Science.gov

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. Effect of Cr doping on structural and magnetic properties of ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Virpal, Singh, Jasvir; Sharma, Sandeep; Singh, Ravi Chand

    2016-05-01

    The structural, optical and magnetic properties of pure and Cr doped ZnS nanoparticles were studied at room temperature. X-ray diffraction analysis confirmed the absence of any mixed phase and the cubic structure of ZnS in pure and Cr doped ZnS nanoparticles. Fourier transfer infrared spectra confirmed the Zn-S stretching bond at 664 cm-1 of ZnS in all prepared nanoparticles. The UV-Visible absorption spectra showed blue shift which became even more pronounced in Cr doped ZnS nanoparticles. However, at relatively higher Cr concentrations a slower red shift was shown by the doped nanoparticles. This phenomenon is attributed to sp-d exchange interaction that becomes prevalent at higher doping concentrations. Further, magnetic hysteresis measurements showed that Cr doped ZnS nanoparticles exhibited ferromagnetic behavior at room temperature.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    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.

  4. 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.

  5. Chromium Doped ZnS Nanostructures: Structural and Optical Characteristics

    NASA Astrophysics Data System (ADS)

    Gogoi, D. P.; Das, U.; Ahmed, G. A.; Mohanta, D.; Choudhury, A.; Stanciu, G. A.

    2009-06-01

    Chromium doped ZnS nanoparticles arranged in the form of fractals were fabricated by using inexpensive physico-chemical route. The Cr:ZnS samples were characterized by diffraction and spectroscopic techniques. Unexpected growth of fractals with several micrometer dimensions and of core size 1 μm (tip to tip) was confirmed through TEM micrographs. At higher magnification, we found that individual fractals consist of spherical nanoparticles of average size <30 nm. The mechanism leading to such organized structures describing fractal pattern is encountered in this work.

  6. Structural, optical and dielectric properties of lead doped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Virpal; Hastir, Anita; Sharma, Sandeep; Singh, Ravi Chand

    2016-05-01

    Pure and lead doped ZnS nanoparticles have been successfully synthesized by chemical precipitation method. Structural analysis using X-ray diffraction confirms the cubic phase of ZnS and formation of an additional cubic phase of lead sulphide in lead doped ZnS nanoparticles. Increase in the band gap of the doped nanoparticles is consistent with the reduction of crystallite size which lies in the quantum confinement regime. A broad green emission was observed in photoluminescence spectra of lead doped ZnS nanoparticles. The green emission arises due to the presence of lead ions at zinc lattice sites in the host lattice of ZnS. Dielectric measurements reveal that dielectric constant is higher for the doped samples indicating that value of the dielectric constant can be tuned by adding suitable amount of the dopant although dielectric losses in these samples are higher and further investigations are required.

  7. 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

  8. Role of magnesium in ZnS structure: Experimental and theoretical investigation

    NASA Astrophysics Data System (ADS)

    Shahid, M. Y.; Asghar, M.; Arbi, H. M.; Zafar, M.; Ilyas, S. Z.

    2016-02-01

    Wide band gap semiconductor materials are extending significant applications in electronics and optoelectronics industry. They are showing continued advancement in ultraviolet to infrared LEDs and laser diodes. Likewise the band gap tunability of ZnS with intentional impurities such as Mg and Mn are found useful for optoelectronic devices. Information from literature indicates slight blue shift in the band gap energy of ZnS by Mg doping but nevertheless, we report a reasonable red shift (3.48 eV/356 nm to 2.58 eV/480 nm) in ZnS band gap energy in Mg-ZnS structure. Theoretical model based on first principle theory using local density approximation revealed consistent results on Mg-ZnS structure. Similarly, structural, morphological, optical and electrical properties of the as grown Mg-ZnS were studied by XRD, SEM, FTIR, EDS, UV-Vis Spectrophotometer and Hall measurement techniques.

  9. 2D double-layer-tube-shaped structure Bi2S3/ZnS heterojunction with enhanced photocatalytic activities

    NASA Astrophysics Data System (ADS)

    Gao, Xiaoming; Wang, Zihang; Fu, Feng; Li, Xiang; Li, Wenhong

    2015-10-01

    Bi2S3/ZnS heterojunction with 2D double-layer-tube-shaped structures was prepared by the facile synthesis method. The corresponding relationship was obtained among loaded content to phase, morphology, and optical absorption property of Bi2S3/ZnS composite. The results shown that Bi2S3 loaded could evidently change the crystallinity of ZnS, enhance the optical absorption ability for visible light of ZnS, and improve the morphologies and microstructure of ZnS. The photocatalytic activities of the Bi2S3/ZnS sample were evaluated for the photodegradation of phenol and desulfurization of thiophene under visible light irradiation. The results showed that Bi2S3 loaded greatly improved the photocatalytic activity of ZnS, and the content of loaded Bi2S3 had an impact on the catalytic activity of ZnS. Moreover, the mechanism of enhanced photocatalytic activity was also investigated by analysis of relative band positions of Bi2S3 and ZnS, and photo-generated hole was main active radicals during photocatalytic oxidation process.

  10. 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.

  11. The influence of doping element on structural and luminescent characteristics of ZnS thin films

    NASA Astrophysics Data System (ADS)

    Kryshtab, T.; Khomchenko, V. S.; Andraca-Adame, J. A.; Rodionov, V. E.; Khachatryan, V. B.; Tzyrkunov, Yu. A.

    2006-10-01

    For the fabrication of green and blue emitting ZnS structures the elements of I, III, and VII groups (Cu, Al, Ga, Cl) are used as dopants. The influence of type of impurity, doping technique, and type of substrate on crystalline structure and surface morphology together with luminescent properties was investigated. The doping of thin films was realized during the growth process and/or post-deposition thermal treatment. ZnS thin films were deposited by physical (EBE) and chemical (MOCVD) methods onto glass or ceramic (BaTiO 3) substrates. Closed spaced evaporation and thermodiffusion methods were used for the post-deposition doping of ZnS films. X-ray diffraction (XRD) techniques, atomic force microscopy (AFM), and measurements of photoluminescent (PL) spectra were used for the investigations. It was shown that the doping by the elements of I (Cu) and III (Al, Ga) groups does not change the crystal structure during the thermal treatment up to 1000 ∘C, whereas simultaneous use of the elements of I (Cu) and VII (Cl) groups leads to decrease of the phase transition temperature to 800 ∘C. The presence of impurities in the growth process leads to a grain size increase. At post-deposition treatment Ga and Cl act as activators of recrystallization process. The transition of ZnS sphalerite lattice to wurtzite one leads to the displacement of the blue emission band position towards the short-wavelength range by 10 nm.

  12. 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.

  13. 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.

  14. Structure and optical properties of one-dimensional ZnS nanostructures synthesized using a single evaporation process

    NASA Astrophysics Data System (ADS)

    Jin, Changhyun; Kim, Hyunsu; Park, Sunghoon; An, Soyeon; Lee, Chongmu

    2013-11-01

    Zinc sulfide (ZnS) nanostructures with different morphologies and microstructures were synthesized using a single thermal evaporation process. The microstructure and photoluminescence properties of the ZnS nanowires produced in four different temperature zones were examined. Scanning electron microscopy showed that as the substrate temperature decreased, the morphology of the ZnS nanowires changed from a longer curved morphology to a shorter earthworm-like morphology. X-ray diffraction (XRD) shows that all samples were mixtures of a zincblende-structured ZnS phase and a wurtzite-structured ZnS phase and that dominance of the zincblende phase tends to increase with decreasing substrate temperature. The zincblende phase appeared to be dominant regardless of the substrate temperature. A closer comparison of the XRD patterns of the products in the different temperature zones showed that dominance of the zincblende phase tends to increase with decreasing substrate temperature. Photoluminescence spectroscopy revealed a decrease in emission intensity with decreasing substrate temperature. ZnS nanostructures synthesized in temperature zones 2, 3 and 4 (∼ 900, ∼ 800 and ∼ 700 °C, respectively) showed green emission, whereas those synthesized in temperature zone 5 (∼ 600 °C) showed yellow emission. The origins of the emissions are also discussed.

  15. Investigation on Spin Dependent Transport Properties of Core-Shell Structural Fe3O4/ZnS Nanocomposites for Spintronic Application

    PubMed Central

    Liu, Er; Yuan, Honglei; Kou, Zhaoxia; Wu, Xiumei; Xu, Qingyu; Zhai, Ya; Sui, Yunxia; You, Biao; Du, Jun; Zhai, Hongru

    2015-01-01

    The core-shell structural Fe3O4/ZnS nanocomposites with controllable shell thickness were well-fabricated via seed-mediate growth method. Structural and morphological characterizations reveal the direct deposition of crystalline II-VI compound semiconductor ZnS shell layer on Fe3O4 particles. Spin dependent electrical transport is studied on Fe3O4/ZnS nanocomposites with different shell thickness, and a large magnetoresistance (MR) ratio is observed under the magnetic field of 1.0 T at room temperature and 100 K for the compacted sample by Fe3O4/ZnS nanocomposites, which is 50% larger than that of sample with pure Fe3O4 particles, indicating that the enhanced MR is contributed from the spin injection between Fe3O4 and ZnS layer. PMID:26053888

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

    NASA Astrophysics Data System (ADS)

    Goktas, A.; Mutlu, İ. H.

    2016-07-01

    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.

  19. 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.

  20. Optical and structural studies of ZnS nanoparticles synthesized via chemical in situ technique

    NASA Astrophysics Data System (ADS)

    Mamiyev, Zamin Q.; Balayeva, Narmina O.

    2016-02-01

    ZnS nanoparticles (NPs) have been synthesized by the facile chemical route with a narrow size distribution in the MA/octene-1 copolymer matrix and effect of reaction time has been discussed. X-ray diffraction pattern confirms the pure cubic phase of ZnS with 5-7 nm average crystal sizes which are in good agreement with the AFM and UV-vis measurements. Absorption spectra exhibit a strong blue shift from the bulk with the 3.98 eV optical band gap which clearly indicates the strong size confinement effect. Thermogravimetric analyses show increased thermal stability of the nanocomposite compared to the copolymer. The possible growth mechanism of the particles formation and stabilization has been discussed.

  1. 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.

  2. 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.

  3. 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.

  4. Influence of Li+ and Nd3+ co-doping on structural and optical properties of l-arginine-passivated ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Talwatkar, S. S.; Sunatkari, A. L.; Tamgadge, Y. S.; Pahurkar, V. G.; Muley, G. G.

    2015-02-01

    We report the effect of Li + and Nd3+ co-doping on structural and optical properties of l-arginine-passivated ZnS nanoparticles (NPs) synthesized by chemical co-precipitation method. High-resolution transmission electron microscopy (HR-TEM) and X-ray diffraction study were used to explore the morphological and structural aspects of prepared NPs. HR-TEM analysis confirmed that the size of ZnS NPs reduces from 5 to 3 nm as the concentration of co-dopant increases from 1 to 5 wt%. Ultraviolet-visible absorption spectra show absorption peaks in the range of 295-315 nm indicating huge blue shift as compared to the bulk ZnS (340 nm, E g = 3.6 eV) due to the quantum confinement effect. The large optical band gap was estimated in the range of 3.95-4.62 eV and found increasing as the co-dopant concentration increases. Photoluminescence spectra showed that co-doped ZnS NPs emit multiple intense violet-colored (370, 375, 380, 388 and 398 nm) and blue-colored (425, 448, 455 and 465 nm) peaks with increasing intensity. Fourier transform infrared study confirmed the strong interaction between ZnS NPs and l-arginine ligands. The presence of co-dopant in the sample is confirmed by energy dispersive X-ray analysis. Based on the results, we proposed that this material is a new class of luminescent material suitable in optoelectronics devices application, especially in light-emitting devices, electroluminescent devices, display devices, etc.

  5. 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.

  6. Effect of Gd doping on the structural, luminescence and magnetic properties of ZnS nanoparticles synthesized by the hydrothermal method

    NASA Astrophysics Data System (ADS)

    Poornaprakash, B.; Chalapathi, U.; Reddeppa, Maddaka; Park, Si-Hyun

    2016-09-01

    This paper reports the synthesis and characterization of ZnS:Gd nanoparticles prepared by a hydrothermal process using different doping concentrations. The chemical, structural, luminescence and magnetic properties of these nanoparticles were investigated by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy, and vibrating sample magnetometer (VSM) measurements. XRD confirmed that all the samples had a cubic structure with good crystallinity. HRTEM showed that the particles were polycrystalline with a mean size of 4-6 nm. XPS revealed the oxidation state of Gd in the ZnS lattice to be +3. The PL spectra of all the nanoparticles exhibited broad emission peaks in the visible region. All the Gd doped nanoparticles exhibited well-defined ferromagnetic behavior at room temperature. The saturation magnetization increased significantly with increasing Gd concentration, reaching a maximum for 3 at.% Gd and decreasing for the 5 at.% Gd doped ZnS nanoparticles.

  7. 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.

  8. Synthesis, structural, optical, and magnetic properties of Co doped, Sm doped and Co+Sm co-doped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Poornaprakash, B.; Poojitha, P. T.; Chalapathi, U.; Subramanyam, K.; Park, Si-Hyun

    2016-09-01

    The compositional, structural, optical and magnetic properties of ZnS, Zn0.98Co0.02S, Zn0.98Sm0.02S and Zn0.96Co0.02Sm0.02S nanoparticles synthesized by a hydrothermal method are presented and discussed. X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) studies revealed that all the samples exhibited cubic structure without any impurity phases. X-ray photoelectron spectroscopy (XPS) results revealed that the Co and Sm ions existed in +2 and +3 states in these samples. The photoluminescence (PL) spectra of all the samples exhibited a broad emission in the visible region. The room temperature magnetization versus applied magnetic field (M-H) curves demonstrated that the Sm+Co doped nanoparticles exhibited enhanced ferromagnetic behavior compare to Co and Sm individually doped ZnS nanoparticles, which is probably due to the exchange interaction between conductive electrons with local spin polarized electrons on the Co2+ or Sm3+ ions. This study intensifies the understanding of the novel performances of co-doped ZnS nanoparticles and also provides possibilities to fabricate future spintronic devices.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. Photoluminescence study of ZnS and ZnS:Pb nanoparticles

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    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.

  14. Preparation and Gas Sensing Properties of Hollow ZnS Microspheres.

    PubMed

    Xiao, Jingkun; Song, Chengwen; Song, Mingyan; Dong, Wei; Li, Chen; Yin, Yanyan

    2016-03-01

    Hollow ZnS microspheres are synthesized by a facile hydrothermal method. Morphology and structure of the ZnS microspheres are analyzed by SEM, TEM, XRD and N2 sorption technique, Gas sensing properties of the as-prepared ZnS sensor are also systematically investigated. The results show that the ZnS microspheres have well-developed porous and hollow nanostructure. The sensor based on the ZnS microspheres exhibits ultra-fast response (1-2 s) and fast recovery time (7-34 s) towards ethanol at the optimal operating temperature of 160 degrees C. Moreover, the ZnS sensor also demonstrates high selectivity to other gases such as methanol, benzene, dichloromethane and hexane, suggesting that it is a promising candidate for ethanol sensing applications. PMID:27455754

  15. 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.

  16. 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.

  17. Effect of temperature on the optical and structural properties of hexadecylamine capped ZnS nanoparticles using Zinc(II) N-ethyl-N-phenyldithiocarbamate as single source precursor

    SciTech Connect

    Onwudiwe, Damian C.; Strydom, Christien; Oluwafemi, Oluwatobi S.; Songca, Sandile P.

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► HDA-capped ZnS nanoparticles were synthesized via thermolysis of a single source precursor. ► Zinc(II) N-ethyl-N-phenyldithiocarbamate was used as the single source precursor. ► The growth temperature was varied to study the optical properties of the nanocrystals. ► Change in growth temperature affects the structural properties of the ZnS nanoparticles. ► Hexagonal wurtzite phase was obtained at lower temperatures while cubic sphalerite phase was obtained at higher growth temperatures. -- Abstract: Reported in this work is the synthesis of HDA (hexadecylamine)-capped ZnS nanoparticles by a single source route using Zinc(II) N-ethyl-N-phenyldithiocarbamate as a precursor. By varying the growth temperature, the temporal evolution of the optical properties and morphology of the nanocrystals were investigated. The as-synthesized nanoparticles were characterized using UV–vis absorption and photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). All the particles exhibited quantum confinement in their optical properties with band edge emission at the early stage of the reaction. The XRD showed transition from hexagonal wurtzite phase to cubic sphalerite phase as the growth temperature increases. The TEM image showed that the particles are small and spherical in shape while the HRTEM image confirmed the crystalline nature of the material.

  18. 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. PMID:24254232

  19. 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%.

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

    NASA Astrophysics Data System (ADS)

    Moon, Junghwan; Cho, Maenghyo; Zhou, Min

    2015-06-01

    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%.

  1. New co-spray way to synthesize high quality ZnS films

    NASA Astrophysics Data System (ADS)

    Bouznit, Y.; Beggah, Y.; Boukerika, A.; Lahreche, A.; Ynineb, F.

    2013-11-01

    In the present study, we report for the first time the synthesis of ZnS films using co-spray method, in which the reactants were mixed in the vapor state contrary to that seen in previous spray configurations. In order to obtain the optimum conditions for growing high quality ZnS thin films related to this approach, a series of samples with different Zn:S atomic ratios were investigated. X-ray diffraction (XRD) analysis indicated that both solid state and phase formation were strongly dependent on Zn:S atomic ratio. In the absence of sulfur element, pure ZnO phase showing hexagonal wurtzite structure with (0 0 2) preferential orientation was obtained. When one eighth of sulfur was implicated, the (0 0 2) diffraction peak of ZnO was broadened and displaced toward lower angles. Once one quarter of sulfur was involved, no discernible diffraction peaks could be seen. Films deposited using solutions with Zn:S ratio of 1:1/2, 1:1 and 1:2 have pure ZnS phase showing hexagonal wurtzite structure with a strong preferential orientation. Near stoichiometric ZnS films were achieved with Zn:S atomic ratio close to 1:1. All films have high transmittance of about 80% in the visible region.

  2. Facile synthesis of water-soluble ZnS quantum dots with strong luminescent emission and biocompatibility

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Liu, Yingbo; Sun, Shuqing

    2013-10-01

    ZnS quantum dots (QDs) are among the most promising emerging fluorescent materials for biolabeling. High-quality colloidal ZnS QDs were synthesized via a new facile chemical precipitation method using the mixture of ethylene glycol (EG) and water as the solvent. The phase structure and morphology of the ZnS QDs were characterized by X-ray powder diffraction and high resolution transmission electron microscopy. The synthesized ZnS QDs have a cubic zinc blende structure with monodispered and small particles. ZnS QDs easily dispersed in water to form stable and clear colloids and the strong tunable trap state emissions from 452 to 516 nm were achieved by varying the reaction time. The hemolysis assay was performed to evaluate the biocompatibility of the ZnS QDs.

  3. The growth of porous ZnO nanowires by thermal oxidation of ZnS nanowires.

    PubMed

    Hung, Chih-Cheng; Lin, Wen-Tai; Wu, Kuen-Hsien

    2011-12-01

    The growth of porous ZnO nanowires (NWs) via phase transformation of ZnS NWs at 500-850 degrees C in air was studied. The ZnS NWs were first synthesized by thermal evaporation of ZnS powder at 1100 degrees C in Ar. On subsequent annealing at 500 degrees C in air, discrete ZnO epilayers formed on the surface of ZnS NWs. At 600 degrees C, polycrystalline ZnO and the crack along the (0001) interface between the ZnO epilayer and ZnS NW were observed. At 700-750 degrees C ZnS NWs transformed to ZnO NWs, meanwhile nanopores and interfacial cracks were observed in the ZnO NWs. Two factors, the evaporation of SO2 and SO3 and the stress induced by the incompatible structure at the interface of ZnO epilayer and ZnS NW, can be responsible for the formation of porous ZnO NWs from ZnS NW templates on annealing at 700-750 degrees C in air. Rapid growth of ZnO at 850 degrees C could heal the pores and cracks and thus resulted in the well-crystallized ZnO NWs. PMID:22409083

  4. Phase transition in ZnS thin film phosphor

    NASA Astrophysics Data System (ADS)

    Kryshtab, T.; Khomchenko, V. S.; Andraca-Adame, J. A.; Khachatryan, V. B.; Mazin, M. O.; Rodionov, V. E.; Mukhlio, M. F.

    2005-02-01

    The effect of an original non-vacuum annealing of thin ZnS films according to the annealing conditions and type of substrate on the film's crystalline structure and surface morphology in relation with photoluminescent (PL) properties was investigated. ZnS thin films were deposited by electron-beam evaporation (EBE) on ceramic (BaTiO 3) and glass substrates heated to 150-200 °C. Three types of the targets such as ZnS, ZnS:Cu and ZnS:Cu, Al were used. The film thickness varied from 0.6 to 1 μm. As-deposited films were annealed at the atmospheric pressure in S 2-rich ambient atmosphere at 600-950 °C for 1 h. The ZnS:Cu films were Ga co-doped by annealing in the same atmosphere and temperature with additional Ga vapor. The ZnS films were doped with Cu, Cl using the thermal diffusion method by embedding the samples in ZnS:Cu, Cl powder. X-ray diffraction (XRD) technique, atomic force microscopy (AFM) and the measurements of PL parameters were used for investigation. The temperature of the ZnS phase transition from the sphalerite to wurtzite structure depends on the presence, type and ratio of additional impurities. It was revealed that Ga and Cl act not only as co-dopant to improve the luminescent properties, but also as activators of recrystallization processes. The transition of ZnS film's sphalerite lattice to wurtzite leads to the displacement of the blue emission band position towards the short-wavelength range by 10 nm.

  5. Structural, electronic and magnetic properties of the (Co, Ni) codoped ZnS: A first-principles study

    NASA Astrophysics Data System (ADS)

    Yin, Zhu-Hua; Zhang, Jian-Min

    2016-08-01

    Using spin-polarized first-principles calculation, we investigate the structural, electronic and magnetic properties of the Zn31Co1S32, Zn31Ni1S32 and Zn30Co1Ni1S32 systems. The results show that the Zn31Co1S32 system is a magnetic semiconductor, while the Zn31Ni1S32 system exhibits a magnetic half-metallic (HM) character. The Zn30Co1Ni1S32 system exhibits a HM ferrimagnetic character explained by the superexchange mechanism. The Co and Ni atoms favorably occupy nearest neighbor positions of the metal sublattice with antiparallel arrangement of their magnetic moments. Furthermore, it is observed that the magnetic moment of Co/Ni atom reduces from an isolated atom magnetic moment due to p-d hybridization which yields small parallel magnetic moments on the nearest S atoms.

  6. Low-temperature phase transition of ZnS: The critical role of ZnO

    SciTech Connect

    Lin, Po-Chang; Hua, Chi Chung; Lee, Tai-Chou

    2012-10-15

    Wurtzite zinc sulfide (WZ-ZnS) is a valuable wide-band-gap semiconductor. However, it is difficult to synthesize due to its high transition temperature (1020 Degree-Sign C). This study investigates the formation of WZ-ZnS particles using a ZnO template. Various phase structures of ZnS with the same size but different levels of ZnO content are generated during the annealing process. The transition temperature can be lowered significantly to below 350 Degree-Sign C. Furthermore, when the powders of ZnO and zinc-blende ZnS are mixed, large ZnS particles are not induced by ZnO to transform into WZ-ZnS. The results strongly suggest that grain size is an essential but not sufficient factor in the formation of WZ-ZnS at lower temperatures. - Graphical abstract: By controlling pH of the precursor, wurtzite ZnS particles can be generated at {approx}350 Degree-Sign C. The ZnO-template mechanism was proposed and discussed. Highlights: Black-Right-Pointing-Pointer Wurtzite ZnS particles were prepared by using simple wet chemistry. Black-Right-Pointing-Pointer pH of the precursor solution was adjusted to decrease the phase transition temperature of ZnS. Black-Right-Pointing-Pointer ZnO-template-inducing mechanism of ZnS phase transition was proposed and discussed.

  7. The hydrothermal evolution of the phase and shape of ZnS nanostructures and their gas-sensing properties.

    PubMed

    Hu, Pengfei; Gong, Guodong; Zhan, Fangyi; Zhang, Yuan; Li, Rong; Cao, Yali

    2016-02-14

    This work presents the evolution of the phase and shape of ZnS along the hydrothermal holding time or the dosage of the surfactant. The ZnS sensor obviously showed phase-/defect-dependent gas-sensing performances indicating that the wurtzite-type structure, as well the defect will improve its gas-sensing activities. PMID:26781594

  8. 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. PMID:27477188

  9. Model for the electronic and vibronic structure of 4T1 levels of d 5 ions coupled to E vibrational modes: Case of the fluorescent level of Mn2+ in ZnS

    NASA Astrophysics Data System (ADS)

    Parrot, R.; Boulanger, D.; Diarra, M. N.; Pohl, U. W.; Litzenburger, B.; Gumlich, H. E.

    1996-07-01

    The four fundamental vibronic lines of a 4T1 level of a d5 ion coupled to E vibrational modes in cubic symmetry have been observed. An analysis of the four fine-structure lines of the fluorescent level 4T1 of Mn2+ in cubic ZnS, which have been observed at high resolution in pure cubic ZnS crystals, shows that the relative energies and dipole strengths (RDS) of the quasidegenerate levels are not those predicted by previous electronic and vibronic models. A model is elaborated in three steps. First, from Ham's model for the coupling of orbital triplet states to E modes, a phenomenological operator describing the first-order and second-order spin-orbit interaction and the spin-spin interaction in terms of three parameters is proposed to account for the energy levels and the RDS's. Two phenomenological descriptions deduced from an analysis of the RDS are proposed for the studied state. Second, a detailed analysis of the spin-orbit and spin-spin interactions in terms of the Huang-Rhys factor and of the energy of the effective phonons shows that the electronic spin-orbit interaction in l.S is of opposite sign to that predicted by the model restricted to the d5 configuration. Finally, a covalent model involving the molecular spin-orbit interaction defined by Misetich and Buch is developed to account for the first-order spin-orbit splitting of the orbital triplet states of Mn2+ in II-VI compounds.

  10. 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. PMID:23299077

  11. 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.

  12. Magnetic properties of ZnS doped with noble metals (X = Ru, Rh, Pd, and Ag)

    NASA Astrophysics Data System (ADS)

    Tan, Zhiyun; Xiao, Wenzhi; Wang, Lingling; Yang, Youchang

    2012-12-01

    Density functional theory calculations are carried out to study the electronic structures and magnetic properties in zinc-blende structure ZnS doped with nonmagnetic noble metals (X = Ru, Rh, Pd, and Ag). Results show robust magnetic ground states for X-doped ZnS. The total magnetic moments are about 2.0, 3.0, and 2.0 μB per supercell for the Ru-, Rh-, and Pd-doped ZnS, respectively. As the atomic number of X element increases, the local magnetic moment tends toward delocalize and the hybridization between X-4d and S-3p states become stronger. This trend is strongly related to the difference in electronegativity between the substitutional X and the cation in the ZnS host. For Ag-doped ZnS, both non-spin- and spin-polarized calculations yield nearly equal total energy. The substitution of Zn in ZnS parent material by the nonmagnetic 4d transition-metals may lead to half-metallic ferromagnetism which stems from the hybridization between X-4d and S-3p states and could be attributed to a double-exchange mechanism. Curie temperature values are estimated using mean-field approximation.

  13. An efficient method to enhance the stability of sulphide semiconductor photocatalysts: a case study of N-doped ZnS.

    PubMed

    Zhou, Yansong; Chen, Gang; Yu, Yaoguang; Feng, Yujie; Zheng, Yi; He, Fang; Han, Zhonghui

    2015-01-21

    Reducing the oxidative capacity of holes (h(+)) in the valence band (VB) of ZnS is one of the most effective ways to prevent the photocatalyst from photocorrosion. In this work, ZnS doped only with nitrogen was prepared for the first time by nitriding ZnS powder in an NH3 atmosphere. We demonstrate theoretically and experimentally that the valence band maximum (VBM) rises obviously by N-doping in ZnS, suggesting the reduction of the oxidative capacity of holes (h(+)) in the valence band. The theoretically predicted band structures were further verified by valence band X-ray photoelectron spectroscopy (VB XPS) and Mott-Schottky measurements. The as-prepared N-doped ZnS exhibited an outstanding stable capability for photocatalytic hydrogen evolution from water under simulated sunlight irradiation for 12 h. However, pristine ZnS showed no capability and was seriously photocorroded under the same conditions. PMID:25474654

  14. Synthesis and different property of yttrium doped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Khawal, H. A.; Raskar, N. D.; Gawai, U. P.; Dole, B. N.

    2016-05-01

    Yttrium doped ZnS samples Zn1-xYxS with nominal compositions (x = 0.00, 0.04 and 0.06) were synthesized by a chemical co - precipitation route at room temperature. The synthesized Zn1-xYxS nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV-VIS spectrometer. XRD patterns revealed that entire peaks corresponding to the various planes of cubic zinc blend structure with no segregation of Y. The lattice parameters were calculated for the Y doped ZnS using XRD data and it found to be slightly smaller than pure ZnS, which indicate substitution of Y in to ZnS lattice. The average crystallite size was calculated using Debye - Scherrer's formula for pure and Y doped ZnS samples. It is observed that grain size is in the range 30 to 12 nm. Band gap of Y doped ZnS nanoparticles has been calculated using UV-Vis spectrometer. It is found that the band gap decreases as content of Y increases, It may be due the smaller average grain size or ionic radii. The functional groups and chemical interactions of Y substituted Zinc sulfide samples were detected peaks using FTIR spectra and observed the presence of functional groups in the samples. It outlines the formation of ZnS with the stretching vibrational mode around at 511 cm-1. It is evidently confirmed from FTIR spectra that yttrium substitutes into ZnS lattice.

  15. Some physical investigations on ZnS 1- xSe x films obtained by selenization of ZnS sprayed films using the Boubaker polynomials expansion scheme

    NASA Astrophysics Data System (ADS)

    Fridjine, S.; Touihri, S.; Boubaker, K.; Amlouk, M.

    2010-01-01

    ZnS 1- xSe x thin films have been grown by selenization process, applied to ZnS sprayed thin films deposited on Pyrex glass substrates at 550 °C. The crystal structure and surface morphology were investigated by the XRD technique and by the atomic force microscopy. This structural study shows that selenium-free ( x=0) ZnS thin films, prepared at substrate temperature TS=450 °C, were well crystallized in cubic structure and oriented preferentially along (1 1 1) direction. The thermal and mechanical properties were also investigated using a photothermal protocol along with Vickers hardness measurements. On the other hand, the analyze of the transmittance T( λ) and the reflectance R( λ), optical measurements of these films depicts a decrease in the band gap energy value Eg with an increase in Se content ( x). Indeed, Eg values vary from 3.6 to 3.1 eV.

  16. Preparation and characterization of surface-coated ZnS nanoparticles

    SciTech Connect

    Chen, S.; Liu, W.

    1999-11-09

    ZnS nanoparticles coated with di-n-hexadecyldithiophosphate (DDP) were chemically synthesized. The structure of the prepared ZnS nanoparticles was investigated by means of transmission electron microscopy, electron diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The thermal stability of DDP coated on nanoparticles was compared with that of pyridinium di-n-hexadecyldithiophosphate (PyDDP) using a thermogravimetric analyzer. The tribiological properties of ZnS nanoparticles as an additive in tetradecane were investigated by a SRV tester in a ball-on-disk configuration. DDP-coated ZnS nanoparticles, with an average diameter of about 4 nm, are able to prevent water adsorption, and oxidation and are capable of being dispersed stably in organic solvents or mineral oil. Thermal stability of DDP coating on ZnS nanoparticles was superior to that of PyDDP. Wear tests show that DDP-coated ZnS nanoparticles as additive in tetradecane are capable of reducing friction and wear of steel.

  17. 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.

  18. Luminance behavior of Ce3+ doped ZnS nanostructures.

    PubMed

    Shanmugam, N; Cholan, S; Kannadasan, N; Sathishkumar, K; Viruthagiri, G

    2014-01-24

    We report the synthesis and characterization of undoped and various levels of Ce(3+) doped ZnS nanocrystal. The structure and size of the products were studied by X-ray diffraction (XRD). The existence of functional groups was identified by Fourier transform infrared spectrometry (FT-IR). The UV-Visible measurements reveal that the synthesized products are blue shifted when compared with bulk phase of ZnS as a result of quantum confinement effect. The PL studies show an enhancement in the intensity of emission band in the UV region on increased Ce(3+) doping. The morphology of the products was evaluated by Field emission scanning electron microscope (FESEM) and High resolution transmission electron microscopy (FESEM). The presence of Ce(3+) was confirmed by Energy dispersive spectral analysis (EDS). The thermal stability of pure and doped products was analyzed by thermo gravimetric and differential thermal analysis (TG-DTA). PMID:24084485

  19. 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.

  20. Shape- and phase-controlled ZnS nanostructures and their optical properties

    SciTech Connect

    Zhou, Xin; Zeng, Xianghua; Yan, Xiaoqing; Xia, Weiwei; Zhou, Yuxue; Shen, Xiaoshuang

    2014-11-15

    Graphical abstract: (a) TEM images of the nanorods, the HRTEM images for the lower (b) and the upper (c) part of the rod in (a). - Highlights: • Stacking faults were observed for ZnS nanocrystals with the size of ∼5 nm. • Nanotwinning structures and stacking faults were observed in ZnS nanorod. • Microstructure defects were found to be formed randomly for nanocrystals and nanorods. • The 1LO phonon mode exhibits a red-shift of 6 cm{sup −1} as the particle size increases from 5 to 15 nm. - Abstract: Single-crystalline ZnS nanoparticles with a zinc-blende crystal structure have some microdefects such as stacking faults and nanotwins. In contrast, ZnS nanorods have a wurtzite crystal structure, which grows along the [0 0 0 1] direction, although some nanorods display the intergrowth of a minor zinc-blende phase and the major wurtzite phase, which forms stacking faults or zinc-blende/wurtzite ZnS nanotwins. Raman spectroscopy measurements reveal surface phonons and longitudinal optical phonons in the nanoparticles, nanorods and doublet phonons that are associated with the transversal optical phonons of the A1 and E1 modes in only the nanorods. The first-order longitudinal optical phonon mode exhibits a blueshift of 6 cm{sup −1} when the particle size increases from 5 to 15 nm, but there is no shift in the range of 15–30 nm because of quantum confinement and microdefects.

  1. 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.

  2. 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.

  3. 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.

  4. Creation of ZnS nanoparticles by laser ablation in water

    NASA Astrophysics Data System (ADS)

    Gan, YuLin; Wang, Li; Wang, RongPing

    2016-02-01

    We have created ZnS nanoparticles using pulsed laser ablation of ceramic target in water with an aim to produce nanoparticles with uniform distribution of the size. The particle size, structure, and physical properties were systematically investigated by X-ray diffraction (XRD), Raman spectra, high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and energy-dispersive spectroscopy. The ZnS nanoparticles were confirmed from XRD, Raman and SAED patterns to possess the sphalerite structure. Chemical composition of the ZnS nanoparticles was found to be stoichiometric. HRTEM images exhibited well-arranged lattices with the space of 0.274 nm for (200) plane and that of 0.317 nm for (111) plane. The present results demonstrate that pulsed laser ablation in water is effective and promising to create nanoparticles with controllable size in a large scale.

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

    PubMed

    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. PMID:22938741

  6. 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.

  7. Optical properties of Mn-doped ZnS semiconductor nanoclusters synthesized by a hydrothermal process

    NASA Astrophysics Data System (ADS)

    Hoa, Tran Thi Quynh; The, Ngo Duc; McVitie, Stephen; Nam, Nguyen Hoang; Vu, Le Van; Canh, Ta Dinh; Long, Nguyen Ngoc

    2011-01-01

    Undoped and Mn-doped ZnS nanoclusters have been synthesized by a hydrothermal approach. Various samples of the ZnS:Mn with 0.5, 1, 3, 10 and 20 at.% Mn dopant have been prepared and characterized using X-ray diffraction, energy-dispersive analysis of X-ray, high resolution electron microscopy, UV-vis diffusion reflection, photoluminescence (PL) and photoluminescence excitation (PLE) measurements. All the prepared ZnS nanoclusters possess cubic sphalerite crystal structure with lattice constant a = 5.408 ± 0.011 Ǻ. The PL spectra of Mn-doped ZnS nanoclusters at room temperature exhibit both the 495 nm blue defect-related emission and the 587 nm orange Mn2+ emission. Furthermore, the blue emission is dominant at low temperatures; meanwhile the orange emission is dominant at room temperature. The Mn2+ ion-related PL can be excited both at energies near the band-edge of ZnS host (the UV region) and at energies corresponding to the Mn2+ ion own excited states (the visible region). An energy schema for the Mn-doped ZnS nanoclusters is proposed to interpret the photoluminescence behaviour.

  8. Detection of ZnS Phases in CZTS Thin-Films by EXAFS

    SciTech Connect

    Hartman, K.; Newman, B. K.; Johnson, J. L.; Du, H.; Fernandes, P. A.; Chawla, V.; Bolin, T.; Clemens, B. M.; Da Cunha, A. F.; Teeter, G.; Scarpulla, M. A.; Buonassisi, T.

    2011-01-01

    Copper zinc tin sulfide (CZTS) is a promising Earth-abundant thin-film solar cell material; it has an appropriate band gap of {approx}1.45 eV and a high absorption coefficient. The most efficient CZTS cells tend to be slightly Zn-rich and Cu-poor. However, growing Zn-rich CZTS films can sometimes result in phase decomposition of CZTS into ZnS and Cu{sub 2}SnS{sub 3}, which is generally deleterious to solar cell performance. Cubic ZnS is difficult to detect by XRD, due to a similar diffraction pattern. We hypothesize that synchrotron-based extended X-ray absorption fine structure (EXAFS), which is sensitive to local chemical environment, may be able to determine the quantity of ZnS phase in CZTS films by detecting differences in the second-nearest neighbor shell of the Zn atoms. Films of varying stoichiometries, from Zn-rich to Cu-rich (Zn-poor) were examined using the EXAFS technique. Differences in the spectra as a function of Cu/Zn ratio are detected. Linear combination analysis suggests increasing ZnS signal as the CZTS films become more Zn-rich. We demonstrate that the sensitive technique of EXAFS could be used to quantify the amount of ZnS present and provide a guide to crystal growth of highly phase pure films.

  9. 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.

  10. Photoluminescence characteristics of ZnS nanocrystallites doped with Ti3+and Ti4+

    NASA Astrophysics Data System (ADS)

    Yang, P.; Lü, M.; Xu, D.; Yuan, D.; Song, C.; Zhou, G.

    Direct synthesis of ZnS nanocrystallites doped with Ti3+ or Ti4+ by precipitation has led to novel photoluminescence properties. Detailed X-ray diffraction (XRD), fluorescence spectrophotometry, UV-vis spectrophotometry and X-ray photoelectron spectroscopy (XPS) analysis reveal the crystal lattice structure, average size, emission spectra, absorption spectra and composition. The average crystallite size doped with different mole ratios, estimated from the Debye-Scherrer formula, is about 2.6+/-0.2 nm. The nanoparticles can be doped with Ti3+ and Ti4+ during the synthesis without the X-ray diffraction pattern being altered. The strong and stable visible-light emission has been observed from ZnS nanocrystallites doped with Ti3+ (its maximum fluorescence intensity is about twice that of undoped ZnS nanoparticles). However, the fluorescence intensity of the ZnS nanocrystallites doped with Ti4+ is almost the same as that of the undoped ZnS nanoparticles. The emission peak of the undoped sample is at 440-450 nm. The emission spectrum of the doped sample consists of two emission peaks, one at 420-430 nm and the other at 510 nm.

  11. Enhanced visible-light photoactivity of La-doped ZnS thin films

    NASA Astrophysics Data System (ADS)

    Chen, Yuan; Huang, Gui-Fang; Huang, Wei-Qing; Zou, B. S.; Pan, Anlian

    2012-09-01

    ZnS and La-doped ZnS thin films were successfully synthesized using chemical-bath deposition on conductive glass substrates. The effects of La-doping on the surface morphology, composition, structure and optical properties of the films were investigated. The photocatalytic performances of undoped and doped ZnS films were evaluated by photodegrading methyl orange aqueous solution under both ultraviolet-light and visible-light irradiation. The results show that the stoichiometry ratio and the properties of ZnS can be tailored by the La-doping concentration. An appropriate amount of La-doping effectively extends the absorption edge to visible-light region, which leads to the significant enhancement of the photocatalytic activity of ZnS thin films under visible-light irradiation. The mechanism of enhanced visible-light photoactivity by La-doping is briefly discussed. The present study provides a simple method for designing the highly efficient semiconductor photocatalysts that can effectively utilize sunlight.

  12. Influence of Deposition Time on ZnS Thin Films Performance with Chemical Bath Deposition

    NASA Astrophysics Data System (ADS)

    Zhou, Limei; Tang, Nan; Wu, Sumei; Hu, Xiaofei; Xue, Yuzhi

    ZnS thin films had been deposited by chemical bath deposition method onto glass substrates in alkaline liquor. The reaction solution is made of ZnSO4, NH4OH and SC(NH2)2. Different deposition times (1 h, 1.5 h, 2 h, 2.5 h and 3 h) were selected to study the performance of ZnS thin films. As the results, the ZnS films' thickness were about 50-207 nm. XRD results showed an amorphous structure. Through comparing the surface morphology before and after annealing, it could be seen that annealing made some particles grow up and the surface smooth and even. The transmittance decreased with the increase of deposition time in the range of 300-800 nm. The transmittance of annealed ZnS film was lower than that of deposited one in the range of 300-800 nm. The ZnS band gap values were calculated in the range of 3.72-3.9 eV.

  13. 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.

  14. 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. PMID:26249588

  15. Photoluminescence in Chemical Vapor Deposited ZnS: insight into electronic defects

    SciTech Connect

    McCloy, John S.; Potter, B.g.

    2013-08-09

    Photoluminescence spectra taken from chemical vapor deposited (CVD) ZnS are shown to exhibit sub-band-gap emission bands characteristic of isoelectronic oxygen defects. The emission spectra vary spatially with position and orientation with respect to the major axis of CVD growth. These data suggest that a complex set of defects exist in the band gap of CVD ZnS whose structural nature is highly dependent upon local deposition and growth conditions, contributing to inherent heterogeneity in optical behavior throughout the material.

  16. 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.

  17. Preparation of Cr-doped ZnS nanosheets with room temperature ferromagnetism via a solvothermal route

    NASA Astrophysics Data System (ADS)

    Zhang, Zhufeng; Li, Jin; Jian, Jikang; Wu, Rong; Sun, Yanfei; Wang, Shengfeng; Ren, Yinshuan; Li, Jiajie

    2013-06-01

    ZnS semiconductor nanosheets doped with different amounts of chromium have been successfully produced via the solvothermal reaction of ZnO and S with CrCl3·6H2O in mixed solvents of ethylenediamine and ethanolamine at 180 °C. X-ray diffraction (XRD) measurements demonstrated that the Cr-doped ZnS nanocrystals had a wurtzite structure. Scanning electron microscopy (SEM) images revealed that the morphologies of ZnS doped with high amounts of chromium consisted of regular nanosheets. Zn1-xCrxS (x=0.0934 or 0.1170) nanosheets produced a regular morphology with thicknesses of 50-100 nm, widths of 300 nm and lengths of 1 µm. This product, composed of Cr, Zn, and S, was observed by an energy dispersive spectrometer (EDS). A vibrating sample magnetometer (VSM) showed that the Cr-doped ZnS nanosheets exhibited ferromagnetism at room temperature, while the pure ZnS nanosheets exhibited diamagnetism. The saturation magnetization of the Cr-doped ZnS nanosheets increased with increasing Cr concentration over the range of x=0.0241-0.0934. The saturation magnetization of the Zn1-xCrxS (x=0.0934) nanosheets was 8.6492 (10-3 emu/g). The experimental results confirmed that Cr-doped ZnS nanosheets exhibit ferromagnetism at room temperature, in good agreement with the ferromagnetic properties of Cr-doped ZnS that were predicted by first-principles computations.

  18. 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.

  19. Self-assembled tin-doped ZnO nanowire and nanoplate structures grown by thermal treatment of ZnS powder

    NASA Astrophysics Data System (ADS)

    Ortega, Y.; Fernández, P.; Piqueras, J.

    2009-05-01

    Sintering of a ZnS-SnO 2 mixture under argon flow leads to the growth of columnar nanoplate arrays as well as arrays of nanowires, nanorods and nanoplates with six-fold symmetry. The six-fold nanoplate structures correspond to a more advanced stage of growth than the nanowire structures. Cathodoluminescence (CL) in the scanning electron microscope (SEM) shows that the structures contain Sn, but the amount of this element is normally under the detection limit of X-ray energy-dispersive spectroscopy (EDS). The formation of branches in the hierarchical structures depends on the presence of Sn and on defects in the mixture powder.

  20. Two-dimensional inorganic–organic hybrid semiconductors composed of double-layered ZnS and monoamines with aromatic and heterocyclic aliphatic rings: Syntheses, structures, and properties

    SciTech Connect

    Wang, Sujing; Li, Jing

    2015-04-15

    As an addition to the II–VI based inorganic–organic hybrid semiconductor family, five new two-dimensional (2D) double-layered structures have been synthesized employing monoamines with different aromatic or heterocyclic aliphatic rings. Zn{sub 2}S{sub 2}(bza) (1), Zn{sub 2}S{sub 2}(mbza) (2), Zn{sub 2}S{sub 2}(fbza) (3), Zn{sub 2}S{sub 2}(pca) (4), and Zn{sub 2}S{sub 2}(thfa) (5) (bza=benzylamine, mbza=4-methoxybenzylamine, fbza=4-flurobenzylamine, pca=3-picolylamine, and thfa=tetrahydrofurfurylamine) are prepared by solvothermal reactions and characterized by different analytical methods, including powder X-ray diffraction, optical diffuse reflection, thermogravimetric analysis and photoluminescence spectroscopy. The powder X-ray diffraction patterns show that all five compounds adopt 2D double-layered structures. Optical diffuse reflectance spectra of these compounds suggest that they have notably lower band gaps than those of the similar compounds composed of aliphatic alkyl amines. Their photoluminescence properties and thermal stability are also analyzed. - Graphical abstract: Five new members of two-dimensional double-layered 2D-Zn{sub 2}S{sub 2}(L) (L=Ligand) structures employing monoamines with different aromatic or heterocyclic aliphatic rings have been designed, synthesized, and characterized. - Highlights: • A new sub-family of II-VI based hybrid semiconductors are designed, synthesized, and structurally characterized using amines with aromatic or aliphatic cyclic rings. • These compounds have notably lower band gaps than those made of aliphatic alkyl amines, greatly broadening the range of band gaps of this material family. • They emit strongly with systematically tunable emission intensity and energy.

  1. Synthesis and characterization of nanostructured Mn-doped ZnS thin films and nanoparticles

    NASA Astrophysics Data System (ADS)

    Singh, S. P.; Perales-Perez, O. J.; Tomar, M. S.; Mata, O. V.

    2004-03-01

    Nanocrystalline ZnS:Mn2+ thin films and powders were prepared by chemical bath deposition (CBD) at 85 ° C for different concentration of Mn ions in bath solutions (Mn molar fraction, x = 0.0, 0.01, 0.02, 0.05, 0.1, 0.2 and 0.5). Produced nanocrystalline films and powders were characterized using X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM) and photoluminescence measurements. XRD patterns for Mn2+ doped and undoped ZnS powders showed broad peaks corresponding to ZnS exhibiting a mixture of cubic and hexagonal structures. Size of nanocrystallites was estimated to be 4 nm using Scherrer's equation. The DTA analyses evidenced the development of the oxide phase from ZnS nanocrystals at lower temperature than for bulk micron size particles. SEM observations showed the presence of nanocrystallites forming spherical aggregates of around 500 nm in diameter. Photoluminescence measurements reveal a strong emission peak at 580 nm which is characteristic emission peak of Mn2+ d-d transition confirming the actual incorporation of Mn2+ into ZnS framework.

  2. Room Temperature Ferromagnetism in Cr-doped ZnS Nanoparticles

    NASA Astrophysics Data System (ADS)

    Reddy, D. Amaranatha; Murali, G.; Vijayalakshmi, R. P.; Reddy, B. K.

    2011-10-01

    Cr-doped ZnS nanoparticles with Cr concentration of 2 atm.% were successfully synthesized by the chemical co-precipitation method using 2-mercapto ethanol as the capping agent. The structural, optical characteristics and magnetic properties of the prepared samples were studied. Energy Dispersive spectroscopy (EDS) measurements showed the existence of Cr ion in the Cr doped ZnS. No mixed phase was observed from X-ray diffraction (XRD) studies and all the peaks were indexed to the cubic phase of ZnS. The diameter is in the range of 5-10 nm, it was confirmed by TEM studies. The photoluminescence spectra of all the samples exhibited a broad emission band located around 435 nm. The luminescence intensity decreased by doping Cr. The magnetic behavior of the nanoparticles for Cr doped ZnS was investigated using a vibrating sample magnetometer (VSM). We determined the magnetic parameters such as saturation magnetization (MS), coercivity (HC) and retentivity (MR) with Cr concentration from M-H loop.

  3. 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.

  4. Magnetic properties in Pd doped ZnS from ab initio calculations

    NASA Astrophysics Data System (ADS)

    Dong, Xinlong; Li, Qiuhang; Xu, Mingxiang

    2013-11-01

    First-principles calculations based on density functional theory within the general gradient approximation (GGA) are performed to study the electronic structure and magnetic properties of Pd doped ZnS. It is found that an isolated Pd atom doped 2 × 2 × 2 ZnS supercell shows half-metallic ferromagnetic character with a total magnetic moment of 2.0 μ B per supercell, which is significantly enhanced compared with the pure ZnS supercell. The strong ferromagnetic coupling of the local magnetic moments can be explained in terms of strong hybridisation between Pd-4 d and S-3 p states. The hybridisation between Pd and the neighbouring S atoms leads to a strong coupling chain Pd(4 d)-S(3 p)-Zn(3 d)-S(3 p)-Pd(4 d), which induces strong indirect long range FM coupling between Pd dopants. The results of several doping configurations demonstrate that ferromagnetic coupling exists between the two doped palladium atoms. These results suggest that Pd doped ZnS can also be considered as suitable candidates for exploring new half-metallic ferromagnetism in semiconductors.

  5. Growth, reaction and nanowire formation of Fe on the ZnS(1 0 0) surface.

    PubMed

    Man, Ka Lun; Pavlovska, Anastassia; Bauer, Ernst; Locatelli, Andrea; Menteş, Tevfik O; Niño, Miguel A; Wong, George K L; Sou, Iam Keong; Altman, Michael S

    2014-08-01

    The growth and reaction of Fe on a ZnS(1 0 0) substrate are studied in situ and with high lateral resolution using low energy electron microscopy (LEEM), micro low energy electron diffraction ( μLEED), x-ray photoemission electron microscopy (XPEEM), microprobe x-ray photoelectron spectroscopy ( μXPS) and x-ray magnetic circular dichroism PEEM (XMCDPEEM) for complementary structural, chemical, and magnetic characterization. Initially, a two-dimensional (Fe, Zn)S reaction layer forms with thickness that depends on growth temperature. Further growth results in the formation of a variety of three-dimensional crystals, most of them strongly elongated in the form of 'nanowires' of two distinct types, labeled as A and B. Type A nanowires are oriented near the ZnS[1 1 0] direction and are composed of Fe. Type B nanowires are oriented predominantly along directions a few degrees off the ZnS[0 0 1] direction and are identified as Greigite (Fe3S4). Both types of nanowires are magnetic with Curie temperatures above 450 °C. The understanding of the reactive growth mechanism in this system that is provided by these investigations may help to develop growth methods for other elemental and transition metal chalcogenide nanostructures on ZnS and possibly on other II-VI semiconductor surfaces. PMID:24934101

  6. Growth, reaction and nanowire formation of Fe on the ZnS(1 0 0) surface

    NASA Astrophysics Data System (ADS)

    Lun Man, Ka; Pavlovska, Anastassia; Bauer, Ernst; Locatelli, Andrea; Menteş, Tevfik O.; Niño, Miguel A.; Wong, George K. L.; Keong Sou, Iam; Altman, Michael S.

    2014-08-01

    The growth and reaction of Fe on a ZnS(1 0 0) substrate are studied in situ and with high lateral resolution using low energy electron microscopy (LEEM), micro low energy electron diffraction ( μLEED), x-ray photoemission electron microscopy (XPEEM), microprobe x-ray photoelectron spectroscopy ( μXPS) and x-ray magnetic circular dichroism PEEM (XMCDPEEM) for complementary structural, chemical, and magnetic characterization. Initially, a two-dimensional (Fe, Zn)S reaction layer forms with thickness that depends on growth temperature. Further growth results in the formation of a variety of three-dimensional crystals, most of them strongly elongated in the form of ‘nanowires’ of two distinct types, labeled as A and B. Type A nanowires are oriented near the ZnS[1 1 0] direction and are composed of Fe. Type B nanowires are oriented predominantly along directions a few degrees off the ZnS[0 0 1] direction and are identified as Greigite (Fe3S4). Both types of nanowires are magnetic with Curie temperatures above 450 °C. The understanding of the reactive growth mechanism in this system that is provided by these investigations may help to develop growth methods for other elemental and transition metal chalcogenide nanostructures on ZnS and possibly on other II-VI semiconductor surfaces.

  7. 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).

  8. Simple and greener synthesis of highly photoluminescence Mn2+-doped ZnS quantum dots and its surface passivation mechanism

    NASA Astrophysics Data System (ADS)

    Wang, Yongbo; Liang, Xuhua; Ma, Xuan; Hu, Yahong; Hu, Xiaoyun; Li, Xinghua; Fan, Jun

    2014-10-01

    In this paper, we reported a simple synthetic method of highly photoluminescent (PL) and stable Mn2+-doped ZnS quantum dots (QDs) with glutathione (GSH) as the capping molecule and focused on mechanism of the surface passivation of QDs. The Mn2+-doped ZnS QDs that was synthesized in basic solution (pH 10) at 120 °C for 5 h exhibited blue trap-state emission around 418 nm and a strong orange-red emission at about 580 nm with an excitation wavelength of 330 nm. The optimum doping concentration is determined to be 1.5 at.%, and the present Mn2+-doped ZnS QDs synthesized under the optimal reaction condition exhibited a quantum yield of 48%. High resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) indicated that the Mn2+-doped ZnS QDs were 3-5 nm in size with a zinc blend structure. More importantly, the PL intensity and chemical stability can be improved using organic ligand modification strategies, it was found that GSH could passivate surface defects very efficiently by comparing and analyzing the results of the different organic ligands modification. The cadmium-free Mn2+-doped ZnS QDs well-passivated with GSH as capping molecule acquired the advantages of strong PL and excellent chemical stability, which are important to QD applications.

  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. 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.

  11. Photoluminescence from doped ZnS nanostructures

    NASA Astrophysics Data System (ADS)

    Karar, N.

    2007-05-01

    Photoluminescence (PL) properties of differently doped nanocrystalline ZnS encapsulated by ZnO (ZnS/ZnO) are reported. It is found that in all cases aluminium as an extra/additional dopant leads to PL enhancement. In comparison to reported blue emitting bulk ZnS:Ag, or green emitting bulk ZnS:Cu, our nanocrystalline samples show a different PL emission profile. This observation is attributed to nanogranule formation, different dopant levels and ZnO capping related energy level modifications.

  12. 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.

  13. Study of interatomic potentials in ZnS -- Crystal-GRID experiments versus ab initio calculations

    SciTech Connect

    Koch, T.; Heinig, K.H.; Jentschel, M.; Boerner, H.G.

    2000-02-01

    Crystal-GRID measurements have been performed with ZnS single crystals. For the first time, an asymmetric Crystal-GRID line shape could be observed. The preliminary data evaluation indicates that the reported lifetime of the 3221 keV level in {sup 33}S is too short. A value of about 60 fs has been found. Due to this long lifetime the line shape is much less structured than calculated with the reported lifetime.

  14. Effect of Molecular Coupling on Ultrafast Electron-Transfer and Charge-Recombination Dynamics in a Wide-Gap ZnS Nanoaggregate Sensitized by Triphenyl Methane Dyes.

    PubMed

    Debnath, Tushar; Maity, Partha; Dana, Jayanta; Ghosh, Hirendra N

    2016-03-01

    Wide-band-gap ZnS nanocrystals (NCs) were synthesized, and after sensitizing the NCs with series of triphenyl methane (TPM) dyes, ultrafast charge-transfer dynamics was demonstrated. HRTEM images of ZnS NCs show the formation of aggregate crystals with a flower-like structure. Exciton absorption and lumimescence, due to quantum confinement of the ZnS NCs, appear at approximately 310 and 340 nm, respectively. Interestingly, all the TPM dyes (pyrogallol red, bromopyrogallol red, and aurin tricarboxylic acid) form charge-transfer complexes with the ZnS NCs, with the appearance of a red-shifted band. Electron injection from the photoexcited TPM dyes into the conduction band of the ZnS NCs is shown to be a thermodynamically viable process, as confirmed by steady-state and time-resolved emission studies. To unravel charge-transfer (both electron injection and charge recombination) dynamics and the effect of molecular coupling, femtosecond transient absorption studies were carried out in TPM-sensitized ZnS NCs. The electron-injection dynamics is pulse-width-limited in all the ZnS/TPM dye systems, however, the back electron transfer differs, depending on the molecular coupling of the sensitizers (TPM dyes). The detailed mechanisms for the above-mentioned processes are discussed. PMID:26548569

  15. Minimizing artifact formation in magnetorheological finishing of chemical vapor deposition ZnS flats.

    PubMed

    Kozhinova, Irina A; Romanofsky, Henry J; Maltsev, Alexander; Jacobs, Stephen D; Kordonski, William I; Gorodkin, Sergei R

    2005-08-01

    The polishing performance of magnetorheological (MR) fluids prepared with a variety of magnetic and nonmagnetic ingredients was studied on four types of initial surface for chemical vapor deposition (CVD) ZnS flats from domestic and foreign sources. The results showed that it was possible to greatly improve smoothing performance of magnetorheological finishing (MRF) by altering the fluid composition, with the best results obtained for nanoalumina abrasive used with soft carbonyl iron and altered MR fluid chemistry. Surface roughness did not exceed 20 nm peak to valley and 2 nm rms after removal of 2 microm of material. The formation of orange peel and the exposure of a pebblelike structure inherent in ZnS from the CVD process were suppressed. PMID:16075880

  16. ZnS Thin Films Deposited by a Spin Successive Ionic Layer Adsorption and Reaction Process

    SciTech Connect

    Han, Seungyeol; Lee, D. H.; Ryu, S. O.; Chang, Chih-hung

    2010-05-20

    In this article, we reported a spin successive ionic layer adsorption and reaction (SILAR) method for the first time. ZnS thin films were deposited by spin SILAR using ZnCl2 and Na2S aqueous precursor solutions at room temperature and atmosphere pressure. The optical, structural, and morphological characterizations of the films were studied by scanning electron microscopy, atomic force microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV/visible spectroscopy. Smooth (average roughness <3 nm), uniform, and highly transparent ZnS (transmittance of over 90% in the visible band) thin films could be successfully deposited using this technique with shorter cycle time and much less solvent usage.

  17. 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.

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

    PubMed

    Khaparde, Rohini; Acharya, Smita

    2016-06-15

    Isovalent (Mn, Cd, Cu, Co)-doped-ZnS nanoparticles having size vary in between 2 to 5nm 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 UVVis 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 5nm. 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 UVVis 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. PMID:27037762

  19. 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.

  20. Computational study of the relative stabilities of ZnS clusters, for sizes between 1 and 4 nm

    NASA Astrophysics Data System (ADS)

    Hamad, Said; Catlow, C. Richard A.

    2006-08-01

    We model the structures and energies of (ZnS) n clusters, where n=18-560. We employ two computational techniques—interatomic potential methods with simulated annealing and density functional theory; both give similar results. Clusters between n=18 and 49 adopt hollow geometries in which all atoms are three coordinated (denoted bubbles), confirming previous studies. Clusters between n=50 and 80 show onion-like structures in which one bubble is inside another. Simulated annealing simulations on (ZnS) 256 and (ZnS) 512 in vacuo yielded crystalline clusters in which the crystal phase is not any of the two observed bulk phases of ZnS (zincblende and wurtzite), but a new one, which has the topology of the BCT zeolite. For clusters between n=80 and 560 we study clusters generated from the three crystalline phases. The lowest energies are for those with BCT structure, followed closely by the wurtzite clusters, while zincblende clusters are the least stable.

  1. Manufacturing of transparent ZnS ceramics by powders sintering

    NASA Astrophysics Data System (ADS)

    Merdrignac-Conanec, O.; Hakmeh, N.; Durand, G.; Zhang, X.-H.

    2016-05-01

    We report the use of the low cost hot-pressing technique to produce ZnS for multispectral operation, from visible up to 12 μm. Considerable progress has been obtained by developing efficient precipitation and combustion powders synthesis procedures. The main emphasis has been on the elaboration of ZnS precursor powders with controlled morphology/chemical composition to reduce extrinsic scattering and impurities. We were able to produce ZnS parts with visible transparency and transmission in the 8-12 μm range that is comparable to that of CVD ZnS. The correlation of processing variables with powders sinterability and optical transmission of the HPed ceramics is discussed.

  2. Synthesis of Mn-doped ZnS architectures in ternary solution and their optical properties

    NASA Astrophysics Data System (ADS)

    Wang, Xinjuan; Zhang, Qinglin; Zou, Bingsuo; Lei, Aihua; Ren, Pinyun

    2011-10-01

    Mn-doped ZnS sea urchin-like architectures were fabricated by a one-pot solvothermal route in a ternary solution made of ethylenediamine, ethanolamine and distilled water. The as-prepared products were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and photoluminescence spectra (PL). It was demonstrated that the as-prepared sea urchin-like architectures with diameter of 0.5-1.5 μm were composed of nanorods, possessing a wurtzite structures. The preferred growth orientation of nanorods was found to be the [0 0 2] direction. The PL spectra of the Mn-doped ZnS sea urchin-like architectures show a strong orange emission at 587 nm, indicating the successful doping of Mn 2+ ions into ZnS host. Ethanolamine played the role of oriented-assembly agent in the formation of sea urchin-like architectures. A possible growth mechanism was proposed to explain the formation of sea urchin-like architectures.

  3. 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.

  4. Synthesis and photoluminescence characteristics of doped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Yang, P.; Lü, M.; Xü, D.; Yuan, D.; Zhou, G.

    2001-10-01

    Free-standing powders of doped ZnS nanoparticles have been synthesized by using a chemical co-precipitation of Zn2+, Mn2+, Cu2+ and Cd2+ with sulfur ions in aqueous solution. X-ray diffraction analysis shows that the diameter of the particles is ˜2-3 nm. The unique luminescence properties, such as the strength (its intensity is about 12 times that of ZnS nanoparticles) and stability of the visible-light emission, were observed from ZnS nanoparticles co-doped with Cu2+ and Mn2+. The nanoparticles could be doped with copper and manganese during the synthesis without altering the X-ray diffraction pattern. However, doping shifts the luminescence to 520-540 nm in the case of co-doping with Cu2+ and Mn2+. Doping also results in a blue shift on the excitation wavelength. In Cd2+-doped ZnS nanometer-scale particles, the fluorescence spectra show a red shift in the emission wavelength (ranging from 450 nm to 620 nm). Also a relatively broad emission (ranging from blue to yellow) has been observed. The results strongly suggest that doped ZnS nanocrystals, especially two kinds of transition metal-activated ZnS nanoparticles, form a new class of luminescent materials.

  5. Optical properties of ZnS1-xSex alloys fabricated by plasma-induced isoelectronic substitution

    NASA Astrophysics Data System (ADS)

    Rujkorakarn, Rong; Nelson, Art J.

    2000-06-01

    Nonequilibrium growth of thin-film ternary ZnS1-xSex semiconductor alloys was accomplished using physical vapor deposition with simultaneous electron cyclotron resonance H2S plasma activation. Substrate temperature, gas flow, and plasma power determine the ZnS1-xSex alloy composition and structure. Integrated optical transmission spectra for the ZnS1-xSex semiconductor alloys as a function of H2S plasma power are presented. Using the α2 vs hν plots for the various ZnS1-xSex films, the optical band gap Eg is extrapolated from each curve. This methodology yields the values of the band gap as a function of stoichiometry. We observe that the plasma induced isoelectronic substitution of S into the ZnSe lattice increases the band gap. This study shows that plasma-induced isoelectronic substitution is technologically feasible and useful for fabricating ternary II-VI alloys under nonequilibrium conditions.

  6. Controlled synthesis of Eu2+ and Eu3+ doped ZnS quantum dots and their photovoltaic and magnetic properties

    NASA Astrophysics Data System (ADS)

    Horoz, Sabit; Yakami, Baichhabi; Poudyal, Uma; Pikal, Jon M.; Wang, Wenyong; Tang, Jinke

    2016-04-01

    Eu-doped ZnS quantum dots (QDs) have been synthesized by wet-chemical method and found to form in zinc blende (cubic) structure. Both Eu2+ and Eu3+ doped ZnS can be controllably synthesized. The Eu2+ doped ZnS QDs show broad photoluminescence emission peak around 512 nm, which is from the Eu2+ intra-ion transition of 4f6d1 - 4f7, while the Eu3+ doped samples exhibit narrow emission lines characteristic of transitions between the 4f levels. The investigation of the magnetic properties shows that the Eu3+ doped samples exhibit signs of ferromagnetism, on the other hand, Eu2+ doped samples are paramagnetic of Curie-Weiss type. The incident photon to electron conversion efficiency is increased with the Eu doping, which suggests the QD solar cell efficiency can be enhanced by Eu doping due to widened absorption windows. This is an attractive approach to utilize benign and environmentally friendly wide band gap ZnS QDs in solar cell technology.

  7. 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

  8. 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. PMID:27283079

  9. 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.

  10. Surface transmission enhancement of ZnS via continuous-wave laser microstructuring

    NASA Astrophysics Data System (ADS)

    Major, Kevin J.; Florea, Catalin M.; Poutous, Menelaos K.; Busse, Lynda E.; Sanghera, Jasbinder S.; Aggarwal, Ishwar D.

    2014-03-01

    Fresnel reflectivity at dielectric boundaries between optical components, lenses, and windows is a major issue for the optics community. The most common method to reduce the index mismatch and subsequent surface reflection is to apply a thin film or films of intermediate indices to the optical materials. More recently, surface texturing or roughening has been shown to approximate a stepwise refractive index thin-film structure, with a gradient index of refraction transition from the bulk material to the surrounding medium. Short-pulse laser ablation is a recently-utilized method to produce such random anti-reflective structured surfaces (rARSS). Typically, high-energy femtosecond pulsed lasers are focused on the surface of the desired optical material to produce periodic or quasi-periodic assemblies of nanostructures which provide reduced surface reflection. This technique is being explored to generate a variety of structures across multiple optical materials. However, femtosecond laser systems are relatively expensive and more difficult to maintain. We present here a low power and low-cost alternative to femtosecond laser ablation, demonstrating random antireflective structures on the surface of Cleartran ZnS windows produced with a continuous-wave laser. In particular, we find that irradiation with a low-powered (<10 mW), defocused, CW 325nm-wavelength laser produces a random surface with significant roughness on ZnS substrates. The transmission through the structured ZnS windows is shown to increase by up to 9% across a broad wavelength range from the visible to the near-infrared.

  11. Investigation of Electroluminescent Degradation in doped ZnS phosphors

    NASA Astrophysics Data System (ADS)

    Bridges, Frank; Stanley, Jacob; Jiang, Yu; Ruhlen, Laurel; Willy, John; Carter, Sue

    2008-03-01

    We present optical and EXAFS data on a series of ZnS samples doped with Cu, Mn and Cl. These materials (30 micron particles) have a strong electroluminescence (EL) when subjected to a 100V square-wave voltage. At 100 kHz, the luminescence decays significantly in a 20 hr period. We show that this degradation can partially be reversed by annealing the sample and that this can be repeated several times. In addition the EL emission centers reoccur at the same points in the 30 micron particles after the anneal. The optimum annealing temperature is about 180C, but varies slightly for different wavelengths. Surprisingly an anneal at somewhat higher temperatures (240C) dramatically reduces the EL intensity. The EXAFS studies show that the local structure about Cu continues to look like CuS for ``as made", EL degraded, rejuvenated samples (annealing at 180C), and thermally degraded samples (annealed at 240C). This means that most of the Cu is in the relatively inert CuS precipitates, and does not change significantly with EL degradation or annealing. Thus the EL active sites must be dilute. We discuss some possible models.

  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. Richardson-Schottky transport mechanism in ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Ali, Hassan; Khan, Usman; Rafiq, M. A.; Falak, Attia; Narain, Adeela; Jing, Tang; Xu, Xiulai

    2016-05-01

    We report the synthesis and electrical transport mechanism in ZnS semiconductor nanoparticles. Temperature dependent direct current transport measurements on the compacts of ZnS have been performed to investigate the transport mechanism for temperature ranging from 300 K to 400 K. High frequency dielectric constant has been used to obtain the theoretical values of Richardson-Schottky and Poole-Frenkel barrier lowering coefficients. Experimental value of the barrier lowering coefficient has been calculated from conductance-voltage characteristics. The experimental value of barrier lowering coefficient βexp lies close to the theoretical value of Richardson-Schottky barrier lowering coefficient βth,RS showing Richardson-Schottky emission has been responsible for conduction in ZnS nanoparticles for the temperature range studied.

  14. Properties of mechanochemically synthesized ZnS nanoparticles.

    PubMed

    Dutková, E; Baláz, P; Pourghahramani, P; Velumani, S; Ascencio, J A; Kostova, N G

    2009-11-01

    The bulk and surface properties of mechanochemically synthesized ZnS nanoparticles were studied. XRD, SEM, TEM (HRTEM), AFM, UV-VIS, low temperature nitrogen sorption as well as TPR characterization methods have been applied. Cubic ZnS nanocrystals (2-4 nm) with characteristic blue shift have been obtained by high-energy milling. There is an evidence of the nanocrystal aggregates formation in products of milling. The surface uniformity, homogeneity as well as enhanced uptake of hydrogen have been documented. PMID:19908571

  15. 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

  16. Effect of phenyl and benzyl group in heterocyclic dithiocarbamates on the ZnS 4N chromophore: Synthesis, spectral, valence-bond parameters and single crystal X-ray structural studies on (pyridine)bis(1,2,3,4-tetrahydroquinolinedithiocarbamato)zinc(II) and (pyridine)bis(1,2,3,4-tetrahydroisoquinolinedithiocarbamato)zinc(II)

    NASA Astrophysics Data System (ADS)

    Srinivasan, N.; Thirumaran, S.; Ciattini, Samuele

    2009-03-01

    Two Zn(II)dithiocarbamates with ZnS 4N chromophores have been synthesized ([Zn(thqdtc) 2(py)] ( 1) and [Zn(thiqdtc) 2(py)] ( 2) (where thqdtc = 1,2,3,4-tetrahydroquinolinedithiocarbamate, thiqtc = 1,2,3,4-tetrahydroisoquinolinedithiocarbamate and py = pyridine)) from [Zn(thqdtc) 2] ( 3) and [Zn(thiqdtc) 2] ( 4), respectively. Their structures and properties have been characterized by IR and NMR spectra. The structures of both the complexes were determined by single crystal X-ray crystallography. The observed deshielding of the H-2 protons for 1 and 3 and H-1 and H-3 protons for 2 and 4 in the 1H NMR spectra is attributed to the drift of electrons from the nitrogen of the NR 2 group, forcing a high electron density towards sulfur via the thioureide π-system. In the 13C NMR spectra, the most important thioureide (N 13CS 2) carbon signals are observed in the region 204-207 ppm. The upfield shift of NCS 2 carbon signal for 1 (204.2 ppm) from the chemical shift value of 2 (206.9 ppm) is due to electron withdrawing resonance effect of phenyl ring thereby decreasing the double bond character in tetrahydroquinolinedithiocarbamate, whereas benzyl group in tetrahydroisoquinolinedithiocarbamate cannot participate in resonance delocalization in the same way. Single crystal X-ray structural analysis of 1 and 2 showed that the zinc atom is pentacoordinated with four sulfur atoms from the dithiocarbamate ligands and one nitrogen atom from the pyridine. VBS values support the correctness of the determined structure. The lower VBS value of 2 is due to the steric effect exerted by the thiqdtc. The phenyl and benzyl group in the heterocyclic dithiocarbamates influences the electronic properties of 1 and 2. The shift of ν C- N(thioureide) and thioureide N 13CS 2 carbon signals are correlated with the electronic effects of the dithiocarbamate ligands.

  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. Dual-donor codoping approach to realize low-resistance n-type ZnS semiconductor

    SciTech Connect

    Li , D. F.; Deng, Bo; Xue, Shuwen; Wang, Zhiguo; Gao, Fei

    2011-08-01

    Based on first-principles calculations, we explored a good candidate for achieving low-resistance and high carrier concentration of n-type ZnS by a dual-donor codoping method, where the ionization energy was effectively reduced. We found that the SnZn-FS pair has a shallow donor level of 17.2 meV, a small formation energy of 1.27 eV and a high binding energy of 1.28 eV. The density of states analysis showed that the SnZn-FS pair induces the downward shift of the conduction band minimum by about 0.15 eV, while the basis electronic structure does not change. Thus, the SnZn-FS pair is likely to be a best n-type dopant for ZnS.

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

    PubMed

    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 Zn(2+) ions from ZnS remain in the shell while the S(2-) 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

  20. 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

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

    PubMed

    Li, Chenghui; Wu, Peng; Hou, Xiandeng

    2016-02-21

    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 Mn(2+) 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. PMID:26838695

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    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 ṡOH 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. 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. PMID:23965531

  4. Luminescence enhancement of Mn doped ZnS nanocrystals passivated with zinc hydroxide

    NASA Astrophysics Data System (ADS)

    Jiang, Daixun; Cao, Lixin; Su, Ge; Qu, Hua; Sun, Dake

    2007-10-01

    Mn-doped ZnS nanocrystals prepared by solvothermal method have been successfully coated with different thicknesses of Zn(OH) 2 shells through precipitation reaction. The impact of Zn(OH) 2 shells on luminescent properties of the ZnS:Mn nanocrystals was investigated. X-ray diffraction (XRD) measurements showed that the ZnS:Mn nanocrystals have cubic zinc blende structure. The morphology of nanocrystals is spherical shape measured by transmission electron microscopy (TEM). ZnS:Mn/Zn(OH) 2 core/shell nanocrystals exhibited much improved luminescent properties than those of unpassivated ZnS:Mn nanocrystals. The luminescence enhancement was observed with the Zn(OH) 2 shell thickening by photoluminescence (PL) spectra at room temperature and the luminescence lifetime of transition from 4T 1 to 6A 1 of Mn 2+ ions was also prolonged. This result was led by the effective, robust passivation of ZnS surface states by the Zn(OH) 2 shells, which consequently suppressed nonradiative recombination transitions.

  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. 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%.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    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.

  8. 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

  9. 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

  10. Ultrasensitive, Real-time and Discriminative Detection of Improvised Explosives by Chemiresistive Thin-film Sensory Array of Mn(2+) Tailored Hierarchical ZnS.

    PubMed

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

    2016-01-01

    A simple method combing Mn(2+) 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 Mn(2+) 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 Mn(2+) concentration, reaching the climate at 5% Mn(2+). 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 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. PMID:26242910

  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. Uniform and continuous silica nanocoatings on ZnS phosphors

    NASA Astrophysics Data System (ADS)

    Yuan, Jiongliang

    2008-04-01

    The penetration depth of the primary electrons into amorphous silica, anatase titania, Y2O3, ZnO, In2O3, indium and tin oxides is compared at lower voltages. It shows that amorphous silica has the largest penetration depth, thus the silica coatings will lead to minimal energy loss and maximal cathodoluminescence intensity. Almost uniform and continuous silica coatings on ZnS phosphors have successfully been obtained by a sol-gel method with the catalysis of ammonia. Zeta potential analysis shows that the ZnS phosphors are covered almost completely. An adsorption-catalysis-growth mechanism is suggested, and used to explain other ammonia-catalyzed coating processes.

  14. Far-infrared spectra of mesoporous ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Trajić, J.; Romčević, M.; Romčević, N.; Babić, B.; Matović, B.; Baláž, P.

    2016-07-01

    ZnS nanoparticles were synthesized mechanochemically by high-energy milling, with three different milling times (5 min, 10 min and 20 min). Nitrogen adsorption method was used for examining specific surface area and texture of obtained powders. It was found that all samples are completely mesoporous. The optical properties were studied by far-infrared spectroscopy at room temperature in spectral region of 50-600 cm-1. The analysis of the far-infrared reflectivity spectra was made by the fitting procedure. The dielectric function of ZnS nanoparticles is modeled as a mixture of homogenous spherical inclusions in air by the Maxwell-Garnet formula. In the analysis of the far-infrared reflection spectra, appearance of combined plasmon-LO phonon modes (CPPMs) with high phonon damping are observed, which causes decrease of coupled plasmon-phonon frequencies.

  15. Optical Properties of Co2+ Doped ZnS Nanocrystals

    NASA Astrophysics Data System (ADS)

    Sarkar, R.; Kumbhakar, P.; Mitra, A. K.

    2010-10-01

    ZnS nanocrystals with Co2+ doping have been prepared through a soft chemical route. The undoped ZnS and Co2+ doped ZnS:Co nanocrystals have been analyzed using X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), and ultraviolet-visible (UV-VIS) spectrophotometer. Undoped sample exhibits room-temperature photoluminescence (PL) emission in the blue region with a broad spectral band peaked at ˜397 nm under UV excitation. But from the 1.5% Co2+ doped samples, a strong blue emission peaked at ˜470 nm is observed and further increase in doping leads to considerable blue shift and enhancement in intensity of the PL spectrum.

  16. Stable and luminescent wurtzite CdS, ZnS and CdS/ZnS core/shell quantum dots

    NASA Astrophysics Data System (ADS)

    Kumar, Hitanshu; Kumar, Manoj; Barman, P. B.; Singh, Ragini Raj

    2014-06-01

    This article presents first report on the highly stable and luminescent wurtzite CdS, ZnS and CdS/ZnS quantum dots (QDs) where the role of precursor selection at room temperature is the key. X-ray diffraction (XRD), optical absorbance spectroscopy, photoluminescence spectroscopy, Fourier transform infrared spectroscopy and transmission electron microscopy have been employed in order to characterize these QDs. XRD indicates the formation of wurtzite CdS, ZnS and CdS/ZnS system. Broadening in XRD peaks revealed the reduction in particle size such as 4.2, 5.2 and 5.8 nm for CdS, ZnS and CdS/ZnS, respectively, compared to their bulk counterparts. Blue shift in absorbance has been observed in each case as particles size decreases. The photoluminescence intensity emission of CdS/ZnS core/shell was strongly superior from that observed in individual CdS and ZnS nanoparticles. We also propose that the core and shell interface leads to favourable conditions that instigate photoluminescence emission in CdS/ZnS core/shell system. One notable result of this work obtained from the photoluminescence analysis is the significant reduction in full width at half maxima, in emission peak of core/shell structure which shows the enhanced monochromaticity. We have found that OH, CH2 and C-O functional groups are present on the QDs surface and that is why these QDs can be easily attachable to biomolecules. TEM analysis has been employed for confirmation of particle size and found to be 5.3, 5.8 and 6.2 nm for CdS, ZnS and CdS/ZnS structures, respectively.

  17. 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.

  18. Polytypism in ZnS, ZnSe, and ZnTe: First-principles study

    NASA Astrophysics Data System (ADS)

    Boutaiba, F.; Belabbes, A.; Ferhat, M.; Bechstedt, F.

    2014-06-01

    We report results of first-principles calculations based on the projector augmented wave (PAW) method to explore the structural, thermodynamic, and electronic properties of cubic (3C) and hexagonal (6H, 4H, and 2H) polytypes of II-VI compounds: ZnS, ZnSe, and ZnTe. We find that the different bond stacking in II-VI polytypes remarkably influences the resulting physical properties. Furthermore, the degree of hexagonality is found to be useful to understand both the ground-state properties and the electronic structure of these compounds. The resulting lattice parameters, energetic stability, and characteristic band energies are in good agreement with available experimental data. Trends with hexagonality of the polytype are investigated.

  19. 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

    2013-06-01

    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. PMID:23576296

  20. 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. PMID:26278468

  1. Symmetry and electronic states of Mn2+ in ZnS nanowires with mixed hexagonal and cubic stacking

    NASA Astrophysics Data System (ADS)

    Chen, Li; Kirilenko, Demid; Stesmans, Andre; Nguyen, Xuan Sang; Binnemans, Koen; Goderis, Bart; Vanacken, Johan; Lebedev, Oleg; Van Tendeloo, Gustaaf; Moshchalkov, Victor V.

    2010-07-01

    Electron spin resonance and electronic spectroscopy techniques were used to study the symmetry and electronic structure of Mn2+ dopants in solvothermally synthesized ZnS nanowires. The average diameter of ˜5 nm leads to the observable quantum confinement effects in the photoluminescence excitation spectra. The results clearly demonstrate the three symmetry locations of Mn2+ incorporation. Together with the inferred Mn2+ center densities, these data indicate a much higher efficiency of Mn2+ substitution in the nanowire sample with about two times larger diameter.

  2. 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

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

    PubMed

    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 10(7) 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

  4. Liquid-Phase Epitaxial Growth of ZnS, ZnSe and Their Mixed Compounds Using Te as Solvent

    NASA Astrophysics Data System (ADS)

    Nakamura, Hiroshi; Aoki, Masaharu

    1981-01-01

    Epitaxial layers of ZnS, ZnSe and their mixed compounds were grown on ZnS substrates by the liquid-phase epitaxial growth (LPE) method using Te as the solvent. The open-tube slide-boat technique was used, and a suitable starting temperature for growth was found to be 850°C for ZnS and 700-800°C for ZnSe. The ZnS epitaxial layers grown on {111}A and {111}B oriented ZnS substrates were thin (˜1 μm) and smooth, had low, uniform Te concentrations (˜0.1 at.%) and were highly luminescent. The ZnSe epitaxial layers were relatively thick (10-30 μm) and had fairly high Te concentrations (a few at.%). Various mixed compound ZnS1-xSex were also grown on ZnS substrates.

  5. Relaxation Dynamics and Threading Dislocations in ZnSe and ZnS y Se1- y /GaAs (001) Heterostructures

    NASA Astrophysics Data System (ADS)

    Kujofsa, T.; Cheruku, S.; Yu, W.; Outlaw, B.; Xhurxhi, S.; Obst, F.; Sidoti, D.; Bertoli, B.; Rago, P. B.; Suarez, E. N.; Jain, F. C.; Ayers, J. E.

    2013-09-01

    The design of lattice-mismatched semiconductor devices requires a predictive model for strains and threading dislocation densities. Previous work enabled modeling of uniform layers but not the threading dislocations in device structures with arbitrary compositional grading. In this work we present a kinetic model for lattice relaxation which includes misfit-threading dislocation interactions, which have not been considered in previous annihilation-coalescence models. Inclusion of these dislocation interactions makes the kinetic model applicable to compositionally graded structures, and we have applied it to ZnSe/GaAs (001) and ZnS y Se1- y /GaAs (001) heterostructures. The results of the kinetic model are consistent with the observed threading dislocation behavior in ZnSe/GaAs (001) uniform layers, and for graded ZnS y Se1- y /GaAs (001) heterostructures the kinetic model predicts that the threading dislocation density may be reduced by the inclusion of grading buffer layers employing compositional overshoot. This "dislocation compensation" effect is consistent with our high-resolution x-ray diffraction experimental results for graded ZnS y Se1- y /GaAs (001) structures grown by photoassisted metalorganic vapor-phase epitaxy.

  6. Strong green luminescence of Ni2+-doped ZnS nanocrystals

    NASA Astrophysics Data System (ADS)

    Yang, P.; Lü, M.; Xü, D.; Yuan, D.; Chang, J.; Zhou, G.; Pan, M.

    ZnS nanoparticles doped with Ni2+ have been obtained by chemical co-precipitation from homogeneous solutions of zinc and nickel salt compounds, with S2- as precipitating anion, formed by decomposition of thioacetamide (TAA). The average size of particles doped with different mole ratios, estimated from the Debye-Scherrer formula, is about 2-2.5 nm. The nanoparticles could be doped with nickel during synthesis without altering the X-ray diffraction pattern. A Hitachi M-850 fluorescence spectrophotometer reveals the emission spectra of samples. The absorption spectra show that the excitation spectra of Ni-doped ZnS nanocrystallites are almost the same as those of pure ZnS nanocrystallites (λex=308-310 nm). Because a Ni2+ luminescent center is formed in ZnS nanocrystallites, the photoluminescence intensity increases with the amount of ZnS nanoparticles doped with Ni2+. Stronger and stable green-light emission (520 nm) (its intensity is about two times that of pure ZnS nanoparticles) has been observed from ZnS nanoparticles doped with Ni2+.

  7. Phase transformation from cubic ZnS to hexagonal ZnO by thermal annealing

    NASA Astrophysics Data System (ADS)

    Mahmood, K.; Asghar, M.; Amin, N.; Ali, Adnan

    2015-03-01

    We have investigated the mechanism of phase transformation from ZnS to hexagonal ZnO by high-temperature thermal annealing. The ZnS thin films were grown on Si (001) substrate by thermal evaporation system using ZnS powder as source material. The grown films were annealed at different temperatures and characterized by X-ray diffraction (XRD), photoluminescence (PL), four-point probe, scanning electron microscope (SEM) and energy dispersive X-ray diffraction (EDX). The results demonstrated that as-deposited ZnS film has mixed phases but high-temperature annealing leads to transition from ZnS to ZnO. The observed result can be explained as a two-step process: (1) high-energy O atoms replaced S atoms in lattice during annealing process, and (2) S atoms diffused into substrate and/or diffused out of the sample. The dissociation energy of ZnS calculated from the Arrhenius plot of 1000/T versus log (resistivity) was found to be 3.1 eV. PL spectra of as-grown sample exhibits a characteristic green emission at 2.4 eV of ZnS but annealed samples consist of band-to-band and defect emission of ZnO at 3.29 eV and 2.5 eV respectively. SEM and EDX measurements were additionally performed to strengthen the argument.

  8. Fabrication and charaterization of silica nanocoatings on ZnS phosphor particles

    NASA Astrophysics Data System (ADS)

    Yuan, Jiongliang; Kajiyoshi, Koji; Sasaoka, Hideki; Nishimura, Kazuhito

    2007-03-01

    With the addition of the cationic surfactant, cetyltrimethylammonium chloride (CTAC), continuous and uniform silica nanocoatings on ZnS phosphors have been successfully obtained. The coatings are proven to cover ZnS phosphors completely by using transmission electron microscopy (TEM), zeta potential and x-ray photoelectron spectroscopy (XPS) analysis. The XPS and Fourier transform infrared red (FT-IR) spectroscopy results provide evidence of the presence of Zn-O-Si bonds between the silica coatings and ZnS phosphors. It is suggested that the bridging effect of CTAC favours the formation of silica coatings, and Zn-O-Si bonds are formed during the annealing procedure.

  9. Synthesis and Characteristics of ZnS Nanospheres for Heterojunction Photovoltaic Device

    NASA Astrophysics Data System (ADS)

    Chou, Sheng-Hung; Hsiao, Yu-Jen; Fang, Te-Hua; Chou, Po-Hsun

    2015-06-01

    The synthesis of ZnS nanospheres produced using the microwave hydrothermal method was studied. The microstructure and surface and optical properties of ZnS nanospheres on glass were characterized using scanning electron microscopy, high-resolution transmission electron microscopy, x-ray diffraction, and ultraviolet-visible spectroscopy. The influence of deposition time on the transmission and photovoltaic performance was determined. The power conversion efficiency of an Al-doped ZnO/ZnS nanosphere/textured p-Si device improved from 0.93 to 1.77% when the thickness of the ZnS nanostructured film was changed from 75 to 150 nm.

  10. N2 Laser Induced Photoluminescence Emission in (ZnS: ZnO):Cu Phosphors

    NASA Astrophysics Data System (ADS)

    Muraleedharan, R.; Khokhar, M. S. K.; Namboodiri, V. P.; Girijavallabhan, C. P.

    Nitrogen laser induced photoluminescence (PL) emissions from (ZnS: ZnO):Cu powder phosphors have been carried out under varying conditions of sample preparation. The conditions for optimum efficiency of PL emission in (ZnS: ZnO):Cu phosphors and their spectral characteristics have been investigated. The emission peak in the PL spectra was found to shift towards longer wavelengths side as the concentrations of ZnO in (ZnS: ZnO) mixture was varied from 0% to 100%. The mechanism of PL emission in the above phosphor is explained on the basis of classical “Schon-Klassen” model.

  11. Photoinduced stiffening and photoplastic effect of ZnS individual nanobelt in nanoindentation

    SciTech Connect

    Zheng, X. J.; Yu, G. C.; Chen, Y. Q.; Mao, S. X.; Zhang, T.

    2010-11-15

    The photoinduced stiffening (PIS) and photoplastic effect (PPE) of ZnS individual nanobelt (NB) were observed by using a nanoindenter in conjunction with an incident ultraviolet (UV) light source system. The results show that the elastic modulus and hardness of ZnS individual NB under UV illumination are at least 32% and 20% larger than those in darkness. The mechanisms of PIS and PPE are interpreted by the increase in electronic strain and Peierls barrier due to the photogeneration of free carriers in ZnS individual NB. The research may offer useful guidelines to the application of optoelectronic devices based on individual nanostructures.

  12. ZnS, CdS and HgS nanoparticles via alkyl-phenyl dithiocarbamate complexes as single source precursors.

    PubMed

    Onwudiwe, Damian C; Ajibade, Peter A

    2011-01-01

    The synthesis of II-VI semiconductor nanoparticles obtained by the thermolysis of certain group 12 metal complexes as precursors is reported. Thermogravimetric analysis of the single source precursors showed sharp decomposition leading to their respective metal sulfides. The structural and optical properties of the prepared nanoparticles were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) UV-Vis and photoluminescence spectroscopy. The X-ray diffraction pattern showed that the prepared ZnS nanoparticles have a cubic sphalerite structure; the CdS indicates a hexagonal phase and the HgS show the presence of metacinnabar phase. The TEM image demonstrates that the ZnS nanoparticles are dot-shaped, the CdS and the HgS clearly showed a rice and spherical morphology respectively. The UV-Vis spectra exhibited a blue-shift with respect to that of the bulk samples which is attributed to the quantum size effect. The band gap of the samples have been calculated from absorption spectra and werefound to be about 4.33 eV (286 nm), 2.91 eV (426 nm) and 4.27 eV (290 nm) for the ZnS, CdS and HgS samples respectively. PMID:22016607

  13. ZnS, CdS and HgS Nanoparticles via Alkyl-Phenyl Dithiocarbamate Complexes as Single Source Precursors

    PubMed Central

    Onwudiwe, Damian C.; Ajibade, Peter A.

    2011-01-01

    The synthesis of II-VI semiconductor nanoparticles obtained by the thermolysis of certain group 12 metal complexes as precursors is reported. Thermogravimetric analysis of the single source precursors showed sharp decomposition leading to their respective metal sulfides. The structural and optical properties of the prepared nanoparticles were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) UV-Vis and photoluminescence spectroscopy. The X-ray diffraction pattern showed that the prepared ZnS nanoparticles have a cubic sphalerite structure; the CdS indicates a hexagonal phase and the HgS show the presence of metacinnabar phase. The TEM image demonstrates that the ZnS nanoparticles are dot-shaped, the CdS and the HgS clearly showed a rice and spherical morphology respectively. The UV-Vis spectra exhibited a blue-shift with respect to that of the bulk samples which is attributed to the quantum size effect. The band gap of the samples have been calculated from absorption spectra and werefound to be about 4.33 eV (286 nm), 2.91 eV (426 nm) and 4.27 eV (290 nm) for the ZnS, CdS and HgS samples respectively. PMID:22016607

  14. Tunability of photonic band gaps in one- and two-dimensional photonic crystals based on ZnS particles embedded in TiO2 matrix

    NASA Astrophysics Data System (ADS)

    Labbani, Amel; Benghalia, Abdelmadjid

    2012-06-01

    Using the Maxwell-Garnett theory, the evolution of the refractive index of titanium dioxide (TiO2) doped with zinc sulfide (ZnS) particles is presented. The presence of the nano-objects in the host matrix allows us to obtain a new composite material with tunable optical properties. We find that the filling factor of ZnS nanoparticles greatly alters photonic band gaps (PBGs). We have calculated also the photonic band structure for electromagnetic waves propagating in a structure consisting of ZnS rods covered with the air shell layer in 2D hexagonal and square lattices by the finite difference time domain (FDTD) method. The rods are embedded in the TiO2 background medium with a high dielectric constant. Such photonic lattices present complete photonic band gaps (CPBGs). Our results show that the existence of the air shell layer leads to larger complete photonic gaps. We believe that the present results are significant to increase the possibilities for experimentalists to realize a sizeable and larger CPBG.

  15. Study on Photocatalytic Degradation of 2,4-Dichlorophenol by ZnS Microsphere.

    PubMed

    Lv, Xiangying; Wang, Yonghao; Wang, Yongjing; Lin, Zhang

    2016-01-01

    The self-supported ZnS microsphere composed of interwoven nanosheets was synthesized by hydrothermal method. The as-prepared ZnS powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The photocatalytic activity of the fabricated ZnS powders was evaluated by the degradation of 2,4-dichlorophenol (DCP) under UV light. Effects of DCP initial concentration, ZnS dosage, solution pH, light source, and dissolved oxygen on DCP photocatalytic degradation efficiency were investigated and optimized systematically. Results demonstrated that 53% of DCP could be effectively degraded under the optimal experimental conditions. Finally, high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) were used to analyze the degradation products. Based on the experimental results obtained, a prob- able degradation pathway was proposed. PMID:27398569

  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. 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.

  18. 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. PMID:17107162

  19. 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. PMID:24322762

  20. 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.

  1. 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.

  2. Luminescent properties of near UV excitable Ba2ZnS3 : Mn red emitting phosphor blend for white LED and display applications

    NASA Astrophysics Data System (ADS)

    Thiyagarajan, P.; Kottaisamy, M.; Ramachandra Rao, M. S.

    2006-07-01

    A bright red colour emitting Mn doped Ba2ZnS3 phosphor was prepared by an ecologically acceptable carbothermal reduction method without an inert gas or hazardous gas (H2S) environment. The phosphor can be excited with UV wavelength radiation to realize emission in the visible range. X-ray diffraction studies confirm an orthorhombic structure with phase group, pnam. The photoluminescence (PL) emission spectrum shows a broad band with emission maximum at 625 nm under the host excitation of 358 nm, which lies in the near UV region. The concentration of Mn was varied from 0.0025 to 0.20 mole with respect to Zn and the optimum PL emission intensity was obtained at the concentration of 0.01 mole of Mn. The CIE (Commission Internationale de l'Eclairage) colour coordinates measurement (x = 0.654 and y = 0.321) shows that the primary emission is in the red region. The triband phosphors blend containing Sr5(PO4)3Cl : Eu2+ (blue), ZnS : Cu,Al (green) and Ba2ZnS3 : Mn (red) shows white light emission under 365 nm excitation having CIE chromaticity (x = 0.292 and y = 0.251). Since phosphor excitation lies in the near UV excitable region, giving a bright red emission, it can be used for applications in near UV phosphor converted white LED lighting and display devices.

  3. Efficient infrared luminescence of Er2S3/ZnS core/shell quantum dots and IR QDs-lED.

    PubMed

    Li, Bo; Zhang, Xiaosong; Ji, Ting; Zhang, Gaofeng; Li, Lan

    2014-06-01

    We have synthesized Er2S3/ZnS core/shell QDs by employing ErSt3, ZnSt2, and sulfur as precursors via a hot solution phase chemistry using a nucleation-doping strategy. X-ray diffraction (XRD), transmission electron microscope (TEM) and photoluminescence (PL) spectra were used to characterize the structure, morphology and luminescence properties of Er2S3/ZnS core/shell QDs. Moreover, the influence of overcoating temperatures on the infrared luminescence properties of QDs was investigated. PL spectra show that the emission intensity from the 4I13/2 --> 4I15/2 transition of Er3+ strongly increases with increasing overcoating temperatures, which was interpreted by the enhancing diffusion of Er3+ ions. IR-LEDs were fabricated combining commercial red GaAs LEDs with Er2S3/ZnS QDs, and luminescence properties of the IR-LED have been investigated. PMID:24738369

  4. 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.

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

    PubMed

    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

  6. Microwave-assisted low temperature synthesis of wurtzite ZnS quantum dots

    SciTech Connect

    Shahid, Robina; Toprak, Muhammet S.; Muhammed, Mamoun

    2012-03-15

    In this work we report, for the first time, on microwave assisted synthesis of wurtzite ZnS quantum dots (QDs) in controlled reaction at temperature as low as 150 Degree-Sign C. The synthesis can be done in different microwave absorbing solvents with multisource or single source precursors. The QDs are less than 3 nm in size as characterized by transmission electron microscopy (TEM) using selected area electron diffraction (SAED) patterns to confirm the wurtzite phase of ZnS QDs. The optical properties were investigated by UV-Vis absorption which shows blue shift in absorption compared to bulk wurtzite ZnS due to quantum confinement effects. The photoluminescence (PL) spectra of QDs reveal point defects related emission of ZnS QDs. - Graphical abstract: Microwave assisted synthesis of wurtzite ZnS quantum dots (QDs) have been achieved in controlled reaction at temperature as low as 150 Degree-Sign C. The synthesis was performed in different microwave absorbing solvents with multisource or single source precursors for very short reaction periods due to effective heating with microwaves. Highlights: Black-Right-Pointing-Pointer Wurtzite a high temperature phase of ZnS was synthesized at low temperature. Black-Right-Pointing-Pointer Low temperature synthesis was possible because of the use of microwave absorbing solvents. Black-Right-Pointing-Pointer Capping agent was used to control the size of Quantum Dots. Black-Right-Pointing-Pointer Two different systems were developed using single molecular precursor and multisource precursors.

  7. Facile production of ZnS quantum dot nanoparticles by Saccharomyces cerevisiae MTCC 2918.

    PubMed

    Sandana Mala, John Geraldine; Rose, Chellan

    2014-01-20

    Microbial synthesis of nanoparticles is a green route towards ecofriendly measures to overcome the toxicity and non-applicability of nanomaterials in clinical uses obtained by conventional physical and chemical approaches. Nanoparticles in the quantum regime have remarkable characteristics with excellent applicability in bioimaging. Yeasts have been commercially exploited for several industrial applications. ZnS nanoparticles as semiconductor quantum dots have mostly been synthesized by bacterial species. Here in, we have attempted to produce ZnS nanoparticles in quantum regime by Saccharomyces cerevisiae MTCC 2918 fungus and characterize its size and spectroscopic properties. Intracellular ZnS nanoparticles were produced by a facile procedure and freeze thaw extraction using 1mM zinc sulfate. The ZnS nanoparticles showed surface plasmon resonance band at 302.57nm. The ZnS nanoparticles were in low yield and in the size range of 30-40nm. Powder XRD analysis revealed that the nanoparticles were in the sphalerite phase. Photoluminescence spectra excited at 280nm and 325nm revealed quantum confinement effects. This suggests that yeasts have inherent sulfate metabolizing systems and are capable fungal sources to assimilate sulfate. Further insights are required to identify the transport/reducing processes that may have caused the synthesis of ZnS nanoparticles such as an oxidoreductase enzyme-mediated mechanism. PMID:24316439

  8. Luminescence characteristics of ZnS nanoparticles co-doped with Ni 2+ and Mn 2+

    NASA Astrophysics Data System (ADS)

    Yang, Ping; Lü, Mengkai; Xu, Dong; Yuan, Duorong; Song, Chunfeng; Liu, Suwen; Cheng, Xiufeng

    2003-12-01

    ZnS nanoparticles doped with Ni 2+ and Mn 2+ have been prepared by co-precipitation from homogeneous solutions of Zn, Ni and Mn salt compounds, with S 2- as precipitating anion formed by decomposition of thioacetamide (TAA). X-ray diffraction analysis shows that the average crystalline particle size of the doped and undoped ZnS nanometer scale samples is about 2-4 nm. A novel luminescent property has been observed in the photoluminescence (PL) spectra of the ZnS nanoparticles co-doped with Ni 2+ and Mn 2+. The ZnS nanoparticles can be doped with Ni 2+ and Mn 2+ during synthesis without altering the X-ray diffraction pattern. However, the emission wavelengths (with a color range from blue to green, λem=475-540 nm) and PL intensities of the co-doped samples vary with changing the impurity mole ratios of Ni 2+ and Mn 2+ in the co-doped samples. When the mole ratios of Ni 2+ and Mn 2+ in the co-doped sample are 0.3% and 2.0%, respectively, the relative fluorescence intensity of the co-doped samples is about four times of that of un-doped ZnS nanocrystals. The PL properties of the co-doped samples are dramatically different from those of Ni 2+- and Mn 2+-doped ZnS nanocrystals.

  9. 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

  10. Surface-enhanced Raman scattering of carbon nanotubes by decoration of ZnS nanoparticles.

    PubMed

    Chang, Jingbo; Lee, Jae-Hyeok; Najeeb, Choolakadavil Khalid; Kim, Jae-Ho

    2011-07-01

    ZnS nanoparticles anchored on the single-walled carbon nanotubes (SWNTs) were fabricated by a chemical vapor deposition (CVD) method. The CVD method shows no selectivity for growth of ZnS nanoparticles on types and defects of the SWNTs, and thus ensures the uniform decoration of all SWNTs on the substrate. ZnS nanoparticles with a diameter of 10 nm were decorated on the SWNTs surface with an interparticle distance of about 20 nm. This method provides the possibility to realize the optimal configurations of ZnS nanoparticles on SWNTs for obtaining surface-enhanced Raman spectroscopy (SERS) of SWNTs. Investigations of mechanism reveal that charge transfer (a small amount of excitation electrons) from ZnS nanoparticles to SWNTs weakly affects Raman intensity, and the coupled surface plasmon resonance (SPR) formed from plenty of excitation electrons on the surface of ZnS nanoparticles contributes to the strong surface enhancement. It would be an alternative approach for SERS after metal (normally gold or silver) nanoparticles' decoration on the SWNTs surface. PMID:22121696

  11. Synthesis, characterization and photoluminescence studies of undoped ZnS nanoparticles

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    The present paper reports the synthesis, characterization and photoluminescence studies of undoped ZnS nanoparticles. The ZnS nanoparticles were prepared by chemical precipitation method and characterized by X-ray diffraction (XRD), field emission gun scanning electron microscope (FEGSEM), and high resolution transmission electron microscope (HRTEM). When the concentrations of capping agent (mercaptoethanol) used are 0 M, 0.01 M, 0.025 M, 0.040 M, and 0.060 M, the sizes of the nanoparticles are 2.86 nm, 2.69 nm, 2.40 nm, 1.90 nm and 1.80 nm, respectively. This means the size of nanoparticles decreases with increasing concentration of capping agent used. The PL spectra of ZnS nanoparticles were measured for different concentrations of merceptoethanol, in which the excitation wavelength was 289 nm for all the samples. One peak is obtained in the photoluminescence (PL) of ZnS, in which the peak shifts from 468 nm to 408 nm with decreasing size of the nanocrystals. The blue emission around the peak of PL intensity is very broad and originates from the radiative recombination involving defect states in the ZnS nanocrystals. The photoluminescence spectra of ZnS nanoparticles for different capping agent concentrations reveals that the emission becomes more intensive and shift towards blue side as the size of the nanoparticles is reduced. The optical absorption spectra of the nanoparticles obtained using UV-Vis spectrophotometer shows the blue-shift with decreasing particle size. The value of band gap energy has been found to be in range 4.60-5.18 eV, which is related to the quantization effect due to small the of the particles. The measurement of exciton luminescence can be used to determine the band gap of pure ZnS crystals.

  12. 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.

  13. 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.

  14. Room temperature d0 ferromagnetism in ZnS nanocrystals

    NASA Astrophysics Data System (ADS)

    Proshchenko, Vitaly; Horoz, Sabit; Tang, Jinke; Dahnovsky, Yuri

    2016-06-01

    Room temperature ferromagnetic semiconductors have a great deal of advantage because of their easy integration into semiconductor devices. ZnS nanocrystals (NCs), bulk, and surfaces exhibit d0 ferromagnetism at room temperature. The experiments reveal that NC ferromagnetism takes place at low and room temperatures only due to Zn vacancies (S vacancies do not contribute). To understand the mechanism of d0 ferromagnetism, we introduce the surface-bulk model of a nanocrystal, which includes both surface and bulk magnetizations. The calculations demonstrate that the surface has the higher than bulk magnetization. We find the mechanism of the ferromagnetism is due to sulfur s- and p-electrons in a tetrahedral crystal field. The bulk magnetic moment increases with Zn vacancy concentration at small concentrations and then goes down at larger concentrations. A surface magnetic moment behaves differently with the concentration. It is always a monotonically rising function. We find that the total NC magnetic moment increases with the size and concentration of Zn vacancies (only low concentrations). We also study the magnetization per unit cell where we find that it decreases for the surface and increases for bulk magnetism with the NC size.

  15. Two-step synthesis of luminescent MoS(2)-ZnS hybrid quantum dots.

    PubMed

    Clark, Rhiannon M; Carey, Benjamin J; Daeneke, Torben; Atkin, Paul; Bhaskaran, Madhu; Latham, Kay; Cole, Ivan S; Kalantar-Zadeh, Kourosh

    2015-10-28

    A surfactant assisted technique has been used to promote the exfoliation of molybdenum disulphide (MoS2) in a water-ethanol mixture, to avoid the use of harsh organic solvents, whilst still producing sufficient concentration of MoS2 in suspension. The exfoliated flakes are converted into MoS2 quantum dots (QDs), through a hydrothermal procedure. Alternatively, when the flakes are processed with precursors for zinc sulphide (ZnS) synthesis, a simultaneous break-down and composite growth is achieved. The products are separated by centrifugation, into large ZnS spheres (200-300 nm) and small MoS2-ZnS hybrid QD materials (<100 nm), of which, the latter show favorable optical properties. Two concurrent photoluminescent (PL) peaks are seen at 380 and 450 nm, which are assigned to MoS2 and ZnS components of QDs, respectively. The PL emission from MoS2-ZnS QDs is of high energy and is more intense than the bare MoS2 flakes or QDs, with a quantum yield as high as 1.96%. The emission wavelength is independent from the excitation wavelength and does not change over time. Due to such properties, the developed hybrid QDs are potentially suitable for imaging and sensing applications. PMID:26399979

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

    SciTech Connect

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

    2013-04-15

    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 Fe{sup 2+} ions in the ZnS NWs was about two times larger than that of the Mn{sup 2+} or Cu{sup 2+} 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 Mn{sup 2+}/Cu{sup 2+}/Fe{sup 2+} related emission peaks can be observed in the Mn{sup 2+},Cu{sup 2+} and Fe{sup 2+} doped ZnS NWs. The ferromagnetic properties of the co-doped samples were investigated at room temperature. - graphical abstract: The stable wurtzite ZnS:TM{sup 2+} (TM=Mn, Cu, Fe) nanowires with room temperature ferromagnetism properties were obtained. The different elongation of unit cell caused by the different doped ions was observed. Highlights: ► The transition metal ions doped wurtzite ZnS nanowires were synthesized at 180 °C. ► There was no phase transformation from hexagonal to cubic even in a large quantity introduced for all the samples. ► The room temperature ferromagnetism properties of the co-doped nanowires were investigated.

  17. 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.

  18. Photoluminescence properties of ZnS nanoparticles co-doped with Pb 2+ and Cu 2+

    NASA Astrophysics Data System (ADS)

    Yang, Ping; Lü, Mengkai; Xü, Dong; Yuan, Duolong; Zhou, Guangjun

    2001-03-01

    Nanometer-scale ZnS, ZnS:Cu, ZnS:Pb, and ZnS co-doped with Cu 2+ and Pb 2+ have been synthesized using a chemical precipitation method. X-ray diffraction analysis shows that the diameter of the particles is 2-4 nm. These nanocrystals can be doped with copper and lead during the synthesis without altering the X-ray diffraction pattern. However, doping has shifted the luminescence to 530 nm (Cu 2+-doped) and 500-550 nm (co-doped with Cu 2+ and Pb 2+). In the case of ZnS:Pb nanocrystals, a relatively broad emission band (color range from blue to yellow) has been observed and its excitation wavelength shows a red shift. The photoluminescence intensity increases as the ZnS nanoparticles co-doped with Pb 2+ and Cu 2+. The results strongly suggest that doped ZnS nanocrystals, especially two kinds of metals activated ZnS nanocrystals, form a new class of luminescent materials.

  19. Band engineering of ZnS by codoping for visible-light photocatalysis

    NASA Astrophysics Data System (ADS)

    Wan, Hui; Xu, Liang; Huang, Wei-Qing; Huang, Gui-Fang; He, Chao-Ni; Zhou, Jia-Hui; Peng, P.

    2014-08-01

    Codoping is demonstrated as an efficient approach to narrow the band gap of ZnS and enhance its photocatalytic activity. Herein, we perform the density-function theory calculations of ZnS by codoping of X (N, F) with transition metals (TM = V, Cu). The band gap is reduced in four different types of codoped ZnS. In particular, CuZnFS codoping, a charge-compensated donor-acceptor pair, leads to an about 32 % reduction of the energy gap, thus extending the absorption edge to visible-light region. The band gap reduction is due to the upshift of the top valence band comprised with the delocalized hybridizing levels of Cu 3d and S 3p states, and the downshift of the bottom conduction band consisting of F 2s states. Moreover, the larger value of m e*/ m h* in CuZnFS-ZnS would result in a lower recombination rate of the electron-hole pairs. Both band gap reduction and low recombination rate are critical elements for efficient light-to-current conversion in codoped ZnS. These findings raise the prospect of using codoped ZnS with specifically engineered electronic properties in a variety of photocatalytic applications.

  20. Growth mechanism and blue shift of Mn2+ luminescence for wurtzite ZnS : Mn2+ nanowires

    NASA Astrophysics Data System (ADS)

    Cao, Jian; Yang, Jinghai; Zhang, Yongjun; Yang, Lili; Wang, Dandan; Wei, Maobin; Wang, Yaxin; Liu, Yang; Gao, Ming; Liu, Xiaoyan

    2010-02-01

    Wurtzite-type ZnS : Mn2+ nanowires were prepared by a hydrothermal method at 180 °C without any surface-active agent. The structure and morphology of the samples were characterized by x-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy and energy dispersive spectroscopy. The average diameter of the nanowires was about 10 nm. An ethylenediamine-mediated template was observed and employed to explain the growth mechanism in detail. A strong yellow-orange emission from the Mn2+ 4T1-6A1 transition was observed in the photoluminescence spectra, which exhibited blue shift as the Mn2+ doped ratio increased.

  1. Enhanced electroluminescence properties of doped ZnS nanorods formed by the self-assembly of colloidal nanocrystals

    NASA Astrophysics Data System (ADS)

    Manzoor, K.; Aditya, V.; Vadera, S. R.; Kumar, N.; Kutty, T. R. N.

    2005-07-01

    Aggregation based meso-scale self-assembly of doped semiconductor nanocrystals leading to the formation of monocrystalline nanorods showing enhanced photo- and electro-luminescence properties is reported. ˜4 nm sized, polycrystalline ZnS nanoparticles of zinc-blende (cubic) structure, doped with Cu +-Al 3+ have been aggregated in the aqueous solution and grown into nanorods of length ˜400 nm and aspect ratio ˜12. Transmission electron microscopic (TEM) images indicate crystal growth mechanisms involving particle-to-particle oriented-attachment assisted by sulphur-sulphur catenation leading to covalent-linkage. The nanorods exhibit self-assembly dependant luminescence properties such as quenching of the lattice defect-related emissions accompanied by the enhancement in the dopant-related emission, efficient low-voltage electroluminescence (EL) and super-linear voltage-brightness EL characteristics. This study demonstrates the technological importance of aggregation based self-assembly in doped semiconductor nanosystems.

  2. Spontaneous organisation of ZnS nanoparticles into monocrystalline nanorods with highly enhanced dopant-related emission

    NASA Astrophysics Data System (ADS)

    Manzoor, K.; Aditya, V.; Vadera, S. R.; Kumar, N.; Kutty, T. R. N.

    2005-07-01

    A natural self-assembly process of semiconductor nanoparticles leading to the formation of doped, monocrystalline nanorods with highly enhanced dopant-related luminescence properties is reported. ˜4 nm sized, polycrystalline ZnS nanoparticles of zinc-blende (cubic) structure, doped with Cu+-Al3+ or Mn2+ have been aggregated in the aqueous solution and grown into nanorods of length ˜400 nm and aspect ratio ˜12. Transmission electron microscopic (TEM) images indicate crystal growth mechanisms involving both Ostwald-ripening and particle-to-particle oriented-attachment. Sulphur sulphur catenation is proposed for the covalent-linkage between the attached particles. The nanorods exhibit self-assembly mediated quenching of the lattice defect-related emission accompanied by multifold enhancement in the dopant-related emission. This study demonstrates that the collective behavior of an ensemble of bare nanoparticles, under natural conditions, can lead to the formation of functionalized (doped) nanorods with enhanced luminescence properties.

  3. Highly luminescent undoped and Mn-doped ZnS nanoparticles by liquid phase pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Aneesh, P. M.; Shijeesh, M. R.; Aravind, Arun; Jayaraj, M. K.

    2014-09-01

    In this paper we report the synthesis of highly luminescent ZnS and Mn-doped ZnS nanoparticles with uniform particle size distribution by liquid phase pulsed laser ablation. The formation of nanosized ZnS crystallites was confirmed by high-resolution transmission electron microscopy (HRTEM) images. The optical properties of these nanoparticles were studied by room temperature photoluminescence (PL) spectra. The PL emission from the ZnS nanoparticles shows a sharp peak in the UV region (334 nm) corresponding to the band edge and a broad peak in the visible region which can be attributed to the sulphur vacancies, cation vacancies and surface states in the nanocrystals. The yellow emission from the Mn-doped ZnS nanoparticles can be attributed to the radiative transition between 4T1 and 6A1 levels within the 3d5 orbital of Mn2+.

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

    PubMed

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

    2016-03-21

    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. PMID:26924069

  5. Bio-functionalized water-soluble ZnS quantum dots using carboxymethylchitosan

    NASA Astrophysics Data System (ADS)

    Mansur, A. A. P.; Mansur, H. S.; Borsagli, F. G. L. M.; Ramanery, F. P.

    2015-03-01

    The major goal of this study was to develop an innovative green route for synthesizing biocompatible water-soluble luminescent QDs using chemically modified chitosan as the ligand in aqueous media. The preparation of ZnS QDs bio-functionalized by carboxymethylchitosan (CMC) was performed using a single-step aqueous colloidal process at room temperature. The results showed that water-dispersible ZnS nanocrystals capped by CMC were produced within the quantum-size confinement regime. Moreover, the luminescent properties of ZnS QDs were significantly affected by the pH during the synthesis due to the size distribution of the nanoparticles and their density of surface states.

  6. Large-scale synthesis well-dispersed ZnS microspheres and their photoluminescence, photocatalysis properties

    SciTech Connect

    Wang Xinjun Wan Fuquan; Han Kun; Chai Chunxia; Jiang Kai

    2008-12-15

    Large-scale and well-dispersed ZnS microspheres were prepared by a simple hydrothermal method using ZnSO{sub 4}{center_dot}7H{sub 2}O and SC(NH{sub 2}){sub 2} as main original reactant and poly(vinyl pyrrolidone) (PVP)(Mr {approx} 10,000) as the surfactant. The products were characterized by X-Ray diffraction, scanning electron microscopy and transmission electron microscopy. The growth process involves a special oriented aggregation of PVP stabilized ZnS nanoparticles into microspheres of 1.5 {approx} 2.0 {mu}m in sizes. The photocatalytic activity of as-prepared ZnS microsphere was evaluated by using methylene blue (MB) as a model organic compound. The optical properties of the products were also examined by means of photoluminescence (PL) spectroscopy.

  7. Effects of Cu Dopant on Lattice and Optical Properties of ZnS Quantum Dots.

    PubMed

    Shuhua, Lu; Aiji, Wang; Tingfang, Chen; Yinshu, Wang

    2016-04-01

    Doped and undoped ZnS colloidal nanocrystals have drawn much attention due to their versatile applications in the fields of optoelectronics and biotechnology. In this paper, Cu doped ZnS quantum dots were synthesized via the simple thermolysis of ethylxanthate salts. The lattice and optical properties of the nanocrystals were then studied in detail. The quantum dot lattice contracted linearly between Cu concentrations of 0.2-2%, while it continued to contract more gradually as Cu concentrations were further increased from 4 to 6%, due in part to the Cu ions located on the surface of the ZnS lattice. Cu incorporation induces a long tail in absorption at long wavelengths. The PL spectrum shows a red shift at first, and then a blue shift with increases in Cu concentration. Cu doped at low concentrations (0.2-1%) enhanced the emission, while high Cu concentrations (2-6%) quenched emissions. PMID:27451716

  8. 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.

  9. Efficient photoelectric converters of ultraviolet radiation based on ZnS and CdS with low-resistivity surface layers

    SciTech Connect

    Bobrenko, Yu. N.; Pavelets, S. Yu. Pavelets, A. M.; Kiselyuk, M. P.; Yaroshenko, N. V.

    2010-08-15

    The formation of thin high- and low-resistivity layers in the space-charge region of Cu{sub 1.8}S-CdS and Cu{sub 1.8}S-ZnS surface-barrier photoconverter structures leads to a considerable increase in photosensitivity and a reduction in the dark tunneling-recombination currents. Highly efficient and stable ultraviolet photoconverters based on CdS and ZnS were obtained, and their electrical and photoelectrical properties were studied. The main operational parameters of the photoconverters are reported.

  10. Chemical vapor deposition synthesis and photoluminescence properties of ZnS hollow microspheres

    SciTech Connect

    Pi Zhengbang; Su Xiaolu; Yang Chao; Tian Xike Pei Fang; Zhang Suxin; Zhen Jianhua

    2008-08-04

    ZnS hollow microspheres were prepared via a facile template-free chemical vapor deposition (CVD) route using metallic zinc powders and sulphur sublimed as reactants. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectrometer (EDX). The results showed that the as-prepared ZnS hollow spheres had uniform size about 4-8 {mu}m in diameter. The growth mechanism of such interesting was discussed. The optical property of the products was also recorded by means of photoluminescence (PL) spectroscopy.

  11. Surface Functionalization of ZnO Photocatalysts with Monolayer ZnS

    SciTech Connect

    Lahiri,J.; Batzill, M.

    2008-01-01

    A fundamental investigation of the interface properties of coupled semiconductor photocatalysts in view of enhancing visible light activity is presented. We show by photoemission spectroscopy that modification of ZnO with submonolayer films of ZnS, two materials with band gaps larger than 3.4 eV, results in an effective surface band gap narrowing to 2.8 eV. This reduces the photoexcitation threshold energy and thus potentially enhances the solar energy conversion capabilities of such a heterostructure photocatalysts. Furthermore, the characterization of the space charge region and work function of ZnS modified ZnO indicate improved surface properties for enhancing photocatalytic activity.

  12. Optical investigations of blue shift in ZnS quantum dots

    NASA Astrophysics Data System (ADS)

    Al-Douri, Y.; Verma, K. D.; Prakash, Deo

    2015-12-01

    ZnS quantum dots were synthesized using sulfur source of sodium sulphide and mercaptoethanol via chemical bath deposition technique. The synthesized ZnS QDs were analyzed and characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and UV-visible (UV-vis) spectrophotometry. The average particle size goes down to 1.9 nm as capping agent concentration increases and corresponding absorption coefficient peak goes down to 265 nm. The blue shift within absorption-wavelength was elaborated. The refractive index and optical dielectric constant are calculated. A correlation between energy gap and absorption coefficient aside and particle size another side is discussed.

  13. 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

  14. Investigation of primary crystallite sizes in nanocrystalline ZnS powders: comparison of microwave assisted with conventional synthesis routes.

    PubMed

    Rath, Thomas; Kunert, Birgit; Resel, Roland; Fritz-Popovski, Gerhard; Saf, Robert; Trimmel, Gregor

    2008-04-21

    ZnS powders with primary crystallite sizes of only a few nanometers were prepared by three different synthesis routes at temperatures below 130 degrees C. The reaction of zinc acetate dihydrate with thioacetamide (TAA) in the presence of pyridine and triphenylphosphite (TPP) was carried out using either conventional heating or microwave heating. The obtained powders exhibit sphalerite structure as determined by X-ray diffraction (XRD). The primary crystallites have diameters between 1 and 7 nm obtained by XRD. Small angle X-ray scattering (SAXS) measurements were analyzed by the model-free inverse Fourier-transformation approach, as well as by a hard sphere-model from which particle size and polydispersity were extracted. The particle sizes by SAXS are in good agreement with the primary crystallite sizes obtained by XRD. It has been found that an increasing amount of sulfur and/or using microwave heating increases crystallite sizes. The presence of TPP decreases the particle sizes but no significant influence on the TPP concentration was observed. In the alternative third preparation route, hexamethyldisilathiane (HMDST) was used as precipitation reagent at ambient temperature, which leads to the smallest crystallite sizes of only 1 nm together with low polydispersities. Scanning electron microscopy, dynamic light scattering and UV-vis spectroscopy showed that all three synthesis routes lead to ZnS powders with aggregate sizes between 650 and 1200 nm. Both of the TAA-precipitation routes lead to spherical agglomerates which consist of spherical substructures, whereas the HMDST agglomerates are assembled from elongated objects. PMID:18351732

  15. 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.

  16. 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.

  17. Study of the Vibrational Spectra of the Mixed Crystal ZnS1-xSex

    NASA Astrophysics Data System (ADS)

    Basak, Tista; Rao, Mala N.; Chaplot, S. L.

    2011-07-01

    A simple transferable potential model has been employed to study the vibrational mode behavior of the mixed system ZnS1-xSex as a function of concentration and pressure. Further, the existence of a localized resonance mode has also been confirmed, in agreement with experimental data from Raman scattering.

  18. Morphology-controlled synthesis of ZnS nanostructures via single-source approaches

    SciTech Connect

    Han, Qiaofeng; Qiang, Fei; Wang, Meijuan; Zhu, Junwu; Lu, Lude; Wang, Xin

    2010-07-15

    ZnS nanoparticles of various morphologies, including hollow or solid spherical, and polyhedral shape, were synthesized from single-source precursor Zn(S{sub 2}COC{sub 2}H{sub 5}){sub 2} without using a surfactant or template. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy. The results indicate that ZnS hollow and solid spheres assembled by nanoparticles can be easily generated by the solution phase thermalysis of Zn(S{sub 2}COC{sub 2}H{sub 5}){sub 2} at 80 {sup o}C using N, N-dimethylformamide (DMF) and ethylene glycol (EG) or water as solvents, respectively, whereas solvothermal process of the same precursor led to ZnS nanoparticles of polyhedral shape with an average size of 120 nm. The optical properties of these ZnS nanostructures were investigated by room-temperature luminescence and UV-vis diffuse reflectance spectra.

  19. Selective Sulfidation of Lead Smelter Slag with Pyrite and Flotation Behavior of Synthetic ZnS

    NASA Astrophysics Data System (ADS)

    Han, Junwei; Liu, Wei; Wang, Dawei; Jiao, Fen; Zhang, Tianfu; Qin, Wenqing

    2016-08-01

    The selective sulfidation of lead smelter slag with pyrite in the presence of carbon and Na salts, and the flotation behavior of synthetic ZnS were studied. The effects of temperature, time, pyrite dosage, Na salts, and carbon additions were investigated based on thermodynamic calculation, and correspondingly, the growth mechanism of ZnS particles was studied at high temperatures. The results indicated that the zinc in lead smelter slag was selectively converted into zinc sulfides by sulfidation roasting. The sulfidation degree of zinc was increased until the temperature, time, pyrite, and carbon dosages reached their optimum values, under which it was more than 95 pct. The growth of ZnS particles largely depended upon roasting temperature, and the ZnS grains were significantly increased above 1373 K (1100 °C) due to the formation of a liquid phase. After the roasting, the zinc sulfides generated had a good floatability, and 88.34 pct of zinc was recovered by conventional flotation.

  20. 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.

  1. Optical characterization of ZnS coated CdS nanorods embedded in liquid crystals

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    The photoluminescence (PL) emission intensity of ZnS coated CdS nanorods, represented by CdS/ZnS system, have been enhanced in presence of liquid crystals (LC) and the enhancement strongly depends on concentration of LC. The highly light scattering liquid crystalline phase causes the enhancement in PL intensity. It is also observed that the PL intensity of CdS nanorods enhances with the coating of ZnS material. This enhancement in PL intensity is ascribed by the fact that the high optical band gap ZnS material prevents the tunneling of the charge carriers from the core CdS nanorods and passivated nonradiative recombination sites which are existed on the core surfaces. Finally, 5 fold enhancements in PL intensity of CdS nanorods have been observed by coating with ZnS material and then embedding in LC. We have also observed the red shift in emission energy band of CdS/ZnS system embedded in LC. This study will provide a possible way to develop smart optoelectronics devices.

  2. Photoacoustic and Photoluminescence Characterization of Passivated and Unpassivated Mn-Doped ZnS Nanoparticles

    NASA Astrophysics Data System (ADS)

    Cruz, Almira Briones; Shen, Qing; Toyoda, Taro

    2005-06-01

    In this study, passivated and unpassivated nanocrystalline ZnS with varying Mn2+ concentrations (ZnS:Mn) were synthesized and their photoacoustic (PA) and photoluminescence (PL) characteristics were studied. The PA intensity peak for the nanocrystalline ZnS was found to be blue-shifted compared with that for the bulk material due to quantum confinement effects. The difference of the PA signals of doped ZnS and undoped ZnS yielded the Mn2+ optical absorption spectra. The intensity of the PA peak increased linearly with Mn concentration. The PL spectra showed a peak position at 2.08 eV corresponding to the d-d transition of Mn2+. For the unpassivated sample, a decrease in the PL intensities for higher Mn concentrations was observed. This could be attributed to concentration quenching. Addition of acrylic acid as a passivator led to an increase in PL intensity for all Mn concentrations and prevented the decrease in the PL intensity for higher Mn concentrations. These could be attributed to the surface passivation, which reduces the nonradiative recombination probabilities, thus increasing PL intensities.

  3. Microstructure and cathodoluminescence study of sprayed Al and Sn doped ZnS thin films

    NASA Astrophysics Data System (ADS)

    El Hichou, A.; Addou, M.; Bubendorff, J. L.; Ebothé, J.; El Idrissi, B.; Troyon, M.

    2004-02-01

    Here we report on the study of ZnS and X-doped ZnS (with 4 at% of X = Al, Sn) thin films, prepared by spray pyrolysis technique using chloride precursors. Cathodoluminescence imaging and spectroscopy, x-ray diffraction, x-ray energy dispersive spectrometry and spectrophotometry have been used for their characterization. Deposited at their optimal substrate temperature (Ts = 773 K), these films are polycrystalline and consist of mixed hexagonal (agr) and cubic (bgr) phases with a predominance of the cubic phase. Their growth is preferentially oriented along the (111)bgr direction and their optical bandgap always remains close to 3.56 eV regardless of the sample considered. The cathodoluminescence spectra of ZnS and Al-ZnS films are similar and are characterized by a blue emission peak at 407 nm (3.05 eV) and a broad blue-green one located at 524 nm (2.36 eV) due to the presence of chlorine. The insertion of Sn2+ ions in the ZnS material leads to the formation of the SnCl2 compound and to the disappearance of the blue-green emission associated with Cl ionized donors.

  4. Selective Sulfidation of Lead Smelter Slag with Pyrite and Flotation Behavior of Synthetic ZnS

    NASA Astrophysics Data System (ADS)

    Han, Junwei; Liu, Wei; Wang, Dawei; Jiao, Fen; Zhang, Tianfu; Qin, Wenqing

    2016-05-01

    The selective sulfidation of lead smelter slag with pyrite in the presence of carbon and Na salts, and the flotation behavior of synthetic ZnS were studied. The effects of temperature, time, pyrite dosage, Na salts, and carbon additions were investigated based on thermodynamic calculation, and correspondingly, the growth mechanism of ZnS particles was studied at high temperatures. The results indicated that the zinc in lead smelter slag was selectively converted into zinc sulfides by sulfidation roasting. The sulfidation degree of zinc was increased until the temperature, time, pyrite, and carbon dosages reached their optimum values, under which it was more than 95 pct. The growth of ZnS particles largely depended upon roasting temperature, and the ZnS grains were significantly increased above 1373 K (1100 °C) due to the formation of a liquid phase. After the roasting, the zinc sulfides generated had a good floatability, and 88.34 pct of zinc was recovered by conventional flotation.

  5. 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.

  6. Two-step synthesis of luminescent MoS2-ZnS hybrid quantum dots

    NASA Astrophysics Data System (ADS)

    Clark, Rhiannon M.; Carey, Benjamin J.; Daeneke, Torben; Atkin, Paul; Bhaskaran, Madhu; Latham, Kay; Cole, Ivan S.; Kalantar-Zadeh, Kourosh

    2015-10-01

    A surfactant assisted technique has been used to promote the exfoliation of molybdenum disulphide (MoS2) in a water-ethanol mixture, to avoid the use of harsh organic solvents, whilst still producing sufficient concentration of MoS2 in suspension. The exfoliated flakes are converted into MoS2 quantum dots (QDs), through a hydrothermal procedure. Alternatively, when the flakes are processed with precursors for zinc sulphide (ZnS) synthesis, a simultaneous break-down and composite growth is achieved. The products are separated by centrifugation, into large ZnS spheres (200-300 nm) and small MoS2-ZnS hybrid QD materials (<100 nm), of which, the latter show favorable optical properties. Two concurrent photoluminescent (PL) peaks are seen at 380 and 450 nm, which are assigned to MoS2 and ZnS components of QDs, respectively. The PL emission from MoS2-ZnS QDs is of high energy and is more intense than the bare MoS2 flakes or QDs, with a quantum yield as high as 1.96%. The emission wavelength is independent from the excitation wavelength and does not change over time. Due to such properties, the developed hybrid QDs are potentially suitable for imaging and sensing applications.A surfactant assisted technique has been used to promote the exfoliation of molybdenum disulphide (MoS2) in a water-ethanol mixture, to avoid the use of harsh organic solvents, whilst still producing sufficient concentration of MoS2 in suspension. The exfoliated flakes are converted into MoS2 quantum dots (QDs), through a hydrothermal procedure. Alternatively, when the flakes are processed with precursors for zinc sulphide (ZnS) synthesis, a simultaneous break-down and composite growth is achieved. The products are separated by centrifugation, into large ZnS spheres (200-300 nm) and small MoS2-ZnS hybrid QD materials (<100 nm), of which, the latter show favorable optical properties. Two concurrent photoluminescent (PL) peaks are seen at 380 and 450 nm, which are assigned to MoS2 and ZnS components of

  7. New observations on the luminescence decay lifetime of Mn2+ in ZnS :Mn2+ nanoparticles

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Aguekian, Vadim F.; Vassiliev, Nikolai; Serov, A. Yu.; Filosofov, N. G.

    2005-09-01

    A fast decay emission peaking at 645nm with a decay lifetime within the experimental resolution of 0.14μs is observed in ZnS :Mn2+ nanoparticles. This short-lived signal is also observed in pure ZnS and MgS :Eu3+ nanoparticles, which has nothing to do with Mn2+-doped ions but is from the deep trap states of the host materials. The short-lived component decreases in intensity relative to the Mn2+ emission at higher excitation powers, while it increases in intensity at low temperatures and shifts to longer wavelengths at longer time delays. Our observations demonstrated further that the emission of Mn2+ in ZnS :Mn2+ nanoparticles behaves basically the same as in bulk ZnS :Mn2+; the fast decay component is actually from the intrinsic and defect-related emission in sulfide compounds.

  8. Evolution of ZnS Nanoparticles via Facile CTAB Aqueous Micellar Solution Route: A Study on Controlling Parameters

    PubMed Central

    2009-01-01

    Synthesis of semiconductor nanoparticles with new photophysical properties is an area of special interest. Here, we report synthesis of ZnS nanoparticles in aqueous micellar solution of Cetyltrimethylammonium bromide (CTAB). The size of ZnS nanodispersions in aqueous micellar solution has been calculated using UV-vis spectroscopy, XRD, SAXS, and TEM measurements. The nanoparticles are found to be polydispersed in the size range 6–15 nm. Surface passivation by surfactant molecules has been studied using FTIR and fluorescence spectroscopy. The nanoparticles have been better stabilized using CTAB concentration above 1 mM. Furthermore, room temperature absorption and fluorescence emission of powdered ZnS nanoparticles after redispersion in water have also been investigated and compared with that in aqueous micellar solution. Time-dependent absorption behavior reveals that the formation of ZnS nanoparticles depends on CTAB concentration and was complete within 25 min. PMID:20592958

  9. 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.

  10. 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

    2016-08-01

    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.

  11. 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.

  12. Magnetic properties of first-row element-doped ZnS semiconductors: A density functional theory investigation

    NASA Astrophysics Data System (ADS)

    Long, Run; English, Niall J.

    2009-09-01

    Based on first-principles calculations, we have investigated the magnetic properties of the first-row element-doped ZnS semiconductors. Calculations reveal that Be, B, and C dopants can induce magnetism while N cannot lead to spin polarization in ZnS. A possible explanation has been rationalized from the elements’ electronegativity and interaction between dopant and host atoms. The total magnetic moments are 2.00, 3.16, and 2.38μB per 2×2×2 supercell for Be, B, and C doping, respectively, and ferromagnetic coupling is generally observed in these cases. The ferromagnetism of Be-, B-, and C-doped ZnS can be explained by hole-mediated s-p or p-p interactions’ coupling mechanisms. The clustering effect was found to be present in Be-, B-, and C-doped ZnS but the degree is more obvious in the former two cases than in the latter case. Analysis revealed that C-doped ZnS displays better potential ferromagnetic behavior than Be- and B-doped ZnS due to its semimetallic characteristics.

  13. Carrier scattering mechanisms in p-type transparent copper-alloyed ZnS: Crystalline vs. amorphous

    NASA Astrophysics Data System (ADS)

    Woods-Robinson, Rachel; Faghaninia, Alireza; Cooper, Jason K.; Pham, Hieu H.; Lo, Cynthia; Wang, Lin-Wang; Ager, Joel W.

    2015-03-01

    Crystalline (wurtzite and sphalerite) and amorphous forms of copper-alloyed ZnS (CuxZn1-xS) are p-type conducting transparent thin film materials with near-record figures of merit for applications in photovoltaics and optoelectronics. Remarkably, the conductivity of amorphous CuxZn1-xS, 42 S/cm at x = 0.30, is nearly as high as crystalline CuxZn1-xS (54 S/cm at x = 0.21). This contrasts with typical observations of poorer carrier transport in amorphous materials. By combining experiment and computation, we investigate the defect physics underlying hole transport in amorphous and crystalline CuxZn1-xS. Structural probes (EXAFS, TEM and wide-angle XRD) are used to determine bonding characteristics and lattice order, and serve as inputs to ab initio hybrid functional HSE calculations of the electronic band structure. Hall effect, temperature dependent conductivity (15K to 500K), and XPS valence band measurements and ab initio calculations show that hole conduction occurs in a hybridized S-3p and Cu-3d valence band for amorphous and crystalline films. The hole scattering mechanisms which limit the conductivity will be discussed in the context of theoretical carrier transport model based on Boltzmann transport equation, ab initio calculated band structure, and phonon dispersion.

  14. 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.

  15. 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; Synergetic Innovation Center of Chemical Science and Engineering, Tianjin 300071 ; 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.

  16. Fabrication of conformal ZnS domes by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Goela, Jitendra S.; Askinazi, Joel

    1999-07-01

    Aspheric shape ZnS domes were fabricated by a scalable and cost-effective chemical vapor deposition (CVD) process to demonstrate the feasibility of producing aerodynamic domes that conform to the shape of the missile body. These domes provide enhanced performance by substantially reducing the missile drag, although they also present issues of CVD deposition, optical fabrication to the required figure and finish, particularly the inside surface, and metrology. Domes were fabricated on 'male' mandrels in a CVD chamber to produce net-shape or precision replicated inside surface and then diamond turned to produce surfaces with figure of a fraction of a wave and finish of 180 angstrom RMS. Important issues involved in near-net-shaping and precision replication of ZnS domes are discussed and data on mandrel and release coating materials, degree of replication achieved and mandrel durability are presented.

  17. Rational synthetic strategy: From ZnO nanorods to ZnS nanotubes

    NASA Astrophysics Data System (ADS)

    Yi, Ran; Qiu, Guanzhou; Liu, Xiaohe

    2009-10-01

    We demonstrate here that ZnS nanotubes can be successfully synthesized via a facile conversion process from ZnO nanorods precursors. During the conversion process, ZnO nanorods are first prepared as sacrificial templates and then converted into tubular ZnO/ZnS core/shell naonocomposites through a hydrothermal sulfidation treatment by using thioacetamide (TAA) as sulfur source. ZnS nanotubes are finally obtained through the removal of ZnO cores of tubular ZnO/ZnS core/shell naonocomposites by KOH treatment. The photoluminescence (PL) characterization of the as-prepared products shows much enhanced PL emission of tubular ZnO/ZnS core/shell nanocomposites compared with their component counterparts. The probable mechanism of conversion process is also proposed based on the experimental results.

  18. Synthesis and characterization of ZnS nanowires by AOT micelle-template inducing reaction

    SciTech Connect

    Lv Ruitao; Cao Chuanbao; Zhu Hesun

    2004-08-03

    ZnS nanowires, with diameters around 30 nm and lengths up to 2.5 {mu}m, had been successfully synthesized from solutions containing an anionic surfactant, sodium bis(2-ethylhexyl)sulfosuccinate (AOT). Powder X-ray diffraction (XRD) pattern, energy-dispersive X-ray spectroscopy (EDS) and selected-area electron diffraction (SAED) pattern indicated that the product was pure polycrystalline cubic-phase {beta}-ZnS. The morphology and size of the as-synthesized product were determined by the transmission electron microscopy (TEM). The effects of some of the key reaction parameters (such as the ratio of surfactant to water, the reactant concentration and reaction temperature, etc.) had been explored in this paper. A growth mechanism of ZnS nanowires by micelle-template inducing reaction was also proposed.

  19. High-resolution three-photon biomedical imaging using doped ZnS nanocrystals

    NASA Astrophysics Data System (ADS)

    Yu, Jung Ho; Kwon, Seung-Hae; Petrášek, Zdeněk; Park, Ok Kyu; Jun, Samuel Woojoo; Shin, Kwangsoo; Choi, Moonkee; Park, Yong Il; Park, Kyeongsoon; Na, Hyon Bin; Lee, Nohyun; Lee, Dong Won; Kim, Jeong Hyun; Schwille, Petra; Hyeon, Taeghwan

    2013-04-01

    Three-photon excitation is a process that occurs when three photons are simultaneously absorbed within a luminophore for photo-excitation through virtual states. Although the imaging application of this process was proposed decades ago, three-photon biomedical imaging has not been realized yet owing to its intrinsic low quantum efficiency. We herein report on high-resolution in vitro and in vivo imaging by combining three-photon excitation of ZnS nanocrystals and visible emission from Mn2+ dopants. The large three-photon cross-section of the nanocrystals enabled targeted cellular imaging under high spatial resolution, approaching the theoretical limit of three-photon excitation. Owing to the enhanced Stokes shift achieved through nanocrystal doping, the three-photon process was successfully applied to high-resolution in vivo tumour-targeted imaging. Furthermore, the biocompatibility of ZnS nanocrystals offers great potential for clinical applications of three-photon imaging.

  20. Low resistivity Al-doped ZnS grown by MOVPE

    NASA Astrophysics Data System (ADS)

    Yasuda, T.; Hara, K.; Kukimoto, H.

    1986-09-01

    Low resistivity Al-doped ZnS layers have been grown by low pressure MOVPE using an adduct of diethylzinc-diethylsulfide (DEZn-DES) and H 2S as source materials and triethylaluminum (TEAl) as a dopant. The lowest resistivity achieved in this study is 3 × 10 -2 Ω cm for layers grown at a temperature of 350°C and at a TEAl transport rate ratio of {[TEAl]}/{[DEZn-DES]} = 4 × 10 -3.

  1. 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. PMID:26334003

  2. Monte Carlo study of electron initiated impact ionization in bulk zincblende and wurtzite phase ZnS

    NASA Astrophysics Data System (ADS)

    Bellotti, E.; Brennan, K. F.; Wang, R.; Ruden, P. P.

    1998-05-01

    This paper presents a theoretical study of the high field electronic transport properties of the cubic and hexagonal phases of zinc sulfide (ZnS) using an ensemble Monte Carlo method. Essential features of the model are the inclusion of realistic energy band structures calculated from a local pseudopotential method and numerically calculated impact ionization transition rates. The polar optical phonon scattering rate has also been computed numerically from the band structure. The relevant transport quantities have been computed for field values between 100 kV/cm and 2 MV/cm. On the basis of these calculations it is predicted that the electron distribution is cooler and the average energy lower in the wurtzite phase than in the zincblende phase over the entire field range examined. The difference in average energy between the two phases becomes pronounced for field magnitudes above 1 MV/cm while it is smaller in the field range between 700 kV/cm and 1 MV/cm. As a result, the ionization coefficients are expected to be higher in the zincblende phase than in the wurtzite phase. This can be attributed to differences in the density of states between the two polytypes. The quantum yield has also been computed. It is found that even though the threshold for impact ionization is relatively hard in both polytypes, the threshold for the wurtzite phase is harder than the threshold for the zincblende phase.

  3. 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.

  4. 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. PMID:26524256

  5. Bright, stable, and water-soluble CuInS2/ZnS nanocrystals passivated by cetyltrimethylammonium bromide

    NASA Astrophysics Data System (ADS)

    Lee, Jun; Han, Chang-Soo

    2015-03-01

    We report a highly bright and stable aqueous dispersion of CuInS2/ZnS (CIS/ZnS) nanocrystals (NCs) using surfactant-assisted microemulsion and cold treatment. CIS/ZnS NCs were facilely synthesized via a stepwise, consecutive hybrid flow reactor approach. To stabilize the optical properties of hydrophobic CIS/ZnS NCs, cetyltrimethylammonium bromide (CTAB) was chosen as a matrix for aqueous phase transfer. As the result, a high quantum yield (QY) of 56.0% and excellent photostability were acquired in aqueous media. For removing excessive surfactants, cold treatment (4°C) of the CTAB-water solution was adopted to prevent further agglomeration of CIS/ZnS NCs, which could secure high stability over 6 months (less 2% reduction in QY). The optical features and structure of the obtained CTAB stabilized CIS/ZnS (CTAB-CIS/ZnS) NCs have been characterized by UV-vis and photoluminescence (PL) spectroscopies, XRD, XPS, EDX, and TEM. The high stability and PL of water soluble CTAB-CIS/ZnS NCs suggest their potential in nanoelectronics and bioapplications.

  6. Band Gap Reduction in ZnO and ZnS by Creating Layered ZnO/ZnS Heterostructures.

    PubMed

    Torabi, Amin; Staroverov, Viktor N

    2015-06-01

    Wurtzite-type zinc oxide (ZnO) and zinc sulfide (ZnS) have electronic band gaps that are too large for light-harvesting applications. Using screened hybrid density-functional methods, we show that the band gaps of ZnO and ZnS can be dramatically reduced by creating layered ZnO/ZnS bulk heterostructures in which m contiguous monolayers of ZnO alternate with n contiguous monolayers of ZnS. In particular, the band gap decreases by roughly 40% upon substitution of every tenth monolayer of ZnS with a monolayer of ZnO (and vice versa) and becomes as low as 1.5 eV for heterostructures with m = 3 to m = 9 contiguous monolayers of ZnO alternating with n = 10 - m monolayers of ZnS. The predicted band gaps of layered ZnO/ZnS heterostructures span the entire visible spectrum, which makes these materials suitable for photovoltaic device engineering. PMID:26266505

  7. Polymer and surfactant-templated synthesis of hollow and porous ZnS nano- and microspheres in a spray pyrolysis reactor.

    PubMed

    Sharma, Munish K; Rohani, Parham; Liu, Sha; Kaus, Mark; Swihart, Mark T

    2015-01-13

    Nanostructured zinc sulfide can provide unique photonic, electronic, and catalytic properties that are of interest for applications ranging from bioimaging to photocatalysis. Here we report an easily controllable continuous method to produce porous and hollow ZnS nano- and microspheres. We used poly(ethylene glycol) methyl ether (PEG), polyvinylpyrrolidone (PVP), ethylene oxide/propylene oxide block copolymer (Pluronic F-38), and cetyltrimethylammonium bromide (CTAB) as templates to synthesize ZnS nano- and microspheres with controlled internal morphology in a spray pyrolysis process, starting from an aqueous solution of chemical precursors and templating agents. Spherical particles were produced by droplet-to-particle conversion of droplets. Zinc acetate and thiourea, used here as precursors for ZnS, react in solution to form bis-thiourea zinc acetate (BTZA), which precipitates with the evaporation of solvent. Upon further heating, BTZA decomposes to yield ZnS. During solvent evaporation, PEG and Pluronic precipitate after BTZA, driving formation of a shell of ZnS and a hollow core. In contrast, PVP and CTAB interact strongly with BTZA and ZnS, such that the PVP and ZnS remain intermixed. After evaporation of solvent, the templating agents can be pyrolyzed at high temperature to leave behind porous or hollow ZnS microspheres composed of many much smaller nanocrystals. PMID:25547202

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

    PubMed

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

    2012-02-21

    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. PMID:22241243

  9. Design and fabrication of multi-layers infrared antireflection coating consisting of ZnS and Ge on ZnS substrate

    NASA Astrophysics Data System (ADS)

    Zarei Moghadam, R.; Ahmadvand, H.; Jannesari, M.

    2016-03-01

    We have designed, fabricated and characterized a multi-layers antireflection coating on multispectral ZnS substrate, suitable for the infrared range of 8-12 μm. The 4-layers coating (Ge/ZnS/Ge/ZnS) with optimized thicknesses was fabricated by PVD technique and studied by FTIR, nanoindentation and AFM. From FTIR spectroscopy it was found that, in the wavelength range of 8-12 μm, the average transmittance of the double-side coated sample increases by about 26% and its maximum reaches about 98%. To improve the mechanical hardness, a bilayer of Y2O3/carbon was deposited on the coating. Nanoindentation test shows that the coating enhances the mechanical properties. The final coating have successfully passed durability and environmental tests.

  10. The pronounced role of impurity phases in the optical properties of Mn catalyzed ZnS nanostructures

    NASA Astrophysics Data System (ADS)

    Nosheen, U.; Shehzad, M. A.; Rehman, S.; Hafeez, M.; Khan, M. A.; Manzoor, U.; Bhatti, A. S.

    2015-09-01

    We report the effect of Mn self-doping in Mn catalyzed ZnS nanostructures grown via vapor liquid solid mechanism, which also resulted in the formation of additional impurity minority phases like ZnO and MnO2. The synthesized ZnS nanostructures were subsequently annealed in the range of 500 °C - 700 °C in an inert environment to remove impurity phases and enhance the incorporation of dopant. Room temperature photoluminescence showed strong defect assisted luminescence. It was observed that green emission due to intrinsic defects of ZnS nanostructures was reduced in magnitude and Mn related orange/red luminescence increased in magnitude in nanostructures annealed at high temperature. The presence of impurity phases led to the observation of surface optical and interface phonon modes as observed in the Raman spectroscopy. Dielectric continuum and phonon confinement models were employed to determine the correlation lengths of the optical phonon modes.

  11. 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.

  12. 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).

  13. Biomolecularly capped uniformly sized nanocrystalline materials: glutathione-capped ZnS nanocrystals

    NASA Astrophysics Data System (ADS)

    Torres-Martínez, Claudia L.; Nguyen, Liem; Kho, Richard; Bae, Weon; Bozhilov, Krassimir; Klimov, Victor; Mehra, Rajesh K.

    1999-09-01

    Micro-organisms such as bacteria and yeasts form CdS to detoxify toxic cadmium ions. Frequently, CdS particles formed in yeasts and bacteria were found to be associated with specific biomolecules. It was later determined that these biomolecules were present at the surface of CdS. This coating caused a restriction in the growth of CdS particles and resulted in the formation of nanometre-sized semiconductors (NCs) that exhibited typical quantum confinement properties. Glutathione and related phytochelatin peptides were shown to be the biomolecules that capped CdS nanocrystallites synthesized by yeasts Candida glabrata and Schizosaccharomyces pombe. Although early studies showed the existence of specific biochemical pathways for the synthesis of biomolecularly capped CdS NCs, these NCs could be formed in vitro under appropriate conditions. We have recently shown that cysteine and cysteine-containing peptides such as glutathione and phytochelatins can be used in vitro to dictate the formation of discrete sizes of CdS and ZnS nanocrystals. We have evolved protocols for the synthesis of ZnS or CdS nanocrystals within a narrow size distribution range. These procedures involve three steps: (1) formation of metallo-complexes of cysteine or cysteine-containing peptides, (2) introduction of stoichiometric amounts of inorganic sulfide into the metallo-complexes to initiate the formation of nanocrystallites and finally (3) size-selective precipitation of NCs with ethanol in the presence of Na+. The resulting NCs were characterized by optical spectroscopy, high-resolution transmission electron microscopy (HRTEM), x-ray diffraction and electron diffraction. HRTEM showed that the diameter of the ZnS-glutathione nanocrystals was 3.45+/-0.5 nm. X-ray diffraction and electron diffraction analyses indicated ZnS-glutathione to be hexagonal. Photocatalytic studies suggest that glutathione-capped ZnS nanocrystals prepared by our procedure are highly efficient in degrading a test model

  14. 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

  15. Energy levels and zero field splitting parameter for Fe{sup 2+} doped in ZnS

    SciTech Connect

    Ivaşcu, Simona

    2013-11-13

    The aim of present paper is to report the results on the modeling of the crystal field parameters of Fe{sup 2+} 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 Fe{sup 2+}:ZnS system. The obtained results were disscused and compared with experimental data. Satisfactory agreement have been obtained.

  16. 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.

  17. 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.

  18. Ion beam synthesis of CdS, ZnS, and PbS compound semiconductor nanocrystals

    SciTech Connect

    White, C.W.; Budai, J.D.; Meldrum, A.L.

    1997-12-01

    Sequential ion implantation followed by thermal annealing has been used to form encapsulated CdS, ZnS, and PbS nanocrystals in SiO{sub 2} and Al{sub 2}O{sub 3} matrices. In SiO{sub 2}, nanoparticles are nearly spherical and randomly oriented, and ZnS and PbS nanocrystals exhibit a bimodal size distribution. In Al{sub 2}O{sub 3}, nanoparticles are faceted and coherent with the matrix. Initial photoluminescence (PL) results are presented.

  19. Solvothermal synthesis of uniform hexagonal-phase ZnS nanorods using a single-source molecular precursor

    SciTech Connect

    Zhang Yongcai . E-mail: zhangyc@yzu.edu.cn; Wang Guiyun; Hu Xiaoya; Chen Weiwei

    2006-10-12

    Pure and uniform hexagonal-phase ZnS nanorods with quantum confinement effect were synthesized by solvothermal decomposition of an air-stable, easily obtained single-source molecular precursor (zinc diethyldithiocarbamate, Zn-(DDTC){sub 2}) in hydrazine hydrate aqueous solutions at 150-200 deg. C, and characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and UV-vis absorption spectra. The possible formation mechanism of one-dimensional ZnS nanostructure in the present system was also briefly discussed.

  20. Optical and Structural Investigations of Manganese Doped ZnS/SiO2 Core-Shell Nanostructure

    NASA Astrophysics Data System (ADS)

    Sana, Prabha; Verma, Shammi; Malik, M. M.

    2015-03-01

    The paper reports room temperature synthesis of wurtzite type manganese doped ZnS nanostructures via colloidal technique. The reaction procedure found to play an important role in the crystal growth of ZnS. Surface encapsulation of ZnS by silica (SiO2) provides effective approach for uniform coating, where 3-Mercaptopropyl Tri methoxysilane (MPS) has been used for silica source as a capping molecule. The obtained silica coated ZnS nanocrystals were well dispersed with hexagonal wurtzite structure of core-shell particles size of about 15 nm. Aggregation of these nanoparticles has been promoted to special shaped structures, which are crystals of 8H wurtzite with prominent pyramidal morphology with curved faces. Growth phenomena of this wurtzite polytype of homologous series 8H is based on screw dislocations and exhibited optimal photoluminescence (PL) spectra.

  1. Recent developments in highly durable protective/antireflection coatings for Ge and ZnS substrates

    NASA Astrophysics Data System (ADS)

    Hasan, Wasim; Propst, Steven H.

    1994-11-01

    Antireflection coated ZnS and Ge substrates erode under severe operational environmental conditions. High velocity water drop impact and high velocity sand particle impact are primarily military concerns that originated with the advent of faster aircraft. High speed flight through rain and sand storms seriously erodes forward facing components such as infrared transmitting windows and/or domes. This erosion of windows and/or domes causes reduction in transmission, resulting in the reduction of detection and recognition sensitivity of the electro-optical sensor. A single film of one quarterwave thick hard-carbon coating has been used on germanium to increase optical transmission (reducing Fresnel's reflection losses on Ge surface) as well as to reduce rain and sand impact damage to some extent, at a lower speed. At high speed, the damage becomes more severe, resulting in unacceptable large transmission losses. Recently, new hard carbon coatings have been developed for Ge which have substantially increased the damage threshold of the coated substrates. The rain erosion test was performed at Wright-Patterson AFB facility in Dayton, Ohio, and the sand tests were performed at PDA Engineering in Santa Ana, California. In addition, a multilayer AR coating utilizing hard carbon film as one of the low index films has also been developed at Hughes for ZnS substrates. The optical properties, rain erosion, sand erosion, and sand abrasion test results of these coatings are also presented in this paper.

  2. Oleic Acid-Induced Atomic Alignment of ZnS Polyhedral Nanocrystals.

    PubMed

    van der Stam, Ward; Rabouw, Freddy T; Vonk, Sander J W; Geuchies, Jaco J; Ligthart, Hans; Petukhov, Andrei V; de Mello Donega, Celso

    2016-04-13

    Ordered two-dimensional (2D) superstructures of colloidal nanocrystals (NCs) can be tailored by the size, shape, composition, and surface chemistry of the NC building blocks, which can give directionality to the resulting superstructure geometry. The exact formation mechanism of 2D NC superstructures is however not yet fully understood. Here, we show that oleic acid (OA) ligands induce atomic alignment of wurtzite ZnS bifrustum-shaped NCs. We find that in the presence of OA ligands the {002} facets of the ZnS bifrustums preferentially adhere to the liquid-air interface. Furthermore, OA ligands induce inter-NC interactions that also orient the NCs in the plane of the liquid-air interface, resulting in atomically aligned 2D superstructures. We follow the self-assembly process in real-time with in situ grazing incidence small-angle X-ray scattering and find that the NCs form a hexagonal superstructure at early stages after which they come closer over time, resulting in a close-packed NC superstructure. Our results demonstrate the profound influence that surface ligands have on the directionality of 2D NC superstructures and highlight the importance of detailed in situ studies in order to understand the self-assembly of NCs into 2D superstructures. PMID:26930124

  3. Optical and Optoelectronic Properties of ZnS Nanostructured Thin Film

    NASA Astrophysics Data System (ADS)

    Borah, J. P.; Sarma, K. C.

    2008-10-01

    ZnS nanocrystalline thin films were grown into the polyvinyl alcohol matrix and were synthesized by chemical route. Films were prepared on glass substrate by varying the deposition parameters and pH of the solution. Nanocrystalline thin film prepared under optimum growth conditions shows band gap value 3.88 eV as observed from optical absorption data. The band gap is found to be higher (3.88 eV) indicating blue shift. The particle size, calculated from the shift of direct band gap, due to quantum confinement effect is 5.8 nm. Photoluminescence spectrum shows the blue luminescence peaks (centered at 425 nm), which can be attributed to the recombination of the defect states. ZnS nanocrystalline thin films are also found to be photosensitive in nature. However, the photosensitivity decreases due to ageing and exposure to oxygen. In case of nanostructured film, the I-V characteristics are observed in dark and under illumination showing photosensitive nature of these films, too. The dark current, however, is found to be greater when observed in vacuum compared to air. Both dark current and photocurrent are found to be ohmic in nature up to a certain applied bias. The observed data shows that nanostructured films are found to be suitable for device application. The surface morphology of the film is also characterized by scanning electron microscope.

  4. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    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.

  6. Enhanced Photocatalytic Performance of ZnS for Reversible Amination of α-oxo Acids by Hydrothermal Treatment

    NASA Astrophysics Data System (ADS)

    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.

  7. Fabrication of hollow ZnO particles and its photocatalytic property by modifying of nano ZnS.

    PubMed

    Song, Ge; Li, Wenjiang

    2013-02-01

    Large scale hollow ZnO spheres were prepared by a solvothermal method with the help of the solvent. And ZnS nanoparticles were successfully fabricated on the surface of ZnO via a hydrothermal process. These heterostructured ZnO/ZnS core/shell particles are around 1-2 microm in diameter, the ZnS shell formed on the surface of hollow ZnO sphere is comprise of the primary crystals about 30 nm in diameter. The products prepared were characterized by field emission scanning electron microscope (FE-SEM), X-ray powder diffraction (XRD), transmission electron microscope (TEM), and photo-luminescence spectroscope (PL). Theoretical calculation and experimental results have demonstrated that the combination of ZnO and ZnS (two wide band gap semiconductors) could yield a novel material with the photoexcitation threshold energy lower than the individual components. The electron transfers between ZnO core and ZnS shell, which strongly affect the photoluminescence and photocatalytic performances. The photocatalytic activities of the products were evaluated by methyl orange degradation as a probe reaction. The relationship of ZnO/ZnS core/shell particles as excellent photocatalyst could be anticipated. PMID:23646638

  8. 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.

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

    NASA Astrophysics Data System (ADS)

    Nawrocki, Grzegorz; Cieplak, Marek

    2014-03-01

    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.

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

    PubMed

    Nawrocki, Grzegorz; Cieplak, Marek

    2014-03-01

    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. PMID:24606380