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Sample records for structural transformationof zns

  1. Kinetics of the water adsorption driven structural transformationof ZnS nanoparticles

    SciTech Connect

    Goodell, C.M.; Gilbert, B.; Weigand, S.J.; Banfield, J.F.

    2007-08-01

    Nanoparticles of certain materials can respond structurally to changes in their surface environments. We have previously shown that methanol, water adsorption, and aggregation-disaggregation can change the structure of 3 nm diameter zinc sulfide (ZnS). However, in prior observations of water-driven structure change, aggregation may also have taken place. Therefore, we investigated the structural consequences of water adsorption alone on anhydrous nanoparticles that were dried to minimize changes in aggregation. Using simultaneously collected small- and wide-angle x-ray scattering (SAXS/WAXS) data, we show that water vapor adsorption alone drives a structural transformation in ZnS nanoparticles in the temperature range 22-40 C. The transition kinetics are strongly temperature dependent, with an activation energy of 58.1 {+-} 9.8 kJ/mol, consistent with atom displacement rather than bond breaking. At 50 C, aggregate restructuring occurred, increasing the transition kinetics beyond the rate expected for water adsorption alone. The observation of isosbestic points in the WAXS data suggests that the particles do not transform continuously between the initial and final structural state but rather undergo an abrupt change from a less ordered to a more ordered state.

  2. CTAB-Assisted Solvothermal Growth and Optical Characterization of Flower-Like ZnS Structures

    NASA Astrophysics Data System (ADS)

    Roy, J. S.; Pal Majumder, T.

    2016-08-01

    Flower-like ZnS structures have been prepared by solvothermal method with the assistance of cetyl trimethyl ammonium bromide (CTAB). The effects of different experimental conditions on the morphology of ZnS structure have been investigated. The performances of ZnS structures have been analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), room temperature photoluminescence (PL), and UV-visible absorption spectroscopy. The XRD patterns indicate that the prepared ZnS structures are highly crystallized, which are of hexagonal phase. The SEM images indicate that the main role of CTAB is to assemble the ZnS flakes together to form the flower-like structures, and the reaction time affects the morphology of ZnS. The growth mechanism for the formation of flower-like ZnS structure is also described. The absorption and emission bands gradually shift towards longer wavelength due to the transformation of flower-like ZnS nanoflowers from ZnS flakes.

  3. A size-dependent structural evolution of ZnS nanoparticles

    PubMed Central

    Khalkhali, Mohammad; Liu, Qingxia; Zeng, Hongbo; Zhang, Hao

    2015-01-01

    Recently, ZnS quantum dots have attracted a lot of attention since they can be a suitable alternative for cadmium-based quantum dots, which are known to be highly carcinogenic for living systems. However, the structural stability of nanocrystalline ZnS seems to be a challenging issue since ZnS nanoparticles have the potential to undergo uncontrolled structural change at room temperature. Using the molecular dynamics technique, we have studied the structural evolution of 1 to 5 nm freestanding ZnS nanoparticles with zinc-blende and wurtzite crystal structures. Simulation results revealed that relaxed configurations of ZnS nanoparticles larger than 3 nm consist of three regions: a) a crystalline core, b) a distorted network of 4-coordinated atoms environing the crystalline core, and c) a surface structure made entirely of 3-coordinated atoms. Decreasing the size of ZnS nanoparticle to 2 nm will cause the crystalline core to disappear. Further reducing the size will cause all of the atoms to become 3-coordinated. Dipole moments of zinc-blende and wurtzite nanoparticles are in the same range when the nanoparticles are smaller than 3 nm. Increasing the size makes dipole moments converge to the bulk values. This makes zinc-blende and wurtzite nanoparticles less and more polar, respectively. PMID:26381583

  4. Structural, compositional and Raman studies of ZnS: Ce, Cu co-doped nanoparticles

    NASA Astrophysics Data System (ADS)

    Harish, G. S.; Reddy, P. Sreedhara

    2013-06-01

    In this present work, Ce, Cu co-doped ZnS nanoparticles were prepared at room temperature using chemical precipitation method. The prepared nanoparticles were characterized by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Energy dispersive analysis of X-rays (EDAX) and High Resolution Raman spectroscopic techniques. X-ray diffraction studies show that the diameter of the particles is 2-4 nm. Broadened XRD peaks confirmed the formation of nanoparticles with face centered cubic (FCC) structure. SEM attached with EDS gave the size, morphology and compositional analysis of as-prepared material. The Raman spectra of unplanted and Cu, Ce ions implanted samples of nano structured ZnS showed LO mode and TO mode. Compared with the Raman modes (276 and 351 cm-1) of undoped ZnS nanoparticles, the Raman modes of Ce, Cu co-doped ZnS nanoparticles are slightly shifted towards lower frequency side.

  5. Controlling crystalline structure of ZnS nanocrystals only by tuning sulfur precursor addition rate.

    PubMed

    Bi, Chong; Pan, Liqing; Xu, Mei; Xiao, John Q

    2010-12-01

    Unlike previous studies that emphasize the important role of thermodynamics or surface energy on the structure stabilization of ZnS nanocrystals, we successfully controlled the crystalline structure of ZnS nanocrystals simply by tuning sulfur precursor addition rate under exactly the same other conditions. We observed the structure of as prepared ZnS nanocrystals was evolved from wurtzite into zinc blende with increasing the addition rate of sulfur precursor. The method may extend to engineer other nanomaterials with desired physicochemical properties by controlling crystalline structure. On the other hand, it also makes a new approach to understand the crucial factors that determine the growth mechanism and the crystal structure of nanomaterials in theory.

  6. Quasi-particle energies and optical excitations of ZnS monolayer honeycomb structure

    NASA Astrophysics Data System (ADS)

    Shahrokhi, Masoud

    2016-12-01

    Using ab-initio density functional theory calculations combined with many-body perturbation formalism we carried out the electronic structure and optical properties of 2D graphene-like ZnS structure. The electronic properties were analyzed at three levels of many-body GW approach (G0W0, GW0 and GW) constructed over a Generalized Gradient Approximation functional. Our results indicate that ZnS sheet has a direct band gap at the Γ-point. Also it is seen that inclusion of electron-electron interaction does not change the sort of direct semiconducting band gap in ZnS sheet. The optical properties and excitonic effects of these materials are investigated using the Bethe-Salpeter equation (BSE) approach. The formation of first exciton peaks at 3.86, 4.26, and 4.57 eV with large binding energy of 0.36, 0.49 and 0.73 eV using G0W0 + BSE, GW0 + BSE and GW + BSE, respectively, was observed. We show that the optical absorption spectrum of 2D ZnS structure is dominated by strongly bound Frenkel excitons. The enhanced excitonic effects in the ZnS monolayer sheet can be useful in designing optoelectronic applications.

  7. Effect of nickel doping on structural and optical properties of ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Sanjeev Kumar, R.; Veeravazhuthi, V.; Muthukumarasamy, N.; Thambidurai, M.; Vishnu Shankar, D.

    2015-10-01

    In the present work, solution based simple chemical precipitation method has been used to prepare undoped and Ni-doped ZnS nanoparticles. Zinc acetate, sodium sulfide, and nickel nitrate have been used as precursors for the preparation of Ni-doped ZnS nanoparticles. The X-ray diffraction results revealed that the undoped and Ni-doped ZnS nanoparticles exhibit hexagonal Structure. The average grain size of the prepared nanoparticles was found to lie in the range of 2.6-4.2 nm. The SEM images show that the particles have smooth surface and the formation of agglomerated nanoparticles. The compositional analysis results confirm the presence of Ni, Zn and S in the prepared samples. The optical properties of undoped and Ni-doped ZnS quantum dots have been studied using absorption spectra. HRTEM results show that undoped and Ni-doped ZnS nanoparticles exhibit a uniform size distribution with average grain size lying in the range of 2.3-3.6 nm. The synthesized nanoparticles exhibited an emission peak centered at around 612 nm in the PL spectrum.

  8. Advancements in the Quantification of the Crystal Structure of ZNS Materials Produced in Variable Gravity

    NASA Astrophysics Data System (ADS)

    Castillo, Martin

    2016-07-01

    Screens and displays consume tremendous amounts of power. Global trends to significantly consume less power and increase battery life have led to the reinvestigation of electroluminescent materials. The state of the art in ZnS materials has not been furthered in the past 30 years and there is much potential in improving electroluminescent properties of these materials with advanced processing techniques. Self-propagating high temperature synthesis (SHS) utilises a rapid exothermic process involving high energy and nonlinearity coupled with a high cooling rate to produce materials formed outside of normal equilibrium boundaries thus possessing unique properties. The elimination of gravity during this process allows capillary forces to dominate mixing of the reactants which results in a superior and enhanced homogeneity in the product materials. ZnS type materials have been previously conducted in reduced gravity and normal gravity. It has been claimed in literature that a near perfect phases of ZnS wurtzite was produced. Although, the SHS of this material is possible at high pressures, there has been no quantitative information on the actual crystal structures and lattice parameters that were produced in this work. Utilising this process with ZnS doped with Cu, Mn, or rare earth metals such as Eu and Pr leads to electroluminescence properties, thus making this an attractive electroluminescent material. The work described here will revisit the synthesis of ZnS via high pressure SHS and will re-examine the work performed in both normal gravity and in reduced gravity within the ZARM drop tower facility. Quantifications in the lattice parameters, crystal structures, and phases produced will be presented to further explore the unique structure-property performance relationships produced from the SHS of ZnS materials.

  9. Comparing the effects of uniaxial and biaxial strains on the structural stability and electronic structure in wurtzite ZnS

    NASA Astrophysics Data System (ADS)

    Lv, Dong; Duan, Yifeng; Zhao, Botao; Qin, Lixia; Shi, Liwei; Tang, Gang; Shi, Hongliang

    2013-07-01

    Structural stability and electronic structure of wurtzite ZnS under uniaxial and biaxial strains are systematically studied using the HSE hybrid functional. The two types of strain display the markedly different influences on the structural and electronic properties: (I) The newly predicted graphite-like phase is observed at large compressive uniaxial strains, not at large tensile biaxial strains, which is attributed to the different elastic responses to uniaxial and biaxial strains. (II) The direct band structures are obtained in wurtzite ZnS under uniaxial and biaxial strains, whereas the indirect band gaps are only observed in graphite-like ZnS under large uniaxial strain. Our results are different from the widely accepted conclusion but are in good agreement with the available experimental data.

  10. Effect of anionic concentration on the structural and optical properties of nanostructured ZnS thin films

    NASA Astrophysics Data System (ADS)

    Safeera, T. A.; Johns, N.; Anila, E. I.

    2016-08-01

    Nanostructured Zinc Sulfide (ZnS) thin films with wurtzite structure were prepared by chemical spray pyrolysis method at low temperature. The effect of sulfur concentration on the structural and optical properties of ZnS thin films was studied. The films were analysed by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), UV-Vis spectroscopy and photoluminescence (PL). Nano grain formation of ZnS was observed from XRD and SEM. Variation in band gap of different films is in agreement with size effects. But there is a red shift in the band gap of these films compared to bulk ZnS. This is due to band tailing effect experienced by the films due to the presence of large number of defects which was verified by PL spectrum. The overall emission was blue in colour for all the films and it was confirmed by Commission International d'Eclairage (CIE) diagram.

  11. Structural and surface morphological study of Ni doped ZnS nanoparticles

    SciTech Connect

    Khawal, H. A. Dole, B. N.

    2014-04-24

    Samples of Zn{sub 1−x}Ni{sub x}S (x=0.00, 0.04, 0.08) nanoparticles were synthesized by using the co-precipitation method at room temperature. Structural parameters were investigated by X – ray diffraction (XRD), it reveals that all samples of Ni doped ZnS exhibit the cubic structure with no additional impurity phase. The average crystallite size of all samples is in the range of 2.70 to 2.90 nm. The lattice parameters, X – ray density, volume of unit cell and grain size were calculated using XRD data. It is found that the lattice parameter increases with increasing Ni concentration. Surface morphology of samples was investigated using field emission scanning electron microscopy (FE-SEM). From this study it is concluded that samples exhibit cubic morphology. Chemical compositions of Ni doped and pure ZnS samples were detected using EDAX spectra. It is confirmed from EDAX that Ni substitute into ZnS lattice.

  12. Probing the local structure of dilute Cu dopants in fluorescent ZnS nanocrystals using EXAFS.

    PubMed

    Car, Brad; Medling, Scott; Corrado, Carley; Bridges, Frank; Zhang, Jin Z

    2011-10-05

    A local structure study of ZnS nanocrystals, doped with very low concentrations of Cu, was carried out using the EXAFS technique to better understand how Cu substitutes into the host lattice and forms Cu luminescence centers. We show that a large fraction of the Cu have three nearest neighbor S atoms and the Cu-S bond is significantly shortened compared to Zn-S, by ∼0.08 Å. In addition, the second neighbor Cu-Cu peak is extremely small. We propose that Cu occupies an interior site next to a S(2-) vacancy, with the Cu displaced towards the remaining S(2-) and away from the vacancy; such a displacement immediately explains the lack of a significant Cu-Cu peak in the data. There is no evidence for interstitial Cu sites (Cu(i)), indicating that no more than 2% of the Cu are Cu(i.) This study provides new insights into the local structure of the Cu dopant in ZnS without the presence of CuS nanoprecipitates that are present at higher Cu doping levels.

  13. Probing the local structure of dilute Cu dopants in fluorescent ZnS nanocrystals using EXAFS

    NASA Astrophysics Data System (ADS)

    Car, Brad; Medling, Scott; Corrado, Carley; Bridges, Frank; Zhang, Jin Z.

    2011-10-01

    A local structure study of ZnS nanocrystals, doped with very low concentrations of Cu, was carried out using the EXAFS technique to better understand how Cu substitutes into the host lattice and forms Cu luminescence centers. We show that a large fraction of the Cu have three nearest neighbor S atoms and the Cu-S bond is significantly shortened compared to Zn-S, by ~0.08 Å. In addition, the second neighbor Cu-Cu peak is extremely small. We propose that Cu occupies an interior site next to a S2- vacancy, with the Cu displaced towards the remaining S2- and away from the vacancy; such a displacement immediately explains the lack of a significant Cu-Cu peak in the data. There is no evidence for interstitial Cu sites (Cui), indicating that no more than 2% of the Cu are Cui. This study provides new insights into the local structure of the Cu dopant in ZnS without the presence of CuS nanoprecipitates that are present at higher Cu doping levels.

  14. Effects of zinc salts on the structural and optical properties of acidic chemical bath deposited ZnS thin films

    SciTech Connect

    Cao, Meng; Zhang, Bin Lei; Li, Liang; Huang, Jian; Zhao, Shou Ren; Cao, Hong; Jiang, Jin Chun; Sun, Yan; Shen, Yue

    2013-02-15

    Graphical abstract: XRD patterns of annealed ZnS films from different zinc salts. Curves a, b, c, d correspond to the annealed ZnS–C1, ZnS–S{sub 3}, ZnS–Cl{sub 2}, ZnS–N{sub 2} thin films. Display Omitted Highlights: ► ZnS thin films were deposited using different zinc salts. ► The grain sizes of deposited ZnS thin films are about 12.5 15.5 nm. ► The band gaps of deposited ZnS thin films were in the range of 3.66–3.83 eV. -- Abstract: ZnS thin films were deposited from different zinc salts by chemical bath deposition (CBD). Structural, morphological and optical characterizations were performed using different methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectra. The particle sizes of as-deposited ZnS thin films were calculated to be about 12.5–15.5 nm and the crystal qualities were improved after annealed at 500 °C in Ar/H{sub 2}S (5%) atmosphere. Optical absorption measurements indicated that the band gaps of ZnS thin films were in the range of 3.66–3.83 eV and they decreased with the increasing of particle sizes. ZnCl{sub 2} was found to the best precursor due to the higher crystal quality and compact surface of deposited ZnS thin films.

  15. Anisotropy in Structural and Optical Properties of Chemical Vapor Deposited ZnS

    SciTech Connect

    McCloy, John S.; Fest, Eruc; Korenstein, Ralph; Poisl, W.Howard

    2011-06-14

    Significant anisotropy in as-deposited CVD ZnS at several length scales has been demonstrated through investigation of structural and optical properties. Compressive strength of cylinders of CVD ZnS oriented in the growth direction is ~50% higher than cylinders taken perpendicular to the growth direction. Lattice parameter measurements of mandrel side (first-to-grow) material is ~0.4% smaller than growth side (last-to-grow) material in a cored sample representing ~500 hours of CVD growth, indicating significant strain along the growth direction. X-ray diffraction also shows evidence of preferred orientations for hexagonality which differ depending on position in the growth history. In cross-section, the cored sample shows several large bands which are correlated with different degrees of infrared absorption and BTDF scattering. However, no universal trend is found that applies to the whole length from the mandrel to the growth side regarding optical properties. The extinction in the visible and infrared is lower for measurements perpendicular to the growth axis than parallel to it, possibly due to scattering from the growth bands.

  16. Laser-assisted synthesis, and structural and thermal properties of ZnS nanoparticles stabilised in polyvinylpyrrolidone

    NASA Astrophysics Data System (ADS)

    Onwudiwe, Damian C.; Krüger, Tjaart P. J.; Jordaan, Anine; Strydom, Christien A.

    2014-12-01

    Zinc sulphide (ZnS) nanoparticles have been synthesised by a green approach involving laser irradiation of an aqueous solution of zinc acetate (Znac2) and sodium sulphide (Na2S·9H2O) or thioacetamide (TAA) in polyvinylpyrrolidone (PVP). The structural and morphological properties of the prepared samples were analysed using a transmission electron microscope, TEM, a high resolution transmission electron microscope, HRTEM, X-ray diffraction, and Raman spectroscopy. The thermal properties were studied using a simultaneous thermal analyser (SDTA). Better dispersed and larger particles were obtained by using sodium sulphide (Na2S) instead of TAA as the sulphur source. X-ray diffraction (XRD) analyses and Raman measurement show that the particles have a cubic structure, which is usually a low temperature phase of ZnS. There were phonon softening and line broadening of the peaks which are attributed to the phonon confinement effect. The average crystallite size of the ZnS nanoparticles estimated from the XRD showed a reduction in size from 13.62 to 10.42 nm for samples obtained from Na2S, and 9.13 to 8.16 nm for samples obtained from TAA, with an increase in the time of irradiation. The thermal stability of PVP was increased due to the incorporation of the ZnS nanoparticles in the matrices. The absorption spectra showed that the nanoparticles exhibit quantum confinement effects.

  17. Advancements in the quantification of the crystal structure of ZnS materials produced in variable gravity

    NASA Astrophysics Data System (ADS)

    Castillo, Martin; Hales, Matthew; Lynn, David; Steinberg, Theodore

    SHS allows for the rapid creation of difficult to produce intermetallic materials, biomedical materials, and cermet materials by taking advantage of internal chemical energy present in the mixture. This manufacturing method utilities a rapid exothermic process involving high energy and nolinearity coupled with a high cooling rate to produce materials formed outside of normal equilibrium boundaries thus possessing unique properties. The elimination of gravity during this process allows capillary forces to dominate mixing of the reactants which results in a superior and enhanced homogeneity in the product materials formed The self-propagating high temperature synthesis (SHS) of ZnS type materials have been previously conducted in reduced gravity and normal gravity. It has been claimed in literature that a near perfect phases of ZnS wurtzite was produced. Although, the SHS of this material is possible at high pressures, there has been no quantitative information on the actual crystal structures and lattice parameters that were produced in this work. Utilizing this process with ZnS doped with Cu, Mn, or rare earth metals such as Eu and Pr leads to electroluminescence properties, thus making this an attractive electroluminescent material. The work described here will revisit the synthesis of ZnS via high pressure SHS and will re-examine the work performed in both normal gravity and in reduced gravity within the Queensland University of Technology Drop Tower Facility. Quantifications in the lattice parameters, crystal structures, and phases produced are presented to further explore the unique structure-property performance relationships produced from the SHS of ZnS materials.

  18. Effect of structure, size and copper doping on the luminescence properties of ZnS

    SciTech Connect

    Kamal, Ch. Satya; Mishra, R.K.; Patel, Dinesh K.; Rao, K. Ramachandra; Sudarsan, V.; Vatsa, R.K.

    2016-09-15

    Highlights: • Blue and green emission intensity form ZnS is sensitive to crystallographic form. • For ZnS nanoparticles, emission characteristics are not affected by copper doping. • Cu solubility poor in ZnS nanoparticles compared to corresponding bulk. - Abstract: Luminescence properties of wurtzite and cubic forms of bulk ZnS have been investigated in detail and compared with that of ZnS nanoparticles. Blue emission observed in both hexagonal and cubic forms of undoped bulk ZnS is explained based on electron–hole recombination involving electron in conduction band and hole trapped in Zn{sup 2+} vacancies where as green emission arises due to electron hole recombination from Zn{sup 2+} and S{sup 2−} vacancies. Conversion of wurtzite form to cubic form is associated with relative increase in intensity of green emission due to increased defect concentration brought about by high temperature heat treatment. Copper doping in ZnS, initially leads to formation of both Cu{sub Zn} and Cu{sub i} (interstitial copper) centers, and latter to mainly Cu{sub Zn} centers as revealed by variation in relative intensities of blue and green emission from the samples.

  19. Optical properties of ZnS and Cu2+ doped ZnS nanostructures

    NASA Astrophysics Data System (ADS)

    Sarkar, A.; Chakrabarty, N.; Bera, S.; Chakraborty, A. K.

    2015-06-01

    Flower like ZnS and ZnS:Cu2+ nanostructures are developed by simple chemical route. Structural, morphological and optical characterizations are carried out by XRD, FESEM, UV-Visible absorption spectroscopy and FTIR. Analysis indicates successful incorporation of Cu2+ ions into ZnS lattice. Optical studies show that the copper doped ZnS enhances the optical property of pristine ZnS by harvesting more visible light.

  20. Substrate dependent structural, optical and electrical properties of ZnS thin films grown by RF sputtering

    NASA Astrophysics Data System (ADS)

    Pathak, Trilok K.; Kumar, Vinod; Purohit, L. P.; Swart, H. C.; Kroon, R. E.

    2016-10-01

    Zinc sulphide (ZnS) films are of great importance for applications in various optoelectronic devices. ZnS thin films were grown on glass, indium tin oxide (ITO) and Corning glass substrates by radio-frequency magnetron sputtering at a temperature of 373 K and a comparative study of the structural, optical and electrical properties was performed using X-ray diffraction (XRD), scanning electron microscopy, optical and current-voltage (I-V) measurements. The XRD patterns showed that the sputtered thin films exhibited good crystallinity with the (111) peak around 2θ=28.3° indicating preferential orientation of the cubic structure. The maximum strain and most densely packed grains were obtained for the Corning glass substrate. The transmittance spectra of the films were measured in the wavelength range from 200 to 800 nm, showing that the films are about 77% transparent in the visible region. A slight change of 3.50 eV to 3.54 eV was found for the bandgap of the films deposited on different substrates. The ZnS thin films deposited on Corning glass show better crystallinity, morphology and I-V characteristics than that deposited on ordinary glass and ITO substrates.

  1. One-step fabrication of single-crystalline ZnS nanotubes with a novel hollow structure and large surface area for photodetector devices

    NASA Astrophysics Data System (ADS)

    An, Qinwei; Meng, Xianquan; Xiong, Ke; Qiu, Yunlei; Lin, Weihua

    2017-03-01

    ZnS nanotubes (NTs) were successfully prepared via a one-step thermal evaporation process without using any templates. The resulting NTs were single crystalline and structurally uniform. Based on experimental analysis, a tube-growth vapor–liquid–solid process was proposed as the growth mechanism of ZnS NTs. A metal–semiconductor–metal full-nanostructured ultraviolet (UV) photodetector with ZnS NTs as the active layer, and Ag nanowires of low resistivity and high transmissivity as electrodes, was fabricated and characterized. The ZnS NT-based device displayed a high I on/I off ratio of up to ∼1.56 × 105 with a high response to UV incident light at low operation voltage. This work is a meaningful exploration for preparing other one-dimensional semiconductor NTs, and developing a high-performance and power-saving UV sensor.

  2. Structural, Optical, and Magnetic Properties of Solution-Processed Co-Doped ZnS Thin Films

    NASA Astrophysics Data System (ADS)

    Goktas, A.; Mutlu, İ. H.

    2016-11-01

    Co-doped ZnS thin films have been grown on glass substrates using solution-processing and dip-coating techniques, and the impact of the Co doping level (0% to 5%) and film thickness on certain characteristics examined. X-ray diffraction study revealed that all the films possessed hexagonal crystal structure. Energy-dispersive x-ray analysis confirmed presence of Zn, Co, and S in the samples. Scanning electron microscopy showed that the film surface was homogeneous and dense with some cracks and spots. X-ray photoelectron spectroscopy confirmed introduction and integration of Co2+ ions into the ZnS thin films. Compared with undoped ZnS, optical studies indicated a reduction in optical bandgap energy ( E g) while the refractive index ( n), extinction coefficient ( k), and dielectric constants ( ɛ 1, ɛ 2) increased with film thickness ( t) and Co doping level (except for 5%). Photoluminescence spectra showed enhanced luminescence intensity as the Co concentration was increased, while the dependence on t showed an initial increase followed by a decrease. The origin of the observed low-temperature (5 K and 100 K) ferromagnetic order may be related to point defects such as zinc vacancies, zinc interstitials, and sulfide vacancies or to the grain-boundary effect.

  3. A ZnS(4) structural zinc site in the Helicobacter pylori ferric uptake regulator.

    PubMed

    Vitale, Sylvia; Fauquant, Caroline; Lascoux, David; Schauer, Kristine; Saint-Pierre, Christine; Michaud-Soret, Isabelle

    2009-06-23

    The ferric uptake regulator, Fur, is a global bacterial transcriptional regulator using iron as a cofactor to bind to specific DNA sequences. This paper describes the biochemical characterization of the native ferric uptake regulator from Helicobacter pylori (HpFur): oligomeric state, metal content, and characterization of a structural metal-binding site. HpFur contains six cysteines with two CxxC motifs, which makes it closer to Bacillus subtilis PerR (BsPerR) than to Escherichia coli Fur (EcFur). Chemical modifications of cysteine residues using iodoacetamide followed by mass spectrometry after enzymatic digestion strongly suggest that these two CxxC motifs containing cysteines 102-105 and 142-145 are involved in zinc binding in a ZnS(4) metal site. The other two cysteines (78 and 150) are not essential for DNA binding activity and do not perturb metal binding as demonstrated with the characterization of a FurC78SC150S double mutant. Chelating agent such as EDTA disrupts the dimeric structure into monomer which did not contain zinc anymore. Reconstitution of dimer from monomer requires reduction and Zn(2+) binding. Cadmium(II) substitution allows also dimer formation from monomer, and Cd(II)-substituted FurC78SC150S mutant presents a characteristic absorption of a Cd(II)Cys(4) metal-binding site. These results establish that coordination of the zinc ion in HpFur is ZnCys(4), therefore closer to the zinc site in BsPerR than in EcFur. Furthermore, the redox state of the cysteines and the zinc binding are essential to hold the H. pylori Fur in a dimeric state.

  4. The Crystal Structure of Micro- and Nanopowders of ZnS Studied by EPR of Mn2+ and XRD

    NASA Astrophysics Data System (ADS)

    Nosenko, Valentyna; Vorona, Igor; Grachev, Valentyn; Ishchenko, Stanislav; Baran, Nikolai; Becherikov, Yurii; Zhuk, Anton; Polishchuk, Yuliya; Kladko, Vasyl; Selishchev, Alexander

    2016-11-01

    The crystal structure of micro- and nanopowders of ZnS doped with different impurities was analyzed by the electron paramagnetic resonance (EPR) of Mn2+ and XRD methods. The powders of ZnS:Cu, ZnS:Mn, ZnS:Co, and ZnS:Eu with the particle sizes of 5-7 μm, 50-200 nm, 7-10 μm, and 5-7 nm, respectively, were studied. Manganese was incorporated in the crystal lattice of all the samples as uncontrolled impurity or by doping. The Mn2+ ions were used as EPR structural probes. It is found that the ZnS:Cu has the cubic structure, the ZnS:Mn has the hexagonal structure with a rhombic distortion, the ZnS:Co is the mixture of the cubic and hexagonal phases in the ratio of 1:10, and the ZnS:Eu has the cubic structure and a distorted cubic structure with stacking defects in the ratio 3:1. The EPR technique is shown to be a powerful tool in the determination of the crystal structure for mixed-polytype ZnS powders and powders with small nanoparticles. It allows observation of the stacking defects, which is revealed in the XRD spectra.

  5. Heterogeneous ZnS hollow urchin-like hierarchical nanostructures and their structure-enhanced photocatalytic properties.

    PubMed

    Liu, Jun; Guo, Zaiping; Wang, Wenjun; Huang, Qingsong; Zhu, Kaixing; Chen, Xiaolong

    2011-04-01

    Hexagonal wurtzite ZnS nanowires radially arrayed on cubic zinc-blende ZnS hollow spheres have been successfully achieved for the first time, and such novel heterogeneous ZnS hollow urchin-like hierarchical nanostructures show greatly enhanced photocatalytic properties due to their two-phase enhanced light-harvesting and high surface-to-volume ratio.

  6. The atomic geometries of GaP(110) and ZnS(110) revisited - A structural ambiguity and its resolution

    NASA Technical Reports Server (NTRS)

    Duke, C. B.; Paton, A.; Kahn, A.

    1984-01-01

    The atomic geometries of GaP(110) and ZnS(110) are reexamined using the R-factor minimization procedure, developed for GaAs(110) and previously applied to GaSb(110), ZnTe(110), InAs(110), and AlP(110), to analyze experimental elastic low-energy electron diffraction intensities. Unlike most of the earlier cases, both GaP(110) and ZnS(110) exhibit two distinct minimum-Rx structures which cannot be distinguished by analysis of the shapes of the intensity profiles alone. One region of best-fit structures exhibits top-layer displacements normal to the surface characterized by a small bond-length-conserving, top-layer rotation (omega aproximately 2-3 deg), a small relaxation of the top layer away from the surface, and a 10 percent expansion of the top-layer bond length. The other region of best-fit structures is the conventional one: nearly bond-length-conserving rotations of omega = 26-28 deg in the top layer and a small (approximately 0.1 A) contraction of the uppermost layer spacing. This ambiguity may be removed, however, by consideration of the integrated beam intensities. The conventional region of structural parameters provides a decisively better description of the relative magnitudes of the integrated beam intensities and hence is the preferred structure.

  7. Molecular beam epitaxial growth and structural characterization of ZnS on (001) GaAs

    NASA Technical Reports Server (NTRS)

    Benz, R. G., II; Huang, P. C.; Stock, S. R.; Summers, C. J.

    1988-01-01

    The effect of surface nucleation processes on the quality of ZnS layers grown on (001) GaAs substrates by molecular beam epitaxy is reported. Reflection high energy electron diffraction indicated that nucleation at high temperatures produced more planar surfaces than nucleation at low temperatures, but the crystalline quality as assessed by X-ray double crystal diffractometry is relatively independent of nucleation temperature. A critical factor in layer quality was the initial roughness of the GaAs surfaces.

  8. Effects of Fe substitution on B3-B1 phase transition and structural, vibrational, and electronic properties of ZnS from DFT calculations

    NASA Astrophysics Data System (ADS)

    Das, Pratik Kr.; Mandal, Nibir; Arya, A.

    2017-02-01

    Naturally occurring zinc sulfide (ZnS) contains a substantial amount of iron (Fe) in its crystal structure. This study explores the possible effects of such Fe impurity on the physical properties of its two phases: B3 and B1, crystallizing in a cubic system with zinc blend (ZB, space group: F-43m) and rock salt (RS, space group: Fm-3m) structures. We have performed ab-initio calculations within density functional theory (DFT) to determine the equilibrium volumes of B3- and B1-ZnS phases, doped with Fe in varying concentrations (0% to 25%), and their corresponding lattice structures. Using the enthalpy cross-over, we determine the pressure-dependent B3 to B1 transition as a function of Fe concentration. Our DFT calculations suggest an inverse relation of the transition pressure with Fe content. For pure ZnS, the transition occurs at 17 GPa, which drops to ˜12 GPa for 25% Fe. This study also provides a first-hand analysis of the elastic constants (C11, C12, and C44) to show the effects of Fe impurity on the mechanical properties of ZnS phases. Their values generally drop due to Fe and the differences widen with increasing pressure. Fe causes large softening of C44, especially for the B1 phase. We have also performed phonon calculations to characterize the vibrational properties and explain the pressure dependent structural instability of the B3- ZnS. Finally, our calculations of the electronic structures show a transition of semi-conductor to conductor behavior of ZnS with incorporation of Fe impurity.

  9. Thermal annealing and UV irradiation effects on structure, morphology, photoluminescence and optical absorption spectra of EDTA-capped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Osman, M. A.; Othman, A. A.; El-Said, Waleed A.; Abd-Elrahim, A. G.; Abu-sehly, A. A.

    2016-02-01

    Monodispersed ZnS nanoparticles (NPs) were prepared by the chemical precipitation method. Thermally induced structural, morphological and optical changes have been investigated using x-ray diffraction, high-resolution transmission electron microscopy, optical absorption, photoluminescence (PL), and Fourier transform infrared and Raman spectroscopy. It was found that D increases with increasing annealing temperature (T a). The onset of the ZnS phase transition from cubic to hexagonal structure takes place at 400 °C, while cubic ZnS transforms into hexagonal ZnO via thermal oxidation in air at 600 °C. It is also noted that increasing T a results in the red shift of the optical band gap (E\\text{g}\\text{opt} ) and the thermal bleaching of exciton absorption. The PL spectrum of as-prepared ZnS nanopowder shows UV emission bands at 363 and 395 nm and blue and green emission at 438 and 515 nm, respectively. With increasing T a up to 500 °C, these bands were quenched and red-shifted. In addition, the UV irradiation effects on colloidal ZnS NPs were investigated. UV irradiation at a dose  <13 J cm-2 leads to a decrease in D, the blue shift of E\\text{g}\\text{opt} and the enhancement of PL intensity. This behavior was explained in terms of surface modification by photopolymerization, the formation of a ZnSO4 passivation layer, as well as the reduction of D by photocorrosion. At a UV irradiation dose  <13 J cm-2 both E\\text{g}\\text{opt} and D did not change and PL intensity was quenched, which were caused by the creation of nonradiative surface states by the photodegradation of the capping agent and photopassivated layer. The mechanism of the PL emission process in ZnS NPs was discussed and an energy band diagram was proposed.

  10. Thermolysis preparation of ZnS nanoparticles from a nano-structure bithiazole zinc(II) coordination compound

    NASA Astrophysics Data System (ADS)

    Hosseinian, Akram; Rahimipour, Hamid Reza; Haddadi, Hedayat; Ashkarran, Ali Akbar; Mahjoub, Ali Reza

    2014-09-01

    Nano-scale and single crystals of a new tris-chelate Zn(II) compound, {[Zn(DADMBTZ)3](SCN)2ṡ4H2O}n, (1), {DADMBTZ = 2,2‧-diamino-5,5‧-dimethyl-4,4‧-bithiazole} have been synthesized by the reaction of zinc(II) sulfate, ammonium thiocyanate and DADMBTZ using sonochemical and branched tube methods, respectively. The new nanoparticles were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and FT-IR spectroscopy. Compound (1) was structurally characterized by single crystal X-ray diffraction. Compound (1) form a tris-chelate complex with nearly C3 symmetry. The coordination number of zinc atom in the compound is six with coordinated environments of distorted octahedral, ZnN6. In reaction with DADMBTZ, the ligand DADMBTZ acts as bidentate in compound to form five-membered chelate rings with the same internal angles in coordination polyhedron. The crystal packing is mainly stabilized by N-H- - - -N hydrogen bonding interactions. The thermal stability of compound (1) was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). ZnS nanostructures were obtained by direct thermolyses of compound (1) at 400 °C under argon atmosphere. The ZnS nanoparticles were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy.

  11. Crystal Structure Determination of Low-Dimensional ZnS Powders Using EPR of Mn2+ Ions

    NASA Astrophysics Data System (ADS)

    Vorona, I. P.; Grachev, V. G.; Ishchenko, S. S.; Baran, N. P.; Bacherikov, Yu. Yu.; Zhuk, A. G.; Nosenko, V. V.

    2016-03-01

    Structures of low-dimensional ZnS powders doped with Cu, Co, and Mn were studied using Mn2+ ions as a paramagnetic probe. Particle sizes were 5-7 μm for ZnS:Cu, 7-10 μm for ZnS:Co, and 50-200 nm for ZnS:Mn. Spin-Hamiltonian parameters describing electron paramagnetic resonance spectra were obtained. Analysis of the spectra revealed that ZnS:Cu powder has cubic structure, ZnS:Mn powder has hexagonal structure with orthorhombic distortion, whereas ZnS:Co powder is a mixture of cubic and hexagonal phases in a 1:10 ratio.

  12. Electronic structure and optical absorption spectra of CdSe covered with ZnSe and ZnS epilayers

    NASA Astrophysics Data System (ADS)

    Yun, So Jeong; Lee, Geunsik; Kim, Jai Sam; Shin, Seung Koo; Yoon, Young-Gui

    2006-02-01

    Using the first-principles methods we compute the electronic structure and the absorption spectra for a wurtzite CdSe (0001) slab covered with zincblende ZnSe and ZnS epilayers. For each structure we compute the DOS and the imaginary part of the dielectric function. We find that the semiconductor passivation shifts the 'near Fermi-level' states of the bare CdSe slab down to lower energy levels. The migration suggests the decrease of surface effects and energy loss. We observe the substantial reduction of the abnormal peaks in the absorption spectra of the bare CdSe slab, which seems to be a consequence of the DOS migration. This is consistent with the experimental results that a proper passivation enhance the luminescence efficiency. We also study the case that the epilayer surface is terminated with PH 3 and find the PH 3 passivation also reduces the surface state to some extent.

  13. Structural and optical properties of Cu-doped ZnS nanoparticles formed in chitosan/sodium alginate multilayer films.

    PubMed

    Wang, Liping; Sun, Yujie; Xie, Xiaodong

    2014-05-01

    Chitosan/alginate multilayers were fabricated using a spin-coating method, and ZnS:Cu nanoparticles were generated within the network of two natural polysaccharides, chitosan and sodium alginate. The synthesized nanoparticles were characterized using an X-ray diffractometer (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and atomic force microscopy (AFM). The results showed that cubic zinc blende-structured ZnS:Cu nanoparticles with an average crystal size of ~ 3 nm were uniformly distributed. UV-vis spectra indicate a large quantum size effect and the absorption edge for the ZnS:Cu nanoparticles slightly shifted to longer wavelengths with increasing Cu ion concentrations. The photoluminescence of the Cu-doped ZnS nanoparticles reached a maximum at a 1% doping level. The ZnS:Cu nanoparticles form and are distributed uniformly in the composite multilayer films with a surface average height of 25 nm.

  14. One-step fabrication of single-crystalline ZnS nanotubes with a novel hollow structure and large surface area for photodetector devices.

    PubMed

    An, Qinwei; Meng, Xianquan; Xiong, Ke; Qiu, Yunlei; Lin, Weihua

    2017-03-10

    ZnS nanotubes (NTs) were successfully prepared via a one-step thermal evaporation process without using any templates. The resulting NTs were single crystalline and structurally uniform. Based on experimental analysis, a tube-growth vapor-liquid-solid process was proposed as the growth mechanism of ZnS NTs. A metal-semiconductor-metal full-nanostructured ultraviolet (UV) photodetector with ZnS NTs as the active layer, and Ag nanowires of low resistivity and high transmissivity as electrodes, was fabricated and characterized. The ZnS NT-based device displayed a high I on/I off ratio of up to ∼1.56 × 10(5) with a high response to UV incident light at low operation voltage. This work is a meaningful exploration for preparing other one-dimensional semiconductor NTs, and developing a high-performance and power-saving UV sensor.

  15. Effect of dopent on the structural and optical properties of ZnS thin film as a buffer layer in solar cell application

    SciTech Connect

    Vashistha, Indu B. Sharma, S. K.; Sharma, Mahesh C.; Sharma, Ramphal

    2015-08-28

    In order to find the suitable alternative of toxic CdS buffer layer, deposition of pure ZnS and doped with Al by chemical bath deposition method have been reported. Further as grown pure and doped thin films have been annealed at 150°C. The structural and surface morphological properties have been characterized by X-Ray diffraction (XRD) and Atomic Force Microscope (AFM).The XRD analysis shows that annealed thin film has been polycrystalline in nature with sphalerite cubic crystal structure and AFM images indicate increment in grain size as well as growth of crystals after annealing. Optical measurement data give band gap of 3.5 eV which is ideal band gap for buffer layer for solar cell suggesting that the obtained ZnS buffer layer is suitable in a low-cost solar cell.

  16. The influence of substrate temperature on the structural and optical properties of ZnS thin films

    SciTech Connect

    Ashraf, M.; Akhtar, S. M. J.; Ali, Z.; Qayyum, A.

    2011-05-15

    Thin films of ZnS were deposited on soda lime glass substrates by a modified close-space sublimation technique. The change in optical and structural properties of the films deposited at various substrate temperatures (150-450 Degree-Sign C) was investigated. X-ray diffraction spectra showed that films were polycrystalline in nature having cubic structure oriented only along (111) plan. The crystallinity of films increased with the substrate temperature up to 250 Degree-Sign C. However, crystallinity decreased with further increase of substrate temperature and films became amorphous at 450 Degree-Sign C. The atomic force microscopy data revealed that the films become more uniform and dense with the increase of substrate temperature. Optical properties of the films were determined from the transmittance data using Swanepoel model. It was observed that the energy band gap is increased from 3.52 to 3.65 eV and refractive index of the films are decreased with the increase of substrate temperature. Moreover, considerable improvement in blue response of the films was noticed with increasing substrate temperature.

  17. Influence of Fe doping on the structural, optical and magnetic properties of ZnS diluted magnetic semiconductor

    NASA Astrophysics Data System (ADS)

    Saikia, D.; Raland, RD.; Borah, J. P.

    2016-09-01

    Fe doped ZnS nanoparticles with different concentrations of Fe, synthesized by microwave assisted co-precipitation method have been reported. The incorporation of Fe2+ and Fe3+ ions into ZnS lattice are confirmed by X-ray diffraction (XRD) and Electron Paramagnetic resonance (EPR) study. XRD and High Resolution Transmission electron Microscope (HRTEM) results confirm the phase purity of the samples and indicate a reduction of the particle size with increase in Fe concentration. EDAX analysis confirms the presence of Zn, S and Fe in the samples. A yellow-orange emission peak is observed in Photoluminescence (PL) spectra which exhibits the Characteristic 4T2 (4G)-6A1 (6S) transition of Fe3+ ion. The room temperature magnetic studies as analyzed from M-H curves were investigated from vibrating samples magnetometer (VSM) which shows a weak ferro and superparamagnetic like behavior in 1% and 3% Fe-doped ZnS nanocrystals, whereas; at 10% Fe-doping concentrations, antiferromagnetism behavior is achieved. The ZFC-FC measurement reveals that the blocking temperature of the nanoparticle is above the room temperature.

  18. Starch-assisted synthesis and optical properties of ZnS nanoparticles

    SciTech Connect

    Tian, Xiuying Wen, Jin; Wang, Shumei; Hu, Jilin; Li, Jing; Peng, Hongxia

    2016-05-15

    Highlights: • ZnS spherical nanostructure was prepared via starch-assisted method. • The crystalline lattice structure, morphologies, chemical and optical properties of ZnS nanoparticles. • The forming mechanism of ZnS nanoparticles. • ZnS spherical nano-structure can show blue emission at 460–500 nm. - Abstract: ZnS nanoparticles are fabricated via starch-assisted method. The effects of different starch amounts on structure and properties of samples are investigated, and the forming mechanism of ZnS nanoparticles is discussed. By X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible (UV–vis) spectroscopy and fluorescence (FL) spectrometer, their phases, crystalline lattice structure, morphologies, chemical and optical properties are characterized. The results show that ZnS has polycrystalline spherical structure with the mean diameter of 130 nm. Sample without starch reveals irregular aggregates with particle size distribution of 0.5–2 μm. The band gap value of ZnS is 3.97 eV. The chemical interaction exists between starch molecules and ZnS nanoparticles by hydrogen bonds. The stronger FL emission peaks of ZnS synthesized with starch, indicate a larger content of sulfur vacancies or defects than ZnS synthesized without starch.

  19. Influence of Mn2+ concentration on Mn2+-doped ZnS quantum dot synthesis: evaluation of the structural and photoluminescent properties

    NASA Astrophysics Data System (ADS)

    Sotelo-Gonzalez, Emma; Roces, Laura; Garcia-Granda, Santiago; Fernandez-Arguelles, Maria T.; Costa-Fernandez, Jose M.; Sanz-Medel, Alfredo

    2013-09-01

    The intentional introduction of transition metal impurities into semiconductor nanocrystals is an attractive approach for tuning quantum dot photoluminescence emission. Particularly, doping of ZnS quantum dots with Mn2+ (Mn:ZnS QDs) results in a phosphorescence-type emission, attributed to the incorporation of manganese ions into the nanocrystal structure, so that delayed radiational deactivation of the energy of nanoparticles, excited through the energy levels of the metal, is enabled. However, the development of effective doping strategies can be challenging, especially if a highly efficient photoluminescent emission within a known crystalline core structure, is required (e.g. for analytical phosphorescence applications). The spectroscopic properties and the crystal structure of Mn2+-doped ZnS QDs are studied here to provide a better understanding on how the luminescence emission and the crystalline composition are influenced by the presence of Mn2+ and its concentration used during the synthesis. In order to further control and optimize the synthesis of doped QDs for future bioanalytical applications, different complementary techniques including photoluminescence and X-ray powder diffraction have been employed. The information obtained has allowed standardization of the synthesis conditions of these doped QDs and the identification and quantification of the crystal phases obtained under different synthesis conditions.The intentional introduction of transition metal impurities into semiconductor nanocrystals is an attractive approach for tuning quantum dot photoluminescence emission. Particularly, doping of ZnS quantum dots with Mn2+ (Mn:ZnS QDs) results in a phosphorescence-type emission, attributed to the incorporation of manganese ions into the nanocrystal structure, so that delayed radiational deactivation of the energy of nanoparticles, excited through the energy levels of the metal, is enabled. However, the development of effective doping strategies can be

  20. Composition dependence of the optical properties and band structure of the zinc-blende ZnS1-xOx: a first principles study

    NASA Astrophysics Data System (ADS)

    Gueddim, A.; Zerroug, S.; Bouarissa, N.

    2015-08-01

    We present first principles calculations of structural, electronic and optical properties of ZnS1-xOx in the zinc-blende phase. We employ the full potential linearized augmented plane wave method within the density functional theory in the generalized gradient approximation and Engel-Vosko generalized gradient approximation. Features such as the lattice constant, the bulk modulus and its pressure derivative are reported. The agreement between our calculated results and available experimental and theoretical data is generally good. Direct and indirect energy band gaps as a function of the oxygen composition in the material of interest are presented and discussed. The material under investigation is found to remain a direct band gap semiconductor over all the alloy composition range (0-1). Furthermore, the optical properties such as the dielectric function, the refractive index, the reflectivity and the electron loss energy have also been reported and analysed.

  1. ZnO nanorods decorated with ZnS nanoparticles

    SciTech Connect

    Joicy, S.; Sivakumar, P.; Thangadurai, P.; Ponpandian, N.

    2015-06-24

    In this study, ZnO nanorods (NRs) and ZnS nanoparticles decorated ZnO-NRs were prepared by a combination of hydrothermal and hydrolysis method. Structural and optical properties of the samples were studied by XRD, FE-SEM, UV-Vis DRS and photoluminescence spectroscopy. Microscopy analysis revealed that the diameter of ZnO-NRs was ∼500 nm and the length was ranging from a few hundred nm to several micrometers and their surface was decorated with ZnS nanoparticles. UV-Vis DRS showed the absorption of ZnS decorated ZnO-NRs was blue shifted with respect to pure ZnO-NRs which enhanced the separation of electron-hole pairs. PL spectrum of ZnS decorated ZnO-NRs showed a decrease in intensity of UV and green emissions with the appearance of blue emission at 436 nm.

  2. Structure and properties of ZnSxSe1-x thin films deposited by thermal evaporation of ZnS and ZnSe powder mixtures

    NASA Astrophysics Data System (ADS)

    Valeev, R. G.; Romanov, E. A.; Vorobiev, V. L.; Mukhgalin, V. V.; Kriventsov, V. V.; Chukavin, A. I.; Robouch, B. V.

    2015-02-01

    Interest to ZnSxSe1-x alloys is due to their band-gap tunability varying S and Se content. Films of ZnSxSe1-x were grown evaporating ZnS and ZnSe powder mixtures onto SiO2, NaCl, Si and ITO substrates using an original low-cost method. X-ray diffraction patterns and Raman spectroscopy, show that the lattice structure of these films is cubic ZnSe-like, as S atoms replace Se and film compositions have their initial S/Se ratio. Optical absorption spectra show that band gap values increase from 2.25 to 3 eV as x increases, in agreement with the literature. Because S atomic radii are smaller than Se, EXAFS spectra confirm that bond distances and Se coordination numbers decrease as the Se content decreases. The strong deviation from linearity of ZnSe coordination numbers in the ZnSxSe1-x indicate that within this ordered crystal structure strong site occupation preferences occur in the distribution of Se and S ions. The behavior is quantitatively confirmed by the strong deviation from the random Bernoulli distribution of the three sight occupation preference coefficients of the strained tetrahedron model. Actually, the ternary ZnSxSe1-x system is a bi-binary (ZnS+ZnSe) alloy with evanescent formation of ternary configurations throughout the x-range.

  3. Synthesis and enhanced humidity detection response of nanoscale Au-particle-decorated ZnS spheres

    PubMed Central

    2014-01-01

    We successfully prepared Au-nanoparticle-decorated ZnS (ZnS-Au) spheres by sputtering Au ultrathin films on surfaces of hydrothermally synthesized ZnS spheres and subsequently postannealed the samples in a high-vacuum atmosphere. The Au nanoparticles were distributed on ZnS surfaces without substantial aggregation. The Au nanoparticle diameter range was 5 to 10 nm. Structural information showed that the surface of the annealed ZnS-Au spheres became more irregular and rough. A humidity sensor constructed using the Au-nanoparticle-decorated ZnS spheres demonstrated a substantially improved response to the cyclic change in humidity from 11% relative humidity (RH) to 33% to 95% RH at room temperature. The improved response was associated with the enhanced efficiency of water molecule adsorption onto the surfaces of the ZnS because of the surface modification of the ZnS spheres through noble-metal nanoparticle decoration. PMID:25520595

  4. Photoluminescence study of ZnS and ZnS:Pb nanoparticles

    SciTech Connect

    Virpal, Hastir, Anita; Kaur, Jasmeet; Singh, Gurpreet; Singh, Ravi Chand

    2015-05-15

    Photoluminescence (PL) study of pure and 5wt. % lead doped ZnS prepared by co-precipitation method was conducted at room temperature. The prepared nanoparticles were characterized by X-ray Diffraction (XRD), UV-Visible (UV-Vis) spectrophotometer, Photoluminescence (PL) and Raman spectroscopy. XRD patterns confirm cubic structure of ZnS and PbS in doped sample. The band gap energy value increased in case of Pb doped ZnS nanoparticles. The PL spectrum of pure ZnS was de-convoluted into two peaks centered at 399nm and 441nm which were attributed to defect states of ZnS. In doped sample, a shoulder peak at 389nm and a broad peak centered at 505nm were observed. This broad green emission peak originated due to Pb activated ZnS states.

  5. Nonlinear optical characterization of ZnS thin film synthesized by chemical spray pyrolysis method

    NASA Astrophysics Data System (ADS)

    G, Sreeja V.; V, Sabitha P.; Anila, E. I.; R, Reshmi; John, Manu Punnan; Radhakrishnan, P.

    2014-10-01

    ZnS thin film was prepared by Chemical Spray Pyrolysis (CSP) method. The sample was characterized by X-ray diffraction method and Z scan technique. XRD pattern showed that ZnS thin film has hexagonal structure with an average size of about 5.6nm. The nonlinear optical properties of ZnS thin film was studied by open aperture Z-Scan technique using Q-switched Nd-Yag Laser at 532nm. The Z-scan plot showed that the investigated ZnS thin film has saturable absorption behavior. The nonlinear absorption coefficient and saturation intensity were also estimated.

  6. Nonlinear optical characterization of ZnS thin film synthesized by chemical spray pyrolysis method

    SciTech Connect

    G, Sreeja V; Anila, E. I. R, Reshmi John, Manu Punnan; V, Sabitha P; Radhakrishnan, P.

    2014-10-15

    ZnS thin film was prepared by Chemical Spray Pyrolysis (CSP) method. The sample was characterized by X-ray diffraction method and Z scan technique. XRD pattern showed that ZnS thin film has hexagonal structure with an average size of about 5.6nm. The nonlinear optical properties of ZnS thin film was studied by open aperture Z-Scan technique using Q-switched Nd-Yag Laser at 532nm. The Z-scan plot showed that the investigated ZnS thin film has saturable absorption behavior. The nonlinear absorption coefficient and saturation intensity were also estimated.

  7. First-principle calculation of the elastic, band structure, electronic states, and optical properties of Cu-doped ZnS nanolayers

    NASA Astrophysics Data System (ADS)

    Lahiji, Mohammadreza Askaripour; Ziabari, Ali Abdolahzadeh

    2016-11-01

    The structural, elastic, electronic, and optical properties of undoped and Cu-doped ZnS nanostructured layers have been studied in the zincblende (ZB) phase, by first-principle approach. Density functional theory (DFT) has been employed to calculate the fundamental properties of the layers using full-potential linearized augmented plane-wave (FPLAPW) method. Mechanical analysis revealed that the bulk modulus increases with the increase of Cu content. Cu doping was found to reduce the band gap value of the material. In addition, DOS effective mass of the electrons and heavy holes was evaluated. Adding Cu caused the decrement/increment of transmission/reflectance of nanolayers in the UV-vis region. The substitution by Cu increased the intensity of the peaks, and a slight red shift was observed in the absorption peak. Moreover, the static dielectric constant, and static refractive index increased with Cu content. The optical conductivity also followed a similar trend to that of the dielectric constants. Energy loss function of the modeled compounds was also evaluated. All calculated parameters were compared with the available experimental and other theoretical results.

  8. Optical and structural characterization of CdS/ZnS and CdS:Cu(2+) /ZnS core-shell nanoparticles.

    PubMed

    Murugadoss, G; Kumar, M Rajesh

    2014-09-01

    Core-shell CdS/ZnS (Zn 0.025-0.125 M) and CdS:Cu(2+) (1%)/ZnS nanoparticles were successfully synthesized using a chemical method. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR TEM), photoluminescence (PL) and UV/Visible (UV/Vis) techniques were used to characterize the novel CdS/ZnS and CdS:Cu(2+) /ZnS core-shell nanoparticles. All absorption peaks of the synthesized samples were highly blue-shifted from the bulk CdS and ZnS. Very narrow and symmetric PL emission was observed in the yellow region for core-shell CdS/ZnS. Furthermore, the PL emission of CdS/ZnS was tuned into orange region by incorporate the Cu ion into the core CdS lattice.

  9. Size- and structure-dependence of thermal and mechanical behaviors of single-crystalline and polytypic superlattice ZnS nanowires

    SciTech Connect

    Moon, Junghwan; Cho, Maenghyo; Zhou, Min

    2015-06-07

    Molecular dynamics (MD) simulations are carried out to study the thermal and mechanical behaviors of single-crystalline wurtzite (WZ), zinc-blende (ZB), and polytypic superlattice ZnS nanowires containing alternating WZ and ZB regions with thicknesses between 1.85 nm and 29.62 nm under tensile loading. The wires analyzed have diameters between 1.77 nm and 5.05 nm. The Green-Kubo method is used to calculate the thermal conductivity of the wires at different deformed states. A non-equilibrium MD approach is used to analyze the thermal transport behavior at the interfaces between different structural regions in the superlattice nanowires (SLNWs). The Young's modulus and thermal conductivity of ZB nanowires are approximately 2%–12% and 23%–35% lower than those of WZ nanowires, respectively. The lower initial residual compressive stress due to higher irregularity of surface atoms causes the Young's modulus of ZB nanowires to be lower. The dependence of the thermal conductivity on structure comes from differences in phonon group velocities associated with the different wires. The thermal conductivity of polytypic superlattice nanowires is up to 55% lower than that of single-crystalline nanowires, primarily because of phonon scattering at the interfaces and the resulting lower effective phonon mean free paths for each structural region. As the periodic lengths (1.85–29.62 nm) and specimen lengths (14.81–59.24 nm) of SLNWs decrease, these effects become more pronounced, causing the thermal conductivity to further decrease by up to 30%.

  10. Epitaxially grown zinc-blende structured Mn doped ZnO nanoshell on ZnS nanoparticles

    SciTech Connect

    Limaye, Mukta V.; Singh, Shashi B.; Date, Sadgopal K.; Gholap, R.S.; Kulkarni, Sulabha K.

    2009-02-04

    Zinc oxide in the bulk as well as in the nanocrystalline form is thermodynamically stable in the wurtzite structure. However, zinc oxide in the zinc-blende structure is more useful than that in the wurtzite structure due to its superior electronic properties as well as possibility of efficient doping. Therefore, zinc oxide shell is grown epitaxially on zinc sulphide core nanoparticles having zinc-blende structure. It is shown that doping of manganese could be achieved in zinc oxide nanoshell with zinc-blende structure.

  11. Characteristics of radio frequency-sputtered ZnS on the flexible polyethylene terephthalate (PET) substrate.

    PubMed

    Yoo, Dongjun; Choi, Moon-Suk; Chung, Chulwon; Heo, Seung Chan; Kim, Dohyung; Choi, Changhwan

    2013-12-01

    Zinc sulfide (ZnS) thin film was deposited on the flexible polyethylene-terephtalate (PET) polymer substrate by radio frequency (RF) magnetron sputtering system. ZnS film has a critical thickness range affecting crystal structure where it shows preferred orientation with intensity peak of X-ray diffractometer at 28.4 degrees for ZnS thinner than 200 nm while hexagonal wurtzite and cubic zinc-blend (101) are co-existed for film thicker than 200 nm. Optical band gap energy (Eg) decreases with increasing RF-powers, resulting from increase in film thickness. Eg of ZnS films on PET is 3.68-3.86 eV, which is lower than that of ZnS on the rigid substrate by 0.27-0.28 eV. This is attributed to amount of incorporated oxygen to ZnS material as well as residual strain and disorder of grain boundary. Transmittance of ZnS on PET degrades due to surface defects and complex internal structure. Energy dispersive spectroscopy reveals out that ZnS film does not have a unity of Zn to S ratio, but it is close to stoichiometric composition with increasing thickness.

  12. Characterization of Zns-GaP Naon-composites

    SciTech Connect

    Voiles, Todd

    1993-12-09

    It proved possible to produce consistent, high-quality nanocrystalline ZnS powders with grain sizes as small as 8 nm. These powders are nano-porous and are readily impregnated with GaP precursor, although inconsistently. Both crystal structure and small grain size of the ZnS can be maintained through the use of GaP. Heat treatment of the impregnated powders results in a ZnS-GaP composite structure where the grain sizes of the phases are on the order of 10--20 nm. Conventional powder processing should be able to produce optically dense ceramic compacts with improved mechanical properties and suitable IR transmission.

  13. Hydrothermal Synthesis of Nanoclusters of ZnS Comprised on Nanowires

    PubMed Central

    Ibupoto, Zafar Hussain; Khun, Kimleang; Liu, Xianjie; Willander, Magnus

    2013-01-01

    Cetyltrimethyl ammonium bromide cationic (CTAB) surfactant was used as template for the synthesis of nanoclusters of ZnS composed of nanowires, by hydrothermal method. The structural and morphological studies were performed by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) techniques. The synthesized ZnS nanoclusters are composed of nanowires and high yield on the substrate was observed. The ZnS nanocrystalline consists of hexagonal phase and polycrystalline in nature. The chemical composition of ZnS nanoclusters composed of nanowires was studied by X-ray photo electron microscopy (XPS). This investigation has shown that the ZnS nanoclusters are composed of Zn and S atoms.

  14. Solution assisted growth mechanism and characterization of ZnS microspheres

    NASA Astrophysics Data System (ADS)

    Ghoderao, Karuna P.; Jamble, Shweta N.; Sawant, Jitendra P.; Kale, Rohidas B.

    2017-02-01

    The ZnS microspheres were synthesized via simple, efficient and cost-effective hydrothermal method. The x-ray diffraction study revealed nanocrystalline nature of the synthesized ZnS with the cubic crystal structure. Scanning and transmission electron microscopy observations revealed the formation of 3D microspheres that consist of numerous ZnS nanocrystals. The grown microspheres are also interconnected with each other by driving force of attachment. The obtained product has excellent elemental stoichiometric proportion as evidenced by the EDS technique. The electron diffraction pattern reveals the polycrystalline nature of obtained ZnS product. The band gap was measured from UV–Vis spectroscopic study and found to be blue shifted from the bulk band gap value. The PL study exhibits negligibly weak band edge emission and dominant, widespread defect-related green emission. The nucleation of a ZnS nanocrystals and subsequent growth into the microspheres is also discussed.

  15. A Theoretical Investigation of the Effect of Pressure on the Structural, Elastic and Mechanical Properties of ZnS Crystals

    NASA Astrophysics Data System (ADS)

    Güler, E.; Güler, M.

    2015-06-01

    Structural, elastic, and mechanical properties of blende-type zinc sulfide ( bt-ZnS) were investigated under pressures up to 20 GPa. Unlike previous theoretical calculations, an existing mixed-type interatomic potential was applied with geometry optimization calculations. B3 → B1 phase transition pressure was obtained as 17 GPa under zero pressure and temperature. Pressure dependence of typical cubic elastic constants, bulk, shear and Young moduli, elastic wave velocities, Kleinman parameter, static and high-frequency dielectric constants of bt-ZnS were also obtained. Overall, our results for the considered parameters of bt-ZnS are in good agreement with experiments and better than those of several available theoretical data.

  16. Enhanced Cu emission in ZnS : Cu,Cl/ZnS core-shell nanocrystals

    NASA Astrophysics Data System (ADS)

    Corrado, Carley; Hawker, Morgan; Livingston, Grant; Medling, Scott; Bridges, Frank; Zhang, Jin Z.

    2010-07-01

    ZnS : Cu,Cl/ZnS core-shell nanocrystals (NCs) have been synthesized via a facile aqueous synthesis method. The shell growth of the NCs was observed via a red-shift in the UV-Vis absorption spectra with increasing NC size. The Cu photoluminescence (PL) emission was enhanced by capping with a thin ZnS shell. The ZnS : Cu (0.2%) and ZnS : Cu (0.5%) show a more pronounced red-shift in the apparent PL peak position as well as a 37% and 67% increase in emission intensity, respectively, in comparison to the undoped NCs. The observed red-shift is mainly due to an increase in intensity of the Cu PL emission. The 1% Cu-doped NCs exhibit very little red-shift because the observed emission is dominated by the Cu-dopant and thus nearly independent of the size of the NCs. The increase in Cu emission is evidence that Cu atoms occupying non-emissive surface sites in doped ZnS NCs were encapsulated by the ZnS shell. Extended X-Ray Absorption Fine Structure (EXAFS) data also suggests that the Cu had slightly more neighbors upon growth of a ZnS shell, indicating its encapsulation into the core of the NCs. The EXAFS Zn edge data also indicate greater disorder in the ZnS structure when the shell is grown, which may be attributed to the ZnS shell being more amorphous than the core NCs. This study demonstrates that core-shell structures can be used as a simple and yet powerful strategy to enhance PL properties of doped semiconductor NCs.

  17. Alloying ZnS in the hexagonal phase to create high-performing transparent conducting materials.

    PubMed

    Faghaninia, Alireza; Bhatt, Kunal Rajesh; Lo, Cynthia S

    2016-08-10

    Alloyed zinc sulfide (ZnS) has shown promise as a relatively inexpensive and earth-abundant transparent conducting material (TCM). Though Cu-doped ZnS has been identified as a high-performing p-type TCM, the corresponding n-doped ZnS has, to date, been challenging to synthesize in a controlled manner; this is because the dopant atoms compete with hole-inducing zinc vacancies near the conduction band minimum as the most thermodynamically stable intrinsic point defects. We thus aim to identify the most promising n-type ZnS-based TCM, with the optimal combination of physical stability, transparency, and electrical conductivity. Using a relatively new method for calculating the free energy of both the sphalerite (cubic) and wurtzite (hexagonal) phases of undoped and doped ZnS, we find that doped ZnS is more stable in the hexagonal structure. This, for the first time, fundamentally explains previous experimental observations of the coexistence of both phases in doped ZnS; hence, it profoundly impacts future work on sulfide TCMs. We also employ hybrid density functional theory calculations and a new carrier transport model, AMSET (ab initio model for mobility and Seebeck coefficient using the Boltzmann transport equation), to analyze the defect physics and electron mobility of the different cation- (B, Al, Ga, In) and anion-doped (F, Cl, Br, I) ZnS, in both the cubic and hexagonal phases, at various dopant compositions, temperatures, and carrier concentrations. Among all doped ZnS candidates, Al-doped ZnS (AZS) exhibits the highest dopant solubility, largest electronic band gap, and highest electrical conductivity of 3830, 1905, and 321 S cm(-1), corresponding to the possible carrier concentrations of n = 10(21), 10(20), and 10(19) cm(-3), respectively, at the optimal 6.25% dopant concentration of Al and the temperature of 300 K.

  18. Enhanced photocatalytic activity of ZnS nanoparticles loaded with MoS2 nanoflakes by self-assembly approach

    NASA Astrophysics Data System (ADS)

    Vattikuti, S. V. Prabhakar; Byon, Chan; Jeon, Sora

    2016-12-01

    A hybrid consisting of ZnS nanoparticles supported on layered MoS2-ZnS was synthesized by a hydrothermal method based on self-assembly technique without using a template. XRD, SEM-EDX, TEM, HR-TEM, TG-DTA, XPS, N2 adsorption-desorption, and UV-Vis spectroscopies were used to characterize the structural features, morphology, and composition of the MoS2-ZnS hybrid. The results show that the MoS2-ZnS hybrid is mainly ZnS nanoparticles on layered MoS2 with a thickness of ca. 5-20 nm. The combination of the MoS2 and ZnS hybrid structure is beneficial for enhancing the photocatalytic degradation of rhodamine B (RhB) under visible light irradiation. A possible photoreaction mechanism of the MoS2-ZnS hybrid in the degradation is proposed. The photoexcited electrons from the ZnS could easily transfer to the conduction band of MoS2, thus decreasing the recombination of photoinduced carriers and enabling the degradation of RhB under visible light irradiation.

  19. First-principles prediction of half-metallic ferromagnetism in Cu-doped ZnS

    NASA Astrophysics Data System (ADS)

    Zhang, Chang-wen; Yan, Shi-shen

    2010-02-01

    The spin-polarized full potential linearized augmented plane wave method in the generalized gradient approximation is carried out for investigation on the magnetism and electronic structures of Cu-doped ZnS. We find that the Cu-doped ZnS supercell shows half-metallic ferromagnetic character with a total magnetic moment of 1.0μB per Cu. The long-range ferromagnetism in Cu-doped ZnS can be explained in terms of p-d like hybridization chain, and the Curie temperature higher than around 350 K is predicted. These results suggest that Cu-doped ZnS may be a promising half-metallic ferromagnetic material for applications in spintronics.

  20. Magnetism in undoped ZnS nanotetrapods.

    PubMed

    Shan, Aixian; Liu, Wei; Wang, Rongming; Chen, Chinping

    2013-02-21

    The magnetism of undoped ZnS nanotetrapods, synthesized by a solvothermal method, has been investigated by magnetization measurements and first principle numerical calculations. The background magnetic impurity concentrations of Fe, Co and Ni were determined at ppm level by inductively coupled plasma mass spectrometry (ICP-MS). Hysteresis loops of weak ferromagnetism were observed, attributable to the magnetic impurities. However, the total magnetic moments analyzed from the paramagnetism are far beyond the explanations from the presence of these magnetic impurities, by about two orders of magnitude larger. It implies a different origin of the magnetic moments. Electron microscopy analysis reveals that there are defects in the sample. Numerical simulations indicate that the excessive magnetic moments might arise from the local band structure of polarized electrons associated with the defects of cation deficiency. This study elaborates on the understanding of magnetic properties in the non-magnetic II-VI semiconductor nanomaterials.

  1. ZnS nanosheets: Egg albumin and microwave-assisted synthesis and optical properties

    NASA Astrophysics Data System (ADS)

    Tian, Xiuying; Wen, Jin; Hu, Jilin; Chen, Zhanjun; Wang, Shumei; Peng, Hongxia; Li, Jing

    2016-09-01

    ZnS nanosheets were prepared via egg albumin and microwave-assisted method. The phases, crystalline lattice structures, morphologies, chemical and optical properties were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscope(FE-SEM), selected area electron diffraction (SAED), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy and fluorescence(FL) spectrometer and growth mechanism of ZnS nanosheets was investigated. The results showed that all samples were pure cubic zinc blende with polycrystalline structure. The width of ZnS nanosheets with a rectangular nanostructure was in the range of 450-750 nm. The chemical interaction existed between egg albumin molecules and ZnS nanoparticles via the amide/carboxylate group. The band gap value calculated was 3.72 eV. The band at around 440 nm was attributed to the sulfur vacancies of the ZnS nanosheets. With increasing volumes of egg albumin, the photoluminescence (PL) intensity of ZnS samples firstly increased and then decreased, attributed to concentration quenching.

  2. An experimental and theoretical investigation on the optical and photocatalytic properties of ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    La Porta, F. A.; Nogueira, A. E.; Gracia, Lourdes; Pereira, W. S.; Botelho, G.; Mulinari, T. A.; Andrés, Juan; Longo, E.

    2017-04-01

    From the viewpoints of materials chemistry and physical chemistry, crystal structure directly determines the electronic structure and furthermore their optical and photocatalytic properties. Zinc sulfide (ZnS) nanoparticles (NPs) with tunable photoluminescence (PL) emission and high photocatalytic activity have been obtained by means of a microwave-assisted solvothermal (MAS) method using different precursors (i.e., zinc nitrate (ZN), zinc chloride (ZC), or zinc acetate (ZA)). The morphologies, optical properties, and electronic structures of the as-synthesized ZnS NPs were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET) isotherms for N2 adsorption/desorption processes, diffuse reflectance spectroscopy (DRS), PL measurements and theoretical calculations. Density functional theory calculations were used to determine the geometries and electronic properties of bulk wurtzite (WZ) ZnS NPs and their (0001), (101 ̅0), (112 ̅0), (101 ̅1), and (101 ̅2) surfaces. The dependence of the PL emission behavior of ZnS NPs on the precursor was elucidated by examining the energy band structure and density of states. The method for degradation of Rhodamine B (RhB) was used as a probe reaction to investigate the photocatalytic activity of the as-Synthesised ZnS NPs under UV light irradiation. The PL behavior as well as photocatalytic activities of ZnS NPs were attributed to specific features of the structural and electronic structures. Increased photocatalytic degradation was observed for samples synthesized using different precursors in the following order: ZAZnS NPs were also briefly discussed.

  3. Photoluminescence study of Mn doped ZnS nanoparticles prepared by co-precipitation method

    NASA Astrophysics Data System (ADS)

    Deshpande, M. P.; Patel, Kamakshi; Gujarati, Vivek P.; Chaki, S. H.

    2016-05-01

    ZnS nanoparticles co-doped with different concentration (5,10,15%) of Mn were synthesized using polyvinylpyrrolidone (PVP) as a capping agent under microwave irradiation. We confirmed doping of Mn in the host ZnS by EDAX whereas powder X-ray diffractogram showed the cubic zinc blende structure of all these samples. TEM images did showed agglomeration of particles and SAED pattern obtained indicated polycrystalline nature. From SAED pattern we calculated lattice parameter of the samples which have close resemblance from that obtained from XRD pattern. The band gap values of pure and doped ZnS nanoparticles were calculated from UV-Visible absorption spectra. ZnS itself is a luminescence material but when we dope it with transition metal ion such as Mn, Co, and Cu they exhibits strong and intense luminescence in the particular region. The photoluminescence spectra of pure ZnS nanoparticles showed an emission at 421 and 485nm which is blue emission which was originated from the defect sites of ZnS itself and also sulfur deficiency and when doped with Mn2+ an extra peak with high intensity was observed at 530nm which is nearly yellow-orange emission which isrelated to the presence of Mn in the host lattice.

  4. Effect of effective mass and spontaneous polarization on photocatalytic activity of wurtzite and zinc-blende ZnS

    SciTech Connect

    Dong, Ming; Zhang, Jinfeng; Yu, Jiaguo

    2015-10-01

    Semiconductor zinc sulphide (ZnS) has two common phases: hexagonal wurtzite and cubic zinc-blende structures. The crystal structures, energy band structures, density of states (DOS), bond populations, and optical properties of wurtzite and zinc-blende ZnS were investigated by the density functional theory of first-principles. The similar band gaps and DOS of wurtzite and zinc-blende ZnS were found and implied the similarities in crystal structures. However, the distortion of ZnS{sub 4} tetrahedron in wurtzite ZnS resulted in the production of spontaneous polarization and internal electric field, which was beneficial for the transfer and separation of photogenerated electrons and holes.

  5. Formation of ZnS nanorods by simple evaporation technique

    NASA Astrophysics Data System (ADS)

    Velumani, S.; Ascencio, J. A.

    Semiconductor nanocrystals and nanorods whose properties are largely determined by the quantum confinement effect are currently being intensively studied by materials scientists, physicists and chemists. Zinc sulphide (ZnS), a II-VI group semiconductor material possessing a direct band gap of 3.66 eV, has recently been extensively investigated due to its multifaceted applications. We report the synthesis of ZnS nanorods by a simple physical vapor deposition method and an in-detail surface analysis for device applications. Our interest in this material mainly lies behind its use as an n-window layer for our investigations on different window layers for CdTe- and CIS (Copper Indium diselenide) based solar cells and for photocatalytic production of hydrogen from water using the photocatalysts CdS/ZnS. ZnS films are deposited onto well-cleaned glass substrates at a vacuum of 5×10-5 Torr and various parameters are determined. The distance between the substrate and the source was maintained at 0.15 cm. The deposition time was about 20 min at a constant rate of evaporation and the substrates were maintained at room temperature. Structural analysis reveals the cubic nature of the crystallites, which is confirmed from atomic force microscopy (AFM) analysis. The AFM analysis reveals the formation of nanorods due to coalescence, which is substantiated from sectional analysis. A further analysis reveals the preferential growth of the nanorods and the coalescence limited by the energy in the (002) face. The composition was analyzed using an energy-dispersive X-ray method (EDX) and the film was found to possess excess sulfur. The band gap of the vacuum-deposited ZnS film was found to be 3.6 eV.

  6. The Combustion Synthesis Zns Doped Materials to Create Ultra-Electroluminscent Materials in Microgravity

    NASA Astrophysics Data System (ADS)

    Castillo, Martin; Steinberg, Theodore

    2012-07-01

    Self-propagating high temperature synthesis (SHS) utilises a rapid exothermic process involving high energy and nonlinearity coupled with a high cooling rate to produce materials formed outside of normal equilibrium boundaries thus possessing unique properties. The elimination of gravity during this process allows capillary forces to dominate mixing of the reactants which results in a superior and enhanced homogeneity in the product materials. ZnS type materials have been previously conducted in reduced gravity and normal gravity. It has been claimed in literature that a near perfect phases of ZnS wurtzite was produced. Although, the SHS of this material is possible at high pressures, there have been no advancements in refining this structure to create ultra-electroluminescent materials. Utilising this process with ZnS doped with Cu, Mn, or rare earth metals such as Eu and Pr leads to electroluminescence properties, thus making this an attractive electroluminescent material. The work described here will revisit the SHS of ZnS and will re-examine the work performed in both normal gravity and in reduced gravity within the Queensland University of Technology Drop Tower Facility. Quantifications in the lattice parameters, crystal structures, and phases produced are presented to further explore the unique structure-property performance relationships produced from the SHS of ZnS materials.

  7. Photomechanical modification of ZnS microcrystal to enhance electroluminescence by ultrashort-pulse laser processing

    NASA Astrophysics Data System (ADS)

    Nabesaka, Kyohei; Ishikawa, Yasuaki; Hosokawa, Yoichiroh; Uraoka, Yukiharu

    2017-02-01

    A ZnS microcrystal was treated with an ultrashort-pulse laser and applied to an inorganic electroluminescence (EL) phosphor. We found that the emission intensity of the EL phosphor was increased by laser-induced photomechanical modification. The pulse duration dependence of the emission enhancement and structural analysis by scanning electron microscopy indicated that the structural modification was induced inside the ZnS microcrystal, although a mechanical grinding would induce the structural modification mainly on the crystal surface. The results suggested a new way of enhancing the emission of inorganic EL devices.

  8. Synthesis of Cu doped ZnS nanostructures on flexible substrate using low cost chemical method

    SciTech Connect

    Kumar, Nitin Purohit, L. P.; Goswami, Y. C.

    2015-08-28

    Flexible electronics is one of the emerging area of this era. In this paper we have reported synthesis of Cu doped Zinc sulphide nanostructures on filter paper flexible substrates. Zinc chloride and Thio urea were used as a precursor for Zinc and Sulphur. The structures were characterized by XRD, FE-SEM and UV visible spectrometer. All the peaks identified for cubic structure of ZnS. Appearance of small Cu peaks indicates incorporation of Cu into ZnS lattice. Zns nanostructures assembled as nanobelts and nanofibers as shown in FE-SEM micrographs. Compound Structures provide the reasonable electrical conductivity on filter paper. Absorption in UV region makes them suitable for flexible electronic devices.

  9. Spin coating of ZnS nanostructures on filter paper and their characterization

    NASA Astrophysics Data System (ADS)

    Kumar, Nitin; Purohit, L. P.; Goswami, Y. C.

    2016-09-01

    In this paper we have reported spin coating of Cu doped Zinc sulphide nanostructures on filter paper flexible substrates. Zinc chloride and thiourea were used as precursors of zinc and sulphur. The samples were characterized by XRD, FE-SEM, EDAX and UV-visible spectrum studies. All the diffractogram peaks confirm the cubic structure of ZnS with small peak of Cu indicates incorporation of Cu into ZnS lattice. FE-SEM micrographs exhibit fibrous morphologies of ZnS structures on filter paper. Compound structures on flexible substrates show ohmic behavior with conductivity about 3.07×106 (Ωcm)-1 to 4.27×106 (Ωcm)-1. Excellent photoluminescence property doped with copper makes them suitable for flexible opto-electronic devices.

  10. Synthesis of Cu doped ZnS nanostructures on flexible substrate using low cost chemical method

    NASA Astrophysics Data System (ADS)

    Kumar, Nitin; Purohit, L. P.; Goswami, Y. C.

    2015-08-01

    Flexible electronics is one of the emerging area of this era. In this paper we have reported synthesis of Cu doped Zinc sulphide nanostructures on filter paper flexible substrates. Zinc chloride and Thio urea were used as a precursor for Zinc and Sulphur. The structures were characterized by XRD, FE-SEM and UV visible spectrometer. All the peaks identified for cubic structure of ZnS. Appearance of small Cu peaks indicates incorporation of Cu into ZnS lattice. Zns nanostructures assembled as nanobelts and nanofibers as shown in FE-SEM micrographs. Compound Structures provide the reasonable electrical conductivity on filter paper. Absorption in UV region makes them suitable for flexible electronic devices.

  11. Post-annealing effects on ZnS thin films grown by using the CBD method

    NASA Astrophysics Data System (ADS)

    Ahn, Heejin; Um, Youngho

    2015-09-01

    Herein, the structural, morphological, and optical properties of zinc sulfide (ZnS) thin films deposited via the chemical bath deposition method are reported. These films were deposited on soda-lime glass (SLG) substrates by using ZnSO4, thiourea, and 25% ammonia at 90 °C. The effect of changing the annealing temperature from 100 °C to 300 °C on the properties of the ZnS thin films was investigated. X-ray diffraction (XRD) patterns showed that the ZnS thin film annealed at 100 °C had an amorphous structure; however, as the annealing temperature was increased, the crystalline quality of the thin film was enhanced. Moreover, transmission measurements showed that the optical transmittance was about 80% for wavelengths above 500 nm. The band gap energy (E g ) value of the film annealed at 300 °C was decreased to about 3.82 eV.

  12. Process and film characterization of chemical-bath-deposited ZnS thin films

    SciTech Connect

    Dona, J.M.; Herrero, J.

    1994-01-01

    Chemical-bath deposition of ZnS thin films from NH{sub 3}/NH{sub 2}-NH{sub 2}/SC(NH{sub 2}){sub 2}/ZnSO{sub 4} solutions has been studied. The effect of various process parameters on the growth and the film quality is presented. A first approach to a mechanistic interpretation of the chemical process is reported. The structural, optical, chemical, and electrical properties of the ZNS thin films deposited by this method have been studied. The electron diffraction (EDS) analysis shows that the films are microcrystalline with a cubic structure. EDS analysis has demonstrated that the films are highly stoichiometric. Scanning electron microscopy studies of the ZnS thin films deposited by this method show that the films are continuous and homogeneous. Electrical conductivity measurements have shown the highly resistivity nature of these films ({sigma} = 10{sup {minus}9} S/cm).

  13. Synthesis and study of optical properties of transition metals doped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Ramasamy, V.; Praba, K.; Murugadoss, G.

    2012-10-01

    ZnS and transition metal (Mn, Co, Ni, Cu, Ag and Cd) doped ZnS were synthesized using chemical precipitation method in an air atmosphere. The structural and optical properties were studied using various techniques. The X-ray diffraction (XRD) analysis show that the particles are in cubic structure. The mean size of the nanoparticles calculated through Scherrer equation is in the range of 4-6.1 nm. Elemental dispersive (EDX) analysis of doped samples reveals the presence of doping ions. The scanning electron microscopic (SEM) and transmission electron microscopic (TEM) studies show that the synthesized particles are in spherical shape. Optical characterization of both undoped and doped samples was carried out by ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy. The absorption spectra of all the samples are blue shifted from the bulk ZnS. An optimum doping level of the transition metals for enhanced PL properties are found through optical study.

  14. Investigation of thioglycerol stabilized ZnS quantum dots in electroluminescent device performance

    NASA Astrophysics Data System (ADS)

    Ethiraj, Anita Sagadevan; Rhen, Dani; Lee, D. H.; Kang, Dae Joon; Kulkarni, S. K.

    2016-05-01

    The present work is focused on the investigation of thioglycerol (TG) stabilized Zinc Sulfide Quantum dots (ZnS QDs) in the hybrid electroluminescence (EL) device. Optical absorption spectroscopy clearly indicates the formation of narrow size distributed ZnS in the quantum confinement regime. X-ray Diffraction (XRD), Photoluminescence (PL), Energy Dispersive X-ray Spectroscopy (EDS) data supports the same. The hybrid EL device with structure of ITO (indium tin oxide)//PEDOT:PSS ((poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate)//HTL (α NPD- N,N'-diphenyl-N,N'-bis(1-naphthyl)-(1,1'-phenyl)-4,4'-diamine// PVK:ZnS QDs//ETL(PBD- 2-tert-butylphenyl- 5-biphenyl-1,3,4-oxadiazole)//LiF:Al (Device 1) was fabricated. Reference device without the ZnS QDs were also prepared (Device 2). The results show that the ZnS QDs based device exhibited bright electroluminescence emission of 24 cd/m2 at a driving voltage of 16 Volts under the forward bias conditions as compared to the reference device without the ZnS QDs, which showed 6 cd/m2 at ˜22 Volts.

  15. Variability in Chemical Vapor Deposited Zinc Sulfide: Assessment of Legacy and International CVD ZnS Materials

    SciTech Connect

    McCloy, John S.; Korenstein, Ralph

    2009-10-06

    Samples of CVD ZnS from the United States, Germany, Israel, and China were evaluated using transmission spectroscopy, x-ray diffraction, photoluminescence, and biaxial flexure testing. Visible and near-infrared scattering, 6 μm absorption, and ultraviolet cut-on edge varied substantially in tested materials. Crystallographic hexagonality and texture was determined and correlated with optical scattering. Transmission cut-on (ultraviolet edge) blue-shifts with annealing and corresponds to visible color but not the 6 μm absorption. Photoluminescence results suggest that CVD ZnS exhibits a complex suite of electronic bandgap defects. All CVD ZnS tested with biaxial flexure exhibit similar fracture strength values and Weibull moduli. This survey suggests that technical understanding of the structure and optical properties CVD ZnS is still in its infancy.

  16. A novel drug delivery of 5-fluorouracil device based on TiO2/ZnS nanotubes.

    PubMed

    Faria, Henrique Antonio Mendonça; de Queiroz, Alvaro Antonio Alencar

    2015-11-01

    The structural and electronic properties of titanium oxide nanotubes (TiO2) have attracted considerable attention for the development of therapeutic devices and imaging probes for nanomedicine. However, the fluorescence response of TiO2 has typically been within ultraviolet spectrum. In this study, the surface modification of TiO2 nanotubes with ZnS quantum dots was found to produce a red shift in the ultra violet emission band. The TiO2 nanotubes used in this work were obtained by sol-gel template synthesis. The ZnS quantum dots were deposited onto TiO2 nanotube surface by a micelle-template inducing reaction. The structure and morphology of the resulting hybrid TiO2/ZnS nanotubes were investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction techniques. According to the results of fluorescence spectroscopy, pure TiO2 nanotubes exhibited a high emission at 380nm (3.26eV), whereas TiO2/ZnS exhibited an emission at 410nm (3.02eV). The TiO2/ZnS nanotubes demonstrated good bio-imaging ability on sycamore cultured plant cells. The biocompatibility against mammalian cells (Chinese Hamster Ovarian Cells-CHO) suggesting that TiO2/ZnS may also have suitable optical properties for use as biological markers in diagnostic medicine. The drug release characteristic of TiO2/ZnS nanotubes was explored using 5-fluorouracil (5-FU), an anticancer drug used in photodynamic therapy. The results show that the TiO2/ZnS nanotubes are a promising candidate for anticancer drug delivery systems.

  17. Single-layer ZnS supported on Au(111): A combined XPS, LEED, STM and DFT study

    NASA Astrophysics Data System (ADS)

    Deng, Xingyi; Sorescu, Dan C.; Lee, Junseok

    2017-04-01

    Single-layer of ZnS, consisting of one atomic layer of ZnS(111) plane, has been grown on Au(111) and characterized using X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). While the LEED measurement indicates a coincidence structure of ZnS-(3×3)/Au(111)-(4×4), high resolution STM images reveal hexagonal unit cells of 6.7×6.7 Å2 and 11.6×11.6 Å2, corresponding to √3 and 3 times the unit cell of the ideal zincblende ZnS-(1×1), respectively, depending on the tunneling conditions. Calculations based on density functional theory (DFT) indicate a significantly reconstructed non-planar structure of ZnS single-layer on Au(111) with 2/3 of the S anions being located nearly in the plane of the Zn cations and the rest 1/3 of the S anions protruding above the Zn plane. The calculated STM image shows similar characteristics to those of the experimental STM image. Additionally, the DFT calculations reveal the different bonding nature of the S anions in ZnS single-layer supported on Au(111).

  18. Surface-treated biocompatible ZnS quantum dots: Synthesis, photo-physical and microstructural properties

    NASA Astrophysics Data System (ADS)

    Taherian, M.; Sabbagh Alvani, A. A.; Shokrgozar, M. A.; Salimi, R.; Moosakhani, S.; Sameie, H.; Tabatabaee, F.

    2014-03-01

    In the present study, the ZnS semiconductor quantum dots were successfully synthesized via an aqueous method utilizing glutathione (GSH), thioglycolic acid (TGA) and polyvinyl pyrrolidone (PVP) as capping agents. The structural, morphological and photo-physical properties and biocompatibility were investigated using comprehensive characterization techniques such as x-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), dynamic light scattering (DLS), Fourier transform infrared spectrometry (FT-IR), UV-Vis optical absorption, photoluminescence (PL) spectrometer and MTT assay. The XRD patterns showed a cubic zinc blende crystal structure and a crystallite size of about 2-3 nm using Scherrer's equation confirmed by the electron micrographs and Effective Mass Approximation (EMA). The DLS and zeta-potential results revealed that GSH capped ZnS nanoparticles have the narrowest size distribution with an average size of 27 nm and relatively good colloidal stability. Also, the FT-IR spectrum confirmed the interaction of the capping agent groups with ZnS nanoparticles. According to the UV-Vis absorption results, optical bandgap of the spherical capped nanoparticles is higher compared to the uncapped sample and could be wider than 3.67 eV (corresponding to the bulk ZnS), which is due to the quantum confinement effect. From photoluminescence spectra, it was found that the emission becomes more intensive and shifts towards the shorter wavelengths in the presence of the capping agent. Moreover, the emission mechanism of uncapped and capped ZnS was discussed in detail. Finally, the MTT results revealed the satisfactory (>94%) biocompatibility of GSH capped ZnS quantum dots which would be a promising candidate applicable in fluorescent biological labels.

  19. Synthesis and luminescence properties of ZnS and metal (Mn, Cu)-doped-ZnS ceramic powder

    NASA Astrophysics Data System (ADS)

    Ummartyotin, S.; Bunnak, N.; Juntaro, J.; Sain, M.; Manuspiya, H.

    2012-03-01

    ZnS and metal (Mn, Cu)-doped-ZnS were successfully prepared by wet chemical synthetic route. The understanding of substituted metal ions (Mn, Cu) into ZnS leads to transfer the luminescent centre by small amount of metal dopant (Mn, Cu). Fourier transform infrared and X-ray diffraction were used to determine chemical bonding and crystal structure, respectively. It showed that small amount of metal (Mn, Cu) can be completely substituted into ZnS lattice. X-ray fluorescence was used to confirm the existence of metal-doped ZnS. Scanning electron microscope revealed that their particles exhibits blocky particle with irregular sharp. Laser confocal microscope and photoluminescence spectroscopy showed that ZnS and metal-doped-ZnS exhibited intense, stable, and tunable emission covering the blue to red end of the visible spectrum. ZnS, Mn-doped-ZnS and Cu-doped-ZnS generated blue, yellow and green color, respectively.

  20. Synthesis of Mn-doped ZnS microspheres with enhanced visible light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Wang, Peng; Huang, Baibiao; Ma, Xiaojuan; Wang, Gang; Dai, Ying; Zhang, Xiaoyang; Qin, Xiaoyan

    2017-01-01

    ZnS microspheres with a series of Mn-doping concentration were synthesized via a facile solvothermal route. The phase structures, morphologies, and chemical states were characterized by X-ray powder diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The phase structure of the synthesized Mn-ZnS microspheres is hexagonal from the XRD patterns. UV-vis diffuse reflectance spectra were employed to analyze the absorption properties of the samples. The Mn-doped ZnS exhibited stronger visible light absorption with the increasing of Mn content. Their photocatalytic activities were evaluated by H2 production from water and reducing Cr6+ under visible light irradiation. The as-prepared Mn-doped ZnS exhibited better photocatalytic performance than that of pure ZnS and the optimal doping concentration was 7%. The enhancement in photocatalytic activity can be attributed to the expansion of light absorption and the increase in life time of photogenerated carriers.

  1. First-principles calculations for transition phase, mechanical and thermodynamic properties of ZnS under extreme condition

    NASA Astrophysics Data System (ADS)

    Yang, Tao; Liu, Daijun; Ji, Junyi; Chen, Jianjun; Yu, Yang; Wu, Ruoxi

    2017-02-01

    The structural and mechanical properties of ZnS in both B3 and B1 phases have been investigated by the generalized gradient approximation (GGA) within the plane-wave pseudopotential density functional theory (DFT). The obtained lattice parameters and bulk modulus of ZnS for both B3 and B1 structures are well in line with the available theoretical and experimental results. Using the enthalpy-pressure data, we have predicted that the phase transition pressure of ZnS from B3 to B1 is 17.26 GPa, which is in good agreement with previous experimental values. The hydrostatic pressure-dependent elastic properties of the two structures, such as bulk modulus, shear modulus and Young’s modulus, are discussed. Then, the mechanical characteristics of ZnS, including ductile/brittle behavior and elastic anisotropy of the two cubic single-crystal structures, are investigated in details. Furthermore, the thermodynamic properties of ZnS under extreme condition are explored by quasi-harmonic Debye modeling. The calculated results show that the ductility and elastic anisotropy increase with pressure clearly except the ductility of B1. Besides, the temperature and pressure dependencies of the heat capacity and the Debye temperature are obtained and analyzed in the wide ranges.

  2. Photo physical studies of PVP arrested ZnS quantum dots

    NASA Astrophysics Data System (ADS)

    Shahi, Ashutosh Kumar; Pandey, Bishnu Kumar; Singh, Bheeshma Pratap; Gupta, Bipin Kumar; Singh, Sukhvir; Gopal, Ram

    2016-12-01

    Monodispersed polyvinylpyrrolidone (PVP) arrested ZnS quantum dots (QDs) having diameter in range 2-5 nm are synthesized by a colloidal precipitation method using PVP as the stabilizing agent. X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selective area electron diffraction (SAED) and Fourier transform infrared (FT-IR) spectroscopy are probed to investigate the structural information. The optical properties are studied using diffuse UV-visible reflectance and photoluminescence (PL) spectroscopy techniques. TEM images as well as XRD reflection peak broadening indicate the nanometer size particles formation with cubic (sphalerite) phase within the polymer matrix. Optical absorbance studies reveal an excitonic peak at around 310 nm dictates the effect of quantum confinement effect in the ZnS QDs. PL emission spectra for ZnS QDs in PVP exhibit four emission peaks at 382 nm, 414 nm, 480 nm and 527 nm are observed. These excitonic emissions from ZnS QDs are caused by the interstitial sulfur/Zn vacancies and surface states.

  3. Photo physical studies of PVP arrested ZnS quantum dots

    NASA Astrophysics Data System (ADS)

    Shahi, Ashutosh Kumar; Pandey, Bishnu Kumar; Singh, Bheeshma Pratap; Gupta, Bipin Kumar; Singh, Sukhvir; Gopal, Ram

    2017-03-01

    Monodispersed polyvinylpyrrolidone (PVP) arrested ZnS quantum dots (QDs) having diameter in range 2-5 nm are synthesized by a colloidal precipitation method using PVP as the stabilizing agent. X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selective area electron diffraction (SAED) and Fourier transform infrared (FT-IR) spectroscopy are probed to investigate the structural information. The optical properties are studied using diffuse UV-visible reflectance and photoluminescence (PL) spectroscopy techniques. TEM images as well as XRD reflection peak broadening indicate the nanometer size particles formation with cubic (sphalerite) phase within the polymer matrix. Optical absorbance studies reveal an excitonic peak at around 310 nm dictates the effect of quantum confinement effect in the ZnS QDs. PL emission spectra for ZnS QDs in PVP exhibit four emission peaks at 382 nm, 414 nm, 480 nm and 527 nm are observed. These excitonic emissions from ZnS QDs are caused by the interstitial sulfur/Zn vacancies and surface states.

  4. Effect of swift heavy ion irradiation on bare and coated ZnS quantum dots

    SciTech Connect

    Chowdhury, S. Hussain, A.M.P.; Ahmed, G.A.; Singh, F.; Avasthi, D.K.; Choudhury, A.

    2008-12-01

    The present study compares structural and optical modifications of bare and silica (SiO{sub 2}) coated ZnS quantum dots under swift heavy ion (SHI) irradiation. Bare and silica coated ZnS quantum dots were prepared following an inexpensive chemical route using polyvinyl alcohol (PVA) as the dielectric host matrix. X-ray diffraction (XRD) and transmission electron microscopy (TEM) study of the samples show the formation of almost spherical ZnS quantum dots. The UV-Vis absorption spectra reveal blue shift relative to bulk material in absorption energy while photoluminescence (PL) spectra suggests that surface state and near band edge emissions are dominating in case of bare and coated samples, respectively. Swift heavy ion irradiation of the samples was carried out with 160 MeV Ni{sup 12+} ion beam with fluences 10{sup 12} to 10{sup 13} ions/cm{sup 2}. Size enhancement of bare quantum dots after irradiation has been indicated in XRD and TEM analysis of the samples which has also been supported by optical absorption spectra. However similar investigations on irradiated coated quantum dots revealed little change in quantum dot size and emission. The present study thus shows that the coated ZnS quantum dots are stable upon SHI irradiation compared to the bare one.

  5. Synthesis and characterization of Ce, Cu co-doped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Harish, G. S.; Sreedhara Reddy, P.

    2015-09-01

    Ce, Cu co-doped ZnS nanoparticles were prepared at room temperature using a chemical co-precipitation method. The prepared nanoparticles were characterized by X- ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive analysis of X-rays (EDAX), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and high resolution Raman spectroscopic techniques. Transmission electron microscopy (TEM) and X-ray diffraction studies showed that the diameter of the particles was around 2-3 nm. Broadened XRD peaks revealed the formation of nanoparticles with a face centered cubic (fcc) structure. DRS studies confirmed that the band gap increased with an increase in the dopant concentration. The Raman spectra of undoped and Ce, Cu ions co-doped ZnS nanoparticles showed longitudinal optical mode and transverse optical mode. Compared with the Raman modes (276 and 351 cm-1) of undoped ZnS nanoparticles, the Raman modes of Ce, Cu co- doped ZnS nanoparticles were slightly shifted towards lower frequency. PL spectra of the samples showed remarkable enhancement in the intensity upon doping.

  6. Effects of pH on the characteristics of ZnS thin films grown by using the CBD method

    NASA Astrophysics Data System (ADS)

    Ahn, Heejin; Lee, Dongchan; Park, Sujung; Um, Youngho

    In CIGS-based thin film solar cells, a chemically deposited ZnS buffer layer with high resistivity is generally used between the absorber layer and transparent conducting oxide layer. In this work, we report a chemical process to prepare ZnS films by the CBD technique based on the typical bath deposition. The influences of ammonia (NH4OH) and Na2EDTA (Na2C10H16N2O8) as complexing agents on structural, morphological, and optical properties of ZnS thin films are investigated ranging pH concentration from 5 to 10. To investigate effects of pH on the characteristics of ZnS thin films, by using UV-visible transmittance, atomic force microscopy, and optical absorption were investigated. With changing the pH range, the ZnS thin films demonstrate high transmittance of 75~80% in the visible region, indicating the films are potentially useful in photovoltaic applications. The results will be presented in detail. This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education (2011-0024709).

  7. Fabrication of micro hole array on the surface of CVD ZnS by scanning ultrafast pulse laser for antireflection

    NASA Astrophysics Data System (ADS)

    Li, Yangping; Zhang, Tianhui; Fan, Siling; Cheng, Guanghua

    2017-04-01

    Chemical vapor deposited (CVD) ZnS is a promising long-wave infrared (8-12 μm) window material. Yet antireflection is necessary since Fresnel reflection from its surface is high due to the high refractive index of ZnS. Sub-wavelength structured surface of micro hole array was fabricated on CVD ZnS by scanning ultrafast pulse laser ablation. The effects of beam profile, pulse width and beam power on the radius and morphology of the holes were studied. Gaussian beam can cause severe melted-resolidified layers around the hole, yet Bessel beam only resulted in thin ribbon around the hole. The picosecond Bessel laser is more suitable than femtosecond laser for ablating holes on ZnS. The radius of the holes increases with increasing the Bessel beam pulse width and the beam power. But larger power may cause circle grooves around the central holes. Ordered hole array was fabricated on single side of CVD ZnS and antireflection was realized.

  8. Tensile properties of a ZnS nanowire determined with a nano-manipulator and force sensor

    NASA Astrophysics Data System (ADS)

    Jang, Hoon-Sik; Nahm, Seung Hoon; Lee, Hak Joo; Kim, Jung Han; Oh, Kyu Hwan

    2012-08-01

    Tensile tests of an individual ZnS nanowire with a cubic structure were performed with a nano-manipulator inside a scanning electron microscope (SEM). To perform the tensile test of ZnS nanowires, a mechanical testing system was installed in the SEM. A nano-manipulator was set up in the SEM, and a cantilever force sensor was mounted on the nano-manipulator. The force sensor could be controlled with the nano-manipulator. The ZnS nanowires were dispersed on the transmission electron microscope (TEM) grid; then, the ends of the ZnS nanowires were welded to the TEM grid and the tip of force sensor by exposing them to the E-beam of the SEM. The tensile tests of the ZnS nanowires were performed by controlling the nano-manipulator in the SEM. The load response during the tensile tests was obtained with a force sensor. The strain-stress curve was obtained from the tensile load-displacement curve after the tensile test. The tensile strengths for nanowires 1, 2, and 3 were 364.7 ± 5.2, 146.2 ± 5.2, and 234.4 ± 5.2 MPa, respectively, and the elastic moduli for nanowires 1, 2, and 3 were 39 ± 5.2, 33.4 ± 5.2, and 37.4 ± 5.2 GPa, respectively.

  9. Luminescent Processes Elucidated by Simple Experiments on ZnS.

    ERIC Educational Resources Information Center

    Schwankner, R.; And Others

    1981-01-01

    Describes some impurity-related optical properties of semiconductors, with special emphasis on the luminescence of zinc sulfide (ZnS). Presents and interprets five experiments using a ZnS screen, ultraviolet lamp, transparent Dewar liquid nitrogen, and a helium/neon gas base. Includes application of luminescence measurements to archaeology. (SK)

  10. Novel photofunctional multicomponent rare earth (Eu3+, Tb3+, Sm3+ and Dy3+) hybrids with double cross-linking siloxane covalently bonding SiO2/ZnS nanocomposite.

    PubMed

    Yan, Bing; Zhao, Yan; Li, Ya-Juan

    2011-01-01

    Zinc sulfide (ZnS) quantum dot is modified with 3-mercaptopropyltrimethoxysilane (MPTMS) to obtain MPTMS functionalized SiO(2)/ZnS nanocomposite. Novel rare earth/inorganic/organic hybrid materials are prepared by using 3-(triethoxysilyl)-propyl isocyanate (TESPIC) as an organic bridge molecule that can both coordinate to rare earth ions (Eu(3+), Tb(3+), Sm(3+) and Dy(3+)) and form an inorganic Si-O-Si network with SiO(2) ZnS nanocomposite after cohydrolysis and copolycondensation through a sol-gel process. These multicomponent hybrids with double cross-linking siloxane (TESPIC-MPTMS) covalently bonding SiO(2)/ZnS and assistant ligands (Phen = 1,10-phenanthroline, Bipy = 2,2'-bipyridyl) are characterized and especially the photoluminescence properties of them are studied in detail. The luminescent spectra of the hybrids show the dominant excitation of TESPIC-MPTMS-SiO(2)/ZnS unit and the unique emission of rare earth ions, suggesting that TESPIC-MPTMS-SiO(2)/ZnS unit behaves as the main energy donor and effective energy transfer take place between it and rare earth ions. Besides, the luminescent performance of Bipy-RE-TESPIC-MPTM-SiO(2)/ZnS hybrids are superior to that of Phen-RE-TESPIC-MPTMS-SiO(2)/ZnS ones (RE=Eu, Tb, Sm, Dy), which reveals that Bipy or Phen only act as structural ligand within the hybrid systems.

  11. First-principles investigation of Cu-doped ZnS with enhanced photocatalytic hydrogen production activity

    NASA Astrophysics Data System (ADS)

    Dong, Ming; Zhou, Peng; Jiang, Chuanjia; Cheng, Bei; Yu, Jiaguo

    2017-01-01

    The band structure and electronic properties of Cu-doped wurtzite ZnS were investigated by density functional theory calculations. According to the formation energies, the substitutional Cu and S vacancy defects are stable among the examined doping species. Particularly, the hybridization of substitutional Cu 3d and S 3p orbitals narrows the band gap of substitutional Cu-doped ZnS (CuZn-ZnS), while the high effective mass ratio of photogenerated holes and electrons (mh∗/me∗) in the CuZn-ZnS is beneficial for the separation and migration of the photogenerated charge carriers. Lab-synthesized CuZn-ZnS sample exhibited enhanced visible-light absorption and photocatalytic hydrogen production activity compared to pure ZnS.

  12. Enhancement of photoluminescence from defect states in ZnS random photonic crystal: An effect of electronic and photonic mode coupling

    SciTech Connect

    Bingi, Jayachandra; Warrier, Anita R.; Vijayan, C.

    2014-01-28

    This paper reports on the enhanced defect state emission from ZnS in the form of a random photonic crystal (RPC) medium. ZnS photonic crystals with varied randomness are fabricated by colloidal self assembly of ZnS nanospheres (215 ± 10 nm). Reflection and transmission studies reveal mid band gap wavelength at ∼435 nm. The band structure calculated for BCC lattice with reduced packing fraction (53%) is in good agreement with experimental results. The reflection due to the photonic band gap diminishes with increased randomness in the nanosphere arrangement. The features of fluorescence from ZnS are modified in the RPC medium, resulting in suppression at wavelengths in the photonic band gap region and an enhancement at band edge wavelengths of 415 and 468 nm. This enhancement becomes less prominent with increasing randomness in the structure. Interestingly these two modes correspond to the electronic defect states of ZnS. Emission enhancement is shown to be due to the strong coupling of electronic defect states and photonic band edge states which is facilitated by randomly scattering slow Bloch modes in the ZnS RPC. Fabrication of RPCs by colloidal self-assembly with specifically designed degrees of randomness (leading to controllable features of emission) provides scope for the design of low threshold random lasing systems.

  13. Room temperature fabrication of dielectric Bragg reflectors composed of a CaF2/ZnS multilayered coating.

    PubMed

    Muallem, Merav; Palatnik, Alex; Nessim, Gilbert D; Tischler, Yaakov R

    2015-01-14

    We describe the design, fabrication, and characterization of mechanically stable, reproducible, and highly reflecting distributed Bragg reflectors (DBR) composed of thermally evaporated thin films of calcium fluoride (CaF2) and zinc sulfide (ZnS). CaF2 and ZnS were chosen as the low and high refractive index components of the multilayer DBR structures, with n = 1.43 and n = 2.38 respectively, because neither material requires substrate heating during the deposition process in order to produce optical quality thin films. DBRs consisting of seven pairs of CaF2 and ZnS layers, were fabricated with thicknesses of 96 and 58 nm, respectively, as characterized by high-resolution scanning electron microscopy (HR-SEM), and exhibited a center wavelength of λc = 550 nm and peak reflectance exceeding 99%. The layers showed good adhesion to each other and to the glass substrate, resulting in mechanically stable DBR coatings. Complete optical microcavities consisting of two such DBR coatings and a CaF2 spacer layer between them could be fabricated in a single deposition run. Optically, these structures exhibited a resonator quality factor of Q > 160. When a CaF2/ZnS DBR was grown, without heating the substrate during deposition, on top of a thin film containing the fluorescent dye Rhodamine 6G, the fluorescence intensity showed no degradation compared to an uncoated film, in contrast to a MgF2/ZnS DBR coating grown with substrate heating which showed a 92% reduction in signal. The ability to fabricate optical quality CaF2/ZnS DBRs without substrate heating, as introduced here, can therefore enable formation of low-loss high-reflectivity coatings on top of more delicate heat-sensitive materials such as organics and other nanostructured emitters, and hence facilitate the development of nanoemitter-based microcavity device applications.

  14. Synthesis and characterization of Zn 3P 2/ZnS core/shell nanowires

    NASA Astrophysics Data System (ADS)

    Sun, T.; Wu, P. C.; Guo, Z. D.; Dai, Y.; Meng, H.; Fang, X. L.; Shi, Z. J.; Dai, L.; Qin, G. G.

    2011-05-01

    Fully-surrounded Zn3P2/ZnS core/shell nanowires (NWs) were synthesized for the first time via a two-step method: a catalyst free chemical vapor deposition followed by a low-pressure vulcanization process. Field emission scanning electron microscopy, high-resolution transmission electron microscopy, and high-angle angular dark field scanning transmission electron microscopy were used to characterize the morphologies, crystal structure, and element composition of the core/shell NWs. The band structure analysis demonstrates that the Zn3P2/ZnS core-shell NW type-II heterostructures have bright potential in photovoltaic nanodevice applications. The core/shell NW growth method used here can be extended to other material system.

  15. Photoluminescence and Raman evidence for mechanico-chemical interaction of polyaniline-emeraldine base with ZnS in cubic and hexagonal phase

    SciTech Connect

    Scocioreanu, M.; Baibarac, M.; Baltog, I.; Pasuk, I.; Velula, T.

    2012-02-15

    The mechanico-chemical interaction of a polyaniline-emeraldine base (PANI-EB) with ZnS in the cubic and wurtzite phases is studied by Raman spectroscopy and photoluminescence (PL). The results demonstrate that such an interaction leads to the formation of a PANI-salt and metallic Zn. Regardless of the structural form of the ZnS, the formation PANI-salt is indicated by a band in the Raman spectrum that shifts from 1162 to 1176 cm{sup -1} and the appearance of a new band at 1330 cm{sup -1} that indicates the protonated structure of a PANI-salt. The presence of the second product is determined by comparative PL studies performed on ZnS that has interacted mechanico-chemically with PANI-EB and metallic Zn powder. The variations of the PL spectra and their associated excitation spectra are explained as resulting from the charge collection processes that occur in the composite materials produced by the mechanico-chemical interaction between ZnS and PANI-EB or metallic Zn. - Graphical abstract: Photoluminescence spectra of ZnS with cubic (a{sub 1}) and wurtzite (a{sub 2}) structure. Highlights: Black-Right-Pointing-Pointer Mechanico-chemical interaction of polyaniline-emeraldine base with ZnS forms a hybrid material. Black-Right-Pointing-Pointer One used ZnS in two structural forms, cubic and hexagonal. Black-Right-Pointing-Pointer The hexagonal structure was obtained from the cubic structure annealed in vacuum at 1050 Degree-Sign C. Black-Right-Pointing-Pointer The hybrid material was studied by photoluminescence and Raman spectroscopy. Black-Right-Pointing-Pointer A charge collection process activated by the presence of polymer molecules is demonstrated.

  16. Enhancement of visible light photocatalytic activity of ZnS and CdS nanoparticles based on organic and inorganic coating

    NASA Astrophysics Data System (ADS)

    Soltani, Nayereh; Saion, Elias; Yunus, W. Mahmood Mat; Erfani, Maryam; Navasery, Manizheh; Bahmanrokh, Ghazaleh; Rezaee, Kadijeh

    2014-01-01

    Coating of ZnS and CdS nanoparticles with organic and inorganic materials can extend their light absorption in the visible region and their stability against photo-corrosion. Such materials could emerge as excellent photocatalysts for the elimination of pollutants from aqueous media using solar energy. In this study, PVP (polyvinyl pyrrolidone)-capped ZnS and CdS nanoparticles, ZnS/CdS and CdS/ZnS core shell nanoparticles were synthesized by microwave irradiation method and characterized using different techniques. The XRD patterns exhibited cubic and hexagonal structures for coated ZnS and CdS nanoparticles, respectively. Morphological evaluation of TEM images showed that the nanoparticles are generally spherical in shape. The UV-visible spectra confirmed a shift in the band gap of coated nanoparticles to longer or shorter wavelengths due to size and potential-well effects. The photocatalytic activity of nanoparticles toward dye degradation under visible light was found to be improved after coating. PVP-capped ZnS and CdS exhibited an enhancement in the initial methylene blue degradation efficiency by a factor of about 1.3. ZnS nanoparticles coated by CdS displayed the initial efficiency 3.2 times higher than bare ZnS. The maximum dye removal was obtained in presence of CdS/ZnS core shells which is 1.4 times more efficient than bare CdS.

  17. Study of Microstructure and Optical Properties of Pva-Capped ZnS: cu Nanocrystalline Thin Films

    NASA Astrophysics Data System (ADS)

    Thi, Tran Minh; van, Bui Hong; Ben, Pham Van

    A study has been carried out on the Cu doping and PVA capping induced optical property changes in ZnS : Cu nanocrystalline powders and thin film. For this study, ZnS : Cu nanopowders with Cu concentrations of 0.1%, 0.15%, 0.2%, 0.3% and 0.4% are synthesized by the wet chemical method. The polyvinyl alcohol (PVA)-capped ZnS thin film with 0.2% Cu concentration and various PVA concentrations are prepared by the spin-coating method. The microstructures of the samples are investigated by the X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM). The results show that the prepared samples belong to the wurtzite structure with the average particle size of about 3-7 nm. The optical properties of samples are studied by measuring absorption and photoluminescence (PL) spectra in the wavelength range from 300 nm to 900 nm at 300 K. It is shown that the luminescent intensity of ZnS : Cu nanopowders reaches the highest intensity for optimal Cu concentration of 0.2% with the corresponding values of its direct band gap estimated to be about 3.90 eV. While the PVA coating does not affect the microstructure of ZnS nanometerials, the PL spectra of the samples are found to be affected by the PVA concentration as well as the exciting power density. The influence of the polymer coating on the optical properties can be explained by the quantum confinement effect of ZnS nanoparticles in the PVA matrix.

  18. Effect of isovalent dopants on photodegradation ability of ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Khaparde, Rohini; Acharya, Smita

    2016-06-01

    Isovalent (Mn, Cd, Cu, Co)-doped-ZnS nanoparticles having size vary in between 2 to 5 nm are synthesized by co-precipitation route. Their photocatalytic activity for decoloration of Cango Red and Malachite Green dyes is tested in visible radiation under natural conditions. Structural and morphological features of the samples are investigated by X-ray diffraction, Raman spectroscopy, Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and UVsbnd Vis spectrometer. Single phase zinc blende structure of as-synthesized undoped and doped-ZnS is confirmed by XRD and revealed by Rietveld fitting. SEM and TEM images show ultrafine nanoparticles having size in the range of 2 to 5 nm. UV-Vis absorption spectra exhibit blue shift in absorption edge of undoped and doped ZnS as compared to bulk counterpart. The photocatalytic activity as a function of dopant concentration and irradiation time is systematically studied. The rate of de-coloration of dyes is detected by UVsbnd Vis absorption spectroscopy and organic dye mineralization is confirmed by table of carbon (TOC) study. The photocatalytic activity of Mn-doped ZnS is highest amongst all dopants; however Co as a dopant is found to reduce photocatalytic activity than pure ZnS.

  19. Surface plasmon resonance in nanostructured Ag incorporated ZnS films

    NASA Astrophysics Data System (ADS)

    Chalana, S. R.; Ganesan, V.; Mahadevan Pillai, V. P.

    2015-10-01

    Silver incorporated zinc sulfide thin films are prepared by RF magnetron sputtering technique and the influence of silver incorporation on the structural, optical and luminescence properties is analyzed using techniques like grazing incidence X-Ray diffraction (GIXRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), micro-Raman spectroscopy, UV-Vis spectroscopy and laser photoluminescence spectroscopy. XRD analysis presents hexagonal wurtzite structure for the films. A reduction of crystallinity of the films is observed due to Ag incorporation. The Raman spectral analysis confirms the reduction of crystallinity and increase of strain due to the Ag incorporation. AFM analysis reveals a rough surface morphology for the undoped film and Ag incorporation makes the films uniform, dense and smooth. A blue shift of band gap energy with increase in Ag incorporation is observed due to quantum confinement effect. An absorption band (450-650 nm region) due to surface plasmon resonance of the Ag clusters present in the ZnS matrix is observed for the samples with higher Ag incorporation. The complex dielectric constant, loss factor and distribution of volume and surface energy loss of the ZnS thin films are calculated. Laser photoluminescence measurements gives an intense bluish green emission from the ZnS films and a quenching of the PL emission is observed which can be due to the metal plasmonic absorption and non-radiative energy transfer due to Ag incorporation.

  20. Surface plasmon resonance in nanostructured Ag incorporated ZnS films

    SciTech Connect

    Chalana, S. R.; Mahadevan Pillai, V. P.; Ganesan, V.

    2015-10-15

    Silver incorporated zinc sulfide thin films are prepared by RF magnetron sputtering technique and the influence of silver incorporation on the structural, optical and luminescence properties is analyzed using techniques like grazing incidence X-Ray diffraction (GIXRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), micro-Raman spectroscopy, UV-Vis spectroscopy and laser photoluminescence spectroscopy. XRD analysis presents hexagonal wurtzite structure for the films. A reduction of crystallinity of the films is observed due to Ag incorporation. The Raman spectral analysis confirms the reduction of crystallinity and increase of strain due to the Ag incorporation. AFM analysis reveals a rough surface morphology for the undoped film and Ag incorporation makes the films uniform, dense and smooth. A blue shift of band gap energy with increase in Ag incorporation is observed due to quantum confinement effect. An absorption band (450-650 nm region) due to surface plasmon resonance of the Ag clusters present in the ZnS matrix is observed for the samples with higher Ag incorporation. The complex dielectric constant, loss factor and distribution of volume and surface energy loss of the ZnS thin films are calculated. Laser photoluminescence measurements gives an intense bluish green emission from the ZnS films and a quenching of the PL emission is observed which can be due to the metal plasmonic absorption and non-radiative energy transfer due to Ag incorporation.

  1. Solar light driven enhanced photocatalytic degradation of brilliant green dye based on ZnS quantum dots

    NASA Astrophysics Data System (ADS)

    Kaur, Sharanjit; Sharma, Shelja; Umar, Ahmad; Singh, Surinder; Mehta, S. K.; Kansal, Sushil Kumar

    2017-03-01

    Herein, we report the successful synthesis, detailed characterization and solar-light driven photocatalytic degradation of zinc sulfide (ZnS) quantum dots. The ZnS quantum dots were synthesized in high yield by co-precipitation method using sodium dodecyl sulfate as a stabilizing agent. The as-synthesized ZnS quantum dots were characterized in detail in terms of their morphological, structural, compositional, thermal and optical properties. The detailed characterizations confirmed that the synthesized quantum dots are well-crystalline, possessing cubic phase of zinc blende structure, pure and exhibiting good optical properties. The synthesized quantum dots were further used as potential photocatalyst for the photocatalytic degradation of brilliant green dye under solar-light irradiation which exhibited 88% degradation. The process parameters, such as pH and catalyst dose, for the photocatalytic degradation of brilliant green dye was elaborately examined in order to evaluate the highest degradation rate of targeted dye. Further, the experimental data were fitted well in the pseudo-first order kinetic model. Finally, a possible mechanism for the photocatalytic degradation of brilliant green dye by ZnS quantum dots was also suggested.

  2. Facile synthesis of ZnS nanorods in PEG and their spectral performance

    NASA Astrophysics Data System (ADS)

    Zhou, Dan-Jie; Xie, Xin-Yuan; Zhang, Yan-li; Guo, Dan-Yi; Zhou, Yi-Jia; Xie, Jin-Feng

    2016-10-01

    Green and one-step synthesis of ZnS nanorods through the interaction of zinc nitrate hexahydrate and S powder in PEG400 was studied. Orthogonal experiments were conducted to study the influence of the experimental conditions including the molar ratio of sulfur (nS) and zinc nitrate hexahydrate (nZn), the heating time and the molecular weight of PEG (200, 400, 600) on the nature and morphology of the products. The results show that the zinc/sulfur molar ratio determines the composition of the products. When the zinc/sulfur molar ratio is 2 mmol:1 mmol with temperature of 160 °C and reaction time of 120 min, homogeneous ZnS nanorods, with diameters and lengths of about 64 nm-110 nm and 110-1100 nm respectively are obtained. The structure, morphology, size, stability and optical properties of the products were investigated by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), ultraviolet-visible (UV-vis) absorption and photoluminescence. The band-gap value estimated from the UV-vis absorption spectrum is 4.15 eV. The as-synthesized ZnS shows blue (469 nm) and green (506 nm) broad emission bands when they are excited by visible light (439 nm). Possible formation mechanism is also discussed.

  3. Synthesis mechanism of sono-chemically prepared mesoporous ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Motejadded Emrooz, H. B.; Jalaly, M.

    2017-03-01

    The mechanism of sono-chemically synthesized mesoporous ZnS nanoparticles has been investigated. ZnS nanoparticles were synthesized with a facile and quick method. The sonication process was carried out for several times up to 60 min. The synthesized particles have been characterized with scanning electron microscopy, transmission electron microscopy, high resolution x-ray diffraction, UV–visible technique, diffuse reflectance spectroscopy, Brunauer–Emmett–Teller and Fourier transformation infrared spectroscopy. Based on x-ray diffraction patterns, crystallite size and lattice strain increase with sonication time. Adsorption–desorption results showed that applying the sono-chemistry synthesizing method in the aqueous atmosphere will cause a mesoporous structure. The obtained specific surface area of the synthesized mesoporous ZnS nanoparticles varied from 53 to 58 m2 · g‑1. Also the surface areas created from the porosity of the particles varied from 27 to 29 m2 · g‑1. Regarding these results, the mechanism of porosity formation during synthesis of nanoparticles has been explained. Photocatalytic behavior of the synthesized particles has been investigated for degradation of methylene blue from aqueous solution. Factors affecting this behavior have been discussed and it was found that interaction between opposing factors caused the specimen synthesized with 40 min sonication time has the best methylene blue degradation efficiency.

  4. ZnS nanostructured thin-films deposited by successive ionic layer adsorption and reaction

    NASA Astrophysics Data System (ADS)

    Deshmukh, S. G.; Jariwala, Akshay; Agarwal, Anubha; Patel, Chetna; Panchal, A. K.; Kheraj, Vipul

    2016-04-01

    ZnS thin films were grown on glass substrate using successive ionic layer adsorption and reaction (SILAR) technique at room temperature. Aqueous solutions of ZnCl2 and Na2S were used as precursors. The X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Raman spectroscopy and optical absorption measurements were applied to study the structural, surface morphology and optical properties of as-deposited ZnS thin films. The X-ray diffraction profiles revealed that ZnS thin films consist of crystalline grains with cubic phase. Spherical nano grains of random size and well covered on the glass substrate were observed from FESEM. The average grain size were found to be 77 nm, 100 nm and 124 nm for 20 cycles, 40 cycles and 60 cycles samples respectively. For 60 cycle sample, Raman spectra show two prominent peaks at 554 cm-1 and 1094 cm-1. The optical band gap values were found to be 3.76 eV, 3.72 eV and 3.67 eV for 20 cycle, 40 cycle and 60 cycle samples respectively.

  5. Multicolor luminescence from transition metal ion (Mn2+ and Cu2+) doped ZnS nanoparticles.

    PubMed

    Datta, Anuja; Biswas, Subhajit; Kar, Soumitra; Chaudhuri, Subhadra

    2007-10-01

    Mn and Cu doped ZnS nanoparticles in powder form were prepared by a simple solvothermal route. Particle size and crystal structure of the products were investigated through X-ray diffraction study revealing the formation of cubic ZnS nanoparticles of average diameter 2.5 nm. Particle size was also verified by the high resolution transmission electron microscopic images. Blue emission at approximately 445 nm was observed from the undoped sample, which was attributed to the presence of large surface defects. With increasing doping concentration the defect related emission gradually quenches and subsequently the impurity related emissions appeared. Mn doped samples exhibited orange emission at approximately 580 nm which may be attributed to the transition between (4)T1 and (6)A1 energy levels of the Mn2+ 3d states. Whereas, the Cu doped ZnS nanoparticles exhibited a red shifted strong blue emission at approximately 466 nm which is attributed to the transition of the electrons from the surface states to the 't2' levels of Cu impurities.

  6. Novel microwave assisted synthesis of ZnS nanomaterials

    NASA Astrophysics Data System (ADS)

    Synnott, Damian W.; Seery, Michael K.; Hinder, Steven J.; Colreavy, John; Pillai, Suresh C.

    2013-02-01

    A novel ambient pressure microwave assisted technique is developed in which silver and indium-modified ZnS is synthesized. The as-prepared ZnS is characterized by x-ray diffraction, UV-vis spectroscopy, x-ray photoelectron spectroscopy and luminescence spectroscopy. This procedure produced crystalline materials with particle sizes below 10 nm. The synthesis technique leads to defects in the crystal which induce mid-energy levels in the band gap and lead to indoor light photocatalytic activity. Increasing the amount of silver causes a phase transition from cubic blende to hexagonal phase ZnS. In a comparative study, when the ZnS cubic blende is heated in a conventional chamber furnace, it is completely converted to ZnO at 600 °C. Both cubic blende and hexagonal ZnS show excellent photocatalytic activity under irradiation from a 60 W light bulb. These ZnS samples also show significantly higher photocatalytic activity than the commercially available TiO2 (Evonik-Degussa P-25).

  7. Magnetic core-shell ZnFe2O4/ZnS nanocomposites for photocatalytic application under visible light.

    PubMed

    Yoo, Pil Sun; Amaranatha Reddy, D; Jia, YueFa; Bae, Sang Eun; Huh, Seong; Liu, Chunli

    2017-01-15

    Magnetic core-shell ZnFe2O4/ZnS composites were synthesized through a two-step chemical process including the hydrothermal and the co-precipitation methods. The structural characterization revealed that the composites consisted of a layer of ZnS clusters on the surface of ZnFe2O4 nanoparticles. The band gap energy of the composite was estimated to be 2.2eV through the Kubelka-Munk plot, implying the possible application as a photocatalyst under the visible light radiation. The improved photocatalytic efficiency of the ZnFe2O4/ZnS composites was confirmed through the photocatalytic degradation of Methyl Orange. The increased absorption of the visible light and the enhanced separation of the electron-hole pairs due to the relative energy band positions in ZnFe2O4 and ZnS are considered as the main advantages. Additionally, the moderate magnetization of the ZnFe2O4 core insured the easy magnetic collection of the composite materials without affecting the photocatalytic performance. Our results showed that ZnFe2O4-based nanocomposites could be used as an effective and magnetic retrievable photocatalyst.

  8. Tunable surface charge of ZnS : Cu nano-adsorbent induced the selective preconcentration of cationic dyes from wastewater

    NASA Astrophysics Data System (ADS)

    Wang, Yongjing; Chen, Dagui; Wang, Yandi; Huang, Feng; Hu, Qichang; Lin, Zhang

    2012-05-01

    A novel environmentally friendly nano-adsorbent is developed by doping Cu+ cations into the lattice of ZnS microspheres. The adsorbent shows selective adsorbability for cationic dyes in low concentrations in wastewater. The adsorbed dye could be successfully eluted with alcohol, resulting in a 1000 fold enrichment of the dye solution.A novel environmentally friendly nano-adsorbent is developed by doping Cu+ cations into the lattice of ZnS microspheres. The adsorbent shows selective adsorbability for cationic dyes in low concentrations in wastewater. The adsorbed dye could be successfully eluted with alcohol, resulting in a 1000 fold enrichment of the dye solution. Electronic supplementary information (ESI) available: Synthesis, structural details of ZnS : Cu, adsorption isotherm of RhB on ZnS : Cu, control experiments for the adsorption measurements, pH effect on the adsorbability, and preliminary assessment of the adsorption efficiency for real industrial wastewater. See DOI: 10.1039/c2nr30689a

  9. Understanding divergent behaviors in the photocatalytic hydrogen evolution reaction on CdS and ZnS: a DFT based study.

    PubMed

    Zhou, Zhaohui; Han, Fengshuang; Guo, Liejin; Prezhdo, Oleg V

    2016-06-22

    It has been a long time that divergent behaviors were observed in many photocatalytic hydrogen evolution reactions (HER) on CdS and ZnS although the two photocatalysts have similar compositions and structures. For example, CdS itself is inactive and loading of cocatalysts is indispensable to achieve high efficiency of hydrogen evolution, but the reverse is true for ZnS. The underlying reasons are still unclear to date. The Volmer reaction of HER on catalysts is H(+) + e(-) + * → H*, and its free energy (ΔGH* = ΔEH* + ΔEZPE - TΔS + eU; the adsorption energy, zero-point energy, entropy and potential energy are on the right side) is a good theoretical descriptor of the electrocatalytic HER activity from the electrocatalytic HER theory. In this paper, we firstly determined the most stable CdS and ZnS(110) termination under the conditions of photocatalytic HER, i.e., pure (110), by calculating the free energies of three reactions related to H2O dissociation on (110). Then we rationalized these behaviors by calculating the free energy of H* adsorption on pure and Pt loaded CdS and ZnS(110) at different pH. The performance of photocatalytic HER on CdS and ZnS was found to be determined jointly by the free energy of H* adsorption and the conduction band minimum (CBM) of the photocatalysts. On pure (110) with large ΔGH*, the photocatalytic HER is favored on ZnS due to its higher CBM; on Pt loaded (110) with small ΔGH*, the photocatalytic HER is favored on CdS due to its lower CBM. These results well explained the divergent behaviors observed in the photocatalytic HER on CdS and ZnS.

  10. Microstructural characterization of textured ZnS thin films

    SciTech Connect

    Kryshtab, T. . E-mail: tkrysh@esfm.ipn.mx; Andraca-Adame, J.A.; Kryvko, A.

    2007-08-15

    During thin film growth texture formation is controlled by several kinetic parameters that determine the grain structural evolution. For highly textured thin films, i.e. only one strong peak can be obtained from X-ray diffraction pattern, it is impossible to separate the effect of grain size and residual strains based on peak broadening. We propose an original method for evaluating residual strains, eliminating their contribution in peak breadth and determining the domain size. A two-axes diffractometer with a Ge monochromator and a K {sub {alpha}}{sub 1,2} doublet was used for this study. The measurements of 2{theta} scans were carried out in the grazing geometry for the incident beam. ZnS thin films as-deposited and annealed were studied. Structural analysis was carried out using a one-axis diffractometer for a {theta}-2{theta} scan in the standard symmetric geometry. Surface morphology was explored by atomic force microscopy. The specification of the proposed method and its application in microstructural characterization are introduced.

  11. Optical spectroscopy reveals transition of CuInS2/ZnS to CuxZn1-xInS2/ZnS:Cu alloyed quantum dots with resultant double-defect luminescence

    NASA Astrophysics Data System (ADS)

    Yan, Ruolin; Zhang, Wenxia; Wu, Wenhui; Dong, Xingmin; Wang, Qiqi; Fan, Jiyang

    2016-12-01

    The structure and luminescence mechanisms of the CuInS2 quantum dots (QDs) after epitaxial growth of ZnS shell are in debate. The light absorption/emission spectroscopy reveals that after ZnS shell growth the cation diffusion at the CuInS2/ZnS interface results in formation of the alloyed CuxZn1- xInS2/ZnS:Cu QDs. These core/shell QDs exhibit dual-color photoluminescence with abnormal blue shift with decreasing excitation photon energy. The results show that the green and orange emissions originate separately from defects in the core and the shell. The absorption tail of the ZnS QDs turns from Urbach to Halperin-Lax type after Cu doping.

  12. Effect of UV irradiation on evaporated ZnS films

    NASA Technical Reports Server (NTRS)

    Hass, G.; Heaney, J. B.; Hunter, W. R.; Angel, D. W.

    1980-01-01

    Evaporated ZnS films used as a component in reflectance enhancing or decreasing multilayer coatings for mirrors, transparent optical materials, and vacuum UV reflecting optics, are investigated with reference to the reflectance loss under UV irradiation and the formation of ZnO as a result of the decomposition of ZnS in the presence of oxygen. Reflectance measurements over a broad wavelength range reveal that the UV induced reflectance losses are generally restricted to wavelengths shorter than 4000 A and are most severe in the vacuum UV region. After 134 hr of UV exposure initially polycrystalline film of 150-200 A thick is completely converted to amorphous ZnO. The results demonstrate that caution should be exercised in employing ZnS as the outer layer in an optical coating system designed for use in the UV and vacuum UV regions.

  13. Research of annular polishing asymmetric ZnS plane window

    NASA Astrophysics Data System (ADS)

    Guo, Weijin; Tong, Yi; Jin, Yuzhu; Lin, Nana

    2016-10-01

    Due the annular polishing technology for planar optical components do not have the sharp selectivity, annular polishing technology is a very import process to fabricate irregular planar elements which with high precision surface shape and low surface roughness. According to the characteristics of annular polishing, the zns asymmetric plane window annular polishing process and key technical parameters control was researched. In this paper, one pair of asymmetric planar ZnS window parts were machined which diagonal length is 147mm, through technology experiments, obtained process test samples. The surface figures of the plane zns window are measured by a Zygo interferometer and the reflect wavefront P-V value is better than 1.5λ, the reflect wavefront local error rms value is better than 0.05λ (λ=632.8nm). Experiments results demonstrate the effectiveness of annular processing technology was used to manufacture zinc sulfide asymmetric shape plane window.

  14. Luminescence from ZnS: Bulk vs nano

    NASA Astrophysics Data System (ADS)

    Mishra, R. K.; Kamal, Satya; Patel, D. K.; Rao, K. Ramachandra; Sudarsan, V.; Vatsa, R. K.

    2015-06-01

    Based on the detailed luminescence studies on bulk and nanoparticles of ZnS, it is inferred that the defect emission due to zinc (VZn) and sulfur (VS) vacancies in ZnS, significantly change in terms of line shape and peak position, when bulk form is converted to nanoparticles. From the XRD studies, this has been explained in terms of difference in the crystalline modifications of ZnS, namely the wurtzite and cubic forms. Copper doping in the sample quenches the luminescence and stabilize the cubic phase. Bright blue electro luminescence (efficiency of around 1.5 %) with CIE coordinates (0.18. 0.11) could be seen from bulk ZnS:Cu sample. Unlike this the nanoparticles did not give any emission due to the quenching of charge carriers/excitons. Lifetime values further supported these inferences.

  15. ZnS micro-Fresnel lens and its uses.

    PubMed

    Hosokawa, H; Yamashita, T

    1990-12-01

    A micro-Fresnel lens replication method by inorganic material deposition has been developed. A ZnS micro-Fresnel lens and a completely flat micro-Fresnel lens have been made by this method. The ZnS microFresnel lens stability characteristics are improved for temperature, humidity, and focusing. Furthermore, higher resolution in electron-beam lithography is made possible by lens thickness reduction. The completely flat micro-Fresnel lens is a new device and improves integration performance. This lens can be applied to stacked planar optics devices for use in the construction of 3-D optical circuits.

  16. Plasma-assisted quadruple-channel optosensing of proteins and cells with Mn-doped ZnS quantum dots

    NASA Astrophysics Data System (ADS)

    Li, Chenghui; Wu, Peng; Hou, Xiandeng

    2016-02-01

    Information extraction from nano-bio-systems is crucial for understanding their inner molecular level interactions and can help in the development of multidimensional/multimodal sensing devices to realize novel or expanded functionalities. The intrinsic fluorescence (IF) of proteins has long been considered as an effective tool for studying protein structures and dynamics, but not for protein recognition analysis partially because it generally contributes to the fluorescence background in bioanalysis. Here we explored the use of IF as the fourth channel optical input for a multidimensional optosensing device, together with the triple-channel optical output of Mn-doped ZnS QDs (fluorescence from ZnS host, phosphorescence from Mn2+ dopant, and Rayleigh light scattering from the QDs), to dramatically improve the protein recognition and discrimination resolution. To further increase the cross-reactivity of the multidimensional optosensing device, plasma modification of proteins was explored to enhance the IF difference as well as their interactions with Mn-doped ZnS QDs. Such a sensor device was demonstrated for highly discriminative and precise identification of proteins in human serum and urine samples, and for cancer and normal cells as well.Information extraction from nano-bio-systems is crucial for understanding their inner molecular level interactions and can help in the development of multidimensional/multimodal sensing devices to realize novel or expanded functionalities. The intrinsic fluorescence (IF) of proteins has long been considered as an effective tool for studying protein structures and dynamics, but not for protein recognition analysis partially because it generally contributes to the fluorescence background in bioanalysis. Here we explored the use of IF as the fourth channel optical input for a multidimensional optosensing device, together with the triple-channel optical output of Mn-doped ZnS QDs (fluorescence from ZnS host, phosphorescence from Mn2

  17. Highly-defective nanocrystals of ZnS formed via dissimilatory bacterial sulfate reduction: A comparative study with their abiogenic analogues

    NASA Astrophysics Data System (ADS)

    Xu, Jie; Murayama, Mitsuhiro; Roco, Charles M.; Veeramani, Harish; Michel, F. Marc; Rimstidt, J. Donald; Winkler, Christopher; Hochella, Michael F.

    2016-05-01

    The physicochemical properties of a (nano)mineral are strongly affected by its formation processes, and thus, may indicate the (nano)mineral's formation environment and mechanism. This correlation, although relevant to a myriad of geological, environmental, and material-science processes, has not yet been fully appreciated and systematically explored. Here, using the Zn-S system, we demonstrate that biological and abiotic processes at similar experimental conditions can produce distinctive particle size, morphology, and crystal structure in the formed ZnS. Specifically, bacterial sulfate reduction led to the formation of highly-defective nanocrystals of mixed sphalerite and wurtzite in a range of ∼4-12 nm. By comparison, the abiotic procedures of titration- or diffusion-controlled precipitation resulted in the formation of polycrystalline aggregates that contained randomly-oriented, ultrafine crystals below ∼2-3 nm. The poor crystallinity in the abiogenic samples, regardless of the sulfide addition rates, reveals an overall nucleation-dominated, crystal growth-restricted pathway for the formation of ZnS from low-temperature aqueous solutions. The difficulty in the ZnS crystallization likely stems from the intrinsic surface instability of the ZnS growth units (i.e., in the form of nanoclusters) resulting from the dipole-dipole interactions of the unit with surrounding water molecules. In the biogenic samples, the ZnS crystallinity was significantly improved, indicating that the presence of bacterial metabolites somehow promoted the crystallization process. With evidence for the enlarged {1 1 1} planes in the biogenic nanocrystals, we attribute this enhancement mainly to the selective interaction of the bacterial metabolites with polar faces of the ZnS growth units, which might have effectively screened the dipole moments in the growth units and enabled their crystallographic assembly. By revealing the intrinsic difficulty and specific pathways for the ZnS

  18. ZnS nanostructure arrays: a developing material star.

    PubMed

    Fang, Xiaosheng; Wu, Limin; Hu, Linfeng

    2011-02-01

    Semiconductor nanostructure arrays are of great scientific and technical interest because of the strong non-linear and electro-optic effects that occur due to carrier confinement in three dimensions. The use of such nanostructure arrays with tailored geometry, array density, and length-diameter-ratio as building blocks are expected to play a crucial role in future nanoscale devices. With the unique properties of a direct wide-bandgap semiconductor, such as the presence of polar surfaces, excellent transport properties, good thermal stability, and high electronic mobility, ZnS nanostructure arrays has been a developing material star. The research on ZnS nanostructure arrays has seen remarkable progress over the last five years due to the unique properties and important potential applications of nanostructure arrays, which are summarized here. Firstly, a survey of various methods to the synthesis of ZnS nanostructure arrays will be introduced. Next recent efforts on exploiting the unique properties and applications of ZnS nanostructure arrays are discussed. Potential future directions of this research field are also highlighted.

  19. TiO2-ZnS Cascade Electron Transport Layer for Efficient Formamidinium Tin Iodide Perovskite Solar Cells.

    PubMed

    Ke, Weijun; Stoumpos, Constantinos C; Logsdon, Jenna Leigh; Wasielewski, Michael R; Yan, Yanfa; Fang, Guojia; Kanatzidis, Mercouri G

    2016-11-16

    Achieving high open-circuit voltage (Voc) for tin-based perovskite solar cells is challenging. Here, we demonstrate that a ZnS interfacial layer can improve the Voc and photovoltaic performance of formamidinium tin iodide (FASnI3) perovskite solar cells. The TiO2-ZnS electron transporting layer (ETL) with cascade conduction band structure can effectively reduce the interfacial charge recombination and facilitate electron transfer. Our best-performing FASnI3 perovskite solar cell using the cascaded TiO2-ZnS ETL has achieved a power conversion efficiency of 5.27%, with a higher Voc of 0.380 V, a short-circuit current density of 23.09 mA cm(-2), and a fill factor of 60.01%. The cascade structure is further validated with a TiO2-CdS ETL. Our results suggest a new approach for further improving the performance of tin-based perovskite solar cells with a higher Voc.

  20. Localized nano-solid-solution induced by Cu doping in ZnS for efficient solar hydrogen generation.

    PubMed

    Li, Naixu; Zhang, Longzhou; Zhou, Jiancheng; Jing, Dengwei; Sun, Yueming

    2014-08-14

    Nanosized photocatalysts have been shown to be important to many modern photocatalytic reactions. Control of the microstructure of the nanocrystals enables regulation of their optical properties and enhancement of specific reactions. Here, Cu(2+)-doped ZnS nanosphere photocatalysts with hierarchical nanostructures and controllable sizes were synthesized via a facile wet-chemical reaction. We demonstrated that small amounts of Cu(2+) doping could give rise to the formation of a variety of localized, nanosized Cu(1-x)Zn(x)S solid solutions that are separated by a continuous ZnS medium. The nano-solid-solutions have predictable band structures and an average size of several nanometers, which ensure facile generation of electron-hole pairs by visible light irradiation and quick migration of the photo-generated charges to the interfaces. With Ru as a cocatalyst, the as-prepared 0.5 mol% Cu(2+)-doped ZnS nanospheres showed a high H2 evolution rate of 1.03 mmol h(-1), corresponding to a quantum efficiency of 26.2% at 425 nm. A hierarchical surface structure with a large surface area is considered crucial for the increased activity. Our work not only showed that the non-toxic metal chalcogenides achieve high efficiency but also provides a new concept of localized nano-solid-solution for photocatalytic applications.

  1. The role of ion exchange in the passivation of In(Zn)P nanocrystals with ZnS

    PubMed Central

    Cho, Deok-Yong; Xi, Lifei; Boothroyd, Chris; Kardynal, Beata; Lam, Yeng Ming

    2016-01-01

    We have investigated the chemical state of In(Zn)P/ZnS core/shell nanocrystals (NCs) for color conversion applications using hard X-ray absorption spectroscopy (XAS) and photoluminescence excitation (PLE). Analyses of the edge energies as well as the X-ray absorption fine structure (XAFS) reveal that the Zn2+ ions from ZnS remain in the shell while the S2− ions penetrate into the core at an early stage of the ZnS deposition. It is further demonstrated that for short growth times, the ZnS shell coverage on the core was incomplete, whereas the coverage improved gradually as the shell deposition time increased. Together with evidence from PLE spectra, where there is a strong indication of the presence of P vacancies, this suggests that the core-shell interface in the In(Zn)P/ZnS NCs are subject to substantial atomic exchanges and detailed models for the shell structure beyond simple layer coverage are needed. This substantial atomic exchange is very likely to be the reason for the improved photoluminescence behavior of the core-shell particles compare to In(Zn)P-only NCs as S can passivate the NCs surfaces. PMID:26972936

  2. A facile solvothermal method to produce ZnS quantum dots-decorated graphene nanosheets with superior photoactivity.

    PubMed

    Yu, Linhui; Ruan, Hong; Zheng, Yi; Li, Danzhen

    2013-09-20

    Zinc sulfide-graphene (ZnS-GR) nanocomposites with a high degree of dispersion and high coverage of ZnS quantum dots (QDs) have been synthesized by a facile solvothermal method without any dispersant, during which the formation of ZnS nanoparticles and the reduction of graphene oxide (GO) occur simultaneously. ZnS-GR nanocomposites exhibit much higher photoactivity than nanoparticle crystal ZnS (NPC-ZnS) prepared in the absence of graphene (GR), as evaluated by degradation of methylene blue (MB) in the liquid phase under ultraviolet (UV) light. Among them, the ZnS-GR nanocomposite with a 5% mass fraction of GR prepared at 120 ° C has the highest photocatalytic activity. The conversion and mineralization over MB are 96.7% and 57.1% respectively, which is much higher than that of NPC-ZnS. The high photoactivity of ZnS-GR nanocomposites can be ascribed to the integrated effect of an extremely high specific surface area and the excellent electron conductivity of GR and its significant influence on the morphology and structure of the samples. Moreover, it is found that the oxidation of MB is driven mainly by the participation of .OH radicals. Accordingly, a potential photocatalytic mechanism of ZnS-GR nanocomposites in the photocatalytic process has been proposed in this work. It is expected that our work could provide valuable information on the design of metal sulfide decorated GR with excellent properties.

  3. Origin of Photoluminescence and XAFS Study of (ZnS)1-x(AgInS2)x Nanocrystals.

    PubMed

    Rao, M Jagadeeswara; Shibata, Tomohiro; Chattopadhyay, Soma; Nag, Angshuman

    2014-01-02

    Donor-Acceptor transition was previously suggested as a mechanism for luminescence in (ZnS)1-x(AgInS2)x nanocrystals. Here we show the participation of delocalized valence/conduction band in the luminescence. Two emission pathways are observed: Path-1 involves transition between a delocalized state and a localized state exhibiting higher energy and shorter lifetime (∼25 ns) and Path-2 (donor-acceptor) involves two localized defect states exhibiting lower emission energy and longer lifetime (>185 ns). Surprisingly, Path-1 dominates (82% for x = 0.33) for nanocrystals with lower x, in sharp difference with prior assignment. Luminescence peak blue shifts systematically by 0.57 eV with decreasing x because of this large contribution from Path-1. X-ray absorption fine structure (XAFS) study of (ZnS)1-x(AgInS2)x nanocrystals shows larger AgS4 tetrahedra compared with InS4 tetrahedra with Ag-S and In-S bond lengths 2.52 and 2.45 Å respectively, whereas Zn-S bond length is 2.33 Å along with the absence of second nearest-neighbor Zn-S-metal correlation.

  4. Synthesis, characterization and thermoluminescence studies of (ZnS)1-x (MnTe)x nanophosphors.

    PubMed

    Pateria, Deepti; Baghel, R N; Bisen, D P; Jha, Piyush; Chandra, V K; Chandra, B P

    2017-05-01

    The present paper reports the thermoluminescence (TL) of (ZnS)1-x (MnTe)x nanophosphors that were prepared by a wet chemical synthesis method. The structure investigated by X-ray diffraction patterns confirms the formation of a sphalerite phase whose space group was found to be F 4¯3m. From XRD, TEM and SEM analyses the average sizes of the particles were found to be 12 nm, 11 nm and 15 nm, respectively. Initially the TL intensity increased with increasing values of x because the number of luminescence centres increased; however, for higher values of x the TL intensity decreased because of the concentration quenching. Thus the TL, mechanoluminescence and photoluminescence intensities are optimum for a particular value of x, that is for x = 0.05. Thermoluminescence of the (ZnS)1-x (MnTe)x nanophosphor has not been reported previously. There were two peaks seen in the thermoluminescence glow curves in which the first peak lay at 105-100 °C and the second peak lay at 183.5-178.5 °C. The activation energies for the first and second peaks were found to be 0.45 eV and 0.75 eV, respectively.

  5. Optical and photocatalytic properties of Corymbia citriodora leaf extract synthesized ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Chen, Jinfeng; Hu, Binjie; Zhi, Jinhu

    2016-05-01

    ZnS nanoparticles were biosynthesized via a green and simple method using Corymbia citriodora leaf extract as reducing and stabilizing agent. The biosynthesized ZnS nanoparticles were in the size range of 45 nm with a surface plasmon resonance band at 325 nm. XRD analysis revealed that the nanoparticles were in the sphalerite phase. Quantum confinement effects of biosynthesized ZnS nanoparticles were observed using photoluminescence spectroscopy. The photocatalytic activity of the ZnS nanoparticles has been investigated by degradation methylene blue under UV light irradiation. Due to the smaller size and excellent dispersicity, the biosynthesized ZnS nanoparticles showed a superior photocatalytic performance compared with that of chemical synthesize ZnS nanoparticles.

  6. Ferromagnetic properties of Cu-doped ZnS: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Yan, Huiyu; Li, Yuqi; Guo, Yanrui; Song, Qinggong; Chen, Yifei

    2011-02-01

    Using plane-wave pseudopotential (PWPP) method, the magnetism and spin-resolved electronic properties of Cu-doped ZnS system are studied. Our calculations indicate that ferromagnetic (FM) state is ground state in Cu-doped ZnS. The FM coupling strength in ZnS doping with Cu fluctuates with the variation of distance between two dopants and the fluctuation gets larger with increase in distance. Room temperature ferromagnetism can be observed in Cu-doped ZnS with high dopant concentration. Formation energy calculation implies that the clustering effect is not obvious in Cu-doped ZnS. Thus, Cu-doped ZnS can be a promising dilute magnetic semiconductor (DMS), which promises to be free of magnetic precipitates.

  7. Electrodeposited ZnS Precursor Layer with Improved Electrooptical Properties for Efficient Cu2ZnSnS4 Thin-Film Solar Cells

    NASA Astrophysics Data System (ADS)

    Mkawi, E. M.; Ibrahim, K.; Ali, M. K. M.; Farrukh, M. A.; Mohamed, A. S.

    2015-10-01

    Zinc sulfide (ZnS) thin films were prepared on indium tin oxide-coated glass by electrodeposition using aqueous zinc sulfate, thiourea, and ammonia solutions at 80°C. The effects of sulfurization at temperatures of 350°C, 400°C, 450°C, and 500°C on the morphological, structural, optical, and electrical properties of the ZnS thin films were investigated. X-ray diffraction analysis showed that the ZnS thin films exhibited cubic zincblende structure with preferred (111) orientation. The film crystallization improved with increasing annealing temperature. Field-emission scanning electron microscopy images showed that the film morphology became more compact and uniform with increasing annealing temperature. The percentage of sulfur in the ZnS thin films increased after sulfurization until a stoichiometric S/Zn ratio was achieved at 500°C. The annealed films showed good adhesion to the glass substrates, with moderate transmittance (85%) in the visible region. Based on absorption measurements, the direct bandgap increased from 3.71 eV to 3.79 eV with annealing temperature, which is attributed to the change of the buffer material composition and suitable crystal surface properties for effective p- n junction formation. The ZnS thin films were used as a buffer layer in thin-film solar cells with the structure of soda-lime glass/Mo/Cu2ZnSnS4/ZnS/ZnO/Al grid. The best solar cell efficiency was 1.86%.

  8. Effect of ZnS nanoparticles on the photoluminescence of Sm3+ ions in methanol

    NASA Astrophysics Data System (ADS)

    Kakoti, D.; Rajkonwar, N.; Dehingia, N.; Boruah, A.; Gogoi, P.; Dutta, P.

    2016-10-01

    ZnS nanoparticles co-doped with Sm3+ ions were prepared in methanol medium for fixed Sm3+ and varying ZnS concentrations. Enhancements in absorption as well as photoluminescence efficiency of the co-doped samples were observed. This enhanced efficiency is attributed to the effective increase in oscillator strengths of the Sm3+ transitions because of the addition of ZnS nanoparticles.

  9. Visible light photocatalytic H2-production activity of wide band gap ZnS nanoparticles based on the photosensitization of grapheme.

    PubMed

    Wang, Faze; Zheng, Maojun; Zhu, Changqing; Zhang, Bin; Chen, Wen; Ma, Li; Shen, Wenzhong

    2015-08-28

    Visible light photocatalytic H(2) production from water splitting is considered an attractive way to solve the increasing global energy crisis in modern life. In this study, a series of zinc sulfide nanoparticles and graphene (GR) sheet composites were synthesized by a two-step hydrothermal method, which used zinc chloride, sodium sulfide, and graphite oxide (GO) as the starting materials. The as-prepared ZnS-GR showed highly efficient visible light photocatalytic activity in hydrogen generation. The morphology and structure of the composites obtained by transmission electron microscope and x-ray diffraction exhibited a small crystallite size and a good interfacial contact between the ZnS nanoparticles and the two-dimensional (2D) GR sheet,which were beneficial for the photocatalysis. When the content of the GR in the catalyst was 0.1%, the ZG0.1 sample exhibited the highest H(2)-production rate of 7.42 μmol h(−1) g(−1), eight times more than the pure ZnS sample. This high visible-light photocatalytic H(2) production activity is attributed to the photosensitization of GR. Irradiated by visible light, the electrons photogenerated from GR transfer to the conduction band of ZnS to participate in the photocatalytic process. This study presents the visible-light photocatalytic activity of wide bandgap ZnS and its application in H(2) evolution.

  10. Ultrasensitive, Real-time and Discriminative Detection of Improvised Explosives by Chemiresistive Thin-film Sensory Array of Mn2+ Tailored Hierarchical ZnS

    PubMed Central

    Zhou, Chaoyu; Wu, Zhaofeng; Guo, Yanan; Li, Yushu; Cao, Hongyu; Zheng, Xuefang; Dou, Xincun

    2016-01-01

    A simple method combing Mn2+ doping with a hierarchical structure was developed for the improvement of thin-film sensors and efficient detection of the explosives relevant to improvised explosive devices (IEDs). ZnS hierarchical nanospheres (HNs) were prepared via a solution-based route and their sensing performances were manipulated by Mn2+ doping. The responses of the sensors based on ZnS HNs towards 8 explosives generally increase firstly and then decrease with the increase of the doped Mn2+ concentration, reaching the climate at 5% Mn2+. Furthermore, the sensory array based on ZnS HNs with different doping levels achieved the sensitive and discriminative detection of 6 analytes relevant to IEDs and 2 military explosives in less than 5 s at room temperature. Importantly, the superior sensing performances make ZnS HNs material interesting in the field of chemiresistive sensors, and this simple method could be a very promising strategy to put the sensors based on thin-films of one-dimensional (1D) nanostructures into practical IEDs detection. PMID:27161193

  11. Visible light-induced degradation of methylene blue in the presence of photocatalytic ZnS and CdS nanoparticles.

    PubMed

    Soltani, Nayereh; Saion, Elias; Hussein, Mohd Zobir; Erfani, Maryam; Abedini, Alam; Bahmanrokh, Ghazaleh; Navasery, Manizheh; Vaziri, Parisa

    2012-09-25

    ZnS and CdS nanoparticles were prepared by a simple microwave irradiation method under mild conditions. The obtained nanoparticles were characterized by XRD, TEM and EDX. The results indicated that high purity of nanosized ZnS and CdS was successfully obtained with cubic and hexagonal crystalline structures, respectively. The band gap energies of ZnS and CdS nanoparticles were estimated using UV-visible absorption spectra to be about 4.22 and 2.64 eV, respectively. Photocatalytic degradation of methylene blue was carried out using physical mixtures of ZnS and CdS nanoparticles under a 500-W halogen lamp of visible light irradiation. The residual concentration of methylene blue solution was monitored using UV-visible absorption spectrometry. From the study of the variation in composition of ZnS:CdS, a composition of 1:4 (by weight) was found to be very efficient for degradation of methylene blue. In this case the degradation efficiency of the photocatalyst nanoparticles after 6 h irradiation time was about 73% with a reaction rate of 3.61 × 10-3 min-1. Higher degradation efficiency and reaction rate were achieved by increasing the amount of photocatalyst and initial pH of the solution.

  12. Visible light photocatalytic H2-production activity of wide band gap ZnS nanoparticles based on the photosensitization of graphene

    NASA Astrophysics Data System (ADS)

    Wang, Faze; Zheng, Maojun; Zhu, Changqing; Zhang, Bin; Chen, Wen; Ma, Li; Shen, Wenzhong

    2015-08-01

    Visible light photocatalytic H2 production from water splitting is considered an attractive way to solve the increasing global energy crisis in modern life. In this study, a series of zinc sulfide nanoparticles and graphene (GR) sheet composites were synthesized by a two-step hydrothermal method, which used zinc chloride, sodium sulfide, and graphite oxide (GO) as the starting materials. The as-prepared ZnS-GR showed highly efficient visible light photocatalytic activity in hydrogen generation. The morphology and structure of the composites obtained by transmission electron microscope and x-ray diffraction exhibited a small crystallite size and a good interfacial contact between the ZnS nanoparticles and the two-dimensional (2D) GR sheet, which were beneficial for the photocatalysis. When the content of the GR in the catalyst was 0.1%, the ZG0.1 sample exhibited the highest H2-production rate of 7.42 μmol h-1 g-1, eight times more than the pure ZnS sample. This high visible-light photocatalytic H2 production activity is attributed to the photosensitization of GR. Irradiated by visible light, the electrons photogenerated from GR transfer to the conduction band of ZnS to participate in the photocatalytic process. This study presents the visible-light photocatalytic activity of wide bandgap ZnS and its application in H2 evolution.

  13. Visible Light-Induced Degradation of Methylene Blue in the Presence of Photocatalytic ZnS and CdS Nanoparticles

    PubMed Central

    Soltani, Nayereh; Saion, Elias; Hussein, Mohd Zobir; Erfani, Maryam; Abedini, Alam; Bahmanrokh, Ghazaleh; Navasery, Manizheh; Vaziri, Parisa

    2012-01-01

    ZnS and CdS nanoparticles were prepared by a simple microwave irradiation method under mild conditions. The obtained nanoparticles were characterized by XRD, TEM and EDX. The results indicated that high purity of nanosized ZnS and CdS was successfully obtained with cubic and hexagonal crystalline structures, respectively. The band gap energies of ZnS and CdS nanoparticles were estimated using UV-visible absorption spectra to be about 4.22 and 2.64 eV, respectively. Photocatalytic degradation of methylene blue was carried out using physical mixtures of ZnS and CdS nanoparticles under a 500-W halogen lamp of visible light irradiation. The residual concentration of methylene blue solution was monitored using UV-visible absorption spectrometry. From the study of the variation in composition of ZnS:CdS, a composition of 1:4 (by weight) was found to be very efficient for degradation of methylene blue. In this case the degradation efficiency of the photocatalyst nanoparticles after 6 h irradiation time was about 73% with a reaction rate of 3.61 × 10−3 min−1. Higher degradation efficiency and reaction rate were achieved by increasing the amount of photocatalyst and initial pH of the solution. PMID:23202896

  14. Synthesis and spectroscopic investigations of Cu- and Pb-doped colloidal ZnS nanocrystals.

    PubMed

    Ehlert, Oliver; Osvet, Andres; Batentschuk, Miroslaw; Winnacker, Albrecht; Nann, Thomas

    2006-11-23

    A novel organometallic synthesis method for the preparation of colloidal ZnS nanoparticles is presented. This method enables the synthesis of undoped ZnS nanocrystals as well as doping with Cu, Pb, or both. The particles can be covered with an undoped layer of ZnS, forming core/shell-type particles with the ZnS:Pb, ZnS:Cu, or ZnS:Cu,Pb cores. The particles were characterized via TEM, XRD, dynamic light scattering, and optical spectroscopy. We investigated the extrinsic surface defects and their coverage with an additional ZnS layer in detail by temperature-dependent luminescence and luminescence lifetime spectroscopy.

  15. Luminescence characteristics of impurities-activated ZnS nanocrystals prepared in microemulsion with hydrothermal treatment

    NASA Astrophysics Data System (ADS)

    Xu, S. J.; Chua, S. J.; Liu, B.; Gan, L. M.; Chew, C. H.; Xu, G. Q.

    1998-07-01

    Cu-, Eu-, or Mn-doped ZnS nanocrystalline phosphors were prepared at room temperature using a chemical synthesis method. Transmission electron microscopy observation shows that the size of the ZnS clusters is in the 3-18 nm range. New luminescence characteristics such as strong and stable visible-light emissions with different colors were observed from the doped ZnS nanocrystals at room temperature. These results strongly suggest that impurities, especially transition metals and rare-earth metals-activated ZnS nanoclusters form a new class of luminescent materials.

  16. Frozen ZnS Aqueous Suspension Nonlinear Optical Properties

    NASA Astrophysics Data System (ADS)

    Ehrlich, H.; Kudryavtseva, A.; Lisichkin, G.; Savranskii, V.; Tcherniega, N.; Zemskov, K.; Zhilenko, M.

    2015-11-01

    The study of nonlinear effects, caused by nanosecond laser pulses' impact on the frozen ZnS nanoparticles' suspension, is presented. Laser pulses excite strong nanoparticles' coherent vibrations in the near-terahertz range which lead to different nonlinear effects: X-ray emission, stimulated low-frequency Raman scattering, and luminescence. X-ray emission was observed as bright spots on the special X-ray film. This provides evidence that an X-ray propagates with narrow beams. Stimulated low-frequency Raman scattering is a result of light scattering by acoustic vibrations of nanoparticles. Its frequency shift corresponds to the nanoparticles' eigenvibration frequencies and depends on the sample material and particle's dimension. It was measured with the help of a Fabri-Perot interferometer in the range of dispersion 16.67 {cm}^{-1}. For ZnS, the first Stokes component frequency shift is equal to 465 GHz. Under excitation by 20 ns ruby laser pulses, the luminescence of the frozen ZnS nanoparticles' suspension was observed in two bands located at 480 nm and 510 nm. Its duration was more than 3 s.

  17. Polymorphism, band-structure, band-lineup, and alloy energetics of the group II oxides and sulfides MgO, ZnO, CdO, MgS, ZnS, CdS

    NASA Astrophysics Data System (ADS)

    Lany, Stephan

    2014-03-01

    The group II chalcogenides are an important class of functional semiconductor materials exhibiting a remarkable diversity in terms of structure and properties. In order to aid the materials design, a consistent set of electronic structure calculations is presented, including data on the polymorphic energy ordering, the band-structures, the band-lineups relative to the vacuum level, surface energies, as well as on the alloy energetics. To this end, current state-of-the-art electronic structure tools are employed, which, besides standard density functional theory (DFT), include totalenergy calculation in the random phase approximation and GW quasiparticle energy calculations. The ionization potentials and electron affinities are obtained by combining the results of bulk GW and surface DFT calculations. Considering both octahedral and tetrahedral coordination symmetries, exemplified by the rock-salt and zinc-blende lattices, respectively, this data reveals both the chemical and structural trends within this materials family.

  18. Protein-directed synthesis of Mn-doped ZnS quantum dots: a dual-channel biosensor for two proteins.

    PubMed

    Wu, Peng; Zhao, Ting; Tian, Yunfei; Wu, Lan; Hou, Xiandeng

    2013-06-03

    Proteins typically have nanoscale dimensions and multiple binding sites with inorganic ions, which facilitates the templated synthesis of nanoparticles to yield nanoparticle-protein hybrids with tailored functionality, water solubility, and tunable frameworks with well-defined structure. In this work, we report a protein-templated synthesis of Mn-doped ZnS quantum dots (QDs) by exploring bovine serum albumin (BSA) as the template. The obtained Mn-doped ZnS QDs give phosphorescence emission centered at 590 nm, with a decay time of about 1.9 ms. A dual-channel sensing system for two different proteins was developed through integration of the optical responses (phosphorescence emission and resonant light scattering (RLS)) of Mn-doped ZnS QDs and recognition of them by surface BSA phosphorescent sensing of trypsin and RLS sensing of lysozyme. Trypsin can digest BSA and remove BSA from the surface of Mn-doped ZnS QDs, thus quenching the phosphorescence of QDs, whereas lysozyme can assemble with BSA to lead to aggregation of QDs and enhanced RLS intensity. The detection limits for trypsin and lysozyme were 40 and 3 nM, respectively. The selectivity of the respective channel for trypsin and lysozyme was evaluated with a series of other proteins. Unlike other protein sensors based on nanobioconjugates, the proposed dual-channel sensor employs only one type of QDs but can detect two different proteins. Further, we found the RLS of QDs can also be useful for studying the BSA-lysozyme binding stoichiometry, which has not been reported in the literature. These successful biosensor applications clearly demonstrate that BSA not only serves as a template for growth of Mn-doped ZnS QDs, but also impacts the QDs for selective recognition of analyte proteins.

  19. Phase transformation and optical properties of Cu-doped ZnS nanorods

    SciTech Connect

    Datta, Anuja Panda, Subhendu K.; Chaudhuri, Subhadra

    2008-09-15

    ZnS nanorods doped with 0-15 mol% of Cu have been prepared by simple solvothermal process. With gradual increase in the Cu concentration, phase transformation of the doped ZnS nanorods from wurtzite to cubic was observed. Twins and stacking faults were developed due to atomic rearrangement in the heavily doped ZnS nanorods during phase transformation. UV-vis-NIR absorbance spectroscopy ruled out the presence of any impure Cu-S phase. The doped ZnS nanorods showed luminescence over a wide range from UV to near IR with peaks at 370, 492-498, 565 and 730 nm. The UV region peak is due to the near-band-edge transition, whereas, the green peak can be related to emission from elementary sulfur species on the surfaces of the nanorods. The orange emission at 565 nm may be linked to the recombination of electrons at deep defect levels and the Cu(t{sub 2}) states present near the valence band of ZnS. The near IR emission possibly originated from transitions due to deep-level defects. - Graphical abstract: ZnS nanorods doped with 0-15 mol% of Cu has been prepared by simple solvothermal route. Interestingly, phase transformation of the doped ZnS nanorods from wurtzite to cubic was observed with gradual increase in the Cu concentration. Doped ZnS nanorods showed luminescence over a wide range from UV to near IR, which is also a rare observation.

  20. Fabrication of TiO2/ZnS nanocomposites for solar energy mediated photocatalytic application

    NASA Astrophysics Data System (ADS)

    Prasannalakshmi, P.; Shanmugam, N.

    2017-03-01

    In the present work, we demonstrate the photocatalytic properties of nanosized TiO2, and different levels of ZnS-loaded TiO2/ZnS composites, for the degradation of the organic dyes brilliant green (BG), and methylene blue (MB) under solar light irradiation. For this process, TiO2 and the composites were synthesized by a sol-gel method. Further, the prepared products were subjected to structural, optical, and morphological characterizations. The results of the photocatalytic activity imply that for the samples studied, TiO2 loaded with an optimum level of zinc (0.25 M), and sulfur (0.5 M) is better able to actively degrade both BG and MB, due to its enhanced BET surface area, reduced band gap, and low charge transfer resistance.

  1. Fabrication of TiO2/ZnS nanocomposites for solar energy mediated photocatalytic application.

    PubMed

    Prasannalakshmi, P; Shanmugam, N

    2017-03-15

    In the present work, we demonstrate the photocatalytic properties of nanosized TiO2, and different levels of ZnS-loaded TiO2/ZnS composites, for the degradation of the organic dyes brilliant green (BG), and methylene blue (MB) under solar light irradiation. For this process, TiO2 and the composites were synthesized by a sol-gel method. Further, the prepared products were subjected to structural, optical, and morphological characterizations. The results of the photocatalytic activity imply that for the samples studied, TiO2 loaded with an optimum level of zinc (0.25M), and sulfur (0.5M) is better able to actively degrade both BG and MB, due to its enhanced BET surface area, reduced band gap, and low charge transfer resistance.

  2. Single-material multilayer ZnS as anti-reflective coating for solar cell applications

    NASA Astrophysics Data System (ADS)

    Salih, Ammar T.; Najim, Aus A.; Muhi, Malek A. H.; Gbashi, Kadhim R.

    2017-04-01

    Multilayer Zinc Sulfide (ZnS) is a promising low cost antireflective coating for solar cell applications, in this work; thin films with novel structure containing cubic and hexagonal phases were successfully deposited by thermal evaporation technique with three different layers. XRD analysis confirms the existence of both phases and high specific surface area. AFM analysis reveals that films with three layers have lower roughness and average grain size than other films. The optical measurements obtained by UV-vis, the calculated values of refractive index and reflectivity using some well known refractive index-band gap relations indicate that thin films with triple layer TL-ZnS have lower refractive index and reflectivity than other films, empirical equations were suggested and show the quantum confinement effects on band gap and reflectivity.

  3. Synthesis of cubic ZnS microspheres exhibiting broad visible emission for bioimaging applications.

    PubMed

    Sajan, P; Jayasree, R S; Agouram, S; Bushiri, M Junaid

    2016-03-01

    Biocompatible ZnS microspheres with an average diameter of 3.85 µm were grown by solvo-hydrothermal (S-H) method using water-acetonitrile-ethylenediamine (EDA) solution combination. ZnS microspheres were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform (FT)-Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) techniques. The broad photoluminescence (PL) emissions from 380-580 nm that were seen from the ZnS microspheres attributed to the increase in carrier concentration, as understood from the observed intense Raman band at 257 cm(-1). Cytotoxicity and haemocompatibility investigations of these ZnS microspheres revealed its biocompatibility. ZnS microspheres, along with biological cell lines, were giving visible light emission and could be used for bioimaging applications.

  4. Photocatalytic degradation of methylene blue with Fe doped ZnS nanoparticles.

    PubMed

    Chauhan, Ruby; Kumar, Ashavani; Chaudhary, Ram Pal

    2013-09-01

    Fe doped ZnS nanoparticles (Zn1-xFexS; where x=0.00, 0.03, 0.05 and 0.10) were synthesized by a chemical precipitation method. The synthesized products were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, UV-Vis and photoluminescence spectrometer. The X-ray diffraction and transmission electron microscope studies show that the size of crystallites is in the range of 2-5 nm. Photocatalytic activities of ZnS and 3, 5 and 10 mol% Fe doped ZnS were evaluated by decolorization of methylene blue in aqueous solution under ultraviolet and visible light irradiation. It was found that the Fe doped ZnS bleaches methylene blue much faster than the undoped ZnS upon its exposure to the visible light as compared to ultraviolet light. The optimal Fe/Zn ratio was observed to be 3 mol% for photocatalytic applications.

  5. Photocatalytic degradation of methylene blue with Fe doped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Chauhan, Ruby; Kumar, Ashavani; Chaudhary, Ram Pal

    2013-09-01

    Fe doped ZnS nanoparticles (Zn1-xFexS; where x = 0.00, 0.03, 0.05 and 0.10) were synthesized by a chemical precipitation method. The synthesized products were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, UV-Vis and photoluminescence spectrometer. The X-ray diffraction and transmission electron microscope studies show that the size of crystallites is in the range of 2-5 nm. Photocatalytic activities of ZnS and 3, 5 and 10 mol% Fe doped ZnS were evaluated by decolorization of methylene blue in aqueous solution under ultraviolet and visible light irradiation. It was found that the Fe doped ZnS bleaches methylene blue much faster than the undoped ZnS upon its exposure to the visible light as compared to ultraviolet light. The optimal Fe/Zn ratio was observed to be 3 mol% for photocatalytic applications.

  6. X-ray excited optical luminescence studies or ZnS and ZnO nanostructures.

    SciTech Connect

    Rosenberg, R. A.; Shenoy, G. K.; Heigl, F.; Lee, S.-T.; Tien, L. -C.; Norton, D.; Pearton, S.; Kim, P.-S. G.; Zhou, X. T.; Sham, T. K.; Experimental Facilities Division; Canadian Synchrotron Radiation Facility; City Univ. of Hong Kong; Univ. of Florida; Univ. of Western Ontario

    2006-01-01

    Due to their potential as optoelectronic devices, luminescing nanostructures have been among the most studied in the recent past. Room-temperature UV lasing has been demonstrated in ZnO nanowires. For highly asymmetric wurtzite structures, the orientation of the emitting luminescent dipole with respect to the excited state polarization can play a role in the luminescence yield. ZnS is an important, wide bandgap (E{sub g} = 3.54 eV for the thermodynamically stable zinc blende form at room temperature) II-VI semiconductor. It has been developed for a number of applications including UV light-emitting diodes, injection lasers and phosphors. In this presentation we will discuss results of a study on ZnS nanostructurees using synchrotron-radiation-based, x-ray-excited optical luminescence (XEOL). Results on ZnO will be presented elsewhere. The experimental approach has been described previously. All measurements were performed on beamline 4-ID-C at the Advanced Photon Source. Samples were prepared by a high-temperature growth technique described previously. Briefly, ZnS powder was placed in the center of a horizontal alumina tube upstream of a Si wafer, which was covered with 2 nm thiol-capped gold nanoparticles (used to catalyze the growth). The tube was heated to 1000 C while an Ar/H{sub 2} gas mixture flowed through the tube. This process resulted in the formation of nanoribbons of lengths in the range 10-100 {micro}m and widths less than 100 nm. The samples were characterized by high-resolution TEM images, which showed large areas of hexagonal wurtzite structure interspersed by nanosized regions with cubic sphalerite structure. Using XEOL, we have determined the local phase of the luminescing sites in ZnS nanowires. The inset of the accompanying figure shows the temperature-dependent optical spectrum obtained when exciting the nanowires with 1100 eV x-rays. There are three main peaks: a band-edge, exiton state at 338 nm, a defect-related emission at 430 nm, and a Au

  7. High-performance ultraviolet photodetectors based on solution-grown ZnS nanobelts sandwiched between graphene layers

    PubMed Central

    Kim, Yeonho; Kim, Sang Jin; Cho, Sung-Pyo; Hong, Byung Hee; Jang, Du-Jeon

    2015-01-01

    Ultraviolet (UV) light photodetectors constructed from solely inorganic semiconductors still remain unsatisfactory because of their low electrical performances. To overcome this limitation, the hybridization is one of the key approaches that have been recently adopted to enhance the photocurrent. High-performance UV photodetectors showing stable on-off switching and excellent spectral selectivity have been fabricated based on the hybrid structure of solution-grown ZnS nanobelts and CVD-grown graphene. Sandwiched structures and multilayer stacking strategies have been applied to expand effective junction between graphene and photoactive ZnS nanobelts. A multiply sandwich-structured photodetector of graphene/ZnS has shown a photocurrent of 0.115 mA under illumination of 1.2 mWcm−2 in air at a bias of 1.0 V, which is higher 107 times than literature values. The multiple-sandwich structure of UV-light sensors with graphene having high conductivity, flexibility, and impermeability is suggested to be beneficial for the facile fabrication of UV photodetectors with extremely efficient performances. PMID:26197784

  8. Semi-empirical scattering model for Chemical Vapor Deposited ZnS

    SciTech Connect

    McCloy, John S.

    2009-10-06

    A model has been created based on scattering from internal surfaces of different refractive index that describes the λ-2 dependence of the extinction in bulk samples of CVD ZnS. The model hinges on the lamellar nanostructure composed of alternating layers of thickness on the order of 10 to 100 nm. A family of solutions is generated which depend on both the difference in refractive index (Δn) and the layer thickness. Reasonable layer thicknesses require Δn for CVD ZnS with higher values than can be explained solely by the Δn between sphalerite and wurtzite phases of ZnS. Other evidence suggests a substantial oxygen component in CVD ZnS that could result in the lower refractive index Zn(O,S) necessary for the model. Differences in transmission for CVD ZnS, elemental ZnS, and multispectral ZnS can be explained simply by a different magnitude of Δn between the layers. Absolute transmission is modeled satisfactorily from the band edge to 10 μm using this approach.

  9. Wurtzite-type ZnS nanoparticles by pulsed electric discharge.

    PubMed

    Omurzak, Emil; Mashimo, Tsutomu; Sulaimankulova, Saadat; Takebe, Shintaro; Chen, Liliang; Abdullaeva, Zhypargul; Iwamoto, Chihiro; Oishi, Yudai; Ihara, Hirotaka; Okudera, Hiroki; Yoshiasa, Akira

    2011-09-07

    The synthesis of wurtzite-type ZnS nanoparticles by an electric discharge submerged in molten sulfur is reported. Using a pulsed plasma between two zinc electrodes of diameter 5 mm in molten sulfur, we have synthesized high-temperature phase (wurtzite-type) ZnS nanocrystals with an average size of about 20 nm. The refined lattice parameters of the synthesized wurtzite-type ZnS nanoparticles were found to be larger than those of the reported ZnS (JCPDS card no 36-1450). Synthesis of ZnMgS (solid solution of ZnS and MgS) was achieved by using ZnMg alloys as both cathode and anode electrodes. UV-visible absorption spectroscopy analysis showed that the absorption peak of the as-prepared ZnS sample (319 nm) displays a blue-shift compared to the bulk ZnS (335 nm). Photoluminescence spectra of the samples revealed peaks at 340, 397, 423, 455 and 471 nm, which were related to excitonic emission and stoichiometric defects.

  10. Wurtzite-type ZnS nanoparticles by pulsed electric discharge

    NASA Astrophysics Data System (ADS)

    Omurzak, Emil; Mashimo, Tsutomu; Sulaimankulova, Saadat; Takebe, Shintaro; Chen, Liliang; Abdullaeva, Zhypargul; Iwamoto, Chihiro; Oishi, Yudai; Ihara, Hirotaka; Okudera, Hiroki; Yoshiasa, Akira

    2011-09-01

    The synthesis of wurtzite-type ZnS nanoparticles by an electric discharge submerged in molten sulfur is reported. Using a pulsed plasma between two zinc electrodes of diameter 5 mm in molten sulfur, we have synthesized high-temperature phase (wurtzite-type) ZnS nanocrystals with an average size of about 20 nm. The refined lattice parameters of the synthesized wurtzite-type ZnS nanoparticles were found to be larger than those of the reported ZnS (JCPDS card no 36-1450). Synthesis of ZnMgS (solid solution of ZnS and MgS) was achieved by using ZnMg alloys as both cathode and anode electrodes. UV-visible absorption spectroscopy analysis showed that the absorption peak of the as-prepared ZnS sample (319 nm) displays a blue-shift compared to the bulk ZnS (335 nm). Photoluminescence spectra of the samples revealed peaks at 340, 397, 423, 455 and 471 nm, which were related to excitonic emission and stoichiometric defects.

  11. Room temperature fabrication of hollow ZnS and ZnO architectures by a sacrificial template route.

    PubMed

    Yan, Chenglin; Xue, Dongfeng

    2006-04-13

    Hollow ZnS and ZnO architectures are fabricated by employing Zn(5)(CO(3))(2)(OH)(6) microspheres as the sacrificial template. Zn(5)(CO(3))(2)(OH)(6) microspheres can be effectively converted into the core/shell structured ZnO/ZnS composites (in the Na(2)S solution) and hollow ZnO architectures (in the KOH solution), by a spontaneous ion replacement reaction at room temperature. Removing the core by the KOH treatment of core/shell structured ZnO/ZnS, hollow ZnS spheres with different shell thicknesses can be effectively achieved. The obtained hollow ZnO architectures exhibit unique geometrical shapes, and their walls are composed of nanocrystals, which are connected to each other to form their hemispherical or circular shape. A possible formation process from Zn(5)(CO(3))(2)(OH)(6) microspheres to core/shell structured ZnO/ZnS composites is proposed by arresting a series of intermediate morphologies.

  12. NH3 and PH3 adsorption through single walled ZnS nanotube: First principle insight

    NASA Astrophysics Data System (ADS)

    Khan, Md. Shahzad; Srivastava, Anurag; Chaurasiya, Rajneesh; Khan, Mohd. Shahid; Dua, Piyush

    2015-09-01

    The density functional theory (DFT) based adsorption analysis of NH3 and PH3 gas molecule has been made for confirming the sensing behaviour of ZnS nanotube. For a particular orientation of XH3 (X = N or P), the ZnS nanotube is found to be a good sensor with Zn as interactive site, discussed in terms of chemisorption and physisorption. Partial density of state (PDOS) analysis reveals strong interaction between few selected fragments from XH3 and ZnS nanotube. The quality of interaction for most favourable orientation is further scrutinized using charge decomposition analysis (CDA) analysis and sensing ability through current-voltage (I-V) characteristics.

  13. Micro-emulsion-assisted synthesis of ZnS nanospheres and their photocatalytic activity

    SciTech Connect

    Li Yao; He Xiaoyan; Cao Minhua

    2008-11-03

    ZnS nanospheres with rough surface were synthesized by using a micro-emulsion-assisted solvothemal process. The molar ratio of [water]/[surfactant] played an important role in controlling the size of the ZnS nanospheres. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), field emission-scanning electron microscope (FE-SEM), and selected area electron diffraction (SAED) were used for the characterization of the resulting ZnS nanospheres. A possible formation mechanism was proposed. These ZnS nanospheres exhibited a good photocatalytic activity for degradation of an aqueous p-nitrophenol solution and the total organic carbon (TOC) of the degradation product has also been investigated.

  14. Self-assembled ZnS nanowire arrays: synthesis, in situ Cu doping and field emission

    NASA Astrophysics Data System (ADS)

    Liu, Baodan; Bando, Yoshio; Jiang, Xin; Li, Chun; Fang, Xiaosheng; Zeng, Haibo; Terao, Takeshi; Tang, Chengchun; Mitome, Masanori; Golberg, Dmitri

    2010-09-01

    Well-aligned single-crystalline ZnS nanowire arrays have been grown on highly conductive Cu substrates through controlling the morphology evolution of self-patterned ZnS nanoparticles. The ZnS nanowires have sharp tips with an average size of ~ 30 nm and a length of ~ 3 µm. Field emission measurements demonstrated that the aligned ZnS nanowires grown on Cu substrates are excellent field emitters having a turn-on field as low as 2.92 V µm - 1 and a field-enhancement factor as high as 3400. The use of highly conductive metal substrate may promote the commercial applications of ZnS-based emitters in flat panel displays and other optoelectronic devices.

  15. Low temperature synthesis, photoluminescence, magnetic properties of the transition metal doped wurtzite ZnS nanowires

    NASA Astrophysics Data System (ADS)

    Cao, Jian; Han, Donglai; Wang, Bingji; Fan, Lin; Fu, Hao; Wei, Maobin; Feng, Bo; Liu, Xiaoyan; Yang, Jinghai

    2013-04-01

    In this paper, we synthesized the transition metal ions (Mn, Cu, Fe) doped and co-doped ZnS nanowires (NWs) by a one-step hydrothermal method. The results showed that the solid solubility of the Fe2+ ions in the ZnS NWs was about two times larger than that of the Mn2+ or Cu2+ ions in the ZnS NWs. There was no phase transformation from hexagonal to cubic even in a large quantity transition metal ions introduced for all the samples. The Mn2+/Cu2+/Fe2+ related emission peaks can be observed in the Mn2+,Cu2+ and Fe2+ doped ZnS NWs. The ferromagnetic properties of the co-doped samples were investigated at room temperature.

  16. Influence of Cu ion implantation on the microstructure and cathodoluminescence of ZnS nanostructures

    NASA Astrophysics Data System (ADS)

    Shang, L. Y.; Zhang, D.; Liu, B. Y.

    2016-07-01

    The microstructure and optical properties of as-synthesized and Cu ion implanted ZnS nanostructures with branched edges are studied by using high-resolution transmission electron microscope (TEM) and spatially-resolved cathodoluminescence measurement. Obvious crystalline deterioration has been observed in Cu-doped ZnS nanostructures due to the invasion of Cu ions into ZnS lattice. It was found that the optical emissions of ZnS nanostructures can be selectively modified through the control of Cu ion dose and subsequent heat treatment. An increase of Cu dopant content will lead to an apparent red-shift of the intrinsic band-gap emission in the UV range and the broadening of defect-related emission in visible range. The influences of Cu ion implantation on the microstructure and related optical properties were discussed.

  17. Photo-Seebeck effect in ZnS

    NASA Astrophysics Data System (ADS)

    Shiraishi, Yuuka; Okazaki, Ryuji; Taniguchi, Hiroki; Terasaki, Ichiro

    2015-03-01

    To explore the thermoelectric transport nature of photo-excited carriers, the electrical conductivity and the Seebeck coefficient are measured under ultraviolet illumination in the wide-gap semiconductor ZnS near room temperature. The conductivity increases linearly as against the photon flux density with little dependence on temperature, indicating the conduction under illumination is mostly governed by the photo-doped carriers. We have found that, in high contrast to the temperature-insensitive photoconductivity, the temperature dependence of the Seebeck coefficient is dramatically varied by illumination, which is unexplained from a simple photo-doping effect for one majority carrier. Such a distinct difference in the transport quantities is rather understood within a two-carrier model, in which only the Seebeck coefficient is strongly affected by photo-excited minority carriers. The present result is also compared with earlier reports of the photo-Hall experiments to discuss the underlying photo-transport mechanism.

  18. Optical properties of colloidal CdS and ZnS quantum dots nanoparticles

    NASA Astrophysics Data System (ADS)

    Amran, Afiqah Shafify; Shamsudin, Siti Aisyah

    2016-11-01

    CdS and ZnS nanoparticles are luminescent semiconductors with great properties to be used in biosensors. Both semiconducting nanoparticles were synthesized in distilled water by using the simple colloidal method. Thioglycolic acid (TGA) was used as a stabilizer and Polyethyleneimine (PEI) was used as a surface modifier. The chemical composition and optical properties of the CdS and ZnS nanoparticles were investigated using Ultra Violet (UV) lamp, UV Spectroscopy and Photoluminescence (PL) Spectroscopy.

  19. Characterization of ZnS thin films synthesized through a non-toxic precursors chemical bath

    SciTech Connect

    Rodríguez, C.A.; Sandoval-Paz, M.G.; Cabello, G.; Flores, M.; Fernández, H.; Carrasco, C.

    2014-12-15

    Highlights: • High quality ZnS thin films have been deposited by chemical bath deposition technique from a non-toxic precursor’s solution. • Nanocrystalline ZnS thin films with large band gap energy were synthesized without using ammonia. • Evidence that the growing of the thin films is carried out by means of hydroxide mechanism was found. • The properties of these ZnS thin films are similar and in some cases better than the corresponding ones produced using toxic precursors such as ammonia. - Abstract: In solar cells, ZnS window layer deposited by chemical bath technique can reach the highest conversion efficiency; however, precursors used in the process normally are materials highly volatile, toxic and harmful to the environment and health (typically ammonia and hydrazine). In this work the characterization of ZnS thin films deposited by chemical bath in a non-toxic alkaline solution is reported. The effect of deposition technique (growth in several times) on the properties of the ZnS thin film was studied. The films exhibited a high percentage of optical transmission (greater than 80%); as the deposition time increased a decreasing in the band gap values from 3.83 eV to 3.71 eV was observed. From chemical analysis, the presence of ZnS and Zn(OH){sub 2} was identified and X-ray diffraction patterns exhibited a clear peak corresponding to ZnS hexagonal phase (1 0 3) plane, which was confirmed by electron diffraction patterns. From morphological studies, compact samples with well-defined particles, low roughness, homogeneous and pinhole-free in the surface were observed. From obtained results, it is evident that deposits of ZnS–CBD using a non-toxic solution are suitable as window layer for TFSC.

  20. Optical and impedance studies of pure and Ba-doped ZnS quantum dots

    NASA Astrophysics Data System (ADS)

    Firdous, Arfat; Baba, M. Aslam; Singh, D.; Bhat, Abdul Hamid

    2015-02-01

    Chemical precipitation method using a high-boiling solvent is used to synthesize ZnS and Ba-doped ZnS quantum dots. The presence of organic ligands in the prepared nanostructures is verified using Fourier transform infra-red spectroscopic studies. The samples have been analysed using X-ray diffraction analysis confirming nanocrystallinity of the as-prepared quantum dots (QD). The mean crystal size obtained by full width half maxima analysis is 3.2 nm for ZnS and 3.9, 4.2 nm for ZnS:Ba (2, 4 mM). TEM micrographs also reveal nanosized particles of ZnS and Ba-doped ZnS. An optical absorption study conducted in UV-Vis range 150-600 nm reveals the transparency of these quantum dots in entire visible range but not in ultraviolet range. The results based on optical analysis yield band gap values as 4.88 eV for ZnS and 4.69, 4.43 eV for ZnS:Ba (2, 4 mM) quantum dots. Impedance analysis of the samples was carried out to reveal the variation of impedance with frequency at room temperature. These results show the capacitive admittance associated with the quantum dots and hence nanostructure ZnS and Ba-doped ZnS can have potential applications in electronics as nano-tuned devices in which resonant frequency can be adjusted by controlling the size and shape of the quantum dots.

  1. The use of imidazolium ionic liquid/copper complex as novel and green catalyst for chemiluminescent detection of folic acid by Mn-doped ZnS nanocrystals

    NASA Astrophysics Data System (ADS)

    Azizi, Seyed Naser; Shakeri, Parmis; Chaichi, Mohammad Javad; Bekhradnia, Ahmadreza; Taghavi, Mehdi; Ghaemy, Mousa

    2014-03-01

    A novel chemiluminescence (CL) method using water-soluble Mn-doped ZnS quantum dots (QDs) as CL emitter is proposed for the chemiluminometric determination of folic acid in pharmaceutical formulation. Water-soluble Mn-doped ZnS QDs were synthesized by using L-cysteine as stabilizer in aqueous solutions. The nanoparticles were structurally and optically characterized by X-ray powder diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), UV-Vis absorption spectroscopy and photoluminescence (PL) emission spectroscopy. The CL of ZnS QDs induced by directly chemical oxidation and its ionic liquid-sensitized effect in aqueous solution were then investigated. It was found that oxidants, especially hydrogen peroxide, could directly oxidize ZnS QDs to produce weak CL emission in basic conditions. In the presence of 1,3-dipropylimidazolium bromide/copper a drastic light emission enhancement is observed, related to a strong interaction between Cu2+ and the imidazolium ring. Therefore, a new CL analysis system was developed for the determination of folic acid. Under the optimum conditions, there is a good linear relationship between the relative CL intensity and the concentration of folic acid in the range of 1 × 10-9-1 × 10-6 M of folic acid with a correlation coefficient (R2) of 0.9991. The limit of detection of this system was found to be 1 × 10-10 M. This method is not only simple, sensitive and low cost, but also reliable for practical applications.

  2. The use of imidazolium ionic liquid/copper complex as novel and green catalyst for chemiluminescent detection of folic acid by Mn-doped ZnS nanocrystals.

    PubMed

    Azizi, Seyed Naser; Shakeri, Parmis; Chaichi, Mohammad Javad; Bekhradnia, Ahmadreza; Taghavi, Mehdi; Ghaemy, Mousa

    2014-03-25

    A novel chemiluminescence (CL) method using water-soluble Mn-doped ZnS quantum dots (QDs) as CL emitter is proposed for the chemiluminometric determination of folic acid in pharmaceutical formulation. Water-soluble Mn-doped ZnS QDs were synthesized by using L-cysteine as stabilizer in aqueous solutions. The nanoparticles were structurally and optically characterized by X-ray powder diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), UV-Vis absorption spectroscopy and photoluminescence (PL) emission spectroscopy. The CL of ZnS QDs induced by directly chemical oxidation and its ionic liquid-sensitized effect in aqueous solution were then investigated. It was found that oxidants, especially hydrogen peroxide, could directly oxidize ZnS QDs to produce weak CL emission in basic conditions. In the presence of 1,3-dipropylimidazolium bromide/copper a drastic light emission enhancement is observed, related to a strong interaction between Cu(2+) and the imidazolium ring. Therefore, a new CL analysis system was developed for the determination of folic acid. Under the optimum conditions, there is a good linear relationship between the relative CL intensity and the concentration of folic acid in the range of 1×10(-9)-1×10(-)(6) M of folic acid with a correlation coefficient (R(2)) of 0.9991. The limit of detection of this system was found to be 1×10(-)(10) M. This method is not only simple, sensitive and low cost, but also reliable for practical applications.

  3. Advanced zirconia-coated carbonyl-iron particles for acidic magnetorheological finishing of chemical-vapor-deposited ZnS and other IR materials

    NASA Astrophysics Data System (ADS)

    Salzman, S.; Giannechini, L. J.; Romanofsky, H. J.; Golini, N.; Taylor, B.; Jacobs, S. D.; Lambropoulos, J. C.

    2015-10-01

    We present a modified version of zirconia-coated carbonyl-iron (CI) particles that were invented at the University of Rochester in 2008. The amount of zirconia on the coating is increased to further protect the iron particles from corrosion when introduced to an acidic environment. Five low-pH, magnetorheological (MR) fluids were made with five acids: acetic, hydrochloric, nitric, phosphoric, and hydrofluoric. All fluids were based on the modified zirconia-coated CI particles. Off-line viscosity and pH stability were measured for all acidic MR fluids to determine the ideal fluid composition for acidic MR finishing of chemical-vapor-deposited (CVD) zinc sulfide (ZnS) and other infrared (IR) optical materials, such as hot-isostatic-pressed (HIP) ZnS, CVD zinc selenide (ZnSe), and magnesium fluoride (MgF2). Results show significant reduction in surface artifacts (millimeter-size, pebble-like structures on the finished surface) for several standard-grade CVD ZnS substrates and good surface roughness for the non-CVD MgF2 substrate when MR finished with our advanced acidic MR fluid.

  4. Influence of number of pitches and substrate on the nanostructure and optical properties of ZnS helical sculptured thin films

    NASA Astrophysics Data System (ADS)

    Abdi, Fateme; Savaloni, Hadi; Placido, Frank

    2016-12-01

    ZnS helical sculptured thin films with different number of pitches were produced on glass (microscope slides) and pre-deposited 7 nm ZnS on glass substrate. Atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) were used for structural analyses. Crystallographic structure of samples was obtained using x-ray diffraction (XRD) method which confirmed the formation of ZnS films on the substrates. Optical spectra of the samples were measured using a single beam spectrophotometer for both s- and p-polarized light and at different incident light angles. Optical results showed a strong dependence on the structural void fraction and number of pitches and, due to anisotropy of the helical structure, a dependence on the incident light angle. It is shown that by controlling the growth of these structures the optical spectra can be controlled. The reversed homogenization theory was used to calculate the complex refractive index of these structures and the percentage of the void fraction in the produced samples. This investigation showed that both real and imaginary parts of the refractive index are dependent on the structural void fraction; structures with larger grains and higher percentage of void fraction having larger real and imaginary parts of the refractive index. Band gap calculations showed that structures with larger grains and higher void fraction have smaller band gaps. A correlation is obtained between the band gap energies and the nano-strain developed in the structure of the produced films; band gap energy decreases with nano-strain.

  5. Tunable visible emission of TM-doped ZnS quantum dots (TM: Mn2+, Co2+, Ag+)

    NASA Astrophysics Data System (ADS)

    Taheri Otaqsara, S. M.

    2012-07-01

    3 d transition-metallic ions doped ZnS quantum dots (Q-dots) were synthesized by the facile wet-chemical process. During synthesis, various ions, i.e. manganese (Mn2+), cobalt (Co2+) and silver (Ag+), were used and their photoluminescence (PL) response investigated. UV-vis absorption studies show that the various dopant ions can effectively tune energy band structure. The PL emission band is red shifted on Mn2+ doping (~575 nm) as compared to pure ZnS Q-dots (~420 nm) which is due to 4T1(G) → 6A1(S) radiative transitions. Blue/green-emission peaks at ~487 nm/~508 nm observed, respectively, on Co2+/Ag+ doping are probably arising from the recombination between the sulfur vacancy level and the new dopant level. Luminescence emission efficiency (LEE) is found to be maximum at 5 mol% Mn2+ doping and then decreases. On doping by Ag+ the LEE is found to be maximum at 2 mol% doping and almost completely quenched at 5 mol% doping. Contrary to the above, Co2+ quenched the overall PL.

  6. Hepatotoxicity assessment of Mn-doped ZnS quantum dots after repeated administration in mice

    PubMed Central

    Yang, Yanjie; Lv, Shuang-Yu; Yu, Bianfei; Xu, Shuang; Shen, Jianmin; Zhao, Tong; Zhang, Haixia

    2015-01-01

    Doped ZnS quantum dots (QDs) have a longer dopant emission lifetime and potentially lower cytotoxicity compared to other doped QDs. The liver is the key organ for clearance and detoxification of xenobiotics by phagocytosis and metabolism. The present study was designed to synthesize and evaluate the hepatotoxicity of Mn-doped ZnS QDs and their polyethylene glycol-coated counterparts (1 mg/kg and 5 mg/kg) in mice. The results demonstrated that daily injection of Mn-doped ZnS QDs and polyethylene glycol-coated QDs via tail vein for 7 days did not influence body weight, relative liver weight, serum aminotransferases (alanine aminotransferase and aspartate aminotransferase), the levels of antioxidant enzymes (catalase, glutathione peroxidase, and superoxide dismutase), or malondialdehyde in the liver. Analysis of hepatocyte ultrastructure showed that Mn-doped ZnS QDs and polyethylene glycol-coated QDs mainly accumulated in mitochondria at 24 hours after repeated intravenous injection. No damage to cell nuclei or mitochondria was observed with either of the QDs. Our results indicate that Mn-doped ZnS QDs did not cause obvious damage to the liver. This study will assist in the development of Mn-doped ZnS QDs-based bioimaging and biomedical applications in the future. PMID:26396512

  7. Magnetism in undoped ZnS studied from density functional theory

    SciTech Connect

    Xiao, Wen-Zhi E-mail: llwang@hun.edu.cn; Rong, Qing-Yan; Xiao, Gang; Wang, Ling-ling E-mail: llwang@hun.edu.cn; Meng, Bo

    2014-06-07

    The magnetic property induced by the native defects in ZnS bulk, thin film, and quantum dots are investigated comprehensively based on density functional theory within the generalized gradient approximation + Hubbard U (GGA + U) approach. We find the origin of magnetism is closely related to the introduction of hole into ZnS systems. The relative localization of S-3p orbitals is another key to resulting in unpaired p-electron, due to Hund's rule. For almost all the ZnS systems under study, the magnetic moment arises from the S-dangling bonds generated by Zn vacancies. The charge-neutral Zn vacancy, Zn vacancy in 1− charge sate, and S vacancy in the 1+ charge sate produce a local magnetic moment of 2.0, 1.0, and 1.0 μ{sub B}, respectively. The Zn vacancy in the neutral and 1− charge sates are the important cause for the ferromagnetism in ZnS bulk, with a Curie temperature (T{sub C}) above room temperature. For ZnS thin film with clean (111) surfaces, the spins on each surface are ferromagnetically coupled but antiferromagnetically coupled between two surfaces, which is attributable to the internal electric field between the two polar (111) surfaces of the thin film. Only surface Zn vacancies can yield local magnetic moment for ZnS thin film and quantum dot, which is ascribed to the surface effect. Interactions between magnetic moments on S-3p states induced by hole-doping are responsible for the ferromagnetism observed experimentally in various ZnS samples.

  8. Natural zinc enrichment in peatlands: Biogeochemistry of ZnS formation

    NASA Astrophysics Data System (ADS)

    Yoon, Soh-joung; Yáñez, Carolina; Bruns, Mary Ann; Martínez-Villegas, Nadia; Martínez, Carmen Enid

    2012-05-01

    Peatlands effectively retain heavy metals and prevent stream and watershed contamination. Sulfate reduction is considered the most significant process of metal immobilization in natural wetlands and microbial sulfate reduction is the presumed mechanism that results in the precipitation of metal sulfides. In this study, we examined the biogeochemical mechanisms involved in zinc retention and accumulation in a metalliferous peatland of western New York. In the reducing conditions of these peatlands zinc sulfides occurred as framboidal aggregates of sphalerite and polytypic wurtzite (2nH, n ⩾ 2) nanocrystallites associated with bacterial cells and organic matter. Bacterial cells were co-located with ZnS inside peat particles where the microenvironment remained anoxic. The peat zinc sulfide was depleted in 34S isotopes relative to the sulfate supplied to the peatland by 18-34 per mill, implicating its biological formation. Extraction of microbial community DNA from peat samples yielded diverse PCR amplicons from dissimilatory sulfite reductase (dsrAB) genes, indicating varied bacterial taxa capable of reducing forms of oxidized sulfur. Nanocrystals with distinct structural features were observed in samples containing contrasting dsrAB sequences. The results of this investigation provide clear evidence that microorganisms can influence the chemical forms of heavy metals in peatland environments. Our findings also provide insight into the conditions necessary to promote the immobilization of chalcophile elements in engineered systems for the treatment of acid mine drainage and wastewater effluents.

  9. Optical Characteristics of La-Doped ZnS Thin Films Prepared by Chemical Bath Deposition

    NASA Astrophysics Data System (ADS)

    Xie, Hai-Qing; Chen, Yuan; Huang, Wei-Qing; Huang, Gui-Fang; Peng, Ping; Peng, Li; Wang, Tai-Hong; Zeng, Yun

    2011-02-01

    Undoped and La-doped ZnS thin films are prepared by chemical bath deposition (CBD) process through the co-precipitation reaction of inorganic precursors zinc sulfate, thiosulfate ammonia and La2O3. Composition of the films is analyzed using an energy-dispersive x-ray spectroscopy (EDS). Absorption spectra and spectral transmittances of the films are measured using a double beam UV-VIS spectrophotometer (TU-1901). It is found that significant red shifts in absorption spectra and decrease in absorptivity are obtained with increasing lanthanum. Moreover, optical transmittance is increased as La is doped, with a transmittance of more than 80% for wavelength above 360 nm in La-doped ZnS thin films. Compared to pure ZnS, the band gap decreases and flat-band potential positively shifts to quasi-metal for the La-doped ZnS. These results indicate that La-doped ZnS thin films could be valuably adopted as transparent electrodes.

  10. Scintillation and luminescence in transparent colorless single and polycrystalline bulk ceramic ZnS

    SciTech Connect

    McCloy, John S.; Bliss, Mary; Miller, Brian W.; Wang, Zheming; Stave, Sean C.

    2015-01-01

    ZnS:Ag is a well-known extremely bright scintillator used in powder form for α-particle detection and, mixed with powdered LiF, for thermal neutron detection. Recently, we discovered some commercial bulk colorless and transparent, single-crystal and polycrystalline (chemical vapor-deposited) ZnS forms that scintillate in response to α-particles. The scintillation light transmits through the sample thickness (mm), challenging the commonly held assumption that ZnS is opaque to its own scintillation light. Individual α-particle events were imaged in space and time using a charged-particle camera originally developed for medical imaging applications. Photoluminescence (PL) and PL excitation show that scintillating bulk ZnS likely depends on different electronic defects than commercial ZnS powder scintillators. These defects, associated with copper and oxygen, are discussed in relation to PL results and extensive literature assessment. Commercial transparent ZnS is routinely produced by chemical vapor deposition to sizes larger than square meters, enabling potentially novel radiation detection applications requiring large, thick apertures.

  11. Cytotoxicity tests of water soluble ZnS and CdS quantum dots.

    PubMed

    Li, Hui; Li, Mengyan; Shih, Wan Y; Lelkes, Peter I; Shih, Wei-Heng

    2011-04-01

    Cytotoxicity tests of zinc sulfide (ZnS) and cadmium sulfide (CdS) quantum dots (QDs) synthesized via all-aqueous process with various surface conditions were carried out with human endothelial cells (EA hy926) using two independent viability assays, i.e., by cell counting following Trypan blue staining and by measuring Alamar Blue (AB) fluorescence. The ZnS QDs with all four distinct types of surface conditions were nontoxic at both 1 microM and 10 microM concentrations for at least 6 days. On the other hand, the CdS QDs were nontoxic only at 1 microM, and showed significant cytotoxicity at 10 microM after 3 days in the cell counting assay and after 4 days in the AB fluorescence assay. The CdS QDs with (3-mercaptopropyl)trimethoxysilane (MPS)-replacement plus silica capping were less cytotoxic than those with 3-mercaptopropionic acid (MPA) capping and those with MPS-replacement capping. Comparing the results of ZnS and CdS QDs with the same particle size, surface condition and concentration, it is indicated that the cytotoxicity of CdS QDs and the lack of it in ZnS QDs were probably due to the presence and absence of the toxic Cd element, respectively. The nontoxicity of the aqueous ZnS QDs makes them favorable for in vivo imaging applications.

  12. Properties of Al-doped ZnS Films Grown by Chemical Bath Deposition

    NASA Astrophysics Data System (ADS)

    Nagamani, K.; Prathap, P.; Lingappa, Y.; Miles, R. W.; Reddy, K. T. R.

    Zinc sulphide (ZnS) buffer layers are a cadmium free, wider energy band gap, alternative to the cadmium sulphide (CdS) buffer layers commonly used in copper indium gallium diselenide (CuInGaSe2)-based solar cells. However extrinsic doping of the ZnS is important to lower the resistivity of the layers and to improve flexibility of device design. In this work, Al-doped ZnS nanocrystalline films have been produced on glass substrates using a chemical bath deposition (CBD) method. The Al- concentration was varied from 0 at. % to 10 at. %, keeping other deposition parameters constant. The elemental composition of a typical sample with 6 at. % 'Al' in ZnS was Zn=44.9 at. %, S=49.8 at. % and Al=5.3 at.%. The X-ray diffraction data taken on these samples showed a broad peak corresponding to the (111) plane of ZnS while the crystallite size varied in the range, 8 - 15 nm, depending on the concentration of Al in the layers. The films with a Al-doping content of 6 at. % had an optical transmittance of 75% in the visible range and the energy band gap evaluated from the data was 3.66 eV. The films n-type electrical conductivities and the electrical resistivity varied in the range, 107-103 Ωcm, it decreasing with an increase of the Al-concentration in the solution.

  13. Optical, phonon and efficient visible and infrared photocatalytic activity of Cu doped ZnS micro crystals

    NASA Astrophysics Data System (ADS)

    Prasad, Neena; Balasubramanian, Karthikeyan

    2017-02-01

    We report, the enhanced photocatalytic behaviour of Cu doped ZnS micro crystals. ZnS and different concentrations of Cu doped ZnS microcrystals were prepared. X-ray diffraction confirms the crystalline and phase of the particles. Morphology and sizes were studied using Scanning Electron Microscopy (SEM). Recorded optical absorption spectra show a band for around 365 nm for pure ZnS, but there is a broad band in the near infrared regime for the Cu-doped ZnS microcrystals which are attributed to the d-d transitions of Cu2 + ions. Phonon properties of as-prepared samples were investigated using Raman spectroscopy. Present work we investigate the potential of ZnS and Cu doped ZnS as a photocatalyst. For this from the degradation of methylene blue dye in aqueous media the photocatalytic activity of pure and highest doped ZnS samples with the irradiation of white light and infrared, enhanced photocatalytic activity were observed. Mechanism of white light an IR light based photocatalytic activity is explained based on the electron-hole pair production.

  14. One-pot process in scalable anoxic vessels for water-dispersed ZnS nanocrystals with the tailored size

    SciTech Connect

    Jung, Hyunsung; Phelps, Tommy Joe; Rondinone, Adam Justin; Jellison Jr, Gerald Earle; Duty, Chad E; Han, Kee Sung; Moon, Ji Won

    2017-01-01

    Well-dispersed ZnS nanocrystals with tailored size in aqueous solutions were synthesized by employing cysteine-sulfur (Cys-S) complexes with low molecular weight in a scalable anoxic vessel. High yield production of water-dispersed ZnS nanocrystals on a 10-L scale was demonstrated in an aqueous solution process. The average crystallite size of ZnS was controlled by changing the ratio of the cysteine to sulfide in the applied Cys-S complexes. A decrease in the crystallite size of ZnS likely resulted in both the blue shift of peak positions and the relative variation of peak intensities in the photoluminescence properties. Additionally, the pH-dependent stability against aggregation of ZnS nanocrystals was investigated to reduce agglomeration.

  15. One-Pot Process in Scalable Bath for Water-Dispersed ZnS Nanocrystals with the Tailored Size

    DOE PAGES

    Jung, Hyunsung; Phelps, Tommy J.; Rondinone, Adam J.; ...

    2017-05-01

    Well-dispersed ZnS nanocrystals with tailored size in aqueous solutions were synthesized by employing cysteine-sulfur (Cys-S) complexes with low molecular weight in a scalable anoxic vessel. High yield production of water-dispersed ZnS nanocrystals on a 10-L scale was demonstrated in an aqueous solution process. The average crystallite size of ZnS was controlled by changing the ratio of the cysteine to sulfide in the applied Cys-S complexes. A decrease in the crystallite size of ZnS likely resulted in both the blue shift of peak positions and the relative variation of peak intensities in the photoluminescence properties. In addition, the pH-dependent stability againstmore » aggregation of ZnS nanocrystals was investigated to reduce agglomeration.« less

  16. Electrical properties of point defects in CdS and ZnS

    NASA Astrophysics Data System (ADS)

    Varley, J. B.; Lordi, V.

    2013-09-01

    We investigate native point defects in CdS and ZnS, which are conventional n-type buffer layers used in thin-film solar cells. Using hybrid functional calculations, we characterize the electrical behavior of these defects and also consider common impurities such as O, H, and their complexes. We find cation vacancies are the dominant compensating acceptors and recombination centers, and their effects are more dramatic in ZnS than in CdS. We also determine the band alignment for conventional Cu(In,Ga)Se2-based solar cells, giving insight into why CdS outperforms ZnS and why Zn oxysulfides are promising due to their improved conduction band offsets.

  17. Raman selection rule for surface optical phonons in ZnS nanobelts

    NASA Astrophysics Data System (ADS)

    Ho, Chih-Hsiang; Varadhan, Purushothaman; Wang, Hsin-Hua; Chen, Cheng-Ying; Fang, Xiaosheng; He-Hau, Jr.

    2016-03-01

    We report Raman scattering results for high-quality wurtzite ZnS nanobelts (NBs) grown by chemical vapor deposition. In the Raman spectrum, the ensembles of ZnS NBs exhibit first order phonon modes at 274 cm-1 and 350 cm-1, corresponding to A1/E1 transverse optical and A1/E1 longitudinal optical phonons, in addition to a strong surface optical (SO) phonon mode at 329 cm-1. The existence of the SO band is confirmed by its shift with different surrounding dielectric media. Polarization dependent Raman spectra were recorded on a single ZnS NB and for the first time a SO phonon band has been detected on a single nanobelt. Different selection rules for the SO phonon mode are shown from their corresponding E1/A1 phonon modes, and were attributed to the breaking of anisotropic translational symmetry on the NB surface.

  18. Large-scale growth of millimeter-long single-crystalline ZnS nanobelts

    SciTech Connect

    Li Jianye Zhang Qi; An Lei; Qin Luchang; Liu Jie

    2008-11-15

    Millimeter-long single-crystalline hexagonal ZnS nanobelts were grown on specific locations on a wafer scale. This is the first time that the millimeter-scale ZnS nanobelt has been synthesized. The longest nanobelts are about 3 mm. The as-grown nanobelts were characterized by means of field emission scanning electron microscopy, X-ray powder diffraction, high-resolution transmission electron microscopy, and selected area electron diffraction. The results indicate that the ultra-long nanobelts are pure single-crystalline hexagonal ZnS. There are two kinds of ZnS nanobelts existing in the products. One is the nanobelts that have two smooth sides and grow along the [0 0 1] longitudinal direction, and the other is the nanobelts that have one smooth side and one saw-teeth-like side, namely nanosaws, and grow along the [2 1 0] longitudinal direction. A vapor-liquid-solid mechanism is suggested for the lengthwise growth of the ZnS nanobelts (nanosaws) and a vapor-solid mechanism for the side direction growth of the saw-teeth of the nanosaws. - Graphical Abstract: Millimeter-long single-crystalline ZnS nanobelts were grown on specific locations on a large scale. There are two kinds of nanobelts in the products-one has two smooth sides, and the other has one smooth side and one saw-teeth-like side, namely nanosaws. Mechanisms for the longitudinal direction growth of the nanobelts/nanosaws and the side saw-teeth direction growth of the nanosaws are discussed.

  19. Energy levels and zero field splitting parameter for Fe2+ doped in ZnS

    NASA Astrophysics Data System (ADS)

    Ivaşcu, Simona

    2013-11-01

    The aim of present paper is to report the results on the modeling of the crystal field parameters of Fe2+ doped in host matrix ZnS, simulate the energy levels scheme and calculate the zero field splitting parameter D of such system. The crystal field parameters were modeled in the frame of the superposition model of crystal field and the simulation of the energy levels scheme and calculation of the zero field splitting parameters done by diagonalization the Hamiltonian of Fe2+:ZnS system. The obtained results were disscused and compared with experimental data. Satisfactory agreement have been obtained.

  20. Comparison of Toxicity of CdSe: ZnS Quantum Dots on Male Reproductive System in Different Stages of Development in Mice

    PubMed Central

    Amiri, Gholamreza; Valipoor, Akram; Parivar, Kazem; Modaresi, Mehrdad; Noori, Ali; Gharamaleki, Hamideh; Taheri, Jafar; Kazemi, Ali

    2016-01-01

    Background Quantum dots (QDs) are new types of fluorescent materials for biological labeling. QDs toxicity study is an essential requirement for future clinical applications. Therefore, this study aimed to evaluate cytotoxic effects of CdSe: ZnS QDs on male reproductive system. Materials and Methods In this experimental study, the different concentrations of CdSe: ZnS QDs (10, 20 and 40 mg/kg) were injected to 32 male mice (adult group) and 24 pregnant mice (embryo group) on day 8 of gestation. The histological changes of testis and epididymis were studied by a light microscopy, and the number of seminiferous tubules between two groups was compared. One-way analysis of variance (one-way Anova) using the Statistical Package for the Social Sciences (SPSS, SPSS Inc., USA) version 16 were performed for statistical analysis. Results In adult group, histological studies of testis tissues showed a high toxicity of CdSe: ZnS in 40 mg/kg dose followed by a decrease in lamina propria; destruction in interstitial tissue; deformation of seminiferous tubules; and a reduction in number of spermatogonia, spermatocytes, and spermatids. However, there was an interesting result in fetal testis development, meaning there was no significant effect on morphology and structure of the seminiferous tubules and number of sperm stem cells. Also histological study of epididymis tissues in both groups (adult and embryo groups) showed no significant effect on morphology and structure of tubule and epithelial cells, but there was a considerable reduction in number of spermatozoa in the lumen of the epididymal duct in 40 mg/kg dose of adult group. Conclusion The toxicity of QDs on testicular tissue of the mice embryo and adult are different before and after puberty. Due to lack of research in this field, this study can be an introduction to evaluate the toxicity of QDs on male reproduction system in different stages of development. PMID:26985339

  1. Bio-conjugated luminescent quantum dots of doped ZnS: a cyto-friendly system for targeted cancer imaging

    NASA Astrophysics Data System (ADS)

    Manzoor, Koyakutty; Johny, Seby; Thomas, Deepa; Setua, Sonali; Menon, Deepthy; Nair, Shantikumar

    2009-02-01

    A heavy-metal-free luminescent quantum dot (QD) based on doped zinc sulfide (ZnS), conjugated with a cancer-targeting ligand, folic acid (FA), is presented as a promising bio-friendly system for targeted cancer imaging. Doped QDs were prepared by a simple aqueous method at room temperature. X-ray diffraction and transmission electron microscopy studies showed the formation of monodisperse QDs of average size ~4 nm with cubic (sphalerite) crystal structure. Doping of the QDs with metals (Al3+), transition metals (Cu+, Mn2+) and halides (F-) resulted in multi-color emission with dopant-specific color tunability ranging from blue (480 nm) to red (622 nm). Luminescent centers in doped QDs could be excited using bio-friendly visible light >400 nm by directly populating the dopant centers, leading to bright emission. The cytotoxicity of bare and FA conjugated QDs was tested in vitro using normal lung fibroblast cell line (L929), folate-receptor-positive (FR+) nasopharyngeal epidermoid carcinoma cell line (KB), and FR-negative (FR-) lung cancer cell line (A549). Both bare and FA-conjugated ZnS QDs elicited no apparent toxicity even at high concentrations of ~100 µM and 48 h of incubation. In contrast, CdS QDs prepared under identical conditions showed relatively high toxicity even at low concentrations of ~0.1 µM and 24 h of incubation. Interaction of FA-QDs with different cell lines showed highly specific attachment of QDs in the FR+ cancer cell line, leaving others unaffected. The bright and stable luminescence of the QDs could be used to image both single cancer cells and colonies of cancer cells without affecting their metabolic activity and morphology. Thus, this study presents, for the first time, the use of non-toxic, Cd-, Te-, Se-, Pb- and Hg-free luminescent QDs for targeted cancer imaging.

  2. Structural transformations in II-VI semiconductor nanocrystals

    NASA Astrophysics Data System (ADS)

    Ricolleau, C.; Audinet, L.; Gandais, M.; Gacoin, T.

    Colloidal CdS and CdS/ZnS nanostructures were obtained by nucleation and growth in colloidal solution. Their mean sizes range between 3 and 10 nm. The structural properties were studied by the use of high-resolution transmission electron microscopy (HRTEM). Phase transition between the metastable cubic blende-type structure and the stable hexagonal wurtzite-type structure was evidenced to be a function of the size of the CdS clusters. The mechanism of the transition involving stacking faults was determined by the heating of CdS clusters at 200 °C for 30 h. Results concerning structural relations between CdS and ZnS that occur during the epitaxial growth of ZnS on the CdS nanocrystals showed the existence of the hexagonal structure of ZnS, which is the high-temperature phase of ZnS.

  3. Spectral-Kinetic Characteristics of ZnS Phosphors Obtained Using the Method of Vapor Transport Synthesis in a Closed System

    NASA Astrophysics Data System (ADS)

    Zakirov, M. I.; Korotchenkov, O. A.; Kuryliuk, V. V.; Optasyuk, S. V.; Podolyan, A. A.; Semen'ko, M. P.; Tsykanyuk, B. I.

    2016-01-01

    Samples of crystalline ZnS phosphors are obtained using the method of vapor transport synthesis in a closed system. Employing X-ray phase and structural analysis, two types of the resulting sample structures are revealed. The structural composition of 70% sphalerite+30% wurtzite is obtained under the oxygen excess conditions, whereas a nearly pure wurtzite modification is produced in the deficiency of oxygen. The spectral and kinetic characteristics of the two types of samples with the photoluminescence peaks at 510 and 630 nm are studied. These are attributed to the photoluminescence mechanisms involving self-activated oxygen centers and donor-acceptor pairs. The biexponential form of the photoluminescence decay in the two types of samples is observed, related to the presence of electron capture traps near the level of interstitial zinc. The proposed method of vapor transport synthesis of ZnS in a closed system allows simple monitoring of the thermodynamic parameters of the system and provides chemical stability to the initial and final synthesis products.

  4. Multiphonon scattering and photoluminescence of two dimensional ZnS nanosheets grown within Na-4 mica

    NASA Astrophysics Data System (ADS)

    Mandal, Amrita; Mitra, Sreemanta; Datta, Anindya; Banerjee, Sourish; Dhara, Sandip; Chakravorty, Dipankar

    2012-10-01

    Two dimensional wurtzite ZnS nanosheets with thickness of 0.6 nm are grown within the interlayer spaces of sodium fluorophlogopite mica (Na-4 mica) using ion-exchange-cum-solution treatment method followed by sulfidation treatment at 873 K. The presence of wurtzite ZnS is confirmed by x-ray diffraction, electron microscopy, and Raman scattering studies. The two dimensional form of ZnS gives rise to a strong quantum confinement with the band gap blue shifted by 1.7 eV. Thickness of the nanosheet is confirmed using atomic force microscopy. Raman scattering studies show higher order transverse optical modes due to increased deformation potential in reduced dimension. In contrast to red shift of optical phonon modes in phonon confinement model, a blue shift observed is ascribed to a compressive stress on ZnS nanosheets grown within Na-4 mica interlayer spaces. An additional band at 315 cm-1 is assigned to surface optical phonon. Unusual broadening in room temperature photoluminescence spectrum may be due to strong coupling of excitons with overtones of longitudinal optical phonon modes.

  5. Spray pyrolysis synthesis of ZnS nanoparticles from a single-source precursor.

    PubMed

    Liu, Sha; Zhang, Hongwang; Swihart, Mark T

    2009-06-10

    ZnS, a II-VI semiconductor with a relatively high direct bandgap (approximately 3.6 eV) in the near-UV region, has potential applications in areas such as solar cells, lasers and displays. In addition, ZnS nanoparticles can be applied as phosphors, probes for bioimaging, emitters in light emitting diodes and photocatalysts. Here, we report synthesis of cubic ZnS nanoparticles from a low-cost single-source precursor in a continuous spray pyrolysis reactor. In this approach, the evaporation and decomposition of precursor and nucleation of particles occur sequentially. Product particles were characterized by HRTEM, XRD, and EDX. Particles with diameters ranging from 2 to 7 nm were produced. HF was used to remove ZnO impurities and other surface contamination. As-synthesized ZnS nanoparticles exhibit blue photoluminescence near 440 nm under UV excitation and have quantum yields up to 15% after HF treatment. This demonstrates a potentially general approach for continuous low-cost synthesis of semiconductor quantum dots for applications where tight control of the size distribution is less important than scalable, economical production.

  6. Scalable production of microbially-mediated ZnS nanoparticles and application to functional thin films

    SciTech Connect

    Moon, Ji Won; Ivanov, Ilia N; Joshi, Pooran C; Armstrong, Beth L; Wang, Wei; Jung, Hyunsung; Rondinone, Adam Justin; Jellison Jr, Gerald Earle; Meyer III, Harry M; Jang, Gyoung Gug; Meisner, Roberta; Duty, Chad E; Phelps, Tommy Joe

    2014-01-01

    A series of semiconducting zinc sulfide (ZnS) nanoparticles were scalably, reproducibly, controllably, and economically synthesized with anaerobic metal-reducing Thermoanaerobacter species. They reduced partially oxidized sulfur sources to sulfides that extracellularly and thermodynamically incorporated with zinc ions to produce sparingly soluble ZnS nanoparticles with ~5 nm crystallites at yields of ~5 g l 1 month 1. A predominant sphalerite formation was facilitated by rapid precipitation kinetics, low cation/anion ratio, higher zinc concentration, water stabilization, or some combination of the four. The sphalerite ZnS nanoparticles exhibited narrow size distribution, high emission intensity, and few native defects. Scale-up and emission tunability using copper-doping were confirmed spectroscopically. Surface characterization was determined using Fourier transform infrared and X-ray photoelectron spectroscopies, which confirmed amine and carboxylic acid not only maintaining a nano-dimensional average crystallite size, but also increasing aggregation. Application of ZnS nanoparticle ink to a functional thin film was successfully tested for potential future applications.

  7. Electron capture processes in ZnS: The role of Al related and other donors

    NASA Astrophysics Data System (ADS)

    Przybylińska, H.; Godlewski, M.

    1986-12-01

    A transient electron spin resonance experiment shows that the Al-related donor in ZnS plays an insignificant role in electron-capture processes, which are dominated by a 35-meV native donor of unknown nature. The methods of determining effective capture cross sections of these donors are discussed.

  8. Highly porous ZnS microspheres for superior photoactivity after Au and Pt deposition and thermal treatment

    SciTech Connect

    Singla, Shilpa; Pal, Bonamali

    2013-11-15

    Graphical abstract: Highly porous ZnS microsphere of size 2–5 μm having large surface area ca. 173.14 m{sup 2} g{sup −1} exhibits superior photocatalytic activity for the oxidation of 4-nitrophenol under UV light irradiation. The rate of photooxidation has been significantly improved by Au and Pt deposition and after sintering, respectively, due to rapid electron acceptance by metal from photoexcited ZnS and growth of crystalline ZnS phase. - Highlights: • Photoactive ZnS microsphere of size 2–5 μm was prepared by hydrothermal route. • Highly porous cubic spherical ZnS crystals possess a large surface area, 173 m{sup 2} g{sup −1}. • 1 wt% Au and Pt photodeposition highly quenched the photoluminescence at 437 nm. • Sintering and metal loading notably improve the photooxidation rate of 4-nitrophenol. • Pt co-catalyst always exhibits superior photoactivity of ZnS microsphere than Au. - Abstract: This work highlights the enhanced photocatalytic activity of porous ZnS microspheres after Au and Pt deposition and heat treatment at 500 °C for 2 h. Microporous ZnS particles of size 2–5 μm with large surface area 173.14 m{sup 2} g{sup −1} and pore volume 0.0212 cm{sup 3} g{sup −1} were prepared by refluxing under an alkaline medium. Photoluminescence of ZnS at 437 nm attributed to sulfur or zinc vacancies were quenched to 30% and 49%, respectively, after 1 wt% Au and Pt loading. SEM images revealed that each ZnS microparticle consist of several smaller ZnS spheres of size 2.13 nm as calculated by Scherrer's equation. The rate of photooxidation of 4-nitrophenol (10 μM) under UV (125 W Hg arc–10.4 mW/cm{sup 2}) irradiation has been significantly improved by Au and Pt deposition followed by sintering due to better electron capturing capacity of deposited metals and growth of crystalline ZnS phase with less surface defects.

  9. Fast imaging of eccrine latent fingerprints with nontoxic Mn-doped ZnS QDs.

    PubMed

    Xu, Chaoying; Zhou, Ronghui; He, Wenwei; Wu, Lan; Wu, Peng; Hou, Xiandeng

    2014-04-01

    Fingerprints are unique characteristics of an individual, and their imaging and recognition is a top-priority task in forensic science. Fast LFP (latent fingerprint) acquirement can greatly help policemen in screening the potential criminal scenes and capturing fingerprint clues. Of the two major latent fingerprints (LFP), eccrine is expected to be more representative than sebaceous in LFP identification. Here we explored the heavy metal-free Mn-doped ZnS quantum dots (QDs) as a new imaging moiety for eccrine LFPs. To study the effects of different ligands on the LFP image quality, we prepared Mn-doped ZnS QDs with various surface-capping ligands using QDs synthesized in high-temperature organic media as starting material. The orange fluorescence emission from Mn-doped ZnS QDs clearly revealed the optical images of eccrine LFPs. Interestingly, N-acetyl-cysteine-capped Mn-doped ZnS QDs could stain the eccrine LFPs in as fast as 5 s. Meanwhile, the levels 2 and 3 substructures of the fingerprints could also be simultaneously and clearly identified. While in the absence of QDs or without rubbing and stamping the finger onto foil, no fluorescent fingerprint images could be visualized. Besides fresh fingerprint, aged (5, 10, and 50 days), incomplete eccrine LFPs could also be successfully stained with N-acetyl-cysteine-capped Mn-doped ZnS QDs, demonstrating the analytical potential of this method in real world applications. The method was also robust for imaging of eccrine LFPs on a series of nonporous surfaces, such as aluminum foil, compact discs, glass, and black plastic bags.

  10. Cu2ZnSnS4 thin films obtained by sulfurization of evaporated Cu2SnS3 and ZnS layers: Influence of the ternary precursor features

    NASA Astrophysics Data System (ADS)

    Robles, V.; Guillén, C.; Trigo, J. F.; Herrero, J.

    2017-04-01

    Cu2ZnSnS4 (CZTS) thin films have been grown by sulfurization of Cu2SnS3 (CTS) and ZnS layers evaporated on glass substrates. Four CTS precursor films have been tested, with two different atomic compositions (Cu/Sn = 1.7 and Cu/Sn = 2.1) and substrate temperatures (350 and 450 °C), together with analogous ZnS layers deposited by maintaining the substrate at 200 °C. The sulfurization of the CTS and ZnS stacked layers was performed at 500 °C during 1 h. The evolution of the crystalline structure, morphology, optical and electrical properties from each CTS precursor to the CZTS compound has been studied, especially the influence of the ternary precursor features on the quaternary film characteristics. The kesterite structure has been identified after sulfurization of the various samples, with main (112) orientation and mean crystallite sizes S112 = 40-56 nm, being higher for the Cu-poor compositions. The CZTS average roughness has varied in a wide interval Ra = 8-66 nm, being directly related to the CTS precursor layer, which becomes rougher for a higher deposition temperature or Cu content. Besides, the band gap energy and the electrical resistivity of the CZTS films have changed in the ranges Eg = 1.54-1.64 eV and ρ = 0.2-40 Ωcm, both decreasing when the Cu content and/or the surface roughness increase.

  11. ZnS nanoparticles electrodeposited onto ITO electrode as a platform for fabrication of enzyme-based biosensors of glucose.

    PubMed

    Du, Jian; Yu, Xiuping; Wu, Ying; Di, Junwei

    2013-05-01

    The electrochemical and photoelectrochemical biosensors based on glucose oxidase (GOD) and ZnS nanoparticles modified indium tin oxide (ITO) electrode were investigated. The ZnS nanoparticles were electrodeposited directly on the surface of ITO electrode. The enzyme was immobilized on ZnS/ITO electrode surface by sol-gel method to fabricate glucose biosensor. GOD could electrocatalyze the reduction of dissolved oxygen, which resulted in a great increase of the reduction peak current. The reduction peak current decreased linearly with the addition of glucose, which could be used for glucose detection. Moreover, ZnS nanoparticles deposited on ITO electrode surface showed good photocurrent response under illumination. A photoelectrochemical biosensor for the detection of glucose was also developed by monitoring the decreases in the cathodic peak photocurrent. The results indicated that ZnS nanoparticles deposited on ITO substrate were a good candidate material for the immobilization of enzyme in glucose biosensor construction.

  12. Two and four photon absorption and nonlinear refraction in undoped, chromium doped and copper doped ZnS quantum dots

    NASA Astrophysics Data System (ADS)

    Sharma, Dimple; Malik, B. P.; Gaur, Arun

    2015-12-01

    The ZnS quantum dots (QDs) with Cr and Cu doping were synthesized by chemical co-precipitation method. The nanostructures of the prepared undoped and doped ZnS QDs were characterized by UV-vis spectroscopy, Transmission electron microscopy (TEM) and X-ray diffraction (XRD). The sizes of QDs were found to be within 3-5 nm range. The nonlinear parameters viz. Two photon absorption coefficient (β2), nonlinear refractive index (n2), third order nonlinear susceptibility (χ3) at wavelength 532 nm and Four photon absorption coefficient (β4) at wavelength 1064 nm have been calculated by Z-scan technique using nanosecond Nd:YAG laser in undoped, Cr doped and Cu doped ZnS QDs. Higher values of nonlinear parameters for doped ZnS infer that they are potential material for the development of photonics devices and sensor protection applications.

  13. Optical and electrical properties of copper-incorporated ZnS films applicable as solar cell absorbers

    NASA Astrophysics Data System (ADS)

    Mehrabian, M.; Esteki, Z.; Shokrvash, H.; Kavei, G.

    2016-10-01

    Un-doped and Cu-doped ZnS (ZnS:Cu) thin films were synthesized by Successive Ion Layer Absorption and Reaction (SILAR) method. The UV-visible absorption studies have been used to calculate the band gap values of the fabricated ZnS:Cu thin films. It was observed that by increasing the concentration of Cu2+ ions, the Fermi level moves toward the edge of the valence band of ZnS. Photoluminescence spectra of un-doped and Cu-doped ZnS thin films was recorded under 355 nm. The emission spectrum of samples has a blue emission band at 436 nm. The peak positions of the luminescence showed a red shift as the Cu2+ ion concentration was increased, which indicates that the acceptor level (of Cu2+) is getting close to the valence band of ZnS.

  14. Observation of nonlinear absorption and visible photoluminescence emission in chemically synthesized Cu2+ doped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Kole, A. K.; Kumbhakar, P.; Chatterjee, U.

    2012-01-01

    Nonlinear optical properties of chemically synthesized ZnS and Cu2+ doped ZnS nanoparticles of average sizes ˜2.5 nm are reported by using open aperture z-scan technique with the Nd:YAG laser second harmonic radiation at 532 nm. Tunable photoluminescence emissions in the visible region due to the increase in concentration of Cu2+ doping in ZnS are observed at room temperature. By analyzing the experimental z-scan data, it is found that three photon absorptions (3PA) are taking place in all the samples. The extracted values of 3PA coefficients of the samples are ˜109 times higher than that of bulk ZnS.

  15. Unique oxide overcoating of CuInS2/ZnS core/shell quantum dots with ZnGa2O4 for fabrication of white light-emitting diode with improved operational stability

    NASA Astrophysics Data System (ADS)

    Song, Woo-Seuk; Jang, Eun-Pyo; Kim, Jong-Hoon; Jang, Ho Seong; Yang, Heesun

    2013-02-01

    CuInS2 quantum dots (QDs) have been recently highlighted as blue-to-yellow color converters for the demonstration of QD-based white light-emitting diodes (LEDs) owing to their advantageous fluorescent attributes including a broadband yellow emission and exceptional quantum yield. Similar to other types of elaborate core/shell structured QDs, however, core/shell QDs of CuInS2/ZnS are also susceptible to the photo-induced degradation, rendering them inappropriate for the practical application to high operational stability white LED. In this study, CuInS2/ZnS QDs are overcoated with the unprecedented oxide phase of ZnGa2O4 to enhance their photostability, and the resulting CuInS2/ZnS/ZnGa2O4 QDs are characterized with X-ray diffraction and transmission electron microscope. The operational stability test of CuInS2/ZnS/ZnGa2O4 QD-based white LED is performed and compared with that of uncoated CuInS2/ZnS QD-based one, and the efficacy of ZnGa2O4 overlayer is proved in mitigating the photodegradation of QDs and thus improving the device stability.

  16. Synthesis, Surface Modification and Optical Properties of Thioglycolic Acid-Capped ZnS Quantum Dots for Starch Recognition at Ultralow Concentration

    NASA Astrophysics Data System (ADS)

    Tayebi, Mahnoush; Tavakkoli Yaraki, Mohammad; Ahmadieh, Mahnaz; Mogharei, Azadeh; Tahriri, Mohammadreza; Vashaee, Daryoosh; Tayebi, Lobat

    2016-11-01

    In this research, water-soluble thioglycolic acid-capped ZnS quantum dots (QDs) are synthesized by the chemical precipitation method. The prepared QDs are characterized using x-ray diffraction and transmission electron microscopy. Results revealed that ZnS QDs have a 2.73 nm crystallite size, cubic zinc blende structure, and spherical morphology with a diameter less than 10 nm. Photoluminescence (PL) spectroscopy is performed to determine the presence of low concentrations of starch. Four emission peaks are observed at 348 nm, 387 nm, 422 nm, and 486 nm and their intensities are quenched by increasing concentration of starch. PL intensity variations in the studied concentrations range (0-100 ppm) are best described by a Michaelis-Menten model. The Michaelis constant ( K m) for immobilized α-amylase in this system is about 101.07 ppm. This implies a great tendency for the enzyme to hydrolyze the starch as substrate. Finally, the limit of detection is found to be about 6.64 ppm.

  17. Magic sized ZnS quantum dots as a highly sensitive and selective fluorescence sensor probe for Ag+ ions.

    PubMed

    Mandal, Abhijit; Dandapat, Anirban; De, Goutam

    2012-02-07

    A green and simple chemical synthesis of magic sized water soluble blue-emitting ZnS quantum dots (QDs) has been accomplished by reacting anhydrous Zn acetate, sodium sulfide and thiolactic acid (TLA) at room temperature in aqueous solution. Refluxing of this mixture in open air yielded ZnS clusters of about 3.5 nm in diameter showing very strong and narrow photoluminescence properties with long stability. Refluxing did not cause any noticeable size increment of the clusters. As a result, the QDs obtained after different refluxing conditions showed similar absorption and photoluminescence (PL) features. Use of TLA as a capping agent effectively yielded such stable and magic sized QDs. The as-synthesized and 0.5 h refluxed ZnS QDs were used as a fluorescence sensor for Ag(+) ions. It has been observed that after addition of Ag(+) ions of concentration 0.5-1 μM the strong fluorescence of ZnS QDs was almost quenched. The quenched fluorescence can be recovered by adding ethylenediamine to form a complex with Ag(+) ions. The other metal ions (K(+), Ca(2+), Au(3+), Cu(2+), Fe(3+), Mn(2+), Mg(2+), Co(2+)) showed little or no effect on the fluorescence of ZnS QDs when tested individually or as a mixture. In the presence of all these ions, Ag(+) responded well and therefore ZnS QDs reported in this work can be used as a Ag(+) ion fluorescence sensor.

  18. Light-activated NO2 gas sensing of the networked CuO-decorated ZnS nanowire gas sensor

    NASA Astrophysics Data System (ADS)

    Park, Sunghoon; Sun, Gun-Joo; Kheel, Hyejoon; Ko, Taegyung; Kim, Hyoun Woo; Lee, Chongmu

    2016-05-01

    CuO-decorated ZnS nanowires were synthesized by the thermal evaporation of ZnS powders followed by a solvothermal process for CuO decoration. The NO2 gas sensing properties of multiple-networked pristine and CuO-decorated ZnS nanowire sensors were then examined. The diameters of the CuO nanoparticles ranged from 20 to 60 nm. The multiple-networked pristine and CuO-decorated ZnS nanowire sensors showed the responses of 394 and 1055 %, respectively, to 5 ppm of NO2 at room temperature under UV illumination at 2.2 mW/cm2. The response and recovery times of the ZnS nanowire sensor to 5 ppm of NO2 were also reduced by decoration with the CuO nanoparticles. The responses of the sensors to NO2 at room temperature increased significantly with increasing UV illumination intensity. The underlying mechanisms for the enhanced response of the ZnS nanowire sensor to NO2 gas by CuO decoration and UV irradiation are discussed.

  19. Synthesis, COSMO-RS analysis and optical properties of surface modified ZnS quantum dots using ionic liquids

    NASA Astrophysics Data System (ADS)

    Shahid, Robina; Muhammad, Nawshad; Gonfa, Girma; Toprak, Muhammet S.; Muhammed, Mamoun

    2015-10-01

    Zinc sulfide (ZnS) quantum dots (QDs) were synthesized using the microwave assisted ionic liquid (MAIL) route. Three ionic liquids (ILs), namely, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4]), trihexyl(tetradecyl) phosphonium bis(trifluoromethanesulfonyl) amide ([P6,6,6,14][TSFA]) and trihexyl(tetradecyl) phosphonium chloride ([P6,6,6,14][Cl]) were used in this study. The size and structure of the QDs were characterized by high-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED) pattern, respectively. The synthesized QDs were of wurtzite crystalline structure with size less than 5 nm. The QDs were more uniformly distributed while using the phosponium based ILs as a reaction medium during synthesis. The optical properties were investigated by UV-vis absorption and photoluminescence (PL) emission spectroscopy. The optical properties of QDs showed the quantum confinement effect in their absorption and the effect of cation and anion structural moiety was observed on their bandedge emission. The QDs emission intensity was measured higher for [P6,6,6,14][Cl] due to their better dispersion as well as high charge density of Cl anion. The capability of the ILs in stabilizing the QDs was interpreted by density functional theory (DFT) computations. The obtained results are in good agreement with the theoretical prediction.

  20. Mechanisms of the degradation of Schottky-barrier photodiodes based on ZnS single crystals

    SciTech Connect

    Korsunska, N. E.; Shulga, E. P.; Stara, T. R. Litvin, P. M.; Bondarenko, V. A.

    2016-01-15

    The effect of ultraviolet (UV) illumination on the electrical and spectral characteristics of Schottky-barrier photodiodes based on ZnS single crystals is studied. It is found that irradiation deteriorates their photosensitivity and changes the current–voltage and capacitance–voltage characteristics and the surface profile of the blocking electrode. It is shown that the main reason for a decrease in the photosensitivity of the diodes is the photoinduced drift of mobile donors in the electric field of the barrier. This drift depends on the crystallographic orientation of the surface being irradiated. Another photoinduced process observed in the diodes is photolysis of the ZnS crystal. This process mainly determines the change in the electrical characteristics of the diodes and in the surface profile of the electrode at an insignificant change in the photosensitivity.

  1. Site spectroscopy of Eu3+ doped- ZnS nanocrystals embedded in sodium carboxymethyl cellulose matrix

    NASA Astrophysics Data System (ADS)

    Ahemen, I.; Meludu, O.; Dejene, F. B.; Viana, B.

    2016-11-01

    The work investigates the incorporation of Eu3+ ion in ZnS crystal through spectroscopic studies. ZnS: Eu3+ nanocrystals was synthesized via the precipitation technique. Elemental composition analysis indicates a non-stoichiometric distribution between Zn and S. X-ray diffraction studies show lattice expansion demonstrating that Eu3+ ions were incorporated in the host lattice. Annealing temperature gave rise to lattice contraction relative to the as-synthesized indicating a partial expulsion of the ion from the crystal due to heat treatment. Eu3+ ions site symmetry probing from optical features show that trivalent europium were situated both at the nanocrystals surface and at the Zn2+ ion site. Weak energy transfer from host to activator ion occurred probably mainly through exchange interaction and the transfer process was defect mediated.

  2. Optical nonlinear dynamics in ZnS from femtosecond laser pulses

    SciTech Connect

    Wu, Yu-E; Ren, Mengxin Wang, Zhenhua; Li, Wenhua; Wu, Qiang; Zhang, Xinzheng Xu, Jingjun; Yi, Sanming

    2014-05-15

    A wavelength swapping nondegenerate pump-probe technique to measure the magnitudes of the nonlinear optical dynamics as well as the relaxation time of electrons in high energy levels is presented using a ZnS single crystal wafer as an example. By pumping the sample with 800 nm femtosecond pulses and probing at 400 nm, nondegenerate two-photon absorption (N-2PA) happens exclusively, and the measured curves only show instantaneous features without relaxation tails. The N-2PA coefficient was derived explicitly as 7.52 cm/GW. Additionally, when the wavelengths of the pump and probe beams are swapped, extra information about the relaxation time of the hot electrons excited in the conduction band is obtained. The combined results above are helpful for evaluating the characteristics of an optical switches based on ZnS or other materials with respect to its nonlinear optical dynamic aspect.

  3. The Cathodoluminescence of Cleartran: A Novel Form of Polycrystalline ZnS.

    DTIC Science & Technology

    1986-12-01

    Theory and Summary of Previous Work. . . . . . . 11 Crystallography of ZnS . . . . . . . . . . . . 11 Crystal Growth Techniques. . . . . . . . . . . 15...perceived that his crystals were phosphorescent. It was not until 1888 that Verneuil ascribed the phosphorescence to the presence of a "foreign...photoconductivity studies of CdS (3). At that time, crystal growth techniques began to improve and single crystals of a variety of II-VI compounds became

  4. Analysis of thermal shock resistance of CVD ZnS dome

    NASA Astrophysics Data System (ADS)

    Zhang, Daijun; Luo, Haibo; Zhou, Peipei; Hou, Xinglin

    2016-10-01

    Since the dome experiences the convective heat loading, thermal stress will be generated in the thickness direction. Thus, estimation of the thermal shock and analysis of the thermal shock resistance of the dome are the key to the design of the dome. In this paper, thermal shock resistance of CVD ZnS dome is analysed based on the flight condition of 6000m altitude and 3.0 Mach. We obtained the critical Reynolds number through a rockets pry experiment, which deduced that there exists a transition from laminar flow to turbulent flow at somewhere over the dome. We calculated the heat transfer coefficient over dome through heat transfer coefficient engineering formula of high-speed sphere with turbulent boundary layer near the stagnation point. The largest heat transfer coefficient is 2590W/(m2.K). Then, we calculated the transient thermal stress of dome by using the finite element method. Then we obtained the temperature and thermal stress distribution of different time through the direction of thickness. In order to obtain the mechanical properties of CVD ZnS at high temperatures, the 3-point bending method was used to test the flexure strength of CVD ZnS at different temperature. When compared the maximum thermal stress with flexure strength at different temperature, we find that the safety factors were not less than 1.75. The result implied that the dome has good safety margin under the proposed application condition. Through the above test and analysis, we can get the conclusion that the thermal shock resistance of the CVD ZnS dome satisfied the requirements of flight conditions.

  5. Synthesis, characterization and optical properties of polymer-based ZnS nanocomposites.

    PubMed

    Tiwari, A; Khan, S A; Kher, R S; Dhoble, S J; Chandel, A L S

    2016-03-01

    Nanostructured polymer-semiconductor hybrid materials such as ZnS-poly(vinyl alcohol) (ZnS-PVA), ZnS-starch and ZnS-hydroxypropylmethyl cellulose (Zns-HPMC) are synthesized by a facile aqueous route. The obtained nanocomposites are characterized using various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV/vis spectroscopy and photoluminescence (PL). XRD studies confirm the zinc blende phase of the nanocomposites and indicate the high purity of the samples. SEM studies indicate small nanoparticles clinging to the surface of a bigger particle. The Energy Dispersive Analysis by X-rays (EDAX) spectrum reveals that the elemental composition of the nanocomposites consists primarily of Zn:S. FTIR studies indicate that the polymer matrix is closely associated with ZnS nanoparticles. The large number of hydroxyl groups in the polymer matrix facilitates the complexation of metal ions. The absorption spectra of the specimens show a blue shift in the absorption edge. The spectrum reveals an absorption edge at 320, 310 and 325 nm, respectively. PL of nanocomposites shows broad peaks in the violet-blue region (420-450 nm). The emission intensity changes with the nature of capping agent. The PL intensity of ZnS-HPMC nanocomposites is found to be highest among the studied nanocomposites. The results clearly indicate that hydroxyl-functionalized HPMC is much more effective at nucleating and stabilizing colloidal ZnS nanoparticles in aqueous suspensions compared with PVA and starch.

  6. Electroluminescence spectra of rare-earth-doped ZnS 1-XSe X thin films

    NASA Astrophysics Data System (ADS)

    Miura, Noboru; Ogawa, Kiyoshi; Kobayashi, Shuko; Matsumoto, Hironaga; Nakano, Ryotaro

    1994-04-01

    Electroluminescence has been measured for ZnS 1- XSe X thin films doped with rare-earth ions. As X increases the band-gap energy of the host decreases. The emission levels of trivalent rare-earth ions are not observed when the band-gap energy is narrower than the excitation levels. This is because of the energy transfer between the host and the emission center.

  7. Microphysics of KCl and ZnS Clouds on GJ 1214 b

    NASA Astrophysics Data System (ADS)

    Gao, Peter; Benneke, Björn

    2016-10-01

    Clouds are ubiquitous in the atmospheres of exoplanets. However, as most of these planets have temperatures between 600 and 2000 K, their clouds are likely composed of exotic condensates such as salts, sulfides, silicates, and metals. Treatment of these clouds in current exoplanet atmosphere models do not consider the microphysical processes that govern their formation, evolution, and distribution, such as nucleation and condensation/evaporation, thus creating a gulf between the cloud properties retrieved from observations and the cloud composition predictions from condensation equilibrium models. In this work, we apply a 1D microphysical cloud model to GJ 1214 b and investigate the properties of potassium chloride (KCl) and zinc sulfide (ZnS) clouds as a function of atmospheric metallicity, the intensity of vertical mixing, and the mode of nucleation. Our cloud model has been widely applied to planets in our own Solar System, and as such our work bridges a gap between planetary science and exoplanets. Using model background atmospheres calculated by the SCARLET code, we find that (1) the cloud distribution is not significantly affected by metallicity unless [Fe/H] > 2, (2) higher intensities of vertical mixing leads to more extended cloud decks, more cloud particles at all altitudes, and smaller mean particle radii, (3) the high surface energy of solid ZnS prevents the homogeneous nucleation of pure ZnS cloud particles, such that KCl clouds dominate; solid ZnS can only manifest by nucleating onto pre-existing surfaces (heterogeneous nucleation), such as KCl cloud particles, resulting in mixed clouds, and (4) formation of KCl clouds results in a KCl vapor abundance above the cloud deck ~5 orders of magnitude less than that calculated from equilibrium chemistry. We also examine the transmission spectra that would result from these different cases. Extension of this model to other planets and condensates will shed light on the observed continuum in the "cloudiness

  8. Synthesis, structural, optical and photocatalytic properties of CdS/ZnS core/shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Reddy, Ch. Venkata; Shim, Jaesool; Cho, Migyung

    2017-04-01

    CdS, ZnS and CdS/ZnS core/shell nanoparticles were successfully synthesized via two-step synthesis method. The as-prepared CdS, ZnS and CdS/ZnS core/shell nanoparticles were used to study the structural, morphological, and optical properties by PXRD, TEM, HRTEM, UV-vis spectroscopy, N2 adsorption-desorption, FT-IR, PL and Raman spectroscopy measurements. The XRD pattern confirms the crystal structure of the prepared ZnS, CdS, and CdS/ZnS core/shell nanoparticles. The crystallinity of the as-prepared samples is confirmed by PXRD, TEM and HRTEM analysis. The BET analysis showed that the CdS/ZnS core/shell nanoparticles had larger surface area and pore diameter than CdS and ZnS. The Raman and FT-IR spectra confirm the fundamental vibrational modes of CdS and ZnS respectively. Compared to pure CdS and ZnS, CdS/ZnS core/shell nanoparticles exhibited higher photocatalytic activity for the degradation of methyl orange (MO). The enhancement of photocatalytic activity in the CdS/ZnS core/shell nanoparticles is due to the interface actions between CdS and ZnS, which greatly reduces the recombination of photogenerated electrons-holes pair. The proposed mechanism for degradation of MO dye is discussed in detail.

  9. Model-free transformation kinetics for ZnS quantum dots synthesized via colloidal reaction

    NASA Astrophysics Data System (ADS)

    Mansour, Sh. A.; Al-Kotb, M. S.; Kotkata, M. F.

    2014-01-01

    Zinc sulfide (ZnS) quantum dots (QDs) were prepared by a simple non-toxic colloidal reaction of zinc acetate dehydrate and sodium sulfate in the presence of sodium dodecyl sulfate (SDS) acting as an anionic coordinated capping material. Differential scanning calorimetry (DSC) measurements for the synthesized ZnS QDs were carried out at various heating rates. The recorded DSC curves exhibit overlapped exothermic peaks accomplishing several nano-sizes groups of the synthesized single-compositional ZnS cubic phase. The temperature at maximum rate of transformation for the main exothermic peak exhibits a monotonic shift to higher temperatures (324-388 °C) as the heating rate increased from 5 °C/min to 30 °C/min, suggesting that the growth process has a kinetic effect. The kinetics of such non-isothermal growth process was studied by applying a model-free isoconversional approach. The obtained values of the activation energy and reaction mode were used to identify the growth mechanism.

  10. Mechano-chemical synthesis and optical properties of ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Pathak, C. S.; Agarwala, V.; Mandal, M. K.

    2012-09-01

    In the present work, we report the synthesis and optical properties of ZnS nanoparticles produced by the mechano-chemical route. We used zinc acetate and sodium sulphide as source materials in a high energy planetary ball mill at rotation speed of 300 rpm and vial rotation speed of 600 rpm with ball to powder (BPR or charge ratio CR) 5:1 for 30 and 90 min. The milled powders were washed with methanol to remove impurity and dried at 300 °C for 1 h. The prepared nanoparticles have been characterized using X-ray diffraction (XRD), Field emission scanning electron microscope (FESEM), UV-vis-NIR spectrophotometer and Fluorescence spectroscopy. The crystallite size of the synthesized ZnS nanoparticles is found to be in the range 7-8 nm which was calculated using Debye-Scherer's formula. The value of optical band gap has been found to be in the range 3.80-4.15 eV. Room temperature photoluminescence (PL) spectrum of ZnS samples exhibit a blue emission peaked at 466 nm under UV excitation.

  11. Local defect-induced red-shift of cathodoluminescence in individual ZnS nanobelts.

    PubMed

    Liu, B D; Yang, B; Dierre, B; Sekiguchi, T; Jiang, X

    2014-11-07

    The luminescence of semiconductor nanostructures is strongly dependent on their size, dimensions, morphology, composition, or defects, and their band emissions can be properly and selectively tailored through the rational manipulation of these parameters during material growth. Using spatially-resolved cathodoluminescence spectroscopy, monochromatic contrast maps and high-resolution transmission electron microscopy, an obvious red-shift of the near-band-edge emission of wurtzite ZnS nanobelts, resulting from a strip of stacking faults or a zinc-blende phase with tens of atomic layers in width, has been observed and its related mechanism has been discussed. This finding is not specific to the defect-dependent optical properties tailoring of ZnS nanostructures and represents a general validity for clarifying the mechanism of peak-shift (band-gap expansion or shrinking) of a wide range of semiconductor nanostructures with various defects. In addition, the general formation mechanism of the belt-like nanostructure was proposed based on precise microstructure analyses on a ZnS nanobelt with atomic terrace growth fronts.

  12. Sulfur L{sub 2,3} soft-x-ray fluorescence of CdS and ZnS

    SciTech Connect

    Zhou, L.; Callcott, T.A.; Jia, J.J.

    1997-04-01

    The II-VI sulfur compounds CdS and ZnS have important electro-optics applications. In addition, they have well characterized and relatively simple structures so that they are good candidates for theoretical model development in solid-state physics. Some experimental results on density of states have been reported, mostly determined from photoemission measurements, and theoretical calculations are available for both materials. Nevertheless the electronic properties of these elements are still not completely understood. It has been established that the d-bands, derived from Cd or Zn, lie in a subband gap between a lower valence band (LVB) derived from the S 3s orbital and an upper valence band (UVB) derived from the 3p states of S and the 4(3)s states of Cd(Zn). The locations of these bands within the gap disagree with the best available calculations, however. The principal problem is that experimental photoemission measurements locate the d-bands about 2 eV lower in the band gap than the best available calculations. Some authors argue that the hole in the d-band in the final state of the photoemission process increases the binding of the d-electrons. In any case, band gaps, band widths and the precise location of d-bands are important parameters for comparing experiment and theory, and no current calculations give good agreement with all of these parameters. Moreover, photoemission data does not adequately define all of these experimental parameters, because the d-state photoemission dominates that from s and p states and sample charging effects can modify the energy of emitted electrons. The authors report photon excited soft x-ray fluorescence (SXF) S L{sub 2,3} spectra from CdS and ZnS. Using excitation between the L{sub 2} and L{sub 3} thresholds, the L{sub 2} spectrum is suppressed, which permits the authors to accurately determine features of the UVB and LVB as well as the placement of the Cd(Zn) d-bands between the UVB and LVB.

  13. Core-satellite ZnS-Ag nanoassemblies: Synthesis, structure, and optical properties.

    PubMed

    Rohani, Parham; Sharma, Munish K; Swihart, Mark T

    2016-02-01

    We synthesized hollow core-satellite nanoassemblies comprised of hollow zinc sulfide (ZnS) shells decorated with silver nanoparticles (Ag NPs). This was achieved by solution-phase attachment of Ag NPs to hollow ZnS nanospheres (NSs) prepared by spray pyrolysis. This produces an aqueous dispersion of ZnS-Ag hybrid structures, 50-500nm in overall diameter. We characterized the nanostructures by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and energy dispersive X-ray spectroscopy (EDX) to elucidate the ZnS (core)-Ag (satellite) morphology and optimize conditions for producing such structures. Optical spectroscopy showed that photoluminescence of ZnS was quenched by Ag while absorbance was enhanced. This work provides a simple and general means of producing hollow core-satellite structures that could be of broad applicability.

  14. Synthesis and characterization of samarium-doped ZnS nanoparticles: A novel visible light responsive photocatalyst

    SciTech Connect

    Hanifehpour, Younes; Soltani, Behzad; Amani-Ghadim, Ali Reza; Hedayati, Behnam; Khomami, Bamin; Joo, Sang Woo

    2016-04-15

    Highlights: • Sm-doped ZnS Nanomaterials were synthesized by hydrothermal method. • The as-prepared compounds were characterized by XRD, TEM, XPS, SEM and UV techniques. • The photocatalytic effect of compounds was determined by Reactive Red 43 degradation. • The degradation of RRed 43 followed the Langmuir–Hinshelwood kinetic model. - Abstract: We prepared pure and samarium-doped ZnS (Sm{sub x}Zn{sub 1−x}S{sub 1+0.5x}) nanoparticles via hydrothermal process at 160 °C for 24 h. XRD analysis shows that the particles were well crystallized and corresponds to a cubic sphalerite phase. SEM and TEM images indicate that the sizes of the particles were in the range of 20–60 nm. The photocatalytic activity of Sm-doped ZnS nanoparticles was evaluated by monitoring the decolorization of Reactive Red 43 in aqueous solution under visible light irradiation. The color removal efficiency of Sm{sub 0.04}Zn{sub 0.96}S and pure ZnS was 95.1% and 28.7% after 120 min of treatment, respectively. Among the different amounts of dopant agent used, 4% Sm-doped ZnS nanoparticles indicated the highest decolorization. We found that the presence of inorganic ions such as Cl{sup −}, CO{sub 3}{sup 2−} and other radical scavengers such as buthanol and isopropyl alcohol reduced the decolorization efficiency.

  15. Correlation between the band gap, elastic modulus, Raman shift and melting point of CdS, ZnS, and CdSe semiconductors and their size dependency

    NASA Astrophysics Data System (ADS)

    Yang, C.; Zhou, Z. F.; Li, J. W.; Yang, X. X.; Qin, W.; Jiang, R.; Guo, N. G.; Wang, Y.; Sun, C. Q.

    2012-02-01

    With structural miniaturization down to the nanoscale, the detectable quantities of solid materials no longer remain constant but become tunable. For the II-VI semiconductors example, the band gap expands, the elastic modulus increases, the melting point drops, and the Raman optical phonons experience red shift associated with creation of low frequency Raman acoustic modes that undergo blue shift with decreasing the dimensional scale. In order to understand the common origin of the size dependency of these seemingly irrelevant properties, we formulated these quantities for CdS, ZnS, and CdSe semiconductors from the perspectives of bond order-length-strength correlation and the local bond averaging approach. Consistency between the theory predictions and the measured size dependence of these quantities clarified that the undercoordination-induced local strain and quantum entrapment and the varied fraction of undercoordinated atoms of the entire solid correlate these quantities and dominate their size effect.

  16. Synthesis, characterization and optical studies of highly luminescent ZnS nanoparticles associated with hypromellose matrix as a green and novel stabilizer.

    PubMed

    Tiwari, Ashish; Khan, S A; Kher, R S; Dhoble, S J

    2014-09-01

    ZnS nanoparticles stabilized by a carbohydrate-based matrix, hypromellose (hydroxypropyl methylcellulose) were prepared via a wet chemical method. The nanocomposite was characterized by X-ray diffraction, transmission electon microscopy and Fourier transform infrared spectroscopy. X-Ray diffraction patterns revealed a zinc blende structure. Thermogravimetric analysis suggested that polymer attached to the surface decomposes at 700 °C. Absorption measurements were carried out and calculation of the diameter polydispersity index (DPI) suggests the formation of monodisperse nanoparticles. The optical properties of the as-prepared samples were studied by UV/vis spectroscopy and steady-state photoluminescence (PL) spectroscopy. The PL studies indicate the applicability of these nanoparticles as biocompatible sensors or luminescence markers in future.

  17. Theoretical study of the low-lying electronic states of ZnO and ZnS

    NASA Technical Reports Server (NTRS)

    Bauschlicher, C. W., Jr.; Langhoff, S. R.

    1986-01-01

    Theoretical spectroscopic constants and dipole moments are determined for the 1 Sigma(+), 1,3 Pi, and 3 Sigma(+) states of ZnO and ZnS, using extended Gaussian basis sets and incorporating correlation using both configuration-interaction and coupled pair (CPF) methods. Relativistic corrections (Darwin plus mass velocity), included using first-order perturbation theory, are relatively small. At the CPF level, both ZnO and ZnS have 1 Sigma(+) ground states, with the 3 Pi state lying 209 and 2075/cm higher, respectively. The 3 Sigma(+) state lies about 1.5 eV higher in ZnO and 2.1 eV higher in ZnS. The 1,3 Pi states are relatively close together since the exchange splitting is small with the sigma electron localized on Zn and the pi electron on oxygen (or sulfur).

  18. ZnS nanocrystals decorated single-walled carbon nanotube based chemiresistive label-free DNA sensor

    PubMed Central

    Rajesh; Das, Basanta K.; Srinives, Sira; Mulchandani, Ashok

    2011-01-01

    We fabricated ZnS nanocrystals decorated single-walled carbon nanotube (SWNT) based chemiresistive sensor for DNA. Since the charge transfer in the hybrid nanostructures is considered to be responsible for many of their unique properties, the role of ZnS nanocrystals toward its performance in DNA sensor was delineated. It was found that the free carboxyl groups surrounding the ZnS nanocrystals allowed large loading of single strand DNA (ssDNA) probe that provided an ease of hybridization with target complementary c-ssDNA resulting in large electron transfer to SWNT. Thus it provided a significant improvement in sensitivity toward c-ssDNA as compared to bare SWNT based DNA sensor. PMID:21286239

  19. Nano-photocatalysts based on ZnS quantum dots/chitosan for the photodegradation of dye pollutants

    NASA Astrophysics Data System (ADS)

    Mansur, H. S.; Mansur, A. A. P.

    2015-03-01

    In this work, nano-photocatalysts based on ZnS quantum dots (QD) functionalized by chitosan were developed using "green" colloidal chemical process in aqueous media at room temperature. The ZnS/chitosan nano-photocatalysts were extensively characterized and the results demonstrated that chitosan was an effective capping ligand for the direct production of water-soluble ZnS QDs with average nanocrystal sizes of approximately 3.5 nm. Methylene blue dye was used as "model organic pollutant", which was effectively oxidized by the photocatalytic surface activity of the ZnS/chitosan nanostructured systems under UV irradiation. In summary, innovative "green" nano-photocatalyst nanomaterials were produced based on a fluorescent inorganic "core" of ZnS QDs and a biocompatible organic "shell" of chitosan for potential use on the photodegradation of hazardous dye pollutants present in industrial wastewater.

  20. Ordered mesoporous necklace-like ZnS on graphene for use as a high performance photocatalyst

    NASA Astrophysics Data System (ADS)

    Bin, Zeng; Xiaohua, Chen; Qianxiang, Tang; Chuansheng, Chen; Aiping, Hu

    2014-07-01

    A simple and effective approach was developed to prepare novel graphene/ordered mesoporous necklace-like ZnS nanocomposite (GR-ZnS). Scanning electron microscopy and transmission electron microscopy observations confirmed that the as-formed necklace-like ZnS, about 50 nm in diameter and more than hundreds of nanometers in length, were distributed on graphene sheets. Each ZnS contained a lot of ordered mesopores. The photocatalytic experimental results indicated that this nanocomposite enhanced photocatalytic performance with 97.5% decomposition of methyl orange (MO) after 30 min under UV-light irradiation. This new nanocomposite is expected to show considerable potential applications in water purification.

  1. Influence of solvent on the morphology and photocatalytic properties of ZnS decorated CeO{sub 2} nanoparticles

    SciTech Connect

    Raubach, Cristiane W. Polastro, Lisânias; Ferrer, Mateus M.; Perrin, Andre; Perrin, Christiane; Albuquerque, Anderson R.; Buzolin, Prescila G. C.; Sambrano, Julio R.; Santana, Yuri B. V. de; Varela, José A.; Longo, Elson

    2014-06-07

    Herein, we report a theoretical and experimental study on the photocatalytic activity of CeO{sub 2} ZnS, and ZnS decorated CeO{sub 2} nanoparticles prepared by a microwave-assisted solvothermal method. Theoretical models were established to analyze electron transitions primarily at the interface between CeO{sub 2} and ZnS. As observed, the particle morphology strongly influenced the photocatalytic degradation of organic dye Rhodamine B. A model was proposed to rationalize the photocatalytic behavior of the prepared decorated systems taking into account different extrinsic and intrinsic defect distributions, including order-disorder effects at interfacial and intra-facial regions, and vacancy concentration.

  2. High durability antireflection coatings for silicon and multispectral ZnS

    NASA Astrophysics Data System (ADS)

    Joseph, Shay; Marcovitch, Orna; Yadin, Ygal; Klaiman, Dror; Koren, Nitzan; Zipin, Hedva

    2007-04-01

    In the current complex battle field, military platforms are required to operate on land, at sea and in the air in all weather conditions both day and night. In order to achieve such capabilities, advanced electro-optical systems are being constantly developed and improved. These systems such as missile seeker heads, reconnaissance and target acquisition pods and tracking, monitoring and alert systems have external optical components (window or dome) which must remain operational even at extreme environmental conditions. Depending on the intended use of the system, there are a few choices of window and dome materials. Amongst the more common materials one can point out sapphire, ZnS, germanium and silicon. Other materials such as spinel, ALON and yittria may also be considered. Most infrared materials have high indices of refraction and therefore they reflect a large part of radiation. To minimize the reflection and increase the transmission, antireflection (AR) coatings are the most common choice. Since these systems operate at different environments and weather conditions, the coatings must be made durable to withstand these extreme conditions. In cases where the window or dome is made of relatively soft materials such as multispectral ZnS, the coating may also serve as protection for the window or dome. In this work, several antireflection coatings have been designed and manufactured for silicon and multispectral ZnS. The coating materials were chosen to be either oxides or fluorides which are known to have high durability. Ellipsometry measurements were used to characterize the optical constants of the thin films. The effects of the deposition conditions on the optical constants of the deposited thin films and durability of the coatings will be discussed. The coatings were tested according to MIL-STD-810E and were also subjected to rain erosion tests at the University of Dayton Research Institute (UDRI) whirling arm apparatus in which one of the coatings showed

  3. Size-depressed critical temperatures for the order-disorder transition of FePt, CoPt, FePb, Cu2S, and ZnS nanostructures

    NASA Astrophysics Data System (ADS)

    Jiang, R.; Zhou, Z. F.; Yang, X. X.; Guo, N. G.; Qi, W. H.; Sun, C. Q.

    2013-01-01

    The size dependency of the critical temperature (TC) for the order-disorder phase transitions of both the bimetallic and the chalcogenide nanoclusters is shown to follow the rule of bond order-length-strength correlation. The loss of the cohesive energy of the undercoordinated atoms in the surface skin dictates the structural stability. Theoretical reproduction of the size TC trends of FePt, CoPt, FePb, Cu2S, and ZnS nanostructures not only confirms our expectations without involving the concepts of surface energy or entropy used for continuum bulk materials but also provides guideline for engineering nanostructured alloys or compounds.

  4. Electron-beam irradiation induced conductivity in ZnS nanowires as revealed by in situ transmission electron microscope

    NASA Astrophysics Data System (ADS)

    Liu, Baodan; Bando, Yoshio; Wang, Mingsheng; Zhi, Chunyi; Fang, Xiaosheng; Tang, Chengchun; Mitome, Masanori; Golberg, Dmitri

    2009-08-01

    Electron transport variations in individual ZnS nanowires synthesized through a chemical vapor deposition process were in situ studied in transmission electron microscope under convergent electron-beam irradiation (EBI). It was found that the transport can dramatically be enhanced using proper irradiation conditions. The conductivity mechanism was revealed based on a detailed study of microstructure and composition evolutions under irradiation. EBI-induced Zn-rich domains' appearance and related O doping were mainly responsible for the conductivity improvements. First-principles theoretical calculations additionally indicated that the generation of midbands within a ZnS band gap might also contribute to the improved conductivity.

  5. Biomolecule-assisted synthesis of ZnS nanocorals and open-benzene ring in supercritical carbon dioxide

    SciTech Connect

    Jiao Jiqing; Chen Liuping Liu Xin; Gao Wei; Feng Huajie

    2009-05-06

    The nanostructured ZnS of cubic nanocorals and open-benzene ring has been synthesized by the biomolecule-assisted method in mixture of supercritical carbon dioxide and water as reaction medium at 150 deg. C and 28 MPa. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, photoluminescence spectrum of sample were characterized. The sodium tripoly phosphate and CO{sub 2} as well as high-pressure condition might be the key factors for formation of the particular morphologies and nanostructures of ZnS. This synthesis method could be employed for preparation of other semiconductor nanomaterials.

  6. Cu-doped CdS and ZnS nanocrystals grown onto thiolated silica-gel

    NASA Astrophysics Data System (ADS)

    Andrade, George Ricardo Santana; Nascimento, Cristiane da Cunha; Xavier, Paulo Adriano; Costa, Silvanio Silverio Lopes; Costa, Luiz Pereira; Gimenez, Iara F.

    2014-11-01

    CdS and ZnS nanocrystals were grown over specific binding sites onto a thiolated silica-gel aiming to favor defect emission processes. This strategy was found to be effective in yielding ZnS nanocrystals with simultaneous blue and blue-green emissions owing to different types of defects. The effects of doping with copper ions have been observed on the photoluminescence properties. The intensity of defect-related emissions from both semiconductor nanocrystals increased with increasing dopant concentration from 0.25% to 1.5% copper, consistent with the presence of sulfur vacancies. Higher dopant concentrations lead to concentration quenching.

  7. High Resolution Cathodoluminescence of Yellow and Waterclear CVD Polycrystalline ZnS.

    DTIC Science & Technology

    1983-12-01

    ZnS or any semiconduc- tor material phosphoresces. Therefore in the "Theory and Summary of Previous Research" chapter the various models are developed...187 (V to V ) in 0 Zn ZnSO solids/DAP 67-8 3920-3960 3.162-30 Mn 59 4300-4485 Range (Due to Cu + coactiva- 4300 2.883 tor such as Al, Cl, Br, 4320...activator predominates it is reasonable to expect the peak to be more characteristic of the co-activa- tor than the activator Cu. This could explain why the

  8. Extinction of photoemission of Mn-Doped ZnS nanofluid in weak magnetic field

    NASA Astrophysics Data System (ADS)

    Vu, Anh-Tuan; Bui, Hong-Van; Pham, Van-Ben; Le, Van-Hong; Hoang, Nam-Nhat

    2016-08-01

    The observation of extinction of photoluminescence of Mn-doped ZnS nanofluid under applying of weak magnetic field is reported. At a constant field of 270 Gauss and above, the exponential decays of photoluminescent intensity was observed in disregard of field direction. About 50% extinction was achieved after 30 minute magnetization and a total extinction after 1 hour. The memory effect preserved for more than 2 hours at room temperature. This extinction was observed in a system with no clear ferromagnetic behavior.

  9. Optimizing ZnS/6LiF scintillators for wavelength-shifting-fiber neutron detectors

    SciTech Connect

    Crow, Lowell; Funk, Loren L; Hannan, Bruce W; Hodges, Jason P; Riedel, Richard A; Wang, Cai-Lin

    2016-01-01

    In this paper we compare the performance of grooved and flat ZnS/6LiF scintillators in a wavelength shifting-fiber (WLSF) detector. Flat ZnS/6LiF scintillators with the thickness L=0.2-0.8 mm were characterized using photon counting and pulse-height analysis and compared to a grooved scintillator of approximately 0.8 mm thick. While a grooved scintillator considerably increases the apparent thickness of the scintillator to neutrons for a given coating thickness, we find that the flat scintillators perform better than the grooved scintillators in terms of both light yield and neutron detection efficiency. The flat 0.8-mm-thick scintillator has the highest light output, and it is 52% higher compared with a grooved scintillator of same thickness. The lower light output of the grooved scintillator as compared to the flat scintillator is consistent with the greater scintillator-WLSF separation and the much larger average emission angle of the grooved scintillator. We also find that the average light cone width, or photon travel-length as measured using time-of-flight powder diffraction of diamond and vanadium, decreases with increasing L in the range of L=0.6-0.8 mm. This result contrasts with the traditional Swank diffusion model for micro-composite scintillators, and could be explained by a decrease in photon diffusion-coefficient or an increase in micro-particle content in the flat scintillator matrix for the thicker scintillators.

  10. Temperature dependent dielectric and electric modulus properties of ZnS nano particles

    NASA Astrophysics Data System (ADS)

    Ali, Hassan; Falak, Attia; Rafiq, M. A.; Khan, Usman; Karim, Shafqat; Nairan, Adeela; Jing, Tang; Sun, Yue; Sun, Sibai; Qian, Chenjiang; Xu, Xiulai

    2017-03-01

    A comprehensive study of the dielectric and electric modulus properties of Zinc Sulfide (ZnS) semiconductor nanoparticles has been conducted using impedance spectroscopy in the frequency range of 200 Hz to 2 MHz and over the temperature range of 300 K to 400 K. Microscopic analysis confirms the formation of spherical nanoparticles with an average size of ∼20 nm. Maxwell–Wagner–Sillars (MWS) interfacial polarization is responsible for the increase in dielectric permittivity and dielectric loss at lower frequencies. Increase in dielectric permittivity and dielectric loss has been observed with a rise in temperature. The electric modulus complex plane plot reveals the presence of the grain (bulk) effect and non-Debye type relaxation processes in the material. The non-Debye type processes have also been confirmed by the asymmetric relaxation peaks of the imaginary part of the electric modulus. The frequency dependent maximum of the imaginary part of the electric modulus follows the Arrhenius law with an activation energy of 0.13 eV. The modulus analysis also establishes that the hopping mechanism is responsible for electrical conduction in the ZnS nanoparticles.

  11. Synthesis of ZnS films on Si(100) wafers by using chemical bath deposition assisted by the complexing agent ethylenediamine

    NASA Astrophysics Data System (ADS)

    Zhu, He-Jie; Wang, Xue-Mei; Gao, Xiao-Yong

    2015-07-01

    Low-cost synthesis of high-quality ZnS films on silicon wafers is of much importance to the ZnSbased heterojunction blue light-emitting device integrated with silicon. Thus, a series of ZnS films were chemically synthesized at low cost on Si(100) wafers at 353 K under a mixed acidic solution with a pH of 4 with zinc acetate and thioacetamide as precursors and with ethylenediamine and hydrochloric acid as the complexing agent and the pH value modifier, respectively. The effects of the ethylenediamine concentration on the crystallization, surface morphology, and optical properties of the ZnS films were investigated by using X-ray diffractometry, scanning electron microscopy, spectrophotometry, and fluorescence spectroscopy. A mechanism for the formation of ZnS film under an acidic condition was also proposed. All of the ZnS films were polycrystalline in nature, with a dominant cubic phase and a small amounts of hexagonal phases. The crystallization and the surface pattern of the films were clearly improved with increasing ethylenediamine concentration due to its enhanced complexing role. The absorption edge of the films almost underwent a blue shift with increasing ethylenediamine concentration, which was largely attributed to the quantum confinement effects caused by the small particle size of the polycrystalline ZnS films. Defect species and the corresponding strengths of the ZnS films were strongly affected by the ethylenediamine concentration.

  12. Synthesis and characterization of ZnS with controlled amount of S vacancies for photocatalytic H2 production under visible light

    PubMed Central

    Wang, Gang; Huang, Baibiao; Li, Zhujie; Lou, Zaizhu; Wang, Zeyan; Dai, Ying; Whangbo, Myung-Hwan

    2015-01-01

    Controlling amount of intrinsic S vacancies was achieved in ZnS spheres which were synthesized by a hydrothermal method using Zn and S powders in concentrated NaOH solution with NaBH4 added as reducing agent. These S vacancies efficiently extend absorption spectra of ZnS to visible region. Their photocatalytic activities for H2 production under visible light were evaluated by gas chromatograph, and the midgap states of ZnS introduced by S vacancies were examined by density functional calculations. Our study reveals that the concentration of S vacancies in the ZnS samples can be controlled by varying the amount of the reducing agent NaBH4 in the synthesis, and the prepared ZnS samples exhibit photocatalytic activity for H2 production under visible-light irradiation without loading noble metal. This photocatalytic activity of ZnS increases steadily with increasing the concentration of S vacancies until the latter reaches an optimum value. Our density functional calculations show that S vacancies generate midgap defect states in ZnS, which lead to visible-light absorption and responded. PMID:25712901

  13. Green and facile synthesis of water-soluble ZnS quantum dots nanohybrids using chitosan derivative ligands

    NASA Astrophysics Data System (ADS)

    Ramanery, Fábio P.; Mansur, Alexandra A. P.; Borsagli, Fernanda G. L. M.; Mansur, Herman S.

    2014-07-01

    Semiconductor quantum dots (QDs) are fluorescent nanocrystals with great potential for use in biomedical and environmental applications. However, eliminating the potential cytotoxicity of the QDs comprised of a core containing heavy metals and using a green chemical process are still challenges faced by the research community. Thus, the aim of this work was to develop a novel green and facile route for synthesizing biocompatible water-soluble QDs using chemically modified chitosan as a capping ligand in aqueous media, with their chemical and optical properties tuned by the nanoparticle size. The synthesis of ZnS QDs capped by carboxymethylchitosan (CMC) was performed using a single-step aqueous colloidal process at room temperature. The nanohybrids were extensively characterized by several imaging and spectroscopic techniques, and the results demonstrated that ultra-small ZnS nanocrystals were produced with average nanoparticles ranging from 3.2 to 4.2 nm. In addition, the luminescent properties of ZnS QDs were influenced by the pH during the synthesis due to the size distribution of the nanoparticles produced. Hence, new "heavy metal free" nanohybrids were successfully developed based on ZnS QDs directly surface-functionalized by biopolymer exhibiting fluorescent activity that may be potentially used in a large number of eco-friendly and biomedical applications.

  14. Photocatalytic decolorization of methylene blue in the presence of TiO2/ZnS nanocomposites.

    PubMed

    Franco, A; Neves, M C; Carrott, M M L Ribeiro; Mendonça, M H; Pereira, M I; Monteiro, O C

    2009-01-15

    The synthesis of distinct nanocrystalline TiO2 capped ZnS samples was carried out using a chemical deposition method. The materials characterization showed that the presence of ZnS onto TiO2 surface results in a red shift of the material band edge when compared with the initial semiconductor. The photocatalytic activity of the prepared nanocomposites was tested on the decolorization of methylene blue (MB) aqueous solutions. The dye photodecolorization process was studied considering the influence of experimental parameters such as catalyst concentration, TiO2/ZnS ratio, pH and methylene blue adsorption rate. The material with the best catalytic activity towards the methylene blue photodecolorization was the TiO2 doped with 0.2% of ZnS. The complete photodecolorization of a 20ppm methylene blue solution, at natural pH was achieved in less than 20min, nearly 70min faster than the TiO2 photoassisted process.

  15. Enhanced photocatalytic performance of ZnS for reversible amination of α-oxo acids by hydrothermal treatment.

    PubMed

    Wang, Wei; Li, Qiliang; Liu, Xiaoyang; Yang, Yanqiang; Su, Wenhui

    2012-08-01

    To understand how life could have originated on early Earth, it is essential to know what biomolecules and metabolic pathways are shared by extant organisms and what organic compounds and their chemical reaction channels were likely to have been primordially available during the initial phase of the formation of prebiotic metabolism. In a previous study, we demonstrated for the first time the reversible amination of α-oxo acids on the surface of photo-illuminated ZnS. The sulfide mineral is a typical component at the periphery of submarine hydrothermal vents which has been frequently argued as a very attractive venue for the origin of life. In this work, in order to simulate more closely the precipitation environments of ZnS in the vent systems, we treated newly-precipitated ZnS with hydrothermal conditions and found that its photocatalytic power was significantly enhanced because the relative crystallinity of the treated sample was markedly increased with increasing temperature. Since the reported experimental conditions are believed to have been prevalent in shallow-water hydrothermal vents of early Earth and the reversible amination of α-oxo acids is a key metabolic pathway in all extant life forms, the results of this work provide a prototypical model of the prebiotic amino acid redox metabolism. The amino acid dehydrogenase-like chemistry on photo-irradiated ZnS surfaces may advance our understanding of the establishment of archaic non-enzymatic metabolic systems.

  16. ZnS nanocrystals and nanoflowers synthesized by a green chemistry approach: rare excitonic photoluminescence achieved by the tunable molar ratio of precursors.

    PubMed

    Xiao, Ningru; Dai, Quanqin; Wang, Yingnan; Ning, Jiajia; Liu, Bingbing; Zou, Guangtian; Zou, Bo

    2012-04-15

    In the present work, we demonstrated a simple and green synthesis route for shape-controlled ZnS nanocrystals, where only environmentally benign chemicals, namely sulfur, zinc oxide and olive oil, were employed. By controlling the experimental conditions, we were able to tune the band edge and trap state photoluminescences of ZnS nanocrystals and obtain pure excitonic photoluminescence that was rarely observed in literature. The trap state emission was derived from sulfur vacancies and would be eliminated when an excess of sulfur was used during the synthesis. Additionally, the morphology of ZnS nanocrystals could be tuned to appear like flowers, where the formation mechanism was systematically discussed.

  17. Low temperature synthesis of ZnS and CdZnS shells on CdSe quantum dots.

    PubMed

    Zhu, Huiguang; Prakash, Arjun; Benoit, Denise N; Jones, Christopher J; Colvin, Vicki L

    2010-06-25

    Methods for synthesizing quantum dots generally rely on very high temperatures to both nucleate and grow core and core-shell semiconductor nanocrystals. In this work, we generate highly monodisperse ZnS and CdZnS shells on CdSe semiconductor nanocrystals at temperatures as low as 65 degrees C by enhancing the precursor solubility. Relatively small amounts of trioctylphosphine and trioctylphosphine oxide have marked effects on the solubility of the metal salts used to form shells; their inclusion in the precursor solutions, which use thiourea as a sulfur source, can lead to homogeneous and fully dissolved solutions. Upon addition to suspensions of quantum dot cores, these precursors deposit as uniform shells; the lowest temperature for shell growth (65 degrees C) yields the thinnest shells (d < 1 nm) while the same process at higher temperatures (180 degrees C) forms thicker shells (d approximately 1-2 nm). The growth of the shell structures, average particle size, size distribution, and shape were examined using optical spectroscopy, transmission electron microscopy, x-ray diffraction, and transmittance small angle x-ray scattering. The photoluminescence quantum yield (QY) of the as-prepared CdSe/ZnS quantum dots ranged from 26% to 46% as compared to 10% for the CdSe cores. This method was further generalized to CdZnS shells by mixing cadmium and zinc acetate precursors. The CdSe/CdZnS nanocrystals have a thicker shell and higher QY (40% versus 36%) as compared to the CdSe/ZnS prepared under similar conditions. These low temperature methods for shell growth are readily amenable to scale-up and can provide a route for economical and less energy intensive production of quantum dots.

  18. Low temperature synthesis of ZnS and CdZnS shells on CdSe quantum dots

    NASA Astrophysics Data System (ADS)

    Zhu, Huiguang; Prakash, Arjun; Benoit, Denise N.; Jones, Christopher J.; Colvin, Vicki L.

    2010-06-01

    Methods for synthesizing quantum dots generally rely on very high temperatures to both nucleate and grow core and core-shell semiconductor nanocrystals. In this work, we generate highly monodisperse ZnS and CdZnS shells on CdSe semiconductor nanocrystals at temperatures as low as 65 °C by enhancing the precursor solubility. Relatively small amounts of trioctylphosphine and trioctylphosphine oxide have marked effects on the solubility of the metal salts used to form shells; their inclusion in the precursor solutions, which use thiourea as a sulfur source, can lead to homogeneous and fully dissolved solutions. Upon addition to suspensions of quantum dot cores, these precursors deposit as uniform shells; the lowest temperature for shell growth (65 °C) yields the thinnest shells (d < 1 nm) while the same process at higher temperatures (180 °C) forms thicker shells (d ~ 1-2 nm). The growth of the shell structures, average particle size, size distribution, and shape were examined using optical spectroscopy, transmission electron microscopy, x-ray diffraction, and transmittance small angle x-ray scattering. The photoluminescence quantum yield (QY) of the as-prepared CdSe/ZnS quantum dots ranged from 26% to 46% as compared to 10% for the CdSe cores. This method was further generalized to CdZnS shells by mixing cadmium and zinc acetate precursors. The CdSe/CdZnS nanocrystals have a thicker shell and higher QY (40% versus 36%) as compared to the CdSe/ZnS prepared under similar conditions. These low temperature methods for shell growth are readily amenable to scale-up and can provide a route for economical and less energy intensive production of quantum dots.

  19. Interactions of aqueous amino acids and proteins with the (110) surface of ZnS in molecular dynamics simulations

    SciTech Connect

    Nawrocki, Grzegorz; Cieplak, Marek

    2014-03-07

    The growing usage of nanoparticles of zinc sulfide as quantum dots and biosensors calls for a theoretical assessment of interactions of ZnS with biomolecules. We employ the molecular-dynamics-based umbrella sampling method to determine potentials of mean force for 20 single amino acids near the ZnS (110) surface in aqueous solutions. We find that five amino acids do not bind at all and the binding energy of the remaining amino acids does not exceed 4.3 kJ/mol. Such energies are comparable to those found for ZnO (and to hydrogen bonds in proteins) but the nature of the specificity is different. Cysteine can bind with ZnS in a covalent way, e.g., by forming the disulfide bond with S in the solid. If this effect is included within a model incorporating the Morse potential, then the potential well becomes much deeper—the binding energy is close to 98 kJ/mol. We then consider tryptophan cage, a protein of 20 residues, and characterize its events of adsorption to ZnS. We demonstrate the relevance of interactions between the amino acids in the selection of optimal adsorbed conformations and recognize the key role of cysteine in generation of lasting adsorption. We show that ZnS is more hydrophobic than ZnO and that the density profile of water is quite different than that forming near ZnO—it has only a minor articulation into layers. Furthermore, the first layer of water is disordered and mobile.

  20. Controllable Synthesis and Optical Properties of ZnS:Mn(2+)/ZnS/ZnS:Cu(2+)/ZnS Core/Multishell Quantum Dots toward Efficient White Light Emission.

    PubMed

    Li, Fei; Xia, Zhiguo; Liu, Quanlin

    2017-03-22

    The ability to control dopants and defects, as well as the core/shell structures, of quantum dots (QDs) is an essential nanotechnology to modify and optimize their photoluminescence properties. Herein, the optimized ZnS:Mn(2+)/ZnS/ZnS:Cu(2+)/ZnS core/multishell QDs have been prepared, and their luminescence properties depending on the ratios of the starting materials and the injection temperature of an extra sulfur source were discussed; finally the white light can be possibly obtained by mixing the blue light (emission peak at 450 nm originating from Cu(2+) dopants or emission peaks at 405 and 430 nm corresponding to a defect emission center) and orange light (emission peak at 585 nm from Mn(2+) dopants). As a controlled synthesis comparison, the optimum core/shell structures and key synthesis parameters have been determined, and the quantum yield (QY) of the as-obtained ZnS:Mn(2+)/ZnS/ZnS:Cu(2+)/ZnS core/multishell white light emitting QDs without defect emission was determined to be 38%. The practical white light device prototype has been also fabricated and the CIE color coordinate of (0.32, 0.34) with a warm white light has been realized upon the excitation of the commercial 370 nm UV LED chip, which demonstrated potential application for micro/nano optical functional devices.

  1. Electrocatalytic activity of ZnS nanoparticles in direct ethanol fuel cells

    NASA Astrophysics Data System (ADS)

    Bredol, Michael; Kaczmarek, Michał; Wiemhöfer, Hans-Dieter

    2014-06-01

    Low temperature fuel cells consuming ethanol without reformation would be a major step toward the use of renewable energy sources from biomass. However, the necessary electrodes and electrocatalysts still are far from being perfect and suffer from various poisoning and deactivation processes. This work describes investigations on systems using carbon/ZnS-based electrocatalysts for ethanol oxidation in complete membrane electrode assemblies (MEAs). MEAs were built on Nafion membranes with active masses prepared from ZnS nanoparticles and Vulcan carbon support. Under operation, acetic acid and acetaldehyde were identified and quantified as soluble oxidation products, whereas the amount of CO2 generated could not be quantified directly. Overall conversion efficiencies of up to 25% were estimated from cells operated over prolonged time. From polarization curves, interrupt experiments and analysis of reaction products, mass transport problems (concentration polarization) and breakthrough losses were found to be the main deficiencies of the ethanol oxidation electrodes fabricated so far.

  2. Photoinduced fluorescence enhancement in CdSe /ZnS quantum dot monolayers: Influence of substrate

    NASA Astrophysics Data System (ADS)

    Uematsu, Takafumi; Maenosono, Shinya; Yamaguchi, Yukio

    2006-07-01

    Photoinduced fluorescence enhancement (PFE) of CdSe /ZnS core/shell quantum dot (QD) films on SiOx substrates was investigated. The fluorescence intensity of the QD film on SiO1.9 was greatly enhanced by continuous irradiation in vacuum, while the same QD film on SiO0.6 showed a small enhancement of the fluorescence intensity. After irradiation, the rate of fluorescence decay of the QD film on SiO0.6 was smaller than that of the QD film on SiO1.9. Our results suggest that the origin of PFE derives from the photoejection of electrons into the substrate, and that the oxygen-excess-related defects work as trap sites for the electrons.

  3. Optimized luminescence properties of Mn doped ZnS nanoparticles for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Le Donne, Alessia; Kanti Jana, Sourav; Banerjee, Sangam; Basu, Sukumar; Binetti, Simona

    2013-01-01

    Mn2+ doped ZnS nanoparticles (ZnS:Mn2+ NPs) are non-toxic systems known for their attractive light emitting properties. This paper discusses the luminescence properties of ZnS:Mn2+ NPs prepared by wet chemical synthesis with the objective of using them as down-shifters. A modification of the incident solar spectrum inducing improved exploitation of the UV region was expected to increase the efficiency of single junction cells with an optimal absorber band gap around 1.1 eV. The potential of ZnS:Mn2+ NPs as down-shifters was therefore demonstrated on both Si and Cu(In,Ga)Se2 solar cells.

  4. Recovering hidden quanta of Cu2+-doped ZnS quantum dots in reductive environment

    NASA Astrophysics Data System (ADS)

    Begum, Raihana; Sahoo, Amaresh Kumar; Ghosh, Siddhartha Sankar; Chattopadhyay, Arun

    2013-12-01

    We report that photoluminescence of doped quantum dots (Qdots)--which was otherwise lost in the oxidized form of the dopant--could be recovered in chemical or cellular reducing environment. For example, as-synthesized Cu2+-doped zinc sulfide (ZnS) Qdots in water medium showed weak emission with a peak at 420 nm, following excitation with UV light (320 nm). However, addition of reducing agent led to the appearance of green emission with a peak at 540 nm and with quantum yield as high as 10%, in addition to the weak peak now appearing as a shoulder. The emission disappeared in the presence of an oxidizing agent or with time under ambient conditions. X-Ray photoelectron spectroscopic (XPS) and electron spin resonance (ESR) measurements suggested the presence of Cu2+ in the as-synthesized Qdots, while formation of its reduced form was indicated (by ESR results) following treatment with a reducing agent. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) studies confirmed the formation of ZnS nanocrystals, the size and shape of which did not undergo any change in the presence of a reducing or oxidizing agent. Nanoparticulate forms of the Qdots and chitosan (a biopolymer) composite exhibited similar emission characteristics. Interestingly, when mammalian cancer cells or non-cancerous cells were treated with the composite nanoparticles (NPs), characteristic green fluorescence was observed. Further, the intensity of the fluorescence diminished when the cells were treated later with pyrogallol--a known reactive oxygen species generator. Overall, the results indicated a new way of probing the reducing nature of mammalian cells using the emission properties of the Qdot based on the redox state of its dopant.We report that photoluminescence of doped quantum dots (Qdots)--which was otherwise lost in the oxidized form of the dopant--could be recovered in chemical or cellular reducing environment. For example, as-synthesized Cu2+-doped zinc sulfide (ZnS) Qdots in

  5. Recovering hidden quanta of Cu(2+)-doped ZnS quantum dots in reductive environment.

    PubMed

    Begum, Raihana; Sahoo, Amaresh Kumar; Ghosh, Siddhartha Sankar; Chattopadhyay, Arun

    2014-01-21

    We report that photoluminescence of doped quantum dots (Qdots)-which was otherwise lost in the oxidized form of the dopant-could be recovered in chemical or cellular reducing environment. For example, as-synthesized Cu(2+)-doped zinc sulfide (ZnS) Qdots in water medium showed weak emission with a peak at 420 nm, following excitation with UV light (320 nm). However, addition of reducing agent led to the appearance of green emission with a peak at 540 nm and with quantum yield as high as 10%, in addition to the weak peak now appearing as a shoulder. The emission disappeared in the presence of an oxidizing agent or with time under ambient conditions. X-Ray photoelectron spectroscopic (XPS) and electron spin resonance (ESR) measurements suggested the presence of Cu(2+) in the as-synthesized Qdots, while formation of its reduced form was indicated (by ESR results) following treatment with a reducing agent. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) studies confirmed the formation of ZnS nanocrystals, the size and shape of which did not undergo any change in the presence of a reducing or oxidizing agent. Nanoparticulate forms of the Qdots and chitosan (a biopolymer) composite exhibited similar emission characteristics. Interestingly, when mammalian cancer cells or non-cancerous cells were treated with the composite nanoparticles (NPs), characteristic green fluorescence was observed. Further, the intensity of the fluorescence diminished when the cells were treated later with pyrogallol-a known reactive oxygen species generator. Overall, the results indicated a new way of probing the reducing nature of mammalian cells using the emission properties of the Qdot based on the redox state of its dopant.

  6. [Synthesis and characterization of non fluorescent ZnS nano clusters].

    PubMed

    Ding, Liang; Yang, Hui; Xi, Ya-nan; Zhang, Jin-chao; Shen, Shi-gang

    2015-01-01

    Zinc sulfide nano clusters were synthesized and characterized. A kind of method using zinc sulfide nanoparticles cluster cation exchange reaction(CX) to detect trace biological molecules was established. Non fluorescent ZnS nanoparticles (NCCs) were synthesized and characterized. The property of nano clusters directly influences the detection results. Through transmission electron microscopy images and X-ray diffraction, nano clusters which could quickly release a mass of Zn2+ from rapid cation exchange reaction were known to be porous and generate fluorescence signal under the action of zinc reagent. The external crystal arranges loosely compared to the internal, which is conducive to rapid cation exchange, and the crystal size is related to heating time. It was demonstrated that the smallest nanocluster had a relative large surface area and higher cationic exchange efficiency through the determination of the specific surface area of nano clusters for detecting surface area and pore size. Three methods (acid dissolution method, cation exchange and micro wave aided by cation exchange) which effected Zn2+ release performance were experimented. It turned out that microwave auxiliary cation exchange method had high SNR, simple operation, and could be used in zinc sulfide nanoparticle immunoassay. Having compared the relations between the release efficiency, target binding force of ZnZ2+ and its average diameter, the results show that the nano cluster size of 44 nm exhibits the highest cation exchange efficiency. All these features make the ZnS nanocluster cation exchange amplifier to be a highly sensitive, fairly biocompatible, low-cost and environment friendly detection tool in the detection of biomolecules.

  7. A simple one-step synthesis of ZnS nanoparticles via salt-alkali-composited-mediated method and investigation on their comparative photocatalytic activity

    SciTech Connect

    Xiang, Donghu; Zhu, Yabo; He, Zhanjun; Liu, Zhangsheng; Luo, Jin

    2013-02-15

    Graphical abstract: The TEM image shows that the as-synthesized ZnS particle size was estimated to be about 40 nm and this newly synthesized ZnS nanoparticles can be as a promising photocatalytic degradation material for the organic pollutant removal. Display Omitted Highlights: ► ZnS nanoparticles with cubic phase have been successfully synthesized via salt-alkali-composited-mediated method (SACM) for the first time and this method has not been found so far. ► Its band gap (E{sub g}) is a little bigger than commercial ZnS particle mainly due to quantum size effect. ► The as-synthesized ZnS nanoparticles show much more efficient photocatalytic degradation on methyl orange than commercial ZnS powder. -- Abstract: ZnS nanoparticles have been successfully synthesized via salt-alkali-composited-mediated method (SACM) for the first time, using a mixture of LiNO{sub 3} and LiOH (LiNO{sub 3}/LiOH = 60.7:39.3) as a reaction solvent, sodium sulfide and zinc nitrate as reactants at temperature of 210 °C for 24 h in the absence of organic dispersant or capping agents. X-ray diffraction, environment scanning electron microscopy (ESEM) and Transmission electron microscopy (TEM) indicated that the as-synthesized products were well crystallized and belonged to nano-scale. Their UV–vis absorption spectrum demonstrated a band gap of 3.6406 eV corresponding to the absorption edge of 340 nm. The experimental result of photocatalytic degradation on methyl orange by the nano-ZnS showed much better photocatalysis than that by the commercial ZnS powder under the irradiation of ultraviolet light and visible light, respectively.

  8. Effects of Temperature, Pressure, and Metal Promoter on the Recrystallized Structure and Optical Transmission of Chemical Vapor Deposited Zinc Sulfide

    SciTech Connect

    McCloy, John S.; Korenstein, Ralph; Zelinski, Brian

    2009-08-01

    Structural changes from processing in polytype-rich ZnS are complex and poorly understood In this study, recrystallization was induced in chemical vapor deposited (CVD) ZnS by annealing and hot isostatic pressing (HIPing). Samples were characterized using optical microscopy, SEM, TEM, electron diffraction, polycrystalline and powder x-ray diffraction, and transmission spectroscopy. Recrystallization was found to reduce the hexagonality and increase the texture of as deposited ZnS. Changes in hexagonality and texture can occur independently of each other. HIP’d ZnS with superior transmission exhibits both a change in texture as well as a reduction in hexagonal content. Reduction in hexagonality, alone, was not sufficient to improve optical transmission from the visible to the infrared. For the first time, the effects of pressure, temperature, and the presence of platinum on recrystallization during commercial ZnS HIPing are separated and identified. Platinum was found to actively promote recrystallization and silver demonstrated a similar effect. Several theories focusing on the unique polytypic nature of ZnS are offered to explain the changes in structure and properties occurring during recrystallization, These findings contribute to a broader understanding of the nature of order-disorder and martensitic phase transformations in ceramic materials.

  9. Optical properties and toxicity of undoped and Mn-doped ZnS semiconductor nanoparticles synthesized through the aqueous route

    NASA Astrophysics Data System (ADS)

    Labiadh, Houcine; Sellami, Badreddine; Khazri, Abdelhafidh; Saidani, Wiem; Khemais, Said

    2017-02-01

    Undoped and Mn-doped ZnS nanoparticles were synthesized at 95 °C in basic aqueous solution using the nucleation-doping strategy. Various samples of the Mn:ZnS NPs with 5, 10 and 20% of Mn dopant have been prepared and characterized using X-ray diffraction, energy-dispersive X-ray analysis, high resolution electron microscopy and photoluminescence (PL) measurements. When increasing the concentration of manganese Mn, the photoluminescence intensity gradually decreases. The PL spectra of the Mn-doped ZnS nanoparticles at room temperature exhibit both, the 450 nm blue defect-related emission and the 592 nm orange Mn2+ emission. It is vital to obtain NPs that meet the application requirements, however their environmental toxicity needs to be investigated. In this study, the induction of oxidative stress within the digestive gland of the Ruditapes decussatus organism (clam) is described. Antioxidant enzyme activities (superoxide dismutase (SOD) and catalase (CAT)) as well as malondialdehyde (MDA) levels have been determined in the digestive gland after exposure to 100 μg/L of ZnS, ZnS:Mn (5%), ZnS:Mn (10%) and ZnS:Mn (20%). The nanomaterials studied exhibit different responses in the digestive gland. Undoped Mn-ZnS has no effect on the markers considered, showing the limited interaction between this nanoparticle and the cells of the test organisms. In contrast, Mn-doped ZnS increases the activities of SOD and CAT and the level of MDA species, although this toxicity is highly dependent on the chemical properties of the material. These findings provide ideas for future considerations of ZnS nanoparticles, as well as information on the interaction between these materials and an aquatic environment. These data are the first evidence available of the formation of ZnS NPs using aqueous method and are an indication of the importance of knowing the biological target of the NPs when testing their potential impact on environmental model organisms.

  10. Size- and shape-dependent growth of fluorescent ZnS nanorods and nanowires using Ag nanocrystals as seeds

    NASA Astrophysics Data System (ADS)

    Shen, Huaibin; Shang, Hangying; Niu, Jinzhong; Xu, Weiwei; Wang, Hongzhe; Li, Lin Song

    2012-09-01

    High-quality, monodisperse, and size-controlled Ag-ZnS nanorods or nanowires have been synthesized successfully using Ag nanocrystals as seeds. Such one-dimensional colloidal Ag-ZnS nanorods or nanowires having a purposefully controlled diameter in the range of 5-9 nm and a length of 18-600 nm were obtained by altering the reaction conditions, such as concentration, reaction time, reaction temperature, and diameter of Ag nanocrystals. The conjunction interface of Ag-ZnS nanorods or nanowires consists of the (200) plane of Ag nanocrystal and (101) plane of ZnS rod or wire, the <101> directions of ZnS nanorods grow preferentially. Based on the photoluminescence and lifetime of Ag-ZnS nanorods, it was found that Ag nanocrystals enhanced the radiative rate eventually, the fluorescence intensity of Ag-ZnS nanorods can be tuned by changing the size of the Ag seeds. The Ag-ZnS nanorods or nanowires showed greatly improved optical properties as compared to ZnS nanocrystals, the maximum emission was around 402 nm and the photoluminescence quantum yield was up to 30% when 5 nm Ag nanocrystals were used as seeds.High-quality, monodisperse, and size-controlled Ag-ZnS nanorods or nanowires have been synthesized successfully using Ag nanocrystals as seeds. Such one-dimensional colloidal Ag-ZnS nanorods or nanowires having a purposefully controlled diameter in the range of 5-9 nm and a length of 18-600 nm were obtained by altering the reaction conditions, such as concentration, reaction time, reaction temperature, and diameter of Ag nanocrystals. The conjunction interface of Ag-ZnS nanorods or nanowires consists of the (200) plane of Ag nanocrystal and (101) plane of ZnS rod or wire, the <101> directions of ZnS nanorods grow preferentially. Based on the photoluminescence and lifetime of Ag-ZnS nanorods, it was found that Ag nanocrystals enhanced the radiative rate eventually, the fluorescence intensity of Ag-ZnS nanorods can be tuned by changing the size of the Ag seeds. The Ag

  11. Incorporation of lanthanide (Eu(3+)) ions in ZnS semiconductor quantum dots with a trapped-dopant model and their photoluminescence spectroscopy study.

    PubMed

    Wang, Yongbo; Liang, Xuhua; Liu, Enzhou; Hu, Xiaoyun; Fan, Jun

    2015-09-18

    Doping quantum dots (QDs) with lanthanide (Ln) ions is promising to modify the optical properties of QDs, but incorporating Ln(3+) ions into QD hosts remains a challenge. In this work, we adopt the trapped-dopant model for fabricating Eu-doped ZnS QDs via direct wet chemical synthesis. Sharp Eu dopant photoluminescence (PL) was observed in the PL spectra of the as-prepared Eu-doped ZnS QDs and the bands at ~590, ~618 and ~695 nm were assigned to transitions from (5)D0 to (7)F1, (7)F2 and (7)F4, respectively. Quenching of the ZnS bandgap PL and enhancement of the Eu dopant PL were observed with increasing Eu(3+) doping concentration, and also, the excitation spectra for Eu emission (618 nm) were similar to the typical excitonic features of the ZnS host. These spectroscopic results, as well as the XRD and EDS data, demonstrated that Eu(3+) ions were incorporated in the ZnS host rather than just on the surface, and the Eu dopant PL was derived from energy transfer from the QD host to Eu(3+) rather than direct excitation of Eu(3+). By surface passivation, the sharp Eu emission was well-separated from the ZnS bandgap emission, which led to a good signal-to-noise ratio for more sensitive detection.

  12. Effect of ZnS shell on optical properties of CdSe-ZnS core-shell quantum dots

    NASA Astrophysics Data System (ADS)

    Mathew, S.; Bhardwaj, Bishwajeet Singh; Saran, Amit D.; Radhakrishnan, P.; Nampoori, V. P. N.; Vallabhan, C. P. G.; Bellare, Jayesh R.

    2015-01-01

    A modified microemulsion technique was used to synthesize CdSe-ZnS core-shell quantum dots (QDs) of ∼5 nm diameter. Their nonlinear optical absorption was observed with nanosecond laser radiation of 532-nm wavelength. Linear optical studies show confinement effects. There is a new emission band around 745 nm under excitation of 532 nm which is an indication of the generation of deep trap states in CdSe QDs. As the ZnS shell thickness increases, there could be an increased electron-hole pair generation leading to large free-carrier concentration which in turn results in enhancement of nonlinear optical absorption. In addition, it was found that the optical limiting threshold gets decreased as the ZnS shell thickness increases.

  13. Study of the morphology of ZnS thin films deposited on different substrates via chemical bath deposition.

    PubMed

    Gómez-Gutiérrez, Claudia M; Luque, P A; Castro-Beltran, A; Vilchis-Nestor, A R; Lugo-Medina, Eder; Carrillo-Castillo, A; Quevedo-Lopez, M A; Olivas, A

    2015-01-01

    In this work, the influence of substrate on the morphology of ZnS thin films by chemical bath deposition is studied. The materials used were zinc acetate, tri-sodium citrate, thiourea, and ammonium hydroxide/ammonium chloride solution. The growth of ZnS thin films on different substrates showed a large variation on the surface, presenting a poor growth on SiO2 and HfO2 substrates. The thin films on ITO substrate presented a uniform and compact growth without pinholes. The optical properties showed a transmittance of about 85% in the visible range of 300-800 nm with band gap of 3.7 eV.

  14. Fabrication of transparent ZnS ceramic by optimizing the heating rate in spark plasma sintering process

    NASA Astrophysics Data System (ADS)

    Chen, Yuanzhi; Zhang, Le; Zhang, Jian; Liu, Peng; Zhou, Tianyuan; Zhang, Hongxiang; Gong, Dongmei; Tang, Dingyuan; Shen, Deyuan

    2015-12-01

    Transparent ZnS ceramics were fabricated at a lower temperature (840 °C) by optimizing the heating rate in the spark plasma sintering (SPS) process. The phase composition, microstructure and the optical properties of the ceramics were investigated by XRD, SEM and FTIR. Under the optimized heating rate of 5 °C/min, ZnS ceramics with the best optical qualities was obtained, and the transmittance reached above 60% in the range of 5.0-12.0 μm and it was higher than 40% in the range of 2.0-3.0 μm. Meanwhile, the content of hexagonal phase was controlled to be lower than 7.5%.

  15. Combinatorial In Situ Photoelectron Spectroscopy Investigation of Sb 2 Se 3 /ZnS Heterointerfaces

    SciTech Connect

    Siol, Sebastian; Schulz, Philip; Young, Matthew; Borup, Kasper A.; Teeter, Glenn; Zakutayev, Andriy

    2016-11-22

    Combinatorial techniques can be utilized to accelerate in situ interface studies. This is demonstrated by investigating the prototypical Sb2Se3/ZnS heterojunction. Film thickness gradients on the substrate are used to minimize the required number of depositions and transfers. Other synthesis parameters such as the substrate temperature or film composition can be systematically covaried with thickness to cover several individual interface experiments on one substrate.

  16. Room temperature atomic layerlike deposition of ZnS on organic thin films: Role of substrate functional groups and precursors

    SciTech Connect

    Shi, Zhiwei; Walker, Amy V.

    2015-09-15

    The room temperature atomic layerlike deposition (ALLD) of ZnS on functionalized self-assembled monolayers (SAMs) was investigated, using diethyl zinc (DEZ) and in situ generated H{sub 2}S as reactants. Depositions on SAMs with three different terminal groups, –CH{sub 3,} –OH, and –COOH, were studied. It was found that the reaction of DEZ with the SAM terminal group is critical in determining the film growth rate. Little or no deposition is observed on –CH{sub 3} terminated SAMs because DEZ does not react with the methyl terminal group. ZnS does deposit on both –OH and –COOH terminated SAMs, but the grow rate on –COOH terminated SAMs is ∼10% lower per cycle than on –OH terminated SAMs. DEZ reacts with the hydroxyl group on –OH terminated SAMs, while on –COOH terminated SAMs it reacts with both the hydroxyl and carbonyl bonds of the terminal groups. The carbonyl reaction is found to lead to the formation of ketones rather than deposition of ZnS, lowering the growth rate on –COOH terminated SAMs. SIMS spectra show that both –OH and –COOH terminated SAMs are covered by the deposited ZnS layer after five ALLD cycles. In contrast to ZnO ALLD where the composition of the film differs for the first few layers on –COOH and –OH terminated SAMs, the deposited film composition is the same for both –COOH and –OH terminated SAMs. The deposited film is found to be Zn-rich, suggesting that the reaction of H{sub 2}S with the Zn-surface adduct may be incomplete.

  17. Characterization of cobalt doped ZnSe and ZnS crystals as saturable absorbers for alexandrite lasers

    NASA Astrophysics Data System (ADS)

    Sims, Robert A.; Kernal, John; Fedorov, Vladimir V.; Mirov, Sergey B.

    2006-02-01

    Cobalt doped ZnSe and ZnS crystals have been studied to determine their effectiveness for passive Q-switching for 700-800nm spectral range (Alexandrite laser). Samples were prepared using Bridgeman technique for single-step growth of Co doped crystals as well as after growth thermal diffusion of Co in undoped crystals. ZnS:Co:Cr crystals, which have been produced using the Bridgeman technique, show maximum initial absorption coefficients of 17 cm -1 at 725nm. Experimental results are reported on effective thermal diffusion of Co 2+ in ZnSe and ZnS polycrystals and thermal diffusion constants of cobalt ions in ZnSe and ZnS are estimated. The nonlinear saturation properties of cobalt doped ZnSe and ZnS crystals have been investigated experimentally. The induced transparency measurements were performed using electro-optically Q-switched, alexandrite laser radiation at 731, 741, and 778 nm with a pulse duration of about 70 ns. The induced transmission measurements were analyzed using a four-level absorber model and the absorption cross sections have been estimated at both 731nm and 741nm to be 9.5 × 10 -18 cm2 and 8.2 × 10 -18 cm2, respectively. Absorption cross sections calculated from saturation measurements at 4A II--> 4T I(4P) transition are in agreement with results earlier reported for mid-infrared spectral region 4A II--> 4T II of Co 2+ ions. The described Co-doped crystals are very promising as passive Q-switches for alexandrite laser resonators. Co 2+ centers feature high cross section of saturation and their absorption bands are nicely matched to the spectral emission of the tunable alexandrite laser. An efficient ZnS:Co:Cr passive Q-switching of the alexandrite laser cavity was realized with output energy of 15 mJ and 50 ns pulse duration.

  18. Photoluminescence properties of AgInS2-ZnS nanocrystals: the critical role of the surface

    NASA Astrophysics Data System (ADS)

    Chevallier, Théo; Le Blevennec, Gilles; Chandezon, Frédéric

    2016-03-01

    AgInS2-ZnS (ZAIS) nanocrystals are very good candidates for easily synthesized, highly efficient cadmium-free nano-phosphors. They can be employed for the development of next generation white-LED technologies, taking advantage of their nanometric size. This paper describes the combined use of time-resolved emission spectroscopy and photoluminescence quantum yield measurements to quantitatively compare the efficiency of each recombination pathway involved in the photoluminescence of ZAIS nanocrystals. This approach, applied to nanocrystals of different sizes, compositions and surface chemistry revealed the critical role of surface effects. Moreover, we developed a new type of surface passivation that increases the photoluminescence quantum yield of all nanocrystal compositions by 15 to 20%. This molecular surface passivation can be applied as a replacement or in addition to the already established ZnS shell passivation method.AgInS2-ZnS (ZAIS) nanocrystals are very good candidates for easily synthesized, highly efficient cadmium-free nano-phosphors. They can be employed for the development of next generation white-LED technologies, taking advantage of their nanometric size. This paper describes the combined use of time-resolved emission spectroscopy and photoluminescence quantum yield measurements to quantitatively compare the efficiency of each recombination pathway involved in the photoluminescence of ZAIS nanocrystals. This approach, applied to nanocrystals of different sizes, compositions and surface chemistry revealed the critical role of surface effects. Moreover, we developed a new type of surface passivation that increases the photoluminescence quantum yield of all nanocrystal compositions by 15 to 20%. This molecular surface passivation can be applied as a replacement or in addition to the already established ZnS shell passivation method. Electronic supplementary information (ESI) available. See DOI: 10.1039/C5NR07082A

  19. Enhanced charge separation at 2D MoS2/ZnS heterojunction: KPFM based study of interface photovoltage

    NASA Astrophysics Data System (ADS)

    Sharma, Intu; Mehta, B. R.

    2017-02-01

    Two dimensional (2D) MoS2/ZnS heterojunctions with MoS2 thickness varying from monolayer to bulk have been prepared by sulfurization of a controlled thickness of Mo deposited on the ZnS thin films. Kelvin probe force microscopy measurements on MoS2/ZnS junction having varying thicknesses of MoS2 layers are carried out in the surface and junction modes, under white light exposure. Differences in the surface potential values of the surface and junction modes represent interface photovoltages at heterojunctions. Enhanced interface photovoltage is observed in junctions having the mono and few layer MoS2 in comparison to bulk MoS2 layer. This suggests the active participation of 2D MoS2 layer in photon absorption and charge separation processes taking place close to the junction. The present study is an effort towards the integration of 2D layered materials with 3D semiconductors, which may be advantageous for the development of 2D material based optoelectronic devices.

  20. One-step colloidal synthesis of biocompatible water-soluble ZnS quantum dot/chitosan nanoconjugates

    NASA Astrophysics Data System (ADS)

    Ramanery, Fábio P.; Mansur, Alexandra AP; Mansur, Herman S.

    2013-12-01

    Quantum dots (QDs) are luminescent semiconductor nanocrystals with great prospective for use in biomedical and environmental applications. Nonetheless, eliminating the potential cytotoxicity of the QDs made with heavy metals is still a challenge facing the research community. Thus, the aim of this work was to develop a novel facile route for synthesising biocompatible QDs employing carbohydrate ligands in aqueous colloidal chemistry with optical properties tuned by pH. The synthesis of ZnS QDs capped by chitosan was performed using a single-step aqueous colloidal process at room temperature. The nanobioconjugates were extensively characterised by several techniques, and the results demonstrated that the average size of ZnS nanocrystals and their fluorescent properties were influenced by the pH during the synthesis. Hence, novel 'cadmium-free' biofunctionalised systems based on ZnS QDs capped by chitosan were successfully developed exhibiting luminescent activity that may be used in a large number of possible applications, such as probes in biology, medicine and pharmacy.

  1. Copper-Filled Through-Hole Electrode of a ZnS Window Material for Sealing a Thermal Infrared Sensor

    NASA Astrophysics Data System (ADS)

    Fukumoto, Takafumi; Okamoto, Naoki; Ohta, Yoshimi; Fukuyama, Yasuhiro; Hirota, Masaki; Kondo, Kazuo

    The through-hole electrode for the wafer level package (WLP) was formed with the aim of lowering the cost of infrared sensors. It has been difficult to plate a ZnS substrate for use as the window material of WLPs because of low adhesion. However, through-hole filling was successfully accomplished in this work by applying a newly developed method of direct nonelectrolyte plating. Concretely, a blast cleaning process was performed on a ZnS substrate of 1 mm thickness. Then, a through-hole with both sides tapered was formed with an aspect ratio of 7. A compound process of Cu substitution plating and Ni nonelectrolyte plating was applied to the through-hole, forming a uniform plating film with high adhesion in the hole. Finally, the through-hole was completely filled by Cu electroplating. A He leak test confirmed that the sample had high sealing properties, with a measured leak rate of 1.0 × 10-10 Pa·m3/sec or less. The results showed that a ZnS substrate can be used effectively for IR window material, making it possible to reduce the cost of infrared cameras.

  2. Protein-mediated synthesis of nanosized Mn-doped ZnS: a multifunctional, UV-durable bio-nanocomposite.

    PubMed

    Makhal, Abhinandan; Sarkar, Soumik; Pal, Samir Kumar

    2012-10-01

    The design of synthetic nanoparticles (NPs) capable of recognizing given chemical entities in a specific and predictable manner is of great fundamental and practical importance. Herein, we report a simple, fast, water-soluble, and green phosphine free colloidal synthesis route for the preparation of multifunctional enzyme-capped ZnS bionanocomposites (BNCs) with/without transitional metal-ion doping. The enzymes α-Chymotrypsin (CHT), associated with the NPs, are demonstrated as an effectual host for organic dye Methylene Blue (MB) revealing the molecular recognition of such dye molecules by the BNCs. An effective hosting of MB in the close proximity of ZnS NPs (with ~3 nm size) leads to photocatalysis of the dyes which has further been investigated with doped-semiconductors. The NP-associated enzyme α-CHT is found to be active toward a substrate (Ala-Ala-Phe-7-amido-4-methyl-coumarin), hence leads to significant enzyme catalysis. Irradiation induced luminescence enhancement (IILE) measurements on the BNCs clearly interpret the role of surface capping agents which protect against deep UV damaging of ZnS NPs.

  3. Photoluminescence of ZnS 1-xSex:Te Prepared by Solution Growth Using Sb-Chalcogenides as Solvent

    NASA Astrophysics Data System (ADS)

    Araki, Hiroyuki; Kanie, Hisashi; Sano, Masatoshi

    1995-06-01

    Photoluminescences due to Te isoelectronic traps were investigated for Te-doped ZnS1-xSex crystals (0 ≤x ≤1) grown from Sb-chalcogenide solutions. The optical depths of the isolated Te atom center and the nearest-neighbor Te Te pair center were determined from the emission spectra and the excitation spectra at 77 K. These depths decreased monotonically with increasing Se composition x. The theoretical relation between the optical depth and the composition x on the basis of the Koster-Slater one-band one-site approximation was best fitted to the experimental data by assuming the values of the matrix element of the impurity potential J ZnS:Te = 2.41 eV, J ZnSe:Te = 1.27 eV, and the effective width of the valence band T ZnS = 6.02 eV, T ZnSe = 6.21 eV. According to the criteria in the theory, excitons bound to the isolated Te atoms exist in ZnS1-xSex:Te for 0 ≤x < 0.85 and excitons bound to the Te Te pairs exist throughout the entire composition range. The emission band observed at 2.61 eV in ZnSe:Te was shown to be due to the excitons bound to the Te Te pairs.

  4. Single step synthesis of ZnS quantum dots and their microstructure characterization and electrical transport below room temperature

    NASA Astrophysics Data System (ADS)

    Mukherjee, P. S.; Patra, S.; Chakraborty, G.; Pradhan, S. K.; Meikap, A. K.

    2016-09-01

    Low dimensional cubic phase ZnS quantum dots (QDs) are formed by mechanical alloying the stoichiometric mixture of Zn and S powders at room temperature. During milling process the primary mixed phase ZnS is formed at about 3.5 h of milling and strain less single phase (cubic) ZnS QDs are formed with ∼4.5 nm in size after 20 h of milling. Detailed microstructure study has been done by both Rietveld analysis of x-ray diffraction pattern and high resolution transmission electron microscope images. Dc resistivity decreases with increasing temperature which can be explained by three-dimensional hopping conduction mechanisms. Observed negative magnetoconductivity has been analyzed by wave function shrinkage model. Alternating current conductivity can be described by the correlated barrier hopping conduction mechanism. Analysis of complex impedance indicates that the grain boundary resistance is found to be dominating over the grain resistance. Relaxation behavior has been explained by the analysis of the electric modulus.

  5. Facile Synthesis of Cu2ZnSnS4 Photovoltaic Absorber Thin Films via Sulfurization of Cu2SnS3/ZnS Layers

    NASA Astrophysics Data System (ADS)

    Kahraman, Süleyman; Podlogar, Mateja; Bernik, Slavko; Güder, Hüsnü Salih

    2014-04-01

    Copper zinc tin sulfide (Cu2ZnSnS4) has been receiving a lot of attention in recent years as a new, alternative absorber for the production of cheap thin film solar cells owing to the high natural abundance of all the constituents, its tunable direct-band-gap energy, and its large optical absorption coefficient. In addition, to overcome the problem of expensive vacuum-based methods, solution-based approaches are being developed for Cu2ZnSnS4 deposition. In this study, Cu2ZnSnS4 thin films were grown on soda lime glass substrates via the sulfurization of solution grown Cu2SnS3/ZnS stacked sulfide layers. A new facile route to overcome the difficulty of depositing Cu2ZnSnS4 thin film with a desired stoichiometric composition in a single cation solution has been presented. The influences of deposition cycles of layers on the morphological, compositional, structural, and optical properties of the samples were investigated. It was observed from scanning electron microscopy (SEM) images that the films were continuous and composed of homogenously distributed large grains. Possible chemical formulations of the best samples were predicted to be Cu1.99Zn1.25Sn1.00S3.76 and Cu1.97Zn1.03Sn1.29S3.71 via energy-dispersive X-ray spectroscopy (EDXS) results. The X-ray diffraction (XRD) patterns of the samples matched very well with the reference values. The Raman-scattering analysis of the films proved the phase purity of the CZTS samples. The optical absorption coefficient of the films was found to be about 104 cm-1 based on absorbance spectroscopy. The optical band gaps of the films were estimated to be between 1.36 and 1.50 eV. From these we are able to conclude that CZTS thin films can be effectively obtained via the vacuum-atmosphere sulfurization of Cu2SnS3/ZnS stacked sulfide layers.

  6. White light tunable emissions from ZnS: Eu3+ nanophosphors over 330-465 nm excitation range for white LED applications

    NASA Astrophysics Data System (ADS)

    Ahemen, I.; De, D. K.; Dejene, F. B.; Viana, B.

    2016-04-01

    (ZnS: Eu3+ - CMC) nanophosphors of cubic (zinc blende) structure were synthesized using a precipitation technique with doping concentrations of Eu3+ ions 1 mol% and 5 mol%. The crystal sizes were 2.56 nm and 2.91 nm respectively. Annealing at 300 °C in a sulfur-rich atmosphere altered the crystal size to 4.35 nm and 3.65 nm respectively and the band gap from 4.2 eV to 3.76 eV and 3.81 eV respectively. The as-synthesized samples gave pure orange-red emission when excited at wavelengths of 394 nm and 465 nm. After thermal annealing of the samples, a broad emission band in the blue-green region assigned to defect related states emerged or were enhanced. Also enhanced were the emission lines of Eu3+ ions in the orange-red region. A combination of these two transitions gave white light of different shades (recorded on the CIE 1931 chromaticity diagram) from cool white through day-light to warm white light, depending on Eu3+ concentration and the excitation wavelengths (UV-330 to blue 465 nm), thus showing great potential of these nano-phosphors in the generation of high quality white light.

  7. Synthesis and characterization of Cu2ZnSnS4 from Cu2SnS3 and ZnS compounds

    NASA Astrophysics Data System (ADS)

    Li, Shi-na; Ma, Rui-xin; Li, Dong-ran; Yang, Fan; Zhang, Xiao-yong; Li, Xiang; Zhu, Hong-min

    2015-07-01

    The Cu2ZnSnS4 (CZTS) powders are successfully synthesized by using ZnS and Cu2SnS3 as raw materials directly without any intermediate phase at 450 °C for 3 h in Ar atmosphere. The crystalline structure, morphology and optical properties of the CZTS powders are characterized by X-ray diffraction (XRD), Raman spectrum, field emission scanning electron microscopy (FESEM) and ultraviolet-visible (UV-vis) spectrophotometer, respectively. The results show that the band gap of the obtained CZTS is 1.53 eV. The CZTS film is fabricated by spin coating a mixture of CZTS powders and novolac resin with a weight percentage of 30%. The photoelectrical properties of such CZTS films are measured, and the results show an incident light density of 100 mW·cm-2 with the bias voltage of 0.40 V, and the photocurrent density can approach 9.80×10-5 A·cm2 within 50 s, giving an on/off switching ratio of 1.64.

  8. Photocatalytic reactions of nanocomposite of ZnS nanoparticles and montmorillonite

    NASA Astrophysics Data System (ADS)

    Praus, P.; Reli, M.; Kočí, K.; Obalová, L.

    2013-06-01

    ZnS nanoparticles stabilized by cetyltrimethylammonium bromide (CTAB) were deposited on montmorillonite (MMT) forming a ZnS-CTA-MMT nanocomposite. The nanocomposite was characterized by scanning electron microscopy (SEM), Fourier transformed infrared (FTIR) and UV diffuse reflectance spectra (DRS) spectrometry, X-ray powder diffraction (XRD) and specific surface area measurements. Thereafter, it was used for photocatalytic reactions under UV irradiation (Hg lamp) in three different reaction media with different pH: NaOH solution, HCl solution and water. Prior to the photocatalytic reactions the dispersions were saturated by carbon dioxide to buffer the systems. The main reaction products in gas phase determined by gas chromatography were hydrogen and methane. The reactions were monitored by measuring oxidation-reduction potentials. The highest yields of hydrogen were obtained in the dispersion acidified by HCl but the concentrations of methane were similar in all tested media. Hydrogen was supposed to be formed by the reaction of two hydrogen radicals. Methane was formed by the reduction of carbon dioxide and by the partial decomposition of CTAB.

  9. Super Exchange-Induced Canted Ferromagnetism in Transition Metal-Doped ZnS Quantum Dots

    NASA Astrophysics Data System (ADS)

    Sharma, Lalit Kumar; Mukherjee, Samrat

    2017-02-01

    ZnS quantum dots doped with magnetic transition metal (Zn1- x TM x S; where x = 0.04, 0.08 and transition metal = Ni, Mn, Fe, Co and Cr) were synthesized using a chemical co-precipitation method. To prevent agglomeration, samples were capped with polyvinylpyrrolidone. X-ray diffraction peaks confirmed pure cubic phases of all samples. The crystallite dimensions of the samples are within the scale of 2.0-2.6 nm, which was calculated using Scherrer formula. A band gap varying from 4.1 eV to 4.24 eV was estimated from their ultraviolet-visible absorption spectroscopy. The synthesized samples show a strong blue shift in their emission spectroscopy along with emissions from inherent Zn and S point defects (interstitial and vacancy). Superconducting quantum interference device studies at 300 K reveal that all samples show room temperature canted ferromagnetism at low magnetic fields which does not saturate even up to a fields of 5 T. We study the defects as seen through emission spectroscopy and correlate with the magnetic properties of the doped semiconducting quantum dots.

  10. Optimization of the ZnS Buffer Layer by Chemical Bath Deposition for Cu(In,Ga)Se2 Solar Cells.

    PubMed

    Jeon, Dong-Hwan; Hwang, Dae-Kue; Kim, Dae-Hwan; Kang, Jin-Kyu; Lee, Chang-Seop

    2016-05-01

    We evaluated a ZnS buffer layer prepared using a chemical bath deposition (CBD) process for application in cadmium-free Cu(In,Ga)Se2 (CIGS) solar cells. The ZnS buffer layer showed good transmittance (above 90%) in the spectral range from 300 to 800 nm and was non-toxic compared with the CdS buffer layers normally used in CIGS solar cells. The CBD process was affected by several deposition conditions. The deposition rate was dependent on the ammonia concentration (complexing agent). When the ammonia concentration was either too high or low, a decrease in the deposition rate was observed. In addition, post heat treatments at high temperatures had detrimental influences on the ZnS buffer layers because portions of the ZnS thin films were transformed into ZnO. With optimized deposition conditions, a CIGS solar cell with a ZnS buffer layer showed an efficiency of 14.18% with a 0.23 cm2 active area under 100 mW/cm2 illumination.

  11. Large Stokes Shift and High Efficiency Luminescent Solar Concentrator Incorporated with CuInS2/ZnS Quantum Dots

    NASA Astrophysics Data System (ADS)

    Li, Chen; Chen, Wei; Wu, Dan; Quan, Dunhang; Zhou, Ziming; Hao, Junjie; Qin, Jing; Li, Yiwen; He, Zhubing; Wang, Kai

    2015-12-01

    Luminescent solar concentrator (LSC) incorporated with quantum dots (QDs) have been widely regarded as one of the most important development trends of cost-effective solar energy. In this study, for the first time we report a new QDs-LSC integrated with heavy metal free CuInS2/ZnS core/shell QDs with large Stokes shift and high optical efficiency. The as-prepared CuInS2/ZnS QDs possess advantages of high photoluminescence quantum yield of 81% and large Stocks shift more than 150 nm. The optical efficiency of CuInS2/ZnS QDs-LSC reaches as high as 26.5%. Moreover, the power conversion efficiency of the QDs-LSC-PV device reaches more than 3 folds to that of pure PMMA-PV device. Furthermore, the PV device is able to harvest 4.91 folds solar energy with the assistance of this new CuInS2/ZnS QDs-LSC for the same size c-Si PV cell. The results demonstrate that this new CuInS2/ZnS QDs-LSC provides a promising way for the high efficiency, nonhazardous and low cost solar energy.

  12. Thermal and optical characterization of biologically synthesized ZnS nanoparticles synthesized from an endophytic fungus Aspergillus flavus: A colorimetric probe in metal detection

    NASA Astrophysics Data System (ADS)

    Uddandarao, Priyanka; Balakrishnan, Raj Mohan

    2017-03-01

    Nanostructured semiconductor materials are of great importance for several technological applications due to their optical and thermal properties. The design and fabrication of metal sulfide nanoparticles with tunable properties for advanced applications have drawn a great deal of attention in the field of nanotechnology. ZnS is a potential II-IV group material which is used in hetero-junction solar cells, light emitting diodes, optoelectronic devices, electro luminescent devices and photovoltaic cells. Due to their multiple applications, there is a need to elucidate their thermal and optical properties. In the present study, thermal and optical properties of biologically synthesized ZnS nanoparticles are determined in detail with Thermal Gravimetric Analysis (TGA), Derivative Thermogravimetric Analysis (DTG), Differential Scanning Calorimeter (DSC), Diffuse Reflectance Spectroscopy (DRS), Photoluminescence (PL) and Raman spectroscopy. The results reveal that ZnS NPs exhibit a very strong quantum confinement with a significant increase in their optical band gap energy. These biologically synthesized ZnS NPs contain protein residues that can selectively bind with metal ions in aqueous solutions and can exhibit an aggregation-induced color change. This phenomenon is utilized to quantitatively measure the metal concentrations of Cu2 + and Mn2 + in this study. Further the stability of nanoparticles for the metal sensing process is accessed by UV-Vis spectrometer, zeta potential and cyclic voltammeter. The selectivity and sensitivity of ZnS NPs indicate its potential use as a sensor for metal detection in the ecosystem.

  13. Large Stokes Shift and High Efficiency Luminescent Solar Concentrator Incorporated with CuInS2/ZnS Quantum Dots

    PubMed Central

    Li, Chen; Chen, Wei; Wu, Dan; Quan, Dunhang; Zhou, Ziming; Hao, Junjie; Qin, Jing; Li, Yiwen; He, Zhubing; Wang, Kai

    2015-01-01

    Luminescent solar concentrator (LSC) incorporated with quantum dots (QDs) have been widely regarded as one of the most important development trends of cost-effective solar energy. In this study, for the first time we report a new QDs-LSC integrated with heavy metal free CuInS2/ZnS core/shell QDs with large Stokes shift and high optical efficiency. The as-prepared CuInS2/ZnS QDs possess advantages of high photoluminescence quantum yield of 81% and large Stocks shift more than 150 nm. The optical efficiency of CuInS2/ZnS QDs-LSC reaches as high as 26.5%. Moreover, the power conversion efficiency of the QDs-LSC-PV device reaches more than 3 folds to that of pure PMMA-PV device. Furthermore, the PV device is able to harvest 4.91 folds solar energy with the assistance of this new CuInS2/ZnS QDs-LSC for the same size c-Si PV cell. The results demonstrate that this new CuInS2/ZnS QDs-LSC provides a promising way for the high efficiency, nonhazardous and low cost solar energy. PMID:26642815

  14. Large Stokes Shift and High Efficiency Luminescent Solar Concentrator Incorporated with CuInS2/ZnS Quantum Dots.

    PubMed

    Li, Chen; Chen, Wei; Wu, Dan; Quan, Dunhang; Zhou, Ziming; Hao, Junjie; Qin, Jing; Li, Yiwen; He, Zhubing; Wang, Kai

    2015-12-08

    Luminescent solar concentrator (LSC) incorporated with quantum dots (QDs) have been widely regarded as one of the most important development trends of cost-effective solar energy. In this study, for the first time we report a new QDs-LSC integrated with heavy metal free CuInS2/ZnS core/shell QDs with large Stokes shift and high optical efficiency. The as-prepared CuInS2/ZnS QDs possess advantages of high photoluminescence quantum yield of 81% and large Stocks shift more than 150 nm. The optical efficiency of CuInS2/ZnS QDs-LSC reaches as high as 26.5%. Moreover, the power conversion efficiency of the QDs-LSC-PV device reaches more than 3 folds to that of pure PMMA-PV device. Furthermore, the PV device is able to harvest 4.91 folds solar energy with the assistance of this new CuInS2/ZnS QDs-LSC for the same size c-Si PV cell. The results demonstrate that this new CuInS2/ZnS QDs-LSC provides a promising way for the high efficiency, nonhazardous and low cost solar energy.

  15. Controlled synthesis of Bi2S3/ZnS microspheres by an in situ ion-exchange process with enhanced visible light photocatalytic activity.

    PubMed

    Wu, Zhudong; Chen, Linlin; Xing, Chaosheng; Jiang, Deli; Xie, Jimin; Chen, Min

    2013-09-28

    A novel Bi2S3/ZnS heterostructure has been synthesized through an in situ cation-exchange method between ZnS and bismuth(III) chloride. The obtained samples were characterized by multiform techniques, such as X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission microscopy, UV-visible diffuse-reflectance spectroscopy, and photoluminescence spectra. The photocatalytic activities of the obtained photocatalysts were measured by the degradation of rhodamine B (RhB) and refractory oxytetracycline (OTC) under visible-light irradiation (λ ≥ 400 nm). The as-prepared Bi2S3/ZnS photocatalysts exhibit wide absorption in the visible-light region and display superior visible-light-driven photocatalytic activities in degradation of RhB and OTC compared with pristine ZnS microspheres and Bi2S3 nanorods. The dramatic enhancement in the visible light photocatalytic performance of the Bi2S3/ZnS composites could be attributed to the effective electron-hole separations at the interfaces of the two semiconductors, which facilitate the transfer of the photoinduced carriers. The present study provides helpful insight into the design of novel and highly efficient sulfate heterostructure photocatalysts.

  16. Revelation of ZnS Nanoparticles Induces Follicular Atresia and Apoptosis in the Ovarian Preovulatory Follicles in the Catfish Mystus tengara (Hamilton, 1822)

    PubMed Central

    Chatterjee, Nilanjana

    2016-01-01

    Important physicochemical characteristics of water like dissolved oxygen content, pH, and so forth were found to change in a dose dependent manner, showing a negative correlation with the nanoparticle concentration, when ZnS nanoparticle (NP) was exposed to water. This observation could be attributed to the enhanced photooxidation property associated with ZnS in its NP form. Under this situation, the catfish Mystus tengara was forced to live in hypoxia in its habitat. This condition was found to hamper the natural oogenesis process of the fish. Due to exposure at relatively lower concentration of ZnS NPs (250 μg/L), most of the maturing follicles of M. tengara failed to complete the process of vitellogenesis properly and underwent preovulatory atresia followed by oocytic apoptosis. For relatively higher concentration of ZnS nanoparticles (500 μg/L), the previtellogenic process continued with increasing number of apoptotic cells; however the vitellogenic process was found to be totally blocked. This unusual reproductive behaviour in female M. tengara can be attributed to the decreased metabolism of the fishes under ZnS nanoparticle induced hypoxia. PMID:27051555

  17. Bicolor Mn-doped CuInS{sub 2}/ZnS core/shell nanocrystals for white light-emitting diode with high color rendering index

    SciTech Connect

    Huang, Bo; Dai, Qian; Zhang, Huichao; Liao, Chen; Cui, Yiping; Zhang, Jiayu; Zhuo, Ningze; Jiang, Qingsong; Shi, Fenghua; Wang, Haibo

    2014-09-07

    We synthesized bicolor Mn-doped CuInS{sub 2} (CIS)/ZnS core/shell nanocrystals (NCs), in which Mn{sup 2+} ions and the CIS core were separated with a ZnS layer, and both Mn{sup 2+} ions and CIS cores could emit simultaneously. Transmission electron microscopy and powder X-ray diffraction measurements indicated the epitaxial growth of ZnS shell on the CuInS{sub 2} core, and electron paramagnetic resonance spectrum indicated that Mn{sup 2+} ions were on the lattice points of ZnS shell. By integrating these bicolor NCs with commercial InGaN-based blue-emitting diodes, tricolor white light-emitting diodes with color rendering index of 83 were obtained.

  18. Using fluorescence measurement of zinc ions liberated from ZnS nanoparticle labels in bioassay for Escherichia coli O157:H7

    NASA Astrophysics Data System (ADS)

    Cowles, Chad L.; Zhu, Xiaoshan; Pai, Chi-Yun

    2011-10-01

    In this study, an alternative approach using ZnS nanoparticle biolabels as fluorescence signal transducers is reported for the immunoassay of E. coli O157:H7 in tap water samples. Instead of measuring the fluorescence of ZnS nanoparticles in the assay, the fluorescence signal is generated through the binding of zinc ions released from nanoparticle labels with zinc-ion sensitive fluorescence indicator Fluozin-3. In the assay, ZnS nanoparticles around 50 nm in diameter were synthesized, bioconjugated, and applied for the detection of E. coli O157:H7. The assay shows a detection range over two orders of magnitude and a detection limit around 1000 colony-forming units (cfu) of E. coli O157:H7.

  19. Effect on photophysical properties of colloidal ZnS quantum dots by doping with cobalt, copper, and cobalt-copper mixtures

    NASA Astrophysics Data System (ADS)

    Iqbal, Muhammad Javed; Iftekhar, Maryam

    2011-05-01

    Colloidal ZnS quantum dots (QDs) are prepared by passing H2S gas through a solution of Zn(CH3COO)2 in acetonitrile. Photophysical properties are investigated using UV-Visible and photoluminescence (PL) spectroscopy. The spectrum shows an absorption shoulder at 271 nm representing a band gap of 4.6 eV. The doping of ZnS QDs with Co, Cu, and a mixture of Co and Cu not only increased the band gap to 0.2 eV but also turns these otherwise colorless QDs to blue in color due to cobalt, and green due to Cu. The observed emission in the visible region suggests that the dopants may have induced additional excited states to the ZnS QDs. This absorbance in the visible region can be utilized in the optoelectronic applications.

  20. Magnetorheological finishing with chemically modified fluids for studying material removal of single-crystal ZnS

    NASA Astrophysics Data System (ADS)

    Salzman, S.; Romanofsky, H. J.; Clara, Y. I.; Giannechini, L. J.; West, Garrett J.; Lambropoulos, J. C.; Jacobs, S. D.

    2013-09-01

    Magnetorheological finishing (MRF) of polycrystalline, chemical-vapor-deposited (CVD) zinc sulfide (ZnS) and zinc selenide (ZnSe) can leave millimeter-size artifacts on the part surface. These pebble-like features come from the anisotropic mechanical and chemical properties of the ceramic material and from the CVD growth process itself. The resulting surface texture limits the use of MRF for polishing aspheric and other complex shapes using these important infrared (IR) ceramics. An investigation of the individual contributions of chemistry and mechanics to polishing of other polycrystalline ceramics has been employed in the past to overcome similar material anisotropy problems. The approach taken was to study the removal process for the different single-crystal orientations that comprise the ceramic, making adjustments to mechanics (polishing abrasive type and concentration) and polishing slurry chemistry (primarily pH) to equalize the removal rate for all crystal orientations. Polishing with the modified slurry was shown to prevent the development of surface texture. Here we present mechanical (microhardness testing) and chemical (acid etching) studies performed on the four single-crystal orientations of ZnS: 100, 110, 111, and 311. We found that the (111) plane is 35% to 55% harder and 30% to 40% more resistant to chemical etching than the other three planes. This relatively high degree of variation in these properties can help to explain the surface texture developed from MRF of the polycrystalline material. Theoretical calculations of microhardness, planar, and bond densities are presented and compared with the experimental data. Here surface characterization of these single-crystal orientations of ZnS for material removal and roughness with chemically modified MR fluids at various pH levels between pH 4 and pH 6 are presented for the first time.

  1. Electronic Levels Of Cr2+ Ion Doped In II-VI Compounds Of ZnS - Crystal Field Treatment

    NASA Astrophysics Data System (ADS)

    Ivaşcu, Simona

    2012-12-01

    The aim of present paper is to report the results on the modeling of the crystal field and spin-Hamiltonian parameters of Cr2+ doped in II-VI host matrix ZnS and simulate the energy levels scheme of such system taken into account the fine interactions entered in the Hamiltonian of the system. All considered types of such interaction are expected to give information on the new peculiarities of the absorption and emission bands, as well as of non-radiative transitions between the electronic states of impurity ions. The obtained results were disscused, compared with similar obtained results in literature and with experimental data.

  2. New insight into the ZnO sulfidation reaction: mechanism and kinetics modeling of the ZnS outward growth.

    PubMed

    Neveux, Laure; Chiche, David; Pérez-Pellitero, Javier; Favergeon, Loïc; Gay, Anne-Sophie; Pijolat, Michèle

    2013-02-07

    Zinc oxide based materials are commonly used for the final desulfurization of synthesis gas in Fischer-Tropsch based XTL processes. Although the ZnO sulfidation reaction has been widely studied, little is known about the transformation at the crystal scale, its detailed mechanism and kinetics. A model ZnO material with well-determined characteristics (particle size and shape) has been synthesized to perform this study. Characterizations of sulfided samples (using XRD, TEM and electron diffraction) have shown the formation of oriented polycrystalline ZnS nanoparticles with a predominant hexagonal form (wurtzite phase). TEM observations also have evidenced an outward development of the ZnS phase, showing zinc and oxygen diffusion from the ZnO-ZnS internal interface to the surface of the ZnS particle. The kinetics of ZnO sulfidation by H(2)S has been investigated using isothermal and isobaric thermogravimetry. Kinetic tests have been performed that show that nucleation of ZnS is instantaneous compared to the growth process. A reaction mechanism composed of eight elementary steps has been proposed to account for these results, and various possible rate laws have been determined upon approximation of the rate-determining step. Thermogravimetry experiments performed in a wide range of H(2)S and H(2)O partial pressures have shown that the ZnO sulfidation reaction rate has a nonlinear variation with H(2)S partial pressure at the same time no significant influence of water vapor on reaction kinetics has been observed. From these observations, a mixed kinetics of external interface reaction with water desorption and oxygen diffusion has been determined to control the reaction kinetics and the proposed mechanism has been validated. However, the formation of voids at the ZnO-ZnS internal interface, characterized by TEM and electron tomography, strongly slows down the reaction rate. Therefore, the impact of the decreasing ZnO-ZnS internal interface on reaction kinetics has been

  3. Aqueous amino acids and proteins near solid surfaces: ZnO, ZnS, Au, and mica

    NASA Astrophysics Data System (ADS)

    Cieplak, Marek

    2015-03-01

    We calculate potentials of the mean force for 20 amino acids in the vicinity of the (111) surface of Au, four surfaces of ZnO, and the (110) surface of ZnS using molecular dynamics simulations combined with the umbrella sampling method. In the case of Au, we compare results obtained within three different force fields: one hydrophobic (for a contaminated surface) and two hydrophilic - with and without polarization of the solid. The properties of water near the surface sensitively depend on the force field. All of these fields lead to good binding with very different specificities and to unlike patterns in the density and polarization of water. We demonstrate that binding energies of dipeptides are distinct from the combined binding energies of their amino acidic components. We show that ZnS is more more hydrophobic than ZnO and that the density profile of water is quite different than that forming near ZnO - it has only a minor articulation into layers. Furthermore, the first layer of water is disordered and mobile. In the case of ZnS, not all amino acids can attach to the surface and when they do, the binding energies are comparable to those found for the surfaces of ZnO (and to hydrogen bonds in proteins) but the nature of the specificity is distinct. The covalent bond with the sulfur atom on cysteine is modeled by the Morse potential. For the hydrophobic Au, adsorption events of a small protein (the tryptophan cage) are driven by attraction to the strongest binding amino acids. This is not so for ZnO, ZnS and for the hydrophilic models of Au - a result of smaller specificities combined with the difficulty for proteins, but sometimes not for single amino acids, to penetrate the first layer of water. Molecular dynamics studies of several proteins near mica with a net charge on its surface indicate existence of two types of states: deformed and unfolded. Using a coarse-grained model, we also study a glassy behavior of protein layers at air-water interfaces. Polish

  4. Cytotoxic effect of ZnS nanoparticles on primary mouse retinal pigment epithelial cells.

    PubMed

    Bose, Karthikeyan; Lakshminarasimhan, Harini; Sundar, Krishnan; Kathiresan, Thandavarayan

    2016-11-01

    The multiple properties of zinc sulphide nanoparticles (ZnS-NPs) are attracting great attention in the field of chemical and biological research. ZnS-NPs also find their application in biosensor and photocatalysis. Zinc is an important metal ion in retina and its deficiency leads to age-related macular degeneration. As of now, not much research is available on bio-interaction of ZnS as nanoform with retinal pigment epithelial (RPE) cells. RPE cells in the retina help in maintaining normal photoreceptor function and vision. To begin with, ZnS-NPs were synthesized and characterized using UV-visible spectra, X-ray diffraction, Fourier transform infrared spectrum, transmission electron microscopy and dynamic light scattering. Followed by the confirmation of nanoparticles, our study extended to investigate the impact of ZnS-NPs in primary mouse RPE (MRPE) cells at different concentrations. ZnS-NPs showed dose-dependent cytotoxicity in MRPE cells and no changes were observed in cells' tight intactness at minimal concentration. In addition, exposure to ZnS-NPs increased cellular permeability in dose- and time-dependent manner in MRPE cells. The findings from DCFH-DA analysis revealed that ZnS-NPs-treated cells had elevated level of reactive oxygen species and partial activation of cell apoptosis was identified after exposure to ZnS-NPs at higher concentration. Furthermore, pre-treatment of the primary MRPE cells with ZnS-NPs led to phosphorylation of Akt (Ser 473), which indicates the crucial role of ZnS-NPs in regulating cell survival at minimal concentration. Altogether, this study enumerates requisite dose of using ZnS-NPs to maintain healthy RPE cells and contributes to future studies in development of therapeutic drug and drug carrier for ocular-related disorders.

  5. Harmonic generation by atomic and nanoparticle precursors in a ZnS laser ablation plasma

    NASA Astrophysics Data System (ADS)

    Oujja, M.; Lopez-Quintas, I.; Benítez-Cañete, A.; de Nalda, R.; Castillejo, M.

    2017-01-01

    Harmonic generation of a driving laser propagating across a laser ablation plasma serves for the diagnosis of multicomponent plumes. Here we study the contribution of atomic and nanoparticle precursors to the generation of coherent ultraviolet and vacuum ultraviolet light as low-order harmonics of the fundamental emission (1064 nm) of a Q-switched Nd:YAG laser in a nanosecond infrared ZnS laser ablation plasma. Odd harmonics from the 3rd up to the 9th order (118.2 nm) have been observed with distinct temporal and spatial characteristics which were determined by varying the delay between the ablation and driving nanosecond pulses and by spatially scanning the plasma with the focused driving beam propagating parallel to the target. At short distances from the target surface (≤1 mm), the harmonic intensity displays two temporal components peaked at around 250 ns and 10 μs. While the early component dies off quickly with increasing harmonic order and vanishes for the 9th order, the late component is notably intense for the 7th harmonic and is still clearly visible for the 9th. Spectral analysis of spontaneous plume emissions help to assign the origin of the two components. While the early plasma component is mainly constituted by neutral Zn atoms, the late component is mostly due to nanoparticles, which upon interaction with the driving laser are subject to breakup and ionization. With the aid of calculations of the phase matching integrals within the perturbative model of optical harmonic generation, these results illustrate how atom and nanoparticle populations, with differing temporal and spatial distributions within the ablation plasma, contribute to the nonlinear medium.

  6. Highly Efficient Copper-Indium-Selenide Quantum Dot Solar Cells: Suppression of Carrier Recombination by Controlled ZnS Overlayers.

    PubMed

    Kim, Jae-Yup; Yang, Jiwoong; Yu, Jung Ho; Baek, Woonhyuk; Lee, Chul-Ho; Son, Hae Jung; Hyeon, Taeghwan; Ko, Min Jae

    2015-11-24

    Copper-indium-selenide (CISe) quantum dots (QDs) are a promising alternative to the toxic cadmium- and lead-chalcogenide QDs generally used in photovoltaics due to their low toxicity, narrow band gap, and high absorption coefficient. Here, we demonstrate that the photovoltaic performance of CISe QD-sensitized solar cells (QDSCs) can be greatly enhanced simply by optimizing the thickness of ZnS overlayers on the QD-sensitized TiO2 electrodes. By roughly doubling the thickness of the overlayers compared to the conventional one, conversion efficiency is enhanced by about 40%. Impedance studies reveal that the thick ZnS overlayers do not affect the energetic characteristics of the photoanode, yet enhance the kinetic characteristics, leading to more efficient photovoltaic performance. In particular, both interfacial electron recombination with the electrolyte and nonradiative recombination associated with QDs are significantly reduced. As a result, our best cell yields a conversion efficiency of 8.10% under standard solar illumination, a record high for heavy metal-free QD solar cells to date.

  7. Highly enhanced photoluminescence of AgInS2/ZnS quantum dots by hot-injection method

    NASA Astrophysics Data System (ADS)

    Liao, Shenghua; Huang, Yu; Zhang, Ying; Shan, Xiaohui; Yan, Zhengyu; Shen, Weiyang

    2015-01-01

    Highly photoluminescent and air-stable AgInS2 quantum dots (AIS QDs) were synthesized by a hot-injection route in N2 atmosphere and dark environment. The as-synthesized AIS QDs were further capped with ZnS shell by one-pot method in order to enhance the photoluminescence (PL) intensity. The photo-electronic property and the morphology of AIS QDs and AIS/ZnS QDs were characterized by ultraviolet-visible spectroscopy (UV), PL spectroscopy and transmission electronic microscopy (TEM). The results indicated that the narrow and symmetrical PL spectra of AIS QDs was time-dependent, and the emission wavelength of AIS QDs could be tunable within 436-610 nm by altering the initial Ag/In ratios. After being capped with ZnS shell, the AIS QDs showed excellent optical characteristics, including PL QYs up to 15%. The TEM results indicated that the spherical AIS/ZnS QDs were nearly monodispersed and homogeneous with an average particle size of 8 nm. The heavy metal free and high luminous AIS/ZnS QDs have great potential in biological application.

  8. ZnS quantum dot induced phase transitional changes and enhanced ferroelectric mesophase in QDs/FLC composites

    NASA Astrophysics Data System (ADS)

    Vimal, T.; Pandey, S.; Singh, D. P.; Gupta, S. K.; Agrahari, K.; Kumbhakar, P.; Kole, A. K.; Manohar, R.

    2017-01-01

    In the present study, we report the dielectric and electro - optical (E - O) study of ZnS quantum dots (QDs) dispersed ferroelectric liquid crystal (FLC) material. Change in the SmC*- SmA phase transition temperature has been investigated by the thermal study. Width of SmC* phase is found to be slightly increased due to the dispersion of ZnS QDs, which has also been observed in the dielectric and E - O study of composites. Fitting of spontaneous polarization curves on the temperature scale has been done theoretically to obtain the change in SmC*- SmA phase transition temperature. A significant modification in the FLC material parameters (like spontaneous polarization, optical response time, tilt angle and rotational viscosity) has been observed after the dispersion of QDs. These modifications are the consequences of the strong dipolar interaction between the FLC molecule and QDs. Significant fastening of the optical response time for low conc. of QDs dispersed FLC composite shows its utilization in advanced display devices.

  9. Silica-coated ZnS quantum dots as fluorescent probes for the sensitive detection of Pb2+ ions

    NASA Astrophysics Data System (ADS)

    Qu, Hua; Cao, Lixin; Su, Ge; Liu, Wei; Gao, Rongjie; Xia, Chenghui; Qin, Junjie

    2014-12-01

    The silica-coated ZnS quantum dots (ZnS@SiO2 QDs) were prepared via a simple and environmentally friendly process. The oil-soluble ZnS cores were successfully transferred to water by the coating of SiO2 shells. The QDs exhibited satisfying dispersion and luminescent properties in water. The ZnS@SiO2 QDs were directly used as fluorescent probes for heavy metal ions without the addition of any buffer solution. The luminescence of QDs was extremely sensitive to Pb2+ ions, and the fluorescence quenching was well described by the Stern-Volmer equation, with an even quenching constant for the Pb2+ ions samples concentration ranging from 10-9 to 2.6 × 10-4 M. An extended hypothesis based on the traditional cation exchange mechanism is proposed to analyze the most significant fluorescence quenching effect by Pb2+ ions. Studies show that ZnS@SiO2 QDs have great potentials to be a sensor for Pb2+ analysis at low to high concentrations.

  10. Aqueous synthesis of Ag and Mn co-doped In2S3/ZnS quantum dots with tunable emission for dual-modal targeted imaging.

    PubMed

    Lai, Pei-Yu; Huang, Chih-Ching; Chou, Tzung-Han; Ou, Keng-Liang; Chang, Jia-Yaw

    2017-03-01

    Here, we present the microwave-assisted synthesis of In2S3/ZnS core/shell quantum dots (QDs) co-doped with Ag(+) and Mn(2+) (referred to as AgMn:In2S3/ZnS). Ag(+) altered the optical properties of the host QDs, whereas the spin magnetic moment (S=5/2) of Mn(2+) efficiently induced the longitudinal relaxation of water protons. To the best of our knowledge, this is the first report of the aqueous synthesis of color-tunable AgMn:In2S3/ZnS core/shell QDs with magnetic properties. The synthetic procedure is rapid, facile, reproducible, and scalable. The obtained QDs offered a satisfactory quantum yield (45%), high longitudinal relaxivity (6.84s(-1)mM(-1)), and robust photostability. In addition, they exhibited excellent stability over a wide pH range (5-12) and high ionic strength (0.15-2.0M NaCl). As seen by confocal microscopy and magnetic resonance imaging, AgMn:In2S3/ZnS conjugated to hyaluronic acid (referred to as AgMn:In2S3/ZnS@HA) efficiently and specifically targeted cluster determinant 44, a receptor overexpressed on cancer cells. Moreover, AgMn:In2S3/ZnS@HA showed negligible cytotoxicity in vitro and in vivo, rendering it a promising diagnostic probe for dual-modal imaging in clinical applications.

  11. Nonlinear optical second harmonic generation in ZnS quantum dots and observation on optical properties of ZnS/PMMA nanocomposites

    NASA Astrophysics Data System (ADS)

    Kole, A. K.; Gupta, S.; Kumbhakar, P.; Ramamurthy, P. C.

    2014-02-01

    ZnS quantum dots (QDs) of different sizes are synthesized by a simple chemical co-precipitation method at room temperature, by varying pH value of the reaction mixture. Samples are characterized by an X-ray diffractometer, transmission electron microscope, energy-dispersive X-ray analysis, etc. Linear optical properties, including UV-visible absorption and photoluminescence emission characteristics, of as-prepared QDs are measured. Size dependent nonlinear optical property, such as second harmonic generation (SHG) of 1064 nm Nd:YAG laser fundamental radiation in the synthesized ZnS QDs, is reported for the first time, to the best of our knowledge, by using the standard Kurtz-Perry powder method. In order to study the possibility of the synthesized ZnS QDs in different device applications ZnS/PMMA (polymethylmethacrylate) nanocomposites are also synthesized. The presence of weak chemical interaction between the polymer matrix and ZnS QDs is confirmed by Fourier transform infrared spectroscopy. Thermal properties of the nanocomposites are studied by differential scanning calorimetry and thermo-gravimetric analysis techniques, which show that the composites are stable up to ~300 °C temperature.

  12. Conjugation of glucose oxidase onto Mn-doped ZnS quantum dots for phosphorescent sensing of glucose in biological fluids.

    PubMed

    Wu, Peng; He, Yu; Wang, He-Fang; Yan, Xiu-Ping

    2010-02-15

    Integrating various enzymes with nanomaterials provides various nanohybrids with new possibilities in biosensor applications. Furthermore, the enzymatic activity and stability are also improved due to the large surface area of nanomaterials. Here we report the conjugation of glucose oxidase (GOD) onto phosphorescent Mn-doped ZnS quantum dots (QDs) using 1-ethyl-3-(3-dimethylaminopropy)carbodiimide (EDC)/N-hydroxysuccinimide (NHS) as coupling reagents for glucose biosensing based on the effective quenching of the room temperature phosphorescence (RTP) of Mn-doped ZnS QDs by the H(2)O(2) generated from GOD-catalyzed oxidation of glucose. The obtained bioconjugate not only provided improved enzymatic performance with Michaelis-Menten constant of 0.70 mM but also favored biological applications because the phosphorescent detection mode avoided the interference from autofluorescence and scattering light from the biological matrix. In addition, the GOD-conjugated Mn-doped ZnS QDs showed better thermal stability in the temperature range of 20-80 degrees C. The GOD-Mn-doped ZnS QDs based RTP sensor for glucose gave a detection limit of 3 microM and two linear ranges from 10 microM to 0.1 mM and from 0.1 to 1 mM. The developed biosensor was successfully applied to the determination of glucose in real serum samples without the need for any complicated sample pretreatments.

  13. Fluorescence resonance energy transfer between ZnSe ZnS quantum dots and bovine serum albumin in bioaffinity assays of anticancer drugs

    NASA Astrophysics Data System (ADS)

    Shu, Chang; Ding, Li; Zhong, Wenying

    2014-10-01

    In the current work, using ZnSe ZnS quantum dots (QDs) as representative nanoparticles, the affinities of seven anticancer drugs for bovine serum albumin (BSA) were studied using fluorescence resonance energy transfer (FRET). The FRET efficiency of BSA-QD conjugates can reach as high as 24.87% by electrostatic interaction. The higher binding constant (3.63 × 107 L mol-1) and number of binding sites (1.75) between ZnSe ZnS QDs and BSA demonstrated that the QDs could easily associate to plasma proteins and enhance the transport efficacy of drugs. The magnitude of binding constants (103-106 L mol-1), in the presence of QDs, was between drugs-BSA and drugs-QDs in agreement with common affinities of drugs for serum albumins (104-106 L mol-1) in vivo. ZnSe ZnS QDs significantly increased the affinities for BSA of Vorinostat (SAHA), Docetaxel (DOC), Carmustine (BCNU), Doxorubicin (Dox) and 10-Hydroxycamptothecin (HCPT). However, they slightly reduced the affinities of Vincristine (VCR) and Methotrexate (MTX) for BSA. The recent work will not only provide useful information for appropriately understanding the binding affinity and binding mechanism at the molecular level, but also illustrate the ZnSe ZnS QDs are perfect candidates for nanoscal drug delivery system (DDS).

  14. Effect of particle size on activation energy and peak temperature of the thermoluminescence glow curve of undoped ZnS nanoparticles.

    PubMed

    Chandra, B P; Chandrakar, Raju Kumar; Chandra, V K; Baghel, R N

    2016-03-01

    This paper reports the effect of particle size on the thermoluminescence (TL) of undoped ZnS nanoparticles. ZnS nanoparticles were prepared using a chemical precipitation method in which mercaptoethanol was used as the capping agent. The nanoparticles were characterized by X-ray diffraction, field emission gun-scanning electron microscopy and high-resolution transmission electron microscopy. When the concentrations of mercaptoethanol used are 0, 0.005, 0.01, 0.015, 0.025, 0.040 and 0.060 M, the sizes of the nanoparticles are 2.86, 2.81, 2.69, 2.40, 2.10, 1.90 and 1.80 nm, respectively. Initially, the TL intensity of UV-irradiated ZnS nanoparticles increases with temperature, attains a peak value Im for a particular temperature Tm, and then decreases with further increases in temperature. The values of both Im and Tm increase with decreasing nanoparticle size. Whereas the activation energy decreases slightly with decreasing nanoparticle size, the frequency factor decreases significantly as the nanoparticle size is reduced. The order of kinetics for the TL glow curve of ZnS nanoparticles is 2. Expressions are derived for the dependence of activation energy (Ea) and Tm on nanoparticle size, and good agreement is found between the experimental and theoretical results.

  15. Fluorescence resonance energy transfer between ZnSe ZnS quantum dots and bovine serum albumin in bioaffinity assays of anticancer drugs.

    PubMed

    Shu, Chang; Ding, Li; Zhong, Wenying

    2014-10-15

    In the current work, using ZnSe ZnS quantum dots (QDs) as representative nanoparticles, the affinities of seven anticancer drugs for bovine serum albumin (BSA) were studied using fluorescence resonance energy transfer (FRET). The FRET efficiency of BSA-QD conjugates can reach as high as 24.87% by electrostatic interaction. The higher binding constant (3.63×10(7)Lmol(-1)) and number of binding sites (1.75) between ZnSe ZnS QDs and BSA demonstrated that the QDs could easily associate to plasma proteins and enhance the transport efficacy of drugs. The magnitude of binding constants (10(3)-10(6)Lmol(-1)), in the presence of QDs, was between drugs-BSA and drugs-QDs in agreement with common affinities of drugs for serum albumins (10(4)-10(6)Lmol(-1)) in vivo. ZnSe ZnS QDs significantly increased the affinities for BSA of Vorinostat (SAHA), Docetaxel (DOC), Carmustine (BCNU), Doxorubicin (Dox) and 10-Hydroxycamptothecin (HCPT). However, they slightly reduced the affinities of Vincristine (VCR) and Methotrexate (MTX) for BSA. The recent work will not only provide useful information for appropriately understanding the binding affinity and binding mechanism at the molecular level, but also illustrate the ZnSe ZnS QDs are perfect candidates for nanoscal drug delivery system (DDS).

  16. High potential of Mn-doped ZnS nanoparticles with different dopant concentrations as novel MRI contrast agents: synthesis and in vitro relaxivity studies

    NASA Astrophysics Data System (ADS)

    Jahanbin, Tania; Gaceur, Meriem; Gros-Dagnac, Hélène; Benderbous, Soraya; Merah, Souad Ammar

    2015-06-01

    Over several decades, metal-doped quantum dots (QDs) with core-shell structure have been studied as dual probes: fluorescence and magnetic resonance imaging (MRI) probes (Dixit et al., Mater Lett 63(30):2669-2671, 2009). However, metal-doped nanoparticles, in which the majority of metal ions are close to the surface, can affect their efficacy as MRI contrast agents (CAs). In this context, herein the high potential of synthesized Mn-doped ZnS QDs via polyol method as imaging probe is demonstrated. The mean diameters of QDs were measured via transmission electron microscopy (TEM) and X-ray diffraction (XRD). Optical and magnetic properties of MnZnS nanoparticles were characterized using fluorescence spectroscopy and super quanducting interference devices magnetometer and electron paramagnetic resonance system, respectively. T1- and T2-weighted images of nanoparticles in aqueous solution were acquired from spin-echo sequences at 3 T. From TEM images and XRD spectra of the prepared nanoparticles, it is observed that the average diameter of particles does not significantly change with Mn dopant content ( 1.6-1.9 nm). All three samples exhibit broad blue emission under UV light excitation. According to the MRI studies, MnZnS nanoparticles generate strong T1 contrast enhancement (bright T1-weighted images) at the low concentration (<0.1 mM). The MnZnS nanoparticles exhibit the high longitudinal ( r 1) relaxivity that increases from 20.34 to 75.5 mM-1 s-1 with the Mn dopant contents varying between 10 and 30 %. Strong signal intensity on T1-weighted images and high r 1 with {r2 }/{r_{1 }} ≈ 1 can demonstrate the high potential of the synthesized Mn:ZnS nanoparticles, which can serve as an effective T1 CA.

  17. Large-scale synthesis of highly emissive and photostable CuInS2/ZnS nanocrystals through hybrid flow reactor

    NASA Astrophysics Data System (ADS)

    Lee, Jun; Han, Chang-Soo

    2014-02-01

    We report a high-yield, low-cost synthesis route to colloidal CuInS2/ZnS (CIS/ZnS) nanocrystals (NCs) with Cu vacancies in the crystal lattice. Yellow-emitting CIS/ZnS core/shell NCs of high luminescence were facilely synthesized via a stepwise, consecutive hybrid flow reactor approach. It is based on serial combination of a batch-type mixer and a flow-type furnace. In this reactor, the flow rate of the solutions was typically 1 mL/min, 100 times larger than that of conventional microfluidic reactors. This method can produce gram quantities of material with a chemical yield in excess of 90% with minimal solvent waste. This is a noninjection-based approach in 1-dodecanethiol (DDT) with excellent synthetic reproducibility and large-scale capability. The optical features and structure of the obtained CIS/ZnS NCs have been characterized by UV-vis and fluorescence spectroscopies, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX) and high-resolution transmission electron microscopy (HRTEM). The resulting CIS/ZnS NCs in chloroform exhibit quantum yield (QY) of 61.4% with photoemission peaking at 561 nm and full width at half maximum (FWHM) of 92 nm. The as-synthesized CIS/ZnS NCs were proven to have excellent photostability. The synthesized CIS/ZnS NCs can be a promising fluorescent probe for biological imaging and color converting material for light-emitting diode due to Cd-free constituents.

  18. Mn-doped ZnS quantum dot imbedded two-fragment imprinting silica for enhanced room temperature phosphorescence probing of domoic acid.

    PubMed

    Dan, Li; Wang, He-Fang

    2013-05-21

    A novel strategy was presented to construct the enhanced molecularly imprinted polymer (MIP)-based room temperature phosphorescence (RTP) probe by combining the RTP of Mn-doped ZnS quantum dots (Mn-ZnS QDs) and two-fragment imprinting. Two fragments or structurally similar parts of the target analytes were used as the dummy templates. Polyethyleneimine capped Mn-ZnS (PEI-Mn-ZnS) QDs, offering the binding sites to interact with the carboxyl groups of templates, were imbedded into MIPs by the hydrolysis of tetraethoxysilane. The rebinding of the target analytes to their fragments' cavities (recognition sites) modulated the selective aggregation of Mn-ZnS QDs in QDs-MIPs and resulted in the RTP enhancement. This new method was suitable for the selective enhanced RTP detection of nonphosphorescent analytes without any derivatization and inducers. The proposed methodology was applied to construct the high selective enhanced MIP-based RTP probe for domoic acid (DA) detection. The RTP enhancement of two-fragment imprinting silica was about 2 times of one-fragment imprinting silica and 4 times of the nonimprinting silica. The two-fragment imprinting silica exhibited the linear RTP enhancement to DA in the range of 0.25-3.5 μM in buffer and 0.25-1.5 μM in shellfish sample. The precision for 11 replicate detections of 1.25 μM DA was 0.65% (RSD), and the limit of detection was 67 nM in buffer and 2.0 μg g(-1) wet weight (w/w) in shellfish sample.

  19. Role of ZnS shell on stability, cytotoxicity, and photocytotoxicity of water-soluble CdSe semiconductor quantum dots surface modified with glutathione

    NASA Astrophysics Data System (ADS)

    Ibrahim, Salwa Ali; Ahmed, Wafaa; Youssef, Tareq

    2014-09-01

    Biomedical applications of quantum dots (QDs) have become a subject of a considerable concern in the past few decades. The present study examines the stability and cytotoxicity of two QDs systems in cell culture medium in the presence and absence of a thin layer of ZnS shell. The two systems were built from core, CdSe QDs, surface modified with glutathione (GSH), named CdSe˜GSH and CdSe/ZnS˜GSH. Our results demonstrated that 0.7 nm layer of ZnS shell played a significant role in the stability of CdSe/ZnS~GSH QDs in supplemented cell culture medium (RPMI). Also, a significant improvement in the physicochemical properties of the core CdSe QDs was shown by maintaining their spectroscopic characteristics in RPMI medium due to the wide band gap of ZnS shell. Both systems showed insignificant reduction in cell viability of HFB-4 or MCF-7 cell lines in the dark which was attributed to the effective GSH coating. Following photoirradiation with low laser power (irradiance 10 mW cm-2), CdSe~GSH QDs showed a significant decrease in cell viability after 60 min irradiation which may result from detachment of GSH molecules. Under the same irradiation condition, CdSe/ZnS~GSH QDs showed insignificant decrease in cell viability or after 2 h incubation from laser irradiation which was attributed to the strong binding between ZnS and GSH coatings. It can be concluded that the stability of CdSe core QDs was significantly improved in cell culture medium by encapsulation with a thin layer of ZnS shell whereas their cytotoxicity and photo-cytotoxicity are highly dependent on surface modification.

  20. Atomistic tight-binding computations in structural and optical properties of CdSe/ZnSe/ZnS core/multi-shell nanocrystals

    NASA Astrophysics Data System (ADS)

    Sukkabot, Worasak

    2016-07-01

    In the present paper, I attempt to theoretically describe, analyze and compare the structural and optical properties in the core/multi-shell nanocrystal structure of a cadmium selenide (CdSe) core surrounded by zinc selenide (ZnSe) inner and zinc sulphide (ZnS) external growth shells. The atomistic tight-binding model (TB) and a configuration interaction method (CI) are implemented to calculate the single-particle spectra, optical band gaps, ground-state wave function overlaps, ground-state oscillation strengths, ground-state coulomb energies, ground-state exchange energies and Stokes shift as a function of ZnS external growth shell thicknesses. I underline that these computations are principally sensitive with the ZnS external growth shell thickness. The reduction of the optical band gaps, overlaps of ground electron-hole wave function, electron-hole interactions and Stokes shift is realized with the increasing ZnS external growth shell thickness. The improvement of the optical intensities is mainly achieved by including the ZnS exterior growth shell encapsulation. Importantly, the optical band gaps based on atomistic tight-binding theory are in a good agreement with the experiment. Finally, this emphasizes that the external passivation shell can now be engineered in a defined way, thus leading to manipulate the natural behaviors of nanodevices based on the scrutinized core/multi-shell nanocrystals.

  1. Charge carrier dynamics investigation of CuInS2 quantum dots films using injected charge extraction by linearly increasing voltage (i-CELIV): the role of ZnS Shell

    NASA Astrophysics Data System (ADS)

    Bi, Ke; Sui, Ning; Zhang, Liquan; Wang, Yinghui; Liu, Qinghui; Tan, Mingrui; Zhou, Qiang; Zhang, Hanzhuang

    2016-12-01

    The role of ZnS shell on the photo-physical properties within CuInS2/ZnS quantum dots (QDs) is carefully studied in optoelectronic devices. Linearly increasing voltage technique has been employed to investigate the charge carrier dynamics of both CuInS2 and CuInS2/ZnS QDs films. This study shows that charge carriers follow a similar behavior of monomolecular recombination in this film, with their charge transfer rate correlates to the increase of applied voltage. It turns out that the ZnS shell could affect the carrier diffusion process through depressing the trapping states and would build up a potential barrier.

  2. Photoinduced fluorescence enhancement in colloidal CdSeTe /ZnS core/shell quantum dots

    NASA Astrophysics Data System (ADS)

    Yuan, C. T.; Chou, W. C.; Chuu, D. S.; Chen, Y. N.; Lin, C. A.; Chang, W. H.

    2008-05-01

    Photoinduced fluorescence enhancement (PFE) in colloidal CdSeTe /ZnS core/shell quantum dots (QDs) was investigated by monitoring ensemble fluorescence and single-QD fluorescence blinking behavior upon illumination. Ensemble fluorescence was increased in air and in vacuum with different enhanced factors. At the single-QD levels, fluorescence was also enhanced for some individual QDs. Relatively long on times, high quantum yields within the on times, and multilevel on states were found in fluorescence time traces. We suggest that the PFE origin from single-QD viewpoint is attributed to the contributions of surface passivation by photoinduced charged carriers and the formation of neutral core/charged shell QD states.

  3. New insight on the interaction of self-activated and Mn-related emission centers in ZnS

    NASA Astrophysics Data System (ADS)

    Bacherikov, Yu Yu; Vorona, I.; Zhuk, A.; Gilchuk, A. V.; Korsunska, N.; Markevich, I.

    2017-02-01

    The photoluminescence (PL) and PL excitation (PLE) spectra of undoped and thermally doped with Mn ZnS single crystals are studied. In the PL spectra, the bands caused by Mn-related and self-activated (SA) emission centers were observed. A number of narrow peaks whose intensity enhanced with increasing Mn content were found in the PLE spectra of SA emission. The same peaks were present in the PLE spectra of the Mn-related emission band. Some of these peaks were previously observed in the absorption spectra and attributed to Mn2+ ions. The appearance of Mn-related peaks in the PLE spectra of SA emission is explained by excitation transfer from the Mn2+ ions to SA emission centers. The conditions required for this transfer and possible mechanisms of the process are discussed.

  4. Differentiation between sources of mechanoluminescence and acoustic emission in impact-loaded ZnSe and ZnS ceramics.

    PubMed

    Chmel, Alexandre; Dunaev, Anatolij; Shcherbakov, Igor

    2017-03-09

    Ductile semiconductor ceramics ZnSe and ZnS were damaged by a falling weight, and the time series of mechanoluminescence (ML) and acoustic emission (AE) pulses were recorded with the nanosecond resolution. The ML lighting appeared in the instance of shock but the AE generation emerged with a delay of 50-100 μsec; however, the maxima of the light and sound emissions coincided in time. This difference in temporal profiles was explained by the difference in prevailing sources of emissions of two types. The detected luminescence in A2 B6 compounds was excited, mainly, by moving and multiplying dislocations, while the sound was generated by nucleating and growing cracks. The statistical analysis showed that at the stage of pre-failure deformation, the ensemble of dislocations exhibited a trend to self-organizing; the cracking was fully random. The effect of intergranular boundaries on the dislocation motion manifested itself in the statistics of mechanoluminescence generation.

  5. Electrical properties of Cu4ZnSnS2/ZnS heterojunction prepared by ultrasonic spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Guitouni, S.; Khammar, M.; Messaoudi, M.; Attaf, N.; Aida, M. S.

    2016-12-01

    Cu2ZnSnS4 (CZTS)/ZnS heterojunctions have been prepared by a successive deposition of ZnS and CZTS thin films by ultrasonic spray pyrolysis technique on glass substrates. The cupric chloride concentration has been varied in the starting solution in order to investigate its influence on device properties. CZTS/ZnS heterojunctions were characterized by recording their current-voltage characteristics at different temperatures. The obtained results exhibit a good rectifying behavior of the realized heterojunction. Analysis of these results yields saturation current, series resistance and ideality factor determination. From the activation energy of saturation current we inferred that the thermal emission through the barrier height is the dominant mechanism of the reverse current rather than the defects contribution.

  6. Temperature and time dependence on ZnS microstructure and phases obtained through hydrothermal decomposition of diethyldithiocarbamate complexes.

    PubMed

    Siqueira, Guilherme Oliveira; Matencio, Tulio; da Silva, Herculano Vieira; de Souza, Yara Gonçalves; Ardisson, José Domingos; de Lima, Geraldo Magela; de Oliveira Porto, Arilza

    2013-05-14

    Zinc sulphide was obtained through hydrothermal decomposition of [Zn(S2CNEt2)] under different experimental conditions such as temperatures and reaction times. Hydrothermal reactions were carried out in a stainless steel autoclave at 160, 180 and 200 °C for 3, 6 and 24 hours. The obtained products were characterized using X-ray diffraction, scanning and high resolution transmission electron microscopies. Particle size and microstrain were determined by Rietveld refinement of experimental X-ray diffraction patterns. The obtained crystal size values were in the range of 6.1 to 30 nm and as the temperature and reaction times increase the particle size also increases. Band gap values are in the range of 3.34 to 3.60 eV and are highly dependent on the crystal microstrain. The catalyst activities were studied through the degradation of methylene blue dye solutions under ultraviolet radiation.

  7. Synthesis and characterization of Cu 2+ doped ZnS nanoparticles using TOPO and SHMP as capping agents

    NASA Astrophysics Data System (ADS)

    Kuppayee, M.; Vanathi Nachiyar, G. K.; Ramasamy, V.

    2011-05-01

    Undoped and Cu 2+ doped (0.2-0.8%) ZnS nanoparticles have been synthesized through chemical precipitation method. Tri-n-octylphosphine oxide (TOPO) and sodium hexametaphosphate (SHMP) were used as capping agents. The synthesized nanoparticles have been analyzed using X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectrometer (FT-IR), UV-vis spectrometer, photoluminescence (PL) and thermo gravimetric-differential scanning calorimetry (TG-DTA) analysis. The size of the particles is found to be 4-6 nm range. Photoluminescence spectra were recorded for ZnS:Cu 2+ under the excitation wavelength of 320 nm. The prepared Cu 2+-doped sample shows efficient PL emission in 470-525 nm region. The capped ZnS:Cu emission intensity is enhanced than the uncapped particles. The doping ions were identified by electron spin resonance (ESR) spectrometer. The phase changes were observed in different temperatures.

  8. First-principles investigation of 67Zn isomer shifts in ZnF2 and the chalcogenides ZnO, ZnS, ZnSe, and ZnTe

    NASA Astrophysics Data System (ADS)

    Mitchell, D. W.; Das, T. P.; Potzel, W.; Kalvius, G. M.; Karzel, H.; Schiessl, W.; Steiner, M.; Köfferlein, M.

    1993-12-01

    All-electron, self-consistent, Hartree-Fock cluster calculations have been carried out to derive electron densities at the zinc nucleus in the series of compounds ZnF2 (rutile-type structure), ZnO (rocksalt structure), ZnO (wurtzite structure), and the compounds ZnS, ZnSe, and ZnTe (all with the sphalerite structure). The derived density differences show a very good linear correlation with the experimental isomer shifts. The isomer shifts and results for the densities at the zinc nucleus have been combined to calculate a value for the change of the mean-square nuclear charge radius for the Mössbauer transition in 67Zn of Δ=+(13.9+/-1.4)×10-3 fm2. Our calculations clearly show the importance of the covalency of the Zn-ligand bond for the origin of the isomer shift and fully corroborate the experimental linear correlation between decreasing isomer shift values and increasing electronegativity of the ligands. The most important contribution to the electron-density differences at the zinc nucleus comes from the Zn(4s) electrons with a smaller but significant contribution from the Zn(3s) electrons appearing to arise primarily from the repulsive influence of the ligand-ion orbitals.

  9. A Facile Hydrothermal Route for Synthesis of ZnS Hollow Spheres with Photocatalytic Degradation of Dyes Under Visible Light

    NASA Astrophysics Data System (ADS)

    Han, Zh.; Wang, N.; Zhang, H.; Yang, X.

    2017-01-01

    A facile hydrothermal method was employed for the synthesis of ZnS hollow spheres by using thioglycolic acid (TGA) as a capping agent under hydrothermal condition. The obtained products were characterized by X-ray powder diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). No diffraction peaks from other crystalline forms were detected, the synthesized ZnS hierarchical hollow spheres were relatively pure. The photocatalytic activities of as-synthesized samples were evaluated by the degradation of methyl orange (MO) and rhodamine B (RhB) under the condition of visible-light irradiation. The higher the initial MO and RhB concentrations, the longer it takes to reach the same residual concentration, implying that the apparent rates of MO and RhB degradation decrease with increase in the initial MO and RhB concentration. The increase of photocatalyst dosage from 0.2 to 0.6 g/L results in a sharp increase of the photodegradation efficiency from 68.50 to 92.66% after 180 min of visible-light irradiation for MO degradation, and the increase of photocatalyst dosage from 0.2 to 0.4 g/L results in a distinct increase of the photodegradation efficiency from 65.72 to 90.85% after 180 min of visible-light irradiation for RhB. The elution of intermediates generated in the photocatalytic mineralization of MO and RhB resulted in an increase in total organic carbon (TOC) level, leading to the difference between TOC removal rate and MO and RhB decolorization rates.

  10. An Analytic Contemplation of the Conspicuous Vicissitudes in the Histomorphology of Corpuscles of Stannius of a Freshwater Catfish Mystus tengara (Hamilton, 1822) due to the Exposure of ZnS Nanoparticles

    PubMed Central

    Chatterjee, Nilanjana

    2015-01-01

    Enhanced surface photooxidation property associated with the ZnS nanoparticles caused the reduction of dissolved oxygen content in water in a dose dependent manner, when ZnS nanoparticles of different sizes are exposed to the water in various concentrations. This property was more prominent for ZnS nanoparticles with smaller sizes. Mystus tengara, exposed to ZnS nanoparticles, responded to hypoxia with varied behavioural, physiological, and cellular responses in order to maintain homeostasis and organ function in an oxygen-depleted environment. The histomorphology of corpuscles of Stannius of the fish showed conspicuous vicissitudes under exposure of ZnS nanoparticles. The population of the cell type with granular cytoplasm showed significant increase at the expense of the other that consisted of agranular cytoplasm with increasing nanoparticle concentration. This can be explained as the defence mechanism of the fish against ZnS nanoparticle induced hypoxia and environmental acidification. The altering histomorphology has been studied employing an analytical approach. PMID:26693386

  11. White Light-Emitting Diodes Based on AgInS2/ZnS Quantum Dots with Improved Bandwidth in Visible Light Communication

    PubMed Central

    Ruan, Cheng; Zhang, Yu; Lu, Min; Ji, Changyin; Sun, Chun; Chen, Xiongbin; Chen, Hongda; Colvin, Vicki L.; Yu, William W.

    2016-01-01

    Quantum dot white light-emitting diodes (QD-WLEDs) were fabricated from green- and red-emitting AgInS2/ZnS core/shell QDs coated on GaN LEDs. Their electroluminescence (EL) spectra were measured at different currents, ranging from 50 mA to 400 mA, and showed good color stability. The modulation bandwidth of previously prepared QD-WLEDs was confirmed to be much wider than that of YAG:Ce phosphor-based WLEDs. These results indicate that the AgInS2/ZnS core/shell QDs are good color-converting materials for WLEDs and they are capable in visible light communication (VLC). PMID:28344270

  12. Effect of Controlled Deposition of ZnS Shell on the Photostability of CdTe Quantum Dots as Studied by Conventional Fluorescence and FCS Techniques.

    PubMed

    Patra, Satyajit; Seth, Sudipta; Samanta, Anunay

    2015-12-21

    The effect of one and two monolayers of ZnS shells on the photostability of CdTe quantum dots (QDs) in aqueous and nonaqueous media has been studied by monitoring the fluorescence behavior of the QDs under ensemble and single-molecule conditions. ZnS capping of the CdTe QDs leads to significant enhancement of the fluorescence brightness of these QDs. Considerable enhancement of the photostability of the shell-protected QDs, including the suppression of photoactivation, is also observed. Fluorescence correlation spectroscopy measurements reveal an increase in the number of particles undergoing reversible fluorescent on-off transitions in the volume under observation with increasing excitation power; this effect is found to be more pronounced in the case of core-only QDs than for core-shell QDs.

  13. Dense and vertically-aligned centimetre-long ZnS nanowire arrays: ionic liquid assisted synthesis and their field emission properties

    NASA Astrophysics Data System (ADS)

    Chen, Shimou; Li, Liang; Wang, Xi; Tian, Wei; Wang, Xuebing; Tang, Dai-Ming; Bando, Yoshio; Golberg, Dmitri

    2012-03-01

    Based on the self-ordering behavior of ionic liquids on solid surface, a gold ion containing ionic liquid was employed to obtain a uniform pattern of gold nanoparticles on Si substrate. Using this catalytic pattern, super-dense, centimetre long, well-crystallized and vertically-aligned ZnS nanowire arrays were then generated. It was found that the densely-packed gold nanoparticles played a key role in the nanowire alignment. Furthermore, the field-emission measurements show that the present ultralong ZnS nanowires arrays possess a low turn-on field of 3.69 V μm-1 and a high field-enhancement factor of 1215.4, indicating they are valuable field emitters.Based on the self-ordering behavior of ionic liquids on solid surface, a gold ion containing ionic liquid was employed to obtain a uniform pattern of gold nanoparticles on Si substrate. Using this catalytic pattern, super-dense, centimetre long, well-crystallized and vertically-aligned ZnS nanowire arrays were then generated. It was found that the densely-packed gold nanoparticles played a key role in the nanowire alignment. Furthermore, the field-emission measurements show that the present ultralong ZnS nanowires arrays possess a low turn-on field of 3.69 V μm-1 and a high field-enhancement factor of 1215.4, indicating they are valuable field emitters. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr11835a

  14. In situ capping for size control of monochalcogenides (ZnS, CdS, and SnS) nanocrystals produced by anaerobic metal-reducing bacteria

    SciTech Connect

    Jang, Gyoung Gug; Jacobs, Christopher B.; Ivanov, Ilia N.; Joshi, Pooran C.; Meyer, III, Harry M.; Kidder, Michelle; Armstrong, Beth L.; Datskos, Panos G.; Graham, David E.; Moon, Ji -Won

    2015-07-24

    Metal monochalcogenide quantum dot nanocrystals of ZnS, CdS and SnS were prepared by anaerobic, metal-reducing bacteria using in situ capping by oleic acid or oleylamine. Furthermore, the capping agent preferentially adsorbs on the surface of the nanocrystal, suppressing the growth process in the early stages, thus leading to production of nanocrystals with a diameter of less than 5 nm.

  15. Surface biofunctionalized CdS and ZnS quantum dot nanoconjugates for nanomedicine and oncology: to be or not to be nanotoxic?

    PubMed Central

    Mansur, Alexandra AP; Mansur, Herman S; de Carvalho, Sandhra M; Lobato, Zélia IP; Guedes, Maria IMC; Leite, Maria F

    2016-01-01

    Herein, for the first time, we demonstrated that novel biofunctionalized semiconductor nanomaterials made of Cd-containing fluorescent quantum dot nanoconjugates with the surface capped by an aminopolysaccharide are not biologically safe for clinical applications. Conversely, the ZnS-based nanoconjugates proved to be noncytotoxic, considering all the parameters investigated. The results of in vitro cytotoxicity were remarkably dependent on the chemical composition of quantum dot (CdS or ZnS), the nature of the cell (human cancerous and embryonic types), and the concentration and time period of exposure to these nanomaterials, caused by the effects of Cd2+ on the complex nanotoxicity pathways involved in cellular uptake. Unexpectedly, no decisive evidence of nanotoxicity of CdS and ZnS conjugates was observed in vivo using intravenous injections in BALB/c mice for 30 days, with minor localized fluorescence detected in liver tissue specimens. Therefore, these results proved that CdS nanoconjugates could pose an excessive threat for clinical applications due to unpredicted and uncorrelated in vitro and in vivo responses caused by highly toxic cadmium ions at biointerfaces. On the contrary, ZnS nanoconjugates proved that the “safe by design” concept used in this research (ie, biocompatible core–shell nanostructures) could benefit a plethora of applications in nanomedicine and oncology. PMID:27695325

  16. ZnS nanoparticles as an efficient and reusable heterogeneous catalyst for synthesis of 1-substituted-1 H-tetrazoles under solvent-free conditions

    NASA Astrophysics Data System (ADS)

    Naeimi, Hossein; Kiani, Fatemeh; Moradian, Mohsen

    2014-09-01

    An efficient and green protocol for the synthesis of 1-substituted-1 H-tetrazoles through cyclization reaction of various primary amines, sodium azide, and triethyl orthoformate was described. In this method, a series of tetrazole derivatives was synthesized by using ZnS nanoparticles as an effective, recoverable, and reusable catalyst under solvent-free conditions. This strategy is a magnificent improvement for the synthesis of these heterocycles due to the non-acidic, clean, and solvent-free conditions via a solid recyclable catalyst. The catalyst was separated by simple filtration and reused seven times without significant loss of activity. The ZnS nanoparticles with high surface area and fine monodisperse particles were prepared using the simple microwave-assisted method without using any surfactant. The ZnS nanoparticle catalyst is a good candidate to replace brønsted acids and metal salts or other catalyst for the preparation of 1-substituted-1 H-tetrazoles in high yields and has potential values for industrial applications.

  17. AgInS2-ZnS Quantum Dots: Excited State Interactions with TiO2 and Photovoltaic Performance.

    PubMed

    Kobosko, Steven M; Jara, Danilo H; Kamat, Prashant V

    2017-02-03

    Multinary quantum dots such as AgInS2 and alloyed AgInS2-ZnS are an emerging class of semiconductor materials for applications in photovoltaic and display devices. The nanocrystals of (AgInS2)x-(ZnS)1-x (for x = 0.67) exhibit a broad emission with a maximum at 623 nm and interact strongly with TiO2 nanostructures by injecting electrons from the excited state. The electron transfer rate constant as determined from transient absorption spectroscopy was 1.8 × 10(10) s(-1). The photovoltaic performance was evaluated over a period of a few weeks to demonstrate the stability of AgInS2-ZnS when utilized as sensitizers in solar cells. We report a power conversion efficiency of 2.25% of our champion cell 1 month after its fabrication. The limitations of AgInS2-ZnS nanocrystals in achieving greater solar cell efficiency are discussed.

  18. Cadmium-free CuInS2/ZnS quantum dots for sentinel lymph node imaging with reduced toxicity.

    PubMed

    Pons, Thomas; Pic, Emilie; Lequeux, Nicolas; Cassette, Elsa; Bezdetnaya, Lina; Guillemin, François; Marchal, Frédéric; Dubertret, Benoit

    2010-05-25

    Semiconductor quantum dots (QDs) could significantly impact the performance of biomedical near-infrared (NIR) imaging by providing fluorescent probes that are brighter and more photostable than conventional organic dyes. However, the toxicity of the components of NIR emitting II-VI and IV-VI QDs that have been made so far (Cd, Hg, Te, Pb, etc.) has remained a major obstacle to the clinical use of QDs. Here, we present the synthesis of CuInS(2)/ZnS core/shell QDs emitting in the NIR ( approximately 800 nm) with good quantum yield and stability even after transfer into water. We demonstrate the potential of these QDs by imaging two regional lymph nodes (LNs) in vivo in mice. We then compare the inflammatory response of the axillary LN induced by different doses of CuInS(2)/ZnS and CdTeSe/CdZnS QDs and show a clear difference in acute local toxicity, the onset of inflammation only occurring at a 10 times more concentrated dose for CuInS(2)/ZnS QDs than for their Cd-containing counterparts.

  19. Energy transfer in aggregated CuInS2/ZnS core-shell quantum dots deposited as solid films

    NASA Astrophysics Data System (ADS)

    Gardelis, S.; Fakis, M.; Droseros, N.; Georgiadou, D.; Travlos, A.; Nassiopoulou, A. G.

    2017-01-01

    We report on the morphology and optical properties of CuInS2/ZnS core-shell quantum dots in solid films by means of AFM, SEM, HRTEM, steady state and time-resolved photoluminescence (PL) spectroscopy. The amount of aggregation of the CuInS2/ZnS QDs was controlled by changing the preparation conditions of the films. A red-shift of the PL spectrum of CuInS2/ZnS core-shell quantum dots, deposited as solid films on silicon substrates, is observed upon increasing the amount of aggregation. The presence of larger aggregates was found to lead to a larger PL red-shift. Besides, as the degree of aggregation increased, the PL decay became slower. We attribute the observed PL red-shift to energy transfer from the smaller to the larger dots within the aggregates, with the emission being realized via a long decay recombination mechanism (100-200 ns), the origin of which is discussed.

  20. Origin of Mechanoluminescence from Cu-Doped ZnS Particles Embedded in an Elastomer Film and Its Application in Flexible Electro-mechanoluminescent Lighting Devices.

    PubMed

    Shin, Seung Wook; Oh, Jeung Pyo; Hong, Chang Woo; Kim, Eun Mi; Woo, Jeong Ju; Heo, Gi-Seok; Kim, Jin Hyeok

    2016-01-20

    Mechanically driven light emission from particles embedded in elastomer films has recently attracted interest as a strong candidate for next-generation light sources on display devices because it is nondestructive, reproducible, real-time, environmentally friendly, and reliable. The origin of mechanoluminescence (ML) obtained from particles embedded in elastomer films have been proposed as the trapping of drifting charge carriers in the presence of a piezoelectric field. However, in this study, we propose a new origin of ML through the study of the microstructure of a Cu-doped ZnS particles embedded in an elastomer composite film with high brightness using transmission electron microscopy (TEM) to clearly demonstrate the origin of ML with respect to the microstructure of ML composite films. The TEM characterization of the ML composite film demonstrated that the Cu-doped ZnS particles were fully encapsulated by a 500 nm thick Al layer, which acts as an electron source for ML emission. Furthermore, we fabricated a flexible electro-mechanoluminescence (EML) device using a Cu-doped ZnS particles embedded in a flexible elastomer composite film. Our research results on a new emission mechanism for ML and its application in flexible light generating elastomer films represent an important step toward environmentally benign and ecofriendly flexible electro-mechanoluminescent lighting devices.

  1. Electron Filtering by an Intervening ZnS Thin Film in the Au Nanoparticle-loaded CdS Plasmonic Photocatalyst.

    PubMed

    Takayama, Kouichi; Fujiwara, Keigo; Kume, Takahiro; Naya, Shin-Ichi; Tada, Hiroaki

    2016-12-12

    In the gold nanoparticle (Au NP)-loaded CdS film on fluorine-doped tin oxide electrode (Au/CdS/FTO), the localized plasmonic resonance excitation-induced electron injection from Au NP to CdS has been proved by photoelectrochemical measurements. Formation of ZnS thin films between the Au NP and CdS film leads to a drastic increase of the photocurrent under visible-light irradiation ( > 610 nm) in a 0.1 M NaClO4 aqueous electrolyte solution due to the electron filtering effect. The photocurrent strongly depends on the thickness of the ZnS film, and the maximum value is obtained at the thickness of as thin as 2.1 nm. Further, the ZnS overlayer significantly stabilizes the photocurrent of the CdS/FTO electrode in a polysulfide/sulfide electrolyte solution even under the excitation of CdS ( > 430 nm). This work presents important information about the design for the new plasmonic photocatalysts consisting of plasmonic metal NP and chalcogenide semiconductors with high conduction band edge.

  2. Electron Filtering by an Intervening ZnS Thin Film in the Gold Nanoparticle-Loaded CdS Plasmonic Photocatalyst.

    PubMed

    Takayama, Kouichi; Fujiwara, Keigo; Kume, Takahiro; Naya, Shin-Ichi; Tada, Hiroaki

    2017-01-05

    In the gold nanoparticle (Au NP)-loaded CdS film on fluorine-doped tin oxide electrode (Au/CdS/FTO), the localized plasmonic resonance excitation-induced electron injection from Au NP to CdS has been proven by photoelectrochemical measurements. Formation of ZnS thin films between the Au NP and CdS film leads to a drastic increase of the photocurrent under visible-light irradiation (λ > 610 nm) in a 0.1 M NaClO4 aqueous electrolyte solution due to the electron filtering effect. The photocurrent strongly depends on the thickness of the ZnS film, and the maximum value is obtained at a thickness as thin as 2.1 nm. Furthermore, the ZnS overlayer significantly stabilizes the photocurrent of the CdS/FTO electrode in a polysulfide/sulfide electrolyte solution even under the excitation of CdS (λ > 430 nm). This work presents important information about the design for new plasmonic photocatalysts consisting of plasmonic metal NPs and chalcogenide semiconductors with high conduction band edge.

  3. Surface biofunctionalized CdS and ZnS quantum dot nanoconjugates for nanomedicine and oncology: to be or not to be nanotoxic?

    PubMed

    Mansur, Alexandra Ap; Mansur, Herman S; de Carvalho, Sandhra M; Lobato, Zélia Ip; Guedes, Maria Imc; Leite, Maria F

    Herein, for the first time, we demonstrated that novel biofunctionalized semiconductor nanomaterials made of Cd-containing fluorescent quantum dot nanoconjugates with the surface capped by an aminopolysaccharide are not biologically safe for clinical applications. Conversely, the ZnS-based nanoconjugates proved to be noncytotoxic, considering all the parameters investigated. The results of in vitro cytotoxicity were remarkably dependent on the chemical composition of quantum dot (CdS or ZnS), the nature of the cell (human cancerous and embryonic types), and the concentration and time period of exposure to these nanomaterials, caused by the effects of Cd(2+) on the complex nanotoxicity pathways involved in cellular uptake. Unexpectedly, no decisive evidence of nanotoxicity of CdS and ZnS conjugates was observed in vivo using intravenous injections in BALB/c mice for 30 days, with minor localized fluorescence detected in liver tissue specimens. Therefore, these results proved that CdS nanoconjugates could pose an excessive threat for clinical applications due to unpredicted and uncorrelated in vitro and in vivo responses caused by highly toxic cadmium ions at biointerfaces. On the contrary, ZnS nanoconjugates proved that the "safe by design" concept used in this research (ie, biocompatible core-shell nanostructures) could benefit a plethora of applications in nanomedicine and oncology.

  4. Development of hybrid organic-inorganic surface imprinted Mn-doped ZnS QDs and their application as a sensing material for target proteins.

    PubMed

    Tan, Lei; Huang, Cong; Peng, Rongfei; Tang, Youwen; Li, Weiming

    2014-11-15

    Applying molecular imprinting techniques to the surface of functionalized quantum dots (QDs) allows the preparation of molecularly imprinted polymers (MIPs) with accessible, surface exposed binding sites and excellent optical properties. This paper demonstrates a new strategy for producing such hybrid organic-inorganic imprinted Mn-doped ZnS QDs for specific recognition of bovine hemoglobin. The technique provides surface grafting imprinting in aqueous solutions using amino modified Mn-doped ZnS QDs as supports, acrylamide and methacrylic acid as functional monomers, γ-methacryloxypropyl trimethoxy silane as the grafting agent, and bovine hemoglobin as a template. The amino propyl functional monomer layer directs the selective occurrence of imprinting polymerization at the QDs surface through copolymerization of grafting agents with functional monomers, but also acts as an assistive monomer to drive the template into the formed polymer shells to create effective recognition sites. Using MIP-QDs composites as a fluorescence sensing material, trace amounts of bovine hemoglobin are signaled with high selectivity by emission intensity changes of Mn-doped ZnS QDs, which is embedded into the imprinted polymers.

  5. Synthesis, structural, and optical properties of stable ZnS:Cu,Cl nanocrystals.

    PubMed

    Corrado, Carley; Jiang, Yu; Oba, Fadekemi; Kozina, Mike; Bridges, Frank; Zhang, Jin Z

    2009-04-23

    Stable water-suspendable Cu+-doped ZnS nanocrystals (NCs) have been synthesized with mercaptopropionic acid (MPA) as a capping molecule. The nanocrystals have been characterized using a combination of experimental techniques including UV-vis and photoluminescence (PL) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma (ICP), and extended X-ray absorption fine structure (EXAFS). The UV-vis electronic absorption spectrum shows an excitonic peak at 310 nm, characteristic of quantum-confined ZnS NCs. This excitonic peak does not change noticeably with Cu+ doping. XRD confirms the formation of ZnS nanocrystals, and the average size of the NCs has been determined to be around 6 nm by TEM. The incorporation of Cu+ into the ZnS is manifested as a substantial red-shift of the emission band in the PL spectra upon addition of Cu2+ that was reduced into Cu+ during the synthesis reaction. EXAFS data were obtained to confirm copper doping as well as determine the local structure about Cu+ and Zn2+ in the NCs. Fitting to the EXAFS data for Cu+ suggests that most Cu+ ions are located near the surface within the ZnS NCs and that a significant fraction may be in the form of CuS as found in bulk material. These combined optical and structural studies have provided important new insight into the relevant electronic energy levels and their correlation to the optical and structural properties of ZnS:Cu,Cl NCs. This has important implications in potential applications of this phosphor material for solid state lighting, imaging, and other photonic devices.

  6. Method of making diode structures

    DOEpatents

    Compaan, Alvin D.; Gupta, Akhlesh

    2006-11-28

    A method of making a diode structure includes the step of depositing a transparent electrode layer of any one or more of the group ZnO, ZnS and CdO onto a substrate layer, and depositing an active semiconductor junction having an n-type layer and a p-type layer onto the transparent electrode layer under process conditions that avoid substantial degradation of the electrode layer. A back electrode coating layer is applied to form a diode structure.

  7. Light-soaking effects and capacitance profiling in Cu(In,Ga)Se2 thin-film solar cells with chemical-bath-deposited ZnS buffer layers.

    PubMed

    Yu, Hye-Jung; Lee, Woo-Jung; Wi, Jae-Hyung; Cho, Dae-Hyung; Han, Won Seok; Chung, Yong-Duck; Kim, Tae-Soo; Song, Jung-Hoon

    2016-12-07

    We fabricated Cu(In,Ga)Se2 (CIGS) solar cells with chemical-bath deposited (CBD) ZnS buffer layers with different deposition times. The conversion efficiency and the fill factor of the CIGS solar cells reveal a strong dependence on the deposition time of CBD-ZnS films. In order to understand the detailed relationship between the heterojunction structure and the electronic properties of CIGS solar cells with different deposition times of CBD-ZnS films, capacitance-voltage (C-V) profiling measurements with additional laser illumination were performed. The light-soaking effects on CIGS solar cells with a CBD-ZnS buffer layer were investigated in detail using current density-voltage (J-V) and C-V measurements with several different lasers with different emission wavelengths. After light-soaking, the conversion efficiency changed significantly and the double diode feature in J-V curves disappeared. We explain that the major reason for the improvement of efficiency by light-soaking is due to the fact that negatively charged and highly defective vacancies in the CIGS absorber near the interface of CBD-ZnS/CIGS were formed and became neutral due to carriers generated by ultra-violet absorption in the buffer layer.

  8. Preparation and application of cysteine-capped ZnS nanoparticles as fluorescence probe in the determination of nucleic acids

    NASA Astrophysics Data System (ADS)

    Li, Yongxin; Chen, Jinlong; Zhu, Changqin; Wang, Lun; Zhao, Danhua; Zhuo, Shujuan; Wu, Yuqin

    2004-07-01

    Cysteine-capped ZnS nanometer-sized fluorescent particles were produced by a colloidal aqueous synthesis. The functionalized nanoparticles are water-soluble and suitable for biological application. A synchronous fluorescence method has been developed for the rapid determination of DNA with functionalized nano-ZnS as a fluorescence probe, based on the synchronous fluorescence enhancement of cysteine-capped nano-ZnS in the presence of DNA. When Δ λ=190 nm, maximum synchronous fluorescence is produced at 267 nm at pH 5.12. Under optimum conditions, the synchronous fluorescence intensity is proportional to the concentration of nucleic acids in the range 0.1-1.2 μg ml -1 for calf thymus DNA, 0.1-0.6 μg ml -1 for fish sperm DNA. The corresponding detection limit is 32.9 ng ml -1 for calf thymus DNA and 24.6 ng ml -1 for fish sperm DNA. This method is simple, inexpensive, rapid and sensitive. The recovery and relative standard deviation are satisfactory.

  9. Intrinsic Doping in Electrodeposited ZnS Thin Films for Application in Large-Area Optoelectronic Devices

    NASA Astrophysics Data System (ADS)

    Madugu, Mohammad Lamido; Olusola, Olajide Ibukun-Olu; Echendu, Obi Kingsley; Kadem, Burak; Dharmadasa, Imyhamy Mudiy

    2016-06-01

    Zinc sulphide (ZnS) thin films with both n- and p-type electrical conductivity were grown on glass/fluorine-doped tin oxide-conducting substrates from acidic and aqueous solution containing ZnSO4 and (NH4)2S2O3 by simply changing the deposition potential in a two-electrode cell configuration. After deposition, the films were characterised using various analytical techniques. X-ray diffraction analysis reveals that the materials are amorphous even after heat treatment. Optical properties (transmittance, absorbance and optical bandgap) of the films were studied. The bandgaps of the films were found to be in the range (3.68-3.86) eV depending on the growth voltage. Photoelectrochemical cell measurements show both n- and p-type electrical conductivity for the films depending on the growth voltage. Scanning electron microscopy shows material clusters on the surface with no significant change after heat treatment at different temperatures. Atomic force microscopy shows that the surface roughness of these materials remain fairly constant reducing only from 18 nm to 17 nm after heat treatment. Thickness estimation of the films was also carried out using theoretical and experimental methods. Direct current conductivity measurements on both as-deposited and annealed films show that resistivity increased after heat treatment.

  10. Facile synthesis and step by step enhancement of blue photoluminescence from Ag-doped ZnS quantum dots.

    PubMed

    Sahai, Sonal; Husain, Mushahid; Shanker, Virendra; Singh, Nahar; Haranath, D

    2011-05-15

    Our results pertaining to the step by step enhancement of photoluminescence (PL) intensity from ZnS:Ag,Al quantum dots (QDs) are presented. Initially, these QDs were synthesized using a simple co-precipitation technique involving a surfactant, polyvinylpyrrolidone (PVP), in de-ionised water. It was observed that the blue PL originated from ZnS:Ag,Al QDs was considerably weak and not suitable for any practical display application. Upon UV (365 nm) photolysis, the PL intensity augmented to ~170% and attained a saturation value after ~100 min of exposure. This is attributed to the photo-corrosion mechanism exerted by high-flux UV light on ZnS:Ag,Al QDs. Auxiliary enhancement of PL intensity to 250% has been evidenced by subjecting the QDs to high temperatures (200 °C) and pressures (~120 bars) in a sulphur-rich atmosphere, which is due to the improvement in crystallanity of ZnS QDs. The origin of the bright-blue PL has been discussed. The results were supported by X-ray phase analysis, high-resolution electron microscopy and compositional evaluation.

  11. Studies on photo- and thermal stability of PVA-encapsulated Mn-doped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Venkataramana, Savadana; Ramanaiah, K.; Sarcar, M. M. M.

    2016-04-01

    In this study, an aqueous-based synthesis route has been developed to prepare highly luminescent polyvinyl alcohol (PVA)-capped manganese-doped ZnS quantum dots (QDs). The QDs showed markedly blue shift in their optical absorbance, indicating strong quantum size effect and the average diameter of the QDs calculated ~3 nm. The QDs showed high-intensity Mn2+-related orange luminescence at 585 nm with a very low-intensity peak at 430 nm for the surface defect states. X-ray powder diffraction, transmission electron microscopy, UV-visible spectroscopy and spectrofluorometry have been used to characterize the doped QDs. Studies on the thermal and photochemical stability of the photoluminescence properties are carried out, which showed that after 5 h of photoexcitation and 30 min of 70 °C treatments, the nanoparticles retain almost 40 % of their initial quantum yield. Our systematic investigation shows that these PVA-capped Mn:ZnS QDs may be used as fluorescent labels in biological applications.

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

    PubMed Central

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

    2015-01-01

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

  13. Photoreductive dehalogenation of halogenated benzene derivatives using ZnS or CdS nanocrystallites as photocatalysts.

    PubMed

    Yin, H; Wada, Y; Kitamura, T; Yanagida, S

    2001-01-01

    ZnS nanocrystallites (nc-ZnS) prepared in N,N-dimethylformamide (DMF) photocatalyze dehalogenation of halogenated benzenes to benzene as the final product from chlorinated benzenes and to difluorobenzenes from fluorinated benzenes in the presence of triethylamine (TEA) as an electron donor under UV light irradiation (lambda > 300 nm). When CdS nanocrystallites (nc-CdS) are used as a photocatalyst (lambda > 400 nm), halogenated benzenes are photoreductively dehalogenated, yielding trichlorobenzene from hexachlorobenzene and tetrafluorobenzene isomers from hexafluorobenzene as the final products. Photoformed electrons on nc-ZnS and nc-CdS have such negative reduction potentials that these electrons reduce polyhalogenated benzenes, leading to the successive dehalogenation. nc-ZnS exhibits higher photocatalytic activitythan nc-CdS due to the more negative potential of the electrons on nc-ZnS than that on nc-CdS. The higher activities of nc-ZnS and nc-CdS compared to their bulk forms are explained as being due to their quantum size effects and the adsorptive interaction between the substrates and the nanosized photocatalysts.

  14. Aqueous, protein-driven synthesis of transition metal-doped ZnS immuno-quantum dots.

    PubMed

    Zhou, Weibin; Baneyx, François

    2011-10-25

    The intentional introduction of transition metal impurities in semiconductor nanocrystals is an attractive approach for tuning quantum dot emission over a wide range of wavelengths. However, the development of effective doping strategies can be challenging, especially if one simultaneously requires a low-toxicity crystalline core, a functional protein shell, and a "green", single-step synthesis process. Here, we describe a simple and environmentally friendly route for the biofabrication of Cu-doped (blue-green) or Mn-doped (yellow-orange) ZnS nanocrystals surrounded by an antibody-binding protein shell. The ZnS:Mn hybrid particles obtained with this method exhibit a 60% enhancement in maximum photoluminescence intensity relative to undoped nanocrystals and have a hydrodynamic diameter inferior to 10 nm. They can be stored for months at 4 °C, are stable over a physiological range of pH and salt concentrations, can be decorated with variable amounts of antibodies by direct mixing, and hold promise for biosensing and imaging applications.

  15. Structural and optical studies of undoped and copper doped zinc sulphide nanoparticles for photocatalytic application

    NASA Astrophysics Data System (ADS)

    Kaur, Jagdeep; Sharma, Manoj; Pandey, O. P.

    2015-01-01

    Photocatalytic activity of semiconductor nanoparticles for their potential application in the area of photocatalysis provides clean source for degradation of organic pollutants. With the aim to utilize it efficiently in photocatalytic degradation of organic pollutants, zinc sulphide nanoparticles capped with thioglycerol and doped with copper (Zn1-xCuxS; x = 0, 0.01, 0.02, 0.03 and 0.04) were synthesized using simple chemical precipitation route. Structural studies were done using X-ray diffraction (XRD) technique. Morphological features of as prepared samples were recorded by high resolution transmission electron microscopy (HRTEM). Fourier transform infrared (FTIR) studies were done to confirm the presence of thioglycerol on the surface of doped ZnS. UV-Vis and photoluminescence studies were carried out to study the effect of doping on optical properties of synthesized material. Degradation of crystal violet has been carried out to investigate the effect of Cu doping on photocatalytic activity of ZnS. It is observed that Cu doping has enhanced the photocatalytic activity of ZnS. Further, UV irradiation study of thioglycerol capped ZnS NPs has been carried out to investigate its effect on photocatalytic performance of the material. The obtained results are interesting and may find applications in photocatalytic degradation of organic pollutants on large scale and also in other related areas.

  16. Photocatalyzed Reduction of Bicarbonate to Formate: Effect of ZnS Crystal Structure and Positive Hole Scavenger.

    PubMed

    Leonard, Daniel P; Pan, Hanqing; Heagy, Michael D

    2015-11-11

    Zinc sulfide is a promising catalyst due to its abundance, low cost, low toxicity and conduction band position that enables the photoreduction of CO2 to formic acid. This study is the first to examine experimentally the photocatalytic differences between wurtzite and sphalerite under the parameters of size (micrometer and nanoscale), crystal lattice, surface area, and band gap on productivity in the photoreduction of HCO3(-). These photochemical experiments were conducted under air mass coefficient zero (AM 0) and AM 1.5 solar simulation conditions. We observed little to no formate production under AM 1.5, but found linear formate production as a function of time using AM 0 conditions. Compared to earlier reports involving bubbled CO2 in the presence of bicarbonate, our results point to bicarbonate as the species undergoing reduction. Also investigated are the effects of three hydroxylic positive hole scavengers, ethylene glycol, propan-2-ol (isopropyl alcohol, IPA) and glycerol on the reduction of HCO3(-). Glycerol, a green solvent derived from vegetable oil, greatly improved the apparent quantum efficiency of the photocatalytic reduction.

  17. Materials Data on ZnS (SG:0) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-06-03

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  18. Materials Data on ZnS (SG:156) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-07-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  19. Materials Data on ZnS (SG:156) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-04-23

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  20. Materials Data on ZnS (SG:0) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-07-14

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  1. Materials Data on ZnS (SG:186) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-07-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  2. Materials Data on Ti9ZnS16 (SG:7) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-02-10

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  3. Materials Data on ZnS (SG:216) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-11-02

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  4. Materials Data on ZnS (SG:160) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-07-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  5. Materials Data on Tm2ZnS4 (SG:62) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-11-02

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  6. Materials Data on ZnS (SG:0) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-05-16

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  7. Materials Data on ZnS (SG:160) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-07-14

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  8. Materials Data on ZnS (SG:0) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-05-18

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  9. Microstructural and electrochemical impedance characterization of bio-functionalized ultrafine ZnS nanocrystals-reduced graphene oxide hybrid for immunosensor applications

    NASA Astrophysics Data System (ADS)

    Mishra, Sujeet K.; Srivastava, Avanish K.; Kumar, Devendra; Biradar, Ashok M.; Rajesh, Affa

    2013-10-01

    We report a mercaptopropionic acid capped ZnS nanocrystals decorated reduced graphene oxide (RGO) hybrid film on a silane modified indium-tin-oxide glass plate, as a bioelectrode for the quantitative detection of human cardiac myoglobin (Ag-cMb). The ZnS nanocrystals were anchored over electrochemically reduced GO sheets through a cross linker, 1-pyrenemethylamine hydrochloride, by carbodiimide reaction and have been characterized by scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. The transmission electron microscopic characterization of the ZnS-RGO hybrid shows the uniform distribution of ultra-fine nanoparticles of ZnS in nano-sheets of GO throughout the material. The protein antibody, Ab-cMb, was covalently linked to ZnS-RGO nanocomposite hybrid for the fabrication of the bioelectrode. A detailed electrochemical immunosensing study has been carried out on the bioelectrode towards the detection of target Ag-cMb. The optimal fitted equivalent circuit model that matches the impedance response has been studied to delineate the biocompatibility, sensitivity and selectivity of the bioelectrode. The bioelectrode exhibited a linear electrochemical impedance response to Ag-cMb in a range of 10 ng to 1 μg mL-1 in PBS (pH 7.4) with a sensitivity of 177.56 Ω cm2 per decade. The combined synergistic effects of the high surface-to-volume ratio of ZnS(MPA) nanocrystals and conducting RGO has provided a dominant charge transfer characteristic (Ret) at the lower frequency region of <10 Hz showing a good biocompatibility and enhanced impedance sensitivity towards target Ag-cMb. The impedance response sensitivity of the ZnS-RGO hybrid bioelectrode towards Ag-cMb has been found to be about 2.5 fold higher than that of a bare RGO modified bioelectrode.

  10. Study of the Characteristics of a Laser Based on the Cr2+-Ion Doped ZnS Polycrystal Obtained by the Method of Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Egorov, A. S.; Savikin, A. P.; Eremeikin, O. N.; Ikonnikov, V. B.; Gavrishchuk, E. M.; Savin, D. V.

    2016-01-01

    We study the lasing characteristics of the Cr2+:ZnS-crystal laser pumped by the pulsed-periodic Tm3+:YLF laser, as well as the lasing polarization properties. The Cr2+:ZnS sample was obtained by chemical vapor deposition of zinc sulfide doped by the chrome ions in the hightemperature isostatic processing. Total efficiency of the pump-power conversion to lasing power at a level of 33% was reached, which corresponds to a laser differential efficiency of about 55% in terms of the absorbed power.

  11. Photocurrent enhancement mechanisms in bilayer nanofilm-based ultraviolet photodetectors made from ZnO and ZnS spherical nanoshells

    PubMed Central

    2014-01-01

    Hollow-sphere bilayer nanofilm-based ultraviolet light photodetectors made from ZnO and ZnS spherical nanoshells show enhanced photocurrent, which are comparable to or even better than those of other semiconductor nanostructures with different shapes. In this work, the photocurrent enhancement mechanisms of these bilayer nanofilm-based ultraviolet light photodetectors are explained, which could be attributed to the strong light absorption based on the whispering gallery mode resonances, the separation of the photogenerated carriers through the internal electric field within the bilayer nanofilms, the hopping-like electrical transport, and the effective charge injection from Cr/Au contacts to the nanofilms. PMID:25136287

  12. The mechanical response of turbostratic carbon nanotubes filled with Ga-doped ZnS: II. Slenderness ratio and crystalline filling effects

    NASA Astrophysics Data System (ADS)

    Costa, Pedro M. F. J.; Cachim, Paulo B.; Gautam, Ujjal K.; Bando, Yoshio; Golberg, Dmitri

    2009-10-01

    Using a sample holder with an integrated force sensor, a collection of carbon nanotubes filled with Ga-doped ZnS, and spanning a broad window of lengths and diameters, has been mechanically studied inside a transmission electron microscope. The successful evaluation of the filled nanostructures was seen to depend on their slenderness ratio. Upon controlled removal of the encapsulated sulfide, the system considerably changed its response to uniaxial compressive stress. This report follows part 1 of the study which was instrument-focused and laid the ground to achieve consistent results with a novel type of nanomechanics setup for one-dimensional nanostructures (Costa et al 2009 Nanotechnology 40 405706).

  13. Evidence of significant down-conversion in a Si-based solar cell using CuInS{sub 2}/ZnS core shell quantum dots

    SciTech Connect

    Gardelis, Spiros Nassiopoulou, Androula G.

    2014-05-05

    We report on the increase of up to 37.5% in conversion efficiency of a Si-based solar cell after deposition of light-emitting Cd-free, CuInS{sub 2}/ZnS core shell quantum dots on the active area of the cell due to the combined effect of down-conversion and the anti- reflecting property of the dots. We clearly distinguished the effect of down-conversion from anti-reflection and estimated an enhancement of up to 10.5% in the conversion efficiency due to down-conversion.

  14. 1,2-Ethanedithiol Treatment for AgIn5S8/ZnS Quantum Dot Light-Emitting Diodes with High Brightness.

    PubMed

    Ji, Changyin; Lu, Min; Wu, Hua; Zhang, Xiaoyu; Shen, Xinyu; Wang, Xiao; Zhang, Yu; Wang, Yiding; Yu, William W

    2017-03-08

    The surface organic ligands of the quantum dots (QDs) play important roles in the performance of QD electronic devices. Here, we fabricated low toxic AgIn5S8/ZnS QDs light-emitting diodes (QD-LEDs) and greatly enhanced the device efficiency through surface ligand exchange treatments. The oleic acid-capped QDs were replaced with a shorter ligand 1,2-ethanedithiol, which was proved by the Fourier transform infrared spectrum measurement. The treated QD films became more compact with higher film mobility and shorter film photoluminescence lifetime. The more conductive QD films fabricated LEDs showed an external quantum efficiency over 1.52%.

  15. Electronic Raman scattering with excitation between localized states observed in the zinc M{sub 2,3} soft x-ray spectra of ZnS

    SciTech Connect

    Zhou, L.; Callcott, T.A.; Jia, J.J.

    1997-04-01

    Zn M{sub 2,3} soft x-ray fluorescence (SXF) spectra of ZnS and ZnS{sub .5}Se{sub .5} excited near threshold show strong inelastic scattering effects that can be explained using a simple model and an inelastic scattering theory based on second order perturbation theory. This scattering is often called electronic resonance Raman scattering. Tulkki and Aberg have developed this theory in detail for atomic systems, but their treatment can be applied to solid systems by utilizing electronic states characteristic of solids rather than of atomic systems.

  16. Resonance Energy Transfer between protein and rhamnolipid capped ZnS quantum dots: Application in in-gel staining of proteins

    NASA Astrophysics Data System (ADS)

    Janakiraman, Narayanan; Mohan, Abhilash; Kannan, Ashwin; Pennathur, Gautam

    The interaction of proteins with quantum dots is an interesting field of research. These interactions occur at the nanoscale. We have probed the interaction of Bovine Serum Albumin (BSA) and Candida rugosa lipase (CRL) with rhamnolipid capped ZnS (RhlZnSQDs) using absorption and fluorescence spectroscopy. Optical studies on mixtures of RhlZnSQDs and proteins resulted in Förster's Resonance Energy Transfer (FRET) from proteins to QDs. This phenomenon has been exploited to detect proteins in agarose gel electrophoresis. The activity of the CRL was unaffected on the addition of QDs as revealed by zymography.

  17. Structural and optical characterization of CuInS2 quantum dots synthesized by microwave-assisted continuous flow methods

    NASA Astrophysics Data System (ADS)

    Fitzmorris, Robert C.; Oleksak, Richard P.; Zhou, Zheng; Mangum, Benjamin D.; Kurtin, Juanita N.; Herman, Gregory S.

    2015-07-01

    Semiconductor quantum dots (QDs) have recently been incorporated into consumer displays and lighting technologies. Now that these materials are being produced on industrial scales, it is important to investigate scalable synthetic methods and less toxic materials and chemistries. To achieve these goals, we have synthesized cadmium-free, visible light-emitting QDs using a microwave-assisted continuous flow reactor. After synthesis, the CuInS2 QD cores underwent a near-complete Zn cation exchange reaction in a batch reactor, followed by the growth of a ZnS shell. Analysis of X-ray diffraction, transmission electron microscopy, and Raman spectroscopy data indicate that the crystal structure changes from CuInS2 (chalcopyrite) to ZnS (zincblende) during the cation exchange reaction. Compositional analysis indicated that the core/shell QDs were 98 % ZnS, with Cu and In present at much lower concentrations. The photoluminescence (PL) peak position was blue shifted for longer cation exchange reactions, and it was found that the ZnS shell was necessary for improved PL stability. The synthesized QDs have a PL down conversion efficiency of 65 % when using a blue LED source.

  18. Stress and morphological development of CdS and ZnS thin films during the SILAR growth on (1 0 0)GaAs

    NASA Astrophysics Data System (ADS)

    Laukaitis, Giedrius; Lindroos, Seppo; Tamulevičius, Sigitas; Leskelä, Markku

    2001-12-01

    Cadmium sulfide and zinc sulfide films were grown on (1 0 0)GaAs substrate by successive ionic layer adsorption and reaction (SILAR) technique from aqueous precursor solutions at room temperature and normal pressure. The stress development of the thin films was characterized by laser interferometry as a function of the thickness of the films. The morphology and roughness of the films were monitored by atomic force microscopy. Additionally the crystallinity and crystallite size were analyzed by X-ray diffraction and composition by electron spectroscopy for chemical analysis. The CdS thin films had significantly higher stress level and also better crystallinity compared with ZnS thin films. Both films were polycrystalline and cubic, but the CdS thin films followed the substrate (1 0 0) orientation, whereas the ZnS films were (1 1 1) orientated. The roughness vs. film thickness curves of both films followed each other in shape, but the CdS films consisted of smaller particles.

  19. Fabrication of MnFe2O4-CuInS2/ZnS Magnetofluorescent Nanocomposites and Their Characterization.

    PubMed

    Demillo, Violeta G; Liao, Mingxia; Zhu, Xiaoshan; Redelman, Doug; Publicover, Nelson G; Hunter, Kenneth W

    2015-01-05

    Magnetofluorescent nanocomposites (MFNCs) providing a single nanoscale platform with multimodal properties are gaining momentum in biological manipulation, biomedical imaging and therapy. In this work, we report the preparation of MFNCs integrating MnFe2O4 magnetic nanoparticles (MNPs), CuInS2/ZnS quantum dots (QDs) and poly(ethylene glycol)-b-poly(lactide-co-glycolide) (PEG-PLGA) in a tetrahydrofuran (THF)/water solvent system. Through sonication and quick solvent displacement, multiple nanoparticles of each type are co-encapsulated within the hydrophobic core of PEG-PLGA micelles. The developed fabrication process is simple and fast. Moreover, due to the low toxicity of CuInS2/ZnS QDs, the fabrication process is environmentally benign. The fabricated MFNCs were further characterized regarding their fundamental physical, chemical and biological properties. Results reveal that the MFNCs possess high (Mn + Fe) recovery rates, and the optical properties and magnetic relaxivity of the MFNCs are sensitive to the MNP:QD mass ratios in the fabrication. Furthermore, the MFNCs present excellent stability in aqueous solutions, minimal cytotoxicity, and capability for bioconjugation. This study opens an avenue for the MFNCs to be employed in broad biological or biomedical applications.

  20. Synthesis and characterization of novel molecularly imprinted polymer - coated Mn-doped ZnS quantum dots for specific fluorescent recognition of cocaine.

    PubMed

    Chantada-Vázquez, María Pilar; Sánchez-González, Juan; Peña-Vázquez, Elena; Tabernero, María Jesús; Bermejo, Ana María; Bermejo-Barrera, Pilar; Moreda-Piñeiro, Antonio

    2016-01-15

    Mn-doped ZnS quantum dots (QDs) coated with a molecularly imprinted polymer (MIP) material selective toward cocaine and its metabolites have been prepared and applied to cocaine (COC) and metabolites assessment by spectrofluorimetry. Ultrasound irradiation (37kHz) was novelty used for performing the Mn-doped ZnS QDs synthesis as well as for preparing the QD based MIP-coated composite by precipitation polymerization (imprinting process). This fact allowed the synthesis to be accomplished in four hours. In addition, the use of ultrasound irradiation during MIP-QDs synthesis increased the homogeneity of the QDs size, and reduced nanoparticles agglomeration. MIP was synthesized using COC as a template molecule, ethylene dimethacrylate (EDMA) as a functional monomer, divinylbenzene (DVB) as a cross-linker, and 2,2'-azobisisobutyronitrile (AIBN) as an initiator. The fluorescence of MIP-coated QDs was quenched by the template (COC) and also by metabolites from COC such as benzoylecgonine (BZE), and ecgonine methyl ester (EME). Quenching was not observed when performing experiments with non-imprinted polymer (NIP)-coated QDs; and also, fluorescence quenching of MIP-coated QDs was not observed by other drugs of abuse and metabolites (heroin and cannabis abuse). This fact indicates that the prepared material recognize only COC (template) and metabolites.

  1. Fabrication of MnFe2O4-CuInS2/ZnS Magnetofluorescent Nanocomposites and Their Characterization

    PubMed Central

    Demillo, Violeta G.; Liao, Mingxia; Zhu, Xiaoshan; Redelman, Doug; Publicover, Nelson G.; Hunter, Kenneth W.

    2014-01-01

    Magnetofluorescent nanocomposites (MFNCs) providing a single nanoscale platform with multimodal properties are gaining momentum in biological manipulation, biomedical imaging and therapy. In this work, we report the preparation of MFNCs integrating MnFe2O4 magnetic nanoparticles (MNPs), CuInS2/ZnS quantum dots (QDs) and poly(ethylene glycol)-b-poly(lactide-co-glycolide) (PEG-PLGA) in a tetrahydrofuran (THF)/water solvent system. Through sonication and quick solvent displacement, multiple nanoparticles of each type are co-encapsulated within the hydrophobic core of PEG-PLGA micelles. The developed fabrication process is simple and fast. Moreover, due to the low toxicity of CuInS2/ZnS QDs, the fabrication process is environmentally benign. The fabricated MFNCs were further characterized regarding their fundamental physical, chemical and biological properties. Results reveal that the MFNCs possess high (Mn + Fe) recovery rates, and the optical properties and magnetic relaxivity of the MFNCs are sensitive to the MNP:QD mass ratios in the fabrication. Furthermore, the MFNCs present excellent stability in aqueous solutions, minimal cytotoxicity, and capability for bioconjugation. This study opens an avenue for the MFNCs to be employed in broad biological or biomedical applications. PMID:25484523

  2. Photo-sensitization of ZnS nanoparticles with renowned ruthenium dyes N3, N719 and Z907 for application in solid state dye sensitized solar cells: A comparative study.

    PubMed

    Nosheen, Erum; Shah, Syed Mujtaba; Hussain, Hazrat; Murtaza, Ghulam

    2016-09-01

    This article presents a comprehensive relative report on the grafting of ZnS with renowned ruthenium ((Ru) dyes i.e. N3, N719 and Z907) and gives insight into their charge transfer interaction and sensitization mechanism for boosting solar cell efficiency. Influence of dye concentration on cell performance is also reported here. ZnS nanoparticles synthesized by a simple coprecipitation method with an average particle size of 15±2nm were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Elemental dispersive X-ray analysis (EDAX), tunneling electron microscopy (TEM) and UV-Visible (UV-Vis) spectroscopy. UV-Vis, photoluminescence (PL) and Fourier transform infra-red (FT-IR) spectroscopy confirms the successful grafting of these dyes over ZnS nanoparticles surface. Low-energy metal-to-ligand charge-transfer transition (MLCT) bands of dyes are mainly affected on grafting over the nanoparticle surface. Moreover their current voltage (I-V) results confirm the efficiency enhancement in ZnS solid state dye sensitized solar cells (SSDSSCs) owing to effective sensitization of this material with Ru dyes and helps in finding the optimum dye concentration for nanoparticles sensitization. Highest rise in overall solar cell efficiency i.e. 64% of the reference device has been observed for 0.3mM N719-ZnS sample owing to increased open circuit voltage (Voc) and fill factor (FF). Experimental and proposed results were found in good agreement with each other.

  3. Organometallic Vapor-Phase Epitaxial Growth and Characterization of GaAs/Zn(S, Se) Multilayered Structures

    NASA Astrophysics Data System (ADS)

    Fujita, Shigeo; Murawala, Prakash A.; Maruo, Seiji; Tsuji, Osamu; Fujita, Shizuo

    1991-01-01

    We report growth conditions of lattice-matched dissimilar semiconductor multilayered structures of GaAs/Zn(S, Se) systems by organometallic vapor-phase epitaxy (OMVPE). Since the optimum growth temperature for GaAs is much higher than that of Zn(S, Se), we performed low-temperature growth (470°C) of GaAs by photo-assisted OMVPE. A smooth growth surface of GaAs on Zn(S, Se) was achieved by lattice-matching, sufficient preflow of triethylarsenic (TEAs) and a Zn-stabilized surface before starting the growth of GaAs; hence we succeeded in the fabrication of a ZnSSe/GaAs/ZnSSe double hetero (DH) structure and a superlattice. Thermal annealing of the DH structure showed no appreciable Zn diffusion into GaAs up to 650°C but showed thermal stability at the interface up to 550°C.

  4. Enhanced photoluminescence due to two-photon enhanced three-photon absorption in Mn{sup 2+}-doped ZnS quantum dots

    SciTech Connect

    Subha, Radhu; Nalla, Venkatram; Ji, Wei; Feng, Xiaobo; Vijayan, C.

    2014-10-15

    In this work, we have investigated the multi-photon absorption induced photoluminescence in Mn{sup 2+}-doped ZnS quantum dots in the wavelength range 860 – 1050 nm (Near-Infrared Window I). The observed three-photon action cross-section has been compared with the theoretical prediction under four band approximation. An enhancement of four to five orders has been observed in the range from 970 to 1050 nm compared to the theoretical value, which is attributed to two-photon enhanced three-photon absorption. Transient lifetime measurements reveal a lifetime of 0.35 ± 0.3 ms, which is four to five orders higher than other conventional fluorescent probes.

  5. Study of photocatalytic activity of ZnS quantum dots as efficient nanoparticles for removal of methyl violet: Effect of ferric ion doping

    NASA Astrophysics Data System (ADS)

    Shamsipur, Mojtaba; Rajabi, Hamid Reza

    2014-03-01

    Zinc sulfide quantum dots (QDs), as pure and doped with Fe3+, were prepared for photodecolorization of methyl violet (MV), as a model dye, under UV light irradiation. The syntheses of QDs were carried out using a simple chemical co-precipitation method. The prepared samples were characterized by various techniques including X-ray diffraction, transmission electron microscopy, UV-Vis spectrophotometry and flame atomic absorption spectroscopy. The influences of operational parameters on the decolorization of MV such as dopant content, pH, dosage of nanophotocatalyst, UV irradiation time and initial dye concentration were studied. The results showed that the QDs presented high efficiency for MV decolorization, and doping of ZnS QDs with Fe3+ enhanced the efficiency and rate of dye removal. Finally, the reproducibility and kinetic model of the dye degradation were discussed.

  6. Study of photocatalytic activity of ZnS quantum dots as efficient nanoparticles for removal of methyl violet: effect of ferric ion doping.

    PubMed

    Shamsipur, Mojtaba; Rajabi, Hamid Reza

    2014-03-25

    Zinc sulfide quantum dots (QDs), as pure and doped with Fe(3+), were prepared for photodecolorization of methyl violet (MV), as a model dye, under UV light irradiation. The syntheses of QDs were carried out using a simple chemical co-precipitation method. The prepared samples were characterized by various techniques including X-ray diffraction, transmission electron microscopy, UV-Vis spectrophotometry and flame atomic absorption spectroscopy. The influences of operational parameters on the decolorization of MV such as dopant content, pH, dosage of nanophotocatalyst, UV irradiation time and initial dye concentration were studied. The results showed that the QDs presented high efficiency for MV decolorization, and doping of ZnS QDs with Fe(3+) enhanced the efficiency and rate of dye removal. Finally, the reproducibility and kinetic model of the dye degradation were discussed.

  7. Room temperature synthesis of Mn{sup 2+} doped ZnS d-dots and observation of tunable dual emission: Effects of doping concentration, temperature, and ultraviolet light illumination

    SciTech Connect

    Kole, A. K.; Kumbhakar, P.; Tiwary, C. S.

    2013-03-21

    Mn{sup 2+} doped (0-50.0 molar %) ZnS d-dots have been synthesized in water medium by using an environment friendly low cost chemical technique. Tunable dual emission in UV and yellow-orange regions is achieved by tailoring the Mn{sup 2+} doping concentration in the host ZnS nanocrystal. The optimum doping concentration for achieving efficient photoluminescence (PL) emission is determined to be {approx}1.10 (at. %) corresponding to 40.0 (molar %) of Mn{sup 2+} doping concentration used during synthesis. The mechanism of charge transfer from the host to the dopant leading to the intensity modulated tunable (594-610 nm) yellow-orange PL emission is straightforwardly understood as no capping agent is used. The temperature dependent PL emission measurements are carried out, viz., in 1.10 at. % Mn{sup 2+} doped sample and the experimental results are explained by using a theoretical PL emission model. It is found that the ratio of non-radiative to radiative recombination rates is temperature dependent and this phenomenon has not been reported, so far, in Mn{sup 2+} doped ZnS system. The colour tuning of the emitted light from the samples are evident from the calculated chromaticity coordinates. UV light irradiation for 150 min in 40.0 (molar %) Mn{sup 2+} doped sample shows an enhancement of 33% in PL emission intensity.

  8. Structural, optical, opto-thermal and thermal properties of ZnS–PVA nanofluids synthesized through a radiolytic approach

    PubMed Central

    Faraji, Nastaran; Mat Hussin, Roslina; Saion, Elias; Yunus, W Mahmood Mat; Behzad, Kasra

    2015-01-01

    Summary This work describes a fast, clean and low-cost approach to synthesize ZnS–PVA nanofluids consisting of ZnS nanoparticles homogeneously distributed in a PVA solution. The ZnS nanoparticles were formed by the electrostatic force between zinc and sulfur ions induced by gamma irradiation at a dose range from 10 to 50 kGy. Several experimental characterizations were conducted to investigate the physical and chemical properties of the samples. Fourier transform infrared spectroscopy (FTIR) was used to determine the chemical structure and bonding conditions of the final products, transmission electron microscopy (TEM) for determining the shape morphology and average particle size, powder X-ray diffraction (XRD) for confirming the formation and crystalline structure of ZnS nanoparticles, UV–visible spectroscopy for measuring the electronic absorption characteristics, transient hot wire (THW) and photoacoustic measurements for measuring the thermal conductivity and thermal effusivity of the samples, from which, for the first time, the values of specific heat and thermal diffusivity of the samples were then calculated. PMID:25821695

  9. Structural, optical and magnetic properties of Zn0.97-xCuxCr0.03S nanoparticles

    NASA Astrophysics Data System (ADS)

    Reddy, D. Amaranatha; Murali, G.; Poornaprakash, B.; Vijayalakshmi, R. P.; Reddy, B. K.

    2012-04-01

    Zn0.97-xCuxCr0.03S (x = 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05) nanoparticles were synthesized by chemical co-precipitation method for the first time. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive analysis of X-rays (EDAX). Diffuse reflectance spectra (DRS) and photoluminescence spectra (PL). EDAX spectra confirmed the presence of Cr and Cu in the samples with expected stoichiometry. XRD patterns showed that dopant atoms of Cr and Cu were incorporated at the Zn sites in the cubic structure without disturbing the original ZnS cubic structure. However, at a concentration of 5 at.% the planes corresponding to Cu were observed. This shows the immiscibility of Cu in ZnS for a concentration of 5 at.%. Reflectance of Cu co-doped samples decreased with increase in Cu concentration. Photoluminescence for pure ZnS was observed in the blue region. 1 at.% Cu doping in ZnS:Cr resulted in a significant enhancement of PL intensity. Higher dopant concentrations resulted in a strong quenching of PL intensity. PL emission peak showed a red shift with increase in Cu content. FTIR studies revealed that the nanoparticles were sterically stabilized by EDTA. Magnetization studies indicated that Cu co-doping enhanced significantly the room temperature ferromagnetism of the samples.

  10. ZnS and ZnSe immersion gratings for astronomical high-resolution spectroscopy - evaluation of internal attenuation of bulk materials in the short NIR region

    SciTech Connect

    Ikeda, Y; Kobayashi, N; Kondo, S; Yasui, C; Kuzmenko, P J; Tokoro, H; Terada, H

    2009-08-12

    We measure the internal attenuation of bulk crystals of CVD-ZnS, CVD-ZnSe, Si, and GaAs, in the short near-infrared (sNIR) region to evaluate the possibility of astronomical immersion gratings with those high refractive index materials. We confirm that multispectral grade CVD-ZnS and CVD-ZnSe are best suited for the immersion gratings, with the smallest internal attenuation of {alpha}{sub att} = 0.01-0.03 cm{sup -1} among the major candidates. The measured attenuation is roughly in proportion to {lambda}{sup -2}, suggesting it is dominated by bulk scattering due to the polycrystalline grains rather than by absorption. The total transmittance in the immersion grating is estimated to be at least > 80 %, even for the spectral resolution of R = 300,000. Two potential problems, the scattered light by the bulk material and the degradation of the spectral resolution due to the gradient illumination in the diffracted beam, are investigated and found to be negligible for usual astronomical applications. Since the remaining problem, the difficulty of cutting grooves on CVD-ZnS and CVD-ZnSe, has recently been overcome by the nanoprecision fly-cutting technique, ZnS and ZnSe immersion gratings for astronomy can be technically realized.

  11. Enhanced Photocurrents with ZnS Passivated Cu(In,Ga)(Se,S)2 Photocathodes Synthesized Using a Nonvacuum Process for Solar Water Splitting.

    PubMed

    Chae, Sang Youn; Park, Se Jin; Han, Sung Gyu; Jung, Hyejin; Kim, Chae-Woong; Jeong, Chaehwan; Joo, Oh-Shim; Min, Byoung Koun; Hwang, Yun Jeong

    2016-12-07

    Chalcopyrite Cu(In,Ga)(Se,S)2 (CIGS) semiconductors are potential candidates for use in photoelectrochemical (PEC) hydrogen generation due to their excellent optical absorption properties and high conduction band edge position. In the present research, CIGS thin film was successfully prepared on a transparent substrate (F:SnO2 glass) using a solution-based process and applied for a photocathode in solar water splitting, which shows control of the surface state associated with sulfurization/selenization process significantly influences on the PEC activity. A ZnS passivation surface layer was introduced, which effectively suppresses charge recombination by surface states of CIGS. The CIGS/ZnS/Pt photocathode exhibited highly enhanced PEC activity (∼24 mA·cm(-2) at -0.3 V vs RHE). The performances of our CIGS photocathode on the transparent substrate were also characterized under front/back light illumination, and the incident photon to current conversion efficiency (IPCE) drastically changed depending on the illumination directions showing decreased IPCE especially under UV region with back illumination. The slow minority carrier (electron) transportation is suggested as a limiting factor for the PEC activity of the CIGS photocathode.

  12. Surface hardening of ZnSe, ZnS, and ZnS/ZnSe optical materials by implantation of 1 MeV hydrogen ions

    NASA Astrophysics Data System (ADS)

    Wu, Richard L. C.; McCormick, A. W.; Pronko, P. P.; Keeley, Joseph

    1991-07-01

    Zinc selenide and zinc sulfide are excellent optical materials for applications in the visible and infrared regions of the spectrum. Since these materials possess low mechanical strength and toughness, they are vulnerable to erosion and impact damage in severe environments. In order to improve their physical hardness without degrading their spectral transmission, high-energy (1 MeV) hydrogen ions were implanted into the surfaces of ZnSe, water-clear ZnS (Cleartran TM), and ZnS/ZnSe composite (Tuftran TM. A systematic study of the effect of ion fluence (0.1 to 3 × 10 17/cm 2) on surface hardness and optical transmission was performed. Substantial improvement in microhardness has been found which increases with dosage. The hardness of Tuftran TM leveled off at a dose of 3 × 10 16/cm 2, while that of ZnSe and Cleartran TM continued to improve with ion fluence. The hardness of ZnSe was increased by a factor of 78% at a dose of 3 × 10 17/cm 2, without degrading important optical properties.

  13. Warm White Light Emitting Diodes with Gelatin-Coated AgInS2/ZnS Core/Shell Quantum Dots.

    PubMed

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

    2015-12-23

    Cadmium-free and water-soluble AgInS2/ZnS core/shell quantum dots (QDs) with a cost of 2.5 $/g are synthesized in an electric pressure cooker. The QD powders with different Ag/In ratios exhibit bright yellow, orange, and orange-red luminescence under UV light. Their absolute photoluminescence quantum yields (PLQYs) can reach as high as 50.5, 57, and 52%, respectively. Because gelatin is used as the capping agent, the concentrated QDs/gelatin solution can be directly utilized as phosphor for the fabrication of white light-emitting diodes (LEDs) by a simple drop-drying process without the need of resin package. Warm-white LEDs are obtained by combining orange-emitting QDs with blue InGaN chip. As-fabricated warm-white LED exhibits a luminous efficacy of 39.85 lm/W, a correlated color temperature (CCT) of 2634 K and a color rendering index (CRI) of 71 at a drive current of 20 mA. Furthermore, the electroluminescence (EL) stability of LED device and thermal stability of as-prepared QDs are evaluated.

  14. Comparative studies on removal of Erythrosine using ZnS and AgOH nanoparticles loaded on activated carbon as adsorbents: Kinetic and isotherm studies of adsorption

    NASA Astrophysics Data System (ADS)

    Ghaedi, M.; Rozkhoosh, Z.; Asfaram, A.; Mirtamizdoust, B.; Mahmoudi, Z.; Bazrafshan, A. A.

    2015-03-01

    Erythrosine adsorption (Er) onto ZnS and AgOH nanoparticle-loaded activated carbon (ZnS-NP-AC and AgOH-NP-AC) was studied and results were compared. Subsequent preparation were fully analyzed by different approach such as BET to obtain knowledge about surface area, pore volume, while FT-IR analysis give comprehensive information about functional group the dependency of removal percentage to adsorbent mass, initial Er concentration and contact time were investigated and optimum conditions for pH, adsorbent dosage, Er concentration and contact time was set as be 3.2, 0.016 g, 20 mg/L and 16 min and 3.2, 0.015 g, 19 mg/L and 2 min for ZnS-NP-AC and AgOH-NP-AC, respectively. The equilibrium data correspond to adsorption strongly follow Langmuir model by ZnS-NP-AC and Freundlich model for AgOH-NP-AC. High adsorption capacity for of 55.86-57.80 mg g-1 and 67.11-89.69 mg g-1 for ZnS-NP-AC and AgOH-NP-AC, respectively. The result of present study confirm the applicability of small amount of these adsorbent (<0.02 g) for efficient removal of Er (>95%) in short reasonable time (20 min).

  15. Phosphorescence detection of L-ascorbic acid with surface-attached N-acetyl-L-cysteine and L-cysteine Mn doped ZnS quantum dots.

    PubMed

    Bian, Wei; Ma, Jing; Guo, Wenrong; Lu, Dongtao; Fan, Meng; Wei, Yanli; Li, Yingfu; Shuang, Shaomin; Choi, Martin M F

    2013-11-15

    N-Acetyl-L-cysteine (NAC) and L-cysteine (Cys) capped Mn doped ZnS quantum dots (NAC-Mn/ZnS QDs and Cys-Mn/ZnS QDs) are firstly prepared by hydrothermal methods. These QDs display strong phosphorescence emission peaks at 583 and 580 nm upon excitation at 315 and 306 nm, respectively. Since their room-temperature phosphorescence is efficiently quenched by L-ascorbic acid (AA), they have been employed as phosphorescence probes for detecting AA. The linear working ranges are 2.5-37.5 and 2.5-47.5 µM and the limits of detection are 0.72 and 1.38 µM for NAC-Mn/ZnS QDs and Cys-Mn/ZnS QDs, respectively. The possible quenching mechanisms have been discussed in detail. The QDs probes are highly selective to AA over other common ions, amino acids, glucose and bovine serum album. Finally, they have been applied successfully for detection of AA in human urine samples with satisfactory results. The recoveries are 98-104%. Our work provides a simple and convenient phosphorescence method to determine AA in real samples.

  16. Comparative studies on removal of Erythrosine using ZnS and AgOH nanoparticles loaded on activated carbon as adsorbents: Kinetic and isotherm studies of adsorption.

    PubMed

    Ghaedi, M; Rozkhoosh, Z; Asfaram, A; Mirtamizdoust, B; Mahmoudi, Z; Bazrafshan, A A

    2015-03-05

    Erythrosine adsorption (Er) onto ZnS and AgOH nanoparticle-loaded activated carbon (ZnS-NP-AC and AgOH-NP-AC) was studied and results were compared. Subsequent preparation were fully analyzed by different approach such as BET to obtain knowledge about surface area, pore volume, while FT-IR analysis give comprehensive information about functional group the dependency of removal percentage to adsorbent mass, initial Er concentration and contact time were investigated and optimum conditions for pH, adsorbent dosage, Er concentration and contact time was set as be 3.2, 0.016g, 20mg/L and 16min and 3.2, 0.015g, 19mg/L and 2min for ZnS-NP-AC and AgOH-NP-AC, respectively. The equilibrium data correspond to adsorption strongly follow Langmuir model by ZnS-NP-AC and Freundlich model for AgOH-NP-AC. High adsorption capacity for of 55.86-57.80mgg(-1) and 67.11-89.69mgg(-1) for ZnS-NP-AC and AgOH-NP-AC, respectively. The result of present study confirm the applicability of small amount of these adsorbent (<0.02g) for efficient removal of Er (>95%) in short reasonable time (20min).

  17. The development of a new optical sensor based on the Mn doped ZnS quantum dots modified with the molecularly imprinted polymers for sensitive recognition of florfenicol

    NASA Astrophysics Data System (ADS)

    Sadeghi, Susan; Jahani, Moslem; Belador, Foroogh

    2016-04-01

    The Mn doped ZnS quantum dots (Mn:ZnS QDs) capped with the florfenicol molecularly imprinted polymer (Mn:ZnS QDs@MIP) were prepared via the sol-gel surface imprinting approach using 3-aminopropyltriethoxysilane (APTES) as the functional monomer and tetraethoxysilane (TEOS) as the cross-linker for the optosensing of the florfenicol. Transmission electron microscopy (TEM), X-ray diffractometer, IR spectroscopy, UV-Vis absorption spectrophotometry, and spectrofluorometry were used to elucidate the formation, morphology, and identification of the products. To illustrate the usefulness of the new imprinted material, the non-imprinted coated Mn:ZnS QDs (Mn:ZnS QDs@NIP) were synthesized without the presence of the florfenicol. It was revealed that the fluorescence (FL) intensity of the Mn:ZnS QDs@MIP increased with increasing the FF concentration. Under the optimal conditions, changes in the FL intensity in the presence of the target molecule showed a linear response in the concentration range of 30-700 μmol L- 1 with a detection limit of 24 μmol L- 1. The developed method was finally applied successfully to the determination of FF in different meat samples with satisfactory recoveries.

  18. The performance of a novel Ho:LuAG ceramic laser Q-switched by a polycrystalline Cr2+:ZnS saturable absorber

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Yao, B. Q.; Cui, Z.; Li, J.; Li, H.; Xie, T. F.; Li, C. Y.; Kou, H. M.; Pan, Y. B.

    2017-01-01

    A novel Ho:LuAG ceramic laser Q-switched by a polycrystalline Cr2+:ZnS saturable absorber was reported for the first time in this paper. We took a diode-pumped Tm:YLF laser emitting at 1.9075 μm as the pump source. The laser operated in both continuous wave mode and passively Q-switching (PQS) mode. The maximum PQS output power of 2.67 W was obtained with a slope efficiency of 26.4%. When the absorbed pump power increased from 4.78 to 10.8 W, with three output couplers of T = 2%, T = 10% and T = 25%, the pulse widths decreased as the pump power increased, from 102.9 to 89.2 ns, from 147.1 to 127.6 ns, and from 173 to 150 ns, respectively, and the repetition frequency varied from 10.2 to 20.1 kHz, from 9.3 to 18.3 kHz, and from 8.45 to 16.66 kHz as well. The central wavelength remained constant 2100.64 nm with the change of output couplers and operation modes. Furthermore, the output laser had a beam quality factor M 2 of 1.1.

  19. Strains and stresses in multilayered elastic structures: The case of chemically vapor-deposited ZnS/ZnSe laminates

    NASA Astrophysics Data System (ADS)

    Klein, Claude A.; Miller, Richard P.

    2000-03-01

    Solid structures consisting of layers of different materials created at elevated temperatures usually exhibit substantial residual stresses. These stresses are caused by intrinsic strains in addition to thermal strains, and originate from the bonding of the layers, which generates internal forces and moments that must be balanced to achieve mechanical equilibrium. It is shown that the solution proposed by Townsend et al. [P. Townsend, D. Barnett, and T. Brunner, J. Appl. Phys. 62, 4438 (1987)] for describing elastic interactions in multilayered, elastically isotropic structures provides a powerful tool for evaluating the strains, the normal stresses off the edges, and the curvature of chemically vapor-deposited (CVD) laminates. The residual stresses acting in each layer are best expressed as follows: σi(z)=Ei'[(ɛi,0-ɛ0¯)+(zN-z)K], where z measures the distance from the bottom surface, Ei' is the biaxial modulus of the layer, (ɛi,0-ɛ0¯) characterizes the strain mismatch prior to any mechanical relaxation, and (zN-z)K defines the bending contribution, which depends linearly on the distance from the neutral plane and stems from the curvature K. For bilayered structures the curvature can be expressed in a relatively simple form. In conjunction with the proper expression for the average stress in the coating, it is seen that Stoney's equation holds for thickness ratios much larger than expected in the context of the thin-film approximation. The case of CVD laminates made of ZnS on ZnSe illustrates how the theory can be applied for designing structures that minimize the deformation and, thus, for obtaining optically desirable configurations. The stresses acting in bilayered ZnS/ZnSe structures are controlled by the strain differential Δɛ0=ɛcintr.+(αc¯-αs¯)ΔT, where ɛcintr. represents the intrinsic strain of the ZnS coating, and (αc¯-αs¯)ΔT defines the contribution originating from the thermal expansion mismatch. For ZnS deposited at 670

  20. Structuralism.

    ERIC Educational Resources Information Center

    Piaget, Jean

    Provided is an overview of the analytical method known as structuralism. The first chapter discusses the three key components of the concept of a structure: the view of a system as a whole instead of so many parts; the study of the transformations in the system; and the fact that these transformations never lead beyond the system but always…

  1. Room-temperature phosphorescent discrimination of catechol from resorcinol and hydroquinone based on sodium tripolyphosphate capped Mn-doped ZnS quantum dots.

    PubMed

    Wang, He-Fang; Wu, Ye-Yu; Yan, Xiu-Ping

    2013-02-05

    A room-temperature phosphorescence (RTP) strategy was developed for direct, additive-free discrimination of catechol from resorcinol and hydroquinone based on sodium tripolyphosphate capped Mn-doped ZnS quantum dots (STPP-Mn-ZnS QDs). The RTP response of STPP-Mn-ZnS QDs to the three isomers was pH-dependent, and the greatest difference in the RTP response to the isomers was observed at pH 8.0: catechol enhanced the RTP intensity of the QDs, while resorcinol and hydroquinone had little effect on the RTP intensity of the QDs. The enhanced RTP intensity of 1 μM catechol was not affected by the coexistence of 30 μM resorcinol and 50 μM hydroquinone at pH 8.0. The detection limit of this RTP method was 53 nM catechol, and the precision was 3.2% (relative standard deviation) for five replicate detections of 1 μM catechol. The discrimination mechanism was ascribed to the weak bonded ligand of STPP-Mn-ZnS QDs and the different interaction between the three isomers and STPP-Mn-ZnS QDs. The strong binding of catechol to Zn resulted in the extraction of Zn from the surface of STPP-Mn-ZnS QDs and the generation of holes that were trapped by Mn(2+) to form Mn(3+). Catechol also promoted the reduction of Mn(3+) into Mn(2+) excited state, thus ultimately inducing the enhanced RTP response of STPP-Mn-ZnS QDs.

  2. Calculated electronic structures and Néel temperatures of half-metallic diluted antiferromagnetic semiconductors.

    PubMed

    Ogura, M; Takahashi, C; Akai, H

    2007-09-12

    The possibility of half-metallic diluted antiferromagnetic semiconductors of II-VI compounds is investigated on the basis of first-principles electronic structure calculation. The electronic structures of ZnS, ZnSe, ZnO, CdS and CdSe doped with two kinds of 3d transition metal ions are calculated using the Korringa-Kohn-Rostoker (KKR) method and their magnetic transition temperatures are determined using a cluster-type approximation. It is predicted that II-VI compound semiconductors doped with two kinds of magnetic ions might be good candidates for half-metallic antiferromagnets.

  3. Infrared, visible and ultraviolet absorptions of transition metal doped ZnS crystals with spin-polarized bands

    SciTech Connect

    Zhang, J.H.; Ding, J.W.; Cao, J.X.; Zhang, Y.L.

    2011-03-15

    The formation energies, electronic structures and optical properties of TM:ZnS systems (TM=Cr{sup 2+}, Mn{sup 2+}, Fe{sup 2+}, Co{sup 2+} and Ni{sup 2+}) are investigated by using the first principles method. It is found that the wurtzite and zinc-blende structures have about the same stability, and thus can coexist in the TM:ZnS system. From the wurtzite TM:ZnS, especially, a partially filled intermediate band (IB) is obtained at TM=Cr{sup 2+}, Ni{sup 2+} and Fe{sup 2+}, while it is absent at TM=Mn{sup 2+} and Co{sup 2+}. The additional absorptions are obtained in infrared, visible and ultraviolet (UV) regions, due to the completely spin-polarized IB at Fermi level. The results are very helpful for both the designs and applications of TM:ZnS opto-electronics devices, such as solar-cell prototype. -- Graphical abstract: Absorption coefficients of w-TM{sub x}Zn{sub 1-x}S crystals (TM=Cr{sup 2+}, Mn{sup 2+}, Fe{sup 2+}, Co{sup 2+} and Ni{sup 2+}) at x=0.028. The results may be helpful for the design and applications of TM:ZnS devices, especially for the new high efficiency solar-cell prototype, UV detector and UV LEDs. Display Omitted Research highlights: > It is found that the wurtzite and zinc-blende structures can coexist in TM:ZnS. > An intermediate band is obtained in TM:ZnS at TM=Cr{sup 2+}, Ni{sup 2+} and Fe{sup 2+}. > The absorption coefficients are obtained in infrared, visible and ultraviolet regions.

  4. Half-metallicity and optoelectronic properties of V-doped zincblende ZnS and CdS alloys

    NASA Astrophysics Data System (ADS)

    El Amine Monir, Mohammed; Baltache, H.; Khenata, R.; Murtaza, G.; Ahmed, R.; Ahmed, Waleed. K.; Omran, S. Bin; Bouhemadou, A.

    2016-02-01

    In this paper, spin-polarized density functional calculations on the structural, electronic, optical and magnetic properties of the zincblende structure of the Zn1-xVxS and Cd1-xVxS alloys at x = 0.25 in the ferromagnetic (FM) ordering has been investigated. The study is accomplished using the full-potential (FP) linearized augmented plane wave plus local orbital (LAPW+lo) self-consistent scheme of calculations. To incorporate the exchange correlation component in the total energy calculations of the crystal, Perdew-Burke and Ernzerhof (PBE) parameterization for the generalized gradient approximation (GGA) and GGA+U are employed. Basically, for both alloys, to address their structural properties, we calculated their equilibrium lattice constants, bulk moduli as well as pressure derivatives. In general, from the analysis of the obtained electronic band structure of these alloys, the half-metallic nature of Zn0.75V0.25S and nearly half-metallic nature of the Cd0.75V0.25S alloy are demonstrated. The plotted density of states (DOS) curves project spin-exchange splitting energy Δx(d) and Δx(pd) as generated by V-3d states. It has been clearly evident that the effective potential results for the spin-down case are more striking than for the spin-up case. In order to describe the magnetic behavior of these alloys, the exchange constants N0α (valence band) and N0β (conduction band) as well as the magnetic moment values are estimated. The calculated results of the magnetic moment show that the main source in the reduction of the local magnetic moment of V in the alloys in comparison with its free value is a p-d orbital hybridization and partial transfer to nonmagnetic sites of (Zn, S) and (Cd, S) in Zn0.75V0.25S and Cd0.75V0.25S alloys. In addition, a study concerning optical properties, such as the refractive index, reflectivity and absorption coefficients is performed to determine their potential for optical and optoelectronic devices.

  5. Effect of process conditions and chemical composition on the microstructure and properties of chemically vapor deposited SiC, Si, ZnSe, ZnS and ZnS(x)Se(1-x)

    NASA Technical Reports Server (NTRS)

    Pickering, Michael A.; Taylor, Raymond L.; Goela, Jitendra S.; Desai, Hemant D.

    1992-01-01

    Subatmospheric pressure CVD processes have been developed to produce theoretically dense, highly pure, void-free and large area bulk materials, SiC, Si, ZnSe, ZnS and ZnS(x)Se(1-x). These materials are used for optical elements, such as mirrors, lenses and windows, over a wide spectral range from the VUV to the IR. We discuss the effect of CVD process conditions on the microstructure and properties of these materials, with emphasis on optical performance. In addition, we discuss the effect of chemical composition on the properties of the composite material ZnS(x)Se(1-x). We first present a general overview of the bulk CVD process and the relationship between process conditions, such as temperature, pressure, reactant gas concentration and growth rate, and the microstructure, morphology and properties of CVD-grown materials. Then we discuss specific results for CVD-grown SiC, Si, ZnSe, ZnS and ZnS(x)Se(1-x).

  6. Investigation of optical properties of multilayer dielectric structures using prism-coupling technique

    SciTech Connect

    Sokolov, V I; Glebov, V N; Malyutin, A M; Molchanova, S I; Khaydukov, E V; Panchenko, V Ya

    2015-09-30

    A method based on resonant excitation of waveguide modes with a prism coupler is proposed for measuring the thickness and refractive index of thin-film layers in multilayer dielectric structures. The peculiarities of reflection of TE- and TM-polarised light beams from a structure comprising eleven alternating layers of zinc sulfide (ZnS) and magnesium barium fluoride (MgBaF{sub 4}), whose thicknesses are much less than the wavelength of light, are investigated. Using the mathematical model developed, we have calculated the coefficients of reflection of collimated TE and TM light beams from a multilayer structure and determined the optical constants and thicknesses of the structure layers. The refractive indices of the layers, obtained for TE and TM polarisation of incident light, are in good agreement. The thicknesses of ZnS and MgBaF{sub 4} layers, found for different polarisations, coincide with an accuracy of ±1%. Thus, we have demonstrated for the first time that the prism-coupling technique allows one to determine the optical properties of thin-film structures when the number of layers in the structure exceeds ten layers. (integrated optics)

  7. Pulsed-laser-induced damage in semiconductors Ge, ZnS, and ZnSe at 10.6um

    NASA Astrophysics Data System (ADS)

    Lefranc, Sebastian; Kudriavtsev, Eugene M.; Autric, Michel L.

    1998-04-01

    Laser irradiation induced damage to several materials of interest for use as 10.6 micrometers laser system windows is investigated in this paper. The irradiation source in these single shot experiments was a pulsed TEA CO2 laser. Damage initiation in semiconductors has been studied during the interaction by measuring the variation of the transmitted intensity of a He- Ne and a CO2 cw lasers through the samples. Results show that damages appear at the beginning of the laser-matter interaction process on both surfaces and in the bulk of the materials. The damaged materials have been characterized for various incident fluences by means of optical microscopy and scanning electron microscopy in terms of topography and morphology. The modified surface chemical analysis and the structural analysis have been carried out using energy dispersive x-ray and Raman spectroscopy.

  8. Structure in multilayer films of zinc sulfide and copper sulfide via atomic layer deposition

    SciTech Connect

    Short, Andrew; Jewell, Leila; Bielecki, Anthony; Keiber, Trevor; Bridges, Frank; Carter, Sue; Alers, Glenn

    2014-01-15

    Multilayer film stacks of ZnS and Cu{sub x}S (x ∼ 2) were made via atomic layer deposition. The precursors were bis(2,2,6,6-tetramethyl-3,5-heptanedionato)zinc, bis(2,2,6,6-tetramethyl-3,5-heptanedionato)copper, and H{sub 2}S generated in situ for sulfur. Samples were deposited at 200 °C, in layers ranging from approximately 2 to 20 nm thick, based on binary growth rates. The properties of the film stacks were studied with atomic force microscopy, ultraviolet–visible spectroscopy, and extended x-ray absorption fine structure. The results demonstrate that the structure of films with the thinnest layers is dominated by Cu{sub x}S, whereas in the thicker films, the structure is determined by whichever material is first deposited. This can be attributed to the crystal structure mismatch of ZnS and Cu{sub x}S.

  9. Cd-free buffer layer materials on Cu2ZnSn(SxSe1-x)4: Band alignments with ZnO, ZnS, and In2S3

    NASA Astrophysics Data System (ADS)

    Barkhouse, D. Aaron R.; Haight, Richard; Sakai, Noriyuki; Hiroi, Homare; Sugimoto, Hiroki; Mitzi, David B.

    2012-05-01

    The heterojunctions formed between Cu2ZnSn(SxSe1-x)4 (CZTSSe) and three Cd-free n-type buffers, ZnS, ZnO, and In2S3, were studied using femtosecond ultraviolet photoemission and photovoltage spectroscopy. The electronic properties including the Fermi level location at the interface, band bending in the CZTSSe substrate, and valence and conduction band offsets were determined and correlated with device properties. We also describe a method for determining the band bending in the buffer layer and demonstrate this for the In2S3/CZTSSe system. The chemical bath deposited In2S3 buffer is found to have near optimal conduction band offset (0.15 eV), enabling the demonstration of Cd-free In2S3/CZTSSe solar cells with 7.6% power conversion efficiency.

  10. First-principles study of valence band offsets at ZnSnP2/CdS, ZnSnP2/ZnS, and related chalcopyrite/zincblende heterointerfaces

    NASA Astrophysics Data System (ADS)

    Hinuma, Yoyo; Oba, Fumiyasu; Nose, Yoshitaro; Tanaka, Isao

    2013-07-01

    The valence band offsets of chalcopyrite ZnSnP2 (ZSP), CdSnP2 (CSP), CuInSe2 (CIS), and CuGaSe2 (CGS) against zincblende CdS and ZnS are obtained using first-principles calculations based on hybrid density functional theory. The ZSP-CSP (ZCSP) alloy is isostructural to the CIS-CGS (CIGS) alloy and is known for its potential usage in photovoltaic applications. Therefore, the band offsets with other semiconductors, such as CdS and ZnS, are important. The calculated valence band offsets are ˜1.0 eV for ZSP/CdS and CSP/CdS, ˜1.2 eV for ZSP/ZnS and CSP/ZnS, ˜1.2 eV for CIS/CdS and CGS/CdS, and ˜1.3 eV for CIS/ZnS and CGS/ZnS. The CdS/ZnS valence band offset is within 0.1 eV. Transitivity of natural valence band offsets in the investigated semiconductors holds within ˜0.1 eV, which is smaller than the error in band alignment of ˜0.2 eV when ionization potential differences are used. The ZSP-CSP and CIS-CGS systems have similar valence and conduction band positions, which is an important piece of information for band offset engineering in the development of photovoltaics using ZCSP alloys.

  11. Aptamer-based turn-on detection of thrombin in biological fluids based on efficient phosphorescence energy transfer from Mn-doped ZnS quantum dots to carbon nanodots.

    PubMed

    Zhang, Lu; Cui, Peng; Zhang, Baocheng; Gao, Feng

    2013-07-08

    This paper presents the first example of a sensitive, selective, and stable phosphorescent sensor based on phosphorescence energy transfer (PET) for thrombin that functions through thrombin-aptamer recognition events. In this work, an efficient PET donor-acceptor pair using Mn-doped ZnS quantum dots labeled with thrombin-binding aptamers (TBA QDs) as donors, and carbon nanodots (CNDs) as acceptors has been constructed. Due to the π-π stacking interaction between aptamer and CNDs, the energy donor and acceptor are taken into close proximity, leading to the phosphorescence quenching of donors, TBA QDs. A maximum phosphorescence quenching efficiency as high as 95.9% is acquired. With the introduction of thrombin to the "off state" of the TBA-QDs-CNDs system, the phosphorescence is "turned on" due to the formation of quadruplex-thrombin complexes, which releases the energy acceptor CNDs from the energy donors. Based on the restored phosphorescence, an aptamer-based turn-on thrombin biosensor has been demonstrated by using the phosphorescence as a signal transduction method. The sensor displays a linear range of 0-40 nM for thrombin, with a detection limit as low as 0.013 nM in pure buffers. The proposed aptasensor has also been used to monitor thrombin in complex biological fluids, including serum and plasma, with satisfactory recovery ranging from 96.8 to 104.3%. This is the first time that Mn-doped ZnS quantum dots and CNDs have been employed as a donor-acceptor pair to construct PET-based biosensors, which combines both the photophysical merits of phosphorescence QDs and the superquenching ability of CNDs and thus affords excellent analytical performance. We believe this proposed method could pave the way to a new design of biosensors using PET systems.

  12. Structure and physical properties of the polar oxysulfide CaZnOS.

    PubMed

    Sambrook, Timothy; Smura, Catherine F; Clarke, Simon J; Ok, Kang Min; Halasyamani, P Shiv

    2007-04-02

    The synthesis, structure, and electrical properties of the oxysulfide CaZnOS are reported. The white compound has a band gap of 3.7(1) eV and crystallizes in hexagonal space group P6(3)mc (No. 186) with a = 3.75726(3) A, c = 11.4013(1) A, and Z = 2. The noncentrosymmetric structure, which has few analogues, is composed of isotypic puckered hexagonal ZnS and CaO layers arranged so that ZnS3O tetrahedra are all aligned parallel, resulting in a polar structure. The compound shows type 1 non-phase-matchable second harmonic generation, determined using 1064 nm radiation, with an efficiency approximately 100 times that of alpha-SiO2 and a piezoelectric coefficient of 38 pm V-1. Although polar, CaZnOS is not ferroelectric and the pyroelectric coefficient is very small, approximately 0.0 microC m-2 K-1 between room temperature and 100 degrees C.

  13. Structural phase modification in Cu incorporated nanostructured zinc sulfide thin films

    NASA Astrophysics Data System (ADS)

    Chalana, S. R.; Jolly Bose, R.; Reshmi Krishnan, R.; Kavitha, V. S.; Sreeja Sreedharan, R.; Mahadevan Pillai, V. P.

    2016-08-01

    Cu incorporated zinc sulfide (ZnS) films are prepared by a RF magnetron sputtering technique and the influence of Cu doping concentration on the structural, morphological and optical properties is systematically analyzed using techniques like grazing incidence X-Ray diffraction (GIXRD), micro-Raman spectroscopy, atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS) and UV-vis spectroscopy. XRD examination of the as-prepared films revealed the presence of polycrystalline structure with co-existence of cubic and hexagonal phases in the pure and lower Cu incorporated films. Increase in Cu doping concentration causes a gradual phase transformation from mixed phase to cubic phase. Micro-Raman spectra further confirms the structural phase modifications with the addition of Cu in ZnS. Morphological analysis shows compact distribution of elongated grain geometry with good connectivity and detectable grain boundary in the pure and Cu incorporated films. Increase in Cu incorporation results in the systematic reduction of RMS surface roughness. EDS analysis confirms the incorporation of Cu and surface vacancy defects in the doped films. All the films are transparent in the visible region and band gap calculation by Tauc plot shows that increase in Cu incorporation results in band gap renormalization.

  14. Sustainable, Rapid Synthesis of Bright-Luminescent CuInS2-ZnS Alloyed Nanocrystals: Multistage Nano-xenotoxicity Assessment and Intravital Fluorescence Bioimaging in Zebrafish-Embryos

    NASA Astrophysics Data System (ADS)

    Chetty, S. Shashank; Praneetha, S.; Basu, Sandeep; Sachidanandan, Chetana; Murugan, A. Vadivel

    2016-05-01

    Near-infrared (NIR) luminescent CuInS2-ZnS alloyed nanocrystals (CIZS-NCs) for highly fluorescence bioimaging have received considerable interest in recent years. Owing, they became a desirable alternative to heavy-metal based-NCs and organic dyes with unique optical properties and low-toxicity for bioimaging and optoelectronic applications. In the present study, bright and robust CIZS-NCs have been synthesized within 5 min, as-high-as 230 °C without requiring any inert-gas atmosphere via microwave-solvothermal (MW-ST) method. Subsequently, the in vitro and in vivo nano-xenotoxicity and cellular uptake of the MUA-functionalized CIZS-NCs were investigated in L929, Vero, MCF7 cell lines and zebrafish-embryos. We observed minimal toxicity and acute teratogenic consequences upto 62.5 μg/ml of the CIZS-NCs in zebrafish-embryos. We also observed spontaneous uptake of the MUA-functionalized CIZS-NCs by 3 dpf older zebrafish-embryos that are evident through bright red fluorescence-emission at a low concentration of 7.8 μg/mL. Hence, we propose that the rapid, low-cost, large-scale “sustainable” MW-ST synthesis of CIZS-NCs, is an ideal bio-nanoprobe with good temporal and spatial resolution for rapid labeling, long-term in vivo tracking and intravital-fluorescence-bioimaging (IVBI).

  15. The effects of doping and shell thickness on the optical and magnetic properties of Mn/Cu/Fe-doped and Co-doped ZnS nanowires/ZnO quantum dots/SiO2 heterostructures

    NASA Astrophysics Data System (ADS)

    Cao, Jian; Yang, Jinghai; Yang, Lili; Wei, Maobin; Feng, Bo; Han, Donglai; Fan, Lin; Wang, Bingji; Fu, Hao

    2012-07-01

    In this paper, we demonstrated the encapsulation of Mn/Cu/Fe-doped and co-doped ZnS nanowires (NWs) and ZnO quantum dots (QDs) with a layer of mesoporous SiO2 shell for the purpose of integrating dual emission and ferromagnetism property into one common nanostructure at room temperature. Within the ZnS:Mn2+Cu2+Fe2+/ZnO@SiO2 nanocomposites, ZnS:Mn2+Cu2+Fe2+ NWs and ZnO QDs provided color-tunable visible emission and UV emission, respectively. The color-tunable visible emission in the ZnS:Mn2+Cu2+Fe2+ NWs can be obtained by adjusting the concentrations of Mn2+, Cu2+, and Fe2+ ions. The ferromagnetism of the ZnS:Mn2+Cu2+Fe2+ NWs was observed around room temperature, the mechanism of which was explained by the super-exchange mechanism. The results of the effect of the ZnO QDs shell thickness on the optical properties of the ZnS:Mn2+/ZnO@SiO2 nanocomposites showed that the luminescence intensity of the yellow-orange emission and UV emission reached the highest value when the ratio of ZnS:Mn2+/ZnO equaled 1:5.

  16. Improved photovoltaic performance and stability of quantum dot sensitized solar cells using Mn-ZnSe shell structure with enhanced light absorption and recombination control.

    PubMed

    Gopi, Chandu V V M; Venkata-Haritha, M; Kim, Soo-Kyoung; Kim, Hee-Je

    2015-08-07

    To make quantum-dot-sensitized solar cells (QDSSCs) competitive, photovoltaic parameters comparable to those of other emerging solar cell technologies are necessary. In the present study, ZnSe was used as an alternative to ZnS, one of the most widely used passivation materials in QDSSCs. ZnSe was deposited on a TiO2-CdS-CdSe photoanode to form a core-shell structure, which was more efficient in terms of reducing the electron recombination in QDSSCs. The development of an efficient passivation layer is a requirement for preventing recombination processes in order to attain high-performance and stable QDSSCs. A layer of inorganic Mn-ZnSe was applied to a QD-sensitized photoanode to enhance the adsorption and strongly inhibit interfacial recombination processes in QDSSCs, which greatly improved the power conversion efficiency. Impedance spectroscopy revealed that the combined Mn doping with ZnSe treatment reduces interfacial recombination and increases charge collection efficiency compared with Mn-ZnS, ZnS, and ZnSe. A solar cell based on the CdS-CdSe-Mn-ZnSe photoanode yielded excellent performance with a solar power conversion efficiency of 5.67%, Voc of 0.584 V, and Jsc of 17.59 mA cm(-2). Enhanced electron transport and reduced electron recombination are responsible for the improved Jsc and Voc of the QDSSCs. The effective electron lifetime of the device with Mn-ZnSe was higher than those with Mn-ZnS, ZnSe, and ZnS, leading to more efficient electron-hole separation and slower electron recombination.

  17. X-ray absorption fine structure and X-ray excited optical luminescence studies of II-VI semiconducting nanostructures

    NASA Astrophysics Data System (ADS)

    Murphy, Michael Wayne

    2010-06-01

    Various II-VI semiconducting nanomaterials such as ZnO-ZnS nanoribbons (NRs), CdSxSe1-x nanostructures, ZnS:Mn NRs, ZnS:Mn,Eu nanoprsims (NPs), ZnO:Mn nanopowders, and ZnO:Co nanopowders were synthesized for study. These materials were characterized by techniques such as scanning electron microscopy, transmission electron microscopy, element dispersive X-ray spectroscopy, selected area electron diffraction, and X-ray diffraction. The electronic and optical properties of these nanomaterials were studied by X-ray absorption fine structure (XAFS) spectroscopy and X-ray excited optical luminescence (XEOL) techniques, using tuneable soft X-rays from a synchrotron light source. The complementary nature ofthe XAFS and XEOL techniques give site, element and chemical specific measurements which allow a better understanding of the interplay and role of each element in the system. Chemical vapour deposition (CVD) of ZnS powder in a limited oxygen environment resulted in side-by-side biaxial ZnO-ZnS NR heterostructures. The resulting NRs contained distinct wurtzite ZnS and wurtzite ZnO components with widths of 10--100 nm and 20 --500 nm, respectively and a uniform interface region of 5-15 nm. XAFS and XEOL measurements revealed the luminescence of ZnO-ZnS NRs is from the ZnO component. The luminescence of CdSxSe1-x nanostructures is shown to be dependent on the S to Se ratio, with the band-gap emission being tunable between that of pure CdS and CdSe. Excitation of the CdSxSe 1-x nanostructures by X-ray in XEOL has revealed new de-excitation channels which show a defect emission band not seen by laser excitation. CVD of Mn2+ doped ZnS results in nanostructures with luminescence dominated by the yellow Mn2+ emission due to energy transfer from the ZnS host to the Mn dopant sites. The addition of EuCl3 to the reactants in the CVD process results in a change in morphology from NR to NP. Zn1-xMnxO and Zn1-xCOxO nanopowders were prepared by sol-gel methods at dopant concentrations

  18. Enhanced luminescence of rare-earth complexes Tb 1- xEu x( m-NBA) 3Phen in ZnS

    NASA Astrophysics Data System (ADS)

    Lv, Yuguang; Zhang, Jingchang; Cao, Weiliang; Song, Lin; Xu, Zheng

    2008-07-01

    Rare-earth ternary complexes Tb 1- xEu x( m-NBA) 3Phen ( X = 1, 0.25, 0.5, 0.75, 1.0) were synthesized and characterized by IR, DTA-TG, UV, fluorescent spectra and elemental analysis. It was found that luminescence of Eu 3+ complex was enhanced by doped with Tb 3+. It is proved by TG curve that the complexes are stable, ranging from ambient temperature to 360 °C in air. The organic-inorganic combined structural device was fabricated, and the electroluminescence intensity of the combined structural device was improved compared with the device of the purely organic components.

  19. Enhanced luminescence of rare-earth complexes Tb(1-x)Eu(x)(m-NBA)3Phen in ZnS.

    PubMed

    Lv, Yuguang; Zhang, Jingchang; Cao, Weiliang; Song, Lin; Xu, Zheng

    2008-07-01

    Rare-earth ternary complexes Tb(1-x)Eu(x)(m-NBA)(3)Phen (X=1, 0.25, 0.5, 0.75, 1.0) were synthesized and characterized by IR, DTA-TG, UV, fluorescent spectra and elemental analysis. It was found that luminescence of Eu(3+) complex was enhanced by doped with Tb(3+). It is proved by TG curve that the complexes are stable, ranging from ambient temperature to 360 degrees C in air. The organic-inorganic combined structural device was fabricated, and the electroluminescence intensity of the combined structural device was improved compared with the device of the purely organic components.

  20. Sustainable, Rapid Synthesis of Bright-Luminescent CuInS2-ZnS Alloyed Nanocrystals: Multistage Nano-xenotoxicity Assessment and Intravital Fluorescence Bioimaging in Zebrafish-Embryos

    PubMed Central

    Chetty, S. Shashank; Praneetha, S.; Basu, Sandeep; Sachidanandan, Chetana; Murugan, A. Vadivel

    2016-01-01

    Near-infrared (NIR) luminescent CuInS2-ZnS alloyed nanocrystals (CIZS-NCs) for highly fluorescence bioimaging have received considerable interest in recent years. Owing, they became a desirable alternative to heavy-metal based-NCs and organic dyes with unique optical properties and low-toxicity for bioimaging and optoelectronic applications. In the present study, bright and robust CIZS-NCs have been synthesized within 5 min, as-high-as 230 °C without requiring any inert-gas atmosphere via microwave-solvothermal (MW-ST) method. Subsequently, the in vitro and in vivo nano-xenotoxicity and cellular uptake of the MUA-functionalized CIZS-NCs were investigated in L929, Vero, MCF7 cell lines and zebrafish-embryos. We observed minimal toxicity and acute teratogenic consequences upto 62.5 μg/ml of the CIZS-NCs in zebrafish-embryos. We also observed spontaneous uptake of the MUA-functionalized CIZS-NCs by 3 dpf older zebrafish-embryos that are evident through bright red fluorescence-emission at a low concentration of 7.8 μg/mL. Hence, we propose that the rapid, low-cost, large-scale “sustainable” MW-ST synthesis of CIZS-NCs, is an ideal bio-nanoprobe with good temporal and spatial resolution for rapid labeling, long-term in vivo tracking and intravital-fluorescence-bioimaging (IVBI). PMID:27188464

  1. The mechanical response of turbostratic carbon nanotubes filled with Ga-doped ZnS: I. Data processing for the extraction of the elastic modulus.

    PubMed

    Costa, Pedro M F J; Cachim, Paulo B; Gautam, Ujjal K; Bando, Yoshio; Golberg, Dmitri

    2009-10-07

    The mechanical response of hybrid carbon nanotubes to applied uniaxial compressive forces has been evaluated inside a transmission electron microscope. The initially crooked nanocolumnar materials had an average elastic modulus of 0.53 GPa, measured in situ via a device based on an atomic force microscope cantilever. To extract this property it was necessary to curtail several sources of error (contact sliding, electronic interferences, etc) and develop the methodology herewith outlined. Since the present study was carried out with a commercially available sample holder, these mechanical studies are pertinent to all those working with one-dimensional structures such as nanorods and nanowires.

  2. The mechanical response of turbostratic carbon nanotubes filled with Ga-doped ZnS: I. Data processing for the extraction of the elastic modulus

    NASA Astrophysics Data System (ADS)

    Costa, Pedro M. F. J.; Cachim, Paulo B.; Gautam, Ujjal K.; Bando, Yoshio; Golberg, Dmitri

    2009-10-01

    The mechanical response of hybrid carbon nanotubes to applied uniaxial compressive forces has been evaluated inside a transmission electron microscope. The initially crooked nanocolumnar materials had an average elastic modulus of 0.53 GPa, measured in situ via a device based on an atomic force microscope cantilever. To extract this property it was necessary to curtail several sources of error (contact sliding, electronic interferences, etc) and develop the methodology herewith outlined. Since the present study was carried out with a commercially available sample holder, these mechanical studies are pertinent to all those working with one-dimensional structures such as nanorods and nanowires.

  3. Structural and optical properties of copper zinc tin sulphide (CZTS) material synthesized using binary sulphide precursors

    NASA Astrophysics Data System (ADS)

    Patel, K. K.; Shah, D. V.; Kheraj, Vipul

    2013-02-01

    Copper Zinc Tin Sulphide (CZTS) is one of the most promising materials for absorber layer in thin film solar cells. However, the synthesis of CZTS requires careful optimization as it is a quaternary material with a high probability of formation of secondary phases during the synthesis. Here we report the synthesis of CZTS from its binary constituents i.e. CuS, SnS and ZnS at 1030 K in laboratory. The effects of excess sulphur in starting precursors on the chemical compositions of the compound are investigated. Structural and optical properties of synthesized compound are studied in context of its application as absorber material in thin film solar cells.

  4. High-efficiency cadmium-free Cu(In,Ga)Se{sub 2} thin-film solar cells with chemically deposited ZnS buffer layers

    SciTech Connect

    Nakada, Tokio; Furumi, Keisuke; Kunioka, Akio

    1999-10-01

    Cadmium-free Cu(In,Ga)Se{sub 2} (CIGS) thin-film solar cells with a MgF{sub 2}/ZnO:Al/CBD-ZnS/CIGS/Mo/SLG structure have been fabricated using chemical bath deposition (CBD)-ZnS buffer layers and high-quality CIGS absorber layers grown using molecular beam epitaxy (MBE) system. The use of CBD-ZnS, which is a wider band gap material than CBD-CdS, improved the quantum efficiency of fabricated cells at short wavelengths, leading to an increase in the short-circuit current. The best cell at present yielded an active area efficiency of 16.9% which is the highest value reported previously for Cd-free CIGS thin-film solar cells. The as-fabricated solar cells exhibited a reversible light-soaking effect under AM 1.5, 100 mW/cm{sup 2} illumination. This paper also presents a discussion of the issues relating to the use of the CBD-ZnS buffer material for improving device performance.

  5. Crystal structure optimisation using an auxiliary equation of state.

    PubMed

    Jackson, Adam J; Skelton, Jonathan M; Hendon, Christopher H; Butler, Keith T; Walsh, Aron

    2015-11-14

    Standard procedures for local crystal-structure optimisation involve numerous energy and force calculations. It is common to calculate an energy-volume curve, fitting an equation of state around the equilibrium cell volume. This is a computationally intensive process, in particular, for low-symmetry crystal structures where each isochoric optimisation involves energy minimisation over many degrees of freedom. Such procedures can be prohibitive for non-local exchange-correlation functionals or other "beyond" density functional theory electronic structure techniques, particularly where analytical gradients are not available. We present a simple approach for efficient optimisation of crystal structures based on a known equation of state. The equilibrium volume can be predicted from one single-point calculation and refined with successive calculations if required. The approach is validated for PbS, PbTe, ZnS, and ZnTe using nine density functionals and applied to the quaternary semiconductor Cu2ZnSnS4 and the magnetic metal-organic framework HKUST-1.

  6. Crystal structure optimisation using an auxiliary equation of state

    SciTech Connect

    Jackson, Adam J.; Skelton, Jonathan M.; Hendon, Christopher H.; Butler, Keith T.; Walsh, Aron

    2015-11-14

    Standard procedures for local crystal-structure optimisation involve numerous energy and force calculations. It is common to calculate an energy–volume curve, fitting an equation of state around the equilibrium cell volume. This is a computationally intensive process, in particular, for low-symmetry crystal structures where each isochoric optimisation involves energy minimisation over many degrees of freedom. Such procedures can be prohibitive for non-local exchange-correlation functionals or other “beyond” density functional theory electronic structure techniques, particularly where analytical gradients are not available. We present a simple approach for efficient optimisation of crystal structures based on a known equation of state. The equilibrium volume can be predicted from one single-point calculation and refined with successive calculations if required. The approach is validated for PbS, PbTe, ZnS, and ZnTe using nine density functionals and applied to the quaternary semiconductor Cu{sub 2}ZnSnS{sub 4} and the magnetic metal-organic framework HKUST-1.

  7. One-step growth of structured ZnO thin films by chemical bath deposition in aqueous ammonia solution

    NASA Astrophysics Data System (ADS)

    Huang, S M; Bian, Z Q; Chu, J B; Wang, Z A; Zhang, D W; Li, X D; Zhu, H B; Sun, Z

    2009-03-01

    Structured ZnO films have been fabricated on soda-lime glass slides at a low temperature (80-85 °C) by a chemical bath deposition method in one step without seed layers. Mixed aqueous solutions of zinc sulfate, ammonia and thiourea were used at alkaline conditions. The influence of the ammonia concentration in the initial solution on the property of the deposited film was investigated systematically. The morphology, structural and optical properties of the deposited films were examined and characterized by x-ray diffraction (XRD), energy-dispersive spectroscopy x-ray diffraction (EDX), scanning electron microscopy (SEM), Raman spectroscopy and photoluminescence (PL) spectroscopy. Structural analyses with XRD, EDX and SEM revealed that the formed films exhibit a wurtzite hexagonal phase. The deposited film was more preferentially oriented in the (0 0 2) direction with an increase in the ammonia concentration from 0.75 to 2 mol l-1. The optical-phonon E2 mode at 437 cm-1 in the Raman spectrum, together with the XRD and EDX analyses, showed that flower-like and columnar crystalline ZnO films were formed in two ammonia concentration ranges, 0.75-1.4 mol l-1 and 1.6-2.0 mol l-1, respectively. Furthermore, PL spectra showed strong and high intensity peaks of UV emission with suppressed green emission for these deposited ZnO films. ZnS films were formed with a high ammonia concentration of 3.0 M. The formation mechanisms of ZnO, Zn(OH)2 and ZnS phases were discussed.

  8. Synthesis of ZnS Whiskers

    DTIC Science & Technology

    1988-07-11

    Lichetensteiger, J. Phys. Chem. Solids 21 (1961) 199-205. [171 T. M. Besman, SOLGASMIX - PV , A Computer Program to Calculate Equilibrium Relationships...performed using the SOLGASMIX computer program written by Eriksson [17-18]. This program is based on the approach developed by White et al. [19] which

  9. Influences of thicknesses and structures of barrier cap layers on As ion profiles and implant damages in HgCdTe epilayers

    NASA Astrophysics Data System (ADS)

    Shi, Changzhi; Lin, Chun; Wei, Yanfeng; Chen, Lu; Ye, Zhenhua

    2016-05-01

    The barrier cap layer (BCL) is considered to be able to absorb partially implant induced damages during ion implantation, thus its structure and property could impact the result of ion implantation. In this paper, for As ion implantation in HgCdTe, the different BCLs were deposited on the CdZnTe-based (LPE) and GaAs-based (MBE) HgCdTe epilayers, respectively. Then, the influences of thicknesses and structures of these BCLs on dopant profiles and implant damages were investigated. The as-grown BCLs include thermally evaporated (TE) ZnS, TE CdTe, electron beam evaporated (EBE) CdTe and in-situ CdTe/ZnTe grown by MBE. The SIMS profiles and TEM characterization indicate: For TE ZnS BCLs, there exists an optimized thickness to obtain the deepest As indiffusion after high temperature annealing, and the end-of-range (EOR) depth is linearly proportional to the thickness ratio of a-MCT layer/damage layer. For TE CdTe BCLs, the barrier layer induced channeling effect (BLICE) occurs to the thin BCL samples, while this effect is suppressed in the thick BCL samples. The phenomenon might be due to that the blocking effect of the layered structure inside each crystal column becomes dominate in the thick BCL samples. Additionally, the EBE CdTe BCL with layered structure can suppress effectively the BLICE effect; in the in-situ CdTe/ZnTe BCL, the short defect layer generated in the CdTe buffer layer and the amorphization of the ZnTe layer during ion implantation also play a significant role in suppressing the BLICE effect.

  10. 'Soft' phonon modes, structured diffuse scattering and the crystal chemistry of Fe-bearing sphalerites

    SciTech Connect

    Withers, Ray L. . E-mail: withers@rsc.anu.edu.au; Welberry, T.R.; Pring, Allan; Tenailleau, Cristophe; Liu Yun

    2005-03-15

    Electron diffraction has been used to carefully investigate the reciprocal lattices of a range of iron-bearing sphalerites looking for evidence of Fe clustering and/or Fe/Zn ordering in the form of either additional satellite reflections or a structured diffuse intensity distribution accompanying the strong Bragg reflections of the underlying sphalerite-type average structure. While a highly structured diffuse intensity distribution in the form of transverse polarized {l_brace}110{r_brace}* sheets of diffuse intensity has been detected and found to be characteristic of all compositions, it does not appear to arise from Fe clustering and/or Fe/Zn ordering. Rather inherently low frequency, and therefore strongly thermally excited, phonon modes propagating along reciprocal space directions perpendicular to each of the six <110> real space directions of the average structure are suggested to be responsible for these {l_brace}110{r_brace}* sheets of diffuse intensity. Monte Carlo simulation (for a range of Zn-S, Zn-Zn and S-S interaction strengths) and subsequent Fourier transformation is used to confirm the existence of these low-frequency phonon modes of distortion as well as to show that they are an intrinsic, predictable property of the corner-connected tetrahedral structure of sphalerite. The low-frequency phonon modes involve coupled (Zn, Fe) and S motion in one-dimensional strings along <110> real space directions.

  11. Variation of the coordination environment and its effect on the white light emission properties in a Mn-doped ZnO-ZnS complex structure.

    PubMed

    Cheng, Yan; Chen, Rui; Feng, Haifeng; Hao, Weichang; Xu, Huaizhe; Wang, Yu; Li, Jiong

    2014-03-14

    Mn-doped ZnO-ZnS complex nanocrystals were fabricated through coating of dodecanethiol on Mn-doped ZnO nanocrystals. The relationship between the component of white light emission and the coordination environments of Mn-dopants were experimentally investigated. It was shown that Mn ions mainly formed Mn(3+)O6 octahedra in as prepared Mn-doped ZnO, while the Mn(3+) ions on the surface of ZnO transferred into Mn(2+) ions at the interface between ZnO and ZnS after dodecanethiol coating. The Mn(2+)S4 tetrahedron density and the orange emission intensity increased upon enhancing the dodecanethiol content. These results provide an alternative way to optimize the white emission spectrum from nanocrystals of Mn-doped ZnS-ZnO complex structures through modulation of the coordination environment of Mn ions.

  12. Vibrational spectra and lattice thermal conductivity of kesterite-structured Cu2ZnSnS4 and Cu2ZnSnSe4

    NASA Astrophysics Data System (ADS)

    Skelton, Jonathan M.; Jackson, Adam J.; Dimitrievska, Mirjana; Wallace, Suzanne K.; Walsh, Aron

    2015-04-01

    Cu2ZnSnS4 (CZTS) is a promising material for photovoltaic and thermoelectric applications. Issues with quaternary semiconductors include chemical disorder (e.g., Cu-Zn antisites) and disproportionation into secondary phases (e.g., ZnS and Cu2SnS3). To provide a reference for the pure kesterite structure, we report the vibrational spectra—including both infra-red and Raman intensities—from lattice-dynamics calculations using first-principles force constants. Three-phonon interactions are used to estimate phonon lifetimes (spectral linewidths) and thermal conductivity. CZTS exhibits a remarkably low lattice thermal conductivity, competitive with high-performance thermoelectric materials. Transition from the sulfide to selenide (Cu2ZnSnSe4) results in softening of the phonon modes and an increase in phonon lifetimes.

  13. Natural nanoparticle structure, properties and reactivity from X-ray studies

    SciTech Connect

    Waychunas, Glenn A.

    2009-10-01

    Synthetic analogs of naturally occurring nanoparticles have been studied by a range of X-ray techniques to determine their structure and chemistry, and relate these to their novel chemical properties and physical behavior. ZnS nanoparticles, formed in large concentrations naturally bymicrobial action, have an interesting core-shell structure with a highly distorted and strained outer layer. The strain propagates through the particles and produces unusual stiffness but can be relieved by changing the nature of the surface ligand binding. Weaker bound ligands allow high surface distortion, but strongly bound ligands relax this structure and reduce the overall strain. Only small amounts of ligand exchange causes transformations from the strained to the relaxed state. Most remarkably, minor point contacts between strained nanoparticles also relax the strain. Fe oxyhydroxide nanoparticles appear to go through structural transformations dependent on their size and formation conditions, and display a crystallographically oriented form of aggregation at the nanoscale that alters growth kinetics. At least one Fe oxyhydroxide mineral may only be stable on the nanoscale, and nonstoichiometry observed on the hematite surface suggests that for this phase and possibly other natural metal oxides, chemistry may be size dependent. Numerous questions exist on nanominerals formed in acid mine drainage sites and by reactions at interfaces.

  14. Structural Investigations of Surfaces and Orientation-SpecificPhenomena in Nanocrystals and Their Assemblies

    SciTech Connect

    Aruguete, Deborah Michiko

    2006-01-01

    Studies of colloidal nanocrystals and their assemblies are presented. Two of these studies concern the atomic-level structural characterization of the surfaces, interfaces, and interiors present in II-VI semiconductor nanorods. The third study investigates the crystallographic arrangement of cobalt nanocrystals in self-assembled aggregates. Crystallographically-aligned assemblies of colloidal CdSe nanorods are examined with linearly-polarized Se-EXAFS spectroscopy, which probes bonding along different directions in the nanorod. This orientation-specific probe is used, because it is expected that the presence of specific surfaces in a nanorod might cause bond relaxations specific to different crystallographic directions. Se-Se distances are found to be contracted along the long axis of the nanorod, while Cd-Se distances display no angular dependence, which is different from the bulk. Ab-initio density functional theory calculations upon CdSe nanowires indicate that relaxations on the rod surfaces cause these changes. ZnS/CdS-CdSe core-shell nanorods are studied with Se, Zn, Cd, and S X-ray absorption spectroscopy (XAS). It is hypothesized that there are two major factors influencing the core and shell structures of the nanorods: the large surface area-to-volume ratio, and epitaxial strain. The presence of the surface may induce bond rearrangements or relaxations to minimize surface energy; epitaxial strain might cause the core and shell lattices to contract or expand to minimize strain energy. A marked contraction of Zn-S bonds is observed in the core-shell nanorods, indicating that surface relaxations may dominate the structure of the nanorod (strain might otherwise drive the Zn-S lattice to accommodate the larger CdS or CdSe lattices via bond expansion). EXAFS and X-ray diffraction (XRD) indicate that Cd-Se bond relaxations might be anisotropic, an expected phenomenon for a rod-shaped nanocrystal. Ordered self-assembled aggregates of cobalt nanocrystals are

  15. Polarized GaN-based LED with an integrated multi-layer subwavelength structure.

    PubMed

    Zhang, Guiju; Wang, Chinhua; Cao, Bing; Huang, Zengli; Wang, Jianfeng; Zhang, Baoshun; Xu, Ke

    2010-03-29

    A novel type of GaN-based LED with a highly polarized output using an integrated multi-layer subwavelength grating structure is proposed. Characteristics of both optical transmission and polarization extinction ratio of the polarized GaN-based LED with three different multi-layer subwavelength structures are investigated. It is found that both TM transmission (T(TM)) and the extinction ratio(ER) of the LED output can be effectively enhanced by incorporating a dielectric transition layer between the metal grating and GaN substrate with a lower refractive index than that of the GaN substrate. Flat sensitivity of the T(TM) on the period, duty cycle of the metallic grating, and the wide range of operating wavelength have been achieved in contrast to the conventional sensitive behavior in single-layer metallic grating. Up to 0.75 high duty cycle of the metallic grating can be employed to achieve >60dB ER while T(TM) maintains higher than ~90%, which breaks the conventional limit of T(TM) and ER being always a pair of trade-off parameters. Typical optimized multilayer structures in terms of material, thickness, grating periods and duty cycle using MgF(2) and ZnS, respectively, as the transition layers are obtained. The results provide guidance in designing, optimizing and fabricating the novel integrated GaN-based and polarized photonic devices.

  16. Room-temperature wide-range luminescence and structural, optical, and electrical properties of SILAR deposited Cu-Zn-S nano-structured thin films

    NASA Astrophysics Data System (ADS)

    Jose, Edwin; Kumar, M. C. Santhosh

    2016-09-01

    We report the deposition of nanostructured Cu-Zn-S composite thin films by Successive Ionic Layer Adsorption and Reaction (SILAR) method on glass substrates at room temperature. The structural, morphological, optical, photoluminescence and electrical properties of Cu-Zn-S thin films are investigated. The results of X-ray diffraction (XRD) and Raman spectroscopy studies indicate that the films exhibit a ternary Cu-Zn-S structure rather than the Cu xS and ZnS binary composite. Scanning electron microscope (SEM) studies show that the Cu-Zn-S films are covered well over glass substrates. The optical band gap energies of the Cu-Zn-S films are calculated using UV-visible absorption measurements, which are found in the range of 2.2 to 2.32 eV. The room temperature photoluminescence studies show a wide range of emissions from 410 nm to 565 nm. These emissions are mainly due to defects and vacancies in the composite system. The electrical studies using Hall effect measurements show that the Cu-Zn-S films are having p-type conductivity.

  17. Changes induced in a ZnS:Cr-based electroluminescent waveguide structure by intrinsic near-infrared laser radiation

    SciTech Connect

    Vlasenko, N. A. Oleksenko, P. F.; Mukhlyo, M. A.; Veligura, L. I.

    2013-08-15

    The causes of changes that occur in a thin-film electroluminescent metal-insulator-semiconductor-insulator-metal waveguide structure based on ZnS:Cr (Cr concentration of {approx}4 Multiplication-Sign 10{sup 20} cm{sup -3}) upon lasing ({lambda} Almost-Equal-To 2.6 {mu}m) and that induce lasing cessation are studied. It is established that lasing ceases because of light-scattering inhomogeneities formed in the structure and, hence, optical losses enhance. The origin of the inhomogeneities and the causes of their formation are clarified by studying the surface topology and the crystal structure of constituent layers of the samples before and after lasing. The studies are performed by means of atomic force microscopy and X-ray radiography. It is shown that a substantial increase in the sizes of grains on the surface of the structure is the manifestation of changes induced in the ZnS:Cr film by recrystallization. Recrystallization is initiated by local heating by absorbed laser radiation in existing Cr clusters and quickened by a strong electric field (>1 MV cm{sup -1}). The changes observed in the ZnS:Cr film are as follows: the textured growth of ZnS crystallites, an increase in the content of Cr clusters, and the appearance of some CrS and a rather high ZnO content. Some ways for improving the stability of lasing in the ZnS:Cr-based waveguide structures are proposed.

  18. Sub-seafloor bacterial community structures within massive sulfide deposits at the Southern Mariana Trough

    NASA Astrophysics Data System (ADS)

    Yamagishi, A.; Kato, S.; Moriya, O.; Urabe, T.

    2012-12-01

    Yet-uncharacterized sub-seafloor bacterial communities within massive sulfide deposits important for ocean elemental flux were investigated by 16S rRNA gene analysis. Shallow sub-seafloor drilling was performed in a deep-sea hydrothermal field (called Pika site) of the Southern Mariana Trough (SMT). The borehole length was 4.252 m and the length of the core sample obtained was 2,920 mm (¬68.7% recovery). The core sample mainly consisted of pyrite (FeS2), sphalerite (ZnS) and chalcopyrite (CuFeS2), and contained barite (BaSO4) as minor components. Three subsamples (upper, middle and lower) of the core sample were picked up from different depth points (0.77, 1.14, 2.37 mbsf). Bacterial 16S rRNA gene analysis was performed for the three subsamples. The community structures based on the detected clones were clearly different from one another. The dominant clone detected in each subsample was related to Gammaproteobacteria, Bacteroidetes and Ignavibacteria, or Nitrospirae, respectively. Many clones detected from the sub-seafloor massive sulfide deposits were similar to those from sulfide chimneys of inactive vents or basaltic lavas on the seafloor including SMT and other areas. Comparative analysis revealed the commonality and difference of the community structures with those in surrounding seafloor environments depending on the sampling depth.

  19. On Carcinomas and Other Pathological Entities

    PubMed Central

    Kumar, Anand; Ceusters, Werner; Rosse, Cornelius

    2005-01-01

    Tumours, abscesses, cysts, scars and fractures are familiar types of what we shall call pathological continuant entities. The instances of such types exist always in or on anatomical structures, which thereby become transformed into pathological anatomical structures of corresponding types: a fractured tibia, a blistered thumb, a carcinomatous colon. In previous work on biomedical ontologies we showed how the provision of formal definitions for relations such as is_a, part_of and transformation_of can facilitate the integration of such ontologies in ways which have the potential to support new kinds of automated reasoning. We here extend this approach to the treatment of pathologies, focusing especially on those pathological continuant entities which arise when organs become affected by carcinomas. PMID:18629199

  20. The ternary yttrium sulfides, CaY{sub 2}S{sub 4}, and BaY{sub 2}S{sub 4}: Structures and properties

    SciTech Connect

    Lowe-Ma, C.K.; Vanderah, T.A.; Smith, T.E.

    1995-07-01

    X-ray single-crystal structure determinations have confirmed that CaY{sub 2}S{sub 4} crystallizes in the orthorhombic [Yb{sub 3}S{sub 4}]-type structure whereas SrY{sub 2}S{sub 4} and BaY{sub 2}S{sub 4} adopt the orthorhombic [CaFe{sub 2}O{sub 4}] structure. Both structure types feature three-dimensional frameworks build of edge- and corner-sharing [YS{sub 6}] octahedra. CaY{sub 2}S{sub 4}, in space group Pnma, has cell dimensions a = 12.953(3) {angstrom}, b = 3.8835(5) {angstrom}, c = 13.081(3) {angstrom}, Vol = 658.0(2) {angstrom}{sup 3}, Z = 4, and D{sub x} = 3.494 g/cm{sup 3} (M{sub f} = 346.1). SrY{sub 2}S{sub 4}, in Pmnb, has a = 3.9775(6), b = 11.974(2), c = 14.294(2) {angstrom}, Vol = 680.8(2) {angstrom}{sup 3}, Z = 4, and D{sub x} = 3.841 g/cm{sup 3} for M{sub F} = 393.7; BaY{sub 2}S{sub 4}, in Pmnb, has a = 4.0263(2), b = 12.2134(8), c = 14.484(1) {angstrom}, Vol = 712.23(9) {angstrom}{sup 3}, Z = 4, and D{sub x} = 4.135 g/cm{sup 3} for M{sub f} = 443.4. Room temperature X-ray powder diffraction data for all three compounds and high-temperature unit cells for CaY{sub 2}S{sub 4} are also reported. The overall average linear thermal expansion of CaY{sub 2}S{sub 4}f are also reported. The overall average linear thermal expansion of CaY{sub 2}S{sub 4} upon heating was found to be approximately 11.9 x 10{sup {minus}6}/{degrees}K as compared to that of 7.2 x 10{sup {minus}6}{degrees}K found for ZnS. The onset oxidative decomposition temperatures for CaY{sub 2}S{sub 4}, SrY{sub 2}S{sub 4}, and BaY{sub 2}S{sub 4} were observed to be 545, 565, and 590{degrees}C, respectively, as compared to 530{degrees}C for ZnS. The properties of these compounds indicate that they are potentially useful as infrared window materials.

  1. Response of nanoparticle structure to different types of surface environments: Wide-angle x-ray scattering and molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Zhang, Hengzhong; Chen, Bin; Ren, Yang; Waychunas, Glenn A.; Banfield, Jillian F.

    2010-03-01

    The structure of nanoparticles is nonstationary and changes in response to the surface environment where the nanoparticles are situated. Nanoparticle-environment interaction determines the nature of the structure change, an important consideration for evaluating subsequent environmental impact. In this work, we used ZnS nanoparticles to interact with surface environments that contain different inorganic salts, water, and organic molecules. From analysis of the pair-distribution function (PDF) derived from wide-angle x-ray scattering experiments, we found that a stronger surface interaction results in a thicker crystalline core and a thinner distorted shell, corresponding to PDF curves having larger peaks and more peaks at longer radial distances. Plane-wave electronic calculations were used to quantify the interaction strength. An analogous atomic view of the nanoparticle-environmental interactions and structures was provided by molecular dynamics simulations. The extent of response of the nanoparticle structure to various surface environments is used as a measure of the interaction strength between them.

  2. Core/shell CdS/ZnS nanoparticles: Molecular modelling and characterization by photocatalytic decomposition of Methylene Blue

    NASA Astrophysics Data System (ADS)

    Praus, Petr; Svoboda, Ladislav; Tokarský, Jonáš; Hospodková, Alice; Klemm, Volker

    2014-02-01

    Core/shell CdS/ZnS nanoparticles were modelled in the Material Studio environment and synthesized by one-pot procedure. The core CdS radius size and thickness of the ZnS shell composed of 1-3 ZnS monolayers were predicted from the molecular models. From UV-vis absorption spectra of the CdS/ZnS colloid dispersions transition energies of CdS and ZnS nanostructures were calculated. They indicated penetration of electrons and holes from the CdS core into the ZnS shell and relaxation strain in the ZnS shell structure. The transitions energies were used for calculation of the CdS core radius by the Schrödinger equation. Both the relaxation strain in ZnS shells and the size of the CdS core radius were predicted by the molecular modelling. The ZnS shell thickness and a degree of the CdS core coverage were characterized by the photocatalytic decomposition of Methylene Blue (MB) using CdS/ZnS nanoparticles as photocatalysts. The observed kinetic constants of the MB photodecomposition (kobs) were evaluated and a relationship between kobs and the ZnS shell thickness was derived. Regression results revealed that 86% of the CdS core surface was covered with ZnS and the average thickness of ZnS shell was about 12% higher than that predicted by molecular modelling.

  3. Influence of annealing temperature on the structural, optical and electrical properties of amorphous Zinc Sulfide thin films

    NASA Astrophysics Data System (ADS)

    Göde, F.; Güneri, E.; Kariper, A.; Ulutaş, C.; Kirmizigül, F.; Gümüş, C.

    2011-11-01

    Zinc sulfide films have been deposited on glass substrates at room temperature by the chemical bath deposition technique. The growth mechanism is studied using X-ray diffraction, scanning electron microscopy, optical absorption spectra and electrical measurements. The as-deposited film was given thermal annealing treatment in air atmosphere at various temperatures (100, 200, 300 400 and 500 °C) for 1 h. The annealed film was also characterized by structural, optical and electrical studies. The structural analyses revealed that the as-deposited film was amorphous, but after being annealed at 500 °C, it changed to polycrystalline. The optical band gap is direct with a value of 4.01 eV, but this value decreased to 3.74 eV with annealing temperature, except for the 500 °C anneal where it only decreased to 3.82 eV. The refractive index (n), extinction coefficient (k), and real (ɛ1) and imaginary (ɛ2) parts of the dielectric constant are evaluated. Raman peaks appearing at ~478 cm-1, ~546 cm-1, ~778 cm-1 and ~1082 cm-1 for the annealed film (500 °C) were attributed to [TOl+LAΣ, 2TOΓ, 2LO, 3LO phonons of ZnS. The electrical conductivities of both as-deposited and annealed films have been calculated to be of the order of ~10-10 (Ω cm)-1 .

  4. Molecular dynamics study of zinc binding to cysteines in a peptide mimic of the alcohol dehydrogenase structural zinc site.

    PubMed

    Brandt, Erik G; Hellgren, Mikko; Brinck, Tore; Bergman, Tomas; Edholm, Olle

    2009-02-14

    The binding of zinc (Zn) ions to proteins is important for many cellular events. The theoretical and computational description of this binding (as well as that of other transition metals) is a challenging task. In this paper the binding of the Zn ion to four cysteine residues in the structural site of horse liver alcohol dehydrogenase (HLADH) is studied using a synthetic peptide mimic of this site. The study includes experimental measurements of binding constants, classical free energy calculations from molecular dynamics (MD) simulations and quantum mechanical (QM) electron structure calculations. The classical MD results account for interactions at the molecular level and reproduce the absolute binding energy and the hydration free energy of the Zn ion with an accuracy of about 10%. This is insufficient to obtain correct free energy differences. QM correction terms were calculated from density functional theory (DFT) on small clusters of atoms to include electronic polarisation of the closest waters and covalent contributions to the Zn-S coordination bond. This results in reasonably good agreement with the experimentally measured binding constants and Zn ion hydration free energies in agreement with published experimental values. The study also includes the replacement of one cysteine residue to an alanine. Simulations as well as experiments showed only a small effect of this upon the binding free energy. A detailed analysis indicate that the sulfur is replaced by three water molecules, thereby changing the coordination number of Zn from four (as in the original peptide) to six (as in water).

  5. Electric and Dielectric Properties of Au/ZnS-PVA/n-Si (MPS) Structures in the Frequency Range of 10-200 kHz

    NASA Astrophysics Data System (ADS)

    Baraz, Nalan; Yücedağ, İbrahim; Azizian-Kalandaragh, Yashar; Ersöz, Gülçin; Orak, İkram; Altındal, Şemsettin; Akbari, Bashir; Akbari, Hossein

    2017-02-01

    Pure polyvinyl alcohol (PVA) capped ZnS semiconductor nanocrystals were prepared by microwave-assisted method, and the optical and structural properties of the as-prepared materials were characterized by x-ray diffraction (XRD) and Ultraviolet-visible (UV-Vis) techniques. The XRD pattern shows the formation of ZnS nanocrystals, and the UV-Vis spectroscopy results show a blue shift of about 1.2 eV in its band gap due to the confinement of very small nanostructures. The concentration of donor atoms (N D), diffusion potential (V D), Fermi energy level (E F), and barrier height (ΦB (C-V)) values were obtained from the reverse bias C -2-V plots for each frequency. The voltage dependent profile of series resistance (R s) and surface states (N ss) were also obtained using admittance and low-high frequency methods, respectively. R s-V and N ss-V plots both have distinctive peaks in the depletion region due to the spatial distribution charge at the surface states. The effect of R s and interfacial layer on the C-V and G/ω-V characteristics was found remarkable at high frequencies. Therefore, the high frequency C-V and G/ω-V plots were corrected to eliminate the effect of R s. The real and imaginary parts of dielectric constant (ɛ' and ɛ″) and electric modulus (M' and M″), loss tangent (tan δ), and ac electrical conductivity (σ ac) were also obtained using C and G/ω data and it was found that these parameters are indeed strong functions of frequency and applied bias voltage. Experimental results confirmed that the N ss, R s , and interfacial layer of the MPS structure are important parameters that strongly influence both the electrical and dielectric properties. The low values of N ss ( 109 eV-1 cm-2) and the value of dielectric constant (ɛ' = 1.3) of ZnS-PVA interfacial layer even at 10 kHz are very suitable for electronic devices when compared with the SiO2. These results confirmed that the ZnS-PVA considerably improves the performance of Au/n-Si (MS

  6. Elastico-mechanoluminescence and crystal-structure relationships in persistent luminescent materials and II-VI semiconductor phosphors

    NASA Astrophysics Data System (ADS)

    Chandra, B. P.; Chandra, V. K.; Jha, Piyush

    2015-04-01

    Elastico-mechanoluminescence (EML) has recently attracted the attention of a large number of researchers because of its potential in different types of mechano-optical devices. For understanding the mechanism of EML the relationships between elastico-mechanoluminescence (EML) and crystal-structure of a large number of persistent luminescent materials and II-VI semiconductor phosphors known to date are investigated. It is found that, although most of the non-centrosymmetric crystals exhibit EML, certain non-centrosymmetric crystals do not show EML. Whereas, many centrosymmetric crystals do not exhibit EML, certain centrosymmetric crystals exhibit EML. Piezoelectric ZnS:Cu,Cl single crystals do not show EML, but piezoelectric ZnS:Cu,Cl microcrystalline phosphors show very intense EML. Piezoelectric single crystals of undoped ZnS do not show EML. It seems that EML is related to local piezoelectrification near the impurities in crystals where piezoelectric constant is high. Suitable piezoelectric field near the local piezoelectric region and stable charge carriers in traps are required for appearance of EML. The EML of persistent luminescent materials and II-VI semiconductor phosphors can be understood on the basis of piezoelectrically-induced trap-depth reduction model of EML. Using suitable dopants both in non-centrosymmetric and centrosymmetric crystals intense elastico-mechanoluminescent materials emitting desired colours can be tailored, which may find applications in several mechano-optical devices.

  7. Structural and electronic properties of CdS/ZnS core/shell nanowires: A first-principles study

    NASA Astrophysics Data System (ADS)

    Kim, Hyo Seok; Kim, Yong-Hoon

    2015-03-01

    Carrying out density functional theory (DFT) calculation, we studied the relative effects of quantum confinement and strain on the electronic structures of II-IV semiconductor compounds with a large lattice-mismatch, CdS and ZnS, in the core/shell nanowire geometry. We considered different core radii and shell thickness of the CdS/ZnS core/shell nanowire, different surface facets, and various defects in the core/shell interface and surface regions. To properly describe the band level alignment at the core/shell boundary, we adopted the self-interaction correction (SIC)-DFT scheme. Implications of our findings in the context of device applications will be also discussed. This work was supported by the Basic Science Research Grant (No. 2012R1A1A2044793), Global Frontier Program (No. 2013-073298), and Nano-Material Technology Development Program (2012M3A7B4049888) of the National Research Foundation funded by the Ministry of Education, Science and Technology of Korea. Corresponding author

  8. Multifunctional Zn{sub 0.99-x}Mn{sub 0.01}Cu{sub x}S nanowires: Structure, luminescence and magnetism

    SciTech Connect

    Cao, Jian; Yang, Jinghai; Zhang, Yongjun; Yang, Lili; Wang, Yaxin; Wang, Dandan; Gao, Ming; Liu, Yang; Liu, Xiaoyan; Xie, Zhi

    2010-06-15

    The wurtzite-type Zn{sub 0.99-x}Mn{sub 0.01}Cu{sub x}S (x = 0, 0.003, 0.01) nanowires were prepared by a simple hydrothermal method at 180 {sup o}C. The structure and morphology of the samples were characterized by X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), field emission scanning electron micrograph (FESEM) and X-ray photoelectron spectrum (XPS). The results showed that both the Mn{sup 2+} and Cu{sup 2+} ions substituted for the Zn{sup 2+} sites in the host ZnS. The ethylenediamine-mediated template was observed, which was used to explain the growth mechanism of the nanowires. The color-tunable emission can be obtained by adjusting the concentrations of Mn{sup 2+} and Cu{sup 2+} ions. The ferromagnetism was observed around room temperature.

  9. Structural ceramics

    SciTech Connect

    Wachtman, J.B. Jr.

    1989-01-01

    The present work discusses opportunities for application of structural ceramics in heat engines, industrial-wear parts, prosthetics and bearings; conceptual and detailed design principles for structural ceramics; the processing, consolidation, and properties of members of the SiC family of structural ceramics; and the silicon nitride and sialon families of hot-pressed, sintered, and reaction-bonded, structural ceramics. Also discussed are partially-stabilized zirconia and zirconia-toughened ceramics for structural applications, the processing methods and mechanisms of fiber-reinforcement in ceramic-matrix fiber-reinforced composites, and the tribological properties of structural ceramics.

  10. Website Structure

    ERIC Educational Resources Information Center

    Jackson, Larry S.

    2009-01-01

    This dissertation reports the results of an exploratory data analysis investigation of the relationship between the structures used for information organization and access and the associated storage structures within state government websites. Extending an earlier claim that hierarchical directory structures are both the preeminent information…

  11. ZnS nanoflakes deposition by modified chemical method

    SciTech Connect

    Desai, Mangesh A. Sartale, S. D.

    2014-04-24

    We report deposition of zinc sulfide nanoflakes on glass substrates by modified chemical method. The modified chemical method involves adsorption of zinc–thiourea complex on the substrate and its dissociation in presence of hydroxide ions to release sulfur ions from thiourea which react with zinc ions present in the complex to form zinc sulfide nanoflakes at room temperature. Influence of zinc salt and thiourea concentrations ratios on the morphology of the films was investigated by scanning electron microscope (SEM). The ratio of zinc and thiourea in the zinc–thiourea complex significantly affect the size of the zinc sulfide nanoflakes, especially width and density of the nanoflakes. The X-ray diffraction analysis exhibits polycrystalline nature of the zinc sulfide nanoflakes with hexagonal phase.

  12. Phase Diagram Studies of ZnS Systems

    DTIC Science & Technology

    1988-09-01

    mechanical, processing of ZnS-base ’alloys’. Knowledge of the phase equilibria of various ZnS-rich systems is essential to achieve our objectives...initial studies of the solid-state phase equilibria in the ZnS-CdS and ZnS-Ga2s3 phase diagrams.

  13. Preparation and Characterization of Colloidal ZnS Particles

    DTIC Science & Technology

    1989-06-15

    dilute to be of any practical value. Later, Wilhelmy and Matijevic (4 1 employed thermaJ decomposition of thioacetamide to prepare micron-sized spherical...1981) 4. D.M. Wilhelmy, E. Matijevic , J. Chem. Soc., Faraday Trans. I 80, 563 (1984). 5. R. Williams, P.N. Yocom, F.S. Sotofko, J. Coll. and Int. Sci

  14. Highly efficient surface enhanced Raman scattering with ZnS@Fe3O4@Ag composite structures as probes

    NASA Astrophysics Data System (ADS)

    Nair, Radhika V.; Siva Gummaluri, Venkata; Gayathri, P. K.; Vijayan, C.

    2017-01-01

    Development of novel composite materials with enhanced optical properties and modified surface morphology is highly significant in surface enhanced Raman spectroscopic (SERS) applications. Dielectric-plasmonic multilayer composites are found to serve this purpose due to the feasibility of tuning their plasmon resonances even to IR region, far away from electronic resonance of analyte molecules. In this work, we introduce a new composite material that can have enormous potential in sensing applications at trace level. Here we demonstrate surface enhanced Raman scattering activity of ZnS@Fe3O4@Ag composite structures using rhodamine 6G (Rh6G) dye molecule as the model analyte. The SERS substrate is prepared by coating these structures on borosilicate glass substrate. ZnS particles of size 300 nm coated successively with Fe3O4 (40 nm thick) and Ag (20 nm thick) nanoparticles are found to be capable of detecting even 10‑11 M concentration of Rh6G. Obtained results are compared with SERS activity of ZnS@Ag particles which could detect only up to 10‑8 M of Rh6G. It is observed that inclusion of Fe3O4 layer increases SERS enhancement by a factor of 102 compared to that of ZnS@Ag. SERS substrates fabricated out of ZnS@Fe3O4@Ag particles resulted in SERS enhancement factor (EF) of around 109 which is large enough for single molecule detection. Theoretical investigations on SERS activity of these structures are carried out using finite difference time domain (FDTD) method. SERS EFs obtained using FDTD are found to be in good agreement with experimental results.

  15. Influence of Ag thickness on structural, optical, and electrical properties of ZnS/Ag/ZnS multilayers prepared by ion beam assisted deposition

    NASA Astrophysics Data System (ADS)

    Leng, Jian; Yu, Zhinong; Xue, Wei; Zhang, Ting; Jiang, Yurong; Zhang, Jie; Zhang, Dongpu

    2010-10-01

    The structural, optical, and electrical characteristics of zinc sulfide (ZnS)/Ag/ZnS (ZAZ) multilayer films prepared by ion beam assisted deposition on k9 glass have been investigated as a function of Ag layer thickness. The characteristics of ZAZ multilayer are significantly improved up insertion of optimal Ag thickness between ZnS layers. The results show that due to bombardment of Ar ion beam, distinct Ag islands evolve into continuous Ag films at a thin Ag thickness of about 4 nm. The thinner Ag film as a thickness of 2 nm leads to high sheet resistance and low transmittance for the interface scattering induced by the Ag islands or noncontinuous films; and when the Ag thickness is over 4 nm, the ZAZ multilayer exhibits a remarkably reduced sheet resistance between 7-80 Ω/sq for the increase in carrier concentration and mobility of Ag layer, and a high transmittance over 90% for the interference phenomena of multilayers and low absorption and surface scattering of Ag layer. The ZAZ multilayer with 14 nm Ag film has a figure of merit up to 6.32×10-2 Ω-1, an average transmittance over 92% and a sheet resistance of 7.1 Ω/sq. The results suggest that ZAZ film has better optoelectrical properties than conditional indium tin oxide single layer.

  16. Reconfigurable structure

    NASA Technical Reports Server (NTRS)

    Curtis, Steven A. (Inventor)

    2010-01-01

    A reconfigurable structure includes a plurality of selectively extensible and retractable limbs, at least one node pivotably receiving respective ends of at least two limbs, and an actuator associated with each limb for extending and retracting the limb. The structure may further include an addressable module associated with each actuator to control the actuator.

  17. Structural Ceramics

    NASA Technical Reports Server (NTRS)

    1986-01-01

    This publication is a compilation of abstracts and slides of papers presented at the NASA Lewis Structural Ceramics Workshop. Collectively, these papers depict the scope of NASA Lewis' structural ceramics program. The technical areas include monolithic SiC and Si3N4 development, ceramic matrix composites, tribology, design methodology, nondestructive evaluation (NDE), fracture mechanics, and corrosion.

  18. Tau Structures

    PubMed Central

    Avila, Jesus; Jiménez, Juan S.; Sayas, Carmen L.; Bolós, Marta; Zabala, Juan C.; Rivas, Germán; Hernández, Felix

    2016-01-01

    Tau is a microtubule-associated protein that plays an important role in axonal stabilization, neuronal development, and neuronal polarity. In this review, we focus on the primary, secondary, tertiary, and quaternary tau structures. We describe the structure of tau from its specific residues until its conformation in dimers, oligomers, and larger polymers in physiological and pathological situations. PMID:27877124

  19. Protein Structure

    ERIC Educational Resources Information Center

    Asmus, Elaine Garbarino

    2007-01-01

    Individual students model specific amino acids and then, through dehydration synthesis, a class of students models a protein. The students clearly learn amino acid structure, primary, secondary, tertiary, and quaternary structure in proteins and the nature of the bonds maintaining a protein's shape. This activity is fun, concrete, inexpensive and…

  20. On Structure.

    ERIC Educational Resources Information Center

    Acland, Henry

    Structure as an aspect of educational setting is discussed and illustrated in the course of an argument indicating that efforts to change schools, including Project Follow Through, should aim to change structures rather than people. It is asserted that educational reform in America usually attempts to change people, especially children, and that…

  1. Organisational Structure

    ERIC Educational Resources Information Center

    National Centre for Vocational Education Research (NCVER), 2006

    2006-01-01

    An understanding of organisational structure can provide guidance for organisations that want to change and innovate. Many writers agree that this understanding allows organisations to shape how their work is done to ultimately achieve their business goals--and that too often structure is given little consideration in business strategy and…

  2. Tetrahedral atom zincophosphate structures: Synthesis, crystal structure, and spectroscopic studies of (Zn(PO2(OC2H5)2)2)x, a one-dimensional inorganic polymer

    NASA Astrophysics Data System (ADS)

    Harrison, William T.; Nenoff, Tina M.; Gier, Thurman E.; Stucky, Galen D.

    1992-05-01

    The synthesis, structure and some properties of a new, anhydrous, zinc ethyl phosphate are described. Zn(O2P(OC2H5)2)2 (ZnPOEt) crystallizes in the monoclinic space group C2/c(No. 15) with a = 22.176(6), b = 8.042(2), c = 9.0883(3) A, beta = 96.553 (8) deg, V = 1610 A(exp 3), rho(sub calc) = 1.533 g/cm(exp 3), mu = 17.8 cm(exp -1) and Z = 4, with R(F(sub 0)) = 6.94 percent for 658 observed reflections (I greater than 3 sigma(I)). The novel structure consists of infinite 1-dimensional chains of vertex-linked zinc-oxygen and phosphorous-oxygen tetrahedra forming 4-rings: two of the phosphate P-0 vertices are coordinated to ethyl (-C2H5) groups, and the herringbone crystal packing is determined by van der Waals' forces between these terminal organic groups. Physical (TGA, DSC) and spectroscopic data (IR, H-1 and P-31 NMR) are presented. The physical data show a melting, followed by a decomposition reaction, eventually resulting in Zn(PO3)2. ZnPOEt is soluble in and recrystallizable from several polar and non-polar solvents: the NMR data suggest that ZnPOEt maintains a polymeric state in solution. ZnPOEt is contrasted with its sulphur-containing analogue, Zn(S2P(OC2H5)2)2.

  3. Reconstructing the energy band electronic structure of pulsed laser deposited CZTS thin films intended for solar cell absorber applications

    NASA Astrophysics Data System (ADS)

    Pandiyan, Rajesh; Oulad Elhmaidi, Zakaria; Sekkat, Zouheir; Abd-lefdil, Mohammed; El Khakani, My Ali

    2017-02-01

    We report here on the use of pulsed KrF-laser deposition (PLD) technique for the growth of high-quality Cu2ZnSnS4 (CZTS) thin films onto Si, and glass substrates without resorting to any post sulfurization process. The PLD-CZTS films were deposited at room temperature (RT) and then subjected to post annealing at different temperatures ranging from 200 to 500 °C in Argon atmosphere. The X-ray diffraction and Raman spectroscopy confirmed that the PLD films crystallize in the characteristic kesterite CZTS structure regardless of their annealing temperature (Ta), but their crystallinity is much improved for Ta ≥ 400 °C. The PLD-CZTS films were found to exhibit a relatively dense morphology with a surface roughness (RMS) that increases with Ta (from ∼14 nm at RT to 70 nm at Ta = 500 °C with a value around 40 nm for Ta = 300-400 °C). The optical bandgap of the PLD-CZTS films, was derived from UV-vis transmission spectra analysis, and found to decrease from 1.73 eV for non-annealed films to ∼1.58 eV for those annealed at Ta = 300 °C. These band gap values are very close to the optimum value needed for an ideal solar cell absorber. In order to achieve a complete reconstruction of the one-dimensional energy band structure of these PLD-CZTS absorbers, we have combined both XPS and UPS spectroscopies to determine their chemical bondings, the position of their valence band maximum (relative to Fermi level), and their work function values. This enabled us to sketch out, as accurately as possible, the band alignment of the heterojunction interface formed between CZTS and both CdS and ZnS buffer layer materials.

  4. Spacecraft Structures

    NASA Video Gallery

    This activity challenges students to solve a real-world problem that is part of the space program using creativity, cleverness and scientific knowledge while learning about forces, structures and e...

  5. Structural Analysis

    NASA Technical Reports Server (NTRS)

    1991-01-01

    After an 800-foot-tall offshore oil recovery platform collapsed, the engineers at Engineering Dynamics, Inc., Kenner, LA, needed to learn the cause of the collapse, and analyze the proposed repairs. They used STAGSC-1, a NASA structural analysis program with geometric and nonlinear buckling analysis. The program allowed engineers to determine the deflected and buckling shapes of the structural elements. They could then view the proposed repairs under the pressure that caused the original collapse.

  6. Structures research

    NASA Technical Reports Server (NTRS)

    Abu-Saba, Elias; Mcginley, Williams; Shen, Ji-Yao

    1992-01-01

    The main objective of the structures group is to provide quality aerospace research with the Center for Aerospace Research - A NASA Center for Excellence at North Carolina Agricultural and Technical State University. The group includes dedicated faculty and students who have a proven record in the area of structures, in particular space structures. The participating faculty developed accurate mathematical models and effective computational algorithms to characterize the flexibility parameters of joint dominated beam-truss structures. Both experimental and theoretical modelling has been applied to the dynamic mode shapes and mode frequencies for a large truss system. During the past few months, the above procedures has been applied to the hypersonic transport plane model. The plane structure has been modeled as a lumped mass system by Doctor Abu-Saba while Doctor Shen applied the transfer matrix method with a piecewise continuous Timoshenko tapered beam model. Results from both procedures compare favorably with those obtained using the finite element method. These two methods are more compact and require less computer time than the finite element method. The group intends to perform experiments on structural systems including the hypersonic plane model to verify the results from the theoretical models.

  7. Structures Division

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The NASA Lewis Research Center Structures Division is an international leader and pioneer in developing new structural analysis, life prediction, and failure analysis related to rotating machinery and more specifically to hot section components in air-breathing aircraft engines and spacecraft propulsion systems. The research consists of both deterministic and probabilistic methodology. Studies include, but are not limited to, high-cycle and low-cycle fatigue as well as material creep. Studies of structural failure are at both the micro- and macrolevels. Nondestructive evaluation methods related to structural reliability are developed, applied, and evaluated. Materials from which structural components are made, studied, and tested are monolithics and metal-matrix, polymer-matrix, and ceramic-matrix composites. Aeroelastic models are developed and used to determine the cyclic loading and life of fan and turbine blades. Life models are developed and tested for bearings, seals, and other mechanical components, such as magnetic suspensions. Results of these studies are published in NASA technical papers and reference publication as well as in technical society journal articles. The results of the work of the Structures Division and the bibliography of its publications for calendar year 1995 are presented.

  8. Centriole structure

    PubMed Central

    Winey, Mark; O'Toole, Eileen

    2014-01-01

    Centrioles are among the largest protein-based structures found in most cell types, measuring approximately 250 nm in diameter and approximately 500 nm long in vertebrate cells. Here, we briefly review ultrastructural observations about centrioles and associated structures. At the core of most centrioles is a microtubule scaffold formed from a radial array of nine triplet microtubules. Beyond the microtubule triplets of the centriole, we discuss the critically important cartwheel structure and the more enigmatic luminal density, both found on the inside of the centriole. Finally, we discuss the connectors between centrioles, and the distal and subdistal appendages outside of the microtubule scaffold that reflect centriole age and impart special functions to the centriole. Most of the work we review has been done with electron microscopy or electron tomography of resin-embedded samples, but we also highlight recent work performed with cryoelectron microscopy, cryotomography and subvolume averaging. Significant opportunities remain in the description of centriolar structure, both in mapping of component proteins within the structure and in determining the effect of mutations on components that contribute to the structure and function of the centriole. PMID:25047611

  9. Composite structural materials. [aircraft structures

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

    1980-01-01

    The use of filamentary composite materials in the design and construction of primary aircraft structures is considered with emphasis on efforts to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, and reliability and life prediction. The redesign of a main spar/rib region on the Boeing 727 elevator near its actuator attachment point is discussed. A composite fabrication and test facility is described as well as the use of minicomputers for computer aided design. Other topics covered include (1) advanced structural analysis methids for composites; (2) ultrasonic nondestructive testing of composite structures; (3) optimum combination of hardeners in the cure of epoxy; (4) fatigue in composite materials; (5) resin matrix characterization and properties; (6) postbuckling analysis of curved laminate composite panels; and (7) acoustic emission testing of composite tensile specimens.

  10. Adenovirus structure.

    PubMed

    Rux, John J; Burnett, Roger M

    2004-12-01

    Structural studies continue to play an essential role as the focus of adenovirus research shifts in emphasis from basic biology to adenovirus-based vector technologies. A crucial step in developing novel therapeutics for gene replacement, cancer, and vaccines is often to modify the virion. Such engineered changes are designed to retarget the virus, or to reduce the immunological responses to infection. These efforts are far more effective when they are based on detailed structural knowledge. This minireview provides a brief summary of the wealth of information that has been obtained from the combined application of X-ray crystallography and electron microscopy. This knowledge now includes a good working model for the architectural organization of the virion, and atomic resolution molecular structures for all the major capsid proteins, hexon, penton, and fiber. We highlight new developments, which include the structure of the penton base and the discovery that adenovirus has several relatives. We sketch how the structural information can be used to engineer novel virions and conclude with the prospects for future progress.

  11. Tension Structure

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The fabric structure pictured is the Campus Center of La Verne College, La Verne, California. Unlike the facilities shown on the preceding pages, it is not air-supported. It is a "tension structure," its multi-coned fabric membrane supported by a network of cables attached to steel columns which function like circus tent poles. The spider-web in the accompanying photo is a computer graph of the tension pattern. The designers, Geiger-Berger Associates PC, of New York City, conducted lengthy computer analysis to determine the the best placement of columns and cables. The firm also served as structural engineering consultant on the Pontiac Silverdome and a number of other large fabric structures. Built by Birdair Structures, Inc., Buffalo, New York, the La Verne Campus Center was the first permanent facility in the United States enclosed by the space-spinoff fabric made of Owens-Corning Beta fiber glass coated with Du Pont Teflon TFE. The flexible design permits rearrangement of the interior to accommodate athletic events, student activities, theatrical productions and other recreational programs. Use of fabric covering reduced building cost 30 percent below conventional construction.

  12. Experiment study on the cutting property of hot press Zinc Sulfide by single point diamond turning

    NASA Astrophysics Data System (ADS)

    Li, Weihao; Tong, Yi; Lian, Weiyan; Liu, Dandan; Zhang, Hao

    2014-08-01

    Microscopic morphology and XRD spectra of Hot Press(HP) ZnS powders and fractrues were tested. Preliminary analysis of the turning characters of HP ZnS was got by associating with the characters of HP ZnS and the processing mechanism of hard and brittle materials. Orthogonal experiment of 3 factors and 3 levers was taken by setting roughness Ra value index of the turning surface, and more analyses of the ultra-precision turning characters of HP ZnS were got by associating with the 3D microscopic morphology of CVD ZnSe ultra-precision turning surface and HP ZnS polishing surface. How to get the lower Ra value was discussed at last. The research shows: the primary removal mechanism of HP ZnS is powder removal; HP ZnS can get good ultra-precision turning surface which Ra value is lower than 10nm; to get the Ra value of the turning surface lower than 4nm, speed of main spindle, blunt edge radius, and the corner radius must be optimized because of the polycrystalline structure of the HP ZnS.

  13. Carbon-coated Zinc Sulfide nano-clusters: synthesis, photothermal conversion and adsorption properties.

    PubMed

    Bao, Chunlin; Zhu, Guoxing; Shen, Mengqi; Yang, Jing

    2014-12-15

    Carbon-coated cluster-like ZnS nanospheres were synthesized by a facile solvothermal route. ZnCl2, thiourea, and glucose were selected as the raw materials. The formed ZnS with hexagonal phase has spherical cluster-like structure, which shows good monodispersity in size. A thin layer carbon is coated on the surface of ZnS cluster-like spheres. The thickness of carbon shell is dependent on the dosage of glucose. The carbon-coated ZnS nano-clusters show the same emission as that of pristine ZnS nano-clusters. Exposure of the aqueous dispersion of carbon-coated ZnS products to 980 nm laser can elevate its temperature by 5.1°C in 8 min. It was found that the photothermal conversion effect mainly comes from the carbon component and at the same time, the heterointerface between ZnS and carbon also provides a positive role for it. In addition, the carbon-coated ZnS products can absorb dye molecular with highest adsorption capacity of 36.8 mg/g toward Rhodamine B. The present finding demonstrates their potential applications in photothermal agents, adsorbents, and related fields.

  14. Luminescent, magnetic and optical properties of ZnO-ZnS nanocomposites

    NASA Astrophysics Data System (ADS)

    Raleaooa, Pule V.; Roodt, Andreas; Mhlongo, Gugu G.; Motaung, David E.; Kroon, Robin E.; Ntwaeaborwa, Odireleng M.

    2017-02-01

    The structure, particle morphology, optical and magnetic properties of ZnO, ZnS and ZnO-ZnS nanoparticles prepared by the sol-gel method are reported. ZnO and ZnS were combined at room temperature by an ex situ synthetic route to prepare ZnO-ZnS nanocomposites. The nanocomposites exhibited particle morphology different from that of ZnO and ZnS nanoparticles. The ZnO and ZnS nanoparticles exhibited quantum confinement as inferred from the widening of their respective bandgap energies. The electron paramagnetic resonance data provided evidence for the existence of magnetic clusters near the surface, electron to nuclei interactions and defect states. The ZnO-ZnS nanocomposites exhibited tunable emission that was dependent on the ratio of ZnO to ZnS. These composites were evaluated for application in different types of light emitting devices.

  15. Synthesis of zinc sulphide nanoparticles and its photodegradation ability towards organic pollutants

    NASA Astrophysics Data System (ADS)

    Giribabu, K.; Suresh, R.; Manigandan, R.; Vijayalakshmi, L.; Stephen, A.; Narayanan, V.

    2014-01-01

    Zinc sulphide (ZnS) nanoparticles were synthesized by thermal decomposition of zinc n-propyl dithiocarbonate (Xanthate). ZnS nanoparticles were characterized by XRD and FE-SEM. XRD peaks match well with the standard ZnS reflections (JCPDS No. 36-1450). It revealed that the synthesized ZnS has a hexagonal structure. The lattice constants are found to be a = 3.08 and c = 6.20 were nanostructures. From FE-SEM image plate like and agglomerated particles was observed. However particles are uniformly distributed in the image. The photodegradation ability of the ZnS nanoparticles was investigated using methylene blue as the model compound.

  16. Surfactant assisted surface studies of zinc sulfide nanoparticles

    NASA Astrophysics Data System (ADS)

    Shahi, Ashutosh K.; Pandey, B. K.; Swarnkar, R. K.; Gopal, R.

    2011-09-01

    We report a simple soft chemical method for the synthesis of ZnS nanoparticles using varying concentration of cationic surfactant CTAB and examine its surface properties. Powder X-ray diffraction, UV-vis spectroscopy, photoluminescence spectroscopy, selective area electron diffraction, and transmission electron microscopy are used to characterize the as prepared ZnS nanoparticles. XRD and TEM measurements show the size of polydispersed ZnS nanoparticles is in the range of 2-5 nm with cubic phase structure. The photoluminescence spectrum of ZnS nanoparticles exhibits four fluorescence emission peaks centered at 387 nm, 412 nm, 489 nm and 528 nm showing the application potential for the optical devices. In Raman spectra of ZnS nanoparticles, the modes around 320, 615 and 700 cm-1 are observed.

  17. Structures protection

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Materials of which an aircraft is made and the methods used to hold these materials together forming the aircraft structure were studied as factors important in protecting a modern aircraft from hazardous natural environments. Since all-metal aircraft are being replaced by aircraft constructed partly of fiber reinforced plastics with desirable light weight and high strength properties but with poor electrical conductivity, the danger of lightning strikes has become more serious. Lightning effects on metal structures were reviewed and design protection was discussed. The expected lightning effects on nonmetallic materials such as fiberglass and advanced composites were also reviewed.

  18. Structural evolution

    SciTech Connect

    Burr, M.T.

    1993-03-01

    In this special report, financial executives discuss key trends in power project finance, new funding sources and evolving project structures. Industry wide, financial firms and developers are striving to improve the cost-effectiveness and efficiency of project financing, for projects in both greenfield development and the growing secondary market.

  19. Nanocrystal structures

    DOEpatents

    Eisler, Hans J.; Sundar, Vikram C.; Walsh, Michael E.; Klimov, Victor I.; Bawendi, Moungi G.; Smith, Henry I.

    2006-12-19

    A structure including a grating and a semiconductor nanocrystal layer on the grating, can be a laser. The semiconductor nanocrystal layer can include a plurality of semiconductor nanocrystals including a Group II–VI compound, the nanocrystals being distributed in a metal oxide matrix. The grating can have a periodicity from 200 nm to 500 nm.

  20. Structural Adaptation

    ERIC Educational Resources Information Center

    Crowley, Julianne; Titmus, Morgan

    2016-01-01

    This article explores an alternative conception held by high school and first-year university biology students regarding the structure of the left and right ventricles of the heart and the significance of the left ventricular wall being thicker than the right. The left ventricular wall of the heart is thicker than the right ventricular wall due to…

  1. Lightweight Structures.

    ERIC Educational Resources Information Center

    Shaver and Co., Michigan City, IN.

    One of the newest and most promising developments in architecture has been the use of lightweight structures for encapsulating space. Using this new technology, builders can enclose large and small areas at a fraction of the cost of conventional construction and at the same time provide interior space that is totally flexible. This brochure shows…

  2. Lightweight Structures

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel

    2001-01-01

    Present structural concepts for hot static structures are conventional "sheet & stringer" or truss core construction. More weight-efficient concepts such as honeycomb and lattice block are being investigated, in combination with both conventional superalloys and TiAl. Development efforts for components made from TiAl sheet are centered on lower cost methods for sheet and foil production, plus alloy development for higher temperature capability. A low-cost casting technology recently developed for aluminum and steel lattice blocks has demonstrated the required higher strength and stiffness, with weight efficiency approach- ing honeycombs. The current effort is based on extending the temperature capability by developing lattice block materials made from IN-718 and Mar-M247.

  3. Superconducting structure

    DOEpatents

    Kwon, Chuhee; Jia, Quanxi; Foltyn, Stephen R.

    2003-04-01

    A superconductive structure including a dielectric oxide substrate, a thin buffer layer of a superconducting material thereon; and, a layer of a rare earth-barium-copper oxide superconducting film thereon the thin layer of yttrium-barium-copper oxide, the rare earth selected from the group consisting of samarium, gadolinium, ytterbium, erbium, neodymium, dysprosium, holmium, lutetium, a combination of more than one element from the rare earth group and a combination of one or more elements from the rare earth group with yttrium, the buffer layer of superconducting material characterized as having chemical and structural compatibility with the dielectric oxide substrate and the rare earth-barium-copper oxide superconducting film is provided.

  4. Superconducting Structure

    DOEpatents

    Kwon, Chuhee; Jia, Quanxi; Foltyn, Stephen R.

    2005-09-13

    A superconductive structure including a dielectric oxide substrate, a thin buffer layer of a superconducting material thereon; and, a layer of a rare earth-barium-copper oxide superconducting film thereon the thin layer of yttrium-barium-copper oxide, the rare earth selected from the group consisting of samarium, gadolinium, ytterbium, erbium, neodymium, dysprosium, holmium, lutetium, a combination of more than one element from the rare earth group and a combination of one or more elements from the rare earth group with yttrium, the buffer layer of superconducting material characterized as having chemical and structural compatibility with the dielectric oxide substrate and the rare earth-barium-copper oxide superconducting film is provided.

  5. Structural Geology

    NASA Astrophysics Data System (ADS)

    Weber, John; Frankel, Kurt L.

    2011-05-01

    Structural geology and continental tectonics were ushered in to the modern quantitative age of geosciences with the arrival of the global plate tectonics paradigm (circa 1968), derived using new data from the oceans' depths, and John Ramsay's 1967 seminal work, Folding and Fracturing of Rocks. Fossen is to be applauded for crafting a unique, high-caliber, and accessible undergraduate textbook on structural geology that faithfully reflects this advance and the subsequent evolution of the discipline. This well-written text draws on Fossen's wealth of professional experience, including his broad and diverse academic research and experience in the petroleum industry. This book is beautifully illustrated, with excellent original color diagrams and with impressive color field photographs that are all keyed to locations and placed into geologic context.

  6. Terminal structure

    DOEpatents

    Schmidt, Frank; Allais, Arnaud; Mirebeau, Pierre; Ganhungu, Francois; Lallouet, Nicolas

    2009-10-20

    A terminal structure (2) for a superconducting cable (1) is described. It consists of a conductor (2a) and an insulator (2b) that surrounds the conductor (2a), wherein the superconducting cable (1) has a core with a superconducting conductor (5) and a layer of insulation that surrounds the conductor (5), and wherein the core is arranged in such a way that it can move longitudinally in a cryostat. The conductor (2a) of the terminal structure (2) is electrically connected with the superconducting conductor (5) or with a normal conductor (6) that is connected with the superconducting conductor (5) by means of a tubular part (7) made of an electrically conductive material, wherein the superconducting conductor (5) or the normal conductor (6) can slide in the part (7) in the direction of the superconductor.

  7. Microplastic Structures

    NASA Astrophysics Data System (ADS)

    Feely, Wayne E.

    1986-07-01

    Thick coatings (5-15μm) of a new dual image, aqueous developable photoresist can be exposed using a light attenuating photomask consisting of clear, opaque and grey areas and then processed to yield thermally stable 3-dimensional structures which are potentially useful as mechanical and optical components of devices. In the positive mode, relief and intaglio images are produced by processing similar to positive novolak based resists with 1- 2μm resolution and with the added feature that the images can be made thermally stable to temperatures >300° C. Negative mode processing of coated wafers imaged with the special mask produces thermally stable structures with tunnels or hollow chambers as well as cantilever beams. Because these structures are crosslinked at the time of development, processing in the negative mode shows much wider latitude than is the case in the positive mode. Images by negative mode processing are capable of submicron resolution, higher aspect ratio (>3 vs <1.6), and inward sloping wall profiles adjustable by exposure. The acid hardening resin compositions cover a broad range of compositions so that resins can be tailored to meet specific property requirements.

  8. Structural representation of data structures

    NASA Astrophysics Data System (ADS)

    Cantoni, Virginio; Gaggia, Alessandro; Gatti, Riccardo; Lombardi, Luca

    2014-06-01

    Study of the morphology of proteins, and their 3D structure, supports investigations of their functions and represents an initial step towards protein-based drug design. The goal of this paper is to define techniques, based on the geometrical and topological structure of protein surfaces, for the detection and analysis of sites of potential protein-protein and protein-ligand interactions. Two protein representation modalities based on the Concavity Tree (CT) and the Enriched Complex Extended Gaussian Image (EC-EGI) are considered. In particular, the concavity tree, in which the interface is usually extended and roughly planar, is considered to be better suited to protein-protein interaction studies. Instead, the EGI is more suited to protein-ligand interactions, in which the small ligand molecule usually has to fit into the protein cavity. In fact, the histogram of the orientations is better suited to representing a mainly convex object and its dual matching region (the cavity). Both these data structures are open, and can be easily integrated with biochemical features.

  9. Airfoil structure

    DOEpatents

    Frey, G.A.; Twardochleb, C.Z.

    1998-01-13

    Past airfoil configurations have been used to improve aerodynamic performance and engine efficiencies. The present airfoil configuration further increases component life and reduces maintenance by reducing internal stress within the airfoil itself. The airfoil includes a chord and a span. Each of the chord and the span has a bow being summed to form a generally ``C`` configuration of the airfoil. The generally ``C`` configuration includes a compound bow in which internal stresses resulting from a thermal temperature gradient are reduced. The structural configuration reduces internal stresses resulting from thermal expansion. 6 figs.

  10. Airfoil structure

    DOEpatents

    Frey, Gary A.; Twardochleb, Christopher Z.

    1998-01-01

    Past airfoil configurations have been used to improve aerodynamic performance and engine efficiencies. The present airfoil configuration further increases component life and reduces maintenance by reducing internal stress within the airfoil itself. The airfoil includes a chord and a span. Each of the chord and the span has a bow being summed to form a generally "C" configuration of the airfoil. The generally "C" configuration includes a compound bow in which internal stresses resulting from a thermal temperature gradient are reduced. The structural configuration reduces internal stresses resulting from thermal expansion.

  11. Local structure analysis of materials for increased energy efficiency

    NASA Astrophysics Data System (ADS)

    Medling, Scott

    In this dissertation, a wide range of materials which exhibit interesting properties with potential for energy efficiency applications are investigated. The bulk of the research was conducted using the Extended X-ray Absorption Fine Structure (EXAFS) technique. EXAFS is a powerful tool for elucidating the local structure of novel materials, and it's advantages are presented in Chapter 2. In Chapter 3, I present details on two new techniques which are used in studies later in this dissertation, but are also promising for other, unrelated studies and, therefore, warrant being discussed generally. I explain the presence of and present a method for subtracting the X-ray Raman background in the fluorescence window when collecting fluorescence EXAFS data of a dilute dopant Z in a Z+1 host. I introduce X-ray magnetic circular dichroism (XMCD) and discuss the process to reduce XMCD data, including the self-absorption corrections for low energy K-edges. In Chapter 4, I present a series of investigations on ZnS:Cu electroluminescent phosphors. Optical microscopy indicates that the emission centers do not degrade uniformly or monotonically, but rather, most of the emission centers blink on and off during degradation. The effect of this on various proposed degradation mechanisms is discussed. EXAFS data of ZnS:Cu phosphors ground to enable thinner, lower-voltage devices indicate that grinding preferentially causes damage to the CuS nanoprecipitates, quenching electroluminescence (EL) and concluding that smaller particles must be built up from nanoparticles instead. EXAFS data of nanoparticles show that adding a ZnS shell outside a ZnS:Cu core provides significant additional encapsulation of the Cu, increasing photoluminescence and indicating that this may increase EL if devices can be fabricated. Data from extremely dilute (0.02% Cu) ZnS:Cu nanoparticles is presented in order to specifically study the non-precipitate and suggests that the Cu dopant substitutes for Zn and is

  12. Structures of

    PubMed

    Kirik; Solovyov; Blokhin; Yakimov

    2000-06-01

    Crystal structures of [Pd(NH3)2X2] complexes, where X = Br or I, diamminediiodo-/-dibromopalladium(II), have been studied by X-ray powder diffraction. The series consists of five complexes: cis-[Pd(NH3)2Br2] (I) [a = 13.3202 (7), b = 12.7223 (6), c = 7.05854 (3) A, Z = 8, space group Pbca], trans-[Pd(NH3)2Br2] (II) [a = 6.7854 (3), b = 7.1057 (3), c = 6.6241 (2) A, alpha = 103.221 (3), beta = 102.514 (2), gamma = 100.386 (3) degrees, Z = 2, space group P1], beta-trans-[Pd(NH3)2Br2] (III) [a = 8.4315 (3), b = 8.4206 (3), c = 8.0916 (2) A, Z = 4, space group Pbca], cis-[Pd(NH3)2I2] (IV) [a = 13.9060 (8), b = 13.5035 (8), c = 7.5050 (4) A, Z = 8, space group Pbca], and beta-trans-[Pd(NH3)2I2] (V) [a = 8.8347 (5), b = 8.8410 (5), c = 8.6081 (2) A, Z = 4, space group Pbca]. Patterson synthesis and Rietveld refinement have been used for structural determination. Molecular structures with column- or parquet-type packing of flat complexes are characteristic of these substances. Corresponding cis- and beta-trans compounds are isostructural. The thermal transformations cis-->trans-->beta-trans (cis-->beta-trans in the case of iodine) are considered. Cl derivatives are also discussed. The transformations proceed irreversibly and are accompanied by decreasing specific volume. Owing to these features, they can be classified as chemical reactions. High-temperature X-ray powder diffraction was used to study the transformations in air. The set of data is consistent with a solid state transformation from cis to trans. According to this model, the columns of molecules remain intact during the process, and the transformation proceeds via the breaking of Pd...X and Pd...N intermolecular bonds. The powder diffraction data have been deposited in ICDD-JCPDS (45-0596, 46-0876, 46-0879, 47-1690, 48-1185).

  13. Digital structural

    USGS Publications Warehouse

    Dohm, J.M.; Anderson, R.C.; Tanaka, K.L.

    1998-01-01

    Magmatic and tectonic activity have both contributed significantly to the surface geology of Mars. Digital structural mapping techniques have now been used to classify and date centers of tectonic activity in the western equatorial region. For example, our results show a center of tectonic activity at Valles Marineris, which may be associated with uplift caused by intrusion. Such evidence may help explain, in part, the development of the large troughs and associated outflow channels and chaotic terrain. We also find a local centre of tectonic activity near the source region of Warrego Valles. Here, we suggest that the valley system may have resulted largely from intrusive-related hydrothermal activity. We hope that this work, together with the current Mars Global Surveyor mission, will lead to a better understanding of the geological processes that shaped the Martian surface.

  14. Armor structures

    DOEpatents

    Chu, Henry Shiu-Hung [Idaho Falls, ID; Lacy, Jeffrey M [Idaho Falls, ID

    2008-04-01

    An armor structure includes first and second layers individually containing a plurality of i-beams. Individual i-beams have a pair of longitudinal flanges interconnected by a longitudinal crosspiece and defining opposing longitudinal channels between the pair of flanges. The i-beams within individual of the first and second layers run parallel. The laterally outermost faces of the flanges of adjacent i-beams face one another. One of the longitudinal channels in each of the first and second layers faces one of the longitudinal channels in the other of the first and second layers. The channels of the first layer run parallel with the channels of the second layer. The flanges of the first and second layers overlap with the crosspieces of the other of the first and second layers, and portions of said flanges are received within the facing channels of the i-beams of the other of the first and second layers.

  15. Asteroid structure

    NASA Astrophysics Data System (ADS)

    Asphaug, E.

    2014-07-01

    Even before the first space missions to asteroids, in the mid-1990s, it was known that asteroids have weird structures. Photometry indicated complicated shapes, and the pioneering radar investigations by Ostro and colleagues followed by adaptive optics campaigns and flybys showed odd binary forms, and confirmed the common presence of satellites, and indications of highly varying surface roughness. Some asteroids turned out to be dominated by a single major cratering event, while others showed no evidence of a major crater, or perhaps for global crater erasure. The first space mission to orbit an asteroid, NEAR, found a mixture of heavily cratered terrains and geomorphically active 'ponds', and indicated evidence for global seismicity from impact. The next mission to orbit an asteroid, Hayabusa, found what most agree is a rubble pile, with no major craters and an absence of fines. There is to date no direct evidence of asteroid interior geology, other than measurements of bulk density, and inferences made for mass distribution asymmetry based on dynamics, and inferences based on surface lineaments. Interpolating from the surface to the interior is always risky and usually wrong, but of course the answer is important since we are someday destined to require this knowledge in order to divert a hazardous asteroid from impact with the Earth. Even considering the near-subsurface, here we remain as ignorant as we were about the Moon in the early 1960s, whether the surface will swallow us up in dust, or will provide secure landing and anchoring points. Laboratory experimentation in close to zero-G is still in its early stages. Adventures such as mining and colonization will surely have to wait until we better know these things. How do we get from here to there? I will focus on 3 areas of progress: (1) asteroid cratering seismology, where we use the surface craters to understand what is going on inside; (2) numerical modeling of collisions, which predicts the internal

  16. Structural Biology Fact Sheet

    MedlinePlus

    ... Home > Science Education > Structural Biology Fact Sheet Structural Biology Fact Sheet Tagline (Optional) Middle/Main Content Area What is structural biology? Structural biology is a field of science focused ...

  17. Magnetic multilayer structure

    DOEpatents

    Herget, Philipp; O'Sullivan, Eugene J.; Romankiw, Lubomyr T.; Wang, Naigang; Webb, Bucknell C.

    2017-03-21

    A mechanism is provided for an integrated laminated magnetic device. A substrate and a multilayer stack structure form the device. The multilayer stack structure includes alternating magnetic layers and diode structures formed on the substrate. Each magnetic layer in the multilayer stack structure is separated from another magnetic layer in the multilayer stack structure by a diode structure.

  18. Magnetic multilayer structure

    SciTech Connect

    Herget, Philipp; O'Sullivan, Eugene J.; Romankiw, Lubomyr T.; Wang, Naigang; Webb, Bucknell C.

    2016-07-05

    A mechanism is provided for an integrated laminated magnetic device. A substrate and a multilayer stack structure form the device. The multilayer stack structure includes alternating magnetic layers and diode structures formed on the substrate. Each magnetic layer in the multilayer stack structure is separated from another magnetic layer in the multilayer stack structure by a diode structure.

  19. Synthesis of wurtzite-zincblende Cu2ZnSnS4 and Cu2ZnSnSe4 nanocrystals: insight into the structural selection of quaternary and ternary compounds influenced by binary nuclei

    NASA Astrophysics Data System (ADS)

    Li, Yingwei; Han, Qifeng; Kim, Tae Whan; Shi, Wangzhou

    2014-03-01

    using SC(NH2)2, which also verified that the binary semiconductors are the determinative factors. Electronic supplementary information (ESI) available: Detailed information about the mole ratios used for reactions, EDS and XPS spectra of the synthesized nanocrystals, a table for structural comparison between quaternary and ternary compounds, Raman scattering spectra of the ternary compounds CTS and CTSe, and XRD patterns of the binary ZnS and ZnSe. See DOI: 10.1039/c3nr05358j

  20. Common structure-balance between spacetime structure and massenergy structure

    NASA Astrophysics Data System (ADS)

    Cao, Daqing; Cao, Dayong

    2017-01-01

    According to Einstein field equation, there is a balance between spacetime structure and massenergy structure. nd the paper consider it as a common structurewhich was brought forward by Daqing Cao in 2011 ecause it is general structure in the universe and everything have the same model of structure in their one system. The Jovian planets is spacetime structure of solar system because they are gas-sphere and they have more density of spacetime (spacetime/massenergy) than the density of massenergy (massenergy/spacetime). The terrestrial planets is massenergy structure of solar system because they are rock-ball and they have more density of massenergy than the density of spacetime. That can explain of that the Jovian planets of big mass is far away from sun. With the idea that the wave is spacetime and the wave effect is spacetime structure, the planets have elliptic orbits and the same direction of their revolution. Because sun is like a massenergy center of the massenergy structure and the terrestrial planets, the paper supposes there is a dark sun-a dark hole who has a spacetime center of spacetime structure and influences on the orbits of the Jovian planets. http://meetings.aps.org/Meeting/APR16/Session/M13.8

  1. Nonlinear Structural Analysis

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Nonlinear structural analysis techniques for engine structures and components are addressed. The finite element method and boundary element method are discussed in terms of stress and structural analyses of shells, plates, and laminates.

  2. Study of Boundary Structures.

    DTIC Science & Technology

    1982-09-01

    THEORY OF ABC-CBA STACKING BOUNDARY IN fcc STRUCTURE .......... 11 - 4 TRANSITIONS AND PHASE EQUILIBRIA AMONG GRAIN BOUNDARY STRUCTURES...19 B THEORY OF ABC-CBA STACKING BOUNDARY IN fcc STRUCTURE .......... 37 C TRANSITIONS AND PHASE EQUILIBRIA AMONG GRAIN BOUNDARY...layer structure. 10 SECTION 3 THEORY OF ABC-CBA STACKING BOUNDARY IN fcc STRUCTURE The (111) planes of the fcc structure is stacked as ABCABC... as

  3. Characterization of biosynthesized zinc sulphide nanoparticles using edible mushroom Pleurotuss ostreatu

    NASA Astrophysics Data System (ADS)

    Senapati, U. S.; Sarkar, D.

    2014-06-01

    We report here green synthesis of ZnS nanoparticles using the extract of an edible mushroom ( Pleurotuss ostreatu). The obtained ZnS nanoparticles are characterized by X-ray diffraction, energy dispersive analysis of X-rays, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, UV-Vis optical absorption, photoluminescence and Fourier Transform Infrared Spectroscopy. XRD analysis confirms ZnS nanoparticles have cubic structure and also there is decrease of particle size and increase of dislocation density and strain with increase of amount of mushroom extract. The variation of crystallite size is in conformity with the results obtained from SEM and TEM. UV-Vis and photoluminescence spectra give the characteristic peak for ZnS nano where as Fourier transform infrared spectra confirm the presence of microbial proteins.

  4. Crystal structure and prediction.

    PubMed

    Thakur, Tejender S; Dubey, Ritesh; Desiraju, Gautam R

    2015-04-01

    The notion of structure is central to the subject of chemistry. This review traces the development of the idea of crystal structure since the time when a crystal structure could be determined from a three-dimensional diffraction pattern and assesses the feasibility of computationally predicting an unknown crystal structure of a given molecule. Crystal structure prediction is of considerable fundamental and applied importance, and its successful execution is by no means a solved problem. The ease of crystal structure determination today has resulted in the availability of large numbers of crystal structures of higher-energy polymorphs and pseudopolymorphs. These structural libraries lead to the concept of a crystal structure landscape. A crystal structure of a compound may accordingly be taken as a data point in such a landscape.

  5. Crystal Structure and Prediction

    NASA Astrophysics Data System (ADS)

    Thakur, Tejender S.; Dubey, Ritesh; Desiraju, Gautam R.

    2015-04-01

    The notion of structure is central to the subject of chemistry. This review traces the development of the idea of crystal structure since the time when a crystal structure could be determined from a three-dimensional diffraction pattern and assesses the feasibility of computationally predicting an unknown crystal structure of a given molecule. Crystal structure prediction is of considerable fundamental and applied importance, and its successful execution is by no means a solved problem. The ease of crystal structure determination today has resulted in the availability of large numbers of crystal structures of higher-energy polymorphs and pseudopolymorphs. These structural libraries lead to the concept of a crystal structure landscape. A crystal structure of a compound may accordingly be taken as a data point in such a landscape.

  6. Analysis of surface and bulk effects in HgCdTe photodetector arrays by variable-area diode test structures

    NASA Astrophysics Data System (ADS)

    Deng, Yi; Lin, Chun; Hu, Xiaoning

    2009-07-01

    This study describes variable-area diode data analysis of surface and bulk effects of HgCdTe infrared photodiodes passivated with dual-layer CdTe/ZnS films. We attempt to present a general analytical relation between the zero-bias resistance-area product and the perimeter-to-area ratio of the diodes by variable-area diode array test structures. We have taken contributions into consideration from surface leakage between HgCdTe and passivant due to band bending, surface generation currents in the depletion region close to the HgCdTe-passivant interface, and the bulk currents. The model we use is based on the one put forward by Vishnu Gopal. The variable-area diode data analysis can be of great practical help in identifying the various possible mechanism contributing to the surface leakage currents. Through data analysis and curve fitting, we can also get some other useful parameters (like junction depth), which can be the reference to other experiment results. The experimental samples we used range from 20μm to 200μm in size and include both square and circular diode geometries. The conventional boron implantation was used to form the p-n junction and Au was used for the metal pads. The insulating layers of CdTe and ZnS were both electron-beam evaporated at a rate of 1.3 Å/sec. The fabricated diode test patterns were wire-bonded and packaged into a dewar system. I-V measurements were performed using a Keithley 4200 parameter analyzer. The data analysis and curve fitting are all dealt with by MATLAB. Through the results we can find that the surface leakage is nearly the same to the bulk current in diameter between 50~150μm, which indicate that surface leakage is still a dominating dark current in small dimension diode. The results also showed that diodes from 50 to 150μm in size have better performance than the larger or smaller ones and this can be explained by the limit of material imperfection and the limit of processing techniques.

  7. Ripple structures associated with ordered surface defects in dielectrics

    NASA Astrophysics Data System (ADS)

    Soileau, M. J.

    1984-05-01

    It is pointed out that laser-generated ripple patterns (LGRP) have been observed in laser-induced damage (LID) to surfaces of various wide bandgaps, such as dielectrics, semiconductors, and metals. The observation of LGRP over a wide range of materials has induced speculations that LGRP are a universal phenomenon common to all laser-surface interactions. The present study is concerned with measurements of the thresholds for LGRP formation on NaCl surfaces. It was attempted to make defects nearly 'resonant' with the impressed laser field by grinding the NaCl surface with particles of average diameter approximately equal to the laser wavelength (10.6 microns). Experiments with ZnS, ZnSe, and CdTe were also conducted. It was found that the threshold for initiation of LGRP was 40 percent lower for the case in which the defects are normal to the impressed laser electric field.

  8. Structural system identification: Structural dynamics model validation

    SciTech Connect

    Red-Horse, J.R.

    1997-04-01

    Structural system identification is concerned with the development of systematic procedures and tools for developing predictive analytical models based on a physical structure`s dynamic response characteristics. It is a multidisciplinary process that involves the ability (1) to define high fidelity physics-based analysis models, (2) to acquire accurate test-derived information for physical specimens using diagnostic experiments, (3) to validate the numerical simulation model by reconciling differences that inevitably exist between the analysis model and the experimental data, and (4) to quantify uncertainties in the final system models and subsequent numerical simulations. The goal of this project was to develop structural system identification techniques and software suitable for both research and production applications in code and model validation.

  9. Representing Substantive Structures.

    ERIC Educational Resources Information Center

    Finley, Fred N.; Stewart, James

    1982-01-01

    Discusses the meaning of Schwab's "substantive structures" of a discipline in terms of science philosophy. Presents three techniques for representing substantive structures and discusses some of their uses in science education research. (SK)

  10. Space Structure Development

    NASA Technical Reports Server (NTRS)

    Smith, Thomas

    2015-01-01

    The duration of my Summer 2015 Internship Tour at NASA's Johnson Space Center was spent working in the Structural Engineering Division's Structures Branch. One of the two main roles of the Structures Branch, ES2, is to ensure the structural integrity of spacecraft vehicles and the structural subsystems needed to support those vehicles. The other main objective of this branch is to develop the lightweight structures that are necessary to take humans beyond Low-Earth Orbit. Within ES2, my four projects involved inflatable space structure air bladder material testing; thermal and impact material testing for spacecraft windows; structural analysis on a joint used in the Boeing CST-100 airbag system; and an additive manufacturing design project.

  11. Photon structure function - theory

    SciTech Connect

    Bardeen, W.A.

    1984-12-01

    The theoretical status of the photon structure function is reviewed. Particular attention is paid to the hadronic mixing problem and the ability of perturbative QCD to make definitive predictions for the photon structure function. 11 references.

  12. Structural Engineering: Overview

    NASA Technical Reports Server (NTRS)

    Castro, Edgar

    2011-01-01

    This slide presentation presents the work of the Structural Engineering Division of the Engineering Directorate. The work includes: providing technical expertise and leadership for the development, evaluation, and operation of structural, mechanical, and thermal spaceflight systems.

  13. Structural materials and components

    NASA Technical Reports Server (NTRS)

    Gagliani, John (Inventor); Lee, Raymond (Inventor)

    1982-01-01

    High density structural (blocking) materials composed of a polyimide filled with glass microballoons. Structural components such as panels which have integral edgings and/or other parts made of the high density materials.

  14. Structural materials and components

    NASA Technical Reports Server (NTRS)

    Gagliani, John (Inventor); Lee, Raymond (Inventor)

    1982-01-01

    High density structural (blocking) materials composed of a polyimide filled with glass microballoons and methods for making such materials. Structural components such as panels which have integral edgings and/or other parts made of the high density materials.

  15. Structural materials and components

    NASA Technical Reports Server (NTRS)

    Gagliani, John (Inventor); Lee, Raymond (Inventor)

    1983-01-01

    High density structural (blocking) materials composed of a polyimide filled with glass microballoons. Structural components such as panels which have integral edgings and/or other parts made of the high density materials.

  16. Lightweight Materials & Structures

    NASA Video Gallery

    The Lightweight Materials and Structures (LMS) project will mature high-payoff structures and materials technologies that have direct application to NASA’s future space exploration needs.One of the...

  17. Reinforced structural plastics

    NASA Technical Reports Server (NTRS)

    Lubowitz, H. R.; Kendrick, W. P.; Jones, J. F.; Thorpe, R. S.; Burns, E. A. (Inventor)

    1972-01-01

    Reinforced polyimide structures are described. Reinforcing materials are impregnated with a suspension of polyimide prepolymer and bonded together by heat and pressure to form a cured, hard-reinforced, polyimide structure.

  18. Structure of "polywater".

    PubMed

    Donohue, J

    1969-11-21

    A structure for "polywater" is proposed. It consists of hydrogen-bonded clusters of water molecules lying at the vertices of rhombic dodecahedra. This structure contains features which are less unattractive than those which are part of several earlier models.

  19. Structural design methodology for large space structures

    NASA Astrophysics Data System (ADS)

    Dornsife, Ralph J.

    1992-02-01

    The Department of Defense requires research and development in designing, fabricating, deploying, and maintaining large space structures (LSS) in support of Army and Strategic Defense Initiative military objectives. Because of their large size, extreme flexibility, and the unique loading conditions in the space environment, LSS will present engineers with problems unlike those encountered in designing conventional civil engineering or aerospace structures. LSS will require sophisticated passive damping and active control systems in order to meet stringent mission requirements. These structures must also be optimally designed to minimize high launch costs. This report outlines a methodology for the structural design of LSS. It includes a definition of mission requirements, structural modeling and analysis, passive damping and active control system design, ground-based testing, payload integration, on-orbit system verification, and on-orbit assessment of structural damage. In support of this methodology, analyses of candidate LSS truss configurations are presented, and an algorithm correlating ground-based test behavior to expected microgravity behavior is developed.

  20. Structural design methodology for large space structures

    NASA Astrophysics Data System (ADS)

    Dornsife, Ralph J.

    The Department of Defense requires research and development in designing, fabricating, deploying, and maintaining large space structures (LSS) in support of Army and Strategic Defense Initiative military objectives. Because of their large size, extreme flexibility, and the unique loading conditions in the space environment, LSS will present engineers with problems unlike those encountered in designing conventional civil engineering or aerospace structures. LSS will require sophisticated passive damping and active control systems in order to meet stringent mission requirements. These structures must also be optimally designed to minimize high launch costs. This report outlines a methodology for the structural design of LSS. It includes a definition of mission requirements, structural modeling and analysis, passive damping and active control system design, ground-based testing, payload integration, on-orbit system verification, and on-orbit assessment of structural damage. In support of this methodology, analyses of candidate LSS truss configurations are presented, and an algorithm correlating ground-based test behavior to expected microgravity behavior is developed.