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Sample records for zno tetrapod lasers

  1. Colloidal ZnO and Zn(1-x)Co(x)O tetrapod nanocrystals with tunable arm lengths.

    PubMed

    Hodges, James M; Fenton, Julie L; Gray, Jennifer L; Schaak, Raymond E

    2015-10-28

    Tetrapod-shaped ZnO nanocrystals exhibit exceptional optoelectronic properties, including intense ultraviolet photoluminescence emission, that make them attractive for applications that include lasers, sensors, and photocatalysts. However, synthetic methods that produce ZnO tetrapods typically include high-temperature vapor-deposition approaches that do not readily achieve characteristic dimensions of less than 100 nm or colloidal methods that require added metal dopants, which modify the inherent properties of ZnO. Here, we report a robust, modified solution-phase synthetic protocol for generating colloidal ZnO tetrapods that does not require the use of metal dopants. The ZnO tetrapod arm lengths can be tuned from 10 to 25 nm by adjusting the amount of Zn reagent used in the reaction. Subsequent seeded-growth produced even larger colloidal ZnO tetrapods with 62 nm arms. Photoluminescence (PL) measurements confirm that the tetrapods are of high crystalline quality, and the ultraviolet PL emission wavelengths that are observed fall between those of previously reported metal-doped colloidal ZnO tetrapods, which exhibit dopant-induced red- or blue-shifts. Furthermore, the reaction strategy can be modified to produce cobalt-substituted ZnO, offering a chemical pathway to tetrapod-shaped Zn1-xCoxO nanocrystals.

  2. Characterization of structural and electrical properties of ZnO tetrapods

    NASA Astrophysics Data System (ADS)

    Gu, Yu-Dong; Mai, Wen-Jie; Jiang, Peng

    2011-12-01

    ZnO tetrapods were synthesized by a typical thermal vapor-solid deposition method in a horizontal tube furnace. Structural characterization was carried out by transmission electron microscopy (TEM) and select-area electron diffraction (SAED), which shows the presence of zinc blende nucleus in the center of tetrapods while the four branches taking hexagonal wurtzite structure. The electrical transport property of ZnO tetrapods was investigated through an in-situ nanoprobe system. The three branches of a tetrapod serve as source, drain, and "gate", respectively; while the fourth branch pointing upward works as the force trigger by vertically applying external force downward. The conductivity of each branch of ZnO-tetrapods increases 3-4 times under pressure. In such situation, the electrical current through the branches of ZnO tetrapods can be tuned by external force, and therefore a simple force sensor based on ZnO tetrapods has been demonstrated for the first time.

  3. Direct growth of ZnO tetrapod on glass substrate by Chemical Vapor Deposition Technique

    NASA Astrophysics Data System (ADS)

    Fadzil, M. F. M.; Rahman, R. A.; Azhar, N. E. A.; Aziz, T. N. T. A.; Zulkifli, Z.

    2018-03-01

    This research demonstrates the growth of ZnO tetrapod structure on glass substrate for different types of flow gas and at different growth temperatures. The study on the morphological structure and electrical properties of ZnO thin film growth by Chemical Vapour Deposition (CVD) technique showed that the optimum growth temperature was obtained at 750°C with ZnO nanotetrapod morphological structure. Introducing Nitrogen gas flow during the growth process exhibited leg-to-leg linking ZnO tetrapods morphology. The electrical properties of ZnO tetrapods film were measured by using two point probes and it shows that, the sample growth in Ar and O2 atmosphere have better I-V characteristic.

  4. Spatially resolved surface-related exciton polariton dynamics in a single ZnO tetrapod

    NASA Astrophysics Data System (ADS)

    Sun, Fangfang; Sun, Liaoxin; Zhang, Bo; Wang, Hailong

    2018-02-01

    The band-edge emission lifetime in a single ZnO tetrapod is studied by using the time-resolved confocal micro-photoluminescence (TR- μPL) spectroscopic technique at room temperature. By performing μPL and TR- μPL mapping along the tapered arm of tetrapod, we observe whispering gallery mode (WGM) polaritons and find that the predominant radiative lifetime of exciton polaritons decreases linearly with increasing the surface-to-volume ratio of the sample. This behavior is ascribed to the surface electric field induced enhancement of the radiative decay rate of the exciton-like polaritons coupling with LO phonons.

  5. Composite multifunctional nanostructures based on ZnO tetrapods and superparamagnetic Fe3O4 nanoparticles.

    PubMed

    Villani, M; Rimoldi, T; Calestani, D; Lazzarini, L; Chiesi, V; Casoli, F; Albertini, F; Zappettini, A

    2013-04-05

    A nanocomposite material is obtained by coupling superparamagnetic magnetite nanoparticles (Fe3O4 NP) and vapor phase grown zinc oxide nanostructures with 'tetrapod' morphology (ZnO TP). The aim is the creation of a multifunctional material which retains the attractive features of ZnO (e.g. surface reactivity, strong UV emission, piezoelectricity) together with added magnetism. Structural, morphological, optical, magnetic and functional characterization are performed. In particular, the high saturation magnetization of Fe3O4 NP (above 50 A m(2) kg(-1)), the strong UV luminescence and the enhanced photocatalytic activity of coupled nanostructures are discussed. Thus the nanocomposite turns out to be suitable for applications in energy harvesting and conversion, gas- and bio-sensing, bio-medicine and filter-free photocatalysis.

  6. Large-scale uniform ZnO tetrapods on catalyst free glass substrate by thermal evaporation method

    SciT

    Alsultany, Forat H., E-mail: foratusm@gmail.com; Hassan, Z.; Ahmed, Naser M.

    2016-07-15

    Highlights: • Investigate the growth of ZnO-Ts on glass substrate by thermal evaporation method. • Glass substrate without any catalyst or a seed layer. • The morphology was controlled by adjusting the temperature of the material and the substrate. • Glass substrate was placed vertically in the quartz tube. - Abstract: Here, we report for the first time the catalyst-free growth of large-scale uniform shape and size ZnO tetrapods on a glass substrate via thermal evaporation method. Three-dimensional networks of ZnO tetrapods have needle–wire junctions, an average leg length of 2.1–2.6 μm, and a diameter of 35–240 nm. The morphologymore » and structure of ZnO tetrapods were investigated by controlling the preparation temperature of each of the Zn powder and the glass substrate under O{sub 2} and Ar gases. Studies were carried out on ZnO tetrapods using X-ray diffraction, field emission scanning electron microscopy, UV–vis spectrophotometer, and a photoluminescence. The results showed that the sample grow in the hexagonal wurtzite structure with preferentially oriented along (002) direction, good crystallinity and high transmittance. The band gap value is about 3.27 eV. Photoluminescence spectrum exhibits a very sharp peak at 378 nm and a weak broad green emission.« less

  7. Joining the un-joinable: adhesion between low surface energy polymers using tetrapodal ZnO linkers.

    PubMed

    Jin, Xin; Strueben, Jan; Heepe, Lars; Kovalev, Alexander; Mishra, Yogendra K; Adelung, Rainer; Gorb, Stanislav N; Staubitz, Anne

    2012-11-08

    Tetrapodal ZnO crystals are used for mechanical interlocking of PTFE and cross-linked PDMS, classically non-adhesive polymers. This novel approach is straightforward and easily applicable and leads to a peel strength that is higher than 200 N m(-1) without chemical modification of the surfaces. The shape of these fillers emerged as a crucial aspect of the interlocking mechanism. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Facile synthesis of Cu/tetrapod-like ZnO whisker compounds with enhanced photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Liu, Hong; Liu, Huarong; Fan, Ximei

    2017-09-01

    Cu/tetrapod-like ZnO whisker (T-ZnOw) compounds were successfully synthesized using N2H4 \\cdot H2O as a reducing agent by a simple reduction method without any insert gas at room temperature. The crystal phase composition and morphology of the as-prepared samples were investigated by XRD, SEM and FESEM tests. The photocatalytic property of the as-prepared samples was detected by the degradation of methyl orange (MO) aqueous solution under UV irradiation. It can be found that Cu nanoparticles (CuNPs) dispersed on the surface of T-ZnOw increased with the increasing of Cu/Zn molar ratios (Cu/Zn MRs), and an octahedral structure of CuNPs was obtained when the sample was prepared with less than and equal to 7.30% Cu/Zn MR, but tended to a spherical or nanorod structure of CuNPs densely arranged on the surface of T-ZnOw, which is prepared by Cu/Zn MRs up to 22.00%. All the compounds exhibited excellent photocatalytic activity in decomposing of MO than T-ZnOw, the photocatalytic property of the samples increased with the increasing of Cu/Zn MRs up to 7.30%, while it decreases when further increasing the Cu/Zn MRs. The Schottky barrier of the Cu/T-ZnOw compound can effectively capture photoinduced electrons from the interface and enhanced the photocatalytic property of T-ZnOw.

  9. Formaldehyde sensor based on Ni-doped tetrapod-shaped ZnO nanopowder induced by external magnetic field

    NASA Astrophysics Data System (ADS)

    Bai, Zikui; Xie, Changsheng; Hu, Mulin; Zhang, Shunping

    2008-12-01

    The sensors based on Ni-doped ZnO nanopowder with tetrapod-shape (T-ZnO) were fabricated by screen-printing technique with external magnetic field in different direction. The morphologies and crystal structures of the thick film were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM), respectively. Gas-sensing property of sensors responded to 100 ppm formaldehyde was also detected. The results show that the direction of magnetic field has crucial effect on the sensor sensitivity. The sensors based on 5 wt% Ni-doped T-ZnO induced by magnetic field in parallel direction to the thick film surface, has the optimization sensitivity, the shortest response and recovery time, which are 10.6, 16 and 15 s, respectively. The magnetic-field induction model and the gas-sensing mechanism of the Ni-doped T-ZnO are proposed.

  10. A new approach to synthesize ZnO tetrapod-like nanoparticles with DC thermal plasma technique

    NASA Astrophysics Data System (ADS)

    Lin, Hsiu-Fen; Liao, Shih-Chieh; Hu, Chen-Ti

    2009-02-01

    The feasibility of fabricating the tetrapod-like zinc oxide (TZ) nanoparticles with a DC thermal plasma reactor was demonstrated in the present study. Advantages of this process include the low cost and high yield rate (0.8-1.0 kg/h) in producing high TZ content mixtures (with small portion of rod-like zinc oxide (RZ) and plate-like zinc oxide (PZ) nanoparticles) from commercial metal zinc powders. ZnO nanopowders with high TZ content could be employed as the starting material for photocatalytic filters. The ratio of TZ to RZ and PZ in the products was observed to be strongly influenced by the plasma power and the plasma gas flow rate. The optical spectrum, photostability and anti-microbial property of the as-grown and annealed TZ mixtures were examined and compared in this study.

  11. Structural, optical, and improved field-emission properties of tetrapod-shaped Sn-doped ZnO nanostructures synthesized via thermal evaporation.

    PubMed

    Zhou, Xiongtu; Lin, Tihang; Liu, Yuhui; Wu, Chaoxing; Zeng, Xiangyao; Jiang, Dong; Zhang, Yong-ai; Guo, Tailiang

    2013-10-23

    High-quality tetrapod-shaped Sn-doped ZnO (T-SZO) nanostructures have been successfully synthesized via the thermal evaporation of mixed Zn and Sn powder. The effects of the Sn dopant on the morphology, microstructure, optical, and field-emission (FE) properties of T-SZO were investigated. It was found that the growth direction of the legs of T-SZO is parallel to the [0001] crystal c-axis direction and that the incorporation of Sn in the ZnO matrix increases the aspect ratio of the tetrapods, leads to blue shift in the UV region, and considerably improves the FE performance. The results also show that tetrapod cathodes with around a 0.84 atom % Sn dosage have the best FE properties, with a turn-on field of 1.95 V/μm, a current density of 950 μA/cm2 at a field of 4.5 V/μm, and a field-enhancement factor as high as 9556.

  12. Nanoscale mapping of plasmon and exciton in ZnO tetrapods coupled with Au nanoparticles

    DOE PAGES

    Bertoni, Giovanni; Fabbri, Filippo; Villani, Marco; ...

    2016-01-12

    Metallic nanoparticles can be used to enhance optical absorption or emission in semiconductors, thanks to a strong interaction of collective excitations of free charges (plasmons) with electromagnetic fields. Herein we present direct imaging at the nanoscale of plasmon-exciton coupling in Au/ZnO nanostructures by combining scanning transmission electron energy loss and cathodoluminescence spectroscopy and mapping. The Au nanoparticles (~30 nm in diameter) are grown in-situ on ZnO nanotetrapods by means of a photochemical process without the need of binding agents or capping molecules, resulting in clean interfaces. Interestingly, the Au plasmon resonance is localized at the Au/vacuum interface, rather than presentingmore » an isotropic distribution around the nanoparticle. Moreover, on the contrary, a localization of the ZnO signal has been observed inside the Au nanoparticle, as also confirmed by numerical simulations.« less

  13. Nanoscale mapping of plasmon and exciton in ZnO tetrapods coupled with Au nanoparticles

    SciT

    Bertoni, Giovanni; Fabbri, Filippo; Villani, Marco

    Metallic nanoparticles can be used to enhance optical absorption or emission in semiconductors, thanks to a strong interaction of collective excitations of free charges (plasmons) with electromagnetic fields. Herein we present direct imaging at the nanoscale of plasmon-exciton coupling in Au/ZnO nanostructures by combining scanning transmission electron energy loss and cathodoluminescence spectroscopy and mapping. The Au nanoparticles (~30 nm in diameter) are grown in-situ on ZnO nanotetrapods by means of a photochemical process without the need of binding agents or capping molecules, resulting in clean interfaces. Interestingly, the Au plasmon resonance is localized at the Au/vacuum interface, rather than presentingmore » an isotropic distribution around the nanoparticle. Moreover, on the contrary, a localization of the ZnO signal has been observed inside the Au nanoparticle, as also confirmed by numerical simulations.« less

  14. Electromagnetic and Microwave Absorption Properties of Carbonyl Tetrapod-Shaped Zno Nanostructures Composite Coatings

    NASA Astrophysics Data System (ADS)

    Yu, Haibo; Qin, Hui; Huang, Yunhua

    2012-08-01

    CIP/T-ZnO/EP composite coatings with carbonyl iron powders (CIP) and tetrapodshaped ZnO (T-ZnO) nanostructures as absorbers, and epoxy resin (EP) as matrix were prepared. The complex permittivity, permeability and microwave absorption properties of the coatings were investigated in the frequency range of 2-18 GHz. The effects of the weight ratio (CIP/T-ZnO/EP), the thickness and the solidification temperature on microwave absorption properties were discussed. When the weight ratio (CIP/TZnO/ EP), the thickness and the solidification temperature is 28:2:22, 1.8 mm, and 10°C, respectively, the optimal wave absorption with the minimum reflection loss (RL) value of -22.38 dB at 15.67 GHz and the bandwidth (RL<-10 dB) of 5.74 GHz was obtained, indicating that the composite coatings may have a promising application in Ku-band (12-18 GHz).

  15. Zinc oxide tetrapods as efficient photocatalysts for organic pollutant degradation

    NASA Astrophysics Data System (ADS)

    Liu, Fangzhou; Leung, Yu Hang; Djurisić, Aleksandra B.; Liao, Changzhong; Shih, Kaimin

    2014-03-01

    Bisphenol A (BPA) and other organic pollutants from industrial wastewater have drawn increasing concern in the past decades regarding their environmental and biological risks, and hence developing strategies of effective degradation of BPA and other organic pollutants is imperative. Metal oxide nanostructures, in particular titanium oxide (TiO2) and zinc oxide (ZnO), have been demonstrated to exhibit efficient photodegradation of various common organic dyes. ZnO tetrapods are of special interest due to their low density of native defects which consequently lead to lower recombination losses and higher photocatalytic efficiency. Tetrapods can be obtained by relatively simple and low-cost vapor phase deposition in large quantity; the micron-scale size would also be advantageous for catalyst recovery. In this study, the photodegradation of BPA with ZnO tetrapods and TiO2 nanostructures under UV illumination were compared. The concentration of BPA dissolved in DI water was analyzed by high-performance liquid chromatography (HPLC) at specified time intervals. It was observed that the photocatalytic efficiency of ZnO tetrapods eventually surpassed Degussa P25 in free-standing form, and more than 80% of BPA was degraded after 60 min. Photodegradation of other organic dye pollutants by tetrapods and P25 were also examined. The superior photocatalytic efficiency of ZnO tetrapods for degradation of BPA and other organic dye pollutants and its correlation with the material properties were discussed.

  16. ZnO synthesized in air by fs laser irradiation on metallic Zn thin films

    NASA Astrophysics Data System (ADS)

    Esqueda-Barrón, Y.; Herrera, M.; Camacho-López, S.

    2018-05-01

    We present results on rapid femtosecond laser synthesis of nanostructured ZnO. We used metallic Zn thin films to laser scan along straight tracks, until forming nanostructured ZnO. The synthesis dependence on laser irradiation parameters such as the per pulse fluence, integrated fluence, laser scan speed, and number of scans were explored carefully. SEM characterization showed that the morphology of the obtained ZnO is dictated by the integrated fluence and the laser scan speed; micro Raman and XRD results allowed to identify optimal laser processing conditions for getting good quality ZnO; and cathodoluminescence measurements demonstrated that a single laser scan at high per pulse laser fluence, but a medium integrated laser fluence and a medium laser scan speed favors a low density of point-defects in the lattice. Electrical measurements showed a correlation between resistivity of the laser produced ZnO and point-defects created during the synthesis. Transmittance measurements showed that, the synthesized ZnO can reach down to the supporting fused silica substrate under the right laser irradiation conditions. The physical mechanism for the formation of ZnO, under ultrashort pulse laser irradiation, is discussed in view of the distinct times scales given by the laser pulse duration and the laser pulse repetition rate.

  17. Femtosecond laser assisted antibacterial activity of ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Luna Palacios, Yryx Yanet; Alvarez, Crysthal; Cuando-Espitia, Natanael; Halaney, David L.; Camacho-Lopez, Santiago; Aguilar, Guillermo

    2017-07-01

    Bacterial infection of cranial implants remains a major cause of implant failure, and often requires surgical intervention to remove and replace the fouled implant. Novel transparent implants may allow for mitigation of infection using optical therapies, without the need for invasive surgeries. In this study, we investigate a combined treatment with ZnO nanoparticles and femtosecond laser pulses to inhibit the growth of Escherichia coli (E. Coli) in vitro. The combined effect has shown a substantial reduction in the number of CFU/mL after incubation compared with no treatment.

  18. Buckminsterfullerene hybridized zinc oxide tetrapods: defects and charge transfer induced optical and electrical response.

    PubMed

    Smazna, Daria; Rodrigues, Joana; Shree, Sindu; Postica, Vasile; Neubüser, Gero; Martins, A F; Ben Sedrine, N; Jena, Naresh K; Siebert, Leonard; Schütt, Fabian; Lupan, Oleg; Ahuja, Rajeev; Correia, M R; Monteiro, Teresa; Kienle, Lorenz; Yang, Ya; Adelung, Rainer; Mishra, Yogendra Kumar

    2018-05-21

    Buckminster fullerene (C60) based hybrid metal oxide materials are receiving considerable attention because of their excellent fundamental and applied aspects, like semiconducting, electron transfer, luminescent behaviors, etc. and this work briefly discusses the successful fabrication of C60 decorated ZnO tetrapod materials and their detailed structure-property relationships including device sensing applications. The electron microscopy investigations indicate that a quite dense surface coverage of ZnO tetrapods with C60 clusters is achieved. The spectroscopy studies confirmed the identification of the C60 vibrational modes and the C60 induced changes in the absorption and luminescence properties of the ZnO tetrapods. An increased C60 concentration on ZnO results in steeper ZnO bandgap absorption followed by well-defined free exciton and 3.31 eV line emissions. As expected, higher amounts of C60 increase the intensity of C60-related visible absorption bands. Pumping the samples with photons with an energy corresponding to these absorption band maxima leads to additional emission from ZnO showing an effective charge transfer phenomenon from C60 to the ZnO host. The density of states model obtained from DFT studies for pure and C60 coated ZnO surfaces confirms the experimental observations. The fabricated C60-ZnO hybrid tetrapod based micro- and nanodevices showed interesting ethanol gas sensing characteristics.

  19. High-speed observation of ZnO microspherical crystals produced by laser ablation (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Nakamura, Daisuke; Tasaki, Ryohei; Fujiwara, Yuki; Nagasaki, Fumiaki; Higashihata, Mitsuhiro; Ikenoue, Hiroshi; Okada, Tatsuo

    2017-03-01

    ZnO nano/microstructures have attracted much attention as building blocks for optoelectronic devices because of their high crystalline quality and unique structures. We have succeeded in synthesizing ZnO microspherical crystals by a simple atmospheric laser ablation method, and demonstrated ultraviolet whispering-gallery-mode lasing from the spheres. In the microsphere synthesis process, molten droplets formed into spherical shapes by surface tension, and crystalized during ejection from the ablation spot. In this study, we observed the generation of ZnO microspheres by high-speed camera. Now we are trying to control and manipulate the microspheres using a vortex beam.

  20. Cu-Doped ZnO Thin Films Grown by Co-deposition Using Pulsed Laser Deposition for ZnO and Radio Frequency Sputtering for Cu

    NASA Astrophysics Data System (ADS)

    Shin, Hyun Wook; Son, Jong Yeog

    2018-05-01

    Cu-doped ZnO (CZO) thin films were fabricated on single-crystalline (0001) Al2O3 substrates by co-deposition using pulsed laser deposition for ZnO and radio frequency sputtering for Cu. CZO thin films with 0-20% molar concentrations are obtained by adjusting the deposition rates of ZnO and Cu. The CZO thin films exhibit room temperature ferromagnetism, and CZO with 5% Cu molar concentration has maximum remanent magnetization, which is consistent with theoretical results.

  1. Fabrication of GaN doped ZnO nanocrystallines by laser ablation.

    PubMed

    Gopalakrishnan, N; Shin, B C; Bhuvana, K P; Elanchezhiyan, J; Balasubramanian, T

    2008-08-01

    Here, we present the fabrication of pure and GaN doped ZnO nanocrystallines on Si(111) substrates by KrF excimer laser. The targets for the ablation have been prepared by conventional ceramic method. The fabricated nanocrystallines have been investigated by X-ray diffraction, photoluminescence and atomic force microscopy. The X-ray diffraction analysis shows that the crystalline size of pure ZnO is 36 nm and it is 41 nm while doped with 0.8 mol% of GaN due to best stoichiometry between Zn and O. Photoluminescence studies reveal that intense deep level emissions have been observed for pure ZnO and it has been suppressed for the GaN doped ZnO structures. The images of atomic force microscope show that the rms surface roughness is 27 nm for pure ZnO and the morphology is improved with decrease in rms roughness, 18 nm with fine crystallines while doped with 1 mol% GaN. The improved structural, optical and morphological properties of ZnO nanocrystalline due to GaN dopant have been discussed in detail.

  2. Study of Doped ZnO Films Synthesized by Combining Vapor Gases and Pulsed Laser Deposition

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, Ching-Hua; Lehoczky, Sandor L.; George, M. A.

    2000-01-01

    The properties and structure of the ZnO material are similar to those of the GaN. Since an excitonic binding energy of ZnO is about 60 meV, it has strong potential for excitonic lasing at the room temperature. This makes synthesizing ZnO films for applications attractive. However, there are several hurdles in fabricating electro-optical devices from ZnO. One of those is in growing doped p-type ZnO films. Although techniques have been developed for the doping of both p-type and n-type ZnO, this remains an area that can be improved. In this presentation, we will report the experimental results of using both thermal vapor and pulsed laser deposition to grow doped ZnO films. The films are deposited on (0001) sapphire, (001) Si and quartz substrates by ablating a ZnO target. The group III and V elements are introduced into the growth chamber using inner gases. Films are characterized by x-ray diffraction, scanning probe microscopy, energy dispersive spectroscopy, Auger electron spectroscopy, and electrical measurements. The full width at half maximum of theta rocking curves for epitaxial films is less than 0.5 deg. In textured films, it rises to several degrees. Film surface morphology reveals an island growth pattern, but the size and density of these islands vary with the composition of the reactive gases. The electrical resistivity also changes with the doped elements. The relationship between the doping elements, gas composition, and film properties will be discussed.

  3. Luminescence studies of laser MBE grown GaN on ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Dewan, Sheetal; Tomar, Monika; Kapoor, Ashok K.; Tandon, R. P.; Gupta, Vinay

    2017-08-01

    GaN films have been successfully fabricated using Laser Molecular Beam Epitaxy (LMBE) technique on bare c-plane sapphire substrate and ZnO nanostructures (NS) decorated Si (100) substrates. The ZnO nanostructures were grown on Si (100) substrate using high pressure assisted Pulsed laser deposition technique in inert gas ambience. Discrete nanostructured morphology of ZnO was obtained using the PLD growth on Si substrates. Photoluminescence studies performed on the prepared GaN/Sapphire and GaN/ZnO-NS/Si systems, revealed a significant PL enhancement in case of GaN/ZnO-NS/Si system compared to the former. The hexagonal nucleation sites provided by the ZnO nanostructures strategically enhanced the emission of GaN film grown by Laser MBE Technique at relatively lower temperature of 700°C. The obtained results are attractive for the realization of highly luminescent GaN films on Si substrate for photonic devices.

  4. Antibacterial studies of ZnO nanoparticle coatings on nanocrystalline YSZ irradiated with femtosecond laser light

    NASA Astrophysics Data System (ADS)

    Alvarez, Crysthal; Garcia, Valeria; Cuando, Natanael; Aguilar, Guillermo

    2018-02-01

    Recently, efforts have been made to create a transparent ceramic cranial implant comprised of nanocrystalline yttriastabilized zirconia (nc-YSZ) that will provide optical access to the brain. This has been referred to as Window to the Brain (WttB) in the literature. WttB will allow the use of laser and photonic treatments and diagnostics in areas with difficult optical access in the brain. Nevertheless, infection is still one of the frequent cranial implant complications. In most cases a second surgery is required to replace the infected implant. To address potential infections in the WttB platform, we have studied the antibacterial effect of a Zinc Oxide (ZnO) nanoparticles coating on nc-YSZ. After coating with ZnO nanoparticles, the implant was irradiated with infrared femtosecond laser light. We synthesized ZnO nanoparticles through the Laser Ablation of Solids in Liquids (LASL) method, using a Zinc solid target in a liquid medium (water/acetone). Antibacterial coatings were obtained by air brush, using a precursor solution of ZnO nanoparticles in distilled water. Escherichia coli (E. coli) have been used as representative, clinical relevant bacteria to probe the antibacterial effect of the coating. Our previous studies suggested that the use of ZnO nanoparticles inhibit bacterial growth. Laser irradiation treatment alone also offers inhibition of bacterial growth, up to 70%. The incorporation of nanoparticles offers an additional 20% inhibition. Thus, this work represents the next step towards the development of a clinically-oriented transparent cranial implant.

  5. Digital selective growth of a ZnO nanowire array by large scale laser decomposition of zinc acetate.

    PubMed

    Hong, Sukjoon; Yeo, Junyeob; Manorotkul, Wanit; Kang, Hyun Wook; Lee, Jinhwan; Han, Seungyong; Rho, Yoonsoo; Suh, Young Duk; Sung, Hyung Jin; Ko, Seung Hwan

    2013-05-07

    We develop a digital direct writing method for ZnO NW micro-patterned growth on a large scale by selective laser decomposition of zinc acetate. For ZnO NW growth, by replacing the bulk heating with the scanning focused laser as a fully digital local heat source, zinc acetate crystallites can be selectively activated as a ZnO seed pattern to grow ZnO nanowires locally on a larger area. Together with the selective laser sintering process of metal nanoparticles, more than 10,000 UV sensors have been demonstrated on a 4 cm × 4 cm glass substrate to develop all-solution processible, all-laser mask-less digital fabrication of electronic devices including active layer and metal electrodes without any conventional vacuum deposition, photolithographic process, premade mask, high temperature and vacuum environment.

  6. Defect studies of thin ZnO films prepared by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Vlček, M.; Čížek, J.; Procházka, I.; Novotný, M.; Bulíř, J.; Lančok, J.; Anwand, W.; Brauer, G.; Mosnier, J.-P.

    2014-04-01

    Thin ZnO films were grown by pulsed laser deposition on four different substrates: sapphire (0 0 0 1), MgO (1 0 0), fused silica and nanocrystalline synthetic diamond. Defect studies by slow positron implantation spectroscopy (SPIS) revealed significantly higher concentration of defects in the studied films when compared to a bulk ZnO single crystal. The concentration of defects in the films deposited on single crystal sapphire and MgO substrates is higher than in the films deposited on amorphous fused silica substrate and nanocrystalline synthetic diamond. Furthermore, the effect of deposition temperature on film quality was investigated in ZnO films deposited on synthetic diamond substrates. Defect studies performed by SPIS revealed that the concentration of defects firstly decreases with increasing deposition temperature, but at too high deposition temperatures it increases again. The lowest concentration of defects was found in the film deposited at 450° C.

  7. Second-harmonic generation of ZnO nanoparticles synthesized by laser ablation of solids in liquids

    NASA Astrophysics Data System (ADS)

    Rocha-Mendoza, Israel; Camacho-López, Santiago; Luna-Palacios, Yryx Y.; Esqueda-Barrón, Yasmín; Camacho-López, Miguel A.; Camacho-López, Marco; Aguilar, Guillermo

    2018-02-01

    We report the synthesis of small zinc oxide nanoparticles (ZnO NPs) based colloidal suspensions and the study of second-harmonic generation from aggregated ZnO NPs deposited on glass substrates. The colloidal suspensions were obtained using the laser ablation of solids in liquids technique, ablating a Zn solid target immersed in acetone as the liquid medium, with ns-laser pulses (1064 nm) of a Nd-YAG laser. The per pulse laser fluence, the laser repetition rate frequency and the ablation time were kept constant. The absorption evolution of the obtained suspensions was optically characterized through absorption spectroscopy until stabilization. Raman spectroscopy, SEM and HRTEM were used to provide evidence of the ZnO NPs structure. HRTEM results showed that 5-8 nm spheroids ZnO NPs were obtained. Strong second-harmonic signal is obtained from random ZnO monocrystalline NPs and from aggregated ZnO NPs, suggesting that the high efficiency of the nonlinear process may not depend on the NPs size or aggregation state.

  8. Pure and Sn-doped ZnO films produced by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Holmelund, E.; Schou, J.; Tougaard, S.; Larsen, N. B.

    2002-09-01

    A new technique, metronome doping, has been used for doping of films during pulsed laser deposition (PLD). This technique makes it possible to dope continuously during film growth with different concentrations of a dopant in one deposition sequence. Films of pure and doped ZnO have been produced with Sn concentrations up to 16%. The specific resistivity is found to increase and the transmission of visible light to decrease with increasing Sn concentration.

  9. Structural characterization of ZnO thin films grown on various substrates by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Novotný, M.; Čížek, J.; Kužel, R.; Bulíř, J.; Lančok, J.; Connolly, J.; McCarthy, E.; Krishnamurthy, S.; Mosnier, J.-P.; Anwand, W.; Brauer, G.

    2012-06-01

    ZnO thin films were grown by pulsed laser deposition on three different substrates: sapphire (0 0 0 1), MgO (1 0 0) and fused silica (FS). The structure and morphology of the films were characterized by x-ray diffraction and scanning electron microscopy and defect studies were carried out using slow positron implantation spectroscopy (SPIS). Films deposited on all substrates studied in this work exhibit the wurtzite ZnO structure and are characterized by an average crystallite size of 20-100 nm. However, strong differences in the microstructure of films deposited on various substrates were found. The ZnO films deposited on MgO and sapphire single-crystalline substrates exhibit local epitaxy, i.e. a well-defined relation between film crystallites and the substrate. Domains with different orientation relationships with the substrate were found in both films. On the other hand, the film deposited on the FS substrate exhibits fibre texture with random lateral orientation of crystallites. Extremely high compressive in-plane stress of σ ˜ 14 GPa was determined in the film deposited on the MgO substrate, while the film deposited on sapphire is virtually stress-free, and the film deposited on the FS substrate exhibits a tensile in-plane stress of σ ˜ 0.9 GPa. SPIS investigations revealed that the concentration of open-volume defects in the ZnO films is substantially higher than that in a bulk ZnO single crystal. Moreover, the ZnO films deposited on MgO and sapphire single-crystalline substrates exhibit a significantly higher density of defects than the film deposited on the amorphous FS substrate.

  10. Effect of CO on the field emission properties of tetrapod zinc oxide cathode.

    PubMed

    Wang, Jinchan; Zhang, Xiaobing; Lei, Wei; Mao, Fuming; Cui, Yunkang; Xiao, Mei

    2012-08-01

    Tetrapod zinc oxide (T-ZnO), being a kind of nano-material, has large specific surface area and surface binding energy, which will make it sensitive to the ambient gas condition. So the field emission properties will be influenced by the gas adsorption when being applied as the cathode materials of field emission devices. Carbon monoxide is the main residual gas in T-ZnO field emission devices. In this paper, carbon monoxide was introduced into a field emission device with T-ZnO emitters. The field emission currents of tetrapod ZnO were compared before and after exposure to CO.

  11. Multi-photon excited coherent random laser emission in ZnO powders

    NASA Astrophysics Data System (ADS)

    Tolentino Dominguez, Christian; Gomes, Maria De A.; Macedo, Zélia S.; de Araújo, Cid B.; Gomes, Anderson S. L.

    2014-11-01

    We report the observation and analysis of anti-Stokes coherent random laser (RL) emission from zinc oxide (ZnO) powders excited by one-, two- or three-photon femtosecond laser radiation. The ZnO powders were produced via a novel proteic sol-gel, low-cost and environmentally friendly route using coconut water in the polymerization step of the metal precursor. One- and two-photon excitation at 354 nm and 710 nm, respectively, generated single-band emissions centred at about 387 nm. For three-photon excitation, the emission spectra showed a strong ultraviolet (UV) band (380-396 nm) attributed to direct three-photon absorption from the valence band to the conduction band. The presence of an intensity threshold and a bandwidth narrowing of the UV band from about 20 to 4 nm are clear evidence of RL action. The observation of multiple sub-nanometre narrow peaks in the emission spectra for excitation above the RL threshold is consistent with random lasing by coherent feedback.

  12. Hierarchical laser-induced periodic surface structures induced by femtosecond laser on the surface of a ZnO film

    NASA Astrophysics Data System (ADS)

    Wang, Shaojun; Jiang, Lan; Han, Weina; Hu, Jie; Li, Xiaowei; Wang, Qingsong; Lu, Yongfeng

    2018-05-01

    We realize hierarchical laser-induced periodic surface structures (LIPSSs) on the surface of a ZnO thin film in a single step by the irradiation of femtosecond laser pulses. The structures are characterized by the high-spatial-frequency LIPSSs (HSFLs) formed on the abnormal bumped low-spatial-frequency LIPSSs (LSFLs). Localized electric-field enhancement based on the initially formed LSFLs is proposed as a potential mechanism for the formation of HSFLs. The simulation results through the finite-difference time-domain method show good agreement with experiments. Furthermore, the crucial role of the LSFLs in the formation of HSFLs is validated by an elaborate experimental design with preprocessed HSFLs.

  13. Optimization of pulsed laser deposited ZnO thin-film growth parameters for thin-film transistors (TFT) application

    NASA Astrophysics Data System (ADS)

    Gupta, Manisha; Chowdhury, Fatema Rezwana; Barlage, Douglas; Tsui, Ying Yin

    2013-03-01

    In this work we present the optimization of zinc oxide (ZnO) film properties for a thin-film transistor (TFT) application. Thin films, 50±10 nm, of ZnO were deposited by Pulsed Laser Deposition (PLD) under a variety of growth conditions. The oxygen pressure, laser fluence, substrate temperature and annealing conditions were varied as a part of this study. Mobility and carrier concentration were the focus of the optimization. While room-temperature ZnO growths followed by air and oxygen annealing showed improvement in the (002) phase formation with a carrier concentration in the order of 1017-1018/cm3 with low mobility in the range of 0.01-0.1 cm2/V s, a Hall mobility of 8 cm2/V s and a carrier concentration of 5×1014/cm3 have been achieved on a relatively low temperature growth (250 °C) of ZnO. The low carrier concentration indicates that the number of defects have been reduced by a magnitude of nearly a 1000 as compared to the room-temperature annealed growths. Also, it was very clearly seen that for the (002) oriented films of ZnO a high mobility film is achieved.

  14. ZnO nanofertilizer and He Ne laser irradiation for promoting growth and yield of sweet basil plant.

    PubMed

    El-Kereti, Mohammed A; El-feky, Souad A; Khater, Mohammed S; Osman, Yasser A; El-sherbini, El-sayed A

    2013-12-01

    This study was conducted to evaluate the effectiveness of zinc nanofertilizer strategy on sweet basil yield, through alone application or combined with pre-sowing laser irradiation. Furthermore, evaluate the growth of plant and the level of active essential oil constituents. Zinc oxide (ZnO) nanoparticles (NPs) were synthesized, and transmission electron microscope revealed particle size of approximately 10.5-15.5 nm. ZnO NPs were applied to sweet basil plants by foliar spray at varying concentrations (10, 20 and 30 mg/L); He Ne laser of power 3mW was used for red light irradiation of sweet basil seeds for 2 min. exposure time. Total chlorophyll, total carbohydrate, essential oil levels, zinc content, plant height, branches/plant and fresh weight were measured. In general, the combined foliar spray application of ZnO nanofertilizer with pre-sowing He Ne laser irradiation showed more effectiveness than ZnO nanofertilizer alone and 20mg/L concentration gave the highest results of all measured traits. Statistical analysis (t-test) showed significant differences among the effects of the various concentrations of zinc oxide NPs on these attributes. The results showed an inverse relationship between the total carbohydrate content and the percentage of essential oil in the leaves. Together these findings support the usefulness and effectiveness of zinc oxide nanofertilizer and laser irradiation treatment to enhance the growth and yield of sweet basil plants. The article presents some promising patents on ZnO nanofertilizer and He Ne laser irradiation.

  15. A supertree of early tetrapods.

    PubMed Central

    Ruta, Marcello; Jeffery, Jonathan E; Coates, Michael I

    2003-01-01

    A genus-level supertree for early tetrapods is built using a matrix representation of 50 source trees. The analysis of all combined trees delivers a long-stemmed topology in which most taxonomic groups are assigned to the tetrapod stem. A second analysis, which excludes source trees superseded by more comprehensive studies, supports a deep phylogenetic split between lissamphibian and amniote total groups. Instances of spurious groups are rare in both analyses. The results of the pruned second analysis are mostly comparable with those of a recent, character-based and large-scale phylogeny of Palaeozoic tetrapods. Outstanding areas of disagreement include the branching sequence of lepospondyls and the content of the amniote crown group, in particular the placement of diadectomorphs as stem diapsids. Supertrees are unsurpassed in their ability to summarize relationship patterns from multiple independent topologies. Therefore, they might be used as a simple test of the degree of corroboration of nodes in the contributory analyses. However, we urge caution in using them as a replacement for character-based cladograms and for inferring macroevolutionary patterns. PMID:14667343

  16. Enhanced photoluminescence and heterojunction characteristics of pulsed laser deposited ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Mannam, Ramanjaneyulu; Kumar, E. Senthil; Priyadarshini, D. M.; Bellarmine, F.; DasGupta, Nandita; Ramachandra Rao, M. S.

    2017-10-01

    We report on the growth of ZnO nanostructures in different gas ambient (Ar and N2) using pulsed laser deposition technique. Despite the similar growth temperature, use of N2 ambient gas resulted in well-aligned nanorods with flat surface at the tip, whereas, nanorods grown with Ar ambient exhibited tapered tips. The Nanorods grown under N2 ambient exhibited additional Raman modes corresponding to N induced zinc interstitials. The nanorods are c-axis oriented and highly epitaxial in nature. Photoluminescence spectroscopy reveals that the UV emission can be significantly enhanced by 10 times for the nanorods grown under Ar ambient. The enhanced UV emission is attributed to the reduction in polarization electric field along the c-axis. n-ZnO nanorods/p-Si heterojunction showed rectifying I-V characteristics with a turn of voltage of 3.4 V.

  17. A study of H and D doped ZnO epitaxial films grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Li, Y. J.; Kaspar, T. C.; Droubay, T. C.; Joly, A. G.; Nachimuthu, P.; Zhu, Z.; Shutthanandan, V.; Chambers, S. A.

    2008-09-01

    We examine the crystal structure and electrical and optical properties of ZnO epitaxial films grown by pulsed laser deposition in a H2 or D2 ambient. n-type electrical conductivity is enhanced by three orders of magnitude as a result of growing in H2 (D2) compared to ZnO films grown in O2. Hall effect measurements reveal very small carrier activation energies and carrier concentrations in the mid-1018 cm-3 range. Optical absorption measurements show that the enhanced conductivity is not a result of ZnO reduction and interstitial Zn formation. Photoluminescence spectra suggest excitonic emission associated with exciton-hydrogen donor complex formation and show no evidence for midgap emission resulting from defects. We have modeled the transport properties of H (D) doped ZnO films using variable range hopping and surface layer conductivity models, but our data do not fit well with these models. Rather, it appears that growth in H2 (D2) promotes the formation of an exceedingly shallow donor state not seen in ZnO crystals annealed in H2 after growth. This new state may be associated with H (D) substitution at O sites in the lattice.

  18. Parameters optimization for synthesis of Al-doped ZnO nanoparticles by laser ablation in water

    NASA Astrophysics Data System (ADS)

    Krstulović, Nikša; Salamon, Krešimir; Budimlija, Ognjen; Kovač, Janez; Dasović, Jasna; Umek, Polona; Capan, Ivana

    2018-05-01

    Al-doped ZnO crystalline colloidal nanoparticles were synthesized by a laser ablation of ZnO:Al2O3 in MilliQ water. Experiments were performed systematically by changing the number of applied laser pulses and laser output energy with the aim to affect the nanoparticle size, composition (Al/Zn ratio) and characteristics (band-gap, crystallinity). Distinctly, set of nanoparticle syntheses was performed in deionized water for comparison. SEM investigation of colloidal nanoparticles revealed that the formed nanoparticles are 30 nm thick discs with average diameters ranging from 450 to 510 nm. It was found that craters in the target formed during the laser ablation influence the size of synthesized colloidal nanoparticles. This is explained by efficient nanoparticle growth through diffusion process which take place in spatially restricted volume of the target crater. When laser ablation takes place in deionized water the synthesized nanoparticles have a mesh-like structure with sparse concentration of disc-like nanoparticles. Al/Zn ratio and band-gap energy of nanoparticles are highly influenced by the number and output energy of applied laser pulses. In addition, the procedure how to calculate the concentration of colloidal nanoparticles synthesized by laser ablation in liquids is proposed. The Al-doped ZnO colloidal nanoparticles properties were obtained using different techniques like scanning electron microscopy, optical microscopy, energy-dispersive X-ray spectroscopy, grazing-incidence X-ray diffraction, photoabsorption, photoluminescence and X-ray photoelectron spectroscopy.

  19. Investigation of room temperature UV emission of ZnO films with different defect densities induced by laser irradiation.

    PubMed

    Zhao, Yan; Jiang, Yijian

    2010-08-01

    We studied the room temperature UV emission of ZnO films with different defect densities which is fabricated by KrF laser irradiation process. It is shown room temperature UV photoluminescence of ZnO film is composed of contribution from free-exciton (FX) recombination and its longitudinal-optical phonon replica (FX-LO) (1LO, 2LO). With increase of the defect density, the FX emission decreased and FX-LO emission increased dramatically; and the relative strengths of FX to FX-LO emission intensities determine the peak position and intensity of UV emission. What is more, laser irradiation with moderate energy density could induce the crystalline ZnO film with very flat and smooth surface. This investigation indicates that KrF laser irradiation could effectively modulate the exciton emission and surface morphology, which is important for the application of high performance of UV emitting optoelectronic devices. Copyright 2010 Elsevier B.V. All rights reserved.

  20. Vertebral architecture in the earliest stem tetrapods.

    PubMed

    Pierce, Stephanie E; Ahlberg, Per E; Hutchinson, John R; Molnar, Julia L; Sanchez, Sophie; Tafforeau, Paul; Clack, Jennifer A

    2013-02-14

    The construction of the vertebral column has been used as a key anatomical character in defining and diagnosing early tetrapod groups. Rhachitomous vertebrae--in which there is a dorsally placed neural arch and spine, an anteroventrally placed intercentrum and paired, posterodorsally placed pleurocentra--have long been considered the ancestral morphology for tetrapods. Nonetheless, very little is known about vertebral anatomy in the earliest stem tetrapods, because most specimens remain trapped in surrounding matrix, obscuring important anatomical features. Here we describe the three-dimensional vertebral architecture of the Late Devonian stem tetrapod Ichthyostega using propagation phase-contrast X-ray synchrotron microtomography. Our scans reveal a diverse array of new morphological, and associated developmental and functional, characteristics, including a possible posterior-to-anterior vertebral ossification sequence and the first evolutionary appearance of ossified sternal elements. One of the most intriguing features relates to the positional relationships between the vertebral elements, with the pleurocentra being unexpectedly sutured or fused to the intercentra that directly succeed them, indicating a 'reverse' rhachitomous design. Comparison of Ichthyostega with two other stem tetrapods, Acanthostega and Pederpes, shows that reverse rhachitomous vertebrae may be the ancestral condition for limbed vertebrates. This study fundamentally revises our current understanding of vertebral column evolution in the earliest tetrapods and raises questions about the presumed vertebral architecture of tetrapodomorph fish and later, more crownward, tetrapods.

  1. Nanosecond laser switching of surface wettability and epitaxial integration of c-axis ZnO thin films with Si(111) substrates.

    PubMed

    Molaei, R; Bayati, M R; Alipour, H M; Estrich, N A; Narayan, J

    2014-01-08

    We have achieved integration of polar ZnO[0001] epitaxial thin films with Si(111) substrates where cubic yttria-stabilized zirconia (c-YSZ) was used as a template on a Si(111) substrate. Using XRD (θ-2θ and φ scans) and HRTEM techniques, the epitaxial relationship between the ZnO and the c-YSZ layers was shown to be [0001]ZnO || [111]YSZ and [21¯1¯0]ZnO || [1¯01](c-YSZ), where the [21¯1¯0] direction lies in the (0001) plane, and the [1¯01] direction lies in the (111) plane. Similar studies on the c-YSZ/Si interface revealed epitaxy as (111)YSZ || (111)Si and in-plane (110)YSZ || (110)Si. HRTEM micrographs revealed atomically sharp and crystallographically continuous interfaces. The ZnO epilayers were subsequently laser annealed by a single pulse of a nanosecond excimer KrF laser. It was shown that the hydrophobic behavior of the pristine sample became hydrophilic after laser treatment. XPS was employed to study the effect of laser treatment on surface stoichiometry of the ZnO epilayers. The results revealed the formation of oxygen vacancies, which are envisaged to control the observed hydrophilic behavior. Our AFM studies showed surface smoothing due to the coupling of the high energy laser beam with the surface. The importance of integration of c-axis ZnO with Si(111) substrates is emphasized using the paradigm of domain matching epitaxy on the c-YSZ[111] buffer platform along with their out-of-plane orientation, which leads to improvement of the performance of the solid-state devices. The observed ultrafast response and switching in photochemical characteristics provide new opportunities for application of ZnO in smart catalysts, sensors, membranes, DNA self-assembly and multifunctional devices.

  2. Super low threshold plasmonic WGM lasing from an individual ZnO hexagonal microrod on an Au substrate for plasmon lasers.

    PubMed

    Dong, H M; Yang, Y H; Yang, G W

    2015-03-05

    We demonstrate an individual ZnO hexagonal microrod on the surface of an Au substrate which can become new sources for manufacturing miniature ZnO plasmon lasers by surface plasmon polariton coupling to whispering-gallery modes (WGMs). We also demonstrate that the rough surface of Au substrates can acquire a more satisfied enhancement of ZnO emission if the surface geometry of Au substrates is appropriate. Furthermore, we achieve high Q factor and super low threshold plasmonic WGM lasing from an individual ZnO hexagonal microrod on the surface of the Au substrate, in which Q factor can reach 5790 and threshold is 0.45 KW/cm(2) which is the lowest value reported to date for ZnO nanostructures lasing, at least 10 times smaller than that of ZnO at the nanometer. Electron transfer mechanisms are proposed to understand the physical origin of quenching and enhancement of ZnO emission on the surface of Au substrates. These investigations show that this novel coupling mode holds a great potential of ZnO hexagonal micro- and nanorods for data storage, bio-sensing, optical communications as well as all-optic integrated circuits.

  3. Zn-vacancy related defects in ZnO grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Ling, F. C. C.; Luo, C. Q.; Wang, Z. L.; Anwand, W.; Wagner, A.

    2017-02-01

    Undoped and Ga-doped ZnO (002) films were grown c-sapphire using the pulsed laser deposition (PLD) method. Znvacancy related defects in the films were studied by different positron annihilation spectroscopy (PAS). These included Doppler broadening spectroscopy (DBS) employing a continuous monenergetic positron beam, and positron lifetime spectroscopy using a pulsed monoenergetic positron beam attached to an electron linear accelerator. Two kinds of Znvacancy related defects namely a monovacancy and a divacancy were identified in the films. In as-grown undoped samples grown with relatively low oxygen pressure P(O2)≤1.3 Pa, monovacancy is the dominant Zn-vacancy related defect. Annealing these samples at 900 oC induced Zn out-diffusion into the substrate and converted the monovacancy to divacancy. For the undoped samples grown with high P(O2)=5 Pa irrespective of the annealing temperature and the as-grown degenerate Ga-doped sample (n=1020 cm-3), divacancy is the dominant Zn-vacancy related defect. The clustering of vacancy will be discussed.

  4. Pulsed laser deposited hexagonal wurzite ZnO thin-film nanostructures/nanotextures for nanophotonics applications

    NASA Astrophysics Data System (ADS)

    John Chelliah, Cyril Robinson Azariah; Swaminathan, Rajesh

    2018-01-01

    The high-quality and transparent thin-film zinc oxide (ZnO) nanostructures/nanotextures deposited on glass and silicon substrates using pulsed laser deposition (PLD) technique are reported. A solid-state, Nd-YAG laser was used for the PLD process. The films were deposited (i) at room temperature of 25°C (as deposited), (ii) at 150°C, (iii) at 300°C, (iv) at 450°C, and (v) at 600°C and annealed in the vacuum chamber. The depositions were also carried out at different laser repetition rates such as 10 and 5 Hz. UV spectroscopy and photoluminescence (PL) spectroscopy were carried out for optical studies. X-ray diffraction studies were carried out for all samples and analyzed the effects of the laser repetition rate, deposition, and annealing temperatures on the structural properties. Field-emission scanning electron microscope images are recorded for the best-structured samples. The electrical parameters were calibrated using the Hall effect measurement system and the IV characterization was performed using a CHI Electrochemical workstation. The deposition temperature has a significant effect on the microstrain and dislocation density of the ZnO thin film and optical phenomena with various electrical parameters, including the electron mobility, conductivity, and magnetoresistance. These promising results are suitable conditions for nanophotonics applications.

  5. A Devonian tetrapod-like fish reveals substantial parallelism in stem tetrapod evolution.

    PubMed

    Zhu, Min; Ahlberg, Per E; Zhao, Wen-Jin; Jia, Lian-Tao

    2017-10-01

    The fossils assigned to the tetrapod stem group document the evolution of terrestrial vertebrates from lobe-finned fishes. During the past 18 years the phylogenetic structure of this stem group has remained remarkably stable, even when accommodating new discoveries such as the earliest known stem tetrapod Tungsenia and the elpistostegid (fish-tetrapod intermediate) Tiktaalik. Here we present a large lobe-finned fish from the Late Devonian period of China that disrupts this stability. It combines characteristics of rhizodont fishes (supposedly a basal branch in the stem group, distant from tetrapods) with derived elpistostegid-like and tetrapod-like characters. This mélange of characters may reflect either detailed convergence between rhizodonts and elpistostegids plus tetrapods, under a phylogenetic scenario deduced from Bayesian inference analysis, or a previously unrecognized close relationship between these groups, as supported by maximum parsimony analysis. In either case, the overall result reveals a substantial increase in homoplasy in the tetrapod stem group. It also suggests that ecological diversity and biogeographical provinciality in the tetrapod stem group have been underestimated.

  6. Comparison on electrically pumped random laser actions of hydrothermal and sputtered ZnO films

    SciT

    Wang, Canxing; Jiang, Haotian; Li, Yunpeng

    2013-10-07

    Random lasing (RL) in polycrystalline ZnO films is an intriguing research subject. Here, we have comparatively investigated electrically pumped RL behaviors of two metal-insulator-semiconductor structured devices using the hydrothermal and sputtered ZnO films as the semiconductor components, i.e., the light-emitting layers, respectively. It is demonstrated that the device using the hydrothermal ZnO film exhibits smaller threshold current and larger output optical power of the electrically pumped RL. The morphological characterization shows that the hydrothermal ZnO film is somewhat porous and is much rougher than the sputtered one, suggesting that in the former stronger multiple light scattering can occur. Moreover, themore » photoluminescence characterization indicates that there are fewer defects in the hydrothermal ZnO film than in the sputtered one, which means that the photons can pick up larger optical gain through stimulated emission in the hydrothermal ZnO film. Therefore, it is believed that the stronger multiple light scattering and larger optical gain contribute to the improved performance of the electrically pumped RL from the device using the hydrothermal ZnO film.« less

  7. In situ detection of the Zn(2+) release process of ZnO NPs in tumour cells by confocal laser scanning fluorescence microscopy.

    PubMed

    Song, Wenshuang; Tang, Xiaoling; Li, Yong; Sun, Yang; Kong, Jilie; Qingguang, Ren

    2016-08-01

    The use of zinc oxide (ZnO) nanoparticles (NPs) for cancer is not yet clear for human clinical applications, which is primarily due to the lack of a better understanding of the action mechanisms and cellular consequences of the direct exposure of cells to these NPs. In this work, the authors have selected zinquin ethyl ester, a Zn(2+)-specific fluorescent molecular probe, to efficiently differentiate ZnO NPs and Zn(2+), and combined with confocal laser scanning microscopy (CLSM) to in situ study the Zn(2+) release process of ZnO NPs in cancer cell system through detecting the change of Zn(2+) level over time. During the experiments, the authors have designed the test group ZnO-2 in addition to assess the influence of a long-term storage on the characteristics of ZnO NPs in aqueous solution, and the Zn(2+) release process of ZnO NPs in cancer cell system. After three-month storage at room temperature, the release process became earlier and faster, which was consistent with previous results of transmission electron microscope, UV-Vis and PL spectra. It is a good detection method that combination of Zn(2+)-specific fluorescent molecular probe and CLSM, which will be helpful for ZnO NPs using in clinical research.

  8. Hidden morphological diversity among early tetrapods.

    PubMed

    Pardo, Jason D; Szostakiwskyj, Matt; Ahlberg, Per E; Anderson, Jason S

    2017-06-29

    Phylogenetic analysis of early tetrapod evolution has resulted in a consensus across diverse data sets in which the tetrapod stem group is a relatively homogenous collection of medium- to large-sized animals showing a progressive loss of 'fish' characters as they become increasingly terrestrial, whereas the crown group demonstrates marked morphological diversity and disparity. The oldest fossil attributed to the tetrapod crown group is the highly specialized aïstopod Lethiscus stocki, which shows a small size, extreme axial elongation, loss of limbs, spool-shaped vertebral centra, and a skull with reduced centres of ossification, in common with an otherwise disparate group of small animals known as lepospondyls. Here we use micro-computed tomography of the only known specimen of Lethiscus to provide new information that strongly challenges this consensus. Digital dissection reveals extremely primitive cranial morphology, including a spiracular notch, a large remnant of the notochord within the braincase, an open ventral cranial fissure, an anteriorly restricted parasphenoid element, and Meckelian ossifications. The braincase is elongate and lies atop a dorsally projecting septum of the parasphenoid bone, similar to stem tetrapods such as embolomeres. This morphology is consistent in a second aïstopod, Coloraderpeton, although the details differ. Phylogenetic analysis, including critical new braincase data, places aïstopods deep on the tetrapod stem, whereas another major lepospondyl lineage is displaced into the amniotes. These results show that stem group tetrapods were much more diverse in their body plans than previously thought. Our study requires a change in commonly used calibration dates for molecular analyses, and emphasizes the importance of character sampling for early tetrapod evolutionary relationships.

  9. Study of Tetrapodal ZnO-PDMS Composites: A Comparison of Fillers Shapes in Stiffness and Hydrophobicity Improvements

    PubMed Central

    Jin, Xin; Deng, Mao; Kaps, Sören; Zhu, Xinwei; Hölken, Iris; Mess, Kristin; Adelung, Rainer; Mishra, Yogendra Kumar

    2014-01-01

    ZnO particles of different size and structures were used as fillers to modify the silicone rubber, in order to reveal the effect of the filler shape in the polymer composites. Tetrapodal shaped microparticles, short microfibers/whiskers, and nanosized spherical particles from ZnO have been used as fillers to fabricate the different ZnO-Silicone composites. The detailed microstructures of the fillers as well as synthesized composites using scanning electron microscopy have been presented here. The tensile elastic modulus and water contact angle, which are important parameters for bio-mimetic applications, of fabricated composites with different fillers have been measured and compared. Among all three types of fillers, tetrapodal shaped ZnO microparticles showed the best performance in terms of increase in hydrophobicity of material cross-section as well as the stiffness of the composites. It has been demonstrated that the tetrapodal shaped microparticles gain their advantage due to the special shape, which avoids agglomeration problems as in the case for nanoparticles, and the difficulty of achieving truly random distribution for whisker fillers. PMID:25208080

  10. Study of tetrapodal ZnO-PDMS composites: a comparison of fillers shapes in stiffness and hydrophobicity improvements.

    PubMed

    Jin, Xin; Deng, Mao; Kaps, Sören; Zhu, Xinwei; Hölken, Iris; Mess, Kristin; Adelung, Rainer; Mishra, Yogendra Kumar

    2014-01-01

    ZnO particles of different size and structures were used as fillers to modify the silicone rubber, in order to reveal the effect of the filler shape in the polymer composites. Tetrapodal shaped microparticles, short microfibers/whiskers, and nanosized spherical particles from ZnO have been used as fillers to fabricate the different ZnO-Silicone composites. The detailed microstructures of the fillers as well as synthesized composites using scanning electron microscopy have been presented here. The tensile elastic modulus and water contact angle, which are important parameters for bio-mimetic applications, of fabricated composites with different fillers have been measured and compared. Among all three types of fillers, tetrapodal shaped ZnO microparticles showed the best performance in terms of increase in hydrophobicity of material cross-section as well as the stiffness of the composites. It has been demonstrated that the tetrapodal shaped microparticles gain their advantage due to the special shape, which avoids agglomeration problems as in the case for nanoparticles, and the difficulty of achieving truly random distribution for whisker fillers.

  11. The effects of Nd2O3 concentration in the laser emission of TeO2-ZnO glasses

    NASA Astrophysics Data System (ADS)

    Moreira, L. M.; Anjos, V.; Bell, M. J. V.; Ramos, C. A. R.; Kassab, L. R. P.; Doualan, D. J. L.; Camy, P.; Moncorgé, R.

    2016-08-01

    The present work reports the modification introduced by different Nd2O3 concentration on optical properties and the laser operation of Nd3+ doped (TeO2-ZnO) bulk tellurite glass. The spectroscopic data are analyzed within the Judd Ofelt formalism framework and the results are compared to the fluorescence lifetime and emission measurements to derive values for the quantum efficiency and the stimulated emission cross section of the considered 4F3/2 → 4I11/2 infrared laser transition around 1062.5 nm. Continuous-wave laser action is achieved with this bulk tellurite glass by pumping the sample inside a standard plan-concave mirror laser cavity with different output couplers. It is possible to observe coherent emission only for the lower concentration (0.5%(wt.) of Nd2 O3). Also laser action could only be observed for this sample with threshold pump power of 73 mW associated with a laser slope efficiency of 8% for an output coupler transmission of 4% indicating that TeO2-ZnO are potential materials for laser action. The results presented in this work together with those previously reported with higher concentration (1.0% (wt) of Nd2O3) determine the adequate Nd2O3 concentration for laser action and guide the correct experimental procedure for TeO2-ZnO glasses preparation.

  12. Comparison of TiO₂ and ZnO solar cells sensitized with an indoline dye: time-resolved laser spectroscopy studies of partial charge separation processes.

    PubMed

    Sobuś, Jan; Burdziński, Gotard; Karolczak, Jerzy; Idígoras, Jesús; Anta, Juan A; Ziółek, Marcin

    2014-03-11

    Time-resolved laser spectroscopy techniques in the time range from femtoseconds to seconds were applied to investigate the charge separation processes in complete dye-sensitized solar cells (DSC) made with iodide/iodine liquid electrolyte and indoline dye D149 interacting with TiO2 or ZnO nanoparticles. The aim of the studies was to explain the differences in the photocurrents of the cells (3-4 times higher for TiO2 than for ZnO ones). Electrochemical impedance spectroscopy and nanosecond flash photolysis studies revealed that the better performance of TiO2 samples is not due to the charge collection and dye regeneration processes. Femtosecond transient absorption results indicated that after first 100 ps the number of photoinduced electrons in the semiconductor is 3 times higher for TiO2 than for ZnO solar cells. Picosecond emission studies showed that the lifetime of the D149 excited state is about 3 times longer for ZnO than for TiO2 samples. Therefore, the results indicate that lower performance of ZnO solar cells is likely due to slower electron injection. The studies show how to correlate the laser spectroscopy methodology with global parameters of the solar cells and should help in better understanding of the behavior of alternative materials for porous electrodes for DSC and related devices.

  13. Direct writing of 150 nm gratings and squares on ZnO crystal in water by using 800 nm femtosecond laser.

    PubMed

    Liu, Jukun; Jia, Tianqing; Zhou, Kan; Feng, Donghai; Zhang, Shian; Zhang, Hongxin; Jia, Xin; Sun, Zhenrong; Qiu, Jianrong

    2014-12-29

    We present a controllable fabrication of nanogratings and nanosquares on the surface of ZnO crystal in water based on femtosecond laser-induced periodic surface structures (LIPSS). The formation of nanogrooves depends on both laser fluence and writing speed. A single groove with width less than 40 nm and double grooves with distance of 150 nm have been produced by manipulating 800 nm femtosecond laser fluence. Nanogratings with period of 150 nm, 300 nm and 1000 nm, and nanosquares with dimensions of 150 × 150 nm2 were fabricated by using this direct femtosecond laser writing technique.

  14. Spectroscopic characterization approach to study surfactants effect on ZnO 2 nanoparticles synthesis by laser ablation process

    NASA Astrophysics Data System (ADS)

    Drmosh, Q. A.; Gondal, M. A.; Yamani, Z. H.; Saleh, T. A.

    2010-05-01

    Zinc peroxide nanoparticles having grain size less than 5 nm were synthesized using pulsed laser ablation in aqueous solution in the presence of different surfactants and solid zinc target in 3% H 2O 2. The effect of surfactants on the optical and structure of ZnO 2 was studied by applying different spectroscopic techniques. Structural properties and grain size of the synthesized nanoparticles were studied using XRD method. The presence of the cubic phase of zinc peroxide in all samples was confirmed with XRD, and the grain sizes were 4.7, 3.7, 3.3 and 2.8 nm in pure H 2O 2, and H 2O 2 mixed with SDS, CTAB and OGM respectively. For optical characterization, FTIR transmittance spectra of ZnO 2 nanoparticles prepared with and without surfactants show a characteristic ZnO 2 absorption at 435-445 cm -1. FTIR spectrum revealed that the adsorbed surfactants on zinc peroxide disappeared in case of CTAB and OGM while it appears in case of SDS. This could be due to high critical micelles SDS concentration comparing with others which is attributed to the adsorption anionic nature of this surfactant. Both FTIR and UV-vis spectra show a red shift in the presence of SDS and blue shift in the presence of CTAB and OGM. The blue shift in the absorption edge indicates the quantum confinement property of nanoparticles. The zinc peroxide nanoparticles prepared in additives-free media was also characterized by Raman spectra which show the characteristic peaks at 830-840 and 420-440 cm -1.

  15. Low temperature sputter-deposited ZnO films with enhanced Hall mobility using excimer laser post-processing

    NASA Astrophysics Data System (ADS)

    Tsakonas, C.; Kuznetsov, V. L.; Cranton, W. M.; Kalfagiannis, N.; Abusabee, K. M.; Koutsogeorgis, D. C.; Abeywickrama, N.; Edwards, P. P.

    2017-12-01

    We report the low temperature (T  <  70 °C) fabrication of ZnO thin films (~140 nm) with Hall mobility of up to 17.3 cm2 V-1 s-1 making them suitable for thin film transistor (TFT) applications. The films were deposited by rf magnetron sputtering at T  <  70 °C and subsequently laser processed in ambient temperature in order to modify the Hall mobility and carrier concentration. Medium-to-low energy laser radiation densities and a high number of pulses were used to avoid damaging the films. Laser annealing of the films after aging in the lab under 25%-35% relative humidity and at an average illuminance of 120 lux resulted in an overall higher mobility and relatively low carrier concentration in comparison to the non-aged films that were laser processed immediately after deposition. A maximum overall measured Hall mobility of 17.3 cm2 V-1 s-1 at a carrier density of 2.3  ×  1018 cm-3 was measured from a 1 GΩ as deposited and aged film after the laser treatment. We suggest that the aging of non-processed films reduces structural defects mainly at grain boundaries by air species chemisorption, with concomitant increase in thermal conductivity so that laser processing can have an enhancing effect. Such a processing combination can act synergistically and produce suitable active layers for TFT applications with low temperature processing requirements.

  16. In situ monitoring of laser-assisted hydrothermal growth of ZnO nanowires: thermally deactivating growth kinetics.

    PubMed

    In, Jung Bin; Kwon, Hyuk-Jun; Lee, Daeho; Ko, Seung Hwan; Grigoropoulos, Costas P

    2014-02-26

    The laser-assisted hydrothermal growth kinetics of a cluster of ZnO nanowires are studied based on optical in situ growth monitoring. The growth yields are orders of magnitude higher than those of conventional hydrothermal methods that use bulk heating. This remarkable improvement is attributed to suppression of precursor depletion occurring by homogeneous growth reactions, as well as to enhanced mass transport. The obtained in situ data show gradually decaying growth kinetics even with negligible precursor consumption. It is revealed that the growth deceleration is caused by thermal deactivation resulting from heat dissipation through the growing nanowires. Finally, it is demonstrated that the tailored temporal modulation of the input power enables sustained growth to extended dimensions. These results provide a key to highly efficient use of growth precursors that has been pursued for industrial use of this functional metal oxide semiconductor. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Tetrapod trackways from the early Middle Devonian period of Poland.

    PubMed

    Niedźwiedzki, Grzegorz; Szrek, Piotr; Narkiewicz, Katarzyna; Narkiewicz, Marek; Ahlberg, Per E

    2010-01-07

    The fossil record of the earliest tetrapods (vertebrates with limbs rather than paired fins) consists of body fossils and trackways. The earliest body fossils of tetrapods date to the Late Devonian period (late Frasnian stage) and are preceded by transitional elpistostegids such as Panderichthys and Tiktaalik that still have paired fins. Claims of tetrapod trackways predating these body fossils have remained controversial with regard to both age and the identity of the track makers. Here we present well-preserved and securely dated tetrapod tracks from Polish marine tidal flat sediments of early Middle Devonian (Eifelian stage) age that are approximately 18 million years older than the earliest tetrapod body fossils and 10 million years earlier than the oldest elpistostegids. They force a radical reassessment of the timing, ecology and environmental setting of the fish-tetrapod transition, as well as the completeness of the body fossil record.

  18. The evolution of locomotor rhythmicity in tetrapods.

    PubMed

    Ross, Callum F; Blob, Richard W; Carrier, David R; Daley, Monica A; Deban, Stephen M; Demes, Brigitte; Gripper, Janaya L; Iriarte-Diaz, Jose; Kilbourne, Brandon M; Landberg, Tobias; Polk, John D; Schilling, Nadja; Vanhooydonck, Bieke

    2013-04-01

    Differences in rhythmicity (relative variance in cycle period) among mammal, fish, and lizard feeding systems have been hypothesized to be associated with differences in their sensorimotor control systems. We tested this hypothesis by examining whether the locomotion of tachymetabolic tetrapods (birds and mammals) is more rhythmic than that of bradymetabolic tetrapods (lizards, alligators, turtles, salamanders). Species averages of intraindividual coefficients of variation in cycle period were compared while controlling for gait and substrate. Variance in locomotor cycle periods is significantly lower in tachymetabolic than in bradymetabolic animals for datasets that include treadmill locomotion, non-treadmill locomotion, or both. When phylogenetic relationships are taken into account the pooled analyses remain significant, whereas the non-treadmill and the treadmill analyses become nonsignificant. The co-occurrence of relatively high rhythmicity in both feeding and locomotor systems of tachymetabolic tetrapods suggests that the anatomical substrate of rhythmicity is in the motor control system, not in the musculoskeletal components. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.

  19. Study of sputtered ZnO modified by Direct Laser Interference Patterning: Structural characterization and temperature simulation

    NASA Astrophysics Data System (ADS)

    Parellada-Monreal, L.; Castro-Hurtado, I.; Martínez-Calderón, M.; Rodriguez, A.; Olaizola, S. M.; Gamarra, D.; Lozano, J.; Mandayo, G. G.

    2018-05-01

    ZnO thin film sputtered on alumina substrate is processed by Direct Laser Interference Patterning (DLIP). The heat transfer equation has been simulated for interference patterns with a period of 730 nm and two different fluences (85 mJ/cm2 and 165 mJ/cm2). A thermal threshold of 900 K, where crystal modification occurs has been calculated, indicating a lateral and depth processing around 173 nm and 140 nm, respectively. The experimentally reproduced samples have been analyzed from the structural and composition point of view and compared to conventional thermal treatments at three different temperatures (600 °C, 700 °C and 800 °C). Promising properties have been observed for the laser treated samples, such as low influence on the thin film/substrate interface, an improvement of the crystallographic structure, as well as a decrease of the oxygen content from O/Zn = 2.10 to 1.38 for the highest fluence, getting closer to the stoichiometry. The DLIP characteristics could be suitable for the replacement of annealing process in the case of substrates that cannot achieve high temperatures as most of flexible substrates.

  20. EXAFS and XANES investigation of (Li, Ni) codoped ZnO thin films grown by pulsed laser deposition.

    PubMed

    Mino, Lorenzo; Gianolio, Diego; Bardelli, Fabrizio; Prestipino, Carmelo; Senthil Kumar, E; Bellarmine, F; Ramanjaneyulu, M; Lamberti, Carlo; Ramachandra Rao, M S

    2013-09-25

    Ni doped, Li doped and (Li, Ni) codoped ZnO thin films were successfully grown using a pulsed laser deposition technique. Undoped and doped ZnO thin films were investigated using extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge spectroscopy (XANES). Preliminary investigations on the Zn K-edge of the undoped and doped ZnO thin films revealed that doping has not influenced the average Zn-Zn bond length and Debye-Waller factor. This shows that both Ni and Li doping do not appreciably affect the average local environment of Zn. All the doped ZnO thin films exhibited more than 50% of substitutional Ni, with a maximum of 77% for 2% Ni and 2% Li doped ZnO thin film. The contribution of Ni metal to the EXAFS signal clearly reveals the presence of Ni clusters. The Ni-Ni distance in the Ni(0) nanoclusters, which are formed in the film, is shorter with respect to the reference Ni metal foil and the Debye-Waller factor is higher. Both facts perfectly reflect what is expected for metal nanoparticles. At the highest doping concentration (5%), the presence of Li favors the growth of a secondary NiO phase. Indeed, 2% Ni and 5% Li doped ZnO thin film shows %Nisub = 75 ± 11, %Nimet = 10 ± 8, %NiO = 15 ± 8. XANES studies further confirm that the substitutional Ni is more than 50% in all the samples. These results explain the observed magnetic properties.

  1. The Improvement of Electrical Characteristics of Pt/Ti Ohmic Contacts to Ga-Doped ZnO by Homogenized KrF Pulsed Excimer Laser Treatment

    NASA Astrophysics Data System (ADS)

    Oh, Min-Suk

    2018-04-01

    We investigated the effect of KrF excimer laser surface treatment on Pt/Ti ohmic contacts to Ga-doped n-ZnO ( N d = 4.3 × 1017 cm-3). The treatment of the n-ZnO surfaces by laser irradiation greatly improved the electrical characteristics of the metal contacts. The Pt/Ti ohmic layer on the laser-irradiated n-ZnO showed specific contact resistances of 2.5 × 10-4 ˜ 4.8 × 10-4 Ω cm2 depending on the laser energy density and gas ambient, which were about two orders of magnitude lower than that of the as-grown sample, 8.4 × 10-2 Ω cm2. X-ray photoelectron spectroscopy and photoluminescence measurements showed that the KrF excimer laser treatments increased the electron concentration near the surface region of the Ga-doped n-ZnO due to the preferential evaporation of oxygen atoms from the ZnO surface by the laser-induced dissociation of Zn-O bonds.

  2. Euryhaline ecology of early tetrapods revealed by stable isotopes.

    PubMed

    Goedert, Jean; Lécuyer, Christophe; Amiot, Romain; Arnaud-Godet, Florent; Wang, Xu; Cui, Linlin; Cuny, Gilles; Douay, Guillaume; Fourel, François; Panczer, Gérard; Simon, Laurent; Steyer, J-Sébastien; Zhu, Min

    2018-06-01

    The fish-to-tetrapod transition-followed later by terrestrialization-represented a major step in vertebrate evolution that gave rise to a successful clade that today contains more than 30,000 tetrapod species. The early tetrapod Ichthyostega was discovered in 1929 in the Devonian Old Red Sandstone sediments of East Greenland (dated to approximately 365 million years ago). Since then, our understanding of the fish-to-tetrapod transition has increased considerably, owing to the discovery of additional Devonian taxa that represent early tetrapods or groups evolutionarily close to them. However, the aquatic environment of early tetrapods and the vertebrate fauna associated with them has remained elusive and highly debated. Here we use a multi-stable isotope approach (δ 13 C, δ 18 O and δ 34 S) to show that some Devonian vertebrates, including early tetrapods, were euryhaline and inhabited transitional aquatic environments subject to high-magnitude, rapid changes in salinity, such as estuaries or deltas. Euryhalinity may have predisposed the early tetrapod clade to be able to survive Late Devonian biotic crises and then successfully colonize terrestrial environments.

  3. Pulsed laser deposited ZnO film on side-polished fiber as a gas sensing element.

    PubMed

    Dikovska, Anna Og; Atanasov, Petar A; Stoyanchov, Toshko R; Andreev, Andrey T; Karakoleva, Elka I; Zafirova, Blagovesta S

    2007-05-01

    A simple sensor element consisting of a side-polished single-mode fiber and a planar metal oxide waveguide is described. The thin ZnO planar waveguide was produced on the polished fiber surface by pulsed laser deposition at optimized processing parameters. A measurement scheme for in situ control of the film thickness during the deposition process was developed and used. X-ray diffraction measurements and scanning electron microscopy were used to characterize the structure and the surface morphology of the planar waveguide, respectively. The numerical evaluation of the sensor sensitivity predicts the possibility to detect refractive index changes of less than 10(-4). Furthermore, preliminary gas sensor tests were performed by using a mixture of 1.5% butane diluted in N(2) and pure butane. A shift of the spectral position of the resonance points was observed from 3 to 5 s after gas exposure, which corresponds to refractive index changes of 3 x 10(-5) and 1.2 x 10(-3) for 1.5% butane and for pure butane, respectively.

  4. Electronic transport in highly conducting Si-doped ZnO thin films prepared by pulsed laser deposition

    SciT

    Kuznetsov, Vladimir L.; Vai, Alex T.; Edwards, Peter P., E-mail: peter.edwards@chem.ox.ac.uk

    2015-12-07

    Highly conducting (ρ = 3.9 × 10{sup −4} Ωcm) and transparent (83%) polycrystalline Si-doped ZnO (SiZO) thin films have been deposited onto borosilicate glass substrates by pulsed laser deposition from (ZnO){sub 1−x}(SiO{sub 2}){sub x} (0 ≤ x ≤ 0.05) ceramic targets prepared using a sol-gel technique. Along with their structural, chemical, and optical properties, the electronic transport within these SiZO samples has been investigated as a function of silicon doping level and temperature. Measurements made between 80 and 350 K reveal an almost temperature-independent carrier concentration consistent with degenerate metallic conduction in all of these samples. The temperature-dependent Hall mobility has been modeled by considering the varying contribution of grainmore » boundary and electron-phonon scattering in samples with different nominal silicon concentrations.« less

  5. Sb-related defects in Sb-doped ZnO thin film grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Luo, Caiqin; Ho, Lok-Ping; Azad, Fahad; Anwand, Wolfgang; Butterling, Maik; Wagner, Andreas; Kuznetsov, Andrej; Zhu, Hai; Su, Shichen; Ling, Francis Chi-Chung

    2018-04-01

    Sb-doped ZnO films were fabricated on c-plane sapphire using the pulsed laser deposition method and characterized by Hall effect measurement, X-ray photoelectron spectroscopy, X-ray diffraction, photoluminescence, and positron annihilation spectroscopy. Systematic studies on the growth conditions with different Sb composition, oxygen pressure, and post-growth annealing were conducted. If the Sb doping concentration is lower than the threshold ˜8 × 1020 cm-3, the as-grown films grown with an appropriate oxygen pressure could be n˜4 × 1020 cm-3. The shallow donor was attributed to the SbZn related defect. Annealing these samples led to the formation of the SbZn-2VZn shallow acceptor which subsequently compensated for the free carrier. For samples with Sb concentration exceeding the threshold, the yielded as-grown samples were highly resistive. X-ray diffraction results showed that the Sb dopant occupied the O site rather than the Zn site as the Sb doping exceeded the threshold, whereas the SbO related deep acceptor was responsible for the high resistivity of the samples.

  6. Dopant-driven enhancements in the optoelectronic properties of laser ablated ZnO: Ga thin films

    NASA Astrophysics Data System (ADS)

    Hassan, Ali; Jin, Yuhua; Chao, Feng; Irfan, Muhammad; Jiang, Yijian

    2018-04-01

    Theoretically and experimentally evaluated optoelectronic properties of GZO (Ga-doped zinc oxide) were correlated in the present article. Density functional theory and Hubbard U (DFT + Ud + Up) first-principle calculations were used for the theoretical study. The pulsed laser deposition technique was used to fabricate GZO thin films on p-GaN, Al2O3, and p-Si substrates. X-ray diffraction graphs show single crystal growth of GZO thin films with (002) preferred crystallographic orientation. The chemical composition was studied via energy dispersive X-ray spectroscopy, and no other unwanted impurity-related peaks were found, which indicated the impurity-free thin film growth of GZO. Field emission scanning electron microscopic micrographs revealed noodle-, seed-, and granular-like structures of GZO/GaN, GZO/Al2O3, and GZO/Si, respectively. Uniform growth of GZO/GaN was found due to fewer mismatches between ZnO and GaN (0.09%). Hall effect measurements in the van der Pauw configuration were used to check electrical properties. The highest mobility (53 cm2/Vs) with a high carrier concentration was found with low laser shots (1800). A 5-fold photoluminescence enhancement in the noodle-like structure of GZO/GaN compared with GZO/Al2O3 and GZO/Si was detected. This points toward shape-driven optical properties because the noodle-like structure is more favorable for optical enhancements in GZO thin films. Theoretical (3.539 eV) and experimental (3.54 eV) values of the band-gap were also found to be comparable. Moreover, the lowest resistivity (3.5 × 10-4 Ωcm) with 80% transmittance is evidence that GZO is a successful alternate of ITO.

  7. Enhancing light emission in flexible AC electroluminescent devices by tetrapod-like zinc oxide whiskers.

    PubMed

    Wen, Li; Liu, Nishuang; Wang, Siliang; Zhang, Hui; Zhao, Wanqiu; Yang, Zhichun; Wang, Yumei; Su, Jun; Li, Luying; Long, Fei; Zou, Zhengguang; Gao, Yihua

    2016-10-03

    Flexible alternating current electroluminescent devices (ACEL) are more and more popular and widely used in liquid-crystal display back-lighting, large-scale architectural and decorative lighting due to their uniform light emission, low power consumption and high resolution. However, presently how to acquire high brightness under a certain voltage are confronted with challenges. Here, we demonstrate an electroluminescence (EL) enhancing strategy that tetrapod-like ZnO whiskers (T-ZnOw) are added into the bottom electrode of carbon nanotubes (CNTs) instead of phosphor layer in flexible ACEL devices emitting blue, green and orange lights, and the brightness is greatly enhanced due to the coupling between the T-ZnOw and ZnS phosphor dispersed in the flexible polydimethylsiloxane (PDMS) layer. This strategy provides a new routine for the development of high performance, flexible and large-area ACEL devices.

  8. New Early Jurassic Tetrapod Assemblages Constrain Triassic-Jurassic Tetrapod Extinction Event

    NASA Astrophysics Data System (ADS)

    Olsen, P. E.; Shubin, N. H.; Anders, M. H.

    1987-08-01

    The discovery of the first definitively correlated earliest Jurassic (200 million years before present) tetrapod assemblage (Fundy basin, Newark Supergroup, Nova Scotia) allows reevaluation of the duration of the Triassic-Jurassic tetrapod extinction event. Present are tritheledont and mammal-like reptiles, prosauropod, theropod, and ornithischian dinosaurs, protosuchian and sphenosuchian crocodylomorphs, sphenodontids, and hybodont, semionotid, and palaeonisciform fishes. All of the families are known from Late Triassic and Jurassic strata from elsewhere; however, pollen and spore, radiometric, and geochemical correlation indicate an early Hettangian age for these assemblages. Because all ``typical Triassic'' forms are absent from these assemblages, most Triassic-Jurassic tetrapod extinctions occurred before this time and without the introduction of new families. As was previously suggested by studies of marine invertebrates, this pattern is consistent with a global extinction event at the Triassic-Jurassic boundary. The Manicouagan impact structure of Quebec provides dates broadly compatible with the Triassic-Jurassic boundary and, following the impact theory of mass extinctions, may be implicated in the cause.

  9. Influence of electron beam irradiation on nonlinear optical properties of Al doped ZnO thin films for optoelectronic device applications in the cw laser regime

    NASA Astrophysics Data System (ADS)

    Antony, Albin; Pramodini, S.; Poornesh, P.; Kityk, I. V.; Fedorchuk, A. O.; Sanjeev, Ganesh

    2016-12-01

    We present the studies on third-order nonlinear optical properties of Al doped ZnO thin films irradiated with electron beam at different dose rate. Al doped ZnO thin films were deposited on a glass substrate by spray pyrolysis deposition technique. The thin films were irradiated using the 8 MeV electron beam from microtron ranging from 1 kG y to 5 kG y. Nonlinear optical studies were carried out by employing the single beam Z-scan technique to determine the sign and magnitude of absorptive and refractive nonlinearities of the irradiated thin films. Continuous wave He-Ne laser operating at 633 nm was used as source of excitation. The open aperture Z-scan measurements indicated the sample displays reverse saturable absorption (RSA) process. The negative sign of the nonlinear refractive index n2 was noted from the closed aperture Z-scan measurements indicates, the films exhibit self-defocusing property due to thermal nonlinearity. The third-order nonlinear optical susceptibility χ(3) varies from 8.17 × 10-5 esu to 1.39 × 10-3 esu with increase in electron beam irradiation. The present study reveals that the irradiation of electron beam leads to significant changes in the third-order optical nonlinearity. Al doped ZnO displays good optical power handling capability with optical clamping of about ∼5 mW. The irradiation study endorses that the Al doped ZnO under investigation is a promising candidate photonic device applications such as all-optical power limiting.

  10. Comparative study of textured and epitaxial ZnO films

    NASA Astrophysics Data System (ADS)

    Ryu, Y. R.; Zhu, S.; Wrobel, J. M.; Jeong, H. M.; Miceli, P. F.; White, H. W.

    2000-06-01

    ZnO films were synthesized by pulsed laser deposition (PLD) on GaAs and α-Al 2O 3 substrates. The properties of ZnO films on GaAs and α-Al 2O 3 have been investigated to determine the differences between epitaxial and textured ZnO films. ZnO films on GaAs show very strong emission features associated with exciton transitions as do ZnO films on α-Al 2O 3, while the crystalline structural qualities for ZnO films on α-Al 2O 3 are much better than those for ZnO films on GaAs. The properties of ZnO films are studied by comparing highly oriented, textured ZnO films on GaAs with epitaxial ZnO films on α-Al 2O 3 synthesized along the c-axis.

  11. Structure and Electric Conduction in Pulsed Laser-Deposited ZnO Thin Films Individually Doped with N, P, or Na

    NASA Astrophysics Data System (ADS)

    Jiao, D. L.; Zhong, X. C.; Qiu, W. Q.; Zhang, H.; Liu, Z. W.; Zhang, G. Q.

    2018-03-01

    N-, P-, and Na-doped ZnO films with c-axis orientation were produced by pulsed laser deposition using N2O or O2 as the reaction gas. The effects of deposition temperature and deposition pressure on the lattice structure, morphology, and electric conduction have been investigated. High gas pressure leads to large-sized grains with large grain barriers, which cause a reduced mobility. P acts as an acceptor and the number of compensating defects in the P-doped film is reduced under high O2 pressure. Na also acts as an acceptor, and the effects of high temperature on Na-doped films are encouraging as the solubility of the dopant is high. However, high temperature may cause less incorporation of N and P in the film. In the present work, p-type conduction has not been obtained in N- and P-doped films despite a wide range of processing parameters employed. Na-doped films display an increasing trend towards p-type films at high temperatures and high O2 pressures. These results provide an insight on how these dopants behave in ZnO films and indicate that the careful selection of the deposition conditions is necessary in order to obtain p-type films by pulsed laser deposition.

  12. Quantitative analysis of doped/undoped ZnO nanomaterials using laser assisted atom probe tomography: Influence of the analysis parameters

    SciT

    Amirifar, Nooshin; Lardé, Rodrigue, E-mail: rodrigue.larde@univ-rouen.fr; Talbot, Etienne

    2015-12-07

    In the last decade, atom probe tomography has become a powerful tool to investigate semiconductor and insulator nanomaterials in microelectronics, spintronics, and optoelectronics. In this paper, we report an investigation of zinc oxide nanostructures using atom probe tomography. We observed that the chemical composition of zinc oxide is strongly dependent on the analysis parameters used for atom probe experiments. It was observed that at high laser pulse energies, the electric field at the specimen surface is strongly dependent on the crystallographic directions. This dependence leads to an inhomogeneous field evaporation of the surface atoms, resulting in unreliable measurements. We showmore » that the laser pulse energy has to be well tuned to obtain reliable quantitative chemical composition measurements of undoped and doped ZnO nanomaterials.« less

  13. Toxicity of Functional Nano-Micro Zinc Oxide Tetrapods: Impact of Cell Culture Conditions, Cellular Age and Material Properties

    PubMed Central

    Papavlassopoulos, Heike; Mishra, Yogendra K.; Kaps, Sören; Paulowicz, Ingo; Abdelaziz, Ramzy; Elbahri, Mady; Maser, Edmund; Adelung, Rainer; Röhl, Claudia

    2014-01-01

    With increasing production and applications of nanostructured zinc oxide, e.g., for biomedical and consumer products, the question of safety is getting more and more important. Different morphologies of zinc oxide structures have been synthesized and accordingly investigated. In this study, we have particularly focused on nano-micro ZnO tetrapods (ZnO-T), because their large scale fabrication has been made possible by a newly introduced flame transport synthesis approach which will probably lead to several new applications. Moreover, ZnO-T provide a completely different morphology then classical spherical ZnO nanoparticles. To get a better understanding of parameters that affect the interactions between ZnO-T and mammalian cells, and thus their biocompatibility, we have examined the impact of cell culture conditions as well as of material properties on cytotoxicity. Our results demonstrate that the cell density of fibroblasts in culture along with their age, i.e., the number of preceding cell divisions, strongly affect the cytotoxic potency of ZnO-T. Concerning the material properties, the toxic potency of ZnO-T is found to be significantly lower than that of spherical ZnO nanoparticles. Furthermore, the morphology of the ZnO-T influenced cellular toxicity in contrast to surface charges modified by UV illumination or O2 treatment and to the material age. Finally, we have observed that direct contact between tetrapods and cells increases their toxicity compared to transwell culture models which allow only an indirect effect via released zinc ions. The results reveal several parameters that can be of importance for the assessment of ZnO-T toxicity in cell cultures and for particle development. PMID:24454775

  14. A problematic early tetrapod from the Mississippian of Nevada

    Thomson, K.S.; Shubin, N.S.; Poole, F.G.

    1998-01-01

    We report here the discovery of a new taxon of Paleozoic tetrapod from the Late Mississippian of Nevada (330-340 Ma). It has a unique vertebral column with principal centra having vertical anterior and posterior faces, ventrally incomplete accessory centra located antero-dorsally in each centrum, and enlarged presacral/sacral vertebrae. The head and pectoral girdle were not preserved but the large femur, robust pelvic girdle and enlarged sacral vertebrae possibly indicate a terrestrial mode of life. This new form significantly extends the western geographic range of known Mississippian tetrapods. It presents a mosaic of primitive and derived features, indicating that continued revision of traditional accounts of vertebral homology and the early diversifications of Paleozoic tetrapods will be necessary.

  15. Sensitive measurement of nonlinear absorption and optical limiting in undoped and Fe-doped ZnO quantum dots using pulsed laser

    NASA Astrophysics Data System (ADS)

    Sharma, D.; Malik, B. P.; Gaur, A.

    2016-11-01

    Zinc oxide quantum dots (QDs) with Fe-doping at different concentrations were prepared by chemical co-precipitation method. The prepared QDs were characterized by UV-Vis spectroscopy, X-ray diffraction and Z-scan technique. The sizes of QDs were found to be within 4.6-6.6 nm range. The nonlinear parameters viz. two-photon absorption coefficient (βTPA) and two-photon absorption cross-section (σTPA) were extracted with the help of open aperture Z-scan technique using nanosecond Nd:YAG laser operating at wavelength 532 nm. Higher values of βTPA and σTPA for Fe doped ZnO implied that they were potential materials for development of photonics devices and sensor protection applications. Fe doped sample (3 % by wt) was found to be the best optical limiter with limiting threshold intensity of 0.64 TW/cm2.

  16. Deposition and composition-control of Mn-doped ZnO thin films by combinatorial pulsed laser deposition using two delayed plasma plumes

    SciT

    Sanchez-Ake, C.; Camacho, R.; Moreno, L.

    2012-08-15

    Thin films of ZnO doped with manganese were deposited by double-beam, combinatorial pulsed laser deposition. The laser-induced plasmas were studied by means of fast photography and using a Langmuir probe, whereas the films were analyzed by x-ray-diffraction and energy-dispersive x-ray spectroscopy. The effect of the relative delay between plasma plumes on the characteristics of the films was analyzed. It was found that using this parameter, it is possible to control the dopant content keeping the oriented wurtzite structure of the films. The minimum content of Mn was found for plume delays between 0 and 10 {mu}s as the interaction betweenmore » plasmas scatters the dopant species away from the substrate, thus reducing the incorporation of Mn into the films. Results suggest that for delays shorter than {approx}100 {mu}s, the expansion of the second plume through the region behind the first plume affects the composition of the film.« less

  17. Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) of low molecular weight organic compounds and synthetic polymers using zinc oxide (ZnO) nanoparticles.

    PubMed

    Watanabe, Takehiro; Kawasaki, Hideya; Yonezawa, Tetsu; Arakawa, Ryuichi

    2008-08-01

    We have developed surface-assisted laser desorption/ionization mass spectrometry using zinc oxide (ZnO) nanoparticles with anisotropic shapes (ZnO-SALDI-MS). The mass spectra showed low background noises in the low m/z, i.e. less than 500 u region. Thus, we succeeded in SALDI ionization on low molecular weight organic compounds, such as verapamil hydrochloride, testosterone, and polypropylene glycol (PPG) (average molecular weight 400) without using a liquid matrix or buffers such as citric acids. In addition, we found that ZnO-SALDI has advantages in post-source decay (PSD) analysis and produced a simple mass spectrum for phospholipids. The ZnO-SALDI spectra for synthetic polymers of polyethylene glycol (PEG), polystyrene (PS) and polymethylmethacrylate (PMMA) showed the sensitivity and molecular weight distribution to be comparable to matrix-assisted laser desorption/ionization (MALDI) spectra with a 2,5-dihydroxybenzoic acid (DHB) matrix. ZnO-SALDI shows good performance for synthetic polymers as well as low molecular weight organic compounds. Copyright (c) 2008 John Wiley & Sons, Ltd.

  18. The integumentary skeleton of tetrapods: origin, evolution, and development

    PubMed Central

    Vickaryous, Matthew K; Sire, Jean-Yves

    2009-01-01

    Although often overlooked, the integument of many tetrapods is reinforced by a morphologically and structurally diverse assemblage of skeletal elements. These elements are widely understood to be derivatives of the once all-encompassing dermal skeleton of stem-gnathostomes but most details of their evolution and development remain confused and uncertain. Herein we re-evaluate the tetrapod integumentary skeleton by integrating comparative developmental and tissue structure data. Three types of tetrapod integumentary elements are recognized: (1) osteoderms, common to representatives of most major taxonomic lineages; (2) dermal scales, unique to gymnophionans; and (3) the lamina calcarea, an enigmatic tissue found only in some anurans. As presently understood, all are derivatives of the ancestral cosmoid scale and all originate from scleroblastic neural crest cells. Osteoderms are plesiomorphic for tetrapods but demonstrate considerable lineage-specific variability in size, shape, and tissue structure and composition. While metaplastic ossification often plays a role in osteoderm development, it is not the exclusive mode of skeletogenesis. All osteoderms share a common origin within the dermis (at or adjacent to the stratum superficiale) and are composed primarily (but not exclusively) of osseous tissue. These data support the notion that all osteoderms are derivatives of a neural crest-derived osteogenic cell population (with possible matrix contributions from the overlying epidermis) and share a deep homology associated with the skeletogenic competence of the dermis. Gymnophionan dermal scales are structurally similar to the elasmoid scales of most teleosts and are not comparable with osteoderms. Whereas details of development are lacking, it is hypothesized that dermal scales are derivatives of an odontogenic neural crest cell population and that skeletogenesis is comparable with the formation of elasmoid scales. Little is known about the lamina calcarea. It is

  19. The African coelacanth genome provides insights into tetrapod evolution.

    PubMed

    Amemiya, Chris T; Alföldi, Jessica; Lee, Alison P; Fan, Shaohua; Philippe, Hervé; Maccallum, Iain; Braasch, Ingo; Manousaki, Tereza; Schneider, Igor; Rohner, Nicolas; Organ, Chris; Chalopin, Domitille; Smith, Jeramiah J; Robinson, Mark; Dorrington, Rosemary A; Gerdol, Marco; Aken, Bronwen; Biscotti, Maria Assunta; Barucca, Marco; Baurain, Denis; Berlin, Aaron M; Blatch, Gregory L; Buonocore, Francesco; Burmester, Thorsten; Campbell, Michael S; Canapa, Adriana; Cannon, John P; Christoffels, Alan; De Moro, Gianluca; Edkins, Adrienne L; Fan, Lin; Fausto, Anna Maria; Feiner, Nathalie; Forconi, Mariko; Gamieldien, Junaid; Gnerre, Sante; Gnirke, Andreas; Goldstone, Jared V; Haerty, Wilfried; Hahn, Mark E; Hesse, Uljana; Hoffmann, Steve; Johnson, Jeremy; Karchner, Sibel I; Kuraku, Shigehiro; Lara, Marcia; Levin, Joshua Z; Litman, Gary W; Mauceli, Evan; Miyake, Tsutomu; Mueller, M Gail; Nelson, David R; Nitsche, Anne; Olmo, Ettore; Ota, Tatsuya; Pallavicini, Alberto; Panji, Sumir; Picone, Barbara; Ponting, Chris P; Prohaska, Sonja J; Przybylski, Dariusz; Saha, Nil Ratan; Ravi, Vydianathan; Ribeiro, Filipe J; Sauka-Spengler, Tatjana; Scapigliati, Giuseppe; Searle, Stephen M J; Sharpe, Ted; Simakov, Oleg; Stadler, Peter F; Stegeman, John J; Sumiyama, Kenta; Tabbaa, Diana; Tafer, Hakim; Turner-Maier, Jason; van Heusden, Peter; White, Simon; Williams, Louise; Yandell, Mark; Brinkmann, Henner; Volff, Jean-Nicolas; Tabin, Clifford J; Shubin, Neil; Schartl, Manfred; Jaffe, David B; Postlethwait, John H; Venkatesh, Byrappa; Di Palma, Federica; Lander, Eric S; Meyer, Axel; Lindblad-Toh, Kerstin

    2013-04-18

    The discovery of a living coelacanth specimen in 1938 was remarkable, as this lineage of lobe-finned fish was thought to have become extinct 70 million years ago. The modern coelacanth looks remarkably similar to many of its ancient relatives, and its evolutionary proximity to our own fish ancestors provides a glimpse of the fish that first walked on land. Here we report the genome sequence of the African coelacanth, Latimeria chalumnae. Through a phylogenomic analysis, we conclude that the lungfish, and not the coelacanth, is the closest living relative of tetrapods. Coelacanth protein-coding genes are significantly more slowly evolving than those of tetrapods, unlike other genomic features. Analyses of changes in genes and regulatory elements during the vertebrate adaptation to land highlight genes involved in immunity, nitrogen excretion and the development of fins, tail, ear, eye, brain and olfaction. Functional assays of enhancers involved in the fin-to-limb transition and in the emergence of extra-embryonic tissues show the importance of the coelacanth genome as a blueprint for understanding tetrapod evolution.

  20. Systems and methods of detecting force and stress using tetrapod nanocrystal

    DOEpatents

    Choi, Charina L.; Koski, Kristie J.; Sivasankar, Sanjeevi; Alivisatos, A. Paul

    2013-08-20

    Systems and methods of detecting force on the nanoscale including methods for detecting force using a tetrapod nanocrystal by exposing the tetrapod nanocrystal to light, which produces a luminescent response by the tetrapod nanocrystal. The method continues with detecting a difference in the luminescent response by the tetrapod nanocrystal relative to a base luminescent response that indicates a force between a first and second medium or stresses or strains experienced within a material. Such systems and methods find use with biological systems to measure forces in biological events or interactions.

  1. Nd3+-doped TeO2-Bi2O3-ZnO transparent glass ceramics for laser application at 1.06 μm

    NASA Astrophysics Data System (ADS)

    Hu, Xiaolin; Luo, Zhiwei; Liu, Taoyong; Lu, Anxian

    2017-04-01

    The high crystallinity transparent glass ceramics based on Nd3+-doped 70TeO2-15Bi2O3-15ZnO (TBZ) compositions were successfully prepared by two-step heat treatment process. The effects of Nd2O3 content on the thermal, structural, mechanical, and optical properties of TBZ glass ceramics were studied. The incorporation of Nd2O3 enhanced the crystallization tendency in the matrix glass composition. The crystal phase and morphology of Bi2Te4O11 in the glass ceramics were confirmed by X-ray diffraction and field emission scanning electron microscopy. Due to precipitate more crystal phase, the hardness values increased from 3.21 to 3.66 GPa. Eight absorption peaks were observed from 400 to 900 nm and three emission bands appeared in the range of 850-1400 nm. With the increasing of Nd2O3 content from 0.5 to 2.5 wt%, the intensity of absorption peaks enhanced and the emission intensity increased up to 1.0 wt% and then fell down for further dopant concentration. The fluorescence decay lifetime decreased rapidly starting from 1.5 wt% Nd2O3 content due to the obvious energy migration among Nd3+. According to the extreme strong emission band around 1062 nm and the optimum Nd2O3 content (1.0 wt%), N10 glass ceramic was considered as a potential material for 1.06 μm laser applications.

  2. Tetrapod-like axial regionalization in an early ray-finned fish

    PubMed Central

    Sallan, Lauren Cole

    2012-01-01

    Tetrapods possess up to five morphologically distinct vertebral series: cervical, thoracic, lumbar, sacral and caudal. The evolution of axial regionalization has been linked to derived Hox expression patterns during development and the demands of weight-bearing and walking on land. These evolutionary and functional explanations are supported by an absence of similar traits in fishes, living and extinct. Here, I show that, Tarrasius problematicus, a marine ray-finned fish from the Mississippian (Early Carboniferous; 359–318 Ma) of Scotland, is the first non-tetrapod known to possess tetrapod-like axial regionalization. Tarrasius exhibits five vertebral regions, including a seven-vertebrae ‘cervical’ series and a reinforced ‘sacrum’ over the pelvic area. Most vertebrae possess processes for intervertebral contact similar to tetrapod zygapophyses. The fully aquatic Tarrasius evolved these morphologies alongside other traits convergent with early tetrapods, including a naked trunk, and a single median continuous fin. Regional modifications in Tarrasius probably facilitated pelagic swimming, rather than a terrestrial lifestyle or walking gait, presenting an alternative scenario for the evolution of such traits in tetrapods. Axial regionalization in Tarrasius could indicate tetrapod-like Hox expression patterns, possibly representing the primitive state for jawed vertebrates. Alternately, it could signal a weaker relationship, or even a complete disconnect, between Hox expression domains and vertebrate axial plans. PMID:22628471

  3. Mediator-free interaction of glucose oxidase, as model enzyme for immobilization, with Al-doped and undoped ZnO thin films laser-deposited on polycarbonate supports.

    PubMed

    V T K P, Fidal; Inguva, Saikumar; Krishnamurthy, Satheesh; Marsili, Enrico; Mosnier, Jean-Paul; T S, Chandra

    2017-01-01

    Al doped and undoped ZnO thin films were deposited by pulsed-laser deposition on polycarbonate sheets. The films were characterized by optical transmission, Hall effect measurement, XRD and SEM. Optical transmission and surface reflectometry studies showed good transparency with thicknesses ∼100nm and surface roughness of 10nm. Hall effect measurements showed that the sheet carrier concentration was -1.44×10 15 cm -2 for AZO and -6×10 14 cm -2 for ZnO. The films were then modified by drop-casting glucose oxidase (GOx) without the use of any mediators. Higher protein concentration was observed on ZnO as compared to AZO with higher specific activity for ZnO (0.042Umg -1 ) compared to AZO (0.032Umg -1 ), and was in agreement with cyclic voltemmetry (CV). X-ray photoelectron spectroscopy (XPS) suggested that the protein was bound by dipole interactions between AZO lattice oxygen and the amino group of the enzyme. Chronoamperometry showed sensitivity of 5.5μAmM -1 cm -2 towards glucose for GOx/AZO and 2.2μAmM -1 cm -2 for GOx/ZnO. The limit of detection (LoD) was 167μM of glucose for GOx/AZO, as compared to 360μM for GOx/ZnO. The linearity was 0.28-28mM for GOx/AZO whereas it was 0.6-28mM for GOx/ZnO with a response time of 10s. Possibly due to higher enzyme loading, the decrease of impedance in presence of glucose was larger for GOx/ZnO as compared to GOx/AZO in electrochemical impedance spectroscopy (EIS). Analyses with clinical blood serum samples showed that the systems had good reproducibility and accuracy. The characteristics of novel ZnO and AZO thin films with GOx as a model enzyme, should prove useful for the future fabrication of inexpensive, highly sensitive, disposable electrochemical biosensors for high throughput diagnostics. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. Triassic tetrapods from antarctica: evidence for continental drift.

    PubMed

    Elliot, D H; Colbert, E H; Breed, W J; Jensen, J A; Powell, J S

    1970-09-18

    During the austral summer of 1969-1970 bones of Lower Triassic vertebrates were excavated from coarse quartzose sandstones forming stream channel deposits of the Fremouw Formation at Coalsack Bluff, in the Transantarctic Mountains of Antarctica. This is the first assemblage of fossil tetrapods of significant geologic age to be found on the Antarctic Continent. The fossils include labyrinthodont amphibians, presumed thecodont reptiles, and therapsid reptiles, including the definitive genus, Lystrosaurus. This genus is typical of the Lower Triassic of southern Africa, and is also found in India and China. Lystrosaurus and associated vertebrates found in Antarctica were land-living animals: therefore their presence on the South Polar Continent would seem to indicate the contiguity of Antarctica, Africa, and India in Early Triassic times.

  5. Semiconducting organic-inorganic nanocomposites by intimately tethering conjugated polymers to inorganic tetrapods

    NASA Astrophysics Data System (ADS)

    Jung, Jaehan; Yoon, Young Jun; Lin, Zhiqun

    2016-04-01

    Semiconducting organic-inorganic nanocomposites were judiciously crafted by placing conjugated polymers in intimate contact with inorganic tetrapods via click reaction. CdSe tetrapods were first synthesized by inducing elongated arms from CdSe zincblende seeds through seed-mediated growth. The subsequent effective inorganic ligand treatment, followed by reacting with short bifunctional ligands, yielded azide-functionalized CdSe tetrapods (i.e., CdSe-N3). Finally, the ethynyl-terminated conjugated polymer poly(3-hexylthiophene) (i.e., P3HT-&z.tbd;) was tethered to CdSe-N3 tetrapods via a catalyst-free alkyne-azide cycloaddition, forming intimate semiconducting P3HT-CdSe tetrapod nanocomposites. Intriguingly, the intimate contact between P3HT and CdSe tetrapod was found to not only render the effective dispersion of CdSe tetrapods in the P3HT matrix, but also facilitate the efficient electronic interaction between these two semiconducting constituents. The successful anchoring of P3HT chains onto CdSe tetrapods was substantiated through Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy measurements. Moreover, the absorption and photoluminescence studies further corroborated the intimate tethering between P3HT and CdSe tetrapods. The effect of the type of bifunctional ligands (i.e., aryl vs. aliphatic ligands) and the size of tetrapods on the device performance of hybrid organic-inorganic solar cells was also scrutinized. Interestingly, P3HT-CdSe tetrapod nanocomposites produced via the use of an aryl bifunctional ligand (i.e., 4-azidobenzoic acid) exhibited an improved photovoltaic performance compared to that synthesized with their aliphatic ligand counterpart (i.e., 5-bromovaleric acid). Clearly, the optimal size of CdSe tetrapods ensuring the effective charge transport in conjunction with the good dispersion of CdSe tetrapods rendered an improved device performance. We envision that the click-reaction strategy enabled by

  6. Comparative analysis of the skeletal changes in tetrapods after brief influence of microgravity.

    PubMed

    Nikitin, V B; Gulimova, V I; Ilyin, E A; Asadchikov, V E; Buzmakov, A V; Okshtein, I L; Saveliev, S V

    2007-07-01

    Experiments involving lower tetrapods demonstrate that the degree of skeletal demineralization in spaceflights is related to the type of environmental behaviour of the animal. Probably the sensing of support reaction decreases the negative effect of spaceflight upon the bone tissue.

  7. Spiracular air breathing in polypterid fishes and its implications for aerial respiration in stem tetrapods

    NASA Astrophysics Data System (ADS)

    Graham, Jeffrey B.; Wegner, Nicholas C.; Miller, Lauren A.; Jew, Corey J.; Lai, N. Chin; Berquist, Rachel M.; Frank, Lawrence R.; Long, John A.

    2014-01-01

    The polypterids (bichirs and ropefish) are extant basal actinopterygian (ray-finned) fishes that breathe air and share similarities with extant lobe-finned sarcopterygians (lungfishes and tetrapods) in lung structure. They are also similar to some fossil sarcopterygians, including stem tetrapods, in having large paired openings (spiracles) on top of their head. The role of spiracles in polypterid respiration has been unclear, with early reports suggesting that polypterids could inhale air through the spiracles, while later reports have largely dismissed such observations. Here we resolve the 100-year-old mystery by presenting structural, behavioural, video, kinematic and pressure data that show spiracle-mediated aspiration accounts for up to 93% of all air breaths in four species of Polypterus. Similarity in the size and position of polypterid spiracles with those of some stem tetrapods suggests that spiracular air breathing may have been an important respiratory strategy during the fish-tetrapod transition from water to land.

  8. Spiracular air breathing in polypterid fishes and its implications for aerial respiration in stem tetrapods.

    PubMed

    Graham, Jeffrey B; Wegner, Nicholas C; Miller, Lauren A; Jew, Corey J; Lai, N Chin; Berquist, Rachel M; Frank, Lawrence R; Long, John A

    2014-01-01

    The polypterids (bichirs and ropefish) are extant basal actinopterygian (ray-finned) fishes that breathe air and share similarities with extant lobe-finned sarcopterygians (lungfishes and tetrapods) in lung structure. They are also similar to some fossil sarcopterygians, including stem tetrapods, in having large paired openings (spiracles) on top of their head. The role of spiracles in polypterid respiration has been unclear, with early reports suggesting that polypterids could inhale air through the spiracles, while later reports have largely dismissed such observations. Here we resolve the 100-year-old mystery by presenting structural, behavioural, video, kinematic and pressure data that show spiracle-mediated aspiration accounts for up to 93% of all air breaths in four species of Polypterus. Similarity in the size and position of polypterid spiracles with those of some stem tetrapods suggests that spiracular air breathing may have been an important respiratory strategy during the fish-tetrapod transition from water to land.

  9. Sequences, stratigraphy and scenarios: what can we say about the fossil record of the earliest tetrapods?

    PubMed

    Friedman, Matt; Brazeau, Martin D

    2011-02-07

    Past research on the emergence of digit-bearing tetrapods has led to the widely accepted premise that this important evolutionary event occurred during the Late Devonian. The discovery of convincing digit-bearing tetrapod trackways of early Middle Devonian age in Poland has upset this orthodoxy, indicating that current scenarios which link the timing of the origin of digited tetrapods to specific events in Earth history are likely to be in error. Inspired by this find, we examine the fossil record of early digit-bearing tetrapods and their closest fish-like relatives from a statistical standpoint. We find that the Polish trackways force a substantial reconsideration of the nature of the early tetrapod record when only body fossils are considered. However, the effect is less drastic (and often not statistically significant) when other reliably dated trackways that were previously considered anachronistic are taken into account. Using two approaches, we find that 95 per cent credible and confidence intervals for the origin of digit-bearing tetrapods extend into the Early Devonian and beyond, spanning late Emsian to mid Ludlow. For biologically realistic diversity models, estimated genus-level preservation rates for Devonian digited tetrapods and their relatives range from 0.025 to 0.073 per lineage-million years, an order of magnitude lower than species-level rates for groups typically considered to have dense records. Available fossils of early digited tetrapods and their immediate relatives are adequate for documenting large-scale patterns of character acquisition associated with the origin of terrestriality, but low preservation rates coupled with clear geographical and stratigraphic sampling biases caution against building scenarios for the origin of digits and terrestrialization tied to the provenance of particular specimens or faunas.

  10. Elbow joint adductor moment arm as an indicator of forelimb posture in extinct quadrupedal tetrapods

    PubMed Central

    Fujiwara, Shin-ichi; Hutchinson, John R.

    2012-01-01

    Forelimb posture has been a controversial aspect of reconstructing locomotor behaviour in extinct quadrupedal tetrapods. This is partly owing to the qualitative and subjective nature of typical methods, which focus on bony articulations that are often ambiguous and unvalidated postural indicators. Here we outline a new, quantitatively based forelimb posture index that is applicable to a majority of extant tetrapods. By determining the degree of elbow joint adduction/abduction mobility in several tetrapods, the carpal flexor muscles were determined to also play a role as elbow adductors. Such adduction may play a major role during the stance phase in sprawling postures. This role is different from those of upright/sagittal and sloth-like creeping postures, which, respectively, depend more on elbow extensors and flexors. Our measurements of elbow muscle moment arms in 318 extant tetrapod skeletons (Lissamphibia, Synapsida and Reptilia: 33 major clades and 263 genera) revealed that sprawling, sagittal and creeping tetrapods, respectively, emphasize elbow adductor, extensor and flexor muscles. Furthermore, scansorial and non-scansorial taxa, respectively, emphasize flexors and extensors. Thus, forelimb postures of extinct tetrapods can be qualitatively classified based on our quantitative index. Using this method, we find that Triceratops (Ceratopsidae), Anhanguera (Pterosauria) and desmostylian mammals are categorized as upright/sagittally locomoting taxa. PMID:22357261

  11. Structural and interfacial defects in c-axis oriented LiNbO3 thin films grown by pulsed laser deposition on Si using Al : ZnO conducting layer

    NASA Astrophysics Data System (ADS)

    Shandilya, Swati; Tomar, Monika; Sreenivas, K.; Gupta, Vinay

    2009-05-01

    Highly c-axis oriented LiNbO3 films are deposited using pulsed laser deposition on a silicon substrate using a transparent conducting Al doped ZnO layer. X-ray diffraction and Raman spectroscopic analysis show the fabrication of single phase and oriented LiNbO3 films under the optimized deposition condition. An extra peak at 905 cm-1 was observed in the Raman spectra of LiNbO3 film deposited at higher substrate temperature and higher oxygen pressure, and attributed to the presence of niobium antisite defects in the lattice. Dielectric constant and ac conductivity of oriented LiNbO3 films deposited under the static and rotating substrate modes have been studied. Films deposited under the rotating substrate mode exhibit dielectric properties close to the LiNbO3 single crystal. The cause of deviation in the dielectric properties of the film deposited under the static substrate mode, in comparison with the bulk, are discussed in the light of the possible formation of an interdiffusion layer at the interface of the LiNbO3 film and the Al : ZnO layer.

  12. Effect of aging on ZnO and nitrogen doped P-Type ZnO

    NASA Astrophysics Data System (ADS)

    Majumdar, Sayanee; Bhunia, S.

    2012-06-01

    The withholding of p-type conductivity in as-prepared and 3% nitrogen (N) doped zinc oxide (ZnO) even after 2 months of preparation was systematically studied. The films were grown on glass substrates by pulsed laser deposition (PLD) at 350 °C under different conditions, viz. under vacuum and at oxygen (O) ambience using 2000 laser pulses. In O ambience for as-prepared ZnO the carrier concentration reduces and mobility increases with increasing number of laser shots. The resistivity of as-prepared and 3% N-doped ZnO is found to increase with reduction in hole concentration after 60 days of aging while maintaining its p-type conductivity irrespective of growth condition. AFM and electrical properties showed aging effect on the doped and undoped samples. For as-prepared ZnO, with time, O migration makes the film high resistive by reducing free electron concentrations. But for N-doped p-type ZnO, O-migration, metastable N and hydrogen atom present in the source induced instability in structure makes it less conducting p-type.

  13. Lasers.

    ERIC Educational Resources Information Center

    Schewe, Phillip F.

    1981-01-01

    Examines the nature of laser light. Topics include: (1) production and characteristics of laser light; (2) nine types of lasers; (3) five laser techniques including holography; (4) laser spectroscopy; and (5) laser fusion and other applications. (SK)

  14. Vertebral Development in Paleozoic and Mesozoic Tetrapods Revealed by Paleohistological Data

    PubMed Central

    Danto, Marylène; Witzmann, Florian; Fröbisch, Nadia B.

    2016-01-01

    Basal tetrapods display a wide spectrum of vertebral centrum morphologies that can be used to distinguish different tetrapod groups. The vertebral types range from multipartite centra in stem-tetrapods, temnospondyls, and seymouriamorphs up to monospondylous centra in lepospondyls and have been drawn upon for reconstructing major evolutionary trends in tetrapods that are now considered textbook knowledge. Two modes of vertebral formation have been postulated: the multipartite vertebrae formed first as cartilaginous elements with subsequent ossification. The monospondylous centrum, in contrast, was formed by direct ossification without a cartilaginous precursor. This study describes centrum morphogenesis in basal tetrapods for the first time, based on bone histology. Our results show that the intercentra of the investigated stem-tetrapods consist of a small band of periosteal bone and a dense network of endochondral bone. In stereospondyl temnospondyls, high amounts of calcified cartilage are preserved in the endochondral trabeculae. Notably, the periosteal region is thickened and highly vascularized in the plagiosaurid stereospondyls. Among “microsaur” lepospondyls, the thickened periosteal region is composed of compact bone and the notochordal canal is surrounded by large cell lacunae. In nectridean lepospondyls, the periosteal region has a spongy structure with large intertrabecular spaces, whereas the endochondral region has a highly cancellous structure. Our observations indicate that regardless of whether multipartite or monospondylous, the centra of basal tetrapods display first endochondral and subsequently periosteal ossification. A high interspecific variability is observed in growth rate, organization, and initiation of periosteal ossification. Moreover, vertebral development and structure reflect different lifestyles. The bottom-dwelling Plagiosauridae increase their skeletal mass by hyperplasy of the periosteal region. In nectrideans, the skeletal

  15. Middle-Upper Triassic and Middle Jurassic tetrapod track assemblages of southern Tunisia, Sahara Platform

    NASA Astrophysics Data System (ADS)

    Niedźwiedzki, Grzegorz; Soussi, Mohamed; Boukhalfa, Kamel; Gierliński, Gerard D.

    2017-05-01

    Three tetrapod track assemblages from the early-middle Mesozoic of southern Tunisia are reported. The strata exposed at the Tejra 2 clay-pit near the Medenine and Rehach site, located in the vicinity of Kirchaou, contain the first tetrapod tracks found in the Triassic of Tunisia. The Middle Jurassic (early Aalenian) dinosaur tracks are reported from the Mestaoua plain near Tataouine. In the Middle Triassic outcrop of the Tejra 2 clay-pit, tridactyl tracks of small and medium-sized dinosauromorphs, were discovered. These tracks represent the oldest evidence of dinosaur-lineage elements in the Triassic deposits of Tunisia. Similar tracks have been described from the Middle Triassic of Argentina, France and Morocco. An isolated set of the manus and pes of a quadrupedal tetrapod discovered in Late Triassic Rehach tracksite is referred to a therapsid tracemaker. The Middle Jurassic deposits of the Mestaoua plain reveal small and large tridactyl theropod dinosaur tracks (Theropoda track indet. A-C). Based on comparison with the abundant record of Triassic tetrapod ichnofossils from Europe and North America, the ichnofauna described here indicates the presence of a therapsid-dinosauromorph ichnoassociation (without typical Chirotheriidae tracks) in the Middle and Late Triassic, which sheds light on the dispersal of the Middle-Upper Triassic tetrapod ichnofaunas in this part of Gondwana. The reported Middle Jurassic ichnofauna show close similarities to dinosaur track assemblages from the Lower and Middle Jurassic of northwestern Africa, North America, Europe and also southeastern Asia. Sedimentological and lithostratigraphic data of each new tracksite have been defined on published data and new observations. Taken together, these discoveries present a tantalizing window into the evolutionary history of tetrapods from the Triassic and Jurassic of southern Tunisia. Given the limited early Mesozoic tetrapod record from the region, these discoveries are of both temporal and

  16. Development and evaluation of tetrapod-shaped granular artificial bones.

    PubMed

    Choi, Sungjin; Liu, I-li; Yamamoto, Kenichi; Igawa, Kazuyo; Mochizuki, Manabu; Sakai, Takamasa; Echigo, Ryosuke; Honnami, Muneki; Suzuki, Shigeki; Chung, Ung-il; Sasaki, Nobuo

    2012-07-01

    We have developed a novel form of granular artificial bone "Tetrabones" with a homogeneous tetrapod shape and uniform size. Tetrabones are four armed structures that accumulate to form the intergranular pores that allow invasion of cells and blood vessels. In this study we evaluated the physicochemical characteristics of Tetrabones in vitro, and compared their biological and biomechanical properties in vivo to those of conventional β-tricalcium phosphate (β-TCP) granule artificial bone. Both the rupture strength and elastic modulus of Tetrabone particles were higher than those of β-TCP granules in vitro. The connectivity of intergranular pores 100, 300, and 400 μm in size were higher in Tetrabones than in the β-TCP granules. Tetrabones showed similar osteoconductivity and biomechanical stiffness to β-TCP at 2 months after implantation in an in vivo study of canine bone defects. These results suggest that Tetrabones may be a good bone graft material in bone reconstruction. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  17. The last diadectomorph sheds light on Late Palaeozoic tetrapod biogeography.

    PubMed

    Liu, Jun; Bever, G S

    2015-05-01

    Diadectomorpha is a clade of Late Palaeozoic vertebrates widely recognized as the sister group of crown-group Amniota and the first tetrapod lineage to evolve high-fibre herbivory. Despite their evolutionary importance, diadectomorphs are restricted stratigraphically and geographically, with all records being from the Upper Carboniferous and Lower Permian of North America and Germany. We describe a new diadectomorph, Alveusdectes fenestralis, based on a partial skull from the Upper Permian of China. The new species exhibits the derived mechanism for herbivory and is recovered phylogenetically as a deeply nested diadectid. Approximately 16 Myr younger than any other diadectomorph, Alveusdectes is the product of at least a 46 Myr ghost lineage. How much of this time was probably spent in Russia and/or central Asia will remain unclear until a specimen is described that subdivides this cryptic history, but the lineage assuredly crossed this region before entering the relatively isolated continent of North China. The discovery of Alveusdectes raises important questions regarding diadectomorph extinction dynamics including what, if any, ecological factors limited the diversity of this group in eastern Pangea. It also suggests that increased sampling in Asia will likely significantly affect our views of clade and faunal insularity leading up to the Permo-Triassic extinction. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  18. The last diadectomorph sheds light on Late Palaeozoic tetrapod biogeography

    PubMed Central

    Liu, Jun; Bever, G. S.

    2015-01-01

    Diadectomorpha is a clade of Late Palaeozoic vertebrates widely recognized as the sister group of crown-group Amniota and the first tetrapod lineage to evolve high-fibre herbivory. Despite their evolutionary importance, diadectomorphs are restricted stratigraphically and geographically, with all records being from the Upper Carboniferous and Lower Permian of North America and Germany. We describe a new diadectomorph, Alveusdectes fenestralis, based on a partial skull from the Upper Permian of China. The new species exhibits the derived mechanism for herbivory and is recovered phylogenetically as a deeply nested diadectid. Approximately 16 Myr younger than any other diadectomorph, Alveusdectes is the product of at least a 46 Myr ghost lineage. How much of this time was probably spent in Russia and/or central Asia will remain unclear until a specimen is described that subdivides this cryptic history, but the lineage assuredly crossed this region before entering the relatively isolated continent of North China. The discovery of Alveusdectes raises important questions regarding diadectomorph extinction dynamics including what, if any, ecological factors limited the diversity of this group in eastern Pangea. It also suggests that increased sampling in Asia will likely significantly affect our views of clade and faunal insularity leading up to the Permo-Triassic extinction. PMID:25948572

  19. Composition and similarity of global anomodont-bearing tetrapod faunas

    NASA Astrophysics Data System (ADS)

    Fröbisch, Jörg

    2009-08-01

    Anomodont synapsids represent the dominant herbivores of Permian and Triassic terrestrial vertebrate ecosystems. Their taxonomic diversity and morphological disparity in combination with their cosmopolitan distribution makes them an ideal study object for macroevolutionary patterns across the most devastating extinction event in earth history. This study provides a thorough review of anomodont-bearing tetrapod faunas to form the basis for a faunal similarity analysis and future studies of anomodont diversity. The stratigraphic correlation and composition of all known anomodont assemblages is revisited, including a discussion of the validity of the globally distributed anomodont species. The similarity analysis of anomodont faunas is performed on the basis of presence-absence data of anomodont taxa, using explorative methods such as cluster analysis (UPGMA) and non-metric multidimensional scaling (NMDS). The recovered faunal groupings indicate a common biostratigraphic age and furthermore reflect biogeographic patterns. Even though endemism and faunal provinciality was a constant element in anomodont faunas of the Permian and Triassic, the available evidence indicates that the end-Permian extinction resulted in a distinct uniformity that was unique to Early Triassic anomodont faunas. This is in particular characterized by the global distribution and overwhelming abundance of the disaster taxon Lystrosaurus. In contrast, cosmopolitan anomodonts also existed in the Late Permian (e.g., Diictodon) and Middle Triassic (e.g., Shansiodon), but those taxa coexisted with endemic faunal elements rather than dominated the fauna as Lystrosaurus did.

  20. Three-dimensional Bragg coherent diffraction imaging of an extended ZnO crystal.

    PubMed

    Huang, Xiaojing; Harder, Ross; Leake, Steven; Clark, Jesse; Robinson, Ian

    2012-08-01

    A complex three-dimensional quantitative image of an extended zinc oxide (ZnO) crystal has been obtained using Bragg coherent diffraction imaging integrated with ptychography. By scanning a 2.5 µm-long arm of a ZnO tetrapod across a 1.3 µm X-ray beam with fine step sizes while measuring a three-dimensional diffraction pattern at each scan spot, the three-dimensional electron density and projected displacement field of the entire crystal were recovered. The simultaneously reconstructed complex wavefront of the illumination combined with its coherence properties determined by a partial coherence analysis implemented in the reconstruction process provide a comprehensive characterization of the incident X-ray beam.

  1. Sea level regulated tetrapod diversity dynamics through the Jurassic/Cretaceous interval

    PubMed Central

    Tennant, Jonathan P.; Mannion, Philip D.; Upchurch, Paul

    2016-01-01

    Reconstructing deep time trends in biodiversity remains a central goal for palaeobiologists, but our understanding of the magnitude and tempo of extinctions and radiations is confounded by uneven sampling of the fossil record. In particular, the Jurassic/Cretaceous (J/K) boundary, 145 million years ago, remains poorly understood, despite an apparent minor extinction and the radiation of numerous important clades. Here we apply a rigorous subsampling approach to a comprehensive tetrapod fossil occurrence data set to assess the group's macroevolutionary dynamics through the J/K transition. Although much of the signal is exclusively European, almost every higher tetrapod group was affected by a substantial decline across the boundary, culminating in the extinction of several important clades and the ecological release and radiation of numerous modern tetrapod groups. Variation in eustatic sea level was the primary driver of these patterns, controlling biodiversity through availability of shallow marine environments and via allopatric speciation on land. PMID:27587285

  2. Characterization of thermal destruction behavior of hybrid composites based on polyoxymethylene, ethylene-octene copolymer impact modifier and ZnO nanofiller

    SciT

    Meri, Remo Merijs; Zicans, Janis; Abele, Agnese

    Hybrid polymer nanocomposites, composed of polyoxymethylene (POM), ethylene octene copolymer (EOC) and plasma synthesized tetrapod shaped zinc oxide (ZnO), were prepared by using melt compounding. The content of EOC in the POM based composites was varied between 10 and 50 mass %, while the content of ZnO was constant (2 mass %). Thermal behaviour of POM based systems was studied by using thermogravimetric analysis coupled with Fourier transform infrared spectroscopy. The influence of the elastomer content and/or ZnO addition on the thermal stability of POM based systems was evaluated. The influence of the α-octene content in the elastomer on themore » thermal decomposition behaviour of POM and its nanocomposites with ZnO was also evaluated. Results of thermogravimetric analysis showed that, by rising either the elastomer or ZnO content, thermal stability of the investigated POM composites was increased. The modifying effect of EOC17 in respect of thermal resistance was somewhat larger than that of EOC38 because of the smaller amount of tertiary carbon atoms in the macromolecular structure of the former elastomer. Improved thermal resistance of ZnO containing POM based composites was because of impermeable structure the inorganic nanofiller allowing decrease gas exchange rate and facilitating non-combustible gases, such as CO{sub 2}, stay in the zone of burning. Addition of ZnO have a potential to influence structure of the polymer blend matrix itself by improving its barrier characteristics.« less

  3. Tetrapod distribution and temperature rise during the Permian–Triassic mass extinction

    PubMed Central

    2018-01-01

    The Permian–Triassic mass extinction (PTME) had an enormous impact on life in three ways: by substantially reducing diversity, by reshuffling the composition of ecosystems and by expelling life from the tropics following episodes of intense global warming. But was there really an ‘equatorial tetrapod gap', and how long did it last? Here, we consider both skeletal and footprint data, and find a more complex pattern: (i) tetrapods were distributed both at high and low latitudes during this time; (ii) there was a clear geographic disjunction through the PTME, with tetrapod distribution shifting 10–15° poleward; and (iii) there was a rapid expansion phase across the whole of Pangea following the PTME. These changes are consistent with a model of generalized migration of tetrapods to higher latitudinal, cooler regions, to escape from the superhot equatorial climate in the earliest Triassic, but the effect was shorter in time scale, and not as pronounced as had been proposed. In the recovery phase following the PTME, this episode of forced range expansion also appears to have promoted the emergence and radiation of entirely new groups, such as the archosaurs, including the dinosaurs. PMID:29321300

  4. Tetrapod distribution and temperature rise during the Permian-Triassic mass extinction.

    PubMed

    Bernardi, Massimo; Petti, Fabio Massimo; Benton, Michael J

    2018-01-10

    The Permian-Triassic mass extinction (PTME) had an enormous impact on life in three ways: by substantially reducing diversity, by reshuffling the composition of ecosystems and by expelling life from the tropics following episodes of intense global warming. But was there really an 'equatorial tetrapod gap', and how long did it last? Here, we consider both skeletal and footprint data, and find a more complex pattern: (i) tetrapods were distributed both at high and low latitudes during this time; (ii) there was a clear geographic disjunction through the PTME, with tetrapod distribution shifting 10-15° poleward; and (iii) there was a rapid expansion phase across the whole of Pangea following the PTME. These changes are consistent with a model of generalized migration of tetrapods to higher latitudinal, cooler regions, to escape from the superhot equatorial climate in the earliest Triassic, but the effect was shorter in time scale, and not as pronounced as had been proposed. In the recovery phase following the PTME, this episode of forced range expansion also appears to have promoted the emergence and radiation of entirely new groups, such as the archosaurs, including the dinosaurs. © 2018 The Authors.

  5. Early tetrapod evolution and the progressive integration of Permo-Carboniferous terrestrial ecosystems

    SciT

    Beerbower, J.R.; Olson, E.C.; Hotton, N. III

    1992-01-01

    Variation among Permo-Carboniferous tetrapod assemblages demonstrates major transformations in pathways and rates of energy and nutrient transfer, in integration of terrestrial ecosystems and in predominant ecologic modes. Early Carboniferous pathways were through plant detritus to aquatic and terrestrial detritivores and thence to arthropod and vertebrate meso-and macro-predators. Transfer rates (and efficiency) were low as was ecosystem integration; the principal ecologic mode was conservation. Late Carboniferous and Early Permian assemblages demonstrate an expansion in herbivory, primarily in utilization of low-fiber plant tissue by insects. But transfer rates, efficiency and integration were still limited because the larger portion of plant biomass, high-fibermore » tissues, still went into detrital pathways; high-fiber'' herbivores, i.e., tetrapods, were neither abundant or diverse, reflecting limited resources, intense predation and limited capabilities for processing fiber-rich food. The abundance and diversity of tetrapod herbivores in upper Permian assemblages suggests a considerable transfer of energy from high-fiber tissues through these animals to tetrapod predators and thus higher transfer rates and efficiencies. It also brought a shift in ecological mode toward acquisition and regulation and tightened ecosystem integration.« less

  6. Efficient color-tunable multiexcitonic dual wavelength emission from Type II semiconductor tetrapods.

    PubMed

    Wu, Wen-Ya; Li, Mingjie; Lian, Jie; Wu, Xiangyang; Yeow, Edwin K L; Jhon, Mark H; Chan, Yinthai

    2014-09-23

    We synthesized colloidal InP/ZnS seeded CdS tetrapods by harnessing the structural stability of the InP/ZnS seed nanocrystals at the high reaction temperatures needed to grow the CdS arms. Because of an unexpected Type II band alignment at the interface of the InP/ZnS core and CdS arms that enhanced the occurrence of radiative excitonic recombination in CdS, these tetrapods were found to be capable of exhibiting highly efficient multiexcitonic dual wavelength emission of equal intensity at spectrally distinct wavelengths of ∼485 and ∼675 nm. Additionally, the Type II InP/ZnS seeded CdS tetrapods displayed a wider range of pump-dependent emission color-tunability (from red to white to blue) within the context of a CIE 1931 chromaticity diagram and possessed higher photostability due to suppressed multiexcitonic Auger recombination when compared to conventional Type I CdSe seeded CdS tetrapods. By employing time-resolved spectroscopy measurements, we were able to attribute the wide emission color-tunability to the large valence band offset between InP and CdS. This work highlights the importance of band alignment in the synthetic design of semiconductor nanoheterostructures, which can exhibit color-tunable multiwavelength emission with high efficiency and photostability.

  7. The impact of coastal defence structures (tetrapods) on decapod crustaceans in the southern North Sea.

    PubMed

    Wehkamp, Stephanie; Fischer, Philipp

    2013-12-01

    Although the use of coastal defence structures is expected to increase, little is known about the ecological impact of such structures on the natural environment. In particular, the temporal and spatial patterns of communities in association with artificial substrate are still poorly understood. This study examined possible effects of experimental tetrapod fields on the decapod crustacean community in a subtidal hard-bottom area in the southern North Sea. We performed in situ studies in the fields and along transects oriented away from the tetrapod fields. Species composition and abundances were assessed before and after the introduction of the artificial material. The study revealed a significant decrease of smaller, less vagile species (Pisidia longicornis, Pilumnus hirtellus, Galathea squamifera) over the entire study area in the years following the tetrapod introduction. For 2 species, Hyas araneus and Homarus gammarus, the tetrapods appeared to be highly attractive as habitat and shelter because their abundance increased over time. No distinct spatial or temporal effects were observed for mobile predatory crabs, such as Cancer pagurus and Liocarcinus spp. The results of the study demonstrate that possible effects of artificial structures on macro-invertebrates in temperate hard-bottom areas are highly species-specific and depend on the size, lifestyle and ecological requirements of the species. This work highlights the importance of long-term studies. Our findings clearly indicate that more time is needed to distinguish between natural and anthropogenic influences on species distributions. Copyright © 2013 Elsevier Ltd. All rights reserved.

  8. Extreme Modification of the Tetrapod Forelimb in a Triassic Diapsid Reptile.

    PubMed

    Pritchard, Adam C; Turner, Alan H; Irmis, Randall B; Nesbitt, Sterling J; Smith, Nathan D

    2016-10-24

    The tetrapod forelimb is one of the most versatile structures in vertebrate evolution, having been co-opted for an enormous array of functions. However, the structural relationships between the bones of the forelimb have remained largely unchanged throughout the 375 million year history of Tetrapoda, with a radius and ulna made up of elongate, paralleling shafts contacting a series of shorter carpal bones. These features are consistent across nearly all known tetrapods, suggesting that the morphospace encompassed by these taxa is limited by some sort of constraint(s). Here, we report on a series of three-dimensionally preserved fossils of the small-bodied (<1 m) Late Triassic diapsid reptile Drepanosaurus, from the Chinle Formation of New Mexico, USA, which dramatically diverge from this pattern. Along with the crushed type specimen from Italy, these specimens have a flattened, crescent-shaped ulna with a long axis perpendicular to that of the radius and hyperelongate, shaft-like carpal bones contacting the ulna that are proximodistally longer than the radius. The second digit supports a massive, hooked claw. This condition has similarities to living "hook-and-pull" digging mammals and demonstrates that specialized, modern ecological roles had developed during the Triassic Period, over 200 million years ago. The forelimb bones in Drepanosaurus represent previously unknown morphologies for a tetrapod and, thus, a dramatic expansion of known tetrapod forelimb morphospace. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Tetrapod localities from the Triassic of the SE of European Russia

    NASA Astrophysics Data System (ADS)

    Tverdokhlebov, Valentin P.; Tverdokhlebova, Galina I.; Surkov, Mikhail V.; Benton, Michael J.

    2003-01-01

    Fossil tetrapods (amphibians and reptiles) have been discovered at 206 localities in the Lower and Middle Triassic of the southern Urals area of European Russia. The first sites were found in the 1940s, and subsequent surveys, from the 1960s to the present day, have revealed many more. Broad-scale stratigraphic schemes have been published, but full documentation of the rich tetrapod faunas has not been presented before. The area of richest deposits covers some 900,000 km 2 of territory between Samara on the River Volga in the NW, and Orenburg and Sakmara in the SW. Continental sedimentary deposits, consisting of mudstones, siltstones, sandstones, and conglomerates deposited by rivers flowing off the Ural Mountain chain, span much of the Lower and Middle Triassic (Induan, Olenekian, Anisian, Ladinian). The succession is divided into seven successive svitas, or assemblages: Kopanskaya (Induan), Staritskaya, Kzylsaiskaya, Gostevskaya, and Petropavlovskaya (all Olenekian), Donguz (Anisian), and Bukobay (Ladinian). This succession, comprising up to 3.5 km of fluvial and lacustrine sediments, documents major climatic changes. At the beginning of the Early Triassic, arid-zone facies were widely developed, aeolian, piedmont and proluvium. These were replaced by fluvial facies, with some features indicating aridity. At the end of the Middle Triassic, deltaic and lacustrine-marsh formations were dominant, indicating more humid conditions. The succession of Early to Mid Triassic tetrapod faunas documents the recovery of life after the end-Permian mass extinction. The earliest faunas consist only of small, aquatic tetrapods, in low-diversity, low-abundance assemblages. Climbing the succession through the Early Triassic, more terrestrially adapted tetrapods appear, and larger herbivorous and carnivorous reptiles come to dominate in the Mid Triassic as ecosystems were rebuilt.

  10. Near-Stasis in the Long-Term Diversification of Mesozoic Tetrapods

    PubMed Central

    Benson, Roger B. J.; Butler, Richard J.; Alroy, John; Mannion, Philip D.; Carrano, Matthew T.; Lloyd, Graeme T.

    2016-01-01

    How did evolution generate the extraordinary diversity of vertebrates on land? Zero species are known prior to ~380 million years ago, and more than 30,000 are present today. An expansionist model suggests this was achieved by large and unbounded increases, leading to substantially greater diversity in the present than at any time in the geological past. This model contrasts starkly with empirical support for constrained diversification in marine animals, suggesting different macroevolutionary processes on land and in the sea. We quantify patterns of vertebrate standing diversity on land during the Mesozoic–early Paleogene interval, applying sample-standardization to a global fossil dataset containing 27,260 occurrences of 4,898 non-marine tetrapod species. Our results show a highly stable pattern of Mesozoic tetrapod diversity at regional and local levels, underpinned by a weakly positive, but near-zero, long-term net diversification rate over 190 million years. Species diversity of non-flying terrestrial tetrapods less than doubled over this interval, despite the origins of exceptionally diverse extant groups within mammals, squamates, amphibians, and dinosaurs. Therefore, although speciose groups of modern tetrapods have Mesozoic origins, rates of Mesozoic diversification inferred from the fossil record are slow compared to those inferred from molecular phylogenies. If high speciation rates did occur in the Mesozoic, then they seem to have been balanced by extinctions among older clades. An apparent 4-fold expansion of species richness after the Cretaceous/Paleogene (K/Pg) boundary deserves further examination in light of potential taxonomic biases, but is consistent with the hypothesis that global environmental disturbances such as mass extinction events can rapidly adjust limits to diversity by restructuring ecosystems, and suggests that the gradualistic evolutionary diversification of tetrapods was punctuated by brief but dramatic episodes of radiation

  11. Study of ZnO nanoparticles: Antibacterial property and light depolarization property using light scattering tool

    NASA Astrophysics Data System (ADS)

    Roy, Sanchita; Barua, Nilakshi; Buragohain, Alak K.; Ahmed, Gazi A.

    2013-03-01

    Investigations on treatment of ZnO nanoparticles on Staphylococcus aureus MTCC 737 strain was essentially made by using standard biochemical method. The anti-microbial assay against S. aureus, and time kill assay revealed the anti-bacterial activity of ZnO nanoparticles. We have substantiated this property of ZnO nanoparticles and light depolarization property by using light scattering tool. Light scattering measurements were carried out for ZnO, S. aureus, and ZnO treated S. aureus as a function of scattering angle at 543.5 and 632.8 nm wavelengths. This was done in order to find the scattering profile of the consequent product after the action of ZnO nanoparticles on bacteria by means of light scattering tool. S. aureus treated with ZnO nanoparticles showed closer agreement of the scattering profiles at both the wavelengths, however, the scattering profiles of ZnO nanoparticles and untreated S. aureus significantly varied for the two different laser wavelengths. It was also observed that there was higher intensity of scattering from all S. aureus treated with ZnO particles compared to the untreated ones. In our work, we have studied ZnO nanoparticles and the possibility of observing its anti-bacterial activity by using light scattering tool.

  12. Unique visible-light-assisted field emission of tetrapod-shaped ZnO/reduced graphene-oxide core/coating nanocomposites

    PubMed Central

    Wu, Chaoxing; Kim, Tae Whan; Guo, Tailiang; Li, Fushan

    2016-01-01

    The electronic and the optoelectronic properties of graphene-based nanocomposites are controllable, making them promising for applications in diverse electronic devices. In this work, tetrapod-shaped zinc oxide (T-ZnO)/reduced graphene oxide (rGO) core/coating nanocomposites were synthesized by using a hydrothermal-assisted self-assemble method, and their optical, photoelectric, and field-emission properties were investigated. The ZnO, an ideal ultraviolet-light-sensitive semiconductor, was observed to have high sensitivity to visible light due to the rGO coating, and the mechanism of that sensitivity was investigated. We demonstrated for the first time that the field-emission properties of the T-ZnO/rGO core/coating nanocomposites could be dramatically enhanced under visible light by decreasing the turn-on field from 1.54 to 1.41 V/μm and by increasing the current density from 5 to 12 mA/cm2 at an electric field of 3.5 V/μm. The visible-light excitation induces an electron jump from oxygen vacancies on the surface of ZnO to the rGO layer, resulting in a decrease in the work function of the rGO and an increase in the emission current. Furthermore, a field-emission light-emitting diode with a self-enhanced effect was fabricated making full use of the photo-assisted field-emission process. PMID:27941822

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

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

    2016-01-01

    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. PMID:27071382

  15. Effect of Ag/Al co-doping method on optically p-type ZnO nanowires synthesized by hot-walled pulsed laser deposition

    PubMed Central

    2012-01-01

    Silver and aluminum-co-doped zinc oxide (SAZO) nanowires (NWs) of 1, 3, and 5 at.% were grown on sapphire substrates. Low-temperature photoluminescence (PL) was studied experimentally to investigate the p-type behavior observed by the exciton bound to a neutral acceptor (A0X). The A0X was not observed in the 1 at.% SAZO NWs by low-temperature PL because 1 at.% SAZO NWs do not have a Ag-O chemical bonding as confirmed by XPS measurement. The activation energies (Ea) of the A0X were calculated to be about 18.14 and 19.77 meV for 3 and 5 at.% SAZO NWs, respectively, which are lower than the activation energy of single Ag-doped NW which is about 25 meV. These results indicate that Ag/Al co-doping method is a good candidate to make optically p-type ZnO NWs. PMID:22647319

  16. Devonian Terrestrial Revolution: the palaeoenvironment of the oldest known tetrapod tracks, Zachełmie Quarry, Poland

    NASA Astrophysics Data System (ADS)

    Niedźwiedzki, G.

    2012-04-01

    Numerous trackways and isolated prints with digit impressions, which are similar to the foot anatomy of early tetrapods such as Ichthyostega, were found on the three dolomite bed-surfaces in the lower part of the Wojciechowice Formation exposed in the Zachełmie Quarry in the Holy Cross Mountains (south-central Poland), (Niedźwiedzki et al., 2010). The age of the tetrapod track-bearing strata is well-constrained, but the detailed sedimentology of the lower section with tetrapod ichnites is still under study. The Wojciechowice Formation represent one of the first carbonate stages of a transgressive succession that begins with Early Devonian continental to marginal marine clastics and culminates in the development of a Givetian coral-stromatoporoid carbonate platform. The tetrapod track-bearing complex is composed of grey to reddish, thin- to medium-bedded dolomitic shales and marly dolomite mudstones. These deposits from the tetrapod track-bearing horizon lack definitive marine body fossils, and may have formed in a marginal marine environment, e.g. around a coastal lagoon. Mudcracks, columnar peds, root traces, and microbially induced sedimentary structures were found in three distinct pedotypes of very weakly to weakly developed paleosols (Retallack, 2011). Conodonts of the costatus zone (mid-Eifelian) were found 20 m above the uppermost surface with tetrapod tracks in limestones of the upper Wojciechowice Formation, which contain also brachiopod and crinoidal debris. The overlying Kowala Formation is a marine coral limestone and dolostone. The parts of profile with tetrapod ichnites and invertebrate and conodont fossils contain also records of invertebrate traces. Seven ichnotaxa are distributed among four recognized ichnoassemblages. The recognized ichnocoenoses are typical for the shallow-marine (Cruziana ichnofacies) and land-water transitional (Skolithos/Psilonichnus ichnofacies) carbonate depositional environments. The ichnocoenoses are dominated by trace

  17. Synthesis of p-type ZnO films

    NASA Astrophysics Data System (ADS)

    Ryu, Y. R.; Zhu, S.; Look, D. C.; Wrobel, J. M.; Jeong, H. M.; White, H. W.

    2000-06-01

    p-Type ZnO obtained by arsenic (As) doping is reported for the first time. Arsenic-doped ZnO (ZnO : As) films have been deposited on (0 0 1)-GaAs substrates by pulsed laser ablation. The process of synthesizing p-type ZnO : As films was performed in an ambient gas of ultra-pure (99.999%) oxygen. The ambient gas pressure was 35 mTorr with the substrate temperature in the range 300-450°C. ZnO films grown at 400°C and 450°C are p-type and As is a good acceptor. The acceptor peak is located at 3.32 eV and its binding energy is about 100 meV. Acceptor concentrations of As atoms in ZnO films were in the range from high 10 17 to high 10 21 atoms/cm 3 as determined by secondary ion mass spectroscopy (SIMS) and Hall effect measurements.

  18. Cretaceous Small Scavengers: Feeding Traces in Tetrapod Bones from Patagonia, Argentina

    PubMed Central

    de Valais, Silvina; Apesteguía, Sebastián; Garrido, Alberto C.

    2012-01-01

    Ecological relationships among fossil vertebrate groups are interpreted based on evidence of modification features and paleopathologies on fossil bones. Here we describe an ichnological assemblage composed of trace fossils on reptile bones, mainly sphenodontids, crocodyliforms and maniraptoran theropods. They all come from La Buitrera, an early Late Cretaceous locality in the Candeleros Formation of northwestern Patagonia, Argentina. This locality is significant because of the abundance of small to medium-sized vertebrates. The abundant ichnological record includes traces on bones, most of them attributable to tetrapods. These latter traces include tooth marks that provde evidence of feeding activities made during the sub-aerial exposure of tetrapod carcasses. Other traces are attributable to arthropods or roots. The totality of evidence provides an uncommon insight into paleoecological aspects of a Late Cretaceous southern ecosystem. PMID:22253800

  19. Mucosal immunoglobulins at respiratory surfaces mark an ancient association that predates the emergence of tetrapods

    PubMed Central

    Xu, Zhen; Takizawa, Fumio; Parra, David; Gómez, Daniela; von Gersdorff Jørgensen, Louise; LaPatra, Scott E.; Sunyer, J. Oriol

    2016-01-01

    Gas-exchange structures are critical for acquiring oxygen, but they also represent portals for pathogen entry. Local mucosal immunoglobulin responses against pathogens in specialized respiratory organs have only been described in tetrapods. Since fish gills are considered a mucosal surface, we hypothesized that a dedicated mucosal immunoglobulin response would be generated within its mucosa on microbial exposure. Supporting this hypothesis, here we demonstrate that following pathogen exposure, IgT+ B cells proliferate and generate pathogen-specific IgT within the gills of fish, thus providing the first example of locally induced immunoglobulin in the mucosa of a cold-blooded species. Moreover, we demonstrate that gill microbiota is predominantly coated with IgT, thus providing previously unappreciated evidence that the microbiota present at a respiratory surface of a vertebrate is recognized by a mucosal immunoglobulin. Our findings indicate that respiratory surfaces and mucosal immunoglobulins are part of an ancient association that predates the emergence of tetrapods. PMID:26869478

  20. Honeybees Prefer to Steer on a Smooth Wall With Tetrapod Gaits

    PubMed Central

    Zhao, Jieliang; Zhu, Fei; Yan, Shaoze

    2018-01-01

    Abstract Insects are well equipped in walking on complex three-dimensional terrain, allowing them to overcome obstacles or catch prey. However, the gait transition for insects steering on a wall remains unexplored. Here, we find that honeybees adopted a tetrapod gait to change direction when climbing a wall. On the contrary to the common tripod gait, honeybees propel their body forward by synchronously stepping with both middle legs and then both front legs. This process ensures the angle of the central axis of the honeybee to be consistent with the crawling direction. Interestingly, when running in an alternating tripod gait, the central axis of honeybee sways around the center of mass under alternating tripod gait to maintain stability. Experimental results show that tripod, tetrapod, and random gaits result in the amazing consensus harmony on the climbing speed and gait stability, whether climbing on a smooth wall or walking on smooth ground. PMID:29722862

  1. Improving nanoparticle dispersion and charge transfer in cadmium telluride tetrapod and conjugated polymer blends.

    PubMed

    Monson, Todd C; Hollars, Christopher W; Orme, Christine A; Huser, Thomas

    2011-04-01

    The dispersion of CdTe tetrapods in a conducting polymer and the resulting charge transfer is studied using a combination of confocal fluorescence microscopy and atomic force microscopy (AFM). The results of this work show that both the tetrapod dispersion and charge transfer between the CdTe and conducting polymer (P3HT) are greatly enhanced by exchanging the ligands on the surface of the CdTe and by choosing proper solvent mixtures. The ability to experimentally probe the relationship between particle dispersion and charge transfer through the combination of AFM and fluorescence microscopy provides another avenue to assess the performance of polymer/semiconductor nanoparticle composites. © 2011 American Chemical Society

  2. Deep-time evolution of regeneration and preaxial polarity in tetrapod limb development.

    PubMed

    Fröbisch, Nadia B; Bickelmann, Constanze; Olori, Jennifer C; Witzmann, Florian

    2015-11-12

    Among extant tetrapods, salamanders are unique in showing a reversed preaxial polarity in patterning of the skeletal elements of the limbs, and in displaying the highest capacity for regeneration, including full limb and tail regeneration. These features are particularly striking as tetrapod limb development has otherwise been shown to be a highly conserved process. It remains elusive whether the capacity to regenerate limbs in salamanders is mechanistically and evolutionarily linked to the aberrant pattern of limb development; both are features classically regarded as unique to urodeles. New molecular data suggest that salamander-specific orphan genes play a central role in limb regeneration and may also be involved in the preaxial patterning during limb development. Here we show that preaxial polarity in limb development was present in various groups of temnospondyl amphibians of the Carboniferous and Permian periods, including the dissorophoids Apateon and Micromelerpeton, as well as the stereospondylomorph Sclerocephalus. Limb regeneration has also been reported in Micromelerpeton, demonstrating that both features were already present together in antecedents of modern salamanders 290 million years ago. Furthermore, data from lepospondyl 'microsaurs' on the amniote stem indicate that these taxa may have shown some capacity for limb regeneration and were capable of tail regeneration, including re-patterning of the caudal vertebral column that is otherwise only seen in salamander tail regeneration. The data from fossils suggest that salamander-like regeneration is an ancient feature of tetrapods that was subsequently lost at least once in the lineage leading to amniotes. Salamanders are the only modern tetrapods that retained regenerative capacities as well as preaxial polarity in limb development.

  3. REVIEW ARTICLE: Structure, microstructure and physical properties of ZnO based materials in various forms: bulk, thin film and nano

    NASA Astrophysics Data System (ADS)

    Singh, Shubra; Thiyagarajan, P.; Mohan Kant, K.; Anita, D.; Thirupathiah, S.; Rama, N.; Tiwari, Brajesh; Kottaisamy, M.; Ramachandra Rao, M. S.

    2007-10-01

    ZnO is a unique material that offers about a dozen different application possibilities. In spite of the fact that the ZnO lattice is amenable to metal ion doping (3d and 4f), the physics of doping in ZnO is not completely understood. This paper presents a review of previous research works on ZnO and also highlights results of our research activities on ZnO. The review pertains to the work on Al and Mg doping for conductivity and band gap tuning in ZnO followed by a report on transition metal (TM) ion doped ZnO. This review also highlights the work on the transport and optical studies of TM ion doped ZnO, nanostructured growth (ZnO polycrystalline and thin films) by different methods and the formation of unique nano- and microstructures obtained by pulsed laser deposition and chemical methods. This is followed by results on ZnO encapsulated Fe3O4 nanoparticles that show promising trends suitable for various applications. We have also reviewed the non-linear characteristic studies of ZnO based heterostructures followed by an analysis on the work carried out on ZnO based phosphors, which include mainly the nanocrystalline ZnO encapsulated SiO2, a new class of phosphor that is suitable for white light emission.

  4. Lunge feeding in early marine reptiles and fast evolution of marine tetrapod feeding guilds.

    PubMed

    Motani, Ryosuke; Chen, Xiao-hong; Jiang, Da-yong; Cheng, Long; Tintori, Andrea; Rieppel, Olivier

    2015-03-10

    Traditional wisdom holds that biotic recovery from the end-Permian extinction was slow and gradual, and was not complete until the Middle Triassic. Here, we report that the evolution of marine predator feeding guilds, and their trophic structure, proceeded faster. Marine reptile lineages with unique feeding adaptations emerged during the Early Triassic (about 248 million years ago), including the enigmatic Hupehsuchus that possessed an unusually slender mandible. A new specimen of this genus reveals a well-preserved palate and mandible, which suggest that it was a rare lunge feeder as also occurs in rorqual whales and pelicans. The diversity of feeding strategies among Triassic marine tetrapods reached their peak in the Early Triassic, soon after their first appearance in the fossil record. The diet of these early marine tetrapods most likely included soft-bodied animals that are not preserved as fossils. Early marine tetrapods most likely introduced a new trophic mechanism to redistribute nutrients to the top 10 m of the sea, where the primary productivity is highest. Therefore, a simple recovery to a Permian-like trophic structure does not explain the biotic changes seen after the Early Triassic.

  5. Tetrapod tracks in Permo–Triassic eolian beds of southern Brazil (Paraná Basin)

    PubMed Central

    Dentzien-Dias, Paula; Lucas, Spencer G.; Schultz, Cesar L.

    2018-01-01

    Tetrapod tracks in eolianites are widespread in the fossil record since the late Paleozoic. Among these ichnofaunas, the ichnogenus Chelichnus is the most representative of the Permian tetrapod ichnological record of eolian deposits of Europe, North America and South America, where the Chelichnus Ichnofacies often occurs. In this contribution, we describe five sets of tracks (one of which is preserved in cross-section), representing the first occurrence of Dicynodontipus and Chelichnus in the “Pirambóia Formation” of southern Brazil. This unit represents a humid desert in southwestern Pangea and its lower and upper contacts lead us to consider its age as Lopingian–Induan. The five sets of tracks studied were compared with several ichnotaxa and body fossils with appendicular elements preserved, allowing us to attribute these tracks to dicynodonts and other indeterminate therapsids. Even though the “Pirambóia Formation” track record is sparse and sub-optimally preserved, it is an important key to better understand the occupation of arid environments by tetrapods across the Permo–Triassic boundary. PMID:29796341

  6. Tetrapod tracks in Permo-Triassic eolian beds of southern Brazil (Paraná Basin).

    PubMed

    Francischini, Heitor; Dentzien-Dias, Paula; Lucas, Spencer G; Schultz, Cesar L

    2018-01-01

    Tetrapod tracks in eolianites are widespread in the fossil record since the late Paleozoic. Among these ichnofaunas, the ichnogenus Chelichnus is the most representative of the Permian tetrapod ichnological record of eolian deposits of Europe, North America and South America, where the Chelichnus Ichnofacies often occurs. In this contribution, we describe five sets of tracks (one of which is preserved in cross-section), representing the first occurrence of Dicynodontipus and Chelichnus in the "Pirambóia Formation" of southern Brazil. This unit represents a humid desert in southwestern Pangea and its lower and upper contacts lead us to consider its age as Lopingian-Induan. The five sets of tracks studied were compared with several ichnotaxa and body fossils with appendicular elements preserved, allowing us to attribute these tracks to dicynodonts and other indeterminate therapsids. Even though the "Pirambóia Formation" track record is sparse and sub-optimally preserved, it is an important key to better understand the occupation of arid environments by tetrapods across the Permo-Triassic boundary.

  7. Origin and evolution of the integumentary skeleton in non-tetrapod vertebrates

    PubMed Central

    Sire, Jean-Yves; Donoghue, Philip C J; Vickaryous, Matthews K

    2009-01-01

    Most non-tetrapod vertebrates develop mineralized extra-oral elements within the integument. Known collectively as the integumentary skeleton, these elements represent the structurally diverse skin-bound contribution to the dermal skeleton. In this review we begin by summarizing what is known about the histological diversity of the four main groups of integumentary skeletal tissues: hypermineralized (capping) tissues; dentine; plywood-like tissues; and bone. For most modern taxa, the integumentary skeleton has undergone widespread reduction and modification often rendering the homology and relationships of these elements confused and uncertain. Fundamentally, however, all integumentary skeletal elements are derived (alone or in combination) from only two types of cell condensations: odontogenic and osteogenic condensations. We review the origin and diversification of the integumentary skeleton in aquatic non-tetrapods (including stem gnathostomes), focusing on tissues derived from odontogenic (hypermineralized tissues, dentines and elasmodine) and osteogenic (bone tissues) cell condensations. The novelty of our new scenario of integumentary skeletal evolution resides in the demonstration that elasmodine, the main component of elasmoid scales, is odontogenic in origin. Based on available data we propose that elasmodine is a form of lamellar dentine. Given its widespread distribution in non-tetrapod lineages we further propose that elasmodine is a very ancient tissue in vertebrates and predict that it will be found in ancestral rhombic scales and cosmoid scales. PMID:19422423

  8. Tuataras and salamanders show that walking and running mechanics are ancient features of tetrapod locomotion

    PubMed Central

    Reilly, Stephen M; McElroy, Eric J; Andrew Odum, R; Hornyak, Valerie A

    2006-01-01

    The lumbering locomotor behaviours of tuataras and salamanders are the best examples of quadrupedal locomotion of early terrestrial vertebrates. We show they use the same walking (out-of-phase) and running (in-phase) patterns of external mechanical energy fluctuations of the centre-of-mass known in fast moving (cursorial) animals. Thus, walking and running centre-of-mass mechanics have been a feature of tetrapods since quadrupedal locomotion emerged over 400 million years ago. When walking, these sprawling animals save external mechanical energy with the same pendular effectiveness observed in cursorial animals. However, unlike cursorial animals (that change footfall patterns and mechanics with speed), tuataras and salamanders use only diagonal couplet gaits and indifferently change from walking to running mechanics with no significant change in total mechanical energy. Thus, the change from walking to running is not related to speed and the advantage of walking versus running is unclear. Furthermore, lumbering mechanics in primitive tetrapods is reflected in having total mechanical energy driven by potential energy (rather than kinetic energy as in cursorial animals) and relative centre-of-mass displacements an order of magnitude greater than cursorial animals. Thus, large vertical displacements associated with lumbering locomotion in primitive tetrapods may preclude their ability to increase speed. PMID:16777753

  9. Tempo and Mode of the Evolution of Venom and Poison in Tetrapods.

    PubMed

    Harris, Richard J; Arbuckle, Kevin

    2016-06-23

    Toxic weaponry in the form of venom and poison has evolved in most groups of animals, including all four major lineages of tetrapods. Moreover, the evolution of such traits has been linked to several key aspects of the biology of toxic animals including life-history and diversification. Despite this, attempts to investigate the macroevolutionary patterns underlying such weaponry are lacking. In this study we analyse patterns of venom and poison evolution across reptiles, amphibians, mammals, and birds using a suite of phylogenetic comparative methods. We find that each major lineage has a characteristic pattern of trait evolution, but mammals and reptiles evolve under a surprisingly similar regime, whilst that of amphibians appears to be particularly distinct and highly contrasting compared to other groups. Our results also suggest that the mechanism of toxin acquisition may be an important distinction in such evolutionary patterns; the evolution of biosynthesis is far less dynamic than that of sequestration of toxins from the diet. Finally, contrary to the situation in amphibians, other tetrapod groups show an association between the evolution of toxic weaponry and higher diversification rates. Taken together, our study provides the first broad-scale analysis of macroevolutionary patterns of venom and poison throughout tetrapods.

  10. Tempo and Mode of the Evolution of Venom and Poison in Tetrapods

    PubMed Central

    Harris, Richard J.; Arbuckle, Kevin

    2016-01-01

    Toxic weaponry in the form of venom and poison has evolved in most groups of animals, including all four major lineages of tetrapods. Moreover, the evolution of such traits has been linked to several key aspects of the biology of toxic animals including life-history and diversification. Despite this, attempts to investigate the macroevolutionary patterns underlying such weaponry are lacking. In this study we analyse patterns of venom and poison evolution across reptiles, amphibians, mammals, and birds using a suite of phylogenetic comparative methods. We find that each major lineage has a characteristic pattern of trait evolution, but mammals and reptiles evolve under a surprisingly similar regime, whilst that of amphibians appears to be particularly distinct and highly contrasting compared to other groups. Our results also suggest that the mechanism of toxin acquisition may be an important distinction in such evolutionary patterns; the evolution of biosynthesis is far less dynamic than that of sequestration of toxins from the diet. Finally, contrary to the situation in amphibians, other tetrapod groups show an association between the evolution of toxic weaponry and higher diversification rates. Taken together, our study provides the first broad-scale analysis of macroevolutionary patterns of venom and poison throughout tetrapods. PMID:27348001

  11. Conserving the functional and phylogenetic trees of life of European tetrapods

    PubMed Central

    Thuiller, Wilfried; Maiorano, Luigi; Mazel, Florent; Guilhaumon, François; Ficetola, Gentile Francesco; Lavergne, Sébastien; Renaud, Julien; Roquet, Cristina; Mouillot, David

    2015-01-01

    Protected areas (PAs) are pivotal tools for biodiversity conservation on the Earth. Europe has had an extensive protection system since Natura 2000 areas were created in parallel with traditional parks and reserves. However, the extent to which this system covers not only taxonomic diversity but also other biodiversity facets, such as evolutionary history and functional diversity, has never been evaluated. Using high-resolution distribution data of all European tetrapods together with dated molecular phylogenies and detailed trait information, we first tested whether the existing European protection system effectively covers all species and in particular, those with the highest evolutionary or functional distinctiveness. We then tested the ability of PAs to protect the entire tetrapod phylogenetic and functional trees of life by mapping species' target achievements along the internal branches of these two trees. We found that the current system is adequately representative in terms of the evolutionary history of amphibians while it fails for the rest. However, the most functionally distinct species were better represented than they would be under random conservation efforts. These results imply better protection of the tetrapod functional tree of life, which could help to ensure long-term functioning of the ecosystem, potentially at the expense of conserving evolutionary history. PMID:25561666

  12. Analysis of the African coelacanth genome sheds light on tetrapod evolution

    PubMed Central

    Amemiya, Chris T.; Alföldi, Jessica; Lee, Alison P.; Fan, Shaohua; Philippe, Hervé; MacCallum, Iain; Braasch, Ingo; Manousaki, Tereza; Schneider, Igor; Rohner, Nicolas; Organ, Chris; Chalopin, Domitille; Smith, Jeramiah J.; Robinson, Mark; Dorrington, Rosemary A.; Gerdol, Marco; Aken, Bronwen; Biscotti, Maria Assunta; Barucca, Marco; Baurain, Denis; Berlin, Aaron M.; Blatch, Gregory L.; Buonocore, Francesco; Burmester, Thorsten; Campbell, Michael S.; Canapa, Adriana; Cannon, John P.; Christoffels, Alan; De Moro, Gianluca; Edkins, Adrienne L.; Fan, Lin; Fausto, Anna Maria; Feiner, Nathalie; Forconi, Mariko; Gamieldien, Junaid; Gnerre, Sante; Gnirke, Andreas; Goldstone, Jared V.; Haerty, Wilfried; Hahn, Mark E.; Hesse, Uljana; Hoffmann, Steve; Johnson, Jeremy; Karchner, Sibel I.; Kuraku, Shigehiro; Lara, Marcia; Levin, Joshua Z.; Litman, Gary W.; Mauceli, Evan; Miyake, Tsutomu; Mueller, M. Gail; Nelson, David R.; Nitsche, Anne; Olmo, Ettore; Ota, Tatsuya; Pallavicini, Alberto; Panji, Sumir; Picone, Barbara; Ponting, Chris P.; Prohaska, Sonja J.; Przybylski, Dariusz; Saha, Nil Ratan; Ravi, Vydianathan; Ribeiro, Filipe J.; Sauka-Spengler, Tatjana; Scapigliati, Giuseppe; Searle, Stephen M. J.; Sharpe, Ted; Simakov, Oleg; Stadler, Peter F.; Stegeman, John J.; Sumiyama, Kenta; Tabbaa, Diana; Tafer, Hakim; Turner-Maier, Jason; van Heusden, Peter; White, Simon; Williams, Louise; Yandell, Mark; Brinkmann, Henner; Volff, Jean-Nicolas; Tabin, Clifford J.; Shubin, Neil; Schartl, Manfred; Jaffe, David; Postlethwait, John H.; Venkatesh, Byrappa; Di Palma, Federica; Lander, Eric S.; Meyer, Axel; Lindblad-Toh, Kerstin

    2013-01-01

    It was a zoological sensation when a living specimen of the coelacanth was first discovered in 1938, as this lineage of lobe-finned fish was thought to have gone extinct 70 million years ago. The modern coelacanth looks remarkably similar to many of its ancient relatives, and its evolutionary proximity to our own fish ancestors provides a glimpse of the fish that first walked on land. Here we report the genome sequence of the African coelacanth, Latimeria chalumnae. Through a phylogenomic analysis, we conclude that the lungfish, and not the coelacanth, is the closest living relative of tetrapods. Coelacanth protein-coding genes are significantly more slowly evolving than those of tetrapods, unlike other genomic features . Analyses of changes in genes and regulatory elements during the vertebrate adaptation to land highlight genes involved in immunity, nitrogen excretion and the development of fins, tail, ear, eye, brain, and olfaction. Functional assays of enhancers involved in the fin-to-limb transition and in the emergence of extra-embryonic tissues demonstrate the importance of the coelacanth genome as a blueprint for understanding tetrapod evolution. PMID:23598338

  13. Lunge feeding in early marine reptiles and fast evolution of marine tetrapod feeding guilds

    PubMed Central

    Motani, Ryosuke; Chen, Xiao-hong; Jiang, Da-yong; Cheng, Long; Tintori, Andrea; Rieppel, Olivier

    2015-01-01

    Traditional wisdom holds that biotic recovery from the end-Permian extinction was slow and gradual, and was not complete until the Middle Triassic. Here, we report that the evolution of marine predator feeding guilds, and their trophic structure, proceeded faster. Marine reptile lineages with unique feeding adaptations emerged during the Early Triassic (about 248 million years ago), including the enigmatic Hupehsuchus that possessed an unusually slender mandible. A new specimen of this genus reveals a well-preserved palate and mandible, which suggest that it was a rare lunge feeder as also occurs in rorqual whales and pelicans. The diversity of feeding strategies among Triassic marine tetrapods reached their peak in the Early Triassic, soon after their first appearance in the fossil record. The diet of these early marine tetrapods most likely included soft-bodied animals that are not preserved as fossils. Early marine tetrapods most likely introduced a new trophic mechanism to redistribute nutrients to the top 10 m of the sea, where the primary productivity is highest. Therefore, a simple recovery to a Permian-like trophic structure does not explain the biotic changes seen after the Early Triassic. PMID:25754468

  14. Defect-induced magnetic order in pure ZnO films

    NASA Astrophysics Data System (ADS)

    Khalid, M.; Ziese, M.; Setzer, A.; Esquinazi, P.; Lorenz, M.; Hochmuth, H.; Grundmann, M.; Spemann, D.; Butz, T.; Brauer, G.; Anwand, W.; Fischer, G.; Adeagbo, W. A.; Hergert, W.; Ernst, A.

    2009-07-01

    We have investigated the magnetic properties of pure ZnO thin films grown under N2 pressure on a -, c -, and r -plane Al2O3 substrates by pulsed-laser deposition. The substrate temperature and the N2 pressure were varied from room temperature to 570°C and from 0.007 to 1.0 mbar, respectively. The magnetic properties of bare substrates and ZnO films were investigated by SQUID magnetometry. ZnO films grown on c - and a -plane Al2O3 substrates did not show significant ferromagnetism. However, ZnO films grown on r -plane Al2O3 showed reproducible ferromagnetism at 300 K when grown at 300-400°C and 0.1-1.0 mbar N2 pressure. Positron annihilation spectroscopy measurements as well as density-functional theory calculations suggest that the ferromagnetism in ZnO films is related to Zn vacancies.

  15. A Temnospondyl Trackway from the Early Mesozoic of Western Gondwana and Its Implications for Basal Tetrapod Locomotion

    PubMed Central

    Marsicano, Claudia A.; Wilson, Jeffrey A.; Smith, Roger M. H.

    2014-01-01

    Background Temnospondyls are one of the earliest radiations of limbed vertebrates. Skeletal remains of more than 190 genera have been identified from late Paleozoic and early Mesozoic rocks. Paleozoic temnospondyls comprise mainly small to medium sized forms of diverse habits ranging from fully aquatic to fully terrestrial. Accordingly, their ichnological record includes tracks described from many Laurasian localities. Mesozoic temnospondyls, in contrast, include mostly medium to large aquatic or semi-aquatic forms. Exceedingly few fossil tracks or trackways have been attributed to Mesozoic temnospondyls, and as a consequence very little is known of their locomotor capabilities on land. Methodology/Principal Findings We report a ca. 200 Ma trackway, Episcopopus ventrosus, from Lesotho, southern Africa that was made by a 3.5 m-long animal. This relatively long trackway records the trackmaker dragging its body along a wet substrate using only the tips of its digits, which in the manus left characteristic drag marks. Based on detailed mapping, casting, and laser scanning of the best-preserved part of the trackway, we identified synapomorphies (e.g., tetradactyl manus, pentadactyl pes) and symplesiomorphies (e.g., absence of claws) in the Episcopopus trackway that indicate a temnospondyl trackmaker. Conclusions/Significance Our analysis shows that the Episcopopus trackmaker progressed with a sprawling posture, using a lateral-sequence walk. Its forelimbs were the major propulsive elements and there was little lateral bending of the trunk. We suggest this locomotor style, which differs dramatically from the hindlimb-driven locomotion of salamanders and other extant terrestrial tetrapods can be explained by the forwardly shifted center of mass resulting from the relatively large heads and heavily pectoral girdles of temnospondyls. PMID:25099971

  16. Confocal Raman microscopy of one dimensional ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Singamaneni, Srikanth; Gupta, Maneesh; Yang, Rusen; Wang, Zhong; Tsukruk, Vladimir

    2009-03-01

    ZnO nanostructures with various shapes (vertically aligned nanorods, nanobelts, nanohelixes, nanorings) have been synthesized using both vapor phase and solution growth methods. In the simplest example of a nanobelt, the fast growth direction can be either (21 1 0) or (011 0) or (0001). Here, we show that confocal Raman microscopy can be employed as a fast and nondestructive analytical technique to identify the crystal planes and reveal the relative orientation of the ZnO nanostructure. Various features of the Raman spectrum of ZnO nanostructures (presence of the A1(TO) mode, width of the E2 mode) were found to be sensitive to relative orientation of the incident source laser and the crystal plane. Furthermore, owing to the optical anisotropy of ZnO, Raman scattering from the substrate is modulated (either enhanced or suppressed with respect to the background) depending on the polarization of the incident light with respect to orientation of the nanobelt. The results presented here describe a novel method to nondestructively identify the growth, relative orientation, and the waveguiding properties of the ZnO nanostructures.

  17. Hedgehog regulation of superficial slow muscle fibres in Xenopus and the evolution of tetrapod trunk myogenesis.

    PubMed

    Grimaldi, Annalisa; Tettamanti, Gianluca; Martin, Benjamin L; Gaffield, William; Pownall, Mary E; Hughes, Simon M

    2004-07-01

    In tetrapod phylogeny, the dramatic modifications of the trunk have received less attention than the more obvious evolution of limbs. In somites, several waves of muscle precursors are induced by signals from nearby tissues. In both amniotes and fish, the earliest myogenesis requires secreted signals from the ventral midline carried by Hedgehog (Hh) proteins. To determine if this similarity represents evolutionary homology, we have examined myogenesis in Xenopus laevis, the major species from which insight into vertebrate mesoderm patterning has been derived. Xenopus embryos form two distinct kinds of muscle cells analogous to the superficial slow and medial fast muscle fibres of zebrafish. As in zebrafish, Hh signalling is required for XMyf5 expression and generation of a first wave of early superficial slow muscle fibres in tail somites. Thus, Hh-dependent adaxial myogenesis is the likely ancestral condition of teleosts, amphibia and amniotes. Our evidence suggests that midline-derived cells migrate to the lateral somite surface and generate superficial slow muscle. This cell re-orientation contributes to the apparent rotation of Xenopus somites. Xenopus myogenesis in the trunk differs from that in the tail. In the trunk, the first wave of superficial slow fibres is missing, suggesting that significant adaptation of the ancestral myogenic programme occurred during tetrapod trunk evolution. Although notochord is required for early medial XMyf5 expression, Hh signalling fails to drive these cells to slow myogenesis. Later, both trunk and tail somites develop a second wave of Hh-independent slow fibres. These fibres probably derive from an outer cell layer expressing the myogenic determination genes XMyf5, XMyoD and Pax3 in a pattern reminiscent of amniote dermomyotome. Thus, Xenopus somites have characteristics in common with both fish and amniotes that shed light on the evolution of somite differentiation. We propose a model for the evolutionary adaptation of

  18. A unique life history among tetrapods: An annual chameleon living mostly as an egg

    PubMed Central

    Karsten, Kristopher B.; Andriamandimbiarisoa, Laza N.; Fox, Stanley F.; Raxworthy, Christopher J.

    2008-01-01

    The ≈28,300 species of tetrapods (four-limbed vertebrates) almost exclusively have perennial life spans. Here, we report the discovery of a remarkable annual tetrapod from the arid southwest of Madagascar: the chameleon Furcifer labordi, with a posthatching life span of just 4–5 months. At the start of the active season (November), an age cohort of hatchlings emerges; larger juveniles or adults are not present. These hatchlings grow rapidly, reach sexual maturity in less than 2 months, and reproduce in January–February. After reproduction, senescence appears, and the active season concludes with population-wide adult death. Consequently, during the dry season, the entire population is represented by developing eggs that incubate for 8–9 months before synchronously hatching at the onset of the following rainy season. Remarkably, this chameleon spends more of its short annual life cycle inside the egg than outside of it. Our review of tetrapod longevity (>1,700 species) finds no others with such a short life span. These findings suggest that the notorious rapid death of chameleons in captivity may, for some species, actually represent the natural adult life span. Consequently, a new appraisal may be warranted concerning the viability of chameleon breeding programs, which could have special significance for species of conservation concern. Additionally, because F. labordi is closely related to other perennial species, this chameleon group may prove also to be especially well suited for comparative studies that focus on life history evolution and the ecological, genetic, and/or hormonal determinants of aging, longevity, and senescence. PMID:18591659

  19. A unique life history among tetrapods: an annual chameleon living mostly as an egg.

    PubMed

    Karsten, Kristopher B; Andriamandimbiarisoa, Laza N; Fox, Stanley F; Raxworthy, Christopher J

    2008-07-01

    The approximately 28,300 species of tetrapods (four-limbed vertebrates) almost exclusively have perennial life spans. Here, we report the discovery of a remarkable annual tetrapod from the arid southwest of Madagascar: the chameleon Furcifer labordi, with a posthatching life span of just 4-5 months. At the start of the active season (November), an age cohort of hatchlings emerges; larger juveniles or adults are not present. These hatchlings grow rapidly, reach sexual maturity in less than 2 months, and reproduce in January-February. After reproduction, senescence appears, and the active season concludes with population-wide adult death. Consequently, during the dry season, the entire population is represented by developing eggs that incubate for 8-9 months before synchronously hatching at the onset of the following rainy season. Remarkably, this chameleon spends more of its short annual life cycle inside the egg than outside of it. Our review of tetrapod longevity (>1,700 species) finds no others with such a short life span. These findings suggest that the notorious rapid death of chameleons in captivity may, for some species, actually represent the natural adult life span. Consequently, a new appraisal may be warranted concerning the viability of chameleon breeding programs, which could have special significance for species of conservation concern. Additionally, because F. labordi is closely related to other perennial species, this chameleon group may prove also to be especially well suited for comparative studies that focus on life history evolution and the ecological, genetic, and/or hormonal determinants of aging, longevity, and senescence.

  20. Carnivorous dinocephalian from the Middle Permian of Brazil and tetrapod dispersal in Pangaea

    NASA Astrophysics Data System (ADS)

    Cisneros, Juan Carlos; Abdala, Fernando; Atayman-Güven, Saniye; Rubidge, Bruce S.; Celâl Şengör, A. M.; Schultz, Cesar L.

    2012-01-01

    The medial Permian (∼270-260 Ma: Guadalupian) was a time of important tetrapod faunal changes, in particular reflecting a turnover from pelycosaurian- to therapsid-grade synapsids. Until now, most knowledge on tetrapod distribution during the medial Permian has come from fossils found in the South African Karoo and the Russian Platform, whereas other areas of Pangaea are still poorly known. We present evidence for the presence of a terrestrial carnivorous vertebrate from the Middle Permian of South America based on a complete skull. Pampaphoneus biccai gen. et sp. nov. was a dinocephalian "mammal-like reptile" member of the Anteosauridae, an early therapsid predator clade known only from the Middle Permian of Russia, Kazakhstan, China, and South Africa. The genus is characterized, among other features, by postorbital bosses, short, bulbous postcanines, and strongly recurved canines. Phylogenetic analysis indicates that the Brazilian dinocephalian occupies a middle position within the Anteosauridae, reinforcing the model of a global distribution for therapsids as early as the Guadalupian. The close phylogenetic relationship of the Brazilian species to dinocephalians from South Africa and the Russian Platform suggests a closer faunistic relationship between South America and eastern Europe than previously thought, lending support to a Pangaea B-type continental reconstruction.

  1. Developmental mechanisms of macroevolutionary change in the tetrapod axis: A case study of Sauropterygia

    PubMed Central

    Soul, Laura C.; Benson, Roger B. J.

    2017-01-01

    Understanding how developmental processes change on macroevolutionary timescales to generate body plan disparity is fundamental to the study of vertebrate evolution. Adult morphology of the vertebral column directly reflects the mechanisms that generate vertebral counts (somitogenesis) and their regionalisation (homeotic effects) during embryonic development. Sauropterygians were a group of Mesozoic marine reptiles that exhibited an extremely high disparity of presacral vertebral/somite counts. Using phylogenetic comparative methods, we demonstrate that somitogenesis and homeotic effects evolved in a co‐ordinated way among sauropterygians, contrasting with the wider pattern in tetrapods, in which somitogenetic and homeotic shifts are uncorrelated. Changes in sauropterygian body proportions were primarily enabled by homeotic shifts, with a lesser, but important, contribution from differences in postpatterning growth among somites. High body plan plasticity was present in Triassic sauropterygians and was maintained among their Jurassic and Cretaceous descendants. The extreme disparity in the body plan of plesiosaurian sauropterygians did not result from accelerated rates of evolutionary change in neck length, but instead reflect this ancestral versatility of sauropterygian axial development. Our results highlight variation in modes of axial development among tetrapods, and show that heterogeneous statistical models can uncover novel macroevolutionary patterns for animal body plans and the developmental mechanisms that control them. PMID:28240769

  2. Strategy for good dispersion of well-defined tetrapods in semiconducting polymer matrices.

    PubMed

    Lim, Jaehoon; Borg, Lisa zur; Dolezel, Stefan; Schmid, Friederike; Char, Kookheon; Zentel, Rudolf

    2014-10-01

    The morphology or dispersion control in inorganic/organic hybrid systems is studied, which consist of monodisperse CdSe tetrapods (TPs) with grafted semiconducting block copolymers with excess polymers of the same type. Tetrapod arm-length and amount of polymer loading are varied in order to find the ideal morphology for hybrid solar cells. Additionally, polymers without anchor groups are mixed with the TPs to study the effect of such anchor groups on the hybrid morphology. A numerical model is developed and Monte Carlo simulations to study the basis of compatibility or dispersibility of TPs in polymer matrices are performed. The simulations show that bare TPs tend to form clusters in the matrix of excess polymers. The clustering is significantly reduced after grafting polymer chains to the TPs, which is confirmed experimentally. Transmission electron microscopy reveals that the block copolymer-TP mixtures ("hybrids") show much better film qualities and TP distributions within the films when compared with the homopolymer-TP mixtures ("blends"), representing massive aggregations and cracks in the films. This grafting-to approach for the modification of TPs significantly improves the dispersion of the TPs in matrices of "excess" polymers up to the arm length of 100 nm. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Skull ontogeny: developmental patterns of fishes conserved across major tetrapod clades.

    PubMed

    Schoch, Rainer R

    2006-01-01

    In vertebrates, the ontogeny of the bony skull forms a particularly complex part of embryonic development. Although this area used to be restricted to neontology, recent discoveries of fossil ontogenies provide an additional source of data. One of the most detailed ossification sequences is known from Permo-Carboniferous amphibians, the branchiosaurids. These temnospondyls form a near-perfect link between the piscine osteichthyans and the various clades of extant tetrapods, retaining a full complement of dermal bones in the skull. For the first time, the broader evolutionary significance of these event sequences is analyzed, focusing on the identification of sequence heterochronies. A set of 120 event pairs was analyzed by event pair cracking, which helped identify active movers. A cladistic analysis of the event pair data was also carried out, highlighting some shared patterns between widely divergent clades of tetrapods. The analyses revealed an unexpected degree of similarity between the widely divergent taxa. Most interesting is the apparently modular composition of the cranial sequence: five clusters of bones were discovered in each of which the elements form in the same time window: (1) jaw bones, (2) marginal palatal elements, (3) circumorbital bones, (4) skull roof elements, and (5) neurocranial ossifications. In the studied taxa, these "modules" have in most cases been shifted fore and back on the trajectory relative to the Amia sequence, but did not disintegrate. Such "modules" might indicate a high degree of evolutionary limitation (constraint).

  4. Ornithorhynchus anatinus (platypus) links the evolution of immunoglobulin genes in eutherian mammals and nonmammalian tetrapods.

    PubMed

    Zhao, Yaofeng; Cui, Huiting; Whittington, Camilla M; Wei, Zhiguo; Zhang, Xiaofeng; Zhang, Ziding; Yu, Li; Ren, Liming; Hu, Xiaoxiang; Zhang, Yaping; Hellman, Lars; Belov, Katherine; Li, Ning; Hammarström, Lennart

    2009-09-01

    The evolutionary origins of mammalian immunoglobulin H chain isotypes (IgM, IgD, IgG, IgE, and IgA) are still incompletely understood as these isotypes differ considerably in structure and number from their counterparts in nonmammalian tetrapods. We report in this study that the platypus (Ornithorhynchus anatinus) Ig H chain constant region gene locus contains eight Ig encoding genes, which are arranged in an mu-delta-omicron-gamma2-gamma1-alpha1-epsilon-alpha2 order, spanning a total of approximately 200 kb DNA, encoding six distinct isotypes. The omicron (omicron for Ornithorhynchus) gene encodes a novel Ig H chain isotype that consists of four constant region domains and a hinge, and is structurally different from any of the five known mammalian Ig classes. This gene is phylogenetically related to upsilon (epsilon) and gamma, and thus appears to be a structural intermediate between these two genes. The platypus delta gene encodes ten heavy chain constant region domains, lacks a hinge region and is similar to IgD in amphibians and fish, but strikingly different from that in eutherian mammals. The platypus Ig H chain isotype repertoire thus shows a unique combination of genes that share similarity both to those of nonmammalian tetrapods and eutherian animals and demonstrates how phylogenetically informative species can be used to reconstruct the evolutionary history of functionally important genes.

  5. A tetrapod-like repertoire of innate immune receptors and effectors for coelacanths

    Boudinot, Pierre; Zou, Jun; Ota, Tatsuya; Buonocore, Francesco; Scapigliati, Giuseppe; Canapa, Adriana; Cannon, John; Litman, Gary; Hansen, John D.

    2014-01-01

    The recent availability of both robust transcriptome and genome resources for coelacanth (Latimeria chalumnae) has led to unique discoveries for coelacanth immunity such as the lack of IgM, a central component of adaptive immunity. This study was designed to more precisely address the origins and evolution of gene families involved in the initial recognition and response to microbial pathogens, which effect innate immunity. Several multigene families involved in innate immunity are addressed, including: Toll-like receptors (TLRs), retinoic acid inducible gene 1 (RIG1)-like receptors (RLRs), the nucleotide-binding domain and leucine-rich repeat containing proteins (NLRs), diverse immunoglobulin domain-containing proteins (DICP) and modular domain immune-type receptors (MDIRs). Our analyses also include the tripartite motif-containing proteins (TRIM), which are involved in pathogen recognition as well as the positive regulation of antiviral immunity. Finally, this study addressed some of the downstream effectors of the antimicrobial response including IL-1 family members, type I and II interferons (IFN) and IFN-stimulated effectors (ISGs). Collectively, the genes and gene families in coelacanth that effect innate immune functions share characteristics both in content, structure and arrangement with those found in tetrapods but not in teleosts. The findings support the sister group relationship of coelacanth fish with tetrapods.

  6. Confusing dinosaurs with mammals: tetrapod phylogenetics and anatomical terminology in the world of homology.

    PubMed

    Harris, Jerald D

    2004-12-01

    At present, three different systems of anatomical nomenclature are available to researchers describing new tetrapod taxa: a nonstandardized traditional system erected in part by Sir Richard Owen and subsequently elaborated by Alfred Romer; a standardized system created for avians, the Nomina Anatomica Avium (NAA); and a standardized system for extant (crown-group) mammals, the Nomina Anatomica Veterinaria (NAV). Conserved homologous structures widely distributed within the Tetrapoda are often granted different names in each system. The recent shift toward a phylogenetic system based on homology requires a concomitant shift toward a single nomenclatural system also based on both evolutionary and functional morphological homology. Standardized terms employed in the NAA and NAV should be perpetuated as far as possible basally in their respective phylogenies. Thus, NAA terms apply to nonavian archosaurs (or even all diapsids) and NAV terms apply to noncrown-group mammals and more basal synapsids. Taxa equally distant from both avians and crown-group mammals may maintain the traditional nonstandardized terminology until a universal anatomical nomenclature for all tetrapods is constructed. (c) 2004 Wiley-Liss, Inc.

  7. Carnivorous dinocephalian from the Middle Permian of Brazil and tetrapod dispersal in Pangaea.

    PubMed

    Cisneros, Juan Carlos; Abdala, Fernando; Atayman-Güven, Saniye; Rubidge, Bruce S; Şengörc, A M Celâl; Schultz, Cesar L

    2012-01-31

    The medial Permian (~270-260 Ma: Guadalupian) was a time of important tetrapod faunal changes, in particular reflecting a turnover from pelycosaurian- to therapsid-grade synapsids. Until now, most knowledge on tetrapod distribution during the medial Permian has come from fossils found in the South African Karoo and the Russian Platform, whereas other areas of Pangaea are still poorly known. We present evidence for the presence of a terrestrial carnivorous vertebrate from the Middle Permian of South America based on a complete skull. Pampaphoneus biccai gen. et sp. nov. was a dinocephalian "mammal-like reptile" member of the Anteosauridae, an early therapsid predator clade known only from the Middle Permian of Russia, Kazakhstan, China, and South Africa. The genus is characterized, among other features, by postorbital bosses, short, bulbous postcanines, and strongly recurved canines. Phylogenetic analysis indicates that the Brazilian dinocephalian occupies a middle position within the Anteosauridae, reinforcing the model of a global distribution for therapsids as early as the Guadalupian. The close phylogenetic relationship of the Brazilian species to dinocephalians from South Africa and the Russian Platform suggests a closer faunistic relationship between South America and eastern Europe than previously thought, lending support to a Pangaea B-type continental reconstruction.

  8. Carnivorous dinocephalian from the Middle Permian of Brazil and tetrapod dispersal in Pangaea

    PubMed Central

    Cisneros, Juan Carlos; Abdala, Fernando; Atayman-Güven, Saniye; Rubidge, Bruce S.; Şengör, A. M. Celâl; Schultz, Cesar L.

    2012-01-01

    The medial Permian (∼270–260 Ma: Guadalupian) was a time of important tetrapod faunal changes, in particular reflecting a turnover from pelycosaurian- to therapsid-grade synapsids. Until now, most knowledge on tetrapod distribution during the medial Permian has come from fossils found in the South African Karoo and the Russian Platform, whereas other areas of Pangaea are still poorly known. We present evidence for the presence of a terrestrial carnivorous vertebrate from the Middle Permian of South America based on a complete skull. Pampaphoneus biccai gen. et sp. nov. was a dinocephalian “mammal-like reptile” member of the Anteosauridae, an early therapsid predator clade known only from the Middle Permian of Russia, Kazakhstan, China, and South Africa. The genus is characterized, among other features, by postorbital bosses, short, bulbous postcanines, and strongly recurved canines. Phylogenetic analysis indicates that the Brazilian dinocephalian occupies a middle position within the Anteosauridae, reinforcing the model of a global distribution for therapsids as early as the Guadalupian. The close phylogenetic relationship of the Brazilian species to dinocephalians from South Africa and the Russian Platform suggests a closer faunistic relationship between South America and eastern Europe than previously thought, lending support to a Pangaea B-type continental reconstruction. PMID:22307615

  9. Tetrapod axial evolution and developmental constraints; Empirical underpinning by a mouse model.

    PubMed

    Woltering, Joost M; Duboule, Denis

    2015-11-01

    The tetrapod vertebral column has become increasingly complex during evolution as an adaptation to a terrestrial life. At the same time, the evolution of the vertebral formula became subject to developmental constraints acting on the size of the cervical and thoraco-lumbar regions. In the course of our studies concerning the evolution of Hox gene regulation, we produced a transgenic mouse model expressing fish Hox genes, which displayed a reduced number of thoraco-lumbar vertebrae and concurrent sacral homeotic transformations. Here, we analyze this mutant stock and conclude that the ancestral, pre-tetrapodial Hox code already possessed the capacity to induce vertebrae with sacral characteristics. This suggests that alterations in the interpretation of the Hox code may have participated to the evolution of this region in tetrapods, along with potential modifications of the HOX proteins themselves. With its reduced vertebral number, this mouse stock violates a previously described developmental constraint, which applies to the thoraco-lumbar region. The resulting offset between motor neuron morphology, vertebral patterning and the relative positioning of hind limbs illustrates that the precise orchestration of the Hox-clock in parallel with other ontogenetic pathways places constraints on the evolvability of the body plan. Copyright © 2015 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

  10. Tetrapod axial evolution and developmental constraints; Empirical underpinning by a mouse model

    PubMed Central

    Woltering, Joost M.; Duboule, Denis

    2015-01-01

    The tetrapod vertebral column has become increasingly complex during evolution as an adaptation to a terrestrial life. At the same time, the evolution of the vertebral formula became subject to developmental constraints acting on the size of the cervical and thoraco-lumbar regions. In the course of our studies concerning the evolution of Hox gene regulation, we produced a transgenic mouse model expressing fish Hox genes, which displayed a reduced number of thoraco-lumbar vertebrae and concurrent sacral homeotic transformations. Here, we analyze this mutant stock and conclude that the ancestral, pre-tetrapodial Hox code already possessed the capacity to induce vertebrae with sacral characteristics. This suggests that alterations in the interpretation of the Hox code may have participated to the evolution of this region in tetrapods, along with potential modifications of the HOX proteins themselves. With its reduced vertebral number, this mouse stock violates a previously described developmental constraint, which applies to the thoraco-lumbar region. The resulting offset between motor neuron morphology, vertebral patterning and the relative positioning of hind limbs illustrates that the precise orchestration of the Hox-clock in parallel with other ontogenetic pathways places constraints on the evolvability of the body plan. PMID:26238020

  11. Synthesis of stable ZnO nanocolloids with enhanced optical limiting properties via simple solution method

    NASA Astrophysics Data System (ADS)

    Ramya, M.; Nideep, T. K.; Vijesh, K. R.; Nampoori, V. P. N.; Kailasnath, M.

    2018-07-01

    In present work, we report the synthesis of stable ZnO nanocolloids through a simple solution method which exhibit enhanced optical limiting threshold. The influences of reaction temperature on the crystal structure as well as linear and nonlinear optical properties of prepared ZnO nanoparticles were carried out. The XRD and Raman analysis reveal that the prepared ZnO nanoparticles retain the hexagonal wurtzite crystal structure. HRTEM analysis confirms the effect of reaction temperature, solvent effect on crystallinity as well as nanostructure of ZnO nanoparticles. It has been found that crystallinity and average diameter increase with reaction temperature where ethylene glycol act as both solvent and growth inhibiter. EDS spectra shows formation of pure ZnO nanoparticles. The direct energy band gap of the nanoparticles increases with decrease in particle size due to quantum confinement effect. The third order nonlinear optical properties of ZnO nanoparticles were investigated by z scan technique using a frequency doubled Nd-YAG nanosecond laser at 532 nm wavelength. The z-scan result reveals that the prepared ZnO nanoparticles exhibit self - defocusing nonlinearity. The two photon absorption coefficient and third - order nonlinear optical susceptibility increases with increasing particle size. The third-order susceptibility of the ZnO nanoparticles is found to be in the order of 10-10 esu, which is at least three order magnitude greater than the bulk ZnO. The optical limiting threshold of the nanoparticles varies in the range of 54 to 17 MW/cm2. The results suggest that ZnO nanoparticles considered as a promising candidates for the future photonic devices.

  12. Zinc Vacancy Formation and its Effect on the Conductivity of ZnO

    NASA Astrophysics Data System (ADS)

    Khan, Enamul; Weber, Marc; Langford, Steve; Dickinson, Tom

    2010-03-01

    Exposing single crystal ZnO to 193-nm ArF excimer laser radiation can produce metallic zinc nanoparticles along the surface. The particle production mechanism appears to involve interstitial-vacancy pair formation in the near-surface bulk. Conductivity measurements made with one probe inside the laser spot and the other outside show evidence for rectifying behavior. Positron annihilation spectroscopy confirms the presence of Zn vacancies. We suggest that Zn vacancies are a possible source of p-type behavior in irradiated ZnO. Quadrupole mass spectroscopy shows that both oxygen and zinc are emitted during irradiation. Electron-hole pair production has previously been invoked to account for particle desorption from ZnO during UV illumination. Our results suggest that preexisting and laser-generated defects play a critical role in particle desorption and Zn vacancy formation.

  13. Effects of vertical wall and tetrapod weights on wave overtopping in rubble mound breakwaters under irregular wave conditions

    NASA Astrophysics Data System (ADS)

    Park, Sang Kil; Dodaran, Asgar Ahadpour; Han, Chong Soo; Shahmirzadi, Mohammad Ebrahim Meshkati

    2014-12-01

    Rubble mound breakwaters protect the coastal line against severe erosion caused by wave action. This study examined the performance of different sizes and properties (i.e. height of vertical wall and tetrapod size) of rubble mound breakwaters on reducing the overtopping discharge. The physical model used in this study was derived based on an actual rubble mound in Busan Yacht Harbor. This research attempts to fill the gap in practical knowledge on the combined effect of the armor roughness and vertical wall on wave overtopping in rubble mound breakwaters. The main governing parameters used in this study were the vertical wall height, variation of the tetrapod weights, initial water level elevation, and the volume of overtopping under constant wave properties. The experimental results showed that the roughness factor differed according to the tetrapod size. Furthermore, the overtopping discharge with no vertical wall was similar to that with relatively short vertical walls ( 1 γv = 1). Therefore, the experimental results highlight the importance of the height of the vertical wall in reducing overtopping discharge. Moreover, a large tetrapod size may allow coastal engineers to choose a shorter vertical wall to save cost, while obtaining better performance.

  14. Lasers.

    PubMed

    Passeron, T

    2012-12-01

    Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

  15. [Lasers].

    PubMed

    Passeron, T

    2012-11-01

    Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

  16. ZnO Thin Film Electronics for More than Displays

    NASA Astrophysics Data System (ADS)

    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

  17. ZnO deposition on metal substrates: Relating fabrication, morphology, and wettability

    NASA Astrophysics Data System (ADS)

    Beaini, Sara S.; Kronawitter, Coleman X.; Carey, Van P.; Mao, Samuel S.

    2013-05-01

    It is not common practice to deposit thin films on metal substrates, especially copper, which is a common heat exchanger metal and practical engineering material known for its heat transfer properties. While single crystal substrates offer ideal surfaces with uniform structure for compatibility with oxide deposition, metallic surfaces needed for industrial applications exhibit non-idealities that complicate the fabrication of oxide nanostructure arrays. The following study explored different ZnO fabrication techniques to deposit a (super)hydrophobic thin film of ZnO on a metal substrate, specifically copper, in order to explore its feasibility as an enhanced condensing surface. ZnO was selected for its non-toxicity, ability to be made (super)hydrophobic with hierarchical roughness, and its photoinduced hydrophilicity characteristic, which could be utilized to pattern it to have both hydrophobic-hydrophilic regions. We investigated the variation of ZnO's morphology and wetting state, using SEMs and sessile drop contact angle measurements, as a function of different fabrication techniques: sputtering, pulsed laser deposition (PLD), electrodeposition and annealing Zn. We successfully fabricated (super)hydrophobic ZnO on a mirror finish, commercially available copper substrate using the scalable electrodeposition technique. PLD for ZnO deposition did not prove viable, as the ZnO samples on metal substrates were hydrophilic and the process does not lend itself to scalability. The annealed Zn sheets did not exhibit consistent wetting state results.

  18. Hearing of the African lungfish (Protopterus annectens) suggests underwater pressure detection and rudimentary aerial hearing in early tetrapods.

    PubMed

    Christensen, Christian Bech; Christensen-Dalsgaard, Jakob; Madsen, Peter Teglberg

    2015-02-01

    In the transition from an aquatic to a terrestrial lifestyle, vertebrate auditory systems have undergone major changes while adapting to aerial hearing. Lungfish are the closest living relatives of tetrapods and their auditory system may therefore be a suitable model of the auditory systems of early tetrapods such as Acanthostega. Therefore, experimental studies on the hearing capabilities of lungfish may shed light on the possible hearing capabilities of early tetrapods and broaden our understanding of hearing across the water-to-land transition. Here, we tested the hypotheses that (i) lungfish are sensitive to underwater pressure using their lungs as pressure-to-particle motion transducers and (ii) lungfish can detect airborne sound. To do so, we used neurophysiological recordings to estimate the vibration and pressure sensitivity of African lungfish (Protopterus annectens) in both water and air. We show that lungfish detect underwater sound pressure via pressure-to-particle motion transduction by air volumes in their lungs. The morphology of lungfish shows no specialized connection between these air volumes and the inner ears, and so our results imply that air breathing may have enabled rudimentary pressure detection as early as the Devonian era. Additionally, we demonstrate that lungfish in spite of their atympanic middle ear can detect airborne sound through detection of sound-induced head vibrations. This strongly suggests that even vertebrates with no middle ear adaptations for aerial hearing, such as the first tetrapods, had rudimentary aerial hearing that may have led to the evolution of tympanic middle ears in recent tetrapods. © 2015. Published by The Company of Biologists Ltd.

  19. Zinc oxide tetrapods inhibit herpes simplex virus infection of cultured corneas

    PubMed Central

    Duggal, Neil; Jaishankar, Dinesh; Yadavalli, Tejabhiram; Hadigal, Satvik; Mishra, Yogendra Kumar; Adelung, Rainer

    2017-01-01

    Purpose Infection of the human cornea by herpes simplex virus type-1 (HSV-1) can cause significant vision loss. The purpose of this study was to develop an ex vivo model to visualize viral growth and spread in the cornea. The model was also used to analyze cytokine production and study the antiviral effects of zinc oxide tetrapods. Methods A β-galactosidase-expressing recombinant virus, HSV-1(KOS)tk12, was used to demonstrate the ability of the virus to enter and develop blue plaques on human corneal epithelial (HCE) cells and corneal tissues. Freshly obtained porcine corneas were cultured and then scratched before infection with HSV-1(KOS)tk12. The blue plaques on the corneas were imaged using a stereomicroscope. Western blot analysis for HSV-1 proteins was performed to verify HSV-1 infection of the cornea. Using the ex vivo model, zinc oxide tetrapods were tested for their anti-HSV-1 potential, and a cytokine profile was developed to assess the effects of the treatment. Results Cultured corneas and the use of β-galactosidase-expressing HSV-1(KOS)tk12 virus can provide an attractive ex vivo model to visualize and study HSV-1 entry and spread of the infection in tissues. We found that unlike cultured HCE cells, which demonstrated nearly 100% infectivity, HSV-1 infection of the cultured cornea was more restrictive and took longer to develop. We also found that the zinc oxide tetrapod–shaped nano- and microstructures inhibited HSV infection of the cultured cells, as well as the cultured corneas. The cytokine profile of the infected samples was consistent with previous studies of HSV-1 corneal infection. Conclusions The ability to visualize HSV-1 growth and spread in corneal tissues can provide new details about HSV-1 infection of the cornea and the efficacy of new cornea-specific antiviral drug candidates. The ex vivo model also demonstrates antiviral effects of zinc oxide tetrapods and adequately portrays the drug delivery issues that cornea-specific treatments

  20. Ultraviolet photodetectors based on ZnO sheets: The effect of sheet size on photoresponse properties

    NASA Astrophysics Data System (ADS)

    Ghasempour Ardakani, Abbas; Pazoki, Meysam; Mahdavi, Seyed Mohammad; Bahrampour, Ali Reza; Taghavinia, Nima

    2012-05-01

    In this work, ultraviolet photodetectors based on electrodeposited ZnO sheet thin films were fabricated on a glass substrate. Before electrodeposition, a thin buffer layer of ZnO was deposited on the glass by pulsed laser deposition method. This layer not only acted as a nucleation site for ZnO sheet growth, but also made it possible to use cheap glass substrate instead of conventional fluorine-doped tin oxide (FTO) substrate. Our results showed that photoresponse properties of the photodetectors strongly depend on the sheet sizes. The smaller sheets exhibited enhanced photosensitivity, shortened fall times and decreased gain compared to larger ones. We showed that photodetectors based on ZnO sheets have a faster response than ones based on polycrystalline films. It was also shown that even less response time could be obtained by using comb-like electrodes instead of two-electrode.

  1. Bipolar charge storage characteristics in copper and cobalt co-doped zinc oxide (ZnO) thin film.

    PubMed

    Kumar, Amit; Herng, Tun Seng; Zeng, Kaiyang; Ding, Jun

    2012-10-24

    The bipolar charge phenomenon in Cu and Co co-doped zinc oxide (ZnO) film samples has been studied using scanning probe microscopy (SPM) techniques. Those ZnO samples are made using a pulsed laser deposition (PLD) technique. It is found that the addition of Cu and Co dopants suppresses the electron density in ZnO and causes a significant change in the work function (Fermi level) value of the ZnO film; this results in the ohmic nature of the contact between the electrode (probe tip) and codoped sample, whereas this contact exhibits a Schottky nature in the undoped and single-element-doped samples. These results are verified by Kelvin probe force microscopy (KPFM) and ultraviolet photoelectron spectroscopy (UPS) measurements. It is also found that the co-doping (Cu and Co) can stabilize the bipolar charge, whereas Cu doping only stabilizes the positive charge in ZnO thin films.

  2. Evolution of bone microanatomy of the tetrapod tibia and its use in palaeobiological inference.

    PubMed

    Kriloff, A; Germain, D; Canoville, A; Vincent, P; Sache, M; Laurin, M

    2008-05-01

    Bone microanatomy appears to track changes in various physiological or ecological properties of the individual or the taxon. Analyses of sections of the tibia of 99 taxa show a highly significant (P tetrapod Discosauriscus (Early Permian), the basal synapsid Dimetrodon (Early Permian), the dicynodont therapsid Dicynodon (Late Permian), an unindentified gorgonopsian (Late Permian); the parareptile Pareiasaurus (Middle or Late Permian) is modelled as being aquatic, but was more likely amphibious.

  3. Tetrapods on the EDGE: Overcoming data limitations to identify phylogenetic conservation priorities

    PubMed Central

    Gray, Claudia L.; Wearn, Oliver R.; Owen, Nisha R.

    2018-01-01

    The scale of the ongoing biodiversity crisis requires both effective conservation prioritisation and urgent action. As extinction is non-random across the tree of life, it is important to prioritise threatened species which represent large amounts of evolutionary history. The EDGE metric prioritises species based on their Evolutionary Distinctiveness (ED), which measures the relative contribution of a species to the total evolutionary history of their taxonomic group, and Global Endangerment (GE), or extinction risk. EDGE prioritisations rely on adequate phylogenetic and extinction risk data to generate meaningful priorities for conservation. However, comprehensive phylogenetic trees of large taxonomic groups are extremely rare and, even when available, become quickly out-of-date due to the rapid rate of species descriptions and taxonomic revisions. Thus, it is important that conservationists can use the available data to incorporate evolutionary history into conservation prioritisation. We compared published and new methods to estimate missing ED scores for species absent from a phylogenetic tree whilst simultaneously correcting the ED scores of their close taxonomic relatives. We found that following artificial removal of species from a phylogenetic tree, the new method provided the closest estimates of their “true” ED score, differing from the true ED score by an average of less than 1%, compared to the 31% and 38% difference of the previous methods. The previous methods also substantially under- and over-estimated scores as more species were artificially removed from a phylogenetic tree. We therefore used the new method to estimate ED scores for all tetrapods. From these scores we updated EDGE prioritisation rankings for all tetrapod species with IUCN Red List assessments, including the first EDGE prioritisation for reptiles. Further, we identified criteria to identify robust priority species in an effort to further inform conservation action whilst

  4. Loss of teeth and enamel in tetrapods: fossil record, genetic data and morphological adaptations

    PubMed Central

    Davit-Béal, Tiphaine; Tucker, Abigail S; Sire, Jean-Yves

    2009-01-01

    Since their recruitment in the oral cavity, approximately 450 million years ago, teeth have been subjected to strong selective constraints due to the crucial role that they play in species survival. It is therefore quite surprising that the ability to develop functional teeth has subsequently been lost several times, independently, in various lineages. In this review, we concentrate our attention on tetrapods, the only vertebrate lineage in which several clades lack functional teeth from birth to adulthood. Indeed, in other lineages, teeth can be absent in adults but be functionally present in larvae and juveniles, can be absent in the oral cavity but exist in the pharyngeal region, or can develop on the upper jaw but be absent on the lower jaw. Here, we analyse the current data on toothless (edentate) tetrapod taxa, including information available on enamel-less species. Firstly, we provide an analysis of the dispersed and fragmentary morphological data published on the various living taxa concerned (and their extinct relatives) with the aim of tracing the origin of tooth or enamel loss, i.e. toads in Lissamphibia, turtles and birds in Sauropsida, and baleen whales, pangolins, anteaters, sloths, armadillos and aardvark in Mammalia. Secondly, we present current hypotheses on the genetic basis of tooth loss in the chicken and thirdly, we try to answer the question of how these taxa have survived tooth loss given the crucial importance of this tool. The loss of teeth (or only enamel) in all of these taxa was not lethal because it was always preceded in evolution by the pre-adaptation of a secondary tool (beak, baleens, elongated adhesive tongues or hypselodonty) useful for improving efficiency in food uptake. The positive selection of such secondary tools would have led to relaxed functional constraints on teeth and would have later compensated for the loss of teeth. These hypotheses raise numerous questions that will hopefully be answered in the near future. PMID

  5. Endocrinology of osmoregulation and thermoregulation of Australian desert tetrapods: A historical perspective.

    PubMed

    Cooper, Christine Elizabeth

    2017-04-01

    Many Australian tetrapods inhabit desert environments characterised by low productivity, unpredictable rainfall, high temperatures and high incident solar radiation. Maintaining a homeostatic milieu intérieur by osmoregulation and thermoregulation are two physiological challenges faced by tetrapods in deserts, and the endocrine system plays an important role in regulating these processes. There is a considerable body of work examining the osmoregulatory role of antidiuretic hormones for Australian amphibians, reptiles and mammals, with particular contributions concerning their role and function for wild, free-living animals in arid environments. The osmoregulatory role of the natriuretic peptide system has received some attention, while the role of adrenal corticosteroids has been more thoroughly investigated for reptiles and marsupials. The endocrinology of thermoregulation has not received similar attention. Reptiles are best-studied, with research examining the influence of arginine vasotocin and melatonin on body temperature, the role of prostaglandins in heart rate hysteresis and the effect of melanocyte-stimulating hormone on skin reflectivity. Australian mammals have been under-utilised in studies examining the regulation, development and evolution of endothermy, and there is little information concerning the endocrinology of thermoregulation for desert species. There is a paucity of data concerning the endocrinology of osmoregulation and thermoregulation for Australian desert birds. Studies of Australian desert fauna have made substantial contributions to endocrinology, but there is considerable scope for further research. A co-ordinated approach to examine arid-habitat adaptations of the endocrine system in an environmental and evolutionary context would be of particular value. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. Regulation of Six1 expression by evolutionarily conserved enhancers in tetrapods.

    PubMed

    Sato, Shigeru; Ikeda, Keiko; Shioi, Go; Nakao, Kazuki; Yajima, Hiroshi; Kawakami, Kiyoshi

    2012-08-01

    The Six1 homeobox gene plays critical roles in vertebrate organogenesis. Mice deficient for Six1 show severe defects in organs such as skeletal muscle, kidney, thymus, sensory organs and ganglia derived from cranial placodes, and mutations in human SIX1 cause branchio-oto-renal syndrome, an autosomal dominant developmental disorder characterized by hearing loss and branchial defects. The present study was designed to identify enhancers responsible for the dynamic expression pattern of Six1 during mouse embryogenesis. The results showed distinct enhancer activities of seven conserved non-coding sequences (CNSs) retained in tetrapod Six1 loci. The activities were detected in all cranial placodes (excluding the lens placode), dorsal root ganglia, somites, nephrogenic cord, notochord and cranial mesoderm. The major Six1-expression domains during development were covered by the sum of activities of these enhancers, together with the previously identified enhancer for the pre-placodal region and foregut endoderm. Thus, the eight CNSs identified in a series of our study represent major evolutionarily conserved enhancers responsible for the expression of Six1 in tetrapods. The results also confirmed that chick electroporation is a robust means to decipher regulatory information stored in vertebrate genomes. Mutational analysis of the most conserved placode-specific enhancer, Six1-21, indicated that the enhancer integrates a variety of inputs from Sox, Pax, Fox, Six, Wnt/Lef1 and basic helix-loop-helix proteins. Positive autoregulation of Six1 is achieved through the regulation of Six protein-binding sites. The identified Six1 enhancers provide valuable tools to understand the mechanism of Six1 regulation and to manipulate gene expression in the developing embryo, particularly in the sensory organs. Copyright © 2012 Elsevier Inc. All rights reserved.

  7. Atmospheric oxygen levels affect mudskipper terrestrial performance: implications for early tetrapods.

    PubMed

    Jew, Corey J; Wegner, Nicholas C; Yanagitsuru, Yuzo; Tresguerres, Martin; Graham, Jeffrey B

    2013-08-01

    The Japanese mudskipper (Periophthalmus modestus), an amphibious fish that possesses many respiratory and locomotive specializations for sojourns onto land, was used as a model to study how changing atmospheric oxygen concentrations during the middle and late Paleozoic Era (400-250 million years ago) may have influenced the emergence and subsequent radiation of the first tetrapods. The effects of different atmospheric oxygen concentrations (hyperoxia = 35%, normoxia = 21%, and hypoxia = 7% O2) on terrestrial performance were tested during exercise on a terrestrial treadmill and during recovery from exhaustive exercise. Endurance and elevated post-exercise oxygen consumption (EPOC; the immediate O2 debt repaid post-exercise) correlated with atmospheric oxygen concentration indicating that when additional oxygen is available P. modestus can increase oxygen utilization both during and following exercise. The time required post-exercise for mudskippers to return to a resting metabolic rate did not differ between treatments. However, in normoxia, oxygen consumption increased above hyperoxic values 13-20 h post-exercise suggesting a delayed repayment of the incurred oxygen debt. Finally, following exercise, ventilatory movements associated with buccopharyngeal aerial respiration returned to their rest-like pattern more quickly at higher concentrations of oxygen. Taken together, the results of this study show that P. modestus can exercise longer and recover quicker under higher oxygen concentrations. Similarities between P. modestus and early tetrapods suggest that increasing atmospheric oxygen levels during the middle and late Paleozoic allowed for elevated aerobic capacity and improved terrestrial performance, and likely led to an accelerated diversification and expansion of vertebrate life into the terrestrial biosphere.

  8. Identification of F impurities in F-doped ZnO by synchrotron X-ray absorption near edge structures

    NASA Astrophysics Data System (ADS)

    Na-Phattalung, Sutassana; Limpijumnong, Sukit; Min, Chul-Hee; Cho, Deok-Yong; Lee, Seung-Ran; Char, Kookrin; Yu, Jaejun

    2018-04-01

    Synchrotron X-ray absorption near edge structure (XANES) measurements of F K-edge in conjunction with first-principles calculations are used to identify the local structure of the fluorine (F) atom in F-doped ZnO. The ZnO film was grown by pulsed laser deposition with an Nd:YAG laser, and an oxyfluoridation method was used to introduce F ions into the ZnO films. The measured XANES spectrum of the sample was compared against the first-principles XANES calculations based on various models for local atomic structures surrounding F atoms. The observed spectral features are attributed to ZnF2 and FO defects in wurtzite bulk ZnO.

  9. Evolution of IFN-λ in tetrapod vertebrates and its functional characterization in green anole lizard (Anolis carolinensis).

    PubMed

    Chen, Shan Nan; Zhang, Xiao Wen; Li, Li; Ruan, Bai Ye; Huang, Bei; Huang, Wen Shu; Zou, Peng Fei; Fu, Jian Ping; Zhao, Li Juan; Li, Nan; Nie, Pin

    2016-08-01

    IFN-λ (IFNL), i.e. type III IFN genes were found in a conserved gene locus in tetrapod vertebrates. But, a unique locus containing IFNL was found in avian. In turtle and crocodile, IFNL genes were distributed in these two separate loci. As revealed in phylogenetic trees, IFN-λs in these two different loci and other amniotes were grouped into two different clades. The conservation in gene presence and gene locus was also observed for the receptors of IFN-λ, IFN-λR1 and IL-10RB in tetrapods. It is further revealed that in North American green anole lizard Anolis carolinensis, a single IFNL gene was situated collinearly in the conserved locus as in other tetrapods, together with its receptors IFN-λR1 and IL-10RB also identified in this study. The IFN-λ and its receptors were expressed in all examined organs/tissues, and their expression was stimulated following the injection of polyI:polyC. The ISREs in promoter of IFN-λ in lizard were responsible to IRF3 as demonstrated using luciferase report system, and IFN-λ in lizard functioned through the receptors, IFN-λR1 and IL-10RB, as the up-regulation of ISGs was observed in ligand-receptor transfected, and also in recombinant IFN-λ stimulated, cell lines. Taken together, it is concluded that the mechanisms involved in type III IFN ligand-receptor system, and in its signalling pathway and its down-stream genes may be conserved in green anole lizard, and may even be so in tetrapods from xenopus to human. Copyright © 2016. Published by Elsevier Ltd.

  10. Skeletal Morphogenesis of Microbrachis and Hyloplesion (Tetrapoda: Lepospondyli), and Implications for the Developmental Patterns of Extinct, Early Tetrapods

    PubMed Central

    Olori, Jennifer C.

    2015-01-01

    The ontogeny of extant amphibians often is used as a model for that of extinct early tetrapods, despite evidence for a spectrum of developmental modes in temnospondyls and a paucity of ontogenetic data for lepospondyls. I describe the skeletal morphogenesis of the extinct lepospondyls Microbrachis pelikani and Hyloplesion longicostatum using the largest samples examined for either taxon. Nearly all known specimens were re-examined, allowing for substantial anatomical revisions that affect the scoring of characters commonly used in phylogenetic analyses of early tetrapods. The palate of H. longicostatum is re-interpreted and suggested to be more similar to that of M. pelikani, especially in the nature of the contact between the pterygoids. Both taxa possess lateral lines, and M. pelikani additionally exhibits branchial plates. However, early and rapid ossification of the postcranial skeleton, including a well-developed pubis and ossified epipodials, suggests that neither taxon metamorphosed nor were they neotenic in the sense of branchiosaurids and salamanders. Morphogenetic patterns in the foot suggest that digit 5 was developmentally delayed and the final digit to ossify in M. pelikani and H. longicostatum. Overall patterns of postcranial ossification may indicate postaxial dominance in limb and digit formation, but also more developmental variation in early tetrapods than has been appreciated. The phylogenetic position and developmental patterns of M. pelikani and H. longicostatum are congruent with the hypothesis that early tetrapods lacked metamorphosis ancestrally and that stem-amniotes exhibited derived features of development, such as rapid and complete ossification of the skeleton, potentially prior to the evolution of the amniotic egg. PMID:26083733

  11. Intra-vaginal Zinc Oxide Tetrapod Nanoparticles as Novel Immunoprotective Agents against Genital Herpes

    PubMed Central

    Antoine, Thessicar E.; Hadigal, Satvik R.; Yakoub, Abraam; Mishra, Yogendra K.; Bhattacharya, Palash; Haddad, Christine; Valyi-Nagy, Tibor; Adelung, Rainer; Prabhakar, Bellur S.; Shukla, Deepak

    2016-01-01

    Virtually all efforts to generate an effective protection against the life-long, recurrent genital infections caused by Herpes simplex virus-2 (HSV-2) have failed. Apart from sexual transmission, the virus can also be transmitted from mothers to neonates, and is a key facilitator of HIV co-acquisition. Here, we uncover a nanoimmunotherapy using specially designed Zinc Oxide Tetrapod Nanoparticles (ZOTEN) with engineered oxygen vacancies. We demonstrate that ZOTEN, when used intravaginally as a microbicide, is an effective suppressor of HSV-2 genital infection in female BALB/c mice. The strong HSV-2 trapping ability of ZOTEN significantly reduced the clinical signs of vaginal infection and effectively decreased animal mortality. In parallel, ZOTEN promoted the presentation of bound HSV-2 virions to mucosal antigen presenting cells, enhancing T cell- mediated and antibody-mediated responses to the infection, and thereby, suppressing a re-infection. We also found that ZOTEN exhibits strong adjuvant-like properties, which is highly comparable to alum, a commonly used adjuvant. Overall, our study provides very first evidence for the protective efficacy of an intravaginal microbicide/vaccine or microbivac platform against primary and secondary female genital herpes infections. PMID:27183601

  12. FoxP2 Expression in a Highly Vocal Teleost Fish with Comparisons to Tetrapods.

    PubMed

    Pengra, Ian G G; Marchaterre, Margaret A; Bass, Andrew H

    2018-04-19

    Motivated by studies of speech deficits in humans, several studies over the past two decades have investigated the potential role of a forkhead domain transcription factor, FoxP2, in the central control of acoustic signaling/vocalization among vertebrates. Comparative neuroanatomical studies that mainly include mammalian and avian species have mapped the distribution of FoxP2 expression in multiple brain regions that imply a greater functional significance beyond vocalization that might be shared broadly across vertebrate lineages. To date, reports for teleost fish have been limited in number and scope to nonvocal species. Here, we map the neuroanatomical distribution of FoxP2 mRNA expression in a highly vocal teleost, the plainfin midshipman (Porichthys notatus). We report an extensive overlap between FoxP2 expression and vocal, auditory, and steroid-signaling systems with robust expression at multiple sites in the telencephalon, the preoptic area, the diencephalon, and the midbrain. Label was far more restricted in the hindbrain though robust in one region of the reticular formation. A comparison with other teleosts and tetrapods suggests an evolutionarily conserved FoxP2 phenotype important to vocal-acoustic and, more broadly, sensorimotor function among vertebrates. © 2018 S. Karger AG, Basel.

  13. Bone strain magnitude is correlated with bone strain rate in tetrapods: implications for models of mechanotransduction

    PubMed Central

    Aiello, B. R.; Iriarte-Diaz, J.; Blob, R. W.; Butcher, M. T.; Carrano, M. T.; Espinoza, N. R.; Main, R. P.; Ross, C. F.

    2015-01-01

    Hypotheses suggest that structural integrity of vertebrate bones is maintained by controlling bone strain magnitude via adaptive modelling in response to mechanical stimuli. Increased tissue-level strain magnitude and rate have both been identified as potent stimuli leading to increased bone formation. Mechanotransduction models hypothesize that osteocytes sense bone deformation by detecting fluid flow-induced drag in the bone's lacunar–canalicular porosity. This model suggests that the osteocyte's intracellular response depends on fluid-flow rate, a product of bone strain rate and gradient, but does not provide a mechanism for detection of strain magnitude. Such a mechanism is necessary for bone modelling to adapt to loads, because strain magnitude is an important determinant of skeletal fracture. Using strain gauge data from the limb bones of amphibians, reptiles, birds and mammals, we identified strong correlations between strain rate and magnitude across clades employing diverse locomotor styles and degrees of rhythmicity. The breadth of our sample suggests that this pattern is likely to be a common feature of tetrapod bone loading. Moreover, finding that bone strain magnitude is encoded in strain rate at the tissue level is consistent with the hypothesis that it might be encoded in fluid-flow rate at the cellular level, facilitating bone adaptation via mechanotransduction. PMID:26063842

  14. Tetrapod-type [Asp1] angiotensin is present in a holostean fish, Amia calva.

    PubMed

    Takei, Y; Itahara, Y; Butler, D G; Watanabe, T X; Oudit, G Y

    1998-05-01

    The renin-angiotensin system has been identified in various vertebrates, from elasmobranchs to mammals. Tetrapod (amphibians to mammals) angiotensin (ANG) has Asp at the N-terminus, but Asp is replaced by Asn in elasmobranch and teleost fish. ANG I has been isolated from incubates of plasma and kidney extracts of the bowfin Amia calva, a holostean fish, using the eel vasopressor activity as an assay system; its sequence was found to be H-Asp-Arg-Val-Tyr-Val-His-Pro-Phe-Asn-Leu-OH after sequence analysis, mass spectrometry, and comparison with the synthetic peptide. This sequence is identical to bullfrog ANG I. [Asn1] ANG I was not detected. Thus the bowfin is the first fish species which contains only [Asp1] ANG I. The bowfin ANG I and II were no more vasopressor than eel peptides in the bowfin, indicating that bowfin ANG II receptors do not distinguish between [Asp1] and [Asn1] peptides. In the rat, bowfin ANG I and rat [Ile5, His9] ANG I have equipressor activities when examined in different animals, but the vasopressor activity of bowfin ANG I decreased following rat ANG I in the same animals, although the activity of rat ANG I was unaffected after bowfin ANG I. The present study directly demonstrates the presence of the renin-angiotensin system in a holostean fish and showed that its ANG II receptors have not yet fully coevolved with the homologous [Asp1] peptide.

  15. Mechanisms of Local Stress Sensing in Multifunctional Polymer Films Using Fluorescent Tetrapod Nanocrystals

    DOE PAGES

    Raja, Shilpa N.; Zherebetskyy, Danylo; Wu, Siva; ...

    2016-07-13

    Nanoscale stress-sensing can be used across fields ranging from detection of incipient cracks in structural mechanics to monitoring forces in biological tissues. We demonstrate how tetrapod quantum dots (tQDs) embedded in block copolymers act as sensors of tensile/compressive stress. Remarkably, tQDs can detect their own composite dispersion and mechanical properties with a switch in optomechanical response when tQDs are in direct contact. Using experimental characterizations, atomistic simulations and finite-element analyses, we show that under tensile stress, densely packed tQDs exhibit a photoluminescence peak shifted to higher energies ("blue-shift") due to volumetric compressive stress in their core; loosely packed tQDs exhibitmore » a peak shifted to lower energies ("red-shift") from tensile stress in the core. The stress shifts result from the tQD's unique branched morphology in which the CdS arms act as antennas that amplify the stress in the CdSe core. Our nanocomposites exhibit excellent cyclability and scalability with no degraded properties of the host polymer. Colloidal tQDs allow sensing in many materials to potentially enable autoresponsive, smart structural nanocomposites that self-predict upcoming fracture.« less

  16. The global distribution of tetrapods reveals a need for targeted reptile conservation.

    PubMed

    Roll, Uri; Feldman, Anat; Novosolov, Maria; Allison, Allen; Bauer, Aaron M; Bernard, Rodolphe; Böhm, Monika; Castro-Herrera, Fernando; Chirio, Laurent; Collen, Ben; Colli, Guarino R; Dabool, Lital; Das, Indraneil; Doan, Tiffany M; Grismer, Lee L; Hoogmoed, Marinus; Itescu, Yuval; Kraus, Fred; LeBreton, Matthew; Lewin, Amir; Martins, Marcio; Maza, Erez; Meirte, Danny; Nagy, Zoltán T; de C Nogueira, Cristiano; Pauwels, Olivier S G; Pincheira-Donoso, Daniel; Powney, Gary D; Sindaco, Roberto; Tallowin, Oliver J S; Torres-Carvajal, Omar; Trape, Jean-François; Vidan, Enav; Uetz, Peter; Wagner, Philipp; Wang, Yuezhao; Orme, C David L; Grenyer, Richard; Meiri, Shai

    2017-11-01

    The distributions of amphibians, birds and mammals have underpinned global and local conservation priorities, and have been fundamental to our understanding of the determinants of global biodiversity. In contrast, the global distributions of reptiles, representing a third of terrestrial vertebrate diversity, have been unavailable. This prevented the incorporation of reptiles into conservation planning and biased our understanding of the underlying processes governing global vertebrate biodiversity. Here, we present and analyse the global distribution of 10,064 reptile species (99% of extant terrestrial species). We show that richness patterns of the other three tetrapod classes are good spatial surrogates for species richness of all reptiles combined and of snakes, but characterize diversity patterns of lizards and turtles poorly. Hotspots of total and endemic lizard richness overlap very little with those of other taxa. Moreover, existing protected areas, sites of biodiversity significance and global conservation schemes represent birds and mammals better than reptiles. We show that additional conservation actions are needed to effectively protect reptiles, particularly lizards and turtles. Adding reptile knowledge to a global complementarity conservation priority scheme identifies many locations that consequently become important. Notably, investing resources in some of the world's arid, grassland and savannah habitats might be necessary to represent all terrestrial vertebrates efficiently.

  17. The axolotl limb blastema: cellular and molecular mechanisms driving blastema formation and limb regeneration in tetrapods

    PubMed Central

    McCusker, Catherine; Bryant, Susan V.

    2015-01-01

    Abstract The axolotl is one of the few tetrapods that are capable of regenerating complicated biological structures, such as complete limbs, throughout adulthood. Upon injury the axolotl generates a population of regeneration‐competent limb progenitor cells known as the blastema, which will grow, establish pattern, and differentiate into the missing limb structures. In this review we focus on the crucial early events that occur during wound healing, the neural−epithelial interactions that drive the formation of the early blastema, and how these mechanisms differ from those of other species that have restricted regenerative potential, such as humans. We also discuss how the presence of cells from the different axes of the limb is required for the continued growth and establishment of pattern in the blastema as described in the polar coordinate model, and how this positional information is reprogrammed in blastema cells during regeneration. Multiple cell types from the mature limb stump contribute to the blastema at different stages of regeneration, and we discuss the contribution of these types to the regenerate with reference to whether they are “pattern‐forming” or “pattern‐following” cells. Lastly, we explain how an engineering approach will help resolve unanswered questions in limb regeneration, with the goal of translating these concepts to developing better human regenerative therapies. PMID:27499868

  18. Olson's Extinction and the latitudinal biodiversity gradient of tetrapods in the Permian

    PubMed Central

    Day, Michael O.; Rubidge, Bruce S.; Fröbisch, Jörg

    2017-01-01

    The terrestrial vertebrate fauna underwent a substantial change in composition between the lower and middle Permian. The lower Permian fauna was characterized by diverse and abundant amphibians and pelycosaurian-grade synapsids. During the middle Permian, a therapsid-dominated fauna, containing a diverse array of parareptiles and a considerably reduced richness of amphibians, replaced this. However, it is debated whether the transition is a genuine event, accompanied by a mass extinction, or whether it is merely an artefact of the shift in sampling from the palaeoequatorial latitudes to the palaeotemperate latitudes. Here we use an up-to-date biostratigraphy and incorporate recent discoveries to thoroughly review the Permian tetrapod fossil record. We suggest that the faunal transition represents a genuine event; the lower Permian temperate faunas are more similar to lower Permian equatorial faunas than middle Permian temperate faunas. The transition was not consistent across latitudes; the turnover occurred more rapidly in Russia, but was delayed in North America. The argument that the mass extinction is an artefact of a latitudinal biodiversity gradient and a shift in sampling localities is rejected: sampling correction demonstrates an inverse latitudinal biodiversity gradient was prevalent during the Permian, with peak diversity in the temperate latitudes. PMID:28381616

  19. Intravaginal Zinc Oxide Tetrapod Nanoparticles as Novel Immunoprotective Agents against Genital Herpes.

    PubMed

    Antoine, Thessicar E; Hadigal, Satvik R; Yakoub, Abraam M; Mishra, Yogendra Kumar; Bhattacharya, Palash; Haddad, Christine; Valyi-Nagy, Tibor; Adelung, Rainer; Prabhakar, Bellur S; Shukla, Deepak

    2016-06-01

    Virtually all efforts to generate an effective protection against the life-long, recurrent genital infections caused by HSV-2 have failed. Apart from sexual transmission, the virus can also be transmitted from mothers to neonates, and it is a key facilitator of HIV coacquisition. In this article, we uncover a nanoimmunotherapy using specially designed zinc oxide tetrapod nanoparticles (ZOTEN) with engineered oxygen vacancies. We demonstrate that ZOTEN, when used intravaginally as a microbicide, is an effective suppressor of HSV-2 genital infection in female BALB/c mice. The strong HSV-2 trapping ability of ZOTEN significantly reduced the clinical signs of vaginal infection and effectively decreased animal mortality. In parallel, ZOTEN promoted the presentation of bound HSV-2 virions to mucosal APCs, enhancing T cell-mediated and Ab-mediated responses to the infection, and thereby suppressing a reinfection. We also found that ZOTEN exhibits strong adjuvant-like properties, which is highly comparable with alum, a commonly used adjuvant. Overall, to our knowledge, our study provides the very first evidence for the protective efficacy of an intravaginal microbicide/vaccine or microbivac platform against primary and secondary female genital herpes infections. Copyright © 2016 by The American Association of Immunologists, Inc.

  20. Acceptors in ZnO

    DOE PAGES

    Mccluskey, Matthew D.; Corolewski, Caleb; Lv, Jinpeng; ...

    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 shows that these point defects have acceptor levels 3.2, 1.5, 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 MoO2 contacts, the electrical resistivity of ZnO:Li was measured and showed behavior consistent with bulk hole conduction for temperatures above 400 K. A photoluminescence peakmore » in ZnO nanocrystals has been attributed to an acceptor, which may involve a zinc vacancy. High field (W-band) electron paramagnetic resonance measurements on the nanocrystals revealed an axial center with g = 2.0033 and g = 2.0075, along with an isotropic center at g = 2.0053.« less

  1. Engineered ZnO nanowire arrays using different nanopatterning techniques

    NASA Astrophysics Data System (ADS)

    Volk, János; Szabó, Zoltán; Erdélyi, Róbert; Khánh, Nguyen Q.

    2012-02-01

    The impact of various masking patterns and template layers on the wet chemically grown vertical ZnO nanowire arrays was investigated. The nanowires/nanorods were seeded at nucleation windows which were patterned in a mask layer using various techniques such as electron beam lithography, nanosphere photolithography, and atomic force microscope type nanolithography. The compared ZnO templates included single crystals, epitaxial layer, and textured polycrystalline films. Scanning electron microscopy revealed that the alignment and crystal orientation of the nanowires were dictated by the underlying seed layer, while their geometry can be tuned by the parameters of the certain nanopatterning technique and of the wet chemical process. The comparison of the alternative nanolithography techniques showed that using direct writing methods the diameter of the ordered ZnO nanowires can be as low as 30-40 nm at a density of 100- 1000 NW/μm2 in a very limited area (10 μm2-1 mm2). Nanosphere photolithography assisted growth, on the other hand, favors thicker nanopillars (~400 nm) and enables large-area, low-cost patterning (1-100 cm2). These alternative lowtemperature fabrication routes can be used for different novel optoelectronic devices, such as nanorod based ultraviolet photodiode, light emitting device, and waveguide laser.

  2. Acceptors in bulk and nanoscale ZnO

    NASA Astrophysics Data System (ADS)

    McCluskey, M. D.

    2012-02-01

    Zinc oxide (ZnO) is a semiconductor that emits bright UV light, with little wasted heat. This intrinsic feature makes it a promising material for energy-efficient white lighting, nano-lasers, and other optical applications. For devices to be competitive, however, it is necessary to develop reliable p-type doping. Although substitutional nitrogen has been considered as a potential p-type dopant for ZnO, theoretical and experimental work indicates that nitrogen is a deep acceptor and will not lead to p-type conductivity. This talk will highlight recent experiments on ZnO:N at low temperatures. A red/near-IR photoluminescence (PL) band is correlated with the presence of deep nitrogen acceptors. PL excitation (PLE) measurements show an absorption threshold of 2.26 eV, in good agreement with theory. Magnetic resonance experiments provide further evidence for this assignment. The results of these studies seem to rule out group-V elements as shallow acceptors in ZnO, contradicting numerous reports in the literature. If these acceptors do not work as advertised, is there a viable alternative? Optical studies on ZnO nanocrystals show some intriguing leads. At liquid-helium temperatures, a series of sharp IR absorption peaks arise from an unknown acceptor impurity. The data are consistent with a hydrogenic acceptor 0.46 eV above the valence band edge. While this binding energy is still too deep for many practical applications, it represents a significant improvement over the ˜ 1.3 eV binding energy for nitrogen acceptors. Nanocrystals present another twist. Due to their high surface-to-volume ratio, surface states are especially important. Specifically, electron-hole recombination at the surface give rises to a red luminescence band. From our PL and IR experiments, we have developed a ``unified'' model that attempts to explain acceptor and surface states in ZnO nanocrystals. This model could provide a useful framework for designing future nanoscale ZnO devices.

  3. The epitaxial growth of wurtzite ZnO films on LiNbO 3 (0 0 0 1) substrates

    NASA Astrophysics Data System (ADS)

    Yin, J.; Liu, Z. G.; Liu, H.; Wang, X. S.; Zhu, T.; Liu, J. M.

    2000-12-01

    ZnO epitaxial films were deposited on LiNbO 3 (0 0 0 1) substrates by pulsed laser deposition. The smaller lattice misfit (-8.5%) between ZnO along <1 0 1¯ 0>- direction and LiNbO 3 (0 0 0 1) along <1 1 2¯ 0>- direction, as compared with that in the case of normally used sapphire (0 0 0 1) substrates, favored the epitaxial growth of ZnO films. The transmittance spectra of ZnO films deposited in vacuum after annealed in pure oxygen show a sharp absorption edge at 375.6 nm (E g=3.31 eV) .

  4. Ferroelectric enhancement in heterostructured ZnO /BiFeO3-PbTiO3 film

    NASA Astrophysics Data System (ADS)

    Yu, Shengwen; Chen, Rui; Zhang, Guanjun; Cheng, Jinrong; Meng, Zhongyan

    2006-11-01

    The authors have prepared heterostructured ZnO /BiFeO3-PbTiO3 (BFO-PT) composite film and BFO-PT film on Pt /Ti/SiO2/Si substrates by pulsed-laser deposition. The structure and morphologies of the films were characterized by x-ray diffraction (XRD) and scanning electron microscope. XRD results show that both films are perovskite structured last with different orientations. The leakage current density in the ZnO /BFO-PT film was found to be nearly two orders of magnitude lower. This could be due to the introduced ZnO layer behaving as a Schottky barrier between the BFO-PT film and top electrodes. The dramatic ferroelectric enhancement in ZnO /BFO-PT film is mostly ascribed to the improved insulation.

  5. Ultraviolet electroluminescence from hetero p-n junction between a single ZnO microsphere and p-GaN thin film.

    PubMed

    Tetsuyama, Norihiro; Fusazaki, Koshi; Mizokami, Yasuaki; Shimogaki, Tetsuya; Higashihata, Mitsuhiro; Nakamura, Daisuke; Okada, Tatsuo

    2014-04-21

    We report ultraviolet electroluminescence from a hetero p-n junction between a single ZnO microsphere and p-GaN thin film. ZnO microspheres, which have high crystalline quality, have been synthesized by ablating a ZnO sintered target. It was found that synthesized ZnO microspheres had a high-optical property and exhibit the laser action in the whispering gallery mode under pulsed optical pumping. A hetero p-n junction was formed between the single ZnO microsphere/ p-GaN thin film, and a good rectifying property with a turn-on voltage of approximately 6 V was observed in I-V characteristic across the junction. Ultraviolet and visible electroluminescence were observed under forward bias.

  6. Hysteretic Characteristics of Pulsed Laser Deposited 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3/ZnO Bilayers.

    PubMed

    Silva, J P B; Wang, J; Koster, G; Rijnders, G; Negrea, R F; Ghica, C; Sekhar, K C; Moreira, J Agostinho; Gomes, M J M

    2018-05-02

    In the present work, we study the hysteretic behavior in the electric-field-dependent capacitance and the current characteristics of 0.5Ba(Zr 0.2 Ti 0.8 )O 3 -0.5(Ba 0.7 Ca 0.3 )TiO 3 (BCZT)/ZnO bilayers deposited on 0.7 wt % Nb-doped (001)-SrTiO 3 (Nb:STO) substrates in a metal-ferroelectric-semiconductor (MFS) configuration. The X-ray diffraction measurements show that the BCZT and ZnO layers are highly oriented along the c-axis and have a single perovskite and wurtzite phases, respectively, whereas high-resolution transmission electron microscopy revealed very sharp Nb:STO/BCZT/ZnO interfaces. The capacitance-electric field ( C- E) characteristics of the bilayers exhibit a memory window of 47 kV/cm and a capacitance decrease of 22%, at a negative bias. The later result is explained by the formation of a depletion region in the ZnO layer. Moreover, an unusual resistive switching (RS) behavior is observed in the BCZT films, where the RS ratio can be 500 times enhanced in the BCZT/ZnO bilayers. The RS enhancement can be understood by the barrier potential profile modulation at the depletion region, in the BCZT/ZnO junction, via ferroelectric polarization switching of the BCZT layer. This work builds a bridge between the hysteretic behavior observed either in the C- E and current-electric field characteristics on a MFS structure.

  7. The Lineage-Specific Evolution of Aquaporin Gene Clusters Facilitated Tetrapod Terrestrial Adaptation

    PubMed Central

    Finn, Roderick Nigel; Chauvigné, François; Hlidberg, Jón Baldur; Cutler, Christopher P.; Cerdà, Joan

    2014-01-01

    A major physiological barrier for aquatic organisms adapting to terrestrial life is dessication in the aerial environment. This barrier was nevertheless overcome by the Devonian ancestors of extant Tetrapoda, but the origin of specific molecular mechanisms that solved this water problem remains largely unknown. Here we show that an ancient aquaporin gene cluster evolved specifically in the sarcopterygian lineage, and subsequently diverged into paralogous forms of AQP2, -5, or -6 to mediate water conservation in extant Tetrapoda. To determine the origin of these apomorphic genomic traits, we combined aquaporin sequencing from jawless and jawed vertebrates with broad taxon assembly of >2,000 transcripts amongst 131 deuterostome genomes and developed a model based upon Bayesian inference that traces their convergent roots to stem subfamilies in basal Metazoa and Prokaryota. This approach uncovered an unexpected diversity of aquaporins in every lineage investigated, and revealed that the vertebrate superfamily consists of 17 classes of aquaporins (Aqp0 - Aqp16). The oldest orthologs associated with water conservation in modern Tetrapoda are traced to a cluster of three aqp2-like genes in Actinistia that likely arose >500 Ma through duplication of an aqp0-like gene present in a jawless ancestor. In sea lamprey, we show that aqp0 first arose in a protocluster comprised of a novel aqp14 paralog and a fused aqp01 gene. To corroborate these findings, we conducted phylogenetic analyses of five syntenic nuclear receptor subfamilies, which, together with observations of extensive genome rearrangements, support the coincident loss of ancestral aqp2-like orthologs in Actinopterygii. We thus conclude that the divergence of sarcopterygian-specific aquaporin gene clusters was permissive for the evolution of water conservation mechanisms that facilitated tetrapod terrestrial adaptation. PMID:25426855

  8. Deep ancestry of mammalian X chromosome revealed by comparison with the basal tetrapod Xenopus tropicalis.

    PubMed

    Mácha, Jaroslav; Teichmanová, Radka; Sater, Amy K; Wells, Dan E; Tlapáková, Tereza; Zimmerman, Lyle B; Krylov, Vladimír

    2012-07-16

    The X and Y sex chromosomes are conspicuous features of placental mammal genomes. Mammalian sex chromosomes arose from an ordinary pair of autosomes after the proto-Y acquired a male-determining gene and degenerated due to suppression of X-Y recombination. Analysis of earlier steps in X chromosome evolution has been hampered by the long interval between the origins of teleost and amniote lineages as well as scarcity of X chromosome orthologs in incomplete avian genome assemblies. This study clarifies the genesis and remodelling of the Eutherian X chromosome by using a combination of sequence analysis, meiotic map information, and cytogenetic localization to compare amniote genome organization with that of the amphibian Xenopus tropicalis. Nearly all orthologs of human X genes localize to X. tropicalis chromosomes 2 and 8, consistent with an ancestral X-conserved region and a single X-added region precursor. This finding contradicts a previous hypothesis of three evolutionary strata in this region. Homologies between human, opossum, chicken and frog chromosomes suggest a single X-added region predecessor in therian mammals, corresponding to opossum chromosomes 4 and 7. A more ancient X-added ancestral region, currently extant as a major part of chicken chromosome 1, is likely to have been present in the progenitor of synapsids and sauropsids. Analysis of X chromosome gene content emphasizes conservation of single protein coding genes and the role of tandem arrays in formation of novel genes. Chromosomal regions orthologous to Therian X chromosomes have been located in the genome of the frog X. tropicalis. These X chromosome ancestral components experienced a series of fusion and breakage events to give rise to avian autosomes and mammalian sex chromosomes. The early branching tetrapod X. tropicalis' simple diploid genome and robust synteny to amniotes greatly enhances studies of vertebrate chromosome evolution.

  9. Deep ancestry of mammalian X chromosome revealed by comparison with the basal tetrapod Xenopus tropicalis

    PubMed Central

    2012-01-01

    Background The X and Y sex chromosomes are conspicuous features of placental mammal genomes. Mammalian sex chromosomes arose from an ordinary pair of autosomes after the proto-Y acquired a male-determining gene and degenerated due to suppression of X-Y recombination. Analysis of earlier steps in X chromosome evolution has been hampered by the long interval between the origins of teleost and amniote lineages as well as scarcity of X chromosome orthologs in incomplete avian genome assemblies. Results This study clarifies the genesis and remodelling of the Eutherian X chromosome by using a combination of sequence analysis, meiotic map information, and cytogenetic localization to compare amniote genome organization with that of the amphibian Xenopus tropicalis. Nearly all orthologs of human X genes localize to X. tropicalis chromosomes 2 and 8, consistent with an ancestral X-conserved region and a single X-added region precursor. This finding contradicts a previous hypothesis of three evolutionary strata in this region. Homologies between human, opossum, chicken and frog chromosomes suggest a single X-added region predecessor in therian mammals, corresponding to opossum chromosomes 4 and 7. A more ancient X-added ancestral region, currently extant as a major part of chicken chromosome 1, is likely to have been present in the progenitor of synapsids and sauropsids. Analysis of X chromosome gene content emphasizes conservation of single protein coding genes and the role of tandem arrays in formation of novel genes. Conclusions Chromosomal regions orthologous to Therian X chromosomes have been located in the genome of the frog X. tropicalis. These X chromosome ancestral components experienced a series of fusion and breakage events to give rise to avian autosomes and mammalian sex chromosomes. The early branching tetrapod X. tropicalis’ simple diploid genome and robust synteny to amniotes greatly enhances studies of vertebrate chromosome evolution. PMID:22800176

  10. Genome size and metabolic intensity in tetrapods: a tale of two lines

    PubMed Central

    Vinogradov, Alexander E; Anatskaya, Olga V

    2005-01-01

    We show the negative link between genome size and metabolic intensity in tetrapods, using the heart index (relative heart mass) as a unified indicator of metabolic intensity in poikilothermal and homeothermal animals. We found two separate regression lines of heart index on genome size for reptiles–birds and amphibians–mammals (the slope of regression is steeper in reptiles–birds). We also show a negative correlation between GC content and nucleosome formation potential in vertebrate DNA, and, consistent with this relationship, a positive correlation between genome GC content and nuclear size (independent of genome size). It is known that there are two separate regression lines of genome GC content on genome size for reptiles–birds and amphibians–mammals: reptiles–birds have the relatively higher GC content (for their genome sizes) compared to amphibians–mammals. Our results suggest uniting all these data into one concept. The slope of negative regression between GC content and nucleosome formation potential is steeper in exons than in non-coding DNA (where nucleosome formation potential is generally higher), which indicates a special role of non-coding DNA for orderly chromatin organization. The chromatin condensation and nuclear size are supposed to be key parameters that accommodate the effects of both genome size and GC content and connect them with metabolic intensity. Our data suggest that the reptilian–birds clade evolved special relationships among these parameters, whereas mammals preserved the amphibian-like relationships. Surprisingly, mammals, although acquiring a more complex general organization, seem to retain certain genome-related properties that are similar to amphibians. At the same time, the slope of regression between nucleosome formation potential and GC content is steeper in poikilothermal than in homeothermal genomes, which suggests that mammals and birds acquired certain common features of genomic organization. PMID:16519230

  11. An examination of the impact of Olson’s extinction on tetrapods from Texas

    PubMed Central

    2018-01-01

    It has been suggested that a transition between a pelycosaurian-grade synapsid dominated fauna of the Cisuralian (early Permian) and the therapsid dominated fauna of the Guadalupian (middle Permian) was accompanied by, and possibly driven by, a mass extinction dubbed Olson’s Extinction. However, this interpretation of the record has recently been criticised as being a result of inappropriate time-binning strategies: calculating species richness within international stages or substages combines extinctions occurring throughout the late Kungurian stage into a single event. To address this criticism, I examine the best record available for the time of the extinction, the tetrapod-bearing formations of Texas, at a finer stratigraphic scale than those previously employed. Species richness is calculated using four different time-binning schemes: the traditional Land Vertebrate Faunachrons (LVFs); a re-definition of the LVFs using constrained cluster analysis; individual formations treated as time bins; and a stochastic approach assigning specimens to half-million-year bins. Diversity is calculated at the genus and species level, both with and without subsampling, and extinction rates are also inferred. Under all time-binning schemes, both at the genus and species level, a substantial drop in diversity occurs during the Redtankian LVF. Extinction rates are raised above background rates throughout this time, but the biggest peak occurs in the Choza Formation (uppermost Redtankian), coinciding with the disappearance from the fossil record of several of amphibian clades. This study, carried out at a finer stratigraphic scale than previous examinations, indicates that Olson’s Extinction is not an artefact of the method used to bin data by time in previous analyses.

  12. Near band edge photoluminescence of ZnO nanowires: Optimization via surface engineering

    NASA Astrophysics Data System (ADS)

    Yan, Danhua; Zhang, Wenrui; Cen, Jiajie; Stavitski, Eli; Sadowski, Jerzy T.; Vescovo, Elio; Walter, Andrew; Attenkofer, Klaus; Stacchiola, Darío J.; Liu, Mingzhao

    2017-12-01

    Zinc oxide (ZnO) nanowire arrays have potential applications for various devices such as ultra-violet light emitting diodes and lasers, where photoluminescence of intense near band edge emission without defect emissions is usually desired. Here, we demonstrate, counter-intuitively, that the near band edge emission may become dominant by introducing certain surface defects to ZnO nanowires via surface engineering. Specifically, near band edge emission (NBE) is effectively enhanced after a low pressure O2 plasma treatment that sputters off surface oxygen species to produce a reduced and oxygen vacancy-rich surface. The effect is attributed to the lowered surface valence band maximum of the reduced ZnO surface that creates an accumulative band bending, which screens the photo-generated minority carriers (holes) from reaching or being trapped by the surface defects.

  13. Near band edge photoluminescence of ZnO nanowires: Optimization via surface engineering

    SciT

    Yan, Danhua; Zhang, Wenrui; Cen, Jiajie

    Zinc oxide (ZnO) nanowire arrays have potential applications for various devices including ultra-violet light emitting diodes and lasers, where photoluminescence of intense near band edge emission without defect emissions is usually desired. Here, we demonstrate, counter-intuitively, that the near band edge emission may become dominant by introducing certain surface defects to ZnO nanowires via surface engineering. Specifically, near band edge emission (NBE) is effectively enhanced after a low pressure O 2 plasma treatment that sputters off surface oxygen species to produce a reduced and oxygen vacancy-rich surface. The effect is attributed to the lowered surface valence band maximum of themore » reduced ZnO surface that creates an accumulative band bending, which screens the photo-generated minority carriers (holes) from reaching or being trapped by the surface defects.« less

  14. Near band edge photoluminescence of ZnO nanowires: Optimization via surface engineering

    DOE PAGES

    Yan, Danhua; Zhang, Wenrui; Cen, Jiajie; ...

    2017-12-04

    Zinc oxide (ZnO) nanowire arrays have potential applications for various devices including ultra-violet light emitting diodes and lasers, where photoluminescence of intense near band edge emission without defect emissions is usually desired. Here, we demonstrate, counter-intuitively, that the near band edge emission may become dominant by introducing certain surface defects to ZnO nanowires via surface engineering. Specifically, near band edge emission (NBE) is effectively enhanced after a low pressure O 2 plasma treatment that sputters off surface oxygen species to produce a reduced and oxygen vacancy-rich surface. The effect is attributed to the lowered surface valence band maximum of themore » reduced ZnO surface that creates an accumulative band bending, which screens the photo-generated minority carriers (holes) from reaching or being trapped by the surface defects.« less

  15. C-Axis-Oriented Hydroxyapatite Film Grown Using ZnO Buffer Layer

    NASA Astrophysics Data System (ADS)

    Sakoishi, Yasuhiro; Iguchi, Ryo; Nishikawa, Hiroaki; Hontsu, Shigeki; Hayami, Takashi; Kusunoki, Masanobu

    2013-11-01

    A method of fabricating c-axis-oriented hydroxyapatite film on a quartz crystal microbalance (QCM) sensor was investigated. ZnO was used as a template to obtain a hexagonal hydroxyapatite crystal of uniaxial orientation. The ZnO was grown as a c-axis film on a Au/quartz with the surface structure of a QCM sensor. Under optimized conditions, hydroxyapatite was deposited by pulsed laser deposition. X-ray diffraction showed the hydroxyapatite film to be oriented along the c-axis. Because Au and ZnO are applied to many devices, the anisotropic properties of hydroxyapatite may be incorporated into these devices as well as QCM sensors.

  16. Vertical resistivity in nanocrystalline ZnO and amorphous InGaZnO

    NASA Astrophysics Data System (ADS)

    McCandless, Jonathan P.; Leedy, Kevin D.; Schuette, Michael L.

    2018-02-01

    The goal is to gain additional insight into physical mechanisms and the role of microstructure on the formation of ohmic contacts and the reduction of contact resistance. We have measured a decreasing film resistivity in the vertical direction with increasing thickness of pulsed-laser deposited ZnO and IGZO. As the ZnO thickness increases from 122 nm to 441 nm, a reduction in resistivity from 3.29 Ω-cm to 0.364 Ω-cm occurred. The IGZO resistivity changes from 72.4 Ω-cm to 0.642 Ω-cm as the film is increased from 108nm to 219 nm. In the ZnO, the size of nanocolumnar grains increase with thickness resulting in fewer grain boundaries, and in the amorphous IGZO, the thicker region exhibits tunnel-like artifacts which may contribute to the reduced resistivity.

  17. Anisotropic magnetism and spin-dependent transport in Co nanoparticle embedded ZnO thin films

    NASA Astrophysics Data System (ADS)

    Li, D. Y.; Zeng, Y. J.; Pereira, L. M. C.; Batuk, D.; Hadermann, J.; Zhang, Y. Z.; Ye, Z. Z.; Temst, K.; Vantomme, A.; Van Bael, M. J.; Van Haesendonck, C.

    2013-07-01

    Oriented Co nanoparticles were obtained by Co ion implantation in crystalline ZnO thin films grown by pulsed laser deposition. Transmission electron microscopy revealed the presence of elliptically shaped Co precipitates with nanometer size, which are embedded in the ZnO thin films, resulting in anisotropic magnetic behavior. The low-temperature resistance of the Co-implanted ZnO thin films follows the Efros-Shklovskii type variable-range-hopping. Large negative magnetoresistance (MR) exceeding 10% is observed in a magnetic field of 1 T at 2.5 K and the negative MR survives up to 250 K (0.3%). The negative MR reveals hysteresis as well as anisotropy that correlate well with the magnetic properties, clearly demonstrating the presence of spin-dependent transport.

  18. Role of Ni doping on transport properties of ZnO thin films

    SciT

    Dar, Tanveer Ahmad, E-mail: tanveerphysics@gmail.com; Agrawal, Arpana; Sen, Pratima

    2015-06-24

    Nickel doped (Ni=0.05) and undoped Zinc Oxide (ZnO) thin films have been prepared by Pulsed laser deposition (PLD) technique. The structural analysis of the films was done by X-ray diffraction (XRD) studies which reveal absence of any secondary phase in the prepared samples. UV transmission spectra show that Ni doping reduces the transparency of the films. X-ray Photoelectron spectroscopy (XPS) also shows the presence of metallic Ni along with +2 oxidation state in the sample. Low temperature magneto transport properties of the ZnO and NiZnO films are also discussed in view of Khosla fisher model. Ni doping in ZnO resultsmore » in decrease in magnitude of negative MR.« less

  19. A carapace-like bony 'body tube' in an early triassic marine reptile and the onset of marine tetrapod predation.

    PubMed

    Chen, Xiao-hong; Motani, Ryosuke; Cheng, Long; Jiang, Da-yong; Rieppel, Olivier

    2014-01-01

    Parahupehsuchus longus is a new species of marine reptile from the Lower Triassic of Yuan'an County, Hubei Province, China. It is unique among vertebrates for having a body wall that is completely surrounded by a bony tube, about 50 cm long and 6.5 cm deep, comprising overlapping ribs and gastralia. This tube and bony ossicles on the back are best interpreted as anti-predatory features, suggesting that there was predation pressure upon marine tetrapods in the Early Triassic. There is at least one sauropterygian that is sufficiently large to feed on Parahupehsuchus in the Nanzhang-Yuan'an fauna, together with six more species of potential prey marine reptiles with various degrees of body protection. Modern predators of marine tetrapods belong to the highest trophic levels in the marine ecosystem but such predators did not always exist through geologic time. The indication of marine-tetrapod feeding in the Nanzhang-Yuan'an fauna suggests that such a trophic level emerged for the first time in the Early Triassic. The recovery from the end-Permian extinction probably proceeded faster than traditionally thought for marine predators. Parahupehsuchus has superficially turtle-like features, namely expanded ribs without intercostal space, very short transverse processes, and a dorsal outgrowth from the neural spine. However, these features are structurally different from their turtle counterparts. Phylogeny suggests that they are convergent with the condition in turtles, which has a fundamentally different body plan that involves the folding of the body wall. Expanded ribs without intercostal space evolved at least twice and probably even more among reptiles.

  20. Interesting electrochemical properties of novel three-dimensional Ag3PO4 tetrapods as a new super capacitor electrode material

    NASA Astrophysics Data System (ADS)

    Li, Shouguang; Teng, Fei; Chen, Mindong; Li, Na; Hua, Xia; Wang, Kai; Li, Min

    2014-05-01

    The novel three-dimensional (3D) silver phosphate tetrapods (TA) are synthesized and employed as a super capacitor electrode material. The electrochemical properties are investigated by cyclic voltammetry (CV), chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS). It is interesting that compared with irregular silver phosphate particles (IA), TA shows a higher capacitance (250 vs. 160 F g-1), and a higher coulombic efficiency (80% vs. 74%), which is mainly ascribed to the 3D microstructure and its high conductivity. To the best of our knowledge, this is the first report on silver phosphate as a super capacitor material.

  1. Rapid green synthesis of ZnO nanoparticles using a hydroelectric cell without an electrolyte

    NASA Astrophysics Data System (ADS)

    Shah, Jyoti; Kumar Kotnala, Ravinder

    2017-09-01

    In this study, zinc oxide (ZnO) nanoparticles were synthesized using a novel environmentally friendly hydroelectric cell without an electrolyte or external current source. The hydroelectric cell comprised a nanoporous Li substituted magnesium ferrite pellet in contact with two electrodes, with zinc as the anode and silver as an inert cathode. The surface unsaturated cations and oxygen vacancies in the nanoporous ferrite dissociated water molecules into hydronium and hydroxide ions when the hydroelectric cell was dipped into deionized water. Hydroxide ions migrated toward the zinc electrode to form zinc hydroxide and the hydronium ions were evolved as H2 gas at the silver electrode. The zinc hydroxide collected as anode mud was converted into ZnO nanoparticles by heating at 250 °C. Structural analysis using Raman spectroscopy indicated the good crystallinity of the ZnO nanoparticles according to the presence of a high intensity E2-(high) mode. The nanoparticle size distribution was 5-20 nm according to high resolution transmission electron microscopy. An indirect band gap of 2.75 eV was determined based on the Tauc plot, which indicated the existence of an interstitial cation level in ZnO. Near band edge and blue emissions were detected in photoluminescence spectral studies. The blue emissions obtained from the ZnO nanoparticles could potentially have applications in blue lasers and LEDs. The ZnO nanoparticles synthesized using this method had a high dielectric constant value of 5 at a frequency of 1 MHz, which could be useful for fabricating nano-oscillators. This facile, clean, and cost-effective method obtained a significant yield of 0.017 g for ZnO nanoparticles without applying an external current source.

  2. Influence of ZnO nanostructures in liquid crystal interfaces for bistable switching applications

    NASA Astrophysics Data System (ADS)

    Pal, Kaushik; Zhan, Bihong; Madhu Mohan, M. L. N.; Schirhagl, Romana; Wang, Guoping

    2015-12-01

    The controlled fabrication of nanometer-scale objects is without doubt one of the central issues in current science and technology. In this article, we exhibit a simple, one-step bench top synthesis of zinc oxide nano-tetrapods and nano-spheres which were tailored by the facial growth of nano-wires (diameter ≈ 24 nm; length ≈ 118 nm) and nano-cubes (≈395 nm edge) to nano-sphere (diameter ≈ 585 nm) appeaded. The possibilities of inexpensive, simple solvo-chemical synthesis of nanostructures were considered. In this article, a successful attempt has been made that ZnO nano-structures dispersed on well aligned hydrogen bonded liquid crystals (HBLC) comprising azelaic acid (AC) with p-n-alkyloxy benzoic acid (nBAO) by varying the respective alkyloxy carbon number (n = 5). The dispersion of nanomaterials with HBLC is an effective route to enhance the existing functionalities. A series of these composite materials were analyzed by polarizing optical microscope's electro-optical switching. An interesting feature of AC + nBAO is the inducement of tilted smectic G phase with increasing carbon chain length. Phase diagrams of the above hybrid ZnO nanomaterial influenced LC complex and pure LC were constructed and compared. The switching times, the contrast ratio and spontaneous polarization of the nanostructures-HBLC composite film were carried out by systematic investigation. The sample preparation parameters, such as the curing time and curing intensity were optimized. The critical applied voltage to achieve the switching bi-stability of our device is only 4.5 V, which is approximately twice its threshold voltage for Freedericksz transition. This performance puts the hybrid structure at the top level in the state of the art in application oriented research in optics of liquid crystalline composite materials.

  3. Development and validation of TOF-SIMS and CLSM imaging method for cytotoxicity study of ZnO nanoparticles in HaCaT cells.

    PubMed

    Lee, Pei-Ling; Chen, Bo-Chia; Gollavelli, Ganesh; Shen, Sin-Yu; Yin, Yu-Sheng; Lei, Shiu-Ling; Jhang, Cian-Ling; Lee, Woan-Ruoh; Ling, Yong-Chien

    2014-07-30

    Zinc oxide nanoparticles (ZnO NPs) exhibit novel physiochemical properties and have found increasing use in sunscreen products and cosmetics. The potential toxicity is of increasing concern due to their close association with human skin. A time-of-flight secondary ion mass spectrometry (TOF-SIMS) and confocal laser scanning microscopy (CLSM) imaging method was developed and validated for rapid and sensitive cytotoxicity study of ZnO NPs using human skin equivalent HaCaT cells as a model system. Assorted material, chemical, and toxicological analysis methods were used to confirm their shape, size, crystalline structure, and aggregation properties as well as dissolution behavior and effect on HaCaT cell viability in the presence of various concentrations of ZnO NPs in aqueous media. Comparative and correlative analyses of aforementioned results with TOF-SIMS and CLSM imaging results exhibit reasonable and acceptable outcome. A marked drop in survival rate was observed with 50μg/ml ZnO NPs. The CLSM images reveal the absorption and localization of ZnO NPs in cytoplasm and nuclei. The TOF-SIMS images demonstrate elevated levels of intracellular ZnO concentration and associated Zn concentration-dependent (40)Ca/(39)K ratio, presumably caused by the dissolution behavior of ZnO NPs. Additional validation by using stable isotope-labeled (68)ZnO NPs as tracers under the same experimental conditions yields similar cytotoxicity effect. The imaging results demonstrate spatially-resolved cytotoxicity relationship between intracellular ZnO NPs, (40)Ca/(39)K ratio, phosphocholine fragments, and glutathione fragments. The trend of change in TOF-SIMS spectra and images of ZnO NPs treated HaCaT cells demonstrate the possible mode of actions by ZnO NP involves cell membrane disruption, cytotoxic response, and ROS mediated apoptosis. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Single Mode ZnO Whispering-Gallery Submicron Cavity and Graphene Improved Lasing Performance.

    PubMed

    Li, Jitao; Lin, Yi; Lu, Junfeng; Xu, Chunxiang; Wang, Yueyue; Shi, Zengliang; Dai, Jun

    2015-07-28

    Single-mode ultraviolet (UV) laser of ZnO is still in challenge so far, although it has been paid great attention along the past decades. In this work, single-mode lasing resonance was realized in a submicron-sized ZnO rod based on serially varying the dimension of the whispering-gallery mode (WGM) cavities. The lasing performance, such as the lasing quality factor (Q) and the lasing intensity, was remarkably improved by facilely covering monolayer graphene on the ZnO submicron-rod. The mode structure evolution from multimodes to single-mode was investigated systematically based on the total internal-wall reflection of the ZnO microcavities. Graphene-induced optical field confinement and lasing emission enhancement were revealed, indicating an energy coupling between graphene SP and ZnO exciton emission. This result demonstrated the response of graphene in the UV wavelength region and extended its potential applications besides many previous reports on the multifunctional graphene/semiconductor hybrid materials and devices in advanced electronics and optoelectronics areas.

  5. One-dimensional ZnO nanostructures.

    PubMed

    Jayadevan, K P; Tseng, T Y

    2012-06-01

    The wide-gap semiconductor ZnO with nanostructures such as nanoparticle, nanorod, nanowire, nanobelt, nanotube has high potential for a variety of applications. This article reviews the fundamentals of one-dimensional ZnO nanostructures, including processing, structure, property, application and their processing-microstructure-property correlation. Various fabrication methods of the ZnO nanostructures including vapor-liquid-solid process, vapor-solid growth, solution growth, solvothermal growth, template-assisted growth and self-assembly are introduced. The characterization and properties of the ZnO nanostructures are described. The possible applications of these nanostructures are also discussed.

  6. Stretchable Random Lasers with Tunable Coherent Loops.

    PubMed

    Sun, Tzu-Min; Wang, Cih-Su; Liao, Chi-Shiun; Lin, Shih-Yao; Perumal, Packiyaraj; Chiang, Chia-Wei; Chen, Yang-Fang

    2015-12-22

    Stretchability represents a key feature for the emerging world of realistic applications in areas, including wearable gadgets, health monitors, and robotic skins. Many optical and electronic technologies that can respond to large strain deformations have been developed. Laser plays a very important role in our daily life since it was discovered, which is highly desirable for the development of stretchable devices. Herein, stretchable random lasers with tunable coherent loops are designed, fabricated, and demonstrated. To illustrate our working principle, the stretchable random laser is made possible by transferring unique ZnO nanobrushes on top of polydimethylsiloxane (PDMS) elastomer substrate. Apart from the traditional gain material of ZnO nanorods, ZnO nanobrushes were used as optical gain materials so they can serve as scattering centers and provide the Fabry-Perot cavity to enhance laser action. The stretchable PDMS substrate gives the degree of freedom to mechanically tune the coherent loops of the random laser action by changing the density of ZnO nanobrushes. It is found that the number of laser modes increases with increasing external strain applied on the PDMS substrate due to the enhanced possibility for the formation of coherent loops. The device can be stretched by up to 30% strain and subjected to more than 100 cycles without loss in laser action. The result shows a major advance for the further development of man-made smart stretchable devices.

  7. Fitting unanchored puzzle pieces in the skeleton: appropriate 3D scapular positions for the quadrupedal support in tetrapods.

    PubMed

    Fujiwara, Shin-Ichi

    2018-05-01

    Deducing the scapular positions of extinct tetrapod skeletons remains difficult, because the scapulae and rib cage are connected with each other not directly by skeletal joint, but by thoracic muscles. In extant non-testudine quadrupedal tetrapods, the top positions of the scapulae/suprascapulae occur at the anterior portion of the rib cage, above the vertebral column and near the median plane. The adequacy of this position was tested using three-dimensional mechanical models of Felis, Rattus and Chamaeleo that assumed stances on a forelimb on a single side and the hindlimbs. The net moment about the acetabulum generated by the gravity force and the contractive forces of the anti-gravity thoracic muscles, and the resistance of the rib to vertical compression between the downward gravity and upward lifting force from the anti-gravity thoracic muscle depend on the scapular position. The scapular position common among quadrupeds corresponds to the place at which the roll and yaw moments of the uplifted portion of the body are negligible, where the pitch moment is large enough to lift the body, and above the ribs having high strength against vertical compression. These relationships between scapular position and rib cage morphology should allow reliable reconstruction of limb postures of extinct taxa. © 2018 Anatomical Society.

  8. Using shape to turn off blinking for two-colour multiexciton emission in CdSe/CdS tetrapods

    NASA Astrophysics Data System (ADS)

    Mishra, Nimai; Orfield, Noah J.; Wang, Feng; Hu, Zhongjian; Krishnamurthy, Sachidananda; Malko, Anton V.; Casson, Joanna L.; Htoon, Han; Sykora, Milan; Hollingsworth, Jennifer A.

    2017-05-01

    Semiconductor nanostructures capable of emitting from two excited states and thereby of producing two photoluminescence colours are of fundamental and potential technological significance. In this limited class of nanocrystals, CdSe/CdS core/arm tetrapods exhibit the unusual trait of two-colour (red and green) multiexcitonic emission, with green emission from the CdS arms emerging only at high excitation fluences. Here we show that by synthetic shape-tuning, both this multi-colour emission process, and blinking and photobleaching behaviours of single tetrapods can be controlled. Specifically, we find that the properties of dual emission and single-nanostructure photostability depend on different structural parameters--arm length and arm diameter, respectively--but that both properties can be realized in the same nanostructure. Furthermore, based on results of correlated photoluminescence and transient absorption measurements, we conclude that hole-trap filling in the arms and partial state-filling in the core are necessary preconditions for the observation of multiexciton multi-colour emission.

  9. Whole-genome sequence of the Tibetan frog Nanorana parkeri and the comparative evolution of tetrapod genomes.

    PubMed

    Sun, Yan-Bo; Xiong, Zi-Jun; Xiang, Xue-Yan; Liu, Shi-Ping; Zhou, Wei-Wei; Tu, Xiao-Long; Zhong, Li; Wang, Lu; Wu, Dong-Dong; Zhang, Bao-Lin; Zhu, Chun-Ling; Yang, Min-Min; Chen, Hong-Man; Li, Fang; Zhou, Long; Feng, Shao-Hong; Huang, Chao; Zhang, Guo-Jie; Irwin, David; Hillis, David M; Murphy, Robert W; Yang, Huan-Ming; Che, Jing; Wang, Jun; Zhang, Ya-Ping

    2015-03-17

    The development of efficient sequencing techniques has resulted in large numbers of genomes being available for evolutionary studies. However, only one genome is available for all amphibians, that of Xenopus tropicalis, which is distantly related from the majority of frogs. More than 96% of frogs belong to the Neobatrachia, and no genome exists for this group. This dearth of amphibian genomes greatly restricts genomic studies of amphibians and, more generally, our understanding of tetrapod genome evolution. To fill this gap, we provide the de novo genome of a Tibetan Plateau frog, Nanorana parkeri, and compare it to that of X. tropicalis and other vertebrates. This genome encodes more than 20,000 protein-coding genes, a number similar to that of Xenopus. Although the genome size of Nanorana is considerably larger than that of Xenopus (2.3 vs. 1.5 Gb), most of the difference is due to the respective number of transposable elements in the two genomes. The two frogs exhibit considerable conserved whole-genome synteny despite having diverged approximately 266 Ma, indicating a slow rate of DNA structural evolution in anurans. Multigenome synteny blocks further show that amphibians have fewer interchromosomal rearrangements than mammals but have a comparable rate of intrachromosomal rearrangements. Our analysis also identifies 11 Mb of anuran-specific highly conserved elements that will be useful for comparative genomic analyses of frogs. The Nanorana genome offers an improved understanding of evolution of tetrapod genomes and also provides a genomic reference for other evolutionary studies.

  10. Impact of coastal defence structures (tetrapods) on a demersal hard-bottom fish community in the southern North Sea.

    PubMed

    Wehkamp, Stephanie; Fischer, Philipp

    2013-02-01

    In the coming decades, artificial defence structures will increase in importance worldwide for the protection of coasts against the impacts of global warming. However, the ecological effects of such structures on the natural surroundings remain unclear. We investigated the impact of experimentally introduced tetrapod fields on the demersal fish community in a hard-bottom area in the southern North Sea. The results indicated a significant decrease in fish abundance in the surrounding area caused by migration effects towards the artificial structures. Diversity (HB) and evenness (E) values exhibited greater variation after the introduction of the tetrapods. Additionally, a distinct increase in young-of-the-year (YOY) fish was observed near the structures within the second year after introduction. We suggest that the availability of adequate refuges in combination with additional food resources provided by the artificial structures has a highly species-specific attraction effect. However, these findings also demonstrate that our knowledge regarding the impact of artificial structures on temperate fish communities is still too limited to truly understand the ecological processes that are initiated by the introduction of artificial structures. Long-term investigations and additional experimental in situ work worldwide will be indispensable for a full understanding of the mechanisms by which coastal defence structures interact with the coastal environment. Copyright © 2012 Elsevier Ltd. All rights reserved.

  11. Delayed recovery of non-marine tetrapods after the end-Permian mass extinction tracks global carbon cycle

    PubMed Central

    Irmis, Randall B.; Whiteside, Jessica H.

    2012-01-01

    During the end-Permian mass extinction, marine ecosystems suffered a major drop in diversity, which was maintained throughout the Early Triassic until delayed recovery during the Middle Triassic. This depressed diversity in the Early Triassic correlates with multiple major perturbations to the global carbon cycle, interpreted as either intrinsic ecosystem or external palaeoenvironmental effects. In contrast, the terrestrial record of extinction and recovery is less clear; the effects and magnitude of the end-Permian extinction on non-marine vertebrates are particularly controversial. We use specimen-level data from southern Africa and Russia to investigate the palaeodiversity dynamics of non-marine tetrapods across the Permo-Triassic boundary by analysing sample-standardized generic richness, evenness and relative abundance. In addition, we investigate the potential effects of sampling, geological and taxonomic biases on these data. Our analyses demonstrate that non-marine tetrapods were severely affected by the end-Permian mass extinction, and that these assemblages did not begin to recover until the Middle Triassic. These data are congruent with those from land plants and marine invertebrates. Furthermore, they are consistent with the idea that unstable low-diversity post-extinction ecosystems were subject to boom–bust cycles, reflected in multiple Early Triassic perturbations of the carbon cycle. PMID:22031757

  12. Using shape to turn off blinking for two-colour multiexciton emission in CdSe/CdS tetrapods

    DOE PAGES

    Mishra, Nimai; Orfield, Noah Jeremiah; Wang, Feng; ...

    2017-05-12

    Here, semiconductor nanostructures capable of emitting from two excited states and thereby of producing two photoluminescence colours are of fundamental and potential technological significance. In this limited class of nanocrystals, CdSe/CdS core/arm tetrapods exhibit the unusual trait of two-colour (red and green) multiexcitonic emission, with green emission from the CdS arms emerging only at high excitation fluences. Here we show that by synthetic shape-tuning, both this multi-colour emission process, and blinking and photobleaching behaviours of single tetrapods can be controlled. Specifically, we find that the properties of dual emission and single-nanostructure photostability depend on different structural parameters—arm length and armmore » diameter, respectively—but that both properties can be realized in the same nanostructure. Furthermore, based on results of correlated photoluminescence and transient absorption measurements, we conclude that hole-trap filling in the arms and partial state-filling in the core are necessary preconditions for the observation of multiexciton multi-colour emission.« less

  13. Using shape to turn off blinking for two-colour multiexciton emission in CdSe/CdS tetrapods

    PubMed Central

    Mishra, Nimai; Orfield, Noah J.; Wang, Feng; Hu, Zhongjian; Krishnamurthy, Sachidananda; Malko, Anton V.; Casson, Joanna L.; Htoon, Han; Sykora, Milan; Hollingsworth, Jennifer A.

    2017-01-01

    Semiconductor nanostructures capable of emitting from two excited states and thereby of producing two photoluminescence colours are of fundamental and potential technological significance. In this limited class of nanocrystals, CdSe/CdS core/arm tetrapods exhibit the unusual trait of two-colour (red and green) multiexcitonic emission, with green emission from the CdS arms emerging only at high excitation fluences. Here we show that by synthetic shape-tuning, both this multi-colour emission process, and blinking and photobleaching behaviours of single tetrapods can be controlled. Specifically, we find that the properties of dual emission and single-nanostructure photostability depend on different structural parameters—arm length and arm diameter, respectively—but that both properties can be realized in the same nanostructure. Furthermore, based on results of correlated photoluminescence and transient absorption measurements, we conclude that hole-trap filling in the arms and partial state-filling in the core are necessary preconditions for the observation of multiexciton multi-colour emission. PMID:28497776

  14. Using shape to turn off blinking for two-colour multiexciton emission in CdSe/CdS tetrapods

    SciT

    Mishra, Nimai; Orfield, Noah Jeremiah; Wang, Feng

    Here, semiconductor nanostructures capable of emitting from two excited states and thereby of producing two photoluminescence colours are of fundamental and potential technological significance. In this limited class of nanocrystals, CdSe/CdS core/arm tetrapods exhibit the unusual trait of two-colour (red and green) multiexcitonic emission, with green emission from the CdS arms emerging only at high excitation fluences. Here we show that by synthetic shape-tuning, both this multi-colour emission process, and blinking and photobleaching behaviours of single tetrapods can be controlled. Specifically, we find that the properties of dual emission and single-nanostructure photostability depend on different structural parameters—arm length and armmore » diameter, respectively—but that both properties can be realized in the same nanostructure. Furthermore, based on results of correlated photoluminescence and transient absorption measurements, we conclude that hole-trap filling in the arms and partial state-filling in the core are necessary preconditions for the observation of multiexciton multi-colour emission.« less

  15. Identification of acoustic waves in ZnO materials by Brillouin light scattering for SAW device applications

    NASA Astrophysics Data System (ADS)

    Zerdali, M.; Bechiri, F.; Hamzaoui, S.; Teherani, F. H.; Rogers, D. J.; Sandana, V. E.; Bove, P.; Djemia, P.; Roussigné, Y.

    2017-03-01

    Brillouin light scattering (BLS) was conducted on melt-grown ZnO bulk crystals and ZnO thin films grown by pulsed laser deposition. The bulk ZnO crystals presented both longitudinal and transverse bulk acoustic waves. Theoretical calculations agreed well with there being one piezoelectric longitudinal branch and two transverse branches. BLS measurements conducted on ZnO thin films also revealed Rayleigh surface acoustic waves (R-SAW) guided by only the surface of the layer and Sezawa modes, guided by the film thickness. Measurements were conducted for three incidence angles in order to investigate different SAW wave numbers. Higher frequency features were identified as being related to a new class of guided longitudinal (LG) SAW modes which are not usually detected for ZnO thin films. The LG-SAW modes were observed for two incidence angles (θ=45° and 55°) corresponding to frequencies of 17.88 and 20.75 GHz, respectively. BLS measurements enable us to estimate the LG-SAW velocity as 6500 m/s. This value is three times higher than that of the currently used R-SAW. Theoretical simulations were coherent with the presence of LG modes in the ZnO layers. Such LG-SAW modes are promising for the development of novel, higher-speed SAW devices operating in the GHz-band and which could be readily incorporated in Si-based integrated circuitry.

  16. Doping Asymmetry Problem in ZnO: Current Status and Outlook. A Review of Experimental and Theoretical Efforts Focused on Achieving P-Type ZnO Suitable for Light-Emitting Optoelectronic Devices for the Blue/Ultraviolet Spectral Range

    DTIC Science & Technology

    2009-04-24

    it seems at a first glance, because the isovalent co- doping of ZnO will result also in an increase of the band gap which usually gives rise to an...J.G. Lu, H.P. He, L.X. Chen, X.Q. Gu, J.Y. Huang, L.P. Zhu, and B.H. Zhao, “Na doping concentration tuned conductivity of ZnO films via pulsed laser...recently as a promising material for a variety of applications. To a large extent, the renewed interest in ZnO is fuelled by its wide direct band gap (3.3

  17. Observation of defect-assisted enhanced visible whispering gallery modes in ytterbium-doped ZnO microsphere

    NASA Astrophysics Data System (ADS)

    Khanum, Rizwana; Moirangthem, Rakesh S.; Das, Nayan Mani

    2017-06-01

    Smooth surfaced and crystalline undoped and ytterbium doped zinc oxide (ZnO) microspheres having an approximate size of 3-5 μm were synthesized by hydrothermal process. Out of these microspheres, a single microparticle was chosen and engaged as a whispering gallery wave microresonator. The defect induced luminescence from an individual ZnO microsphere was investigated with micro-photoluminescence measurement in the spectral range of 565 to 740 nm under the excitation of a green laser having a centered wavelength at 532 nm. The defects-related emissions from a single ZnO microsphere show optical resonance peaks so-called "whispering gallery modes" (WGMs) which are confirmed with the theoretical calculation. Further, ZnO microspheres were chemically doped with the different molar percentages of Ytterbium (Yb), and enhancement in their emission properties was investigated. Our experimental results show that ZnO microspheres with 0.5 mol. % doping of Yb gives the strongest optical emission and has highest Q-factor which can be employed in the development of WGM based optical biosensor or laser.

  18. Preparation of ZnO nanoparticles showing upconversion luminescence through simple chemical method

    SciT

    Anjana, R.; Subha, P. P.; Markose, Kurias K.

    2016-05-23

    Upconversion luminescence is an interesting area while considering its applications in a vast variety of fields. Rare earth ions like erbium is the most studied and efficient candidate for achieving upconversion. Erbium and ytterbium co-doped ZnO nanoparticles were prepared through co-precipitation method. A strong red emission has been obtained while exciting with 980 nm laser. Dependence of luminescence emission colour on ytterbium concentration has been studied.

  19. Placoderm Assemblage from the Tetrapod-Bearing Locality of Strud (Belgium, Upper Famennian) Provides Evidence for a Fish Nursery

    PubMed Central

    Clément, Gaël; Daeschler, Edward B.; Dupret, Vincent

    2016-01-01

    The placoderm fauna of the upper Famennian tetrapod-bearing locality of Strud, Belgium, includes the antiarch Grossilepis rikiki, the arthrodire groenlandaspidid Turrisaspis strudensis and the phyllolepidid Phyllolepis undulata. Based on morphological and morphometric evidence, the placoderm specimens from Strud are predominantly recognised as immature specimens and this locality as representing a placoderm nursery. The Strud depositional environment corresponds to a channel in an alluvial plain, and the presence of a nursery in such environment could have provided nutrients and protection to the placoderm offspring. This represents one of the earliest pieces of evidence for this sort of habitat partitioning in vertebrate history, with adults living more distantly from the nursery and using the nursery only to spawn or give live birth. PMID:27552196

  20. A new captorhinid reptile from the Lower Permian of Oklahoma showing remarkable dental and mandibular convergence with microsaurian tetrapods

    NASA Astrophysics Data System (ADS)

    Reisz, R. R.; LeBlanc, Aaron R. H.; Sidor, Christian A.; Scott, Diane; May, William

    2015-10-01

    The Lower Permian fossiliferous infills of the Dolese Brothers Limestone Quarry, near Richards Spur, Oklahoma, have preserved the most diverse assemblage of Paleozoic terrestrial vertebrates, including small-bodied reptiles and lepospondyl anamniotes. Many of these taxa were previously known only from fragmentary remains, predominantly dentigerous jaw elements and numerous isolated skeletal elements. The recent discovery of articulated skulls and skeletons of small reptiles permits the recognition that dentigerous elements, previously assigned at this locality to the anamniote lepospondyl Euryodus primus, belong to a new captorhinid eureptile, Opisthodontosaurus carrolli gen. et sp. nov. This mistaken identity points to a dramatic level of convergence in mandibular and dental anatomy in two distantly related and disparate clades of terrestrial tetrapods and sheds light on the earliest instance of durophagy in eureptiles.

  1. A new captorhinid reptile from the Lower Permian of Oklahoma showing remarkable dental and mandibular convergence with microsaurian tetrapods.

    PubMed

    Reisz, R R; LeBlanc, Aaron R H; Sidor, Christian A; Scott, Diane; May, William

    2015-10-01

    The Lower Permian fossiliferous infills of the Dolese Brothers Limestone Quarry, near Richards Spur, Oklahoma, have preserved the most diverse assemblage of Paleozoic terrestrial vertebrates, including small-bodied reptiles and lepospondyl anamniotes. Many of these taxa were previously known only from fragmentary remains, predominantly dentigerous jaw elements and numerous isolated skeletal elements. The recent discovery of articulated skulls and skeletons of small reptiles permits the recognition that dentigerous elements, previously assigned at this locality to the anamniote lepospondyl Euryodus primus, belong to a new captorhinid eureptile, Opisthodontosaurus carrolli gen. et sp. nov. This mistaken identity points to a dramatic level of convergence in mandibular and dental anatomy in two distantly related and disparate clades of terrestrial tetrapods and sheds light on the earliest instance of durophagy in eureptiles.

  2. Non-polar a-plane ZnO films grown on r-Al2O3 substrates using GaN buffer layers

    NASA Astrophysics Data System (ADS)

    Xu, C. X.; Chen, W.; Pan, X. H.; Chen, S. S.; Ye, Z. Z.; Huang, J. Y.

    2016-09-01

    In this work, GaN buffer layer has been used to grow non-polar a-plane ZnO films by laser-assisted and plasma-assisted molecular beam epitaxy. The thickness of GaN buffer layer ranges from ∼3 to 12 nm. The GaN buffer thickness effect on the properties of a-plane ZnO thin films is carefully investigated. The results show that the surface morphology, crystal quality and optical properties of a-plane ZnO films are strongly correlated with the thickness of GaN buffer layer. It was found that with 6 nm GaN buffer layer, a-plane ZnO films display the best crystal quality with X-ray diffraction rocking curve full-width at half-maximum of only 161 arcsec for the (101) reflection.

  3. Effect of Li doping on the electric and pyroelectric properties of ZnO thin films

    NASA Astrophysics Data System (ADS)

    Trinca, L. M.; Galca, A. C.; Boni, A. G.; Botea, M.; Pintilie, L.

    2018-01-01

    Un-doped ZnO (UDZO) and Li-doped ZnO (LZO) polycrystalline thin films were grown on platinized silicon by pulsed laser deposition (PLD). The electrical properties were investigated on as-grown and annealed UDZO and LZO films with capacitor configuration, using top and bottom platinum electrodes. In the case of the as-grown films it was found that the introduction of Li increases the resistivity of ZnO and induces butterfly shape in the C-V characteristic, suggesting ferroelectric-like behavior in LZO films. The properties of LZO samples does not significantly changes after thermal annealing while the properties of UDZO samples show significant changes upon annealing, manifested in a butterfly shape of the C-V characteristic and resistive-like switching. However, the butterfly shape disappears if long delay time is used in the C-V measurement, the characteristic remaining non-linear. Pyroelectric signal could be measured only on annealed films. Comparing the UDZO results with those obtained in the case of Li:ZnO, it was found that the pyroelectric properties are considerably enhanced by Li doping, leading to pyroelectric signal with about one order of magnitude larger at low modulation frequencies than for un-doped samples. Although the results of this study hint towards a ferroelectric-like behavior of Li doped ZnO, the presence of real ferroelectricity in this material remains controversial.

  4. Uncooled pulsed zinc oxide semiconductor laser

    NASA Astrophysics Data System (ADS)

    Bogdankevich, O. V.; Darznek, S. A.; Zverev, M. M.; Kostin, N. N.; Krasavina, E. M.

    1985-02-01

    An optimized ZnO laser which operates at ambient temperature without cooling is reported, along with extension of the design to form a multielement high-power laser. ZnO single crystal plane-parallel wafers 0.22 mm thick, covered with total and semi-transparent coatings, were exposed to a 200 keV electron beam with a 10 nsec pulse and a current density up to 1 kA/sq cm. No damage was observed in the crystals at saturation. A 7 percent maximum efficiency at a reflection coefficient (RC) of 0.4 was associated with a maximum output of 25 kW and a light power density of 3 MW/sq cm. Cementing a ZnO wafer to a sapphire substrate, applying the same type of coatings and working with a RC of 0.6 yielded a maximum power of 300 kW/sq cm.

  5. Multifunctional transparent ZnO nanorod films.

    PubMed

    Kwak, Geunjae; Jung, Sungmook; Yong, Kijung

    2011-03-18

    Transparent ZnO nanorod (NR) films that exhibit extreme wetting states (either superhydrophilicity or superhydrophobicity through surface chemical modification), high transmittance, UV protection and antireflection have been prepared via the facile ammonia hydrothermal method. The periodic 1D ZnO NR arrays showed extreme wetting states as well as antireflection properties due to their unique surface structure and prevented the UVA region from penetrating the substrate due to the unique material property of ZnO. Because of the simple, time-efficient and low temperature preparation process, ZnO NR films with useful functionalities are promising for fabrication of highly light transmissive, antireflective, UV protective, antifogging and self-cleaning optical materials to be used for optical devices and photovoltaic energy devices.

  6. Development of Room Temperature Excitonic Lasing From ZnO and MgZnO Thin Film Based Metal-Semiconductor-Metal Devices

    NASA Astrophysics Data System (ADS)

    Suja, Mohammad Zahir Uddin

    efficiency up to 6 times is demonstrated. Threshold current for lasing is decreased by as much as 30% while the output power is increased up to 350% at an injection current of 40 mA. A numerical simulation study reveals that hole carriers are generated in the ZnO MSM devices from impact ionization processes for subsequent plasmon-exciton coupled lasing. Our results suggest that plasmon-enhanced ZnO MSM random lasers can become a competitive candidate of efficient ultraviolet light sources. Semiconductor lasers in the deep ultraviolet (UV) range have numerous potential applications ranging from water purification and medical diagnosis to high-density data storage and flexible displays. Nevertheless, very little success was achieved in the realization of electrically driven deep UV semiconductor lasers to date. In this thesis, we report the fabrication and characterization of deep UV MgZnO semiconductor lasers. These lasers are operated with continuous current mode at room temperature and the shortest wavelength reaches 284 nm. The wide bandgap MgZnO thin films with various Mg mole fractions were grown on c-sapphire substrate using radio-frequency plasma assisted molecular beam epitaxy. Metal-semiconductor-metal (MSM) random laser devices were fabricated using lithography and metallization processes. Besides the demonstration of scalable emission wavelength, very low threshold current densities of 29 33 A/cm2 are achieved. Numerical modeling reveals that impact ionization process is responsible for the generation of hole carriers in the MgZnO MSM devices. The interaction of electrons and holes leads to radiative excitonic recombination and subsequent coherent random lasing.

  7. Superhydrophobicity of Hierarchical and ZNO Nanowire Coatings

    DTIC Science & Technology

    2014-01-01

    AFRL-RX-WP-TP-2014-0141 SUPERHYDROPHOBICITY OF HIERARCHICAL ZNO NANOWIRE COATINGS (POSTPRINT) Shin Mou AFRL/RXAN JANUARY... SUPERHYDROPHOBICITY OF HIERARCHICAL ZNO NANOWIRE COATINGS (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...or disclose the work. The final publication is available at www.rsc.org/MaterialsA. 14. ABSTRACT Hierarchical superhydrophobic surfaces were

  8. Electrical and optical properties of p-type codoped ZnO thin films prepared by spin coating technique

    NASA Astrophysics Data System (ADS)

    Pathak, Trilok Kumar; Kumar, Vinod; Swart, H. C.; Purohit, L. P.

    2016-03-01

    Undoped, doped and codoped ZnO thin films were synthesized on glass substrates using a spin coating technique. Zinc acetate dihydrate, ammonium acetate and aluminum nitrate were used as precursor for zinc, nitrogen and aluminum, respectively. X-ray diffraction shows that the thin films have a hexagonal wurtzite structure for the undoped, doped and co-doped ZnO. The transmittance of the films was above 80% and the band gap of the film varied from 3.20 eV to 3.24 eV for undoped and doped ZnO. An energy band diagram to describe the photoluminescence from the thin films was also constructed. This diagram includes the various defect levels and possible quasi-Fermi levels. A minimum resistivity of 0.0834 Ω-cm was obtained for the N and Al codoped ZnO thin films with p-type carrier conductivity. These ZnO films can be used as a window layer in solar cells and in UV lasers.

  9. Comparative pelvic development of the axolotl (Ambystoma mexicanum) and the Australian lungfish (Neoceratodus forsteri): conservation and innovation across the fish-tetrapod transition.

    PubMed

    Boisvert, Catherine Anne; Joss, Jean Mp; Ahlberg, Per E

    2013-01-23

    The fish-tetrapod transition was one of the major events in vertebrate evolution and was enabled by many morphological changes. Although the transformation of paired fish fins into tetrapod limbs has been a major topic of study in recent years, both from paleontological and comparative developmental perspectives, the interest has focused almost exclusively on the distal part of the appendage and in particular the origin of digits. Relatively little attention has been paid to the transformation of the pelvic girdle from a small unipartite structure to a large tripartite weight-bearing structure, allowing tetrapods to rely mostly on their hindlimbs for locomotion. In order to understand how the ischium and the ilium evolved and how the acetabulum was reoriented during this transition, growth series of the Australian lungfish Neoceratodus forsteri and the Mexican axolotl Ambystoma mexicanum were cleared and stained for cartilage and bone and immunostained for skeletal muscles. In order to understand the myological developmental data, hypotheses about the homologies of pelvic muscles in adults of Latimeria, Neoceratodus and Necturus were formulated based on descriptions from the literature of the coelacanth (Latimeria), the Australian Lungfish (Neoceratodus) and a salamander (Necturus). In the axolotl and the lungfish, the chondrification of the pelvic girdle starts at the acetabula and progresses anteriorly in the lungfish and anteriorly and posteriorly in the salamander. The ilium develops by extending dorsally to meet and connect to the sacral rib in the axolotl. Homologous muscles develop in the same order with the hypaxial musculature developing first, followed by the deep, then the superficial pelvic musculature. Development of the pelvic endoskeleton and musculature is very similar in Neoceratodus and Ambystoma. If the acetabulum is seen as being a fixed landmark, the evolution of the ischium only required pubic pre-chondrogenic cells to migrate posteriorly. It

  10. Effect of an Electrochemically Oxidized ZnO Seed Layer on ZnO Nanorods Grown by using Electrodeposition

    NASA Astrophysics Data System (ADS)

    Jeon, Woosung; Leem, Jae-Young

    2018-05-01

    ZnO nanorods were prepared on a Si substrate with and without a ZnO seed layer formed by electro-oxidation to investigate the effect of the seed layer on their growth. The ZnO nanorods grown on the ZnO seed layer had top surfaces that were flat whereas those grown without it had rough top surfaces, as observed in field-emission scanning electron microscopy images. In the Xray diffraction analysis, all ZnO nanorods showed preferential orientation with the (002) plane. In the case of ZnO nanorods prepared with a ZnO seed layer, the residual stress decreased, and the full width at half maximum of the ZnO (002) plane peak decreased. The photoluminescence spectra show a strong and narrow near-band-edge emission peak and high near-band-edge emission to deep-level emission peak ratio for the ZnO nanorods prepared with the seed layer. With respect to the photoresponse properties, the ZnO nanorods grown with the ZnO seed layer showed higher responsivity and faster rise/decay curves than those grown without it. Thus, the ZnO seed layer formed by electro-oxidation improves the structural, optical, and photoresponse properties of the ZnO nanorods formed on it. This method could serve as a new route for improving the properties of optoelectronic devices.

  11. Comparative anatomy, evolution, and homologies of tetrapod hindlimb muscles, comparison with forelimb muscles, and deconstruction of the forelimb-hindlimb serial homology hypothesis.

    PubMed

    Diogo, Rui; Molnar, Julia

    2014-06-01

    For more than two centuries, the idea that the forelimb and hindlimb are serially homologous structures has been accepted without serious question. This study presents the first detailed analysis of the evolution and homologies of all hindlimb muscles in representatives of each major tetrapod group and proposes a unifying nomenclature for these muscles. These data are compared with information obtained previously about the forelimb muscles of tetrapods and the muscles of other gnathostomes in order to address one of the most central and enigmatic questions in evolutionary and comparative anatomy: why are the pelvic and pectoral appendages of gnathostomes generally so similar to each other? An integrative analysis of the new myological data, combined with a review of recent paleontological, developmental, and genetic works and of older studies, does not support serial homology between the structures of these appendages. For instance, many of the strikingly similar forelimb and hindlimb muscles found in each major extant tetrapod taxon were acquired at different geological times and/or have different embryonic origins. These similar muscles are not serial homologues, but the result of evolutionary parallelism/convergence due to a complex interplay of ontogenetic, functional, topological, and phylogenetic constraints/factors. Copyright © 2014 Wiley Periodicals, Inc.

  12. When and how did the terrestrial mid-Permian mass extinction occur? Evidence from the tetrapod record of the Karoo Basin, South Africa

    PubMed Central

    Day, Michael O.; Ramezani, Jahandar; Bowring, Samuel A.; Sadler, Peter M.; Erwin, Douglas H.; Abdala, Fernando; Rubidge, Bruce S.

    2015-01-01

    A mid-Permian (Guadalupian epoch) extinction event at approximately 260 Ma has been mooted for two decades. This is based primarily on invertebrate biostratigraphy of Guadalupian–Lopingian marine carbonate platforms in southern China, which are temporally constrained by correlation to the associated Emeishan Large Igneous Province (LIP). Despite attempts to identify a similar biodiversity crisis in the terrestrial realm, the low resolution of mid-Permian tetrapod biostratigraphy and a lack of robust geochronological constraints have until now hampered both the correlation and quantification of terrestrial extinctions. Here we present an extensive compilation of tetrapod-stratigraphic data analysed by the constrained optimization (CONOP) algorithm that reveals a significant extinction event among tetrapods within the lower Beaufort Group of the Karoo Basin, South Africa, in the latest Capitanian. Our fossil dataset reveals a 74–80% loss of generic richness between the upper Tapinocephalus Assemblage Zone (AZ) and the mid-Pristerognathus AZ that is temporally constrained by a U–Pb zircon date (CA-TIMS method) of 260.259 ± 0.081 Ma from a tuff near the top of the Tapinocephalus AZ. This strengthens the biochronology of the Permian Beaufort Group and supports the existence of a mid-Permian mass extinction event on land near the end of the Guadalupian. Our results permit a temporal association between the extinction of dinocephalian therapsids and the LIP volcanism at Emeishan, as well as the marine end-Guadalupian extinctions. PMID:26156768

  13. Comparative anatomy, homologies and evolution of the pectoral and forelimb musculature of tetrapods with special attention to extant limbed amphibians and reptiles

    PubMed Central

    Abdala, Virginia; Diogo, Rui

    2010-01-01

    The main aim of the present work is to synthesize the information obtained from our dissections of the pectoral and forelimb muscles of representative members of the major extant taxa of limbed amphibians and reptiles and from our review of the literature, in order to provide an account of the comparative anatomy, homologies and evolution of these muscles in the Tetrapoda. The pectoral and forelimb musculature of all these major taxa conform to a general pattern that seems to have been acquired very early in the evolutionary history of tetrapods. Although some muscles are missing in certain taxa, and a clear departure from this general pattern is obviously present in derived groups such as birds, the same overall configuration is easily distinguishable in these taxa. Among the most notable anatomical differences between the groups, one that seems to have relevant evolutionary and functional implications, concerns the distal insertion points of the forearm musculature. In tetrapods, the muscles of the radial and ulnar complexes of the forearm are pleisomorphically mainly inserted onto the radius/ulna or onto the more proximal carpal bones, but in mammals some of these muscles insert more distally onto bones such as the metacarpals. Interestingly, a similar trend towards a more distal insertion of these muscles is also found in some non-mammalian tetrapod taxa, such as some anurans (e.g. Phyllomedusa). This may be correlated with the acquisition of more subtle digital movement abilities in these latter taxa. PMID:20807270

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

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

    2017-06-16

    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.

  16. Effect of Pt Nanoparticles on the Photocatalytic Activity of ZnO Nanofibers

    NASA Astrophysics Data System (ADS)

    Di Mauro, Alessandro; Zimbone, Massimo; Scuderi, Mario; Nicotra, Giuseppe; Fragalà, Maria Elena; Impellizzeri, Giuliana

    2015-12-01

    For this study, we originally realized ZnO nanofibers (˜50 nm in mean radius) mixed with Pt nanoparticles (˜30 nm in mean radius), prepared by pulsed laser ablation in liquid, and investigated their photocatalytic performance. The material was synthesized by the simple electrospinning method coupled with subsequent thermal treatments. Methylene blue was employed as a representative dye pollutant to evaluate the photocatalytic activity of the nanofibers. It was found that the Pt-ZnO fibers exhibit a photodegradation reaction rate that is ˜40 % higher than the one obtained for reference ZnO fibers. These encouraging results demonstrate that Pt-ZnO nanofibers can be fruitfully applied for environmental applications.

  17. Enhanced H2 sensitivity at room temperature of ZnO nanowires functionalized by Pd nanoparticles

    NASA Astrophysics Data System (ADS)

    Ren, Shoutian; Fan, Guanghua; Qu, Shiliang; Wang, Qiang

    2011-10-01

    For sensitive detection of H2, ZnO nanowires networks decorated with photo-decomposed Pd nanoparticles were fabricated between femtosecond laser-writing interdigitated electrodes by chemical vapor deposition method. When H2 concentration is increased from 20 to 4000 ppm at room temperature, sensitivity of the sample is increased from 3.7% to 1017.9%. The high sensitivity can be explained by considering the reaction between the adsorbed O2- and the disassociated H atoms facilitated by Pd nanoparticles. This mechanism is further supported by the H2 response results under UV light illumination, which can reduce the amount of O2- on the ZnO surface, leading to depressed sensitivity. The sensor also shows high selectivity, long-term stability, and ultra-low power consumption of nanowatt level, due to the novel fabrication process.

  18. Single ZnO nanowire-PZT optothermal field effect transistors.

    PubMed

    Hsieh, Chun-Yi; Lu, Meng-Lin; Chen, Ju-Ying; Chen, Yung-Ting; Chen, Yang-Fang; Shih, Wan Y; Shih, Wei-Heng

    2012-09-07

    A new type of pyroelectric field effect transistor based on a composite consisting of single zinc oxide nanowire and lead zirconate titanate (ZnO NW-PZT) has been developed. Under infrared (IR) laser illumination, the transconductance of the ZnO NW can be modulated by optothermal gating. The drain current can be increased or decreased by IR illumination depending on the polarization orientation of the Pb(Zr(0.3)Ti(0.7))O(3) (PZT) substrate. Furthermore, by combining the photocurrent behavior in the UV range and the optothermal gating effect in the IR range, the wide spectrum of response of current by light offers a variety of opportunities for nanoscale optoelectronic devices.

  19. Time resolved optical diagnostics of ZnO plasma plumes in air

    SciT

    Gupta, Shyam L.; Singh, Ravi Pratap; Thareja, Raj K.

    2013-10-15

    We report dynamical evolution of laser ablated ZnO plasma plumes using interferometry and shadowgraphy; 2-D fast imaging and optical emission spectroscopy in air ambient at atmospheric pressure. Recorded interferograms using Nomarski interferometer and shadowgram images at various time delays show the presence of electrons and neutrals in the ablated plumes. The inference drawn from sign change of fringe shifts is consistent with two dimensional images of the plume and optical emission spectra at varying time delays with respect to ablating pulse. Zinc oxide plasma plumes are created by focusing 1.06 μm radiation on to ZnO target in air and 532more » nm is used as probe beam.« less

  20. Complex and oriented ZnO nanostructures.

    PubMed

    Tian, Zhengrong R; Voigt, James A; Liu, Jun; McKenzie, Bonnie; McDermott, Matthew J; Rodriguez, Mark A; Konishi, Hiromi; Xu, Huifang

    2003-12-01

    Extended and oriented nanostructures are desirable for many applications, but direct fabrication of complex nanostructures with controlled crystalline morphology, orientation and surface architectures remains a significant challenge. Here we report a low-temperature, environmentally benign, solution-based approach for the preparation of complex and oriented ZnO nanostructures, and the systematic modification of their crystal morphology. Using controlled seeded growth and citrate anions that selectively adsorb on ZnO basal planes as the structure-directing agent, we prepared large arrays of oriented ZnO nanorods with controlled aspect ratios, complex film morphologies made of oriented nanocolumns and nanoplates (remarkably similar to biomineral structures in red abalone shells) and complex bilayers showing in situ column-to-rod morphological transitions. The advantages of some of these ZnO structures for photocatalytic decompositions of volatile organic compounds were demonstrated. The novel ZnO nanostructures are expected to have great potential for sensing, catalysis, optical emission, piezoelectric transduction, and actuations.

  1. Nondegenerate n-type doping phenomenon on molybdenum disulfide (MoS{sub 2}) by zinc oxide (ZnO)

    SciT

    Kang, Dong-Ho; Hong, Seong-Taek; Oh, Aely

    Highlights: • We have demonstrated nondegenerate n-type doping phenomenon of MoS{sub 2} by ZnO. • ZnO doping improved the electrical parameters of MoS{sub 2} transistor (I{sub on}↑, μ{sub FE}↑, n↑). • The reduction of ZnO doping effect (ΔV{sub TH}: ∼75% ↓) was observed in air. • The highest photoresponsivity of ZnO-doped MoS{sub 2} photodetector was 3.18 × 10{sup 3} A/W. • The highest detectivity of ZnO-doped MoS{sub 2} photodetector was 5.94 × 10{sup 12} Jones. - Abstract: In this paper, we have demonstrated nondegenerate n-type doping phenomenon of MoS{sub 2} by ZnO. The ZnO doping effects were systematically investigated bymore » Raman spectroscopy and electrical/optical measurements (I{sub D}–V{sub G} with/without exposure to 520, 655, 785, and 850 nm laser sources). The ZnO doping improved the performance parameters of MoS{sub 2}-based electronics (I{sub on}↑, μ{sub FE}↑, n↑) owing to reduction of the effective barrier height between the source and the MoS{sub 2} channel. We also monitored the effects of ZnO doping during exposure to air; reduction in ΔV{sub TH} of about 75% was observed after 156 h. In addition, the optoelectronic performance of the MoS{sub 2} photodetector was enhanced due to the reduction of the recombination rate of photogenerated carriers caused by ZnO doping. In our results, the highest photoresponsivity (about 3.18 × 10{sup 3} A/W) and detectivity (5.94 × 10{sup 12} Jones) of the ZnO-doped photodetector were observed for 520 nm laser exposure.« less

  2. Phosphate base laser glasses

    SciT

    Izumitani, T.; Tsuru, M.

    1980-12-16

    A phosphate base laser glass comprising 55-70% P2O5, 1-15% Al2O3, 0-25% Li2O, 0-25% Na2O, 0-8% K2O, the total proportion of Li2O, Na2O, and K2O being 10-25%, 0-15% BaO, 0-15% ZnO, 0-15% CaO , 0-15%, sro, 0-15% MgO, the total proportion of BaO, ZnO, CaO, SrO, and MgO being 5-15%, 0-5% Y2O3, 0-5% La2O3, 0-5% GeO2, 0-5% CeO2, 0-3% Nb2O5, 0-3% MnO2, 0-2% Ta2O5, 0-1% Sb2O3, and 0.01-5% Nd2O3, all % being mole %. The phosphate base laser glass of this invention has a high induced emission cross section, a low non-linear refractive index coefficient, and excellent acid resistance and divitrificationmore » resistance. By replacing partially or wholely one or more of LiO2, Na2O, K2O, BaO, ZnO, CaO, SrO, MgO or Al2O3 by LiF, NaF, KF , BaF2ZnF2, CaF2, SrF2, MgF2 or AlF3, respectively, the above properties of the laser glass are further improved.« less

  3. Preliminary Analysis of Osteocyte Lacunar Density in Long Bones of Tetrapods: All Measures Are Bigger in Sauropod Dinosaurs

    PubMed Central

    Stein, Koen W. H.; Werner, Jan

    2013-01-01

    Osteocytes harbour much potential for paleobiological studies. Synchrotron radiation and spectroscopic analyses are providing fascinating data on osteocyte density, size and orientation in fossil taxa. However, such studies may be costly and time consuming. Here we describe an uncomplicated and inexpensive method to measure osteocyte lacunar densities in bone thin sections. We report on cell lacunar densities in the long bones of various extant and extinct tetrapods, with a focus on sauropodomorph dinosaurs, and how lacunar densities can help us understand bone formation rates in the iconic sauropod dinosaurs. Ordinary least square and phylogenetic generalized least square regressions suggest that sauropodomorphs have lacunar densities higher than scaled up or comparably sized mammals. We also found normal mammalian-like osteocyte densities for the extinct bovid Myotragus, questioning its crocodilian-like physiology. When accounting for body mass effects and phylogeny, growth rates are a main factor determining the density of the lacunocanalicular network. However, functional aspects most likely play an important role as well. Observed differences in cell strategies between mammals and dinosaurs likely illustrate the convergent nature of fast growing bone tissues in these groups. PMID:24204748

  4. Preliminary analysis of osteocyte lacunar density in long bones of tetrapods: all measures are bigger in sauropod dinosaurs.

    PubMed

    Stein, Koen W H; Werner, Jan

    2013-01-01

    Osteocytes harbour much potential for paleobiological studies. Synchrotron radiation and spectroscopic analyses are providing fascinating data on osteocyte density, size and orientation in fossil taxa. However, such studies may be costly and time consuming. Here we describe an uncomplicated and inexpensive method to measure osteocyte lacunar densities in bone thin sections. We report on cell lacunar densities in the long bones of various extant and extinct tetrapods, with a focus on sauropodomorph dinosaurs, and how lacunar densities can help us understand bone formation rates in the iconic sauropod dinosaurs. Ordinary least square and phylogenetic generalized least square regressions suggest that sauropodomorphs have lacunar densities higher than scaled up or comparably sized mammals. We also found normal mammalian-like osteocyte densities for the extinct bovid Myotragus, questioning its crocodilian-like physiology. When accounting for body mass effects and phylogeny, growth rates are a main factor determining the density of the lacunocanalicular network. However, functional aspects most likely play an important role as well. Observed differences in cell strategies between mammals and dinosaurs likely illustrate the convergent nature of fast growing bone tissues in these groups.

  5. Descriptive Anatomy and Three-Dimensional Reconstruction of the Skull of the Early Tetrapod Acanthostega gunnari Jarvik, 1952

    PubMed Central

    Porro, Laura B.; Rayfield, Emily J.; Clack, Jennifer A.

    2015-01-01

    The early tetrapod Acanthostega gunnari is an iconic fossil taxon exhibiting skeletal morphology reflecting the transition of vertebrates from water onto land. Computed tomography data of two Acanthostega skulls was segmented using visualization software to digitally separate bone from matrix and individual bones of the skull from each other. A revised description of cranial and lower jaw anatomy in this taxon based on CT data includes new details of sutural morphology, the previously undescribed quadrate and articular bones, and the mandibular symphysis. Sutural morphology is used to infer loading regime in the skull during feeding, and suggests Acanthostega used its anterior jaws to initially seize prey while smaller posterior teeth were used to restrain struggling prey during ingestion. Novel methods were used to repair and retrodeform the skull, resulting in a three-dimensional digital reconstruction that features a longer postorbital region and more strongly hooked anterior lower jaw than previous attempts while supporting the presence of a midline gap between the nasals and median rostrals. PMID:25760343

  6. Urocortins of the South African clawed frog, Xenopus laevis: conservation of structure and function in tetrapod evolution.

    PubMed

    Boorse, Graham C; Crespi, Erica J; Dautzenberg, Frank M; Denver, Robert J

    2005-11-01

    Several corticotropin-releasing factor (CRF) family genes have been identified in vertebrates. Mammals have four paralogous genes that encode CRF or the urocortins 1, 2, and 3. In teleost fishes, a CRF, urotensin I (a fish ortholog of mammalian urocortin 1) and urocortin 3 have been identified, suggesting that at least three of the four mammalian lineages arose in a common ancestor of modern bony fishes and tetrapods. Here we report the isolation of genes orthologous to mammalian urocortin 1 and urocortin 3 from the South African clawed frog, Xenopus laevis. We characterize the pharmacology of the frog peptides and show that X. laevis urocortin 1 binds to and activates the frog CRF1 and CRF2 receptors at picomolar concentrations. Similar to mammals, frog urocortin 3 is selective for the CRF2 receptor. Only frog urocortin 1 binds to the CRF-binding protein, although with significantly lower affinity than frog CRF. Both urocortin genes are expressed in brain, pituitary, heart, and kidney of juvenile frogs; urocortin 1 is also expressed in skin. We also identified novel urocortin sequences in the genomes of pufferfish, zebrafish, chicken, and dog. Phylogenetic analysis supports the view that four paralogous lineages of CRF-like peptides arose before the divergence of the actinopterygian and sarcopterygian fishes. Our findings show that the functional relationships among CRF ligands and binding proteins, and their anorexigenic actions mediated by the CRF2 receptor, arose early in vertebrate evolution.

  7. Cranial Morphology of the Carboniferous-Permian Tetrapod Brachydectes newberryi (Lepospondyli, Lysorophia): New Data from µCT

    PubMed Central

    Pardo, Jason D.; Anderson, Jason S.

    2016-01-01

    Lysorophians are a group of early tetrapods with extremely elongate trunks, reduced limbs, and highly reduced skulls. Since the first discovery of this group, general similarities in outward appearance between lysorophians and some modern lissamphibian orders (specifically Urodela and Gymnophiona) have been recognized, and sometimes been the basis for hypotheses of lissamphibian origins. We studied the morphology of the skull, with particular emphasis on the neurocranium, of a partial growth series of the lysorophian Brachydectes newberryi using x-ray micro-computed tomography (μCT). Our study reveals similarities between the braincase of Brachydectes and brachystelechid recumbirostrans, corroborating prior work suggesting a close relationship between these taxa. We also describe the morphology of the epipterygoid, stapes, and quadrate in this taxon for the first time. Contra the proposals of some workers, we find no evidence of expected lissamphibian synapomorphies in the skull morphology in Brachydectes newberryi, and instead recognize a number of derived amniote characteristics within the braincase and suspensorium. Morphology previously considered indicative of taxonomic diversity within Lysorophia may reflect ontogenetic rather than taxonomic variation. The highly divergent morphology of lysorophians represents a refinement of morphological and functional trends within recumbirostrans, and is analogous to morphology observed in many modern fossorial reptiles. PMID:27563722

  8. A ZnO nanowire resistive switch

    NASA Astrophysics Data System (ADS)

    Karthik, K. R. G.; Ramanujam Prabhakar, Rajiv; Hai, L.; Batabyal, Sudip K.; Huang, Y. Z.; Mhaisalkar, S. G.

    2013-09-01

    An individual ZnO nanowire resistive switch is evaluated with Pt/ZnO nanowire/Pt topology. A detailed DC I-V curve analysis is performed to bring both the conduction mechanism and the device characteristics to light. The device is further studied at various vacuum pressures to ascertain the presence of polar charges in ZnO nanowires as the phenomenon leading to the formation of the switch. The disappearance of the resistive switching is also analyzed with two kinds of fabrication approaches Focused Ion/Electron Beam involved in the making the device and a summary of both length and fabrication dependences of resistive switching in the ZnO nanowire is presented.

  9. Magnetic properties of ZnO nanoparticles.

    PubMed

    Garcia, M A; Merino, J M; Fernández Pinel, E; Quesada, A; de la Venta, J; Ruíz González, M L; Castro, G R; Crespo, P; Llopis, J; González-Calbet, J M; Hernando, A

    2007-06-01

    We experimentally show that it is possible to induce room-temperature ferromagnetic-like behavior in ZnO nanoparticles without doping with magnetic impurities but simply inducing an alteration of their electronic configuration. Capping ZnO nanoparticles ( approximately 10 nm size) with different organic molecules produces an alteration of their electronic configuration that depends on the particular molecule, as evidenced by photoluminescence and X-ray absorption spectroscopies and altering their magnetic properties that varies from diamagnetic to ferromagnetic-like behavior.

  10. Electrochemical modification of properties of ZnO films

    NASA Astrophysics Data System (ADS)

    Abe, Koji; Okubo, Takamasa; Ishikawa, Hirohito

    2017-12-01

    The properties of Al-doped ZnO films and Li- and Al-doped ZnO films were modified by electrochemical treatment. A constant current was applied between a ZnO film and a Pt electrode in an electrolyte solution. The sheet resistance of the ZnO film increased and decreased depending on the direction of current flow during the electrochemical treatment. When the ZnO film was used as a cathode (forward biased condition), the sheet resistance of the ZnO film decreased with increasing treatment time. The optical bandgap of the H2-annealed ZnO film also depended on the direction of current flow and increased under the forward biased condition. The electrochemical treatment caused the Burstein-Moss effect.

  11. Miniaturized accelerometer made with ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Song, Sangho; Kim, Jeong Woong; Kim, Hyun Chan; Yun, Youngmin; Kim, Jaehwan

    2017-04-01

    Miniaturized accelerometer is required in many applications, such as, robotics, haptic devices, gyroscopes, simulators and mobile devices. ZnO is an essential semiconductor material with wide direct band gap, thermal stability and piezoelectricity. Especially, well aligned ZnO nanowire is appropriate for piezoelectric applications since it can produce high electrical signal under mechanical load. To miniaturize accelerometer, an aligned ZnO nanowire is adopted to implement active piezoelectric layer of the accelerometer and copper is chosen for the head mass. To grow ZnO nanowire on the copper head mass, hydrothermal synthesis is conducted and the effect of ZnO nanowire length on the accelerometer performance is investigated. Refresh hydrothermal synthesis can increase the length of ZnO nanowire. The performance of the fabricated ZnO accelerometers is compared with a commercial accelerometer. Sensitivity and linearity of the fabricated accelerometers are investigated.

  12. Semipolar III-nitride laser diodes with zinc oxide cladding.

    PubMed

    Myzaferi, Anisa; Reading, Arthur H; Farrell, Robert M; Cohen, Daniel A; Nakamura, Shuji; DenBaars, Steven P

    2017-07-24

    Incorporating transparent conducting oxide (TCO) top cladding layers into III-nitride laser diodes (LDs) improves device design by reducing the growth time and temperature of the p-type layers. We investigate using ZnO instead of ITO as the top cladding TCO of a semipolar (202¯1) III-nitride LD. Numerical modeling indicates that replacing ITO with ZnO reduces the internal loss in a TCO clad LD due to the lower optical absorption in ZnO. Lasing was achieved at 453 nm with a threshold current density of 8.6 kA/cm 2 and a threshold voltage of 10.3 V in a semipolar (202¯1) III-nitride LD with ZnO top cladding.

  13. Intrinsic and extrinsic doping of ZnO and ZnO alloys

    NASA Astrophysics Data System (ADS)

    Ellmer, Klaus; Bikowski, André

    2016-10-01

    In this article the doping of the oxidic compound semiconductor ZnO is reviewed with special emphasis on n-type doping. ZnO naturally exhibits n-type conductivity, which is used in the application of highly doped n-type ZnO as a transparent electrode, for instance in thin film solar cells. For prospective application of ZnO in other electronic devices (LEDs, UV photodetectors or power devices) p-type doping is required, which has been reported only minimally. Highly n-type doped ZnO can be prepared by doping with the group IIIB elements B, Al, Ga, and In, which act as shallow donors according to the simple hydrogen-like substitutional donor model of Bethe (1942 Theory of the Boundary Layer of Crystal Rectifiers (Boston, MA: MIT Rad Lab.)). Group IIIA elements (Sc, Y, La etc) are also known to act as shallow donors in ZnO, similarly explainable by the shallow donor model of Bethe. Some reports showed that even group IVA (Ti, Zr, Hf) and IVB (Si, Ge) elements can be used to prepare highly doped ZnO films—which, however, can no longer be explained by the simple hydrogen-like substitutional donor model. More probably, these elements form defect complexes that act as shallow donors in ZnO. On the other hand, group V elements on oxygen lattice sites (N, P, As, and Sb), which were viewed for a long time as typical shallow acceptors, behave instead as deep acceptors, preventing high hole concentrations in ZnO at room temperature. Also, ‘self’-compensation, i.e. the formation of a large number of intrinsic donors at high acceptor concentrations seems to counteract the p-type doping of ZnO. At donor concentrations above about 1020 cm-3, the electrical activation of the dopant elements is often less than 100%, especially in polycrystalline thin films. Reasons for the electrical deactivation of the dopant atoms are (i) the formation of dopant-defect complexes, (ii) the compensation of the electrons by acceptors (Oi, VZn) or (iii) the formation of secondary phases, for

  14. Random lasing from dye-doped negative liquid crystals using ZnO nanoparticles as tunable scatters

    NASA Astrophysics Data System (ADS)

    Li, Long-Wu; Shang, Zhen-Zhen; Deng, Luogen

    2016-09-01

    This work demonstrates the realization of a lasing in scattering media, which contains dispersive solution of ZnO nanoparticles (NPs) and laser dye 4-dicyanomethylene-2-methyle-6-(p-dimethylaminostyryl)-4H-pyran(DCM) in negative liquid crystals (LCs) that was injected into a cell. The lasing intensity of the dye-doped negative LC laser can be tuned from low to high if the NPs concentration is increased. The tunability of the laser is attributable to the clusters-sensitive feature in effective refractive index of the negative LCs. Such a tunable negative liquid crystal laser can be used in the fabrication of new optical sources, optical communication, and liquid crystal laser displays. Project supported by the Doctoral Science Research Start-up Funding of Guizhou Normal University, China (Grant No. 11904-0514162) and the National Natural Science Foundation of China (Grant No. 11474021).

  15. Synthesis and photonic property study of ZnO nanowires for a real time photodynamic therapy monitoring probe

    NASA Astrophysics Data System (ADS)

    Sridhar, D.; Xie, Jining; Abraham, Jose K.; Varadan, Vijay K.

    2007-04-01

    In this paper, we present how the photonic properties of zinc oxide (ZnO) nanowires can be used to potentially advance the effectiveness of Photodynamic therapy (PDT), one of the most recent and promising approaches among cancer therapies. Presently, PDT employs laser light to activate intravenously or topically administered photosensitizers to give rise to highly reactive singlet oxygen which has a very short lifetime and is capable of biochemical damage to cell membranes of the tumor. A probe that can monitor in real time the penetration depth of the laser in the tumor and also the evolution of the singlet oxygen, which is critical for tumor eradication, is capable of improving the efficacy of PDT quite significantly. Such a probe, by providing real time feedback, can help us determine whether to increase or decrease the light exposure dose and also if further local administration of photosensitizers is required or not. ZnO nanowires are known to be photoconductive and recent research also demonstrated the temperature dependence of the photocurrent in the nanowires. They are also sensitive to blue and other near UV spectra which is same range of activation wavelengths of most photosensitizers, and hence making them a good candidate for a potential PDT monitoring probe. ZnO nanowires were fabricated on silicon substrates by vapor phase deposition using e-beam evaporated gold as a catalyst. Control of the dimensions of the nanowires could be achieved by varying the dimensions of the catalyst by means of e-beam evaporation process. Photoluminescence properties of ZnO nanowires were investigated at UV and near UV wavelengths. Further, ZnO is also known for its antimicrobial properties, thereby ruling out any possibility of bacterial infection because of the implanted probe. This study was done to compliment the existing expertise of our research group in the design and fabrication of several nanowire based probes and microsensors specifically for neuroelectronic and

  16. Nonlinear absorption properties of ZnO and Al doped ZnO thin films under continuous and pulsed modes of operations

    NASA Astrophysics Data System (ADS)

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

    2018-06-01

    In the present investigation, we present the variations in nonlinear optical (NLO) properties of undoped and Al doped ZnO (AZO) films under two different off-resonant regimes using continuous and pulsed mode lasers. Z-scan open aperture experiment is performed to quantify nonlinear absorption constant and imaginary component of third order susceptibility. Reverse saturable absorption (RSA) and saturable absorption (SA) behaviors are noticed in both undoped and AZO films under pulsed mode and continuous wavelength (CW) regime respectively. The RSA and SA behavior observed in the films are attributed to two photon absorption (TPA) and thermal lensing properties respectively. The thermal lensing is assisted by the thermo-optic effects within the films due to the continuous illumination of the laser.

  17. A Giant Chelonioid Turtle from the Late Cretaceous of Morocco with a Suction Feeding Apparatus Unique among Tetrapods

    PubMed Central

    Bardet, Nathalie; Jalil, Nour-Eddine; de Lapparent de Broin, France; Germain, Damien; Lambert, Olivier; Amaghzaz, Mbarek

    2013-01-01

    Background Secondary adaptation to aquatic life occurred independently in several amniote lineages, including reptiles during the Mesozoic and mammals during the Cenozoic. These evolutionary shifts to aquatic environments imply major morphological modifications, especially of the feeding apparatus. Mesozoic (250–65 Myr) marine reptiles, such as ichthyosaurs, plesiosaurs, mosasaurid squamates, crocodiles, and turtles, exhibit a wide range of adaptations to aquatic feeding and a broad overlap of their tooth morphospaces with those of Cenozoic marine mammals. However, despite these multiple feeding behavior convergences, suction feeding, though being a common feeding strategy in aquatic vertebrates and in marine mammals in particular, has been extremely rarely reported for Mesozoic marine reptiles. Principal Findings A relative of fossil protostegid and dermochelyoid sea turtles, Ocepechelon bouyai gen. et sp. nov. is a new giant chelonioid from the Late Maastrichtian (67 Myr) of Morocco exhibiting remarkable adaptations to marine life (among others, very dorsally and posteriorly located nostrils). The 70-cm-long skull of Ocepechelon not only makes it one of the largest marine turtles ever described, but also deviates significantly from typical turtle cranial morphology. It shares unique convergences with both syngnathid fishes (unique long tubular bony snout ending in a rounded and anteriorly directed mouth) and beaked whales (large size and elongated edentulous jaws). This striking anatomy suggests extreme adaptation for suction feeding unmatched among known turtles. Conclusion/Significance The feeding apparatus of Ocepechelon, a bony pipette-like snout, is unique among tetrapods. This new taxon exemplifies the successful systematic and ecological diversification of chelonioid turtles during the Late Cretaceous. This new evidence for a unique trophic specialization in turtles, along with the abundant marine vertebrate faunas associated to Ocepechelon in the Late

  18. A new rhynchocephalian from the late jurassic of Germany with a dentition that is unique amongst tetrapods.

    PubMed

    Rauhut, Oliver W M; Heyng, Alexander M; López-Arbarello, Adriana; Hecker, Andreas

    2012-01-01

    Rhynchocephalians, the sister group of squamates (lizards and snakes), are only represented by the single genus Sphenodon today. This taxon is often considered to represent a very conservative lineage. However, rhynchocephalians were common during the late Triassic to latest Jurassic periods, but rapidly declined afterwards, which is generally attributed to their supposedly adaptive inferiority to squamates and/or Mesozoic mammals, which radiated at that time. New finds of Mesozoic rhynchocephalians can thus provide important new information on the evolutionary history of the group. A new fossil relative of Sphenodon from the latest Jurassic of southern Germany, Oenosaurus muehlheimensis gen. et sp. nov., presents a dentition that is unique amongst tetrapods. The dentition of this taxon consists of massive, continuously growing tooth plates, probably indicating a crushing dentition, thus representing a previously unknown trophic adaptation in rhynchocephalians. The evolution of the extraordinary dentition of Oenosaurus from the already highly specialized Zahnanlage generally present in derived rhynchocephalians demonstrates an unexpected evolutionary plasticity of these animals. Together with other lines of evidence, this seriously casts doubts on the assumption that rhynchocephalians are a conservative and adaptively inferior lineage. Furthermore, the new taxon underlines the high morphological and ecological diversity of rhynchocephalians in the latest Jurassic of Europe, just before the decline of this lineage on this continent. Thus, selection pressure by radiating squamates or Mesozoic mammals alone might not be sufficient to explain the demise of the clade in the Late Mesozoic, and climate change in the course of the fragmentation of the supercontinent of Pangaea might have played a major role.

  19. Structural and plasmonic properties of noble metal doped ZnO nanomaterials

    NASA Astrophysics Data System (ADS)

    Pathak, Trilok K.; Swart, H. C.; Kroon, R. E.

    2018-04-01

    Noble metal doped ZnO has been synthesized by the combustion method and the effect of different metals (Ag, Au, Pd) on the structural, morphological, optical, photoluminescence and localized surface plasmon resonance (LSPR) properties has been investigated. X-ray diffraction analysis revealed that the ZnO had a hexagonal wurtzite structure and the crystallite sizes were affected by the doping. The formation of noble metal nanoparticles (NPs) was investigated using transmission electron microscopy and diffuse reflectance spectra. The LSPR of the metallic NPs was predicted using Mie theory calculations. The absorption spectra were calculated using the Kubelka-Munk function and the optical bandgap varied from 3.06 to 3.18 eV for the different doping materials. The experimental results suggest that the origin of enhanced emission was due to direct interaction between the laser photons and the noble material NPs which in turn leads to photoemission transfer of electrons from the noble metals NPs to the conduction band of ZnO.

  20. Optical absorption edge of ZnO thin films: The effect of substrate

    NASA Astrophysics Data System (ADS)

    Srikant, V.; Clarke, D. R.

    1997-05-01

    The optical absorption edge and the near-absorption edge characteristics of undoped ZnO films grown by laser ablation on various substrates have been investigated. The band edge of films on C [(0001)] and R-plane [(1102)] sapphire, 3.29 and 3.32 eV, respectively, are found to be very close to the single crystal value of ZnO (3.3 eV) with the differences being accounted for in terms of the thermal mismatch strain using the known deformation potentials of ZnO. In contrast, films grown on fused silica consistently exhibit a band edge ˜0.1 eV lower than that predicted using the known deformation potential and the thermal mismatch strains. This behavior is attributed to the small grain size (50 nm) realized in these films and the effect of electrostatic potentials that exist at the grain boundaries. Additionally, the spread in the tail (E0) of the band edge for the different films is found to be very sensitive to the defect structure in the films. For films grown on sapphire substrates, values of E0 as low as 30 meV can be achieved on annealing in air, whereas films on fused silica always show a value >100 meV. We attribute this difference to the substantially higher density of high-angle grain boundaries in the films on fused silica.

  1. Effects of silver impurity on the structural, electrical, and optical properties of ZnO nanowires

    PubMed Central

    2011-01-01

    1, 3, and 5 wt.% silver-doped ZnO (SZO) nanowires (NWs) are grown by hot-walled pulsed laser deposition. After silver-doping process, SZO NWs show some change behaviors, including structural, electrical, and optical properties. In case of structural property, the primary growth plane of SZO NWs is switched from (002) to (103) plane, and the electrical properties of SZO NWs are variously measured to be about 4.26 × 106, 1.34 × 106, and 3.04 × 105 Ω for 1, 3, and 5 SZO NWs, respectively. In other words, the electrical properties of SZO NWs depend on different Ag ratios resulting in controlling the carrier concentration. Finally, the optical properties of SZO NWs are investigated to confirm p-type semiconductor by observing the exciton bound to a neutral acceptor (A0X). Also, Ag presence in ZnO NWs is directly detected by both X-ray photoelectron spectroscopy and energy dispersive spectroscopy. These results imply that Ag doping facilitates the possibility of changing the properties in ZnO NWs by the atomic substitution of Ag with Zn in the lattice. PMID:21985620

  2. Triple-wavelength passively Q-switched ytterbium-doped fibre laser using zinc oxide nanoparticles film as a saturable absorber

    NASA Astrophysics Data System (ADS)

    Mohsin Al-Hayali, Sarah Kadhim; Hadi Al-Janabi, Abdul

    2018-07-01

    We report on the generation of a triple-wavelength passively Q-switched ytterbium-doped fibre laser using a saturable absorber (SA) based on zinc oxide nanoparticles (ZnO NPs) film. The SA was fabricated by embedding ZnO NPs powder into a polyvinyl alcohol as a host polymer. By properly adjusting the pump power and the polarization state, single-, dual- and triple-wavelength Q-switching are stably generated without additional components (such as optical filter, or fibre grating). For the triple wavelength operation, the fibre laser generates a maximum pulse repetition of 87.9 kHz with the shortest pulse duration of 2.7 μs. To the best of authors' knowledge, it's the first demonstration of triple-wavelength passively Q-switching fibre laser using ZnO NPs as a SA. Our results suggest that ZnO is a promising SA for multi-wavelength laser operation.

  3. Comparative anatomy, homologies and evolution of the pectoral and forelimb musculature of tetrapods with special attention to extant limbed amphibians and reptiles.

    PubMed

    Abdala, Virginia; Diogo, Rui

    2010-11-01

    The main aim of the present work is to synthesize the information obtained from our dissections of the pectoral and forelimb muscles of representative members of the major extant taxa of limbed amphibians and reptiles and from our review of the literature, in order to provide an account of the comparative anatomy, homologies and evolution of these muscles in the Tetrapoda. The pectoral and forelimb musculature of all these major taxa conform to a general pattern that seems to have been acquired very early in the evolutionary history of tetrapods. Although some muscles are missing in certain taxa, and a clear departure from this general pattern is obviously present in derived groups such as birds, the same overall configuration is easily distinguishable in these taxa. Among the most notable anatomical differences between the groups, one that seems to have relevant evolutionary and functional implications, concerns the distal insertion points of the forearm musculature. In tetrapods, the muscles of the radial and ulnar complexes of the forearm are pleisomorphically mainly inserted onto the radius/ulna or onto the more proximal carpal bones, but in mammals some of these muscles insert more distally onto bones such as the metacarpals. Interestingly, a similar trend towards a more distal insertion of these muscles is also found in some non-mammalian tetrapod taxa, such as some anurans (e.g. Phyllomedusa). This may be correlated with the acquisition of more subtle digital movement abilities in these latter taxa. © 2010 The Authors. Journal of Anatomy © 2010 Anatomical Society of Great Britain and Ireland.

  4. Comparative pelvic development of the axolotl (Ambystoma mexicanum) and the Australian lungfish (Neoceratodus forsteri): conservation and innovation across the fish-tetrapod transition

    PubMed Central

    2013-01-01

    Background The fish-tetrapod transition was one of the major events in vertebrate evolution and was enabled by many morphological changes. Although the transformation of paired fish fins into tetrapod limbs has been a major topic of study in recent years, both from paleontological and comparative developmental perspectives, the interest has focused almost exclusively on the distal part of the appendage and in particular the origin of digits. Relatively little attention has been paid to the transformation of the pelvic girdle from a small unipartite structure to a large tripartite weight-bearing structure, allowing tetrapods to rely mostly on their hindlimbs for locomotion. In order to understand how the ischium and the ilium evolved and how the acetabulum was reoriented during this transition, growth series of the Australian lungfish Neoceratodus forsteri and the Mexican axolotl Ambystoma mexicanum were cleared and stained for cartilage and bone and immunostained for skeletal muscles. In order to understand the myological developmental data, hypotheses about the homologies of pelvic muscles in adults of Latimeria, Neoceratodus and Necturus were formulated based on descriptions from the literature of the coelacanth (Latimeria), the Australian Lungfish (Neoceratodus) and a salamander (Necturus). Results In the axolotl and the lungfish, the chondrification of the pelvic girdle starts at the acetabula and progresses anteriorly in the lungfish and anteriorly and posteriorly in the salamander. The ilium develops by extending dorsally to meet and connect to the sacral rib in the axolotl. Homologous muscles develop in the same order with the hypaxial musculature developing first, followed by the deep, then the superficial pelvic musculature. Conclusions Development of the pelvic endoskeleton and musculature is very similar in Neoceratodus and Ambystoma. If the acetabulum is seen as being a fixed landmark, the evolution of the ischium only required pubic pre

  5. ZnO PN Junctions for Highly-Efficient, Low-Cost Light Emitting Diodes

    SciT

    David P. Norton; Stephen Pearton; Fan Ren

    2007-09-30

    light emission. The project engaged established expertise at the University of Florida in ZnO film growth (D. Norton), device fabrication (F. Ren) and wide bandgap photonics (S. Pearton). It addressed p-type doping and junction formation in (Zn,Mg)O alloy thin films. The project employed pulsed laser deposition for film growth. The p-type dopant of interest was primarily phosphorus, given the recent results in our laboratory and elsewhere that this anions can yield p-type ZnO-based materials. The role of Zn interstitials, oxygen vacancies, and/or hydrogen complexes in forming compensating shallow donor levels imposes the need to simultaneously consider the role of in situ and post-growth processing conditions. Temperature-dependent Hall, Seebeck, C-V, and resistivity measurements was used to determine conduction mechanisms, carrier type, and doping. Temperature-dependent photoluminescence was used to determine the location of the acceptor level, injection efficiency, and optical properties of the structures. X-ray diffraction will used to characterize film crystallinity. Using these materials, the fabrication and characterization of (Zn,Mg)O pn homojunction and heterojunction devices was pursued. Electrical characterization of the junction capacitance and I-V behavior was used to extract junction profile and minority carrier lifetime. Electroluminescence from biased junctions was the primary property of interest.« less

  6. Effect of Copper Oxide Nanoparticles as a barrier for Efficiency Improvement in ZnO Dye-Sensitized Solar Cells

    NASA Astrophysics Data System (ADS)

    Sonthila, A.; Ruankham, P.; Choopun, S.; Wongratanaphisan, D.; Phadungdhitidhada, S.; Gardchareon, A.

    2017-09-01

    CuO nanoparticles (CuO NPs) were used as a barrier layer in ZnO dye-sensitized solar cells (DSSCs) to obtain high power conversion efficiency. The barrier layer was investigated in terms of the size of CuO NPs by varying power of pulsed Nd:YAG (1064 nm) laser ablation. Morphological and optical properties of CuO NPs were characterized by transmission electron microscopy (TEM), UV-visible spectrophotometry (UV-vis) and dynamic light scattering (DLS). It was found that the CuO NPs are rather spherical in shape with diameter in between 20 - 132 nm. In addition, the energy gap of CuO decreases with the increase of CuO NPs size. The power conversion efficiency of ZnO DSSCs was measured under illumination of simulated sunlight obtained from a solar simulator with the radiant power of 100 mW/cm2. The results showed that the ZnO DSSC with the CuO NPs with size of 37 nm exhibits the optimum power conversion efficiency of 1.01% which is higher than that of one without CuO NPs. Moreover, the power conversion efficiency of the ZnO DSSCs decreases with the increase of CuO NPs size.

  7. ZnO nanopowder induced light scattering for improved visualization of emission sites in carbon nanotube films and arrays

    NASA Astrophysics Data System (ADS)

    Meško, Marcel; Ou, Qiongrong; Matsuda, Takafumi; Ishikawa, Tomokazu; Veis, Martin; Antoš, Roman; Ogino, Akihisa; Nagatsu, Masaaki

    2009-06-01

    We report on ZnO nanopowder induced light scattering for improved visualization of emission sites in carbon nanotube films and arrays. We observed a significant reduction of the internal multiple light scattering phenomena, which are characteristic for ZnO micropowders. The microsized grains of the commercially available ZnO:Zn (P 15) were reduced to the nanometre scale by pulsed laser ablation at an oxygen ambient pressure of 10 kPa. Our investigations show no crystalline change and no shift of the broad green emission peak at 500 nm for the ZnO nanopowder. For the application in field emission displays, we demonstrate the possibility of achieving cathodoluminescence with a fine pitch size of 100 µm of the patterned pixels without requiring additional electron beam focusing and without a black matrix. Moreover, the presented results show the feasibility of employing ZnO nanopowder as a detection material for the phosphorus screen method, which is able to localize emission sites of carbon nanotube films and arrays with an accuracy comparable to scanning anode field emission microscopy.

  8. Highly stable precursor solution containing ZnO nanoparticles for the preparation of ZnO thin film transistors.

    PubMed

    Huang, Heh-Chang; Hsieh, Tsung-Eong

    2010-07-23

    ZnO particles with an average size of about 5 nm were prepared via a sol-gel chemical route and the silane coupling agent, (3-glycidyloxypropyl)-trimethoxysilane (GPTS), was adopted to enhance the dispersion of the ZnO nanoparticles in ethyl glycol (EG) solution. A ZnO surface potential as high as 66 mV was observed and a sedimentation test showed that the ZnO precursor solution remains transparent for six months of storage, elucidating the success of surface modification on ZnO nanoparticles. The ZnO thin films were then prepared by spin coating the precursor solution on a Si wafer and annealing treatments at temperatures up to 500 degrees C were performed for subsequent preparation of ZnO thin film transistors (TFTs). Microstructure characterization revealed that the coalescence of ZnO nanoparticles occurs at temperatures as low as 200 degrees C to result in a highly uniform, nearly pore-free layer. However, annealing at higher temperatures was required to remove organic residues in the ZnO layer for satisfactory device performance. The 500 degrees C-annealed ZnO TFT sample exhibited the best electrical properties with on/off ratio = 10(5), threshold voltage = 17.1 V and mobility (micro) = 0.104 cm(2) V(-1) s(-1).

  9. Anatomy of the pectoral and forelimb muscles of wildtype and green fluorescent protein-transgenic axolotls and comparison with other tetrapods including humans: a basis for regenerative, evolutionary and developmental studies.

    PubMed

    Diogo, R; Tanaka, E M

    2012-12-01

    The axolotl Ambystoma mexicanum is one of the most used model organisms in evolutionary, developmental and regenerative studies, particularly because it can reconstitute a fully functional and complete forelimb/hindlimb. Surprisingly, there is no publication that describes all the pectoral and forelimb muscles of this species or provides a comparative framework between these muscles and those of other model organisms and of modern humans. In the present paper we describe and illustrate all these muscles in A. mexicanum and provide the first report about the myology of adults of a model organism that is based on analyses and dissections of both wildtype animals and transgenic animals that express green fluorescent protein (GFP) in muscle fibers. On the one hand, the inclusion of GFP-transgenic animals allows us to show the muscles as more commonly seen, and thus easier to understand, by current developmental and regenerative biologists. On the other hand, by including wildtype and GFP-transgenic animals and by visualizing these latter animals with and without a simultaneous transmission laser light, we were able to obtain a more complete and clearer understanding of the exact limit of the fleshy and tendinous parts of the muscles and their specific connections with the skeletal elements. This in turn allowed us to settle some controversies in previous anatomical and comparative studies. As most developmental, regenerative and evolutionary biologists are interested in comparing their observations of A. mexicanum with observations in other model organisms, and ultimately in using this information to increase the understanding of human evolution and medicine, we also provide tables showing the homologies between the pectoral and forelimb muscles of axolotls, of model organisms such as mice, frogs and chicken, and of Homo sapiens. An example illustrating the outcomes of using our methodology and of our observations is that they revealed that, contrary to what is often

  10. Anatomy of the pectoral and forelimb muscles of wildtype and green fluorescent protein-transgenic axolotls and comparison with other tetrapods including humans: a basis for regenerative, evolutionary and developmental studies

    PubMed Central

    Diogo, R; Tanaka, E M

    2012-01-01

    The axolotl Ambystoma mexicanum is one of the most used model organisms in evolutionary, developmental and regenerative studies, particularly because it can reconstitute a fully functional and complete forelimb/hindlimb. Surprisingly, there is no publication that describes all the pectoral and forelimb muscles of this species or provides a comparative framework between these muscles and those of other model organisms and of modern humans. In the present paper we describe and illustrate all these muscles in A. mexicanum and provide the first report about the myology of adults of a model organism that is based on analyses and dissections of both wildtype animals and transgenic animals that express green fluorescent protein (GFP) in muscle fibers. On the one hand, the inclusion of GFP-transgenic animals allows us to show the muscles as more commonly seen, and thus easier to understand, by current developmental and regenerative biologists. On the other hand, by including wildtype and GFP-transgenic animals and by visualizing these latter animals with and without a simultaneous transmission laser light, we were able to obtain a more complete and clearer understanding of the exact limit of the fleshy and tendinous parts of the muscles and their specific connections with the skeletal elements. This in turn allowed us to settle some controversies in previous anatomical and comparative studies. As most developmental, regenerative and evolutionary biologists are interested in comparing their observations of A. mexicanum with observations in other model organisms, and ultimately in using this information to increase the understanding of human evolution and medicine, we also provide tables showing the homologies between the pectoral and forelimb muscles of axolotls, of model organisms such as mice, frogs and chicken, and of Homo sapiens. An example illustrating the outcomes of using our methodology and of our observations is that they revealed that, contrary to what is often

  11. Synthesis and characterization of ZnO thin films

    SciT

    Anilkumar, T. S., E-mail: anil24march@gmail.com; Girija, M. L., E-mail: girija.ml.grt1@gmail.com; Venkatesh, J., E-mail: phph9502@yahoo.com

    2016-05-06

    Zinc oxide (ZnO) Thin films were deposited on glass substrate using Spin coating method. Zinc acetate dehydrate, Carbinol and Mono-ethanolamine were used as the precursor, solvent and stabilizer respectively to prepare ZnO Thin-films. The molar ratio of Monoethanolamine to Zinc acetate was maintained as approximately 1. The thickness of the films was determined by Interference technique. The optical properties of the films were studied by UV Vis-Spectrophotometer. From transmittance and absorbance curve, the energy band gap of ZnO is found out. Electrical Conductivity measurements of ZnO are carried out by two probe method and Activation energy for the electrical conductivitymore » of ZnO are found out. The crystal structure and orientation of the films were analyzed by XRD. The XRD patterns show that the ZnO films are polycrystalline with wurtzite hexagonal structure.« less

  12. Enhanced photoluminescence properties of Al doped ZnO films

    NASA Astrophysics Data System (ADS)

    Chen, H. X.; Ding, J. J.

    2018-01-01

    Al doped ZnO films are fabricated by radio frequency magnetron sputtering. In general, visible emission is related to various defects in ZnO films. However, too much defects will cause light emission quench. So it is still a controversial issue to control appropriate defect concentrations. In this paper, based on our previous results, appropriate Al doping concentration is chosen to introduce more both interstitial Zn and O vacancy defects, which is responsible for main visible emission of ZnO films. A strong emission band located at 405 nm and a long tail peak is observed in the samples. As Al is doped in ZnO films, the intensity of emission peaks increases. Zn interstitial might increase with the increasing Al3+ substitute because ZnO was a self-assembled oxide compound. So Zn interstitial defect concentration in Al doped ZnO films will increase greatly, which results in the intensity of emission peaks increases.

  13. Room temperature ferromagnetism in Cu doped ZnO

    NASA Astrophysics Data System (ADS)

    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.

  14. Cranial muscle development in the model organism ambystoma mexicanum: implications for tetrapod and vertebrate comparative and evolutionary morphology and notes on ontogeny and phylogeny.

    PubMed

    Ziermann, Janine M; Diogo, Rui

    2013-07-01

    There is still confusion about the homology of several cranial muscles in salamanders with those of other vertebrates. This is true, in part, because of the fact that many muscles present in early ontogeny of amphibians disappear during development and specifically during metamorphosis. Resolving this confusion is important for the understanding of the comparative and evolutionary morphology of vertebrates and tetrapods because amphibians are the phylogenetically most plesiomorphic tetrapods, concerning for example their myology, and include two often used model organisms, Xenopus laevis (anuran) and Ambystoma mexicanum (urodele). Here we provide the first detailed report of the cranial muscle development in axolotl from early ontogenetic stages to the adult stage. We describe different and complementary types of general muscle morphogenetic gradients in the head: from anterior to posterior, from lateral to medial, and from origin to insertion. Furthermore, even during the development of neotenic salamanders such as axolotls, various larval muscles become indistinct, contradicting the commonly accepted view that during ontogeny the tendency is mostly toward the differentiation of muscles. We provide an updated comparison between these muscles and the muscles of other vertebrates, a discussion of the homologies and evolution, and show that the order in which the muscles appear during axolotl ontogeny is in general similar to their appearance in phylogeny (e.g. differentiation of adductor mandibulae muscles from one anlage to four muscles), with only a few remarkable exceptions, as for example the dilatator laryngis that appears evolutionary later but in the development before the intermandibularis. Copyright © 2013 Wiley Periodicals, Inc.

  15. Unexpected skeletal histology of an ichthyosaur from the Middle Jurassic of Patagonia: implications for evolution of bone microstructure among secondary aquatic tetrapods.

    PubMed

    Talevi, Marianella; Fernández, Marta S

    2012-03-01

    During the Mesozoic, one of the most significant evolutionary processes was the secondary adaptation of tetrapods to life in water. Several non-related lineages invaded from the terrestrial realms and from the oceans of the entire world. Among these lineages, ichthyosaurs were particularly successful. Advance parvipelvian ichthyosaurs were the first tetrapods to evolve a fish-shaped body profile. The deep skeletal modifications of their bodies, as well as their biology, depict advance ichthyosaurs as the paradigm of secondary adaptation of reptiles to marine life. Functional inferences point to them as off-shore cruising forms, similar to a living tuna, and some of them were capable of deep diving. Bone histology of some genera such as Temnodontosaurus, Stenopterygius, Ichthyosaurus, and Caypullisaurus, characterized by overall cancellous bone, is consistent with the idea of a fish-shaped ichthyosaurs as fast and far cruisers. Here, we provide histological examination of the ribs of the Middle Jurassic parvipelvian Mollesaurus. Contrasting with the bone histology of other parvipelvian, Mollesaurus ribs are characterized by a compact and thick cortex. Our data indicate that the rib cage was heavy and suggest that not all advanced ichthyosaurs were fast cruisers. The compact and dense ribs in these parvipelvian show that advance ichthyosaurs were ecologically more diverse than previously thought and that the lightening of the skeleton reversed, as also occurred in the evolution of cetacean, at least once along the evolutionary history of ichthyosaurs.

  16. Prediction of microwave absorption properties of tetrapod-needle zinc oxide whisker radar absorbing material without prior knowledge

    NASA Astrophysics Data System (ADS)

    Zhao, Yu-Chen; Wang, Jie; Liu, Jiang-Fan; Song, Zhong-Guo; Xi, Xiao-Li

    2017-07-01

    The radar absorbing material (RAM) containing a tetrapod-needle zinc oxide whisker (T-ZnOw) has been proved to have good efficiency of microwave absorption. However, the available theoretical models, which are intended to predict the microwave absorbing properties of such an interesting composite, still cannot work well without some prior knowledge, like the measured effective electromagnetic parameters of the prepared T-ZnOw composite. Hence, we propose a novel predictive method here to calculate the reflectivity of T-ZnOw RAM without prior knowledge. In this method, the absorbing ability of this kind of material is divided into three main aspects: the unstructured background, the conductive network, and the nanostructured particle. Then, the attenuation properties of these three parts are represented, respectively, by three different approaches: the equivalent spherical particle and the static strong fluctuation theory, the equivalent circuit model obtained from the complex impedance spectra technology, and the combination of four different microscopic electromagnetic responses. The operational calculation scheme can be obtained by integrating these three absorption effects into the existing theoretical attenuation model. The reasonable agreement between the theoretical and experimental data of a T-ZnON/SiO2 composite in the range of 8-14 GHz shows that the proposed scheme can predict the microwave absorption properties of the T-ZnOw RAM. Furthermore, a detailed analysis of these three mechanisms indicates that, on the one hand, the background plays a dominant role in determining the real part of the effective permittivity of the T-ZnOw composite while the network and the particle are the decisive factors of its material loss; on the other hand, an zero-phase impedance, i.e., a pure resistance, with appropriate resonance characteristic might be a rational physical description of the attenuation property of the conductive network, but it is difficult to realize

  17. Selective nature of end-Triassic tetrapod extinctions consistent with scenarios of extreme volcanic winters not a super-greenhouse

    NASA Astrophysics Data System (ADS)

    Olsen, P. E.

    2016-12-01

    Eruptions of the giant Central Atlantic Magmatic Province (CAMP) are temporally linked to the end-Triassic extinction event (ETE). Continental tetrapod extinctions were highly selective affecting specific higher taxa and different latitudinal zones. The Late Triassic tropics were strongly dominated by diverse crocodile-line archosaurs while dinosaurs were rare, represented only by relatively small carnivores. Triassic high-latitudes had higher dinosaur diversity with abundant and often large dinosaurian herbivores. Only two small-bodied crocodile-line lineages survived the ETE, with a near-global homogenization of continental assemblages. Herbivorous dinosaurs spread globally while carnivorous dinosaurs became much larger. CAMP-sourced CO2 doublings (1,2) over 10s to 100s of thousands of years produced significant warming and some tropical lethality, but how this led to higher latitude extinctions is hard to see. In contrast, the taxonomic and geographic selectivity is consistent with many brief but severe sulfate "volcanic winters" (3) plausibly leading to freezing tropics. Crocodile-line archosaurs, dinosaurs, and pterosaurs and were relatively resistant to heat induced water stress, but the Crocodile-line archosaurs lacked insolation, while the latter had it. The lengthy super-greenhouse events allowed small crocodile-line archosaurs to escape to cooler climes or burrow, but during volcanic winters larger forms had nowhere to go. I hypothesize that crocodile-line and other herptile extinctions resulted from extreme cold events, for which they had no adaptations. In contrast, dinosaurs, other insulated forms, as well as burrowers survived the cold. This hypothesis is consistent with global post-ETE faunal homogenization, when the higher latitude dinosaurs spreading globally and becoming ecologically dominant. Tropical freezing predicts that ice crystal impressions should be found in facies that typically have reptile footprints in eastern North America deposited

  18. Characterization of ZnO Nanoparticles using Superconducting Tunnel Junction Cryodetection Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Plath, Logan D.; Wang, Zongyu; Yan, Jiajun; Matyjaszewski, Krzysztof; Bier, Mark E.

    2017-06-01

    Zinc oxide (ZnO) nanoparticles coated with either n-octylamine (OA) or α-amino poly(styrene- co-acrylonitrile) (PSAN) ligands (L) have been analyzed using laser desorption/ionization and matrix assisted laser desorption/ionization (MALDI) time-of-flight (TOF) superconducting tunnel junction (STJ) cryodetection mass spectrometry. STJ cryodetection has the advantage of high m/ z detection and allows for the determination of average molecular weights and dispersities for 500-600 kDa ZnO-L nanoparticles. The ability to detect the relative energies deposited into the STJs has allowed for investigation of ZnO-L metastable fragmentation. ZnO-L precursor ions gain enough internal energy during the MALDI process to undergo metastable fragmentation in the flight tube. These fragments produced a lower energy peak, which was assigned as ligand-stripped ZnO cores whereas the individual ligands were at too low of an energy to be observed. From these STJ energy resolved peaks, the average weight percentage of inorganic material making up the nanoparticle was determined, where ZnO-OA and ZnO-PSAN nanoparticles are comprised of 62% and 68% wt ZnO, respectively. In one example, grafting densities were calculated based on the metastable fragmentation of ligands from the core to be 16 and 1.1 nm-2 for ZnO-OA and ZnO-PSAN, respectively, and compared with values determined by thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). [Figure not available: see fulltext.

  19. Sodium doping in ZnO crystals

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Spin noise spectroscopy of ZnO

    NASA Astrophysics Data System (ADS)

    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.

  2. The Phase Relations in the In 2O 3-Al 2ZnO 4-ZnO System at 1350°C

    NASA Astrophysics Data System (ADS)

    Nakamura, Masaki; Kimizuka, Noboru; Mohri, Takahiko; Isobe, Mitsumasa

    1993-08-01

    Phase relations in the In 2O 3-Al 2ZnO 4-ZnO system at 1350°C are determined by a classical quenching method. This system consists of In 2O 3, Al 2ZnO 4, ZnO, and homologous phases InAlO 3(ZnO) m ( m = 2, 3, …) having solid solutions with LuFeO 3(ZnO) m-type crystal structures. These solid solution ranges are as follows: In 1+ x1Al 1- x1O 3(ZnO) 2 ( x1 = 0.70)-In 1+ x2Al 1- x2O 3(ZnO) 2 ( x2 = 0.316-0.320), In 2O 3(ZnO) 3-In 1+ xAl 1- xO 3(ZnO) 3 ( x = 0.230), In 2O 3(ZnO) 4-In 1+ xAl 1- xO 3(ZnO) 4 ( x = 0.15-0.16), In 2O 3(ZnO) 5-In 1+ xAl 1- xO 3(ZnO) 5 ( x = 0.116-0.130), In 2O 3(ZnO) 6-In 1+ xAl 1- xO 3(ZnO) 6 ( x = 0.000-0.111), In 2O 3(ZnO) 7-In 1+ xAl 1- xO 3(ZnO) 7 ( x = 0.08), In 2O 3(ZnO) 8-In 1+ xAl 1- xO 3(ZnO) 8 ( x: undetermined), and In 2O 3(ZnO) m-InAlO 3(ZnO) m ( m = 9, 10, 11, 13, 15, 17, and 19). The space groups of these homologous phases belong to R3¯ m for m = odd or P6 3/ mmc for m = even. Their crystal structures, In 1+ xAl 1- xO 3(ZnO) m (0 < x < 1), consist of three kinds of layers: an InO 1.5 layer, an (In xAl 1- xZn)O 2.5 layer, and ZnO layers. A comparison of the phase relations in the In 2O 3- M2ZnO 4-ZnO systems ( M = Fe, Ga, or Al) is made and their characteristic features are discussed in terms of the ionic radii and site preferences of the M cations.

  3. Humidity Sensing Properties of Paper Substrates and Their Passivation with ZnO Nanoparticles for Sensor Applications

    PubMed Central

    Niarchos, Georgios; Dubourg, Georges; Afroudakis, Georgios; Georgopoulos, Markos; Tsouti, Vasiliki; Makarona, Eleni; Crnojevic-Bengin, Vesna; Tsamis, Christos

    2017-01-01

    In this paper, we investigated the effect of humidity on paper substrates and propose a simple and low-cost method for their passivation using ZnO nanoparticles. To this end, we built paper-based microdevices based on an interdigitated electrode (IDE) configuration by means of a mask-less laser patterning method on simple commercial printing papers. Initial resistive measurements indicate that a paper substrate with a porous surface can be used as a cost-effective, sensitive and disposable humidity sensor in the 20% to 70% relative humidity (RH) range. Successive spin-coated layers of ZnO nanoparticles then, control the effect of humidity. Using this approach, the sensors become passive to relative humidity changes, paving the way to the development of ZnO-based gas sensors on paper substrates insensitive to humidity. PMID:28273847

  4. Ultracompact Pseudowedge Plasmonic Lasers and Laser Arrays.

    PubMed

    Chou, Yu-Hsun; Hong, Kuo-Bin; Chang, Chun-Tse; Chang, Tsu-Chi; Huang, Zhen-Ting; Cheng, Pi-Ju; Yang, Jhen-Hong; Lin, Meng-Hsien; Lin, Tzy-Rong; Chen, Kuo-Ping; Gwo, Shangjr; Lu, Tien-Chang

    2018-02-14

    Concentrating light at the deep subwavelength scale by utilizing plasmonic effects has been reported in various optoelectronic devices with intriguing phenomena and functionality. Plasmonic waveguides with a planar structure exhibit a two-dimensional degree of freedom for the surface plasmon; the degree of freedom can be further reduced by utilizing metallic nanostructures or nanoparticles for surface plasmon resonance. Reduction leads to different lightwave confinement capabilities, which can be utilized to construct plasmonic nanolaser cavities. However, most theoretical and experimental research efforts have focused on planar surface plasmon polariton (SPP) nanolasers. In this study, we combined nanometallic structures intersecting with ZnO nanowires and realized the first laser emission based on pseudowedge SPP waveguides. Relative to current plasmonic nanolasers, the pseudowedge plasmonic lasers reported in our study exhibit extremely small mode volumes, high group indices, high spontaneous emission factors, and high Purell factors beneficial for the strong interaction between light and matter. Furthermore, we demonstrated that compact plasmonic laser arrays can be constructed, which could benefit integrated plasmonic circuits.

  5. Competition between second harmonic generation and two-photon-induced luminescence in single, double and multiple ZnO nanorods.

    PubMed

    Dai, Jun; Zeng, Jian-Hua; Lan, Sheng; Wan, Xia; Tie, Shao-Long

    2013-04-22

    The nonlinear optical properties of single, double and multiple ZnO nanorods (NRs) were investigated by using a focused femtosecond (fs) laser beam. The excitation wavelength of the fs laser was intentionally chosen to be 754 nm at which the energy of two photons is slightly larger than that of the exciton ground state but smaller than the bandgap energy of ZnO. Second harmonic generation (SHG) or/and two-photon-induced luminescence (TPL) were observed and their dependences on excitation density were examined. For single ZnO NRs, only SHG was observed even at the highest excitation density we used in the experiments. The situation was changed when the joint point of two ZnO NRs perpendicular to each other was excited. In this case, TPL could be detected at low excitation densities and it increased rapidly with increasing excitation density. At the highest excitation density of ~15 MW/cm(2), the intensity of the TPL became comparable to that of the SHG. For an ensemble of ZnO NRs packed closely, a rapid increase of TPL with a slope of more than 7.0 and a gradual saturation of SHG with a slope of ~0.34 were found at high excitation densities. Consequently, the nonlinear response spectrum was eventually dominated by the TPL at high excitation densities and the SHG appeared to be very weak. We interpret this phenomenon by considering both the difference in electric field distribution and the effect of heat accumulation. It is suggested that the electric field enhancement in double and multiple NRs plays a crucial role in determining the nonlinear response of the NRs. In addition, the reduction in the bandgap energy induced by the heat accumulation effect also leads to the significant change in nonlinear response. This explanation is supported by the calculation of the electric field distribution using the discrete dipole approximation method and the simulation of temperature rise in different ZnO NRs based on the finite element method.

  6. Fast synthesize ZnO quantum dots via ultrasonic method.

    PubMed

    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.

  7. Optical properties of P ion implanted ZnO

    NASA Astrophysics Data System (ADS)

    Pong, Bao-Jen; Chou, Bo-Wei; Pan, Ching-Jen; Tsao, Fu-Chun; Chi, Gou-Chung

    2006-02-01

    Red and green emissions are observed from P ion implanted ZnO. Red emission at ~680 nm (1.82 eV) is associated with the donor-acceptor pair (DAP) transition, where the corresponding donor and acceptor are interstitial zinc (Zn i) and interstitial oxygen (O i), respectively. Green emission at ~ 516 nm (2.40 eV) is associated with the transition between the conduction band and antisite oxygen (O Zn). Green emission at ~516nm (2.403 eV) was observed for ZnO annealed at 800 oC under ambient oxygen, whereas, it was not visible when it was annealed in ambient nitrogen. Hence, the green emission is most likely not related to oxygen vacancies on ZnO sample, which might be related to the cleanliness of ZnO surface, a detailed study is in progress. The observed micro-strain is larger for N ion implanted ZnO than that for P ion implanted ZnO. It is attributed to the larger straggle of N ion implanted ZnO than that of P ion implanted ZnO. Similar phenomenon is also observed in Be and Mg ion implanted GaN.

  8. Photoluminescent ZnO Nanoparticles and Their Biological Applications

    PubMed Central

    Zhang, Zheng-Yong; Xiong, Huan-Ming

    2015-01-01

    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.

  9. Influence of Dopants in ZnO Films on Defects

    NASA Astrophysics Data System (ADS)

    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.

  10. ZnO Schottky barriers and Ohmic contacts

    NASA Astrophysics Data System (ADS)

    Brillson, Leonard J.; Lu, Yicheng

    2011-06-01

    ZnO has emerged as a promising candidate for optoelectronic and microelectronic applications, whose development requires greater understanding and control of their electronic contacts. The rapid pace of ZnO research over the past decade has yielded considerable new information on the nature of ZnO interfaces with metals. Work on ZnO contacts over the past decade has now been carried out on high quality material, nearly free from complicating factors such as impurities, morphological and native point defects. Based on the high quality bulk and thin film crystals now available, ZnO exhibits a range of systematic interface electronic structure that can be understood at the atomic scale. Here we provide a comprehensive review of Schottky barrier and ohmic contacts including work extending over the past half century. For Schottky barriers, these results span the nature of ZnO surface charge transfer, the roles of surface cleaning, crystal quality, chemical interactions, and defect formation. For ohmic contacts, these studies encompass the nature of metal-specific interactions, the role of annealing, multilayered contacts, alloyed contacts, metallization schemes for state-of-the-art contacts, and their application to n-type versus p-type ZnO. Both ZnO Schottky barriers and ohmic contacts show a wide range of phenomena and electronic behavior, which can all be directly tied to chemical and structural changes on an atomic scale.

  11. Variable range hopping in ZnO films

    NASA Astrophysics Data System (ADS)

    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.

  12. Development of mandibular, hyoid and hypobranchial muscles in the zebrafish: homologies and evolution of these muscles within bony fishes and tetrapods

    PubMed Central

    Diogo, Rui; Hinits, Yaniv; Hughes, Simon M

    2008-01-01

    Background During vertebrate head evolution, muscle changes accompanied radical modification of the skeleton. Recent studies have suggested that muscles and their innervation evolve less rapidly than cartilage. The freshwater teleostean zebrafish (Danio rerio) is the most studied actinopterygian model organism, and is sometimes taken to represent osteichthyans as a whole, which include bony fishes and tetrapods. Most work concerning zebrafish cranial muscles has focused on larval stages. We set out to describe the later development of zebrafish head muscles and compare muscle homologies across the Osteichthyes. Results We describe one new muscle and show that the number of mandibular, hyoid and hypobranchial muscles found in four day-old zebrafish larvae is similar to that found in the adult. However, the overall configuration and/or the number of divisions of these muscles change during development. For example, the undivided adductor mandibulae of early larvae gives rise to the adductor mandibulae sections A0, A1-OST, A2 and Aω, and the protractor hyoideus becomes divided into dorsal and ventral portions in adults. There is not always a correspondence between the ontogeny of these muscles in the zebrafish and their evolution within the Osteichthyes. All of the 13 mandibular, hyoid and hypobranchial muscles present in the adult zebrafish are found in at least some other living teleosts, and all except the protractor hyoideus are found in at least some extant non-teleost actinopterygians. Of these muscles, about a quarter (intermandibularis anterior, adductor mandibulae, sternohyoideus) are found in at least some living tetrapods, and a further quarter (levator arcus palatini, adductor arcus palatini, adductor operculi) in at least some extant sarcopterygian fish. Conclusion Although the zebrafish occupies a rather derived phylogenetic position within actinopterygians and even within teleosts, with respect to the mandibular, hyoid and hypobranchial muscles it

  13. Lasers '81

    SciT

    Collins, C.B.

    1982-01-01

    Progress in lasers is discussed. The subjects addressed include: excimer lasers, surface spectroscopy, modern laser spectroscopy, free electron lasers, cavities and propagation, lasers in medicine, X-ray and gamma ray lasers, laser spectroscopy of small molecules and clusters, optical bistability, excitons, nonlinear optics in the X-ray and gamma ray regions, collective atomic phenomena, tunable IR lasers, far IR/submillimeter lasers, and laser-assisted collisions. Also treated are: special applications, multiphoton processes in atoms and small molecules, nuclear pumped lasers, material processing and applications, polarization, high energy lasers, laser chemistry, IR molecular lasers, laser applications of collision and dissociation phenomena, solid state laser materials,more » phase conjugation, advances in laser technology for fusion, metal vapor lasers, picosecond phenomena, laser ranging and geodesy, and laser photochemistry of complex molecules.« less

  14. Toward blue emission in ZnO based LED

    NASA Astrophysics Data System (ADS)

    Viana, Bruno; Pauporté, Thierry; Lupan, Oleg; Le Bahers, Tangui; Ciofini, Ilaria

    2012-03-01

    The bandgap engineering of ZnO nanowires by doping is of great importance for tunable light emitting diode (LED) applications. We present a combined experimental and computational study of ZnO doping with Cd or Cu atoms in the nanomaterial. Zn1-xTMxO (TM=Cu, Cd) nanowires have been epitaxially grown on magnesium-doped p-GaN by electrochemical deposition. The Zn1-xTMxO/p-GaN heterojunction was integrated in a LED structure. Nanowires act as the light emitters and waveguides. At room temperature, TM-doped ZnO based LEDs exhibit low-threshold emission voltage and electroluminescence emission shifted from ultraviolet to violet-blue spectral region compared to pure ZnO LEDs. The emission wavelength can be tuned by changing the transition metal (TM) content in the ZnO nanomaterial and the shift is discussed, including insights from DFT computational investigations.

  15. Contrasting emission behaviour of phenanthroimidazole with ZnO nanoparticles.

    PubMed

    Karunakaran, C; Jayabharathi, J; Sathishkumar, R; Jayamoorthy, K; Vimal, K

    2013-11-01

    A new fluorophore 2-(4-fluorophenyl)-1-phenyl-1H-phenanthro [9,10-d]imidazole has been synthesized and characterized by spectroscopic techniques. Nanoparticulate ZnO enhances the fluorescence of the synthesised fluorophore. The absorption, fluorescence, lifetime, cyclic voltammetry and infrared studies reveal that fluorophore is attached to the surface of ZnO semiconductor. Photo-induced electron transfer (PET) explains the enhancement of fluorescence by nanoparticulate ZnO and the apparent binding constant has been obtained. Adsorption of the fluorophore on ZnO nanoparticle lowers the HOMO and LUMO energy levels of the fluorophore. The strong adsorption of the phenanthrimidazole derivative on the surface of ZnO nanocrystals is likely due to the chemical affinity of the nitrogen atom of the organic molecule to the zinc ion on the surface of nanocrystal. Copyright © 2013 Elsevier B.V. All rights reserved.

  16. Fabrication and Performance Study on Individual Zno Nanowires Based Bioelectrode

    NASA Astrophysics Data System (ADS)

    Zhao, Yanguang; Yan, Xiaoqin; Kang, Zhuo; Lin, Pei

    2012-08-01

    One-dimensional zinc oxide nanowires (ZnO NWs) have unique advantages for use in biosensors as follows: oxide stable surface, excellent biosafety, high specific surface area, high isoelectric point (IEP = 9.5). In this work, we have prepared a kind of electrochemical bioelectrode based on individual ZnO NWs. Here, ZnO NWs with high quality were successfully synthesized by CVD method, which were characterized by scanning electron microscopy, X-ray diffraction and photoluminescence. Then the Raman spectra and electrical characterization demonstrated the adsorption of uricase on ZnO wires. At last, a series of electrochemical measurements were carried out by using an electrochemical workstation with a conventional three-electrode system to obtain the cyclic voltammetry characteristics of the bioelectrodes. The excellent performance of the fabricated bioelectrode implies the potential application for single ZnO nanowire to construct electrochemical biosensor for the detection of uric acid.

  17. [Smart drug delivery systems based on nanoscale ZnO].

    PubMed

    Huang, Xiao; Chen, Chun; Yi, Caixia; Zheng, Xi

    2018-04-01

    In view of the excellent biocompatibility as well as the low cost, nanoscale ZnO shows great potential for drug delivery application. Moreover, The charming character enable nanoscale ZnO some excellent features (e.g. dissolution in acid, ultrasonic permeability, microwave absorbing, hydrophobic/hydrophilic transition). All of that make nanoscale ZnO reasonable choices for smart drug delivery. In the recent decade, more and more studies have focused on controlling the drug release behavior via smart drug delivery systems based on nanoscale ZnO responsive to some certain stimuli. Herein, we review the recent exciting progress on the pH-responsive, ultrasound-responsive, microwave-responsive and UV-responsive nanoscale ZnO-based drug delivery systems. A brief introduction of the drug controlled release behavior and its effect of the drug delivery systems is presented. The biocompatibility of nanoscale ZnO is also discussed. Moreover, its development prospect is looked forward.

  18. Role of low O 2 pressure and growth temperature on electrical transport of PLD grown ZnO thin films on Si substrates

    NASA Astrophysics Data System (ADS)

    Pandis, Ch.; Brilis, N.; Tsamakis, D.; Ali, H. A.; Krishnamoorthy, S.; Iliadis, A. A.

    2006-06-01

    Undoped ZnO thin films have been grown on (100) Si substrates by pulsed laser deposition. The effect of growth parameters such as temperature, O 2 partial pressure and laser fluence on the structural and electrical properties of the films has been investigated. It is shown that the well-known native n-type conductivity, attributed to the activation of hydrogenic donor states, exhibits a conversion from n-type to p-type when the O 2 partial pressure is reduced from 10 -4 to 10 -7 Torr at growth temperatures lower than 400 °C. The p-type conductivity could be attributed to the dominant role of the acceptor Zn vacancies for ZnO films grown at very low O 2 pressures.

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

    PubMed

    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.

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

    PubMed Central

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

    2013-01-01

    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. PMID:28811454

  1. Trioctylphosphine-assisted morphology control of ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    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.

  2. Trioctylphosphine-assisted morphology control of ZnO nanoparticles.

    PubMed

    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.

  3. Changing palaeoenvironments and tetrapod populations in the Daptocephalus Assemblage Zone (Karoo Basin, South Africa) indicate early onset of the Permo-Triassic mass extinction

    NASA Astrophysics Data System (ADS)

    Viglietti, Pia A.; Smith, Roger M. H.; Rubidge, Bruce S.

    2018-02-01

    Important palaeoenvironmental differences are identified during deposition of the latest Permian Daptocephalus Assemblage Zone (DaAZ) of the South African Beaufort Group (Karoo Supergoup), which is also divided into a Lower and Upper subzone. A lacustrine floodplain facies association showing evidence for higher water tables and subaqueous conditions on the floodplains is present in Lower DaAZ. The change to well-drained floodplain facies association in the Upper DaAZ is coincident with a faunal turnover as evidenced by the last appearance of the dicynodont Dicynodon lacerticeps, the therocephalian Theriognathus microps, the cynodont Procynosuchus delaharpeae, and first appearance of the dicynodont Lystrosaurus maccaigi within the Ripplemead member. Considering the well documented 3-phased extinction of Karoo tetrapods during the Permo-Triassic Mass Extinction (PTME), the facies transition between the Lower and Upper DaAZ represents earlier than previously documented palaeoenvironmental changes associated with the onset of this major global biotic crisis.

  4. Polymorphism, selection and tandem duplication of transferrin genes in Atlantic cod (Gadus morhua) - Conserved synteny between fish monolobal and tetrapod bilobal transferrin loci

    PubMed Central

    2011-01-01

    Background The two homologous iron-binding lobes of transferrins are thought to have evolved by gene duplication of an ancestral monolobal form, but any conserved synteny between bilobal and monolobal transferrin loci remains unexplored. The important role played by transferrin in the resistance to invading pathogens makes this polymorphic gene a highly valuable candidate for studying adaptive divergence among local populations. Results The Atlantic cod genome was shown to harbour two tandem duplicated serum transferrin genes (Tf1, Tf2), a melanotransferrin gene (MTf), and a monolobal transferrin gene (Omp). Whereas Tf1 and Tf2 were differentially expressed in liver and brain, the Omp transcript was restricted to the otoliths. Fish, chicken and mammals showed highly conserved syntenic regions in which monolobal and bilobal transferrins reside, but contrasting with tetrapods, the fish transferrin genes are positioned on three different linkage groups. Sequence alignment of cod Tf1 cDNAs from Northeast (NE) and Northwest (NW) Atlantic populations revealed 22 single nucleotide polymorphisms (SNP) causing the replacement of 16 amino acids, including eight surface residues revealed by the modelled 3D-structures, that might influence the binding of pathogens for removal of iron. SNP analysis of a total of 375 individuals from 14 trans-Atlantic populations showed that the Tf1-NE variant was almost fixed in the Baltic cod and predominated in the other NE Atlantic populations, whereas the NW Atlantic populations were more heterozygous and showed high frequencies of the Tf-NW SNP alleles. Conclusions The highly conserved synteny between fish and tetrapod transferrin loci infers that the fusion of tandem duplicated Omp-like genes gave rise to the modern transferrins. The multiple nonsynonymous substitutions in cod Tf1 with putative structural effects, together with highly divergent allele frequencies among different cod populations, strongly suggest evidence for positive

  5. Polymorphism, selection and tandem duplication of transferrin genes in Atlantic cod (Gadus morhua)--conserved synteny between fish monolobal and tetrapod bilobal transferrin loci.

    PubMed

    Andersen, Øivind; De Rosa, Maria Cristina; Pirolli, Davide; Tooming-Klunderud, Ave; Petersen, Petra E; André, Carl

    2011-05-25

    The two homologous iron-binding lobes of transferrins are thought to have evolved by gene duplication of an ancestral monolobal form, but any conserved synteny between bilobal and monolobal transferrin loci remains unexplored. The important role played by transferrin in the resistance to invading pathogens makes this polymorphic gene a highly valuable candidate for studying adaptive divergence among local populations. The Atlantic cod genome was shown to harbour two tandem duplicated serum transferrin genes (Tf1, Tf2), a melanotransferrin gene (MTf), and a monolobal transferrin gene (Omp). Whereas Tf1 and Tf2 were differentially expressed in liver and brain, the Omp transcript was restricted to the otoliths. Fish, chicken and mammals showed highly conserved syntenic regions in which monolobal and bilobal transferrins reside, but contrasting with tetrapods, the fish transferrin genes are positioned on three different linkage groups. Sequence alignment of cod Tf1 cDNAs from Northeast (NE) and Northwest (NW) Atlantic populations revealed 22 single nucleotide polymorphisms (SNP) causing the replacement of 16 amino acids, including eight surface residues revealed by the modelled 3D-structures, that might influence the binding of pathogens for removal of iron. SNP analysis of a total of 375 individuals from 14 trans-Atlantic populations showed that the Tf1-NE variant was almost fixed in the Baltic cod and predominated in the other NE Atlantic populations, whereas the NW Atlantic populations were more heterozygous and showed high frequencies of the Tf-NW SNP alleles. The highly conserved synteny between fish and tetrapod transferrin loci infers that the fusion of tandem duplicated Omp-like genes gave rise to the modern transferrins. The multiple nonsynonymous substitutions in cod Tf1 with putative structural effects, together with highly divergent allele frequencies among different cod populations, strongly suggest evidence for positive selection and local adaptation in

  6. Structure and Properties of Al and Ga- Doped ZnO

    NASA Astrophysics Data System (ADS)

    Temizer, Namik Kemal

    . Micro-structural, transport, optical and magnetic properties in ZnGa0.002Al 0.02O films grown by pulsed laser deposition under different growth conditions was studied. In ZnO films grown at substrate temperatures of 600°C most interesting features are the concomitant occurrence of high temperature resistivity minima and room temperature ferromagnetism with a high saturation magnetic moment and considerable coercivity. The temperature dependent resistivity data has been interpreted in the light of quantum corrections to conductivity in disordered systems, suggesting that the e-e interactions is the dominant mechanism in the weak-localization (WL) limit in the case of films showing resistivity minima. We propose that formation of oxygen vacancy-Zinc interstitial defect complex (VO-IZn) is responsible for the enhancement in n-type conductivity, and zinc vacancies (VZn) for the observed room temperature ferromagnetism. ZnO nanostructures are gaining importance in various applications, from gas sensing to thin film transistors (TFTs). We have studied the micro-structural, transport, optical and magnetic properties in ZnO nanostructured films grown by pulsed laser deposition under different ambient conditions. We have investigated the nanostructures in detail through x-ray diffraction, SEM and TEM techniques. We have achieved relatively low room temperature resistivity and the occurrence of room temperature ferromagnetism with significant saturation magnetic moment of 1000 A/m with coercivity in the range of 100-150 Oe. Photoluminescence measurements were conducted to get an insight about the types of defects that occur under different growth conditions. Correlations between transport, optical and magnetic properties has been established in terms of these defects and their complexes. These nanostructured oxides with magnetic and optical properties are promising candidates in multifunctional spintronic and photonic devices.

  7. Velocity surface measurements for ZnO films over /001/-cut GaAs

    NASA Technical Reports Server (NTRS)

    Kim, Yoonkee; Hunt, William D.; Liu, Yongsheng; Jen, Cheng-Kuei

    1994-01-01

    A potential application for a piezoelectic film deposited on a GaAs substrate is the monolithic integration of surface acoustic wave (SAW) devices with GaAs electronics. Knowledge of the SAW properties of the filmed structure is critical for the optimum design of such devices. In this article, the measurements of the velocity surface, which directly affects the SAW diffraction, on the bare and metallized ZnO/SiO2 or Si3N4/GaAs /001/-cut samples are reported using two different techniques: (1) knife-edge laser probe, (2) line-focus-beam scanning acoustic microscope. Comparisons, such as measurement accuracy and tradeoffs, between the former (dry) and the latter (wet) method are given. It is found that near the group of zone axes (110) propagation direction the autocollimating SAW property of the bare GaAs changes into a noncollimating one for the layered structure, but a reversed phenomenon exists near the group of zone axes (100) direction. The passivation layer of SiO2 or Si3N4 (less than 0.2 micrometer thick) and the metallization layer change the relative velocity but do not significantly affect the velocity surface. On the other hand, the passivation layer reduces the propagation loss by 0.5-1.3 dB/microseconds at 240 MHz depending upon the ZnO film thickness. Our SAW propagation measurements agree well with theorectical calculations. We have also obtained the anisotropy factors for samples with ZnO films of 1.6, 2.8, and 4.0 micrometer thickness. Comparisons concerning the piezoelectric coupling and acoustic loss between dc triode and rf magnetron sputtered ZnO films are provided.

  8. Laser Technology.

    ERIC Educational Resources Information Center

    Gauger, Robert

    1993-01-01

    Describes lasers and indicates that learning about laser technology and creating laser technology activities are among the teacher enhancement processes needed to strengthen technology education. (JOW)

  9. Preparation, characterization and properties of ZnO nanomaterials

    NASA Astrophysics Data System (ADS)

    Luo, Jiaolian; Zhang, Xiaoming; Chen, Ruxue; Wang, Xiaohui; Zhu, Ji; Wang, Xiaomin

    2017-06-01

    In this paper, using the hydrothermal synthesis method, NaOH, Zn(NO3)2, anhydrous ethanol, deionized water as raw material to prepare ZnO nanomaterial, and by X ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectroscopy (PL) on the synthesis of nano materials, surface morphology and phase luminescence characterization. The results show that the nano materials synthesized for single-phase ZnO, belonging to the six wurtzite structure; material surface shaped, arranged evenly distributed, and were the top six party structure; ZnO nano materials synthesized with strong emission spectra, emission peak is located at 394nm.

  10. Hierarchical structures of ZnO spherical particles synthesized solvothermally

    NASA Astrophysics Data System (ADS)

    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.

  11. The growth of ZnO nanostructures using Arginine

    NASA Astrophysics Data System (ADS)

    Singh, Baljinder; Moudgil, Lovika; Singh, Gurinder; Kaura, Aman

    2018-05-01

    The growth mechanism of Zinc oxide (ZnO) nanomaterial with amino acid (Arginine) is explained at different shapes. The present study of ZnO nanostructures (NSs) in the presence of Arginine has enabled us to not only determine the growth mechanism of ZnO NSs but also to determine the effect of Arginine at different temperature of reactants. The synthesized samples are characterized using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Results reveal that Arginine is responsible for formation of NSs. Based on these results, a plausible mechanism is explained.

  12. Fabrication and Characterization of Fully Transparent ZnO Thin-Film Transistors and Self-Switching Nano-Diodes

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Ashida, K.; Sasaki, S.; Koyama, M.; Maemoto, T.; Sasa, S.; Kasai, S.; Iñiguez-de-la-Torre, I.; González, T.

    2015-10-01

    Fully transparent zinc oxide (ZnO) based thin-film transistors (TFTs) and a new type of rectifiers calls self-switching nano-diodes (SSDs) were fabricated on glass substrates at room temperature by using low resistivity and transparent conducting Al- doped ZnO (AZO) thin-films. The deposition conditions of AZO thin-films were optimized with pulsed laser deposition (PLD). AZO thin-films on glass substrates were characterized and the transparency of 80% and resistivity with 1.6*10-3 Ωcm were obtained of 50 nm thickness. Transparent ZnO-TFTs were fabricated on glass substrates by using AZO thin-films as electrodes. A ZnO-TFT with 2 μm long gate device exhibits a transconductance of 400 μS/mm and an ON/OFF ratio of 2.8*107. Transparent ZnO-SSDs were also fabricated by using ZnO based materials and clear diode-like characteristics were observed.

  13. The shift of optical band gap in W-doped ZnO with oxygen pressure and doping level

    SciT

    Chu, J.; Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Science, Chongqing 400714; Peng, X.Y.

    2014-06-01

    Highlights: • CVD–PLD co-deposition technique was used. • Better crystalline of the ZnO samples causes the redshift of the optical band gap. • Higher W concentration induces blueshift of the optical band gap. - Abstract: Tungsten-doped (W-doped) zinc oxide (ZnO) nanostructures were synthesized on quartz substrates by pulsed laser and hot filament chemical vapor co-deposition technique under different oxygen pressures and doping levels. We studied in detail the morphological, structural and optical properties of W-doped ZnO by SEM, XPS, Raman scattering, and optical transmission spectra. A close correlation among the oxygen pressure, morphology, W concentrations and the variation of bandmore » gaps were investigated. XPS and Raman measurements show that the sample grown under the oxygen pressure of 2.7 Pa has the maximum tungsten concentration and best crystalline structure, which induces the redshift of the optical band gap. The effect of W concentration on the change of morphology and shift of optical band gap was also studied for the samples grown under the fixed oxygen pressure of 2.7 Pa.« less

  14. Temperature- and frequency-dependent dielectric behaviors of insulator/semiconductor (Al2O3/ZnO) nanolaminates with various ZnO thicknesses

    NASA Astrophysics Data System (ADS)

    Li, Jin; Bi, Xiaofang

    2016-07-01

    Al2O3/ZnO nanolaminates (NLs) with various ZnO sublayer thicknesses were prepared by atomic layer deposition. The Al2O3 sublayers are characterized as amorphous and the ZnO sublayers have an oriented polycrystalline structure. As the ZnO thickness decreases to a certain value, each NL exhibits a critical temperature at which its dielectric constant starts to rise quickly. Moreover, this temperature increases as the ZnO thickness is decreased further. On the other hand, the permittivity demonstrates a large value of several hundred at a frequency  ⩽1000 Hz, followed by a steplike decrease at a higher frequency. The change in the cut-off frequency with ZnO thickness is characterized by a hook function. It is revealed that the Coulomb confinement effect becomes predominant in the dielectric behaviors of the NLs with very thin ZnO. As the ZnO thickness decreases to about the same as or even smaller than the Bohr radius of ZnO, a great change in the carrier concentration and effective mass of ZnO is induced, which is shown to be responsible for the peculiar dielectric behaviors of Al2O3/ZnO with very thin ZnO. These findings provide insight into the prevailing mechanisms to optimize the dielectric properties of semiconductor/insulator laminates with nanoscale sublayer thickness.

  15. Morphological driven photocatalytic activity of ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Abbas, Khaldoon N.; Bidin, Noriah

    2017-02-01

    Using a simple combination of pulse laser ablation in liquid and hydrothermal (PLAL-H) approaches, we control the morphology of ZnO nanostructures (ZNSs) to determine the feasibility of their photocatalytic efficacy. These ZNSs are deposited on Si (100) substrates and two different morphologies are achieved. In this synergistic approach, PLAL synthesized NSs are used as a nutrient solution with different pH for further hydrothermal treatment at 110 °C under varying growth time (5, 30 and 60 min). Surface morphology, structure, composition, and optical characteristics of the prepared ZNSs are determined using FESEM, XRD, FTIR and Photoluminescence (PL) and UV-vis absorption measurements. The morphology revealed remarkable transformation from nanorods (NRs)/nanoflowers (NFs) (at pH 7.6) to nanoparticles (NPs)-like (at pH 10.5) structure. XRD patterns showed better polycrystallinity for NPs with enlarged band gap than NR/NF-like structures. Both PL and UV-vis spectral analysis of ZNPs exhibited higher surface area and deep level defects density dependent morphology, where the nutrient pH and growth time variation are found to play a significant role towards structural evolution. Furthermore, the photocatalytic activities of, such ZNSs are evaluated via sunlight driven photo-degradation of methylene blue (MB) dye. The photocatalytic efficiency of ZNPs is demonstrated to be much superior (97.4%) than ZNRs/ZNFs-like morphology (86%). Such enhanced photocatalytic activities of as-synthesized ZNPs is attributed to the synergism of the improved surface area and defects density, which is useful for promoting the adsorption of the MB dye and suppressed surface recombination of photo-generated charge carriers.

  16. Exploration of Al-Doped ZnO in Photovoltaic Thin Films

    NASA Astrophysics Data System (ADS)

    Ciccarino, Christopher; Sahiner, M. Alper

    The electrical properties of Al doped ZnO-based thin films represent a potential advancement in the push for increasing solar cell efficiency. Doping with Aluminum will theoretically decrease resistivity of the film and therefore achieve this potential as a viable option in the P-N junction phase of photovoltaic cells. The n-type semi-conductive characteristics of the ZnO layer will theoretically be optimized with the addition of Aluminum carriers. In this study, Aluminum doping concentrations ranging from 1-3% by mass were produced, analyzed, and compared. Films were developed onto ITO coated glass using the Pulsed Laser Deposition technique. Target thickness was 250 nm and ellipsometry measurements showed uniformity and accuracy in this regard. Active dopant concentrations were determined using Hall Effect measurements. Efficiency measurements showed possible applications of this doped compound, with upwards of 7% efficiency measured, using a Keithley 2602 SourceMeter set-up. XRD scans showed highly crystalline structures, with effective Al intertwining of the hexagonal wurtzile ZnO molecular structure. This alone indicates a promising future of collaboration between these two materials.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Multiscale modeling of nanostructured ZnO based devices for optoelectronic applications: Dynamically-coupled structural fields, charge, and thermal transport processes

    NASA Astrophysics Data System (ADS)

    Abdullah, Abdulmuin; Alqahtani, Saad; Nishat, Md Rezaul Karim; Ahmed, Shaikh; SIU Nanoelectronics Research Group Team

    Recently, hybrid ZnO nanostructures (such as ZnO deposited on ZnO-alloys, Si, GaN, polymer, conducting oxides, and organic compounds) have attracted much attention for their possible applications in optoelectronic devices (such as solar cells, light emitting and laser diodes), as well as in spintronics (such as spin-based memory, and logic). However, efficiency and performance of these hybrid ZnO devices strongly depend on an intricate interplay of complex, nonlinear, highly stochastic and dynamically-coupled structural fields, charge, and thermal transport processes at different length and time scales, which have not yet been fully assessed experimentally. In this work, we study the effects of these coupled processes on the electronic and optical emission properties in nanostructured ZnO devices. The multiscale computational framework employs the atomistic valence force-field molecular mechanics, models for linear and non-linear polarization, the 8-band sp3s* tight-binding models, and coupling to a TCAD toolkit to determine the terminal properties of the device. A series of numerical experiments are performed (by varying different nanoscale parameters such as size, geometry, crystal cut, composition, and electrostatics) that mainly aim to improve the efficiency of these devices. Supported by the U.S. National Science Foundation Grant No. 1102192.

  19. Sensing based on surface-enhanced Raman scattering using self-forming ZnO nanoarrays coated with gold as substrates

    NASA Astrophysics Data System (ADS)

    Tang, Feng; Adam, Pierre-Michel; Rogers, David J.; Sandana, Vinod E.; Bove, Philippe; Teherani, Ferechteh H.

    2018-03-01

    Surface-Enhanced Raman spectroscopy (SERS) is a widely used technique adopted in both academia and industry for the detection of trace quantities of Raman active molecules. This is usually accomplished by functionalizing distributions of plasmonic metal nanoparticles with the analyte molecules. Recently metal-coated nanostructures have been investigated as alternatives to dispersions of metal nanoparticles in order to avoid clustering and homogeneity/reproducibility issues. In this paper, several samples of Au-coated ZnO nanoarrays are adopted as SERS substrates in order to investigate the molecular sensing capacity for methylene blue (MB) molecules. Self-forming ZnO nanoarrays were grown on both c-sapphire and silicon substrates by pulsed laser deposition. The nanoarrays were then coated with 30 nm of gold using thermal evaporation and the SERS signals of MB functionalized samples were obtained with a Raman microspectrometer. The ratio of SERS intensity to that of an MB functionalized glass substrate (ISERS/IRaman) was calculated based on the averaged SERS signals. A relatively good within-wafer homogeneity of the enhancement effect was found with ISERS/IRaman values as high as 64.2 for Au-coated nano ZnO grown on silicon substrates. The experimental results show that the Au-coated ZnO nanoarrays can be excellent SERS substrates for molecular/chemical analyte sensing.

  20. Exciton polariton spectra and limiting factors for the room-temperature photoluminescence efficiency in ZnO

    NASA Astrophysics Data System (ADS)

    Chichibu, S. F.; Uedono, A.; Tsukazaki, A.; Onuma, T.; Zamfirescu, M.; Ohtomo, A.; Kavokin, A.; Cantwell, G.; Litton, C. W.; Sota, T.; Kawasaki, M.

    2005-04-01

    Static and dynamic responses of excitons in state-of-the-art bulk and epitaxial ZnO are reviewed to support the possible realization of polariton lasers, which are coherent and monochromatic light sources due to Bose condensation of exciton-polaritons in semiconductor microcavities (MCs). To grasp the current problems and to pave the way for obtaining ZnO epilayers of improved quality, the following four principal subjects are treated: (i) polarized optical reflectance (OR), photoreflectance (PR) and photoluminescence (PL) spectra of the bulk and epitaxial ZnO were recorded at 8 K. Energies of PR resonances corresponded to those of upper and lower exciton-polariton branches, where A-, B- and C-excitons couple simultaneously to an electromagnetic wave. PL peaks due to the corresponding polariton branches were observed. Longitudinal-transverse splittings (ωLT) of the corresponding excitons were 1.5, 11.1 and 13.1 meV, respectively. The latter two values are more than two orders of magnitude greater than that of GaAs being 0.08 meV. (ii) Using these values and material parameters, corresponding vacuum-field Rabi splitting of exciton-polaritons coupled to a model MC mode was calculated to be 191 meV, which is the highest value ever reported for semiconductor MCs and satisfies the requirements to observe the strong exciton-light coupling regime necessary for polariton lasing above room temperature. (iii) Polarized OR and PR spectra of an out-plane nonpolar (1\\,1\\,\\bar{2}\\,0) ZnO epilayer grown by laser-assisted molecular beam epitaxy (L-MBE) were measured, since ZnO quantum wells (QWs) grown in nonpolar orientations are expected to show higher emission efficiencies due to the elimination of spontaneous and piezoelectric polarization fields normal to the QW plane. They exhibited in-plane anisotropic exciton resonances according to the polarization selection rules for anisotropically-strained wurzite material. (iv) Impacts of point defects on the nonradiative

  1. Hydrodynamic fabrication of structurally gradient ZnO nanorods.

    PubMed

    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.

  2. Inverter Circuits using Pentacene and ZnO Transistors

    NASA Astrophysics Data System (ADS)

    Iechi, Hiroyuki; Watanabe, Yasuyuki; Kudo, Kazuhiro

    2007-04-01

    We report two types of integrated circuits based on a pentacene static-induction transistor (SIT), a pentacene thin-film transistor (TFT) and a zinc oxide (ZnO) TFT. The operating characteristics of a p-p inverter using pentacene SITs and a complementary inverter using a p-channel pentacene TFT and an n-channel ZnO TFT are described. The basic operation of logic circuits at a low voltage was achieved for the first time using the pentacene SIT inverter and complementary circuits with hybrid inorganic and organic materials. Furthermore, we describe the electrical properties of the ZnO films depending on sputtering conditions, and the complementary circuits using ZnO and pentacene TFTs.

  3. Hexagonal and prismatic nanowalled ZnO microboxes.

    PubMed

    Zhao, Fenghua; Lin, Wenjiao; Wu, Mingmei; Xu, Ningsheng; Yang, Xianfeng; Tian, Z Ryan; Su, Qiang

    2006-04-17

    We hereby report hydrothermal syntheses of new microstructures of semiconducting ZnO. Single-crystalline prismatic ZnO microboxes formed by nanowalls and hexagonal hollow microdisks closed by plates with micron-sized inorganic fullerene-like structures have been made in a base-free medium through a one-step hydrothermal synthesis with the help of n-butanol (NB). Structures and morphologies of the products were confirmed by results from powder X-ray diffraction and scanning electron microscopy. NB has been found to play a crucial role in the growth of these hollow structures. It is indicated that these hollow ZnO crystals were grown from redissolution of interiors. These ZnO microboxes exhibit a band emission in the visible range, implying the possession of a high content of defects.

  4. Nanostructured ZnO Films for Room Temperature Ammonia Sensing

    NASA Astrophysics Data System (ADS)

    Dhivya Ponnusamy; Sridharan Madanagurusamy

    2014-09-01

    Zinc oxide (ZnO) thin films have been deposited by a reactive dc magnetron sputtering technique onto a thoroughly cleaned glass substrate at room temperature. X-ray diffraction revealed that the deposited film was polycrystalline in nature. The field emission scanning electron micrograph (FE-SEM) showed the uniform formation of a rugby ball-shaped ZnO nanostructure. Energy dispersive x-ray analysis (EDX) confirmed that the film was stoichiometric and the direct band gap of the film, determined using UV-Vis spectroscopy, was 3.29 eV. The ZnO nanostructured film exhibited better sensing towards ammonia (NH3) at room temperature (˜30°C). The fabricated ZnO film based sensor was capable of detecting NH3 at as low as 5 ppm, and its parameters, such as response, selectivity, stability, and response/recovery time, were also investigated.

  5. Enhanced antimicrobial activity in biosynthesized ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    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.

  6. Thermoelectric Properties of Al-Doped ZnO Thin Films

    NASA Astrophysics Data System (ADS)

    Saini, S.; Mele, P.; Honda, H.; Matsumoto, K.; Miyazaki, K.; Ichinose, A.

    2014-06-01

    We have prepared 2 % Al-doped ZnO (AZO) thin films on SrTiO3 substrates by a pulsed laser deposition technique at various deposition temperatures ( T dep = 300-600 °C). The thermoelectric properties of AZO thin films were studied in a low temperature range (300-600 K). Thin film deposited at 300 °C is fully c-axis-oriented and presents electrical conductivity 310 S/cm with Seebeck coefficient -65 μV/K and power factor 0.13 × 10-3 Wm-1 K-2 at 300 K. The performance of thin films increases with temperature. For instance, the power factor is enhanced up to 0.55 × 10-3 Wm-1 K-2 at 600 K, surpassing the best AZO film previously reported in the literature.

  7. ZnO for solar cell and thermoelectric applications

    NASA Astrophysics Data System (ADS)

    Zhou, Chuanle; Ghods, Amirhossein; Yunghans, Kelcy L.; Saravade, Vishal G.; Patel, Paresh V.; Jiang, Xiaodong; Kucukgok, Bahadir; Lu, Na; Ferguson, Ian

    2017-03-01

    ZnO-based materials show promise in energy harvesting applications, such as piezoelectric, photovoltaic and thermoelectric. In this work, ZnO-based vertical Schottky barrier solar cells were fabricated by MOCVD de- position of ZnO thin films on ITO back ohmic contact, while Ag served as the top Schottky contact. Various rapid thermal annealing conditions were studied to modify the carrier density and crystal quality. Greater than 200 nm thick ZnO films formed polycrystalline crystal structure, and were used to demonstrate Schottky solar cells. I-V characterizations of the devices showed photovoltaic performance, but but need further development. This is the first demonstration of vertical Schottky barrier solar cell based on wide bandgap ZnO film. Thin film and bulk ZnO grown by MOCVD or melt growth were also investigated in regards to their room- temperature thermoelectric properties. The Seebeck coefficient of bulk ZnO was found to be much larger than that of thin film ZnO at room temperature due to the higher crystal quality in bulk materials. The Seebeck coefficients decrease while the carrier concentration increases due to the crystal defects caused by the charge carriers. The co-doped bulk Zn0:96Ga0:02Al0:02O showed enhanced power factors, lower thermal conductivities and promising ZT values in the whole temperature range (300-1300 K).

  8. ZnO nanorods for electronic and photonic device applications

    NASA Astrophysics Data System (ADS)

    Yi, Gyu-Chul; Yoo, Jinkyoung; Park, Won Il; Jung, Sug Woo; An, Sung Jin; Kim, H. J.; Kim, D. W.

    2005-11-01

    We report on catalyst-free growth of ZnO nanorods and their nano-scale electrical and optical device applications. Catalyst-free metalorganic vapor-phase epitaxy (MOVPE) enables fabrication of size-controlled high purity ZnO single crystal nanorods. Various high quality nanorod heterostructures and quantum structures based on ZnO nanorods were also prepared using the MOVPE method and characterized using scanning electron microscopy, transmission electron microscopy, and optical spectroscopy. From the photoluminescence spectra of ZnO/Zn 0.8Mg 0.2O nanorod multi-quantum-well structures, in particular, we observed a systematic blue-shift in their PL peak position due to quantum confinement effect of carriers in nanorod quantum structures. For ZnO/ZnMgO coaxial nanorod heterostructures, photoluminescence intensity was significantly increased presumably due to surface passivation and carrier confinement. In addition to the growth and characterizations of ZnO nanorods and their quantum structures, we fabricated nanoscale electronic devices based on ZnO nanorods. We report on fabrication and device characteristics of metal-oxidesemiconductor field effect transistors (MOSFETs), Schottky diodes, and metal-semiconductor field effect transistors (MESFETs) as examples of the nanodevices. In addition, electroluminescent devices were fabricated using vertically aligned ZnO nanorods grown p-type GaN substrates, exhibiting strong visible electroluminescence.

  9. Synthesis of ZnO Photocatalysts Using Various Surfactants

    NASA Astrophysics Data System (ADS)

    Yao, Chengli; Zhu, Jinmiao; Li, Hongying; Zheng, Bin; Wei, Yanxin

    2017-12-01

    Zinc oxide (ZnO) nanostructured materials have received significant attention because of their unique physicochemical and electronic properties. In particular, the functional properties of ZnO are owed to its morphology and defect structure. ZnO particles were successfully synthesized by chemical precipitation. CTAB (cetyltrimethylammonium bromide), BS-12 (dodecyl dimethyl betaine) and graphene oxide (GO) were selected as templates to induce the formation of ZnO, respectively. By varying the amount of surfactant added during the synthesis process, the structural properties and the crystalline phase of the synthesized nanospheres were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet and visible spectrophotometry (UV‒Vis). Simultaneously, photo catalytic degradation of Rhodamine B (RhB) was carried out under natural sunlight irradiation while ZnO or ZnO/GO particles were used as catalyst. GO is prone to induce formation of wurtzite hexagonal phase of ZnO. Compared with CTAB and BS-12, ZnO/GO composites had a remarkably photocatalytic degradation.

  10. Photoluminescent properties of electrochemically synthetized ZnO nanotubes

    SciT

    Gracia Jiménez, J.M.

    ZnO nanotubes were prepared by a sequential combination of electrochemical deposition, chemical attack and regeneration. ZnO nanocolumns were initially electrodeposited on conductive substrates and then converted into nanotubes by a process involving chemical etching and subsequent regrowth. The morphology of these ZnO nanocolumns and derived nanotubes was monitored by Scanning Electron Microscopy and their optical properties was studied by photoluminescence spectroscopy. Photoluminescence were measured as a function of temperature, from 6 to 300 K, for both nanocolumns and nanotubes. In order to study the behaviour of induced intrinsic defect all ZnO films were annealed in air at 400 °C andmore » their photoluminescent properties were also registered before and after annealing. The behaviour of photoluminescence is explained taking into account the contribution of different point defects. A band energy diagram related to intrinsic defects was proposed to describe the behaviour of photoluminescence spectra. - Highlights: •ZnO nanotubes were obtained after etching and regrowth of electrodeposited ZnO films. •Photoluminescence spectra contain two parts involving excitonic and defects transitions. •Annealing produces a blue shift in the PL peaks in both ZnO nanocolumns and nanotubes. •Etching causes a blue shift in PL peaks due to confinement effect in nanotubes walls.« less

  11. ZnO based potentiometric and amperometric nanosensors.

    PubMed

    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.

  12. ZnO Nanostructures for Tissue Engineering Applications

    PubMed Central

    Laurenti, Marco; Cauda, Valentina

    2017-01-01

    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. PMID:29113133

  13. Theory of copper impurities in ZnO

    NASA Astrophysics Data System (ADS)

    Lyons, John; Alkauskas, Audrius; Janotti, Anderson; van de Walle, Chris G.

    Due to its connection to deep luminescence signals and its potential use as an acceptor dopant, copper has been one the most studied impurities in ZnO. From experiment, copper incorporating on the Zn site (CuZn) is known to lead to an acceptor level residing near the conduction band of ZnO, making CuZn an exceedingly deep acceptor. CuZn in ZnO has also long been linked with broad 2.4 eV green luminescence (GL) signals. In this work we explore the electrical and optical properties of Cu in ZnO using density functional theory (DFT). Due to the limitations of traditional forms of DFT, an accurate theoretical description of the electrical and optical properties of such deep centers has been difficult to achieve. Here we employ a screened hybrid density functional (HSE) to calculate the properties of Cu in ZnO. We determine the thermodynamic transition levels associated with CuZn in ZnO as well as the associated luminescence lineshapes of characteristic optical transitions. We find that HSE-calculated optical transitions are in close agreement with experimental studies. This work was supported in part by NSF and by ARO.

  14. Synthesis, characteristics and antimicrobial activity of ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    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.

  15. N doped ZnO and ZnO nanorods based p-n homojunction fabricated by ion implantation

    NASA Astrophysics Data System (ADS)

    Chakraborty, Mohua; Thangavel, R.; Asokan, K.

    2018-05-01

    Nitrogen (N) doped and undoped Zinc Oxide (ZnO) nanorod p-n homojunctions were fabricated by ion implantation method. The structural and optical characterizations showed that the N atoms doped into the ZnO crystal lattice. The UV-Vis absorption spectra revealed shift in optical absorption edge towards higher wavelength with ion implantation on ZnO, which attributed N acceptor levels above the valence band. The current-voltage (I-V) measurements exhibit a typical semiconductor rectification characteristic indicating the electrical conductivity of the N-doped ZnO nanorod have p-type conductivity. Moreover, a high photocurrent response has been observed with these p-n homojunctions.

  16. Resonant tunneling diodes based on ZnO for quantum cascade structures (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Hinkov, Borislav; Schwarz, Benedikt; Harrer, Andreas; Ristanic, Daniela; Schrenk, Werner; Hugues, Maxime; Chauveau, Jean-Michel; Strasser, Gottfried

    2017-02-01

    The terahertz (THz) spectral range (lambda 30µm - 300µm) is also known as the "THz-gap" because of the lack of compact semiconductor devices. Various real-world applications would strongly benefit from such sources like trace-gas spectroscopy or security-screening. A crucial step is the operation of THz-emitting lasers at room temperature. But this seems out of reach with current devices, of which GaAs-based quantum cascade lasers (QCLs) seem to be the most promising ones. They are limited by the parasitic, non-optical LO-phonon transitions (36meV in GaAs), being on the same order as the thermal energy at room temperature (kT = 26meV). This can be solved by using larger LO-phonon materials like ZnO (E_LO = 72meV). But to master the fabrication of ZnO-based QC structures, a high quality epitaxial growth is crucial followed by a well-controlled fabrication process including ZnO/ZnMgO etching. We use devices grown on m-plane ZnO-substrate by molecular beam epitaxy. They are patterned by reactive ion etching in a CH4-based chemistry (CH4:H2:Ar/30:3:3 sccm) into 50μm to 150μm square mesas. Resonant tunneling diode structures are investigated in this geometry and are presented including different barrier- and well-configurations. We extract contact resistances of 8e-5 Omega cm^2 for un-annealed Ti/Au contacts and an electron mobility of above 130cm^2/Vs, both in good agreement with literature. Proving that resonant electron tunneling can be achieved in ZnO is one of the crucial building blocks of a QCL. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 665107.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Flower-like ZnO nanorod arrays grown on HF-etched Si (111): constraining relation between ZnO seed layer and Si (111)

    NASA Astrophysics Data System (ADS)

    Brahma, Sanjaya; Liu, C.-W.; Huang, R.-J.; Chang, S.-J.; Lo, K.-Y.

    2015-11-01

    We demonstrate the formation of self-assembled homogenous flower-like ZnO nanorods over a ZnO seed layer deposited on a HF-etched Si (111) substrate. The typical flower-like morphology of ZnO nanorod arrays is ascribed to the formation of the island-like seed layer which is deposited by the drop method followed by annealing at 300 °C. The island-like ZnO seed layer consists of larger ZnO grains, and is built by constraining of the Si (111) surface due to pattern matching. Pattern matching of Si with ZnO determines the shape and size of the seed layer and this controls the final morphology of ZnO nanorods to be either flower like or vertically aligned. The high quality of the island-like ZnO seed layer enhances the diameter and length of ZnO nanorods. Besides, while the amorphous layer formed during the annealing process would influence the strained ZnO grain, that subsequent amorphous layer will not block the constraining between the ZnO grain and the substrate.

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

    SciT

    Sun, Fazhe; Zhao, Zengdian; Qiao, Xueliang, E-mail: xuelqiao@163.com

    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 formationmore » 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.« less

  20. Chemical manipulation of oxygen vacancy and antibacterial activity in ZnO.

    PubMed

    V, Lakshmi Prasanna; Vijayaraghavan, Rajagopalan

    2017-08-01

    Pure and doped ZnO (cation and anion doping) compositions have been designed in order to manipulate oxygen vacancy and antibacterial activity of ZnO. In this connection, we have synthesized and characterized micron sized ZnO, N doped micron sized ZnO, nano ZnO, nano Na and La doped ZnO. The intrinsic vacancies in pure ZnO and the vacancies created by N and Na doping in ZnO have been confirmed by X-ray Photoelectron Spectroscopy(XPS) and Photoluminiscence Spectroscopy(PL). Reactive oxygen species (ROS) such as hydroxyl radicals, superoxide radicals and H 2 O 2 responsible for antibacterial activity have been estimated by PL, UV-Vis spectroscopy and KMnO 4 titrations respectively. It was found that nano Na doped ZnO releases highest amount of ROS followed by nano ZnO, micron N doped ZnO while micron ZnO releases the least amount of ROS. The concentration of vacancies follows the same sequence. This illustrates directly the correlation between ROS and oxygen vacancy in well designed pure and doped ZnO. For the first time, material design in terms of cation doping and anion doping to tune oxygen vacancies has been carried out. Interaction energy (E g ), between the bacteria and nanoparticles has been calculated based on Extended Derjaguin-Landau-Verwey-Overbeek (EDLVO) theory and is correlated with antibacterial activity. Copyright © 2017 Elsevier B.V. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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.

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

    PubMed Central

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

    2013-01-01

    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. PMID:28788336

  5. Synthesis and Characterization of Nano-Structure Metal Oxides and Peroxides Prepared by Laser Ablation in Liquids

    NASA Astrophysics Data System (ADS)

    Drmosh, Qasem Ahmed Qasem

    Pulsed laser ablation technique was applied for synthesize of ZnO, ZnO 2 and SnO2 nanostructure using metallic target in different liquids. For this purpose, a laser emitting pulsed UV radiations generated by the third harmonic of Nd:YAG (λ= 355 nm) was applied. For the synthesis of ZnO nanoparticles (NPs), a high-purity metallic plate of Zn was fixed at the bottom of a glass cell in the presence of deionized water and was irradiated at different laser energies (80- 100- 120) mJ per pulse. The average sizes and lattice parameters of ZnO produced by this method were estimated by X-ray diffraction (XRD). ZnO nanoparticles were also produced by ablation of zinc target in the presence of deionized water mixed with two types of surfactants: cetyltrimethyl ammonium bromide (CTAB) and octaethylene glycol monododecyl (OGM). The results showed that the average grain sizes decreased from 38 nm in the case of deionized water to 27 nm and 19 nm in CTAB and OGM respectively. The PL emission in CTAB and OGM showed two peaks: the sharp UV emission at 380 nm and a broad visible peak ranging from 450 nm to 600 nm. Zinc peroxide (ZnO2) nanoparticles having grain size less than 5 nm were also synthesized using pulsed laser ablation in aqueous solution in the presence of different surfactants and solid zinc target in 3 % hydrogen peroxide H2O2 for the first time. The effect of surfactants on the optical and structure of ZnO2 was studied by applying different spectroscopic techniques. The presence of the cubic phase of zinc peroxide in all samples was confirmed with XRD, and the grain sizes were 4.7 nm, 3.7 nm, 3.3 nm and 2.8 nm in pure H2O2; and H2O 2 mixed with SDS, CTAB and OGM respectively. For optical characterization, FTIR transmittance spectra of ZnO2 nanoparticles prepared with and without surfactants showed characteristic peaks of ZnO2 absorption at 435-445 cm-1. FTIR spectrum also revealed that the adsorbed surfactants on zinc peroxide disappeared in case of CTAB and OGM

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

    SciT

    Shirahata, Yasuhiro; Tanaike, Kohei; Akiyama, Tsuyoshi

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  8. Defect evolution in ZnO and its effect on radiation tolerance.

    PubMed

    Lv, Jinpeng; Li, Xingji

    2018-05-03

    The origin of ZnO radiation resistance is fascinating but still unclear. Herein, we found that radiation tolerance of ZnO can be tuned by engineering intrinsic defects into the ZnO. The role played by native defects in the radiation tolerance of ZnO was systematically explored by carrying out N+ implantation on a set of home-grown ZnO nanocrystals with various lattice defect types and concentrations. Interestingly, decreasing the VO and Zni concentration significantly aggravated N+ radiation damage, indicating the presence of O-deficient defects to be the potential cause of the radiation hardness of ZnO. A similar phenomenon was also observed for H+-implanted ZnO. This work offers a new way to manipulate ZnO and endow it with desired physicochemical properties, and is expected to pave the way for its application in radiative environments.

  9. Zinc oxide nanocolloids prepared by picosecond pulsed laser ablation in water at different temperatures

    NASA Astrophysics Data System (ADS)

    D'Urso, Luisa; Spadaro, Salvatore; Bonsignore, Martina; Santangelo, Saveria; Compagnini, Giuseppe; Neri, Fortunato; Fazio, Enza

    2018-01-01

    Zinc oxide with wide direct band gap and high exciton binding energy is one of the most promising materials for ultraviolet (UV) light-emitting devices. It further exhibits good performance in the degradation of non-biodegradable pollutants under UV irradiation. In this work, zinc oxide (ZnO) and zinc oxide/gold (ZnO/Au) nanocolloids are prepared by picosecond pulsed laser ablation (ps-PLA), using a Zn and Au metallic targets in water media at room temperature (RT) and 80°C. ZnO and Au nanoparticles (NPs) with size in the 10-50 nm range are obtained at RT, while ZnO nanorods (NRs) are formed when water is maintained at 80°C during the ps-PLA process. Au NPs, added to ZnO colloids after the ablation process, decorate ZnO NRs. The crystalline phase of all ZnO nanocolloids is wurtzite. Methylene blue dye is used to investigate the photo-catalytic activity of all the synthesised nanocolloids, under UV light irradiation.

  10. Effects of the ZnO layer on the structure and white light emission properties of a ZnS:Mn/GaN nanocomposite system.

    PubMed

    Wang, Cai-Feng; Hu, Bo

    2017-10-01

    ZnO films were inserted between the ZnS:Mn films and GaN substrates by pulsed laser deposition (PLD). The structure, morphology, and optical properties of the ZnS:Mn/ZnO/GaN nanocomposite systems have been investigated. X-ray diffraction results show that there are three diffraction peaks located at 28.4°, 34.4°, and 34.1°, which correspond to the β-ZnS(111), ZnO(002), and GaN(002) planes, respectively. Due to the insertion of ZnO films, the diffraction peak intensity of ZnS:Mn in ZnS:Mn/ZnO/GaN is stronger than that of ZnS:Mn in ZnS:Mn/GaN, and the full width at half-maximum is smaller. Though the transmittance of ZnS:Mn/ZnO films is slightly lower than that of ZnS:Mn films, the transmittance is still higher than 80%. Compared with ZnS:Mn/GaN, an ultraviolet (UV) emission at 387 nm (originated from the near-band emission of ZnO) and a green light emission at about 520 nm appeared in the photoluminescence (PL) spectra of ZnS:Mn/ZnO/GaN, in addition to the blue emission at 435 nm and the orange-red emission at 580 nm. The emission at 520 nm may be related to the deep-level emission from ZnO and the interface of ZnS:Mn/ZnO. The PL spectrum of ZnS:Mn/ZnO/GaN covers the visible region from the blue light to the red light (400-700 nm), and its color coordinate and color temperature are (0.3103,0.3063) and 6869 K, respectively, presenting strong white light emission.

  11. Complex shaped ZnO nano- and microstructure based polymer composites: mechanically stable and environmentally friendly coatings for potential antifouling applications.

    PubMed

    Hölken, Iris; Hoppe, Mathias; Mishra, Yogendra K; Gorb, Stanislav N; Adelung, Rainer; Baum, Martina J

    2016-03-14

    Since the prohibition of tributyltin (TBT)-based antifouling paints in 2008, the development of environmentally compatible and commercially realizable alternatives is a crucial issue. Cost effective fabrication of antifouling paints with desired physical and biocompatible features is simultaneously required and recent developments in the direction of inorganic nanomaterials could play a major role. In the present work, a solvent free polymer/particle-composite coating based on two component polythiourethane (PTU) and tetrapodal shaped ZnO (t-ZnO) nano- and microstructures has been synthesized and studied with respect to mechanical, chemical and biocompatibility properties. Furthermore, antifouling tests have been carried out in artificial seawater tanks. Four different PTU/t-ZnO composites with various t-ZnO filling fractions (0 wt%, 1 wt%, 5 wt%, 10 wt%) were prepared and the corresponding tensile, hardness, and pull-off test results revealed that the composite filled with 5 wt% t-ZnO exhibits the strongest mechanical properties. Surface free energy (SFE) studies using contact angle measurements showed that the SFE value decreases with an increase in t-ZnO filler amounts. The influence of t-ZnO on the polymerization reaction was confirmed by Fourier transform infrared-spectroscopy measurements and thermogravimetric analysis. The immersion tests demonstrated that fouling behavior of the PTU/t-ZnO composite with a 1 wt% t-ZnO filler has been decreased in comparison to pure PTU. The composite with a 5 wt% t-ZnO filler showed almost no biofouling.

  12. Microstructure of ZnO Thin Films Deposited by High Power Impulse Magnetron Sputtering (Postprint)

    DTIC Science & Technology

    2015-03-01

    AFRL-RX-WP-JA-2015-0185 MICROSTRUCTURE OF ZNO THIN FILMS DEPOSITED BY HIGH POWER IMPULSE MAGNETRON SPUTTERING (POSTPRINT) A. N. Reed...COVERED (From – To) 29 January 2013 – 16 February 2015 4. TITLE AND SUBTITLE MICROSTRUCTURE OF ZNO THIN FILMS DEPOSITED BY HIGH POWER IMPULSE MAGNETRON...ABSTRACT High power impulse magnetron sputtering was used to deposit thin (~100 nm) zinc oxide (ZnO) films from a ceramic ZnO target onto substrates

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

    NASA Astrophysics Data System (ADS)

    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).

  14. Hierarchical Carbon Fibers with ZnO Nanowires for Volatile Sensing in Composite Curing (Postprint)

    DTIC Science & Technology

    2014-07-01

    needed to demonstrate the use of Zinc Oxide (ZnO) nanowire coated carbon fibers as a volatile sensor. ZnO nanowires are demonstrated to function as...processing. For this work, we report on the foundational study needed to demonstrate the use of Zinc Oxide (ZnO) nanowire coated carbon fibers as a...array of ZnO nanowires. Zinc oxide nanowires become more conductive in the presence of ethanol – as analyte sorbs to the surface, electron density

  15. Investigation of ZnO Nanowire Interfaces for Multi-Scale Composites

    DTIC Science & Technology

    2012-03-06

    growth of zinc oxide ( ZnO ) nanowires on the surface of the...through the growth of zinc oxide ( ZnO ) nanowires on the surface of the reinforcing fibers. The nanowires functionally grade the interface, improve bonding...bulk composite. This has been accomplished through the growth of zinc oxide ( ZnO ) nanowires on the surface of the reinforcing fibers. ZnO

  16. Sulfur-Doped Zinc Oxide (ZnO) Nanostars: Synthesis and Simulation of Growth Mechanism

    DTIC Science & Technology

    2011-10-01

    Zinc Oxide ( ZnO ) Nanostars: Synthesis and Simulation of Growth Mechanism Jinhyun Cho1, Qiubao Lin2,3, Sungwoo...characterization, and ab initio simulations of star-shaped hexagonal zinc oxide ( ZnO ) nanowires. The ZnO nanostructures were synthesized by a low...Introduction Zinc oxide ( ZnO ) is a wide bandgap (3.37 eV), Ⅱ–Ⅵ semiconductor of great interest for optoelectronic applications [1–3]. Its

  17. Fishes and tetrapods in the upper pennsylvanian (kasimovian) cohn coal member of the mattoon formation of illinois, United States: Systematics, paleoecology, and paleoenvironments

    Carpenter, D.; Falcon-Lang, H. J.; Benton, M.J.; Nelson, W.J.

    2011-01-01

    A newly discovered vertebrate assemblage is reported from the Upper Pennsylvanian (mid-to upper Kasimovian) Cohn Coal Member of the Mattoon Formation of southeast Illinois, United States. Teeth, scales, and spines of xenacanth (Dicentrodus, Orthacanthus, Triodus, Xenacanthus) and euselachian (Sphenacanthus) sharks dominate the assemblage. Less common are the teeth, scales, and centra of holocephalan (Helodus) and actinopterygian fishes, together with rare tetrapod (mainly pelycosaur) phalanges and centra. The assemblage occurs within a broad, shallow channel incised into a prominent Vertisol. The channel is interpreted as having been cut during a seasonally dry glacial phase when sea level was low, but filled during a subsequent transgression triggered by deglaciation. We interpret this as a brackish water (estuarine) assemblage, based on the co-occurrence of the vertebrate material with spirorbids (putative microconchids) and paleoecological inferences gleaned from a critical analysis of the literature dealing with Pennsylvanian fish ecology. This interpretation is broadly consistent with taphonomic data and the results of 87Sr/86Sr isotope analysis of shark material. The pelycosaur material may have been reworked from the lowstand Vertisol, however, and these animals occupied dryland niches that developed during glacial phases. ?? 2011 SEPM (Society for Sedimentary Geology).

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Gd{sup 3+} incorporated ZnO nanoparticles: A versatile material

    SciT

    Kumar, Surender, E-mail: surender40@gmail.com; Sahare, P.D.

    Graphical abstract: - Highlights: • Chemically synthesized Gd{sup 3+} doped ZnO nanoparticles. • The broad visible emission of the ZnO is dependent on the surface defects and can be tailored by Gd{sup 3+} doing. • PL and magnetic properties are modified by Gd{sup 3+} doping. • Photocatalysis experiment reveals that the ZnO: Gd{sup 3+} degrades the Rh B dye faster than the undoped ZnO. - Abstract: Gd{sup 3+} doped ZnO nanoparticles are synthesized by wet chemical route method and investigated through structural, optical, magnetic and photocatalytic properties. Transmission Electron Microscopy technique has been performed on undoped and Gd{sup 3+} dopedmore » ZnO nanoparticles. X-ray diffraction, X-ray photoelectron spectroscopy and Raman analyses are carried out in order to examine the desired phase formation and substitution of Gd{sup 3+} in the ZnO matrix. Gd{sup 3+} doped ZnO nanoparticles show enhanced photoluminescent and ferromagnetic properties as compared to undoped ZnO. The broad visible emission of ZnO is found to be largely dependent on the surface defects and these surface defects can be tailored by Gd{sup 3+} doping concentration. Furthermore, Gd{sup 3+} doped ZnO nanoparticles also show improved photocatalytic properties as compared with undoped ZnO nanoparticles under ultraviolet irradiation.« less

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

    SciT

    Son, Hyo-Soo; Choi, Nak-Jung; Kim, Kyoung-Bo

    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 contentmore » 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.« less

  1. Nanoporous structures on ZnO thin films

    NASA Astrophysics Data System (ADS)

    Gür, Emre; Kılıç, Bayram; Coşkun, C.; Tüzemen, S.; Bayrakçeken, Fatma

    2010-01-01

    Porous structures were formed on ZnO thin films which were grown by an electrochemical deposition (ECD) method. The growth processes were carried out in a solution of dimethylsulfoxide (DMSO) zinc perchlorate, Zn(ClO 4) 2, at 120 ∘C on indium tin oxide (ITO) substrates. Optical and structural characterizations of electrochemically grown ZnO thin films have shown that the films possess high (0002) c-axis orientation, high nucleation, high intensity and low FWHM of UV emission at the band edge region and a sharp UV absorption edge. Nanoporous structures were formed via self-assembled monolayers (SAMs) of hexanethiol (C 6SH) and dodecanethiol (C 12SH). Scanning electron microscope (SEM) measurements showed that while a nanoporous structure (pore radius 20 nm) is formed on the ZnO thin films by hexanathiol solution, a macroporous structure (pore radius 360 nm) is formed by dodecanethiol solution. No significant variation is observed in X-ray diffraction (XRD) measurements on the ZnO thin films after pore formation. However, photoluminescence (PL) measurements showed that green emission is observed as the dominant emission for the macroporous structures, while no variation is observed for the thin film nanoporous ZnO sample.

  2. Chemical Sensing Applications of ZnO Nanomaterials

    PubMed Central

    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

  3. Hydrogen-Induced Plastic Deformation in ZnO

    NASA Astrophysics Data System (ADS)

    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.

  4. The thermodynamic activity of ZnO in silicate melts

    NASA Astrophysics Data System (ADS)

    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.

  5. Fabrication of ZnO and doped ZnO waveguides deposited by Spin Coating

    NASA Astrophysics Data System (ADS)

    Mohan, Rosmin Elsa; R, Neha P.; T, Shalu; C, Darshana K.; Sreelatha, K. S.

    2015-02-01

    In this paper, the synthesis of ZnO and doped Zn1-xAgxO (where x=0.03) nanoparticles by co- precipitation is reported. The precursors used were Zinc Nitrate and Potassium hydroxide pellets. For doping, 3% AgNO3 in ZnNO3 was considered as a separate buffer solution. The prepared nanoparticles were subsequently spin coated onto silica glass substrates at a constant chuck rate of 3000 rpm. The substrate acts as the lower cladding of a waveguide structure. The upper cladding is assumed to be air in the present investigation. The nanostructures of the ZnO powders in the doped and undoped cases were studied using X-ray Diffraction patterns. There was a decrease in the grain size with doping which increase the tunability of the powders to be used as photoluminescent devices. The optical characteristics of the sample were also investigated using UV-Visible spectrophotometer at 200-900 nm wavelengths. The photoluminescence peaks also report a dramatic increase in intensity at the same wavelength for the doped case compared to the undoped one.

  6. Phosphate glass useful in high energy lasers

    DOEpatents

    Hayden, Yuiko T.; Payne, Stephen A.; Hayden, Joseph S.; Campbell, John H.; Aston, Mary Kay; Elder, Melanie L.

    1996-01-01

    In a high energy laser system utilizing phosphate laser glass components to amplify the laser beam, the laser system requires a generated laser beam having an emission bandwidth of less than 26 nm and the laser glass components consist essentially of (on an oxide composition basis) in mole percent: P{sub 2}O{sub 5}, 50--75; Al{sub 2}O{sub 3}, {gt}0--10; K{sub 2}O, {gt}0--30; MgO, 0--30; CaO, 0--30; Li{sub 2}O, 0--20; Na{sub 2}O, 0--20; Rb{sub 2}O, 0--20; Cs{sub 2}O, 0--20; BeO, 0--20; SrO, 0--20; BaO, 0--20; ZnO, 0--20; PbO, 0--20; B{sub 2}O{sub 3}, 0--10; Y{sub 2}O{sub 3}, 0--10; La{sub 2}O{sub 3}, 0--8; Ln{sub 2}O{sub 3}, 0.01--8; wherein the sum of MgO and CaO is >0--30; the sum of Li{sub 2}O, Na{sub 2}O, Rb{sub 2}O, and Cs{sub 2}O is 0--20; the sum of BeO, SrO, BaO, ZnO, and PbO is 0--20; the sum of B{sub 2}O{sub 3} and Y{sub 2}O{sub 3} is 0--10; and Ln{sub 2}O{sub 3} represents the sum of the oxides of active lasing lanthanides of atomic number 58--71. 21 figs.

  7. Phosphate glass useful in high energy lasers

    DOEpatents

    Hayden, Y.T.; Payne, S.A.; Hayden, J.S.; Campbell, J.H.; Aston, M.K.; Elder, M.L.

    1996-06-11

    In a high energy laser system utilizing phosphate laser glass components to amplify the laser beam, the laser system requires a generated laser beam having an emission bandwidth of less than 26 nm and the laser glass components consist essentially of (on an oxide composition basis) in mole percent: P{sub 2}O{sub 5}, 50--75; Al{sub 2}O{sub 3}, {gt}0--10; K{sub 2}O, {gt}0--30; MgO, 0--30; CaO, 0--30; Li{sub 2}O, 0--20; Na{sub 2}O, 0--20; Rb{sub 2}O, 0--20; Cs{sub 2}O, 0--20; BeO, 0--20; SrO, 0--20; BaO, 0--20; ZnO, 0--20; PbO, 0--20; B{sub 2}O{sub 3}, 0--10; Y{sub 2}O{sub 3}, 0--10; La{sub 2}O{sub 3}, 0--8; Ln{sub 2}O{sub 3}, 0.01--8; wherein the sum of MgO and CaO is >0--30; the sum of Li{sub 2}O, Na{sub 2}O, Rb{sub 2}O, and Cs{sub 2}O is 0--20; the sum of BeO, SrO, BaO, ZnO, and PbO is 0--20; the sum of B{sub 2}O{sub 3} and Y{sub 2}O{sub 3} is 0--10; and Ln{sub 2}O{sub 3} represents the sum of the oxides of active lasing lanthanides of atomic number 58--71. 21 figs.

  8. Effect of Water on Ethanol Conversion over ZnO

    SciT

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

    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 oxidationmore » of acetaldehyde to acetic acid, and then to acetone via ketonization at high temperature (i.e., 400 °C).« less

  9. Mobility of indium on the ZnO(0001) surface

    SciT

    Heinhold, R.; Reeves, R. J.; Allen, M. W.

    2015-02-02

    The mobility of indium on the Zn-polar (0001) surface of single crystal ZnO wafers was investigated using real-time x-ray photoelectron spectroscopy. A sudden transition in the wettability of the ZnO(0001) surface was observed at ∼520 °C, with indium migrating from the (0001{sup ¯}) underside of the wafer, around the non-polar (11{sup ¯}00) and (112{sup ¯}0) sidewalls, to form a uniform self-organized (∼20 Å) adlayer. The In adlayer was oxidized, in agreement with the first principles calculations of Northrup and Neugebauer that In{sub 2}O{sub 3} precipitation can only be avoided under a combination of In-rich and Zn-rich conditions. These findings suggest that unintentionalmore » In adlayers may form during the epitaxial growth of ZnO on indium-bonded substrates.« less

  10. Synthesis and characterization of Ni doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Tamgadge, Y. S.; Gedam, P. P.; Ganorkar, R. P.; Mahure, M. A.; Pahurkar, V. G.; Muley, G. G.

    2018-05-01

    In this paper, we present synthesis of L-valine assisted surface modification of Ni doped ZnO nanoparticles (NPs) using chemical precipitation method. Samples were calcined at 500oC for 2h. Uncalcined and calcined samples were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultraviolet-visible (UV-vis) spectroscopy. Ni doped ZnO NPs with average particle size of 8 nm have been successfully obtained using L-valine as surface modifying agent. Increase in the particle size was observed after the calcination. XRD and TEM studies confirmed the purity, surface morphology and hexagonal wurtzite crystal structure of ZnO NPs. UV-vis spectroscopy indicated the blue shift of excitons absorption wavelength and surface modification by L-valine.

  11. ZnO nanodisk based UV detectors with printed electrodes.

    PubMed

    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.

  12. Low temperature synthesis of hexagonal ZnO nanorods and their hydrogen sensing properties

    NASA Astrophysics Data System (ADS)

    Qurashi, Ahsanulhaq; Faiz, M.; Tabet, N.; Alam, Mir Waqas

    2011-08-01

    The growth of hexagonal ZnO nanorods was demonstrated by low temperature chemical synthesis approach. X-ray diffraction (XRD) analysis revealed a wurtzite hexagonal structure of the ZnO nanorods. The optical properties were measured by UV-vis spectrophotometer at room temperature. X-ray photoelectron spectroscopy (XPS) confirmed high purity of the ZnO nanorods. The hydrogen sensor made of the ZnO nanorods showed reversible response. The hydrogen gas tests were carried out in presence of ambient air and the influence of operation temperature on the hydrogen gas sensing property of ZnO nanorods was also investigated.

  13. Effect of bath temperature on surface morphology and photocatalytic activity of ZnO nanorods

    SciT

    Sriharan, N.; Senthil, T. S., E-mail: tssenthi@gmail.com; Muthukumarasamy, N.

    2016-05-06

    ZnO nanorods were prepared by using simple hydrothermal method using four different bath temperatures. All the prepared ZnO nanorods are annealed at 450°C and are characterized by using various techniques such as X-ray diffraction, UV spectra and scanning electron microscopy. Photocatalytic activity of the prepared ZnO nanorods is analyzed. A novel photocatalytic reactor designed with ZnO nanorods prepared at 90°C shows enhanced catalytic efficiency. The role of light irradiation time, bath temperature and surface morphology of the ZnO nanorods on the performance of photocatalytic reaction is analyzed.

  14. Growth of ZnO nanorods on glass substrate deposited using dip coating method

    NASA Astrophysics Data System (ADS)

    Rani, Rozina Abdul; Ghafar, Safiah Ab; Zoolfakar, Ahmad Sabirin; Rusop, M.

    2018-05-01

    ZnO unique properties make it attractive for electronics and optoelectronics application. There are varieties synthesis of ZnO nanostructure but one of the best ways is by using dip coating method due to its simplicity, low cost and reliability. This research investigated the effect of precursor concentration on the morphology of ZnO nanorods using dip coating technique. ZnO nanorods is synthesized by using zinc nitrate as precursor and glass slide as substrate. The morphology of ZnO is characterized using Field Emission Scanning Electron Microscope (FESEM). By using different concentration of precursor, each outcome demonstrated diverse morphologies.

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

    NASA Astrophysics Data System (ADS)

    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.

  16. Investigation and characterization of ZnO single crystal microtubes

    SciT

    Al-Naser, Qusay A.H.; Zhou, Jian, E-mail: jianzhou@whut.edu.cn; Liu, Guizhen

    2016-04-15

    Morphological, structural, and optical characterization of microwave synthesized ZnO single crystal microtubes were investigated in this work. The structure and morphology of the ZnO microtubes are characterized using X-ray diffraction (XRD), single crystal diffraction (SCD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The results reveal that the as-synthesized ZnO microtube has a highly regular hexagonal cross section and smooth surfaces with an average length of 650–700 μm, an average outer diameter of 50 μm and wall thickness of 1–3 μm, possessing a single crystal wurtzite hexagonal structure. Optical properties of ZnOmore » single crystal microtubes were investigated by photoluminescence (PL) and ultraviolet-visible (UV-vis) absorption techniques. Room-temperature PL spectrum of the microtube reveal a strong UV emission peak at around 375.89 nm and broad and a weak visible emission with a main peak identified at 577 nm, which was assigned to the nearest band-edge emission and the deep-level emission, respectively. The band gap energy of ZnO microtube was found to be 3.27 eV. - Highlights: • ZnO microtube length of 650–700 μm, diameter of 50 μm, wall thickness of 1–3 μm • ZnO microtube possesses a single crystal wurtzite hexagonal structure. • The crystal system is hexahedral oriented along a-axis with indices of (100). • A strong and sharp UV emission at 375.89 nm (3.29 eV) • One prominent absorption band around 378.88 nm (3.27 eV)« less

  17. Photoluminescence of Sequential Infiltration Synthesized ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    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.

  18. Laser principles.

    PubMed

    Bogdan Allemann, Inja; Kaufman, Joely

    2011-01-01

    Since the construction of the first laser in the 1960s, the role that lasers play in various medical specialities, including dermatology, has steadily increased. However, within the last 2 decades, the technological advances and the use of lasers in the field of dermatology have virtually exploded. Many treatments have only become possible with the use of lasers. Especially in aesthetic medicine, lasers are an essential tool in the treatment armamentarium. Due to better research and understanding of the physics of light and skin, there is now a wide and increasing array of different lasers and devices to choose from. The proper laser selection for each indication and treatment requires a profound understanding of laser physics and the basic laser principles. Understanding these principles will allow the laser operator to obtain better results and help avoid complications. This chapter will give an in-depth overview of the physical principles relevant in cutaneous laser surgery. Copyright © 2011 S. Karger AG, Basel.

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

    NASA Astrophysics Data System (ADS)

    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.

  20. Nanostructured ZnO films on stainless steel are highly safe and effective for antimicrobial applications.

    PubMed

    Shim, Kyudae; Abdellatif, Mohamed; Choi, Eunsoo; Kim, Dongkyun

    2017-04-01

    The safety and effectiveness of antimicrobial ZnO films must be established for general applications. In this study, the antimicrobial activity, skin irritation, elution behavior, and mechanical properties of nanostructured ZnO films on stainless steel were evaluated. ZnO nanoparticle (NP) and ZnO nanowall (NW) structures were prepared with different surface roughnesses, wettability, and concentrations using an RF magnetron sputtering system. The thicknesses of ZnO NP and ZnO NW were approximately 300 and 620 nm, respectively, and ZnO NW had two diffraction directions of [0002] and [01-10] based on high-resolution transmission electron microscopy. The ZnO NW structure demonstrated 99.9% antimicrobial inhibition against Escherichia coli, Staphylococcus aureus, and Penicillium funiculosum, and no skin irritation was detected using experimental rabbits. Approximately 27.2 ± 3.0 μg L -1 Zn ions were eluted from the ZnO NW film at 100 °C for 24 h, which satisfies the WHO guidelines for drinking water quality. Furthermore, the Vickers hardness and fracture toughness of ZnO NW films on stainless steel were enhanced by 11 and 14% compared to those of the parent stainless steel. Based on these results, ZnO NW films on STS316L sheets are useful for household supplies, such as water pipes, faucets, and stainless steel containers.

  1. Investigation of Excitonic Polaritons in ZnO Microcavities

    DTIC Science & Technology

    2006-07-28

    defects on the nonradiative processes in L-MBE ZnO were studied using time-resolved PL making a connection with the results of positron annihilation...IMPLANTATION DEPTH (nm) S PA R A M E T E R POSITRON ENERGY (keV) 150010005003001000 0 5 10 15 20 25 30 0.42 0.44 0.46 0.48 0.50 ZnO single crystal 0.42...photoluminescence (TRPL) and monoenergetic positron annihilation methods, and elimination of point defects as a fundamental pathway in improving

  2. Nature of native defects in ZnO.

    PubMed

    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.

  3. Fabrication of highly efficient ZnO nanoscintillators

    NASA Astrophysics Data System (ADS)

    Procházková, Lenka; Gbur, Tomáš; Čuba, Václav; Jarý, Vítězslav; Nikl, Martin

    2015-09-01

    Photo-induced synthesis of high-efficiency ultrafast nanoparticle scintillators of ZnO was demonstrated. Controlled doping with Ga(III) and La(III) ions together with the optimized method of ZnO synthesis and subsequent two-step annealing in air and under reducing atmosphere allow to achieve very high intensity of UV exciton luminescence, up to 750% of BGO intensity magnitude. Fabricated nanoparticles feature extremely short sub-nanosecond photoluminescence decay times. Temperature dependence of the photoluminescence spectrum within 8-340 K range was investigated and shows the absence of visible defect-related emission within all temperature intervals.

  4. Permanent bending and alignment of ZnO nanowires.

    PubMed

    Borschel, Christian; Spindler, Susann; Lerose, Damiana; Bochmann, Arne; Christiansen, Silke H; Nietzsche, Sandor; Oertel, Michael; Ronning, Carsten

    2011-05-06

    Ion beams can be used to permanently bend and re-align nanowires after growth. We have irradiated ZnO nanowires with energetic ions, achieving bending and alignment in different directions. Not only the bending of single nanowires is studied in detail, but also the simultaneous alignment of large ensembles of ZnO nanowires. Computer simulations reveal how the bending is initiated by ion beam induced damage. Detailed structural characterization identifies dislocations to relax stresses and make the bending and alignment permanent, even surviving annealing procedures.

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

    NASA Astrophysics Data System (ADS)

    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.

  6. Elemental, morphological, structural, optical, and magnetic properties of erbium doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Poornaprakash, B.; Chalapathi, U.; Purusottam Reddy, B.; Prabhakar Vattikuti, S. V.; Siva Pratap Reddy, M.; Park, Si-Hyun

    2018-03-01

    The sensible tuning of the structural, optical, and magnetic properties of ZnO nanoparticles (NPs) with suitable doping can enhance their applicability in diverse fields. In this study, we synthesized ZnO NPs with Er (0-4 at%) doping and their elemental, structural, optical, and magnetic properties were studied. Both field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) studies of the suspensions consist of hexagonal shaped NPs. All the prepared NPs exhibited hexagonal phase as demonstrated by powder x-ray diffraction studies. A blue shift was observed in the Er doped ZnO NPs compared to pure ZnO, indicating the increased optical bandgap. Vibrating sample magnetometer studies exhibited the pure ZnO NPs was typical diamagnetic feature whereas all the Er doped ZnO NPs were paramagnetic feature at 300 K. This is the first paramagnetic report on Er doped ZnO NPs.

  7. Nanostructured ZnO - its challenging properties and potential for device applications

    NASA Astrophysics Data System (ADS)

    Dimova-Malinovska, D.

    2017-01-01

    Nanostructured ZnO possessing interesting structural and optical properties offers challenging opportunities for innovative applications. In this lecture the review of the optical and structural properties of ZnO nanostructured layers is presented. It is shown that they have a direct impact on the parameters of devices involving ZnO. An analysis of current trends in the photovoltaic (PV) field shows that improved light harvesting and efficiency of solar cells can be obtained by implementing nanostructured ZnO layers to process advanced solar cell structures. Because of amenability to doping, high chemical stability, sensitivity to different adsorbed gases, nontoxicity and low cost ZnO attracted much attention for application as gas sensors. The sensitivity of nano-grain ZnO gas elements is comparatively high because of the grain-size effect. Application of nanostructured ZnO for gas sensors and for increasing of light harvesting in solar cells is demonstrated.

  8. Vertical growth of ZnO nanorods on ZnO seeded FTO substrate for dye sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Marimuthu, T.; Anandhan, N.

    2018-04-01

    Zinc oxide (ZnO) nanorods (NRs) were electrochemically grown on fluorine doped tin oxide (FTO) and ZnO seeded FTO substrates. X-ray diffraction (XRD) patterns, Raman spectra and photoluminescence (PL) spectra reveal that the hexagonal wurtzite structured ZnO grown on a seeded FTO substrate has a high crystallinity, crystal quality and less atomic defects. Felid emission scanning electron microscope (FE-SEM) images display a high growth density of NRs grown on seeded FTO substrate compared to NRs grown on FTO substrate. The efficiency of the DSSCs based on NRs grown on FTO and seeded FTO substrates is 0.85 and 1.52 %, respectively. UV-Vis absorption spectra and electrochemical impedance spectra depict that the NRs grown on seeded FTO photoanode have higher dye absorption and charge recombination resistance than that of the NRs grown on FTO substrate.

  9. Study of ZnO and Mg doped ZnO nanoparticles by sol-gel process

    SciT

    Ansari, Mohd Meenhaz, E-mail: meenhazphysics@gmail.com; Arshad, Mohd; Tripathi, Pushpendra

    Nano-crystalline undoped and Mg doped ZnO (Mg-ZnO) nanoparticles with compositional formula Mg{sub x}Zn{sub 1-x}O (x=0,1,3,5,7,10 and 12 %) were synthesized using sol-gel process. The XRD diffraction peaks match with the pattern of the standard hexagonal structure of ZnO that reveals the formation of hexagonal wurtzite structure in all samples. SEM images demonstrates clearly the formation of spherical ZnO nanoparticles, and change of the morphology of the nanoparticles with the concentration of the magnesium, which is in close agreement with that estimated by Scherer formula based on the XRD pattern. To investigate the doping effect on optical properties, the UV–VIS absorptionmore » spectra was obtained and the band gap of the samples calculated.« less

  10. Physical, structural and spectroscopic investigations of Sm3+ doped ZnO mixed alkali borate glass

    NASA Astrophysics Data System (ADS)

    Sailaja, B.; Joyce Stella, R.; Thirumala Rao, G.; Jaya Raja, B.; Pushpa Manjari, V.; Ravikumar, R. V. S. S. N.

    2015-09-01

    Glass of 20ZnO-15 Li2O-15 Na2O-49.9 B2O3 doped with 0.1 mol% of Sm3+ (ZLNB) was prepared by the melt quenching technique. Physical properties were studied and analysed. The XRD studies confirm the amorphous nature of sample. The FT-IR spectral investigation discloses the BO3, BO4 groups, H and OH bonds. Optical absorption and emission spectra were recorded and characterized. Judd-Ofelt theory was applied to f ↔ f transitions to evaluate Judd-Ofelt intensity parameters (Ωλ). The oscillator strengths and bonding parameters were determined from absorption spectra. The trend observed was Ω4 > Ω6 > Ω2. High value of Ω4 reveals higher rigidity and covalency around the Sm3+ ion. Low value of Ω2 implies ionic nature of ligands and site symmetry around Sm3+ ion. luminescence data and Judd-Ofelt parameters Ωλ (λ = 2, 4, and 6) were used to evaluate various radiative probabilities like spontaneous radiative emission probabilities (AR), radiative lifetime (τR) and branching ratios (βR) stimulated emission cross section (σe) and CIE colour coordinates were measured, CCT temperature evaluated and the values were used to ascertain potential laser transitions at the optimum mixed alkali effect observed for the glass sample prepared. The preparedness of the material as the efficient laser active material is examined.

  11. Ultrafast Three-Dimensional X-ray Imaging of Deformation Modes in ZnO Nanocrystals

    SciT

    Cherukara, Mathew J.; Sasikumar, Kiran; Cha, Wonsuk

    Imaging the dynamical response of materials following ultrafast excitation can reveal energy transduction mechanisms and their dissipation pathways, as well as material stability under conditions far from equilibrium. Such dynamical behaviour is challenging to characterize, especially operando at nanoscopic spatiotemporal scales. In this letter, we use x-ray coherent diffractive imaging to show that ultrafast laser excitation of a ZnO nanocrystal induces a rich set of deformation dynamics including characteristic ‘hard’ or inhomogeneous and ‘soft’ or homogeneous modes at different time scales, corresponding respectively to the propagation of acoustic phonons and resonant oscillation of the crystal. By integrating the 3D nanocrystalmore » structure obtained from the ultrafast x-ray measurements with a continuum thermo-electro-mechanical finite element model, we elucidate the deformation mechanisms following laser excitation, in particular, a torsional mode that generates a 50% greater electric potential gradient than that resulting from the flexural mode. Furthermore, understanding of the time-dependence of these mechanisms on ultrafast scales has significant implications for development of new materials for nanoscale power generation.« less

  12. Ultrafast Three-Dimensional X-ray Imaging of Deformation Modes in ZnO Nanocrystals.

    PubMed

    Cherukara, Mathew J; Sasikumar, Kiran; Cha, Wonsuk; Narayanan, Badri; Leake, Steven J; Dufresne, Eric M; Peterka, Tom; McNulty, Ian; Wen, Haidan; Sankaranarayanan, Subramanian K R S; Harder, Ross J

    2017-02-08

    Imaging the dynamical response of materials following ultrafast excitation can reveal energy transduction mechanisms and their dissipation pathways, as well as material stability under conditions far from equilibrium. Such dynamical behavior is challenging to characterize, especially operando at nanoscopic spatiotemporal scales. In this letter, we use X-ray coherent diffractive imaging to show that ultrafast laser excitation of a ZnO nanocrystal induces a rich set of deformation dynamics including characteristic "hard" or inhomogeneous and "soft" or homogeneous modes at different time scales, corresponding respectively to the propagation of acoustic phonons and resonant oscillation of the crystal. By integrating the 3D nanocrystal structure obtained from the ultrafast X-ray measurements with a continuum thermo-electro-mechanical finite element model, we elucidate the deformation mechanisms following laser excitation, in particular, a torsional mode that generates a 50% greater electric potential gradient than that resulting from the flexural mode. Understanding of the time-dependence of these mechanisms on ultrafast scales has significant implications for development of new materials for nanoscale power generation.

  13. Ultrafast Three-Dimensional X-ray Imaging of Deformation Modes in ZnO Nanocrystals

    DOE PAGES

    Cherukara, Mathew J.; Sasikumar, Kiran; Cha, Wonsuk; ...

    2016-12-27

    Imaging the dynamical response of materials following ultrafast excitation can reveal energy transduction mechanisms and their dissipation pathways, as well as material stability under conditions far from equilibrium. Such dynamical behaviour is challenging to characterize, especially operando at nanoscopic spatiotemporal scales. In this letter, we use x-ray coherent diffractive imaging to show that ultrafast laser excitation of a ZnO nanocrystal induces a rich set of deformation dynamics including characteristic ‘hard’ or inhomogeneous and ‘soft’ or homogeneous modes at different time scales, corresponding respectively to the propagation of acoustic phonons and resonant oscillation of the crystal. By integrating the 3D nanocrystalmore » structure obtained from the ultrafast x-ray measurements with a continuum thermo-electro-mechanical finite element model, we elucidate the deformation mechanisms following laser excitation, in particular, a torsional mode that generates a 50% greater electric potential gradient than that resulting from the flexural mode. Furthermore, understanding of the time-dependence of these mechanisms on ultrafast scales has significant implications for development of new materials for nanoscale power generation.« less

  14. Different magnetic origins of (Mn, Fe)-codoped ZnO powders and thin films

    SciT

    Fan, Jiuping; Jiang, Fengxian; Quan, Zhiyong

    2012-11-15

    Graphical abstract: The effects of the sample forms, fabricated methods, and process conditions on the structural and magnetic properties of (Mn, Fe)-codoped ZnO powders and films were systematically studied. The origins of ferromagnetism in the vacuum-annealed powder and PLD-deposited film are different. The former originates from the impurities of magnetic clusters, whereas the latter comes from the almost homogenous phase. Highlights: ► The magnetic natures of Zn{sub 0.98}Mn{sub 0.01}Fe{sub 0.01}O powders and thin films come from different origins. ► The ferromagnetism of the powder is mainly from the contribution of magnetic clusters. ► Whereas the ferromagnetic behavior of the filmmore » comes from the almost homogenous phase. -- Abstract: The structural and magnetic properties of (Mn, Fe)-codoped ZnO powders as well as thin films were investigated. The X-ray diffraction and magnetic measurements indicated that the higher sintering temperature facilitates more Mn and Fe incorporation into ZnO. Magnetic measurements indicated that the powder sintered in air at 800 °C showed paramagnetic, but it exhibited obvious room temperature ferromagnetism after vacuum annealing at 600 °C. The results revealed that magnetic clusters were the major contributors to the observed ferromagnetism in vacuum-annealed Zn{sub 0.98}Mn{sub 0.01}Fe{sub 0.01}O powder. Interestingly, the room temperature ferromagnetism was also observed in the Zn{sub 0.98}Mn{sub 0.01}Fe{sub 0.01}O film deposited via pulsed laser deposition from the air-sintered paramagnetic target, but the secondary phases in the film were not detected from X-ray diffraction, transmission electron microscopy, and zero-field cooling and field cooling. Apparently, the magnetic natures of powders and films come from different origins.« less

  15. Implantation of Tetrapod-Shaped Granular Artificial Bones or β-Tricalcium Phosphate Granules in a Canine Large Bone-Defect Model

    PubMed Central

    CHOI, Sungjin; LIU, I-Li; YAMAMOTO, Kenichi; HONNAMI, Muneki; SAKAI, Takamasa; OHBA, Shinsuke; ECHIGO, Ryosuke; SUZUKI, Shigeki; NISHIMURA, Ryouhei; CHUNG, Ung-il; SASAKI, Nobuo; MOCHIZUKI, Manabu

    2013-01-01

    ABSTRACT We investigated biodegradability and new bone formation after implantation of tetrapod-shaped granular artificial bone (Tetrabone®) or β-tricalcium phosphate granules (β-TCP) in experimental critical-size defects in dogs, which were created through medial and lateral femoral condyles. The defect was packed with Tetrabone® (Tetrabone group) or β-TCP (β-TCP group) or received no implant (control group). Computed tomography (CT) was performed at 0, 4 and 8 weeks after implantation. Micro-CT and histological analysis were conducted to measure the non-osseous tissue rate and the area and distribution of new bone tissue in the defect at 8 weeks after implantation. On CT, β-TCP was gradually resorbed, while Tetrabone® showed minimal resorption at 8 weeks after implantation. On micro-CT, non-osseous tissue rate of the control group was significantly higher compared with the β-TCP and Tetrabone groups (P<0.01), and that of the β-TCP group was significantly higher compared with the Tetrabone group (P<0.05). On histology, area of new bone tissue of the β-TCP group was significantly greater than those of the Tetrabone and control groups (P<0.05), and new bone distribution of the Tetrabone group was significantly greater than those of the β-TCP and control groups (P<0.05). These results indicate differences in biodegradability and connectivity of intergranule pore structure between study samples. In conclusion, Tetrabone® may be superior for the repair of large bone defects in dogs. PMID:24161964

  16. Implantation of tetrapod-shaped granular artificial bones or β-tricalcium phosphate granules in a canine large bone-defect model.

    PubMed

    Choi, Sungjin; Liu, I-Li; Yamamoto, Kenichi; Honnami, Muneki; Sakai, Takamasa; Ohba, Shinsuke; Echigo, Ryosuke; Suzuki, Shigeki; Nishimura, Ryouhei; Chung, Ung-Il; Sasaki, Nobuo; Mochizuki, Manabu

    2014-03-01

    We investigated biodegradability and new bone formation after implantation of tetrapod-shaped granular artificial bone (Tetrabone®) or β-tricalcium phosphate granules (β-TCP) in experimental critical-size defects in dogs, which were created through medial and lateral femoral condyles. The defect was packed with Tetrabone® (Tetrabone group) or β-TCP (β-TCP group) or received no implant (control group). Computed tomography (CT) was performed at 0, 4 and 8 weeks after implantation. Micro-CT and histological analysis were conducted to measure the non-osseous tissue rate and the area and distribution of new bone tissue in the defect at 8 weeks after implantation. On CT, β-TCP was gradually resorbed, while Tetrabone® showed minimal resorption at 8 weeks after implantation. On micro-CT, non-osseous tissue rate of the control group was significantly higher compared with the β-TCP and Tetrabone groups (P<0.01), and that of the β-TCP group was significantly higher compared with the Tetrabone group (P<0.05). On histology, area of new bone tissue of the β-TCP group was significantly greater than those of the Tetrabone and control groups (P<0.05), and new bone distribution of the Tetrabone group was significantly greater than those of the β-TCP and control groups (P<0.05). These results indicate differences in biodegradability and connectivity of intergranule pore structure between study samples. In conclusion, Tetrabone® may be superior for the repair of large bone defects in dogs.

  17. Structural studies of ZnO nanostructures by varying the deposition parameters

    NASA Astrophysics Data System (ADS)

    Yunus, S. H. A.; Sahdan, M. Z.; Ichimura, M.; Supee, A.; Rahim, S.

    2017-01-01

    The effect of Zinc Oxide (ZnO) thin film on the growth of ZnO nanorods (NRs) was investigated. The structures of ZnO NRs were synthesized by chemical bath deposition (CBD) method in aqueous solution of N2O6Zn.6H2O and C6H12N4 at 90°C of deposition temperature. One of the ZnO NRs samples was deposited on a ZnO seed layer coated on a glass substrate to investigate the properties of ZnO NRs without receiving effect of other materials. Next, for diode application, the ZnO NRs was deposited on tin monosulfide (SnS) coated on indium-tin-oxide (ITO) coated glass substrate (SnS/ITO). The next, the ZnO structural properties were studied from surface morphology, X-ray diffractometer (XRD) spectra, and chemical composition by using field emission scanning electron microscope (FESEM), XRD and energy dispersive X-ray Spectroscopy (EDX). The growth of ZnO NRs on ZnO seed layer was investigated by ZnO seed layer condition while the growth of ZnO NRs on SnS/ITO was investigated by deposition time and deposition temperature parameters. From FESEM images, aligned ZnO NRs were obtained, and the diameters of ZnO NRs were 0.024-3.94 µm. The SnS thin film was affected by the diameter of ZnO NRs which are the ZnO NRs grow on SnS thin films has a larger diameter compared to ZnO NRs grow on ZnO seed layer. Besides that, all of ZnO peaks observed from XRD corresponding to the wurzite structure and preferentially oriented along the c-axis. In addition, EDX shows a high composition of zinc (Zn) and oxygen (O) signals, which indicated that the NRs are indeed made up of Zn and O.

  18. Electrochemical synthesis of one-dimensional ZnO nanostructures on ZnO seed layer for DSSC applications

    NASA Astrophysics Data System (ADS)

    Marimuthu, T.; Anandhan, N.; Thangamuthu, R.

    2018-01-01

    Electrochemical deposition of vertically aligned zinc oxide (ZnO) nanorods were prepared on ZnO seeded fluorine doped tin oxide (FTO) substrate in the solutions consisting of different concentrations of hexamethylenetetramine (HMTA). The electrochemical, structural, morphological, vibrational and optical properties were characterized by cyclic voltammetry (CV), X-ray diffraction (XRD), scanning electron microscope (SEM), Raman spectroscopy and photoluminescence (PL) spectroscopy, respectively. CV curves confirm that metallic zinc phase is not deposited as the HMTA concentration is about 9 mM in a deposition solution. XRD patterns of the as-prepared films show that the increasing HMTA concentrations from 0 mM to 9 mM not only increase the formation of zinc hydrate chloride (Zn5(OH)8Cl2·H2O) but also decrease and finally disappear the metallic Zn deposition. After the as-prepared films annealed at 450 ° C, the crystalline phases of Zn and Zn5(OH)8Cl2·H2O are completely converted to ZnO hexagonal wurtzite phase with high intense growth (002) plane orientation. SEM images support that the vertical growth of ZnO nanostructures (nanorods and petals) with a few flowers is found to be in the cordillera structure as the films are deposited in the solutions consisting of 3 mM, 6 mM and 9 mM HMTA respectively. Raman and PL spectra confirm that the ZnO film deposited in the solution consisting of 9 mM HMTA has a higher crystalline nature with lesser atomic defects and is also higher c-axis growth than that of other films deposited in the solutions consisting of 0 mM, 3 mM and 6 mM, respectively. UV-vis absorbance spectra corroborate that the ZnO film deposited in the solution consisting of 9 mM HMTA shows a high dye absorbance as compared with other films. The efficiency of DSSCs based on ZnO photoanodes deposited in the solutions consisting of 0 mM and 9 mM HMTA was 1.79 and 3.75%, respectively. Electrochemical impedance spectra revealed that DSSC based on ZnO photoanode

  19. PHOTONICS AND NANOTECHNOLOGY Laser synthesis and modification of composite nanoparticles in liquids

    NASA Astrophysics Data System (ADS)

    Tarasenko, N. V.; Butsen, A. V.

    2010-12-01

    The works devoted to the formation and modification of nanoparticles using laser ablation of solid targets in liquids are reviewed. Several approaches to implement laser ablation in liquids, aimed at synthesising nanoparticles of complex composition, are considered: direct laser ablation of a target of corresponding composition, laser ablation of a combined target composed of two different metals, laser irradiation of a mixture of two or more colloidal solutions, and laser ablation in reactive liquids. The properties of two-component bimetallic systems (Ag — Cu, Ag — Au), semiconductor nanocrystals (ZnO, CdSe), chalcopyrite nanoparticles, and doped oxide nanoparticles (ZnO:Ag, Gd2O2:Tb3+) formed as a result of single- and double-pulse laser ablation in different liquids (water, ethanol, acetone, solutions of polysaccharides) are discussed.

  20. Effect of time varying phosphorus implantation on optoelectronics properties of RF sputtered ZnO thin-films

    NASA Astrophysics Data System (ADS)

    Murkute, Punam; Ghadi, Hemant; Saha, Shantanu; Chavan, Vinayak; Chakrabarti, Subhananda

    2018-03-01

    ZnO has potential application in the field of short wavelength devices like LED's, laser diodes, UV detectors etc, because of its wide band gap (3.34 eV) and high exciton binding energy (60 meV). ZnO possess N-type conductivity due to presence of defects arising from oxygen and zinc interstitial vacancies. In order to achieve P-type or intrinsic carrier concentration an implantation study is preferred. In this report, we have varied phosphorous implantation time and studied its effect on optical as well structural properties of RF sputtered ZnO thin-films. Implantation was carried out using Plasma Immersion ion implantation technique for 10 and 20 s. These films were further annealed at 900°C for 10 s in oxygen ambient to activate phosphorous dopants. Low temperature photoluminescence (PL) spectra measured two distinct peaks at 3.32 and 3.199 eV for 20 s implanted sample annealed at 900°C. Temperature dependent PL measurement shows slightly blue shift in peak position from 18 K to 300 K. 3.199 eV peak can be attributed to donoracceptor pair (DAP) emission and 3.32 eV peak corresponds to conduction-band-to-acceptor (eA0) transition. High resolution x-ray diffraction revels dominant (002) peak from all samples. Increasing implantation time resulted in low peak intensity suggesting a formation of implantation related defects. Compression in C-axis with implantation time indicates incorporation of phosphorus in the formed film. Improvement in surface quality was observed from 20 s implanted sample which annealed at 900°C.

  1. Self-focused ZnO transducers for ultrasonic biomicroscopy

    NASA Astrophysics Data System (ADS)

    Cannata, J. M.; Williams, J. A.; Zhou, Q. F.; Sun, L.; Shung, K. K.; Yu, H.; Kim, E. S.

    2008-04-01

    A simple fabrication technique was developed to produce high frequency (100MHz) self-focused single element transducers with sputtered zinc oxide (ZnO) crystal films. This technique requires the sputtering of a ZnO film directly onto a curved backing substrate. Transducers were fabricated by sputtering an 18μm thick ZnO layer on 2mm diameter aluminum rods with ends shaped and polished to produce a 2mm focus or f-number equal to one. The aluminum rod served a dual purpose as the backing layer and positive electrode for the resultant transducers. A 4μm Parylene matching layer was deposited on the transducers after housing and interconnect. This matching layer was used to protect the substrate and condition the transfer of acoustic energy between the ZnO film and the load medium. The pulse-echo response for a representative transducer was centered at 101MHz with a -6dB bandwidth of 49%. The measured two way insertion loss was 44dB. A tungsten wire phantom and an adult zebrafish eye were imaged to show the capability of these transducers.

  2. Ligand induced ferromagnetism in ZnO nanostructures.

    PubMed

    Wang, Qian; Sun, Qiang; Jena, P

    2008-10-28

    Complementary to the experimental finding that ZnO nanoparticles become ferromagnetic when coated with N and S containing ligands such as dodecylamine and dodecanethiol [Garcia et al., Nano Lett. 7, 1489 (2007)], we provide the first theoretical understanding of the origin of magnetism in ligated ZnO nanoparticles as well as the structural properties of the ligated systems by using density functional theory and generalized gradient approximation for exchange and correlation, and a cluster model for the nanoparticles. We show that N or S atoms of the ligand bind to the Zn sites. The accompanying changes in the Zn-O bond length, hybridization between Zn 4s orbitals with N 2p or S 3p orbitals, and consequently the redistribution of charges between Zn and O atoms result in a magnetic system where the 2p electrons in O and N, and 3p electrons in S sites are spin polarized. Furthermore, the sites nearest to the Zn atom attached to the ligand carry bulk of the magnetic moment. Studies, as a function of cluster size, also illustrate that magnetism resides only on the surface. Our results confirm that the use of ligands can pave a new way for introducing magnetism in ZnO nanostructures, which can be used to develop magnetic sensors to detect N and S containing molecules.

  3. Co-Doped ZnO nanoparticles: minireview.

    PubMed

    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.

  4. Growth Kinetics and Modeling of ZnO Nanoparticles

    ERIC Educational Resources Information Center

    Hale, Penny S.; Maddox, Leone M.; Shapter, Joe G.; Voelcker, Nico H.; Ford, Michael J.; Waclawik, Eric R.

    2005-01-01

    The technique for producing quantum-sized zinc oxide (ZnO) particles is much safer than a technique that used hydrogen sulfide gas to produce cadmium sulfide and zinc sulfide nanoparticles. A further advantage of this method is the ability to sample the solution over time and hence determine the growth kinetics.

  5. Field emission and photoluminescence of ZnO nanocombs

    NASA Astrophysics Data System (ADS)

    Wang, B.; Wu, H. Y.; Zheng, Z. Q.; Yang, Y. H.

    2013-11-01

    Three kinds of new comb-shape nanostructures of ZnO have been grown on single silicon substrates without catalyst-assisted thermal evaporation of Zn and active carbon powders. The morphology and structure of the prepared nanorods are determined on the basis of field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and x-ray diffraction (XRD). The growth mechanism of the ZnO nanocombs can be explained on the basis of the vapor-solid (VS) processes. In nanocombs 1 and nanocombs 2, the comb teeth grow along [0001] and the comb stem grows along [], while in nanocombs 3, nanoteeth grow along [] and stem grows along [0001]. The photoluminescence and field-emission properties of ZnO nanocombs 1-3 have been investigated. The turn-on electric field of ZnO nanocombs 1-3, which is defined as the field required to producing a current density of 10 μA/cm2, is 9, 7.7 and 7.1 V/μm, respectively. The field-emission performance relies not only on the tip’s radius of curvature and field enhancement factor, but also on the factor evaluating the degree of the screening effect.

  6. Ecotoxicity of Manufactured ZnO Nanoparticles - A Review

    EPA Science Inventory

    This report presents an exhaustive literature review on the toxicity of manufactured ZnO nanoparticles (NPs) to ecological receptors across different phylum: bacteria, algae and plants, aquatic and terrestrial invertebrates and freshwater fish. Results show that the majority of s...

  7. Annealing effect on the photoluminescence properties of ZnO nanorod array prepared by a PLD-assistant wet chemical method

    SciT

    Wei Sufeng; Lian Jianshe; Wu Hua, E-mail: weisufeng@gmail.com

    2010-11-15

    Well-aligned ZnO nanorod arrays were synthesized by a wet chemical method on the glass substrate with ZnO thin film as seed layer prepared by pulsed laser deposition. The effect of annealing temperature on the luminescence characteristics was investigated. As the annealing temperature increased, the photoluminescence properties show a general enhancing tendency. The nanorod array with high ultraviolet emission and negligible visible light emission (designated by the photoluminescence intensity ratio of ultraviolet to visible emission of 66.4) is obtained by annealing the sample at 700 deg. C for 1 h. Based on the results of X-ray photoelectron spectroscopy and photoluminescence spectra,more » the mechanisms of visible emission were discussed. - Research Highlights: {yields} ZnO nanorod array with good crystallography, low defects concentration and good optical property was obtained after annealed at 700 deg. C for 1 h. {yields} The transition from the conduction band to the O{sub i} level may be responsible for the yellow-green emission. {yields} The yellow emission may originate from the presence of Zn(OH){sub 2} on the surface or the band transition from conduction band to V{sub o}Zn{sub i} level. {yields} The transition from the Zn{sub i} level to the level should produce an orange emission or an orange-red emission.« less

  8. Raman spectroscopy of ZnMnO thin films grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Orozco, S.; Riascos, H.; Duque, S.

    2016-02-01

    ZnMnO thin films were grown by Pulsed Laser Deposition (PLD) technique onto Silicon (100) substrates at different growth conditions. Thin films were deposited varying Mn concentration, substrate temperature and oxygen pressure. ZnMnO samples were analysed by using Raman Spectroscopy that shows a red shift for all vibration modes. Raman spectra revealed that nanostructure of thin films was the same of ZnO bulk, wurzite hexagonal structure. The structural disorder was manifested in the line width and shape variations of E2(high) and E2(low) modes located in 99 and 434cm-1 respectively, which may be due to the incorporation of Mn ions inside the ZnO crystal lattice. Around 570cm-1 was found a peak associated to E1(LO) vibration mode of ZnO. 272cm-1 suggest intrinsic host lattice defects. Additional mode centred at about 520cm-1 can be overlap of Si and Mn modes.

  9. Development of nanostructured ZnO thin film via electrohydrodynamic atomization technique and its photoconductivity characteristics.

    PubMed

    Duraisamy, Navaneethan; Kwon, Ki Rin; Jo, Jeongdai; Choi, Kyung-Hyun

    2014-08-01

    This article presents the non-vacuum technique for the preparation of nanostructured zinc oxide (ZnO) thin film on glass substrate through electrohydrodynamic atomization (EHDA) technique. The detailed process parameters for achieving homogeneous ZnO thin films are clearly discussed. The crystallinity and surface morphology of ZnO thin film are investigated by X-ray diffraction and field emission scanning electron microscopy. The result shows that the deposited ZnO thin film is oriented in the wurtzite phase with void free surface morphology. The surface roughness of deposited ZnO thin film is found to be ~17.8 nm. The optical properties of nanostructured ZnO thin films show the average transmittance is about 90% in the visible region and the energy band gap is found to be 3.17 eV. The surface chemistry and purity of deposited ZnO thin films are analyzed by fourier transform infrared and X-ray photoelectron spectroscopy, conforming the presence of Zn-O in the deposited thin films without any organic moiety. The photocurrent measurement of nanostructured ZnO thin film is examined in the presence of UV light illumination with wavelength of 365 nm. These results suggest that the deposited nanostructured ZnO thin film through EHDA technique possess promising applications in the near future.

  10. Long-term effect of ZnO nanoparticles on waste activated sludge anaerobic digestion.

    PubMed

    Mu, Hui; Chen, Yinguang

    2011-11-01

    The increasing use of zinc oxide nanoparticles (ZnO NPs) raises concerns about their environmental impacts, but the potential effect of ZnO NPs on sludge anaerobic digestion remains unknown. In this paper, long-term exposure experiments were carried out to investigate the influence of ZnO NPs on methane production during waste activated sludge (WAS) anaerobic digestion. The presence of 1 mg/g-TSS of ZnO NPs did not affect methane production, but 30 and 150 mg/g-TSS of ZnO NPs induced 18.3% and 75.1% of inhibition respectively, which showed that the impact of ZnO NPs on methane production was dosage dependant. Then, the mechanisms of ZnO NPs affecting sludge anaerobic digestion were investigated. It was found that the toxic effect of ZnO NPs on methane production was mainly due to the release of Zn(2+) from ZnO NPs, which may cause the inhibitory effects on the hydrolysis and methanation steps of sludge anaerobic digestion. Further investigations with enzyme and fluorescence in situ hybridization (FISH) assays indicated that higher concentration of ZnO NPs decreased the activities of protease and coenzyme F(420), and the abundance of methanogenesis Archaea. Copyright © 2011 Elsevier Ltd. All rights reserved.

  11. Effect of nanocomposite packaging containing ZnO on growth of Bacillus subtilis and Enterobacter aerogenes.

    PubMed

    Esmailzadeh, Hakimeh; Sangpour, Parvaneh; Shahraz, Farzaneh; Hejazi, Jalal; Khaksar, Ramin

    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. Copyright © 2015. Published by Elsevier B.V.

  12. Room temperature photoluminescence properties of ZnO nanorods grown by hydrothermal reaction

    SciT

    Iwan, S., E-mail: iwan-sugihartono@unj.ac.id; Prodi Ilmu Material, Departemen Fisika, FMIPA, Universitas Indonesia, Kampus UI Depok; Fauzia, Vivi

    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] diffractionmore » 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.« less

  13. Synthesis, characterization and photocatalysis enhancement of Eu2O3-ZnO mixed oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    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.

  14. A review on biogenic synthesis of ZnO nanoparticles using plant extracts and microbes: A prospect towards green chemistry.

    PubMed

    Ahmed, Shakeel; Annu; Chaudhry, Saif Ali; Ikram, Saiqa

    2017-01-01

    Nanotechnology is emerging as an important area of research with its tremendous applications in all fields of science, engineering, medicine, pharmacy, etc. It involves the materials and their applications having one dimension in the range of 1-100nm. Generally, various techniques are used for syntheses of nanoparticles (NPs) viz. laser ablation, chemical reduction, milling, sputtering, etc. These conventional techniques e.g. chemical reduction method, in which various hazardous chemicals are used for the synthesis of NPs later become liable for innumerable health risks due to their toxicity and endangering serious concerns for environment, while other approaches are expensive, need high energy for the synthesis of NPs. However, biogenic synthesis method to produce NPs is eco-friendly and free of chemical contaminants for biological applications where purity is of concerns. In biological method, different biological entities such as extract, enzymes or proteins of a natural product are used to reduce and stabilised formation of NPs. The nature of these biological entities also influence the structure, shape, size and morphology of synthesized NPs. In this review, biogenic synthesis of zinc oxide (ZnO) NPs, procedures of syntheses, mechanism of formation and their various applications have been discussed. Various entities such as proteins, enzymes, phytochemicals, etc. available in the natural reductants are responsible for synthesis of ZnO NPs. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Effect of ZnO seed layer on the morphology and optical properties of ZnO nanorods grown on GaN buffer layers

    SciT

    Nandi, R., E-mail: rajunandi@iitb.ac.in; Mohan, S., E-mail: rajunandi@iitb.ac.in; Major, S. S.

    2014-04-24

    ZnO nanorods were grown by chemical bath deposition on sputtered, polycrystalline GaN buffer layers with and without ZnO seed layer. Scanning electron microscopy and X-ray diffraction show that the ZnO nanorods on GaN buffer layers are not vertically well aligned. Photoluminescence spectrum of ZnO nanorods grown on GaN buffer layer, however exhibits a much stronger near-band-edge emission and negligible defect emission, compared to the nanorods grown on ZnO buffer layer. These features are attributed to gallium incorporation at the ZnO-GaN interface. The introduction of a thin (25 nm) ZnO seed layer on GaN buffer layer significantly improves the morphology andmore » vertical alignment of ZnO-NRs without sacrificing the high optical quality of ZnO nanorods on GaN buffer layer. The presence of a thick (200 nm) ZnO seed layer completely masks the effect of the underlying GaN buffer layer on the morphology and optical properties of nanorods.« less

  16. Effects of surface morphology of ZnO seed layers on growth of ZnO nanostructures prepared by hydrothermal method and annealing.

    PubMed

    Yim, Kwang Gug; Kim, Min Su; Leem, Jae-Young

    2013-05-01

    ZnO nanostructures were grown on Si (111) substrates by a hydrothermal method. Prior to growing the ZnO nanostructures, ZnO seed layers with different post-heat temperatures were prepared by a spin-coating process. Then, the ZnO nanostructures were annealed at 500 degrees C for 20 min under an Ar atmosphere. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) were carried out at room temperature (RT) to investigate the structural and optical properties of the as-grown and annealed ZnO nanostructures. The surface morphologies of the seed layers changed from a smooth surface to a mountain chain-like structure as the post-heating temperatures increased. The as-grown and annealed ZnO nanostructures exhibited a strong (002) diffraction peak. Compared to the as-grown ZnO nanostructures, the annealed ZnO nanostructures exhibited significantly strong enhancement in the PL intensity ratio by almost a factor of 2.

  17. Comparative in vitro genotoxicity study of ZnO nanoparticles, ZnO macroparticles and ZnCl2 to MDCK kidney cells: Size matters.

    PubMed

    Kononenko, Veno; Repar, Neža; Marušič, Nika; Drašler, Barbara; Romih, Tea; Hočevar, Samo; Drobne, Damjana

    2017-04-01

    In the present study, we evaluated the roles that ZnO particle size and Zn ion release have on cyto- and genotoxicity in vitro. The Madin-Darby canine kidney (MDCK) cells were treated with ZnO nanoparticles (NPs), ZnO macroparticles (MPs), and ZnCl 2 as a source of free Zn ions. We first tested cytotoxicity to define sub-cytotoxic exposure concentrations and afterwards we performed alkaline comet and cytokinesis-block micronucleus assays. Additionally, the activities of both catalase (CAT) and glutathione S-transferase (GST) were evaluated in order to examine the potential impairment of cellular stress-defence capacity. The amount of dissolved Zn ions from ZnO NPs in the cell culture medium was evaluated by an optimized voltammetric method. The results showed that all the tested zinc compounds induced similar concentration-dependent cytotoxicity, but only ZnO NPs significantly elevated DNA and chromosomal damage, which was accompanied by a reduction of GST and CAT activity. Although Zn ion release from ZnO NPs in cell culture medium was significant, our results show that this reason alone cannot explain the ZnO genotoxicity seen in this experiment. We discuss that genotoxicity of ZnO NPs depends on the particle size, which determines the physical principles of their dissolution and cellular internalisation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. ZnO nanofiber (NFs) growth from ZnO nanowires (NWs) by controlling growth temperature on flexible Teflon substrate by CBD technique for UV photodetector

    NASA Astrophysics Data System (ADS)

    Farhat, O. F.; Halim, M. M.; Ahmed, Naser M.; Qaeed, M. A.

    2016-12-01

    In this study, ZnO nanofibers (ZnO NFs) were successfully grown for the first time on Teflon substrates using CBD technique. The well-aligned ZnO nanorods (ZnO NRs) were transformed to ZnO nanofibers (NFs) by varying growth temperature and growth time. The high intensity and distinct growth orientation of peaks observed in the XRD spectra of the NFs indicate high crystal quality. The field emission scanning electron microscopy (FESEM) revealed high density of small diameter sized and long ZnO nanofibers (NFs) that are distributed in random directions. Raman analyses revealed a high E2 (high) peak at 436 nm, which indicates the wurtzite structure of ZnO. A flexible ZnO nanofiber (NFs)-based metal-semiconductor-metal UV detector was fabricated and analyzed for photo response and sensitivity under low power illumination (375 nm, 1.5 mW/cm2). The results showed a sensitivity of 4045% which can be considered a relatively high response and baseline recovery for UV detection.

  19. Laser ignition

    DOEpatents

    Early, James W.; Lester, Charles S.

    2002-01-01

    In the apparatus of the invention, a first excitation laser or other excitation light source is used in tandem with an ignitor laser to provide a compact, durable, engine deployable fuel ignition laser system. The beam from the excitation light source is split with a portion of it going to the ignitor laser and a second portion of it being recombined with the first portion after a delay before injection into the ignitor laser. Reliable fuel ignition is provided over a wide range of fuel conditions by using a single remote excitation light source for one or more small lasers located proximate to one or more fuel combustion zones.

  20. High Efficiency, Room Temperature Mid-Infrared Semiconductor Laser Development for IR Countermeasures

    DTIC Science & Technology

    2009-05-01

    voltage (I-V) characteristics of several infrared LEDs, including a type-II W-well laser grown by Molecular Beam Epitaxy at Naval Research Laboratory...Injection Cavity (OPIC) lasers includes >4 um emission from a broadband laser and the measurement of spatial and temporal beam profiles. From August 2006...argon) at 15 mTorr, 400W ICP, and 70W RIE power, with an etch rate of 300 nm/min. Epitaxial ZnO layers were plasma etched using BCl3/SF0gas mixtures

  1. Domain matched epitaxial growth of (111) Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} thin films on (0001) Al{sub 2}O{sub 3} with ZnO buffer layer

    SciT

    Krishnaprasad, P. S., E-mail: pskrishnaprasu@gmail.com, E-mail: mkj@cusat.ac.in; Jayaraj, M. K., E-mail: pskrishnaprasu@gmail.com, E-mail: mkj@cusat.ac.in; Antony, Aldrin

    2015-03-28

    Epitaxial (111) Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} (BST) thin films have been grown by pulsed laser deposition on (0001) Al{sub 2}O{sub 3} substrate with ZnO as buffer layer. The x-ray ω-2θ, Φ-scan and reciprocal space mapping indicate epitaxial nature of BST thin films. The domain matched epitaxial growth of BST thin films over ZnO buffer layer was confirmed using Fourier filtered high resolution transmission electron microscope images of the film-buffer interface. The incorporation of ZnO buffer layer effectively suppressed the lattice mismatch and promoted domain matched epitaxial growth of BST thin films. Coplanar inter digital capacitors fabricated on epitaxial (111) BSTmore » thin films show significantly improved tunable performance over polycrystalline thin films.« less

  2. Investigations into the impact of various substrates and ZnO ultra thin seed layers prepared by atomic layer deposition on growth of ZnO nanowire array

    PubMed Central

    2012-01-01

    The impact of various substrates and zinc oxide (ZnO) ultra thin seed layers prepared by atomic layer deposition on the geometric morphology of subsequent ZnO nanowire arrays (NWs) fabricated by the hydrothermal method was investigated. The investigated substrates included B-doped ZnO films, indium tin oxide films, single crystal silicon (111), and glass sheets. Scanning electron microscopy and X-ray diffraction measurements revealed that the geometry and aligment of the NWs were controlled by surface topography of the substrates and thickness of the ZnO seed layers, respectively. According to atomic force microscopy data, we suggest that the substrate, fluctuate amplitude and fluctuate frequency of roughness on ZnO seed layers have a great impact on the alignment of the resulting NWs, whereas the influence of the seed layers' texture was negligible. PMID:22759838

  3. Gas Lasers

    NASA Astrophysics Data System (ADS)

    Dixit, S. K.

    The field of gas lasers, started with the invention of He-Ne laser in 1961, has witnessed tremendous growth in terms of technology development, research into gaseous gain medium, resonator physics and application in widely diverse arenas. This was possible due to high versatility of gas lasers in terms of operating wavelengths, power, beam quality and mode of operation. In recent years, there is a definite trend to replace the gas lasers, wherever possible, by more efficient and compact solid-state lasers. However, for many industrial, medical and military applications, the gas lasers still rule the roost due to their high-power capabilities with good beam quality at specific wavelengths. This chapter presents a short review covering the operating principle, important technical details and application potential of all the important gas lasers such as He-Ne, CO2, argon ion, copper vapour, excimer and chemical lasers. These neutral atoms, ions and molecule gas lasers are discussed as per applicable electrical, chemical and optical excitation schemes. The optically pumped gas lasers, recently experiencing resurgence, are discussed in the context of far infrared THz molecular lasers, diode-pumped alkali lasers and optically pumped gas-filled hollow-core fibre lasers.

  4. Fabrication and characterization of hexagonally patterned quasi-1D ZnO nanowire arrays

    PubMed Central

    2014-01-01

    Quasi-one-dimensional (quasi-1D) ZnO nanowire arrays with hexagonal pattern have been successfully synthesized via the vapor transport process without any metal catalyst. By utilizing polystyrene microsphere self-assembled monolayer, sol–gel-derived ZnO thin films were used as the periodic nucleation sites for the growth of ZnO nanowires. High-quality quasi-1D ZnO nanowires were grown from nucleation sites, and the original hexagonal periodicity is well-preserved. According to the experimental results, the vapor transport solid condensation mechanism was proposed, in which the sol–gel-derived ZnO film acting as a seed layer for nucleation. This simple method provides a favorable way to form quasi-1D ZnO nanostructures applicable to diverse fields such as two-dimensional photonic crystal, nanolaser, sensor arrays, and other optoelectronic devices. PMID:24521308

  5. Hydrothermal temperature effect on crystal structures, optical properties and electrical conductivity of ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    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.

  6. Single-walled carbon nanotubes coated with ZnO by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Pal, Partha P.; Gilshteyn, Evgenia; Jiang, Hua; Timmermans, Marina; Kaskela, Antti; Tolochko, Oleg V.; Kurochkin, Alexey V.; Karppinen, Maarit; Nisula, Mikko; Kauppinen, Esko I.; Nasibulin, Albert G.

    2016-12-01

    The possibility of ZnO deposition on the surface of single-walled carbon nanotubes (SWCNTs) with the help of an atomic layer deposition (ALD) technique was successfully demonstrated. The utilization of pristine SWCNTs as a support resulted in a non-uniform deposition of ZnO in the form of nanoparticles. To achieve uniform ZnO coating, the SWCNTs first needed to be functionalized by treating the samples in a controlled ozone atmosphere. The uniformly ZnO coated SWCNTs were used to fabricate UV sensing devices. An UV irradiation of the ZnO coated samples turned them from hydrophobic to hydrophilic behaviour. Furthermore, thin films of the ZnO coated SWCNTs allowed us switch p-type field effect transistors made of pristine SWCNTs to have ambipolar characteristics.

  7. Single-walled carbon nanotubes coated with ZnO by atomic layer deposition.

    PubMed

    Pal, Partha P; Gilshteyn, Evgenia; Jiang, Hua; Timmermans, Marina; Kaskela, Antti; Tolochko, Oleg V; Karppinen, Maarit; Nisula, Mikko; Kauppinen, Esko I; Nasibulin, Albert G

    2016-12-02

    The possibility of ZnO deposition on the surface of single-walled carbon nanotubes (SWCNTs) with the help of an atomic layer deposition (ALD) technique was successfully demonstrated. The utilization of pristine SWCNTs as a support resulted in a non-uniform deposition of ZnO in the form of nanoparticles. To achieve uniform ZnO coating, the SWCNTs first needed to be functionalized by treating the samples in a controlled ozone atmosphere. The uniformly ZnO coated SWCNTs were used to fabricate UV sensing devices. An UV irradiation of the ZnO coated samples turned them from hydrophobic to hydrophilic behaviour. Furthermore, thin films of the ZnO coated SWCNTs allowed us switch p-type field effect transistors made of pristine SWCNTs to have ambipolar characteristics.

  8. Defect-induced ferromagnetism in ZnO nanoparticles prepared by mechanical milling

    NASA Astrophysics Data System (ADS)

    Phan, The-Long; Zhang, Y. D.; Yang, D. S.; Nghia, N. X.; Thanh, T. D.; Yu, S. C.

    2013-02-01

    Though ZnO is known as a diamagnetic material, recent studies have revealed that its nanostructures can be ferromagnetic (FM). The FM origin has been ascribed to intrinsic defects. This work shines light on an alternate method based on mechanical milling to induce defect-related ferromagnetism in ZnO nanoparticles (NPs) from initial diamagnetic ZnO powders. Our idea is motivated by the fact that mechanical milling introduces more defects to a ground material. We point out that the FM order increases with increasing the density of defects in ZnO NPs. The experimental results obtained from analyzing X-ray absorption, electron spin resonance, and Raman scattering spectra demonstrate that the ferromagnetism in ZnO NPs is due to intrinsic defects mainly related to oxygen and zinc vacancies. Among these, zinc vacancies play a decisive role in introducing a high FM order in ZnO NPs.

  9. UV-Enhanced Ethanol Sensing Properties of RF Magnetron-Sputtered ZnO Film.

    PubMed

    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.

  10. Room temperature synthesis and optical properties of small diameter (5 nm) ZnO nanorod arrays.

    PubMed

    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.

  11. III-nitrides on oxygen- and zinc-face ZnO substrates

    NASA Astrophysics Data System (ADS)

    Namkoong, Gon; Burnham, Shawn; Lee, Kyoung-Keun; Trybus, Elaissa; Doolittle, W. Alan; Losurdo, Maria; Capezzuto, Pio; Bruno, Giovanni; Nemeth, Bill; Nause, Jeff

    2005-10-01

    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 ˜108cm-2, while a dislocation density of ˜1010cm-2 was obtained on the on-axis ZnO substrates.

  12. Theoretical prediction of low-density hexagonal ZnO hollow structures

    SciT

    Tuoc, Vu Ngoc, E-mail: tuoc.vungoc@hust.edu.vn; Huan, Tran Doan; Thao, Nguyen Thi

    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-dynamicsmore » 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.« less

  13. Structural, Optical, and Photocatalytic Properties of Quasi-One-Dimensional Nanocrystalline ZnO, ZnOC:nC Composites, and C-doped ZnO

    NASA Astrophysics Data System (ADS)

    Shalaeva, E. V.; Gyrdasova, O. I.; Krasilnikov, V. N.; Melkozerova, M. A.; Baklanova, I. V.; Buldakova, L. Yu.

    Various thermolysis rotes of zinc glicolate complexes are considered for the synthesis of quasi-one-dimensional nanostructured aggregates ZnO and Zn-O-C used as photocatalysts. Structural features of quasi-one-dimensional aggregates Zn-O-C and ZnO are investigated in detail. Transmission electron microscopy, Raman spectroscopy, and electron paramagnetic resonance spectroscopy methods demonstrate that the aggregates Zn-O-C have either composite structure (ZnO crystallites in amorphous carbon matrix) or a C-doped ZnO single-phase structure depending on heat treatment conditions, and that all the aggregates exhibit as a rule a tubular morphology, a nanocrystalline structure with a high specific surface area, and a high concentration of singly charged oxygen vacancies. The mechanism of the nanocrystalline structure formation is discussed and the effect of thermolysis condition on the formation of the textured structure of aggregates is investigated. The results of examination of the photocatalytic and optical absorption properties of the synthesized aggregates are presented. The photocatalytic activity for the hydroquinone oxidation reaction under ultraviolet and visible light increases in the series: the reference ZnO powder, quasi-one-dimensional ZnO, quasi-one-dimensional aggregates C-doped ZnO, and this tendency correlates with the reduction of the optical gap width. As a result of our studies, we have arrived at an important conclusion that thermal treatment of ZnO:nC composites allows a C-doped ZnO with high catalytic activity. This increasing photoactivity of C-doped ZnO aggregates is attributed to the optimal specific surface area and electron-energy spectrum restructuring to be produced owing to the presence of singly charged oxygen vacancies and carbon dissolved in the ZnO lattice.

  14. Laser microphone

    DOEpatents

    Veligdan, James T.

    2000-11-14

    A microphone for detecting sound pressure waves includes a laser resonator having a laser gain material aligned coaxially between a pair of first and second mirrors for producing a laser beam. A reference cell is disposed between the laser material and one of the mirrors for transmitting a reference portion of the laser beam between the mirrors. A sensing cell is disposed between the laser material and one of the mirrors, and is laterally displaced from the reference cell for transmitting a signal portion of the laser beam, with the sensing cell being open for receiving the sound waves. A photodetector is disposed in optical communication with the first mirror for receiving the laser beam, and produces an acoustic signal therefrom for the sound waves.

  15. Spectroscopy and visible frequency upconversion in Er3+-Yb3+: TeO2-ZnO glass.

    PubMed

    Mohanty, Deepak Kumar; Rai, Vineet Kumar

    2014-01-01

    The UV-Vis-NIR absorption studies of the Er(3+)/Er(3+)-Yb(3+) doped/codoped TeO2-ZnO (TZO) glasses fabricated by the melting and quenching method has been performed. The spectroscopic radiative parameters viz. radiative transition probabilities, branching ratios and lifetimes have been determined from the absorption spectrum by using Judd-Ofelt theory. The near infrared (NIR) to visible frequency upconversion (UC) have been monitored by using an excitation of 976 nm wavelength radiation from a CW diode laser. The effect of codoping with Yb(3+) ions on the intensity of the UC emission bands from the Er(3+) ions throughout visible region has been studied. The mechanism responsible for the observed upconversion emissions in the prepared samples have been explained on the basis of excited state absorption and efficient energy transfer processes. Copyright © 2013 Elsevier B.V. All rights reserved.

  16. Functional Fe3O4@ZnO magnetic nanoparticle-assisted enrichment and enzymatic digestion of phosphoproteins from saliva.

    PubMed

    Chen, Wei-Yu; Chen, Yu-Chie

    2010-11-01

    Saliva contains various proteins, particularly abundant are phosphoproteins, that may be related to disease occurrences and that play significant roles in a biological system. Thus, medical diagnostics will benefit tremendously if disease-related protein biomarkers are discovered from saliva. In this paper, we propose and demonstrate an approach using functional zinc oxide coated iron oxide magnetic nanoparticles (Fe(3)O(4)@ZnO MNPs) as affinity probes to selectively enrich phosphoproteins from complex saliva samples and as microwave absorbers to assist the enrichment and subsequent tryptic digestion of trapped proteins under microwave heating. The target species trapped by MNPs were characterized by matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) combined with protein database search. Entire analysis time was shortened to less than 20 min. The detection limit of this approach for a monophosphopeptide was as low as 250 pM (10 μL).

  17. Influence of the morphology of ZnO nanostructures on luminescent and photovoltaic properties

    NASA Astrophysics Data System (ADS)

    Ibrayev, N. Kh.; Ilyassov, B. R.; Afanasyev, D. A.

    2017-03-01

    Arrays of ZnO nanorods and nanoplates are synthesized by the hydrothermal and electrochemical methods, respectively. The photoluminescence spectra indicate that the nanoplates have a more defective structure than the nanorods. The obtained ZnO nanostructures are used as the basis to construct dye-sensitized solar cells. The influence of morphology and defectiveness of ZnO nanostructures on the luminescent and photovoltaic properties of the cells is studied.

  18. Oxygen vacancy-induced ferromagnetism in un-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    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.

  19. The effect of ZnO nanoparticles on liver function in rats

    PubMed Central

    Tang, Hua-Qiao; Xu, Min; Rong, Qian; Jin, Ru-Wen; Liu, Qi-Ji; Li, Ying-Lun

    2016-01-01

    Zinc oxide (ZnO) is widely incorporated as a food additive in animal diets. In order to optimize the beneficial effects of ZnO and minimize any resultant environmental pollution, ZnO nanoparticles are often used for delivery of the zinc. However, the possible toxic effects of ZnO nanoparticles, including effects on cytochrome P450 (CYP450) enzymes, have not been evaluated. In this study, we investigated the effect of ZnO nanoparticles, in doses used in animal feeds, on CYP450 enzymes, liver and intestinal enzymes, liver and kidney histopathology, and hematologic indices in rats. We found that liver and kidney injury occurred when the concentrations of ZnO nanoparticles in feed were 300–600 mg/kg. Also, liver mRNA expression for constitutive androstane receptor was suppressed and mRNA expression for pregnane X receptor was induced when feed containing ZnO nanoparticles was given at a concentration of 600 mg/kg. Although the expression of mRNA for CYP 2C11 and 3A2 enzymes was induced by ZnO nanoparticles, the activities of CYP 2C11 and 3A2 were suppressed. While liver CYP 1A2 mRNA expression was suppressed, CYP 1A2 activity remained unchanged at all ZnO nanoparticle doses. Therefore, it has been concluded that ZnO nanoparticles, in the doses customarily added to animal feed, changed the indices of hematology and blood chemistry, altered the expression and activity of hepatic CYP enzymes, and induced pathological changes in liver and kidney tissues of rats. These findings suggest that greater attention needs to be paid to the toxic effects of ZnO nanoparticles in animal feed, with the possibility that the doses of ZnO should be reduced. PMID:27621621

  20. Morphology, Microstructure and Transport Properties of ZnO Decorated SiO2 Nanoparticles (Preprint)

    DTIC Science & Technology

    2010-04-15

    ZnO decorated SiO2 nanoparticles . While the growth conditions we employ for synthesis of ZnO nanocrys- tals are similar to... oxide nanocrystal synthesis on semiconductor oxide nanoparticles is an area yet to be fully explored. One advantage of this approach is that it enables... nanoparticles were resuspended. This washing process was repeated three times. In the hydrolytic ZnO synthesis method, a 1 ml suspension of SiO2 nanoshells

  1. Laser ignition

    DOEpatents

    Early, James W.; Lester, Charles S.

    2004-01-13

    Sequenced pulses of light from an excitation laser with at least two resonator cavities with separate output couplers are directed through a light modulator and a first polarzing analyzer. A portion of the light not rejected by the first polarizing analyzer is transported through a first optical fiber into a first ignitor laser rod in an ignitor laser. Another portion of the light is rejected by the first polarizing analyzer and directed through a halfwave plate into a second polarization analyzer. A first portion of the output of the second polarization analyzer passes through the second polarization analyzer to a second, oscillator, laser rod in the ignitor laser. A second portion of the output of the second polarization analyzer is redirected by the second polarization analyzer to a second optical fiber which delays the beam before the beam is combined with output of the first ignitor laser rod. Output of the second laser rod in the ignitor laser is directed into the first ignitor laser rod which was energized by light passing through the first polarizing analyzer. Combined output of the first ignitor laser rod and output of the second optical fiber is focused into a combustible fuel where the first short duration, high peak power pulse from the ignitor laser ignites the fuel and the second long duration, low peak power pulse directly from the excitation laser sustains the combustion.

  2. Microchip Lasers

    DTIC Science & Technology

    2016-10-31

    microchip laser : (top) schematic and (bottom) photograph of working device mounted on 12.7-mm- dia. post. switch 17 (355-nm UV ), 1.5 µJ of fourth......USA E-mail: zayhowski@ll.mit.edu Abstract Microchip lasers are a rich family of solid-state lasers defined by their small size, robust integration

  3. ZnO films on /001/-cut (110)-propagating GaAs substrates for surface acoustic wave device applications

    NASA Technical Reports Server (NTRS)

    Hickernell, Frederick S.; Higgins, Robert J.; Jen, Cheng-Kuei; Kim, Yoonkee; Hunt, William D.

    1995-01-01

    A potential application for piezoelectric films substrates is the monolithic integration of surface acoustic wave (SAW) devices with GaAs electronics. Knowledge of the SAW properties of the layered structure is critical for the optimum and accurate design of such devices. The acoustic properties of ZnO films sputtered on /001/-cut group of (110) zone axes-propagating GaAs substrates are investigated in this article, including SAW velocity, effective piezoelectric coupling constant, propagation loss, diffraction, velocity surface, and reflectivity of shorted and open metallic gratings. The measurements of these essential SAW properties for the frequency range between 180 and 360 MHz have been performed using a knife-edge laser probe for film thicknesses over the range of 1.6-4 micron and with films of different grain sizes. The high quality of dc triode sputtered films was observed as evidenced by high K(sup 2) and low attenuation. The measurements of the velocity surface, which directly affects the SAW diffraction, on the bare and metalized ZnO on SiO2 or Si3N4 on /001/-cut GaAs samples are reported using two different techniques: (1) knife-edge laser probe, (2) line-focus-beam scanning acoustic microscope. It was found that near the group of (110) zone axes propagation direction, the focusing SAW property of the bare GaAs changes into a nonfocusing one for the layered structure, but a reversed phenomenon exists near the (100) direction. Furthermore, to some extent the diffraction of the substrate can be controlled with the film thickness. The reflectivity of shorted and open gratings are also analyzed and measured. Zero reflectivity is observed for a shorted grating. There is good agreement between the measured data and theoretical values.

  4. ZnO Films on {001}-Cut <110>-Propagating GaAs Substrates for Surface Acoustic Wave Device Applications

    NASA Technical Reports Server (NTRS)

    Kim, Yoonkee; Hunt, William D.; Hickernell, Frederick S.; Higgins, Robert J.; Jen, Cheng-Kuei

    1995-01-01

    A potential application for piezoelectric films on GaAs substrates is the monolithic integration of surface acoustic wave (SAW) devices with GaAs electronics. Knowledge of the SAW properties of the layered structure is critical for the optimum and accurate design of such devices. The acoustic properties of ZnO films sputtered on {001}-cut <110> -propagating GaAs substrates are investigated in this article, including SAW Velocity effective piezoelectric coupling constant, propagation loss. diffraction, velocity surface, and reflectivity of shorted and open metallic gratings. The measurements of these essential SAW properties for the frequency range between 180 and 360 MHz have been performed using a knife-edge laser probe for film thicknesses over the range of 1.6-4 micron and with films or different grain sizes. The high quality of dc triode sputtered films was observed as evidenced by high K(exp 2) and low attenuation. The measurements of the velocity surface, which directly affects the SAW diffraction, on the bare and metalized ZnO on SiO2, or Si3N4 on {001}-cut GaAs samples are reported using two different techniques: 1) knife-edge laser probe, 2) line-focus-beam scanning acoustic microscope. It was found that near the <110> propagation direction, the focusing SAW property of the bare GaAs changes into a nonfocusing one for the layered structure, but a reversed phenomenon exists near the <100> direction. Furthermore, to some extent the diffraction of the substrate can be controlled with the film thickness. The reflectivity of shorted and open gratings are also analyzed and measured. Zero reflectivity is observed for a shorted grating. There is good agreement between the measured data and theoretical values.

  5. Tunable Spectrum Selectivity for Multiphoton Absorption with Enhanced Visible Light Trapping in ZnO Nanorods.

    PubMed

    Tan, Kok Hong; Lim, Fang Sheng; Toh, Alfred Zhen Yang; Zheng, Xia-Xi; Dee, Chang Fu; Majlis, Burhanuddin Yeop; Chai, Siang-Piao; Chang, Wei Sea

    2018-04-17

    Observation of visible light trapping in zinc oxide (ZnO) nanorods (NRs) correlated to the optical and photoelectrochemical properties is reported. In this study, ZnO NR diameter and c-axis length respond primarily at two different regions, UV and visible light, respectively. ZnO NR diameter exhibits UV absorption where large ZnO NR diameter area increases light absorption ability leading to high efficient electron-hole pair separation. On the other hand, ZnO NR c-axis length has a dominant effect in visible light resulting from a multiphoton absorption mechanism due to light reflection and trapping behavior in the free space between adjacent ZnO NRs. Furthermore, oxygen vacancies and defects in ZnO NRs are associated with the broad visible emission band of different energy levels also highlighting the possibility of the multiphoton absorption mechanism. It is demonstrated that the minimum average of ZnO NR c-axis length must satisfy the linear regression model of Z p,min = 6.31d to initiate the multiphoton absorption mechanism under visible light. This work indicates the broadening of absorption spectrum from UV to visible light region by incorporating a controllable diameter and c-axis length on vertically aligned ZnO NRs, which is important in optimizing the design and functionality of electronic devices based on light absorption mechanism. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Toxicity evaluation of ZnO nanostructures on L929 fibroblast cell line using MTS assay

    NASA Astrophysics Data System (ADS)

    Bakhori, Siti Khadijah Mohd; Mahmud, Shahrom; Ann, Ling Chuo; Mohamed, Azman Seeni; Saifuddin, Siti Nazmin; Masudi, Sam'an Malik; Mohamad, Dasmawati

    2015-04-01

    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.

  8. Superior photoelectrochemical properties of ZnO nanorods/poly(3-hexylthiophene) hybrid photoanodes

    NASA Astrophysics Data System (ADS)

    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.

  9. High-mobility low-temperature ZnO transistors with low-voltage operation

    NASA Astrophysics Data System (ADS)

    Bong, Hyojin; Lee, Wi Hyoung; Lee, Dong Yun; Kim, Beom Joon; Cho, Jeong Ho; Cho, Kilwon

    2010-05-01

    Low voltage high mobility n-type thin film transistors (TFTs) based on sol-gel processed zinc oxide (ZnO) were fabricated using a high capacitance ion gel gate dielectric. The ion gel gated solution-processed ZnO TFTs were found to exhibit excellent electrical properties. TFT carrier mobilities were 13 cm2/V s, ON/OFF current ratios were 105, regardless of the sintering temperature used for the preparation of the ZnO thin films. Ion gel gated ZnO TFTs are successfully demonstrated on plastic substrates for the large area flexible electronics.

  10. Toxicity evaluation of ZnO nanostructures on L929 fibroblast cell line using MTS assay

    SciT

    Bakhori, Siti Khadijah Mohd; Mahmud, Shahrom; Ann, Ling Chuo

    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 shiftedmore » 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.« less

  11. Highly Sensitive and Selective Ethanol Sensor Fabricated with In-Doped 3DOM ZnO.

    PubMed

    Wang, Zhihua; Tian, Ziwei; Han, Dongmei; Gu, Fubo

    2016-03-02

    ZnO is an important n-type semiconductor sensing material. Currently, much attention has been attracted to finding an effective method to prepare ZnO nanomaterials with high sensing sensitivity and excellent selectivity. A three-dimensionally ordered macroporous (3DOM) ZnO nanostructure with a large surface area is beneficial to gas and electron transfer, which can enhance the gas sensitivity of ZnO. Indium (In) doping is an effective way to improve the sensing properties of ZnO. In this paper, In-doped 3DOM ZnO with enhanced sensitivity and selectivity has been synthesized by using a colloidal crystal templating method. The 3DOM ZnO with 5 at. % of In-doping exhibits the highest sensitivity (∼88) to 100 ppm ethanol at 250 °C, which is approximately 3 times higher than that of pure 3DOM ZnO. The huge improvement to the sensitivity to ethanol was attributed to the increase in the surface area and the electron carrier concentration. The doping by In introduces more electrons into the matrix, which is helpful for increasing the amount of adsorbed oxygen, leading to high sensitivity. The In-doped 3DOM ZnO is a promising material for a new type of ethanol sensor.

  12. Interaction and photodegradation characteristics of fluorescein dye in presence of ZnO nanoparticles.

    PubMed

    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.

  13. Synthesis and characterization of rod like C doped ZnO nanoparticles with enhanced photocatalytic activities

    NASA Astrophysics Data System (ADS)

    Labhane, P. K.; Sapkal, B. M.; Sonawane, G. H.

    2018-05-01

    Carbon (C) doped ZnO rod like nanoparticles were prepared by simple co-precipitation method. The effect of C doping on ZnO has been evaluated by using XRD, Williamson-Hall Plot, FESEM and EDX data. UV light assisted photocatalytic activities of prepared samples were evaluated spectrophotometrically by the degradation of methylene blue (MB). C doped ZnO shows excellent catalytic efficiency compared to pure ZnO, degrading MB completely within 100 min under UV light. Photocatalysis follows the first order kinetics law and the calculated apparent reaction kinetics rate constant suggest the better activity of C-ZnO.

  14. Improved luminescence intensity and stability of thermal annealed ZnO incorporated Alq3 composite films.

    PubMed

    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.

  15. Positron annihilation spectroscopy in doped p-type ZnO

    NASA Astrophysics Data System (ADS)

    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.

  16. Emission and Structure-Varying ZnO and Carbon Nanocrystal Composite in Mechanical Processing

    NASA Astrophysics Data System (ADS)

    Torchynska, T.; Perez Millan, B.; Polupan, G.; Kakazey, M.

    2018-03-01

    Morphology, photoluminescence (PL), and Raman scattering spectra have been investigated for mixtures of ZnO+0.1%C nanocrystals (NCs) at different stages of mechanical processing (MP). The transformation of graphite into graphene monolayers covering the ZnO NC surface is revealed for the first MP stage. The interaction with oxygen has been detected in the second MP stage which leads to the dissolution of oxygen interstitials in the ZnO NCs and to the formation of graphene (graphite) oxides. Increasing the concentration of the oxygen interstitials in ZnO NCs also enhances the intensity stimulation of the orange PL band (2.18eV). Simultaneously, the PL band peaking at 2.82-2.90 eV is detected in the PL spectra of the ZnO+0.1%C NC mixture after MP for 9-90 min. Then, the variation of the ZnO NC shape, agglomeration of ZnO NCs, modification of ZnO defects and decreasing PL intensity have been detected after prolonged MP for 390 min. It is expected that short stages of MP can be useful for ZnO NC surface covering by graphene layers or graphene (graphite) oxides.

  17. Anomalous antibacterial activity and dye degradation by selenium doped ZnO nanoparticles.

    PubMed

    Dutta, Raj Kumar; Nenavathu, Bhavani Prasad; Talukdar, Soumita

    2014-02-01

    Selenium doped ZnO nanoparticles synthesized by mechanochemical method were spherically shaped of size distribution of 10.2±3.4 nm measured by transmission electron microscopy. Diffused reflectance spectroscopy revealed increase in the band gap, ranging between 3.47 eV and 3.63 eV due to Se doping in ZnO nanoparticles. The antibacterial activity of pristine and Se doped ZnO nanoparticles was attributed to ROS (reactive oxygen species) generation in culture media confirmed by TBARS assay. Compared to complete inhibition of growth by 0.45 mg/mL of pristine ZnO nanoparticles, the batches of 0.45 mg/mL of selenium doped ZnO nanoparticles exhibited only 51% inhibition of growth of Escherichia coli. The reduced antibacterial activity of selenium doped ZnO nanoparticles was attributed to two opposing factors, e.g., ROS generation for inhibition of growth, countered by sustaining growth of E. coli due to availability of Se micronutrients in culture media, confirmed by inductively coupled plasma mass spectrometer measurement. Higher ROS generation by selenium doped ZnO nanoparticles was attributed to creation of oxygen vacancies, confirmed from green emission peak observed at 565 nm. The impact of higher ROS generation by selenium doped ZnO nanoparticles was evident from enhanced photocatalytic degradation of trypan blue dye, than pristine ZnO nanoparticles. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Tunable, flexible antireflection layer of ZnO nanowires embedded in PDMS.

    PubMed

    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.

  19. Improved conversion efficiency of amorphous Si solar cells using a mesoporous ZnO pattern

    PubMed Central

    2014-01-01

    To provide a front transparent electrode for use in highly efficient hydrogenated amorphous silicon (a-Si:H) thin-film solar cells, porous flat layer and micro-patterns of zinc oxide (ZnO) nanoparticle (NP) layers were prepared through ultraviolet nanoimprint lithography (UV-NIL) and deposited on Al-doped ZnO (AZO) layers. Through this, it was found that a porous micro-pattern of ZnO NPs dispersed in resin can optimize the light-trapping pattern, with the efficiency of solar cells based on patterned or flat mesoporous ZnO layers increased by 27% and 12%, respectively. PMID:25276101

  20. Effect of morphology on the non-ohmic conduction in ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    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.

  1. EFFECTS OF Au ON THE GROWTH OF ZnO NANOSTRUCTURES ON Si BY MOCVD

    NASA Astrophysics Data System (ADS)

    Cong, Chen; Fan, Lu Yang; Ping, He Hai; Wei, Wu Ke; Zhen, Ye Zhi

    2013-06-01

    The effects of Au on the growth of ZnO nanostructures on Si by metal organic chemical vapor deposition (MOCVD) at a relatively low temperature (450°C) were investigated. The experimental results showed that Au nanoparticles played a critical role during the growth of the ZnO nanostructures and affected their morphology and optical properties. It was found that Au nanoparticles particularly affected the nucleation of ZnO nanostructures during the growth process and the Au-assisted growth mechanism of ZnO nanostructures should be ascribed to the vapor-solid (VS) mechanism. The formation of a nanoneedle may be attributed to a more reactive interface between Au and ZnO, which leads to more zinc gaseous species absorbed near the interface. Different nucleation sites on ZnO nuclei resulted in the disorder of ZnO nanoneedles. Moreover, the crystalline quality of nano-ZnO was improved due to the presence of Au, according to the smaller full width at half maximum (FWHM) of the low-temperature exciton emission. We confirmed that ZnO nanoneedles showed better crystalline quality than ZnO nanorods through the HRTEM images and the SAED patterns. The reason for the improvement of the crystalline quality of nano-ZnO may be due to the less lattice mismatch.

  2. CW laser pumped emerald laser

    SciT

    Shand, M.L.; Lai, S.T.

    1984-02-01

    A CW laser-pumped emerald laser is reported. A 34 percent output power slope efficiency is observed with longitudinal pumping by a krypton laser in a nearly concentric cavity. The laser has been tuned from 728.8 to 809.0 nm. Losses in emerald are larger than those of alexandrite determined in a similar cavity. The present data also indicate that the excited state absorption minimum is shifted from that of alexandrite. 13 references.

  3. ZnO Nanostructures for Drug Delivery and Theranostic Applications.

    PubMed

    Martínez-Carmona, Marina; Gun'ko, Yurii; Vallet-Regí, María

    2018-04-23

    In the last two decades, zinc oxide (ZnO) semiconductor Quantum dots (QDs) have been shown to have fantastic luminescent properties, which together with their low-cost, low-toxicity and biocompatibility have turned these nanomaterials into one of the main candidates for bio-imaging. The discovery of other desirable traits such as their ability to produce destructive reactive oxygen species (ROS), high catalytic efficiency, strong adsorption capability and high isoelectric point, also make them promising nanomaterials for therapeutic and diagnostic functions. Herein, we review the recent progress on the use of ZnO based nanoplatforms in drug delivery and theranostic in several diseases such as bacterial infection and cancer.

  4. Nanostructured hybrid ZnO thin films for energy conversion

    PubMed Central

    2011-01-01

    We report on hybrid films based on ZnO/organic dye prepared by electrodeposition using tetrasulfonated copper phthalocyanines (TS-CuPc) and Eosin-Y (EoY). Both the morphology and porosity of hybrid ZnO films are highly dependent on the type of dyes used in the synthesis. High photosensitivity was observed for ZnO/EoY films, while a very weak photoresponse was obtained for ZnO/TS-CuPc films. Despite a higher absorption coefficient of TS-CuPc than EoY, in ZnO/EoY hybrid films, the excited photoelectrons between the EoY levels can be extracted through ZnO, and the porosity of ZnO/EoY can also be controlled. PMID:21711909

  5. ZnO nanoparticles based fiber optic gas sensor

    SciT

    Narasimman, S.; Sivacoumar, R.; Alex, Z. C.

    In this work, ZnO nanoparticles were synthesized by simple aqueous chemical route method. The synthesized ZnO nanoparticles were characterized by X-ray diffraction and scanning electron microscope. The sensitivity of the nanoparticles was studied for different gases like acetone, ammonia and ethanol in terms of variation in spectral light intensity. The XRD and SEM analysis confirms the formation of hexagonal wurtzite structure with the grain size of 11.2 nm. The small cladding region of the optical fiber was replaced with the synthesized nanoparticles. The light spectrum was recorded for different gas concentrations. The synthesized nanoparticles showed high sensitivity towards ammonia in lowmore » ppm level and acetone in high ppm level.« less

  6. ZnO Nanostructures for Drug Delivery and Theranostic Applications

    PubMed Central

    Martínez-Carmona, Marina

    2018-01-01

    In the last two decades, zinc oxide (ZnO) semiconductor Quantum dots (QDs) have been shown to have fantastic luminescent properties, which together with their low-cost, low-toxicity and biocompatibility have turned these nanomaterials into one of the main candidates for bio-imaging. The discovery of other desirable traits such as their ability to produce destructive reactive oxygen species (ROS), high catalytic efficiency, strong adsorption capability and high isoelectric point, also make them promising nanomaterials for therapeutic and diagnostic functions. Herein, we review the recent progress on the use of ZnO based nanoplatforms in drug delivery and theranostic in several diseases such as bacterial infection and cancer. PMID:29690644

  7. Room-temperature ferromagnetism in hydrogenated ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Xue, Xudong; Liu, Liangliang; Wang, Zhu; Wu, Yichu

    2014-01-01

    The effect of hydrogen doping on the magnetic properties of ZnO nanoparticles was investigated. Hydrogen was incorporated by annealing under 5% H2 in Ar ambient at 700 °C. Room-temperature ferromagnetism was induced in hydrogenated ZnO nanoparticles, and the observed ferromagnetism could be switched between "on" and "off" states through hydrogen annealing and oxygen annealing process, respectively. It was found that Zn vacancy and OH bonding complex (VZn + OH) was crucial to the observed ferromagnetism by using the X-ray photoelectron spectroscopy and positron annihilation spectroscopy analysis. Based on first-principles calculations, VZn + OH was favorable to be presented due to the low formation energy. Meanwhile, this configuration could lead to a magnetic moment of 0.57 μB. The Raman and photoluminescence measurements excluded the possibility of oxygen vacancy as the origin of the ferromagnetism.

  8. Efficient Auger Charge-Transfer Processes in ZnO

    NASA Astrophysics Data System (ADS)

    Stehr, J. E.; Chen, S. L.; Svensson, B. G.; Buyanova, I. A.; Chen, W. M.

    2018-05-01

    Photoluminescence and magneto-optical measurements are performed on a line peaking at 3.354 eV (labeled as NBX) in electron-irradiated ZnO. Even though the energy position of the NBX line is close to that for bound excitons in ZnO, it has distinctively different magneto-optical properties. Photoelectron paramagnetic resonance measurements reveal a connection and a charge-transfer process involving NBX and Fe and Al centers. The experimental results are explained within a model which assumes that the NBX is a neutral donor bound exciton at a defect center located near a Fe impurity and an Auger-type charge-transfer process occurs between NBX and Fe3 + . While the NBX dissociates, its hole is captured by an excited state of Fe3 + and the released energy is transferred to the NBX electron, which is excited to the conduction band and subsequently trapped by a substitutional AlZn shallow donor.

  9. Dielectric behavior and transport properties of ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Soosen Samuel, M.; Koshy, Jiji; Chandran, Anoop; George, K. C.

    2011-08-01

    Highly optical, good crystalline and randomly aligned ZnO nanorods were synthesized by the hydrothermal method. The dielectric properties of ZnO nanorods were attributed to the interfacial polarization at low frequencies (below 10 kHz) and orientational polarization at higher frequencies. The observed ω( n-1) dependence of dielectric loss was discussed on the basis of the Universal model of dielectric response. Dielectric loss peak was composed of the Debye like loss peak at higher frequencies and interfacial loss peak at lower frequencies. Charge transport through the grain and grain boundary region was investigated by impedance spectroscopy. At higher temperatures the conductivity of the nanorod was mainly through the grain interior and the overall impedance was contributed by the grain boundary region. The activation energy of nanorod was calculated as 0.078 eV, which is slightly higher than the reported bulk value.

  10. Photoinduced Effects in the ZnO Luminescence Spectra

    NASA Astrophysics Data System (ADS)

    Akopyan, I. Kh.; Labzovskaya, M. E.; Novikov, B. V.; Lisachenko, A. A.; Serov, A. Yu.; Filosofov, N. G.

    2018-02-01

    The effect of intense UV irradiation on the photoluminescence (PL) spectra of ZnO powders and nanocrystalline films obtained by atomic layer deposition (ALD) was investigated. At room temperature, the behavior of the spectra under continuous UV irradiation in multiple vacuum-atmosphere cycles was studied. The changes in the intensities of exciton radiation and radiation in the "green" band region, associated with the phenomena of oxygen photodesorption and photoadsorption, are discussed. In the temperature range of 5-300 K, the effect of strong UV irradiation on the near-edge luminescence spectrum of ZnO films was studied. The nature of a new line arising in the photoluminescence spectra of an irradiated film in the region of emission of bound excitons is discussed.

  11. Study of quantum confinement effects in ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Movlarooy, Tayebeh

    2018-03-01

    Motivation to fact that zinc oxide nanowires and nanotubes with successful synthesis and the mechanism of formation, stability and electronic properties have been investigated; in this study the structural, electronic properties and quantum confinement effects of zinc oxide nanotubes and nanowires with different diameters are discussed. The calculations within density functional theory and the pseudo potential approximation are done. The electronic structure and energy gap for Armchair and zigzag ZnO nanotubes with a diameter of about 4 to 55 Angstrom and ZnO nanowires with a diameter range of 4 to 23 Å is calculated. The results revealed that due to the quantum confinement effects, by reducing the diameter of nanowires and nanotubes, the energy gap increases. Zinc oxide semiconductor nanostructures since having direct band gap with size-dependent and quantum confinement effect are recommended as an appropriate candidate for making nanoscale optoelectronic devices.

  12. Laser device

    DOEpatents

    Scott, Jill R [Idaho Falls, ID; Tremblay, Paul L [Idaho Falls, ID

    2007-07-10

    A laser device includes a target position, an optical component separated a distance J from the target position, and a laser energy source separated a distance H from the optical component, distance H being greater than distance J. A laser source manipulation mechanism exhibits a mechanical resolution of positioning the laser source. The mechanical resolution is less than a spatial resolution of laser energy at the target position as directed through the optical component. A vertical and a lateral index that intersect at an origin can be defined for the optical component. The manipulation mechanism can auto align laser aim through the origin during laser source motion. The laser source manipulation mechanism can include a mechanical index. The mechanical index can include a pivot point for laser source lateral motion and a reference point for laser source vertical motion. The target position can be located within an adverse environment including at least one of a high magnetic field, a vacuum system, a high pressure system, and a hazardous zone. The laser source and an electro-mechanical part of the manipulation mechanism can be located outside the adverse environment. The manipulation mechanism can include a Peaucellier linkage.

  13. Laser device

    DOEpatents

    Scott, Jill R.; Tremblay, Paul L.

    2004-11-23

    A laser device includes a target position, an optical component separated a distance J from the target position, and a laser energy source separated a distance H from the optical component, distance H being greater than distance J. A laser source manipulation mechanism exhibits a mechanical resolution of positioning the laser source. The mechanical resolution is less than a spatial resolution of laser energy at the target position as directed through the optical component. A vertical and a lateral index that intersect at an origin can be defined for the optical component. The manipulation mechanism can auto align laser aim through the origin during laser source motion. The laser source manipulation mechanism can include a mechanical index. The mechanical index can include a pivot point for laser source lateral motion and a reference point for laser source vertical motion. The target position can be located within an adverse environment including at least one of a high magnetic field, a vacuum system, a high pressure system, and a hazardous zone. The laser source and an electro-mechanical part of the manipulation mechanism can be located outside the adverse environment. The manipulation mechanism can include a Peaucellier linkage.

  14. Laser ignition

    DOEpatents

    Early, James W.; Lester, Charles S.

    2003-01-01

    In the apparatus of the invention, a first excitation laser or other excitation light source is used in tandem with an ignitor laser to provide a compact, durable, engine deployable fuel ignition laser system. Reliable fuel ignition is provided over a wide range of fuel conditions by using a single remote excitation light source for one or more small lasers located proximate to one or more fuel combustion zones. In a third embodiment, alternating short and long pulses of light from the excitation light source are directed into the ignitor laser. Each of the embodiments of the invention can be multiplexed so as to provide laser light energy sequentially to more than one ignitor laser.

  15. ZnO layers prepared by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Messaoudi, C.; Abd-Lefdil, S.; Sayah, D.; Cadene, M.

    1998-02-01

    Highly transparent undoped and indium doped ZnO thin films have been grown on glass substrates by using the spray pyrolysis process. Conditions of preparation have been optimized to get good quality and reproducible films with required properties. Polycrystalline films with an hexagonal Wurtzite-type structure were easily obtained under the optimum spraying conditions. Both of samples have shown high transmission coefficient in the visible and infrared wavelength range with sharp absorption edge around 380 nm which closely corresponds to the intrinsic band-gap of ZnO (3.2 eV). Orientation and crystallites size were remarkably modified by deposition temperature and indium doping. Des couches minces de ZnO, hautement transparentes, non dopées et dopées à l'indium ont été élaborées sur un substrat en verre par le procédé de pulvérisation chimique réactive spray. Les conditions de préparation ont été optimisées pour l'obtention de couches reproductibles, de bonne qualité et ayant les propriétés requises. Des films polycristallins, présentant une structure hexagonale de type Wurtzite, ont été aisément obtenus dans les conditions optimales de pulvérisation. Tous les échantillons ont présenté un coefficient de transmission élevé dans le domaine du visible et du proche infrarouge, avec une absorption brutale au voisinage de 380 nm, correspondant au gap optique du ZnO (3,2 eV). L'orientation et la taille des cristallites ont été remarquablement modifiées par la température du dépôt et par le dopage à l'indium.

  16. Bulk ZnO: Current Status, Challenges, and Prospects

    DTIC Science & Technology

    2009-04-01

    von Wenckstern, H. Schmidt, M. Lorenz, and M. Grundmann, “Defects in virgin and N+-implanted ZnO single crystals studied by positron annihilation...characterization, and device applications of semiconductor and complex oxide thin films. He is a co-author of more than 50 papers in referred...REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Abstract— Rediscovered in the last decade, zinc oxide

  17. Laser photocoagulation - eye

    MedlinePlus

    Laser coagulation; Laser eye surgery; Photocoagulation; Laser photocoagulation - diabetic eye disease; Laser photocoagulation - diabetic retinopathy; Focal photocoagulation; Scatter (or pan retinal) photocoagulation; Proliferative ...

  18. GaN and ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Fündling, Sönke; Sökmen, Ünsal; Behrends, Arne; Al-Suleiman, Mohamed Aid Mansur; Merzsch, Stephan; Li, Shunfeng; Bakin, Andrey; Wehmann, Hergo-Heinrich; Waag, Andreas; Lähnemann, Jonas; Jahn, Uwe; Trampert, Achim; Riechert, Henning

    2010-07-01

    GaN and ZnO are both wide band gap semiconductors with interesting properties concerning optoelectronic and sensor device applications. Due to the lack or the high costs of native substrates, alternatives like sapphire, silicon, or silicon carbide are taken, but the resulting lattice and thermal mismatches lead to increased defect densities which reduce the material quality. In contrast, nanostructures with high aspect ratio have lower defect densities as compared to layers. In this work, we give an overview on our results achieved on both ZnO as well as GaN based nanorods. ZnO nanostructures were grown by a wet chemical approach as well as by VPT on different substrates - even on flexible polymers. To compare the growth results we analyzed the structures by XRD and PL and show possible device applications. The GaN nano- and microstructures were grown by metal organic vapor phase epitaxy either in a self- organized process or by selective area growth for a better control of shape and material composition. Finally we take a look onto possible device applications, presenting our attempts, e.g., to build LEDs based on GaN nanostructures.

  19. Impedance measurement of Cobalt doped ZnO Quantum dots

    NASA Astrophysics Data System (ADS)

    Tiwari, Ram; Kaphle, Amrit; Hari, Parameswar

    We investigated structural, thermal and electrical properties of ZnO Quantum dots grown by precipitation method. QDs were spin coated on ITO and annealed at various temperatures ranging from 1000C to 300 0C. ZnO QDs were doped with cobalt for concentration ranging from 0-15%. XRD measurement showed increase in bond length, strain, dislocation density and Cell volume as the doping level varied from 0% to 15%. Impedance Spectroscopy measurements represented by Cole-Cole plot showed reduction in resistance as the cobalt doping concentration increased from 0-15%. Thermal activation energy was obtained by plotting resistivity Vs temperature for doped samples at temperatures from 1000C to 3000C. The thermal activation energy decreased from 85.13meV to 58.21meV as doping increased from 0-15%. Relaxation time was extracted by fitting data to RC model. Relaxation time varied from 61.57 ns to 3.76 ns as the cobalt concentration increased from 0% to 15%. We will also discuss applications of cobalt doped ZnO QDs on improving conversion efficiency of solar cells.

  20. Electron paramagnetic resonance in Cu-doped ZnO

    NASA Astrophysics Data System (ADS)

    Buchheit, R.; Acosta-Humánez, F.; Almanza, O.

    2016-04-01

    In this work, ZnO and Cu-doped ZnO nanoparticles (Zn1-xCuxO, x = 3%), with a calcination temperature of 500∘C were synthesized using the sol-gel method. The particles were analyzed using atomic absorption spectroscopy (AAS), X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) at X-band, measurement in a temperature range from 90 K to room temperature. AAS confirmed a good correspondence between the experimental doping concentration and the theoretical value. XRD reveals the presence of ZnO phase in hexagonal wurtzite structure and a nanoparticle size for the samples synthesized. EPR spectroscopy shows the presence of point defects in both samples with g-values of g = 1.959 for shallow donors and g = 2.004 for ionized vacancies. It is important when these materials are required have been used as catalysts, as suggested that it is not necessary prepare them at higher temperature. A simulation of the Cu EPR signal using an anisotropic spin Hamiltonian was performed and showed good coincidence with the experimental spectra. It was shown that Cu2+ ions enter interstitial octahedral sites of orthorhombic symmetry in the wurtzite crystal structure. Temperature dependence of the EPR linewidth and signal intensity shows a paramagnetic behavior of the sample in the measurement range. A Néel temperature TN = 78 ± 19 K was determined.

  1. Effect of substrate on thermoelectric properties of Al-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Mele, P.; Saini, S.; Honda, H.; Matsumoto, K.; Miyazaki, K.; Hagino, H.; Ichinose, A.

    2013-06-01

    We have prepared 2% Al doped ZnO (AZO) thin films on SrTiO3 (STO) and Al2O3 substrates by Pulsed Laser Deposition technique at various deposition temperatures (Tdep = 300 °C-600 °C). Transport and thermoelectric properties of AZO thin films were studied in low temperature range (300 K-600 K). AZO/STO films present superior performance respect to AZO/Al2O3 films deposited at the same temperature, except for films deposited at 400 °C. Best film is the fully c-axis oriented AZO/STO deposited at 300 °C, which epitaxial strain and dislocation density are the lowest: electrical conductivity 310 S/cm, Seebeck coefficient -65 μV/K, and power factor 0.13 × 10-3 W m-1 K-2 at 300 K. Its performance increases with temperature. For instance, power factor is enhanced up to 0.55 × 10-3 W m-1 K-2 at 600 K, surpassing the best AZO film previously reported in literature.

  2. Micro-patterned ZnO semiconductors for high performance thin film transistors via chemical imprinting with a PDMS stamp.

    PubMed

    Seong, Kieun; Kim, Kyongjun; Park, Si Yun; Kim, Youn Sang

    2013-04-07

    Chemical imprinting was conducted on ZnO semiconductor films via a chemical reaction at the contact regions between a micro-patterned PDMS stamp and ZnO films. In addition, we applied the chemical imprinting on Li doped ZnO thin films for high performance TFTs fabrication. The representative micro-patterned Li doped ZnO TFTs showed a field effect mobility of 4.2 cm(2) V(-1) s(-1) after sintering at 300 °C.

  3. Fabrication of Semiconductor ZnO Nanostructures for Versatile SERS Application

    PubMed Central

    Yang, Lili; Yang, Yong; Ma, Yunfeng; Li, Shuai; Wei, Yuquan; Huang, Zhengren; Long, Nguyen Viet

    2017-01-01

    Since the initial discovery of surface-enhanced Raman scattering (SERS) in the 1970s, it has exhibited a huge potential application in many fields due to its outstanding advantages. Since the ultra-sensitive noble metallic nanostructures have increasingly exposed themselves as having some problems during application, semiconductors have been gradually exploited as one of the critical SERS substrate materials due to their distinctive advantages when compared with noble metals. ZnO is one of the most representative metallic oxide semiconductors with an abundant reserve, various and cost-effective fabrication techniques, as well as special physical and chemical properties. Thanks to the varied morphologies, size-dependent exciton, good chemical stability, a tunable band gap, carrier concentration, and stoichiometry, ZnO nanostructures have the potential to be exploited as SERS substrates. Moreover, other distinctive properties possessed by ZnO such as biocompatibility, photocatcalysis and self-cleaning, and gas- and chemo-sensitivity can be synergistically integrated and exerted with SERS activity to realize the multifunctional potential of ZnO substrates. In this review, we discuss the inevitable development trend of exploiting the potential semiconductor ZnO as a SERS substrate. After clarifying the root cause of the great disparity between the enhancement factor (EF) of noble metals and that of ZnO nanostructures, two specific methods are put forward to improve the SERS activity of ZnO, namely: elemental doping and combination of ZnO with noble metals. Then, we introduce a distinctive advantage of ZnO as SERS substrate and illustrate the necessity of reporting a meaningful average EF. We also summarize some fabrication methods for ZnO nanostructures with varied dimensions (0–3 dimensions). Finally, we present an overview of ZnO nanostructures for the versatile SERS application. PMID:29156600

  4. ZnO Nanoparticles Affect Bacillus subtilis Cell Growth and Biofilm Formation.

    PubMed

    Hsueh, Yi-Huang; Ke, Wan-Ju; Hsieh, Chien-Te; Lin, Kuen-Song; Tzou, Dong-Ying; Chiang, Chao-Lung

    2015-01-01

    Zinc oxide nanoparticles (ZnO NPs) are an important antimicrobial additive in many industrial applications. However, mass-produced ZnO NPs are ultimately disposed of in the environment, which can threaten soil-dwelling microorganisms that play important roles in biodegradation, nutrient recycling, plant protection, and ecological balance. This study sought to understand how ZnO NPs affect Bacillus subtilis, a plant-beneficial bacterium ubiquitously found in soil. The impact of ZnO NPs on B. subtilis growth, FtsZ ring formation, cytosolic protein activity, and biofilm formation were assessed, and our results show that B. subtilis growth is inhibited by high concentrations of ZnO NPs (≥ 50 ppm), with cells exhibiting a prolonged lag phase and delayed medial FtsZ ring formation. RedoxSensor and Phag-GFP fluorescence data further show that at ZnO-NP concentrations above 50 ppm, B. subtilis reductase activity, membrane stability, and protein expression all decrease. SDS-PAGE Stains-All staining results and FT-IR data further demonstrate that ZnO NPs negatively affect exopolysaccharide production. Moreover, it was found that B. subtilis biofilm surface structures became smooth under ZnO-NP concentrations of only 5-10 ppm, with concentrations ≤ 25 ppm significantly reducing biofilm formation activity. XANES and EXAFS spectra analysis further confirmed the presence of ZnO in co-cultured B. subtilis cells, which suggests penetration of cell membranes by either ZnO NPs or toxic Zn+ ions from ionized ZnO NPs, the latter of which may be deionized to ZnO within bacterial cells. Together, these results demonstrate that ZnO NPs can affect B. subtilis viability through the inhibition of cell growth, cytosolic protein expression, and biofilm formation, and suggest that future ZnO-NP waste management strategies would do well to mitigate the potential environmental impact engendered by the disposal of these nanoparticles.

  5. Physiological effects of nanoparticulate ZnO in green peas (Pisum sativum L.) cultivated in soil.

    PubMed

    Mukherjee, Arnab; Peralta-Videa, Jose R; Bandyopadhyay, Susmita; Rico, Cyren M; Zhao, Lijuan; Gardea-Torresdey, Jorge L

    2014-01-01

    The toxicological effects of zinc oxide nanoparticles (ZnO NPs) in plants are still largely unknown. In the present study, green pea (Pisum sativum L.) plants were treated with 0, 125, 250, and 500 mg kg(-1) of either ZnO NPs or bulk ZnO in organic matter enriched soil. Corresponding toxicological effects were measured on the basis of plant growth, chlorophyll production, Zn bioaccumulation, H2O2 generation, stress enzyme activity, and lipid peroxidation using different cellular, molecular, and biochemical approaches. Compared to control, all ZnO NP concentrations significantly increased (p ≤ 0.05) root elongation but no effects were observed in the stem. Whereas all bulk ZnO treatments significantly increased both root and stem length. After 25 days, chlorophyll in leaves decreased, compared to control, by ~61%, 67%, and 77% in plants treated with 125, 250, and 500 mg kg(-1) ZnO NPs, respectively. Similar results were found in bulk ZnO treated plants. At all ZnO NP concentrations CAT was significantly reduced in leaves (p ≤ 0.05), while APOX was reduced in both roots and leaves. In the case of bulk ZnO, APOX activity was down-regulated in the root and leaf and CAT was unaffected. At 500 mg kg(-1) treatment, the H2O2 in leaves increased by 61% with a twofold lipid peroxidation, which would be a predictive biomarker of nanotoxicity. This study could be pioneering in evaluating the phytotoxicity of ZnO NPs to green peas and can serve as a good indicator for measuring the effects on ZnO NPs in plants grown in organic matter enriched soil.

  6. ZnO Nanoparticles Affect Bacillus subtilis Cell Growth and Biofilm Formation

    PubMed Central

    Hsueh, Yi-Huang; Ke, Wan-Ju; Hsieh, Chien-Te; Lin, Kuen-Song; Tzou, Dong-Ying; Chiang, Chao-Lung

    2015-01-01

    Zinc oxide nanoparticles (ZnO NPs) are an important antimicrobial additive in many industrial applications. However, mass-produced ZnO NPs are ultimately disposed of in the environment, which can threaten soil-dwelling microorganisms that play important roles in biodegradation, nutrient recycling, plant protection, and ecological balance. This study sought to understand how ZnO NPs affect Bacillus subtilis, a plant-beneficial bacterium ubiquitously found in soil. The impact of ZnO NPs on B. subtilis growth, FtsZ ring formation, cytosolic protein activity, and biofilm formation were assessed, and our results show that B. subtilis growth is inhibited by high concentrations of ZnO NPs (≥ 50 ppm), with cells exhibiting a prolonged lag phase and delayed medial FtsZ ring formation. RedoxSensor and Phag-GFP fluorescence data further show that at ZnO-NP concentrations above 50 ppm, B. subtilis reductase activity, membrane stability, and protein expression all decrease. SDS-PAGE Stains-All staining results and FT-IR data further demonstrate that ZnO NPs negatively affect exopolysaccharide production. Moreover, it was found that B. subtilis biofilm surface structures became smooth under ZnO-NP concentrations of only 5–10 ppm, with concentrations ≤ 25 ppm significantly reducing biofilm formation activity. XANES and EXAFS spectra analysis further confirmed the presence of ZnO in co-cultured B. subtilis cells, which suggests penetration of cell membranes by either ZnO NPs or toxic Zn+ ions from ionized ZnO NPs, the latter of which may be deionized to ZnO within bacterial cells. Together, these results demonstrate that ZnO NPs can affect B. subtilis viability through the inhibition of cell growth, cytosolic protein expression, and biofilm formation, and suggest that future ZnO-NP waste management strategies would do well to mitigate the potential environmental impact engendered by the disposal of these nanoparticles. PMID:26039692

  7. Study of annealing effect on the growth of ZnO nanorods on ZnO seed layers

    NASA Astrophysics Data System (ADS)

    Sannakashappanavar, Basavaraj S.; Pattanashetti, Nandini A.; Byrareddy, C. R.; Yadav, Aniruddh Bahadur

    2018-04-01

    A zinc oxide (ZnO) seed layer was deposited on the SiO2/Si substrate by RF sputtering. To study the effect of annealing, the seed layers were classified into annealed and unannealed thin films. Annealing of the seed layers was carried at 450°C. Surface morphology of the seed layers were studied by Atomic force microscopy. ZnO nanorods were then grown on both the types of seed layer by hydrothermal method. The morphology and the structural properties of the nanorods were characterized by X-ray diffraction and Scanning electron microscopy. The effect of seed layer annealing on the growth and orientation of the ZnO nanorods were clearly examined on comparing with the nanorods grown on unannealed seed layer. The nanorods grown on annealed seed layers were found to be well aligned and oriented. Further, the I-V characteristic study was carried out on these aligned nanorods. The results supports positively for the future work to further enhance the properties of developed nanorods for their wide applications in electronic and optoelectronic devices.

  8. Engineering future light emitting diodes and photovoltaics with inexpensive materials: Integrating ZnO and Si into GaN-based devices

    NASA Astrophysics Data System (ADS)

    Bayram, C.; Shiu, K. T.; Zhu, Y.; Cheng, C. W.; Sadana, D. K.; Teherani, F. H.; Rogers, D. J.; Sandana, V. E.; Bove, P.; Zhang, Y.; Gautier, S.; Cho, C.-Y.; Cicek, E.; Vashaei, Z.; McClintock, R.; Razeghi, M.

    2013-03-01

    Indium Gallium Nitride (InGaN) based PV have the best fit to the solar spectrum of any alloy system and emerging LED lighting based on InGaN technology and has the potential to reduce energy consumption by nearly one half while enabling significant carbon emission reduction. However, getting the maximum benefit from GaN diode -based PV and LEDs will require wide-scale adoption. A key bottleneck for this is the device cost, which is currently dominated by the substrate (i.e. sapphire) and the epitaxy (i.e. GaN). This work investigates two schemes for reducing such costs. First, we investigated the integration of Zinc Oxide (ZnO) in InGaN-based diodes. (Successful growth of GaN on ZnO template layers (on sapphire) was illustrated. These templates can then be used as sacrificial release layers for chemical lift-off. Such an approach provides an alternative to laser lift-off for the transfer of GaN to substrates with a superior cost-performance profile, plus an added advantage of reclaiming the expensive single-crystal sapphire. It was also illustrated that substitution of low temperature n-type ZnO for n-GaN layers can combat indium leakage from InGaN quantum well active layers in inverted p-n junction structures. The ZnO overlayers can also double as transparent contacts with a nanostructured surface which enhances light in/out coupling. Thus ZnO was confirmed to be an effective GaN substitute which offers added flexibility in device design and can be used in order to simultaneously reduce the epitaxial cost and boost the device performance. Second, we investigated the use of GaN templates on patterned Silicon (100) substrates for reduced substrate cost LED applications. Controlled local metal organic chemical vapor deposition epitaxy of cubic phase GaN with on-axis Si(100) substrates was illustrated. Scanning electron microscopy and transmission electron microscopy techniques were used to investigate uniformity and examine the defect structure in the GaN. Our

  9. Change in structural morphology on addition of ZnO and its effect on fluorescence of Yb³⁺/Er³⁺ doped Y₂O₃.

    PubMed

    Yadav, R V; Verma, R K; Kaur, G; Rai, S B

    2013-02-15

    Yb(3+)/Er(3+) codoped Y(2)O(3) phosphor and its composite with ZnO have been synthesized by combustion method. Morphology of the materials has been investigated using X-ray diffraction pattern (XRD) and scanning electron microscopy (SEM) techniques. XRD confirms the constituents as Y(2)O(3) and ZnO, with average crystallite size of 112 nm. On addition of ZnO, a small shifting in XRD pattern of Y(2)O(3) is observed. SEM pattern suggests that the average particle size lies in micro-range (0.5 μm). A dumble like structure is observed for hybrid material on annealing at 1473 K. A strong green (525, 546 nm) with weak blue (411 nm) and red (657 nm) emissions through upconversion has been observed from the phosphor on excitation with 976 nm diode laser. The observed emissions involve (2)H(9/2)→(4)I(15/2), (2)H(11/2)→(4)I(15/2), (4)S(3/2)→(4)I(15/2) and (4)F(9/2)→(4)I(15/2) electronic transitions, respectively. The upconversion process has been confirmed by power dependence measurements and its slope value was found to be 1.85, 1.72 for green and red emissions, respectively. On addition of ZnO, the intensity of these emissions is enhanced several times. The reason behind the enhancement is discussed with the help of the emitting level lifetime. An interesting dual mode property (upconversion and downconversion) to the same material has been observed on excitation with 532 nm laser source. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. Laser ignition

    DOEpatents

    Early, James W.; Lester, Charles S.

    2002-01-01

    In the apparatus of the invention, a first excitation laser or other excitation light source is used in tandem with an ignitor laser to provide a compact, durable, engine deployable fuel ignition laser system. Reliable fuel ignition is provided over a wide range of fuel conditions by using a single remote excitation light source for one or more small lasers located proximate to one or more fuel combustion zones. In the embodiment of the invention claimed herein, the beam from the excitation light source is split with a portion of it going to the ignitor laser and a second portion of it being combined with either the first portion after a delay before injection into the ignitor laser.

  11. Theoretical investigation on thermodynamic properties of ZnO1-x Te x alloys

    NASA Astrophysics Data System (ADS)

    Long, Debing; Li, Mingkai; Luo, Minghai; Zhu, Jiakun; Yang, Hui; Huang, Zhongbing; Ahuja, Rajeev; He, Yunbin

    2017-05-01

    In this study, the formation energy, phase diagram (with/without phonon contribution) and the relationship between bond stiffness and bond length for wurtzite (WZ) and zincblende (ZB) structures of ZnO1-x Te x (0  ⩽  x  ⩽  1) alloys have been investigated by combining first-principles calculations and cluster expansion method. The formation energy of ZnO1-x Te x alloys is very high in both structures, which means that it is difficult for ZnO and ZnTe to form stable ternary alloys ZnO1-x Te x . In the phase diagrams, both structures do not have stable phase of ternary alloys and ZnO1-x Te x ternary alloys can only exist in the form of metastable phase. These results indicate that ZnO and ZnTe easily form solid solubility gap when they form alloys. After considering vibrational free energy, we found the solubility of Te in ZnO and O in ZnTe was increased and the vibrational entropy improved the solubility furthermore. The phonon contribution is not ignorable to improve solid solubility. The phonon density of states was analyzed for ZnO1-x Te x alloys and the contribution from vibrational entropy was discussed.

  12. Photoelectrocatalytic activity of a hydrothermally grown branched Zno nanorod-array electrode for paracetamol degradation.

    PubMed

    Lin, Chin Jung; Liao, Shu-Jun; Kao, Li-Cheng; Liou, Sofia Ya Hsuan

    2015-06-30

    Hierarchical branched ZnO nanorod (B-ZnR) arrays as an electrode for efficient photoelectrocatalytic degradation of paracetamol were grown on fluorine-doped tin oxide substrates using a solution route. The morphologic and structural studies show the ZnO trunks are single-crystalline hexagonal wurtzite ZnO with a [0001] growth direction and are densely covered by c-axis-oriented ZnO branches. The obvious enhancement in photocurrent response of the B-ZnR electrode was obtained than that in the ZnO nanoparticle (ZnO NP) electrode. For the photoelectrocatalytic degradation of paracetamol in 20 h, the conversion fraction of the drug increased from 32% over ZnO NP electrode to 62% over B-ZnR arrays with about 3-fold increase in initial reaction rate. The light intensity-dependent photoelectrocatalytic experiment indicated that the superior performance over the B-ZnR electrode was mainly ascribed to the increased specific surface area without significantly sacrificing the charge transport and pollutant diffusion efficiencies. Two aromatic intermediate compounds were observed and eventually converted into harmless carboxylic acids and ammonia. Hierarchical tree-like ZnO arrays can be considered effective alternatives to improve photoelectro degradation rates without the need for expensive additives. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. High quantum yield ZnO quantum dots synthesizing via an ultrasonication microreactor method.

    PubMed

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

    2016-11-01

    Green emission ZnO quantum dots were synthesized by an ultrasonic microreactor. Ultrasonic radiation brought bubbles through ultrasonic cavitation. These bubbles built microreactor inside the microreactor. The photoluminescence properties of ZnO quantum dots synthesized with different flow rate, ultrasonic power and temperature were discussed. Flow rate, ultrasonic power and temperature would influence the type and quantity of defects in ZnO quantum dots. The sizes of ZnO quantum dots would be controlled by those conditions as well. Flow rate affected the reaction time. With the increasing of flow rate, the sizes of ZnO quantum dots decreased and the quantum yields first increased then decreased. Ultrasonic power changed the ultrasonic cavitation intensity, which affected the reaction energy and the separation of the solution. With the increasing of ultrasonic power, sizes of ZnO quantum dots first decreased then increased, while the quantum yields kept increasing. The effect of ultrasonic temperature on the photoluminescence properties of ZnO quantum dots was influenced by the flow rate. Different flow rate related to opposite changing trend. Moreover, the quantum yields of ZnO QDs synthesized by ultrasonic microreactor could reach 64.7%, which is higher than those synthesized only under ultrasonic radiation or only by microreactor. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Hydrothermal Synthesis of Various Hierarchical ZnO Nanostructures and Their Methane Sensing Properties

    PubMed Central

    Zhou, Qu; Chen, Weigen; Xu, Lingna; Peng, Shudi

    2013-01-01

    Hierarchical flower-like ZnO nanorods, net-like ZnO nanofibers and ZnO nanobulks have been successfully synthesized via a surfactant assisted hydrothemal method. The synthesized products were characterized by X-ray powder diffraction and field emission scanning electron microscopy, respectively. A possible growth mechanism of the various hierarchical ZnO nanostructures is discussed in detail. Gas sensors based on the as-prepared ZnO nanostructures were fabricated by screen-printing on a flat ceramic substrate. Furthermore, their gas sensing characteristics towards methane were systematically investigated. Methane is an important characteristic hydrocarbon contaminant found dissolved in power transformer oil as a result of faults. We find that the hierarchical flower-like ZnO nanorods and net-like ZnO nanofibers samples show higher gas response and lower operating temperature with rapid response-recovery time compared to those of sensors based on ZnO nanobulks. These results present a feasible way of exploring high performance sensing materials for on-site detection of characteristic fault gases dissolved in transformer oil. PMID:23666136

  15. Luminescence dynamics of bound exciton of hydrogen doped ZnO nanowires

    DOE PAGES

    Yoo, Jinkyoung; Yi, Gyu -Chul; Chon, Bonghwan; ...

    2016-04-11

    In this study, all-optical camera, converting X-rays into visible photons, is a promising strategy for high-performance X-ray imaging detector requiring high detection efficiency and ultrafast detector response time. Zinc oxide is a suitable material for all-optical camera due to its fast radiative recombination lifetime in sub-nanosecond regime and its radiation hardness. ZnO nanostructures have been considered as proper building blocks for ultrafast detectors with spatial resolution in sub-micrometer scale. To achieve remarkable enhancement of luminescence efficiency n-type doping in ZnO has been employed. However, luminescence dynamics of doped ZnO nanostructures have not been thoroughly investigated whereas undoped ZnO nanostructures havemore » been employed to study their luminescence dynamics. Here we report a study of luminescence dynamics of hydrogen doped ZnO nanowires obtained by hydrogen plasma treatment. Hydrogen doping in ZnO nanowires gives rise to significant increase in the near-band-edge emission of ZnO and decrease in averaged photoluminescence lifetime from 300 to 140 ps at 10 K. The effects of hydrogen doping on the luminescent characteristics of ZnO nanowires were changed by hydrogen doping process variables.« less

  16. Anti-cancer activity of ZnO chips by sustained zinc ion release.

    PubMed

    Moon, Seong-Hee; Choi, Won Jin; Choi, Sik-Won; Kim, Eun Hye; Kim, Jiyeon; Lee, Jeong-O; Kim, Seong Hwan

    2016-01-01

    We report anti-cancer activity of ZnO thin-film-coated chips by sustained release of zinc ions. ZnO chips were fabricated by precisely tuning ZnO thickness using atomic layer deposition, and their potential to release zinc ions relative to the number of deposition cycles was evaluated. ZnO chips exhibited selective cytotoxicity in human B lymphocyte Raji cells while having no effect on human peripheral blood mononuclear cells. Of importance, the half-maximal inhibitory concentration of the ZnO chip on the viability of Raji cells was 121.5 cycles, which was comparable to 65.7 nM of daunorubicin, an anti-cancer drug for leukemia. Molecular analysis of cells treated with ZnO chips revealed that zinc ions released from the chips increased cellular levels of reactive oxygen species, including hydrogen peroxide, which led to the down-regulation of anti-apoptotic molecules (such as HIF-1α, survivin, cIAP-2, claspin, p-53, and XIAP) and caspase-dependent apoptosis. Because the anti-cancer activity of ZnO chips and the mode of action were comparable to those of daunorubicin, the development and optimization of ZnO chips that gradually release zinc ions might have clinical anti-cancer potential. A further understanding of the biological action of ZnO-related products is crucial for designing safe biomaterials with applications in disease treatment.

  17. Ultrasound assisted synthesis of WO3-ZnO nanocomposites for brilliant blue dye degradation.

    PubMed

    Hunge, Y M; Yadav, A A; Mathe, V L

    2018-07-01

    The present work deals with the preparation of WO 3 and WO 3 -ZnO nanocomposites in presence of ultrasonic irradiation, and its use in the sonocatalytic degradation of brilliant blue dye. WO 3 -ZnO nanocomposite is prepared using one step in-situ ultrasound assisted method. The successfully prepared WO 3 and WO 3 -ZnO nanocomposites were characterized using different characterization techniques such as XRD, Raman, BET, FE-SEM and EDS. The XRD pattern reveals that the formation of monoclinic and hexagonal crystal structures of WO 3 and ZnO respectively. BET study shows that WO 3 -ZnO nanocomposite have maximum surface area than that of the WO 3 . EDS study confirms the formation of WO 3 -ZnO nanocomposites. Further the use of the prepared WO 3 and WO 3 -ZnO nanocomposites as a sonocatalyst for the degradation of brilliant blue dye. The rate constant (k) was evaluated as a function of the initial concentration of brilliant blue dye. It is found that WO 3 -ZnO nanocomposites exhibits maximum sonocatalytic activity as compared to WO 3 photocatalyst. Copyright © 2018 Elsevier B.V. All rights reserved.

  18. Visible electroluminescence from a ZnO nanowires/p-GaN heterojunction light emitting diode.

    PubMed

    Baratto, C; Kumar, R; Comini, E; Faglia, G; Sberveglieri, G

    2015-07-27

    In the current paper we apply catalyst assisted vapour phase growth technique to grow ZnO nanowires (ZnO nws) on p-GaN thin film obtaining EL emission in reverse bias regime. ZnO based LED represents a promising alternative to III-nitride LEDs, as in free devices: the potential is in near-UV emission and visible emission. For ZnO, the use of nanowires ensures good crystallinity of the ZnO, and improved light extraction from the interface when the nanowires are vertically aligned. We prepared ZnO nanowires in a tubular furnace on GaN templates and characterized the p-n ZnO nws/GaN heterojunction for LED applications. SEM microscopy was used to study the growth of nanowires and device preparation. Photoluminescence (PL) and Electroluminescence (EL) spectroscopies were used to characterize the heterojunction, showing that good quality of PL emission is observed from nanowires and visible emission from the junction can be obtained from the region near ZnO contact, starting from onset bias of 6V.

  19. Effects of ZnO nanoparticles on wastewater biological nitrogen and phosphorus removal.

    PubMed

    Zheng, Xiong; Wu, Rui; Chen, Yinguang

    2011-04-01

    With the increasing utilization of nanomaterials, zinc oxide nanoparticles (ZnO NPs) have been reported to induce adverse effects on human health and aquatic organisms. However, the potential impacts of ZnO NPs on wastewater nitrogen and phosphorus removal with an activated sludge process are unknown. In this paper, short-term exposure experiments were conducted to determine whether ZnO NPs caused adverse impacts on biological nitrogen and phosphorus removal in the unacclimated anaerobic-low dissolved oxygen sequencing batch reactor. Compared with the absence of ZnO NPs, the presence of 10 and 50 mg/L of ZnO NPs decreased total nitrogen removal efficiencies from 81.5% to 75.6% and 70.8%, respectively. The corresponding effluent phosphorus concentrations increased from nondetectable to 10.3 and 16.5 mg/L, respectively, which were higher than the influent phosphorus (9.8 mg/L), suggesting that higher concentration of ZnO NPs induced the loss of normal phosphorus removal. It was found that the inhibition of nitrogen and phosphorus removal induced by higher concentrations of ZnO NPs was due to the release of zinc ions from ZnO NPs dissolution and increase of reactive oxygen species (ROS) production, which caused inhibitory effect on polyphosphate-accumulating organisms and decreased nitrate reductase, exopolyphosphatase, and polyphosphate kinase activities.

  20. Enhanced bioactivity of ZnO nanoparticles—an antimicrobial study

    NASA Astrophysics Data System (ADS)

    Padmavathy, Nagarajan; Vijayaraghavan, Rajagopalan

    2008-07-01

    In this study, we investigate the antibacterial activity of ZnO nanoparticles with various particle sizes. ZnO was prepared by the base hydrolysis of zinc acetate in a 2-propanol medium and also by a precipitation method using Zn(NO3)2 and NaOH. The products were characterized by x-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. Bacteriological tests such as minimum inhibitory concentration (MIC) and disk diffusion were performed in Luria-Bertani and nutrient agar media on solid agar plates and in liquid broth systems using different concentrations of ZnO by a standard microbial method for the first time. Our bacteriological study showed the enhanced biocidal activity of ZnO nanoparticles compared with bulk ZnO in repeated experiments. This demonstrated that the bactericidal efficacy of ZnO nanoparticles increases with decreasing particle size. It is proposed that both the abrasiveness and the surface oxygen species of ZnO nanoparticles promote the biocidal properties of ZnO nanoparticles.