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Sample records for suspended zno clusters

  1. Vacancy defect and defect cluster energetics in ion-implanted ZnO

    Science.gov (United States)

    Dong, Yufeng; Tuomisto, F.; Svensson, B. G.; Kuznetsov, A. Yu.; Brillson, Leonard J.

    2010-02-01

    We have used depth-resolved cathodoluminescence, positron annihilation, and surface photovoltage spectroscopies to determine the energy levels of Zn vacancies and vacancy clusters in bulk ZnO crystals. Doppler broadening-measured transformation of Zn vacancies to vacancy clusters with annealing shifts defect energies significantly lower in the ZnO band gap. Zn and corresponding O vacancy-related depth distributions provide a consistent explanation of depth-dependent resistivity and carrier-concentration changes induced by ion implantation.

  2. First principles calculations for interaction of tyrosine with (ZnO)3 cluster

    Science.gov (United States)

    Singh, Satvinder; Singh, Gurinder; Kaura, Aman; Tripathi, S. K.

    2018-04-01

    First Principles Calculations have been performed to study interactions of Phenol ring of Tyrosine (C6H5OH) with (ZnO)3 atomic cluster. All the calculations have been performed under the Density Functional Theory (DFT) framework. Structural and electronic properties of (ZnO)3/C6H5OH have been studied. Gaussian basis set approach has been adopted for the calculations. A ring type most stable (ZnO)3 atomic cluster has been modeled, analyzed and used for the calculations. The compatibility of the results with previous studies has been presented here.

  3. From Stable ZnO and GaN Clusters to Novel Double Bubbles and Frameworks

    Directory of Open Access Journals (Sweden)

    Matthew R. Farrow

    2014-05-01

    Full Text Available A bottom up approach is employed in the design of novel materials: first, gas-phase “double bubble” clusters are constructed from high symmetry, Th, 24 and 96 atom, single bubbles of ZnO and GaN. These are used to construct bulk frameworks. Upon geometry optimization—minimisation of energies and forces computed using density functional theory—the symmetry of the double bubble clusters is reduced to either C1 or C2, and the average bond lengths for the outer bubbles are 1.9 Å, whereas the average bonds for the inner bubble are larger for ZnO than for GaN; 2.0 Å and 1.9 Å, respectively. A careful analysis of the bond distributions reveals that the inter-bubble bonds are bi-modal, and that there is a greater distortion for ZnO. Similar bond distributions are found for the corresponding frameworks. The distortion of the ZnO double bubble is found to be related to the increased flexibility of the outer bubble when composed of ZnO rather than GaN, which is reflected in their bulk moduli. The energetics suggest that (ZnO12@(GaN48 is more stable both in gas phase and bulk frameworks than (ZnO12@(ZnO48 and (GaN12@(GaN48. Formation enthalpies are similar to those found for carbon fullerenes.

  4. Smoothing of ZnO films by gas cluster ion beam

    International Nuclear Information System (INIS)

    Chen, H.; Liu, S.W.; Wang, X.M.; Iliev, M.N.; Chen, C.L.; Yu, X.K.; Liu, J.R.; Ma, K.; Chu, W.K.

    2005-01-01

    Planarization of wide-band-gap semiconductor ZnO surface is crucial for thin-film device performance. In this study, the rough initial surfaces of ZnO films deposited by r.f. magnetron sputtering on Si substrates were smoothed by gas cluster ion beams. AFM measurements show that the average surface roughness (R a ) of the ZnO films could be reduced considerably from 16.1 nm to 0.9 nm. Raman spectroscopy was used to monitor the structure of both the as-grown and the smoothed ZnO films. Rutherford back-scattering in combination with channeling effect was used to study the damage production induced by the cluster bombardment

  5. Ferromagnetism and suppression of metallic clusters in Fe implanted ZnO -- a phenomenon related to defects?

    International Nuclear Information System (INIS)

    Arenholz, Elke; Zhou, S.; Potzger, K.; Talut, G.; Reuther, H.; Kuepper, K.; Grenzer, J.; Xu, Q.; Mucklich, A.; Helm, M.; Fassbender, J.; Arenholz, E.

    2008-01-01

    We investigated ZnO(0001) single crystals annealed in high vacuum with respect to their magnetic properties and cluster formation tendency after implant-doping with Fe. While metallic Fe cluster formation is suppressed, no evidence for the relevance of the Fe magnetic moment to the observed ferromagnetism was found. The latter along with the cluster suppression is discussed with respect to defects in the ZnO host matrix, since the crystalline quality of the substrates was lowered due to the preparation as observed by x-ray diffraction

  6. Ferromagnetism and suppression of metallic clusters in Fe implanted ZnO: a phenomenon related to defects?

    International Nuclear Information System (INIS)

    Zhou Shengqiang; Potzger, K; Talut, G; Reuther, H; Kuepper, K; Grenzer, J; Xu Qingyu; Muecklich, A; Helm, M; Fassbender, J; Arenholz, E

    2008-01-01

    We investigated ZnO(0 0 0 1) single crystals annealed in high vacuum with respect to their magnetic properties and cluster formation tendency after implant-doping with Fe. While metallic Fe cluster formation is suppressed, no evidence for the relevance of the Fe magnetic moment to the observed ferromagnetism was found. The latter along with the cluster suppression is discussed with respect to defects in the ZnO host matrix, since the crystalline quality of the substrates was lowered due to the preparation as observed by x-ray diffraction

  7. Understanding the presence of vacancy clusters in ZnO from a kinetic perspective

    Science.gov (United States)

    Bang, Junhyeok; Kim, Youg-Sung; Park, C. H.; Gao, F.; Zhang, S. B.

    2014-06-01

    Vacancy clusters have been observed in ZnO by positron-annihilation spectroscopy (PAS), but detailed mechanisms are unclear. This is because the clustering happens in non-equilibrium conditions, for which theoretical method has not been well established. Combining first-principles calculation and kinetic Monte Carlo simulation, we determine the roles of non-equilibrium kinetics on the vacancies clustering. We find that clustering starts with the formation of Zn and O vacancy pairs (VZn - Vo), which further grow by attracting additional mono-vacancies. At this stage, vacancy diffusivity becomes crucial: due to the larger diffusivity of VZn compared to VO, more VZn-abundant clusters are formed than VO-abundant clusters. The large dissociation energy barriers, e.g., over 2.5 eV for (VZn - Vo), suggest that, once formed, it is difficult for the clusters to dissociate. By promoting mono-vacancy diffusion, thermal annealing will increase the size of the clusters. As the PAS is insensitive to VO donor defects, our results suggest an interpretation of the experimental data that could not have been made without the in-depth calculations.

  8. Understanding the presence of vacancy clusters in ZnO from a kinetic perspective

    International Nuclear Information System (INIS)

    Bang, Junhyeok; Zhang, S. B.; Kim, Youg-Sung; Park, C. H.; Gao, F.

    2014-01-01

    Vacancy clusters have been observed in ZnO by positron-annihilation spectroscopy (PAS), but detailed mechanisms are unclear. This is because the clustering happens in non-equilibrium conditions, for which theoretical method has not been well established. Combining first-principles calculation and kinetic Monte Carlo simulation, we determine the roles of non-equilibrium kinetics on the vacancies clustering. We find that clustering starts with the formation of Zn and O vacancy pairs (V Zn  − Vo), which further grow by attracting additional mono-vacancies. At this stage, vacancy diffusivity becomes crucial: due to the larger diffusivity of V Zn compared to V O , more V Zn -abundant clusters are formed than V O -abundant clusters. The large dissociation energy barriers, e.g., over 2.5 eV for (V Zn  − Vo), suggest that, once formed, it is difficult for the clusters to dissociate. By promoting mono-vacancy diffusion, thermal annealing will increase the size of the clusters. As the PAS is insensitive to V O donor defects, our results suggest an interpretation of the experimental data that could not have been made without the in-depth calculations.

  9. Understanding the presence of vacancy clusters in ZnO from a kinetic perspective

    Energy Technology Data Exchange (ETDEWEB)

    Bang, Junhyeok; Zhang, S. B., E-mail: zhangs9@rpi.edu, E-mail: kimyongsung@gmail.com [Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Kim, Youg-Sung, E-mail: zhangs9@rpi.edu, E-mail: kimyongsung@gmail.com [Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of); Department of Nano Science, University of Science and Technology, Daejeon 305-350 (Korea, Republic of); Park, C. H. [Research Center for Dielectric and Advanced Matter Physics, Pusan National University, Busan 609-735 (Korea, Republic of); Gao, F. [Pacific Northwest National Laboratory, MS K8-93, P.O. Box 999, Richland, Washington 99352 (United States)

    2014-06-23

    Vacancy clusters have been observed in ZnO by positron-annihilation spectroscopy (PAS), but detailed mechanisms are unclear. This is because the clustering happens in non-equilibrium conditions, for which theoretical method has not been well established. Combining first-principles calculation and kinetic Monte Carlo simulation, we determine the roles of non-equilibrium kinetics on the vacancies clustering. We find that clustering starts with the formation of Zn and O vacancy pairs (V{sub Zn} − Vo), which further grow by attracting additional mono-vacancies. At this stage, vacancy diffusivity becomes crucial: due to the larger diffusivity of V{sub Zn} compared to V{sub O}, more V{sub Zn}-abundant clusters are formed than V{sub O}-abundant clusters. The large dissociation energy barriers, e.g., over 2.5 eV for (V{sub Zn} − Vo), suggest that, once formed, it is difficult for the clusters to dissociate. By promoting mono-vacancy diffusion, thermal annealing will increase the size of the clusters. As the PAS is insensitive to V{sub O} donor defects, our results suggest an interpretation of the experimental data that could not have been made without the in-depth calculations.

  10. Amorphous clusters in Co implanted ZnO induced by boron pre-implantation

    Energy Technology Data Exchange (ETDEWEB)

    Potzger, K.; Shalimov, A.; Zhou, S.; Schmidt, H.; Mucklich, A.; Helm, M.; Fassbender, J.; Liberati, M.; Arenholz, E.

    2009-02-09

    We demonstrate the formation of superparamagnetic/ferromagnetic regions within ZnO(0001) single crystals sequently implanted with B and Co. While the pre-implantation with B plays a minor role for the electrical transport properties, its presence leads to the formation of amorphous phases. Moreover, B acts strongly reducing on the implanted Co. Thus, the origin of the ferromagnetic ordering in local clusters with large Co concentration is itinerant d-electrons as in the case of metallic Co. The metallic amorphous phases are non-detectable by common X-ray diffraction.

  11. Vacancy clustering and acceptor activation in nitrogen-implanted ZnO

    Science.gov (United States)

    Børseth, Thomas Moe; Tuomisto, Filip; Christensen, Jens S.; Monakhov, Edouard V.; Svensson, Bengt G.; Kuznetsov, Andrej Yu.

    2008-01-01

    The role of vacancy clustering and acceptor activation on resistivity evolution in N ion-implanted n -type hydrothermally grown bulk ZnO has been investigated by positron annihilation spectroscopy, resistivity measurements, and chemical profiling. Room temperature 220keV N implantation using doses in the low 1015cm-2 range induces small and big vacancy clusters containing at least 2 and 3-4 Zn vacancies, respectively. The small clusters are present already in as-implanted samples and remain stable up to 1000°C with no significant effect on the resistivity evolution. In contrast, formation of the big clusters at 600°C is associated with a significant increase in the free electron concentration attributed to gettering of amphoteric Li impurities by these clusters. Further annealing at 800°C results in a dramatic decrease in the free electron concentration correlated with activation of 1016-1017cm-3 acceptors likely to be N and/or Li related. The samples remain n type, however, and further annealing at 1000°C results in passivation of the acceptor states while the big clusters dissociate.

  12. Highly sensitive hydrogen detection of catalyst-free ZnO nanorod networks suspended by lithography-assisted growth

    International Nuclear Information System (INIS)

    Huh, Junghwan; Kim, Gyu Tae; Park, Jonghyurk; Park, Jeong Young

    2011-01-01

    We have successfully demonstrated a ZnO nanorod-based 3D nanostructure to show a high sensitivity and very fast response/recovery to hydrogen gas. ZnO nanorods have been synthesized selectively over the pre-defined area at relatively low temperature using a simple self-catalytic solution process assisted by a lithographic method. The conductance of the ZnO nanorod device varies significantly as the concentration of the hydrogen is changed without any additive metal catalyst, revealing a high sensitivity to hydrogen gas. Its superior performance can be explained by the porous structure of its three-dimensional network and the enhanced surface reaction of the hydrogen molecules with the oxygen defects resulting from a high surface-to-volume ratio. It was found that the change of conductance follows a power law depending on the hydrogen concentration. A Langmuir isotherm following an ideal power law and a cross-over behavior of the activation energy with respect to hydrogen concentration were observed. This is a very novel and intriguing phenomenon on nanostructured materials, which suggests competitive surface reactions in ZnO nanorod gas sensors.

  13. Highly sensitive hydrogen detection of catalyst-free ZnO nanorod networks suspended by lithography-assisted growth.

    Science.gov (United States)

    Huh, Junghwan; Park, Jonghyurk; Kim, Gyu Tae; Park, Jeong Young

    2011-02-25

    We have successfully demonstrated a ZnO nanorod-based 3D nanostructure to show a high sensitivity and very fast response/recovery to hydrogen gas. ZnO nanorods have been synthesized selectively over the pre-defined area at relatively low temperature using a simple self-catalytic solution process assisted by a lithographic method. The conductance of the ZnO nanorod device varies significantly as the concentration of the hydrogen is changed without any additive metal catalyst, revealing a high sensitivity to hydrogen gas. Its superior performance can be explained by the porous structure of its three-dimensional network and the enhanced surface reaction of the hydrogen molecules with the oxygen defects resulting from a high surface-to-volume ratio. It was found that the change of conductance follows a power law depending on the hydrogen concentration. A Langmuir isotherm following an ideal power law and a cross-over behavior of the activation energy with respect to hydrogen concentration were observed. This is a very novel and intriguing phenomenon on nanostructured materials, which suggests competitive surface reactions in ZnO nanorod gas sensors.

  14. Clustered vacancies in ZnO: chemical aspects and consequences on physical properties

    Science.gov (United States)

    Pal, S.; Gogurla, N.; Das, Avishek; Singha, S. S.; Kumar, Pravin; Kanjilal, D.; Singha, A.; Chattopadhyay, S.; Jana, D.; Sarkar, A.

    2018-03-01

    The chemical nature of point defects, their segregation, cluster or complex formation in ZnO is an important area of investigation. The evolution of a defective state with MeV Ar ion irradiation fluence 1  ×  1014 and 1  ×  1016 ions cm-2 has been monitored here using x-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and Raman spectroscopy. The XPS study shows the presence of oxygen vacancies (V O) in Ar irradiated ZnO. Zn(LMM) Auger spectra clearly identifies a transition involving metallic zinc in the irradiated samples. An intense PL emission from interstitial Zn (I Zn)-related shallow donor bound excitons (DBX) is visible in the 10 K spectra for all samples. Although overall PL is largely reduced with irradiation disorder, DBX intensity is increased for the highest fluence irradiated sample. The Raman study indicates damage in both the zinc and oxygen sub-lattice by an energetic ion beam. Representative Raman modes from defect complexes involving V O, I Zn and I O are visible after irradiation with intermediate fluence. A further increase of fluence shows, to some extent, a homogenization of disorder. A huge reduction of resistance is also noted for this sample. Certainly, high irradiation fluence induces a qualitative modification of the conventional (and highly resistive) grain boundary (GB) structure of granular ZnO. A low resistive path, involving I Zn related shallow donors, across the GB can be presumed to explain resistance reduction. Open volumes (V Zn and V O) agglomerate more and more with increasing irradiation fluence and are finally transformed to voids. The results as a whole have been elucidated with a model which emphasizes the possible evolution of a new defect microstructure that is distinctively different from the GB-related disorder. Based on the model, qualitative explanations of commonly observed radiation hardness, colouration and ferromagnetism in disordered ZnO have been put forward. A coherent scenario

  15. Formation and vibrational structure of Si nano-clusters in ZnO matrix

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Serrano, J. [Universidad Autonoma del Estado de Hidalgo, Hidalgo (Mexico); Pal, U. [Universidad Autonoma de Puebla, Puebla (Mexico); Koshizaki, N.; Sasaki, T. [National Institute of Materials and Chemical Research, Ibaraki (Japan)

    2001-02-01

    We have studied the formation and vibrational structure of Si nano-clusters in ZnO matrix prepared by radio-frequency (r.f.) co-sputtering, and characterized by Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS) and Infrared (IR) spectroscopy techniques. The composite films of Si/ZnO were grown o quartz substrates by co-sputtering of Si and ZnO targets. TEM images show a homogeneous distribution of clusters in the matrix with average size varied from 3.7 nm to 34 nm depending on the temperature of annealing. IR absorption measurements revealed the bands correspond to the modes of vibrations of Si{sub 3} in its triangular geometrical structure. By analysing the IR absorption and XPS spectra we found that the nano-clusters consist of a Si{sub 3} core and a SiO{sub x} cap layer. With the increase of annealing temperature, the vibrational states of Si changed from the triplet {sup 3}B1(C2{sub v}) and {sup 3}A'{sub 2}(D{sub 3h}) states to its singlet ground state {sup 1}A{sub 1}(C2{sub v}) and the oxidation state of Si in SiO{sub x} increased. The evolution of the local atomic structure of the Si nano-clusters with the variation of Si content in the film and with the variation of the temperature of annealing are discussed. [Spanish] Se estudia la formacion y estructura vibracional de nano-cumulos de Si en matriz de ZnO preparados por la tecnica de radio-frecuencia (r.f.) co-sputtering, y caracterizados por Microscopia Electronica de Transmision (TEM), Espectroscopia Fotoelectronica de rayos X (XPS) y Espectroscopia de Infrarrojo (IR). Las peliculas compositas de Si/ZnO fueron crecidas sobre sustratos de cuarzo mediante el co-sputtering de blancos de Si y ZnO. Las imagenes de TEM mostraron una distribucion homogenea de cumulos en la matriz con un tamano promedio de 3.7 nm a 34 nm dependiendo de la temperatura de tratamiento. Las mediciones de IR relevaron las bandas correspondientes a los modos de vibracion de Si{sub 3} en su estructura

  16. Treatment of delocalized electron transfer in periodic and embedded cluster DFT calculations: The case of Cu on ZnO (10(1)0).

    Science.gov (United States)

    Hellström, Matti; Spångberg, Daniel; Hermansson, Kersti

    2015-12-15

    We assess the consequences of the interface model-embedded-cluster or periodic-slab model-on the ability of DFT calculations to describe charge transfer (CT) in a particularly challenging case where periodic-slab calculations indicate a delocalized charge-transfer state. Our example is Cu atom adsorption on ZnO(10(1)0), and in fact the periodic slab calculations indicate three types of CT depending on the adsorption site: full CT, partial CT, and no CT. Interestingly, when full CT occurs in the periodic calculations, the calculated Cu atom adsorption energy depends on the underlying ZnO substrate supercell size, since when the electron enters the ZnO it delocalizes over as many atoms as possible. In the embedded-cluster calculations, the electron transferred to the ZnO delocalizes over the entire cluster region, and as a result the calculated Cu atom adsorption energy does not agree with the value obtained using a large periodic supercell, but instead to the adsorption energy obtained for a periodic supercell of roughly the same size as the embedded cluster. Different density functionals (of GGA and hybrid types) and basis sets (local atom-centered and plane-waves) were assessed, and we show that embedded clusters can be used to model Cu adsorption on ZnO(10(1)0), as long as care is taken to account for the effects of CT. © 2015 Wiley Periodicals, Inc.

  17. Investigation on structure, electronic and magnetic properties of Cr doped (ZnO)12 clusters: First-principles calculations

    Science.gov (United States)

    Liu, Huan; Zhang, Jian-Min

    2018-05-01

    The structural, electronic, and magnetic properties of (ZnO)12 clusters doped with Cr atoms have been investigated by using spin-polarized first-principles calculations. The exohedral a3 isomer is favorable than endohedral a2 isomer. The isomer a1 and a5 respectively have the narrowest and biggest gap between highest unoccupied molecular orbital and the lowest unoccupied molecular orbital (HOMO-LUMO) of 0.473 and 1.291 eV among these five monodoped isomers. The magnetic moment may be related to the local environment around the Cr atom that the a2 isomer whose total magnetic moment is 6 μB while the other monodoped isomers which all isomers have nearly total magnetic moments 4 μB . For Cr-doped (ZnO)12 on a1 or a3 isomer, the DOS of spin-up channel cross the Fermi level EF showing a finite magnitude near the Fermi level which might be useful for half metallic character. For the bidoped cases, the exohedral isomers are found to be most favorable. Including all bipoed isomers of substitutional, exohedral and endohedral bidoped clusters, the total magnetic moment of the ferromagnetic (antiferromagnetic) state is 8 (0) μB and the HOMO-LUMO gap of antiferromagnetic state is slightly larger than that of ferromagnetic state. The magnetic coupling between the Cr atoms in bidoped configurations is mainly governed by the competition between direct Cr and Cr atoms antiferromagnetic interaction and the ferromagnetic interaction between two Cr atoms via O atom due to strong p-d hybridization. Most importantly, we show that the exohedral bidoped (ZnO)12 clusters favor the ferromagnetic state, which may have the future applications in spin-dependent magneto-optical and magneto-electrical devices.

  18. Visible tunable lighting system based on polymer composites embedding ZnO and metallic clusters: from colloids to thin films

    OpenAIRE

    Truong, Thai Giang; Dierre, Benjamin; Grasset, Fabien; Saito, Noriko; Saito, Norio; Nguyen, Thi Kim Ngan; Takahashi, Kohsei; Uchikoshi, Tetsuo; Amela-Cortes, Marian; Molard, Yann; Cordier, St?phane; Ohashi, Naoki

    2016-01-01

    Abstract The development of phosphor devices free of heavy metal or rare earth elements is an important issue for environmental reasons and energy efficiency. Different mixtures of ZnO nanocrystals with Cs2Mo6I8(OOC2F5)6 cluster compound (CMIF) dispersed into polyvinylpyrrolidone matrix have been prepared by very simple and low cost solution chemistry. The resulting solutions have been used to fabricate highly transparent and luminescent films by dip coating free of heavy metal or rare earth ...

  19. Visible tunable lighting system based on polymer composites embedding ZnO and metallic clusters: from colloids to thin films

    Science.gov (United States)

    Truong, Thai Giang; Dierre, Benjamin; Grasset, Fabien; Saito, Noriko; Saito, Norio; Nguyen, Thi Kim Ngan; Takahashi, Kohsei; Uchikoshi, Tetsuo; Amela-Cortes, Marian; Molard, Yann; Cordier, Stéphane; Ohashi, Naoki

    2016-01-01

    The development of phosphor devices free of heavy metal or rare earth elements is an important issue for environmental reasons and energy efficiency. Different mixtures of ZnO nanocrystals with Cs2Mo6I8(OOC2F5)6 cluster compound (CMIF) dispersed into polyvinylpyrrolidone matrix have been prepared by very simple and low cost solution chemistry. The resulting solutions have been used to fabricate highly transparent and luminescent films by dip coating free of heavy metal or rare earth elements. The luminescence properties of solution and dip-coated films were investigated. The luminescence of such a system is strongly dependent on the ratios between ZnO and CMIF amounts, the excitation wavelength and the nature of the system. By varying these two parameters (ratio and wavelength), a large variety of colors, from blue to red as well as white, can be achieved. In addition, differences in the luminescence properties have been observed between solutions and thin films as well as changes of CMIF emission band maximum wavelength. This may suggest some possible interactions between the different luminophore centers, such as energy transfer or ligands exchange on the Mo6 clusters.

  20. Chemical inhomogeneity in In{sub x}Ga{sub 1-x}N and ZnO. A HRTEM study on atomic scale clustering

    Energy Technology Data Exchange (ETDEWEB)

    Bartel, T.P.

    2008-10-08

    Nanostructuration as well as the nucleation and growth of nanoparticles pervades the development of modern materials and devices. Quantitative high resolution transmission electron microscopy (HRTEM) is currently being developed for a structural and chemical analysis at an atomic scale. It is used in this thesis to study the chemical inhomogeneity and clustering in In{sub x}Ga{sub 1-x}N, InN and ZnO. A methodology for reliable quantitative HRTEM is rst de ned: it necessitates a damage free sample, the avoidance of electron beam damage and the control of microscope instabilities. With these conditions satis ed, the reliability of quantitative HRTEM is demonstrated by an accurate measurement of lattice relaxation in a thin TEM sample. Clustering in an alloy can then be distinguished from a random distribution of atoms. In In{sub x}Ga{sub 1-x}N for instance, clustering is detected for concentrations x>0.1. The sensitivity is insufficient to determine whether clustering is present for lower concentrations. HRTEM allows to identify the amplitude and the spatial distribution of the decomposition which is attributed to a spinodal decomposition. In InN, nanometer scale metallic indium inclusions are detected. With decreasing size of the metallic clusters, the photoluminescence of the sample shifts towards the infrared. This indicates that the inclusions may be responsible for the infrared activity of InN. Finally, ZnO grown homoepitaxially on zinc-face and oxygen-face substrates is studied. The O-face epilayer is strained whereas the Zn-face epilayer is almost strain free and has a higher crystalline quality. Quantitative analysis of exit wave phases is in good agreement with simulations, but the signal to noise ratio needs to be improved for the detection of single point defects. (orig.)

  1. Chemical inhomogeneity in InxGa1-xN and ZnO. A HRTEM study on atomic scale clustering

    International Nuclear Information System (INIS)

    Bartel, T.P.

    2008-01-01

    Nanostructuration as well as the nucleation and growth of nanoparticles pervades the development of modern materials and devices. Quantitative high resolution transmission electron microscopy (HRTEM) is currently being developed for a structural and chemical analysis at an atomic scale. It is used in this thesis to study the chemical inhomogeneity and clustering in In x Ga 1-x N, InN and ZnO. A methodology for reliable quantitative HRTEM is rst de ned: it necessitates a damage free sample, the avoidance of electron beam damage and the control of microscope instabilities. With these conditions satis ed, the reliability of quantitative HRTEM is demonstrated by an accurate measurement of lattice relaxation in a thin TEM sample. Clustering in an alloy can then be distinguished from a random distribution of atoms. In In x Ga 1-x N for instance, clustering is detected for concentrations x>0.1. The sensitivity is insufficient to determine whether clustering is present for lower concentrations. HRTEM allows to identify the amplitude and the spatial distribution of the decomposition which is attributed to a spinodal decomposition. In InN, nanometer scale metallic indium inclusions are detected. With decreasing size of the metallic clusters, the photoluminescence of the sample shifts towards the infrared. This indicates that the inclusions may be responsible for the infrared activity of InN. Finally, ZnO grown homoepitaxially on zinc-face and oxygen-face substrates is studied. The O-face epilayer is strained whereas the Zn-face epilayer is almost strain free and has a higher crystalline quality. Quantitative analysis of exit wave phases is in good agreement with simulations, but the signal to noise ratio needs to be improved for the detection of single point defects. (orig.)

  2. Carbon doped ZnO: Synthesis, characterization and interpretation

    International Nuclear Information System (INIS)

    Mishra, D.K.; Mohapatra, J.; Sharma, M.K.; Chattarjee, R.; Singh, S.K.; Varma, Shikha; Behera, S.N.; Nayak, Sanjeev K.; Entel, P.

    2013-01-01

    A novel thermal plasma in-flight technique has been adopted to synthesize nanocrystalline ZnO and carbon doped nanocrystalline ZnO matrix. Transmission electron microscopy (TEM) studies on these samples show the average particle sizes to be around 32 nm for ZnO and for carbon doped ZnO. An enhancement of saturation magnetization in nanosized carbon doped ZnO matrix by a factor of 3.8 has been found in comparison to ZnO nanoparticles at room temperature. Raman measurement clearly indicates the presence of Zn–C complexes surrounded by ZnO matrix in carbon doped ZnO. This indicates that the ferromagnetic signature in carbon doped ZnO arises from the creation of defects or the development of oxy-carbon clusters, in the carbon doped ZnO system. Theoretical studies based on density functional theory also support the experimental analyses. - Highlights: ► Synthesis of nanocrystalline ZnO and carbon doped ZnO matrix by inflight thermal plasma reactor. ► Enhancement of ferromagnetism in nanosized carbon doped ZnO in comparison to ZnO nanoparticles. ► Raman measurement indicates the presence of Zn–C complexes surrounded by ZnO matrix. ► Ferromagnetic signature in carbon doped ZnO arises from the development of oxy-carbon clusters. ► DFT supports experimental evidence of ferromagnetism in C doped ZnO nanoparticles.

  3. Suspended ceilings

    Energy Technology Data Exchange (ETDEWEB)

    Talamo, C.

    1991-05-01

    The retrofitting of existing conventional ceiling systems to suspended ceiling type systems represents an interesting energy savings solution since this method, in addition to providing additional protection against space heat loss and thermal bridges, also creates the possibility of housing, in the void, additional mechanical and electrical lines which may be necessary due to other savings interventions. This paper reviews the various suspended ceiling systems (e.g., those making use of mineral fibre, gypsum panels, wood, vermiculite, etc.) currently marketed in Europe, and reports, for each, some key technical, economic and architectural advantages which include thermal efficiency, noise abatement, as well as, resistance to fire and humidity. Information is also given on the relative installation and maintenance requirements.

  4. clusters

    Indian Academy of Sciences (India)

    2017-09-27

    Sep 27, 2017 ... Author for correspondence (zh4403701@126.com). MS received 15 ... lic clusters using density functional theory (DFT)-GGA of the DMOL3 package. ... In the process of geometric optimization, con- vergence thresholds ..... and Postgraduate Research & Practice Innovation Program of. Jiangsu Province ...

  5. clusters

    Indian Academy of Sciences (India)

    environmental as well as technical problems during fuel gas utilization. ... adsorption on some alloys of Pd, namely PdAu, PdAg ... ried out on small neutral and charged Au24,26,27, Cu,28 ... study of Zanti et al.29 on Pdn (n = 1–9) clusters.

  6. Suspended graphene variable capacitor

    OpenAIRE

    AbdelGhany, M.; Mahvash, F.; Mukhopadhyay, M.; Favron, A.; Martel, R.; Siaj, M.; Szkopek, T.

    2016-01-01

    The tuning of electrical circuit resonance with a variable capacitor, or varactor, finds wide application with the most important being wireless telecommunication. We demonstrate an electromechanical graphene varactor, a variable capacitor wherein the capacitance is tuned by voltage controlled deflection of a dense array of suspended graphene membranes. The low flexural rigidity of graphene monolayers is exploited to achieve low actuation voltage in an ultra-thin structure. Large arrays compr...

  7. Site specific interaction between ZnO nanoparticles and tyrosine: A density functional theory study

    Science.gov (United States)

    Singh, Satvinder; Singh, Janpreet; Singh, Baljinder; Singh, Gurinder; Kaura, Aman; Tripathi, S. K.

    2018-05-01

    First Principles Calculations have been performed on ZnO/Tyrosine atomic complex to study site specific interaction of Tyrosine and ZnO nanoparticles. Calculated results shows that -COOH group present in Tyrosine is energetically more favorable than -NH2 group. Interactions show ionic bonding between ZnO and Tyrosine. All the calculations have been performed under the Density Functional Theory (DFT) framework. Structural and electronic properties of (ZnO)3/Tyrosine complex have been studied. Gaussian basis set approach has been adopted for the calculations. A ring type most stable (ZnO)3 atomic cluster has been modeled, analyzed and used for the calculations.

  8. Room temperature ferromagnetism in ZnO prepared by microemulsion

    Directory of Open Access Journals (Sweden)

    Qingyu Xu

    2011-09-01

    Full Text Available Clear room temperature ferromagnetism has been observed in ZnO powders prepared by microemulsion. The O vacancy (VO clusters mediated by the VO with one electron (F center contributed to the ferromagnetism, while the isolated F centers contributed to the low temperature paramagnetism. Annealing in H2 incorporated interstitial H (Hi in ZnO, and removed the isolated F centers, leading to the suppression of the paramagnetism. The ferromagnetism has been considered to originate from the VO clusters mediated by the Hi, leading to the enhancement of the coercivity. The ferromagnetism disappeared after annealing in air due to the reduction of Hi.

  9. Comparative study of ZnO nanorods and thin films for chemical and biosensing applications and the development of ZnO nanorods based potentiometric strontium ion sensor

    Science.gov (United States)

    Khun, K.; Ibupoto, Z. H.; Chey, C. O.; Lu, Jun.; Nur, O.; Willander, M.

    2013-03-01

    In this study, the comparative study of ZnO nanorods and ZnO thin films were performed regarding the chemical and biosensing properties and also ZnO nanorods based strontium ion sensor is proposed. ZnO nanorods were grown on gold coated glass substrates by the hydrothermal growth method and the ZnO thin films were deposited by electro deposition technique. ZnO nanorods and thin films were characterised by field emission electron microscopy [FESEM] and X-ray diffraction [XRD] techniques and this study has shown that the grown nanostructures are highly dense, uniform and exhibited good crystal quality. Moreover, transmission electron microscopy [TEM] was used to investigate the quality of ZnO thin film and we observed that ZnO thin film was comprised of nano clusters. ZnO nanorods and thin films were functionalised with selective strontium ionophore salicylaldehyde thiosemicarbazone [ST] membrane, galactose oxidase, and lactate oxidase for the detection of strontium ion, galactose and L-lactic acid, respectively. The electrochemical response of both ZnO nanorods and thin films sensor devices was measured by using the potentiometric method. The strontium ion sensor has exhibited good characteristics with a sensitivity of 28.65 ± 0.52 mV/decade, for a wide range of concentrations from 1.00 × 10-6 to 5.00 × 10-2 M, selectivity, reproducibility, stability and fast response time of 10.00 s. The proposed strontium ion sensor was used as indicator electrode in the potentiometric titration of strontium ion versus ethylenediamine tetra acetic acid [EDTA]. This comparative study has shown that ZnO nanorods possessed better performance with high sensitivity and low limit of detection due to high surface area to volume ratio as compared to the flat surface of ZnO thin films.

  10. Cluster-cluster clustering

    International Nuclear Information System (INIS)

    Barnes, J.; Dekel, A.; Efstathiou, G.; Frenk, C.S.; Yale Univ., New Haven, CT; California Univ., Santa Barbara; Cambridge Univ., England; Sussex Univ., Brighton, England)

    1985-01-01

    The cluster correlation function xi sub c(r) is compared with the particle correlation function, xi(r) in cosmological N-body simulations with a wide range of initial conditions. The experiments include scale-free initial conditions, pancake models with a coherence length in the initial density field, and hybrid models. Three N-body techniques and two cluster-finding algorithms are used. In scale-free models with white noise initial conditions, xi sub c and xi are essentially identical. In scale-free models with more power on large scales, it is found that the amplitude of xi sub c increases with cluster richness; in this case the clusters give a biased estimate of the particle correlations. In the pancake and hybrid models (with n = 0 or 1), xi sub c is steeper than xi, but the cluster correlation length exceeds that of the points by less than a factor of 2, independent of cluster richness. Thus the high amplitude of xi sub c found in studies of rich clusters of galaxies is inconsistent with white noise and pancake models and may indicate a primordial fluctuation spectrum with substantial power on large scales. 30 references

  11. Magnetically suspended railway

    Energy Technology Data Exchange (ETDEWEB)

    Guenther, C

    1977-07-28

    The invention concerns the emergency support of a magnetically suspended railway. On failure of the magnetic suspension/tracking system, the vehicles touch down on the rail configuration by means of emergency gliding elements like sliding shoes, skids, or the like. In doing this, the touch-down shock of the emergency gliding elements has to be limited to a force maximum as small as possible. According to the invention a spring-attenuator combination is used for this purpose, the spring characteristic being linear while the attenuator has a square-law characteristic for the compressing and a linear characteristic for the yielding motion. The force maximum thus achieved is exactly half the size of the physically smallest possible force maximum for an emergency gliding element springed without damping.

  12. Effect of ZnO nanoparticles in the oxygen uptake during aerobic wastewater treatment

    Energy Technology Data Exchange (ETDEWEB)

    Cervantes-Avilés, Pabel; Brito, Elcia M. S. [University of Guanajuato, Engineering Division, Department of Civil Engineering & Environmental Engineering (Mexico); Duran, Robert [Université de Pau et des Pays de l’Adour, Equipe Environment et Microbiologie (France); Martínez, Arodí Bernal; Cuevas-Rodríguez, Germán, E-mail: german28@ugto.mx [University of Guanajuato, Engineering Division, Department of Civil Engineering & Environmental Engineering (Mexico)

    2016-07-15

    The increased use of ZnO nanoparticles (NPs) in everyday products indicates the importance of studying NPs release to the wastewater and its possible effect on biological process for wastewater treatment. Therefore, the aim of this work was to study the effect of the presence of ZnO NPs in aerobic wastewater treatment. The results indicated that the oxygen uptake rate of microorganisms is inhibited for concentrations higher than 473 mg L{sup −1} of ZnO NPs. The diversity of microorganisms involved in wastewater treatment was reduced in presence of ZnO NPs. Related to morphological interaction between ZnO NPs and suspended biomass, physical damage in flocs structure were observed in presence of ZnO NPs. However, the internalization of Zn compounds in microorganisms not presented mechanical damage in the membrane cell. These findings suggest that inhibition in oxygen uptake was caused for negative effect that ZnO NPs induces in aerobic microorganisms involved in wastewater treatment.

  13. Recovery of thermal-degraded ZnO photodetector by embedding nano silver oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Zhan-Shuo [Institute of Microelectronics, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Hung, Fei-Yi, E-mail: fyhung@mail.ncku.edu.tw [Institute of Nanotechnology and Microsystems Engineering, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Chen, Kuan-Jen [Institute of Nanotechnology and Microsystems Engineering, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); The Instrument Center, National Cheng Kung University, Tainan 701, Taiwan (China); Chang, Shoou-Jinn [Institute of Microelectronics, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Institute of Microelectronics and Department of Electrical Engineering, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Hsieh, Wei-Kang; Liao, Tsai-Yu; Chen, Tse-Pu [Institute of Microelectronics, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China)

    2013-08-15

    The degraded performance of annealed ZnO-based photodetector can be recovered by embedding Ag{sub 2}O nanoparticles resulted from the transformation of as-deposited Ag layer. After thermal treatment, the electrons were attracted at the interface between ZnO and Ag{sub 2}O. The excess Ag{sup +} ions form the cluster to incorporate into the interstitial sites of ZnO lattice to create a larger amount of lattice defects for the leakage path. The photo-current of ZnO film with Ag{sub 2}O nanoparticles is less than annealed ZnO film because the photo-induced electrons would flow into Ag{sub 2}O side. ZnO photodetector with the appropriate Ag{sub 2}O nanoparticles possesses the best rejection ratio.

  14. Defect engineering of ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Weber, M.H. [Center for Materials Research and Department of Physics and Astronomy, Washington State University, Pullman, WA 99164-2711 (United States)], E-mail: m_weber@wsu.edu; Selim, F.A.; Solodovnikov, D.; Lynn, K.G. [Center for Materials Research and Department of Physics and Astronomy, Washington State University, Pullman, WA 99164-2711 (United States)

    2008-10-31

    The defect responsible for the transparent to red color change of nominally undoped ZnO bulk single crystals is investigated. Upon annealing in the presence of metallic Zn as reported by Halliburton et al. and also Ti and Zr a native defect forms with an energy level about 0.7 eV below the conduction band. This change is reversible upon annealing in oxygen. Optical transmission data along with positron depth profiles and annealing studies are combined to identify the defect as oxygen vacancies. Vacancy clustering occurs at about 500 deg. C if isolated zinc and oxygen vacancies. In the absence of zinc vacancies, clusters form at about 800 deg. C.

  15. Defect engineering of ZnO

    International Nuclear Information System (INIS)

    Weber, M.H.; Selim, F.A.; Solodovnikov, D.; Lynn, K.G.

    2008-01-01

    The defect responsible for the transparent to red color change of nominally undoped ZnO bulk single crystals is investigated. Upon annealing in the presence of metallic Zn as reported by Halliburton et al. and also Ti and Zr a native defect forms with an energy level about 0.7 eV below the conduction band. This change is reversible upon annealing in oxygen. Optical transmission data along with positron depth profiles and annealing studies are combined to identify the defect as oxygen vacancies. Vacancy clustering occurs at about 500 deg. C if isolated zinc and oxygen vacancies. In the absence of zinc vacancies, clusters form at about 800 deg. C

  16. Suspended solids in liquid effluents

    International Nuclear Information System (INIS)

    McGrath, J.J.

    1988-06-01

    An international literature review and telephone mail survey was conducted with respect to technical and regulatory aspects of suspended solids in radioactive liquid wastes from nuclear power stations. Results of the survey are summarized and show that suspended solids are an important component of some waste streams. The data available, while limited, show these solids to be associated largely with corrosion products. The solids are highly variable in quantity, size and composition. Filtration is commonly applied for their removal from liquid effluents and is effective. Complex interactions with receiving waters can result in physical/chemical changes of released radionuclides and these phenomena have been seen as reason for not applying regulatory controls based on suspended solids content. 340 refs

  17. Suspending Zeolite Particles In Tanks

    International Nuclear Information System (INIS)

    Poirier, M.R.

    1999-01-01

    The Savannah River Site (SRS) is in the process of removing waste (sludge and salt cake) from million gallon waste tanks. The current practice for removing waste from the tanks is adding water, agitating the tanks with long shaft vertical centrifugal pumps, and pumping the sludge/salt solution from the tank to downstream treatment processes. This practice has left sludge heels (tilde 30,000 gallons) in the bottom of the tanks. SRS is evaluating shrouded axial impeller mixers for removing the sludge heels in the waste tanks. The authors conducted a test program to determine mixer requirements for suspending sludge heels using the shrouded axial impeller mixers. The tests were performed with zeolite in scaled tanks which have diameters of 1.5, 6.0, and 18.75 feet. The mixer speeds required to suspend zeolite particles were measured at each scale. The data were analyzed with various scaling methods to compare their ability to describe the suspension of insoluble solids with the mixers and to apply the data to a full-scale waste tank. The impact of changes in particle properties and operating parameters was also evaluated. The conclusions of the work are: Scaling of the suspension of fast settling zeolite particles was best described by the constant power per unit volume method. Increasing the zeolite particle concentration increased the required mixer power needed to suspend the particles. Decreasing the zeolite particle size from 0.7 mm 0.3 mm decreased the required mixer power needed to suspend the particles. Increasing the number of mixers in the tank decreased the required mixer power needed to suspend the particles. A velocity of 1.6 ft/sec two inches above the tank bottom is needed to suspend zeolite particles

  18. ZnO Film Photocatalysts

    Directory of Open Access Journals (Sweden)

    Bosi Yin

    2014-01-01

    Full Text Available We have synthesized high-quality, nanoscale ultrathin ZnO films at relatively low temperature using a facile and effective hydrothermal approach. ZnO films were characterized by scanning electron microscope (SEM, X-ray diffraction (XRD, Raman spectroscopy, photoluminescence spectra (PL, and UV-vis absorption spectroscopy. The products demonstrated 95% photodegradation efficiency with Congo red (CR after 40 min irradiation. The photocatalytic degradation experiments of methyl orange (MO and eosin red also were carried out. The results indicate that the as-obtained ZnO films might be promising candidates as the excellent photocatalysts for elimination of waste water.

  19. А mathematical model study of suspended monorail

    OpenAIRE

    Viktor GUTAREVYCH

    2012-01-01

    The mathematical model of suspended monorail track with allowance for elastic strain which occurs during movement of the monorail carriage was developed. Standard forms for single span and double span of suspended monorail sections were established.

  20. А mathematical model study of suspended monorail

    Directory of Open Access Journals (Sweden)

    Viktor GUTAREVYCH

    2012-01-01

    Full Text Available The mathematical model of suspended monorail track with allowance for elastic strain which occurs during movement of the monorail carriage was developed. Standard forms for single span and double span of suspended monorail sections were established.

  1. Structural and optical characterization of indium-antimony complexes in ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Türker, M.; Deicher, M., E-mail: manfred.deicher@tech-phys.uni-sb.de; Johnston, K.; Wolf, H.; Wichert, Th. [Universität des Saarlandes, Experimentalphysik (Germany)

    2015-04-15

    One of the main obstacles to the technical application of the wide-gap semiconductor ZnO represents the difficulty to achieve reliable p-type doping of ZnO with group V elements (N, P, As, Sb) acting as acceptors located on O lattice sites. The theoretically proposed concepts of cluster-doping or codoping may lead to an enhanced and stable p-type conductivity of ZnO. We report on PAC results obtained by codoping experiments of ZnO by ion implantation using the donor {sup 111}In and the group-V acceptor Sb. The formation of In-Sb pairs has been observed. Based on these PAC results, there is no evidence for the formation of In-acceptor complexes involving more than one Sb acceptor. These results has been complemented by photoluminescence measurements.

  2. Hydrophobic ZnO nanostructured thin films on glass substrate by simple successive ionic layer absorption and reaction (SILAR) method

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, P. Suresh; Raj, A. Dhayal [Thin Film and Nanomaterials Laboratory, Department of Physics, Bharathiar University, Coimbatore-641046 (India); Mangalaraj, D., E-mail: dmraj800@yahoo.co [Department of Nanoscience and Technology, Bharathiar University, Coimbatore-641046 (India); Nataraj, D. [Thin Film and Nanomaterials Laboratory, Department of Physics, Bharathiar University, Coimbatore-641046 (India)

    2010-10-01

    In the present work, ZnO nanostructured thin films were grown on glass substrates by a simple successive ionic layer absorption and reaction method (SILAR) process at relatively low temperature for its self cleaning application. X-ray diffraction, scanning electron microscopy and Photoluminescence (PL) spectra were used to characterize the prepared ZnO nanostructured film. XRD pattern clearly reviles that the grown ZnO nanostructure film reflect (002) orientation with c-direction. SEM image clearly shows the surface morphology with cluster of spindle and flower-like nanostructured with diameter various around 350 nm. Photoluminescence (PL) spectra of ZnO nanostructures film exhibit a UV emission around 385nm and visible emission in the range around 420-500 nm. Good water repellent behavior were observed for ZnO nanostructured film without any surface modification.

  3. Hydrophobic ZnO nanostructured thin films on glass substrate by simple successive ionic layer absorption and reaction (SILAR) method

    International Nuclear Information System (INIS)

    Kumar, P. Suresh; Raj, A. Dhayal; Mangalaraj, D.; Nataraj, D.

    2010-01-01

    In the present work, ZnO nanostructured thin films were grown on glass substrates by a simple successive ionic layer absorption and reaction method (SILAR) process at relatively low temperature for its self cleaning application. X-ray diffraction, scanning electron microscopy and Photoluminescence (PL) spectra were used to characterize the prepared ZnO nanostructured film. XRD pattern clearly reviles that the grown ZnO nanostructure film reflect (002) orientation with c-direction. SEM image clearly shows the surface morphology with cluster of spindle and flower-like nanostructured with diameter various around 350 nm. Photoluminescence (PL) spectra of ZnO nanostructures film exhibit a UV emission around 385nm and visible emission in the range around 420-500 nm. Good water repellent behavior were observed for ZnO nanostructured film without any surface modification.

  4. Effect of growth temperature on the epitaxial growth of ZnO on GaN by ALD

    Science.gov (United States)

    Särkijärvi, Suvi; Sintonen, Sakari; Tuomisto, Filip; Bosund, Markus; Suihkonen, Sami; Lipsanen, Harri

    2014-07-01

    We report on the epitaxial growth of ZnO on GaN template by atomic layer deposition (ALD). Diethylzinc (DEZn) and water vapour (H2O) were used as precursors. The structure and the quality of the grown ZnO layers were studied with scanning electron microscope (SEM), X-ray diffraction (XRD), photoluminescence (PL) measurements and positron annihilation spectroscopy. The ZnO films were confirmed epitaxial, and the film quality was found to improve with increasing deposition temperature in the vicinity of the threshold temperature of two dimensional growth. We conclude that high quality ZnO thin films can be grown by ALD. Interestingly only separate Zn-vacancies were observed in the films, although ZnO thin films typically contain fairly high density of surface pits and vacancy clusters.

  5. Suspended Solids Profiler Shop Test Report

    International Nuclear Information System (INIS)

    STAEHR, T.W.

    2000-01-01

    The Suspended Solids Profiler (SSP) Instrument is planned to be installed in the AZ-101 tank to measure suspended solids concentrations during mixer pump testing. The SSP sensor uses a reflectance measurement principle to determine the suspended solids concentrations. The purpose of this test is to provide a documented means of verifying that the functional components of the SSP operate properly

  6. Mechanisms of electrical isolation in O+ -irradiated ZnO

    Science.gov (United States)

    Zubiaga, A.; Tuomisto, F.; Coleman, V. A.; Tan, H. H.; Jagadish, C.; Koike, K.; Sasa, S.; Inoue, M.; Yano, M.

    2008-07-01

    We have applied positron annihilation spectroscopy combined with sheet resistance measurements to study the electrical isolation of thin ZnO layers irradiated with 2 MeV O+ ions at various fluences. Our results indicate that Zn vacancies, the dominant defects detected by positrons, are produced in the irradiation at a relatively low rate of about 2000cm-1 when the ion fluence is at most 1015cm-2 and that vacancy clusters are created at higher fluences. The Zn vacancies introduced in the irradiation act as dominant compensating centers and cause the electrical isolation, while the results suggest that the vacancy clusters are electrically inactive.

  7. Antibacterial properties of F-doped ZnO visible light photocatalyst

    Energy Technology Data Exchange (ETDEWEB)

    Podporska-Carroll, Joanna, E-mail: joannapcarroll@gmail.com [Center for Research in Engineering Surface Technology (CREST), DIT FOCAS Institute, Kevin St., Dublin (Ireland); Myles, Adam [Center for Research in Engineering Surface Technology (CREST), DIT FOCAS Institute, Kevin St., Dublin (Ireland); School of Chemical and Pharmaceutical Sciences, Dublin Institute of Technology, Kevin St., Dublin (Ireland); Quilty, Brid [School of Biotechnology, Dublin City University, Dublin (Ireland); McCormack, Declan E.; Fagan, Rachel [Center for Research in Engineering Surface Technology (CREST), DIT FOCAS Institute, Kevin St., Dublin (Ireland); School of Chemical and Pharmaceutical Sciences, Dublin Institute of Technology, Kevin St., Dublin (Ireland); Hinder, Steven J. [The Surface Analysis Laboratory, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Dionysiou, Dionysios D., E-mail: dionysios.d.dionysiou@uc.edu [Environmental Engineering and Science Program, Department of Biomedical, Chemical and Environmental Engineering (DBCEE), 705 Engineering Research Center, University of Cincinnati, Cincinnati, OH 45221-0012 (United States); Pillai, Suresh C., E-mail: Pillai.Suresh@itsligo.ie [Center for Research in Engineering Surface Technology (CREST), DIT FOCAS Institute, Kevin St., Dublin (Ireland); Nanotechnology Research Group, Department of Environmental Science, PEM Centre, Institute of Technology Sligo, Sligo (Ireland)

    2017-02-15

    Highlights: • F doped ZnO nano-powders were obtained by a modified sol–gel method. • These materials were found to be effective against S. aureus and E. coli. • Enhanced visible light photocatalytic and antimicrobial properties were obtained. • The toxic effect of ZnO on bacteria can be due to the release of zinc cations. • Production of reactive oxidation species influences bacterial viability. - Abstract: Nanocrystalline ZnO photocatalysts were prepared by a sol–gel method and modified with fluorine to improve their photocatalytic anti-bacterial activity in visible light. Pathogenic bacteria such as Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) were employed to evaluate the antimicrobial properties of synthesized materials. The interaction with biological systems was assessed by analysis of the antibacterial properties of bacteria suspended in 2% (w/w) powder solutions. The F-doping was found to be effective against S. aureus (99.99% antibacterial activity) and E. coli (99.87% antibacterial activity) when irradiated with visible light. Production of reactive oxygen species is one of the major factors that negatively impact bacterial growth. In addition, the nanosize of the ZnO particles can also be toxic to microorganisms. The small size and high surface-to-volume ratio of the ZnO nanoparticles are believed to play a role in enhancing antimicrobial activity.

  8. Distribution and transportation of suspended sediment

    International Nuclear Information System (INIS)

    Schubel, J.R.

    1975-01-01

    A number of studies of the distribution and character of suspended matter in the waters of the Atlantic shelf have documented the variations in the concentration of total suspended matter in both time and space. Very little is known, however, about the ultimate sources of inorganic suspended matter, and even less is known about the routes and rates of suspended sediment transport in shelf waters. Suspended particulate matter constitutes a potential vehicle for the transfer of energy-associated contaminants, radionuclides and oil, back to the coast and therefore to man. The concentrations of total suspended matter in shelf waters are typically so low, however, that the mechanism is ineffective. Studies of suspended particulate matter have a high scientific priority, but in this investigator's opinion the state of knowledge is adequate for preparation of the environmental impact statements that would be required for siting of offshore nuclear power plants and for oil drilling on the Atlantic Continental Shelf

  9. Positron annihilation lifetime measurement of electron-irradiated ZnO crystals

    International Nuclear Information System (INIS)

    Tomiyama, N.; Takenaka, M.; Kuramoto, E.

    1992-01-01

    In order to clarify the basic properties of radiation-induced defects in ZnO crystals positron annihilation lifetime measurements were performed for the ZnO crystals irradiated by 28 MeV electrons at 77 K. The electron-irradiation induced the color change of the specimens from the original yellowish-white to the orange and long lifetime component of about 200 psec. The isochronal annealing experiments showed that the decrease of the positron annihilation lifetime appeared in the temperature range between 423 and 473 K and between 723 and 923 K. The radiation-induced color change disappeared in the first temperature range. It can be considered that the first stage corresponds to migration and recovery of radiation-induced oxygen vacancies. It is difficult to identify the second stage, but it might be the recovery stage of small ZnO interstitial clusters formed through clustering of Zn and O interstitials

  10. Suspended dust in Norwegian cities

    International Nuclear Information System (INIS)

    2001-01-01

    According to calculations, at least 80 000 people in Oslo and 8 000 in Trondheim were annoyed by too much suspended dust in 2000. The dust concentration is greatest in the spring, presumably because dust is swirling up from melting snow and ice on the streets. Car traffic is the main source of the dust, except for some of the most highly exposed regions where wood-firing from old stoves contributes up to 70 percent of the dust. National targets for air quality include suspended dust, nitrogen dioxide, sulphur dioxide and benzene. Calculations show that nitrogen dioxide emissions exceeding the limit affected 4 000 people in Oslo and 1 000 people in Trondheim. The sulphur dioxide emissions in the major cities did non exceed the national quality limit; they did exceed the limit in some of the smaller industrial centres. In Trondheim, measurements show that the national limit for benzene was exceeded. Most of the emission of nitrogen dioxide comes from the road traffic. Local air pollution at times causes considerable health- and well-being problems in the larger cities and industrial centres, where a great part of the population may be at risk of early death, infection of the respiratory passage, heart- and lung diseases and cancer

  11. Defect mediated magnetic interaction and high Tc ferromagnetism in Co doped ZnO nanoparticles.

    Science.gov (United States)

    Pal, Bappaditya; Giri, P K

    2011-10-01

    Structural, optical and magnetic studies have been carried out for the Co-doped ZnO nanoparticles (NPs). ZnO NPs are doped with 3% and 5% Co using ball milling and ferromagnetism (FM) is studied at room temperature and above. A high Curie temperature (Tc) has been observed from the Co doped ZnO NPs. X-ray diffraction and high resolution transmission electron microscopy analysis confirm the absence of metallic Co clusters or any other phase different from würtzite-type ZnO. UV-visible absorption and photoluminescence studies on the doped samples show change in band structure and oxygen vacancy defects, respectively. Micro-Raman studies of doped samples shows defect related additional strong bands at 547 and 574 cm(-1) confirming the presence of oxygen vacancy defects in ZnO lattice. The field dependence of magnetization (M-H curve) measured at room temperature exhibits the clear M-H loop with saturation magnetization and coercive field of the order of 4-6 emu/g and 260 G, respectively. Temperature dependence of magnetization measurement shows sharp ferromagnetic to paramagnetic transition with a high Tc = 791 K for 3% Co doped ZnO NPs. Ferromagnetic ordering is interpreted in terms of overlapping of polarons mediated through oxygen vacancy defects based on the bound magnetic polaron (BMP) model. We show that the observed FM data fits well with the BMP model involving localised carriers and magnetic cations.

  12. Electronic structure, magnetic and structural properties of Ni doped ZnO nanoparticles

    International Nuclear Information System (INIS)

    Kumar, Shalendra; Vats, Prashant; Gautam, S.; Gupta, V.P.; Verma, K.D.; Chae, K.H.; Hashim, Mohd; Choi, H.K.

    2014-01-01

    Highlights: • XRD, and HR-TEM results show the single phase nature of Ni doped ZnO nanoparticles. • dc magnetization results indicate the RT-FM in Ni doped ZnO nanoparticles. • Ni L 3,2 edge NEXAFS spectra infer that Ni ions are in +2 valence state. • O K edge NEXAFS spectra show that O vacancy increases with Ni doping in ZnO. - Abstract: We report structural, magnetic and electronic structural properties of Ni doped ZnO nanoparticles prepared by auto-combustion method. The prepared nanoparticles were characterized by using X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), near edge X-ray absorption fine structure (NEXAFS) spectroscopy, and dc magnetization measurements. The XRD and HR-TEM results indicate that Ni doped ZnO nanoparticles have single phase nature with wurtzite lattice and exclude the presence of secondary phase. NEXAFS measurements performed at Ni L 3,2 -edges indicates that Ni ions are in +2 valence state and exclude the presence of Ni metal clusters. O K-edge NEXAFS spectra indicate an increase in oxygen vacancies with Ni-doping, while Zn L 3,2 -edge show the absence of Zn-vacancies. The magnetization measurements performed at room temperature shows that pure and Ni doped ZnO exhibits ferromagnetic behavior

  13. Clustering of near clusters versus cluster compactness

    International Nuclear Information System (INIS)

    Yu Gao; Yipeng Jing

    1989-01-01

    The clustering properties of near Zwicky clusters are studied by using the two-point angular correlation function. The angular correlation functions for compact and medium compact clusters, for open clusters, and for all near Zwicky clusters are estimated. The results show much stronger clustering for compact and medium compact clusters than for open clusters, and that open clusters have nearly the same clustering strength as galaxies. A detailed study of the compactness-dependence of correlation function strength is worth investigating. (author)

  14. Viscous bursting of suspended films

    Science.gov (United States)

    Debrégeas, G.; Martin, P.; Brochard-Wyart, F.

    1995-11-01

    Soap films break up by an inertial process. We present here the first observations on freely suspended films of long-chain polymers, where viscous effects are dominant and no surfactant is present. A hole is nucleated at time 0 and grows up to a radius R(t) at time t. A surprising feature is that the liquid from the hole is not collected into a rim (as it is in soap films): The liquid spreads out without any significant change of the film thickness. The radius R(t) grows exponentially with time, R~exp(t/τ) [while in soap films R(t) is linear]. The rise time τ~ηe/2γ where η is viscosity, e is thickness (in the micron range), and γ is surface tension. A simple model is developed to explain this growth law.

  15. Intermodal resonance of vibrating suspended cables

    NARCIS (Netherlands)

    Rienstra, S.W.

    2010-01-01

    The weakly nonlinear free vibrations of a single suspended cable, or a coupled system of suspended cables, may be classified as gravity modes (no tension variations to leading order) and elasto-gravity modes (tension and vertical displacement equally important). It was found earlier [12] that the

  16. Ion-implantation induced defects in ZnO studied by a slow positron beam

    International Nuclear Information System (INIS)

    Chen, Z.Q.; Maekawa, M.; Kawasuso, A.; Sekiguchi, T.; Suzuki, R.

    2004-01-01

    Introduction and annealing behavior of defects in Al + -implanted ZnO have been studied using an energy variable slow positron beam. Vacancy clusters are produced after Al + -implantation. With increasing ion dose above 10 14 Al + /cm 2 the implanted layer is amorphized. Heat treatment up to 600 C enhances the creation of large voids that allow the positronium formation. The large voids disappear accompanying the recrystallization process by further heat treatment above 600 C. Afterwards, implanted Al impurities are completely activated to contribute to the n-type conduction. The ZnO crystal quality is also improved after recrystallization. (orig.)

  17. Ion-implantation induced defects in ZnO studied by a slow positron beam

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Z.Q.; Maekawa, M.; Kawasuso, A. [Japan Atomic Energy Research Institute, Gunma (Japan); Sekiguchi, T. [National Inst. for Materials Science, Tsukuba, Ibaraki (Japan); Suzuki, R. [National Inst. of Advanced Industrial Science and Technology, Tsukuba, Ibaraki (Japan)

    2004-07-01

    Introduction and annealing behavior of defects in Al{sup +}-implanted ZnO have been studied using an energy variable slow positron beam. Vacancy clusters are produced after Al{sup +}-implantation. With increasing ion dose above 10{sup 14} Al{sup +}/cm{sup 2} the implanted layer is amorphized. Heat treatment up to 600 C enhances the creation of large voids that allow the positronium formation. The large voids disappear accompanying the recrystallization process by further heat treatment above 600 C. Afterwards, implanted Al impurities are completely activated to contribute to the n-type conduction. The ZnO crystal quality is also improved after recrystallization. (orig.)

  18. Acceptors in ZnO

    Energy Technology Data Exchange (ETDEWEB)

    McCluskey, Matthew D., E-mail: mattmcc@wsu.edu; Corolewski, Caleb D.; Lv, Jinpeng; Tarun, Marianne C.; Teklemichael, Samuel T. [Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814 (United States); Walter, Eric D. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Norton, M. Grant; Harrison, Kale W. [School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164-2920 (United States); Ha, Su [Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164-6515 (United States)

    2015-03-21

    Zinc oxide (ZnO) has potential for a range of applications in the area of optoelectronics. The quest for p-type ZnO has focused much attention on acceptors. In this paper, Cu, N, and Li acceptor impurities are discussed. Experimental evidence indicates these point defects have acceptor levels 3.2, 1.4, and 0.8 eV above the valence-band maximum, respectively. The levels are deep because the ZnO valence band is quite low compared to conventional, non-oxide semiconductors. Using MoO{sub 2} contacts, the electrical resistivity of ZnO:Li was measured and showed behavior consistent with bulk hole conduction for temperatures above 400 K. A photoluminescence peak in ZnO nanocrystals is attributed to an acceptor, which may involve a Zn vacancy. High field (W-band) electron paramagnetic resonance measurements on the nanocrystals revealed an axial center with g{sub ⊥} = 2.0015 and g{sub //} = 2.0056, along with an isotropic center at g = 2.0035.

  19. Fabrication and characterizations of ZnO nanorods/Au nanoparticle composites on the electropolished Ti substrate

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hsiang, E-mail: hchen@ncnu.edu.tw [National Chi Nan University, No.1, Daxue Rd., Puli Township, Nantou County 545, Taiwan, ROC (China); Yeh, Yih-Min [WuFeng University, No. 117, Sec 2, Chiankuo Rd, Minhsiung, Chiayi County 62153, Taiwan, ROC (China); Chen, Jian-Zhi [National Chi Nan University, No.1, Daxue Rd., Puli Township, Nantou County 545, Taiwan, ROC (China); Liu, Song-Ming [WuFeng University, No. 117, Sec 2, Chiankuo Rd, Minhsiung, Chiayi County 62153, Taiwan, ROC (China); Huang, Bo Yun; Wu, Zhi-Huei; Tsai, Shaung-Lin; Chang, Hung-Wei; Chu, Yu-Cheng; Liao, Chuan Hao [National Chi Nan University, No.1, Daxue Rd., Puli Township, Nantou County 545, Taiwan, ROC (China)

    2013-12-31

    Au nanoparticles (NPs) were spread on ZnO nanorods (NRs) on the polished Ti substrate to form Au/ZnO nanocomposites. Multiple material analyses including field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) analyses, Fourier-transform infrared spectrometer (FTIR) and images taken by optical microscope were performed on Au NPs of 2 nm and 20 nm on ZnO NRs. The FESEM and optical images under optical microscope indicate that 20 nm NPs can form more and larger clusters than 2 nm NPs on ZnO nanorod. Furthermore, more Au can be detected by EDS and XRD. We studied the behaviors of Au NPs on ZnO NR applications for future potential biosensing and antiseptic devices. - Highlights: • Nanocomposites of Au nanoparticles were spread on ZnO nanorods on Ti substrate. • Multiple material analyses were performed on 2 nm and 20 nm nanoparticles. • 20 nm nanoparticles formed more and larger clusters. • Optical images show well-distributed nanoparticle ZnO nanorods.

  20. Zn nanoparticle formation in FIB irradiated single crystal ZnO

    Science.gov (United States)

    Pea, M.; Barucca, G.; Notargiacomo, A.; Di Gaspare, L.; Mussi, V.

    2018-03-01

    We report on the formation of Zn nanoparticles induced by Ga+ focused ion beam on single crystal ZnO. The irradiated materials have been studied as a function of the ion dose by means of atomic force microscopy, scanning electron microscopy, Raman spectroscopy and transmission electron microscopy, evidencing the presence of Zn nanoparticles with size of the order of 5-30 nm. The nanoparticles are found to be embedded in a shallow amorphous ZnO matrix few tens of nanometers thick. Results reveal that ion beam induced Zn clustering occurs producing crystalline particles with the same hexagonal lattice and orientation of the substrate, and could explain the alteration of optical and electrical properties found for FIB fabricated and processed ZnO based devices.

  1. A New Measure for Transported Suspended Sediment

    Science.gov (United States)

    Yang, Q.

    2017-12-01

    Non-uniform suspended sediment plays an important role in many geographical and biological processes. Despite extensive study, understanding to it seems to stagnate when times to consider non-uniformity and non-equilibrium scenarios comes. Due to unsatisfactory reproducibility, large-scaled flume seems to be incompetent to conduct more fundamental research in this area. To push the realm a step further, experiment to find how suspended sediment exchanges is conducted in a new validated equipment, in which turbulence is motivated by oscillating grids. Analysis shows that 1) suspended sediment exchange is constrained by ωS invariance, 2) ωS of the suspended sediment that certain flow regime could support is unique regardless of the sediment gradation and 3) the more turbulent the flow, the higher ωS of the suspension the flow could achieve. A new measure for suspended sediment ωS, the work required to sustain sediment in suspension transport mode if multiplied by gravitational acceleration, is thus proposed to better describe the dynamics of transported suspended sediment. Except for the further understanding towards suspended sediment transportation mechanics, with this energy measure, a strategy to distribute total transport capacity to different fractions could be derived and rational calculation of non-uniform sediment transport capacity under non-equilibrium conditions be possible.

  2. Writing and functionalisation of suspended DNA nanowires on superhydrophobic pillar arrays

    KAUST Repository

    Miele, Ermanno; Accardo, Angelo; Falqui, Andrea; Marini, Monica; Giugni, Andrea; Leoncini, Marco; De Angelis, Francesco De; Krahne, Roman; Di Fabrizio, Enzo M.

    2014-01-01

    Nanowire arrays and networks with precisely controlled patterns are very interesting for innovative device concepts in mesoscopic physics. In particular, DNA templates have proven to be versatile for the fabrication of complex structures that obtained functionality via combinations with other materials, for example by functionalisation with molecules or nanoparticles, or by coating with metals. Here, the controlled motion of the a three-phase contact line (TCL) of DNA-loaded drops on superhydrophobic substrates is used to fabricate suspended nanowire arrays. In particular, the deposition of DNA wires is imaged in situ, and different patterns are obtained on hexagonal pillar arrays by controlling the TCL velocity and direction. Robust conductive wires and networks are achieved by coating the wires with a thin layer of gold, and as proof of concept conductivity measurements are performed on single suspended wires. The plastic material of the superhydrophobic pillars ensures electrical isolation from the substrate. The more general versatility of these suspended nanowire networks as functional templates is outlined by fabricating hybrid organic-metal-semiconductor nanowires by growing ZnO nanocrystals onto the metal-coated nanowires.

  3. Writing and functionalisation of suspended DNA nanowires on superhydrophobic pillar arrays

    KAUST Repository

    Miele, Ermanno

    2014-08-08

    Nanowire arrays and networks with precisely controlled patterns are very interesting for innovative device concepts in mesoscopic physics. In particular, DNA templates have proven to be versatile for the fabrication of complex structures that obtained functionality via combinations with other materials, for example by functionalisation with molecules or nanoparticles, or by coating with metals. Here, the controlled motion of the a three-phase contact line (TCL) of DNA-loaded drops on superhydrophobic substrates is used to fabricate suspended nanowire arrays. In particular, the deposition of DNA wires is imaged in situ, and different patterns are obtained on hexagonal pillar arrays by controlling the TCL velocity and direction. Robust conductive wires and networks are achieved by coating the wires with a thin layer of gold, and as proof of concept conductivity measurements are performed on single suspended wires. The plastic material of the superhydrophobic pillars ensures electrical isolation from the substrate. The more general versatility of these suspended nanowire networks as functional templates is outlined by fabricating hybrid organic-metal-semiconductor nanowires by growing ZnO nanocrystals onto the metal-coated nanowires.

  4. Porous nanostructured ZnO films deposited by picosecond laser ablation

    International Nuclear Information System (INIS)

    Sima, Cornelia; Grigoriu, Constantin; Besleaga, Cristina; Mitran, Tudor; Ion, Lucian; Antohe, Stefan

    2012-01-01

    Highlights: ► We deposite porous nanostructured ZnO films by picoseconds laser ablation (PLA). ► We examine changes of the films structure on the experimental parameter deposition. ► We demonstrate PLA capability to produce ZnO nanostructured films free of particulates. - Abstract: Porous nanostructured polycrystalline ZnO films, free of large particulates, were deposited by picosecond laser ablation. Using a Zn target, zinc oxide films were deposited on indium tin oxide (ITO) substrates using a picosecond Nd:YVO 4 laser (8 ps, 50 kHz, 532 nm, 0.17 J/cm 2 ) in an oxygen atmosphere at room temperature (RT). The morpho-structural characteristics of ZnO films deposited at different oxygen pressures (150–900 mTorr) and gas flow rates (0.25 and 10 sccm) were studied. The post-deposition influence of annealing (250–550 °C) in oxygen on the film characteristics was also investigated. At RT, a mixture of Zn and ZnO formed. At substrate temperatures above 350 °C, the films were completely oxidized, containing a ZnO wurtzite phase with crystallite sizes of 12.2–40.1 nm. At pressures of up to 450 mTorr, the porous films consisted of well-distinguished primary nanoparticles with average sizes of 45–58 nm, while at higher pressures, larger clusters (3.1–14.7 μm) were dominant, leading to thicker films; higher flow rates favored clustering.

  5. Investigation of the Optimal Parameters in Hydrothermal Method for the Synthesis of ZnO Nanorods

    Directory of Open Access Journals (Sweden)

    Ying-Chung Chen

    2014-01-01

    Full Text Available We investigated a two-step method to deposit the ZnO-based nanostructure films, including nanorods and nanoflowers. In the first step, sputtering method was used to deposit the ZnO films on SiO2/Si substrates as the seed layer. In the second step, Zn(NO32–6H2O and C6H12N4 were used as precursors and hydrothermal process was used as the method to synthesize the ZnO films. After that, the ZnO films were measured by an X-ray diffraction pattern and a FESEM to analyze their crystallization and morphology. We had found that the ZnO films had three different morphologies synthesized on ZnO/SiO2/Si substrates, including irregular-plate structure films, nanorod films, and beautiful chrysanthemum-like clusters (nanoflower films. We would prove that the face direction of ZnO/SiO2/Si substrates in the hydrothermal bottle and deposition time were two important factors to influence the synthesized results of the ZnO films.

  6. Understanding lattice defects to influence ferromagnetic order of ZnO nanoparticles by Ni, Cu, Ce ions

    Energy Technology Data Exchange (ETDEWEB)

    Verma, Kuldeep Chand, E-mail: dkuldeep.physics@gmail.com [Department of Physics, Panjab University, Chandigarh 160014 (India); Kotnala, R.K., E-mail: rkkotnala@gmail.com [CSIR-National Physical Laboratory, New Delhi 110012 (India)

    2017-02-15

    Future spintronics technologies based on diluted magnetic semiconductors (DMS) will rely heavily on a sound understanding of the microscopic origins of ferromagnetism in such materials. It remains unclear, however, whether the ferromagnetism in DMS is intrinsic - a precondition for spintronics - or due to dopant clustering. For this, we include a simultaneous doping from transition metal (Ni, Cu) and rare earth (Ce) ions in ZnO nanoparticles that increase the antiferromagnetic ordering to achieve high-T{sub c} ferromagnetism. Rietveld refinement of XRD patterns indicate that the dopant ions in ZnO had a wurtzite structure and the dopants, Ni{sup 2+}, Cu{sup 2+}, Ce{sup 3+} ions, are highly influenced the lattice constants to induce lattice defects. The Ni, Cu, Ce ions in ZnO have nanoparticles formation than nanorods was observed in pure sample. FTIR involve some organic groups to induce lattice defects and the metal-oxygen bonding of Zn, Ni, Cu, Ce and O atoms to confirm wurtzite structure. Raman analysis evaluates the crystalline quality, structural disorder and defects in ZnO lattice with doping. Photoluminescence spectra have strong near-band-edge emission and visible emission bands responsible for defects due to oxygen vacancies. The energy band gap is calculated using Tauc relation. Room temperature ferromagnetism has been described due to bound magnetic polarons formation with Ni{sup 2+}, Cu{sup 2+}, Ce{sup 3+} ions in ZnO via oxygen vacancies. The zero field and field cooling SQUID measurement confirm the strength of antiferromagnetism in ZnO. The field cooling magnetization is studied by Curie-Weiss law that include antiferromagnetic interactions up to low temperature. The XPS spectra have involve +3/+4 oxidation states of Ce ions to influence the observed ferromagnetism. - Graphical abstract: The lattice defects/vacancies attributed by Ni and Ce ions in the wurtzite ZnO structure are responsible in high T{sub c} -ferromagnetism due to long-range magnetic

  7. Positron annihilation lifetime spectroscopy of ZnO bulk samples

    International Nuclear Information System (INIS)

    Zubiaga, A.; Plazaola, F.; Garcia, J. A.; Tuomisto, F.; Munoz-Sanjose, V.; Tena-Zaera, R.

    2007-01-01

    In order to gain a further insight into the knowledge of point defects of ZnO, positron annihilation lifetime spectroscopy was performed on bulk samples annealed under different atmospheres. The samples were characterized at temperatures ranging from 10 to 500 K. Due to difficulties in the conventional fitting of the lifetime spectra caused by the low intensity of the defect signals, we have used an alternative method as a solution to overcome these difficulties and resolve all the lifetime components present in the spectra. Two different vacancy-type defects are identified in the samples: Zn vacancy complexes (V Zn -X) and vacancy clusters consisting of up to five missing Zn-O pairs. In addition to the vacancies, we observe negative-ion-type defects, which are tentatively attributed to intrinsic defects in the Zn sublattice. The effect of the annealing on the observed defects is discussed. The concentrations of the V Zn -X complexes and negative-ion-type defects are in the 0.2-2 ppm range, while the cluster concentrations are 1-2 orders of magnitude lower

  8. doped ZnO thick film resistors

    Indian Academy of Sciences (India)

    The characterization and ethanol gas sensing properties of pure and doped ZnO thick films were investigated. Thick films of pure zinc oxide were prepared by the screen printing technique. Pure zinc oxide was almost insensitive to ethanol. Thick films of Al2O3 (1 wt%) doped ZnO were observed to be highly sensitive to ...

  9. Suspended and localized single nanostructure growth across a nanogap by an electric field

    International Nuclear Information System (INIS)

    Lee, Chung-Hoon; Schneider, Susan C; Josse, Fabien; Han, Jun Hyun

    2011-01-01

    Direct growth of a suspended single nanostructure (SSN) at a specific location is presented. The SSN is grown across a metallic nanoscale gap by migration in air at room temperature. The nanogap is fabricated by industrial standard optical lithography and anisotropic wet chemical silicon etching. A DC current bias, 1 nA, is applied across the metallic gap to induce nanoscale migration of Zn or ZnO. The history of the voltage drop across the gap as a function of time clearly indicates the moment when migration begins. The shape of SSNs grown across the nanogap by the migration is asymmetric at each electrode due to the asymmetric electric field distribution within the nanogap. An SSN can be used as the platform for two-terminal active or passive nanoscale electronics in optoelectronics, radio frequency (RF) resonators, and chemical/biological sensors.

  10. Transport of suspended matter through rock formations

    International Nuclear Information System (INIS)

    Wahlig, B.G.

    1980-01-01

    It may be hypothesized that significant quantities of some waste nuclides could be adsorbed on the surfaces of particles suspended in the flowing groundwater and thereby migrate farther or faster than they would in dissolved form. This thesis deals with one aspect of this proposed migration mechanism, the transport of suspended matter through rock formations. A theoretical examination of the forces effecting suspended particles in flowing groundwater indicates that only two interaction energies are likely to be significant compared to the particles' thermal energies. The responsible interactions are van der Waals attraction between the particles and the rock, and electrolytic double-layer repulsion between the atmospheres of ions near the surfaces of the particles and the rock. This theoretical understanding was tested in column flow adsorption experiments using fine kaolin particles as the suspended matter and crushed basalt as the rock medium. The effects of several parameters on kaolin mobility were explored, including the influences of the following: solution ion concentration, solution cation valence, degree of solution oxygen saturation, solution flow velocity, and degree of rock surface ageing. The experimental results indicate that the migration of suspended matter over kilometer distances in the lithosphere is very unlikely unless the average pore size of the conducting mediumis fairly large (> 1mm), or the flow occurs in large fractures

  11. Investigating the adsorption of H2O on ZnO nanoclusters by first principle calculations

    KAUST Repository

    Al-Sunaidi, Abdullah A.

    2011-04-01

    The interaction of a single H2O molecule on selected ZnO nanoclusters is investigated by carrying out calculations based on the density-functional theory at the hybrid-GGA (B97-2) level. These clusters have ring, drum, tube and bubble shapes and their physical properties like the binding energy and the band gap energy depend strongly on the shape and size of the cluster. Depending on the stability of the cluster, H2O show both chemisorption and dissociation on the surfaces of the clusters. We analyzed the effect of H2O adsorption on the properties of clusters of size n = 12 via the density of state, HOMO-LUMO orbitals and the changes in the IR frequencies. © 2011 Elsevier B.V. All rights reserved.

  12. ZnO nanocrystals and allied materials

    CERN Document Server

    Okada, Tatsuo

    2014-01-01

    ZnO has been the central theme of research in the past decade due to its various applications in band gap engineering, and textile and biomedical industries. In nanostructured form, it offers ample opportunities to realize tunable optical and optoelectronic properties and it was also termed as a potential material to realize room temperature ferromagnetism. This book presents 17 high-quality contributory chapters on ZnO related systems written by experts in this field. These chapters will help researchers to understand and explore the varied physical properties to envisage device applications of ZnO in thin film, heterostructure and nanostructure forms.

  13. Catalyst growth of single crystal aligned ZnO nanorods on ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Dongxu; Andreazza, Caroline; Andreazza, Pascal [Centre de Recherche sur la Matiere Divisee, CNRS-Universite d' Orleans, 1b rue de la Ferollerie, 45071 Orleans cedex 2 (France)

    2005-02-01

    One dimensional ZnO nanorods were successfully fabricated on Si substrates via a simple physical vapor-phase transport method at 950 C. A ZnO shell covered Au/Zn alloy is assumed as the nucleation site, then ZnO nanorods grow following a vapor-solid (VS) process. In order to guide the nanorod growth a c-axis oriented ZnO thin film and Au catalyst were first deposited on Si (100) surface. SEM images show nanorods grown on this substrate are vertical to the substrate surface. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Nuclear reactor with a suspended vessel

    International Nuclear Information System (INIS)

    Lemercier, Guy.

    1977-01-01

    This invention relates to a nuclear reactor with a suspended vessel and applies in particular when this is a fast reactor, the core or active part of the reactor being inside the vessel and immersed under a suitable volume of flowing liquid metal to cool it by extracting the calories released by the nuclear fission in the fuel assemblies forming this core [fr

  15. Bed-levelling experiments with suspended load

    NARCIS (Netherlands)

    Talmon, A.M.; De Graaff, J.

    1991-01-01

    Bed-levelling experiments are conducted in a straight laboratory channel. The experiments involve a significant fraction of suspended sediment transport. The purpose of the experiments is to provide data for modelling of the direction of sediment transport on a transverse sloping alluvial river bed,

  16. The Shape of Breasts Suspended in Liquid

    NARCIS (Netherlands)

    De Kleijn, S.C.; Rensen, W.H.J.

    2007-01-01

    Philips has designed an optical mammography machine. In this machine the breast is suspended into a cup in which the measurements take place. A special fluid is inserted into the cup to prevent the light from going around the breast instead of going through it but this fluid also weakens the signal.

  17. (suspended solids and metals) removal efficiencies

    African Journals Online (AJOL)

    ABSTRACT. Presented in this paper are the results of correlational analyses and logistic regression between metal substances (Cd, Cu,. Pb, Zn), as well as suspended solids removal, and physical pond parameters of 19 stormwater retention pond case studies obtained from the International Stormwater BMP database.

  18. Photocatalytic degradation of trichloroethylene in aqueous phase using nano-ZNO/Laponite composites

    International Nuclear Information System (INIS)

    Joo, Jin Chul; Ahn, Chang Hyuk; Jang, Dae Gyu; Yoon, Young Han; Kim, Jong Kyu; Campos, Luiza; Ahn, Hosang

    2013-01-01

    Highlights: • Stable nano-ZnO/Laponite composites (NZLc) as an alternative to TiO 2 were produced. • Nanoscale ZnO complexed with NZLc was found to be an effective photocatalyst. • TCE removal efficiency of NZLc was greater than that of bare nanoscale ZnO. • Nanoscale ZnO-mediated photodegradation varied with experimental conditions. • Developed NZLc overcame drawbacks (e.g., filtration and recovery of photocatalysts). -- Abstract: The feasibility of nano-ZnO/Laponite composites (NZLc) as a valid alternative to TiO 2 to mineralize trichloroethylene (TCE) without difficulties for recovery of photocatalysts was evaluated. Based on the experimental observations, the removal of TCE using NZLc under UV irradiation was multiple reaction processes (i.e., sorption, photolysis, and photocatalysis). Sorption of TCE was thermodynamically favorable due to the hydrophobic partitioning into crosslinked poly vinyl alcohol, and the adsorption onto high-surface-area mineral surfaces of both ZnO and Laponite. The degradation efficiency of TCE can be significantly improved using NZLc under UV irradiation, indicating that ZnO-mediated heterogeneous photocatalytic degradation occurred. However, the degradation efficiency was found to vary with experimental conditions (e.g., initial concentration of TCE, loading amount of NZLc, the intensity of light and initial solution pH). Although the removal of TCE by NZLc was found to be a complex function of sorption, photolysis, and photocatalysis, the photocatalytic degradation of TCE on the surface of ZnO was critical. Consequently, developed NZLc can be applied as a valid alternative to suspended TiO 2 powder, and overcome drawbacks (e.g., filtration and recovery of photocatalysts) in degradation of TCE for various water resources

  19. Photocatalytic degradation of trichloroethylene in aqueous phase using nano-ZNO/Laponite composites

    Energy Technology Data Exchange (ETDEWEB)

    Joo, Jin Chul; Ahn, Chang Hyuk; Jang, Dae Gyu; Yoon, Young Han [Korea Institute of Construction Technology, Water Resource and Environment Research Department (Korea, Republic of); Kim, Jong Kyu; Campos, Luiza [University College London, Department of Civil, Environmental, and Geomatic Engineering (United Kingdom); Ahn, Hosang, E-mail: hahn@kict.re.kr [Korea Institute of Construction Technology, Water Resource and Environment Research Department (Korea, Republic of)

    2013-12-15

    Highlights: • Stable nano-ZnO/Laponite composites (NZLc) as an alternative to TiO{sub 2} were produced. • Nanoscale ZnO complexed with NZLc was found to be an effective photocatalyst. • TCE removal efficiency of NZLc was greater than that of bare nanoscale ZnO. • Nanoscale ZnO-mediated photodegradation varied with experimental conditions. • Developed NZLc overcame drawbacks (e.g., filtration and recovery of photocatalysts). -- Abstract: The feasibility of nano-ZnO/Laponite composites (NZLc) as a valid alternative to TiO{sub 2} to mineralize trichloroethylene (TCE) without difficulties for recovery of photocatalysts was evaluated. Based on the experimental observations, the removal of TCE using NZLc under UV irradiation was multiple reaction processes (i.e., sorption, photolysis, and photocatalysis). Sorption of TCE was thermodynamically favorable due to the hydrophobic partitioning into crosslinked poly vinyl alcohol, and the adsorption onto high-surface-area mineral surfaces of both ZnO and Laponite. The degradation efficiency of TCE can be significantly improved using NZLc under UV irradiation, indicating that ZnO-mediated heterogeneous photocatalytic degradation occurred. However, the degradation efficiency was found to vary with experimental conditions (e.g., initial concentration of TCE, loading amount of NZLc, the intensity of light and initial solution pH). Although the removal of TCE by NZLc was found to be a complex function of sorption, photolysis, and photocatalysis, the photocatalytic degradation of TCE on the surface of ZnO was critical. Consequently, developed NZLc can be applied as a valid alternative to suspended TiO{sub 2} powder, and overcome drawbacks (e.g., filtration and recovery of photocatalysts) in degradation of TCE for various water resources.

  20. Room temperature ferromagnetism in Co doped ZnO within an optimal doping level of 5%

    International Nuclear Information System (INIS)

    Mohapatra, J.; Mishra, D.K.; Mishra, Debabrata; Perumal, A.; Medicherla, V.R.R.; Phase, D.M.; Singh, S.K.

    2012-01-01

    Highlights: ► Zn 1−x Co x O ((0 ≤ x ≤ 0.1)) system synthesized by solid state reaction technique. ► Observation of room temperature ferromagnetism for 3 and 5% Co doped ZnO. ► XPS and EPMA studies predict the occurrence of segregated CoO clusters. ► Suppresses ferromagnetic ordering in higher doping percentage of Co (>5%). -- Abstract: We report on the structural, micro-structural and magnetic properties of Zn 1−x Co x O (0 ≤ x ≤ 0.1) system. Electron probe micro-structural analysis on 5% Co doped ZnO indicates the presence of segregated cobalt oxide which is also confirmed from the Co 2p core level X-ray photoelectron spectrum. The presence of oxygen defects in lower percentage of Co doped ZnO (≤5%) enhances the carrier mediated exchange interaction and thereby enhancing the room-temperature ferromagnetic behaviour. Higher doping percentage of cobalt (>5%) creates weak link between the grains and suppresses the carrier mediated exchange interaction. This is the reason why room temperature ferromagnetism is not observed in 7% and 10% Co doped ZnO.

  1. Cluster headache

    Science.gov (United States)

    Histamine headache; Headache - histamine; Migrainous neuralgia; Headache - cluster; Horton's headache; Vascular headache - cluster ... Doctors do not know exactly what causes cluster headaches. They ... (chemical in the body released during an allergic response) or ...

  2. Intrinsic defects in ZnO varistors

    International Nuclear Information System (INIS)

    Mahan, G.D.

    1983-01-01

    Theoretical calculations are presented for equilibrium concentrations of zinc and oxygen vacancies in ZnO. Results are presented at the sintering temperature, and also at room temperature. Theoretical calculations of reaction constants show that the intrinsic donor is the oxygen vacancy, rather than the zinc interstitial. The depletion of vacancies in the surface region, as the ZnO is cooled from the sintering temperature, is also calculated. Homojunction effects which are caused by such depletion are shown to be small

  3. Bactericidal, structural and morphological properties of ZnO2 nanoparticles synthesized under UV or ultrasound irradiation

    International Nuclear Information System (INIS)

    Colonia, R; Solís, J L; Gómez, M

    2014-01-01

    Nanoparticles of ZnO 2 were synthesized by a sol–gel method using Zn(CH 3 COO) 2 and H 2 O 2 in an aqueous solution exposed to either ultraviolet (UV) or ultrasound irradiation. X-ray diffraction and scanning electron microscopy showed that the nanostructures consisted of spherical blackberry-like clusters. Nanoparticles fabricated by using UV irradiation had smaller sizes and narrower size distributions than nanoparticles prepared by using ultrasound. Bacillus subtilis (B. subtilis), Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were used as test microorganisms, and the antibacterial activity of the ZnO 2 nanoparticles was studied by use of the well diffusion agar bacteriological test. ZnO 2 nanoparticles synthetized using UV had the best antibacterial properties. The inhibition zone was largest for B. subtilis but was present also for S. aureus and E. coli. (paper)

  4. Positron annihilation studies in ZnO nanoparticles

    Science.gov (United States)

    Sharma, S. K.; Pujari, P. K.; Sudarshan, K.; Dutta, D.; Mahapatra, M.; Godbole, S. V.; Jayakumar, O. D.; Tyagi, A. K.

    2009-04-01

    We report results on positron annihilation spectroscopic (PAS) studies using lifetime and coincidence Doppler broadening techniques in zinc oxide (ZnO) nanoparticles (4 to 40 nm) synthesized by solid state pyrolytic reaction followed by annealing in the temperature range of 200 ∘C to 800 ∘C. Positron lifetime in the nanoparticles are observed to be higher than bulk lifetime in all the cases. Theoretical calculation of lifetime indicates the presence of either Zn or (Zn, O) vacancy clusters which migrate and anneal out at high temperature. Comparison of ratio spectra from coincidence Doppler broadening measurement and calculated electron momentum distribution indicates the presence of either Zn or (Zn, O) vacancies. In addition, photoluminescence (PL) measurements have been carried out to examine the role of defects on the intensity of emission in the visible region.

  5. Growth of vertically aligned ZnO nanorods using textured ZnO films

    Directory of Open Access Journals (Sweden)

    Meléndrez Manuel

    2011-01-01

    Full Text Available Abstract A hydrothermal method to grow vertical-aligned ZnO nanorod arrays on ZnO films obtained by atomic layer deposition (ALD is presented. The growth of ZnO nanorods is studied as function of the crystallographic orientation of the ZnO films deposited on silicon (100 substrates. Different thicknesses of ZnO films around 40 to 180 nm were obtained and characterized before carrying out the growth process by hydrothermal methods. A textured ZnO layer with preferential direction in the normal c-axes is formed on substrates by the decomposition of diethylzinc to provide nucleation sites for vertical nanorod growth. Crystallographic orientation of the ZnO nanorods and ZnO-ALD films was determined by X-ray diffraction analysis. Composition, morphologies, length, size, and diameter of the nanorods were studied using a scanning electron microscope and energy dispersed x-ray spectroscopy analyses. In this work, it is demonstrated that crystallinity of the ZnO-ALD films plays an important role in the vertical-aligned ZnO nanorod growth. The nanorod arrays synthesized in solution had a diameter, length, density, and orientation desirable for a potential application as photosensitive materials in the manufacture of semiconductor-polymer solar cells. PACS 61.46.Hk, Nanocrystals; 61.46.Km, Structure of nanowires and nanorods; 81.07.Gf, Nanowires; 81.15.Gh, Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.

  6. Synthesis of 1-D ZnO nanorods and polypyrrole/1-D ZnO ...

    Indian Academy of Sciences (India)

    1-D ZnO nanorods and PPy/1-D ZnO nanocomposites were prepared by the surfactant-assisted precipitation and in situ polymerization method, respectively. The synthesized nanorods and nanocomposites were characterized by UV–Vis spectrophotometer, Fourier transform-infrared spectroscopy (FTIR), X-ray diffraction ...

  7. The suspended sentence in French Criminal Law

    Directory of Open Access Journals (Sweden)

    Jovašević Dragan

    2016-01-01

    Full Text Available From the ancient times until today, criminal law has provided different criminal sanctions as measures of social control. These coercive measures are imposed on the criminal offender by the competent court and aimed at limitting the offender's rights and freedoms or depriving the offender of certain rights and freedoms. These sanctions are applied to the natural or legal persons who violate the norms of the legal order and injure or endanger other legal goods that enjoy legal protection. In order to effectively protect social values, criminal legislations in all countries predict a number of criminal sanctions. These are: 1 imprisonment, 2 precautions, 3 safety measures, 4 penalties for juveniles, and 5 sanctions for legal persons. Apart and instead of punishment, warning measures have a significant role in the jurisprudence. Since they emerged in the early 20th century in the system of criminal sanctions, there has been an increase in their application to criminal offenders, especially when it comes to first-time offenders who committed a negligent or accidental criminal act. Warnings are applied in case of crimes that do not have serious consequences, and whose perpetrators are not hardened and incorrigible criminals. All contemporary criminal legislations (including the French legilation provide a warning measure of suspended sentence. Suspended sentence is a conditional stay of execution of sentence of imprisonment for a specified time, provided that the convicted person does not commit another criminal offense and fulfills other obligations. This sanction applies if the following two conditions are fulfilled: a forma! -which is attached to the sentence of imprisonment; and b material -which is the court assessment that the application of this sanction is justified and necessary in a particular case. In many modern criminal legislations, there are two different types of suspended (conditional sentence: 1 ordinary (classical suspended

  8. Application of cluster computing in materials science

    International Nuclear Information System (INIS)

    Kuzmin, A.

    2006-01-01

    Solution of many problems in materials science requires that high performance computing (HPC) be used. Therefore, a cluster computer, Latvian Super-cluster (LASC), was constructed at the Institute of Solid State Physics of the University of Latvia in 2002. The LASC is used for advanced research in the fields of quantum chemistry, solid state physics and nano materials. In this work we overview currently available computational technologies and exemplify their application by interpretation of x-ray absorption spectra for nano-sized ZnO. (author)

  9. 40 CFR 230.21 - Suspended particulates/turbidity.

    Science.gov (United States)

    2010-07-01

    ... Impacts on Physical and Chemical Characteristics of the Aquatic Ecosystem § 230.21 Suspended particulates/turbidity. (a) Suspended particulates in the aquatic ecosystem consist of fine-grained mineral particles..., and man's activities including dredging and filling. Particulates may remain suspended in the water...

  10. Swing damped movement of suspended objects

    International Nuclear Information System (INIS)

    Jones, J.F.; Petterson, B.J.; Werner, J.C.

    1990-01-01

    Transportation of large objects such as nuclear waste shipping casks using overhead cranes can induce pendular motion of the object. Residual oscillation from transportation typically must be damped or allowed to decay before the next process can take place. By properly programming the acceleration of the transporting device (e.g., crane) an oscillation damped transport and swing free stop are obtainable. This report reviews the theory associated with formulating such oscillation damped trajectories for a simply suspended object (e.g., simple pendulum). In addition, the use of force servo damping to eliminate initial oscillation of simply suspended objects is discussed. This is often needed to provide a well defined initial state for the system prior to executing an oscillation damped move. Also included are descriptions of experiments using a CIMCORP XR6100 gantry robot and results from these experiments. Finally, sources of error resulting in small residual oscillations are identified and possible solutions presented

  11. Molybdenum-rhenium superconducting suspended nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Aziz, Mohsin; Christopher Hudson, David; Russo, Saverio [Centre for Graphene Science, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF (United Kingdom)

    2014-06-09

    Suspended superconducting nanostructures of MoRe 50%/50% by weight are fabricated employing commonly used fabrication steps in micro- and nano-meter scale devices followed by wet-etching with Hydro-fluoric acid of a SiO{sub 2} sacrificial layer. Suspended superconducting channels as narrow as 50 nm and length 3 μm have a critical temperature of ≈6.5 K, which can increase by 0.5 K upon annealing at 400 °C. A detailed study of the dependence of the superconducting critical current and critical temperature upon annealing and in devices with different channel widths reveals that desorption of contaminants is responsible for the improved superconducting properties. These findings pave the way for the development of superconducting electromechanical devices using standard fabrication techniques.

  12. Positron annihilation study of the interfacial defects in ZnO nanocrystals: Correlation with ferromagnetism

    Science.gov (United States)

    Wang, Dong; Chen, Z. Q.; Wang, D. D.; Qi, N.; Gong, J.; Cao, C. Y.; Tang, Z.

    2010-01-01

    High purity ZnO nanopowders were pressed into pellets and annealed in air between 100 and 1200 °C. The crystal quality and grain size of the ZnO nanocrystals were investigated by x-ray diffraction 2θ scans. Annealing induces an increase in the grain size from 25 to 165 nm with temperature increasing from 400 to 1200 °C. Scanning electron microscopy and high-resolution transmission electron microscopy observations also confirm the grain growth during annealing. Positron annihilation measurements reveal vacancy defects including Zn vacancies, vacancy clusters, and voids in the grain boundary region. The voids show an easy recovery after annealing at 100-700 °C. However, Zn vacancies and vacancy clusters observed by positrons remain unchanged after annealing at temperatures below 500 °C and begin to recover at higher temperatures. After annealing at temperatures higher than 1000 °C, no positron trapping by the interfacial defects can be observed. Raman spectroscopy studies confirm the recovery of lattice disorder after annealing. Hysteresis loops are observed for the 100 and 400 °C annealed samples, which indicate ferromagnetism in ZnO nanocrystals. However, the ferromagnetism disappears after annealing above 700 °C, suggesting that it might originate from the surface defects such as Zn vacancies.

  13. Characterisation of irradiation-induced defects in ZnO single crystals

    International Nuclear Information System (INIS)

    Prochazka, I; Cizek, J; Lukac, F; Melikhova, O; Valenta, J; Havranek, V; Anwand, W; Skuratov, V A; Strukova, T S

    2016-01-01

    Positron annihilation spectroscopy (PAS) combined with optical methods was employed for characterisation of defects in the hydrothermally grown ZnO single crystals irradiated by 167 MeV Xe 26+ ions to fluences ranged from 3×10 12 to 1×10 14 cm -2 . The positron lifetime (LT), Doppler broadening as well as slow-positron implantation spectroscopy (SPIS) techniques were involved. The ab-initio theoretical calculations were utilised for interpretation of LT results. The optical transmission and photoluminescence measurements were conducted, too. The virgin ZnO crystal exhibited a single component LT spectrum with a lifetime of 182 ps which is attributed to saturated positron trapping in Zn vacancies associated with hydrogen atoms unintentionally introduced into the crystal during the crystal growth. The Xe ion irradiated ZnO crystals have shown an additional component with a longer lifetime of ≈ 360 ps which comes from irradiation-induced larger defects equivalent in size to clusters of ≈10 to 12 vacancies. The concentrations of these clusters were estimated on the basis of combined LT and SPIS data. The PAS data were correlated with irradiation induced changes seen in the optical spectroscopy experiments. (paper)

  14. Characterisation of irradiation-induced defects in ZnO single crystals

    Science.gov (United States)

    Prochazka, I.; Cizek, J.; Lukac, F.; Melikhova, O.; Valenta, J.; Havranek, V.; Anwand, W.; Skuratov, V. A.; Strukova, T. S.

    2016-01-01

    Positron annihilation spectroscopy (PAS) combined with optical methods was employed for characterisation of defects in the hydrothermally grown ZnO single crystals irradiated by 167 MeV Xe26+ ions to fluences ranged from 3×1012 to 1×1014 cm-2. The positron lifetime (LT), Doppler broadening as well as slow-positron implantation spectroscopy (SPIS) techniques were involved. The ab-initio theoretical calculations were utilised for interpretation of LT results. The optical transmission and photoluminescence measurements were conducted, too. The virgin ZnO crystal exhibited a single component LT spectrum with a lifetime of 182 ps which is attributed to saturated positron trapping in Zn vacancies associated with hydrogen atoms unintentionally introduced into the crystal during the crystal growth. The Xe ion irradiated ZnO crystals have shown an additional component with a longer lifetime of ≈ 360 ps which comes from irradiation-induced larger defects equivalent in size to clusters of ≈10 to 12 vacancies. The concentrations of these clusters were estimated on the basis of combined LT and SPIS data. The PAS data were correlated with irradiation induced changes seen in the optical spectroscopy experiments.

  15. Electrodialytic remediation of suspended mine tailings

    DEFF Research Database (Denmark)

    Hansen, Henrik K.; Rojo, Adrian; Pino, Denisse

    2008-01-01

    This work shows the laboratory results of nine electrodialytic remediation experiments on copper mine tailings. A newly designed remediation cell, where the solids were kept in suspension by airflow, was tested. The results show that electric current could remove copper from suspended tailings...... efficiency from 1% to 80% compared to experiments with no stirring but with the same operational conditions. This showed the crucial importance of having the solids in suspension and not settled during the remediation....

  16. Sedimentation of suspended solids in ultrasound field

    Directory of Open Access Journals (Sweden)

    Vikulina Vera

    2018-01-01

    Full Text Available Physical and chemical effects of aquatic environment that occur in an ultrasonic field change the sedimentation rate of coagulated suspension. This might only happen in case of cavitation of ultrasonic filed that causes a change of potentials of the medium. Research of the influence of ultrasonic vibrations on coagulation of suspended solids within water purification allows expanding their scope of implementation. The objective of the research is to estimate the effect of ultrasound on the sedimentation of the suspended solids, to determine of the efficiency of the process in relation to the dose of the coagulant, and to calculate the numerical values of the constants in the theoretical equation. The experiment condition was held in the water with the clay substances before the introduction of the coagulant. The method of magnetostriction ultrasonic generator was applied to receive ultrasonic vibration. Estimate of concentration of clay particles in water was performed using photometry. As a result of the research, the obtained data allow determining the increase in efficiency of suspended particles sedimentation related to the dose of coagulant, depending on time of ultrasonic treatment. The experiments confirmed the connection between the effect of sedimentation in the coagulation process, the coagulant dose and the time of scoring. Studies have shown that the increase in the duration of ultrasonic treatment causes a decrease of administered doses of coagulant.

  17. Weighted Clustering

    DEFF Research Database (Denmark)

    Ackerman, Margareta; Ben-David, Shai; Branzei, Simina

    2012-01-01

    We investigate a natural generalization of the classical clustering problem, considering clustering tasks in which different instances may have different weights.We conduct the first extensive theoretical analysis on the influence of weighted data on standard clustering algorithms in both...... the partitional and hierarchical settings, characterizing the conditions under which algorithms react to weights. Extending a recent framework for clustering algorithm selection, we propose intuitive properties that would allow users to choose between clustering algorithms in the weighted setting and classify...

  18. Morphology engineering of ZnO nanostructures for high performance supercapacitors: enhanced electrochemistry of ZnO nanocones compared to ZnO nanowires

    Science.gov (United States)

    He, Xiaoli; Yoo, Joung Eun; Lee, Min Ho; Bae, Joonho

    2017-06-01

    In this work, the morphology of ZnO nanostructures is engineered to demonstrate enhanced supercapacitor characteristics of ZnO nanocones (NCs) compared to ZnO nanowires (NWs). ZnO NCs are obtained by chemically etching ZnO NWs. Electrochemical characteristics of ZnO NCs and NWs are extensively investigated to demonstrate morphology dependent capacitive performance of one dimensional ZnO nanostructures. Cyclic voltammetry measurements on these two kinds of electrodes in a three-electrode cell confirms that ZnO NCs exhibit a high specific capacitance of 378.5 F g-1 at a scan rate of 20 mV s-1, which is almost twice that of ZnO NWs (191.5 F g-1). The charge-discharge and electrochemical impedance spectroscopy measurements also clearly result in enhanced capacitive performance of NCs as evidenced by higher specific capacitances and lower internal resistance. Asymmetric supercapacitors are fabricated using activated carbon (AC) as the negative electrode and ZnO NWs and NCs as positive electrodes. The ZnO NC⫽AC can deliver a maximum specific capacitance of 126 F g-1 at a current density of 1.33 A g-1 with an energy density of 25.2 W h kg-1 at the power density of 896.44 W kg-1. In contrast, ZnO NW⫽AC displays 63% of the capacitance obtained from the ZnO NC⫽AC supercapacitor. The enhanced performance of NCs is attributed to the higher surface area of ZnO nanostructures after the morphology is altered from NWs to NCs.

  19. Studies on intrinsic defects related to Zn vacancy in ZnO nanoparticles

    International Nuclear Information System (INIS)

    Singh, V.P.; Das, D.; Rath, Chandana

    2013-01-01

    Graphical abstract: Display Omitted Highlights: ► Williamson–Hall analysis of ZnO indicates strain in the lattice and size is of 20 nm. ► PL shows a broad emission peak in visible range due to native defects. ► Raman active modes corresponding to P6 3 mc and a few additional modes are observed. ► FTIR detects few local vibrational modes of hydrogen attached to zinc vacancies. ► V Zn -H and Zn + O divacancies are confirmed by PAS. -- Abstract: ZnO being a well known optoelectronic semiconductor, investigations related to the defects are very promising. In this report, we have attempted to detect the defects in ZnO nanoparticles synthesized by the conventional coprecipitation route using various spectroscopic techniques. The broad emission peak observed in photoluminescence spectrum and the non zero slope in Williamson–Hall analysis indicate the defects induced strain in the ZnO lattice. A few additional modes observed in Raman spectrum could be due to the breakdown of the translation symmetry of the lattice caused by defects and/or impurities. The presence of impurities can be ruled out as XRD pattern shows pure wurtzite structure. The presence of the vibrational band related to the Zn vacancies (V Zn ), unintentional hydrogen dopants and their complex defects confirm the defects in ZnO lattice. Positron life time components τ 1 and τ 2 additionally support V Zn attached to hydrogen and to a cluster of Zn and O di-vacancies respectively.

  20. The suspended sentence in German criminal law

    Directory of Open Access Journals (Sweden)

    Jovašević Dragan

    2017-01-01

    Full Text Available From the ancient times until today, criminal law in all countries has provided different criminal sanctions as social control measures. These are court-imposed coercive measures that take away or limit certain rights and freedoms of criminal offenders. Sanctions are applied to natural or legal persons who violate the norms of the legal order and cause damage or endanger other legal goods that enjoy legal protection. In order to effectively protect social values jeopardized by the commission of crime, state legislations prescribe several kinds of criminal sanctions: 1 penalties, 2 precautions, 3 safety measures, 4 penalties for juvenile offenders, and 5 sanctions for legal persons. Penalties are the basic, the oldest and the most important type of criminal sanctions. They are prescribed for the largest number of criminal offences. Imposed instead of or alongside with penalties, warning measures have particularly important role in jurisprudence. Since they were introduced in the system of criminal sanctions in the early 20th century, there has been a notable increase in the application of these measures, particularly in cases involving negligent and accidental offences, and minor offences that do not cause serious consequences, whose perpetrators are not persons with criminal characteristics. Warning measures (suspended sentence are envisaged in all contemporary criminal legislations, including the German legislation. Suspended sentence is a conditional stay of execution of the sentence of imprisonment for a specified time, provided that the convicted person fulfills the imposed obligations and does not commit another criminal offense. Two conditions must be fulfilled for the application of these sanctions: a the formal requirement, which is attached to the sentence of imprisonment; and b the substantive requirement, which implies the court assessment that the application of these sanctions is justified and necessary in a particular case. Many

  1. N+ ion-implantation-induced defects in ZnO studied with a slow positron beam

    International Nuclear Information System (INIS)

    Chen, Z Q; Sekiguchi, T; Yuan, X L; Maekawa, M; Kawasuso, A

    2004-01-01

    Undoped ZnO single crystals were implanted with multiple-energy N + ions ranging from 50 to 380 keV with doses from 10 12 to 10 14 cm -2 . Positron annihilation measurements show that vacancy defects are introduced in the implanted layers. The concentration of the vacancy defects increases with increasing ion dose. The annealing behaviour of the defects can be divided into four stages, which correspond to the formation and recovery of large vacancy clusters and the formation and disappearance of vacancy-impurity complexes, respectively. All the implantation-induced defects are removed by annealing at 1200 deg. C. Cathodoluminescence measurements show that the ion-implantation-induced defects act as nonradiative recombination centres to suppress the ultraviolet (UV) emission. After annealing, these defects disappear gradually and the UV emission reappears, which coincides with positron annihilation measurements. Hall measurements reveal that after N + implantation, the ZnO layer still shows n-type conductivity

  2. The magnetic ordering in high magnetoresistance Mn-doped ZnO thin films

    KAUST Repository

    Venkatesh, S.

    2016-03-24

    We studied the nature of magnetic ordering in Mn-doped ZnO thin films that exhibited ferromagnetism at 300 K and superparamagnetism at 5 K. We directly inter-related the magnetisation and magnetoresistance by invoking the polaronpercolation theory and variable range of hopping conduction below the metal-to-insulator transition. By obtaining a qualitative agreement between these two models, we attribute the ferromagnetism to the s-d exchange-induced spin splitting that was indicated by large positive magnetoresistance (∼40 %). Low temperature superparamagnetism was attributed to the localization of carriers and non-interacting polaron clusters. This analysis can assist in understanding the presence or absence of ferromagnetism in doped/un-doped ZnO.

  3. The magnetic ordering in high magnetoresistance Mn-doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Venkatesh, S.; Baras, A.; Roqan, I. S., E-mail: Iman.roqan@kaust.edu.sa [Physical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900 (Saudi Arabia); Lee, J.-S. [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States)

    2016-03-15

    We studied the nature of magnetic ordering in Mn-doped ZnO thin films that exhibited ferromagnetism at 300 K and superparamagnetism at 5 K. We directly inter-related the magnetisation and magnetoresistance by invoking the polaron percolation theory and variable range of hopping conduction below the metal-to-insulator transition. By obtaining a qualitative agreement between these two models, we attribute the ferromagnetism to the s-d exchange-induced spin splitting that was indicated by large positive magnetoresistance (∼40 %). Low temperature superparamagnetism was attributed to the localization of carriers and non-interacting polaron clusters. This analysis can assist in understanding the presence or absence of ferromagnetism in doped/un-doped ZnO.

  4. Near band edge emission characteristics of sputtered nano-crystalline ZnO films

    International Nuclear Information System (INIS)

    Kunj, Saurabh; Sreenivas, K.

    2016-01-01

    Sputtered zinc oxide (ZnO) thin films deposited on unheated glass substrate under different sputtering gas mixtures (Ar+O_2) have been investigated using X-ray diffraction and photo luminescence spectroscopy. Earlier reported studies on ZnO films prepared by different techniques exhibit either a sharp/broad near band edge (NBE) emission peak depending on the crystalline quality of the film. In the present study zinc oxide films, grown on unheated substrates, are seen to possess a preferred (002) orientation with a microstructure consisting of clustered nano-sized crystallites. The splitting in the near band edge emission (NBE) into three characteristic peaks is attributed to quantum confinement effect, and is observed specifically under an excitation of 270 nm. Deep level emission (DLE) in the range 400 to 700 nm is not observed indicating absence of deep level radiative defects.

  5. Near band edge emission characteristics of sputtered nano-crystalline ZnO films

    Science.gov (United States)

    Kunj, Saurabh; Sreenivas, K.

    2016-05-01

    Sputtered zinc oxide (ZnO) thin films deposited on unheated glass substrate under different sputtering gas mixtures (Ar+O2) have been investigated using X-ray diffraction and photo luminescence spectroscopy. Earlier reported studies on ZnO films prepared by different techniques exhibit either a sharp/broad near band edge (NBE) emission peak depending on the crystalline quality of the film. In the present study zinc oxide films, grown on unheated substrates, are seen to possess a preferred (002) orientation with a microstructure consisting of clustered nano-sized crystallites. The splitting in the near band edge emission (NBE) into three characteristic peaks is attributed to quantum confinement effect, and is observed specifically under an excitation of 270 nm. Deep level emission (DLE) in the range 400 to 700 nm is not observed indicating absence of deep level radiative defects.

  6. Near band edge emission characteristics of sputtered nano-crystalline ZnO films

    Energy Technology Data Exchange (ETDEWEB)

    Kunj, Saurabh; Sreenivas, K. [Department of Physics & Astrophysics, University of Delhi, Delhi 110007 INDIA (India)

    2016-05-06

    Sputtered zinc oxide (ZnO) thin films deposited on unheated glass substrate under different sputtering gas mixtures (Ar+O{sub 2}) have been investigated using X-ray diffraction and photo luminescence spectroscopy. Earlier reported studies on ZnO films prepared by different techniques exhibit either a sharp/broad near band edge (NBE) emission peak depending on the crystalline quality of the film. In the present study zinc oxide films, grown on unheated substrates, are seen to possess a preferred (002) orientation with a microstructure consisting of clustered nano-sized crystallites. The splitting in the near band edge emission (NBE) into three characteristic peaks is attributed to quantum confinement effect, and is observed specifically under an excitation of 270 nm. Deep level emission (DLE) in the range 400 to 700 nm is not observed indicating absence of deep level radiative defects.

  7. Adsorption property of volatile molecules on ZnO nanowires ...

    Indian Academy of Sciences (India)

    7

    Keywords: ZnO; interaction; ammonia; band structure; density of states. 1. 2. 3 .... Virtual NanoLab [18] software was utilized to construct the ZnO nanowires with 24 Zn ..... But in reality, the ZnO NWs shows a better response (80.2) towards NH3.

  8. Cluster management.

    Science.gov (United States)

    Katz, R

    1992-11-01

    Cluster management is a management model that fosters decentralization of management, develops leadership potential of staff, and creates ownership of unit-based goals. Unlike shared governance models, there is no formal structure created by committees and it is less threatening for managers. There are two parts to the cluster management model. One is the formation of cluster groups, consisting of all staff and facilitated by a cluster leader. The cluster groups function for communication and problem-solving. The second part of the cluster management model is the creation of task forces. These task forces are designed to work on short-term goals, usually in response to solving one of the unit's goals. Sometimes the task forces are used for quality improvement or system problems. Clusters are groups of not more than five or six staff members, facilitated by a cluster leader. A cluster is made up of individuals who work the same shift. For example, people with job titles who work days would be in a cluster. There would be registered nurses, licensed practical nurses, nursing assistants, and unit clerks in the cluster. The cluster leader is chosen by the manager based on certain criteria and is trained for this specialized role. The concept of cluster management, criteria for choosing leaders, training for leaders, using cluster groups to solve quality improvement issues, and the learning process necessary for manager support are described.

  9. Synthesis of Fe-Doped ZnO Nanorods by Rapid Mixing Hydrothermal Method and Its Application for High Performance UV Photodetector

    Directory of Open Access Journals (Sweden)

    Chan Oeurn Chey

    2014-01-01

    Full Text Available We have successfully synthesized Fe-doped ZnO nanorods by a new and simple method in which the adopted approach is by using ammonia as a continuous source of OH- for hydrolysis instead of hexamethylenetetramine (HMT. The energy dispersive X-ray (EDX spectra revealed that the Fe peaks were presented in the grown Fe-doped ZnO nanorods samples and the X-ray photoelectron spectroscopy (XPS results suggested that Fe3+ is incorporated into the ZnO lattice. Structural characterization indicated that the Fe-doped ZnO nanorods grow along the c-axis with a hexagonal wurtzite structure and have single crystalline nature without any secondary phases or clusters of FeO or Fe3O4 observed in the samples. The Fe-doped ZnO nanorods showed room temperature (300 K ferromagnetic magnetization versus field (M-H hysteresis and the magnetization increases from 2.5 μemu to 9.1 μemu for Zn0.99Fe0.01O and Zn0.95Fe0.05O, respectively. Moreover, the fabricated Au/Fe-doped ZnO Schottky diode based UV photodetector achieved 2.33 A/W of responsivity and 5 s of time response. Compared to other Au/ZnO nanorods Schottky devices, the presented responsivity is an improvement by a factor of 3.9.

  10. Electrical characterization of ZnO nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Schlenker, E.; Bakin, A.; Postels, B.; Mofor, A.C.; Wehmann, H.H.; Waag, A. [Institute of Semiconductor Technology, Technical University Braunschweig, Hans-Sommer-Strasse 66, 38106 Braunschweig (Germany); Weimann, T.; Hinze, P. [Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig (Germany)

    2007-05-15

    Zinc oxide (ZnO) nanorods were grown by a wet chemical approach and by vapor phase transport. To explore the electrical properties of individual nanostructures current-voltage (I-V) characteristics were obtained by using an atomic force microscope (AFM) with a conductive tip or by detaching the nanorods from the growth substrate, transferring them to an isolating substrate and contacting them with evaporated Ti/Au electrodes patterned by electron-beam lithography. The AFM-approach only yields a Schottky diode behavior, while the Ti/Au forms ohmic contacts to the ZnO. For the latter method the obtained I-V curves reveal a resistivity of the nanorods in the order of 10{sup -5} {omega} cm which is unusually low for undoped ZnO. We therefore assume the existence of a highly conductive surface channel. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Photoluminescence measurements of ZnO heterostructures

    International Nuclear Information System (INIS)

    Adachi, Yutaka; Sakaguchi, Isao; Ohashi, Naoki; Haneda, Hajime; Ryoken, Haruki; Takenaka, Tadashi

    2003-01-01

    ZnO thin films were grown on TbAlO 3 single crystal substrates by pulsed laser deposition. In photoluminescence (PL) measurements, strong emissions from TbAlO 3 were observed with the emission from ZnO when the film thickness was less than 100 nm. The relationship between the ZnO film thickness and the emission intensity from TbAlO 3 was investigated in order to determine the penetration depth of excitation light. Information on the heterostructures ranging from the surface to a depth of 300 nm was obtained by PL measurements in this study, and the absorption coefficient for a wavelength of 325 nm was estimated to be 1.31x10 5 cm -1 . (author)

  12. Photoluminescence properties of Co-doped ZnO nanocrystals

    DEFF Research Database (Denmark)

    Lommens, P.; Smet, P.F.; De Mello Donega, C.

    2006-01-01

    We performed photoluminescence experiments on colloidal, Co -doped ZnO nanocrystals in order to study the electronic properties of Co in a ZnO host. Room temperature measurements showed, next to the ZnO exciton and trap emission, an additional emission related to the Co dopant. The spectral...... position and width of this emission does not depend on particle size or Co concentration. At 8 K, a series of ZnO bulk phonon replicas appear on the Co-emission band. We conclude that Co ions are strongly localized in the ZnO host, making the formation of a Co d-band unlikely. Magnetic measurements...

  13. A treatise on first-principles studies of ZnO as diluted magnetic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Nayak, Sanjeev Kumar

    2012-04-24

    simulations to estimate the critical temperature. A case study for Co doped ZnO is discussed, where we have calculated the magnetic phase diagram of the system. Apart from this, supercell calculations with Vienna ab-initio simulation package (VASP) have been done to compare the role of various treatment to the E{sub xc}. In case of GGA+U, the U is separately treated on Zn d-orbitals and TM d-orbitals, and then together. From the total energy differences in magnetic states, it is observed that with incorporation of U, all the TM favor antiferromagnetic interactions. Similar conclusion is also reached for most cases in HSE and HSE+U approach. One of the recent topics under discussion for polar semiconductor materials like ZnO is d{sup 0} magnetism. In present study based on GGA it is shown that Zn-vacancy (V{sub Zn}) and C substitution on O site (C{sub O}) lead to spin-polarized solution. The magnetic energy is mostly below the room-temperature. Related to this, some perspectives of experimental situations which could lead to quenching of such magnetization is also presented. Furthermore, studies on pure ZnO clusters based on GGA and HSE functionals are presented. A general tendency which is observed is that the bond length predicted in HSE calculations are larger than those predicted by GGA. Characteristic arrangement of magnetization density in V{sub Zn} and C{sub O} in clusters as calculated from GGA is presented.

  14. DYNAMIC SUFFICIENCY OF THE MAGNETICALLY SUSPENDED TRAIN

    Directory of Open Access Journals (Sweden)

    V. A. Polyakov

    2013-11-01

    Full Text Available Purpose. The basic criterion of the magnetically suspended train's consumer estimation is a quality of its mechanical motion. This motion is realized in unpredictable conditions and, for purposefulness preservation, should adapt to them. Such adaptation is possible only within the limits of system’s dynamic sufficiency. Sufficiency is understood as presence at system of resources, which allow one to realize its demanded motions without violating actual restrictions. Therefore presence of such resources is a necessary condition of preservation of required purposefulness of train's dynamics, and verification of the mentioned sufficiency is the major component of this dynamic research. Methodology. Methods of the set theory are used in work. Desirable and actual approachability spaces of the train are found. The train is considered dynamically sufficient in zones of the specified spaces overlapping. Findings. Within the limits of the accepted treatment of train's dynamic sufficiency, verification of its presence, as well as a stock (or deficiency of preservations can be executed by the search and the subsequent estimation of such overlapping zones. Operatively (directly during motion it can be realized on the train's ODC with use, for example, of computer mathematics system Mathematica. It possesses extensive opportunities of highly efficient and, at the same time, demanding an expense concerning small resources information manipulation. The efficiency of using of created technique is illustrated on an example of vehicle's acceleration research. Calculation is executed with use of the constructed computer model of interaction of an independent traction electromagnetic subsystem of an artifact with its mechanical subsystem. Originality. The technique of verification of the high-speed magnetically suspended train's dynamic sufficiency is developed. The technique is highly efficient, it provides sufficient presentation and demands an expense of the

  15. Isotopic clusters

    International Nuclear Information System (INIS)

    Geraedts, J.M.P.

    1983-01-01

    Spectra of isotopically mixed clusters (dimers of SF 6 ) are calculated as well as transition frequencies. The result leads to speculations about the suitability of the laser-cluster fragmentation process for isotope separation. (Auth.)

  16. Cluster Headache

    Science.gov (United States)

    ... a role. Unlike migraine and tension headache, cluster headache generally isn't associated with triggers, such as foods, hormonal changes or stress. Once a cluster period begins, however, drinking alcohol ...

  17. Geodetic monitoring of suspended particles in rivers

    Science.gov (United States)

    Kamnik, Rok; Maksimova, Daria; Kovačič, Boštjan

    2017-10-01

    There is a trend in modern approach to the management of space of collecting the spatial data, in order to obtain useful information. In this paper a research of suspended particles in the river Drava and Mura will be introduced. The goal is to connect different fields of water management in countries where the rivers Drava and Mura flows in purpose of water management sustainability. The methods such as GNSS for mapping cross sections of the river, the use of ADCP (Acoustic Doppler Current Profiler) measurement system and water sampling to monitor sediment in the water will be presented.

  18. Cluster Headache

    OpenAIRE

    Pearce, Iris

    1985-01-01

    Cluster headache is the most severe primary headache with recurrent pain attacks described as worse than giving birth. The aim of this paper was to make an overview of current knowledge on cluster headache with a focus on pathophysiology and treatment. This paper presents hypotheses of cluster headache pathophysiology, current treatment options and possible future therapy approaches. For years, the hypothalamus was regarded as the key structure in cluster headache, but is now thought to be pa...

  19. Categorias Cluster

    OpenAIRE

    Queiroz, Dayane Andrade

    2015-01-01

    Neste trabalho apresentamos as categorias cluster, que foram introduzidas por Aslak Bakke Buan, Robert Marsh, Markus Reineke, Idun Reiten e Gordana Todorov, com o objetivo de categoriíicar as algebras cluster criadas em 2002 por Sergey Fomin e Andrei Zelevinsky. Os autores acima, em [4], mostraram que existe uma estreita relação entre algebras cluster e categorias cluster para quivers cujo grafo subjacente é um diagrama de Dynkin. Para isto desenvolveram uma teoria tilting na estrutura triang...

  20. Meaningful Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Sanfilippo, Antonio P.; Calapristi, Augustin J.; Crow, Vernon L.; Hetzler, Elizabeth G.; Turner, Alan E.

    2004-05-26

    We present an approach to the disambiguation of cluster labels that capitalizes on the notion of semantic similarity to assign WordNet senses to cluster labels. The approach provides interesting insights on how document clustering can provide the basis for developing a novel approach to word sense disambiguation.

  1. Horticultural cluster

    OpenAIRE

    SHERSTIUK S.V.; POSYLAYEVA K.I.

    2013-01-01

    In the article there are the theoretical and methodological approaches to the nature and existence of the cluster. The cluster differences from other kinds of cooperative and integration associations. Was develop by scientific-practical recommendations for forming a competitive horticultur cluster.

  2. Effect of Al and Fe doping in ZnO on magnetic and magneto-transport properties

    International Nuclear Information System (INIS)

    Kumar, Santosh; Deepika; Tripathi, Malvika; Vaibhav, Pratyush; Kumar, Aman; Kumar, Ritesh; Choudhary, R.J.; Phase, D.M.

    2016-01-01

    The structural, magnetic and magneto-transport of undoped ZnO, Zn_0_._9_7Al_0_._0_3O, Zn_0_._9_5Fe_0_._0_5O and Zn_0_._9_2Al_0_._0_3Fe_0_._0_5O thin films grown on Si(100) substrate using pulsed laser deposition were investigated. The single phase nature of the films is confirmed by X-ray diffraction and Raman spectroscopy measurements. The possibility of Fe metal cluster in Fe doped/co-doped films is ruled out by Fe 2p core level photoelectron spectra. From O 1s core level spectra it is observed that oxygen vacancy is present in all the films. The undoped ZnO film shows magnetic ordering below ∼175 K, whereas Fe doped/codoped samples show magnetic ordering even at 300 K. The Al doped sample reveals paramagnetic behavior. The magneto-transport measurements suggest that the mobile carriers undergo exchange interaction with local magnetic moments. - Highlights: • Al, Fe, Al–Fe co-doped and undoped films of ZnO are deposited on Si by PLD. • Single phase (002) oriented Wurtzite ZnO phase is formed for all films. • Fe doped and Fe–Al co-doped ZnO films reveal magnetic hysteresis at 300 K. • Negative magnetoresistance is observed in undoped and Fe–Al co-doped ZnO film. • It is apparent that charge carriers are coupled with the local magnetic moment.

  3. Effect of Al and Fe doping in ZnO on magnetic and magneto-transport properties

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Santosh, E-mail: skphysics@yahoo.co.in [Department of Physics, College of Commerce, Arts & Science, Patna 800020, Bihar (India); Deepika [Department of Physics, College of Commerce, Arts & Science, Patna 800020, Bihar (India); Tripathi, Malvika [UGC DAE, Consortium for scientific research, Indore 452001, Madhya Pradesh (India); Vaibhav, Pratyush [Jaypee University of Engineering and Technology, Guna 473226, Madhya Pradesh (India); Kumar, Aman [Indian Institute of Technology, Roorkee (India); Kumar, Ritesh [Department of Physics, College of Commerce, Arts & Science, Patna 800020, Bihar (India); Choudhary, R.J., E-mail: ram@csr.res.in [UGC DAE, Consortium for scientific research, Indore 452001, Madhya Pradesh (India); Phase, D.M. [UGC DAE, Consortium for scientific research, Indore 452001, Madhya Pradesh (India)

    2016-12-01

    The structural, magnetic and magneto-transport of undoped ZnO, Zn{sub 0.97}Al{sub 0.03}O, Zn{sub 0.95}Fe{sub 0.05}O and Zn{sub 0.92}Al{sub 0.03}Fe{sub 0.05}O thin films grown on Si(100) substrate using pulsed laser deposition were investigated. The single phase nature of the films is confirmed by X-ray diffraction and Raman spectroscopy measurements. The possibility of Fe metal cluster in Fe doped/co-doped films is ruled out by Fe 2p core level photoelectron spectra. From O 1s core level spectra it is observed that oxygen vacancy is present in all the films. The undoped ZnO film shows magnetic ordering below ∼175 K, whereas Fe doped/codoped samples show magnetic ordering even at 300 K. The Al doped sample reveals paramagnetic behavior. The magneto-transport measurements suggest that the mobile carriers undergo exchange interaction with local magnetic moments. - Highlights: • Al, Fe, Al–Fe co-doped and undoped films of ZnO are deposited on Si by PLD. • Single phase (002) oriented Wurtzite ZnO phase is formed for all films. • Fe doped and Fe–Al co-doped ZnO films reveal magnetic hysteresis at 300 K. • Negative magnetoresistance is observed in undoped and Fe–Al co-doped ZnO film. • It is apparent that charge carriers are coupled with the local magnetic moment.

  4. Enhanced field emission of ZnO nanoneedle arrays via solution etching at room temperature

    DEFF Research Database (Denmark)

    Ma, Huanming; Qin, Zhiwei; Wang, Zaide

    2017-01-01

    ZnO nanoneedle arrays (ZnO nns) were synthesized by a facile two-step solution-phase method based on the etching of pre-synthesized ZnO nanowire arrays (ZnO nws) with flat ends at room temperature. Field emission measurement results showed that the turn-on electronic fields of ZnO nns and nws wer...

  5. Acoustic measuring techniques for suspended sediment

    Science.gov (United States)

    Gruber, P.; Felix, D.; Storti, G.; Lattuada, M.; Fleckenstein, P.; Deschwanden, F.

    2016-11-01

    Acoustic signals can be used in various ways for suspended sediment monitoring. One possibility which lends itself particularly well in the context of hydropower plants (HPPs), is to use installations for acoustic discharge measurement (ADM). Such installations already exist at waterways of many HPPs. Similar to certain turbidimeters, the attenuation of the forward scattered signal travelling through the water-sediment mixture is correlated with suspended sediment concentration (SSC). This correlation can be based on reference SSCs, e.g. from gravimetric analyses of bottle samples. Without the need of additional sensors and practically maintenance-free, this method is used successfully in the HPP Fieschertal to warn the HPP operator of high SSC to prevent excessive turbine abrasion. Acoustic methods and systems that allow for estimating both SSC and particle size distribution (PSD) are under development. The simultaneous determination of SSC and PSD is not possible using a single frequency. Therefore, multi-frequency approaches are investigated for generally scattered signals. When backscattered signals are used, a stronger frequency dependency can be exploited. However, the reliable simultaneous determination of particle size (and distribution) and concentration is still a major challenge due to a low signal-to-noise ratio and an ill- posed problem of estimating concentration and size from recorded signals. The optimal setup configuration (angles, frequencies) for such a system is not unique and further investigations are recommended.

  6. Cluster Matters

    DEFF Research Database (Denmark)

    Gulati, Mukesh; Lund-Thomsen, Peter; Suresh, Sangeetha

    2018-01-01

    sell their products successfully in international markets, but there is also an increasingly large consumer base within India. Indeed, Indian industrial clusters have contributed to a substantial part of this growth process, and there are several hundred registered clusters within the country...... of this handbook, which focuses on the role of CSR in MSMEs. Hence we contribute to the literature on CSR in industrial clusters and specifically CSR in Indian industrial clusters by investigating the drivers of CSR in India’s industrial clusters....

  7. Dependence of displacement fields on the damage cluster nucleus geometry

    International Nuclear Information System (INIS)

    Grigor'ev, A.N.; Zabela, A.G.; Nikolajchuk, L.I.; Prokhorenko, E.M.; Khizhnyak, N.A.

    1988-01-01

    Displacement fields in doped crystals of cubic and hexagonal structures containing extended defects are studied. The numerical results are presented depending on the damage cluster nucleus geometry. All calculations are based on analytical representations of displacement fields in an integral form using elasticity theory equations. The investigation results are vital for radiation physics as they permit to predict and calculate both the character and geometry of distortions near damaged region cluster and determine cluster parameters on the basis of the known structure of distortions. Dependences are obtained for the following monocrystals: Mg, ZnO, CdS, W, Au. 6 refs.; 3 figs

  8. Experimental and numerical optical characterization of plasmonic copper nanoparticles embedded in ZnO fabricated by ion implantation and annealing

    Energy Technology Data Exchange (ETDEWEB)

    Le, Khai Q. [Faculty of Science and Technology, Hoa Sen University, Ho Chi Minh City (Viet Nam); Department of Physics, Faculty of Science, Jazan University, P.O. Box 114, 45142 Jazan (Saudi Arabia); Nguyen, Hieu P.T. [Department of Electrical and Computer Engineering, New Jersey Institute of Technology, NJ 07102 (United States); Ngo, Quang Minh [Institute of Material Sciences, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi (Viet Nam); Canimoglu, Adil [Nigde University, Faculty of Arts and Sciences, Physics Department, Nigde (Turkey); Can, Nurdogan, E-mail: cannurdogan@yahoo.com [Celal Bayar University, Faculty of Arts and Sciences, Department of Physics, Muradiye, Manisa (Turkey); Department of Physics, Faculty of Science, Jazan University, P.O. Box 114, 45142 Jazan (Saudi Arabia)

    2016-06-05

    Here we describe the successfully fabrication of metal nanoparticle crystals by implanting copper (Cu) ions into single zinc oxide (ZnO) crystals with ion energy of 400 keV at ion doses of 1 × 10{sup 16} to 1 × 10{sup 17} ions/cm{sup 2}. After implantation and post-annealing treatment, the Cu implanted ZnO produces a broad range of luminescence emissions, ranging from green to yellow. A green luminescence peak at 550 nm could be ascribed to the isolated Cu ions. The changes in luminescence emission bands between the initial implant and annealed suggest that the implants give rise to clustering Cu nanoparticles in the host matrix but that the annealing process dissociates these. Numerical modelling of the Cu nanoparticles was employed to simulate their optical properties including the extinction cross section, electron energy loss spectroscopy and cathodoluminescence. We demonstrate that the clustering of nanoparticles generates Fano resonances corresponding to the generation of multiple resonances, while the isolation of nanoparticles results in intensity amplification. - Highlights: • We present the fabrication of metal nanoparticle crystals by implanting Cu into ZnO. • The luminescence properties were studied at different annealing temperature. • Numerical modelling of the Cu nanoparticles was employed. • We demonstrate that the clustering of nanoparticles generates Fano resonances.

  9. Interaction of nitrogen with vacancy defects in N+-implanted ZnO studied using a slow positron beam

    International Nuclear Information System (INIS)

    Chen, Z.Q.; Maekawa, M.; Kawasuso, A.; Suzuki, R.; Ohdaira, T.

    2005-01-01

    ZnO crystals were implanted with N + , O + , and Al + , and co-implanted with O + /N + and Al + /N + ions. Positron annihilation measurements indicate introduction of vacancy clusters upon implantation. In the N + -implanted and Al + /N + co-implanted samples, these vacancy clusters are only partially annealed at 800 deg. C, as compared with their entire recovery in the O + - and Al + -implanted samples at 800-900 deg. C, suggesting a strong interaction between nitrogen and vacancy clusters. However, in the O + /N + co-implanted sample, most vacancy clusters disappear at 800 deg. C. Probably oxygen scavenges nitrogen to enhance the annealing of the vacancy clusters. Upon further annealing at 1000-1100 deg. C, nitrogen also forms stable complexes with thermally generated vacancies. These nitrogen-related vacancy complexes need high-temperature annealing at 1200-1250 deg. C to be fully removed

  10. Field evaporation of ZnO: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Yu, E-mail: yuxia@dal.ca; Karahka, Markus; Kreuzer, H. J. [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 3J5 (Canada)

    2015-07-14

    With recent advances in atom probe tomography of insulators and semiconductors, there is a need to understand high electrostatic field effects in these materials as well as the details of field evaporation. We use density functional theory to study field effects in ZnO clusters calculating the potential energy curves, the local field distribution, the polarizability, and the dielectric constant as a function of field strength. We confirm that, as in MgO, the HOMO-LUMO gap of a ZnO cluster closes at the evaporation field strength signaling field-induced metallization of the insulator. Following the structural changes in the cluster at the evaporation field strength, we can identify the field evaporated species, in particular, we show that the most abundant ion, Zn{sup 2+}, is NOT post-ionized but leaves the surface as 2+ largely confirming the experimental observations. Our results also help to explain problems related to stoichiometry in the mass spectra measured in atom probe tomography.

  11. Strategies of making TiO2 and ZnO visible light active

    International Nuclear Information System (INIS)

    Rehman, Shama; Ullah, Ruh; Butt, A.M.; Gohar, N.D.

    2009-01-01

    In modern purification techniques employing semiconductor mediated photooxidation of toxic substances, zinc oxide (ZnO) and titanium dioxide (TiO 2 ) are the most widely used metal oxides due to their unique blend of properties. However, the band edges of these semiconductors lie in the UV region which makes them inactive under visible light irradiation. Researchers have been interested in the modification of electronic and optical properties of these metal oxides for their efficient use in water and air purification under visible light irradiation. Visible light activity has been induced in TiO 2 and ZnO by surface modification via organic materials/semiconductor coupling and band gap modification by doping with metals and nonmetals, co-doping with nonmetals, creation of oxygen vacancies and oxygen sub-stoichiometry. This paper encompasses the progress and developments made so far through these techniques in the visible light photocatalysis with TiO 2 and ZnO. Recently, nitrogen doping in titania has been extensively carried out and therefore somewhat detailed discussion in this respect has been presented. Visible light activation of titania clusters encapsulated in zeolite-Y by nitrogen doping and incorporation of dye or organic sensitizers inside the zeolite framework, has also been highlighted in this review.

  12. Reducing ZnO nanoparticles toxicity through silica coating

    Directory of Open Access Journals (Sweden)

    Sing Ling Chia

    2016-10-01

    Full Text Available ZnO NPs have good antimicrobial activity that can be utilized as agents to prevent harmful microorganism growth in food. However, the use of ZnO NPs as food additive is limited by the perceived high toxicity of ZnO NPs in many earlier toxicity studies. In this study, surface modification by silica coating was used to reduce the toxicity of ZnO NPs by significantly reducing the dissolution of the core ZnO NPs. To more accurately recapitulate the scenario of ingested ZnO NPs, we tested our as synthesized ZnO NPs in ingestion fluids (synthetic saliva and synthetic gastric juice to determine the possible forms of ZnO NPs in digestive system before exposing the products to colorectal cell lines. The results showed that silica coating is highly effective in reducing toxicity of ZnO NPs through prevention of the dissociation of ZnO NPs to zinc ions in both neutral and acidic condition. The silica coating however did not alter the desired antimicrobial activity of ZnO NPs to E. coli and S. aureus. Thus, silica coating offered a potential solution to improve the biocompatibility of ZnO NPs for applications such as antimicrobial agent in foods or food related products like food packaging. Nevertheless, caution remains that high concentration of silica coated ZnO NPs can still induce undesirable cytotoxicity to mammalian gut cells. This study indicated that upstream safer-by-design philosophy in nanotechnology can be very helpful in a product development.

  13. Data Clustering

    Science.gov (United States)

    Wagstaff, Kiri L.

    2012-03-01

    On obtaining a new data set, the researcher is immediately faced with the challenge of obtaining a high-level understanding from the observations. What does a typical item look like? What are the dominant trends? How many distinct groups are included in the data set, and how is each one characterized? Which observable values are common, and which rarely occur? Which items stand out as anomalies or outliers from the rest of the data? This challenge is exacerbated by the steady growth in data set size [11] as new instruments push into new frontiers of parameter space, via improvements in temporal, spatial, and spectral resolution, or by the desire to "fuse" observations from different modalities and instruments into a larger-picture understanding of the same underlying phenomenon. Data clustering algorithms provide a variety of solutions for this task. They can generate summaries, locate outliers, compress data, identify dense or sparse regions of feature space, and build data models. It is useful to note up front that "clusters" in this context refer to groups of items within some descriptive feature space, not (necessarily) to "galaxy clusters" which are dense regions in physical space. The goal of this chapter is to survey a variety of data clustering methods, with an eye toward their applicability to astronomical data analysis. In addition to improving the individual researcher’s understanding of a given data set, clustering has led directly to scientific advances, such as the discovery of new subclasses of stars [14] and gamma-ray bursts (GRBs) [38]. All clustering algorithms seek to identify groups within a data set that reflect some observed, quantifiable structure. Clustering is traditionally an unsupervised approach to data analysis, in the sense that it operates without any direct guidance about which items should be assigned to which clusters. There has been a recent trend in the clustering literature toward supporting semisupervised or constrained

  14. Organics and Suspended Solids Removal from Hospital

    Directory of Open Access Journals (Sweden)

    Fakhri Y. Hmood

    2013-05-01

    Full Text Available The Sequencing Batch Reactor (SBR method is used for treating samples of waste water taken from hospitals in Mosul. Many run periods are used (6-24 hours for             6 months. It is found that the organics and suspended solids removal increase with increasing the period of run, it is in the range ( 96-82 % and ( 100-95 % respectively, while the pH values are nearly neutral (7.05 to 7.5.     BOD5 and SS concentrations of the effluent are within the limits of Iraqi standards,  40:30 mg/l respectively. Hence, SBR method could be used for treating hospitals, small factories and some  residential sectors waste waters.  

  15. Batch fabrication of nanotubes suspended between microelectrodes

    DEFF Research Database (Denmark)

    Mateiu, Ramona Valentina; Stöckli, T.; Knapp, H. F.

    2007-01-01

    be done with a simple lift-off process with standard photolithographic resist. An applied electric field is sustained between the microelectrodes during CVD to guide the nanotube growth. Comparison with simulations shows that the location and the orientation of the grown carbon nanotubes (CNT) correspond...... to the regions of maximum electric field, enabling accurate positioning of a nanotube by controlling the shape of the microelectrodes. The CNT bridges are deflected tens of nm when a DC voltage is applied between the nanotube and a gate microelectrode indicating that the clamping through the catalyst particles...... is not only mechanically stable but also electrical conducting. This method could be used to fabricate nanoelectromechanical systems based on suspended double clamped CNTs depending only on photolithography and standard Cleanroom processes....

  16. ZnO nanowire co-growth on SiO2 and C by carbothermal reduction and vapour advection

    International Nuclear Information System (INIS)

    Vega, N C; Caram, J; Grinblat, G; Comedi, D; Wallar, R; LaPierre, R R; Tirado, M

    2012-01-01

    Vertically aligned ZnO nanowires (NWs) were grown on Au-nanocluster-seeded amorphous SiO 2 films by the advective transport and deposition of Zn vapours obtained from the carbothermal reaction of graphite and ZnO powders. Both the NW volume and visible-to-UV photoluminescence ratio were found to be strong functions of, and hence could be tailored by, the (ZnO+C) source–SiO 2 substrate distance. We observe C flakes on the ZnO NWs/SiO 2 substrates which exhibit short NWs that developed on both sides. The SiO 2 and C substrates/NW interfaces were studied in detail to determine growth mechanisms. NWs on Au-seeded SiO 2 were promoted by a rough ZnO seed layer whose formation was catalysed by the Au clusters. In contrast, NWs grew without any seed on C. A correlation comprising three orders of magnitude between the visible-to-UV photoluminescence intensity ratio and the NW volume is found, which results from a characteristic Zn partial pressure profile that fixes both O deficiency defect concentration and growth rate. (paper)

  17. Identification of Zn-vacancy-hydrogen complexes in ZnO single crystals: A challenge to positron annihilation spectroscopy

    Science.gov (United States)

    Brauer, G.; Anwand, W.; Grambole, D.; Grenzer, J.; Skorupa, W.; Čížek, J.; Kuriplach, J.; Procházka, I.; Ling, C. C.; So, C. K.; Schulz, D.; Klimm, D.

    2009-03-01

    A systematic study of various, nominally undoped ZnO single crystals, either hydrothermally grown (HTG) or melt grown (MG), has been performed. The crystal quality has been assessed by x-ray diffraction, and a comprehensive estimation of the detailed impurity and hydrogen contents by inductively coupled plasma mass spectrometry and nuclear reaction analysis, respectively, has been made also. High precision positron lifetime experiments show that a single positron lifetime is observed in all crystals investigated, which clusters at 180-182 ps and 165-167 ps for HTG and MG crystals, respectively. Furthermore, hydrogen is detected in all crystals in a bound state with a high concentration (at least 0.3at.% ), whereas the concentrations of other impurities are very small. From ab initio calculations it is suggested that the existence of Zn-vacancy-hydrogen complexes is the most natural explanation for the given experimental facts at present. Furthermore, the distribution of H at a metal/ZnO interface of a MG crystal, and the H content of a HTG crystal upon annealing and time afterward has been monitored, as this is most probably related to the properties of electrical contacts made at ZnO and the instability in p -type conductivity observed at ZnO nanorods in literature. All experimental findings and presented theoretical considerations support the conclusion that various types of Zn-vacancy-hydrogen complexes exist in ZnO and need to be taken into account in future studies, especially for HTG materials.

  18. Cluster evolution

    International Nuclear Information System (INIS)

    Schaeffer, R.

    1987-01-01

    The galaxy and cluster luminosity functions are constructed from a model of the mass distribution based on hierarchical clustering at an epoch where the matter distribution is non-linear. These luminosity functions are seen to reproduce the present distribution of objects as can be inferred from the observations. They can be used to deduce the redshift dependence of the cluster distribution and to extrapolate the observations towards the past. The predicted evolution of the cluster distribution is quite strong, although somewhat less rapid than predicted by the linear theory

  19. ZnO quantum dots–decorated ZnO nanowires for the enhancement of antibacterial and photocatalytic performances

    International Nuclear Information System (INIS)

    Wu, Jyh Ming; Tsay, Li-Yi

    2015-01-01

    We demonstrate highly antibacterial activities for killing off Staphylococcus aureus and Escherichia coli using ZnO nanowires decorated with ZnO quantum dots (so-called ZnO QDs/NWs) under visible-light irradiation and dark conditions. The average size of the ZnO QDs is in the range of 3–5 nm; these were uniformly dispersed on the ZnO nanowires’ surface to form the ZnO QDs/NWs. A significant blue-shift effect was observed using photoluminescence (PL) spectra. The size of the ZnO QDs is strongly dependent on the material’s synthesis time. The ZnO QDs/NWs exhibited an excellent photocatalytic activity under visible-light irradiation. The ZnO QDs’ active sites (i.e. the O–H bond and Zn"2"+) accelerate the photogenerated-carrier migration from the QDs to the NWs. As a consequence, the electrons reacted with the dissolved oxygen to form oxygen ions and produced hydroperoxyl radicals to enhance photocatalytic activity. The antibacterial activities (as indicated by R-factor-inhibiting activity) of the ZnO QDs/NWs for killing off Staphylococcus aureus and Escherichia coli is around 4.9 and 5.5 under visible-light irradiation and dark conditions, respectively. The hydroxyl radicals served as an efficient oxidized agent for decomposing the organic dye and microorganism species. The antibacterial activities of the ZnO QDs/NWs in the dark may be attributed to the Zn"2"+ ions that were released from the ZnO QDs and infused into the microbial solution against the growth of bacteria thus disrupting the microorganism. The highly antibacterial and photocatalytic activity of the ZnO QDs/NWs can be well implanted on a screen window, thus offering a promising solution to inhibit the spread of germs under visible-light and dark conditions. (paper)

  20. Energy values of suspended detritus in Andaman Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Krishnakumari, L.; Royan, J.P.; Sumitra-Vijayaraghavan

    Energy content of suspended detritus was determined in Andaman Sea waters during April-May 1988. The caloric content of suspended detritus ranged from 987 to 7040 cal. per gram dry wt with an average value of 5530 cal. per gram dry wt. The results...

  1. Dynamic model of movement of mine suspended monorail

    Directory of Open Access Journals (Sweden)

    Viktor GUTAREVYCH

    2014-03-01

    Full Text Available In the article we have developed the dynamic model of interaction of rolling stock during the movement, on the suspended monorail, taking into account the side-sway. We have received the motion equations, carried out their analysis and determined the own oscillation frequencies of rolling stock of suspended monorail.

  2. Characterization and morphology of solids suspended in rain water

    International Nuclear Information System (INIS)

    Iturbe G, J.L.; Lopez M, B.E.; Torre O, J. De la

    2000-01-01

    This work presents the results obtained from the analysis of rain water in Mexico. The study treats over the characterization and morphology of the solids suspended in form of particles in the atmosphere. The solids suspended were obtained of the pluvial precipitations after these have been centrifuged. Subsequently of the separation, the particulate matter was analysed by Sem and X-ray dispersive energy

  3. Admittance spectroscopy of spray-pyrolyzed ZnO film

    International Nuclear Information System (INIS)

    Kavasoglu, Nese; Kavasoglu, A. Sertap

    2008-01-01

    A ZnO film was deposited using the spray pyrolysis method. The admittance spectroscopy method was used to establish the contributions to electrical behavior from grains, grain boundaries, and electrodes of film. Proper equivalent electrical circuit of a ZnO film composed of a single parallel resistor, capacitor, and inductor network connected with a series resistance was proposed. Moreover, we displayed metal-semiconductor transition (MST) in the ZnO film via admittance spectroscopy

  4. Room temperature ferromagnetism in Cu doped ZnO

    Science.gov (United States)

    Ali, Nasir; Singh, Budhi; Khan, Zaheer Ahmed; Ghosh, Subhasis

    2018-05-01

    We report the room temperature ferromagnetism in 2% Cu doped ZnO films grown by RF magnetron sputtering in different argon and oxygen partial pressure. X-ray photoelectron spectroscopy was used to ascertain the oxidation states of Cu in ZnO. The presence of defects within Cu-doped ZnO films can be revealed by electron paramagnetic resonance. It has been observed that saturated magnetic moment increase as we increase the zinc vacancies during deposition.

  5. Optical Properties of ZnO Nanoparticles Capped with Polymers

    Directory of Open Access Journals (Sweden)

    Atsushi Noguchi

    2011-06-01

    Full Text Available Optical properties of ZnO nanoparticles capped with polymers were investigated. Polyethylene glycol (PEG and polyvinyl pyrrolidone (PVP were used as capping reagents. ZnO nanoparticles were synthesized by the sol-gel method. Fluorescence and absorption spectra were measured. When we varied the timing of the addition of the polymer to the ZnO nanoparticle solution, the optical properties were drastically changed. When PEG was added to the solution before the synthesis of ZnO nanoparticles, the fluorescence intensity increased. At the same time, the total particle size increased, which indicated that PEG molecules had capped the ZnO nanoparticles. The capping led to surface passivation, which increased fluorescence intensity. However, when PEG was added to the solution after the synthesis of ZnO nanoparticles, the fluorescence and particle size did not change. When PVP was added to the solution before the synthesis of ZnO nanoparticles, aggregation of nanoparticles occurred. When PVP was added to the solution after the synthesis of ZnO nanoparticles, fluorescence and particle size increased. This improvement of optical properties is advantageous to the practical usage of ZnO nanoparticles, such as bioimaging

  6. Preparation of ZnO nanocrystals via ultrasonic irradiation

    DEFF Research Database (Denmark)

    Qian, D.; Jiang, Jianzhong; Hansen, P. L.

    2003-01-01

    A simple and rapid process has been developed for the preparation of nanometer-sized ZnO crystals via ultrasonic irradiation, by which pure ZnO nanocrystals with an average size of 6 nm and narrow size distribution can be synthesized in a short time and without using any solvents for the precipit......A simple and rapid process has been developed for the preparation of nanometer-sized ZnO crystals via ultrasonic irradiation, by which pure ZnO nanocrystals with an average size of 6 nm and narrow size distribution can be synthesized in a short time and without using any solvents...

  7. Sodium doping in ZnO crystals

    Science.gov (United States)

    Parmar, N. S.; Lynn, K. G.

    2015-01-01

    ZnO bulk single crystals were doped with sodium by thermal diffusion. Positron annihilations spectroscopy confirms the filling of zinc vacancies, to >6 μm deep in the bulk. Secondary-ion mass spectrometry measurement shows the diffusion of sodium up to 8 μm with concentration (1-3.5) × 1017 cm-3. Broad photoluminescence excitation peak at 3.1 eV, with onset appearance at 3.15 eV in Na:ZnO, is attributed to an electronic transition from a NaZn level at ˜(220-270) meV to the conduction band. Resistivity in Na doped ZnO crystals increases up to (4-5) orders of magnitude at room temperature.

  8. Sodium doping in ZnO crystals

    International Nuclear Information System (INIS)

    Parmar, N. S.; Lynn, K. G.

    2015-01-01

    ZnO bulk single crystals were doped with sodium by thermal diffusion. Positron annihilations spectroscopy confirms the filling of zinc vacancies, to >6 μm deep in the bulk. Secondary-ion mass spectrometry measurement shows the diffusion of sodium up to 8 μm with concentration (1–3.5) × 10 17  cm −3 . Broad photoluminescence excitation peak at 3.1 eV, with onset appearance at 3.15 eV in Na:ZnO, is attributed to an electronic transition from a Na Zn level at ∼(220–270) meV to the conduction band. Resistivity in Na doped ZnO crystals increases up to (4–5) orders of magnitude at room temperature

  9. Sodium doping in ZnO crystals

    Energy Technology Data Exchange (ETDEWEB)

    Parmar, N. S., E-mail: nparmar@wsu.edu; Lynn, K. G. [Center for Materials Research, Washington State University, Pullman, Washington 99164-2711 (United States)

    2015-01-12

    ZnO bulk single crystals were doped with sodium by thermal diffusion. Positron annihilations spectroscopy confirms the filling of zinc vacancies, to >6 μm deep in the bulk. Secondary-ion mass spectrometry measurement shows the diffusion of sodium up to 8 μm with concentration (1–3.5) × 10{sup 17 }cm{sup −3}. Broad photoluminescence excitation peak at 3.1 eV, with onset appearance at 3.15 eV in Na:ZnO, is attributed to an electronic transition from a Na{sub Zn} level at ∼(220–270) meV to the conduction band. Resistivity in Na doped ZnO crystals increases up to (4–5) orders of magnitude at room temperature.

  10. Annealing temperature dependence of the structures and properties of Co-implanted ZnO films

    International Nuclear Information System (INIS)

    Chen, Bin; Tang, Kun; Gu, Shulin; Ye, Jiandong; Huang, Shimin; Gu, Ran; Zhang, Yang; Yao, Zhengrong; Zhu, Shunming; Zheng, Youdou

    2014-01-01

    Highlights: • To avoid the forming of Co clusters and explore the origin of the magnetism, detailed investigation on the properties of the Co-implanted ZnO films with a rather low dose of 8 × 10 15 cm −2 and high implantation energy of 1 MeV were carried out. • The crystalline structure of the damaged region caused by ion-implantation has been recovered via the thermal annealing treatment at the temperature of 900 °C and above. • The low temperature magnetic hysteresis loops have indicated paramagnetism for the annealed films with weak ferromagnetic characteristics. • The zero-field cooling (ZFC) magnetization curves of the Co-implanted ZnO samples have varied from concave shape to convex one as the annealing temperature increased from 750 °C to 1000 °C. - Abstract: The effects of thermal annealing treatment on the structural, electrical, optical and magnetic properties of Co-implanted ZnO (0 0 0 1) films have been investigated in detail. The crystalline structure of the damaged region caused by ion implantation has been recovered via the thermal annealing at the temperature of 900 °C and above, and no Co clusters or its related oxide phases have been observed. The electrical and optical properties of the annealed films have shown strong dependence on the annealing temperature. The zero field cooling magnetization curves of the annealed films have varied from concave shape to convex one as the annealing temperature increased from 750 °C to 1000 °C, which are possibly tuned by the changes of the ratio of the itinerant carriers over the localized spin density. The low temperature magnetic hysteresis loops have indicated paramagnetic behavior for the annealed films with weak ferromagnetic characteristics. The ferromagnetism is attributed to the substituted Co 2+ ions and vacancy defects, while the paramagnetism could be induced by ionized interstitial Zn defects

  11. Preparation, structural and optical characterization of ZnO, ZnO: Al nanopowder

    Energy Technology Data Exchange (ETDEWEB)

    Mohan, R. Raj [Department of ECE, Gojan School of Business and Technology, Chennai (India); Rajendran, K. [Department of Electronics, Government Arts College for Women, Ramanathapuram, TN (India); Sambath, K. [Department of ECS, Sri Krishna Arts and Science College, Coimbatore, TN (India)

    2014-01-28

    In this paper, ZnO and ZnO:Al nanopowders have been synthesized by low cost hydrothermal method. Zinc nitrate, hexamethylenetetramine (HMT) and aluminium nitrate are used as precursors for ZnO and AZO with different molar ratios. The structural and optical characterization of doped and un-doped ZnO powders have been investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDAX), photoluminescence (PL) and ultra violet visible (UV-Vis) absorption studies. The SEM results show that the hydrothermal synthesis can be used to obtain nanoparticles with different morphology. It is observed that the grain size of the AZO nanoparticles increased with increasing of Al concentration. The PL measurement of AZO shows that broad range of green emission around 550nm with high intensity. The green emission resulted mainly because of intrinsic defects.

  12. Improving ultraviolet photodetection of ZnO nanorods by Cr doped ZnO encapsulation process

    Science.gov (United States)

    Safa, S.; Mokhtari, S.; Khayatian, A.; Azimirad, R.

    2018-04-01

    Encapsulated ZnO nanorods (NRs) with different Cr concentration (0-4.5 at.%) were prepared in two different steps. First, ZnO NRs were grown by hydrothermal method. Then, they were encapsulated by dip coating method. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy, and ultraviolet (UV)-visible spectrophotometer analyses. XRD analysis proved that Cr incorporated into the ZnO structure successfully. Based on optical analysis, band gap changes in the range of 2.74-3.84 eV. Finally, UV responses of all samples were deeply investigated. It revealed 0.5 at.% Cr doped sample had the most photocurrent (0.75 mA) and photoresponsivity (0.8 A/W) of all which were about three times greater than photocurrent and photoresponsivity of the undoped sample.

  13. Photoluminescence lineshape of ZnO

    Directory of Open Access Journals (Sweden)

    Bruno Ullrich

    2014-12-01

    Full Text Available The merger of the absorption coefficient dispersion, retrieved from transmission by the modified Urbach rule introduced by Ullrich and Bouchenaki [Jpn. J. Appl. Phys. 30, L1285, 1991], with the extended Roosbroeck-Shockley relation reveals that the optical absorption in ZnO distinctively determines the photoluminescence lineshape. Additionally, the ab initio principles employed enable the accurate determination of the carrier lifetime without further specific probing techniques.

  14. Spin noise spectroscopy of ZnO

    Science.gov (United States)

    Horn, H.; Berski, F.; Balocchi, A.; Marie, X.; Mansur-Al-Suleiman, M.; Bakin, A.; Waag, A.; Hübner, J.; Oestreich, M.

    2013-12-01

    We investigate the thermal equilibrium dynamics of electron spins bound to donors in nanoporous ZnO by optical spin noise spectroscopy. The spin noise spectra reveal two noise contributions: A weak spin noise signal from undisturbed localized donor electrons with a dephasing time of 24 ns due to hyperfine interaction and a strong spin noise signal with a spin dephasing time of 5 ns which we attribute to localized donor electrons which interact with lattice defects.

  15. Spin noise spectroscopy of ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Horn, H.; Berski, F.; Hübner, J.; Oestreich, M. [Institute for Solid State Physics, Leibniz Universität Hannover, Appelstr. 2, 30167 Hannover (Germany); Balocchi, A.; Marie, X. [INSA-CNRS-UPS, LPCNO, Université de Toulouse, 135 Av. de Rangueil, 31077 Toulouse (France); Mansur-Al-Suleiman, M.; Bakin, A.; Waag, A. [Institute of Semiconductor Technology, Technische Universität Braunschweig, Hans-Sommer-Straße 66, 38106 Braunschweig (Germany)

    2013-12-04

    We investigate the thermal equilibrium dynamics of electron spins bound to donors in nanoporous ZnO by optical spin noise spectroscopy. The spin noise spectra reveal two noise contributions: A weak spin noise signal from undisturbed localized donor electrons with a dephasing time of 24 ns due to hyperfine interaction and a strong spin noise signal with a spin dephasing time of 5 ns which we attribute to localized donor electrons which interact with lattice defects.

  16. Clustering Dycom

    KAUST Repository

    Minku, Leandro L.

    2017-10-06

    Background: Software Effort Estimation (SEE) can be formulated as an online learning problem, where new projects are completed over time and may become available for training. In this scenario, a Cross-Company (CC) SEE approach called Dycom can drastically reduce the number of Within-Company (WC) projects needed for training, saving the high cost of collecting such training projects. However, Dycom relies on splitting CC projects into different subsets in order to create its CC models. Such splitting can have a significant impact on Dycom\\'s predictive performance. Aims: This paper investigates whether clustering methods can be used to help finding good CC splits for Dycom. Method: Dycom is extended to use clustering methods for creating the CC subsets. Three different clustering methods are investigated, namely Hierarchical Clustering, K-Means, and Expectation-Maximisation. Clustering Dycom is compared against the original Dycom with CC subsets of different sizes, based on four SEE databases. A baseline WC model is also included in the analysis. Results: Clustering Dycom with K-Means can potentially help to split the CC projects, managing to achieve similar or better predictive performance than Dycom. However, K-Means still requires the number of CC subsets to be pre-defined, and a poor choice can negatively affect predictive performance. EM enables Dycom to automatically set the number of CC subsets while still maintaining or improving predictive performance with respect to the baseline WC model. Clustering Dycom with Hierarchical Clustering did not offer significant advantage in terms of predictive performance. Conclusion: Clustering methods can be an effective way to automatically generate Dycom\\'s CC subsets.

  17. Clustering analysis

    International Nuclear Information System (INIS)

    Romli

    1997-01-01

    Cluster analysis is the name of group of multivariate techniques whose principal purpose is to distinguish similar entities from the characteristics they process.To study this analysis, there are several algorithms that can be used. Therefore, this topic focuses to discuss the algorithms, such as, similarity measures, and hierarchical clustering which includes single linkage, complete linkage and average linkage method. also, non-hierarchical clustering method, which is popular name K -mean method ' will be discussed. Finally, this paper will be described the advantages and disadvantages of every methods

  18. Cluster analysis

    CERN Document Server

    Everitt, Brian S; Leese, Morven; Stahl, Daniel

    2011-01-01

    Cluster analysis comprises a range of methods for classifying multivariate data into subgroups. By organizing multivariate data into such subgroups, clustering can help reveal the characteristics of any structure or patterns present. These techniques have proven useful in a wide range of areas such as medicine, psychology, market research and bioinformatics.This fifth edition of the highly successful Cluster Analysis includes coverage of the latest developments in the field and a new chapter dealing with finite mixture models for structured data.Real life examples are used throughout to demons

  19. Cluster editing

    DEFF Research Database (Denmark)

    Böcker, S.; Baumbach, Jan

    2013-01-01

    . The problem has been the inspiration for numerous algorithms in bioinformatics, aiming at clustering entities such as genes, proteins, phenotypes, or patients. In this paper, we review exact and heuristic methods that have been proposed for the Cluster Editing problem, and also applications......The Cluster Editing problem asks to transform a graph into a disjoint union of cliques using a minimum number of edge modifications. Although the problem has been proven NP-complete several times, it has nevertheless attracted much research both from the theoretical and the applied side...

  20. Methods of and system for swing damping movement of suspended objects

    Science.gov (United States)

    Jones, J.F.; Petterson, B.J.; Strip, D.R.

    1991-03-05

    A payload suspended from a gantry is swing damped in accordance with a control algorithm based on the periodic motion of the suspended mass or by servoing on the forces induced by the suspended mass. 13 figures.

  1. Ultrasonic synthesis of fern-like ZnO nanoleaves and their enhanced photocatalytic activity

    International Nuclear Information System (INIS)

    Ma, Qing Lan; Xiong, Rui; Zhai, Bao-gai; Huang, Yuan Ming

    2015-01-01

    Graphical abstract: - Highlights: • Fern-like ZnO nanoleaves were synthesized by ultrasonicating Zn microcrystals in water. • A fern-like ZnO nanoleaf is a self-assembly of ZnO nanoplates along one ZnO nanorod. • Fern-like ZnO nanoleaves exhibit enhanced photocatalytic activity than ZnO nanocrystals. • The branched hierarchical structures are responsible for the enhanced photocatalytic activity. - Abstract: Two-dimensional fern-like ZnO nanoleaves were synthesized by ultrasonicating zinc microcrystals in water. The morphology, crystal structure, optical property and photocatalytic activity of the fern-like ZnO nanoleaves were characterized with scanning electron microscopy, X-ray diffraction, transmission electron microscopy, photoluminescence spectroscopy and ultraviolet–visible spectroscopy, respectively. It is found that one fern-like ZnO nanoleaf is composed of one ZnO nanorod as the central trunk and a number of ZnO nanoplates as the side branches in opposite pairs along the central ZnO nanorod. The central ZnO nanorod in the fern-like nanoleaves is about 1 μm long while the side-branching ZnO nanoplates are about 100 nm long and 20 nm wide. Further analysis has revealed that ZnO nanocrystals are the building blocks of the central ZnO nanorod and the side-branching ZnO nanoplates. Under identical conditions, fern-like ZnO nanoleaves exhibit higher photocatalytic activity in photodegrading methyl orange in aqueous solution than spherical ZnO nanocrystals. The first-order photocatalytic rate constant of the fern-like ZnO nanoleaves is about four times as large as that of the ZnO nanoparticles. The branched architecture of the hierarchical nanoleaves is suggested be responsible for the enhanced photocatalytic activity of the fern-like ZnO nanoleaves

  2. Evolution of voids in Al+-implanted ZnO probed by a slow positron beam

    International Nuclear Information System (INIS)

    Chen, Z.Q.; Maekawa, M.; Yamamoto, S.; Kawasuso, A.; Yuan, X.L.; Sekiguchi, T.; Suzuki, R.; Ohdaira, T.

    2004-01-01

    Undoped ZnO single crystals were implanted with aluminum ions up to a dose of 10 15 Al + /cm 2 . Vacancy defects in the implanted layers were detected using positron lifetime and Doppler broadening measurements with slow positron beams. It shows that vacancy clusters, which are close to the size of V 8 , are generated by implantation. Postimplantation annealing shows that the Doppler broadening S parameter increases in the temperature range from 200 deg. C to 600 deg. C suggesting further agglomeration of vacancy clusters to voids. Detailed analyses of Doppler broadening spectra show formation of positronium after 600 deg. C annealing of the implanted samples with doses higher than 10 14 Al + /cm 2 . Positron lifetime measurements further suggest that the void diameter is about 0.8 nm. The voids disappear and the vacancy concentration reaches the detection limit after annealing at 600-900 deg. C. Hall measurement shows that the implanted Al + ions are fully activated with improved carrier mobility after final annealing. Cathodoluminescence measurements show that the ultraviolet luminescence is much stronger than the unimplanted state. These findings also suggest that the electrical and optical properties of ZnO become much better by Al + implantation and subsequent annealing

  3. Anodized ZnO nanostructures for photoelectrochemical water splitting

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Mao-Chia [Institute of Materials Science and Engineering, National Central University, Taoyuan 32001, Taiwan (China); Wang, TsingHai [Department of Biomedical Engineering and Environment Sciences, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Wu, Bin-Jui [Institute of Materials Science and Engineering, National Central University, Taoyuan 32001, Taiwan (China); Lin, Jing-Chie, E-mail: jclin4046@gmail.com [Institute of Materials Science and Engineering, National Central University, Taoyuan 32001, Taiwan (China); Wu, Ching-Chen [Green Energy and Environment Research Laboratories, Industrial Technology Research Institute, Hsinchu 310, Taiwan (China)

    2016-01-01

    Highlights: • ZnO nanostructures were synthesized by electrochemical anodic process. • The parameter of ZnO nanostructure was anodic potential. • The model of growth of ZnO nanostructure was investigated. - Abstract: Zinc oxide (ZnO) nanostructures were fabricated on the polished zinc foil by anodic deposition in an alkaline solution containing 1.0 M NaOH and 0.25 M Zn(NO{sub 3}){sub 2}. Potentiostatic anodization was conducted at two potentials (−0.7 V in the passive region and −1.0 V in the active region vs. SCE) which are higher than the open circuit potential (−1.03 V vs. SCE) and as-obtained ZnO nanostrcutures were investigated focusing on their structural, optical, electrical and photoelectrochemical (PEC) characteristics. All samples were confirmed ZnO by X-ray photoelectron spectroscopy and Raman spectra. Observations in the SEM images clearly showed that ZnO nanostructures prepared at −0.7 V vs. SCE were composed of nanowires at while those obtained at −1.0 V vs. SCE possessed nanosheets morphology. Result from transmission electron microscope and X-ray diffraction patterns suggested that the ZnO nanowires belonged to single crystalline with a preferred orientation of (0 0 2) whereas the ZnO nanosheets were polycrystalline. Following PEC experiments indicated that ZnO nanowires had higher photocurrent density of 0.32 mA/cm{sup 2} at 0.5 V vs. SCE under 100 mW/cm{sup 2} illumination. This value was about 1.9 times higher than that of ZnO nanosheets. Observed higher photocurrent was likely due to the single crystalline, preferred (0 0 2) orientation, higher carrier concentration and lower charge transfer resistance.

  4. Occupational Clusters.

    Science.gov (United States)

    Pottawattamie County School System, Council Bluffs, IA.

    The 15 occupational clusters (transportation, fine arts and humanities, communications and media, personal service occupations, construction, hospitality and recreation, health occupations, marine science occupations, consumer and homemaking-related occupations, agribusiness and natural resources, environment, public service, business and office…

  5. Fuzzy Clustering

    DEFF Research Database (Denmark)

    Berks, G.; Keyserlingk, Diedrich Graf von; Jantzen, Jan

    2000-01-01

    A symptom is a condition indicating the presence of a disease, especially, when regarded as an aid in diagnosis.Symptoms are the smallest units indicating the existence of a disease. A syndrome on the other hand is an aggregate, set or cluster of concurrent symptoms which together indicate...... and clustering are the basic concerns in medicine. Classification depends on definitions of the classes and their required degree of participant of the elements in the cases' symptoms. In medicine imprecise conditions are the rule and therefore fuzzy methods are much more suitable than crisp ones. Fuzzy c......-mean clustering is an easy and well improved tool, which has been applied in many medical fields. We used c-mean fuzzy clustering after feature extraction from an aphasia database. Factor analysis was applied on a correlation matrix of 26 symptoms of language disorders and led to five factors. The factors...

  6. Cluster generator

    Science.gov (United States)

    Donchev, Todor I [Urbana, IL; Petrov, Ivan G [Champaign, IL

    2011-05-31

    Described herein is an apparatus and a method for producing atom clusters based on a gas discharge within a hollow cathode. The hollow cathode includes one or more walls. The one or more walls define a sputtering chamber within the hollow cathode and include a material to be sputtered. A hollow anode is positioned at an end of the sputtering chamber, and atom clusters are formed when a gas discharge is generated between the hollow anode and the hollow cathode.

  7. Cluster Bulleticity

    OpenAIRE

    Massey, Richard; Kitching, Thomas; Nagai, Daisuke

    2010-01-01

    The unique properties of dark matter are revealed during collisions between clusters of galaxies, such as the bullet cluster (1E 0657−56) and baby bullet (MACS J0025−12). These systems provide evidence for an additional, invisible mass in the separation between the distributions of their total mass, measured via gravitational lensing, and their ordinary ‘baryonic’ matter, measured via its X-ray emission. Unfortunately, the information available from these systems is limited by their rarity. C...

  8. Cluster headache

    OpenAIRE

    Leroux, Elizabeth; Ducros, Anne

    2008-01-01

    Abstract Cluster headache (CH) is a primary headache disease characterized by recurrent short-lasting attacks (15 to 180 minutes) of excruciating unilateral periorbital pain accompanied by ipsilateral autonomic signs (lacrimation, nasal congestion, ptosis, miosis, lid edema, redness of the eye). It affects young adults, predominantly males. Prevalence is estimated at 0.5–1.0/1,000. CH has a circannual and circadian periodicity, attacks being clustered (hence the name) in bouts that can occur ...

  9. Cation vacancies and electrical compensation in Sb-doped thin-film SnO2 and ZnO

    International Nuclear Information System (INIS)

    Korhonen, E; Prozheeva, V; Tuomisto, F; Bierwagen, O; Speck, J S; White, M E; Galazka, Z; Liu, H; Izyumskaya, N; Avrutin, V; Özgür, Ü; Morkoç, H

    2015-01-01

    We present positron annihilation results on Sb-doped SnO 2 and ZnO thin films. The vacancy types and the effect of vacancies on the electrical properties of these intrinsically n-type transparent semiconducting oxides are studied. We find that in both materials low and moderate Sb-doping leads to formation of vacancy clusters of variable sizes. However, at high doping levels cation vacancy defects dominate the positron annihilation signal. These defects, when at sufficient concentrations, can efficiently compensate the n-type doping produced by Sb. This is the case in ZnO, but in SnO 2 the concentrations appear too low to cause significant compensation. (invited article)

  10. Cation vacancies and electrical compensation in Sb-doped thin-film SnO2 and ZnO

    Science.gov (United States)

    Korhonen, E.; Prozheeva, V.; Tuomisto, F.; Bierwagen, O.; Speck, J. S.; White, M. E.; Galazka, Z.; Liu, H.; Izyumskaya, N.; Avrutin, V.; Özgür, Ü.; Morkoç, H.

    2015-02-01

    We present positron annihilation results on Sb-doped SnO2 and ZnO thin films. The vacancy types and the effect of vacancies on the electrical properties of these intrinsically n-type transparent semiconducting oxides are studied. We find that in both materials low and moderate Sb-doping leads to formation of vacancy clusters of variable sizes. However, at high doping levels cation vacancy defects dominate the positron annihilation signal. These defects, when at sufficient concentrations, can efficiently compensate the n-type doping produced by Sb. This is the case in ZnO, but in SnO2 the concentrations appear too low to cause significant compensation.

  11. Introduction to suspended-sediment sampling

    Science.gov (United States)

    Nolan, K. Michael; Gray, John R.; Glysson, G. Douglas

    2005-01-01

    Knowledge of the amount and timing of sediment transport in streams is important to those directly or indirectly responsible for developing and managing water and land resources. Such data are often used to judge the health of watershed and the success or failure of activities designed to mitigate adverse impacts of sediment on streams and stream habitats. This training class presents an introduction to methods currently used by the U.S. Geological Survey (USGS) to sample suspended-sediment concentrations in streams. The presentation is narrated, but you control the pace of the presentation. If the computer you are using can view 'MPEG' videos you will be able to take advantage of videos interspersed in the presentation. A test, found at the end of the presentation, can be taken to assess how well you understood the training material. The class, which is registered as class SW4416 with the National Training Center of the USGS, should take two or three hours to complete. In order to use the presentation provided via this Web page, you will need to download a large disc images (linked below) and 'burn' it to a blank CD-ROM using a CD-ROM recorder on your computer. The presentation will only run on a Windows-based personal computer (PC). The presentation was developed using Macromedia Director MX 20041 and is contained in the file 'SIR05-5077.exe' which should autolaunch. If it does not, the presentation can be started by double-clicking on the file name. A sound card and speakers are necessary to take advantage of narrations that accompany the presentation. Text of narrations is provided, if you are unable to listen to narrations. Instructions for installing and running the presentation are included in the file 'Tutorial.htm', which is on the CD. 1 Registered Trademark: Macromedia Incorporated

  12. Suspended sediment drift and dispersion at Hibernia

    International Nuclear Information System (INIS)

    Tedford, T.; Drozdowski, A.; Hannah, C.G.

    2003-01-01

    Surface water waves and near-bottom currents around the Hibernia oil production platform on the Grand Banks of Newfoundland were examined to determine how the different seasons affect changes in wave magnitude and directions of water currents. Wave observations revealed a strong correlation with seasons, with the larger waves occurring in fall and early winter. There was no obvious seasonality in the size or direction of currents. The benthic boundary layer transport (BBLT) model was used to predict the drift and dispersion pathways of suspended drilling muds discharged from the Hibernia platform. The 2-year study from March 1998 to May 2000 involved 5-day BBLT model simulations covering the complete period of current meter deployment. The study focused on the sensitivity of the drift and dispersion to variability in the physical environment and uncertainty in the bottom stress calculation and particle settling velocity. The BBLT model incorporates a stress dependent particle settling velocity that includes the main features of the flocculations of drill mud fines under marine conditions. The study provides a better understanding of how drill mud concentration levels can change with variations in waves, currents, and bottom stress. It was determined that drift is generally oriented along the northwest/southeast axis, with a typical magnitude of 0.8 cm/sec for the fast settling velocity and 3.1 cm/sec for the slow settling velocity. It was concluded that near-surface or mid-depth discharges of drilling mud in the summer may not reach the sea floor. 17 refs., 13 tabs., 36 figs

  13. Photoluminescent ZnO Nanoparticles and Their Biological Applications

    Directory of Open Access Journals (Sweden)

    Zheng-Yong Zhang

    2015-05-01

    Full Text Available During the past decades, numerous achievements concerning luminescent zinc oxide nanoparticles (ZnO NPs have been reported due to their improved luminescence and good biocompatibility. The photoluminescence of ZnO NPs usually contains two parts, the exciton-related ultraviolet (UV emission and the defect-related visible emission. With respect to the visible emission, many routes have been developed to synthesize and functionalize ZnO NPs for the applications in detecting metal ions and biomolecules, biological fluorescence imaging, nonlinear multiphoton imaging, and fluorescence lifetime imaging. As the biological applications of ZnO NPs develop rapidly, the toxicity of ZnO NPs has attracted more and more attention because ZnO can produce the reactive oxygen species (ROS and release Zn2+ ions. Just as a coin has two sides, both the drug delivery and the antibacterial effects of ZnO NPs become attractive at the same time. Hence, in this review, we will focus on the progress in the synthetic methods, luminescent properties, and biological applications of ZnO NPs.

  14. Variable range hopping in ZnO films

    Science.gov (United States)

    Ali, Nasir; Ghosh, Subhasis

    2018-04-01

    We report the variable range hopping in ZnO films grown by RF magnetron sputtering in different argon and oxygen partial pressure. It has been found that Mott variable range hopping dominant over Efros variable range hopping in all ZnO films. It also has been found that hopping distance and energy increases with increasing oxygen partial pressure.

  15. Photochemical events during photosensitization of colloidal ZnO ...

    Indian Academy of Sciences (India)

    The photosensitization of colloidal ZnO nanoparticles with riboflavin (RF) was investigated using absorption, fluorescence spectroscopic measurements and time resolved fluorescence measurements. Riboflavin adsorbed strongly on the surface of ZnO nanoparticles. Apparent association constant was obtained from the ...

  16. Fast synthesize ZnO quantum dots via ultrasonic method.

    Science.gov (United States)

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

    2016-05-01

    Green emission ZnO quantum dots were synthesized by an ultrasonic sol-gel method. The ZnO quantum dots were synthesized in various ultrasonic temperature and time. Photoluminescence properties of these ZnO quantum dots were measured. Time-resolved photoluminescence decay spectra were also taken to discover the change of defects amount during the reaction. Both ultrasonic temperature and time could affect the type and amount of defects in ZnO quantum dots. Total defects of ZnO quantum dots decreased with the increasing of ultrasonic temperature and time. The dangling bonds defects disappeared faster than the optical defects. Types of optical defects first changed from oxygen interstitial defects to oxygen vacancy and zinc interstitial defects. Then transformed back to oxygen interstitial defects again. The sizes of ZnO quantum dots would be controlled by both ultrasonic temperature and time as well. That is, with the increasing of ultrasonic temperature and time, the sizes of ZnO quantum dots first decreased then increased. Moreover, concentrated raw materials solution brought larger sizes and more optical defects of ZnO quantum dots. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Influence of Dopants in ZnO Films on Defects

    Science.gov (United States)

    Peng, Cheng-Xiao; Weng, Hui-Min; Zhang, Yang; Ma, Xing-Ping; Ye, Bang-Jiao

    2008-12-01

    The influence of dopants in ZnO films on defects is investigated by slow positron annihilation technique. The results show S that parameters meet SAl > Sun > SAg for Al-doped ZnO films, undoped and Ag-doped ZnO films. Zinc vacancies are found in all ZnO films with different dopants. According to S parameter and the same defect type, it can be induced that the zinc vacancy concentration is the highest in the Al-doped ZnO film, and it is the least in the Ag-doped ZnO film. When Al atoms are doped in the ZnO films grown on silicon substrates, Zn vacancies increase as compared to the undoped and Ag-doped ZnO films. The dopant concentration could determine the position of Fermi level in materials, while defect formation energy of zinc vacancy strongly depends on the position of Fermi level, so its concentration varies with dopant element and dopant concentration.

  18. Ultrasonic-assisted fabrication of superhydrophobic ZnO nanowall ...

    Indian Academy of Sciences (India)

    The results suggested that the synergistic effect of the aluminium oxide seed layer and sonochemical process can enable the formation of ZnO nanowall structures favourable for superhydrophobic property. A possible growth mechanism of ZnO nanowalls formation during sonication process has been discussed in detail.

  19. Hybrid ZnO:polymer bulk heterojunction solar cells from a ZnO precursor

    NARCIS (Netherlands)

    Beek, W.J.E.; Slooff, L.H.; Wienk, M.M.; Kroon, J.M.; Janssen, R.A.J.; Kafafi, Z.H.

    2005-01-01

    We describe a simple and new method to create hybrid bulk heterojunction solar cells consisting of ZnO and conjugated polymers. A gel-forming ZnO precursor, blended with conjugated polymers, is converted into crystalline ZnO at temperatures as low as 110 °C. In-situ formation of ZnO in MDMO-PPV

  20. Hydrogen absorption in thin ZnO films prepared by pulsed laser deposition

    International Nuclear Information System (INIS)

    Melikhova, O.; Čížek, J.; Lukáč, F.; Vlček, M.; Novotný, M.; Bulíř, J.; Lančok, J.; Anwand, W.; Brauer, G.; Connolly, J.; McCarthy, E.; Krishnamurthy, S.; Mosnier, J.-P.

    2013-01-01

    Highlights: ► Thin ZnO films and high quality ZnO crystal were electrochemically doped with hydrogen. ► Hydrogen absorbed in ZnO causes plastic deformation both in ZnO crystal and thin films. ► In ZnO crystal a sub-surface region with very high density of defects was formed. ► Moreover, plastic deformation causes specific surface modification of ZnO crystal. ► In ZnO films hydrogen-induced plastic deformation introduced defects in the whole film. -- Abstract: ZnO films with thickness of ∼80 nm were grown by pulsed laser deposition (PLD) on MgO (1 0 0) single crystal and amorphous fused silica (FS) substrates. Structural studies of ZnO films and a high quality reference ZnO single crystal were performed by slow positron implantation spectroscopy (SPIS). It was found that ZnO films exhibit significantly higher density of defects than the reference ZnO crystal. Moreover, the ZnO film deposited on MgO substrate exhibits higher concentration of defects than the film deposited on amorphous FS substrate most probably due to a dense network of misfit dislocations. The ZnO films and the reference ZnO crystal were subsequently loaded with hydrogen by electrochemical cathodic charging. SPIS characterizations revealed that absorbed hydrogen introduces new defects into ZnO

  1. Hydrogen absorption in thin ZnO films prepared by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Melikhova, O., E-mail: oksivmel@yahoo.com [Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, CZ-180 00 Praha 8 (Czech Republic); Čížek, J.; Lukáč, F.; Vlček, M. [Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, CZ-180 00 Praha 8 (Czech Republic); Novotný, M.; Bulíř, J.; Lančok, J. [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague (Czech Republic); Anwand, W.; Brauer, G. [Institut für Strahlenphysik, Helmholtz-Zentrum Dresden-Rossendorf, PO Box 510 119, D-01314 Dresden (Germany); Connolly, J.; McCarthy, E.; Krishnamurthy, S.; Mosnier, J.-P. [National Centre for Plasma Science and Technology, School of Physical Sciences, Glasnevin, Dublin 9 (Ireland)

    2013-12-15

    Highlights: ► Thin ZnO films and high quality ZnO crystal were electrochemically doped with hydrogen. ► Hydrogen absorbed in ZnO causes plastic deformation both in ZnO crystal and thin films. ► In ZnO crystal a sub-surface region with very high density of defects was formed. ► Moreover, plastic deformation causes specific surface modification of ZnO crystal. ► In ZnO films hydrogen-induced plastic deformation introduced defects in the whole film. -- Abstract: ZnO films with thickness of ∼80 nm were grown by pulsed laser deposition (PLD) on MgO (1 0 0) single crystal and amorphous fused silica (FS) substrates. Structural studies of ZnO films and a high quality reference ZnO single crystal were performed by slow positron implantation spectroscopy (SPIS). It was found that ZnO films exhibit significantly higher density of defects than the reference ZnO crystal. Moreover, the ZnO film deposited on MgO substrate exhibits higher concentration of defects than the film deposited on amorphous FS substrate most probably due to a dense network of misfit dislocations. The ZnO films and the reference ZnO crystal were subsequently loaded with hydrogen by electrochemical cathodic charging. SPIS characterizations revealed that absorbed hydrogen introduces new defects into ZnO.

  2. Photocatalysis and Bandgap Engineering Using ZnO Nanocomposites

    Directory of Open Access Journals (Sweden)

    Muhammad Ali Johar

    2015-01-01

    Full Text Available Nanocomposites have a great potential to work as efficient, multifunctional materials for energy conversion and photoelectrochemical reactions. Nanocomposites may reveal more improved photocatalysis by implying the improvements of their electronic and structural properties than pure photocatalyst. This paper presents the recent work carried out on photoelectrochemical reactions using the composite materials of ZnO with CdS, ZnO with SnO2, ZnO with TiO2, ZnO with Ag2S, and ZnO with graphene and graphene oxide. The photocatalytic efficiency mainly depends upon the light harvesting span of a material, lifetime of photogenerated electron-hole pair, and reactive sites available in the photocatalyst. We reviewed the UV-Vis absorption spectrum of nanocomposite and photodegradation reported by the same material and how photodegradation depends upon the factors described above. Finally the improvement in the absorption band edge of nanocomposite material is discussed.

  3. Processing of ZnO nanocrystals by solochemical technique

    International Nuclear Information System (INIS)

    Gusatti, M.; Speckhahn, R.; Silva, L.A.; Rosario, J.A.; Lima, R.B.; Kuhnen, N.C.; Riella, H.G.; Campos, C.E.M.

    2009-01-01

    In the present work, we report the synthesis of high quality ZnO nanocrystals by solochemical technique. This synthetic strategy has been shown to have advantages over other methods of producing nanostructures in terms of low cost, efficiency, simplicity and uniformity of crystal structure. Zinc chloride solution at room temperature was mixed with sodium hydroxide solution at 50°C to produce ZnO nanocrystals. Transmission electronic microscopy (TEM) and X-ray powder diffraction (XRD) were used to characterize the ZnO nanocrystals obtained. The structure of ZnO was refined by the Rietveld Method from X-ray diffraction data. These methods showed that the product consisted of pure ZnO nanocrystals and has, predominantly, a rod-like morphology. (author)

  4. Power-dependent photocatalytic activity of ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Chun, So Yeon; Han, Noh Soo; Jeong, Seong Hyun; Park, Seung Min; Song, Jae Kyu [Dept. of Chemistry, Kyung Hee University, Seoul (Korea, Republic of); Moon, Cheol Joo; Choi, Myong Yong [Dept. of Chemistry (BK21) and Research Institute of Natural Science, Gyeongsang NationalUniversity, Jinju (Korea, Republic of)

    2017-03-15

    the power-dependent photocatalytic activity of ZnO was examined for the photoreduction processes of Rh101 and AN in the presence of hole scavengers, where the fluorescence spectra were measured as a function of irradiation time and excitation intensity. The concentration of the reactants decreased, while the concentration of the products increased accordingly, which indicated the single-electron reduction process by electrons supplied from the conduction band of ZnO. Despite the single-electron process, the efficiency of the photoreaction depended nonlinearly on the excitation intensity, which was explained by the saturation of defect states in ZnO. The enhanced ratio of available electrons in ZnO led to a superlinear increase in the photoreduction efficiency, while the single-electron process linearly reflected the electrons available in ZnO.

  5. Air pollution in Aleppo city, gases,suspended particulates

    International Nuclear Information System (INIS)

    Othman, I.; Sabra, Sh.; Al-Kharfan, K.

    1994-06-01

    Total suspended particulates measured by using High Volume Air Sampler. The Co and O 3 were measured during weekday and weekend. The concentration of all pollutants at city center are higher than other measured areas. (author). 10 figs., 10 tabs

  6. Improved Methods for Correlating Turbidity and Suspended Solids for Monitoring

    National Research Council Canada - National Science Library

    2000-01-01

    This technical note describes techniques normally used to measure turbidity and suspended solids in waters, how the two parameters relate to each other and to various environmental impacts, and why...

  7. Particles matter: Transformation of suspended particles in constructed wetlands

    NARCIS (Netherlands)

    Mulling, B.T.M.

    2013-01-01

    This thesis shows that constructed wetlands transform suspended particles in (treated) municipal wastewater through selective precipitation in ponds, biological filtering by plankton communities and physical and biological retention in reed beds. These processes effectively remove faecal indicator

  8. The Ages in a Self-Suspended Nanoparticle Liquid

    KAUST Repository

    Agarwal, Praveen; Qi, Haibo; Archer, Lynden A.

    2010-01-01

    Telomers ionically tethered to nanometer-sized particles yield self-suspended, nanoparticle-Iaden liquids with unusual dynamical features. By subjecting these suspensions to controlled, modest shear strains, we find that their flow behaviors

  9. Elemental compositions of suspended particles released in glass manufacture

    Energy Technology Data Exchange (ETDEWEB)

    Mamuro, T; Mizohata, A; Kubota, T [Radiation Center of Osaka Prefecture, Sakai (Japan)

    1980-03-01

    Suspended particles released in glass manufacture were subjected to multielement analysis by means of instrumental neutron activation method and energy dispersive X-ray fluorescence spectrometry. Suspended particles emitted from glass manufacture generally consist of both particles emitted from glass fusion and those produced through fuel combustion (mainly oil combustion). Elemental compositions of suspended particles emitted from glass fusion were found to be strongly dependent on the kind and recipe of raw materials and additives. Of the various metallic elements involved in suspended particles emitted from glass fusion, the elements, As, Se, Cd, Sb, Pb and so on are regarded to produce the most serious air pollution. The amount of emission of these elements to the environment is, howerer, quite varied from manufacturer to manufacturer. The replacement of electric furnace by oil combustion in opal glass manufacture remarkably reduced the emission of metallic elements to the environment.

  10. Self-suspended permanent magnetic FePt ferrofluids

    KAUST Repository

    Dallas, Panagiotis; Kelarakis, Antonios; Sahore, Ritu; DiSalvo, Francis J.; Livi, Sebastien; Giannelis, Emmanuel P.

    2013-01-01

    on the surface of L10 FePt nanoparticles. In contrast, all types of ferrofluids previously reported employ either volatile solvents as the suspending media or superparamagnetic iron oxide nanoparticles (that lacks permanent magnetization) as the inorganic

  11. Novel Resuscitation from Lethal Hemorrhage - Suspended Animation for Delayed Resuscitation

    National Research Council Canada - National Science Library

    Safar, Peter

    2002-01-01

    .... We have conceived and documented "suspended animation for delayed resuscitation" with the use of hypothermic saline flush into the aorta within the first 5 minute of no blood flow, using novel...

  12. Evaluation of the suspending properties of Abizia zygia gum on ...

    African Journals Online (AJOL)

    Purpose: Some excipients are currently available for the formulation of pharmaceutical suspensions. ... Method: The suspending properties of Albizia zygia gum (family ... Characterization tests were carried out on purified Albizia zygia gum.

  13. Suspended sediment apportionment in a South-Korean mountain catchment

    Science.gov (United States)

    Birkholz, Axel; Meusburger, Katrin; Park, Ji-Hyung; Alewell, Christine

    2016-04-01

    Due to the rapid agricultural expansion and intensification during the last decades in South-Korea, large areas of hill slope forests were transformed to paddies and vegetable fields. The intensive agriculture and the easily erodible soils in our catchment are a major reason for the increased erosion causing suspended sediments to infiltrate into the close drinking water reservoir. The drinking water reservoir Lake Soyang provides water supply for over ten million people in Seoul. Landscape managers need to know the exact origin of these sediments before they can create landscape amelioration schemes. We applied a compound-specific stable isotope (CSSI) approach (Alewell et al., 2015) to apportion the sources of the suspended sediments between forest and agricultural soil contribution to the suspended sediments in a different catchment and applied the same approach to identify and quantify the different sources of the suspended sediments in the river(s) contributing to Lake Soyang. We sampled eight soil sites within the catchment considering the different landuse types forest, rice paddies, maize and vegetables. Suspended sediments were sampled at three outlets of the different sub-catchments. Soils and suspended sediments are analysed for bulk carbon and nitrogen isotopes, compound-specific carbon isotopes of plant-wax derived long-chain fatty acids and long-chain n-alkanes. Fatty acid and alkane isotopes are then used in mixing calculations and the mixing model software IsoSource to find out the contribution of the different source soils to the suspended sediments. We present first data of the source soils and the suspended sediments. C. Alewell, A. Birkholz, K. Meusburger, Y. Schindler-Wildhaber, L. Mabit, 2015. Sediment source attribution from multiple land use systems with CSIA. Biogeosciences Discuss. 12: 14245-14269.

  14. Hydrothermal Growth of Vertically Aligned ZnO Nanorods Using a Biocomposite Seed Layer of ZnO Nanoparticles.

    Science.gov (United States)

    Ibupoto, Zafar Hussain; Khun, Kimleang; Eriksson, Martin; AlSalhi, Mohammad; Atif, Muhammad; Ansari, Anees; Willander, Magnus

    2013-08-19

    Well aligned ZnO nanorods have been prepared by a low temperature aqueous chemical growth method, using a biocomposite seed layer of ZnO nanoparticles prepared in starch and cellulose bio polymers. The effect of different concentrations of biocomposite seed layer on the alignment of ZnO nanorods has been investigated. ZnO nanorods grown on a gold-coated glass substrate have been characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. These techniques have shown that the ZnO nanorods are well aligned and perpendicular to the substrate, and grown with a high density and uniformity on the substrate. Moreover, ZnO nanorods can be grown with an orientation along the c -axis of the substrate and exhibit a wurtzite crystal structure with a dominant (002) peak in an XRD spectrum and possessed a high crystal quality. A photoluminescence (PL) spectroscopy study of the ZnO nanorods has revealed a conventional near band edge ultraviolet emission, along with emission in the visible part of the electromagnetic spectrum due to defect emission. This study provides an alternative method for the fabrication of well aligned ZnO nanorods. This method can be helpful in improving the performance of devices where alignment plays a significant role.

  15. Hydrothermal Growth of Vertically Aligned ZnO Nanorods Using a Biocomposite Seed Layer of ZnO Nanoparticles

    Directory of Open Access Journals (Sweden)

    Zafar Hussain Ibupoto

    2013-08-01

    Full Text Available Well aligned ZnO nanorods have been prepared by a low temperature aqueous chemical growth method, using a biocomposite seed layer of ZnO nanoparticles prepared in starch and cellulose bio polymers. The effect of different concentrations of biocomposite seed layer on the alignment of ZnO nanorods has been investigated. ZnO nanorods grown on a gold-coated glass substrate have been characterized by X-ray diffraction (XRD and field emission scanning electron microscopy (FESEM techniques. These techniques have shown that the ZnO nanorods are well aligned and perpendicular to the substrate, and grown with a high density and uniformity on the substrate. Moreover, ZnO nanorods can be grown with an orientation along the c-axis of the substrate and exhibit a wurtzite crystal structure with a dominant (002 peak in an XRD spectrum and possessed a high crystal quality. A photoluminescence (PL spectroscopy study of the ZnO nanorods has revealed a conventional near band edge ultraviolet emission, along with emission in the visible part of the electromagnetic spectrum due to defect emission. This study provides an alternative method for the fabrication of well aligned ZnO nanorods. This method can be helpful in improving the performance of devices where alignment plays a significant role.

  16. Trioctylphosphine-assisted morphology control of ZnO nanoparticles

    Science.gov (United States)

    Hong, Yun-Kun; Cho, GeonHee; Park, YoonSu; Oh, Soong Ju; Ha, Don-Hyung

    2018-06-01

    This study investigates the morphological change in colloidal ZnO nanoparticles (NPs) synthesized with trioctylphosphine (TOP). The addition of TOP to the synthesis causes an evolution in the shape of ZnO NPs to tadpole-like particles from quasi-spherical particles at 300 °C. The total length of the tadpole-like ZnO NPs can be modified by controlling the molar ratio of TOP to oleylamine (OLAM). The tadpole-like particles are elongated as the concentration of TOP increased but decreased when the addition of TOP is excessive. These tadpole-like ZnO NPs transform to quasi-spherical NPs regardless of the amount of TOP at a reaction time of 3 h at 300 °C. At 200 °C, the effect of TOP on the ZnO NP synthesis differs from that at 300 °C. The ZnO NPs synthesized by controlling the molar ratios of surfactant ligands (TOP:OLAM = 2:100 and 70:100) at 200 °C share similar amorphous structures, while a crystalline ZnO phase is formed when the reaction time is 3 h. X-ray photoelectron spectroscopy analysis shows that TOP influences the oxidation of ZnO and suggests that a combination of OLAM and TOP plays a role in controlling the shape of ZnO NPs. These results provide critical insights to the utilization of TOP for a shape controlling ligand in ZnO NPs and suggest a new route to design oxide NPs.

  17. Morphological transition of ZnO nanostructures influenced by magnesium doping

    International Nuclear Information System (INIS)

    Premkumar, T.; Zhou, Y.S.; Gao, Y.; Baskar, K.; Jiang, L.; Lu, Y.F.

    2012-01-01

    Wurtzite zinc oxide (ZnO) nanochains have been synthesized through high-pressure pulsed laser deposition. The chain-like ZnO nanostructures were obtained from magnesium (Mg) doped ZnO targets, whereas vertically aligned nanorods were obtained from primitive ZnO targets. The Mg doping has influenced the morphological transition of ZnO nanostructures from nanorods to nanochains. The field emission scanning electron microscope images revealed the growth of beaded ZnO nanochains. The ZnO nanochains of different diameters 40 and 120 nm were obtained. The corresponding micro-Raman spectra showed strong E 2H mode of ZnO, which confirmed the good crystallinity of the nanochains. In addition to near band edge emission at 3.28 eV, ZnO nanochains show broad deep level emission at 2.42 eV than that of ZnO nanorods.

  18. Size dependent emission stimulation in ZnO nanosheets

    International Nuclear Information System (INIS)

    Torchynska, T.V.; El Filali, B.

    2014-01-01

    Photoluminescence (PL), X ray diffraction (XRD) and Raman scattering have been studied in crystalline ZnO nanosheets (NSs) of different sizes, estimated by scanning electronic microscopy (SEM). ZnO NSs with the size from the range of 60–600 nm were created by the electrochemical (anodization) method and followed thermal annealing at 400 °C for 2 h in ambient air. XRD study confirms the wurtzite structure of ZnO NSs and has revealed that the lattice parameters increase monotonically with decreasing NS sizes. Simultaneously the intensity of a set of Raman peaks increases and Raman peaks shift into the low energy range. The surface phonon has been detected in smallest size ZnO NSs. Two types of PL bands deal with a set of phonon replicas of free excitons and the defect related emission have been detected in ZnO NSs. The intensity enhancement of exciton- and defect-related PL bands with decreasing ZnO NS sizes has been detected. The intensity stimulation of exciton-related PL bands is attributed to the realization of the week confinement and the exciton-light coupling with the formation of polariton in small size ZnO NSs of 67–170 nm. The intensity rising of defect-related PL bands is attributed to the concentration enlargement of surface defects when the surface to volume ration increases at decreasing ZnO NS sizes. Numerical simulations of radiative lifetimes and exciton radiative recombination rates in ZnO NSs for different emission wavelengths have been done using the exciton-light coupling model. Then the experimental and numerically simulated PL results have been compared and discussed. - Highlights: • Optical and structural investigations of the ZnO nanosheets with the sizes 60–600 nm. • The enlargement of interplanar distances in the wurtzite ZnO crystal lattice is detected. • The change of optic phonon energy and surface phonon appearing are reveled. • ZnO emission stimulation at the week confinement and electron-light coupling with the

  19. Clustering Dycom

    KAUST Repository

    Minku, Leandro L.; Hou, Siqing

    2017-01-01

    baseline WC model is also included in the analysis. Results: Clustering Dycom with K-Means can potentially help to split the CC projects, managing to achieve similar or better predictive performance than Dycom. However, K-Means still requires the number

  20. Nanostructured porous ZnO film with enhanced photocatalytic activity

    International Nuclear Information System (INIS)

    Wang Lina; Zheng Yingying; Li Xiaoyun; Dong Wenjun; Tang Weihua; Chen Benyong; Li Chaorong; Li Xiao; Zhang Tierui

    2011-01-01

    Well-defined ZnO nanostructured films have been fabricated directly on Zn foil via hydrothermal synthesis. During the fabrication of the ZnO nanostructured films, the Zn foil serves as the Zn source and also the substrate. Porous nanosheet-based, nanotube-based and nanoflower-based ZnO films can all be easily prepared by adjusting the alkali type, reaction time and reaction temperature. The composition, morphology and structure of ZnO films are characterized by X-ray diffraction, scanning electron microscope and high-resolution transmission electron microscope. The porous ZnO nanosheet-based film exhibits enhanced photocatalytic activity in the degradation of Rhodamine B under UV light irradiation. This can be attributed to the high surface area of the ZnO nanosheet and the large percentage of the exposed [001] facet. Moreover, the self-supporting, recyclable and stable ZnO photocatalytic film can be readily recovered and potentially applied for pollution disposal.

  1. Polarized Raman scattering of single ZnO nanorod

    International Nuclear Information System (INIS)

    Yu, J. L.; Lai, Y. F.; Wang, Y. Z.; Cheng, S. Y.; Chen, Y. H.

    2014-01-01

    Polarized Raman scattering measurement on single wurtzite c-plane (001) ZnO nanorod grown by hydrothermal method has been performed at room temperature. The polarization dependence of the intensity of the Raman scattering for the phonon modes A 1 (TO), E 1 (TO), and E 2 high in the ZnO nanorod are obtained. The deviations of polarization-dependent Raman spectroscopy from the prediction of Raman selection rules are observed, which can be attributed to the structure defects in the ZnO nanorod as confirmed by the comparison of the transmission electron microscopy, photoluminescence spectra as well as the polarization dependent Raman signal of the annealed and unannealed ZnO nanorod. The Raman tensor elements of A 1 (TO) and E 1 (TO) phonon modes normalized to that of the E 2 high phonon mode are |a/d|=0.32±0.01, |b/d|=0.49±0.02, and |c/d|=0.23±0.01 for the unannealed ZnO nanorod, and |a/d|=0.33±0.01, |b/d|=0.45±0.01, and |c/d|=0.20±0.01 for the annealed ZnO nanorod, which shows strong anisotropy compared to that of bulk ZnO epilayer

  2. On Suspended matter grain size in Baltic sea

    Science.gov (United States)

    Bubnova, Ekaterina; Sivkov, Vadim; Zubarevich, Victor

    2016-04-01

    Suspended matter grain size data were gathered during the 25th research vessel "Akademik Mstislav Keldysh" cruise (1991, September-October). Initial quantitative data were obtained with a use of the Coulter counter and subsequently modified into volume concentrations (mm3/l) for size intervals. More than 80 samples from 15 stations were analyzed (depth range 0-355 m). The main goal of research was to illustrate the spatial variability of suspended matter concentration and dispersion in Baltic Sea. The mutual feature of suspended matter grain size distribution is the logical rise of particle number along with descending of particle's size. Vertical variability of grain size distribution was defined by Baltic Sea hydrological structure, including upper mixed layer - from the surface to the thermocline - with 35 m thick, cold intermediate layer - from the thermocline to the halocline- and bottom layer, which lied under the halocline. Upper layer showed a rise in total suspended matter concentration (up to 0.6 mm3/l), while cold intermediate level consisted of far more clear water (up to 0.1 mm3/l). Such a difference is caused by the thermocline boarding role. Meanwhile, deep bottom water experienced surges in suspended matter concentration owing to the nepheloid layer presence and "liquid bottom" effect. Coastal waters appeared to have the highest amount of particles (up to 5.0 mm3/l). Suspended matter grain size distribution in the upper mixed layer revealed a peak of concentration at 7 μ, which can be due to autumn plankton bloom. Another feature in suspended matter grain size distribution appeared at the deep layer below halocline, where both O2 and H2S were observed and red/ox barrier is. The simultaneous presence of Fe and Mn (in solutions below red/ox barrier) and O2 leads to precipitation of oxyhydrates Fe and Mn and grain size distribution graph peaking at 4.5 μ.

  3. On the role of Al in ultrasonically sprayed ZnO films

    Energy Technology Data Exchange (ETDEWEB)

    Kurtaran, S., E-mail: skurtaran@ogu.edu.tr; Aldag, S.; Ofofoglu, G.; Akyuz, I.; Atay, F.

    2017-01-01

    In this work, Al incorporated ZnO films have been deposited by Ultrasonic Spray Pyrolysis technique. Behavior of Al element in the structure has been tried to be clarified by investigating the structural, optical, surface and electrical properties. Compositional analysis has been performed by EDX and Al contents in the coatings have been determined as 1.1, 2.8 and 3.1 at %. X-ray diffraction patterns have shown that all films are polycrystalline with hexagonal wurtzite structure and the dominant peak is (002) ZnO for films except the one containing the highest amount of Al. Above the Al content of 2.8 at %, appearance of new phases such as Al{sub 2}O{sub 3} and ZnAl{sub 2}O{sub 4} in XRD patterns refers a solubility limit at this doping rate. Thicknesses and optical constants (refractive index and extinction coefficient) have been determined by spectroscopic ellipsometry technique using Cauchy-Urbach model. Al doping above the solubility limit has caused ZnO films to have lower refractive index values. Also, AFM images have shown that surface morphologies of the films lose their spherical and granular texture and transform to a randomly clustered formation with sharper upper edges above the solubility limit. Transmittance and electrical resistivity measurements have shown that Al incorporation below solubility limit (1.1 and 2.8 at %) allows maintaining the transparency together with low resistivity values. These films have value to work on and may be promising materials for optoelectronic applications. - Highlights: • Resistivity was evaluated in terms of solubility limit using different mechanisms. • Spectroscopic ellipsometry was used to determine the optical constants. • Samples with 1.1–3.1 at %Al were obtained to express the behavior of Al.

  4. Suspended-Bed Reactor preliminary design, 233U--232Th cycle. Final report (revised)

    International Nuclear Information System (INIS)

    Karam, R.A.; Alapour, A.; Lee, C.C.

    1977-11-01

    The preliminary design Suspended-Bed Reactor is described. Coated particles about 2 mm in diameter are used as the fuel. The coatings consist of three layers: (1) low density pyrolytic graphite, 70 μ thick, (2) silicon carbide pressure vessel, 30 μ thick, and (3) ZrC layer, 50 μ thick, to protect the pressure vessel from moisture and oxygen. The fuel kernel can be either uranium-thorium dicarbide or metal. The coated particles are suspended by helium gas (coolant) in a cluster of pressurized tubes. The upward flow of helium fluidizes the coated particles. As the flow rate increases, the bed of particles is lifted upward to the core section. The particles are restrained at the upper end of the core by a suitable screen. The overall particle density in the core is just enough for criticality condition. Should the helium flow cease, the bed in the core section will collapse, and the particles will flow downward into the section where the increased physical spacings among the tubes brings about a safe shutdown. By immersing this section of the tubes in a large graphite block to serve as a heat sink, dissipation of decay heat becomes manageable. This eliminates the need for emergency core cooling systems

  5. Space-filling, multifractal, localized thermal spikes in Si, Ge and ZnO

    Science.gov (United States)

    Ahmad, Shoaib; Abbas, Muhammad Sabtain; Yousuf, Muhammad; Javeed, Sumera; Zeeshan, Sumaira; Yaqub, Kashif

    2018-04-01

    The mechanism responsible for the emission of clusters from heavy ion irradiated solids is proposed to be thermal spikes. Collision cascade-based theories describe atomic sputtering but cannot explain the consistently observed experimental evidence for significant cluster emission. Statistical thermodynamic arguments for thermal spikes are employed here for qualitative and quantitative estimation of the thermal spike-induced cluster emission from Si, Ge and ZnO. The evolving cascades and spikes in elemental and molecular semiconducting solids are shown to have fractal characteristics. Power law potential is used to calculate the fractal dimension. With the loss of recoiling particles' energy the successive branching ratios get smaller. The fractal dimension is shown to be dependent upon the exponent of the power law interatomic potential D = 1/2m. Each irradiating ion has the probability of initiating a space-filling, multifractal thermal spike that may sublime a localized region near the surface by emitting clusters in relative ratios that depend upon the energies of formation of respective surface vacancies.

  6. Hierarchical structures of ZnO spherical particles synthesized solvothermally

    Science.gov (United States)

    Saito, Noriko; Haneda, Hajime

    2011-12-01

    We review the solvothermal synthesis, using a mixture of ethylene glycol (EG) and water as the solvent, of zinc oxide (ZnO) particles having spherical and flower-like shapes and hierarchical nanostructures. The preparation conditions of the ZnO particles and the microscopic characterization of the morphology are summarized. We found the following three effects of the ratio of EG to water on the formation of hierarchical structures: (i) EG restricts the growth of ZnO microcrystals, (ii) EG promotes the self-assembly of small crystallites into spheroidal particles and (iii) the high water content of EG results in hollow spheres.

  7. Resistive Switching Characteristics in Electrochemically Synthesized ZnO Films

    Directory of Open Access Journals (Sweden)

    Shuhan Jing

    2015-04-01

    Full Text Available The semiconductor industry has long been seeking a new kind of non-volatile memory technology with high-density, high-speed, and low-power consumption. This study demonstrated the electrochemical synthesis of ZnO films without adding any soft or hard templates. The effect of deposition temperatures on crystal structure, surface morphology and resistive switching characteristics were investigated. Our findings reveal that the crystallinity, surface morphology and resistive switching characteristics of ZnO thin films can be well tuned by controlling deposition temperature. A conducting filament based model is proposed to explain the switching mechanism in ZnO thin films.

  8. Oriented ZnO nanostructures and their application in photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Man, Minh Tan [Department of Physics, Research Institute of Physics and Chemistry, Chonbuk National University, Jeonju 54896 (Korea, Republic of); Kim, Ji-Hee [Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 16419 (Korea, Republic of); Sungkyunkwan University (SKKU), Suwon, 16419 (Korea, Republic of); Jeong, Mun Seok [Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 16419 (Korea, Republic of); Department of Energy Science, Sungkyunkwan University, Suwon, 16419 (Korea, Republic of); Do, Anh-Thu Thi [Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Caugiay, Hanoi (Viet Nam); Lee, Hong Seok, E-mail: hslee1@jbnu.ac.kr [Department of Physics, Research Institute of Physics and Chemistry, Chonbuk National University, Jeonju 54896 (Korea, Republic of)

    2017-05-15

    We report a chemical bath deposition approach for the preparation of large arrays of oriented ZnO nanostructures by activated substrate processes, and precipitated ZnO nanorods by passive occupation of the crystal surface. Photoluminescence dynamics showed that various visible emission characteristics associated with defects such as oxygen vacancy, zinc interstitial or their complexes. In addition, the precipitated ZnO nanorods exhibited excellent performance in the adsorption and photocatalytic decomposition of organic dyes, achieving 95% photodegradation of Rhodamine 6B. Moreover, oxygen defects function as trap sites with strong adsorption abilities towards organic dyes and showed high performance in the photocatalytic degradation of the dye molecules.

  9. Temperature signal in suspended sediment export from an Alpine catchment

    Science.gov (United States)

    Costa, Anna; Molnar, Peter; Stutenbecker, Laura; Bakker, Maarten; Silva, Tiago A.; Schlunegger, Fritz; Lane, Stuart N.; Loizeau, Jean-Luc; Girardclos, Stéphanie

    2018-01-01

    Suspended sediment export from large Alpine catchments ( > 1000 km2) over decadal timescales is sensitive to a number of factors, including long-term variations in climate, the activation-deactivation of different sediment sources (proglacial areas, hillslopes, etc.), transport through the fluvial system, and potential anthropogenic impacts on the sediment flux (e.g. through impoundments and flow regulation). Here, we report on a marked increase in suspended sediment concentrations observed near the outlet of the upper Rhône River Basin in the mid-1980s. This increase coincides with a statistically significant step-like increase in basin-wide mean air temperature. We explore the possible explanations of the suspended sediment rise in terms of changes in water discharge (transport capacity), and the activation of different potential sources of fine sediment (sediment supply) in the catchment by hydroclimatic forcing. Time series of precipitation and temperature-driven snowmelt, snow cover, and ice melt simulated with a spatially distributed degree-day model, together with erosive rainfall on snow-free surfaces, are tested to explore possible reasons for the rise in suspended sediment concentration. We show that the abrupt change in air temperature reduced snow cover and the contribution of snowmelt, and enhanced ice melt. The results of statistical tests show that the onset of increased ice melt was likely to play a dominant role in the suspended sediment concentration rise in the mid-1980s. Temperature-driven enhanced melting of glaciers, which cover about 10 % of the catchment surface, can increase suspended sediment yields through an increased contribution of sediment-rich glacial meltwater, increased sediment availability due to glacier recession, and increased runoff from sediment-rich proglacial areas. The reduced extent and duration of snow cover in the catchment are also potential contributors to the rise in suspended sediment concentration through

  10. Cluster forcing

    DEFF Research Database (Denmark)

    Christensen, Thomas Budde

    The cluster theory attributed to Michael Porter has significantly influenced industrial policies in countries across Europe and North America since the beginning of the 1990s. Institutions such as the EU, OECD and the World Bank and governments in countries such as the UK, France, The Netherlands...... or management. Both the Accelerate Wales and the Accelerate Cluster programmes target this issue by trying to establish networks between companies that can be used to supply knowledge from research institutions to manufacturing companies. The paper concludes that public sector interventions can make...... businesses. The universities were not considered by the participating companies to be important parts of the local business environment and inputs from universities did not appear to be an important source to access knowledge about new product development or new techniques in production, distribution...

  11. Regional Innovation Clusters

    Data.gov (United States)

    Small Business Administration — The Regional Innovation Clusters serve a diverse group of sectors and geographies. Three of the initial pilot clusters, termed Advanced Defense Technology clusters,...

  12. Cluster analysis

    OpenAIRE

    Mucha, Hans-Joachim; Sofyan, Hizir

    2000-01-01

    As an explorative technique, duster analysis provides a description or a reduction in the dimension of the data. It classifies a set of observations into two or more mutually exclusive unknown groups based on combinations of many variables. Its aim is to construct groups in such a way that the profiles of objects in the same groups are relatively homogenous whereas the profiles of objects in different groups are relatively heterogeneous. Clustering is distinct from classification techniques, ...

  13. ZnO film deposition on Al film and effects of deposition temperature on ZnO film growth characteristics

    International Nuclear Information System (INIS)

    Yoon, Giwan; Yim, Munhyuk; Kim, Donghyun; Linh, Mai; Chai, Dongkyu

    2004-01-01

    The effects of the deposition temperature on the growth characteristics of the ZnO films were studied for film bulk acoustic wave resonator (FBAR) device applications. All films were deposited using a radio frequency magnetron sputtering technique. It was found that the growth characteristics of ZnO films have a strong dependence on the deposition temperature from 25 to 350 deg. C. ZnO films deposited below 200 deg. C exhibited reasonably good columnar grain structures with highly preferred c-axis orientation while those above 200 deg. C showed very poor columnar grain structures with mixed-axis orientation. This study seems very useful for future FBAR device applications

  14. Intrinsic and spatially nonuniform ferromagnetism in Co-doped ZnO films

    Science.gov (United States)

    Tseng, L. T.; Suter, A.; Wang, Y. R.; Xiang, F. X.; Bian, P.; Ding, X.; Tseng, A.; Hu, H. L.; Fan, H. M.; Zheng, R. K.; Wang, X. L.; Salman, Z.; Prokscha, T.; Suzuki, K.; Liu, R.; Li, S.; Morenzoni, E.; Yi, J. B.

    2017-09-01

    Co doped ZnO films have been deposited by a laser-molecular beam epitaxy system. X-ray diffraction and UV spectra analysis show that Co effectively substitutes the Zn site. Transmission electron microscopy (TEM) and secondary ion mass spectroscopy analysis indicate that there are no clusters. Co dopants are uniformly distributed in ZnO film. Ferromagnetic ordering is observed in all samples deposited under an oxygen partial pressure, PO2=10-3 , 10-5, and 10-7 torr, respectively. However, the magnetization of PO2=10-3 and 10-5 is very small at room temperature. At low temperature, the ferromagnetic ordering is enhanced. Muon spin relaxation (μ SR ) measurements confirm the ferromagnetism in all samples, and the results are consistent with magnetization measurements. From μ SR and TEM analysis, the film deposited under PO2=10-7 torr shows intrinsic ferromagnetism. However, the volume fraction of the ferromagnetism phase is approximately 70%, suggesting that the ferromagnetism is not carrier mediated. Resistivity versus temperature measurements indicate Efros variable range hopping dominates the conductivity. From the above results, we can confirm that a bound magnetic polaron is the origin of the ferromagnetism.

  15. Growth of ZnO heterostructures in an ultra compact MBE system

    Energy Technology Data Exchange (ETDEWEB)

    Ruth, Marcel [University of Duisburg-Essen, Institute of Experimental Physics, Duisburg (Germany); University of Paderborn (Germany). Group Nanophotonics and Nanomaterials; Meier, Cedrik [University of Paderborn (Germany). Group Nanophotonics and Nanomaterials

    2009-07-01

    Due to its unique properties such as the large direct bandgap of 3.37 eV and its high exciton binding energy, zinc oxide (ZnO) is a very promising semiconductor for optoelectronic and photonic applications even at room temperature. By adding cadmium (Cd) or magnesium (Mg) the bandgap can be tuned between 3.0 eV and 4.0 eV. It has already been shown that plasma assisted molecular beam epitaxy (PA-MBE) is a very suitable technique for growing high-quality epilayers of ZnO. Especially for research issues small samples are often sufficient. By using ultra compact MBE-systems the running costs can be kept down. However, the special system geometry and the very compact design lead to high requirements on the system. It is not trivial that in such a system stoichiometric and homogeneous growth conditions be achieved anyway. Furthermore, very high growth-rates can be obtained. By working in the zinc- (Zn) or oxygen-rich (O) regime completely different surface morphologies free of any metallic clusters are created. We present a systematic study on the growth conditions in such a compact system. Especially, the determination of the flux is discussed, and the grown heterostructures are characterised for their usability for nanophotonic devices.

  16. Enhanced room temperature ferromagnetism in electrodeposited Co-doped ZnO nanostructured thin films by controlling the oxygen vacancy defects

    Energy Technology Data Exchange (ETDEWEB)

    Simimol, A. [Nanomaterials Research Lab, Surface Engineering Division, CSIR-National Aerospace Laboratories, Post Bag No. 1779, Bangalore 560017 (India); Department of Physics, National Institute of Technology Calicut, Calicut 673601 (India); Anappara, Aji A. [Department of Physics, National Institute of Technology Calicut, Calicut 673601 (India); Greulich-Weber, S. [Department of Physics, Nanophotonic Materials, Faculty of Science, University of Paderborn, 33095 Paderborn (Germany); Chowdhury, Prasanta [Nanomaterials Research Lab, Surface Engineering Division, CSIR-National Aerospace Laboratories, Post Bag No. 1779, Bangalore 560017 (India); Barshilia, Harish C., E-mail: harish@nal.res.in

    2015-06-07

    We report the growth of un-doped and cobalt doped ZnO nanostructures fabricated on FTO coated glass substrates using electrodeposition method. A detailed study on the effects of dopant concentration on morphology, structural, optical, and magnetic properties of the ZnO nanostructures has been carried out systematically by varying the Co concentration (c.{sub Co}) from 0.01 to 1 mM. For c.{sub Co }≤ 0.2 mM, h-wurtzite phase with no secondary phases of Co were present in the ZnO nanostructures. For c.{sub Co} ≤ 0.2 mM, the photoluminescence spectra exhibited a decrease in the intensity of ultraviolet emission as well as band-gap narrowing with an increase in dopant concentration. All the doped samples displayed a broad emission in the visible range and its intensity increased with an increase in Co concentration. It was found that the defect centers such as oxygen vacancies and zinc interstitials were the source of the visible emission. The X-ray photoelectron spectroscopy studies revealed, Co was primarily in the divalent state, replacing the Zn ion inside the tetrahedral crystal site of ZnO without forming any cluster or secondary phases of Co. The un-doped ZnO nanorods exhibited diamagnetic behavior and it remained up to a c.{sub Co} of 0.05 mM, while for c.{sub Co }> 0.05 mM, the ZnO nanostructures exhibited ferromagnetic behavior at room temperature. The coercivity increased to 695 G for 0.2 mM Co-doped sample and then it decreased for c.{sub Co }> 0.2 mM. Our results illustrate that up to a threshold concentration of 0.2 mM, the strong ferromagnetism is due to the oxygen vacancy defects centers, which exist in the Co-doped ZnO nanostructures. The origin of strong ferromagnetism at room temperature in Co-doped ZnO nanostructures is attributed to the s-d exchange interaction between the localized spin moments resulting from the oxygen vacancies and d electrons of Co{sup 2+} ions. Our findings provide a new insight for tuning the

  17. Suspended microstructures of epoxy based photoresists fabricated with UV photolithography

    DEFF Research Database (Denmark)

    Hemanth, Suhith; Anhøj, Thomas Aarøe; Caviglia, Claudia

    2017-01-01

    In this work we present an easy, fast, reliable and low cost microfabrication technique for fabricating suspended microstructures of epoxy based photoresistswith UV photolithography. Two different fabrication processes with epoxy based resins (SU-8 and mr-DWL) using UV exposures at wavelengths...... of 313 nm and 405 nm were optimized and compared in terms of structural stability, control of suspended layer thickness and resolution limits. A novel fabrication process combining the two photoresists SU-8 and mr-DWL with two UV exposures at 365 nm and 405 nm respectively provided a wider processing...... window for definition of well-defined suspended microstructures with lateral dimensions down to 5 μmwhen compared to 313 nm or 365 nm UV photolithography processes....

  18. Flywheel Energy Storage System Suspended by Hybrid Magnetic Bearing

    Science.gov (United States)

    Owusu-Ansah, Prince; Hu, Yefa; Misbawu, Adam

    This work presents a prototype flywheel energy storage system (FESS) suspended by hybrid magnetic bearing (HMB) rotating at a speed of 20000rpm with a maximum storage power capacity of 30W with a maximum tip speed of 300m/s. The design presented is an improvement of most existing FESS, as the design incorporates a unique feature in that the upper and the lower rotor and stator core are tapered which enhances larger thrust and much lower radial force to be exerted on the system. Without any adverse effect being experienced by the model. The work also focuses on the description of developing a prototype FESS suspended by HMB using solid works as a basis of developing in the nearer future a more improved FESS suspended by HMB capable of injecting the ever increasing high energy demand situation in the 21st century and beyond.

  19. Analysis of the Danube river suspended load regime

    International Nuclear Information System (INIS)

    Lukac, M.

    2004-01-01

    In this presentation author deals with the analysis of the Danube river suspended load regime at the Slovak section of Danube. It is concluded and recommended: Suspended load transport at the Slovak section of Danube decreases in the downstream directions - annual averages: Utilize relation of the Water Research Institute in Medvedov, the relation of the Slovak Hydrometeorological Institute is probably slightly underestimated; Distribution of suspended load concentration in the cross-section is influenced mainly with local hydraulic and morphological conditions; Measured flow velocity in the range 0.6 - 2.65 m/sec -1 , influenced with water level slope; Silt particles the most numerous, less numerous sandy and clayey particles; Bratislava 3.54 mil. tonnes, Medvedov 2.22 mil. tonnes, and Komarno 1.96 mil. tonnes; Recommendation to measure actual volume of the Cunovo reservoir, in order to validate sediment transport balance; Recommendation to continue in a complex monitoring programme of sediment transport

  20. ZNO and AG-ZNO crystals: synthesis, characterization, and application in heterogeneous photocatalysis

    Directory of Open Access Journals (Sweden)

    Adriana Campano Lucilha

    2016-05-01

    Full Text Available ZnO and Ag-ZnO were synthesized in a simple and efficient manner by thermal decomposition of zinc oxalate and silver/zinc mixed oxalate. The influence of the addition of metallic silver on ZnO particles and the effect of temperature in the thermal treatment were investigated. The samples were characterized by thermogravimetric analysis, Raman, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, specific surface area (Brunauer-Emmett-Teller and diffuse reflectance spectroscopy. The photocatalytic activity of these materials in the decolorization of direct red 23 diazo dye was studied. The complete conversion into oxides from oxalates at lower temperatures was determinant in the photocatalytic efficiency of both the oxides. The presence of silver in zinc oxide, treated at 400 °C, more than doubled the rate constant of diazo dye decolorization (6.87×10-3 min-1 with respect to ZnO, treated at 600 °C, resulting in 3.07×10-3 min-1 under UV irradiation at 30 °C.

  1. ZnO 1-D nanostructures: Low temperature synthesis and ...

    Indian Academy of Sciences (India)

    Wintec

    high-resolution transmission electron microscope (HRTEM;. JEOL 2010). ... low magnification image of the ZnO nanorod arrays show- ing uniformity of the .... in inverted nail like shape. .... where E (local) is the local electric field at the emitting.

  2. Hydrothermal growth of ZnO nanoflowers and their photocatalyst ...

    Indian Academy of Sciences (India)

    ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy and photoluminescence. ZnO nanoflowers with star-like morphology were of pure wurtzite phase.

  3. Hydrodynamic fabrication of structurally gradient ZnO nanorods.

    Science.gov (United States)

    Kim, Hyung Min; Youn, Jae Ryoun; Song, Young Seok

    2016-02-26

    We studied a new approach where structurally gradient nanostructures were fabricated by means of hydrodynamics. Zinc oxide (ZnO) nanorods were synthesized in a drag-driven rotational flow in a controlled manner. The structural characteristics of nanorods such as orientation and diameter were determined by momentum and mass transfer at the substrate surface. The nucleation of ZnO was induced by shear stress which plays a key role in determining the orientation of ZnO nanorods. The nucleation and growth of such nanostructures were modeled theoretically and analyzed numerically to understand the underlying physics of the fabrication of nanostructures controlled by hydrodynamics. The findings demonstrated that the precise control of momentum and mass transfer enabled the formation of ZnO nanorods with a structural gradient in diameter and orientation.

  4. Optoelectronic properties of doped hydrothermal ZnO thin films

    KAUST Repository

    Mughal, Asad J.; Carberry, Benjamin; Oh, Sang Ho; Myzaferi, Anisa; Speck, James S.; Nakamura, Shuji; DenBaars, Steven P.

    2017-01-01

    , or In were evaluated for their optoelectronic properties. Inductively coupled plasma atomic emission spectroscopy was used to determine the concentration of dopants within the ZnO films. While Al and Ga-doped films showed linear incorporation rates

  5. Reducing ZnO nanoparticle cytotoxicity by surface modification.

    Science.gov (United States)

    Luo, Mingdeng; Shen, Cenchao; Feltis, Bryce N; Martin, Lisandra L; Hughes, Anthony E; Wright, Paul F A; Turney, Terence W

    2014-06-07

    Nanoparticulate zinc oxide (ZnO) is one of the most widely used engineered nanomaterials and its toxicology has gained considerable recent attention. A key aspect for controlling biological interactions at the nanoscale is understanding the relevant nanoparticle surface chemistry. In this study, we have determined the disposition of ZnO nanoparticles within human immune cells by measurement of total Zn, as well as the proportions of extra- and intracellular dissolved Zn as a function of dose and surface coating. From this mass balance, the intracellular soluble Zn levels showed little difference in regard to dose above a certain minimal level or to different surface coatings. PEGylation of ZnO NPs reduced their cytotoxicity as a result of decreased cellular uptake arising from a minimal protein corona. We conclude that the key role of the surface properties of ZnO NPs in controlling cytotoxicity is to regulate cellular nanoparticle uptake rather than altering either intracellular or extracellular Zn dissolution.

  6. Enhanced antimicrobial activity in biosynthesized ZnO nanoparticles

    Science.gov (United States)

    Kumari, Niraj; Kumari, Priti; Jha, Anal K.; Prasad, K.

    2018-05-01

    Biological synthesis of different metallic and/or oxide nanoparticles and their applications especially in agriculture and biomedical sciences are gaining prominence nowadays due to their handy and reproducible synthetic protocols which are cost-effective and eco-friendly. In this work, green synthesis of zinc oxide nanoparticles (ZnO NPs) using the alcoholic extract of Azadirachta indica as a reducing and stabilizing agent has been presented. Formation of ZnO NPs was confirmed by X-ray diffraction, scanning and transmission electron microscopy techniques. The phytochemicals responsible for nano-transformation were principally alkaloids, flavanoids, terpenoids, tannins and organic acids present in the Azadirachta indica leaves. The synthesized ZnO NPs were used for antimicrobial assays by disc diffusion method against Staphylococcus aureus and Candida albicans. Results showed that ZnO NPs may act as antimicrobial agent especially against skin infections.

  7. Investigation of the pulsed electrochemical deposition of ZnO

    International Nuclear Information System (INIS)

    Dunkel, Christian; Lüttich, Franziska; Graaf, Harald; Oekermann, Torsten; Wark, Michael

    2012-01-01

    The influence of pulse parameters on the morphology of ZnO prepared by pulsed cathodic electrodeposition from oxygen-saturated aqueous ZnCl 2 solution on ITO (indium tin oxide)/glass substrates was investigated. It was found that the ratio between the pulse and the pause duration has a crucial influence on the crystal growth, reaching the highest density of the films with pause/pulse-ratios between 0.25 and 1. Longer pauses cause an Ostwald-like ripening of the ZnO crystals and therewith a strong change in the crystal morphology from roundly shaped to hexagonal. Also the hydrophilicity of the substrate resulting from pre-treatment has a crucial influence on the deposited films, leading to films only consisting of few large and separately grown ZnO crystals for highly hydrophilic substrates and an increasing fraction of small densely grown ZnO crystals with increasing hydrophobicity.

  8. Biogenic ZnO nanoparticles synthesized using L. aculeata leaf ...

    Indian Academy of Sciences (India)

    The antifungal activity of ZnO nanoparticles were determined using the well diffusion method. All the ... 1. Introduction. Nanoparticles have gained increasing importance because ... The synthesis of nanoparticles by conventional physical.

  9. Sonochemical effects on ZnO particles

    Directory of Open Access Journals (Sweden)

    Bruna C. Costa

    2014-01-01

    Full Text Available La variedad de aplicaciones tecnológicas relacionadas a los dispositivos basados en óxidos semiconductores nanoestructurados ha despertado un gran interés en la comunidad científica, haciendo con que los estudios relacionados a estos materiales han aumentado en los últimos años. Entre estos materiales, se encuentra el óxido de zinc (ZnO, que presenta aplicaciones en las más diversas áreas, desde diodos emisores de luz (LEDs a los dispositivos fotovoltaicos en células solares. Con el conocimiento de que las propiedades químicas y físicas que confieren a estos materiales las posibilidades de aplicación en dispositivos tecnológicos son fuertemente dependientes de las rutas de síntesis empleadas para la obtención de los mismos, presentamos en este trabajo una investigación con respecto de las modificaciones morfológicas ocurridas en partículas de ZnO, cuando el mismo es expuesto a un tratamiento sonoquímico, además de las influencias de los parámetros relacionados a éste método de síntesis en la obtención de este material. Para analizar los parámetros presentados anteriormente, tres muestras fueron preparadas, dos de ellas manteniendo la amplitud y variando el tiempo de sonicación y otra manteniendo el tiempo y variando la amplitud de sonicación, durante el tratamiento sonoquímico. El análisis de los resultados obtenidos indica que el tratamiento sonoquímico conduce a modificaciones morfológicas superficiales en las partículas de ZnO, además estas modificaciones se presentaron más evidentes cuando una mayor amplitud y un mayor tiempo de sonicación fueron utilizados en la síntesis de las muestras.

  10. Colorimetry Technique for Scalable Characterization of Suspended Graphene.

    Science.gov (United States)

    Cartamil-Bueno, Santiago J; Steeneken, Peter G; Centeno, Alba; Zurutuza, Amaia; van der Zant, Herre S J; Houri, Samer

    2016-11-09

    Previous statistical studies on the mechanical properties of chemical-vapor-deposited (CVD) suspended graphene membranes have been performed by means of measuring individual devices or with techniques that affect the material. Here, we present a colorimetry technique as a parallel, noninvasive, and affordable way of characterizing suspended graphene devices. We exploit Newton's rings interference patterns to study the deformation of a double-layer graphene drum 13.2 μm in diameter when a pressure step is applied. By studying the time evolution of the deformation, we find that filling the drum cavity with air is 2-5 times slower than when it is purged.

  11. Optical fiber end-facet polymer suspended-mirror devices

    Science.gov (United States)

    Yao, Mian; Wu, Jushuai; Zhang, A. Ping; Tam, Hwa-Yaw; Wai, P. K. A.

    2017-04-01

    This paper presents a novel optical fiber device based on a polymer suspended mirror on the end facet of an optical fiber. With an own-developed optical 3D micro-printing technology, SU-8 suspended-mirror devices (SMDs) were successfully fabricated on the top of a standard single-mode optical fiber. Optical reflection spectra of the fabricated SU- 8 SMDs were measured and compared with theoretical analysis. The proposed technology paves a way towards 3D microengineering of the small end-facet of optical fibers to develop novel fiber-optic sensors.

  12. Hydrogen absorption in thin ZnO films prepared by pulsed laser deposition

    OpenAIRE

    Meilkhova, O.; Čížek, J.; Lukáč,, F.; Vlček, M.; Novotný, M.; Bulíř, J.; Lančok, J.; Anwand, W.; Brauer, G.; Connolly, J.; McCarthy, E.; Krishnamurthy, S.; Mosnier, J.-P.

    2013-01-01

    ZnO films with thickness of ~80 nm were grown by pulsed laser deposition (PLD) on MgO (1 0 0) single crystal and amorphous fused silica (FS) substrates. Structural studies of ZnO films and a high quality reference ZnO single crystal were performed by slow positron implantation spectroscopy (SPIS). It was found that ZnO films exhibit significantly higher density of defects than the reference ZnO crystal. Moreover, the ZnO film deposited on MgO substrate exhibits higher concentration of defects...

  13. Photocatalytic Water Oxidation on ZnO: A Review

    Directory of Open Access Journals (Sweden)

    Sharifah Bee Abdul Hamid

    2017-03-01

    Full Text Available The investigation of the water oxidation mechanism on photocatalytic semiconductor surfaces has gained much attention for its potential to unlock the technological limitations of producing H2 from carbon-free sources, i.e., H2O. This review seeks to highlight the available scientific and fundamental understanding towards the water oxidation mechanism on ZnO surfaces, as well as present a summary on the modification strategies carried out to increase the photocatalytic response of ZnO.

  14. ZnO based potentiometric and amperometric nanosensors.

    Science.gov (United States)

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

    2014-09-01

    The existence of nanomaterials provides the solid platform for sensing applications due to owing of high sensitivity and a low concentration limit of detection. More likely used nanomaterials for sensing applications includes gold nanoparticles, carbon nanotubes, magnetic nanoparticles such as Fe3O4, quantum dots and metal oxides etc. Recently nanomaterial and biological detection becomes an interdisciplinary field and is very much focussed by the researchers. Among metal oxides ZnO is largely considered due to its less toxic nature, biocompatible, cheap and easy to synthesis. ZnO nanomaterial is highly used for the chemical sensing, especially electrochemical sensing due to its fascinating properties such as high surface to volume ratio, atoxic, biosafe and biocompatible. Moreover, ZnO nanostructures exhibit unique features which could expose a suitable nanoenviroment for the immobilization of proteineous material such as enzymes, DNA, antibodies, etc. and in doing so it retains the biological efficiency of the immobilized bio sensitive material. The following review describes the two different coatings (i.e., ionophore and enzyme) on the surface of ZnO nanorods for the chemical sensing of zinc ion detection, thallium (I) ion detection, and L-lactic acid and the measurement of galactose molecules. ZnO nanorods provide the excellent transducing properties in the generation of strong electrical signals. Moreover, this review is very much focused on the applications of ZnO nanostructures in the sensing field.

  15. Synthesis, characteristics and antimicrobial activity of ZnO nanoparticles

    Science.gov (United States)

    Janaki, A. Chinnammal; Sailatha, E.; Gunasekaran, S.

    2015-06-01

    The utilization of various plant resources for the bio synthesis of metallic nano particles is called green technology and it does not utilize any harmful protocols. Present study focuses on the green synthesis of ZnO nano particles by Zinc Carbonate and utilizing the bio-components of powder extract of dry ginger rhizome (Zingiber officinale). The ZnO nano crystallites of average size range of 23-26 nm have been synthesized by rapid, simple and eco friendly method. Zinc oxide nano particles were characterized by using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectroscopy (EDX). FTIR spectra confirmed the adsorption of surfactant molecules at the surface of ZnO nanoparticles and the presence of ZnO bonding. Antimicrobial activity of ZnO nano particles was done by well diffusion method against pathogenic organisms like Klebsiella pneumonia, Staphylococcus aureus and Candida albicans and Penicillium notatum. It is observed that the ZnO synthesized in the process has the efficient antimicrobial activity.

  16. ZnO Nanostructures for Tissue Engineering Applications

    Directory of Open Access Journals (Sweden)

    Marco Laurenti

    2017-11-01

    Full Text Available This review focuses on the most recent applications of zinc oxide (ZnO nanostructures for tissue engineering. ZnO is one of the most investigated metal oxides, thanks to its multifunctional properties coupled with the ease of preparing various morphologies, such as nanowires, nanorods, and nanoparticles. Most ZnO applications are based on its semiconducting, catalytic and piezoelectric properties. However, several works have highlighted that ZnO nanostructures may successfully promote the growth, proliferation and differentiation of several cell lines, in combination with the rise of promising antibacterial activities. In particular, osteogenesis and angiogenesis have been effectively demonstrated in numerous cases. Such peculiarities have been observed both for pure nanostructured ZnO scaffolds as well as for three-dimensional ZnO-based hybrid composite scaffolds, fabricated by additive manufacturing technologies. Therefore, all these findings suggest that ZnO nanostructures represent a powerful tool in promoting the acceleration of diverse biological processes, finally leading to the formation of new living tissue useful for organ repair.

  17. Aqueous chemical growth and application of ZnO nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Postels, Bianca; Kasprzak, Anna; Mofor, Augustine C.; Wehmann, Hergo-Heinrich; Bakin, Andrey; Waag, Andreas [Institute of Semiconductor Technology, Technical University Braunschweig, Hans-Sommer-Str. 66, 38106 Braunschweig (Germany)

    2007-07-01

    A very promising fabrication process for ZnO nanostructures is the aqueous chemical growth (ACG), since it is a cost efficient and low temperature approach. Using this growth technique we generated wafer-scale ZnO nanorod arrays on Si, sapphire, ITO coated glass and even on flexible polymer substrates. ACG is found to be only weakly influenced by the substrate material and we are also able to control the dimensions of the ZnO nanorods. Another benefit of ACG is the ability to fabricate patterned arrays of ZnO nanorods by a selective growth process on structured metallised surfaces. Results of structural analysis with SEM and XRD are reported. Additionally, optical properties were investigated by PL measurements. First attempts on the preparation of dye sensitised solar cells (DSSCs) are also reported. Here, the traditional sintered TiO{sub 2} nanoparticles are replaced by a densely packed and vertically aligned array of ACG ZnO nanorods. The size and morphology of the ZnO nanorods can be controlled. The influence of the length of the nanorods on the cell properties is investigated. A vapour phase transport technique was also used as alternative growth method.

  18. High efficient ZnO nanowalnuts photocatalyst: A case study

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Feng [College of Chemistry and Chemical Engineering, Mudanjiang Normal University, Mudanjiang 157011 (China); College of Chemistry and Chemical Engineering, Harbin Normal University, Harbin 150025 (China); Zhang, Siwen; Liu, Yang [College of Chemistry and Chemical Engineering, Harbin Normal University, Harbin 150025 (China); Liu, Hongfeng [School of Basic Medical Sciences, Mudanjiang Medical University, Mudanjiang 157011 (China); Qu, Fengyu [College of Chemistry and Chemical Engineering, Harbin Normal University, Harbin 150025 (China); Cai, Xue, E-mail: xuecai@mail.sdu.edu.cn [College of Chemistry and Chemical Engineering, Mudanjiang Normal University, Mudanjiang 157011 (China); Wu, Xiang, E-mail: wuxiang@hrbnu.edu.cn [College of Chemistry and Chemical Engineering, Harbin Normal University, Harbin 150025 (China)

    2014-11-15

    Highlights: • Walnut-like ZnO nanostructures are synthesized through a facile hydrothermal method. • Morphologies and microstructures of the as-obtained ZnO products were investigated. • The photocatalytic results demonstrate that methyl orange (MO) aqueous solution can be degraded over 97% after 45 min under UV light irradiation. - Abstract: Walnut-like ZnO nanostructures are successfully synthesized through a facile hydrothermal method. The structure and morphology of the as-synthesized products were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The photocatalytic properties of ZnO nanowalnuts are investigated by photodegradating several organic dyes, such as Congo red (CR), methyl orange (MO) and eosin red aqueous solutions under UV irradiation, respectively. The results demonstrate that methyl orange (MO) aqueous solution can be degraded over 97% after 45 min under UV light irradiation. In addition, eosin red and Congo red (CR) aqueous solution degradation experiments are also conducted in the same condition, respectively. It showed that ZnO nanowalnuts represent high photocatalytic activities with a degradation efficiency of 87% for CR with 115 min of irradiation and 97% for eosin red with 55 min of irradiation. The reported ZnO products may be promising candidates as the photocatalysts in waste water treatment.

  19. High efficient ZnO nanowalnuts photocatalyst: A case study

    International Nuclear Information System (INIS)

    Yan, Feng; Zhang, Siwen; Liu, Yang; Liu, Hongfeng; Qu, Fengyu; Cai, Xue; Wu, Xiang

    2014-01-01

    Highlights: • Walnut-like ZnO nanostructures are synthesized through a facile hydrothermal method. • Morphologies and microstructures of the as-obtained ZnO products were investigated. • The photocatalytic results demonstrate that methyl orange (MO) aqueous solution can be degraded over 97% after 45 min under UV light irradiation. - Abstract: Walnut-like ZnO nanostructures are successfully synthesized through a facile hydrothermal method. The structure and morphology of the as-synthesized products were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The photocatalytic properties of ZnO nanowalnuts are investigated by photodegradating several organic dyes, such as Congo red (CR), methyl orange (MO) and eosin red aqueous solutions under UV irradiation, respectively. The results demonstrate that methyl orange (MO) aqueous solution can be degraded over 97% after 45 min under UV light irradiation. In addition, eosin red and Congo red (CR) aqueous solution degradation experiments are also conducted in the same condition, respectively. It showed that ZnO nanowalnuts represent high photocatalytic activities with a degradation efficiency of 87% for CR with 115 min of irradiation and 97% for eosin red with 55 min of irradiation. The reported ZnO products may be promising candidates as the photocatalysts in waste water treatment

  20. Atomic absorption photometry of excess Zn in ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Lott, K.; Shinkarenko, S.; Tuern, L. [Department of Materials Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia); Kirsanova, T.; Grebennik, A.; Vishnjakov, A. [Department of Physical Chemistry, D. Mendelejev University of Chemical Technology of Russia, Miusskaya Sq. 9, 125047 Moscow (Russian Federation)

    2005-02-01

    Zn excess in ZnO is built up automatically at high temperatures. Excess Zn in hydrothermally grown ZnO single crystals were investigated by the atomic absorption photometry (AAP) method. To determine the excess zinc in ZnO samples, the AAP of zinc vapour was used in the conditions of solid-vapour equilibrium. Zn AAP allowed to eliminate excess Zn connected differentially in ZnO samples. To fix Zn non-stoichiometry, all the ZnO samples tested were previously heat treated at temperature interval from 850 to 900 C and at fixed Zn vapour pressures from 0.1 to 0.9 of saturated zinc vapour pressure at given treatment temperature. The analysis of temperature dependence of zinc vapour pressure indicated that the impurity metals take active role in the determination of non-stoichiometric zinc. The impurities Mn, Fe, Co, Ni and Cu form oxides which will reduce during annealing in Zn vapor up to metals form. During AAP measurement in optical cuvette, these metals react with ZnO and give additional Zn vapor pressure. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Stimulated emission from ZnO nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Hauschild, R.; Lange, H.; Priller, H.; Klingshirn, C.; Kalt, H. [Institut fuer Angewandte Physik, Universitaet Karlsruhe (T.H.), 76128 Karlsruhe (Germany); Kling, R. [Abteilung Halbleiterphysik, Universitaet Ulm, Albert-Einstein Allee 45, 89081 Ulm (Germany); Waag, A. [Institut fuer Halbleitertechnik, TU-Braunschweig, H.-Sommer-Str. 66, 38106 Braunschweig (Germany); Fan, H.J.; Zacharias, M. [Max-Planck-Institut fuer Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany)

    2006-03-15

    By means of time resolved spectroscopy we compare two samples of ZnO nanorods with respect to their suitability as stimulated emitters. In the case of narrow nanorods their wave guiding quality causes a suppression of exciton-exciton scattering whereas no laser emission is detectable. Unlike their narrow counterparts, wide nanorods not only benefit from a larger overlap of the guided mode with the gain medium but a variation in VLS growth results in gold nanoparticles being present at the bottom of nanorods. Consequently, laser emission from single wide rods is evidenced up to 150 K. In addition to experimental studies we carry out 3D numerical simulations of the electric field distribution to evaluate the influence of gold nanoparticles at the nanorod/substrate interface. This finite element analysis confirms that gold leads to an enhancement of confinement within the resonator. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. [Distribution and origin of polycyclic aromatic hydrocarbons in suspended particulate matters from the Yangtze estuarine and nearby coastal areas].

    Science.gov (United States)

    Ou, Dong-ni; Liu, Min; Xu, Shi-yuan; Cheng, Shu-bo; Hou, Li-jun; Gao, Lei

    2008-09-01

    Parent PAHs have been quantified in suspended particulate matters from the Yangtze Estuarine and Coastal Areas. The results show that the concentrations of total PAHs ranged from 2278.79-14293.98 ng/g, and were characterized by greatest content near sewage discharge point with trend to decrease by increasing distance. As for PAHs composition, 4-6 rings PAHs were dominant while 2-3 rings PAHs were relative low. Cluster analysis found that except urban sewage discharge, the hydrodynamic force was influencing PAHs distribution patterns. Moreover, the content of suspended particulate matters, organic carbon and soot carbon of suspended particulate matters also play the important roles in PAHs distribution from the Yangtze estuarine and nearby coastal areas. Principal component analysis and PAH ratios demonstrated that uncompleted combustion of fossil fuels was the main source of PAHs in coastal areas, as well as a few anthropogenic releases of oil and oil products. Ecological risk assessment indicated that most of PAH compounds exceeded the effects range ER-L values and ISQV-L values, which might certain potential damage to the Yangtze Estuary ecosystem.

  3. Effect of Mg doping in ZnO buffer layer on ZnO thin film devices for electronic applications

    Science.gov (United States)

    Giri, Pushpa; Chakrabarti, P.

    2016-05-01

    Zinc Oxide (ZnO) thin films have been grown on p-silicon (Si) substrate using magnesium doped ZnO (Mg: ZnO) buffer layer by radio-frequency (RF) sputtering method. In this paper, we have optimized the concentration of Mg (0-5 atomic percent (at. %)) ZnO buffer layer to examine its effect on ZnO thin film based devices for electronic and optoelectronic applications. The crystalline nature, morphology and topography of the surface of the thin film have been characterized. The optical as well as electrical properties of the active ZnO film can be tailored by varying the concentration of Mg in the buffer layer. The crystallite size in the active ZnO thin film was found to increase with the Mg concentration in the buffer layer in the range of 0-3 at. % and subsequently decrease with increasing Mg atom concentration in the ZnO. The same was verified by the surface morphology and topography studies carried out with scanning electron microscope (SEM) and atomic electron microscopy (AFM) respectively. The reflectance in the visible region was measured to be less than 80% and found to decrease with increase in Mg concentration from 0 to 3 at. % in the buffer region. The optical bandgap was initially found to increase from 3.02 eV to 3.74 eV by increasing the Mg content from 0 to 3 at. % but subsequently decreases and drops down to 3.43 eV for a concentration of 5 at. %. The study of an Au:Pd/ZnO Schottky diode reveals that for optimum doping of the buffer layer the device exhibits superior rectifying behavior. The barrier height, ideality factor, rectification ratio, reverse saturation current and series resistance of the Schottky diode were extracted from the measured current voltage (I-V) characteristics.

  4. Microwave synthesis and photocatalytic activities of ZnO bipods with different aspect ratios

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Fazhe; Zhao, Zengdian [Analysis and Testing Center, Shandong University of Technology, Zibo 255100 (China); Qiao, Xueliang, E-mail: xuelqiao@163.com [State Key Laboratory of Plastic Forming Simulation and Die and Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, Hubei (China); Tan, Fatang; Wang, Wei [State Key Laboratory of Plastic Forming Simulation and Die and Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, Hubei (China)

    2016-02-15

    Highlights: • We synthesized linked ZnO nanorods by a facile microwave method. • The effect of reaction parameters on ZnO was investigated. • ZnO bipods with different aspect ratios were prepared. • The photocatalytic performance of ZnO bipods was evaluated. - Abstract: Linked ZnO nanorods have been successfully prepared via a facile microwave method without any post-synthesis treatment. The X-ray diffraction (XRD) patterns indicated the precursor had completely transformed into the pure ZnO crystal. The images of field emitting scanning electron microscope (FESEM) and transmission electron microscope (TEM) showed that linked ZnO nanorods consisted predominantly of ZnO bipods. The formation process of the ZnO bipods was clearly discussed. ZnO bipods with different aspect ratios have been obtained by tuning the concentrations of reagents and microwave power. Moreover, the photocatalytic performance of ZnO bipods with different aspect ratios for degradation of methylene blue was systematically evaluated. The results of photocatalytic experiments showed that the photocatalytic activity increased with the aspect ratios of ZnO bipods increased. The reason is that ZnO bipods with larger aspect ratio have higher surface area, which can absorb more MB molecules to react with ·OH radicals.

  5. Physical and chemical contributions of a plasma treatment in the growth of ZnO nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Jang, J.T. [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Obang-dong, Gimhae, Gyeongnam 621-749 (Korea, Republic of); Ryu, H., E-mail: hhryu@inje.ac.kr [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Obang-dong, Gimhae, Gyeongnam 621-749 (Korea, Republic of); Lee, W.J. [Department of Materials and Components Engineering, Dong-Eui University, 995 Eomgwangno, Busanjin-gu, Busan 614-714 (Korea, Republic of); Yun, J. [Department of Nano Science and Engineering, Kyungnam University, Changwon, Gyeongnam 631-701 (Korea, Republic of)

    2013-11-15

    Highlights: •ZnO nanorods were grown by hydrothermal synthesis. •Oxygen plasma was done on the surface of seed ZnO nanorods. •The ZnO nanorods with and without plasma treatment were characterized. •The results showed that the optical and structural properties of ZnO nanorods with plasma treatment were enhanced. -- Abstract: We analyzed the enhancement of optical and structural properties of ZnO nanorods by using a plasma treatment. In this study, seed ZnO nanorods were grown by hydrothermal synthesis for 1 h on a ZnO buffered Si substrate. The seed ZnO nanorods were then treated with an oxygen plasma. Next, ZnO was grown for an additional 4 h by hydrothermal synthesis. The resultant ZnO nanorods were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS), X-ray diffraction (XRD) and photoluminescence (PL). The measurements showed that the plasma treatment of the seed ZnO nanorods increased the roughness of the buffer layer and the concentration of oxygen ions on the surfaces of the seed ZnO nanorods and the buffer layer, leading to improved optical and structural properties. In this study, we found that the plasma treatment on the seed ZnO nanorods enhanced the optical and structural properties of the ZnO nanorods.

  6. Assessments of lake profiling on temperature, Total Suspended ...

    African Journals Online (AJOL)

    Interpolation were performed on temperature, total suspended solid (TSS) and turbidity (TUR) based on in-situ and ex-situ analyses according to the correlation matrix and linear regression at 14 different depths for the Chomor River and Mahadir Island. The result showed outlet significantly decreased over depth caused the ...

  7. Discrete Dynamics of Nanoparticle Channelling in Suspended Graphene

    DEFF Research Database (Denmark)

    Booth, Tim; Pizzocchero, Filippo; Andersen, Henrik

    2011-01-01

    We have observed a previously undescribed stepwise oxidation of mono- and few layer suspended graphene by silver nanoparticles in situ at subnanometer scale in an environmental transmission electron microscope. Over the range of 600–850 K, we observe crystallographically oriented channelling...

  8. Self-Suspended Suspensions of Covalently Grafted Hairy Nanoparticles

    KAUST Repository

    Choudhury, Snehashis

    2015-03-17

    © 2015 American Chemical Society. Dispersions of small particles in liquids have been studied continuously for almost two centuries for their ability to simultaneously advance understanding of physical properties of fluids and their widespread use in applications. In both settings, the suspending (liquid) and suspended (solid) phases are normally distinct and uncoupled on long length and time scales. In this study, we report on the synthesis and physical properties of a novel family of covalently grafted nanoparticles that exist as self-suspended suspensions with high particle loadings. In such suspensions, we find that the grafted polymer chains exhibit unusual multiscale structural transitions and enhanced conformational stability on subnanometer and nanometer length scales. On mesoscopic length scales, the suspensions display exceptional homogeneity and colloidal stability. We attribute this feature to steric repulsions between grafted chains and the space-filling constraint on the tethered chains in the single-component self-suspended materials, which inhibits phase segregation. On macroscopic length scales, the suspensions exist as neat fluids that exhibit soft glassy rheology and, counterintuitively, enhanced elasticity with increasing temperature. This feature is discussed in terms of increased interpenetration of the grafted chains and jamming of the nanoparticles. (Chemical Presented).

  9. Turbidity-controlled sampling for suspended sediment load estimation

    Science.gov (United States)

    Jack Lewis

    2003-01-01

    Abstract - Automated data collection is essential to effectively measure suspended sediment loads in storm events, particularly in small basins. Continuous turbidity measurements can be used, along with discharge, in an automated system that makes real-time sampling decisions to facilitate sediment load estimation. The Turbidity Threshold Sampling method distributes...

  10. Nature of suspended particulate matter and concentrations of heavy ...

    African Journals Online (AJOL)

    The concentrations of metals in bottom sediment in the Tanzanian waters of Lake Victoria and the nature of suspended particulate matter (SPM) were analysed. The objective of the study was to compare levels of metals in sediment from different locations and to establish their sources. Metal concentrations were higher in ...

  11. Comparison of Suspended Solid Separation in Advanced Storm Overflow Structures

    DEFF Research Database (Denmark)

    Larsen, Torben; Sørensen, Morten Steen

    1990-01-01

    This paper describes a laboratory investigation of the separation of suspended solids in a circular weir overflow and a vortex separator. The basic idea is to evaluate the efficiency of a vortical flow in the overflow chamber, and to compare these results with other overflow structures....

  12. Investigation of suspended sediment transport using ultrasonic techniques

    DEFF Research Database (Denmark)

    Bjørnø, Irina; Jensen, Leif Bjørnø

    1994-01-01

    The results of the initial experimental studies involving the scattering of ultrasonic signals from canonical and non-canonical shaped suspended particles with known elastical qualities are reported. These results have formed the basis for the development of a numerical model for ultrasound...... propagation through low-concentration suspensions of sand particles...

  13. Reduction in density of suspended - sediment - laden natural waters

    Digital Repository Service at National Institute of Oceanography (India)

    Joseph, A.; Desa, E.; Desa, E.; Smith, D.; Peshwe, V.B.; VijayKumar, K.; Desa, J.A.E.

    to 0.4% - 4.5%) that of the density of the same water without suspended sediment. Teh values of peff in a given site differed from one tidal cycle to another (approx equal to 1.9%). These values varied slightly (less than 0.8%) from mid-tide to slack...

  14. A suspended sediment yield predictive equation for river basins in ...

    African Journals Online (AJOL)

    The fit was found to be better than those relating mean annual specific suspended sediment yield to basin area or runoff only. Since many stream gauging stations in the country have no records on fluvial sediment, the empirical equation can be used to obtain preliminary estimates of expected sediment load of streams for ...

  15. Geochemistry of suspended and settling solids in two freshwater lakes.

    NARCIS (Netherlands)

    Koelmans, A.A.

    1998-01-01

    This study describes the 1987–1992 time variationof the bulk chemical composition, levels of heavymetals, arsenic, nitrogen and phosporous insuspended and settling solids in Lake Volkerak andLake Zoom (The Netherlands). Suspended and setlingsolids were collected with continuous flowcentrifuges and

  16. Opportunities Suspended: The Disparate Impact of Disciplinary Exclusion from School

    Science.gov (United States)

    Losen, Daniel J.; Gillespie, Jonathan

    2012-01-01

    Well over three million children, K-12, are estimated to have lost instructional "seat time" in 2009-2010 because they were suspended from school, often with no guarantee of adult supervision outside the school. That's about the number of children it would take to fill every seat in every major league baseball park and every NFL stadium…

  17. Microscopic characterisation of suspended graphene grown by chemical vapour deposition

    NARCIS (Netherlands)

    Bignardi, L.; Dorp, W.F. van; Gottardi, S.; Ivashenko, O.; Dudin, P.; Barinov, A.; de Hosson, J.T.M.; Stöhr, M.; Rudolf, P.

    2013-01-01

    We present a multi-technique characterisation of graphene grown by chemical vapour deposition (CVD) and thereafter transferred to and suspended on a grid for transmission electron microscopy (TEM). The properties of the electronic band structure are investigated by angle-resolved photoelectron

  18. A direct simulation method for flows with suspended paramagnetic particles

    NARCIS (Netherlands)

    Kang, T.G.; Hulsen, M.A.; Toonder, den J.M.J.; Anderson, P.D.; Meijer, H.E.H.

    2008-01-01

    A direct numerical simulation method based on the Maxwell stress tensor and a fictitious domain method has been developed to solve flows with suspended paramagnetic particles. The numerical scheme enables us to take into account both hydrodynamic and magnetic interactions between particles in a

  19. Suspended Education Department Official Had Approved Waiver for Former Employer

    Science.gov (United States)

    Basken, Paul

    2007-01-01

    Matteo Fontana, the student-aid official in the U.S. Department of Education who was suspended last month in an ethics case, issued a controversial high-stakes legal ruling in 2004 that benefited his former employer, Sallie Mae, on the day before the nation's top student lender completed its transition from a government-founded lender into a…

  20. Evaluation of the Suspending Properties of the Coprecipitate of ...

    African Journals Online (AJOL)

    The suspending ability of the different ratios was evaluated in magnesium trisilicate suspension, and compared with a suspension prepared with Compound Tragacanth Powder BP (CTP) as well as a commercially available magnesium trisilicate suspension (MTS). The parameters tested were sedimentation rate, flow rate, ...

  1. Evaluation of the suspending properties of Cola acuminata gum on ...

    African Journals Online (AJOL)

    Calamine suspensions were formulated with CAG between the concentration range of 1 – 4 % w/v and compared with suspensions formulated with two standard suspending agents (tragacanth and acacia gums). Sedimentation volume, flow rate, rheology and redispersibility were used as evaluating parameters.

  2. Turbidity threshold sampling for suspended sediment load estimation

    Science.gov (United States)

    Jack Lewis; Rand Eads

    2001-01-01

    Abstract - The paper discusses an automated procedure for measuring turbidity and sampling suspended sediment. The basic equipment consists of a programmable data logger, an in situ turbidimeter, a pumping sampler, and a stage-measuring device. The data logger program employs turbidity to govern sample collection during each transport event. Mounting configurations and...

  3. Structural, optical, and LED characteristics of ZnO and Al doped ZnO thin films

    Science.gov (United States)

    Sandeep, K. M.; Bhat, Shreesha; Dharmaprakash, S. M.

    2017-05-01

    ZnO (pristine) and Al doped ZnO (AZO) films were prepared using sol-gel spin coating method. The XRD analysis showed the enhanced compressive stress in AZO film. The presence of extended states below the conduction band edge in AZO accounts for the redshift in optical bandgap. The PL spectra of AZO showed significant blue emission due to the carrier recombination from defect states. The TRPL curves showed the dominant DAP recombination in ZnO film, whereas defect related recombination in Al doped ZnO film. Color parameters viz: the dominant wavelength, color coordinates (x,y), color purity, luminous efficiency and correlated color temperature (CCT) of ZnO and AZO films are calculated using 1931 (CIE) diagram. Further, a strong blue emission with color purity more than 96% is observed in both the films. The enhanced blue emission in AZO significantly increased the luminous efficiency (22.8%) compared to ZnO film (10.8%). The prepared films may be used as blue phosphors in white light generation.

  4. Synthesis of ZnO nanorods and observation of resistive switching memory in ZnO based polymer nanocomposites

    Science.gov (United States)

    Nair, Manjula G.; Malakar, Meenakshi; Mohapatra, Saumya R.; Chowdhury, Avijit

    2018-05-01

    This research reports the observation of bipolar resistive switching memory in ZnO nanorod based polymer nanocomposites. We synthesized ZnO nanorods by wet-chemical method and characterized them using XRD, UV-VIS spectroscopy and SEM. The synthesized materials have hexagonal ZnO phase with grain size of 24 nm and having strong orientation along (101) direction as observed from XRD. The SEM micrograph confirms the formation of ZnO nanorods with diameter in the range of 10 to 20 nm and length of the order of 1 µm. From optical absorption spectra the band gap is estimated to be 2.42 eV. ZnO nanorods were dispersed in PVDF-HFP polymer matrix to prepare the nanocomposite. This nanocomposite was used as active layer in the devices having sandwich structure of ITO/PVDF-HFP+ZnO nanorods/Al. Bipolar non-volatile memory was observed with ON-OFF resistance ratio of the order of 103 and with a wide voltage window of 2.3V. The switching mechanism could be due to the trapping and de-trapping of electrons by the ZnO nanorods in the nanocomposite during ON and OFF states respectively.

  5. Fabrication of Well-Aligned ZnO Nanorods Using a Composite Seed Layer of ZnO Nanoparticles and Chitosan Polymer.

    Science.gov (United States)

    Khun, Kimleang; Ibupoto, Zafar Hussain; AlSalhi, Mohamad S; Atif, Muhammad; Ansari, Anees A; Willander, Magnus

    2013-09-30

    In this study, by taking the advantage of both inorganic ZnO nanoparticles and the organic material chitosan as a composite seed layer, we have fabricated well-aligned ZnO nanorods on a gold-coated glass substrate using the hydrothermal growth method. The ZnO nanoparticles were characterized by the Raman spectroscopic techniques, which showed the nanocrystalline phase of the ZnO nanoparticles. Different composites of ZnO nanoparticles and chitosan were prepared and used as a seed layer for the fabrication of well-aligned ZnO nanorods. Field emission scanning electron microscopy, energy dispersive X-ray, high-resolution transmission electron microscopy, X-ray diffraction, and infrared reflection absorption spectroscopic techniques were utilized for the structural characterization of the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods on a gold-coated glass substrate. This study has shown that the ZnO nanorods are well-aligned, uniform, and dense, exhibit the wurtzite hexagonal structure, and are perpendicularly oriented to the substrate. Moreover, the ZnO nanorods are only composed of Zn and O atoms. An optical study was also carried out for the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods, and the obtained results have shown that the fabricated ZnO nanorods exhibit good crystal quality. This study has provided a cheap fabrication method for the controlled morphology and good alignment of ZnO nanorods, which is of high demand for enhancing the working performance of optoelectronic devices.

  6. Fabrication of Well-Aligned ZnO Nanorods Using a Composite Seed Layer of ZnO Nanoparticles and Chitosan Polymer

    Directory of Open Access Journals (Sweden)

    Anees A. Ansari

    2013-09-01

    Full Text Available In this study, by taking the advantage of both inorganic ZnO nanoparticles and the organic material chitosan as a composite seed layer, we have fabricated well-aligned ZnO nanorods on a gold-coated glass substrate using the hydrothermal growth method. The ZnO nanoparticles were characterized by the Raman spectroscopic techniques, which showed the nanocrystalline phase of the ZnO nanoparticles. Different composites of ZnO nanoparticles and chitosan were prepared and used as a seed layer for the fabrication of well-aligned ZnO nanorods. Field emission scanning electron microscopy, energy dispersive X-ray, high-resolution transmission electron microscopy, X-ray diffraction, and infrared reflection absorption spectroscopic techniques were utilized for the structural characterization of the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods on a gold-coated glass substrate. This study has shown that the ZnO nanorods are well-aligned, uniform, and dense, exhibit the wurtzite hexagonal structure, and are perpendicularly oriented to the substrate. Moreover, the ZnO nanorods are only composed of Zn and O atoms. An optical study was also carried out for the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods, and the obtained results have shown that the fabricated ZnO nanorods exhibit good crystal quality. This study has provided a cheap fabrication method for the controlled morphology and good alignment of ZnO nanorods, which is of high demand for enhancing the working performance of optoelectronic devices.

  7. Suspended matter and heavy metal content of the Elbe Estuary

    International Nuclear Information System (INIS)

    Vollbrecht, K.

    1980-01-01

    (1) In the River Elbe estuary there is a turbidity zone which is closely bound to the region of brackish waters. Its suspended matter content changes strongly with the tidal rhythm. Suspended matter and river bed sediments influence each other by exchanging their particles. Owing to that mechanism, the heavy metal ions bound or taken up by the suspended matter (sorption) enter the sediments. To obtain an estimation of the estuary's ability to cope with ( self purify ) a strong burden of industrial wastes, it is neccessary to take into consideration the absorbing capacity of both the mean suspension load and the sediments. (2) The concentration of nearly all heavy metal ions investigated in the suspension load decreases remarkably at the very beginning of the turbid zone already, in the Hamburg region. It indicates that the binding process are going on very rapidly and that the metal ion absorbing capacity of the Elbe estuary still requires only the first few miles of this self purification system. The results gained indicate that the suspended matter in Hamburg waters could bind or take up more heavy metal ions than are discharged into this area. (3) The concentration of most ions bound to the suspension material correlates very well with the grain size distribution of the (anorganic) particles. The concentration values decrease along the estuary and lead to a continuous transition to the values of the open sea. Cu, Ni and Cd appear to be captured preferably by organic suspended matter. This behaviour, however, is solely restricted to the turbid zone. In the open sea, after oxidation of the binding organic material, Cu and Ni correspond to the anorganic grain size distribution. (orig./HP) [de

  8. An analysis of bedload and suspended load interactions

    Science.gov (United States)

    Recking, alain; Navratil, Oldrich

    2013-04-01

    Several approaches were used to develop suspension equations. It includes semi-theoretical equations based on the convection diffusion equation (Einstein 1950; Van Rijn 1984; Camenen and Larson 2008; Julien 2010), semi-empirical tools based on energy concept (Velikanov 1954; Bagnold 1966), empirical adjustments (Prosser and Rusttomji 2000). One essential characteristic of all these equations is that most of them were developed by considering continuity between bedload and suspended load, and that the partitioning between these two modes of transport evolves progressively with increasing shear stress, which is the case for fine bed materials. The use of these equations is thus likely to be welcome in estuaries or lowland sandy rivers, but may be questionable in gravel-bed rivers and headwater streams where the bed is usually structured vertically and fine sediments potentially contributing to suspension are stored under a poorly mobile surface armour comprising coarse sediments. Thus one question this work aimed to answer is does the presence of an armour at the bed surface influence suspended load? This was investigated through a large field data set comprising instantaneous measurements of both bedload and suspension. We also considered the river characteristics, distinguishing between lowland rivers, gravel bed rivers and headwater streams. The results showed that a correlation exist between bedload and suspension for lowland and gravel bed rivers. This suggests that in gravel bed rivers a large part of the suspended load is fed by subsurface material, and depends on the remobilization of the surface material. No correlation was observed for head water streams where the sediment production is more likely related to hillslope processes. These results were used with a bedload transport equation for proposing a method for suspended load estimate. The method is rough, but especially for gravel bed rivers, it predicts suspended load reasonably well when compared to

  9. Nuclear clustering - a cluster core model study

    International Nuclear Information System (INIS)

    Paul Selvi, G.; Nandhini, N.; Balasubramaniam, M.

    2015-01-01

    Nuclear clustering, similar to other clustering phenomenon in nature is a much warranted study, since it would help us in understanding the nature of binding of the nucleons inside the nucleus, closed shell behaviour when the system is highly deformed, dynamics and structure at extremes. Several models account for the clustering phenomenon of nuclei. We present in this work, a cluster core model study of nuclear clustering in light mass nuclei

  10. Electrochemical Sensing, Photocatalytic and Biological Activities of ZnO Nanoparticles: Synthesis via Green Chemistry Route

    Science.gov (United States)

    Yadav, L. S. Reddy; Archana, B.; Lingaraju, K.; Kavitha, C.; Suresh, D.; Nagabhushana, H.; Nagaraju, G.

    2016-05-01

    In this paper, we have successfully synthesized ZnO nanoparticles (Nps) via solution combustion method using sugarcane juice as the novel fuel. The structure and morphology of the synthesized ZnO Nps have been analyzed using various analytical tools. The synthesized ZnO Nps exhibit excellent photocatalytic activity for the degradation of methylene blue dye, indicating that the ZnO Nps are potential photocatalytic semiconductor materials. The synthesized ZnO Nps also show good electrochemical sensing of dopamine. ZnO Nps exhibit significant bactericidal activity against Klebsiella aerogenes, Pseudomonas aeruginosa, Eschesichia coli and Staphylococcus aureus using agar well diffusion method. Furthermore, the ZnO Nps show good antioxidant activity by potentially scavenging 1-diphenyl-2-picrylhydrazyl (DPPH) radicals. The above studies clearly demonstrate versatile applications of ZnO synthesized by simple eco-friendly route.

  11. Fabrication and photovoltaic properties of ZnO nanorods/perovskite solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Shirahata, Yasuhiro; Tanaike, Kohei; Akiyama, Tsuyoshi; Fujimoto, Kazuya; Suzuki, Atsushi; Balachandran, Jeyadevan; Oku, Takeo, E-mail: oku@mat.usp.ac.jp [Department of Materials Science, The University of Shiga Prefecture, 2500 Hassaka, Hikone, Shiga 522-8533 (Japan)

    2016-02-01

    ZnO nanorods/perovskite solar cells with different lengths of ZnO nanorods were fabricated. The ZnO nanorods were prepared by chemical bath deposition and directly confirmed to be hexagon-shaped nanorods. The lengths of the ZnO nanorads were controlled by deposition condition of ZnO seed layer. Photovoltaic properties of the ZnO nanorods/CH{sub 3}NH{sub 3}PbI{sub 3} solar cells were investigated by measuring current density-voltage characteristics and incident photon to current conversion efficiency. The highest conversion efficiency was obtained in ZnO nanorods/CH{sub 3}NH{sub 3}PbI{sub 3} with the longest ZnO nanorods.

  12. Photoluminescence and lasing properties of ZnO nanorods

    International Nuclear Information System (INIS)

    Lee, Geon Joon; Lee, Young Pak; Min, Sun Ki; Han, Sung Hwan; Lim, Hwan Hong; Cha, Myoung Sik; Kim, Sung Soo; Cheong, Hyeon Sik

    2010-01-01

    In this study, we investigated the structures, photoluminescence (PL), and lasing characteristics of the ZnO nanorods prepared by using chemical bath deposition. The continuous-wave HeCd laser excited PL spectra of the ZnO nanorods exhibited two emission bands, one in the UV region and the other in the visible region. The UV emission band has its peak at 3.25 eV with a bandwidth of 160 meV. However, the PL spectra under 355-nm, 35-ps pulse excitation exhibited a spectrally-narrowed UV emission band with a peak at 3.20 eV and a spectral width of 35 meV. The lasing phenomena were ascribed to the amplified spontaneous emission (ASE) caused by coupling of the microcavity effect of ZnO nanorods and the high-intensity excitation. Above the lasing threshold, the ASE peak intensity exhibited a superlinear dependence on the excitation intensity. For an excitation pulse energy of 3 mJ, the ASE peak intensity was increased by enlarging the length of the ZnO nanorods from 1 μm to 4 μm. In addition, the PL spectrum under 800-nm femtosecond pulse excitation exhibited second harmonic generation, as well as the multiphoton absorption-induced UV emission band. In this research, ZnO nanorods were grown on seed layers by using chemical bath deposition in an aqueous solution of Zn(NO 3 ) 2 and hexamethyltetramine. The seed layers were prepared on conducting glass substrates by dip coating in an aqueous colloidal dispersion containing 50% 70-nm ZnO nanoparticles. Scanning electron microscopy clearly revealed that ZnO nanorods were successfully grown on the seed layers.

  13. Solution precursor plasma deposition of nanostructured ZnO coatings

    International Nuclear Information System (INIS)

    Tummala, Raghavender; Guduru, Ramesh K.; Mohanty, Pravansu S.

    2011-01-01

    Highlights: → The solution precursor route employed is an inexpensive process with capability to produce large scale coatings at fast rates on mass scale production. → It is highly capable of developing tailorable nanostructures. → This technique can be employed to spray the coatings on any kind of substrates including polymers. → The ZnO coatings developed via solution precursor plasma spray process have good electrical conductivity and reflectivity properties in spite of possessing large amount of particulate boundaries, porosity and nanostructured grains. -- Abstract: Zinc oxide (ZnO) is a wide band gap semiconducting material that has various applications including optical, electronic, biomedical and corrosion protection. It is usually synthesized via processing routes, such as vapor deposition techniques, sol-gel, spray pyrolysis and thermal spray of pre-synthesized ZnO powders. Cheaper and faster synthesis techniques are of technological importance due to increased demand in alternative energy applications. Here, we report synthesis of nanostructured ZnO coatings directly from a solution precursor in a single step using plasma spray technique. Nanostructured ZnO coatings were deposited from the solution precursor prepared using zinc acetate and water/isopropanol. An axial liquid atomizer was employed in a DC plasma spray torch to create fine droplets of precursor for faster thermal treatment in the plasma plume to form ZnO. Microstructures of coatings revealed ultrafine particulate agglomerates. X-ray diffraction confirmed polycrystalline nature and hexagonal Wurtzite crystal structure of the coatings. Transmission electron microscopy studies showed fine grains in the range of 10-40 nm. Observed optical transmittance (∼65-80%) and reflectivity (∼65-70%) in the visible spectrum, and electrical resistivity (48.5-50.1 mΩ cm) of ZnO coatings are attributed to ultrafine particulate morphology of the coatings.

  14. Solution precursor plasma deposition of nanostructured ZnO coatings

    Energy Technology Data Exchange (ETDEWEB)

    Tummala, Raghavender [Department of Mechanical Engineering, University of Michigan - Dearborn, MI 48128 (United States); Guduru, Ramesh K., E-mail: rkguduru@umich.edu [Department of Mechanical Engineering, University of Michigan - Dearborn, MI 48128 (United States); Mohanty, Pravansu S. [Department of Mechanical Engineering, University of Michigan - Dearborn, MI 48128 (United States)

    2011-08-15

    Highlights: {yields} The solution precursor route employed is an inexpensive process with capability to produce large scale coatings at fast rates on mass scale production. {yields} It is highly capable of developing tailorable nanostructures. {yields} This technique can be employed to spray the coatings on any kind of substrates including polymers. {yields} The ZnO coatings developed via solution precursor plasma spray process have good electrical conductivity and reflectivity properties in spite of possessing large amount of particulate boundaries, porosity and nanostructured grains. -- Abstract: Zinc oxide (ZnO) is a wide band gap semiconducting material that has various applications including optical, electronic, biomedical and corrosion protection. It is usually synthesized via processing routes, such as vapor deposition techniques, sol-gel, spray pyrolysis and thermal spray of pre-synthesized ZnO powders. Cheaper and faster synthesis techniques are of technological importance due to increased demand in alternative energy applications. Here, we report synthesis of nanostructured ZnO coatings directly from a solution precursor in a single step using plasma spray technique. Nanostructured ZnO coatings were deposited from the solution precursor prepared using zinc acetate and water/isopropanol. An axial liquid atomizer was employed in a DC plasma spray torch to create fine droplets of precursor for faster thermal treatment in the plasma plume to form ZnO. Microstructures of coatings revealed ultrafine particulate agglomerates. X-ray diffraction confirmed polycrystalline nature and hexagonal Wurtzite crystal structure of the coatings. Transmission electron microscopy studies showed fine grains in the range of 10-40 nm. Observed optical transmittance ({approx}65-80%) and reflectivity ({approx}65-70%) in the visible spectrum, and electrical resistivity (48.5-50.1 m{Omega} cm) of ZnO coatings are attributed to ultrafine particulate morphology of the coatings.

  15. Tuning magnetism by biaxial strain in native ZnO.

    Science.gov (United States)

    Peng, Chengxiao; Wang, Yuanxu; Cheng, Zhenxiang; Zhang, Guangbiao; Wang, Chao; Yang, Gui

    2015-07-07

    Magnetic ZnO, one of the most important diluted magnetic semiconductors (DMS), has attracted great scientific interest because of its possible technological applications in optomagnetic devices. Magnetism in this material is usually delicately tuned by the doping level, dislocations, and local structures. The rational control of magnetism in ZnO is a highly attractive approach for practical applications. Here, the tuning effect of biaxial strain on the d(0) magnetism of native imperfect ZnO is demonstrated through first-principles calculations. Our calculation results show that strain conditions have little effect on the defect formation energy of Zn and O vacancies in ZnO, but they do affect the magnetism significantly. For a cation vacancy, increasing the compressive strain will obviously decrease its magnetic moment, while tensile strain cannot change the moment, which remains constant at 2 μB. For a singly charged anion vacancy, however, the dependence of the magnetic moment on strain is opposite to that of the Zn vacancy. Furthermore, the ferromagnetic state is always present, irrespective of the strain type, for ZnO with two zinc vacancies, 2VZns. A large tensile strain is favorable for improving the Curie temperature and realizing room temperature ferromagnetism for ZnO-based native semiconductors. For ZnO with two singly charged oxygen vacancies, 2Vs, no ferromagnetic ordering can be observed. Our work points the way to the rational design of materials beyond ZnO with novel non-intrinsic functionality by simply tuning the strain in a thin film form.

  16. Analysis on the energetics, magnetism and electronic properties in a 45° ZnO grain boundary doped with Gd

    KAUST Repository

    Devi, Assa Aravindh Sasikala

    2018-04-13

    The structural stability and magnetic properties of a grain boundary (GB) formed by aligning two ZnO single crystals oriented at an angle of 45° is investigated by density functional theory, using generalized gradient approximation (GGA) and taking the U parameter into consideration for the 4f impurity states. We found that the GB is stable with no dangling bonds and inter-granular structures. The stability of defects such as Gd substituted to the Zn site (Gd), Zn vacancy (V) and O vacancy (V) as well as defect complexes Gd-Gd, Gd-V, and Gd-V are analyzed using formation energy calculations. It is found that Gd-Gd clusters prefers to form at the GB. The spin polarization at the Gd sites is too localized and the exchange coupling energy is insufficient to overcome the thermal fluctuations. However, we show that the presence of V increases the hybridization between p orbitals of O as well as d orbitals of Zn, which can assist in increasing the magnetic polarization of the system. This work advances the understanding of the ferromagnetism in Gd-doped ZnO, indicating that Gd clustering at the GB is not likely to contribute to the ferromagnetism.

  17. Structural, optical and magnetic properties of Mn doped ZnO thin films prepared by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Aravind, Arun, E-mail: aruncusat@gmail.com [Nanophotonic and Optoelectronic Devices Laboratory, Department of Physics, Cochin University of Science and Technology, Kochi 682 022, Kerala (India); Jayaraj, M.K., E-mail: mkj@cusat.ac.in [Nanophotonic and Optoelectronic Devices Laboratory, Department of Physics, Cochin University of Science and Technology, Kochi 682 022, Kerala (India); Kumar, Mukesh; Chandra, Ramesh [Nano Science Laboratory, Institute Instrumentation Centre, IIT Roorkee, Roorkee 247 667, Uttarakhand (India)

    2012-08-01

    Highlights: Black-Right-Pointing-Pointer Defect induced Raman active modes in Mn doped ZnO thin films. Black-Right-Pointing-Pointer Room temperature ferromagnetism. Black-Right-Pointing-Pointer Morphological variations of ZnO thin films with Mn doping. Black-Right-Pointing-Pointer Variation of refractive index of ZnO thin films with Mn doping. - Abstract: Zn{sub 1-x}Mn{sub x}O thin films were grown by pulsed laser deposition. The phase purity and the structure were confirmed by X-ray diffraction studies. The films have a transmittance more than 80% in the visible region. The refractive index of Zn{sub 0.90}Mn{sub 0.10}O films is found to be 1.77 at 550 nm. The presence of non-polar E{sub 2}{sup high} and E{sub 2}{sup low} Raman modes in thin films indicates that 'Mn' doping does not change the wurtzite structure of ZnO. Apart from the normal modes of ZnO the Zn{sub 1-x}Mn{sub x}O ceramic targets show two additional modes at 332 cm{sup -1} (I{sub 1}) and 524 cm{sup -1} (I{sub 2}). The broad Raman peaks (340-600 cm{sup -1}) observed Zn{sub 0.90}Mn{sub 0.10}O thin films can be deconvoluted into five peaks, denoted as P{sub 1}-P{sub 5}. The possible origins of Raman peaks in Zn{sub 1-x}Mn{sub x}O films are the structural disorder and morphological change caused by the Mn dopant. The B{sub 1}{sup low}, {sup 2}B{sub 1}{sup low}, B{sub 1}{sup high} and A{sub 1}{sup LO} modes as well as the surface phonon mode have been observed in heavily Mn-doped ZnO films. Zn{sub 0.98}Mn{sub 0.02}O thin film shows room temperature ferromagnetism. The saturation magnetic moment of the Zn{sub 0.98}Mn{sub 0.02}O thin film is 0.42{mu}{sub B}/Mn atom. The undoped ZnO film prepared under the same condition shows diamagnetic nature. At higher doping concentrations the formation of Mn clusters suppress the room temperature ferromagnetism in Zn{sub 1-x}Mn{sub x}O thin films and shows paramagnetism. XPS confirms the incorporation of Mn{sup 2+} into the ZnO lattice.

  18. Effects of Chromium Dopant on Ultraviolet Photoresponsivity of ZnO Nanorods

    Science.gov (United States)

    Mokhtari, S.; Safa, S.; Khayatian, A.; Azimirad, R.

    2017-07-01

    Structural and optical properties of bare ZnO nanorods, ZnO-encapsulated ZnO nanorods, and Cr-doped ZnO-encapsulated ZnO nanorods have been investigated. Encapsulated ZnO nanorods were grown using a simple two-stage method in which ZnO nanorods were first grown on a glass substrate directly from a hydrothermal bath, then encapsulated with a thin layer of Cr-doped ZnO by dip coating. Comparative study of x-ray diffraction patterns showed that Cr was successfully incorporated into the shell layer of ZnO nanorods. Moreover, energy-dispersive x-ray spectroscopy confirmed presence of Cr in this sample. It was observed that the thickness of the shell layer around the core of the ZnO nanorods was at least about 20 nm. Transmission electron microscopy of bare ZnO nanorods revealed single-crystalline structure. Based on optical results, both the encapsulation process and addition of Cr dopant decreased the optical bandgap of the samples. Indeed, the optical bandgap values of Cr-doped ZnO-encapsulated ZnO nanorods, ZnO-encapsulated ZnO nanorods, and bare ZnO nanorods were 2.89 eV, 3.15 eV, and 3.34 eV, respectively. The ultraviolet (UV) parameters demonstrated that incorporation of Cr dopant into the shell layer of ZnO nanorods considerably facilitated formation and transportation of photogenerated carriers, optimizing their performance as a practical UV detector. As a result, the photocurrent of the Cr-doped ZnO-encapsulated ZnO nanorods was the highest (0.6 mA), compared with ZnO-encapsulated ZnO nanorods and bare ZnO nanorods (0.21 mA and 0.06 mA, respectively).

  19. Ion species dependence of the implantation-induced defects in ZnO studied by a slow positron beam

    International Nuclear Information System (INIS)

    Chen, Z.Q.; Maekawa, M.; Kawasuso, A.; Naramoto, H.

    2007-01-01

    In this work, we implanted B + , O + , Al + , and P + ions into ZnO with energy of 50-380 keV and total doses of 4 x 10 15 cm -2 for each ion. The implantation-induced defects and their thermal recovery were studied using a slow positron beam. Vacancy clusters are produced in all the implanted samples. It is found that the thermal recovery of these vacancies induced by different ions shows much difference. In case of B + and Al + -implantation, the vacancy clusters agglomerate to much larger size and might evolve to microvoids during annealing. However, for O + and P + ions, which are heavier than B + and Al + , the vacancies show a much weaker agglomeration process. The mechanism of such difference is discussed. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Temperature signal in suspended sediment export from an Alpine catchment

    Directory of Open Access Journals (Sweden)

    A. Costa

    2018-01-01

    Full Text Available Suspended sediment export from large Alpine catchments ( >  1000 km2 over decadal timescales is sensitive to a number of factors, including long-term variations in climate, the activation–deactivation of different sediment sources (proglacial areas, hillslopes, etc., transport through the fluvial system, and potential anthropogenic impacts on the sediment flux (e.g. through impoundments and flow regulation. Here, we report on a marked increase in suspended sediment concentrations observed near the outlet of the upper Rhône River Basin in the mid-1980s. This increase coincides with a statistically significant step-like increase in basin-wide mean air temperature. We explore the possible explanations of the suspended sediment rise in terms of changes in water discharge (transport capacity, and the activation of different potential sources of fine sediment (sediment supply in the catchment by hydroclimatic forcing. Time series of precipitation and temperature-driven snowmelt, snow cover, and ice melt simulated with a spatially distributed degree-day model, together with erosive rainfall on snow-free surfaces, are tested to explore possible reasons for the rise in suspended sediment concentration. We show that the abrupt change in air temperature reduced snow cover and the contribution of snowmelt, and enhanced ice melt. The results of statistical tests show that the onset of increased ice melt was likely to play a dominant role in the suspended sediment concentration rise in the mid-1980s. Temperature-driven enhanced melting of glaciers, which cover about 10 % of the catchment surface, can increase suspended sediment yields through an increased contribution of sediment-rich glacial meltwater, increased sediment availability due to glacier recession, and increased runoff from sediment-rich proglacial areas. The reduced extent and duration of snow cover in the catchment are also potential contributors to the rise in suspended sediment

  1. USING TURBIDITY DATA TO PREDICT SUSPENDED SEDIMENT CONCENTRATIONS: POSSIBILITIES, LIMITATIONS, AND PITFALLS

    Science.gov (United States)

    This talk will look at the relationships between turbidity and suspended sediment concentrations in a variety of geographic areas, geomorphic river types, and river sizes; and attempt to give guidance on using existing turbidity data to predict suspended sediment concentrations.

  2. Seasonal changes in suspended sediment load in the Gauthami-Godavari Estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Reddy, N.P.C.; Rao, B.P.; Rao, K.M.; Rao, V.S.

    Studies carried out on suspended matter characteristics of the the Gautami Godavari Estuary revealed that the concentration of suspended matter (CSM) during southwest monsoon influenced mainly by the increased run off at both Neelarevu and Vrudha...

  3. Impact of sound attenuation by suspended sediment on ADCP backscatter calibrations

    NARCIS (Netherlands)

    Sassi, M.G.; Hoitink, A.J.F.; Vermeulen, B.

    2012-01-01

    Although designed for velocity measurements, acoustic Doppler current profilers (ADCPs) are widely being used to monitor suspended particulate matter in rivers and in marine environments. To quantify mass concentrations of suspended matter, ADCP backscatter is generally calibrated with in situ

  4. Design, analysis and control of cable-suspended parallel robots and its applications

    CERN Document Server

    Zi, Bin

    2017-01-01

    This book provides an essential overview of the authors’ work in the field of cable-suspended parallel robots, focusing on innovative design, mechanics, control, development and applications. It presents and analyzes several typical mechanical architectures of cable-suspended parallel robots in practical applications, including the feed cable-suspended structure for super antennae, hybrid-driven-based cable-suspended parallel robots, and cooperative cable parallel manipulators for multiple mobile cranes. It also addresses the fundamental mechanics of cable-suspended parallel robots on the basis of their typical applications, including the kinematics, dynamics and trajectory tracking control of the feed cable-suspended structure for super antennae. In addition it proposes a novel hybrid-driven-based cable-suspended parallel robot that uses integrated mechanism design methods to improve the performance of traditional cable-suspended parallel robots. A comparative study on error and performance indices of hybr...

  5. Piezoelectric Nanogenerator Using p-Type ZnO Nanowire Arrays

    KAUST Repository

    Lu, Ming-Pei; Song, Jinhui; Lu, Ming-Yen; Chen, Min-Teng; Gao, Yifan; Chen, Lih-Juann; Wang, Zhong Lin

    2009-01-01

    Using phosphorus-doped ZnO nanowire (NW) arrays grown on silicon substrate, energy conversion using the p-type ZnO NWs has been demonstrated for the first time. The p-type ZnO NWs produce positive output voltage pulses when scanned by a conductive

  6. Enhanced ultraviolet photo-response in Dy doped ZnO thin film

    Science.gov (United States)

    Kumar, Pawan; Singh, Ranveer; Pandey, Praveen C.

    2018-02-01

    In the present work, a Dy doped ZnO thin film deposited by the spin coating method has been studied for its potential application in a ZnO based UV detector. The investigations on the structural property and surface morphology of the thin film ensure that the prepared samples are crystalline and exhibit a hexagonal crystal structure of ZnO. A small change in crystallite size has been observed due to Dy doping in ZnO. AFM analysis ascertains the grain growth and smooth surface of the thin films. The Dy doped ZnO thin film exhibits a significant enhancement in UV region absorption as compared to the pure ZnO thin film, which suggests that Dy doped ZnO can be used as a UV detector. Under UV irradiation of wavelength 325 nm, the photocurrent value of Dy doped ZnO is 105.54 μA at 4.5 V, which is 31 times greater than that of the un-doped ZnO thin film (3.39 μA). The calculated value of responsivity is found to increase significantly due to the incorporation of Dy in the ZnO lattice. The observed higher value of photocurrent and responsivity could be attributed to the substitution of Dy in the ZnO lattice, which enhances the conductivity, electron mobility, and defects in ZnO and benefits the UV sensing property.

  7. Preparation and photocatalytic property of a novel dumbbell-shaped ZnO microcrystal photocatalyst

    DEFF Research Database (Denmark)

    Sun, Jian-Hui; Dong, Shu-Ying; Wang, Yong-Kui

    2009-01-01

    achieved 68.0%, 99.0% and 98.5%, the TOC removal efficiencies achieved 43.2%, 59.4% and 70.6%, respectively. Compared to commercial ZnO, 16-22% higher TOC removal efficiency was obtained by the dumbbell-shaped ZnO. The results indicated that the prepared dumbbell-shaped ZnO microcrystal photocatalyst...

  8. Hierarchical nanoflowers assembled with Au nanoparticles decorated ZnO nanosheets toward enhanced photocatalytic properties

    DEFF Research Database (Denmark)

    Yu, Cuiyan; Yu, Yanlong; Xu, Tao

    2017-01-01

    Hierarchical nanoflowers assembled with Au nanoparticles (NPs) decorated ZnO nanosheets (Au-ZnO nanosheet flowers, AZNSFs) were successful synthesized. The AZNSFs showed more efficient activity to photodegradation of RhB than that of pure ZnO nanosheet flowers and commercial ZnO nanopowders. The ...

  9. Enhanced fluorescence imaging performance of hydrophobic colloidal ZnO nanoparticles by a facile method

    International Nuclear Information System (INIS)

    Zang, Zhigang; Tang, Xiaosheng

    2015-01-01

    Highlights: • A dual phase hydrothermal method was developed to synthesize ZnO nanoparticles. • ZnO nanoparticles show a stability and solubility in the aqueous environment. • ZnO nanoparticles with a blue emission wavelength at around 420 nm and small size (30 nm). • ZnO nanoparticles as biological labeling agent was also shown. - Abstract: A facile synthesis method for the formation of ZnO nanoparticles by using a double-phase reaction was demonstrated in this paper. The morphology of the synthesized ZnO nanoparticles shows a flower-shape. Hydrogen peroxide was used as a unique oxygenic source to promote the formation of ZnO in the presence of organic zinc precursor. The as-synthesized ZnO nanoparticles also show a stability and solubility in the aqueous environment. The structure and properties of ZnO nanoparticles were investigated by the transmission electron microscopy (TEM) and X-ray diffraction (XRD) as well as UV–vis and photoluminescence spectroscopy. The as-prepared hydrophobic colloidal ZnO nanoparticles could be modified to become water-soluble via ligand exchange with amineothanethiol⋅HCl while retaining the photoluminescence properties. In addition, the potential application for biological label of water-soluble ZnO nanoparticles were also demonstrated. These results not only have applications towards using colloidal ZnO nanoparticles effectively in biological fluorescence imaging, but also promote its application in the field of targeted drug delivery

  10. Wafer-Scale High-Throughput Ordered Growth of Vertically Aligned ZnO Nanowire Arrays

    KAUST Repository

    Wei, Yaguang; Wu, Wenzhuo; Guo, Rui; Yuan, Dajun; Das, Suman; Wang, Zhong Lin

    2010-01-01

    -synthesized morphology. The development of textured ZnO seed layers for replacing single crystalline GaN and ZnO substrates extends the large-scale fabrication of vertically aligned ZnO NW arrays on substrates of other materials, such as polymers, Si, and glass

  11. ZnO Thin Film Electronics for More than Displays

    Science.gov (United States)

    Ramirez, Jose Israel

    Zinc oxide thin film transistors (TFTs) are investigated in this work for large-area electronic applications outside of display technology. A constant pressure, constant flow, showerhead, plasma-enhanced atomic layer deposition (PEALD) process has been developed to fabricate high mobility TFTs and circuits on rigid and flexible substrates at 200 °C. ZnO films and resulting devices prepared by PEALD and pulsed laser deposition (PLD) have been compared. Both PEALD and PLD ZnO films result in densely packed, polycrystalline ZnO thin films that were used to make high performance devices. PEALD ZnO TFTs deposited at 300 °C have a field-effect mobility of ˜ 40 cm2/V-s (and > 20 cm2/V-S deposited at 200 °C). PLD ZnO TFTs, annealed at 400 °C, have a field-effect mobility of > 60 cm2/V-s (and up to 100 cm2/V-s). Devices, prepared by either technique, show high gamma-ray radiation tolerance of up to 100 Mrad(SiO2) with only a small radiation-induced threshold voltage shift (VT ˜ -1.5 V). Electrical biasing during irradiation showed no enhanced radiation-induced effects. The study of the radiation effects as a function of material stack thicknesses revealed the majority of the radiation-induced charge collection happens at the semiconductor-passivation interface. A simple sheet-charge model at that interface can describe the radiation-induced charge in ZnO TFTs. By taking advantage of the substrate-agnostic process provided by PEALD, due to its low-temperature and excellent conformal coatings, ZnO electronics were monolithically integrated with thin-film complex oxides. Application-based examples where ZnO electronics provide added functionality to complex oxide-based devices are presented. In particular, the integration of arrayed lead zirconate titanate (Pb(Zr, Ti)O3 or PZT) thin films with ZnO electronics for microelectromechanical systems (MEMs) and deformable mirrors is demonstrated. ZnO switches can provide voltage to PZT capacitors with fast charging and slow

  12. Al-doped ZnO seed layer-dependent crystallographic control of ZnO nanorods by using electrochemical deposition

    Energy Technology Data Exchange (ETDEWEB)

    Son, Hyo-Soo; Choi, Nak-Jung [Department of Nano-Optical Engineering, Korea Polytechnic University, Siheung 429-793 (Korea, Republic of); Kim, Kyoung-Bo [Department of Metallurgical and Materials Engineering, Inha Technical College, Incheon 402-752 (Korea, Republic of); Kim, Moojin [Department of Renewable Energy, Jungwon University, Goesan-gun, Chungbuk 367-805 (Korea, Republic of); Lee, Sung-Nam, E-mail: snlee@kpu.ac.kr [Department of Nano-Optical Engineering, Korea Polytechnic University, Siheung 429-793 (Korea, Republic of)

    2016-10-15

    Highlights: • Polar and semipolar ZnO NRs were successfully achieved by hydrothermal synthesis. • Semipolar and polar ZnO NRs were grown on ZnO and AZO/m-sapphire, respectively. • Al % of AZO/m-sapphire enhanced the lateral growth rate of polar ZnO NRs. - Abstract: We investigated the effect of an Al-doped ZnO film on the crystallographic direction of ZnO nanorods (NRs) using electrochemical deposition. From high-solution X-ray diffraction measurements, the crystallographic plane of ZnO NRs grown on (1 0 0) ZnO/m-plane sapphire was (1 0 1). The surface grain size of the (100) Al-doped ZnO (AZO) film decreased with increasing Al content in the ZnO seed layer, implying that the Al dopant accelerated the three-dimensional (3D) growth of the AZO film. In addition, it was found that with increasing Al doping concentration of the AZO seed layer, the crystal orientation of the ZnO NRs grown on the AZO seed layer changed from [1 0 1] to [0 0 1]. With increasing Al content of the nonpolar (1 0 0) AZO seed layer, the small surface grains with a few crystallographic planes of the AZO film changed from semipolar (1 0 1) ZnO NRs to polar (0 0 1) ZnO NRs due to the increase of the vertical [0 0 1] growth rate of the ZnO NRs owing to excellent electrical properties.

  13. Chemical Sensing Applications of ZnO Nanomaterials

    Science.gov (United States)

    Chaudhary, Savita; Umar, Ahmad; Bhasin, K. K.

    2018-01-01

    Recent advancement in nanoscience and nanotechnology has witnessed numerous triumphs of zinc oxide (ZnO) nanomaterials due to their various exotic and multifunctional properties and wide applications. As a remarkable and functional material, ZnO has attracted extensive scientific and technological attention, as it combines different properties such as high specific surface area, biocompatibility, electrochemical activities, chemical and photochemical stability, high-electron communicating features, non-toxicity, ease of syntheses, and so on. Because of its various interesting properties, ZnO nanomaterials have been used for various applications ranging from electronics to optoelectronics, sensing to biomedical and environmental applications. Further, due to the high electrochemical activities and electron communication features, ZnO nanomaterials are considered as excellent candidates for electrochemical sensors. The present review meticulously introduces the current advancements of ZnO nanomaterial-based chemical sensors. Various operational factors such as the effect of size, morphologies, compositions and their respective working mechanisms along with the selectivity, sensitivity, detection limit, stability, etc., are discussed in this article. PMID:29439528

  14. Epitaxial GaN around ZnO nanopillars

    Energy Technology Data Exchange (ETDEWEB)

    Fikry, Mohamed; Scholz, Ferdinand [Institut fuer Optoelektronik, Universitaet Ulm, Albert-Einstein-Allee 45, 89081 Ulm (Germany); Madel, Manfred; Tischer, Ingo; Thonke, Klaus [Institut fuer Quantenmaterie, Universitaet Ulm, Albert-Einstein-Allee 45, 89081 Ulm (Germany)

    2011-07-01

    We report on an investigation of the epitaxial quality of GaN layers overgrown coaxially around ZnO nanopillars. In a first step, regularly arranged ZnO nanopillars were grown using pre-patterning by e-beam lithography or self-organized hexagonal polystyrene sphere masks. Alternatively, ZnO pillars were also successfully grown on top of GaN pyramids. In a second step, GaN layers were grown around the ZnO pillars by Metal Organic Vapor Phase Epitaxy. At growth temperatures above 800 C, the ZnO pillars are dissolved by the hydrogen carrier gas leaving hollow GaN nanotubes. Characterization involved photoluminescence (PL), scanning electron microscopy and cathodoluminescence. The fair quality of the deposited GaN layers is confirmed by a sharp low temperature PL peak at 3.48 eV attributed to the donor bound exciton emission. Further peaks at 3.42 eV and 3.29 eV show the possible existence of basal plane and prismatic stacking faults.

  15. Vapour transport growth of ZnO nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Mofor, A.C.; Bakin, A.S.; Elshaer, A.; Waag, A. [Technical University Braunschweig, Institute of Semiconductor Technology, Braunschweig (Germany); Fuhrmann, D.; Hangleiter, A. [Technical University Braunschweig, Institute of Applied Physics, Braunschweig (Germany); Bertram, F.; Christen, J. [University of Magdeburg, Department of Solid State Physics, Magdeburg (Germany)

    2007-07-15

    The fabrication of low-dimensional ZnO structures has attracted enormous attention as such nanostructures are expected to pave the way for many interesting applications in optoelectronics, spin electronics gas sensor technology and biomedicine. Many reported fabrication methods, especially for ZnO nanorods are mostly based on catalyst-assisted growth techniques that employ metal-organic sources and other contaminating agents like graphite to grow ZnO nanorods at relatively high temperatures. We report on catalyst-free vapour-phase epitaxy growth of ZnO nanorods on 6H-SiC and (11-20)Al{sub 2}O{sub 3} using purely elemental sources at relatively low temperatures and growth pressure. ZnO nanorods with widths of 80-900 nm and lengths of up to 12 {mu}m were obtained. Nanorod density on the order of 10{sup 9} cm{sup -2} with homogenous luminescence and high purity was also noted. (orig.)

  16. The thermodynamic activity of ZnO in silicate melts

    Science.gov (United States)

    Reyes, R. A.; Gaskell, D. R.

    1983-12-01

    The activity of ZnO in ZnO-SiO2 and CaO-ZnO-SiO2 melts has been measured at 1560 °C using a transpiration technique with CO-CO2 mixtures as the carrier gas. The activities of ZnO in dilute solution in 42 wt pct SiO2-38 wt pct CaO-20 wt pct A12O3 in the range 1400° to 1550 °C and in 62 wt pct SiO2-23.3 wt pct CaO-14.7 wt pct A12O3 at 1550 °C have also been measured. The measured free energies of formation of ZnO-SiO2 melts are significantly more negative than published estimated values and this, together with the behavior observed in the system CaO-Al2O3-SiO2, indicate that ZnO is a relatively basic oxide. The results are discussed in terms of the polymerization model of binary silicate melts and ideal silicate mixing in ternary silicate melts. The behavior of ZnO in dilute solution in CaO-Al2O3-SiO2 melts is discussed in terms of the possibility of the fluxing of ZnO by iron blast furnace slags.

  17. Hydrogen-Induced Plastic Deformation in ZnO

    Science.gov (United States)

    Lukáč, F.; Čížek, J.; Vlček, M.; Procházka, I.; Anwand, W.; Brauer, G.; Traeger, F.; Rogalla, D.; Becker, H.-W.

    In the present work hydrothermally grown ZnO single crystals covered with Pd over-layer were electrochemically loaded with hydrogen and the influence of hydrogen on ZnO micro structure was investigated by positron annihilation spectroscopy (PAS). Nuclear reaction analysis (NRA) was employed for determination of depth profile of hydrogen concentration in the sample. NRA measurements confirmed that a substantial amount of hydrogen was introduced into ZnO by electrochemical charging. The bulk hydrogen concentration in ZnO determined by NRA agrees well with the concentration estimated from the transported charge using the Faraday's law. Moreover, a subsurface region with enhanced hydrogen concentration was found in the loaded crystals. Slow positron implantation spectroscopy (SPIS) investigations of hydrogen-loaded crystal revealed enhanced concentration of defects in the subsurface region. This testifies hydrogen-induced plastic deformation of the loaded crystal. Absorbed hydrogen causes a significant lattice expansion. At low hydrogen concentrations this expansion is accommodated by elastic straining, but at higher concentrations hydrogen-induced stress exceeds the yield stress in ZnO and plastic deformation of the loaded crystal takes place. Enhanced hydrogen concentration detected in the subsurface region by NRA is, therefore, due to excess hydrogen trapped at open volume defects introduced by plastic deformation. Moreover, it was found that hydrogen-induced plastic deformation in the subsurface layer leads to typical surface modification: formation of hexagonal shape pyramids on the surface due to hydrogen-induced slip in the [0001] direction.

  18. Cluster headache

    Directory of Open Access Journals (Sweden)

    Ducros Anne

    2008-07-01

    Full Text Available Abstract Cluster headache (CH is a primary headache disease characterized by recurrent short-lasting attacks (15 to 180 minutes of excruciating unilateral periorbital pain accompanied by ipsilateral autonomic signs (lacrimation, nasal congestion, ptosis, miosis, lid edema, redness of the eye. It affects young adults, predominantly males. Prevalence is estimated at 0.5–1.0/1,000. CH has a circannual and circadian periodicity, attacks being clustered (hence the name in bouts that can occur during specific months of the year. Alcohol is the only dietary trigger of CH, strong odors (mainly solvents and cigarette smoke and napping may also trigger CH attacks. During bouts, attacks may happen at precise hours, especially during the night. During the attacks, patients tend to be restless. CH may be episodic or chronic, depending on the presence of remission periods. CH is associated with trigeminovascular activation and neuroendocrine and vegetative disturbances, however, the precise cautive mechanisms remain unknown. Involvement of the hypothalamus (a structure regulating endocrine function and sleep-wake rhythms has been confirmed, explaining, at least in part, the cyclic aspects of CH. The disease is familial in about 10% of cases. Genetic factors play a role in CH susceptibility, and a causative role has been suggested for the hypocretin receptor gene. Diagnosis is clinical. Differential diagnoses include other primary headache diseases such as migraine, paroxysmal hemicrania and SUNCT syndrome. At present, there is no curative treatment. There are efficient treatments to shorten the painful attacks (acute treatments and to reduce the number of daily attacks (prophylactic treatments. Acute treatment is based on subcutaneous administration of sumatriptan and high-flow oxygen. Verapamil, lithium, methysergide, prednisone, greater occipital nerve blocks and topiramate may be used for prophylaxis. In refractory cases, deep-brain stimulation of the

  19. Approximate Series Solutions for Nonlinear Free Vibration of Suspended Cables

    Directory of Open Access Journals (Sweden)

    Yaobing Zhao

    2014-01-01

    Full Text Available This paper presents approximate series solutions for nonlinear free vibration of suspended cables via the Lindstedt-Poincare method and homotopy analysis method, respectively. Firstly, taking into account the geometric nonlinearity of the suspended cable as well as the quasi-static assumption, a mathematical model is presented. Secondly, two analytical methods are introduced to obtain the approximate series solutions in the case of nonlinear free vibration. Moreover, small and large sag-to-span ratios and initial conditions are chosen to study the nonlinear dynamic responses by these two analytical methods. The numerical results indicate that frequency amplitude relationships obtained with different analytical approaches exhibit some quantitative and qualitative differences in the cases of motions, mode shapes, and particular sag-to-span ratios. Finally, a detailed comparison of the differences in the displacement fields and cable axial total tensions is made.

  20. Superior thermal conductivity in suspended bilayer hexagonal boron nitride

    Science.gov (United States)

    Wang, Chengru; Guo, Jie; Dong, Lan; Aiyiti, Adili; Xu, Xiangfan; Li, Baowen

    2016-01-01

    We reported the basal-plane thermal conductivity in exfoliated bilayer hexagonal boron nitride h-BN that was measured using suspended prepatterned microstructures. The h-BN sample suitable for thermal measurements was fabricated by dry-transfer method, whose sample quality, due to less polymer residues on surfaces, is believed to be superior to that of PMMA-mediated samples. The measured room temperature thermal conductivity is around 484 Wm−1K−1(+141 Wm−1K−1/ −24 Wm−1K−1) which exceeds that in bulk h-BN, providing experimental observation of the thickness-dependent thermal conductivity in suspended few-layer h-BN. PMID:27142571

  1. Piezoresistance of top-down suspended Si nanowires

    International Nuclear Information System (INIS)

    Koumela, A; Mercier, D; Dupre, C; Jourdan, G; Marcoux, C; Ollier, E; Duraffourg, L; Purcell, S T

    2011-01-01

    Measurements of the gauge factor of suspended, top-down silicon nanowires are presented. The nanowires are fabricated with a CMOS compatible process and with doping concentrations ranging from 2 x 10 20 down to 5 x 10 17 cm -3 . The extracted gauge factors are compared with results on identical non-suspended nanowires and with state-of-the-art results. An increase of the gauge factor after suspension is demonstrated. For the low doped nanowires a value of 235 is measured. Particular attention was paid throughout the experiments to distinguishing real resistance change due to strain modulation from resistance fluctuations due to charge trapping. Furthermore, a numerical model correlating surface charge density with the gauge factor is presented. Comparison of the simulations with experimental measurements shows the validity of this approach. These results contribute to a deeper understanding of the piezoresistive effect in Si nanowires.

  2. Relationship between dioxin concentration and particle size for suspended sediment

    Energy Technology Data Exchange (ETDEWEB)

    Kitamura, K.; Sakurai, T.; Choi, J.W.; Suzuki, N.; Morita, M. [National Inst. for Environmental Studies, Tsukuba (Japan)

    2004-09-15

    The purpose of the present study was to find out how the amounts of adsorbed dioxins, i.e., polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs), mono-ortho-polychlorinated biphenyls (PCBs) and non-ortho-PCBs, vary with the particle size of suspended sediment. As dioxins are hydrophobic, they tend to adsorb onto particles suspended in water, and the determination of which dioxin congeners readily dissolve in water or adsorb onto particles is central to the characterization of dioxin behavior in water/sediment systems. Presumably suspension of sediments and the size of the particles govern the transfer of dioxins to aquatic organisms. Therefore, in the present study, we investigated the relationship between the amount of dioxins and the particle-size distribution of resuspended, rather than settled, sediment.

  3. Structural and optical properties of ZnO rods hydrothermally formed on polyethersulfone substrates

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Chang Mi; Jang, Jin Tak; Kim, Chang Yong; Ryu, Hyuk Hyun [Inje University, Gimhae (Korea, Republic of); Lee, Won Jae [Dong-Eui University, Busan (Korea, Republic of); Chang, Ji Ho [Korea Maritime University, Busan (Korea, Republic of); Son, Chang Sik [Silla University, Busan (Korea, Republic of); Choi, Hee Lack [Pukyong National University, Busan (Korea, Republic of)

    2012-06-15

    Various unique ZnO morphologies, such as cigar-like and belt-like structures and microrod and nanorod structures, were formed on flexible polyethersulfone (PES) substrates by using a low temperature hydrothermal route. The structural properties of ZnO depended highly on the precursor concentration. The effect of a thin ZnO seed layer deposited the on PES substrate by using atomic layer deposition on the structural and the optical properties of ZnO hydrothermally grown on the ZnO seed layer/PES substrates was studied. Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and photoluminescence (PL) measurements were employed to analyze the characteristics of hydrothermally-grown ZnO. The diameter of the ZnO nanorods grown on the ZnO seed layer/PES substrates increased with increasing precursor concentration from 0.025 to 0.125 M due to the Ostwald ripening process. ZnO hydrothermally-grown on the ZnO seed layer/PES substrates at a low precursor concentration showed better structural properties than ZnO formed without a seed layer. Well-formed ZnO nanorods deposited on the ZnO seed layer/PES substrates showed two PL peaks, one in the ultraviolet and the other in the visible region, whereas horizontally positioned ZnO formed on the PES substrate in the absence of a seed layer emitted only one broad PL peak in the violet region. The ZnO grown on PES substrates in this work can be used as high-quality transparent electrodes for solar cells fabricated on flexible substrates.

  4. Structural and optical properties of ZnO rods hydrothermally formed on polyethersulfone substrates

    International Nuclear Information System (INIS)

    Shin, Chang Mi; Jang, Jin Tak; Kim, Chang Yong; Ryu, Hyuk Hyun; Lee, Won Jae; Chang, Ji Ho; Son, Chang Sik; Choi, Hee Lack

    2012-01-01

    Various unique ZnO morphologies, such as cigar-like and belt-like structures and microrod and nanorod structures, were formed on flexible polyethersulfone (PES) substrates by using a low temperature hydrothermal route. The structural properties of ZnO depended highly on the precursor concentration. The effect of a thin ZnO seed layer deposited the on PES substrate by using atomic layer deposition on the structural and the optical properties of ZnO hydrothermally grown on the ZnO seed layer/PES substrates was studied. Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and photoluminescence (PL) measurements were employed to analyze the characteristics of hydrothermally-grown ZnO. The diameter of the ZnO nanorods grown on the ZnO seed layer/PES substrates increased with increasing precursor concentration from 0.025 to 0.125 M due to the Ostwald ripening process. ZnO hydrothermally-grown on the ZnO seed layer/PES substrates at a low precursor concentration showed better structural properties than ZnO formed without a seed layer. Well-formed ZnO nanorods deposited on the ZnO seed layer/PES substrates showed two PL peaks, one in the ultraviolet and the other in the visible region, whereas horizontally positioned ZnO formed on the PES substrate in the absence of a seed layer emitted only one broad PL peak in the violet region. The ZnO grown on PES substrates in this work can be used as high-quality transparent electrodes for solar cells fabricated on flexible substrates.

  5. Elemental Spatiotemporal Variations of Total Suspended Particles in Jeddah City

    OpenAIRE

    Kadi, Mohammad W.

    2014-01-01

    Elements associated with total suspended particulate matter (TSP) in Jeddah city were determined. Using high-volume samplers, TSP samples were simultaneously collected over a one-year period from seven sampling sites. Samples were analyzed for Al, Ba, Ca, Cu, Mg, Fe, Mn, Zn, Ti, V, Cr, Co, Ni, As, and Sr. Results revealed great dependence of element contents on spatial and temporal variations. Two sites characterized by busy roads, workshops, heavy population, and heavy trucking have high lev...

  6. Segment Fixed Priority Scheduling for Self Suspending Real Time Tasks

    Science.gov (United States)

    2016-08-11

    a compute- intensive system such as a self - driving car that we have recently developed [28]. Such systems run computation-demanding algorithms...Applications. In RTSS, 2012. [12] J. Kim et al. Parallel Scheduling for Cyber-Physical Systems: Analysis and Case Study on a Self - Driving Car . In ICCPS...leveraging GPU can be modeled using a multi-segment self -suspending real-time task model. For example, a planning algorithm for autonomous driving can

  7. Remote Sensing of Suspended Sediment Dynamics in the Mississippi Sound

    Science.gov (United States)

    Merritt, D. N.; Skarke, A. D.; Silwal, S.; Dash, P.

    2016-02-01

    The Mississippi Sound is a semi-enclosed estuary between the coast of Mississippi and a chain of offshore barrier islands with relatively shallow water depths and high marine biodiversity that is wildly utilized for commercial fishing and public recreation. The discharge of sediment-laden rivers into the Mississippi Sound and the adjacent Northern Gulf of Mexico creates turbid plumes that can extend hundreds of square kilometers along the coast and persist for multiple days. The concentration of suspended sediment in these coastal waters is an important parameter in the calculation of regional sediment budgets as well as analysis of water-quality factors such as primary productivity, nutrient dynamics, and the transport of pollutants as well as pathogens. The spectral resolution, sampling frequency, and regional scale spatial domain associated with satellite based sensors makes remote sensing an ideal tool to monitor suspended sediment dynamics in the Northern Gulf of Mexico. Accordingly, the presented research evaluates the validity of published models that relate remote sensing reflectance with suspended sediment concentrations (SSC), for similar environmental settings, with 51 in situ observations of SSC from the Mississippi Sound. Additionally, regression analysis is used to correlate additional in situ observations of SSC in Mississippi Sound with coincident observations of visible and near-infrared band reflectance collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor aboard the Aqua satellite, in order to develop a site-specific empirical predictive model for SSC. Finally, specific parameters of the sampled suspended sediment such as grain size and mineralogy are analyzed in order to quantify their respective contributions to total remotely sensed reflectance.

  8. Suspended biofilm carrier and activated sludge removal of acidic pharmaceuticals

    DEFF Research Database (Denmark)

    Falås, Per; Baillon-Dhumez, Aude; Andersen, Henrik Rasmus

    2012-01-01

    Removal of seven active pharmaceutical substances (ibuprofen, ketoprofen, naproxen, diclofenac, clofibric acid, mefenamic acid, and gemfibrozil) was assessed by batch experiments, with suspended biofilm carriers and activated sludge from several full-scale wastewater treatment plants. A distinct...... and attached solids for the carriers) of diclofenac, ketoprofen, gemfibrozil, clofibric acid and mefenamic acid compared to the sludges. Among the target pharmaceuticals, only ibuprofen and naproxen showed similar removal rates per unit biomass for the sludges and biofilm carriers. In contrast...

  9. Suspended particulate studies over the Madeira Abyssal Plain

    International Nuclear Information System (INIS)

    Simpson, W.R.

    1987-01-01

    Various aspects relating to suspended matter over the Madeira Abyssal Plain are discussed. Special attention is paid to the nepheloid layer including resuspension and transport processes; time variabilities in particle concentrations and fluxes; particle morphology, microbiology and chemical composition; phase association of metals. Also, tentative predictions of the behaviour of some radionuclides are made based on theory and data on rare earth elements. Instrumentation developed for the project is detailed - the deep water particle sampler. (author)

  10. Brightest Cluster Galaxies in REXCESS Clusters

    Science.gov (United States)

    Haarsma, Deborah B.; Leisman, L.; Bruch, S.; Donahue, M.

    2009-01-01

    Most galaxy clusters contain a Brightest Cluster Galaxy (BCG) which is larger than the other cluster ellipticals and has a more extended profile. In the hierarchical model, the BCG forms through many galaxy mergers in the crowded center of the cluster, and thus its properties give insight into the assembly of the cluster as a whole. In this project, we are working with the Representative XMM-Newton Cluster Structure Survey (REXCESS) team (Boehringer et al 2007) to study BCGs in 33 X-ray luminous galaxy clusters, 0.055 < z < 0.183. We are imaging the BCGs in R band at the Southern Observatory for Astrophysical Research (SOAR) in Chile. In this poster, we discuss our methods and give preliminary measurements of the BCG magnitudes, morphology, and stellar mass. We compare these BCG properties with the properties of their host clusters, particularly of the X-ray emitting gas.

  11. Suspended sediment in a high-Arctic river

    DEFF Research Database (Denmark)

    Ladegaard-Pedersen, Pernille; Sigsgaard, Charlotte; Kroon, Aart

    2017-01-01

    -2012) of daily measurements from the high-Artic Zackenberg River in Northeast Greenland to estimate annual suspended sediment fluxes based on four commonly used methods: M1) is the discharge weighted mean and uses direct measurements, while M2-M4) are one uncorrected and two bias corrected rating curves......-1 and 61,000±16,000ty-1. Extreme events with high discharges had a mean duration of 1day. The average suspended sediment flux during extreme events was 17,000±5000ty-1, which constitutes a year-to-year variation of 20-37% of the total annual flux. The most accurate sampling strategy was bi...... extrapolating a continuous concentration trace from measured values. All methods are tested on complete and reduced datasets. The average annual runoff in the period 2005-2012 was 190±25mio·m3 y-1. The different estimation methods gave a range of average annual suspended sediment fluxes between 43,000±10,000ty...

  12. The Influence of Turbulent Coherent Structure on Suspended Sediment Transport

    Science.gov (United States)

    Huang, S. H.; Tsai, C.

    2017-12-01

    The anomalous diffusion of turbulent sedimentation has received more and more attention in recent years. With the advent of new instruments and technologies, researchers have found that sediment behavior may deviate from Fickian assumptions when particles are heavier. In particle-laden flow, bursting phenomena affects instantaneous local concentrations, and seems to carry suspended particles for a longer distance. Instead of the pure diffusion process in an analogy to Brownian motion, Levy flight which allows particles to move in response to bursting phenomena is suspected to be more suitable for describing particle movement in turbulence. And the fractional differential equation is a potential candidate to improve the concentration profile. However, stochastic modeling (the Differential Chapmen-Kolmogorov Equation) also provides an alternative mathematical framework to describe system transits between different states through diffusion/the jump processes. Within this framework, the stochastic particle tracking model linked with advection diffusion equation is a powerful tool to simulate particle locations in the flow field. By including the jump process to this model, a more comprehensive description for suspended sediment transport can be provided with a better physical insight. This study also shows the adaptability and expandability of the stochastic particle tracking model for suspended sediment transport modeling.

  13. Simplified Entropic Model for the Evaluation of Suspended Load Concentration

    Directory of Open Access Journals (Sweden)

    Domenica Mirauda

    2018-03-01

    Full Text Available Suspended sediment concentration is a key aspect in the forecasting of river evolution dynamics, as well as in water quality assessment, evaluation of reservoir impacts, and management of water resources. The estimation of suspended load often relies on empirical models, of which efficiency is limited by their analytic structure or by the need for calibration parameters. The present work deals with a simplified fully-analytical formulation of the so-called entropic model in order to reproduce the vertical distribution of sediment concentration. The simplification consists in the leading order expansion of the generalized spatial coordinate of the entropic velocity profile that, strictly speaking, applies to the near-bed region, but that provides acceptable results also near the free surface. The proposed closed-form solution, which highlights the interplay among channel morphology, stream power, secondary flows, and suspended transport features, allows reducing the needed number of field measurements and, therefore, the time of field activities. Its accuracy and robustness were successfully tested based on the comparison with laboratory data reported in literature.

  14. MEMS-Based Fuel Reformer with Suspended Membrane Structure

    Science.gov (United States)

    Chang, Kuei-Sung; Tanaka, Shuji; Esashi, Masayoshi

    We report a MEMS-based fuel reformer for supplying hydrogen to micro-fuel cells for portable applications. A combustor and a reforming chamber are fabricated at either side of a suspended membrane structure. This design is used to improve the overall thermal efficiency, which is a critical issue to realize a micro-fuel reformer. The suspended membrane structure design provided good thermal isolation. The micro-heaters consumed 0.97W to maintain the reaction zone of the MEMS-based fuel reformer at 200°C, but further power saving is necessary by improving design and fabrication. The conversion rate of methanol to hydrogen was about 19% at 180°C by using evaporated copper as a reforming catalyst. The catalytic combustion of hydrogen started without any assistance of micro-heaters. By feeding the fuel mixture of an equivalence ratio of 0.35, the temperature of the suspended membrane structure was maintained stable at 100°C with a combustion efficiency of 30%. In future works, we will test a micro-fuel reformer by using a micro-combustor to supply heat.

  15. Optimal control of suspended sediment distribution model of Talaga lake

    Science.gov (United States)

    Ratianingsih, R.; Resnawati, Azim, Mardlijah, Widodo, B.

    2017-08-01

    Talaga Lake is one of several lakes in Central Sulawesi that potentially to be managed in multi purposes scheme because of its characteristic. The scheme is addressed not only due to the lake maintenance because of its sediment but also due to the Algae farming for its biodiesel fuel. This paper governs a suspended sediment distribution model of Talaga lake. The model is derived from the two dimensional hydrodynamic shallow water equations of the mass and momentum conservation law of sediment transport. An order reduction of the model gives six equations of hyperbolic systems of the depth, two dimension directional velocities and sediment concentration while the bed elevation as the second order of turbulent diffusion and dispersion are neglected. The system is discreted and linearized such that could be solved numerically by box-Keller method for some initial and boundary condition. The solutions shows that the downstream velocity is play a role in transversal direction of stream function flow. The downstream accumulated sediment indicate that the suspended sediment and its changing should be controlled by optimizing the downstream velocity and transversal suspended sediment changing due to the ideal algae growth need.

  16. Studying Suspended Sediment Mechanism with Two-Phase PIV

    Science.gov (United States)

    Matinpour, H.; Atkinson, J. F.; Bennett, S. J.; Guala, M.

    2017-12-01

    Suspended sediment transport affects soil erosion, agriculture and water resources quality. Turbulent diffusion is the most primary force to maintain sediments in suspension. Although extensive previous literature have been studying the interactions between turbulent motion and suspended sediment, mechanism of sediments in suspension is still poorly understood. In this study, we investigate suspension of sediments as two distinct phases: one phase of sediments and another phase of fluid with turbulent motions. We designed and deployed a state-of-the-art two-phase PIV measurement technique to discriminate these two phases and acquire velocities of each phase separately and simultaneously. The technique that we have developed is employing a computer-vision based method, which enables us to discriminate sediment particles from fluid tracer particles based on two thresholds, dissimilar particle sizes and different particle intensities. Results indicate that fluid turbulence decreases in the presence of suspended sediments. Obtaining only sediment phase consecutive images enable us to compute fluctuation sediment concentration. This result enlightens understanding of complex interaction between the fluctuation velocities and the fluctuation of associated mass and compares turbulent viscosity with turbulent eddy diffusivity experimentally.

  17. Photosensitivity of nanocrystalline ZnO films grown by PLD

    International Nuclear Information System (INIS)

    Ayouchi, R.; Bentes, L.; Casteleiro, C.; Conde, O.; Marques, C.P.; Alves, E.; Moutinho, A.M.C.; Marques, H.P.; Teodoro, O.; Schwarz, R.

    2009-01-01

    We have studied the properties of ZnO thin films grown by laser ablation of ZnO targets on (0 0 0 1) sapphire (Al 2 O 3 ), under substrate temperatures around 400 deg. C. The films were characterized by different methods including X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM). XPS analysis revealed that the films are oxygen deficient, and XRD analysis with θ-2θ scans and rocking curves indicate that the ZnO thin films are highly c-axis oriented. All the films are ultraviolet (UV) sensitive. Sensitivity is maximum for the films deposited at lower temperature. The films deposited at higher temperatures show crystallite sizes of typically 500 nm, a high dark current and minimum photoresponse. In all films we observe persistent photoconductivity decay. More densely packed crystallites and a faster decay in photocurrent is observed for films deposited at lower temperature

  18. Giant negative photoresistance of ZnO single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Barzola-Quiquia, Jose; Esquinazi, Pablo [Division of Superconductivity and Magnetism, University of Leipzig (Germany); Heluani, Silvia [Laboratorio de Fisica del Solido, FCEyT, Universidad Nacional de Tucuman, 4000 S. M. de Tucuman (Argentina); Villafuerte, Manuel [Dept. de Fisica, FCEyT, Universidad Nacional de Tucuman (Argentina); CONICET, Tucuman (Argentina); Poeppl, Andreas [Division of Magnetic Resonance of Complex Quantum Solids, University of Leipzig, D-04103 Leipzig (Germany)

    2011-07-01

    ZnO is a wide band gap semiconductor exhibiting the largest charge-carrier mobility among oxides. ZnO is a material with potential applications for short-wavelength optoelectronic devices, as a blue light emitting diodes and in spintronics. In this contribution we have measured the temperature dependence (30 K < T < 300 K) of the electrical resistance of ZnO single crystals prepared by hydrothermal method in darkness and under the influence of light in the ultraviolet range. The resistance decreases several orders of magnitude at temperatures T < 200 K after illumination. Electron paramagnetic resonance studies under illumination reveal that the excitation of Li acceptor impurities is the origin for the giant negative photoresistance effect. Permanent photoresistance effect is also observed, which remains many hours after leaving the crystal in darkness.

  19. Activities towards p-type doping of ZnO

    International Nuclear Information System (INIS)

    Brauer, G; Kuriplach, J; Ling, C C; Djurisic, A B

    2011-01-01

    Zinc oxide (ZnO) is an interesting and promising semiconductor material for many potential applications, e.g. in opto-electronics and for sensor devices. However, its p-type doping represents a challenging problem, and the physical reasons of its mostly n-type conductivity are not perfectly clear at present. Efforts to achieve p-type conductivity by ion implantation are reviewed, and ways to achieve p-type ZnO nanorods and thin films through various growth conditions are summarized. Then, issues associated with the preparation of Schottky contacts is discussed in some detail as this is a requirement of the device formation process. Finally, the possible incorporation of hydrogen and nitrogen into structural defects, which can act as trapping sites for positrons, is discussed in the context of experimental and theoretical positron results and the estimated H and N content in a variety of ZnO materials.

  20. Activities towards p-type doping of ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Brauer, G [Institut fuer Ionenstrahlphysik und Materialforschung, Forschungszentrum Dresden-Rossendorf, Postfach 510119, D-01314 Dresden (Germany); Kuriplach, J [Department of Low Temperature Physics, Charles University, V Holetovickach 2, CZ-18000 Prague (Czech Republic); Ling, C C; Djurisic, A B, E-mail: g.brauer@fzd.de [Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong)

    2011-01-10

    Zinc oxide (ZnO) is an interesting and promising semiconductor material for many potential applications, e.g. in opto-electronics and for sensor devices. However, its p-type doping represents a challenging problem, and the physical reasons of its mostly n-type conductivity are not perfectly clear at present. Efforts to achieve p-type conductivity by ion implantation are reviewed, and ways to achieve p-type ZnO nanorods and thin films through various growth conditions are summarized. Then, issues associated with the preparation of Schottky contacts is discussed in some detail as this is a requirement of the device formation process. Finally, the possible incorporation of hydrogen and nitrogen into structural defects, which can act as trapping sites for positrons, is discussed in the context of experimental and theoretical positron results and the estimated H and N content in a variety of ZnO materials.

  1. Ultraviolet lasing behavior in ZnO optical microcavities

    Directory of Open Access Journals (Sweden)

    Hongxing Dong

    2017-12-01

    Full Text Available Zinc oxide (ZnO optical microcavity modulated UV lasers have been attracting a wide range of research interests. As one of the most important materials in developing high quality microcavity and efficient UV–visible optoelectronic devices due to its wide band gap (3.37 eV and large exciton binding energy (∼60 meV. In this review, we summarized the latest development of ZnO optical cavity based microlasers, mainly including Fabry-Perot mode lasers and whispering gallery mode lasers. The synthesis and optical studies of ZnO optical microcavities with different morphologies were discussed in detail. Finally, we also consider that the research focus in the near future would include new nanotechnology and physical effects, such as nano/micro fabrication, surface plasmon enhancement, and quantum dot coupling, which may result in new and interesting physical phenomena.

  2. Nanosheet-Assembled ZnO Microflower Photocatalysts

    Directory of Open Access Journals (Sweden)

    Siwen Zhang

    2014-01-01

    Full Text Available Large scale ZnO microflowers assembled by numerous nanosheets are synthesized through a facile and effective hydrothermal route. The structure and morphology of the resultant products are characterized by X-ray diffraction (XRD and scanning electron microscope (SEM. Photocatalytic properties of the as-synthesized products are also investigated. The results demonstrate that eosin red aqueous solution can be degraded over 97% after 110 min under UV light irradiation. In addition, methyl orange (MO and Congo red (CR aqueous solution degradation experiments also are conducted in the same condition, respectively. It showed that nanosheet-assembled ZnO microflowers represent high photocatalytic activities with a degradation efficiency of 91% for CR with 90 min of irradiation and 90% for MO with 60 min of irradiation. The reported ZnO products may be promising candidates as the photocatalysts in waste water treatment.

  3. Effect of Water on Ethanol Conversion over ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, Muhammad Mahfuzur; Davidson, Stephen D.; Sun, Junming; Wang, Yong

    2015-10-01

    This work focuses on understanding the role of water on ethanol conversion over zinc oxide (ZnO). It was found that a competitive adsorption between ethanol and water occurs on ZnO, which leads to the blockage of the strong Lewis acid site by water on ZnO. As a result, both dehydration and dehydrogenation reactions are inhibited. However, the extent of inhibition for dehydration is orders of magnitude higher than that for dehydrogenation, leading to the shift of reaction pathway from ethanol dehydration to dehydrogenation. In the secondary reactions for acetaldehyde conversion, water inhibits the acetaldehyde aldol-condensation to crotonaldehyde, favoring the oxidation of acetaldehyde to acetic acid, and then to acetone via ketonization at high temperature (i.e., 400 °C).

  4. High mobility ZnO nanowires for terahertz detection applications

    International Nuclear Information System (INIS)

    Liu, Huiqiang; Peng, Rufang; Chu, Shijin; Chu, Sheng

    2014-01-01

    An oxide nanowire material was utilized for terahertz detection purpose. High quality ZnO nanowires were synthesized and field-effect transistors were fabricated. Electrical transport measurements demonstrated the nanowire with good transfer characteristics and fairly high electron mobility. It is shown that ZnO nanowires can be used as building blocks for the realization of terahertz detectors based on a one-dimensional plasmon detection configuration. Clear terahertz wave (∼0.3 THz) induced photovoltages were obtained at room temperature with varying incidence intensities. Further analysis showed that the terahertz photoresponse is closely related to the high electron mobility of the ZnO nanowire sample, which suggests that oxide nanoelectronics may find useful terahertz applications.

  5. ZnO nanodisk based UV detectors with printed electrodes.

    Science.gov (United States)

    Alenezi, Mohammad R; Alshammari, Abdullah S; Alzanki, Talal H; Jarowski, Peter; Henley, Simon John; Silva, S Ravi P

    2014-04-08

    The fabrication of highly functional materials for practical devices requires a deep understanding of the association between morphological and structural properties and applications. A controlled hydrothermal method to produce single crystal ZnO hexagonal nanodisks, nanorings, and nanoroses using a mixed solution of zinc sulfate (ZnSO4) and hexamethylenetetramine (HMTA) without the need of catalysts, substrates, or templates at low temperature (75 °C) is introduced. Metal-semiconductor-metal (MSM) ultraviolet (UV) detectors were fabricated based on individual and multiple single-crystal zinc oxide (ZnO) hexagonal nanodisks. High quality single crystal individual nanodisk devices were fabricated with inkjet-printed silver electrodes. The detectors fabricated show record photoresponsivity (3300 A/W) and external quantum efficiency (1.2 × 10(4)), which we attribute to the absence of grain boundaries in the single crystal ZnO nanodisk and the polarity of its exposed surface.

  6. Characterization of donor states in ZnO

    International Nuclear Information System (INIS)

    Seghier, D.; Gislason, H.P.

    2007-01-01

    We performed electrical and optical measurements on as-grown ZnO which exhibits n-type conductivity. So far, neither the origin of the residual conductivity nor the electrical properties of the responsible defects is fully understood. We investigated shallow and deep donors in ZnO materials grown with pulsed laser injection using admittance spectroscopy. We identifed shallow donors with ionization energies as low as 15 meV which may be attributed to native defects. Annealing in nitrogen ambient enhances the conductivity by further lowering the ionization energy of the shallow donors. Using optically excited admittance spectroscopy we also found deep defects. They are strongly metastable and account for a significant part of the persistent photoconductivity in our ZnO materials

  7. Single-Crystal Mesoporous ZnO Thin Films Composed of Nanowalls

    KAUST Repository

    Wang, Xudong

    2009-02-05

    This paper presents a controlled, large scale fabrication of mesoporous ZnO thin films. The entire ZnO mesoporous film is one piece of a single crystal, while high porosity made of nanowalls is present. The growth mechanism was proposed in comparison with the growth of ZnO nanowires. The ZnO mesoporous film was successfully applied as a gas sensor. The fabrication and growth analysis of the mesoporous ZnO thin film gi ve general guidance for the controlled growth of nanostructures. It also pro vides a unique structure with a superhigh surface-to-volume ratio for surface-related applications. © 2009 American Chemical Society.

  8. Enhancement in the photodetection of ZnO nanowires by introducing surface-roughness-induced traps

    International Nuclear Information System (INIS)

    Park, Woojin; Jo, Gunho; Hong, Woong-Ki; Yoon, Jongwon; Choe, Minhyeok; Ji, Yongsung; Kim, Geunjin; Kahng, Yung Ho; Lee, Kwanghee; Lee, Takhee; Lee, Sangchul; Wang, Deli

    2011-01-01

    We investigated the enhanced photoresponse of ZnO nanowire transistors that was introduced with surface-roughness-induced traps by a simple chemical treatment with isopropyl alcohol (IPA). The enhanced photoresponse of IPA-treated ZnO nanowire devices is attributed to an increase in adsorbed oxygen on IPA-induced surface traps. The results of this study revealed that IPA-treated ZnO nanowire devices displayed higher photocurrent gains and faster photoswitching speed than transistors containing unmodified ZnO nanowires. Thus, chemical treatment with IPA can be a useful method for improving the photoresponse of ZnO nanowire devices.

  9. Partitional clustering algorithms

    CERN Document Server

    2015-01-01

    This book summarizes the state-of-the-art in partitional clustering. Clustering, the unsupervised classification of patterns into groups, is one of the most important tasks in exploratory data analysis. Primary goals of clustering include gaining insight into, classifying, and compressing data. Clustering has a long and rich history that spans a variety of scientific disciplines including anthropology, biology, medicine, psychology, statistics, mathematics, engineering, and computer science. As a result, numerous clustering algorithms have been proposed since the early 1950s. Among these algorithms, partitional (nonhierarchical) ones have found many applications, especially in engineering and computer science. This book provides coverage of consensus clustering, constrained clustering, large scale and/or high dimensional clustering, cluster validity, cluster visualization, and applications of clustering. Examines clustering as it applies to large and/or high-dimensional data sets commonly encountered in reali...

  10. In-situ PXRD studies of ZnO nanoparticle growth: How do various salts influence the hydrothermal growth of ZnO?

    DEFF Research Database (Denmark)

    Bøjesen, Espen Drath

    ZnO is a material of great scientific and everyday relevance; it is used widely in all sorts of application. Synthesis of ZnO nanoparticles can be performed by a wide assortment of methods and a tremendous variety of sizes and shapes, it has been suggested that ZnO is the one known compound showing...... the broadest range of nanostructures. Previously many different in-situ characterization methods have been used to investigate the ZnO formation under various synthesis conditions; these include UV-VIS and SAXS. These methods were primarily used to give information on particle size of ZnO formed using soft...... chemical methods and non-aqueous solvents. In our work we have studied the formation of ZnO during hydrothermal syntheses using in-situ powder X-ray diffraction, thus enabling us to extract crystallographic as well as microstructural information. The data was analyzed using Rietveld refinement and whole...

  11. Effects of seed layers on controlling of the morphology of ZnO nanostructures and superhydrophobicity of ZnO nanostructure/stearic acid composite films

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jing; Liu, Zhihua, E-mail: sdwfliu@163.com; Liu, Junqi; E, Lei; Liu, Zhifeng, E-mail: tjulzf@163.com

    2016-11-01

    Hydrophobic ZnO self-cleaning thin films with the nanobundles and nanocarpets structures fabricated on indium tin oxides (ITO) glass substrate are reported. The water contact angle of ZnO nanobundles and nanocarpets structures (79° and 67° respectively) is higher than that of unmodified ZnO nanorods. A subsequent chemical treatment with stearic acid (SA) contributed to a superhydrophobic surface with a water contact angle of 159°. Its superhydrophobic property is originated from the nanobundles or nanocarpets structures and surface energy of SA/ZnO nanobundles and SA/ZnO nanocarpets composite nanostructures. Moreover, this promising ZnO nanostructured materials show an important application in self-cleaning smart coatings. - Highlights: • PEG and CTAB are firstly introduced to modify the morphology of ZnO seed layers. • ZnO nanobundles and nanocarpets obtained from different seed layers. • Superhydrophobic surfaces obtained by chemcial treatment using SA.

  12. Surface potential driven dissolution phenomena of [0 0 0 1]-oriented ZnO nanorods grown from ZnO and Pt seed layers

    Science.gov (United States)

    Seo, Youngmi; Kim, Jung Hyeun

    2011-06-01

    Highly oriented ZnO nanorods are synthesized hydrothermally on ZnO and Pt seed layers, and they are dissolved in KOH solution. The rods grown on ZnO seed layer show uniform dissolution, but those grown on Pt seed layer are rod-selectively dissolved. The ZnO nanorods from both seed layers show the same crystalline structure through XRD and Raman spectrometer data. However, the surface potential analysis reveals big difference for ZnO and Pt seed cases. The surface potential distribution is very uniform for the ZnO seed case, but it is much fluctuated on the Pt seed case. It suggests that the rod-selective dissolution phenomena on Pt seed case are likely due to the surface energy difference.

  13. Photoluminescence of Sequential Infiltration Synthesized ZnO nanostructures

    Science.gov (United States)

    Ocola, Leonidas; Gosztola, David; Yanguas-Gil, Angel; Connolly, Aine

    We have investigated a variation of atomic layer deposition (ALD), called sequential infiltration synthesis (SiS), as an alternate method to incorporate ZnO and other oxides inside polymethylmethacrylate (PMMA) and other polymers. Energy dispersive spectroscopy (EDS) results show that we synthesize ZnO up to 300 nm inside a PMMA film. Photoluminescence data on a PMMA film shows that we achieve a factor of 400X increase in photoluminescence (PL) intensity when comparing a blank Si sample and a 270 nm thick PMMA film, where both were treated with the same 12 alternating cycles of H2O and diethyl zinc (DEZ). PMMA is a well-known ebeam resist. We can expose and develop patterns useful for photonics or sensing applications first, and then convert them afterwards into a hybrid polymer-oxide material. We show that patterning does indeed affect the photoluminescence signature of native ZnO. We demonstrate we can track the growth of the ZnO inside the PMMA polymer using both photoluminescence and Raman spectroscopy and determine the point in the process where ZnO is first photoluminescent and also at which point ZnO first exhibits long range order in the polymer. This work was supported by the Department of Energy under Contract No. DE-AC02-06CH11357. Use of the Center for Nanoscale Materials was supported by the U. S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

  14. A high power ZnO thin film piezoelectric generator

    Science.gov (United States)

    Qin, Weiwei; Li, Tao; Li, Yutong; Qiu, Junwen; Ma, Xianjun; Chen, Xiaoqiang; Hu, Xuefeng; Zhang, Wei

    2016-02-01

    A highly efficient and large area piezoelectric ZnO thin film nanogenerator (NG) was fabricated. The ZnO thin film was deposited onto a Si substrate by pulsed laser ablation at a substrate temperature of 500 °C. The deposited ZnO film exhibited a preferred c-axis orientation and a high piezoelectric value of 49.7 pm/V characterized using Piezoelectric Force Microscopy (PFM). Thin films of ZnO were patterned into rectangular power sources with dimensions of 0.5 × 0.5 cm2 with metallic top and bottom electrodes constructed via conventional semiconductor lithographic patterning processes. The NG units were subjected to periodic bending/unbending motions produced by mechanical impingement at a fixed frequency of 100 Hz at a pressure of 0.4 kg/cm2. The output electrical voltage, current density, and power density generated by one ZnO NG were recorded. Values of ∼95 mV, 35 μA cm-2 and 5.1 mW cm-2 were recorded. The level of power density is typical to that produced by a PZT NG on a flexible substrate. Higher energy NG sources can be easily created by adding more power units either in parallel or in series. The thin film ZnO NG technique is highly adaptable with current semiconductor processes, and as such, is easily integrated with signal collecting circuits that are compatible with mass production. A typical application would be using the power harvested from irregular human foot motions to either to operate blue LEDs directly or to drive a sensor network node in mille-power level without any external electric source and circuits.

  15. Transient behaviors of ZnO thin films on a transparent, flexible polyethylene terephthalate substrate

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yong Jun [Department of Nano-Physics, Gachon University, 1342 Seongnamdaero, Sujeong-gu, Seongnam-si, Gyeonggi-do 461-701 (Korea, Republic of); Lee, Ho Seok [Department of Materials Science and Engineering, Korea University, 5-1 Anam-dong, Seongbuk-gu, Seoul 136-713 (Korea, Republic of); Noh, Jin-Seo, E-mail: jinseonoh@gachon.ac.kr [Department of Nano-Physics, Gachon University, 1342 Seongnamdaero, Sujeong-gu, Seongnam-si, Gyeonggi-do 461-701 (Korea, Republic of)

    2016-03-31

    Thickness-dependent electrical, structural, and optical properties of zinc oxide (ZnO) thin films on polyethylene terephthalate (PET) substrates have been investigated in the very thin thickness range of 20 to 120 nm. In this thickness range, the electrical resistance of ZnO film increased with an increase in film thickness. This unusual transition behavior was explained in terms of structural evolution from Zn-phase-incorporating non-crystalline ZnO to hexagonal-structured ZnO. A critical thickness for the full development of hexagonal ZnO crystal was estimated at approximately 80 nm in this study. ZnO thin films on PET substrates exhibit a high optical transmittance of > 70% and good endurance to bending cycles over the measured thickness range. The results of this study indicate that a trade-off should be sought between structural, electrical, optical, and mechanical properties for practical applications of very thin ZnO films on organic substrates. - Highlights: • Very thin ZnO films were sputter-deposited on the PET substrate. • The ZnO film resistance increases with an increase in film thickness until saturation. • Hexagonal crystal structures gradually develop with increasing film thickness. • A Zn phase appears in a 20-nm-thick ZnO film. • ZnO films show high optical transmittance of > 80% and good endurance to bending.

  16. Transient behaviors of ZnO thin films on a transparent, flexible polyethylene terephthalate substrate

    International Nuclear Information System (INIS)

    Kim, Yong Jun; Lee, Ho Seok; Noh, Jin-Seo

    2016-01-01

    Thickness-dependent electrical, structural, and optical properties of zinc oxide (ZnO) thin films on polyethylene terephthalate (PET) substrates have been investigated in the very thin thickness range of 20 to 120 nm. In this thickness range, the electrical resistance of ZnO film increased with an increase in film thickness. This unusual transition behavior was explained in terms of structural evolution from Zn-phase-incorporating non-crystalline ZnO to hexagonal-structured ZnO. A critical thickness for the full development of hexagonal ZnO crystal was estimated at approximately 80 nm in this study. ZnO thin films on PET substrates exhibit a high optical transmittance of > 70% and good endurance to bending cycles over the measured thickness range. The results of this study indicate that a trade-off should be sought between structural, electrical, optical, and mechanical properties for practical applications of very thin ZnO films on organic substrates. - Highlights: • Very thin ZnO films were sputter-deposited on the PET substrate. • The ZnO film resistance increases with an increase in film thickness until saturation. • Hexagonal crystal structures gradually develop with increasing film thickness. • A Zn phase appears in a 20-nm-thick ZnO film. • ZnO films show high optical transmittance of > 80% and good endurance to bending.

  17. Preparation and characterization of Ce-doped ZnO nanofibers by an electrospinning method

    Directory of Open Access Journals (Sweden)

    Jong-Pil Kim

    2011-02-01

    Full Text Available ZnO and Ce-doped ZnO Nanofibers on (111 Pt/SiO2/Si substrates were produced using an electrospinning technique. The as-prepared composite fibres were subjected to high-temperature calcination to produce inorganic fibers. After calcining at a temperature of 500 °C, the average diameter of the ZnO and Ce-doped ZnO nanofibers were determined to be 170 nm and 225 nm, respectively. The average grain size of the ZnO and Ce-doped ZnO nanofibers were about 50 nm and 57 nm, respectively. The microstructure, chemical bonding state and photoluminescence of the produced ZnO and Ce-doped ZnO nanofibers were investigated. The Ce-doped ZnO nanofiber can be assigned to the presence of Ce ions on substitutional sites of Zn ions and the Ce3+ state from X-ray photoelectron spectra. Compared with PL spectra of ZnO nanofibers, the peak position of the UV emission of the Ce-doped ZnO nanofibers is sharply suppressed while the green emission band is highly enhanced.

  18. Laser-induced grating in ZnO

    DEFF Research Database (Denmark)

    Ravn, Jesper N.

    1992-01-01

    A simple approach for the calculation of self-diffraction in a thin combined phase and amplitude grating is presented. The third order nonlinearity, the electron-hole recombination time, and the ambipolar diffusion coefficient in a ZnO crystal are measured by means of laser-induced self-diffracti......A simple approach for the calculation of self-diffraction in a thin combined phase and amplitude grating is presented. The third order nonlinearity, the electron-hole recombination time, and the ambipolar diffusion coefficient in a ZnO crystal are measured by means of laser-induced self...

  19. Permanent bending and alignment of ZnO nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Borschel, Christian; Spindler, Susann; Oertel, Michael; Ronning, Carsten [Institut fuer Festkoerperphysik, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Lerose, Damiana [MPI fuer Mikrostrukturphysik, Weinberg 2, 06120 Halle/Saale (Germany); Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); Bochmann, Arne [Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); Christiansen, Silke H. [Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); MPI fuer die Physik des Lichts, Guenther-Scharowsky-Str. 1, 91058 Erlangen (Germany); Nietzsche, Sandor [Zentrum fuer Elektronenmikroskopie, Friedrich-Schiller-Universitaet Jena, Ziegelmuehlenweg 1, 07743 Jena (Germany)

    2011-07-01

    Ion beams can be used to bend or re-align nanowires permanently, after they have been grown. We have irradiated ZnO nanowires with ions of different species and energy, achieving bending and alignment in various directions. We study the bending of single nanowires as well as the simultaneous alignment of large ensembles of ZnO nanowires in detail. Computer simulations show that the bending is initiated by ion beam induced damage. Dislocations are identified to relax stresses and make the bending and alignment permanent and resistant against annealing procedures.

  20. Raman scattering of quasimodes in ZnO

    International Nuclear Information System (INIS)

    Alarcon-Llado, E; Cusco, R; Artus, L; Jimenez, J; Wang, B; Callahan, M

    2008-01-01

    The angular dependence of the optical phonons of high-quality bulk ZnO has been systematically studied by means of Raman scattering. We report the observation of quasi-TO and quasi-LO modes for propagation directions covering the whole a-c mixing plane using a beveled ZnO single crystal sample. Scattering experiments performed in two different configuration geometries indicate that birefringence effects are not relevant for the phonon analysis in this material. The observed angular dependence of the quasimode frequencies is in good agreement with Loudon's model.

  1. Surface roughness of sputtered ZnO films

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Y S [Department of Materials Science and Engineering, National Dong Hwa University, 1, Sec. 2, Da Hsueh Rd. Shou-Feng, Hualien, Taiwan (China); Hsu, K C [Department of Photonics and Institute of Electro-Optical Engineering, National Chiao-Tung University, Hsinchu, Taiwan (China); Huang, Y M [Institute of Electronics Engineering, Southern Taiwan University of Technology, 1 Nan-Tai Street, Taiwan (China)

    2006-09-01

    ZnO films are grown on Si and glass substrates by radio-frequency (RF) magnetron sputtering. The crystalline structures are investigated by x-ray diffraction (XRD). Moreover, the roughness characteristics of the films are examined by atomic force microscopy (AFM) and field-emission scanning electron microscopy (FE-SEM). All films exhibit strong (002) preferential orientation. The influence of the RF power and target-to-substrate distance (D{sub ts}) on the properties of ZnO is studied. Under the optimized conditions of the RF power and D{sub ts}, root-mean-square (RMS) surface roughnesses of <0.8 nm are achieved.

  2. Surface roughness of sputtered ZnO films

    International Nuclear Information System (INIS)

    Lin, Y S; Hsu, K C; Huang, Y M

    2006-01-01

    ZnO films are grown on Si and glass substrates by radio-frequency (RF) magnetron sputtering. The crystalline structures are investigated by x-ray diffraction (XRD). Moreover, the roughness characteristics of the films are examined by atomic force microscopy (AFM) and field-emission scanning electron microscopy (FE-SEM). All films exhibit strong (002) preferential orientation. The influence of the RF power and target-to-substrate distance (D ts ) on the properties of ZnO is studied. Under the optimized conditions of the RF power and D ts , root-mean-square (RMS) surface roughnesses of <0.8 nm are achieved

  3. Properties of Mn-doped ZnO nanopowder

    Energy Technology Data Exchange (ETDEWEB)

    Schlenker, E.; Bakin, A.; Wehmann, H.H.; Al-Suleiman, M.; Waag, A. [Technical University Braunschweig, Institute of Semiconductor Technology, Braunschweig (Germany); Schmid, H.; Mader, W. [Universitaet Bonn, Institut fuer Anorganische Chemie, Bonn (Germany); Bremers, H.; Hangleiter, A. [Technical University Braunschweig, Institute of Applied Physics, Braunschweig (Germany); Luedke, J.; Albrecht, M. [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany)

    2008-06-15

    The structural and magnetic properties of Mn-doped ZnO nanopowder are investigated and compared to undoped ZnO crystals. Mn incorporation leads to an increase in the lattice constants as revealed by X-ray diffraction measurements. An inhomogeneous distribution of the Mn atoms within the nanopowder was detected by energy-dispersive X-ray and electron-energy-loss spectroscopy measurements. Magnetic features are investigated by means of SQUID magnetometry on ensembles of powder particles as well as by magnetic force microscopy to study the behavior of single grains. (orig.)

  4. Piezoelectric ZnO nanostructure for energy harvesting

    CERN Document Server

    Leprince-Wang, Yamin

    2015-01-01

    Over the past decade, ZnO as an important II-VI semiconductor has attracted much attention within the scientific community over the world owing to its numerous unique and prosperous properties. This material, considered as a "future material", especially in nanostructural format, has aroused many interesting research works due to its large range of applications in electronics, photonics, acoustics, energy and sensing. The bio-compatibility, piezoelectricity & low cost fabrication make ZnO nanostructure a very promising material for energy harvesting.

  5. Optical function of bionic nanostructure of ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Xu, C X [Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing 210096 (China); Zhu, G P [Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing 210096 (China); Liu, Y J [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, 639798 (Singapore); Sun, X W [Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing 210096 (China); Li, X [Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing 210096 (China); Liu, J P [Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing 210096 (China); Cui, Y P [Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing 210096 (China)

    2007-10-15

    A novel bionic network nanostructure of zinc oxide (ZnO), which is similar to the microstructure of a butterfly wing, was first fabricated by a vapor-phase transport method using zinc powder as a source. These bionic nanostructures are composed of three ordered multi-aperture gratings. Similar to the optical effect of butterfly wings, the diffraction patterns of the bionic network of ZnO were observed. The mechanism of the optical function was discussed based on the physical model of multi-aperture diffraction.

  6. Optical function of bionic nanostructure of ZnO

    International Nuclear Information System (INIS)

    Xu, C X; Zhu, G P; Liu, Y J; Sun, X W; Li, X; Liu, J P; Cui, Y P

    2007-01-01

    A novel bionic network nanostructure of zinc oxide (ZnO), which is similar to the microstructure of a butterfly wing, was first fabricated by a vapor-phase transport method using zinc powder as a source. These bionic nanostructures are composed of three ordered multi-aperture gratings. Similar to the optical effect of butterfly wings, the diffraction patterns of the bionic network of ZnO were observed. The mechanism of the optical function was discussed based on the physical model of multi-aperture diffraction

  7. Nature of native defects in ZnO.

    Science.gov (United States)

    Selim, F A; Weber, M H; Solodovnikov, D; Lynn, K G

    2007-08-24

    This study revealed the nature of native defects and their roles in ZnO through positron annihilation and optical transmission measurements. It showed oxygen vacancies are the origin for the shift in the optical absorption band that causes the red or orange coloration. It also revealed experimental evidence that the donor nature of oxygen vacancy is approximately 0.7 eV. In addition, this work showed the Zn interstitial was not the donor in the as-grown ZnO and supported recent calculations that predicted hydrogen in an oxygen vacancy forms multicenter bonds and acts as a shallow donor.

  8. Performance of Cr-doped ZnO for acetone sensing

    Energy Technology Data Exchange (ETDEWEB)

    Al-Hardan, N.H., E-mail: naif_imen@ukm.my [Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Abdullah, M.J.; Aziz, A. Abdul [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia)

    2013-04-01

    Zinc oxide (ZnO) doped with chromium (Cr) was synthesized by reactive co-sputtering for gas sensing applications. The effect of varying the contents of Cr (from 1 to 4 at%) on the ZnO gas sensor response was studied. X-ray diffraction analysis reveals the high orientation of c-axis of the prepared films. The optimum operating temperature of the undoped ZnO was 400 °C and shifted to 300 °C for the Cr-doped ZnO under the acetone vapour. The 1% Cr doping ZnO gas sensor was most sensitive for the acetone vapour. The ability of the 1% Cr-doped ZnO to produce repeatable results under different acetone vapour concentrations was tested. The timing properties of the doped Cr ZnO gas sensor were 70 and 95 s for the rise and recovery time respectively.

  9. Electronic Transport Properties of One Dimensional Zno Nanowires Studied Using Maximally-Localized Wannier Functions

    Science.gov (United States)

    Sun, Xu; Gu, Yousong; Wang, Xueqiang

    2012-08-01

    One dimensional ZnO NWs with different diameters and lengths have been investigated using density functional theory (DFT) and Maximally Localized Wannier Functions (MLWFs). It is found that ZnO NWs are direct band gap semiconductors and there exist a turn on voltage for observable current. ZnO nanowires with different diameters and lengths show distinctive turn-on voltage thresholds in I-V characteristics curves. The diameters of ZnO NWs are greatly influent the transport properties of ZnO NWs. For the ZnO NW with large diameter that has more states and higher transmission coefficients leads to narrow band gap and low turn on voltage. In the case of thinner diameters, the length of ZnO NW can effects the electron tunneling and longer supercell lead to higher turn on voltage.

  10. Controllable synthesis of periodic flower-like ZnO nanostructures on Si subwavelength grating structures

    International Nuclear Information System (INIS)

    Ko, Yeong Hwan; Leem, Jung Woo; Yu, Jae Su

    2011-01-01

    We report on the periodic well-defined flower-like zinc oxide (ZnO) nanostructures (NSs) self-assembled through a simple hydrothermal method using silicon (Si) subwavelength grating (SWG) structures. The Si SWGs serve as building blocks for constructing a two-dimensional (2D) periodic architecture to integrate the one-dimensional (1D) ZnO NSs. Various controlled morphologies of ZnO NSs with high crystallinity are obtained by changing the growth conditions. For 1D ZnO NSs integrated on periodic hexagonal Si SWG structures, the reflection characteristics are investigated in comparison with the conventional ZnO nanorod (NR) arrays. For a three-dimensional (3D) flower-like ZnO NS on Si SWGs, a relatively low total reflectance of < 8% at wavelengths of 300-1050 nm is achieved compared to the ZnO NRs on Si substrate.

  11. In vitro antibacterial activity of ZnO and Nd doped ZnO nanoparticles against ESBL producing Escherichia coli and Klebsiella pneumoniae

    Science.gov (United States)

    Hameed, Abdulrahman Syedahamed Haja; Karthikeyan, Chandrasekaran; Ahamed, Abdulazees Parveez; Thajuddin, Nooruddin; Alharbi, Naiyf S.; Alharbi, Sulaiman Ali; Ravi, Ganasan

    2016-04-01

    Pure ZnO and Neodymium (Nd) doped ZnO nanoparticles (NPs) were synthesized by the co-precipitation method. The synthesized nanoparticles retained the wurtzite hexagonal structure. From FESEM studies, ZnO and Nd doped ZnO NPs showed nanorod and nanoflower like morphology respectively. The FT-IR spectra confirmed the Zn-O stretching bands at 422 and 451 cm-1 for ZnO and Nd doped ZnO NPs respectively. From the UV-VIS spectroscopic measurement, the excitonic peaks were found around 373 nm and 380 nm for the respective samples. The photoluminescence measurements revealed that the broad emission was composed of ten different bands due to zinc vacancies, oxygen vacancies and surface defects. The antibacterial studies performed against extended spectrum β-lactamases (ESBLs) producing strains of Escherichia coli and Klebsiella pneumoniae showed that the Nd doped ZnO NPs possessed a greater antibacterial effect than the pure ZnO NPs. From confocal laser scanning microscopic (CLSM) analysis, the apoptotic nature of the cells was confirmed by the cell shrinkage, disorganization of cell wall and cell membrane and dead cell of the bacteria. SEM analysis revealed the existence of bacterial loss of viability due to an impairment of cell membrane integrity, which was highly consistent with the damage of cell walls.

  12. Effects of ZnO Seed Layers Prepared with Various Precursor Concentrations on Structural and Defect Emission Properties of ZnO Nanorods Grown by Hydrothermal Method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Soaram; Nam, Giwoong; Leem, Jae-Young; Kim, Yangsoo [Inje University, Gimhae (Korea, Republic of); Kim, Ghun Sik; Yoon, Sung Pil [Korea Institute of Science and Technology, Seoul (Korea, Republic of)

    2013-07-15

    ZnO nanorods were grown by a hydrothermal method on ZnO seed layers that had previously been prepared from solutions containing various precursor concentrations. The effects of the ZnO seed layers prepared with various precursor concentrations on the structural and defect emissions of the ZnO nanorods were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) spectroscopy. The surface morphology of the ZnO seed layers changed with an increasing precursor concentration, and the diameters and densities of the ZnO nanorods depended on the morphologies of the ZnO seed layers. The ZnO seed layers prepared with various precursor concentrations affected the residual stress in the nanorods grown on the seed layers, the intensity and full widths at half maximum of the 2-theta angle in the XRD spectra for the nanorods, and the intensity and position of the defect emission peak in deep-level emission (DLE) PL spectra for the ZnO nanorods.

  13. Diversity among galaxy clusters

    International Nuclear Information System (INIS)

    Struble, M.F.; Rood, H.J.

    1988-01-01

    The classification of galaxy clusters is discussed. Consideration is given to the classification scheme of Abell (1950's), Zwicky (1950's), Morgan, Matthews, and Schmidt (1964), and Morgan-Bautz (1970). Galaxies can be classified based on morphology, chemical composition, spatial distribution, and motion. The correlation between a galaxy's environment and morphology is examined. The classification scheme of Rood-Sastry (1971), which is based on clusters's morphology and galaxy population, is described. The six types of clusters they define include: (1) a cD-cluster dominated by a single large galaxy, (2) a cluster dominated by a binary, (3) a core-halo cluster, (4) a cluster dominated by several bright galaxies, (5) a cluster appearing flattened, and (6) an irregularly shaped cluster. Attention is also given to the evolution of cluster structures, which is related to initial density and cluster motion

  14. What Makes Clusters Decline?

    DEFF Research Database (Denmark)

    Østergaard, Christian Richter; Park, Eun Kyung

    2015-01-01

    Most studies on regional clusters focus on identifying factors and processes that make clusters grow. However, sometimes technologies and market conditions suddenly shift, and clusters decline. This paper analyses the process of decline of the wireless communication cluster in Denmark. The longit...... but being quick to withdraw in times of crisis....

  15. Clustering of correlated networks

    OpenAIRE

    Dorogovtsev, S. N.

    2003-01-01

    We obtain the clustering coefficient, the degree-dependent local clustering, and the mean clustering of networks with arbitrary correlations between the degrees of the nearest-neighbor vertices. The resulting formulas allow one to determine the nature of the clustering of a network.

  16. An experimental study on suspended sodium droplet combustion (3)

    International Nuclear Information System (INIS)

    Sato, Kenji

    2005-03-01

    As part of studies for phenomenological investigation of sodium droplet burning behavior, in our previous experimental studies for suspended single sodium droplet, behavior of ignition process and succeeding combustion, ignition delay time, and droplet temperature history had been investigated. In this study, combustion experiments of suspended sodium droplet were performed in upward dry air flow by expanding the range of free-stream velocity U of air flow into 400 cm/s with initial droplet temperature Ti=300, 350, and 400degC and initial droplet diameter 4 mm at first. Then, the combustion experiments were also performed by changing the initial droplet diameter from 2.3 to 4.4 mm with Ti=350 and 400degC and U=100 cm/s. From the experimental results, the effects of free-stream velocity, initial droplet temperature, and initial droplet diameter on the ignition/burning behavior and ignition delay time were examined. The obtained results are as follows: (1) Ignition phenomena of suspended droplet were observed for all examined experimental conditions up to 400 cm/s. The orange emission observed at the moment of ignition occurs simultaneously over whole droplet surface except the top region of it. (2) The feature of the dependence of ignition delay time on the free-stream velocity is independent of the initial droplet temperature. With the increase of the free-stream velocity, up to 300 cm/s the ignition delay time decreases with decreasing dependency, and then the dependency increases more. (3) The ignition delay time increases with the increase of initial droplet diameter. The dependency increases as the initial droplet diameter increases. The ignition delay time extrapolated toward zero diameters from the obtained results becomes to be essentially zero. (author)

  17. Particles of bottom and suspended sediments: height of rise

    Directory of Open Access Journals (Sweden)

    Khodzinskaya Anna Gennadievna

    2014-12-01

    Full Text Available In the article, characteristic values of dynamic sizes of bottom and suspended sediments, including their probabilistic assessment, are considered. The article presents the processing results in respect of the experimental data for bottom and suspended sediments, obtained in the laboratory environment using samples and filming methods. The experiments have proven that the dynamic hydraulic size determines the height of rise for the particles of the saltation load, rather than suspended ones. In the laboratory environment, the maximal height of rise is mainly driven by the relative flow depth. According to the assessment made by the co-authors, depths of flows employed in the experiments designated for the identification of heights of rises, were comparable to saltation heights of particles. Besides, the saltation height of particles, having relative density well below 2.65, nearly always exceeded half of the depth of the laboratory flow. Hydrodynamic conditions favourable for the separation and motion of artificial particles in coarse surface tanks are far different from the motion of sand particles on the bottom of lowland rivers. Values of hydraulic resistance ratios typical for laboratory experiments by far exceed their values typical for lowland rivers, and it means that the conditions of the experiments performed in the laboratory were similar to those typical for mountain rivers. The research findings have proven that the particle separation and motion pattern, if artificial particles are made of the materials demonstrating variable density and elasticity values and if loose particles travel over fixed ones, is different from the pattern typical for natural particles having variable coarseness.

  18. Super-bridges suspended over carbon nanotube cables

    Science.gov (United States)

    Carpinteri, Alberto; Pugno, Nicola M.

    2008-11-01

    In this paper the new concept of 'super-bridges', i.e. kilometre-long bridges suspended over carbon nanotube cables, is introduced. The analysis shows that the use of realistic (thus defective) carbon nanotube bundles as suspension cables can enlarge the current limit main span by a factor of ~3. Too large compliance and dynamic self-excited resonances could be avoided by additional strands, rendering the super-bridge anchored as a spider's cobweb. As an example, we have computed the limit main spans of the current existing 19 suspended-deck bridges longer than 1 km assuming them to have substituted their cables with carbon nanotube bundles (thus maintaining the same geometry, with the exception of the length) finding spans of up to ~6.3 km. We thus suggest that the design of the Messina bridge in Italy, which would require a main span of ~3.3 km, could benefit from the use of carbon nanotube bundles. We believe that their use represents a feasible and economically convenient solution. The plausibility of these affirmations is confirmed by a statistical analysis of the existing 100 longest suspended bridges, which follow a Zipf's law with an exponent of 1.1615: we have found a Moore-like (i.e. exponential) law, in which the doubling of the capacity (here the main span) per year is substituted by the factor 1.0138. Such a law predicts that the realization of the Messina bridge using conventional materials will only occur around the middle of the present century, whereas it could be expected in the near future if carbon nanotube bundles were used. A simple cost analysis concludes the paper.

  19. Super-bridges suspended over carbon nanotube cables

    International Nuclear Information System (INIS)

    Carpinteri, Alberto; Pugno, Nicola M

    2008-01-01

    In this paper the new concept of 'super-bridges', i.e. kilometre-long bridges suspended over carbon nanotube cables, is introduced. The analysis shows that the use of realistic (thus defective) carbon nanotube bundles as suspension cables can enlarge the current limit main span by a factor of ∼3. Too large compliance and dynamic self-excited resonances could be avoided by additional strands, rendering the super-bridge anchored as a spider's cobweb. As an example, we have computed the limit main spans of the current existing 19 suspended-deck bridges longer than 1 km assuming them to have substituted their cables with carbon nanotube bundles (thus maintaining the same geometry, with the exception of the length) finding spans of up to ∼6.3 km. We thus suggest that the design of the Messina bridge in Italy, which would require a main span of ∼3.3 km, could benefit from the use of carbon nanotube bundles. We believe that their use represents a feasible and economically convenient solution. The plausibility of these affirmations is confirmed by a statistical analysis of the existing 100 longest suspended bridges, which follow a Zipf's law with an exponent of 1.1615: we have found a Moore-like (i.e. exponential) law, in which the doubling of the capacity (here the main span) per year is substituted by the factor 1.0138. Such a law predicts that the realization of the Messina bridge using conventional materials will only occur around the middle of the present century, whereas it could be expected in the near future if carbon nanotube bundles were used. A simple cost analysis concludes the paper.

  20. Luminescence properties of hydrothermally grown ZnO nanorods

    Czech Academy of Sciences Publication Activity Database

    Yatskiv, Roman; Grym, Jan

    2016-01-01

    Roč. 99, 1November (2016), s. 214-220 ISSN 0749-6036 R&D Projects: GA MŠk(CZ) LD14111; GA ČR GA15-17044S Institutional support: RVO:67985882 Keywords : Photoluminescence * Annealing * ZnO nanorods Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 2.123, year: 2016

  1. Pulsed-laser deposited ZnO for device applications

    NARCIS (Netherlands)

    King, S.L.; Gardeniers, Johannes G.E.; Boyd, I.W.

    1996-01-01

    The study investigates the growth by pulsed-laser deposition (PLD) of ZnO thin films for the eventual incorporation into piezo-electric actuators and other sensors being developed at the University of Twente. All films are purely c-axis oriented, and results are presented which suggest the

  2. ZnO processing for integrated optic sensors

    NARCIS (Netherlands)

    Horsthuis, Winfried H.G.

    1986-01-01

    ZnO thin films were sputter deposited onto oxidized silicon wafers. The film quality increased with increasing applied r.f. power. Characterization of the films was performed by measurements of the attenuation of the transverse electric TE0 optical guided mode. For an applied r.f. power of 2000 W,

  3. Random laser action in 3-D ZnO nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Miao, L.; Tanemura, S. [Key Laboratory of Renewable Energy and Gas Hydrate, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, No. 2 Nengyuan Rd. Tianhe district, Guangzhou (China); Materials R and D Laboratory, Japan Fine Ceramics Centre, Mutsuno, Atsuta-ku, Nagoya 456-8587 (Japan); Yang, H.Y.; Lau, S.P. [School of Electrical and Electronic Engineering, Nanyang Technological University (Singapore); Xu, G. [Key Laboratory of Renewable Energy and Gas Hydrate, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, No. 2 Nengyuan Rd. Tianhe district, Guangzhou (China)

    2009-05-15

    Room-temperature ultraviolet random lasing with low threshold pumping power was successfully achieved by ZnO 3-D random-wall nanostructure fabricated on ZnO/SiO{sub 2}/Si substrate through a thermal chemical reaction and vapor transportation deposition method in a simple horizontal tube furnace from the mixed ZnO and graphite powders. The nanorods grown along c-axis on the substrate are coalesced to form the 3-D nano-wall with 80{proportional_to}100 nm in wall thickness and irregular height ranging of 95-250 nm. Mueller matrix spectroscopic ellipsometry reveals that evaluated refractive indices n(E) of ZnO nanowalls are well interpreted by taking account of the ratio between ZnO and void achieved by effective medium theory analysis and isotropic depolarization feature of the designated nanowalls. Random lasing action observed in the wide wavelength range between 375 and 395 nm is realized by coherent amplification of the closed-loop scattered light inside 3-D random-wall nanostructure. It is demonstrated that both transverse electric (TE) and transverse magnetic (TM) modes show the same threshold and pumping power dependent trend, while the intensity of TM lasing is weaker than that of TE due to the different scattering strength originated from the features of the inside of nanowall. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Laser nanostructuring of ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Nedyalkov, N., E-mail: nned@ie.bas.bg [Department of Electronics and Electrical Engineering, Keio University, 3-14-1 Hiyoshi Kohoku-ku, Yokohama-shi, Kanagawa-ken 223-8522 (Japan); Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko shousse 72, Sofia 1784 (Bulgaria); Koleva, M.; Nikov, R.; Atanasov, P. [Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko shousse 72, Sofia 1784 (Bulgaria); Nakajima, Y.; Takami, A.; Shibata, A.; Terakawa, M. [Department of Electronics and Electrical Engineering, Keio University, 3-14-1 Hiyoshi Kohoku-ku, Yokohama-shi, Kanagawa-ken 223-8522 (Japan)

    2016-06-30

    Highlights: • Nanosecond laser pulse nanostructuring of ZnO thin films on metal substrate is demonstrated. • Two regimes of the thin film modification are observed depending on the applied laser fluence. • At high fluence regime the ZnO film is homogeneously decomposed into nanosized particles. • The characteristic size of the formed nanostructures corresponds to the domain size of the thin film. - Abstract: In this work, results on laser processing of thin zinc oxide films deposited on metal substrate are presented. ZnO films are obtained by classical nanosecond pulsed laser deposition method in oxygen atmosphere on tantalum substrate. The produced films are then processed by nanosecond laser pulses at wavelength of 355 nm. The laser processing parameters and the film thickness are varied and their influence on the fabricated structures is estimated. The film morphology after the laser treatment is found to depend strongly on the laser fluence as two regimes are defined. It is shown that at certain conditions (high fluence regime) the laser treatment of the film leads to formation of a discrete nanostructure, composed of spherical like nanoparticles with narrow size distribution. The dynamics of the melt film on the substrate and fast cooling are found to be the main mechanisms for fabrication of the observed structures. The demonstrated method is an alternative way for direct fabrication of ZnO nanostructures on metal which can be easy implemented in applications as resistive sensor devices, electroluminescent elements, solar cell technology.

  5. Hyperfine interaction study of F+ center in ZnO

    International Nuclear Information System (INIS)

    Gonzalez, C.; Galland, D.; Herve, A.

    1975-01-01

    Irradiation of ZnO monocrystals with 3MeV electron creates isolated zinc vacancies and F + centres. Analysis of angular variations of the ESR spectrum enabled the parameters of interaction of the F + centre with a Zn 67 nucleus to be determined [fr

  6. Co-Doped ZnO nanoparticles: minireview.

    Science.gov (United States)

    Djerdj, Igor; Jaglicić, Zvonko; Arcon, Denis; Niederberger, Markus

    2010-07-01

    Diluted magnetic semiconductors with a Curie temperature exceeding 300 K are promising candidates for spintronic devices and spin-based electronic technologies. We review recent achievements in the field of one of them: Co-doped ZnO at the nanoparticulate scale.

  7. High Temperature Thermoelectric Properties of ZnO Based Materials

    DEFF Research Database (Denmark)

    Han, Li

    of the dopants and dopant concentrations, a large power factor was obtainable. The sample with the composition of Zn0.9Cd0.1Sc0.01O obtained the highest zT ∼0.3 @1173 K, ~0.24 @1073K, and a good average zT which is better than the state-of-the-art n-type thermoelectric oxide materials. Meanwhile, Sc-doped Zn......This thesis investigated the high temperature thermoelectric properties of ZnO based materials. The investigation first focused on the doping mechanisms of Al-doped ZnO, and then the influence of spark plasma sintering conditions on the thermoelectric properties of Al, Ga-dually doped Zn......O. Following that, the nanostructuring effect for Al-doped ZnO was systematically investigated using samples with different microstructure morphologies. At last, the newly developed ZnCdO materials with superior thermoelectric properties and thermal stability were introduced as promising substitutions...

  8. ZnO nanostructures induced by microwave plasma

    Directory of Open Access Journals (Sweden)

    Khaled A. Elsayed

    2015-07-01

    Full Text Available Microwave induced hydrogen plasma is used to fabricate ZnO thin films at low ambient gas pressure and controlled oxygen content in the gas mixture. The emission spectra have been observed. Optical emission spectroscopy was used to identify the chemical reaction mechanism. Structural quality of the so-obtained nanoparticles was studied by X-ray diffraction (XRD and high resolution scanning electron microscopy (SEM. SEM results showed that nanorods were formed in the process, and XRD results along with nanorod dimensions obtained from SEM are consistent with the formation of single and poly-crystalline ZnO nanorods. The alignment of these nanorods with respect to the substrates depends on the lattice mismatch between ZnO and the glass substrate. The minimum crystallite grain size as obtained from the SEM measurements was ∼24 nm and the average diameter is 70 nm with a length of 1–2 μm. The deposited ZnO thin films have a wide energy band gap that equals ∼3 eV.

  9. Characterization of Mn doped ZnO nanopowder

    Energy Technology Data Exchange (ETDEWEB)

    Schlenker, Eva; Bakin, Andrey; Al-Suleiman, Mohamed; Wehmann, Hergo-Heinrich; Waag, Andreas [Institute of Semiconductor Technology, TU Braunschweig (Germany); Schmid, Herbert; Mader, Werner [Institute for Inorganic Chemistry, University Bonn (Germany); Bremers, Heiko; Hangleiter, Andreas [Institute of Applied Physics, TU Braunschweig (Germany)

    2008-07-01

    In the quest of materials for spintronic applications, diluted magnetic semiconductors recently attracted much attention. The main challenge is finding a ferromagnetic material with Curie temperature T{sub c}>300 K whose magnetic properties can be controlled electrically. The interest was particularly focused on Zn(TM)O since theoretical calculations predict that ZnO containing Mn could exhibit ferromagnetism with T{sub c} above room temperature. In the present study, the structural and magnetic properties of Mn doped ZnO nanopowder are investigated and compared to undoped ZnO crystals. Doping of ZnO with Mn results in increased lattice constants as revealed by XRD. However, an inhomogeneous distribution of the Mn dopants within the nanopowder was revealed by energy-dispersive X-ray and electron energy-loss spectroscopy. Magnetic properties are investigated by means of SQUID measurements on aggregates of powder particles as well as by MFM to study the behavior of single grains. The MFM image differs significantly from the topography as imaged by AFM and suggests the existence of long-ranging magnetic signals emerging from the sample.

  10. Electrical properties of ZnO nanorods and layers

    Energy Technology Data Exchange (ETDEWEB)

    Schlenker, Eva; Bakin, Andrey; Peters, Ole; Mofor, Augustine C.; Postels, Bianca; El-Shaer, Hamid; Wehmann, Hergo-Heinrich; Waag, Andreas [Institut fuer Halbleitertechnik, TU Braunschweig (Germany); Weimann, Thomas; Hinze, Peter [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany)

    2007-07-01

    ZnO has attracted a lot of interest in the scientific community due to its outstanding properties. With a band gap of 3.37 eV and an exciton binding energy of 60 meV it is a promising candidate for micro- and optoelectronic applications. The growth of ZnO nanostructures and epitaxial layers is well under control and their optical and structural properties are already thoroughly characterized. However, due to contacting difficulties, less reports exist on the electrical properties of single ZnO nanostructures. In this contribution we present various contacting methods in order to explore the electrical properties of individual nanorods either grown by aqueous chemical growth or vapor phase transport. Current-Voltage characteristics were obtained by using an atomic force microscope with a conductive tip or by patterning contacts with e-beam lithography. The results are compared to the ones obtained from measurements on epitaxially grown ZnO layers and first applications are presented.

  11. NANO CRYSTALLINE ZnO CATALYZED ONE POT THREE ...

    African Journals Online (AJOL)

    advances in nanoscience and nanotechnology have led to new research interests in using nanometer-sized particles as .... dichloromethane and then filtered to separate the nano ZnO catalyst. ..... 104, 4063. 31. Matsubara, K.; Fons, P.; Iwata, K.; Yamada, A.; Sakurai, K.; Tampo, N.; Niki, S. Thin Solid. Films 2003, 431, 369.

  12. Synthesis and characterization of ZnO nanostructures with varying ...

    Indian Academy of Sciences (India)

    2017-05-13

    May 13, 2017 ... Composition of the reactant solution, pH and temperature ... due to the broad spectrum of UV radiation absorption, supe- ... In addition, ZnO is very useful to cure various other skin ... be used as promising candidate for coating of orthopedic ... tape and then coated with gold for 40 s in an auto-fine coater.

  13. Mechanical, microstructure and electrical properties of ternary ZnO ...

    Indian Academy of Sciences (India)

    V2O5–Mn3O4 (ZVM)-based varis- tors were investigated at different sintering temperatures of 825–950◦C. The microstructure of the samples consists mainly of ZnO grains with Zn3(VO4)2, ZnV2O4 and VO2 as minor secondary phases.

  14. Direct Precipitation and Characterization of ZnO Nanoparticles

    Directory of Open Access Journals (Sweden)

    A. H. Moharram

    2014-01-01

    Full Text Available ZnO nanoparticles are prepared through hydrolysis and condensation of zinc acetate dihydrate by potassium hydroxide in alcoholic medium at low temperatures. Thermal gravimetric analysis (TGA of the precursor is made in order to specify the temperature range over which the weight loss and thermal effect are significant. X-ray diffraction of the as-prepared specimens shows that the hexagonal (a=3.2459 Å, c=5.1999 Å structure is the predominant crystallographic structure. According to Scherer’s formula, the average size of the nanoparticles is 22.4 ± 0.6 nm. The structural properties of the synthesized ZnO nanoparticles have been confirmed using the TEM micrographs. The optical energy gap of the ZnO nanoparticles, as obtained from applying Tauc’s equation, is equal to 3.52 eV, which is higher than that of the bulk material. Absorption peak of the as-prepared sample is 298 nm which is highly blue shifted as compared to the bulk (360 nm. Large optical energy gap and highly blue shifted absorption edge confirm that the prepared ZnO nanoparticle exhibits strong quantum confinement effect.

  15. The Applications of Morphology Controlled ZnO in Catalysis

    Directory of Open Access Journals (Sweden)

    Yuhai Sun

    2016-11-01

    Full Text Available Zinc oxide (ZnO, with the unique chemical and physical properties of high chemical stability, broad radiation absorption range, high electrochemical coupling coefficient, and high photo-stability, is an attractive multifunctional material which has promoted great interest in many fields. What is more, its properties can be tuned by controllable synthesized morphologies. Therefore, after the success of the abundant morphology controllable synthesis, both the morphology-dependent ZnO properties and their related applications have been extensively investigated. This review concentrates on the properties of morphology-dependent ZnO and their applications in catalysis, mainly involved reactions on green energy and environmental issues, such as CO2 hydrogenation to fuels, methanol steam reforming to generate H2, bio-diesel production, pollutant photo-degradation, etc. The impressive catalytic properties of ZnO are associated with morphology tuned specific microstructures, defects or abilities of electron transportation, etc. The main morphology-dependent promotion mechanisms are discussed and summarized.

  16. Electronic properties of assemblies of zno quantum dots

    NARCIS (Netherlands)

    Roest, Aarnoud Laurens

    2003-01-01

    Electron transport in an assembly of ZnO quantum dots has been studied using an electrochemically gated transistor. The electron mobility shows a step-wise increase as a function of the electron occupation per quantum dot. When the occupation number is below two, transport occurs by tunnelling

  17. Photoluminescence of spray pyrolysis deposited ZnO nanorods

    Directory of Open Access Journals (Sweden)

    Mikli Valdek

    2011-01-01

    Full Text Available Abstract Photoluminescence of highly structured ZnO layers comprising well-shaped hexagonal rods is presented. The ZnO rods (length 500-1,000 nm, diameter 100-300 nm were grown in air onto a preheated soda-lime glass (SGL or ITO/SGL substrate by low-cost chemical spray pyrolysis method using zinc chloride precursor solutions and growth temperatures in the range of 450-550°C. We report the effect of the variation in deposition parameters (substrate type, growth temperature, spray rate, solvent type on the photoluminescence properties of the spray-deposited ZnO nanorods. A dominant near band edge (NBE emission is observed at 300 K and at 10 K. High-resolution photoluminescence measurements at 10 K reveal fine structure of the NBE band with the dominant peaks related to the bound exciton transitions. It is found that all studied technological parameters affect the excitonic photoluminescence in ZnO nanorods. PACS: 78.55.Et, 81.15.Rs, 61.46.Km

  18. Red luminescence from ZnO : Cr nanophosphors under visible ...

    Indian Academy of Sciences (India)

    Administrator

    400 nm and blue emission peak at 447 nm. Cr3+-doped ZnO shows .... The CIE colour co-ordinates measured from PL emis- ... 'BLUE' emission, whereas CIE x and y values for Cr3+- .... EPR studies of transition metal and rare earth ion doped.

  19. Synthesis and characterization of thermally oxidized ZnO films

    Indian Academy of Sciences (India)

    Administrator

    Synthesis and characterization of thermally oxidized ZnO films. A P RAMBU1,* and N IFTIMIE2 .... R. −. Δ. = = (1) where Ra is the sensor resistance in the air and Rg is the .... ple, Aida and coworkers (2006) reported that the total oxidation is ...

  20. Chronic toxicity of ZnO nanoparticles, non-nano ZnO and ZnCl2 to Folsomia candida (Collembola) in relation to bioavailability in soil

    International Nuclear Information System (INIS)

    Kool, Pauline L.; Diez Ortiz, Maria; Gestel, Cornelis A.M. van

    2011-01-01

    The chronic toxicity of zinc oxide nanoparticles (ZnO-NP) to Folsomia candida was determined in natural soil. To unravel the contribution of particle size and free zinc to NP toxicity, non-nano ZnO and ZnCl 2 were also tested. Zinc concentrations in pore water increased with increasing soil concentrations, with Freundlich sorption constants K f of 61.7, 106 and 96.4 l/kg (n = 1.50, 1.34 and 0.42) for ZnO-NP, non-nano ZnO and ZnCl 2 respectively. Survival of F. candida was not affected by ZnO-NP and non-nano ZnO at concentrations up to 6400 mg Zn/kg d.w. Reproduction was dose-dependently reduced with 28-d EC50s of 1964, 1591 and 298 mg Zn/kg d.w. for ZnO-NP, non-nano ZnO and ZnCl 2 , respectively. The difference in EC50s based on measured pore water concentrations was small (7.94-16.8 mg Zn/l). We conclude that zinc ions released from NP determine the observed toxic effects rather than ZnO particle size. - Highlights: → ZnO nanoparticles and non-nano ZnO were equally toxic to Folsomia candida in soil. → Pore water from soil spiked with ZnO nanoparticles showed saturation with zinc suggesting aggregation. → Pore water based EC50 values for ZnO nanoparticles and ZnCl 2 were similar. → ZnO nanoparticle toxicity in soil was most probably due to Zn dissolution from the nanoparticles. - ZnO nanoparticle toxicity to springtails in soil can be explained from Zn dissolution but not from particle size.

  1. Relevant Subspace Clustering

    DEFF Research Database (Denmark)

    Müller, Emmanuel; Assent, Ira; Günnemann, Stephan

    2009-01-01

    Subspace clustering aims at detecting clusters in any subspace projection of a high dimensional space. As the number of possible subspace projections is exponential in the number of dimensions, the result is often tremendously large. Recent approaches fail to reduce results to relevant subspace...... clusters. Their results are typically highly redundant, i.e. many clusters are detected multiple times in several projections. In this work, we propose a novel model for relevant subspace clustering (RESCU). We present a global optimization which detects the most interesting non-redundant subspace clusters...... achieves top clustering quality while competing approaches show greatly varying performance....

  2. Analysis towards VMEM File of a Suspended Virtual Machine

    Science.gov (United States)

    Song, Zheng; Jin, Bo; Sun, Yongqing

    With the popularity of virtual machines, forensic investigators are challenged with more complicated situations, among which discovering the evidences in virtualized environment is of significant importance. This paper mainly analyzes the file suffixed with .vmem in VMware Workstation, which stores all pseudo-physical memory into an image. The internal file structure of .vmem file is studied and disclosed. Key information about processes and threads of a suspended virtual machine is revealed. Further investigation into the Windows XP SP3 heap contents is conducted and a proof-of-concept tool is provided. Different methods to obtain forensic memory images are introduced, with both advantages and limits analyzed. We conclude with an outlook.

  3. Easy process to obtain suspended graphene flakes on TEM grids

    International Nuclear Information System (INIS)

    Gonçalves, Hugo; Fernandes, Joel; Moura, Cacilda; Schellenberg, Peter; Belsley, Michael; Alves, Luís

    2015-01-01

    Much of the ongoing research on graphene requires free-hanging (suspended) graphene to eliminate any influence from underlying substrates. Several methods have been developed for its preparation but they are either very complex or not completely reliable. Here, we describe a simple method for the transfer of graphene single layers from glass or silicon substrates onto TEM grids. The method uses a carrier film for the transfer process. By optimizing the process yields greater than 60% were achieved. The integrity of the transferred films was confirmed using Raman spectroscopy; successful suspension of both mono- and double-layer graphene sheets was obtained. (paper)

  4. The Ages in a Self-Suspended Nanoparticle Liquid

    KAUST Repository

    Agarwal, Praveen

    2010-01-13

    Telomers ionically tethered to nanometer-sized particles yield self-suspended, nanoparticle-Iaden liquids with unusual dynamical features. By subjecting these suspensions to controlled, modest shear strains, we find that their flow behaviors observed using experiments performed on time scales of tens of seconds can be projected to obtain maps of their dynamical response on geological time scales. That such extraordinarily slow dynamic processes can be uncovered from real-time measurements by simply stretching a system provides a simple but powerful tool for interrogating extremely slow motions in other jammed physical states. © 2010 American Chemical Society.

  5. LAGRANGIAN MODELING OF A SUSPENDED-SEDIMENT PULSE.

    Science.gov (United States)

    Schoellhamer, David H.

    1987-01-01

    The one-dimensional Lagrangian Transport Model (LTM) has been applied in a quasi two-dimensional manner to simulate the transport of a slug injection of microbeads in steady experimental flows. A stationary bed segment was positioned below each parcel location to simulate temporary storage of beads on the bottom of the flume. Only one degree of freedom was available for all three bead simulations. The results show the versatility of the LTM and the ability of the LTM to accurately simulate transport of fine suspended sediment.

  6. Genesis of ZnO nanoparticles

    International Nuclear Information System (INIS)

    Silva, M.N. da; Pulcinelli, S.H.; Santilli, C.V.

    2014-01-01

    Zinc oxide is a semiconductor with direct band gap, of 3,37 eV, and high excitons energy (60 MeV). The main key for comprehension of the mechanisms that rules particle formation, lay in a full understanding of the first step of formation and growing of this nanoparticle. Zinc oxide nanoparticle were prepared through modification in the method first proposed by Spanhel & Anderson, the characterization techniques were followed by UV-Vis spectroscopy and small angle X ray scattering (SAXS). The results have shown that in the reaction first step we have nanoparticle size between 0,32 e 2,0 nm, whose growing steps can be described by Diffusion-limited cluster-cluster aggregation (DLCA), where self-similar primary structures aggregate keeping the initial morphology. (author)

  7. Chemical effect of Si+ ions on the implantation-induced defects in ZnO studied by a slow positron beam

    Science.gov (United States)

    Jiang, M.; Wang, D. D.; Chen, Z. Q.; Kimura, S.; Yamashita, Y.; Mori, A.; Uedono, A.

    2013-01-01

    Undoped ZnO single crystals were implanted with 300 keV Si+ ions to a dose of 6 × 1016 cm-2. A combination of X-ray diffraction (XRD), positron annihilation, Raman scattering, high resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) was used to study the microstructure evolution after implantation and subsequent annealing. A very large increase of Doppler broadening S parameters in Si+-implanted region was detected by using a slow positron beam, indicating that vacancy clusters or microvoids are induced by implantation. The S parameters increase further after annealing up to 700 °C, suggesting agglomeration of these vacancies or microvoids to larger size. Most of these defects are removed after annealing up to 1100 °C. The other measurements such as XRD, Raman scattering, and PL all indicate severe damage and even disordered structure induced by Si+ implantation. The damage and disordered lattice shows recovery after annealing above 700 °C. Amorphous regions are observed by HRTEM measurement, directly testifies that amorphous phase is induced by Si+ implantation in ZnO. Analysis of the S - W correlation and the coincidence Doppler broadening spectra gives direct evidence of SiO2 precipitates in the sample annealed at 700 °C, which strongly supports the chemical effect of Si ions on the amorphization of ZnO lattice.

  8. Numerical Simulation of Flow and Suspended Sediment Transport in the Distributary Channel Networks

    Directory of Open Access Journals (Sweden)

    Wei Zhang

    2014-01-01

    Full Text Available Flow and suspended sediment transport in distributary channel networks play an important role in the evolution of deltas and estuaries, as well as the coastal environment. In this study, a 1D flow and suspended sediment transport model is presented to simulate the hydrodynamics and suspended sediment transport in the distributary channel networks. The governing equations for river flow are the Saint-Venant equations and for suspended sediment transport are the nonequilibrium transport equations. The procedure of solving the governing equations is firstly to get the matrix form of the water level and suspended sediment concentration at all connected junctions by utilizing the transformation of the governing equations of the single channel. Secondly, the water level and suspended sediment concentration at all junctions can be obtained by solving these irregular spare matrix equations. Finally, the water level, discharge, and suspended sediment concentration at each river section can be calculated. The presented 1D flow and suspended sediment transport model has been applied to the Pearl River networks and can reproduce water levels, discharges, and suspended sediment concentration with good accuracy, indicating this that model can be used to simulate the hydrodynamics and suspended sediment concentration in the distributary channel networks.

  9. Cluster ion beam facilities

    International Nuclear Information System (INIS)

    Popok, V.N.; Prasalovich, S.V.; Odzhaev, V.B.; Campbell, E.E.B.

    2001-01-01

    A brief state-of-the-art review in the field of cluster-surface interactions is presented. Ionised cluster beams could become a powerful and versatile tool for the modification and processing of surfaces as an alternative to ion implantation and ion assisted deposition. The main effects of cluster-surface collisions and possible applications of cluster ion beams are discussed. The outlooks of the Cluster Implantation and Deposition Apparatus (CIDA) being developed in Guteborg University are shown

  10. Hydrothermal growth of upright-standing ZnO sheet microcrystals

    International Nuclear Information System (INIS)

    Shi, Ruixia; Yang, Ping; Dong, Xiaobin; Jia, Changchao; Li, Jia

    2014-01-01

    Highlights: • Upright-standing ZnO sheet microcrystals were hydrothermally fabricated. • The ZnO sheets were prepared with sodium oxalate at 70 °C without any surfactant. • The preferable adsorption of oxalate anions causes the formation of ZnO sheet. • The continuous growth in six directions leads to the formation of hexagonal sheets. - Abstract: Large-scale upright-standing ZnO sheet microcrystals were fabricated on Zn substrate using sodium oxalate as structure-directing agent by a hydrothermal method at low temperature (70 °C) without any surfactant. The sheets are about 3–5 μm in dimension and 100–300 nm in thickness. The strong and narrow diffraction peaks of ZnO indicate that the sample has a good crystallinity and size. The morphology of sheet-like ZnO varied with the concentrations of sodium oxalate and reaction time. The sheet-like ZnO would transform into rod-like ones when sodium oxalate was substituted by equivalent sodium acetate. The formation of sheet-like ZnO is attributed to the preferable adsorption of oxalate anions on (0 0 0 1) face of ZnO, which inhibits the intrinsic growth of ZnO. Additionally, the continuous growth in six (0 1 −1 0) directions that have the lowest surface energy leads to the formation of hexagonal sheets

  11. Orientation-dependent chemistry and band-bending of Ti on polar ZnO surfaces.

    Science.gov (United States)

    Borghetti, Patrizia; Mouchaal, Younes; Dai, Zongbei; Cabailh, Gregory; Chenot, Stéphane; Lazzari, Rémi; Jupille, Jacques

    2017-04-19

    Orientation-dependent reactivity and band-bending are evidenced upon Ti deposition (1-10 Å) on polar ZnO(0001)-Zn and ZnO(0001[combining macron])-O surfaces. At the onset of the Ti deposition, a downward band-bending was observed on ZnO(0001[combining macron])-O while no change occurred on ZnO(0001)-Zn. Combining this with the photoemission analysis of the Ti 2p core level and Zn L 3 (L 2 )M 45 M 45 Auger transition, it is established that the Ti/ZnO reaction is of the form Ti + 2ZnO → TiO 2 + 2Zn on ZnO(0001)-Zn and Ti + yZnO → TiZn x O y + (y - x)Zn on ZnO(0001[combining macron])-O. Consistently, upon annealing thicker Ti adlayers, the metallic zinc is removed to leave ZnO(0001)-Zn surfaces covered with a TiO 2 -like phase and ZnO(0001[combining macron])-O surfaces covered with a defined (Ti, Zn, O) compound. Finally, a difference in the activation temperature between the O-terminated (500 K) and Zn-terminated (700 K) surfaces is observed, which is tentatively explained by different electric fields in the space charge layer at ZnO surfaces.

  12. Room temperature photoluminescence properties of ZnO nanorods grown by hydrothermal reaction

    Energy Technology Data Exchange (ETDEWEB)

    Iwan, S., E-mail: iwan-sugihartono@unj.ac.id [Jurusan Fisika, FMIPA-UNJ, Rawamangun, Jakarta (Indonesia); Prodi Ilmu Material, Departemen Fisika, FMIPA, Universitas Indonesia, Kampus UI Depok (Indonesia); Fauzia, Vivi [Prodi Ilmu Material, Departemen Fisika, FMIPA, Universitas Indonesia, Kampus UI Depok (Indonesia); Umar, A. A. [Institute of Microengineering and Nanoelectronics, Universiti Kebangsaan Malaysia, UKM Bangi, Selangor (Malaysia); Sun, X. W. [School of Electrical & Electronic Engineering, Nanyang Technological University, Nanyang Avenue (Singapore)

    2016-04-19

    Zinc oxide (ZnO) nanorods were fabricated by a hydrothermal reaction on silicon (Si) substrate at 95 °C for 6 hours. The ZnO seed layer was fabricated by depositing ZnO thin films on Si substrates by ultrasonic spray pyrolisis (USP). The annealing effects on crystal structure and optical properties of ZnO nanorods were investigated. The post-annealing treatment was performed at 800 °C with different environments. The annealed of ZnO nanorods were characterized by X-ray diffraction (XRD) and photoluminescence (PL) in order to analyze crystal structure and optical properties, respectively. The results show the orientations of [002], [101], [102], and [103] diffraction peaks were observed and hexagonal wurtzite structure of ZnO nanorods were vertically grown on Si substrates. The room temperature PL spectra show ultra-violet (UV) and visible emissions. The annealed of ZnO nanorods in vacuum condition (3.8 × 10{sup −3} Torr) has dominant UV emission. Meanwhile, non-annealed of ZnO nanorods has dominant visible emission. It was expected that the annealed of ZnO in vacuum condition suppresses the existence of native defects in ZnO nanorods.

  13. Effect of ALD surface treatment on structural and optical properties of ZnO nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Jin-Tak [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Obang-dong, Gimhae, Gyeongnam 621-749 (Korea, Republic of); Ryu, Hyukhyun, E-mail: hhryu@inje.ac.kr [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Obang-dong, Gimhae, Gyeongnam 621-749 (Korea, Republic of); Lee, Won-Jae [Department of Materials and Components Engineering, Dong-Eui University, 995 Eomgwangno, Busanjin-gu, Busan 614-714 (Korea, Republic of)

    2013-07-01

    In this study, we report on the improvement of the optical and structural properties of ZnO nanorods using atomic layer deposition (ALD) on seed ZnO nanorods. After the initial growth of ZnO seed nanorods by hydrothermal synthesis for 1 h, a ZnO layer with a thickness of 10 nm was deposited on the initial ZnO seed nanorods using ALD. Then ZnO was further grown by hydrothermal synthesis for 4 h. The samples were characterized using room temperature photoluminescence (PL), field emission-scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). From this experiment, it was found that the ZnO nanorods with the ALD surface treatment show improved optical and structural properties when compared with the ZnO nanorods grown only by hydrothermal synthesis. The ZnO nanorods with the ALD surface treatment show about 2.7 times higher XRD (0 0 2) peak intensity, about 2.64 times higher PL NBE peak intensity, and about 3.1 times better NBE/DLE ratio than the ZnO nanorods without an ALD surface treatment.

  14. Radio-frequency magnetron sputtering and wet thermal oxidation of ZnO thin film

    International Nuclear Information System (INIS)

    Liu, H. F.; Chua, S. J.; Hu, G. X.; Gong, H.; Xiang, N.

    2007-01-01

    The authors studied the growth and wet thermal oxidation (WTO) of ZnO thin films using a radio-frequency magnetron sputtering technique. X-ray diffraction reveals a preferred orientation of [1010]ZnO(0002)//[1120]Al 2 O 3 (0002) coexisted with a small amount of ZnO (1011) and ZnO (1013) crystals on the Al 2 O 3 (0001) substrate. The ZnO (1011) and ZnO (1013) crystals, as well as the in-plane preferred orientation, are absent from the growth of ZnO on the GaAs(001) substrate. WTO at 550 deg. C improves the crystalline and the photoluminescence more significantly than annealing in air, N 2 and O 2 ambient; it also tends to convert the crystal from ZnO (1011) and ZnO (1013) to ZnO (0002). The evolution of the photoluminescence upon WTO and annealing reveals that the green and orange emissions, centered at 520 and 650 nm, are likely originated from oxygen vacancies and oxygen interstitials, respectively; while the 420 nm emission, which is very sensitive to the postgrowth thermal processing regardless of the substrate and the ambient gas, is likely originated from the surface-state related defects

  15. Structural interpretation of chemically synthesized ZnO nanorod and its application in lithium ion battery

    International Nuclear Information System (INIS)

    Kundu, Samapti; Sain, Sumanta; Yoshio, Masaki; Kar, Tanusree; Gunawardhana, Nanda; Pradhan, Swapan Kumar

    2015-01-01

    Graphical abstract: - Highlights: • ZnO nanorods are synthesized at room temperature via a simple chemical route. • Growth direction of ZnO nanorods has been determined along 〈0 0 2〉. • ZnO nanorods constructed anode shows a high discharge capacity in first cycle. • It retains good reversible capacity compared to other ZnO morphologies. - Abstract: ZnO nanorods are synthesized at room temperature via a simple chemical route without using any template or capping agent and its importance is evaluated as a suitable candidate for anode material in lithium ion battery. Structural and microstructure characterizations of these nanorods are made by analyzing the X-ray diffraction data employing the Rietveld method of powder structure refinement. It reveals that the ZnO nanorods are grown up with a preferred orientation and elongated along 〈0 0 2〉. FESEM images reveal that these uniform cylindrical shaped nanorods are of different lengths and diameters. These synthesized ZnO nanorods are tested as an anode material for lithium ion batteries. The nano grain size of the ZnO rods results in less volume expansion and/or contraction during the alloying/de-alloying process and causes in good cyclability. In addition, synthesized ZnO nanorods deliver high charge/discharge capacities compared to other reported ZnO materials

  16. Structural interpretation of chemically synthesized ZnO nanorod and its application in lithium ion battery

    Energy Technology Data Exchange (ETDEWEB)

    Kundu, Samapti; Sain, Sumanta [Materials Science Division, Department of Physics, The University of Burdwan, Golapbag, Burdwan 713104, West Bengal (India); Yoshio, Masaki [Advanced Research and Education Centre, Saga University, 1341 Yoga-machi, Saga 840-0047 (Japan); Kar, Tanusree [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, West Bengal (India); Gunawardhana, Nanda, E-mail: nandagunawardhana@pdn.ac.lk [International Research Centre, Senate Building, University of Peradeniya, Peradeniya 20400 (Sri Lanka); Pradhan, Swapan Kumar, E-mail: skpradhan@phys.buruniv.ac.in [Materials Science Division, Department of Physics, The University of Burdwan, Golapbag, Burdwan 713104, West Bengal (India)

    2015-02-28

    Graphical abstract: - Highlights: • ZnO nanorods are synthesized at room temperature via a simple chemical route. • Growth direction of ZnO nanorods has been determined along 〈0 0 2〉. • ZnO nanorods constructed anode shows a high discharge capacity in first cycle. • It retains good reversible capacity compared to other ZnO morphologies. - Abstract: ZnO nanorods are synthesized at room temperature via a simple chemical route without using any template or capping agent and its importance is evaluated as a suitable candidate for anode material in lithium ion battery. Structural and microstructure characterizations of these nanorods are made by analyzing the X-ray diffraction data employing the Rietveld method of powder structure refinement. It reveals that the ZnO nanorods are grown up with a preferred orientation and elongated along 〈0 0 2〉. FESEM images reveal that these uniform cylindrical shaped nanorods are of different lengths and diameters. These synthesized ZnO nanorods are tested as an anode material for lithium ion batteries. The nano grain size of the ZnO rods results in less volume expansion and/or contraction during the alloying/de-alloying process and causes in good cyclability. In addition, synthesized ZnO nanorods deliver high charge/discharge capacities compared to other reported ZnO materials.

  17. Structure and photoluminescence properties of Ag-coated ZnO nano-needles

    Energy Technology Data Exchange (ETDEWEB)

    Li Xiaozhu, E-mail: Lixiaozhu1019@21cn.com [Department of Physics, Shaoguan University, Shaoguan, Guangdong 512005 (China) and Department of Physics and Key Laboratory of Acoustic and Photonic Materials and Devices of Ministry of Education, Wuhan University, Wuhan, Hubei 430072 (China); Wang Yongqian [Engineering Research Center of Nano-Geomaterials of Ministry of Education (China University of Geosciences), Wuhan, Hubei 430074 (China)

    2011-05-12

    Highlights: > ZnO nano-needles were synthesized by thermal oxidation. > Their surfaces were coated with Ag by pulse electro-deposition technique. > The uncoated and coated ZnO nano-needles were characterized. > The results showed that the prepared ZnO nano-needles have been coated with Ag successfully. > The photoluminescence spectrums of ZnO nano-needles with Ag-coated and uncoated were analyzed, finding that the Ag-coated ZnO nano-needles can increase the absorption of UV light. - Abstract: A large number of zinc oxide (ZnO) nano-needles were synthesized by thermal oxidation of pure zinc. The surfaces of ZnO nano-needles were coated with a layer of Ag by pulse electro-deposition technique. The uncoated and coated ZnO nano-needles were characterized by using the X-ray diffraction and the scanning electron microscope (SEM). The results showed that the uncoated samples were close-packed hexagonal structure, which showed needle-like morphology. Their average diameter is about 40 nm, lengths up to 5 {mu}m. At the same time we observed that the prepared ZnO nano-needles have been coated with Ag successfully. The photoluminescence spectrums of ZnO nano-needles with Ag-coated and uncoated were analyzed, finding that the uncoated ZnO nano-needles have two fluorescence peaks at 388 nm and 470.8 nm, respectively, the relative intensity of 143.4 and 93.61; and the Ag-coated ZnO nano-needles showed a pair of strong peaks at 387.4 nm and 405.2 nm, the relative intensity of 1366 and 1305, respectively, indicating that the Ag-coated ZnO nano-needles can increase the absorption of UV light.

  18. Structure and photoluminescence properties of Ag-coated ZnO nano-needles

    International Nuclear Information System (INIS)

    Li Xiaozhu; Wang Yongqian

    2011-01-01

    Highlights: → ZnO nano-needles were synthesized by thermal oxidation. → Their surfaces were coated with Ag by pulse electro-deposition technique. → The uncoated and coated ZnO nano-needles were characterized. → The results showed that the prepared ZnO nano-needles have been coated with Ag successfully. → The photoluminescence spectrums of ZnO nano-needles with Ag-coated and uncoated were analyzed, finding that the Ag-coated ZnO nano-needles can increase the absorption of UV light. - Abstract: A large number of zinc oxide (ZnO) nano-needles were synthesized by thermal oxidation of pure zinc. The surfaces of ZnO nano-needles were coated with a layer of Ag by pulse electro-deposition technique. The uncoated and coated ZnO nano-needles were characterized by using the X-ray diffraction and the scanning electron microscope (SEM). The results showed that the uncoated samples were close-packed hexagonal structure, which showed needle-like morphology. Their average diameter is about 40 nm, lengths up to 5 μm. At the same time we observed that the prepared ZnO nano-needles have been coated with Ag successfully. The photoluminescence spectrums of ZnO nano-needles with Ag-coated and uncoated were analyzed, finding that the uncoated ZnO nano-needles have two fluorescence peaks at 388 nm and 470.8 nm, respectively, the relative intensity of 143.4 and 93.61; and the Ag-coated ZnO nano-needles showed a pair of strong peaks at 387.4 nm and 405.2 nm, the relative intensity of 1366 and 1305, respectively, indicating that the Ag-coated ZnO nano-needles can increase the absorption of UV light.

  19. Hydrothermal growth and characterizations of dandelion-like ZnO nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Kale, Rohidas B., E-mail: rb_kale@yahoo.co.in [Department of Physics, The Institute of Science, Madam Cama Road, Mumbai 400 032, (M.S.) (India); Lu, Shih-Yuan, E-mail: sylu@nthu.edu.tw [Department of Chemical Engineering, National Tsing-Hua University, Hsinchu 30013, Taiwan, ROC (China)

    2013-12-05

    Highlights: •The simple, low cost, environmental benign hydrothermal method has been used to synthesize ZnO nanostructure. •The SEM images reveal the interesting 3D dandelion-like morphology of synthesized ZnO nanostructure. The SAED pattern and HRTEM study confirms that the ZnO nanorods are single crystalline. •Change in experimental conditions dramatically changes the morphologies of the synthesized ZnO. •The room temperature PL study reveals strong band edge emission along with much weaker defect related blue emission. •The reaction and growth mechanism of ZnO nanostructure is also discussed. -- Abstract: Three dimensional (3D) ZnO nanostructures have been synthesized by using a facile low-cost hydrothermal method under mild conditions. Aqueous alkaline ammonia solution of Zn(CH{sub 3}COO){sub 2} is used to grow 3D ZnO nanostructures. The X-ray diffraction (XRD) study reveals the well crystallized hexagonal structure of ZnO. SEM observations depict that the ZnO product grows in the form of nanorods united together to form 3D dandelion-like nanostructures. The elemental analysis using EDAX technique confirms the stoichiometry of the ZnO nanorods. The product exhibits special optical properties with red-shifts in optical absorption peak (376 nm) as compared with those of conventional ZnO nanorods. PL spectra show emission peak (396 nm) at the near band-edge and peak (464 nm) originated from defects states that are produced during the hydrothermal growth. TEM and SAED results reveal single crystalline structure of the synthesized product. The reaction and growth mechanisms on the morphological evolution of the ZnO nanostructures are discussed. The morphology of ZnO product is investigated by varying the reaction time, temperature, and type of complexing reagent.

  20. Synthesis, characterization and photocatalysis enhancement of Eu2O3-ZnO mixed oxide nanoparticles

    Science.gov (United States)

    Mohamed, W. S.; Abu-Dief, Ahmed M.

    2018-05-01

    Pure ZnO nanoparticles (NPs) and mixed Eu2O3 and ZnO NPs with different Eu2O3 ratios (5%, 10%, and 15%) were synthesized by a precipitation method under optimum conditions. The synthesized samples were characterized by means of X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and UV-vis diffuse reflectance spectroscopy. The as-synthesized ZnO NPs exhibit high phase purity and a highly crystalline wurtzite ZnO structure. The mixed Eu2O3 and ZnO NPs exhibit a Eu2O3 zinc blend phase in addition to the wurtzite phase of pure ZnO, confirming the high purity and good crystallinity of the as-synthesized samples. The high-purity formation of ZnO and Eu2O3 phases was confirmed by FTIR and Raman spectra. Microstructural analysis by SEM and TEM confirmed the sphere-like morphology with different particle sizes (29-40 nm) of the as-synthesized samples. The photocatalytic activities of pure ZnO NPs and mixed Eu2O3 and ZnO NPs for the degradation of methylene blue were evaluated under ultraviolet (UV) irradiation. The results show that Eu2O3 plays an important role in the enhancement of the photocatalytic properties of ZnO NPs. We found that mixed 5% Eu2O3 and ZnO NPs exhibit the highest photocatalytic activity (degradation efficiency of 96.5% after 180 min of UV irradiation) as compared with pure ZnO NPs (degradation efficiency of 80.3% after 180 min of UV irradiation). The increased photocatalytic activity of the optimum mixed Eu2O3 and ZnO NPs is due to the high crystallinity, high surface area with small particle size, and narrow energy gap.

  1. Enormous enhancement of ZnO nanorod photoluminescence

    International Nuclear Information System (INIS)

    Wang, Y.H.; Duan, W.J.; Wu, Z.L.; Zheng, D.; Zhou, X.W.; Zhou, B.Y.; Dai, L.J.; Wang, Y.S.

    2012-01-01

    ZnO nanorod arrays were grown on quartz slices in the aqueous solution of zinc acetate and hexamethylenetetramine at 90 °C. Then ZnO:Mg shells were epitaxially grown on the nanorods to form core/shell structures in the aqueous solution of zinc acetate, magnesium acetate and hexamethylenetetramine at the same temperature. Effects of the shells and UV laser beam irradiation on the crystal structure and photoluminescence properties of ZnO nanorods were studied. ZnO:Mg shells suppress the green emission and enhance the UV emission intensity of the nanorods by 38 times. Enhancement of the UV emission depends on the Mg content in the shells. Short time UV laser beam irradiation could improve ZnO nanorod emission efficiently. The UV emission intensity of ZnO nanorods is enhanced by 71 times by capping and subsequent UV laser beam irradiation. - Highlights: ► ZnO nanorod arrays were grown on quartz slices in solution at 90 °C. ► The nanorods were capped by ZnO:Mg layers to form core/shell structures. ► ZnO:MgO shells suppress the green emission and enhance the UV emission intensity by 38 times. ► The enhancement depends on the Mg content in the shells. ► Exposing the nanorods to 325 laser beam improves the UV emission efficiently. ► Capping and 325 nm laser beam irradiation could enhance the nanorod UV emission intensity by 71 times.

  2. Function of NaOH hydrolysis in electrospinning ZnO nanofibers via using polylactide as templates

    International Nuclear Information System (INIS)

    Liu, Mengzhu; Wang, Yongpeng; Cheng, Zhiqiang; Song, Lihua; Zhang, Mingyue; Hu, Meijuan; Li, Junfeng

    2014-01-01

    Graphical abstract: - Highlights: • PLA was used as templates to electrospin ZnO nanofibers for the first time. • Without NaOH hydrolysis, only ZnO film was prepared. • Under function of NaOH, ZnO nanofibers were obtained. • The function of NaOH was discussed. • ZnO nanofibers showed much higher photocatalytical efficiency than ZnO film. - Abstract: Mixture of polylactide (8 wt%), zinc acetate (6 wt%) and hexafluoroisopropanol was first used as electrospinning solution to fabricate ZnO nanofibers. Unfortunately, after direct calcination of the precursor polylactide/zinc acetate nanofibers, only ZnO film was prepared. Surprisingly, when the precursor fibers were pre-hydrolyzed with NaOH, ZnO nanofibers with diameter of 678 nm were obtained. The mechanism analysis showed that the preserve of fiber structure was attributed to the formation of zinc polylactic acid in the process of hydrolyzation. After characterized by scanning electron microscope and transmission electron microscope, the ZnO film was found to be an aggregation of irregular nanoparticles and the ZnO nanofiber was a necklace-like arrangement of cylindrical grains. X-ray diffraction and photoluminescence measurements indicated that the crystalline quality of the ZnO nanofibers was higher than the film. Furthermore, photocatalytic performance of the ZnO samples was investigated. Comparing with ZnO film, ZnO nanofibers exhibited much higher activity

  3. Green method for producing hierarchically assembled pristine porous ZnO nanoparticles with narrow particle size distribution

    International Nuclear Information System (INIS)

    Escobedo-Morales, A.; Téllez-Flores, D.; Ruiz Peralta, Ma. de Lourdes; Garcia-Serrano, J.; Herrera-González, Ana M.; Rubio-Rosas, E.; Sánchez-Mora, E.; Olivares Xometl, O.

    2015-01-01

    A green method for producing pristine porous ZnO nanoparticles with narrow particle size distribution is reported. This method consists in synthesizing ZnO 2 nanopowders via a hydrothermal route using cheap and non-toxic reagents, and its subsequent thermal decomposition at low temperature under a non-protective atmosphere (air). The morphology, structural and optical properties of the obtained porous ZnO nanoparticles were studied by means of powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and nitrogen adsorption–desorption measurements. It was found that after thermal decomposition of the ZnO 2 powders, pristine ZnO nanoparticles are obtained. These particles are round-shaped with narrow size distribution. A further analysis of the obtained ZnO nanoparticles reveals that they are hierarchical self-assemblies of primary ZnO particles. The agglomeration of these primary particles at the very early stage of the thermal decomposition of ZnO 2 powders provides to the resulting ZnO nanoparticles a porous nature. The possibility of using the synthesized porous ZnO nanoparticles as photocatalysts has been evaluated on the degradation of rhodamine B dye. - Highlights: • A green synthesis method for obtaining porous ZnO nanoparticles is reported. • The obtained ZnO nanoparticles have narrow particle size distribution. • This method allows obtaining pristine ZnO nanoparticles avoiding unintentional doping. • A growth mechanism for the obtained porous ZnO nanoparticles is proposed

  4. Growth and characterization of polar and nonpolar ZnO film grown on sapphire substrates by using atomic layer deposition

    International Nuclear Information System (INIS)

    Kim, Ki-Wook; Son, Hyo-Soo; Choi, Nak-Jung; Kim, Jihoon; Lee, Sung-Nam

    2013-01-01

    We investigated the electrical and the optical properties of polar and nonpolar ZnO films grown on sapphire substrates with different crystallographic planes. High resolution X-ray results revealed that polar c-plane (0001), nonpolar m-plane (10-10) and a-plane (11-20) ZnO thin films were grown on c-plane, m- and r-sapphire substrates by atomic layer deposition, respectively. Compared with the c-plane ZnO film, nonpolar m-plane and a-plane ZnO films showed smaller surface roughness and anisotropic surface structures. Regardless of ZnO crystal planes, room temperature photoluminescence spectra represented two emissions which consisted of the near bandedge (∼ 380 nm) and the deep level emission (∼ 500 nm). The a-plane ZnO films represented better optical and electrical properties than c-plane ZnO, while m-plane ZnO films exhibited poorer optical and electrical properties than c-plane ZnO. - Highlights: • Growth and characterization of a-, c- and m-plane ZnO film by atomic layer deposition. • The a-plane ZnO represented better optical and electrical properties than c-plane ZnO. • The m-plane ZnO exhibited poorer optical and electrical properties than c-plane ZnO

  5. PREFACE: Nuclear Cluster Conference; Cluster'07

    Science.gov (United States)

    Freer, Martin

    2008-05-01

    The Cluster Conference is a long-running conference series dating back to the 1960's, the first being initiated by Wildermuth in Bochum, Germany, in 1969. The most recent meeting was held in Nara, Japan, in 2003, and in 2007 the 9th Cluster Conference was held in Stratford-upon-Avon, UK. As the name suggests the town of Stratford lies upon the River Avon, and shortly before the conference, due to unprecedented rainfall in the area (approximately 10 cm within half a day), lay in the River Avon! Stratford is the birthplace of the `Bard of Avon' William Shakespeare, and this formed an intriguing conference backdrop. The meeting was attended by some 90 delegates and the programme contained 65 70 oral presentations, and was opened by a historical perspective presented by Professor Brink (Oxford) and closed by Professor Horiuchi (RCNP) with an overview of the conference and future perspectives. In between, the conference covered aspects of clustering in exotic nuclei (both neutron and proton-rich), molecular structures in which valence neutrons are exchanged between cluster cores, condensates in nuclei, neutron-clusters, superheavy nuclei, clusters in nuclear astrophysical processes and exotic cluster decays such as 2p and ternary cluster decay. The field of nuclear clustering has become strongly influenced by the physics of radioactive beam facilities (reflected in the programme), and by the excitement that clustering may have an important impact on the structure of nuclei at the neutron drip-line. It was clear that since Nara the field had progressed substantially and that new themes had emerged and others had crystallized. Two particular topics resonated strongly condensates and nuclear molecules. These topics are thus likely to be central in the next cluster conference which will be held in 2011 in the Hungarian city of Debrechen. Martin Freer Participants and Cluster'07

  6. Sparking deposited ZnO nanoparticles as double-layered photoelectrode in ZnO dye-sensitized solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Hongsith, Kritsada [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics (ThEP center), CHE, Bangkok 10400 (Thailand); Hongsith, Niyom [Thailand Center of Excellence in Physics (ThEP center), CHE, Bangkok 10400 (Thailand); School of Science, University of Phayao, Phayao 56000 (Thailand); Wongratanaphisan, Duangmanee; Gardchareon, Atcharawon; Phadungdhitidhada, Surachet [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics (ThEP center), CHE, Bangkok 10400 (Thailand); Singjai, Pisith [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Choopun, Supab, E-mail: supab99@gmail.com [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics (ThEP center), CHE, Bangkok 10400 (Thailand)

    2013-07-31

    The semiconducting layers of ZnO nanoparticles (ZN), ZnO powder (ZP) and ZnO nanopowder (ZNP) were designed and fabricated for double-layered semiconducting photoelectrode in dye-sensitized solar cells (DSSCs). The under-layer was ZN, which was prepared by simple and cost-effective sparking technique onto F-doped tin oxide (FTO) glass substrate and its thickness was controlled by number of sparking cycles for 0, 10, 25, 50 and 100 rounds under atmospheric pressure. Then, ZP or ZNP was screened on to ZN to form double-layered photoelectrode. Here, the DSSC structures were FTO/double-layered ZnO/Eosin Y/electrolyte/Pt counterelectrode. The best results of DSSCs were observed with J{sub sc} of 4.71 mA/cm{sup 2} and 5.56 mA/cm{sup 2} and photoconversion efficiency of 1.11% and 1.14% at 50 sparking cycles for ZP and ZNP over-layers, respectively. The efficiency enhancement can be explained by combination effects of electron and light scattering. Moreover, the modified equation of short circuit current density was developed and effectively used to explain the efficiency enhancement. - Highlights: • Effect of under-layer thickness is investigated. • Simple and cost-effective sparking technique is used for ZnO nanoparticles. • Efficiency enhancement can be explained by both electron and light scattering. • Modified equation of short circuit current density was developed for enhancement.

  7. Sparking deposited ZnO nanoparticles as double-layered photoelectrode in ZnO dye-sensitized solar cell

    International Nuclear Information System (INIS)

    Hongsith, Kritsada; Hongsith, Niyom; Wongratanaphisan, Duangmanee; Gardchareon, Atcharawon; Phadungdhitidhada, Surachet; Singjai, Pisith; Choopun, Supab

    2013-01-01

    The semiconducting layers of ZnO nanoparticles (ZN), ZnO powder (ZP) and ZnO nanopowder (ZNP) were designed and fabricated for double-layered semiconducting photoelectrode in dye-sensitized solar cells (DSSCs). The under-layer was ZN, which was prepared by simple and cost-effective sparking technique onto F-doped tin oxide (FTO) glass substrate and its thickness was controlled by number of sparking cycles for 0, 10, 25, 50 and 100 rounds under atmospheric pressure. Then, ZP or ZNP was screened on to ZN to form double-layered photoelectrode. Here, the DSSC structures were FTO/double-layered ZnO/Eosin Y/electrolyte/Pt counterelectrode. The best results of DSSCs were observed with J sc of 4.71 mA/cm 2 and 5.56 mA/cm 2 and photoconversion efficiency of 1.11% and 1.14% at 50 sparking cycles for ZP and ZNP over-layers, respectively. The efficiency enhancement can be explained by combination effects of electron and light scattering. Moreover, the modified equation of short circuit current density was developed and effectively used to explain the efficiency enhancement. - Highlights: • Effect of under-layer thickness is investigated. • Simple and cost-effective sparking technique is used for ZnO nanoparticles. • Efficiency enhancement can be explained by both electron and light scattering. • Modified equation of short circuit current density was developed for enhancement

  8. Study of copper doping effects on structural, optical and electrical properties of sprayed ZnO thin films

    International Nuclear Information System (INIS)

    Mhamdi, A.; Mimouni, R.; Amlouk, A.; Amlouk, M.; Belgacem, S.

    2014-01-01

    Highlights: • The sprayed Cu-doped ZnO thin layers films were well crystallised in hexagonal wurtzite phase. • Nanoncrystallites on clusters were observed whose density decreases especially at 2% Cu content. • This parallel circuit R–C represents the contribution of the grain boundaries delineating the oriented columnar microcrystallites along c-axis. - Abstract: Copper-doped zinc oxide thin films (ZnO:Cu) at different percentages (1–3%) were deposited on glass substrates using a chemical spray technique. The effect of Cu concentration on the structural, morphology and optical properties of the ZnO:Cu thin films were investigated. XRD analysis revealed that all films consist of single phase ZnO and were well crystallised in würtzite phase with the crystallites preferentially oriented towards (0 0 2) direction parallel to c-axis. The Film surface was analyzed by contact atomic force microscopy (AFM) in order to understand the effect of the doping on the surface structure. Doping by copper resulted in a slight decrease in the optical band gap energy of the films and a noticeably change in optical constants. From the spectroscopy impedance analysis we investigated the frequency relaxation phenomenon and the circuit equivalent circuit of such thin layers. Finally, all results have been discussed in terms of the copper doping concentration

  9. N{sup +} ion-implantation-induced defects in ZnO studied with a slow positron beam

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Z Q [Japan Atomic Energy Research Institute, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan (Japan); Sekiguchi, T [Nanomaterials Laboratory, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Yuan, X L [Nanomaterials Laboratory, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Maekawa, M [Japan Atomic Energy Research Institute, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan (Japan); Kawasuso, A [Japan Atomic Energy Research Institute, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan (Japan)

    2004-01-21

    Undoped ZnO single crystals were implanted with multiple-energy N{sup +} ions ranging from 50 to 380 keV with doses from 10{sup 12} to 10{sup 14} cm{sup -2}. Positron annihilation measurements show that vacancy defects are introduced in the implanted layers. The concentration of the vacancy defects increases with increasing ion dose. The annealing behaviour of the defects can be divided into four stages, which correspond to the formation and recovery of large vacancy clusters and the formation and disappearance of vacancy-impurity complexes, respectively. All the implantation-induced defects are removed by annealing at 1200 deg. C. Cathodoluminescence measurements show that the ion-implantation-induced defects act as nonradiative recombination centres to suppress the ultraviolet (UV) emission. After annealing, these defects disappear gradually and the UV emission reappears, which coincides with positron annihilation measurements. Hall measurements reveal that after N{sup +} implantation, the ZnO layer still shows n-type conductivity.

  10. The origin of room temperature ferromagnetism mediated by Co–VZn complexes in the ZnO grain boundary

    KAUST Repository

    Devi, Assa Aravindh Sasikala

    2016-05-20

    Ferromagnetism in polycrystalline ZnO doped with Co has been observed to be sustainable in recent experiments. We use first-principle calculations to show that Co impurities favorably substitute at the grain boundary (GB) rather than in the bulk. We reveal that room-temperature ferromagnetism (RTFM) at the Co-doped ZnO GB in the presence of Zn vacancies is due to ferromagnetic exchange coupling of a pair of closely associated Co atoms in the GB, with a ferromagnetic exchange coupling energy of ∼300 meV, which is in contrast to a previous study that suggested the O vacancy-Co complex induced ferromagnetism. Electronic structure analysis was used to predict the exchange coupling mechanism, showing that the hybridization of O p states with Co and Zn d states enhances the magnetic polarization originating from the GB. Our results indicate that RTFM originates from Co clusters at interfaces or in GBs. © 2016 The Royal Society of Chemistry.

  11. Analysis of heavy metals in the re-suspended road dusts from different functional areas in Xi'an, China.

    Science.gov (United States)

    Wang, Qian; Lu, Xinwei; Pan, Huiyun

    2016-10-01

    A study on heavy metal pollution was undertaken in the re-suspended road dusts from different functional areas in Xi'an City of China to investigate the impacts of human activities and land uses on urban environment. The concentrations of Co, Cr, Cu, Mn, Ni, Pb, V, and Zn were determined using X-ray fluorescence spectrometry, and their accumulations were analyzed using enrichment factor. Correlation analysis, principal component analysis, and cluster analysis, combined with the concentration property and enrichment factor, were used to identify the possible sources of heavy metals investigated. The investigated re-suspended road dusts had Co, Cr, Cu, Pb, and Zn concentrations higher than background levels. Samples from different functional areas had diverse heavy metal concentration levels. Co, Cr, Cu, Pb, and Zn presented moderate/significant enrichment in the samples. The source analyses indicated that Mn, Ni, V, Pb, and Zn had the mixed sources of nature and traffic, Cr and Cu mainly originated from traffic source, while Co was primarily derived from construction source. Traffic and construction activities had a significant impact on urban environment. This preliminary research provides a valuable basis for urban environment protection and management.

  12. Atomic layer deposition of B-doped ZnO using triisopropyl borate as the boron precursor and comparison with Al-doped ZnO

    NARCIS (Netherlands)

    Garcia - Alonso, D.; Potts, S.E.; Helvoirt, van C.A.A.; Verheijen, M.A.; Kessels, W.M.M.

    2015-01-01

    Doped ZnO films are an important class of transparent conductive oxides, with many applications demanding increased growth control and low deposition temperatures. Therefore, the preparation of B-doped ZnO films by atomic layer deposition (ALD) at 150 °C was studied. The B source was triisopropyl

  13. Optical properties and photocatalytic activities of spherical ZnO and flower-like ZnO structures synthesized by facile hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Yongling [Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164 (China); Li, Zhongyu, E-mail: zhongyuli@mail.tsinghua.edu.cn [Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164 (China); Changzhou Expansion New Stuff Technology Limited Company, Changzhou 213122 (China); Jilin Institute of Chemical Technology, Jilin 132022 (China); Xu, Song [Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164 (China); Han, Dandan; Lu, Dayong [Jilin Institute of Chemical Technology, Jilin 132022 (China)

    2013-10-25

    Highlights: •Spherical ZnO and flower-like ZnO were prepared via a facile hydrothermal method. •The as-prepared ZnO showed high photocatalytic activity over MO degradation. •The as-prepared ZnO were well crystallized and exhibited good optical properties. -- Abstract: Spherical ZnO and flower-like ZnO were prepared by facile hydrothermal method at 180 °C and 160 °C, respectively. The as-prepared samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and UV–vis diffuse reflectance spectroscopy (DRS) spectra. The optical properties of as-prepared sample, such as photoluminescence (PL) spectra and Raman spectra were studied. The photocatalytic activities of the as-prepared ZnO particles were investigated by degrading the methyl orange (MO) under UV light irradiation. The photocatalytic studies showed that the organic pollutants have been almost completely degraded and mineralized after irradiation of the UV light. These results indicated that the as-prepared ZnO particles exhibited good optical properties and high photocatalytic activities.

  14. Water and suspended sediment dynamics in the Sungai Selangor estuary

    International Nuclear Information System (INIS)

    Abdul Kadir Ishak; Kamarudin Samuding; Nazrul Hizam Yusoff

    2000-01-01

    Observations of salinity, temperature, suspended sediment concentration (SSC) and tidal current velocity were made in the lower and along the longitudinal axis sungai Selangor estuary over near-spring cycles. The variations of these parameters at the measurement stations and along the channel are presented to illustrate the water and sediment dynamics in the estuary. The results shows that the Sungai Selangor estuary changes from a partially-mixed type during neaps to a well-mixed one during springs. promoted by stronger tidal energy during the higher tidal ranges. The strong neap density stratification is also promoted by the high river discharges during the measurement period maximum concentration of suspended sediment 2000 mg,'/) occurs during maximum current velocities both during flood and ebb. The maximum salinity was achieved during high water slack but the salt water was totally flushed out of estuary during low water springs. The longitudinal axis measurement indicates that a partially-developed zone of turbidity maximum with a sediment concentration over 1000 mg/l was observed at the limit of salt water intrusion in salinity range less than 1 ppt. Tidal pumping as oppose to the estuarine circulation is the more dominant factor in the maximum formation as the salt water is totally excluded at low water. (author)

  15. Self-suspended permanent magnetic FePt ferrofluids

    KAUST Repository

    Dallas, Panagiotis

    2013-10-01

    We present the synthesis and characterization of a new class of self-suspended ferrofluids that exhibit remanent magnetization at room temperature. Our system relies on the chemisorption of a thiol-terminated ionic liquid with very low melting point on the surface of L10 FePt nanoparticles. In contrast, all types of ferrofluids previously reported employ either volatile solvents as the suspending media or superparamagnetic iron oxide nanoparticles (that lacks permanent magnetization) as the inorganic component. The ferrofluids do not show any sign of flocculation or phase separation, despite the strong interactions between the magnetic nanoparticles due to the strong chemisorption of the ionic liquid as evidenced by Raman spectroscopy and thermal analysis. Composites with high FePt loading (40 and 70. wt%) exhibit a pseudo solid-like rheological behavior and high remanent magnetization values (10.1 and 12.8. emu/g respectively). At lower FePt loading (12. wt%) a liquid like behavior is observed and the remanent and saturation magnetization values are 3.5 and 6.2. emu/g, respectively. The magnetic and flow properties of the materials can be easily fine tuned by controlling the type and amount of FePt nanoparticles used. © 2013 Elsevier Inc.

  16. Suspended animation-like state protects mice from lethal hypoxia.

    Science.gov (United States)

    Blackstone, Eric; Roth, Mark B

    2007-04-01

    Joseph Priestley observed the high burn rate of candles in pure oxygen and wondered if people would "live out too fast" if we were in the same environment. We hypothesize that sulfide, a natural reducer of oxygen that is made in many cell types, acts as a buffer to prevent unrestricted oxygen consumption. To test this, we administered sulfide in the form of hydrogen sulfide (H2S) to mice (Mus musculus). As we have previously shown, H2S decreases the metabolic rate of mice by approximately 90% and induces a suspended animation-like state. Mice cannot survive for longer than 20 min when exposed to 5% oxygen. However, if mice are first put into a suspended animation-like state by a 20-min pretreatment with H2S and then are exposed to low oxygen, they can survive for more than 6.5 h in 5% oxygen with no apparent detrimental effects. In addition, if mice are exposed to a 20-min pretreatment with H2S followed by 1 h at 5% oxygen, they can then survive for several hours at oxygen tensions as low as 3%. We hypothesize that prior exposure to H2S reduces oxygen demand, therefore making it possible for the mice to survive with low oxygen supply. These results suggest that H2S may be useful to prevent damage associated with hypoxia.

  17. Elastic properties of suspended multilayer WSe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Rui, E-mail: rui.zhang@ed.ac.uk; Cheung, Rebecca [Scottish Microelectronics Centre, Alexander Crum Brown Road, The University of Edinburgh, King' s Buildings, Edinburgh EH9 3FF (United Kingdom); Koutsos, Vasileios [Institute for Materials and Processes, School of Engineering, The University of Edinburgh, King' s Buildings, Edinburgh EH9 3FB (United Kingdom)

    2016-01-25

    We report the experimental determination of the elastic properties of suspended multilayer WSe{sub 2}, a promising two-dimensional (2D) semiconducting material combined with high optical quality. The suspended WSe{sub 2} membranes have been fabricated by mechanical exfoliation of bulk WSe{sub 2} and transfer of the exfoliated multilayer WSe{sub 2} flakes onto SiO{sub 2}/Si substrates pre-patterned with hole arrays. Then, indentation experiments have been performed on these membranes with an atomic force microscope. The results show that the 2D elastic modulus of the multilayer WSe{sub 2} membranes increases linearly while the prestress decreases linearly as the number of layers increases. The interlayer interaction in WSe{sub 2} has been observed to be strong enough to prevent the interlayer sliding during the indentation experiments. The Young's modulus of multilayer WSe{sub 2} (167.3 ± 6.7 GPa) is statistically independent of the thickness of the membranes, whose value is about two thirds of other most investigated 2D semiconducting transition metal dichalcogenides, namely, MoS{sub 2} and WS{sub 2}. Moreover, the multilayer WSe{sub 2} can endure ∼12.4 GPa stress and ∼7.3% strain without fracture or mechanical degradation. The 2D WSe{sub 2} can be an attractive semiconducting material for application in flexible optoelectronic devices and nano-electromechanical systems.

  18. KINETICS OF SUSPENDED EMULSION POLYMERIZATION OF METHYL METHACRYLATE

    Institute of Scientific and Technical Information of China (English)

    Yong-zhong Bao; Cheng-xi Wang; Zhi-ming Huang; Zhi-xue Weng

    2004-01-01

    The kinetics of suspended emulsion polymerization of methyl methacrylate (MMA), in which water acted as the dispersed phase and the mixture of MMA and cyclohexane as the continuous phase, was investigated. It showed that the initial polymerization rate (Rp0) and steady-state polymerization rate (Rp) were proportional to the mass ratio between water and oil phase, and increased as the polymerization temperature, the potassium persulphate concentration ([I]) and the Tween20 emulsifier concentration ([S]) increased. The relationships between the polymerization rate and [I] and [S] were obtained as follows: Rp0 ∝ [I]0.73[S]0.32 and Rp ∝ [I]0.71[S]0.23. The above exponents were close to those obtained from normal MMA emulsion polymerization. It also showed that the average molecular weight of the resulting poly(methyl methacrylate) decreased as the polymerization temperature, [I] and [S] increased. Thus, MMA suspended emulsion polymerization could be considered as a combination of many miniature emulsion polymerizations proceeding in water drops and obeyed the classical kinetics of MMA emulsion polymerization.

  19. Regional estimation of extreme suspended sediment concentrations using watershed characteristics

    Science.gov (United States)

    Tramblay, Yves; Ouarda, Taha B. M. J.; St-Hilaire, André; Poulin, Jimmy

    2010-01-01

    SummaryThe number of stations monitoring daily suspended sediment concentration (SSC) has been decreasing since the 1980s in North America while suspended sediment is considered as a key variable for water quality. The objective of this study is to test the feasibility of regionalising extreme SSC, i.e. estimating SSC extremes values for ungauged basins. Annual maximum SSC for 72 rivers in Canada and USA were modelled with probability distributions in order to estimate quantiles corresponding to different return periods. Regionalisation techniques, originally developed for flood prediction in ungauged basins, were tested using the climatic, topographic, land cover and soils attributes of the watersheds. Two approaches were compared, using either physiographic characteristics or seasonality of extreme SSC to delineate the regions. Multiple regression models to estimate SSC quantiles as a function of watershed characteristics were built in each region, and compared to a global model including all sites. Regional estimates of SSC quantiles were compared with the local values. Results show that regional estimation of extreme SSC is more efficient than a global regression model including all sites. Groups/regions of stations have been identified, using either the watershed characteristics or the seasonality of occurrence for extreme SSC values providing a method to better describe the extreme events of SSC. The most important variables for predicting extreme SSC are the percentage of clay in the soils, precipitation intensity and forest cover.

  20. IUTAM symposium on hydrodynamic diffusion of suspended particles

    Energy Technology Data Exchange (ETDEWEB)

    Davis, R.H. [ed.

    1995-12-31

    Hydrodynamic diffusion refers to the fluctuating motion of nonBrownian particles (or droplets or bubbles) which occurs in a dispersion due to multiparticle interactions. For example, in a concentrated sheared suspension, particles do not move along streamlines but instead exhibit fluctuating motions as they tumble around each other. This leads to a net migration of particles down gradients in particle concentration and in shear rate, due to the higher frequency of encounters of a test particle with other particles on the side of the test particle which has higher concentration or shear rate. As another example, suspended particles subject to sedimentation, centrifugation, or fluidization, do not generally move relative to the fluid with a constant velocity, but instead experience diffusion-like fluctuations in velocity due to interactions with neighboring particles and the resulting variation in the microstructure or configuration of the suspended particles. In flowing granular materials, the particles interact through direct collisions or contacts (rather than through the surrounding fluid); these collisions also cause the particles to undergo fluctuating motions characteristic of diffusion processes. Selected papers are indexed separately for inclusion in the Energy Science and Technology Database.

  1. A Passively-Suspended Tesla Pump Left Ventricular Assist Device

    Science.gov (United States)

    Izraelev, Valentin; Weiss, William J.; Fritz, Bryan; Newswanger, Raymond K.; Paterson, Eric G.; Snyder, Alan; Medvitz, Richard B.; Cysyk, Joshua; Pae, Walter E.; Hicks, Dennis; Lukic, Branka; Rosenberg, Gerson

    2009-01-01

    The design and initial test results of a new passively suspended Tesla type LAVD blood pump are described. CFD analysis was used in the design of the pump. Overall size of the prototype device is 50 mm in diameter and 75 mm in length. The pump rotor has a density lower than that of blood and when spinning inside the stator in blood it creates a buoyant centering force that suspends the rotor in the radial direction. The axial magnetic force between the rotor and stator restrain the rotor in the axial direction. The pump is capable of pumping up to 10 liters/min at a 70 mmHg head rise at 8000 RPM. The pump has demonstrated a normalized index of hemolysis level below .02 mg/dL for flows between 2 and 9.7 L/min. An inlet pressure sensor has also been incorporated into the inlet cannula wall and will be used for control purposes. One initial in vivo study showed an encouraging result. Further CFD modeling refinements are planned as well as endurance testing of the device. PMID:19770799

  2. Pressurized polyol synthesis of Al-doped ZnO nanoclusters with high electrical conductivity and low near-infrared transmittance

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ho-Nyun; Shin, Chi-Ho [Surface Technology R& BD Group, Korea Institute of Industrial Technology (KITECH), Incheon 406-840 (Korea, Republic of); Hwang, Duck Kun [Department of Corporate Diagnosis, Small and Medium Business Corporation, Seoul 150-718 (Korea, Republic of); Kim, Haekyoung [School of Materials Science and Engineering, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of); Oh, Kyeongseok [Department of Chemical and Environmental Technology, Inha Technical College, Incheon 402-752 (Korea, Republic of); Kim, Hyun-Jong, E-mail: hjkim23@kitech.re.kr [Surface Technology R& BD Group, Korea Institute of Industrial Technology (KITECH), Incheon 406-840 (Korea, Republic of)

    2015-09-25

    Highlights: • Low-temperature pressurized polyol method synthesized Al-doped ZnO nanoclusters. • Reaction time affected the doping efficiency, resistivity, and NIR transmittance. • The near-IR blocking efficiency of Al-doped ZnO (AZO) nanoclusters reached 85%. • AZO nanocluster coatings could be used for heat reflectors or artificial glasses. - Abstract: In this study, a novel pressurized polyol method is proposed to synthesize aluminum-doped ZnO (AZO) nanoclusters without utilizing additional thermal treatment to avoid the merging of nanoclusters. The size of the AZO nanoclusters range from 100 to 150 nm with a resistivity of 204 Ω cm. The AZO nanoclusters primarily consist of approximately 10-nm nanocrystals that form a spherically clustered morphology. A two-stage growth model has been proposed based on the results of scanning electron microscopy and transmission electron microscopy images, nanocluster sizes, and X-ray diffraction patterns. The primary AZO nanocrystals first nucleate under pressurized conditions and then spontaneously aggregate into larger nanoclusters. Optically, the AZO nanoclusters exhibit a significant decrease in the near-infrared (NIR) transmittance compared to pure ZnO nanoparticles. The NIR blocking efficiency of AZO nanoclusters reached 85%. Moreover, the doping efficiency, resistivity, and NIR transmittance of AZO nanoclusters are influenced by the reaction time in the pressurized polyol solution. On the other hand, the reaction time has no effect on the particle size and crystallinity. An optically transparent coating for the AZO nanoclusters, which consisted of iso-propanol solvent and ultraviolet-curable acrylic binder, was also demonstrated.

  3. Management of cluster headache

    DEFF Research Database (Denmark)

    Tfelt-Hansen, Peer C; Jensen, Rigmor H

    2012-01-01

    The prevalence of cluster headache is 0.1% and cluster headache is often not diagnosed or misdiagnosed as migraine or sinusitis. In cluster headache there is often a considerable diagnostic delay - an average of 7 years in a population-based survey. Cluster headache is characterized by very severe...... or severe orbital or periorbital pain with a duration of 15-180 minutes. The cluster headache attacks are accompanied by characteristic associated unilateral symptoms such as tearing, nasal congestion and/or rhinorrhoea, eyelid oedema, miosis and/or ptosis. In addition, there is a sense of restlessness...... and agitation. Patients may have up to eight attacks per day. Episodic cluster headache (ECH) occurs in clusters of weeks to months duration, whereas chronic cluster headache (CCH) attacks occur for more than 1 year without remissions. Management of cluster headache is divided into acute attack treatment...

  4. Symmetries of cluster configurations

    International Nuclear Information System (INIS)

    Kramer, P.

    1975-01-01

    A deeper understanding of clustering phenomena in nuclei must encompass at least two interrelated aspects of the subject: (A) Given a system of A nucleons with two-body interactions, what are the relevant and persistent modes of clustering involved. What is the nature of the correlated nucleon groups which form the clusters, and what is their mutual interaction. (B) Given the cluster modes and their interaction, what systematic patterns of nuclear structure and reactions emerge from it. Are there, for example, families of states which share the same ''cluster parents''. Which cluster modes are compatible or exclude each other. What quantum numbers could characterize cluster configurations. There is no doubt that we can learn a good deal from the experimentalists who have discovered many of the features relevant to aspect (B). Symmetries specific to cluster configurations which can throw some light on both aspects of clustering are discussed

  5. Effects of the annealing duration of the ZnO buffer layer on structural and optical properties of ZnO rods grown by a hydrothermal process

    Energy Technology Data Exchange (ETDEWEB)

    Shin, C.M.; Lee, J.Y.; Heo, J.H.; Park, J.H.; Kim, C.R. [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Obang-dong, Gimhae, Gyeongnam 621-749 (Korea, Republic of); Ryu, H., E-mail: hhryu@inje.ac.kr [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Obang-dong, Gimhae, Gyeongnam 621-749 (Korea, Republic of); Chang, J.H. [Major of Nano Semiconductor, Korea Maritime University, 1 Dongsam-dong, Yeongdo-Ku, Busan 606-791 (Korea, Republic of); Son, C.S. [Department of Electronic Materials Engineering, Silla University, Gwaebeop-dong, Sasang-gu, Busan 617-736 (Korea, Republic of); Lee, W.J. [Department of Nano Engineering, Dong-Eui University, 995 Eomgwangno, Busanjin-gu, Busan 614-714 (Korea, Republic of); Tan, S.T. [Institute of Microelectronics, 11 Science Park Road, Science Park II, Singapore 117685 (Singapore); Zhao, J.L. [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore); Sun, X.W. [Institute of Microelectronics, 11 Science Park Road, Science Park II, Singapore 117685 (Singapore); School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore)

    2009-07-30

    In this study, the effects of the annealing duration of a zinc oxide (ZnO) buffer layer on structural and optical properties of ZnO rods grown by a hydrothermal process are discussed. A ZnO buffer layer was deposited on p-type Si (1 1 1) substrates by the metal organic chemical vapor deposition (MOCVD) method. After that, ZnO rods were grown on the ZnO-buffer/Si (1 1 1) substrate by a hydrothermal process. In order to determine the optimum annealing duration of the buffer layer for the growth of ZnO rods, durations ranging from 0.5 to 30 min were tried. The morphology and crystal structure of the ZnO/ZnO-buffer/Si (1 1 1) were measured by field emission scanning electron microscopy (FE-SEM) and x-ray diffraction (XRD). The optical properties were investigated by photoluminescence (PL) measurement.

  6. Operational Test Report for the 241-AZ-101 Suspended Solids Profiler

    International Nuclear Information System (INIS)

    STENKAMP, D.M.

    2000-01-01

    This document comprises the Operational Test Report for the 241-AZ-101 Suspended Solids Profiler. This document presents the results of Operational Testing of the 241-AZ-101 Suspended Solids Profiler (SSP). Testing of the SSP was performed in accordance with OTP-260-005, ''SUSPENDED SOLIDS PROFILER OPERATIONAL TEST PROCEDURE''. The objective of the testing was to verify that all equipment and components functioned as designed, following construction completion and turnover to operations

  7. Influence of Wheel Eccentricity on Vertical Vibration of Suspended Monorail Vehicle: Experiment and Simulation

    OpenAIRE

    Kaikai Lv; Kaiyun Wang; Zhihui Chen; Chengbiao Cai; Lirong Guo

    2017-01-01

    This paper investigates the influence of wheel eccentricity on vertical vibration of suspended monorail vehicle based on experiment and simulation. Two sets of tests are conducted in the first Chinese suspended monorail, and the tested acceleration is analyzed and exhibited. A multibody dynamic model of the suspended monorail vehicle is established to simulate the vertical vibration of car body excited by wheel eccentricity. The results show that there are three factors which may cause an abn...

  8. The Prediction Methods for Potential Suspended Solids Clogging Types during Managed Aquifer Recharge

    Directory of Open Access Journals (Sweden)

    Xinqiang Du

    2014-04-01

    Full Text Available The implementation and development of managed aquifer recharge (MAR have been limited by the clogging attributed to physical, chemical, and biological reactions. In application field of MAR, physical clogging is usually the dominant type. Although numerous studies on the physical clogging mechanism during MAR are available, studies on the more detailed suspended clogging types and its prediction methods still remain few. In this study, a series of column experiments were inducted to show the process of suspended solids clogging process. The suspended solids clogging was divided into three types of surface clogging, inner clogging and mixed clogging based on the different clogging characteristics. Surface clogging indicates that the suspended solids are intercepted by the medium surface when suspended solids grain diameter is larger than pore diameter of infiltration medium. Inner clogging indicates that the suspended solids particles could transport through the infiltration medium. Mixed clogging refers to the comprehensive performance of surface clogging and inner clogging. Each suspended solids clogging type has the different clogging position, different changing laws of hydraulic conductivity and different deposition profile of suspended solids. Based on the experiment data, the ratio of effective medium pore diameter (Dp and median grain size of suspended solids (d50 was proposed as the judgment index for suspended solids clogging types. Surface clogging occurred while Dp/d50 was less than 5.5, inner clogging occurred while Dp/d50 was greater than 180, and mixed clogging occurred while Dp/d50 was between 5.5 and 180. In order to improve the judgment accuracy and applicability, Bayesian method, which considered more ratios of medium pore diameter (Dp and different level of grain diameter of suspended solids (di, were developed to predict the potential suspended solids types.

  9. Controlled Synthesis of Hierarchically Assembled Porous ZnO Microspheres with Enhanced Gas-Sensing Properties

    Directory of Open Access Journals (Sweden)

    Shengsheng You

    2015-01-01

    Full Text Available The ZnO microspheres constructed by porous nanosheets were successfully synthesized by calcinating zinc hydroxide carbonate (ZHC microspheres obtained by a sample hydrothermal method. The samples were characterized in detail with scanning electron microscopy (SEM, transmission electron microscopy (TEM, X-ray diffraction (XRD, and thermogravimetric and differential scanning calorimetry (TG-DSC. The results indicated that the prepared ZnO microspheres were well crystalline with wurtzite hexagonal phase. The effects of reaction time, temperature, the amount of trisodium citrate, and urea on the morphology of ZnO microspheres were studied. The formation mechanism of porous ZnO microspheres was discussed. Furthermore, the gas-sensing properties for detection of organic gas of the prepared porous ZnO microspheres were investigated. The results indicated that the prepared porous ZnO microspheres exhibited high gas-sensing properties for detection of ethanol gas.

  10. Room-temperature deposition of crystalline patterned ZnO films by confined dewetting lithography

    Energy Technology Data Exchange (ETDEWEB)

    Sepulveda-Guzman, S., E-mail: selene.sepulvedagz@uanl.edu.mx [Centro de Innovacion, Investigacion y Desarrollo en Ingenieria y Tecnologia. UANL, PIIT Monterrey, CP 66629, Apodaca NL (Mexico); Reeja-Jayan, B. [Texas Materials Institute, University of Texas at Austin, Austin, TX 78712 (United States); De la Rosa, E. [Centro de Investigacion en Optica, Loma del Bosque 115 Col. Lomas del Campestre C.P. 37150 Leon, Gto. Mexico (Mexico); Ortiz-Mendez, U. [Centro de Innovacion, Investigacion y Desarrollo en Ingenieria y Tecnologia. UANL, PIIT Monterrey, CP 66629, Apodaca NL (Mexico); Reyes-Betanzo, C. [Instituto Nacional de Astrofisica Optica y Electronica, Calle Luis Enrique Erro No. 1, Santa Maria Tonanzintla, Puebla. Apdo. Postal 51 y 216, C.P. 72000 Puebla (Mexico); Cruz-Silva, R. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, UAEM. Av. Universidad 1001, Col. Chamilpa, CP 62210 Cuernavaca, Mor. (Mexico); Jose-Yacaman, M. [Physics and Astronomy Department University of Texas at San Antonio 1604 campus San Antonio, TX 78249 (United States)

    2010-03-15

    In this work patterned ZnO films were prepared at room-temperature by deposition of {approx}5 nm size ZnO nanoparticles using confined dewetting lithography, a process which induces their assembly, by drying a drop of ZnO colloidal dispersion between a floating template and the substrate. Crystalline ZnO nanoparticles exhibit a strong visible (525 nm) light emission upon UV excitation ({lambda} = 350 nm). The resulting films were characterized by scanning electron microscopy (SEM) and atomic force microscope (AFM). The method described herein presents a simple and low cost method to prepare crystalline ZnO films with geometric patterns without additional annealing. Such transparent conducting films are attractive for applications like light emitting diodes (LEDs). As the process is carried out at room temperature, the patterned crystalline ZnO films can even be deposited on flexible substrates.

  11. Efficient solution route to transparent ZnO semiconductor films using colloidal nanocrystals

    Directory of Open Access Journals (Sweden)

    Satoshi Suehiro

    2016-09-01

    Full Text Available ZnO nanocrystals (NCs were synthesized by heating Zn (II acetylacetonate in oleic acid/oleylamine in the presence of 1,2-hexadecanediol at 220 °C. Transmission electron microscopy (TEM and dynamic light scattering (DLS measurements revealed the formation of monodispersed ZnO NCs of ca. 7 nm. ZnO NC assembled films were fabricated on a glass substrate by deposition with the colloidal ZnO NCs dispersed in toluene. The film composed of the NCs showed good optical transparency in the visible to near-infrared region. A device coupling the ZnO NC film with a p-type Cu2ZnSnS4 (CZTS NC film exhibited an obvious diode-like current–voltage behavior. The results suggest that the transparent ZnO film has a potentiality to be used for an n-type window layer in some optoelectronic applications.

  12. The effects of addition of citric acid on the morphologies of ZnO nanorods

    International Nuclear Information System (INIS)

    Yang Zao; Liu Quanhui; Yang Lei

    2007-01-01

    ZnO nanorods of 25-100 nm in diameter and 0.2-1 μm in length were fabricated through citric acid assisted annealing process. The microstructure of ZnO nanorods was characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and field-emission scanning electron microscopy, respectively. As a result, it was found that ZnO nanorods were single crystalline and pure. The effects of the growth conditions such as addition of citric acid, annealing temperature on the morphologies of ZnO nanostructures have also been investigated. At the given temperature the length decreased but the diameter increased with addition of the mass of citric acid. With the rising of the calcining heat, the shape of ZnO changed from rod to granule for a given amount of citric acid. Finally, the mechanism for citric acid assisted annealing synthesis of the ZnO nanostructure is discussed

  13. Room-temperature deposition of crystalline patterned ZnO films by confined dewetting lithography

    International Nuclear Information System (INIS)

    Sepulveda-Guzman, S.; Reeja-Jayan, B.; De la Rosa, E.; Ortiz-Mendez, U.; Reyes-Betanzo, C.; Cruz-Silva, R.; Jose-Yacaman, M.

    2010-01-01

    In this work patterned ZnO films were prepared at room-temperature by deposition of ∼5 nm size ZnO nanoparticles using confined dewetting lithography, a process which induces their assembly, by drying a drop of ZnO colloidal dispersion between a floating template and the substrate. Crystalline ZnO nanoparticles exhibit a strong visible (525 nm) light emission upon UV excitation (λ = 350 nm). The resulting films were characterized by scanning electron microscopy (SEM) and atomic force microscope (AFM). The method described herein presents a simple and low cost method to prepare crystalline ZnO films with geometric patterns without additional annealing. Such transparent conducting films are attractive for applications like light emitting diodes (LEDs). As the process is carried out at room temperature, the patterned crystalline ZnO films can even be deposited on flexible substrates.

  14. Synthesis and microstructural characterization of growth direction controlled ZnO nanorods using a buffer layer

    International Nuclear Information System (INIS)

    Park, Dong Jun; Kim, Dong Chan; Lee, Jeong Yong; Cho, Hyung Koun

    2006-01-01

    The growth direction and morphology of one-dimensional ZnO nanostructures grown by metal-organic chemical vapour deposition (MOCVD) were modulated by changing the growth temperature of previously deposited ZnO buffer layers that were used as a template. The ZnO nanorods grown on the low-temperature deposited buffer layer were regularly inclined with respect to the substrate surface and show in-plane alignment with azimuthally six-fold symmetry. In contrast, deposition of the buffer layer at higher growth temperature led to the formation of vertically well-aligned ZnO nanorods. In addition, the ZnO nanorods grown on the buffer layer deposited at low growth temperature show a growth direction of [1 0 1-bar 0], unlike the conventional ZnO nanorods showing a growth direction of [0001]. The microstructural analysis and atomic modelling of the formation of regularly inclined nanorods using transmission electron microscopy are presented

  15. III-nitrides on oxygen- and zinc-face ZnO substrates

    International Nuclear Information System (INIS)

    Namkoong, Gon; Burnham, Shawn; Lee, Kyoung-Keun; Trybus, Elaissa; Doolittle, W. Alan; Losurdo, Maria; Capezzuto, Pio; Bruno, Giovanni; Nemeth, Bill; Nause, Jeff

    2005-01-01

    The characteristics of III-nitrides grown on zinc- and oxygen-face ZnO by plasma-assisted molecular beam epitaxy were investigated. The reflection high-energy electron diffraction pattern indicates formation of a cubic phase at the interface between III-nitride and both Zn- and O-face ZnO. The polarity indicates that Zn-face ZnO leads to a single polarity, while O-face ZnO forms mixed polarity of III-nitrides. Furthermore, by using a vicinal ZnO substrate, the terrace-step growth of GaN was realized with a reduction by two orders of magnitude in the dislocation-related etch pit density to ∼10 8 cm -2 , while a dislocation density of ∼10 10 cm -2 was obtained on the on-axis ZnO substrates

  16. Quenching of the surface-state-related photoluminescence in Ni-coated ZnO nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Tang Yang [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16 East Nan-Hu Road, Open Economic Zone, Changchun 130033 (China); Graduate School of the Chinese Academy of Sciences (China); Zhao Dongxu, E-mail: dxzhao2000@yahoo.com.c [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16 East Nan-Hu Road, Open Economic Zone, Changchun 130033 (China); Zhang Jiying; Shen Dezhen [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16 East Nan-Hu Road, Open Economic Zone, Changchun 130033 (China)

    2010-11-01

    Nickel-coated ZnO nanowires (NWs) were fabricated by electrodepositing Ni particles on ZnO NW arrays. The morphological, magnetic, and photoluminescent properties of the Ni-coated ZnO NWs were investigated. The Ni particles were deposited on the ZnO NWs' surface along its length to form a Ni/ZnO shell-core structure. The Ni-coated ZnO NWs exhibited more isotropic characteristic than the electrodeposited Ni films owing to the isotropic sphere structure of the Ni particles. A strong ultraviolet emission can be obtained from the Ni-coated ZnO NWs, while the green emission related to surface states was quenched by the passivated layer.

  17. Quenching of the surface-state-related photoluminescence in Ni-coated ZnO nanowires

    International Nuclear Information System (INIS)

    Tang Yang; Zhao Dongxu; Zhang Jiying; Shen Dezhen

    2010-01-01

    Nickel-coated ZnO nanowires (NWs) were fabricated by electrodepositing Ni particles on ZnO NW arrays. The morphological, magnetic, and photoluminescent properties of the Ni-coated ZnO NWs were investigated. The Ni particles were deposited on the ZnO NWs' surface along its length to form a Ni/ZnO shell-core structure. The Ni-coated ZnO NWs exhibited more isotropic characteristic than the electrodeposited Ni films owing to the isotropic sphere structure of the Ni particles. A strong ultraviolet emission can be obtained from the Ni-coated ZnO NWs, while the green emission related to surface states was quenched by the passivated layer.

  18. UV-Enhanced Ethanol Sensing Properties of RF Magnetron-Sputtered ZnO Film.

    Science.gov (United States)

    Huang, Jinyu; Du, Yu; Wang, Quan; Zhang, Hao; Geng, Youfu; Li, Xuejin; Tian, Xiaoqing

    2017-12-26

    ZnO film was deposited by the magnetron sputtering method. The thickness of ZnO film is approximately 2 μm. The influence of UV light illumination on C₂H₅OH sensing properties of ZnO film was investigated. Gas sensing results revealed that the UV-illuminated ZnO film displays excellent C₂H₅OH characteristics in terms of high sensitivity, excellent selectivity, rapid response/recovery, and low detection limit down to 0.1 ppm. The excellent sensing performance of the sensor with UV activation could be attributed to the photocatalytic oxidation of ethanol on the surface of the ZnO film, the planar film structure with high utilizing efficiency of UV light, high electron mobility, and a good surface/volume ratio of of ZnO film with a relatively rough and porous surface.

  19. Site-specific growth of Au particles on ZnO nanopyramids under ultraviolet illumination

    KAUST Repository

    Yao, Kexin

    2011-01-01

    In this work, wurtzite ZnO nanocrystals with unique "pyramid" morphology were firstly prepared via solvothermal synthesis. It was determined that the ZnO nanopyramids are grown along the polar c-axis with the vertexes pointing to the [001] direction. When the mixture of ZnO nanopyramids and Au precursor (HAuCl4) was exposed to ultraviolet (UV) illumination, Au particles were site-specifically formed on the vertexes of ZnO nanopyramids. The obtained Au/ZnO nanocomposite showed significantly enhanced photocatalytic activity as compared to the bare ZnO nanopyramids. First-principles based calculations well explained the formation of ZnO nanopyramids as well as the site-specific growth of Au, and revealed that during the photocatalysis process the Au particles can accommodate photoelectrons and thus facilitate the charge separation. © 2011 The Royal Society of Chemistry.

  20. Theoretical prediction of low-density hexagonal ZnO hollow structures

    Energy Technology Data Exchange (ETDEWEB)

    Tuoc, Vu Ngoc, E-mail: tuoc.vungoc@hust.edu.vn [Institute of Engineering Physics, Hanoi University of Science and Technology, 1 Dai Co Viet Road, Hanoi (Viet Nam); Huan, Tran Doan [Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269-3136 (United States); Thao, Nguyen Thi [Institute of Engineering Physics, Hanoi University of Science and Technology, 1 Dai Co Viet Road, Hanoi (Viet Nam); Hong Duc University, 307 Le Lai, Thanh Hoa City (Viet Nam); Tuan, Le Manh [Hong Duc University, 307 Le Lai, Thanh Hoa City (Viet Nam)

    2016-10-14

    Along with wurtzite and zinc blende, zinc oxide (ZnO) has been found in a large number of polymorphs with substantially different properties and, hence, applications. Therefore, predicting and synthesizing new classes of ZnO polymorphs are of great significance and have been gaining considerable interest. Herein, we perform a density functional theory based tight-binding study, predicting several new series of ZnO hollow structures using the bottom-up approach. The geometry of the building blocks allows for obtaining a variety of hexagonal, low-density nanoporous, and flexible ZnO hollow structures. Their stability is discussed by means of the free energy computed within the lattice-dynamics approach. Our calculations also indicate that all the reported hollow structures are wide band gap semiconductors in the same fashion with bulk ZnO. The electronic band structures of the ZnO hollow structures are finally examined in detail.

  1. Study of the thermal conductivity of ZnO nanowires/PMMA composites

    International Nuclear Information System (INIS)

    Igamberdiev, Kh. T.; Yuldashev, Sh. U.; Cho, H. D.; Kang, T. W.; Rakhimova, Sh. M.; Akhmedov, T. Kh.

    2012-01-01

    From thermal conductivity measurements on ZnO nanowires (NWs)/poly(methyl methacrylate) PMMA composites, the thermal conductivities of the ZnO nanowires were determined. The thermal conductivity of a ZnO NW decreases considerably with decreasing nanowire diameter, and for a ZnO nanowire with a diameter of 250 nm, the thermal conductivity at room temperature is approximately two times lower than that of bulk ZnO at the same temperature. The results of this study show that the thermal conductivity of a ZnO NW is mainly determined by increased phonon-surface boundary scattering. These results could be useful for the design of ZnO-nanowire-based devices.

  2. Microwave absorption properties and mechanism of cagelike ZnO /SiO2 nanocomposites

    Science.gov (United States)

    Cao, Mao-Sheng; Shi, Xiao-Ling; Fang, Xiao-Yong; Jin, Hai-Bo; Hou, Zhi-Ling; Zhou, Wei; Chen, Yu-Jin

    2007-11-01

    In this paper, cagelike ZnO /SiO2 nanocomposites were prepared and their microwave absorption properties were investigated in detail. Dielectric constants and losses of the pure cagelike ZnO nanostructures were measured in a frequency range of 8.2-12.4GHz. The measured results indicate that the cagelike ZnO nanostructures are low-loss material for microwave absorption in X band. However, the cagelike ZnO /SiO2 nanocomposites exhibit a relatively strong attenuation to microwave in X band. Such strong absorption is related to the unique geometrical morphology of the cagelike ZnO nanostructures in the composites. The microcurrent network can be produced in the cagelike ZnO nanostructures, which contributes to the conductive loss.

  3. Room temperature synthesis and optical properties of small diameter (5 nm) ZnO nanorod arrays.

    Science.gov (United States)

    Cho, Seungho; Jang, Ji-Wook; Lee, Jae Sung; Lee, Kun-Hong

    2010-10-01

    We report a simple wet-chemical synthesis of ∼5 nm diameter ZnO nanorod arrays at room temperature (20 °C) and normal atmospheric pressure (1 atm) and their optical properties. They were single crystalline in nature, and grew in the [001] direction. These small diameter ZnO nanorod arrays can also be synthesized at 0 °C. Control experiments were also conducted. On the basis of the results, we propose a mechanism for the spontaneous growth of the small diameter ZnO structures. The optical properties of the 5 nm diameter ZnO nanorod arrays synthesized using this method were probed by UV-Visible diffuse reflectance spectroscopy. A clear blue-shift, relative to the absorption band from 50 nm diameter ZnO nanorod arrays, was attributed to the quantum confinement effects caused by the small nanocrystal size in the 5 nm diameter ZnO nanorods.

  4. Hydrothermal temperature effect on crystal structures, optical properties and electrical conductivity of ZnO nanostructures

    Science.gov (United States)

    Dhafina, Wan Almaz; Salleh, Hasiah; Daud, Mohd Zalani; Ghazali, Mohd Sabri Mohd; Ghazali, Salmah Mohd

    2017-09-01

    ZnO is an wide direct band gap semiconductor and possess rich family of nanostructures which turned to be a key role in the nanotechnology field of applications. Hydrothermal method was proven to be simple, robust and low cost among the reported methods to synthesize ZnO nanostructures. In this work, the properties of ZnO nanostructures were altered by varying temperatures of hydrothermal process. The changes in term of morphological, crystal structures, optical properties and electrical conductivity were investigated. A drastic change of ZnO nanostructures morphology and decreases of 002 diffraction peak were observed as the hydrothermal temperature increased. The band gap of samples decreased as the size of ZnO nanostructure increased, whereas the electrical conductivity had no influence on the band gap value but more on the morphology of ZnO nanostructures instead.

  5. Synthesis and characterization of Mn-doped ZnO column arrays

    International Nuclear Information System (INIS)

    Yang Mei; Guo Zhixing; Qiu Kehui; Long Jianping; Yin Guangfu; Guan Denggao; Liu Sutian; Zhou Shijie

    2010-01-01

    Mn-doped ZnO column arrays were successfully synthesized by conventional sol-gel process. Effect of Mn/Zn atomic ratio and reaction time were investigated, and the morphology, tropism and optical properties of Mn-doped ZnO column arrays were characterized by SEM, XRD and photoluminescence (PL) spectroscopy. The result shows that a Mn/Zn atomic ratio of 0.1 and growth time of 12 h are the optimal condition for the preparation of densely distributed ZnO column arrays. XRD analysis shows that Mn-doped ZnO column arrays are highly c-axis oriented. As for Mn-doped ZnO column arrays, obvious increase of photoluminescence intensity is observed at the wavelength of ∼395 nm and ∼413 nm, compared to pure ZnO column arrays.

  6. Cluster Decline and Resilience

    DEFF Research Database (Denmark)

    Østergaard, Christian Richter; Park, Eun Kyung

    Most studies on regional clusters focus on identifying factors and processes that make clusters grow. However, sometimes technologies and market conditions suddenly shift, and clusters decline. This paper analyses the process of decline of the wireless communication cluster in Denmark, 1963......-2011. Our longitudinal study reveals that technological lock-in and exit of key firms have contributed to impairment of the cluster’s resilience in adapting to disruptions. Entrepreneurship has a positive effect on cluster resilience, while multinational companies have contradicting effects by bringing...... in new resources to the cluster but being quick to withdraw in times of crisis....

  7. Enhanced photovoltaic performance of ZnO nanorod-based dye-sensitized solar cells by using Ga doped ZnO seed layer

    Energy Technology Data Exchange (ETDEWEB)

    Dou, Yuanyao [State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400044 (China); Department of Applied Physics, College of Physics, Chongqing University, Chongqing 401331 (China); Wu, Fang, E-mail: fang01234@163.com [State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400044 (China); Department of Applied Physics, College of Physics, Chongqing University, Chongqing 401331 (China); Mao, Caiying [Department of Applied Physics, College of Physics, Chongqing University, Chongqing 401331 (China); Fang, Liang, E-mail: lfang@cqu.edu.cn [State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400044 (China); Department of Applied Physics, College of Physics, Chongqing University, Chongqing 401331 (China); Guo, Shengchun [Department of Applied Physics, College of Physics, Chongqing University, Chongqing 401331 (China); Zhou, Miao [State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400044 (China)

    2015-06-05

    Highlights: • ZnO nanorods were grown on Ga-doped ZnO seed layers using hydrothermal method. • Using the ZnO nanorods as photoanodes for fabricated dye-sensitized solar cells. • The highest η of 1.23% can be achieved in a DSSC with 3 at.% Ga-doped in seeds. • The effects of ZnO seed layers on electron transport properties were investigated. • The enhancement performance of DSSCs contributed to higher dye loading and η{sub cc}. - Abstract: Zinc oxide (ZnO) nanorod arrays were grown on FTO substrates with a Ga-doped ZnO (GZO) seed layer by a hydrothermal method. GZO seed layers were obtained via sol–gel technology with Ga concentration in the range of 0–4 at.%. The dye sensitized solar cells (DSSCs) using ZnO nanorod arrays as the photoanode layers were prepared. The effect of Ga dopant concentrations in ZnO seed layer on the morphology features of ZnO nanorod arrays and the performance of DSSCs were systematically investigated. Results indicate that the average diameter and density of ZnO nanorod arrays decrease with increasing Ga concentration, but their length shows an opposite trend. The photocurrent density–voltage (J–V) characteristics reveal that the DSSCs with GZO seed layer exhibit significantly improved photovoltaic performance. In particular, the highest energy conversion efficiency (η) of 1.23% can be achieved in a DSSC with 3 at.% Ga doping, which is increased by 86.36% compared with that of the undoped DSSC. The external quantum efficiency (EQE) spectra and electrochemical impedance spectroscopy (EIS) were employed to explore the photon-to-electron conversion process in DSSCs. It is demonstrated that the performance enhancement of DSSCs based on GZO seed layer can be attributed to higher amount of dye loading, more efficient electron transportation and better electrons collection efficiency.

  8. Performance of inverted polymer solar cells with randomly oriented ZnO nanorods coupled with atomic layer deposited ZnO

    International Nuclear Information System (INIS)

    Zafar, Muhammad; Yun, Ju-Young; Kim, Do-Heyoung

    2017-01-01

    Highlights: • Hydrothermally grown, randomly oriented, and low areal density ZnO nanorods have been successfully adopted as the electron transport layer in inverted organic solar cells. • The addition of atomic layer deposited ZnO on the ZnO nanorods effectively enhance the photovoltaic performances of inverted organic solar cells. • The inverted organic solar cells with 5 nm thick-ALD ZnO showed the highest power conversion efficiency of 3.08%, which is an enhancement of approximately 80% compared to the cells without the ALD ZnO layer (PCE = 1.67%). - Abstract: Nanostructuring of the electron transport layer (ETL) in organic photovoltaic cells (OPV) is of great interest because it increases the surface area of the cell and electron transport. In this work, hydrothermally grown, randomly oriented, and low areal density ZnO nanorods (NRs) have been adopted as the ETL, and the effect of adding atomic layer deposited (ALD) ZnO on the ZnO NRs on the inverted organic solar cell performance has been investigated. The fabricated inverted organic solar cell with 5-nm-thick ALD-ZnO grown on the ZnO NRs showed the highest power conversion efficiency (PCE) of 3.08%, which is an enhancement of 85% from that of the cell without ALD-ZnO (PCE = 1.67%). The ultrathin ALD-ZnO was found to act as a curing layer of the surface defects on the hydrothermally grown ZnO NRs, resulting in an improvement in photovoltaic performance.

  9. Performance of inverted polymer solar cells with randomly oriented ZnO nanorods coupled with atomic layer deposited ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Zafar, Muhammad [School of Chemical Engineering, Chonnam National University, 300 Youngbong-dong, Gwangju 500-757 (Korea, Republic of); Yun, Ju-Young [Center for Vacuum, Korea Research Institute of Standards and Science, 267 Gajeong-ro, Daejeon 305-600 (Korea, Republic of); Kim, Do-Heyoung, E-mail: kdhh@chonnam.ac.kr [School of Chemical Engineering, Chonnam National University, 300 Youngbong-dong, Gwangju 500-757 (Korea, Republic of)

    2017-03-15

    Highlights: • Hydrothermally grown, randomly oriented, and low areal density ZnO nanorods have been successfully adopted as the electron transport layer in inverted organic solar cells. • The addition of atomic layer deposited ZnO on the ZnO nanorods effectively enhance the photovoltaic performances of inverted organic solar cells. • The inverted organic solar cells with 5 nm thick-ALD ZnO showed the highest power conversion efficiency of 3.08%, which is an enhancement of approximately 80% compared to the cells without the ALD ZnO layer (PCE = 1.67%). - Abstract: Nanostructuring of the electron transport layer (ETL) in organic photovoltaic cells (OPV) is of great interest because it increases the surface area of the cell and electron transport. In this work, hydrothermally grown, randomly oriented, and low areal density ZnO nanorods (NRs) have been adopted as the ETL, and the effect of adding atomic layer deposited (ALD) ZnO on the ZnO NRs on the inverted organic solar cell performance has been investigated. The fabricated inverted organic solar cell with 5-nm-thick ALD-ZnO grown on the ZnO NRs showed the highest power conversion efficiency (PCE) of 3.08%, which is an enhancement of 85% from that of the cell without ALD-ZnO (PCE = 1.67%). The ultrathin ALD-ZnO was found to act as a curing layer of the surface defects on the hydrothermally grown ZnO NRs, resulting in an improvement in photovoltaic performance.

  10. Comprehensive cluster analysis with Transitivity Clustering.

    Science.gov (United States)

    Wittkop, Tobias; Emig, Dorothea; Truss, Anke; Albrecht, Mario; Böcker, Sebastian; Baumbach, Jan

    2011-03-01

    Transitivity Clustering is a method for the partitioning of biological data into groups of similar objects, such as genes, for instance. It provides integrated access to various functions addressing each step of a typical cluster analysis. To facilitate this, Transitivity Clustering is accessible online and offers three user-friendly interfaces: a powerful stand-alone version, a web interface, and a collection of Cytoscape plug-ins. In this paper, we describe three major workflows: (i) protein (super)family detection with Cytoscape, (ii) protein homology detection with incomplete gold standards and (iii) clustering of gene expression data. This protocol guides the user through the most important features of Transitivity Clustering and takes ∼1 h to complete.

  11. Suspended particle and drug ingredient concentrations in hospital dispensaries and implications for pharmacists' working environments.

    Science.gov (United States)

    Inaba, Ryoichi; Hioki, Atsushi; Kondo, Yoshihiro; Nakamura, Hiroki; Nakamura, Mitsuhiro

    2016-03-01

    The aim of this study was to assess the present status of working environments for pharmacists, including the concentrations of suspended particles and suspended drug ingredients in dispensaries. We conducted a survey on the work processes and working environment in 15 hospital dispensaries, and measured the concentrations of suspended particles and suspended drug ingredients using digital dust counter and high-performance liquid chromatography tandem mass spectrometry (LC-MS/MS), respectively. Of 25 types of powdered drugs that were frequently handled in the 15 dispensaries surveyed, 11 could be quantitatively determined. The amounts of suspended particles were relatively high, but below the reference value, in three dispensaries without dust collectors. The sedative-hypnotic drug zopiclone was detected in the suspended particles at one dispensary that was not equipped with dust collectors, and the antipyretic and analgesic drug acetaminophen was detected in two dispensaries equipped with dust collectors. There was no correlation between the daily number of prescriptions containing powdered drugs and the concentration of suspended particles in dispensaries. On the basis of the suspended particle concentrations measured, we concluded that dust collectors were effective in these dispensaries. However, suspended drug ingredients were detected also in dispensaries with dust collectors. These results suggest that the drug dust control systems of individual dispensaries should be properly installed and managed.

  12. Remote sensing of suspended sediment water research: principles, methods, and progress

    Science.gov (United States)

    Shen, Ping; Zhang, Jing

    2011-12-01

    In this paper, we reviewed the principle, data, methods and steps in suspended sediment research by using remote sensing, summed up some representative models and methods, and analyzes the deficiencies of existing methods. Combined with the recent progress of remote sensing theory and application in water suspended sediment research, we introduced in some data processing methods such as atmospheric correction method, adjacent effect correction, and some intelligence algorithms such as neural networks, genetic algorithms, support vector machines into the suspended sediment inversion research, combined with other geographic information, based on Bayesian theory, we improved the suspended sediment inversion precision, and aim to give references to the related researchers.

  13. Enhancement of Inverted Polymer Solar Cells Performances Using Cetyltrimethylammonium-Bromide Modified ZnO

    Directory of Open Access Journals (Sweden)

    Chung-Kai Wu

    2018-03-01

    Full Text Available In this study, the performance and stability of inverted bulk heterojunction (BHJ polymer solar cells (PSCs is enhanced by doping zinc oxide (ZnO with 0–6 wt % cetyltrimethylammonium bromide (CTAB in the sol-gel ZnO precursor solution. The power conversion efficiency (PCE of the optimized 3 wt % CTAB-doped ZnO PSCs was increased by 9.07%, compared to a PCE of 7.31% for the pristine ZnO device. The 0–6 wt % CTAB-doped ZnO surface roughness was reduced from 2.6 to 1 nm and the number of surface defects decreased. The X-ray photoelectron spectroscopy binding energies of Zn 2p3/2 (1021.92 eV and 2p1/2 (1044.99 eV shifted to 1022.83 and 1045.88 eV, respectively, which is related to strong chemical bonding via bromide ions (Br− that occupy oxygen vacancies in the ZnO lattice, improving the PCE of PSCs. The concentration of CTAB in ZnO significantly affected the work function of PSC devices; however, excessive CTAB increased the work function of the ZnO layer, resulting from the aggregation of CTAB molecules. In addition, after a 120-hour stability test in the atmosphere with 40% relative humidity, the inverted device based on CTAB-doped ZnO retained 92% of its original PCE and that based on pristine ZnO retained 68% of its original PCE. The obtained results demonstrate that the addition of CTAB into ZnO can dramatically influence the optical, electrical, and morphological properties of ZnO, enhancing the performance and stability of BHJ PSCs.

  14. Mn{sup 2+} ions distribution in doped sol–gel deposited ZnO films

    Energy Technology Data Exchange (ETDEWEB)

    Stefan, Mariana, E-mail: mstefan@infim.ro [National Institute of Materials Physics, P.O. Box MG-7, 077125 Magurele (Romania); Ghica, Daniela; Nistor, Sergiu V.; Maraloiu, Adrian V. [National Institute of Materials Physics, P.O. Box MG-7, 077125 Magurele (Romania); Plugaru, Rodica [National Institute for R & D in Microtechnologies (IMT), Erou Iancu Nicolae Str. 126A, 077190 Bucharest (Romania)

    2017-02-28

    Highlights: • Several Mn{sup 2+} centers observed by EPR in sol–gel ZnO films. • Mn{sup 2+} ions localized at Zn{sup 2+} sites in ZnO grains and disordered ZnO phase. • Sixfold coordinated Mn{sup 2+} ions localized in inter-grain region. • Aggregated Mn in insular-like regions between ZnO grains in the ZnO:5%Mn film. • Aggregated Mn phase presence and distribution observed by EPR and EDX-STEM. - Abstract: The localization and distribution of the Mn{sup 2+} ions in two sol–gel deposited ZnO films doped with different manganese concentrations were investigated by electron paramagnetic resonance spectroscopy and analytical transmission electron microscopy. In the lightly doped sample the Mn{sup 2+} ions are mainly localized substitutionally at isolated tetrahedrally coordinated Zn{sup 2+} sites in both crystalline ZnO nanograins (34%) and surrounding disordered ZnO (52%). In the highly doped ZnO film, a much smaller proportion of manganese substitutes Zn{sup 2+} in the crystalline and disordered ZnO (10%). The main amount (85%) of manganese aggregates in a secondary phase as an insular-like distribution between the ZnO nanograins. The remaining Mn{sup 2+} ions (14% and 5% at low and high doping levels, respectively) are localized at isolated, six-fold coordinated sites, very likely in the disordered intergrain region. Annealing at 600 °C induced changes in the Mn{sup 2+} ions distribution, reflecting the increase of the ZnO crystallization degree, better observed in the lightly doped sample.

  15. The surface defect-related electroluminescence from the ZnO microwire

    Energy Technology Data Exchange (ETDEWEB)

    Ding Meng; Zhao Dongxu; Yao Bin; Li Binghui; Zhang Zhenzhong; Shan Chongxin; Shen Dezhen, E-mail: dxzhao2000@yahoo.com.cn [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130021 (China)

    2011-02-23

    Surface defect-related electroluminescence (EL) was realized from a single ZnO microwire-based metal-semiconductor-metal structure on a glass substrate. ZnO microwires were successfully fabricated using a simple chemical vapour deposition approach. Schottky contacts were detected between Au electrodes and the ZnO microwire. The EL spectrum showed a broad emission band covering the visible range from 400 to 700 nm. The possible EL emission mechanism is discussed in detail in this paper.

  16. Ultraviolet photodetection of flexible ZnO nanowire sheets in polydimethylsiloxane polymer

    OpenAIRE

    Jinzhang Liu; Nunzio Motta; Soonil Lee

    2012-01-01

    Summary ZnO nanowires are normally exposed to an oxygen atmosphere to achieve high performance in UV photodetection. In this work we present results on a UV photodetector fabricated using a flexible ZnO nanowire sheet embedded in polydimethylsiloxane (PDMS), a gas-permeable polymer, showing reproducible UV photoresponse and enhanced photoconduction. PDMS coating results in a reduced response speed compared to that of a ZnO nanowire film in air. The rising speed is slightly reduced, while the ...

  17. Effect of nanocomposite packaging containing ZnO on growth of Bacillus subtilis and Enterobacter aerogenes

    Energy Technology Data Exchange (ETDEWEB)

    Esmailzadeh, Hakimeh [National Nutrition and Food Technology Research Institute, Faculty of Nutrition and Food Technology, Shahid Beheshti University of Medical Sciences, Tehran (Iran, Islamic Republic of); Sangpour, Parvaneh, E-mail: Sangpour@merc.ac.ir [Nanotechnology and Advanced Materials Department, Materials and Energy Research Center, Karaj (Iran, Islamic Republic of); Shahraz, Farzaneh [National Nutrition and Food Technology Research Institute, Faculty of Nutrition and Food Technology, Shahid Beheshti University of Medical Sciences, Tehran (Iran, Islamic Republic of); Hejazi, Jalal [Department of Biochemistry and Nutrition, Faculty of Medicine, Zanjan University of Medical Sciences, Zanjan (Iran, Islamic Republic of); Khaksar, Ramin [National Nutrition and Food Technology Research Institute, Faculty of Nutrition and Food Technology, Shahid Beheshti University of Medical Sciences, Tehran (Iran, Islamic Republic of)

    2016-01-01

    Recent advances in nanotechnology have opened new windows in active food packaging. Nano-sized ZnO is an inexpensive material with potential antimicrobial properties. The aim of the present study is to evaluate the antibacterial effect of low density Polyethylene (LDPE) containing ZnO nanoparticles on Bacillus subtilis and Enterobacter aerogenes. ZnO nanoparticles have been synthesized by facil molten salt method and have been characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM). Nanocomposite films containing 2 and 4 wt.% ZnO nanoparticles were prepared by melt mixing in a twin-screw extruder. The growth of both microorganisms has decreased in the presence of ZnO containing nanocomposites compared with controls. Nanocomposites with 4 wt.% ZnO nanoparticles had stronger antibacterial effect against both bacteria in comparison with the 2 wt.% ZnO containing nanocomposites. B. subtilis as Gram-positive bacteria were more sensitive to ZnO containing nanocomposite films compared with E. aerogenes as Gram-negative bacteria. There were no significant differences between the migration of Zn ions from 2 and 4 wt.% ZnO containing nanocomposites and the released Zn ions were not significantly increased in both groups after 14 days compared with the first. Regarding the considerable antibacterial effects of ZnO nanoparticles, their application in active food packaging can be a suitable solution for extending the shelf life of food. - Highlights: • ZnO containing nanocomposites decreased growth of both B. subtilis and E. aerogenes. • B. subtilis was more sensitive to ZnO containing nanocomposites. • The migration of Zn ions from nanocomposites was negligible.

  18. Recent progress on doped ZnO nanostructures for visible-light photocatalysis

    International Nuclear Information System (INIS)

    Samadi, Morasae; Zirak, Mohammad; Naseri, Amene; Khorashadizade, Elham; Moshfegh, Alireza Z.

    2016-01-01

    Global environmental pollution and energy supply demand have been regarded as important concerns in recent years. Metal oxide semiconductor photocatalysts is a promising approach to apply environmental remediation as well as fuel generation from water splitting and carbon dioxide reduction. ZnO nanostructures have been shown promising photocatalytic activities due to their non-toxic, inexpensive, and highly efficient nature. However, its wide band gap hinders photo-excitation for practical photocatalytic applications under solar light as an abundant, clean and safe energy source. To overcome this barrier, many strategies have been developed in the last decade to apply ZnO nanostructured photocatalysts under visible light. In this review, we have classified different approaches to activate ZnO as a photocatalyst in visible-light spectrum. Utilization of various nonmetals, transition metals and rare-earth metals for doping in ZnO crystal lattice to create visible-light-responsive doped ZnO photocatalysts is discussed. Generation of localized energy levels within the gap in doped ZnO nanostructures has played an important role in effective photocatalytic reaction under visible-light irradiation. The effect of dopant type, ionic size and its concentration on the crystal structure, electronic property and morphology of doped ZnO with a narrower band gap is reviewed systematically. Finally, a comparative study is performed to evaluate two classes of metals and nonmetals as useful dopants for ZnO nanostructured photocatalysts under visible light. - Highlights: • Metals and nonmetals used as a dopant to shift ZnO band gap toward visible-light. • Modification of electronic structure played a crucial role in doped ZnO activity. • Correlation between dopant's characteristics and ZnO visible activity was reviewed. • Photo-degradation of doped ZnO was studied and compared for different dopants.

  19. Oxygen vacancy-induced ferromagnetism in un-doped ZnO thin films

    Science.gov (United States)

    Zhan, Peng; Wang, Weipeng; Liu, Can; Hu, Yang; Li, Zhengcao; Zhang, Zhengjun; Zhang, Peng; Wang, Baoyi; Cao, Xingzhong

    2012-02-01

    ZnO films became ferromagnetic when defects were introduced by thermal-annealing in flowing argon. This ferromagnetism, as shown by the photoluminescence measurement and positron annihilation analysis, was induced by the singly occupied oxygen vacancy with a saturated magnetization dependent positively on the amount of this vacancy. This study clarified the origin of the ferromagnetism of un-doped ZnO thin films and provides possibly an alternative way to prepare ferromagnetic ZnO films.

  20. Recent progress on doped ZnO nanostructures for visible-light photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Samadi, Morasae; Zirak, Mohammad [Department of Physics, Sharif University of Technology, P.O. Box 11555-9161, Tehran (Iran, Islamic Republic of); Naseri, Amene [Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 11365-8639, Tehran (Iran, Islamic Republic of); Khorashadizade, Elham [Department of Physics, Sharif University of Technology, P.O. Box 11555-9161, Tehran (Iran, Islamic Republic of); Moshfegh, Alireza Z., E-mail: moshfegh@sharif.edu [Department of Physics, Sharif University of Technology, P.O. Box 11555-9161, Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 11365-8639, Tehran (Iran, Islamic Republic of)

    2016-04-30

    Global environmental pollution and energy supply demand have been regarded as important concerns in recent years. Metal oxide semiconductor photocatalysts is a promising approach to apply environmental remediation as well as fuel generation from water splitting and carbon dioxide reduction. ZnO nanostructures have been shown promising photocatalytic activities due to their non-toxic, inexpensive, and highly efficient nature. However, its wide band gap hinders photo-excitation for practical photocatalytic applications under solar light as an abundant, clean and safe energy source. To overcome this barrier, many strategies have been developed in the last decade to apply ZnO nanostructured photocatalysts under visible light. In this review, we have classified different approaches to activate ZnO as a photocatalyst in visible-light spectrum. Utilization of various nonmetals, transition metals and rare-earth metals for doping in ZnO crystal lattice to create visible-light-responsive doped ZnO photocatalysts is discussed. Generation of localized energy levels within the gap in doped ZnO nanostructures has played an important role in effective photocatalytic reaction under visible-light irradiation. The effect of dopant type, ionic size and its concentration on the crystal structure, electronic property and morphology of doped ZnO with a narrower band gap is reviewed systematically. Finally, a comparative study is performed to evaluate two classes of metals and nonmetals as useful dopants for ZnO nanostructured photocatalysts under visible light. - Highlights: • Metals and nonmetals used as a dopant to shift ZnO band gap toward visible-light. • Modification of electronic structure played a crucial role in doped ZnO activity. • Correlation between dopant's characteristics and ZnO visible activity was reviewed. • Photo-degradation of doped ZnO was studied and compared for different dopants.

  1. A LCAO-LDF study of Brønsted acids chemisorption on ZnO(0001)

    Science.gov (United States)

    Casarin, Maurizio; Maccato, Chiara; Tabacchi, Gloria; Vittadini, Andrea

    1996-05-01

    The local density functional theory coupled to the molecular cluster approach has been used to study the chemisorption of Br∅nsted acids (H 2O, H 2S, HCN, CH 3OH and CH 3SH) on the ZnO(0001) polar surface. Geometrical parameters and vibrational frequencies for selected species molecularly and dissociatively chemisorbed have been computed. The agreement with literature experimental data, when available, has been found to be good. The nature of the interaction between the conjugate base of the examined Br∅nsted acids and the Lewis acid site available on the surface has been elucidated, confirming its leading role in determining the actual relative acidity scale obtained by titration displacement reactions. The strength of this interaction follows the order OH - ≈ CN - > CH 3O - > SH - > CH 3S -.

  2. An experimental study on suspended sodium droplet combustion (2)

    International Nuclear Information System (INIS)

    Sato, Kenji

    2004-03-01

    As part of studies for phenomenological investigation of sodium droplet burning behavior, in our previous experimental studies for suspended single sodium droplet, behavior of ignition process and succeeding combustion, ignition delay time, and droplet temperature history had been investigated. In the present study, by using 4 mm diam. suspended sodium droplet, combustion experiments were performed for extended free-stream velocity range of dry air up to 200 cm/s, and for the initial droplet temperature T i =300degC and 400degC, and the effects of the free-stream velocity and initial droplet temperature on the ignition/burning behavior and ignition delay time were examined by using high speed video camera. The obtained experimental results are as follows: (1) Ignition phenomena of suspended spherical shape droplet were observed for all examined experimental conductions except the case of free-stream velocity U=200 cm/s at 300degC, where detachment of droplet from the support due to strained oxide film occurred. (2) The ignition delay time defined as the time to evolution of orange-light emitting zone or flame zone decreases with the increase of the free-stream velocity or of initial droplet temperature. Examples of typical ignition delay time are 0.68 s at U=20 cm/s, 0.52 s at U=100 cm/s, and 0.37 s at 200 cm/s for T i =400degC. (3) The orange-light emission at the moment of ignition occurs simultaneously over whole surface except the top region of the droplet. The intensity of the emission at the moment of ignition takes its maximum at the bottom region or upstream region of the droplet, and the emission intensity during the stable burning period increases with the increase of U. (4) When T i is 300degC, formation of temporal multiple short projections are observed before ignition for all examined free-stream velocities. The projections often do not disappear before ignition when the velocity is relatively high. (5) The layer or cloud composed of aerosol is formed

  3. Integrated ZnO nanotube arrays as efficient dye-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Xi, Y., E-mail: yxi6@cqu.edu.cn [Department of Applied Physics, Chongqing University, Chongqing 400044 (China); School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245 (United States); Wu, W.Z.; Fang, H. [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245 (United States); Hu, C.G. [Department of Applied Physics, Chongqing University, Chongqing 400044 (China)

    2012-07-15

    Highlights: Black-Right-Pointing-Pointer Tuning the reaction parameters, we got the best reaction conditions on ITO glass. Black-Right-Pointing-Pointer Introduce ZnO NTs design of photoanode featuring high aspect ratio structure. Black-Right-Pointing-Pointer The design strategy integrates the optical fibers or ITO with ZnO NTs grown. - Abstract: Zinc oxide (ZnO) is a wide band gap semiconducting material and has been considered as an alternative material in dye-sensitized solar cell (DSSC) applications. A high-performance nanotube (NT) photoanode must have a large surface area for dye adsorption in order to enhance conversion efficiency. In this work, the way of hydrothermally grown ZnO NT arrays on the indium tin oxide (ITO) substrate is presented by utilizing a systematic study. By adjusting the hydrothermal reaction parameters, we attained the optimizing reaction conditions on the ITO substrate. Moreover, ZnO NT arrays are introduced as a photoanode on various substrates, such as optical fiber and ITO glass, for DSSCs applications. We took the contrast test with conversion efficiency of the DSSC based on ZnO NT arrays versus ZnO nanowire arrays on the ITO substrate, which the DSSC based on ZnO NT arrays shows significantly enhanced power conversion efficiency. Furthermore, the conversion efficiency of DSSC based on the ZnO NT arrays grown on an optical fiber substrate is enhanced up to 1.44%.

  4. Effect of growth temperature on photoluminescence and piezoelectric characteristics of ZnO nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Water, Walter [Institute of Electro-Optical and Materials Science, National Formosa University, Yunlin 632, Taiwan (China); Fang, T.-H. [Institute of Electro-Optical and Materials Science, National Formosa University, Yunlin 632, Taiwan (China); Institute of Mechanical and Electromechanical Engineering, National Formosa University, Yunlin 632, Taiwan (China)], E-mail: fang.tehua@msa.hinet.net; Ji, L.-W.; Lee, C.-C. [Institute of Electro-Optical and Materials Science, National Formosa University, Yunlin 632, Taiwan (China)

    2009-02-25

    ZnO nanowire arrays were synthesized on Au-coated silicon (1 0 0) substrates by using vapour-liquid-solid process in this work. The effect of growth temperatures on the crystal structure and the surface morphology of ZnO nanowires were investigated by X-ray diffraction and scanning electron microscope. The absorption and optical characteristics of the nanowires were examined by Ultraviolet/Visible spectroscopy, and photoluminescence, respectively. The photoluminescence results exhibited ZnO nanowires had an ultraviolet and blue emission at 383 and 492 nm. Then a nanogenerator with ZnO nanowire arrays was fabricated and demonstrated Schottky-like current-voltage characteristics.

  5. From Bloch to random lasing in ZnO self-assembled nanostructures

    DEFF Research Database (Denmark)

    Garcia-Fernandez, Pedro David; Cefe, López

    2013-01-01

    In this paper, we present measurements on UV lasing in ZnO ordered and disordered nanostructures. Bloch lasing is achieved in the ordered structures by exploiting very low group-velocity Bloch modes in ZnO photonic crystals. In the second case, random lasing is observed in ZnO photonic glasses. We...... study the lasing threshold in both cases and its dependence on the structural parameters. Finally, we present the transition from Bloch to random lasing by deliberately doping a ZnO inverse photonic crystal with a controlled amount of lattice vacancies effectively converting it into a translationally...

  6. Enhanced wetting of Cu on ZnO by migration of subsurface oxygen vacancies

    DEFF Research Database (Denmark)

    Beinik, Igor; Helström, Matti; Jensen, Thomas Nørregaard

    2015-01-01

    is of utmost importance. The Cu/ZnO system is among the most investigated of such systems in model studies, but the presence of subsurface ZnO defects and their important role for adhesion on ZnO have been unappreciated so far. Here we reveal that the surface-directed migration of subsurface defects affects...... the Cu adhesion on polar ZnO(0001) in the technologically interesting temperature range up to 550 K. This leads to enhanced adhesion and ultimately complete wetting of ZnO(0001) by a Cu overlayer. On the basis of our experimental and computational results we demonstrate a mechanism which implies...

  7. UV irradiation assisted growth of ZnO nanowires on optical fiber surface

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Bo; Shi, Tielin; Liao, Guanglan; Li, Xiaoping; Huang, Jie; Zhou, Temgyuan; Tang, Zirong, E-mail: zirong@mail.hust.edu.cn

    2017-06-01

    Highlights: • A new fabrication process combined a hydrothermal process with UV irradiation from optical fiber is developed. • The growth of ZnO nanowires is efficient in the utilization of UV light. • A novel hybrid structure which integrates ZnO nanowires on optical fiber surface is synthesized. • The UV assisted growth of ZnO nanowires shows preferred orientation and better quality. • A mechanism of growing ZnO nanowires under UV irradiation is proposed. - Abstract: In this paper, a novel approach was developed for the enhanced growth of ZnO nanowires on optical fiber surface. The method combined a hydrothermal process with the efficient UV irradiation from the fiber core, and the effects of UV irradiation on the growth behavior of ZnO nanowires were investigated. The results show that UV irradiation had great effects on the preferred growth orientation and the quality of the ZnO nanowires. The crystallization velocity along the c-axis would increase rapidly with the increase of the irradiation power, while the growth process in the lateral direction was marginally affected by the irradiation. The structure of ZnO nanowires also shows less oxygen vacancy with UV irradiation of higher power. The developed approach is applicable for the efficient growth of nanowires on the fiber surface, and the ZnO nanowires/optical fiber hybrid structures have great potentials for a wide variety of applications such as optical fiber sensors and probes.

  8. Mn-doped ZnO nanocrystals synthesized by sonochemical method: Structural, photoluminescence, and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Othman, A.A., E-mail: aaelho@yahoo.com [Assiut University, Faculty of Science, Department of Physics, Assiut 71516 (Egypt); Osman, M.A. [Assiut University, Faculty of Science, Department of Physics, Assiut 71516 (Egypt); Ibrahim, E.M.M. [Sohag University, Faculty of Science, Department of Physics, Sohag 82524 (Egypt); Ali, Manar A.; Abd-Elrahim, A.G. [Assiut University, Faculty of Science, Department of Physics, Assiut 71516 (Egypt)

    2017-05-15

    Highlights: • Mn-doped ZnO nanostructures were synthesized by the sonochemical method. • Structural, morphological, optical, photoluminescence and magnetic properties were investigated. • Mn-doped ZnO nanostructures reveal a blue shift of the optical band gap. • Photoluminescence spectra of Mn-doped ZnO nanostructures show quenching in the emission intensity. • Mn-doped ZnO nanostructures exhibit ferromagnetic ordering at room temperature. - Abstract: This work reports the synthesis of Mn-doped ZnO nanostructures using ice-bath assisted sonochemical technique. The impact of Mn-doping on structural, morphological, optical, and magnetic properties of ZnO nanostructures is studied. The morphological study shows that the lower doped samples possess mixtures of nanosheets and nanorods while the increase in Mn content leads to improvement of an anisotropic growth in a preferable orientation to form well-defined edge rods at Mn content of 0.04. UV–vis absorption spectra show that the exciton peak in the UV region is blue shifted due to Mn incorporation into the ZnO lattice. Doping ZnO with Mn ions leads to a reduction in the PL intensity due to a creation of more non-radiative recombination centers. The magnetic measurements show that the Mn-doped ZnO nanostructures exhibit ferromagnetic ordering at room temperature, as well as variation of the Mn content can significantly affect the ferromagnetic behavior of the samples.

  9. Morphology evolution of hydrothermally grown ZnO nanostructures on gallium doping and their defect structures

    Energy Technology Data Exchange (ETDEWEB)

    Pineda-Hernandez, G. [Facultad de Ingenieria Quimica, Benemerita Universidad Autonoma de Puebla, C.P. 72570 Puebla, Pue. (Mexico); Escobedo-Morales, A., E-mail: alejandroescobedo@hotmail.com [Facultad de Ingenieria Quimica, Benemerita Universidad Autonoma de Puebla, C.P. 72570 Puebla, Pue. (Mexico); Pal, U. [Instituto de Fisica, Benemerita Universidad Autonoma de Puebla, Apdo. Postal J-48, C.P. 72570 Puebla, Pue. (Mexico); Chigo-Anota, E. [Facultad de Ingenieria Quimica, Benemerita Universidad Autonoma de Puebla, C.P. 72570 Puebla, Pue. (Mexico)

    2012-08-15

    In the present article, the effect of gallium doping on the morphology, structural, and vibrational properties of hydrothermally grown ZnO nanostructures has been studied. It has been observed that incorporated gallium plays an important role on the growth kinetics and hence on the morphology evolution of the ZnO crystals. Ga doping in high concentration results in the contraction of ZnO unit cell, mainly along c-axis. Although Ga has high solubility in ZnO, heavy doping promotes the segregation of Ga atoms as a secondary phase. Incorporated Ga atoms strongly affect the vibrational characteristics of ZnO lattice and induce anomalous Raman modes. Possible mechanisms of morphology evolution and origin of anomalous Raman modes in Ga doped ZnO nanostructures are discussed. -- Highlights: Black-Right-Pointing-Pointer Ga doped ZnO nanostructures were successfully grown by hydrothermal chemical route. Black-Right-Pointing-Pointer Ga doping has strong effect on the resulting morphology of ZnO nanostructures. Black-Right-Pointing-Pointer Anomalous vibrational modes in wurtzite ZnO lattice are induced by Ga doping. Black-Right-Pointing-Pointer Incorporated Ga atoms accommodate at preferential lattice sites.

  10. Effect of morphology on the non-ohmic conduction in ZnO nanostructures

    Science.gov (United States)

    Praveen, E.; Jayakumar, K.

    2016-05-01

    Nanostructures of ZnO is synthesized with nanoflower like morphology by simple wet chemical method. The structural, morphological and electrical characterization have been carried out. The temperature dependent electrical characterization of ZnO pellets of thickness 1150 µm is made by the application of 925MPa pressure. The morphological dependence of non-ohmic conduction beyond some arbitrary tunneling potential and grain boundary barrier thickness is compared with the commercially available bulk ZnO. Our results show the suitability of nano-flower like ZnO for the devices like sensors, rectifiers etc.

  11. Interaction and photodegradation characteristics of fluorescein dye in presence of ZnO nanoparticles.

    Science.gov (United States)

    Bardhan, Munmun; Mandal, Gopa; Ganguly, Tapan

    2011-04-01

    The interaction between xanthene dye Fluorescein (Fl) and zinc oxide (ZnO) nanoparticles is investigated under physiological conditions. From the analysis of the steady state and time resolved spectroscopic studies in aqueous solution static mode is found to be responsible in the mechanism of fluorescence quenching of the dye Fl in presence of ZnO. ZnO nanoparticles are used as photocatalyst in order to degrade Fl dye. At pH 7, a maximum degradation efficiency of 44.4% of the dye has been achieved in presence of ZnO as a nanophotocatalyst and the photodegradation follows second-order kinetics.

  12. Controllable growth and magnetic properties of nickel nanoclusters electrodeposited on the ZnO nanorod template

    International Nuclear Information System (INIS)

    Tang Yang; Zhao Dongxu; Shen Dezhen; Zhang Jiying; Wang Xiaohua

    2009-01-01

    The ZnO nanorods were used as a template to fabricate nickel nanoclusters by electrodeposition. The ZnO nanorod arrays act as a nano-semiconductor electrode for depositing metallic and magnetic nickel nanoclusters. The growth sites of Ni nanoclusters could be controlled by adjusting the applied potential. Under -1.15 V the Ni nanoclusters could be grown on the tips of ZnO nanorods. On increasing the potential to be more negative the ZnO nanorods were covered by Ni nanoclusters. The magnetic properties of the electrodeposited Ni nanoclusters also evolved with the applied potentials.

  13. Controllable growth and magnetic properties of nickel nanoclusters electrodeposited on the ZnO nanorod template

    Energy Technology Data Exchange (ETDEWEB)

    Tang Yang; Zhao Dongxu; Shen Dezhen; Zhang Jiying [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16 East Nan-Hu Road, Open Economic Zone, Changchun 130033 (China); Wang Xiaohua, E-mail: dxzhao2000@yahoo.com.c [National Key Laboratory of High Power Semiconductor Laser, Changchun University of Science and Technology, 7089 WeiXing Road, ChangChun 130022 (China)

    2009-12-09

    The ZnO nanorods were used as a template to fabricate nickel nanoclusters by electrodeposition. The ZnO nanorod arrays act as a nano-semiconductor electrode for depositing metallic and magnetic nickel nanoclusters. The growth sites of Ni nanoclusters could be controlled by adjusting the applied potential. Under -1.15 V the Ni nanoclusters could be grown on the tips of ZnO nanorods. On increasing the potential to be more negative the ZnO nanorods were covered by Ni nanoclusters. The magnetic properties of the electrodeposited Ni nanoclusters also evolved with the applied potentials.

  14. Tunable, flexible antireflection layer of ZnO nanowires embedded in PDMS.

    Science.gov (United States)

    Kim, Min Kyu; Yi, Dong Kee; Paik, Ungyu

    2010-05-18

    In this article, we report the fabrication of ordered hybrid structures composed of ZnO nanowires and a polymeric matrix with a polymer precursor infiltrating the nanowire arrays. The antireflective properties of the resulting ZnO nanowire-embedded polydimethylsiloxane composite (ZPC) were investigated at various ZnO nanowire lengths and ZPC bending angles. Interestingly, we found that whereas the antireflective properties showed a strong dependence on the length of the embedded ZnO nanowires in PDMS, the bending of ZPC has little effect on the antireflective properties.

  15. Electric field gradient calculation at atomic site of In implanted ZnO samples

    International Nuclear Information System (INIS)

    Abreu, Y.; Cruz, C. M.; Leyva, A.; Pinnera; Van Espen, P.; Perez, C.

    2011-01-01

    The electric field gradient (EFG) calculated for 111 In→ 111 Cd implanted ZnO samples is reported. The study was made for ideal hexagonal ZnO structures and super-cells considering the In implantation environment at the cation site using the 'WIEN2k' code within the GGA(+U) approximation. The obtained EFG values are in good agreement with the experimental reports for ideal ZnO and 111 In→ 111 Cd implanted structures; measured by perturbed angular correlation (PAC) and Moessbauer spectroscopy. The attribution of substitutional incorporation of 111 In at the ZnO cation site after annealing was confirmed. (Author)

  16. Explanation of ferromagnetism origin in C-doped ZnO by first principle calculations

    International Nuclear Information System (INIS)

    El Amiri, A.; Lassri, H.; Hlil, E.K.; Abid, M.

    2015-01-01

    By ab-initio calculations, we systematically study possible source of ferromagnetism C-doped ZnO compound. The electronic structure and magnetic properties of C-doped ZnO with / without ZnO host and C defects were investigated using the Korringa–Kohn–Rostoker (KKR) method combined with coherent potential approximation (CPA). We show that Zn vacancy and presence of C defects (substitutional, interstitial or combination of both) induce the ferromagnetism in C-doped ZnO. From density of state (DOS) analysis, we show that p–p interaction between C atoms and/or C and O atoms is the mechanism of ferromagnetic coupling in C-doped ZnO. - Highlights: • We study the effect of ZnO host and C defects on ferromagnetism in C-doped ZnO. • Details of KKR method calculations performed to investigate both magnetic and electronic structures. • Magnetic moments, total and partial DOS for C-doped ZnO are well calculated and discussed. • Based on DOS calculations we interpret a origin of ferromagnetism in C-doped ZnO. • Mechanism of ferromagnetic coupling is well proposed

  17. Explanation of ferromagnetism origin in C-doped ZnO by first principle calculations

    Energy Technology Data Exchange (ETDEWEB)

    El Amiri, A., E-mail: aelamiri@casablanca.ma [Laboratoire de Physique Fondamentale et Appliquée (LPFA), Faculté des Sciences Ain Chock, Université Hassan II, B.P. 5366 Mâarif, Casablanca, Maroc (Morocco); Lassri, H. [Laboratoire de Physique des Matériaux, Micro-électronique, Automatique et Thermique (LPMMAT). Faculté des Sciences Ain Chock, Université Hassan II, B.P. 5366 Mâarif, Casablanca, Maroc (Morocco); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, 38042 Grenoble (France); Abid, M. [Laboratoire de Physique Fondamentale et Appliquée (LPFA), Faculté des Sciences Ain Chock, Université Hassan II, B.P. 5366 Mâarif, Casablanca, Maroc (Morocco)

    2015-01-15

    By ab-initio calculations, we systematically study possible source of ferromagnetism C-doped ZnO compound. The electronic structure and magnetic properties of C-doped ZnO with / without ZnO host and C defects were investigated using the Korringa–Kohn–Rostoker (KKR) method combined with coherent potential approximation (CPA). We show that Zn vacancy and presence of C defects (substitutional, interstitial or combination of both) induce the ferromagnetism in C-doped ZnO. From density of state (DOS) analysis, we show that p–p interaction between C atoms and/or C and O atoms is the mechanism of ferromagnetic coupling in C-doped ZnO. - Highlights: • We study the effect of ZnO host and C defects on ferromagnetism in C-doped ZnO. • Details of KKR method calculations performed to investigate both magnetic and electronic structures. • Magnetic moments, total and partial DOS for C-doped ZnO are well calculated and discussed. • Based on DOS calculations we interpret a origin of ferromagnetism in C-doped ZnO. • Mechanism of ferromagnetic coupling is well proposed.

  18. Improved luminescence intensity and stability of thermal annealed ZnO incorporated Alq3 composite films.

    Science.gov (United States)

    Cuba, M; Muralidharan, G

    2015-11-01

    The 30 wt% of ZnO (weight percentage of ZnO has been optimised) incorporated tris- (8-hydroxyquinoline)aluminum (Alq3) has been synthesised and coated on to glass substrates using dip coating method. The structural and optical properties of the Alq3/ZnO composite film after thermal annealing from 50 to 300 °C insteps 50° has been studied and reported. XRD pattern reveals the presence of crystalline ZnO in all the annealed films. The films annealed above 150 °C reveal the presence of crystalline Alq3 along with crystalline ZnO. The FTIR spectra confirm the presence of hydroxyquinoline and ZnO vibration in all the annealed composite films. The composite films annealed above 150 °C show a partial sublimation and degradation of hydroxyquinoline compounds. The ZnO incorporated composite films (Alq3/ZnO) exhibit two emission peaks, one corresponding to ZnO at 487 nm and another at 513 nm due to Alq3. The films annealed at 200 °C exhibit maximum photoluminescence (PL) intensity than pristine film at 513 nm when excited at 390 nm.

  19. Toxicity evaluation of ZnO nanostructures on L929 fibroblast cell line using MTS assay

    International Nuclear Information System (INIS)

    Bakhori, Siti Khadijah Mohd; Mahmud, Shahrom; Ann, Ling Chuo; Mohamed, Azman Seeni; Saifuddin, Siti Nazmin; Masudi, Sam’an Malik; Mohamad, Dasmawati

    2015-01-01

    ZnO has wide applications in medical and dentistry apart from being used as optoelectronic devices such as solar cells, photodetectors, sensors and light emitting diodes (LEDs). Therefore, the toxicity evaluation is important to know the toxicity level on normal cell line. The toxicity of two grades ZnO nanostructures, ZnO-4 and ZnO-8 have been carried out using cytotoxicity test of MTS assay on L929 rat fibroblast cell line. Prior to that, ZnO-4 and ZnO-8 were characterized for its morphology, structure and optical properties using FESEM, X-ray diffraction, and Photoluminescence respectively. The two groups revealed difference in morphology and exhibit slightly shifted of near band edge emission of Photoluminescence other than having a similar calculated crystallite size of nanostructures. The viability of cells after 72h were obtained and the statistical significance value was calculated using SPSS v20. The p value is more than 0.05 between untreated and treated cell with ZnO. This insignificant value of p>0.05 can be summarized as a non-toxic level of ZnO-4 and ZnO-8 on the L929 cell line

  20. Microwave-assisted silica coating and photocatalytic activities of ZnO nanoparticles

    International Nuclear Information System (INIS)

    Siddiquey, Iqbal Ahmed; Furusawa, Takeshi; Sato, Masahide; Suzuki, Noboru

    2008-01-01

    A new and rapid method for silica coating of ZnO nanoparticles by the simple microwave irradiation technique is reported. Silica-coated ZnO nanoparticles were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), high-resolution transmission electron microscopy (HR-TEM), CHN elemental analysis and zeta potential measurements. The FT-IR spectra and XPS clearly confirmed the silica coating on ZnO nanoparticles. The results of XPS analysis showed that the elements in the coating at the surface of the ZnO nanoparticles were Zn, O and Si. HR-TEM micrographs revealed a continuous and uniform dense silica coating layer of about 3 nm in thickness on the surface of ZnO nanoparticles. In addition, the silica coating on the ZnO nanoparticles was confirmed by the agreement in the zeta potential of the silica-coated ZnO nanoparticles with that of SiO 2 . The results of the photocatalytic degradation of methylene blue (MB) in aqueous solution showed that silica coating effectively reduced the photocatalytic activity of ZnO nanoparticles. Silica-coated ZnO nanoparticles showed excellent UV shielding ability and visible light transparency

  1. Dynamic recovery and optical properties changes in He-implanted ZnO nanoparticles

    International Nuclear Information System (INIS)

    Lee, J.-K.; Harriman, T.A.; Lucca, D.A.; Jung, H.S.; Ryan, D.B.; Nastasi, M.

    2007-01-01

    A study of the effects of ion-implanted He + on the photoluminescence (PL) of ZnO nanoparticles is presented. This investigation is motivated by the need to further understand the effects of damage resulting from the implantation process on the luminescence response of the nanoparticles. ZnO nanoparticles were synthesized by reacting zinc acetate with lithium hydroxide. The nanoparticle suspension was then dip coated on SiO 2 substrates producing thin films of ZnO nanoparticles, which were then implanted with He + ions at either room temperature or 400 deg. C. Following implantation, the PL spectrum of the ZnO nanoparticles was investigated and compared to that obtained from He-implanted bulk ZnO. Change in the overall luminescence efficiency was found to depend on both the size of the nanoparticles and the implantation temperature, and is attributed to the dynamic recovery of collision cascades in the ZnO nanoparticles. In addition, a comparison of He + -implanted ZnO nanoparticles with He + -implanted ZnO single crystals indicates that the origin of the green luminescence occurring from the ZnO nanoparticles is near-surface complex defects

  2. Toxicity evaluation of ZnO nanostructures on L929 fibroblast cell line using MTS assay

    Energy Technology Data Exchange (ETDEWEB)

    Bakhori, Siti Khadijah Mohd; Mahmud, Shahrom; Ann, Ling Chuo [Nano-optoelectronics Research and Technology Laboratory (NOR.), School of Physics, Universiti Sains Malaysia, 11800, USM, Pulau Pinang (Malaysia); Mohamed, Azman Seeni; Saifuddin, Siti Nazmin [Integrative Medicine Cluster, Advanced Medical and Dental Institute, Universiti Sains Malaysia, Bandar Putra Bertam, 13200 Kepala Batas, Pulau Pinang (Malaysia); Masudi, Sam’an Malik; Mohamad, Dasmawati [Craniofacial Science Laboratory, School of Dentistry, Health Campus, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan (Malaysia)

    2015-04-24

    ZnO has wide applications in medical and dentistry apart from being used as optoelectronic devices such as solar cells, photodetectors, sensors and light emitting diodes (LEDs). Therefore, the toxicity evaluation is important to know the toxicity level on normal cell line. The toxicity of two grades ZnO nanostructures, ZnO-4 and ZnO-8 have been carried out using cytotoxicity test of MTS assay on L929 rat fibroblast cell line. Prior to that, ZnO-4 and ZnO-8 were characterized for its morphology, structure and optical properties using FESEM, X-ray diffraction, and Photoluminescence respectively. The two groups revealed difference in morphology and exhibit slightly shifted of near band edge emission of Photoluminescence other than having a similar calculated crystallite size of nanostructures. The viability of cells after 72h were obtained and the statistical significance value was calculated using SPSS v20. The p value is more than 0.05 between untreated and treated cell with ZnO. This insignificant value of p>0.05 can be summarized as a non-toxic level of ZnO-4 and ZnO-8 on the L929 cell line.

  3. Defect studies in annealed ZnO by positron annihilation spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sanyal, D; Roy, Tapatee Kundu; Chakrabarti, Mahuya; Dechoudhury, Siddhartha; Bhowmick, Debasis; Chakrabarti, Alok [Variable Energy Cyclotron Centre, 1/AF, Bidhannagar, Kolkata 700064 (India)

    2008-01-30

    Coincidence Doppler broadening of the positron annihilation technique has been employed to identify the defects in thermally annealed 'as-received' ZnO and thermally annealed ball-milled nanocrystalline ZnO. Results indicate that a significant amount of oxygen vacancy has been created in ZnO due to annealing at about 500 deg. C and above. The results also indicate that the Zn vacancy created during the ball milling process can be easily removed by annealing the sample at about 500 deg. C and above. The defect characterization has also been correlated with the magnetic properties of ZnO.

  4. Positron annihilation spectroscopy in doped p-type ZnO

    Science.gov (United States)

    Majumdar, Sayanee; Sanyal, D.

    2011-07-01

    Positron annihilation lifetime (PAL) spectroscopy has been used to investigate the vacancy type defect of the Li and N doped ZnO. The mono-vacancies, shallow -vacancies and open volume defects have been found in both the Li and N doped ZnO. The mono-vacancies, shallow-vacancies and open volume defects increase in N-doped ZnO as the size of N is quite high compared to Li. Positron annihilation study showed that the doping above 1-3% Li and 3-4% N in ZnO are not required in order to achieve low resistivity, high hole concentration and good mobility.

  5. Defect studies in annealed ZnO by positron annihilation spectroscopy

    International Nuclear Information System (INIS)

    Sanyal, D; Roy, Tapatee Kundu; Chakrabarti, Mahuya; Dechoudhury, Siddhartha; Bhowmick, Debasis; Chakrabarti, Alok

    2008-01-01

    Coincidence Doppler broadening of the positron annihilation technique has been employed to identify the defects in thermally annealed 'as-received' ZnO and thermally annealed ball-milled nanocrystalline ZnO. Results indicate that a significant amount of oxygen vacancy has been created in ZnO due to annealing at about 500 deg. C and above. The results also indicate that the Zn vacancy created during the ball milling process can be easily removed by annealing the sample at about 500 deg. C and above. The defect characterization has also been correlated with the magnetic properties of ZnO

  6. Photovoltaic Properties of Co-doped ZnO Thin Film on Glass Substrate

    International Nuclear Information System (INIS)

    Sabia Aye; Zin Ma Ma; May Nwe Oo; Than Than Win; Yin Maung Maung; Ko Ko Kyaw Soe

    2011-12-01

    Cobalt (Co) 0.4 mol doped zinc oxide (ZnO) fine powder was prepared by solid state mixed oxide route. Phase formation and crystal structure of Co-doped ZnO (CZO) powder were examined by X-ray diffraction (XRD). Scanning Electron Microscopy (SEM) was used to observe the micro structure of Co doped ZnO powder. Energy Dispersive X-ray Fluorescent (EDXRF) technique gave the elemental content of cobalt and zinc. Co-doped ZnO film was formed on glass substrate by spin coating technique. Photovoltaic properties of CZO/glass cell were measured.

  7. Superior photoelectrochemical properties of ZnO nanorods/poly(3-hexylthiophene) hybrid photoanodes

    Science.gov (United States)

    Majumder, T.; Hmar, J. J. L.; Dhar, S.; Mondal, S. P.

    2017-06-01

    Photoelectrochemical properties of ZnO nanorods (ZnO NRs) and poly(3-hexylthiophene) (P3HT) polymer hybrid photoanodes have been studied. The hybrid photoanodes demonstrated higher photoconversion efficiency, incident photon to current conversion efficiency (IPCE) and lower interfacial resistance compared to pristine ZnO nanorods and P3HT based electrodes. The origin of superior photoelectrochemical properties of ZnO/P3HT photoanodes has been explained using carrier transport mechanism at semiconductor/electrolyte junction. The stability of ZnO NRs/P3HT photoanode has been demonstrated.

  8. Effects of the Absorption Behaviour of ZnO Nanoparticles on Cytotoxicity Measurements

    Directory of Open Access Journals (Sweden)

    Nigar Najim

    2014-01-01

    Full Text Available ZnO absorbs certain wavelengths of light and this behavior is more pronounced for nanoparticles of ZnO. As many toxicity measurements rely on measuring light transmission in cell lines, it is essential to determine how far this light absorption influences experimental toxicity measurements. The main objective was to study the ZnO absorption and how this influenced the cytotoxicity measurements. The cytotoxicity of differently sized ZnO nanoparticles in normal and cancer cell lines derived from lung tissue (Hs888Lu, neuron-phenotypic cells (SH-SY5Y, neuroblastoma (SH-SY5Y, human histiocytic lymphoma (U937, and lung cancer (A549 was investigated. Our results demonstrate that the presence of ZnO affected the cytotoxicity measurements due to the absorption characteristic of ZnO nanoparticles. The data revealed that the ZnO nanoparticles with an average particle size of around 85.7 nm and 190 nm showed cytotoxicity towards U937, SH-SY5Y, differentiated SH-SY5Y, and Hs888Lu cell lines. No effect on the A549 cells was observed. It was also found that the cytotoxicity of ZnO was particle size, concentration, and time dependent. These studies are the first to quantify the influence of ZnO nanoparticles on cytotoxicity assays. Corrections for absorption effects were carried out which gave an accurate estimation of the concentrations that produce the cytotoxic effects.

  9. Synthesis of ordered large-scale ZnO nanopore arrays

    International Nuclear Information System (INIS)

    Ding, G.Q.; Shen, W.Z.; Zheng, M.J.; Fan, D.H.

    2006-01-01

    An effective approach is demonstrated for growing ordered large-scale ZnO nanopore arrays through radio-frequency magnetron sputtering deposition on porous alumina membranes (PAMs). The realization of highly ordered hexagonal ZnO nanopore arrays benefits from the unique properties of ZnO (hexagonal structure, polar surfaces, and preferable growth directions) and PAMs (controllable hexagonal nanopores and localized negative charges). Further evidence has been shown through the effects of nanorod size and thermal treatment of PAMs on the yielded morphology of ZnO nanopore arrays. This approach opens the possibility of creating regular semiconducting nanopore arrays for the application of filters, sensors, and templates

  10. Growth of Single- and Bilayer ZnO on Au(111) and Interaction with Copper

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Xingyi; Yao, Kun; Sun, Keju; Li, Wei-Xue; Lee, Junseok; Matranga, Christopher

    2013-05-02

    The stoichiometric single- and bi-layer ZnO(0001) have been prepared by reactive deposition of Zn on Au(111) and studied in detail with X-ray photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory calculations. Both single- and bi-layer ZnO(0001) adopt a planar, graphite-like structure similar to freestanding ZnO(0001) due to the weak van der Waals interactions dominating their adhesion with the Au(111) substrate. At higher temperature, the single-layer ZnO(0001) converts gradually to bi-layer ZnO(0001) due to the twice stronger interaction between two ZnO layers than the interfacial adhesion of ZnO with Au substrate. It is found that Cu atoms on the surface of bi-layer ZnO(0001) are mobile with a diffusion barrier of 0.31 eV, and likely to agglomerate and form nanosized particles at low coverages; while Cu atoms tend to penetrate a single layer of ZnO(0001) with a barrier of 0.10 eV, resulting in a Cu free surface.

  11. Selective growth of ZnO thin film nanostructures: Structure, morphology and tunable optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Krishnakanth, Katturi Naga; Sunandana, C. S. [School of Physics, University of Hyderabad, Hyderabad-50046 (India); Rajesh, Desapogu, E-mail: rajesh.esapogu@gmail.com, E-mail: mperd@nus.edu.sg [School of Physics, University of Hyderabad, Hyderabad-50046 (India); Dept. of Mechanical Engineering, National University of Singapore (Singapore)

    2016-05-23

    The ZnO nanostructures (spherical, rod shape) have been successfully fabricated via a thermal evaporation followed by dip coating method. The pure, doped ZnO thin films were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FESEM) and UV-Vis spectroscopy, respectively. A possible growth mechanism of the spherical, rod shape ZnO nanostructures are discussed. XRD patterns revealed that all films consist of pure ZnO phase and were well crystallized with preferential orientation towards (002) direction. Doping by PVA, PVA+Cu has effective role in the enhancement of the crystalline quality and increases in the band gap.

  12. Oxidant-Dependent Thermoelectric Properties of Undoped ZnO Films by Atomic Layer Deposition

    KAUST Repository

    Kim, Hyunho

    2017-02-27

    Extraordinary oxidant-dependent changes in the thermoelectric properties of undoped ZnO thin films deposited by atomic layer deposition (ALD) have been observed. Specifically, deionized water and ozone oxidants are used in the growth of ZnO by ALD using diethylzinc as a zinc precursor. No substitutional atoms have been added to the ZnO films. By using ozone as an oxidant instead of water, a thermoelectric power factor (σS) of 5.76 × 10 W m K is obtained at 705 K for undoped ZnO films. In contrast, the maximum power factor for the water-based ZnO film is only 2.89 × 10 W m K at 746 K. Materials analysis results indicate that the oxygen vacancy levels in the water- and ozone-grown ZnO films are essentially the same, but the difference comes from Zn-related defects present in the ZnO films. The data suggest that the strong oxidant effect on thermoelectric performance can be explained by a mechanism involving point defect-induced differences in carrier concentration between these two oxides and a self-compensation effect in water-based ZnO due to the competitive formations of both oxygen and zinc vacancies. This strong oxidant effect on the thermoelectric properties of undoped ZnO films provides a pathway to improve the thermoelectric performance of this important material.

  13. LMC clusters: young

    International Nuclear Information System (INIS)

    Freeman, K.C.

    1980-01-01

    The young globular clusters of the LMC have ages of 10 7 -10 8 y. Their masses and structure are similar to those of the smaller galactic globular clusters. Their stellar mass functions (in the mass range 6 solar masses to 1.2 solar masses) vary greatly from cluster to cluster, although the clusters are similar in total mass, age, structure and chemical composition. It would be very interesting to know why these clusters are forming now in the LMC and not in the Galaxy. The author considers the 'young globular' or 'blue populous' clusters of the LMC. The ages of these objects are 10 7 to 10 8 y, and their masses are 10 4 to 10 5 solar masses, so they are populous enough to be really useful for studying the evolution of massive stars. The author concentrates on the structure and stellar content of these young clusters. (Auth.)

  14. Star clusters and associations

    International Nuclear Information System (INIS)

    Ruprecht, J.; Palous, J.

    1983-01-01

    All 33 papers presented at the symposium were inputted to INIS. They dealt with open clusters, globular clusters, stellar associations and moving groups, and local kinematics and galactic structures. (E.S.)

  15. Cluster beam injection

    International Nuclear Information System (INIS)

    Bottiglioni, F.; Coutant, J.; Fois, M.

    1978-01-01

    Areas of possible applications of cluster injection are discussed. The deposition inside the plasma of molecules, issued from the dissociation of the injected clusters, has been computed. Some empirical scaling laws for the penetration are given

  16. Interactions of radionuclides with sediments and suspended particles

    International Nuclear Information System (INIS)

    Carpenter, R.

    1997-01-01

    This chapter reviews fundamental principles of the rates and extents of radionuclide uptake by sedimentary and suspended particles, defines sediment-water partition coefficients, and shows how they can explain first order features of radionuclide partitioning in aquatic environments. It then explains how sediment accumulation and mixing rates can be calculated from profiles of radionuclide activity measured in sediment cores. Such rates can be combined with profiles of other chemicals to establish the extent of temporal changes in chemical composition of the overlying water body. Since sediment processing and counting in the laboratory take much longer than the time required to collect the sample, suggestions are made to ensure that the sediment samples are not ruined or comprised during collection and handling in the field, and so are worth all the subsequent time and effort to analyze. (author)

  17. Heat Transfer Correlations for Free Convection from Suspended Microheaters

    Directory of Open Access Journals (Sweden)

    David GOSSELIN

    2016-08-01

    Full Text Available Portability and autonomy for biomedical diagnostic devices are two rising requirements. It is recognized that low-energy heating of such portable devices is of utmost importance for molecular recognition. This work focuses on screen-printed microheaters based on on Joule effect, which constitute an interesting solution for low-energy heating. An experimental study of the natural convection phenomena occurring with such microheaters is conducted. When they are suspended in the air, and because of the thinness of the supporting film, it is shown that the contributions of both the upward and downward faces have to be taken into account. A total Nusselt number and a total convective heat transfer coefficient have been used to describe the natural convection around these microheaters. In addition a relation between the Nusselt number and the Rayleigh number is derived, leading to an accurate prediction of the heating temperature (MRE< 2 %.

  18. Suspended 3D pyrolytic carbon microelectrodes for electrochemistry

    DEFF Research Database (Denmark)

    Hemanth, Suhith; Caviglia, Claudia; Keller, Stephan Sylvest

    2017-01-01

    with cyclic voltammetry (CV) and impedance spectroscopy (EIS) using potassium ferri-ferrocyanide redox probe in a custom made batch system with magnetic clamping. Different 3D pyrolytic carbon microelectrodes were compared and the optimal design displayed twice the peak current and half the charge transfer......Carbon microelectrodes have a wide range of applications because of their unique material properties and biocompatibility. This work presents the fabrication and characterization of suspended pyrolytic carbon microstructures serving as three-dimensional (3D) carbon microelectrodes...... for electrochemical applications. A 3D polymer template in epoxy based photoresist (SU-8) was fabricated with multiple steps of UV photolithography and pyrolysed at 900 °C to obtain 3D carbon microelectrodes. The pyrolytic carbon microstructures were characterized by SEM, Raman spectroscopy and XPS to determine...

  19. Fluorine and sulfur simultaneously co-doped suspended graphene

    Science.gov (United States)

    Struzzi, C.; Sezen, H.; Amati, M.; Gregoratti, L.; Reckinger, N.; Colomer, J.-F.; Snyders, R.; Bittencourt, C.; Scardamaglia, M.

    2017-11-01

    Suspended graphene flakes are exposed simultaneously to fluorine and sulfur ions produced by the μ-wave plasma discharge of the SF6 precursor gas. The microscopic and spectroscopic analyses, performed by Raman spectroscopy, scanning electron microscopy and photoelectron spectromicroscopy, show the homogeneity in functionalization yield over the graphene flakes with F and S atoms covalently bonded to the carbon lattice. This promising surface shows potential for several applications ranging from biomolecule immobilization to lithium battery and hydrogen storage devices. The present co-doping process is an optimal strategy to engineer the graphene surface with a concurrent hydrophobic character, thanks to the fluorine atoms, and a high affinity with metal nanoparticles due to the presence of sulfur atoms.

  20. Drift of suspended ferromagnetic particles due to the Magnus effect

    Science.gov (United States)

    Denisov, S. I.; Pedchenko, B. O.

    2017-01-01

    A minimal system of equations is introduced and applied to study the drift motion of ferromagnetic particles suspended in a viscous fluid and subjected to a time-periodic driving force and a nonuniformly rotating magnetic field. It is demonstrated that the synchronized translational and rotational oscillations of these particles are accompanied by their drift in a preferred direction, which occurs under the action of the Magnus force. We calculate both analytically and numerically the drift velocity of particles characterized by single-domain cores and nonmagnetic shells and show that there are two types of drift, unidirectional and bidirectional, which can be realized in suspensions composed of particles with different core-shell ratios. The possibility of using the phenomenon of bidirectional drift for the separation of core-shell particles in suspensions is also discussed.