nuclear Information System (INIS)

    Wang, X.F.

    2007-01-01

    The ground state binding energy and the average interparticle distances for a hydrogenic impurity in double quantum dots with Gaussian confinement potential are studied by the variational method. The probability density of the electron is calculated, too. The dependence of the binding energy on the impurity position is investigated for GaAs quantum dots. The result shows that the binding energy has a minimum as a function of the distance between the two quantum dots when the impurity is located at the center of one quantum dot or at the center of the edge of one quantum dot. When the impurity is located at the center of the two dots, the binding energy decreases monotonically

  20. Synthesis and optical properties of core-multi-shell CdSe/CdS/ZnS quantum dots: Surface modifications

    Science.gov (United States)

    Ratnesh, R. K.; Mehata, Mohan Singh

    2017-02-01

    We report two port synthesis of CdSe/CdS/ZnS core-multi-shell quantum dots (Q-dots) and their structural properties. The multi-shell structures of Q-dots were developed by using successive ionic layer adsorption and reaction (SILAR) technique. The obtained Q-dots show high crystallinity with the step-wise adjustment of lattice parameters in the radial direction. The size of the core and core-shell Q-dots estimated by transmission electron microscopy images and absorption spectra is about 3.4 and 5.3 nm, respectively. The water soluble Q-dots (scheme-1) were prepared by using ligand exchange method, and the effect of pH was discussed regarding the variation of quantum yield (QY). The decrease of a lifetime of core-multi-shell Q-dots with respect to core CdSe indicates that the shell growth may be tuned by the lifetimes. Thus, the study clearly demonstrates that the core-shell approach can be used to substantially improve the optical properties of Q-dots desired for various applications.

  1. Growth and temperature dependent photoluminescence of InGaAs quantum dot chains

    International Nuclear Information System (INIS)

    Yang, Haeyeon; Kim, Dong-Jun; Colton, John S.; Park, Tyler; Meyer, David; Jones, Aaron M.; Thalman, Scott; Smith, Dallas; Clark, Ken; Brown, Steve

    2014-01-01

    Highlights: • We examine the optical properties of novel quantum dot chains. • Study shows that platelets evolve into quantum dots during heating of the InGaAs platelets encapsulated with GaAs. • Single stack of quantum dots emits light at room temperature. • Quantum dots are of high quality, confirmed by cross-section TEM images and photoluminescence. • Light emission at room temperature weakens beyond the detection limit when the quantum dots form above the critical annealing temperature. - Abstract: We report a study of growth and photoluminescence from a single stack of MBE-grown In 0.4 Ga 0.6 As quantum dot chains. The InGaAs epilayers were grown at a low temperature so that the resulting surfaces remain flat with platelets even though their thicknesses exceed the critical thickness of the conventional Stranski–Krastanov growth mode. The flat InGaAs layers were then annealed at elevated temperatures to induce the formation of quantum dot chains. A reflection high energy electron diffraction study suggests that, when the annealing temperature is at or below 480 °C, the surface of growth front remains flat during the periods of annealing and growth of a 10 nm thick GaAs capping layer. Surprisingly, transmission electron microscopy images do indicate the formation of quantum dot chains, however, so the dot-chains in those samples may form from precursory platelets during the period of temperature ramping and subsequent capping with GaAs due to intermixing of group III elements. The optical emission from the quantum dot layer demonstrates that there is a critical annealing temperature of 480–500 °C above which the properties of the low temperature growth approach are lost, as the optical properties begin to resemble those of quantum dots produced by the conventional Stranski–Krastanov technique

  2. Purification processes of cadmium based quantum dots in aqueous medium: a comparative study

    Science.gov (United States)

    Petris, Dimitri; Freitas, Denilson V.; dos Santos, Rayany K. V.; Dias, Jéssica M. M.; Navarro, Marcelo

    2017-07-01

    Three different purification methods for CdTe-MPA quantum dot (QD) were performed in aqueous medium: acid titration (HCl, HClO4, H2SO4 and CH3COOH), non-selective precipitation by addition of acetone and co-precipitation of the QD in the presence of inorganic salts. The QD stock solutions were prepared by an electrochemical method of synthesis, in four different heating times (1 h, 4 h, 8 h and 12 h). After purifications, the QD solids were redispersed in distilled water and analyzed by absorption and emission spectra. The λ abs and λ em of the purified QDs showed similar data observed for QD stock solutions, and the recovery rate varied from 71% to 99%. Co-precipitation method showed some advantages: quantum yield maintenance of the QD redispersed solution, longer period of storage (over 6 months) in solution and in solid state (QD embedded into the KCl crystal lattice). CdSe-MPA and CdS-MPA solutions were also purified by co-precipitation method with KCl, showing good results as observed for CdTe-MPA.

  3. Infrared Colloidal Quantum Dots for Photovoltaics: Fundamentals and Recent Progress

    KAUST Repository

    Tang, Jiang; Sargent, Edward H.

    2010-01-01

    of the solar radiation enable potential efficient and low-cost photovoltaic devices. Careful optimization of quantum dot passivation and device configuration leads to solar cells with AM1.5G efficiency as high as 5.1% Copyright © 2011 WILEY-VCH Verlag GmbH & Co

  4. Differential expression gene profiling in human lymphocyte after 6 h irradiated

    International Nuclear Information System (INIS)

    Li Jianguo; Qin Xiujun; Zhang Wei; Xu Chaoqi; Li Weibin; Dang Xuhong; Zuo Yahui

    2011-01-01

    Objective: To provide the evidence of health damage for the staff irradiated from the gene level. Methods: The study analyzed the differential transcriptional profile of normal human lymphocyte and human lymphocyte irradiated with 0.1 Gy, 0.2 Gy, 0.5 Gy, 1.0 Gy by whole genome chip after 6 h irradiated. Results: The results showed that there were 1177 differentially expressed genes with 0.1 Gy after 6 h irradiation, and there were 1922 differentially expressed genes with 0.2 Gy after 6 h irradiation, and there were 492 differentially expressed genes with 0.5 Gy after 6 h irradiation, 2615 differentially expressed genes with 1.0 Gy after 6 h irradiation, 114 differentially expressed genes in 4 dose points after 6 h irradiation. RT-PCR results indicated that the relative quantity's result of EGR1, HLA-DMB and TAIAP1 was consistent with gene chip data. Conclusion: The study found many significant different genes in human lymphocyte with different doses after 6 h irradiation, which will provide a basis for the further radiation-different-genes and the mechanism of radiation damage. (authors)

  5. Synthesis of (R)-5-(Di[2,3-3H2]propylamino)-5,6-dihydro-4H-imidazo[4,5,1-ij]quinolin-2(1H)-one-([3H]U-86170) and (R)-5-([2,3-3H2]propylamino)-5,6-dihydro-4H-imidazo(4,5,1-ij) quinolin-2(1H)-one ([3H]U-91356)

    International Nuclear Information System (INIS)

    Moon, M.W.; Hsi, R.S.P.

    1992-01-01

    (R)-5-(diallylamino)-5,6-dihydro-4H-imidazo[4,5,1-ij]quinolin-2(1H)-one (12b) was prepared in 9% overall yield from 3-aminoquinoline. Reaction of 12b in ethyl acetate with tritium gas in presence of a 5% platinum on carbon catalyst afforded a mixture of (R)-5-(di[2,3- 3 H 2 ]propylamino)-5,6-dihydro-4H-imidazo[4,5,1-ij]-quinolin-2(1H)-one ([ 3 H]U-86170, 69 Ci/mmol) and (R)-5-([2,3- 3 H 2 ]-propylamino)5,6-dihydro-4H-imidazo-[4,5,1-ij]quinolin-2(1H)-one ( [ 3 H]U-91356, 34 Ci/mmol) which was separated by preparative reverse-phase chromatography. U-86170 and U-91356 are potent dopamine D2 agonists. The labelled compounds are useful for drug disposition studies. [ 3 H]U-86170 is also useful as a dopamine D2 agonist radioligand for receptor binding studies. (author)

  6. Colour centres in germanosilicate glass and optical fibres

    International Nuclear Information System (INIS)

    Neustruev, V.B.

    1994-01-01

    This review presents the state of the art of the study of germanium-related colour centres in silica glass and silica-based fibres. Most attention is concentrated on the dominant colour centres such as the Ge-related oxygen-deficient centres and paramagnetic Ge(n) centres, all of them having ultraviolet absorption bands. The hypothetical models and formation mechanisms proposed so far for these colour centres are discussed in detail. The origins of the models and formation mechanisms and their weak and strong points are analysed. The origin of the less well studied Ge-related colour centres in the visible spectral range (GeH, GeX, drawing-dependent defects) is also discussed. (author)

  7. Quantum Dot Systems: a versatile platform for quantum simulations

    International Nuclear Information System (INIS)

    Barthelemy, Pierre; Vandersypen, Lieven M.K.

    2013-01-01

    Quantum mechanics often results in extremely complex phenomena, especially when the quantum system under consideration is composed of many interacting particles. The states of these many-body systems live in a space so large that classical numerical calculations cannot compute them. Quantum simulations can be used to overcome this problem: complex quantum problems can be solved by studying experimentally an artificial quantum system operated to simulate the desired hamiltonian. Quantum dot systems have shown to be widely tunable quantum systems, that can be efficiently controlled electrically. This tunability and the versatility of their design makes them very promising quantum simulators. This paper reviews the progress towards digital quantum simulations with individually controlled quantum dots, as well as the analog quantum simulations that have been performed with these systems. The possibility to use large arrays of quantum dots to simulate the low-temperature Hubbard model is also discussed. The main issues along that path are presented and new ideas to overcome them are proposed. (copyright 2013 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Colloidal quantum dot solids for solution-processed solar cells

    KAUST Repository

    Yuan, Mingjian

    2016-02-29

    Solution-processed photovoltaic technologies represent a promising way to reduce the cost and increase the efficiency of solar energy harvesting. Among these, colloidal semiconductor quantum dot photovoltaics have the advantage of a spectrally tuneable infrared bandgap, which enables use in multi-junction cells, as well as the benefit of generating and harvesting multiple charge carrier pairs per absorbed photon. Here we review recent progress in colloidal quantum dot photovoltaics, focusing on three fronts. First, we examine strategies to manage the abundant surfaces of quantum dots, strategies that have led to progress in the removal of electronic trap states. Second, we consider new device architectures that have improved device performance to certified efficiencies of 10.6%. Third, we focus on progress in solution-phase chemical processing, such as spray-coating and centrifugal casting, which has led to the demonstration of manufacturing-ready process technologies.

  9. Structure and phase transitions of the 6,6-cyclopropane isomer of C61H2

    International Nuclear Information System (INIS)

    Stetzer, M.R.; Heiney, P.A.; Stephens, P.W.; Dinnebier, R.E.; Zhu, Q.; McGhie, A.R.; Strongin, R.M.; Brandt, B.M.; Smith, A.B. III

    2000-01-01

    We have used x-ray powder diffraction and differential scanning calorimetry to study the crystalline structures and thermal behavior of the 6,6-cyclopropane isomer of C 61 H 2 . At room temperature, the C 61 H 2 cyclopropane molecules, like those of the 6,5-annulene isomer and C 60 O epoxide, are orientationally disordered and crystallize on a face-centered-cubic lattice such that their methylene groups are statistically disordered among the octahedral voids. Unlike 6,5-C 61 H 2 and C 60 O, the low-temperature structure is not Pa3-bar, but rather a low-symmetry orthorhombic lattice in which a≅b< c. The orientational melting takes place via a two-step transition centered around 198-213 K

  10. A 2x2 quantum dot array with controllable inter-dot tunnel couplings

    OpenAIRE

    Mukhopadhyay, Uditendu; Dehollain, Juan Pablo; Reichl, Christian; Wegscheider, Werner; Vandersypen, Lieven M. K.

    2018-01-01

    The interaction between electrons in arrays of electrostatically defined quantum dots is naturally described by a Fermi-Hubbard Hamiltonian. Moreover, the high degree of tunability of these systems make them a powerful platform to simulate different regimes of the Hubbard model. However, most quantum dot array implementations have been limited to one-dimensional linear arrays. In this letter, we present a square lattice unit cell of 2$\\times$2 quantum dots defined electrostatically in a AlGaA...

  11. Stochastic simulation of thermally assisted magnetization reversal in sub-100 nm dots with perpendicular anisotropy

    International Nuclear Information System (INIS)

    Purnama, Budi; Koga, Masashi; Nozaki, Yukio; Matsuyama, Kimihide

    2009-01-01

    Thermally assisted magnetization reversal of sub-100 nm dots with perpendicular anisotropy has been investigated using a micromagnetic Langevin model. The performance of the two different reversal modes of (i) a reduced barrier writing scheme and (ii) a Curie point writing scheme are compared. For the reduced barrier writing scheme, the switching field H swt decreases with an increase in writing temperature but is still larger than that of the Curie point writing scheme. For the Curie point writing scheme, the required threshold field H th , evaluated from 50 simulation results, saturates at a value, which is not simply related to the energy barrier height. The value of H th increases with a decrease in cooling time owing to the dynamic aspects of the magnetic ordering process. Dependence of H th on material parameters and dot sizes has been systematically studied

  12. Systems Li[sub 2]B[sub 4]O[sub 7] (Na[sub 2]B[sub 4]O[sub 7], K[sub 2]B[sub 4]O[sub 7])-N[sub 2]H[sub 3]H[sub 4]OH-H[sub 2]O at 25 deg C. Sistemy Li[sub 2]B[sub 4]O[sub 7] (Na[sub 2]B[sub 4]O[sub 7], K[sub 2]B[sub 4]O[sub 7])-N[sub 2]H[sub 3]H[sub 4]OH-H[sub 2]O pri 25 grad S

    Energy Technology Data Exchange (ETDEWEB)

    Skvortsov, V G; Sadetdinov, Sh V; Akimov, V M; Mitrasov, Yu N; Petrova, O V; Klopov, Yu N [Chuvashskij Gosudarstvennyj Pedagogicheskij Inst., Cheboksary (Russian Federation) Universitet Druzhby Narodov, Moscow (Russian Federation)

    1994-02-01

    Phase equilibriums in the Li[sub 2]B[sub 4]O[sub 7] (Na[sub 2]B[sub 4]O[sub 7], K[sub 2]B[sub 4]O[sub 7])-N[sub 2]H[sub 3]H[sub 4]OH-H[sub 2]O systems were investigated by methods of isothermal solubility, refractometry and PH-metry at 25 deg C for the first time. Lithium and sodium tetraborates was established to form phases of changed composition mM[sub 2]B[sub 4]O[sub 7][center dot]nN[sub 2]H[sub 3]C[sub 2]H[sub 4]OH[center dot]XH[sub 2]O, where M=Li, Na with hydrazine ethanol. K[sub 2]B[sub 4]O[sub 7][center dot]4H[sub 2]O precipitates in solid phase in the case of potassium salt. Formation of isomorphous mixtures was supported by X-ray diffraction and IR spectroscopy methods.

  13. Perspective: The future of quantum dot photonic integrated circuits

    Directory of Open Access Journals (Sweden)

    Justin C. Norman

    2018-03-01

    Full Text Available Direct epitaxial integration of III-V materials on Si offers substantial manufacturing cost and scalability advantages over heterogeneous integration. The challenge is that epitaxial growth introduces high densities of crystalline defects that limit device performance and lifetime. Quantum dot lasers, amplifiers, modulators, and photodetectors epitaxially grown on Si are showing promise for achieving low-cost, scalable integration with silicon photonics. The unique electrical confinement properties of quantum dots provide reduced sensitivity to the crystalline defects that result from III-V/Si growth, while their unique gain dynamics show promise for improved performance and new functionalities relative to their quantum well counterparts in many devices. Clear advantages for using quantum dot active layers for lasers and amplifiers on and off Si have already been demonstrated, and results for quantum dot based photodetectors and modulators look promising. Laser performance on Si is improving rapidly with continuous-wave threshold currents below 1 mA, injection efficiencies of 87%, and output powers of 175 mW at 20 °C. 1500-h reliability tests at 35 °C showed an extrapolated mean-time-to-failure of more than ten million hours. This represents a significant stride toward efficient, scalable, and reliable III-V lasers on on-axis Si substrates for photonic integrate circuits that are fully compatible with complementary metal-oxide-semiconductor (CMOS foundries.

  14. Perspective: The future of quantum dot photonic integrated circuits

    Science.gov (United States)

    Norman, Justin C.; Jung, Daehwan; Wan, Yating; Bowers, John E.

    2018-03-01

    Direct epitaxial integration of III-V materials on Si offers substantial manufacturing cost and scalability advantages over heterogeneous integration. The challenge is that epitaxial growth introduces high densities of crystalline defects that limit device performance and lifetime. Quantum dot lasers, amplifiers, modulators, and photodetectors epitaxially grown on Si are showing promise for achieving low-cost, scalable integration with silicon photonics. The unique electrical confinement properties of quantum dots provide reduced sensitivity to the crystalline defects that result from III-V/Si growth, while their unique gain dynamics show promise for improved performance and new functionalities relative to their quantum well counterparts in many devices. Clear advantages for using quantum dot active layers for lasers and amplifiers on and off Si have already been demonstrated, and results for quantum dot based photodetectors and modulators look promising. Laser performance on Si is improving rapidly with continuous-wave threshold currents below 1 mA, injection efficiencies of 87%, and output powers of 175 mW at 20 °C. 1500-h reliability tests at 35 °C showed an extrapolated mean-time-to-failure of more than ten million hours. This represents a significant stride toward efficient, scalable, and reliable III-V lasers on on-axis Si substrates for photonic integrate circuits that are fully compatible with complementary metal-oxide-semiconductor (CMOS) foundries.

  15. Conjugated polymer dots for ultra-stable full-color fluorescence patterning.

    Science.gov (United States)

    Chang, Kaiwen; Liu, Zhihe; Chen, Haobin; Sheng, Lan; Zhang, Sean Xiao-An; Chiu, Daniel T; Yin, Shengyan; Wu, Changfeng; Qin, Weiping

    2014-11-12

    Stable full-color fluorescence patterning are achieved by multicolor polymer-dot inks. The fluorescent patterns show extraordinary stability upon various treatments, offering a superior combination of bright fluorescence, excellent photostability, chemical resistance, and eco-friendship. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Ratiometric, visual, dual-signal fluorescent sensing and imaging of pH/copper ions in real samples based on carbon dots-fluorescein isothiocyanate composites.

    Science.gov (United States)

    Zhu, Xinxin; Jin, Hui; Gao, Cuili; Gui, Rijun; Wang, Zonghua

    2017-01-01

    In this article, a facile aqueous synthesis of carbon dots (CDs) was developed by using natural kelp as a new carbon source. Through hydrothermal carbonization of kelp juice, fluorescent CDs were prepared and the CDs' surface was modified with polyethylenimine (PEI). The PEI-modified CDs were conjugated with fluorescein isothiocyanate (FITC) to fabricate CDs-FITC composites. To exploit broad applications, the CDs-FITC composites were developed as fluorescent sensing or imaging platforms of pH and Cu 2+ . Analytical performances of the composites-based fluorescence (FL) sensors were evaluated, including visual FL imaging of pH in glass bottle, ratiometric FL sensing of pH in yogurt samples, visual FL latent fingerprint and leaf imaging detection of [Cu 2+ ], dual-signal FL sensing of [Cu 2+ ] in yogurt and human serum samples. Experimental results from ratiometric, visual, dual-signal FL sensing and imaging applications confirmed the high feasibility, accuracy, stabilization and simplicity of CDs-FITC composites-based FL sensors for the detection of pH and Cu 2+ ions in real samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Room-temperature light-emission from Ge quantum dots in photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Xia Jinsong [Advanced Research Laboratories, Musashi Institute of Technolgy, 8-15-1 Todoroki, Setagaya-ku, Tokyo 158-0082 (Japan)], E-mail: jxia@sc.musashi-tech.ac.jp; Nemoto, Koudai; Ikegami, Yuta [Advanced Research Laboratories, Musashi Institute of Technolgy, 8-15-1 Todoroki, Setagaya-ku, Tokyo 158-0082 (Japan); Usami, Noritaka [Institute of Materials Research, Tohoku University, 2-2-1 Katahira, Aoba-ku, Sendai Japan (Japan)], E-mail: usa@imr.tohoku.ac.jp; Nakata, Yasushi [Horiba, Ltd., 1-7-8 Higashi-Kanda, Chiyoda-ku, Tokyo 101-0031 (Japan)], E-mail: yasushi.nakata@horiba.com; Shiraki, Yasuhiro [Advanced Research Laboratories, Musashi Institute of Technolgy, 8-15-1 Todoroki, Setagaya-ku, Tokyo 158-0082 (Japan)

    2008-11-03

    Multiple layers of Ge self-assembled quantum dots were embedded into two-dimensional silicon photonic crystal microcavities fabricated on silicon-on-insulator substrates. Microphotoluminescence was used to study the light-emission characteristic of the Ge quantum dots in the microcavities. Strong resonant room-temperature light-emission was observed in the telecommunication wavelength region. Significant enhancement of the luminescence from Ge dots was obtained due to the resonance in the cavities. Multiple sharp resonant peaks dominated the spectrum, showing strong optical resonance inside the cavity. By changing the lattice constant of photonic crystal structure, the wavelengths of the resonant peaks are tuned in the wide wavelength range from 1.2 to 1.6 {mu}m.

  18. The lowest 5g-6h supermultiplet of Fe II

    International Nuclear Information System (INIS)

    Biemont, E.; Palmeri, P.

    1997-01-01

    The 3d 6 ( 5 D)6h subconfiguration of Fe II is established by means of 74 newly identified 5g-6h transitions. These lines are observed in a Fourier-transform spectrum of iron emitted from a hollow-cathode discharge in the region 5350-5410 cm -1 . The application of the ''quadrupolic'' approximation shows that the JK coupling is well represented in the 3d 6 6h configuration. The identification of the lines in the spectra was facilitated by the comparison of the observed intensities with oscillator strengths calculated in the framework of the relativistic Hartree-Fock (HFR) approximation and also by consideration of the full width at half maximum (FWHM) of the profiles. (orig.)

  19. Dicke states in multiple quantum dots

    Science.gov (United States)

    Sitek, Anna; Manolescu, Andrei

    2013-10-01

    We present a theoretical study of the collective optical effects which can occur in groups of three and four quantum dots. We define conditions for stable subradiant (dark) states, rapidly decaying super-radiant states, and spontaneous trapping of excitation. Each quantum dot is treated like a two-level system. The quantum dots are, however, realistic, meaning that they may have different transition energies and dipole moments. The dots interact via a short-range coupling which allows excitation transfer across the dots, but conserves the total population of the system. We calculate the time evolution of single-exciton and biexciton states using the Lindblad equation. In the steady state the individual populations of each dot may have permanent oscillations with frequencies given by the energy separation between the subradiant eigenstates.

  20. Utilizing a CdTe quantum dots-enzyme hybrid system for the determination of both phenolic compounds and hydrogen peroxide.

    Science.gov (United States)

    Yuan, Jipei; Guo, Weiwei; Wang, Erkang

    2008-02-15

    In this paper, we attempt to construct a simple and sensitive detection method for both phenolic compounds and hydrogen peroxide, with the successful combination of the unique property of quantum dots and the specificity of enzymatic reactions. In the presence of H2O2 and horseradish peroxidase, phenolic compounds can quench quantum dots' photoluminescence efficiently, and the extent of quenching is severalfold to more than 100-fold increase. Quinone intermediates produced from the enzymatic catalyzed oxidation of phenolic compounds were believed to play the main role in the photoluminescence quenching. Using a quantum dots-enzyme system, the detection limits for phenolic compounds and hydrogen peroxide were detected to be approximately 10(-7) mol L(-1). The coupling of efficient quenching of quantum dot photoluminescence by quinone and the effective enzymatic reactions make this a simple and sensitive method for phenolic compound detection and great potential in the development of H2O2 biosensors for various analytes.

  1. Optical properties and the use of CdSe quantum dot for biolabeling applications

    International Nuclear Information System (INIS)

    Tran Hong Nhung; Nguyen Thi Van; Vu Xuan Hoa; Pham Minh Tan; Tong Kim Thuan; Tran Thi Thu Thuy; Jean Claude Brochon; Patrick Tauc

    2008-01-01

    The quantum dots CdSe type Qtracker 565 and 605 of Quantum Dot Company have been investigated by size, chemical structure and optical properties. The Qtracker 605 QDs were introduced into Lipomyces Starkeyi yeast cells. It was found that for the young cells (36 h of culture), the labeling QDs are mainly located in vacuoles, and the emission remains narrow with the maximum is clearly around 605 nm. For age cells (96 h of culture), the labeling QDs are concentrated in the cell cytoplasm, the emission is broaden with the maximum shifted to 580 nm. The live cell image was still observed after two months of introduction. The Qtracker 605 QDs were also successfully introduced into mouse blood cancerous cells. (author)

  2. Investigation of carrier dynamics in InAs/GaAsSb quantum dots with different silicon delta-doping levels

    Energy Technology Data Exchange (ETDEWEB)

    Ban, Keun-Yong [Arizona State Univ., Tempe, AZ (United States). School of Electrical, Computer and Energy Engineering; Kim, Yeongho [Korea Research Inst. of Chemistry Technology (KRICT), Daejeon (Korea, Republic of). Division of Metrology for Future Technology; Kuciauskas, Darius [National Renewable Energy Lab. (NREL), Golden, CO (United States); Bremner, Stephen P. [Univ. of New South Wales, Sydney, NSW (Australia). School of Photovoltaic and Renewable Energy Engineering; Honsberg, Christiana B. [Arizona State Univ., Tempe, AZ (United States). School of Electrical, Computer and Energy Engineering

    2016-11-10

    The optical properties of InAs quantum dots (QDs) embedded in a GaAsSb matrix with different delta (d)-doping levels of 0, 2, 4, and 6 electrons per dot (e-/dot), incorporated to control the occupation of QD electronic states, are studied by photoluminescence (PL) spectroscopy. The time-resolved PL data taken at 10 K reveal that the increase of δ-doping density from 2 to 6 e-/dot decreases the recombination lifetime of carriers at ground states of the QDs from 996 ± 36 to 792 ± 19 ps, respectively. Furthermore, the carrier lifetime of the sample with 4 e-/dot is found to increase at a slower rate than that of the undoped sample as temperature increases above 70 K. An Arrhenius plot of the temperature dependent PL intensity indicates that the thermal activation energy of electrons in the QDs, required for carrier escape from the dot ground state to continuum state, is increased when the d-doping density is high enough (>4 e-/dot). These results are attributed to the enhanced Coulomb interaction of electrons provided by the d-doping, leading to reduced thermal quenching of the PL.

  3. Study of NaBH4 reaction with RhCl3·4H2O and H2PtCl6·6H2O in dimethylformamide

    International Nuclear Information System (INIS)

    Khain, V.S.; Val'kova, V.P.

    1988-01-01

    Data on study of NaBH 4 reactions with RhCl 3 x4H 2 O and H 2 PtCl 6 x6H 2 O in dimethylformamide, which is a good solvent of both complex hydride and compounds of platinum metals are presented. Rhodium (3) and platinum (4) reduction by sodium tetrahydridoborate in dimethylformamide proceeds quantitatively up to element state. Depositions of powder-like rhodium and platinum or their sols stable up to 8 months are formed depending on the ratio of concentrations of the reacting substances. Stoichiometry of redox-reactions is established based on spectrophotometric, gasovolumetric measurements,

  4. Electron stimulated desorption of cations from C sub 6 H sub 6 and C sub 6 H sub 1 sub 2 molecules adsorbed on Pt(1 1 1) and Ar spacer layer

    CERN Document Server

    Kawanowa, H; Hanatani, K; Gotoh, Y; Souda, R

    2003-01-01

    Mechanisms of electron stimulated cation desorption have been investigated for adsorbed C sub 6 H sub 6 and C sub 6 H sub 1 sub 2 molecules on the Pt(1 1 1) surface and the Ar spacer layer formed on it. The ion yields from the molecules adsorbed on the Ar spacer layer are highly enhanced at the smallest coverage and decay steeply with increasing coverage. No such enhancement was observed when they are adsorbed directly on the Pt(1 1 1) substrate. This behavior is explained in terms of the Coulombic repulsion of cations confined in nanoclusters, together with the delocalization of valence holes on the Pt(1 1 1) substrate as well as in the multilayer hydrocarbons. The holes in the C sub 6 H sub 6 molecule are more delocalized than those in the C sub 6 H sub 1 sub 2 molecule due to the overlap of pi orbitals.

  5. Synthesis and characterization of C@CdS dots in aqueous solution and their application in labeling human gastric carcinoma cells

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Wei, E-mail: dongwei5873@126.com [Shenyang Medical College, Department of Chemistry (China); Zhou, Siqi [Fengtian Hospital Affiliated to Shenyang Medical College, ICU (China); Dong, Yan [Shenyang Pharmaceutical University, Experiment Center of Traditional Chinese Medicine Department (China); Wang, Jingwen; Liu, Shuang; Zhu, Pengxia [Shenyang Medical College, Department of Chemistry (China)

    2015-03-15

    Colloidal carbon spheres coated with cadmium sulfide nanoparticle quantum dots (C@CdS dots) with the particle size smaller than 50 nm were synthesized by an aqueous approach. The effects of different reaction times, temperatures, and pH values were carefully investigated to optimize the synthesis conditions. The as-prepared C@CdS dots were linked with mouse anti-human carcinoembryonic antigen antibody and goat anti-mouse immunoglobulin (IgG) to directly and indirectly label fixed human gastric carcinoma cells, respectively. The cytotoxicity of the C@CdS dots was also tested using the human gastric carcinoma cells. No apparent cytotoxicity was observed, which suggested the potential application of the as-prepared C@CdS dots in bioimaging.

  6. DotU and VgrG, core components of type VI secretion systems, are essential for Francisella LVS pathogenicity.

    Directory of Open Access Journals (Sweden)

    Jeanette E Bröms

    Full Text Available The Gram-negative bacterium Francisella tularensis causes tularemia, a disease which requires bacterial escape from phagosomes of infected macrophages. Once in the cytosol, the bacterium rapidly multiplies, inhibits activation of the inflammasome and ultimately causes death of the host cell. Of importance for these processes is a 33-kb gene cluster, the Francisella pathogenicity island (FPI, which is believed to encode a type VI secretion system (T6SS. In this study, we analyzed the role of the FPI-encoded proteins VgrG and DotU, which are conserved components of type VI secretion (T6S clusters. We demonstrate that in F. tularensis LVS, VgrG was shown to form multimers, consistent with its suggested role as a trimeric membrane puncturing device in T6SSs, while the inner membrane protein DotU was shown to stabilize PdpB/IcmF, another T6SS core component. Upon infection of J774 cells, both ΔvgrG and ΔdotU mutants did not escape from phagosomes, and subsequently, did not multiply or cause cytopathogenicity. They also showed impaired activation of the inflammasome and marked attenuation in the mouse model. Moreover, all of the DotU-dependent functions investigated here required the presence of three residues that are essentially conserved among all DotU homologues. Thus, in agreement with a core function in T6S clusters, VgrG and DotU play key roles for modulation of the intracellular host response as well as for the virulence of F. tularensis.

  7. Dot gain compensation in the blue noise mask

    Science.gov (United States)

    Yao, Meng; Parker, Kevin J.

    1995-04-01

    Frequency modulated (FM) halftoning or 'stochastic screening,' has attracted a great deal of attention in the printing industry in recent years. It has several advantages over conventional halftoning. But one serious problem that arises in FM halftoning is dot gain. One approach to stochastic screening uses a specially constructed halftone screen, the blue noise mask (BNM), to produce an unstructured and visually appealing pattern of halftone dots at any gray level. In this paper, we will present methods to correct dot gain with the BNM. Dot gain is related to the area-to-perimeter ration of printed spots. We can exploit this feature in different ways. At a medium level, a B>NM pattern will have 'connected' as well as 'isolated' dots. Normally, as we build down BNM patterns to lower levels, a specific number of white dots will be replace by black dots. Since connected white dots are more likely to be picked than isolated white dots, this will results in substantial dot gain because of the increasing number of isolated white dots. We show that it is possible to constrain the process of constructing a BNM such that isolated dots are preferentially removes, thus significantly reducing dot gain in a BNM.

  8. Effect of hydrogen on change carrier dissipation in 60Co irradiated by γ-quanta and non-alloyed n-type GaAs

    International Nuclear Information System (INIS)

    Korshunov, F.P.; Kurilovich, N.F.; Prokhorenko, T.A.; Shesholko, V.K.; Bumaj, Yu.A.

    2001-01-01

    The pretreatment in hydrogen plasma (the hydrogenation) influences on the charge carrier dissipation processes in the non-alloyed gallium arsenide of n-type with no = (5...7) centre dot 10 15 cm -3 and μo = (5...6) centre dot 10 13 cm 2 / (V centre dot c) irradiated by γ-quantum 60 Co was studied. The comparison of experimental dependence μ (T) with the designed one in the temperature range 77...291 K for non-hydrogenized and hydrogenized non irradiated and γ-quantum irradiated crystals was carried out. It is shown that the main dissipative mechanism that determine the charged carrier mobility in the non hydrogenized material is the dissipation on the charged centers - the radiation defects in the γ-quantum irradiated GaAs; the presence of double ionized defects is possible

  9. Catalytic and peroxidase-like activity of carbon based-AuPd bimetallic nanocomposite produced using carbon dots as the reductant

    International Nuclear Information System (INIS)

    Yang, Liuqing; Liu, Xiaoying; Lu, Qiujun; Huang, Na; Liu, Meiling; Zhang, Youyu; Yao, Shouzhuo

    2016-01-01

    In this report, carbon-based AuPd bimetallic nanocomposite (AuPd/C NC) was synthesized using carbon dots (C-dots) as the reducing agent and stabilizer by a simple green sequential reduction strategy, without adding other agents. The as synthesized AuPd/C NC showed good catalytic activity and peroxidase-like property. The structure and morphology of these nanoparticles were clearly characterized by UV–Vis spectroscopy, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The AuPd/C NC catalyst exhibits noticeably higher catalytic activity than Pd and Au nanoparticles in catalysis reduction of 4-nitrophenol (4-NP). Moreover, based on the high peroxidase-like property of AuPd/C NC, a new colorimetric detection method for hydrogen peroxide (H 2 O 2 ) has been designed using 3,3′,5,5′-tetramethyl-benzidine (TMB) as the substrate, which provides a simple and sensitive means to detect H 2 O 2 in wide linear range of 5 μM–500 μM and 500 μM–4 mM with low detection limit of 1.6 μM (S/N = 3). Therefore, the facile synthesis strategy for bimetallic nanoparticles by the mild reductant of carbon dot will provide some new thoughts for preparing of carbon-based metal nanomaterials and expand their application in catalysis and analytical chemistry areas. - Highlights: • Carbon-based AuPd bimetallic nanocomposite was synthesized using carbon dots. • The green sequential reduction strategy synthesis method is simple, green, convenient and effective. • The as synthesized AuPd/C NC showed good catalytic activity and peroxidase-like activity. • The AuPd/C NC exhibits noticeably higher catalytic activity in reduction of 4-nitrophenol. • A new colorimetric detection method for hydrogen peroxide based on AuPd/C NC was proposed.

  10. Catalytic and peroxidase-like activity of carbon based-AuPd bimetallic nanocomposite produced using carbon dots as the reductant

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Liuqing [Key Laboratory of Chemical Biology & Traditional Chinese Medicine Research (Ministry of Education, China), College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081 (China); Liu, Xiaoying [College of Science, Science and Technological Innovation Platform, Hunan Agricultural University, Hunan, Changsha 410128 (China); Lu, Qiujun; Huang, Na [Key Laboratory of Chemical Biology & Traditional Chinese Medicine Research (Ministry of Education, China), College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081 (China); Liu, Meiling, E-mail: liumeilingww@126.com [Key Laboratory of Chemical Biology & Traditional Chinese Medicine Research (Ministry of Education, China), College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081 (China); Zhang, Youyu; Yao, Shouzhuo [Key Laboratory of Chemical Biology & Traditional Chinese Medicine Research (Ministry of Education, China), College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081 (China)

    2016-08-03

    In this report, carbon-based AuPd bimetallic nanocomposite (AuPd/C NC) was synthesized using carbon dots (C-dots) as the reducing agent and stabilizer by a simple green sequential reduction strategy, without adding other agents. The as synthesized AuPd/C NC showed good catalytic activity and peroxidase-like property. The structure and morphology of these nanoparticles were clearly characterized by UV–Vis spectroscopy, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The AuPd/C NC catalyst exhibits noticeably higher catalytic activity than Pd and Au nanoparticles in catalysis reduction of 4-nitrophenol (4-NP). Moreover, based on the high peroxidase-like property of AuPd/C NC, a new colorimetric detection method for hydrogen peroxide (H{sub 2}O{sub 2}) has been designed using 3,3′,5,5′-tetramethyl-benzidine (TMB) as the substrate, which provides a simple and sensitive means to detect H{sub 2}O{sub 2} in wide linear range of 5 μM–500 μM and 500 μM–4 mM with low detection limit of 1.6 μM (S/N = 3). Therefore, the facile synthesis strategy for bimetallic nanoparticles by the mild reductant of carbon dot will provide some new thoughts for preparing of carbon-based metal nanomaterials and expand their application in catalysis and analytical chemistry areas. - Highlights: • Carbon-based AuPd bimetallic nanocomposite was synthesized using carbon dots. • The green sequential reduction strategy synthesis method is simple, green, convenient and effective. • The as synthesized AuPd/C NC showed good catalytic activity and peroxidase-like activity. • The AuPd/C NC exhibits noticeably higher catalytic activity in reduction of 4-nitrophenol. • A new colorimetric detection method for hydrogen peroxide based on AuPd/C NC was proposed.

  11. Electron correlations in quantum dots

    International Nuclear Information System (INIS)

    Tipton, Denver Leonard John

    2001-01-01

    Quantum dot structures confine electrons in a small region of space. Some properties of semiconductor quantum dots, such as the discrete energy levels and shell filling effects visible in addition spectra, have analogies to those of atoms and indeed dots are sometimes referred to as 'artificial atoms'. However, atoms and dots show some fundamental differences due to electron correlations. For real atoms, the kinetic energy of electrons dominates over their mutual Coulomb repulsion energy and for this reason the independent electron approximation works well. For quantum dots the confining potential may be shallower than that of real atoms leading to lower electron densities and a dominance of mutual Coulomb repulsion over kinetic energy. In this strongly correlated regime the independent electron picture leads to qualitatively incorrect results. This thesis concentrates on few-electron quantum dots in the strongly correlated regime both for quasi-one-dimensional and two-dimensional dots in a square confining potential. In this so-called 'Wigner' regime the ground-state electronic charge density is localised near positions of classical electrostatic minima and the interacting electronic spectrum consists of well separated spin multiplets. In the strongly correlated regime the structure of low-energy multiplets is explained by mapping onto lattice models with extended-Hubbard and Heisenberg effective Hamiltonians. The parameters for these effective models are calculated within a Hartree approximation and are shown to reproduce well the exact results obtained by numerical diagonalisation of the full interacting Hamiltonian. Comparison is made between square dots and quantum rings with full rotational symmetry. In the very low-density regime, direct diagonalisation becomes impractical due to excessive computer time for convergence. In this regime a numerical renormalisation group method is applied to one-dimensional dots, enabling effective spin-interactions to be

  12. Highly stable cesium lead iodide perovskite quantum dot light-emitting diodes

    Science.gov (United States)

    Zou, Chen; Huang, Chun-Ying; Sanehira, Erin M.; Luther, Joseph M.; Lin, Lih Y.

    2017-11-01

    Recently, all-inorganic perovskites such as CsPbBr3 and CsPbI3, have emerged as promising materials for light-emitting applications. While encouraging performance has been demonstrated, the stability issue of the red-emitting CsPbI3 is still a major concern due to its small tolerance factor. Here we report a highly stable CsPbI3 quantum dot (QD) light-emitting diode (LED) with red emission fabricated using an improved purification approach. The device achieved decent external quantum efficiency (EQE) of 0.21% at a bias of 6 V and outstanding operational stability, with a L 70 lifetime (EL intensity decreases to 70% of starting value) of 16 h and 1.5 h under a constant driving voltage of 5 V and 6 V (maximum EQE operation) respectively. Furthermore, the device can work under a higher voltage of 7 V (maximum luminance operation) and retain 50% of its initial EL intensity after 500 s. These findings demonstrate the promise of CsPbI3 QDs for stable red LEDs, and suggest the feasibility for electrically pumped perovskite lasers with further device optimizations.

  13. Magnon-driven quantum dot refrigerators

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yuan; Huang, Chuankun; Liao, Tianjun; Chen, Jincan, E-mail: jcchen@xmu.edu.cn

    2015-12-18

    Highlights: • A three-terminal quantum dot refrigerator is proposed. • The effects of magnetic field, applied voltage, and polarization are considered. • The region that the system can work as a refrigerator is determined. • Two different magnon-driven quantum dot refrigerators are compared. - Abstract: 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.

  14. Multi-Excitonic Quantum Dot Molecules

    Science.gov (United States)

    Scheibner, M.; Stinaff, E. A.; Doty, M. F.; Ware, M. E.; Bracker, A. S.; Gammon, D.; Ponomarev, I. V.; Reinecke, T. L.; Korenev, V. L.

    2006-03-01

    With the ability to create coupled pairs of quantum dots, the next step towards the realization of semiconductor based quantum information processing devices can be taken. However, so far little knowledge has been gained on these artificial molecules. Our photoluminescence experiments on single InAs/GaAs quantum dot molecules provide the systematics of coupled quantum dots by delineating the spectroscopic features of several key charge configurations in such quantum systems, including X, X^+,X^2+, XX, XX^+ (with X being the neutral exciton). We extract general rules which determine the formation of molecular states of coupled quantum dots. These include the fact that quantum dot molecules provide the possibility to realize various spin configurations and to switch the electron hole exchange interaction on and off by shifting charges inside the molecule. This knowledge will be valuable in developing implementations for quantum information processing.

  15. Photoluminescence Enhancement of Silole-Capped Silicon Quantum Dots Based on Förster Resonance Energy Transfer.

    Science.gov (United States)

    Kim, Seongwoong; Kim, Sungsoo; Ko, Young Chun; Sohn, Honglae

    2015-07-01

    Photoluminescent porous silicon were prepared by an electrochemical etch of n-type silicon under the illumination with a 300 W tungsten filament bulb for the duration of etch. The red photoluminescence emitting at 650 nm with an excitation wavelength of 450 nm is due to the quantum confinement of silicon quantum dots in porous silicon. HO-terminated red luminescent PS was obtained by an electrochemical treatment of fresh PS with the current of 150 mA for 60 seconds in water and sodium chloride. As-prepared PS was sonicated, fractured, and centrifuged in toluene solution to obtain photoluminescence silicon quantum dots. Dichlorotetraphenylsilole exhibiting an emission band at 520 nm was reacted with HO-terminated silicon quantum dots to give a silole-capped silicon quantum dots. The optical characterization of silole-derivatized silicon quantum dots was investigated by UV-vis and fluorescence spectrometer. The fluorescence emission efficiency of silole-capped silicon quantum dots was increased by about 2.5 times due to F6rster resonance energy transfer from silole moiety to silicon quantum dots.

  16. Improved Dehydrogenation Properties of 2LiNH2-MgH2 by Doping with Li3AlH6

    Directory of Open Access Journals (Sweden)

    Shujun Qiu

    2017-01-01

    Full Text Available Doping with additives in a Li-Mg-N-H system has been regarded as one of the most effective methods of improving hydrogen storage properties. In this paper, we prepared Li3AlH6 and evaluated its effect on the dehydrogenation properties of 2LiNH2-MgH2. Our studies show that doping with Li3AlH6 could effectively lower the dehydrogenation temperatures and increase the hydrogen content of 2LiNH2-MgH2. For example, 2LiNH2-MgH2-0.1Li3AlH6 can desorb 6.43 wt % of hydrogen upon heating to 300 °C, with the onset dehydrogenation temperature at 78 °C. Isothermal dehydrogenation testing indicated that 2LiNH2-MgH2-0.1Li3AlH6 had superior dehydrogenation kinetics at low temperature. Moreover, the release of byproduct NH3 was successfully suppressed. Measurement of the thermal diffusivity suggests that the enhanced dehydrogenation properties may be ascribed to the fact that doping with Li3AlH6 could improve the heat transfer for solid–solid reaction.

  17. On the detection of high-redshift black holes with ALMA through CO and H(2) emission

    NARCIS (Netherlands)

    Spaans, Marco; Meijerink, Rowin

    2008-01-01

    Many present-day galaxies are known to harbor supermassive, >= 10(6) M(circle dot), black holes. These central black holes must have grown through accretion from less massive seeds in the early universe. The molecules CO and H 2 can be used to trace this young population of accreting massive black

  18. The Bruce Energy Centre

    International Nuclear Information System (INIS)

    Jones, R.I.

    1982-06-01

    The Bruce Energy Centre Development Corporation is a joint venture of the Ontario Energy Corporation and 6 private companies formed to market surplus steam from the Bruce Nuclear Power Development. The corporation will also sell or lease land near Bruce NPD. The Bruce Energy Centre has an energy output of 900 BTU per day per dollar invested. Potential customers include greenhouse operators, aquaculturalists, food and beverage manufacturers, and traditional manufacturers

  19. Biocompatible Quantum Dots for Biological Applications

    Science.gov (United States)

    Rosenthal, Sandra J.; Chang, Jerry C.; Kovtun, Oleg; McBride, James R.; Tomlinson, Ian D.

    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, sizetunable, 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. PMID:21276935

  20. Quantum measurement of coherent tunneling between quantum dots

    International Nuclear Information System (INIS)

    Wiseman, H. M.; Utami, Dian Wahyu; Sun, He Bi; Milburn, G. J.; Kane, B. E.; Dzurak, A.; Clark, R. G.

    2001-01-01

    We describe the conditional and unconditional dynamics of two coupled quantum dots when one dot is subjected to a measurement of its occupation number by coupling it to a third readout dot via the Coulomb interaction. The readout dot is coupled to source and drain leads under weak bias, and a tunnel current flows through a single bound state when energetically allowed. The occupation of the quantum dot near the readout dot shifts the bound state of the readout dot from a low conducting state to a high conducting state. The measurement is made by continuously monitoring the tunnel current through the readout dot. We show that there is a difference between the time scale for the measurement-induced decoherence between the localized states of the dots, and the time scale on which the system becomes localized due to the measurement

  1. Room-temperature luminescence decay of colloidal semiconductor quantum dots: Nonexponentiality revisited

    Energy Technology Data Exchange (ETDEWEB)

    Bodunov, Evgeny N. [Department of Physics, Petersburg State Transport University, St. Petersburg (Russian Federation); Danilov, Vladimir V. [Department of Physics, Petersburg State Transport University, St. Petersburg (Russian Federation); Vavilov State Optical Institute, St. Petersburg (Russian Federation); Panfutova, Anastasia S. [Vavilov State Optical Institute, St. Petersburg (Russian Federation); Simoes Gamboa, A.L. [Center of Information Optical Technologies, ITMO University, St. Petersburg (Russian Federation)

    2016-04-15

    While time-resolved luminescence spectroscopy is commonly used as a quantitative tool for the analysis of the dynamics of photoexcitation in colloidal semiconductor quantum dots, the interpretation of the virtually ubiquitous nonexponential decay profiles is frequently ambiguous, because the assumption of multiple discrete exponential components with distinct lifetimes for resolving the decays is often arbitrary. Here, an interpretation of the room-temperature luminescence decay of CdSe/ZnS semiconductor quantum dots in colloidal solutions is presented based on the Kohlrausch relaxation function. It is proposed that the decay can be understood by using the concept of Foerster resonance energy transfer (FRET) assuming that the role of acceptors of photoexcitation energy is played by high-frequency anharmonic molecular vibrations in the environment of the quantum dots. The term EVFRET (Electronic - Vibrational Foerster Resonance Energy Transfer) is introduced in order to unequivocally refer to this energy transfer process. (copyright 2016 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. A study on socio-demographic profile and feasibility of DOTS provider registered under RNTCP in Varanasi district Uttar Pradesh

    Directory of Open Access Journals (Sweden)

    Mohd. Afzalul Haque

    2014-03-01

    Full Text Available Introduction: Tuberculosis is a major chronic disorder affecting the larger population more than any other disease in the country. DOTS was introduced in India in 1993 as part of the Revised National Tuberculosis Programme (RNTCP following a review of India’s National Tuberculosis Programme (NTP a year earlier (1 .Patient satisfaction is an important parameter for assessing the quality of patient care services. There is need to assess the health care provider regarding the consumer satisfaction as often as possible, this paper summarizes our experience about role of DOTS provider in the management of TB patient in rural population of Varanasi districts Utter Pradesh. Objective: (1 To assess the perception of registered tuberculosis patients regarding DOTS provider for the treatment of tuberculosis. (2 To assess the accessibility, acceptability & availability of community DOTS provider. Design: A longitudinal study. Setting: Three microscopic centre of Cholapur Tuberculosis unit of Varanasi districts. Methods: Registered patients were interviewed twice: once in the beginning and another at the completion of the treatment or after the permanent discontinuation of the treatment. Patients were interviewed for their socio-demographic profiles, opinion about DOTS and its providers. Side effects experienced and action taken etc. Data was collected on a semi-structured, pre-tested questionnaire. DOTS providers were interviewed and treatment cards analyzed for any interruption of treatment and action taken. Data was collected from 1st June 2004 to 31th June 2005 till the completion of the regimen. Results: Majority of DOTS providers were young males (82.7% of 26 years to 40 years, while the representation of females was only 5 (17.3%. Almost more than 80% of the patients started their treatment within 1-10 days. For majority of cases (83% the distance of DOTS provider from patient’s house was within 1 km. Mean time spent to go to DOTS provider was 27

  3. High-performance liquid chromatographic method to evaluate the hydrogen atom transfer during reaction between 1,1-diphenyl-2-picryl-hydrazyl radical and antioxidants

    Energy Technology Data Exchange (ETDEWEB)

    Boudier, Ariane; Tournebize, Juliana [CITHEFOR - EA 3452, Faculte de Pharmacie, Nancy-Universite, 5 Rue Albert Lebrun, BP 80403, 54001 Nancy Cedex (France); Bartosz, Grzegorz [Department of Molecular Biophysics, University of Lodz, Lodz (Poland); El Hani, Safae; Bengueddour, Rachid [Laboratoire de Nutrition et Sante, Biology Department, Faculty of Sciences, Ibn Tofail University, Kenitra (Morocco); Sapin-Minet, Anne [CITHEFOR - EA 3452, Faculte de Pharmacie, Nancy-Universite, 5 Rue Albert Lebrun, BP 80403, 54001 Nancy Cedex (France); Leroy, Pierre, E-mail: pierre.leroy@pharma.uhp-nancy.fr [CITHEFOR - EA 3452, Faculte de Pharmacie, Nancy-Universite, 5 Rue Albert Lebrun, BP 80403, 54001 Nancy Cedex (France)

    2012-01-20

    Highlights: Black-Right-Pointing-Pointer Both 1,1-diphenyl-2-picrylhydrazyl radical and its product measurement by HPLC. Black-Right-Pointing-Pointer Lowest limit of detection by monitoring 1,1-diphenyl-2-picryl-hydrazine. Black-Right-Pointing-Pointer Adsorption problem of the radical on HPLC parts have been pointed out. - Abstract: 1,1-Diphenyl-2-picrylhydrazyl (DPPH{center_dot}) is a stable nitrogen centred radical widely used to evaluate direct radical scavenging properties of various synthetic or natural antioxidants (AOs). The bleaching rate of DPPH{center_dot} absorbance at 515 nm is usually monitored for this purpose. In order to avoid the interference of complex coloured natural products used as antioxidant supplements or cosmetics, HPLC systems have been reported as alternative techniques to spectrophotometry. They also rely upon measurement of DPPH{center_dot} quenching rate and none of them permits to identify and measure 1,1-diphenyl-2-picryl-hydrazine (DPPH-H), the reduced product of DPPH{center_dot} resulting from hydrogen atom transfer (HAT), which is the main mechanism of the reaction between DPPH{center_dot} and AOs. We presently report an HPLC method devoted to the simultaneous measurement of DPPH{center_dot} and DPPH-H. Both were fully separated on a C18 column eluted with acetonitrile-10 mM ammonium citrate buffer pH 6.8 (70:30, v/v) and detected at 330 nm. Adsorption process of DPPH{center_dot} onto materials of the HPLC system was pointed out. Consequently, the linearity range observed for DPPH{center_dot} was restricted, thus a much lower limit of detection was obtained for DPPH-H than for DPPH{center_dot} using standards (0.02 and 14 {mu}M, respectively). The method was applied to three commonly used AOs, i.e. Trolox{sup Registered-Sign }, ascorbic acid and GSH, and compared with spectrophotometry. Further application to complex matrices (cell culture media, vegetal extracts) and nanomaterials demonstrated (i) its usefulness because of

  4. An alternative route towards monodisperse CdS quantum dots for hybrid solar cells

    International Nuclear Information System (INIS)

    Cao, Fengfeng; Wang, Hao; Xia, Zhouhui; Dai, Xiao; Cong, Shan; Dong, Chao; Sun, Baoquan; Lou, Yanhui; Sun, Yinghui; Zhao, Jie; Zou, Guifu

    2015-01-01

    Monodisperse CdS quantum dots (QDs) are synthesized by thermal decomposition of organic complexes in the system of the cost-effective commercial 0 # diesel at 200 °C. The prepared CdS QDs have a good dispersion and high crystallization. When the CdS QDs are doped into the blends of poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6, 6)C61 (PCBM) for hybrid solar cells (HSCs), the HSCs achieve about 25% increase of power conversion efficiency in comparison to the reference device without the CdS QDs. The improvement of the cell performance mainly attributes to the increased short-circuit current density arising from the absorption enhancement in the wavelength range of 350–550 nm by introducing the synthesized CdS QDs into the P3HT: PCBM active layer. - Highlights: • Monodisperse CdS quantum dots. • A cost-effective route to synthesize crystalline CdS quantum dots. • CdS quantum dots based hybrid solar cells with power conversion efficiency enhancement

  5. An alternative route towards monodisperse CdS quantum dots for hybrid solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Fengfeng; Wang, Hao [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Xia, Zhouhui [Institute of Functional Nano and Soft Materials, Soochow University, Suzhou 215123 (China); Dai, Xiao; Cong, Shan [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Dong, Chao [Department of Chemistry and Biology, University of New Mexico, ABQ 87120 (United States); Sun, Baoquan [Institute of Functional Nano and Soft Materials, Soochow University, Suzhou 215123 (China); Lou, Yanhui, E-mail: yhlou@suda.edu.cn [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Sun, Yinghui; Zhao, Jie [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Zou, Guifu, E-mail: zouguifu@suda.edu.cn [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China)

    2015-01-15

    Monodisperse CdS quantum dots (QDs) are synthesized by thermal decomposition of organic complexes in the system of the cost-effective commercial 0{sup #} diesel at 200 °C. The prepared CdS QDs have a good dispersion and high crystallization. When the CdS QDs are doped into the blends of poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6, 6)C61 (PCBM) for hybrid solar cells (HSCs), the HSCs achieve about 25% increase of power conversion efficiency in comparison to the reference device without the CdS QDs. The improvement of the cell performance mainly attributes to the increased short-circuit current density arising from the absorption enhancement in the wavelength range of 350–550 nm by introducing the synthesized CdS QDs into the P3HT: PCBM active layer. - Highlights: • Monodisperse CdS quantum dots. • A cost-effective route to synthesize crystalline CdS quantum dots. • CdS quantum dots based hybrid solar cells with power conversion efficiency enhancement.

  6. Experimental studies on cycling stable characteristics of inorganic phase change material CaCl2·6H2O-MgCl2·6H2O modified with SrCl2·6H2O and CMC

    Science.gov (United States)

    He, Meizhi; Yang, Luwei; Zhang, Zhentao

    2018-01-01

    By means of mass ratio method, binary eutectic hydrated salts inorganic phase change thermal energy storage system CaCl2·6H2O-20wt% MgCl2·6H2O was prepared, and through adding nucleating agent 1wt% SrCl2·6H2O and thickening agent 0.5wt% carboxy methyl cellulose (CMC), inoganic phase change material (PCM) modified was obtained. With recording cooling-melting curves simultaneously, this PCM was frozen and melted for 100 cycles under programmable temperature control. After per 10 cycles, the PCM was charaterized by differential scanning calorimeter (DSC), X-ray diffraction (XRD) and density meter, then analysing variation characteristics of phase change temperature, supercooling degree, superheat degree, latent heat, crystal structure and density with the increase of cycle index. The results showed that the average values of average phase change temperature for cooling and heating process were 25.70°C and 27.39°C respectively with small changes. The average values of average supercooling and superheat degree were 0.59°C and 0.49°C respectively, and the maximum value was 1.10°C. The average value and standard deviation of latent heat of fusion were 120.62 J/g and 1.90 J/g respectively. Non-molten white solid sediments resulted from phase separation were tachyhydrite (CaMg2Cl6·12H2O), which was characterized by XRD. Measuring density of the PCM after per 10 cycles, and the results suggested that the total mass of tachyhydrite was limited. In summary, such modified inoganic PCM CaCl2·6H2O-20wt% MgCl2·6H2O-1wt% SrCl2·6H2O-0.5wt% CMC could stay excellent circulation stability within 100 cycles, and providing reference value in practical use.

  7. Metamorphic quantum dots: Quite different nanostructures

    International Nuclear Information System (INIS)

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

    2010-01-01

    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.

  8. Templated self-assembly of SiGe quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Dais, Christian

    2009-08-19

    This PhD thesis reports on the fabrication and characterization of exact aligned SiGe quantum dot structures. In general, SiGe quantum dots which nucleate via the Stranski-Krastanov growth mode exhibit broad size dispersion and nucleate randomly on the surface. However, to tap the full potential of SiGe quantum dots it is necessary to control the positioning and size of the dots on a nanometer length, e.g. for electronically addressing of individual dots. This can be realized by so-called templated self-assembly, which combines top-down lithography with bottom-up selfassembly. In this process the lithographically defined pits serve as pre-defined nucleation points for the epitaxially grown quantum dots. In this thesis, extreme ultraviolet interference lithography at a wavelength of e=13.4 nm is employed for prepatterning of the Si substrates. This technique allows the precise and fast fabrication of high-resolution templates with a high degree of reproducibility. The subsequent epitaxial deposition is either performed by molecular beam epitaxy or low-pressure chemical vapour deposition. It is shown that the dot nucleation on pre-patterned substrates depends strongly on the lithography parameters, e.g. size and periodicity of the pits, as well as on the epitaxy parameters, e.g. growth temperature or material coverage. The interrelations are carefully analyzed by means of scanning force microscopy, transmission electron microscopy and X-ray diffraction measurements. Provided that correct template and overgrowth parameters are chosen, perfectly aligned and uniform SiGe quantum dot arrays of different period, size as well as symmetry are created. In particular, the quantum dot arrays with the so far smallest period (35 nm) and smallest size dispersion are fabricated in this thesis. Furthermore, the strain fields of the underlying quantum dots allow the fabrication of vertically aligned quantum dot stacks. Combining lateral and vertical dot alignment results in three

  9. Decomobil, Deliverable 3.6, Human Centred Design for Safety Critical Transport Systems

    OpenAIRE

    PAUZIE, Annie; MENDOZA, Lucile; SIMOES, Anabela; BELLET, Thierry; MOREAU, Fabien

    2014-01-01

    The scientific seminar on 'Human Centred Design for Safety Critical Transport Systems' organized in the framework of DECOMOBIL has been held the 8th of September 2014 in Lisbon, Portugal, hosted by ADI/ISG. The aims of the event were to present the scientific problematic related to the safety of the complex transport systems and the increasing importance of human-­centred design, with a specific focus on Resilience Engineering concept, a new approach to safety management in highly complex sys...

  10. Infrared laser spectroscopy of H2 and D2 Rydberg states. II. Diode laser spectra and assignment of 5g--4f, 6h--5g, and 8i--6h systems

    International Nuclear Information System (INIS)

    Davies, P.B.; Guest, M.A.; Stickland, R.J.

    1990-01-01

    Infrared diode laser absorption spectra of portions of the 5g--4f, 6h--5g, and 8i--6h Rydberg bands of H 2 and D 2 have been measured at Doppler limited resolution in low pressure A. C. discharges. The spectra, arising from L uncoupled states of H 2 and D 2 , are assigned using an ab initio polarization model supported by intensity calculations. Details of the different implementations of this polarization model are given in the preceding paper. The most useful was the single channel vibrationally extended (1)/(2) V 6 model which became progressively better at higher n (and L). Results of multichannel calculations for a selected set of transitions are also reported

  11. High orbital angular momentum states in H2 and D2. II. The 6h--5g and 6g--5f transitions

    International Nuclear Information System (INIS)

    Jungen, C.; Dabrowski, I.; Herzberg, G.; Kendall, D.J.W.

    1989-01-01

    A group of lines accompanying the first line of the Pfund series of the H atom has been observed by Fourier transform infrared spectrometry. The lines are due to transitions in molecular hydrogen of a nonpenetrating Rydberg electron possessing a high-orbital angular momentum, which is coupled only loosely to the vibrations and rotations of the H + 2 core. Lines belonging to the 6h--5g and 6g--5f (v=0--3) transitions of H 2 have been identified. The identifications are based on a calculation of the spectrum from first principles by multichannel quantum defect theory. The interaction between the nonpenetrating electron and the core was evaluated in terms of the permanent and induced molecular moments of H + 2 as calculated by Bishop and collaborators. The analogous transitions in D 2 have also been observed and assigned

  12. Quantum dots: Rethinking the electronics

    Energy Technology Data Exchange (ETDEWEB)

    Bishnoi, Dimple [Department of Physics, S. S. Jain Subodh PG College, Jaipur, Rajasthan Pin-302004 (India)

    2016-05-06

    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.

  13. Tuneable light-emitting carbon-dot/polymer flexible films prepared through one-pot synthesis

    Science.gov (United States)

    Bhunia, Susanta Kumar; Nandi, Sukhendu; Shikler, Rafi; Jelinek, Raz

    2016-02-01

    Development of efficient, inexpensive, and environmentally-friendly light emitters, particularly devices that produce white light, have drawn intense interest due to diverse applications in the lighting industry, photonics, solar energy, and others. We present a simple strategy for the fabrication of flexible transparent films exhibiting tuneable light emission through one-pot synthesis of polymer matrixes with embedded carbon dots assembled in situ. Importantly, different luminescence colours were produced simply by preparing C-dot/polymer films using carbon precursors that yielded C-dots exhibiting distinct fluorescence emission profiles. Furthermore, mixtures of C-dot precursors could be also employed for fabricating films exhibiting different colours. In particular, we successfully produced films emitting white light with attractive properties (i.e. ``warm'' white light with a high colour rendering index) - a highly sought after goal in optical technologies.Development of efficient, inexpensive, and environmentally-friendly light emitters, particularly devices that produce white light, have drawn intense interest due to diverse applications in the lighting industry, photonics, solar energy, and others. We present a simple strategy for the fabrication of flexible transparent films exhibiting tuneable light emission through one-pot synthesis of polymer matrixes with embedded carbon dots assembled in situ. Importantly, different luminescence colours were produced simply by preparing C-dot/polymer films using carbon precursors that yielded C-dots exhibiting distinct fluorescence emission profiles. Furthermore, mixtures of C-dot precursors could be also employed for fabricating films exhibiting different colours. In particular, we successfully produced films emitting white light with attractive properties (i.e. ``warm'' white light with a high colour rendering index) - a highly sought after goal in optical technologies. Electronic supplementary information (ESI

  14. The electronic properties of semiconductor quantum dots

    International Nuclear Information System (INIS)

    Barker, J.A.

    2000-10-01

    This work is an investigation into the electronic behaviour of semiconductor quantum dots, particularly self-assembled quantum dot arrays. Processor-efficient models are developed to describe the electronic structure of dots, deriving analytic formulae for the strain tensor, piezoelectric distribution and diffusion- induced evolution of the confinement potential, for dots of arbitrary initial shape and composition profile. These models are then applied to experimental data. Transitions due to individual quantum dots have a narrow linewidth as a result of their discrete density of states. By contrast, quantum dot arrays exhibit inhomogeneous broadening which is generally attributed to size variations between the individual dots in the ensemble. Interpreting the results of double resonance spectroscopy, it is seen that variation in the indium composition of the nominally InAs dots is also present. This result also explains the otherwise confusing relationship between the spread in the ground-state and excited-state transition energies. Careful analysis shows that, in addition to the variations in size and composition, some other as yet unidentified broadening mechanism must also be present. The influence of rapid thermal annealing on dot electronic structure is also considered, finding that the experimentally observed blue-shift and narrowing of the photoluminescence linewidth may both be explained in terms of normal In/Ga interdiffusion. InAs/GaAs self-assembled quantum dots are commonly assumed to have a pyramidal geometry, so that we would expect the energy separation of the ground-state electron and hole levels in the dot to be largest at a positive applied field. This should also be the case for any dot of uniform composition whose shape tapers inwards from base to top, counter to the results of experimental Stark-shift spectroscopy which show a peak transition energy at a negative applied field. It is demonstrated that this inversion of the ground state

  15. The DotA protein from Legionella pneumophila is secreted by a novel process that requires the Dot/Icm transporter

    OpenAIRE

    Nagai, Hiroki; Roy, Craig R.

    2001-01-01

    Legionella pneumophila requires the dot/icm genes to create an organelle inside eukaryotic host cells that will support bacterial replication. The dot/icm genes are predicted to encode a type IV-related secretion apparatus. However, no proteins have been identified that require the dot/icm genes for secretion. In this study we show that the DotA protein, which was previously found to be a polytopic membrane protein, is secreted by the Dot/Icm transporter into culture supernatants. Secreted Do...

  16. Experimental investigation of slow-positron emission from 4H-SiC and 6H-SiC surfaces

    International Nuclear Information System (INIS)

    Ling, C.C.; Beling, C.D.; Fung, S.; Weng, H.M.

    2002-01-01

    Slow-positron emission from the surfaces of as-grown n-type 4H-SiC and 6H-SiC (silicon carbide) with a conversion efficiency of ∼10 -4 has been observed. After 30 min of 1000 deg. C annealing in forming gas, the conversion efficiency of the n-type 6H-SiC sample was observed to be enhanced by 75% to 1.9x10 -4 , but it then dropped to ∼10 -5 upon a further 30 min annealing at 1400 deg. C. The positron work function of the n-type 6H-SiC was found to increase by 29% upon 1000 deg. C annealing. For both p-type 4H-SiC and p-type 6H-SiC materials, the conversion efficiency was of the order of ∼10 -5 , some ten times lower than that for the n-type materials. This was attributed to the band bending at the p-type material surface which caused positrons to drift away from the positron emitting surface. (author)

  17. Selective biosensing of Staphylococcus aureus using chitosan quantum dots

    Science.gov (United States)

    Abdelhamid, Hani Nasser; Wu, Hui-Fen

    2018-01-01

    Selective biosensing of Staphylococcus aureus (S. aureus) using chitosan modified quantum dots (CTS@CdS QDs) in the presence of hydrogen peroxide is reported. The method is based on the intrinsic positive catalase activity of S. aureus. CTS@CdS quantum dots provide high dispersion in aqueous media with high fluorescence emission. Staphylococcus aureus causes a selective quenching of the fluorescence emission of CTS@CdS QDs in the presence of H2O2 compared to other pathogens such as Escherichia coli and Pseudomonas aeruginosa. The intrinsic enzymatic character of S. aureus (catalase positive) offers selective and fast biosensing. The present method is highly selective for positive catalase species and requires no expensive reagents such as antibodies, aptamers or microbeads. It could be extended for other species that are positive catalase.

  18. Aggregation, sedimentation, dissolution and bioavailability of quantum dots in estuarine systems.

    Science.gov (United States)

    To understand their fate and transport in estuarine systems, the aggregation, sedimentation, and dissolution of CdSe quantum dots (QDs) in seawater were investigated. Hydrodynamic size increased from 40 to 60 nm to >1 mm within 1 h in seawater, and the aggregates were highly p...

  19. Physics colloquium: Electron counting in quantum dots in and out of equilibrium

    CERN Multimedia

    Geneva University

    2011-01-01

    GENEVA UNIVERSITY Ecole de physique Département de physique nucléaire et corspusculaire 24, quai Ernest-Ansermet 1211 Genève 4 Tél.: (022) 379 62 73 Fax: (022) 379 69 92olé   Lundi 31 octobre 2011 17h00 - Ecole de Physique, Auditoire Stueckelberg PHYSICS COLLOQUIUM « Electron counting in quantum dots in and out of equilibrium » Prof. Klaus Ensslin Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland   Electron transport through quantum dots is governed by Coulomb blockade. Using a nearby quantum point contact the time-dependent charge flow through quantum dots can be monitored on the basis of single electrons. This way electron transport has been investigated in equilibrium as well as out of equilibrium. Recently it has become possible to experimentally verify the fluctuation theorem. The talk will also address electron counting experiments in grapheme. Une verrée ...

  20. Design of quaternary logic circuit using quantum dot gate-quantum dot channel FET (QDG-QDCFET)

    Science.gov (United States)

    Karmakar, Supriya

    2014-10-01

    This paper presents the implementation of quaternary logic circuits based on quantum dot gate-quantum dot channel field effect transistor (QDG-QDCFET). The super lattice structure in the quantum dot channel region of QDG-QDCFET and the electron tunnelling from inversion channel to the quantum dot layer in the gate region of a QDG-QDCFET change the threshold voltage of this device which produces two intermediate states between its ON and OFF states. This property of QDG-QDCFET is used to implement multi-valued logic for future multi-valued logic circuit. This paper presents the design of basic quaternary logic operation such as inverter, AND and OR operation based on QDG-QDCFET.

  1. Intrinsic peroxidase-like catalytic activity of nitrogen-doped graphene quantum dots and their application in the colorimetric detection of H2O2 and glucose

    International Nuclear Information System (INIS)

    Lin, Liping; Song, Xinhong; Chen, Yiying; Rong, Mingcong; Zhao, Tingting; Wang, Yiru; Jiang, Yaqi; Chen, Xi

    2015-01-01

    Highlights: • The highly intrinsic peroxidase-like catalytic activity of N-GQDs is revealed. • The activity of N-GQDs depended on pH, temperature and H 2 O 2 concentration. • The activity of N-GQDs has been used to the detection of H 2 O 2 and glucose. • This assay was suitable for the detection of glucose concentrations in real samples. - Abstract: In this paper, the highly intrinsic peroxidase-like catalytic activity of nitrogen-doped graphene quantum dots (N-GQDs) is revealed. This activity was greatly dependent on pH, temperature and H 2 O 2 concentration. The experimental results showed that the stable N-GQDs could be used for the detection of H 2 O 2 and glucose over a wide range of pH and temperature, offering a simple, highly selective and sensitive approach for their colorimetric sensing. The linearity between the analyte concentration and absorption ranged from 20 to 1170 μM for H 2 O 2 and 25 to 375 μM for glucose with a detection limit of 5.3 μM for H 2 O 2 and 16 μM for glucose. This assay was also successfully applied to the detection of glucose concentrations in diluted serum and fruit juice samples

  2. 2,6-Bis(9-ethyl-9H-carbazolylmethylenecyclohexanone

    Directory of Open Access Journals (Sweden)

    Abdullah M. Asiri

    2009-10-01

    Full Text Available The title compound, 2,6-bis(ethyl-9-ethyl-9H-carbazolylmethylenecyclohexanone has been synthesized by condensation of 9-ethylcarbazole-3-aldehyde and cyclohexanone in ethanol in the presence of pyridine. The structure of this new compound was confirmed by elemental analysis, IR, 1H NMR, 13C NMR and EI-MS spectral analysis.

  3. Investigation of some critical parameters of buffer conditions for the development of quantum dots-based optical sensors

    International Nuclear Information System (INIS)

    Yuan Jipei; Guo Weiwei; Wang Erkang

    2008-01-01

    The unique surface-sensitive properties make quantum dots (QDs) great potential in the development of sensors for various analytes. However, quantum dots are not only sensitive to a certain analyte, but also to the surrounding conditions. The controlled response to analyte may be the first step in the designing of functional quantum dots sensors. In this study, taking the quenching effect of benzoquinone (BQ) on CdTe QDs as model, several critical parameters of buffer solution conditions with potential effect on the sensors were investigated. The pH value and the concentration of sodium citrate in the buffer solution critically influenced the quenching effects of BQ. Dozens folds elevation of the quenching extents were observed with the increase of concentrations of H + and sodium citrate, and the quenching mechanisms were also fundamentally different with the changes of the surrounding buffer solutions. The quenching models were proposed and analyzed at different buffer conditions. Taking pH values for example, QDs quenching obeyed the sphere of effective quenching model with the sphere radii of 8.29 nm at pH 8.0, the linear Stern-Volmer equation with Stern-Volmer constant of 2.0 x 10 3 mol -1 L at pH 7.0, and the two binding site static quenching model at basic conditions. The elucidation of parameters for assay performance was important in the development of QDs-based optical sensors

  4. Semiconductor quantum-dot lasers and amplifiers

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher; Borri, Paola; Ledentsov, N. N.

    2002-01-01

    -power surface emitting VCSELs. We investigated the ultrafast dynamics of quantum-dot semiconductor optical amplifiers. The dephasing time at room temperature of the ground-state transition in semiconductor quantum dots is around 250 fs in an unbiased amplifier, decreasing to below 50 fs when the amplifier...... is biased to positive net gain. We have further measured gain recovery times in quantum dot amplifiers that are significantly lower than in bulk and quantum-well semiconductor optical amplifiers. This is promising for future demonstration of quantum dot devices with high modulation bandwidth...

  5. Temperature-dependent photoluminescence of water-soluble quantum dots for a bioprobe

    International Nuclear Information System (INIS)

    Liu Tiancai; Huang Zhenli; Wang Haiqiao; Wang Jianhao; Li Xiuqing; Zhao Yuandi; Luo Qingming

    2006-01-01

    The photoluminescence of water-soluble CdSe/ZnS core/shell quantum dots is found to be temperature-dependent: as temperature arising from 280 K to 351 K, the photoluminescence declines with emission peak shifting towards the red at a rate of ∼0.11 nm K -1 . And the studies show that the photoluminescence of water-soluble CdSe/ZnS quantum dots with core capped by a thinner ZnS shell is more sensitive to temperature than that of ones with core capped by a thicker one. That is, with 50% decrement of the quantum yield the temperature of the former need to arise from 280 K to 295 K, while the latter requires much higher temperature (315.6 K), which means that the integrality of shell coverage is a very important factor on temperature-sensitivity to for the photoluminescence of water-soluble CdSe/ZnS quantum dots. Moreover, it is found that the water-soluble CdSe quantum dots with different core sizes, whose cores are capped by thicker ZnS shells, possess almost the same sensitivity to the temperature. All of the studies about photoluminescence temperature-dependence of water-soluble CdSe/ZnS core/shell quantum dots show an indispensable proof for their applications in life science

  6. Temperature-dependent photoluminescence of water-soluble quantum dots for a bioprobe

    Energy Technology Data Exchange (ETDEWEB)

    Liu Tiancai [Key Laboratory of Biomedical Photonics of Ministry of Education - Hubei Bioinformatics and Molecular Imaging Key Laboratory, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Huang Zhenli [Key Laboratory of Biomedical Photonics of Ministry of Education - Hubei Bioinformatics and Molecular Imaging Key Laboratory, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Wang Haiqiao [Key Laboratory of Biomedical Photonics of Ministry of Education - Hubei Bioinformatics and Molecular Imaging Key Laboratory, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Wang Jianhao [Key Laboratory of Biomedical Photonics of Ministry of Education - Hubei Bioinformatics and Molecular Imaging Key Laboratory, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Li Xiuqing [Key Laboratory of Biomedical Photonics of Ministry of Education - Hubei Bioinformatics and Molecular Imaging Key Laboratory, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Zhao Yuandi [Key Laboratory of Biomedical Photonics of Ministry of Education - Hubei Bioinformatics and Molecular Imaging Key Laboratory, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)]. E-mail: zydi@mail.hust.edu.cn; Luo Qingming [Key Laboratory of Biomedical Photonics of Ministry of Education - Hubei Bioinformatics and Molecular Imaging Key Laboratory, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)

    2006-02-10

    The photoluminescence of water-soluble CdSe/ZnS core/shell quantum dots is found to be temperature-dependent: as temperature arising from 280 K to 351 K, the photoluminescence declines with emission peak shifting towards the red at a rate of {approx}0.11 nm K{sup -1}. And the studies show that the photoluminescence of water-soluble CdSe/ZnS quantum dots with core capped by a thinner ZnS shell is more sensitive to temperature than that of ones with core capped by a thicker one. That is, with 50% decrement of the quantum yield the temperature of the former need to arise from 280 K to 295 K, while the latter requires much higher temperature (315.6 K), which means that the integrality of shell coverage is a very important factor on temperature-sensitivity to for the photoluminescence of water-soluble CdSe/ZnS quantum dots. Moreover, it is found that the water-soluble CdSe quantum dots with different core sizes, whose cores are capped by thicker ZnS shells, possess almost the same sensitivity to the temperature. All of the studies about photoluminescence temperature-dependence of water-soluble CdSe/ZnS core/shell quantum dots show an indispensable proof for their applications in life science.

  7. Enhanced Photon Extraction from a Nanowire Quantum Dot Using a Bottom-Up Photonic Shell

    Science.gov (United States)

    Jeannin, Mathieu; Cremel, Thibault; Häyrynen, Teppo; Gregersen, Niels; Bellet-Amalric, Edith; Nogues, Gilles; Kheng, Kuntheak

    2017-11-01

    Semiconductor nanowires offer the possibility to grow high-quality quantum-dot heterostructures, and, in particular, CdSe quantum dots inserted in ZnSe nanowires have demonstrated the ability to emit single photons up to room temperature. In this paper, we demonstrate a bottom-up approach to fabricate a photonic fiberlike structure around such nanowire quantum dots by depositing an oxide shell using atomic-layer deposition. Simulations suggest that the intensity collected in our NA =0.6 microscope objective can be increased by a factor 7 with respect to the bare nanowire case. Combining microphotoluminescence, decay time measurements, and numerical simulations, we obtain a fourfold increase in the collected photoluminescence from the quantum dot. We show that this improvement is due to an increase of the quantum-dot emission rate and a redirection of the emitted light. Our ex situ fabrication technique allows a precise and reproducible fabrication on a large scale. Its improved extraction efficiency is compared to state-of-the-art top-down devices.

  8. A giant enhancement of CMR in Eu{sub 0.6}Ca{sub 0.4}B{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Glushkov, V V; Bogach, A V; Demishev, S V; Sluchanko, N E [A.M.Prokhorov General Physics Institute of RAS, 38, Vavilov str., Moscow 119991 (Russian Federation); Anisimov, M A [Moscow Institute of Physics and Technology, 9, Institutskii per., Dolgoprudny, Moscow Region 141700 (Russian Federation); Churkin, O A; Kuznetsov, A V [Moscow Engineering Physics Institute, 31, Kashirskoe Shosse, Moscow 115409 (Russian Federation); Filipov, V B; Levchenko, A V; Shitsevalova, N Yu [I. Frantsevich Institute for Problems of Materials Science NAS, 3, Krzhyzhanovsky str., Kiev 03680 (Ukraine); Flachbart, K, E-mail: glushkov@lt.gpi.r [Centre of Low Temperature Physics, IEP SAS and IPS FS UPJS, Kosice SK-04001 (Slovakia)

    2010-01-15

    The transport and magnetic properties of Eu{sub 0.6}Ca{sub 0.4}B{sub 6} single crystals have been studied at temperatures 1.8-300 K in magnetic fields up to 80 kOe. It was found that lowering of temperature results in a drastic increase of magnetoresistance up to the values of {rho}(0)/{rho}(H){approx}7{center_dot}10{sup 5} detected below 6K. The Hall and Seebeck effect measurements showed that colossal magnetoresistance (CMR) observed in Eu{sub 0.6}Ca{sub 0.4}B{sub 6} is accompanied by a crossover from hole-like to electron-like regime of charge transport induced by applied magnetic field. Hall mobility values {mu}{sub H{approx}}200-350 cm{sup 2}/(Vs) estimated for the high conductive state of Eu{sub 0.6}Ca{sub 0.4}B{sub 6} in the presence of strong substitutional disorder were proved to be comparable with these ones measured for undoped EuB{sub 6}. The anomalous behaviour of transport and magnetic parameters is discussed in terms of metal-insulator transition earlier predicted for this low carrier density system within double exchange model by V M Pereira et al., Phys. Rev. Lett. 93 147202 (2004).

  9. Determination of sparfloxacin with CdSe/CdS quantum dots as fluorescent probes

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Ming, E-mail: gxglzws@foxmail.com; Yan, Xiaoya; Xiong, Ling

    2015-01-15

    Water-soluble CdSe/CdS quantum dots (QDs) modified with thioglycolic acid (TGA) were synthesized. A novel method for determination of sparfloxacin (SPFX) has been developed based on quenching of the fluorescence of QDs at 556 nm wavelength. The optimum fluorescence intensity was found in 0.067 mol L{sup −1} KH{sub 2}PO{sub 4}–Na{sub 2}HPO{sub 4} buffer solution at pH 6.47 of 3.0×10{sup −5} mol L{sup −1} QDs. When the concentration of quantum dots is 3.0×10{sup −5} mol L{sup −1} the fluorescence quenching intensity of QDs is linearly proportional to the concentration of SPFX from 0.5 μg mL{sup −1} to 30 μg mL{sup −1}, with correlation coefficient R=0.9983. The detection limit for SPFX was 0.1391 μg mL{sup −1}. The method was used for determination of SPFX in tablets, and the results agreed with the claimed value. Trace amounts of SPFX in milk were also determined with the recovery of 95.3–106.8%. - Highlights: • Water-soluble CdSe/CdS quantum dots modified with thioglycolic acid were synthesized. • Determination of sparfloxacin was based on quenching of the fluorescence of QDs. • The detection limit for sparfloxacin was 0.1391 μg mL{sup −1}. • The method has been used successfully to determine SPFX in tablets and milk.

  10. Transport properties of a Kondo dot with a larger side-coupled noninteracting quantum dot

    International Nuclear Information System (INIS)

    Liu, Y S; Fan, X H; Xia, Y J; Yang, X F

    2008-01-01

    We investigate theoretically linear and nonlinear quantum transport through a smaller quantum dot in a Kondo regime connected to two leads in the presence of a larger side-coupled noninteracting quantum dot, without tunneling coupling to the leads. To do this we employ the slave boson mean field theory with the help of the Keldysh Green's function at zero temperature. The numerical results show that the Kondo conductance peak may develop multiple resonance peaks and multiple zero points in the conductance spectrum owing to constructive and destructive quantum interference effects when the energy levels of the large side-coupled noninteracting dot are located in the vicinity of the Fermi level in the leads. As the coupling strength between two quantum dots increases, the tunneling current through the quantum device as a function of gate voltage applied across the two leads is suppressed. The spin-dependent transport properties of two parallel coupled quantum dots connected to two ferromagnetic leads are also investigated. The numerical results show that, for the parallel configuration, the spin current or linear spin differential conductance are enhanced when the polarization strength in the two leads is increased

  11. Space charge spectroscopy of self assembled Ge quantum dots in Si

    Energy Technology Data Exchange (ETDEWEB)

    Asperger, T.; Miesner, C.; Brunner, K.; Abstreiter, G. [Technische Univ. Muenchen, Garching (Germany). Walter-Schottky-Inst. fuer Physikalische Grundlagen der Halbleiterelektronik

    2001-03-01

    Admittance spectroscopy was used to investigate the density of states in self assembled Ge quantum dots (QDs) of different size embedded in Si Schottky diodes. From the admittance results, activation energies of hole in the QDs have been determined as a function of the external bias which shifts the Fermi level with respect to the energy states in the QDs. The activation energy of a quantum well sample remains constant up to 6 V bias voltage. Large Ge dots (70 nm diameter) show a continuum of activation energies and a low continuous averaged density of states. In small Ge dots (20 nm diameter) a discrete energy level structure with level separations of 40 to 4 meV are observed. They are attributed to strongly quantum confined hole states with significant Coulomb blockade energies. (orig.)

  12. Influence of gamma-ray irradiation on 6H-SiC MOSFETs

    International Nuclear Information System (INIS)

    Ohshima, Takeshi; Yoshikawa, Masahito; Itoh, Hisayoshi; Nashiyama, Isamu; Okada, Sohei

    1998-01-01

    Enhancement-type n-channel MOSFETs were fabricated on 6H-SiC epitaxial films using pyrogenic or dry oxidation process. Oxide-trapped charges and interface traps produced in 6H-Sic MOSFETs by gamma-ray irradiation are evaluated from changes in the subthreshold-current curve. The net numbers of radiation-induced-oxide-trapped charges and interface traps depend on the oxidation process. The 6H-SiC MOSFETs exhibit higher radiation resistance than Si MOSFETs. (author)

  13. Curcumin Quantum Dots Mediated Degradation of Bacterial Biofilms

    Directory of Open Access Journals (Sweden)

    Ashish K. Singh

    2017-08-01

    Full Text Available Bacterial biofilm has been reported to be associated with more than 80% of bacterial infections. Curcumin, a hydrophobic polyphenol compound, has anti-quorum sensing activity apart from having antimicrobial action. However, its use is limited by its poor aqueous solubility and rapid degradation. In this study, we attempted to prepare quantum dots of the drug curcumin in order to achieve enhanced solubility and stability and investigated for its antimicrobial and antibiofilm activity. We utilized a newer two-step bottom up wet milling approach to prepare Curcumin Quantum Dots (CurQDs using acetone as a primary solvent. Minimum inhibitory concentration against select Gram-positive and Gram-negative bacteria was performed. The antibiofilm assay was performed at first using 96-well tissue culture plate and subsequently validated by Confocal Laser Scanning Microscopy. Further, biofilm matrix protein was isolated using formaldehyde sludge and TCA/Acetone precipitation method. Protein extracted was incubated with varying concentration of CurQDs for 4 h and was subjected to SDS–PAGE. Molecular docking study was performed to observe interaction between curcumin and phenol soluble modulins as well as curli proteins. The biophysical evidences obtained from TEM, SEM, UV-VIS, fluorescence, Raman spectroscopy, and zeta potential analysis confirmed the formation of curcumin quantum dots with increased stability and solubility. The MICs of curcumin quantum dots, as observed against both select gram positive and negative bacterial isolates, was observed to be significantly lower than native curcumin particles. On TCP assay, Curcumin observed to be having antibiofilm as well as biofilm degrading activity. Results of SDS–PAGE and molecular docking have shown interaction between biofilm matrix proteins and curcumin. The results indicate that aqueous solubility and stability of Curcumin can be achieved by preparing its quantum dots. The study also demonstrates

  14. A third-generation dispersion and third-generation hydrogen bonding corrected PM6 method: PM6-D3H+

    Directory of Open Access Journals (Sweden)

    Jimmy C. Kromann

    2014-06-01

    Full Text Available We present new dispersion and hydrogen bond corrections to the PM6 method, PM6-D3H+, and its implementation in the GAMESS program. The method combines the DFT-D3 dispersion correction by Grimme et al. with a modified version of the H+ hydrogen bond correction by Korth. Overall, the interaction energy of PM6-D3H+ is very similar to PM6-DH2 and PM6-DH+, with RMSD and MAD values within 0.02 kcal/mol of one another. The main difference is that the geometry optimizations of 88 complexes result in 82, 6, 0, and 0 geometries with 0, 1, 2, and 3 or more imaginary frequencies using PM6-D3H+ implemented in GAMESS, while the corresponding numbers for PM6-DH+ implemented in MOPAC are 54, 17, 15, and 2. The PM6-D3H+ method as implemented in GAMESS offers an attractive alternative to PM6-DH+ in MOPAC in cases where the LBFGS optimizer must be used and a vibrational analysis is needed, e.g., when computing vibrational free energies. While the GAMESS implementation is up to 10 times slower for geometry optimizations of proteins in bulk solvent, compared to MOPAC, it is sufficiently fast to make geometry optimizations of small proteins practically feasible.

  15. Synthesis of blue photoluminescent WS2 quantum dots via ultrasonic cavitation

    International Nuclear Information System (INIS)

    Bayat, A.; Saievar-Iranizad, E.

    2017-01-01

    Blue photoluminescent WS 2 quantum dots (QDs) were synthesized using a simple top-down method from natural raw mineral tungsten disulfide via tip ultrasonication followed by centrifugation in a water-ethanol (0.7/0.3 ratio) as eco-friendly solvent. Cavitation process at a high power (300 W) led to the breaking of bulk WS 2 flakes to its quantum dots. The as synthesized WS 2 QDs showed blue photoluminescence upon UV excitation. The synthesized WS 2 QDs were analysed by UV–vis and photoluminescence spectrophotometry, transmission electron microscopy, atomic force microscopy and X-ray diffraction. According to the transmission electron microscopy images, the size of WS 2 QDs was obtained as 5 nm in average. - Highlights: •Large scale blue photoluminescent WS 2 quantum dots was synthesized using Ultrasonic probe (Cavitation Process). •A solution of water/ethanol (0.7/0.3) was used as eco-friendly solvent instead of unsuitable solvent such as NMP and ACN. •Edges of bulk WS 2 was increased with formation of its quantum dots. •Solution of WS 2 QDs was stable after 6 months.

  16. Large quantum dots with small oscillator strength

    DEFF Research Database (Denmark)

    Stobbe, Søren; Schlereth, T.W.; Höfling, S.

    2010-01-01

    We have measured the oscillator strength and quantum efficiency of excitons confined in large InGaAs quantum dots by recording the spontaneous emission decay rate while systematically varying the distance between the quantum dots and a semiconductor-air interface. The size of the quantum dots...... is measured by in-plane transmission electron microscopy and we find average in-plane diameters of 40 nm. We have calculated the oscillator strength of excitons of that size assuming a quantum-dot confinement given by a parabolic in-plane potential and a hard-wall vertical potential and predict a very large...... intermixing inside the quantum dots....

  17. Photoluminescent (PL) or electroluminescent (EL) quantum dots for display, lighting, and photomedicine (Conference Presentation)

    Science.gov (United States)

    Dong, Yajie

    2017-02-01

    Quantum dots (QDs) have gone through a long journey before finding their ways into the display field. This talk will briefly touch on the history before trying to answer several key questions related to QDs applications in display: What are QDs? How are they made? What properties do they have and Why? How can these properties be used to improve color and efficiency of display, in either photoluminescence (PL) or electroluminescence (EL) mode? And what are the remaining challenges for QDs wide adoption in display industry? Lastly, some most recent progresses in our UCF lab at both PL and EL fronts will be highlighted. For PL, a cadmium-free perovskite-polymer composite films with exceptionally narrow emission green peaks (FWHM 20 nm) and good water and thermal stability will be reported. Together with red quantum dots or PFS/KSF phosphors as down-converters for blue LEDs, a white-light source with 95% Rec. 2020 color gamut was demonstrated [1]. For EL, red quantum dot light emitting devices (QLEDs) with record luminance of 165,000 Cd/m2 has been obtained at a current density of 1000 mA/cm2 with a low driving voltage of 5.8 V and CIE coordinates of (0.69, 0.31). [2] The potential of using these QLEDs for light sources for integrated sensing platform [3] or high efficiency, high color quality hybrid white OLED [4] will be discussed. [1] Y. N. Wang, J. He, H. Chen, J. S. Chen, R. D. Zhu, P. Ma, A. Towers, Y. Lin, A. J. Gesquiere, S. T. Wu, Y. J. Dong. Ultrastable, Highly Luminescent Organic-Inorganic Perovskite - Polymer Composite Films, Advanced Materials, accepted, (2016). [2] Y. J. Dong, J.M. Caruge, Z. Q. Zhou, C. Hamilton, Z. Popovic, J. Ho, M. Stevenson, G. Liu, V. Bulovic, M. Bawendi, P. T. Kazlas, S. Coe-Sullivan, and J. Steckel Ultra-bright, Highly Efficient, Low Roll-off Inverted Quantum-Dot Light Emitting Devices (QLEDs). SID Symp. Dig. Tech. Pap. 46, 270-273 (2015). [3] J. He, H. Chen, S. T. Wu, and Y. J. Dong, Integrated Sensing Platform Based on Quantum

  18. EPR of VHal centres in SrS

    International Nuclear Information System (INIS)

    Seeman, V.; Danilkin, M.; Must, M.; Ots, A.; Paernoja, E.; Pung, L.; Tarkpea, K.

    2006-01-01

    V Hal centres were studied by EPR in SrS doped with halogens after X-raying the samples at 77 K. V Hal centre arises when a hole is captured by sulphide-ion next to a cation vacancy with a halogen ion substituting the opposite sulphide-ion. EPR parameters and thermal decay characteristics are measured for V Cl , V Br , and V I centres. The efficiency of different halogens to produce and stabilise cation vacancies is shown to vary for different alkaline earth sulphides. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Specific IgE to peanut 2S albumin Ara h 7 has a discriminative ability comparable to Ara h 2 and 6.

    Science.gov (United States)

    Blankestijn, M A; Otten, H G; Suer, W; Weimann, A; Knol, E F; Knulst, A C

    2018-01-01

    Little is known on the clinical relevance of peanut 2S albumin Ara h 7. To investigate the discriminative ability of Ara h 7 in peanut allergy and assess the role of cross-reactivity between Ara h 2, 6 and Ara h 7 isoforms. Sensitization to recombinant peanut storage proteins Ara h 1, 2, 3, 6, and 7 was assessed using a line blot in sera from 40 peanut-tolerant and 40 peanut-allergic patients, based on food challenge outcome. A dose-dependent ELISA inhibition experiment was performed with recombinant Ara h 2, 6 and Ara h 7 isoforms. For Ara h 7.0201, an area under the ROC curve was found of 0.83, comparable to Ara h 2 (AUC 0.81) and Ara h 6 (AUC 0.85). Ara h 7 intensity values strongly correlated with those from Ara h 2 and 6 (r s = 0.81). Of all patients sensitized to 2S albumins Ara h 2, 6, or 7, the majority was co-sensitized to all three (n = 24, 68%), although mono-sensitization to either 2S albumin was also observed in selected patients (Ara h 2: n = 6, 17%; Ara h 6: n = 2, 6%; Ara h 7: n = 2, 6%). Binding to Ara h 7.0101 could be strongly inhibited by Ara h 7.0201, but not the other way around. Specific IgE against Ara h 7.0201 has a predictive ability for peanut allergy similar to Ara h 2 and 6 and possesses unique IgE epitopes as well as epitopes shared between the other Ara h 7 isoform and Ara h 2 and 6. While co-sensitization to all three 2S albumins is most common, mono-sensitization to either Ara h 2, 6, or 7 occurs in selected patients, leading to a risk of misdiagnosis when testing for a single 2S albumin. © 2017 John Wiley & Sons Ltd.

  20. The impact of doped silicon quantum dots on human osteoblasts

    Czech Academy of Sciences Publication Activity Database

    Ostrovská, L.; Brož, Antonín; Fučíková, A.; Bělinová, T.; Sugimoto, H.; Kanno, T.; Fujii, M.; Valenta, J.; Kalbáčová, M.H.

    2016-01-01

    Roč. 6, č. 68 (2016), s. 63403-63413 ISSN 2046-2069 Institutional support: RVO:67985823 Keywords : silicon quantum dots * osteoblasts * cytotoxicity * photoluminiscence bioimaging Subject RIV: EI - Biotechnology ; Bionics Impact factor: 3.108, year: 2016

  1. Thermally oxidized formation of new Ge dots over as-grown Ge dots in the Si capping layer

    International Nuclear Information System (INIS)

    Nie Tianxiao; Lin Jinhui; Shao Yuanmin; Wu Yueqin; Yang Xinju; Fan Yongliang; Jiang Zuimin; Chen Zhigang; Zou Jin

    2011-01-01

    A Si-capped Ge quantum dot sample was self-assembly grown via Stranski-Krastanov mode in a molecular beam epitaxy system with the Si capping layer deposited at 300 deg. C. After annealing the sample in an oxygen atmosphere at 1000 deg. C, a structure, namely two layers of quantum dots, was formed with the newly formed Ge-rich quantum dots embedded in the oxidized matrix with the position accurately located upon the as-grown quantum dots. It has been found that the formation of such nanostructures strongly depends upon the growth temperature and oxygen atmosphere. A growth mechanism was proposed to explain the formation of the nanostructure based on the Ge diffusion from the as-grown quantum dots, Ge segregation from the growing oxide, and subsequent migration/agglomeration.

  2. Fine and hyperfine collisional excitation of C6H by He

    Science.gov (United States)

    Walker, Kyle M.; Lique, François; Dawes, Richard

    2018-01-01

    Hydrogenated carbon chains have been detected in interstellar and circumstellar media and accurate modelling of their abundances requires collisional excitation rate coefficients with the most abundant species. Among them, the C6H molecule is one of the most abundant towards many lines of sight. Hence, we determined fine and hyperfine-resolved rate coefficients for the excitation of C6H(X2Π) due to collisions with He. We present the first interaction potential energy surface for the C6H-He system, obtained from highly correlated ab initio calculations and characterized by a large anisotropy due to the length of the molecule. We performed dynamical calculations for transitions among the first fine structure levels (up to J = 30.5) of both spin-orbit manifolds of C6H using the close-coupling method, and rate coefficients are determined for temperatures ranging from 5 to 100 K. The largest rate coefficients for even ΔJ transitions conserve parity, while parity-breaking rate coefficients are favoured for odd ΔJ. Spin-orbit changing rate coefficients are several orders of magnitude lower than transitions within a single manifold. State-to-state hyperfine-resolved cross-sections for the first levels (up to J = 13.5) in the Ω = 3/2 spin-orbit manifold are deduced using recoupling techniques. Rate coefficients are obtained and the propensity rule ΔJ = ΔF is seen. These new data will help determine the abundance of C6H in astrophysical environments such as cold dense molecular clouds, star-forming regions and circumstellar envelopes, and will help in the interpretation of the puzzling C6H-/C6H abundance ratios deduced from observations.

  3. Impacts of Post-metallisation Processes on the Electrical and Photovoltaic Properties of Si Quantum Dot Solar Cells.

    Science.gov (United States)

    Di, Dawei; Perez-Wurfl, Ivan; Gentle, Angus; Kim, Dong-Ho; Hao, Xiaojing; Shi, Lei; Conibeer, Gavin; Green, Martin A

    2010-08-01

    As an important step towards the realisation of silicon-based tandem solar cells using silicon quantum dots embedded in a silicon dioxide (SiO(2)) matrix, single-junction silicon quantum dot (Si QD) solar cells on quartz substrates have been fabricated. The total thickness of the solar cell material is 420 nm. The cells contain 4 nm diameter Si quantum dots. The impacts of post-metallisation treatments such as phosphoric acid (H(3)PO(4)) etching, nitrogen (N(2)) gas anneal and forming gas (Ar: H(2)) anneal on the cells' electrical and photovoltaic properties are investigated. The Si QD solar cells studied in this work have achieved an open circuit voltage of 410 mV after various processes. Parameters extracted from dark I-V, light I-V and circular transfer length measurement (CTLM) suggest limiting mechanism in the Si QD solar cell operation and possible approaches for further improvement.

  4. Optical properties of quantum-dot-doped liquid scintillators

    International Nuclear Information System (INIS)

    Aberle, C; Winslow, L; Li, J J; Weiss, S

    2013-01-01

    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

  5. Optical Signatures of Coupled Quantum Dots

    Science.gov (United States)

    Stinaff, E. A.; Scheibner, M.; Bracker, A. S.; Ponomarev, I. V.; Korenev, V. L.; Ware, M. E.; Doty, M. F.; Reinecke, T. L.; Gammon, D.

    2006-02-01

    An asymmetric pair of coupled InAs quantum dots is tuned into resonance by applying an electric field so that a single hole forms a coherent molecular wave function. The optical spectrum shows a rich pattern of level anticrossings and crossings that can be understood as a superposition of charge and spin configurations of the two dots. Coulomb interactions shift the molecular resonance of the optically excited state (charged exciton) with respect to the ground state (single charge), enabling light-induced coupling of the quantum dots. This result demonstrates the possibility of optically coupling quantum dots for application in quantum information processing.

  6. Mononuclear, trinuclear, and hetero-trinuclear supramolecular complexes containing a new tri-sulfonate ligand and cobalt(II)/copper(II)-(1, 10-phenanthroline)(2) building blocks

    NARCIS (Netherlands)

    Yu, Yunfang; Wei, Yongqin; Broer, Ria; Sa, Rongjian; Wu, Kechen

    Novel mononuclear, trinuclear, and hetero-trinuclear supermolecular complexes, [Co(phen)(2)(H2O)(HTST)] center dot 2H(2)O (1), [CO3(phen)(6) (H2O)(2)(TST)(2)]center dot 7H(2)O (2), and [CO2Cu(phen)(6)(H2O)(2)(TST)(2)]center dot 10H(2)O (3), have been synthesized by the reactions of a new

  7. Investigation of defects in electron-irradiated diamond of the type Ia by positron annihilation

    International Nuclear Information System (INIS)

    Novikov, N.V.; Ositinskaya, T.D.; Mikhalenkov, V.S.; Chernyashevskij, A.V.; Shakhovtsov, V.I.; AN Ukrainskoj SSR, Kiev; AN Ukrainskoj SSR, Kiev

    1997-01-01

    To produce vacancy defects, type Ia diamond was irradiated with 3.5 MeV electrons at doses of 5 centre dot 10 16 , 2 centre dot 10 17 , 4 centre dot 10 17 , and 2 centre dot 10 18 e/cm -2 . After each dose, the specimen was investigated using positron annihilation (ACAR), optical spectroscopy in IR, visible regions, and EPR. From ACAR spectra, the S-parameters were found and positron trapping rates were determined. Their behaviour with increasing irradiation doses shows that, in type Ia diamond along with neutral vacancies V degree, deeper traps of positrons are formed, which are most likely vacancies in the negative charge state V - . Specific trapping rates of the V 0 and V - defects are found to be 1.3 centre dot 10 15 and 3.8 centre dot 10 15 s -1 , respectively; trapping cross sections for these defects are also estimated

  8. Influence of the quantum dot geometry on p -shell transitions in differently charged quantum dots

    Science.gov (United States)

    Holtkemper, M.; Reiter, D. E.; Kuhn, T.

    2018-02-01

    Absorption spectra of neutral, negatively, and positively charged semiconductor quantum dots are studied theoretically. We provide an overview of the main energetic structure around the p -shell transitions, including the influence of nearby nominally dark states. Based on the envelope function approximation, we treat the four-band Luttinger theory as well as the direct and short-range exchange Coulomb interactions within a configuration interaction approach. The quantum dot confinement is approximated by an anisotropic harmonic potential. We present a detailed investigation of state mixing and correlations mediated by the individual interactions. Differences and similarities between the differently charged quantum dots are highlighted. Especially large differences between negatively and positively charged quantum dots become evident. We present a visualization of energetic shifts and state mixtures due to changes in size, in-plane asymmetry, and aspect ratio. Thereby we provide a better understanding of the experimentally hard to access question of quantum dot geometry effects. Our findings show a method to determine the in-plane asymmetry from photoluminescence excitation spectra. Furthermore, we supply basic knowledge for tailoring the strength of certain state mixtures or the energetic order of particular excited states via changes of the shape of the quantum dot. Such knowledge builds the basis to find the optimal QD geometry for possible applications and experiments using excited states.

  9. Quantum dot-polymer conjugates for stable luminescent displays.

    Science.gov (United States)

    Ghimire, Sushant; Sivadas, Anjaly; Yuyama, Ken-Ichi; Takano, Yuta; Francis, Raju; Biju, Vasudevanpillai

    2018-05-23

    The broad absorption of light in the UV-Vis-NIR region and the size-based tunable photoluminescence color of semiconductor quantum dots make these tiny crystals one of the most attractive antennae in solar cells and phosphors in electrooptical devices. One of the primary requirements for such real-world applications of quantum dots is their stable and uniform distribution in optically transparent matrices. In this work, we prepare transparent thin films of polymer-quantum dot conjugates, where CdSe/ZnS quantum dots are uniformly distributed at high densities in a chitosan-polystyrene copolymer (CS-g-PS) matrix. Here, quantum dots in an aqueous solution are conjugated to the copolymer by a phase transfer reaction. With the stable conjugation of quantum dots to the copolymer, we prevent undesired phase separation between the two and aggregation of quantum dots. Furthermore, the conjugate allows us to prepare transparent thin films in which quantum dots are uniformly distributed at high densities. The CS-g-PS copolymer helps us in not only preserving the photoluminescence properties of quantum dots in the film but also rendering excellent photostability to quantum dots at the ensemble and single particle levels, making the conjugate a promising material for photoluminescence-based devices.

  10. Enantiopure Ferrocene-Based Planar-Chiral Iridacycles: Stereospecific Control of Iridium-Centred Chirality.

    Science.gov (United States)

    Arthurs, Ross A; Ismail, Muhammad; Prior, Christopher C; Oganesyan, Vasily S; Horton, Peter N; Coles, Simon J; Richards, Christopher J

    2016-02-24

    Reaction of [IrCp*Cl2 ]2 with ferrocenylimines (Fc=NAr, Ar=Ph, p-MeOC6 H4 ) results in ferrocene C-H activation and the diastereoselective synthesis of half-sandwich iridacycles of relative configuration Sp *,RIr *. Extension to (S)-2-ferrocenyl-4-(1-methylethyl)oxazoline gave highly diastereoselective control over the new elements of planar chirality and metal-based pseudo-tetrahedral chirality, to give both neutral and cationic half-sandwich iridacycles of absolute configuration Sc ,Sp ,RIr . Substitution reactions proceed with retention of configuration, with the planar chirality controlling the metal-centred chirality through an iron-iridium interaction in the coordinatively unsaturated cationic intermediate. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Trapping {BW12}2 tungstoborate: synthesis and crystal structure of hybrid [{(H2BW12O42)2O}{Mo6O6S6(OH)4(H2O)2}]14- anion.

    Science.gov (United States)

    Korenev, V S; Abramov, P A; Vicent, C; Mainichev, D A; Floquet, S; Cadot, E; Sokolov, M N; Fedin, V P

    2012-12-28

    Reaction between monolacunary {BW(11)} tungstoborate and oxothiocationic building block, {Mo(2)O(2)S(2)}, results in the formation of a new polyoxothiometalate with a unique architecture in which two [H(2)BW(12)O(43)](9-) tungstoborate subunits are linked together with a hexamolybdate [Mo(V)(6)O(6)S(6)(OH)(4)(H(2)O)(2)](2+) bridge.

  12. 5-[(3-Fluorophenyl(2-hydroxy-6-oxocyclohex-1-en-1-ylmethyl]-6-hydroxy-1,3-dimethylpyrimidine-2,4(1H,3H-dione

    Directory of Open Access Journals (Sweden)

    Assem Barakat

    2016-09-01

    Full Text Available 5-[(3-Fluorophenyl(2-hydroxy-6-oxocyclohex-1-en-1-yl-methyl]-6-hydroxy-1,3-di-methylpyrimidine-2,4(1H,3H-dione 3 was synthesized via a multicomponent reaction. The Aldol–Michael addition reactions of N,N-dimethylbarbituric acid, cyclohexane-1,3-dione, and 3-fluorobenzaldehyde in aqueous solution gave the product in high yield. The molecular structure of the compound was confirmed by spectroscopic methods and X-ray crystallography. The title compound (C19H19FN2O5·H2O crystallizes in the Monoclinic form, P21/c, a = 7.8630 (5 Å, b = 20.0308 (13 Å, c = 11.3987 (8 Å, β = 104.274 (3°, V = 1739.9 (2° Å3, Z = 4, Rint = 0.117, wR(F2 = 0.124, T = 100 K.

  13. Raman scattering and lattice stability of NaAlH{sub 4} and Na{sub 3}AlH{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Yukawa, H. [Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya University, Chikusa-Ku, Nagoya 464-8603 (Japan)], E-mail: hiroshi@numse.nagoya-u.ac.jp; Morisaku, N.; Li, Y.; Komiya, K.; Rong, R.; Shinzato, Y. [Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya University, Chikusa-Ku, Nagoya 464-8603 (Japan); Sekine, R. [Department of Chemistry, Faculty of Science, Shizuoka University, 836 Ohya, Shizuoka 422-8529 (Japan); Morinaga, M. [Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya University, Chikusa-Ku, Nagoya 464-8603 (Japan)

    2007-10-31

    In situ Raman spectroscopy measurements have been performed during the decomposition of NaAlH{sub 4} in order to investigate the transition from the four-coordinated complex anion, [AlH{sub 4}]{sup -}, in NaAlH{sub 4} to the six-coordinated complex anion, [AlH{sub 6}]{sup 3-}, in Na{sub 3}AlH{sub 6}. Also, the local geometry and the Al-H vibrations are analyzed theoretically by the first-principle calculations of the electronic structures. It is found that the Raman sift at 1765 cm{sup -1} for the Al-H stretching vibration in NaAlH{sub 4} shifts towards the higher frequency side, 1801 cm{sup -1} upon melting. This Raman spectrum for the liquid phase recovers to the original position when it is cooled down to room temperature before Na{sub 3}AlH{sub 6} start to appear. The Raman peak around 1800 cm{sup -1} is still observed after the decomposition of NaAlH{sub 4} occurs to precipitate Na{sub 3}AlH{sub 6}. However, this peak does not recover to its original position by cooling, but still persists in the sample cooled down to room temperature. From these results, the intermediate transition state during the decomposition of NaAlH{sub 4} into Na{sub 3}AlH{sub 6} is discussed. In addition, it is shown from a series of calculation that the highest frequency of the Al-H vibration correlates with the shortest Al-H bond length in the MAlH{sub 4}-type and its derivative complex hydrides.

  14. Polarized Fine Structure in the Photoluminescence Excitation Spectrum of a Negatively Charged Quantum Dot

    Science.gov (United States)

    Ware, M. E.; Stinaff, E. A.; Gammon, D.; Doty, M. F.; Bracker, A. S.; Gershoni, D.; Korenev, V. L.; Bădescu, Ş. C.; Lyanda-Geller, Y.; Reinecke, T. L.

    2005-10-01

    We report polarized photoluminescence excitation spectroscopy of the negative trion in single charge-tunable InAs/GaAs quantum dots. The spectrum exhibits a p-shell resonance with polarized fine structure arising from the direct excitation of the electron spin triplet states. The energy splitting arises from the axially symmetric electron-hole exchange interaction. The magnitude and sign of the polarization are understood from the spin character of the triplet states and a small amount of quantum dot asymmetry, which mixes the wave functions through asymmetric e-e and e-h exchange interactions.

  15. Ambient-Processed Colloidal Quantum Dot Solar Cells via Individual Pre-Encapsulation of Nanoparticles

    KAUST Repository

    Debnath, Ratan; Tang, Jiang; Barkhouse, D. Aaron; Wang, Xihua; Pattantyus-Abraham, Andras G.; Brzozowski, Lukasz; Levina, Larissa; Sargent, Edward H.

    2010-01-01

    We report colloidal quantum dot solar cells fabricated under ambient atmosphere with an active area of 2.9 mm2 that exhibit 3.6% solar power conversion efficiency. The devices are based on PbS tuned via the quantum size effect to have a first excitonic peak at 950 nm. Because the formation of native oxides and sulfates on PbS leads to p-type doping and deep trap formation and because such dopants and traps dramatically influence device performance, prior reports of colloidal quantum dot solar cells have insisted on processing under an inert atmosphere. Here we report a novel ligand strategy in which we first encapsulate the quantum dots in the solution phase with the aid of a strongly bound N-2,4,6-trimethylphenyl-N-methyldithiocarbamate ligand. This allows us to carry out film formation and all subsequent device fabrication under an air atmosphere. © 2010 American Chemical Society.

  16. Ambient-Processed Colloidal Quantum Dot Solar Cells via Individual Pre-Encapsulation of Nanoparticles

    KAUST Repository

    Debnath, Ratan

    2010-05-05

    We report colloidal quantum dot solar cells fabricated under ambient atmosphere with an active area of 2.9 mm2 that exhibit 3.6% solar power conversion efficiency. The devices are based on PbS tuned via the quantum size effect to have a first excitonic peak at 950 nm. Because the formation of native oxides and sulfates on PbS leads to p-type doping and deep trap formation and because such dopants and traps dramatically influence device performance, prior reports of colloidal quantum dot solar cells have insisted on processing under an inert atmosphere. Here we report a novel ligand strategy in which we first encapsulate the quantum dots in the solution phase with the aid of a strongly bound N-2,4,6-trimethylphenyl-N-methyldithiocarbamate ligand. This allows us to carry out film formation and all subsequent device fabrication under an air atmosphere. © 2010 American Chemical Society.

  17. Schottky Quantum Dot Solar Cells Stable in Air under Solar Illumination

    KAUST Repository

    Tang, Jiang

    2010-01-07

    (Figure Presented) The air stability and power conversion efficiency of solution-processed PbS quantum dot solar cells is dramatically improved by the insertion of 0.8 nm LiF between the PbS nanoparticle film and the Al contact. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA.

  18. Quantum Dot Nanobioelectronics and Selective Antimicrobial Redox Interventions

    Science.gov (United States)

    Goodman, Samuel Martin

    use of cadmium telluride quantum dots as light-activated therapeutics for treating multi-drug resistant bacterial infectoins. A review of the physiological effects of cadmium chalcogenide quantum dots is first presented in Chapter 5 which provides a foundation for understanding the inherent toxicity of these materials. The phototoxic effect induced by CdTe quantum dots is then introduced in Chapter 6 showing the reduction in growth of gram-negative bacteria. Additional insight is provided in Chapter 7 which discusses the therapeutic mechanism and the oxygen-centered radical species which are formed by the application of light in aqueous media. The section closes with Chapter 8 describing efforts to improve the stability and bio-compatibility of the dots using various surface treatments, and shows that stability can be improved by the passivation of the quantum dots' anionic facets, though at the cost of overall radical generation.

  19. Positron annihilation spectroscopic studies of 6H silicon carbide

    International Nuclear Information System (INIS)

    Hu, Y.F.; Lam, C.H.; Ling, C.C.; Fung, S.; Beling, C.D.; Weng, H.M.

    2001-01-01

    Positron lifetime measurements have been performed on p-type and n-type 6H-SiC with temperatures varying from 10 K to 290 K. The V C V Si divacancy is observed in both types of 6H-SiC where the V Si related defect is only found in the n-type material. Positron trapping into a defect with lifetime value close to the bulk was found to compete with positron trapping into V Si or V C V Si at temperatures lower than 80 K. The positron diffusion length of the 1400 C annealed n-type 6H-SiC has also been measured at different temperatures with the use of a positron beam. Positron diffusion was found to be limited by acoustic phonon scattering at T=150-300 K. However, at T=50-150 K, D + follows T 2.12±0.02 and the details of the physical process is not yet known. (orig.)

  20. Detection of Escherichia coli O157:H7 and Salmonella in ground beef by a bead-free quantum dot-facilitated isolation method.

    Science.gov (United States)

    Wang, Luxin; Wu, Chung-Shieh; Fan, Xudong; Mustapha, Azlin

    2012-05-01

    The aims of this study were to introduce a new immunological bead-free cell detection method using quantum dots (QDs) as reporter markers for foodborne pathogen detection. QDs are nanosized particles with long-term photostability, high quantum yield, broad absorption spectra, and narrow, symmetric emission and high signal-to-noise ratio. The chemical compound [(1-ethyl-3-3-dimethylaminopropyl) carbodiimide hydrochloride] (EDC) and protein A were used as crosslinkers for manufacturing QD-antibody conjugates. To minimize the inhibition of QD fluorescence by the magnetic beads, the beads were removed after the primary pathogen isolation and before fluorescence measurement. Detection signals were increased four-fold after employing the bead-free isolation method. With a 24-h enrichment, the bead-free QD-facilitated detection method was able to detect 10 CFU/g Escherichia coli O157:H7 and Salmonella from artificially contaminated ground beef. To our knowledge, this detection method is the first research that combined a new EDC-protein A QD-labeling technique and bead-free fluorescence measurement to detect E. coli O157:H7 and Salmonella in ground beef. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. Andreev molecules in semiconductor nanowire double quantum dots.

    Science.gov (United States)

    Su, Zhaoen; Tacla, Alexandre B; Hocevar, Moïra; Car, Diana; Plissard, Sébastien R; Bakkers, Erik P A M; Daley, Andrew J; Pekker, David; Frolov, Sergey M

    2017-09-19

    Chains of quantum dots coupled to superconductors are promising for the realization of the Kitaev model of a topological superconductor. While individual superconducting quantum dots have been explored, control of longer chains requires understanding of interdot coupling. Here, double quantum dots are defined by gate voltages in indium antimonide nanowires. High transparency superconducting niobium titanium nitride contacts are made to each of the dots in order to induce superconductivity, as well as probe electron transport. Andreev bound states induced on each of dots hybridize to define Andreev molecular states. The evolution of these states is studied as a function of charge parity on the dots, and in magnetic field. The experiments are found in agreement with a numerical model.Quantum dots in a nanowire are one possible approach to creating a solid-state quantum simulator. Here, the authors demonstrate the coupling of electronic states in a double quantum dot to form Andreev molecule states; a potential building block for longer chains suitable for quantum simulation.

  2. Optical performance evolutions of reductive glutathione coated CdSe quantum dots in different environments

    International Nuclear Information System (INIS)

    Wang Lili; Jiang Jisen

    2011-01-01

    Optical performances of reductive glutathione coated CdSe quantum dots were studied under different ageing conditions. The enhancements of luminescence were obviously occurred for the samples ageing under illumination. The quantum yield of CdSe was enhanced continuously over 44 days at room temperature, and reached as high as 36.6%. O 2 was proved to make a certain contribute to the enhancement. The evolutions of the systems during the ageing time were deduced according to the variations of pH values with ageing time and the XRD results of the samples ageing in air with illumination. We conferred that the reduction of surface defects resulted from the photo-induced decomposition of CdSe quantum dots was the main reason for the enhancement of fluorescence. The production of CdO as a result of the surface reaction with O 2 made contributions to the enhancement for a certain extent. The curves of quantum yield versus ageing time were fitted with a stretched exponential function. It was found that the course of fluorescence enhancement accorded with the dynamics of system with strongly coupled hierarchical degrees of freedom.

  3. Quantum optics with single quantum dot devices

    International Nuclear Information System (INIS)

    Zwiller, Valery; Aichele, Thomas; Benson, Oliver

    2004-01-01

    A single radiative transition in a single-quantum emitter results in the emission of a single photon. Single quantum dots are single-quantum emitters with all the requirements to generate single photons at visible and near-infrared wavelengths. It is also possible to generate more than single photons with single quantum dots. In this paper we show that single quantum dots can be used to generate non-classical states of light, from single photons to photon triplets. Advanced solid state structures can be fabricated with single quantum dots as their active region. We also show results obtained on devices based on single quantum dots

  4. Studies of the pressure-induced phase transition of C sub 3 N sub 6 H sub 6

    CERN Document Server

    Ma Hong An; Cui Qi Liang; Pan Yue Wu; Zhu Pin Wen; Guo Wei; Chen Li Xue; Ren Guo Zheng; Zou Guang Tian; LiuJing

    2002-01-01

    In situ high pressure energy dispersive X-ray diffraction experiments have been carried out on C sub 3 N sub 6 H sub 6 by using diamond anvil cell (DAC) device with synchrotron radiation source. Two structural phase transitions of C sub 3 N sub 6 H sub 6 have been observed within 14.7 GPa pressure range, from monoclinic to triclinic structure at 1.3 GPa and from triclinic to orthorhombic structure at 8.2 GPa, respectively

  5. PREFACE: Quantum Dot 2010

    Science.gov (United States)

    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

  6. A facile microwave assisted one-pot synthesis of novel 1-methylhexahydroquinazolin-5(6H-ones and bis-1-methylhexahydroquinazolin-5(6H-ones

    Directory of Open Access Journals (Sweden)

    Madhusudhan Saha

    2011-03-01

    Full Text Available Novel hexahydroquinazolin-5(6H-ones 3a-j have been synthesized in good yields by the reaction of enaminones 2a-b with primary amines and formaldehyde under the influence microwaves. Enaminones 2a-b have also been reacted with diamines and formaldehyde under similar conditions resulting in hitherto unreported bis- hexahydroquinazolin-5(6H-ones 4a-d and 5a-d. The structures of the molecules have been established with the help of spectral and analytical data.

  7. A modified gradient approach for the growth of low-density InAs quantum dot molecules by molecular beam epitaxy

    Science.gov (United States)

    Sharma, Nandlal; Reuter, Dirk

    2017-11-01

    Two vertically stacked quantum dots that are electronically coupled, so called quantum dot molecules, are of great interest for the realization of solid state building blocks for quantum communication networks. We present a modified gradient approach to realize InAs quantum dot molecules with a low areal density so that single quantum dot molecules can be optically addressed. The individual quantum dot layers were prepared by solid source molecular beam epitaxy depositing InAs on GaAs(100). The bottom quantum dot layer has been grown without substrate rotation resulting in an In-gradient across the surface, which translated into a density gradient with low quantum dot density in a certain region of the wafer. For the top quantum dot layer, separated from the bottom quantum dot layer by a 6 nm thick GaAs barrier, various InAs amounts were deposited without an In-gradient. In spite of the absence of an In-gradient, a pronounced density gradient is observed for the top quantum dots. Even for an In-amount slightly below the critical thickness for a single dot layer, a density gradient in the top quantum dot layer, which seems to reproduce the density gradient in the bottom layer, is observed. For more or less In, respectively, deviations from this behavior occur. We suggest that the obvious influence of the bottom quantum dot layer on the growth of the top quantum dots is due to the strain field induced by the buried dots.

  8. TO EVALUATE PREVALENCE OF DIABETES AND HIV IN NEWLY-DIAGNOSED MULTIDRUGRESISTANT TUBERCULOSIS PATIENTS ADMITTED FOR PRETREATMENT EVALUATION IN DOTS PLUS CENTRE, THANJAVUR

    Directory of Open Access Journals (Sweden)

    Namasivayam Kuppusamy

    2017-07-01

    Full Text Available BACKGROUND More than 9 million people fall sick with tuberculosis every year in the world. People with weak immune system as a result of disease like diabetes and HIV are at high risk of developing MDR-TB infection. Proper monitoring and evaluation are needed to control MDR-TB in HIV and diabetes patients. The aim of the study is to find the prevalence of diabetes and HIV among MDR-TB patients admitted for pretreatment evaluation in Dots Plus Centre, Thanjavur Medical College, Tamilnadu. MATERIALS AND METHODS The medical records with datas of 96 patients with MDR-TB who are having diabetes and HIV infection were examined. These cases were diagnosed and registered during January 2015 to December 2015. These patients had drug resistant to first line antituberculosis drugs (isoniazid and rifampicin. Duration of diabetes and HIV infection were noted. Age were categorised in to four groups- 20-29 years, 30-39 years, 40-49 years and above 50 years. The potential risk of association of diabetes, HIV or both with MDR-TB was evaluated by univariate conditional logistic regression model. RESULTS Out of 96 newly-diagnosed MDR-TB patients, prevalence of diabetes is about 34.37%, out of which (84.84% were males and (15.15% were females. Out of 34.37%, 38.54% of patients had controlled diabetes, 61.45% patients had uncontrolled diabetes. Nearly, more than half of diabetes patient falls under uncontrolled diabetes. More number of male patients had diabetes with MDR-TB when compared to females. 10.4% of these persons got oral hypoglycaemic agent and 6.3% got insulin as treatment for diabetes. 1% had irregular treatment with poor compliance. Prevalence of HIV is about 4.16% out of which 75% were males and 25% were females. One patient had both diabetes and HIV with MDR tuberculosis. CONCLUSION In our retrospective study, prevalence of diabetes in MDR-TB patients were more common in males than in females, most of them were in the age groups of 40 years and above

  9. Power-law photoluminescence decay in quantum dots

    Czech Academy of Sciences Publication Activity Database

    Král, Karel; Menšík, Miroslav

    2013-01-01

    Roč. 5, č. 6 (2013), s. 608-610 ISSN 2164-6627 R&D Projects: GA MŠk(CZ) OC10007; GA MŠk LH12236; GA MŠk LH12186 Institutional support: RVO:68378271 ; RVO:61389013 Keywords : quantum dots * indirect gap * photoluminescence * electron-phonon interaction * non-adiabatic Subject RIV: BM - Solid Matter Physics ; Magnetism; JA - Electronics ; Optoelectronics, Electrical Engineering (UMCH-V)

  10. Determination of band structure parameters and the quasi-particle gap of CdSe quantum dots by cyclic voltammetry.

    Science.gov (United States)

    Inamdar, Shaukatali N; Ingole, Pravin P; Haram, Santosh K

    2008-12-01

    Band structure parameters such as the conduction band edge, the valence band edge and the quasi-particle gap of diffusing CdSe quantum dots (Q-dots) of various sizes were determined using cyclic voltammetry. These parameters are strongly dependent on the size of the Q-dots. The results obtained from voltammetric measurements are compared to spectroscopic and theoretical data. The fit obtained to the reported calculations based on the semi-empirical pseudopotential method (SEPM)-especially in the strong size-confinement region, is the best reported so far, according to our knowledge. For the smallest CdSe Q-dots, the difference between the quasi-particle gap and the optical band gap gives the electron-hole Coulombic interaction energy (J(e1,h1)). Interband states seen in the photoluminescence spectra were verified with cyclic voltammetry measurements.

  11. Elimination of Bimodal Size in InAs/GaAs Quantum Dots for Preparation of 1.3-μm Quantum Dot Lasers.

    Science.gov (United States)

    Su, Xiang-Bin; Ding, Ying; Ma, Ben; Zhang, Ke-Lu; Chen, Ze-Sheng; Li, Jing-Lun; Cui, Xiao-Ran; Xu, Ying-Qiang; Ni, Hai-Qiao; Niu, Zhi-Chuan

    2018-02-21

    The device characteristics of semiconductor quantum dot lasers have been improved with progress in active layer structures. Self-assembly formed InAs quantum dots grown on GaAs had been intensively promoted in order to achieve quantum dot lasers with superior device performances. In the process of growing high-density InAs/GaAs quantum dots, bimodal size occurs due to large mismatch and other factors. The bimodal size in the InAs/GaAs quantum dot system is eliminated by the method of high-temperature annealing and optimized the in situ annealing temperature. The annealing temperature is taken as the key optimization parameters, and the optimal annealing temperature of 680 °C was obtained. In this process, quantum dot growth temperature, InAs deposition, and arsenic (As) pressure are optimized to improve quantum dot quality and emission wavelength. A 1.3-μm high-performance F-P quantum dot laser with a threshold current density of 110 A/cm 2 was demonstrated.

  12. Quantum-dot-in-perovskite solids

    KAUST Repository

    Ning, Zhijun; Gong, Xiwen; Comin, Riccardo; Walters, Grant; Fan, Fengjia; Voznyy, Oleksandr; Yassitepe, Emre; Buin, Andrei; Hoogland, Sjoerd; Sargent, Edward H.

    2015-01-01

    © 2015 Macmillan Publishers Limited. All rights reserved. Heteroepitaxy - atomically aligned growth of a crystalline film atop a different crystalline substrate - is the basis of electrically driven lasers, multijunction solar cells, and blue-light-emitting diodes. Crystalline coherence is preserved even when atomic identity is modulated, a fact that is the critical enabler of quantum wells, wires, and dots. The interfacial quality achieved as a result of heteroepitaxial growth allows new combinations of materials with complementary properties, which enables the design and realization of functionalities that are not available in the single-phase constituents. Here we show that organohalide perovskites and preformed colloidal quantum dots, combined in the solution phase, produce epitaxially aligned 'dots-in-a-matrix' crystals. Using transmission electron microscopy and electron diffraction, we reveal heterocrystals as large as about 60 nanometres and containing at least 20 mutually aligned dots that inherit the crystalline orientation of the perovskite matrix. The heterocrystals exhibit remarkable optoelectronic properties that are traceable to their atom-scale crystalline coherence: photoelectrons and holes generated in the larger-bandgap perovskites are transferred with 80% efficiency to become excitons in the quantum dot nanocrystals, which exploit the excellent photocarrier diffusion of perovskites to produce bright-light emission from infrared-bandgap quantum-tuned materials. By combining the electrical transport properties of the perovskite matrix with the high radiative efficiency of the quantum dots, we engineer a new platform to advance solution-processed infrared optoelectronics.

  13. Quantum-dot-in-perovskite solids

    KAUST Repository

    Ning, Zhijun

    2015-07-15

    © 2015 Macmillan Publishers Limited. All rights reserved. Heteroepitaxy - atomically aligned growth of a crystalline film atop a different crystalline substrate - is the basis of electrically driven lasers, multijunction solar cells, and blue-light-emitting diodes. Crystalline coherence is preserved even when atomic identity is modulated, a fact that is the critical enabler of quantum wells, wires, and dots. The interfacial quality achieved as a result of heteroepitaxial growth allows new combinations of materials with complementary properties, which enables the design and realization of functionalities that are not available in the single-phase constituents. Here we show that organohalide perovskites and preformed colloidal quantum dots, combined in the solution phase, produce epitaxially aligned \\'dots-in-a-matrix\\' crystals. Using transmission electron microscopy and electron diffraction, we reveal heterocrystals as large as about 60 nanometres and containing at least 20 mutually aligned dots that inherit the crystalline orientation of the perovskite matrix. The heterocrystals exhibit remarkable optoelectronic properties that are traceable to their atom-scale crystalline coherence: photoelectrons and holes generated in the larger-bandgap perovskites are transferred with 80% efficiency to become excitons in the quantum dot nanocrystals, which exploit the excellent photocarrier diffusion of perovskites to produce bright-light emission from infrared-bandgap quantum-tuned materials. By combining the electrical transport properties of the perovskite matrix with the high radiative efficiency of the quantum dots, we engineer a new platform to advance solution-processed infrared optoelectronics.

  14. Detection of alien genetic introgressions in bread wheat using dot-blot genomic hybridisation.

    Science.gov (United States)

    Rey, María-Dolores; Prieto, Pilar

    2017-01-01

    Simple, reliable methods for the identification of alien genetic introgressions are required in plant breeding programmes. The use of genomic dot-blot hybridisation allows the detection of small Hordeum chilense genomic introgressions in the descendants of genetic crosses between wheat and H. chilense addition or substitution lines in wheat when molecular markers are difficult to use. Based on genomic in situ hybridisation, DNA samples from wheat lines carrying putatively H. chilense introgressions were immobilised on a membrane, blocked with wheat genomic DNA and hybridised with biotin-labelled H. chilense genomic DNA as a probe. This dot-blot screening reduced the number of plants necessary to be analysed by molecular markers or in situ hybridisation, saving time and money. The technique was sensitive enough to detect a minimum of 5 ng of total genomic DNA immobilised on the membrane or about 1/420 dilution of H. chilense genomic DNA in the wheat background. The robustness of the technique was verified by in situ hybridisation. In addition, the detection of other wheat relative species such as Hordeum vulgare , Secale cereale and Agropyron cristatum in the wheat background was also reported .

  15. Contemporary avian influenza A virus subtype H1, H6, H7, H10, and H15 hemagglutinin genes encode a mammalian virulence factor similar to the 1918 pandemic virus H1 hemagglutinin.

    Science.gov (United States)

    Qi, Li; Pujanauski, Lindsey M; Davis, A Sally; Schwartzman, Louis M; Chertow, Daniel S; Baxter, David; Scherler, Kelsey; Hartshorn, Kevan L; Slemons, Richard D; Walters, Kathie-Anne; Kash, John C; Taubenberger, Jeffery K

    2014-11-18

    Zoonotic avian influenza virus infections may lead to epidemics or pandemics. The 1918 pandemic influenza virus has an avian influenza virus-like genome, and its H1 hemagglutinin was identified as a key mammalian virulence factor. A chimeric 1918 virus expressing a contemporary avian H1 hemagglutinin, however, displayed murine pathogenicity indistinguishable from that of the 1918 virus. Here, isogenic chimeric avian influenza viruses were constructed on an avian influenza virus backbone, differing only by hemagglutinin subtype expressed. Viruses expressing the avian H1, H6, H7, H10, and H15 subtypes were pathogenic in mice and cytopathic in normal human bronchial epithelial cells, in contrast to H2-, H3-, H5-, H9-, H11-, H13-, H14-, and H16-expressing viruses. Mouse pathogenicity was associated with pulmonary macrophage and neutrophil recruitment. These data suggest that avian influenza virus hemagglutinins H1, H6, H7, H10, and H15 contain inherent mammalian virulence factors and likely share a key virulence property of the 1918 virus. Consequently, zoonotic infections with avian influenza viruses bearing one of these hemagglutinins may cause enhanced disease in mammals. Influenza viruses from birds can cause outbreaks in humans and may contribute to the development of pandemics. The 1918 pandemic influenza virus has an avian influenza virus-like genome, and its main surface protein, an H1 subtype hemagglutinin, was identified as a key mammalian virulence factor. In a previous study, a 1918 virus expressing an avian H1 gene was as virulent in mice as the reconstructed 1918 virus. Here, a set of avian influenza viruses was constructed, differing only by hemagglutinin subtype. Viruses with the avian H1, H6, H7, H10, and H15 subtypes caused severe disease in mice and damaged human lung cells. Consequently, infections with avian influenza viruses bearing one of these hemagglutinins may cause enhanced disease in mammals, and therefore surveillance for human infections

  16. CsPbBr3 Perovskite Quantum Dots-Based Monolithic Electrospun Fiber Membrane as an Ultrastable and Ultrasensitive Fluorescent Sensor in Aqueous Medium.

    Science.gov (United States)

    Wang, Yuanwei; Zhu, Yihua; Huang, Jianfei; Cai, Jin; Zhu, Jingrun; Yang, Xiaoling; Shen, Jianhua; Jiang, Hao; Li, Chunzhong

    2016-11-03

    Perovskite quantum dots with excellent optical properties and robust durability stand as an appealing and desirable candidate for fluorescence resonance energy transfer (FRET) based fluorescence detection, a powerful technique featuring excellent accuracy and convenience. In this work, a monolithic superhydrophobic polystyrene fiber membrane with CsPbBr 3 perovskite quantum dots encapsulated within (CPBQDs/PS FM) was prepared via one-step electrospinning. Coupling CPBQDs with PS matrix, this CPBQDs/PS FM composite exhibits high quantum yields (∼91%), narrow half-peak width (∼16 nm), nearly 100% fluorescence retention after being exposed to water for 10 days and 79.80% fluorescence retention after 365 nm UV-light (1 mW/cm 2 ) illumination for 60 h. Thanks to the outstanding optical property of CPBQDs, an ultralow detection limit of 0.01 ppm was obtained for Rhodamine 6G (R6G) detection, with the FRET efficiency calculated to be 18.80% in 1 ppm R6G aqueous solution. Electrospun as well-designed fiber membranes, CPBQDs/PS FM composite also possesses good tailorability and recyclability, showing exciting potential for future implementation into practical applications.

  17. The interactions between CdTe quantum dots and proteins: understanding nano-bio interface

    Directory of Open Access Journals (Sweden)

    Shreeram S. Joglekar

    2017-01-01

    Full Text Available Despite remarkable developments in the nanoscience, relatively little is known about the physical (electrostatic interactions of nanoparticles with bio macromolecules. These interactions can influence the properties of both nanoparticles and the bio-macromolecules. Understanding this bio-interface is a prerequisite to utilize both nanoparticles and biomolecules for bioengineering. In this study, luminescent, water soluble CdTe quantum dots (QDs capped with mercaptopropionic acid (MPA were synthesized by organometallic method and then interaction between nanoparticles (QDs and three different types of proteins (BSA, Lysozyme and Hemoglobin were investigated by fluorescence spectroscopy at pH= 7.4. Based on fluorescence quenching results, Stern-Volmer quenching constant (Ksv, binding constant (Kq and binding sites (n for proteins were calculated. The results show that protein structure (e.g.,globular, metalloprotein, etc. has a significant role in Protein-Quantum dots interactions and each type of protein influence physicochemical properties of Quantum dots differently.

  18. Quantum dots for quantum information technologies

    CERN Document Server

    2017-01-01

    This book highlights the most recent developments in quantum dot spin physics and the generation of deterministic superior non-classical light states with quantum dots. In particular, it addresses single quantum dot spin manipulation, spin-photon entanglement and the generation of single-photon and entangled photon pair states with nearly ideal properties. The role of semiconductor microcavities, nanophotonic interfaces as well as quantum photonic integrated circuits is emphasized. The latest theoretical and experimental studies of phonon-dressed light matter interaction, single-dot lasing and resonance fluorescence in QD cavity systems are also provided. The book is written by the leading experts in the field.

  19. Coherent transport through interacting quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Hiltscher, Bastian

    2012-10-05

    The present thesis is composed of four different works. All deal with coherent transport through interacting quantum dots, which are tunnel-coupled to external leads. There a two main motivations for the use of quantum dots. First, they are an ideal device to study the influence of strong Coulomb repulsion, and second, their discrete energy levels can easily be tuned by external gate electrodes to create different transport regimes. The expression of coherence includes a very wide range of physical correlations and, therefore, the four works are basically independent of each other. Before motivating and introducing the different works in more detail, we remark that in all works a diagrammatic real-time perturbation theory is used. The fermionic degrees of freedom of the leads are traced out and the elements of the resulting reduced density matrix can be treated explicitly by means of a generalized master equation. How this equation is solved, depends on the details of the problem under consideration. In the first of the four works adiabatic pumping through an Aharonov-Bohm interferometer with a quantum dot embedded in each of the two arms is studied. In adiabatic pumping transport is generated by varying two system parameters periodically in time. We consider the two dot levels to be these two pumping parameters. Since they are located in different arms of the interferometer, pumping is a quantum mechanical effect purely relying on coherent superpositions of the dot states. It is very challenging to identify a quantum pumping mechanism in experiments, because a capacitive coupling of the gate electrodes to the leads may yield an undesired AC bias voltage, which is rectified by a time dependent conductance. Therefore, distinguishing features of these two transport mechanisms are required. We find that the dependence on the magnetic field is the key feature. While the pumped charge is an odd function of the magnetic flux, the rectified current is even, at least in

  20. Coherent transport through interacting quantum dots

    International Nuclear Information System (INIS)

    Hiltscher, Bastian

    2012-01-01

    The present thesis is composed of four different works. All deal with coherent transport through interacting quantum dots, which are tunnel-coupled to external leads. There a two main motivations for the use of quantum dots. First, they are an ideal device to study the influence of strong Coulomb repulsion, and second, their discrete energy levels can easily be tuned by external gate electrodes to create different transport regimes. The expression of coherence includes a very wide range of physical correlations and, therefore, the four works are basically independent of each other. Before motivating and introducing the different works in more detail, we remark that in all works a diagrammatic real-time perturbation theory is used. The fermionic degrees of freedom of the leads are traced out and the elements of the resulting reduced density matrix can be treated explicitly by means of a generalized master equation. How this equation is solved, depends on the details of the problem under consideration. In the first of the four works adiabatic pumping through an Aharonov-Bohm interferometer with a quantum dot embedded in each of the two arms is studied. In adiabatic pumping transport is generated by varying two system parameters periodically in time. We consider the two dot levels to be these two pumping parameters. Since they are located in different arms of the interferometer, pumping is a quantum mechanical effect purely relying on coherent superpositions of the dot states. It is very challenging to identify a quantum pumping mechanism in experiments, because a capacitive coupling of the gate electrodes to the leads may yield an undesired AC bias voltage, which is rectified by a time dependent conductance. Therefore, distinguishing features of these two transport mechanisms are required. We find that the dependence on the magnetic field is the key feature. While the pumped charge is an odd function of the magnetic flux, the rectified current is even, at least in

  1. Proton exchange mechanism of synthesizing CdS quantum dots in nafion

    International Nuclear Information System (INIS)

    Nandakumar, P.; Vijayan, C.; Murti, Y.V.G.S.; Dhanalakshmi, K.; Sundararajan, G.

    1999-01-01

    Nanocrystals of CdS are synthesized in the proton exchange membrane nafion in different sizes in the range 1.6 to 6 nm. To understand the process leading to the formation of these quantum dots, we have probed the proton exchange by ac conductance measurements in the frequency range 100 Hz to 13 MHz. Nafion shows good electrical conductivity due to proton transport probably via the Grothus mechanism. Incorporation of cadmium ions by replacement of the hydrogen ions in the sulphonic acid group resulted in a large decrease in conductance indicating the reduction of the mobile carrier density. The conductivity plots all show strong frequency dependence with higher conductance towards the higher frequencies where a near-flat frequency response is seen. After the formation of CdS clusters, there is a partial recovery of conductance corresponding to the reinstatement of the protonic carriers on the side groups. The conductivity of the nafion films embedded with the semiconductor quantum dots exhibits a size-dependence with the highest conductivity obtained for the largest clusters. These findings lend clear experimental evidence for the model of synthesis of quantum dots in nafion by the exchange mechanism. (author)

  2. Graphene quantum dots

    CERN Document Server

    Güçlü, Alev Devrim; Korkusinski, Marek; Hawrylak, Pawel

    2014-01-01

    This book reflects the current status of theoretical and experimental research of graphene based nanostructures, in particular quantum dots, at a level accessible to young researchers, graduate students, experimentalists and theorists. It presents the current state of research of graphene quantum dots, a single or few monolayer thick islands of graphene. It introduces the reader to the electronic and optical properties of graphite, intercalated graphite and graphene, including Dirac fermions, Berry's phase associated with sublattices and valley degeneracy, covers single particle properties of

  3. Calibration of the cameras of the H.E.S.S. {gamma}-ray astronomy experiment and observations of the Galactic Centre above 100 GeV; Etalonnage des cameras de l'experience d'astronomie {gamma} H.E.S.S. et observations du centre galactique au-dela de 100 GeV

    Energy Technology Data Exchange (ETDEWEB)

    Rolland, L

    2005-05-15

    The H.E.S.S. experiment (High Energy Stereoscopic System) consists of four imaging atmospheric Cherenkov telescopes to study the southern astrophysical sources above 100 GeV. This thesis presents the detector as well as the analysis chain. The calibration methods are described in details and the systematic errors on the image amplitude are derived. Then, an analysis based on a semi-analytical model of the electromagnetic shower development in the atmosphere is presented. Tools to reconstruct the energy spectrum and the morphology of the very high energy {gamma}-ray sources are presented and applied to the Crab Nebula. Systematic errors associated to the spectrum analysis are estimated. All these techniques were applied to study the Galactic Centre emission above 100 GeV. The nature of the source detected in 2003 and 2004 observations is still unknown and its spectrum, variability and morphology are studied. Various candidates are proposed, among them the supermassive black hole Sgr A* located at the dynamical centre of the Milky Way, the supernova remnant Sgr A Est or interactions of accelerated particles with the dense medium of this region. In this thesis, the signal was interpreted in terms of dark matter annihilation (neutralinos or Kaluza-Klein bosons) in a dense halo located at the Galactic Centre. This analysis showed that, in the framework of these models, dark matter annihilation alone can not explain the H.E.S.S. signal. The main component would thus come from astrophysical sources. (author)

  4. Magneto-optical absorption in semiconducting spherical quantum dots: Influence of the dot-size, confining potential, and magnetic field

    Directory of Open Access Journals (Sweden)

    Manvir S. Kushwaha

    2014-12-01

    Full Text Available Semiconducting quantum dots – more fancifully dubbed artificial atoms – are quasi-zero dimensional, tiny, man-made systems with charge carriers completely confined in all three dimensions. The scientific quest behind the synthesis of quantum dots is to create and control future electronic and optical nanostructures engineered through tailoring size, shape, and composition. The complete confinement – or the lack of any degree of freedom for the electrons (and/or holes – in quantum dots limits the exploration of spatially localized elementary excitations such as plasmons to direct rather than reciprocal space. Here we embark on a thorough investigation of the magneto-optical absorption in semiconducting spherical quantum dots characterized by a confining harmonic potential and an applied magnetic field in the symmetric gauge. This is done within the framework of Bohm-Pines’ random-phase approximation that enables us to derive and discuss the full Dyson equation that takes proper account of the Coulomb interactions. As an application of our theoretical strategy, we compute various single-particle and many-particle phenomena such as the Fock-Darwin spectrum; Fermi energy; magneto-optical transitions; probability distribution; and the magneto-optical absorption in the quantum dots. It is observed that the role of an applied magnetic field on the absorption spectrum is comparable to that of a confining potential. Increasing (decreasing the strength of the magnetic field or the confining potential is found to be analogous to shrinking (expanding the size of the quantum dots: resulting into a blue (red shift in the absorption spectrum. The Fermi energy diminishes with both increasing magnetic-field and dot-size; and exhibits saw-tooth-like oscillations at large values of field or dot-size. Unlike laterally confined quantum dots, both (upper and lower magneto-optical transitions survive even in the extreme instances. However, the intra

  5. Magneto-optical absorption in semiconducting spherical quantum dots: Influence of the dot-size, confining potential, and magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kushwaha, Manvir S. [Department of Physics and Astronomy, Rice University, P.O. Box 1892, Houston, TX 77251 (United States)

    2014-12-15

    Semiconducting quantum dots – more fancifully dubbed artificial atoms – are quasi-zero dimensional, tiny, man-made systems with charge carriers completely confined in all three dimensions. The scientific quest behind the synthesis of quantum dots is to create and control future electronic and optical nanostructures engineered through tailoring size, shape, and composition. The complete confinement – or the lack of any degree of freedom for the electrons (and/or holes) – in quantum dots limits the exploration of spatially localized elementary excitations such as plasmons to direct rather than reciprocal space. Here we embark on a thorough investigation of the magneto-optical absorption in semiconducting spherical quantum dots characterized by a confining harmonic potential and an applied magnetic field in the symmetric gauge. This is done within the framework of Bohm-Pines’ random-phase approximation that enables us to derive and discuss the full Dyson equation that takes proper account of the Coulomb interactions. As an application of our theoretical strategy, we compute various single-particle and many-particle phenomena such as the Fock-Darwin spectrum; Fermi energy; magneto-optical transitions; probability distribution; and the magneto-optical absorption in the quantum dots. It is observed that the role of an applied magnetic field on the absorption spectrum is comparable to that of a confining potential. Increasing (decreasing) the strength of the magnetic field or the confining potential is found to be analogous to shrinking (expanding) the size of the quantum dots: resulting into a blue (red) shift in the absorption spectrum. The Fermi energy diminishes with both increasing magnetic-field and dot-size; and exhibits saw-tooth-like oscillations at large values of field or dot-size. Unlike laterally confined quantum dots, both (upper and lower) magneto-optical transitions survive even in the extreme instances. However, the intra-Landau level

  6. Technology of preparation for low density 6Li(H,D) solid micro-target

    International Nuclear Information System (INIS)

    Wang Xisheng; Zeng Jiaquan; Li Qiang

    2002-01-01

    Low density 6 Li(H,D) micro-targets are prepared by loose sintering 6 LiH or 6 LiD powder in a tiny gold cylinder and soaking for 30 min up to 430 degree C at the rate of 10 degree C/h in argon. The dimension of the micro-targets is as tiny as 0.6-1.0 mm for diameter and 1-2 mm for length. Densities of 6 LiH and 6 LiD without Parylene C is (0.283 +- 0.009) g/cm 3 and (0.369 +- 0.009) g/cm 3 , respectively while 6 LiD targets with Parylene C is only (0.301 +- 0.010) g/cm 3 . The Parylene C has no effect on purity, deuterium abundance and 6 Li abundance of the sintered micro-targets. It's effective to keep 6 Li(H,D) purity by strict control of argon atmosphere

  7. Formation and properties of selected quantum dots in maize amylopectin matrix

    Energy Technology Data Exchange (ETDEWEB)

    Khachatryan, Karen, E-mail: rrchacza@cyf-kr.edu.pl [Department of Chemistry and Physics, Agricultural University, Balicka Street 122, 30 149 Krakow (Poland); Khachatryan, Gohar; Fiedorowicz, Maciej [Department of Chemistry and Physics, Agricultural University, Balicka Street 122, 30 149 Krakow (Poland); Tomasik, Piotr [Krakow College of Health Promotion, Krowoderska Street 73, 31 158 Krakow (Poland)

    2014-09-01

    Highlights: • Synthesis of quantum dots in aqueous gel of amylopectin. • Generation of quantum dots in non-ionic polysaccharide. • Preparation of CdS, Ga{sub 2}S{sub 3} and ZnS quantum dots of the size below 10 nm. • The amylopectin matrix is not suitable for generation of CaS and Cs{sub 2}S quantum dots. - Abstract: CdS, ZnS, Ga{sub 2}S{sub 3}, CaS and Cs{sub 2}S quantum dots (QDs) were generated in the amylopectin (Ap) matrix. They all emitted a light between 460 (ZnS) and 475 (CdS) nm. Sizes of Ga{sub 2}S{sub 3} and CdS QDs were 7–9 nm and 5–7 nm, respectively. Single ZnS QDs had 6–7 nm but they readily aggregated. The CaS and Cs{sub 2}S appeared mainly as 30–100 nm aggregates. There were no significant interactions between QDs and the Ap matrix. Presented method appeared unsuitable for the generation of CaS and Cs{sub 2}S QDs as they as well as their substrates [Ca(NO{sub 3}){sub 2}] hydrolyzed. Calcium compounds formed complexes with Ap and alkaline solution from CsOH could produce cesium salts of Ap as well as cause oxidation of Ap.

  8. Electrically active defects in n-type 4H- and 6H-SiC

    Energy Technology Data Exchange (ETDEWEB)

    Doyle, J.P. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Solid State Electronics]|[IBM Research Div., T.J. Watson Research Center, Yorktown Heights, NY (United States); Aboelfotoh, M.O. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Solid State Electronics]|[North Carolina State Univ., Dept. of Materials Science and Engineering, Raleigh, NC (United States); Svensson, B.G. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Solid State Electronics

    1998-06-01

    We have found that in 6H-SiC, irradiation induced defects can become mobile at temperatures as low as 200 C. Through isochronal and isothermal annealing a level at 0.51 eV below the conduction band (with a capture cross-section of 2 x 10{sup -14} cm{sup 2}), appears to disassociate through a first order process with an activation energy of 1.45 eV+/-0.1 eV. In 4H-SiC, we have observed two irradiation induced defects assigned the positions 0.62 eV and 0.68 eV below E{sub c} (with capture cross-sections of 4 x 10{sup -14} cm{sup 2} and 5 x 10{sup -15} cm{sup 2}, respectively) which are found to be unstable at room temperature with time. SIMS analysis indicates that in both 6H- and 4H-SiC the defect levels are not due to the incorporation of the transition metals Ti, V, or Cr. Additionally, in both polytypes of SiC that were examined, the defects are found to display acceptor-like behavior as no evidence of a Poole-Frenkel shift was observed during DLTS measurements. (orig.) 10 refs.

  9. DYNAMISM OF DOT SUBRETINAL DRUSENOID DEPOSITS IN AGE-RELATED MACULAR DEGENERATION DEMONSTRATED WITH ADAPTIVE OPTICS IMAGING.

    Science.gov (United States)

    Zhang, Yuhua; Wang, Xiaolin; Godara, Pooja; Zhang, Tianjiao; Clark, Mark E; Witherspoon, C Douglas; Spaide, Richard F; Owsley, Cynthia; Curcio, Christine A

    2018-01-01

    To investigate the natural history of dot subretinal drusenoid deposits (SDD) in age-related macular degeneration, using high-resolution adaptive optics scanning laser ophthalmoscopy. Six eyes of four patients with intermediate age-related macular degeneration were studied at baseline and 1 year later. Individual dot SDD within the central 30° retina were examined with adaptive optics scanning laser ophthalmoscopy and optical coherence tomography. A total of 269 solitary SDD were identified at baseline. Over 12.25 ± 1.18 months, all 35 Stage 1 SDD progressed to advanced stages. Eighteen (60%) Stage 2 lesions progressed to Stage 3 and 12 (40%) remained at Stage 2. Of 204 Stage 3 SDD, 12 (6.4%) disappeared and the rest remained. Twelve new SDD were identified, including 6 (50%) at Stage 1, 2 (16.7%) at Stage 2, and 4 (33.3%) at Stage 3. The mean percentage of the retina affected by dot SDD, measured by the adaptive optics scanning laser ophthalmoscopy, increased in 5/6 eyes (from 2.31% to 5.08% in the most changed eye) and decreased slightly in 1/6 eye (from 10.67% to 10.54%). Dynamism, the absolute value of the areas affected by new and regressed lesions, ranged from 0.7% to 9.3%. Adaptive optics scanning laser ophthalmoscopy reveals that dot SDD, like drusen, are dynamic.

  10. Syntheses of 24R,25-dihydroxy-[6,19,19-3H]vitamin D3 and 24R,25-dihydroxy-[6,19,19-2H]vitamin D3

    International Nuclear Information System (INIS)

    Yamada, S.; Shimizu, M.; Fukushima, K.; Niimura, K.; Maeda, Y.

    1989-01-01

    24R,25-Dihydroxy-[6,19,19-3H]vitamin D3 with a specific activity of 54 Ci/mmol and 24R,25-dihydroxy-[6,19,19-2H]vitamin D3 with 2.6 deuterium atoms/mol were synthesized in four steps starting from 24R,25-Dihydroxyvitamin D3 via its sulfur dioxide adduct

  11. Geometry and bonding in the ground and lowest triplet state of D{sub 6h} symmetric crenellated edged C{sub 6[3m(m-1)+1]}H{sub 6(2m-1)} (m = 2,..., 6) graphene hydrocarbon molecules

    Energy Technology Data Exchange (ETDEWEB)

    Philpott, Michael R., E-mail: philpott@imr.edu [Center for Computational Materials Science, Institute of Materials Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, 980-8577 Sendai (Japan); Kawazoe, Yoshiyuki [Center for Computational Materials Science, Institute of Materials Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, 980-8577 Sendai (Japan)

    2009-03-30

    Ab initio plane wave all valence electron based DFT calculations were used to explore the dichotomy of perimeter vs. interior in the electronic and geometric structure of the D{sub 6h} singlet ground state and D{sub 2h} lowest triplet state of planar graphene hydrocarbon molecules with crenellated (arm chair) edges and the general formula C{sub 6[3m(m-1)+1]} H{sub 6(2m-1)} where m = 2,...,6. The largest molecule C{sub 546}H{sub 66} was 4.78 nm across and contained 2250 valence electrons. These molecules are nominally 'fully benzenoid hydrocarbons'. However with increasing size, the core of central atoms abandoned any fully benzenoid geometry they had in small systems and organized into single layer graphite (graphene) structure. The perimeter atoms of the crenellation adopted a conjugated geometry with unequal bonds and between core and perimeter there were some C{sub 6} rings retaining remnants of aromatic sextet-type properties. Compared to a zigzag edge the crenellated edge conferred stability in all the systems studied as measured by the singlet homo-lumo level gap BG{sub 0} and the singlet-lowest triplet energy gap {Delta}E{sub ST}. For the largest crenellated system (m = 6) BG{sub 0} and {Delta}E{sub ST} were approximately 0.7 eV, larger in value than for similarly sized hexagonal graphenes with zigzag edges. Triplet states were identified for all the molecules in the series and in the case of the m = 2 molecule hexabenzocoronene C{sub 42}H{sub 18}, two conformations with D{sub 2h} symmetry were identified and compared to features on the triplet state potential energy surface of benzene.

  12. Ultra-large scale synthesis of high electrochemical performance SnO{sub 2} quantum dots within 5 min at room temperature following a growth self-termination mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Hongtao, E-mail: htcui@ytu.edu.cn; Xue, Junying; Ren, Wanzhong; Wang, Minmin

    2015-10-05

    Highlights: • SnO{sub 2} quantum dots were prepared at an ultra-large scale at room temperature within 5 min. • The grinding of SnCl{sub 2}⋅2H{sub 2}O and ammonium persulphate with morpholine produces quantum dots. • The reactions were self-terminated through the rapid consumption of water. • The obtained SnO{sub 2} quantum dots own high electrochemical performance. - Abstract: SnO{sub 2} quantum dots are prepared at an ultra-large scale by a productive synthetic procedure without using any organic ligand. The grinding of solid mixture of SnCl{sub 2}⋅2H{sub 2}O and ammonium persulphate with morpholine in a mortar at room temperature produces 1.2 nm SnO{sub 2} quantum dots within 5 min. The formation of SnO{sub 2} is initiated by the reaction between tin ions and hydroxyl groups generated from hydrolysis of morpholine in the released hydrate water from SnCl{sub 2}⋅2H{sub 2}O. It is considered that as water is rapidly consumed by the hydrolysis reaction of morpholine, the growth process of particles is self-terminated immediately after their transitory period of nucleation and growth. As a result of simple procedure and high toleration to scaling up of preparation, at least 50 g of SnO{sub 2} quantum dots can be produced in one batch in our laboratory. The as prepared quantum dots present high electrochemical performance due to the effective faradaic reaction and the alternative trapping of electrons and holes.

  13. Compression of glycolide-h4 to 6GPa

    DEFF Research Database (Denmark)

    Hutchison, Ian B.; Bull, Craig L.; Marshall, William G.

    2017-01-01

    This study details the structural characterization of glycolide-h4 as a function of pressure to 6GPa using neutron powder diffraction on the PEARL instrument at ISIS Neutron and Muon source. Glycolide-h4, rather than its deuterated isotopologue, was used in this study due to the difficulty...... of deuteration. The low background afforded by zirconia-toughened alumina anvils nevertheless enabled the collection of data suitable for structural analysis to be obtained to a pressure of 5GPa. Glycolide-h4 undergoes a reconstructive phase transition at 0.15GPa to a previously identified form (II), which...

  14. [Analysis on workload for hospital DOTS service].

    Science.gov (United States)

    Nagata, Yoko; Urakawa, Minako; Kobayashi, Noriko; Kato, Seiya

    2014-04-01

    A directly observed treatment short course (DOTS) trial was launched in Japan in the late 1990s and targeted patients with social depression at urban areas. Based on these findings, the Ministry of Health, Labour and Welfare established the Japanese DOTS Strategy in 2003, which is a comprehensive support service ensuring the adherence of tuberculosis patients to drug administration. DOTS services are initially provided at the hospital to patients with infectious tuberculosis who are hospitalized according to the Infectious Diseases Control Law. After being discharged from the hospital, the patients are referred to a public health center. However, a survey conducted in 2008 indicated that all the patients do not receive appropriate DOTS services at some hospitals. In the present study, we aimed to evaluate the protocols and workload of DOTS at hospitals that are actively involved in tuberculosis medical practice, including DOTS, to assess whether the hospital DOTS services were adequate. We reviewed a series of articles on hospital DOTS from a Japanese journal on nursing for tuberculosis patients and identified 25 activities regarding the hospital DOTS service. These 25 items were then classified into 3 categories: health education to patients, support for adherence, and coordination with the health center. In total, 20 hospitals that had > 20 authorized tuberculosis beds were selected--while considering the geographical balance, schedule of this survey, etc.--from 33 hospitals where an ex-trainee of the tuberculosis control expert training program in the Research Institute of Tuberculosis (RIT) was working and 20 hospitals that had collaborated with our previous survey on tuberculosis medical facilities. All the staff associated with the DOTS service were asked to record the total working time as well as the time spent for each activity. The data were collected and analyzed at the RIT. The working times for each activity of the DOTS service for nurses, pharmacists

  15. 49 CFR 41.119 - DOT regulated buildings.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 1 2010-10-01 2010-10-01 false DOT regulated buildings. 41.119 Section 41.119 Transportation Office of the Secretary of Transportation SEISMIC SAFETY § 41.119 DOT regulated buildings. (a) Each DOT Operating Administration with responsibility for regulating the structural safety of buildings...

  16. Neuromodulatory properties of fluorescent carbon dots: effect on exocytotic release, uptake and ambient level of glutamate and GABA in brain nerve terminals.

    Science.gov (United States)

    Borisova, Tatiana; Nazarova, Anastasia; Dekaliuk, Mariia; Krisanova, Natalia; Pozdnyakova, Natalia; Borysov, Arsenii; Sivko, Roman; Demchenko, Alexander P

    2015-02-01

    Carbon dots (C-dots), a recently discovered class of fluorescent nano-sized particles with pure carbon core, have great bioanalytical potential. Neuroactive properties of fluorescent C-dots obtained from β-alanine by microwave heating were assessed based on the analysis of their effects on the key characteristics of GABA- and glutamatergic neurotransmission in isolated rat brain nerve terminals. It was found that C-dots (40-800 μg/ml) in dose-dependent manner: (1) decreased exocytotic release of [(3)H]GABA and L-[(14)C]glutamate; (2) reduced acidification of synaptic vesicles; (3) attenuated the initial velocity of Na(+)-dependent transporter-mediated uptake of [(3)H]GABA and L-[(14)C]glutamate; (4) increased the ambient level of the neurotransmitters, nevertheless (5) did not change significantly the potential of the plasma membrane of nerve terminals. Almost complete suppression of exocytotic release of the neurotransmitters was caused by C-dots at a concentration of 800 μg/ml. Fluorescent and neuromodulatory features combined in C-dots create base for their potential usage for labeling and visualization of key processes in nerve terminals, and also in theranostics. In addition, natural presence of carbon-containing nanoparticles in the human food chain and in the air may provoke the development of neurologic consequences. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Electrochemical Determination of Uric Acid at CdTe Quantum Dot Modified Glassy Carbon Electrodes.

    Science.gov (United States)

    Pan, Deng; Rong, Shengzhong; Zhang, Guangteng; Zhang, Yannan; Zhou, Qiang; Liu, Fenghai; Li, Miaojing; Chang, Dong; Pan, Hongzhi

    2015-01-01

    Cyclic voltammetry and differential pulse voltammetry were used to investigate the electrochemical behavior of uric acid (UA) at a CdTe quantum dot (QD) modified the glassy carbon electrode (GCE). CdTe QDs, as new semiconductor nanocrystals, can greatly improve the peak current of UA. The anodic peak current of UA was linear with its concentration between 1.0×10(-6) and 4.0×10(-4) M in 0.1 M pH 5.0 phosphate buffer solution. The LOD for UA at the CdTe electrode (1.0×10(-7) M) was superior to that of the GCE. In addition, we also determined the effects of scan rate, pH, and interferences of UA for the voltammetric behavior and detection. The results indicated that modified electrode possessed excellent reproducibility and stability. Finally, a new and efficient electrochemical sensor for detecting UA was developed.

  18. Official Centre Hospitality

    International Development Research Centre (IDRC) Digital Library (Canada)

    Sylvain Dufour

    Approved by the Management Executive Committee. - 1 -. Version 3.1.0 effective 2017-06-28. Official Centre Hospitality. 1. Objective. 2. Application. 3. Definitions. 4. Roles and Responsibilities. 5. Authorization. 6. Consultants and Contractors. 7. Reimbursement. 1. Objective. To define the circumstances under which ...

  19. Ultrafast photoluminescence spectroscopy of InAs/GaAs quantum dots

    Czech Academy of Sciences Publication Activity Database

    Neudert, K.; Trojánek, F.; Kuldová, Karla; Oswald, Jiří; Hospodková, Alice; Malý, P.

    2009-01-01

    Roč. 6, č. 4 (2009), 853-856 ISSN 1862-6351 R&D Projects: GA ČR GA202/06/0718 Institutional research plan: CEZ:AV0Z10100521 Keywords : quantum dots * photoluminescence * MOVPE Subject RIV: BM - Solid Matter Physics ; Magnetism

  20. MOVPE grown InGaAs quantum dots of high optical quality as seed layer for low-density InP quantum dots

    International Nuclear Information System (INIS)

    Richter, D; Hafenbrak, R; Joens, K D; Schulz, W-M; Eichfelder, M; Rossbach, R; Jetter, M; Michler, P

    2010-01-01

    To achieve a low density of optically active InP-quantum dots we used InGaAs islands embedded in GaAs as a seed layer. First, the structural InGaAs quantum dot properties and the influence of the annealing technique was investigated by atomic force microscope measurements. High-resolution micro-photoluminescence spectra reveal narrow photoluminescence lines, with linewidths down to 11 μeV and fine structure splittings of 25 μeV. Furthermore, using these InGaAs quantum dots as seed layer reduces the InP quantum dot density of optically active quantum dots drastically. InP quantum dot excitonic photoluminescence emission with a linewidth of 140 μeV has been observed.

  1. Graded Doping for Enhanced Colloidal Quantum Dot Photovoltaics

    KAUST Repository

    Ning, Zhijun

    2013-02-05

    A novel approach to improving all-inorganic colloidal quantum dot (CQD) homojunction solar cells by engineering the doping spatial profile to produce a doping gradient within the n-type absorber is presented. The doping gradient greatly improves carrier collection and enhances the voltages attainable by the device, leading to a 1 power point power conversion efficiency (PCE) improvement over previous inorganic CQD solar cells. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. A novel quantum dot-laccase hybrid nanobiosensor for low level determination of dopamine.

    Science.gov (United States)

    Shamsipur, Mojtaba; Shanehasz, Maryam; Khajeh, Khosro; Mollania, Nasrin; Kazemi, Sayyed Habib

    2012-12-07

    This work reports a novel nanobiosensor based on a thioglycolic acid (TGA)-capped CdTe quantum dot-laccase (Lac) enzyme system for sensitive detection of dopamine (DA). The enzyme used catalyzes the oxidation of DA to dopamine-o-quinone (DOQ), which can selectively quench the strong luminescence of CdTe nanocrystals at neutral pH. The relationship between luminescence intensity of CdTe nanocrystals and DA concentration is nicely described by the Stern-Volmer equation. At an optimum pH of 7.4, the proposed sensor gives a linear calibration over a DA concentration range of 0.3 to 100 μM, with a limit of detection of 0.16 μM and a response time of 2 min. The relative standard deviation for seven replicate determinations of 6.0 μM of DA was found to be 3.7%. The sensor was successfully applied to the determination of DA in a blood plasma sample and in a DA injection formulation.

  3. Spin current through quantum-dot spin valves

    International Nuclear Information System (INIS)

    Wang, J; Xing, D Y

    2006-01-01

    We report a theoretical study of the influence of the Coulomb interaction on the equilibrium spin current in a quantum-dot spin valve, in which the quantum dot described by the Anderson impurity model is coupled to two ferromagnetic leads with noncollinear magnetizations. In the Kondo regime, electrons transmit through the quantum dot via higher-order virtual processes, in which the spin of either lead electrons or a localized electron on the quantum dot may reverse. It is found that the magnitude of the spin current decreases with increasing Coulomb interactions due to spin flip effects on the dot. However, the spatial direction of the spin current remains unchanged; it is determined only by the exchange coupling between two noncollinear magnetizations

  4. TEMA and Dot Enumeration Profiles Predict Mental Addition Problem Solving Speed Longitudinally.

    Science.gov (United States)

    Major, Clare S; Paul, Jacob M; Reeve, Robert A

    2017-01-01

    Different math indices can be used to assess math potential at school entry. We evaluated whether standardized math achievement (TEMA-2 performance), core number abilities (dot enumeration, symbolic magnitude comparison), non-verbal intelligence (NVIQ) and visuo-spatial working memory (VSWM), in combination or separately, predicted mental addition problem solving speed over time. We assessed 267 children's TEMA-2, magnitude comparison, dot enumeration, and VSWM abilities at school entry (5 years) and NVIQ at 8 years. Mental addition problem solving speed was assessed at 6, 8, and 10 years. Longitudinal path analysis supported a model in which dot enumeration performance ability profiles and previous mental addition speed predicted future mental addition speed on all occasions, supporting a componential account of math ability. Standardized math achievement and NVIQ predicted mental addition speed at specific time points, while VSWM and symbolic magnitude comparison did not contribute unique variance to the model. The implications of using standardized math achievement and dot enumeration ability to index math learning potential at school entry are discussed.

  5. Magnesium hexafluoridozirconates MgZrF{sub 6}.5H{sub 2}O, MgZrF{sub 6}.2H{sub 2}O, and MgZrF{sub 6}. Structures, phase transitions, and internal mobility of water molecules

    Energy Technology Data Exchange (ETDEWEB)

    Gerasimenko, Andrey V.; Gaivoronskaya, Kseniya A.; Slobodyuk, Arseny B.; Didenko, Nina A. [Institute of Chemistry, Russian Academy of Sciences, Vladivostok (Russian Federation)

    2017-12-04

    The MgZrF{sub 6}.nH{sub 2}O (n = 5, 2 and 0) compounds were studied by the methods of X-ray diffraction and {sup 19}F, MAS {sup 19}F, and {sup 1}H NMR spectroscopy. At room temperature, the compound MgZrF{sub 6}.5H{sub 2}O has a monoclinic C-centered unit cell and is composed of isolated chains of edge-sharing ZrF{sub 8} dodecahedra reinforced with MgF{sub 2}(H{sub 2}O){sub 4} octahedra and uncoordinated H{sub 2}O molecules and characterized by a disordered system of hydrogen bonds. In the temperature range 259 to 255 K, a reversible monoclinic <-> two-domain triclinic phase transition is observed. The phase transition is accompanied with ordering of hydrogen atoms positions and the system of hydrogen bonds. The structure of MgZrF{sub 6}.2H{sub 2}O comprises a three-dimensional framework consisting of chains of edge-sharing ZrF{sub 8} dodecahedra linked to each other through MgF{sub 4}(H{sub 2}O){sub 2} octahedra. The compound MgZrF{sub 6} belongs to the NaSbF{sub 6} type and is built from regular ZrF{sub 6} and MgF{sub 6} octahedra linked into a three-dimensional framework through linear Zr-F-Mg bridges. The peaks in {sup 19}F MAS spectra were attributed to the fluorine structural positions. The motions of structural water molecules were studied by variable-temperature {sup 1}H NMR spectroscopy. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Entangled exciton states in quantum dot molecules

    Science.gov (United States)

    Bayer, Manfred

    2002-03-01

    Currently there is strong interest in quantum information processing(See, for example, The Physics of Quantum Information, eds. D. Bouwmeester, A. Ekert and A. Zeilinger (Springer, Berlin, 2000).) in a solid state environment. Many approaches mimic atomic physics concepts in which semiconductor quantum dots are implemented as artificial atoms. An essential building block of a quantum processor is a gate which entangles the states of two quantum bits. Recently a pair of vertically aligned quantum dots has been suggested as optically driven quantum gate(P. Hawrylak, S. Fafard, and Z. R. Wasilewski, Cond. Matter News 7, 16 (1999).)(M. Bayer, P. Hawrylak, K. Hinzer, S. Fafard, M. Korkusinski, Z.R. Wasilewski, O. Stern, and A. Forchel, Science 291, 451 (2001).): The quantum bits are individual carriers either on dot zero or dot one. The different dot indices play the same role as a "spin", therefore we call them "isospin". Quantum mechanical tunneling between the dots rotates the isospin and leads to superposition of these states. The quantum gate is built when two different particles, an electron and a hole, are created optically. The two particles form entangled isospin states. Here we present spectrocsopic studies of single self-assembled InAs/GaAs quantum dot molecules that support the feasibility of this proposal. The evolution of the excitonic recombination spectrum with varying separation between the dots allows us to demonstrate coherent tunneling of carriers across the separating barrier and the formation of entangled exciton states: Due to the coupling between the dots the exciton states show a splitting that increases with decreasing barrier width. For barrier widths below 5 nm it exceeds the thermal energy at room temperature. For a given barrier width, we find only small variations of the tunneling induced splitting demonstrating a good homogeneity within a molecule ensemble. The entanglement may be controlled by application of electromagnetic field. For

  7. Approche de l’état podologique du patient diabétique hémodialysé chronique dans un centre hospitalier Marocain

    OpenAIRE

    Benabdellah, Nawal; Karimi, Ilham; Bentata, Yassamine; Haddiya, Intissar

    2013-01-01

    De plus en plus de patients diabétiques sont pris en charge en HDC. Les conséquences sont multiples, notamment les problèmes de pied diabétique qui demeurent mal connus du patient diabétique et des soignants ce qui retentit considérablement sur la qualité de prise en charge. Nous avons réalisé une Etude transversale en Novembre 2011 au centre d'hémodialyse de l'hôpital Al Farabi d'Oujda, incluant tous nos patients diabétiques HDC. Nous avons relevé les données démographiques, clinico-biologiq...

  8. Synthesis of CdSe quantum dots for quantum dot sensitized solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Neetu, E-mail: singh.neetu1985@gmail.com; Kapoor, Avinashi [Department of Electronic Science, University of Delhi South Campus, New Delhi-110 021 (India); Kumar, Vinod [Department of Physics, University of the Free State, Bloemfontein, ZA9300 (South Africa); Mehra, R. M. [School of Engineering and Technology, Sharda University, Greater Noida-201 306, U.P. (India)

    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.

  9. Self-Assembled BN and BCN Quantum Dots Obtained from High Intensity Ultrasound Exfoliated Nanosheets

    Czech Academy of Sciences Publication Activity Database

    Štengl, Václav; Henych, Jiří; Kormunda, M.

    2014-01-01

    Roč. 6, č. 6 (2014), s. 1106-1116 ISSN 1947-2935 Institutional support: RVO:61388980 Keywords : Ultrasound * Exfoliation * BN * BCN * Quantum Dots Subject RIV: CA - Inorganic Chemistry Impact factor: 2.598, year: 2014

  10. Prediction of superconducting ternary hydride MgGeH6: from divergent high-pressure formation routes.

    Science.gov (United States)

    Ma, Yanbin; Duan, Defang; Shao, Ziji; Li, Da; Wang, Liyuan; Yu, Hongyu; Tian, Fubo; Xie, Hui; Liu, Bingbing; Cui, Tian

    2017-10-18

    Invigorated by the high temperature superconductivity in some binary hydrogen-dominated compounds, we systematically explored high-pressure phase diagrams and superconductivity of a ternary Mg-Ge-H system using ab initio methods. Stoichiometric MgGeH 6 with high hydrogen content exhibiting Pm3[combining macron] symmetry was predicted from a series of high-pressure synthesis paths. We performed an in-depth study on three distinct formation routes to MgGeH 6 , i.e., Mg + Ge + 3H 2 → MgGeH 6 , MgGe + 3H 2 → MgGeH 6 and MgH 2 + GeH 4 → MgGeH 6 at high pressures. By directly squeezing three elemental solids Mg + Ge + 3H 2 , we obtained ternary MgGeH 6 at 200 GPa. By adding a little bit of the MgGe alloy into hydrogen, we found that MgGeH 6 can form and stabilize at about 200 GPa. More intriguingly, upon compressing MgH 2 and GeH 4 to 250 GPa, we also predicted the same MgGeH 6 . Electron structure calculations reveal that the cubic MgGeH 6 is a good metal and takes on ionic character. Electron-phonon coupling calculation reveals a large λ = 1.16 for MgGeH 6 at 200 GPa. In particular, we found that ternary MgGeH 6 could be a potential high temperature superconductor with a superconducting transition temperature T c of ∼67 K at 200 GPa.

  11. ONE STEP GREEN SYNTHESIS OF CARBON QUANTUM DOTS AND ITS APPLICATION TOWARDS THE BIOELECTROANALYTICAL AND BIOLABELING STUDIES

    International Nuclear Information System (INIS)

    Shereema, Rayammarakkar M.; Sankar, Vandana; Raghu, K.G; Rao, Talasila P.; Shankar, S.Sharath

    2015-01-01

    Highlights: • A green method was adopted for the synthesis of carbon quantum dots. • Being green fluorescent it was used for the cell imaging. • The carbon paste based carbon quantum dot was fabricated. • This quantum dots/carbon paste electrode was found to be capable of detecting dopamine in the nano molar level. • Possible interference from ascorbic acid and uric acid was successfully eliminated by the fabricated electrode. - Abstract: A green luminescent carbon quantum dots were prepared from maltose by Microwave assisted method followed by passivation with NaOH (pH = 7.4). The TEM measurement confirmed the average size of prepared carbon quantum dots to be 2 nm. Surface characterization such as XPS, FTIR and Raman spectroscopy confirm that the functional groups (C=O, C-OH) were attached on the surface of sp 2 hybridized carbon. Electrochemical characterization studies on carbon paste electrode (CPE) revealed that the synthesized carbon quantum dots showed higher electrocatalytic property, conductivity and surface area. Therefore, herein we report the synthesized carbon quantum dots could find its applicability as an electrochemical sensor for the detection of neurotransmitter, dopamine. Cyclic voltammetry and differential pulse voltammetry (DPV) was employed for the detection of DA in presence of common interferences like UA, and AA with carbon quantum dots modified carbon paste electrode. The developed sensor was effectively applied for the real sample analysis with satisfactory results. Moreover, biological studies in He La cell lines proclaimed that the cell viability was unaffected (100% viability) on incubation with the carbon dots. Significant cellular uptake as revealed by fluorescence imaging makes them suitable for cell labeling studies.

  12. Mitochondrial genomic analysis of late onset Alzheimer's disease reveals protective haplogroups H6A1A/H6A1B: the Cache County Study on Memory in Aging.

    Directory of Open Access Journals (Sweden)

    Perry G Ridge

    Full Text Available Alzheimer's disease (AD is the most common cause of dementia and AD risk clusters within families. Part of the familial aggregation of AD is accounted for by excess maternal vs. paternal inheritance, a pattern consistent with mitochondrial inheritance. The role of specific mitochondrial DNA (mtDNA variants and haplogroups in AD risk is uncertain.We determined the complete mitochondrial genome sequence of 1007 participants in the Cache County Study on Memory in Aging, a population-based prospective cohort study of dementia in northern Utah. AD diagnoses were made with a multi-stage protocol that included clinical examination and review by a panel of clinical experts. We used TreeScanning, a statistically robust approach based on haplotype networks, to analyze the mtDNA sequence data. Participants with major mitochondrial haplotypes H6A1A and H6A1B showed a reduced risk of AD (p=0.017, corrected for multiple comparisons. The protective haplotypes were defined by three variants: m.3915G>A, m.4727A>G, and m.9380G>A. These three variants characterize two different major haplogroups. Together m.4727A>G and m.9380G>A define H6A1, and it has been suggested m.3915G>A defines H6A. Additional variants differentiate H6A1A and H6A1B; however, none of these variants had a significant relationship with AD case-control status.Our findings provide evidence of a reduced risk of AD for individuals with mtDNA haplotypes H6A1A and H6A1B. These findings are the results of the largest study to date with complete mtDNA genome sequence data, yet the functional significance of the associated haplotypes remains unknown and replication in others studies is necessary.

  13. Core–shell quantum dots: Properties and applications

    Energy Technology Data Exchange (ETDEWEB)

    Vasudevan, D., E-mail: vasudevand@rediffmail.com [Electrodics and electrocatalysis division, CSIR-CECRI, Karaikudi 630006 (India); Gaddam, Rohit Ranganathan [Amity Institute of Nanotechnology, Amity University, Noida 201301 (India); Trinchi, Adrian; Cole, Ivan [CSIRO Materials Science and Engineering, Clayton South MDC, 3169 (Australia)

    2015-07-05

    Fluorescent quantum dots (QDs) are semiconducting nanocrystals (NCs) that find numerous applications in areas, such as bio labelling, sensors, lasers, light emitting diodes and medicine. Core–shell quantum dots were developed to improve the photoluminescence efficiency of single quantum dots. Capping their surface with organic ligands as well as their extraction into aqueous media enables their use in sensing applications. The current review highlights the importance and applications of core shell quantum dots as well as their surface modifications and applications in the field of medicine and as sensors for chemical and biochemical analysis.

  14. Core–shell quantum dots: Properties and applications

    International Nuclear Information System (INIS)

    Vasudevan, D.; Gaddam, Rohit Ranganathan; Trinchi, Adrian; Cole, Ivan

    2015-01-01

    Fluorescent quantum dots (QDs) are semiconducting nanocrystals (NCs) that find numerous applications in areas, such as bio labelling, sensors, lasers, light emitting diodes and medicine. Core–shell quantum dots were developed to improve the photoluminescence efficiency of single quantum dots. Capping their surface with organic ligands as well as their extraction into aqueous media enables their use in sensing applications. The current review highlights the importance and applications of core shell quantum dots as well as their surface modifications and applications in the field of medicine and as sensors for chemical and biochemical analysis

  15. Correlation effects in side-coupled quantum dots

    International Nuclear Information System (INIS)

    Zitko, R; Bonca, J

    2007-01-01

    Using Wilson's numerical renormalization group (NRG) technique, we compute zero-bias conductance and various correlation functions of a double quantum dot (DQD) system. We present different regimes within a phase diagram of the DQD system. By introducing a negative Hubbard U on one of the quantum dots, we simulate the effect of electron-phonon coupling and explore the properties of the coexisting spin and charge Kondo state. In a triple quantum dot (TQD) system, a multi-stage Kondo effect appears where localized moments on quantum dots are screened successively at exponentially distinct Kondo temperatures

  16. Carbon dots decorated vertical SnS_2 nanosheets for efficient photocatalytic oxygen evolution

    International Nuclear Information System (INIS)

    Cheng, Zhongzhou; Wang, Fengmei; Shifa, Tofik Ahmed; Liu, Kaili; Huang, Yun; Jiang, Chao; He, Jun; Liu, Quanlin

    2016-01-01

    Metal sulfides are highly desirable materials for photocatalytic water splitting because of their appropriate energy bands. However, the poor stability under light illumination in water hinders their wide applications. Here, two-dimensional SnS_2 nanosheets, along with carbon dots of the size around 10 nm, are uniformly grown on fluorine doped tin oxide glasses with a layer of nickel nanoparticles. Significantly, strong light absorption and enhanced photocurrent density are achieved after integration of SnS_2 nanosheets with carbon dots. Notably, the rate of oxygen evolution reached up to 1.1 mmol g"−"1 h"−"1 under simulated sunlight irradiation featuring a good stability.

  17. Solar Cells Based on Inks of n-Type Colloidal Quantum Dots

    KAUST Repository

    Ning, Zhijun; Dong, Haopeng; Zhang, Qiong; Voznyy, Oleksandr; Sargent, Edward H.

    2014-01-01

    © 2014 American Chemical Society. New inorganic ligands including halide anions have significantly accelerated progress in colloidal quantum dot (CQD) photovoltaics in recent years. All such device reports to date have relied on halide treatment during solid-state ligand exchanges or on co-treatment of long-aliphatic-ligand-capped nanoparticles in the solution phase. Here we report solar cells based on a colloidal quantum dot ink that is capped using halide-based ligands alone. By judicious choice of solvents and ligands, we developed a CQD ink from which a homogeneous and thick colloidal quantum dot solid is applied in a single step. The resultant films display an n-type character, making it suitable as a key component in a solar-converting device. We demonstrate two types of quantum junction devices that exploit these iodide-ligand-based inks. We achieve solar power conversion efficiencies of 6% using this class of colloids.

  18. Solar Cells Based on Inks of n-Type Colloidal Quantum Dots

    KAUST Repository

    Ning, Zhijun

    2014-10-28

    © 2014 American Chemical Society. New inorganic ligands including halide anions have significantly accelerated progress in colloidal quantum dot (CQD) photovoltaics in recent years. All such device reports to date have relied on halide treatment during solid-state ligand exchanges or on co-treatment of long-aliphatic-ligand-capped nanoparticles in the solution phase. Here we report solar cells based on a colloidal quantum dot ink that is capped using halide-based ligands alone. By judicious choice of solvents and ligands, we developed a CQD ink from which a homogeneous and thick colloidal quantum dot solid is applied in a single step. The resultant films display an n-type character, making it suitable as a key component in a solar-converting device. We demonstrate two types of quantum junction devices that exploit these iodide-ligand-based inks. We achieve solar power conversion efficiencies of 6% using this class of colloids.

  19. Wannier-Frenkel hybrid exciton in organic-semiconductor quantum dot heterostructures

    International Nuclear Information System (INIS)

    Birman, Joseph L.; Huong, Nguyen Que

    2007-01-01

    The formation of a hybridization state of Wannier Mott exciton and Frenkel exciton in different hetero-structure configurations involving quantum dots is investigated. The hybrid excitons exist at the interfaces of the semiconductors quantum dots and the organic medium, having unique properties and a large optical non-linearity. The coupling at resonance is very strong and tunable by changing the parameters of the systems (dot radius, dot-dot distance, generation of the organic dendrites and the materials of the system etc...). Different semiconductor quantum dot-organic material combination systems have been considered such as a semiconductor quantum dot lattice embedded in an organic host, a semiconductor quantum dot at the center of an organic dendrite, a semiconductor quantum dot coated by an organic shell

  20. Spin manipulation and spin-lattice interaction in magnetic colloidal quantum dots

    OpenAIRE

    Moro, F.; Turyanska, L.; Granwehr, J.; Patane, A.

    2014-01-01

    We report on the spin-lattice interaction and coherent manipulation of electron spins in Mn-doped colloidal PbS quantum dots (QDs) by electron spin resonance. We show that the phase memory time,TM, is limited by Mn-Mn dipolar interactions, hyperfine interactions of the protons (H1) on the QD capping ligands with Mn ions in their proximity (

  1. The quantum Hall effect in quantum dot systems

    International Nuclear Information System (INIS)

    Beltukov, Y M; Greshnov, A A

    2014-01-01

    It is proposed to use quantum dots in order to increase the temperatures suitable for observation of the integer quantum Hall effect. A simple estimation using Fock-Darwin spectrum of a quantum dot shows that good part of carriers localized in quantum dots generate the intervals of plateaus robust against elevated temperatures. Numerical calculations employing local trigonometric basis and highly efficient kernel polynomial method adopted for computing the Hall conductivity reveal that quantum dots may enhance peak temperature for the effect by an order of magnitude, possibly above 77 K. Requirements to potentials, quality and arrangement of the quantum dots essential for practical realization of such enhancement are indicated. Comparison of our theoretical results with the quantum Hall measurements in InAs quantum dot systems from two experimental groups is also given

  2. Silicon quantum dots: surface matters

    Czech Academy of Sciences Publication Activity Database

    Dohnalová, K.; Gregorkiewicz, T.; Kůsová, Kateřina

    2014-01-01

    Roč. 26, č. 17 (2014), 1-28 ISSN 0953-8984 R&D Projects: GA ČR GPP204/12/P235 Institutional support: RVO:68378271 Keywords : silicon quantum dots * quantum dot * surface chemistry * quantum confinement Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.346, year: 2014

  3. N-doped carbon dots derived from bovine serum albumin and formic acid with one- and two-photon fluorescence for live cell nuclear imaging.

    Science.gov (United States)

    Tan, Mingqian; Li, Xintong; Wu, Hao; Wang, Beibei; Wu, Jing

    2015-12-01

    Carbon dots with both one- and two-photon fluorescence have drawn great attention for biomedical imaging. Herein, nitrogen-doped carbon dots were facilely developed by one-pot hydrothermal method using bovine serum albumin and formic acid as carbon sources. They are highly water-soluble with strong fluorescence when excited with ultraviolet or near infrared light. The carbon dots have a diameter of ~8.32 nm and can emit strong two-photon induced fluorescence upon excitation at 750 nm with a femtosecond laser. X-ray photoelectron spectrometer analysis revealed that the carbon dots contained three components, C, N and O, corresponding to the peak at 285, 398 and 532 eV, respectively. The Fourier-transform infrared spectroscopy analysis revealed that there are carboxyl and carboxylic groups on the surface, which allowed further linking of functional molecules. pH stability study demonstrated that the carbon dots are able to be used in a wide range of pH values. The fluorescence mechanism is also discussed in this study. Importantly, these carbon dots are biocompatible and highly photostable, which can be directly applied for both one- and two-photon living cell imaging. After proper surface functionalization with TAT peptide, they can be used as fluorescent probes for live cell nuclear-targeted imaging. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Artful and multifaceted applications of carbon dot in biomedicine.

    Science.gov (United States)

    Jaleel, Jumana Abdul; Pramod, K

    2018-01-10

    Carbon dots (C-dots) are luminescent carbon nanomaterial having good biocompatibility and low toxicity. The characteristic fluorescence emission property of C-dots establishes their role in optical imaging. C-dots which are superior to fluorescent dyes and semiconductor quantum dots act as a safer in vivo imaging probe. Apart from their bioimaging application, other applications in biomedicine such as drug delivery, cancer therapy, and gene delivery were studied. In this review, we present multifaceted applications of C-dots along with their synthesis, surface passivation, doping, and toxicity profile. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Protease-activated quantum dot probes

    International Nuclear Information System (INIS)

    Chang, Emmanuel; Miller, Jordan S.; Sun, Jiantang; Yu, William W.; Colvin, Vicki L.; Drezek, Rebekah; West, Jennifer L.

    2005-01-01

    We have developed a novel nanoparticulate luminescent probe with inherent signal amplification upon interaction with a targeted proteolytic enzyme. This construct may be useful for imaging in cancer detection and diagnosis. In this system, quantum dots (QDs) are bound to gold nanoparticles (AuNPs) via a proteolytically degradable peptide sequence to non-radiatively suppress luminescence. A 71% reduction in luminescence was achieved with conjugation of AuNPs to QDs. Release of AuNPs by peptide cleavage restores radiative QD photoluminescence. Initial studies observed a 52% rise in luminescence over 47 h of exposure to 0.2 mg/mL collagenase. These probes can be customized for targeted degradation simply by changing the sequence of the peptide linker

  6. Investigation of CO, C2H6 and aerosols over Eastern Canada during BORTAS 2011 using ground-based and satellite-based observations and model simulations

    Science.gov (United States)

    Griffin, Debora; Franklin, Jonathan; Parrington, Mark; Whaley, Cynthia; Hopper, Jason; Lesins, Glen; Tereszchuk, Keith; Walker, Kaley A.; Drummond, James R.; Palmer, Paul; Strong, Kimberly; Duck, Thomas J.; Abboud, Ihab; Dan, Lin; O'Neill, Norm; Clerbaux, Cathy; Coheur, Pierre; Bernath, Peter F.; Hyer, Edward; Kliever, Jenny

    2013-04-01

    We present the results of total column measurements of CO and C2H6 and aerosol optical depth (AOD) during the Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites (BORTAS-B) campaign over Eastern Canada. Ground-based observations, using Fourier transform spectrometers (FTSs) and sun photometers, were carried out in July and August 2011. They were taken in Halifax, Nova Scotia, which is an ideal location to monitor the outflow of boreal fires from North America, and in Toronto, Ontario. Measurements of enhanced fine mode AOD were highly correlated with enhancements in coincident trace gas (CO and C2H6) observations between 19 and 21 July 2011, which is typical for a smoke plume event. In this study, we will focus on the identification of the origin and the transport of this smoke plume. We use back-trajectories calculated by the Canadian Meteorological Centre (CMC) as well as FLEXPART forward-trajectories to demonstrate that the enhanced CO, C2H6 and fine mode AOD seen near Halifax and Toronto did originate from forest fires in Northwestern Ontario, that occurred between 17 and 19 July 2011. In addition, total column measurements of CO from the satellite-borne Infrared Atmospheric Sounding Interferometer (IASI) have been used to trace the smoke plume and to confirm the origin of the CO enhancement. Furthermore, the emission ratio (ERC2H6-CO) and the emission factor (EFC2H6) of C2H6 (with respect to the CO emission) were estimated from these ground-based observations. The C2H6 emission results from boreal fires in Northwestern Ontario agree well with C2H6 emission measurements from other boreal regions, and are relatively high compared to other geographical regions. The ground-based CO and C2H6 observations were compared with output from the 3-D global chemical transport model GEOS-Chem, using the inventory of the Fire Locating And Monitoring of Burning Emissions (FLAMBE). Good agreement was found for

  7. Investigations on the structural and optical properties of the swift heavy ion irradiated 6H-SiC

    International Nuclear Information System (INIS)

    Viswanathan, E.; Katharria, Y.S.; Selvakumar, S.; Arulchakkaravarthi, A.; Kanjilal, D.; Sivaji, K.

    2011-01-01

    Research highlights: → We have reported the structural and optical properties of SHI irradiated 6H-SiC. → The change in Raman modes evidences the disorder accumulation with respect to ion fluence. → The disorder also causes the modification in the optical properties. → The time resolved photoluminescence reflects multiple lifetimes due to the degenerate defects states. → The study also reveals the presence of partial amorphous region due to SHI irradiation. -- Abstract: Single crystal 6H-SiC wafers have been irradiated with 150 MeV Ag 12+ ions with fluences ranging from 1 x 10 11 to 1 x 10 13 ions/cm 2 at 300 K. The defect accumulation as a function of fluence was studied to determine changes in structural and optical properties. The variation in the fundamental Raman modes of the crystalline 6H-SiC due to irradiation has been correlated with the disorder accumulation. The creation of defect states due to irradiation in the bandgap affects the blue-green photoluminescence emission in the irradiated samples. The UV-Visible absorption studies support the existence of defect states in the bandgap which is observed by the shift in the absorption edge towards the lower energy side with increasing fluence. Time Correlated Single Photon Counting photoluminescence decay results suggest that the existing defect states are radiative, exhibiting three lifetimes when irradiated with a fluence 5 x 10 11 ions/cm 2 . The total number of lifetime components was reduced for a fluence 1 x 10 13 ions/cm 2 as the defect states produced increase the non-radiative defect centres. These results suggest that the accumulation of defects due to irradiation at fluences 5 x 10 11 and 1 x 10 13 ions/cm 2 are degenerate configurations which exhibit multiple lifetimes in photoluminescence studies. It is inferred that the optically active defect states influence the transition rate of charge carriers in this device material.

  8. Investigations on the structural and optical properties of the swift heavy ion irradiated 6H-SiC

    Energy Technology Data Exchange (ETDEWEB)

    Viswanathan, E. [Materials Science Centre, Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600025 (India); Katharria, Y.S. [Laboratoire de Physique des Interactions Ioniques et Moleculaires, Equipe Plasma-Surface, case 241, 13397 Marseille Cedex 20 (France); Selvakumar, S. [Materials Science Centre, Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600025 (India); Arulchakkaravarthi, A. [Sinmat Inc., 2153 SE Hawthorne Rd., Gainesville Fl-32641 (United States); Kanjilal, D. [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, P.O. Box 10502, New Delhi 110067 (India); Sivaji, K., E-mail: sivaji.krishnan@yahoo.co [Materials Science Centre, Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600025 (India)

    2011-05-15

    Research highlights: {yields} We have reported the structural and optical properties of SHI irradiated 6H-SiC. {yields} The change in Raman modes evidences the disorder accumulation with respect to ion fluence. {yields} The disorder also causes the modification in the optical properties. {yields} The time resolved photoluminescence reflects multiple lifetimes due to the degenerate defects states. {yields} The study also reveals the presence of partial amorphous region due to SHI irradiation. -- Abstract: Single crystal 6H-SiC wafers have been irradiated with 150 MeV Ag{sup 12+} ions with fluences ranging from 1 x 10{sup 11} to 1 x 10{sup 13} ions/cm{sup 2} at 300 K. The defect accumulation as a function of fluence was studied to determine changes in structural and optical properties. The variation in the fundamental Raman modes of the crystalline 6H-SiC due to irradiation has been correlated with the disorder accumulation. The creation of defect states due to irradiation in the bandgap affects the blue-green photoluminescence emission in the irradiated samples. The UV-Visible absorption studies support the existence of defect states in the bandgap which is observed by the shift in the absorption edge towards the lower energy side with increasing fluence. Time Correlated Single Photon Counting photoluminescence decay results suggest that the existing defect states are radiative, exhibiting three lifetimes when irradiated with a fluence 5 x 10{sup 11} ions/cm{sup 2}. The total number of lifetime components was reduced for a fluence 1 x 10{sup 13} ions/cm{sup 2} as the defect states produced increase the non-radiative defect centres. These results suggest that the accumulation of defects due to irradiation at fluences 5 x 10{sup 11} and 1 x 10{sup 13} ions/cm{sup 2} are degenerate configurations which exhibit multiple lifetimes in photoluminescence studies. It is inferred that the optically active defect states influence the transition rate of charge carriers in this

  9. Modelling of phase equilibria in CH4–C2H6–C3H8–nC4H10–NaCl–H2O systems

    International Nuclear Information System (INIS)

    Li, Jun; Zhang, Zhigang; Luo, Xiaorong; Li, Xiaochun

    2015-01-01

    Highlights: • A new model was established for the phase equilibria of C1–C2–C3–nC4–brine systems. • The model can reproduce of hydrocarbon–brine equilibria to high T&P and salinity. • The model can well predict H 2 O solubility in light hydrocarbon rich phases. - Abstract: A thermodynamic model is presented for the mutual solubility of CH 4 –C 2 H 6 –C 3 H 8 –nC 4 H 10 –brine systems up to high temperature, pressure and salinity. The Peng–Robinson model is used for non-aqueous phase fugacity calculations, and the Pitzer model is used for aqueous phase activity calculations. The model can accurately reproduce the experimental solubilities of CH 4 , C 2 H 6 , C 3 H 8 and nC 4 H 10 in water or NaCl solutions and H 2 O solubility in the non-aqueous phase. The experimental data of mutual solubility for the CH 4 –brine subsystem are sufficient for temperatures exceeding 250 °C, pressures exceeding 1000 bar and NaCl molalities greater than 6 molal. Compared to the CH 4 –brine system, the mutual solubility data of C 2 H 6 –brine, C 3 H 8 –brine and nC 4 H 10 –brine are not sufficient. Based on the comparison with the experimental data of H 2 O solubility in C 2 H 6 -, C 3 H 8 - or nC 4 H 10 -rich phases, the model has an excellent capability for the prediction of H 2 O solubility in hydrocarbon-rich phases, as these experimental data were not used in the modelling. Predictions of hydrocarbon solubility (at temperatures up to 200 °C, pressures up to 1000 bar and NaCl molalities greater than 6 molal) were made for the C 2 H 6 –brine, C 3 H 8 –brine and nC 4 H 10 –brine systems. The predictions suggest that increasing pressure generally increases the hydrocarbon solubility in water or brine, especially in the lower-pressure region. Increasing temperature usually decreases the hydrocarbon solubility at lower temperatures but increases the hydrocarbon solubility at higher temperatures. Increasing water salinity dramatically decreases

  10. Yellowish dots in the retina: a finding of ocular syphilis?

    Directory of Open Access Journals (Sweden)

    Renan Albert Mendonça Rodrigues

    2014-10-01

    Full Text Available Here we report the occurrence of pale yellowish perivascular preretinal dots in 12 patients with ocular syphilis. A case series of these patients was examined between March and October 2012 at the Uveitis Sector of Universidade Federal de São Paulo. After diagnostic confirmation of syphilis, fundus photographs and optical coherence tomography (OCT were performed to verify the localization of the dots, and patients were treated with IV crystalline penicillin for 14 days. The study comprised 11 men (91.6%, 19 eyes, median presentation age of 38.1 years, and panuveitis as the main clinical manifestation (seven patients, 58.3%, being bilateral in four. Ten patients were taking oral prednisone (83.3%. Serum panels performed by the Venereal Disease Research Laboratory (VDRL showed positive results in eight patients (66.7%, whereas VDRL cerebrospinal fluid (CSF tests were negative in seven of nine collected (77.8%. However, serum FTA-Abs was positive in 100% of patients, and eight patients (66.7% had HIV infection. The best corrected visual acuity (BCVA presented after treatment improved in 10 eyes (55.6%, did not change in seven eyes (38.9%, and worsened in one eye (5.6%. Although not yet acknowledged in the literature as a typical manifestation of ocular syphilis, these are very common findings in clinical practice. We believe that preretinal dots are due to perivasculitis secondary to treponema infection. It is important recognize them and remember that syphilis can present in several forms, including the one presented in this study.

  11. Synthesis, crystal structure and characterization of a 1D polyoxometalate-based compound: {l_brace}[Pr(H{sub 2}O){sub 7}][CrMo{sub 6}H{sub 6}O{sub 24}]{r_brace} . 4H{sub 2}O

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Lijie; Shen Shuchang; Yu Haiming [Qiqihar Univ., HL (China). Dept. of Chemistry and Chemical Engineering

    2008-07-15

    A novel polyoxometalated-based compound, {l_brace}[Pr(H{sub 2}O){sub 7}][CrMo{sub 6}H{sub 6}O{sub 24}]{r_brace} . 4H{sub 2}O, was prepared and characterized by elemental analysis, infrared and ultraviolet spectroscopy, TG measurement and single crystal X-ray diffraction. A chain-like coordination polymer is formed from a heteropolyanion [CrMo{sub 6}H{sub 6}O{sub 24}]{sup 3} as a building unit and [Pr(H{sub 2}O){sub 7}]{sup 3+} cations as linker. The chains are linked into an extensive three-dimensional supramolecular network through hydrogen bonding. The synthesis of 1 is accomplished only from pre-synthesized Anderson clusters, but not from simple starting materials. (orig.)

  12. Li4FeH6: Iron-containing complex hydride with high gravimetric hydrogen density

    Directory of Open Access Journals (Sweden)

    Hiroyuki Saitoh

    2014-07-01

    Full Text Available Li4FeH6, which has the highest gravimetric hydrogen density of iron-containing complex hydrides reported so far, is synthesized by hydrogenation of a powder mixture of iron and LiH above 6.1 GPa at 900 °C. In situ synchrotron radiation X-ray diffraction measurements reveal that while kinetics require high temperature and thus high pressure for the synthesis, Li4FeH6 is expected to be thermodynamically stable slightly below room temperature at ambient pressure; further synthetic studies to suppress the kinetic effects may enable us to synthesize Li4FeH6 at moderate pressures. Li4FeH6 can be recovered at ambient conditions where Li4FeH6 is metastable.

  13. Fingerprints of transversal and longitudinal coupling between induced open quantum dots in the longitudinal magneto-conductance through anti-dot lattices

    International Nuclear Information System (INIS)

    Ujevic, Sebastian; Mendoza, Michel

    2011-01-01

    Full text. We propose numerical simulations of longitudinal magneto conductance through a finite anti dot lattice located inside an open quantum dot with a magnetic field applied perpendicular to the plane. The system is connected to reservoirs using quantum point contacts. We discuss the relationship between the longitudinal magneto conductance and the generation of transversal couplings between the induced open quantum dots in the system. The system presents longitudinal magneto conductance maps with crossovers (between transversal bands) and closings (longitudinal decoupling) of fundamental quantum states related to the open quantum dots induced by the anti dot lattice. A relationship is observed between the distribution of anti dots and the formed conductance bands, allowing a systematic follow-up of the bands as a function of the applied magnetic field and quantum point contact width. We observed a high conductance intensity (between n- and (n + 1)-quantum of conductance, n = 1; 2...) in the regions of crossover and closing of states. This suggests transversal couplings between the induced open quantum dots of the system that can be modulated by varying both the anti dots potential and the quantum point contact width. A new continuous channel (not expected) is induced by the variation of the contact width and generate Fano resonances in the conductance. These resonances can be manipulated by the applied magnetic field

  14. Quantum dot optoelectronic devices: lasers, photodetectors and solar cells

    International Nuclear Information System (INIS)

    Wu, Jiang; Chen, Siming; Seeds, Alwyn; Liu, Huiyun

    2015-01-01

    Nanometre-scale semiconductor devices have been envisioned as next-generation technologies with high integration and functionality. Quantum dots, or the so-called ‘artificial atoms’, exhibit unique properties due to their quantum confinement in all 3D. These unique properties have brought to light the great potential of quantum dots in optoelectronic applications. Numerous efforts worldwide have been devoted to these promising nanomaterials for next-generation optoelectronic devices, such as lasers, photodetectors, amplifiers, and solar cells, with the emphasis on improving performance and functionality. Through the development in optoelectronic devices based on quantum dots over the last two decades, quantum dot devices with exceptional performance surpassing previous devices are evidenced. This review describes recent developments in quantum dot optoelectronic devices over the last few years. The paper will highlight the major progress made in 1.3 μm quantum dot lasers, quantum dot infrared photodetectors, and quantum dot solar cells. (topical review)

  15. Novel H7N2 and H5N6 Avian Influenza A Viruses in Sentinel Chickens: A Sentinel Chicken Surveillance Study

    Directory of Open Access Journals (Sweden)

    Teng Zhao

    2016-11-01

    Full Text Available In 2014, surveillance of sentinel chicken for avian influenza virus was conducted in aquatic bird habitat near Wuxi City, Jiangsu Province, China. Two H7N2, one H5N6, and two H9N2 viruses were isolated. Sequence analysis revealed that the H7N2 virus is a novel reassortant of H7N9 and H9N2 viruses and H5N6 virus is a reassortant of H5N1 clade 2.3.4 and H6N6 viruses. Substitutions V186 and L226 (H3 numbering in the hemagglutinin (HA gene protein was found in two H7N2 viruses but not in the H5N6 virus. Two A138 and A160 mutations were identified in the HA gene protein of all three viruses but a P128 mutation was only in the H5N6 virus. A deletion of three and eleven amino acids in the neuraminidase stalk region was found in two H7N2 and H5N6 viruses, respectively. Moreover, a mutation of N31 in M2 protein was observed in both two H7N2 viruses. High similarity of these isolated viruses to viruses previously identified among poultry and humans, suggests that peridomestic aquatic birds may play a role in sustaining novel virus transmission. Therefore, continued surveillance is needed to monitor these avian influenza viruses in wild bird and domestic poultry that may pose a threat to poultry and human health.

  16. Molybdenum (6) determination by the method of high-frequency and pH titration

    International Nuclear Information System (INIS)

    Lukianets, I.G.; Kulish, N.G.

    1981-01-01

    A possibility to determine Mo(6) using the method of high frequency and pH-metric titration is investigated. By means of the high frequency contact R-cell Mo(6) titration is performed using different precipitators: 8-oxiquinoline, lead nitrate and acetate and silver nitrate. It is established that the best conditions are achieved during titration of 67.2-1343 mg/10 ml Mo(6) with lead acetate (pH 4.5-6.5). Relative standard deviation Ssub(r) constitutes 0.005 pH-metric titration of Mo(6) with complexone 3 is studied. The range of Mo(6) concentrations determined constitutes 13.43-134.3 mg at pH initial value of 3.5-5.5. Relative standard deviation Ssub(r) constitutes 0.003. Techniques of molybdenum determination in ferromolybdenum using the method of high frequency and pH-metric titration are developed [ru

  17. DNA derived fluorescent bio-dots for sensitive detection of mercury and silver ions in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Song, Ting [Laboratory of Environmental Science and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhu, Xuefeng, E-mail: zhuxf@ms.xjb.ac.cn [Laboratory of Environmental Science and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China); Zhou, Shenghai [Laboratory of Environmental Science and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China); Yang, Guang [Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education and International Center for Dielectric Research, Xi’an Jiaotong University, Xi’an 710049 (China); Gan, Wei [Laboratory of Environmental Science and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China); Yuan, Qunhui, E-mail: yuanqh@ms.xjb.ac.cn [Laboratory of Environmental Science and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China)

    2015-08-30

    Highlights: • First application of a DNA derived fluorescent bio-dot for metal sensing. • Bio-dot was conveniently obtained via a mild thermal hydro-thermal synthesis. • Bio-dot was directly used for fluorescent sensing without further modification. • Bio-dot showed good fluorescent sensing property for Hg(II) and Ag(I). • Formation of T–Hg–T and C–Ag–C structures played key roles in sensing. - Abstract: Inspired by the high affinity between heavy metal ions and bio-molecules as well as the low toxicity of carbon-based quantum dots, we demonstrated the first application of a DNA derived carbonaceous quantum dots, namely bio-dots, in metal ion sensing. The present DNA-derived bio-dots contain graphitic carbon layers with 0.242 nm lattice fringes, exhibit excellent fluorescence property and can be obtained via a facile hydrothermal preparation procedure. Hg(II) and Ag(I) are prone to be captured by the bio-dots due to the existence of residual thymine (T) and cytosine (C) groups, resulting in a quenched fluorescence while other heavy metal ions would cause negligible changes on the fluorescent signals of the bio-dots. The bio-dots could be used as highly selective toxic-free biosensors, with two detecting linear ranges of 0–0.5 μM and 0.5–6 μM for Hg(II) and one linear range of 0–10 μM for Ag(I). The detection limits (at a signal-to-noise ratio of 3) were estimated to be 48 nM for Hg(II) and 0.31 μM for Ag(I), respectively. The detection of Hg(II) and Ag(I) could also be realized in the real water sample analyses, with satisfying recoveries ranging from 87% to 100%.

  18. DNA derived fluorescent bio-dots for sensitive detection of mercury and silver ions in aqueous solution

    International Nuclear Information System (INIS)

    Song, Ting; Zhu, Xuefeng; Zhou, Shenghai; Yang, Guang; Gan, Wei; Yuan, Qunhui

    2015-01-01

    Highlights: • First application of a DNA derived fluorescent bio-dot for metal sensing. • Bio-dot was conveniently obtained via a mild thermal hydro-thermal synthesis. • Bio-dot was directly used for fluorescent sensing without further modification. • Bio-dot showed good fluorescent sensing property for Hg(II) and Ag(I). • Formation of T–Hg–T and C–Ag–C structures played key roles in sensing. - Abstract: Inspired by the high affinity between heavy metal ions and bio-molecules as well as the low toxicity of carbon-based quantum dots, we demonstrated the first application of a DNA derived carbonaceous quantum dots, namely bio-dots, in metal ion sensing. The present DNA-derived bio-dots contain graphitic carbon layers with 0.242 nm lattice fringes, exhibit excellent fluorescence property and can be obtained via a facile hydrothermal preparation procedure. Hg(II) and Ag(I) are prone to be captured by the bio-dots due to the existence of residual thymine (T) and cytosine (C) groups, resulting in a quenched fluorescence while other heavy metal ions would cause negligible changes on the fluorescent signals of the bio-dots. The bio-dots could be used as highly selective toxic-free biosensors, with two detecting linear ranges of 0–0.5 μM and 0.5–6 μM for Hg(II) and one linear range of 0–10 μM for Ag(I). The detection limits (at a signal-to-noise ratio of 3) were estimated to be 48 nM for Hg(II) and 0.31 μM for Ag(I), respectively. The detection of Hg(II) and Ag(I) could also be realized in the real water sample analyses, with satisfying recoveries ranging from 87% to 100%

  19. Quantum dot systems: artificial atoms with tunable properties

    International Nuclear Information System (INIS)

    Weis, J.

    2005-01-01

    Full text: Quantum dots - also called zero-dimensional electron systems or artificial atoms - are physical objects where the constituent electrons are confined in a small spatial region, leading to discrete eigenvalues for the energies of the confined electrons. Large quantum dots offer a dense energy spectrum comparable to that of metallic grains, whereas small quantum dots more closely resemble atoms in their electronic properties. Quantum dots can be linked to leads by tunnel barriers, hence permitting electrical transport measurements: Coulomb blockade and single-electron charging effects are observed due to the repulsive electron electron interaction on the quantum dot site. Usually fabricated by conventional semiconductor growth and processing technology, the advantage is that both simple and also more complex quantum dot systems can be designed to purpose, acting as model systems with in-situ tunable parameters such as the number of confined electrons in the quantum dot and the strength of the tunnel coupling to the leads, electrostatically controlled by the applied voltages to gate electrodes. With increasing the tunnel coupling to the leads, the virtual occupation of the quantum dot from the leads becomes more and more important -- the simple description of electrical transport by single-electron tunneling events breaks down. The basic physics is described by the Kondo physics based on the Anderson impurity model. A system consisting of strongly electrostatically coupled quantum dots with separate leads to each quantum dot represent another realization of the Anderson impurity model. Experiments to verify the analogy are presented. The experimental data embedded within this tutorial have been obtained with Alexander Huebel, Matthias Keller, Joerg Schmid, David Quirion, Armin Welker, Ulf Wilhelm, and Klaus von Klitzing. (author)

  20. Tuning of the charge in octahedral ferric complexes based on pyridoxal-N-substituted thiosemicarbazone ligands

    NARCIS (Netherlands)

    Tido, Eddy W. Yemeli; Faulmann, Christophe; Roswanda, Robby; Meetsma, Auke; van Koningsbruggen, Petra J.

    2010-01-01

    Four novel mononuclear coordination compounds namely: [Fe(Hthpy)(2)](SO(4))(1/2)center dot 3.5H(2)O 1, [Fe(Hthpy)(2)]NO(3)center dot 3H(2)O 2, [Fe(H(2)mthpy)(2)](CH(3)C(6)H(4)SO(3))(3)center dot CH(3)CH(2)OH 3 and [Fe(Hethpy)(ethpy)]center dot 8H(2)O 4, (H(2)thpy = pyridoxalthiosemicarbazone,